'/. •«-* ,*u '1- Bitf? r« r^m .. ^" .y ..^•' * ♦ || Surgeon General's Office jl erection, Crl&±M C: non-metallic. The latter group may be arranged into three pairs:— INTRODUCTION. vii 1st. The gaseous bodies, Hydrogen and Azote; 2d. The fixed and infusible solids, Carbon and Boron; 3d. The fusible and volatile solids, Sulphur and Phosphorus. The forty-three metallic bodies are distinguishable by their habitudes with oxygen, into two great divisions, the Basifiable and Acidifiable metals. The former are thirty-six in number, the latter seven. Of the thirty-six metals, which yield by their union with oxygen salifi- able bases, three are convertible into alkalies, ten into earths,* and twenty- three into ordinary metallic oxides. Some of the latter, however, by a maximum dose of oxygen, seem to graduate into the acidifiable group, or at least cease to form salifiable bases. We shall now delineate a general chart of Chemistry, enumerating its various leading objects in a somewhat tabular form, and pointing out their most important relations, so that the readers of this Dictionary may have it in their power to study its contents in a systematic order. CHEMISTRY Is the science which treats of the specific differences in the nature of bodies, and the permanent changes of constitution, towhich their mutual actions give rise.f This diversity in the nature of bodies is derived either from the aggre- gation or composition of their integrant particles. The state of aggre- gation seems to depend on the relation between the cohesive attraction of these integrant particles, and the antagonizing force of heat. Hence, the three general forms of solid, liquid, and gaseous, under one or other of which every species of material being may be classed. For instruction on these general forms of matter, the student ought to read, 1st, The early part of the article Attraction; 2d, Crystalliza- tion; 3d, That part of Caloric entitled, " Of the change of state pro- duced in bodies by caloric, independent of change of composition." He may then peruse the introductory part of the article Gas and Balance, and Laboratory. He will now be sufficiently prepared for the study of the rest of the article Caloric, as well as that of its correlative subjects, Temperature, Thermometer, Evaporation, Congelation, Cryo- meter, Dew, and Climate. The order now prescribed will be found convenient. In the article Caloric, there are a few discussions, which the beginner may perhaps find somewhat difficult. These he may pass over at the first reading, and resume their consideration in the sequel. After Caloric he may peruse Light, and the first three sections of Elec- tricity. The article Combustion, will be most advantageously examined, after he has become acquainted with some of the diversities of Composition; viz. with the three vitreo-polar dissolvents, oxygen, chlorine, and iodine; and the six non-metallic rcsino-polar elements, hydrogen, azote, carbon, boron, sulphur, and phosphorus. Let him begin with oxygen, and then peruse, for the sake of connexion, hydrogen, and water. Should he wish to know how the specific gravity of gaseous matter is ascertained, he may consult the fourth section of the article Gas. The next subject to which he should direct his attention is Chlorine; on which he will meet with ample details in the present Work. This article will bear a second perusal. It describes a series of the most splen- * I here regard silica feting as a base to fluoric acid, in the fluosilicic confound; but the subject is mysterious. Sec Acid (Fluoiuc). .,/.,... ... c + I do not know whether this definition be my own, or borrowed. I nnd it in the syllabus ot my Belfast Lectures, printed many years ago. Another definition Ii.t; been given in the Dictionary, article Chemistry. Viii INTRODUCTION. did efforts ever made by the sagacity of man, to unfold the mysteries of nature. In connexion with it he may read the articles Chlorous and Chlo- ric Oxides, or the protoxide and deutoxide of Chlorine. Let him next study the copious article Iodine, from beginning to end. Carbon, boron, sulphur, phosphorus, and azote, must now come under review. Related closely with the first, he will study the carbonous oxide, carburetted and subcarburetted hydrogen. What is known of the element boron, will be speedily learned; and he may then enter on the examination of sulphur, sulphuretted hydrogen, and carburet of sulphur. Phosphorus and phosphuretted hydrogen, with nitrogen or azote, and its oxides and chlorides, will form the conclusion of the first division of chemical study, which re- lates to the elements of most general interest and activity. The general articles Combustible, Combustion, and Safe-lamp may now be read with ad- vantage; as well as the remainder of the article attraction, which treats of affinity. Since in the present work the alkaline and earthy salts are annexed to their respective acids, it will be proper, before commencing the study of the latter, to become acquainted with the alkaline and earthy bases. The order of reading may therefore be the following : first, The gene- ral article alkali, then potash and potassium, soda and sodium, lithia, and ammonia. Next, the general article earth; afterwards calcium and lime, barium and barytes, strontia, magnesia, alumina, silica, glucina, zirconia, yttria, and thorina. Let him now peruse the general articles acid and salt; and then the non- metallic oxygen acids, with their subjoined salts, in the following order:__ sulphuric, sulphurous, hyposulphurous, and hyposulphuric; phosphoric, phos- phorous and hypophosphorous; carbonic and chloro-carbonous; boracic; and lastly, the nitric and nitrous. The others may be studied conveniently with the hydrogen group. The order of perusing them may be, the mu- riatic (hydrochloric of M. Gay-Lussac), chloric and perchloric ; the hydri- •dic, iodic and chloriodic; the fluoric, fiuoboric, and fiuosilicic; the prussic (hydrocyanic of M. Gay-Lussac), ferroprussic, chloroprussic, and sulphuro- prussic. The hydrosulphurous and hydrotellurous, are discussed in this Dic- tionary, under the names of sulphuretted hydrogen, and telluretted hydrogen. These compound bodies possess acid powers, as well perhaps as arsenuret- ted hydrogen. It would be advisable to peruse the article prussine (cy- anogen) either before or immediately after prussic acid. As to the vegetable and animal acids, they may be read either in their alphabetical order or in any other which the student or his teacher shall think fit. Thirty-eight of them are enumerated in the sequel of the article Acid; of which two or three are of doubtful identity. The metallic acids fall naturally under metallic chemistry; on the study of which I have nothing to add to the remarks contained in the general article Metal. Along with each metal in its alphabetical place, its na- tive state, or ores, may be studied. See Ores. The chemistry of organized matter may be methodically studied by perusing, first of all, the article vegetable kingdom, with the various pro- ducts of vegetation there enumerated; and then the article animal king- dom, with the subordinate animal products and adipocere. The article analysis may be now consulted; then mineral waters; equivalents (chemical); and analysis of ores. The mineralogical department should be commenced with the gene- ral articles mineralogy, and crystallography; after which the different spe- cies and varieties may be examined under their respective titles. The enumeration of the genera of M. Mohs, given in the first article, will INTRODUCTION. ix guide the student to a considerable extent in their methodical considera- tion. Belonging to mineralogy, are the subjects, blow-pipe, geology with its subordinate rocks, ores, and meteorolite. The medical student may read with advantage, the articles, acid (arseni- ous,) antimony, bile, blood, calculus (urinary), the sequel of co/iper, digestion, gall-stones, galvanism, intestinal concretion, lead, mercury, poisons, respira- Hon, urine, isfc. The agriculturist will find details not unworthy of his attention, under the articles, absorbent, analysis of soils, carbonate, lime, manure, and soils. Among the discussions interesting to manufacturers are, acetic, and other acids, alcohol, alum, ammonia, beer, bleaching, bread, caloric, coal, and coal- gas, distillation, dyeing, ether, fat, fermentation, glass, ink, iron, ores, potash, pottery, salt, soap, soda, steel, sugar, tanning, tsfc. The general reader will find, it is hoped, instruction blended with enter- tainment, in the articles, aerostation, air, climate, combustion, congelation, dew, electricity, equivalents, galvanism, geology, light, meteorolite, rain, and several other articles formerly noticed. It may be proper now to say something concerning the execution of the present Work. In the month of June, a gentleman, from London, who had become possessed of the copy-right of Nicholson's Dictionary, waited on me in Glasgow, requesting that I would superintend the revision of a new edition, which he purposed immediately to send to the press. I stated to him, that, however valuable Nicholson's compilation might have been at its appearance in 1808, the science of chemistry had undergone such altera- tions since, as would require a Dictionary to be written in a great measure anew. To this he replied, that the above work had enjoyed great popu- larity; that he was certain a new edition of it would be well received; that he did not expect me to compose original articles or dissertations, but merely to add, from recent publications, such notices of new discoveries and improvements as might seem proper, and to retrench what appeared obsolete or useless; taking care to comprise the whole in such a compass as would render the price moderate, and thus place the book within the reach of manufacturers, medical students, and general readers. The terms offered appearing reasonable relative to the work required, I entered into an engagement to revise the new edition in time for the winter classes. Having assembled complete series of all the British scientific journals, with several of the foreign, and the various chemical compilations from Newman and Macquer, to the present day, I commenced the stipulated revision. I had advanced a very little way, however, when I became alarmed at the dilemna in which I found myself placed. A large propor- tion of the articles which I had reckoned on reprinting, as having under- gone little change since 1808, were found to have been quite obsolete at that period. They had been evidently copied, with scarcely any alteration, through Nicholson's quarto Dictionary, from Macquer and Newman, back I believe to the era of Stahl, Becher, and Agricola. Under the article acid (acetic), 36 pages of Crell's Annals had been copied verbatim • t seriatim on the concentration of vinegar by charcoal, 8cc. A larger space was al- lotted to the separation of silver, under the articles silver, parting, and as- say, than was dedicated to all the gases and earths. The article Caloric was meagre and vapid, while desulphuration or roasting of pyrites, Brazil wood, and safflower, occupied a far greater extent. Putrefaction consist- ed of extracts from Becher's subterranean world, and other details belong- ing to a former age of chemistry. The contents of the 8vo Diction ry vwe made up from four sources. 1st, From his quarto Dictionary of 1'."95. The long article Ores, for X INTRODUCTION. example, Was taken chiefly from Cramer, while the labours of Klaproth and Vauquelin were seldom noticed. Large excerpts were also given from obsolete Dispensatories, concerning substances of no chemical importance, and destitute of all medicinal power. 2d, From the contemporary systems of Brongniart, Henry, Murray t Thonison, &c. about another fourth was copied in continuous articles. This formed the best part of the whole. 3d, Large excerpts were given from his own Journal, quite dispropor- tionate to the rest of the work, and to the exclusion of numerous interest- ing topics. Indeed a journalist, who compiles a system, has great tempta- tions to fall into this practice. 4th, The fourth portion was composed by himself. This seems to have constituted about one-twentieth of the Dictionary, and related chiefly to nhysics, in which he was experimentally versant. These articles were very respectable, and have been in some measure retained; see Attrac- tion, Balance, Hydrometer, and Laboratory. What follows the first asterisk in Attraction, has been now added. Mr. Nicholson was indeed a man of candour, intelligence, and ingenuity. His original papers on electricity, and mechanical science, do him much honour; and the ab- stracts of experimental chemical memoirs, which he occasionally drew up for his Journal, were ably executed. Had he bestowed corresponding- pains on his 8vo Dictionary, my present task would have been greatly lighter. After making such a survey, the feelings under which I began to labour were similar to those of an architect, who having undertaken to repair a building within a certain period, by replacing a few unsightly or moulder- ing stones, finds himself, on his first operations, overwhelmed in its rubbish. Reverence to public opinion, and anxiety to fulfil my engagement, how- ever irksome, have induced me to make every possible exertion to restore the edifice, and renew the decayed parts with solid materials. If it has not all the symmetry, or compactness, of an original design, leisurely exe- cuted, still I trust it will prove not altogether unworthy the attention of the chemical world. I have investigated the foundation of almost every fact or statement which it contains, and believe they merit general confi- dence. Many inaccurate positions and deductions, in our most elaborate modern system, I have taken the liberty of pointing out; aware that the influence of Dr. Thomson's name and manner is capable of giving consi- derable currency to his opinions, however erroneous they may be. His in- dustry deserves the highest praise ; and his chemical experience would entitle his decisions to deference, were they less precipitate, and less dog- matical. Many of my embarrassments in compiling the present volume, have arisen from his contradictory judgments, pronounced in the Annals of Philosophy; see Acids Phosphoric, Prussic, 8tc. If under the in- fluence of the feelings thus excited, a hasty expression has escaped me in the ardour of composition, I hope it will not be imputed to personal ani- mosity. I have always lived on amicable terms with this distinguished chemist, and trust to continue so to do. Perhaps in commenting on his opinions, I may have unconsciously caught the plain manner of his criti- cisms. My sole object, however, was the establishment of truth. The refutation of error was undertaken, only when its existence seemed in- compatible with that object. On our other valuable systematic works, I have made no critique, because Dr. Thomson's is the most comprehen- sive, professedly taken from original memoirs, and of highest authority. I have long meditated to publish a methodical treatise on chemistry, in which both its study and practice would be greatly simplified, and its applications to the phenomena of nature, medicine, and the arts, faithfully INTRODUCTION. XI detailed. In my memoir on sulphuric acid, inserted in the Journal of Science and the Arts, for October 1817, is the following passage: " I was led to examine the subject very minutely, in preparing for publication a general system of chemical instructions, to enable apothecaries, manufac- turing chemists, and dealers, to practise analysis with accuracy and des- patch, as far as their respective arts and callings require. I hope that this work will soon appear. Meanwhile, the following details will afford a specimen of the experimental researches executed with this view." The three years and a half which have elapsed since the above paper was com- posed, would have enabled me to fulfil the promise, but for various un- foreseen interruptions to my labours. If the public, after this larger specimen of my chemical studies, shall deem me qualified for the task, I may promise its completion within a year from this date. The work will be comprised in four octavo volumes, and will con- tain the results of numerous investigations into the various objects of prac- tical chemistry, joined to a systematic view of its principles. By several simple instruments, tables, and rules of calculation, chemical analysis, the highest and most intricate part of the science, may, I apprehend, be, in many cases, brought within the reach of the busy manufacturer; while, by the same means, such accuracy and despatch may be insured, as to render the analysis of saline mixtures, complex minerals, and mineral waters, the work of an hour or two; the proportions of the constituents being deter* mined to one part in the thousand. In prosecution of this plan of simplifying analysis, I contrived, about five years ago, an alkalimeter and acidimeter. Being then connected by a biennial engagement with the Belfast Academical Institution, I was oc- casionally called upon to examine the barillas and potashes so extensively employed in the linen manufacture, the staple trade of Ireland. I was sorry to observe, that while these materials of bleaching differed exces- sively in their qualities, no means was possessed by those who imported or who used them, of ascertaining their value; and that a generous people, with whom every stranger becomes a friend, frequently paid an exorbitant price for adulterated articles. The method which I devised for analyzing alkaline and acid matter, was laid before the Honourable Linen Board in Dublin, and by them referred to a competent chemical tribunal. The most decisive testimonies of its accuracy and importance were given by that tribunal; and it was finally submitted, by desire of the Board, to a public meeting of bleachers assembled at Belfast. Unexceptionable docu- ments of its practicability and value were thence returned to Dublin, accompanied by an official request, that measures might immediately be taken to introduce the method into general use. Descroizilles had seve- ral years before described, in the Annales de Chimie, an alkalimeter, but so clumsv.operose, and indirect, as to be not at all adapted to the purposes of the'linen manufacture. My instrument, indeed, was founded, as well as his, on the old principle of neutralizing alkali with acid; but in every other respect it was different. . After spending about two months on this project, and no answer being returned either to the public request of the bleachers, or to my own me- morial I set off on an intended tour to France, and have never since re- amed the negotiation.* The terms on which I had offered the instru- ment were merely honorary; for the sum proposed, would not have re- paid the expense of my journey and attendance. However important there- * The Rieht Hon John Foster, who took the chief direction of the Board, showed me Pve J posS attention; but from the absence of many of its members m England, a quorum could not be assembled at the time. xu INTRODUCTION. fore the adoption of that instrument was to Ireland, it was of no pecuniary importance whatever to me. Of the two hundred and ten thousand pounds expended that year (1815-1816) on imported alkalies, a very large pro- portion might have been saved by the application of my alkalimeter; and what is perhaps of more consequence, the alkaline leys used in bleaching, would, by its means, have been rendered of a regulated strength, suited to the stage of the process, and fabric of the cloth. What would we say of a company, who imported spirituous liquors to an enormous amount, and paid for them all as proof, though they were diluted with fifty per cent, ot water? Now, though this neglect of the hydrometer would have a happy moral influence on the consumer, it would be vastly absurd in the dealer. No such apology can be offered for neglecting the alkalimeter. The following is an extract from the Belfast News-Letter of July 9, 1816:— •' I now submit the following document to public inspection, and hum- bly ask, whether any such experiment has been ever made publicly be- fore; or whether there is described in any publication prior to my late exhibition in Dublin, and in the Linen Hall of Belfast, an instrument by which it can be performed? " This day, one of the porters of the Linen Hall, Belfast, was called into the Library-room, at the request of Dr. Ure, who, being quite un- known to Dr. Ure, and never having seen any experiments made with acids and alkalies, he took the instrument at our desire, which, being filled with coloured acid, by pouring it slowly on adulterated alkali, which we had previously prepared, he ascertained exactly the per centage of genuine alkali in the mixture.—Belfast, 25th June, 1816. (Signed) John S. Ferguson, Chairman. James M'Donnel, M. D. John M. Stoupe, S. Thomson, M. D. " The above experiment did not occupy the porter above five minutes. I believe it is a new document, though, after the egg has been placed on end, others will set to work to do the same. " Though the instrument was entirely the result of my own experiments and calculations, I never claimed a greater share in its invention, than I hope its peculiarity merits. The following excerpt from a letter addressed to the Right Hon. John Foster,prior to any public discussion on its me- rits, will satisfy the public on this head. " Dublin, June 12, 1816. " Sir,—In the letter which I had yesterday the honour of addressing you, I omitted some scientific details, which I now beg leave to submit to your consideration. That the quantity of alkali, present in any portion of potash or barilla, is directly proportional to the quantity of acid requisite to produce saturation, is a fact which has been known for upwards of a century to every chemist, and forms a fundamental law of his science. In establishing my instrument on this law, the principle of it may be said not to be new." &c. " The practica application of the established laws of nature, or "f the general deductions of science, to the uses of life, is, perhaps, the most beneficial and meritorious employment of the philosophic mind. The novelty which I lay claim to in my contrivance, is this, that it enables a person versant neither in chemical researches nor in arithmetical computa- tion, to determine by inspection of a scale, as simple as that of a thermo- meter, the purity or value to one part in the hundred, of the alkalies, oil of vitriol, and oxymuriate of lime, so extensively, and often so injudiciously employed by the linen-bleacher." INTRODUCTION. xiii In my journey through England to France, I submitted my Essay on Alkalimetry, &c. to Dr. Henry, in the confidence of friendship, and under the injunction of secrecy. From the unreserved communication of ideas, however, which subsists between this chemist and his townsman Mr. Dal- ton, he soon gave him a perusal of the Essay. In the then existing edi- tion of Dr. Henry's Elements, Descroizilles' plan for testing alkalies was alone given; in the edition published since, he has inserted four supple- mentary pages entitled, " Improved Alkalimeter and Acidimeter." This instrument is essentially mine, very slightly disguised. He concludes by saying, " No chemical operation can be more simple, or more easily managed, than the measurement of the strength of alkalies by acid liquors, and of acids by alkaline ones, in the way which has been described." This is exactly Columbus's egg, or Roger Bacon's gunpowder; et sic fades tonitru, si scias artificium. By comparing his new way taken from my Essay, with the methods which he formerly gave, the world will see whence the simplification originated. I offered to give him an abridged account of my plan, for insertion in his Elements, after my negotiation about the alkalimeter was finished. Without consulting me on the sub- ject, he publishes to the whole world, what he conceives to be the essence of my improvement.* Two motives have hitherto withheld me from laying the instrument before the public. First, a desire to render it as complete as possible; and secondly, an expectation, that the Honourable Board, who superin- tend the linen manufactures of Ireland with extensive powers, might wish that an instrument originally presented to them, and which is capable of giving light and precision to all the processes of bleaching, should appear under their auspices. As it now exists, the instrument is greatly superior to that described by Dr. Henry. For the commercial alkalies and acids, I use only two test liquids and one scale; and these are such, that a man unacquainted with science, may prepare the first, and verify the second. The instrument is at once an alkalimeter, an acidimeter, a complete lactometer, a nitrometer for estimating the value of nitre, an indigometer for ascertaining the dyeing quality of indigo, and a blanchimeter for measuring the bleaching power of oxymuriate (chloride) of lime and potash. With it, a busy manufac- turer or illiterate workman may solve all these useful problems in a few minutes ; and many others, such as the composition of alloys of silver, of copper, tin, lead, &c. the purity of white lead, and other pigments. It is, moreover, a convenient hydrometer, comprehending in its range, light and heavy liquids, from ether to oil of vitriol; and is particularly adapted to take the specific gravity of soils. It may be said, that the solution of the above problems may be accom- plished by any skilful chemist. But surely, in a manufacturing nation, the person who brings the science of Klaproth, Sir H. Davy, Dr. Wollas- ton, and M. Gay-Lussac, into the workshop of the manufacturer, is not a useless member of the community. The result of numerous researches made with that view, has shown me the possibility of rendering analysis in general, a much easier, quicker, and more certain operation, than it seems hitherto to have been, in ordi- * It uould seem that Dr. Ure has since been satisfied that Dr. Henry intended him no in- justice, as this gentleman has explained to him, that in a passage of his Elements, "page 512, vol ii. he intended to give Dr. Ure the credit of inventing an instrument on the principle of directly, and v, ithout calculation, indicating the per centage of alkali in any specimen, and that he pretended to nothing more than a modification of Dr. Ure's method" See Letter of Dr Ure, in the Journal of Science, No. 22, p. 401, July, 1820.—American Editor. xiv INTRODUCTION. nary hands. To these practical applications of science, my attention has been particularly directed, in conducting that department of Anderson's Institution, destined to diffuse among the manufacturers and mechanics of Glasgow and its neighbourhood, a knowledge of the scientific principles of their respective arts. In a public address, delivered to the members of this class, on a gratifying occasion in April 1816, 1 remarked, "That Europe affords no similar example of a class, composed of several hun- dred artisans, mechanicians, and engineers, weekly assembled,* with exemplary decorum, to study the scientific principles of the useful arts; to have the great practical truths of philosophy, first revealed by Newton and Lavoisier, made level to their various capacities by familiar descrip- tions, models, and experiments. The original design of the mechanic's class was limited, as you know, to the exhibition and explanation of me- chanical models. But a subject deserving particular attention, was that of the chemical arts, in which many of you are engaged; a knowledge of the scientific principles of which, as taught in the Colleges, circumstances permit few of you to acquire. You have listened to my chemical lessons with the keenest interest; and have applied your studies to conspicuous advantage. Need I adduce, among other things, the unrivalled beauty of the Adrianople madder dye, as executed on the most extensive scale,f by individuals who have been my faithful pupils, for nearly the whole course of my public career. By a steady prosecution of this expanded system of instruction, your class has progressively increased in number and impor- tance; so that, within the last twelve years, I have delivered twenty-one courses of lectures to upwards of six thousand students in this department alone?' It is much to be desired, that similar courses of prelections were insti- tuted in all the large towns of the British empire. The deportment of the mechanic's class, amounting occasionally to five hundred members, might serve as a pattern to more dignified assemblies. I have never seen any University class so silent and attentive. Though the evening on which the workmen meet, be that in which they receive their wages, and when, therefore, they might be expected to indulge themselves in drinking, yet no instance of intemperance has ever occurred to annoy the audience. And even during the alarms of insurrection with which our city was dis- turbed last winter, the artisans continued with unaltered docility and punctuality to frequent the lectures. Of the actual result of such a system of instruction, a stranger is pro- bably the best judge. I shall therefore quote a few sentences from the Scientific Tour through Great Britain, recently published by an accom- plished member of the Institute of France, M. Ch. Dupin. " It is easier to visit the establishments and manufactures of Glasgow, than those of any other city in the British empire. The liberal spirit of the inhabitants, is, in this respect, carried as far as possible, among a manufacturing people, who must naturally dread, and seek to prevent, not only the loss of their preponderance, but their foreign rivalry. " The rich inhabitants of Glasgow have founded the Andersonian In- stitution, where are taught, in the evenings of winter, the elements of mechanics, physics, and chemistry, as applied to the arts. These courses are especially designed for young artisans, who have to pay only about five shillings in the season (course of three months.) * Every Saturday evening at eight o'clock. t Particularly at the establishment of H. Monteith, Esq. M. P. where the sciences of me- chanics and chemistry co-operate, in a degree of precision au 1 elegance, which 1 believe to be unparalleled in the world. INTRODUCTION. XV «This trifling fee is exacted, in order that the class may include only students actuated by the love of instruction, and willing to make some small sacrifice for it. « The Andersonian Institution has produced astonishing effects. It is an admirable thing now, to see in many Glasgow manufactories, simple workmen, who understand, and explain when necessary, the principles of their operations, and the theoretical means of arriving at the most perfect possible practical results." The philanthropist may perhaps wish to know, at what expense of patronage this useful department is carried on. I shall satisfy this desire, by the following statement from the above mentioned public address. " The original design of the mechanic's class was limited, as you know, to the exhibition and explanation of mechanical models. But the pro- gress of machinery in your workshops, has now so far outrun the state of the models left by the venerable Founder of the Institution, as to render their display, with a very few exceptions, useless, except as historical documents of the rudeness of the times in which they were framed. I have, accordingly, for ten years, employed chiefly modern apparatus, pro- cured at my own expense, and by rendering the instructions miscella- neous, have adapted them better to the diversity of your pursuits. Be- sides teaching the usual elements of mechanics and their general combi- nations, I have made it my business to explain the properties of the at- mosphere, on which the action of pumps depends ; the nature of hydro- static equilibrium, and hydraulic impulse, as subservient to the construc- tion of Bramah's press, and water-wheels ; the beautiful laws of heat so admirably applied to perfect the steam-engine, by our illustrious fellow- citizen; nor have I declined, in compliance with your wishes, to lay be- fore you from time to time, such views of the constitution of nature, in electricity, optics, and astronomy, as might awaken the powers of your minds, and reward your attention to the less attractive branches of science. But a subject, deserving particular attention, was that of the chemical arts," fee. (as above quoted.) The whole experimental means at present employed in carrying on this Polytechnic School, have been derived from the exertions and sacri- fices of the Professor, and the generous aid and contributions of his pupils. They have supplied him with much valuable practical information on their respective arts, with many curious models, and subsidiary instruments of illustration; while he, in return, has expended large sums of money, in framing popular representations of the scientific discoveries and im- provements, in which the present age is so prolific. To the mechanic's cla-os a library is attached, consisting of the best treatises on the sciences and arts, with some valuable works on general literature, such as history, geography, travels, &c. of which they have the exclusive management and perusal. The foundation of it was laid in the year 1807, by a voluntary subscription, amounting, I think, to about 60/; and several books which I collected from my friends, with about lOo'volumcs from my own library. Many members of the class have contributed from time to time; and it has recently acquired consider- able extension, from the receipts of lectures which I delivered for its ^Besides the acknowledged and palpable effect of such a plan of tuition, on the improvement of the useful arts, it has another operation, more. silent, but neither less certain, nor less important, namely, its influence in meliorating the moral condition of the operative order of society. A taste for science elevates the character, and creates a disrelish, and disgust, at the debasement of intoxication. Philosophy dressed in an at- xvi INTRODUCTION. tractive garb, leads away from the temptations of the tavern. Thus, too, the transition from the drudgery or turmoil of the week, to the tranquillity of Sunday, is secured by the preceding evening's occupation. The man indeed whose Saturday night is spent in rioting or drunkenness, will make a bad Christian on the Sabbath, an indifferent workman on Monday, and an un- happy husband and father through the week. To promote this moral ope- ration of science, I have always taken occasion to point out the beneficent design which the whole mechanism of nature displays. If the contemplation of the miseries and crimes which stain the page of history, have led some speculators to cavil at the government of a benevolent Creator; the con- templation of the harmonious laws, and benignant adjustments which the science of nature discloses, must satisfy every candid student, of the pre- sence and providence of a wise and beneficent Lawgiver. The first and most exalted function of physics, then, is to dissipate the gloomy and be- wildering mists of metaphysics. A second function of supreme importance, is to point out the mysterious and impassable barriers, to which the clearest paths of physical demonstration ultimately lead the human mind; and thence to inculcate docility to the analogous mysteries of Revelation. I hope that the preceding statements and remarks, will remove every possible objection to the establishment of schools for teaching the elements of science to artisans, and that they will induce other cities to follow the example so happily set by Glasgow, of popularizing philosophy. Having detailed the circumstances under which I have struggled to re- generate this Dictionary, I hope the candid Public will make allowance for occasional faults of expression and arrangement. All the articles to which the asterisks are affixed, were, with trifling exceptions, printed from my manuscript, written expressly for this work, within the last five months. From the style of its typography, and the manner of stating proportions of constituents, each page of this volume is fully equivalent to two pages of our octavo systems of chemistry, and required rather more than four pages of closely written manuscript. There is however a great advantage to the reader of a scientific work, (which must necessarily be compiled from many quarters), in an author being his own amanuensis. Every fact and detail will thus be exposed to a much severer scrutiny, than if excerpts were made by the scissars, or the pen of an assistant. Hence many of the pas- sages which may seem, at first sight, to be merely copied from other works, will be found to have corrections and remarks either interwoven with the details, or enclosed in parentheses. Thus, for example, in transcribing Mr. Hatchett's admirable analyses of the magnetic iron ores, computation will be found within parentheses, deduced from Dr.Wollaston's equivalent scale. Numerous insertions and corrections are made in the reprinted parts to which no asterisk is affixed. M. Vauquelin's general mode of analyzing minerals is now introduced, Professor Gahn's instructions relative to the blow-pipe, a long passage under Arsenious Acid, and many other unnoted insertions, such as Chlorophyle, Cholesterine, Comptonite. The dissertations on Caloric, Combustion, Dew, Distillation, Electricity, Gan, Light,Thermometer, Isfc. which form a large proportion of the volume, are beyond the letter and spirit of my engagement with the publisher. I receive no remuneration for them, not even at the most moderate rate of literary labour. They are therefore voluntary contributions to the che- mical student, and have been substituted for what I deemed frivolous and uninteresting details on some unimportant dye-stuffs, and articles from old dispensatories, such as althea, chamomile, Sec. For whatever is valuable in the mineralogical department, the reader is ultimately indebted to Professor Jameson. The chief part of the descrip- tions of mineral species, is abridged from the third edition of his exccl- ^*. INTRODUCTION. xvii lent System. In compiling the early part of the Dictionary, I collated several mineralogical works, both British and foreign; but I soon found that this had been done to my hand by Professor Jameson, with much greater ability than I could pretend to rival; and that he had enriched the whole with many important remarks of his own. Much of the purely chemical part is drawn from that treasure of facts, Sir H. Davy's elements. When the subject permitted me, I was happy to repose on his never-failing precision, like the wave-tossed mariner in a secure haven. With regard to the language used by him, Dr. Wollaston, M. Gay-Lussac, and some other original investigators, I have used no further freedom than was necessary to accommodate it to the context. Their expressions can very seldom be changed with impunity. There are other chemical writers again, whose thoughts acquire intellectual spring only by great condensation. If the curious reader compare the article distillation, in this Dictionary, with that in the Supplement to the Encyclopaedia Britannica, he will understand my meaning. In the discussion on the Atomic Theory of Chemistry, under tho article Equivalents, reference is made to a table of the relative weights of the atoms, or of the numbers representing the prime equivalents of chemical bodies. On subsequent consideration, it was perceived, that such a list would be merely a repetition of numbers already given in their alphabetical places, and therefore most readily found; whilst it would have caused the omission of requisite tables of a different kind; the space allotted to the volume being entirely occupied. In my paper on Sulphuric Acid, published in the 7th number of the Journal of Science, I assigned the numbers 4, 5, 6, as respectively denot- ing the prime equivalents of soda, sulphuric acid, and potash. Minute researches, subsequently made, on the nitrates, (Journal of Science, No. xii.) led me to regard 3.96, and 5.96, as better approximations for soda and potash. Throughout this Dictionary, the numbers 3.95 and 5.95 have been used. It is, however, very possible that the number 6, origi- nally assigned by Sir H. Davy for potash, may be correct; as also 4 for soda. Dr. Thomson has just published a paper in his Annals, (November 1820) " On the true weight of the atoms of barytes, potash, soda," &c. In his experiments to determine these fundamental quantities, he has adopted Richter's original plan of reciprocal saturation of two neutro-salinc compounds. But the Doctor seems to have forgotten, that for want of an initial experiment, none of his ratios is referable to the oxygen scale, or to any atomic radix. He assumes the atom of barytes to be 9.75, and that of potash to be 6; that of sulphuric acid being 5. He then proceeds to show that the atomic weight 13.25 of dry muriate of barytes (chloride of barium), and 11, that of sulphate of potash, produce perfect reciprocal decomposition, when their aqueous solutions are mixed. But had he called the atom of barytes 9.7, with Sir H. Davy and Dr. Wollaston, (tho chloride would become 13.2), and the atom of sulphate of potash 10.96, as found in my experiments on nitric acid, he would have obtained, by mixing the two, in these atomic proportions, as perfect an experimental result as with his own numbers: For 13.25 : 11:: 13.2 : 10.96. His atomic chain wants, in fact, its first link; it floats loosely; and may therefore be accommodated to a variety of different numbers, provided the arithmetical proportions be observed. He ought to have commenced with a clear demonstration, that the atom of barytes is 9.75, and the atom of potash 6, referred to oxygen as unity. The idea, however, suggested by Dr. Prout, that the numbers repre senting the weights of the different atoms, are multiples by a whole nuuv c xviii INTRODUCTION. ber of that denoting hydrogen, is very ingenious, and most probably just. And therefore, as well as for experimental reasons, which I cannot here detail, I would willingly adopt 9.75 for barytes, 4 for soda, 6 for potash, and 4.5 for chlorine. The atomic numbers given in this volume, for the various simple and compound objects of chemistry, are directly deduced from a mean of the most exact experiments; and I believe them to be more worthy of confidence, than those deducible from theoretic considerations. Thus, Dr. Thomson, from these, assigns 3.625 for the atom of lime; from experiment, it is certainly not so high. I have stated it from my own, at 3.56. Dr. Marcet's analysis of the carbonate would make it about 3.5. In the article Equivalents (Chemical), as well as under the individual substances, the reader will find the primitive combining ratios, or atoms as they are hypothetically called, fully, and I trust fairly, investigated from experiment. This is the sheet-anchor of scientific research, which we must never part with, or we shall drift into interminable intricacies. We should continually bear in mind this aphorism of the master of che- mical Logic: " The substitution of analogy for fact is the bane of chemi- cal philosophy; the legitimate use of analogy is to connect facts together, and to guide to new experiments."—Sir H. Davy, Journal of Science, vol. i. These analogical substitutions appear to be the predominant defect of Dr. Thomson's otherwise valuable compilation. The typographical economy of this work precluded me from multiply- ing references at the bottom of the page; a plan which authors readily adopt to show the extent of their reading. The authorities for facts will be generally found interwoven with the text. The desire to condense much practical information, in a small compass, made me abridge many historical details. The progressive steps of an investigation, however, occasionally required to be traced, in order to make the existing state of our knowledge more intelligible. Whenever this seemed necessary, I have offered such a retrospect, and have endeavoured to take truth and justice for my sole guides. As the only recompense which the man of science usually receives or can expect, is the credit of his discoveries, neither prejudice nor passion should be suffered to influence the compiler, in awarding honour to whom honour is due. One of the most elegant investigations which the Science of Chemistry affords, is contained in M. Gay-Lussac's short letter to M. Clement, pub- lished in the Annales de Chimie et de Physique for July 1815, and reprint- ed in 1816, by M. Thenard in his valuable Traite de Chimie, iv. p. 238. It is there demonstrated that her most judiciously discarded the appel- ation oxymuriatic acid, and introduced in its place the name chlorine, which merely indicates an obvious and permanent char- acter of the substance, its greenish yellow colour. The more recent investigations of chemists on fluoric, hydriodic, and hy- drocyanic acids have brought powerful analogies in support of the chloridic theory, by showing that hydrogen alone can con- vert certain undecompounded bases into acids well characterized, without the aid of oxygen. Dr. Murray indeed has en- deavoured to revive and new-model the early opinion of Sir II. Davy, concerning the necessity of the presence of water, or its elements, to the constitution of acids. He conceives that many acids are ternary compounds of a radical with oxygen and hydrogen; but that the two latter ingre- dients do not necessarily exist in them in the state of water. Oil of vitriol, for in- stance, in this view, instead of consisting of 81. 5 real acid, and 18. 5 water in 100 parts may be regarded as a compound of 32.6 sulphur + 65.2 oxygen -t- 2.2 hydro- Een. When it is saturated with an alka- ne base, and exposed to heat, the hvdro- gen unites to its equivalent quantity of ox- ygen, to form water, which evaporates, and the remaining oxygen and the sulphur combine with the base. But when the acid is made to act on a metal, the oxygen part- ly unites to it, and hydrogen alone es- capes. " Nitric acid, in its highest state of con- centration, is not a definite compound of real acid, with about a fourth of its weight of water, but a tenary compound of ni- trogen, oxygen, and hydrogen. Phospho- ric acid is a triple compound of phospho- rus, oxygen, and hydrogen; and phospho- rous acid is the proper binary compound of phosphorus and oxygen. The oxalic, tar- taric, and other vegetable acids, are ad- mitted to be ternary compounds of carbon, oxygen, and hydrogen ; and are therefore in strict conformity to the doctrine now illustrated. " A relation of the elements of bodies to acidity is thus discovered different from what has hitherto been proposed. When a series of compounds exists, which have certain common characteristic properties and when these compounds all contain a common element, we conclude, with jus- tice, that these properties are derived more peculiarly from the action of this element. On this ground Lavoisier infer- red, by an ample induction, that oxygen is a principle of acidity. Rerthollet brought into view the conclusion, that it is not ex- clusively so, from the examples of prussic acid and sulphuretted hydrogen. In the latter, acidity appeared to be produced by the action of hydrogen. The discovery by Gay-Lussac, of the compound radical cyanogen, and its conversion into prussic acid by the addition of lndrogen, confirm- ed this conclusion; and the discovery of the relations of iodine still further established it. And now, if the preceding views are just, the svstem must be still further modi- fied. While each of these conclusions are just to a certain extent, each of them requires to be limited in some of the ca- ses to which they are applied; and while acidity is sometimes exclusively connected with oxygen, sometimes with hydrogen, the principle must also be admitted, that it is more frequently the result of their combined operation. " There appears even sufficient reason to infer, that, from the united action of these elements, a higher degree of acidity is acquired than from the action of either alone. Sulphur affords a striking exam- ple of this. With hydrogen it forms a weak acid. With oxygen it also forms an acid, which, though of superior energy, still does not display much power. With hydrogen and oxygen it seems to receive the acidifying influence of both, and its acidity is proportionally exalted. " Nitrogen, with hydrogen, forms a com- pound altogether destitute of acidity, and possessed even of qualities the reverse.— With oxygen, in two definitive propor- tions, it forms oxides; and it is doubtful if, in any proportion, it can establish with oxygen an insulated acid. But with oxy- gen and hydrogen in union it forms nitric acid, a compound more permanent, and of energetic action." It is needless to give at more detail Dr. Murray's speculations, which, supposing them plausible in a theoretical point of view, seem barren in practice; at least their practical tendency cannot be perceiv- ed by the editor of this work. It is suffi- ciently singular, that, in an attempt to avoid the mysterious and violent transfor- mations, which, on the chloridic theory, a little moisture operates on common salt, instantly changing it from chlorine and so- dium, into muriatic acid and soda, Dr. Murray should have actually multiplied, with one hand, the very difficulties which he had laboured, with the other, to re- move. He thinks it doubtful if nitrogen and oxygen can alone form an insulated acid.— Hydrogen he conceives essential to its en- ergetic action. What, we may ask then, exists in dry nitre, which contains no hy- ACI ACI drogen ?f Is it nitric acid, or merely two of its elements, in want of a little water to furnish the requisite hydrogen ? The same questions may be asked relative to the sul- phate of potash. Since he conceives hy- drogen necessary to communicate full force to sulphuric and nitric acids, the mo- ment they lose their water they should lose their saturating power, and become incapable of retaining caustic potash in a neutral state. Out of this dilemma he may indeed try to escape, by saying, that moisture or hydrogen is equally essential to alkaline strength, and that therefore the same desiccation or de-hydrogenation which impairs the acid power, impairs also that of its alkaline antagonist. The result must evidently be, that, in a saline hydrate or solution, we have the reciprocal attrac- tions of a strong acid and alkali, while, in a dry salt, the attractive forces are those of relatively feeble bodies. On this hypo- thesis, the difference ought to be great between dry and moistened sulphate of potash. Carbonic acid he admits to be destitute of hydrogen ; yet its saturating power is very conspicuous in neutralizing dry lime. Now, oxalic acid, by the last analysis of Berzelius, contains no hydro- gen. It differs from the carbonic only in the proportion of its two constituents. And oxalic acid is appealed to by Dr. Murray as a proof of the superior acidity bestowed by hydrogen. On what grounds he decides carbonic to be a feebler acid than oxalic, it if difficult to see. By Berthollet's test of acidity, the former is more energetic than the latter in the proportion of J00 to about 58 ; for these numbers are inversely as the quan- tity of each requisite to saturate a given base. If he be inclined to reject this rule, and appeal to the decomposition of the carbonates by oxalic acid, as a criterion of relative acid power, let us adduce his own commentary on the statical affinities of Berthollet, where he ascribes such chan- ges not to a superior attraction in the de- composing substance, but to the elastic tendency of that which is evolved. Am- monia separates magnesia fi omits muri- atic solution at common temperatures ; at the boiling heat of water, magnesia separ- ates ammonia. Carbonate of ammonia, at temperatures under 230°, precipitates car- bonate of lime from the muriate ; at. high- er temperatures the inverse decomposi- tion takes place with the same ingredients. If the oxalic be a more energetic acid than f The acid in dry nitre contains water, and of course hydrogen. Liquid nitric acid is obtained from dry nitre by strong sul- phuric acid, and holds, according to the a- ble m this work, under the head of nitric acid, more than a fifth of water. the carbonic, or rank higher in the scale of acidity, then, on adding to a given weight of liquid muriate of lime, a mix- ture of oxalate and carbonate of ammonia, each in equivalent quantity to the calca- reous salt, oxalate of lime ought alone to be separated. It will be found, on the contrary, by the test of acetic acid, that a;; much carbonate of lime will precipitate as is sufficient to unsettle these speculations. Finally, dry nitre, and dry sulphate of potash, are placed, by this supposition, in as mysterious a predicament as dry muri- ate of soda in the chloridic theory. De- prived of hydrogen, their acid and alkali are enfeebled or totally changed. W ith a little water both instantly recruit the,/ . powers. In a word, the solid sulphuric acid of Nordhausen, and the dry potash o'. potassium, are alone sufficient to subvert this whole hypothesis of hydrogenation. We shall introduce, under the head of alkali, some analogous speculations by Dr. Murray on the influence of the elements of water on that class of bodies. Edin. PMl. Trans, vol. viii. part 2f birch-wood. In about a fortnight it is found to be clarified, and is then fit for the market. It must be kept in close casks. The manufacturers at Orleans prefer wine of a y ear old for making vinegar. But if by age the wine has lost its extractive matter, it does not readily undergo the acetous fer- mentation. In this case, acetitication, as the Trench term the process, may be deter- mined by adding slips of vines, bunches of grapes or green woods. It has been asserted that alcohol, added to fermentable liquor, docs not increase the product of vinegar.But this is a mistake. Stahl observed long ago, that if we moisten roses, or lilies with al- cohol, and place them in vessels in which they are stirred from time to time, vinegar will be formed. He also informs us, if after abstracting the citric acid from lemon juice by crabs' eyes (carbonate of lime), we add a little "alcohol to the supernatent li- quid, and place the mixture in a proper temperature, vinegar will be formed. Chaptal savs, that two pounds of weak spirits, sp. gr, U.985, mixed with 300 grains of beer \ east, and a little starch water, pro- duced extremely strong vinegar. The acid was developed on the 5th day. The same quantity of starch and yeast, without the spirit, fermented more slowly, and yielded a weaker vinegar. A slight motion is found to favour the formation of vinegar, and to endanger its decomposition after it is made. Chaptal ascribes to agitation the operation of thunder; though it is well known, that when the atmosphere is highly electrified, beer is apt to become suddenly sour, with- out the concussion of a thunder-storm. In cellars exposed to the vibrations occasioned by the rattling of carriages,vinegar does not keep well. The lees, which had been de- posited by means of isinglass and repose, are thus jumbled into the liquor, and make the fermentation recommence. Almost all the vinegar of the north of France being prepared at Orleans, the manufactory of that place has acquired such celebrity, as to render their process wor- thy of a separate consideration. The Orleans' casks contain nearly 400 pints of wine. Those which have been al- ready used are preferred. They are placed in three rows, one over another, and in the top have an aperture of two inches diam- eter, kept always open. The wine for ace- tification is kept in adjoining casks.contain- ing beech shavings, to which the lees ad- here. The wine thus clarified is drawn off to make vinegar. One hundred pints of good vinegar, boiling hot, are first poured into each cask, and left there for eight days. Ten pints of wine are mixed in, every eight days, till the vessels are full. The vinegar is allowed to remain in this state fifteen days, before it is exposed to sale. The vsed casks, called movers, are never emptied more than half,but are successively filled again,to acetifynew portions of wine. In order to judge if the mother works, the vinegar makers plunge a spatula into the liquid; and according to the quantity of froth which the spatula shows, they add more or less wine. In summer, the atmos- pheric heat is sufficient. In winter, stoves heated to about 75° Fahr. maintain the requisite temperature in the manufactory. In some country districts, the people keep in a place, where the temperature is mild and equable, a -vinegar cask, into ACI ACI which they pour such wine as they wish to acetify; and it is always preserved full, by replacing the vinegar drawn off", by new wine. To establish this household manu- facture, it is only necessary to buy at first a small cask of good vinegar. At Gand a vinegar from beer is made, in which the following proportions of grain are found to be most advantageous : — 1880 Paris lbs. malted barley. 700 wheat. 500 buckwheat. These grains are ground, mixed, and boil- ed, along with twenty-seven casks-full of river water, for three hours. Eighteen casks of good beer for vinegar are obtain- ed. By a subsequent decoction, more fer- mentable liquid is extracted, which is mix- ed with the former. The whole brewing yields 3000 English quarts. In this country, vinegar is usually made from malt. By mashing with hot water, 100 gallons of wort are extracted in less than two hours from 1 boll of malt. When the liquor has fallen to the temperature of 75° Fahr. 4 gallons of the barm of beer are added. After thirty-six hours it is racked offinto casks, which are laid on their sides, and exposed, with their bung-holes loose- ly covered, to the influence of the sun in summer; but in winter they are arranged in a stove-room. In three months this vinegar is ready for the manufacture of su- gar of lead. To make vinegar for domes- tic use, however, the process is somewhat different. The above liquor is racked off into casks placed upright, having a false cover pierced with holes fixed at about a foot from their bottom. On this a consid- erable quantity of rape, or the refuse from the makers of British wine, or otherwise a quantity of low priced raisins, is laid. The liquor is turned into another barrel every twenty-four hours, in which time it has begun to grow warm. Sometimes, indeed, the vinegar is fully fermented, as above, without the rape, which is added towards the end, to communicate flavour. Two large casks are in this case worked togeth- er, as is described long ago by Boerhaave, as follows. " Take two large wooden vats, or hogs- heads, and in each of these place a wooden grate or hurdle, at the distance of a foot from the bottom. Set the vessel upright, and on the grate place a moderately.close layer of green twigs, or fresh cuttings of the vine. Then fill up the vessel with the footstalks of grapes, commonly called the rape, to the top of the vessel, which must be left quite open. " Having thus prepared the two vessels, pour into them the wine to be converted into vinegar, so as to fill one of them quite up, and the other but half full. Leave them thus for twentv-four hours, and then Vor.. i. [2 3 fill up the half filled vessel with liquor from that which is quite full, and which will now in its turn only be left half full. Four-and-twenty hours afterwards repeat the same operation, and thus go on, keep- ing the vessels alternately full and haif full during twenty-four hours, till the vinegar be made. On the second or third day there will arise in the half filled vessel, a fermen- tative motion, accompanied with a sensible heat, which will gradually increase from day to day. On the contrary, the^erment- ing motion is almost imperceptible in the full vessel; and as the two vessels are al- ternately full and half full, the fermenta- tion is bv this means in some measure in- terrupted, and is only renewed every other day in each vessel. " When this motion appears to have en- tirely ceased, even in the half filled vessel, it is a sign that the fermentation is finished; and therefore the vinegar is then to be put into casks close stopped, and kept in a cool place. " A greater or less degree of warmth accelerates or checks this, as well as the spirituous fermentation. In France it is finished in about fifteen days, during the summer; but if the heat of the air be very great, and exceed the twenty-fifth degree of Reaumur's thermometer, (88±° Fahr.) the half filled vessel must be filled up eve- ry twelve hours; because, if the fermen- tation be not so checked in that time, it will become violent, and the hquor will be so heated, that many of the spirituous-parts, on which the strength of the vinegar de- pends, will be dissipated, so that nothing will remain after the fermentation but a vapid liquor, sour indeed, but effete. The better to prevent the dissipation of the spirituous parts, it is a proper and usual precaution to close the mouth of the half filled vessel, in which the liquor ferments, with a cover made of oak wood. As to the full vessel, it is always left open, that the air may act freely on the liquor it con- tains ; for it is not liable to the same in- conveniences, because it ferments but very slowly." Good vinegar may be made from a weak sirup, consisting of 18 oz. of sugar to eve- ry gallon of water. The yeast and rape are to be here used, as above described. Whenever the vinegar (from the taste and flavour) is considered to be complete, it ought to be decanted into tight barrels or bottles, and well secured from access of. air. A momentary ebullition before it is bottled is found favourable to its preserva- tion. In a large manufactory of malt vine- gar, a considerable revenue is derived from the sale of yeast to the bakers. Vinegar obtained by the preceding methods has more or less of a brown colour, and a pe- culiar but rather grateful smell. By iis» ACI ACI ligation in glass vessels the colouring mat- ter, which resides in a mucilage, is sepa- rated, but the fragrant odour is generally replaced by an empyreumatic one. The best French wine vinegars, and also some from malt, contain a little alcohol, which comes over early with the watery part, and renders the first product of distillation scarcely denser, sometimes even less dense than water. It is accordingly rejected.— Towards the end of the distillation the em- pyreuma increases. Hence only the inter- mediate portions are retained as distilled vinegar. Its specific gravity varies from 1.005 to 1.015, while that of common vin- egar of equal strength varies from 1.010 to 1.025. A crude vinegar has been long prepared for the calico printers, by subjecting wood in iron retorts to a strong red heat. The following arrangement of apparatus has been found to answer well. A series of cast-iron cylinders, about 4 feet diameter, and 6 feet long, are built horizontally in brick work, so that the flame of one fur- nace may play round about two cylinders. Both ends project a little from the brick work. One of them has a disc of cast-iron well fitted and firmly bolted to it, from the centre of which disc an iron tube about 6 inches diameter proceeds, and enters at a right angle the main tube of refrigeration. The diameter of this tube may be from 9 to 14 inches, according to the number of cylinders. The other end of the cylinder is called the mouth of the retort. This is closed by a disc of iron, smeared round its edge with clay-lute, and secured in its place by wedges. The charge of wood for such a cylinder is about 8 cwt. The hard woods, oak, ash, birch, and beech, are alone used. Fir does not answer. The heat is kept up during the day-time, and the furnace is allowed to cool during the night. Next morning the door is opened, the charcoal removed, and a new charge of wood is introduced. The average product of crude vinegar called pyrolignous acid is 35 gallons. It is much contaminated with tar; is of a deep brown colour; and has a sp. gr. of 1.025. Its total weight is there- fore about 3 00 lbs. But the residuary char- coal is found to weigh no more than one- fifth of the wood employed. Hence nearly one half of the ponderable matter of the wood is dissipated in incondensable gases. Count Rumford states, that charcoal is equal in weight to more than four-tenths of the wood from which it is made. And M. Clement says that it is equal to one- half. The Count's error seems to have arisen from the slight heat of an oven to ■which his wood was exposed in a glass cylinder. The result now given is the ex- perience of an eminent manufacturing chemist at Glasgow. The crude pyrolig- nous acid is rectified by a second distilla- tion in a copper still, in the body of which about 20 gallons of viscid tarry matter are left from every 100. It has now become a transparent brown vinegar, having a con- siderable empyreumatic smell, and a sp. gr. of 1.013. Its acid powers are superioi' to those of the best household vinegar, in the proportion of 3 to 2. By redistillation, saturation with quick-lime, evaporation of the liquid acetate to dryness, and gentle torrefaction, the empyreumatic matter is so completely dissipated, that on decora- posing the calcareous salt by sulphuric acid, a pure, perfectly colourless, and grateful vinegar rises in distillation. Its strength will be proportional to the con- centration of the decomposing acid. The acetic acid of the chemist may be prepared in the following modes: 1st, Two parts of fused acetate of potash with one of the strongest oil of vitriol yield, by slow distillation from a glass retort into a refrigerated receiver, concentrated acetic acid. A small portion of sulphurous acid, which contaminates it, may be removed by redistillation, from a little acetate of lead. 2d, Or 4 parts of good sugar of lead, with 1 part of sulphuric acid treated in the same way, afford a slightly weaker acetic acid. 3d, Gently calcined sulphate of iron, or green vitriol, mixed with sugar of lead in the proportion of 1 of the former to 2£ of the latter, and carefully distilled from a porcelain retort into a cooled receiver, may be also considered a good economi- cal process. Or without distillation, if 100 parts of well dried acetate of lime be cau- tiously added to 60 parts of strong sulphu- ric acid, diluted with 5 parts of water, and digested for 24 hours, and strained,a good acetic acid, sufficiently strong for every ordinary purpose, will be obtained. The distillation of acetate of copper or of lead per se, has also been employed for obtaining strong acid. Here, however, the product is mixed with a portion of the fra- grant pyro-acetic spirit, which it is trou- blesome to get rid of. Undoubtedly the best process for the strong acid is that first described, and the cheapest the second or third. When of the utmost possible strength its sp. gravity is 1. 062. At the temperature of 50° F. it assumes the solid form, crystallizing in oblong rhomboidal plates. It lias an.extremely pungent odour, affecting the nostrils and eyes even painfully, when its vapour is incautiously snuffed up. Its taste is eminently acid and acrid. It excoriates and inflames the skin. The purified wood vinegar, which is used for pickles and culinary purposes, has commonly a specific gravity of about 1.009; when it is equivalent in acid strength to good wine or malt vinegar of ACI ACI 1.014. It contains about of J its weight of absolute acetic acid, and i' of water. An excise duty of 4d. is levied on every gallon of vinegar of the above strength. This, however, is not estimated directly by its sp. gr. but by the sp. gr. which re- sults from its saturation with quick-lime. The decimal number of the sp. gr. of the calcareous acetate, is nearly double that of the pure wood vinegar. Thus 1.009 in vinegar, becomes 1.018 in liquid acetate. But the vinegar of fermentation =1.014 will become only 1.023 in acetate, from which, if 0.005 be subtracted for mucilage or extractive, the remainder will agree with the density of the acetate from wood. A glass hydrometer of Fahrenheit's con- struction is used for finding the specific gravities. It consists of a globe about 3 inches diameter, having a little ballast ball drawn out beneath, and a stem above of about 3 inches long, containing a slip of paper with a transverse line in the middle, and surmounted with a little cup for re- ceiving weights or poises. The experi- ments on which this instrument, called an .icetometer, is constructed, have been de- tailed in the sixth volume of the Journal of Science. They do not differ essentially from those of MoIIerat, The following points were determined by this chemist. The acid ot sp. gr. 1.063 requires 2$ times its weight of crystallized subcarbonate of soda for saturation, whence M. Thenard regards it as a compound of 11 of water, and 89 of real acid in the 100 parts. Com- bined with water in the proportion of 100 to 112.2, it does not change its density, but it then remains liquid several degrees below the freezing point of water. By di- luting it with a smaller quantity of water, its sp. gr. augments, a circumstance pecu- liar to this acid. It is 1.079, or at its maxi- mum, when the water forms one-third of the weight of the acid. —Ann. de Cldmie, torn. 66. The following table is given by Messrs Taylor as the basis of their acetome- ter:— Revenue proof acid, called by the man- ufacturer No. 24. sp. gr. 1.0085 contains real acid in 100, 5 1.0170 .-.-...- 10 1.0257........15 1.0320........20 1.0470........30 1.0580........40 An acetic acid of very considerable strength may also be prepared by satu- rating perfectly dry charcoal with common vinegar, and then distilling. The water easily comes off, and is separated at first; hut a stronger heat is required to expel the acid. Or by exposing vinegar to very cold, air, or to freezing mixtures, its water sepa- rates in the state of ice, the interstices of which are occupied by a strong acetic acid, which may be procured by draining. The acetic acid or radical vinegar of the apo- thecaries, in which they dissolve a little camphor, or fragrant essential oil, has a specific gravity of about 1.070. It contains fully 1 part of water to 2 of the crystalliz- ed acid. The pungent smelling salt con- sists of sulphate of potash moistened with that acid. Acetic acid acts on tin, iron, zinc, copper, and nickel; and it combines readily with the oxides of many other me- tals, by mixing a solution of their sulphates with that of an acetate of lead. This acid, as it exists in the acetates of barytes and lead, has been analyzed by M. M. Gay-Lussac and Thenard, and also by Berzelius. Gay-Lussac found 50.224 carbon, 5.629 hydrogen, and 44.147 oxygen ; or, in other terms, 50.224 carbon, 49.665 of water, or its elementary constituents, and 0.111 hy- drogen in excess. Berzelius.—46.83 carb. 6.35 hydr. and 46.82 oxygen in the hundred parts. Their methods are described under Ve- getable (Analysis). By saturating known weights of bases with acetic acid, and as- certaining the quantity of acetates obtain- ed after cautious evaporation to dryness, Berzelius obtained with lime (3.56) 6.5 for the prime equivalent of acetic acid, and with yellow oxide of lead 6.4^2. Recent re- searches, which will be published in a de- tailed form, induce me to fix the prime of acetic acid at 6.63. It would seem to con- sist, by Berzelius's analysis, of 3 Primes of hydrogen 3.75 6.2 4 carbon 30. 46.9 3 oxygen 30. 46.9 63.75 100.0 The quantity of hydrogen is probably much underrated. Acetic acid dissolves resins, gum-resins, camphor, and essential oils. Its odour is employed in medicine to relieve nervous headaches, faintingfits, or sickness occasioned by crowded rooms. In a slightly dilute state, its application has been found to check hemorrhagy from the nostrils. Its anticontagious powers are now little trusted to. It is very largely used in calico printing. Moderately rec- tifiedpyrolignous acid hasbeen recommen- ded for the preservation of animal food ; but the empyreumatic taint it communi- cates to bodies immersed in it, is not quite removed by their subsequent ebullition in, water. See Acid, Pyrolignous). Acetic acid an C common vinegar are sometimes fraudi 'entry mixed with sul- ACI phuric acid to give them strength. This adulteration may be detected by the ad- dition of a little chalk, short of their satu- ration. With pure vinegar the calcareous base forms a limpid solution, but with sulphuric acid a white insoluble gypsum. Muriate of barytes is a still nicer test. British fermented vinegars are allowed by law to contain a little sulphuric acid, but the quantity is frequently exceeded. Copper is discovered in vinegars by super- saturating them with ammonia, when a fine blue colour is produced ; and lead by sulphate of soda, hydrosulphurets, sulph- uretted hydrogen, and-gallic acid. None of these should prod.ice any change on genuine vinegar. See Lead.* * Acid (Oxf-acetic). Acetic acid dis- solves deutoxide of barium without effer- vescence. By precipitating the barytes with sulphuric acid, there remains an ox- ygenized acid, which, being saturated with potash, and heated, allows a great quantity of oxygen gas to escape. There is disengaged at the same time a notable quantity of carbonic acid gas. This shows that the oxygen, when assisted by heat, unites in part with the carbon, and doubt- less likewise w ith the hydrogen of the acid. It is in fact acetic deutoxide of hy- drogen. Salts consisting of the several bases, united in definite proportions to acetic acid, are called acetates. They are char- acterized by the pungent smell of vinegar, which they exhale on the affusion of sul- phuric acid; and by their yielding on dis- tillation in a moderate red heat a very light, odorous, and combustible liquid called pyro-acetic (spirit) ; which see. They are all soluble in water; many of them so much so as to be uncrystallizable. About 30 different acetates have been formed, of which only a very few have been applied to the uses of life.* The acetic acid unites with all the alka- lis and most of the earths, and with these bases it forms compounds, some of which are crystallizable, and others have not yet been reduced to a rcgular.ty of figure. The salts it forms are distinguished by their great solubility; their decomposition by tire, which carbonizes them ; the spontan- eous alteration of their solution; and their decomposition by a great number of..c ds, •which extricate from them the acetic ;.cid in a concentrated state. It unites likewise with most of the metallic oxides. With barytes the saline mass formed by the acetic acid does not crystallize; hut, when evaporated to dryness, it deliques- ces by exposure to air. This muss is not decomposed by acid of arsenic By spon- taneous evaporation, however, it will crystallize in fine transparent prismatic ijcedles, of a bitterish acid taste, whivhdo ACI not deliquesce when exposed to the an. but rather effloresce. With potash this acid unites, and forms h deliquescent salt scarcely crystallizable, called formerly foliated earth of tartar, and regenerated tartar. The solution of this salt, even in closely stopped vessels, is spontaneously decomposed: it deposites a thick, mucous, flocculent sediment, at first gray, and at length black ; till at the end of a few months nothing remains in the liquor but carbonate of potash, rendered impure by a little coaly oil. With soda it forms a crystallizable salt, which does not deliquesce. This salt has very improperly been called mineral foli- ated earth. According to the new nomen- clature it is acetate of soda. The salt formed by dissolving chalk or other calcareous earth in distilled vinegar, formerly called salt of chalk, or fixed vege- table sal ammoniac, and by Bergman calx acetata, has a sharp bitter taste, appears in the form of crystals resembling somewhat cars of corn, which remain dry when ex- posed to the air, unless the acid has been super-abundant, in which case they deli- quesce. By distilling without addition, the acid is separated from the earth, and appears in the form of a white, acid, and in- flammable vapour, which smells like acetic ether, somewhat empyreumatic, and which condenses into a reddish brown liquor. This liquor, being rectified, is very vola- tile and inflammable : upon adding water it acquires a milky appearance, and drops of oil seem to swim upon the surface. After the rectification, a reddish brown li- quor remains behind in the retort, toge- ther with a black thick oil. When this earthy salt is mixed with a solution of sul- phate of soda, the calcareous earth is pre- cipitated along with the sulphuric acid; the acetic acid uniting with the soda, makes a crystallizable salt, by the calcination of which to whiteness, the soda may be ob- tained. This acetic calcareous salt is not soluble in spirit of wine. Of the acetate of strontian little isknown, but that it has a sweet taste, is very solu- ble, and is easily decomposed by a strong heat. The salt formed by uniting vinegar with ammonia, called by the various names of spirit of Mindercrus, liquid sal ammoniac, acetous sal ammoniac, and by Bergman al- kali volatile acetatum, is generally in a liquid state, and is commonly believed not to be crystallizable, as in distillation it pass- es entirely over into the receiver. It ne- vertheless may be reduced into the form of small needle-shaped crystals, when this liquor is evaporated to the consistence of a sirup. Westendorf, by adding his concentrated vinegar to carbonate of ammonia, obtained ACI ACI a pellucid liquid, which did not crystallize j and which by distillation was totally expell- ed from the retort, leaving only a white spot. In the receiver, under the clear fluid, a transparent saline mass appeared, which being separated from the fluid, and expo- sed to gentle warmth, melted and threw out abundance of white vapours, and in a few minutes shot into sharp crystals resembling those of nitre. These crystals remain un- changed while cold, but they melt at 120° and evaporate at about 250°. Their taste at first is sharp and then sweet, and they possess the general properties of neutral salts. With magnesia the acetic acid unites, and, after a perfect saturation, forms a vis- cid saline mass, like a solution of gum ara- bic, which does not shoot into crystals, but remains deliquescent, has a taste sweetish at first, and afterwards bitter, and is soluble in spirit of wine. The acid of this saline mass may be separated by distillation with- out addition. Glucine is readily dissolved by acetic acid. This solution, as Vauquclin informs us, does not crystallize; but is reduced by evapora- tion to a gummy substance, which slowly becomes dryr and brittle ; retaining a kind of ductility for a long time. It has a sac- charine and pretty strongly astringent taste, in which that of vinegar however, is distin- guishable. Yttria dissolves readily in acetic acid, and the solution yields by evaporation crystals of acetate of yttria. These have common- ly the form of thick six-sided plates, and are not altered by exposure to the air. Alumine, obtained by boiling alum with alkali, and edulcorated by digesting in an alkaline lixivium, is dissolved by distilled vinegar in a very inconsiderable quantity. A considerable quantity of the earth of al- um, precipitated by alkali, and edulcorated by hot water in MargrafPs manner, is solu- ble in vinegar, and a whitish saline mass is then obtained, which is not crystallizable. From this mass a concentrated acetic acid may be obtained by distillation. Or to a boiling solution of alum in water gradually add a solution of acetate of lead till no fur- ther precipitate ensues. The sulphate of lead having subsided, decant the superna- tant liquor, evaporate, and the acetate of alumine may be obtained in small needle- shaped crystals, having a strong styptic and acetous taste. This salt is of great use in dyeing and calico printing. See Alumina. Acetate of zircone may be formed by pouring acetic acid on newly precipitated zircone. It has an astringent taste. It does not crystallize ; but, when evaporated to dryness, forms a powder, which does not attract moisture from the air. It is very soluble both in water and alcohol; and is not so easily decomposed by heat as nitrate of zircone. The acetic acid has no- action upon sili- ceous earth; for the needle-shaped crys- tals observed by Durande in a mixture of vinegar with the earth precipitated from a liquor of flints, do not prove the solubility of siliceous earth, as Leonhardi observes. Concerning the action of vinegar on al- cohol, see Etueii. This acid has no effect upon fat oils, except that when distilled to- gether, some kind of mixture takes place, as the Abbe Rozier observes. Neither does distilled vinegar act upon essential oils; but Westendorf's concentrated acid dissolved about a sixth part of oil of rosemary, or one half its weight of camphor; which latter so- ' lution was inflammable ; and the camphov was precipitated from it by adding water. Vinegar dissolves the true gums, and part. ly the gum-resins, by means of digestion. Boerhaave observes, that vinegar by long boiling dissolves the flesh,cartilages, bones, and ligaments of animals. Acid. (Amniotic). On evaporating the liquor amnii of the cow to one-fourth, Vau- quelin and Buniva found, that crystals form in it by cooling. These are contaminated by a portion of extract! ve matter,from which they may be freed by washing with a very small quantity of water. These crystals are white and shining, slightly acid to the taste, redden litmus paper, and are a little more solute in hot than cold water. They are likewise soluble in alcohol. On ignited coals they swell, turn black, give out am- monia and prussic acid, and leave a bulky coal. With the alkalis this acid forms very soluble salts, but it does not decompose the carbonate without the assistance of heat. It does not precipitate the earthy salts, or the nitrates of mercury, lead, or silver. The acids precipitate it from its combinations with alkalis in a white crystaline powder. Whether it exist in the amniotic hquor of any other animal is not known. Acin (Arsenic). The earlier chemists were embarrassed in the determination of the nature of the white sublimate, which is obtained during the roasting of cobalt and other metallic ores, known in commerce by the name of arsenic: its solubility in water, its power of combining with metals in their simple state, together with other apparent- ly heterogeneous properties, rendered it difficult to determine whether it ought to be classed with metals or salts. Subse- quent discoveries have shown the relation it bears to both. When treated with com- bustible matter, in close vessels, it sublimes in the metallic form, (See Arsenic) ; com- bustion, or any analogous process, converts it into an oxide; and when the combustion is carried still further, the arsenical basis becomes itself converted into an acid. ACI ACI We are indebted to the illustrious Scheele for the discovery of this acid, though Macquer had before noticed its combinations. It may be obtained by va- rious methods. If six parts of nitric acid be poured on one of the concrete arsenious acid, or white arsenic of the shops, in the pneumato-chemical apparatus, and heat be applied, nitrous gas will be evolved, and a white concrete substance, differing in its properties from the arsenious acid, will re- main in the retort. This is the arsenic acid. It may equally be procured by means of aqueous chlorine, or by heating concen- trated nitric acid with twice its weight of the solution of the arsenious acid in muri- atic acid. The concrete acid should be ex- posed to a dull red heat for a few minutes. In either case an acid is obtained, that does not crystallize, but attracts the moisture of the air, has a sharp caustic taste, reddens blue vegetable colours, is fixed in the fire, and of the specific gravity of 3.391. If the arsenic acid be exposed to a red heat in a glass retort, it melts and becomes transparent, but assumes a milky hue on cooling. If the heat be increased, so that the retort begins to melt, the acid boils, and sublimes into the neck of the retort. If a covered crucible be used instead of the glass retort, and a violent heat applied, the acid boils strongly, and in a quarter of an hour begins to emit fumes. These, on be- ing received in a glass bell, are found to be arsenious acid; and a small quantity of a transparent glass, difficult to fuse, will be found lining the sides of the crucible. This is arseniate of alumina. Combustible substances decompose this acid. If two parts of arsenic acid be mixed with about one of charcoal, the mixture in- troduced into a glass retort, coated, and a matrass adapted to it; and the retort then gradually heated in a reverberatory furnace, till the bottom is red; the mass will be in- flamed violently, and the acid reduced, and rise to the neck of the retort in the metal- Ec state mixed with a little oxide and char- coal powder. A few drops of water, de- void of acidity, will be found in the receiv- er. With sulphur the phenomena are differ- ent. If a mixture of six parts of arsenic acid, and one of powdered sulphur, be di- gested together, no change will take place; but on evaporating to dryness, and distill- ing in a glass retort, fitted with a receiver, « violent combination will ensue, as soon as the mixture is sufficiently heated to melt the sulphur. The whole mass rises almost at once, forming a red sublimate, and sul- phurous acid passes over into the receiver. If pure arsenic acid be diluted with a small quantity of water, and hydrogen gas, as it is evolved by the action of sulphuric acid on iron, be received into this transpa- rent solution, the liquor grows turbid, and a blackish precipitate is formed, which, be- ing well washed with distilled water, ex- hibits all the phenomena of arsenic. Some- times, too, a blackish gray oxide of arsenic is found in this process. If sulphuretted hydrogen gas be employ- ed instead of simple hydrogen gas, water and a sulphuret of arsenic are obtained. With phosphorus, phosphoric acid is ob- tained, and a phosphuret of arsenic, which sublimes. The arsenic acid is much more soluble than the arsenious. According to Lagrange, two parts of water are sufficient for this pur- pose. It cannot be crystallized by .any means; but, on evaporation, assumes a thick honey-like consistence. No acid has any action upon it: if some of them dissolve it by means of the water that renders them fluid, they do not pro- duce any alteration in it. The boracic and phosphoric are verifiable with it by means of heat, but without any material alteration in their natures. If phosphorous acid be heated upon it for some time, it saturates itself with oxygen, and becomes phospho- ric acid. The arsenic acid combines with the ear- thy and alkaline bases, and forms salts very different from those furnished by the ar- senious acid. All these arseniates are decomposable by charcoal,which separates arsenic from them by means of heat. * Berzelius, from the result of accurate experiments on the arseniates of lead and barytes, infers the prime equivalent of ar- senic acid to be 7.25, oxygen being 1.0; but Dr. Thomson, from his experiments ou the arseniates of potash and soda, conceives that the double of the above number ought to be preferred, viz. 14.5. Ann. of Phil. vol. xv. On the latter supposition, Berzclius's in- soluble salts will consist of two primes of base and one of acid; and the acid itself will be a compound of 5 of oxygen = 5, + 9.5. of the metallic base = 14.5; for direct ex- periments have shown it to consist of 100 metal, and from 52 to 53 oxygen. But 152.5: 100:: 14.5: 9.5 nearly. All its salts, with the exception of those of potash, soda, and ammonia, are insoluble in water ; but except arseniate of bismuth, and one or two more, very soluble in an excess of arsenic acid. Hence, after ba- rytes or oxide of lead has been precipitated by this acid, its farther addition redissolves the precipitate. This is a useful criterion of the acid, joined to its reduction to the metallic state by charcoal, and Ihe other characters already detailed. Sulphuric acid decomposes the arseniates at a low temperature, but the sulphates are de- composed by arsenic acid at a red heat, ACI ACI owing to the greater fixity of the latter. Phosphoric, nitric, muriatic, and fluoric acids, dissolve, and probably convert into subsalts all the arseniates. The whole of them, as well as arsenic acid itself when decomposed at a red heat by charcoal, yield the characteristic garlic smell of the metallic vapour. Nitrate of silver gives a pulverulent brick-coloured precipitate, or, according to Dr. Thomson, a flesh red, with arsenic acid. The acid itself does not disturb the transparency of a solution of sulphate of copper; but a neutral arseni- ate gives with it a bluish green precipitate; with sulphate of cobalt, a dirty red, and with sulphate of nickel, an apple green precipitate. These precipitates redissolve, on adding a small quantity of the acid which previously held them in solution. Orfila says, that arsenic acid gives, with acetate of copper, a bluish white precipi- tate, but that it exercises no action either on the muriate or acetate of cobalt; but with the ammonia-muriate it gives a rose- coloured precipitate. Arsenic acid ought to be accounted a more violent poison than even the arsenious. According to Mr. Brodie, it is absorbed, and occasions death by acting on the brain and the heart. * The arseniate of barytes is insoluble, uncrystallizable, soluble in an excess of its acid, and decomposable by sulphuric acid, which precipitates a sulphate of barytes. Of the arseniate of strontian nothing is known, but no doubt it resembles that of barytes. With lime-water this acid forms a pre- cipitate of arseniate of lime, soluble in an excess of its base, or in an excess of its acid, though insoluble alone. The acidu- lous arseniate of lime affords on evapora- tion little crystals, decomposable by sul- phuric acid. The same salt may be formed by adding carbonate of lime to the solu- tion of arsenic acid. This acid does not decompose the nitrate or muriate of lime; but the saturated alkaline arseniates de- compose them by double affinity, precipi- tating the insoluble calcareous arseniate. If arsenic acid be saturated with magne- sia, a thick substance is formed near the point of saturation. This arseniate of mag- nesia is soluble in an excess of acid; and on being evaporated takes the form of a jelly, without crystallizing. Neither the sulphate, nitrate, nor muriate of magne- sia is decomposed by arsenic acid, though they are by the saturated alkaline arseni- ates. Arsenic acid saturated with potash does not easily crystallize. This arseniate, be- ing evaporated to dryness, attracts the hu- midity of the air, and turns the sirup of violets green, vyithout altering the solu- tion of litmus. It fuses into a white glass, and with a Strang fire is converted into an acidule, part of the alkali being abstracted by the silex and alumina of the crucible. If exposed to a red heat with charcoal in close vessels it swells up very much, and arsenic is sublimed. It is decomposed by sulphuric acid; but in the humid way the decomposition is not obvious, as the arse- nic acid remains in solution. On evapora- tion, howev er, this acid and sulphate of potash are obtained. If arsenicacid be added to the preceding salt, till it ceases to have any effect on the sirup of violets, it will redden the solu- tion of litmus; and in this state it affords very regular and very transparent crystals, of the figure of quadrangular prisms, ter- minated by two tetraedral pyramids, the angles of which answer to those of the prisms. These crystals are the arsenical neutral salt of Macquer. As this salt dif- fers from the preceding arseniate by its crystallizability, its reddening solution of litmus, its not decomposing the calcareous and magnesian salts like it, and its capa- bility of absorbing an additional portion of potash, so as to become neutral, it ought to be distinguished from it by the term of acidulous arseniate of potash. With soda in sufficient quantity to satu- rate it, arsenic acid forms a salt crystalli- zable like the acidulous arseniate of pot- ash. Pelletier says, that the crystals are hexaedral prisms terminated by planes perpendicular to their axis. This neutral arseniate of soda, however, while it differs completely from that of potash in this re- spect, and in becoming deliquescent in- stead of crystallizable on the addition of a surplus portion of arsenic acid, resembles the arseniate of potash in its decomposi- tion by charcoal, by acids, and by the earths. Combined with ammonia, arsenic acid forms a salt affording rhomboidal crystals analogous to those of the nitrate of soda. The arseniate of ammonia, which is pro- duced likewise in the decomposition of nitrate of ammonia by arsenious acid, is decomposable in two ways by the action of heat. If it be gently heated, the ammo* nia is evolved, and the arsenic acid is left pure. If it be exposed to a violent and rapid heat, part of the ammonia and part of the acid reciprocally decompose each other; water is formed; azotic gas is given out; and the arsenic sublimes in a shining metallic form. Magnesia partly decompo- ses the arseniate of ammonia, and forms a triple salt with a portion of it- Arsenic acid saturated with alumina. forms a thick solution, which, being eva porated to dryness, yields a salt insoluble in water, and decomposable by the snl phuric, nitric and muriatic acids, as we'i as by all the other earthy and alkaline ba- ses. The arsenic acid rerul!ly dis^H\esth<* ACI ACI alumina of the crucibles in which it is re- duced to a state of fusion ; and thus it at- tacks silex also, on which it has no effect in the humid way. A\ e know nothing of the combination of this acid with zircone. By the assistance of a strong fire, as Fourcroy assert s, arsenic acid decompo- ses the alkaline and earthy sulphates, even that of barytes ; the sulphuric acid flying off in vapour, and the arseniate remaining in the retort. It acts in the same manner on the nitrate, from which it expels the pure acid. It likewise decomposes the muriates at a high temperature, the muri- atic acid being evolved in the form of gas, and the arsenic acid combining with their bases, which it saturates; while the arse- nious acid is too volatile to have this effect. It acts in the same manner on the filiates, and still more easily on the carbonates, with which, by the assistance of heat, it excites a brisk effervescence. Lagrange, however, denies that it acts on any of the neutral salts, except the sulphate of pot- ash, and soda, the nitrate of potash, and the muriates of soda and ammonia, and this by means of heat. It does not act on the phos- phates, but precipitates the boracic acid from solutions of borates when heated. Arsenic acid docs not act on gold or platina; neither does it on mercury or silver without the aid of a strong heat; but it oxidizes copper, iron, lead, tin, zinc, bismuth, antimony, cobalt, nickel, manga- nese, and arsenic. This acid is not used in the arts, at least directly, though indirectly it forms a part of some composition used in dyeing. It is likewise one of the mineralizing acids combined by nature with some of the me- tallic oxides. Acid (Aiisbniqcs). Fourcroy was the frrst who distinguished by this name the white arsenic of the shops, which Scheele had proved to be a compound of the metal arsenic with oxygen, and which the au- thors of the new chemical nomenclature had consequently termed oxide of arsenic. As, however, it manifestly exhibits the properties of an acid, though in a slight degree, it has a fair claim to the title; for many oxides and acids are similar in this, that both consist of a base united with oxygen, and the only difference between them is, that the compound in which the acid properties are manifest is termed an acid, and that in which they are not is called an oxide. This acid, which is one of the most vi- rulent poisons known, frequently occurs in a native state, if not very abundantly; and it is obtained in roasting several ores, particularly those of cobalt. In the chim- neys of the furnaces where this operation ft conducted, it generally condenses in thick semi-transparent masses; though sometimes it assumes the form of a pow- der, or of little needles, in which slate it was formerly called flowers of arsenic. The arsenious acid reddens the most sensible blue vegetable colours, though it turns the sirup of violets green. On ex- posure to the air it becomes opaque, and covered with a slight efflorescence.— Thrown on incandescent coals, it evapo- rates in white fumes, with a strong smell of garlic. In close vessels it is volatilized; and, if the heat be strong, vitrified. The result of this vitrification is a transparent glass, capable of crystallizing in tetraedra, the angles of which are truncated. It is easily altered by hydrogen and carbon, which deprive it of its oxygen at a red heat, and reduce the metal, the one form- ing water, the other carbonic acid, with the oxygen taken from it: as it is by phos- phorus, and by sulphur, which are in part converted into acids by its oxygen, and in part form an arsenical phosphuret or sul- phuret with the arsenic reduced to the metallic state. Hence Margraafand Pel- letier, who particularly examined the phosphurets of metals, have asserted they might be formed with arsenious acid. Its specific gravity is 3.7. It is soluble in thirteen times its weight of boiling water, but requires eighty times its weight of cold. The solution crystal- lizes, and the acid assumes the form of re- gular tetraedrons according to Fourcroy; but, according to Lagrange, of octaedrons, and these frequently varying in figure by different laws of decrement. It crystallizes much better by slow evaporation than by simple cooling. * The solution is very acrid, reddens blue colours, unites with the earthy bases, and decomposes the alkaline sulphurets. Arsenious acid is also soluble in oils, spir- its, and alcohol; the last taking up from 1 to 2 per cent. It is composed of 9.5 of me- tal -+• 3 oxygen; and its prime equivalent is therefore 12.5. Dr. Wollaston first ob- served, that when a mixture of it with quick-lime is heated in a glass tube, at a certain temperature, ignition suddenly per- vades the mass, and metallic arsenic sub- limes. As arseniate of lime is found at the bottom of the tube, we perceive that a portion of the arsenious acid is robbed of its oxygen, to complete the acidification of the rest.* There are even some metals, which act upon the solution, and have a tendency to decompose the acid, so as to form a black- ish precipitate, in which the arsenic is very slightly oxidized. The action of the other acids upon the arsenious is very different from that which they exert on the metal arsenic. By boil- ing, sulphuric acid dissolves a small por- ACI Aci tion of it, which is precipitated as the so- lution cools. The nitric acid roes not dis- solve it, but by the help of heat converts it into arsenic acid. Neither the phospho- ric nor the carbonic acid acts upon it; yet it enters into a vitreous combination with the phosphoric and boracic acids. The muriatic acid dissolves it by means of heat, and forms with it a volatile compound, which water precipitates; and aqueous chlorine acidifies it completely, so as to convert it into arsenic acid. The arsenious acid combines with the earthy and alkaline bases. The earthy ar- seniates possess little solubility, and hence the solutions of barytes, strontian, and lime, form precipitates with that of arse- nious acid. The acid enters into another kind of combination with the earths, that formed by vitrification. Though a part of this vola- tile acid sublimes before the glass enters into fusion, part remains fixed in the vitri- fied substance, to which it imparts trans- parency, a homogeneous density, and con- siderable gravity. The arsenical glasses appear to contain a kind of triple salt, since the salt and alkahs enter into an in- timate combination at the instant of fusion, and remain afterwards perfectly mixed. All of them have the inconvenience of quick- ly growing dull by exposure to the air. With the fixed alkalis the arsenious acid forms thick arsenites, which do not crys- tallize ; which are decomposable by fire, the arsenious acid being volatilized by the heat; and from which all the other acids precipitate this in powder. These saline compounds were formerly termed livers, because they were supposed to be analo- gous to the combinations of sulphur with the alkalis. With ammonia it forms a salt capable of crystallization. If this be heated a little, the ammonia is decomposed, the nitrogen is evolved, while the hydrogen, uniting with part ofthe oxygen ofthe acid, forms water. Neither the earthy nor alkaline arsen- ites have yet been much examined ; what is known of them being only sufficient to distinguish them from the arseniates. The nitrates act on the arsenious acid in a very remarkable manner. On treating the nitrates and arsenious acid together, the nitrous acid, or nitrous vapour, is ex- tricated in a state very difficult to be con- fined, as Kunckel long ago observed; part of its oxygen is absorbed by the arsenious acid; it is thus converted into arsenic acid, and an arseniate is left in the retort. The same phenomena take place on detonating nitrates with arsenious acid ; for it is still sufficiently combustible to produce a de- tonation, in which no sparks are seen, it is true, but with commotion and efferves- cence ; and a true arseniate remains at the bottom ofthe crucible. It was in this Vol. I. [3] way chemists formerly prepared their fixed arsenic, which was the acidulous arseni- ate of potash. The nitrate of ammonia ex- hibits different phenomena in its decom- position by arsenious acid, and requires considerable precaution. Pelletier, having mixed equal quantities, introduced the mixture into a large retort of coated glass, placed in a reverberatorv furnace, with a globular receiver. He began with a very slight fire; for the decomposition is so ra- pid, and the nitrous vapours issue with such force, that a portion of the arsenious acid is carried off' undecomposed, unless you proceed very gently. If due care be taken that the decomposition proceeds more slowly, nitrous acid first comes over; if the fire be continued, or increased, am- monia is next evolved; and lastly, if the fire be urged, a portion of oxide of arsen- ic sublimes in the form of a white pow- der, and a vitreous mass remains in the re- tort, which powerfully attacks and cor- rodes it. This is arsenic acid. The chlo- rate of potash, too, by completely oxidiz- ing the arsenious acid, converts it into ar- senic acid, which by the assistance of heat, is capable of decomposing the muriate of potash that remains. The arsenious acid is used in numerous instances in the arts, under the name of white arsenic, or of arsenic simply. In many cases it is reduced, and acts in its metallic state. Many attempts have been made to in- troduce it into medicine; but as it is known to be one of the most violent poi-« sons, it is probable that the fear of its bad effects may deprive society ofthe advan- tages it might afford in this way. An ar- senite of potash was extensively used by the late Dr. Fowler of York, who publish- ed a treatise on it, in intermittent and re- mittent fevers. He likewise assured the writer, that he had found it extremely effi- cacious in periodical headache, and as a to- nic in nervous and other disorders; and that he never saw the least ill effect from its use, due precaution being employed in preparing and administering it. Exter- nally it has been employed as a caustic to extirpate cancer, combined with sulphur, with bole, with antimony, and with the leaves of crowfoot; but it always gives great pain, and is not unattended with danger. Febure's remedy was water one pint, extract of hemlock ^j, Goulard's ex- tract Jiij, tincture of opium !Jj, arsenious acid gr. x. With this the cancer was wel- ted morning and evening; and at the same time a small quantity of a weak solution was administered internally.- A still milder application of this kind has been made from a solution of one grain in a quart of water, formed into a poultice with crumb of bread. * It has been more lately used as an al« ACI ACI Icrativc with advantage in chronic rheu- matism. The symptoms which show the system to be arsenified are thickness, red- ness, and stiffness of ihepal[>ebt\c, soreness of the gums, ptyalism, itching over the surface of the body, restlessness, cough, pain at stomach, and headache. When the latter symptoms supervene, the admi- nistration ofthe medicine ought to be im- mediately suspended. It has also been re- commended against chincough; and has been used in considerable doses with suc- cess, to counteract the poison of venomous serpents. Since it acts on the animal economy as a deadly poison in quantities so minute as to be insensible to the taste when diffused in water or other vehicles, it has been often given with criminal intentions and fatal ef- fects. It becomes therefore a matter of the utmost importance to present a systematic view of the phenomena characteristic of the poison, its operation, and consequen- ces. 1st, It is a dense substance, subsiding speedily after agitation in water. I find its sp. gr. to vary from 3.728 to 3.730, which is a little higher than the number given above ; 72 parts dissolve in 1000 of boiling water, of which 30 remain in it, after it cools. Cold water dissolves, however, on- ly T7J55 or jV of the preceding quanti- ty. This water makes the sirup of violets green, and reddens litmus paper. Lime water gives a fine white precipitate with it of arsenite of lime, soluble in an excess ofthe arsenious solution. Sulphuretted hy- drogen gas, and hydrosulphuretted water precipitate a golden yellow sulphuret of arsenic. By this means -njsstre of arsen- ious acid may be detected in water. This sulphuret dried on a filter, and heated in a glass tube with a bit of caustic potash, is decomposed in a few minutes, and con- verted into sulphuret of potash, which re- mains at the bottom, and metallic arsenic of a bright steel lustre, which sublimes, coating the sides of the tube. The hydco- sulphurets of alkalis do not affect the ar- senious solution, unless a drop or two of nitric or muriatic acid be poured in, when the characteristic golden yellow precipi- tate falls. Nitrate of silver is decomposed bj- the arsenious acid, and a very peculiar yellow arsenite of silverprecipitates, which however, is apt to be redissolved by nitric acid, and therefore a very minute addition of ammonia is requisite. Even this how- ever, also, if in much excess, redissolves the silver precipitate. As the nitrate of silver is justly regarded as one ofthe best precipitant tests of arsen- ic, the mode of using it has been a sub- ject of much discussion. The presence of muriate of soda indeed, in the arsenical so- lution, obstructs, to a certain degree, the operation of this reagent. But, that salt is almost always present in the prima vix, and is a usual ingredient in soups, and other vehicles ofthe poison. If, after the water of ammonia has been added, by plunging the end of a glass rod dipped iu it into the supposed poisonous liquid, we dip another rod into a solution of pure nitrate of silver, and transfer it into the arsenious solution, either a fine yellow cloud will be formed, or at first merely a white curdy precipitate. But at the se- cond or third immersion ofthe nitrate rod, a central spot of yellow will be perceived surrounded with "the white muriate of sil- ver. At the next immersion this yellow cloud on the surface will become very conspicuous. Sulphate of soda does not interfere in the least with the silver test. The ammoniaco-sulphate, or rather ammo- niaco-acetate of copper, added in a some- what dilute state to an arsenious solution, gives a fine grass green and very charac- teristic precipitate. This green arsenite of copper, well washed, being acted on by an excess of sulphuretted hydrogen water, changes its colour ai id becomes of a brown- ish red. Ferro-Prussiate of potash changes it into a blood red. Nitrate of silver con- verts it into the yellow arsenite of silver. Lastly, if the precipitate be dried on a fil- ter, and placed on a bit of burning coal, it will diffuse a garlic odour. The cupreous test will detect -jToffTFff OI" tne weight of the arsenic in water. The voltaic battery, made to act by two wires on a little arse- nious solution placed on a bit of window- glass, developes metallic arsenic at the ne- gative pole ; and if this wire be copper, it will be whitened like tombac. We may herc remark, however, that the most ele- gant mode of using all these precipitation reagents is upon a plane of glass, a mode practised by Dr. Wollaston in general chemical research, to an extent, and with a success, which would be incred.ble in other hands than his. Concentrate by heat in a capsule the suspected poisonous so- lution, having previously filtered it if ne- cessary. Indeed, if it be very much dis- guised with animal or vegetable matters, it is better first of all to evaporate to dry- ness, and by a few drops of nitric acid to dissipate the organic products. The clear liquid being now placed in the middle of the bit of glass, lines are to be drawn out from it in different directions. To one of these a particle of weak ammoniacal water being applied, the weak nitrate of silver may then be brushed over it with a hair pencil. By placing the glass in different lights, either over white paper or oblique- ly before the eye, the slightest change of tint will be perceived. The amruoniaco- ACI ACI acetate should be applied to another fila- ment ofthe drop, dcut-acetate of iron to a third, weak ammoniaco-acetate of cobalt to a fourth, sulphuretted water to a fifth, lime water to a sixth, a drop of violet sirup to a seventh, and the two galvanic wires at the opposite edges ofthe whole. Thus with one single drop of solution many- exact experiments may be made. But the chief, the decisive trial or experimentum crucis remains, which is to take a little of the dry matter, mix it with a small pinch of dry black flux, put it into a narrow glass tube sealed at one end, and after cleansing its sides with a feather, urge its bottom with a blow-pipe till it be distinctly red hot for a minute. Then garlic fumes will be smelt, and the steel-lustred coating of metallic arsenic will be seen in the tube about one-fourth of an inch above its bot- tom. Cut the tube across at that point by means of a fine file, detach the scale of arsenic with the point of a penknife ; put a fragment of it into the bottom of a small wine glass along with a few drops of am- moniaco-acetate of copper, and triturate them well together for a few minutes with a round headed glass rod. The mazarine Hue colour will soon be transmuted into a lively grass green, while the metallic scale will vanish. Thus we distinguish perfect- ly between a particle of metallic arsenic and one of animalized charcoal. \notiier particle of the scale may be placed be- tween two smooth and bright surfaces of copper, with a touch of fine oil; and whilst they are firmly pressed together, exposed to a red heat. The tombac alloy will ap- pear as a white stain. A third particle may be placed on a bit of heated metal, and held a little Under the nostrils, when the garlic odour will be recognized. No dan- ger can be apprehended, as the fragment need not exceed the tenth of a grain. It is to be observed, that one or two of the precipitation tests may be equivocal from admixtures of various substances. Thus tincture of ginger gives with the cupreous reagent a green precipitate;—and the writer of this article was at first led to sus- pect from that appearance, that an empi- rical tincture, put into his hands for ex- amination, did contain arsenic. But a care- ful analysis satisfied him of its genuineness. Tea covers arsenic from the cupreous test. Such poisoned tea becomes by its addi- tion of an obscure olive or violet red, but yields scarcely any precipitate. Sulphu- retted hydrogen, however, throws down a fine yellow sulphuret of arsenic. Another way of obviating all these sources of fallacy, is to evaporate careful- ly to dryness, and expose the residue to heat in u'glass tube. The arsenic sublimes, and may be operated on without ambigui- ty, Mr. Odila has gone into ample details on the modifications produced by wine, coffee, tea, broth, &c. on arsenical tests, of which a good tabular abstract is given in Mr. Thomson's London Dispensatory. But it is evident that the differences in these menstrua, as also in beers, are so great as to render precipitations and changes of colour by reagents very unsa- tisfactory witnesses, in a case of life and death. Hence the method of evaporation above described, should never be neglect- ed. Should the arsenic be combined with oil, the mixture ought to be boiled with water, and the oil then separated by the rapillary action of wick-threads. If with resinous substances, these may be remov- ed by oil of turpentine, not by alcohol, (as directed by Dr. Black,) which is a good solvent of arsenious acid. It may more- over be observed, that both tea and coffee should be freed from their tannin by gela- tin, which does not act on the arsenic, pre- vious to the use of reagents for the poison. When one part of arsenious acid in watery solution is added to 10 parts of milk, the sulphuretted hydrogen present in the lat- ter, occasions the white colour to pass in- to a canary yellow; the cupreous test gives it a slight green tint, and the nitrate of sil- ver produces no visible change, though even more arsenic be added; but the hy- drosulphurets throw down a golden yel- low, with the aid of a few drops of an acid. The liquid contained in the stomach of a rabbit poisoned with a solution of 3 grains of arsenious acid, afforded a white preci- pitate with nitrate of silver, grayish white with lime water, green with the ammoni- aco-sulphate, and deep yellow with sul- phuretted hydrogen water. The preceding copious description of the habitudes of arsenious acid in differ- ent circumstances, is equally applicable to the soluble arsenites. Their poisonous operation, as well as that of the arsenic acid, has been satisfactorily referred by Mr. Brodie to the suspension of the func- tions ofthe heart and brain, occasioned by the absorption of these substances into the circulation, and their consequent determi- nation to the nervous system and the ali- mentary canal. This proposition was es- tablished by numerous experiments on rabbits and dogs. Wounds were inflicted, and arsenic being applied to them, it was found that in a short time death superve- ned with the same symptoms of inflamma- tion of the stomach and bowels as if the poison had been swallowed. He divides the morbid affections into three classes : 1st, Those depending on the nervous sys- tem, as palsy at first of the posterior ex- tremities, and then ofthe rest ofthe body, convulsions, dilatation of the pupils, and general insensibility : 2d, Those which in- dicate disturbance in the organs of circu- ACI ACI lation; for example, the feeble, slow, and internrtting pulse, weak contractions of the heart immediately after death, and the impossibility of prolonging them, as may be done in sudden deaths from other causes, by artificial respiration • 3d, Lastly, Those which depend on lesion of the ali- mentary canal, as the pains of the abdo- men, nauseas and vomitings, in those ani mals which were suffered to vomit. At one time it is the nervous system that is most remarkably affected, and at another the organs of circulation. Hence inflam- mation of die stomach and intestines, ought not to be considered as the immediate cause of death, in the greater number of cases of poisoning by arsenic. However, should an animal not sink under the first violence ofthe poison, if the inflammation has had time to be developed, there is no doubt that it may destroy life. Mr. Earle states, that a woman who had taken arsenic resisted the alarming symptoms which at first appeared, but died on 'he fourth day. On opening her body the mucous mem- brane of the stomach and intestines was ulcerated to a great extent. Authentic cases of poison are recorded, where no trace of inflammation was perceptible on the prima vix. The symptoms of a dangerous dose of arsenic have been graphically represented by T^r. Black: " The symptoms produced by a langcrous d<«se of arsenic begin to appear in a quarter of an hour, or not much longer, afier it is taken. First sick- ness, and great distress at stomach, soon followed by thirst, and burning heat in the bowels. Then come on violent vomiting, and severe cholic pains, and excessive and painful purging. This brings on faintings, with cold sweats, and other signs of great debility. To this succeed painful cramps and contractions of the legs and thighs, and extreme weakness, and death." Simi- lar results have followed the incautious sprinking of schirrous ulcers with powder- ed arsenic, or the application of arsenical pastes. The following more minute spe- cification of symptoms is given by Orfila: " An austere taste in the mouth; frequent ptyalism ; continual spitting; constriction of the/>Aarj/7trand 1.42.* It is well known as a stimulant usually put into smelling-bottles, frequently with the addition of some odoriferous oil. Fourcroy has found, that an ammoniaco- magnesian carbonate is formed on some occasions. Thus, if carbonate of ammonia be decomposed by magnesia in the moist way, leaving these two substances in con- tact with each other in a bottle closely stopped, a complete decomposition will not take place, but a portion of this trisalt will be formed. The same will take place, if a solution of carbonate of magnesia in water, impregnated with carbonic acid, be precipitated by pure ammonia; or if am- moniaco-magnesian sulphate, nitrate, or muriate, be precipitated by carbonate of potash or of soda. The properties of this triple salt are not yet known, but it crystallizes differently from the carbonate of either of its bases, and has its own laws of solubility and de- composition. The carbonate of glucine has been ex- amined by Vauquelin, and is, among the salts of that earth, that of which he has most accurately ascertained the proper- ties. It is in a white, dull, clotty powder, never dry, but greasy, and soft to the feel. It is not sweet, like the other salts of glu- cine, but insipid. It is very light, insolu- ble in water, perfectly unalterable by the air, but very readily decomposed by fire. A saturated solution of carbonate of am- monia takes up a certain portion of this carbonate, and forms with it a triple salt. This property enabled Vauquelin to sepa- rate glucine from alumina, and was one of the means of his distinguishing that earth. Carbonic acid does not appear to he much disposed to unite with argillaceous earth. Most clays, however, afford a small quantity of this acid by heat; and Fourcroy says, that the fat clays effervesce with acids. " The snowy white substance resembling chalk, and known by the name of lac lima, is found to consist almost wholly of alumina saturated with carbonic acid. A saline substance, consisting of two six-sided pyramids joined at one com- mon base, weighing five or six grains, and of a taste somewhat resembling alum, was produced by leaving an ounce phial of wa- ter impregnated with carbonic acid, and a redundancy of alumina, exposed to spon- taneous evaporation for some months. Vauquelin has found, that carbonate of zircone may be formed by evaporating muriate of zircone, redissolving it in wa- ter, and precipitating by the alkaline car- bonates. He also adds, that it very readily combines so as to form a triple salt with either of the three alkaline carbonates. * Acin (Caskic). The name given by Proust to an acid found in cheese, to which he ascribes their flavour. Acid (Cetic). The name given by M. Chevreul to a supposed peculiar principle of spermaceti, which he has lately found to be the substance he has called Marga- rine, combined with a fatty matter.* Acm (Chloiuodic). See Acid (Ht- diuodic). Acih (Chlouocaubonic). See Chlo- iiine, and Chlohocaiibonoits Acid. Acid (Chlouocyajuc). See Acid (Patrs- sic). Acid (Ciihomic). This acid has been examined principally by Vauquelin, who first discovered it, and by count Mussin Puschkin; yet we are better acquainted with it than with the metal that forms its basis. However, as the chromate of iron has lately been found in abundance in the department of Var, in France, and in some oilier places, we may expect its proper- ties to be more amply investigated, and applied with advantage in the arts, as the chromates of lead and iron are of excellent use in painting and enamelling. It was extracted from the red lead ore of Siberia, by treating this ore with car- bonate of potash, and separating the al- kali by means of a more powerful acid. In this state it is a red or orange-coloured powder, of a peculiar rough metallic taste, which is more sensible in it than in any other metallic acid. If this powder be exposed to the action of light and heat, it loses its acidity, and is converted into green oxide of chrome, giving out pure oxygen gas. The chromic acid is the first ACI ACI that has been found to de-oxygenate itself easily by the action of heat, and afford oxy- gen gas by this simple operation. It ap- pears that several of its properties are ow- ing to the weak adhesion of a part at least of its oxygen. The tureen oxide of chrome cannot be brought back to the state of an acid, unless its oxygen be restored by treating it wi>h some other acid. The chromic acid is soluble in water, and crystallizes, by cooling and evapora- tion, in longish prisms of a ruby red. Its taste is acrid and styptic. Its specific gra- vity is not exactly known ; but it always exceeds that of water. It powerfully red- dens the tincture of turnsole. Its action on combustible substances is little known. If it be strongly heated with charcoal, it grows black, and passes to the metallic state without melting. Ofthe acids, the action of the muriatic on it is the most remarkable. If this be distilled with the chromic acid, by a gentle heat, it is readily converted into chlorine. It likewise imparts to it by mixture the property of dissolving gold; in which the chromic resembles the nitric acid. This is owing to the weak adhesion of its oxy- gen, and it is the only one of the metallic acids that possesses this property. * The extraction of chromic acid from the French ore, is performed by igniting it with is own weight of nitre in a cruci- ble. The residue is lixiviated with water, which being then filtered, contains the chromate of potash. On pouring into this a litde nitric acid and muriate of barytes, an instantaneous precipitate of the chro- ma1 e of barytes takes place. After having procured a certain quantity of this salt, it must be put in its moist state into a cap- sule, and dissolved in the smallest possible quantity of weak nitric acid. The barytes is to be then precipitated by very dilute sulphuric acid, taking care not to add an excess of it. When the liquid is found by trial to contain neither sulphuric acid nor barytes, it must be filtered. It now con- sists of water, with nitric and chromic acids. The whole is to be evaporated to dryness, conducting the heat at the end, so as not to endanger the decomposition ofthe chmmic acid, which will remain in the capsule under the form of a reddish matter. It must be kept in a glass phial well corked. Chromic acid, heated with a powerful acid, becomes chromic oxide; while the latter, heated with the hydrate of an alka- li becomes chromic acid. As thesolution of the oxide is green and that of the acid yellow, these transmuta ions become very remarkable to the eye. From Berzelius's experiments on the combinations of the chromic acid with barytes. and oxide of lead, its prime equivalent seems to be 6.5 ; consisting of 3.5 chromium, and 3.0 oxy- gen.* See Chromium. It readily unites with alkalis, and is the only acid that has the property of colouring its salts, whence the name of chromic has been given it. If two parts ofthe red lead ore of Siberia in fine powder be boiled with one of an alkali saturated with car- bonic acid, in forty parts of water, a car- bonate of lead will be precipitated, and the chromate remain dissolved. The so- lutions are of a lemon colour, and afford crystals of a somewhat deeper hue. Those of chromate of ammonia are in yellow la- minae, having the metallic lustre of gold. The chromate of barytes is very little soluble, and that of lime still less. They are both of a pale yellow, and when heat- ed give out oxygen gas, as do the alkaline chromates. If the chromic acid be mixed with filings of tin and the muriatic acid, it becomes at first yellowish brown, and afterwards as- sumes a bluish green colour, which pre- serves the same shade after desiccation. Ether alone gives it the same dark colour. With a solution of nitrate of mercury, it gives a precipitate of a dark cinnabar co- lour. With a solution of nitrate of silver it gives a precipitate, which, the moment it is formed, appears of a beautiful carmine colour, but becomes purple by exposure to the light. This combination, exposed to the heat ofthe blow-pipe, melts before the charcoal is inflamed, and assumes a blackish and metallic appearance. If it be then pulverized, the pow der is still pur- ple; but after the blue flame of the lamp is brought into contact with this powder, it assumes a green colour, and the silver appears in globules disseminated through its substance. With nitrate of copper it gives a chesnut red precipitate. With the solution of sul- phate of zinc, muriate of bismuth, muriate of antimony, nitrate of nickel, and muriate of platina, it produces yellowish precipi- tates, when the solutions do not contain an excess of acid. With muriate of gold it produces a greenish precipitate. When melted with borax, or glass, or acid of phosphorus, it communicates to it a beautiful emerald green colour. If paper be impregnated with it, and ex- posed to the sun a few days, it acquires a green colour, which remains permanent in the dark. A slip of iron, or tin, put into its solu- tion, imparts to it the same colour. The aqueous solution of tannin produces a flocculent precipitate of a brown fawn colour. Sulphuric acid, when cold, produces no effect on it; but when warm it makes it assume a bluish green colour. Acid (Citiiic). The juice of lemons, ACI ACI or limes, has all the characters of an acid of considerable strength; but on account of the mucilaginous matter with which it is mixed, it is very soon altered by spon- taneous decomposition. Various methods have been contrived to prevent this effect from taking place, in order that this whole- some and agreeable acid might be pre- served for use in long voyages, or other domestic occasions. The juice may be kept in bottles under a thin stratum of oil, which indeed prevents, or greatly retards, its total decomposition; though the origi- nal fresh taste soon gives place to one which is much less grateful. In the East Indies it is evaporated to the consistence of a thick extract. If this operation be carefully performed by a very gentle heat, it is found to be very effectual. When the juice is thus heated, the mucilage thickens, and separates in the form of flocks, part of which subsides, and part rises to the sur- face : these must be taken out. The va- pours which arise are not acid. If the evaporation be not carried so far as to de- prive the liquid of its fluidity, it may be long preserved in well closed bottles; in which, after some weeks' standing, a far- ther portion of mucilage is separated, without any perceptible change in the acid. Of all the methods for preserving le- mon-juice, that of concentrating it by frost appears to be the best, though in the warmer climates it cannot conveniently be practised. Lemcn-juice, exposed to the air, in a temperature between 50° and 60°, deposites in a few hours a white semi- transparent mucilaginous matter, which leaves the fluid, after decantation and fil- tration, much less alterable than before. This mucilage is not of a gummy nature, but resembles the gluten of wheat in its properties: it is not soluble in water when dried. More mucilage is separated from lemon-juice by standing in closed vessels. If this depurated lemon-juice be exposed to a degree of cold of about seven or eight degrees below the freezing point, the aqueous part will freeze, and the ice may be taken away as it forms; and if the pro- cess be continued until the ice begins to exhibit signs of acidity, the remaining acid will be found to be reduced to about one-eighth of its original quantity, at the same time that its acidity will be eight times as intense, as is proved by its re- quiring eight times the quantity of alkali to saturate an equal portion of it. This concentrated acid may be kept for use, or, if preferred, it may be made into a dry le- monade, by adding six times its weight of fine loaf sugar in powder. The above processes may be used when the acid of lemons is wanted for domestic purposes, because they leave it in posses- sion of the oils, or other principles, on which its flavour peculiarly depends; but in chemical researches, where the acid it- self is required to be had in the utmost purity, a more elaborate process must be- used. Boiling lemon-juice is to be satu- rated with powdered chalk, the weight of which is to be noted, and the powder must be stirred up from the bottom, or the vessel shaken from time to time. The, neutral saline compound is scarcely more soluble in water than selenite; it there- fore falls to the bottom, while the mucil- age remains suspended in the watery fluid, which must be decanted off; the remain- ing precipitate must then be washed with warm water until it comes off clear. To the powder thus edulcorated, a quantity of sulphuric acid, equal the chalk in weight, and diluted with ten parts of wa- ter, must be added, and the mixture boil- ed a few minutes. The sulphuric acid combines with the earth, and forms sul- phate of lime, which remains behind when the cold liquor is filtered, while the disen- gaged acid of lemons remains dissolved in the fluid. This last must be evaporated to the consistence of a thin sirup, which yields the pure citric acid in little needle- like crystals. It is necessary that the sul- phuric acid should be rather in excess, because the presence of a small quantity of lime will prevent the crystallization. This excess is allowed for above. M. Dize, a skilful apothecary in Paris, who has repeated this process of Scheele on a verv extensive scale, asserts, that an excess of sulphuric acid is necessary, not only to obtain the citric acid pure, but to destroy the whole of the mucilage, part of which would otherwise remain, and occa- sion its spoiling. It is not certain, how- ever, but the sulphuric acid may act on the citric itself, and by decomposing it, produce the charcoal that M. Dize as- cribes to the decomposition of mucilage; and if so, the smaller the excess of sulphu- ric acid the better. He also adds, that to have it perfectly pure it must be repeated- ly crystallized, and thus it forms very large and accurately defined crystals in rhom- boidal prisms, the sides of which are in- clined in angles of 60° and 120°, termina- ted at each end by tetra'edral summits, which intercept the solid angles These, however, will not be obtained when ope- rating on small quantities. Its taste is extremely sharp, so as to ap. pear caustic. Distilled in a retort, part rises without being decomposed; it ap- pears to give out a portion of vinegar; it then evolves carbonic acid gas, and a little carburetted hydrogen; and a light coal re- mains. It is among the vegetable acids the one which most powerfully resists de- composition by fire. ACI In a dry and warm air it seems to efflo- resce ; but it absorbs moisture when the air is damp, and at length loses its crystal- line form. A hundred parts of this acid are soluble in seventy-five of water at 60°, according to Vauquelin. Though it is less alterable than most other solutions of vegetable acids, it will undergo decom- position when long kept. Fourcroy thinks it probable that it is converted into acetic acid before its final decomposition. It is not altered by any combustible sub- stance ; charcoal alone appears to be capa- ble of whitening it. The most powerful acids decompose it less easily than they do other vegetable acids ; but the sulphu- ric evidently converts it into acetic acid. The nitric acid likewise, according to Fourcroy and Vauquelin, if employed in large quantity, and heated on it a long time, converts the greater part of it into acetic acid, and a small portion into oxalic. Scheele indeed could not effect this; but Westrumb supposes that it was owing to his having used too much nitric acid; for on treating 60 grains of citric acid with 200 of nitric he obtained 30 grains of oxalic acid; with 300 grains of nitric acid he got 15 ; and with 600 grains no vestige of oxa- lic acid appeared If a solution of barytes be added gradu- ally to a solution of citric acid, a flocculent precipitate is formed, soluble by agitation, till the whole of the acid is saturated. This salt at first falls down in powder, and then collects in silky tufts, and a kind of very beautiful and shining silvery bushes. It requires a large quantity of water to dissolve it. The citrate of lime has been mentioned already in treating of the mode of purify- ing the acid. The citrate of potash is very soluble and deliquescent. The citrate of soda has a dull saline taste; dissolves in less than twice its weight of water; crystallizes in six-sided prisms with flat summits; effloresces slightly, but does not fall to powder; boils up, swells, and is reduced to a coal on the fire. Lime-water decomposes it, but does not render the solution turbid, notwithstanding the little solubility of ci- trate of lime. Citrate of ammonia is very soluble; does not crystallize unless its solution be great- ly concentrated; and forms elongated prisms. Citrate of magnesia does not crystallize. When its solution had been boiled down, and it had stood some days, on being slightly shaken itfixed in one white opaque mass, which remained soft, separating from the sides of the vessel, contracting its dimensions, and rising in the middle like a kind of mushroom. ACJI Its combination with the other earths has not been much examined; and its ac- tion upon metals has been little studied. Scheele however found, that it did not precipitate the nitric solutions of metals, as the malic acid does. Ml the citrates are decomposed by the powerful acids, which do not form a pre- cipitate with them, as with the oxalates and tartrates. The oxalic and tartaric acids decompose them, and form crystal- lized or insoluble precipitates in their so- lutions. All afford traces of acetic acid, or a product ofthe same nature, on being exposed to distillation: this character exists particularly in the metallic citrates. Placed on burning coals they melt, swell up, emit an empvreumatic smell of acetic acid, and leave a light coal. All of them, if dissolved in water, and left to stand for a time, undergo decomposition, deposite a flocculent mucus which grows black, and leave their bases combined with carbonic acid, one of the products of the decompo- sition. Before they are completely de- composed, they appear to pass to the state of acetates. The affinities of the citric acid are ar- ranged by Vauquelin in the following or- der: barytes, lime, potash, soda, strontian, magnesia, ammonia, alumina. Those for zircone, glucine, and the metallic oxides, are not ascertained. The citric acid is found in many fruits united with the malic acid; which see for the process of separating them in this case. * From the composition ofthe citrate of lead, as determined by Berzelius, it ap- pears that dry citric acid has for its prime equivalent 7.368, compared to yellow oxide of lead 14, and oxygen 1.0. The crystals, according to the same accurate chemist, consist of 79 real acid, and 21 water, in 100 parts. This would make the equivalent ofthe crystallized acid 9.3. Its ultimate constituents are, by the analy- sis of Hydrog. Carbon. Oxyg. G Thenard "^ } 6.330+33.811+59.859 Berzelius, ' 3.800+41.369+54.831 Citric acid being more costly than tar- taric, may be occasionally adulterated with it. This fraud is discovered, by add- ing slowly to the acid dissolved in water a solution of sub-carbonate of potash, which will give a white pulverulent precipitate of tartar, if the citric be contaminated with the tartaric acid. When one part of the citric acid is dissolved in 19 of water, the solution may be used as a substitute for lemon-juice. If before solution the crys- tals be triturated with a little sugar and a few drops of the oil of lemons, the resern- ACI ACI blance to the native juice will be com- plete. It is an antidote against sea scurvy; but the admixture of mucilage and other vegetable matter in the recent fruit ofthe lemon, has been supposed to render it preferable to the pure acid of the che- mist.* Acid (Chloric). See Acid (Muriatic) * Acid (Columbic). The experiments of Mr. Hatchett have proved, that a pecu- liar mineral from Massachusetts, deposited in the British Museum, consisted of one part of oxide of iron, and somewhat more than three parts of a white coloured sub- stance, possessing the properties of an acid. Its basis was metallic. Hence he named this olumbium, and the acid the Columbic. Dr. V\ oliaston, by very exact analytical comparisons, proved, that the acid of Mr. Hatchett, was the oxide of the metal lately discovered in Sweden by Mr. Ekeberg, in the mineral yttrotantallte, and thence called tantalum. Dr. Wollaston's method of separating the acid from the mineral is peculiarly elegant. One part of tantalite, five parts of carbonate of pot- ash, and two parts of borax, are fused to- gether in a platina crucible. The mass, after being softened in water, is acted on by muriatic acid. The iron and manga- nese dissolve, while the columbic acid re- mains at the bottom. It is in the form of a white powder, which is insoluble in ni- tric and sulphuric acids, but partially in muriatic. It forms with barytes an insolu- ble salt, of which the proportions, accord- ing to Berselius, are 24.4 acid, and 9.75 barytes. By oxidizing a portion of the re- vived tantalum or columbium, Berzelius infers the composition of the acid to be 100 metal and 5.485 oxygen. Acid (Cvamc). See Acid (Pncssic). Acid (Ftconic). The fusible spar which is generally distinguished by the name of Derbyshire spar, consists of calcareous earth in combination with the acid at pre- sent under our consideration. If the pure fluor, or spar, be placed in a retort of lead or silver, witb a receiver of the same me- tal adapted, and its weight of sulphuric acid be then poured upon it, the fluoric acid will be disengaged by the application of a moderate heat. This acid gas readily combines with water; for which purpose it is necessary that the receiver should previously be half filled with that fluid. * If the receiver be cooled with ice, and no water put in it, then the condensed acid is an intensely active liquid, first pro- cured by M. Gay-Lussac. The best account of it, however, has been given by Sir H. Davy. It has the appearance of sulphuric acid, but is much more volatile, and sends off" white fumes when exposed to air. Its specific gravity is only 1.0609. It must be examined with great caution, for when applied to the skin it instantly disorganizes it, and produces very painful wounds. When potassium is introduced into it, it acts with intense energy, and produces hydrogen gas and a neutral salt; when lime is made to act upon it, there is a vio- lent heat excited, water is formed, and the same substance as fluor spar is pro- duced. With water in a certain propor- tion, its density increases to 1.25. When it is dropped into water, a hissing noise is produced with much heat, and an acid fluid not disagreeable to the taste is form- ed if the water be in sufficient quantity. It instantly corrodes and dissolves glass. It appears extremely probable, from all the facts known respecting the fluoric combinations, that fluor spar contains a peculiar acid matter; and that this acid matter is united to lime in the spar, seems evident from the circumstance, that gyp- sum or sulphate of lime is the residum of the distillation of fluor spar and sulphuric acid. The results of experiments on fluor spar have been differently stated by chem- ists. Sir H. Davy states, that 100 floor spar yield 175.2 sulphate of lime; whence we deduce the prime equivalent of fluoric acid to be 1.3260, to lime, 3.56, and oxygen 1.00. From fluate of potash the equiva- lent comes out for the acid, «= 1.2495, potash being reckoned 5.95. Berzelius in his last series of experiments gives from fluate of lime, 1.374 for the equivalent of fluoric acid. The dense fluid obtained in silver vessels, may be regarded as hydro- fluoric acid; and, supposing all the water in oil of vitriol transferred to it, would con- sist of 1.326 or 1.374 acid,+ 1.125 water; which is a prime of each. Dr. Thomson, in his System of Chemistry fifth edition, vol. i. p. 203, deduces the equivalent of fluoric acid from the decom- position of fluate of lime by sulphuric acid, to be 1.0095; and, from the lowness of this number, he afterwards endeavours to prove that fluoric acid cannot be a com- pound of oxygen with a base. Now taking his own data of 100 parts of fluor spar yielding, according to Sir II. Davy's latest experiments, 175.2 sulphate of lime ; and admitting that these contain 73.582 of lime; leaving consequently 26.418 for the proportion of acid in 100 of fluorspar, we shall find 1.3015 to be the equivalent or atom of fluoric acid. For 73.582: 3.625 : -6.418: 1.3015, taking his own number 3.625 for the atom of lime. Hence the whole difficulties stated by him in the fol- lowing passage, page 206, disappear:—" If we suppose fluate of lime to be a com- pound of fluoric acid and lime, its compo- sition will be, Fluoric acid, 1.0095. Lime. 3.625 From this we see that the weight of an integrant particle of fluoric acid must be ACI 1.0095. If it be supposed a compound of one atom of oxygen, and one atom of an unknown inflammable basis, then as the weight of an atom of oxygen is 1, the weight of an atom ofthe inflammable base can be only 0.0095, which is only the thirteenth part of the weight of an atom of hydrogen. On that supposition, fluoric acid would be composed of Inflammable basis, 1.00 Oxygen, 105.67. So very light a body, being contrary to all analogy, cannot be admitted to exist without stronger proofs than have hitherto been adduced. On the other hand, if fluorspar be in reality a fluoride of calci- um, then its composition will be, Fluorine, 2.0095 Calcium, 2.625 So that the weight of an atom of fluorine would be 2.0095, or almost exactly twice the weight of an atom of oxygen. This is surely a much more probable supposition than the former." It is not possible to find a more instruc- tive example than the one now afforded by this systematic chemist, of the danger of prosecuting, on slippery grounds, hy- pothetical analogies. The atom of fluoric acid, when rightly computed with his own data, is not 1*0095. but 1.3015, and hence none of his consequences need be consi- dered. It may consist of 1 of oxygen combined with 0.3015 of an unknown rad- ical ; or there may, for aught we know, be a substance analogous to chlorine and iodine, to be called therefore fluorine, whose prime equivalent will be 2.3015 From the mode in which liquid fluoric acid is produced viz. from a mixture of fluor spar, and oil of vitriol, it may obvious- ly contain water, and may consist, as we have seen, probably of a prime or atom of real acid, and an atom of water. Hence the phenomena occasioned by adding pot- assium to it, present nothing different from those exhibited bjj the same metal added to concentrated hydro-nitric or hydro-sulphuric acid. Sir H. Davy indeed has been induced in his last researches to infer, from the action of ammoniacal gas on the liquid fluoric acid, that it contains no water. On this subject Dr. Thomson has the following aphorism: " When any acid that contains water is combined in this manner with ammoniacal gas, if we heat the salt formed, water is always disengag- ed. Thus sulphuric acid, or nitric acid, or phosphorous acid, when saturated with ammoniacal gas and heated, give out always abundance of water. But fluate of ammonia, when thus treated, gave out no water. Hence we have no evidence that fluoric acid contains any water." The whole of this reasoning is visionary. ACI It has been proved in my experimental researches on the ammoniacal salts, in- serted in the tenth volume ofthe Annals of Philosophy, that the sulphate and ni- trate of ammonia, in the driest state to which they can be brought by heat, short of their decomposition, contain one atom or prime equivalent of water, which is in- deed essential to their very existence, and which water cannot be separated by heat alone. If concentrated oil of vitriol be sa- turated with dry ammoniacal gas, a solid salt will be obtained, from which heat alone will not separate the proportion of water it contains, and which amounts to 13.6 per cent. A stronger heat will merely separate a portion of the ammonia from the acid, or volatilize both. In the former case the acid retains its atom of water. Hence we see, that no inference whatever can be drawn from the ammoniacal com- bination with liquid fluoric acid, to nega- tive the probability that it may contain, from the mode of its extraction, combined water, like the sulphuric and nitric acids. The inferences from the analogous ac- tions of potassium on the muriate and fluate of ammonia, are all liable to the same Fallacy. If the combined water of the fluoric acid pass into the salt, as with sulphuric acid it undoubtedly does, then hydrogen and fluate of potash ought to result, from the joint actions of potassium and the %r/ro-fluoric acid. The chocolate powder which is evolved at the positive pole, and the hydrogen at the negative, when liquid fluoric acid was subjected by Sir H. Davy to the voltaic power, can justify no decisive opinion on this in ricate research. The mere coating of the platinum wire may as well be re- garded as the fluate of platinum, as a fluor- ide. Nor does the decomposition ofthe filiates of silver and mercury, when heated in glass vessels with chlorine, seem to prove any thing whatever. The oxygen evolved, is obviously separated from the oxides ofsilveror mercury when acted on bv chlorine; and the dry fluoric acid unites to the silica of the glass, forming silicated fluoric gas, or fluo-silicic acid. In thus showing the inconclusiveness of Dr. Thomson's four different arguments, to prove that fluoric acid is a compound of an unknown radical, fluorine, with hydro- gen, and not of an unknown radical, which might be termed fluor, with oxygen; one cannot help, however, expressing a high admiration of Sir H. Davy's experimental researches on fluoric acid, which were published in the second part ofthe Phil- osophical Transactions for 1813. He did all which the existing resources of science could enable genius and judgment to ac- complish. The mystery in which the subject obviously and confessedly re mains; ACI ACI must be removed by further investigations, and not by analogical assumptions. These, indeed, by giving resting points to the imagination, of which it becomes found, powerfully tend to obstruct the advance- ment of truth. The principal reason for considering fluoric acid as a compound of fluorine with hydrogen, seems on the whole to be the analogy of chlorine. But the analogy is in- complete. Certainly it is consonant to the true logic of chemical science to regard chlorine as a simple body, since every at- tempt to resolve it into simpler forms of matter has failed. But fluorine has not been exhibited in an insulated state like chlorine ; and here therefore the analogy does not hold. With the view of separating its hydro- gen, Sir H. Davy applied the power ofthe great voltaic batteries of the royal Institu- tion to the liquid fluoric acid. " In this case, gas appeared to be produced from both the negative and positive surfaces; but it was probably only the undecom- pounded acid rendered gaseous, which was evolved at the positive surface ; for during the operation the fluid became very hot, and speedly diminished." " In the course of these investigations I made several attempts to detach hydrogen from the liquid fluoric acid, by the agency of oxygen and chlorine. It was not decom- posed when passed through a plat'.natube heated red hot with chlorine, nor by being distilled from salts containing abundance of oxygen, or those containing abundance Of chlorine." By the strict rules of chem- ical logic, therefore, fluoric acid ought to be regarded as a simple body, for we have no evidence of its ever having been de- composed ; and nothing but analogy with the other acid bodies has given rise to the assumption of its being a compound. There is no difficulty in imagining a radical to exist, whose saturating powers are exactly one-third of those of hydrogen; for 0.375 is precisely thrice 0.125, the weight of the prime equivalent of hydro- gen; and one-half of 0.750, the equivalent of carbon. Those who are allured by the harmony of numbers, might possibly con- sider these examples of accordance, as of some value in the discussion. The marvellous activity of fluoric acid may be inferred from the following re- marks of Sir II. Davy, from which also may be estimated in some measure the prodigious difficulty attending refined in- vestigations on this extraordinary sub- stance. " I undertook the experiment of elec- trizing pure liquid fluoric acid with con- siderable interest, as it seemed to offer the most probable method of ascertaining its real nature ; but considerable difficulties occurred in executing the process. The liquid fluoric acid immediately destroys glass, and all animal and vegetable sub- stances ; it acts on all bodies contain- ing metallic oxides; and I know of no sub- stances which are not rapidly dissolved or decomposed by it, except metals, char- coal, phosphorus, sulphur, and certain combinations of chlorine. I attempted to make tubes of sulphur, of muriates of lead and of copper containingmetallic wires, by which it might be electrized, but with- out success. I succeeded, however, in bor- ing a piece of horn silver in such a man- ner that I was able to cement a platina wire into it by means of a spirh lamp; and by inverting this in a tray of platina, filled with liquid fluoric acid, I contrived to submit the fluid to the agency of elec- tricity in such a manner, that, in succes- sive experiments, it was possible to col- lect any elastic fluid that might be pro- duced Operating in this way with a very weak voltaic power, and keeping the apparatus cool by a freezing mixture I ascertained that the pla ina wire at the positive pole rapidly corroded, and be- came covered with a chocolate powder; gaseous matter separated at the negative pole, which I could never obtain in suffi- cient quantities to analyze with accuracy, but it inflamed like hydrogen. No other inflammable matter was produced when the acid was pure." We beg to refer the reader to the Philosophical Transactions for 1813 and 1814; or the 42d and 43d vols, of Tilloch's Magazine, where he will see philosophical sagacity and experimen- tal skill in their utmost variety and vigour, struggling with the most mysterious and intractable powers of matter. If instead of being distilled in metallic vessels, the mixture of fluor spar and oil of vitriol be distilled in glass vessels, little ofthe corrosive liquid will be obtained ; but the glass will be acted upon, and a peculiar gaseouf substance will be pro- duced, which must be collected over mer- cury. The best mode of procuring this gaseous body is to mix the fluor spar with pounded glass or quartz; and in this case, the glass retort may be preserved from corrosion, and the gas obtained in greater. quantities. This gas, which is called sili- cated fluoric gas, is possessed of very ex- traordinary properties. It is very heavy ; 100 cubic inches of it weigh 110.77 gr. andhenceitssp.gr is to that of air, as 3.632 is to 1.000. It is about 48 times denser than hydrogen. When brought into contact with water, it instantly deposites a white gelatinous sub- stance, which is hydrate of silica; it pro- duces white fumes when suffered to pass into the atmosphere. It is not affected by any of the common combustible bodies; ACI ACI but when potassium is strongly heated in it, it takes fire and burns with a deep red light; the gas is absorbed, and a fawn-co- loured substance is formed, which yields alkali to water with slight effervescence, and contains a combustible body. The washings afford potash and a salt, from which the strong acid fluid previously de- scribed, may be separated by sulphuric acid. The gas formed by the action of liquid sulphuric acid on a mixture containing silica and fluor spar, the silicated fluoric gas orfluo-silicic acid, may be regarded aS a compound of fluoric acid and silica. It affords, when decomposed by solution of ammonia, 61.4 per cent of silica; and hence was at first supposed by Sir H. Da- vy to consist of two prime proportions of acid = 2.652 and one of silica = 4.066, the sum of which numbers may represent its equivalent = 6.718. One volume of it con- denses two volumes of ammonia, and they form together a peculiar saline substance which is decomposed by water. The com- position of this salt is easily reconciled to the numbers given as representing silica and fluoric acid, on the supposition that it contains I prime of ammonia to 1 of the fluosilicic gas; for 200 cubic inches of am- monia weigh 36.2 gr. and 100 of the acid gas 110.77. Now 36.2 : 2.13 : : 110.77 : 6.52. Dr. John Davy ob'ained, by exposing this gas to the action of water,^*^. of its weight of silica; and from the action of water of ammonia he separated -AVi of its weight. Hence 100 cubic inches consist by weight of 68 silica and 42 of unknown fluoric matter, the gas which holds the silica in solution. Sir H. Davy, however, conceives that this gas is a compound of the basis of silica, or silicon, with fluorine, the supposed basis of fluoric acid. If, instead of glass or silica, the fluor spar be mixed with dry vitreous boracic acid, and distilled in a glass vessel with sulphu- ric acid, the proportions being one part boracic acid, two fluor spar, and twelve oil of vitriol, the gaseous substance formed is of a different kind, and is called thefluo- boric gas. 100 cubic inches of it weigh 73.5 gr. according to Sir II. Davy, which makes its density to that of air as 2.41 is to 1.00; but M. Thenard, from Dr. John Davy, states its density to that of air as 2.371 to 1.000. It is colourless; its smell is pungent, and resembles that of muriatic acid; it cannot be breathed without suf- focation ; it extinguishes combustion ; and reddens strongly the tincture of turnsole. It has no manner of action on glass; but a very powerful one on vegetable and ani- mal matter: It attacks them with as much force as concentrated sulphuric acid, and appears to operate on these bodies by Vol.. i. [ 6 ] the production of water; for while it car* bonizes them, or evolves carbon, they may be touched without any risk of burning. Exposed to a high temperature, it is not decomposed; it is condensed by cold without changing its form. When it is put in contact with oxygen, or air, either at a high or low temperature, it experiences no change, except seizing, at ordinary temperatures, the moisture which these gases contain. It becomes in consequence a liquid which emits extremely dense va- pours It operates in the same way with all the gases which contain hy grometric yater. However little they may contain, it occasions in them very perceptible va- pours. It day hence be employed with ad- vantage to show whether or not a gas con- tains moisture. No combustible body, simple or com- pound, attacks ftuoboric gas, if we except the alkaline metals. Potassium and sodi- um with the aid of heat, burn in this gas, almost as brilliantly as in oxygen. Boron and fluate of potash, are the products of this decomposition. It might hence be in- ferred that the metal seizes the oxygen of the boracic acid, sets the boron at liberty, and is itself oxidized and combined with the fluoric acid. According to Sir H. Da- vy's views, the fluoboric gas being a com- pound of fluorine and boron, the potassium unites to the former, giving rise to the fluoride of potassium, while the boron re« mains disengaged. Fluoboric gas is very soluble in water. Dr. John Davy sa)s, water can combine with 700 times its own volume, or twice its weight at the ordinary temperature and pressure of the air. The hquid has a spe- cific gravity of 1.770. If a bottle contain- ing this gas be uncorked under water, the liquid will rush in and fill it with explosive violence. Water saturated with this gas is limpid, fuming and very caustic. By heat, about one-fifth of the absorbed gas may be expelled; but it is impossible to abstract more. It then resembles concentrated sul- phuric acid, and boils at a temperature considerably above 212°. It afterwards condenses altogether, in strix, although it contains still a very large quantity of gas. It unites with the bases, forming salts, call- ed fluoborates, none of which has been applied to any use. The most important will be described under their respective bases. The 2d part of the Phil. Transactions for 1812, contains an excellent paper by Dr. John Davy on fluosilicic and fluoboric gases, and the combinations of the latter with ammoniacal gas. When united in equal volumes, a pulverulent salt is form- ed; a second volume of ammonia, howev- er, gives a liquid compound; and a third of ammonia, which is the limit of combr- ACI ACI nation, affords still a liquid; both of them curious on many accounts. " They are," savs he, " the first salts that have been ob- served hquid at the common temperature ofthe atmosphere. And they are addition- al facts in support of the doctrine of defi- nite proportions, and ofthe relation of vol- umes." The fluosilicic acid also unites to bases forming fluosilicates. If we regard fluoric acid as capab'e of combining, like the sulphuric, nitric, and carbonic acids, with the oxidized bases, the weight of its prime equivalent is 1.375; whence all its neutral compounds may be inferred ; but if we suppose that it is fluo- rine alone which unites to the metallic bases, then the prime of oxygen must be subtracted from them and added to its weight, which will make it 2.375. This is exactly like a man taking a piece of money out of the one pocket, and putting it in the other. All the proportions experimen- tally associated with the compound, re- main essentially the same.* From the remarkable property fluoric acid possesses of corroding glass, it has been employed for etching on it, both in the gaseous state and combined with wa- ter; and an ingenious apparatus for this purpose is given by Mr. Richard Knight, in the Philosophical Magazine, vol. xvii. p. 357. M. Kortum, of Warsaw, having found that some pieces of glass were more easily acted upon by it than others, tried its ef- fect on various stones. Rock crystal, ruby, sapphire, lux sapphire, emerald, oriental garnet, amethyst, chrysolite, aventurine, girasol, a Saxon topaz, a Brazilian topaz burnt, and an opal, being exposed to the fluoric gas at a temperature of 122° F. was not acted upon. Diamond exposed to the vapour on a c mmon German stove for four days, was unaffected. Of polished granite, neither the quarts nor mica ap- peared to be attacked, but the feldspar was rendered opaque and muddy, and co- vered with a white powder. Chrysoprase, an opal from Hungary, onyx, a carnelian from Persia, agate, chalcedony, green Si- berian jasper, and common flint, were etched by it in twenty-four hours; the chrysoprase near half a line deep, the onyx pretty deeply, the opal with the finest and most regular strokes, and all the rest more or less irregularly. The un- covered part of the brown flint had be- come white, but was still compact: water, alcohol, and other liquids, rendered the whiteness invisible, but as soon as the flint became dry, it appeared again. The same effect was produced on carnelian, and on a dark brown jasper, if the operation of the acid were stopped, as soon as it had whitened the part exposed, without de- stroying its texture. A piece of black flint, with efflorescent white spots, and partly covered with the common white crust, be- ing exposed five davs to the g;»s at a heat of about 68° F. was reduced from 103 grains to 91, and rendered white through- out. Some parts of it were rendered fria- ble. White Carrara marble in twenty four hours, at 77°, lost l-30th of its weight, but the shining surface of its crystallized tex- ture was distinguishable. Black marble was not affected, either in weight or co- lour, and agate was not attacked. Trans- parent foliated gypsum fell into white powder on its surface, in a few hours ; but this powder was not soluble in dilute ni- tric acid,—so that the fluoric acid had not destroyed the combination of its princi- ples ; but deprived it of its water of crys- tallization. A striated zeolite, weighing 102 grains, was rendered friable on its sur- face in forty-eight hours, and weighed only 851 grains. On being immersed in water, and then dried, it gained 2£ grains, but did not recover its lustre. Barytes of a fi- brous texture remained unchanged. A thin plate of Venetian talc, weighing 124 gr. was reduced to 81 grains in forty-eight hours, and had fallen into a soft powder, which floated on water. M. Kortum pour- ed water on the residuum in the appara- tus, and the next day the sides were in- crusted with small crystalline glittering flakes, adhering in detached masses, which could not be washed off with dilute ni- trous acid. Ofthe combinations of this acid with most of the bases little is known. The native fluate of lime, the fluor spar already mentioned, is the most common. It is rendered phosphorescent by heat, but this property gradually goes off, and can« not be produced a second time. With a strong heat it decrepitates. At a heat of 130° of Wedgwood, it enters into fusion in a clay crucible. It is not acted upon by the air, and is insoluble in water. Concen- trated sulphuric acid deprives it ofthe flu- oric acid with effervescence, at the com- mon temperature, but heat promotes its action. Besides its use for obtaining this acid, it is much employed in chimney or- naments, and as a flux for some ores and stones. The fluoric acid takes barytes from the nitric and muriatic, and forms a salt very little soluble, that effloresces in the air. With magnesia, it precipitates, accord- ing to Scheele, in a gelatinous mass. But Bergmann says, that a part remains in so- lution, and by spontaneous evaporation, shoots on the sides of the vessel into crys- talline threads, resembling a transparent mass. The bottom of the vessel affords al- so crystals in hexagonal prisms, ending in a low pyramid of three rhombs. He adds, that no acid decomposes it in the moist ACI ACI Way, and that it is unalterable by the most violent fire. The fluate of potash is not crystalliza- ble ; and if it be evaporated to dryness, it soon deliquesces. Its taste is somewhat acrid and saline. It melts with a strong heat, is afterward caustic, and attracts moisture. This fluate, as well as those of soda and ammonia, are commonly obtained, as Four- croy conceives, in the state of triple salts, being combined with siliceous earth. The fluate of soda affords small crystals in cubes and parallelograms, of a bitterish and astringent taste, decrepitating on burn- ing coals, and melting into semitransparent globules with the blowpipe, without losing their acid. It is not deliquescent, and dif- ficultly soluble. The concentrated acids disengage its acid with efferv esence- The fluate of ammonia maybe prepared by adding carbonate of ammonia to diluted fluoric acid in a leaden vessel, observing, that there is a small excess of acid. This is a very delicate test of lime. Fourcroy informs us, that ammonia and magnesia form a triple salt with the fluoric acid. Scheele observed, that the fluor acid united with alumina into a salt that could not be crystallized, but assumed a gela- tinous form. Fourcroy adds, that the solu- tion is always acid, astringent, decompo- sable and precipitabie by all the earthy and alkaline bases, but capable of uniting with silex and the alkalis into various triple salts. A native combination of alumina and soda with fluoric acid, has been found late- ly in a semitransparent stone from Green- land. See Cnroi.iTE. The affinity of the fluoric acid for silex, has already appeared. If the acid solution of fluate of silex, obtained by keeping the solution of the acid in glass vessels, be evaporated to dryness, the fluoric acid may be disengaged from the solid salt remain- ing, as Fourcroy informs us, either by the powerful acids, or by a strong heat; and if the solution be kept in a vessel that ad- mits of a slow evaporation, small brilliant crystals, transparent, hard, and apparently of a rhomboidal figure, will form on the bottom ofthe vessel, as Bergmann found in the course of two years' standing. Besides the fluor spar and cryolite, in which it is abundant, fluoric acid has been detected in the topaz ; in wavellite, in which, however, it is not rendered sensi- ble by sulphuric acid; and in fossil teeth and fossil ivory, though it is not found in either of these in their natural state. Acids (Ferropklssic and Fkrulextted Chtazic). See Acid (Pbussic). Acid (Formic). It has long been known, that ants contain a strong acid, which they occasionally emit; and which may be ob- tained from the ants, either by simple dis- tillation, or by infusion of them in boiling water, and subsequent distillation of as much ofthe water as can be brought over without burning the residue. After this it may be purified by repeated rectifications, or by boiling to separate the impurities; or after rectification it may be conoentrated by frost. * This acid has a very sour taste, and continues liquid even at very low temper- atures. Its specific gravity is 1.1168 at 68Q, which is much denser than acetic acid ever is. Berzelius finds, that the formiate of lead consists of 4.696 acid, and 14 oxide of lead ; and that the ultimate constituents ofthe dry acid are hydrogen 2.84 + car- bon 32.40+ oxygen 64.76 = 100.* We have been informed, that it has been employed among quacks, as a wonderful remedy for the toothach, by applying it to the tooth with the points of the forefinger and thumb. * Acid (Fungic). The expressed juice ofthe boletus juglandis, boletus pseudo-igni- arius, the phallus impudicus, merulius can- tharellus, or the peziza nigra, being boiled to coagulate the albumen, then filtered, evaporated to the consistence of an ex- tract, and acted on by pure alcohol, leaves a substance which has been called by Braconnot Fungic Acid. He dissolves that residue in water, added solution of acetate of lead, whence resulted fungate of lead, which be decomposed at a gentle heat by dilute sulphuric acid. The evolved fun- gic acid being saturated with ammonia, yielded a crystallized fungate of ammonia, which he purified by repeated solution and crystallization. From this salt by ace- tate of lead, and thereafter sulphuric acid as above detailed, he procured the pure fungic acid. It is a colourless, uncrystallizable, and deliquescent mass, of a very sour taste. The fungates of potash and soda, are un- crystallizable ; that of ammonia forms re- gular six-sided prisms; that of lime is moderately soluble, and is not affected by the air; that of barytes is soluble in IS times its weight of water, and crystallizes with difficulty; that of magnesia appears in soluble granular crystals. This acid pre- cipitates from the acetate of lead a white flocculent fungate, which is soluble in dis- tilled vinegar. When insulated, it does not affect solution of nitrate of silver; but the fungates decompose this salt.* Acin (Gallic). This acid is found in different vegetable substances possessing astringent properties, but most abundant- ly in the excrescences termed galls, or nut- galls, whence it derives its name. It may be obtained by macerating galls in water, filtering, and suffering the liquor to stand exposed to the air. It will grow moiidy, ACI ACI be covered with a thick glutinous pellicle, abundance of glutinous flocks will fall down, and, in the course of two or three months, the sides ofthe vessel will appear covered with small yellowish crystals, abundance of which will likewise be found on the under surface of the supernatant pellicle- These crystals may be purified by solution in alcohol, and evaporation to dryness. Or muriate of tin may be added to the infusion of galls, till no more precipitate falls down ; the excess of oxide of tin re- maining in the solution, may then be pre- cipitated by sulphuretted hydrogen gas, and the hquor will yield crystals of gallic acid by evaporation. A more simple process, however, is that of M. Fiedler. Boil an ounce of powdered galls in sixteen ounces of water to eight, and strain. Dissolve two ounces of alum in water, precipitate the alumina by car- bonate of potash ; and, after edulcorating it completely by repeated ablutions, add it to the decoction, frequently stirring the mixture with a glass rod. The next day filter the mixture ; wash the precipitate with warm water, till this will no longer blacken sulphate of iron; mix the wash- ings with the filtered liquor, evaporate, and the gallic acid will be obtained in fine needled crystals. These crystals obtained in any of these ways, however, according to Sir H. Davy, are contaminated w ith a small portion of extractive matter; and to purify them they may be placed in a glass capsule in a sand heat, and sublimed into another capsule, inverted over this and kept cool. M. De- yeux indeed recommends to procure the acid by sublimation in the first instance ; putting the powdered galls into a glass retort, and applying heat slowly and cau- tiously; when the acid will rise, and be condensed in the neck of the retort. This process requires great care, as, if the heat be carried so far as to disengage the oil, the crystals will be dissolved immediately. The crystals thus obtained are pretty large, laminated, and brilliant. The gallic acid, placed on a red-hot iron, burns with flame, and emits an aro- matic smell, not unlike that of benzoic acid. It is soluble in 20 parts of cold water, and in 3 parts at a boiling heat. It is more so- luble in alcohol, which takes up an equal weight if heated, and one-fourth of its weight cold. * It has an acido-astringent taste, and reddens tincture of litmus. It does not at- tract humidity from the air. From the gallate of lead, Berzelius infers the equivalent of this acid to be 8.00. Its ultimate constituents are, hydrogen 5.00 + carbon 56.64 + oxygen 38.36 = 100. This acid, in its combinations with the salifiable bases, presents some remarkable phenomena. If we pour its aqueous solu- tion by slow degrees into lime, barytes, or strontian water, there will first be formed a greenish white precipitate. As the quan- tity of acid is increased, the precipitate changes to a violet hue, and eventually disappears. The liquid has then acquired a reddish tint. Among the salts those only of black oxide, and red oxide of iron, are decomposed by the pure gallic acid. It forms a blue precipitate with the first, and a brown with the second. But when this acid is united with tannin, it decom- poses almost all the salts ofthe permanent metals.* Concentrated sulphuric acid decompo- ses and carbonizes it; and the nitric acid converts it into malic and oxalic acids. United with ban tes, stuontian, lime, and magnesia, it forms salts of a dull y ellow colour, which are little soluble, but more so if their base be in excess. With alkalis, it forms salts that are not very soluble in general. Its most distinguishing characteristic is its great affinity for metallic oxides, so as, when combined with tannin, to take them from powerful acids. The more readily the metallic oxides part with their oxy- gen, the more they are alterable by the gallic acid. To a solution of gold, it im- parts a green hue; and a brown precipi- tate is formed, which -readily passes to the metallic state, and covers the solution with a shining golden pellicle. With ni- tric solution of silver, it produces a similar effect. Mercury it precipitates of an orange yellow; copper, brown; bismuth, of a le- mon colour; lead, white; iron, black. Pla- tina, zinc, tin, cobalt, and manganese, are not precipitated by it. The gallic acid is of extensive use in the art of dyeing, as it constitutes one of the principal ingredients in all the shades of black, and is employed to fix or improve several other colours. It is well known as an ingredient in ink. See Galls, Dte- inb and Ink. * Arid (Hydrocyanic). See Acn» (Pnussic). * Acid (Hydhiodic). This acid resem- bles the muriatic in being gaseous in its insulated state. If four parts of iodine be mixed with one of phosphorus, in a small glass retort, applying a gentle heat, and adding a lew drops of water from time to time, a gas comes over, which must be received in the mercurial bath. Its spe- cific gravity is 4.4; 100 cubic inches, therefore, weigh 134 2 grains. It is elas- tic and invisible, but has a smell some- what similar to that of muriatic acid. Mer- cury after some time decomposes it, seiz- ing its iodine, and leaving its hydrogen equal to one-half the original bulk, at li- ACI ACI berty. Chlorine, on the other hand, unites to its hydrogen, and precipitates the iodine. From these experiments, it evidently consists of vapour of iodine and hydrogen, which combine in equal vo- lumes, without change of their primitive bulk. Its composition by weight, is there- fore 8.61 of iodine + 0.0694 hydrogen, which is the relation of their gasiform densities; and if 8.t»l be divided by U.0694, it will give the prime of iodine 124 times greater than hydrogen; and as the prime of oxygen is eight times more than that of hydrogen, on dividing 124 by 8, we have 15.5 for the prime equivalent of iodine ; to which, if we add 0.125, the sum 15.625 represents the equivalent of hydriodic acid. The number deduced for iodine, from the relation of iodine to hydrogen in volume, approaches very nearly to 15.6 Jl, which was obtained in the other experi- ments of M. Gay-Lussac. Hydriodic acid is partly decomposed at a red heat, and the decomposition is complete, if it be mixed with oxygen. Water is formed and iodine separated. M. Gay-Lussac, in his admirable memoir on iodine and its combinations, published in the Ann. de Chimie, vol. xci. says, that the specific gravity he there gives for hy- driodic gas, viz. 4.443, must be a little too great, for traces of moisture were seen in the inside of the bottle. In fact, if we take 15.621 as the prime of iodine to oxy- gen, whose specific gravity is 1.1111; and multiply one-half of this number by 15 621, as he does, we shall have a pro- duct of 8.6696, to which adding 0.0694 for the density of hydrogen, we get the sum 8.7390, one-half of which is obvious- ly the density of the hydriodic gas = 4.3695. When the prime of iodine is ta- ken at 15.5, then the density of the gas comes out 4.3. We can easily obtain an aqueous hy- driodic acid very economically, by pass- ing sulphuretted hydrogen gas through a mixture of water and iodine in a Woolfe's bottle. On heating the liquid obtained, the excess of sulphur flies off, and leaves liquid hydriodic acid. At temperatures below 262°, it parts with its water; and becomes of a density = 1.7. At 262° the acid distils over. When exposed to the air, it is speedily decomposed, and iodine is evolved. Concentrated sulphuric and nitric acids also decompose it. When poured into a saline solution of lead, it throws down a fine orange precipitate. With solution of persxide of mercury, it gives a red precipitate ; and with that of silver, a white precipitate insoluble in am- monia. Hydriodic acid may also be form- ed, by passing hydrogen over iodine at an elevated temperature. The compounds of hydriodic acid with the salifiable bases may be easily formed, either by direct combination, or by acting on the basis in water, with iodine. The latter mode is most economical. Upon a determinate quantity of iodine, pour solu- tion of potash or soda, till the liquid ceases to be coloured. Evaporate to dryness, and digest the dry salt in alcohol of the specific gravity 0.810, or 0.820. As the iodate is not soluble in this liquid, while the hydriodate is very soluble, the two salts easily separate from each other. Af- ter having washed the iodate two or three times with alcohol, dissolve it in water, and neutralize it with aceic acid. Eva- porate to dryness, and digest the dry salt in alcohol, to remove the acetate. After two or three washings, the iodate is pure. As for the alcohol containing the hydrio- date, distil it off', and then complete the neutralization of the potash, by means of a little by driodic acid separately obtained. Sulphurous and muriatic acids, as well as sulphuretted hydrogen, produce no change on the hydriodates, at the usual tempera- ture of the air. Chlorine, iiitric acid, and concentrated sulphuric, instantly decompose them, and separate the iodine. With solution of silver, they give a white precipitate insoluble in ammonia; with the pernitrate of mercury, a greenish yellow precipitate; with corrosive sublimate, a precipitate of a fine orange red, very so- luble in an excess of hydriodate; and with nitrate of lead, a precipitate of an orange yellow colour. They dissolve iodine, and acquire a deep reddish brown colour. Hydriodate of potash, or in the dry state, iodide of potassium, yields crystals hke sea-salt, which melt and sublime at a red heat. This salt is not changed by being heated in contact with air. 100 parts of water at 64°, dissolve 143 of it. It con- sists of 15.5 iodine, and 4.95 potassium. Hydriodate of soda, called in the dry state iodide of sodium, may be obtained in pretty large flat rhomboidal prisms. These prisms unite together with larger ones, terminated in echellon, and striated long- ways, like those of sulphate of soda. This is a true hydriodate, for it contains much water of crystallization. It consists, when dry, of 15.5 iodine + 2.95 so- dium. Hydriodate of barytes crystallizes in fine prisms, similar to muriate of strontian. In its dry state, it consists of 15.5 iodine + 8.7 or 8.75 barium. The hydriodates of lime and strontian are very soluble; and the first exceedingly deliquescent. Hydriodate of ammonia results from the combination of equal volumes of ammonia- cal and hydriodic gases; though it is usual- ly prepared by saturating the liquid acid ACI ACI with ammonia. It is nearly as volatile as sal ammoniac; but it is more soluble and more deliquescent. It crystallizes in cubes. From this compound, we may infer the prime of hydriodic acid, from the specific gravity ofthe hydriodic gas; or having the prime, we may determine the sp. gr. If we call 15.625 its equivalent, then we have this proportion:—As a prime of am- monia, to a prime of hydriodic acid, so is the density of ammoniacal, to that of hy- driodic gas. 2.13 : 15.625 : : 0.59 : 4.328. ^ This would make 100 cubic inches weigh exactly 132 grains. Hydriodate of magnesia is formed by unit- ing its constituents together; it is deli- quescent, and crystallizes with difficulty. It is decomposed by a strong heat. Hydriodate of zinc is easily obtained, by putting iodine into water with an excess of zinc, and favouring their action by heat. When dried it becomes an iodide. All the hydriodates have the property of dissolving abundance of iodine; and thence they acquire a deep reddish brown colour. They part with it on boiling, or when exposed to the air after being dried.* * Acid (Iodic). When barytes water is made to act on iodine, a soluble hydrio- date, and an insoluble iodate of barytes, are formed. On the latter, well washed, pour sulphuric acid equivalent to the ba- rytes present, diluted with twice its weight of water, and heat the mixture. The iodic acid quickly abandons a portion of its base, and combines with the water; but though even less than the equivalent proportion of sulphuric acid has been used, a little of it will be found mixed with the liquid acid. If we endeavour to separate this portion, by adding barytes water, the two acids precipitate together. The above economical process is that of M. Gay-Lussac; but Sir H. Davy, who is the first discoverer of this acid, invented one more elegant, and which yields a fmrer acid. Into a long glass tube, bent ike the letter L inverted (7), shut at one end, put 100 grayis of chlorate of potash, and pour over it 400 grains of muriatic acid, specific gravity 1.105. Put 40 grains of iodine into a thin long-necked receiver. Into the open end of the bent tube put some muriate of lime, and then connect it with the receiver. Apply a gentle heat to the sealed end of the former. Pro- toxide of chlorine is evolved, which, as it comes in contact with the iodine, pro- duces combustion, and two new com- pounds, a compound of iodine and oxy- gen, and one of iodine and chlorine. The latter is easily separable by heat, while the former remains in a state of purity. The iodic acid of Sir H. Davy is a white semi-transparent solid. It has a strong acido-astringent tasie, but no smell. Its density is considerably greater than that of sulphuric acid, in which it rapidly sinks. It melts, and is decomposed into iodine and oxygen, at a temperature of about 620°. A grain of iodic acid gives out 176.1 grain measures of oxygen gas. It would appear from this, that iodic acid consists of 15.5 iodine, to 5 oxygen. This agrees with the determination of M. Gay-Lussac, obtained from much greater quantities; and must therefore excite ad- miration at the precision of result derived by sir H. from the very minute propor- tions which he used. 176.1 grain mea- sures, are equal to 0.7 of a cubic inch; which, calling 100 cubic inches 33.88, will weigh 0 237 of a grain, leaving 0.763 for iodine. And 0.763 : 0.2.57 : : 15.5 : 5.0. Iodic acid deliquesces in the air, and is, of course, very soluble in water. It first reddens, and then destroys the blues of vegetable infusions. It blanches other ve- getable colours. By concentration ofthe liquid acid of Gay-Lussac, it acquires the consistence of sirup. Had not the happy genius of Sir H. Davy produced it in the solid state, his celebrated French rival would have persuaded us to suppose that state impossible. " Hitherto," says M. Gay-Lussac, "iodic acid has only been obtained in combination with water, and it is very probable that this liquid is as necessary as a base, to keep the elements of this acid united, as we see is the case with sulphuric acid, nitric acid," &c. M. Gay-Lussac's Memoir was read to the Institute on the 1st August 1814; and, on the 10th February following, Sir H. dates at Rome his communication to the Royal Society, written before he had seen the French paper. When the temperature of inspissated iodic acid is raised to about 392°, it is resolved into iodine and oxygen. Here we see the influence of water is ex- actly the reverse of what M. Gay-Lussac assigns to it; for, instead of giving fixity like a base to the acid, it favours its de- composition. The dry acid may be raised to upwards of 600° without being decom- posed. Sulphurous acid, and sulphuret- ted hydrogen immediately separate iodine from it. Sulphuric and nitric acids have no action on it. With solution of silver, it gives a white precipitate, very soluble in ammonia. It combines with all the bases, produces all the iodates which we can obtain by making the alkaline bases act upon iodine in water. It likewise forms with ammonia a salt, which fulmin- ates when heated. Between the acid prepared by M. Gay-Lussac, and that of Sir H. Davy, there is one important dif- ference. The latter being dissolved may, by evaporation of the water, pass not only ACI ACI to the inspissated sirupy state, but can be made to assume a pasty consistence ; and finally, by a stronger heat, yields the solid substance unaltered. When a mix- ture of it, with charcoal, sulphur, rosin, sugar, or the combustible metals, in a finely divided state, is heated, detonations are produced; and its solution rapidly corrodes all the metals to which Sir H. Davy exposed it, both gold and platinum, but much more intensely the first of these metals. It appears to form combinations with all the fluid or solid acids which it does not decompose. When sulphuric acid is drop- ped into a concentra.ed solution of it in hot water, a solid substance is precipita- ted, which consists of the acids in com- bination; for, on evaporating the s lu- tion by a gentle heat, nothing rises but water. On increasing the heat in an ex- periment of this kind, the solid substance formed fused; and on cooling the mixture, rhomboidal crystals formed of a pale yel- low colour, which were very fusible, and which did not change at the heat at which the compound of oxygen and iodine de- composes, but sublimed unaltered. When urged by a much stronger heat, it par- tially sublimed and partially decomposed, affording oxygen, iodine, and sulphuric acid. With hydro phosphoric, the compound presents phenomena precisely similar, and they form together a solid, yellow, crys- talline combination. With hydro-nitric acid, it yields white crystals in rhomboidal plates, which, at a lower heat than the preceding acid com- pounds, are resolved into hydro-nitric acid, oxygen, and iodine. By liquid mu- riatic acid, the substance is immediately decomposed, and the compound of chlo- rine and iodine is formed. All these acid compounds redden vegetable blues, taste sour, and dissolve gold and platinum. From these curious researches, Sir H. Davy infers, that M. Gay-Lussac's iodic acid, is a sulpho-iodic acid, and probably a definite compound. However minute the quan" ity of sulphuric acid made to act on the iodide of barium may be, a part of it is always employed to form the compounfl acid ; and the residual fluid contains both the compound acid and a certain quantity ofthe original salt. In treating of hydriodic acid, we have already described the method of forming the iodates, a class of salts distinguished chiefly for their property of deflagrating when heated with combustibles.* * Acid (Chloriodic). The discovery of this interesting compound, constitutes an- other of Sir H. Davy's contributions to the advancement of science. In a communi- cation from Florence to the Royal Socie- ty, in March 1814, he gives a curious de- tail of its preparation and properties. He formed it, by admitting chlorine in excess to known quantities of iodine, in vessels exhausted of air, and repeatedly heating the sublimate. Operating in this way, he found that iodine absorbs less than one- third of its weight of chlorine. Chloriodic acid is a very volatile sub- stance, and in consequence of its action upon mercury, he was not able to deter- mine the elastic force of its vapour. In the most considerable experiment which he made to determine proportions, 20 grains caused the disappearance of 9.6 cubical inches of chlorine. These weigh 7.296 grains. And 20 : 7.296 :: 15.5 : 5.6, a num. ber certainly not far from 4.5, the prime equivalent of chlorine; and in the very delicate circumstances of the experiment, an approximation not to be disparaged. Indeed, the first result in close vessels, giving less than one-third of the weight of chlorine absorbed, comes sufficiently near 4.5, which is just a little less than one-third of 15.5, the prime equivalent of iodine. The chloriodic acid formed by the sub- limation of iodine in a great excess of chlorine, is of a bright yellow colour; when fused it becomes of a deep orange, and when rendered elastic, it forms a deep orange coloured gas. It is capable of combining with much iodine when they are heated together, its colour becomes, in consequence, deeper, and the chloriodic acid and the iodine rise together in the elastic state. The solution of the chlo- riodic acid in water, likewise dissolves large quantities of iodine, so that it is pos- sible to obtain a fluid containing very dif- ferent proportions of iodine and chlorine. When two bodies so similar in their characters, and in the compounds they form as iodine and chlorine, act upon sub- stances at the same time, it is difficult, Sir H. observes, to form a judgment of the different parts that they play in the new chemical arrangement produced. It ap- pears most probable, that the acid pro- perty of the chloriodic compound de- pends upon the combination of the two bodies; and its action upon solutions of the alkalis and earths may be easily ex- plained, when it is considered that chlo- rine has a greater tendency than iodine to form double compounds with the metals, and that iodine has a greater tendency than chlorine to form triple compounds with oxygen and the metals. A triple compound of this kind with so- dium may exist in sea water, and would be separated with the first crystals that are formed by its evaporation. Hence, it may exist in common salt. Sir H. Davy ascertained, by feeding birds with bread ACI ACI soaked with water, holding some of it in solution, that it is not poisonous like iodine itself.* Acid (Htdrothioitic). Some of the German chemists distinguish sulphuretted hydrogen by this name, on account of its properties resembling those of an acid. * Acid (Kinic). A peculiar acid ex- tracted by M. Vauquelin from cinchona. Let a watery extract from hot infusions of the bark in powder be made. Alcohol re- moves the resinous part of this extract, and leaves a viscid residue, of a brown co- lour, which has hardly any bitter taste, and which consists of kinite of lime and a mucilaginous matter. This residue is dis- solved in water, the liquor is filtered and left to spontaneous evaporation, in a warm place. It becomes thick like sirup, and then deposites by degrees crystalline plates, sometimes hexahedral, sometimes rhomboidal, sometimes square, and al- ways coloured slightly of a reddish brown. These plates of kinate of lime must be pu- rified by a second crystallization. They are then dissolved in 10 or 12 times their weight of water, and very dilute aqueous oxalic acid is poured into the solution, till no more precipitate is formed. Ry filtra- tion, the oxalate of lime is separated, and the kinic acid being concentrated by spon- taneous evaporation, yields regular crys- tals. It is decomposed by heat. While it forms a soluble salt with lime, it does not precipitate lead or silver from their solu- tions. These are characters sufficiently distinctive. The kinates are scarcely known; that of lime constitutes 7 per cent •f cinchona* Acid (Laccic) of Dr. John. * This chemist made a watery extract ef powdered stick lac, and evaporated it to dryness. He digested alcohol on this extract, and evaporated the alcoholic ex- tract to dryness. He then digested this mass in ether, and evaporated the etherial solution; when he obtained a sirupy mass of a light yellow colour, which was again dissolved in alcohol. On adding water to this solution a little resin fell. A. peculiar acid united to potash and lime remains in the solution, which is obtained free, by forming with acetate of lead an insoluble laccate, and decomposing this with the equivalent quantity of sulphuric acid. Laccic acid crystallizes; it has a wine yel- low colour, a sour taste, and is soluble, as we have seen, in water, alcohol, and ether. It precipitates lead and mercury white; but it does not affect lime, bary tes, or sil- ver, in their solutions. It throws down the salts of iron white. Writh lime, soda, and potash, it forms deliquescent salts, soluble in alcohol.* Acid (Lactic). By evaporating sour whey to one-eightb, filtering, precipitating with lime-water, and separating the lime by oxalic acid, Scheele obtained an aqueous solution of what he supposed to be a peculiar acid, which has accordingly been termed the lactic. To procure it separate, he evaporated the solution to the consistence of honey, poured on it al- cohol, filtered this solution, and evapora- ted the alcohol. The residuum was an acid of a yellow colour, incapable of being crystallized, attracting the humidity of the air, and forming deliquescent salts with the earths and alkalis. Bouillon Lagrange since examined it more narrowly; and from a series of ex- periments concluded, that it consists of acetic acid, muriate of potash, a small por- tion of iron probably dissolved in the ace- tic acid, and an animal matter. * This judgment of M. Lagrange was afterwards supported by the opinions of MM. Fourcroy and Vauquelin. But since then Berzelius has investigated its nature very fully, and has obtained, by means of a long and often repeated series of differ- ent experiments, a complete conviction that Scheele was in the right, and that the lactic acid is a peculiar acid, very dis- tinct from all others. The extract which is obtained when dried whey is digested with alcohol, contains uncombined lactic acid, lactate of potash, muriate of potash, and a proper animal matter. As the elimi- nation of the acid affords an instructive example of chemical research, we shall present it at some detail, from the 2d vo- lume of Berzelius's Animal Chemistry. He mixed the above alcoholic solution with another portion of alcohol, to which \ of concentrated sulphuric acid had been added, and continued to add fresh por- tions of this mixture as long as any saline precipitate was formed, and until the fluid had acquired a decidedly acid taste. Some sulphate of potash was precipitated, and there remained in the alcohol, muriatic acid, lactic acid, sulphuric acid, and a mi- nute portion of phosphoric acid, detached from some bone earth which had been held in solution. The acid liquor was filtered, and afterwards digested with car- bonate of lead, which with the lactic acid affords a salt soluble in alcohol. As soon as the mixture had acquired a sweetish taste, the three mineral acids had fallen down in combination with the lead, and the lactic acid remained behind, imper- fectly saturated by a portion of it, from which it was detached by means of sul- phuretted hydrogen, and then evaporated to the consistence of a thick varnish, of a dark-brown colour, and sharp acid taste, but altogether without smell. In order to free it from the animal matter which might remain combined with it, he boiled^itwith a mixture of a large quantity ACI ACI of fresh lime and water, so that the ani- mal substances were precipitated and de- stroyed by the lime. The lime became yellow brown, and the solution almost colourless, while the mass emitted a smell of soap lees, which disappeared as the boiling was continued. The fluid thus obtained was filtered and evaporated, until a great part ofthe superfluous lime held in solution was precipitated. A small por- tion of it was then decomposed by oxalic acid, and carbonate of silver was dissolved in the uncombined lactic acid, until it was fully saturated. With the assistance ofthe lactate of silver thus obtained, a further quantity of muriatic acid was separated from the lactate of lime, which was then decomposed by pure oxalic acid, free from nitric acid, taking care to leave it in such a state that neither the oxalic acid nor lime water afforded a precipitate. It was then evaporated to dryness, and dis- solved again in alcohol, a small portion of oxalate of lime, before retamed in union with the acid, now remaining undissolved. The alcohol was evaporated until the mass was no longer fluid while warm; it be- came a brown clear transparent acid, which was the lactic acid, free from all substances that we have hitherto had reason to think likely to contaminate it. The lactic acid, thus purified, has a brown yellow colour, and a sharp sour taste, which is much weakened bv dilu- ting it with water. It is without smell in the cold, but emits, when heated, a sharp sour smell, not unlike that of sublimed oxalic acid. It cannot be made to crystal- lize, and does not exhibit the slightest ap- pearance of a saline substance, but dries into a thick and smooth varnish, which slowly attracts moisture from the air. It is very easily soluble in alcohol. Heated in a gold spoon over the flame of a candle, it first boils, and then its pungent acid smell becomes very manifest, but extreme- ly distinct from that of the acetic acid ; afterwards it is charred, and has an empy- reumatic, but by no means an animal smell. A porous charcoal is left behind, which does not readily burn to ashes. When distilled, it gives an empyreumatic oil, water, empyreumatic vinegar, carbon- ic acid, and inflammable gases. With alkalis, earths, and metallic oxides, it af- fords peculiar salts : and these are distin- guished by being soluble in alcohol, and in general by not having the least disposi- tion to crystallize, but drying into a mass like gum, which slowly becomes moist in the air. Lactate of potash is obtained, when the lactate of lime, purified as has been men- tioned, is mixed warm with a warm solu- tion of carbonate of potash. It forms, in drving, a gummy, light yellow brown, Vol. i. [7] transparent mass, which cannot easily be made liard. If it is mixed with concentra- ted sulphuric acid, no smell of acetic acid is perceived; but if the mixture is heated, it acquires a disagreeable pungent smell, which is observable in all animal substan- ces mixed with the sulphuric acid. The extract which is obtained direct y from milk, contains this salt; but this affords, when mixed with sulphuric acid, a sharp acid smell, not unlike that of the acetic acid. This, however, depends not on acetic but on muriatic acid, which in its concentrated state introduces this modifi- cation into the smell of almost all organic bodies. The pure lactate of potash is easily soluble in alcohol; that which contains an excess of potash, or is still contaminated with the animal matter soluble in alcohol, which is destroyed by the treatment with lime, is slowly soluble, and requires about 14 parts of warm alcohol for its solution. It is dissolved in boiling alcohol more abundantly than in cold, and separates from it, while it is cooling, in the form of hard drops. The lactate of sodi resembles that of potash, and can only be distinguished from it by analysis. Lactate of ammonia. If concentrated lactic acid is saturated with caustic am- monia in excess, the mixture acquires a strong volatile smell, not unlike that of the acetate or formiate of ammonia, which, however, soon ceases. The salt which is left has sometimes a slight tendency to shoot into crystals. It affords a gummy mass, which in the air acquires an excess of acidity. When heated, a great part of the alkali is expelled, and a very acid salt remains, which deliquesces in the air. The lactate of barytes may be obtained in the same way as that of lime; but it then contains an excess ofthe base. When evaporated, it affords a gummy mass, soluble in alcohol. A portion remains undissolved, which is a sub-salt, is doughy, and has a browner colour. That which is dissolved in the alcohol affords by evapo- ration an almost colourless gummy mass, which hardens into a stiff' but not a brittle varnish. It does not show the least tenden- cy to crystallize. The salt, which is less soluble in alcohol, may be further purified from the animal matter adhering to it, by adding to it more barytes, and then be* comes more soluble. The lactate of lime is obtained in the manner above described. It affords a gummy mass, which is also divided by alco- hol into two portions. The larger portion is soluble, and gives a shining varnish inclining to a light yellow colour, which, when slowly dried, cracks all over, and becomes opaque. This is pure lactate of lime. That which is insoluble in alcohol te ACI ACI a powder, with excess of the base ; re. The lactate of lead may be obtained in ceived on a filter, it becomes smooth in several different degrees of saturation. If the air like gum, or like malate of lime, the lactic acid is digested with the carbon- Ry boiling with more lime, and by the ate of lead, it becomes browner than be- precipitation of the superfluous base upon fore, but cannot be fully saturated with exposure to the air, it becomes pure and the oxide ; and we obtain an acid salt, soluble in alcohol. which does not crystallize, but dries into Lactate of magnesia, evaporated to the a sirup-like brown mass, with a sweet consistence of a thin sirup, and left in a austere taste. When a solution of lactic warm place, shoots into small granular acid in alcohol is digested with finely pow- crystals. When hastily evaporated to dered litharge, until the solution becomes dryness, it affords a gummy mas^. With sweet, and is then slowly evaporated to regard to alcohol, its properties resemble the consistence of honey, the neutral lac- those ofthe two preceding salts. tate of lead crystallizes in small grayish Ammoniaco-magnesian lactate is obtained grains, which may be rinsed with alcohol, by mixing the preceding salt with caustic to wash off the viscid mass that adheres to ammonia, as long as any precipitation con- them, and will then appear as a gray granu- tinues. By spontaneous evaporation this lar salt, which when dry is light and salt shoots into needle-shaped prisms, silvery. which are little coloured, and do not This silver grained salt is not changed change in the air. Berzelius has once in the air; treated with sulphuretted hy- seen these crystals form in the alcoholic drogen it affords pure lactic acid. If the extract of milk boiled to dryness; but lactic acid is digested with a greater por- this is by no means a common occur- tion of levigated litharge than is required rence. for its saturation, the fluid acquires first a The lactate of silver is procured by dis- browner colour, and as the digestion is solving the carbonate in the lactic acid, continued the colour becomes more and Thesolution is of a light yellow, somewhat more pale, and the oxide swells into a inclining to green, and has an unpleasant bulky powder, of a colour somewhat taste of verdigris. When evaporated in a lighter than before. If the fluid is evapo- flat vessel, it dries into a very transparent rated, and water is then poured on the greenish yellow varnish, which has exter- dry mass, a very small portion of it only is nally an unusual splendour like that of a dissolved; the solution is not coloured, looking-glass. If the evaporation is con- and when it is exposed to the air, a pellicle ducted in a deeper vessel, and with a of carbonate of lead is separated from it. stronger heat, a part of the salt is decom- If the dried salt of lead be boiled with posed, and remains brown from the reduc- water, and the solution be filtered while tion ofthe silver. If this salt is dissolved hot, a great part of that which had been, in water, no inconsiderable portion ofthe dissolved will be precipitated while it silver is reduced and deposited, even cools, in the form of a white, or light yellow when the salt has been transparent; and powder, which is a sublactate of lead. the concentrated solution has a fine green- This salt is of a light flame colour; when ish yellow colour, which by dilution be- dried,it remains mealy, and soft to the comes yellow. If we dissolve the oxide touch, and it is decomposed by the weak- of silver in an impure acid, the salt be- est acids, while the acid salt is dissolved comes brown, and more silver is revived in water, exhibiting a sweet taste and a during the evaporation. brown colour. When moistened with The lactate ofthe protoxide of mercury is water, it undergoes this change from the obtained when the lactic acid is saturated operation ofthe carbonic acid diffused in with black oxidated mercury. It has a the air. It this salt is warmed and then light yellow colour, which disappears by set on fire at one point, it burns like tin- means of repeated solution and evapora- der, and leaves the lead in great measure tion. The salt exhibits acid properties, reduced. A hundred parts of this salt, deliquesces in the air, and is partially dis- dissolved in nitric acid, and precipitated solved in alcohol, but is at the same time with carbonate of potash, gave exactly decomposed, and deposites carbonate of 100 parts of carbonate of lead; consequent- mercury, while the mixture acquires a ly its component parts, determined from slight smell of ether. The lactic acid dis- those ofthe carbonate, must be 83 ofthe solves also the red oxide of mercury, and oxide of lead, and 17 of the lactic acid. gives with it a red gummy deliquescent At the same time we cannot wholly de- salt. If it is left exposed to a warm and pend on this proportion, and it certainly moist atmosphere, it deposites, aftertheex- makes the quantity of lead somewhat too piration of some weeks, a light semi-crys- great. The relation of the lactic acid to talline powder, which he has not examin- lead affords one of the best methods of ed, but which probably must be acetate of recognizing it, and Berzelius always mercury. principally employed it in extracting this ACI ACI acid from animal fluids; it gives the clearest distinction between the lactic acid and the acetic. The lactate of iron is of a red brown co- lour, does not crystallize, and is not solu- ble in alcohol. The lactate of zinc crystal- lizes. Both these metals are dissolved by the lactic acid, with an extrication of hydrogen gas. The lactate of copper, ac- cording to its different degrees of satura- tion, varies from blue to green and dark blue. It does not crystallize. It is only necessary to compare the de- scriptions of these salts with what we know of the salts which are formed with the same bases by other acids, for example, the acetic, the malic, and others, in order to be completely convinced that the lactic acid must be a peculiar acid, perfectly dis- tinct from all others. Its prime equivalent may be called 5.8. The nanceicacid of Braconnot resembles the lactic in many respects.* * Acid (Lampic). Sir H. Davy, during his admirable researches on the nature and properties of flame, announced the singu- lar fact, that combustible bodies might be made to combine rapidly with oxygen, at temperatures below what were necessary to their visible inflammation. Among the phenomena resulting from these new combinations, he remarked the production of a peculiar acid and pungent vapour from the slow combustion of ether; and from its obvious qualities he was led to suspect, that it might be a product yet new to the chemical catalogue. Mr. Fara- day, in the 3d volume of the Journal of Science and the Arts, has given some ac- count of the properties of this new acid; but from the very small quantities in which he was able to collect it, was prevented from performing any decisive experiments upon it. In the 6th volume ofthe same Journal, we have a pretty copious investigation of the properties and compounds of this new acid, by Mr. Daniell. From the slow combustion of ether during six weeks, by means of a coil of platina wire sitting on the cotton wick ofthe lamp, (See Flame), he condensed with the head of an alembic, whose beak was inserted 'in a receiver, a pint and a half of the lampic acid liquor. When first collected it is a colourless fluid of an intensely sour taste, and pun- gent odour. Its vapour, when heated, is extremely irritating and disagreeable, and when received into the lungs produces an oppression at the chest very much resem- bling the effect of chlorine. Its specific gravity varies according to the care with which it has been prepared, from less than 1.000 to 1.008. It may be purified by careful evaporation; and it is worthy of remark, that the vapour which rises from it is that of alcohol, with which it is slightly contaminated, and not of ether. Thus rectified, its specific gravity is 1.015. It reddens vegetable blues, and decomposes all the earthy and alkaline carbonates, forming neutral salts with their bases, which are more or less deliquescent. Lampate of soda is a very deliquescent salt, of a not unpleasant saline taste. It is decomposed by heat. It consists of 62.1 acid and 37.9 soda. Hence its prime equivalent comes out 6.47. Lampate of potash is not quite so deliquescent. Lampate of ammonia evaporates at a tem- perature below 212°. It is a brown salt. Lampate of barytes crystallizes in colour- less transparent needles. Its composition is 39.5 acid and 60.5 base; and hence the prime is 6.365, barytes being reckoned 9.75, with Dr. Wollaston. Lampate of lime is deliquescent, and has a caustic bitter taste. Lampate of magnesia has a sweet, astringent taste, like sulphate of iron. All these salts burn with flame. Lampic acid reduces gold from the muriate instantly ; and the lampates ofpotash and ammonia produce the same effect more slowly. A mixture of these two lampates, throws down metallic platinum from its solution. Nitrate of silver also gives a metallic preci- pitate ; but what ls» singular, the oxide of silver is soluble in lampic acid, but at a boiling heat falls down in the metallic state. A hot solution of nitrated protoxide of mercury exhibits a very beautiful phe- nomenon, when mixed with the acid. A shower of mercurial globules falls down through the liquid. Red oxide forms with lampic acid a bulky white salt, of sparing solubility, from which, after a few days, metallic mercury separates. Lampate of copper affords by evaporation under an exhausted receiver, blue rhomboidal crys- tals. When the solution is boiled, metal- lic copper falls. Lampate of lead is a white, sweetish, and easily crystallized salt. By analysis of the lampate of barytes in M. M. G. Lussac and Thenard's apparatus, (See Vegetable Analysis), Mr. Daniell infers the composition of the acid to be 40.7 carbon, + 7.7 hydrogen, + 51.6 of oxygen and hydrogen,in their aqueous ratio = 100. These numbers correspond, he says, with what we may suppose to re- sult from I atom of carbon, 1 of hydrogen, and 1 of water, or its elements. The excess of hydrogen explains, he imagines, the property which the acid possesses of reviving the metals, whence it may be usefully applied in the arts, to plate deli- cate works with gold and platinum. The weight of its equivalent, and some* ofthe properties of the salts, might had to the opinion of the lampic acid of Mr ACI ACI Daniell being merely the acetic, combined with some etherous matter. This conjec- ture must be leftforfuture verification.* Acid (Lithic). This was discovered about the year 1776 by Scheele, in analy- zing human calculi of many of which it constitutes the greater part and of some, particularly that which resembles wood in appearance, it forms almost the whole. It is likewise present in human urine, and in that of the camel; and Dr. Pearson found it in those arthritic concretions com- monly called chalkstones, which Mr. Ten- nant has since confirmed. It is often called uric acid. The following are the results of Scheele's experiments on calculi, which were found to consist almost wholly of this acid : 1. Dilute sulphuric acid produced no ef- fect on the calculus, but the concentrated dissolved it; and the solution distilled to dryness left a black coal, giving off sulphu- rous acid fumes. 2. The muriatic acid, either diluted or concentrated, had no ef- fect on it even with ebullition. 3. Dilute nitric acid attacked it cold; and with the assistance of heat produced an efferves- cence and red vapour, carbonic acid was evolved, and the calculus was entirely dis solved. The solution was acid, even when saturated with the calculus, and gave a beautiful red colour to the skin in half an hour after it was applied; when evaporat- ed, it became of a blood red, but the co- lour was destroyed by adding a drop of acid : it did not precipitate muriate of ba- rytes, or metallic solutions, even with the addition of an alkali; alkalis rendered it more yellow, and, if superabundant, chang- ed it by a strong digesting heat to a rose colour; and this mixture imparts a similar colour to the skin, and is capable of pre- cipitating sulphate of iron black, sulphate of copper green, nitrate of silver gray, su- per-oxygenated muriate of mercury, and solutions of lead and zinc, white. Lime- water produced in the nitric solution a white precipitate, which dissolved in the nitric and muriatic acids without efferves- cence, and without destroying their acidi- ty. Oxalic acid did not precipitate it. 4. Carbonate of potash did not dissolve it, either cold or hot, but a solution of per- fectly pure potash dissolved it even cold. The solution was yellow; sweetish to the taste; precipitated by all the acids, even the carbonic; did not render lime-water turbid; decomposed and precipitated so- lution of iron brown, of copper gray, of silver black, of zinc, mercury, and lead, white; and exhaled a smell of ammonia. 5. About 200 parts of lime-water dissolved the calculus by digestion, and lost its acrid taste. The solution was partly precipita- ted by acids. 6. Pure water dissolved it entirely, but it was necessary to boil for some time 360 parts with one of the cal- culus in p.wder. This solution reddened tincture of litmus, did not render lime- water turbid, and on cooling deposited in small crystals almost the whole of what it had taken up. 7. Seventy-two grains dis- tilled in a small glass retort over an open fire, and gradually brought to a red heat, produced water of ammonia mixed with a little animal oil. and a brown sublimate weighing 28 grains, and 12 grains of coal remained, which preserved its black co- lour on red hot iron in the open air. The brown sublimate was rendered white by a second sublimation; was destitute of smell, even when moistened by an alkali; was acid to the taste; dissolved in boiling wa- ter, and also in alcohol, but in less quanti- ty; did not precipitate lime-water; and appeared to resemble succinic acid. Fourcroy has found, that this acid is al- most entirely soluble in 2000 times its weight of cold water, when the powder is repeatedly treated with it. From his ex- periments he infers, that it contains azote, with a considerable portion of carbon, and but little hydrogen, and little oxygen. Of its combinations with the bases we know but little. The lithate of lime is more soluble than the acid itself; but on exposure to the air it is soon decomposed, the carbonic acid in the atmosphere com- bining with the lime, and precipitating both the lithic acid and new formed car- bonate of lime separate from each other. The lithate of soda appears from the ana- lysis of Mr. Tennant to constitute the chief part ofthe concretions formed in the joints of gouty persons. The lithate of potash is obtained by digesting calculi in caustic lixivium ; and Fourcroy recommends the precipitation of the lithic acid from this solution by acetic acid, as a good process for obtaining the acid pure in small, white, shining, and almost pulverulent needles. * Much additional information has been obtained within these few years on the na- ture and habitudes of the lithic acid. Dr. Henry wrote a medical thesis, and after- wards published a paper, on the subject, in the second volume ofthe new series of the Manchester Memoirs, both of which contain many important facts. He pro- cured the acid in the manner above pre- scribed by Fourcroy. It has the form of white shin'ng plates, which are denser than water. Has no taste nor smell. It dissolves in about 1400 parts of boiling water. It reddens the infusion of litmus. When dissolved in nitric acid, and evapo- rated to dry ness, it leaves a pink sediment. The dry acid is not acted on nor dissolved by the alkaline carbonates, or sub-carbo- nates. It decomposes soap when assisted by heat; as it does also the alkaline sul- phurets, and bydrosulphurcts. No acid ACI ACI acts on it, except those that occasion its decomposition. It dissolves in hot solu- tions of potash and soda, and likewise in ammonia, but less readil . The lithates may be formed, either by mutually satura- ting the two constituents, or we may dis- solve the acid in an excess of base, and we may then precipitate by carbonate of am- monia. The lithates are all tasteless, and resemble in appearance lithic acid itself. They are not altered by exposure to the atmosphere. They are very sparingly so- luble in water. They are decomposed by a red heat, which destroys the acid. The lithic acid is precipitated from these salts, by all the acids except the prussic and car- bonic. They are decomposed by the ni- trates, muriates, and acetates of barytes, strontites, lime, magnesia, and alumina. They are precipitated by all the metallic solutions except that of gold. When li- thic acid is exposed to heat, the products are carburetted hydrogen, and carbonic acid, prussic acid, carbonate of ammonia, a sublimate, consisting of ammonia com- bined with a peculiar acid, which has the following properties:— Its colour is yellow, and it has a cooling bitter taste. It dissolves readily in water, and in alkaline solutions, from which it is not precipitated by acids. It dissolves al- so sparingly in alcohol It is volatile, and when sublimed a second time, becomes much whiter. The watery solution red- dens vegetable blues, but a very small quantity of ammonia destroys this proper- ty. It does not cause effervescence with alkaline carbonates. By evaporation it yields permanent crystals, but ill defined, from adhering animal matter. These red- den vegetable bines. Potash when added to these crystals, disengages ammonia. When dissolved in nitric acid, they do not leave a red stain, as happens with uric acid; nor does their solution in water decom- pose the earthy salts, as happens with al- kaline lithates (or urates.) Neither has it any action on the salts of copper, iron, gold, platinum, tin, or mercury. With ni- trates of silver, and mercury, and acetate of lead, it forms a white precipitate, solu- ble in an excess of nitric acid. Muriatic acid occasions no precipitate in the solu- tion of thee crystals in water. These properties show, that the acid of the sub- limate is different from the uric, and from every other known acid. Dr. Austin found, that by repeated distillations, lithic acid was resolved into ammonia, nitrogen, and prussic acid. See Acin (Pvrolithic.) When lithic acid is projected into a flask with chlorine, there is formed, in a little time, muriate of ammonia, oxalate of am- monia, carbonic acid, muriatic acid, and malic acid; the same results are obtained by passing chlorine through water, hold'- ing this acid in suspension. M. Gay-Lussac mixed lithic acid with 20 times its weight of oxide of copper, put the mixture into a glass tube, and covered it with a quantity of copper filings. The copper filings being first heated to a dull red heat, was applied to the mixture. The gas which came over, was composed of 0.69 carbonic acid, and 0.31 nitrogen. He conceives, that the bulk of the carbonic acid would have been exactly double that of the nitrogen, had it not been for the formation of a little carbonate of ammonia. Hence, uric acid contains two prime equi- valents of carbon, and one of nitrogen. This is the same proportion as exists in cyanogen. Probably, a prime equivalent of oxygen is present. Dr. Prout, in the eighth vol. of the Med. Chir. Trans, de- scribes the result of an analysis of lithic acid, effected also by ignited oxide of cop- per, but so conducted as to determine the product of oxygen and hydrogen. Four grains of lithic acid yielded, water 1.05, carbonic acid 11.0 c. inches, nitrogen 5.5 do. Hence, it consisted of Hvdrogen 2.857 or 1 prime = 0.125 Carbon 34 286 2 = 1.500 Oxvgen 22.857 1 «= 1.000 Nitrogen 40.000 1 = 1.750 100.000 4.375 M. Berard has published an analysis of lithic acid since Dr. Prout, in which he al- so employed oxide of copper. The following are the results:— Carbon 3^.61 T2 Carbon Oxygen 18.89 which ap-J 1 Oxygen Hydrogen 8.34 proach tdS 4 Hydrogen Nitrogen 39.16 * 1^1 Nitrogen 100.00 Here we find the nitrogen and carbon nearly in the same quantity as by Dr. Prout, but there is much more hydrogen and less oxygen. By urate of barytes, we have the prime equivalent of uric acid equal to 15.67; and by urate of potash it appears to be 14.0. It is needless to try to accom- modate an arrangement of prime equiva- lents to these discrepancies. The lowest number would require, on the Daltonian plan, an association of more than twenty atoms, the grouping of which is rather a sport of fancy, than an exercise of reason. For what benefit could accrue to chemical science, by stating, that if we consider the atom of lithic acid to be 16.75, then it would probably consist of 7 atoms Carbon = 5.25 31.4 3 Oxygen = 3.00 17.90 12 Hydrogen— 1.500 8.90 4 Nitrogen = 7.00 41.80 26 16.75 100.0* ACI ACI * Acid (Malic.) The acid of apples; the same with that which is extracted from the fruit of the mountain ash. See Acid (Sorbic.*) * Acid (Margaric.) When weimmerse soap made of pork-grease and potash, in a large quantity of water, one part is dissolv- ed, while another part is precipitated, in the form of several brilliant pellets. These are separated, dried, washed in a large quantity of water, and then dried on a fil- ter, l'hey are now dissolved in boiling alcohol, sp. gr. 0.820, from which, as it cools, the pearly substance falls down pure. On acting on this with dilute muriatic acid, a substance of a peculiar kind, which M. Chevreul, the discoverer, calls margarine, or margaric acid, is separated. It must be well washed with water dissolved in boil- ing alcohol, from which it is recovered in the same crystalline pearly form, when the solution cools. Margaric acid is pearly white, and taste- less. Its smell is feeble, and a little simi lar to that of melted wax. Its specific gra- vity is inferior to water. It melts at 134° F. into a very limpid, colourless liquid, which crystallizes on cooling, into brilliant needles of the finest white. It is insoluble in water, but very soluble in alcohol, sp. gr. 0.800. Cold margaric acid has no ac- tion on the colour of litmus; but when heated so as to soften without melting, the blue was reddened. It combines with the salifiable bases, and forms neutral com- pounds. 100 parts of it unite to a quantity of base containing three parts of oxygen, supposing that 100 of potash contain 17 of oxygen. Two orders of margarates are formed, the majgarates, and the super- margarates, the former being converted into the latter, by pouring a large quanti- ty of water on them. Other fats besides that^of the hog yield this substance. Acid, Base. Margarate of potash consists of 100 17 77 Supermargarate .... 100 8.88 Margarate of soda - - - - 100 12.72 Barytes.......100 28.93 Strontites......100 20.23 Lime........100 11.06 Potash Supermargarate of Human fat 100 8.85 Sheep fat 100 8.68 Ox fat 100 8.78 Jaguar fat 100 8.60 Goose fat 100 8.77 If wc compare the above numbers, we shall find 35 to be the prime equivalent of margaric acid. That of man is obtained under three dif- ferent forms. 1st, In very fine long nee- dles, disposed in flat stars. 2d, In very fine and very short needles, forming waved figures, like those of the margaric acid of carcasses. 3d, In very large brilliant crys- tals disposed in stars, similar to the mar* garic acid ofthe hog. The margaric acids of man and the hog resemble each other; as do those ofthe ox and the sheep ; and ofthe goose and the jaguar. The com- pounds with the bases, are real soaps. The solution of alcohol affords the transparent soap of this country.—Annates de Chimie, several volumes.* * Acid (Meconic). This acid is a consti- tuent of opium. It was discovered by M. Sertuerner, who procured it in the follow- ing way: After precipitating the morphia, from a solution of opium, by ammonia, he added to the residual fluid a solution of the muriate of barytes. A precipitate is in this way formed, which is supposed to be a quadruple compound, of barytes, mor- phia, extract, and the meconic acid. I he extract is removed by alcohol, and the barytes by sulphuric acid; when the me- conic acid is left, merely in combination with a portion of the morphia; and from this it is purified by successive solutions and evaporations. The acid, when sub- limed, forms long colourless needles; it has a strong affinity for the oxide of iron, so as to take it from the muriatic solution, and form with it a cherry-red precipitate It forms a crystallizable salt with lime, which is not decomposed by sulphuric acid ; and what is curious, it seems to pos- sess no particular power over the human body, when received into the stomach. The essential salt of opium, obtained in M. Derosne's original experiments, was probably the meconiate of morphia. Mr. Robiquet has made a useful modifi- cation ofthe process for extracting mecon- ic acid. He treats the opium with magne- sia, to separate the morphia, while me- coniate of magnesia is also formed. The magnesia is removed by adding muriate of barytes, and the barytes is afterwards se- parated by dilute sulphuric acid. A lar- ger proportion of meconic acid is thus ob- tained. Mr. Robiquet denies that meconic acid precipitates iron from the muriate ; but, according to M. Vogel, its power of red- dening solutions of iron is so great, as to render it a more delicate test of this metal, than even the prussiate of potash. To obtain pure meconic acid from the meconiate of barytes, M. Choulant tritu- rated it in a mortar, with its own weight of glassy boracic acid. This mixture being put into a small glass flask, which was surrounded with sand in a sand pot, in the usual manner, and the red heat being gradually raised, the meconic acid sublimed, in the state of fine white scales or plates. It has a strong sour taste, which leaves be- hind it an impression of bitterness. It dis- solves readily in water, alcohol, and ether. It reddens the greater number of vegeta- ACI ACI ble blues, and changes the solutions of iron to a cherry-red colour. When these solutions are heated, the iron is precipi- tated in the state of protoxide. The meconiates examined by Choulant, are the following:— 1st, Meconiate of potash. It crystallizes in four sided tables, is soluble in twice its weight of water, and is composed of Meconic acid 27 2.7 Potash 60 6.0 Water 13 100 It is destroyed by heat. 2d, Meconiate of soda. It crystallizes in soft prisms, is soluble in five times its weight of water, and seems to effloresce. It is destroyed by heat. It consists of Acid " 32 3.2 Soda 40 4.0 Water 28 100 3d. Meconiate of ammonia. It crystal- lizes in star-form needles, which, when sublimed, lose their water of crystalliza- tion, and assume the shape of scales. The crystals are soluble in 1£ their weight of water, and are composed of Acid 40 2.03 Ammonia 42 2.13 Water 18 100 If two parts of sal ammoniac be tritura- ted with 3 parts of meconiate of barytes, and heat be applied to the mixture, me- eoniate of ammonia sublimes, and muriate of barytes remains. 4th, Meconiate of lime. It crystallizes in prisms, and is soluble in eight times its weight of water. It consists of Acid 34 2 882 Lime 42 3.560 Water 24 100 As the potash and lime compounds give nearly the same acid ratio, we may take their mean of it, as the true prime = 2.8.* * Acid (Melassic). The acid present in melasses, which has been thought a pe- culiar acid by some, by others, the acetic* Acid (Mellitic). M. Klaproth disco- vered in the mellite, or honey-stone, what he conceives to be a peculiar acid of the vegetable kind, combined with alu- mina. This acid is easily obtained by re- ducing the stone to powder, and boiling it in about 70 times its weight of water; when the acid will dissolve, and may be separated from the alumina by filtration. By evaporating the solution, it may be ob- tained in the form of crystals. The fol« lowing are its characters t— It crystallizes in fine needles or globules by the union of these, or small prisms. Its taste is at first a sweetish sour, which leaves a bitterness behind. On a plate of hot metal it is readily decomposed, and dissipated in copious gray fumes, which affect not the smell; leaving behind a small quantity of ashes, that do not change either red or blue tincture of litmus. Neu- tralized by potash it crystallizes in groups of long prisms: by soda, in cubes, or tri- angular laminae, sometimes in groups, sometimes single; and by ammonia, in beautiful prisms with six planes, which soon lose their transparency, and acquire a silvery white hue. If the mellitic acid be dissolved in lime-water, and a solution of calcined strontian or barytes be drop- ped into it, a white precipitate is thrown down, which is redissolved on adding mu- riatic acid. With a solution of acetate of barytes, it produces likewise a white pre- cipitate, which nitric acid redissolves. With solution of muriate of barytes, it pro- duces no precipitate, or even cloud; but after standing some time, fine transparent needly crystals are deposited. The mel- litic acid produces no change in a solution of nitrate of silver. From a solution of nitrate of mercury, either hot or cold, it throws down a copious white precipitate, which an addition of nitric acid imme- diately redissolves. With nitrate of iron it gives an abundant precipitate of a dun yellow colour, which may be redissolved by muriatic acid. With a solution of ace- tate of lead, it produces an abundant pre- cipitate, immediately redissolved on add- ing nitric acid. With acetate of copper, it produces a grayish-green precipitate; but it does not affect a solution of muriate of copper. Lime-water precipitated by it, is immediately redissolved on adding nitric acid. M. Klaproth was never able to convert this acid into the oxalic by means of nitric acid, which only changed its brownish co- lour to a pale yellow. * The mellite, or native mellate of alu- mina, consists, according to Klaproth, of 46 acid +16 alumina + 38 water = 100; from which, calling the prime of alumina 3.2, that of mellitic acid appears to be 9.2.* * Acid (Menispermic). The seeds of menispermum cocculus being macerated for 24 hours in 5 times their weight of water, first cold, and then boiling hot, yield an infusion, from which solution of subacetate of lead throws down a menispermate of lead. This is to be washed and drained. diffused through water, and decomposed by a current of sulphuretted hydrogen gas. The liquid thus freed from lead, is to be deprived of sulphuretted hydrogen by heat, and then forms solution of minis- ACI ACI permic acid. By repeated evaporations and solutions in alcohol, it loses its bitter taste, and becomes a purer acid. It occa- sions no precipitate with lime-water; with nitrate of barytes it yields a gray precipi- tate ; with nitrate of silver, a deep yellow; and with sulphate of magnesia, a copious precipitate* * Acid (Molybdic). The native sulphu- ret of molybdenum being roasted for some time, and dissolved in water of ammonia, when nitric acid is added to this solution, the molybdic acid precipitates in fine white scales, which become yellow, on melting and subliming them. It changes the vegetable blues to red, but less readi- ly and powerfully than the following acid. M. Bucholz found that 100 parts of the sulphuret gave 90 parts of molybdic acid. In other experiments in which he oxidized molybdenum, he found that 100 of the metal combined with from 49 to 50 of oxy- gen. Berzelius, after some vain attempts to analyze the molybdates of lead and ba- rytes, found that the only method of ob- taining an exact result was to form a mo- lybdate of lead. He dissolved 10 parts of neutral nitrate of lead in water, and pour- ed an excess of solution of crystallized molybdate of ammonia into the liquid. The molybdate of lead, washed, dried and heated to redness, weighed 11.068. No traces of lead were found in the liquid by sulphate of ammonia; hence these 11.068 of lead, evince 67.3 per cent of oxide of lead. This salt then is composed of Molybdic acid 39 194 9.0 Oxide of lead 60.806 14.0 100.000 And from Bucholz we infer, that this prime equivalent 9, consists of 3 of oxy- gen + 6 metal; while molybdous acid will be 2 oxygen + 6 metal = 8.0. Molybdic acid has a specific gravity of 3.460. In an open vessel it sublimes into brilliant yellow scales; 960 parts of boiling water dissolve one of it, affording a pale vellow solution, which reddens litmus, but has no taste. Sulphur, charcoal, and several metals decompose the molybdic acid. Molybdate of potash is a colourless salt. Molybdic acid gives, with nitrate of lead, a white precipitate, soluble in nitric acid; with the nitrates of mercury and silver, a white flaky precipitate ; with ni- trate of copper, a greenish precipitate; with solutions of the neutral sulphate of zinc, muriate of bismuth, muriate of anti- mony, nitrate of nickel, muriates of gold and platinum, it produces white precipi- tates. When melted with borax, it yields a bluish colour; and paper dipped in its solution becomes, in the sun, of a beauti- ful blue.* The neutral alkaline molybdates preci- pitate all metallic solutions. Gold, mu- riate of mercury, zinc, and manganese, are precipitated in the form of a white powder; iron and tin, from their sol t;ons in muriatic acid, of a brown colour; cobalt, of a rose colour; copper, blue; and the solutions of alum and quicklime, white. If a dilute solution of recent muriate of tin be precipitated by a dilute solution oi molybdate of potash, a beautiful blue powder is obtained The concentrated sulphuric acid dis- solves a considerable quantity of the mo- lybdic acid, the solution becoming of a fine blue colour as it cools, at the same time that it thickens; the colour disap- pears again on the application of heat, but returns again by cooling. A strong heat expels the sulphuric acid. The nitric acid has no effect on it; but the muriatic dissolves it in considerable quantity, and leaves a dark blue residuum when dis- tilled. V\ ith a strong heat it expels a por- tion of sulphuric acid from sulphate of potash. It also disengages the acid from nitre and common salt by distillation. It has some action upon the filings ofthe me- tals in the moist way. The molybdic acid has not yet been em- ployed in the arts. * Acid (Molybdofs). The deutoxide of molybdenum is of a blue colour, and possesses acid properties. Triturate 2 parts of molybdic acid, with 1 part of the metal, along with a little hot water, in a porcelain mortar, till the mixture assumes a blue colour. Digest in 10 parts of boil- ing water, filter, and evaporate the liquid in a heat of 120°. The blue oxide sepa- rates. It reddens vegetable blues, and forms salts with the bases. Air or water, when left for some nme to act on molyb- denum, convert it into this acid. It con- sists of about 100 metal to 34 oxygen,* Acid (Mouoxylic). In the botanic gar- den at Palermo, Mr. Thompson found an uncommon saline substance on the trunk of a white mulberry tree. It appeared as a coating on the surface of the bark in lit- tle granulous drops of a yellowish and blackish brown colour, and had likewise penetrated its substance. M. Klaproth, who analyzed it, found that its taste was somewhat like that of succinic acid; on burning coals it swelled up a little, emit- ted a pungent vapour scarcely visible to the eye, and left a slight earthy residuum. Six hundred grains of the bark loaded with it were lixiviated with water, and afforded 320 grains of a light salt, resem- bling in colour a light wood, and compos- ed of short needles united in radii. It was not deliquescent; and though the crystals did not form till the solution was greatly condensed by evaporation, it is not very ACI ACI soluble, since 1000 parts of water dissolve but 35 with heat, and 15 cold. This salt was found to be a compound of lime and a peculiar vegetable acid, with some extractive matter. To obtain the acid separate, M. Klap- roth decomposed the calcareous salt by acetate of lead, and separated the lead by sulphuric acid. He likewise decomposed it directly by sulphuric acid. The pro- duct was still more hke succinic acid in taste; was not deliquescent; easily dis- solved both in water and alcohol; and did not precipitate the metallic solutions, as it did in combination with lime. Twenty grains being slightly heated in a small glass retort, a number of drops of an acid liquor first came over; next a concrete salt arose, that adhered flat against the top and part of the neck of the retort in the form of prismatic crystals, colourless and transparent; and a coaly residuum re- mained. The acid was then washed out. and crystallized by spontaneous evapora- tion. Thus sublimation appears to be the best mode of purifying the salt, but it ad- hered too sirongly to the lime to be sepa- rated from it directly by heat without be- ing decomposed. Not having a sufficient quantity to de- termine its specific characters, though he conceives it to be a peculiar acid, coming nearest to the succinic both in taste and other qualities, Mr. Klaproth has pro- visionally given it the name of moroxylic, and the calcareous salt containing it that of moroxylate of lime. Acid (Mocic). This acid has been gene rally known by the name of saccholaetic, because it was first obtained from sugar of milk ; but as all the gums appear to afford it, and the principal acid in sugar of milk is the oxalic, chemists in general now dis- tinguish it by the name of mucic acid. It was discovered by Scheele. Having poured twelve ounces of diluted nitric acid on four ounces of powdered sugar of milk in a glass retort on a sand bath, the mixture became gradually hot, and at length effervesced violently, and contin- ued to do so for a considerable time after the retort was taken from the fire. It is necessary therefore to use a lar.^e retort, and not to lute the receiver too tight. The effervescence having nearly subsided, the retort was again placed on the sand heat, and the nitric acid distilled off, till the mass had acquired a yellowish colour. This exhibiting no crystals, eight ounces more ofthe same acid were added, and the distillation repeated, till the yellow colour of the fluid disappeared. As the fluid was inspissated by cooling, it was redissolved in eight ounces of water, and filtered. The filtered liquor held oxalic acid in solution, and seven drams and a Vol. i [8] half of a white powder remained on the filter. This powder was the acid under consideration. If one part of gum be heated gently with two of nitric acid, till a small quantity of nitrous gas and of carbonic acid is disen- gaged, the dissolved mass willdeposite on cooling the mucic acid. According to Fourcroy and Vauquelin, different gums yield from 14 to 26 hundredths of this acid. This pulverulent acid is soluble in about 60 parts of hot water, and by cooling, a fourth part separates in small shining scales, that grow white in the air. It de- composes the muriate of barytes, and both the nitrate and muriate of lime. It acts very little on the metals, but forms with their oxides salts scarcely soluble. It pre- cipitates the nitrates of silver, lead, and mercury. With potash it forms a salt solu- ble in eight parts of boiling water, and crystallizable by cooling. That of soda re- quires but five parts of water, and is equal- ly crystallizable. Both tuese salts are still more soluble when the acid is in excess. That of ammonia is deprived of its base by heat. The salts of bary tes, lime, and mag- nesia, are nearly insoluble. * Mucic or saccholaetic acid has been analyzed recently with much care; Hydrogen. Carbon. Oxygen. Gay-Lussac, 3.62+33.69 +62.69 =100 Berzelius, 5.105 +33.430+ 61.465=100 From saclactate of lead, Berzelius has inferred the prime equivalent of the acid to be 13.1.* * Acid (Muriatic). Let 6 parts of pure and well dried sea salt be put into a glass retort, to the beak of which is luted, in a horizontal direction, a long glass tube arti- ficially refrigerated, and containing a quan- tity of ignited mtuiate of lime. Upon the salt pour at intervals 5 parts of concentrat- ed oil of vitriol, through a syphon funnel, fixed, air-tight, in the tubulure of the re- tort. The free end of the long tube being recurved, so as to dip into the mercury of a pneumatic trough, a gas will issue, which on coming in contact with the air, will form a visible cloud, or haze, presenting, when viewed in a vivid light, prismatic colours. This gas is muriatic acid. When received in glass jars over dry mercury, it is invisi- ble, and possesses all the mechanical pro- perties of air. Its odour is pungent and peculiar. Its taste acid and corrosive. Its specific gravity, according to Sir H. Davy, is such, that 100 cubic inches weigh 39 grains, while by estimation, he says, they ought to be 38.4 gr. By the latter num- ber the specific gravity, compared to air, becomes 1.2590. By the former number the density comes out 1.2800. M. Gay- Lussac states the sp. gr.at 1.2780. Sir H.'s second number makes the prime equiva- ACI ACI lent of chlorine 4.43, which comes near to Berzelius's latest result; while his first number makes it 4.48, (See Cihorine). As the attraction of muriatic acid gas for hygrometric water is very strong, it is very probable that 38.4 grs. may be the more exact weight of 100 cubic inches, regard- ing the same bulk of air as = 30.5. If an inflamed taper be immersed in it, it is in- stantly extinguished. It is destructive of animal life; but the irritation produced by it on the epiglottis scarcely permits its de- scent into the lungs. It is merely changed in bulk by alterations of temperature ; it experiences no change of state. When potassium, tin, or zinc, is heated in con- tact with this gas over mercury, one-half of the volume disappears, and the remain- der is pure hydrogen. On examining the solid residue, it is found to be a metallic chloride. Hence muriatic acid gas con- sists of chlorine and hydrogen, united in equal volumes. This view of its nature was originally given by Scheele, though obscured by terms derived from the vague and visionary hypothesis of phlogiston. The French school afterwards introduced the belief that muriatic acid gas was a compound of an unknown radical and water; and that chlorine consisted of this radical and oxygen. Sir H. Davy has the distinguished glory ot refuting the French hvpothesis, and of proving by decisive ex- periments, that in the present state of out knowledge, chlorine must be regarded as a simple substance; and muriatic acid gas as a compound of it with hydrogen. This gaseous acid unites rapidly, and in large quantity, with water. The following table of its aqueous combinations, was con- structed after experiments made by Mr. E. Davy, in the laboratory ofthe Royal In- stitution, under the inspection of Sir H. Davy. At temperature 45°, barometer 30. 100 parts of solution of muriatic gas, in Of muriat water, of sp. gravity gas , parts. 1.21 contain 42.43 1.20 40.80 1.19 38.38 1.17 34.34 1.16 32.32 115 30.30 1.14 28.28 LIS 26.26 1 12 24.24 1.11 22.30 1.10 20.20 1.'J9 18.18 1.08 16.16 1.07 14.14 1.06 12.12 105 10.10 1.04 8.08 1.03 6.06 100 parts of solution of muriatic gas, in Of muriatic acitt water, of sp. gravitv gas, parts. 1.02 c6ntain 4.04 1.01 2.02 At the temperature of 40° Fahrenheit, water absorbs about 480 times its bulk of gas, and forms solution of muriatic acid gas in water, the specific gravity of which is 1.2109.—Sir H. Davy's Elements. In the Annals of Philosophy for Octo- ber and November 1817, there are two papers on the constitution of liquid muri- atic acid with tables, by Dr. Ure, which coincide nearly with the preceding results. They were founded on a great number of experiments carefully performed, which are detailed in the October number. In mixing strong liquid acid with water, he found' that some heat is evolved, and a small condensation of volume is experien- ced, contrary to the observation of Mr Kirwan. Hence this acid forms no longer an exception, as that eminent chemist taught, to the general law of condensa- tion of volume, which liquid acids obey in their progressive dilutions. Hitherto in- deed many chemists have, without due consideration, assumed the half-sum or arithmetical mean of two specific gravities, to be the truly comfmted mean ; and on comparing the number thus obtained with that derived from experiment, they have inferred the change of volume, occasion- ed by chemical combination. The errors into which this false mode of computation leads are excessively great, when the two bodies differ considerably in their specific gravities. A view of these erroneous re- sults was given in Dr. Ure's third table of sulphuric acid, published in the 7th num- ber of the Journal of Sciences and the Arts, and reprinted in this Dictionary, ar- ticle Specific Gravity. When, however, the two specific gravities do not differ much, the errors become less remarkable. It is a singular fact, that the arithmetical mean, which is always greater than the rightly computed mean specific gravity, gives in the case of hquid muriatic acid, an error in excess, very nearly equal to the actual increase of density. The curious coincidence thus accidentally produced, between accurate experiments and a false mode of calculation is very instructive, and ought to lead chemists to verify every anomalous phenomenon, by independent modes of research. Had Mr. Kirwan, for example, put into a nicely graduated tube 50 measures of strong muriatic acid, and poured gently over it 50 measures of water, he would have found after agita- tion, and cooling the mixture to its former temperature, that there was a decided diminution of volume, as Dr. Ure experi mentally ascertained.* ACI ACI TABLE of real Muriatic Acid, &c. in 100 of the Liquid Acid, by Dr. Uns. Sp.Gr. Dry Acid 1 Chlo- Sp.Gr. Dry [Acid Chlo- cftGr Dry Acid Chlo- Acid. Gas. 1 rine. Acid. Gas. rine. op* txr. Acid. Gas. rine. 1.1920 28.3 37.6036.50 1.1272 18.68 24.82 24.09 1.0610 9.05 12 03 11.68 1.1900 28.02 37.2236.13 1.1253 18.39 24.44 23.72 1.0590 8.77 11.65 11.31 1.1881 27.73 36.85 35.77 1.1233 18.11 24.06 23.36 1.0571 8.49 11.28 10.95 1.1863 27 45 36.47 35.40 1.1214 17.83 23.69122.99 1.0552 8.21 10.90 10.58 1.1845 27.17 36.10 35.04 1.1194 17.55 23.51122.63 1.05>3 7.92 10.53 10.22 1.1827 26.88 35.72 54.67 1.1173 17.26 22.93'22.26 1.0514 7.64 10.15 9.85 1.1808 26.60 35.34 34.31 1.1155 16.98 22.56 21.90 1.0495 7.36 9.77 9.49 1.1790 26.32 34.97 33.94 1.1134 16.7U 22.18 21.53 1.0477 7.07 9.40 9.12 1.1772 26.04 34.59 33.58 1.1115 16.4121.81 2117 1.0457 6.79 9.02 8.7G 1.1753 25.75 34.22 33.21 1.1097 16.13|21.43 20.80 1.0438 6.51 8.65 8.39 1.1735 25.47 33.84 32.85 1.1077 15.8521.05 20.44 1.0418 6.23 8.27 8.03 1.1715 25.19 33.46 32.48 1.1058 15.56 20.68 19.07 1.0399 5.94 7.89 7.66 1.1698 24.90 33.09 32.12 1.1037 15.28 20.30 19.71 1.0380 5.66 7.52 7.30 1.1679 24.62 32.71 31.75 1.1018 15 00 19.93 19.34 1.0361 5.38 7.14 6.93 1.1661 24.34 33L34 31.39 1.0999 14.72 19.55 18.9 1.0342 5.09 6.77 6.57 1.1642 24.05 31.96 31.02 1.0980 14.43 19.17 18.61 1.0324 4.81 6.39 6.20 1.1624 23.77 31.58 30.66 1.0960 14.15 18.80 18.25 1.0304 4.53 6.02 5.84 1.1605 23.49 31.21 30.29 1.0941 13.87 18.42 17.88 1.0285 4.24 5.64 5.47 1.1587 23.20 30.83 29.93 1.0922 13.5818.04 17.52 1.0266i 3.96 5.26 5.11 1.1568 22.92 30.46 29.56 1.0902 13.30 17.67 17.15 1.0247 3.68 4.89 4.74 1.1550 22.64 30.08 29.20 I.G883 13.02:17.29 16.79 1.0228 3.39 4.51 4.38 1.1531 22.36 29.7'J 28 83 1.0863 12.7316.9 2 16.42 1.0209 3.11 4.14 4.01 1.1510 22.07 29.33 28.47 1.0844 12.45 16.54 16.06 1.0190 2.83 3.76 3.65 1.1491 21.79 29.95 28.10 1.0823 12.17 16.17 15.69 1.0171 2.55 3.38 3.28 1.1471 21.51 28.57 27.74 1.0805 11.88 15.79 15.33 1.0152 2.26 3.01 2.92 1.145S 21.22 28.20 2737 1.0785 11.60 15.42 14.96 1.0133 1.98 2.63 2.55 1.1431 20.94 27.82 27.01 1.0765 11.32 15.04 14.60 1.0114 1.70 2.26 2.19 1.1410 20.66 27.45 26.64 1.0746 11.04 14.66 14.23 1.0095 1.41 1.88 1.82 1.1391 20.37 27.07 26.28 1.0727 10.75 14.29 13.87 1.0076 1.13 1.50 1.46 1.1371 20.09 26.69 25.91 1.0707 10.47 13.91 13.50 1.0056 0.85 1.13 1.09 1.135119.81 26.52 25.55 1.0688 10.19 13.54 13.14 1.0037 0.56 0.752 0.73 1.133219.53 29.94 25.18 1.0669 9.90 13.16 12.77 1.0019 0.28 0.376 0.365 1.1312.19.24 25.57 24.82 1.0649 9.62 12.78 12.41 1.000 0.00 0.000 0.000 l.li'93|18.96 25.19 24.45 | 1.0629 9.3412.41 12.04 1 The fundamental density ofthe acid of the preceding table is 1.1920, which is as strong as it is comfortable to make or to use in chemical researches. To find the quantity of real acid in that possessed of greater density, we have only to dilute it with a known proportion of water, till it come within the range ofthe table. The short memoir in the Annals for November, contains the logarithmic series correspon- ding to the range of densities and acid strengths; but for all ordinary purposes the following simple rule will serve: Multiply the decimal part of the number denoting the specific gravity by 147, the product will be very nearly the percen- tage of dry acid, or by 197 when we wish to know the per-centage of the acid %**■ Examples. 1. The specific gravity is 1.141; required the proportion of dry acid in 100 parts. 0.141 X 147 = 20.72. By the table it is 20.66. 2. The specific gravity is 1.096; the quantity of acid gas is sought. 0.096 X 197 = 18.9. By the table it is 18.8. According to the new doctrine of Sir H. Davy there is no such substance as the dry acid; and therefore in a theoretical point of view, the column containing it might have been expunged. But for practical purposes it is very useful, for it showsdirectly the increase of weight which any alkaline or earthy base will acquire, by combining with the liquid acid. Thus, if we unite 100 grs. of liquid acid sp. gravity 1.1134 with quicklime, we see that the base will, on evaporation to dryness, be heavier by 16.7 grains. We would require a little calculation to determine this amount from the other columns. We have seen it stated that water, in absorb- ing 480 times its bulk of the acid gas, be- comes of specific gravity 1.2109. If we compute from these data the increase of its bulk, we shall find it equal to 1,42, o: ACI ACI nearly one and a half the volume ofthe water. 481 parts occupy only 1.42 in bulk, a condensation of about 340 into one. The consequence of this approximation ofthe particles, is the evolution of their latent heat; and accordingly the heat produced in the condensation ofthe gas is so great that it melts ice almost as rapidly as the steam of boiling water does. Hence also in passing the gas from the beak of a retort into a Woulfe's apparatus containing water to be impregnated, it is necessary to sur- round the bottles with cold water or ice, if we wish a considerable condensation. Dr. Thomson, in the second volume of his System of Chemistry, 5th edition, has committed some curious mistakes in treat- ing ofthe aqueous combination of muriatic acid gas. He says, " A cubic inch of water at the temperature of 60°, barome- ter 29.4, absorbs 515 cubic inches of muri- atic acid gas, which is equivalent to 308 grains nearly. Hence water thus impreg- nated contains 0.548, or more than half of its weight of muriatic acid, in the same state of purity, as when gaseous. I caused a current of gas to pass through water, till it refused to absorb any more. The specific gravity of the acid thus obtained was 1.203. If we suppose that the water in this experiment absorbed as much gas as in the last, it will follow from it that 6 parts of water, being saturated with this gas, expanded so as to occupy very nearly the bulk of 11 parts; but in all my trials the expansion was only to 9 parts. This would indicate a specific gravity of 1.477; yet upon actually trying water thus saturated, its specific gravity was only 1.203. Is this difference owing to the gas that escapes during the taking of the specific gravity ?" page 232. We are here presented with a puzzle for the chemical student; and an instruc- tive example, when one takes the trouble of unravelling the hank, of a contest be- tween experimental results and false computation. Granting all the experimen- tal statements to be exact, none of the consequences follow. For, in the first place, 515 cubic inches of muriatic acid gas do not weigh 308 grains nearly, but only 201 grains; and hence, secondly, his liquid acid could contain at utmost only 0.443 of its weight of gas, instead of 0.548; and, in the third place, the calculated en- largement of bulk is 1.5, or from 6 to 9, and not to 11; so that the quere with which he concludes is superseded. But another quere may here be started, about the experimental results themselves. Dr. Thomson says, that a cubic inch of water absorbs 515 cubic inches of gas, and ac- quires the specific gravity by experiment of 1.203. Sir H. Davy states, that a cubic inch of water absorbs about 480 cubic inches of gas, and forms a liquid of specific gravity 1.2109. Now it is remarkable that Dr. Thomson's additional condensation of 35 inches of gas gives a less specific gravity than we have in the stronger acid of Sir H. Davy. But farther, the table constructed by Sir H. and E. Davy presents for its funda- mental density the number 1.20 of Dr. Thomson. Mow this particular acid of 1.20 was carefully analyzed by nitrate of silver, and is stated by Sir II. to contain in 100 grains 40.8 grains «if condensed gas. Of course we have a remainder of 59.2 grains of water. 40.8 gr. of gas have a vol- ume at the ordinary pressure and temper- ature of 104 cubic inches, reckoning the weight of 100 cubic inches to be 39.162 gr. with Dr. Thomson- And as 59 2 gr. of water have absorbed 104 cubic inches, we liave the following proportion, 59.2: 104:: 252.5:443. Thus a cubic inch has con. densed only 443 cubic inches, instead of 515. as by Dr. Thomson. And whatever error may be supposed to be in their table, it is but minute, and undoubtedly does not consist in underrating the quan- tity of condensed gas. By uniting the base of this gas with silver, and also with potassium, Berzelius has lately determined the prime equivalent of muriatic acid to be 3.4261, whence chlorine comes out 4.4261, and muriatic gas 4.4 61 + 0.125 (the prime of hydro- gen) = 4.5511. But if we take 1.278 as the specific gravity of this acid gas, then the specific gravity of chlorine will be twice that number, minus the specific gravity of hydrogen, or (1.278 X 2) —0.U694 =- 2.4866; and as chlorine and hydrogen unite volume to volume, then the relation of the prime of chlorine will 2.4866 be to that of hydrogen =------= 35.83. 0.0694 If we divide this by 8, we shall have 4.48, to represent the prime equivalent of chlo- rine, and 4 48 + 0.125 = 4.605 for that of muriatic acid gas. But if we call the specific gravity of dry muriatic acid gas 1.2590, as Sir H. Davy says it should be by calculation, then the sp. gravity of chlorine becomes 2.4486, and its prime 4.42, a number agreeing nearly with the latest researches of Berzelius. Muriatic acid, from its composition, has been termed by M. Gay-Lussac the hydro- chloric acid; a name objected to, on good grounds, by Sir H. Davy. It was prepar- ed by the older chemists in a very rude manner, and was called by them spirit of salt.* In the ancient method, common salt wa9 previously decrepitated, then ground with dried clay, and kneaded or wrought ACI ACI with water to a moderately stiff consis- tence, after which it was divided into balls of the size of a pigeon's egg: these balls, being previously well dried, were put into a retort, so as to fill the vessel two-thirds full; distillation being then proceeded upon, the muriatic acid came over when the heat was raised to ignition. In this process eight or ten parts of clay to one of salt are to be used. The retort must be of stone-ware well coated, and the furnace musi be of that kind called rcverberatory. It was formerly thought, that the salt was merely divicL d in this operation by the clay, and on this account more readily gave out its acid; but there can be little doubt, that the effect is produced by the siliceous earth, which abounds in large proportions in all natural clays, and de- tains the alkali of the salt by combining with it. * Sir H. Davy first gave the just ex- planation of this decomposition. Common salt is a compound of sodium and chlorine. The sodium may be conceived to combine with the oxygen of the water in the earth, and with the earth itself, to form a vitreous compound; and the chlorine to unite with the hydrogen of the water, forming muriatic acid gas. " It is also easy," adds he, " according to these new ideas, to ex- plain the decomposition of salt by moisten- ed litharge, the theory of which has so much perplexed the most acute chemists. It may be conceived to be an instance of compound affinity; the chlorine is attrac- ted by the lead, and the sodium combines with the oxygen of the litharge, and with water, to form hydrate of soda, which gradually attracts carbonic acid from the air. When common salt is decomposed by oil of vitriol, it was usual to explain the phenomenon by saying, that the acid by its superior affinity, aided by heat, expelled the gas, and united to the soda. But as neither muriatic acid nor soda exists in common salt, we must now modify the explanation, by saying that the water of the oil of vitriol is first decomposed, its oxygen unites to the sodium to form soda, which is seized on by the sulphuric acid, while the chlorine combines with the hy- drogen of the water, and exhales in the form of muriatic acid gas." As 100 parts of dry sea salt, are capable of yielding 62 parts by weight of muriatic acid gas, these ought to afford by econo- mical management nearly 221 parts of liquid acid, specific gravity 1.142, as pre- scribed by the London College, or 200 parts of acid sp. gr. 1.160, as directed by the Edinburgh and Dublin Pharmacopeias. The fluid ounce ofthe London College being ^g of a wine pint, is equal in weight to 1.265817 UV., Troy, divided by 16, which gives 453.7 grains Troy. Thi* weight multiplied by 1.142 = the specific gravity of their standard acid, gives the product 520.4; which being multiplied by 0.2763, the muriatic gas in 1.00 by Dr. Ure's table, we have 143.8 or 144 for the acid gas in the liquid ounce, of the above density. We find this quantity equivalent to 200 gr. of carbonate of lime. Had the fundamental number 28.3 of Dr. Ure's table been made 28.6, as one of his ex- periments related in the Annals of Philoso- phy indicates, then a liquid ounce ofthe above acid would have dissolved upwards of 202 grains of pure calcareous carbonate. But when the results fluctuate between 28.3 and 28.6, they become exceedingly difficult to decide upon. As the difference is altogether unimportant in practice, he does not feel himself justified in making any alteration in his table. The limit of its error is certainly a fraction of one percent. \\ ere 29.0 the leading number, then a liquid oz. of acid of 1.142, would dissolve 205 grains of calc spar. It is obvious that the series of specific gravities given in the above table, is altogether independent of this question. If 28.6 should be prefer- red bv any person, let him multiply this number by 0.9, 0.8, 0.7, 0.6, &c. and he will have a series of numbers represen- ting the quantities of dry acids correspon- ding to the specific gravities 1.190,1.1735, 1.1550, 1.1351, &c. for these densities are opposite to 90, 80, 70, 60, 8tc. per cent of the strong acid. When this acid is con- taminated with sulphuric acid, it affords precipitates with muriates of barytes and strontites.* We have described the ancient method of extracting the gas from salt, which is now laid aside. The English manufacturers use iron stills for this distillation, with earthen heads: the philosophical chemist, in making the acid of commerce, will doubtless prefer glass. Five parts, by weight, of strong sulphuric acid are to be added to six of decrepitated sea salt, in a retort, the upper part of which is furnished with a tube or neck, through which the acid is to be poured upon the salt. The aperture of this tube must be closed with a ground stopper immediately after the pouring. The sulphuric acid im- mediately combines with the alkali, and expels the muriatic acid in the form of a peculiar air, which is rapidly absorbed by water. As this combination and disen- gagement take place without the applica- tion of heat, and the aerial fluid escapes very rapidly, it is necessary to arrange and lute the vessels together before the sul- phuric acid is added, and not to make any fire in the furnace until the disengagement begins to slacken; at which time it must be very gradually raised. Before the mo- ACI ACI dern improvements in chemistry were made, a great part ofthe acid escaped for want of water to combine with; but by the use of Woulfe's apparatus, (See Labora- tory,) the acid air is made to pass through water, in which it is nearly condensed, and forms muriatic acid of double the weight ofthe water, though the bulk of this fluid is increased one-half only. The acid con- densed in the first receiver, which con- tains no water, is of a yellow colour, aris- ing from the impurities ofthe salt. The marine acid in commerce has a straw colour: but this is owing to accidental im- purity ; for it does not obtain in the acid produced by the impregnation of water with the pure aeriform acid. The muriatic acid is one of those longest known, and some of its compounds are among those salts with which we are most familiar. * The muriates, when in a state of dry- ness, are actually chlorides, consisting of chlorine and the metal; but since moisture makes them instantly pass to the state of muriates, we shall describe them under this article. The sulphates and nitrates, when destitute of water, may in like man- ner be regarded as containing neither acid nor alkali, and might therefore be trans- ported to some new department of classi- fication, to be styled sulphides and nitrides, as we shall see in treating of salts.* The muriate of barytes crystallizes in ta- bles bevelled at the edges, or in octaedral pvramids applied base to base. It is solu- ble in five parts of water at 60°, in still less at a boiling heat, and also in alcohol. It is not altered in the air, and but partly de- composable by heat. The sulphuric acid separates its base; and the alkaline carbo- aates and sulphates decompose it by dou- ble affinity. It is best prepared by dis- solving the carbonate in dilute muriatic acid; and if contaminated with iron or lead, which occasionally happens, these may be separated by the addition of a small quan- tity of liquid ammonia, or by boiling and stirring the solution with a little barytes. Mt. Goettling recommends to prepare it from the sulphate of barytes: eight parts of which in fine powder are to be mixed with two of muriate of soda, and one of charcoal powder. This is to be pressed hard into a Hessian crucible, and exposed for an hour and a half to a red heat in a wind furnace. The cold mass, being pow- dered, is to be boiled a minute or two in sixteen parts of water, and then filtered. To this liquor muriatic acid is to be added by little and little, till sulphuretted hydro- gen ceases to be evolved; it is then to be filtered, a little hot water to be poured on the residuum, the liquor evaporated to a pellicle, filtered again, and then set to crys- tallize. As the muriate of soda is much more soluble than the muriate of barytes^ and does not separate by cooling, the mu- riate of barytes will crystallize into a per- fectly white salt, and leave the muriate of soda in the mother water, which may be evaporated repeatedly till no more muriate of barytes is obtained. This salt was first employed in medicine by Dr. Crawford, chiefly in scrofulous complaints and can- cer, beginning with doses of a few drops of the saturated solution twice a-day, and increasing it gradually, as far as forty or fifty drops in some instances. In large do- ses it excites nausea, and has deleterious effects. Fourcroy says it has been found very successful in scrofula in France. It has likewise been recommended as a ver- mifuge; and it has been given with much apparent advantage, even to very young children, where the usual symptoms of worms occurred, though none were ascer- tained to be present. As a test of sulphu- ric acid it is of great use. The muriate of potash, formerly known by the names of febrifuge salt of Sylvius, digestive salt, and regenerated sea salt, crys- tallizes in regular cubes, or in rectangular parallelopipedons; decrepitating on the fire, without losing much of their acid, and acquiring a little moisture from damp air, and giving it out again in dry. Their taste is saline and bitter. They are soluble in thrice their weight of cold water, and in but little less of boiling water, so as to re- quire spontaneous evaporation for crystal- lizing. Fourcroy recommends, to cover the vessel with gauze, and suspend hairs in it, for the purpose of obtaining regular crystals. It is sometimes prepared in decompo- sing sea salt by common potash for the purpose of obtaining soda; and may be formed by the direct combination of its constituent parts. It is decomposable by the sulphuric and nitric acids. Barytes decomposes it, though not completely. And both silex and alu- mina decomposed it partially in the dry way. It decomposes the earthy nitrates, so that it might be used in saltpetre manu- factories to decompose the nitrate of lime. Muriate of soda, or common salt, is of con- siderable use in the arts, as well as a ne- cessary ingredient in our food. It crystal- lizes in cubes, which are sometimes group- ed together in various ways, and not unfre- quently form hollow quadrangular pyra- mids. In the fire it decrepitates, melts, and is at length volatilized. When pure it is not deliquescent. One part is soluble in 2 J of cold water, and in little less of hot, so that it cannot be crystallized but by eva. poration. According to M. Chenevix, it is soluble in alcohol also, particularly when it is mixed with the chlorate. Common salt is found in large masses, or ACI ACI in rocks under the earth, in England and elsewhere. In the solid form it is called sal gem or rock salt. If it be pure and trans- parent, it may be immediately used in the state in which it is found; but if it contain any impure earthy particles, it should be previously freed from them. In some •ountries it is found in incredible quanti- ties, and dug up like metals from the bow- els of the earth. In this manner has this salt been dug out of the celebrated salt mines near Bochnia and Wieliczka, in Po- land, ever since the middle of the 13th century, consequently above these 500 years, in such amazing quantities, that sometimes there have been 20,000 tons ready for sale. In these mines, which are said to reach to the depth of several hun- dred fathoms, 500 men are constantly em- ployed. The pure and transparent salt needs no other preparation than to be beaten to small pieces, or ground in a mill. But that which is more impure must be elutriated, purified, and boiled. That which is quite impure, and full of small stones, is sold under the name of rock salt, and is applied to ordinary uses; it may likewise be used for strengthening weak and poor brine-springs. Though the salt mines of Wieliczka, near Cracow in Poland, have long asto- nished the philosopher and traveller, yet it deserves to be remarked, that the quan- tity of rock salt obtained from the mines of Northwich is greatly superior to that •btained at Cracow. The bishop of Llan- daff affirms, that a single pit, into which he descended, yielded at a medium 4000 tons of salt in a year, which alone is about two-thirds of that raised in the Polish mines. This rock salt is never used on our tables in its crude state, as the Polish rock salt is; and though the pure transpa- rent salt might be used with our food, with- out any danger, yet it is prohibited under a penalty of 40s. for every pound of rock salt so applied. It is partly purified in water, and a great part of it is sent to Li- verpool and other places, where it is used either for strengthening brine-springs or sea water. Beside the salt mines here mentioned, where the common salt is found in a con- crete state, under the name of rock salt, there is at Cordova, in the province of Ca- talonia in Spain, a remarkable solid moun- tain of rock salt; this mountain is between four and five hundred feet in height, and a league in circuit; its depth below the sur- face of the earth is not known. This mountain contains the rock salt without the least admixture of any other matter. The waters of the ocean every where abound with common salt, though in diffe- rent proportions. The water of the Bal- tic sea is said to contain one sixty-fourth of its weight of salt; that of the sea be* tween England and Flanders contains one thirty-second part; that on the coast of Spain one sixteenth part; and between the tropics it is said, erroneously, to con- tain from an eleventh to an eighth part. The water of the sea contains, besides" the common salt, a considerable propor- tion of muriate of magnesia, and some sul- phate of lime, of soda, and potash. The former is the chief ingredient of the re- maining liquid which is left after the ex- traction ofthe common salt,and is called the mother water. Sea water, if taken up near the surface, contains also the putrid re- mains of animal substances, which render it nauseous, and in a long continued calm cause the sea to stink. The whole art of extracting salt from waters which contain it, consists in evapo- rating the water in the cheapest and most convenient manner. In England, a brine composed of sea water, with the addition of rock salt, is evaporated in large shallow iron boilers; and the crystals of salt are taken out in baskets. In Russia, and pro- bably in other northern countries, the sea water is exposed to freeze ; and the ice, which is almost entirely fresh, being taken out, the remaining brine is much stronger, and is evaporated by boiling. In the southern parts of Europe the salt-makers take advantage of spontaneous evapora- tion. A flat piece of ground near the sea is chosen, and banked round, to prevent its being overflowed at high water. The space within the banks is divided by low walls into several compartments, which successively communicate with each other. At flood tide, the first of these is filled with sea water; which, by remaining a certain time, deposites its impurities, and loses part of its aqueous fluid. The resi- due is then suffered to run into the next compartment: and the former is again filled as before. From the second com- partment, after a due time, the water is transferred into a third, which is lined with clay well rammed and levelled. At this period the evaporation is usually brought to that degree, that a crust of salt is formed on the surface of the water, which the workmen break, and it imme- diately falls to the bottom. They continue to do this, until the quantity is sufficient to be raked out, and dried in heaps. This is called bay salt. In some parts of France, and also on the coast of China, they wash the dried sands of the sea with a small proportion of wa- ter, and evaporate this brine in leaden boilers. There is no difference between this salt and the lake salt extracted from different lakes, excepting such as may be occasion- ed by theeasual intervention of some sub= ACI ACI stances. In this respect the Jeltonic salt water lake, in the Russian dominions, near Saratow and Dmitrewsk, deserves our at- tention. In the year 1748, when the Rus- sians first fetched salt thence, the lake was almost solid with salt; and that to such a degree, that they drove their heavy wagons over it, as over a frozen river, and broke up the salt.+ But since the year 1757 the water has increased so much, that at this time it is nothing more than a lake very strongly impregnated with salt. The Jeltonic lake salt contains at the same time alum and sulphate of magnesia. At several places in Germany, and at Montmarot in France, the waters of salt springs are pumped up to a large reser- voir at the top of a building or shed; from which it drops or trickles through small apertures upon boards covered with brush- wood. The large surface of the water thus exposed to the air causes a very con- siderable evaporation ; and the brine is af- terward conveyed to the boilers for the perfect separation ofthe salt. To free common salt from those mix- tures that render it deliquescent, and less fit for the purposes to which it is applied, it may be put into a conical vessel with a small aperture at the point, and a satura- ted solution of the muriate of soda boiling hot be poured on it. This solution will dissolve and carry oft' any other salt mix- ed with the muriate of soda, and leave it quite pure, by repeating the process three or four times. From this salt, as already observed, the muriatic acid is extracted; and of late years to obtain its base separate, in the most economical mode, for the purposes ofthe arts, has been an object of research. The process of Scheele, which consists in mixing the muriate of soda with red oxide of lead, making this into a soft paste with water, and allowing it to stand thus for some time, moistening it with water as it gets dry, and then separating the soda from the muriate of lead by lixiviation, has been resorted to in this country. Mr. Turner some years ago had a patent for it; converting the muriate of lead into a a pigment, which was termed mineral or patent yellow, by heating it to fusion. The oxide of lead should be at least twice the weight of the salt. This would have an- swered extremely well, had there been an adequate and regular demand for the pigment. At present, we understand,the greater part of the carbonate of soda in the market is furnished by decomposing the sulphate of soda left after the muriatic T Why did it not sink? Does salt swim like ice ? I question the truth of this ac- count. acid is expelled in the usual way of manu- facturing it from common salt. Various processes for this purpose were tried in France and made public by the French government, all depending on the princi- ple of decomposing the acid of the sul- phate, by charcoal, and at the same tune adding some other material to prevent the soda from formini; a sulphuret. What they consider as the best, is to mix the sul- phate of soda with an equal weight of chalk and rather more than half its weight of charcoal powder, and to expose the mix- ture in a reverberatory furnace to a heat sufficient to bring them to a state of im- perfect liquefaction. Much of the sulphur formed will be expelled in vapour and burned, the mixture being frequently stirred to promote this; and this is conti- nued till the mass on cooling assumes a fine grain. It is then left exposed to a humid amosphere, and the carbonate of soda may be extracted by lixiviation, the sulphur not consumed having united with the lime. Tinmen's shreds, or old iron, may be employed instead of chalk, in the proportion of 65 parts to 200 of sulphate of soda, and 62 of charcoal; or chalk and iron may be used at the same time in dif- ferent proportions. The muriate of soda might be decomposed in the first instance by the sulphate of iron, instead ofthe sul- phuric acid. The carbonate of soda thus prepared, however, is not free from sul- phur, and Dize recommends the abstrac- tion of it by adding litharge to the lixi- vium in a state of ebullition, which will render the alkali pure. Oxide of manga- nese was substituted in the same way with equal success; and this may be used re- peatedly, merely by calcining it after each time to expel the sulphur. Mr. Accum gives the following method, as having answered extremely well in a soda manufactory in which he was em- ployed :—Five hundred pounds of sulphate of soda, procured from the bleachers, who make a large quantity in preparing their muriatic acid from common salt, were put into an iron boiler with a sufficient quan- tity of soft water. Into another boiler were put 560 lbs. of good American potash, or 570, if the potash were indifferent, dis- solved in about 30 pails of water, or as lit- tle as possible. When both were brought to boil, the solution of potash was ladled into that of sulphate of soda, agitating the mixture, and raising the fire as quickly as possible. When the whole boiled, it was ladled into a wooden gutter, that convey- ed it to a wooden cistern lined with lead near half an inch thick, in a cool place. Sticks were placed across the cistern, from which slips of sheet lead, two or three inches wide, hung down into the fluid about four inches distant from each ACI ACI other. When the whole was cold, which in winter was in about three days, the fluid was drawn off, the crystalized salt was de- tached from the slips of lead, and the rock of salt fixed to the bottom was separ- ated by a chisel and mallet. The salt being washed in the same cistern, to free it from impurities, was then returned to the boil- er, dissolved in clear water, and evaporat- ed till a strong pellicle formed. Letting it cool till the hand could be dipped into it, it was kept at this temperature as long as pellicles would form over the whole sur- faoe, and fall to the bottom. When no more pellicles appeared without blowing on the surface, the fire was put out, and the solution returned into the cistern to crystallize. If the solution be suffered to cool pretty low, very little sulphate of potash will be found mixed with the soda; but the rocky masses met with in the mar- ket generally contain a pretty large quan- tity. In the process above described, the produce ofthe mixed salt from 100 lbs. of sulphate of soda was in general from 136 to 139 lbs. Besides its use in seasoning our food, and preserving meat both for domestic consumption and during the longest voy- ages, and in furnishing us with the muri- atic acid and soda, salt forms a glaze for coarse pottery, by being thrown into the oven where it is baked; it improves the whiteness and clearness of glass ; it gives greater hardness to soap ; in melting me- tals it preserves their surface from calci- nation, by defending them from the air, and is employed with advantage in some assays ; it is used as a mordant, and for im- proving certain colours, and enters more or less into many other processes of the arts. The muriate of strontian has not long been known. Dr. Hope first distinguished it from muriate of bary tes. It crystallizes in very slender hexagonal prisms, has a cool pungent taste, without the austerity ofthe muriate of barytes, or the bitterness of the muriate of lime ; is soluble in 0.75 of water at 60°, and to almost any amount in boiling water; is likewise soluble in alcohol, and gives a blood-red colour to its flame. It has never been found in nature, but may be prepared in the same way as the muriate of barytes. The muriate of lime has been known by the names of murine selenite, calcareous marine salt, muria, and fixed sal ammoniac. It crystallizes in hexaedral prisms, termi- nated by acute pyramids; but if the solu- tion be greatly concentrated, and exposed to a low temperature, it is condensed in confused bundles ofneedly crystals. Its taste is acrid, bitter, and very disagreea- ble. It is soluble in half its weight of cold Vol. r. [ 9 ] water, and by heat in its own water of crystallization. It is one of the most de- liquescent salts known; and when deli- quesced has been called oil of lime. It exists in nature, but neither very abun- dantly nor very pure. It is formed in chemical laboratories, in the decomposi- tion of muriate of ammonia; and Homberg found, that, if it were urged by a violent heat, till it condensed, on cooling, into a vitreous mass, it emitted a phosphoric light upon being struck by any hard body, in which state it was called Homberg's phos- phorus. Hitherto it has been little used except for frigorific mixtures; and with snow it produces a very great degree of cold. Fourcroy, indeed, says he has found it of great utility in obstructions of the lym- phatics, and in scrofulous affections. The muriate of ammonia has long been known by the name of sal ammonia, or am- nionic. It is found native in the neigh- bourhood of volcanoes, where it is sub- limed sometimes nearly pure, and in dif- ferent parts of Asia and Africa. A great deal is carried annually to Russia and Si- beria from Bucharian Tartary; and we formerly imported large quantities from Egypt, but now manufacture it at home. See Ammonia. This salt is usually in the form of cakes, with a convex surface on one side, and concave on the other, from being sub- limed into large globular vessels; but by solution it may be obtained in regular quadrangular crystals. It is remarkable for possessing a certain degree of ductili- ty, so that it is not easily pulverable. It is soluble in 3£ parts of water at 60°, and in little more than its own weight of boil- ing water. Its taste is cool, acrid, and bit- terish. Its specific gravity is 1.42. It attracts moisture from the air but very slightly. Muriate of ammonia has been more em- ployed in medicine than it is at present. It is sometimes useful as an auxiliary to the bark in intermittents; in gargles it is beneficial, and externally it is a good dis- cuticnt. In dyeing it improves or height- ens different colours. In tinning and sol- dering it is employed to preserve the sur- face ofthe metals from oxidation. In as- paying it discovers iron, and separates it from some of its combinations. The muriate of magnesia is extremely deliquescent, soluble in an equal weight of water, and difficultly crystallizable. It dis- solves also in five parts of alcohol. It is decomposable by heat, which expels its acid. Its taste is intensely bitter. With ammonia this muriate forms a tri- ple salt, crystallizable in little polyedrons, which separate quickly from the water, but arc net very regularly formed. Its ACI ACI taste partakes of that of both the prece- ding saits. The best mode of preparing it, is by mixing a solution of 27 parts of muriate of ammonia with a solution of 73 of muriate of magnesia; but it may be formed by a semi-decomposition of either of these muriaics by the base ofthe other. It is decomposable by heat, and requires six or seven times its weight of water to dissolve it. Of the muriate ot glucine we know but little. It appears to crystallize in very small crystals; to be decomposable by heat; and, dissolved in alcohol and diluted with water, to form a pleasant saccharine liquor. .Muriate of alumina is scarcely crystal- lizable, as on evaporation it assumes the state of a thick jelly. It has an acid, styp- tic, acrid taste. It is extremely soluble in water, and deliquescent. Fire decom- poses it. It may be prepared by directly combining the muriatic acid with alumina, but the acid always remains in excess. The muriate of zircon crystallizes in small needles, which are very soluble, at- tract moisture, and lose their transparency in the air. It has an austere taste, with somewhat of acrimony. It is decomposa- ble by heat. The gallic acid precipitates from its solution, if it be free from iron, a white powder. Carbonate of ammonia, if added in excess, redissolves the preci- pitate it had before thrown down. Muriate of yttria does not crystallize when evup.rated, but forms a jelly: it dries with difficulty, and deliquesces. Fourcroy observes, that when siliceous stones, previously fused with potash, are treated with muriatic acid, a limpid solu- tion is formed, which may be reduced to a transparent jelly by slow evaporation. But a boiling heat decomposes the sili- ceous muriate, and the earth is deposited. The solution is always acid. * Acid (Muriatic, Oxxgekatbd). See Chlorine.* * Acin (Muriatic, Oxtgemzed). This supposed acid was lately described by M. Thenard. He saturated common muriatic acid of moderate strength with deutoxide of barium, reduced into a soft paste by trituration with water. He then precipi- tated the barytes from the liquid, by ad- ding the requisite quantity of sulphuric acid. He next took this oxygenized mu riatic acid, and treated it with deutoxide of barium and sulphuric acid, to oxygenate it anew. In this way he charged it with oxygen as often as 15 times. He thus ob- tained a liquid acid which contained 32 tin.es its volume of oxygen at the tempe- rature of 68y Fahr. and at the ordinary atmospherical pressure, and only 4J times its volume of muriatic acid, which gives about 26 equivalent primes of oxygen to one of muriatic acid. For the ratio of oxygen to the acid, by weight, is 1. to 4.6; but by measure the ratio will be as these two numbers respectively divided by the specific gravity of the gases, or its r-l rr to T.^7,which by reduction makes near; ly one volume of oxygen, equivalent to four of muriatic acid. Now, the oxygen in the above result, instead of being 1 4th of the volume of the acid gas, was seven times greater, whence we derive the num- ber 28. Still more oxygen may however be added. On putting the above oxygen- ized acid in contact with sulphate of sil- ver, an insoluble chloride of this metal subsides, and the liquid is oxygenized sulphuric acid. When this is passed through the filter, muriatic acid is added to it, but in smaller quantity than existed in the original oxygenized acid. A quan- tity of barytes, just sufficient to precipi- tate the sulphuric acid, is then added. In- stantly the oxygen, leaving the sulphuric acid to unite with the muriatic acid, brings that acid to the highest point of oxy gena- tion. Thus we see that we can transfer the whole of the oxygen from one of these acids to the other; and on a little reflection it v\ ill be evident, that to obtain sulphuric acid in the highest degree of oxygenation, it will be merely necessary to pour barytes water into oxygenated sulphuric acid, so as to precipitate only a part of the acid. All these operations, with a little prac- tice, may be performed without the least difficulty. By combining the two methods just'described, M. Thenard found that lie could obtain oxygenized muriatic acid, containing nearly 16 times as many vo- lumes of oxygen as of muriatic acid, which represents about 64 equivalent primes of the former to one of the latter. This oxygenized acid leaves no residuum when evaporated. It is a very acid, colourless liquid, almost destitute of smell, and pow- erfully reddens turnsole. When boiled for some time, its oxygen is expelled. It dissolves zinc without effervescence. Its action on the oxide of silver is curious. These two bodies occasion as lively an ef- fervescence as if an acid were poured upon a carbonate. Water and a chloride are formed, while the oxygen is evolved. This oxide enables us to determine the quantity of oxygen present in the oxygen- ized acid. Pour mercury into a graduated glass tube, leaving a small determinate space, which must be filled with the above acid, invert the tube in mercury, let up oxide of silver diffused in water; instantly the oxygen is separated. We ought, however, to regard this ap- parent oxygenation of the acid, merely as the conversion of a portion of its com- ACI ACI bined water into deutoxide of hydrogen. The same explanation may be extended to the other oxygenized acids of M. Thenard. See Watkb.* * Acm (Chloric). We place this acid after the muriatic acid, because it has chlorine also for its Ijase. It was first eli- minated from the salts containing it by M. Gay-Lussac, and described by him in his admirable memoir on iodine, published in the yist volume of the Annates de Chimie. When a current of chlorine is passed for some time through a solution of bary tic earth in warm water, a substance called hyperoxymuriate of baryrtes by its first discoverer, M. Chenevix, is formed, as well as some common muriate. The lat- ter is separated, by boiling phosphate of silver in the compound solution. The for- mei may then be obtained by evaporation, in fine rhomboidal prisms. Into a dilute solution of this salt, M. Gay-Lussac poured weak sulphuric acid. Though he added only a few drops of acid, not nearly enough to saturate the barytes, the liquid became sensibly acid, and not a bubble of oxygen escaped. By continuing to add sulphuric acid with caution, he succeeded in obtain- ing an acid liquid entirely free from sul- phuric acid and barytes, and not precipi- tating nitrate of silver. It was chloric acid dissolved in water. Its characters are the following. This acid has no sensible smell. Its so- lution in water is perfectly colourless. Its taste is very acid, and it reddens litmus without destroyingthe colour. It produces no alteration on solution of indigo in sul- phuric acid. Light does not decompose it. It may be concentrated by a gentle heat, without undergoing decomposition, or without evaporating. It was kept a long time exposed to the air without sensible diminution of its quantity. When con- centrated, it has something of an oily con- sistency. When exposed to heat, it is partly decomposed into oxygen and chlo- rine, and partly volatilized without altera- tion. Muriatic acid decomposes it in the same way, at the common temperature. Sulphurous acid, and sulphuretted hydro- gen, have the same property; but nitric acid produces no change upon it. Com- bined with ammonia, it forms a fulminating salt, formerly described by M. Chenevix. It does not precipitate any metallic solu- tion. It readily dissolves zinc, disengaging hydrogen; but it acts slowly on mercury. It cannot be obtained in the gaseous state. It is composed of 1 volume chlorine -f- 2.5 oxvgen, or, by weight, of 100 chlorine + 1.11.70 oxygen, if we consider the spe- cific gravity of chlorine to be 24866. But if it be called 2.420, as M. Gay-Lussac does in his memoir, it will then come out 100 chlorine -f 114.7 oxygen. This last num- ber is however too great, in consequence of estimating the specific gravity of oxy- gen 1.1111, while M. Gay-Lussac makes it 1.10359. Chloric acid is at any rate a com- pound of 5 primes of oxygen + 1 of chlo- rine = 5. -\- 4.43 by Berzelius, or 5. -f- 4.45 by Dr. Ure's estimate ofthe atom of chlorine. M. Vauquelin, in making phosphate of silver act on the mixed saline solution above described, tried to accelerate its action by dissolving it previously in acetic acid. But on evaporating the chlorate of barytes so obtained to dryness, and ex- posing about 30 grains to a decomposing heat, a tremendous explosion took place, which broke the furnace, rent a thick platina crucible, and drove its lid into the chimney, where it stuck. It was the em- ployment of acetic acid which occasioned this accident, and therefore it ought never to be used in this way. To the preceding account of the pro- perties of chloric acid, M. Vauquelin has added the following : Its taste is not only acid, but astringent, and its odour, when concentrated, is somewhat pungent. It differs from chlorine, in not precipitating gelatin. When paper stained with litmus is left for some time in contact with it, the colour is destroyed. Mixed with muriatic acid, water is formed, and both acids are converted into chlorine. Sulphurous acid is converted into sulphuric, by taking oxy- gen from the chloric acid, which is con- sequently converted into chlorine. Chloric acid combines with the bases, and forms the chlorates, a set of salts for- merly known by the name ofthe hyperoxy- genized muriates. They may be formed either directly by saturating the alkali or earth with the chloric acid, or by the old process of transmitting chlorine through the solutions of the bases, in Woulfe's bottles. In this case the water is decom- posed. Its oxygen unites to one portion of the chlorine, forming chloric acid, while its hydrogen unites to another portion of chlorine, forming muriatic acid; and hence, chlorates and muriates must be contemporaneously generated, and must be afterwards separated by crystalliza- tion, or peculiar methods. The chlorate of potash, or hyperoxymu- riate, has been long known. When ex- posed to a red heat, 100 grains of this salt yield 38.88 of oxy gen, and are converted into the chloride of potassium, or the dry muriate. This remainder of 61.12 grains consists of 32.19 potassium and 28.9^ chlo- rine. But 32.19 potassium require 6.50 oxygen, to form the potash which existed in the original chlorate. Therefore, sub- tracting this quantity from 38.88, we have 32.38 for the oxygen combined with the ACI ACI chlorine, constituting 61.31 of chloric acid, to 38.69 of potash.* To its compounds we shall proceed, premising, that we are indebted to M. Chenevix for the first accurate descrip- tion of the chlorates, or hyperoxy muriates. Chlorate, or hyperoxymuriate of potash, may be procured by receiving chlorine, as it is formed, into a solution of potash. When the solution is saturated, it may be evaporated gently, and the first crystals produced will be the salt desired, this crystallizing before the simple muriate, which is produced at the same time with it. Its crystals are in shining hexae'dral laminae, or rhomboidal plates. It is solu- ble in 17 parts of cold water; and, but very sparingly, in alcohol. * Its taste is cooling, and rather unpleasant. Its speci- fic gravity is 2.0. 16 parts of water, at 60°, dissolve one of it, and 2 J of boiling water. The purest oxygen is extracted from this salt, by exposing it to a gentle red heat. One hundred grains yield about 115 cubic inches of gas. It consists of 9.45 chloric acid + 5-95 potash = 15.4, which is the prime equivalent of the salt.* It is not de- composed by the direct rays of the sun. Subjected to distillation in a coated retort, it first fuses, and on increasing the heat, gives out oxygen gas. It is incapable of discharging vegetable colours; but the addition of a little sulphuric acid developes this property. So likewise a few grains of it, added to an ounce of muriatic acid, give it this property. It is decomposed by the sulphuric and nitric acids. If a few grains be dropped into strong sulphuric acid, an of- fensive smell is produced, resembling that of a brick-kiln, mixed with that of nitrous gas; and if the quantity be large enough, an explosion will en«ue. If the vessel be deep, it will be filled with a thick, heavy vapour, of a greenish yellow colour, but not producing the symptoms of catarrh, at least in so violent a degree as the fumes of chlorine. Underneath this vapour is a bright orange-coloured fluid. This vapour inflames alcohol, oil of turpentine, cam- phor, resin, tallow, elastic gum, and some other inflammable substances, if thrown into it. If the sulphuric acid be poured upon the salt, a violent decrepitation takes place, sometimes, though rarely, accom- panied by a flash. M. Chenevix attempted to disengage the chloric acid from this salt, by adding sulphuric acid to it in a re- tort ; but almost as soon as the fire was kindled, an explosion took place, by which a French gentleman present was severely wounded, and narrowly escaped the loss of an eye. The effects of this salt on inflammable bodies are very powerful. Rub two grains into powder in a mortar, add a grain of sul- phur, mix them well by gentle trituration, then collect the powder into a heap, and press upon it suddenly and forcibly with the pestle, a loud detonation will ensue. If the mixture be wrapped in strong pa- per, and struck with a hammer, the report will be still louder. Five grains ofthe salt, mixed in the same manner with two and a half of charcoal, will be inflamed by strong trituration, especially if a grain or two of sulphur be added, but without much noise. If a little sugar be mixed with half its weight ofthe chlorate, and a little strong sulphuric acid poured on it, a sudden and vehement inflammation will ensue ; but this experiment requires caution, as well as the following. To one grain of the pow- dered salt in a mortar, add half a grain of phosphorus, it will detonate, with a loud report, on the gentlest trituration. In this experiment the hand should be defended by a glove, and great care should be taken that none ofthe phosphorus get into the eyes. Phosphorus may be inflamed by it under water, by putting into a wine glass one part of phosphorus and two ofthe chlo- rate, nearly filling the glass with water, and then pouring in through a glass tube reaching to the bottom, three or four parts of sulphuric acid. This experiment, too, is very hazardous to the eyes. If olive or linseed oil be taken instead of phosphorus, it may be inflamed by similar means on the surface ofthe water. This salt should not be kept mixed with sul- phur, or perhaps any inflammable sub- stance, as in this state it has been known to detonate spontaneously. As it is the common effect of mixtures of this salt with inflammable substances of every kind, to take fire on being projected into the stron- ger acids, M. Chenevix tried the experi- ment with it mixed with diamond powder in various proportions, but without success. Chlorate of soda may be prepared in the same manner as the preceding, by sub- stituting soda for potash ; but it is not easy to obtain it separate, as it is nearly as so- luble as the muriate of soda, requiring on- ly 3 parts of cold water. * Vauquelin formed it, by saturating chloric acid with soda; 500 parts ofthe dry carbonate yield- ing 1100 parts of crystallized chlorate. It consists of 3.95 soda -|- 9.45 acid = 13.4, which is its prime equivalent.* It crystal- lizes in square plates, produces a sensation of cold in the mouth, and a saline taste ; is slightly deliquescent, and in its other properties resembling the chlorate of pot- ash. Barytes appears to be the next base in order of affinity for this acid. The best method of forming it is to pour hot water on a large quantity of this earth, and to pass a current of chlorine through the liquid kept warm, so that a fresh portion of barytes may be taken up as the former ACI ACI is saturated. This salt is soluble in about four parts of cold water, and less of warm, and crystallizes like the simple muriate. It may be obtained, however, by the agen- cy of double affinity ; for phosphate of silver boiled in the solution will decom- pose the simple muriate, and the muriate of silver and phosphate of barytes being insoluble, will both fall down and leave the chlorate in solution alone. The phos- phate of silver employed in this process must be perfectly pure, and not the least contaminated with copper. The chlorate of strontites may be obtain- ed in the same manner. It is deliquescent, melts immediately in the mouth and pro- duces cold; is more soluble in alcohol than the simple muriate, and crystallizes in needles. The chlorate of lime, obtained in a si- milar way, is extremely deliquescent, li- quefies at a low heat, is very soluble in alcohol, produces much cold in solution, and has a sharp bitter taste. Chlorate of ammonia is formed by dou- ble affinity, the carbonate of ammonia de- composing the earthy salts of this genus, giving up its carbonic acid to their base, and combining with their acid into chlo- rate of ammonia, which may be obtained by evaporation. It is very soluble both in water and alcohol, and decomposed by a moderate heat. The chlorate of magnesia much resem- bles that of lime. To obtain chlorate of alumina, M. Chene- vix put some alumina, precipitated from the muriate, and well washed, but still moist, into a Woulfe's apparatus, and treat- ed it as the other earths. The alumina shortly disappeared ; and on pouring sul- phuric acid into the liquor, a strong smell of chloric acid was perceivable; but on at- tempting to obtain the salt pure by means of phosphate of silver, the whole was de- composed, and nothing but chlorate of silver was found in the solution. M. Chene- vix adds, however, that the aluminous salt appears to be very deliquescent, and so- luble in alcohol. * Acid (Perchloric). If about 3 parts of sulphuric acid be poured on one of chlo- rate of potash in a retort, and after the first violent action is over, heat be gradu- ally applied, to separate the deutoxide of chlorine, a saline mass will remain, con- sisting of bisulphate of potash and per- chlorate of potash. By one or two crystal- lizations, the latter salt may be separated from the former. It is a neutral salt, with a taste somewhat similar to the common muriate of potash. It is very sparingly so- luble in cold water, since at 60°, only-jV is dissolved; but in boiling water it is more soluble. Its crystals are elongated octahe- drons. It detonates feebly when triturated with sulphur in a mortar. At the heat oi 412°, it is resolved into oxygen and muri- ate of potash, in the proportion of 46 of the former to 54 of the latter. Sulphuric acid, at 280°, disengages the perchloric acid. For these facts science is indebted to Count Von Stadion. It seems to consist of 7 primes of oxygen, combined with 1 of chlorine, or 7.0 + 4.45. These curious discoveries has been lately verified by Sir H Davy. The other perchlorates are not known. Before leaving the acids of chlorine, we shall describe the ingenious method em- ployed by Mr. Wheeler to procure chloric acid from the chlorate of potash. He mix- ed a warm solution of this salt with one of fluosilicic acid. He kept the mixture mo- derately hot for a few minutes, and to en- sure the perfect decomposition ofthe salt, added a slight excess of the acid. Aque- ous solution of ammonia will show, by the separation of silica, whether any of the fluosilicic acid be left after the decompo- sition ofthe chlorate. Thus we can effect its complete decomposition. The mixture becomes turbid, and fluosilicatc of potash is precipitated abundantly in the form of a gelatinous mass. The supernatant liquid will then contain nothing but chloric acid, contaminated with a small quantity of fluo- silicic. This may be removed by the cau- tious addition of a small quantity of solu- tion of chlorate. Or after filtration, the whole acid may be neutralized by carbo- nate of barytes, and the chlorate of that earth being obtained in crystals, is employ- ed to procure the acid, as directed by M. Gay-Lussac* Acid (Nitric.) The two principal con- stituent parts of our atmosphere, when in certain proportions, are capable, under particular circumstances, of combining chemically into one of the most powerful acids, the nitric. If these gases be mixed in a proper proportion in a glass tube about a line in diameter, over mercury, and a se- ries of electric shocks be passed through them for some hours, they will form nitric acid; or, if a solution of potash be present with them, nitrate of potash will be obtain- ed. The constitution of this acid may be further proved, analytically, by driving it through a red hot porcelain tube, as thus it will be decomposed into oxygen and ni- trogen gases. For all practical purposes, however, the nitric acid is obtained from nitrate of potash, from which it is expelled by sulphuric acid. Three parts of pure nitrate of potash,| coarsely powdered, are to be put into a glass retort, with two of strong sulphu- f Deprived of its water of crystalliza- tion by heating it nearly red hot in an iron pan. ACI ACI ric acid. This must be cautiously added, taking care to avoid the fumes that arise. Join to the retort a tubulated receiver of large capacity, with an adopter interposed, and lute the junctures with glazier's put- ty. In the tubulure fix a glass tube, ter- minating in another large receiver, in which is a small quantity of water; and, if you wish to collect the gaseous products, let a bent glass tube from this receiver communicate with a pneumatic trough. Apply heat to the retort by means of a sand bath. The first product that passes into the receiver is generally red and fu- ming; but the appearances gradually di- minish, till the acid comes over pale, and even colourless, if the materials used were clean. After this it again becomes more and more red and fuming, till the end of the operation; and the whole mingled to- gether will be of a yellow or orange colour. * Empty the receiver, and again replace it. Then introduce by a small funnel, ve- ry cautiously, one part of boiling water in a slender stream, and continue the distilla- tion. A small quantity of a weaker acid will thus be obtained, which can be kept apart. The first will have a specific gra- vity of about 1.500, if the heat have been properly regulated, and if the receiver was refrigerated by cold water or ice. Acid of that density, amounting to two-thirds of the weight of the nitre, may thus be pro- cured. But commonly the heat is pushed too high, whence more or less of the acid is decomposed, and its proportion of water uniting to the remainder, reduces its strength. It is not profitable to use a smaller proportion of sulphuric acid, when a concentrated nitric is required. But when only a dilute acid, called in com- merce aquafortis, is required, then less sulphuric acid will suffice, provided a por- tion of water be added. One hundred parts of good nitre, sixty of strong sulphu- ric acid, and twenty of water, form econo- mical proportions.* In the large way, and for the purposes of the arts, extremely thick c:ist iron or earthen retorts are employed, to which an earthen head is adapted, and connected with a range of proper condensers. The strength of the acid too is varied, by put- ting more or less water in the receivers. The nitric acid thus made generally con- tains sulphuric acid, and also muriatic, from the impurity of the nitrate employed. If the former, a solution of nitrate of* bary- tes will occasion a white precipitate ; if the latter, nitrate of silver will render it milky. The sulphuric acid may be sepa- rated by a second distillation from very pure nitre, equal in weight to an eighth of that originally employed; or by preci- pitating with nitrate of barytes, decanting the clear liquid, and distilling it. The mu- riatic acid may be separated by proceed- ing in the same way with nitrate of s.lvcr, or with litharge, decanting the clear li- quor, and re-distilling it, leaving an eighth or tenth part in the retort. The acid for the last process should be condensed as much as possible, and the re-distillation conducted very slowly; and if it be stop- ped when half is come over, beautiful crys- tals of muriate of lead will be obtained on cooling the remainder, if litharge be used, as M. Steinacher informs us; who also adds, that the vessels should be made to fit tight by grinding, as any lute is liable to contaminate the product. As this acid still holds in solution more or less nitrous gas, it is not in fact nitric acid, but a kind of nitrous: it is therefore necessary to put it into a retort, to which a receiver is added, the two vessels not being luted, and to apply a very gentle heat for several hours, changing the re- ceiver as soon as it is filled with red va- pours. The nitrous gas will thus be ex- pelled, and the nitric acid will remain in the retort as limpid and colourless as wa- ter. It should be kept in a bottle secluded from the light, otherwise it will lose part of its oxygen. What remains in the retort is a bisul- phate of potash, from which the superflu- ous acid may be expelled by a pretty strong heat, and the residuum, being dissolved and crystallized, will be sulphate of potash. As nitric acid in a fluid state is always mixed with water, different attempts have been made to ascertain its strength, or the quantity of real acid contained in it. Mr. Kirwan supposed, that the nitrate of soda contained the pure arid undiluted with wa- ter, and thus calculated its strength from the quantity requisite to saturate a given portion of soda. Sir H. Davy more recent- ly took the acid in the form of gas as the standard, and found how much of this is contained in an acid of a given specific gravity in the liquid state. * Mr. Kirwan gave 68 as the quantity of real acid in 100 ofthe liquid acid of speci- fic gravity 1.500; Sir II. Davy's determi- natioa was 91; Dr. Wollaston's, as infer- red from the experiments of Mr R. Philips, 75; and Mr. Dalton's corrected result from Kirwan's table, was 68. In this state of discordance Dr. Ure performed a series of experiments, with the view of determining the constitution of liquid nitric acid, and published an account of them, with some new tables, in the fourth and sixth vo- lumes of the Journal of Science and the Arts. From regular prisms of nitre, he procur- ed by slow distillation, with concentrated oil of vitriol, nitric acid; which by the tests of nitrates of silver and of barytes, was found to be pure. Only the first portion ACI ACI that came over was employed for the ex- periments. It was nearly colourless, and had a specific gravity of 1.500. A re-dis- tilled and colourless nitric acid, prepared in London, was also used for experiments of verification, in estimating the quantity of dry acid in liquid acid of a known den- sity. The above acid of 1.500 being mixed in numbered phiuls, with pure water, in the different proportions of 95 -f- 5, 90 -f- 10, 80 -f- 20, &c. he ob ained, after due agita- tion, and an interval of 24 hours, liquids whose specific gravities, at 60° Fahren- heit, were determined by means of an ac- curate balance, with a narrow-necked glass globe of known capacity By considering the series of numbers thus obtained, he discovered the geometrical law which re- gulates them. The specific gravity of di- lute acid, containing 10 parts in the 100 of that whose density is 1.500, is 1.054. Ta- king this number as the root, its successive powers will give us the successive densi- ties, at the terms of 20, 30, 40, &c. per cent. Thus 1.0542 = 1.111 is the speci- fic gravity corresponding to 20 ofthe strong liquid acid + 80 water; 1.0543 = 1.171 is that for 30 per cent, of strong acid; 1.054+ = 1.-34 is the specific gravity at 4J per cent. The specific gravities are therefore a series of numbers in geometri- cal progression, corresponding to the terms of dilution, another series in arithmetical progression, exactly as he had shown in the 7th number of the Journal of Science with regard to sulphuric acid. Hence if one term be given, the whole series may be found. On uniting the strong acid with water, a considerable condensation of vo- lume takes place. The maximum conden- sation occurs, when 58 of acid are mixed with 42 of water. Above this point, the curve of condensation has a contrary flex- ure; and therefore a small modification must be made on the root 1.054, in order to obtain with final accuracy, in the higher part of the range, the numerical powers which represent the specific gravities. The modification is however very simple. To obtain the number for 50 per cent, the root is 1.053 ; and for each decade up to 70, the root must be diminished by 0.002. Thus for 60, it will become 1.051, and for 70, 1.049. Above this we shall obtain a precise correspondence with experiment, up to 1.500 sp. gravity, if for each succes- sive decade we subtract 0.0025 from the last diminished root, before raising it to the desired power, which represents the per centage of liquid acid. It is established by the concurring ex- periments of Sir H. Davy and M. Gay-Lus- sac, that dry nitric acid is a compound of 2£ volumes of oxygen combined with 1 of nitrogen; of which the weights are 2.5 x 1.111 — 2.777 for the proportion of oxygen, and 0.9722 for that of nitrogen; and in 100 parts, of 73% of the former -f- 261 of the latter. But nitrogen combines with several inferior proportions of oxy- gen, which are all multiples of its prime equivalent 1.0; and the present compound is exactly represented by making 1 prime of nitrogen = 1 75, and 5 of oxygen -= 5.0; whence the acid prime is the sum of these two numbers, or 6.75. Now this re- sult deduced from its constituents, coin- cides perfectly with that derived from the quantity in which this acid saturates defi- nite quantities of the salifiable bases, pot- ash, soda, lime, &c. There can be no doubt, therefore, that the prime equiva- lent of the acid is 6.75; and as little that it consists of 5 parts of oxygen and 1.75 of nitrogen. Possessed of these data, we may perhaps see some reason why the greatest condensation of volume, in diluting strong liquid acid, should take place with 58 of it, and 42 of water. Since 100 parts of acid of 1.500 contain, by Dr. Ure's expe- riments, 79.7 of dry acid, therefore acid of the above dilution will contain 46 dry acid, and 54 water; or reducing the numbers to prime proportions, we have the ratio of 6.75 to 7.87J. being that of one prime of real acid to 7 primes of water. But we have seen that the real acid prime, is made up of 1 of nitrogen associated by chemical affinity with 5 of oxygen. Now imagine a figure, in which the central prime of ni- trogen is surrounded by 5 of oxygen. To the upper and under surface of the nitro- gen let a prime of water be attached; and one also to each of the primes of oxygen. We have thus the 7 primes distributed in the most compact and symmetrical man- ner. By this hypothesis, we can understand how the elements of acid and water may have such a collocation and proportion, as to give the utmost efficacy to their reci- procal attractions, whence the maximum condensation will result. A striking analo- gy will be found in the dilution of sulphu- ric acid. If on 58 parts by weight of acid of 1.500, we pour cautiously 42 of water in a graduated measure, of which the whole occupies 100 divisions, and then mix them intimately, the temperature will rise from 60° to 140°, and after cooling to 60° again, the volume will be found only 92.65. No other proportion of water and acid causes the evolution of so much heat. When 90 parts ofthe strong acid are united with 10 of water, 100 in volume become 97; and when 10 parts of the same acid arc com- bined with 90 of water, the resulting vo- lume is 98, It deserves notice, that 80 of acid -f- 20 water, and 30 of acid -f- 70 wa- ter, each gives a dilute acid, whose degree of condensation is the same, namely, 100 measures become 94.8. , ACI ACI TABLE of Nitric Liq. Dry L,q. Dry Sp.Gr. Acid Acid Sp.Gr. Acid Acid in 100 in 100. in 100 in 100. 1.5000 100 79.700 1.4189 75 59.775 1.4980 99 78.903 1.4147 74 58.978 1.4960 98 78.106 1.4107 73 58.181 1.4940 97 77.309 1.4065 72 57.384 1.4910 96 76.512 1.4023 71 56.587 1.4880 95 75.715 1.3978 70 55.790 1.4850 94 74 918 1.3945 69 54.993 1.4820 93 74.121 1.3882 68 54.196 1.4790 92 73.324 1.3833 67 53.399 1.4760 91 72.527 1.3783 66 52.602 1.4730 90 71.730 1.3732 65 51.8U5 1*4700 89 70.933 1.3681 64 51.068 1.4670 88 70.1J6 1.3630 63 50.211 1.464A 1.4600 y,87 69.339 1.3579 62 49.414 86 68.542 1.3529 61 48.617 1.4570 85 67.745 1.3477 60 47.820 1.4530 84 66.948 1.3427 59 47.023 1.4500 83 66.155 1.3376 58 46.226 1.4460 82 65.354 1.332o 57 45.429 1.4424 81 64.557 1.3270 56 44.632 1.4385 80 63.76 < 1.3216 55 43.835 1.4346 79 62.963 1.3163 54 43.038 1.4306 78 62.166 1.3110 53 42.241 1.4269 77 61.369 1.3056 52 41.444 1.4228 76 60.572 1.3001 51 40.647 The column of dry acid shows the weight which any salifiable base would gain, by uniting with 100 parts of the liquid acid of the corresponding specific gravity. But it may be proper here to observe, that Sir H. Davy, in extending his views rela- tive to the constitution ofthe dry muriates, to the nitrates, has suggested, that the latter when dry may be considered as consisting, not of a dry nitric acid com- bined with the salifiable oxide, but of the oxygen and nitrogen of the nitric acid with the metal itself in triple union. A view of his reasoning will be found under the article Salt. He regards liquid nitric acid at its utmost density as a com- pound of 1 prime of hydrogen, 1 of nitro- gen, and 6 of oxygen.* The strongest acid that Mr. Kirwan could procure at 60° was 1.5543; but Rouelle professes to have obtained it of 1.583. Nitric acid should be of the specific gravity of 1.5, or a little more, and colour- less. * That of Mr. Kirwan seems to have consisted of one prime of real acid and one of water, when the suitable correc- tions are made ; but no common chemical use requires it of such a strength. The following table of boiling points has been given by Mr. Daltom :id, by Dr. Ure. Li it congeals at—40°.3. The first has a specific gravity of 1.330 nearly, and con- sists of 1 prime of dry acid -j- 7 of water; the second has a specific gravity of 1.420, and contains exactly one prime of dry acid + four of water; while the third has a specific gravity of 1.215, consisting of one prime of acid -f- 14 of water. We perceive, that the liquid acid of 1.420, composed of 4 primes of water -f- one of dry acid, possesses the greatest power of resisting the influence of temperature to change its state. It requires the maximum heat to boil it, when it distils unchanged; and the maximum cold to effect its con- gelation.* It has already been observed, that the nitric acid, when first distilled over, holds in solution a portion of nitric oxide, which is greater in proportion as the heat has been urged toward the end, and much increased by even a small portion of in- flammable matter, should any have been present. The colour of the acid, too, is affected by the quantity of nitric oxide it holds, and Sir H. Davy has given us the following table of proportions answering to its different hues. Colour. Pale yellow Bright yellow Dark orange Light olive Dark olive Bright green Blue green But these colours are not exact indica- tions of the state of the acid, for an addition of water will change the colour into one lower in the scide, so that a considerable portion of water will change the dark orange to a blue green. The nitric acid is of considerable use in the arts. It is employed for etching on copper; as a solvent of tin to form with that metal a mordant for some ofthe finest dyes; in metallurgy and assaying; in va- , rious chemical processes, on account of , the facility with which it parts with oxy- v, gen and dissolves metals; in medicine as a tonic, and as a substitute for merc.irial preparations in syphilis and affections of the liver; as alse in form of vapour to de- stroy contagion. For the purposes ofthe arts it is commonly used in a diluted state, and contaminated with the sulphuric and muriatic acids, by the name of aquafortis. This is generally prepared by mixing Vox. i. [10 ] Real Acid. Nitric Oxide. WateH 90.5 1.2 8.3 88.94 2.96 8.10 8C.84 5.56 7.6 86.0 6.45 7.55 85.4 7.1 7.5 84.8 7.76 7.44 84.6 8. 7.4 common nitre with an equal weight of sulphate of iron, and half its weight ofthe same sulphate calcined, and distilling the mixture ; or by mixing nitre with twice its weight of dry powdered clay, and dis- tilling in a reverberatory furnace. Two kinds are found in the shops, one called double aquafortis, which is about half the strength of nitric acid ; the other simply aquafortis, which is half the strength of the double. A compound made by mixing two parts of the nitric acid with one of muriatic, known formerly by the name of aqua regia, and now by that of nilro-muriutic acid, has the property of dissolving gold and platina. On mixing the two acids, heat is given out, an effervescence takes place, and the mixture acquires an orange colour. This is likewise made by adding gradually to an ounce of powdered muriate of ammonia, four ounces of double aqua. ACI ACI fortis, and keeping the mixture in a sand- heat till the salt is dissolved; taking care to avoid the fumes, as the vessel must be left open ; or by distilling nitric acid with an equal weight, or rather more, of com- mon salt. * On this subject we are indebted to Sir H. Davy for some excellent observa- tions, published by him in the first volume ofthe Journal of Science. If strong nitrous acid, saturated with nitrous gas, be mixed with a saturated solution of muriatic acid gas, no other effect is produced than might be expected from the action of nitrous acid of the same strength on an equal quantity of water; and the mixed acid so formed has no power of action on gold or platina. Again, if muriatic acid gas, and nitrous gas in equal volumes, be mixed together over mercury, and half a volume of oxygen be added, the immediate con- densation will be more than might be ex- pected from the formation of nitrous acid gas. And when this is decomposed, or absorbed by the mercury, the muriatic acid gas is found unaltered, mixed with a certain portion of nitrous gas. It appears then that nitrous acid, and muriatic acid gas, have no chemical action on each other. If colourless nitric acid, and muriatic acid of commerce, be mixed to- gether, the mixture immediately becomes yellow, and gains the power of dissolving gold and platinum. If it be gently heated, pure chlorine arises from it, and the co- lour becomes deeper. If the heat be lon- ger continued, chlorine still rises, but mix- ed with nitrous acid gas. When the pro- cess has been very long continued till the colour becomes very deep, no more chlo- rine can be procured, and it loses its power of acting upon platinum and gold. It is now nitrous and muriatic acid. It appears then from these observations, which have been very often repeated, that nitro-mu- riatic acid owes its peculiar properties to a mutual decomposition of the nitric and muriatic acids; and that water, chlorine, and nitrous acid gas, are the results. Though nitrous gas and chlorine have no action on each other when perfectly dry, yet if water be present there is an imme- diate decomposition, and nitrous acid and muriatic acid are formed. 118 parts of strong liquid nitric acid being decompos- ed in this case, yield 67 of chlorine. Aqua regia does not oxidize gold and platina. It merely causes their combination with chlorine. A bath made of nitro-muriatic acid, di- luted so much as to taste no sourer than vinegar, or of such a strength as to prick tlve skin a little, after being exposed to it for twenty minutes or half an hour, has been introduced by Dr. Scott of Bombay as a remedy in chronic syphilis, a variety of ulcers, and diseases ofthe skin, chronic hepatitis, bilious dispositions, general dc bility, and languor. He considers every trial as quite inconclusive, where a ptyalism, some affection of the gums, or some very evident constitutional effect, has not arisen from it. The internal use ofthe same acid has been recommended to be conjoined with that ofthe partial or general bath.* AVith the different bases the nitric acid forms nitrates. The nitrate of barytes, when perfectly- pure, is in regular octaedral crystals. though it is sometimes obtained in small shining scales. It may be prepared by uniting barytes directly with nitric acid, or by decomposing the carbonate or sul- phuret of barytes with this acid Exposed to heat it decrepitates, and at length gives out its acid, which is decomposed; but if the heat be urged too far, the barytes is apt to vitrify with the earth of the cruci- ble. It is soluble in 12 parts of cold, and 3 or 4 of boiling water. It is said to exist in some mineral waters. * It consists of 6.75 acid -f- 9.75, or 9.7 base.* The nitrate of potash is the salt well known by the name of nitre or saltpetre It is found ready formed !in the East In- dies, in Spain, in the kingdom of Naples, and elsewhere, in considerable quantities ; but nitrate of lime is still more abundant. Far the greater part of the nitrate made use of is produced by a combination of circumstances which tend to compose and condense nitric acid. This acid appears to be produced in all situations, where animal matters are completely decompos- ed, with access of air and of proper sub- stances with which it can readily combine. Grounds frequently trodden by cattle and impregnated with their excrements, or the walls of inhabited places where putrid animal vapours abound, such as slaughter- houses, drains, or the like, afford nitre by long exposure to the air. Artificial nitre beds are made by an attention to the cir* cumstances in which this salt is produced by nature. Dry ditches are dug, and co- vered with sheds, open at the sides, to keep oft" the rain: these are filled with animal substances—such as dung, or other excrements, with the remains of vegeta- bles, and old mortar, or other loose calca- reous earth; this substance being found to be the best and most convenient recep- tacle for the acid to combine with. Occa- sional watering, and turning up from time to time, are necessary, to accelerate the process, and increase the surfaces to which the air may apply; but too much moisture is hurtful. When a certain portion of ni- trate is formed, the process appears to go on more quickly; but a certain quantity stops it altogether, and after this cessation the materials will go on to furnish more, ACI ACI if what is formed be extracted by lixivia- tion. After a succession of many months, more or less, according to the manage- ment ofthe operation, in which the action cf a regular current of fresh air is of the greatest importance, nitre is found in the mass. If the beds contained much vege- table matter, a considerable portion ofthe nitrous salt will be common saltpetre, but, if otherwise, the acid will, for the most part, be combined with the calca- reous earth. * It consists of 6.75 acid -+- 5.95 potash.* To extract the saltpetre from the mass of earthy matter, a number of large casks are prepared, with a cock at the bottom of each, and a quantity of straw within, to prevent its being stopped up. Into these the matter is put, together with wood- ashes, either strewed at top, or added during the filling. Boiling water is then poured on, and suffered to stand for some time; after which it is drawn off', and other water added in the same manner, as long as any saline matter can be thus extracted. The weak brine is heated, and passed through other tubs, until it be- comes of considerable strength. It is then carried to the boiler, and contains nitre and other salts; the chief of which is com- mon culinary salt, and sometimes muriate of magnesia. It is the property of nitre to be much more soluble in hot than cold water; but common salt is very nearly as soluble in cold as in hot water. When- ever, therefore, the evaporation is carried by boiling to a certain point, much of the common salt will fall to the bottom, for want of water to hold it in solution, though the nitre will remain suspended by virtue ofthe heat. The common salt thus sepa- rated is taken out with a perforated ladle, and a small quantity ofthe fluid is cooled, from time to time, that its concentration may be known by the nitre which crystal- lizes in it. When the fluid is sufficiently evaporated, it is taken out and cooled, and great part of the nitre separates in crys- tals; while the remaining common salt con- tinues dissolved, because equally soluble in cold and inhot water. Subsequent evapora- tion of the residue will separate more nitre in the same manner. * By the suggestion of Lavoisier, a much simpler plan was adopted; reducing the crude nitre to powder, and washing it twice with water.* This nitre, which is called nitre of the first boiling, contains some common salt; from which it may be purified by solution in a small quantity of water, and subse- quent evaporation; for the crystals thus obtained are much less contaminated with common salt than before; because the proportion of water is so much larger, with respect to the small quantity con- fined by the nitre, that very little of it will crystallize. For nice purposes, the solution and crystallization of nitre are repeated four times. The crystals of nitre are usually ofthe form of six-sided flatten- ed prisms, with diedral summits. Its taste is penetrating; but the cold produced by placing the salt to dissolve in the mouth is such as to predominate over the real taste at first. Seven parts of water dis- solve two of nitre, at the temperature of sixty degrees; but boiling water dissolves its own weight. 100 parts of alcohol, at a heat of 176°, dissolve only 2.9. On being exposed to a gentle heat, nitre fuses; and in this state being poured into moulds, so as to form little round cakes, for balls, it is called sal prunella, or crystal mineral. This at least is the way in which this salt is now usually prepared, conforma- bly to the directions of Boerhaave; though in most dispensatories a twenty-fourth part of sulphur was directed to be defla- grated on the nitre before it was poured out. This salt should not be left on the fire after it has entered into fusion, other- wise it will be converted into a nitrite of potash. If the heat be increased to red- ness, the acid itself is decomposed, and a considerable quantity of tolerably pure oxygen gas is evolved, succeeded by ni? trogen. This salt powerfully promotes the com- bustion of inflammable substances. Two or three parts mixed with one of charcoal, and set on fire, burn rapidly; azote and carbonic acid gas are given out, and a small portion of the latter is retained by the alkaline residuum, which was formerly called clyssus of nitre. Three parts of nitre, two of subcarbonate of potash, and one of sulphur, mixed together in a warm mor- tar, form the fulminating powder; a small quantity of which, laid on a fire-shovel, and held over the fire till it begins to melt, explodes with a loud sharp noise. Mixed with sulphur and charcoal, it forms gunpowder. See Gdnpowdkr. Three parts of nitre, one of sulphur, and one of fine saw-dust, well mixed, con- stitute what is called the powder of fusion. If a bit of base copper be folded up and covered with this powder in a walnut- shell, and the powder be set on fire with a lighted paper, it will detonate rapidly, and fuse the metal into a globule of sul- phuret, without burning the shell. If nitrate of potash be heated in a retort with half its weight of solid phosphoric or boracic acid, as soon as this acid begins to enter into fusion, it combines with the pot- ash, and the nitric acid is expelled, ac- companied with a small portion of oxygen gas and nitric oxide. Silex, alumina, and barytes, decompose this salt in a high temperature by uniting with its base. The alumina will effect ACI ACI this even after it has been made into pottery. 1 he uses of nitre are various. Beside those already indicated, it enters into the composition of fluxes, and is extensively employed in metallurgy ; it serves to pro- mote the combustion of sulphur in fabri- cating its acid; it is used in the art of dyeing; it is added to common salt for preserv ing meat, to which it gives a red hue; it is an ingredient in some frigorific mixtures; and it is prescribed in medi- cine, as cooling, febrifuge, and diuretic; and some have recommended it mixed with vinegar as a very powerful remedy for the sea scurvy. Nitrate of soda, formerly called cubic or quadrangular nitre, approaches in its pro- perties to the nitrate of potash; but dif- fers from it in being somewhat move solu- ble in cold water, though less in hot, which takes up little more than its own weight; in being inclined to attract moisture from the atmosphere; and in crystallizing in rhombs, or rhomboidal prisms. It may be prepared by saturating soda with the ni- tric acid; by precipitating nitric solutions of the metals, or of the earths, except barytes, by soda; by lixiviating and crys- tallizing the residuum of common salt dis- tilled with three-fourths its weight of ni- tric acid; or by saturating the mother waters of nitre with soda instead of potash. This salt has been considered as use- less ; but professor Proust says, that five parts of it, with one of charcoal and one of sulphur, will burn three times as long as common powder, so as to form an econo- mical composition for fire-works. *It con- sists of 6.75 acid + 3.95 soda.* Nitrate of strontian may be obtained in the same manner as that of barytes, with which it agrees in the shape of its crystals, and most of its properties. It is much more soluble, however, requiring but four or five parts of water according to Vaii- quelin, and only an equal weight accord- ing to Mr. Henry. Boiling water dissolves nearly twice as much as cold. Applied to the wick of a candle, or added to burning alcohol, it gives a deep red colour to the flame. On this account it may be useful, perhaps, in the art of pyrotechny. *It con- sists of 6.75 acid -\- 6.5 strontian. * Nitrate of lime, the calcareous nitre of older writers, abounds in the mortar of old buildings, particularly those that have been much exposed to animal effluvia, or processes in which azote is set free. Hence it abounds in nitre beds, as was ob- served when treating ofthe nitrate of pot- ash. It may also be prepared artificially, by pouring dilute nitric acid on carbonate of lime. If the solution be boiled down to a tirupy consistence, and exposed in a c?o! nlace, it crystallizes in long prisms, resembling bundles of needles diverging from a centre. These are soluble, accord- ing to Henry, in an equal weight of boil- ing water, and twice their weight of cold ; soon deliquesce on exposure to the air, and are decomposed to a red heat. Four- croy says, that cold water dissolves four times its weight, and that its own water of crystallization is sufficient to dissolve it at a boiling heat. It is likewise soluble in less than its weight of alcohol. By evaporat- ing the aqueous solution to dryness, con- tinuing the heat till the nitrate fuses, keep- ing it in this state five or ten minutes, and then pouring it into an iron pot previous- ly heated, we obtain Baldwin's phosphorus. This, which is perhaps more properly ni- trite of lime, being broken to pieces, and kept in a phial closely stopped, will emit a beautiful white light in the dark, after having been exposed some time to the rays of the sun. At present no use is made of this salt, except for drying some ofthe gases by attracting their moisture; but it might be employed instead of the nitrate of potash for manufacturing aquafortis. The nitrate of ammonia possesses the property of exploding, and being totally decomposed, at the temperature of 600° ; whence it acquired the name of nitrum fiammans. The readiest mode of preparing it is by adding carbonate of ammonia to dilutef nitric acid till saturation takes place. If this solution be evaporated in a heat between 70° and 100° and the evapo- ration not carried too far, it crystallizes in hexacdral prisms terminating in very acute pyramids: if the heat rise to 212g, it will afford, on cooling, long fibrous silky crys- tals : if the evaporation be carried so far as for the salt to concrete immediately on a glass rod by cooling, it will form a com- pact mass. According to Sir H. Davy, these differ but little from each other, ex- cept in the water they contain, their com- ponent parts being as follows: Prismatic-\ con-r69.5 rl8.4 r\2.\ Fibrous £ tains-? 72.5 am"! 4 19..rwa'3 8.2 Compact 3 acid C74.5r,l0n,Hl9.8ter \ 5.7 All these are completely deliquescent, but they differ a little in solubility. Alco- hol at 176° dissolves nearly 90.9 of its own weight. * When dried as much as possible with- out decomposition, it consists of 6.75 acid -f- 2.13 ammonia-|-1.125 water.* The chief use of this salt is for affording nitrous oxide on being decomposed by heat. See Nitrogen, (Oxide of). Nitrate of magnesia, magnesian nitre, crys- jl have ascertained, that very strong nitric acid, saturated by carbonate of am- monia, yields the compact nitrate extem- poraneously. ACI ACI tallizes in four-sided rhomboidal prisms, with oblique or truncated summits, and sometimes in bundles of small needles. Its taste is bitter, and very similar to that of nitrate of lime, but less pungent. It is fu- sible, and decomposable by heat, giving out first a little oxygen gas, then nitrous oxide, and lastly nitric acid. It deliquesces slowly. It is soluble in an equal weight of cold water, and in but little more hot, so that it is scarcely crystallizable but by spontaneous evaporation. The two preceding species are capable of combining into a triple salt, an ammo- niaco-magnesian nitrate, either by uniting the two in solution, or by a partial decom- position of either by means ofthe base of the other. This is slightly inflammable when suddenly heated; and by a lower heat is decomposed, giving out oxygen, azote, more water than it contained, ni- trous oxide, and nitric acid. The residuum is pure magnesia. It is disposed to attract moisture from the air, but is much less de- liquescent than either of the salts that compose it, and requires eleven parts of water at 60° to dissolve it. Boiling water takes up more, so that it will crystallize by cooling. It consists of 78 parts of ni- tra e of magnesia, and 22 of nitrate of am- monia. From the activity of the nitric acid as a solvent of earths in analyzation, the nitrate of glucine is better known than any other ofthe salts of this new earth. Its form is either pulverulent, or a tenacious or duc- tile mass. Its taste is at first saccharine, and afterwards astringent. It grows soft by exposure to heat, soon melts, its acid is decomposed into oxygen and azote, and its base alone is left behind. It is very so- luble and very deliquescent. Nitrate, or rather supernitrate, of alu- mina crystallizes, though with difficulty, in thin, soft, pliable flakes. It is of an aus- tere and acid taste, and reddens blue veg- etable colours. It may be formed by dis- solving in diluted nitric acid, with the as- sistance of heat, fresh precipitated alumi- na, well washed but not dried. It is deli- quescent, and soluble in a very small por- tion of water. Alcohol dissolves its own weight. It is easily decomposed by heat. Nitrate of zircone was first discovered by Klaproth, and has since been examined by Guyton-Morveau and Vauquelin. Its crystals are small, capillary, silky needles. Its taste is astringent. It is easily decom- posed by fire, very soluble in water, and deliquescent. It may be prepared by dis- solving zircone in strong nitric acid; but, hke the preceding species, the acid is al- ways in excess. Nitrate of yttria may be prepared in a similar manner. Its taste is sweetish and astringent. It is scarcely to be obtained in crystals; and if it be evaporated by too strong a heat, the salt becomes soft hke honey, and on cooling concretes into a stony mass. Acid (Nitrots). It was formerly called fuming nitrous acid. It appears to form a distinct genus of salts, that may be termed nitrites. But these cannot be made by a direct union of their component parts, be- ing obtainable only by exposing a nitrate to a high temperature, which expels a por- tion of its oxygen in the state of gas, and leaves the remainder in the state of a nU trite, if the heat be not urged so far, or continued so long, as to effect a complete decomposition of the salt. In this way the nitrites of potash and soda may be obtain- ed, and perhaps those of barytes, strontian, lime, and magnesia. The nitrites are par- ticularly characterized, by being decom- posable by all the acids except the car- bonic, even by the nitric acid itself, all of which expel from them nitrous acid. We are little acquainted with any one except that of potash, which attracts moisture from the air, changes blue vegetable colours to green, is somewhat acrid to the taste, and when powdered, emits a smell of nitric oxide. * The acid itself is best obtained by ex- posing nitrate of lead to heat in a glass re- tort. Pure nitrous acid comes over in the form of an orange coloured liquid. It is so volatile, as to boil at the temperature of 82°. Its specific gravity is 1.450. When mixed with water it is decomposed, and nitrous gas is disengaged, occasioning ef- fervescence. It is composed of one volume of oxygen united with two of nitrous gas. It therefore consists by weight of 1.75 ni- trogen-f-4 oxygen; by measure of 1J oxygen -f- 1 nitrogen. The various co- loured acids of nitre are not nitrous acids, but nitric acid impregnated with nitrous gas, the deutoxide of nitrogen, or azote. (See the preceding table of Sir II. Davy, concerning the coloured acid.)* * Acid (Nitric Oxygenized). In our general remarks on acidity, we have de- scribed Mr. Thenard's newly discovered method of oxygenizing the liquid acids. The first that he examined was the com- bination of nitric acid and oxygen. When the peroxide of barium, prepared by satu- rating barytes with oxygen, is moistened, it falls to powder, without much increase of temperature. If in this state it be mixed with seven or eight times its weight of water, and dilute nitric acid be gradually poured upon it, it dissolves gradually by agitation, without the evolution of any gas: The solution is neutral, or has no action on turnsole or turmeric. When we add to this solution the requisite quantity of sulphuric acid, a copious precipitate of sulphate of barytes falls, and the filtered ACI ACI Kquor is merely water, holding in solution oxygenized nitric acid. This acid is liquid and colourless; it strongly reddens turn- sole, and resembles in aU its properties nitric acid. When heated it immediately begins to discharge oxygen; but its decomposition is never complete unless it be kept boiling for some time. The only method which M. Thenard found successful for concen- trating it, was to place it in a capsule, under the receiver of an air pump, along with another capsule full of lime, and to exhaust the receiver. By this means he obtained an acid sufficiently concentrated to give out 11 times its bulk of oxygen gas. This acid combines very well with ba- rytes, potash, soda, ammonia, and neu- tralizes them. When crystallization com- mences in the liquid, by even a sponta- neous evaporation, these salts are instant- ly decomposed. The exhausted receiver also decomposes them. The oxygenized nitrates, when changed into common nitrates, do not change the state of their neutralization. Strong solution of potash poured into their solutions decomposes them. Oxygenized nitric acid does not act on gold; but it dissolves all the metals which the common acid acts on, and when it is not too concentrated, it dissolves them without effervescence. Deutoxide, or peroxide of barium, contains just double the proportion of oxygen that its protoxide does. But M. Thenard says, that the barytes obtained from the nitrate by ignition contains always a little of the peroxide. When oxygenized nitric acid is poured upon oxide of silver, a strong effervescence takes place, owing to the disengagement of oxygen. One portion of the oxide of silver is dissolved, the other is reduced at first, and then dissolves likewise, provided the quantity of acid be sufficient. The solution being completed, if we add potash to it, by little and little, a new effervescence takes place, and a dark violet precipitate falls; at least this is always the colour of the first deposite. It is insoluble in ammonia, and accord- ing to all appearance, is a protoxide of silver. As soon as we plunge a tube containing oxide of silver into a solution of oxygen- ized nitrate of potash, a violent efferves- cence takes place, the oxide is reduced, the silver precipitates, the whole oxygen of the oxygenized nitrate is disengaged at the same time with that of the oxide ; and the solution, which contains merely common nitrate of potash, remains neutral, if it was so at first. But the most unac- countable phenomenon is the following : If silver, in a state of extreme division (fine filings), be put into the oxygenized nitrate, or oxygenized muriate of potash, the whole oxygen is immediately disen- gaged. The silver itself is not attacked, and the salt remains neutral as before. Iron, zinc, copper, bismuth, lead, and platinum, likewise possess this property of separating the oxygen of the oxygen- ized nitrate. Iron and zinc are oxidized, and at the same time occasion the evolution of oxygen. The other metals are not sensibly oxidized. They were all employ- ed in the state of filings. Gold scarcely acts. The peroxides of manganese and of lead decompose the oxynitrates. A verv small quantity of these oxides, in powder, is sufficient to drive off the whole oxygen from the saline solution. The effervescence is lively. The peroxide of manganese undergoes no alteration. Though nitric acid itself has no action on the peroxides of lead and manganese, the oxygenized acid dissolves both of them with the greatest facility. The so- lution is accompanied by a great disen- gagement of oxygen gas. The effect of 6'ilver, he thinks, may probably be ascri- bed to voltaic electricity. The remarks appended to our account of M. Thenard's oxygenized muriatic acid, are equally applicable to the nitric ; but the phenomena are too curious to be omitted in a work ofthe present kind.* * Acid (Oleic). When potash and hog's lard are saponified, the margarate of the alkali separates in the form of a pearly looking solid, while the fluid fat remains in solution, combined with the potash. When the alkali is separated by tartaric acid, the oily principle of fat is obtained, which M. Chevreul purifies by saponify- ing it again and again, recovering it two or three times, by which means the whole of the margarine is separated. As this oil has the property of saturating bases and forming neutral compounds, he has called it oleic acid. In his sixth memoir, he gives the following table of results. 100 Oleic acid of human fat Saturate Barytes Strontian Lead 26.00 19.41 82.48 100 Oleic acid of sheep fat 26.77 19.38 81.81 100 Oleic acid of ox fat 28.93 19.41 81.81 100 Oleic acid of goose fat 26.77 19.38 81.34 100 Oleic acid of hog fat 27.00 29.38 81.80 Oleic acid is an oily fluid without taste and smell. Its specific gravity is 0.914. It is generally soluble in its own weight of boiling alcohol, of the specific gravity of 0.7952; but some of the varieties are still more soluble. 100 ofthe oleic acid satu« ACI ACI rate 16.58 of potash, 10.11 of soda, 7.52 of magnesia, 14.83 of zinc, and 13.93 perox- ide of copper. M. Chevreul's experi- ments have finally induced him to adopt the quantities of 100 acid to 27 barytes, as the most correct; whence calling barytes 9-75, we have the equivalent prime of oleic acid = 36.0.* Aein (Oxalic). This acid, which a- bounds in wood sorrel, and which, com- bined with a small portion of potash, as it exists in that plant, has been sold under the name of salt of lemons, to be used as a substitute for the juice of that fruit, par- ticularly for discharging ink spots and iron-moulds, was long supposed to be analogous in that of tartar. In the year 1776, however, Bergmann discovered,that a powerful acid might be extracted from sugar by means ofthe nitric; and a few years afterwards Scheele found this to be identical with the acid existing naturally in sorrel. Hence the acid began to be distinguished by the name of saccharine, but has since been known in the new nomenclature by that of oxalic. Scheele extracted this acid from the salt of sorrel, or acidulous oxalate of pot- ash, as it exists in the juice of that plant, by saturating it with ammonia, when it becomes a very soluble triple salt, and adding to the solution nitrate of barytes dissolved in water. Having well washed the oxalate of barytes, which is precipita- ted, he dissolved it in boiling water, and precipitated its base by sulphuric acid. To ascertain that no sulphuric acid re- mained in the supernatant liquor, he added a little of a boiling solution of oxalate of barytes till no precipitate took place, and then filtered the hquor, which contained nothing but pure oxalic acid, which he crystallized by evaporation and cooling. It may be obtained, however, much more readily and economically from sugar in the following way: To six ounces of nitric acid in a stoppered retort, to which a large receiver is luted, add, by degrees, one ounce of lump sugar coarsely pow- dered. A gentle heat may be applied during the solution, and nitric oxide will be evolved in abundance. When the whole of the sugar is dissolved, distil off a part ofthe acid, till what remains in the retort has a sirupy consistence, and this will form regular crystals, amounting to 58 parts from 100 of sugar. These crys- tals must be dissolved in water, re-crystal- lized, and dried on blotting paper. A variety of other substances afford the oxalic acid when treated by distillation with the nitric. Bergmann procured it from honey, gum arabic, alcohol, and the calculous concretions in the kidneys and bladders of animals. Scheele and Hermb- stadt from sugar of milk. Scheele from a sweet matter contained in fat oils, arid also from the uncrystallizable part of the juice of lemons. Hermbstadt from the acid of cherries, and the acid of tartar. Goetling from beech wood. Kohl from the residuum in the distillation of ar- dent spirits. Westrumb not only from the crystallized acids of currants, cherries, ci- trons, raspberries, but also from the sac- charine matter of these fruits, and from the uncrys'allizable parts of the acid jui- ces. Hoffmann from the juice ofthe bar- berry ; and Berthollet from silk, hair, ten- dons, wool; also from other animal sub- stances, especially from the coagulum of blood, whites of eggs, and likewise from the amylaceous and glutinous parts of flour. M. Berthollet observes, that the quantity of the oxalic acid obtained by treating wool with nitric acid was very considerable, being above half the weight of the wool employed. He mentions a difference which he observed between animal and vegetable substances thus treat- ed with nitric acid, namely, that the for- mer yielded, beside ammonia, a large quan- tity of an oil which the nitric acid could not decompose; whereas the oily parts of vegetables were totally destroyed by the action of this acid: and he remarks, that in this instance the glutinous part of flour resembled animal substances, whereas the amylaceous part of the flour retained its vegetable properties. He further remarks, that the quantity of oxalic acid furnished by vegetable matters thus treated is pro- portionable to their nutritive quality, and particularly that, from cotton, he could not obtain any sensible quantity. Deyeux, having cut with scissars the hairs of the chick pea, found they gave out an acid li- quor, which, on examination, proved to be an aqueous solution of pure oxalic acid. Proust and other chemists had before ob- served, that the shoes of persons walking through a field of chick pease were corro- ded. Oxalic acid crystallizes in quadrilateral prisms, the sides of which are alternately broad and narrow, and summits diedral; ot, if crystallized rapidly, in small irregu- lar needles. They are efflorescent in dry air, but attract a little humidity if it be damp; are soluble in one part of hot and two of cold water; and are decomposable by a red heat, leaving a small quantity of coaly residuum.—100 parts of alcohol take up near 56 at a boiling heat, but not above 40 cold. Their acidity is so great, that when dissolved in 3600 times their weight of water, the solution reddens litmus pa- per, and is perceptibly acid to the taste. The oxalic acid is a good test for de- tecting lime, which it separates from all the other acids, unless they are present in excess. It has likewise a greater affinity ACI ACI for lime than for any other of the bases, and forms with it a pulverulent insoluble salt, not decomposable except by fire, and turning sirup of violets green. * From the oxalate of lead, Berzelius infers its prime equivalent to be 4.552, and by igneous decomposition he finds it re- solved into 66.534 oxygen, 33.222 carbon, and 0.244 hydrogen. The quantity of the latter, when reduced to primitive ratios, gives only, as Dr Thomson admits, l-12th of an atom of hydrogen, which makes this analysis of Berzelius and the Atomic theory incompatible. Since Berzelius pub- lished his analysis, oxalic acid has been made the subject of some ingenious re- marks by Dobereiner, in the 16th vol. of Schweigger's Journal. AVe see that the carbon and oxygen are to each other in the simple ratio of 1 to 2; or referred to their prime equivalent, as 2 of carbon = 1.5, to 3 of oxygen = 3. This propor- tion is what would result from a prime of carbonic acid = C -f- 2.0, combined with one of carbonic oxide = C + O. C being carbon, and O oxygen. The sum of the above weights gives 4.5 for the prime equivalent of oxalic acid, disregarding hy- drogen, which constitutes but l-37th of the whole, and may possibly be referred to the imperfect desiccation ofthe oxalate of lead subjected to analysis. Oxalic acid acts as a violent poison when swallowed in the quantity of 2 or 3 drachms; and several fatal accidents have lately occur- red in London, in consequence of its being improperly sold instead of Epsom salts. Its vulgar name of salts, under which the acid is bought for the purpose of whiten- ing boot-tops, occasions these lamentable mistakes. But the powerfully acid taste of the latter substance, joined to its prismatic or needle-formed crystallization, are suffi- cient to distinguish it from every thing else. The immediate rejection from the stomach of this acid, by an emetic, aided by copious draughts of warm water con- taining bicarbonate of potash, or soda, chalk, or carbonate of magnesia, are the proper remedies.* AVith barytes it forms an insoluble salt; but this salt will dissolve in water acidu- lated with oxalic acid, and afford angular crystals. If, however, we attempt to dis- solve these crystals in boiling water, the excess of acid will unite with the water, and leave the oxalate, which will be pre- cipitated. The oxalate of strontian too is a nearly insoluble compound. Oxalate of magnesia too is insoluble, un- less the acid be in excess. The oxalate of potash exists in two states, that of a neutral salt, and that of an acidule. The latter is generally obtained from the juice ofthe leaves ofthe oxalia acetosella, wood sorrel, or nmex aretosa, common sorrel. The expressed juice, be- ing diluted with water, should be set by for a few days, till the feculent parts have subsided, and the supernatant fluid is be- come clear; or it may be clarified, when expressed, with the whites of eggs. It is then to be strained off, evaporated to a pellicle, and set in a cool place to crystal- lize. The first product of crystals being taken out, the liquor may be further evap- orated, and crystallized; and the same process repeated till no more can be ob- tained. In this way Schlereth informs us about nine drachms of crystals may be ob- tained from two pounds of juice, which are generally afforded by ten pounds of wood sorrel. Savary, however, says, that ten parts of wood sorrel in full vegetation yield five parts of juice, which give little more than a two-hundredth of tolerably pure salt. He boiled down the juice, how- ever, in the first instance, without clari- fying it; and was obliged repeatedly to dissolve and re-crystallize the salt to ob- tain it white. This salt is in small, white, needly, or lamellar crystals, not alterable in the air. It unites with barytes, magnesia, soda, am- monia, and most ofthe metallic oxides, in- to triple salts. Vet its solution precipitates the nitric solutions of mercury and silver in the state of insoluble oxalate of these metals, the nitric acid in this case com- bining with the potash. It attacks iron, lead, tin, zinc, and antimony. Thi* salt, besides its use in taking out ink spots, and as a test of lime, forms with sugar and water a pleasant cooling bever- age ; and according to Berthollet, it pos- sesses considerable powers as an antisep- tic. The neutral oxalate of potash is very soluble, and assumes a gelatinous form, but may be brought to crystallize in hex- ae'dral prisms with diedral summits, by ad- ding more potash to the liquor than is suf- ficient to saturate the acid. Oxalate of soda likewise exists in two different states, those of an acidulous and a neutral salt, which in their properties are analogous to those of potash. The acidulous oxalate of ammonia is crystallizable, not very soluble, and capa- ble, like the preceding acidules, of com- bining with other bases, so as to form triple salts. But if the acid be saturated with ammonia, we obtain a neutral oxalate, which on evaporation yields very fine crystals in tetraedral prisms with ditdral summits, one of the planes of which cuts off three sides of the prism. This salt is decomposable by fire, which raises from it carbonate of ammonia, and leaves onlv some light traces of a coaly residuum. Lime, barytes, and strontian unite with ACI ACI its acid, and the ammonia flies off in the form of gas. The oxalic acid readily dissolves alumi- na, and the solution gives on evaporation a yellowish transparent mass, sweet and a little astringent to the taste, deliquescent, and reddening tincture of litmus, but not sirup of violets. This salt swells up in the fire, loses its acid, and leaves the alumina a little coloured. * The composition of the different oxa- lates may be ascertained by considering the neutral salts as consisting of one prime of acid = 4.552 to 1 of base, and the bin- oxalate of potash of 2 of acid to 1 of base, as was first proved by Dr. Wollaston. But this eminent philosopher has further shown, that oxalic acid is capable of com- bining in four proportions with the oxides, whence result neutral oxalates, suboxa- lates, acidulous oxalates, and acid oxalates. The neutral contain twice as much acid as the suboxalates; one-half of the quantity of acid in the acidulous oxalates; and one- quarter of that in the acid oxalates.* Acid (Per^ate). This name was given by Bergmann to the acidulous phosphate of soda, Haupt having called the phosphate of soda sal mirabile perlatum. Acid (Phosphoric.) The base of this acid, or the acid itself, abounds in the mi- neral, vegetable, and animal kingdoms. In the mineral kingdom it is found in combi- nation with lead, in the green lead ore; with iron, in the bog ores which afford cold short iron; and more especially with calcareous earth in several kinds of stone. Wbole mountains in the province of Es- tremadura in Spain are composed of this combination of phosphoric acid and lime. Mr. Bowles affirms, that the stone is whi- tish and tasteless, and affords a blue flame without smell when thrown upon burning coals. Mr. Proust describes it as a dense stone, not hard enough to strike fire with steel; and say s that it is found in strata, which always lie horizontally upon quartz, and which are intersected with veins of quartz. When this stone is scattered up- on burning coals, it does not decrepitate, but burns with a beautiful green light, which lasts a considerable time. It melts into a white enamel by the blow-pipe; is soluble with heat, and some effervescence in the nitric acid, and forms sulphate of lime with the sulphuric acid, while the phosphoric acid is set at liberty in the fluid. The vegetable kingdom abounds with phosphorus, or its acid. It is principally found in plants that grow in marshy places, in turf, and several species of the white woods. Aarious seeds, potatoes, agaric, soot, and charcoal afford phosphoric acid,§ § To this Prof. Bartholdi ascribes two accidents at the powder-mills at Essone, where spontaneous combustion appeared Voi. i [ 11 ] by abstracting the nitric acid from theity and lixiviating the residue. The lixivium contains the phosphoric acid, which may either be saturated with lime by the addi- tion of lime-water, in which case it forms a solid compound; or it may be tried by examination of its leading properties by other chemical methods. In the animal kingdom it is found in al- most every part of the bodies of animals which are not considerably volatile. There is not, in all probability, any part of these organized beings which is free from it. It has been obtained from blood, flesh, both of land and water animals; from cheese; and it exists in large quantities in bones, combined with calcareous earth. Urine contains it, not only in a disengaged state, but also combined with ammonia, soda, and lime. It was by the evaporation, and distillation of this excrementitious fluid with charcoal that phosphorus was first made; the charcoal decomposing the dis- engaged acid and the ammoniacal salt. (See Phospborus.) But it is more cheaply ob- tained by the process of Scheele, from bones, by the application of an acid to their earthy residue after calcination. In this process the sulphuric acid ap- pears to be the most convenient, because it forms a nearly insoluble compound with the lime of the bones. Bones of beef, mutton, or veal, being calcined to white- ness in an open fire, lose almost half of their weight. This must be pounded, and sifted, or the trouble may be spared by buying the powder that is sold to make cupels for the assayers, and is, in fact, the powder of burned bones ready sifted. Tq three pounds of the powder there may be added about two pounds of concentrated sulphuric acid. Four or five pounds of water must be afterward added to assist the action of the acid; and during the whole process the operator must remem- ber to place himself and his vessels so that the fumes may be blown from him. The whole may then be left on a gentle sand bath for twelve hours or more, taking care to supply the loss of water which happens by evaporation. The next day a large quantity of water must be added, the whole strained through a sieve, and the residual matter, which is sulphate of lime, must be edulcorated by repeated affusions of hot water, till it passes tasteless. The waters contain phosphoric acid nearly free from lime, and by evaporation, first in glazed earthen, and then in glass vessels, to have taken place in one instance in the charcoal store-room, in the other in the box into which the charcoal was sifted; as well as three successive explosions at the powder-m'lls < i" Vosges. This cer- tainb merits the attention of gunpbwdet manufacturers. ACI ACI or rather in vessels of platina or silver, for the hot acid acts upon glass, afford the acid in a concentrated state, which, by the force of a strong heat in a crucible, may be made to acquire the form of a transpa- rent consistent glass, though indeed it is usually of a milky, opaque appearance. For making phosphorus, it is not neces- sary to evaporate the water further than to bring it to the consistence of sirup; and the small portion of lime it contains is not an impediment worth the trouble of removing, as it affects the produce very little. But when the acid is required in a purer state, it is proper to add a quantity of carbonate of ammonia, which, by dou- ble elective attraction, precipitates the lime that was held in solution by the phos- phoric acid. The fluid being then evapo- rated, affords a crystallized ammoniacal salt, which may be melted in a silver ves- sel, as the acid acts upon glass or earthen vessels. The ammonia is driven off by the heat, and the acid acquires the form of a compact glass as transparent as rock crystal, acid to the taste, soluble in water, and deliquescent in the air. This acid is commonly pure, but never- theless may contain a small quantity of so- da, originally existing in the bones, and not capable of being taken away by this process, ingenious as it is. The only une- quivocal method of obtaining a pure acid appears to consist in first converting it in- to phosphorus by distillation of the mate- rials with charcoal, and then converting it again into acid by rapid combustion, at a high temperature, either in oxygen or at- mospheric air, or some other equivalent process. Phosphorus may also be converted into the acid state by treating it with nitric acid. In this operation, a tubulated retort with a ground stopper, must be half filled with nitric acid, and a gentle heat applied. A small piece of phosphorus being then introduced through the tube will be dis- solved with effervescence, produced by the escape of a large quantity of nitric ox- ide. The addition of phosphorus must be continued until the last piece remains undissolved. The fire being then raised to drive over the remainder of the nitric acid, the phosphoric acid will be found in the retort, partly in the concrete and part- ly in the liquid form. Sulphuric acid produces nearly tke same effect as the nitric; a large quantity of sulphurous acid flying off. But as it re- quires a stronger heat to drive off the last portions of this acid, it is not so well adapt- ed to the purpose. The hquid chlorine likewise acidifies it. AV'hen phosphorus is burned by a strong heat, sufficient to cause it to flame rapid- ly, it is almost perfectly converted into dry acid, sonic of which is thrown up by the force of the combustion, and the rest remains upon the supporter. This substance has also been acidified by the direct application of oxygen gas passed through hot water, in which the phosphorus was liquefied or fused. The general characters of phosphoric acid are: 1. It is soluble in water in all proportions, producing a specific gravity, which increases as the quantity of acid is greater, but does not exceed 2.687, which is that of the glacial acid. 2. It produces heat when mixed with water, though not very considerable. 3. It has no smell when pure, and its taste is sour, but not corrosive. 4. AVhen perfectly dry, it sub- limes in close vessels; but loses this pro- perty by the addition of water; in which circumstance it greatly differs from the boracic acid, which is fixed when dry, but rises by the help of water. 5. When con- siderably diluted with water, and evapo- rated, the aqueous vapour carries up a small portion ofthe acid. 6. With char- coal or inflammable matter, in a strong heat.it loses its oxygen, and becomes con- verted into phosphorus. Phosphoric acid is difficult of crystalli- zins- Though the phosphoric acid is scarcely corrosive, yet, when concentrated, it acts upon oils, which it discolours, and at length blackens, producing heat, and a strong smell like that of ether and oil of turpen- tine ; but does not form a true acid soap. It has most effect on essential oils, less on drying oils, and least of all on fat oils. Spirit of wine and phosphoric acid have a weak action on each other Some heat is excited by this mixture, and the product which comes over in distillation of the mix- ture is strongly acid, of a pungent arsenical smell, inflammable with smoke, miscible in all proportions with water, precipitating silver and mercury from their solutions, but not gold; and although not an ether, yet it seems to bean approximation to that kind of combination. * From the syntheses ofthe phosphates of soda, barytes, and lead, Berzelius de- duces the prime equivalent of phosphoric acid to be 4.5. But the experiments of Berzelius on the synthesis of the acid it- self, show it to be a compound of about 100 phosphorus + 133 oxygen ; or of 2 oxygen+1.5 phosphorus"= 3.5 for the prime equivalent ofthe acid. Lavoisier's synthesis gave 2 oxygen-f- 1.33 phospho- rus. So did that of Sir H. Davy by rapid combustion in oxygen gas, as published in the Phil. Trans, for 1812. Dr. Thomson, in his account of the improvements in Phy- sical Science, published in his Annals for January 1817, says, " It is quite clear from these analyses (of Berzelius) that the ACI ACI equivalent number for phosphoric acid is 4.5." M. Dulong, in an elaborate paper published in the third volume of the Me- moires d'Arcueil, gives as the result of di- versified experiments, the proportions of 100 phosphorus to 123 oxygen; or of 2 oxygen 4- 1.627 phosphorus = 3.627 for the acid equivalent. In the Annals of Philosophy for April 1816, page 305, Dr. Thomson gives the following statement: " From this result it follows that the acid is composed of Phosphorus, 100 Oxygen, 123.46. "To verify this result, the author (Dr. Thomson) had recourse to the phosphate of lead, which is a compound of 2 atoms phosphoric acid -f- 1 atom yellow oxide of lead." He gives three analyses of this salt; one by Dr. Wollaston ; one by Pro- fessor Berzelius; and one by himself. These analyses are as follow :— Acid. Base. Bv AVollaston, 400 -f 370.72 ' Berzelius, 100+ 380.56 Thomson, 100 + 398.49 Mean, 100 + 383.26. This mean, which corresponds nearly with the analysis of Berzelius, is consid- ered by him as exhibiting the true com- position of phosphate of lead From this the weight of an atom of phosphoric acid is shown to be 3.649. But after a com- parison of results by different methods, he says, " This gives us 1.634 for the weight of an atom of phosphorus; 2.634 for the weight of an atom of phosphorous acid; and 3.634 for the weight of an atom of phosphoric acid." Page 306. In the subsequent January, when he gives an Account of Physical Science for the same year 1816, however, he says, "It is quite clear from these analyses," (of Berzelius, whom he there properly styles one of the most accurate chemists of the present day), " that the equivalent num- ber for phosphoric acid is 4.5." And far- ther, in the fifth edition of his System of Chemistry, published in 1817, from an ex- tremely large collection of experiments, he determines the equivalent of phospho- rus to be 1.5; and that of phosphoric acid to be 4.5. Finally, in March 1820, without hinting in the least at his abandonment of the number 3.634, and adoption of 4.5, he merely says, " that a set of experiments he published some years ago seem to me to demonstrate the constitution of these two acids in a satisfactory manner." And he immediately fixes on 3.5 for phosphoric acid. Amid all these perplexities, it is com- fortable to resort to Sir H. Davy's clear and decisive paper, read before the Royal Society on the 9th April 1818. With his well known sagacity, he invented a new method of research, to elude the former sources of error. He burned the vapour of phosphorus as it issues from a small tube, contained in a retort filled with oxy- gen gas. By adopting this proces, he de- termined the composition of phosphoric acid to be 100 phosphorus -f- 134.5 oxy- gen ; whence its equivalent comes out 3.500. Phosphorous acid he then shows to consist of 1 oxygen + 1.500 phosphorus = 2.500. AVe shall therefore fix on Sir H. Davy's number 3.500 for the prime equivalent of phosphoric acid. We see, indeed, in the Annals of Philos. for 1816, in a paper on phosphuretted hy- drogen by Dr. Thomson, that this chemist had determined the atom of phosphorus to be 1.5, and that of phosphoric acid 3.5, but he subsequently renounced them. It will be instructive to place his fluctuations of opinion in one view. In the Annals for April 1816, the report of Dr. Thomson's paper, read at the Royal Society, on phosphoric acid and the phos- phates, makes the acid equivalent 3.634; in the Annals for August 1816, the phos- phuretted hydrogen experiments make it 3.5: the history of 1816 improvements, inserted in January 1817, gives us 4.5 as the equivalent, and an explicit renuncia- tion of 3.5; the System of Chemistry in October 1817, confirms this number 4.5 by multiplied facts and reasonings ; and, finally, after Sir H. Davy's experiments appeared in 1818, which demonstrated 3.500 to be the real number, Dr. Thomson resumes 3.5; and to show his claim to pri- ority, refers simply to his former paper on phosphuretted hydrogen. From this ex- ample, beginners in the study of chemistry will learn the danger of dogmatizing has- tily on experimental subjects.* * Acid (Phosphorous) was discovered in 1812 by Sir H. Davy. When phospho- rus and corrosive sublimate act on each other at an elevated temperature, a liquid called protochloride of phosphorus is form- ed. Water added to this, resolves it into muriatic and phosphorous acids. A mo- derate heat suffices to expel the former, and the latter remains, associated with water. It has a very sour taste, reddens vegetable blues, and neutralizes bases. When heated strongly in open vessels, it inflames. Phosphuretted hydrogen flies off, and phosphoric acid remains. Ten parts of it heated in close vessels give off li of bihydroguret of phosphorus, and leave 81 of phosphoric acid. Hence the liquid acid consists of 80.7 acid -f- 19.3 water. Its prime equivalent is 2.5.* * Acid (Hvpophosphorous), lately dis- covered by M. Dulong. Pour water on the phosphuret of barytes, and wait till all the phosphuretted hydrogen be disengag- ACI ACI e59 and that of nitrogen, - - - - 0.96913 air being reckoned, .... 1.00000 Or compared to water as unity,— .Nitrogen is 0.^01182338 Oxygen, 0.001346379 And 0.8 nitrogen = 0.00094587 0.2 oxygen =■ 0.00026927 0.00121514 And 0.79 nitrogen =- 0.000934 0.21 oxygen = 0.000283 0.001217 A number which approaches very nearly to the result of experiment. Many ana- logies, it must be confessed, favour Dr. Prout's proportions; but the greater num- ber of experiments on the composition and density ofthe atmosphere agree with Biot's results. Nothing can decide these fundamental chemical proportions except a new, elaborate, and most minutely accu- rate series of experiments. We shall then know whether the atmosphere contains in volume 20 or 21 percent of oxygen. See Meteorology.* Alaraster. Among the stones which are known by the name of marble, and have been distinguished by a considerable variety of denominations by statuaries, and others whose attention is more directed to their external character and appear-* ance than their component parts, alabas- ters are those which have a greater or less degree of imperfect transparency, a gran- ular texture, are softer, take a duller po- lish than marble, and are usually of a whiter colour. Some stones, however, of a veined and coloured appearance, have been considered as alabasters, from their possessing the first mentioned criterion ; and some transparent and yellow sparry stones have also received this appellation. Chemists are at present agreed in ap- plying this name only to such opaque, consistent, and semi-transparent stones, as are composed of lime united with the sul- phuric acid. But the term is much more frequent among masons and statuaries than chemists. Chemists in general con- found the alabasters among the selenites, gypsums, or plaster of Paris, more espe- cially when they allude only to the com- ponent parts, without having occasion to consider the external appearance, in which only these several compounds dif- fer from each other. As the semi-opaque appearance and granular texture arise merely from a dis- turbed or successive crystallization, which would else have formed transparent spars, it is accordingly found, that the calcareous Stalactites, or drop-stones, formed by the transition of water through the roofs ot caverns in a calcareous soil, do not differ in appearance from the alabaster, most of which is also formed in this manner. But the calcareous stalactites here spoken of consist of calcareous earth and carbonic acid; while the alabaster of the chemists is formed of the same earth and sulphuric acid, as has already been remarked. * Albin. A mineral discovered at Mo- Aaberg, near Aussig, in Bohemia; and be- ing of an opaque white colour, has been called, by Werner, albin. Aggregated crystalline laminae constitute massive albin. Small crystals of it in right prisms, whose summits consist of four quadrangular planes, are found sprinkled over mamme- lated masses in cavities.* See Zeolite. Album Grjecum. Innumerable are the in- stances of fanciful speculation and absurd credulity in the invention and application of subjects in the more ancient materia medica. The white and solid excrement of dogs, which subsist chiefly on bones, has been received as a remedy in the medical art, under the name of Album Grsecum. It consists, for the most part,' of the earth of bones, or lime in combin- ation with phosphoric acid. Albumlv. This substance, which derives its name from the Latin for the white of an egg, in which it exists abundantly, and in its purest natural state, is one ofthe chief constituent principles of all the animal solids. Beside the white of egg, it abounds in the serum of blood, the vitreous and crystalline humours of the eye, and the fluid of dropsy. Fourcroy claims to himself the honour of having discovered it in the green feculae of plants in general, particularly in those of the cruciform order, in very young ones, and in the fresh shoots of trees, though Rouelle appears to have detected it there long before. Vauquelin says it exists also in the mineral water of Plombieres. Mr. Seguin has found it in remarkable quantity in such vegetables as ferment without yeast, and afford a vinous liquor; and from a series of experiments he infers that albumen is the true principle of fermentation, and that its action is more powerful in proportion to its solubility, three different degrees of which he found it to possess. The chief characteristic of albumen is its coagulability by the action of heat. If the white of an egg he exposed to a heat of about 134° F. white fibres begin to appear in it, and at 160° it coagulates into a solid mass. In a heat not exceeding 212° it dries, shrinks, and assumes the appearance of horn. It is soluble in cold water before it has been coagulated, but not after; and when diluted with a very large portion, it does not coagulate easily, ALU ALB Pure alkalis dissolve it, even after coagu- lation. It is precipitated by muriate of mercury, nitro-muriate of tin, acetate of lead, nitrate of silver, muriate of gold, infusion of galls, and tannin. The acids and metallic oxides coagulate albumen. On the addition of concentrated sulphuric acid, it becomes black, and exhales a nauseous smell. Strong muriatic acid gives a violet tinge to the coagulum, and at length becomes saturated with ammonia. Nitric acid, at 70° F. disengages from it abundance of azotic gas ; and if the heat be increased prussic acid is formed, after which carbonic acid and carburetted hy- drogen are evolved, and the residue consists of water containing a little oxalic acid, and covered with a lemon coloured fat oil. If dry potash or soda be triturated with albumen, either liquid or solid, ammoniacal gas is evolved, and the cal- cination ofthe residuum yields an alkaline prussiate. On exposure to the atmosphere in a moist state, albumen passes at once to the state of putrefaction. * Solid albumen may be obtained by agitating white of egg with ten or twelve times its weight of alcohol. This seizes the water which held the albumen in solu- tion; and this substance is precipitated under the form of white flocks or filaments, which cohesive attraction renders insolu- ble, and which consequently may be freely washed with water. Albumen thus ob- tained is like fibrin, solid, white, insipid, inodorous, denser than water, and without action on vegetable colours. It dissolves in potash and soda more easily than fibrin; but in acetic acid and ammonia with more difficulty. When these two animal principles are separately dissolved in potash, muriatic acid added to the albuminous does not disturb the solution, but it produces a cloud in the other. Fourcroy and several other chemists have ascribed the characteristic coagula- tion of albumen by heat to its oxygenation. But cohesive attraction is the real cause ofthe phenomenon. In proportion as the temperature rises, the particles of water and albumen recede from each other, their affinity diminishes, and then the albu- men precipitates. However, by uniting albumen with a large quantity of water, we diminish its coagulating property to such a degree, that heat renders the solu- tion merely opalescent. A new-laid egg yields a soft coagulum by boiling; but when, by keeping, a portion ofthe water has transuded so as to leave a void space within the shell, the concentrated albu- men affords a firm coagulum. An analo- gous phenomenon is exhibited by acetate of alumina, a solution of which, being heat- ed, gives a precipitate in flakes, which re- dissolve as the caloric which separated the particles of acid and base escapes, or as the temperature falls. A solution containing T^ of dry albumen forms by heat a solid coagulum; but when it contains only TXy, it gives a glairy liquid. One thousandth part, however, on applying heat, occa- sions opalescence. Putrid white of egg, and the pus of ulcers, have a similar smell. According to Dr. Bostock, a drop of a saturated solution of corrosive sublimate letfall into water containing ^^ of albu- men, occasions a milkiness and curdy pre- cipitate. On adding a slight excess of the mercurial solution to the albuminous li- quid, and applying heat, the precipitate which falls, being dried, contains in every 7 parts, 5 of albumen. Hence that salt is the most delicate test of this animal pro- duct. The yellow pitchy precipitate oc- casioned by tannin, is brittle when dried, and not liable to putrefaction. But tannin, or infusion of galls, is a much nicer test of gelatin than of albumen. The cohesive attraction of coagulated albumen makes it resist putrefaction. In this state it may be kept for weeks under water without suffering change. By long digestion in weak nitric acid, albumen seems convertible into gelatin. By the analy sis of Gay-Lussac and Thenard, 100 parts of albumen are forced of 52 883 car- bon, 23.872 oxygen, 7.540 hydrogen, 15.705 nitrogenjor, in other terms,of 52.883 carbon, 27.127 oxygen and hydrogen, in the proportions for constituting water, 15.705 nitrogen, and 4.285 hydrogen in excess. The negative pole of a voltaic Eile in high activity coagulates albumen; ut if the pile be feeble, coagulation goes on only at the positive surface. Albumen, in such a state of concentration as it exists in serum of blood, can dissolve some me- tallic oxides, particularly the protoxide of iron. Orfila has found white of egg to be the best antidote to the poisoning effects of corrosive sublimate on the human sto- mach. As albumen occasions precipitates with the solutions of almost every metal- lic salt, probably it may act beneficially against other species of mineral poison.* From its coagulability albumen is of great use in clarifying liquids. See Cla- rification. It is likewise remarkable for the pro- perty of rendering leather supple, for which purpose a solution of whites of eggs in water is used by leather-dressers; and hence Dr. Lobb of Yeovil in Somerset- shire was induced to employ this solution in cases of contraction and rigidity of the tendons, and derived from it apparent success. Whites of eggs beaten in a basin with a lump of alum, till they coagulate, form the ALC ALC nlumcurdof Riverius, or alum cataplasm of the London Pharmacopoeia, used to re- move inflammations ofthe eyes. * Alburnum. The interior white bark of trees.* * Alcarrazas. A species of porous pottery made in Spain, for the purpose of cooling water by its transudation and co- pious evaporation from the sides of the vessel. M. Darcet gives the following as the analysis of the clay which is employed for the purpose: 60 calcareous earth, mixed with alumina and a little peroxide of iron, and 36 of siliceous earth, mixed with a little alumina. In working up the earths with water, a quantity of salt is ad- ded, and dried in it. The pieces are only half baked.* * Alchemy. A title of dignity, given in the dark ages, by the adepts, to the mystical art by which they professed to find the philosopher's stone, that v\ as to transmute base metals into gold, and pre- pare the elixir of life. Though avarice, fraud, and folly were their motives, yet their experimental researches were instru- mental in promoting the progress of che- mical discovery. Hence, in particular, metallic pharmacy derived its origin.* Alcohol. This term is applied in strict- ness only to the pure spirit obtainable by distillation and subsequent rectification from all liquids that have undergone vi- nous fermentation, and from none but such as are susceptible of it. But it is common- ly used to signify this spirit more or less imperfectly freed from water, in the state in which it is usually met with in the shops, and in which, as it was first obtained from the juice of the grape, it was long distin- guished by the name of spirit of wine. At present it is extracted chiefly from grain or molasses in Europe, and from the juice of the sugar-cane in the West Indies; and in the diluted state in which it commonly occurs in trade, constitutes the basis of the several spirituous liquors called bran- dy, rum, gin, whiskey, and cordials, how- ever variously denominated or disguised. As we are not able to compound alco- hol immediately from its ultimate consti- tuents, we have recourse to the process of fermentation, by which its principles are first extricated from the substances in which they were combined, and then uni- ted into a new compound; to distillation, by which this new compound, the alcohol is separated in a state of dilution with wa- ter, and contaminated with essential oil; and to rectification, by which it is ultimate- ly freed from these. It appears to be essential to the fermen- tation of alcohol, that the fermenting fluid should contain saccharine matter, which is indispensable to that species of fermen- tation called yinous. In France, where a great deal of wine is made, particularly at the commencement of the vintage, that is too weak to be a saleable commodity, it is a common practice to subject this wine to distillation, in order to draw off the spirit; and as the essential oil that rises in this process is of a more pleasant flavour than that of malt or molasses, the French brandies are preferred lo any other; though even in the flavour of these there is a difference, according to the wine from which they are produced. In the West Indies a spirit is obtained from the juice ofthe sugar-cane, which is highly impreg- nated with its essential oil, and well known by the name of rum. The distillers in this country use grain, or molasses, whence they distinguish the products by the name of malt spirits, and mo'axses spirits. It is said that a very good spirit may be ex- tracted from the husks of gooseberries or currants, after wine has been made from them. As the process of malting- developes the saccharine principle of grain, it would ap- pear to render it fitter for the purpose; though it is the common practice to use about three parts of raw grain with one of malt. Fortius, two reasons may be assign- ed : by using raw gram the expense of malting is saved, as well as the duty on mait; and the process of malting requires some nicety of attention, since, if it be carried Joo far, part ofthe saccharine mat- ter is lost, and if it be stopped too soon, this matter will not be wholly developed. Besides, if the malt be dried too quickly, or by an unequal heat, the spirit it yields will be less in quantity, and more unplea- sant in flavour. Another object of econo- mical consideration is, what grain will af- ford the most spirit in proportion to its price, as well as the best in quality. Bar- ley appears to produce less spirit than wheat; and if three parts of raw wheat be mixed with one of malted barley, the produce is said to be particularly fine. This is the practice ofthe distillers in Hol- land for producing a spirit of the finest quality; but in England they are express- ly prohibited from using more than one part of wheat to two of other grain. Rye, however, affords still more spirit than wheat. * The practice with the distillers in Scotland is to use one part of malted with from four to nine parts of unmalted grain. This mixture yields an equal quantity of spirit, and at a much cheaper rate than when the former proportions are taken.* Whatever be the grain employed, it may be coarsely ground, and then mixed care- fully with a little cold water, to prevent its running into lumps; water about 90Q F. may then be added, till it is sufficiently diluted j and, lastly, a sufficient quantity ALC ALC »f yeast. The whole is then to be allow- ed to ferment in acovered vessel, to which, however, the air can have access. Atten- tion must be paid to the temperature ; for if it exceed 77° F. the fermentation will be too rapid ; if it be below 6UV, the fer- mentation will cease.f The mean between these will generally be found most favour- able. In this country it is the more com- mon practice to mash the grain as for brewing malt liquors, and boil the wort. But in whichever way it be prepared, or if the wash, so the liquor intended for dis- tillation is called, be made from molasses and water, due attention must be paid to the fermentation, that it be continued till the liquor grows fine, and pungent to the taste, which will generally be about the third day, but not so long as to permit the acetous fermentation to commence. In this state the wash is to be commit- ted to the still, of which, including the head, it should occupy at least three- fourths ; and distilled with a gentle heat as long as any spirit comes over, which will be till about half the wash is consum- ed. The more slowly the distillation is conducted, the less will the product be contaminated with essential oil, and the less danger will there be of empyreuma. A great saving of time and fuel, however, may be obtained by making the still very broad and shallow, and contriving a free exit for the steam. This has been carried to such a pitch in Scotland, that a still mea- suring 43 gallons, and containing 16 gal- lons of wash, has been charged and work- ed no less than four hundred and eighty times in the space of twenty-four hours. This would be incredible, were it not esta- blished by unquestionable evidence. See Laboratory, article Still. * The above wonderful rapidity of dis- tillation has now ceased, since the excise duties have been levied on the quantity of spirit produced, and not, as formerly, by the size of the still. Hence, too, the spi- rit is probably improved in flavour.* The first product, technically termed low wine, is again to be subjected to dis- tillation, the latter portions of what comes over, called fuints, being set apart to put into the wash still at some future opera- tion. Thus a large portion of the watery partis left behind. This second product, termed raw spirit, being distilled again, is called rectified spirit. It is calculated, that ahundred gallons of malt or corn wash will not produce above twenty of spirit, con- taining 60 parts of alcohol to 50 of water; the same of cyder wash, 15 gallons; and of molasses wash, 22 gallons. The most ■j- This is a mistake ; fermentation will go on very slowly 10 degrees lower. spirituous wines of France, those of Lan- guedoc, Guienne, and Rousillon, yield, ac- cording to Chaptal, from 20 to 25 gallons of excellent brandy from 100; but those of Burgundy and Champagne much less. Brisk wines, containing much carbonic acid, from the fermentation having been stopped at an early period, yield the least spirit. The spirit thus obtained ought to be co- lourless, and free from any disagreeable flavour; and in this state it is fittest for pharmaceutical purposes, or the extraction of tinctures. But for ordinary sale some- thing more is required. The brandy of France, which is most in esteem here, though perfectly colourless when first made, and often preserved so for use in that country, by being kept in glass or stone bottles, is put into new oak casks for exportation, whence it soon acquires an amber colour, a peculiar flavour, and something like an unctuosity of consis- tence. As it is not only prized for these qualities, but they are commonly deemed essential to it, the English distiller imi- tates by design these accidental qualities. The most obvious and natural method of doing this would be by impregnating a pure spirit with the extractive, resinous, and colouring matter of oak shaving3; but other modes have been contrived. The dulcified spirit of nitre, as it is called, is commonly used to give the flavour; and catechu, or burnt sugar, to impart the de- sired colour. A French writer has recom- mended three ounces and a half of finely powered charcoal, and four ounces and a half of ground rice, to be digested for a fortnight in a quart of malt spirit. The finest gin is said to be made in Hol- land, from a spirit drawn from wheat mix- ed with a third or fourth part of malted barley, and twice rectified over juniper berries; but in general, rye meal is used instead of wheat. They pay so much re- gard to the water employ ed, that many send vessels to fetch it on purpose from the Meuse; but all use the softest and clearest river water they can get. In Eng- land it is the common practice to add oil of turpentine, in the proportion of two ounces to ten gallons of raw spirit, with three handfuls of bay salt, and draw oft'till the faints begin to rise. But corn or molasses spirit is flavoured likewise by a variety of aromatics, with or without sugar, to please different palates; all of which are included under the gene- ral technical term of compounds or cordials. Other articles have been employed, though not generally, for the fabrication of spirit, as carrots and potatoes; and we are lately informed by Professor Proust, that from the fruit of the carob tree he ALC ALC Has obtained good brandy in the propor- tion ot a pint from five pounds of the dried fruit. To obtain pure alcohol, different pro- cesses have been recommended; but the purest rectified spirit obtained as above described, being that which is least con- taminated with foreign matter, should be employed. Rouelle recommends to draw oft half the spirit in a water bath; to rec- tify this twice more, drawing off two-thirds each time; to add water to this alcohol, which will turn it milky by separating the esseutal oil remaining in it; to distil the spirit from this water; and finally rectify it by one more distillation. Bauniw sets apart the first running, when about a fourth is come over, and contin ues the distillation till he has drawn oft' about as much more, or till the liquor runs off' milky. The last running he puts into the still again, and mixes the first half of what comes over with the preceding first product. Plus process is again repeated, and all the first products being mixed to- gether, are distilled afresh. When about halt' the hquor is come over, this is to be set apart as pure alcohol. Alcohol in this state, however, is not so pure as when, to use the language of the old chemists, it has been dephlegmated, or still further freed from water, by means of some alkaline salt. Boerhaave recom- mended, for this purpose, the muriate of soda, deprived 01 its water of crystalliza-' tion by heat, and added hot to the spirit. But the subcarbonate of potash is prefera- ble. About a third of the weight of the alcohol should be added to it in a glass vessel, well shaken, and then suffered to subside. The salt will be moistened by the water absorbed from the alcohol; which being decanted, more of the salt is to be added,and this is to be continued till the salt falls dry to the bottom of the vessel. The alcohol in this state will be reddened by a portion ot the pure potash, which it will hold in solution, from which it must be freed by distillation in a water bath. Dry muriate of lime may be substi- tuted advantageously for the alkali. As alcohol is much lighter than water, its specific gravity is adopted as the test of its purity. Fourcroy considers it as rectified to the highest point when its spe- cific gravity is 829, that of water being 1000; and perhaps this is nearly as far as it can be carried by the process of Rou- elle or Baume simply. Mr.Bories found the first measure that came over from twenty of spirit at 836 to be 820, at the temperature of 71° F. Sir Charles Blag- den, by the addition of alkali, brought it to 813, at 60° F. Chaussier professes to have reduced it to 798 ; but he gives 998.35 as the specific gravity of water. Lewitz asserts, that he has obtained it at 791, by adding as much alkali as nearly to absorb the spirit; but the temperature is not indicated. In the shops it is about 835 or 840; according to the London College it should be 815. It is by no means an easy undertaking to determine the strength or relative value of spirits, even with sufficient accuracy for commercial purposes. The following re- quisites must be obtained before this can be well done: the specific gravity of a certain number of mixtures of alcohol and water must be taken so near each other, as that the intermediate specific gravities may not perceptibly differ from those de- duced from the supposition of a mere mix- ture of the fluids; the expansions of varia- tions of specific gravity in these mixtures must be determined at different tempera- tures ; some easy method must be con- trived of determining the presence and quantity of saccharine or oleaginous mat- ter which the spirit may hold in solution, and the effect of such solution on the spe- cific gravity ; and lastly, the specific gra- vity of the fluid must be ascertained by a proper floating instrument with a graduat- ed stem, or set of weights ; or, which may be more convenient, with both. The strength of brandies in commerce is judged by the phial, or by burning. The phial proof consists in agitating the spirit in a bottle, and observing the form and magnitude ofthe bubbles that collect round the edge of the liquor, technically termed the bead, which are larger the stronger the spirit. These probably de- pend on the solution of resinous matter from the cask, which is taken up in greater quantities, the stronger the spirit. It is not difficult, however, to produce this ap- pearance by various simple additions to weak spirit. The proof by burning is also fallacious; because the magnitude of the flame, and quantity of residue, in the same spirit, vary greatly with the form of the vessel it is burned in. If the vessel be kept cool, or suffered to become hot, if it be deeper or shallower, the results will not be the same in each case. It does not follow, however, but that manufactu- rers and others may in many instances re- ceive considerable information from these signs, in circumstances exactly alike, and in the course of operations wherein it would be inconvenient to recur continu- ally to experiments of specific gravity. The importance of this object, as well for the purposes of revenue as of com- merce, induced the British government to employ Dr. Blagden, now Sir Charles, to institute a very minute and accurate series of experiments. These may be consider- ed as fundamental results; for which rea- son, I shall give a summary oftheminthis ALC ALC place, from the Philosophical Transactions for 1790. The first object to which the experi- ments were directed was to ascertain the quantity and law resulting from the mutual penetration of water and spirit. All bodies in general expand by heat; but the quantity of this expansion, as well as the law of its progression, is probably not the same in any two substances. In water and spirit they are remarkably dif- ferent. The whole expansion of pure spi- rit from 30° to 100° of Fahrenheit's ther- mometer is not less than l-25th of its whole bulk at 30°; whereas that of water, in the same interval is only l-145th of its bulk. The laws of their expansion are still more different than the quantities. If the expansion of quicksilver be, as usual, taken for the standard, (our thermome- ters being constructed with that fluid,) the expansion of spirit is, indeed, progres- sively increasing with respect to that stan- dard, but not much so within the above- mentioned interval; while water kept from freezing to 30°, which may easily be done, will absolutely contract as it is heat- ed for ten or more degrees, that is, to 40° or 42° of the thermometer, and will then begin to expand as its heat is augmented, at first slowly, and afterward gradually more rapidly, so as to observe upon the whole a very increasing progression. Now, mixtures of these two substances will, as may be supposed, approach to the less or the greater of these progressions, accord- ing as they are compounded of more spi- rit or more water, while their total expan- sion will be greater, according as more spirit enters into their composition; but the exact quantity of the expansion, as well as law of the progression, in all of them, can be determined only by trials. These were, therefore, the two other prin- cipal objects to be ascertained by experi- ment. The person engaged to make these ex- periments was Dr. Dollfuss, an ingenious Swiss gentleman then in London, who had distinguished himself by several publica- tions on chemical subjects. As he could not conveniently get the quantity of spirit he wanted lighter than 825, at 60° F., he fixed upon this strength as the standard for alcohol. These experiments of Dr. Dollfuss were repeated by Mr. Gilpin, clerk ofthe Roy- al Society; and as the deductions in this account will be taken chiefly from that last set of experiments, it is proper here to describe minutely the method observed by Mr. Gilpin in his operation. This natu- rally resolves itself into two parts: the way of making the mixtures, and the way of ascertaining their specific gravity. 1. The mixtures were made by weight, as the only accurate method of fixing the proportions. In fluids of such very une- qual expansions by heat as water and alco- hol, if measures had been employed, in- creasing or decreasing in regular propor- tions to each other, the proportions ofthe masses would have been sensibly irregu- lar : now the latter was the object in view, namely, to determine the real quantity of spirit in any given mixture, abstracting the consideration of its temperature. Be- sides, if the proportions had been taken by measure, a different mixture should have been made at every different degree of heat. But the principal consideration was, that with a very nice balance, such as was employed on this occasion, quantities can be determined to much greater exact- ness by weight than by any practicable way of measurement. The proportions were therefore always taken by weight. A phial being provided of such a size as that it should be nearly full with the mix- ture, was made perfectly clean and dry, and being counterpoised, as much of the pure spirit as appeared necessary was poured into it. The weight of this spirit was then ascertained, and the weight of distilled water required to make a mixture of the intended proportions was calcula- ted. This quantity of water was then add- ed, with all the necessary care, the last portions being put in by means of a well- known instrument, which is composed of a small dish terminating in a tube drawn to a fine point: the top ofthe dish being covered with the thumb, the liquor in it is prevented from running out through the tube by the pressure of the atmosphere, but instantly begins to issue by drops, or a very small stream, upon raising the thumb. Water being thus introduced in- to the phial, till it exactly counterpoised the weight, which having been previously computed, was put into the opposite scale, the phial was shaken, and then well stop- ped with its glass stopple, over which leather was tied very tight, to prevent evaporation. No mixture was used till it had remained in the phial at least a month, for the full penetration to have taken place; and it was always well shaken be- fore it was poured out to have its specific gravity tried. 2. There are two common methods of taking the specific gravity of fluids; one, by finding the weight which a solid body loses by being immersed in them; the other, by filling a convenient vessel with them, and ascertaining the. increase of weight it acquires. In both cases a stan- dard must have been previously taken, which is usually distilled water; namely, in the first method, by finding the weight lost by the solid body in the water; and in the second method, the weight of the ALC ALC vessel filled with water. The latter was preferred, for the following reasons:— When a ball of glass, which is the pro- perest kind of solid body, is weighed in any spirituous or watery fluid, the adhe- sion of the fluid occasions some inaccura- cy, and renders the balance comparatively sluggish. To what degree this effect pro- ceed- is uncertain; but from some expe- riments made by Mr. Gilpin with that view, it appears to be very sensible. Moreover, in this method a large surface must be exposed to the air during the operation of weighing, which, especially in the higher temperatures, would give oc- casion to such an evaporation as to alter essentially the strength ofthe mixture. It seemed also as if the temperature of the fluid under trial could be determined more exactly in the method of filling a vessel, than in the other: for the fluid cannot well be stirred while the ball to be weigh- ed remains immersed in it; and as some time must necessarily be spent in the weighing, the change of heat which takes place during that period will be unequal through the mass, and may occasion a sen- sible error. It is true, on the other hand, that in the method of filling a vessel, the temperature could not be ascertained with the utmost precision, because the neck of the vessel employed, containing about ten grains, was filled" up to the mark with spi- rit not exactly of the same temperature, as will be explained presently: but this error, it is supposed, would by no means equal the other, and the utmost quantity of it may be estimated very nearly. Fi- nally, it was much easier to bring the fluid to any given temperature when it was in a vessel to be weighed, than when it was to have a solid body weighed in it; be- cause in the former case the quantity was smaller, and the vessel containing it more manageable, being readily heated with the hand or warm water, and cooled with cold water: and the very circumstance, that so much ofthe fluid was not required, prov- ed a material convenience. The particu- lar disadvantage in the method of weigh- ing in a vessel, is the difficulty of filling it with extreme accuracy; but when the ves- sel is judiciously and neatly marked, the error of filling will, with due care, be ex- ceedingly minute. By several repetitions ofthe same experiments, Mr. Gilpin seem- ed to bring it within the l-15000th part of the whole weight. The above-mentioned considerations in- duced Dr. Blagden, as well as the gentle- men employed in the experiments, to give the preference to weighing the fluid it- self; and that was accordingly the method practised both by Dr. Dollfuss and Mr. Gilpin in their operations. The vessel chosen as most convenient Vol. i. f 181 for the purpose was a hollow glass ball, terminating in a neck of small bore. That which Dr. Dollfuss used held 5800 grains of distilled water; but as the balance was so extremely accurate, it was thought ex- pedient, upon Mr. Gilpin's repetition of the experiments, to use one of only 2965 grains capacity, as admitting the heat of any fluid contained in it to be more nicely determined. The ball of this vessel, which may be called the weighing bottle, mea- sured about 2.8 inches in diameter, and was spherical, except a slight flattening on the part opposite to the neck, which served as a bottom for it to stand upon. Its neck was formed of a portion of a ba- rometer tube, .25 of an inch in bore, and about 1£ inch long; it was perfectly cy- lindrical, and, on its outside, very near the middle of its length, a fine circle or ring was cut round it with a diamond, as the mark to which it was to be filled with the liquor. This mark was made by fixing the bottle in a lathe, and turning it round with great care, in contact with the dia- mond. The glass of this bottle was not very thick; it weighed 916 grains, and with its silver cap 936. When the specific gravity of any liquor was to be taken by means of this bottle, the liquor was first brought nearly to the required temperature, and the bottle was filled with it up to the beginning of the neck only, that there might be room for shaking it. A very fine and sensible ther- mometer was then passed through the neck of the bottle into the contained li- quor, which showed whether it was above or below the intended temperature. In the former case the bottle was brought in- to colder air, or even plunged for a mo- ment into cold water; the thermometer in the mean time being frequently put in- to the contained liquor, till it was found to sink to the right point. In like man- ner, when the liquor was too cold, the bottle was brought into warmer air, im- mersed in warm water, or more common- ly held between the hands, till upon re- peated trials with the thermometer the just temperature was found. It will be understood, that during the course of this heating or cooling, the bottle was very frequently shaken between each immer- tion of the thermometer; and the top of the neck was kept covered, either with the finger, or a silver cap made on pur- pose, as constantly as possible. Hot wa- ter was used to raise the temperature only in heats of 80° and upwards, inferior heats being obtained by applying the hands to the bottle; when the hot water was em- ployed, the ball ofthe bottle was plunged into it, and again quickly lifted out, with the necessary shaking interposed, as often as was necessarv for communicating the ALC ALC required heat to the liquor; but care was taken to wipe the bottle dry after each immersion, before it was shaken, lest any adhering moisture might by accident get into it. The liquor having by these means been brought to the desired temperature; the next operation was to fill up the bot- tle exactly to the mark upon the neck, which was done with some ofthe same li- quor, by means of a glass funnel with a very small bore. Mr. Gilpin endeavoured to get that portion of the liquor which was employed for this purpose, pretty nearly to the temperature of the liquor contained in the bottle; but as the whole quantity to be added never exceeded ten grains, a difference of ten degrees in the heat of that small quantity, which is more than it ever amounted to, would have oc- casioned an error of only l-30th of a de- gree in the temperature of the mass. Enough ofthe liquor was put in to fill the neck rather above the mark, and the su- perfluous quantity was then absorbed to great nicety, by bringing into contact with it the fine point of a small roll of blotting paper. As the surface ofthe hquor in the neck would be always concave, the bot- tom or centre of this concavity was the part made to coincide with the mark round the glass; and in viewing it care was ta- ken, that the near and opposite sides of the mark should appear exactly in the same fine, by which means all parallax was avoided. A silver cap, which fitted tight, was then put upon the neck, to prevent evaporation; and the whole apparatus was in that state laid in the scale of the balance, to be weighed with all the exact- ness possible. The spirit employed by Mr. Gilpin was furnished to him by Dr. Dollfuss, under whose inspection it had been rectified from rum supplied by government. Its speci- fic gravity, at 60 degrees of heat, was .82514. It was first weighed pure, in the above-mentioned bottle, at every Ave de- grees of heat, from 30 to 100 inclusively. Then mixtures were formed of it, and dis- tilled water, in every proportion, from 1 -20th of the water to equal parts of water and spirit -r the quantity of water added being successively augmented, in the pro- portion of five grains to one hundred of the spirit; and these mixtures were also weighed in the bottle, like the pure spirit, at every five degrees of heat. The num- bers hence resulting are delivered in the following table; where the first column shows the degrees of heat; the second gives the weight of the pure spirit con- tained in the bottle at those different de- grees ; the third gives the weight of a mixture in the proportions of 100 parts by weight of that spirit to 5 of water, and so on successively till the water is to the spirit as 100 to 5. They are the mean of three several experiments at least, as Mr. Gilpin always filled and weighed the bottle over again that number of times, if not oftener. The heat was taken at the even degree, as shown by the thermometer, without any allowance in the first instance, because the coincidence ofthe mercury with a division can be perceived more accurately than any fraction can be estimated; and the er- rors of the thermometers, if any, it was supposed would be less upon the grand divisions of 5 degrees than in any others. It must be observed, that Mr. Gilpin used the same mixture throughout all the dif- ferent temperatures, heating it up from 30° to 100°; hence some small error in its strength may have been occssioned in the higher degrees, by more spirit evaporat- ing than water: but this, it is believed, must have been trifling, and greater in- convenience would probably have result- ed from interposing a fresh mixture. The precise specific gravity ofthe pure spirit employed was .82514; but to avoid an inconvenient fraction, it is taken, in constructing the table of specific gravi- ties, as .825 only, a proportional deduc- tion being made from all the other num- bers. Thus the following table gives the true specific gravity, at the different de- grees of heat, of a pure rectified spirit, the specific gravity of which at 60° is .825, together with the specific gravities of different mixtures of it with water, at those different temperatures 100 grains of spirit to 50 gr. of water n^toaont>.oi(N«iHoiioiowi NHOl001OP)Ol>->')rtfl0OK"*H OOOlOMHOlK'i'MOKtOMrtOl HOOOOOlOl»(Jl(M»MCO»K o>o>oio>o>oooooooooooooooooooo 100 grains of spirit to 45 gr. of water KVH^Oi^WNtOWflOHOOiTtH «i.K ojo-. Oioooooooooooooooooooooooo 100 grains of spirit to 40 gr. of water ^OlKtO^fOOOTflXHOOO^Ol K)t1HOiN*NaiflHKO>tOHK OMtOM-lOlK'i'WOK'OnHOO 00»CTlOlOlQOOOOOOOCOKKKSIO OJOOOOOOOOOOOOOOOOCOCOOOOOOOOO _ »'C S>*S —>C>J^'*©C0OO:NGN00-'#O S S S.« S >0'MOC010nHOlK^(MOK ?, S 1 o>o>CT>oeoooooob.i^is.t-»t^iotol^'-lOOtO'*i-HOltO S-J?«S 1 C0C0C0C000»^N.h.»^tOtOO ShO1" | 00 30 00 00 OO 00 00 00 00 00 00 00 00 00 00 boo S o • 100 grains af spirit to 25 gr. of water fflti»nwfloioH03>nHto|')HKn MOOOtOf5HOitO'*(MOiN,')NO ae»K.M>.KtOtOtOtO'Otr)ioto'fl 000000000000000000000000000000 100 grains »f spirit to 20 gr. of water V)t^-*")tO-00tOtOtO00tON300 oO'OMO^Tlioistioi'tnsi'ori tOOHOitOifCTOiN^MO^'no b»h-N.(0-*,l''* 000000000000000000000000000000 100 grains of spirit to 15 gr. of water 'ONHHN'i'OTnOMflrtflro (MMtC^OtOCOOHOHtO^OlflH »iOC)H31tD*HOiNiiN3S"l <0«OVOV5»0»0'n 'n»o>Jl>^-'*T}<>i<-'*cococoeo .• u |V5CTs!?lO<0-*CJlCM-*:J0.-lliJOOK ■«'E y*H 1 Ol lO « H K 'T 9i to N N W Ol V) O v; -•5«M>* ■^<4ji^'-*tJtjio<0-0tjC V) fjirj oiaoiOiOtOiOiOiOiOiO) 55 grains of spirit tc 100 gr. of water. p*OOjeOw*00o»o»ovo>ov>Tj<^i<4i OiOiOtOiOiOiOiOtOiOiOi 65 grains of spirit to 100 gr. of water. 'JMfNnnMOOlOrtM 4KO(M^«)t>.00000 aNto^MaootofjnS OtOiOiOiOtOiOiOiOiOiO. 70 grains of spirit to 100 gr. of water. h n oo n oo h. oi oo c. oi vi OOONTfirjtONXOiOOOO N'flCOr*riCOCTitOl>. ■^•■*-^«TfTJ.COCOCOCOCO(N OiOiOiOiOiOiOiOiOiOiOi 90 grains of spirit to 100 gr. of water. lO'*V)tONtOCOOtO h. oo a oi oi o> oi oo k to ■<)( tO*WOCOtO^(NOOOtO ■^Tr^Tfcoco "ococoo»C9 OiOiOiOiOiOiOiOiOiOiOi 95 , grains of spirit to 100 gr.of water. N.O100O00CNN.O00C0C0 ■* * ") tO IT) V) ■* ■* IN H OI "S1 Pt O 00 tO if (M O CO to « T*,'<3,-*roeococococ}eNOtOtO>v»>.0O 100 gr. of spirit to loo gr. of water 1---- NNN(NHOOOiOOtO^«V)CO« 2QCOtOTjWO>OlOl0lO10iO»OlO>O>OlO> 100 grains of spirit to 95 gr. of water HO(NO)t^«COtOC)««OlHOiO rj>o>o>cot^-tov>Tf«co»-iO}(N*-'0>to OiKlOC5-HOi(^tr)«^eOKlr)(NO c1COC1n«(NN(MN[)rtnHrtrt OTOlOiOlOlOiOlOlOlCTiOlOlOlOlOl •ct"S ****TinOi^Oic<)OiOia*r>oooi*r> o»-&S •*'*-*co-i©O>00tO"*(N<©-*c^© S .5 S.O 5 ^")COHOiKTi'(NOOOtO'*C»000 too 2 ^3 I&>0i0i0i0i0i0i0i0i0i0i0i0i0i0i 100 grains of spirit to 85 gr. of water ^^ffJOiNtOiOOCIOiQiONNM N.N.f^»C^lC0(Nr-(OltO'^<00tO'^0000N.vj'*co»-iO>h-''*00tOTi'r-4 "OiKfinHOiK^NOCOtO-^W nMIMNMOlHHHHrtOOOO OiOiOiOiOiOiOiOiOiOiOiOiOiOiOi 100 grains ot spirit to 75 gr. of water CJ>otOTj<^Htv.fMO«C»COOOC<» Oi Oi COCONtoiocoNOOOTir/qiO^HCO ooto->*f>»oooto,*»-|Oii^«oco<-ioo NNP)M(NHHHHO o o © o o> cjo>o»o>oioio>cjio>o>o^o>o»cj>oo 100 grains of spirit to 70 gr. of water cov5**N.co00e0iO tO««»OCOCN©00<0'*-*OOOCO»o>o>oiCT>do>o>o»a>ooooeo 100 grains of spirit to 65 gr. of water h~O^OlTtKoi050»o^o>o>o»o»o^eooooooo 1100 grains of spirit to 60 gr. of water KQM-(K00OlC0Tli(N0lOOM01 '3!7*Q~40i<0-<*C*Ot^C')<0r')G><0 OOto^CNO-. N.iOM-iCOtO^?)OK hhhhOOOOO01010>0»0i00 o>o>o>o>o>o>oio>o>oooooooooooo 100 1 grains of spirit to 55 gr-of water Qj-^tOCNtOr^-tO'«JtOO»T)<^H00>O ^(MOMVlCOHOHO^NOOOtflCO HHHOOOOOlOiOlOIOlOOMOO o>a>o>0)a>o>o»oooooooooooococo o oioowoKio^OKioiooioo COcO'*-^'vo>OtOCTiO ALC ALC moirs of the Turin Academy. The alco- hol he employed was carefully freed from superabundant water by repeated rectifi- cations, without addition of any interme- diate substance. The salts employed in his experiments were previously deprived of their water of crystallization by a care- ful drying. He poured into a matrass, upon each ofthe salts thus prepared, half an ounce of his alcohol, and set the mat- rass in a sand-bath. When the spirit be- gan to boil, he filtrated it while it was hot, and left it to cool, that he might observe the crystallizations which took place. He then evaporated the spirit, and weighed the saline residuums. He repeated these experiments a second time, with this dif- ference, that instead of evaporating the spirit in which the salt had been digested, he set fire to it in order to examine the phenomena which its flame might exhibit. The principal results of his experiments are subjoined. Quantity Salts soluble in »fgrains. 200 grains of spirit. 4 Nitrate of potash 5 Muriate of potash 0 Sulphate of soda 15 Nitrate of soda 0 Muriate of soda 0 Sulphate of ammonia 108 Nitrate of ammonia 24 Muriate of ammonia 288 Nitrate of lime 288 84 204 4 36 Muriate of lime Nitrate of silver Muriate of mercury Nitrate of iron Muriate of iron 48 Nitrate of copper 48 Muriate of copper Peculiar phenomena of the fame. C Flame larger, higher, more ardent, yellow, (_ and luminous. Large, ardent, yellow, and luminous. Considerably red. Yellow, luminous, detonating. Larger, more ardent, and reddish. None. Whiter, more luminous. None. C Larger, more luminous, red and decrepitat- d »ng. Like that ofthe calcareous nitre. None. Large, yellow, luminous and decrepitating. lied and decrepitating. More white, luminous and sparkling. CMore white, luminous and green, much ■\ smoke. The saline residuum became C black and burnt. Fine green, white, and red fulgurations. Macquer accompanies the relation of his experiments with many judicious re- flections, not easily capable of abridg- ment. * The alcohol he employed in the above experiments had a specific gravity of 0.840. In analytical researches, alcohol affords frequently a valuable agent for separating salts from each other. We shall there- fore introduce the following additional table, derived chiefly from the experi- ments of Wenzel;— 100 parts of alcohol dissolve of Temp. Nitrate of Cobalt at 54.5° 100 parts Copper 54.5 100 Alumina 54.5 100 Lime 125 Magnesia 180.5 290 Muriate of Zinc 54.5 100 Alumina 54.5 100 Magnesia 180.5 547 Iron 180.5 100 Copper 180.5 100 Acetate of Lead 154.5 100 At the boiling point, 100 parts of alco- hol dissolve of muriate of lime 100 parts Nitrate of ammonia, 89 Corrosive sublimate, 88.8 Succinic acid, 74.0 parts Acetate of soda, 46.5 Nitrate of silver, 41.7 Refined sugar, 24.6 Boracic acid, 20.0 Nitrate of soda, 9.6 Acetate of copper, 7.5 Muriate of ammonia, 7.1 Superarseniate of potash, 3.75 Oxalate of potash, - 2.92 Nitrate of potash, - 2.08 Muriate of potash, 2.08 Arseniate of soda, - 1.58 Arsenious acid, - 1.25 Tartrate of potash, 0.42 It appears from the experiments of Kir- wan, that dried muriate of magnesia dis- solves more abundantly in strong than in weak alcohol. 100 parts of specific gravi- ty 0.900, dissolve 21.25; of 0.848, 23.75; of 0.834, 36.25; and of 0.817, 50 parts. The same holds to a more limited extent with acetate of lime ; 2.4 grains being so- luble*^ 100 of the first alcohol, and 4.88 in 100 of the last. The other salts which he tried dissolved more sparingly in the stronger than in the weaker alcohol. The temperature of the spirit was generally 60°. All deliquescent salts are soluble in al- ALC ALC cohol. Alcohol holding the strontitic salts in solution, gives a flame of a rich purple. The cupreous salts and boracic acid give a green; the soluble calcareous, a reddish; the barytic, a yellowish. For the effect of other salts on the colour of the flame, see a preceding table. The alcohol of 0.825 has been subjected to a cold of — 91Q without congealing. But Mr. Hutton has given, in the Edin- burgh Encyclopaedia, article Cold, an ac- count of his having succeeded in solidify- ing it by a cold of— 110°. The alcohol he employed had a density of 0.798 at 60p. His process has been kept secret. The boiling point of alcohol of 0.8J5 is 176°, Alcohol of 0.810 boils at 173.5°. For the force of its vapour at different tempera- tures, and its specific heat, see Vapour. M. Gay-Lussac having shown that this liquid is a compound of olefiant gas and water, potassium ought to disengage from it, hydrogen and olefiant gas. In the absolute alcohol of Richter there is no water, independent of that which is essential to its constitution. See Fermen- tation. When chlorine is made to pass through alcohol in a Woulfe's apparatus, there is a mutual action. Water, an oily looking substance, muriatic acid, a little carbonic acid, and carbonaceous matter, are the products. This oily substance does not redden turnsole, though its analysis by heat shows it to contain muriatic acid. It is white, denser than water, has a cooling taste analogous to mint, and a peculiar, but not ethereous odour. It is very solu- ble in alcohol, but scarcely in water. The strongest alkalis hardly operate on it. It was at one time maintained, that al- cohol did not exist in wines, but was ge- nerated and evolved by the heat of distil- lation. On this subject M. Gay-Lussac made some decisive experiments. He agitated wine with litharge in fine powder, till the liquid became as limpid as water, and then saturated it with subcarbonate of potash. The alcohol immediately sepa- rated and floated on the top. He distilled another portion of wine in vacuo, at 59° Fahr. a temperature considerably below that of fermentation. Alcohol came over. Mr. Brande proved the same position by saturating wine with subacetate of lead, and adding potash. MM. Adam and Duportal have substitut- ed for the redistillations used in converting wine or beer into alcohol, a single process of great elegance. From the capital of the still a tube is led into a large copper recipient. This is joined by a second tube, to a second recipient, and so on through a series of four vessels, arranged like a Woulfe's apparatus. The last vessel com- municates with the worm of the first re- frigeratory, This, the body of the still and the two recipients nearest it, are charged with the wine or fermented li- quor. When ebullition takes place in the still, the vapour issuing from it communi- cates soon the boiling temperature to the liquor in the two recipients. From these the volatilized alcohol will rise and pas- into the third vessel, which is empty. After communicating a certain heat to it, a portion ofthe finer or less condensable spirit will pass into the fourth, and thence, in a little, into the worm of the first refri- geratory. The wine round the worm will likewise acquire heat, but more slowly. The vapour that in that event may pass uncondensed through the first worm, is conducted into a second, surrounded with cold water. Whenever the still is worked off, it is replenished by a stop-cock from the nearest recipient, which, in its turn, is filled from the second, and the second from the first worm tub. It is evident, from this arrangement, that by keeping the 3d and 4th recipients at a certain tem- perature, we may cause alcohol, of any degree of lightness, to form directly at the remote extremity of the apparatus. The utmost economy of fuel and time is also secured, and a better flavoured spirit is obtained. The arriere gout-of bad spirit can scarcely be destroyed by infusion with charcoal and redistillation. In this mode of operating, the taste and smell are ex- cellent, from the first Several stills on the above principle have been constructed at Glasgow for the West India distillers, and have been found extremely advanta- geous. The excise laws do not permit their employment in the home trade.* If sulphur in sublimation meet with the vapour of alcohol, a very small portion combines with it, which communicates a hydrosulphurous smell to the fluid. The increased surface of the two substances appears to favour the combination. It had been supposed, that this was the only way in which they could be united; but M. Favre has lately asserted, that, having di- gested two drams of flowers of sulphur in an ounce of alcohol, over a gentle fire not sufficient to make it boil, for twelve hours, he obtained a solution that gave twenty-three grains of precipitate. A si- milar mixture left to stand for a month in a place exposed to the solar rays, afforded sixteen grains of precipitate; and another, from which the light was excluded, gave thirteen grains. If alcohol be boiled with one-fourth of its weight of sulphur for an hour, and filtered hot, a small quantity of minute crystals will be deposited on cool- ing ; and the clear fluid will assume an opaline hue on being diluted with an equal quantity of water, in which state it will pass the filter, nor will any sediment ALC ALK be deposited for several hours. The al- cohol used in the last-mentioned experi- ment did not exceed .840. Phosphorus is sparingly soluble in alco- hol, but in greater quantity by heat than in cold. The addition of water to this solution affords an opaque milky fluid, which gradually becomes clear by the subsidence of the phosphorus. Earths seem to have scarcely any action upon alcohol. Quick-lime, however, pro- duces some alteration in this fluid, by changing its flavour and rendering it of a yellow colour. A small portion is proba- bly taken up. Soaps are dissolved with great facility in alcohol, with which they combine more readily than with water. None of the me- tals, or their oxides, are acted upon by this fluid. Resins, essential oils, camphor, bitumen, and various other substances, are dissolved with great facility in alcohol, from which they may be precipitated by the addition of water. From its property of dissolving resins, it becomes the men- struum of one class of varnishes. See Varnish. Camphor is not only extremely soluble in alcohol, but assists the solution of re- sins in it. Fixed oils, when rendered dry- ing by metallic oxides, are soluble in it, as well as when combined with alkalis. Wax, spermaceti, biliary calculi, urea, and all the animal substances of a resinous nature, are soluble in alcohol; but it cur- dles milk, coagulates albumen, and har- dens the muscular fibre and coagulum of the blood. The uses of alcohol are various. As a solvent of resinous substances and essen- tial oils, it is employed both in pharmacy and by the perfumer. When diluted with an equal quantity of water, constituting what is called proof spirit, it is used for extracting tinctures from vegetable and other substances, the alcohol dissolving the resinous parts, and the water the gum- my. From giving a steady heat without smoke when burnt in a lamp, it was for- merly much employed to keep water boiling on the tea-table. In thermometers for measuring great degrees of cold, it is preferable to mercury, as we cannot bring it to freeze. It is in common use for pre- serving many anatomical preparations, and certain subjects of natural history; but to some it is injurious, the molluscs for instance, the calcareous covering of which it in time corrodes. It is of con- siderable use too in chemical analysis, as appears under the different articles to which it is applicable. From the great expansive power of al- cohol, it has been made a question, whe- ther it might notbe applied with advantage in the working of steam engines. From a series of experiments made by Betan- court, it appears, that the steam of alco- hol has, in all cases of equal temperature, more than double the force of that of wa- ter ; and that the steam of alcohol at 174° F. is equal to that of water at 212° : thus there is a considerable diminution of the consumption of fuel, and where this is so expensive as to be an object of great im- parlance, by contriving the machinery so as to prevent the alcohol from being lost, it may possibly at some future time be used with advantage, if some other fluid of great expansive power, and inferior price, be not found more economical. It was observed at the beginning of this article, that alcohol might be decomposed by transmission through a red-hot tube : it is also decomposable by the strong acids, and thus affords that remarkable product, Ether and Oleum Vini. Ale. See Beer. Alembic, or Still. This part of che- mical apparatus, used for distilling or separating volatile products, by first rais- ing them by heat, and then condensing them into the liquid state by cold, is oi" extensive use in a variety of operations. It is described under the article Labora- tory. Alembroth Salt. Corrosive muriate of mercury is rendered much more solu- ble in water, by the addition of muriate of ammonia. From this solution crystals are separated by cooling, which were called sal alembroth by the earlier chemists, and appeared to consist of ammonia, muriatic acid, and mercury. Alga roth (Powder of). Among the numerous preparations which the alchemi- cal researches into the nature of antimony have afforded, the powder of algaroth is one. When butter of antimony is thrown into water, it is not totally dissolved; but part of the metallic oxide falls down in the form of a white powder, which is the powder of algaroth. It is violently purga- tive and emetic in small doses of three or four grains. See Antimony. Alkahest. The pretended universal solvent, or menstruum, ofthe ancient che- mists. Kunckel has very well shown the absurdity of searching for a universal sol- vent, by asking, " If it dissolve all substan- ces, in what vessels can it be contained?" Alkalescent. Any substance in which alkaline properties are beginning to be developed, or to predominate, is termed alkalescent. The only alkali usually ob- served to be produced by spontaneous de- composition is the volatile; and from their tendency to produce this, some spe- cies of vegetables, particularly the cruci- form, are styled alkalescent, as are some animal substances. See Fermentation (Putrid). ALK * Alkali. A term derived from kali the Arabic name of a plant, from the ashes of which one species of alkaline substance can be extracted. Alkalis may be defined, those bodies which combine with acids, so as to neutralize or impair their activity, and produce salts. Acidity and alkalinity are therefore two correlative terms of one species of combination. \V hen Lavoisier introduced oxygen as the acidifying prin- ciple, Morveau proposed hydrogen as the alkalifymg principle, from its being a con- stituent of volatile alkali or ammonia. But the splendid discovery by Sir II. Davy, of the metallic bases of potash and soda, and of their conversion into alkalis, by combi- nation with oxygen, has banished for ever that hypothetical conceit. It is the mode in which the constituents are combined, rather than the nature of the constituents themselves, which gives rise to the acid or alkaline condition. Some metals, com- bined with oxygen in one proportion, pro- duce a body possessed of alkaline proper- ties, in another proportion of acid proper- ties. And on the other hand, ammonia and prussic acid prove that both the alka- line and acid conditions can exist inde- pendent of oxygen. These observations by generalizing our notions of acids and alkalis, have rendered the definitions of them very imperfect. The difficulty of tracing a limit between the acids and al- kalis is still increased, when we find a body sometimes performing the functions of an acid, sometimes of an alkali. Nor can we diminish this difficulty by having recourse to the beautiful law discovered by Sir II. Davy, that oxygen and acids go to the positive pole, and hydrogen, alkalis, and inflammable bases to the negative pole. Vie cannot in fact give the name of acid to all the bodies which go to the first of these poles, and that of alkali to those that go to the second; and if we wished to define the alkalis by bringing into view their electric energy, it would be neces- sary to compare them with the electric energy which is opposite to them. Thus we are always reduced to define alkalini- ty by the property which it has of saturat- ing acidity, because alkalinity and acidity are two correlative and inseparable terms. M. Gay-Lussac conceives the alkalinity which the metallic oxides enjoy to be the result of two opposite properties, the al- kalifv ing property of the metal, and the acidifying of oxygen, modified both by the combination and by the proportions. The alkalis may be arranged into three classes : 1st, Those which consist of a me- tallic basis combined with oxygen. These are three in number, potash, soda and lithia. 2d, That which coniainsno oxygen, viz. ammonia. 3d, Those containing oxy- gen, hydrogen, and carbon. In this class we. Vor. i. J 19] ALK have aconita, atropia, brucia,cicuta,datur| delphia, hyosciama, morphia, strychnia* and perhaps some o her truly vegetable alkalis. The order of vegetable alkalis may be as numerous as that of vegetable acids. The earths, lime, barytes, and strontites were enrolled among the alka* lis by Fourcroy j but they have been kept apart by other systematic writers, and are called alkaline earths. Besides neutralizing acidity, and there- by giving birth to salts, the first four alka- lis have the following properties: 1st, They change the purple colour of many vegetables to a green, the reds to a purple, and the yellows to a brown. If the purple have been reddened by acid, alkalis restore the purple. 2d, They possess this power on vege-^ table colours after being saturated with carbonic acid, by which criterion they are distinguishable from the alkaline earths. 3d, They have an acrid and urinous taste. 4th, They are powerful solvents or cor- rosives of animal matter; with which, as well as with oils in general, they combine, so as to produce neutrality. 5th, They are decomposed, or volati- lized, at a strong red heat. 6th, They combine with water in every proportion, and also largely with alcohol. 7th, They continue to be soluble in water when neutralized with carbonic acid; while the alkaline earths thus be- come insoluble. It is needless to detail at length Dr. Murray's speculations on alkalinity. They seem to flow from a partial view of che- mical phenomena. According to him, either oxygen or hydrogen may generate alkalinity, but the combination of both principles is necessary to give this condi- tion its utmost energy. " Thus the class of alkalis will exhibit the same relations as the class of acids. Some are compounds of a base with oxygen ; such are the greater number ofthe metallic oxides, and probably of the earths. Ammonia is a compound of a base with hydrogen. Pot- ash, soda, barytes, strontites, and proba- bly lime, are compounds of bases with oxygen and hydrogen; and these last, like the analogous order among the acids, possess the highest power." Now, surely, perfectly dry and caustic barytes, lime, and strontites, as well as the dry potash and soda obtained by Gay-Lussac and Thenard, are not inferior in alkaline pow- er to the same bodies after they are slack- ed or combined with water. 100 parts of lime destitute of hydrogen, that is, pure oxide of calcium, neutralize 78 parts of carbonic acid. But 132 parts of Dr. Mur- ray's strongest lime, that is the hydrate, are required to produce the-same alka- ALK ALL Lne effect. If we ignite nitrate of barytes, we obtain, as is well known, a perfectly dry barytes, or protoxide of barium; but if we ignite crystallized barytas, we ob- tain the same alkaline earth combined with a prime equivalent of water. These two different states of barytes were de- monstrated by M. Berthollet in an excel- lent paper published in the 2d volume of the Memoires D'Arcueil, so far back as 1809. ' The first barytes," (that from crystallized barytes), says he, " presents all the characters of a combination; it is engaged with a substance which diminish- es its action on other bodies, which ren- ders it more fusible, and which gives it by fusion the appearance of glass. This sub- stance is nothing else but water; but in fact, by adding a little water to the second barytes (that from ignited nitrate), and by urging it at the fire, we give it the pro- perties ofthe first." Page 47. 100 parts of barytes void of hydrogen, or dry bary- tes, neutralize 28£ of dry carbonic acid. Whereas 111* parts of the hydrate, or what Dr. Murray has styled the most en- ergetic, are required to produce the same effect. In fact, it is not hydrogen which combines with the pure barytic earth, but hydrogen and oxygen in the state of wa- ter. The proof of this is, that when car- bonic acid and that hydrate unite, the ex- act quantity of water is disengaged. The protoxide of barium, or pure barytes, has never been combined with hydrogen by any chemist.* Alkali (Phc.obisticated, or Prussian.) When a fixed alkali is ignited with bul- lock's blood, or other animal substances, and lixiviated, it is found to be in a great measure saturated with the prussic acid: from the theories formerly adopted re- specting this combination, it was distin- guished by the name of phlogisticated al- kali. See Acid (Pr'Ssic.) Alkali (Volatile.) See Ammonia. * Alkalimeter. The name first given by M. Descroizilles to an instrument or measure of his graduation, for determining the quantity of alkali in commercial pot- ash and soda, by the quantity of dilute sul- phuric acid of a known strength which a certain weight of them could neutralize. His method was unnecessarily operose. A much simpler, and very accurate mode, was exhibited by Dr. Ure before the Li- nen Board of Dublin in June 1816, and soon afterwards submitted in manuscript to Dr. Henry, who has since then expung- ed the description of M. Descroizilles' al- kalimeter from his valuable elements, and substituted one on Dr. Ure's principle. More recently Dr. Ure has been occupied in completing the arrangement of an in- strument for giving increased facility and dispatch to chemical analysis in general. It will apply to alkalis, acids, earths, me- tals, &c. He hopes to be able, very soon, to submit its construction and performance to the tribunal ofthe public. Meanwhile directions will be given in this work under the individual alkalis, for ascertaining the quality of commercial specimens.* Alkanet. The alkanet plant is a kind of bugloss, which is a native ofthe warm- er parts of Europe, and cultivated in some of our gardens. The greatest quantities are raised in Germany and France, parti- cularly about Montpelier, whence wc are chiefly supplied with the roots. These are of a superior quality to such as are raised in England.. This root imparts an elegant deep red colour to pure alcohol, to oils, to wax, and to all unctuous sub- stances. The aqueous tincture is of a dull brownish colour; as is likewise the spiri- tuous tincture wheninspissatedto the con- sistence of an extract. The principal use of alkanet root is, that of colouring oils, unguents, and lip-salves. W ax tinged with it, and applied on warm marble, stains it of a flesh colour, which sinks deep inta the stone; as the spirituous tincture gives it a deep red stain.f As the colour of this root is confined to the bark, and the small roots have more bark in proportion to their bulk than the great ones, these also afford most colour. * Allanite. A mineral first recognized as a distinct species by Mr. Allan, of Edin- burgh, to whose accurate knowledge, and splendid collection, the science of mine- ralogy has been so much indebted in Scot- land. Its analysis and description, by Dr. Thomson, were published in the 6th vo- lume of the Edinburgh Ph. Trans. M. Giesecke found it in a granite rock in West Greenland. It is massive and of a brownish black colour. External lustre, dull; internal, shining and resinous—frac- ture small conchoidal—opaque - greenish gray streak—scratches glass and horn- blende—brittle—spec. grav. 3.5 to 4.0. Froths and melts imperfectly before the f On making an infusion of alkanet roots. in alcohol, I was surprised to find the co- lour a deep blue, instead of being red. Remembering that the alcohol had stood over an alkali, I added some acid to the blue infusion. It became instantly red; and the same colour appeared to be pro- duced originally, when the roots were steeped in pure alcohol. 1 am surprised, that I have not met with any account of habitudes so interesting, and which ac quire additional value, when contrasted with those of litmus and other vegetable colours, originally blue. These, redden- ed by an acid, are restored by an alkali; while alkanet, made blue by alkalis, is restored by acids. ALL ALL "»iow-pipe, into a black scoria. It con- sists in 100 parts, of silica 35.4, oxide of cerium 33.9, oxide of iron 25 4, lime 9.2, alumina 4.1, and moisture 4.0. It has been also found crystallized in four, six, or eight- sided prisms. It closely resembles gado- linite, but may be distinguished, from the thin fragments of the latter being trans lucent on the edges, and of a fine green colour, whereas those of the former are commonly opaque and of a yellowish brown The ores of cerium analyzed by Berzelius, under the name of cerin, ap- proach very closely in their composition to allanite.* * Allochroite. A massive opaque mi- neral of a grayish, yel'owish, or reddish colour Quartz scratches it, but it strikes fire with steel. It has externally, a glis- tening, and internally, a glimmering lustre. Its fracture is uneven, and its fragments are translucent on the edges: sp. gr. 3.5 to 3.6. It melts before the blow-pipe into a black opaque enamel. Vauquelin's ana- lysis is the following: Silica 35, lime 30.5, oxide of iron 17, alumina 8, carbonate of lime 6, oxide of manganese 3.5. M. Brong- niart says it is absolutely infusible without addition, and that it requires a flux as phosphae of soda or ammonia. With these it passes through a beautiful grada- tion o" colours. It is covered at first with a species of enamel, which becomes on cooling reddish yellow, then greenish, and lastly of a dirty } ellowish white. He re- presents it as pretty difficult to break. It was found by M. Dandrada in the iron mine of Virums, near Drammen in Norway. It is accompanied by carbonate of lime, proox:de of iron, and sometimes brown garnets-* * Ailophane. A mineral of a blue, and sometimes a green or brown colour, which occurs massive, or in imitative shapes. Lustre vitreous; fracture imperfectly con- choidal; transparent or translucent on the edges. Moderately hard, but very brittle. Sp. gr. 1.89. Composition, silica 21.92, alumina 32.2, lime 0.73, sulphate of lime 0.52, carbonate of copper 3.06, hydrate of iron 0.27, water 41.3. Stromeyer. It ge- latinizes in acids: It is found in a bed of ironshot limestone in graywacke slate, in the forest of Thiiringia. it was called Rie- mannite. * Allay, or Alloy. Where any precious metal is mixed with another of less value, the assayers call the latter the alloy, and do not in general consider it in any other point of view than as debasing or dimi- nishing the value of the precious metal. Philosophical chemists have availed them- selves of this term to distinguish all metal- lic compounds in general. Thus brass is called an alloy of copper and zinc; bell metal an alloy of copper and tin, "* Every alloy is distinguished by the metal which predominates in its composi- tion, or which gives it its value. Thus English jewellery trinkets are ranked un- der alloys of gold, though most of them deserve to be placed under the head of copper. When mercury is one of the com- ponent metals, the alloy is called amalgam. Thus we have an amalgam of gold, silver, tin, &c. Since there are about 30 differ- ent permanent metals, independent of those evanescent ones that constitute the bases of the alkalis and earths, there ought to be about 870 different species of binary alloy. But only 132 species have been hitherto made and examined. Some me- tals have so little affinity for others, that as yet no compound of them has been ef- fected, whatever pains have been taken. Most of these obstacles to alloying arise from the difference in fusibility and vola- tility. Yet a few metals whose melting point is nearlv the same, refuse to unite. It is obvious that two bod'eswill not com- bine, unless their affinity or reciprocal at- traction, be stronger than the cohesive at- traction of their individual particles. To overcome this cohesion of the solid bo- dies, and render affinity predominant, they must be penetrated by caloric, if one be very difficult of fusion, and the other very volatile, they will not unite unless the re- ciprocal attraction be exceedingly strong. But if their degree of fusibility be almost the same, they are easily placed in the cir- cumstances most favourable for making an alloy. If we are therefore far from know- ing all the binary alloys which are possi- ble, we are still further removed from knowing all the triple, quadruple, &c. which may exist. It must be confessed, moreover, that this department of chemis- try has been imperfectly cultivated. Besides, alloys are not, as far as we know, definitely regulated like oxides in the proportions of their component parts. 100 parts of mercury will combine with 4, or 8, parts of oxygen, to form two distinct oxides, the black and the red; but with no greater, less, or intermediate propor- tions. But 100 parts of mercury will unite with 1, 2, 3, or with anv quantity up to a 100 or 1000, of tin or 'lead. The alloys have the closest relations in their physical properties with the metals. They are all solid at the temperature ofthe atmosphere, except some amalgams; they possess me- tallic lustre, even when reduced to a coarse powder; are completely opaque, and more or less dense, according to the metals which compose them; are excellent con- ductors of electricity; crystallize more or less perfectly; some are brittle, others ductile and malleable; some have a pecu- liar odour; several are very sonorous and elastic. When an alloy consists of metals ALL ALL differently fusible, it is usually malleable while cold, but brittle while hot; as is ex- emplified in brass. The density of an alloy is sometimes greater, sometimes less than the mean density of its components, showing that, at the instant of their union, a diminution, or augmentation of volume takes place. The relation between the expansion ofthe separate metals, and that of their alloys, has been investigated only in a very few cases. Alloys containing a volatile metal are decomposed, in whole or in part, at a strong heat. This happens with those of arsenic, mercury, tellurium and zinc. Those that consist of two differently fusi- ble metals, may often be decomposed, by exposing them to a temperature capable of melting only one of them. This opera- tion is called eliquation. It is practised on the great scale to extract silver from copper. The argentiferous copper is melt- ed with 3£ times its weight of lead; and the triple alloy is exposed to a sufficient heat. The lead carries off the silver in its fusion, and leaves the copper under the form of a spongy lump. The silver is afterwards recovered from the lead by another operation. Some alloys oxidize more readily by heat and air, than when the metals are se- parately treated. Thus 3 of lead, and 1 of tin, at a dull red, burn visibly, and are almost instantly oxidized. Each by itself in the same circumstances, would oxidize slowly, and without the disengagement of light. The formation of an alloy must be regu- lated by the nature of the particular me- tals; to which therefore we refer. The degree of affinity between metals may be in some measure estimated by the greater or less facility with which, when of different degrees of fusibility or vola- tility, they unite, or with which they can after union be separated by heat. The reater or less tendency to separate into ifferent proportional alloys, by long con- tinued fusion, may also give some informa- tion on this subject. Mr. Hatchett re- marked, in his admirable researches on metallic alloys, that gold made standard with the usual precautions by silver, cop- per, lead, antimony, &c. and then cast in- to vertical bars, was by no means a uni- form compound; but that the top of the bar, corresponding to the metal at the bot- tom of the crucible, contained the larger proportion of gold. Hence, for thorough combination, two red-hot crucibles should be employed; and the liquefied metals should be alternately poured from the one into the other. And to prevent unneces- sary oxidizement by exposure to air, the crucibles should contain, besides the me- .i.) a mixture of common salt and pound- ed charcoal. The melted alloy should al« so be occasional!) stirred up with a rod of pottery. The most direct evidence of a chemical change having taken place in the two me- tals by combination, is when the alloy melts at a much lower temperature than the fusing points of its components. Iron which is nearly infusible, when alloyed with gold, acquires almost the fusibility of this metal. Tin and lead form solder, an allo\ more fusible than either of its components ; but the triple compound of tin, lead, and bismuth, is most remarkable on this account. The analogy is here strong, with the increase of solubility, which salts acquire by mixture, as is exem- plified in the uncrystallizable residue of saline solutions, or mother waters, as they are called. Sometimes two metals will not directly unite, which yet, by the in- tervention of a third, are made to com- bine. This happens with nierciuy and iron, as has been shown by Messrs. Aikin, who effected this difficult amalgamation by previously uniting the iron ito tin or zinc. The tenacity of alloys is generally, though not always, inferior to the mean of the separate metals. One part of lead will destroy the compactness and tenacity of a. thousand of gold. Brass, ma: e with a small proportion of zinc, is more ductile than copper itself; but when one-third of zinc enters into its composition, it be- comes brittle. In common cases, the specific gravity affords a good criterion whereby to judge of the proportion in an alloy, consisting of two metals of different densities. But a very fallacious rule has been given in some respectable works, for comparing the specific gravity that should result from given quantities of two metals of known densities alloyed together, supposing no chemical penetration or expansion of vo- lume to take place. Thus it has been taught, that if gold and copper be united in equal weights, the computed or mathe- matical specific gravity of the alloy is the arithmetical mean of the two specific gra- vities. This error was pointed out by me in a paper published in the 7th number of the Journal of Science and the Arts; and the correct rule was at the same time given. The details belong to the article Specific Gravity; but the rule merits a place here. The specific gravity of the alloy is found by dividing the sum of the weights by the sum ofthe volumes, com- pared to water, reckoned unity. Or in another form, the rule may be stated thus: Multiply the sum of the weights into the product of the two specific gravities for a numerator, and multiply each specific gravity into the weight ofthe other body, ALM ALO and add the two products together for a denominator. The quotient obtained by dividing the numerator by the denomina- tor, is the true computed mean specific gravity; and that found by experiment, being compared with it, will shew whe- ther expansion or condensation of volume has attended the chemical combination. Gold having a specific gravity of 19. 6, and copper of 8.87, being alloyed in equal weights, give on the Fallacious rule of the arithmetical mean of the densities, 19.36 + 8.87 ------------- = 14.11; whereas the rightly calculated mean specific gravity is only 12.16. It is evident that by compar- ing the former number with chemical ex- periment, we should be led to infer a pro- digious condensation of volume beyond what really occurs. A circumstance was observed by Mr. Hatchett to influence the density ot me- tals, which a priori might be thought un- important. When a bar of gold was cast in a vertical position, the density of the metal at the lower end of the bar was greater tian that of the top, in the pro- portion of 17. j64 to 17.035. Are we to infer that melted metal is a compressible fluid, or rather, that particles passing in- to the solid state under pressure, exert their cohesive attraction with adventitious strength ? Under the title metal, a tabular view of metallic combinations will be found, and under that of the particular metal, the requisite information about its alloys. Alluvia-. Formations, in geology, are recent deposites in valleys or in plains, of the detritus of the neighbouring moun- tains. Gravel, loam, clay, sand, brown coal, wood coal, bog iron ore, and calc tuff", compose the alluvial deposites. The gravel and sand sometimes contain gold and tin, if the ores exist in the adjoining mountains. Petrified wood and animal skeletons are found in the alluvial clays and sand.* Almonds. Almonds consist chiefly of an oil of the nature of fat oils, together with farinaceous matter. The oil is so plentiful, and so loosely combined or mix- ed with the other principles, that it is ob- tained by simple pressure, and part of it may be squeezed out with the fingers. Five pounds and a half have yielded one pound six ounces of oil by cold expression, and three quarters of a pound more on heating them. There are two kinds of almonds, the sweet and bitter. The bit- ter almonds yield an oil as tasteless as that ofthe other, all the bitter matter remain- ing in the -cake after the expression. Great part of the bitter matter dissolves be digestion, both in watery and spirituous liquors ; and part arises with both in dis- tillation. Rember obtained from them 1-jd of watery extract, and 3-32ds of spiri- tuous. Bitter almonds are poisonous to birds, and to some animals. A water dis- tilled from them, when made of a certain degree of strength, has been found from experiment to be poisonous to brutes; and there are instances of cordial spirits impregnated with them bcii.g poisonous to men. It seems, indeed, that the vege- table principle of bitterness in almonds and the kernels of other fruits, is destruc- tive to animal life, when separated by dis- tillation from the oil and farinaceous mat- ter. The distilled water from laiirel leaves appears to be of this nature, and its poi- sonous effects are well known. Sweet almonds are made into an emul- sion by trituration with water, which on standing separates a thick cream floating on the top. The emulsion may be cur- dled by heat, or the addition of alcohol or acids. The whey contains gum, extractive matter, and sugar, according to Professor Proust; and the curd, when washed and dried, yields oil by expression, and after- wards by distillation the same products as cheese. The whey is a good diluent. * Prussic or hydrocyanic acid is the de- leterious ingredient in bitter almonds. The best remedy after emetics is a com- bination of sulphate of iron with bicarbo- nate of potash.* Aloes. This is a bitter juice, extracted from the leaves of a plant of the same name. Three sorts of aloes are distin- guished in the shops by the names of aloe socotrina, aloe hepatica, and aloe caballina. The first denomination, which is applied to the purest kind, is taken from the island of Zocotora; the second, or next in quality, is called liepatica, from its liver colour; and the third, caballina, from the use of this species being confined to horses. These kinds of aloes are said to differ only in purity, though, from the difference of their flavours, it is probable that they may be obtained in some in- stances from different species of the same plant. It is certain, however, that the dif- ferent kinds are all prepared at Morviedro in Spain, from the same leaves ofthe com- mon aloe. Deep incisions are made in the leaves, from which the juice is suffered to flow; and this, after decantation from its sediment, and inspissation in the sun, is exposed to sale in leathern bags by the name of socotrine aloes. An additional quantity of juice is obtained by pressure from the leaves; and this, when decanted from its sediment and dried, is the hepatic aloes. And lastly, a portion of juice is obtained by strong pressure ofthe leaves, and is mixed with the dregs of tbe two preceding kinds to form the caballine ALU aloes. The first kind is said to contain much less resin. The principal characters of good aloes are these: it must be glossy, not very black, but brown; when rubbed or cut, of a yellow colour; compact, but easy to break; easily soluble; of an un- pleasant peculiar smell, which cannot be described, and an extremely bitter taste. Aloes appears to be an intimate combi- nation of gummy resinous matter, so well blended together, that watery or spiri- tuous solvents, separately applied, dissolve the greater part of both. It is not deter- mined whether there be any difference in the medical properties of these solutions. Both are purgative, as is likewise the aloes in substance; and, if used too freely, are apt to prove heating, and produce hemor- rhoidal complaints. * Braconnot imagines he has detected in aloes a peculiar principle, similar to the bitter resinous which Vauquelin has found in many febrifuge barks. The recent juice of the leaves absorbs oxygen, and be- comes a fine reddish purple pigment.* Aludkl. The process of sublimation differs from distillation in the nature of its protiuci, which, instead of becoming con- densed in a fluid, assumes the solid state, and the form of the receivers may of course be very different. The receivers for sublimates are ofthe nature of chim- neys, in which the elastic products are condensed, and adhere to their internal surface. It is evident that the head of an alembic will serve very well to receive and condense such sublimates as are not very volatile. The earlier chemists, whose notions of simplicity were not always the most perfect, thought proper to use a number of similar heads, one above the other, communicating in succession by means of a perforation in the superior part of each, which received the neck of the capital immediately above it. These heads, differing in no respect from the usual heads of alembics, excepting in their hav- ing no nose or beak, and in the other cir- cumstances here mentioned, were called aludels. They are seldom now to be seen in chemical laboratories, because the op- erations of this art may be performed with greater simplicity of instruments, provi- ded attention be paid to the heat and other circumstances. * Alum. See Alumina, Sulphate of.* * Alum-E4rth. A massive mineral, of a blackish brown colour, a dull lustre, an earthy and somewhat slaty fracture, sec- tile, and rather soft. By Klaproth's analy- sis it contains, charcoal 19.65, silica 40, alumina 16, oxide of iron 6.4, sulphur 2.84, sulphates of lime and potash, each 1.5, sul- phate of iron 1.8, magnesia and muriate of potash 0.5, and water 10.75. * Alum-Slate. 1. Common, Tfch mine- ALU ral occurs both massive and in insnlatefl balls, of a grayish black colour, dull lus- tre, straight slaty fracture, tabular frag- ments, streak coloured like itself; though soft it is not very brittle. Effloresces, ac- quiring the taste of alum. 2. Glossy Alum-slate. A massive mine- ral of a bluish black colour. The rents display a variety of lively purple tints. It has a semi-metallic lustre in the fracture, which is straight, slaty, or undulating. There is a soft variety of it approaching in appearance to slate clay. Bv exposure to air, its thickness is prodigiously aug- mented by the formation of a saline efflo- rescence, which separates its thinnest plates. These afterwards exfoliate in brit- tle sections, causing entire disintegration* * Alimina. One ofthe primitive earths, which, as constituting the plastic princi- ple ot all clays, loams and boles, was cal- led argil orthe argillaceous earth; but now, as being obtained in greatest purity from alum, is styled alum na. It was deemed elementary matter till Sir H. Davy's cele- brated electro-chemical researches led to the belief of its being, like barytes and 1 me, a metallic oxide. The purest native alumina is found in the oriental gems, the sapphire and ruby. They consist of nothing but this earth, and a small portion of colouring matter. The native porcelain clays or kaolins, however white and soft, can never be re- garded as pure alumina. They usually contain fully half their weight of silica, and frequently other earths. To obtain pure alumina we dissolve alum in 20 times its weight of water, and add to it a little of the solution of carbonate of soda, to throw down any iron which may be "present. We then drop the supernatant liquid into a quantity of the water of ammonia, taking care not to add so much ofthe aluminous solution as will saturate the ammonia. The volatile alkali unites with the sul- phuric acid of the alum, and the earthy basis ofthe latter is separated in a white spongy precipitate. This must be thrown on a filter, washed, or edulcorated as the old chemists expressed it, by repeated af- fusions of water, and then dried. Or if an alum, made with ammonia instead of pot- ash, as is the case with some French alums, can be got, simple ignition dissi- pates its acid and alkaline constituents, leaving pure alumina. Alumina prepared by the first process is white, pulverulent, soft to the touch, ad- heres to the tongue, forms a smooth paste without grittiness in the mouth, insipid, inodorous, produces no change in vege- table colours, insoluble in water, but mix- es with it readily in every proportion, and retains a small quantity with con- siderable force; is infusible in the strong- ALU ALU est heat of a furnace, experiencing mere- ly a condensation of volume and conse- quent hardness, but it is in small quanti- ties melted by the oxy-hydrogen blow- pipe. Its specific gravity is 2.000, in the sjtate of powder, but by ignition it is aug- mented. Every analogy leads to the belief that alumina contains a peculiar metal, which may be called aluminum. The first evi- dences obtained of this position are pre- sented in Sir H. Davy's researches. Iron negatively electrified by a very high pow- er being fused in contact with pure alu- mina, formed a globule whiter than pure iron, which effervesced slowly in water, becoming covered with a white powder. The solution of this in muriatic acid, de- composed by an alkali, afforded alumina and oxide of iron. By passing potassium in vapour through alumina heated to whiteness, the greatest part of the potas- sium became converted into potash, which formed a coherent mass with that part of the alumina not decompounded; and in this mass there were numerous gray par- ticles, having the metallic lustre, and which became white when heated in the air, and which slowly effervesced in wa- ter. In a similar experiment made by the same illustrious chemist a strong red heat only being applied to the alumina, a mass was obtained, which took fire spon- taneously by exposure to air, and which effervesced violently in water. This mass was probably an alloy of aluminum and potassium. The conversion of potassium into its deutoxide, dry potash, by alumina, proves the presence of oxygen in the lat- ter. When regarded as an oxide, Sir H. Davy estimates its oxygen and basis to be to one another as 15 to 33; or as 10 to 22. The prime equivalent of alumina would thus appear to be 1.0 + 2.2 = 3.2. But Berzehus's analysis of sulphate of alumina seems to indicate 2.136 as the quantity ofthe earth which combines with 5. ofthe acid. Hence aluminum will come *o b« represented by 2.136 — 1. = 1.136. But we shall presently show that his ana- lysis, both of alum and sulphate of alumi- na, may be reconciled to Sir. II Davy's equivalent prime = 3.2. That of alumi- num will become of course 2.2. Alumina which has lost its plasticity by ignition, recovers it by being dissolved in an acid or alkaline menstruum, and then Precipitated. In this state k is called a ydrate, for when dried in a steam-heat it retains much water; and therefore re- sembles in composition wavellite, a beau- tiful mineral, consisting almost entirely of alumina, with about 28 per cent of water. Alumina is widely diffused in nature. It is a constituent of every soil, and of almost every rock. It is the basis of porcelain, pottery, bricks, and crucibles. Its affinity tor vegetable colouring matter, is made use of in the preparation of lakes, and in the arts of dyeing and calico printing. Native combinations of alumina, constitute the fuller's earth, ochres, boles, pipe-clays, 8cc* * Alumina, (Salts of). These salts have the following general characters: 1. Most of them are very soluble in wa- ter, and their solutions have a sweetish acerb taste. 2. Ammonia throws down their earthy base, even though they have been previ- ously acidulated with muriatic acid. 3. At a strong red heat they give out a portion of their acid. 4. Phosphate of ammonia gives a white precipitate. 5. Hydriodate of potash produces a floc- culent precipitate of a white colour, pass- ing into a permanent yellow. 6. They are not affected by oxalate of ammonia, tartaric acid, ferroprussiate of potash, or tincture of galls; by the first two tests they are distinguished from yttria, and by the last two from that earth and glucina. 7. If bisulphate of potash be added to a solution of an aluminous salt, moderately concentrated, octahedral crystals of alum will form. Acetate of Alumina. By digesting strong acetic acid on newly precipitated alumina, this saline combination can be directly formed. Vinegar of ordinary strength scarcely acts on the earth. But the salt is seldom made in this way. It is prepared in large quantities for the calico printers, by decomposing alum with acetate of lead; or more economically with aqueous ace- tate of lime, having a specific gravity of about 1.050; a gallon of which, equivalent to nearly half a pound avoirdupois of dry acetic acid, is employed for every 2$ lb. of alum. A sulphate of lime is formed by complex affinity, which precipitates, and an acetate of alumina floats above. The above proportion of alum is much beyond the equivalent quantity; and the specific gravity of the liquid is consequently raised by the excess of salt. It is usually 1.080. By careful evaporation capillary crystals are formed, which readily deliquesce. M. Gay-Lussac made some curious observa- tions on the solutions of this salt. Even when made with cold saturated solutions of alum and acetate of lead, and conse- quently but little concentrated, it be- comes turbid when heated to 122° Fahr.; and at a boiling heat a precipitate falls of about one-half ofthe whole salt. On cool- ing, it is redissolved. This decomposition by heat, which would be prejudicial to the calico printer, is prevented by the excess ALU ALU of alum, which is properly used in actual practice. M. Gay-Lussac thinks this phe- nomenon has considerable analog), with the coagulation of albumen by heat; the particles of the water, and ofthe solid mat- ter, being carried by the heat out of their sphere of activity, separate. It is probably a subacetate which falls down, as well as that which is obtained by drying the crys- tals. Wenzel's analysis of acetate of alu- mina gives 73.81 acid to 26.19 base in WO parts. If we suppose it to consist, like the sulphate, of three primes of acid to two of alumina, we shall have for its equivalent proportions, 2U of dry acid-f-6.4 earth, or 75.8 -f- 24.2 = 100. As alum contains, in round numbers, about l-9th of earthy base, 8 oz. of real acetic acid present in the gallon of the redistilled pyrolignous, would require about 2' lbs. of alum, for exact decomposition. 1 he excess employ- ed is found to be >-seful. The affinity between the constituents of this salt is very feeble. Hence the at- traction of cotton fibre for alumina, aided by a moderate heat, is sufficient to decom- pose it. The following salts of alumina are in- soluble in water -Arseniate, borate, phos- phate, tungstate, mellate, saclactate, lith- ate, malate, camphorate. The oxalate is un- erystallizable. It consists of 56 acid and water, and 44 alumina. The tartrate does not crystallize. But the tartrate of potash and alumina is remarkable, according to Thenard, for yielding no precipitate, either by alkalis or alkaline carbonates. The supergallate crystallizes. There seems to be no dry carbonate. A super- nitrate exists very difficult to crystallize. Its specific gravity is 1.645. A moderate heat drives off' the acid. The muriate is easily made by digesting muriatic acid on gelatinous alumina. It is colourless, astrin- gent, deliquescent, uncrystallizable, red- dens turnsole, and forms a gelatinous mass by evaporation. Alcohol dissolves at 60° half its weight of this salt. A dull red heat separates the acid from the alumina. Its composition is, according to Bucholz, 29.8 acid, 30.0 base, 40.2 water, in 100 parts. Sulphate of alumina exists under several modifications. The simple sulphate is ea- sily made, by digesting sulphuric acid on pure clay. The salt thus formed crystalli- zes in thin soft plates, having a pearly lus- tre. It has an astringent taste, and is so soluble in water as to crystallize with dif- ficulty. AVhen moderately heated the wa- ter escapes, and, at a higher temperature, the acid. Berzelius has chosen this salt for the purpose of determining the equi- valent of alumina. He considers the dry sulphate as a compound of 100 parts of sulphuric acid with 42.722 earth. This makes the equivalent 21.361, oxygen be- ing reckoned 10, if we consider it a com- pound of a prime proportion of each. But if we regard it as consisting of 3 of acid and 2 of base, we shall have 32.0 for the prime equivalent of alumina. The reason for preferring this number will appear in treating ofthe next salt.* * Ai.ni. This important salt has been the object of innumerable researches, both with regard to its fabrication and compo- sition.* It is produced, but in a very small quantity, in the native state ; and this is mixed with heterogeneous maters. It ef- floresces in various forms upon ores dur- ing calcination, but it seldom occurs Ciys- tallized. The greater part of this salt is factitious, being extracted from various minerals called alum ores, such as, 1. sul- phuretted clay. This constitutes the pu- rest of all aluminous ores, namely, that of la Tolfa, near Civita Vecchia, in Italy. It is white, compact, and as hard as indurat- ed clay, whence r is called petra alumina- ris. It is tasteless and mealy; one hun- dred parts of this ore contain above forty of sulphur and fifty of clay, a small quan- tity of potash, and a little iron. Bergmann says it contains forty-three of sulphur in one hundred, thirty-five of clay, and twen- ty two of siliceous earth. This ore is first torrefied to aci Jify the sulphur, which then acts on the clay, and forms the alum. 2. The pyritaceous clay, which is found at Schwemsal, in Saxony, at the depth of ten or twelve feet. It is a black and hard, but brittle substance, consisting of clay, pyrites, and bitumen. It is exposed to the air for two years; by which means the py- rites are decomposed, and the alum is formed. The alum ores of Hesse and Liege are of this kind; but they are first torre- fied, which is said to be a disadvantageous method. 3. The schistus aluminaris contains a variable proportion of petroleum and py- rites intimately mixed with it. When the last are in a very large quantity, this ore is rejected as containing too much iron. Professor Bergmann very properly sug- gested, that by adding a proportion of clay, this ore may turn out advantageously for producing alum. But if the petrol be considerable, it must be torrefied. The mines of Becket in Normandy, and those of Whitby in Yorkshire, are of this spe- cies. 4. Volcanic aluminous ore. Such is that of Solfaterra near Naples It is in the form of a white saline earth, after it has ef- floresced in the air ; or else it is in a stony form. 5. Bituminous alum ore is called shale, and is in the form of a shistus, impregnat- ed with so much oily matter, or bitumen, as to be inflammable. It is found in Swe- ALU ALU Sen, and also in the coal mines at White- haven, and elsewhere. Chaptal has fabricated alum on a large scale from its component parts. For this purpose he constructed a chamber 91 feet long, 48 wide, and 31 high in the middle. The walls are of common masonry, lined with a pretty thick coating of plaster. The floor is paved with bricks, bedded in a mixture of raw and burnt clay ; and this pavement is covered with another, the joints of which overlap those of the first, and instead of mortar the bricks are joined with a cement of equal parts of pitch, tur- pentine, and wax, which, after having been boiled till it ceases to swell, is used hot. The roof is of wood, but the beams are very close together, and grooved length- wise, the intermediate space being filled up by planks fitted into the grooves, so that the whole is put together without a l.uil. Lastly, the whole of the inside is covered with three or four successive coalings ofthe cement above mentioned, the first being laid on as hot as possible; and the outside of the wooden roof was varnished in the same manner. The purest and whitest clay being made into a paste with water, and formed into balls half a foot in diameter, these are calcined in a furnace, broken to pieces, and a stratum <;f the fragments laid on the floor. A due proportion of sulphur is then ignited in tue chamber, in the same manner as for the fabrication of sulphuric acid ; and the fragments of burnt clay, imbibing this as it forms, begin after a few days to crack and open, and exhibit an efflorescence of sulphate of alumina. \\ hen the earth has completely effloresced, it is taken out of the chamber, exposed for some time in an open shed, that it may be the more inti- mately penetrated by the acid, and is then lixiviated and crystallized in the usual manner. The cement answers the pur- pose of lead on this occasion very effec- tually, and accordingly to M. Chaptal, costs no more than lead would at three farthings a pound. Curaudau has lately recommended a process for making alum without evapo- ration. One hundred parts of clay and five of muriate of soda are kneaded into a paste with water, and formed into loaves. With these a reverberatory furnace is filled, and a brisk fire is kept up for two hours. Be- ing powdered, and put into a sound cask, one fourth of their weight of sulphuric acid is poured over them by degrees, stirring the mixture well at each addition. As soon as the muriatic gas is dissipated, a quantity of water equal to the acid is added, and the mixture stirred as before. When the heat is abated, a little more wa- ter is poured in, and this is repeated till eight or ten times as much water as there Vou n [20 ] was acid is added. When the whole has settled, the clear liquor is drawn off into leaden vessels, and a quantity of water equal to this liquor is poured on the sedi- ment. The two liquors being mixed, a solution of potash is added to them, the alkali in which is equal to one-fourth of the weight of the sulphuric acid. Sul- phate of potash may be used, but twice as much of this as of the alkali is necessary. After a certain time the liquor by cooling affords crystals of alum equal to three times the weight of the acid used. It is refined bj dissolving it in the smallest pos- sible quantity of boiling water. The re- sidue max be washed with more water, to be employed in lixiviating a fresh portion ofthe ingredients. As the mother water still contains alum, with sulphate of iron very much oxided, it is well adapted to the fabrication of prus. sian blue. This mode of making alum is particularly advantageous to the manufac- turers of prussian blue, as they may calcine their clay at the same time with their ani- mal matters, without additional expense ; they will have no need in this case to add potash ; and the presence of iron, instead of being injurious, will be very useful. If they wished to make alum for sale, they might use the solution of sulphate of pot- ash, arising from the washing of their prus* sian blue, instead of water, to dissolve the combination of alumina and sulphuric acid. The residuums of distillers of aquafortis are applicable to the same purposes, as they contain the alumina and potash re- quisite, and only require to be reduced to powder, sprinkled with sulphuric acid, and lixiviated with water, in the manner directed above. The mother waters of these alums are also useful in the fabrica- tion of prussian blue. As the residuum of aquafortis contains an over-proportion of potash, it will be found of advantage to add an eighth of its weight of clay calcin- ed as above. * The most extensive alum manufacto- ry in Great Britain is at Hurlett, near Pais- ley, on the estate of the Earl of Glasgow. The next in magnitude is at V\ hitby ; of whose state and processes an instructive account was published by Mr. Winter, in the 25th volume of Nicholson's Journal. The stratum of aluminous schistus is about 29 miles in width, and it is covered by- strata of alluvial soil, sandstone, ironstone, shell, and clay. The alum schist is gene- rally found disposed in horizontal laminae. The upper part of the rock is the most abundant in sulphur ; so that a cubic yard taken from the tnp of the stratum, is & times more valuable than the same bulk, 100 feet below. If a quantity of (he schistus be laid in a ALU ALU heap and moistened with sea water, it will take fire spontaneously, and will continue to burn till the whole inflammable matter be consumed. Its colour is bluish gray. Its specific gravity is 2.48. It imparts a bituminous principle to alcohol. Fused with an alkali, muriatic acid precipitates a large proportion of silex. The expense of digging and removing to a distance of 200 yards one cubic yard of the schistose rock, is about sixpence- halfpenny. A man can earn from 2s. 6d. to 3s. a-day. The rock, broken into small pieces, is laid on a horizontal bed of fuel, composed of brushwood, &c. When about 4 feet in height of the rock is piled on, fire is set to the bottom, and fresh rock continually poured upon the pile. This is continued until the calcined heap be raised to the height of 90 or 100 feet. Its horizontal area has also been progressive- ly extended at the same time, till it forms a great bed nearly 200 feet square, having about 100,000 yards of solid measurement. The rapidity ofthe combustion is allayed by plastering up the crevices with small schist moistened. Notwithstanding of this precaution, a great deal of sulphuric or sulphurous acid is dissipated. 130 tons of calcined schist produce on an average 1 ton of alum. This result has been de- ducedfrom an average of 150,000 tons. The calcined mineral is digested in wa- ter contained in pits that usually contain about 60 cubic yards. The liquid is drawn oft' into cisterns, and afterwards pumped up again upon fresh calcined mine. This is repeated until the specific gravity be- comes i.l5. The half exhausted schist is then covered with water, to take up the whole soluble matter- The strong liquor is drawn oft' into settling cisterns, where the sulphate of lime, iron, and earth, are deposited. At some works the liquid is boiled, which aids its purification. It is then run into leaden pans, iO feet long, 4 feet 9 inches wide, 2 feet 2 inches deep at the one end, and 2 feet 8 inches at the other. This slope makes them be easily emptied. Here the liquor is concentra- ted at a boiling heat. Every morning the pans are emptied into a settling cistern, and a solution of muriate of potash, either pretty pure from the manufacturer, or crude and compound from the soap-boiler, is added. The quantity of muriate neces- sary is determined by a previous experi- ment in a basin, and is regulated for tbe workmen by the hydrometer. By this addition, the pan liquor, which had ac- quired a specific gravity of 1.4 or 1.5, is reduced to 1.35. After being allowed to settle for two hours, it is run oft' into the coolers to be crystallized. At a greater sp. gravity than 1.35, the liquor, instead of crystallizing, would, when it cools, pre- sent us with a solid magma, resembling grease. Urine is occasionally added, to bring it down to the proper density. After standing 4 days, the mother wa- ters are drained off, to be pumped into the pans on the succeeding day. The crys- tals of alum are washed in a tub, and drain- ed. They are then put into a lead pan, with as much water as will make a satu- rated solution at the boiling point. V\ hen- ever this is effected, the solution is run off into casks. At the end of 10 or 16 days, the casks are unhooped and taken asun- der. The alum is found exteriorily in a solid cake, but in the interior cavity, in large pyramidal crystals, consisting of oc- tahedrons, inserted successively into one another. This last process is called roch- ing. Mr. Winter says, that 22 tons of mu- riate of potash will produce 100 tons of alum, to which 31 tons ofthe black ashes ofthe soap-boiler, or 7>> of kelp, are equi- valent. Where much iron exists in the alum ore, the alkaline muriate, by its de- composition, gives birth to an uncrystalli- zable muriate of iron. 1'he alum manu- factured in the preceding mode is a super- sulphate of alumina and potash. There i.9 another alum which exactly resembles it. This is a supersulphate of alumina and am- monia. Both crystallize in regular oc ahe- drons, formed by two four-sided p> ramids joined base to base. Alum has an astrin- gent sweetish taste. Its sp. gravity is about 1.71. It reddens the vegetable blues. It is soluble in 16 parts of water at 60°, and in |thsof its weight at212.° It effloresces superficially on exposure to air, but the interior remains long unchang- ed. Its water of crystallization is suffi- cient at a gentle heat to fuse it. If the heat be increased it froths up, and loses fully 45 per cent, of its weight in water. The spongy residue is called burnt or cal- cined alum, and is used by surgeons as a mild escharotic. A violent heat separates a great portion of its acid. Alum thus was analyzed by Berzelius: 1st, 20 parts (grammes) of pure alum lost by the heat of a spirit lamp 9 parts, which gives 45 per cent, of water. The dry salt was dissolved in water, and its acid preci- pitated by muriate of barytes; the sul- phate of which, obtained after ignition, weighed 20 parts; indicating in 100 parts 34.3 of dry sulphuric acid. 2d, Ten parts of alum were dissolved in water, and di- gested with an excess of ammonia. Alu- mina, well washed and burnt, equivalent to 10.67 per cent, was obtained. In ano- ther experiment, 10.86 per cent, resulted. 3d, Ten parts of alum dissolved in water, were digested with carbonate of strontites, till the earth was completely separated. ALU ALU The 6ulphate of potash, after ignition, weighed 1.815, corresponding to 0.981 potash, or in 100 parts to 9.81. Alum, therefore, consists of Sulphuric acid, 34.33 Alumina, 10.86 Potash, 9.81 Water, 45.00 100.00 or, Sulphate of alumina, 36.85 Sulphate of potash, 18.15 Water, .... 45.00 100.00 _ Thenard's analysis, Ann. de Chimie, vol. 59. or Nicholson's Journal, vol. 18. coin- cides perfectly with that of Berzelius in the product of sulphate of barytes. From 490 parts of alum, he obtained 490 ofthe ignited barytic salt; but the alumina was in greater proportion, equal to 12.54 per cent, and the sulphate of potash less, or 15.7 in 100 parts. Dr. Thomson considers it as a com- pound of 3 atoms sulphate of alumina, 1 atom sulphate of potash, and 23 atoms water, as follows: Sulphate of alumina, 36.70 Sulphate of potash, 18.88 Water, .... 44.42 100.00 But Vauquelin, in his last analysis, found 48.58 water; and by Thenard's statement there are indicated 34.23 dry acid, 7.14 potash, 12.54 alumina, 46.09 water, 100.00 It deserves to be remarked, that the analysis of Professor Berzelius agrees with the supposition that alum contains, 4 sulphuric acid, = 20.0 34.36 2 alumina, «= 6.4 11.00 1 potash, = 6.0 10.30 23 water, = 25.8 44.34 58.2 100.00 If we rectify Vauquelin's erroneous esti- mate ofthe sulphate of barytes, his analy- sis will also coincide with t le above. Alum, therefore, differs from the simple sulphate of alumina previously described, which consisted of 3 prime equivalents of acid, and 2 of earth, merely by its assump- tion of a prime of sulphate of potash. It is probable that all the aluminous salts have a similar constitution. It is to be ob- served, moreover, that the number 34.36 resulting from the theoretic proportions, is, according to Gilbert's remarks on the essay of Berzelius, the just representation ofthe dry acid in 100 of sulphate of bary- tes, by a corrected analysis, which maket the prime of barytes V.57. Should ammonia be suspected in alum, it may be detected, and its quantity esti- mated, by mixing quicklime with the sa- line solution, and exposing the mixture to heat in a retort, connected with a Woulfe's apparatus. The water of ammonia being afterwards saturated with an acid, and evaporated to a dry salt, will indicate the quantity of pure ammonia in the alum. A variety of alum, containing both potash and ammonia, may also be found. I his will occur where urine has been used, as well as muriate of potash, in its fabrica- tion. If any of these bisulphates of alu- mina and potash be acted on in a watery solution, by gelatinous alumina, a neutral triple salt is formed, which precipitates in a nearly insoluble state. When alum in powder is mixed with flour or sugar, and calcined, it forms the pyrophorus of Homberg. Mr. Winter first mentioned, that another variety of alum can be made with soda, in- stead of potash. This salt, which crystal- lizes in octahedrons, hasf»een also made with pure muriate of s«da, and bisulphate of alumina, at the laboratory of Hurlett, by Mr. W. Wilson. It is extremely diffi- cult to form, and effloresces like the sul- phate of soda. The only injurious contamination of alum is sulphate of iron. It is detected by ferroprussiate of potash. To get rid of it cheaply, M. Thenard recommended dissolving the alum in boiling water, and agitating the solution with rods as it cools. The salt is thus reduced to a fine granular powder, which being washed two or three times with cold water, and drained, yields a perfectly pure alum. For a very advan- tageous mode of concentrating alum li- quors, as well as those of other salts, on the great scale, see Evaporation. Oxymuriate of alumina, or the chloride, has been proposed by Mr. Wilson of Dub- lin as preferable to solution of chlorine, for discharging the turkey-red dye. He prepares it by adding to a solution of oxy- muriate of lime, at asp. gravity of 1.060, a solution of alum of the sp. grav. 1 100, as long as any precipitate falls. '1 he clear liquid is to be drawn off from the precipi- tate, and kept in close vessels. He says that it does not injure the cloth, nor annoy the the workmen, like the liquor of un< combined chlorine.—Ann. of Pldl. vol. viii.* Alum is used in large quantities in many manufactories. When added to tallow, it renders it harder. Printer's cushions, and the blocks used in the calico manufactory, are rubbed with burnt alum to remove any greasiness, which might prevent the ink AMA AMB or colour from sticking. Mood sufficient- ly soaked in a solution of alum does not easily take fire; and the same is true of paper impregnated with it, which is fitter to keep gunpowder, as it also excludes moisture. Paper impregnated with alum is useful in whitening silver, and silvering brass without heat. Alum mixed in milk helps the separation of its butter. If add- ed in a very small quantity to turbid wa- ter, in a few minutes it renders it perfect- ly limpid, without any bad taste or quali- ty ; while the sulphuric acid imparts to it a very sensible acidity, and does not pre- cipitate so soon, or so well, the opaque earthy mixtures that render it turbid, as I have often tried. It is used in making p\rophorus, in tanning and many other manufactories, particularly in the art of dyeing, in which it is ofthe greatest and most important use, by cleansing and opening the pores on the surface of the substance to be dyed, rendering it fit for receiving the colouring particles, (by which the alum is generally decompo- sed,) and at the same time making the co- lour fixed. Croons generally consist of the earth of alumjWinely powdered, and tinged for the purpose. In medicine it is employed as an astringent. * Aluminite. A mineral of a snow- white colour, dull, opaque, and having a fine earthy fracture. It has a glistening streak. It is found in kidney-shaped pieces, which are soft to the touch, and ad- here slightly to the tongue. Sp. gravity, 1.67. It consists of Sulphuric acid, 19.25 Alumina, 32 50 Water, 47.00 Silica, lime, and oxide of iron, 1.25 100.00 It may be represented very exactly by 2 primes of acid, 10 = 20 5 alumina, 16 = 32 .21 water, 23.6 = 47.'J Foreign matter, 0.4 = 0.8 50.0 100.0 The conversion of the above into alum is easily explained. When the three primes composing bisulphate of potash come into play, they displace precisely three primes (or atoms) of alumina. Two additional primes of water are also intro- duced at the same time, by the strong af- finity of the bisulphate for the particles of that liquid. The above alum ore is found chiefly in the alluvial strata round Halle in Sax- ony.* * Amadou. It is a variety ofthe boletus igniarius, found on old ash and other trees. It is boiled in water to extract its soluble parts, then dried, and beat with a mallet to loosen its texture. It has now the ap- pearance of very spongy doc-skin leather. It is lastly impregnated with a solution of nitre, and dried when it is called spunk, or German tinder; a substance much used on,the continent for lighting fire, either from the collision of flint and steel, or from the sudden condensation of air in the at- mospheric pvrophorus.* Amalgam This name is applied to the combinations of mercury with other me- tallic substances. See Muiclrt. Amber is a hard, brittle, tasteless sub- stance, sometimes perfectly transparent, but mostly semi-transparent or opaque, and of a glossy surface : it is found of all colours, but chiefly yellow or orange, and often contains leaves or insects; its speci- fic gravity is from 1.065 to 1.100 ; its frac- ture is even, smooth, and glossy; it is ca- pable of a fine polish, and becomes elec- tric by friction; when rubbed or heated, it gives a peculiar agreeable smell, par- ticularly when it melts, that is at 550° of Fahrenheit, but it then loses its transpa- rency ; projected on burning coals, it burns with a whitish flame, and a whitish yellow smoke, but gives very little soot, and leaves brownish ashes ; it is insoluble in water and alcohol, though the latter, when highly rectified, extracts a reddish colour from it; but it is soluble in the sul- phuric acid, which then acquires a reddish purple colour, and is precipitable from it by water; no other acid dissolves it, nor is it soluble in essential or expressed oils, without some decomposition and long di- gestion ; but pure alkali dissolves it. By distillation it affords a small quantity of water, with a little acetous acid, an oil, and a peculiar acid. See Acid (Succi- nic). The oil rises at first colourless; but, as the heat increases, becomes brown, thick, and empyreumatic. The oil may be rectified by successive distillations, or it may be obtained very light and lim- pid at once, if it be put into a glass alem- bic with water, as the elder Rouelle di- rects, and distilled at a heat not greater than 212° Fahr. It requires to be kept in stone bottles, however, to retain this state ; for in glass vessels it becomes brown by the action of light. Amber is met with plentifully in regu- lar mines in some parts of Prussia. The upper surface is composed of sand, under which is a stratum of loam, and under this a bed of wood, partly entire, but chiefly mouldered or changed into a bituminous substance. Under the wood is a stratum of sulphuric or rather aluminous mineral, in which the amber is found. Strong sul- phureous exhalations are often perceived in the pits*. * Detached pieces are also found occa- sionally on the s^a-coast in various conn- AMB tries, it has been found in gravel beds near London. In the Royal Cabinet at Berlin there is a mass of 18 lbs. weight, supposed to be the largest ever found. Jussieu asserts, that the delicate insects in umber, which pr ve the tranquillity of its formation, are not I'.uropean. M. Hauy has pointed out the following distinctions between mellite and copal, the bodies which most closely resemble amber. Mel- lite is infusible by heat. A bit of copal heated at the end of a knife takes fire, melting into drops, which flatten as they fall; whereas amber burns with spitting and frothing; and when its liquefied par- ticles drop, they rebound from the plane which receives them. The origin of am- ber is at present involved in perfect ob- scurity, though the rapid progress of ve- getable chemistrv premises soon to throw light on it. Various frauds are practised with this substance. Neumann states as the common practices of workmen the two following: The one consists in surround- ing the amber with sand i-i an iron pot, and cementing it with a gradual fire for forty hours, some small pieces placed near the sides of the vessel being occasionally taken out for judging of the effect cf the operation: the second method, which he says is that most generally practised, is by digesting and boiling the amber about twenty hours with rapeseed oil, by which it is rendered both clear and hard. * Werner has divided it into two sub- species, the white and the yellow; but there is little advantage in the distinction. Its ultimate constituents are the same with those of vegetable bodies in general; viz. carbon, hydrogen, and oxygen; but the proportions have not been ascertained. In the second volume ofthe Edinburgh Philosophical Journal, Dr. Brewster has given an account of some optical proper- ties of amber, from which he considers it established beyond a doubt that amber is an indurated vegetable juice; and that the traces of a regular structure, indicated by its action upon polarized light, are not the effect of the ordinary laws of crystalliza- tion by which mellite'h^s been formed, but are produced by the same causes which influence the mechanical condition of gum arabic, and other gums, which are known to be formed by the successive deposition and induration of vegetable fluids.* Amber is also used in varnishes. See Varnish, and On. of Amber. Ambergris is found in the sea, near the coasts of various tropical countries; and has also been taken out of the intestines ofthe physeter macrocephalus, the sper- maceti whale. As it has not been found in any whales but such as are dead or sick, it* production is generally supposed to be owing to disease, though some have a lit- AMB tie too peremptorily affirmed it to be the cause of the morbid affection. As no large piece has ever been found without a grea- ter or less quantity ofthe beaks ofthe se- pia octopodia, the common food of the. spermaceti whale, interspersed throughout its substance, there can be little doubt of its originating in the intestines of the whale; for if it were occasionally swallow- ed by it only, and then caused disease, it must much more frequently be found with- out these, when it is met with floating in the sea, or thrown upon the shore, Ambergris is found of various sizes, ge- nerally in small fragments, but sometimes so large as to weigh near two hundred pounds. When taken from the whale, it is not so hard as it becomes afterward on ex- posure to the air. Its specific gravity ranges from 780 to 926. If good, it ad- heres like wax to the edge of a knife with which it is scraped, retains the impression ofthe teeth or nails, and emits a fat odo- riferous liquid on being penetrated with a hot needle. It is generally brittle; but, on rubbing it with the nail, it becomes smooth like hard soap. Its colour is cither white, black, ash coloured, yellow, or blackish; or it is variegated, namely, gray with black specks, or gray with yellow specks. Its smell is peculiar, and not easy to be counterfeited. At 144° it melts, and at 212° is volatilized in the form of a white vapour. But, on a red-hot coal, it burns, and is entirely dissipated. Water has no action on it; acids, except nitric, act fee- bly on it; alkalis combine with it, and form a soap; ether and the volatile oils dissolve it; so do the fixed oils, and also ammonia, when assisted by heat; alcohol dissolves a portion of it, and is of great use in analy- zing it, by separating its constituent parts. According to Bouillon la Grange- who has given the latest analysis of it, 3820 parts of ambergris consist of adipocere 2016 parts, a resinous substance 1167, benzoic acid 425, and coal 212. * But Bucholz could find no benzoic acid in it. Dr. Ure examined two different specimens with considerable attention. The one yielded benzoic acid, the other, equally genuine to all appearance, afforded none. See Adipocere and Intestinal Concretion. An alcoholic solution of ambergris, add- ed in minute quantity to lavender-water, tooth powder, hair powder, wash balls, &c. communicates its peculiar fragrance. Its retail price being in London so high a* a guinea per oz. leads to many adultera- tions. These consist of various mixtures of benzoin, labdanum, meal, &c. scented with musk. The greasy appearance and smell which heated ambergris exhibits, nf- ford good criteria, joined to its solubility in hot ether and alcohol. * It has occasionally been employed in AMM medicine, but its use is now confined to the perfumer. Dr. Swediaur took thirty grains of it without perceiving any sensi- ble effect. A sailor, who took half an ounce of it, found it a good purgative. * Amblygovite. A greenish coloured mineral of different pale shades, marked on the surface with reddish and yellowish brown spots. It occurs massive and crys- tallized in oblique four-sided prisms. Lus- tre vitreous; cleavage parallel with the sides of an oblique four-sided prism of 106° 10' and 77° 50'; fracture uneven; fragments rhomboidal; translucent; hard- ness, as feldspar; brittle; sp. gr. 3.0. In- tumesces with the blow-pipe, and fuses with a reddish-yellow phosphorescence into a white enamel. It occurs in granite, along with green topaz and tourmaline, near Pinig- in Saxony. It seems to be a species of spodumene.* Amethyst. The amethyst is a gem of a violet colour, and great brilliancy, said to be as hard as the ruby or sapphire, from which it only differs in colour. This is called the oriental amethyst, and is very rare. When it inclines to the purple or rosy colour, it is more esteemed than when it is nearer to the blue. These ame- thysts have the same figure, huxlness, spe- cific gravity, and other qualities, as the best sapphires or rubies, and come from the same places, particularly from Persia, Arabia, Armenia, and the West Indies. The occidental amethysts are merely co- loured crystals or quartz. See Quartz and Sapphire. Amianthus, Mountain Flax. See As- BF.STUS. * Ammonia, called also Volatile Alkali. We shall first consider this substance in its purely scientific relations, and then de- tail its manufacture on the great scale, and its uses in the arts. There is a saline bo- dy, formerlv brought from Egypt, where it was separated from soot by sublimation, but which is now made abundantly in Eu- rope, called sal ammoniac. From this salt, pure ammonia can be readily obtain- ed by the following process: Mix unslack- ed quicklime with its own weight of sal ammoniac, each in fine powder, and intro- duce them into a glass retort. Join to the beak of the retort, by a collar of caout- chouc, (a neck of an Indian rubber bottle answers well,) a glass tube about 18 inch- es long, containing pieces of ignited mu- riate of lime. This tube should lie in a horizontal position, and its free end, pre- viously bent obliquely by the blow-pipe, should dip into dry mercury in a pneuma- tic trough. A slip of porous paper, as an additional precaution, may be tied round the tube, and kept moist with ether. If a gentle heat from a charcoal chauffer or lamp be now applied to the bottom ofthe AMM retort, a gaseous body will bubble up through the mercury. Fill a little glass tube, sealed at one end, with the gas, and transfer it, closely stopped at the other end, into a basin containing water. If the water rise instantly and fill the whole tube, the gas is pure, and may be received for examination. Ammonia is a transparent, colourless, and consequently invisible gas, possessed of elasticity, and the other mechanical properties of the atmospherical air. Its specific gravity is an important datum in chemical researches, and has been rather differently stated. Now, as no aeriform body is more easily obtained in a pure state than ammonia, this diversity among accurate experimentalists, shows the nice- ty of this statical operation. MM. Biot and Arago make it = 0.59669 by experi- ment, and by calculation from its elemen- tary gases, they make it = 0.59438. Kir- wan savs, that 100 cubic inches weigh 18.16 g'r. at 30 inches of bar. and 61° F., which compared to air reckoned 30.519, gives 0.59540. Sir H. Davy determines its density to be = 0.590, with which esti- mate the theoretic calculations of Dr. Prout, in the 6th volume ofthe Annals of Philosophy, agree. This gas has an exceedingly pungent smell, well known by the old name of spi- rits of hartshorn. An animal plunged into it speedily dies. It extinguishes combus- tion, but being itself to a certain degree combustible, the flame of a taper immers- ed in it, is enlarged before going out It has a very acrid taste. Water condenses it very rapidly. The following valuable table of its aqueous combinations has been given by Sir H. Davy. Sp. Gr. Ammonia. Water. 0.8750 32.50 67.50 0.8875 29.25 70.75 0.9000 26.00 74.00 0.9054 25.37 74.63 0.9166 22.07 77.93 0.9255 19.54 80.46 0.9326 17.52 82.48 0.9385 15.88 84.12 0.9435 14.53 85.47 0.9476 13.46 86.54 0.9513 12.40 87.60 0.9545 11.56 88.44 0.9573 10.82 89.18 0.9597 10.17 89.83 0.9619 9.60 90.40 0.9692 9.50 90.50 Water is capable of dissolving easily about one-third of its weight of ammonia- cal gas, or 460 times its bulk. Hence, when placed in contact with a tube filled with this gas, water rushes into it with ex- plosive velocity. Probably the quantity of ammonia stated in the above table is too high by about one per cent. AMM Dr. Thomson states, in his System, vol. 2d. page 29. " Water, by my trials, is ca- pable of absorbing 780 times its bulk of this gas; while, in the mean time, the bulk ofthe liquid increases from 6 to 10. The specific gravity of this solution is 0.900, which just accords with the increase of bulk." Correcting the first error where 6 is substituted tor 9, a less excusable error comes to be examined. Taking the Doc- tor's own number for the specific gravity ofthe gas, it is evident that 780 times the volume, combined with water, would give nearly 36 by weight of gas in 100 ofthe liquid. But in the very same page he says, " It follows, from the experiments of Daw, that a saturated solution of ammo- nia is composed of 74.63 water and 25.37 ammonia." Hence, if that be correct, a liquid containing 36 per cent of ammonia is a manifest impossibility. In the very same page he gives Mr. Dalton's table, " which exhibits the quantity of ammonia contain- ed in ammoniacal solutions of different specific gravities." In this table, opposite to the specific gravity 0.90 of the liquid ammonia, such as he made in his own tri- als, we have 22.2, a far different quantity from the number 36 equivalent to his 780 volumes. Sir H. Davy's table differs very little from that of Mr. Dalton, the truth probably lying between them. It is cer- tain, indeed, that 100 parts of ammoniacal water, sp. gr. 0.900, instead of containing 36 parts, or 780 v olumes, do not contain above 24 parts, or 520 volumes. Had Dr. Thomsom consulted Sir H. Davy's Ele- ments of Chemical Philosophy, he would have found the following statement, p. 268. " At the temperature of 50c, under a pressure equal to 29.8 inches, water, I find, absorbs about 670 times its volume of gas, and becomes of specific gravity 0.875." in the table of Sir II. Davy, oppo- site 0.875, we have 32.5 per cent of am- monia. If any person will take the trouble of calculating, he will find that 670 inches of a gas, of which 100 cubic inches weigh 18 grs. in combining with one cubic inch of water weighing 252.5 grains, form a so- lution that must contain just 32.3 per cent of the condensed gas. We thus perceive, that liquid ammonia, as the aqueous compound is termed, may like spirits be very accurately valued by its specific gravity. But it differs remarka- bly from alcoholic mixtures in this respect, that the strongest ammoniacal liquor, when it is diluted with water, suffers no condensation of volume. The specific gravity of the dilute, is the mean of that of its components. Hence, having one point accurately, we can compute all be- low it, by paying attention to the rule given under Specific Ghavitt. To pro- cure aqueous ammonia, wc may use either AMM a common still and refrigeratory or * Woulfe's apparatus. The latter should be preferred. Into a retort we put a mixture of twt» parts of slaked lime, and one part of pulverized sal ammoniac, and having connected the beak ofthe retort with the Woulfe's apparatus, containing pure wa- ter, we then disengage the ammonia, by the application of heat. \\ hen gas ceases to be evolved, the addition of a little hot water will renew its disengagement, and ensure complete decomposition of the salt. Since sal ammoniac contains nearly | its weight of ammonia, ten pounds of it should yield by economical treatment, 30 pounds of liquid, whose specific gravity is 0.950, which is as strong as the ordinary purposes of chemistry and medicine re- quire ; and it will form twice that quanti- ty, or 6J pounds of the common water of ammonia, sold by apothecaries, which has rarelj a smaller density than 0.978 or 0.980. There is no temptation to make it with the ammoniacal carbonate; but if this salt be accidentally present, it is instantly de- tected by its causing a milkiness in lime water. Ammoniacal gas, perfectly dry, when mixed with oxygen, explodes with the electric spark, and is converted into water and nitrogen, as has been shown in an in- genious paper by Dr. Henry. But the simplest, and perhaps most accurate mode of resolving ammonia into its elementary constituents, is that first practised by M. Berthollet, the ' celebrated discoverer of its composition. This consists in making the pure gas traverse very slowly an igni- ted porcelain tube of a small diameter. The process, as lately repeated by M. Gay-Lussac, yielded from 100 cubic inches of ammonia, 2 >0 cubic inches of consti- tuent gases; of which by subsequent ana- lysis, 50 were found to be nitrogen, and 150 hydrogen. Hence we see, that the reciprocal affinity of the ammoniacal ele- ments had effected a condensation equal to one-half of the volume of the free gases. It appears, by the most recent determina- tions, that the specific gravity of hydro- gen is 0.0694, compared to air as unity, and that of nitrogen, 0.9722. Three vo- lumes of the former will therefore weigli 0.2082, and one of the latter, 0.9722; the sum of which numbers, 1.1804, divided by 2, ought to coincide with the experimen- tal density of ammonia. Now, it is 0.5902, being an exact correspondence. And the ratio ofthe two weights, reduced to 100 parts, will be 82.36 nitrogen to 17.64 hy- drogen. To reduce ammonia to the sys- tem of equivalents, or to find its saturating ratio on that scale where oxygen repre- sents unity, we have this proportion 0.9722 : 1 75 : : 1.1804 : 2.1-J25. so that 2.125 may be called its prime equivalent. AMM We shall find this number deduced from analysis, confirmed by the synthesis of all the ammoniacal salts. Dr. Prout, in an able memoir on the relation between the specific gravities of gaseous bodies, and the weights of their atoms, published in the 6th vol. ofthe An nals of Philosophy, makes the theoretical weight ofthe atom or'ammonia to be only 1.9375 considering it as a compound of 1 atom of azote, and lh atoms of hydrogen. This statement appears to be a logical in- ference from Mr. Dalton'a hypothesis of utomical combination. For water, the great groundwork of his atomic structure, is represented as a compound of one atom oxygen with one atom of hydrogen ; and this atomical unit of hydrogen consists of two volumes ofthe gas. Hence three vo- lumes of the gas must represent an atom and an half. But an atom is, by its very definition, indivisible. Dr. Prout in the 38th number of the Annals, restores the true proportions of 3 atoms hvdrogen, -f- 1 azote. Our doctrine of equivalent primes, resting on the bas^s of experimental induc- tion, claims no knowledge ofthe atomical constitution of bodies. The alkaline nature of ammonia is de- monstrated, not only by its neutralizing acidity, and changing the vegetable reds to purple or green, but also by its being attracted to the negative pole of a voltaic arrangement. When a pretty strongelec- tric power is applied to ammonia in its li- quid or solid combinations, simple decom- position is effected; but in contact with mercury, very mysterious phenomena oc- cur. If a globule of mercury be surround- ed with a little water of ammonia, or pla- ced in a little cavity in a piece of sal am- moniac, and then subjected to the voltaic power by two wires, the negative touch- ing the mercury, and the positive the am- moniacal compound, the globule is instant- ly covered with a circulating film, a white smoke rises from it, and its volume en- larges, whilst it shoots out ramifications of •a semisolid consistence over the salt. The amalgam has the consistence of soft but- ter, and may be cut with a knife. When- ever the electrization is suspended, the erab-like fibres retract towards the cen- tral mass, which soon, by the constant formation of white saline films, resumes its pristine globular shape and size. The enlargement of volume seems to amount occasionally to ten times that ofthe mer- cury, when a small globule is employed. Sir H. Davy, Berzelius, and MM. Gay- Lussac and Thenard, have studied this singular phenomenon with great care. They produced the very same substance by putting an amalgam of mercury and potassium info the moistened cupel of sal ammoniac. It becomes five or six times AMM larger, assumes the consistence of butter, whilst it retains its metallic lustre. What takes place in these experiments ? In the second case, the substance of me- tallic aspect which we obtain is an ammo- niacal hydruret of mercury and potassium. There is formed, besides, muriate of pot- ash. Consequently a portion of the po- tassium of the amalgam, decomposes the water, becomes potash, which itself de- composes the muriate of ammonia. Thence result hydrogen and ammonia, which, in the nascent state, unite to the undecom- posed amalgam. In the first experiment, the substance, which, as in the second, presents the metallic aspect, is only an ammoniacal hydruret of mercury ; its for- mation is accompanied by the perceptible evolution of a certain quantity of chlorine at the positive pole. It is obvious, there- fore, that the salt is decomposed by the electricity. The hydrogen ofthe muria- tic acid, and the ammonia, boih combine with the mercury. These hydrurets pos- sess the following properties. Their sp. gravity is in general below 3.0; exposed for some time to the tem- perature of 32u F. they assume consider- able hardness, and crystallize in cubes, which are often as beautiful and large as those of bismuth. Ether and alcohol in- stantly destroy these amalgams, exciting a brisk effervescence with them, and re- producing the pure mercurial globule. These amalgams are slightly permanent in the air, if undisturbed; but the least agi- tation is fatal to their existence. MM. Gay-Lussac and Thenard found, by im- mersion in water, that mercury, in passing to the state of a hydruret, absorbed o\ times its volume of hydrogen. The am- moniacal hydruret of mercury and potas- sium may exist by itself; but as soon as we attempt to separate or oxidize the potassium, its other constituent principles also separate. Hence this hydruret is speedily decomposed by the air, by oxv- gen gas, and in general by all bodies that act upon potassium. It "is even aff'ected by mercury, so that in treating it with this metal, we may easily determine the rela- tive quantity of ammonia and hvdrogen which it contains. We need onlv for this purpose take up the interior parts of the hydruret with a little iron spoon, fill up with it a little glass tube, already nearly full of mercury ; and closing this with a very dry stopper, invert it in mercury equa ly dry. The hydruret will rise to the upper part of the tube, will be decompos- eu, especially by a slight agitation, and will give out hvdrogen and ammonia in the ratio of I to 2.5. The mere ammoniacal hydrurets con- tain but a very small quantity of hydrogen aud ammonia. By supposing that in tiie AMM AMM ammoniacal hydruret of mercury, the hy- drogen is to the ammonia in the same pro- portion as in the ammoniacal hydruret of mercury and potassium, it will appear that the first is formed in volume, of 1 of mercury, 3.47 hydrogen, and 8.67 ammo- niacal gas, at the mean pressure and tem- perature of 30. and 60°; or in weight, of about 1800 parts of mercury, with 1 part of hydrogen, and 1 of ammonia. Ammonia is not affected by a cherry-red heat. According to Guyton de Morveau, it becomes a liquid at about 40°—0°, or at0°, the freezing point of mercury ; but it is uncertain whether the appearances he observed may not have been owing to hy- grometric water, as happens with chlorine gas. The ammoniacal hquid loses its pun- gent smell as its temperature sinks, till at —50°, it gelatinizes, if suddenly cooled; but if slowly cooled, it crystallizes. Oxygen, by means of electricity, or a mere red heat, resolves ammonia into wa- ter and nitrogen. When there is a consi- derable excess of oxygen, it acidifies a portion of the nitrogen into nitrous acid, whence many fallacies in analysis have arisen. Chlorine and ammonia exercise so powerful an action on each other, that when mixed suddenly, a sheet of white flame pervades them. The simplest way of making this fine experiment, is to in- vert a mattrass, with a wide mouth and conical neck, over another with a taper neck, containing a mixture of sal ammo- niac and lime, heated by a lamp. As soon as the upper vessel seems to be full of am- monia, by the overflow of the pungent gas, it is to be cautiously lifted up, and in- serted, in a perpendicular direction, into a wide-mouthed glass decanter or flask, filled with chlorine. On seizing the two vessels thus joined, with the two hands covered with gloves, and suddenly invert- ing them, like a sandglass, the heavy chlo- rine and fight ammonia, rushing in oppo- site directions, unite, with the evolution of flame. As one volume of ammonia con- tains, in a condensed state, one and a half of hydrogen, which requires for its satura- tion just one and a half of chlorine, this quantity should resolve the mixture into muriatic acid and nitrogen, and thereby give a ready analysis of the alkaline gas. If the proportion of chlorine be less, sal ammoniac and nitrogen are the results. The same thing happens on mixing the aqueous solutions of ammonia and chlo- rine. But if large bubbles of chlorine be letup into ammoniacal water of moderate strength, luminous streaks are seen in the dark to pervade the liquid, and the same reciprocal change ofthe ingredients is ef- fected. MM. Gay-Lussac and Thenard state that when 3 parts of ammoniacal gas, and 1 of Vol. r. [21] chlorine, are mixed together, they con* dense into sal ammoniac; and azote, equal to l-10th the whole volume, is given out. This result is at variance with their own theory of volumes. Three of ammoniacal gas consist of 4£ hydrogen, and 1^ nitrogen in a condensed state; 1 of chlorine seizes 1 of hydrogen, to form 2 of muriatic acid gas, which pre- cipitate with 2 of ammonia, in a pulveru- lent muriate. But the third volume of ammonia had parted with 1 volume of its hydrogen to the chlorine, and another half-volume of hydrogen, will unite with 0.166 of a volume of nitrogen, to form 0.66 —-- = 0.33 of redundant ammonia, while 0.33 of a volume of nitrogen is left un- employed. Hence \ of a volume, or £ ofthe original bulk ofthe mixed gases, ought to remain ; consisting of equal parts of ammonia and nitrogen, instead of 1-lOth. of azote, as the French chemists state. Iodine has an analogous action on am- monia j seizing a portion of its hydrogen to form hydriodic acid, whence hydriodate of ammonia results; while another portion of iodine unites with the liberated- nitro- gen, to form the explosive pulverulent iodide. Cyanogen and ammoniacal gas begin to act upon each other whenever they come into contact, but some hours are requisite to render the effect complete. They unite in the proportion nearly of 1 to 1A, forming a compound which gives a dark orange-brown colour to water, but dis- solves in only a very small quantity in wa- ter. The solution does not produce prus- sian blue with the salts of iron. By transmitting ammoniacal gas through charcoal ignited in a tube, prussic or hy- drocyanic acid is formed. The action of the alkaline metals on gaseous ammonia is very curious. When potassium is fused in that gas, a very fusi- ble olive green substance, consisting of potassium, nitrogen, and ammonia, is form- ed ; and a volume of hydrogen remains, exactly equal to what would result from the action on water, of the quantity of potassium employed. Hence, according to M. Thenard, the ammonia is divided into two portions. One is decomposed, so that its nitrogen combines with the po- tassium, and its hydrogen remains free, whilst the other is absorbed in whole or in part by the nitroguret of potassium. Sodium acts in the same manner. The olive substance is opaque, and it is only when in plates of extreme thinness that it appears semi-transparent; and it has no- thing of the metallic appearance; it is heavier than water; and on minute in- spection seems imperfectly crystallize AMM AMM When it is exposed to a heat progressive- ly increased, it melts, disengages ammo- nia, and hydrogen and nitrogen, in the proportions constituting ammonia; then it becomes solid, still preserving its green colour, and is converted into a nitroguret of potassium or sodium. Exposed to the air at the ordinary temperature, it attracts only its humidity, but not its oxygen, and is slowly transformed into ammoniacal gas, and potash or soda. It burns vividly when projected into a hot crucible, or when heated in a vessel containing oxygen. Water and acids produce also sudden de- composition, with the extrication of heat. Alkalis or alkaline salts are produced. Alcohol likewise decomposes it with sim- ilar results. The preceding description of the compound of ammonia with potas- sium, as prepared by MM. Gay-Lussac and Thenard, was controverted by Sir H. Davy. The experiments of this accurate che- mist led to the conclusion, that the pre- sence of moisture had modified their re- sults. In proportion as more precautions are taken to keep every thing absolutely dry, so in proportion, is less ammonia re- generated. He seldom obtained as much as tv01' ^e quantity absorbed; and he never could procure hydrogen and nitro- gen in the proportions constituting ammo- nia; there was always an excess of nitro- gen. The following experiment was conducted with the utmost nicety. 3jJ gr. of potassium were heated in 12 cubic inches of ammoniacal gas; 7.5 were ab- sorbed, and 3.2 of hydrogen evolved. On distilling the olive-coloured solid in a tube of platina, 9 cubical inches of gas were given off, and half a cubical inch remained in the tube and adopters. Ofthe 9 cubi- cal inches, one-fifth of a cubical inch only was ammonia; 10 measures ofthe perma- nent gas mixed with 7.5 of oxygen, and acted upon by the electrical spark, left a residuum of 7.5. He infers that the re- sults of the analysis of ammonia, by elec- tricity and potassium, are the same. On the whole, we may legitimately in- fer that there is something yet unexplain- ed in these phenomena. The potassium separates from ammonia, as much hydro- gen, as an equal weight of it would from water. If two volumes of hydrogen be thus detached from the alkaline gas, the remaining volume, with the volume of nitrogen, will be left to combine with the potassium, forming a triple compound, somewhat analagous to the cyanides, a compound capable of condensing ammo- nia. For an account of a singular com- bination of ammonia, by which its volatili- ty seems destroyed, see Chlorine. When ammoniacal gas is transmitted over ignited wires of iron, copper, plati- na, &c. it is decomposed completely, and though the metals are not increased in weight they have become extremely brittle. Iron, at the same temperature decomposes the ammonia, with double the rapidity that platinum docs. At a high temperature, the protoxide of ni- trogen decomposes ammonia. Ofthe ordinary metals, zinc is the only one which liquid ammonia oxidizes and then dissolves. But it acts on many of the metallic oxides. At a high tempera- ture the gas deoxidizes all those which are reducible by hydrogen. The oxides soluble in liquid ammonia, are the oxide of zinc, the protoxide and peroxide of copper, the oxide of silver, the third and fouth oxides of antimony, the oxide of tellurium, the protoxides of nickel, cobalt, and iron, the peroxides of tin, mercury, gold, and platinum. The first five are very soluble, the rest less so. These combinations can be obtained by evapo- ration, in the dry state, only with copper, antimony, mercury, gold, platinum, and silver; the four last of which, are very re- markable for their detonating property. See the particular metals. All the acids are susceptible of combi- ning with ammonia, and they almost all form with it neutral compounds. M. Gay- Lussac made the important discovery, that whenever the acid is gaseous, its combination with ammoniacal gas, takes place in a simple ratio of determinate volumes, whether a neutral or a subsalt be formed. Ammoniacal Salts have the following general characters.— 1st, When treated with a caustic fixed alkali or earth, they exhale the peculiar smell of ammonia. 2d, They are generally soluble in wa- ter, and crystallizable. 3d, They are all decomposed at a mo- derate red heat; and if the acid be fixed, as the phosphoric or boracic, the ammo- nia comes away pure. 4th, When they are dropped into a so- lution of muriate of platina, a yellow pre- cipitate falls. 1. Acetate. This saline compound was formerly called the spirit of Mindererus, who introduced it into medicine as a fe- brifuge sudorific. By saturating a pretty strong acetic acid with subcarbonate of ammonia, enclosing the liquid under the receiver of an air-pump, along with a saucerful of sulphuric acid, and exhaust- ing the air, the salt will concrete in acicu- lar crystals, which are nearly neutral. It may also be made very conveniently, by mixing hot saturated solutions of acetate of lead, and sulphate of ammonia, taking 100 of the first salt in its ordinary state, to 34.4 ofthe second, well dried at a heat AMM AMM of 212a. Or even muriate of ammonia will answer in the proportion of 27.9 to 100 of the acetate. Acetate of ammonia has a cooling sweetish taste. It is deli- quescent, and volatile at all temperatures; but it sublimes in the solid state at 250°. It consists of 75* of dry acetic acid, and 242 ammonia. AVhen intended for medi- cine, it should always be prepared from pure acetic acid, and subcarbonate of am- monia. Arseniate of ammonia may be formed by saturating the arsenic acid with ammonia, and evaporating the hquid. Crystals of a rhomboidal prismatic form are obtained. A binarseniate may also be made by using an excess of acid. At a red heat, the am- monia of both salts is decomposed, and the acid is reduced to the metallic state. Under the respective acids, an account of several ammoniacal salts will be found. As the muriate, however, constitutes an extensive manufacture, we shall enter here into some additional details concern- ing its production. Sal ammoniac was originally fabricated in Egypt. The dung of camels and other animals constitutes the chief fuel used in that country. The soot is carefully col- lected. Globular glass vessels, about a foot in diameter, are filled within a few inches of their mouth with it, and are then ar- ranged in an oblong furnace, where they are exposed to a heat gradually increased. The upper part ofthe glass balloon stands out ofthe furnace, and is kept relatively cool by the air. On the 3d day the oper- ation is completed, at which time they plunge an iron rod occasionally into the mouths of the globes, to prevent them from closing up, and thus endanger the bursting ofthe glass. The fire is allowed to go out; and on breaking the cooled globes, their upper part is found to be lined with sal ammoniac in hemispherical lumps, about 2} inches thick, of a grayish white colour, semi- transparent, and possessed of a degree of elasticity. 26 pounds of soot yield 6 of sal ammoniac. The ordinary mode of manufacturing sal ammoniac in Europe, is by combining with muriatic acid the am- monia resulting from the igneous decom- position of animal matters in close vessels. Cylinders of cast iron, fitted up as we have described under Acbtic Acin, are charged with bones, horns, parings of hides, and other animal matters; and being exposed to a full red heat, an immense quantity of an impure liquid carbonate of ammonia dis- tils over. Mr. Minish contrived a cheap method of converting this liquid into sal ammoniac. He digested it with pulve- ized gypsum, or simply made it percolate through a stratum of bruised gypsum; whence resulted a liquid sulphate of am« monia, and an insoluble carbonate of lime. The liquid, evaporated to dryness, was mixed with muriate of soda, put into large glass balloons, and decomposed by a sub- liming heat. Sal ammoniac was found above in its characteristic cake, while sul- phate of soda remained below. M. Leblanc of St. Denis, near Paris, in- vented another method of much ingenui- ty, which is described by a commission of eminent French chemists in the 19th vo- lume of the Annales de Chimie, and in the Journal de Physique for the year 1794. He used tight brick kilns, instead of iron cylinders, for holding the materials to be decomposed. Into one he put a mixture of common salt and oil of vitriol; into ano- ther, animal matters. Heat extricated from the first, muriatic acid gas, and from the second, ammonia; which bodies being conducted by their respective flues into a third chamber lined with lead, and con- taining a stratum of water on its bottom, entered into combination, and precipitat- ed in solid sal ammoniac on the roof and sides, or liquid at the bottom. In the 20th volume of the Annales, a plan for employing bittern or muriate of magnesia to furnish the acid ingredient is described. An ingenious process on the same principles, was some time ago com- menced at Borrowstounness in Scotland, by Mr. Astley. He imbued in a stove- room, heated by brick flues, parings of skins, horns, and other animal matters, with the muriate of magnesia, or mother water of the sea-salt works. The matters thus impregnated and dried, were sub- jected in a close kiln to a red heat, when the sal ammoniac vapour sublimed, and was condensed either in a solid form, into an adjoining chamber or chimney, or else into a stratum of water on its bottom. Mu- riate of magnesia at a red heat, evolves muriatic acid gas ; an evolution probably aided in the present case, by the affinity of ammonia. From coal soot likewise a considerable quantity of ammonia, in the state of carbo- nate and sulphate, may be obtained, either by sublimation or lixiviation with water. These ammoniacal products can after- wards be readily converted into the mu- riate, as above described. M. Leblanc used a kettle or eolipile for projecting steam into the leaden chamber to promote the combination. It is evident, that the exact neutralization, essential to sal am- moniac, might not be hit at first in these operations; but it could be afterwards ef- fected by the separate addition of a por- tion of alkaline or acid gas. As the mo- ther waters of the Cheshire salt-works contain only 3£ per cent, of muriate of magnesia, they are not suitable, like thost ANA ANA of sea-salt works, for the above manufac- ture.* * Ammoniac (Gum). This is a gum-re- sin, which consists, according to Bracon- not, of 70 resin, 18.4 gum, 4.4 glutinous matter, 6 water, and 1.2 loss in 100 parts. It forms a milky solution with water ; is partially soluble in alcohol; entirely in ether, nitric acid, and alkalis. Sp. gr. 1.200. It has a rather heavy smell, and a bitter sweet taste. It is in small aggluti- nated pieces of a yellowish white colour. It is used in medicine as an expectorant and antispasmodic* Ammonites, These petrifactions, which have likewise been distinguished by the name of cornua ammonis, and are called snake-stones by the vulgar, consist chiefly of lime-stone. They are found of all si- zes, from the breadth of half an inch to more than two feet in diameter; some of them rounded, others greatly compress- ed, and lodged in different strata of stones and clays. They appear to owe their ori- gin to shells ofthe nautilus kind, Amomum. See Pimento. * Amphibole, See Hornblende and Actxnolite.* * Amphioene. See Vesuvian.* * Amygdaloid. A compound mineral, consisting of spheroidal particles or vesi- cles of lithomarge, green earth, calc spar, steatite, imbedded in a basis of fine grain- ed green-stone, or wacke, containing sometimes also crystals of hornblende.* Anacardium, Cashew Nut, or Marking Nut. At one extremity ofthe fruit ofthe cashew tree is a flatfish kidney-shaped nut, between the rind of which and the thin outer shell is a small quantity of a red, thickish, inflammable, and very caustic li- quor. This liquor forms a useful marking ink, as any thing written on linen or cot- ton with it, is of a brown colour, which gradually grows blacker, and is very du« rable. * Analcime, Cubic Zeolite, This mi- neral is generally found in aggregated or cubic crystals, whose solid angles are replaced by three planes. External lus- tre between vitreous and pearly; fracture, flat conchoidal; colours, white, gray, or reddish; translucent. From its becoming feebly electrical by heat it has got the name analcime. Its sp. gr. is less than 2.6. It consists of 58 silica, 18 alumina, 2 lime, 10 soda, 8£ water, and 3£ loss in 100 parts. It is found in granite, gneiss, trap rocks and lavas, at Calton Hill Edinburgh, at Talisker in Skye, in Dumbartonshire, in the Hartz, Bohemia, and at the Ferroe Islands, The variety found at Somma has been called sarcolite, from its flesh colour.* Analtsis. Chemical analysis consists ef a great variety of operations, perform- ed for the purpose of separating the com- ponent parts of bodies. In these opera- tions the most extensive knowledge of such properties of bodies as are already discovered must be applied, in order to produce simplicity of effect, and certainty in the results. Chemical analysis can hardly be executed with success by one who is not in possession of a considerable number of simple substances in a state of great purity, many of which, from their effects, are called reagents. The word analysis is applied by chemists to denote that series of operations, by which the component parts of bodies are determined, whether they be merely separated, or ex- hibited apart from each other; or whether these distinctive properties be exhibited by causing them to enter into new com- binations, without the perceptible inter- vention of a separate state. The forming of new combinations is called synthesis; and, in the chemical examination of bo- dies, analysis or separation can scarcely ever be effected, without synthesis taking place at the same time. As most of the improvements in the science of chemistry consist in bringing the art of analysis nearer to perfection, it is not easy to give any other rule to the learner than the general one of consulting and remarking the processes of the best chemists, such as Scheele, Bergmann, Berthollet, Kirwan, Vauquelin, and Ber- zelius. The bodies which present them- selves more frequently for examination than others, are minerals and mineral waters. In the examination of the former, it was the habit of the earlier chemists to avail themselves ofthe action of fire, with very few humid processes, which are such as might be performed in the usual tem- perature of the atmosphere. Modern chemists have improved the process by fire, by a very extensive use of the blow- pipe (see Blow-pipe); and have succeed- ed in determining the component parts of minerals to great accuracy in the humid way. For the method of analyzing min- eral waters,see Waters (Mineral); and for the analysis of metallic ores, see Ores. Several authors have written on the ex- amination of earths and stones. The first step in the examination of con- sistent earths or stones is somewhat dif- ferent from that of such as are pulveru- lent. Their specific gravity should first be examined; also their hardness, whe- ther they will strike fire with steel, or can be scratched by the nail, or only by crys- tal, or stones of still greater hardness; also their texture, perviousness to light, and whether they be manifestly homogeneous or compound species, &c. 2d, In some cases, we should try whe- ther they imbibe water, or whether water ANA ANA can extract any thing from them by ebul- lition or digestion. 3d, Whether they be soluble in, or ef- fervesce with, acids, before or after pul- verization; or whether decomposable by boiling in a strong solution of potash, &c. as gypsums and ponderous spars are. 4th, Whether they detonate with nitre. 5th, Whether they yield the fluor acid by distillation with sulphuric acid, or am- monia by distilling them with potash. 6th, Whether they be fusible pei' se with a blow-pipe, and how they are affected by soda, borax, and microcosmic salt; and whether they decrepitate when gradually heated. 7th, Stones that melt per se with the blow-pipe are certainly compound, and contain at least three species of earth, of which the calcareous is probably one ; and if they give fire with steel, the siliceous is probably another. The general process prescribed by the celebrated Vauquelin, in the 30th volume ofthe Annales de Chimie, is the clearest which has yet been offered to the chemi- cal student. If the mineral be very hard, it is to be ignited in a covered crucible of platinum, and then plunged into cold water, to ren- der it brittle and easily pulverizable. The weight should be noted before and after this operation, in order to see if any vola- tile matter has been emitted. For the pur- pose of reducing stones to an impalpable powder, little mortars of highly hardened steel are now made, consisting of a cylin- drical case and pestle. A mortar of agate is also used for subsequent levigation, About ten grains ofthe mineral should be treated at once; and after the whole 100 grains have been reduced in succession to an impalpable powder, they should be weighed, to find what increase may have been derived from the substance of the agate. This addition may be regarded as silica. Of the ten primary earths, only four are usually met with in minerals, viz. silica, alumina, magnesia, and lime, associated with some metallic oxides, which are com- monly iron, manganese, nickel, copper and chromium. If neither acid nor alkali be expected to be present, the mineral is mixed in a sil- ver crucible, with thrice its weight of pure potash and a little water. Heat is gradually applied to the covered crucible, and is finally raised to redness; at which temperature it ought to be maintained for an hour. If the mass, on inspection, be a perfect glass, silica may be regarded as the chief constituent of the stone; but if the vitrification be very imperfect and the bulk much increased, alumina may be supposed to predominate. A brownish or dull green colour indicates the presence of iron; a bright grass-green, which is imparted to water, that of manganese; and from a greenish-yellow, chromium may be expected. The crucible, still a little hot, being first wiped, is put into a capsule of porcelain or platinum; When, warm distilled water is poured upon the alkaline earthy mass, to detach it from the crucible. Having transferred the whole of it into the capsule, muriatic acid is pour- ed on, and a gentle heat applied, if neces- sary, to accomplish its solution. If the li- quid be of an orange-red colour, we infer the presence of iron; if of a golden-yellow, that of chromium; and if of a purplish- red, that of manganese. The solution is next to be evaporated to dryness, on a sand-bath, or over a lamp, taking care so to regulate the heat, that no particles be thrown out. Towards the end of the evaporation, it assumes a gelatinous con- sistence. At this period it must be stirred frequently with a platinum spatula or glass rod, to promote the disengagement ofthe muriatic acid gas. After this, the heat may be raised to fully 212° F. for a few minutes. Hot water is to be now poured on in considerable abundance, which dis- solves every thing except the silica. By filtration, this earth is separated from the liquid; and being edulcorated with hot water, it is then dried, ignited, and weigh- ed. It constitutes a fine white powder, in- soluble in acids, and feeling gritty be- tween the teeth. If it be coloured, a lit- tle dilute muriatic acid must be digested on it, to remove the adhering metallic particles, which must be added to the first solution. This must now be reduced by evaporation to the bulk of half a pint. Carbonate of potash being then added, till it indicates alkaline excess, the liquid must be made to boil for a little. A copious precipitation of the earth and oxides is thus produced. The whole is thrown on a filter, and after it is so drained as to as- sume a semi-solid consistence, it is re- moved by a platinum blade, and boiled in a capsule for some time, with solution of pure potash. Alumina and glucina are thus dissolved, while the other earths and the metallic oxides remain. This alkalino-earthy solution, separated from the rest by filtration, is to be treated with an excess of muriatic acid; after which carbonate of ammonia being added also in excess, the alumina is thrown down while the glucina continues dissolved. The first earth separated by filtration, washed, dried, and ignited, gives the quantity of alumina. The nature of this may be further demonstrated, by treating it with dilute sulphuric acid, and sulphate of potash, both in equivalent quantities, when the whole will be converted into ANA alum. (See Alum). The filtered liquid will deposite its glucina, on dissipating the ammonia, by ebullition. It is to be sepa- rated by filtration, to be washed, ignited, and weighed. The matter undissolved by the diges- tion of the liquid potash, may consist of lime, magnesia, and metallic oxides. Di- lute sulphuric acid must be digested on it for some time. The solution is to be evap- orated to dryness, and heated to expel the excess of acid. The saline solid mat- ter being now diffused in a moderate quantity of water, the sulphate of magne- sia will be dissolved, and along with the metallic sulphates, may be separated from the sulphate of lime by the filter. The latter being washed with a little water, dried, ignited, and weighed, gives, by the scale of equivalents, the quantity of lime in the mineral. The magnesian and metal- lic solution being diluted with a large quantity of water, is to be treated with bicarbonate of potash, which will precipi- tate the nickel, iron, and chromium, but ictain the magnesia and manganese, by the excess of carbonic acid. Hydrosulphu- ret of potash will throw down the manga- nese, from the magnesian solution. The addition of pure potash, aided by gentle ebullition, wiH then precipitate the mag- nesia. The oxide of manganese may be freed from the sulphuretted hydrogen,by ustulation. The mingled metallic oxides must be digested with abundance of nitric acid, to acidify the chromium. The liquid is next treated with potash, which forms a soluble chromate, while it throws down the iron and nickel. The chromic acid may be se- parated from the potash by muriatic acid, and digestion with heat, washed, dried till it becomes a green oxide, and weighed. The nickel is separated from the iron, by treating their solution in muriatic acid, with water of ammonia. The latter oxide which falls, may be separated by the filter, dried and weighed. By evaporating the liquid, and exposing the dry residue to a moderate heat, the ammoniacal salt will sublime and leave the oxide of nickel be- hind. The whole separate weights must now be collected in one amount, and if they constitute a sum within two per cent. of the primitive weight, the analysis may be regarded as giving a satisfactory ac- count of the composition of the mineral. But if the deficiency be considerable, then some volatile ingredient, or some alkali or alkaline salt, may be suspected. A portion of the mineral broken into small fragments, is to be ignited in a p»r- celain retort, to which a refrigerated re- ceiver is fitted. The water or other vola- tile and condensable matter, if any be pre- sent, will thus be obtained. But if no loss ANA of weight be sustained by ignition, alkali, or a volatile acid, may be looked for. The latter is usually the fluoric. It may be ex- pelled by digestion with sulphuric acid. It is exactly characterized by its property of corroding glass.* Beside this general method, some oth- ers may be used in particular cases. Thus, to discover a small portion of alu- mina or magnesia in a solution of a large quantity of lime, pure ammonia may be applied, which will precipitate the alumi- na or magnesia (if any be), but not the lime. Distilled vinegar applied to the pre- cipitate will discover whether it be alu- mina or magnesia. 2dly, A minute portion of lime or bary- tes, in a solution of alumina or magnesia, may be discovered by the sulphuric acid, which precipitates the lime and barytes : the solution should be dilute, else the alu- mina also would be precipitated. If there be not an excess of acid, the oxalic acid is btill a nicer test of lime: 100 grains of gypsum contain at out 33 of lime! 100 grains of sulphate of barytes contain 66 of barytes; 100 gTains of oxalate of lime con- tain 43.8 of lime. The insolubility of sul- phate of barytes in 500 times its weight of boiling water, sufficiently distinguishes it. From these data the quantities are easily investigated. Sdly, A minute proportion of alumina in a large quantity of magnesia may be dis- covered, either by precipitating the whole, and treating it with distilled vinegar; or by heating the solution nearly to ebulli- tion, and adding more carbonate of mag- nesia, until the solution is perfectly neu- tral, which it never is when alumina is con- tained in it, as this requires an excess of acid to keep it in solution. By these means the alumina is precipitated in the state of embryon alum, which contains about half its weight of alumina (or, for greater exactness, it may be decomposed by boiling it in volatile alkali). After the precipitation, the solution should be large- ly diluted, as the sulphate of magnesia, which remained in solution while hot, would precipitate when cold, and mix with the embryon alum. 4thly, A minute portion of magnesia in a large quantity of alumina is best separat- ed by precipitating the whole, and treat- ing the precipitate with distilled vinegar. Lastly, Lime and barytes are separated by precipitating both with the sulphuric acid, and evaporating the solution to a small compass, pouring off the liquor, and treating the dried precipitate with 500 times its weight of boiling water; what remains undissolved is sulphate of bary- tes. The inconveniences of employing much heat, are obvious, aud Mr. Lowitz informs ANA ANA us, that they may be avoided without the least disadvantage. Over the flame of a spirit lamp, that will hold an ounce and half, and is placed in a cylindrical tin fur- nace four inches high and three in diame- ter, with air-holes, and a cover perforated to hold the crucible, he boils the stone prepared as directed above, stirring it fre- quently. His crucible, which, as well as the spatula, is of very fine silver, holds two ounces and a half, or three ounces. As soon as the matter is boiled dry, I12 pours in as much hot witer as he used at first; and this he repeats two or three times more, if the refractoriness ofthe fos- sil require it. Large tough bubbles ari- sing during the boiling, are in general a sign that the process will be attended with success. Even the sapphire, though the most refractory of all Mr. Lowitz tried, was not more so in this than in the dry way. Sir H. Davy observes, that the boracic acid is very useful in analyzing stones that contain a fixed alkali; as its attraction for the different earths at the heat of ignition is considerable, and the compounds it forms with them are easily decomposed by the mineral acids dissolved in water. His process is as follows: Let 100 grains of the stone to be examined be reduced to a fine powder, mixed with 200 grains of boracic acid, and fused for about half an hour at a strong red heat in a crucible of platina or silver. Digest the fused mass in an ounce and half of nitric acid diluted with seven or eight times the quantity of water, till the whole is decomposed; and then evaporate the solution till it is re- duced to an ounce and half, or two ounces. If the stone contained silex, it will sepa- rate in this process, and must be collect- ed on a filter, and edulcorated with dis- tilled water, to separate the saline matter. The fluid, mixed with all the water that has been passed through the filter, being evaporated till reduced to about half a pint, is to be saturated with carbonate of ammonia, and boiled with an excess of this salt, till all that will precipitate has fallen down. The earths and metallic oxides being separated by filtration, mix nitric acid with the clear fluid till it has a strongly sour taste, and then evaporate till the boracic acid remains free. Filter the fluid, evaporate it to dryness, and ex- pose it to a heat of 450° F. when the ni- trate of ammonia will be decomposed, and the nitrate of potash or soda will re- main in the vessel. The earths and me- tallic oxides, that remained on the filter, may be distinguished by the common pro- cesses. The alumina may be separated by solution of potash, the lime by sulphu- ric acid, the oxide of iron by succinate of ammonia, the manganese by hydrosul- phuret of potash, and the magnesia by pure soda. * Lately carbonate or nitrate of barytes has been introduced into mineral analysis* with great advantage, for the fluxing of stones, that may contain alkaline matter. See the English Translation of M. The- nard's volume on analysis.* Under the head of mineral analysis, no- thing is of so much general importance as the examination of soils, with a view to the improvement of such as are less pro- ductive, by supplying the ingredients they want in due proportions to increase their fertility. To Lord Dundonald and Mr. Kirwan we are much indebted for their labours in this field of inquiry ; but Sir H. Davy, assisted by the labours of these gentlemen, the facts and observations of Mr. Young, and his own skill in chemis- try, having given at large, in a manner best adapted for the use of the practical farmer, an account ofthe methods to be pursued for this purpose, we shall here copy them. The substances found in soils are cer- tain mixtures or combinations of some of the primitive earths, animal and vegetable matter in a decomposing state, certain sa- line compounds, and the oxide of iron. These bodies always retain water, and ex- ist in very different proportions in differ- ent lands, and the end of analytical ex- periments is the detection of their quanti- ties and mode of union. The earths commonly found in soils are principally silex, or the earth of flints; alu- mina, or the pure matter of clay ; lime, or calcareous earth; and magnesia: for the characters of which see the articles. Si; lex composes a considerable part of hard gravelly soils, hard sandy soils, and hard stony lands. Alumina abounds most in clayey soils, and clayey loams; but even in the smallest particles of these soils, it is ge- nerally united with silex and oxide of iron. Lime always exists in soils in a state of com- bination, and chiefly with carbonic acid, when it is called carbonate of lime. This carbonate in its hardest state is marble ; in its softest, chalk. Lime united with sulphuric acid is sulphate of hme, or gyp- sum ; with phosphoric acid, phosphate of lime, or the earth of bones. Carbonate of lime, mixed with other substances, com- poses chalky soils and marls, and is found in soft sandy soils. Magnesia is rarely found in soils: when it is; it is combined with carbonic acid, or with silex and alu- mina. Animal decomposing matter exists in different states, contains much carbo- naceous substance, volatile alkali, inflam- mable aeriform products, and carbonic acid. It is found chiefly in lands lately manured. Vegetable decomposing mat- ter usually contains still more earbonacr- ANA ANA bus substance, and differs from the pre- ceding principally in not producing vola- tile alkali. It forms a great proportion of all peats, abounds in rich mould, and is found in larger or smaller quantities in all lands. The saline compounds are few, and in small quantity: they are chiefly muriate of soda, or common salt, sulphate of magnesia, muriate and sulphate of pot- ash, nitrate of lime, and the mild alkalis. Oxide of iron, which is the same with the »ust produced by exposing iron to air and water, is found in all soils, but most abun- dantly in red and yellow clays, and red and yellow siliceous sands. The instruments requisite for the analy- sis of soils are few. A pair of scales capa- ble of holding a quarter of a pound of common soil, and turning with a single grain when loaded: a set of weights, from a quarter of a pound troy to a grain: a wire sieve, coarse enough to let pepper- oorn pass through: an Argand lamp and stand : a few glass bottles, Hessian cruci- bles, and china or queen's ware evapora- ting basins : a Wedgwood pestle and mor- tar : some filters made of half a sheet of blotting paper, folded so as to contain a pint of liquid, and greased at the edges: a bone knife : and an apparatus for collect- ing and measuring aeriform fluids. The reagents necessary are muriatic acid, sulphuric acid, pure volatile alkali dissolved in water, solution of prussiate of potash, soap lye, and solutions of carbo- nate of ammonia, muriate of ammonia, neutral carbonate of potash, and nitrate of ammonia. 1. When the general nature ofthe soil •f a field is to be ascertained, specimens of it should be taken from different places, two or three inches below the surface, and examined as to the similarity of their pro- perties. It sometimes happens, that on plains the whole of the upper stratum of the land is of the same kind, and in this case one analysis will be sufficient. But in valleys, and near the beds of rivers, there are very great differences, and it now and then occurs, that one part of a field is calcareous, and another part silice- ous; and in this and analogous cases, the portions different from each other should be analyzed separately. Soils when col- lected, if they cannot be examined imme- diately, should be preserved in phials quite filled with them, and closed with ground glass stopples. The most conve- nient quantity for a perfect analysis is from two hundred grains to four hundred. It should be collected in dry weather, and exposed to the air till it feels dry. Its specific gravity may be ascertained, by in- troducing into a phial, which will contain a known quantity of water, equal bulks of water and of the soil; which may easi- ly be done, by pouring in water till th« phial is half full, and then adding the soil till the fluid rises to the mouth. The dif- ference between the weight of the water, and that of the soil, will give the result. Then if the bottle will contain four hun- dred grains of water, and gains two hun- dred grains when half filled with water and half with soil, the specific gravity of the soil will be 2; that is, it will be twice as heavy as water: and if it gained one hundred and sixty-five grains, its specific gravity would be 1825, water being 1000. It is of importance that the specific gravi- ty of a soil should be known, as it affords an indication of the quantity of animal and vegetable matter it contains; these sub- stances being always most abundant in the lighter soils. The other physical proper- ties of soils should likewise be examined before the analysis is made, as they de- note, to a certain extent, their composi- tion, and serve as guides in directing the experiments. Thus siliceous soils are generally rough to the touch, and scratch glass when rubbed upon it: aluminous soils adhere strongly to the tongue, and emit a strong earthy smell when breathed upon: and calcareous soils are soft, and much less adhesive than aluminous soils. 2. Soils, when as dry as they can be made by exposure to the air, still retain a considerable quantity of water, which ad- heres with great obstinacy to them, and cannot be driv en off without considerable heat: and the first process of analysis is to* free them from as much of this water as possible, without affecting their composi- tion in other respects. This may be done by heating the soil for ten or twelve minutes in a china basin over an Argand lamp, at a temperature equal to 300° F.; and if a thermometer be not used, the pro- per degree of heat may easily be ascer- tained by keeping a piece of wood in the basin in contact with its bottom; for as long as the colour ofthe wood remains un- altered, the heat is not too high; but as soon as it begins to be charred, the pro- cess must be stopped. In several expe- riments, in which Sir II. Davy collected the water that came over at this degree of heat, he found it pure, without any sensi- ble quantity of other volatile matter being produced. The loss of weight in this process must be carefully noted; and if it amount to 50 grains in 400 of the soil, this may be considered as in the greatest degree absorbent and retentive of water, and will generally be found to contain a large proportion of aluminous earth: if the loss be not more than 10 or 20 grains, the land may be considered as slightly ab- sorbent and retentive, and the siliceous earth as most abundant. 3. None of the loose stones, gravel, or ANA ANA 'large vegetable fibres, should be separa- ted from the soil, till the water is thus ex- pelled ; for these bodies are often highly absorbent and retentive, and consequent- ly influence the fertility ofthe land. But after the soil has been heated as above, these should be separated by the sieve, after the soil has been gently bruised in a mortar. The weights of the vegetable fibres or wood, and of the gravel and stones, should be separately noted down, and the nature of the latter ascertained: if they be calcareous, they will ell'erv esce with acids ; if siliceous, they will scratch glass ; if aluminous, they will be soft, easi- ly scratched with a knife, and incapable of effervescing with acids. 4. Most soils, beside stones and gravel, contain larger or smaller proportions of sand of different degrees of fineness; and the next operation necessary is to separate this sand from the parts more minutely di- vided, such as clay, loam, marl, and vege- table and animal matter. This may be done sufficientl. by mixing the soil well with water; as the coarse sand will gene- rally fall to the bottom in the space of a minute, and the finer in two or three ; so that by pouring the water off' after one, two, or three minutes, the sand will be for the most part separated from the other substances; which, with the water con- taining them, must be poured into a filter. After the water has passed through, what remains on the filter must be dried and weighed; as must also the sand; and their respective quantities must be noted down. The water must be preserved, as it will contain the saline matter, and the soluble animal or vegetable matter, if any existed in the soil. 5. A minute anatysis of the sand thus separated is seldom or never necessary, and its nature may be detected in the same way as that of the stones and gravel. It is always siliceous sand, or calcareous sand, or both together. If it consist wholly of carbonate of lime, it will dis- solve rapidly in muriatic acid with effer- vescence ; but if it consists partly of this and partly of siliceous matter, a residuum will be left after the acid has ceased to act on it, the acid being added till the mixture has a sour taste, and has ceased to effervesce. This residuum is the sili- ceous part; which being washed, dried, and heated strongly in a crucible, the difference of its weight from that ofthe whole, will indicate the quantity of the calcareous sand. 6. The finely divided matter .of the soil is usually very compound in its na- ture ; it sometimes contains all the four primitive earths of soils, as well as animal and vegetable matter; and to ascertain the proportions of these with tolerable Vo.fc. i> £22] accuracy, is the most difficult part of tlf? subject. The first process to be perform- ed in this part of the analysis is the expo- sure of the fine matter ofthe soil to the action of muriatic acid. This acid, dilu- ted with double its bulk of water, should be poured upon the earthy matter in an evaporating basin, in a quantity equal to twice the weight of the earthy matter. The mixture siiould be often s.irred, and suffered to remain for an hour, or an hour and half, before it is examined. If any carbonate of lime, or of magnesia, exist in the soil, they will have been dissolved in this time by the acid, which sometimes takes up likewise a little oxide of iron, but very seldom any alumina. The fluid should be passed through a filter; the solid matter collected, washed with dis- tilled or rain water, dried at a moderate heat, and weighed. Its loss will denote the quantity of solid matter taken up. The washings must be added to the solu- tion ; which, if not sour to the taste, must be made so by the addition ot fresh acid ; and a little solution of prussiate of potash must be mixed with the liquor. If a blue precipitate occur, it denotes the presence of oxide of iron, and the solu- tion ofthe prussiate must be dropped in, till no further effect is produced. To as- certain its quantity, it must be collected on a filter in the same manner as the other solid precipitates, and heated red: the result will be oxide of iron. Into the fluid freed from oxide of iron a solution of carbonate of potash must be poured till all effervescence ceases in it, and till its taste and smell indicate a considerable excess of alkaline salt. The precipitate that falls down is carbonate of lime; which must be collected qn a filter,, dried at a heat below that of redness, and after- ward weighed. The remaining fluid must be boiled for a quarter of an hour, when the magnesia, if there be any, will be pre- cipitated combined with carbonic acid, and its quantity must be ascertained in the same manner as that of the carbonate of lime. If any minute proportion of alu- mina should, from peculiar circumstances, be dissolved by the acid, it will be found in the precipitate with the carbonate of lime, and it may be separated from it by boiling for a few minutes with soap lye sufficient to cover the solid matter: for this lye dissolves alumina, without acting upon carbonate of lime. Should the fine- ly divided soil be sufficiently calcaieousto effervesce very strongly with acids, a sim- ple method of ascertaining the quantity of carbonate of lime, sufficiently accurate in all common cases, may be adopted. As carbonate of lime in all its states contains a determinate quantity of acid, which is abont 45 parts in a hundred by weight, ANA ANA the quantity of this acid given out during the effervescence occasioned by its solu- tion in a stronger acid, will indicate the quantity of carbonate of lime present. Thus, if you weigh separately one part of the matter of the soil, and two parts of the acid diluted with an equal quantity of water, and mix the acid slowly in small portions with the soil, till it ceases to oc- casion any effervescence, by weighing the mixture, and the acid that remains, you will find the quantity of carbonic acid lost; and for every four grains and half so lost you will estimate ten grains of carbonate of lime. You may also collect the carbonic acid in the pneumatic appa- ratus for the analysis of soils, described in the article Lakohvtoky; and allow for every ounce measure ofthe carbonic acid, two grains of carbonate of lime. 7. The quantity of insoluble animal and vegetable matter may next be ascertained with sufficient precision, by heating it to a strong red heat in a crucible over a com- mon fire, till no blackness remains in the mass, stirring it frequently meanwhile with a metallic wire. The loss of weight will ascertain the quantity of animal and vegetable matter there was, but not the proportions of each. If the smell emitted, during this process, resemble that of burnt feathers, it is a certain indication of the presence of some animal matter; and a copious blue flame almost always de- notes a considerable proportion of vege- table matter. Nitrate of ammonia, in the proportion of twenty grains to a hundred ofthe residuum of the soil, will greatly accelerate this process, if the operator be in haste; and not affect the result, as it will be decomposed and evaporate. 8. What remains after this decomposi- tion of the vegetable and animal matter, consists generally of minute particles of earthy matter, which are usually a mixture of alumina and silex with oxide of iron. To separate these, boil them two or three hours in sulphuric acid diluted with four times its weight of water, allowing a hun- dred and twenty grains of acid for every hundred grains of the residuum. If any thing remain undissolved by this acid, it may be considered as silex, and be sepa- rated, washed, dried, and weighed, in the usual manner. Carbonate of ammonia be- ing added to the solution in quantity more than sufficient to saturate the acid, the alumina will be precipitated; and the ox- ide of iron, if any, may be separated from the remaining liquid by boiling it. It scarcely ever happens, that any magnesia or lime escapes solution in the muriatic acid; but if it should, it will be found in the sulphuric acid; from which it maybe separated as directed above for the muri- atic, 'this method of analysis is sufficient- ly precise for all common purposes: but if very great accuracy be an object, the residuum after the incineration must be treated with potash, and in the manner in which stones are analyzed, as given in the first part of this article. 9. If the soil contained any salts, or soluble vegetable or animal matter, they will be found in the water used for sepa- rating the sand. This water must be evaporated to dryness at a heat below boiling. If the solid matter left be of a brown colour, and inflammable, it may be considered as partly vegetable extract. If its smell, when exposed to heat, be strong and fetid, it contains animal mu- cilaginous, or gelatinous matter. If it be white and transparent, it may be consid- ered as principally saline. Nitrate of pot- ash or of lime is indicated in this saline matter by its sparkling when thrown on burning coals: sulphate of magnesia may be detected by its bitter taste : and sul- phate of potash produces no alteration in a solution of carbonate of ammonia, but precipitates a solution of muriate of ba- rytes. 10. If sulphate or phosphate of lime be suspected in the soil, a particular process is requisite to detect it. A given weight of the entire soil, as four hundred grains for instance, must be mixed with one third as much powdered charcoal, and kept at a red heat in a crucible for half an hour. The mixture must then be boil- ed a quarter of an hour in half a pint of water, and the solution, being filtered, exposed some days to the open air. If any soluble quantity of sulphate of lime, or gypsum, existed in the soil, a while precipitate will gradually form in the fluid, and the weight of it will indicate the proportion. Phosphate of lime, if any be present, may be separated from the soil after the process for gypsum. Muriatic acid must be digested upon the soil in quantity more than sufficient to saturate the solu- ble earths. The solution must be eva- porated, and water poured upon the solid matter. This fluid will dissolve the com- pounds of earths with the muriatic acid, and leave the phosphate of lime un- touched. 11. When the examination of a soil is completed, the products should be classed, and their quantities added together; and if they nearly equal the original quantity of soil, the analysis may be considered as accurate. It must however be observed, that when phosphate or sulphate of lime is discovered by the independent process, No. 10, just mentioned, a correction must be made for the general process, by sub- tracting a sum equal to their weight from the quantity of carbonate of lime obtain- ANA ANA ed by precipitation from the muriatic acid. In arranging the products, the form should be in the order of the experiments by which they are obtained. Thus 400 grains of a good siliceous sandy soil may be sup- posed to contain, grains. Of water of absorption, 18 Of loose stones and gravel principal- ly siliceous, .... 42 Of undecompounded vegetable fi- bres, .....10 Of fine siliceous sand, - - 200 Of minutely divided matter, separa- ted by filtration, and consisting of, Carbonate of lime, - 25 Carbonate of magnesia, - 4 Matter destructible by heat, principally vegetable, - 10 Silex, .... 40 Alumina, ... 32 Oxide of iron, - - 4 Soluble matter, principally sul- phate of potash and vegeta- ble extract, 5 Gypsum, ... 3 Phosphate of lime, - 2 — 125 Amount of all the products, 395 Loss, ... 5 400 Tn this instance the loss is supposed small; but in general, in actual experi- ments, it will be found much greater, in consequence ofthe difficulty of collecting the whole quantities of the different pre- cipitates; and when it is within thirty for four hundred grains, there is no reason to suspect any want of due precision in the processes. 12. When the experimenter is become acquainted with the use of the different instruments, the properties of the re- agents, and the relations between the ex- ternal and chemical qualities of soils, he will seldom find it necessary to perform, in any one case, all the processes that have been described. When his soil, for instance, contains no notable proportion of calcareous matter, the action of the muriatic acid, No. 6. may be omitted: in examining peat soils, he will principally have to attend to the operation by fire and air, No. 7.; and in the analysis of chalks and loams, he will often be able to omit the experiment with sulphuric acid, No. 8. In the first trials that are made by per- sons unacquainted with chemistry, they must not expect much precision of result. Many difficulties will be met with ; but in overcoming them the most useful kind of practical knowledge will be obtained; and nothing is so instructive in experimen- tal science as the detection of mistakes. The correct analyst ought to be well grounded in general chemical informa- tion ; but perhaps there is no better mode of gaining it than that of attempting origi- nal investigations. In pursuing his ex- periments, he will be continually obliged to learn from books the history of the sub- stances he is employing or acting upon ; and his theoretical ideas will be more va- luable in being connected with practical operation, and acquired for the purpose of discovery. The analysis of vegetables requires vari- ous manipulations, and peculiar attention, as their principles are extremely liable to be altered by the processes to which they are subjected. It was long before this analysis was brought to any degree of per- fection. Some of the immediate materials of vegetables are separated to our hands by- Nature in a state of greater or less purity ; as the gums, resins, and balsams, that ex- ude from plants. The expressed juices contain various matters, that may be sepa- rated by the appropriate reagents. Mace- ration, infusion, and decoction in water, take up certain parts soluble in this men- struum ; and alcohol will extract others that water will not dissolve. The mode of separating and distinguishing these ma- terials will easily be collected from their characters, as given under the head Vege- table Kingdom, and under the different articles themselves. * As the ultimate constituents of all ve- getable substances are carbon, hydrogen, and oxygen, with occasionally azote, the problem of their final analysis resolves into a method of ascertaining the proportion of these elementary bodies. AIM. Gay-Lus- sac and Thenard contrived a very elegant apparatus for vegetable and animal analy- sis, in which the matter in a dried state was mixed with chlorate of potash, and formed into minute pellets. These pel- lets being projected through the interven- tion of a stop-cock of peculiar structure into an ignited glass tube, were instantly resolved into carbonic acid and water. The former product was received over mercury, and estimated by its condensa- tion with potash; the latter was intercep- ted by ignited muriate of lime, and was measured by the increase of weight which it communicates to this substance. By previous trials, the quantity of oxygen which a given weight of the chlorate of potash yielded by ignition was known ; and hence the carbon, hydrogen, and oxy- gen, derived from the organic substance, as well as the residual azote, of the gase- ous products. M. Berzelius modified the above appa- ratus, and employed the organic product ANA AMI in combination with a base, generally ox- ide of lead. He mixed a certain weight of this neutral compound with a known quantity of pure chlorate of potash, and triturated the whole with a large quantity of muriate of soda, for the purpose of mo- derating the subsequent combustion. This mingled dry powder is put into a glasstube about half an inch diameter, and eight or ten inches long, which is partially enclosed in a fold of tin-plate, hooped with iron wire. One end of the tube is hermeti- cally sealed beforehand, the other is now drawn to a pretty fine point by the blow pipe. This termination is inserted into a glass globe about an inch diameter, which joins it to a long tube containing dry muriate of lime in its middle, and dip- ping at its other extremity into the mer- cury of a pneumatic trough. The first tube, with its protecting tin case, being exposed gradually to ignition, the enclo- sed materials are resolved into carbonic acid, water, and azote, which come over, and are estimated as above described. M. Gay-Lussac has more recently employed peroxide of copper to mix with ihe or- ganic substance to be analyzed ; because while it yields its oxygen to hydrogen and carbon, it is not acied on by azote ; anu thus the errors resulting from the forma- tion of nitric acid with the chlorate of pot- ash are avoided. Berzelius has afforded satisfactory evidence by his analyses, that the simple apparatus which he employed is adequate to every purpose of chemical research. Dr. Prout has described, in the Annals of Philosophy for March 18 0, a very neat form of apparatus for comple- ting analyses of organic substances with the heat of a lamp. Hydrogen having the power in minute quantities of modifying the constitution ofthe organic bodies, re- quires to be estimated with corresponding minuteness. Mr. Porrett has very inge- niously suggested, that its quantity may be more accurately determined by the proportion of oxide of copper that is re- vived, than by the product of water. Di- lute sulphuric acid being digested on the residual cupreous powder, will instantly dissolve the oxide, and leave the reduced metal; whose weight will indicate, by the scale of equivalents, the hydrogen expen- ded in its reduction. One of hydrogen corresponds to 9 of water, and o2 of cop- per. Under the different vegetable and ani- mal products, we shall take care to state their ultimate constituents by the most correct and recent analyses. The pecu- liar substances which w ater, alcohol, ether, and other solvents, can separate from an organic body may be called the immedi- ate products of the vegetable or animal kingdom; while the carbon, hydrogen, oxygen, and azote, discoverable by i;.;ue' ous anal*, sis, are the ultimate constituent elements. To the former class belong sugar, gum, starch, oils, res.ns, gelaiin, urea, organic acids and alkalis, 6«.c. which see.* * Anatase. Octohedrite, oxide of tita- nium, rutile, and titam rutile. This mi- neral shows a variety of colours by re- flected light, from indigo-blue to reddish- brown. By transmitted light, it appears greenish-v ellow. It is found usually in small crystals, octohedrons, with isosceles triangular faces. Structure lamellar; it is semi-transparent, or opaque ; fragments splendent, adamantine; scratches glass; brittle ; sp. gr. 3.H5. It is a pure oxide of titanium. It has been found only in Dau- phiny and Norway; and is a very rare mi- neral. It occurs in granite, gneiss, mica slate, and transition limestone.* * Amia.usite. A massive mineial, of a flesh and sometimes rose-red colour. It is, however, occasionally crystallized in rectangular four-sided prisms, verging on rhomboids. The structure of the prisms is lamellar, with join's parallel to their sides. Translucent; scratches quartz; is easily broken; sp. gr. 3.165. Infusible by the blow-pipe ; in which respect it dif- fers from feldspar, though called felspath apyre by Haiiy. It is composed of 52 alu- mina, 32 silica, 8 potash. 2 oxide of iron, and 6 loss, Yauq. It belongs to primi* tive countries, and was first found in An- dalusia in Spain. It is found in mica slate in Aberdeenshire, and in the Isle of Unst; Dartmoor in Devonshire ; in mica slate at Killiney, near Dublin, and at Douce Moun- tain, county Wicklow.* * Andhlolitk. See Hahmotome.* * Anhydrite. Anhydrous gypsum. There are six varieties of it.— 1. Compact, has various shades, of white, blue, and red; massive and kidney-sha- ped ; dull aspect; splintery or conchoidal fracture ; translucent on the edges; is scratched by fluor, but scratches calc spar ; somewhat tough ; specific gravity 2.850. It is dry sulpha-, e of lime, with a trace of sea salt. It is found in the salt mines of Austria and Salzburg, and at the foot ofthe Harz mountains. 2. Granular, the scaly of Jameson. Is found in mas- sive concretions, of which the structure is confusedly foliated. White or bluish co- lour, of a pearly lustre; composition as above, with one per cent, of sea salt. It occurs in the salt mines of Halle ; sp. gr. 2.957. 3. Fibrous. Massive ; glimmer- ing, pearly lustre; fracture in delicate parallel fibres ; scarcely translucent; easi- ly broken. Found at Halle, Ischel, and near Brunswick. 4. Kadiated. Blue, some- times spotted with red; radiated, splen- dent fracture; partly splintery $ translti- ANI AN I i^ent; not bard; sp. gr. 2.940. 5. Spar- ry, or cube spar. Milk-white colour, pas- sing sometimes into grayish and reddish white; short four-sided prisms, having two of the opposite sides much broader than the other two ; and occasionally die lateral edges are truncated, whence re- sults an etglu-sided prism ; lustre, splen- dent, pearly. Foliated fracture. Three- fold rectangular cleavage. Cubical frag- ments. Translucent. Scratches calc spar. Brittle. Sp. gr. 2.9. This is tiie muna- •ue of some writers. It is doubly re- fracting. It is said to contain one per cent. of sea salt. It is found at Bex in Switzer- land, and Halle in the Tyrol. 6. Silicit'e- rous, or vulpinite. Massive concretions of a laminated structure, translucent on the edges splendent, and brittle. Gray- ish-white, veined with bluish-gray. Sp. gr. 2.88. It contains eight per cent, silex. The rest is sulphate of lune. tt is called by statuaries, Marmo bardiglio di Berga- mo, and takes a fine polish. It derives its name from Yulpino in Italy, where it accompanies lime.* Axil, or Nil This plant, from the leaves of which indigo is prepared, grows in America. Anmmal Kingdom. The various bodies around us, which form the objects of che- mical research, have all undergone a num- ber of combinations and decompositions before we take them in hand for exami- nation. These are all consequences of the same attractions or specific proper- ties that we avail ourselves of; and are modified likewise by virtue of the situa- tions and temperatures ofthe bodies pre- sented to each other. In the great mass of unorganized matter, the combinations appear to be much more simple than such as take place in the vessels of organized beings, namely, plants and animals : in the former of which there is not any pecu- liar structure of tubes conveying various fluids; and in the latter there is not only an elaborate system of vessels, but like- wise, for the most part, an augmentation of temperature. From such causes as these it is, that some of the substances afforded by animal bodies are never found either in vegetables or minerals; and so likewise in vegetables are found certain products never unequivocally met with among minerals. Hence, among the sys- tematical arrangements used by chemists, the most general is that which divides bodies into three kingdoms, the animal, the vegetable, and the mineral. Animal, as well as vegetable bodies, may be considered as peculiar apparatus for carrying on a determinate series of chemical operations. Vegetables seem capable of operating with fluids only, and at the temperature of the atmosphere, as we have just noticed. But most animals have a provision for mechanically divi- ding solids by mastication, which answers the same purpose as grinding, pounding, or levigation, does in our experiments; that is to say, it enlarges the quantity of surface to be acted upon by solvents. The process carried on in the stomach ap- pears to be ofthe same kind as that which we distinguish by the name of digestion; and the bowels, whatever other uses they may serve, evidently form an apparatus for filtering or conveying off the fluids ; while the more solid parts of the aliments, which are probably of such a nature as not to be rendered fluid, but by an alteration which would perhaps destroy the texture of the machine itself, are rejected as use- less. When this filtered fluid passes into the circulatory vessels, through which it is driven with considerable velocity Jiy the mechanical action of the heart, it is subjected, not only to all those changes which the chemical action of its parts is capable of producing, but is likewise ex- posed to the air of the atmosphere in the lungs, into which that elastic fluid is ad- mitted by the act of respiration. Here it undergoes a change of the same nature as happens to other combustible bodies when they combine with its vital part, or oxygen. This vital part becomes con- densed, and combines with the blood, at the same time that it gives out a large quantity of heat, in consequence of its own capacity for heat being diminished. A small portion of azote likewise is ab- sorbed, and carbonic acid is given out. Some curious experiments of Spallanza- ni show, that the lungs are not the sole organs by which these changes are ef- fected. Worms, insects, shells of land and sea animals, egg shells, fishes, dead animals, and parts of animals, even after they have become putrid, are capable of absorbing oxygen from the air, and giving out carbonic acid. They deprive atmos- pheric air of its oxygen as completely as phosphorus. Shells, however, lose this property when their organization is de- stroyed by age. Amphibia, deprived of their lungs, lived much longer in the open air, than others in air destitute of oxygen. It is remarkable, that a larva, weighing a few grains, would consume almost as much oxygen in a given time as one ofthe am- phibia a thousand times its bulk. Fishes, alive and dead, animals, and parts of ani- mals, confined under water in jars, ab- sorbed the oxygen ofthe atmospheric air over the water. Muscles, tendons, bones, brain, fat, and blood, all absorbed oxygen in different proportions; but the blood did not absorb most, and bile appeared not to absorb any. It would lead as too far from our pur- ANI ANI pose, if we were to attempt an explana- tion of the little we know respecting the manner in which the secretions or combi- nations that produce the various animal and vegetable substances are effected, or the uses of those substances in the economy of plants and animals. Most of them are very different from any of the products of the mineral kingdom. We shall therefore only add, that these or- ganized beings are so contrived, that their existence continues, and all their func- tions are performed, as long as the ves- sels are supplied with food or materials to occupy the place of such as are carried off' by evaporation from the surface, or otherwise; and as long as no great change is made, either by violence or disease, in those vessels, or the fluids they contain. But as soon as the entire process is inter- rupted in any very considerable degree, the^hemical arrangements become alter- ed; the temperature in land animals is changed; the minute vessels are acted upon and destroyed ; life ceases, and the admirable structure, being no longer suf- ficiently perfect, loses its figure, and re- turns, by new combinations and decom- positions, to the general mass of unorgani- zed matter, with a rapidity which is usual- ly greater, the more elaborate its construc- tion. \ Within the sphere of vitality, peculiar laws of decomposition and recomposition seem to prevail, in like manner as within the sphere ofthe voltaic circuit. Indeed each gland seems to have a capacity to induce peculiar corpuscular reactions, giving rise to its appropriate secretions. In the living stomach, food passes to the state of chyme ; when in the absence of life, the same matter, at the same tempera- ture, would putrefy.f The parts of vegetable or animal sub- stances may be obtained, for chemical examination, either by simple pres- sure, which empties the vessels of their contents; by digestion in water, or in other fluids, which dissolve certain parts, and often change their nature; by destruc- tive distillation, in which the application of a strong heat alters the combination of the parts, and causes the new products to pass over into the receiver in the order of their volatility; by spontaneous decom- position or fermentation, wherein the component parts take a new arrangement, and form compounds which did not for the most part exist in the organized sub- stance; or, lastly, the judicious chemist will avail himself of all these several methods singly, or in combination. He will, according to circumstances, separate the parts of an animal or vegetable sub- stance by pressure, assisted by heat; or by digestion or boiling in various fluids, added in the retort which contains the substance under examination. He will attend particularly to the products which pass over, whether they be permanently elastic, or subject to condensation in the temperatures we are able to produce. In some cases, he will suffer the spontaneous decomposition to precede the application of chemical methods; and in others, he will attentively mark the changes which the products of his operations undergo in the course of time, whether in closed ves- sels, or exposed to the open air. Thus it is, that, in surveying the ample field of nature, the philosophical chemist posses- ses numerous means of making discove- ries, if applied with judgment and sagaci- ty ; though the progress of discovery, so far from bringing us nearer the end of our pursuit, appears continually to open new scenes; and, by enlarging our powers of investigation, never fails to point out ad- ditional objects of enquiry. Animal and vegetable substances ap. proach each other by insensible gTada- tions; so that there is no simple product of the one which may not be found in greater or less quantity in the other. The most general distinctive character of ani- mal substances is that of affording volatile alkali by destructive distillation. Some plants, however, afford it likewise. Nei- ther contain it ready formed; but it ap- pears to be produced by the combination of hydrogen and azote, during the changes produced either by fire, or the putrefac- tive process. See Ammonia. Our knowledge of the products of the animal kingdom, by the help of chemical analysis, is not yet sufficiently matured to enable us to arrange them according to the nature of their component parts, which appear to consist chiefly of hydro- gen, oxygen, carbon, and azote ; and with these, sulphur, phosphorus, lime, magne- sia, and soda, are frequently combined in variable proportions. * The following are the peculiar chem- ical products of animal organization. Ge- latin, albumen, fibrin, caseous matter, co- louring matter of blood, mucus, urea, pi- cromel, osmazome, sugar of milk, and sugar of diabetes. The compound animal products are the various solids and fluids, whether healthy or morbid, that are found in the animal body; such as muscle, skin, bone, blood, urine, bile, morbid concre- tions, brain, 8cc* When animal substances are left expo- sed to the air, or immersed in water or other fluids, they suffer a spontaneous change, which is more or less rapid ac- cording to circumstances. The sponta- neous change of organized bodies is dis- tinguished by the name of fermentation. In vegetable bodies there are distinct sta- ANN ANN ges or periods of this process, which have been divided into the vinous, acetous, and putrefactive fermentations. Animal sub- stances are susceptible only of the two latter, during which, as in all other spon- taneous changes, the combinations of chemical principles become in general more and more simple. There is no doubt but much instruction might be obtained from accurate observations of the putre- factive processes in all their several va- rieties and situations; but the loathsome- ness and danger attending on such enqui- ries have hitherto greatly retarded our progress in this department of chemical science. See Fermentation (Putrefac- tive). . r . Anime, improperly called gum anime, is a resinous substance imported from New Spain and the Brazils. There are two kinds, distinguished by the names of ori- ental and occidental. The former is dry, and of an uncertain colour, some speci- mens being greenish, some reddish, and some of the brown colour of myrrh. The latter is in yellowish, white, transparent, somewhat unctuous tears, and partly in larger masses, brittle, of a light pleasant taste, easily melting in the fire, and burn- ing with an agreeable smell. Like resins, it is totally soluble in alcohol, and also in oil. Water takes up about l-16th of the weight of this resin by decoction. The spirit, drawn off by distillation, has a con- siderable degree of the taste and flavour ofthe anime ; the distilled water discovers on its surface some small portion of essen- tial oil. This resin is used by perfumers, and also in certain plasters, wherein it has been supposed to be of service in nervous affections ofthe head and other parts; but there are no reasons to think that, for medical purposes, it differs from common resins. Anneal. We know too little of the arrangement of particles, to determine what it is that constitutes or produces brittleness in any substance. In a consid- erable number of instances of bodies which are capable of undergoing ignition, it is found that sudden cooling renders them hard and brittle. This is a real in- convenience in glass, and also in steel, when this metallic substance is required to be soft and flexible. The inconve- niences are avoided by cooling them very gradually, and this process is called an- nealing. Glass vessels, or other articles, are carried into an oven or apartment near the great furnace, called the leer, where they are permitted to cool, in a greater or less time, according to their thickness and bulk. The annealing of steel, or other metallic bodies, consists simply in heating them, and suffering them to cool again either upon the hearth of the furnace, or in any other situation where the heat is moderate, or at least the temperature is not very cold. \ Malleability, ductility and toughness, in substances susceptible ofthe annealing process, are probably dependent on the quantity of caloric remaining in combina- tion with their particles, while in the solid state. When malleable metals are ham- mered, they give out heat and become harder, more rigid and more dense, until a certain maximum is attained. After- wards they neither heat nor harden, and crush to pieces, if the process be not suspended. Exposed to the fire until softened, on cooling they are found to have regained the properties of which percussion had deprived them ; and they may be again hammered, heated, harden- ed, and condensed. The sudden abstrac- tion of caloric from the exterior strata of particles in a piece of thick glass, is not attended by a corresponding abstraction of this principle from among the particles within, owing to the slowness, with which glass conducts heat. Hence cohesion is not general; and the particles are not ar- ranged uniformly, unless the cooling be very slow, so as to allow the refrigera- tion, within and without, to be nearly si- multaneous. As it never can be perfectly simultaneous in thick glass, it is never perfectly well annealed. The process would be more perfect, were the articlei subjected to radiant heat only; as this, when projected from red-hot surfaces, penetrates through glass, as I have ascer- tained. By gradually making up fires of charcoal at about 4 inches distance on each side of a glass tube of about an inch and a quarter in thickness, and with a very small bore, I was enabled to heat and bend it. From its situation, it was only subjected to radiant heat.f Annotto. The pellicles of the seeds of the bixa orellana, a liliaceous shrub, from 15 to 20 feet high in good ground, afford the red masses brought into En- rope, under the name of Annotto, Orlean, and Roucou. The annotto commonly met with among us is moderately hard, of a brown colour on the outside, and a dull red within. It is difficultly acted upon by water, and tin- ges the liquor only of a pale brownish yellow colour. In rectified spirit of wine it very readily dissolves, and communi- cates a high orange or yellowish-red. Hence it is used as an ingredient in var- nishes, for giving more or less of an orange cast to the simple yellows. Alka- line salt renders it perfectly soluble in boiling water, without altering its colour. Besides its use in dyeing, it is employed for colouring cheese ANT ANT * Anthophtllite. A massive mineral of a brownish colour; sometimes also crys- tallized, in thin fiat six sided prisms, streaked lengthwise. It has a false metal- lic lustre, glistening and pearly. In crys- tals, transparent. Massive, only translu- cent on the edges. It does not scratch glass, but fluate ot lime. Specific grav- ity 3.2. Somewhat hard but exceeding- ly brittle. Infusible alone before the blow-pipe, but with borax it gives a grass- green transparent bead. It consists of 56 silica, 13.3 alumina, 14 magnesia. 3.33 lime, 6 oxide of iron, 3 oxide of manganese, 1.43 water, and 2.94 loss in 100. It is found Konigsberg in Norway.* * Anthracite. Blind coal, Kilkenny coal, or glance-coal. There are three va- rieties. 1. Massive, the conchoidal of Ja- meson. Its colour is iron-black, some- times tarnished on the surface, with a splendent metallic lustre. Fracture con- choidal, with a pseudo-metallic lustre. It is brittle and light. It yields no flame, and leaves whitish ashes. It is found in the newest floetz formations, at Mcissner in Hesse a-.id Walsall in Staffordshire. 2. Slaty anthracite. Colour black, or brown- ish-black. Imperfect slaty in one direc- tion, with a slight metallic lustre. Brittle. Specific gravity 1.4 to 1.8. Consumes without flame. It is composed of 72 car- bon, 13 silica, 3.3 alumina, and 3.5 oxide of iron. It is found in both primitive and se- condary rocks; at Calton Hill, Edinburgh; near Walsall Staffordshire ; in the south- ern parts of Brecknockshire, Carmarthen- shire, and Pembrokeshire, whence it is called Welsh culm; near Cumnock, and Kilmarnock, Ayrshire; and most abun- dantly at Kilkenny, Ireland. 3. Colum- nar anthracite. In small short prisma- tic concretions, of an iron-black colour with a tarnished metallic lustre. It isbrittle, soft, and light. It yields no flame or smoke. It forms a thick bed near Sanquhar, in Dumfries-shire; at Saltcoats and New Cumnock, in Ayrshire, It occurs also at Meissner in Hesse.* Antimont. The word antimony is al- ways used in commerce to denote a metal- lic ore, consisting of sulphur combined with the metal, which is properly called antimony. Sometimes this sulphuret is termed crude antimony, to distinguish it from the pure metal, or regulus, as it was formerly called. According to Professor Proust, the sulphuret contains 26 per cent of sulphur. He heated 100 parts of anti- mony with an equal weight of sulphur in a glass retort, till the whole was well fu- sed and the excess of sulphur expelled, and the sulphuret remaining was 135. The result was the same after repeated trials: 100 parts of antimony, with 300 of red sulphuret of mercury, afforded 135 to 136 of sulphuret. These artificial sulphu- rets lost nothing by being kept in fusion an hour; and heated with an equal weight of sulphur, they could not be made to take up more. Some ofthe native sulphu- rets of the shops, however, appear to have a small portion more of sulphur uni- ted with them, as they will take up an ad- dition of 7 or 8 per cent of antimony. Antimony is of a dusky white colour, ven brittle, and of a plated or scaly tex- ture. Its specific gravity, according to Brisson, is 6.7^21, but Bergmann makes it 6.86. Soon after ignition it melts, and by a continuance of the heat it becomes oxidized, and rises in white fumes, which may afterwards be volatilized a second time, or fused into a hyacinthine glass, ac- cording to the management of the heat: the first were formerly called argentine flowers of regulus of antimony. In closed vessels the antimony rises totally without decomposition. This metallic substance is not subject to rust by exposure to air, though its surface becomes tarnished by that means Its oxides are a little soluble in water; and in this respect they resem- ble the oxide of arsenic, by an approach toward the acid state. * There are certainly three, probably four, distinct combinations of antimony and ox\ gen : 1. The protoxide of Berze- lius is a blackish-gray powder, obtained fromamixture of powder of antimony and water, at the positive pole of a voltaic cir- cuit. Heat enables this oxide to absorb oxygen rapidly, converting it into the tri- toxide. According to Berzelius, it con- sists of 100 of metal, and 4.65 oxygen. It must be confessed, however, that the data for fixing these proportions are very doubtful. 2. The deutoxide may be ob- tained by digesting the metal in powder in muriatic ac d, and pouring the solution into water of potash. Wash and dry the precipitate. It is a powder of a dirty white colour, which melts at a moderate red heat, and crystallizes as it cools. Accord- ing to Berzelius, it consists of 84.3 metal -f- 15.7 oxygen. 3. The tritoxide, or an- timonious acid, is the immediate product of the combustion of the metal, called of old from its fine white colour, the a'gen- tine flowers of ant mony. It may also be formed by digesting hot nitric acid on an- timony. When fused with one-fourth of antimony, the whole becomes deutoxide. It forms the salts called antimonites with the different bases. According to Berze- lius, the tritoxide consists of about 80 me- tal -f- 20 oxygen. 4. The peroxide, or antimonic acid, is formed, when the metal in powder is ignited along with six times its weight of nitre in a silver crucible. The excess of potash and nitre being af- terwards separated by hot water, the a«ti« ANT ANT inornate of potash is then to be decomposed by muriatic acid, when the insoluble anti- monic acid of a straw colour will be ob- tained. Nitro-muriatic acid likewise con- verts the metal into the peroxide. Though insoluble in water, it reddens the vegeta- ble blues. It does not combine with acids. At a red heat oxygen is disengaged, and antimonious acid results. Berzelius infers its composition to be 73.5 metal -f- 26.5 oxygen. It is difficult to reconcile the above three portions of oxygen to one prime equivalent for antimony. The num- ber 11. gives the best approximation to Ber- zelius's analyses. We shall then have the In 100 parts. Protoxide llmetal+loxy.or9l.f+ 8.13 Deutoxide 11 +2 84.6+15.4 Tritoxide 11 +3 78.64-21.4 Peroxide 11 +4- 73.4+26.6 The second and fourth numbers agree perfectly with experiment; the first ox- ide is too imperfectly known to enter into the argument; and the third number, though it indicates a little more oxygen than Berzelius assigns, gives less than Proust. Chlorine gas and antimony combine with combustion, and a bichloride results. This was formerly prepared by distilling a mixture of two parts of corrosive subli- mate with one of antimony. The sub- stance which came over having a fatty consistence, was called butter of antimony. It is frequently crystallized in four-sided prisms. It is fusible and volatile at a mo- derate heat; and is resolved by water alone into the white oxide and muriatic acid. Being a bichloride, it is eminently corrosive, like the bichloride of mercury, from which it is formed. It consists of 45.7 chlorine + 54.3 antimony, according to Dr. John Davy's analysis, when the com- position ofthe sulphuret is corrected by its recent exact analysis by Berzelius. But 11. antimony + 2 primes chlorine = 9.0, give the proportion per cent of 44.1 + 55.5; a good coincidence, if we consider the circuitous process by which Dr. Da- vy's analysis was performed. Three parts of corrosive sublimate, and one of metallic antimony, are the equivalent proportions for making butter of antimo- ny. Iodine and antimony combine by the aid of heat into a solid iodide, of a dark-red colour. The phosphuret of this metal is obtained by fusing it with solid phosphoric acid. It it a white semi-crys- talline substance. The sulphuret of.anti- mony exists abundantly in nature. See Ores of Antimony. It consists, according to Berzelius, of 100 antimony + 37.25 sulphur The proportion given by the equivalent ratio is 100 + 36.5. Other Vol. i. [ 23 J. * analysts have found 30, 33, and 35 to 100 of metal. Berzelius admits that there may be a slight error in his numbers. The on- ly important alloys of antimony are those of lead and tin; the former constitutes type metal, and contains about one-six- teenth of antimony; the latter alloy is em- ployed for making the plates on which music is engraved. The salts of antimony are of two diffe- rent orders; in the first, the deutoxide acts the part of a salifiable base; in the second, the tritoxide and peroxide, act the part of acids, neutralizing the alkaline and other bases, to constitute the antimo- nites and antimoniates. The only distinct combination of the first order entitled to our attention, is the triple salt called tartrate of potash and an- timony, or tartar emetic, and which, by M. Gay-Lussac's new views, would be styled cream-tartrate of antimony. This constitutes a valuable and powerful medi- cine, and therefore the mode of preparing it should be correctly and clearly defined. As the dull white deutoxide of antimony is the true basis of this compound salt, and as that oxide readily passes by mis- management into the tritoxide or antimo- nious acid, which is altogether unfit for the purpose, adequate pains should be taken to guard against so capital an error. In former editions of the British Pharma- copoeias, the glass of antimony was pre- scribed as the basis of tartar emetic. More complex and precarious formulae have been since introduced. The new edition of the PharmacopJe Francaise has given a recipe, which appears, with a slight change of proportions, to be unexception- able. Take of the sulphuretted vitreous oxide of antimony levigated, and acidulous tartrate of potash, equal parts. Form a powder, which is to be put into an earthen or silver vessel, with a sufficient quantity of pure water. Boil the mixture for half an hour, adding boiling water from time to time ; filter the hot liquor, and evapo- rate to dryness in a porcelain capsule; dissolve in boiling water the result ofthe. evaporation, evaporate till the solution ac- quires the spec. grav. 1.161, and then let it repose, that crystals be obtained, which, by this process, will be pure. By another recipe, copied, with some alteration from Mr. Phillips's prescription, into the ap- pendix of the French Pharmacopoeia, a subsulphate of antimony is formed first of all, by digesting two parts of sulphuret of antimony in a moderate heat, with three parts of oil of vitriol. This insoluble sub- sulphate being well washed, is then di- gested in a quantity of boiling water, with its own weight of cream of tartar, and eva- porated to the density 1.161, after which it is filtered hot. On cooling, crystals of ANT ANT the triple tartrate are obtained. One might imagine, that there is a chance of obtaining by this process, a mixture of sul- phate of potash, and perhaps of a triple sulphate of antimony, along with the tartar emetic. Probably this does not happen, for it is said to yield crystals, very pure, very white, and without any mixture whatever. Pure tartar emetic is in colourless and transparent tetrahedrons or octohedrons. It reddens litmus. Its taste is nauseous and caustic. Exposed to the air, it efflo- resces slowly. Boiling water dissolves half its weight, and cold water a fifteenth part. Sulphuric, nitric, and muriatic acids, when poured into a solution of this salt, precipitate its cream of tartar; and soda, potash, ammonia, or their carbonates, throw down its oxide of antimony. Bary- tes, strontites, and lime waters, occasion not only a precipitate of oxide of antimo- ny, like the alkalis, but also insoluble tar- trates of these earths. That produced by the alkaline hydrosulphurets, is wholly forme J of kermes ; while that caused by sulphuretted hydrogen, contains both kermes and cream of tartar. The decoc- tions of several varieties of cinchona, and of several bitter and astringent plants, equally decompose tartar emetic ; and the precipitate then always consists ofthe ox- ide of antimony, combined with the vege- table matter and cream of tartar. Physi- cians ought therefore to beware of such incompatible mixtures. When tartar eme- tic is exposed to a red heat, it first black- ens, like all organic compounds, and af- terwards leaves a residuum of metallic an- timony and subcarbonate of potash. From this phenomenon, and the deep brownish- red precipitate, by hydrosulphurets, this antimonial combination may readily be re- cognized. The precipitate may further be dried on a filter, and ignited with black flux, when a globule of metallic antimony will be obtained. Infusion of galls is an active precipitant of tartar emetic. This salt, in an undue dose, is capable of acting as a poison. The best antidotes are demulcent drinks, infusions of bark, tea, and sulphuretted hydrogen water, which instantly converts the energetic salt into a relatively mild sulphuret: ano- dynes are useful afterwards. The powder of tartar emetic, mixed with hog's-lard, and applied to the skin of the human bo- dy, raises small vesications. The composition of this salt, according to M. Thenard, is 35.4 acid, 39.6 oxide, 16.7 potash, and 8.2 water. The presence of the latter ingredient is obvious, from the undisputed phenomenon of efflores- cence. If we adopt the new views of M. Gay-Lussac, this salt may be a compound of a prime equivalent of tartar = 23.825, with a prime equivalent of deutoxide ot antimony = 13. On this hypothesis we would have the following proportions: 2 primes acid = 16.75 45.4 1 prime potash = 5.95 16.2 1 prime water = 1.125 3.1 1 oxide of antimony = 13.00 35.3 36.825 100.0 But very little confidence can be reposed in such atomical representations. The deutoxide seems to have the pro- perty of combining with sulphur in vari- ous proportions. To this species of com- pound must be referred the liver of anti- mony, glass of antimony, and crocus metal- lorum of the ancient apothecaries. Sul- phuretted hydrogen forms, with the deu- toxide of antimony, a compound which possessed at one time great celebrity in medicine, and of which a modification has lately been introduced into the art of cal- ico printing. By dropping hydrosulphu- ret of potash, or of ammonia, into the cream-tartrate, or into mild muriate of an- timony, the hydrosulphuret of the metal- lic oxide precipitates of a beautiful deep orange colour. This is kermes mineral. Cluzcl's process for obtaining a fine ker- mes, light, velvety, and of a deep purple- brown, is the following: one part of pul- verized sulphuret of antimony, 22$ parts of crystallized subcarbonate of soda, and 200 parts of water, are to be boiled to- gether in an iron pot. Filter the hot li- quor into warm earthen pans, and allow them to cool very slowly. At the end of 24 hours the kermes is deposited. Throw it on a filter, wash it with water which had been boiled and then cooled out of contact with air. Dry the kermes at a temperature of 85°, and preserve in cork- ed phials. Whatever may be the process employed, by boiling the liquor after cool- ing and filtration, on new sulphuret of an- timony, or upon that which was left in the former operation, this new liquid will de- posite, on cooling, a new quantity of ker- mes. Besides the hydrosulphuretted oxide of antimony, there is formed a sulphuret- ted hydrosulphuret of potash or soda. Consequently, the alkali seizes a portion ofthe sulphur from the antimonial sulphu- ret, water is decomposed, and whilst a portion of its hydrogen unites to the alka- line sulphuret, its oxygen, and the other portion of its hydrogen, combine with the sulphuretted antimony. It seems, that the resulting kermes remains dissolved in the sulphuretted hydrosulphuret of potash or soda; but as it is less soluble in the cold than the hot, it is partially precipitated by refrigeration. If we pour into the super- natant liquid, after the kermes is deposi- ted and removed, any acid, as the dilute ANT APL "Uric, sulphuric, or muriatic, we decom- pose the sulphuretted hydrosulphuret of potash or soda. The alkaline base being laid hold of, the sulphuretted hydrogen and sulphur to which they were united are set at liberty; the sulphur and kermes fall together, combine with it, and form an orange-coloured compound, called the golden sulphuret of antimony. It is a hy- droguretted sulphuret of antimony. Hence, when it is digested with warm muriatic acid, a large residuum of sulphur is ob- tained, amounting sometimes to 12 per cent. Kermes is composed by Thenard, of 20.3 sulphuretted hydrogen, 4.15 sul- phur, 72 76 oxide of antimony, 2.79 water and loss; and the golden sulphuret con- sists of 17.87 sulphuretted hydrogen, 68.3 oxide of antimony, and 12 sulphur. By evaporating the supernatant kermes liquid, and cooling, crystals form, which have been lately employed by the calico printer, to give a topical orange. These crystals are dissolved in water, and the so- lution being thickened with paste or gum, is applied to cloth in the usual way. When the cloth is dried, it is passed through a dilute acid, when the orange precipitate is deposited and fixed on the vegetable fibres. An empirical antimonial medicine, called James's powder, has been much used in this country. The inventor called it his fever powder, and was so successful in his practice with it, that it obtained very great reputation, which it still in some measure retains. Probably, the success of Dr. James was in great measure owing to his free use ofthe bark, which he always gave as largely as the stomach would bear, as soon as he had completely evacu- ated the primx viae by the use of his antimo- nial preparation, with which at first he used to combine some mercurial. His spe- cification, lodged in chancery, is as follows: " Take antimony, calcine it with a con- tinued protracted heat, in aflat, unglazed, earthen vessel addingto it from time to time a sufficient quantity of any animal oil and salt, well dephlegmated; then boil it in melted nitre for a considerable time, and separate the powder from the nitre by •dissolving it in water." The real recipe has been studiously concealed, and a false one published in its stead. Different for- mulae have been offered for imitating it. That of Dr. Pearson furnishes a mere mix- ture of an oxide of antimony, with phos- phate of lime. The real powder of James, according to this chemist, consists of 57 oxide of antimony, with 43 phosphate of lime. It seems highly probable that super- phosphate of lime would act on oxide of antimony, in a way somewhat similar to cream of tartar, and produce a more che- mical combination, than what can be de- rived from a precarious ustulation and cal- cination of hartshorn shavings and sul- phuret of antimony, in ordinary hands. The antimonial medicines are powerful deobstruents, promoting particularly the cuticular discharge. The union of this metallic oxide with sulphuretted hydro- gen, ought undoubtedly to favour its me- dicinal agency in chronic diseases of the skin. The kermes deserves more credit than it has hitherto received from British physicians. The compounds formed by the antimo- nious and antimonic acids, with the bases, have not been applied to any use. Muriate of barytes may be employed as a test for tartar emetic. It will show, by a precipi- tate insoluble in nitric acid, if sulphate of potash be present. If the crystals be re- gularly formed, mere tartar need not be suspected.* For its ores, and the reduction of the metals, see Ores. Ants. See Acid (Formic). * Apatite. Phosphate of lime. This mineral occurs both massive and crystal- lized. The crystals are six-sided prisms, low, and sometimes passing into the six- sided table. Lateral edges, frequently truncated, and the faces smooth. Lustre splendent. Translucent, rarely transpa- rent. Scratched by fluor spar. Brittle. Colours, white, wine-yellow, green, and red. Sp. grav. 3.1. Phosphoresces on coals. Electric by heat and friction. Con- sists of 53.75 lime + 46.25 phosphoric acid, by Klaproth's analysis of the variety called asparagus stone. It occurs in pri- mitive rocks; in the tin veins of the gra- nite of St. Michael's Mount, Cornwall; near Chudleigh in Devonshire ; at Nantes in France ; in St. Gothard, and in Spain ; and with molybdena in granite, near Col- beck, Cumberland. Phosphorite is mas- sive, forming great beds in the province of Estremadura. Yellowish-white colour. Dull or glimmering lustre. Semi-hard. Fracture, imperfect curved foliated. Brit- tle. Sp. grav. 2.8. Phosphorescent with heat. Its composition by Pelletier is 59 lime, 34 phosphoric acid, 1 carbonic acid, 2.5 fluoric acid, 2 silica, 1 oxide of iron, and 0.5 muriatic acid.* * Aiuirite. Earth foam; Schaumcrde. This carbonate of lime occurs usually in a friable state; but sometimes solid. Co- lour, almost silver-white. Massive, or in fine particles. Shining lustre, between semi-metallic and pearly. Fracture, curved foliated. Opaque; soils a little. Aery soft, and easily cut. Feels fine and light. It is usually found in calcareous veins, at Gera in Misnia, andEisleben in Thiiringia. It consists, by Bucholz, of 51.5 liinc, 39 acid, 1 water, 5.7 silica, 3.3 oxide of iron.* * Aplome. Tiiis is commonly consider- AQTJ ARC ed to be a variety ofthe garnet; but the difference between these minerals is this: the planes of the aplome dodecahedrons are striated parallel with their smaller di- agonal, which, according to Haiiy, indi- cates the primitive form to be a cube, and not a dodecahedron. Its colour is deep orange-brown. It is opaque, and harder than quartz. Sp. grav. is much less than garnet, viz. 3.44. It consists, by Laugier's analysis, of 4U silica, 20 alumina, 14.5 lime, 14 oxide of iron, 2 oxide of manga- nese, 2 silica and iron. It is fusible into a black glass, while garnet fuses into a black enamel. It is found on the river Lena in Siberia, and also in New Holland.* * ArorHYLLiTE. Ichthvophthalmite. Fisheyestone. It is found both massive and crystallized. It occurs in square prisms, whose solid angles are sometimes replaced by triangular planes, or the prisms are terminated by pyramids con- sisting of 4 rhomboidal planes. Structure lamellar; cross fracture, fine grained, un- even. External lustre, splendent, and pe- culiar; internal, glistening and pearly. Semi-transparent, or translucent. Mode- rately hard, and easily broken. Sp. gr. 2.49. It exfoliates, then froths, and melts into an opaque bead before the blow-pipe. It consists of 51 silica, 28 lime, 4 potash, 17 water. Vauquelin. It is found in the iron mine of Utoe in Sweden; at the cop- per mine of Fahlun ; at Arendahl, Faroe, the Tyrol; and Dr. Mac Culloch met with a solitary crystal in Dunvegan, in the Isle of Sky.* Apparatus. See Laboratory. Apples. See Acid (Malic). Apyrous. Bodies which sustain the ac- tion of a strong heat for a considerable time, without change of figure or other properties, have been called apyrous; but the word is seldom used in the art of chemistry. It is synonymous with re- fractory. Aquafortis. This name is given to a weak and impure nitric acid, commonly used in the arts. It is distinguished by the terms double and single, the single being only half the strength ofthe other. The artists who use these acids call the more concentrated acid, which is much stronger even than the double aquafortis, spirit of nitre. 1'his distinction appears to be of some utility, and is therefore not im- properly retained by chemical writers. See Acid (Nitric). * Aq.ua Marine. See Beryl.* Aqua Reoia, or Regis. This acid, be- ing compounded of a mixture ofthe nitric and muriatic acids, is now termed by chemists nitro-muriatic acid. Aqua Vit.e. Ardent spirit of the first distillation has been distinguished in com- merce by tills name. The distillers of malt and molasses spirits call it low* wines. AauiLA Alba. One ofthe names given to the combination of muriatic acid and mercury in that state, which is more com- monly known by the denomination of mercurius dulcis, calomel, or mild muriate of mercury. Arabic (Gu?i). This is reckoned the purest of gums, and does not greatly dif- fer from gum Senegal, vulgarly called gum seneca, which is supposed to be the strongest, and is on this account, as well as its greater plenty and cheapness, most- ly used by calico printers and other ma- nufacturers. The gums of the plum and cherry-tree have nearly the same qualities as gum arabic. All these substances fa- cilitate the mixture of oils with water. Arabie Lands. It is a problem in che- mistry, and by no means one of the least importance to society to determine what are the requisites which distinguish fruit- ful lands from such as are less productive. See Soils, and Analysis of Soils. Arbor Dian^e. See Silver. Archil, Archilla, Rocella, Orsetlle. A whitish lichen, growing upon rocks in the Canary and Cape Verd Islands, which yields a rich purple tincture, fugitive in- deed, but extremely beautiful. This weed is imported to us as it is gathered : those who prepare it for the use of the dyer, grind it betwixt stones, so as thoroughly to bruise, but not to reduce it into pow- der, and then moisten it occasionally with a strong spirit of urine, or urine itself mixed with quicklime : in a few days it acquires a purplish-red, and at length a blue colour; in the first state it is called archil, in the latter lacmus or litmus. The dyers rarely employ this drug by itself, on account of its dearness, and the perishableness of its beauty. The chief use they make of it is for giving a bloom to other colours, as pinks, &c. This is effected by passing the dyed cloth or silk through hot water slightly impregnated with the archil. The bloom thus commu- nicated soon decays upon exposure to the air. Mr. Hellot informs us, that by the addition of a little solution of tin, this drug gives a durable dye; that its colour is at the same time changed toward a scarlet; and that it is the more permanent, in pro- portion as it recedes the more from its natural colour. Prepared archil very readily gives out its colour to water, to volatile spirits, and to alcohol; it is the substance principally made use of for colouring the spirits of thermometers. As exposure to the air destroys its colour upon cloth, the exclu- sion ofthe air produces a like effect in those hermetically sealed tubes, the spirits of large thermometers becoming in a few ARG AllS years colourless. The Abbe Nollet ob- serves, (in the French Memoirs for the year 1742), that the colourless spirit, upon breaking the tube, soon resumes its co- lour, and this for a number of times suc- cessively ; that a watery tincture of ar- chil, included in the tubes of thermome- ters, lost its colour in three days; and that in an open deep vessel, it became colourless at the bottom, while the upper part retained its colour. A solution of archil in water, applied on cold marble, stains it of a beautiful violet or purplish-blue colour, far more durable than the colour which it communicates to other bodies. M. du Fay says, he has seen pieces of marble stained with it, which in two vears had suffered no sensi- ble change. It sinks deep into the mar- ble, sometimes above an inch, and at the same time spreads upon the surface, un- less the edges be bounded by wax or some similar substance. It seems to make the marble somewhat more brittle. There is a considerable consumption of an article of this kind, manufactured in Glasgow by Mr Mackintosh. It is much esteemed and sold by the name of cud- bear. We have seen beautiful specimens of silk thus dyed, the colours of which were said to be very permanent, of va- rious shades, from pink and crimson to a bright mazarine blue. Litmus is likewise used in chemistry as a test, either staining paper with it, or by infusing it in water, when it is very com. monly, but with great impropriety, called tincture of turnsole. The persons by whom this article w as prepared, formerly gave it the name of turnsole, pretending that it was extracted from the turnsole, heliotro- pium tricoccum, in order to keep its true source a secret. The tincture should not be too strong, otherwise it will have a violet tinge, which, however, may be re- moved by dilution. The light of the sun turns it red even in close vessels. It may be made with spirit instead of water. This tincture, or paper stained with it, is presently turned red by acids: and if it be first reddened by a small quantity of vinegar, or some weak acid, its blue co- Jour will be restored bv an alkali. + Litmus gives out its colouring matter but feebly to strong alcohol; and watery infusions do not keep. To preserve it in a state for use, an infusion in weak spirit is best.-j" * Arctizite. See Wernerite.* Ardent Spirit. See Alcohol. *Arf.ndate. See Pistacite.* Areometer. See Hydrometer. Argal. Crude tartar, in the state in which it is taken from the inside of wine vessels, is known in the shops by tins name. Aroentate of Ammonia, fulminating silver. Al«GILLACF.OUS F.ARTH, or ALUMINA. * Ahgillite. See Clay-slate.* Ahomatus. Plants which possess a fragrant smell united with pungency, and at the same time are warm to the taste, are called aromatics. Their peculiar fla- vour appears to reside in their essential oil, and rises in distillation either with wa- ter or spirit. Arrack. A spirituous liquor imported from the East Indies. It is chiefly manu- factured at Batavia, and at Goa upon the Malabar coast. * Ahragontte. This mineral occurs massive, in fibres of a silky lustre ; and in the form of fibrous branches, diverging from a centre, Flos-ferri. It is frequently crystallized in what appeal- at first sight to be regular six-sided prisms. On close inspection a longitudinal crack will be ob- served down each lateral face. It occurs also in elongated octohedrons. Lustre glassy, fracture foliated and fibrous. Co- lours greenish and pearl-gray; often violet and green in the middle; and arranged in the direction of the fibres, so that the longitudinal fibres are green, the trans- verse violet-blue. Double cleavage— translucent—refracts doubly—scratches calcareous spar, and sometimes even glass—brittle—sp. grav. 2.90. It consists of carbonate of lime, with occasionally a little carbonate of strontites. It is found in Arragon in Spain, at Leogany in Salz- burg, at Marienberg in Saxony, and Ster- zing in the Tyrol. In the cavities of Ba- salt near Glasgow. The finest specimens of Flos-ferri ramifications, come from the mines of Eisenerz in Stiria. Beautiful spe- cimens have been also found in the Duf- ton-lead mines in England, in the work- ings of an old coal mine, called Lufton- hi'll pit near Durham. It also occurs in the trap rocks of Scotland.* Arsenic, in the metallic state, is of a bluish white colour, subject to tarnish, and grows first yellowish, then black, by exposure to air. It is brittle, and when broken exhibits a laminated texture. Its specific gravity is 5 763. In close vessels it sublimes entire at 356° F. but burns with a small flame if respirable air be pre- sent. The arsenic met with in commerce has the form of a white oxide. It is brought chiefly from the cobalt works in Saxony, where zaffre is made. Cobalt ores con- tain much arsenic, which is driven off by long torrefaction. The ore is thrown into a furnace resembling a baker's oven, with a flue, or horizontal chimney, nearly two hundred yards long, into which the fumes pass, and are condensed into a grayish or blackish powder. This is refined by a AllS AI1S second sublimation in close vessels, with a little potash, to detain the impurities. As the heat is considerable, it melts the sublimed flowers into those crystalline masses which are met with in commerce. See Acid (Arsemois). The metal may be obtained from this, •ither by quickly fusing it together with twice its weight of soft soap and an equal quantity of alkali, and pouring it out, when fused, into a hot iron cone; or by mixing it in powder with oil, and exposing it in a matrass to a sand heat. This pro- cess is too offensive to be performed, ex- cept in the open air, or where a current of air carries off the fumes. The decom- posed oil first rises; and the arsenic is af- terwards sublimed, in the form of a flaky metallic substance. It may likewise be obtained by mixing two parts of the ar- senious acid with one of black flux; put- ting the mixture into a crucible, with another inverted over it, and luted to it with clay and sand ; and applying a red heat to the lower crucible. The metal will be reduced, and line the inside of the upper crucible. It is among the most combustible ofthe metals, burns with a blue flame, and gar- lic smell, and sublimes in the state of ar- senious acid. f A very striking characteristic of this metal is, that it sublimes before it fuses.f Concentrated sulphuric acid does not attack arsenic when cold; but if it be boiled upon this metal, sulphurous acid gas is emitted, a small quantity of sulphur sublimes, and the arsenic is reduced to an oxide. Nitrous acid readily attacks arsenic, and converts it into arsenious acid, or, if much be employed, into arsenic acid. Boiling muriatic acid dissolves arsenic, but affects it very little when cold. This solution affords precipitates upon the ad- dition of alkalis. The addition of a little nitric acid expedites the solution; and this solution, first heated and condensed in a close vessel, is wholly sublimed into a thick liquid, formerly termed butter of arsenic. Thrown in powder into chlorine gas, it burns with a bright white flame, and is converted into a chloride. None of the earths or alkalis act upon it, unless it be boiled a long while in fine powder, in a large proportion of alkaline solution. Nitrates detonate with arsenic, convert it into arsenic acid, and this, combining with the base of the nitrate, forms an arseniate, that remains at the bottom of the vessel. Muriates have no action upon it; but if three parts of chlorate of potash be mixed with one part of arsenic in fine powder, which must be done with great precaution, and a very light hand, a very small quan- tity of this mixture, placed onan anvil, and struck with a hammer, will explode with flame and a considerable report; if touch- ed with fire, it will burn with considerable rapidity; and if thrown into concentrated sulphuric acid, at the instant of contact a flame rises into the air like a flash of light- ning, which is so bright as to dazzle the eye. Arsenic readily combines with sulphur by fusion and sublimation, and forms a yellow compound called orpiment, or a red called realgar. The nature of these, and theirdifference, are not accurately known, but Fourcroy considers the first as a com- bination of sulphur with the oxide, and the second as a combination of sulphur with the metal itself, as he found the red sulphuret converted into the yellow by the action of acids. Arsenic is soluble in fat oils in a boiling heat; the solution is black, and has the consistence of an ointment when cold. Most metals unite with arsenic ; which exists in the metallic state in such alloys as possess the metallic brilliancy. * Iodine and arsenic unite, forming an iodide of a dark purple-red colour, pos- sessing the properties of an acid. It is soluble in water, and its solution forms a soluble compound with potash. Arsenic combines with hydrogen into a very nox- ious compound, called arsenuretted hy- drogen gas. To prepare it, fuse in a co- vered crucible, 3 parts of granulated tin, and 1 of metallic arsenic in powder; and submit this alloy, broken in pieces, to the action of muriatic acid in a glass retort. On applying a moderate heat, the arsenu- retted hydrogen comes over, and may be received in a mercurial or water pneuma- tic trough. Protomuriate of tin remains in the retort. When 1 of arsenic is used for 15 of tin, the former metal is entirely carried off in the evolved hydrogen. 100 parts of this gas contain 140 of hydrogen, as is proved by heating it with tin. Its specific gravity, according to Sir H. Davy, is 0.5552 ; according to Trommsdorf, 0.5293. Stromeyer states, that by a cold of — 22°, it condenses into a liquid. Ex- ploded with twice its bulk of oxygen, wa- ter and oxide of arsenic are formed. When arsenuretted hydrogen issuing from a tube is set on fire, it deposites a hydruret of ar- senic. Sulphur, potassium, sodium, and tin, decompose this gas, combine with its metal, and in the case of sulphur, sulphu- retted hydrogen results. By subtracting from the specific gravity ofthe arsenuret- ted gas, that of hydrogen gas |*«,wc have the proportion of arsenic present; 0.55520 — 0.09716 = 0.45804 = the arsenic in 100 measures of arsenuretted hydrogen; which gives the proportion by weight of about 6 arsenie to 1 hydrogen; but S'romcyci's ASA ASB analysis by nitric acid gives about 50 ar- senic to 1 hydrogen, which is probably much nearer the true composition. A prime equivalent of hydrogen is to one of arsenic as 1 to 76 ; and 2 consequently as 1 to 38. Gehlen fell a victim to his re- searches on this gas; and therefore the new experiments requisite to elucidate its constitution must be conducted with cir- cumspection. If chlorine be added to a mixture of arsenuretted and sulphuretted hydrogen, the bulk diminishes, and yellow coloured flakes are deposited. Concen- trated nitric acid occasions an explosion in this gas, preceded by nitrous fumes; but if the acid be diluted, a silent decom- position ofthe gas is effected. The den- sity ofthe hydrogen in this compound gas is 0.09716. Therefore, by Stromeyer's analysis, we have this proportion to cal- culate the specific gravity of the gas, 2.19 : 0.09716 : : (2.19+106) : 4.827 ; a quantity nearly 9 times greater than what experiment has given. This gas extinguishes flame, and instant- ly destroys animal life. Water has no ef- fect upon it. From the experiments of Sir H. Davy and MM. Gay-Lussac and Thenard, there appears to be a solid com- pound of hydrogen and arsenic, or a hy- druret. It is formed by acting with the negative pole of a voltaic battery on arse- nic plunged in water. It is reddish-brown, without lustre, taste, and smell. It is not decomposed at a heat approaching to cherry-red; but at this temperature it ab- sorbs oxygen ; while water and arsenious acid are formed, with the evolution of heat and light. The proportion of the two constituents is not known.* Arsenic is used in a variety of arts. It enters into metallic combinations, wherein a white colour is required. Glass manu- facturers use it; but its effect in the com- position of glass does not seem to be clear- ly explained. Orpiment and realgar are used as pigments. See Acins (Arsenic, and Arsenious). As vfcetida is obtained from a large um- belliferous plant growing in Persia. The root resembles a large parsnep externally, of a black colour: on cutting it transverse- ly, the assafoetida exudes in form of a white thick juice, like cream; which, from ex- posure to the air, becomes yellower and yellower, and at last of a dark-brown co- lour. It is very apt to run into putrefac- tion'; and hence those who collect it care- fully'defend it from the sun. The fresh mice has an excessively strong smell, which grows weaker and weaker upon keeping: a single dram of the fresh fluid juice smells more than a hundred pounds of the dry asafcetida brought to us. The Persians are commonly obliged to hire ships on purpose for its carriage, as scarce- ly any one will receive it along with other commodities, its stench infecting every thing that comes near it. The common asafcetida of the shops is of a yellowish or brownish colour, unctu- ous and tough, of an acrid or biting taste, and a strong disagreeable smell, resem- bling that of garlic. From four ounce* Neumann obtained, by rectified spirit, two ounces six drams and a half of resi- nous extract; and afterward, by water, three drams and half a scruple of gummy extract; about six drams and a scruple of earthy matter remaining undissolved. On applying water at first, he gained, from four ounces, one ounce three scruples and a half of gummy extract. Asafcetida is administered in nervous and hysteric affections, as a dcobstruent, and sometimes as an anthelmintic. A tinc- ture of it is kept in the shops, and it en- ters into the composition ofthe compound galbanum pill ofthe London college, the gum pill of former dispensatories. * Asbestos or Asbestus. A mineral of which there are five varieties, all more or less flexible and fibrous. 1. Amianthus occurs in very long, fine, flexible, elastic fibres, of a white, greenish, or reddish colour. It is somewhat unctu- ous to the touch, has a silky or pearly lus- tre, and is slightly translucent. Sectile ; tough; sp. grav. from 1 to 2.3. Melts with difficulty before the blow-pipe, into a white enamel. It is usually found in serpentine; in the Tarentaise in Savoy; in long and beautiful fibres, in Corsica; near Bareges, in the Pyrenees; in Dau- phiny and St. Gothard; at St. Keverne, Cornwall; at Portsoy, Scotland; in mica slate at Glenelg, Invernesshire, and near Durham. It consists of 59 silex, 25 mag- nesia, 9.5 hme, 3 alumina, and 2.25 oxide of iron.* The ancients manufactured cloth out of the fibres of asbestos, for the purpose, it is said, of wrapping up the bodies of the dead, when exposed on the funeral pile. Several moderns have likewise succeeded in making this cloth ; the chief artifice of which seems to consist in the admixture of flax and a liberal use of oil ; both which substances are afterwards consumed by exposing the cloth for a certain time to a red heat. Although the cloth of asbestos, when soiled, is restored to its primitive whiteness by heating in the fire; it is found, nevertheless, by several authentic experiments, that its weight diminishes by such treatment. The fibres of asbestos, exposed to the violent heat ofthe blow- pipe, exhibit slight indications of fusion; though the parts, instead of running to- gether, moulder away, and part fall down, while the rest seem to disappear before the current of air. Ignition impairs the ASP ASS flexibility of asbestos in a slight de- gree. * 2. Common Asbestus occurs in masses of fibres of a dull greenish colour, and of a somewhat pearly lustre. Fragments splintery. It is scarcely flexible, and great- ly denser than amianthus. It is slightly unctuous to the touch. Sp. grav. 2.7. Fuses with difficulty into a grayish-black scoria. It is composed of 63.9 silica, 16 magnesia, 12.8 lime, 6 oxide of iron, and 1.1 alumina. It is more abundant than amianthus, and is found usually in serpen- tine, as at Portsoy, the Isle of Anglesea, and the Lizard in Cornwall. It was found in the limestone of Glentilt, by Dr. M'Cul- loch, in a pasty state, but it soon hardened by exposure to air. 3. Mountain Leather consists not of parallel fibres like the preceding, but in- terwoven and interlaced so as to become tough. When in very thin pieces it is called mountain paper. Its colour is yel- lowish-white, and its touch meagre. It is found at Wanlockhead, in Lanarkshire. Its specific gravity is uncertain. 4. Mountain Cork, or Elastic Asbestus, is, like the preceding, of an interlaced fibrous texture; is opaque, has a meagre feel and appearance, not unlike common cork, and like it too, is somewhat elastic. It swims on water. Its colours are, white, gray, and yellowish-brown. Receives an impression from the nail; very tough ; cracks when handled, and melts with dif- ficulty before the blow-pipe. Sp. grav. from 0.68 to 0.99. It is composed of sili- ca 62, carbonate of lime 12, carbonate of magnesia 23, alumina 2.8, oxide of iron 3. 5. Mountain Wood. Ligniform asbestus. Is usually massive, of a brown colour, and having the aspect of wood. Internal lus- tre glimmering. Soft, sectile and tough ; opaque; feels meagre; fusible into a black slag. Sp. grav. 2.0. It is found in the Tyrol; Dauphiny; and in Scotland, at Glentilt, Portsoy, and Kildrumie.* Ashes. The fixed residue of combusti- ble substances, which remains after they have been burned, is called ashes. In chemistry it is most commonly used to de- note the residue of vegetable combustion. * Asparagin. White transparent crys- tals, of a peculiar vegetable principle, which spontaneously form in asparagus juice which has been evaporated to the consistence of sirup. They are in the form of rhomboidal prisms, hard and brittle, having a cool and slightly nauseous taste. They dissolve in hot water, but sparingly in cold water, and not at all in alcohol. On being heated they swell, and emit pen- etrating vapours, which affect the eyes and nose like wood-smoke. Their solution does not change vegetable blues: nor is it affected by hydrosulphuret of potash, oxalate of ammonia, acetate of lead, or in- fusion of galls. Lime disengages ammonia from it; though none is evolved by tritu- rating it with potash. The asparagus juice should be first heated to coagulate the al- bumen, then filtered and left to sponta- neous evaporation for 15 or 20 days. Along with the asparagin crystals, others in needles of little consistency appear, analogous to mannite, from which the first can be easily picked out. Vauquelin and Robiquet. Annales de Chimie, vol. 55. and Nicholson's Journal, 15.* Asphaltum1. This substance, likewise called Bitumen Judaicum, or Jews' Pitch, is a smooth, hard, brittle, black or brown substance, which breaks with a polish, melts easily when heated, and when pure burns without leaving any ashes. It is found in a soft or liquid state on the sur- face of the Dead Sea,§ but by age grows dr\ and hard. The same kind of bitumen is likewise found in the earth in other parts of the world; in China; America, particularly in the island of Trinidad; and some parts of Europe, as the Carpathian hills, France, Neufchattel, &c. Its speci- fic gravity, according to Boyle, is 1.400, to Kirwan, from 1.07 to 1.65. A specimen from Albania, of the specific gravity of 1.205, examined by Mr. Klaproth, was found to be soluble only in oils and in ether. Five parts of rectified oil of petro- leum dissolved one of the asphaltum, without heat, in 24 hours. Analyzed in the dry way, 100 grains afforded 32 of bi- tuminous oil, 6 of water faintly ammonia- cal 30 of charcoal, 7a of silex, 7\ of alu- mina, J of lime, 1 r oxide of iron, $ oxide of manganese, and 36 cubic inches of hy- drogen gas. According to Neumann, the asphaltum ofthe shops is a very different compound from the native bitumen; and varies, of course, in its properties, according to the nature of the ingredients made use of in forming it. On this account, and probably from other reasons, the use of asphaltum, as an article of the materia medica, is al- most totally laid aside. * The Egyptians used asphaltum in em- balming, under the name of mumia mine- ralis for which it is well adapted. It was used for mortar at Babylon.* Assay, or Essay. This operation con- sists in determining the quantity of valua- ble or precious metal contained in any § In the Mem. of the Academy of Sci- ences of Paris for 1778, there is an analy- sis of the water of this sea by Messrs. Mac- quer, Lavoisier, and Sage ; by wh'ch it appears to contain 22 per cent of muriate of magnesia, 16^ of muriate of lime, and 6$ of muriate of soda. Its specific gravity is 1.25. It is limpid, and without smell. ASS •mineral ot metallic mixture, by analyzing a small part thereof. The practical differ- ence between the analysis and the assay of an ore, consists in this i The analysis, if properly made, determines the nature and quantities of all the parts of the com- pound; whereas, the object of the assay consists in ascertaining how much of the particular metal in question may be con- tained in a certain determinate quantity ofthe material under examination. Thus, in the assay of gold or silver, the baser metals are considered as of no value or consequence ; and the problem to be re- solved is simply, how much of each is con- tained in the ingot or piece of metal in- tended to be assayed. The examination of metallic ores may be seen under their respective titles; the present article will therefore consist of an account of the as- saying of gold and silver. To obtain gold or silver in a state of pu- rity, or to ascertain the quantity of alloy it may contain, it is exposed to a strong heat, together with lead, in a porous cru- cible. This operation is called cupellation, and is performed as follows: The preci- ous metal is put, together with a due pro- portion of lead, into a shallow crucible, made of burned bones, called a cupel; and the fusion of the metals is effected by exposing them to a considerable heat in a muffle, or small earthen oven, fixed in the midst of a furnace. The lead continually vitrifies, or becomes converted into a glassy calx, which dissolves all the imper- fect metals. This fluid glass, with its con- tents, soaks into the cupel, and leaves the precious metals in a state of purity. Du- ring the cupellation, the scoriae running down on all sides ofthe metallic mass, pro- duce an appearance called circulation; by which the operator judges whether the process be going on well. When the metal is nearly pure, certain prismatic colours flash suddenly across the surface of the globule, which soon afterwards appears very brilliant and clean: this is called the brightening, and shows that the separa- tion is ended. After gold has passed the cupel, it may still contain either of the other perfect metals, platina, or silver. The former is seldom suspected; the latter is separated bv the operations called quartation and parting. Quartation consists in adding three parts of silver to tbe'supposed gold, and fusing them together; by which means the gold becomes. at most one-fourth of the mass only. The intention of this is to separate the" particles of gold from each other, so that they may not cover and de- fend the silver from the action ofthe nitric acid, which is to be used in the process of parting. Parting consists in exposing the mass, previouslv hammered or rolled out Vol. i'. [24] ASS thin, to the action of seven or eight times its weight of boiling nitric acid of a due strength. The first portion of nitric acid being poured off, about half the quantity, of a somewhat greater strength, is to be poured on the remaining gold; and if it be supposed that this has not dissolved all the silver, it may even be repeated a second time. For the first operation an acid of the specific gravity of 1 280 may be used, diluted with an equal quantity of water; for the second, an acid about 1.26 maybe taken undiluted. Iftlu-acidbe not too concentrated, it dissolves the sil- ver, and leaves the gold in a porous mass, of the original form; but, if too strong, the gold is in a powdery form, which may be washed and dried. The weight ofthe original metal before cupellation, and in all the subsequent stages, serves to ascer- tain the degree of fineness ofthe ingot, or ore, of which it is a part. In estimating or expressing the fineness of gold, the whole mass spoken of is sup- posed to weigh twenty-four carats of twelve grains each, either real, or merely proportional, like the assayer's weights ; and the pure gold is called fine. Thus, if gold be said to be 23 carats fine, it is to be understood, that, in a mass weighing 24- carats, the quantity of pure gold amounts to 23 carats. In such small works as cannot be assay- ed by scraping off a part, and cupelling it, the assayers endeavour to ascertain its quality or fineness by the touch. This is a method of comparing the colour, and other properties of a minute portion of the metal, with those of small bars, the composition of which is known. These bars are called touch-needles; and they are rubbed upon the black basaltes, which, for this reason, is called the touchstone. Black flint or pottery will serve the same purpose. Sets of gold needles may con- sist of—pure gold; pure gold 231 carats, with half a carat of silver; 23 carats of gold, with one carat of silver; 22^ carats of gold, with 1$ carats of silver; and so on, till the silver amounts to four carats; af- ter which the additions may proceed by whole carats. Other needles may be made in the same manner, with copper instead of silver; and. other sets may have the ad- dition consisting either of equal parts sil- ver and copper, or such proportions as the occasions of business require. The examination by the touch may be advan- tageously employed previous to quarta- tion, to indicate the quantity of silver ne- cessary to be added. In foreign countries, where trinkets and small work are required to be submitted to the assay of the touch, a variety of needles are necessary ; but they are not much trsed hi England. They afford, how- ASS ASS ever, a degree of information, which is more considerable than might at first be expected. The attentive assayer not only compares the colour of the stroke made upon the touchstone by the metal under examination, with that produced by his needle; but will likewise attend to the sensation of roughness, dry ness, smooth- ness, or greasiness, which the texture of the rubbed metal excites, when abraded by the stone. When two strokes, perfect- ly alike in colour, are made upon the stone, he may then wet them with aqua- fortis, which will affect them very differ- ently, if they be not similar compositions; or the stone itself may be made red-hot by the fire, or by the blow-pipe, if thin black pottery be used; in which case the phe- nomena of oxidation will differ, according to the nature and quantity ofthe alloy. The French government has from time to time caused various experimental in- quiries to be made respecting the art of assaying gold, which have thrown much light on this subject, and greatly tend to produce uniformity in the results of the operation. The latest report on this sub- ject may be seen in the Annates de Chi- mie, vol vi. p. 64.; which may be con- sulted for a full account ofthe experi- ments and history of former proceedings. The general result is as follows, nearly in the words ot the authors: Six principal circumstances appear to affect the operation of parting: namely, the quantity of acid used in parting, or in the first boiling; the concentration of this acid; the time employed in its applica- tion ; the quantity of acid made use of in the reprise, or second operation; its con- centration ; and the time during which it is applied. From the experiments it has been shown, that each of these unfavour- able circumstances might easily occasion a loss of from the half of a thirty-second part of a carat, or two thirty-second parts. The writers explain their technical lan- guage by observing, that, the whole mass consisting of twenty-four carats, this thir- ty-second part denotes l-768th part ofthe mass. It may easily be conceived, there- fore, that if the whole six circumstances were to exist, and be productive of errors falling the same way, the loss would be very considerable. It is therefore indispensibly necessary, that one uniform process should be fol- lowed in the assays of gold; and it is a matter of astonishment, that such an accu- rate process sliould not have been pre- scribed by Government.for assayers in an operation of such great commercial im- portance, instead of every one being left to follow his own judgment. The pro- cess recommended in the report before us is as follows :— Twelve grains ofthe gold intended to be assayed must be mixed with thirty grains of fine silver, and cupelled with 108 grains^ of lead. The cupellation must be carefully- attended to, and all the imperfect buttons rejected. When the cupellation is end- ed, the button must be reduced by lami- nation into a plate of I1 inch, or rather more, in length, and four or five lines in breadth. This must be rolled up upon a quill, and placed in a matrass capable of holding about three ounces of liquid, when filled up to its narrow part. Two ounces and a half of very pure aquafortis, ofthe strength of 20 degrees of Baume's areo- meter, must then be poured upon it; and the matrass being placed upon hot ashes or sand, the acid must be kept gently boil- ing for a quarter of an hour; the acid must then be cautiously decanted and an additional quantity of 1£ ounce, must be poured on the metal, and slightly boiled for twelve minutes. This being likewise carefully decanted, the small spiral piece of metal must be washed with filtered ri- ver water, or distilled water, by filling the matrass with this fluid. The vessel is then to be reversed, by applying the extremi- ty of its neck against the bottom of a cru- cible of fine earth, the internal surface of which is very smooth. The annealing must then be made, after having separated the portion of water which had fallen into the crucible; and, lastly the annealed gold must be weighed. For the certainty of this operation, two assays must be made in the same manner, together with a third assay upon gold of twenty-four carats, or upon gold the fineness of which is perfect- ly and generally known. No conclusion must be drawn from this assay, unless the latter gold should prove to be of the finaness of twenty-four carats exactly, or of its known degree of fine- ness; for if there be either loss or surplus, it may be inferred that the other two as- says, having undergone the same opera- tion, must be subject to the same error. The operation being made according to this process, by several assayers, in cir- cumstances of importance, such as those which relate to large fabrications, the fine- ness of the gpld must not be depended on, nor considered as accurately known, § 1$ gross. Though these doses of sil- ver and lead appeared to be proper for all operations of assaying gold, the commissa- ries observe, nevertheless, that gold of a lower title than eighteen carats may be alloyed with two parts, and even less, of silver -, in order that the small mass of me- tal, when it comes to be laminated,roay not be too thin, so as to break in pieces during the parting. ATH ATR unless all the assayers have obtained a uni- when filled, was closely shut by a well- form result, without communication with fitted cover; and the lower part commu- each other. The authors observe, however, nicated with the fire-place of the furnace. that this identity must be considered as In consequence of this disposition, the existing to the accuracy of half of the charcoal subsided into the fire-place gra- thirty-second part of a carat. For not- dually as the consumption made room for withstanding every possible precaution or it; but that which was contained in the uniformity, it very seldom happens that an tower was defended from combustion by absolute agreement is obtained between the exclusion of u proper supply of air. the different assays of one and the same * Atmometer. The name of an instru- ingot, because the ingot itself may differ ment contrived by Professor Leslie, to in its fineness in different parts of its mass, measure the quantity of exhalation from The assaying of silver does not differ a humid surface in a given time. It con- from that of gold, excepting that the part- sists of a thin ball of porous earthen-ware, ing operation is not necessary. A cer- two or three inches in diameter, with a tain small portion of the silver is ab- small neck, to which is firmlv cemented a sorbed by the cupel, and the more when long and rather wide tube of glass, bear- a larger quantity of lead is used, un- ing divisions, each of them corresponding less the quantity of lead be excessive; to an internal annular section, equal o a in which case most of it will be scori- film of liquid that would cover the outer fied before it begins to act upon the surface of the ball to the thickness of the silver. Messrs. Heilot, Tillet, and Mac- thousandth part of an inch. These divi- quer, from their experiments made by or- sions are ascertained by a simple calcula- der of the French Government, have as- tion, and numbered downwards to the ex- certained, that four parts of lead are re- tent of 100 or 200. To the top ofthe tube quisite for silver of eleven pennyweights is fitted a brass cap, having a collar of lea- twelve grains fine, or containing this ther, and w hich, after the cavity has been weight of pure silver, and twelve grains filled with distilled or boiled water, is of alloy, in twelve pennyweights; six screwed tight. The outside of the ball parts of lead for silver of eleven pen- being now wiped dry, the instrument is nyweights; eight parts of lead for silver suspended out of doors, and exposed to of ten pennyweights; ten parts of lead for the free action of the air. The quantity silver of nine pennyweights; and so on in of evaporation from a wet ball is the same the same progression. as from a circle having twice the diameter Astringent Prisciplr. The effect of the sphere. In the atmometer, the called astringency, considered as distin- humidity transudes through the porous guishable by the taste, is incapable of be- substance, just as fast as it evaporates ing defined. It is perceived in the husks of from the external surface; and this waste nuts, ot walnuts, in green tea, and emi- is measured by the corresponding descent nently in the nut-gall This is probably of water in the stem. At the same time, owing to the circumstance, that acids have the tightness of the collar taking off the likewise the property of corrugating the pressure of the column of liquid, prevents fibres of the mouth and tongue, which is it from oozing so profusely as to drop from considered as characteristic ofastringency the ball; an inconvenience which, in the as it relates to taste; and hence the gallic case of very feeble evaporation, might acid, which is commonly found united otherwise take place. As the process with the true as ringent principle, was long goes on, a corresponding portion of air is mistaken for it. Seguin first distinguished likewise imbibed by the moisture on the them, and, from the use of this principle outside, and being introduced into the in tanning skins, has given it the name of ball, rises in a small stream to replace the tannin. Their characteristic differences water. The rate of evaporation is nowise are, the gallic acid forms a black precipi- affected by the quality ofthe porous ball. tate with iron; the astringent principle It continues exactly the same when the forms an insoluble compound with albu- exhaling surface appears almost dry, as men. See Tannin. when it glistens with superfluous mois- Atha>-oh. A kind of furnace, which ture. When the consumption of water is has long since fallen into disuse. The excessive, it may be allowed to percolate very long and durable operations of the by unscrewing the cap, taking care, how- ancient chemists rendered it a desirable ever, to let no drops fall.* Leslie on Heat requisite, that their fires should be con- and Moisture. stantly supplied with fuel in proportion to Atmosphere. See Air (Atmospheri- the consumption. The athanor furnace cal). was peculiarly adapted to this purpose. * Atomic Theory. See Equivalemts Beside the usual parts, it was provided (Chemical).* with a hollow tower, into which charcoal * Athoima. A new vegetable alkali, was put. The upper part of the tower, extracted by Dr. Brandes from the Atrupa ATT ATT belladonna, or deadly nightshade. It is white, brilliant, crystallizes in long nee- dles, is tasteless, and little soluble in wa- ter or alcohol. It resists a moderate heat. With acids, it forms regular salts, and is capable of neutralizing a considerable pro- portion of acid. Sulphate of atropia is composed of, Sulphuric acid, 36.52 5.00 Atropia, 38 93 5.33 \V ater, 24.55 100.00.* Attraction. The instances of attrac- tion which are exhibited by the phenome- na around us, are exceedingly numerous, and continually present themselves to our observation. The effect of gravity, which causes the weight of bodies, is so universal, that we can scarcely form an idea how the universe could subsist without it. Other attractions, such as those of magnetism and electricity, are likewise observable; and every experiment in chemistry tends to show, that bodies are composed of va- rious principles or substances, which ad- here to each other with various degrees of force, and may be separated by known methods. It is a question among philo- sophers, whether all the attractions which obtain between bodies be referable to one general cause modified by circumstances; or whether various original and distinct causes act upon the particles of bodies at one and the same time. The philosophers at the beginning of the present century were di-posed to consider the several at- tractions as essentially different, because the laws of their action differ from each other; but the moderns appear disposed to, generalize this subject, and to consider all the attractions which exist between bodies, or at least those which are perma- nent, as depending upon one and the same cause, whatever it may be, which re- gulates at once the motions of the im- mense bodies that circulate through the celestial spaces, and those minute parti- cles that are transferred from one combi- nation to another in the operations of che- mistry. The earlier philosophers ob- served, for example, that the attraction of gravitation acts upon bodies with a force which is inversely as the squares of the distances; and from mathematical deduc- tion they have inferred, that the law of at- traction between the particles themselves follows the same ratio; but when their observations were applied to bodies very near each other, or in contact, an adhesion took place, which is found to be much greater than could be deduced from that law applied to the centres of gravity. Hence they concluded, that the cohesive attraction is governed by a much higher ratio, and probably the cubes of the dis- tances. The moderns, on the contrary, among whom are Bergmann, Guyton-Mor- veau, and others, have remarked, that these deductions are too general, because, for the most part, drawn from the conside- ration of spherical bodies, which admit ot no contact but such as is indefinitely small, and exert the same powers on each other, whichever side may be obverted. They remark, likewise, that the consequence depending on the sum of the attractions in bodies not spherical, and at minute distances from each other, will not follow the inverted ratio of the square ofthe dis- tance taken from any point assumed as the centre of gravity, admitting the parti- cles to be governed by that law ; but that it will greatly differ, according to the sides of the solid which are presented to each other, and their respective distances; in- somuch that the attractions of certain par- ticles indefinitely near each other will be indefinitely increased, though the ratio of the powers acting upon t e remoter parti- cles may continue nearly the same. This doctrine, which however requires to be much more strictly examined by the application of mathematical principles, obviously points to a variety of interesting consequences. The polarity of panicles, or their disposition to present themselves in their approach to each other in certain aspects, though it has been treated as a chimerical notion by a few writers, is one ofthe first of these results. These are speculations, which, with re- gard to the present state of chemistry, stand in much the same situation as the theory of gravity, which is minutely de- scribed in Plutarch, did with regard to as- tronomy before the time of Newton. As the celestial phenomena were formerly ar- ranged from observation merely, but are now computed from the physical cause, gravitation; so, at present, chemistry is the science of matter of fact duly arranged, without the assistance of any extensive theory immediately deduced from the fi- gures, volumes, densities, or mutual ac- tions of the particles of bodies. What it may hereafter be, must depend on the ability and research of future chemists; but at present we must dismiss this remo- ter part of theory, to attend more imme- diately to the facts. That the parts of bodies do attract each other, is evident from that adhesion which produces solidity, and requires a certain force to overcome it. For the sake of per- spicuity, the various effects of attraction have been considered as difi'erent kinds of affinity or powers. That power which physical writers call the attraction of co- hesion, is generally called the attraction of aggregation by chemists. Aggregation is considered as the adhesion of parts of ATT ATT the same kind. Thus a number of pieces of brimstone united by fusion, form an ag- gregate, the parts of which may be sepa- rated again by mechanical means. These parts have been called integrant parts; that is to say, the minutest parts into which a body can be divided, either really or by the imagination, so as not to change its nature, are called integrant parts. Thus, if sulphur and an alkali be combined together, and form liver of sulphur, we may conceive the mass to be divided and subdivided to an extreme degree, until at length the mass consists of merely a par- ticle of brimstone and a paricle of alkali. This then is an integrant part; and if it be divided further, the effect which chemists call decomposition will take place; and the particles consisting no longer of liver of sulphur, but of sulphur alone, and al kali alone, will be what chemists call com- ponent parts 6r principles. The union of bodies in a gross way is called mixture. Thus sand and an alkali may be mixed together. But when the very minute parts of a body unite with those of another so intimately as to form a body, which has properties different from those of either of them, the union is called combination, or composition. Thus, if sand and an alkali be exposed to a strong heat, the minute parts of the mixture com- bine, and form glass. The earlier chemists were very desirous of ascertaining the first principles, or ele- ments of bodies; and they distinguished by this name such substances as their art was incapable of rendering more simple. They seem however to have overlooked the obvious circumstance, that the limits of art are not the limits of nature. At pre- sent we hear little concerning elements. Those substances which we have n»t hitherto been able to analyze, or which, if decomposed, have hitherto eluded the ob- servation of chemiss, are indeed con- sidered as simple substances relative to the present state of our knowledge, but in no other respect; for a variety of ex- periments give us reason to hope, that future enquiries may elucidate their na- ture and composition. Some writers, cal- ling these simple substances by the name of Primary Principles, have distinguished compounds of these by the name of Se- condary Principles, which they suppose to enter again into combinations without decomposition or change. It must be confessed, nevertheless, that no means have yet been devised to show whether any such subordination of principles ex- ists. We may indeed discover that a com- pound body consists of three or more prin- ciples; but whether two of these be pre- viously united, so as to form a simple sub- stance witji relation to the third, or what in other respects may be their arrange- ment, we do not know. That it does ex- ist, however, seems clear by making com- binations in varied orders. Thus a weak solution of alkali will not dissolve oil; but a combination of oil and alkali will not separate by the addition of water. The alkali therefore adheres to that with which it was first combined. See also the article Vegetables. If two solid bodies, disposed to combine together, be brought into contact with each other, the particles which touch will combine, and form a compound; and if the temperature at which this new com- pound assumes the fluid form be higher than the temperature of the experiment, the process will go no further, because this new compound being interposed be- tween the two bodies, will prevent their further access to each other; but if, on the contrary, the freezing point of the compound be lower than this temperature, liquefaction will ensue; and the fluid par- ticles being at liberty to arrange them- selves according to the law of their at- tractions, the process will go on, and the whole mass will gradually be converted into a new compound in the fluid state. An instance of this may be exhihited by mixing common salt and perfectly dry pounded ice together. The crystals of the salt alone will not liquefy unless very much heated ; the crystals of the water, that is to say, the ice, will not liquefy un- less heated as high as thirty-two degrees of Fahrenheit; and we have of course supposed the temperature of the experi- ment to be lower than this, because our water is in the solid state. Now it is a well known fact, that brine, or the satu- rated solution of sea salt in water, cannot be frozen unless it be cooled thirty-eight degrees lower than the freezing point of pure water. It follows then, that, if the temperature of the experiment be higher than this, the first combinations of salt and ice will produce a fluid brine, and the combination will proceed until the tem- perature of the mass has gradually sunk as low as the freezing point of brine; af- ter which it would cease, if it were not that surrounding bodies continually tend to raise the temperature. And according- ly it is found by experiment, that, if the ice and the salt be previously cooled be- low the temperature of freezing brine, the combination and liquefaction will not take place. See Caloric The instances in which solid bodies thus combine together not being very nume- rous, and the fluidity which ensues imme- diately after the commencement of this kind of experiment, have induced several chemists to consider fluidity in one or both of the bodies applied to each other, ATT ATT tf> be a necessary circumstance, in order that they may produce chemical action upon each other. Corpora non agunt nisi sint fimda. If one of two bodies applied to each other be fluid at the temperature ofthe experiment, its parts will successively unite with the parts of the solid, which will by that means be suspended in the fluid, and disappear. Such a fluid is called a solvent or menstruum; and the solid body is said to be dissolved. Some substances unite together in all proportions. In this way the acids unite with water. But there are likewise many substances which cannot be dissolved in a fluid, at a settled temperature, in any quantity beyond a certain proportion. Thus, water will dissolve only about one- third of its weight of common salt; and if more salt be added, it will remain so- lid. A fluid which holds in solution as much of any subsiance as it can dissolve, is said to be saturated with it. But satu- ration with one substance is so far from preventing a fluid from dissolving another body, that it very frequently happens, that the solvent power of the compound exceeds that of the original fluid itself. Chemists likewise use the word saturation in another sense; in which it denotes, such a union of two bodies as produces a compound the most remote in its proper- ties from the properties of the component parts themselves. In combinations where one ofthe principles predominates, the one is said to be supersaturated, and the other principle is said to be subsaturated Heat in general increases the solvent power of fluids, probably by preventing part of the dissolved substance from con- gealing, or assuming the solid form. It often happens, that bodies which have no tendency to unite are made to combine together by means of a third, which is then called the medium. Thus, water and fat oils are made to unite by the medium of an alkali, in the combination called soap. Some writers, who seem desirous of multiplying terms, call this tendency to unite the affinity of intermedium. This case has likewise been called disposing affinity; but Berthollet more properly styles it re- ciprocal affinity. He likewise distinguish- es affinity into elementary, when it is be- tween the elementary parts of bodies; and resultmg, when it is to a compound only, and would not take place with the elements of that compound. It very frequently happens, on the con- trary, that the tendency of two bodies to unite, or remain in combination together, is weakened or destroyed by the addition of a third. Thus, alcohol unites with wa- ter in such a manner as to separate most salts from it. A striking instance of this is seen in a saturated or strong solution of nitre in water. If to this there be added an equal measure of alcohol, the greater part of the nitre instantly falls down. Thus magnesia is separated from a solu- tion of Epsom salt, by the addition of an alkali, which combines with the sulphuric acid, and separates the earth. The prin- ciple which falls down is said to be pre- cipitated, and in many instances is called a precipitate. Some modern chemists use the term precipitation in a more extended, and rather forced sense; for they apply it to all substances thus separated. In this enunciation, therefore, they would say, that potash precipitates soda from a solu- tion of common salt, though no visible separation or precipitation takes place; for the soda, when disengaged from its acid, is still suspended in the water by reason of its solubility. From a great number of facts of this na- ture, it is clearly ascertained, not as a pro- bable hypothesis, but as simpla matter of fact, that some bodies have a stronger ten- dency to unite than others ; and that the union of any substance with another will exclude, or separate, a third substance, which might have been previously united with one of them; excepting only in those cases wherein the new compound has a tendency to unite with that third sub- stance, and form a triple compound. This preference of uniting, which a given sub- stance is found to exhibit with regard to other bodies, is by an easy metaphor call- ed elective attraction, and is subject to a variety of cases, according to the number and the powers ofthe principles which are respectively presented to each other. The cases which have been most frequently observed by chemists, are those called sim- ple elective attractions, and double elec- tive attractions. When a simple substance is presented or applied to another substance compoun- ded of two principles, and unites with one of these two principles so as to separate or exclude the other, this effect is said to be produced by simple elective attrac- tion. It may be doubted whether any of our operations have been carried to this de- gree of simplicity. All the chemical prin- ciples we are acquainted with are simple only with respect to our power of decom- posing them; and the daily discoveries of our contemporaries tend to decompose those substances, which chemists a few years ago considered as simple. Without insisting, however, upon this difficulty, we may observe, that water is concerned in all the operations which are called humid, and beyond a doubt modifies all the effects of such bodies as are suspended in it; and the variations of temperature, whether ATT ATT arising from an actual igneous fluid, or from a mere modification of the parts of bodies, also tend greatly to disturb the ef- fects of elective attraction. These causes sender it difficult to point out an example of simple elective attraction, which may in strictness be reckoned as such. Double elective attraction takes place when two bodies, each consisting of two principles, are presented to each other, and mutually exchange a principle of each; by which means two new bodies, or com- pounds, are produced, of a different na- ture from the original compounds. Under the same limitations as were pointed out in speaking of simple elective attraction, we may offer instances of dou- ble elective attraction. Let oxide of mer- cury be dissolved to saturation in the ni- tric acid, the water will then contain ni- trate of mercury. Again, let potash be dissolved to saturation in the sulphuric acid, and the result will be a solution of sulphate of potash. If mercury were ad- ded to the latter solution, it would indeed tend to unite with the acid, but would pro- duce no decomposition; because the elec- tive attrac ion of the acid to the alkali is the strongest, ro likewise, if the nitric acid alone be added to it, its tendency to unite with the alkali, strong as it is, will not effect any change, because the alkali is already in combination with a stronger acid. But if the nitrate of mercury be added to the solution of sulphate of pot- ash, a change of principles will take place, the sulphuric acid will quit the alkali, and unite w'uh the mercury, while the nitric acid combines with the alkali; and these two new salts, namely, nitrate of potash, and sulphate of mercury, may be obtained separately by crystallization. The most remarkable circumstance in this process is, that the joint effects of the attractions ofthe sulphuric acid to mercu- ry, and the nitric acid to alkali, prove to be stronger than the sum ofthe attractions between the sulphuric acid and the alkali, and between the nitrous acid and the mer- cury ; for, if the sum of these two last had not been weaker, the original combinations would not have been broken. + j- The influence of insolubility and of gravity is here too much overlooked. It is a general law, that when compounds are mixed, new combinations will take place between those substances, which, when united, are most insoluble. The mercury is of itself perfectly insoluble, and it is many times heavier than potash or nitric acid. The sulphuric acid is much heavier than the nitric, and forms with mercury an insoluble salt. Hence the superior affinity of the nitric acid and potash to water, as well as gravitation, tends to pre- cipitate the sulphate of mercury. Mr. Kirwan, who first, in the year 17*82, considered this subject with that attention it deserves, called the affinities which tend to preserve the original combinations, the quiescent affinities. He distinguished the affinities or attractions, which tend to pro- duce a change of principles, by the name ofthe divellent affinities. Some eminent chemists are disposed to consider as effects of double affinities, those changes of principles only, which would not have taken place without the assistance of a fourth principle. Thus, the mutual decomposition of sulphate of soda and nitrate of potash, in which the alkalis are changed, and sulphate of potash and nitrate of soda are produced, is not considered by them as an instance of dou- ble decomposition ; because the nitre would have been decomposed by simple elective attraction, upon the addition of the acid only. There are various circumstances which modify the effects of elective attraction, and have from time to time misled che- mists in their deductions. The chief of these is the temperature, which, acting differently upon the several parts of com- pounded bodies, seldom fai's to alter, and frequently reverses the effects of the af- finities. Thus, if alcohol be'added to a solution of nitrate of potash, it unites with the water, and precipitates the salt at a common temperature. But if the tempe- rature be raised, the alcohol rises on ac- count of its volatility, and the salt is again dissolved. Thus again, if sulphuric acid be added, in a common temperature, to a combination of phosphoric acid and lime, it will decompose the salt, and disengage the phosphoric acid ; but if this same mix- ture of these principles be exposed to a considerable heat, the sulphuric acid will have its attraction to the lime so much di- minished, that it will rise, and give place again to the phosphoric, which will com- bine with the lime. Again, mercury kept in a degree of heat very nearly equal to volatilizing it will absorb oxygen, and be- come converted into the red oxide for- merly called precipitate per se / but if the heat be augmented still more, the oxygen will assume the elastic state, and fly off, leaving the mercury in its original state. Numberless instances of the like nature continually present themselves to the ob- servation of chemists, which are sufficient to establish the conclusion, that the elec- tive attractions are not constant but at one and the same temperature. Many philosophers are of opinion, that the variations produced by change of tem- perature arise from the elective attraction of the matter of heat itself. But there are no decisive experiments either in con- firmation or refutation of this hypothesis. If wc except the operation of heat, ATT ATT which really produces a change in the elective attractions, we shall find, that most of the other difficulties attending this subject arise from the imperfect state of chemical science. If to a compound of two principles a third be added, the effect of this must necessarily be diff'erent ac- cording to its quantity, and likewise ac- cording to the state of saturation of the two principles of the compounded body. If the third principle which is added be in excess, it may dissolve and suspend the compound which may be newly formed, and likewise that which might have been precipitated. The metallic solutions, de- composed by the addition of an alkali, af- ford no precipitate in various cases when the alkali is in excess; because this ex- cess dissolves the precipitate, which would else have fallen down. If, on the other hand, one of the two principles of the compound body be in excess, the addition of a third substance may combine with that excess, and leave a neutral substance, ex- hibiting very diff'erent properties from the former. Thus, if cream of tartar, which is a salt of difficult solubility, consisting of potash united to an excess ot the acid of tartar, be dissolved in water, and chalk be added, the excess unites with part of the lime ofthe chalk, and forms a scarcely so- luble salt; and the neutral compound, which remains after the privation of this excess of acid, is a very soluble salt, great- ly differing in taste and properties from the cream of tartar. The metals and the acids likewise afford various phenomena, according to their degree of oxidation. A determinate oxidation is in general neces- sary for the solution of metals in acids; and the acids themselves act very differ- ently, accordingly as they are more or less acidified. Thus, the nitrous acid gives place to acids which are weaker than the nitric acid : the sulphurous acid gives place to acids greatly inferior in attractive power or affinity to the sulphuric acid. The deception arising from effects of this na- ture is in a great measure produced by the want of discrimination on the part of chemical philosophers; it being evident, that the properties of any compound sub- stance depend as much upon the propor- tion of its ingredients, as upon their re- spective nature. The presence and quantity of water is probably of more consequence than is yet supposed. Thus, bismuth is dissolved in nitrous acid, but falls when the water is much in quantity. The same is true of antimony. Ribaucout has shown the last (Annales de Chimie, xv. 122.) in alum, and it is likely that the fact is more com- mon than is suspected. Whether the at- traction and strength, as to quantity in saturation, be not variable by the presence or absence of water, must be referred t# experiment. The power of double elective attrac- tions too, is disturbed by thiscircumstance. If muriate of lime be added to a solution of carbonate of soda, they are both decom- posed, and the results, are muriate of soda and carboiate of lime. But if lime and muriate of soda be mixed with just water sufficient to make them into a paste, and this be exposed to the action ot carbonic acid gas, a saline efflorescence consisting of carbonate of soda will be formed on the surface, and the bottom of the vessel will be occupied by muriate of lime in a state of deliquescence. M. Berthollet made a great number of experiments, from which he deduced the following law :—that in elective attrac- tions the power exerted is not in the ratio of the affinity simply, but in a ratio com- pounded of the force of affinity and the quantity of the agent; so that quantity may compensate for weaker affinity Thus an acid which has a weaker affinity than another for a given base, if it be employed in a certain quantity, is capable of taking part of that base from the acid which has a stronger affinity for it; so that the base will be divided between them in the com- pound ratio of their affinity and quantity. This division of one substance between two others, for which it has different af- finities, always takes place, according to him, when three such are present under circumstances in which they can mutually act on each other. And hence it is, that the force of affinity acts most powerfully, when two sub tances first come into con- tact, and continues to decrease in power as either approaches the point of satura- tion. For the same reason it is so diffi- cult to separate the last portions of any substance adhering to another. Hence, if the doctrine laid down by M. Berthollet be true, to its utmost extent, it must be impossible ever to free a compound com- pletely from any one of its constituent parts by the agency of elective attraction ; so that all our best established analyses are more or less inaccurate. The solubility or insolubility of princi- ples, at the temperature of any experi- ment, has likewise tended to mislead chemists, who have deduced consequen- ces from the first effects of their experi- ments. It is evident, that many separations may ensue without precipitation; because this circumstance does not take place un- less the separated principle be insoluble, or nearly so. The soda cannot be preci- pitated from a solution of sulphate of soda, by the addition of potash, because of its great solubility; but, on the contrary, the new compound itself, or sulphate of pot- ash, which is much less soluble, may fall ATT ATT tfown, if there be not enough water pre- sent to suspend it. No certain knowledge can therefore be derived from the appear- ance or the want of precipitation, unless the products be carefully examined. In some instances all the products remain suspended, and in others they all fall down, as may be instanced in the decom- position of sulphate of iron by lime. Here the acid unites with the lime, and forms sulphate of lime, which is scarcely at all soluble; and the still less soluble oxide of iron, which was disengaged, falls down along with it. Many instances present themselves, in which decomposition does not take place, but a sort of equilibrium of affinity is per- ceived. Thus, soda, added to the super- tartrate of potash, forms a triple salt by combining with its excess of acid. So likewise ammonia combines with a por- tion of the acid of muriate of mercury, and forms the triple compound formerly distinguished by the barbarous name of sal alembroth. When we reflect maturely upon all the circumstances enumerated, or slightly touched upon, in the foregoing pages, we may form some idea ofthe extensive field of research, which yet remains to be ex plored by chemists. If it were possible to procure simple substances, and combine two together, and to this combination of two to add one more of the other simple substances, the result of the experiment would in many cases determine, by the exclusion of one ofthe three, that its af- finity to either ofthe remaining two was less than that between those two respec- tively. In this way it would be ascertain- ed, in the progress of experimental in- quiry, that the simple attractions of a se- ries of substances were gradually increas- ing or diminishing in strength. Thus, am- monia separates alumina from the sulphu- ric acid; magnesia, in like manner, sepa- rates the ammonia; lime predominates, in the strength of affinity, over magnesia, as appears by its separating this last earth ; the soda separates the lime, and itself gives place to the potash; and, lastly, potash yields its acid to barytes. The sim- ple elective attractions of these several substances to sulphuric acid, are therefore in the inverted order of their effects: barvtes is the strongest; and this is suc- ceeded regularly by potash, soda, lime, magnesia, ammonia, and alumina. Itisevi- dent, that results of this nature, being tabulated, as was first done by the cele- brated Geoffroy, and afterwards by Berg- mann, must afford a valuable mass of che- mical knowledge. It must be remarked, however, that these results merely indi- cate, that the powers are greater or less than each other,- but how much greater or less is not determined, either absolute' Vol. n [25] ly or relatively. Tables of this nature can- not therefore inform us of the effects which may take place in the way ot dou- ble affinity, for want ofthe numerical re- lations between the attracting powers. Thus, when we are in possession of the order of the simple elective attractions between the sulphuric acid and a series of substances, and also between the nitrous acid and the same substances; and when, in addition to this, the respective powers of each ofthe acids upon every one ofthe substances singly taken, are known, so far as to determine which will displace the other; y et we cannot thence foretell the result of applying two combinations to each other, each containing an acid united with one ofthe number ot simple substan- ces. Or, more concisely, a table of simple elective attractions can be of no use to determine the effects of double elective attraction, unless the absolute power of the attractions be expressed by number instead of their order merely. * It has been often remarked, that the action of a substance is diminished in pro- portion as it approaches to a state of satu- ration ; and this diminution of power has been employed to explain several chemi- cal phenomena. It is likewise known, that the resistance found in expelling a sub- stance from the last portions of a combi- nation, either by affinity or heat, is much greater than at the commencement ofthe decomposition, and sometimes such, that its entire decomposition cannot be effec- ted. Thus the black oxide of manganese exposed to heat will part with only a cer- tain definite quantity of its oxygen. No degree of heat can expel the whole. According to Berthollet, when two sub- stances are in competition to combine with a third, each of them obtains a de- gree of saturation proportionate to its af- finity multiplied by its quantity, a product, which he denominates mass. The subject ofthe combination divides its action in proportion to the masses, and by varying the latter, this illustrious chemist thinks, that the results also will be varied. The following are the forces which he regards as exercising a great influence upon che- mical combinations and phenomena, by concurring with or opposing the mutual affinity ofthe substances brought into ac - tion. 1. The action of solvents, or the af- finity which they exert according to their proportion. Thus, if into a v^ry dilute so- lution of muriate of lime, a solution of sul- phate of soda be poured, no precipitate of sulphate of lime will happen, though the quantity of the solvent water be less than is necessary to dissolve the calcare- ous sulphate. If the same two saline solu- tions be mixed with less water, the sul- phate of lime will fall in a few seconds, or a few minutes, according to the strength ATT ATT ofthe mingled solutions. 2. The force of cohesion, which is the effect of the mutu- al affinity ofthe particles of a substance or combination. Hence we can easily sec why a solution of pure potash, which so readily dissolves pulverulent alumina, has no effect on alumina concreted and con- densed in the oriental gems. The lowest red heat kindles charcoal, or determines its combination with atmospherical oxy- gen ; but a much higher temperature is requisite to burn the same carbonaceous matter, more densely aggregated in the diamond. 3. Elasticity, whether natural or producedby heaf; whichhas.by some,been considered as the affinity of caloric, (f 1) Ofthe influence of this power a fine illus- tration is afforded by muriate of lime and carbonate of ammonia When a solution of the latter salt is poured into one of the former, a double decomposition instantly takes place : carbonate of lime falls to the bottom in powder, and muriate of ammo- nia floats above. Let this liquid mixture be boiled for some time; exhalation of ammoniacal gas will be perceived by the nostrils, and the carbonate of lime will be redissolved ; as may be proved by the fur- ther addition of carbonate of ammonia.(f 2) This will cause an earthy precipitate from the liquid, which prior to ebullition was merely muriate of ammonia. 4. Efflores- cence, a power which acts only under very rare circumstances. It is exemplified in the natron lakes of Egvpt ; on the mar- gin of which, according to Berthollet, car- bonate of lime decomposes muriate of so- da, in consequence of the efflorescing property of the resulting carbonate. 5. Gravity likewise exerts its influence, par- ticularly when it produces the compres- sion of elastic fluids; but it may always without inconvenience be confounded with the force of cohesion. M. Berthollet thinks, that as the tables of affinity have all been constructed upon the supposition, that substances possess different degrees of affinity, which pro- (tl) This is obscure. Elasticity, as an an- tagonist of chemical affinity, seems always to result from calorific repulsion. Par- ticles evidently arrange themselves of choice in certain angles, from which they may be made to deviate, to a certain ex- tent, in obedience to exterior force; and yet they regain their figure, as soon as unconstrained. Perhaps this is what the author means by natural elasticity. For " affinity of caloric" we ought probably to read effects of caloric. (j-2) It is not the carbonate of lime, but the lime ofthe carbonate, that is redissolv- ed. I question if the " exhalation" be not carbonate of ammonia, instead of ammonia- cal gas. duce the decompositions and combinations that are formed, independently ofthe pro- portions and other conditions which con- tribute to the results ; these tables are cal- culated only to give a false idea of the de- grees of chemical action ofthe substances arranged in them. " The denomination of elective affinity," says he, " is in itself erroneous, since it supposes the union of one entire substance with another, in pre- ference to a third, while there is only a division of action, s.bject to other chemi- cal conditions." The force of cohesion, which was formerly considered merely as an obstacle to solution, limits not only the quantities of substances which may be brought into action in a liquid, and conse- quently modifies the conditions of the sa- turation which follows; but it is the pow- er which causes the precipitations and crystallizations that take place, and deter- mines the proportions of such combina- tions as are made by quitting the liquid; it is this force which sometimes even pro- duces the separation of a subs'ance, with- out its forming any combination with another substance, as has been remarked in metallic precipitations. Elasticity acts by producing effects opposite to those of cohesion, and which consists either in withdrawing some substances from the ac- tion of others in a liquid, or in diminishing the proportion which exists wirhin the sphere of activity; but when all the sub- stances are in the elastic state, their ac- tion is subjected to the same conditions. If tables were formed which would repre- sent the disposition to insolubility or vo- latility, in the different combinations, they would serve to explain a great number of combinations which take their origin from the mixture of difi'erent substances, and from the influence of heat. These con- siderations need not prevent us, says Berthollet, from using the term affinity to denote the whole chemical power of a body exerted in a given situation, even by its present constitution, its proportion, or even by the concurrence of other affini- ties; but we must avoid considering this power as a constant force, which produces compositions and decompositions All substances, according to him, exert a mu- tual action during the time they are in the liquid state; so that in a solution, for example, of sulphate of potash and muri- ate of soda, these two salts are not distinct, while there is no cause to determine the separation from their combination; but there exists in this liquid, sulphuric acid, muriatic acid, soda, and potash. In like manner, when the proper quantity of car- bonate of potash is added to muriate of soda, the mingled solution does not con- sist of carbonate of soda and muriate of potash, resulting from complex affinity, but contains simply muriatic and carbonic ATT ATT acids with potash and soda, in quadruple union and saturation. It is the crystalli- zing property of the soda carbonate, which, after due evaporation, determines the definite decomposition, and not any power of elective attraction. Or gene- rally, when one subs ance separates from a combination by the introduction of an- other, it is not merely from being sup- planted by the superior affinity of an an- tagonist, but because its intrinsic tenden- cy to the solid or gaseous form educes it from its former associate. There is cer- tainly much truth in the proposition of Berthollet. But with regard to the indefinite parti- tion of a base between two rival acids, and of an acid between two rival bases, a doctrine which that profound philosopher laboured to establish by a wide experi- mental induction, many facts of an irre- concileable nature occur. Sir H. Davy has remarked with his usual good judg- ment, that were this proposition correct, it is evident that there could be scarcely any definite proportions; a salt crystalli- zing in a strong alkaline solution would be strongly alkaHhe ; in a weak one less alkaline; while in an acid solution it would be acid. But this does not seem to be the case. In combinations of gaseous bodies, whose constitution gives their par- ticles perfect freedom of motion, the pro- portions are definite and unchangeable, however we may change the proportions ofthe aeriform mixture. And in all solid compounds that have been accurately ex- amined, in which there is no chance of mechanical mixture, the same law seems to prevail. Different bodies may indeed be dissolved in different menstrua in very various proportions, but the result may be regarded as a mixture of different solu- tions, rather than a combination. With regard to glasses and metallic alloys, ad- duced by Berthollet, it is sufficient to know that the points of fusion of alkali, glass, and oxides of lead and tin, are so near each other, that transparent mixtures of them may be formed. The attractive power of matter is undoubtedly general, but in the formation of aggregates, cer- tain definite arrangements take place. Bergmann observed long ago, that when nitric acid was digested on sulphate of potash, a portion of nitre was formed, in apparent contradiction to the superior af- finity which he had assigned to sulphuric acid for the potash. But he also gave what appears to be a satisfactory explana- tion of this seeming anomaly, which Ber- thollet has adduced in support of his views of indefinite and universal partition. Sulphuric acid tends to combine in two distinct but definite proportions with pot- ash, forming the neutral sulphate and the bisulphate. Nitric acid may therefore ab- stract from the neutral salt, that portion of potash which it should lose to pass into the acidulous salt; but it will not deprive it of any more. Hence this very example is decidedly adverse to the indefinite combinations and successive partitions taught by Berthollet. The above decom- position resolves itself evidently, there- fore, into a case of double affinity. That a large quantity of pure potash can separate a little sulphuric acid from the sulphate of barytes, has been stated by Berthollet; but it is a circumstance difficult to demon- strate. If the operation be conducted with access of air, then carbonate of pot- ash is readily formed, and a well known double affinity comes into play, viz. that of barytes for carbonic acid on one hand, and of sulphuric acid for potash on the other. Supposing the agency of carbon- ic acid to be excluded, then are we to believe that the potash having become a soluble sulphate, exists in liquid union with pure barytes? See M. Dulong'sex- periments further on. When M. Berthollet separated a little potash from sulphuric acid by soda, he merely formed a little bisulphate of pot- ash, while the free potash united to the water and alcohol, for which it has a strong affinity, and sulphate of soda was also formed. This, therefore, is a very in- telligible case of compound attraction. According to M. Berthollet, whenever an earth is precipitated from a saline com- bination, by an alkali, it should carry down with it a portion of its acid associate. But sulphate of magnesia acted on by potash, yields an earthy precipitate, which, after proper washing, betrays the presence of no retained sulphuric acid. The neutral salts of soda and potash part with none of their acid to magnesia, by the longest digestion in their solutions. If on the tartrate of lime, or oxalate of lead, the portion of sulphuric acid adequate to saturate these respective bases be poured, entire decomposition will be effected without any partition whatever. Now, sulphate of lime, which is the result in the first case, being actually a much more soluble salt than the tartrate, we should expect a portion ofthe latter to resist de- composition by the aid of its cohesive force. A plate of iron plunged into a so- lution of sulphate of copper, separates the whole of the latter metal. An equally absolute decomposition is effected by zinc on the saline solutions of lead and tin. The sum total of oxygen and acid is here transferred to the decomposing body, without any partition whatever. We have already observed, that sul- phate of barytes digested in a hot solution of carbonate of potash, gives birth to a portion of carbonate of barytes and sul- phate of potash. But by M. Dulong's ex- ATT ATT periment, the reverse decomposition is possible, viz. carbonate of barytes being digested in solution of sulphate of potash, we obtain sulphate of bary tes and carbo- nate of potash. Are we hence to infer, that sulphate of barytes and carbonate of potash having for some time amused the operator by the production of an alkaline sulphate and earthy carbonate, will change their mood, and retracing their steps, restore things to their pristine condition; and thus in alternate oscillation for ever? If chlorine gas be made to act on the oxides of mercury, tin, or antimony, it will unite to the metallic base, and dis- place every particle ofthe oxygen. Now, the resulting chlorides cannot owe their purity to any superiority of cohesive force which they possess over the oxides, which, on the contrary, are both denser and more fixed than the new compounds. Finally, if 25 parts of pure magnesia mix- ed with 35.6 of dry lime, be digested in 85 parts of nitric acid, sp. gr. 1.500, dilu- ted with water, we shall find that the whole lime will be dissolved, but not a particle of the magnesia. On decanting the neutral calcareous nitrate, washing and drying the earthy residuum, we shall procure the 25 parts of magnesia un- changed. We are, therefore, entitled to affirm, that affinity is elective, acting in the dif- ferent chemical bodies with gradations of attractive force, liable however to be modified, as we have shown in the case of muriate of lime and carbonate of ammo- nia, by temperature, and other adventi- tious powers. Decompositions which cannot be pro- duced by single attractions, may be effect- ed by double affinity; and that, we may- expect with the greater certainty, a pri- ori, if one of the two resulting compounds of the double interchange, naturally ex- ists in the solid or aeriform state. And if the one resulting compound be solid and the other gaseous, then decomposition will be certain and complete. This ap- plies with equal force to single affinities, or decompositions. Thus when sulphuric acid and muriate of lime indue propor- tions are exposed to heat, a perfect de- composition is accomplished, and pure sulphate of lime and muriatic acid gas are produced. But when the various mixed ingredients remain in solution, it is then reasonable to think with Berthollet, that a reciprocal attraction pervades the w hole, modifying its nature and properties. Thus solution of sulphate of copper is blue, that of muriate of copper is green. Now, if into a solution of the former salt, we pour muriatic acid, we shall observe this robbing the sulphuric acid of a quantity of the cupreous oxide, proportional to its mass; for the more muriatic acid we add, the greener will the liquid become. But if, by concentration, the sulphate of cop- per be suffered to crystallize, the pheno- mena change; a new force, that of cry stal- lization, is superadded, which aids the af- finity of the sulphuric acid, and decides the decomposition. The surplus ot each of these acids is employed in counterba- lancing the surplus of its antagonist, and need not be considered as combined with the copper. Here, however, we verge on the obscure and unproductive domain of chemical metaphysics, a region in which a late respectable systematist delighted to expatiate. M. Bethollet estimates the attractive forces or affinities of bodies of the same class, to be inversely as their saturating quantities. Thus, among acids, 50 parts of real sulphuric, will saturate as much potash or soda as 67 y of real nitric, and as 27£ of carbonic. Thus too, 21i of ammo- nia will saturate as much acid as 25 of magnesia, 35i, of lime, and 59£ of potash. Hence he infers that the carbonic acid is endowed with a higher affinity than the sulphuric; and this, than the nitric. The same proposition appljes to ammonia, magnesia, lime and potasli. But in direct hostility to this doctrine, we have seen lime exercise a greater affinity for the acids than magnesia. And though M. Berthollet has ingeniously sought to ex- plain away the difficulty about potash, am- monia, and carbonic acid, by referring to the solid or gaseous results of their action; yet it is hard to conceive of solidity opera- ting in producing an effect, before solidity exists, and of elasticity operating while the substance is solid or liquid. On this point a good syllogism has been offered by Sir H. Davy. " The action," says this profound chemist, "between the consti- tuents of a compound must be mutual. Sulphuric acid, there is every reason to believe, has as much attraction for barytes, as barytes has for sulphuric acid, and ba- rytes is the alkaline substance of which the largest quantity is required to satu- rate sulphuric acid; therefore, on M. Ber- thollet's view, it has the weakest affinity for that acid; but less sulphuric acid satu- rates this substance than any other earthy or alkaline body. Therefore, according to M. Berthollet, sulphuric acid has a stronger affinity for barytes than for any other substance; which is contradictory." In the table of chemical equivalents at the end of the Dictionary, will be found a view of the definite proportions in which the various chemical bodies com- bine, referred to their primary or lowest numerical terms, vulgarly called the weights of the atoms. Mr. Higgins, the real author of the Atomic Theory, in first promulgating its principles inhis Comparative! View of the ATT ATT Phlogistic and Antiphlogistic Hypotheses, connected their exposition with general views of the relative forces of affinity among the combining particles. These forces he illustrates by diagrams, to which I have adverted, in the article Equiva- lents (Chemical). This joint considera- tion of combining/orce and combining ra- tio, lias been neglected by subsequent wri- ters; whence, Mr. Higgins says, "The atomic doctrine has been applied by me in abtruse and difficult researches. Its ap- plication by Mr. Dalton, has been in a ge- neral and popular way; and it is from these circumstances alone, that it gained the name of Dalton's Theory." Since the chemical statics appeared, perhaps no chemist has contributed so many important facts to the doc rines of affinity as M. Dulong. His admirable in- quiries concerning the mutual decompo- sition of soluble and insoluble salts, were presented to the National Institute, and afterwards published in the Annales de Chimie, torn. 82; from which they were translated into the 5th and 36th volumes of Nicholson's Jouriia1, and an abstract of them was given in the 41st vol. ofthe Phil. Mag. Notwithstanding such means of notoriety, it is amusing to observe so unwearied a compiler as Dr. Thomson, recently appropriating to his friend Mr. Phillips, the discovery of a fact observed and recorded years before by M. Dulong; and treating as an anomaly, what the French philosopher had shownto be none, but had referred with equal sagacity and industry to general principles. After the labours of Bergmann and Ber- thollet, chemistry seemed to leave little further to be desired, relative to the mu- tual decomposition of soluble salts. But the insoluble salts are likewise susceptible of exchanging their principles with a great number of the soluble salts. " This class of phenomena," says M. Dulong, ««though almost as numerous as that which embraces the soluble salts, and capable of affording new resources to analysis, has not vet been examined in a general man- ner." The action ofthe soluble carbonates on the insoluble salts, is the only one which had been at all studied. Thus carbonates of potash and soda in solution, had been employed conveniently to decompose sul- phate of barvtes. M. Dulong had an op- portunity in some particular researches, to observe a considerably extensive number of facts, relating to the mutual decompo- sition of the soluble and insoluble salts, and endeavoured, he says, to determine the general cause of these phenomena, and the method of foreseeing their results, without being obliged to retain by an ef- fort of memory, of which few persons would be capable, all the direct observa- tions which would be requisite to ascer- tain them. M. Dulong found by experiment, that all the insoluble salts are decomposable by the carbonate of potasli or the carbo- nate of soda, and in some instances with curious phenomena. When sulphate of bary tes, phosphate of barytes, or oxalate of lime, is boiled with solution of bicarbo- nate, or carbonate of potash, a considera- ble part of the insoluble sulphate is con- stantly transformed into a carbonate of the same base; but on reaching a certain li- mit, the decomposition stopped, although there remained sometimes a very conside- rable quantity of the soluble carbonate not decomposed. M. Dulong convinced him- self, that the different degrees of concen- tration of the alkaline solution, produced but very slight v ariations in the results of this decomposition. He took 10 grammes of dry subcarbonate of potash, and 7.66, being their equivalent proportion, of dry subcarbonate of soda; quantities contain- ing each 3.07 grammes of carbonic acid. They were separately dissolved in 250 grammes of water, and each solution was kept in ebullition for two hours, on 8 grammes of the sulphate of barytes. On analyzing the two residues, it was found that the potash experiment yielded 2.185 grammes, and the soda only 1.833; or in the proportion of 6 to 5. Is this difference to be ascribed to the difference in the at- tractive forces of the two alkalis; to the more sparing solubility, or greater attrac- tive force of the sulphate of potash; or to both causes conjointly ? Since the alkaline carbonates lose their decomposing agency when a certain pro- portion ofthe alkaline sulphate is formed, M. Dulong tried to ascertain the limits by the'following experiment: 7grammes of sulphate of potash, with 6 of subcarbo- nate, dissolved in 250 of water, were boil- ed with the sulphate of bary tes for several hours, without the least trace of decompo- sition being evinced. The supernatant li- quid, filtered, and boiled on carbonate of barytes, produced a considerable quantity of sulphate; but ceased acting before this sulphate of potash was exhausted. The same phenomena were obtained with car- bonate and sulphate of soda. " Lastly, the sulphate of potash and the sulphate of soda alone, and perfectly neutral, re-acted likewise upon the carbonate of barytes, and produced on one part, sulphate of barytes, but on the other the subcarbonate of potash or soda which remained in solu- tion, together with the portion of the sul- phate which resisted the decomposition. 20 grammes of crystallized sulphate of so- da, and 10 grammes of sulphate of potash, were separately dissolved in 260 of water. Each solution was boiled for 2 hours on 20 grains of carbonate of barytes. The ATT ATT sr.lphate of soda produced 10.17 gr. of sulphate of barytes, and the sulphate of potash 9.87." Had 108 of sulphate of potash been employed, which is the true equivalent of 200 sulphate of soda in crys- tals, a somewhat larger product would have been obtained than 9.87. This ex- periment, however, is most satisfactory with regard to the amount of decomposi- tion. The mutual action of the insoluble carbonates, with the soluble salts, whose acids form, with the bases of these carbo- nates, insoluble salts, is equally general with that of the soluble carbonates on the insoluble salts. The following is M. Du- long's table of results: Carbonate of Barytes. "atto"flLa.r^!laLb°; Stron- tian- Sulphate of Potash ----------Soda ----------Lime ----------Ammonia ----------Magnesia Phosphate of Soda -----------Ammonia Sulphite of Potash Phosphite of Potash -----------Soda ------------Ammonia Borate of Soda Arseniate of Potash -----------Soda Oxalate of Potash ■ Ammonia Fluate of Soda Chromate of Potash Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. nate of '.nate of Lime. Lead. 0 0 0 Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. Id Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. Id. All those salts which have ammonia for their base, are completely decomposed by the insoluble carbonatesfound in the same column. The new insolqble salt replaces the carbonate which is decomposed, and the carbonate of ammonia flies oft'. Hence, if a sufficient quantity of insoluble carbo- nate be present, the liquid will become pure water. When the soluble salt has an insoluble base, the decomposition does not meet with any obstacle, but continues until the liquid becomes mere water. Thus, solu- tion of sulphate of magnesia, boiled with carbonate of barytes, will be resolved into an insoluble carbonate and sulphate, pro- vided enough of carbonate of barytes be present. Otherwise a portion ofthe mag- nesian carbonate being dissolved in its own sulphate, gives alkaline properties to the solution. If the base be metallic, it almost always forms a salt with excess of oxide, which being insoluble, precipitates. The general inferences of M. Dulong's inquiries are the following: 1. That all the insoluble salts are decomposed by the subcarbonates of potash or soda, but that a mutual exchange of the principles of these salts cannot in any case be complete- ly made; or in other words, that the de- composition of the subcarbonates is only partial. 2. That all the soluble salts, of which the acid forms, with .he base of the insoluble carbonates, an insoluble salt, are decomposed by these carbonates, un- til the decomposition has reached a certain limit which it cannot pass. When a soluble subcarbonate acts on an insoluble salt, in proportion as the carbonic acid is precipitated on the base of the in- soluble salt, it is replaced in the solution by a quantity of another acid, capable of completely neutralizing the alkali. Thus, during the whole course ofthe decompo- sition, fresh quantities of neutral salt re- place the corresponding quantities of an imperfectly saturated alkaline compound; and if we view the excess of alkaline pow- er in the undecomposed subcarbonate, or its unbalanced capacity of saturation, as acting upon both acids, it is evident that in proportion as the decomposition ad- vances, the liquid approaches more and more to the neutral state. In 1he inverse experiment, a contrary change supervenes. Each portion of the acid ofthe soluble salt, (sulphate of soda for example), which is precipitated on the base of the insoluble carbonate, is replaced by a quantity of carbonic acid, which forms with the cor- responding base, an alkaline subcarbo- nate ; and the more ofthe first acid is pre- cipitated upon the earthy base, the more subcarbonate the liquid contains, and the further does its state recede from neutrali- zation. This consideration seems to lead directly to the following theory of these decompositions. It is known, says M. Dulong, that all the salts, even those which possess the great- est cohesion, yield to caustic potash or so- da, a more or less considerable portion of their acid, according to circumstances. Now the alkaline subcarbonates may be considered as weak alkalis, which may take from all the insoluble salts a small quantity of their acids. This effect would soon be limited if the alkali were pure, in consequence of the resistance offered by the pure and soluble base. But the latter meeting in the liquid, an acid with which it can form an insoluble salt, unites with it, and thus re-establishes the primitive con- ditions ofthe experiment. The same ef- fects are produced successively on new portions of the bodies, till the degree of saturation of the liquid is in equilibrium with the cohesive force of the insoluble salt, so that the feebler this resistance may be, the more progress the decomposition will make. And again, when an insoluble carbonate is in contact with a neutral solu- ble salt, the base ofthe carbonate will tend ATT ATT to take part ofthe acid of the neutral salt; and if, from this union, an insoluble salt can result, the force of cohesion peculiar to this compound, will determine the forma tion. The carbonic acid, released from the attraction of the earthy base by the fixed acid, instantly attaches itself to the surrounding alkali, forming a subcarbo- nate which replaces the decomposed neu- tral salt. The precipitation of the fixed acid on the insoluble carbonate, and the absorption of carbonic acid by the liquid continues, until the alkalinity thereby de- veloped, becomes so strong as to resist the precipitation ofthe acid; thus forming a counterpoise to the force by which that precipitation was accomplished. All ac- tion then ceases, so that the more cohesion the insoluble salt possesses, the greater will be the proportion of acid taken from the soluble salt. When the carbonate of potash can no longer decompose the sulphate of barytes, the carbonic acid which remains in the so- lution, is to the sulphuric acid nearly in the ratio of 3 to 1; and when the sulphate of potash can no longer act upon the car- bonate of barytes, these two acids are nearly in the ratio of 3 to 2; whence it follows, that the first hquor is much more alkaline than the second. It is easy to account for this difference by examining the conditions ofthe equili- brium established in the two cases. When the sulphate of potash no longer decom- poses the carbonate of barytes, it is be- cause the excess of alkali, developed in the liquid, forms a counterpoise to the power with which sulphate of barytes tends to be produced in these circumstan- ces. And when the subcarbonate of pot- ash can no longer decompose the sulphate of barytes, it is because there is not such an excess of alkali in the hquid, as is capa- ble of overcoming the cohesion and attrac- tion between the elements of that salt. Now we know, that it requires a greater force to overcome an existing attractive power, than to maintain the quiescent con- dition. Therefore the subcarbonate of potash ought to cease to decompose the sulphate of barytes, before the sulphuric and carbonic acids are in the same rela- tion in which they are found, when the equilibrium is established by the inverse experiment. Hence we see, that a mix- ture of sulphate and subcarbonate of pot- ash, in which the proportions of their two acids shall be within the limits pointed out, will have no action either on the sul- phate or carbonate of barytes. For the other insoluble salts, there will be other relations of quantity; but there is always a certain interval, more or less considera- ble, between their limits. The mutual action of sulphate of soda and carbonate of barytes is almost instantaneous. It is sufficient to pour a boiling hot solution of the sulphate, on the carbonate placed on a filter, in order that more than three- fourths of the sulphuric acid be precipi- tated, and replaced by a corresponding quantity of carbonic acid. In the first part of the Philosophical Transactions for 1809, we have tables of elective attractions by Dr. Thomas Young, a philosopher of the very first rank, whom the late ingenious Dr. Wells pronounced the most learned man in England. These have been unaccountably overlooked by our different systematic writers, though they are, both in accuracy and ingenuity, far superior to the tables which, with un- varying routine of typography, are copied into their compilations, I conceive it will be doing an essential service to chemical students, to lay before them the tables of Dr. Young, accompanied with his admira- ble remarks on the sequences of double decompositions. Attempts have been made, by several chemists, to obtain a series of numbers, capable of representing the mutual attrac- tive forces of the component parts of dif- ferent salts ; but these attempts have hitherto been confined within narrow li» mits, and have indeed been so hastily abandoned, that some very importantcon- sequences, which necessarily follow from the general principle of a numerical re- presentation, seem to have been entirely overlooked. It appears that nearly all the phenomena ofthe mutual actions of a hun- dred different salts may be correctly re- presented by a hundred numbers, while, in the usual manner of relating every case as a different experiment, above two thou- sand separate articles would be required. Having been engaged in the collection of a few of the principal facts relating to chemistry and pharmacy, Dr. Young was induced to attempt the investigation of a series of these numbers ; and he has suc- ceeded in obtaining such as appear to agree sufficiently well with all the cases of double decompositions which are fully established, the exceptions not exceeding twenty, out of about twelve hundred case* enumerated by Fourcroy. The same num- bers agree in general with the order of simple elective attractions, as usually laid down by chemical authors; but it was of so much less importance to accommodate them to these, that he has not been very solicitous to avoid a few inconsistencies in this respect; especially as many ofthe ba- Bes of the calculation remain uncertain, and as the common tables of simple elec- tive attractions are certainly imperfect, if they are considered as indicating the order of the independent attractive forces ofthe substances concerned. Although it can- not be expected that these numbers should be accurate measures of the forces which ATT ATT they represent, yet they may be supposed to be tolerable approximations to such measures ; at least, if any two of them are nearly in the true proportion, it is proba- ble that the rest cannot deviate very far from it: thus, if the attractive force of the phosphoric acid for potash is about eight- tenths of that of the sulphuric acid for ban tes, that of the phosphoric acid for barytes must be about nine-tenths as great. But they are calculated only to agree with a certain number of phenomena, and will probably require many alterations, as well as additions, when all other similar phe- nomena shall have been accurately inves- tigated. " There must be a sequence," says Dr. "Young, " in the simple elective attrac- tions. For example, there must be an error in the common tables of elective at- tractions, in which magnesia stands above ammonia under the sulphuric acid, and be- low it under the phosphoric; and the phosphoric acid stands above the sulphuric under magnesia, and below it under am- monia ; since such an arrangement im- plies that the order ofthe attractive forces is this: phosphate of magnesia, sulphate •of magnesia, sulphate of ammonia, phos- phate of ammonia, and again phosphate of magnesia; which forms a circle, and not a sequence. We must therefore either place magnesia above ammonia under the phosphoric acid, or the phosphoric acid below the sulphuric under magnesia; or we must abandon the principle of a nume- rical representation in this particular case. " In the second place, there must be an agreement between the simple and dou- ble elective attractions. Thus, if the flu- oric acid stands above the nitric under ba- rita, and below it under lime, the fluate of barita cannot decompose the nitrate of lime, since the previous attractions of these two salts are respectively greater than the divellent attractions of the nitrate of barita and the fluate of lime. Probably, there- fore, we ought to place the fluoric acid below the nitric under barita ; and we may suppose, that when the fluoric acid has appeared to form a precipitate with the nitrate of barita, there has been some fal- lacy in the experiment. "The third proposition is somewhat less obvious, but perhaps of greater utility: there must be a continued sequence in the order of double elective attractions; that is, between any two acids we may place the different bases in such an order, that any two salts, resulting from their union, shall always decompose each other, un- less each acid be united to the base near- est to it; for example, sulphuric acid, ba- rita, potash, soda, ammonia, strontia, mag- nesia, glucina, alumina, zirconia, lime, phosphoric acid. The sulphate of potash decomposes the phosphate of barita, be- cause the difference of the attractions of barita for the sulphuric and phosphoric acids is greater than the difference of the similar attractions of potash; and in the same manner, the difference of the attrac- tions of potash is greater than that of the attractions of soda ; consequently the dif- ference of the attractions of barita must be much greater than that of the attrac- tions of soda, and the sulphate of soda must decompose the phosphate of barita; and in the same manner it may be shown, that each base must preserve its relations of priority or posteriority to every other in the series. It is also obvious, that, for similar reasons, the acids may be arranged in a continued sequence between the dif- ferent bases ; and when all the decompo- sitions of a certain number of salts have been investigated, we may form two cor- responding tables, one ofthe sequences of the bases with the acids, and another of those ofthe acids with the different bases; and if either or both of the tables are im- perfect, their deficiencies may often be supplied, and their errors corrected by a repeated comparison with each other." In the table of simple elective attrac- tions, he has retained the usual order of the different substances; inserting again in parentheses such of them as require to be transposed, in order to avoid inconse- quences in the simple attractions : He has attached to each combination marked with an asterisk the number deduced from the double decompositions, as expressive of its attractive force; and where the num- ber is inconsistent with the corrected or- der ofthe simple elective attractions, he has enclosed it in a parenthesis. Such an apparent inconsistency may perhaps in some cases be unavoidable, as it is pos- sible that the diff'erent proportions of the masses concerned in the operations of sim- ple and compound decomposition, may sometimes cause a real difference in the comparative magnitude of the attractive forces. Those numbers to which no aste- risk is affixed, are merely inserted by in- terpolation, and they can only be so far employed for determining the mutual ac- tions ofthe salts to which they belong, as the results which they indicate would fol- low from the comparison of any other numbers intermediate to the nearest of those which are more correctly determi- ned, lie was not able to obtain a suffi- cient number of facts relating to the me- tallic salts, to enable him to comprehend many of them in he tables. He thought it necessary to make some alterations in the orthography generally adopted by chemists, not from a want of deference to their individual avthority, but because it appeared to him that there are certain rules of etymology, which no modern author has a right to set aside. TABLES OF ELECTIVE ATTRACTIONS, By Dr. Young. Eh < 1. TABLE of the Sequences ofthe Bases with the different Acids. In all mixtures ofthe aqueous solutions of two salts, each acid remains united to the base, which stands nearest to it in this Table. SULPHURIC ACID. < Barita Barita Strontia Strontia Lime Lime (Silver?) Potash (Mercury?) Soda Potash (Mercury?) Soda (Iron ?) C Zinc ~) Magnesia s Iron £■ Ammonia (! (.Copper j Glycina Magnesia Alumina (2) Ammonia (1) Zirconia Glycina (Copper?) Alumina Zirconia Nitric Muriatic Phosphoiiic Barita Barita Potash Potash Soda Soda Ammonia Strontia Strontia Ammonia Magnesia (3) Magnesia Glycina Glvcina Alumina Alumina Zirconia Zirconia Lime Lime Barita Barita Potash Barita Barita Lead Potash Potash Soda Strontia Potash Mercury Soda Soda Barita Lime Soda ("Iron "1 Strontia Strontia Strontia Potash Ammonia J Potash I Ammonia (4) Ammonia (5) Ammonia (6) Soda Strontia Ssoda _ f Magnesia (4) Magnesia Lime Magnesia ? Magnesia I MagnesiaJ Glycina Lime Magnesia Ammonia Glycina --- Alumina Glycina Glvcina Glvcina Alumina Lead Zirconia Alumina Alumina Alumina Zirconia Zinc Lime Zirconia Zirconia Zirconia Lime ? Copper Fluoric Sulphurous Boracic Carbonic (Nitrous) (Phosphorous) (Acktic) (1.) Ammonia stands above magnesia when cold. (2.) A triple salt is formed. (3.) Perhaps magnesia ought to stand lower. (4.) A compound salt is formed, and when hot, magnesia stands above ammonia. (5.) Fourcroy says, that sulphate ot strontia is decomposed by borate of ammonia. (6.) With heat, ammonia stands below lime and magnesia. ATT ATT TABLE II. By Dr. Young. NITRIC ACID. NITRIC AND MURIATIC ACIDS. Barita Potash Barita Potash Barita (10) Potash Potash Soda Potash Soda Potash Soda Soda Ammonia Soda Ammonia Soda Barita (10) Strontia Magnesia Ammonia Magnesia Ammonia Ammonia (7,11) Lime Glycina Magnesia Glycina Magnesia Magnesia (7) Magnesia C7) Alumina Glycina Alumina Glycina Strontia Ammonia (7) Zirconia (8) Alumina Zirconia Alumina Lime Glycina Barita Zirconia Barita Zirconia Glycina Alumina Strontia Strontia (9) Strontia Strontia Alumina Zirconia Lime Lime Lime Lime Zirconia Muriatic Phosphoric FLUORIC Sulphurous Boracic Carbonic. (7.) A triple salt is formed. (8.) Fourcroy says, that the muriate of zirconia decom- poses the phosphates of barita and strontia, (9.) According to Fourcroy's account, the fluate of strontia decomposes the muriates of ammonia, and of all the bases below it; but he says in another part ofthe same volume, that the fluate of strontia is an un- known salt. (10.) According to Fourcroy's account of these combinations, barita should stand immediately below ammonia in both of these columns. (11.) With heat, the carbonate of lime decomposes the muriate of ammonia. PHOSPHORIC ACID. Barita Lime Barita Potash Barita Lime Barita Lime Soda Lime Potash Potash Potash Barita Potash Soda Soda Soda Lime (13) Soda Strontia Strontia Strontia Strontia Strontia Magnesia Magnesia Ammonia(12) Ammonia Magnesia Ammonia Ammonia Magnesia Magnesia Glycina ? Glycina Glycina Glycina Glycina Alumina Alumina Alumina Alumina Alumina Zirconia Zirconia Zirconia Zirconia Zirconia Fluoric Sulphurous Bor^cio Carbonic (Phosphorous) (12.) According to Fourcroy, the phosphate of ammonia decomposes the borate of magnesia. (13.) Fourcroy says, that the carbonate of lime decomposes the phos< phates of potash and of soda. FLUORIC ACID. Lime Lime Potash Potash Barita Soda Soda Strontia Lime Magnesia Potash Barita Ammonia Soda Strontia Glycina Ammonia Ammonia (14) Alumina Magnesia Magnesia Zirconia Glycina Glycina Strontia Alumina Alumina Barita Zirconia Zirconia Sulphurous Bokacic Carbonic fl4.) According to Fourcroy, the carbonate of ammonia decomposes the fluate; arita and strontia. ATT ATT Dr. Young's SECOND TABLE—(concluded.) SULPHUROUS ACID. BORACIC ACID. Barita Potash Strontia Soda Potash Barita (15.) Soda Strontia Ammonia Ammonia Magnesia Lime Lime Magnesia Glycina Glycina Alumina Alumina Zirconia Zirconia Boracic Carbonic Lime Zirconia Potash Strontia Alumina Soda Barita Glycina Lime Zirconia Ammonia Barita Alumina Magnesia Strontia Glycina Strontia Magnesia Magnesia Soda Ammonia Ammonia Potash Glycina Soda Barita Alumina Potash Lime Zirconia (NlTROCs) (Phosphorous ?) Carbonic (15.) Fourcroy says, that the sulphite of barita decomposes the carbonate of ammonia. ,in. A Table ofthe Sequences of the Acids -with different Bases, by Dr. Young. BARITA. STRONTIA. LIME. Potash Soda MAG-NESIA. Sulphuric S C S S C S P S C P P P Magn.=Amm. fS B Nitric N S P N SS P S P P F F F Glycina N C Muriatic M P SS M F SS SS SS F B B SS Alumina Phosphoric SS SS N SS P F F F B SS C S Zirconia M P Sulphurous P N M C B B B B SS S SS B Each with every P F Fluoric C M F B S C C N S C S N subsequent base Boracic B F D F M N N M M N N M in this order, < F SS Carbonic F B C Strontia im pt mc P N M M C LM pt mo au GL \ M M C PT MO AM GL SS s SD AM SD AL SB AL B N OL ZR ZB C M AL ZR j. AJH The comparative use of this Table maybe understood from an example: If we sup- pose that the nitrate of barita decomposes the borate of ammonia, we must place the boracic acid above the nitric, between barita and ammonia in this Table, and conse- quently barita below ammonia, between the fluoric and boracic in the former: hence the boracic and fluoric acids must also be transposed between barita and strontia, and between barita and potash ; or if we place the fluoric still higher than the boracic in the first instance, we must place barita below ammonia between the nitric and fluoric acids, where indeed it is not impossible that it ought to stand. ATT ALT IV. A Numerical Table of Elective Attractions, by Dr. Younk B\RlTA. Sulphuric acid 1000* Oxalic 950 Succinic 930 Fluoric Phosphoric 906* Mucic 900 Nitric 849* Muriatic 840* Suberic 800 Citric Tartaric 760 Arsenic 733$ (Citric) 730 Lactic 729 (Fluoric) 706* Benzoic 597 Acetic 594 Boracic (515)* Sulphurous 592* Nitrous 450 Carbonic 420* Prussic 400 Strontia. Sulphuric acid 903* Phosphoric 827* Oxalic 825 Tartaric 757 Fluoric Nitric 754* Muriatic 748* (Succinic) 740 (Fluoric) 703 Succinic Citric ? 618 Lactic 603 Sulphurous 527* Acetic Arsenic (733$) Boracic 513* (Acetic) 480 Nitrous ? 430 Carbonic 419* Magnesia. Oxalic acid 820 Phosphoric Sulphuric 810* (Phosphoric) 736* Fluoric Arsenic 733 Mucic 732$ Succinic 732$ Nitric 732* Muriatic 728* Suberic ? 700 (Fluoric) 620* Tartaric 618 Citric 615 Malic ? 600? Lactic 575 Benzoic 560 Acetic Boracic 459* Sulphurous 4-39* (Acetic) 430 Nitrous 410 Carbonic 366* Prussic 280 Ammonia. Sulphuric acid 808* Nitric 731* Muriatic 729* Phosphoric 728* Suberic ? 720 Fluoric 613* Oxalic 611 Tartaric 609 Arsenic 607 Succinic 605 Citric 603 Lactic 601 Benzoic 599 Sulphurous 433* Acetic 432 Mucic 431 Boracic 430* Nitrous 400 Carbonic 339* Prussic 270 Potash. Sulphuric acid Nitric Muriatic Phosphoric Suberic ? Fluoric Oxalic Tartaric Arsenic Succinic Citric Lactic Benzoic Sulphurous Acetic Mucic Boracic Nitrous Carbonic Prussic S'MIA. 894* 885* 812* 804* 804* 797* 801* 795* 745 740 671* 666* 650 645 616 611 614 609 612 607 610 605 609 604 608 603 488* 484* 486 482 484 480 482* 479* 440 437 306* 304* 300 298 Li we. Oxalic acid 96Q Sulphuric 868* Tartaric 867 Succinic 866 Phosphoric 865* Mucic 860 Nitric 741* Muriatic 736* Suberic 735 Fluoric 734* Arsenic 733| Lactic 732 Citric 731 Malic 700 Benzoic 590 Acetic Boracic 537* Sulphurous 516* (Acetic) 470 Nitrous 425 Carbonic 423* Prussic 290 Glycina ? Sulphuric acid Nitric Muriatic Oxalic Arsenic Suberic ? Fluoric Tartaric Succinic Mucic Citric Phosphoric Lactic Benzoic Acetic Boracic Sulphurous Nitrous Carbonic Prussic Alumina. 718* 709* 642* 634* 639* 632* 600 594 580 575 535 530 534* 529* 520 515 510 505 425 420 415 410 (648)* (642)* 410 405 400 395 395 391 388* 385* 355* 351* 340 338 325* 32.3* 260 258 Zirconia!1 700* 626 625* 588 570 525 524* 510 500 415 405 (636)* 400 390 387 382* 347* 332 321* 256 Sulphuric. Barita 1000* Strontia 903* Potash 894* Soda 885* Lime 868* Magnesia 810+ Ammonia 808* Glycina 718* Itria 712 Alumina 709* Zirconia 700* Acids. Nitric. MrniATic. Barita 849* Barita 840* Potash 812* Potasli 804* Soda 804* Soda 797+ Strontia 754* Strontia 748* Lime 741* Lime 736* Magnesia 732* Ammonia 729* Ammonia 731* Magnesia 728* Glvcina 642* Glycina 639* Alumina 634* Alumina 632* Zirconia 626* Zirconia 6J5* Phosphoric Barita 906* Strontia 827* Lime (865)* Potash 801* Soda 795* Ammonia (728)* Magnesia 736* Glycina 648* Alumina 642* Zirconia 636* ATT ATT Fluoric. Lime 734* Barita 706* Strontia 703* Magnesia (620)* Potash 671* Soda 666* Ammonia 613* Glycina 534* Alumina 529* Zirconia 524* Oxalic Lime 960 Barita 930 Strontia 825 Magnesia 820 Potash 650 Soda 645 Ammonia 611 Glycina? 600 Alumina 594 Zirconia ? 588 Tartaric Arsknic 867 Lime 733| 760 Barita 733] 757 Strontia 733| 618 Magnesia 733 616 Potash 614 611 Soda 609 609 Ammonia 607 520 Glycina 580 515 Alumina 575 510 Zirconia 570 Tungstic Lime Barita Strontia Magnesia Potash Soda Ammonia Glycina Alumina Zirconia Succinic Barita 930 Lime 866 Strontia? 740 (Magnesia)732i Potash 612 Soda 607 Ammonia 605 Magnesia Glycina ? 510 Alumina 505 Zirconia? 500 Suberic Barita 800 Potash 745 Soda 740 Lime 735 Ammonia 720 Magnesia 700 Glycina ? 5:i5 ? Alumina 530 Zirconia ? 525 ? Camphoric. Lime Potash Soda Barita Ammonia Glycina? Alumina Zirconia ? Magnesia Citric Lime 731 Barita 730 Strontia 618 Magnesia 615 Potash 610 Soda 605 Ammonia 603 GUcina? 415? Alumina 410 Zirconia 405 Lactic Barita 729 Potash 609 Soda 604 Strontia 603 Lime (732) Ammonia 601 Magnesia 575 Metallic oxides Glycina 410 Alumina 405 Zirconia 400 Mucic ? Barita 900 Lime 860 Potash 484 Soda 480 Ammonia 431 Glycina 425 Alumina 420 Zirconia 415 Benzoic White oxide of Potash 608 Soda 603 Ammonia 599 Barita 597 Lime 590 Magnesia 560 Glycina ? 400? Alumina 395 Zirconia ? 390? Boraci c. Lime 537* Barita 515+ Strontia 513* Magnesia '459)* Potasli 482* Soda 479* Ammonia 430* Glycina 388* Alumina 385* Zirconia 382* Sulphurous. Barita 592* Lime 516* Potash 488* Soda 484* Strontia (527)* Magnesia 439* Ammonia 433* Glycina 355* Alumina 351* Zirconia 347* Nitrous ? Barita 450 Potash Soda Strontia Lime Magnesia 410 Ammonia 400 Glycina 340 Alumina 336 Zirconia 332 440 437 430 425 486 482 480 470 Acetic Barita 594 Potash Soda Strontia Lime Ammonia 432 Magnesia 430 Metallic oxides Glycina 395 Alumina 391 Zirconia 387 Phosphorous. Lime Barita Strontia Potash Soda Magnesia? Ammonia Glycina Alumina Zirconia Carbonic Barita 420* Strontia 419* Lime (423)* Potash > 306* Soda 304* Magnesia (366 )* Ammonia 33'J* Glvcina 325* Alumina 323* Zirconia 321* Prussic Barita 400 Strontia Potash Soda Lime Magnesia Ammonia Glycina ? Alumina ? 258 Zirconia ? 256 300 298 290 280 270 260 ATT ATT TABLES OF SIMPLE ELECTIVE ATTRACTIONS, FROM BERGMANN. I.—WATER AND COMBUSTIBLE SUBSTANCES IN THE HUMID WAY. Water. Sulphur. Saline sulphurets. Alcohol. Ether. Potash Oxygen Oxygen Water Alcohol Soda Molybdic oxide Oxide of gold Ether Volatile oils Ammonia and acid silver Volatile oils Water Deliquescent Oxide of lead mercury Ammonia Sulphur salts tin arsenic Fixed alkali i i Alcohol silver antimony Alkaline sul- j Carbonate of mercury bismuth phurets j ammonia arsenic copper Sulphur Ether antimony tin Muriates Sulphuric acid iron lead Phosphoric acid Non-deliques-cent salts Potash Soda Barytes nickel cobalt manganese Fat Oils. Volatile Oils. Strontian iron Lime Other metallic Barytes ? Ether Magnesia oxides Strontian ? Alcohol Phosphorus Carbon Lime Fat oils Fat oils Water Metallic oxides Fixed alkalis Ammonia Alcohol Ether Sulphur Ether Ether Volatile oils Phosphorus Hydrogen? Fixed alkalis Ammonia Sulphur Phosphorus ^———— IN THE L IRY WAY. sulphcretted Hydrogen. Oxygen Potash Manganese Iron Barytes Soda Copper Potash Iron Tin Soda Copper Lead Lime Tin Silver Ammonia Lead Gold Magnesia Silver Antimony Zircon Cobalt Cobalt Nickel Nickel j Bismuth Bismuth j Antimony Mercury ! Mercury Arsenic j Arsenic Carbon ? i Uranium ? \ Molybdena '< • Tellurium ATT ATT TABLE or Simple Elective Attractions. II__OXYGEN AND METALS. FN THE HUMID WAY. OXYGEN. Oxide of Gold. Oxide of Silver. Oxide of Platina. Oxide of Mercury. Oxide of Lead. Zinc Iron Tin Antimony Arsenic Lead Bismuth Copper Platinum Mercury ("Palladium J Rhodium j Iridium (.Osmium Silver Gold j Acids, gallic muriatic nitric sulphuric arsenic fluoric tartaric phospho-ric acetic sebacic prussic Fixed alkalis Ammona Sulphuretted hydrogen Acids, gallic muriatic oxalic sulphuric mucic phospho-ric sulphu-rous nitric arsenic fluoric tartaric citric succinic acetic prussic carbonic Ammonia Acids, gallic muriatic nitric sulphuric arsenic fluoric tartaric phospho-ric oxalic citric acetic succinic prussic carbonic Ammonia Acids, gallic muriatic oxalic succinic phospho-ric sulphuric mucic tartaric citric malic sulphu-rous nitric fluoric acetic benzoic boracic prussic carbonic Ammonia Acids, gallic sulphuric mucic oxalic arsenic tartaric phospho-ric muriatic sulphu-rous suberic nitric fluoric citric malic succinic acetic benzoic boracic prussic carbonic Fixed alkalis Fat oils Ammonia IN THE DRY WAY. Titanium Manganese Zinc Iron Tin Uranium Molybdena Tungsten Cobalt 'Antimony INickel JArsenic iChromium IBismuth J.ead jCopper iTellurium Hatinum Mercury-Silver Gold Gold. Silver. Platiha. Mercury. Lead. Mercury Copper Silver Lead Bismuth Tin Antimony Iron Platina Zinc Nickel Arsenic Cobalt Manganese Alkaline sul-phurets Lead Copper Mercury Bismuth Tin Gold Antimony Iron Manganese Zinc Arsenic Nickel Platina Alkaline sul-phurets Arsenic Gold Copper Tin Bismuth Zinc Antimony Nickel Cobalt Manganese Iron Lead Silver Mercury Alkaline sul-phurets Gold Silver Platina Lead Tin Zinc Bismuth Copper Antimony Arsenic Iron Alkaline sul-phurets Sulphur Gold Silver Copper Mercury Bismuth Tin Antimony Platina Arsenic Zinc Nickel Iron Alkaline sul-phurets Sulphur Hydrogen Carbon Boron Phosphorus Sulphur Azote Chlorine The column under oxygen is divided into two parts. The first exhibits the order in which the metals precipitate one another from acid solutions ; the second, according to Vauquelin, shows the affinities of the metals for ovygen, represented by the difficulty with which their oxides are decompo-sed bv heat. It is different from Bergmann's column. ATT ATT TABLE or Simple Elective Attractions. METALS—(continued). IN THE HUMID WAY. 1 Oxide of f Copper. Oxide of Iron. Oxide of Tin. Oxide of Bismuth. Oxide of Nickel. Oxide of Arsenic. Acids, gallic oxalic tartaric muriatic sulphuric mucic nitric arsenic phospho-ric succinic fluoric citric acetic boracic prussic carbonic Potash Soda Ammonia Compound salts Fat oils Acids, gallic oxalic tartaric campho-ric sulphuric mucic muriatic nitric phospho-ric arsenic fluoric succinic citric acetic boracic prussic carbonic Acids, gallic tartaric muriatic sulphuric oxalic arsenic phospho-ric nitric succinic fluoric mucic citric acetic boracic prussic Potasli Soda Ammonia Acids, oxalic arsenic tartaric phospho-ric sulphuric muriatic nitric fluoric mucic succinic citric acetic prussic carbonic Ammonia Acids, oxalic muriatic sulphuric tartaric nitric sebacic phospho-ric fluoric mucic succinic citric acetic arsenic boracic prussic carbonic Ammonia ^.cids, gallic muriatic oxalic sulphuric nitric sebacic tartaric phospho-ric fluoric mucic succinic citric arsenic acetic prussic Fixed alkahs Ammonia Fat oils Water IN THE DRY WAY. Copper. Iron. Tin. Bismuth. Nickel. Arsenic. Gold Silver Iron Arsenic Manganese Zinc Antimony Platina Tin Lead Nickel Bismuth Cobalt Mercury Alkaline sul phurets Sulphur Nickel Cobalt Manganese Arsenic Copper Gold Silver Tin Antimony Platina Bismuth Lead Alkaline sul-phurets ■ Sulphur Zinc Mercury Copper Antimony Gold Silver Lead Iron Manganese Nickel Arsenic Platina Bismuth Cobalt Alkaline sul phurets Sulphur Lead Silver Gold Mercury Antimony Tin Copper Platina Nickel Iron Zinc Alkaline sul-phurets Sulphur Iron Cobalt Arsenic Copper Gold Tin Antimony Platina Bismuth Lead Silver Zinc Alkaline sul phurets Sulphur Nickel Cobalt Copper Iron Silver Tin Lead Gold Platina Zinc Antimony Alkaline sul-phurets Sulphur ATT ATT TABLE of Simm.e Elective Attraction. METALS—(concluded.) IN THE HUMID WAY. OXIUK OF Oxide of Oxide of Oxide of Oxide of 1 Oxide of Con ALT. Zinc Axtimont. IIanc.anf.se. L'ki.luhiu.m. Titanium. Acids, oxalic Acids, gallic Acids, gallic Vcids, oxalic Acids, nitric Acids,sulphu- muriatic oxalic muriatic tartaric nitro-mu- ric sulphuric sulphuric benzoic citric riatic nitric tartaric muriatic oxalic fluoric Sulphuric muriatic nitric mucic sulphuric phospho- Sulphur prussic phospho- nitric nitric ric Alkalis ric tartaric tartaric nitric Mercury fluoric mucic phospho-ric mucic phospho- sulphuric muriatic succinic citric ric arsenic Oxide of citric acetic succinic fluoric citric succinic acetic prussic Uranium. arsenic arsenic fluoric carbonic Acids, sulphu- boracic acetic arsenic ric prussic boracic acetic nitro-mu- carbonic prussic boracic riatic Ammonia carbonic prussic muriatic Fixed alkalis carbonic nitric Ammonia Sulphur Fixed alkahs Ammonia phospho-ric acetic gallic prussic carbonic IN 1 rHE DRY WAY. Sulphur Cobalt. Zinc. Antimony. Manganese. Telixrium. Iron Copper Iron Copper Mercury Nickel Antimony Copper Iron Gold Sulphur Arsenic Tin Tin Copper Mercury L.cad Silver Gold Silver Nickel Tin Platina Gold Silver Alkaline sul- Tin Cobalt Bismuth phurets Antimony Arsenic Zinc Zinc Platina Gold Alkaline sul- B'smuth Platina phurets Lead Mercury Sulphur Nickel iron Arsenic Cobalt Alkaline sul-phurets 1 Sulphur 1 Vol. f P27n ATT ATT SCHEMES OF DOUBLE AFFINITIES IN THE HUMID WAV {"Sulphuric j acid Sulphate I of «( 50 sia | | Fluoric (.Magnesia acid r ~v~ '—rr» Muriatic^ acid 0\v Awem- J Oxygen"! Igenated ous ^ I Oxygen f-muriati fPotash 26 Acetic acid Sulphuret of potash .Sulphur Sulphate of lime "Lime Sulphuret of lime 54 Sulphuric acid ^Sulphur Muriate of potash _______A_______ fPotash 32 Muriatic"" acid Sulphate | ,«„„„[ Muriate of pot- ^ 62 + 23=85j>oflime ash , 54 Sulphn- Lric acid 86 Lime Sulphate ofUme Nitre ___A._ Sulphate of pot- • ash fPotash 58 Nitric acid 62 Sulphuric Oxide of l_ acid lead _ «-------v--------< Sulphate of lead Nitrate oftead fPotash 62 Sulphu-^ ric acid Muriate of pot- < ash Sul- 33 + 51 = 86 Vphate o? [ lime Muriatic ^ acid 85 Lime J Sulpbate of am- monia Nitrate of ammorta t--------*-----~7> Ainrao> 38 Nitr-iO nia acid j J Nitrate 46 Sof mer- j cury Sulphuric Oxide of j acid mercury J Sulphate of mercury Nitrate of soda fSoda Com- mon salt Nitric " acid >Nitrate of silver Muriatic V_ acid Silver^ _____) Muriate of silv«f AUK AX1 * Augtte. Pyroxene of Haiiy. This mineral is for the most part crystallized in small six or eight-sided prisms, with dihe- dral summits. It is found also in grains. Its colours are green, brown, and black. Internal luster shining. Uneven fracture. Translucent. Easily broken. It Scratches glass. Sp. gr. 3.3. Molts into a black enamel. Its composition according to Klaproth, is 48 silica, 24 lime, 1* oxide of iron, 8.75 magnesia, 5 alumina, 1 manga- nese It is met with among volcanic rocks but is supposed to have existed prior to the eruption, and ejection of the lava. Large crystals of it are also found in ba- salt, of a finer green and more brilliant than those found in lavas. It occurs with olivin in the basalt of Teesdale; in the trap rocks round Edinburgh; and in seve- ral ofthe Hebrides. Sahlite and coccolite are considered to be varieties of augite.* Aurum Fclmisans. See Fulminating. • Aurum GuArnicuM. See Ores of Gold* Aurum Musivum, or Mosaicum. A com- bination of tin and sulphur, which is thus made: Melt 12 ounces of tin, and add to it three ounces of merenry; triturate this amalgam with seven ounces of sulphur and three of muriate of ammonia. Put the powder into a matrass, bedded rather deep in sand, and keep it for several hours in a gentle heat; which is afterward to be raised, and continued for several hours longer. If the heat have been moderate and not continued too long, the golden- coloured scaly porous mass, called aurum musivum, will be found at the bottom of the vessel; but if it have been too strong, the aurum musivum fuses to a black mass of a striated texture. This process is thus explained : As the heat increases, the tin, by stronger affinity, seizes and combines with the muriatic acid of the muriate of ammonia; while the alkali of that salt, combining with a portion of the sulphur, flies off in the form of a sulphuret. The combination of tin and muriatic acid sub- limes ; and is found adhering to the sides ofthe matrass. The mercury which served todi^'idethe tin, combines with part of the sulphur, and forms cinnabar, which also sublimes; and the remaining sulphur, with the remaining tin forms the aurum ^musivum, which occupies the lower part ofthe vessel. It must be admitted, how- ever, that this explanation does not in- dicate the reasons why such an indirect ■and complicated process should be re- quired to form a simple combination of tin and sulphur. It does not appear that the proportions of the materials require to be strictly at- tended to. The process of the Marquis de Bullion, as described by Chaptal in his Elements of Chemistry. consists in amal- gamating eight ounces of tin with eight ounces of mercury, and mixing this with six ounces of sulphur, and four of muri- ate of ammonia. This mixture is to be exposed for three hours on a sand heat sufficient to render the bottom of the ma- trass obscurely red-hot. But Chaptal him- self found, that if the matrass containing the mixture were exposed to a naked fire and violently heated, the mixture took fire and a sublimate was formed in the neck of the matrass, consisting of the most beau- tiful aurum musivum in large hexagonal plates. Aurum musivum has no taste, though some specimens exhibit a sulphureous smell. It is not soluble in water, acids, or alkaline solutions. But in the dry way it forms a yellow sulphuret, soluble in water. It deflagrates with nitre. Bergmann men- tions a native aurum musivum from Sibe- ria, containing tin, sulphur, and a small pro- portion of copper. Aurum musivum is used as a pigment for giving a golden colour to small statue or plaster figures. It is likewise said to be mixed with melted glass to imitate la- pis lazuli. * Mosaic gold is composed of 100 tin-f- 56.25 sulphur, by Dr. John Davy; and of 100 tin -f- 52.3 sulphur, by Professor Ber- zelius ; the mean of which, or 100 -f- 54.2 is probably correct. It will then consist of 1 prime of tin = 7.375 -}- 2 sulphur= 4.C.* * AvAWTuniNE. A variety of quartz rock containing mica spangles. The most beau- tiful comes from Spain, but Dr. M'Culloch found specimens at Glen Fernat in Scot- land, which, when polished, were equal in beauty to any of the foreign. The most usual colour of the base of avanturine is brown, or reddish-brown, enclosing gold- en coloured spangles.* * Axf.-stose. A subspecies of jade, from which it differs in not being of so light a green, and in having a somewhat slaty texture. The natives of New Zea- land work it into hatchets. It is found in Corsica, Switzerland, Saxony, and on the banks of the river Amazons, whence it has been called Amazonian stone. Its constituents are silica 50.5, magnesia Jl, alumina 10, oxide of iron 5.5, water 2.75, oxide of chromium 0.05.* * Axinite, or Thumerstonr. This mineral is sometimes massive, but most usually crystallized. The crystals resem- ble an axe in the form and sharpness of their edges; being flat rhomboidal pa- rallelopipeds, with two of the opposite edges wanting, and a small face instead of each. They are translucent, and of a vio- let colour, whence called violet schorl. They become electric by heat. The usual colour is clove-brown. J^ustre splendent. AZU AZU Hard, but yields to the file, and easily broken. Sp. gr. 3.25. It froths like zeo- lite before the blow-pipe, melting into a black enamel, or a dark green glass. Ac- cording to Vauquelin's analysis, it con- tains 44 silica, 18 alumina, 19 lime, 14 ox- ide of iron, and 4 oxide of manganese. It is found in beds at Thum in Saxony; in Killas at Botallack near the Land's-end, Cornwall; and at Trewellard in that neigh- bourhood.* Azote. See Gas (Nitrogen). * Azure-stone, or Lapis Lazuli. This massive mineral is of a fine azure blue co- lour. Lustre glistening. Fine grained uneven fracture. Scratches glass, but scarcely strikes fire with steel. Opaque, or translucent on the very edges. Easily broken. Sp. grav. 2.85. In a very strong heat it intumesces, and melts into a yel- lowish-black mass. After calcination it forms a jelly with acids. It consists of 46 silica, 28 lime, 14.5 alumina, 3 oxide of iron, 6.5 sulphate of lime, and 2. water, according to Klaproth. But by a later and most interesting research of MM. Cle- ment and Desormes, lapis lazuli appears to be composed of 34 silica, 33 alumina, 3 sulphur, and 22 soda. (Ann. de Chimie, torn. 57.) In this analysis, however, a loss of eight per cent was experienced. These distinguished chemists consider the above ingredients essential, and the 2.4 of lime and 1.5 of iron, which they have oc- casionally met with, as accidental. It is from azure-stone that the beautiful and un- changeable blue colour ultramarine i* pre- pared. The finest specimens are brought from China, Persia, and Great Bucharia. They are made red-hot in the fire, and thrown into water to render them easily pulverizable. They are then reduced to a fine powder, and intimately combined with a varnish, formed of rosin, wax, and boiled linseed oil. This pasty mixture is put into a linen cloth, and repeatedly kneaded with hot water: the first water, which is usually dirty, is thrown away ; the second gives a blue ofthe first quality -, and the third yields one of less value. The process is founded on the property which the colouring matter of azure-stone has of adhering less firmly to the resinous cement, than the foreign matter with which it is associated. When azure-stone has its co- lour altered by a moderate heat, it is reck- oned bad. Messrs. Clement and Desormes consider the extraction of ultramarine as a species of saponification.* * Azurite, the Lazulite of Werner and Hatty. This mineral is often found in oblique quadrangular crystals of a fine blue colour. It is translucent only on the edges, brittle,and nearly as hard as quartz. When massive, it is either in grains, or bits like a hazel nut. It occurs imbedded in mica slate. Its lustre is vitreous. Its constituents are 66 alumina, 18 magnesia, 10 silica, 2.5 oxide of iron, 2 lime. It oc- curs in Vorau in Stiria in a gangue of quartz; but the finest specimens come from the bishopric of Salzburg.* B BALANCE. The beginning and end of every exact chemical process consists in weighing. With imperfect instruments this operation will be tedious and inaccu- rate; but with a good balance, the result will be satisfactory; and much time, which is so precious in experimental researches, will be saved. The balance is a lever, the axis of mo- tion of which is formed with an edge like that of a knife; and the two dishes at its ex- tremities a*e hung upon edges of the same kind. These edges are first made sharp, and then rounded with a fine hone, or a piece of buff leather. The excellence of the instrument depends, in a great nieasure, on the regular form of this rounded part. When the lever is considered as a mere line, the two >outer edges are called points of suspension, and the inner the fulcrum. The points of suspension are supposed to be at equal distances from the fulcrum, and to be pressed with equal weights when loaded. 1. If the fulcrum be placed in the centre of gravity of the beam, and the three ed- ges lie all in the same right line, the bal- ance will have no tendency to one position more than another, but will rest in any po- sition it may be placed in, whether the scales be on or off", empty or loaded. 2. If the centre of gravity of the beam, when level, be immediately above the ful- crum, it will overset by the smallest action; that is, the end which is lowest will descend: and it will do this with more swiftness, the higher the centre of gravity, and the less the points of suspension are loaded. 3. But if the centre of gravity of the beam be immediately below the fulcrum, the beam will not rest in any position but when level: and, if disturbed from this po- sition, and then left at liberty, it will vi- brate, and at last come to rest on the level. Its vibrations will be quicker, and its ho- rizontal tendency stronger, the lower the centre of gravity, and the less the weights upon the points of suspension. 4. If the fulcrum be below the line join- ing the points of suspension, and these be loaded, the beam will overset, unless pre- vented by the weight of the beam tending to produce a horizontal position, as in § 3. In this last case, small weights will equili- brate, as in § 3.; a certain exact weight will rest in any position ofthe beam, as in § 1.; and all greater weights will cause the beam to overset, as in § 2. Many scales are often made this way, and will overset with any considerable load. 5. If the fulcrum be above the line join- ing the points of suspension, the beam will come to the horizontal position, unless pre- vented by its own weight, as in § 2. If the centre of gravity of the beam be nearly in the fulcrum, all the vibrations of the loaded beam will be made in times nearly equal, unless the weights be very small, when they will be slower. The vibrations of balances are quicker, and the horizontal tendency stronger, the higher the fulcrum. 6. If the arms of a balance be unequal, the weights in equipoise will he unequal in the same proportion. It is a severe check upon a workman to keep the arms equal, while he is making the other adjustments in a strong and indexible beam. 7. The equality ofthe arms of a balance is of use, in scientific pursuits, chiefly in making weights by bisection. A balance with unequal arms will weigh as accurately as another of the same workmanship with equal arms, provided the standard weight itself be first counterpoised, then taken out of the scale, and the thing to be weighed be put into the scale, and adjusted against the counterpoise; or when proportional quantities only are considered, as in che- mical and in other philosophical experi- ments, the bodies and products under exa- mination may be weighed against the weights, taking care always to put the weights into the same scale. For then, though the bodies may not be really equal to the weights, yet their proportions among each other may be the same as if they had been accurately so. 8. But though the equality of the arms may be well dispensed with, yet it is indis- pensably necessary, that their relative lengths, whatever they may be, should con- tinue invariable. For this purpose, it is ne- cessary, either that the three edges be all truly parallel, or that the points of suspen- sion and support should be always in the same part of the edge. This last requisite is the most easily obtained. The balances made in London are usual- ly constructed in such a manner, that the bearing parts form notches in the other parts ofthe edges; so that the scales being set to vibrate, all the parts naturally fall into the same bearing. The balances mado in the country have the fulcrum edge straight, and confined to one constant bear- ing by two side plates. But the points of suspension are referred to notches in the edges, like the London balances. The bal- ances here mentioned, which come from the country, are enclosed in a small iron japanned box; and are to be met with at the Birmingham and Sheffield warehouses, though less frequently than some years ago; because a pocket contrivance for weighing guineas and half-guineas has got posses- sion of the market. They are, in general, well made and adjusted, turn with the twentieth of a grain when empty, and will sensibly show the tenth of a grain, with an ounce in each scale. Their price is from 22 BAL BAL five shillings to half a guinea; but those which are under seven shillings have not their edges hardened, and consequently are not durable. This may be ascertained by the purchaser, by passing the point of a penknife across the small piece which goes through one of the end boxes: if it makes any mark or impression, the part is soft. 9. If a beam be adjusted so as to have no tendency to any one position, as in § 1. and the scales be equally loaded; ihen, if a small weight be added in one ofthe scales, that balance will turn, and the points of suspen- sion will move with an accelerated motion, similar to that of falling bodies, but as much slower, in proportion, very nearly, as the added weight is less than the whole weight borne by the fulcrum. 10. The stronger the tendency to a hori- zontal position in any balance, or the quicker its vibrations, §§ 3. 5. the greater additional weight will be required to cause it to turn, or incline to any given angle. No balance, therefore, can turn so quick as the motion deduced in § 9. Such a balance as is there described, if it were to turn with the ten-thousandth part ofthe weight, would move at quickest ten thousand times slower than falling bodies; that is, the dish contain- ing the weight, instead of falling through sixteen feet in a second of time, would fall through only two hundred parts of an inch, and it would require four seconds to move through one-third part of an inch; conse- quently all accurate weighing must be slow. If the indexes of two balances be of equal lengths, that index which is connected with the shorter balance will move proportional- ly quicker than the other Long beams are the most in request, because they are thought to have less friction; this is doubt- ful; but the quicker angular motion, greater strength, and less weight of a short balance, are certainly advantages. 11. Very delicate balances are not only useful in nice experiments, but are likewise much more expeditious than others in com- mon weighing If a pair of scales with a certain load be barely sensible to one-tenth of a grain, it will require a considerable time to ascertain the weight to that degree of accuracy, because the turn must be ob- served several times over, and is very small. But if no greater accuracy were required, and scales were used, which would turn with the hundredth of a grain, a tenth of a grain, more or less, would make so great a difference in the turn, that it would be seen immediately. 12. If a balance be found to turn with a certain addition, and is not moved by any smaller weight, a greater sensibility may be given to that balance, by producing a tre- mulous motion in its parts. Thus, if the edge of a blunt saw, a file, or other similar instrument, be drawn along any part of the case or support of a balance, it will pro- duce a jarring, which will diminish the friction on the moving parts so much, that the turn will be evident with one-third or one-fourth of the addition that would else have been required. In this way, a beam which would barely turn by the addition of one-tenth of a grain, will turn with one- thirtieth or fortieth of a grain. 13. A balance, the horizontal tendency of which depends only on its ojim weight, as in § 3. will turn with the same addition, whatever may be the load; except so far as a greateaload will produce a greater fric- tion. 14. But a balance, the horizontal tenden- cy of which depends only on the elevation of the fulcrum, as in $ 5. will be less sen- sible the greater the load; and the addition requisite to produce an equal turn will be in proportion to the load itself. 15. In order to regulate the horizontal tendency in some beams, the fulcrum is placed below the points of suspension, as in § 4. and a sliding weight is put upon the cock or index, by means of which the centre of gravity may be raised or depressed. This is a useful contrivance. 16. Weights are made by a subdivision of a standard weight. If the weight be con- tinually halved, it will produce the common pile, which is the smallest number for weighing between its extremes, without placing any weight in the scale with the body under examination. Granulated lead is a very convenient substance to be used in this operation of halving, which, how- ever, is very tedious. The readiest way to subdivide small weights, consists in weigh- ing a certain quantity of small wire, and afterward cutting it into such parts, by measure, as are desired; or the wire may be wrapped close round two pins, and then cut asunder with a knife. By this means it will be divided into a great number of equal lengths, or small rings. The wire ought to be so thin, as that one of these rings may barely produce a sensible effect on the beam. If any quantity (as, for ex- ample, a grain) of these rings be weighed, and the number then reckoned, the grain may be subdivided in any proportion, by di- viding that number, and makingthe weights equal to as many of the rings as the quo- tient of the division denotes. Then, if 750 of the rings amounted to a grain, and it were required to divide the grain decimally, downwards, 9-10ths would be equal to 675 rings, 8-10ths would be equal to 600 rings, 7-10ths to 525 rings, &c. Small weights may be made of thin leaf brass. Jewellers' foil is a good material for weights below l-10th of a grain, as low as to l-100th of a grain; and all lower quantities may be either esti- BAL BAL mated by the position of the index, or shown by actually counting the rings of wire, the value of which has been deter- mined. 17. In philosophical experiments, it will be found very convenient to admit no more than one dimension of weight. The grain is of that magnitude as to deserve the pre- ference. With regard to the number of weights the chemists ought to be provided with, writers have differed according to their habits and views. .Mathematicians have computed the least possible number, with which all weights within certain lim- its might be ascertained; but their deter- mination is of little use. Because, with so small a number, it must often happen, that the scales will be heavily loaded with weights on each side, put in with a view only to determine the difference between them. It is not the least possible number of weights which it is necessary an operator should buy to effect his purpose, that we ought to inquire after, but the most con- venient number for ascertaining his in- quiries with accuracy and expedition. The error of adjustment is the least possible, when only one weight is in the scale; that is, a single weight of five grains is twice as likely to be true, as two weights, one of three, and the other of two grains, put into the dish to supply the place of the single five; because each of these last has its own probability of error in adjustment. But since it is as inconsistent with convenience to provide a single weight, as it would be to have a single character for every num- ber; and as we have nine characters, which we use in rotation, to express higher values according to their position, if will be found very serviceable to mt.ke the set of weights correspond with our numerical system. This directs us to the set of weights as follows: 1000 grains, 900 g. 800 g. 700 g. 600 g. 500 g. 490 g. 3u0 g. 200 g. 100 g 90 g. 80 g. 70 g. 60 g. 50 g. 40 g. 30 g. 20 g. 10 g. 9g. 8g. 7 g. 6g. 5g. 4 g. 3g- 2g. lg- t% t- A S TV g- To g fV g' TV g" To" gs TTT ± TO £• T77 g" dhr g- ih> g- TTo »• TTHT g- Too 5- ToSr g TCTg'TW?- With these the philosopher will always have the same number of weights in his scales, as there are figures in the number expressing the weights in grains. Thus 742 5 grains will be weighed by the weights 700, 40, 2, and 5-10ths. I shall conclude this chapter with an ac- count of some balances I have seen or heard of, and annex a table of the corres- pondence of weights of different countries. Muschenbroek, in his Cours de Physique, (French translation, Paris, 1769), torn. ii. p. 247. says, he used an ocular balance of great accuracy, which turned (trebuchoit) with -i^ of a grain. The substances he weighed were between 200 and 300 grains. Hisbalance therefore weighedtothe -j-j ^j-y part of the whole; and would ascertain such weights truly to four places of figures. In the Philosophical Transactions, vol. lxvi. p. 509. mention is made of two accu- rate balances of Mr. Bolton; and it is said that one would weigh a pound, and turn with -J.- of a grain. This, if the pound be avoirdupois, is y^^oo of t,,e weignti and shews that the balance could be well depend- ed on to four places of figures, and probably to five. The other weighed half an ounce, and turned with -j-i^ of a grain. This is *?kn> of t,,e weiS"t. In the same volume, p. 511 a balance of Mr. Read's is mentioned, which readily turned with less than one pennyweight, when loaded with 55 pounds, before the Royal Society, but very distinctly turned with four grains, when tried more patiently. This is about 7-6^00 part of the weight; and therefore this balance may be depend- ed on to five places of figures Also, page 576. a balance of Mr. White- hurst's weighs one pennyweight, and is sen- sibly affected with 17^ of a grain. This is xg-^jro Part of the weight. I have a pair of scales of the common construction, § 8. made expressly for me by a skilful workman in London. With 1200 grains in each scale, it turns with -fg of a grain. This is T-^7o- of the whole; and therefore about this weight may be known to five places of figures. The proportional delicacy is less in greater weights. The beam will weigh near a pound troy; and when the scales are empty, it is affected by 1 _ of a grain. On the whole, it may be usefully applied to determine all weights be- tween 100 grains and 4000 grains to four places of figures. A balance belonging to Mr Alchorne of the Mint in London, is mentioned, vol. lxxvii. p. 205. of the Philosophical Transac- tions. It is true to 3 grains with 15 lb. an end. If these were avoirdupois pounds, the weight is known to -g^l-^ Part» or t0 four places of figures, or bare.y five. A balance, (made by Uamsden, and turn- ing on points instead of edges) in the pos- session of Dr. George Fordyce, is mentioned in the seventy-fifth volume of the Philoso- phical Transactions. With a load of four or five ounces, a difference of one division in the index was made by TSVo- °* a £ram- This is yg-rVrro- Pa't of t,ie weight, and consequently this beam will ascertain such weights to five places of figures, beside an estimate figure. BAL BAL I have seen a strong balance in the pos- session of my friend Mr. Magellan, of the kind mentioned in § 15. which would bear several pounds, and showed i of a grain, with one pound an end. This is ^0000 of the weight, and answers to five figures. But I think it would have done more by a more patient trial than I had time to make. The Royal Society's balance, which was lately made by Ramsden, turns on steel edges, upon planes of polished crystal. I was assured, that it ascertained a weight to the seven-millionth part. 1 was not present at this trial, which must have required great care and patience, as the point of suspension could not have moved over much more than the T|^ of an inch in the first half minute; but, from some trials which I saw, I think it probable that it may be used in general practice to determine weights to five places and better. From this account of balances, the stu- dent may form a proper estimate of the value of those tables of specific gravities, which are carried to five, six, and even seven places of figures, and likewise of the theoretical deductions in chemistry, that depend on a supposed accuracy in weighing, which practice does not authorise. In gene- ral, where weights are given to five places of figures, the last figure is an estimate, or guess figure; and where they are carried farther, it may be taken for granted, that the author deceives either intentionally, or from want of skill in reducing his weights to fractional expressions, or otherwise. The most exact standard weights were procured, by means of the ambassadors of Franco, resident in various places; and these were compared by Mons. Tillet with the standard mark in the pile preserved in the Gourde Monnoies de Paris. His experiments were made with an exact balance made to weigh one marc, and sensible to one quarter of a grain. Now, as the marc contains 18432 quarter grains, it follows that this balance was a good one, and would exhibit proportions to four places, and a guess figure. The results are contained in the fol- lowing table, extracted from Mons. Tillet's excellent paper in the Memoirs of the Royal Academy of Sciences for the year 1767. I have added the two last columns, which show the number of French and English grains contained in the compound quantities against which they stand. I'he t.nglish grains are computed to one-tenth of a grain, although the accuracy of weigh- ing came no nearer than about two-tenths. The weights of the kilogramme, gramme, decigramme, and centigramme, which are now frequently occurring in the French che- mical writers, are added at the bottom of this table, according to their respective values. Table of the Weights of different Countries. Place and Denomination of Weights. Berlin. The marc of 16 loths, - - - - Berne. Goldsmiths' weight of 8 ounces, Berne. Pound of 16 ounces, for merchan- dise, ...... The common pound varies very consi- derably in other towns of the canton. Berne. Apothecaries' weight of 8 ounces, Bonn. ..... Brussels. The marc, or original troyes wt. Cologn. The marc of 16 loths, Constantinople. The chtki, or 100 drachms, Copenhagen. Goldsmiths' weight, com-"\ monly supposed equal to the marc > of Cologn, J Copenhagen. Merchants' weight of 16 loths, Dantzic weight, commonly supposed equal to the marc of Cologn, Florence. The pound (anciently used by , the Romans), ' C Genoa. The peso sottile, . . - Genoa. The peso grosso, ... Hamburgh weight, commonly supposed J equal to the Cologn marc, C Hamburgh. Another weight, Liege. The Brussels marc used; but the weight proved, Lisbon. The marc, or half pound, marc. oz. gros. grains. F. grains. E. grains 1 7 % 16 4 4408 4648 3616.3 3813.2 2 1 h 6 9834 8067.7 1 1 7 7 7 2 5* 5 5 3 26 6| 21 11 28 4454 4398| 4629 4403 6004 3654. 3608.6 3797.6 3612-2 4925.6 — 7 51 i«4 44381 3641.2 1 — 1 224 4702$ 3857.9 — 7 5 H 4395* 3606. 1 3 i 20 6392 5244. 1 1 2 2 24 3 30 5 5970 5981 4897.7 4906.7 — 7 5 n 4399| 3609.4 — 7 7 23 4559 3740.2 1 — 24 4632 3800.1 7 1 3i 34 ' 4318 3542.4 BAL BAL Place and Denomination of Weights. London. The pound troy, London. The pound avoirdupois, Lucca. The pound, - Madrid. The marc royal of Castile, Malta. The pound, .... Manheim. (The Cologn marc), Milan. The marc, .... Milan. The libra grossa, Munich. (The Cologn marc), J\"aples. The pound of 12 ounces, Batisbon.The weight for gold:of 128crown9 Ratisbon. The weight for ducats: of 64^ ducats, 5 Ratisbon. The marc of 8 ounces, Ratisbon. The pound of 16 ounces, - - Rome. The pound of 12 ounces, Stockholm. The pound of 2 marcs, - - Stuttgard. (The Cologn marc), Turin. The marc of 8 ounces, At Turin they have also a pound of 12 of the above ounces. But, in their apothecaries' pound of 12 ounces, the ounce is one-sixth lighter. Warsaw. The pound, - - . - Venice. The libra grossa of 12 ounces, - Venice. The peso sottile of 12 ounces, - In the pounds dependent on Venice, the pound differs considerably in each. Vienna. The marc of commerce, - Vienna. The marc of money, England. The grain, - France. The grain, .... The kilogramme, The gramme, ... The decigramme, ... The centigramme, marc. 1 1 1 1 grot, grains. 1 6 23 8i 21 10 ,:i 11 274 24 32 24 6 14 8 "i 22* 12 24 16 26 F. grains. E. grains. 7021 5760. 8538 7004.5 6359+. 5217. 4328 3550.7 5961 4890.4 44U2 3611.5 4425 3660.2 143644 11784. 4403$ 3612.3 6039 4954.3 8088 6635.3 4208 3452.3 4632 3800.1 10698 8776.5 6386 5239. 8000 6563.1 4403$ 3612.6 4630* 3799. 7644 89894 5676 5272 5282 1.21895 - I 1- 35 18827.15 18.827 1.8827 .18827 6271. 7374.5 4656.5 4325. 4333.3 1. 0.82039 15445.5 15.445 1.5445 .15445 See Tables of Weights and Measures in the Appendix. * The commissioners, appointed by the British government for considering the sub- ject of weights and measures, gave in their first report on the 24th June 1819. The fol- lowing is the substance of it: " 1. With respect to the actual magnitude of the standards of length, the commis- sioners are of opinion, that there is no suffi- cient reason for altering those generally employed, as there is no practical advan- tage in having a quantity commensurable to any original quantity existing, or which may be imagined to exist, in nature, except as affording some little encouragement to its common adoption by neighbouring nations. " 2. The subdivisions of weights and measures at present employed in this coun- try, appear to be far more convenient for practical purposes than the decimal scale. The power of expressing a third, a fourth, and a sixth of a foot in inches, without a fraction, is a peculiar advantage in the duo- decimal scale; and for the operation of weighing and of measuring capacities, the continual division by two, renders it practi- cable to make up any given quantity with the smallest possible number of weights and measures, and is far preferable in this res- pect to any decimal scale. The commis- sioners therefore recommend, that all the multiples and subdivisions of the standard to be adopted, should retain the same re- lative proportions to each other as are at present in general use. " 3. That the standard yard should be that employed by Gen. Roy in the measurement of a base on Ilounslow Heath, as a founda- tion of the great trigonometrical survey. " 4. That in case this standard should be lost or impaired, it shall be declared, that the length of a pendulum, vibrating seconds of mean solar time in London, on the level of the sea, and in a vacuum, is 39.1372 in- ches of the standard scale, and that the length of the French metre, as the 10 mil- lionth part of the quadrantal arc of the meridian, has been found equal to 39.3694 inches. BAL BAH 44 5. That 10 ounces troy, or 4800 grains, should be declared equal to the weight of 19 cubic inches of distilled water, at the temperature of 50*, and that one pound avoirdupois must contain 7000 of these grains. " 6. That the standard ale and corn gal- lon should contain exactly ten pounds avoir- dupois of distilled water at 6..° Fahr. being nearly equal to 277.2 cubic inches, and agreeing with the standard pint in the Ex- chequer, which is found to contain exactly 20 ounces of water. The customary ale gal- lon contains 282 cubic inches, and the Win- chester corn gallon 269, or according to other statutes 272i cubic inches; so that no inconvenience can possibly be felt from the introduction of a new gallon of 2772 inches. The commissioners have not decided upon Captain Kater has lately made a small correction on his first determination of the length of the pendulum vibrating seconds in the latitude of London. Instead of 39 13860 inches, as given in the Ph. Trans. for 1818, he has made it 39.13929 inches of Sir Geo. Shuckburgh's standard scale. Mr. Watts, in the 5th number ofthe Edin- burgh Philosophical Journal, makes it = 39.138666 of the above scale, or = 39.1372405 of General Roy's scale, at Cap- tain Kater's temperature of 62° Fahr. and 0.9941 of a metre.* * Baikalite. See Tremolite, as- BESTIFORM.* Balas, or Balais Ruby. See Spi- NELLE. Balloon. Receivers of a spherical form are called balloons. the propriety of abolishing entirely the use of the wine gallon." The following elegantly simple relations of weight and measure were suggested by Dr. Wollaston, in his examination before the committee; and it is to be hoped they will be adopted in the national system: "There is one standard of capacity that would he particularly advantageous, because it would bear simple proportions to the mea- sures now in use, so that one of the great inconveniences arising from change of the standard would be obviated, by the facility of making many necessary computations without reference to tables. " If the gallon measure be defined to be that which contains 10 lbs. of water at 564° F.; then, since the cubic foot of water weighs 1000 oz. at 564*, Balloon. See Aerostatics. * Balsams, are vegetable juices, either liquid, or which spontaneously become concrete, consisting of a substance of a re- sinous nature, combined with benzoic acid, or which are capable of affording benzoic acid, by being heated alone, or with water. They are insoluble in water, but readily dissolve in alcohol and ether. The liquid balsams are copaiva, opobalsam, Peru, sty- rax, tolu; the concrete are benzoin,dragon's blood, and storax; which see.* Balsam of Sulphur. A solution of sulphur in oil. * Baldwin's Phosphorus. Ignited ni- trate of lime.* * Barium. The metallic basis of the earth barytes has been called barium by its discoverer, Sir H. Davy. Take pure barytes, 4 pint = 10 oz. = T^- cubic foot = 17.28 inches. Pint = 20 oz. = 34.56 inches. Bushel = 80 lb. = 2211M And the simple proportions above alluded to will be found as follows: Cubic Inches. The gallon of 10 lb. = 276.48 X 4? = 282.01 Also, = 276.48 X rf = 230.40 The pint of U lb. = 34.56 X 3 = 103.68 Bushel of 80 lb. = 2211.84 X |f = 2150.40 A cylinder of 18J in. diam. X 8 = 2208.93 Ditto 18| X 8.0105 282 beer gallon. 231 wine gallon. 103.4 Stirlg. jug. 2150,42 Winch, bush. Approximate bush. 221.184 new bush. " The following mode of defining the standards of length, weight, and capacity, is submitted to the committee on weights and measures, as the most distinct answer to their inquiries: O 1 flfi " h 1** sucn» tnat a pendulum of 39.13 inches, vibrates seconds v ' '5 in London. Avoir. £one JJ™*1, °f ? is such, that one cubic foot of water at 564°, weighs 1000 oz. Troy. JO5r60°Uraiiis *" \ is SUch'that 700° grainS = * poUnd (avoirdupois). One irall f 8 n' t Z ma^ *e sucn as t0 contam *0 pounds of distilled water at the ° ' P1 » C temperature of 564° Fahr. with great convenience." BAR BAR make it into a paste with water, and put this on a plate of platinum. Make a cavity in the middle of the barytes, into which a globule of mercury is to be placed. Touch the glob- ule with the negative wire and the platinum with the positive wire, of a voltaic battery of about 100 pairs of plates in good action. In a short time an amalgam will be formed, con- sisting of mercury and barium. This amal- gam must be introduced into a little bent tube, made of glass free from lead, sealed at one end, which being filled with the vapour of naphtha, is then to be hermetically sealed at the other end. Heat must be applied to the recurved end of the tube, where the amalgam lies. The mercury will distil over, while the barium will remain. This metal is of a dark grey colour, with a lustre inferior to that of cast-iron. It is fu- sible at a red heat. Its density is superior to that of sulphuric acid; for though sur- rounded with globules of gas, it sinks im- mediately in that liquid. When exposed to air, it instantly becomes covered with a crust of barytes; and when gently heated in air, burns with a deep red light. It efferves- ces violently in water, converting this li- quid into a solution of barytes. Sir H. Davy thinks it probable that barium may be pro- cured by chemical as well as electrical de- composition. When chloride of barium, or even the dry earth, ignited to whiteness, is exposed to the vapour of potassium, a dark grey substance is found diffused through the barytes or the chloride, not volatile, which effervesces copiously in water, and possesses a metallic appearance, which dis- appears in the air. The potassium, by being thus transmitted, is converted into potash. From indirect experiments, Sir H. Davy was inclined to consider barytes as composed of 89.7 barium -f 10.3 oxygen = 100 This would make the prime equivalent of barium 8.7, and that of barytes 97, compared to that of oxygen 1.0; a determination probably very exact. Dr. Clark of Cambridge, by ex- posing dry nitrate of barytes on charcoal, to the intense heat of the condensed hydroxy- gen flame, observed metallic globules in the midst of the boiling fluid, and the charcoal was found to be studded over with innumer- able globules of a pure metal of the most brilliant lustre and whiteness. On letting these globules fall from the charcoal into water, hydrogen was evolved in a continued stream. When the globules are plunged in naphtha, they retain their brilliancy but for a few days. Barium combines with oxygen in two proportions forming, 1st, barytes, and 2d, the deutoxide of barium. Pure barytes is best obtained by igniting in a covered crucible, the pure crystallized nitrate of barytes. It is procured in the state of hydrate, by adding caustic potash or soda to a solution ofthe muriate or nitrate. And barytes, slightly coloured with charcoal, may be obtained by strongly igniting the carbonate and charcoal mixed together in fine powder. Barytes obtained from the ig- nited nitrate is of a whitish-grey colour; more caustic than strontites, or perhaps even lime. It renders the syrup of violets green, and the infusion of turmeric red. Its specific gravity by Fourcroy is 4. When water in small quantity is poured on the dry earth, it slakes like quicklime, but perhaps with evolution of more heat. When swal- lowed it acts as a violent poison. It is des- titute of smell. When pure barytes is exposed, in a porce- lain tube, at a heat verging on ignition, to a stream of dry oxygen gas, it absorbs the gas rapidly, and passes to the state of deutoxide of barium. But when it is calcined in con- tact with atmospheric air, we obtain at first this deutoxide and carbonate of bary- tes; the former of which passes very slowly into the latter, by absorption of carbonic acid from the atmosphere. The deutoxide of barium is of a greenish- grey colour; it is caustic, renders the syrup of violets green, and is not decomposable by heat or light. The voltaic pile reduces it. Exposed at a moderate heat to carbonic acid, it absorbs it, emitting oxygen, and be- coming carbonate of barytes. The deutoxide is probably decomposed by sulphuretted hy- drogen at ordinary temperatures. Aided by heat, almost all combustible bodies, as well as many metals, decompose it.The action of hydrogen is accompanied with remarkable phenomena. At about 392° F. the absorption of this gas commences; but at a heat ap- proaching to redness it is exceedingly ra- pid, attended with luminous jets proceed- ing from the surface of the deutoxide. Al- though much water be formed, none of it appears on the sides of the vessel. It is all retained in combination with the protoxide, which in consequence becomes a hydrate, and thus acquires the property of fusing easily. By heating a certain quantity of ba- rytes with an excess of oxygen in a small curved tube standing over mercury, M. Thenard ascertained, that in the deutoxide the quantity of the oxvgen is the double of that in the protoxide. Hence the former will consist of 8.7 barium -j- 2 oxygen = 10.7 for its prime equivalent. From the fa- cility with which the protoxide passes into the deutoxide, we may conceive that the former may frequently contain a proportion of the latter, to which cause may be as- cribed in some degree the discrepancies among chemists, in estimating the equiva- lent of barytes. Water at 50° F. dissolves one-twentieth of its weight of barytes, and at 212° about one-half of its weight; though M. Thenard BAR BAS in a table, has stated it at only one-tenth. As the solution cools, hexagonal prisms, termi- nated at each extremity with a four-sided pyramid, form. These crystals are often attached to one another, so as to imitate the leaves of fern. Sometimes they are deposit- ed in cubes. They contain about 53 per cent of water, or 20 prime proportions. The su- pernatant liquid is barytes water. It is co- lourless, acrid, and caustic. It acts power- fully on the vegetable purples and yellows. Exposed to the air, it attracts carbonic acid, and the dissolved barytes is converted into carbonate, which falls down in insoluble crusts. It appears from the experiments of M. Berthollet, that heat alone cannot de- prive the crystallized hydrate of its wa- ter. After exposure to a red heat, when it fuses like potash, a proportion of water re- mains in combination. This quantity is a prime equivalent = 1.125, to 9.7 of barytes. —The ignited hydrate is a solid of a whi- tish-grey colour, caustic, and very dense. It fuses at a heat a little under a cherry red; is fixed in the fire; attracts, but slowly, carbonic acid from the atmosphere. It yields carburetted hydrogen and carbonate of barytes when heated along with charcoal, provided this be not in excess. Sulphur combines with barytes, when they arc mixed together, and heated in a crucible. The same compound is more eco- nomically obtained by igniting a mixture of sulphate of barytes and charcoal in fine powder. This sulphuret is of a reddish- yellow colour, and when dry without smell. When this substance is put into hot water, a powerful action is manifested. The water is decomposed, and two new products are formed; namely, hydrosulphuret, and hy- droguretled sulphuret of barytes The first crystallizes as the liquid cools, the second remains dissolved. The hydrosulphuret is a compound of 97 of barytes with 2.125 sul- phuretted hydrogen. Its crystals should be quickly separated by filtration, and dried by pressure between the folds of porous pa- per. They are white scales, have a silky lustre, are soluble in water, and yield a so- lution having a greenish tinge. Its taste is acrid, sulphureous, and when mixed with the liydroguretted sulphuret, eminently corrosive. It rapidly attracts oxygen from the atmosphere, and is converted into the sulphate of barytes. The liydroguretted sul- phuret is a compound of 9.70 barytes with 4.125 bisulphuretted hydrogen; but con- taminated with sulphite and hyposulphite in unknown proportions. The dry sulphuret consists probably of 2 sulphur -\- 9.7 bary- tes. The readiest way of obtaining barytes water is to boil the solution ofthe sulphuret with deutoxide of copper, which seizes the sulphur, while the hydrogen flies off", and the barytes remains dissolved. Phosphuret of barytes may be easily formed by exposing the constituents to- gether to heat in a glass tube. Their reci- procal action is so intense as to cause igni- tion. Like phosphuret of lime, it decom- poses water, and causes the disengagement of phosphuretted hydrogen gas, which spontaneously inflames with contact of air. When sulphur is made to act on the deu- toxide of barytes, sulphuric acid is formed, which unites to a portion of the earth into a sulphate. The salts of barytes are white, and more or less transparent. All the soluble sulphates cause in the soluble salts of barytes, a preci- pitate insoluble in nitric acid. They are all poisonous except the sulphate; and hence the proper counter-poison is dilute sulphu- ric acid for the carbonate, and sulphate of soda for the soluble salts of barytes. An ac- count has been given of the most useful of these salts under the respective acids. What remains of any consequence will be found in the table of Salts. For some in- teresting facts on the decomposition of the sulphate and carbonate, see Attraction. When the object is merely to procure ba- rytes or the sulphuret, form the powdered carbonate or sulphate into a paste with lamp black and coal tar, and subject to strong ignition in a covered crucible.* Barbadoes Tar. See Petroleum. BARii.LA,or Barillor.The term given in commerce to the impure soda imported from Spain and the Levant. It is made by burning to ashes different plants that grow on the sea-shore, chiefly of the genus sal- sola, and is brought to us in hard porous masses, of a speckled brown colour. Kelp, a still more impure alkali made in this country by burning various sea weeds, is sometimes called British barilla. See Soda. Barolite. Carbonate of barytes. * Barras. The resinous incrustation on the wounds made in fir trees. It is also called galipot.* Barytes. See Barium. * Basalt. Occurs in amorphous mas- ses, columnar, amygdaloidal, and vesicular. Its colours are greyish-black, ash-grey, and raven-black. Massive. Dull lustre. Granular structure. Fracture uneven or conchoidal. Concretions, columnar, globular, or tabular. It is opaque, yields to the knife, but not easily frangible. Streak light ash-grey. Sp. grav. 3. Melts into a black glass. It is found in beds and veins in granite and mica slate, the old red sandstone, limestone, and coal formations. It is distributed over the whole world; but nowhere is met with in greater variety than in Scotland. The German basalt is supposed to be a watery deposite; and that of France to be of volcanic origin.* The most remarkable is the columnar ba- BAS BAT saltes, which form immense masses, com- posed of columns thirty, forty, or more feet in height, and of enormous thickness. Nay, those at Fairhead are two hundred and fif- ty feet high. These constitute some of the most astonishing scenes in nature, for the immensity and regularity of their parts. The coast of Antrim in Ireland, for the space of three miles in length, exhibits a very magnificent variety of columnar cliffs; and" the Giant's Causeway consists of a point of that coast formed of similar co- lumns, and projecting into the sea, upon a descent for several hundred feet. These co- lumns are, for the most part, hexagonal, and fit very accurately together; but most fre- quently not adherent to each other, though water cannot penetrate between them. And the basaltic appearances on the Hebrides Islands on the coast of Scotland, as de- scribed by Sir Joseph Banks, who visited them in 1772, are upon a scale very strik- ing for their vastness and variety. An extensive field of inquiry is here offer- ed to the geological philosopher, in his at- tempts to ascertain the alterations to which the globe has been subjected. The inquiries ofthe chemist equally co-operate in these researches, and tend likewise to show to what useful purposes this and other substan- ces may be applied. Bergmann found that the component parts of various specimens of basaltes were, at a medium 52 parts silex, 15 alumina, 8 carbonate of lime, and 25 iron. The differences seem, however, to be considerable; for Faujas de St. Fond gives these proportions: 46 silex, 30 alumina, 10 lime, 6 magnesia, and 8 iron. The amor- phous basaltes, known by the name of row- ley rag, the ferrilite of Kirwan, ofthe speci- fic gravity of 2.748, afforded Dr. Withering 47.5 of silex, 32.5 of alumina, and 20 ot iron, at a very low degree of oxidation probably. Dr. Kennedv, in his analysis of the basaltes of Staffa, gives the following as its compo- nent parts: silex 48, alumina 16, oxide of iron 16, lime 9, soda 4, muriatic acid 1, wa- ter and volatile parts 5. Klaproth gives for the analysis of the prismatic basaltes of Ha- senberg: silex 44.5, alumina 16.75, oxide of iron 20, lime 9.5, magnesia 2.25, oxide of manganese 0.12, soda 2.60, water 2. On a subsequent analysis, with a view to detect the existence of muriatic acid, he found slight indications of it, but it was in an ex- tremely minute proportion. * Sir James Hall and Mr. Gregory AVatt have both proved, by admirably conducted experiments, that basalt when fused into a perfect glass will resume the stony struc- ture by slow cooling; and hence have endea- voured to show, that the earthy structure affords no argument against the igneous formation of basalt in the terrestrial globe.* Basaltes, when calcined and pulverized, is said to be a good substitute for puzzolana in the composition of mortar, giving it the property of hardening under water. Wine bottles have likewise been manufactured with it, but there appears to be some nicety requisite in the management to ensure suc- cess. Mr Castelveil, who heated his furnace with wood, added soda to the basaltes to render it more fusible; while Mr. Giral, who used pit coal, found it necessary to mix with his basaltes a very refractory sand. The best mode probably would be to choose basaltes of a close fine grain and uniform texture, and to employ it alone, taking care to regu- late the heat properly; for if this be carried too high, it will drop from the iron almost like water. * Basaltic Hornblende It usually occurs in opaque six-sided single crystals, which sometimes act on the magnetic needle. It is imbedded in basalt or wacke. Colour velvet black. Lustre vitreous. Scrat- ches glass. Sp. gr. 3.25. Fuses with difficulty into a black glass. It consists of 47 silica, 26 alumina, 8 lime, 2 magnesia, 15 iron, and 0.5 water. It is found in the basalt of Ar- thur's Seat, in that of Fifeshire, and in the Isles of Mull, Canna, Kigg, and SKy. It is found also in the basaltic and floetz trap- rocks of England, Ireland, Saxony, Bohemia, Silesia, Bavaria, Hungary, Spain, Italy, and France.* * Basanite. See Flinty Slate.* * Base or Basis. A chemical term usu- ally applied to alkalis, earths, and metallic oxides, in their relations to the acids and salts. It is sometimes also applied to the particular constituents of an acid or oxide, on the supposition that the substance com- bined with the oxygen, &c. is the basis of the compound to which it owes its particu- lar qualities. This notion seems unphiloso- phical, as these qualities depend as much on the state of combination as on the nature ofthe constituent.* Bath. The heat communicated from bodies in combustion must necessarily vary according to circumstances; and this varia- tion not only influences the results of opera- tions, but in many instances endangers the vessels, especially if they be made of glass. Among the several methods of obviating this inconvenience, one of the most usual consists in interposing a quantity of sand, or other matter between the fire and the vessel intended to be heated. The sand bath and the water bath are most commonly used; the latter of which was called Balneum Ma- ris by the elder chemists. A bath of steam may, in some instances, be found preferable to the water bath. Some chemists have pro- posed baths of melted lead, of tin, and of other fusible substances. These may per- haps be found advantageous in a few pecu- liar operations, in which the intelligent ope- 23 BEE BEE rator must indeed be left to his own sa- gacity. * A considerably greater heat may be given to the water bath by dissolving vari- ous salts in it. Thus a saturated solution of common salt boils at 225°.3, or lo°.3 Fahr. above the boiling point of water. By using solution of muriate of lime, a bath of any temperature from 212 to 25i° may be con- veniently obtained.* Bdellium. A gum resin, supposed to be of African origin. The best bdellium is of a yellowish brown, or dark brown colour, ac- cording to its age; unctuous to the touch, brittle, but soon softening, and growing tough betwixt the fingers; in some degree transparent, not unlike myrrh; of a bitterish taste, and a moderately strong smell. It does not easily take flame, and, when set on fire, soon goes out. In burning it sputters a little, owing to its aqueous humidity. * Its sp. grav. is 1.371. Alcohol dissolves about three-fifths of bdellium, leaving a mixture of gum and cerasin. Its constituents, accord- ing to Pelletier, are 59 resin, 9.2 gum, 30.6 cerasin, 1.2 volatile oil and loss.* * Bean. The seed of the vicia faba, a small esculent bean, which becomes black as it ripens, has been analyzed by Einholf. He found 3840 parts to consist of 600 vo- latile matter, 386 skins, 610 fibrous starchy matter, 1312 starch, 417 vegeto-animal mat- ter, 31 albumen, 136 extractive, soluble in alcohol, 177 gummy matter, 374 earthy phosphate, 1334 1<>SS- Fourcroy and Vau- quelin found its incinerated ashes to contain the phosphates of lime, magnesia, potash, and iron, with uncombined potash. They found no sugar in this bean. Kidney beans, the seeds of the phaseolus vulgaris, yielded to Einholf 288 skins, 425 fibrous starchy matter, 1380 starch, 799 vegeto-animal mat- ter, not quite free from starch, 131 extrac- tive, 52 albumen, with some vegeto-animal matter, 744 mucilage, and 21 loss in 3840.* • Bee. The venom ofthe bee according to Fontana, bears a close resemblance to that of the viper. It is contained in a small vesicle, and has a hot and acrid taste, like that ofthe scorpion.* Beer is the wine of grain. Malt is usu- ally made of barley. The grain is steeped for two or three days in water until it swells, becomes somewhat tender, and tinges the water of a bright reddish-brown color. The water being then drained away, the barley is spread about two feet thick upon a floor, where it heats spontaneously, and begins to grow, by first shooting out the radicle. In this state the germination is stopped by spreading it thinner, and turning it over for two days;f after which it is again made into ■j-The time varies very much with the weather, and is never so short as two days. a heap, and suffered to become sensibly hot, which usually happens in little more than a day. Lastly, it is conveyed to the kiln, where, by a gradual and low heat, it is ren- dered dry and crisp. This is malt; and its qualities differ according as it is more or less soaked, drained,germinated, dried, and baked. In this, as in other manufactories, the intelligent operators often make a mys- tery of their processes from views of pro- fit; and others pretend to peculiar secrets who really possess none. Indian corn, and probably all large grain, requires to be suffered to grow into the blade, as well as root, before it is fit to be made into malt. For this purpose it is buried about two or three inches deep in the ground, and covered with loose earth; and in ten or twelve days it springs up. In this state it is taken up and washed, or fanned, to clear it from its dirt; and then dried in the kiln for use. * Barley, by being converted into malt, becomes one-fifth lighter, or 20 per cent; 12 of which are owing to kiln drying, 1.5 are carried off by the steep-water, 3 dis- sipated on the floor, 3 lost in cleaning the roots, and 0.5 waste or loss.* The degree of heat to which the malt is exposed in this process, gradually changes its colour from very pale to actual black- ness, as it simply dries it, or converts it to charcoal. The colour of the malt not only affects the colour of the liquor brewed from it; but, in consequence ofthe chemical opera- tion, of the heat applied, on the principles that are developed in the grain during the process of malting, materially alters the quality of the beer, especially with regard The perfection of the process is judged of, by the length of the roots and the germ; of the latter especially. When this has passed two-thirds of the length of the grain, it is time to check the vegetation. Heaping it up is unnecessary. If allowed to lie in heaps so long as to heat much, the malt would be injured. The drying cannot be well effected by heat in a close vessel. A current of dry air is the desi- deratum. I have seen malt made by dry air at the heat of 90 degrees. Our summer sun would answer. Greater heat gives more colour and stronger flavour, but less strength to the wort Neither Indian corn nor rice are improved by malting, for the purpose of fermentation. Those grains only are improved by it, which have the germ to pass internally from one end to the other before coming out. One-third raw Indian corn meal, ground up with two- thirds malt, gives more strength than all malt. BEE BEE to the properties of becoming fit for drink- ing and growing fine. Beer is made from maltpreviously ground, or cut to pieces by a mill. This is placed in a tun, or tub with a false bottom; hot water is poured upon it, and the whole stirred about with a proper instrument. The tem- perature ofthe water in this operation, cal- led Mashing, must not be equal to boiling; for, in that case, the malt would be convert- ed into a paste, from which the impregna- ted water could not be separated. This is called Setting.fl After the infusion has re- mained for some time upon the malt, it is drawn off, and is then distinguished by the name of Sweet Wort. By one or more sub- sequent infusions of water, a quantity of weaker wort is made, which is either added to the foregoing, or kept apart, according to the intention of the operator. The wort is then boiled with hops, which gives it an aromatic bitter taste, and is supposedf2 to render it less liable to be spoiled in keep- ing; after which it is cooled in shallow vessels, and suffered to ferment,-j-3 with the fl The temperature should never be above 180 degrees of Fahrenheit. |2 It is well known, that other things be- ing equal, the liquor keeps in proportion to the quantity of hops. Fresh beer may have from a pound to a pound and a half to a barrel of 32 gallons. June beer, two pounds and a half: beer for the month of August, three pounds; and for a second summer, three and an half. For India voy- ages, four pounds. f3 It ought not to ferment in shallow ves- sels, but in vessels of a cubical or deep cylindrical form. The fermentation should be commenced not lower than fifty-eight nor higher than sixty-six F. The smaller the fermenting tun and the colder the wea- ther, the warmer the wort should be, and vice versa. The fall of the head resulting from the loss of the viscidity, which ena- bles it to confine the carbonic acid, is the most obvious mark to determine when the fermentation should stop. The hydrome- ter or saccharometer affords a better mean of judging, since the same degree of at- tenuation takes place in all infusions over a certain strength, or 22 lbs. to the London barrel, according to instruments made in that city. From 15 to 17 pounds to the bar- rel of diminution will generally be observ- ed. The fermentation is then to be stop- ped, by allowing the liquor to run into smaller vessels of about sixty gallons, and in these it becomes depurated by the yeast, which, evolved by the fermentation, entan- gles the carbonic acid, and is brought to the top ofthe beer by it, so as to roll out at the bung: this is called cleansing. addition of a proper quantity of yeast. The fermented liquor is beer; and differs great- ly in its quality, according to the nature of the grain, the malting, the mashing, the quantity and kind ofthe hops and the yeast, the purity or admixtures ofthe water made use of, the temperature and vicissitudes of the weather, &c. Beside the various qualities of malt li- quors of a similar kind, there are certain leading features by which they are distin- guished, and classed under diff'erent names, and to produce which, different modes of management must be pursued. The princi- pal distinctions are into beer, properly so called; ale; table or small beer; and porter, which is commonly termed beer in London. Beer is a strong, fine, and thin liquor; the greater part of the mucilage having been se- parated by boiling the wort longer than for ale, and carrying the fermentation farther, so as to convert the saccharine matter into alcohol. Ale is of a more sirupy consistence, and sweeter taste; more ofthe mucilage be- ing retained in it, and the fermentation not having been carried so far as to decompose all the sugar.f Small beer, as its name im- plies, is a weaker liquor; and is made, either by adding a large portion of water to the malt, or by mashing with a fresh quantity of water what is left after the beer or ale wort is drawn off. Porter was probably made originally from very high dried malt; but it is said, that its peculiar flavour can- not be imparted by malt and hops alone. 'Mr. Brande obtained the following quan- tities of alcohol from 100 parts of different species of beers. Burton ale, 8.88, Edin- burgh ale, 6.2, Dorchester ale, 5.56; the average being = §.87. Brown stout, 6 8, London porter (average) 4.2, London small beer, (average) 1.28.* As long ago as the reign of Queen Anne, brewers were forbid to mix sugar, honey, Guinea pepper, essentia bina, cocculus in- dicus, or any other unwholesome ingredi- ent, in beer, under a certain penalty; from which we may infer, that such at least was the practice of some; and writers, who pro- fess to discuss the secrets of the trade, mention most of these and some other arti- cles as essentially necessary. The essentia bina is sugar boiled down to a dark colour, and empyreumatic flavour. Broom tops, wormwood, and other bitter plants, were formerly used to render beer fit for keep- ing, before hops were introduced into this f There is no essential difference be- tween the mode of brewing ale and beer. The colour and flavour of the malt is the principal ground of distinction. Keep- ing ale is boiled longer than fresh beer. The more sirupy consistence is in conse- quence of more malt being used. BEE country; but now are prohibited to be used in beer made for sale. * By the present law of this country, nothing is allowed to enter into the com- position of beer, except malt and hops. Quassia and wormwood are often fraudu- lently introduced; both of which are ea- sily discoverable by their nauseous bitter taste. They form a beer which does not preserve so well as hop beer. Sulphate of iron, alum, and salt, are often added by tile publicans, under the name of beer-head- ing, to impart a frothing property to beer, when it is poured out of one vessel into another. Molasses and extract of gentian root are added with the same view. Cap- sicum, grains of paradise, ginger root, co- riander seed, and orange peel, are also em- ployed to give pungency and flavour to weak or bad beer. The following is a list of some ofthe unlawful substances seized at diff'erent breweries, and brewers' drug- gists' laboratories, in London, as copied from the minutes of the committee of the House of Commons. Coculus indicus, mul- tum, (an extract of the cocculus), colour- ing, honey, hartshorn shavings, Spanish juice, orange powder, ginger, grains of paradise, quassia, liquorice, caraway seeds, copperas, capsicum, mixed drugs. Sulphu- ric acid is very frequently added to bring beer forward, or make it hard, giving new beer instantly the taste of what is 18 months old. According to Mr. Accum, the present entire beer of the London brewer is composed of all the waste and spoiled beer of the publicans, the bottoms of butts, the leavings of the pots, the drippings of the machines for drawing the beer, the remnants of beer that lay in the leaden pipes of the brewery, with a portion of brown stout, bottling beer, and mild beer. He says that opium, tobacco, nux vomica, and extract of poppies, have likewise been used to adulterate beer. For an account of the poisonous qualities of the cocculus in- dicus, see Picrotoxia, and for those of nux vomica, see Strychnia. By evapo- rating a portion of beer to dryness, and ig- niting the residuum with chlorate of pot- ash, the iron ofthe copperas will be pro- cured in an insoluble oxide. Muriate of barytes will throw down an abundant pre- cipitate from beer contaminated with sul- phuric acid or copperas* which precipitate may be collected, dried, and ignited. It will be insoluble in nitric acid.* Beer appears to have been of ancient use, as Tacitus mentions it among the Germans, and has been usually supposed to have been peculiar to the northern na- tions: but the ancient Egyptians, whose country was not adapted to the culture of the grape, had also contrived this substi- tute for wine; and Mr. Park has found the BEN art of making malt, and brewing from it very good beer, among the negroes in the interior parts of Africa. Beet. The root of the beet affords a considerable quantity of sugar, and has lately been cultivated for the purpose of extracting it to some extent in Germany. See Sugar. It is likewise said, that if beet roots be dried in the same manner as malt, after the greater part of their juice is pressed out, very good beer may be made from them. *Bellmetai.. See Copper* * Bellmetal Ore. See Ores of Tin.* Ben (Oil of) This is obtained from the ben nut, by simple pressure. It is re- markable for its not growing rancid in keep- ing, or at least not until it has stood for a number of years; and on this account it is used in extracting the aromatic principle of such odoriferous flowers as yield little or no essential oil in distillation. •Benzoic Acid. See Acid (Bex- 2.0IC).* Benzoin or Benjamin. The tree which produces Benzoin is a native of the East Indies, particularly of the island Siam and Sumatra.§ The juice exudes from in- cisions, in the form of a thick white bal- sam. If collected as soon as it has grown somewhat solid, it proves internally white like almond, and hence it is called Ben- zoe Amygdaloides; if suffered to lie long exposed to the sun and air, it changes more and more to a brownish, and at last to a quite reddish-brown colour. This resin is moderately hard and brit- tle, and yields an agreeable smell when rubbed or warmed. When chewed, it im- presses a slight sweetness on the palate. Tt is totally soluble in alcohol; from which, like other resins, it may be precipitated by the addition of water. Its specific gra- vity is 1.092. The white opaque fluid thus obtained has been called Lac Virginale; and is still sold, with other fragrant additions, by per- fumers, as a cosmetic. Boiling water sepa- rates the peculiar acid of benzoin. The products Mr. Brande obtained by distillation were, from a hundred grains, benzoic acid 9 grains, acidulated water 5.5, butyraceous and empyreumatic oil 60, brittle coal 22, and a mixture of carburet- ted hydrogen and carbonic acid gas, com- puted at 3.5. On treating the empyreuma- tic oil with water, however, 5 grains more of acid were extracted, making 14 in the whole. * From 1500 grains of benzoin, Bucholz § Consult the Philosophical Transactions, vol. lxxvii. page 307, for a botanical de- scription and drawing of the tree, by Dry- ander. BEZ obtained 1250 of resin, 187 benzoic acid, 25 of a substance similar to balsam of Peru, 8 of an aromatic substance soluble in water and alcohol, and 30 of woody fibres and im- purities. Ether, sulphuric and acetic acids, dis- solve benzoin; so do solutions of potash and soda. Nitric acid acts violently on it, and a portion of artificial tannin is formed- Am monia dissolves it sparingly.* * Bergmannite. A massive mineral of a greenish, greyish-white, or reddish co- lour. Lustre intermediate between pearly and resinous. Fracture fibrous, passing into fine grained, uneven. Slightly translucent on the edges. Scratches felspar. Fuses into a transparent glass, or a semi-transparent ena- mel. It is found at Frederickswarn in Nor- way, in quartz and in felspar.* * Beryl. This precious mineralf is most commonly green, of various shades, passing into honey-yellow, and sky-blue. It is crys- tallized in hexahedral prisms deeply striat- ed longitudinally, or in 6 or 12 sided prisms, terminated by a 6 sided pyramid, whose summit is replaced. It is harder than the emerald, but more readily yields to cleav- age. Its sp. grav. is 2.7. Its lustre is vitre- ous. It is transparent, and sometimes only translucent. It consists by Vauquelin of 68 silica, 15 alumina, 14 glucina", 1 oxide of iron, 2 lime. Berzelius found in it a trace of oxide of tantalum. It occurs in veins tra- versing granite in Daouria; in the Altaic chain in Siberia; near Limoges in France; in Saxony; Brazil; at Kinloch Raimoch, and Cairngorm, Aberdeenshire, Scotland; above Dundrum, in the county of Dublin, and near Cronebane, county of Wicklow, in Ireland. It differs from emerald in hardness and co- lour. It has been called aqua marine, and greenish-yellow emerald. It is electric by friction and not by heat.* * Bezoar. This name, which is derived from a Persian word implying an antidote to poison, was given to a concretion found in the stomach of an animal ofthe goat kind, which was once very highly valued for this imaginary quality, and has thence been ex- tended to all concretions found in animals. These are of eight kinds, according to Fourcroy, Vauquelin, and Berthollet. 1. Su- perphosphate of lime, which forms concre- tions in the intestines of many mammalia. 2. Phosphate of magnesia, semi-transparent and yellowish, and of sp. grav. J.160. 3. Phosphate of ammonia and magnesia. A concretion of a grey or brown colour, com- posed of radiations from a centre. It is f <;und in the intestines of herbivorous animals, the elephant, horse, &c. 4. Biliary, colour rcd- f Beryl is not always precious, and even when transparent, as in the lorm of aqua marina, has little value. BIL dish-brown, found frequently in the intes- tines and gall bladder of oxen, and used by painters for an orange-yellow pigment. It is inspissated bile. 5. Resinous. The oriental bezoars, procured from unknown animals, belongto t'is class of concretions. They con- sist of concentric layers, are fusible, com- bustible, smooth, soft, and finely polished. They are composed of bile and resin. 6. Fungous, consisting of pieces ofthe boletus igniarius, swallowed by the animal. 7. Hairy. 8. Ligniform. Three bezoars sent to Bona- parte by the king of Persia, were found by Berthollet to be nothing but woody fibre agglomerated.* Bihydroguret of Carbon. See Carburetted Hydrogen. Bihydroguret of Phosphorus. See Phosphuretted Hydrogen. * Bildstein, Agalmatoli te, or Fi- gurestone. A massive mineral, with sometimes an imperfectly slaty structure. Colour gray, brown, flesh red, and some- times spotted, or with blue veins. It is trans- lucent on the edges, unctuous to the touch, and yields to the nail. Sp. grav. 2.8. It is composed of 56 silica, 29 alumina, 7 potash, 2 lime, 1 oxide of iron, and 5 water, by Vau- quelin. Klaproth found in a specimen from China, 54.5 silica, 34 alumina, 6.25 potash, 0.75 oxide of iron, and 4 water. It fuses into a transparent glass. M. Brongniart calls it steatitepagodite, from its coming from China cut into grotesque figures. It wants the magnesia, which is a constant ingredient of steatites. It is found at Naygag in Transyl- vania, and Glyder-bach in Wales. * Bice. A bitter liquid, of a yellowish or greenish-yellow colour, more or less viscid, of a sp. gravity greater than that of water, common to a great number of animals, the peculiar secretion of their liver. It is the prevailing opinion of physiologists, that the bile is separated from the venous, and not like the other secretions, from the arterial blood. The veins which receive the blood distributed to the abdominal viscera, unite into a large trunk called the vena porta, which divides into two branches, that pene- trate into the liver, and divide into innumer- able ramifications. The last of these termi- nate partly in the biliary ducts, and partly in the hepatic veins, which restore to the circulation the blood not needed for the formation ofbile. This liquid passesdirectly into the duodenum by the ductus choledochus, when the animal has no gall bladder; but when it has one, ay more frequently hap- pens, the bile flows back into it by the cys- tic duct, and remaining there for a longer or shorter time, experiences remarkable al- terations. Its piincipal use seems to be, to promote the duodenal digestion, in concert with the pancreatic juice. Boeihaave, by an extravagant error, re- BIL BIR garded the bile as one of the most putresci- b)e fluids; and hence originated many hypo- thetical and absurd theories on diseases and their treatment. We shall follow the ar- rangement of M. Thenard, in a subject Which owes to him its chief illustration. 1. Ox bile is usually of a greenish-yellow colour, rarely a deep green. By its colour it changes the blue of turnsole and violet to a reddish-yellow. At once very bitter, and slightly sweet, its taste is scarcely support- able. Its smell, though feeble, is easy to recognize, and approaches somewhat to the nauseous odour of certain fatty matters when they are heated. Its specific gravity varies very little. It is about 1.026 at 43° F. It is sometimes limpid, and at others dis- turbed with a yellow matter, from which it may be easily separated by water; its con- sistence varies from that of a thin mucilage, to viscidity. Cadet regarded it as a kind of soap. This opinion was first refuted by M. Thenard. According to this able chemist, 800 parts of ox bile, are composed of 700 water, 15 resinous matter, 69 picromel, about 4 of a yellow matter, 4 of soda, 2 phosphate of soda, 3.5 muriates of soda and potash, 0.8 sulphate of soda, 12 phosphate of lime, and a trace of oxide of iron. When distilled to dryness, it leaves from l-8th to 8-9th of solid matter, which, urged with a higher heat, is resolved into the usual ig- neous products of animal analysis; only with more oil and less carbonate of ammonia. Exposed for some time in an open ves- sel, the bile gradually corrupts and lets fall a small quantity of a yellowish matter; then its mucilage decomposes. Thus the putrefactive process is very inactive, and the odour it exhales is not insupportable, but in some cases has been thought to re- semble that of musk. Water and alcohol combine in all proportions with bile. When a very little acid is poured into bile, it be- comes slightly turbid, and reddens litmus; when more is added, the precipitate aug- ments, particularly if sulphuric acid be em- ployed. It is formed of a yellow animal mat- ter, with very little resin. Potash and soda increase the thinness and transparency of bile. Acetate of lead precipitates the yel- low matter and the sulphuric and phospho- ric acids ofthe bile. The solution ofthe sub- acetate precipitates not only these bodies, but also the picromel and the muriatic acid, all combined with the oxide of lead. The a- eetic acid remains in the liquidunited to the soda. The greater number of fatty substan- ces are capable of being dissolved by bile. This property, which made it be considered a soap, is owing to the soda, and to the tri- ple compound of soda, resin, and picromel. Scourers sometimes prefer it to soap, for cleansing woollen. The bile of the calf, the dog, and the sheep, is similar to that of the ox. The bile of the sow contains no picro- mel. It is merely a soda-resinous soap. Hu- man bile is peculiar. It varies in colour, sometimes being green, generally yellow- ish-brown, occasionally almost colourless. Its taste is not very bitter. In the gall blad- der it is seldom limpid, containing often, like that of the ox, a certain quantity of yellow matter in suspension. At times this is in such quantity, as to render the bile somewhat grumous. Filtered and boiled, it becomes very turbid, and diffuses the odour of white of egg. When evaporated to dry- ness, there results a brown extract, equal in weight to 1-1 lth of the bile. By calcina- tion we obtain the same salts as from ox bile. All the acids decompose human bile, and occasion an abundant precipitate of albu- men and resin, which are easily separable by alcohol. One part of nitric acid, sp. grav. 1.210, saturates 100 ofbile. On pour- ing into it a solution of sugar of lead, it is changed into a liquid of a light yellow co- lour, in which no picromel can be found, and which contains only acetate of soda, and some traces of animal matter. Human bile appears hence to be formed, by The- nard, in 1100 parts; of 1000 water; from 2 to 10 yellow insoluble matter; 42 albumen; 41 resin; 3.6-soda: and 45 phosphates of so- da and lime, sulphate of soda, muriate of soda and oxide of iron. But by Berzelius, its constituents are in 1000 parts: 908.4 water; 80 picromel; 3 albumen; 4.1 soda; 0.1 phosphate of lime; 34 common salt, and 1. phosphate of soda, with some phos- phate of lime.* Birdlime. The best birdlime is made of the middle bark of the holly, boiled se- ven or eight hours in water, till it is soft and tender; then laid in heaps in pits in the ground and covered with stones, the water being previously drained from it; and in this state left for two or three weeks to ferment till it is reduced to a kind of mucilage. This bei»g taken from the pit is pounded in a mortar to a paste, washed in river water, and kneaded, till it is freed from extraneous matters. In this state it is left four or five days in earthen vessels, to ferment and purify itself, when it is fit for use. It may likewise be obtained from the misleto, the viburnum lantana, young shoots of elder, and other vegetable sub- stances. It is sometimes adulterated with turpen- tine, oil, vinegar, and other matters. Good birdlime is of a greenish colour and sour flavour; gluey, stringy, and tena- cious; and in smell resembling linseed oil. By exposure to the air it becomes dry and brittle, so that it may be powdered; but its viscidity is restored by wetting it. It red- BIS BIS dens tincture of litmus. Exposed to a gen- tle heat it liquefies slightly, swells in bub- bles, becomes grumous, emits a smell re- sembling that of animal oils, grows brown, but recovers its properties on cooling, if not heated too much.. With a greater heat it burns, giving out a brisk flame and much smoke. The residuum contains sulphate and muriate of potash, carbonate of lime and alumina, with a small portion of iron Bismuth is a metal of a yellowish or reddish-white colour, little subject to change in the air f It is somewhat harder than lead, and is scarely, if at all, mallea- ble; being easily broken, and even reduced to powder, by the hammer. The internal face, or place of fracture, exhibits large shining plates, disposed in a variety of po- sitions; thin pieces are considerably sono- rous. At a temperature of 480° Fahrenheit, it melts; and its surface becomes covered with a greenish-grey, or brown oxide. A stronger heat ignites it, and causes it to burn with a small blue flame; at the same time that a yellowish oxide, known by the name of flowers of bismuth, is driven up. This oxide appears to rise in consequence of the combustion; for it is very fixed, and runs into a greenish glass when exposed to heat alone. * This oxide consists of 100 metal -J- 11.275 oxygen, whence its prime equiva- lent will be 9.87, and that of the metal it- self 8.87. The specific gravity of the me- tal is 9.85.* Bismuth, urged by a strong heat in a closed vessel, sublimes entire, and crystal- lizes very distinctly when gradually cooled. The sulphuric acid has a slight action upon bismuth, when it is concentrated and boiling. Sulphurous acid gas is exhaled, and part of the bismuth is converted into a white oxide. A small portion combines with the sulphuric acid, and affords a de- liquescent salt in the form of small needles. The nitric acid dissolves bismuth with the greatest rapidity and violence; at the same time that much heat is extricated, and a large quantity of nitric oxide escapes. The solution, when saturated, affords crys- tals as it cools; the salt detonates weakly, and leaves a yellow oxide behind, which effloresces in the air. Upon dissolving this 6alt in water, it renders that fluid of a milky white, and lets fall an oxide of the same colour. The nitric solution of bismuth exhibits the same property when diluted with wa- ter, most of the metal falling down in the form of a white oxide, called magistery of bismuth. This precipitation of the nitric solution, by the addition of water, is the ■j- It is more properly tin or silver-white with a blush of red. criterion by which bismuth is distinguished from most other metals. The magistery or oxide is a very white and subtile powder: when prepared by the addition of a large quantity of water, it is used as a paint for the complexion, and is thought gradually to impair the skin. The liberal use of any paint for the skin seems indeed likely to do this; but there is reason to suspect, from the resemblance between the general pro- perties of lead and bismuth, that the oxide of this metal may be attended with effects similar to those which the oxides of lead are known to produce. If a small portion of muriatic acid be mixed with the nitric, and the precipitated oxide be washed with but a small quantity of cold water, it will ap- pear in minute scales of a pearly lustre, constituting the pearl powder of perfumers. These paints are liable to be turned black by sulphuretted hydrogen gas. The muriatic acid does not readily act upon bismuth. * When bismuth is exposed to chlorine gas it takes fire, and is converted into a chloride, which, formerly prepared by heat- ing the metal with corrosive sublimate, was called butter of bismuth. The chloride is of a grayish-white colour, a granular tex- ture, and is opaque. It is fixed at a red heat. According to Dr. John Davy, it is composed of 33.6 chlorine, -|- 66.4 bismuth, = 100; or in equivalent numbers, of 4.45 chlorine, -f- 8.87 bismuth, = 13.32. When iodine and bismuth are heated together, they readily form an iodide of an orange-yellow colour, insoluble in water, but easily dissolved in potash ley.* Alkalis likewise precipitate its oxide; but not of so beautiful a white colour as that afforded by the affusion of pure water. The gallic acid precipitates bismuth of a greenish-yellow, as ferroprussiate of potash does of a yellowish colour. * There appears to be two sulphurets, the first a compound of 100 bismuth to 22.34 sulphur; the second of 100 to 46 5; the se- cond is a bisulphuret.* This metal unites with most metallic substances, and renders them in general more fusible. When calcined with the im- perfect metals, its glass dissolves them, and produces the same effect as lead in cupellation; in which process it is even said to be preferable to lead. Bismuth is used in the composition of pewter, in the fabrication of printers' types, and in various other metallic mixtures. With an equal weight of lead, it forms a brilliant white alloy, much harder than lead, and more malleable than bismuth, though not ductile; and if the proportion of lead be increased, it is rendered still more malleable. Eight parts of bismuth, five of lead, and three of tin, constitute BIT BIT the fusible metal, sometimes called New- ton's; from its discoverer, which melts at the heat of boiling water, and may be fused over a candle in a piece of stiff paper without burning the paper. One part of bismuth, with five of lead, and three of tin, forms plumbers' solder. It forms the basis of a sympathetic ink. The oxide of bismuth, precipitated by potash from ni- tric acid, has been recommended in spas- modic disorders ofthe stomach, ami gi\tn in doses of four grains four times a day. A writer in the Jena Journal says he has known the dose carried gradually to one scruple without injury. Bismuth is easily separable, in the dry way, from its ores, on account of its great fusibility. It is usual, in the processes at large, to throw the bismuth ore into a fire of wood; beneath which a hole is made in the ground to receive the metal, and de- fend it from oxidation. The same process may be imitated in the small way, in the examination of the ores of this metal; no- thing more being necessary, than to expose it to a moderate heat in a crucible, with a quantity of reducing flux; taking care, at the same time, to perform the operation as speedily as possible, that the bismuth may be neither oxidized nor volatilized. Bistre. A brown pigment, consisting of the finer parts of wood soot, separated from the grosser by washing. The soot of the beech is said to make the best. * Bitter Principle, of which there are several varieties. When nitric acid is digested on silk, in- digo, or white willow, a substance of a deep yellow colour, and an intensely bitter taste, is formed. It dyes a permanent yel- low. It crystallizes, in oblong plates, and saturates alkalis, like an acid, producing crystallizable salts. That with potash, is in yellow prisms. They are bitter, per- manent in the air, and less soluble than the insulated bitter principle. On hot char- coal they deflagrate. When struck smart- ly on an anvil, they detonate with much violence, and with emission of a purple light. Ammonia deepens the colour of the bitter principle solution, and forms a salt in yellow spiculse. It unites also with the alkaline earths and metallic oxides. M. Chevreul considers it a compound of nitric acid, with a peculiar substance of an oily nature. Quassia, cocculus lndicus, daphne Alpina, coffee, squills, colocynth, and bry- ony, as well as many other medicinal plants, yield bitter principles, peculiarly modified.* Bittern. The mother waterwhich re- mains after the crystallization of common- salt in sea water, or the water of salt springs. It abounds with sulphate and muriate of magnesia, to which its bitterness is owing. See Water (Sea). • Bitterspar, or Rhombspa*. This mineral crystallizes in rhomboids, which were confounded with those of calcareous spar, till Dr. Wollaston applied his admi- rable reflecting goniometer, and proved the peculiarity of the angles in bitterspar, which are 106° 15', and ?3° 4j'. Its colour is grayish or yellow, with a somewhat pear- ly lustre. It is brittle, senu-transparcnt, splendent, and harder than calcareous spar. Fracture straight foliated with a threefold cleavage. Its sp. gr. is 2.88. It consists of from 68 to 73 carbonate of lime, 25 carbo- nate of magnesia, and 2 oxide of manga- nese. It is usually imbedded in serpentine, chlorite or steatite; and is found in the Ty- rol, Salzburg, and Dauphiny. In Scotland, on the borders of Loch Lomond in the chlo- rite slate, and near Newton-Stewart in Gal- loway; as also in the Isle of Mann. It bears the same relation to dolomite and magne- sian limestone, that calcareous spar does to common limestone.* Bitumen. This term includes a consi- derable range of inflammable mineral sub- stances, burning with flame in the open air. They are of different consistency, from a thin fluid to a solid; but the solids are for the most part liquefiable at a moderate heat. The fluid are, 1. Naphtha; a fine, white, thin, fragrant, colourless oil, which issues out of white, yellow, or black clays in Persia and Media. This is highly in- flammable, and is decomposed by distilla- tion. It dissolves resins, and the essential oils of thyme and lavender; but is not it- self soluble either in alcohol or ether. It is the lightest of all the dense fluids, its spe- cific gravity being 0.708. 2. Petroleum, which is a yellow, reddish, brown, green- ish, or blackish oil, found dropping from rocks, or issuing from the earth, in the duchy of Modena, and in various other parts of Europe and Asia. This likewise is insoluble in alcohol, and seems to consist of naphtha, thickened by exposure to the atmosphere. It contains a portion of the succinic acid. 3. Barbadoes tar, which is a viscid, brown, or black inflammable sub- stance, insoluble in alcohol, and contain- ing the succinic acid. This appears to be the mineral oil in its third state of altera- tion. The solid are, 1. Asphaltum, mineral pitch, of which there are three varieties: the cohesive; the semi-compact, maltha; the compact, or asphaltum. These are smooth, more or less hard or brittle, in- flammable substances, which melt easily, and burn without leaving any or but little ashes, if they be pure. They are slightly and partially acted on by alcohol and ether. 2. Mineral tallow, which is a white sub- stance of the consistence of tallow, and as greasy, although more brittle. It was found in the sea on the coasts of Finland, in the BLA BLE year 1736; and is also met with in some rocky parts of Persia. It is nearly one-fifth lighter than tallow; burns with a blue flame, and a smell of grease, leaving a black viscid matter behind, which is more difficultly con- sumed. 3. Elastic bitumen, or mineral Caoutchouc, of which there are two vari- eties. Beside these, there are other bitumi- nous substances, as jet and amber, which approach the harder bitumens in their na- ture; and all the varieties of pit-coal, and the bituminous schistus, or shale, which contain more or less of bitumen in their composition. See the different kinds of bi- tutnen and bituminous substances, in their respective places in the order ofthe alpha- bet. j There are no two substances more op- posite in their habitudes with caloric, than carbon and hydrogen. The last is, of all ponderable substances, the most volatile; and, per se, probably the most incondensi- ble. Charcoal, on the other hand, cannot even be fused, much less volatilized, per 6e. It has, perhaps, of all substances, the least disposition to combine with caloric. Hence, in the combinations of hydrogen and carbon, we find a gradation of proper- ties from substances, fixed like anthracite, to naphtha, or inflammable matter, almost as volatile as air, accordingly as the carbon or hydrogen predominates in the com- pound. The distillation of rosin yields, besides carburetted hydrogen, a species of petro- leum; and this by rectification yields an essential oil, like oil of tar, and afterwards some heavier and less volatile products, some of which though white at first turn black by keeping. In like manner, mineral bitumens and bituminous coals yield petroleum, and vol- atile oil. A quantity of acetic acid comes over in combination with the petroleum of rosin, and is retained till the heat is con- siderable. It is then evolved with explosive violence.-} * Bituminous Limestone is of a la. mellar structure; susceptible of polishing; emits an unpleasant smell when rubbed, and has a brown or black colour. Heat con- verts it into quicklime. It contains 8.8 alu- mina; 0.6 silica; 0.6 bitumen; and 89.75 car- bonate of lime. It is found near Bristol, and in Galway in Ireland. The Dalmatian is so charged with bitumen that it may be cut like soap, and is used for building houses. When the walls are reared, fire is applied to them and they burn white.* * Black Chalk. This mineral has a bluish-black colour; a slaty texture; soils the fingers, and is meagre to the touch. It contains about 64 silica, 11 alumina, 11 car- bon, with a little iron and water. It is found in primitive mountains, and also sometimes Vol. I, near coal formations. It occurs in Caernar. vonshire, and in the Island of Isla.* Black Jack. The miners distinguish blende, or mock lead, by this name. It is an ore of zinc. Black Lead. See Plumbago. Black Wadd. One of the ores of manganese. * Bleaching. The chemical art by which the various articles used for clothing are deprived of their natural dark colour and rendered white. The colouring principle of silk is un« doubtedly resinous. Hence, M. Iiaumepio. posed the following process, as the best mode of bleaching it. On six pounds of yeU low raw silk, disposed in an earthen pot, 48 pounds of alcohol, sp. gr. 0,867, mixed with 12 oz. muriatic acid, sp. gr. 1.100, are to be poured. After a day's digestion, the liquid passes from a fine green colour to a dusky brown. The silk is then to be drain, ed, and washed with alcohol. A second in. fusion with the above acidulated alcohol is then made, for four or six days, after which the silk is drained and washed with alcohol, The spiiit may be recovered by saturating the mingled acid with alkali or lime, and distilling. M. Baume' sjve medicine enters the circulation, and passing off" by the bladder, is useful in retaining, particularly, the triple phosphate in solution, as was first pointed out by Dr. Wollaston. The bovvelsshouldbekept regular by medicine and moderate exercise. The febrile affections of children are fre- quently attended by an apparently formida- ble deposite of white sand in the urine. A dose of calomel will generally carry off both the fever ar.d the sand. Air, exercise, bark, bitters, mineral tonics, are in like manner often successful in removing the urinary complaints of grown up persons. In considering the red gravel, it is neces. sary to distinguish between those cases in which the sand is actually voided, and those in which it is deposited, after some hours, from originally limpid urine. In the first, the sabulous appearance rs an alarming in- CAL CAL dication of a tendency to form calculi; in the second, it is often merely a fleeting symp- tom of indigestion. Should it frequently re- cur, however, it is not to be disregarded. Bicarbonate of potash or soda is the pro- per remedy for the red sand, or lithic acid deposite. The alkali may often be benefi- cially combined with opium. Ammonia, or its crystallized carbonate, may be resorted to with advantage, where symptomsof indiges- tion are brought on by the other alkalis; and particularly in red gravel connected with gout; in which the joints and kidneys are aff'ected by turns. Where potash and soda have been so long employed as to dis- agree with the stomach, to cieate nausea, flatulency, a sense of weight, pain and other symptoms of indigestion, magnesia may be prescribed with the best effects. The ten- dency which it has to accumulate in danger- ous quantities in the intestines, and to form a white sediment in urine, calls on the prac- titioner to look minutely after its adminis- tration. It should be occasionally alternated with other laxative medicines. Magnesia dissolved in carbonic acid, as Mr. Scheweppe used to prepare it many years ago, by the direction of Mr. Brande, is an elegant form of exhibiting this remedy. Care must be had not to push the alkaline medicines too far, lest they give rise to the deposition of earthy phosphates in the urine. Cases occur in which the sabulous depo- site consists of a mixture of lithic acid with the phosphates. The sediment of urine in inflammatory disorders is sometimes of this nature; and of those persons who habitually indulge in excess of wine; and also of those who, labouring under hepatic affections, se- crete much albumen in their urine. Purges, tonics, and nitric acid, which is the solvent of both the above sabulous matters, are the appropriate remedies. The best diet for pa- tients labouring under the lithic deposite, is a vegetable. Dr. Wollaston's fine observa- tion, that the excrement of birds fed solely upon animal matter, is in a great measure lithic acid, and the curious fact since ascer- tained, that the excrement of the boa con- strictor, fed also entirely on animals, is pure lithic acid, concur in giving force to the above dietetic prescription. A week's ab- stinence from animal food has been known to relieve a fit of lithic acid gravel, where the alkalis were of little avail. But we must not carry the vegetable system so far as to produce flatulency and indigestion. Such are the principal circumstances con- nected with the disease of gravel in its inci- pient or sabulous state. The calculi formed in the kidneys are, as we have said above, either lithic, oxalic, or cystic; and very rare- ly indeed of the phosphate species. An aqueous regimen, moderate exercise on horseback when not accompanied with much :rritation, cold bathing, and mild aperients, along with the appropriate chemical medi- cines, must be prescribed in kidney cases. These are particularly requisite immediately after acute pain in the region of the ureter, and inflammatory symptoms have led «o the belief that a nucleus has descended into ihe bladder. Purges, diuretics, and diluents, ought to be liberally enjoined. A large quantity of mucus streaked with blood, or of a purulent aspect, and usemorriiagy, are frequent symptoms ot the passage of the stone into the bladder When a stone has once lodged in the bladder, and increased there to such a size as no longer to be capable of passing through the urethra, it is generally allowed, by all who have candidly considered the suljct, and who are qualified by experience to oe judges, that the stone can never again be dissolved; and although ic is possible that it may become so loosened n its texture, as to be voided piecemeal, or gradually to crumble away, the event is so rare us to be barely probable. By examining collections of calculi we learn, that in by far the greater number of cases, a nucleus ot lithic acid is enveloped in a crust of the phosphates. Our endea- vours must therefore be directed towards re- ducing the excess of lithic acid in the urine to its natural standard; or, on the oilier hand, to lessen the tendency to the deposition ofthe phosphates. The urine must be sub- mitted to chemical examination, and a suit- able course ofdiet and medicines prescribed. But the chemical remedies must be regu- lated nicely, so as to hit the happy equili- brium, in which no deposite wih be formed. Here is a powerful call on the physicians and surgeons to make themselves thoroughly versant in chemical science; for they will otherwise commit the most dangerous blun- ders in calculous complaints. *l The idea of dissolving a calculus of uric acid in the bladder by the internal use of the caustic alkalis," says Mr. Brande, "appears too absurd to merit serious refuta- tion." In respect to the phosphates, it seems possible, by keeping up an unusual acidity in the urine, so tar to soften a crust of the calculus, as to make it crumble down, or ad- mit of being abraded by the sound; but this is the utmost that can be looked for; and the lithic nucleus will still remain. u These considerations," adds Mr. Brande, " inde- pendent of more urgent reasons, show the futility of attempting the solution of a stone of the bladder by the injection of acid and alkaline solutions. In respect to the alkalis, if sufficiently strong to act upon the uric crust of the calculus, they w ould certainly injure the coats of the bladder; they would otherwise become inactive by combination with the acids of the urine, and they would form a dangerous precipitate from the same cause."—*' It therefore appears to me, that CAL CAL Fourcroy, and others who have advised the plan of injection, have thought little of all these obstacles to success, and have regarded the bladder as a lifeless receptacle into which, as into an India rubber bottle, almost any solvent might be injected with impunity."— Journal of Science, vol. vii, p. 216. I have judged it an imperative duty to in- sert the above cautions, from an eminent chemist who has studied this subject in its medical relations, lest the medical student, misled by Dr. Thomson's favourable tran- script ofthe injection scheme, might be hur- ried into very dangerous practice. It does not appear that the peculiarities of water in different districts, have any influence upon the production of calculous disorders. Dr. Wollaston's discovery of the analogy be- tween urinary and gouty concretions, has led to the trial in gravel ofthe rintim colchx- «', the specific for gout. By a note to Mr. Brande's dissertation we learn, that benefit has been derived from it in a case of red gravel. ^k Dr Henry confirmlfce above precepts in the following decidea language. " These cases, and others of the same kind, which I think it unnecessary to mention, tend to dis- courage all attempts to dissolve a stone sup- posed to consist of uric acid, after it has at- tained considerable size in the bladder; all that can be effected under such circum- stances by alkaline medicines appears, as Mr. Brande has remarked,to be the precipitating upon it a coating of the earthy phosphates from the urine, a sort of concretion which, as has been observed by various practical writers, increases much more rapidly than that consisting of uric acid only. The same unfavourable inference may be drawn also from the dissections of those persons in whom a stone was supposed to be dissolved by al- kaline medicines; for in these instances it has been found either encysted, or placed out of the reach of the sound by an enlargement of the prostate gland.* The urinary calculus of a dog, examined by Dr. Pearson, was found to consist princi- pally of the phosphates of lime and ammo- nia, with animal matter. Several taken from horses, were of a similar composition. One of a rabbit consisted chiefly of carbo- nate of lime and animal matter, with perhaps a little phosphoric acid. A quantity of sabu- lous matter, neither crystallized nor con- crete, is sometimes found in the bladder of the horse: in one instance there were nearly 45 pounds. These appear to consist of car- bonate of lime and animal matter. A cal- culus of a cat gave Fourcroy three parts of carbonate, and one of phosphate of lime. That of a pig, according to Bertholdi, was phosphate of lime. • The renal calculus in man appears to be of the same nature as the urinary. In that of the horse, Fourcroy found 3 parts of car- VOL. I. bonate, and one of phosphate of lime. Dr. Pearson, in one instance, carbonate of lime, and animal matter; in two others, pnos- phates of lime and ammonia, with animal matter. Arthritic calculi, or those formed in the joints of gouty persons, were once supposed to be carbonate of lime, whence they were called chalkstones; afterward it was sup- posed that they were phosphate of lime; but Dr. Wollaston has shown, that they ar« lithate of soda. The calculi found some- times in the pineal, prostate, salivary, and bronchial glands, in the pancreas, in the cor- pora cavernosa penis, and between the mus- cles, as well as the tartar, as it is called, that encrusts the teeth, appear to be phosphate of lime. Dr. Crompton, however, examined a calculus taken from the lungs of a de- ceased soldier, which consisted of lime 45, carbonic acid 37, albumen and water 18. It was very hard, irregularly spheroidal, and measured about 6£ inches in circumfer- ence. For the biliary calculi, see Gall. Those called bezoars have been already noticed un- der that article. It has been observed, that the lithic acid, which constitutes the chief part of most hu- man urinary calculi, and abounds in the arth- ritic, has been found in no phy tivorous ani- mal; and hence has been deduced a practi- cal inference, that abstinence from animal food would prevent their formation. But we are inclined to think this conclusion too has- ty . The cat is carnivorous; but it appeared above, that the calculus of that animal is equally destitute of lithic acid. If, therefore, we would form any deduction with respect to regimen, we must look for something used by man, exclusively of all other animals; and this is obviously found in fermented liquors, but apparently in nothing else: and this prac- tical inference is sanctioned by the most re* spectable medical authorities. On Caloric. By Dr. Ure. * Calohic The Agent to which the phe- nomena of heat and combustion are ascribed. This is hypotheticnlly regarded as a fluid, of inappreciable tenuity, whose particles are endowed with indefinite idio-repulsive pow- ers, and which by their distribution in various Eroportions amoag the particles of pondera- le matter, modify cohesive attraction, giv- ing birth to the three general forms of ga- seous, liquid, and solid. Many eminent philosophers, however, have doubted the separate entity of a calorific mat- ter, and have adduced evidence to show that the phenomena might be rather referred to a vibratory or intestinal motion of the par- ticles of common matter. The most distin- guished advocate of this opinion in modern times is Sir H. Davy, the usual justness and 28 CAL CAL profundity of whose views entitle them to deference. The following sketch of his ideas on this intricate subject, though it graduates perhaps into the poetry of science, cannot tail to increase our admiration of his genius, and to inculcate moderation on the partisans of the opposite doctrine. " Calorific repulsion has been accounted for by supposing a subtile fluid capable of combining with bodies, and of separating their parts from each other, which has been named the matter of heat or caloric. " Many ofthe phenomena admit of a hap- py explanation on this idea, such as the cold produced during the conversion of solids into fluids or gases, and the increase of tem- perature connected with the condensation of gases and fluids." In the former case we say the matter of heat is absorbed or com- bined; in the latter it is extruded or disen- gaged from combination. " But there are other facts which are not so easily reconciled to the opinion. Such are the production of heat by friction and percussion; and some of the chemical changes which have been just referred to." These are the violent heat produced in the explosion of gunpowder, where a large quantity of aeriform matter is disengaged; and the fire which appears in the decomposition of the euchlorine gas, or protoxide of chlorine, though the resulting gases occupy a greater volume. " AVhen thetempcrature of bodies is raised by friction, there seems to be no diminution of their capacities, using the word in its com- mon sense; and in many chemical changes, connected with an increase of temperature, there appears to be likewise an increase of capacity. A piece of iron made red-hot by hammering, cannot be strongly heated a se- cond time by the same means, unless it has been previously introduced into a fire. This fact has heen explained by supposing that the fluid of heat has been pressed out of it, by the percussion, which is recovered in the fire; but this is a very rude mechanical idea: the arrangements of its parts are altered by hammering in this way, and it is rendered brittle. By a moderate degree of friction, as would appear from Rumford's experi- ments, the same piece of metal may be kept hot for any length of time; so that if heat be pressed out, the quantity must be inexhaust- ible. When any body is cooled, it occupies a smaller volume than before; it is evident therefore that its parts must have approached to each other; when the body is expanded by heat, it is equally evident that its parts must have separated from each other. The immediate cause of the phenomena of heat, then, is motion, and the laws of its commu- nication are precisely the same as the laws of the communication of motion." Since all matter may be made to fill a smaller volume by cooling, it is evident that the particles of matter must have space betw eeu theui; and since every body can communicate the pow* er of expansion to a body of a lower tempe- rature, that is, can give an expansive mo- tion to its particles, it is a probable infer- ence that its own particles are posses* *d of motion; but as there is no change in the po- sition of its parts as lonjr as its temperature is uniform, the motion, if it exist, must be a vibratory or undulatory motion, or a motion of the particle s round their axes, or a mo- tion of particles round each other. "It seems possible to account for all the phenomena of heat, if it be supposed that in solids the particles arc in a constant state of vibratory motion, the particles of the hottest bodies moving with the greatest velocity, and through the greatest space; that in li- quids and elastic fluids, besides the vibratory motion, which must be conceived greatest in the last, the particles have a motion round their own axes, with diff'erent velocities, the particles of elastic fluids moving with the greatest quickness: and that in ethereal sub- stances," the particl^fciove round their own axes, and separate aErri each other, penetra- ting in right lines through space. Tempe- rature may be conceived to depend upon the velocities cf the vibrations; increase of capa- city on the motion being performed in great- er space ;and the diminution of temperature, during the conversion of solids into flu ids or gases, may be explained on the idea of ihe loss of vibratory motion, in consequence of the revolution of particles round their axes, at the moment when the body becomes li- quid or aeriform; or from the ioss of rapidi- ty of vibration, in consequence of the mo- tion of the particles through greater space. " If a specific fluid of heat be admitted, it must be supposed liable to most ofthe af- fections which the particles of common mat- ter are assumed to possess, to account for the phenomena; such as losing its motion when combining with bodies, producing motion when transmitted from one body to another, and gaining projectile motion when pass- ing into free space; so that many \w potheses must be adopted to account for it's agency, which renders this view ofthe subject less simple than the other. Very delicate expe- riments have been made, which show that bodies, when heated, do not increase in weight This, as far as it goes, is an evi- dence against a subtile clastic fluid, produc- ing the calorific expansion; but it cannot be considered as decisive, on account ofthe im- perfection of our instruments. A cubical inch of inflammable air requires a good ba- lance to ascertain that it has any sensible weight, and a substance bearing the same re- lation to this, that this bears to platinum, could not perhaps be weighed by any method in our possession."f f'l'his view ofthe subject is to me unsa- tisfactory. Jt is trae that the idea of heat CAL CAL It has been supposed, on the other hand, that the observations of Sir Win. Herschel being motion, is sanctioned by Newton, as well as bv the illustrious chemist above named. But the former adopted his opinion at a time, when the existence of heat in a latent state was as yet unsuspected, and when many phenomena unfavourable to the notion he suggested were unknown. It is fully established in mechanics, that when a body in motion is blended with and thus made to communicate motion to another body, previously at rest, or moving slower, the velocity ofthe compound mass after the impact will be found, by multiplying the weight of each body, by its respective ve- locity, and dividing the sum ofthe products, by the aggregate weight of both bodies. Of course it will be more than a mean or less than a mean,accordingly as the quicker body was lighter or heavier than the other. Now according to Sir Humphrey Davy, the particles of substances which are unequally heated are moving with unequal degrees of velocity; ef course when they are reduced by contact to a common temperature, the heat, or what is the same (in his view), the velocity ofthe movements of their particles, ought to be found by multiplying the heat of each by its weight and dividing the sum of the product by the aggregate weight. Hence if equal weights of matter be mixed, the temperature ought to be a mean; and if equal bulks, it ought to be as much nearer the previous temperature of the heavier substance as the weight of the latter is greater; but the opposite is in most in- stances true. When equiponderant quanti- ties of mercury and water are mixed at different temperatures, the result is such as might be expected from the mixture of the water, were it three times heavier; so much nearer to the previous heat of the water, is the consequent temperature. It may be said that this motion is not measurable upon mechanical principles. How then, I ask does it produce mechanical effects? These must be produced by the force of the vibrations, which are by the hypothesis mechanical: for whatever laws hold good in relation to mov- ing matter in mass, must operate in regard to each particle of that matter; the effect of the former, can only be a multiple of that of the latter. Indeed, one of Sir Hum- phrey Davy's reasons for thinking heat to consist of corpuscular motions is that me- chanical attrition generates it. Surely then a motion, produced by mechanical incan«, and which produces mechanical effects, may be estimated on mechanical principles. In the case cited above, the power of re- ciprocal communication of heat in two fluid*, is shown to be inconsistent with the views of this ingenious theorist. If we compare the same power in solids, the result will be on the calorific rays winch accompany thosfe. of light in the solar beam, afford decisive equally objectionable. Thus the heating power of glass being 443, that of an equal bulk of lead will be 487, though so many times heavier; and if equal weights be »om- pared, the effect of the glass, will be four times greater than that ofthe lead. If it be said, that the movements of the,denser mat- ter are made in less space and therefore re- quire less motion, I answer that if they be made with equal velocity, they must go through equal space in the same time, their alternations being more frequent. And if they be not made with the same velocity, they could not communicate to matter of a lighter kind, a heat equally greati since agreeably to experience no superiority of weight will enable a body, acting di- rectly on another to produce in it a motion quicker than its own. Consistently with this doctrine, the particles of an aeriform fluid, when they oppose a mechanical resistance, do it by aid of a certain movement, which causes them effectively to occupy a greater space than when at rest. It is true, a body, by moving backwards and forwards, may keep off other bodies from the space in which it moves. Thus let a weight be par- tially counterbalanced by means of a scale beam, so that if left to itself it would de- scend gently. Place exactly under it another equally solid mass, on which the weight would fall if unobstructed. If between the two bodies thus situated, a third be caused to undergo an alternate motion, it may keep the upper weight from descending, pro- vided the force with which the latter de- scends, be no greater than that of the move- ment in the interposed mass, and the latter acts with such celerity, that between each stroke the time be too small for the weight to move any sensible distance. Here then we have a case analagous to that supposed, in which the alternate movements or vibra- tions of matter enable it to preserve to it- self a greater space in opposition to a force impressed; and it must be evident that length- ening or shortening the extent of the vibra- tions of the interposed body, provided they are made in the same time, will increase or diminish the space apparently occupied by it, as the volume of substances is affected by an increase or reduction of heat. It ought however to be recillected that in the case we have imagined, there is a constant expenditure of momentum to compensate for that generated in the weight by gravity, during each vibration In the vibrations conceived to constitute heat, there is no generating power to make up for this loss. A body preserves the expansion communi- cated by heat in vacuo, where, insulated from all other matter, the only momentum, by which the vibrations of its' particles exn CAL CAL evidence of the materiality of caloric, or at least place the proof of its existence and i hat of light, on the same foundation. That cele- be supported, must have been received be- fore its being thus situated. If we pour mercury into a glass tube shaped like a shepherd's crook, the hook being down- wards, the fluid will be prevented from oc- cupying that part ofthe tube where the air is in such position as not to escape. In this case, according to the hvpothesis in question, the mercury is prevented from entering the space the air occupies, by a series of im- palpable gyratory movements; so that the collision of the aerial particles against each other, causes each to occupy a larger share of space in the manner above illustrated by the descending weight and interposed body. The analogy will be greater, if we suppose a row of interposed bodies alternately striking against each other, and the descending weight; or we may imagine a vibration in all the particles of the interposed mass, equal in aggregate extent and force to that of tbe whole, when performing a common movement. If the aggregate extent of the vibration of the particles very much exceed that which when performed in mass would be necessary to preserve a certain space, it may be supposed productive of a substance like the air by which the mercury is re- sisted. But whence is tht momentum ade- quate in such rare media to resist a pressure of a fluid so heavy as mercury, which in this case performs a part similar to that of the weight, cited for the purpose of illus- tration? If it be said that the mercury and glass being at the same temperature as the air, the particles of these substances vibrate in a manner to keep up the aerial pulsations; I ask, when the experiment is tried in an exhausted receiver, what is to supply mo- mentum to the mercury and glass? There is no small difficulty in conceiving under the most favourable circumstances, that a spe- cies of motion, that exists according to the hypothesis as the cause of expansion in a heated solid, should cause a motion produc- tive of fluidity or vaporization, as when by means of a hot iron, we convert ice into water, and water into vapour. How inconceivable is it that the iron boiler of a steam engine should give to the particles of water, a motion so totally differ- ent from any it can itself possess, and at the Same time capable of such wonderful effects, as are produced by the agency of steam. Is it to be imagined that in particles whose weight does not exceed a few ounces, suffi- cient momentum can be accumulated to move as many tons? There appears to me another very serious obstacle to this expla- nation of the nature of heat. How are we to account for its radiation in vacuo, which the distinguished advocate of the hypothesis brated astronomer discovered that when si- milar thermometers were placed in the dif- ferent parts of the solar beam, decomposed by the prism into the primi'ive colours, they indicated different temperatures. He esti- mates the power of heating in the red rays, to be to that of the green rays, as 55, to 26, and to that of the violet rays as 55 to 16. And in a space beyond the red rays, where there is no visible light, the increase of temperature is greatest of all. Thus, a thermometer in the full red ray rose 7° Fahr. in ten minutes; beyond the confines of the coloured beam entirely, it rose in aw equal time 9°. These experiments were repeated by Sir H. Englefield with similar results. Mr. Be- rard, however, came to a somewhat diffe- rent conclusion. To render his experiments more certain, and their effects more sensible, this ingenious philosopher availed himself of the heliostat, an instrument by which the sun- beam can be steadily directed to one spot during the whole of its diurnal period. He decomposed by a prism the sunbeam, re- flected from the mirror ofthe heliostat, and placed a sensible thermometer in each ofthe seven coloured rays. The calorific faculty was found to increase progressively from the violet to the red portion of the spectrum, in which the maximum heat existed, and not beyond it, in the unilluminated space. The greatest rise in the thermometer took place, while its bulb was still entirely covered by the last red rays; and it was observed pro- gressively to sink as the bulb entered into the dark. Finally, on placing the bulb qnite has himself shown to ensue? There can be no motion witiiout matter. To surmount this difficulty, he calls up a suggestion of Newton's, that the calorific vibrations of matter may send off radiant particles, which lose their own momentum in communicating vibrations to bodies remote from those, whence they emanate. Thus according to Sir Humphrey, there is radiant matter pro- ducing heat, and radiant matter producing light. Now, the only serious objection made by him to the doctrine which considers heat as material, will apply equally against the existence of material calorific emana- tions. That the cannon, heated by friction in the noted experiment of Rumford, would have radiated as well as if heated in any other way, there can, I think, be no doubt; and as well in vacuo, as the heat excited by Sir Humphrey in a similar situation. 'That its emission in this way would have been as inexhaustible as by the conducting pro- cess cannot be questioned. Why then is it not as easy to have an inexhaustible supply of heat as a material substance, as to have ' an inexhaustible supply of radiant matter, communicating the vibrations in which he represents heat to con6i6t? CAL CAL out of the visible spectrum, where Herschel fixed the maximum of heat, the elevation of its temperature above the ambient air was found, by M. Berard, to be only one-fifth of what it was in the extreme red ray. He af- terwards made similar experiments on the double spectrum produced by Iceland crys- tal, and also on polarized light, and he found in both cases that the calorific principle ac- companied the luminous molecules; and that .in the positions where light ceased to be re- flected, heat also disappeared. Newton has shown that the different re- frangibility of the rays of light may be ex- plained by supposing them composed of par- ticles differing in size, the largest being at the red, and the smallest at the violet ex- tremity of the spectrum. The same great man has put the query, Whether light and common matter are not convertible into each other? and adopting the idea that the phe- nomena of sensible heat depend upon vibra- tions ofthe particles of bodies, supposes that a certain intensity of vibrations may send off particles into free space; and that particles in rapid motion in right fines, in losing their own motion, may communicate a vibratory motion to the particles of terrestrial bodies. In this way we can readily conceive how the red rays should impinge most forcibly, and therefore excite the greatest degree of beat. Enough has now been said to show how little room there is to pronounce dogmatic decisions on the abstract nature of heat. If the essence of the cause be still involved in mystery, many of its properties and effects have been ascertained, and skilfully applied to the cultivation of science and the uses of life.f ■(• We see the same matter, at different times, rendered self-attractive, or self-repel- lent; now cohering in the solid form with great tenacity, and now flying apart with explosive violence in the state of vapour. Hence the existence, in nature, of two op. posite kinds «f reaction, between particles, is self evident There can be no property, without matter, in which it may be inher- ent. Nothing can have no property. The question then is, whether these opposite properties can belong to the same particles. Is it not evident, that the same particles can- not, at the same time, be self-repellent, and self-attractive? Suppose them to be so, one or tlie other must predominate, and in that case we should not perceive the existence of the other. It would be useless, and the particles would in effect, possess the predo- minant property alone, whether attraction or repulsion. If the properties were equal in power, they would annihilate each other, and the matter would be, as if void ot ei- ther property. There must, therefore, be a matter, in which the setf-repellent power We shall consider them in the following order; 1. Of the measure of temperature. 2. Of the distribution of heat. 3. Of the general habitudes of heat with the diff'erent forms of matter. It will be convenient to make use of the popular language, and to speak of heat as existing in bodies in greater or smaller quan- tities, without meaning thereby to decide on the question of its nature. 1. Of the measure of temperature. If a rod or ring of metal of considerable size, which is fitted to an oblong or circular guage in its ordinary state, be moderately heated, it will be found, on applying it to the cool guage, to have enlarged its dimen- sions. It is thus that coachmakers enlarge their strong iron rims, so as to make them embrace and firmly bind, by their retraction when cooled, the wooden frame-work of their wheels. Ample experience has proved, that bo- dies, by being progressively heated, pro- resides, as well as matter in which attraction resides. There must also be as many kinds of mat- ter, as there are kinds of repulsion, of which the affinities, means of production, or laws of communication are different. Hence I do firmly believe in the existence of mate- rial fluids, severally producing the pheno- mena of heat, light and electricity. Sub- stances, endowed with attraction, make tiiemselves known to us, by that species of this power, which we call gravitation, by which they are drawn towards the earth, and are therefore heavy and called ponde- rable; by their resistance to our bodies, pro- ducing the sensation of feeling or touch; and by the vibrations or movements in other matter, affecting the ear with sounds, and the eye by a modified reflection of light. Where we perceive none of these usual concomitants of matter, we are prone to in- fer its absence. Hence ignorant people have no idea of air, except in the state of wind; and when even in a quiescent state desig- nate it by this word. But that the princi- ples, the existence of which has been de- monstrated, should not be thus perceived, is far from being a reason for doubting their existence. A very slight attention to their qualities will make it evident, that they could not produce any of the effects, by which the existence of matter in its ordina- ry tbrm is recognized. The self-repellent property rendera it impossible that they should resist penetration; their deficiency of weight, renders their momentum nugato- ry When in combination, they are not per- ceived, but the bodies with which they com- bine; and it is only by the changes they pro- duce in such bodies, or their effects upon our nerves, that they c«n be detected.. CAL CAL pressively increase in bulk. On this princi- ple are constructed the various instruments for measuring temperature. If the body se- lected for indicating, by its increase of bulk, the increase of heat, suffered equal expan- sions by equal increments of the calorific power, then the instrument would be per- fect, and we should have a just thermometer, or pyrometer. But it is very doubtful whe- ther any substance, solid, liquid, or aeriform, preserves this equable relation, between its increase of volume and increase of heat. The following quotation from a paper which the Royal Society did me the honour to publish in their Transactious for 1818, con- veys my notions on this subject: " I think it indeed highly probable, that every species of matter, both solid and liquid, follows an increasing rate in its en- largement by caloric. Each portion that enters into a body must weaken the antago- nist force, cohesion, and must therefore ren- der more efficacious the operation of the next portion that is introduced. Let 1000 represent the cohesive attraction at the com- mencement, then, after receiving one incre- ment of caloric, it will become 1000— 1 *■ 999. Since the next unit of that divel- lent agent will have to combat only this di- minished cohesive force, it will produce an effect greater than the first, in the propor- tion of 1000 to 999, and so on in continued Eregression. That the increasing ratio is, owever, greatly less than Mr. Dalton main- tains, may, I think, be clearly demonstrated." P. 34. The chief object ofthe second chapter of that memoir, is the measure of temperature. The experiments on which the reasoning of that part is founded, were made in the years 1812 and 1813, in the presence of many phi- losophical friends and pupils. By means of two admirable micrometer microscopes of Mr. Troughton's construction, attached to a peculiar pyrometer, I found, that between the temperatures of melting ice, and the 540th degree Fahr., the apparent elongations of rods of pure copper and iron correspond- ed pari passu with the indications of two mer- curial thermometers of singular nicety, made by Mr. Crighton ot Glasgow, one of which cost three guineas, and the other two, and they were compared with a very fine one of Mr Troughton's. I consider the above results, and others contained in that same paper, as decisive against Mr. Oalton's hy- pothetical graduation of thermometers. They were obtained and detailed in public lec- tures many years before the elaborate re- searches of Messrs. Petit and Dulong on the same subject appeared; and indeed the pa- Eer itself passed through Dr. Thomson's ands, to London, many months before the excellent dissertation of the French philo- sophers wag published. 1'heir memoir gain- ed a well-merited prize, voted by the Aca- demy of Sciences, on the 16th of March 1818. My paper was submitted the preced- ing summer, in its finished state, to three professors of the University of Glasgow, as well as to Dr. Brewster and Dr. Murray. The researches of MM. Dulong and Petit are contained in the 7th volume of the Annales de Chimie et Physique. They commence with some historical details, in which they observe, " that Mr. Dalton, con- sidering this question from a point of view much more elevated, has endeavoured to establish general laws applicable to the mea- surement of all temperatures. These lavvs^ it must be acknowledged, form an imposing whole by their regularity and simplicity. Unfortunately, this skilful philosopher pro- ceeded with too much rapidity to generalize his very ingenious notions, but which de- pended on uncertain data. The consequence is, that there is scarcely one of his assertions but what is contradicted by the result of the researches, which we are now going to make known." M. Gay-Lussac had previously shown, that between the limits of freezing and boiling water, a mercurial and air ther- mometer did not present any sensible dis- cordance. The following table of MM. Du- long and Petit gives the results from nearly the freezing to the boiling point of mercury. TABLE of Comparison of the Mercurial and Air Thermometer. Temperature indicated by the mercurial. Corresponding von. of the same mass of air. Temperature indicated by an air thermometer, corrected for the dilatation of glass. Centigr- Fabr. Centigr. Fahr. —36° 0 100 150 200 250 300 Boiling, 360 —32.8° + 32. 212 302 392 482 572 680 0.8650 1.0000 1.3750 1.5576 1.7389 1.9189 2. 76 2.3125 —36.00° 0.00 100.00 148.70 197.05 245.05 292.70 350 00 —32.8° + 32.0 212.0 299.66 386.69 475o9 558.86 662.00 CAL CAL The well known uniformity in the princi- pal physical properties of all the gases, and pun icularly the perfect identity in the laws of their dilatation, render it very probable, that in this class of bodies the disturbing causes, to which I have adverted in my pa- per, have not the same influence as in solids and liquids; and that consequently the changes in volume produced by the action of heat upon .or and gases, are more immedi- ately dependent upon the force which pro- duces them. It is therefore very probable, that the greatest number ofthe phenomena relating to heat will present themselves un- der a more simple form, if we measure the temperatures by an air thermometer. I coincide with these remarks of the French chemists, and think they were justified by such considerations to employ the scale of an air thermometer in their subsequent re- searches, which form the second part of their memoir on the laws of the communi- cation of heat. The boiling point of mercury, according to M M. Dulong and Petit, measured by a true thermometer, is 662° of Fahr. degrees Now by Mr. Crighton's thermometer the boiling point is 656°, a difference of only 6C in that prodigious range. Hence we see, as I pointed out in my paper, that there is a compensation produced between the une- quable expansions of mercury and glass, and the lessening mass of mercury remaining in the bulo as the temperature rises whereby his thermometer becomes a trn»measurer of the increments of sensible caloric. From all the experiments which have been made with .are, we are safe in assuming the appa- ren. expansion of mercury in glass to be 1.63d part of its volume on an average for every 180c Fahr. between 32° and 662°, or through an interval of 7 times 90 degrees. Hence the apparent expansion in glass for the whole is, — = , = — = 35° Fahr. lito 18 i» Were the whole body of the thermome- ter, stem and bulb, immersed in boiling mer- cury, it would therefore indicate 35° more thanitdoeswhen the bulb alone is immersed, or it would mark nearly 691° by Crighton. But the abstraction made ot these 35°, in consequence of the bulb alone being im- mersed in the heated liquids, brings back the common mercurial scale, when well exe- cuted, near to the absolute and lust scale of an air thermometer, corrected for the ex- pansions of the containing glass. Dr. Thomson in his Annals for March, 1819, has, in his account of my paper, ha- zarded some remarks on this subject, which it will be necessary merely to quote in order to see their futility: " From Mr. Crigbton's mode of graduating thermometers," says he, "it is obvious that in the higher parts ofthe scale the degrees are below the truth. Thus mercury boils, as determined by his thermo- meters, at 556°, the real boiling point, as determined by Dulong and Petit, is 580°. It is probable that Dr. Ure also employed a thermometer, made bv Crighton. But it is unlikely that it should be better than mine, as Mr. Crighton was at great pains to make mine as correct as possible, and I paid him a high price for it." Making due allowance for the oblique censure of this insinuation, as well as for the tv pographical error of 580° instead of 680°, it is obvious that Dr. Thomson has misunderstood the merits of the discussion. The real temperature of boiling mercurv by Dulong and Petit is b62° F.; the apparent temperature, measur- ed by mercury in glass, both heated to the boiling point of the former, is 660°. But the latter is a false indication, and Mr. Crighton's compensated number 656° is very near the truth. We may therefore con- sider a well made mercurial thermometer as a sufficiently just measurer of temperature. For its construction and graduation, see Thermometer. 2. '^fthe distribution of heat. This head naturally divides into two parts; first, the modes of distribution, or the laws of cooling, and the communication of heat among aeriform, liquid, and solid substances, and, secondly, the specific heats of different bodies at the same and at different tempe- ratures. The first views relative to the laws of the communication of heat are to be found in the opuseula of Newton. This great philo- sopher assumes a priori, that a heated body exposed to a constant cooling cause, such as the uniform action of a current of air, ought to lose at each instant a quantity of heat proportional to the exc ss of is temperature above that ofthe ambient air; and that con- sequently its losses of heat in equal and suc- cessive portions of time ought to form a de- creasing geometrical progression. Though Martin, in his Essays on Heat, pointed out long ago the inaccuracy of the preceding law, which indeed could not fail to strike any person, as it struck me forcibly the mo- ment »hat 1 watched the progressive cooling of a sphere of oil which had been heated to the 500th degree, jet the proposition has been passed from one sy stematist to ano- ther without contradiction. Erxleben proved, by very accurate obser- vations, that the deviation of the supposed law increases more and more as we consider greater differences of temperatures; and con- cludes that we should fall into very great errors if we extended the law much b yond the temperature at which it has been veri- fied. Yet Mr. Leslie since, in his ingenious researches on heat, has made this law the basis of several determinations, which from that very cause are inaccurate, as has been proved by Dulong and Petit. At length these gentlemen have investigated the true latf in a masterly manner. CAL CAL *rVhen a body cools in vacuo, its heat is entirely dissipated by radiation. When it is placed in air, or in any other fluid, its cool- ing becomes more rapid, the heat carried off' by the fluid being in that case added to that which is dissipated by radiation. It is natural therefore to distinguish these two effects; and as they are subject in all proba- bility to diff'erent laws, they ought to be separately studied. MM. Dulong and Petit employed in this research mercurial thermometers, whose bulbs were from 0.8 of an inch to 2.6; the latter containing about three lbs. of mercury. They found by preliminary trials, that the ratio of cooling was not affected by the size ofthe bulb, and that it held also in compari- sons of mercury, with water, with absolute alcohol, and with sulphuric acid, through a range of temperature, from 60>to 30 of the centigrade scale; so that the ratio of the velocity of cooling between 60 and 50, and 40 and 30, was sensibly the same. On cooling water in tin plate, and in a glass sphere, they found the law of cooling to be more rapid in the former, at temperatures under the boiling point; but by a very re- markable casualty, the contrary effect takes place in bodies heated to high temperatures, when the law of cooling in tin plate becomes least rapid. Hence, generally, that which cools by a most rapid law at the lowei; part of the scale, becomes the least rapid at high temperatures. " Mr. Leslie obtained such inaccurate re- sults respecting this question, because he did not make experiments on the cooling of bo- dies raised to high temperatures," say MM. Dulong and Petit, who terminate their preli- minary researches by experiments on the cooling of water in three tin-plate vessels of the same capacity, the first of which was a sphere, the second and third cylinders; from which we learn that the law of cooling is not affected by the difference of shape. The researches on cooling in a vacuum "were made with an exhausted balloon; and a compensation was calculated for the mi- Bute quantity of residuary gas. The follow- ing series was obtained when the balloon Was surrounded with ice. The degrees are centigrade. Excess of the therm. Corresponding ve- above the balloon. locities of cooling. 2-10° 10.69 220 8 81 200 7.40 180 6.10 160 4.89 140 3 88 120 3.02 100 2.30 80 1.74 The first column contains the excesses of temperature above the walls of the balloon; that is to say, tiie temperatures themselves, since the balloon was at 0°. The second co- lumn contains the corresponding velocities of cooling, calculated and corrected. The c ve- locities are the numbers of degrees that the thermometer would sink in a minute. f he first series shows clearly the inaccuracy of the geometrical law of Richmann; for according to that law, the velocity of cooling at 2U0 should be double of that at 100°; whereas we find it as 7.4 to 2.3, or more than triple; and in like manner, when we compare the loss of heat at 240° and at 80°, we find the first about 6 times greater than the last; while, according to the law of Richmann, it ought to be merely triple. From the above and some analogous experiments, the fol- lowing law has been deduced; When a budy cools in vacuo surrounded by a medium whose temperature is constant, the velocity of cooling for excess of temperature in arithmetical pro- gression, increases as the terms of a geometri- cal progression, diminished by a certain quan- tity Or, expressed in algebraic language, the following equation contains the law of 8 t cooling in vacuo: V = m.a (a—1). 6 is the temperature ofthe substance sur- rounding the vacuum; and t that ofthe heated body above the former. The ratio a of this progression is easily found for the thermome- ter, whose cooling is recorded above; for when 8 augments by 20°, t remaining the same, the velocity of cooling is then multi- plied by 1.165; which number is the mean of all the ratios experimentally determined. 20 _________ We have th*en a = y/ l.ioo - 1.0077. It only remains, in order to verify the ac- curacy of this law, to compare it with the diff'erent series contained in the table insert- ed above. In that case, n which the sur- rounding medium was 0°, it is necessary to make m «= 2.037, for m log. a -, and n is an intermediate number; we have then V t - 2.037 (a — 1). Excesses of temp. Values of Values of V or values oft. T observed, calculated. 240° 10 69 10.68 220 8 81 8.89 200 7.40 7 34 180 6.10 6.03 160 4.89 4.87 140 3.88 3.89 120 3.02 3.05 100 2.30 2.33 80 1.74 1.72 The laws of cooling in vacuo being known, nothing is more simple than to separate from the total cooling of a body surrounded with air, or with any other gas, the portion of the effect due to the contact of the fluid. For this, it is obviously sufficient to sub- tract from the real velocities of cooling, those velocities which would take place if the body eateris paribus were placed t» va- CAL CAL cuo. This subtraction may be easily accom- plished now that we have a formula, which represents this velocity with great preci- sion, and for all possible cases. From numerous experimental compari- sons the following law was deduced: The velocity of cooling of a body, oviing to the sole contact of a gas, depends for the same excess of temperature, on the density and tempera- ture of the fluid; but this dependence is such, that the velocity of cooling remains the same, if the density and the temperature of the gas change in such a way that the elasticity re- mains constant. If we call P the cooling power of air un- der the pressure p, this power will become P (1366) under a pressure 2/v P (1.066)2 under a pressure 4 p; and under a pressure n n P' p 2 , it will be P (1.366) . Hence — = P (£ \ 0.45 I p J . We shall find in the same way ; ' p' (p1\o.3s for hydrogen, -^ = I j J For carbonic acid, the exponent will be 0.517, and for olefiant gas 0.501, while for air as we see it is 0.45. These last three numbers differing little from 0.5 or %, we may say that in the aeriform bodies to which they belong, the cooling power is nearly as the square root of the elasticity. " If we compare the law which we have thus announced," say MM. Dulong and Petit, " with the approximations of Leslie and Dalton, we shall be able to judge of the errors into which they have been led by the inaccurate suppositions which serve as the basis of all their calculations, and by the little precision attainable by the methods which they have followed." But for these discussions, we must refer to the memoir itself. The influence of the nature of the sur- face of bodies in the distribution of heat, was first accurately examined by Mr. Les- lie. This branch of the subject is usually called the radiation of caloric. To measure the amount of this influence with precision, he contrived a peculiar instrument, called a differential thermometer. It consists of a glass tube, bent into the form ofthe letter U, terminated at each end with a bulb. The bore is about the size of that of large ther- mometers, and the bulbs have a diameter of l-3d of an inch and upwards. Before hermetically closing the instrument, a small portion of sulphuric acid, tinged with car- mine is introduced. The adjustment of this liquid so as to make it stand at the top of one ofthe stems, immediately below the bulb, requires dexterity in the operator. To this stem a scale divided into 100 parts Vol. I. is attached, and the instrument is then fixed upright by a little cement on a wooden sole. If the liiiijfr, or any body warmer than the ambient uir.be uppie I tooueof t.icse bulbs, the air within wdi be heated, uiid will of course expand, nnd issuing in part from the bulb, depress before it the tinged liquor. The amount of this depression observed upon the scale, will denote the difference of temperature of tie two balls. But if the instrument be merely carried without touch- ing either ball, from a warmer to a cooler, or from a coole to a warmer air, or me- dium of any kind, it will not be affected; because the equality of contraction or ex- pansion in the enclosed air of both bulbs, will maintain the equilibrium of the liquid in the stem. liciug thus independent ofthe fluctuations ofthe surrounding medium, it is well adapted to measure the calorific emanations of different surfaces, success- ively converged by a concave reflector, upon one of its bulbs. Dr. Howard has de- scribed, in the 16th number ofthe Journal of Science, a differential thermometer of his contrivance, which he conceives to pos- sess some advantages. Its form is an imi- tation of Mr. Leslie's; but it contains mere- ly tinged alcohol, or ether, the air being expelled by ebullition previous to the her- metical closure of the instrument. The va- pour of ether, or of spirit in vacuo, affords, he finds, a test of superior delicacy to air. He makes the two legs of different lengths; since it is in some cases very convenient to have the one bulb standing quite aloof from the other. In Mr. Leslie's, when they are on the same level, their distance asunder varies from l-3d of an inch to 1 or up- wards, according to the size ofthe instru- ment. The general length of the legs of the syphon is about 5 or G inches. His reflecting mirrors, of about 14 inches diameter, consisted of planished tin-plate, hammered into a parabolical form by the guidance of a curvilinear gauge. A hollow tin vessel, 6 inches cube, was the usual source of calorific emanation in his experi- ments. He coated one of its sides with lampblack, another with paper, a third with glass, and a fourth was left bare. Having then filled it with hot water, and set it in the line ofthe axis, and 4 or 6 feet in front of one of the mirrors, in whose focus the bulb of a differential thermometer stood, he noted the depression of the coloured liquid produced on presenting the different sides of the cube towards the mirror in succes- sion. The following table gives a general view of the results, with these, and other coatings: Lampblack, - - 100 Water by estimate, - 100-f Writing paper, - - 98 Rosin, ... 96 £9 CAL CAL Sealing wax, . 95 Crown glass, - 90 China ink, . 88 Ice, . 85 Bed lead, . 80 Plumbago, . 75 Isinglass, - 75 Tarnished lead . 45 Mercury, . 20 -f Clean lead, . 19 Iron polished, - 15 Tin plate, - 12 Gold, Silver, C( PP er, 12 Similar results were obtained by Leslie and Rumford in a simpler form. Vessels of similar shapes and capacities, but of dif- ferent materials, were filled with hot li- quids, and their rates of refrigeration no- ted. A blackened tin globe cooled a certain number of degrees in 81 m.nutes; while a bright one took nearly double the time, or 156 minutes; a naked brass cylinder in 55 minutes cooled ten degrees, while its fellow cased in linen, was 36i minutes in cooling the same quantity. If rapid motions beex-v cited in the air, the difference of cooling between bright and dark metallic surfaces becomes less manifest. Mr. Leslie esti- mates the diminution of effect from a ra- diating surface to be directly as its dis- tance, so that double the distance gives one-half, and treble one-third ofthe primi- tive heating impression on thermometers and other bodies. Some of his experi- ments do not seem in accordance with this simple law. One would have expected cer- tainly, that, like light, electricity, and other qualities emanating from a centre, its di- minution of intensity would have been as the square of the distance; and particular- ly as Mr. Leslie found the usual analogy of the sine of inclination to hold, in present- ing the faces of the cube to the plane of the mirror under different angles of obli- quity. Some practical lessons flow from the pre- ceding results. Since brigl t metals project heat most feebly, vessels which are intend- ed to retain their heat, as tea and coffee- pots, should be made of bright sold polish- ed metals. Steam-pipes intended to convey heat to a distant apartment, should be like- wise bright in their course, but darkened when they reach their destination. By coating the bulb of his thermometer with diff'erent substances, Mr. Leslie inge- niously discovered the power of different surfaces to absorb heat; and he found this to follow the same order as the radiating or projecting quality The same film of silver leaf which obstructs the egress of heat from a body to those surrounding it, prevents it from receiving their calorific emanations in return. On this principle we can understand how a metallic minor placed before a fire, should scorch sub- stances in its focus, while itself remains cold; and, on the other hand, how a mirror of darkened or even of silvered glass, should become intolerably hot to the touch, while it throws little heat before it From this absorbent faculty it comes, that a thin pane of glass intercepts almost the whole heat of a blazing fire, while the light is scarcely diminished across it. By degrees indeed, itself becoming heated, constitutes anew focus of emanation, but still the ener- gy of the fire is greatly interrupted. Hence also we see why the thinnest sheet of bright tin-foil is a perfect fire-screen; so impervi- ous indeed to heat, that with a masque coated with it, our face may encounter without inconvenience, the blaze of a glass- house furnace. Since absorption of heat goes hand in hand with radiation in the above table, we perceive that the inverse of absorption, that is reflection, must be possessed in in- verse powers by the different substances composing the list. Thus bright metals re- flect most heat, and so on upwards in suc- cession. Mr. Leslie is anxious to prove that elas- tic fluids, by their pulsatory undulations, are the media of the projection or radiation of heat: and that therefore liquids, as well as a perfect vacuum, should obstruct the operation of this faculty. The laws of the cooling of bodies in vacuo, experimentally established by MM. Dulong and Petit, are fatal to Mr. Leslie's hypothesis, which in- deed was not tenable against the numerous objections which had previously assailed it. The following beautiful experiment of Sir H. Davy seems alone to settle the ques- tion. He had an apparatus made, by which platina wire could be heated in any elas- tic medium or in vacuo,- and by which the effects of radiation could be distinctly ex- hibited by two mirrors, the heat being ex- cited by a voltaic battery. In several expe- riments in which the same powers were employed to produce the ignition, it was found that the temperature of a thermo- meter rose nearly three times as much in the focus of radiation, when the air in the receiver was exhausted to -rio"' as when it was in its natural state of condensation. 'The cooling power, by contact ofthe rare- fied air, was much less than that ofthe air in its common state, for the glow of the platina was more intense in the first case than in the last; and this circumstance per- haps renders the experiment not altoge- tl.er decisive, but the results seem favour- able to the idea, that the terrestrial radia- tion of heat is not dependent upon any motions or affections of the atmosphere. The plane of the two mirrors was placed paiallel to tiie hoiizun, the ignited body CAL CAL being in the focus of the upper, and the thermometer in that of the under mirror. It is evident that a diminished density of the elastic medium, amounting to •%)-■$■ should, on Mr. Leslie's views, have occa- sioned a greatly diminished temperature in the inferior focus, and not a threefold increase, as happened; making every al- lowance for the diminished intensity of glow resulting from the cooling power of atmospheric air. The experiments with screens of glass, paper, &c which Mr. Leslie adduced in support of his undula- tory hypothesis, have been since confront- ed with the experiments on screens of Dr. Delaroche, who, by varying them, obtain- ed results incompatible with Mr. Leslie's views, and favourable to those on the inti- mate connexion between light and heat, with which our account of heat was pre- faced. He shows that invisible radiant heat, in some circumstances, passes directly through glass, in a quantity so much great- er relative to the whole radiation, as the temperature of the source of heat is more elevated. The following table shows the ratio between the rays passing through clear glass, and the rays acting on the thermometer, when no screen was inter- posed, at successive temperatures. Temperature Rays transmit- Total of the hot body ted through the Rays. in the focus. glass screen. 357° 10° 263° 655 10 139 800 10 75 1760 10 34 Argand's lamp with- out its chimney, 10 29 Do. with glass cl imney, 10 18 He next shows that the calorific rays which have already passed through a screen of glass, experience, in passing through a se- cond glass screen of a similar nature, a much smaller diminution of their intensity than they did in passing through the first screen; and that the rays emitted by a hot body differ from each other in their faculty to pass through glass; that a thick glass, though as much as, or more permeable to light than a thin glass of worse quality, allows a much smaller quantity of radiant heat to pass, the difference being so much the less, the higher the temperature ofthe radiating source. This curious fact, that radiating heat becomes more and more capable of penetrating glass, as the tem- perature increases, till at a certain tempe- rature the rays become luminous, leads to the notion that heat is nothing else than a modification of light, or that the two sub- stances are capable of passing into each other. Dr. Delaroche's last proposition is, that the quantity of heat which a hot body yields in a given time by radiation to a cold body situated at a distance, increases c&teris paribus, in a greater ratio than the excess of temperature of the first body above the second. This proposition, which Dr. Thomson declared in his Vnnals, vol. ii. p 1.2. to be "somewhat puzzling," is in philosophical accordance with the laws of Dulong and Petit. For some additional facts on radiation, see Light, to which subject indeed, the whole discussion probably belongs. Even ice, which appears so cold to the organs of touch, would become a focus of heat if transported into a chamber where the temperature of the air was at 0* P.; and a mass of melting ice placed before the mirror, would affect the bulb of the thermometer, just as the cube of heated water did. A mixture of snow and salt at C . would in like manner become a warm body when carried into an atmosphere at —40°. In all this, as well as in our sensa- tions, we see nothing absolute, nothing but mere differences We are thus led to con- sider all bodies as projecting heat at every temperature, but with unequal intensities, according to their nature, their surfaces, and their temperature. The constancy or steadiness of the temperature of a body, will consist in the equality of the quan- tities of radiating caloric which it emits and receives in an equal time, and the equality of temperature between several bodies which influence one another by their mutual radiation, will consist in the per- fect compensation ofthe momentary inter- changes effected among one and all. Such is the ingenious principle of a moveable equilibrium, proposed by Professor Pre- vost, a principle whose application, direct- ed with discretion, and combined with th« properties peculiar to different surfaces, explains all the phenomena which we ob- serve in the distribution of radiating calo- ric. Thus, when we put a ball of snow in the focus of one concave mirror, and a thermometer in that of an opposite mirror placed at some distance, we perceive the temperature inst.ntly to fall, as if there were a real radiation of frigorific particles, according to the ancient notion. The true explanation is derived from the abstrac- tion of that return of heat which the ther- moscope mirror had previously derived from the one now influenced by the snow, and now participating in its inferior radi- ating tension. Thus, also a black body placed in the focus of one mirror, would. diminish the light in the focus of the other; and, as Sir II Davy happily remarks, the eye is, to the rays producing light, a mea- sure, similar to that which the thermome- ter is to rays producing heat. This interchange of heat is finely exem- CAL CAL plifled in the relation which subsists be- tween any portion of the sky and the tem- perature of the subjacent surface of the earth In the year 1788 Mr Six of Canter- bury mentioned, in a paper transmitted to the Royal Society, that on clear and dewy nights he always found the mercury lower in a thermometer laid up-in the ground, in a meadow in his neighbourhood, than it Was in a similar thermometer suspended in the air 6 feet above the former; and that upon one night the difference amounted to 5° of Fahrenheit's scale. And Dr. Wells, in autumn 181 i, on laying a thermometer upon grass wet with dew, and suspending a second in the air 2 feet above the sur- face, found in an hour afterwards, that the former stood 8° lower than the latter. He at first regarded this coldness of the sur- face to be the effect of the evaporation of the moisture, but subsequent observations and experiments convinced him, that the cold was not the effect, but the cause of deposition of dew. Under a cloudless sky, the earth projects its heat without return, into empty space; but a canopy of cloud is a concave mirror, which restores the equi- librium by counter-radiation. See Dew. On this principle Professor Leslie has constructed a pretty instrument, which he calls JEthrioscope, whose function it is to denote the clearness and coolness of the sky. It consists of a polished metallic cup, of an oblong spheroidal shape; wry like a silver porter-cup, standing upright, with the bulb of a differential thermometer placed in its a\is, and the stem lying parallel to the stalk ofthe cup. The other ball is gilt, and turned outwards and upwards, so as to rest against the side of the vessel. The best form of the cup is an ellipsoid, whose eccentricity is equal to half the transverse axis, and the focus consequently placed at the third part of tbe whole height of the cavity; while the diameter of the thermos- cope ball should be nearly the third part of the orifice of the cup. A lid of the same thin metal unpolished, is fitted to the mouth of the cup, and removed only when an observation is to be made. The scale at- tached to the stem of the thermoscope, may extend to 60 or 70 millesimal degrees above the zero, and about 15 degrees be- low it. This instrument exposed to the open air in clear weather, will at all times, both dur- ing the day and the night, " indicate an im- pression of cold shot downward from the higher regions," in the figurative language of the inventor. Yet the effect varies ex- ceedingly. It is greatest while the sky has the pure azure hue; it diminishes fast as the atmosphere becomes loaded with spreading clouds; and it is almost extinguished when low fogs settle on the surface. The liquid in the stem falls and rises with every pas- sing cloud. Dr. Howard's modification ot the thermoscope would answer well here. The diffusion of heat among the particles of fluids themselves,''depends upon their specific gravity and specific heat conjunct- ly, and therefore must vary for each par- ticular substance. The mobility ofthe par- ticles in a fluid, and their reciprocal inde- pendence on one another, permit them to change their places whenever they are ex- panded or contracted by alternations of temperature; and hence the immediate and inevitable effect of communicating heat to the under stratum of a fluid mass, or of ab- stracting it from the upper stratum, is to determine a series of intestine movements. The colder particles, by their superior den- sity, descend in a perpetual current, and force upwards those rarefied by the heat. When however the upper stratum primari- ly acquires an elevated temperature, it seems to have little power of imparting heat to the subjacent strata of fluid parti- cles. Water may be kept long in ebullition at the surface of a vessel, while the bottom remains ice cold, provided we take mea- sures to prevent the heat passing down- wards through the sides ofthe vessel itself. Count Rumford became so strongly per- suaded ofthe impossibility of communica- ting heat downwards through fluid parti- cles, that he regarded them as utterly des- titute of the faculty of transmitting that power from one to another, and capable of acquiring heat, only in individual rotation and directly, from a foreign source. The proposition thus absolutely announced is absurd, for we know that by intermixture and many other modes, fluid particles im- part heat to each other; and experiments have been instituted, which prove the ac- tual descent of heat through fluids by com- munication from one stratum to another. But unquestionably this communication is amazingly difficult and slow. We are hence led to conceive, that it is an actual contact of particles, which in the solid condition facilitates the transmission of heat so speedily from point to point through their mass. This contact of certain poles in the molecules, is perfectly consistent with void spaces, in which these molecules may slide over each other in every direction; by which movements or condensations, heat may be excited The fluid condition reverts or averts the touching and cohering poles, whence mobility results. This statement may be viewed either as a representation of facts, or an hypothesis to aid concep- tion. r Since the diffusion of heat through a fluid mass is accomplished almost solely by the intestine currents, whatever ob- structs these must obstruct the change of CAL CAL temperature. Hence fluids intermingled with porous matter, such as silk, wool, cot- ton, downs, fur, hair, starch, mucilage, &c. are more slowly cooled than in their pure and limpid state. Hence apple-tarts and pottages retain their heat very long, in comparison of the same bulk of water heat- ed to the same degree, and exposed in similar covered vessels to the cool air. Of the conducting power of gaseous bodies, we have already taken a view. 1 know of no experiments which have satisfactorily de- termined in numbers, the relative conduct- ing power of liquids. Mercury for a liquid, possesses a high conducting faculty, due to its density and metallic nature, and small specific heat. The transmission of heat through solids was made the subject of some pleasing po- pular experiments by Dr. Ingenhausz. He took a number of metallic rods of the same length and thickness, and having coated one of the ends of them for a few inches with bees wax, he plunged their other ends into a heated liquid. The heat travelled on- wards among the matter of each rod, and soon became manifest by the softening of the wax. The following is the order in which the wax melted; and according to that experiment, therefore, the order of conducting power relative to heat 1. Silver. 2. Gold 3. Copper, 7 near]v equal. 4. Tin, 5 " Platinum, i Iron, \ much inferior to Steel, I the others. Lead, ) In my repetition of the experiment, I found silver by much the best conductor, next copper, then brass, iron, tin, much the same, then cast iron, next zinc, and last of all, lead. Dense stones follow metals in conducting power, then bricks, pottery, and at a long interval, glass. A rod of this singular body may be held in the fingers for a long time, at a distance of an inch from where it is ignited and fused by the blow-pipe. It is owing to the inferior con- ducting power of stone, pottery, glass, and cast iron, that the sudden application of heat so readily cracks them. The part acted on by the caloric expands, while the adjacent parts retaining their pristine form and volume, do not accommodate them- selves to the change; whence a fissure must necessarily ensue. Woods and bones are better conductors than glass; but the pro- gress of heat in them at elevated tempera- tures, may be aided by the vaporization of their juices. Charcoal and saw-dust rank very low in conducting power. Hence the former is admirably fitted for arresting the dispersion of heat in metal furnaces. If the sides of these be formed of double plates, with an interval between them of an inch filled with pounded charcoal, an intense heat may exist within, while the outside is scarcely aff'ected. Morveau has rated the conducting power of charcoal to that of fine sand, as 2 to 3, a difference much too small. Spongy organic substances, silk, wool, cotton, &c. are still worse conduct- ors than any of the above substances; and the finer the fibres, the less conducting power they possess. The theory of clothing depends on this principle. The heat gene- rated by the animal powers, is accumula- ted round the body by the imperfect con- ductors of which clothing is composed. To discover the exact law of the distri- bution of heat in solids, let us take a pris- matic bar of iron, three feet long, and with a drill form three cavities in one of its sides, at lU, 20, and 30 inches from its end, each cavity capable of receiving a little mercury, and the small bulb of a delicate thermometer. Cut a hole fitting exactly the pnsmic bar, in the middle of a sheet of tin-plate, which is then to be fixed to the bar, to screen it and the thermometer, from tfie focus of heat. Immerse the ex- tremity of the bar obliquely into oil or mercury heated to any known degree, and place the thermometers in their cavities surrounded with a little mercury. Or the bar may be kept horizontal, if an inch or two at its end be incurvated, at right an- gles to its length. Call the thermometers A, B, C. Were there no dissipation of the heat, each thermometer would continue to mount till it attained the temperature of the source of heat. But in actual experi- ments, projection and aerial currents mo- dify that result, making the thermometers rise more slowly, and preventing them from ever reaching the temperature of the end of the bar. Their state becomes in- deed stationary whenever the excess of temperature, each instant communicated by the preceding section ofthe bar, merely compensates what they lose by the contact of the succeeding section of the bar, and the other outlets of heat. The three ther- mometers now indicate three steady tem- peratures, but in diminishing progression. In forming an equation from the experi- mental results, M. Laplace has shown, that the difficulties ofthe calculation can be re- moved only by admitting, that a deter- minate point is influenced not only by those points which touch it, but by others at a small distance before and behind it. Then the laws of homogeneity, to which differ- entials are subject, are re-established, and all the rules of the differential calculus are observed. Now, in order that the calorific influence may thus extend to a distance in the interior of the bar, there must operate CAL CAL through the very substance ofthe solid ele- ments a true radiation, analogous to that observed in air, but whose sensible influ- ence is bounded to distances incomparably smaller. This result is in no respect impro- bable. In fact, Newton has taught us, that all bodies, even the most opaque, become transparent when rendered sufficiently thin; and the most exact researches on ra- diating caloric, prove that it does not eman- ate solely from the external surface of bo- dies, but also from material particles situa- ted within this surface, becoming no doubt insensible at a very slight depth, which probably varies in the same body, with its temperature. M. Biot, M. Fourier, and M. Poisson, three of the most eminent mathematicians and philosophers of the age, have distin- guished themselves in this abstruse inves- tigation. The following is the formula of M. Biot, when one end of the bar is main- tained at a constant temperature, and the other is so remote as to make the influ- ence of the source insensible. Let y repre- sent, in degrees of the thermometer, the temperature of the air by which the bar is surrounded; let the temperature of the fo- cus be y -j- Y; then the integral becomes, log. y = log. Y —£- s/±% "*■ a x is the distance from the hot end of the bar; a and b are two coefficients, supposed constant for the whole length of the bar, which serve to accommodate the formula to every possible case, and which must be assigned in such case, agreeably to two ob- servations. M is the modulus of the or- dinary logarithmic tables, or the number 2.302585. M. Biot presents several tables of observations, in which sometimes 8, and sometimes 14 thermometers were applied all at once to successive points of the bar; and then be computes by the above formu- la, what ought to be the temperature of these successive points, having given the temperature of the source; and vice versa, what should be the temperature of the source from the indications of the ther- mometers. A perfect accordance is shown to exist between fact and theory. Whence we may regard the view opened up by the latter, as a true representation of the con- dition of the bar. With regard to the ap- plication of this theorem, to discover for example, the temperature of a furnace, by thrusting the end of a thermoscopic iron bar into it, we must regret its insufficiency. M. Biot himself after showing its exact co- incidence at all temperatures, up to that of melting lead, declares that it ought not to apply at high heats. But I see no diffi- culty in making a very useful instrument of this kind, by experiment, to give very valuable pyrometrical indications. The end of the bar which is to be exposed to the heat, being coated with fire-clay, or sheath- ed with platinum, should be inserted a few inches into the flame, and drops of oil be- ing put into three successive cavities of the bar, we should measure the tempera- tures of the oil, when they have become stationary and note the time elapsed, to pro- duce this effect. A pyroscope of this kind could not fail to give useful information to the practical chemist, as well as to the manufacturers of glass, pottery, steel, &c. 2. Of specific heat.—If we take equal weights, or equal bulks, of a series of sub- stances; for example, a pound or a pint of water, oil, alcohol, mercury, and having heated each separately, in a thin vessel, to the same temperature, say to 80° or 100* Fahr. from an atmospherical temperature of 60°, then in the subsequent cooling of these four bodies to their former state, they will communicate to surrounding me- dia very different quantities of heat. And conversely, the quantity of heat requisite to raise the temperature of equal masses of different bodies, an equal number of thermometric degrees, is different, but specific for each body. There is another point of view in which specific heats of bo- dies may be considered relative to their change of form, from gaseous to liquid, and from liquid to solid. Thus the steam of water, at 2K'0, in becoming a liquid, does not change its thermometric tempe- rature 212°, yet it communicates, by this change, a vast quantity of heat to sur- rounding bodies; and, in like manner, li- quid water at 32°, in becoming the solid called ice, does not change its temperature as measured by a thermometer, yet it im- parts much heat to surrounding matter. We therefore divide the study of specific heats into two branches: 1. The specific heats of bodies while they retain the same state; and 2. The specific heats, connected with, or developed by, change of state. The first has been commonly called the capacities of bodies for caloric; the second, the latent heat of bodies. The latter we shall consider after change of state. 1. Ofthe specific heats of bodies, while they experience no change of state. Three distinct experimental modes have been employed to determine the specific heats of bodies; in the whole of which modes, that of water has been adopted for the standard of comparison or unity. 1. In the first mode, a given weight or bulk of the body to be examined, being heated to a certain point, is suddenly mixed with a given weight or bulk of another body, at a different temperature; and the resulting temperature ofthe mixture shows the re- lation between their specific heats. Hence, if the second body be water, or any other substance whose relation to water is aster- CAL tained, the relative heat of the first to that of water will be known. It is an essential precaution in using this mode, to avoid all such chemical action as happens in mixing water with alcohol or acids. Let us take oil for an example. If a pound of it, at 9o° Fahr. be mixed with a pound of water at 60°, the resulting temperature will not be the mean 75°, but only 70°. And converse- ly, if we mix a pound of water heated to 90°, with a pound of oil at 60°, the tempe- rature ofthe mixture will be 80°. We see here, that the water in the first case ac- quired 10°, while the oil lost %J°; and in the second case, that the water lost 10° while the oil gained 20°. Hence we say, that the specific heat of water is double to that of oil; or that the same quantity or in- tensity of heat which will change the tem- perature of oil 20B, will change that of wa- ter only 10°; and therefore if the specific beat, or capacity for heat, of water be call- ed 1.000, that of oil will be 0.500. When the experiment has been, from particular circumstances,made with unequal weights, the obvious arithmetical reduction, for the difference, must be made. This is the ori- ginal method of Black, Irvine, and Craw- ford. The second mode is in some respects a modification of tbe first. The heated mass ofthe matter to be investigated, is so sur- rounded by a large quantity of the stand- ard substance at an inferior temperature, that the whole heat evolved by the first, in cooling, is received by the second. We may refer to this mode, 1st, Wilcke's prac- tice of suspending a lump of heated metal in the centre of a mass of cold water con- tained in a tin vessel: ?d, The plan of La- voisier and Laplace, in which a heated mass of matter was placed by means of their ele- gant Calorimeter, in the centre of a shell of ice; and the specific heat was in- ferred from the quantity of ice that was li- quefied: And 3d, The method of Beiurd and Delaroche, in which gaseous matter, heated to a known temperature, was made to traverse, slowly and uniformly, the con- volutions of a spiral pipe, fixed in a cylin- der of cool water, till this water rose to a stationary temperature; when " reckon- ing from this point, the excess ofthe tem- perature ofthe cylinder, above that ofthe ambient air, becomes proportional to the quantity of heat given out by the current of gas that passed through the cylinder." Each gas was definitely heated, by being passed through a straight narrow tube, placed in the axis of a large tube, filled with the steam of boiling water. The spc cific heats were then compared to water by two methods. The first consists in sub- jecting the cylinder, which they call the calorimeter, to the action of a current of water perfectly regular, and so &lu\v, that CAL it will hardly produce a greater effect than the current of the different gases. The se- cond method consists in determining, by calculation, the real quantity of iieat which the calorimeter, come to its stationary tem- perature, can lose in a given time; for since, after it reaches this point, it does not be- come hotter, though the source of heat continues to be applied to it, it is evident that it loses as much heat as it receives. MM. Berard and Delaroche employed these two methods in succession. From the sin- gular ingenuity of their apparatus, and pre- cision of their observations, we may regard their determinations as deserving a degree of confidence to which the previous results, on the specific heat of the gases, are not at all entitled They have completely over- turned the hypothetical structures of Black,- Lavoisier, and Crawford, on the heat de- veloped in combustion and respiration, while they give great countenance to the profound views of Sir H. Davy. See Com- bustion. The third method of determining the specific heats of bodies, is by raising a given mass to a certain temperature, sus- pending it in a uniform cool medium, till it descends through a certain number of thermometric degrees, and carefully noting by a watch the time elapsed. It is evident, that if the bodies be invested with the same coating, for instance, glass or bur- nished metals; if they be suspended in the same medium, with the same excess of temperature, and if their interior constitu- tion relative to the conduction of heat be also the same, then their specific heats will be directly as the times of cooling. I have tried tins method, and find that it readily gives, in common cases, good approxima- tions Som> of my results were published in the Annals of Phil, for October 1817, on water, sulphuric acid, spermaceti oil, and oil of turpentine. " A thin glass globe, ca- pable of holding 18J0 grains of water, was successively filled with this liquid, and with the others; and being in each case heated to the same degree, was suspended, with a delicate thermometer immersed in it, in a large room of uniform temperature. The comparative times of cooling, through an equal range of the thermometric scale, were carefully noted by a watch in each case." The difference of mobility in the li- qu; one another, and at equal distances, through whi h strong iron bars were introduced so as to travel se tbe chamber. Their ends outside of the wall were furnished with thick iron discs, firtniy screwed on These Were sufficient to retain the nails in their actual position. But to bring them nearer together would have surpassed every effort •f human strength. All the alternate bars of the series were now heated at once by lamps, in consequence of which they were elongated. The exterior discs being thus freed from contact of the walls, permitted them to be advanced farther, on the screw- ed ends of the bars. On removing the lamps, the bars cooled, contracted, and drew in the opposite walls. The other bars became in consequence loose at their ex- tremities, and permitted their end plates to be further screwed on. The first series of bars being again heated, the above pro- cess was repeated in each of its steps. By a succession of these experiments they re- stored the walls to the perpendicular posi- tion; and could easily have reversed their curvature inwards, if they had chosen. The gallery still exists with its bars, to at- test the ingenuity of its preserver M. Mo- lard. 2d, Of the change of state produced in bodies by caloric, independent of change of composition. The three forms of matter, the solid, liquid, and gaseous, seem immediate- ly referable to the power of heat, modify- ing, balancing, or subduing cohesive attrac- tion. In the article blow-pipe, we have shown that every solid may be liquefied, and many of them, as well as all liquids, may be va- porized at a certain elevation of tempera- ture. And conversely almost every known liquid may be solidified by the reduction of its u mperature. If we have not hitherto been able to convert the air and other elas- tic fluids into liquids or solids, it is proba- bly owing to the limited power we possess over thermometric depression. But we know, that by mechanical approximation of their elastic particles, an immense evo- lution of htat is occasioned, which must convince us that their gaseity is intimately dependent on the operation of that repul- sive power. CAL CAL Sulphuric ether, always a liquid in our climate, if exposed to the rigors of a Sibe- rian winter, would become a solid, and, transported to the torrid zone, would form a permanent gas. The same transitions are familiar to us with regard to water, only its vaporizing point, being much higher, leads us at first to suppose steam an unna- tural condition. But by generalizing our ideas, we learn that there is really no state of bodies which can be called more natural than another. Solidity, liquidity, the state of vapours and gases, are only accidents connected with a particular level of tempe- rature. If we pass the easily condensed vapour of nitric acid through a red-hot glass tube, we shall convert it into gases which are incondensable by any degree of cold which we can command. The particles which formed the liquid can no longer join together to reproduce it, because their dis- tances are changed, and with these have also changed the reciprocal attractions which united them. Were our planet removed much further from the sun, liquids and gases would so- lidify; were it brought nearer that lumi- nary, the bodies which appear to us the most solid, would be reduced into thin in- visible air. We see, then, that the princi- ple of heat, whatever it may be, whether matter or quality, separates the particles of bodies when its energy augments, and suffers them to approach when its power is enfeebled. By extending this view, it has been drawn into a general conclusion, that this principle was itselfthe force w hich maintains the particles of bones in equi- libria against the effort of their reciprocal attraction, which tends continually to bring them together. But although this conclu- sion be extremely probable, we must re- member that it is hypothetical, and goes further than the facts. We see that the force which balances attraction in bodies may be favoured or opposed by the princi- ple of heat, but this does not necessarily prove that these forces are of the same na- ture. The instant of equilibrium which sepa- rates the solid from the liquid state, de- serves consideration. Whatever may be the cause and law ofthe attractions which the particles exercise on one another, the effect which results ought to be modified by their forms. When all the other quali- ties are equal, a particle which may be cy- lindrical, for example, will not exercise the same attraction as a sphere, on a point pla- ced at an equal distance from its centre of gravity. Thus in the law of celestial gravi- tation, the attraction of an ellipsoid on an exterior point, will be stronger in the di- rection of its smaller than in that of its larger axis, at the same distance from its Surface. Now whatever be the law of at- tractions which holds together the parti- cles of bodies, similar differences must ex- ist. These particles must be attracted more strongly by certain sides than by others. 'Thence must result differences in the man- ner of their arrangement, when they are sufficiently approximated for their attrac- tions to overcome the repulsive power. This explains to us in a very probable man- ner, the regular crystallization which most solid bodies assume,when they concrete un- disturbed. We may easily conceive how the diff'erent substance of the particles, as well as their diff'erent forms, may produce in crystals all the varieties which we observe. The system of the world presents mag- nificent effects of this attraction dependent on figure. Such are the phenomena of nu- tation and the precession ofthe equinoxes, produced by the attractions ofthe sun and moon on the flattened spheroid ofthe earth. These sublime phenomena would not have existed, had the earth been a sphere; they are connected with its oblateness and rota- tion, in a manner which may be mathemati- cally deduced, and subjected to calculation. But,the investigation shows, that this part of the attraction dependent on figure, de- creases more rapidly than the principal force. The latter diminishes as the square of the distance; the part dependent on figure diminishes as the cube of the dis- tance Thus also, in the attractions which hold the parts of bodies united, we ought to expect an analogous difference to occur. Hence the force of crystallization may be subdued, before the principal attractive force is overcome. When the particles are brought to this distance, they will be indif- ferent to all the positions which they can assume round their centre of gravity; this will constitute the liquid condition. Sup- pose now that the temperature falling, the particles approach slowly to each other, and tend to solidify anew; then the forces de- pendent on their figure will come again in- to play, and in proportion as they increase, the particles solicited by these forces will take movements round their centres of gravity They will turn towards each other their faces of greatest attraction, to arrive finally at the positions which their crystal- lization demands. Now according to the figure of the particles, we may conceive that these movements may react on their centre of gravity, and cause them to ap- proach or recede gradually from each other, till they finally give to their assemblage the volume due to the solid state; a volume which in certain cases may be greater, and in others smaller, than that which they oc- cupied as liquids. These mechanical con- siderations thus explain, in the most prob- able and satisfactory manner, the dilatations and contractions of an irregular kind, which certain liquids, such as water and mercu- CAL CAL ry, experience, on approaching the term of their congelation. Having given these gen- eral views, we may now content ourselves with stating the facts as much as possible in a tabular form. TABLE of the Concreting or Congealing Temperatures of various Liquids, by Fah- renheit's Scale. Sulphuric ether, - — 46- Liquid ammonia, - - — 46 Nitric acid, sp gr. 1.424 — 45.5 Sulphuric acid, sp. gr. 1.6415 — 45 Mercury, - - — 39 Nitric acid, sp. gr. 1.407 — 30.1 Sulphuric acid, - 1.8064 — 26 Nitric acid, - - 1.3880 — 18.1 Do. do. - 12583 — 17.7 Do. do. 1.3290 — 2.4 Brandy, - - — 7.0 Sulphuric acid, - 1.8376 + 1. Pure prussic acid, - 4 to 5 Common salt, 25 -4- water 75 4 Do. 22.2 -f do. 77.8 7.2 Sal ammoniac, 20 -j- do. 80 8 C. salt, 20 + do. 80 9.5 Do. 16.1 -+• do. 83.9 13.5 Oil of turpentine, - - 14. Strong wines, - - - 20 Rochelle salt, 50 -f water 50 21. C. salt, 10 -f do. 90 21.5 Oil of bergamot, - - 23 Blood, ... 25 C. salt, 6.25 -f water 93.75 25.5 Eps. salts, 41.6 -f do. 58.4 25.5 Nitre, 12.5 -f do. 87.5 26. C. salt, 4.16 + do. '95.84 27.5 Copperas, 41.6 -f- do. 58.4 28 Vinegar, - - 28 Sul. of zinc, 53.3 + water 46.7 286 Milk, ... 30 Water, 32 Olive oil, - - - 36 Sulphur and phosphorus, eq. parts, 40 Sulphuric acid, sp. gr. 1.741 42 Do. do. - 1.780 46 Oil of anise, - - 50 Concentrated acetic acid, 50 Tallow, Dr. Thomson, - 92 Phosphorus, - 108 Stearin from hog's lard, - - 109 Spermaceti, - - - - 112 Tallow, Nicholson, - - - 127 • Margaric acid, .... 134 Potassium, .... 136.4 Yellow wax, - 142 Do. Do......149 White wax, - - - - 155 Sodium,.....194 Sulphur, Dr. Thomson, • - 218 Do. Dr. Hope, - - - 234 Tin,......442 Bismuth,.....476 Lead,.....612 Zinc, by Sir H .Davy, - - 680 Zink, Brongniart, - - - 698" Antimony, .... 809? See Pyrometer for higher heats. The solidifying temperature of the bo- dies above tallow, in the table, is usually called their freezing or congealing point; and of tallow and the bodies below it, the fusing or melting point Now, though these temperatures be stated, opposite to some of the articles, to fractions of a thermo- metric degree, it must be observed, that various circumstances modify the concret- ing point of the liquids, through several degrees; but the liquefying points of the same bodies, when once solidified, are uni- form and fixed, to the preceding tempera- tures. The preliminary remarks which we of- fered on the forces concerned in the-tran- sition from liquidity to solidity, will in some measure explain these variations; and we shall now illustrate them by some instruc- tive examples. If we fill a narrow-mouthed matrass with newly distilled water, and expose it very gradually to a temperature considerably below 32°, the liquid water will be observ- ed, by the thermometer left in it, to have sunk 10 or 11 degrees below its usual point of congelation. M. Gay-Lussac, by cover- ing the surface of the water with oil, has caused it to cool i,T$ degrees Fahr. below the ordinary freezing temperature. Its vo- lume at the same time expanded as much as if it had been heated 21£ degrees above 3^°. According to Sir Charles Blagden, to whom the first of these two observations belongs, its dilatation may amount to l-7th of the total enlargement, which it receives by solidifying. Absolute repose of the li- quid particles is not necessary to ensure the above phenomenon, for Sir Charles stir- red water at 21° without causing it to freeze, but the least vibration of their mass, or the application of icy spiculx, by the atmosphere, or the hand, determines an instantaneous congelation. We may remark here, that the dilatation of the water increasing as it cools, but to a less extent than when it concretes, is a proof that its constituent particles, in obedience to the cooling process, turn their poles more and more towards the position of the maximum attraction, which constitutes their solid state. But this position may be determined instantaneously by the ready formed aqueous solid, the particles of which presenting themselves to those of the liquid, by their sides of greatest attrac- tion, will compel them to turn into similar positions. Then the particles of the liquid first reverted will act on their neighbours like the exterior crystal, and thus from point to point the movement will be pro- pagated through the whole mass, till all be congealed. The vibratory movements act by CAL CAL throwing the particles, into positions favor- able for their mutual attraction. The very same phenomena occur with saline solutions. If a hot saturated solution of Glauber's salt be cooled to 5vj° under a film of oil, it will remain liquid, and will bear to be moved about in the hand with- out any change; but if the phial containing it be placed on a vibrating table, crystal- lization will instantly take place. In a paper on saline crystallization which I published in the 9th number of the Journal of Science, I gave the following illustration of the above phenomena. " The effect of mechani- cal disturbance in determining cry stalliza- tion, is illustrated by the symmetrical dis- position of particles of dust and iron, by electricity and magnetism. Strew these up- on a plane, and present magnetic and elec- tric forces at a certain distance from it, no effect will be produced. Communicate to the plane a vibrating movement; the parti- cles, at the instant of being liberated from the friction of the surface, will arrange themselves according to the laws of their respective magnetic or electric attractions. The water of solution in counteracting so- lidity, not only removes the particles to dis- tances beyond the sphere of mutual attrac- tion, but probably also inverts their attract- ing poles." Perhaps the term avert would be more appropriate to liquidity, to denote an obliquity of direction in the attracting poles; and revert might be applied to gasei- ty, when a repulsive state succeeds to the feebly attractive powers of liquid particles. The above table presents some interest- ing particulars relative to the acids. I have expressed their strengths, by specific gra- vity, from my tables of the acids, instead of by the quantity of marble which lOuO grains of them could dissolve, in the original state- ment of Mr. Cavendish. Under the heads of nitric acid and equivalent, some observa- tions will be found on these peculiarities with regard to congelation. We see that common salt possesses the greatest effica- cy in counteracting the congelation of wa- ter; and next to it, sal ammoniac. Mr. Crigh- ton of Glasgow, whose accuracy of obser- vation is well known, has remarked, that when a mass of melted bismuth cools in the air, its temperature falls regularly to 468°, from which term it however instantly springs up to 476°, at which point it re- mains till the whole be consolidated. Tin in like manner sinks and then rises 4 de- grees; while melted lead, in cooling, be- comes, stationary whenever it descends to 612°. We shall presently find the probable cause of these curious phenomena. Water, all crystallizable solutions, and th three metals, cast-iron, bismuth, and antimony, expand considerably in volume, at the instant of solidification. The greatest obstacles cannot resist the exertion of this expansive force. Thus glass bottles, trunks of trees ,iron and lead pipes, even mountain rocks, are burst by the dilatation ofthe wa- ter in their cavities, when it is converted into ice. In the same way our pavements are raised in winter. The beneficial opera- tion of this cause is exemplified in the com- minution or loosening the texture of dense clay soils, by the winter's frost, whereby the delicate fibres of plants can easily penetrate them. Major Williams of Quebec, burst bombs, which were filled with water and plugged up, by exposing them to a freezing cold. There is an important circumstance oc- curs in the preceding experiments on the sudden congelation of a body kept liquid below its usual congealing temperature, to which we must now advert The mass, at the moment its crystallization commences, rises in temperature to the term marked in the preceding table, whatever number of degrees it may have previously sunk below it. Suppose a globe of water suspended in an atmosphere at 21° F.; the liquid will cool and remain stationary at this temperature, till vibration of the vessel, or contact of a spicula of ice, determines its concretion, when it instantly becomes 11 degrees hot- ter than the surrounding medium. We owe the explanation of this fact, and its exten- sion to many analogous chemical phenome- na, to the sagacity of Dr Black. His truly philosophical mind was particularly struck by the slowness with which a mass of ice liquefies when placed in a genial atmos- phere. A lump of ice at 22° freely suspend- ed in a room heated to 5U°, which will rise to 3_° in 5 minutes, will take 14 times 5, or 70 minutes, to melt into water, whose temperature will be only 32°. Dr. Black sus- pended in an apartment two glass globes of the same size alongside of each other, one of which was filled with ice at 32°, the other with water at 33°. In half an hour the water had risen to 40°; but it took 10$ hours to liquefy the ice and heat the result- ing water to 40°. Both these experiments concur therefore in showing that the fusion of ice is accompanied with the expenditure of 140 degrees of calorific energy, which have no effect on the thermometer. For the first experiment tells us that 10 degrees of heat entered the ice in the space of 5 mi- nutes, and yet 14 times that period passed in its liquefaction. 'The second experiment shows that 7 degrees of heat entered the globes in half an hour; but 21 half hours were required for the fusion ofthe ice, and for heating of its water to 40°. If from the product of 7 into 21 = 147, we subtract the 7 degrees which the water was above 33, wc have 140 as before. But the most simple and decisive experiment is to mingle a pound of ice in small fragments with a pound of water at 172°. Its liquefaction is CAL CAL instantly accomplished, but the tempera- ture of the mixture is only 32°. Therefore 140° of heat seem to have disappeared. Had we mixed a pound of ice-cold water with a pound of water at 172°, the result- ing temperature would have been 102°, proving that the 70° which had left the hot- ter portion, were manifestly transferred to that which was cooler The converse of the preceding experiments may also be de- monstrated; for in suspending a flask of water, at 35° for example, in an atmosphere at 20°, if it cool to 32° in 3 minutes, it will take 140 minutes to be converted into ice of 32°; because the heat emanating at the rate of 1° per minute, it will require that time for l-t0° to escape. The latter experi- ment, however, from the inferior conduct- ing power of ice, and the uncertainty when all is frozen is not susceptible of the pre- cision which the one immediately preceding admits. The tenth of 140 is obviously 14; and hence we may infer that when a certain quantity of water, cooled to 22°, or 10°, be- low 32°, is suddenly caused to congeal, l-l4th of the weight will become solid. We can now understand how the thaw which supervenes after an intense frost; should so slowly melt the wreaths of snow, and beds of ice, a phenomenon observable in these latitudes from the origin of time, but whose explanation was reserved for Dr Black. Indeed, had the transition of water from its solid into its liquid state not been accompanied by this great change in its re- lation to heat, every thaw would have occa- sioned a frightful inundation, and a single night's frost would have solidified our ri- vers and lakes. Neither animal nor vegeta- ble life could have subsisted under such sudden and violent transitions. Mr. Caven- dish, who had discovered the above fact, before he knew of its being inculcated by Dr. Black in his lectures, states the quan- tity of heat which ice seems to absorb in its fusion to be 15u°; Lavoisier and Laplace make it 135°; a number probably correct, from the pains they took in constructing, on this basis, their calorimeter. The fixity of the melting points of bodies exposed to a strong heat need no linger surprise us; because till the whole mass be melted, the heat incessantly introduced, is wholly ex- pended in constituting liquidity, without increasing the temperature. We can also comprehend how a liquid metal, a saline solution, or water, should in the career of refrigeration, sink below the term of its congelation, and suddenly remount to it. Those substances, in which the attractive force that reverts the poles into the solid arrangement acts most slowly or feebly, will most readily permit this depression of temperature, before liquidity begins to cease. Thus bismuth, a brittle metal, takes 8° of cooling below its melting point, to de- termine its solidification; tin takes 4 , but lead passes so readily into the solid ar- rangement that its cooling is at once arrest- ed at its fusing temperature. In illustration of this statement, we may remark, that the particles of bismuth and tin lose their co- hesive attraction in a great measure long before they are heated to the melting point; though lead continues relatively cohesive till it begins to melt. Tin may be easily pul- verized at a moderate elevation of tempe- rature, and bismuth in its cold state. The instant, however, that these two metals, when melted, begin to congeal, they rise to the proper fusing temperature, because the caloric of liquidity is then disengaged. Drs. Irvine, father and son, to both of whom the science of heat is deeply in- debted, investigated the proportion of ca- loric disengaged by several other bodies in their passage from the liquid to the so- lid state, and obtained the following re- sults: Caloric of Do. referred to the liquidity. sp. heat of-water. Sulphur, 143.68 27.14 Spermaceti, 145. Lead, 162. 5.6 Bees wax, 175. Zinc, 493. 48.3 Tin, 500. 33. Bismuth, 550 23.25 The quantities in the second column are the degrees by which the temperatures of each ofthe bodies in its solid state, would have been raised by the heat disengaged during its concretion. An exception must be made for wax and spermaceti; which are supposed to be in the fluid state, when indicating the above elevation. Dr. Black imagined that the new relation to heat which solids acquire by liquefaction, was derived from the absorption, and intimate combination of a portion of that fluid, which thus employingall its repulsive ener- gies in subduing the stubborn force of co- hesion, ceased to have any thermometric tension, or to be perceptible to our senses. L'e termed this supposed quantity of calo- ric, their latent heat; a term very conveni- ent and proper, while we regard it simply as expressing the relation which the calo- rific agent bears to the same body in its fluid and solid states. To the presence of a cer- tain portion of latent or combined heat in solids, Dr. Black ascribed their peculiar de- grees of softness, toughness, malleability. Thus we know that the condensation of a metal by the hammer, or under the die, never fails to render it brittle, while, at the same time, heat is disengaged. Berthol- let subjected equal pieces of copper and silver to repeated strokes of a fly press. The elevation of their temperature, which was considerable by the first blow, dimin- CAL CAL ished greatly at each succeeding one, and became insensible whenever the condensa- tion of volume ceased. The copper suffered greatest condensation, and evolved most heat. Here the analogy of a sponge, yield- ing" its water to pressure, has been employ- ed to illustrate the materiality of heat sup- posed deducible from these experiments. But the phenomenon may be referred to the intestine actions between the ultimate particles which must accompany the vio- lent dislocation of their attracting poles. The cohesiveness of the metal is greatly impaired. The enlarged capacity for heat, to use the popular expression, which solids ac- quire in liquefying, enables us to under- stand and apply the process of artificial cooling, by what are called freezing mix- tures. When two solids, such as ice and salt, by their reciprocal affinity, give birth to a liquid, then a very great demand for heat is made on the surrounding bodies; or they are powerfully stripped of their ^ieat, and their temperature sinks of course. Pulverulent snow and salt mixed at 32°, will produce a depression of the thermo- meter plunged into them of about 38°. The more rapid the liquefaction, the greater the cold. Hence the paradoxical experi- ment of setting a pan on the fire contain- ing the above freezing mixture with a small vessel of water plunged into it. In a few seconds the water will be found to be fro- zen. The solution of all crystallized salts is attended with a depression of tempera- ture, which increases generally with the solubility ofthe salt. The table of freezing mixtures in the Appendix, presents a copious choice of such means of refrigeration. Equal parts of sal ammoniac and nitre, in powder, form the most convenient mixture for procuring moderate refrigeration; because the water of solution being afterwards removed by evaporation, the pulverized salts are equal- ly efficacious as at first. Under the articles Climate, Congelation, Tempera- ture, Ther mom ETER,and Water, some additional facts will be found on the pre- sent subject. But the diminution of temperature by liquefaction is not confined to saline bodies. When a solid amalgam of bismuth, and a solid amalgam of lead, are mixed together, they become fluid, and the thermometer sinks during the time of their action. The equilibrium between the attractive and repulsive forces which constitutes the liquid condition of bodies, is totally sub- verted by a definite elevation of tempera- ture, when the external compressing forces do not vary. The transition from the liquid state into that of elastic fluidity is usually. accompanied with certain explosive move- VOL. I. ments, termed ebullition. The peculiar tern. peratures at which different liquids under* go this change is therefore called their boiling point; and the resulting elastic fluid is termed a vapour, to distinguish it from a gas, a substance permanently elastic, and not condensable as vapours are, by mode- rate degrees of refrigeration. It is evident that when the attractive forces, however feeble in a liquid, are supplanted by strong repulsive powers, the distances between the particles must be greatly enlarged. 'Thus a cubic inch of water at 40° becomes a cubic inch and l-25th on the verge of 212°, and at 21'-° it is converted into 1600 cubic inches of steam. 'The existence of this steam indicates a balance between its elastic force and the pressure of the at- mosphere. If the latter be increased beyond its average quantity by natural or artificial means, then the elasticity of the steam will be partially overcome, and a portion of it will return to the liquid condition. And conversely, if the pressure of the air be less than its mean quantity, liquids will assume elastic fluidity by a less intensity of calo- rific repulsion, or at a lower thermometric tension. Professor Robison performed a set of ingenious experiments, which appear to prove, that when the atmospheric pres- sure is wholly withdrawn, that is, in vacuo, liquids become elastic fluids 124° below their usual boiling points. Hence water in vacuo will boil and distil over at 21i° — 124 = 88° Fahr. This principle was long ago employed by the celebrated Watt in his researches on the steam engine, and has been recently applied in a very ingenious way by Mr. Tritton in his patent still, (Phil. Mag-, vol. 51.), and Mr. Barry, in his eva- porator for vegetable extracts, (Med. Chir. Trans, vol. 10). See Alcohol, Distilla- tion, Extracts. On the same principle ofthe boiling, vary- ing with the atmospheric pressure, the Rev. Mr. Wollaston has constructed his beauti- ful thermometric barometer for measuring heights. He finds that a difference of 1° in the boiling point of water is occasioned by a difference of 0.589 of an inch on the ba- rometer. This corresponds to nearly 520 feet of difference of elevation. By using the judicious directions which he has given, the elevation of a place may thus be rigor- ously determined, and with great conveni- ence. The whole apparatus, weighing 20 ounces, packs in a cylindrical tin case, 2 inches diameter, and 10 inches long. When a vessel containing water is placed over a flame a hissing sound or simmer- ing is soon perceived. This is ascribed to the vibrations occasioned by the successive vaporization and condensation ofthe parti- cles in immediate contact with the bottom of the veksel. The sound becomes louder as 32 CAL CAL the liquid is heated, and terminates in ebul- lition. The temperature becomes now of a sudden stationary when the vessel is open, however rapidly it rose before, and whate- ver force of fire be applied. Dr. Black set a tin cup full of water at 50°, on a red hot iron plate. In four minutes it reached the boiling point, and in twenty minutes it was all boiled off. From 50° to 212°, the eleva- tion is 162°; which interval, divided by 4, gives 40£° of heat, which entered the tin cup per minute. Hence 20 minutes, or 5 times 4 multiplied into 40J = 810, will represent the quantity of heat that passed into the boiling water to convert it into a vapour. But the temperature of this is still only 212°. Hence, according to Black, these 810° have been expended solely in giving elastic tension, or, according to Irvine, in supplying the vastly increased capacity of of the aeriform state; and therefore they may be denominated latent heat, being in- sensible to the thermometer. The more ex- act experiments of Mr. Watt have shown, that whatever period be assigned for the heating of a mass of water from 50° to 212°, 6 times this period is requisite with a uniform heat for its total vaporization. But 6 X 162° = 972 = the latent heat of steam; a result which accords with my ex- periments made in a different way, as will be presently shown. Every attentive opera- tor must have observed the greater explo- sive violence and apparent difficulty of the ebullition of water exposed to a similar heat in glass, than in metallic vessels. M. Gay-Lussac has studied this subject with bis characteristic sagacity. He discovered that water boiling in a glass vessel has a temperature of 214.2°, and in a tin vessel contiguous to it, of only 212°. A few par- ticles of pounded glass thrown into the former vessel, reduces the thermometer plunged in it to 212.6, and iron filings to 212. When the flame is withdrawn for a few seconds from under a glass vessel of boiling water, the ebullition will recom- mence on throwing in a pinch of iron filings. Professors Munche and Gmelin of Hei- delberg have extended these researches, and given the curious results as to the boil- ing points, expressed in the following table: Ther ^°' ^ l"C^ Substance of the , ,.' below sur- 17,1"* f°"°f«" water. Silver, 211.775° 211. 55° Platina, 211.775 210.875 Copper, 212900 212 225 Tinned iron, 213.24 211.66 Marble, 212. 10 211. 66 Lead, 212. 45 211.775 Tin, 212. 7 211.775 Porcelain, 212. 1 211.900 White glass, 212. 7 212. 00 Green glass, 213. 8 213. 35 Ditto, 212. 7° 212. 00* Delft ware, 213. 8 212. 7 Common earthen ware 213. 8 212. 45 It is difficult to reconcile these varia- tions to the results of M. Gay-Lussac." The vapour formed at the surface of a liquid," he remarks, " may be in equilibrio with the atmospheric pressure; while the interior portion may acquire a greater degree of heat than that of the real boiling point, pro- vided the fluid be enclosed in a vessel, and heated at the bottom. In this case, the ad- hesion of the fluid to the vessel may be considered as analogous in its action to vis- cidity, in raising the temperature of ebul- lition. On this principle we explain the sud- den starts which sometimes take place in the boiling of fluids. This frequently oc- curs to a great degree in distilling sulphu- ric acid, by which the vessels are not un- frequently broken when they are of glass. This evil may be effectually obviated by putting into the retort some small pieces of platina wire, when the sudden disen- gagement of gas will be prevented and con* sequently the vessels not be liable to be bro- ken."—Innalesde Chimie, March 1818. See my remarks on this subject under the Dis- tillation of Sulphuric Acid, extract- ed from the Journal of Science, October 1817. If we throw a piece of paper, a crust of bread, or a powder, into a liquid slight- ly impregnated with carbonic acid, its evo- lution will be determined. See some cu- rious observations by M. Thenard under our articles Oxygenized Nitric Acid, or Oxygenized Water. In a similar manner, the asperities of the surface of a glass or other vessel, act like points in elec- tricity, in throwing off gas or vapour pre- sent in the liquid which it contains. In all the examples of the preceding ta- ble, the temperature is greater at the bot- tom than near the surface of the liquid; and the specific differences must be ascribed to the attractive force of the vessel to wa- ter, and its conduction of heat. We must thus try to explain why tinned iron gives a temperature to boiling water in contact with it, 1.67 degrees higher than silver and platina. Between water, and iron, tin, or lead, there are reciprocal relations at ele- vated temperatures, which do not appa- rently exist with regard to silver and pla- tina. The following is a tabular view of the boiling points by Fahrenheit's scale of the most important liquids, under a mean baro- metrical pressure of thirty inches:— Boiling points. Ether, sp. gr. 0.7365 at 48°. G. Lussac, 100° Carburet of sulphur, - do. 113 Alcohol, sp. gr. 0.813 Ure, 173.5 Nitric acid, 1.500 Dalton, 210 Water, - 212 Saturated sol. of Glaub. salt. Biot, 213 j CAL CAL Boiling points. Saturated sol. of sugar of lead, Biot, 215|° Do. do. sea salt, do. 2244 Muriate of hme 2 -f- water 1 Ure, 230 Do. 35.5 -f- do. 64.5 do. 235 Do. 40.5 -f do. 59.5 do. 240 Muriatic acid , 1.094 Dalton 232 Do. 1.127 do. 222 Do. 1.047 do. 222 Nitric acid, 1.45 do. 240 Do. 1.42 do. 248 Do. 1.40 do. 247 Do. 1.35 do. 242 Do. 1.30 do. 236 Do. 1.16 do. 220 Rectified petroleum, Ure, 306 Oil of turpentine, do. 316 Sulp. acid sp. gr. 1.30 -j- Dalton ,240 Do. 1.408 do. 260 Do. 1.520 do. 290 Do. 1.650 do. 350 Do. 1.670 do. 360 Do. 1.699 do. 374 Do. 1.730 do. 391 Do. 1.780 do. 435 Do. 1.810 do. 473 Do. 1.819 do. 487 Do. 1.827 do. 501 Do. 1.833 do. 515 Do. 1.842 do. 545 Do. 1.847 do. 575 Do. 1.848 do. 590 Do. 1.849 do. 605 Do. 1.850 do. 620 Do. 1.848 Ure, 600 Phosphorus, . . 554 Sulphur, - . 570 Linseed oil, . . 640? Mercury, (Dulong, 662°), 656 These liquids emit vapours, which, at their respective boiling points, balance a pressure of the atmosphere, equivalent to thirty vertical inches of mercury. But at inferior temperatures they yield vapours of inferior elastic power. It is thus that the vapour of quicksilver rises into the va- cuum of the barometer tube; as is seen par- ticularly in warm climates, by the mercu- rial dew on the glass at its summit. Hence aqueous moistures adhering to the mercu- ry, causes it to fall below the true barome- ter level, by a quantity proportional to the temperature. The determination ofthe elas- tic force of vapours, in contact with their respective liquids, at different tempera- tures, has been the subject of many ex- periments. The method of measuring their elasticities, described in my paper on Heat, seems convenient, and susceptible of precision. A glass tube about one-third of an inch internal diameter, and 6 feet long, is seal- ed at one end, and bent with a round cur- vature in the middle, into the form of a syphon, with its two legs parallel, and about 2£ inches asunder. A rectangula* piece of cork is adapted to the interval be- tween the legs, and fixed firmly by twine, about 6 inches from the ends of the sy- phon. Dry mercury is now introduced, so as to fill the sealed leg, and the bottom of the curvature. On suspending this syphon barometer in a vertical direction, by the cork, the level of the mercury will take a position in each of the legs, corresponding to the pressure of the atmosphere. The dif- ference is of course the true height of the barometer at the time, which may be mea- sured by the application of a separate scale of inches and tenths. Fix rings of fine pla- tinum wire round the tube at the two levels of the mercury. Introduce now into the tube a few drops of distilled water, recent- ly boiled, and pass them up through the mercury. 'The vapour rising from the wa- ter will depress the level of the mercury in the sealed leg, and raise it in the open leg.bya quantity equalin each to one-half of the real depression. To measure distinctly this difference of level with minute accu- racy, would be difficult; but the total de- pression, which is the quantity sought, may be readily found, by pouring mercury in a slender stream into the open leg, till the surface of the mercury in the sealed leg becomes once more a tangent to the pla- tina ring, which is shewn by a delicate film of light, as in the mountain barome- ter. The vertical column of mercury above the lower initial level being measured, it represents precisely the elastic force ofthe vapour, since that altitude of mercury was required to overcome the elasticity of the vapour. The whole object now is to apply a regulated heat to the upper portion of the sealed leg, from an inch below the mercurial level, to its summit. This is easi- ly accomplished, by passing it through a perforated cork into an inverted phial, 5 inches diameter and 7 long, whose bottom has been previously cracked off by a hot iron. Or a phial may be made on purpose. When the tapering elastic cork is now Btrongly pressed into the mouth of the bot- tle, it renders it perfectly water-tight. By inclining the syphon, we remove a little of the mercury, so that when reverted, the level in the lower leg may nearly coincide with the ring. Having then suspended it in the vertical position from a high frame, or the roof of an apartment, we introduce wa- ter at 32° into the cylindrical glass vessel. When its central tube, against the side of which the bulb of a delicate thermometer rests, acquires the temperature ofthe sur- rounding medium, mercury is slowly add- ed to the open leg, till the primitive level is restored at the upper platina ring. The column of mercury above the ring in the open leg, is equivalent, to the i'-irce of aqueous vapour at 32°. The effect of lower CAL CAL temperatures may be examined, by putting 210*." I have investigated also simple ra- saline freezing mixtures in the cylinder, tios, which express the connexion between To procure measures of elastic force at the temperature and elasticity of the va- higher temperatures, two feeble Argand pours of alcohol, ether, petroleum, and oil . flames are made to send up heated air, on of turpentine, for which 1 must refer to the paper itself. Mr. W. Creighton of Soho communicated in March 1819, to the Philosophical Maga- zine, the following ingenious formula for aqueous vapour. " Let the degrees of Fah- the opposite shoulders of the cylinder. By adjusting the flames, and agitating the li- quid, very uniform temperatures may be given to the tube in the axis. At every 5° or 10° of elevation, we make a measurement by pouring mercury into the open .leg, till renheit -f- 85 = D, and the corresponding the primitive level is restored in the oilier. force of steam in inches of mercury — For temperatures above 2L°, I employ q.09 = I. Then Log. D — 2.22679X6 = the same plan of apparatus, slightly modi- Log. I. fied. The sealed leg of the syphon has a Fxample. length of 6 or 7 inches, while the open leg is 10 or 12 feet long, secured in the groove 212° + 85= 297Log. = 2.47276 of a graduated wooden prism The initial level becomes 212° when the mercury in each leg is in a horizontal plane, and the heat is now communicated through the me- dium of oil. If the bending ofthe tube, be made to an angle of about 35° from paral- lelism of the legs, a tubulated globular re- ceiver becomes a convenient vessel for holding the oil. The tapering cork through which the sealed end ofthe syphon is pas- sed, being thrust into the tapering mouth of the receiver, remains perfectly tight at all higher temperatures, being progres- sively swelled with the heat. One who has not made such trials, may be disposed to cavil at the probable tightness of such a contrivance, but I who have used it in ex- periments for many months together, know that only extreme awkwardness in the — 2.22679 constant number. 0.24579 X 6 Log. 1.47582: = 2991=1 +0.09 Inches 30.00 D He then gives a satisfactory tabular view of the near correspondences between the results of his formula, and my experi- ments. By determining experimentally the vo- lume of vapour which a given volume of liquid can produce at 212°, M. Gay-Lussac h is happily solved the very difficult prob- lem ofthe specific gravity of vapours. He . y • .u j • 4. c took a spherule of thin glass, with a short operator, can occasion the dropping out ot " ... ' , c f . , . u f. . '. _ _•. _rr B r:im r volatile oil. Mr. Dalton's must be excepted, for he says, " several authors have it, that oil of tur- pentine boils at 560°. I do not know how the mistake originated, but it boils below 212°, like the rest of the essential oils " Dr. Thomson makes it 314°; a number which, from the great price he paid for his thermometer, he insinuates to be more ex- act than mine of 316°; and a fortiori than 320°, as found by the manufacturer ofthe oil, to whom I had referred. But the dif- ference of our two numbers is in reality frivolous, and to be ascribed to the state of the oil and of the heat, as much as to er- rors of the instruments or of observation. It is probable that our thermometers were equally correct, and used with equal care. But what will Dr. Thomson say of Mr. Dal- ton's emendation? From the above quotation it may be in- ferred, that the conversion at all tempera- tures, however low, of any liquid or solid whatever, into a vapour, is uniformly ac- companied with the abstraction of heat from surrounding bodies, or in popular lan- guage, the production of cold; and that the degree of refrigeration will be proportional to the capacity of the vapour for heat, and the rapidity of its formation. The applica- tion of this principle to the uses of life, first suggested by Drs. Cullen and Black, has been improved and extended by Mr. Leslie. W e shall describe his methods under Con- gelation. It appears, moreover, probable, that the permanent gases have the same superior relation to heat with the vapours. Hence, their transition to the liquid or solid states ought to be attended with the evolution of heat. Accordingly, in the combustion of hydrogen, phosphorus, and metals, gaseous matter is copiously fixed; to which cause Black and Lavoisier ascribed the whole of the heat and light evolved. We shall see, however, in the article CoMBusTioN.many difficulties to the adoption of this plausible hypothesis. The best illustration of the common notion as to the latent heat of gases, is afforded by the condensed air tin- der-tube; in which mechanical compression appears to extrude from cold air its latent stores of both heat and light. A glass tube, eight inches long, and half inch wide, of uniform calibre, shut at one end, and fitted with a short piston, is best adapted for the exhibition of this pleasing experiment. When the object, however, is merely to kindle agaric-tinder, a brass tube 3-8ths wide and 4£ inches long will suffice. A dexterous condensation of air into l-5th of the volume, produces the heat of ignition. Under the head of specific heat, it has been shown to diminish in a gas, more ra- pidly than the diminution of its volume; and therefore, heat will be disengaged by its condensation, whether we regard the phenomenon as the expulsion of a fluid, or intense actions excited among the particles by their violent approximation. The con- verse ofthe above phenomenon is exhibited on a great scale, in the Scheninitz mines of Hungary. The hydraulic machine for drain- ing them, consists essentially of two strong air-tight copper cylinders, 96 feet verti- cally distant from each other, and connec- ted by a pipe. The uppermost, which is at the mouth ofthe pit, can be charged with water by the pressure of a reservoir, ele- vated 136 feet above it. The air suddenly dislodged by this vast hydrostatic pressure, is condensed through the pipe, on the sur- face ofthe water standing in the lower cylin- der, which it forces up a rising water-pipe to the surface, and then takes its place. When the stop-cocks are turned to re- charge the lower cylinder with water, the imprisoned air expanding to its natural volume, absorbs the heat so powerfully, as to convert the drops of water that issue with it, into hail and snow. M. Gay-Lus- sac has lately proposed a miniature imita- tion of this machine for artificial refrigera- tion. He exposes the small body to be cooled, to a stream of air escaping by a small orifice, from a box in which it had CAL CAL been strongly condensed. In the autumn of 1816,1 performed an analogous experiment in the house of M. Breguet, in Paris. This celebrated artist having presented me with one of his elegant metallic thermometers, I immediately proposed to determine by means of it, the heat first abstracted, and subsequently disengaged, in the exhaustion of air, and its readmission into the receiver of an air-pump. MM. Breguet politely fa- voured me with their assistance, and the use of their excellent air-pump. Having enclosed in the receiver their thermometer, and a delicate one by Crighton, which I happened to have with me, we found, on rapidly exhausting the receiver, that M. Breguet's thermometer indicated a refrige- ration of 50° F. while Crighton's sunk only 7°. After the two had arrived at the same temperature, the air was rapidly admitted into the receiver. M. Breguet's thermome- ter now rose 50°, while Crighton's mounted 7° as before. See Thermometer. Dr. Darwin has ingeniously explained the production of snow on the tops ofthe high- est mountains, by the precipitation of va- pour from the rarefied air which ascends from plains and valleys. " The Andes," says Sir H. Davy, " placed almost under the line, rise in the midst of burning sands; about the middle height is a pleasant and mild climate; the summits are covered with unchanging snows; and these ranges of temperature are always distinct; the hot winds from below, if they ascend, become cooled in consequence of expansion and the cold air; if by any force of the blast it is driven downwards, it is condensed, and rendered warmer as it descends." Evaporation and rarefaction, the grand means employed by nature to temper the excessive heats ofthe torrid zone, operate very powerfully among mountains and seas. But the level sands are devoured by un- mitigated heat. In milder climates, the fer- vours ofthe solstitial sun ate assuaged by the vapours copiously raised from every river and field, while the wintry cold is moderated by the condensation of atmos- pheric vapours in the form of snow. The equilibrium of animal temperature is maintained, by the copious discharge of vapour from the lungs and the skin. The suppression of this exhalation is a common cause of many formidable diseases. Among these, fever takes the lead. The ardour of the body in this case of suppressed pers- piration, sometimes exceeds the standard of health by six or seven degrees. The di- rect and natural means of allaying this morbid temperature, were first systemati- cally enjoined by Dr. Currie of Liverpool. He showed, that the dashing or affusion of cold water on the skin of a fever patient, lias most sanatory effects, when the heat is steadily above 98°, and when there is no sensation of chilliness, and no moisture an the surface. Topical refrigeration is ele- gantly procured, by applying a piece of muslin or tissue paper to any part of the skin, and moistening it with ether, carbu- ret of sulphur, or alcohol. By pouring a succession of drops of ether, on the sur- face of a thin glass tube containing water, a cylinder of ice may be formed at mid- summer. The most convenient plan which the chemist can employ, to free a gas from vapour, is to pass it slowly through a long tortuous tube wrapt in porous paper wet- ted with ether. On the other hand, when he wishes to expose his vessels to a regulated heat, he makes hot vapour be condensed on their cold surface. The heat thus disengaged from the vapour, passes into the vessel, and speedily raises it to a temperature which he can adjust with the nicest precision. A vapour bath ought therefore to be provided for every laboratory. That which I got con- structed a few years ago for the Institution, is so simple and efficacious as to merit a description.—A square tin box, about 18 inches long, 12 broad, and 6 deep, has its bottom hollowed a little by the hammer to- wards its centre, in which a round hole is cut of five or six inches diameter. Into this, a tin tube three or four inches long is sol- dered. This tube is made to fit tightly into the mouth of a common tea-kettle, which has a folding handle. The top of the box has a number of circular holes cut into it, of diff'erent diameters, into which evaporat- ing capsules of platina, glass, or porcelain, are placed. When the kettle, filled with wa- ter, and with its nozzle corked, is set on a stove, the vapour, playing on the bottoms of the capsules, heats them to any required temperature; and being itself continually condensed, it runs back into the kettle, to be raised again, in ceaseless cohobation. With a shade above, to screen the vapour chest from soot, the kettle may be placed over a common fire. The orifices not in use, are closed with tin lids. In drying precipi- tates, I cork up the tube ofthe glass funnel, and place it, with its filter, directly into the proper sized opening. F'or drying red cab- bage, violet petals, &c. a tin tray is provid- ed, which fits close on the top of the box, within the rim which goes about it. The round orifices are left open when this tray is applied. Such a form of apparatus is well adapted to inspissate the pasty mass, from which lozenges and troches are to be made. But the most splendid trophy erected to the science of caloric, is the steam-engine of Watt. "This illustrious philosopher, from a mistake of his friend Dr. Robison, has been hitherto defrauded of a part of his claims to the admiration and gratitude of mankind. The fundamental researches on the constitution ofsteam, which formed the CAL CAL solid basis.of his gigantic superstructure, though they coincided perfectly with Dr. Black's results, were not drawn from them. In some conversations with which this great ornament and benefactor of his country ho- noured me a short period before his death, he described, with delightful nuivtie" the simple, but decisive experiments, by which he discovered the latent heat of steam. His means and his leisure not then permitting an expensive and complex appaiatus, lie- used apothecaries' phials. With these, he ascertained the two main facts, first, that a cubic inch of water would form about a cu- bic foot of ordinary steam, or 1728 inches; and that the condensation of that quantity of steam would heat six cubic inches of water from the atmospheric temperature to the boiling point. Hence he saw that six times the difference of temperature, or ful- ly 90b° of heat had been employed in giv- ing elasticity to steam; which must be all abstracted before a complete vacuum could be procured under the piston of the steam- engine. These practical determinations he afterwards found to agree pretty nearly with the observations of Dr. Black. Though Mr. Watt was then known to the Doctor, he was not on those terms of intimacy with him, which he afterwards came to be, nor was he a member of his class. Mr. Watt's three capital improvements, which seem to have nearly exhausted the resources of science and art, were the fol- lowing 1. The separate condensing chest, immersed in a body of cold water, and con- nected merely by a slender pipe with the great cylinder, in which the impelling pis- ton moved. On opening a valve or stop-cock of communication, the elastic steam which had floated the ponderous^piston, rushed into the distant chest with magical veloci- ty, leaving an almost perfect vacuum in the cylinder, into which the piston was forced by atmospheric pressure. What had appear- ed impossible to all previous engineers was thus accomplished. A vacuum was formed without cooling the cylinder itself. Thus it remained boiling hot, ready the next instant to receive and maintain the elastic steam. 2. His second grand improve- ment consisted in closing the cylinder at top, making the piston rod slide through a stuffing box in the lid, and causing the steam to give the impulsive pressure in- stead of the atmosphere. Henceforth the waste of heat was greatly diminished. 3. The final improvement was the double im- pulse, whereby the power of his engines, which was before so great, was in a mo- ment more than doubled. The counter- weight required in the single stroke en- gine, to depress the pump-end of the work- ing beam, was now laid aside. He thus freed the machine from a dead weight or Vol. I. drag of many hundred pounds, which had hung upon it from its birth, about seventy years before. The application of steam to heat apart- ments, is another valuable fruit of these studies. Safety, chanliness, and comfort, thus combine in giving a genial warmth for every purpose of private accommodation, or public manufacture. It has been ascer- taiiu d, that one cubic foot of boiler will heat about two thousand feet of space, in a cot- ton mill, whose average heat is from 70° to 80° Fahr. And if we allow 25 cubic feet of a boiler for a horse's power in a steam-en- gine supplied by it, such a boiler would be adequate-to the warming of fifty thousand cubic feet of .space. It has been also ascer- tained, that one square foot of surface of ster.m pipe, is adequate to the warming of two hundivd cubic feet of space. This quan- tity is adapted to a well finished ordinary brick or stone building. The safety valve on the boiler should be loaded with 2$ pounds for an area of a square inch, as is the rule for Mr. Watt's engines. Cast iron pipes are preferable to all others, for the diffusion of he:;t. Freedom of expansion must be al- lowed, which in cast iron may be taken at about a tenth of an inch for every ten feet in length. The pipes should be distribu- ted within a few inches ofthe floor. Steam is now used extensively for dry- ing muslin and calicoes. Large cylinders are filled with it, which, diffusing in the apartment a temperature of 100° or 130°, rapidly dry the suspended cloth. Occasion- ally the cloth is made to glide in a serpen- tine manner closely round a series of steam cylinders, arranged in parallel rows. It is thus safely and thoroughly dried in the course of a minute. Experience has shown, that bright dyed yarns like scarlet, dried in a common stove heat of 128°, have their colour darkened, and acquire a harsh feel; while similar hanks, laid on a steam pipe heated up to 16 s0, retain the shade and lustre they possessed in the wetted state. The people who work in steam drying- rooms are healthy; those who were former- ly employed in the stove-heated apart- ments, became soon sickly and emaciated. These injurious effects must be ascribed to the action of cast iron at a high tempera- ture on the atmosphere. Tiie heating by steam of large quantities of water or other liquids, e;iher for baths or manufactures, may be effected in two ways; that is, the steam pipe may be plung- ed with an open end into the water cistern; or the steam may be diffused around the liquid in the interval between the wooden vessel and an interior metallic case. The second mode is of universal applicability. Since a gallon of water in the form of steam will heat 6 gallons at 50°, up to the 33 CAL CAL boiling point, or 162°; 1 gallon of the for- mer will be adequate to heat 18 gallons of the latter up to 100°, making a liberal al- lowance for waste in the conducting pipe. Cooking of food for man and cattle is likewise another useful application of steam; " for," says Dr. Black, " it is the most effectual carrier of heat that can be conceived, and will deposite it only on such bodies as are colder than boiling water." Hence in a range of. pots, whenever the first has reached the boiling point, but no sooner, the steam will go onwards to the second, then to the third, and thus in suc- cession. Inspection of the last will there- fore satisfy us of the condition of the pre- ceding vessels. Distillation has been lately practised, by surrounding the still with a strong metallic case, and filling the inter- stice with steam heated up to 260° or 280°. But notwithstanding of safety valves, and every ordinary attention, dangerous explo- sions have happened. Distillation in vacuo, by the heat of external steam of ordinary strength, would be a safe and elegant pro- cess. The old, and probably very exact ex- periments of Mr. Watt on this subject, do not lead us, however, to expect any saving of fuel, merely by the vacuum distillation. " The unexpected result of these experi- ments is, that there is no advantage to be expected in the manufacture of ardent spirits by distillation in vacuo. For we find, that the latent heat of the steam is at least as much increased as the sensible heat is diminished."—Dr. Black's Lectures, vol. i. p. 190. By advantage is evidently meant saving of fuel. But in preparing spirits, ethers, vinegars, and essential oils, there would undoubtedly be a great advantage relative to flavour. Every risk of empyreuma is re- moved. Chambers filled with steam heated to about 125* Fahr. have been introduced with advantage into medicine, under the name of vapour baths. Dry air has also been used. It can be tolerated at a much greater heat than moist air; see 'Tempe- rature. A large cradle, containing saw- dust heated with steam, should be kept in readiness at the houses erected by the Hu- mane Society, for the recovery of drowned persons; or a steam chamber might be at- tached to them for this purpose, as well as general medicinal uses. I have thus completed what I conceive to belong directly to caloric in a chemical dic- tionary. Under alcohol, attraction, blow-pipe, climate, combustion, congelation, digester, dis- tillation, electricity, gas, light, pyrometer, thermometer, water, some interesting corre- lative facts will be found. * Calorimeter. An instrument con- trived by Lavoisier and Laplace, to mea- sure the heat given out by a body in cooling, from the quantity of ice it melts. It consists of 3 vessels, one placed within the other, so as to leave 2 cavities between them; and a frame of iron network, to be suspended in the middle of the inner vessel. This network is to hold the heated body. The The two exterior concentric interstices are filled with bruised ice. The outermost serves to screen, from the atmosphere, the ice in the middle space, by the fusion of which the heat given out by the central hot body is measured. The water runs off through the bottom, and terminates in the shape of a funnel, with a stop-cock.* f Calorimotor. This is an appellation given by me to galvanic instruments, in which the calorific influence or effects are attended by scarcely any electrical power; and especially to apparatus, employed by me, consisting of one or two galvanic pairs of enormous size. Volta considered all galvanic apparatus as consisting of one or more electromo- tors, or movers of the electric fluid. To me, it appeared, that they were movers of both heat and electricity; the ratio of the quantity of the latter put in motion, to the quantity of the former put in motion, be- ing as the number of the series to the superficies. Hence the word electromotor can'only be applicable, when the caloric be- comes evanescent, and electricity almost the sole product, as in De Luc's and Zam- boni's Columns; and the word calorimotor ought to be used, when electricity becomes evanescent, and caloric appears the sole product. The heat evolved by one galvanic pair has been found by the experiments which 1 instituted, to increase in quantity, but to diminish in intensity, as the size of the sur- faces may be enlarged. A pair containing about fifty square feet of each metal, will not fuse platina, nor deflagrate iron, how- ever small may be the wire employed; for the heat produced in metallic wires is not improved by a reduction in their size be- yond a certain point. Yet the metals above- mentioned are easily fused or deflagrated by smaller pairs, which w ould have no per- ceptible influence on masses that might be sensibly ignited by larger pairs. These cha- racteristics were fully demonstrated, not only by my own apparatus, but by those constructed by Messrs. Wetberill and Peale, and which were larger, but less ca- pable of exciting intense ignition. Mr. Peale's apparatus contained nearly seventy square feet, Mr. Wetherill's nearly one hundred, in the form of concentric coils; yet neither could produce a heat above red- ness on the smallest wires. At my sugges- tion, Mr. Peale separated the two surfaces in his coils into four alternating, constitut- ing two galvanic pairs in one recipient. Iron wire was then easily burned and pla- CAM CAM tina fused by it. These facts, together with the incapacity of the calorific fluid extri- cated by the calorimotor to permeate char- coal, next to metals the best electrical con- ductor, must sanction the position I assign- ed to it, as being in the opposite extreme from the columns of De Luc and Zamboni. For as in these, the phenomena are such as are characteristic of pure electricity, so in one very large galvanic pair, they almost exclusively demonstrate the agency of pure caloric. A plate of a calorimotor will be found at the end of this work, with a description. When this instrument is lowered into a solution, containing about a seventieth of sulphuric acid, a wire, placed between the poles, becomes white hot, and takes fire, emitting the most brilliant sparks. In the interim, an explosion usually gives notice ofthe extrication of hydrogen in a quantity adequate to reach the burning wire. Imme- diately after the explosion, the hydrogen is reproduced with less intermixture of air, and rekindles, corruscating from among the forty interstices, and passing from one side of the machine to the other, in oppo- site directions and at various times, so that the combinations are innumerable. The flame assumes various hues, from the so- lution of more or less of the metals, and a froth, apparently on fire, rolls over the sides of the recipient. When the calorimotor is withdrawn from the acid solution, the sur- face of this fluid for many seconds, pre- sents a sheet of fiery foam. I ascertained that the galvanic fluid, as extricated by this apparatus, does not per- meate charcoal. This demonstrates that it cannot be electricity, as of the latter, char- coal is next to metals the best conductor. See Memoirs on a *\'eit> Theory of Gal- vanism in Silliman's Journal, Annals of Phi- losophy, and Philosophical Mogaxine.\ * Cai.p. An argillo-ferruginous lime- stone.* • Cameleon Mineral. When pure potash and black oxide of manganese are fused together in a crucible, a compound is formed whose solution in water, at first green, passes spontaneously through the whole scries of coloured rays to the red. From this latter tint, the solution may be made to retrograde in colour to the origi- nal green, by the addition of potash; or it may be rendered altogether colourless, by adding either sulphurous acid or chlorine to the solution, in which case there may or may not be a precipitate, according to cir- cumstances. MM. Chevillot and Edouard have lately read some interesting memoirs on this substance, before the Academy of Sciences. They found, that when potash and the green oxide of manganese were heated in close vessels, containing azote, no cameleon is formed. The same result fol- lowed with the brown oxide, and ultimate- ly with the black. They therefore ascribe the phenomena to the absorption of oxygen, which is greatest when the oxide of man- ganese equals the potash in weight. They regard it as a manganesiate of potash, though they have hitherto failed in their attempts to separate this supposed tetrox- ide, or manganesic acid. When acids are poured upon the green cameleon, or an al- kali upon the red, they arc equally changed from one colour to the other; even boiling and agitation are sufficient to disengage the excess of potash in the green cameleon, and to change it into red. Many acids also, when used in excess, decompose the came- leon entirely, by taking the potash from it, disengaging the oxygen, and precipitating the manganese in the state of black oxide. Sugar, gums, and several other substances, capable of taking away the oxygen, also de- compose the cameleon, and an exposure to the air likewise produces the same effect. Soda, barytes, and strontites, also afford peculiar cameleons. The red potash ca- meleon is perfectly neutral. Phosphorus brought in contact with it produces a de- tonation; and it sets some other combusti- bles on fire. Exposed alone to heat, it is re- solved into oxygen, black oxide of manga- nese, and green cameleon, or submangane- siate of potash.* Campeachy Wood. See Logwood. Camphor. There are two kinds grow in the East, the one produced in the islands of Sumatra and Borneo, and the other pro- duced in Japan and China. Camphor is extracted from the roots, wood, and leaves of two species of laurus, the roots affording by far the greatest abundance. The method consists in distil- ling with water in large iron pots, serving as the body of a still, with earthen heads adapted, stuffed with straw, and provided with receivers. Most of the camphor be- comes condensed in the solid form among the straw, and part comes over with the water. The sublimation of camphor is perform- ed in low flat-bottomed glass vessels placed in sand; and the camphor becomes con- crete in a pure state against the upper part, whence it is afterwards separated with a knife, after breaking the glass. Lewis as- serts that no addition is requisite in the purification of camphor; but that the chief point consists in managing the fire, so that the upper part of the vessel may be hot enough to bake the sublimate together in- to a kind of cake. Chaptal says, the Hollan- ders mix an ounce of quicklime with every pound of camphor previous to the distilla- tion. Purified camphor is a white concrete crystalline substance, not brittle, but easily crumbled, having a peculiar consistence re- CAM CAN sembling that of spermaceti, but harder. It has a strong lively smell, and an acrid taste; is so volatile as totally to exhale when left exposed in a warm air; is light enough to swim on water; and is very inflammable, burning with a very white flame and smoke, without any residue. The roots of zedoary, thyme, rosemary, sage, the inula hellenium, the anemony, the pasque flower or pnlsatilla, and other vegetables, afford camphor by distillation. It is observable, that all these plants afford a much larger quantity of oaniphor, when the sap has been suffered to pass to the concrete state by several months' drying. Thyme and peppermint, slowly dried, af- ford much camphor; and Mr. Achard has observed, that a smell of camphor is disen- gaged when volatile oil of fennel is treated with acids. Mr. Kind, a German chemist, endeavour- ing to incorporate muriatic acid gas with oil of turpentine, by putting this oil into the vessels in which the gas Was received when extricated, found the oil change first yel- low, then brown, and lastly, to be almost wholly coagulated into a crystalline mass, which comported itself in every respect like camphor. TromsdnrfT'and Boullay con- firm this. A small quantity of camphor may be obtained from oil of turpentine by sim- ple distillation at a very gentle heat- Other essential oils, however, afford more. By evaporation in shallow vessels, at a heat not exceeding 57° F. Mr. Proust obtained from oil of lavender .25, of sage .21, of marjoram .1014, of rosemary .0625. He conducted the operation on a pretty large scale. Camphor is not soluble in water in any perceptible degree, though it communi- cates its smell to that fluid, and may be burned as it floats on its surface. It is said, however, that a surgeon at Madrid has ef- fected its solution in water by means ofthe carbonic acid. Camphor may be powdered by moisten- ing it with alcohol, and triturating it till dry. It may be formed into an emulsion by previous grinding with near three times its weight of almonds, and afterwards gradu- ally adding the water. Yolk of egg and mucilages are also effectual for this pur- pose; but sugar does not answer well. It has been observed by Homieu, that small pieces of camphor floating on water have a rotatory motion. Alcohol, ethers, and oils, dissolve cam- phor. The addition of water to the spirituous or acid solutions of camphor, instantly se- parates it. Mr. Hatchett has particularly examined the action of sulphuric acid on camphor. A hundred grains of camphor were digested in an ounce of concentrated sulphuric acid for two days. A gentle heat was then ap- plied, and the digestion continued for two days longer. Six ounces of water were then added, and the whole distilled to dryness. Three grains of an essential oil, having a mixed odour of lavender and peppermint, came over with the water. The residuum being treated twice with two ounces of al- cohol each time, fifty-three grains of com- pact coal in small fragments remained un- dissolved. The alcohol, being evaporated in a water bath, yielded forty-nine grains of a blackish-brown substance which was bit- ter, astringent, had the smell of caromel, and formed a dark brown solution with wa- ter. This solution threw down very dark brown precipitates, with sulphate of iron, acetate of lead, muriate of tin, and nitrate of lime. It precipitated gold in the metal- lic state. Isinglass threw down the whole of what was dissolved in a nearly black precipitate. When nitric acid is distilled repeatedly in large quantities from camphor, it con- verts it into a peculiar acid. See Acid (Camphoric). * Camphor melts at 288°, and boils at the temperature of 400°. By passing it in vapour through peroxide of copper, Dr. Thomson converted it into carbonic acid and water. He operated upon a single grain. He infers its composition to be Carbon, 0.738 8 J at'ms. = 6.375 73.91 Hydrogen, 0.144 10 = 1.250 14.49 Oxygen, 0.118 1 =1.000 11.60. 1.000 8.625 10000 As an internal medicine, camphor has been frequently employed in doses of from 5 to 20 grains, with much advantage; to pro- cure sleep in mania, and to counteract gangrene. Though a manifest stimulant, when externally applied, it appears from the reports of Cullen and others, rather to diminish the animal temperature and the frequency of the pulse. In large doses it acts as a poison, an effect best counteract- ed by opium. It is administered to alleviate the irritating effects of cantharides, meze- reon, the saline preparations of mercury and drastic purgatives. It lessens the nau- seating tendency of squill, and prevents it from irritating the bladder. It is employed externally as a discutient* Dissolved in acetic acid, with some essential oils, it forms the aromatic vinegar, for which we are indebted to the elder Mr. Henry. It re- markably promotes the solution of copal. Its effluvia are very noxious to insects, on which account it is much used to defend subjects of natural history from their ra- vages. * Cancer, Matter of. This morbid secretion was found by Dr. Crawford to give a green colour to sirup of violets, and CAN CAO treated with sulphuric, acid, to emit a gas resembling sulphuretted hydrogen, which he supposes to have existed in combination with ammonia in the ulcer. Hence the ac- tion of virulent pus on metallic salts. He likewise observed, that its odour was des- troyed by aqueous chlorine, which he there- fore recommends for washing cancerous sores.* * Candles. Cylinders of tallow or wax, containing in their axis a spongy cord of cotton or hemp. A few years ago I made a set of experiments on the relative intensi- ties of light, and duration of different can- dles, the result of which is contained in the following table:— JYumber in : Duration of Weight in Consumption Proportion Economy Candles a Pound. a Candle. grains. per hour, of of equal 1 grains. Light Light one argand. 10 mould. 5h. 9 m. 682 132 12± 68 5.7 10 dipped. 4 36 672 150 13 65J 5.25 8 mould. 6 31 856 132 10J 594 6.6 6 do. 7 2* 1160 163 144 20* 66 5.0 4 do. 9 36 1787 186 80 3.5 Argand oil flame. 512 694 100 A Scotch mutchkin, or l-8th of a gallon of good seal oil, weighs 6010 gr. or 13 and l-10th oz. avoirdupois, and lasts in a bright argand lamp, 11 hours 44 min. The weight of oil it consumes per hour, is equal to four times the weight of tallow in candles, 8 to the pound, and 3 l-7th times the weight of tallow in candles 6 to the pound. But its light, being equal to that of 5 of the latter candles, it appears from the above table, that 2 pounds weight of oil, value Is. in an argand, are equivalent in illuminating pow- er to 3 pounds of tallow candles, which cost about three shillings. The larger the flame, in the above candles, the greater the eco- nomy of light.* * Caxnei. Coal. See Coal.* •Cannon Meiai.. See Copper.* •Cantharides. Insects vulgarly called Spanish flies: lytta vesicatoria is the name adopted from Gmelin, by the London col- lege. This insect i3 two-thirds of an inch in length, one-fourth in breadth, oblong, and of a gold shining colour, with soft ely- tera or wing sheathes, marked with three longitudinal raised stripes, and covering brown membranous wings. An insect of a square form, with black feet, but possessed of no vesicating property, is sometimes mixed with the cantharides. They have a heavy disagreeable odour, and acrid taste. If the inspissated watery decoction of these insects be treated with pure alcohol, a solution of a resinous matter is obtained, which being separated by gentle evapora- tion to dryness, and submitted for some time to the action of sulphuric ether, forms a yellow solution. By spontaneous evapora- tion crystalline plates are deposited, which may be freed from some adhering colour- ing matter by alcohol. 'Their appearance is like spermaceti. They are soluble in boil- ing alcohol, but precipitate as it cools. They do not dissolve in water. According to M. Robiquet, who first discovered them, these plates form the true blistering prin- ciple. They might be called Vesicato- rin. Besides the above peculiar bodv, can- tharides contain, according to M. Robiquet, a green bland oil, insoluble in Water, solu- ble in alcohol; a black matter, soluble in water, insoluble in alcohol, without blister- ing properties; a yellow viscid matter, mild, soluble in water and alcohol; the crystal- line plates; a fatty bland matter; phosphates of lime and magnesia; a little acetic acid, and much lithic or uric acid. The blister- ing fly taken into the stomach in doses of a few grains, acts as a poison, occasioning horrible satyriasis, delirium, convulsions, and death. Some frightful cases are related by Orfila, vol. i. part 2d. Oils, milk, sirups, frictions on the spine, with volatile lini- ment and laudanum, and draughts contain- ing musk, opium, and camphorated emul- sion, are the best antidotes.* Caoutchouc. This substance, which has been improperly ttrmed elastic gum, and vulgarly, from its common application to rub out pencil marks on paper, India rubber, is obtained from the milky juice of different plants in hot countries. The chief of these are the Jutropha elastica, and Ur- ceola elastica. 'The juice is applied in successive coat- ings on a mould of clay, and dried by the fire or in the sun; and when of a sufficient thickness, the mould is crushed, and the pieces shaken out. Acids separate the ca- outchouc from the thinner part of the juice at once by coagulating it. The juice of old plants yields nearly two-thirds of its weight; that of younger plants less. Its colour, when fresh, is yellowish white, but it grows darker by exposure to the air. The elasticity of this substance is its CAO CAR most remarkable property: when warmed, as by immersion in hot water, slips of it may be drawn out to seven or eight times their original length, and will return to their former dimensions nearly. Cold ren- ders it stiff and rigid, but warmth restores its original elasticity. Exposed to the fire it softens, swells up, and burns with a bright flame. In Cayenne it is used to give light as a candle Its solvents are ether, vo- latile oils, and petroleum. The ether, how- ever, requires to be washed with water re- peatedly, and in this state it dissolves it completely. Pelletier recommends to boil the caoutchouc in water for an hour; then to cut it into slender threads; to boil it again about an hour; and then to put it into rectified sulphuric ether in a vessel close stopped. In this way he says it will be totally dissolved in a few days, without heat, ex- cept the impurities, which will fall to the bottom, if ether enough be employed. Ber- niard says, the nitrous ether dissolves it better than the sulphuric. If this solution be spread on any substance, the ether evapo- rates very quickly, and leaves a coating of caoutchouc unaltered in its properties. Naphtha, or petroleum, rectified into a co- lourless liquid, dissolves it, and likewise leaves it unchanged by evaporation. Oil of turpentine softens it, and forms a pasty mass, that may be spread as a varnish, but is very long in drying. A solution of caout- chouc in five times its weight of oil of tur- pentine, and this solution dissolved in eight times its weight of drying linseed oil by boiling, is said to form the varnish of air- balloons. Alkalis act upon it so as in time to destroy its elasticity. Sulphuric acid is decomposed by it; sulphurous acid being evolved, and the caoutchouc converted into charcoal. Nitric acid acts upon it with heat; nitrous gas being given out, and oxalic acid crystallizing from the residuum. On distil- lation it gives out ammonia, and carburet- ted hydrogen. Caoutchouc may be formed into various articles without undergoing the process of solution. If it be cut into a uniform slip of a proper thickness, and wound spirally round a glass or metal rod, so that the edges shall be in close contact, and in this state be boiled for some time, the edges will adhere so as to form a tube. Pieces of it may be readily joined by touching the edges with the solution in ether: but this is not absolutely necessary, for, if they be merely softened by heat, and then pressed together, they will unite very firmly. If linseed oil be rendered very drying by digesting it upon an oxide of lead, and afterwards applied with a small brush on any surface, and dried by the sun or in the smoke, it will afford a pellicle of consider- able firmness, transparent, burning like caoutchouc, and wonderfully elastic. A pound of this oil, spread upon a stone, and exposed to the air for six or seven months, acquired almost all the properties of ca- outchouc: it was used to make catheters and bougies, to varnish balloons, and An- other purp'oses. Of the mineral caoutchouc there are se- rai varieties: 1 Of a blackish-brown inclin- ing to olive, soft, exceedingly compressi- ble, unctuous, with a slightly aromatic smell. It burns with a bright flame, leaving a black oily residuum, which does not be- come dry. 2. Black, dry, and cracked on the surface, but, when cut into, of a yellow- ish-white. A fluid resembling pyrolignic acid exudes from it when recently cut. It is pellucid on the edges, and nearly of a hyacinthine red colour. 3. Similar to the preceding, but of a somewhat firmer tex- ture, and ligneous appearance, from having acquired consistency in repeated layers. 4. Resembling the first variety, but of a darker colour, and adhering to gray calca- reous spar, with some grains of galaena. 5. Of a liver-brown colour, having the as- pect of the vegetable caoutchouc, but pass- ing by gradual transition into a brittle bi- tumen, of vitreous lustre, and a yellowish colour. 6. Dull reddish-brown, of a spongy or cork-like texture, containing blackish- gray nuclei of impure caoutchouc. Many more varieties are enumerated. One specimen of this caoutchouc has been found in a petrified marine shell en- closed in a rock, and another enclosed in crystallized fluor spar. The mineral caoutchouc resists the ac- tion of solvents still more than the vegeta- ble. The rectified oil of petroleum affects it most, particularly when by partial burn- ing it is resolved into a pitchy viscous sub- stance. A hundred grains of a specimen analyzed in the dry way by Klaproth, af- forded carburetted hydrogen gas 38 cubic inches, carbonic acid gas 4, bituminous oil 73 grains, acidulous phlegm 1.5, charcoal 6.25, lime 2, silex 1.5, oxide of iron .75, sulphate of lime .5, alumina .25. Carat. See Assay. Carbon. When vegetable matter, parti- cularly the more solid, as wood, is exposed to heat in close vessels, the volatile parts fly off, and leave behind a black porous substance, which is charcoal. If this be suffered to undergo combustion in contact with oxygen, or with atmospheric air, much the greater part of it will combine with the oxygen, and escape in the form of gas; leaving about a two-hundredth part, which consists chiefly of different saline and me- tallic substances. This pure inflammable part of the charcoal is what is commonly called carbon; and if the gas be received into proper vessels, the carbon will be found to have been converted by the oxy- CAM CAR gen into an acid, called the carbonic. See Acid (Carbonic). From the circumstance, that inflammable substances refract light, in a ratio greater than that of their densities, Newton infer- red, that the diamond was inflammable. The quantity of the inflammable part of charcoal requisite to form a hundred parts of carbonic acid, was calculated by Lavoi- sier to be twenty-eight parts. From a care- ful experiment of Mr. Tennant, 27.6 parts of diamond, and 72.4 of oxygen, formed 100 of carbonic acid; and hence he infer- red the identity of the diamond, and the inflammable part of charcoal. * Diamonds had been frequently con- sumed in the open air with burning glasses; but Lavoisier first consumed them in oxy- gen gas, and discovered carbonic acid to be the only result. Sir George Mackenzie showed, that a red heat, inferior to what melts silver, is sufficient to burn diamonds. They first enlarge somewhat in volume, and then waste with a feeble flame. M. Guy ton Morve..u was tbe first who dropped diamonds into melted nitre, and observed the formation of carbonic acid. F'rom a number of experiments M. Biot has made on the refraction of different sub- stances, he has been led to form a differ- ent opinion. According to him, if the ele- ments of which a substance is composed be known, their proportions may be calcula- ted with the greatest accuracy from their refractive powers. Thus he finds, that the diamond cannot be pure carbon, but re- quires at least one-fourth of hydrogen, which has the greatest refractive power of any substance, to make its refraction com- mensurate to its density. In 1809, Messrs. Allen and Pepys made some accurate researches on the combus- tion of various species of carbon in oxygen, by means of an elegant apparatus of their own contrivance. A platina tube traversing a furnace, and containing a given weight of the carbonaceous substance, was con- nected at the ends with two mercurial gas- ometers, one of which was filled with oxy- gen gas, and the other was empty. The same weight of diamond, carbon, and plum- bago, yielded very nearly the same volume of carbonic acid. Sir H. Davy was the first to show that the diamond was capable of supporting its own combustion in oxygen, without the continued application of ex- traneous heat, and he thus obviated one of the apparent anomalies of this body, com- pared with charcoal. This phenomenon, by his method, can now be easily exhibit- ed. If the diamond, supported in a per- forated cup, be fixed at the end of a jet, so that a stream of hydrogen can be thrown on it, it is easy, by inflaming the jet, to ig- nite the gem, and whilst in that state to introduce it into a globe or flask containing oxygen. On turning off the hydrogen, the diamond enters into combustion, and will go on burning till nearly consumed. The loss of weight, and corresponding produc- tion of carbonic acid, were thus beautifully shown. A neat form of apparatus for this purpose is delineated by Mr. Faraday, in the 9th volume of the Journal of Science. Sir. II. Davy found, that diamonds gave a volume of pure carbonic acid, equal to the oxygen consumed; charcoal and plumbago afforded a minute portion of hydrogen.* See Diamond. Well-burned charcoal is a conductor of electricity, though wood simply deprived of its moisture by baking is a non-conductor; but it is a very bad conductor of caloric, a property of considerable use on many oc- casions, as in lining crucibles. It is insoluble in water, and hence the utility of charring the surface of wood ex- posed to that liquid, in order to preserve it, a circumstance not unknown to the an- cients. This preparation of timber has been proposed as an effectual preventive of what is commonly called the dry rot. It has an attraction, however, for a certain portion of water, which it retains very forcibly. Heat- ed red-hot, or nearly so, it decomposes water; forming with its oxygen, carbonic acid, or carbonic oxide, according to the quantity present; and with the hydrogen a gaseous carburet, called carburetted hy- drogen, or heavy inflammable air. Charcoal is infusible by any heat. If ex- posed to a very fflgh temperature in close vessels it loses little or nothing of its weight, but shrinks, becomes more compact, and acquires a deeper black colour. Recently prepared charcoal has a re- markable property of absorbing different gases, and condensing them in its pores, without any alteration of their properties or its own. * The following are the latest results of M. Theodore de Saussure, with boxwood charcoal, the most powerful species: Gaseous ammonia, 90 vols. Ditto muriatic acid, 85 Ditto sulphurous acid, 65 Sulphuretted hydrogen, 55 Nitrous oxide, 40 Carbonic oxide, 35 Olefiant gas, - 35 Carbonic oxide, 9.42 Oxygen, 9 25 Azote, 7.5 Light gas from moist char :oal, 5.0 Hydrogen, 1.75 Very light charcoal, such as that of cork, absorbs scarcely any air; while the pit-coal of Rastiberg, sp. gr. 1.326, absorbs 10£ times its volume. The abso rption was al- ways completed in 24 hours. This curious faculty, which is common to all porous bo- CAR CAR dies, resembles the action of capillary tubes on liquids. When a piece of charcoal, charged with one gas, is transferred into another, it absorbs some of it, and parts with a portion of that first condensed. In the experiments of Messrs. Allen and Pe- pys, charcoal was found to imbibe from the atmosphere in a day about l-8th of its weight of water. For a general view of ab- sorption, see Gas. When oxygen is condensed by charcoal, carbonic acid is observed to form at the end of several months. But the most re- markable property displayed by charcoals impregnated w ith gas, is that with sulphu- retted hydrogen, when exposed to the air or oxygen gas. The sulphuretted hydro- gen is speedily destroyed, and water and sulphur result, with the disengagement of considerable heat. Hydrogen alone has no such effects. When charcoal was exposed by Sir II. Davy to intense ignition in vacuo, and in condensed azote, by means of Mr. Children's magnificent voltaic battery, it slowly volatilized, and gave out a little hydrogen. The remaining part was always much harder than before; and in one case so hard as to scratch glass, while its lustre was increased. This fine experiment may be regarded as a near approach to the pro- duction of diamond.* Charcoal has a powerful affinity for oxy- gen, whence its use in disoxygenaling me- tallic oxides, and restoring their base to its original metallic state, ot reviving the me- tal. Thus too it decomposes several ofthe acids, as the phosphoric and sulphuric, from which it abstracts their oxygen, and leaves the phosphorus and sulphur free. Carbon is capable of combining with sul- phur, and with hydrogen. With iron it forms steel; and it unites with copper into a carburet, as observed by Dr. Priestley A singular and important property of charcoal is that of destroying the smell, colour, and taste of various substances: for the first accurate experiments on which we are chiefly indebted to Mr- Lowitz of Pe- tersburgh, though it had been long before recommended to correct the fcetor of foul ulcers, and as an antiseptic. On this ac- count it is certainly the best dentifrice. Water that has become putrid by long keeping in wooden casks, is rendered sweet by filtering through charcoal powder, or by agitation with it; particularly if a few drops of sulphuric acid be added. Com- mon vinegar boiled with charcoal powder becomes perfectly limpid. Saline solutions, that are tinged yellow or brown, are ren- dered colourless in the same way, so as to afford perfectly white crystals. The impure carbonate of ammonia obtained from bones, is deprived both of its colour and fetid smell by sublimation with an equal weight of charcoal powder. Malt spirit is freed from its disagreeable flavour by distillation from charcoal; but if too much be used, part of the spirit is decomposed. Simple maceration, for eight or ten days, in the proportion of about 1-150th of the weight ofthe spirit, improves the flavour much. It is necessary, that the charcoal be well burned, brought to a red heat before it is used, and used as soon as may be, or at least be carefully excluded from the air. The proper proportion too should be as- certained by experiment on a small scale. The charcoal may be used repeatedly, by exposing it for some time to a red heat before it is again employed. Charcoal is used on particular occasions as fuel, on account of its giving a strong and steady heat without smoke. It is em- ployed to convert iron into steel by ce- mentation. It enters into the composition of gunpowder. In its finer states, as in ivory black, lampblack, &c. it forms the basis of black paints, Indian ink, and printers' ink. * The purest carbon for chemical pur- poses is obtained by strongly igniting lamp- black in a covered crucible. This yields, like the diamond, unmixed carbonic acid by combustion in oxygen. Carbon unites with all the common sim- ple combustibles, and with azote, forming a series of most important compounds. With sulphur it forms a curious limpid liquid called carburet of sulphur, or sul- phuret of carbon. With phosphorus it forms a species of compound, whose properties are imperfectly ascertained. It unites with hydrogen in two definite proportions, con- stituting sub-carburetted and carburetted hydrogen gases. With azote it forms prus- sic gas, the cyanogen of M. Gay-Lussac. Steel and plumbago are two different com- pounds of carbon with iron. In black chalk we find this combustible intimately asso- ciated with silica and alumina. The prim- itive combining proportion, or prime equi- valent of carbon, is 0.75 on the oxygen scale.* * Carbon (Mineral), is of a grayish- black colour. It is charcoal, w:ith various proportions of earth and iron, without bi- tumen. It has a silky lustre, and the fibrous texture of wood. It is found in small quan- tities, stratified with brown coal, slate coal, and pitch coal.* * Carbonates. Compounds of carbo- nic acid with the salifiable bases. They are composed either of one prime of the acid and one of the base, or of two of the acid and one of the base. The former set of compounds is called carbonates, the latter bicarbonates. See Carbonic Acid. As the system of chemical equivalents, or atomic theory of chemical combination, derives some of its fundamental or prime proportions from the constitution of the carbonates, their analysis requires peculiar CAR precautions. In the Annals of Philosophy for October 1817,1 gave a description of a new instrument for accomplishing this pur- pose with the minutest precision. The usual mode of analysis is to put a given weight of the carbonate in a phial, and add to it a certain quantity of a liquid acid which will dissolve the base, and dis- engage the carbonic acid. I found, with every care I could take in this method, that variable and uncertain quantities of the liquid acid were apt to be carried off in vapour with the carbonic gas, while a portion of this gaseous acid was generally retained in the saline liquid. Hence, in the analysis of crystallized carbonate of Line, the most uniform of all compounds, we nave the following discordant results, which are of importance in the doctrine of equiva- lents:— Mr. Kirwan makes it consist of 45 acid + 55 hme. MM. Aiken, 44 + 56 Dr. Marcet, 43.9 -f 56.1 Dr. Wollaston, 43.7 + 56.3 M. Vauquelin, 43.5 + 56.5 M. Thenard, 43.28 -f 56.72 Dr. Thomson, 43.137 -f 56.863 If we deduce the equivalent of lime from the analysis of Dr. Marcet, so well known for his philosophical accuracy we shall have Lime = 35.1 to carb. acid 27.5 Dr. Thomson's is 36.25 to do. 27.5 I adduced the following experiment, se- lected from among many others, as capable of throwing light on the cause of these varia- tions: " Into a small pear-shaped vessel of glass, with a long neck, and furnished with a hollow spherical stopper, drawn out, above and below, into a tube almost capil- lary, some dilute muriatic acid was put. The whole being poised in a delicate ba- lance, 100 grains of calc spar in rhomboi- dal fragments were introduced, and the stopper was quickly inserted. A little while after the solution was completed, the di- minution of weight, indicating the loss of carbonic acid, was found to be 422 grains. Withdrawing the stopper, inclining the vessel to one side for a few minutes, to al- low the dense gas to flow out, the diminu- tion became 43.3. Finally, on heating the body of the vessel to about 70°, while the hollow stopper was kept cool, small bub- bles of gas escaped from the liquid, and the loss of weight was found to be 43 65, at which point it was stationary. This is a tedious process." The instrument which I subsequently employed is quick in its ope- ration, and still more accurate in its results. It consists of a glass tube of the same strength and diameter with that usually employed for barometers, having a strong egg-shaped bulb, about 2 inches long, and if wide, blown at one of its ends, while Yol. I. CAR the other is open and recurved hke a sy- phon. The straight part of the tube, be- tween the ball and bend, is about 7 inches long. The capacity, exclusive of the cur- ved part, is a little more than 5 cubic inches. It is aocurately graduated into cu- bic inches and hundredth parts, by the successive additions of equal weights of quicksilver, from a measure thermometric tube. Seven troy ounces and 66 grains of quicksilver occupy the bulk of one cubic inch. Four and a half such portions being introduced, will fill the ball, and the be- ginning ofthe stem. The point in the tube, which is a tangent to the surface of the mercury, is marked with a file or a dia- mond. Then 34* grains, equal in volume to l-100th of a cubic inch, being drawn up into the thermometric tube, rest at a cer- tain height, which is also marked. The same measure of mercury is successively introduced and marked off, till the tube is filled. " In the instrument thus finished, l-200th of a cubic inch occupies on the stem about l-14th of an inch, a space very distinguisha- ble. The weight of carbonic acid, equiva- lent to that number, is less than l-400th of a grain. The mode of using it is perfectly simple and commodious, and the analytical result is commonly obtained in a few mi- nutes." For example, five grains of calcareous spar in three or four rhomboids were weighed with great care in a balance by Crighton, which turns with TorVoTT of the weight in the scales. These are intro- duced into the empty tube, and made to slide gently along into the spheroid. The instrument is then held in nearly a hori- zontal position with the left hand, the top of the spheroid resting against the breast, with a small funnel bent at its point, in- serted into the orifice of the tube. Quick- silver is now poured in till it be filled, which in this position is accomplished in a few seconds. Should any particles of air be entangled among the mercury, they are discharged by inverting the instrument, having closed the orifice with the finger. On reverting it, and tapping the ball with the finger, the fragments of spar rise to the top. Three or four hundredth parts of a cubic inch of mercury being displaced from the mouth of the tube, that bulk of dilute muriatic acid is poured in; then pressing the forefinger on the orifice, and inclining the instrument forwards, the acid is made to rise through the quicksilver. This, as it is displaced by the cooled car- bonic acid, falls into a stone-ware or glass basin, within which the instrument stands in a wooden frame. When the solution is completed, the apparent volume of gas is noted, the mercury in the two legs of the 34 CAR CAR syphon is brought to a level, or the differ- ence of height above the mercury in the ba- sin is observed, as also the temperature of the apartment, and the height of the baro- meter. Then the ordinary corrections being made, we have" the exact volume of carbo- nic acid contained in five grains of calc spar. In very numerous experiments, which I have made in very different circumstances of atmospherical pressure and tempera- ture, the results have not varied one-hun- dredth of a cubic inch, on five grains, care being had to screen the instrument, from the radiation of the sun or a fire. As there is absolutely no action exer- cised on mercury by dilute muriatic acid at ordinary temperatures; as no perceptible difference is made in the bulk of air, by introducing to it over the mercury a little of the acid by itself; and as we can expel every atom of carbonic acid from the mu- riate of lime, or other saline solution, by gently heating that point of the tube which contains it, it is evident that the total vo- lume of gaseous product must be accu- rately determined. When a series of ex- periments is to be performed in a short space of time, I wash the quicksilver with water, dry it with a sponge first, and then with warm muslin. The tube is also wash- ed out and drained. According to my ex- periments with the above instrument, 5 grains of calcareous spar yield, 4.7 cubic inches of carbonic acid, equivalent to 43.616 per cent. The difference between this num- ber and Dr. Wollaston's is inconsiderable. Among other results which I obtained from the use of the above instrument, it enabled me to ascertain the true composi- tion of the sublimed carbonate of ammo- nia, which chemists had previously mis- taken. I showed in the Annals of Philoso- phy for September 1817, that this salt con- tained 54.5 of carbonic acid, 30.5 ammo- nia, and 15 water, in 100 parts; numbers which, being translated into the language of equivalents, approach to the following proportions:— Carbonic acid, 3 primes, 8.25 55.89 Ammonia, 2 4.26 28.86 Water, 2 225 15.25 14.76 100.00 As this volatile salt possesses the cu- rious property of passing readily from one system of definite proportions to another, absolute accordance between experiment and theory cannot be expected. The other salt gave for its constituents, 54.5 car- bonic acid-f-22.8 ammonia-f 22.75 wa- ter = 100. Now, if these numbers be re- ferred to Dr. Wollaston's oxygen scale, we shall have,— Theory. Expt. 2 primes carbonic acid, 5 50 55.66 54.50 1 ammonia 2.13 21.56 22.80 3 water, 2.25 22 78 22.75 These near approximations to the equi- valent ratios in compounds of a variable nature, do not seem to have attracted no- tice at the time. Dr. Thomson describes in his System the solid subcarbonate found in the shops as indefinite in the proportion of its constituents In the 14th Number of the Journal of Science, his friend, Mr. Phil- lips, whose attention to minute accuracy is well known, has published an ingenious pa- per on the subject, which begins with the following handsome acknowledgment of my labours: " During some late researches, my attention being directed to the compo- sition of the carbonates of ammonia, I be- gan, and had nearly completed an examina- tion of them, before I observed that they had been recently analyzed by Dr. Ure; and 1 consider his results to be so nearly accurate, that I should have suppressed mine, if I had not noticed some circum- stances respecting the compounds in ques- tion, which have, I believe, hitherto escaped observation." Mr. Phillips's communication is valua- ble. It presents a luminous systematic view of the carbonates of ammonia and soda. Dr. Thomson, in his Annals for July 1820, enumerates that account of the carbonates of ammonia among the improvements made in 1819, without any allusion to my expe- riments on the ammoniacal salts, publish- ed in his own Magazine, nearly three years before he printed his retrospect. The indications of the above analytical instrument are so minute, as to enable us, by the help of the old and well known theorem for computing the proportions of two metals from the specific gravity of an alloy, to deduce the proportions of the bases from the volume of gas disengaged by a given weight of a mixed carbonate. A chemical problem of this nature was practically solvedfby me, in presence of two distinguished Professors of the University of Dublin, in May 1816. But such an appli- cation is more curious than useful, since a slight variation in the quantity of gas, as well as accidental admixtures of other sub- stances, are apt to occasion considerable errors. It determines, however, the nature and value of a limestone with sufficient practical precision. As 100 grains of mag- nesian limestone yield 99 cubic inches of gas, a convenient rule for it is formed when we say, that 10 grains will yield 10 cubic inches. In the same way marls and com- mon limestones may be examined, by sub- jecting a certain number of grains, in a graduated syphon tube, to the action of a little muriatic acid over mercury. From the bulk of evolved gas, expressed in cubic inches and tenths, deduct l-20th, the remainder will express the proportion of real limestone pre- sent in the grains employed.* CAR CAR •Carbonate of Barytes. SeeWiTH- erite.* * CARBONATEofLime. See Calcare- ous Spar.* * Carbonate of Strontian. See Strontian and Heavy Spar.* * Carbonic Acid. See Acid Carbo- nic* * Carbonic Oxide. A gaseous com- pound of one prime equivalent of carbon, and one of oxygen, consisting by weight of 0.75 of the former, and 1.00 of the latter. Hence the prime of the compound is 175, the same as that of azote. This gas can- not be formed by the chemist by the direct combination of its constituents; for at the temperature requisite for effecting a union, the carbon attracts its full dose of oxygen, and thus generates carbonic acid. It may- be procured by exposing charcoal to a long continued heat. The last products consist chiefly of carbonic oxide. To obtain it pure, however, our only plan is to abstract one proportion of oxygen from carbonic acid, either in its gaseous state, or as condensed in the carbonates. Thus by introducing well calcined char- coal into a tube traversing a furnace, as is represented plate I. fig. 2.; and when it is heated to redness, passing over it back- wards and forwards, by means of two at- tached mercurial gasometers or bladders, a slow current of carbonic acid, we con- vert the acid into an oxide more bulky than itself. Each prime of the carbon be- comes now associated with only one of oxygen, instead of two, as before. The carbon acting here, by its superior mass, is enabled to effect the thorough satura- tion ofthe oxygen. If we subject to a strong heat, in a gun barrel or retort, a mixture of any dry earthy carbonate, such as chalk, or carbonate of strontites, with metallic filings or charcoal, the combined acid is resolved as before into the gaseous oxide of carbon. The most convenient mixture is equal parts of dried chalk and iron, or zinc filings. By passing a numerous succession of electric explo- sions through one volume of carbonic acid, confined over mercury, two volumes of carbonic oxide, and one of oxygen, are formed, according to Sir H. Davy. The specific gravity of this gas is stated by Gay-Lussac and Thenard, from theore- tical considerations, to be 0.96782, though Mr. Cruickshank's experimental estimate was 0.9569. As the gas is formed by with- drawing from a volume of carbonic acid half a volume of oxygen, while the bulk of the gas remains unchanged, we obtain its specific gravity by subtracting from that of carbonic acid half the specific gravity of oxygen. Hence 1.5277 — 0.5555 = 0.9722, differing slightly from the above, in consequence of the French chemists rating the specific gravity of the two ori- ginal gases at 1.51961 and 1.10359. Hence 100 cubic inches weigh 29-f grains at mean pressure and temperature. This gas burns with a dark-blue flame. Sir H. Davy has shown, that though carbo- nic oxide in its combustion produces less heat than other inflammable gases, it may be kindled at a much lower tempera- ture. It inflames in the atmosphere, when brought into contact with an iron wire heated to dull redness, whereas carburet- ted hydrogen is not inflammable by a si- milar wire, unless it is heated to whiteness, so as to burn with sparks. It requires, for its combustion, half its volume of oxygen gas, producing one volume of carbonic acid. It is not decomposable by any of the simple combustibles, except potassi- um and sodium. When potassium is heat- ed in a portion of the gas, potash is formed with the precipitation of charcoal, and the disengagement of heat and light. Perhaps iron, at a high temperature, would condense the oxygen and carbon by its strong affinity for these substances. Water condenses -$\ of its bulk of the gas. The above processes are those usually pre- scribed in our systematic works, for pro- curing the oxide of carbon. In some of them, a portion of carbonic acid is evolved, which may be withdrawn by washing the gaseous product with weak solution of potash, or milk of lime. We avoid the chance of this impurity by extricating the gas from a mixture of dry carbonate of ba- rytes and iron filings, or of oxide of zinc, and previously calcined charcoal. The ga- seous product, from the first mixture, is pure oxide of carbon. Oxide of iron, and pure barytes, remain in the retort. Carbonic oxide, when respired, is fatal to animal life. Sir H. Davy took three inspirations of it, mixed with about one-fourth of common air; the effect was a temporary loss of sen- sation, which was succeeded by giddiness, sickness, acute pains in different parts of the body, and extreme debility. Some days elapsed before he entirely recovered. Since then, Mr. Witter of Dublin was struck down in an apoplectic condition, by breath- ing this gas; but he was speedily restored, by the inhalation of oxygen. See an inte- resting account of this experiment, by Mr. Witter, in the Phil. Mag. vol. 43. When a mixture of it and chlorine is ex- posed to sunshine, a curious compound, discovered by Dr. John Davy, is formed, to which he gave the name of phosgene gas. I shall describe its properties in treat- ing of chlorine. It has been called chloro- carbonic acid, though chlorocarbonous acid seems a more appropriate name.* * Carbuncle, a gem highly prized by the ancients, probably the alumundine, a variety of noble Garnet* CAR CAR ♦Carburet of Sulphur. Called also sulphuret of carbon, and alcohol of sul- phur. This interesting liquid was originally ob- tained by Lampadius in distilling a mixture of pulverized pyrites and charcoal in an earthen retort, and was considered by him as a peculiar compound of sulphur and hy- drogen. But MM. Clement and Desormes, with the precision and ingenuity which dis- tinguish all their researches, first ascer- tained its true constitution to be carburet- ted sulphur; and they invented a process of great simplicity, for at once preparing it, and proving its nature. Thoroughly cal- cined charcoal is to be put into a porcelain tube, that traverses a furnace, at a slight angle of inclination. To the higher end of the tube, a retort of glass, containing sul- phur, is luted; and to the lower end is at- tached an adopter tube, which enters into a bottle with two tubulures, half full of water, and surrounded with very cold wa- ter or ice. From the other aperture of the bottle, a bent tube proceeds into the pneu- matic trough. When the porcelain tube is brought into a state of ignition, feat is applied to the sulphur, which subliming into the tube, combines with the charcoal, forming the liquid carburet. 'The conclu- sive demonstration of such an experiment was however questioned by M. Berthollet, jun. and Cluzel. But MM. Berthollet, The- nard and Vauquelin, the reporters on M. Cluzel's memoir, having made some expe- riments of their own upon the subject, concluded that the liquid in question was a compound of sulphur and carbon only. Finally, an excellent paper was written on the carburet by M. Berzelius and Dr. Marcet, who confirmed the results of MM. Clement and Desormes, and added likewise several important facts. If about ten parts of well calcined char- coal in powder, mixed with fifty parts of pulverized native pyrites (bisulphuret of iron), be distilled from an earthen retort, into a tubulated receiver surrounded with ice, more than one part of sulphuret of carbon may be obtained. If we employ the elegant process of M. Clement, we must take care that the charcoal be perfectly calcined, otherwise no carburet will be ob- tained. In their early experiments, they at- tached to the higher end of the porcelain tube a glass one, containing the sulphur in small pieces, and pushed these succes- sively forwards by a wire passing air-tight through a cork, at the upper end of the tube. Besides the liquid carburet, there is formed some carburetted and sulphuretted hydrogen, and a reddish-brown solid and very combustible matter, which seems to be sulphur slightly carburetted. This sub- Stance remains almost entirely in the adopt- er tube. The liquid carburet occupies the bottom of the receiver bottle, and may be separated from the supernatant water, by putting the whole into a funnel, whose tube is closed with the finger, and letting the denser brown carburet flow out below, whenever the distinction of the liquid into two strata is complete. Thus obtained, the carburet is always yellowish, containing a small excess of sulphur, which may be re- moved by distillation from a glass retort, plunged in water, at a temperature of 115°. It is now transparent and colourless, of a penetrating, fetid smell, and an acrid burn- ing taste. Its specific gravity varies from 1.263 to 1.272. According to Dr. Marcet, it boils below 110°; according to M. The- nard at 113° F.; and the tension of its va- pour at 72 5° is equivalent to a column of 12.53 inches of mercury. At 53.5°, accord- ing to Marcet and Berzelius, the tension is equivalent to a column of 7.4 inches, or one-fourth of the mean atmospheric pres- sure; hence one-third is added to the bulk of any portion of air, with which the li- quid may be mixed. A spirit of wine ther- mometer, having its bulb surrounded with cotton cloth or lint, if dipped in sulphuret of carbon, and suspended in the air, sinks from 60° to 0°. If it be put into the receiver of an air pump, and a moderate exhaustion be made, it sinks rapidly from 60° to — 81°. If a tube containing mercury be treat- ed in the same way, the mercury may be readily frozen even in summer. The drier the air in the receiver, the more easily is the cold produced. Hence the presence of sulphuric acid may be of some service in removing the vapour from the air in the receiver. This carburet may be cooled to — 80° without congealing; a conclusive proof that combination changes completely the con- stitution of bodies, since two substances usually solid, form a fluid which we can- not solidify. When a lighted body approach- es the surface of the carburet, it immedi- ately catches fire, and burns with a blue sulphurous flame. Carbonic and sulphurous acids are exhaled, and a little sulphur is deposited. A heat of about 700° inflames the vapour ofthe carburet. Oxygen dilated by it over mercury explodes by the electric spark, with a violent detonation. My eudi- ometer is peculiarly adapted to the exhi- bition of this experiment. A portion of oxy- gen being introduced into the sealed leg, we pour a few drops of the carburet on the surface of the merpury in the open leg, and closing this with the finger, transfer the liquid to the other by a momentary in- clination of the syphon. The expansion of volume can be now most accurately mea- sured by bringing the mercury to a level in each leg. The subsequent explosion occasions no CAR (All danger, and a scarcely audible report. 'The result is a true analysis, if we have mixed oxygen saturated with the vapour at ordi- nary pressure and temperature, with about its volume of pure oxygen. Otherwise, all the sulphur would not be oxygenated. We obtain, then,sulphurous and carbonic acids, with the excess of oxygen. The carburet of sulphur dissolves cam- phor. It does not unite with water; but very readily with alcohol and ether. With chloride of azote it forms a non-detonating compound. The waters of potash, barytes, and lime, slowly decompose it, with the evolution of carbonic acid gas. It combines with ammonia and lime, forming carbo- sulphurets. The carburet, saturated with ammoniacal gas, forms a yellow pulveru- lent substance, which sublimes unaltered in close vessels, but is so deliquescent that it cannot be passed from one v essel to ano- ther without absorbing moisture.. When heated in that state, crystals of hydrosul- phuret of ammonia form. The compound with lime is made by heating some quick- lime in a tube, and causing the vapour of carburet to pass through it. The hme be- comes incandescent at the instant of com- bination. When the carburet is left for some weeks in contact with nitro-muriatic acid, it is converted into a substance having very much the appearance and physical proper- ties of camphor; being soluble in alcohol and oils, and insoluble in water. This sub- stance is, according to Berzelius, a triple acid, composed of two atoms of muriatic acid, one atom of sulphurous acid, and one atom of carbonic acid. He calls it, muria- tico-sulphurous-carbonic acid. When potassium is heated in the vapour of the carburet, it burns with a reddish flame, and a black film appears on the sur- face. On admitting water, a greenish solu- tion of sulphuret of potash is obtained, containing a mixture of charcoal. From its vapour passing through ignited muriate of silver, without occasioning any reduction of the metal, it is demonstrated that this carburet is destitute of hydrogen. When the compound of potash, water, and carburet of sulphur, is added to me- tallic solutions, precipitates of a peculiar kind, called carbo-sulphurets, are obtain- ed. The following is a table of the colours of the precipitates: Muriate of Cerium, White or yellowish- white. Sulphate of Manga- nese, Greenish-gray. Sulphate of Zinc, White. Permuriate of iron, Dark red. Submuriate of Anti- mony, Orange. Muriate of tin, Pale orange, then brown. Dark olive-green, at last black. A fine scarlet. Dark brown. Black. Orange. Reddish-brown. Nitrate of Cobalt, Nitrate of lead, Nitrate of copper, Protomuriate of mer- cury, Permuriate of mer- cury. Muriate of silver, Carburet of sulphur was found by Dr. Brewster to exceed all fluid bodies in re- fractive power, and even the solids, flint- glass, topaz, and tourmaline. In dispersive power it exceeds every fluid substance ex- cept oil of cassia, holding an intermediate place between piiosphorus and balsam of tolu. The best method of analyzing the car- buret of sulphur, is to pass its vapour over ignited peroxide of iron; though the ana- lysis was skilfully effected by MM. Ber- thollet, Vauquelin, and Thenard, by trans- mitting the vapour through a red-hot cop- per tube, or a porcelain one containing copper turnings. Both the first method, as employed by Berzelius, and the second, concur in showing the carburet to consist of 1 prime of carbon, 0.75 15.79 2 primes of sulphur, 4.00 84.21 4.75 100.00 Vauquelin's experimental numbers are, from 15 to 16 carbon, and from 86 to 85 sulphur; and those of Berzelius and Mar- cet are 15.17 carbon, and 84.83 sulphur, in 10U parts. Of the cold produced by the evaporation of the carburet of sulphur, the following account is given by Dr. Thomson in the third volume of his Annals, being the ex- tract of a letter which he received from Mr. J. Murray, philosophical lecturer:—" A glass of water has remained on the table since the preceding evening, and though it might be some degrees below 32° Fahr. it indicated no disposition for congelation. A few drops of sulphuret of carbon were ap- plied to the surface, instantly the globules became cased with a shell of icy spiculz of retiform texture. Where they were in contact with the water, plumose branches darted from the sulphuret as from a centre to the bottom of the vessel, and the whole became solidified. The sulphuret of carbon in the interim volatilized, and during this period the spicules exhibited the colours of the solar spectrum in beautiful array."* • Carburetted Hydrogen Gas. Of this compound gas, formerly called heavy inflammable air, we have two species, dif- fering in the proportions of the constitu- ents. The first, consisting of 1 prime equi- valent of each, is carburetted hydrogen; the second, of 1 prime of carbon, and 2 of hy- drogen, is subcarburetted hydrogen. l.Car- buretted hydrogen, the percarburetted hy« CAR CAR drogen of the French chemists, is, accord- ing to Mr. Brande, the only definite com- pound of these two elements. 'To prepare it, we mix in a glass retort, 1 part of alco- hol, and 4 of sulphuric acid, and expose the retort to a moderate heat. The gas is usually received over water: though De Saussure states that this liquid absorbs more than l-7th of its volume of the gas. It is destructive of animal life. Its specific gravity is 0.978, according to Saussure. 100 cubic inches weigh 28.80 gr. It possesses all the mechanical properties of air. It is invisible, and void of taste and smell, when it has been washed from a little ethereous vapour. The effect of heat on this gas is curious. When passed through a porcelain tube, heated to a cherry red, it lets fall a portion of charcoal, and nearly doubles its volume. At a higher temperature it depo- sites more charcoal, and augments in bulk; till finally, at the greatest heat to which we can expose it, it lets fall almost the whole of its carbon, and assumes a volume 34 times greater than it had at first. These re- markable results, observed with great care, have induced the illustrious Berthollet to conclude, with much plausibility, that hy- drogen and carbon combine in many suc- cessive proportions. 'The transmission of a series of electric sparks through this gas, produces a similar effect with that of sim- ple heat. Carburetted hydrogen burns with a splendid white flame When mixed with three times its bulk of oxygen, and kind- led by a taper or the electric spark, it ex- plodes with great violence, and the four volumes are converted into two volumes of carbonic acid. But two volumes of carbonic acid contain two volumes of oxygen. The remaining volume of oxygen therefore has been expended in forming water with two volumes of hydrogen. Hence the original volume of carburetted hydrogen was made up of these two volumes of hydrogen = 0.1398 (0.0694 X 2) + 2 volumes of gase- ous carbon = 0.8333, constituting 1 con- densed volume = 0.9731. By gaseous car- bon is meant the vapour of this solid, as it exists in carbonic acid; the density of which vapour is found by subtracting the specific gravity of oxygen, from that of carbonic acid. Hence 1.5277— 1.1111 = 0.4166, re- presents the density of gaseous carbon. M. Thenard says, that if we mix the percarbu- retted hydrogen at once with three times its volume of oxygen, the eudiometer would be broken; so sudden and powerful is the expansion. The eudiometer referred to is that of Volta, which costs three guineas in Paris. My eudiometer, which does not cost three shillings, bears the explosive violence of the above mixture, without any danger. (See Eudiometer). When it is detonated with only an equal volume of oxygen, it ex- pands greatly, and the two volumes become more than three and a half. In this case on- ly l-8th or l-10th of a volume of carbonic acid is formed; but more than a volume and a half of carbonic oxide; a little hydrogen is consumed, but the greatest part remains untouched and mixed with the carbonic oxide. It may be separated by combustion with chlorine. If we refer the weights above found, from the combining volumes, to the equivalent oxygen scale, we shall have the gas con- sisting of 1 prime of each constituent. For 0.1398: 0.125: :8333: 0.752; now 0.125 and 0.750 represent the prime equivalents of hydrogen and carbon. When this gas is mixed with its own bulk of chlorine, the gaseous mixture is condensed over water into a peculiar oily- looking compound. Hence this carburetted hydrogen was called by its discoverers, the associated Dutch chemists, olefiant gas. MM Robiquet and Colin formed this liquid in considerable quantities, by making two currents of its constituent gases meet in a glass globe. The olefiant gas should be in rather larger quantity than the chlorine, otherwise the liquid becomes of a green colour, and acquires acid properties. When it is washed with water, and distilled off dry muriate of lime, it may be regarded as pure. It is then a limpid colourless essence of a pleasant flavour, and a sharp, sweet, and not disagreeable taste. At 45° its spe- cific gravity is 2.2201. Its boiling point is 152°. At 49° is vapour is said to be capable of sustaining a column of 24§ inches of mercury. The specific gravity of the va- pour is 3.4434, compared to atmospheric air. But that quantity is the sum of the densities of chlorine and olefiant gas. It will consist therefore by weight of Olefiant gas, 0.9731 (2 X 0.875) 1.75 Chlorine, 2.4733 4.45 3.4464 6.20 or two primes of the first and one of the second. Its ultimate constituents are there- fore 1 chlorine, 2 carbon, and 2 hydrogen. This substance burns with a green flame, from which charcoal is deposited, and mu- riatic acid gas flies off. Decomposition, with similar results, is effected by passing the liquid through a red-hot porcelain tube. Its constitution probably resembles that of muriatic ether. Olefiant gas is elegantly analyzed by beating sulphur in it over mercury. One cubic inch of it, with 2 grains of sulphur, yields two cubic inches of sulphuretted hy- drogen, and charcoal is deposited. Now we know that the latter gas contains just its own volume of hydrogen. 2. Subcarburetted hydrogen. This gas is supposed to be procured in a state of defi- nite composition, from the mud of stagnant CAR CAR pools or ditches. We have only to fill a wide mouthed goblet with water, and in- verting it in the ditch-water, stir the bot- tom with a stick. Gas rises into the goblet. The fire-damp of mines is a similar gas to that of ditches. There is in both cases an admixture of carbonic acid, which lime or potash-water will remove. A proportion of air is also present, tbe quantity of which can be ascertained by analysis. By igniting acetate of potash in a gun-barrel, an ana- logous species of gas is obtained. Accord- ing to M. Berthollet, the sp. gr. of the car- buretted hydrogen from ditch mud, exclu- sive of the azote, is 0.5382. 1 volume of gaseous carbon = 2 do. hydrogen = Here we see the specific gravity 0.5564, is very near the determination of Berthol- let We also perceive the compound prime to be 1.000, the same as oxygen. Berthol- let says that the carburetted hydrogen ob- tained by exposing olefiant gas to an intense heat contains 2 of hydrogen to 1 of carbon by weight. 'This proportion corresponds to 12 primes of hydrogen = 1.5 And 1 do. of carbon =075 As the gas of ditches and the choke- damp of mines are evidently derived from the action of water on decaying vegetable or carbonaceous matter, we can under- stand that a similar product will be obtain- ed by passing water over ignited charcoal, or by heating moistened charcoal or vege- table matter in retorts. The gases are here, however, a somewhat complex mixture, as well as what we obtain by igniting pit-coal and wood in iron retorts. (See Coal Gas). The combustion of subcarburetted hydro- gen with common air takes place only when they are mixed in certain propor- tions. If from 6 to 12 parts of air be mixed with 1 of carburetted hydrogen, we have explosive mixtures. Proportions beyond these limits will not explode. In like man- ner, from 1 to 24 of oxygen, must be mix- ed with 1 of the combustible gas, other- wise we have no explosion. Sir H. Davy says that this gas has a disagreeable em- pyreumatic smell, and that water absorbs l-30th of its volume of it* Carica Papaya. Papaw tree. Every part of the papaw tree, except the ripe fruit, affords a milky juice, which is used in the Isle of France as an effectual remedy for the tape-worm. In Europe, however, whither it has been sent in the concrete state, it has not answered. The most remarkable circumstance re- garding the papaw tree, is the extraction from its juice of a matter exactly resem- Subcarburetted hydrogen is destitute of colour, taste, and smell. It burns with a yellow flame, like that of a candle. When mixed with twice its volume of oxygen and exploded, we obtain exactly its own bulk of carbonic acid, while water is precipi- tated. We can hence infer the composition of subcarburetted hydrogen. For ofthe two volumes of oxygen, one remains gaseous in the carbonic acid, and another is condens- ed with two volumes of hydrogen into wa- ter. 1 volume of vapour of carbon -f- 2 vo- lumes of hydrogen, condensed into 1 vo- lume, compose subcarburetted hydrogen gas. Thus in numbers, bling the flesh or fibre of animals, and hence called vegetable fibrin,- which see. Carmine. A red pigment prepared from cochineal. See Lake. * Carnelian is a sub-species of calce- dony. Its colours are white, yellow, brown, and red. It has a conchoidal fracture and a specific gravity of 2.6. It is semi-transpa- rent, and has a glistening lustre. It consists of 94 silica, 3.5 alumina, and 0.75 oxide of iron. The finest specimens come from Cam- bay and Surat in India. It is found in the channels of torrents in Hindostan, in no- dules of a blackish olive, passing into gray. After exposure for some weeks to the sun, these are subjected to heat in earthen pots, whence proceed the lively colours for which they are valued in jewelry. It is softer than common calcedony.* * Caromel. The smell exhaled by su- gar, at a calcining heat.* Carthamus, Safflower, or Bas- tard Saffron. In some ofthe deep red- dish, yellow, or orange-coloured flowers, the yellow matter seems to be of the same kind with that of the pure yellow flowers; but the red to be of a different kind from the pure red ones. Watery menstrua take up only the yellow, and leave the red, which may afterward be extracted by alcohol, or by a weak solution of alkali. Such particu- larly are the saffron-coloured flowers ofcar- thamus. These after the yellow matter has been extracted by water, are said to give a tincture to ley; from which, on standing at rest for some time, a deep red fecula subsides, called safflower, and from the countries whence it is commonly brought to us, Spanish red and China lake. This pigment impregnates alcohol with a beauti- ful red tincture; but communicates no co« lour to water. Rouge is prepared from carthamus. For this purpose the red colour is extract- ed by a solution of the subcarbonate of 0.4166 0.75 = 1 prime 0.1398 (0.125 X 2) = 0.25 = 2 primes 0.5564 1.00 CAS CAT soda, and precipitated by lemon juice, pre- viously depurated by standing. This pre- cipitate is dried on earthen plates, mixed with talc, or French chalk, reduced to a powder by means of the leaves of shave- grass, triturated with it till they are both very fine, and then sifted. The fineness of the powder and proportion of the precipi- tate constitute the difference between the finer and cheaper rouge. It is likewise spread very thin on saucers, and sold in this state for dyeing. Carthamus is used for dyeing silk of a poppy, cherry, rose, or bright orange red. After the yellow matter is extracted as above, and thee akes opened, it is put in- to a deal trough, and sprinkled at different times with pearl ashes, or rather soda well powdered and sifted, in the proportion of six pounds to a hundred, mixing the al- kali well as it is put in. The alkali should be saturated with carbonic acid The carthamus is then put on a cloth in a trough with a grated bottom, placed on a larger trough, and cold water poured on, till the large trough is filled. And this is repeated, with the addition of a little more alkali toward the end, till the carthamus is exhausted and becomes yellow. Lemon juice is then poured into the bath, till it is turned of a fine cherry colour, and after it is well stirred the silk is immersed in it. The silk is wrung, drained, and passed through fresh baths, washing and drying after every operation, till it is of a proper colour; when it is brightened in hot water and lemon juice. For a poppy or fire colour a slight annotta ground is first given; but the silk should not be alumed. For a pale carnation a little soap sliould be put into the bath. All these baths must be used as soon as they are made; and cold, because heat destroys the colour of the red feculse. * Cartilage. An elastic, semi-transpa- rent, animal solid, which remains of the shape, and one-third the weight of the bones, when the calcareous salts are re- moved by digestion in dilute muriatic acid. It resembles coagulated albumen. Nitric acid converts it into gelatin. With alkalis it forms an animal soap. Cartilage is the primitive paste, into which the calcareous salts are deposited in the young animal. In the disease rickets, the earthy matter is withdrawn by morbid absorption, and the bones return into the state nearly of flexi- ble cartilage. Hence arise the distortions characteristic of this disease.* Case-Hardening. Steel when harden- ed is brittle, and iron alone is not capable of receiving the hardness steel may be brought to possess. There is nevertheless a variety of articles in which it is desirable to possess all the hardness of steel, to- gether with the toughness of iron. These requisites are united in the art of case- hardening, which does not differ from the making of steel, except in the shorter du- ration of the process. Tools, utensils, or ornaments intended to be polished, are first manufactured in iron and nearly finished, after which they are put into an iron box, together with vegetable or animal coals in powder, and cemented for a certain lime. This treatment converts the external part into a coating of steel, which is usually very thin, because the time allowed for the ce- mentation is much shorter than when the whole is intended to be made into steel. Immersion of the heated pieces into water hardens the surface, which is afterward polished by the usual methods. Moxon's Mechanic Exercises, p. 56, gives the fol- lowing receipt:—Cow's horn or hoof is to be baked or thoroughly dried and pulver- ized. To this add an equal quantity of bay salt: mix them with stale chamber-ley, or white wine vinegar: cover the iron with this mixture, and bed it in the same in loam, or enclose it in an iron box: lay it then on the hearth of the forge to dry and harden: then put it into the fire, and blow till the lump have a blood-red heat, and no higher, lest the mixture be burned too much. Take the iron out, and immerse it in water to harden. * Caseic Acid. The name which Proust gave to a substance of an acid nature, which he extracted from cheese; and to which he ascribes many of the properties of this spe- cies of food.* * Cassava. An American plant, the^'a- tropha manihat, contains the nutritive starch cassava, curiously associated with a deadly poisonous juice. The roots of jatropha are squeezed in a bag. The cassava remains in it; and the juice, which is used by the In- dians to poison their arrows, gradually lets fall some starch of an innocent and very nutritious quality. The whole solid matter is dried in smoke, ground, and made into bread.* •Cassius's purple precipitate. See Gold.* Castor. A soft grayish-yellow or light brown substance, found in four bags in the inguinal region of the beaver. In a warm air it grows by degrees hard and brittle, and of a darker colour, especially when dried in chimneys, as is usually done. According to Bouillon La Grange, it con- sists of a mucilage, a bitter extract, a resin, an essential oil, in which its peculiar smell appears to reside, and a flaky crystalline matter, much resembling the adipocere of biliary calculi. Castor is regarded as a powerful anti- spasmodic. Catechu. A brown astringent substance formerly known by the name of Japan earth. It is a dry extract, prepared from the wood of a species of sensitive plant, the mimosa catechu. It is imported into this CAW CEL country from Bombay and Bengal. Accord- ing to Sir H. Davy, who analyzed it, that from Bombay is of uniform texture, red- brown colour, and specific gravity 1.39: that from Bengal is more friable and less consistent, of a chocolate colour externally, but internally chocolate, streaked with red- brown, and specific gravity 1.28 The cate- chu from either place differs little in its properties. Its taste is astringent, leaving behind a sensation of sweetness. It is al- most wholly soluble in water. Two hundred grains of picked catechu from Bombay afforded 109 grains of tan- nin, 68 extractive matter, 13 mucilage, 10 residuum, chiefly sand and calcareous earth. The same quantity from Bengal: tannin 97 grains, extractive matter 73, mu- cilage 16, residual matter, being sand, with a small quantity of calcareous and alumi- nous earths, 14. Of the latter the darkest parts appeared to afford most tannin, the lightest most extractive matter. The Hin- doos prefer the lightest coloured, which has probably most sweetness, to chew with the betel-nut. Of all the astringent substances we know, catechu appears to contain the largest pro- portion of tannin, and Mr. Purkis found, that one pound was equivalent to seven or eight of oak bark for the purpose of tan- ning leather. As a medicine it has been recommended as a powerful astringent, and a tincture of it is used for this purpose, but its aqueous solution is less irritating. Made into troches with gum arabic and sugar, it is an elegant preparation, and in this way is said much to assist the clearness of the voice, and to be remarkably serviceable in disorders of the throat. * Cat's Eye. A mineral of a beautiful appearance, brought from Ceylon. Its colours are gray, green, brown, red, of various shades. Its internal lustre is shining, its fracture imperfectly conchoidal, and it is translucent. From a peculiar play of light, arising from white fibres interspersed, it has derived its name. The French call the ap- pearance chatoyant. It scratches quartz, is easily broken, and resists the blow-pipe.— Its sp. gr. is 2.64. Its constituents are, ac- cording to Klaproth, 95 silica, 1.75 alumina, 1.5 lime, and 0.25 oxide of iron. It is va- lued for setting as a precious stone.* Caustic (Lunar.) Fused nitrate of sil- ver. See Silver. Causticity. All substances which have so strong a tendency to combine with the principles of organized substances, as to de- stroy their texture, are said to be caustic. The chief of these are the concentrated acids, pure alkalis, and the metalic salts. * Cauteht Potential. Caustic* Gawk. A term by which the miners dfe- VOL. J. tinguish the opaque specimens of sulphate of barytes. -1 *Cklf.stivk. Native sulphate of stron- tites. This mineral is so named from its oc- casional delicate blue colour; though it is frequently found of other shades, as white, grayish and yellowish-white, and red. It occurs both massive and crystallized. Some- times also in fibrous and stellated forms.— According to Haiiv, the primitive form is iv rijcht rhomboidal prism, of 104° 48' and 75° 12'. The reflecting- goniometer makes these angles 104° and 76°. The varieties of its crystals may be referred to four or six-sided prisms, terminated by two, four, or eight- sided summits. It has a shining lustre, and is either transparent, translucent, or opaque. It scratches calcareous spar, but is scratched by fluor. It is very brittle. Its sp. gr. is 3.6. Before the blow-pipe it fuses into a white, opaque, and friable enamel. The three subspecies are, 1st. The com- pact found in Montmartre near Paris, of a yellowish-gray colour, in rounded pieces, of a dull lustre, opaque, and consisting, by Vauquelin's analysis, of 91.42 sulphate of strontites, 8 33 carbonate of lime, and 0.25 oxide of iron. 2d, The fibrous, whose co- lours are indigo-blue and bluish-gray; some- times white. It occurs both massive and crystallized. Shining and somewhat pearly lustre. It is translucent. Sp. grav. 8.83. 3d, The foliated, of a milk white colour, falling into blue. Massive and in grouped cry St..Is, of a shining lustre and straight fo- liated Uxuire. Translucent. Celestine oc- curs most abundantly near Bristol in the red marl formation; and crystallized in red sand- stone, at Inverness in Scotland. Mr. Gruner Ober Berg of Hanover has lately favoured the world with an analysis of a crystallized celestine, found in the neigbourhood of that city, of rather pecu- liar composition. Its sp.gr. is only 3.59, and yet it contains a large proportion of sulphate of barytes: Sulphate of strontites, 73.000 Sulphate of ban tes, 26.166 Fe rrugi nous c lay, 0.21) Loss, 0.621 100.000 Had the result been 75 of sulphate of stron- ties -+- 25 sulphate of barytes, we should have considered the mineral as a compound of 4 primes of the first salt -j- 1 of the se- cond. Now the analysis, in my opinion, can- not be confided in, within these limits; for the mingled muriates of the earths were se- parated by digestion in 16 times their weight of boiling alcohol, of a strength not named. Besides, the previous perfect conversion of the sulphates into carbonates, by merely fu- sing the mineral with thrice its weight of carbonate of potash, is, to say the least, problematical. Dr. Thomson adapts h\' 35 CEM CEM Ober Berg's analysis to 7 atoms of sulphate of strontian, and 2 atoms of sulphate of ba- ryte-.* Cement. Whatever is employed to unite or cement together things of the same or diff'erent kinds, may be called a cement. In this sense it includes lutes, gluks, and sol ders of every kind, which see; but it is more commonly employed to signify those of which the basis is an earth or earthy salt. See Lime. We shall here enumerate, chiefly from the Philosophical Magazine, some cements that are used for particular purposes. Seven or eight parts of resin, and one of wax, melted together, and mixed with a small quantity of plaster of Paris, is a very good cement to unite pieces of Derbyshire spar, or other stone. The stone should be made hot enough to melt the cement, and the pieces should be pressed together as close- ly as possible, so as to leave as little as may be of the cement between them. 1 his is a general rule in cementing, as the thinner the stratum of cement interposed, the firm- er it will hold. Melted brimstone used in the same way will answrer sufficiently well, if the joining be not required to be very strong. It sometimes happens, that jewellers, in setting precious stones, break off' pieces by accident; in this case they join them so that it cannot easily be seen, with gum mastic, the stone being previously made hot enough to melt it. By the same medium cameos of white enamel or coloured glass are often joined to a real stone as a ground, to pro- duce the appearance of an onyx. Mastic is likewise used to cement false backs or doub- lets to stones, to alter their hue. The jewellers in Turkey, who are gene- rally Armenians, ornament watch-cases and other trinkets with gems, by glueing them on. The stone is set in silver or gold, and the back of the setting made flat to corres- pond with the part to which it is to be ap- plied. It is then fixed on with the follow- ing cement. Isinglass, soaked in water till it swells up and becomes soft, is dissolved in .French brandy, or in rum, so as \o form a strong glue. Two small bits of gum gal- banum, or gum ammoniacum, are dissolved in two ounces of this by trituration; and five or six bits of mastic, as big as peas, being dissolved in as much alcohol as will render them fluid, are to be mixed with this by means of a gentle heat. This cement is to be kept in a phial closely stopped; and when used, it is lo be liquefied by immersing the phial in hot water. This cement resists mois- ture. A solution of shell lac in alcohol, added to a solution of isinglass in proof spirit, makes another cement that will resist mo sture. So does common glue melted witiiout wa- ter, with half its weight of resin, with the addition of n little red ochre to give it a hor dy. 'This is particularly useful for cement- ing hones to their frames. If clay and oxide of iron be mixed with oil, according to Mr. Gad of Stockholm, they will form a cement that will harden under water. A strong cement,insoluble in water, may be made from cheese. The cheese should be that of skimmed milk, cut into slices, throwing away the rind, and boiled till it becomes a strong glue, which however does not dissolve in the water. This water being poured off, it is to be washed in cold water, and then kneaded in warm water. This pro- cess is to be repeated several times. The glue is then to be put warm on a levigating stone, and kneaded with quicklime. This cement may be used cold, but it is better to warm it; and it will join marble, stone, or earthen-ware, so that the joining is scarcely to be discovered. Boiled linseed oil, litharge, red lead, and white lead, mixed together to a proper con- sistence, and applied on each side of a piece of flannel, or even linen or paper, and put between two pieces of metal before they are brought home, or close together, w dlmake a close and durable joint, that will resist boiling water, or even a considerable pres- sure of steam. The proportions of the in- gredients are not material, but the more the red lead predominates, the sooner the cement will dry, and the more the white lead the contrary. This cement answers well for joining stones of any dimensions. The following is an excellent cement for iron, as in time it unites with it into one mass. Take two ounces of muriate of am- monia, one of flowers of sulphur, and 16 of cast-iron filings or borings. Mix them well in a mortar, and keep the powder dry. When the cement is wanted for use, take one part of this mixture, twenty parts of clear iron borings or filings, grind them to- gether in a mortar, mix them with water to a proper consistence, and apply them be- tween the joints. Powdered quicklime mixed with bullock's blood is often used by coppersmiths to lay over the rivets and edges of the sheets of copper in large boilers, as a security to tiie junctures, and also to prevent cocks from leaking. Six parts of clay, one of iron filings, and linseed oil sufficient to form a thick paste, make a good cement for stopping cracks in iron boilers. Temporary cements are wanted in cutting, grinding, or polishing optical glasses, stones, and various small articlesof jewellery, which it is necessary to fix on blocks, or handles, for the purpose. Four ounces of resin, a quarter of on ounce of wax, and four ounces of whiting made previously red-hot, form a good cemment of this kind; as any of tbe CEM CER above articles may be fastened to it by heat- ing them, and removed at pleasure in the same manner, though they adhere very firm- ly to it when cold. Pitch, resin, and a small quantity of tallow, thickened with brick- ilust, is much used at Birmingham for these purposes- Four parts of resin, one of bees wax, and one of brick dust, likewise make a good cement This answers extremely well for fixing knives and forks in their hafts; but the manufacturers of cheap articles of this kind too commonly use resin and brick- dust alone, On some occasions, in which a very tough cement is requisite, that will not crack though exposed to repeated blows; as in fastening to a block metallic articles that are to be cut with a hammer and punch, workmen usually mix some tow with the oement, the fibres of which hold its parts together. ♦Mr. Singer recommends the following oomposition as a good cement for electrical apparatus: Five pounds of resin, one of bees wax, one of red ochre, and two table spoon- fuls of plaster of Paris, all melted together. A cheaper one for cementing voltaic plates into wooden troughs is made with six ounds of resin, one pound of red ochre, alf a pound of plaster of Paris, and a quar- ter of a pint of linseed oil. The ochre and plaster of Paris should be well dried, and added to the other ingredients, in a melted state.*f * Cement, for buildings. See Mortar Ce- ments.* f The meal of oil cake, or the residuum of flaxseed, after the expression of the oil, is a good lute; and when mixed with clay will enable it to bear very high temperatures without cracking. It acts, no doubt, in that ease, by creating pores in consequence of its carbonization. Calcined gypsum, or sulphate of lime, when powdered and made into a paste w ith water, sets in a few minutes. It is more cleanly for electrical apparatus, and more easily applied than the cements above recommended. Shell lac, in sticks, has been imposed up- on the public, in Philadelphia, as a new ce- ment of a peculiarly costly kind; and as much has been demanded for a stick, weighing a few penny weights, as would buy a pound. Applied to potters' ware, or glass heated above the temperature of boiling water, it is an excellent cement. The application is much facilitated, by dis- solving the lac in its weight of very strong boiling alcohol, so as to make a thick paste. This being smeared over the edges of the fractured pieces, they must be bound to- gether and subjected to the rays of a fire, till water will boil when dropped on them. When a crack is to be mended, more spirit must be used, so that the solution may be thin enough to run in. Cementation. A chemical process, which consists in surrounding a body in the solid state with the powder of some other bodies, and exposing the whole for a time in a clos- ed vessel, to a degree of heat not sufficient to fuse the contents. Thus iron is con- verted into steel by cementation with char- coal; green bottle glass is converted into porcelain by cementation with sand &c. See Iuon and Porcelain. ♦Cerasin. The name given by Dr. John of Berlin to those gummy substances which swell in cold water, but do not readily dis- solve in it. Cerasin is soluble in boiling water, but separates in a jelly when the water cools. Water acidulated with sulphuric, nitric, or muriatic acid, by the aid of a gentle heat, forms a permanent solution of cerasin. Gum tragacanth is the best example of this spe- cies of vegetable product.* ♦Cerate. The compound of oil or lard with bees wax, used by surgeons to screen ulcerated surfaces from the air.* ♦(fcuijf. A peculiar substance which pre- cipitates, on evaporation, from alcohol, which has been digested on grated cork, Suber- cerin would have been a fitter name. Chev- reul, the discoverer, describes this substance as consisting of small white needles, which sink and merely soften in boiling water. 1000 parts of boiling alcohol dissolve 2.42 of cerin, and only 2 of wax. Nitric acid con- verts it into oxalic acid It is insoluble in an alcoholic solution of potash.* *Cerin-. The name given by Dr. John to the part of common wax which dissolves in alcohol.* ♦Cerin. A variety of the mineral allan- ite, lately examined by Berzelius. It con- sists of oxide of cerium 28.19, oxide of iron 20.72, oxide of copper 0.87, silica 30.17, alumina 11.31, lime 9.12, volatile water 0.40*. * Cerite The siliciferous oxide of ce- rium. This rare mineral is of a rose-red or flesh-red colour, occasionally tinged with clove-brown. Its powder is reddish-gray. It is found massive and disseminated. In- ternal lustre resinous, but scarcely glim- mering. Its fracture is fine splintery, with in- determinate fragments. It is opaque, scratch- es glass, gives sparks with steel, is difficult to break, scarcely yields to the knife, and gives a grayish-white streak. It is infusible before the blow-pipe; but heat changes the gray colour ofthe powder to yellow. It con- sists, by Hisinger's analysis, of 18 silica, 68.59 oxide of cerium, 2 oxide of iron, 1 25 lime, 9.6 water and carbonic acid, and 0 56 loss, in 10U parts. Klaproth found 54.5 oxide of cerium, and 34.5 silica, in the hundred parts. It is found only in the copper mine of Bastnaes near Riddarhytta in Sweden, accompanied by the ores of copper, molyb- dena, and bismuth. Its sp. gr. is from 4.6 to 4.9.* CER CHA •Ceriwm. The metal whose oxide exists in the preceding mineral.* To obtain the oxide of the new metal, the cerite is calcined, pulverized, and dissolved in nitromuriatic acid. 'The filtered solution being neutralized with pure potash, is to be pr« ci oitated bv tartrate of potash, and the precipitate, we'll washed, and afterward cal- cined, is oxide of cerium. *The attempts to obtain the pure metal, by igniting the oxide purified from iron by oxalic acid, in contact with tartaric acid, oil, and lampblack, have in a great measure failed. \ white brittle carburet was only obtained.* Cerium is susceptible of two stages of oxidation; in the first it is white, and this by calcination becomes of a fallow-red. The white oxide exposed to the blow- pipe soon becomes red, but does not melt, or even agglutinate. With a large proportion ' of borax it fuses into a transparent globule. The white oxide becomes yellowish in the open air, but never so red as by calcination, because it absorbs carbonic acid, which pre- vents its saturating itself with oxygen, and retains a portion of water, which diminishes its colour. Alkalis do not act on it; but caustic potash in the dry way takes part of the oxygen from the red oxide, so as to convert it into the white without altering its nature. ♦The protoxide of cerium is composed by Hisinger of 85.17 metal 4- 14 83 oxygen, and the peroxide of 79.3 metal 4- -0.7-. The protoxide ba-, been supposed a binary com- pound of cerium 5.75 + oxygen l,andthe per- oxide a compound of 5.75 X 2 ot' cerium 4- 3 oxygen. An alloy of this metal with iron was obtained by Vauquelin. The salts of cerium are white or yellow coloured, have a sweet taste, yield a white precipitate with hydrosulphuret of potash, but none with sulphuretted hydrogen; a milk-white precipitate, soluble in nitric and muriatic acids, with ferroprussiate of potash and oxalate of ammonia, none with infusion of galls, and a white one with arseniate of potash* Equal parts ofthe sulphuric acid and red cxide, with four parts of water, unite by the assistance of heat into a crystalline mass, which may be completely dissolved by add- ing more acid, and heating them together a long time This solution yields, by gen- tle evaporation, small crystals, some of an orange, others of a lemon colour. The sul- phate of cerium is soluble in water only with V)i excess of acid. Its taste is acid and saccha- rine. The sulphuric acid combines readily with the white oxide, particularly in the State of carbonate. The solution has a saccha- rine taste, and readily affords white crystals. Nitric acid does not readily dissolve the red oxide without heat. With an excess of ^cid, white deliquescent crystals are formed. which are decomposable by heat. Their taste is at first pungent, afterward very su- gary. The white oxide unites more readily with the acid. Muriatic acid dissolves the red oxide with eff'ervescence. Thesolution crystallizes con- fusedly. The salt is deliquescent, soluble in an equal weight of cold water, and in three or four times its weight of alcohol. The flame of this solution, if concentrated, is yellow and sparkling; if not, colourless; but on agitation it emits white, red, and pur- ple sparks. Carbonic acid readily unites with the ox- ide. This is best done by adding carbo- nate of potash to the nitric and muriatic solution of the white oxide, when a light precipitate will be thrown down, which on drying assumes a shining silvery appear- ance, and consists of 23 acid-f- 65 oxide + 12 water. The white oxide unites directly with tar- taric acid, but requires an excess to render it soluble. *Cerumen of the ear. It is a yellow co- loured secretion, which lines the external auditory canal, rendered viscid and concrete by exposure to air. It has a bitter taste, melts at a low heat, and evolves a slightly aromatic odour. On ignited coals, it gives out a white smoke, similar to that of burn- ing fat, swells, emits a fetid ammoniacal odour, and is converted into a light coal. g Alcohol dissolves 7 of it, and on evapora- tion leaves a substance resembling the resin ofbile. The "8 which remained are albumen mixed ffith oil, which by incineration leave soda and phosphate of lime. Hence, the whole constituents are five; albumen, an in- spissated oil, a colouring matter, soda, and calcareous phosphate.* Ceruse, or Wuite Lead. See Lead. ♦Cetinb. The name given by Chevreul to spermaceti. According to Berard, who analyzed it on M. Gay-Lussac's plan, by pass- ing its vapour through ignited peroxide of copper, cetine consists of 81 carbon, 6 oxy- gen, aud 13 hydrogen, in 100 parts.* *Ceila.nite. This mineral, the pleonaste of Hauy, comes from Ceylon, commonly in rounded pieces, but occasionally in crystals. The primitive form of its crystals is a regu- lar octahedron, in which form, or with the edges truncated, it frequently occurs. Its colour is indigo-blue, passing into black, winch on minute inspection appears green- ish. It has a rough surface, with little exter- nal lustre, but splendent internally. The fracture is perfect flat conchoidal, with very sharp-'uged fragments. It scarcely scratches quar: z, and is softer than spinell. It is easily broken, has a sp. gr. of 3. 77, and is infusi- ble by the blow-pipe.* * Cuabasite. This mineral occurs in crys- CHA CHA tals, whose primitive form is nearly a eube, since the angle at the summit is only 93f • It is found in that form, and also with 6 of its edges truncated, and the truncatures united 3 and 3 at the two opposite angles, while the other six angles are truncated. It occurs also in double six-sided pyramids, applied base to base, having the six angles at the base, and the three acute edges of each pyramid truncated. It is white, or with a tinge of rose colour, and sometimes transparent. It scratches glass, fuses by the blow-pipe into a white spongy mass, and has a sp. gr. of 2. 72- Its constituents are 43.33 silica, 22.66 alumina, 3.34 lime, 9.34 soda and potash, water 21. It is found in scatter- ed crystals in the fissures of some trap rocks, and in the hollows of certain geodes, dissemi- nated in the same rocks. It occurs in tiie quarry of Alteberg near Oberstein.* Chalk. A very common species of cal- oareous earth, of an opaque white colour, very soft, and without the least appearance of a polish in its fracture. Its specific gravity is from 24 to 2.6, according to Kirwan. It contains a little siliceous earth, and about two per cent of clay. Some specimens, and perhaps most, contain a little iron, and Berg- mann affirms that muriate of lime, or magne- sia, is often found in it; for which reason he directs the powder of chalk to be several times boiled in dist illed water, before it is dissolved for the purpose of obtaining pure calcareous earth. * Chalk (Black). Drawing slate. The Colour of this mineral is grayish or bluish- black. Massive. The principal fracture is glimmering and slaty, the cross fracture dull, and fine earthy. It is in opaque, tabular fragments, stains paper black, streak glisten- ing, and the same colour as the surface; easily cut and broken; sp gr. 2.4; becomes red in the fire, and falls to pieces in water. It occurs in primitive mountains, often ac- companied by alum slate. It is used in cray- on drawing, whence its name.* ♦Chalk Stones. Gouty concretions whose true nature was first discovered by Dr. Wol- laston, and described by him in his admira- ble dissertation on urinary calculi, published in the Phil. Trans, for 1797. See Goutx Concretions * Chalk (Red). This is a clay coloured by the oxide of iron, of which it contains from 16 to 18 parts in the hundred, according to Binman. Chalk (Spanish). The soap rock is fre- quently distinguished by this name. Characters (Chemical). The chemical characters were invented by the earlier che- mists, probably with no other view than to save time in writing the names of substances that frequently occurred, in the same man- ner as we avoid repetitions by the use of pronouns. But the modents seem te hare considered them as relics of alchemistical obscurity, and have almost totally rejected their use. Very little of system appears in the ancient characters of chemists: the char- acters of Bergmann are chiefly grounded on the ancient characters, with additions and improvements. But the characters of Has- senfratz and Adet are systematical through- out. 'The former are exhibited in Plate III. and the latter in Plate IV. Charcoal. When vegetable substances are exposed to a strong heat in the appara- tus for distillation, the fixed residue is called charcoal. For general purposes, wood is con- verted into charcoal by building it up in a pyramidal form, covering the pile with clay or earth, and leaving a few air-holes, which are closed as soon as the mass is well light- ed; and by this means the combustion is car- ried on in an imperfect manner. In the fo- rest of Benon, near Rochelle, great attention is paid to the manufacture, so that the char- coal made there fetches 25 or 30 per cent more than any other. The wood is that of the black oak. It is taken from ten to fif- teen years old, the trunk as well as the branches cut into billets about four feet long, and not split. 'The largest pieces, however, seldom exceed six or seven inches in dia- meter. I'he end that rests on the ground is cut a little sloping, so as to touch it mere- ly with an edge, and they are piled nearly upright, but never in more than one story. The wood is covered all over about four in- ches thick with dry grass or fern, before it is enclosed in the usual manner with clay; and when the wood is charred, half a barrel of water is thrown over the pile, and earth to the thickness of five or six inches is thrown on, after which it is left four-and- twenty hours to cool. The wood is always used in the year in which it is cut In charring wood it has been conjectured, that a portion of it is sometimes converted into a pyrophorus, and that the explosions that happen in powder-mills are sometimes owing to this. * Charcoal is made on the great scale, by igniting wood in iron cylinders, as I have described under Acetic Acin. When the resulting charcoal is to be used in the ma- nufacture of gunpowder, it is essential that the last portion of vinegar and tar be suffer- ed to escape, and that the reabsorption of the crude vapours be prevented, by cutting off' the communication between the interior of the cylinders and the apparatus for con- densing the pyrolignous acid, whenever the fire is withdrawn from the furnace. If this precaution be not observed, the gunpowder made with the charcoal would be of inferior quality. In the third volume of Tilloch's Magazine, we have some valuable facts on charcoal, by Mr. Mushet. He justly observes, that the produce of charcoal in the snmlhvay, difleffr CHA CHE from that on the large scale, in which the quantity of char depends more upon the hardness, and compactness of the texture of wood, and the skill of the workman in ma- naging the pyramid of faggots, than on the Parts in 100. Oak, Ash, Birch, Norway Pine, Volatile Matter. 76.895 8126U 8^717 80.441 Charcoal. 22.682 17.972 17491 19.204 Ashes. 0.423 0.768 1792 0.355 Mahogany, Sycamore, 73.528 79.20 25.492 19.734 0.980 l.o66 Holly, 78.92 19.918 1.162 Scotch Pine, B'ech, Elm, Walnut, American Maple, 83.095 79.104 79.655 78.521 79.331 16.456 19.941 19.574 20 663 19.901 0.449 0.955 0.761 0.816 0.768 Do. Black Beech, Laburnum, 77.512 74.234 21.445 24 586 1.033 1.180 Lignum Vitae, Sallow, 72.643 8J.371 26.857 18.497 0.500 1.132 absolute quantity of carbon it contains. The following is his table of results, reduced to 100 parts, from experiments on one pound avoirdupois of wood. Charcoal by Proust. Rumford: 20. 17. 20. Black Ash. 25. Willow. 17. Heart of Oak, 19. 43.00 44.18 43 27 42.28 Guaiacum. ^4. Chesnut, 76.304 23.280 0.416 Poplar. 43.57 Lime. 43.59 MM. Clement and Desormes say, that wood affords one-half its weight of charcoal. I con- sider the statements of Mr. Mishet and M. Proust, much more correct. They coincide with the experiments to which I have refer- red in treating of the extraction of vinegar from wood. (See Acetic Acid.) M. Proust says, that good pit-coals afford 70, 75, or 80 per cent of charcoal or coak; from which only two or three parts in the hundred of ashes remain after combustion. Tilloch's Mag. vol. viii* Charcoal is black, sonorous, and brittle, and in general retains the figure of the ve- getable it was obtained from. If, however, the vegetable consist for the most part of water or other fluids, these in their extrica- tion will destroy the connexion of the more fixed parts. In this case the quantity of charcoal is much less than in the former. The charcoal of oily or bituminous sub- stances is of a light pulverulent form, and rises in soot. This charcoal ot oils is called lampblack. A very fine kind is obtained from burning alcohol. Turf or peat has been charred lately in prance, it is said by a peculiar process, and, according to the account given in Sonnini's Journal, is superior to wood for this purpose. Charcoal of turf kindles slower than that of wood, but emits more flame, and burns long- er. In a goldsmith's furnace it fused eleven ounces of gold in eight minutes, while wood charcoal required sixteen. The malleability ofthe gold, too, was preserved in the form- er instance, but not in the latter. Iron heat- ed red-hot by it in a forge, was rendered more malleable. From the scarcity of wood in this country, pit-coal charred, is much used instead of char- coal by the name of Coak. See Carbon. Chat, or <:haya-Root. This is the root of the Oldenlandia umbellata, which grows wild on the coast of Coromandel, and is likewise cultivated there for the use of the dyers and calico printers. It is used for the same purposes as madder with us, to which it is said to be far superior, giving the beau- tiful red so much admired in the Madras cotr tons. Cheesf.. Milk consists of butter, cheese, a saccharine matter called sugarof milk, and a small quantity of common salt, together with much water. If any vegetable or mineral acid be mix- ed with milk, the cheese separates, and, if assisted by heat, coagulates into a mass. The quantity of cheese is less when a mine- ral acid is used. Neutral salts, and likewise all earthy and metallic salts, separate the ch e from the whey. Sugar and gum ara- bic produce the same effect. Caustic alka- lis will dissolve the curd by the assistance of a boiling heat, and acids occasion a pre- CHE CHL .capitation a^ain. Vegetable acids have ve- ry little solvent power upon curd. This ac- counts for a greater quantity of curl be- ing obtained when a vegetable acid s used. But what answers best is rennet, w hich is made by macerating in water a piece of the last stomach of a calf, salted and dried for tli is purpose. Scheele observed, that cheese has a consi- derable analogy to albumen, which it resem- bles in being coagnlable by fire and acids, soluble in ammonia, and affording the same products by distillation or treatment with nitric acid. There are, however, certain dif- ferences between them. Kouelle observed likewise, a striking analogy betw-en cheese and tiie gluten of wheat, and that foun in the feculse of green vegetables. By knead- ing the gluten of wheat with a little salt and a small portion of a solution of starch, he gave it the taste, smell, and unctt.osity of cheese, so that after it had been kept a cer- tain time, it was not to be distinguished from the celebrated Kochefort cheese, of which it had all the pungency. This caseous substance from gluten, as well as the cheese of milk, appears to contain acetate of ammonia, after it lias been kept long enough to have under- gone the requisite fermentation, as may be proved by examining it with sulphuric acid, and with potash. The pungency of strong cheese, too, is destroyed by alcohol. * In the 11th volume of Tilloch's Magazine there is an excellent account of the mode of making Cheshire cheese, taken from the Agricultural Keport of the county. " If the milk," says the reporter, " be set together very warm, the curd, as before observed, will be firm; in this case, the usual mode is to take a common case-knife, and make inci- sions across it to the full depth ofthe knife's blade, at tiie distance of abouc one inch; and again crossway s in the same manner, the in- cisions intersecting each other at right an- gles. The whey rising through these inci- sions is of a fine pale-green colour. The cheese-maker and two assistants then pro- ceed to break the curd; this is performed by their repeatedly putting their handsdown into the tub; the cheese-maker, with the skimming dish in one hand, breaking every part of it as they catch it, raising tbe curd from the bottom, and still breaking it. This r. art ofthe business is continued till the whole is broken uniformly small; it generally takes up about 40 minutes, and the curd is then left covered over with a cloth for about half an hour to subside. If the milk has been set cool together, the curd, as before men- tioned, will be much more tender, the whey will not be so green, but rather of a milky appearance " The above account of cheese- making is evidently at variance with that fiven by Dr. Thomson in the 4th volume of is system.* * Cuemistrt may be defined, the science which investigates the composition of mate- rial substances, and the permanent changes of constitution which their mutual actions produce * * CufvopodiumOltdum. A plant remark- able, according to MM. Chevalier and Las- seigne, for containing uncombined ammonia, which is probably the vehicle ofthe remark- ably nauseous odour which it exhales, strong- ly resembling that of putrid fish. When the plant is bruised with water, and the liquor expressed and afterwards distilled, we pro- cure a fluid which contains the subcarbonate of ammonia, and an oily matter, which gives the fluid a milky appearance. If the ex- pressed juice ofthe chenopodiuui be evapo- rated to the consistence of an extract, it is found to be alkaline; there seems to be ace- tic acid in it. Its basis is said to be of an al- buminous nature. It is stated also to contain a small quantity ofthe substance vv'iirh the French call osmazome, a little <>f an aroma- tic resin, and a bitter matu-r, soluble both in alcohol and water, as well as several saline bodies. The following is stated as the re- sult of their analysis, which, however, seems somewhat complex: 1. Subcarbonate ufam- mmiia, 2. Albumen, 3. Osmazone, 4. An aro- matic resin, 5 A bitter matter, 6. Nitrate of potash in large quantity, 7. Acetate and phosphate of potash, 8 Tart'ate of pot- ash. It is said that 100 parts of the dried plant produce 18 of ashes, of which 51 are potash* * Chert. See Hornstone.* * Chiastolitk. A mineral crystallized in four-sided, nearly rectangular prisms. On looking into the end ofthe prism, we per- ceive in the axis of it a blackish prism, sur- rounded by the other, which is of a grayish, yellowish, or reddish-white colour. From each angle of the interior prisms, a blackish line extends to the corresponding angle of the exterior. In each of these outer angles there is usually a small rhomboidal space, filled with the same darK substance which composes the central prism. The black matter is the same clay-slate with the rock in which the chiastolite is imbedded. Frac- ture, foliated with double cleavage. Trans- lucent. Scratches glass. Rubbed on seal- ing-wax, it imparts negative electricity. Its sp. gr. is 2.94. Before the blow-pipe it is convertible into a whitish enamel. The on- ly mineral with which chiastolite or made can be confounded, were it not crystallized, is steatite; but the latter communicates posi- tive electricity to sealing-wax. It has been found in Britanny, in the Pyrenees, in the valley of Barege, and in Galicia in Spain, near St. James of Compostella. The inte- rior black crystal is properly an elongated four-sided pvramid.* * Chlorates. Compounds of chloric acid with the salifiable bases. Sje Chioric Acid.* CHL CHL * Cntomc Actd. See Acid (drconir) * * Chlorides. Compounds of chlorine with combustible bodies. See Chlorine and the respective substances.* * Chlorine. The introduction of this term, marks an era in chemical science. It originated from the masterly researches of Sir II. Davy on the oxymuriatic acid gas of the French school, a substance which, after resisting the most powerful means of de- composition which his sagacity could invent, or his ingenuity apply, he declared to be, according to the true logic of chemistry, an elementary body, and not a compound of muriatic acid and oxygen, as was previous- ly imagined, and as its name seemed to denote. He accordingly assigned to it the term chlorine, descriptive of its colour; a name now generally used. The chloridic theory of combustion, though more limited in its applications to the chemical phenome- na of nature, than the antiphlogistic of 1a- voisier, may justly be regarded as of equal importance to the advancement of the sci- ence itself. When we now survey the Trans- actions ofthe Koyal Society for "1808, 1809, 1810, and 1811, we feel overwhelmed with astonishment at the unparalleled skill, la- bour, and sagacity, by which the great Eng- lish chemist, in so short a space, prodigiously multiplied the objects and resources of the science, while he promulgated a new code of laws, flowing from views of elementary action, equally profound, original, and su- blime. The importance of the revolution produced by his researches on chlorine, will justify us in presenting a detaded account of the steps by which it has been effected. How entirely the glory of this great work belongs to Sir H. Davy, notwithstanding some invi- dious attempts in this country, to tear the well-earned laurel from his brow, and trans- fer it to the French chemists, we may rea- dily judge by the following decisive tacts. The second part of the Phil. Trans, for 1809 contains researches on oxymuriatic acid, its nature and combinations, by Sir H. Davy, from which I shall make a few inter- esting extracts. " In the Bakerian lecture for 1808," says he, " 1 have given an account of the action of potassium upon muriatic acid gas, by whic'i more than one-third of its volume of hydngen is produced; and I have stated, that .nuriatic acid can in no instance be pro- cured from oxymuriatic acid, or from dry muriates, unless water or its elements be present. " In the second volume of the Me'moires D'Arcueil, MM. Gay-Lussac and Thenard have detailed an extensive series of facts up- on muriatic acid, and oxymuriatic acid. Some of their experiments are similar to those 1 have detailed in the paper just re- ferred to; others are peculiarly their own, and of a very curious kind; their general conclusion is, that muriatic acid gas contains about one quarter of its weight of water; and that oxymuriatic acid is not decomposa- ble by any substances but hydrogen, or such as can form triple combinations with it " One of the most singular facts that I have observed on this subject and which I have before referred to, is that charcoal, even when ignited to whiteness in oxymu- riatic or muriatic acid gases, by the voltaic battery, effects no change in them, if it has been previously freed from hydrogen and moisture, by intense ignition in vacuo. " This experiment, which I have several times repeated, led me to doubt of the ex- istence of oxygen in that substance, which has been supposed to contain it, above all others, in a loose and active state; ami to make a more rigorous investigation, than had hitherto been attempted for its detec- tion" He then proceeds to interrogate nature, with every artifice of experiment and rea- soning, till he finally extorts a confession of the true constitution of this mysterious mu- riatic essence. The above paper, and his Bakerian lecture, read before the Koyal So- ciety in Nov. and Dec. 1810, and published in the first part of their transactions for 1811, present the whole body of evidence for the undecompounded nature of oxy muriatic acid gas, thenceforward styled chlorine, and they will be studied in every enlightened age and country, as a just and splendid pattern of in- ductive Baconian logic. 'These views were slowly and reluctantly admitted by tiie che- mical philosophers of Europe. The hypo- thesis of Lavoisier,that combustion was mere- ly the combination of oxygen with a basis, had become as favourite an idol with the learned, as the previous hypothesis of Stahl, that one phlogistic principle pervaded all combustible bodies, which was either evolved in heat and light or quietly transferred to an incombustible, imparting that inflammability to the new substance, which its former com- panion had secretly lost. Stahl's idea of com- bustion is the more comprehensive, and may still be true; Lavoisier's as a general propo- sition, is certainly false.-j- In 1812 Sir H. Davy published his Ele- ments of Chemical Philosophy; containing a systematic account of his new doctrines con- cerning the combination of simple bodies. j- It appears to me that Stahl's doctrine is false, both as a general and particular pro- position. According to him, metals are com- pounds of their own oxides, now known to be compounds containing metals as ingredients; and this error was extended to explain the relation between every combustible, and its compounds formed with oxygen. The doctrine of Stahl never can be true, until it ceases to be an axiom, that flie less eannot contain the greater. CHL CHL Chlorine is there placed in the same rank with oxygen, and finally removed from the class of acids. In 1813, M. Thenard pub- lished the first volume of his Traite de Chi- mie Elemdntaire TMorique et Pratiq'.ie. 'This distinguished chemist, the fellow-labourer of M. Gay -Lussac, in those able researches on the alkalis and oxymuriatic acid, which form tbe honourable rivalry ofthe French school to the brilliant career of Sir H. Davy, states at page 584. of the above volume, the com- position of oxymuriatic acid as follows: " Com- position. The oxygenated muriatic gas, con- tains the half of its volume of oxygen gas, not including that which we may suppose in muriatic acid. It thence follows, that it is formed of 1.9183 of muriatic acid, and 0.5517 of oxygen; for the specific gravity of oxyge- nated muriatic gas is 2.47, and that of oxy- gen gas, 1.1034." " M. Chenevix first de- termined the proportion of its constituent principles. MM. Gay-Lussac and Thenard determined it more exactly, and showed that we could not decompose the oxygenated muriatic gas, but by putting it in contact with a body capable of uniting with the two elements of this gas, or with muriatic acid. They announced at the same time, that they could explain all the phenomena which it presents, by considering it as a simple, or as a compound body. However, this last opinion appeared more probable to them. M. Davy on the contrary, embraced the first, admitted it exclusively, and sought to fortify it, by experiments which are peculiar to him." P. 585. In the second volume of M. Thenard's work, published in 1814, he explains the mu- tual action of chlorine and ammonia gases solely on the oxygenous theory. " On peut de"montrer par ce dernier precede, que le gas muriatique oxigene' doit contenir la moitie de son volume d'oxigene, uni a l'acide muriatique." P. 147-—In the 4th volume which appeared in 1816, we find the following passages: " Oxygenated mu- riatic gas. Oxygenated muriatic gas, in combining with the metals, gives rise to the neutral muriates. Now, 107.6 of oxide of silver, contain 7.6 of oxygen, and absorb 26.4 of muriatic acid, to pass to the state of neutral muriate. Of consequence, 348 of this last acid supposed dry, and 100 of oxy- gen, form this gas. But the sp gr. of oxy- gen is 1.1034, and that of oxygenated mu- riatic gas is 2.47; hence, this contains the half of its volume of oxygen." P. 52. The force of Sir H. Davy's demonstra- tions, pressing for six years on the public mind ofthe French philosophers, now be- gins to transpire in a note to the above passage.---" We reason here," says M. Thenard, "obviously, on the hypothesis, which consists in regarding oxygenated vol. I. muriatic gas as a compound body." This pressure of public opinion becomes conspi- cuous at the end ofthe volume. Among the additions, we have the following decisive evidence, ofthe lingering attachment to the old theory of Lavoisier and Berthollet —"A pretty considerable number of persons who have subscribed for this work, desiring a de- tailed explanation of the phenomena, which oxygenated muriatic gas presents, on the supposition that this gas is a simple body, we are now going to explain these pheno- mena, on this supposition, by considering them attentively. The oxygenated muriatic gas will take the name of chlorine; its com- binations with phosphorus, sulphur, azote, metals, will be called chlorures; the muriatic acid, which results from equal parts in vol- ume of hydrogen and oxygenated muriatic gases, will be hydrochloric acid; the super- oxygenated muriatic acid, will be chlorous acid; and the hyperoxygenated muriatic, chloric acid; the first, comparable to the hydriodic acid, and the last to the iodic acid." In fact, therefore, we evidently see, that so far from the chloridic theory origin- ating in France, as has been more than insinuated, it was only the researches on iodine, so admirably conducted by M. Gay- Lussac, that by their auxiliary attack of the oxygen hypothesis, eventually opened the minds of its adherents, to the evidence long ago advanced by Sir H. Davy. It will be peculiarly instructive, to give a general outline of that evidence, which has been mutilated in s.;me systematic works on che- mistry, or frittered away into fragments. Sir H. Davy subjected oxymuriatic gas, to the action of many simple combustibles, as well as metals, and from the compounds formed, endeavoured to eliminate oxygen, by the most energetic powers of affinity and voltaic electricity, but without success, as the following abstract will show. If oxymuriatic acid gas be introduced in- to a vessel exhausted of air, containing tin; and the tin be gently heated, and the gas in sufficient quantify, the tin and the gas dis- appear; and a limpid fluid, precisely the same as Libavius's liquor is formed: If this substance is a combination of muriatic acid and oxide of tin, oxide of tin ought to be separated from it by means of ammonia.— He admitted ammoniacal gas over mercury to a small quantity of the liquor of Libavius; it was absorbed with great heat, and no gas was generated; a solid result was obtained, which was of a dull white colour: some of it was heated, to ascertain if it contained oxide of tin; but the whole volatilized, pro- ducing dense pungent furnes. Another experiment of the same kind, made with great care, and in which the am- monia was used in great excess, proved that 36 CHL CHL the liquor of Libavius cannot be decom- pounded by ammonia; but that it forms a new combination with this substance. He made a considerable quantity of the solid compound of oxymuriatic acid and phosphorus by combustion, and saturated it ■with ammonia, by heating it in a proper re- ceiver filled with ammoniacal gas, on which it acted with great energy, prodncing much heat; and they formed a white opaque pow- der. Supposing that this substance was composed of the dry muriates and phos- phates of ammonia; as muriate of ammonia is very volatile, and as ammonia is driven off from phosphoric acid, by a heat below red- ness, he conceived that, by igniting the pro- duct obtained, he should procure phosphoric acid; he therefore introduced some of the powder into a tube of green glass, and heated it to redness, out ofthe contact of air, by a spirit lamp; but found, to his great^urprise, that it was not at all volatile nor decomposa- ble at this degree of heat, and that it gave off' no gaseous matter. The circumstance, that a substance com- posed principally of oxymuriatic acid, and ammonia, should resist decomposition* or change at so high a temperature, induced him to pay particular attention to the pro- perties of this new body. It has been said, and taken for granted by many chemists, that when oxymuriatic acid and ammonia act upon each other, water is formed; he several times made the experi- ment, and was convinced that this is not the case. He mixed together sulphuretted hydrogen in a high degree of purity, and oxymuriatic acid gas, both dried, in equal volumes. In this instance the condensation was not 40i sulphur, which seemed to contain a little oxymuriatic acid, was formed on the sides of the vessel; no vapour was deposited; and 10 the residual gas contained about ^"of muri. atic acid gas, and the remainder was inflam- mable. When oxymuriatic acid is acted upon by nearly an equal volume of hydrogen, a com- bination takes place between them, and mu- riatic acid gas results. When muriatic acid gas is acted on by mercury, or any other metal, the oxymuriatic acid is attracted from the hydrogen, by the stronger affinity of the metal; and an oxymuriate, exactly similar to that formed by combustion, is produced. The action of water upon those com- pounds, which have been usually considered as muriates, or as dry muriates, but which are properly combinations of oxymuriatic acid with inflammable bases, may be easily explained, according to these views of the subject. When water is added in certain quantities to Libavius's liquor, a solid crys- tallized mass is obtained, from which oxide of tin and muriate of ammonia can be pro- cured by ammonia. In this case, oxygen may be conceived to be supplied to the tin, and hydrogen to the oxv muriatic acid. The compound formed by burning phos- phorus in oxymuriatic acid, is in a similar relation to water. If that substance be add- ed to it, it is resolved into two powerful acids; oxygen, it may be supposed, is fur- nished to the phosphorus to form phosphoric acid, hydrogen to the oxymuriatic acid to form common muriatic acid gas. He caused strong explosions from an electrical jar to pass through oxymuriatic gas, by means of points of platina, for several hours in succession; but it seemed not to undergo the slightest change. He electrized the oxymuriates of phos- phorus and sulphur for some hours, by the power ofthe voltaic apparatus of 1000 dou- ble plates. No gas separated, but a minute quantity of hydrogen, which he was inclined to attribute to the presence of moisture in the apparatus employed; for he once ob- tained hydrogen from Libavius's liquor by a similar operation. But he ascertained that this was owing to the decomposition of wa- ter adhering to the mercury; and in some late experiments made with 2000 double plates, in which the discharge was from pla- tina wires, and in which the mercury used for confining the liquor was carefully boiled, there was no production of any permanent elastic matter. b'cw substances, perhaps, have less claim to be considered as acid, than oxymuriatic acid. As yet we have no right to say that it has been decompounded; and as its ten- dency of combination is with pure inflam- mable matters, it may possibly belong to the same class of bodies as oxygen. May it not in fact be a peculiar acidifying and dissolving principle, forming compounds with combustible bodies, analogous to acids containing oxy gen, or oxides, in their proper- ties and powers of combination; but differ- ing from them, in being for the most part decomposable by water? On this idea mu- riatic acid may be considered as having hy- drogen for its basis, and oxy muriatic acid for its acidifying principle. And the phosphoric sublimate as having phosphorus for its basis, and oxymuriatic acid for its acidifying matter. And Libavius's liquor, and the compounds of arsenic with oxymuriatic acid, may be regard- ed as analogous bodies. The combinations of oxymuriatic acid with lead, silver, mer- cury, potassium, and sodium, in this view, would be considered as a class of bodies re- lated more to oxides than acids, in their powers of attraction.—Bak. Lee. 1809. On the Combinations of the Common Metals with Oxygen and Oxymuriatic Gas. Sir H. used in all cases small retorts of CHL CHL green glass, containing from three to six cu- bical inches, furnished with stop-cocks. The metallic substances were introduced, the re- tort exhausted and filled with the gas to be acted upon, heat was applied by means of a spirit lamp, and after cooling, the results were examined, and the residual gas ana- lyzed. All the metals he tried, except silver, lead, nickel, cobalt, and gold, when heated, burnt in the oxymuriatic gas, and the vola- tile metals with flame. Arsenic, antimony, tellurium, and zinc, with a white flame, mercury with a red flame. Tin became ignited to whiteness, and iron and copper to redness; tungsten and manganese to dull redness; platina was scarcely acted upon at the heat of fusion ofthe glass. The product from mercury was corrosive sublimate. That from zinc was similar in colour to that from antimony, but was much less volatile. Silver and lead produced horn-silver and horn-lead; and bismuth, butter of bismuth. In acting upon metallic oxides by oxy- muriatic gas, he found that those of lead, silver, tin, copper, antimony, bismuth, and tellurium, were decomposed in a heat below redness, but the oxides of the volatile metals more readily than those of the fixed ones. The oxides of cobalt and nickel were scarcely acted upon at a dull red heat. The red oxide of iron was not affected at a strong red heat, whilst the black oxide was readily decomposed at a much lower temperature; arsenical acid underwent no change at the greatest heat that could be given it in the glass retort, whilst the white oxide readily decomposed. In cases where oxygen was given off", it was found exactly the same in quantity as that which has been absorbed by the metal. Thus two grains of red oxide of mercury ab. sorbed—of a cubical inch of oxymuriatic 10 J gas, and afforded 0.45 of oxygen. Two grains of dark olive oxide from calomel de- composed by potash, absorbed about—Q of oxyn.uriatic gas, anil afforded — of cxy. gen, and corrosive sublimate wi.s produced in both cases. In the decomposition of the white oxide of zinc, oxygen was expelled exactly equal to half the volume of the oxymuriatic acid absorbed. In the case of the decomposition of the black oxide of iron, and the white oxide of arsenic, the changes that occurred were of a very beautiful kind; no oxygen was given off' in either case, but butter of arsenic and arsenical acid formed in one in- stance, and the ferruginous sublimate and red oxide of iron in the other. General Conclusions and Observations, ittus- truted by Experiments. Oxymuriatic gas combines with inflam- mable bodies, to form simple binary com- pounds; and in these cases, when it acts upon oxides, it either produces the expulsion of their oxygen, or causes it to enter into new combinations. If it be said that the oxygen arises from the decomposition of the oxymuriatic gas, and not from the oxides, it may be asked, why it is always the quantity contained in the oxide? and why in some cases, as those ofthe peroxides of potassium and sodium, it bears no relation to the quantity of gas? If there existed any acid matter in oxy- muriatic gas, combined with oxygen, it ought to be exhibited in the fluid compound of one proportion of phosphorus, and two of oxymuriatic gas; for this, on such an as- sumption, should consist of muriatic acid (on the old hypothesis, free from water) and phosphorous acid; but this substance has no effect on litmus paper, and does not act under common circumstances on fixed alkaline bases, such as dry lime or magne- sia. Oxymuriatic gas, like oxygen, must be combined in large quantity with pecu- liar inflammable matter, to form acid mat- ter. In its union with hydrogen, it instantly reddens the driest litmus paper, though a gaseous body. Contrary to acids, it expels oxygen from protoxides; and combines with peroxides. When potassium is burnt in oxymuriatic gas, a dry compound is obtained. If potas- sium combined with oxygen is employed, the whole of the oxygen is expelled, and the same compound formed. It is contrary to sound logic to say, that this exact quan- tity of oxygen is given off from a body not known to be compound, whf-n we are cer- tain of its existence in another; and all the cases are parallel. Scheele explained the bleaching powers of the oxymuriatic gas, by supposing that it destroyed colours by combining with phlogiston. Berthollet considered it as act- ing by supplying oxygen. He made an ex- periment, which seems to prove that the pure gas is incapable of altering vegetable colours, and that its operation in bleaching depends entirely upon its property of de- composing water, and liberating its oxygen. He filled a glass globe, containing dry powdered muriate of lime, with oxymuri- atic gas. He introduced some dry papt r tinged with litmus that had been just heat- ed, into another globe containing dry mu- riate of lime; after some time this glole was exhausted, and then connected with the globe containing the oxymuriatic gas, and by an appropriate set of stop-cocks, the paper was exposed to the action of the gas. No change of colour took place, and after two days there was scarcely a per- ceptible alteration. Some similar paper dried, introduced in- CHL CIIL to gas that had not been exposed to mu- riate of lime, was instantly rendered white. ft is generally stated in chemical books, that oxymuriatic gas is capable of being condensed and crystallized at a low tem- perature. He found by several experiments that this is not the case. The solution of oxy- muriatic gas in water freezes more readi- ly than pure water, but the pure gas dried by muriate of lime undergoes no change whatever, at a temperature of 40 below U° of Fahrenheit. The mistake seems to have arisen from the exposure of the gas to cold in bottles containing moisture. He attempted to decompose boracic and phosphoric acids by oxymuriatic gas, but without success; from which it seems pro- bable, that the attractions of boracium and phosphorus for oxygen are stronger than for oxymuriatic gas. And from the experi- ments already detailed, iron and arsenic are analogous in this respect, and proba- bly some other metals. Potassium, sodium, calcium, strontium, barium, zinc, mercury, tin, lead, and proba- bly silver, antimony, and gold, seem to have a stronger attraction for oxymuriatic gas than for oxygen. " To call a body which is not known to contain oxygen, and which cannot contain muriatic acid, oxy muriatic acid, is contrary to the principles of that nomenclature in which it is adopted; and an alteration of it Beems necessaiy to assist the progress of discussion, and to diffuse just ideas on the subject. If the great discoverer of this sub- stance had signified it by any simple name, it would have been proper to have recur- red to it; but dephlogisticated marine acid is a term which can hardly be adopted in the present advanced era of the science. After consulting some of the most emi- nent chemical philosophers in this country, it has been judged most proper to suggest a name founded upon one of its obvious and characteristic properties—its colour, and to call it chlorine, or chloric gas. Should it hereafter be discovered to be compound, and even to contain oxygen, this name can imply no error, and cannot neces- sarily require a change. Most of the salts which have been called muriates, are not known to contain any mu- riatic acid, or any oxygen. Thus Libavius's liquor, though converted into a muriate by water, contains only tin and oxymuriatic gas; and horn-silver seems incapable of be- ing converted into a true muriate."—Bak. Lee. 1811. We shall now exhibit a summary view of the preparation and properties of chlo- rine. Mix in a mortar 3 parts of common salt and 1 of black oxide of manganese. Intro- duce them into a glass rciovt, and add 2 parts of sulphuric acid. Gas will issue, which must be collected in the water-pneu- matic trough. A gentle heat will favour its extrication. In practice, the above pasty- consistenced mixture is apt to boil over in- to the neck. A mixture of liquid muriatic acid and manganese is therefore more con- venient for the production of chlorine. A very slight heat is adequate to its expul- sion from the retort. Instead of manganese, red oxide of mercury, or puce-coloured ox- ide of lead, may be employed. This gas, as we have already remarked, is of a greenish-yellow colour, easily recog- nized by day-light, but scarcely distinguish- able by that of candles. Its odour and taste are disagreeable, strong, and so charac- teristic, that it is impossible to mistake it for anv other gas. When we breathe it, even much diluted with air, it occasions a sense of strangulation, constriction ofthe thorax, and a copious discharge from the nostrils. If respired in larger quantity, it excites violent coughing, with spitting of blood, and would speedily destroy the individual, amid violent distress. Its specific gravity is 2.4733. This is better inferred from the specific gravities of hydrogen and muriatic acid gases, than from the direct weight of chlorine, from the impossibility of confin- ing it over mercury. One volume of hydro- gen, added to one of chlorine, form two of the acid gas. Hence, if from twice the specific gravity of muriatic gas = 2 5427, we subtract that of hydrogen = 0.0694, the difference 2-4733 is the speci- fic gravity of clUorine. 100 cubic inches at mean pressure and temperature weigh 75% grains. See Gas. In its perfectly dry state, it has no effect on dry vegetable colours. With the aid of a little moisture, it bleaches them into a yellowish-white. Scheele first remarked this bleaching property; Berthollet applied it to the art of bleaching in France, and from him Mr. Watt introduced its use into Great Britain. If a lighted wax taper be immersed ra- pidly into this gas, it consumes very fast, with a dull reddish flame, and much smoke. The taper will not burn at the surface of the gas. Hence, if slowly introduced, it is apt to be extinguished. The alkaline me- tals, as well as copper, tin, arsenic, zinc, antimony, in fine laminae or filings, spon- taneously burn in chlorine. Metallic chlo- rides result. Phosphorus also takes fire at ordinary temperatures, and is converted into a chloride. Sulphur may be melted in the gas without taking fire. It forms a li- quid chloride, of a reddish colour. When dry, it is not altered by any change of tem- perature. Enclosed in a phial with a little moisture, it concretes into crystalline nee- dles, at 40° Fahr. According to M. Thenard, water con- denses, at the temperature of 68° Fahr. CHL and at 29.92 barom. l£ times its volume of chlorine, and forms aqueous chlorine, for- merly called liquid oxymuriatic acid. This combination is best made in the second bottle of a Woulfe's apparatus, the first be- ing charged with a little water, to inter- cept the muriatic acid gas, while the third bottle may contain potash-water or milk of lime, to condense the superfluous gas. M. Thenard says, that a kilogramme of salt is sufficient for saturating from 10 to 12 litres of water. These measures corres- pond to 2 and l-3d libs, avoirdupois, and from 21 to 25 pints English. There is an ingenious apparatus for making aqueous chlorine, described in Berthollet's Ele- ments of Dyeing, vol. i.; which, however, the happy substitution of slaked lime for water, by Mr. Charles Tennent of Glasgow, has superseded, for the purposes of manu- facture. It congeals by cold at 40° Fahr. and affords crystallized plates, of a deep yellow, containing a less proportion of water than the liquid combination. Hence when chlorine is passed into water at tem- peratures under 40°, the liquid finally be- comes a concrete mass, which at a gentle heat liquefies with eff'ervescence, from the escape of the excess of chlorine. When steam and chlorine are passed together through a red-hot porcelain tube, they are converted into muriatic acid and oxygen. A like result is obtained by exposing aque- ous chlorine to the solar rays; with this dif- ference, that a little chloric acid is formed. Hence aqueous chlorine should be kept in a dark place. Aqueous chlorine attacks al- most all the metals at an ordinary tempe- rature, forming muriates or chlorides, and heat is evolved It has the smell, taste, and colour of chlorine; and acts like it, on ve- getable and animal colours. Its taste is somewhat astringent, but not in the least degree acidulous. When we put in a perfectly dark place at the ordinary temperature, a mixture of chlorine and hydrogen, it experiences no kind of alteration, even in the space of a great many days. But if, at the same low temperature, we expose the mixture to the diffuse light of day, by degrees the two gases enter into chemical combination, and form muriatic acid gas. There is no change in the volume of the mixture, but the change of its nature may be proved, by its rapid ab- sorbability by water, its not exploding by the lighted taper, and the disappearance of the chlorine hue. To produce the complete discoloration, we must expose the mixture finally for a few minutes to the sunbeam. If exposed at first to this intensity of light, it explodes with great violence, and instant- ly forms muriatic acid gas. 'The same ex- plosive combination is produced by the electric spark and the lighted taper. M. Thenard says, a heat of 392° is sufficient CHL to cause the explosion. The proper pro. portion is an equal volume of each gas Chlorine and nitrogen combine into a re-. markable detonating compound, by expos- ing the former gas to a solution of an am- moniacal salt. See Nitrogen. Chlorine is the most powerful agent for destroying contagious miasmata. The disinfecting phi- als of Moi-veau evolve this gas. See Chlo- rous Oxide.* f •Chlorite is a mineral usually friable or very easy to pulverize, composed of a multitude of little spangles, or shining small grains, falling to powder under the pressure of the fingers. There are four sub-species. 1. Chlorite earth. In green, glimmering and somewhat pearly scales, with a shining green streak. It adheres to the skin, and has a greasy feel. Sp. gr. 2.6. It consists of 50 silica, 26 alumina, 1.5 lime, 5 oxide of iron, 17 5 potash. This mineral is found chiefly in clay-slate, in Germany and Switzerland. Al Altenberg, in Saxony, it is intermingled with sulphurets of iron and arsenic; and amphibole in mass. 2 Com- mon chlorite. A massive mineral of a black- ish-green colour, a shining lustre, and a fo- liated fracture passing into earthy. Streak is lighter green; it is soft, opaque, easily cut and broken, and feels greasy. Sp. gr. 2.83. Its constituents are 26 silica, 18.5 alumina, 8 magnesia, 43 oxide of iron, and 2 muriate of potash. 3. Chlorite slate. A massive, blackish-green mineral, with re- sinous lustre, and curve slaty or scaly-foli- ated fracture. Double cleavage. Easily cut. Feels somewhat greasy. Sp. gr. 2.82. It occurs particularly along with clay-slate, and is found in Corsica, Fahlun in Sweden, and Norway. 4. Foliated chlorite. Colour between mountain and blackish-green. Massive; but commonly crystallized in six- sided tables, in cylinders terminated by two cones, and in double cones with the bases joined. Surface streaked. Lustre shining pearly; foliated fracture, translucent on the edges; soft, sectile, and folia usually flexi- ble. Feels rather greasy. Sp. gr. 2.82. It is found at St. Gothard, in Switzerland, and in the island of Java. Its constituents are 35 silica, 18 alumina, 29.9 magnesia, 9.7 oxide of* iron, 2 7 water.* * Chlorophane. A violet fluor spar; found in Siberia.* * Chloro-carbonous Acid. The term f It is surprising, that I have no where met with any mention of one of the most distinctive and obvious properties of this gas. When the exterior air was about the temperature of 60°, and a mercurial ther- mometer detected no difference between the temperature of the chlorine and that of the surrounding medium, the hand, im- mersed in it, would experience a sensa- tion of warmth, indicating 80 or 90°. CHL CHL cbloro-carbonic which has been given to this compound is incorrect, leading to the belief of its being a compound of chlorine and acidified charcoal, instead of being a compound of chlorine and the protoxide of charcoal. Chlorine has no immediate ac- tion on carbonic oxide, when they are ex- posed to each other in common day-light over mercury; not even when the electric spark is passed through them. Experiments made by Dr. John Davy, in the presence of his brother Sir H. Davy, prove that they combine rapidly when exposed to the di- rect solar beams, and one volume of each is condensed into one volume of the com- pound. The resulting gas possesses very curious properties, approaching to those of an acid. From the peculiar potency of the sunbeam in effecting this combination, Dr. Davy called it phosgene gas. The con- stituent gases, dried over muriate of lime, ought to be introduced from separate re- servoirs into an exhausted globe, perfectly dry, and exposed for fifteen minutes to bright sunshine, or for twelve hours to day-light. The colour of the chlorine dis- appears, and on opening the stop-cock be- longing to the globe under mercury re- cently boiled, an absorption of one-half the gaseous volume is indicated. The resulting gas possesses properties perfectly distinct from those belonging to either carbonic oxide or chlorine. It does not fume in the atmosphere. Its odour is difi'erent from that of chlorine, something like that which might be ima- gined to result from the smell of chlorine combined with that of ammonia. It is in fact more intolerable and suffocating than chlorine itself, and affects the eyes in a peculiar manner, producing a rapid flow of tears, and occasioning painful sensations. It reddens dry litmus paper; and con- denses four volumes of ammonia into a white salt, while heat is evolved. This am- moniacal compound is neutral, but has no odour, but a pungent saline taste; is deli- quescent, decomposable by the liquid mi- neral acids, dissolves without effervescing in vinegar, and sublimes unaltered in mu- riatic, carbonic, and sulphurous acid gases. Sulphuric acid resolves it into carbonic and muriatic acids, in the proportion of two in volume of the latter, and one of the former. Tin, zinc, antimony, and arsenic, heated in chloro-carbonous i:cid, abst;.ict the chlorine, and leave the carbonic oxide expanded to its original volume. There is neither ignition nor explosion takes place, though the action of the metals is rapid. Potassium acting on the compound gas produces a solid chloride and charcoal. White oxide of zinc, with chloro-carbonous acid, gives a metallic chloride, and carbo- nic acid. Neither sulphur,phosphorus,oxy- gen, nor hydrogen, though aided by heat, produce any change on the acid gas. But oxygen and hvdrogen together, in due pro- portions, explode in it; or mere exposure to water, converts it into muriatic and car- bonic acid gases. From its completely neutralizing ammo- nia, which carbonic acid does not; from its separating carbonic acid from the subcar- bonate of this alkali, while itself is not se- parable by the acid gases, or acetic acid; and its reddening vegetable blues, there can be no hesitation in pronouncing the chloro-carbonous compound to be an acid. Its saturating powers indeed surpass every other substance. None condenses so large a proportion of ammonia. One measure of alcohol condenses twelve of chloro-carbonous gas without decompos- ing it; and acquires the peculiar odour and power of affecting the eyes. To prepare the gas in a pure state, a good air pump is required, perfectly tight stop-cocks, dry gases, and dry vessels. Its specific gravity may be inferred from the specific gravity of its constituents, of which it is the sum. Hence 2.4733 -4- 0.9722 = 3.4455, is the specific gravity of chloro- carbonous gas; and 100 cubic inches weigh 105.15. grains. It appears that when hydro- gen, carbonic oxide, and chlorine, mixed in equal volumes, are exposed to light, muriatic and chloro-carbonous acids are formed, in equal proportions, indicating an equality of affinity. The paper in the Phil. Trans, for 1812, from which the preceding facts are taken, does honour to the school of Sir H. Davy. MM. Gay-Lussac and Thenard, as well as Dr. Murray, made controversial investiga- tions on the subject at the same time, but without success. .VI. Thenard has, however, recognized its distinct existence and pro- perties, by the name of carbo-mnriatic acid, in the 2d volume of his System, published in 1814, where he considers it as a com- pound of muriatic and carbonic acids, re- sulting from the mutual actions of the oxy- genated muriatic acid, and carbonic oxide.* * Chlorous and Chloric Oxides, or the protoxide and deutoxide of chlorine. Both of these interesting gaseous com- pounds were discovered by Sir H. Davy. 1st, The experiments which led him to the knowledge of the first, were instituted in consequence of the difference he had observed between the properties of chlo- rine, prepared in different modes. The pa- per describing the production and proper- ties of the chlorous oxide, was published in the first part of the Phil. Trans, for 1811. To prepare it, we put chlorate of potash into a small retort, and pour in twice as much muriatic acid as will cover it, diluted with an equal volume of water. By the ap- plication of a gentle heat, the gas is evolved. It must be collected over mercury. CHL CHL Its tint is much more lively, and more yellow than chlorine, and hence its illus- trious discoverer named it euchlorine. Its smell is peculiar, and approaches to that of burnt sugar. It is not respirable. It is soluble in water, to which it gives a lemon colour. Water absorbs 8 or 10 times its vo- lume of this gas. Its specific gravity is to that of common air nearly as 2.40 to 1; for 100 cubic inches weigh, according to Sir H. Davy, between 74 and 75 grains. If the compound gas result from 4 volumes of chlorine -\- 2 of oxygen, weighing 12.1154, which undergo a condensation of one-sixth, then the specific gravity comes out 2.423, in accordance with Sir H. Davy's expe- riments. He found that 50 measures deto- nated in a glass tube over pure mercury, lost their brilliant colour, and became 60 measures; of which 40 were chlorine, and 20 oxygen. Dr. Thomson states 2.407 for the sp. gr., though his own data, when rightly calculated upon, give 2.444. This gas must be collected and examined With much prudence, and in very small quantities. A gentle heat, even that of the hand, will cause its explosion, with such force as to burst thin glass. From this fa- cility of decomposition, it is not easy to ascertain tiie action of combustible bodies upon it. None of the metals that burn in chlorine act upon this gas at common tem- peratures; but when the oxygen is sepa- rated, they then inflame in the chlorine. This may be readily exhibited by first in- troducing into the protoxide a little Dutch foil, which will not be even tarnished; but on applying a heated glass tube to the gas in the neck of the bottle, decomposition instantly takes place, and the foil burns with brilliancy. When already in chemical union, therefore, chlorine has a stronger attraction for oxygen than for metals; but when insulated, its affinity for the latter is predominant. Protoxide of chlorine has no action on mercury, but chlorine is rapidly condensed by this metal into calomel. Thus the two gases may be completely separated. When phosphorus is introduced into the protoxide, it instantly burns, as it would do in a mixture of two volumes of chlorine and one of oxygen; and a chloride and acid of phosphorus result. Lighted taper and burning sulphur likewise instantly decom- pose it. When the protoxide freed from water is made to act on dry vegetable co- lours, it gradually destroys them, but first gives to the blues a tint of red; from which, from its absorbability by water, and the strongly acrid taste of the solution ap- proaching to sour, it may be considered as approximating to an acid in its nature. Since 2 volumes of chlorine weigh (2 X 2.4733) 4.9466, and 1 of oxygen 1.1111; we have 4.45 -f- 1. = 5.45 for the prime equi- valent of chlorous oxide, on tbe oxygen scale. The proportion by weight in 100 parts is 81.65 chlorine -f- 18.55 oxygen. 2d, Deutoxide of Chlorine, or Chloric Ox- ide. " On 'Thursday the 4th May, a paper by Sir H. Davy was read at the Royal So- ciety, on the action of acids on hyper-oxy- munate of potash. When sulphuric acid is poured upon this salt in a wine-glass, very little effervescence takes' place, but the acid gradually acquires an orange colour, and a dense yellow vapour, of a peculiar and not disagreeable smell, floats on the surface. 'These phenomena led the author to believe, that the substance extricated from the salt is held in solution by the acid. After various unsuccessful attempts to ob- tain this substance in a separate state, he at last succeeded by the following method: About 60 grains of the salt are triturated with a little sulphuric acid, just sufficient to convert them into a very solid paste. This is put into a retort, which is heated by means of hot water. The water must never be allowed to become boiling hot, for fear of explosion. The heat drives off the new gas, which may be received over mercury. This new gas has a much more intense colour than euchlorine. It does not act on mercury. Water absorbs more of it than of euchlorine. Its taste is astringent It destroys vegetable blues without red- dening them. W hen phosphorus is intro- duced into it, an explosion takes place. When heat is applied, the gas explodes with more violence, and producing more light than euchlorine. When thus exploded, two measures of it are converted into nearly three measures, which consist of a mixture of one measure chlorine, and two measures oxygen. Hence, it isfcomposed of one atom chlorine and four atoms oxygen." I have transcribed the above abstract of Sir H. Davy's paper from the number of Dr. Thomson's Annals for June 1815, in or- der to confront it with the following state- ment in his System, 5th edition, vol. i, page 189: " The deutoxide of chlorine was dis- covered about the same time by Sir Hum- phry Davy and Count Von Stadion of Vi- enna; but Davy's account of it was publish- ed sooner than that of Count Von Stadion. Davy's account is published in the Philoso- phical Transactions for 1815, p. 214. Count Von Stadion's in (.ilbert's Annalen der Phy- sick, 52. 179. published in February, 1816." Sir 11. Davy's paper bears date " Rome, February 15th, 1815." There is therefore an interval of fully twelve months between the transmission of Sir H. Davy's discovery for publication, and the promulgation of Count Von Stadion's paper; and an in- terval of nine months between the actual publication of the first, by the reading of it before the Royal Society of England, and the appearance of the second, in Gil- bert's Annalen. I do not wish to insinuate CHL CHR that the Count copied from the English philosopher; but I maintain, that according to every principle of literary justice, the reputation of the discovery entirely belongs to Sir H. Davy. Even the v olume of the Transactions for 1815, which one is left to infer might come forth only in 1816, must have been pub- lished earlier, for Tilloch's Magazine for December 1815, contains the whole of Sir H. Davy's paper. The preceding abstract, circulated over Europe seven or eight months before the 52d volume of Gilbert's Annalen appeared is so copious as to require few additions. Deutoxide of chlorine has a peculiar aro- matic odour, unmixed with any smell of chlorine. A little chlorine is always ab- sorbed by the mercury during the explo- sion ofthe gas. Hence the small deficiency of the resulting measure is accounted for. At common temperatures none of the sim- ple combustibles which Sir H Davy tried, decomposed the gas, except phosphorus. The taste ofthe aqueous solution is ex- tremely astringent and corroding, leaving for a long while a very disagreeable sensa- tion. The action of liquid nitric acid on the chlorate of potash affords the same gas, and a much larger quantity of this acid may be safely employed than of the sul- phuric. But as the gas must be procured by solution of the salt, it is always mixed with about one-fifth of oxygen. Since two measures of this gas, at 212°, explode and form three measures of min- gled gases, of which two are oxygen and one chlorine; its composition by weight is Oxygen, 2.2222 4 primes, 400 47.33 Chlorine, 2.4733 1 do. 4.45 52.67 8.45 100.00 Its specific gravity is 2.3477; and hence 100 cubic inches of it weigh about 77 grains. Having completed the account of this in- teresting compound, it may be worth while to copy a note from the 190th page of Dr. Thomson's 1st volume, to show the con- sistency of his opinions, in one leaf of his System. " According to Count Von Stadion, its constituents are two volumes chlorine, and three volumes oxygen. This would make it a compound of one atom chlorine, and three atoms oxygen. But the proper- ties of the substance described by the Count differ so much from those of the gas examined by Davy, that it is probable they are distinct substances." So that after all, Count Von Stadion has got a deutoxide of chlorine to himself, without interfering with Sir. H. Davy's property. We shall leave him to enjoy it, with the following intima- tion by his commentator:—" The reader will find an account of the properties ofthe deutoxide of chlorine of Count Von Stadion, in the Annals of Philosophy, vol. ix. p. 22." Chlorophile. The name lately given by MM. Pelletier and Caventou to the green matter of the leaves of plants. They obtained it, by pressing and then washing in water, the substance of many leaves, and afterwards treating it with alcohol. A mat- ter was dissolved, which when separated by evaporation, and purified by washing in hot water, appeared as a deep green resin- ous substance. It dissolves entirely in alco- hol, ether, oils, or akalis; it is not altered by exposure to air; it is softened by beat, but does not melt; it burns with flame, and leaves a bulky coal. Hot water slightly dis- solves it. Acetic acid is the only acid that dissolves it in great quantity. If an earthy or metallic salt be mixed with the alco- holic solution, and then alkali or alkaline subcarbonate be added, the oxide or earth is thrown down in combination with much of the green substance, forming a lake. These lakes appear moderately permanent when exposed to the air. It is supposed to be a peculiar proximate principle. The above learned term should be spel- led with a y, chlorophyle, to signify the green of leaf, or leaf-green: chlorophile, with an i, has a diff'erent etymology, and a diff'erent meaning. It signifies fond of green. Cholesterine. The name given by M. Chevreul to the pearly substance of human biliary calculi. It consists of 72 carbon, 6.66 oxygen, and 21.33 hydrogen, by Be- rard. CholestericAcid. Byheatingcholes- terine with its own weight of strong nitric acid until it ceases to give off nitrous gas, MM. Pelletier and Caventou obtained a yellow substance, which separated on cool- ing, and was scarcely soluble in water. When well washed, this is cholesteric acid. It is soluble in alcohol, and may be crystal- lized by evaporation. It is decomposed by a heat above that of boiling water, and gives products having oxygen, hydrogen, and charcoal, for their elements. It com- bines with bases, and forms salts. Those of soda, potash, and ammonia, are very solu- ble; the rest are nearly insoluble. * Chromium. This rare metal may be extracted either from the native chromate of lead or of iron. The latter being cheap- est and most abundant, is usually employ- ed. The brown chromate of iron is not acted upon by nitric acid, but most readily by ni- trate of potash, with the aid of a red heat. A chromate of potash, soluble in water, is thus formed. The iron oxide thrown out of combination may be removed from the residual part of the ore by a short diges- tion in dilute muriatic acid. A second fu- sion with ^th of nitre, will give rise to a new portion of chromate of patash. Having decomposed the whole of the ore, we satu- CHR rate the alkaline excess with nitric acid, evaporate and crystallize. The pure crys- tals dissolved in water, are to be added to a solution of neutral nitrate of mercury; whence by complex affinity, red chromate of mercury precipitates. Moderate ignition expels the mercury from the chromate, and the remaining chromic acid may be re- duced to the metallic state, by being ex- posed, in contact of the charcoal from su- gar, to a violent heat. Chromium thus procured, is a porous mass of agglutinated grains. It is very brit- tle, and of a grayish-white, intermediate between tin and steel. It is sometimes ob- tained in needleform crystals, which cross each other in all directions. Its sp. gravity is 5.9. It is susceptible of a feeble magnet- ism. It resists all the acids except nitro- muriatic, which, at a boiling heat, oxidizes it and forms a muriate. M. Thenard de- scribes only one oxide of chromium; but there are probably two, besides the acid already described. 1. The protoxide is green, infusible, in- decomposable by heat, reducible by voltaic electricity, and not acted on by oxygen or air. When heated to dull redness with the half of its weight of potassium or sodium, it forms a brown matter, which, cooled and exposed to the air, burns with flame, and is transformed into chromate of potash or soda, of a canary-yellow colour. It is this oxide which is obtained by calcining the chromate of mercury in a small earthen retort for about | of an hour. The beak of the retort is to be surrounded with a tube of wet linen, and plunged into water, to fa- cilitate the condensation of the mercury. The oxide, newly precipitated from acids, has a dark green colour, and is easily re- dissolved; but exposure to a dull red heat ignites it, and renders it denser, insoluble, and of a light green colour. This change arises solely from the closer aggregation of the particles, for the weight is not al- tered. 2. The deutoxide is procured by expos- ing the protonitrate to heat, till the fumes of nitrous gas cease to issue. A brilliant brown powder, insoluble in acids, and scarcely soluble in alkalis, remains. Mu- riatic acid digested on it, exhales chlorine, showing the increased proportion of oxy- gen in this oxide. 3. The tritoxide has been already descri- bed among the acids. It may be directly procured by adding nitrate of lead to the above nitrochromate of potash, and digest- ing the beautiful orange precipitate of chromate of lead with moderately strong muriatic acid, till its power of action be ex- hausted. The fluid produced is to be pass- ed through a filter, and a little oxide of silver, very gradually added, till the whole Vor, 1. CHR solution becomes of a deep red tint. This liquor, by slow evaporation, deposites small ruby-red crystals, which are the hydrated chromic acid. The prime equivalent of chromic acid deduced from the chromatea of barytes and lead by Berzelius, is 6.544, if we suppose them to be neutral salts. Ac- cording to this chemist, the acid contains double the oxygen that the green oxide does. But if these chromates be regarded as subsalts, then the acid prime would be 13 088, consisting of 6 oxygen -f- 7.088, metal; while the protoxide would consist of 3 oxygen-f-7 088 metal; and the deutox- ide, of an intermediate proportion.* * Chrysoberyl. Cymophane of Haiiy. This mineral is usually got in round pieces about the size of a pea, but it is found crys- tallized in eight-sided prisms, terminated by six-sided summits. Colour, asparagus green; lustre, vitreous; fracture, conchoi- dal; it is semi-transparent, and brittle, but scratches quartz and beryl. Sp. gr. 3.76. It is infusible before the blow-pipe. It has double refraction, and becomes electric by friction. Its primitive form is a rectangular parallelopiped. Its constituents, according to Klaproth, are 71 alumina, 18 silica, 6 lime, and 1£ oxide of iron. The summits of the prisms of chrysobe- ryl, are sometimes so cut into facettes, that the solid acquires 28 faces It is found at Brazil, Ceylon, Connecticut, and perhaps Nertschink in Siberia. This mineral has no- thing to do with the chrysoberyl of Pliny, which was probably a variety of beryl of a greenish-yellow colour.* Chrysocolla. The Greek name for borax. •Chrysolite. Peridot of Haiiy. Topaz of the ancients, while our topaz is their chrysolite. Chrysolite is the least hard of all the gems. It is scratched by quartz and the file. Its crystals are well formed com- pressed prisms, of eight sides at least, ter- minated by a wedged form or pyramidal summit, truncated at the apex. Its primi- tive form is a right prism, with a rectan- gular base. It has a strong double refrac- tion, which is observed in looking across one of the large sides of the summit, and the opposite face ofthe prism The lateral planes are longitudinally streaked. The co- lour is pistachio green, and other shades. External lustre splendent. Transparent; fracture, conchoidal. Scratches feldspar. Brittle. Sp. gr. 3.4. With borax, it fuses in- to a pale green glass. Its constituents are 39 silica, 43.5 magnesia, 19 of oxide of iron, according to Klaproth; but Vauquelin found 38, 50.5, and 9.5. Chrysolite comes from Egypt, where it is found in alluvial strata. It has also been found in Bohemia, and in the circle of Bunzlau.* •Chrysoprase. A variety of calcedony. 37 CHY CIX It is either of an apple or leek-green colour. Its fracture is even, waxy, sometimes a lit- tle splintery. 'Translucent, with scarcely any lustre. Softer than calcedony, and rather tough Sp. gr. 2 5. A strong heat whitens it. It consists of 96.16 silica, 0.08 alumina, 0.83 lime, 0.08 oxide of iron, and 1 oxide of nickel, to which it probably owes its co- lour. It has been found hitherto only at Kosemutz in Upper Silesia. The mountains which enclose it, are composed chiefly of serpentine, potstone, talc, snd other unctu- ous rocks that almost all contain magnesia. It is found in veins or interrupted beds in the midst of a green earth which contains nickel. It is used in jewellery * ■ C'husite. A mineral found by Saus- sure in the cavities of porphyries in the environs of Limbourg. It is yellowish or greenish and translucent; its fracture is sometimes perfectly smooth, and its lustre greasy; at other times it is granular. It is very brittle. It melts easily into a translucid enamel, enclosing air bubbles. It dissolves entirely and without effervescence in acids.* •Chyle. By the digestive process in the stomach of animals, the food is converted into a milky fluid, called chyme, which pass- ing into the intestines is mixed with pan- creatic juice and bile, and thereafter re- solved into chyle and feculent matter. The former is taken up by the lacteal absorbent vessels of the intestines, which coursing along the mesenteric web, terminate in the thoracic duct. This finally empties its con- tents into the vena cava. Chyle taken soon after the death of an animal, from the thoracic duct, resembles milk in appearance. It has no smell, but a slightly acido-saccharine taste; yet it blues reddened litmus paper, by its unsaturated alkali. Soon after it is drawn from the duct, it senarates by coagulation into a thicker and thinner matter. 1. The former, or curd, sterns intermediate between albumen and fibrin. Potash and soda dissolve it, with a slight exhalation of ammoria. Water of ammonia forms with it a reddish solution. Dilute sulphuric acid dissolves the coagu- lum,- and very weak nitric acid changes it into adipocere. By heat, it is converted in- to a charcoal of difficult incineration, which contains common salt and phosphate of lime, with minute traces of iron. 2. From the serous portion, heat, alcohol, and acids, precipitate a copious coagulum of albumen. If the alcohol be hot, a little matter analo- gous to the substance of brain is subse. quently deposited. By evaporation and cool- ing, Mr. Brande obtained crystals analo- gous to the sugar of milk. Dr. Marcet found the chyle of graminivorous animals thinner and darker, and less charged with albumen, than that of carnivorous. In the former, the weight of the fluid part to that of the coagulum was nearly 2 to 1; but a serous matter afterwards oozed out, which reduced the clot to a very small volume.• *• hyme. Dr. Marcet examined chyme from the stomach of a turkey. It was a ho- mogeneous, brownish opaque pulp, having the smell peculiar to poultry. It was nei- ther acid nor alkaline, and left one-fifth of solid matter by evaporation. It contained albumen. From the incineration of 1000 parts, 12 parts of charcoal resulted, in which iron, lime, and an alkaline muriate were distinguished. See Digestion.* Cimolite, or (imoli an Earth. The cimolia of Pliny, which was used both me- dicinally and for cleaning cloths by the ancients, and which has been confounded with fullers' earth and tobacco-pipe clay, has lately been brought from Argentiera, the ancient Cimolus by Mr. Hawkins, and examined by Klaproth. It is of a light grayish-white colour, ac- quiring superficially a reddish tint by ex- posure to the air; massive; of an earthy, uneven, more or less slaty fracture; opaque; when shaved with a knife, smooth and of a greasy lustre; tenacious, so as not without difficulty to be powdered or broken; and adhering pretty firmly to the tongue. Its specific gravity is 2- It is immediately pe- netrated by water, and developes itself into thin laminae of a curved slaty form. Tritu- rated with water it forms a pappy mass; and 100 grains will give three ounces of water the appearance and consistence of a thickish cream. If left to dry after being thus ground, it detaches itself in hard bands, somewhat flexible, and still more difficult to pulverize than before. It appeared on analysis to consist of si- lex 63, alumina 23, oxide of iron 1.25, wa- ter 12. Ground with water, and applied to silk and woollen, greased with oil of almonds, the oil was completely discharged by a slight washing in water, after the stuffs had been hung up a day to dry, without the least injury to the beauty of the colour. Mr. Klaproth considers it as superior to our best fullers' earth; and attributes its properties to the minutely divided state of the silex, and its intimate combination with the alu- mina. It is still used by the natives of Ar- gentiera for the same purposes as of old. According to Olivier the island of Argen- tiera is entirely volcanic, and the cimolian earth is produced by a slow and gradual decomposition ofthe porphyries, occasion- ed by subterranean fires. He adds, that he collected specimens of it in all the states through which it passes. * Cinchona. The quinquina and kinaof the French, is the bark of several species of cinchona, which grow in South America. Of this bark there are three varieties, the red, the yellow, and the pale. 1. The red is in large, easily pulverized CIN CLA pieces, which furnish a reddish-brown pow- der, having a bitter astringent taste. The watery infusion reddens vegetable blues, from some free citric acid. It contains also muriates of ammonia and lime. The bark contains extractive, resin, bitter principle, and tannin. 2. The yellow Peruvian bark, was first brought to this country about the year 1790; and it resembles pretty closely in composition, the red species, only it yields a good deal of kinate of lime in plates. 3 The pale cinchona is that generally em- ployed in medical practice, as a tonic and febrifuge. M. Vauquelin made infusions of all the varieties of cinchona he could pro- cure, using the same quantities ofthe barks and water, and leaving the powders infus- ed for the same time. He observed, 1. That certain infusions were precipitated abun- dantly by infusion of galls, by solution of glue, and tartar emetic. 2. That some were precipitated by glue, but not by the two other reagents; and 3. That others were, on the contrary, by nutgalls and tartar emetic, without being aff'ected by glue. 4. And that there were some which yielded no precipi- tate by nutgalls, tannin, or emetic tartar. The cinchonas that furnished the first infu- sion were of excellent quality; those that afforded the fourth were not febrifuge, while those that gave the second and third, were febrifuge, but in a smaller degree than the first. Uesides mucilage, kinate of lime, and woody fibre, he obtained in his analyses, a resinous substance, which ap- pears not to be identic in all the species of bark. It is very bitter; very soluble in alco- hol, in acids and alkalis; scarcely soluble in cold water, but more soluble in hot. It is this body which gives to infusions of cin- chona, the property of yielding precipitates by emetic tartar, galls, gelatin; and in it, the febrifuge virtue seems to reside. It is this substance in part, which falls down, on cooling decoctions of cinchona, and from concentrated infusions. A table of precipi- tations by glue, tannin, and tartar emetic, from infusions of diff'erent barks, has been given by M. Vauquelin; but as the particu- lar species are difficult to define, we shall not copy it* Cinchoniv, See the preceding article. Cinnabar. An ore of mercury, consist- ing of that metal united with sulphur. * Cinnamon Stone. The colours of this rare mineral are blood-red, and hya- cinth-red, passing into orange-yellow. It is found always in roundish pieces; lustre splendent; fracture imperfect conchoidal; fragments angular; transparent and semi- transparent; scratches quartz with difficul- ty; somewhat brittle; sp. gr. 3.53; fuses in- to a brownish-black enamel. Its constitu- ents are 38.8 silica, 21.2 alumina, 31.25 lime, and 6.5 oxide of iron. It is found in the sand of rivers, in Ceylon.* Cipolin. The cipolin from Rome is a green marble with white zones: it gives fire with steel, though difficultly. One hun- dred parts of it contain 67.8 of carbonate of lime; 25 of quartz; 8 of schistus; 0.2 of iron, beside the iron contained in the schis- tus. The cipolin from Autun, 83 part9 car- bonate of lime, 12 of green mica, and one of iron. •Cistic Oxide. A peculiar animal pro- duct, discovered by Dr. Wollaston. It con- stitutes a variety of urinary Calculus, which see.* * Citric Acid. Acid of limes. It has been found nearly unmixed, with other acids, not only in lemons, oranges and limes, but also in the berries of vavdnium oxycoccos, or cranberry, vaccmium vitis id9 0 42 .7.0 40.0 41.6 42.7 March, 35 36.7 .9 6 4 J.3 39.4 40.2 41.7 4'..'. 5 April, 39.7 38 4 41 4 43.8 45.0 42 4 42.6 42.6 May, 44.0 43.3 13.4 44 0 46.8 44.7 44.6 442 line, 51.6 5').u 47.1 45.8 51.1 49.4 47 6 47.8 .'ulv, .54.0 52.5 55 4 47.7 55.2 55.0 51.4 49.6 \ll'. USt, ,0.0 52 5 50.6 49 4 53.4 53.9 52.0 50.0 '■•| ember. -.1.6 51 3 ..1.8 50.0 53.0 52.7 52.0 50.7 October, 1-7 0 49.3 497 49.6 45.7 49.4 49.4 498 November, ■;.8 43.8 463 45.6 41.0 44 7 47.0 47.6 December, 35.7 40.O 43 0 46.0 37.9 40.8 44.9 46.4 Mean of 43.8 44.1 45.1 46. 44.9 45.9 46.2 46 6 whole year. Had the thermometers been sunk deep- er, they would undoubtedly have indicated 47.7, which is the mean temperature ofthe place, as is shown by a copious spring. The lake of Geneva, at the depth of 1000 feet, was found by Saussure to be 42°; and below 160 feet from the surface there is no monthly variation of temperature. The lake of Thun, at 370 of depth, and Lucerne at 640, had both a temperature of 41°, while the waters at the surface indicated respec- tively 64e and 68^° Fahr. Barlocci observ- ed, that the Lago Sabatino, near Rome, at the depth of 490 feet, was only 44£°, while the thermometer stood on its surface at 77°. Mr. Jardine has made accurate obser- vations on the temperatures of some ofthe Scottish lakes, by wltich it appears, that the temperature continues uniform all the year round, about 20 fathoms under the surface. In like manner, the mine of Dan- nemora in Sweden, which presents an im- mense excavation, 200 or 300 feet deep, was observed at a period when the work- ing was stopped, to have great blocks of ice lying at the bottom of it. The bottom of the main shaft of the silver mine of Kongsberg in Norway, about 300 feet deep, is covered with perpetual snow. Hence, likewise, in the deep crevices on iEtna and the Pyrenees, the snows are preserved all the year round. It is only, however, in such confined situations that the lower strata of air are thus permanently cold. In a free atmosphere, the gradation of temperature is reversed, or the upper regions are cold- er, in consequence ofthe increased capaci- ty for heat ofthe air, by the diminution of the density. In the milder climates, it will be sufficiently accurate, in moderate eleva- tions, to reckon an ascent of 540 feet for each centesimal degree, or 100 yards for each degree on Fahrenheit's scale, of di- minished temperature. Dr. Francis Bu- chanan found a spring at Chitlong, in the lesser valley of Nepal, in Upper India, which indicated the temperature of 14.7 centesimal degrees, which is 8.1° below the standard, for its parallel of latitude, 27° 38'. Whence, 8.1 X 540 = 4374 feet, is the elevation of that valley. At the height of a mile this rule would give about 33 feet too much. The decrements of tem- perature augment in an accelerated pro- gression as we ascend. Ben Nevis, the highest mountain in Great Britain, stands in latitude 57°, where the curve of congelation reaches to 4534 feet. But the altitude ofthe summit ofthe moun- tain is no more than 4J80 feet; and there- fore, during two or three weeks in July, the snow disappears. The curve of conge- lation must evidently rise higher in sum- mer, and sink lower in winter, producing a zone of fluctuating ice, in which the gla- ciers are formed. In calculating the mean temperature of countries at diff'erent distances from the equator, the warmth has been referred solely to the sun. But Mr. Bald has pub- lished, in the first number of the Edin- burgh Philosophical Journal, some facts apparently incompatible with the idea of the interior temperature of the earth being deducible from the latitude of the place, or the mean temperature at the surface. The following table presents, at one view, the temperature of air and water, in the deepest coal-mines in Great Britain. Whitehaven Colliery, county of Cumberland. Air at the surface, - - - 55° F. A spring at the surface, - - 49 Water at the depth of 480 feet, 60 Air at same depth, 63 Air at depth of 600 feet, - - 66 Difference between water at surface and at 480 feet, 11 Workington Colliery, county of Cumberland. Air at the surface, 56 A spring at the surface, 48 CLI CLI Water 180 feet down, - - 50° F. Water 504 feet under the level of the ocean, and immediately beneath the Irish sea, 60 Difference between water at surface and bottom, .... 12 Teem Colliery, county of Durham. Air at pit bottom, 444 feet deep, 68 Water at same depth, - - 61 Difference between the mean tempe- rature of water at surface = 49°, and 444 feet down, - - 12 Percy Main Colliery, county of Northum- berland. Air at the surface, 42 Water about 900 feet deeper than the level of the sea, and under the bed of the river Tyne, - - 68 Air at the same depth, 70 At this depth Leslie's hygrometer in- dicated dryness = 8o°. Difference between mean tempera- ture of water at surface = 49°, and at 900 feet down, - - 19 Jarrow Colliery, county of Durham. Air at surface, ... 49$ Water 882 feet down, - - 68 Air at same depth, 70 Air at pit bottom, 64 Difference between the mean tempe- rature of water at surface = 4y°, and 882 feet down, - - 19 The engine-pit of Jarrow is the deep- est perpendicular shaft in Great Britain, being 900 feet to the foot ofthe pumps. Killingworth Colliery, county of Northum- berland. Air at the surface, ... 48 Air at bottom of pit, 790 feet down, 51 Air at depth of 900 feet from the surface, after having traversed a mile and a half from the bottom of the downcast pit, - - 70 Water at the most distant forehead or mine, and at the great depth of 1200 feet from the surface, 74 Air at the same depth, - - 77 Difference betwixt the mean tempe- rature of the water at the surface = 49°, and water at the depth of 1200 feet, 25 Distilled water boils at this depth at 213 Do. do. at surface, - 210£ M. Humboldt has stated, that the tem- perature of the siher mine of Valenciana in New Spain is 11° above the mean tem- perature of Jamaica and Pondicherry, and that this temperature is not owing to the miners and their lights, but to local and geological causes. To tiie same local and geological causes we must ascribe the ex- traordinary elevation of temperature ob- served by Mr. Bald. He further remarks, that the deeper we descend, the drier we find the strata, so that the roads through the mines require to be watered, in order to prevent the horsedrivers from being an- noyed by the dust. This fact is adverse to the hypothesis of the heat proceeding from the chemical action of water on the strata of coal. As for the pyrites intermixed with these strata, it does not seem to be ever decomposed, while it is in situ. The per- petual circulation of air for the respiration of the miners, must prevent the lights from having any considerable influence on the temperature of the mines. The meteorological observations now made and published with so much accura- cy and regularity in various parts of the world, will soon, it is hoped, make us bet- ter acquainted with the various local causes which modify climates, than we can pre- tend to be at present. 'The accomplished philosophical traveller, VI. de Humboldt, published an admirable systematic view of the mean temperatures of different places, in the third volume ofthe Memoirs of the Society of Arcueil. His paper is entitled, of Isothermal Lines (lines of the same tem- perature), and the Distribution of Heat over the Globe. By comparing a great num- ber of observations made between 46° and 48° N. lat., he found, that at the hour of sun-set the temperature is very nearly the mean, of that at sun-rise and two hours af- ter noon. Upon the whole, however, he thinks, that the two observations of the extreme temperatures, will give us more correct results. The difference which we observe in cul- tivated plants, depends less upon mean tem- perature, than upon direct light, and the serenity ofthe atmosphere; but wheat will not ripen if the mean temperature descend to 47.6°. Europe may be regarded as the western part of a great continent, and subject to all those influences, which make the western sides of all continents warmer than the eas- tern. The same difference that we observe on the two sides of the Atlantic, exists on the two sides of the Pacific. In the north of China, the extremes of the seasons are much more felt than in the same latitudes in New California, and at the mouth ofthe Columbia. On the eastern side of North America, we have the same extremes as in China; New-York has the summer of Home, and the winter of Copenhagen; Quebec has the summer of Paris, and the winter of Petersburgh And in the same way in Pi-kin, which has the mean temperature of Britain; the heats of summer are greater than those at Cairo, and the cold of winter, as severe as that at Upsal. This analogy CLI CLI between the eastern coasts of Asia and of America, sufficiently proves, that the in- equalities of the seasons, depend upon the prolongation and enlargement of the conti- nents towards the pole, and upon the fre- quency of N. W. winds, and not upon the proximity of any elevated tracts of coun- try. Ireland, says Humboldt, presents one of the most remarkable examples of the com- bination of very mild winters with cold summers; the mean temperature in Hunga- ry for the month of August is 71.6°; while in Dublin it is only 60.8°. In Belgium and Scotland, the winters are milder than at Milan. In the article Climate, Supplement to the Encyclopaedia Britannica, the following ve- ry simple rule is given, for determining the change of temperature produced by sudden rarefaction or condensation of air. Multi- ply 25 by the difference between the density of air, and its reciprocal, the product will be the difference of temperature on the centigrade scale. Thus, if the density be twice, or one half 25° X (2—^) = 37l° cent. = 67.5° Pahr. indicates the change of temperature by doubling the density or rarity of air. Were it condensed 30 times, then, by this formula, we have 749° for the elevation of temperature, or 25° (30 — -$\). But M. Gay-Lussac says, that a condensation of air into one-fifth of its volume, is sufficient to ignite tinder; a degree of heat which he states at 300° centigrade = 572° Fahr. (Journal of Science, vol. vii. p. 177). This experimental result is incompatible with Professor Leslie's Formula, which gives only 112.5°, for the heat produced by a condensation into one-fifth. It appears very probable, that the cli- mates of European countries were more severe in ancient times than they are at present. Caesar says, that the vine could not be cultivated in Gaul, on account of its winter-cold. The rein-deer, now found on- ly in the zone of Lapland, was then an in- habitant of the Pyrenees. The Tiber was frequently frozen over, and the ground about Rome covered with snow for several weeks together, which almost never hap- pens in our times. The Rhine and the Dan- ube, in the reign of Augustus, were gene- rally frozen over, for several months of winter. The barbarians who overran the Roman empire a few centuries afterwards, transported their armies and wagons across the ice of these rivers. The improvement that is continually taking place in the cli- mate of America, proves, that the power of man extends to phenomena, which from the magnitude and variety of their causes, seemed entirely beyond his controul. At Guiana, in South America, within five de- grees of the line, the inhabitants living amid immense forests, a century ago, were obliged to alleviate the severity of the cold, by evening fires. Even the duration of the rainy season has been shortened by the clearing of the country, and the warmth is so increased, that a fire now would be deemed an annoyance. It thun- ders continually in the woods, rarely in the cultivated parts. Drainage of the ground, and removal of forests, however, cannot be reckoned among the sources ofthe increased warmth of the Italian winters. Chemical writers have omitted to notice an astronomical cause of the progressive amelioration of the climates of the northern hemisphere. In consequence of the apogee fportion of the terrestrial orbit being contained be- tween our vernal and autumnal equinox, our summer half of the year, or the interval which elapses between the sun's crossing the equator in spring, and in autumn, is about seven days longer than our winter half year. Hence also, one reason for the relative coldness of the southern hemis- phere.* Isothermal Bands, and Distribution of Heat over the Globe. The temperatures are expressed in de- grees of Fahrenheit's thermometer; the lon- gitudes are counted from east to west, from the first meridian of the observatory of Paris. The mean temperature of the sea- sons has been calculated, so that tbe months of December, January, and Feb- ruary, form the mean temperature of the winter. The mark * is prefixed to those places, the mean temperatures of which have been determined with the most pre- cision, generally by a mean of 8000 obser- vations. The isothermal curves having a concave summit in Europe, and two con- vex summits in Asia and Eastern America, the climate is denoted to which the indivi- dual places belong:— CLI 5 a J S •a § I S H 1 5 S — °° C "a ^ o !I o CN p O HK^ilOWO i ** © w» cn k -^ 06 oi >oo"-*covd CN CN i-S CN CO CN CO CO COdCOCNCNcOCOCOCOCN O J0 O »h fj >o o 1 VJ «0 ■* V)iO 5 ~ S 'too © (N oq oq p •* -* oq odrr «o co n! ■* c4 ■-< si -« CN CO O «0 •* OCOOOiOSOIMO'i'lOIOOHa © -^ oo cn oo cn vd co oov -* * co cri co oi o ivl oi ifllOlOiO <0 <0<0'010<0<0 -5 o iv. p ■* * :n m cm cn p co r«j vj vd Oi hi CO CO" v: Tj< 20 o»NloiKoi« TfCOCO'* •<* '*'*-sl''si<'^'-vf,Nt irj t* CO 0(3 ©vOOi^OC^cdlC'NoiCNTfCOeM CN CN i-l CN CN COCOCOCOCOCNCOCNCOCOCOCOCOCO Mean temp, of the year. O MO ■"*• OONOOOIN'* ••o »C o ri ci ri »' d d d CM otj!tj! CO »H »-l rH »-< -Si o ^ H a ac ;- s: a a a a OK. CO OOi03>CNflW ■<* CM CO *0 "O r- >1 CO 30 <0 CO co Iv. h. 00 "O Ci vO i-i OOH00000(N — 't CO -N —< i- i-l CO >"" CO Tj< ^ CO ■* 1OW1C0 00 00 O")CNiMb.«O<000tv.00«0e0<0'%f B k3 SO O SD CO © (O •# «n N-CO co WJ Vj CN ^ CN (v. 30 «D H V) « Oi ") «5 3 'Q vO tP K (O lO "O iO ") O —«ON.'0 Iv. rtK.'OiOCKNlvT'OHVKMOlN 'Off<'v1«>0 -vf" ■vTi-iCN C0CN»O-^v>CN HC0-ti»O ^* >O'0>O'0«O-*l<5»0'vf<'O'vl<^i^»Tjl s,» «j -3 r Nam, ... •Enontekies, Hospice de St. ") Gothard, 3 North Cape, -•Ulea, - - -'Umea, ... •Petersburg, Drontheim, Moscow, - - •Upsal, - - -•Stockholm, - -Quebec, - - -Christiana, - -•Convent of Pey-") senburg, 3 •Copenhagen, -* Kendal, - - -Malouin Islands, •Prague, - - -Gottingen, - -•Zurich, ... •Edinburgh,- -Warsaw, - -•Coire, ... Dublin, - - -Berne, - - -•Geneva,... •Manheim, - -Vienna, ... Isothermal bands. •0I* oj 0S£ uio.li 'pueq reujoqjosi 'oOS oi 0ifr uiojj «pmjq reuuairiosi Vol. I. CLI CLI p p 00 © CO 00 ■* p Oi N. ■* CN| OCi © ■* CN © 30 K, oi vd n! k vJ *d CN CN »d C> r* oo' Oi vd i-< ^CNCNCOCOCOCOCOcocoCNCO-vfcococOTr' ■* © CN ■* ■* © ■* cn cn -<©©'-<»-0»0»OV5»0»0 © © p -* cn p O -* CN -vf* -* >d VO VO VO VO VO VO CN CN b-b. »o p © p © oo Oi Oi b- tv, tv.lv. ■* CN ■* p CN p 00 CN CN 0 CN 00 © VO VO © 00 ■* co -# •* co' CO «■> vd tvl ■* Oi" CN vd oo" CN co o' VOVOVOvOVOVOVOVOVOtv.tv,h.vOvO00tv,f- «C CO CN p O CN CN vi vj -* co oi tv. h- tv. tv. 00 tv. V5 CN CN ©" b. 00 HKIMO V} -• CO CN oo oo oo oo 'OOvOCNvOppCNprJJCN-vJ'CN'flCO^OO di-ii^oio6oo^cor4-HTJ'*cN'*tdOiO»0*0»0*0«0«5>0>0«0 p © « p p rj Nl tvl |vl O tvl V> •O »o «1 VO «1 VO oo vo >d vj VO VO iqoiqvo co bl oi co tv. N. tv. CO (v.o©v0v0"*00v0v0CNC00iCN^}i00'>*O ■* y-1 -«ji 00 oi M vd vd vO CN oi CN CN o' vd vO CN CO CO CO CO CO CO CO CO CO CO CN CO ■» * CN CO •* >o © p ■* ■* to id tj> «S ed oi oo ■*•<*** •vf CO ■* 00 ■* T» -H VO VO ■* O CN CN 00 CN -^ C5 <0 b-b.00 ©O'*p-vfv0ppP'<*00p'vI»pCNp'<(i dHdHddHHHciMcixii'iiiovjib 0"iOlOONON(NlOOOOHMNi-i'* ^r -v}" CN CN CO CO i-l e* »0 «0 'O OvOCO©CNOCNCN-v}Otv.CN00^»-ieN©CNC7>©Oi00tv.Oi>O'vii TJCV5»O>OC0'vI'C01v1<-*C0'vim?q pjuxraqiosi 1 'oil oi '•" °l D89 u»ojj 96ciuojiput;q[ pUT!q „m puiaaqjos! .a;)qj0SI ■0ll OAoqn spunqreui -Jaqiosj CLO CLO • Clinkstone. A stone of an imper- fectly slaty structure, which rings like me- tal when struck with a hammer. Its co- lour is gray of various shades; it is brittle; as hard as feldspar, and translucent on the edge s. It occurs in columnar and tabular concretions. Sp. gr. 2.57. Fuses easily in- to a nearly colourless glass. Its consti- tuents are 57.25 silica, 25.5 alumina, 2.75 lime, 8.1 soda, 3.25 oxide of iron, 0.25 oxide of manganese, and 3 of water.— Klaproth. This stone generally rests on basalt. It occurs in the Ochil and Pent- land hills, the Bass-rock, the islands of Mull, Lamlash, and Islay, in Scotland; the Breidden hills in Montgomeryshire, and in the Devis Mountain, in the county of An- trim. It is found in Upper Lusace and Bo- hemia.* • Clinometer. An instrument for measuring the dip of mineral strata. It was originally invented by R. Griffith, Esq. Professor of Geology to the Dublin Society, and subsequently modified by Mr. Jardine and Lord Webb Seymour. See a descrip- tion and drawing by the latter, in the third volume of the Geological Transactions. Lord Webb's instrument was a very per- fect one. It was made by that unrivalled artist, Mr. Troughton.* • Cloud. A mass of vapour, more or less opaque, formed and sustained at con- siderable heights in the atmosphere, pro- bably by the joint agencies of heat and electricity. The first successful attempt to arrange the diversified forms of clouds, under a few general modifications, was made by Luke Howard, Esq. We shall give here a brief account of his ingenious classification. The simple modifications are thus named and defined. 1. Cirrus. Parallel, flexu- ous, or diverging fibres, extensible in any or in all directions. 2. Cumulus. Convex or conical heaps, increasing upwards from a horizontal base. 3. Stratus. A widely extended, continuous horizontal sheet, in- creasing from below. The intermediate modifications which require to be noticed are, 4. Cirro-cumulus. Small well-defined roundish masses, in close horizontal arrangement. 5. Cirro- stratus. Horizontal, or slightly inclined masses, attenuated towards a part or the whole of their circumference, bent down- ward, or undulated, separate or in groups, consisting of small clouds having these characters. The compound modifications are, 6. Cu- mulo-stratus. The cirro-stratus, blended with the cumulus, and either appearing in- termixed with the heaps of the latter, or superadding a widespread structure to its base. 7. Cumulo-cirro-stratus, vol Nimbus. The rain cloud. A cloud or system of clouds from which rain is falling. It is a hori- zontal sheet, above which the cirrus spreads, while the cumulus enters it la- terally and from beneath. The cirrus appears to have the least density, the greatest elevation, the great- est variety of extent and direction, and to appear earliest on serene weather, being indicated by a few threads pencilled on the sky. Before storms they appear lower and denser, and usually in the quarter oppo- site to that from which the storm arises. Steady high winds are also preceded and attended by cirrus streaks, running quite across the sky in the direction they blow in. The cumulus has the densest structure, is formed in the lower atmosphere, and moves along with the current next the earth. A small irregular spot first appears and is as it were the nucleus on which they increase. The lower surface continues ir- regularly plane, while the upper rises into conical or hemispherical heaps; which may afterwards continue long nearly ofthe same bulk, or rapidly rise into mountains. They will begin, in fair weather, to form some hours after sunrise, arrive at their max- imum in the hottest part of the afternoon, then go on diminishing and totally dis- perse about sunset. Previous to rain, the cumulus increases rapidly, appears lower in the atmosphere, and with its surface full of loose fleeces or protuberances. The formation of large cumuli to leeward in a strong wind, indicates the approach of a calm with rain. When they do not disap- pear or subside about sunset but continue to rise, thunder is to be expected in the night. The stratus has a mean degree of density, and is the lowest of clouds, its in- ferior surface commonly resting on the earth or water. This is properly the cloud of night, appearing about sunset. It com- prehends all those creeping mists which in calm weather ascend in spreading sheets (like an inundation of water), from the bottom of valleys, and the surfaces of lakes and rivers. On the return of the sun, the level surface of this cloud begins to put on appearance of cumulus, the whole at the same time separating from the ground. The continuity is next destroyed, and the cloud ascends and evaporates, or passes ofF with the appearance of the nascent cu- mulus. This has long been experienced as a prognostic of fair weather. The cirrus having continued for some time increasing or stationary, usually passes either to the cirro-cumulus or the cirro-stratus, at the same time descending to a lower station in the atmosphere This modification forms a very beautiful sky; is frequent in summer, an attendant on warm and dry weather. The cirro-stratus, when seen in the distance, frequently gives the COA COA idea of shoals of fish. It precedes wind and rain; is seen in the intervals of storms; and sometimes alternates with the cirro- cumulus in the same cloud, when tbe dif- ferent evolutions form a curious spectacle. A judgment may be formed of the weather likely to ensue by observing which modifi- cation prevails at last. The solar and lu- nar halos, as well as the parhelion and paraselene, (mock sun and mock moon), prognostics of foul weather, are occasioned by this cloud. The cumulo-stratus pre- cedes, and the nimbus accompanies rain. See Rain. Mr. Howard gives a view of the origin of clouds, which will be found, accompa- nied with many useful remarks, in the 16lh and 17th volumes ofthe Fhilos. Magazine.* Clyssus. A word formerly used to de- note the vapour produced by the detona- tion of nitre with any inflammable sub- stance. Coak. Coal is charred in the same man- ner as wood to convert it into charcoal. An oblong square hearth is prepared by beat- ing the earth to a firm flat surface, and puddling it over with clay. On this, the pieces of coal are piled up, inclining to- ward one another, and those of the lower strata are set up on their acutest angle, so as to touch the ground with the least surface possible. The piles are usually from 30 to 50 inches high, from 9 to 16 feet broad, and contain from 40 to 100 tons of coal. A number of vents are left, reaching from top to bottom, into which the burning fuel is thrown, and they are then immediately closed with small pieces of coal beaten hard in. Thus the kindled fire is forced to creep along the bottom, and when that of all the vents is united, it rises gradually, and bursts out on every side at once. If the coal contain pyrites, the combustion is allowed to continue a considerable time after the disappearance ofthe smoke, to extricate the sulphur, part of which will be found in flowers on the surface: If it contain none, the fire is cover- ed up soon after the smoke disappears, be- ginning at the bottom, and proceeding gra- dually to the top. In 50, 60, or 70 hours, the fire is in general completely covered with the ashes of char formerly made, and in 12 or 14 days the coak may be removed for use. In this way a ton of coals com- monly produces from 700 to 1100 pounds of coak. In this way the volatile products of the coal, however, which might be turned to good account, are lost: but some years ago, Lord Dunclonald conceived and car- ried into effect, a plan for saving them. By burning the coal in a range of 18 or 20 stoves, with as little access of air as may be, at the bottom; and conducting the smoke, through proper horizontal tunnels, to a capacious close tunnel 100 yards or more in length, built of brick, supported on brick arches, and covered on the top by a shallow pond of water; the bitumen is condensed in the form of tar: 120 tons of coal yield about 3$ of tar, though some coals are said to be so bituminous as to afford l-8th of their weight. Part of the tar is inspissated into pitch, 21 barrels of which are made of 28 of tar; and the vola- tile parts arising in this process are con- densed into a varnish, used for mixing with colours for out-door painting chiefly. A quantity of ammonia too is collected, and used for making sal ammoniac. The cakes thus made are likewise of superior quality. •Coal. This very important order of combustible minerals, is divided by Pro- fessor Jameson into the following speoies and sub-species: Species 1. Brown coal, already described. Species 2. Black coal, of which there are four sub-species, slate coal, cannel coal, foliated coal, and coarse coal. 1. Slate coal. Its colour is intermediate between velvet-black, and dark grayish- black. It has sometimes a peacock-tail tarnish. It occurs massive, and in colum- nar and egg-shaped concretions. It has a resinous lustre. Principal fracture slaty; cross fracture, imperfect conchoidal. Hard- er than gypsum, but softer than calcareous spar. Brittle. Sp. gr. 1.26 to 1.38 It buri\s longer than cannel coal; cakes more or less, and leaves a slag. The constitu- ents of the slate coal of Whitehaven, by Kirwan, are 56.8 carbon, with 43.2 mixture of asphalt and maltha, in which the former predominates. This coal is found in vast quantities at Newcastle; in the coal for- mation which stretches from Bolton, by Allonby and Workington, to Whitehaven. In Scotland, in the river district of Forth and Clyde; at Cannoby, Sanquhar, and Kir- connel, in Dumfries-shire; in Thuringia, Saxony, and many other countries of Ger- many. It sometimes passes into cannel and foliated coal. 2. Cannel coal. Colour between velvet and grayish-black. Massive. Resinous lus- tre. Fracture, flat-conchoidal, or even. Fragments trapezoidal. Hardness as in the preceding sub-species. Brittle. Sp. gr. 1.23 to 1.27. It occurs along with the preceding. It is found near Whitehaven, at Wigan, in Lancashire, Brosely, in Shrop- shire, near Sheffield; in Scotland, at Gil- merton and Muirkirk, where it is called parret-coal. It has been worked on the lathe into drinking vessels, snuff-boxes, &c. 3. Foliated coal. Its colour is velvet- black, sometimes with iridescent tarnish. Massive, and in lamellar concretions. Re- sinous or splendent lustre; uneven fracture, fragments approaching to trapezoidal. Soft- COA COA er than cannel coal; between brittle and sectile. Easily broken. Sp. gr. 1.34 to 1.4. The Whitehaven variety consists, by Kir- wan, of 57 carbon, 41.3 bitumen; and 1.7 ashes. It occurs in the coal formations of this and other countries. It is distinguish- ed by its lamellar concretions, splendent lustre, and easy frangibility. 4. Coarse coal. Colour dark, grayish- black, inclining to brownish-black. Mas- sive, and in granular concretions. Glisten ing lustre. F'racture imperfect scaly. Frag- ments indeterminate angular. Hardness as above. Easily frangible. Sp. gr. 1.454. It occurs in the German coal formations. To the above, Professor Jameson has ad- ded soot-coal; which has a dark grayish- black colour; is massive; with a dull semi- metallic lustre. Fracture uneven; some- times earthy. Shining streak; soils; is soft, light, and easily frangible. It burns with a bituminous smell, cakes, and leaves a small quantity of ashes. It occurs along with slate-coal in West-Lothian and the Forth district; in Saxony and Silesia. Species 3d. Glance-coal, of which the Professor gives two sub-species, pitch-coal, and glance-coal. 1. Pitch-coal. Colour vel- vet-black. Massive, or in plates and bo- trioidal branches, with a woody texture. Splendent and resinous. Fracture, large perfect conchoidal. Fragments sharp-edged and indeterminate angular; opaque; soft; streak brown coloured. Brittle Does not soil. Sp. gr. 1.3. It burns with a greenish flame. It occurs along with brown coal in beds, in floetz, trap, and limestone rocks, and in bituminous shale. It is found in the Isles of Sky and Faroe; in Hessia, Bavaria, Bohemia, and Stiria. It is used for fuel, and for making vessels and snuff-boxes. It is called black amber in Prussia, and is cut into rosaries and necklaces. It is dis- tinguished by its splendent lustre and con- choidal fracture. It was formerly called jet, from the river Gaga in Lesser Asia. 2. Glance-coal,- of which we have four kinds, conchoidal, slaty, columnar, and fi- brous. The conchoidal has an iron-black colour, inclining to brown, with sometimes a tempered steel-varnish. Massive and ve- sicular. Splendent, shining and imperfect metallic lustre. Fracture flat-conchoidal; fragments sharp-edged. Hardness as above. Brittle, and easily frangible. In thin pieces, it yields a ringing sound. It burns without flame or smell, and leaves a white coloured ash. Its constituents are 96.66 inflamma- ble matter, 2 alumina, and 1.38 silica and iron. It occurs in beds in clay-slate, gray- wacke, and alum-slate; but it is more abun- dant in secondary rocks, as in coal and trap formations. It occurs in beds in the coal formations of Ayrshire, near Cumnock and Kilmarnock; in the coal district of the Forth; and in Staffordshire. It appears to pass into slaty glance-coal. Slaty glance-coal Colour iron-black. Massive. Lustre shining, and imperfect metallic. Principal fracture slaty; coarse fracture impeitect conchoidal. Fragments trapezoidal. Softer than conchoidal glance- coal. Easily frangible; between sectile and •brittle. Sp. gr. 1.50. It burns without flame or odour. It consists, by Dolomieu, of 72.05 carbon, 13.19 silica, 3.29 alumina, 3.47 oxide of iron, and 8 loss. It occurs in beds or veins in different rocks. In Spain, in gneiss; in Switzerland, in mica-slate and clay-slate; in the trap rock of the Calton- hill, Edinburgh; in the coal formations of the Forth district. It is found also in the floetz districts of Westcraigs, in West Lo- thian, Dunfermline, Cumnock, Kilmarnock, and Anan; in Brecknock, Caermarthen- shire, and Pembrokeshire, in England; and at Kilkenny, Ireland; and abundantly in the United States. In this country it is called blind coal Columnar glance-coal. Colour velvet-black and grayish-black. Massive, disseminated, and in prismatic concretions. Lustre glistening, and imperfect metallic. Frac- ture conchoidal. Fragments sharp-edged. Opaque. Brittle. Sp. gr. 1.'4. It burns without flame or smoke. It forms a bed several feet thick in the coal-field of San- quhar, in Dumfries-shire; at Saltcoats, in Ayrshire, it occurs in beds and in green- stone; in basaltic columnar rows near Cum- nock, in Ayrshire. Fibrous coal. Colour dark grayish-black. Massive, in thin layers, and in fibrous con- cretions. Lustre glimmering, or pearly. It soils strongly. It is soft, passing into friable. It burns without flame; but some varieties scarcely yield to the most intense heat. It is met with in the different coal- fields of Great Britain. Its fibrous concre- tions and silky lustre distinguish it from all the other kinds of coal. It is not certain that this mineral is wood mineralized. Several ofthe varieties may be original carbonaceous matter, crys- tallized in fibrous concretions.—Jameson. Parts. Charcoal. Earth. 100 Kilkenny coal contain 97.3 3.7 Anthracite, - 90.0 10.0 Ditto, - - 72.0 20.0 Ditto, - - 97.25 2.7 Coal of Notre Dame de Vaux, 78.5 20 The following table exhibits the results of Mr. Mushet's experiments on the car- bonization and incineration of coals: COA COA Volatile Char- Ashes. Sp- gr. Sp. gr. of matter. coal. of coal. coak. Welsh furnace coal, .... 8.50 88.068 3.432 1.337 1. 45.50 52.456 2.044 1.235 less than 1. 42.83 52.882 4.288 1.264 1.1 8.00 89.700 2. <00 1.368 1.39 Welsh slaty do. - - - - 9.10 8-1.175 6.725 1.409 Derbyshire cannel do. . - - 47.00 48.362 4.638 1.278 425 92.877 2.373 1.602 1.657 Stone-coal found under basalt, 16.66 69.74 13.600 Kilkenny slaty coal, ... 13.00 80.475 6525 1.445 Scotch cannel-coal, .... 56.57 39.430 4.000 Bonlarooneen do. ' ~) ' 13.80 82.960 3.240 1.436 1.596 Corgee coal, - - - > Irish. 9.10 87.491 3.409 1.403 1.656 Queen's County, No. 39. j 10.30 86.560 3.140 1.403 1.622 Stone-wood, Giant's Causeway, 33 37 54.697 11933 1 150 80.00 19.500 0.500 It was remarked long ago by Macquer, that nitre detonates with no oily or in- flammable matter, until such matter is reduced to coal, and then only in propor- tion to the carbonaceous matter it contains. Hence it occurred to Mr. Kirwan, that as coals appear in distillation to be for the most part merely compounds of carbon and bitumen, it should follow, that by the de- composition of nitre, the quantity of car- bon in a given quantity of every species of coal may be discovered, and the pro- portion of bitumen inferred. This cele- brated chemist accordingly projected on a certain portion of nitre in a state of fu- sion, successive fragments of various kinds of coal, till the deflagration ceased. Coal, when in fine powder, was thrown out of the crucible. The experiments seem to have been judiciously performed, and the results are therefore entitled to as much confidence as the method permits. Lavoi- sier and Kirwan state, that about 13 parts of dry wood-charcoal decompose 100 of nitre. 100 parts. Charcoal. Bitumen. Earth. Sp. gr. Kilkenny coal, 97 3 0 3.7 1.526 Comp.cannel, 75.2 21 68 maltha 3.1 1.232 Swansey, 73.53 23.14 mixt. 3.33 1.357 Leitrim, 71.43 23.37 do. 5.20 1.351 Wigan, 61.73 36.7 do. 1 57 1 268 Newcastle, 58.00 40.0 do. — 1.271 Whitehaven 57-0 41.3 1.7 1.257 Slaty-cannel, 47.62 32.52 mal. 20.0 1.426 Asphalt, 31.0 68.0 bitumen —1.117 Maltha, 8.0 _ 2.07 100 parts of the best English coal give, of coak, - - 63. by Mr. Jars. 100 do. - - 73. Hielm. 100 do. Newcastle do. 58. Dr. Watson. Mr. Kirwan says he copied the result, for Newcastle coal, from Dr. Watson. The foliated or cubical coal, and slate coal, are chiefly used as fuel in private houses; the caking coals, f >r smithy forges; the slate coal, from its keeping open, an- swers best for giving great heats in a wind furnace, as in distillation on the great scale; and glance coal is used for drying grain and malt. The coals of South Wales contain less volatile matter than either the English or the Scotch; and hence, in equal weight, produce a double quantity of cast iron in smelting the ores of this metal. It is supposed that 3 parts of good Newcas- tle coals, are equivalent as fuel to 4 parts of good Scotch coals. Werner has ascertained three distinct coal formations, without including the beds of coal found in sandstone and limestone formations. The first or oldest formation, he calls the independent coal formation, because the individual depositions of which it is composed, are independent of each other, and are not connected. The second is that which occurs in the newest floetz- trap formation; and the third occurs in al- luvial land. Werner observes, that a fourth formation might be added, which would comprehend peat and other similar sub- stances; so that we would have a beautiful and uninterrupted series, from the oldest formation to the peat, which is daily form- ing under the eye. The independent formation contains ex- clusively coarse coal, foliated coal, cannel coal, slate coal, a kind of pitch coal, and slaty glance coal. The latter was first found in this formation in Arran, Dum- fries-shire, Ayrshire, and at Westcraigs, by Professor Jameson. The formation in the newest floetz-trap contains distinct pitch coal, columnar coal, and conchoidal glance coal. The alluvial formation con- tains almost exclusively earth coal and bituminous wood. The first formation be- sides coal, contains three rocks which are peculiar to it; these are a conglomerate, which is more or less coarse-grained; a friable sandstone, which is always mica- ceous; and lastly, slate-clay. But besides these, there occur also beds of harder sand- COA COA stone, marl, limestone, porphyrinic stone, bituminous shale, clay-ironstone; and as dis- covered by Professor Jameson, greenstone, amygdaloid, and graphite. The slate-clay is well characterized, by the great variety of vegetable impressions of such plants as flourish in marshes and woods. The smaller plants and reeds occur in casts or impressions always laid in the direction of the strata; but the larger arborescent plants often stand erect, and their stems are fil- led with the substance ofthe superincum- bent strata, which seems to show that these stems are in their original position. The leaves and stems resemble those of palms and ferns. The central, northern and western coal mines of England; the river coal districts of the Forth and the Clyde, and the Ayrshire, and in part the Dum- fries-shire coals, belong to this formation, as well as the coals in the northern and western parts of France. By far the most valuable and extensive beds of coal which have been found and wrought, are in Great Britain. The gene- ral form of our great independent coal- beds, is semi-circular, or semi-elliptical, being the segment of a great basin. The strata have a dip or declination to the horizon of from 1 in 5, to 1 in 20. They are rarely vertical, and seldom perfectly horizontal to any considerable extent. Slips and dislocations of the strata, how- ever, derange more or less the general form of the basin. Those who wish to understand the most improved modes of working coal mines, will be amply gratified by consulting, A Report on the Leinster Coal District, by Richard Griffith, Esq. Professor of Ge- ology, and Mining Engineer to the Dublin Society. The author has given a most lu- minous view of Mr. Buddie's ingenious system of working and ventilating, in which from 7-8ths to 9-10ths of the whole coal may be raised; instead of only $, which was the proportion obtained in the former modes. Mr. Griffith has since published some other reports, the whole constituting an invaluable body of mining information • • Coal Gas. When coal is subjected in close vessels to a red heat, it gives out a vast quantity of gas, which being col- lected and purified, is capable of affording a beautiful and steady light, in its slow combustion through small orifices. Dr. Clayton seems to have been the first who performed this experiment, with the view of artificial illumination, though its appli- cation to economical purposes was unac- countably neglected for about 60 years. At length Mr. Murdoch of the Soho Foundry, instituted a series of judicious experiments on the extraction of gas from ignited coal; and succeeded in establishing one of the most capital improvements which the arts of life have ever derived from philosophical research and sagacity. In the year 1798, Mr. Murdoch, after se- veral trials on a small scale five years be- fore, constructed at the Foundry of Messrs. Bolton and Watt, an apparatus upon a large scale, w hich during many successive nights was applied to the lighting of their prin- cipal building; and various new methods were practised of washing and purifying the gas. In the year 1805, the cotton mill of Messrs. Philips and Lee, reckoned the most extensive in the kingdom, was partly lighted by gas under Mr. Murdoch's di- rection; and the light was soon extended over the whole manufactory. In the same year, I lighted up the large lecture-room of Anderson's Institution with coal-gas, generated in the laboratory; and continued the illumination every evening through that and the succeeding winter. Hence I was induced to pay particular attention to the theory and practice of its production and use. If coal be put into a cold retort, and slowly exposed to heat, its bitumen is merely volatilized in the state of conden- sible tar. Little gas, and that of inferior illuminating power, is produced. This dis- tillatory temperature may be estimated at about 600° to 700° F. If the retort be previously brought to a bright cherry-red heat, then the coals, the instant after their introduction, yield a copious supply of good gas, and a moderate quantity of tarry and ammoniacal vapour. But when the re- tort is heated to nearly a white incandes- cence, the part ofthe gas richest in light, is attenuated into one of inferior quality, as I have shown in detailing Berthollet's experiments on Carburetted Hydro- gen. A pound of good cannel coal, pro- perly treated in a small apparatus, will yield five cubic feet of gas, equivalent in illuminating power to a mould candle, six in the pound See Candle. On the great scale, however, 3$ cubic feet of good gas are all that should be ex- pected from 1 pound of coal. A gas jet, which consumes half a cubic foot per hour, affords a steady light equal to that of the above candle. According to Mr. Murdoch's statement, presented to the Koyal Society, 2500 cu- bic feet of gas were generated in Mr. Lee's retort from 7 cwt.=784 lbs. of cannel coal. This is nearly 3j cubic feet for every pound of coal, and indicates judicious management. The price of the best Wi- gan cannel is 13^d. per cwt. (22*. 6d. per ton) delivered at Mr. Lee's mill at Man- chester; or about 8s. for the seven hundred weight. About 4 ofthe above quantity of of good common coal at 10s. per ton, is required for fuel to heat the retorts. Near- COA COA ly -| of the weight of the coal remains in the retort in the form of coak, which is sold on the spot at 1*. 4d. per cwt. The quantity of tar produced from each ton of cannel coal, is from 11 to 12 ale gallons. The economical statement for one year is given by Mr Murdoch thus: Cost of 110 tons of cannel coal, J.125 Ditto of 40 tons of common ditto, 20 145 Deduct the value of 70 tons of coak, 93 The annual expenditure in coal, with- out allowing any thing for tar, is 52 And the interest of capital, and wear and tear of apparatus, - - 350 Making the total annual expense of gas apparatus about - - 600 That of candles to give the same light, 2000 If the comparison had been made upon an average of three hours per day, instead of two hours, (all the year round), then the cost from gas would be only - - - 650 Ditto candles, .... 3000 The peculiar softness and clearness of this light, with its almost unvarying inten- sity, soon brought it into great favour with the work-people. And its being free from the inconvenience and danger, resulting from the sparks and frequ«nt snuffing of candles, is a circumstance of material im- portance, tending to diminish the hazard of fire, and lessening the high insurance premium on cotton-mills. The cost of the attendance upon candles would be fully more than upon the gas apparatus; and upon lamps greatly more, in such an es- tablishment as Mr. Lee's. The preceding statements are of standard authority, far above the suspicion of empiricism or ex- aggeration, from which many subsequent statements by gas-book compilers are by no means exempt. At the same manufactory, Dr. Henry has lately made some useful experiments on the quality of the gas disengaged from the same retort at different periods of the de- composition. I have united in the follow- ing table, the chief part of his results. He collected in a bladder the gas, as it issued from an orifice in the pipe, between the retorts and the tar pit; and purified it af- terwards by agitation in contact of quick- lime and water. Ten cwt. or 1120 lbs. of coal were contained in the retorts. 100 measures 100 measures of 1 100 measures 100 combustible of impure gas purified gas of purified gas, exclusive from com-mencement. contain, contain, gas of azote, Su'ph. hydr. Carb. Other Con- Give Take Carb. V n c u acid. Olef 16 mfi. gases. Azote 20 sume oxyg. car. ac. oxygen acid. i o* 5* 180 94 225 118 to l 3 3* 18 17\ ^ 210 112 220 117 £ 3 2* 2* 15 80 5 200 108 210 114 5 2* 2* 13 72 15 176 94 206 108 7 2 2* 9 76 15 170 83 200 98 9 0* 24 8 77 15 150 73 176 85 10* 0 2 6 74 20 120 54 150 70 12 0 0i 4 76 20 82 36 103 45' 1 3 3 10 90 0 164 91 164 | 91 O Z. 3 2 2 9 91 0 168 93 168 93 - -jZ 5 3 2 6 94 0 132 70 132 70 r 'J> 7 1 3 5 80 15 120 64 140 75 £ 5 9 1 24 2 89 9 112 60 123 66 £-- 11 1 1 0 85 15 90 43 106 50 1 Dr. Henry conceives that gas to have the greatest illuminating power, which, in a given volume, consumes the largest quan- tity of oxygen; and that hence the gas of cannel coal is one-third better, than the gasTrom common coal. 3500 cubic feet of gas were collected from 1120 ponnds of the cannel coal; and only 3000 from the same weight of the Clifton coal. From the preceding table, we see also that the gas which issues at the third hour contains, in 100 pails, of sulphuretted hy- drogen and carbonic acid, each 2\, of azote 4\, olefiant gas 14-}, and of other inflam- mable gases 76 parts. A cubic foot of carbonic acid weighs 800 gr. A cubic foot of ^sulphuretted hydro- gen weighs 620. The first takes about 1026 gr. of lime for its saturation; the second about 1070; and hence 1050, the quantity assigned by Dr. Henry for either, is suffi- ciently exact. 100 cubic feet of the above impure gas, containing 5 cubic feet of these two gases, will require at least 2100 grains COA COA of lime, or about 5 oz. avoirdupois for their Complete condensation. The proportion employed by Mr. Lee, is 5 pounds of fresh burned lime to 200 cu- bic feet of gas. The lime, after being slaked, issifted, and mixed with a cubic foot (748 wine gallons) of water. This qtiantitj'of'cream of lime, is adequate to the ordinary purification of tiie gas. Yet it will still slightly darken a card, coated with moistened white lead. A second ex- posure to lime makes it absolutely pure. Measures. Oxygen. Carb. acid- 100 crude gas, consume 190 give 108 100 gas, once washed, 175 100 100 do. twice washed, 175 100 What is separated by the first washing is probably vapour of bitumen or petrole- um, which would injure the pipes by its deposition, more than it would profit, by any increased quantity of light. Though we thus see that the second washing in the above experiment condensed none of the olefiant gas, it is prudent not to use unne- cessary agitation in a large body of water. The carbonate of lead precipitated from a cold solution ofthe acetate, by carbonate of ammonia, washed with water, and mixed with a little of that liquid into the consist- ence of cream, is well adapted to the sepa- ration of sulphuretted hydrogen from coal gas The carbonic acid may then be with- drawn from the residuary gas, by a little water of potash. We must now determine the azote present, which is easily done by firing a volume of this gas with thrice its volume of pure oxygen. What remains af- ter agitation with water of potash, is a mix- ture of azote and oxygen. Explode it with hydrogen; one-third of the diminution of volume shows the oxygen; the rest is azote. We have now to eliminate three quanti- ties, viz. the volume of olefiant gas, that of common carburetted hydrogen, and that of carbonic oxide. Mr. Faraday has proved that chlorine acts pretty speedily on the second species of carburetted hydrogen, and therefore it cannot be employed with the view of condensing merely the first species. In contact with moisture, chlo- rine acts also rapidly on carbonic oxide, giving birth to muriatic and carbonic acids. If we be therefore deprived of all known means of chemical elimination, we shall find a ready and successful resource in the doc- trines of specific gravity. In any mixture of two solids, two liquids, or two gases, whose specific gravities are known, it is easy to infer from the specific gravity of the compound (when the mixture is effect- ed without change of volume) the relative weights of the two constituents. Thus if we apply to an alloy of gold and zinc, the old problem of Archimedes, we shall de- ' Vol. I. termine exactly the proportion of each me- tal present, because the volume of the al- loy is very nearly the sum of the volumes of its ingredients. 1 have long applied this problem to gaseous mixtures, and found it a very convenient means of verification on many occasions, particularly in examining the nature ofthe residuary air in the lungs ofthe galvanized criminal, of which an ac- count is given in the 12th Number of the Journal of Science. Problem.— In 100 measures of mixed gases, consisting, for example, of olefiant gas, carbonic oxide, and subcarburetted hydrogen, in unknown proportions, to determine the quan- tity of each. The first step is to find the quantity of the two denser gases, which have the same specific gravity = 0.9720. Rule.—Multiply by 100, the difference between the specific gravity ofthe mixture, and that of the lighter gas. Divide that number, by the sum of the differences of the sp. gr. ofthe mixture, and that of the denser and lighter gas; the quotient is the per-centage of the denser- See Gregory's Mechanics, vol. 1. p. 364. Example—A mixture of olefiant gas, carbonic oxide, and subcarburetted hydro- gen, has a sp gr. of 0.6.38. What is the proportion per cent of the first two? Sp. gr. of subcarb. hydrogen, is 0 555; 0.638—0555 = 0.083 .-. 100 X 0083 = ° 972 difference 0332 mtn _ n *< , 0 638 , a- n no., sum = 0.*15 n c-r difference 0.083 And ff'rTT = 20 = volume of the two hea- vier gases; and therefore there are 80 ofthe lighter gas. I! nee, having fired the whole with oxygen, we must allow 160 of oxygen, for saturating the 80 measures of the sub- carburetted hydrogen. Then let us sup- pose 35 cubic inches more oxygen to have been consumed We know that the satu- rating power of olefiant gas, and of carbonic oxide with oxygen, is in the ratio of 3 to 0.5. Therefore, the quantity of olef. gas = 35—(20 X 0.5) 25 ----3=0l "" 275 ~ 10 measures. We see now, that a gas of sp. gr. 0.638 consists of 0.8 measures subcarb. hydrogen = 0.444 0.1 do. olefiant gas = 0.097 0.1 po. carb. oxide = 0.097 0 638 For further details see Gas. Dr. Henry gives, at the end of his expe- riments, (Manchester Memoirs, vol. iii. se- cond series), some hypothetical represent- ations ofthe constitution of coal gases, in one of which he assigns, 39 COA COA 2 of carburetted hydrogen, 2 of carbonic oxide, and 15 of pure hydrogen, in 18§ mea- sures. With mixtures of three gaseous bodies, the problem of eliminating the proportion of the constituents, by explosion with oxy- gen, becomes complex, and several hypo- thetical proportions may be proposed. But I can hardly imagine, that pure hydrogen should be disengaged from ignited coal. There is no violation of the doctrine of multiple proportions, in conceiving a com- pound to exist in which three or more atoms of hydrogen may be united with one of carbon. Berthollet's experiments ren- der this view highly probable. If the above hypothetical numbers were altered to 1.6; 2.4; and 15; their accordance with Dr. Hen- ry's experiments would be improved. Now, this is a considerable latitude of adjust- ment. The principles laid down at the com- mencement of this article show, that the more uniformly the coal undergoes igneous decomposition, the richer is the gas. The retorts, if cylindrical, should not exceed, therefore, 12 or 14 inches diameter, and six or seven feet in length. Compressed cy- linders, whose length is 4^ feet, breadth 2 feet, and inside vertical diameter about 10 inches, have been found to answer well at Glasgow. The cast iron of which they are composed, must be screened from the direct impulse of the fire, by a case of fire- brick. On the maximum quantity of gas pro- curable from coal, it is difficult to acquire satisfactory information, at the great gas establishments. Exaggeration seems to be the prevailing foible. Mr. Accum gives the following tables, as the maximum results of his own experiments, made at the Royal Mint gas-works;— Cubic feet of gas. Scotch cannel coal, - - 19.890 Lancashire \V igan cannel, - 19.608 Yorkshire cannel, Wakefield, - 18.860 Staffordshire coal, 1st variety, - 9.748 By experim. at ~\ 2d do. - 10.223 Birmingham C 3d do. - 10.866 gas works, j 4th do. - 9.796 Gloucester coal, High Delph, - 16.584 Do. Low Delph, - 12.852 Do. Middle Delph, - 12.096 Newcastle coal, Hartley, - 16.120 Cowper's High Main,15.876 Tanfield Moor, - 16.920 Pontops, - 15.112 The following varieties of coal, accord- ing to Mr. Accum, contain a less quantity of bitumen, and a larger quantity of car- bon than the preceding. They soften, swell, and cake on the fire, and are well calcu- lated for the production of coal gas:—- One chaldron produces, Newcastle coal, Russcl's Wall's-end, 16.876 Bcwicke and Cras- tor's Wall's-end, 16.897 Heaton Main, - 15.876 Bleyth, - - 12.096 Eden Main, - 9.600 Primrose Main, - 8.348 Concerning the duration of the decom- position of a retort-charge of one cwt., va- rious opinions are maintained. Mr. Peck- ston's experiments at the gas light and coak company's works, Westminster sta- tion, seem to prove, that decided advan- tages attend the continuance of the process for eight hours, in preference to six, or any shorter period. The average product of gas, from one chaldron of Newcastle coals, at six hours' charges, he states at 8,300 cubic feet, and at those of eight hours, at 10,000. On 76 retorts, worked for a week at the latter rate, he gives a state- ment to prove, that there is a saving of 771. 18s. above the former rate of working. Two men, one by day, and one by night, can attend nine or ten retorts, at eight hours charges, of 100 pounds of coal each. Scotch cannel yields its gas most rea- dily, or .....1.00 Newcastle coal, ... 1.04 Gloucester Low Delph, - - 1.08 Newcastle. Brown's Wall's-end, - 1.18 Warwickshire, - - - 1.65 Hence, the latter kinds afford good gas, long after the former are exhausted. The following table by Mr. Peckston exhibits the ratio at which the gas is evolved from Bewicke and Crastor's Wall's- end coal, when the retorts are worked at eight hours' charges:— Cubic feet. Sum. During the 1st hour are ge- nerated, 2000 2d, 1495 3495 3d, 1387 4882 4th, 1279 6161 5th, 1189 7350 6th, 991 8341 7th, 884 9225 8th, 775 10000 We have already explained the princi- ples of purifying gas by milk of lime. But previous to its agitation with that liquid, it should be made to traverse a series of refrigeratory pipes submersed under cold water. A vast variety of apparatus, some very ingenious, but many absurd, have been contrived within these few years, for ex- posing gas to lime in the hquid or dry state. Mr. Accum and Mr. Peckston have been at much pains in describing several of them. The gas holder is now generally preferred of a cylindrical shape, like an im- mense drum, open at bottom; and flat, or slightly conical attop. The diameter is from COA COA 33 to 45 feet in the large establishments, and the height from 18 to 24. The average capacity is from 15000 to 20000 cubic feet. It is suspended in a tank of water by a strong iron chain fixed to the centre of its summit, which passing round a pulley, bears the counter-weight. When totally im- mersed in water, the sheet-iron, of which the gas holder is composed, loses hydrostatical- ly about yy of its weight; or if equipoised when immersed, it becomes tt heavier when in air, minus the buoyancy ofthe in- cluded gas. The mean sp. gr. of well pu- rified coal-gas by Dr. Henry's late experi- ments may be computed at 0.676, to air called 1.000; or in round numbers, its den- sity may be reckoned two-thirds of that of air. One cubic foot of air weighs 527 gr., one cubic foot of gas weighs 351 gr.; the difference is 176 gr. Hence, 40 cubic feet have a buoyancy of one pound avoirdupois. The hydrostatic compensation is obtain- ed by making the weight of that length of the suspending chain which is between the top of the immersed gasometer and the tangential point of the pulley-wheel, equal to one-fifteenth the weight of the gasometer in pounds, minus its capacity in cubic feet, divided by twice 40, or 80. Thus, if its weight be 4 tons, or 8960 lbs.; and its capa- city 15000 cubic feet, a length of chain equal to the height of the gasometer, or to its vertical play, should weigh 597 lbs. with- out allowing for buoyancy. In this case, the gasometer, when out of water, would have the buoyancy of that liquid, replaced by the passage of these 597 lbs. to the op- posite side of the wheel-pulley, so that twice that weight = 1194 lbs. would then be added to the constant counterpoise. When the gasometer again sinks, and loses its weight by the displacement of the li- quid, successive links of the chain come over above it, augmenting its weight, and diminishing that of the counterpoise, by a twofold operation, as in taking a weight out of one scale, and putting it in the other. But we must now introduce the correc- tion for the buoyancy of the combustible gas. In ordinary cases, we must regard it as holding a portion of petroleum vapour diffused through it, and cannot fairly esti- mate its specific gravity at less than 0.750; whence nearly 50 cubic feet have a buoy- ancy of one pound over the same bulk of atmospheric air. If we divide 15000 by 50, the quotient = 300 is the double of what must be deducted in pounds weight from the hydrostatic compensation. Thus, 597 __ 150 = 447, is the weight of the above portion of chain. When the gasometer at- tains its greatest elevation, these 447 lbs. hang on the opposite side of the wheel, constituting an increased counterpoise of twice 447 = 894, to which, if we add the total buoyancy of the included gas = 300 lbs. we have the sum 1194, equal to the total increase of the weight of the iron ves- sel on its suspension in air. f The following plan for suspending ga- someters was devised by me several years ago, and published in the Analeclic Maga- zine of this city for May 1817- " Account of an improved mode of sus- pending gasometers; by Dr. Hare. " It is well known to all who are con- versant in gas light apparatus, that no mode has been heretofore devised to ren- der gasometers accurately equiponderant at all points of their immersion in the wa- ter; a circumstance so indispensable to their action. The mode adopted in the large London establishments, and which appears to be the most approved, is that of the gas- ometer chain. This is costly; difficult to execute well, and not susceptible of cor- rection, when erroneously proportioned to the desired effect; especially after the ap- paratus is in operation. From all these faults, the method of suspension on a beam, like that in the following cut, is entirely free. In practice it has answered perfectly: and, when we have described the mode of constructing such a beam, we think the ra- tionale of its operation will become self- evident. Find (by trial, if possible; if not, by cal- culation) the weight ofthe gasometer when sunk so low, as that the top will be as near as possible to the water, without touching it. In the same way find the weight of the gasometer at the highest point of immer- sion, to which it is to rise, when in use. Then, as the weight in the last case, is to the weight in the first; so let the length of the arm A, be to the length of the arm B. From the centre D, with the radius A, de- scribe a circle; on which set off an arch C, equal to the whole height through which the gasometer is to move. Divide this into as many parts as there are spaces in it, equal each to one-sixth of the radius or length of arm A. Through the points thus) found, draw as many diameters; which will,. GOA COA of courss, form a corresponding number of radii and divisions, on the opposite side of the circle. Divide the difference between the length of A and B, by the sum of these divisions: .and let the quotient be q. From the centre D towards the side E, on radius 2, set off a distance equal to the length of tfie arm A, less the quotient or q. On radius 3, set off a distance equal to A, less 2 q, or twice the quotient; and so set off distances on each of the radii; the last being always less than the preceding, by the value of q. A curve line bounding the distances thus found, will be that of the arch head E. The beam being sup- ported on a gudgeon at D, let the gasome- ter be appended at G; and let a weight be appended at F, adequate to balance it at any one point of immersion. This same weight will balance it at all other points of its immersion—provided the quantity of water displaced by equal sections of the gasometer be equal. But as the weights on which A and B were predicated, may not be quite correct, and as, in the con- struction of large vessels, equability of thickness and shape cannot be sufficiently attained—the consequent irregular buoy- ancy is compensated by causing the weight to hang nearer to, or farther from the cen- tre, at any of the points taken in making the curve. This object is accomplished by varying the sliders seen opposite to the figures 1, 2, 3, 4, 5, 6. ' When they are properly adjusted, they are made firm by the screws of which the heads are visible in the diagram. The drawing is of a beam twelve feet in length; and of course the length of the arm A is six feet—that of B, four feet— their difference two feet; which divided by 6, the number of points taken in making the curve E, gives four inches for the quo- tient q. Hence the distance on radius 2, was five feet eight inches—on radius 3, five feet four inches—on radius 4, five feet—on radius 5, four feet eight inches—on radius 6, four feet four inches—and lastly four feet. The iron gudgeon, where it enters the beam, is square. The projecting parts are turned true, and should be bedded in brass or steel dies; placed, of course, on a com- petent fi ame. The sixth part of a revolu- tion of the portions of the gudgeon thus supported, is the only source of friction to which this beam is subject during the whole period of the descent of the gasom- eter;—which, in largt ones, does not ordi- narily take place in less than six hours."-(- The principles ofthe distribution of gas are exhibited in the following table, given by Mr. Peckston. The gas holder is work- ed at a pressure of one vertical inch of wa- ter, and each argand burner consumes five cubic feet per hour. nter. diamr. of pipe in inches. Cubic feet passing per hour. Burners supplied. *«t 3 8" 20 4 3 50 10 4 T 90 18 5 160 32 f 250 50 7 T 380 76 1 500 100 2 2000 400 3 4500 900 4 8000 1600 5 12500 2500 6 18000 3600 7 24500 4900 8 32000 6400 9 40500 8100 10 50000 10000 12 72000 14400 14 98000 19600 16 128000 25600 18 162000 32400 The following statement is given by Mr. Accum. An argand burner, which mea- sures in the upper rim half an inch in dia- meter between the holes from which the gas issues, when furnished with five aper- tures l-25tb part of an inch diameter, con- sumes two cubic feet of gas in an hour, when the gas flame is one and a half inch high. The illuminating power of this burner is equal to three tallow candles eight in the pound. An argand burner three-fourths of an inch in diameter as above, and perforated with holes l-30th of an inch diameter (what number? probably 15) consumes three cu- bic feet of gas in an hour when the flame is 2i inches high, giving the light of four candles eight to the pound. And an argand burner seven-eighths of an inch diameter as above, perforated with 18 holes l-32d of an inch diameter, consumes, when the flame is three inches high, four cubic feet of gas per hour, producing the light of six tallow candles eight to the pound. Increas- ed length of flame makes imperfect com- bustion, and diminished intensity of light. \nd if the hole s be made lai ger than l-25th of an inch, the gas is incompletely burnt. The height of the glass chimney should never be less than five inches. The argand burner called No. 4, when burnt in shops from sunset till nine o'clock, is charged three pounds a-year. The dia- meter of its circle of holes is five-eighths of an inch, and of each hole 1-32d of an inch. It is drilled with 12 holes, 5-32ds of an inch from the centre of one to the cen- COA COB tre of another. Height of this burner 1 \ inches. No. 6, argand burner. 15 apertures of l-32d of an inch; diameter of their circle three-fourths of an inch; height of burner two inches; charge per ann. four guineas. According to Mr. Accum, one gas lamp, consuming 4 cubic feet of gas in an hour, if situated 20 feet distant from the main, which supplies the gas, requires a tube not less than a quarter of an inch in the bore; 2 lamps, 3 feet distance, require a tube three-eighths of an inch; 3 lamps, 30 feet distance, require a tube three-eighths: 4 lamps at 40 feet, one-half inch bore; 10 lamps, at 100 feet distance, require a tube three-fourths of an inch; and 20, 150 feei distant, 1\ inch bore. We have seen that the average product in London from 1 pound of coal in 8 hours, is 3$ cubic feet. In the Glasgow coal gas establishment, which is conducted by en- gineers skilled in the principles of che- mistry and mechanics, fully 4 cubic feet of gas are extracted from every pound of coal of the splent kind in 4 hour charges, from retorts containing each i20 lbs; which is about two-thirds of their capacity. 1 he decomposing heat is much the same as that used in London, but the retorts are com- pressed cylinders, a little concave below. Hence in 8 hours, fully double the London quantity of gas, is obtained from a retort in Glasgow. An ingenious pupil of mine, lately em- ployed by a projected gas company in Glas- gow to visit the principal factories of gas in England, made a series of accurate experi- ments on its illuminating quality in the dif- ferent towns. For this purpose, he carried along with him a mould candle, six in the pound, and a single-;et gas-nozzle. By at- taching this to a gas-pipe, and producing a flame of determinate length, (three inches), he could then, by the method of shadows, compare the flame of the gas with that of his candle, and ascertain their relative proportions of light. He found that the average illuminating power ofthe gas in the English establishments, was to that of the Glasgow company, as four to five; the worst being so low as three to five, and the best as five to six. If we therefore multiply this ratio, into the dou- ble product of gas obtained in the Glasgow gas-work, we shall have the proportion of light generated here, and in London, from an equal sized retort, in an equal time, as 100 to 40 I his result merits entire con- fidence. In the sequel of the article Light, in this Dictionary, instructions will be given how to calculate the relative illuminating powers of different flames. When the tar is passed through ignited iron pipes, it yields from 10 to 15 cubic feet of gas per pound. The deposite of re- fractory asphaltum, however, is very apt to obstruct the pipes; and the light afforded is perhaps of inferior quality. Hence tar is decomposed in very few establishments. The film of petroleum, which floats on the water of the gasometer tank, and that procured from the tar by distillation, have been used instead of oil for street-lamps. The lamp fountain is kept on the outside ofthe glass lantern, and the flame is made small, to prevent an explosion ofthe vapo- rized naphtha. 1430 lbs. of tar by boiling yield 9 cwt. of good pitch. From a chaldron of New- castle coal about 200 lbs. of ammoniacal liquor are obtained; a solution chiefly of the carbonate and sulphate. The strongest liquor comes from the caking coal. A gal- lon, or 8£ lbs. usually requires for satura- tion from fifteen to sixteen ounces of oil of vitriol, sp. gr. 1.84. To obtain subcarbo- nate of ammonia, 125 lbs. of calcined gyp- sum in fine powder are added to 108 gal- lons of the ammoniacal liquor. The mix- ture is stirred, and the cask containing it, is then closed for three or four hours. Six- teen ounces of sulphuric acid are now mix- ed in; and the whole allowed to remain at rest for four or six hours. The superna- tant sulphate of ammonia is next evaporat- ed till it crystalUze. One hundred weight ofthe dry crystals is mixed with one-fourth of their weight of dry chalk in powder, and sublimed from a cylindrical iron retort into a barrel-shaped receiver of lead. A charge of 120 lbs. of the mixture, is usually de- composed in the course of twenty-four hours. One hundered weight of dry sul- phate of ammonia, is said to produce from sixty to sixty-five pounds of solid subcar- bonate of ammonia. If the sulphate of am- monia, mixed with common salt, is expos- ed to a subliming heat, sal ammoniac is ob- tained. For oil gas, see Oil.* Coating, or Lorication. Chaptal recommends a soft mixture of marly earth, first soaked in water, and then kneaded with fresh horse-dung, as a very excellent coating. The valuable method used by Mr. Willis of Wapping to secure or repair his retorts used in the distillation of phosphorus, de- serves to be mentioned here. The retorts are smeared with a solution of borax, to which some slaked lime has been added, and when dry, they are again smeared with a thin paste of slaked lime and linseed oil. This paste being made somewhat thicker, is applied with success, during the distil- lation, to mend such retorts as crack by the fire. •Cobalt. A brittle, somewhat soft, but difficultly fusible metal, of a reddish-gray colour, of little lustre, and a sp. fcr. of 8.6. Its melting po.nt is said to be 130* M edge- wood. It is generally associated in its ores COB COB with nickel, arsenic, iron, and copper; and the cobalt of commerce usually contains a proportion of these metals. To separate them, calcine with 4 parts of nitre, and wash away, with hot water, the soluble ar- senite of potash. Dissolve the residuum in dilute nitric acid, and immerse a plate of iron in the solution, to precipitate the cop- per. F'ilter the liquid and evaporate to dryness. Digest the mass with water of am- monia, which will dissolve only the oxides of nickel and cobalt. Having expelled the excess of alkali by a gentle heat from the clear ammoniacal solution, add cautious- ly water of potash, which will precipitate the oxide of nickel. Filter immediately, and boil the liquid, which will throw down the pure oxide of cobalt. It is reduced to the metallic state by ignition in contact with lampblack and oil. Mr. Laugier treats the above ammoniacal solution with oxalic acid. He then redissolves the precipitated oxalates of nickel and cobalt in concentrat- ed water of ammonia, and exposes the so- lution to the air. As the ammonia exhales, oxalate of nickel, mixed with ammonia, is deposited. The nickel is entirely sepa- rated from the liquid by repeated crystal- lizations. There remains a combination of oxalate of cobalt and ammonia, which is easily reduced by charcoal to the metallic state. The small quantity of cobalt re- maining in the precipitated salt of nickel, is separated by digestion in water of am- monia. Cobalt is susceptible of magnetism, but in a lower degree than steel and nickel. Oxygen combines with cobalt in two pro- portions; forming the dark blue protoxide, and the black deutoxide. The first dis- solves in acids without effervescence. It is procured by igniting gently in a retort the oxide precipitated bypotash,from the nitric solution. Proust says, the first oxide con- sists of 100 metal + 19.8 oxygen; and Ro- thoff makes the composition of the deutox- ide 100 + 36.77. If we call the first 18.5 and the second 37; then the prime equiva- lent of cobalt will be 5.4; and the two ox- ides will consist of „ C Cobalt, 5.4 100 84.38 i-rotox. "£0xv&en> j.o 18.5 15.62 ~ . f Cobalt, 5.4 100 Deutox. |0xygen) 20 37 100.00 73 27 100 The precipitated oxide of cobalt, wash- ed and gently heated in contact with air, passes into the state of black peroxide. When cobalt is heated in chlorine, it takes fire, and forms the chloride. The iodide, phosphuret, and sulphuret of this metal have not been much examined. The salts of cobalt are interesting from the remarkable changes of colour which they can exhibit. Their solution is red in the neutral state, but green, with a slight excess of acid; the alkalis occasion a blue coloured precipitate from the salts of pure cobalt, but reddish- brown when arsenic acid is present; sul- phuretted hydrogen produces no precipi- tate, but hydrosulphurets throw down a black powder, soluble in excess of the pre- cipitant; tincture of galls gives a yellow- ish-white precipitate; oxalic acid throws down the red oxalate. Zinc does not pre- cipitate this metal. The sulphate is formed by boiling sul- phuric acid on the metal, or by dissolving the oxide in the acid. By evaporation, the salt may be obtained in acicular rhomboi- dal prisms of a reddish colour. These are insoluble in alcohol, but soluble in 24 parts of water. It consists, by the analy- sis of Bucholz, of; Exper't. Theory. Acid, 26 or 1 prime 5.0 24.4 Protoxide, 30 1 do. 6.4 31.4 Water, 44 8 do. 9. 44.2 100 20.4 Dr. Thomson's hypothetical synthesis differs widely from the experimental, in consequence of his assuming 3.625 for an atom ofthe metal, and 4.625 for that of its oxide. He gives 28.57 acid •+- 26.43 pro- toxide -+- 45 water. The nitrate forms prismatic red deliques- cent crystals. It is decomposable by gen- tle ignition. The muriate is easily formed by dissolving the oxide in muriatic acid. The neutral solution is blue when concen- trated, and red when diluted; but a slight excess of acid makes it green. According to Klaproth, a solution of the pure muriate forms a sympathetic ink, whose traces be- come blue when the paper is heated; but if the salt be contaminated with iron, the traces become green. I find that the addi- tion of a little nitrate of copper to the so- lution forms a sympathetic ink, which by heat gives a rich greenish-yellow colour. When a small quantity of muriate of soda, of magnesia, or of lime is added to the ink, its traces disappear very speedily on re- moval from the fire; showing that the vivid green, blue, or yellow colour, is owing to the concentration of the saline traces by heat, and their disappearance, to the reab- sorption of moisture. At a red heat, the greater part of the muriate sublimes in a gray coloured chloride. The acetate forms a sympathetic ink, whose traces be- ing heated, become of a dull blue colour. The arseniate of cobalt is found native in a fine red efflorescence, and in crystals. See .Ores of Cobalt. A creara-tartrate o COC COF cobalt may be obtained in large rhomboi- dal crystals, by adding the tartrate of pot- ash to cobaltic solutions, and slow evapo- ration. An ammonia-nitrate of cobalt may be formed in red cubical crystals, by add- ing ammonia in excess to the nitric solu- tion, and evaporating at a very gentle heat. They have a urinous taste, and are perma- nent in the air. The red oxalate is soluble in an excess of oxalic acid, and hence neu- tral oxalate of potash is the proper reagent for precipitating cobalt. The phosphate may be formed by double decomposition. It is an insoluble purple powder, which, heated along with eight parts of gelatinous alumina, produces a beautiful blue pig- ment, a substitute for ultra-marine. The colouring power of oxide of cobalt on vitri- fiable mixtures, is greater perhaps than that of any other metal. One grain gives a full blue to 240 grains of glass. Zaffre is a mixture of flint powder and an impure oxide of cobalt, prepared by calcination of the ores. Smalt and azure blue are mere- ly cobaltic glass in fine powder. See Glass.* • Cobalus The demon of mines, which obstructed and destroyed the miners. The church service of Germany formerly con- tained a form of prayer for the expulsion of the fiend. The ores of the preceding metal being at first mysterious and in- tractable, were nicknamed cobalt.* * Co ceo lite. A mineral of green co- lour of various shades, which occurs, mas- sive; in loosely aggregated concretions; and crystallized in six-sided prisms, with two opposite acute lateral edges, and bevelled on the extremities, with the bevelled planes set on the acute lateral edges; or in four-sided prisms. The crystals are gene- rally rounded on the angles and edges. The internal lustre is vitreous. Cleavage, double oblique angular. Fracture uneven. Translucent on the edges. It scratches apatite, but not feldspar. Is brittle. Sp. gr. 3.3. It fuses with difficulty before the blow- pipe. Its constituents are silica 50, lime 24, magnesia 10, alumina 1.5, oxide of iron 7, oxide of manganese 3, loss 4.5. Vauquelin. It occurs along with granular limestone, garnet and magnetic ironstone, in beds subordinate to the trap formation. It is found at Arendal in Norway, Nericke in Sweden, Barkas in Findland, the Hartz, Lower Saxony, and Spain.* Cochineal was at first supposed to be a grain, which name it still retains by way of eminence among dyer^, but naturalists soon discovered that it was an insect. It is brought to us from Mexico, where the insect lives upon different species of the opuntia. Fine cochineal, which has been well dried and properly kept, ought to be of a gray colour inclining to purple. The gray, is owing to a powder which covers it na- turally, a part of which it still retains: the purple tinge proceeds from the colour ex- tracted by the water in which it has been killed. Cochineal will keep a long time in a dry place. Hellot says, that he tried some, one hundred and thirty years old, and found it produced the same effect as new. * MM. Pelletier and Caventou have lately found that the very remarkable colouring matter which composes the principal part of cochineal, is mixed with a peculiar ani- mal matter, a fat like common fat, and with different salts. The fat having been separated by ether, and the residuum treated with boiling alcohol, they allowed the alcohol to cool as they gently evapora- ted it, and by this means they obtained the colouring matter; but still mixed with a little fat and animal matter. These were separated from it, by again dissolving it in cold alcohol, which left the animal mat- ter untouched, and by mixing the solution with ether, and thus precipitating the co- louring matter in a state of great purity, which they have called carminium. It melts at 122° Fahr. becomes puffy, and is de- composed, but does not yield ammonia. It is very soluble in water, slightly in alcohol, and not at all in ether, unless by the in- termediation of fat. Acids change it from crimson, first to bright red, and then to yellow; alkalis, and, generally speaking, all protoxides turn it to violet; alumina takes it from water. Lake is composed of car- minium and alumina. Carmine is a triple compound of an animal matter, carminium, and an acid which enlivens the colour. The action of muriatic acid in changing the crimson colour of cochineal into a fine scarlet, is similar. Dr. John calls the red colouring matter cochenilin. He says, the insect consists of Cochenilin, 50.0 Jelly, 10.5 Waxy fat, 10.0 Gelatinous mucus, 14.0 Shining matter, 14.0 Salts, 1.5 100.0 Coffee. The seeds of the coffea ara- bica are contained in an oval kernel, enclo- sed in a pulpy berry, somewhat like a cherry. The ripe fruit is allowed slightly to ferment, by which the pulp is more easily detached from the seeds. These are afterwards washed, carefully dried in the sun, and freed from adhering mem- branes by winnowing. Besides the pecu- liar bitter principle, which we have de- scribed under the name caffein, coffee con- tains several other vegetable products. According to Cadet, 64 parts of raw coffee COH COH consist of 8 gum, 1 resin, 1 extractive and bitter principle, 3.5 gallic acid, 0.14 albu- men, 43.5 fibrous insoluble matter, and 6.86 loss. Hermann found in 1920 grains of Levant Coffee. Mart. Coffee. Resin, 74 68 Extractive, 320 310 Gum, 130 144 Fibrous matter, 1335 1386 Loss, 61 12 1920 1920 The nature ofthe volatile fragrant prin- ciple, developed in coffee by roasting, has not been ascertained. The Dutch in Su- rinam improve the flavour of their coffee by suspending bags of it, for two years, in a dry atmosphere. They never use new coffee.* Coffee is diuretic, sedative, and a cor- rector of opium. It should be given as medicine in a strong infusion, and is best cold. In spasmodic asthma it has been par- ticularly serviceable; and it has been re- commended in gangrene of the extremities arising from hard drinking. • Cohesion, or attraction of cohesion, is that power by which the particles of bo- dies are held together. The absolute co- hesion of solids is measured by the force necessary to pull them asunder. Heat is excited at the same time. At the iron cable manufactory of Captain Brown, a cylindrical bar of iron, 1£ inch diameter, was drawn asunder by a force of 43 tons. Before the rupture, the bar lengthened about 5 inches, and the section of fracture was reduced nearly ^ of an inch. About this part, a degree of heat was generated, which, according to Mr. Barlow of Wool- wich, rendered it unpleasant, if not in a slight degree painful, to grasp the bar in the hand. The same thing is shown in a greater degree in wire-drawing. When the force is applied to compress the body, it becomes shorter in the direction of the force, which is called the compression; and the area of its section at right angles to the force, expands. The cohesion, calcu- lated from the transverse strength, is as near, or perhaps nearer, the real cohesion, than that obtained by pulling the body asunder. The cohesive force of metals is much increased by wire-drawing, rolling, and hammering them. In the elaborate tables of cohesion drawn up by Mr. Thomas Tredgold, and published in the 50th vol. of Tilloch's Magazine, the specific cohe- sion of plate glass (a pretty uniform body) is denoted by unity. The following table is the result of ex- periments by George Rennie, Jun. Esq. pubhshed in the first part of the Phil. Transactions for 1818. Mr. Rennie found a cubical inch of the following bodies crushed by the following weights: lbs av. Elm,.....1284 American pine, ... 1606 White deal, .... 1928 English oak, .... 3o60 Ditto of five inches long, slipped with, 2572 Ditto of four inches, ditto, - 5147 A prism of Portland stone, two inches long, .... 805 Ditto statuary marble, - - 3216 Craigleith stone, - - - 8688 Cubes of li inch. sp. gr. Chalk, - - - - — 1127 Brick of a pale red colour, 2.085 1265 Roe-stone, Gloucestershire, — 1449 Red brick, mean of two trials, 2.168 1817 Yellow face baked Hammer- smith paviors, three times, — 2254 Burnt ditto, mean of two trials, — 3243 Stourbridge, or fine brick, — 3864 Derby grit, a red friable sand- stone, - - . 2.316 7070 Derby grit from another quar- ry, .... 2.428 9776 Killaly white freestone, not stratified, - - - 2.423 10264 Portland, - - - 2.428 10284 Craigleith, white freestone, 2.452 12346 Yorkshire paving, with the strata, - - - 2.507 12856 Ditto, against the strata, 2.507 12856 White statuary marble, not veined, - - . 2.760 13632 Bramley-Fall sandstone, near Leeds, with strata, - 2.506 13632 Ditto, against strata, - 2.506 13632 Cornish granite, . 2.662 14302 Dundee Sandstone, or breccia, two kinds, - . 2.530 14918 A two inch cube of Portland, 2.423 14918 Craigleith, with strata, 2.452 15560 Devonshire red marble, varie- gated, - - — 16712 Compact limestone, - 2.584 17354 Peterhead granite,hard close- grained, - - — 18636 Black compact limestone, Li- merick, - - 2.598 19924 Purbeck, - - 2.599 20610 Black Brabant marble, 2.697 20742 Very hard freestone, 2.528 21254 White Italian veined marble, 2.726 21783 Aberdeen granite, blue kind, 2.625 24556 Cubes of different metals of ith inch were crushed by the following weights. Cast iron, .... 9773 Cast copper, - - - - 7318 Fine yellow brass, ... 10304 Wrought copper, ... 6440 Cast tin, - ... 966 Cast lead, - ... 483 COL COL Bars of different metals, six inches long, and a quarter of an inch square, were suspended by nippers, and broken by the following weights: Cast iron, horizontal, - - 1166 Ditto, vertical, . . . 1218 Cast steel, previously tilted, - 8391 Blistered steel, reduced by the ham- mer, 8322 Shear steel ditto, - - - 7977 Swedish iron ditto, - - 4504 English iron ditto, - - - 3492 Hard gun metal, mean of two trials, 2273 Wrought copper, reduced by ham- mer, .....2112 Cast copper, .... H92 Fine yellow brass, - - - 1123 Cast tin,.....296 Cast lead, .... 114 For the experiments on the twist of bars we must refer to the paper. The strengths of Swedish and English iron do not bear the same proportionto each other in these experiments, that they do when we compare the trials of Count sickingen with those made at Woolwich, of which an ac- count was given in the Annals of Philosophy, vii. 320. From that comparison, the propor- tional strengths were as follows: English iron, Swedish iron, 348.38 549.25 But from Mr. Rennie's experiments, the pro- portional strengths are: English iron, Swedish iron, 348.38 449.34 A very material difference, which ought to be attended to. The following Table contains a view of some former experiments, on the cohesive strengths or tenacities of bodies. A wire Do. lead Do. tin Do. copper Do. brass Do. silver Do. iron Do. gold A cylinder 1 inch iron According to Sickingen, the relative co- kesive strengths of the metals are as fol- lows: Gold, Silver, Platina, Copper, Soft iron, Hard iron, 150955 190771 262361 304696 362927 559880 A wire of iron 0.078 or — of an inch, will just support 549.25 pounds. Emerson's number tor gold is excessively incorrect. In general, iron is about 4 times stronger than oak, and 6 times stronger than deal.* • Cohobation. The continuous redistil- lation of the same liquid, from the same ma- terials.* Colcothah. The brown-red oxide of iron, which remains after the distillation ofthe acid from sulphate of iron: it is used for polishing glass and other substances by artists, who call it crocus, or crocus martis. Cold. The privation of heat. See Calo- ric, Congelation, and Temperature. Colophony. Colophony, or black resin, is the resinous residuum after the distilla- tion of the light oil, and thick dark reddish balsam, from turpentine VOL. I'. 'ith 26 pounds. Mechenbroek 29J Emerson. 49* do. 2^9^ do. 360 do. 370 do. 450 do. 500 do. 63320 Rumford. * Columbittm. If the oxide of columbium described under Acid (Columbic) be mixed with charcoal, and exposed to a violent heat in a charcoal crucible, the metal columbium will be obtained. It has a dark gray colour; and when newly abraded, the lustre nearly of iron. Its sp. gr., when in agglutinated particles, was found by Dr. Wollaston to be 5.61 These metallic grains scratch glass, and are easy pulverized. Neither nitric, mu- riatic, nor nitro-muriatic acid produces any change in this metal, though digested on it for several days. It has been alloyed with iron and tungsten. See Acid (Columbic)* *Colchicum Autumnale. A medicinal plant, the vinous infusion of whose root has been shown by Sir E. Home to possess spe- cific powers of alleviating gout, similar to those of the empirical preparation called Euu medicinale D'Husson. The sediment of the infusion ought to be removed by filtra- tion, as it occasions gripes, sickness, and vomiting.* ♦Colophonite. A mineral of a blackish, or yellowish-brown, or orange-red colour; of a resino-adamantine lustre; and conchoir dal fracture, lis sp. gr. is 4.0. It consists of silica 35, alumina 13.5, lime 290, magnesia 6.5, oxide of iron 7.5, oxide of manganese 4.75, and oxide of titanium 0.5. It occurs massive, in angulo-gratiular concretion's, and 40 COM COM in rhomboidal dodecahedrons, whose sur- faces have a melted appearance. It is the resinous garnet of Haiiy and Jameson. It is found in magnetic ironstone at Arendal in Norway. It occurs also in Piedmont and Ceyb.,,.* ♦Combination. The intimate union of the particles of different substances by che- mical attraction, so as to form a compound possessed of new and peculiar properties. See \tthaction, Eucivalent, and Gas." •Combustible. \ body which, in it3 rapid union with others, causes a disengage- ment of heat and light. To determine this rapidity of combination, or intensity of che- mical action, a certain elevation of tempera- ture is necessary, which differs for every dif- ferent combustible. This difference thrown into a ta mlar form, would constitute their scale of arcendibility, or degree of accension. Stihl adopted, and refined on the vulgar belu f of the heat and light coming from the combustible itself; Lavoisier advanced the oppos.te and more limited doctrine, that the luat and light proceeded from the oxy- genous gas, in air and other b( dies, which he regarded as the true pabulum of fire. Stahl's opinion is perhaps more just than Lavoisier's; fur many combustibles burn to- gether, without the presence of oxygen or of any analogous fancied supporters; as chlorine, and the adjuncts to oxygen, have been nnphilosophically called. Sulphur, hy- drogen, carbon, and azote, are as much entitled to be styled supporters, as oxygen and chlorine; for potassium burns vividly in sulph.iretted Indrogen, and in prussine, and most ofthe metals burn with sulphur alone. H> at and light are disengaged, with a change of properties, and reciprocal saturation of the combining bodies. All the combustible gases are certainlv capable of affording heat, to the degree of incandescence, as is shown by their mechanical condensation. Sound logic would justify us in regard- ing oxygen, chlorine, and iodine, to be in reality combustible bodies; perhaps more so, than those substances vulgarly called com- bustible. Experiments with the condensing syringe, and the phenomena of the decom- position of euchlorine, prove that light as well as heat, may be afforded by oxygen and chlorine. If the body, tlierefore, which emits, or can emit, light and beat in copious streams, by its action on others, be a combustible, then chlorine and oxygen merit that desig- nation, as much as charcoal and sulphur. A vote is declared by the expounders of the I.u' cisierian creed, to be a simple incombus- tible- Yet its mechanical condensation proves that it ca,u afford, from its own resources, an incandescenthea ; andwitli chlorine, iodine, and metallic oxides, all iwombustibles on the antiphlogistic notion, it forms com- pounds possessed of combustible properties, in a pre-eminent and a tremendous degree ofconcentration. It is melancholy to reflect with what easy credulity, the fictions of the Lavoisierian faith have been received and propagated by chemical compilers, some- times sufficiently incredulous on subjects of rational belief. See the next article. The electric polarities unquestionably show, what no person can wish to deny, that be- tween oxygen, chlorine, iodine, on one hand, and hydrogen, charcoal, sulphur, phospho- rus, and the metals, on the other, there exist striking differences. The former are attracted by the positive pole, the latter by the negative, in voltaic arrangements. But still nothing definitive can be inferred from th:s fact; because in the actions of what are called combustibles, on each other, without the presence ofthe other class, we have an exhibition of opposite electrical polarities. Sulphur and metallic plates, by mutual friction or mere contact, produce electrical changes, which apparently prove that sul- phur should be ranked along with oxygen, chlorine, and acids, apart from combusti- bles, whose polarities are negative. Sul- phuretted hydrogen in its electrical relations to metals, ranks also with oxygen and acids. How vague and fallacious a rule of classifi- cation electrical polarity would afford, may be judged of from the following unquestion- able facts; " Among the substances that combine chemically, all those, the electrical energies of which "are well known, exhibit opposite states; thus copper and zinc, gold and quicksilver, sulphur and the metals, the acid and alkaline substances, afford opposite instances. In the voltaic combination of diluted nitrous acid, zinc and copper, as is well known, the side ofthe zinc exposed to the acid is positive. But in combinations of zinc, water, and diluted nitric acid, the sur- face exposed to the acid is negative; though if the chemical action of the acid on the zinc had been the cause of the effect, it ought to be the same in both cases." On some chemical agencies of electricity by Sir H. Davy, Phil. Trans. 1807. Combustibles have been arranged into simple and compound. The former consist of hydrogen, carbon, boron, sulphur, phos- phorus, and nitrogen, besides all the metals. The latter class comprehends the hydrurets, carburets, sulphurets, phosphurets, metallic alloys, and organic products.* *Combcstio\. The disengagement of heat and light which accompanies chemical combination. It is frequently made to be synonymous with inflammation, a term which might be restricted, however, to that pi ou- liar species of combustion, in which gaseous matter is burned. Ignition is the incandes- cence of a body, produced by extrinsic means, without change of its chemical con- stitution. Beccher and Stahl, feeling daily the neces- sity of tire to human existence, and astonish- COM COM ed with the metamorphoses which this power seemed to cause charcoal, sulphur, and me- tals to undergo, came to regard combustion as the single phenomenon of chemistry. Un- der this impression Stahl framed his chemi- cal system, the I'heoria C/umke Dogmatic*, a title characteristic of the dogmatic spirit with which it was inculcated by chemical potessors, as the infallible code of their science for almost a century. When the dis- coveries of Scheele, Cavendish, and Priest- ley, had fully demonstrated the essential part which air played, in many instances of combustion, the French school made a small modification of the German hypothesis. In- stead of supposing, with Stahl, that the lit at and light were occasioned by the emission of a common inflammable principle from the combustible itself, Lavoisier and his asso- ciates dexterously availed themselves of Black's hypothesis of latent heat, and main- tained, that the heat and light emanated from the oxygenous air, at the moment of its union or fixation with the inflammable basis. How thoroughly the chemical mind has been perverted by these conjectural notions, all our existing 53 stems of chemis- try, with one exception, abundantly prove. Dr. Robison, in his preface to Black's lectures, after tracing with perhaps super- fluous zeal, the expanded ideas of Lavoi- sier, to the neglected germs of Hooke and Mayhow, says, "This doctrine concerning combustion, the great, the characteristic phenomenon of chemical nature, has at last received almost universal adoption, though not till after considerable hesitation and opposition; and it has made a complete revolution in chemical science." Tbe French theory of chemistry, as it was called, or hypothesis of combustion, as it should have been named, was for some time classed in certainty with the theory of gravitation.— Alas! it is vanishing with tiie luminous phantoms of the day, but the sound logic, the pure candour, the numerical precision of inference, which characterize Lavoisier's elements, will cause his name to be held in everlasting admiration. It was the rival logic of Sir H. Davy, aided by his unrivalled felicity ,of investiga- tion, which first recalled chemistry from the pleasing labyrinths of fancy, to the more arduous but far more profitable and pro- gressive career of reason. His researches on combustion and flame, already rich in blessings to mankind, would alone place him in tbe first rank of scientific genius. I shall give a pretty copious account of them, since by some fatality it has happened, that in our best and largest system, where so many pages are devoted to the reveries ot ancient chemists, the splendid and useful truths, made known by the great chemist of England, have been totally overlooked. Whenever the chenricid forces, which determine either combination or decompo- sition, are energetically exercised, the phe- nomena of combustion, or incandesence with a change of properties, are displayed. The distinction, therefore, between sup- porters of combustion and combustible s, on which some late systems are arrangril, is frivolous and partial. In fact, one substance frequently acts in both capacities, being a supporter apparently at one tune, anil a combustible at another. But in both cases the heat and light depend on the same cause, and merely indicate the energy and rapidity with which reciprocal attractions are exerted. Thus, sulphuretted hydrogen is a com- bustible with oxygen and chlorine; a sup- porter with potassium. Sulphur, with chlorine and oxygen, has been called a combustible basis; with metals it acts the part of a supporter; for incandescence and reciprocal saturation result. In like man- ner, potassium unites so powerfully with arsenic and tellurium as to produce the phe- nomena of combustion. Nor can we as- cribe the phenomena to extrusion of latent heat, in consequence of condensation of volume. The protoxide of chlorine, a bo- dy destitute of any combustible constitu- ent, at the instant of decomposition, evolves light and heat with explosive violence; and its volume becomes one-half greater. Chlo- ride and iodide of azote, compounds alike destitute of any inflammable matter, ac- cording to the ordinary creed, are resolved into their respective elements with tremen- dous force of inflammation; and the first expands into more than 600 times its bulk. Now, by the prevailing hypothesis of latent heat, instead of heat and light, a prodigious cold ought to accompany such an expansion. The chlorates and nitrates, in like manner, treated with charcoal, sulphur, phosphorus, or metals, deflagrate or detonate, while the volume of the combining substances is greatly enlarged. The same thing may be said of the nitrogurets of gold and siher. In truth, the combustion of gunpowder, a phenomenon too familiar to mankind, should have been a bar to the reception of Lavoi- sier's hypothesis of combustion. The sub- terfuges which have been adopted, and ad- mitted, in order to reconcile them, are un- worthy to be detailed. From the preceding facts it is evident 1st, That combustion is not necessarily de- pendent on the agency of oxygen; 2d, That the evolution of the heat is not to be as- cribed simply to a gas parting with its la- tent store of that ethereal fluid, on its fixa- tion, or combustion; and, 3dl\: That "no peculiar substance or f'01 ni of matter is ne- cessary for producing the effect, but that it is a general result of the actions ot any sub- stances possessed of strong chemical at- tractions, er different electrical rejutionsj COM COM and that it takes place in all cases in which an intense and violent motion, can be con- ceived to be communicated to the corpus- cles of bodies." All chemical phenomena indeed may be justly ascribed to motions among the ulti- mate particles of matter, tending to change the constitution of the mass. It was fashionable for a while, to attribute the caloric evolved in combustion to a di- minished capacity for heat of the resulting substance. Some phenomena, inaccurately observed, gave rise to this generalization. On this subject I shall content myselt with stating the conclusions to which M M. Du- long and Petit have come, in consequence of their own recent researches on the laws of heat, and those of Berard and Delaroche. "We may likewise," say these able chemists, "deduce from our researches another very important consequence f .r the general the- ory of chemical action, that the quantity of heat developed at the instant ofthe combi- nation of bodies, has no relation to the ca- pacity of the elements, and that in the greatest number of cases, this loss of heat is not followed by any diminution in tiie ca- pacity of the compounds formed. Thus, for example, the combination of oxvgen and hydrogen, or of sulphur and lead, which produces so great a quantity of heat, occasions no greater alteration in the capa- city of water, or of sulphuret of lead, than the combination of oxygen with copper, lead, silver, or of sulphur with carbon, pro- duces in the capacities of the oxides of these metals, or of carburet of sulphur."— A We conceive that the relations which we have pointed out between tiie specific heats of simple bodies, and of those of their com- pounds, prevent the . possibility of suppos- ing, that the heat developed in chemical actions, owes its origin merely to the heat produced by change of state, or to that sup- posed to be combined with the material molecules;" Annales de Chimie el Physique, x. Mr. Dalton, in treating ot the constitution ef elastic fluids, lays it down as an axiom, that diminution of volume is the criterion of chemical affinity being exercised; and hence maintains, that the atmospheric air is a mere mixture. Thus, also, the extrication of heat from chemical union, has been usu- ally referred to tiie condensation of volume. The following examples will show the falla- cy of such crude hypotheses. 1. Chlorine and hydrogen mixed, explode by the sun- beam, electric spark, or inflamed taper with the disengagement of much heat and light; and the volume of the mixture, which is greatly enlarged at the instant of combination, suffers no condensation afterwards. Muri- atic acid gas, having the mean densi.y of its components, is produced. 2. When one volume of olefiant gas and one of oxygen avedetonated^together, three and a hall'ga- seous volumes result, the greater part of tbe hydrogen remains untouched, and a volume and a half of carbonic oxide is formed, with about l-10th of carbonic acid. 3. The following experiments of M. Gay-Lussac on liquid combinations are to the same purpose. 1. A saturated solution of nitrate of ammo- nia, at the temperature of 61°, and of the density 1.302, was mixed with water in the proportion of 44.05. to 33.76. The tempe- rature of the mixture sank 8.9°; but the density at 61° was 1.159, while tiie mean density was only 1 51. 2. On adding wa- ter to the preceding mixture, in the pro- portion of 33.64 to 39 28, the temperature sank 3.4°, while the density continued 0.003 above the mean. Other saline solutions pre- sented the same result, though none to so great a degree That the internal motions which accom- pany the change id the mode of combination, independent of change of form, occasion the evolution of heat and light, is evident from the following observations of Berzelius:— In the year 1811, when he was occupied with examining the combinations of antimony, he discovered, accidentally, that several me- talline antimoniates, when they begin to grow red-hot, exhibit a sudden appearance of fire, and then the temperature again sinks to that of the surrounding combusti- bles. He made numerous experiments to elucidate the nature of this appearance, and ascertained that the weight of the salt was not altered, and that the appearance took place without the presence of oxygen. Be- fore the appearance of fire, these salts are very easily decomposed, but afterwards they are attacked neither by acids nor alkaline leys—a proof that their constituents are now held together by a stronger affinity, or that they are more intimately combined. Since that time he has observed these appearances in many other bodies, as, for example, in green oxide of chromium, the oxides of tan- talum and rhodium (See Chromium.) Mr. Edmund Davy found, that when a neutral solution of platinum was precipitat- ed by hydro-sulphuret of potash, and the precipitate dried in air deprived of oxygen, a black compound was obtained, which when heated out of the contact of air, gave out sulphur, and some sulphuretted hydro- gen gas, while a combustion similar to that in the formation of the metallic sulphurets appeared, and common sulphuret of plati- num remained behind. When we heat the oxide of rhodium, obtained from the soda- muriate, water first comes over; and on in- creasing the temperature, combustion takes place, oxygen gas is suddenly disengaged, and a suboxide of rhodium remains behind The two last cases are analogous to that of the protoxide of chlorine, the euchlorine of Sir H. Davy. Gadohnite, the s'diciate of yttria, was first observed by Dr. Wollaston COM COM *B display a similar lively incandescence.— The variety of this mineral with a glassy fracture, answers better than the splintery variety, It is to be heated before the blow- pipe, so that the whole piece becomes equal- ly hot. At a red-heat it catches fire. The colour becomes greenish-gray, and the so- lubility in acids is destroyed. Two small pieces of gadolinite, one of which had been heated to redness, were put in aqua regia; the first was dissolved in a few hours; the second was not attacked in two months. Fi- nally, Sir H. Davy observed a similar phe- nomenon on heating hydrate of zirconia. The verbal hypothesis of thermoxygen by Brugnatelli, with Dr. Thomson's supporters, partial supporters, andsemicombustion, need not detain us a moment from the substantial tacts, the noble truths, first revealed by Sir H Davy, concerning the mysterious process of combustion. Of the researches which brought them to light, it has been said, with- out any hyperbole, that " it Bacon were to revisit the earth, this is exactly such a case as we should chuse to place before him, in order to give him, in a small compass, an idea of the advancement which philosophy has made since the time, when he had point- ed out to her the route which she ought to pursue." The coal mines of England, alike essen- tial to the comfort of her population and her financial resouices, had become infested with fire-damp, or inflammable air, to such a de- gree as to render the mutilation and destruc- tion ofthe miners, by frequent and tremen- dous explosions, subjectsof sympathy and dis- may to the whole nation. By a late explo- sion in one of the Newcastle collieries, no less than one hundred and one persons per- ished in an instant; and the misery heaped on their forlorn families, consisting of more than three hundred persons, is inconceivable. To subdue this gigantic power was the task which Sir H. Davy assigned to himself; and which, had his genius been baffled, the king- dom could scarcely hope to see achieved by another. But the stubborn forces of nature can only be conquered, as Lord Bacon just- ly pointed out, by examining them in the nascent state, and subjecting them to expe- rimental interrogation, under every diver- sity of circumstance and form. It was this investigation, which first laid open the hi- therto unseen and inaccessible sanctuary of Fire. As some invidious attempts, however, have been made, to insinuate that Sir H. Davy stole the germ of his discoveries from the late Mr. Tennant, it may be proper to pre- face the account of them by the following extract from " Resolutions of a Meeting held for considering the facts relating to the Dis- covery of tiie Lamp of Safety." "Soho Square, JVor. 20, 1817. " 3d—That Sir H. Davy not only disco- vered, independently of all others, and with- out any knowledge of the unpublished expe-s riments of the late Mr. Tennant on Flame, the principle of the non-communication ot' explosions through small apertures, but that he has also the sole merit of having first ap- plied it to the very important purpose of a safety-lamp, which has evidently been imi- tated in the latest lamps of Mr. George Ste- phenson. (Signed) Joseph Banks, P. R. S. William J. Brande, Charles Hatchett, William Hyde Wollaston, Thomas Young." See the whole document in Tilloch's Maga- zine, vol. 50. p. 387. The phenomena of combustion may be conveniently considered under six heads: 1st. The temperature necessary to inflame different bodies. 2d, The nature of flame, and the relation between the light and heat which compose it. 3d. The heat disengaged by diff'erent combustibles in burning. 4th, The causes which modify and extinguish combustion, and of the safe-lamp. 5th, Invisible combustion 6th, Practical Infe- rences. 1st. Of the temperature necessary to inflame different bodies. 1st. A simple experiment shows the successive combustibilities of diff'erent bodies. Into a long bottle with a narrow neck, introduce a lighted taper, and let it burn till it is extinguished. Carefully stop the bottle and introduce another light- ed taper. It will be extinguished, before it reaches the bottom of the neck. Then in- troduce a small tube, containing zinc and dilute sulphuric acid, at the aperture of which the hydrogen is inflamed. The hy- drogen will be found to burn in whatever part ofthe bottle the tube is placed. After the hydrogen is extinguished, introduce lighted sulphur. This will burn for some time; and after its extinction phosphorus will be as luminous as in the air, and, if heated in the bottle, will produce a pale yellow flame of considerable density. Phosphorus is said to take fire when heat- ed to 150° and sulphur to 550°. Hydrogen inflames with chlorine at a lower tempera- ture than with oxygen. By exposing oxygen and hydrogen, confined in glass tubes, to a very dull red (about 800 F.) they explode. When the heat was about 700 F. they com- bine rapidly with a species of silent com- bustion. A mixture of common air and hy- drogen was introduced into a small copper tube, having a stopper not quite tight; the copper tube was placed in a charcoal fire; before it became visibly red-hot an explo- sion took place, and the stopper was driven out. We see, therefore, that the inflaming temperature is independent tf compression or rarefcicnom COM COM The ratio ofthe combustibility ofthe dif- ferent gaseous matters, is likewise to a cer- tain extent, as the masses of heated matters required to inflame them. Thus, an iron wire l-40th of an inch, heated cherry-red, will not inflame olefiant gas, but it will in- flame hydrogen gas. A wire of l-8th, heat- ed to the same degree, will inflame olefiant eras. But a wire X- of an inch, must be heat- * 500 ed to whiteness to inflame hydrogen, though ata low led-heat it will inflame bi-phosphu- retted gas. Yet wire of l-40th, heated even to whiteness, will not inflame mixtures of fire-damp. Carbonic oxide inflames in the atmosphere when brought into contact with an iron wire heated to dull redness; whereas carburetted hydrogen is not inflammable, un- less the iron is heated to whiteness, so as to burn with sparks. These circumstances will explain, why a mesh of wire, so much finer or smaller, is required to prevent the explosion from hy- drogen and oxygen, from passing; and why so course a texture and wire are sufficient to prevent the explosion of the fire-damp, fortunately the least combustible of all the inflammable gases known. The flame of sul- phur, which kindles at so low a temperature, will exist under refrigerating processes, which extinguish the flame of hydrogen and all carburetted gases. Let the smallest possible flame be made by a single thread of cotton immersed in oil, and burning immediately upon the sur- face of the oil. it will be found to yield a flame about l-30th of an inch in diameter. Let a fine iron wire of —- of an inch, made mo ' into a ring of 1 -10th of an inch diameter, be brought over the flame. Though at such a distance, it wdl instantly extinguish the flame, if it be cold; but if it be held above the flame, so as to be slightly heated, the flame may be passed through it without be- ing extinguished. That the effect depends entirely on the pow er of the metal to ab- stract the heat of flame, is shown by bring- ing a glass capillary ring of the same diame- ter and size over the flame. This being a much worse conductor of heat, will not, even when cold, extinguish it. If its size, how- ever, be made greater, and its circumference smaller, it will act like the metallic wire, and require to be heated to prevent it from ex- tinguishing the flame. Now, a flame of sul- phur may be made much smaller than that of hydrogen; one of hydrogen may be made much smaller than that of a wick fed with oil; and that of a wick fed with oil smaller than that of carburetted hydrogen. A ring of cool wire, which instantly extinguishes the flame of carburetted hydrogen, diminish- es but slightly the size of a flame of sulphur, ofthe same dimensions. By the following simple contrivance, we may determine the relative facility of burn- ing, among different combustibles. Prepare a series of metallic globules ol'different sizes, by fusion at the end of iron wires, and light a series of very minute flames of different bodies all of one size. If a globule -20th of an inch diameter be brought near a.i oil flame of l-3uth in diameter, it will extinguish it, when cold, at the distance of a diameter. The size of the spherule, adequate to the extinction of the particular flame, will be a measure of its combustibility. If the glo- bule be heated, however, the distance will diminish at winch it produces extinction. At a white heat, the globule, in the above in- stance, does not extinguish it by actual con- tact, though at a dull red-heat it immediately produces the effect. 2d Of the nature of fame, and of the rela- tion between the light and the heat which com- pose it. The flame of combustible bodies may in all cases be considered, as the com- bustion of an explosive mixture of inflammable gas, or vapour, with air. It cannot be re- garded as a mere combustion, at the surface of contact, ofthe inflammable matter. This fact is proved by holding a taper, or a piece of burning phosphorus, within a large flame made by the combustion of alcohol, Tie flani'- of the taper, or of the phosphorus, will appear in the centre of the other flame, proving that there is oxygen even in its in- terior part. When a wire-gauze safe-lamp is made to burn in a very explosive mixture of coal-gas and air, the light is Reble and of a pale colour. Whereas the flame of a cur- rent of coal gas burnt in the atmosphere, as is well known by the phenomena ofthe gas lights, is extremely brilliant. It becomes, therefore, a problem of some interest, " v. ny the combustion of explosive mixtures, under diff'erent circumstances, should produce such diff'erent appearances?" In reflecting on the circumstances of these two species of com- bustion, Sir H. Davy was led to imagine that the cause of the superiority of the light of the stream of coal gas, might We owing to the decomposition of a part of the gas, towards the interior of the flame, where the air was in the smallest quantity, and tiie deposition of solid charcoal, which first by its ignition, and afterwards by its combustion, increased, in a high degree, the intensity ofthe light. The following experiments show, that this is the true solution ofthe problem. li we hold a piece of wire-gauze, of about 900 apertures to the square inch, over a stream of coal gas issuing from a small pipe, and if we inflame the gas above the wire- gauze, left almost in contact with the orifice of the pipe, it burns with its usual bright light. On raising the wire-gauze so as to cause the gas to be mixed with more air he- fore it inflames, the light becomes feebler, and at a certain distance tbe flame assumes the precise character of that of an explo- sive mixture burning within the lamp. But though the light is s® feeble m this ease, the COM COM heat is greater than when the light is- much more vivid. A piece of wire of platina, held in this feeble blue flame, becomes instantly white-hot. On reversing the experiment by inflaming a stream of coal-gas, and passing a piece of wire gauze gradually from the summit of the flame to the orifice of the pipe, the re- sult is still more instructive. It is found that the apex of the flame, intercepted by the wire-gauze, affords no solid charcoal; but in passing it downwards, solid charcoal is given off in considerable quantities, and prevented from burning by the cooling agen- cy of the wire-gauze. At the bottom of the flame, where the gas burned blue, in its immediate contact with the atmosphere,char- coal ceased to be deposited in visible quan- tities. The principle of the increase of the brilli- ancy and density of flame, by the production and ignition of solid matter, appears to ad- mit of many applications. Thus, olefiant gas gives the most brilliant white light of all combustible gases, because, as we learn from Berthollet's l xperiments, related under carburetted hydrogen, at a very high tem- perature, it deposites a very large quantity of solid carbon- Phosphorus, which rises in vapour at common temperatures, and the vapour of which combines with oxygen at those temperatures, is always luminous; for each particle of acid formed, must, there is every reason to believe, be white-hot. So few of these particles, however, exist in a given space, that they scarcely raise the tem- perature of a solid body exposed to them, though, as in the rapid combustion of phos phorus, where immense numbers are exist- ing in a small space, they produce a most intense heat. The above principle readily explains the appearances of the diff'erent parts of the flames of burning bodies, and of flame urged by the blow-pipe. The point of the inner blue flame, where the heat is greatest, is the point where the whole of the charcoal is burned in its gaseous combinations, without previous deposition. It explains also the intensity of the light of those flames in which fixed solid matter is produced in combustion, such as the flame of phosphorus and of zinc in oxygen, &c. and of potassium in chlorine, and the feeble- ness of the light of those flames in which gaseous and volatile matter alone is pro- duced, such as those of hydrogen and of sul- phur in oxygen, phosphorus in chlorine, &c. It offers means of increasing the light of certain burning substances, by placing in their flames even incombustible substances. Thus the intensity of the light of burning sulphur, hydrogen, carbonic oxide, &c. is wonderfully increased by throwing into them oxide of zinc, or by placing in them very fine amianthus or metallic gauze, It leads to deductions concerning the ehemic 1 nature of bodies, and various phe- nomena of their decomposition. Thus ether burns with a flame, which seems to indicate the presence of olefiant gas in that substance. Alcohol burns with a flame similar to that of a mixture of carbonic oxide and hydro- gen. Hence the first is probably a binary compound of olefiant gas and water, and the second of carbonic oxide and hydrogen. When protochloride of copper is introduced into the flame of a candle or lamp, it affords a peculiar dense and brilliant red light, tinged with green and blue towards the edges, which seems to depend upon the chlorine being separated from the copper by the hydrogen, and the ignition and com- bustion of the solid copperand charcoal. Similar explanations may be given of the phenomena presented by the action of other combinations of chlorine on flame; and it is probable, in many of those cases, when the colour of flame is changed by the intro- duction of incombustible compounds, that the effect depends on the production, and subsequent ignition or combustion of in- flammable matter from them. Thus the rose-coloured light given to flame by the compounds of strontium and calcium, and the yellow colour given by those of barium, and the green by those of boron, may de- pend upon a temporary production of these bases, by the inflammable matter ofthe flame. Dr. Clarke's experiments on the reduction of barytes, by the hydroxy gen lamp, is fa- vourable to this idea. Nor should any sup- posed inadequacy of heat in ordinary flame, prevent us from adopting this conclusion. Flame, or gaseous matter heated so highly as to be luminous, possesses a temperature beyond the white heat of solid bodies, as is shown by the circumstance, that air not luminous will communicate this degree of heat. This is proved by a simple experi- ment. Hold a fine wire of plantinum about l-20th of an inch from the exterior of the middle of the flame of a spirit-lamp, and conceal the flame by an opaque body. The wire will become white-hot in a space, where there is no visible light. The real tem- perature of visible flame is perhaps as high as any we are acquainted with. Mr. Ten- nant used to illustrate this position, by fusing a small filament of platinum, in the flame of a common caudle. These views will probably offer illustra- tions of electrical light. The voltaic arc of" flame from the great battery, differs in co- lour and intensity, according to the substan- ces employed in the circuit, and is infinitely more brilliant and dense with charcoal than with any other substance. May not this de- pend, says Sir H. Davy, upon particles of the substances separated by the electrical attractions? And the particles of charcoal, being the lightest among solid bodies (i\\ COM COM their prime equivalent shows), and the least coherent, would be separated in the largest quantities. The heat of flames may be actually dimi- nished by increasing their light (at least the beat communicable to other matter) and vice versa. The flame from combustion, which produces the most intense heat amongst those which have been examined, is that of a mixture of oxygen and hydrogen compressed in Newman's blow-pipe apparatus. (See Btow-Pipx). This flame is hardly visible in bright day-light, yet it instantly fuses the most refractory bodies; and the light from Solid bodies ignited m it, is so vivid as to be painful to the eye. This application cer- tainly originated from Sir H. Davy's dis- covery, that the fttplosion from oxygen and hydrogen would not communicate through very small apertures, and he himself first tried the experiment with a fine glass capil- lary tube. The flame was not visible at the end of this tube, being overpowered by the brilliant star of the glass, ignited at the aperture. 3. Of the heat disengaged by different com- bustibles in the act of burning. Lavoisier, Crawford, Dalton, and Rum- ford, in succession, made experiments to de- termine the quantity of heat evolved in the combustion of various bodies. The appa- ratus used by the last was perfectly simple, and perhaps the most precise of the whole. The heat was conducted by flattened pipes of metal, into the heart of a body of water, and was measured by the temperature im- parted. The following is a general table of results:— Ice melted in Ibi. Oxygen Substances burned, 1 lb. consumed in lbs. L»T»isier. Crawford. Dalton. Rumford- Hydrogen, 7.5 295.6 480 32 0 Carburetted hydrogen, 4 85 Olefiant gas, 3.50 88 Carbonic oxide, 0.58 25 Olive oil, 3.00 149 89 104 94.07 Rape oil, 3.0 124.10 Wax, -Tallow, 3.0 133 97 104 126 24 3.0 96 104 111.58 Oil of turpentine, 60 Alcohol, - 2.0? 58 67.47 Ether sulphuric, 3 62 107.03 Naphtha, - 97.83 Phosphorus, 1.33 100 60 Charcoal, 2.66 96.5 69 40 Sulphur, 1.00 20 Camphor, 70 Caoutchouc, 42 The discrepancies in the preceding table, are sufficient to show the necessity of new experiments on the subject. Count Rum- ford made a series of experiments on the heat given out during the combustion of dif- ferent woods. He found that one pound of wood by burning, produced as much heat as would have melted from about 34 to 54 pounds of ice. The average quantity is about 40. MM. Clement and Desormes find that woods give out heat in the ratio of their respective quantities of carbon; which they state to be equal to one half of their total weight. Hence they assign 48 pounds as the quantity of ice melted, in burning one of wood. In treating of acetic acid and carbon, I have already taken occasion to state, that they appear greatly to overrate the propor- tion of carbon in woods. The preceding table is incorrectly given in several respects by our systematic writers; Dr. Thomson, for example, states, that 1 pound of hydrogen consumes only 6 pounds of oxygen, though the saturating proportion assigned by him is 8 pounds. The propor- tions of oxygen consumed by olive oil, phos- phorus, charcoal, and sulphur, are all in hke manner erroneous. In vol. i p. 184. of Dr. Black's lectures, we have the following notes." 100 pounds weight of the best Newcastle coal, when applied by the most judiciously constructed furnace, will convert about 1$ wine hogsheads of water, into steam that supports the pressure ofthe atmosphere." 1$ hogsheads of water, weigh about 790 pounds. Hence 1 part of coal will convert nearly 8 parts of water into steam. Count Rumford says, that the heat generated in the combustion of 1 pound of pit coal, would make 36— pounds of ice-cold water boil. But we know that it requires fully 5& COM COM times as much heat to convert the boiling water into steam. Therefore, —1 =- 6— is the weight of water that would be converted into steam by one pound of coal. Mr. Watt found, that it requires 8 feet Surface of boiler to be exposed to fire to boil off one cubic foot of water per hour, and that a bushel, or 84 pounds of Newcastle coal so applied, will boil off from 8 to 12 cu- bic feet. He rated the heat expended in boil- ing off a cubic foot of water, to be about six times as much as would bring it to a boiling heat from the medium temperature (55°), in this climate. The mean quantity is 10 cu- bic feet, wiiich weigh 625 pounds. Hence 1 pound of coal burnt, is equivalent to boil oft in steam, nearly 7£ lbs. of water, at the temperature of 55°. In situations where wood was employed for fuel to Mr. Watt's engines, he allowed three times the weight of it, that he did of Newcastle coal. The cubical coal of the Glasgow coal district, is reckoned to have only | the calorific power of the Newcastle ooal; and the small coal or culm, requires to be used in double weight, to produce an equal heat with the larger pieces. A bushel of Newcastle coal is equivalent to a hundred weight ofthe Glasgow. I shall now describe the experiments re- cently made on this subject by Sir H. Davy, subservient to his researches "on the nature of flame. A mercurial gas-holder, furnished with a system of stop-cocks, terminated in a strong tube of platinum, having a minute aperture. Above this, was fixed a copper cup filled with olive oil, in which a thermo- meter was placed. The oil was heated to 212°, to prevent any difference in the com- munication of heat, by the condensation of aqueous vapour; tbe pressure was the same for the diff'erent gases, and they were con- sumed as nearly as possible in the same time, and the flame applied to the same point of the copper cup, the bottom of which was wiped after each experiment. The results were as follows:— Substance* Riseofihorm. Oxygen Ratios of from 212° to consumed, beat. Olefiant gas, 270° 6.0 9.66 Hydrogen, 238 1.0 26.0 Sulph. hydrogen, 232 3.0 6.66 Coal gas, 236 4.0 6.00 Carbonic oxide, 218 1.0 6.00 The data on which Sir II. calculates the ratios of heat, are the elevations of tempera- ture, and the quantities of oxygen consumed conjointly. We see that hydrogen produces more heat in combustion than any of its com- pounds, a fact accordant with Mr. Dalton's results in the former table.; only Sir H. Davy's ratio is more than double that of Mr. Dalton's, as to hydrogen, and carburetted hydrogen. On this point, however, Sir H. V«i. P. with his usual sagacity remarks, that it will be useless to reason upon the ratios as exact, for charcoal was deposited from both the olefiant gas and coal gas during the experi- ment, and much sulphur was deposited from the sulphuretted hydrogen. It confirms, however, the general conclusions, and proves that hydrogen stands at the head of the scale, and carbonic oxide at tiie bottom. It might at first view be imagined, that, according to this scale, the flame of carbonic oxide ought to be extinguished by rarefaction at the same degree as that of carburetted hydrogen; but it must be remembered, as has been already shown, that carbonic oxide is a much more easily kindled, a more accendible gas. 4 Of the causes which modify or extinguish combustion or fame. The earlier experimenters upon the Boy- lean vacuum observed, that flame ceased in highly rarefied air; but the degree of rare- faction necessary for this effect has been differently stated. On this point, Sir H. Da- vy's investigations are peculiarly beautiful and instructive. When hydrogen gas, slow- ly produced from a proper mixture, was in- flamed at a fine orifice of a glass tube, as in Priestley's philosophical candle, so as to make a jet of flame of about l-6th of an inch in height, and introduced under the receiver of an air-pump, containing from 200 to 300 cubical inches of air, the flame enlarged as the receiver became exhausted; and when the gauge indicated a pressure, between 4 and 5 times less than that of the atmosphere, was at its maximum of size; it then gradually diminished below, but burn- ed above, till its pressure was between 7 and 8 times less: when it became extin- guish ed To ascertain whether the effect depended upon the deficiency of oxygen, he used a larger jv t with the same apparatus, when the flame to his surprise, burned longer; even when the atmosphere was rarefied 10 timesj and this in repeated trials. When the larger and this is in repeated trials. When the larger jet came white-hot, and continued red-hot till the flame was extinguished. It immediately occurred to him, that the heat communicat- ed to the gas by this tube, was the cause that the combustion continued longer in the last trials when the larger flame was used; and the following experiments confirmed the conclusion. A piece of wire of plati- num was coiled round the top of the tube, so as to reach into and above the flame.— The jetof gas of l-6th of an inch in height was iighted, and the exhaustion made.— The wire of platinum soon became white- hot in the centre of the flame, and a small point of u ire near the top fused. It contin- ued white-hot, till the pressure was 6 times less. When it was 10 times, it continued red-hot at the upper part, and as long as it was dull red, the gay, though certainly ox* 41 COM COM tinguished below, continued to burn in con- tact with the hot wire, and the combustion did not cease, until the pressure was re- duced 13 times It appears from this result, that the flame of hydrogen is extinguished in rarefied at- mospheres, only when the heat it produces is insufficient to keep up the combustion: which appears to be when it is incapable of communicating visible ignition to metal; and as this is the temperature required for the inflammation of hydrogen, (see section 1st,) at common pressure, it appears that its com- bustibility is neither diminished nor increased by rarefaction from the removal of pressure. According to this view, with respect to hydrogen, it should follow, that those a- mougst other combustible bodies, which re- qu.re less heat for their accension, ought to burn in more rarefied air than those that re- quire more heat; and those which produce much heat in their combustion ought to burn, other circumstance!' being the same, in more rarefied air, than those that produce little heat. Every experiment since made, con- firu.s these conclusions Thus olefiant gas, which approaches nearly to hydrogen, in the temperature produced by its combustion, and which does not require a much higher temperature for its accension, when its flame was made by a jet of gas from a bladder connected with a small tube, furnished with a wire of plantinum, under the same circum- stances as hydrogen, ceased to burn when the pressure was diminished between 10 and 11 times. And the flames of alcohol and of the wax taper, which require a greater con- sumption of caloric for the volatilization and decomposition of their combustible matter, were extinguished when the pressure was 5 or 6 times less without the wire of platinum, and 7 or 8 times less when the wire was kept in the flame. Light carburetted hydro- gen, which produces, as we have seen, less heat in combustion than any of the common combustible gases, except carbonic oxide, and which requires a higher temperature for its accension than any other, has its flame extinguished, even though the tube was fur- nished with the wire when the pressure was below l-4th. The flame of carbonic oxide, which though it produces little heat in combustion, is as accendible as hydrogen, burned when the wire was used, the pressure being 1-6'h. The flame of sulphuretted hydrogen, the heat of which is in some measure carried off' by the sulphur, produced by its decomposi- tion during its combustion in rare air, when burned in the same apparatus as the olefiant and other gases, was extinguished when the pressure w s l-7th. Sulphur, winch requires a lower tempera- ti re for its ao\ nsion, than any common in- fl.mmable substance, except phosphorus, burned with a very feeble blue flame in air rarefied 15 times $ and at this pressure the flame heated a wire of plantinum to dull red- ness; nor was it extinguished till the pres- sure was reduced to l-20th. From the pre- ceding experimental facts we may infer, that the taper would be extinguished at a height of between 9 and 10 miles, hydrogen be- tween 12 and 13; and sulphur between 15 and 16. Phosphorus, as has been shown by M. Van Marum, burns in an atmosphere rare- fied 60 times. Sir H. Davy found, that phosphuretted hydrogen produced a flash of light when admitted into the best \acuum that could be made, by an excellent pump of Nairn's construction. Chlorine and hydrogen inflame at a much lower temperature, than oxygen and hydro- gen. Hence the former mixture explodes when rarefied 24 times; the latter ceases to explode when rarefied 18 times. Heat ex. trinsically applied, carries on combustion, when it would otherwise be extinguished. Camphor in a thick metallic tube, which disperses the heat, ceases to burn in air rare- fied 6 times; in a glass tube which becomes ignited, the flame of camphor exists under a ninefold rarefaction. Contact with a red- hot iron, makes naphtha glow with a lam- bent flame at a rarefaction of 30 times; though without foreign heat, its flame dies at an atmospheric rarefaction of 6. If the mixture of oxygen and hydrogen expanded to its non-explosive tenuity; be exposed to the ignition of a glass tube, the electric spark will then cause an explosion, at least in the heated portion of the gases. We shall now detail briefly the effects of rarefaction by heat on combustion and ex- plosion. Under Caloiuc we have shown, that air by being heated from 32° to 212° expands — ^ or 8 parts become 11; hence the expansion of one volume of air at 212° into 2 i, or the augmentation of 1.5 = ii which Sir H. Davy found to take place when the enclosing glass tube began to soften with ignition, will indicate 932°. For ~ : 180°: : ~ : 720°, to which if we add 212°, the sum is 932°. One of air at 212 becoming 2|, as took place in the other experiment of Sir H. Davy, will give us (180° X —) + 212° — 812°, for the heat of fusible metal lumin- ous in the shade. I believe these experi- ments to be much more accurate than a iy hitherto given, relative to the temperature of incandescence. This philosopher, whose ingenuity of research is usually guided by the most rigorous arithmetic, estimates the first temperature from the above data of Gay-Lussac, at 1035° Farenheit. I there- fore hesitate to offer a discordant computa- tion. One volume of air at 212°, should be- come at a temperature of 1035°, accord- COM COM ihg to the rule I use, 2.715 parts, instead of 2.5. Sir H. introduced into a small glass tube over well boiled mercury, a mixture of two parts of hydrogen and one of oxygen, and heated the tube by a spirit lamp, till the volume of the gas was increased from 1 to 2.5. By means of a blow-pipe and another lamp, he made the upper part of the tube - red-hot, when an explosion instantly took place. This experiment refutes tiie notions of M. de Grotthus, on the non-explosiveiiess of that mixture, when expanded by heat.— He introduced into a bladder a mixture of oxygen and hydrogen, and connected this biadder with a thick: glass tube of about one- sixth of an inch in diameter, and three feet long, curved 60 that it could be gradually heated in a charcoal furnace; two spirit- lamps were placed under the tube, where it entered the charcoal fire, and the mixture was very slowly passed through. An ex- plosion took place, before the tube w^s red- hot This fine experiment shows, that ex- pansion by heat, instead of dim nishing tiie accendibility of nases, enables them, on the contrary, to explode apparently at a lower temperature; which seems perfectly reason- able, as a part of the heat communicated by any ignited body, must be lost in gradually raising the temperature. M. de Grotthus has stated, that if a glow- ing coal be brought into contact with a mix- ture of oxygen and hydrogen, it only rare- fies them, but does not explode them. This depends on the degree of heat communica- ted by the coal. If it is red in day-light, and free from ashes, it uniformly t xplodes the mixture. If its redness be barely visi- ble in the shade, it will not explode them, but cause their slow combination. The gen- eral phenomenon is wholly unconnected with rarefaction; as is shown by the following cir- cumstance : When the heat is greatest, and before the invisible combination is comple- ted, if an iron wire, heated to whiteness, be placed upon the coal within the vessel, the mixture instantly explodes. Subcarburetted hydrogen, or fire-damp, as has been shown, requires a very strong heat for its inflammation. It therefore ottered a good substance for an experiment, on the effect of high degrees of rarefaction, by heat on combustion. One part of this gas, and eight of air, were mixed together, and in- troduced into a bladder furnished with a capillary tube. This tube was heated till it began to melt. The mixture was then pass- ed through it, into the flame of a spirit-lamp, when it took fire, and burned with its own peculiar explosive light, beyond the flame of the lamp; and when withdrawn, though the aperture was quite white-hot, it continued to burn vividly. That the compression in one part of an explosive mixture, produped by the sudden expansion of another part by heat, or the electric spark, is not the cause of combus- tion, as has been supposed by Mr. Higgins, M. Berthollet, and others, appears to be evident from what has been stated, and is rendered still more so by the following facts: A mixture of bi-phosphtiretted hydrogen gas and oxygen, winch explode at a heat a little above that of boiling water, was con- fined by mercury, and vi ry gradually heated on a sand bath. Wien the temperature of the mercury was 242°, the mixture explo- ded. A similar mixture was placed in a re- ceiver communicating with a condensing syringe, and condensed over mercurv till it occupied only one-fifth of its original vo- lume. No explosion took place, and no che- mical change had occurred; for when its volume was restored it was instantly explo- ded by the spirit-lamp. It would appear then that the heat given out by the compression of gases, is the real cause ofthe combustion which it pioducesj and that at certain elevations of temperature, whether in rarefied or compressed atmos- pheres, explosion or combustion occurs; that is, bodies combine with the production of heat and light. Since it appears that gaseous matter ac- quires a double, triple, quadruple, &.c. bulk, by the successive increments of 48u° F 2 X 480°, 3 X 480°, &c. we may gain ap- proximations to the temperature of flame, by measuring ihe expansion of a gaseous mixture at the instant of explosion, provided the resulting compound gas occupy, after cooling, the same bulk as the sum of its con- stituents. Now this is the case with chlo- rine and hydrogen, and with prussine and oxygen. The latter detonated in the pro- portion of one to two, in a tube of about two-fifths of an inch diameter, displaced a quantity of water, which demonstrated an expansion of 15 times their original bulk. Hence 15 X 480° «= 7200° of Fahr. and the real temperature is probably much higher} for heat must be lost by communication to the tube and the water. The heat of the gaseous carbon in combustion in this gas, appears more intense than that of hydro- gen ; for it was found that a filament ot pla- tinum was fused by a flame of prussine (cy- anogen) in the air, which was not fused by a similar flame of hydrogen. We have thus detailed the modifications produced in combustion by rarefaction, me- chanical and calorific. It remains on this head to state the effects of the mixture of diff'erent gases, and those of different cool- ing orifices, on flame. In Sir II. Davy's first paper on the fire- damp of coal mines, he mentioned that car- bonic acid had a greater influence in de- stroying the explosive powei of mixtures of fire-damp ana air, than azote; and he sup- pose ctn tcaase to be its greater density and COM COM •apacity for heat, in consequence of which it might exert a greater cooling agency, and thus prevent the temperature ofthe mixture from being raised to that degree neces-ary for combustion. He subsequently made a Series of experiments with the view of de- termining how far this idea is correct, and for the purpose of ascertaining the general phenomena, of the effects of the mixture of faseous substances upon explosion and com- ustion. Prevented by Of hydrogen, 8 Oxygen, 9 Nitrous oxide, 11 Subcarburetted hydrogen, 1 Sulphuretted hydrogen, 2 Olefiant gas, £ Muriatic acid gas, 2 Chlorine, -..-.- Silicated fluoric gas, ?~ Azote,...... Carbonic acid, - The first column of the preceding table shows, that other causes, besides density and capacity for heat, interfere with the pheno- mena. Thus nitrous oxide, which is nearly one-third denser than oxygen, and which, according to Delaroche and Berard, has a greater capacity for heat, in the ratio of 1.3503 to 0.9765 by volume, has lower pow- ers of preventing explosion. Hydrogen al- so, which is fifteen times lighter than oxy- gen, and which in equal volumes has a small- er capacity for heat, certainly has a higher power of preventing explosion; and olefi- ant gas exceeds all other gaseous substan- ces, in a much higher ratio than could have been expected, from its density and capacity. I have deduced the third column, from Sir II. Davy's experiments on the relative times in which a thermometer, heated to 160°, when plunged into a volume of 21 cubic inches ofthe respective gases at 52°, took to cool down to 106°. Where an elastic fluid exerts a cooling influence on a solid surface, the effect must depend principally upon the rapidity with which its particles change their places; but where the cooling particles are mixed throughout a mass with other gaseous particles, their effect must depend principally upon the power they possess of rapidly abstracting heat from the contiguous particles; and this will depend probably upon two causes, the simple ab- stracting power by which they become quickly heated, and their capacity for heat, which is great in proportion as their tempe- ratures are less raised by this abstraction.— The power of elastic fluids to abstract heat from solids, appears from the abo\e experi- ments to be in some inverse ratio to their density; and there seems to be something He took given volumes, of a mixture q£ two parts of hydrogen and one p^rt of oxy- gen by measure, and diluti ig them with various quantities of different elastic finds, he ascertained at what degree of dilution, the power of inflammation by a strong spark from a Leyden phial was destroyed. He found that for one of the mixture, inflamma* tion was Peimitted with. Cooling power, air = L N 6 7 10 I 1* 2.66 1.12 0.75 (the mean) 2.18 (coal gas) 1.6 H - 0.66 u - 1.33 in the constitution ofthe light gases, which enables them to carry off heat from solid surfaces in a different manner from that in which they would abstract it in gaseous mix- tures, depending probably on the mobility of their parts. Those particles which are lightest must be conceived most capable of changing place, and would therefore cool solid surfaces most rapidly; in the cooling of gaseous mixtures, the mobility of the par-, tides can be of little consequence. Whatever be the cause of the diff'erent cooling powers ofthe diff'erent elastic fluids in preventing inflammation, very simple ex- periments show that they operate uniformly with respect to the different species of com- bustion; and that those explosive mixtures, or inflammable bodies, which require least heat for their combustion, require larger quantities of the diff'erent gases to prevent the effect, and vice versa. Thus one of chlo- rine and one of hydrogen still inflame when mixed \v ith eighteen times their bulk of oxy- gen; whereas a mixture of carburetted hy- drogen and oxygen, in the proper propor- tions (one and two) for combination, have their inflammation prevented by less than three times their volume of oxy gen. A wax taper was instantly extinguished in air mixed with one-tenth of silicated fluoric acid, and in air mixed with one-sixth of muriatic acid gas; but the flame of hydrogen burned rea- dily in those mixtures; and in mixtures which extinguished the flame of hydrogen, the flame of sulphur burned. (See the beginning of sec- tion 1st.) In cases, however, in which the heat re- quired for chemical union is very small, as in the instance of hydrogen and chlorine, a mixture which prevents inflammation will not prevent combination, tkat is, the gas«*s COM COM wiH combine without any flash. If twe v#. lumes of carburetted hydrogen be added to a mixture of one of chlorine with one of hydrogen, muriatic acte is formed through- out the mixture and heat produced, as was evident from the expansion when the spark assed, and the rapid contraction afterwards, ut the heat was so rapidly carried off by the quantity of carburetted hydrogen, that no flash was visible. Experiments on combustion in condensed air, to see if the cooling power was much increased thereby, show that, as rarefaction does not diminish considerably the heat of flame in atmospherical air, so neither does condensation consideiably increase it; a cir- cumstance of great importance in the con- stitution of our atmosphere, which at all heights or depths, at which man can exist, still preserves the same relations to combus- tion. It may be concluded from the general law, that at high temperatures, gases not concerned in combustion will have less power of preventing that operation, and likewise that steam and vapours, which re- quire a considerable heat for their formation, will have less effect in preventing combus- tion, particularly of those bodies requiring low temperatures, than gases at the usual heat of the atmosphere. Thus, a very large quantity of steam is required to prevent sul- phur from burning. A mixture of oxygen and hydrogen will explode hy the electric spark, though diluted with five times its vo- lume of steam; and even a mixture of air and carburetted hydrogen gas, the least ex- plosive of all mixtures, requires a third of steam to prevent its explosion, whereas one- fifth of azote will produce that effect. These trials were made over mercury. Heat was- applied to water over the mercury, and 37.5 for 100 parts =— was regarded as the cor- rection for the expansion of the gases. We shall now treat of the effects of cooling orifices onfiume. The knowledge of the cooling power of elastic media, in preventing the explosion of the fire-damp, led the illus- trious English chemist, to those practical researches, which terminated in his grand discovery ofthe wire-gauze safe-lamp. The general investigation of the relation and ex- tent of those powers, serves to elucidate tbe operation of wire-gauze and other tissues or systems of apertures, permeable to light and air, in intercepting flame, and confirms the views originally given of this marvellous phenomenon. We have seen that flame is gaseous matter, heated so highly as to be luminous, and that to a degree of tempera- ture beyond the white heat of solid bodies; for air not luminous will communicate this degree of heat. When an attempt is made to pass flame through a very fine mesh of wke-gauze ofthe common temperature, the gauze cools each portion of the elastic mat- ter that passes through it, so as to reduce its temperature below that degree at which it is luminous. This diminution of temperature is proportional to the smalhw ss of the mesh, and to the mass of the metal. The power of a metallic or other tissue to prevent ex- plosion, will depend upon the heat required to produce the combustion, as compared with that acquired by the tissue. Hence, the fl.inie of the mos inflammable sub- stances, and of those that produce most heat in combustion, will pass through a metallic tissue, that will interrupt the flame of less inflammable subs'ances, or those that produce little heat in combustion. Or the tissue being the same, and impermeable to all flames at common temperatures, the flames of die most combustible substances, and of those which produce most heat, will most readily pass through it, when it, is heated, and each will pass through it at a different degree of tempeiature In short, all the circamstances wh:ch apply to tiie effect of cooling mixtures upon flame, will apply to cooling perforated surfaces. Thus, trie flame ot phosphuretted hydrogen, at common tem- peratures, will pass through a tissue suffix ciently large, not to be immediately choaked up by the phosphoric acid formed, and the phosphorus depoxited. If a tissue, contain- ing above 70u apertures to the square inch, be held over the flame of phosphorus or phosphuretted hydrogen, it does not trans- mit the flame till it is sufficiently heated to enable the phosphorus to pass th rough it in vapour. Phosphuretted hydrogen is decom- posed by flame, and acts exactly like phos- phorus. Jn like manner a tissue of 109 aper. ures to the square inch, made of a wire °* 6o"> w'^» ** common temperatures, inter- cept the flame of a spirit-lamp, but not that of hydrogen. But when strongly heated, it no longer arrests the flame of alcohoL A tissue which will not interrupt the flame of hydrogen when red-hot, will still intercept that of olefiant gas; and a heated tissue, which would communicate explosion from a mixture of olefiant gas and air, will stop an explosion from a mixture of fire-damp, or carburetted hydrogen. The latter gas re- quires a considerable mass of heated metal to inflame it, or contact with an extensive heated surface. An iron wire of l-20th of an inch, and eight inches long, red-hot, when held perpendicularly in a stream of coal gas, did not inflame it; nor did a short wire of one-sixth of an inch produce the eff'ect, when held horizontally. But wire of the latter size, when six inches of it were red-hot, and when it was held perpendicu- larly, in a bottle containing an explosive mixture, so that heat was communicated successively to portions of the gas, produced its explosion. COM COM The scale of gaseous accension, given in the first section, explains, why so fine a mesh of wire is required to hinder the ex- plosion from hydrogen and oxygen, to pass; and why so coarse a texture and wire, con- troul the explosion of fire-damp. The ge- neral doctrine, indeed, of the operation of wire-gauze, cannot be better elucidated, than in its effects upon the flame of sulphur. When wire-gauze, of 600 or 700 apertures to the square inch, is held over the flame, fumes of condensed sulphur immediately come through it, and the flame is intercept- ed. The fumes continue for some instants, but on the increase of the heat, they dimi- nish; and at the moment when they disap- pear, which is long before the gauze be- comes red-hot, the flame passes; the tem- perature at which sulphur burns being that at which it is gaseous. Where rapid currents of explosive mix- tures, however, are made to act upon wire- gauze, it is ot course much more rapidly heated: and tlierefore, the same mesh which arrests the flames of explosive mixtures at rest, will suffer them to pass when in rapid motion. But, by increasing the cooling sur- face, by diminishing the apertures in size, or increasing their depth, all fames, however rapid their motion, may be arrested. Pre- cisely the same law applies to explosions acting in close vessels Very minute aper- tures, when they are only few in number, will permit explosions to pass, which are arrested by m xh larger apertures when they fill a whole surface. A small aperture was drilled at the bottom of a wire-gauze lamp, in the cylindrical ring, which confines the gauze. This, though less than -i- ofan inch in diameter, transmitted the flame, and fired the external atmosphere, in conse- quence ofthe whole force ofthe explosion ofthe thin stratum of the mixture, included within the cylinder, driving the flame through the aperture. Had the whole ring, however, been composed of such apertures separated by wires, it would have been perfectly safe. Nothing can demonstrate more decidedly, than these simple facts and observations, that the interruption of flame, by solid tis- sues, permeable to light and air, depends upon no recondite or mysterious cause, but on their cooling powers, simply considered as such. When a light, included in a cage of wire-gauze, is introduced into an explo- sive atmosphere of fire-damp at rest, the maximum of heat is soon obtained; the ra- diating power of the wire, and the cooling eff'ect of the atmosphere, more efficient from the admixture of inflammable air, prevent it from ever arriving at a temperature equal to that of dull redness. In rapid currents of explosive mixtures of fire-damp, which heat common gauze to a higher tempera- ture, twilled gauze, in which the radiating surface is considerably greater, and the cir- culation of air less, preserves an equable temperature. Indeed, the heat communi- cated to the wire by combustion of the fire- damp in wire-gauze X^nj/s, is completely in the power of the manufacturer. By diminish- ing the apertures, and increasing the mass of metal, or the radiating surface, it may be diminished to any extent. Thick twilled gauze, made of wires — 16 to the warp, and 30 to the weft, rivetted to the screw, to prevent the possibility of displacement, forms a lamp cage, which, from its flexibility, can- not be broken, and from its strength cannot be crushed, except by a very violent blow. The lamp which has been found most con- venient for the miner, is that composed" of a cylinder of strong wire-gauze, fastened round the flame by a screw, and in which the wick is trimmed by a wire passing through a safe aperture. Such have now been used for many years, in the most dan- gerous mines of England, without any acci- dent. Whatever explosive disasters have happened since, may be imputed to the ne- glect, or gross and culpable mismanagement, of that infallible protector. See Lamp. When the fire-damp is inflamed in the wire-gauze cylinders, coal dust thrown into the lamp, burns with strong flashes and scin- tillations. The miners were at first alarmed by an effect of this kind, produced by the dust naturally raised during the working of the coals. But Sir H. Davy showed, by decisive ex- periments, that explosion could never be communicated by them, to the gas of any mine. He repeatedly threw coal dust, pow- dered rosin, and witch-meal, through lamps burning in more explosive mixtures, than ever occur in coal mines; and though he kept these substances floating in the explo- sive atmosphere, and heaped them upon the top of the lamp when it was red-hot, no ex- plosion could ever be communicated. Phos- phorus or sulphur, are the only substances which can produce explosion, by being ap- plied to the outside of' the lamp ; and sul- phur, to produce the eff'ect, must be appli- ed in large quantities, and fanned by a cur- rent of fresh air. He has even blown re- peatedly, fine coal dust mixed with minute quantities ofthe finest dust of gunpowder, through the lamp burning in explosive mix- tures, without any communication of explo- sion. The most timorous female might traverse an explosive coal mine, guided by the light ofthe double cylinder- lamp, with- out feeling the slightest apprehension. 5. We have now arrived at the most cu- rious of all Sir H.'s discoveries relative to fire, namely, invisible combustion. On passing mixtures of hydrogen and oxygen through tubes heated below redness, steam appeared to 'be formed without any combustion. This led him to expose mix- tures of oxygen and hydrogen to keat, in COM COM tubes, in which they were confined by fluid fusible metal. He found, that, by carefully applying a heat between the boiling point of mercury, which is not sufficient for the effect, and a heat approaching to the great- est heat that can be given without making glass luminous in darkness, the combina- tion was effected without any violence, and without any light; and commencing with 212, the volume of steam formed at the point of combination, appeared exactly equal to that of the original gases. So that the first effect in experiments of this kind, is an expansion, afterwards a contraction, and then the restoration of the primitive volume. When this change is going on, if the heat be quickly raised to redness, an ex- plosion takes place. With small quantities of gas, the invisible combustion is complet- ed in less than a minute. It is probable that the slow combination without combus- tion, long ago observed with respect to hy- drogen and chlorine, oxygen and metals, will happen at certain temperatures with most substances that unite by heat. On trying charcoal, he found, that at a tempe- rature which appeared to be a little above the boiling point of quicksilver, it convert- ed oxygen pretty rapidly into carbonic acid, without any luminous appearance; and at a dull red-heat, the elements of olefiant gas combined in a similar manner with oxygen, slowly and witiiout explo- sion. The effect of the slow combination of oxygen and hydrogen is not connected with their rarefaction by heat, for it took place when the gases were confined in a rube by fusible metal, rendered solid at its upper surface; and certainly as rapidly, and without any appearance of light. As the temperature of flame has been shown to be infinitely higher than that ne- cessary for the ignition of solid bodies, it appeared probable, that in these silent combinations of gaseous bodies, when the increase of temperature may not be suffi- cient to render the gaseous matters them- selves luminous, yet it still might be ade- quate to ignite solid matters exposed to them. Sir H. Davy had devised several experi- ments on this subject. He had intended to expose fine wires to oxygen and olefiant gas, and to oxygen and hydrogen, during their slow combination under different cir- cumstances, when he was accidentally led to the knowledge of the fact, and at the same time to the discovery of a new and curious series of phenomena. He was making experiments on the in- crease of the limits of the combustibility of gaseous mixtures of coal-gas and air, by increase of temperature. For this pur- pose, a small wire-gauze safe-lamp, with some fine wire of platinum fixed above the flame, was introduced into a combustible mixture, containing the maximum of coal- gas. When the inflammation had taken place in the wire-gauze cylinder, he threw in more coal-gas, expecting that the heat acquired by the mixed gas, in passing through the wire-gauze, would prevent the excess from extinguishing the flame. The flame continued for two or three seconds after the coal gas was introduced; and when it was extinguished, that part ofthe wire of platinum which had been hottest, remained ignited, and continued so for many minutes. When it was removed into a dark room, it was evident that there was no flame in the cylinder. It Was immediately obvious that this was the result which he had hoped to attain by other methods, and the oxygen and coal- gas in contact with the hot wire, combin- ed without flame, and yet produced heat enough to preserve the wire ignited, and keep up their own secret combustion. The truth of this conclusion was proved by in- troducing a heated wire of platinum into a similar mixture. It immediately became ignited nearly to whiteness, as if it had been in actual combustion itself, and con- tinued glowing for a long while. When it ■was extinguished, the inflammability of the mixture was found to be entirely destroyed. A temperature much below ignition only, was necessary for producing this curious phenomenon, and the wire was repeatedly taken out and cooled in the atmosphere till it ceased to be visibly red; yet when admitted again, it instantly became red- hot. The same phenomena were produced with mixtures of olefiant gas and air, car- bonic oxide, prussic gas, and hydrogen; and in this last case with a rapid produc- tion of water. The degree of heat could be regulated by the thickness of the wire. When of the same thickness, the wire be- came more ignited in hydrogen, than in mixtures of olefiant gas, and more in mix- tures of olefiant gas, than in those of gase- ous oxide of carbon. When the wire was very fine, as l-80th of an inch in diameter, its heat increased in very combustible mixtures, so as to ex- plode them. The same wire in less com- bustible mixtures, continued merely bright red, or dull red, according to the nature of the mixture. In mixtures not explosive by flame within certain limits, these curious phenomena took place, whether the air or the inflammable gas was in excess. The same circumstances occurred with certain inflammable vapours Those of ether, al- cohol, oil of turpentine, naphtha, and cam- phor, have been tried. There cannot be a better mode of illustrating the fact, than by an experiment on the vapour of ether •r of alcohol, which any person may m*ke COM COM in a minute. Let a drop of ether be thrown into a cold glass, or a drop of alcohol into a Warm one; let a few coils of wire of pla- tinum, of the l-60th or 1.70th of an inch, be heated at a hot poker or a candle, and let it be brought into the glass: In some part of the glass, it will become glowing, almost white-hot, and will continue so, as long as a sufficient quantity of vapour and of air, remain in the glass. When the experiment on the slow com- bustion of ether is made in the dark, a pale phosphorescent light is perceived above the wire, which is of course most distinct when the wire ceases to be ignited This appearance is conneded with the forma- tion of a peculiar acrid volatile substance, possessed of acid properties. See Acid (Lampic). The above experiment has been ingeniously varied by sticking loose- ly on the wick of a spirit lamp, a coil of fine platinum wire, about -j-jcr of an inch in thickness. There should be aboul 16 spiral turns, one-half of winch should sur- round the wick, and the other rise above it. Having lighted the lain]) for an instant, on blowing it out, the wire will become brightly ignited, and will continue to glow as long as any alcohol remains. A cylin- der of camphor may be substituted for both wick and spirit. The ignition is very bright, and exhales an odoriferous vapour. With oil of turpentine, the lamp burns in- visibly without igniting the wire; for a dense column of vapour is perceived to as- cend from the wire, diffusing a smell by many thought agreeable. By adding essen- tial oils in small quantities to the alcohol, various aromas may be made to perfume the air of an apartment. But the film of charcoal which in this case collects on the platina coil, must be removed by ignition over another spirit flame, otherwise the ef- fect ceases after a certain time. The chemical changes in general, pro- duced by slow combustion, appear worthy of investigation. A wire of platinum in- troduced under the usual circumstances into a mixture of prussic gas (cyanogen), and oxygen in excess, became ignited to whiteness, and the yellow vapours of ni- trous acid were observed in the mixture. In a mixture of olefiant gas, non-explosive from the excess of inflammable gas, much carbonic oxide was formed. PLtinum and palladium, metals of low conducting powers, and small capacities for heat, alone succeed in producing the above phenome- na. A film of carbon or sulphur deprives even these metals of this property. Thin laminae of the metals, if their form admits of a free circulation of air, answer as well as fine wires; and a large surface of plati- num may be made red-hot in the vapour of ether, or in a combustible mixture of coal gas and air. Sir H. Davy made an admirable practical application of these new facts. By hang- ing some coils of fine platinum wire, or a fine sheet of platinum or palladium, above the wick ofthe safe-lamp in the wire-gauze cylinder, he has supplied the coal-miner with light in mixtures of fire-damp n» longer explos've. Should the flame be ex- tinguished by the quantity of fire-damp, the glow of the platinum will continue to guide him; and by placing the lamp in dif- ferent parts of the gallery, the relative brightness of the wire will show the state ofthe atmosphere in these parts Nor can there be any danger with respect to respi- ration wherever the wire continues ignit- ed; for even this phenomenon ceases, when the foul air forms about ■§ of the volume of the atmosphere. Into a wire-gauze safe-lamp, a small cage made of fine wire of platinum, of l-70th of an inch in thickness, was introduced, and fixed by means of a thick wire of pla- tinum, about 2 inches above the lighted wirk. This apparatus was placed in a large receiver, in which, by means of a gas-holder, the air could be contaminated to any extent with coal-gas. As soon as there was a slight admixture of coal-gas, the platinum became ignited. The igni- tion continued to increase till the flame of the wick was extinguished, and till the whole cylinder became filled with flame. It then diminished. When the quantity of coal-gas was increased so as to extinguish the flame, the cage of platinum, at the mo- ment of the extinction, became white hot, presenting a most brilliant light. By in- creasing the quantity of the coal-gas still further, the ignition of the platinum be- came less vivid. When Hs light was bare- ly sensible, small quantities of air were ad- mitted, and it speedily increased. By re- gulating the admission of coal-gas and air, it aga'n became white-hot, and soon after lighted the flame in the cylinder, which as usual, by the addition of more atmosphe- ric air, rekindled the flame of the wick. This beautiful experiment has been very often repeated, and always with the same results. When the wire for the support of the cage, whether of platinum, silver, or copper, was very thick, it retained suffi- cient heat, to enable the fine platinum wire to rekindle in a proper mixture half a mi- nute after its light had been entirely des- troyed, by an atmosphere of pure coal-gas. The phenomenon of the ignition of the pla- tinum, takes place feebly in a mixture con- sisting of two of air and one of coal-gas; and brilliantly in a mixture consisting of three of air and one of coal-gas The greater the quantity of heat produced, the greater may be the quantity of the coal- gas, so that a large tissue of wire made white-hot, will burn in a more inflammable COM COM mixture (that is, containing more inflam- mable gas), than one made red-hot. If a mixture of three parts of air and one of fire-damp, be introduced into a bottle, and inflamed at its point of contact with the atmosphere, it will not explode, but will burn like a pure inflammable substance. If a fine wire of platinum, coiled at its end, be slowly passed through the flame, it will continue ignited in the body of the mix- ture, and the same gaseous matter will be found to be inflammable, and to be a sup- porter of combustion. When a large cage of wire of platinum is introduced into a very small safe-lamp, even explosive mix- tures of fire-damp are burned without flame; and by placing any cage of platinum in the bottom of the lamp round the wick; the wire is prevented from being smoked. Care should be taken of course, that no filament of the platinum protrude through the wire-gau/:e. It is truly wonderful, that a slender tissue of platinum, which does not cost one shilling, and which is imper- ishable, sliould afford in the dark and dan- gerous recesses of a coal mine, a most bril- liant light, perfectly safe, in atmospheres in which the flame of the safety-lamp is extinguished; and which glows in every mixture of carburetted hydrogen gas that is respirable. When the atmosphere be- comes again explosive, the fame is re- lighted. It is no less surprising, that thus also we can burn any inflammable vapour, either with or without fl..me, at pleasure, and make a slender wire consume it, either with a white or red heat. 6. We shall conclude the subject of combustion with some practical inferences. The facts detailed on insensible com- bustion, explain why so much more heat is obtained from fuel, when it is burned quickly than slowly; and they show, that in all cases the temperature of the acting bo- dies should be kept as high as possible, not only because the general increment of heat is greater, but likewise because those combinations are prevented, which, at lower temperatures, take place without any considerable production of heat. Thus, in the argand lamp, and in the best fire-places, the increase of eff'ect does not depend merely upon the rapid current of air, but likewise upon the heat preserved by the arrangement of the materials of the chimney, and communicated to the matters entering into inflammation. These facts likewise explain, the source ofthe great error, into which .\ir. Dalton has fallen in estimating the heat given out in the combustion of charcoal; and they in- dicate methods by which temperature may be increased, and the limits to certain me- thods. Currents of flame can never raise Vot. I. the heat of bodies exposed to them, high- er than a certain degree, that is, their own temperature. But by compression, there can be no doubt, that the heat of flames from pure supporters and combustible matter may be greatly increased, probably in the ratio of their compression. In the blow-pipe of oxygen and hydrogen, the maximum of temperature is close to the aperture from which the gases are disen- gaged, that is, where their density is greatest. Probably a degree of tempera- ture far beyond any that has yet been at- tained, may be produced by throwing tho flame from compressed oxygen and hydro- gen into the voltaic arc, and thus combin- ing the two most powerful agents for in- creasing temperature. The nature of the light, and form of flames, can now be clearly understood. When in flames pure gaseous matter is burnt, the light is extremely feeble. The density of a common flame, is proportional to the quantity of solid charcoal, the first deposited and afterwards burned. The form of the flame is conical, because the greatest heat is in the centre of the explo- sive mixture. In looking stedfastly at flame, the part where the combustible mat- ter is volatilized is seen, and it appears dark, contrasted with the part in which it begins to burn; that is, where it is so mixed with air as to become explosive. The heat diminishes towards the top of the flame, because in this part the quanti- ty of oxygen is least. When the wick in- creases to a considerable size, from col- lecting charcoal, it cools the flame by ra- diation, and prevents a proper quantity of air from mixing with its central part; in consequence, the charcoal thrown off from the top of the flame is only red-hot, and the greater part of it escapes unconsumed. The intensity of the light of flames in the atmosphere is increased by condensa- tion and diminished by rarefaction, appa- rently in a higher ratio than their heat: More particles capable of emitting light exist in the denser atmospheres, and yet most of these particles in becoming capa- ble of emitting light, absorb heat, which could not be the case in the condensation of a pure supporting medium. The facts on rarefaction of inflammable gases show, that the luminous appearances of shooting stars and meteors, cannot be owing to any inflammation of elastic fluids, but must depend on the ignition of solid bodies. Dr. Hallcy calculated the height of a meteor at ninety miles, and the great American meteor which threw down showers of stones, was estimated at seven- teen miles high. The velocity of motion of these bodies must in all cases be im- mensely great, and the heat produced by CON CON the compression of the most rarified air, from the velocity of motion, must be pro- bably sufficient to ignite the mass. All the phenomena may be explained, if falling stars be supposed to be small solid bodies moving around the earth in very eccentric orbits, which become ignited only when they pass with immense velocity through the upper regions of the atmosphere; and if the meteoric bodies which throw down stones with explosions, be supposed to be similar bodies which contain either com- bustible or elastic matter. When the common electrical or voltaic electrical spark is taken in rare air, the light is considerably diminished, as well as the heat. Yet, in a receiver that con- tained air 60 times rarer than that of the atmosphere, a piece of wire of platinum, placed by Sir H. Davy in the centre of the luminous arc, produced by the great voltaic apparatus of the Royal Institution, became white-hot; and that this was not owing to the electrical conducting powers of the platinum, was proved by repeating the experiment with a filament of glass, which instantly fused in the same position. It is evident from this, that electrical heat and light may appear in atmospheres, in which the flame of combustible bodies could not exist; and the fact is interesting from its possible application in explaining the phenomena of (lie Aurora Borealis and Australis. Finally, we may establish it as an axiom, that combustion is not the great phenomenon of chemical nature; but an adventitious ac- cidental accessory to chemical combination, or decomposition; that is, to the internal motions of the particles of bodies, tending to arrange them in a new chemical constitution. Several cases of death, from spontaneous combustion of the body, are on record. The appearances resemble those which would be produced by phosphuretted hy- drogen.* Comptonite. A new mineral, found in drusy cavities, in ejected masses, on Mount Vesuvius. It occurs crystallized, in straight four-sided prisms, which are usually truncated on their lateral edges, so as to form eight-sided prisms, termina- ted with flat summits. Transparent, or semi-transparent. Gelatinizes with acids. It is sometimes accompanied with acicular Arragonite. It was first brought to this country by Lord Compton, in 1818. * Concretions (Morbid). Solid de- posites, formed by disease in the soft parts, or in the cavities of animal bodies. The former are usually called ossifications, as they seem to consist of calcareous phosphate. They are named, according to the part in which they are deposited, pineal, salivary, pulmonary, pancreatic, hepatic, prostatic, gouty. Deposites in cavities are generally styled calculi, from their resemblance to pebbles. These are intestinal, gall-stones or biliary, renal, and urinary. See the respective articles' • Congelation. In addition to the methods pointed out under Calohic, for effecting artificial congelation, we shall here describe the elegant mode by the air- pump, recently perfected by Professor Leslie. The very ingenious Dr. Cullen seems to have been the first who applied the vacuum of an air-pump to quicken the evaporation of liquids, with a view to the abstraction of heat, or artificial congelation. In the year 1755, he plunged a full phial of ether into a tumbler of water, and on placing it under the receiver, and exhausting the air, the ether boiled, and the surrounding water froze. In the year 1777, Mr. Edward Nairne, a very eminent London optician, published in the Transactions ofthe Royal Society, " an account of some experiments made with an air-pump." After stating that at a certain point of rarefaction, the moisture about the pump furnished an atmosphere of vapour, which affected his comparative results with the mercurial gauge and pear guage, he says, " 1 now put some sulphu- ric acid into the receiver, as a means of trying to make the remaining contents of the receiver, when exhausted as much as possible, to consist of permanent air only, unadulterated with vapour." He was thus enabled by this artificial dryness to exhibit certain electrical phenomena to great ad- vantage. The next step which Mr. Nairne took, was to produce artificial cold by the air-pump. " Having lately received from my friend Dr. Lind," he says, " some ether prepared by the ingenious Mr. Woulfe, I was very desirous to try whether I could produce any considerable degree of cold by the evaporation of ether under a receiver whilst exhausting." Accordingly he suc- ceeded in sinking a thermometer, whose bulb was from time to time dipped into the ether in vacuo, 103° below 56°, the temperature ofthe apartment. Mr. Nairne made no attempt to condense the vapour in vacuo by chemical means, and thus to favour its renewed formation from the li- quid surface; which I consider to be the essence of Professor Leslie's capital im- provement, on Cullen's plan of artificial re- frigeration. After Nairne's removing the vapour of water by sulphuric acid to pro- duce artificial dryness, there was indeed but a slight step to the production of arti- ficial cold, by the very same arrangement; but still this step does not appear to have been attempted by any person from the year 1777 till 1810, when Professor Leslie was naturally led to make it, by the train CON of his researches on evaporation and hy- grometry. The extreme rapidity of evaporation in vacuo, may be inferred from Dr. Robison's position, that all liquids boil in it, at a temperature 120° to 125° lower than their usual boiling point in the atmosphere. Could we find a liquid or solid substance which would rapidly imbibe alcohol, ether or sulphuret of carbon, we would probably be able to effect reductions of temperature prodigiously greater than any hitherto reached. Water, however, has no doubt one advantage, in the superior latent heat of its vapour, which must compensate in a considerable degree for its inferior ra- pidity of vaporization. In the month of June 1810, Professor Leslie having introduced a surface of sul- phuric acid under the receiver of an air- pump, and also a watch-glass filled with water, he found that after a few strokes of the pump, the water was converted into a solid cake of ice, which being left in the rarefied medium, continued to evaporate, and after the interval of about an hour, to- tally disappeared. When the air has been rarefied 250 times, the utmost that under such circumstances can perhaps be effect- ed, the surface of evaporation is cooled down 120° Fahrenheit in winter, and would probably, from more copious evaporation and condensation, sink near 200° in sum- mer. If the air be rarefied only 50 times, a depression of 80°, or even 100°, will be produced. We are thus enabled by this elegant com- bination, to freeze a mass of water in the hottest weather, and to keep it frozen, till it gradually wastes away, by a continued but invisible process of evaporation. The only thing required is, that the surface of the acid should approach tolerably near to that ofthe water, and should have a great- er extent; for otherwise the moisture would exhale more copiously than it could be transferred and absorbed, and consequent- ly the dryness of the rarefied medium would become reduced, and its evaporating energy essentially impaired. The acid should be poured to the depth of perhaps half an inch, in a broad flat dish, which is covered by a receiver of a form nearly hemispherical; the water exposed to con- gelation may be contained in a shallow cup, about half the width ofthe dish, and hav- ing its rim supported by a narrow porce- lain ring, upheld above the surface of the acid by three slender feet. It is of conse- quence that the water should be insulated as much as possible, or should present only a humid surface to the contact of the sur- rounding medium; for the dry sides ofthe cup might receive, by radiation from the external air, such accessions of heat, as CON greatly to diminish, if not to counteract the refrigerating effects of evaporation. This inconvenience is in a great measure obviated, by investing the cup with an outer case, at the interval of about half an inch. If both the cup and its case consist of glass, the process of congelation is view- ed most completely; yet when they are formed of a bright metal, the effect ap- pears, on the whole, more striking. But the preferable mode, and that which pre- vents any waste of the powers of refrigera- tion, is to expose the water in a saucer of porous earthen ware. At the instant of congelation, a beautiful network of icy spi- cule pervades the liquid mass. The disposition of the water to fill the receiver with vapour, will seldom permit even a good air-pump to produce greater rarefaction than that indicated by 3-10ths of an inch of mercury, beneath the baro- metrical height, at the time. But every practical object may be obtained by more moderate rarefactions, and a considerable surface of acid. The process goes on more slowly, but the ice is very solid, especially if the* water have been previously purged of its air by distillation, or boiling for a considerable time. If we use a receiver, with a sliding wire passing down from its top through a collar of leathers, and attach to it a disc of glass; on applying this to the surface of the'water cup, we may instantly suspend the process of congelation; and raising the disc as suddenly, permit the advancement of the process. In exhibiting the different modifications of this system of congelation to my pupils, I have been accustomed for many years to recommend the employment of a series of cast-iron plates, attachable by screws and stop-cocks to the air-pump. Each iron disc has a receiver adapted to it. Thus, we may with one air-pump, successively put any number of freezing processes in ac- tion. A cast-iron drum of considerable di- mensions being filled with steam, by heat- ing a small quantity of water in it, will sufficiently expel the air for producing the requisite vacuum. When it is cooled by affusion of water, one of the above trans- ferrer plates being attached to the stop- cock on its upper surface, would easily enable us, without any air-pump, to effect congelation by means of sulphuric acid, in the attenuated atmosphere. Suppose the capacity of the receiver, to be l-60th of the iron cylinder; an aeriform rarefaction to this degree would be effected in a moment by a turn of the stop-cock; and on its be- ing returned, the moisture below would be cut off, and the acid would speedily condense the small quantity of vapour which had ascended. This cheap and powerful plan was pub- CON COP licly recommended by me upwards of ten years ago, when I had a glass model of it made for class illustration. The combined powers of rarefaction, va- porization, and absorption, are capable of effecting the congelation of quicksilver. If this metal, contained in a hollow pear- shaped piece of ice, be suspended by cross threads near a broad surface of sulphuric acid, under a receiver, on urging the rare- faction, it will become frozen, and may be kept in the solid state for several hours. Or otherwise, having introduced mercury into the large bulb of a thermometer, and attached the stem to the sliding rod of the receiver, place this over the sulphuric acid, and water cup on the air-pump plate. Af- ter the air has been rarefied about 50 times, let the bulb be dipped repeatedly into the very cold but unfrozen water, and again drawn up about an inch. In this way it will become incrusted with successive coats of ice, to the twentieth of an inch thick. The cup of water being now withdrawn from the receiver, the pendent icicle cut away from the bulb, and the surface of the ice smoothed with a warm finger, the re- ceiver is again to be replaced, and the bulb being let down within half an inch of the acid, the exhaustion must be pushed to the utmost. When the syphon-gauge arrives at the tenth of an inch, the icy crust opens with fissures, and the mercury having gradually descended in the tube, till it reach its point of congelation, or 59° be- low zero, sinks by a sudden contraction almost into the cavity of the bulb. The apparatus being now removed, and the ball speedily broken, the metal appears a solid shining mass, that will bear the stroke of a hammer. A still greater degree of cold may be produced, by applying the same process to cool the atmosphere, which sur- rounds the receiver. When the acid has acquired one-tenth of water, its refrigerating power is diminish- ed only one-hundredth. When the quan- tity of moisture is equal to one-fourth of the concentrated acid, the power of gene- rating cold is reduced by a twentieth; and when the dilution is one-half, the cooling powers become one-half or probably less. Sulphuric acid is hence capable of effect- ing the congelation of more than twenty times its weight of water, before it has im- bibed nearly its own bulk of that liquid, or has lost about one-eighth of its refrige- rating power. The acid should then be removed, and reconcentrated by heat. The danger of using a corrosive acid in unskilful hands, may be obviated by using oatmeal,desiccated nearly to brownness be- fore a kitchen-fire, and allowed to cool in close vessels. With a body of this, a foot in diameter, and an inch deep, Professor Leslie froze a pound and a quarter of wa- ter, contained in a hemispherical porous cup. Muriate of hme in ignited porous pieces, may also be employed as an ab- sorbent. Even mouldering trap or whin- stone, has been used for experimental il- lustration with success. By the joint operation of radiation and evaporation from the surface of water, the natives of India are enabled to procure a supply of ice, when the temperature ofthe air is many degrees above the freezing point. Not far from Calcutta, in large open plains, three or four excavations are made in the ground, about 30 feet square, and 2 feet deep, the bottom of which is covered to the thickness of nearly a foot with su- gar canes, or dried stalks of Indian corn. On this bed are placed rows of small un- glazed earthen pans, about an inch and a quarter deep, and somewhat porous. In the dusK of the evening, during the months of December, January, and February, they are filled with soft water, previously boiled and suffered to cool. VVhen the weather is very fine and clear, a great part of the water becomes frozen during the night. The pans are regularly visited at sunrise, and their contents emptied into baskets which retain the ice. These are now car- ried to a conservatory made by sinking a pit 14 or 15 feet deep, lined with straw un- der a layer of coarse blanketing. The small sheets of ice are thrown down into the ca- vity, and rammed into a solid mass. The mouth of the pit is then closed up with straw and blankets, and sheltered by a thatched roof. For some additional facts, on this inte- resting subject, see the sequel of the arti- cle Dew.* * Conite. An ash or greenish-gray co- loured mineral, which becomes brown on exposure to the air. It is massive or stalac- titic, is dull internally, and has a small grained uneven fracture. It is brittle; sp. gr. 2.85. It dissolves in nitric acid, with slight effervescence, and blackens without fusing before the blow-pipe. Its constitu- ents are 67.5 carbonate of magnesia, 28 carbonate of lime, 3.5 oxide of iron, and 1 water. It is found in the Meissner trap hill in Hessia, in Saxony, and Iceland. Dr. Macculloch has given the name Conite to a pulverulent mineral, as fusible as glass, into a transparent bead, which he found in Mull and Glenfarg, in the trap hills of Kil- patrick, and the Isle of Sky.* Copal, improperly called gum copal,is a hard, shining, transparent, citron-colour- ed, odoriferous, concrete juice of an Ame- rican tree, but which has neither the solu- bility in water common to gums, nor the solubility in alcohol common to resins, at least in any considerable degree. By these properties it resembles amber. It may be dissolved by digestion in linseed oil, ren- COP COP dered drying by quicklime, with a heat very little less than sufficient to boil or de- compose the oil. This solution, diluted with oil of turpentine, forms a beautiful transparent varnish, which, when properly applied, and slowly dried, is very hard, and very durable. This varnish is applied to snuff-boxes, tea-boards, and other utensils. It preserves and gives lustre to paintings, and greatly restores the decayed colours of old pictures, by filling up the cracks, and rendering the surfaces capable of re- flecting light more uniformly. Mr. Sheldrake has found, that camphor has a powerful action on copal; for if pow- dered copal be triturated with a little cam- phor, it softens, and becomes a coherent mass; and camphor added either to alcohol or oil of turpentine, renders it a solvent of copal. Half an ounce of camphor is suffi- cient for a quart of oil of turpentine, which should be of the best quality; and the co- pal, about the quantity of a large walnut, should be broken into very small pieces, but not reduced to a fine powder. The mixture should be set on a fire so brisk as to make the mixture boil almost immedi- ately; and the vessel Mr. S. recommends to be of tin or other metal, strong, shaped like a wine bottle with a long neck, and capable of holding two quarts. The mouth should be stopped with a cork, in which a notch is cut to prevent the vessel from bursting. It is probably owing to the quan- tity of camphor it contains, that oil of la- vender is a solvent of copal. Camphor and alcohol dissolve copal still more readily than camphor and oil of turpentine. Lewis had observed, that solution of am- monia enabled oil of turpentine to dissolve copal; but it requires such nice manage- ment of the fire that it seldom succeeds completely. • In the 51st volume of Tilloch's Maga- zine, Mr. Cornelius Varley states, that a good varnish may be made by pouring upon the purest lumps of copal, reduced to a fine mass, in a mortar, colourless spirits of tur- pentine, to about one-third higher than the copal, and triturating the mixture occa- sionally in the course of the day. Next morning it may be poured off into a bottle for use. Successive portions of oil of tur- pentine may thus be worked with the same copal mass. Camphorated oil of turpen- tine, and oil of spike-lavender, are also re- commended as separate solvents without trituration. The latter, however, though very good for drawings or prints, will not do for varnishing pictures, as it dissolves the paint underneath, and runs down while drying.* Co pp er is a metal of a peculiar reddish- brown colour; hard, sonorous, very mallea- ble and ductile; of considerable tenacity, and of a specific gravity from 8.6 to 8.9. At a degree of heat far below ignition, the surface of a piece of polished copper be- comes covered with various ranges of pris- matic colours, the red of each order being nearest the end which has been most heat- ed; an effect which must doubtless be at- tributed to oxidation, the stratum of oxide being thickest where the heat is greatest, and growing gradually thinner and thinner towards the colder part A greater de- ree of heat oxidizes it more rapidly, so that it contracts thin powdery scales on its surface, which may be easily rubbed off; the flame of the fuel becoming at the same time of a beautiful bluish-green colour. In a heat, nearly the same as is necessary to melt gold or silver, it melts and exhibits a bluish-green flame; by a violent heat it boils, and is volatilized partly in the me- tallic state. Copper rusts in the air; but the corroded part is very thin, and preserves the metal beneath from farther corrosion. * We have two oxides of copper, the black, procurable by heat, or by drying the hydrated oxide, precipitated by potash from the nitrate. It consists of 8 copper -f- 2 oxygen. It is a deutoxide. The pro- toxide is obtained by digesting a solution of muriate of copper with copper turn- ings, in a close phial. The colour passes from green to dark brown, and gray crys- talline grains are deposited. The solution of these yields, by potash, a precipitate of an orange colour, which is the protoxide. It consists of 8 copper 4- 1 oxygen. Pro- toxide of copper has been lately found by Mr. Mushet, in a mass of copper, which had been exposed to heat for a considera- ble time, in one of the melting furnaces of the mint under his superintendence. Copper, in filings, or thin laminx, intro- duced into chlorine, unites with flame into the chloride, of which there are two varie- ties; the protochloride, a fixed yellow sub- stance, and the deutochloride, a yellowish- brown pulverulent sublimate. 1. The crys- talline grains deposited from the above mu- riatic solution, are protochloride. The pro- tochloride is conveniently made by heating together two parts of corrosive sublimate, and one of copper filings. An amber- coloured translucent substance, first dis- covered by Boyle, who called it resin of copper, is obtained. It is fusible at a heat just below redness; and in a close vessel, or a vessel with a narrow orifice, is not de- composed or sublimed by a strong red heat. Rut if air be admitted it is dissipated in dense white fumes. It is insoluble in wa- ter. It effervesces in nitric acid. It dis- solves silently in muriatic acid, from which it may be precipitated by water. By slow cooling of the fused mass Dr. John Davy obtained it crystallized, apparently in small plates, semitransparent, and of a light yel- COP COP low colour. It consists, by the same inge- nious chemist, of Chlorine, 36 or 1 prime = 4.45 35.8 Copper, 64 or 1 prime 8.00 64.2 100 12.45 100.0 2. Deutochloride is best made by slowly evaporating to dryness, at a temperature not much above 400° Fahr. the deliques- cent muriate of copper. It is a yellow pow- der. By absorption of moisture from the air, it passes from yellow to white, and then green, reproducing common muriate. Heat converts it into protochloride, with the disengagement of chlorine. Dr. Davy ascertained the chemical constitution of both these compounds, by separating the copper with iron, and the chlorine by ni- trate of silver. The deutochloride consists of Chlorine, 53 2 primes 8.9 52.7 Copper, 47 1 do. 8.0 47.3 100 16.9 100 0 The iodide of copper is formed by drop- ping aqueous hydriodate of potash into a solution of any cupreous salt It is an in- soluble dark brown powder. Phosphuret of copper is made by project- ing phosphorus into red-hot copper. It is of a white colour, harder than iron, pretty fusible, but not ductile. Its sp. gr. is 7.12. It crystallizes in four-sided prisms. Proust, its discoverer, says it consists of 20 phos- phorus -4- 80 copper. 1.5 or 3.0 phospho- rvis -f- 8.0 copper, form the equivalent pro- portions by theory. Heat burns out the phosphorus, and scorifies the copper. Sulphuret of copper is formed by mixing together eight parts of copper filings, and two of sulphur, and exposing the mixture to a gentle heat. Whenever the sulphur is raised a little above its melting tempera- ture, combustion suddenly pervades the whole mass with explosive violence. Ignition, with reciprocal saturation, con- stitutes a true combustion, of which every character is here. And since the experi- ment succeeds perfectly well in vacuo, or in azote, we are entitled to consider sul- phur as a true supporter of combustion, if this name be retained in chemistry; a name indicating, what no person can prove, that one ofthe combining bodies is a mere sup- porter, and the other a mere combustible. Combustion is, on the contrary, shown by this beautiful experiment, to be indepen- dent of those bodies vulgarly reckoned supporters Indeed, sulphur bears to cop- per the same electrical relation, that oxy- gen and chlorine bear to this metal. Hence sulphur is at once a supporter and com- bustible, in the fullest sense; a fact fatal to this technical distinction, since one body cannot be possessed of diametrically op- posite qualities. When a disc of copper, with an insulat- ed handle, is made to touch a disc of sul- phur, powerful electrical changes ensue; and at a higher temperature we see, that the reciprocal attractive forces, or the cor- puscular movements which accompany en- ergetic affinity, excite the phenomena of combustion. To say that one of the com- bining bodies contains a latent magazine of heat and light, to feed the flame of the other body, is an hypothesis altogether des- titute of proof, which should therefore have no place in one ofthe exact sciences, far less be made the groundwork of a che- mical system. Sulphuret of copper consists, according to Berzelius, of very nearly 8 copper + 2 sulphur. Wre may regard it as containing a prime of each constituent.* The sulphuric acid, when concentrated and boiling, dissolves copper. If water be added to this, it forms a blue solution of copper, which, by evaporation, affords blue crystals, that require about four times their weight of water to dissolve them. The solutions of copper in sulphuric acid are slightly caustic. Magnesia, lime, and the fixed alkalis, precipitate the metal from them in the form of oxide. Volatile alkali precipitates all the solution of cop- per, but redissolves the oxide, and pro- duces a deep blue colour. There are cer- tain mineral waters in Hungary, Sweden, Ireland, and in various parts of England, which contain sulphate of copper, and from which it is precipitated by the addi- tion of pieces of old iron. Nitric acid dissolves copper with great rapidity, and disengages a large quantity of nitrous gas. Part of the metal falls down in the form of an oxide; and the fil- trated or decanted solution, which is of a much deeper blue colour than the sulphu- ric solution, affords crystals by slow eva- poration. This salt is deliquescent, very soluble in water, but most plentifully when the fluid is heated. Its solution, exposed to the air in shallow vessels, deposites an oxide of a green colour. Lime precipi- tates the metal of a pale blue, fixed alkalis of a bluish-white. Volatile alkali throws down bluish flocks, which are quickly re- dissolved, and produce a lively blue colour in the fluid. * The saline combinations of copper were formerly called sales veneris, because Venus was the mythological name of cop- per. They have the following general cha- racters: I. They are mostly soluble in water, and their solutions have a green or blue colour, or acquire one of these co- lours on exposure to air. 2. Ammonia added to the solutions, produces a deep blue colour. 3. Ferroprussiate of potash gives a reddish-brown precipitate, with cu- preous salts. 4. Gallic acid gives a brown COP COP preciqitate. 5. Hydrosulphuret of potash gives a black precipitate. 6. A plate of iron immersed in these solutions throws down metallic copper, and very rapidly if there be a shglit excess of acid. The prot- oxide of copper can be combined with the acids only by very particular management. All the ordinary salts of copper have the peroxide for a base. Acetate of copper. The joint agency of air and acetic acid, is necessary to the pro- duction of the cupreous acetates. By ex- posing copper plates to the vapours of vine- gar, the bluish-green verdigris is formed, which by solution in vinegar constitutes acetate of copper. This salt crystallizes in four-sided truncated pyramids. Its colour is a fine bluish-green. Its sp. gr is 1.78. It has an austere metallic taste; and swal- lowed, proves a violent poison. Boiling water dissolves one-fifth of the salt, of which it deposites the greater part on cool- ing. It is soluble also in alcohol. It ef- floresces by exposure to air. By heat, in a retort, it yields acetic acid, and pyro-ace- tic spirit. Sulphuretted hydrogen throws down the copper from solutions of this salt, in the state of sulphuret. Dr. Thom- son gives the following account of its com- position: " According to Proust, the ace- tate of copper is composed of 61 acid and water, 39 oxide, 100 " If we suppose it a compound of 1 atom acid, 1 atom oxide, and 8 atoms water, its constituents will be Acetic acid, 25.12 Peroxide of copper, 39.41 Water, 35.47 100.00 "I consider these to be its true constitu- ents." Here we have an amusing specimen of atomical reasoning; beginning the syllo- gism with a supposition, and concluding it with a certainty. I had occasion to ana- lyze this salt with some care about two years ago, and found it to consist by expe- riment of Exper. Theory. Acetic acid, 52.0 2 atoms 13.26 51.98 Perox of cop. 39.6 1 do. 10.00 39 20 Water, 8.4 1 do. 2.25 8.82 100.0 25.51 100.00 Instead of 35§ per cent of water, which the Doctor pitches on at random, it has not 9; and instead of only 25 of acid, it really contains more than double that quantity. The crystallized salt is a binacetate of cop- The subacetate of Proust, obtained by dissolving verdigris in water, is said to consist of acid and water, 37 Oxide, 63 The proportion of 40 acid -f- 60 oxide, is that of 1 atom of each, to use the hypo- pothetical term. Now Proust's experiments seem to leave uncertainty to the amount of that difference. This salt should be called probably the acetate. Proust's insoluble part of verdigris will become the subace- tate. This constitutes 44 per cent, and the other 56. But the proportions will fluctu- ate; and an intermixture of carbonate may be expected occasionally.^ Arseniate of copper presents us with many sub-species which are found native. The arseniate may be formed artificially by di- gesting arsenic acid on copper, or by ad- ding arseniate of potash to a cupreous sa- line solution. 1. Obtuse octohedral arseniate, consisting of two four-sided pyramids, applied base to base, of a deep sky-blue or grass-green colour. Their sp. gr. is 2.88. They con- sist, according to Chenevix, of 14.3 acid + 50 brown oxide -f 35.7 water. 2. Hex- ahedral arseniate is found in fine six-sided laminae, divisible into thin scales. Its co- lour is a deep emerald-green; and its sp. gr. 2.548. It consists, by Vauquelin, of 43 acid -f 39 oxide -j- 18 water. When arse- niate of ammonia is poured into nitrate of copper, this variety precipitates in small blue crystals. 3. Acute octohedral arseniate, com- posed of two four-sided pyramids, applied base to base, and sometimes in rhomboidal prisms, with dihedral summits. It con- sists of 29 acid -f 50 oxide -f 21 water. The last ingredient is sometimes wanting. 4. Trihedral arseniate occurs also in other forms. Colour bluish-green. It consists, by Chenevix, of 30 acid + 54 oxide +16 water. 5. Super arseniate. On evaporating the supernatant solution in the second va- riety artificially made, and adding alcohol, M. Chenevix obtained a precipitate in small blue rhomboidal crystals. They were composed of 40.1 acid + 35.5 oxide -f- 24.4 water. The following is a general ta- ble ofthe composition of these arseniates:— Acid. Oxide. Water. 1.00 3.70 250 1.00 276 1.00 1.00 1.72 0.70 1.00 1.80 0.53 1.00 0.88 0.60 It will require the atomical couch of Pro- crustes, to accommodate these proportions to the number 14.5, recently pitched upon for arsenic acid by Dr. Thomson. Arsenite of copper, called Scheele's green, is prepared by the old prescription of mix- ing a solution of 2 parts of sulphate of copper in 44 of water, with a solution of 2 parts of potash of commerce, and 1 of pulverized arsenious acid, also in 44 of COP COP water. Both solutions being warm, the first is to be gradually poured into the second. The grass-green insoluble precipitate is to be well washed with water. Carbonate of copper. Of this compound there are three native varieties, the green, the blue, and the anhydrous. According to Mr. R. Phillips, the following is the or- der of their composition:— 1st. 2d. 3d. Carbonic acid, 2.75 11.00 2.75 Deutox. copper, 10.00 30.00 10.00 Water, # 1.125 2.25 0.00 Weights of primes, 13.875 43.25 12.75 The artificial carbonate, obtained by Proust, on adding an alkaline carbonate to a solution of the nitrate of copper, is the same with the second kind. Chlorate of copper is a deflagrating deli- quescent green salt. Fluate of copper is in small blue-coloured crystals. Hydriodate of copper is a grayish-white powder. Protomuriate of copper has already been described in treating of the chlorides. Deutomuriate of copper, formed by dis- solving the deutoxide in muriatic acid, or by heating muriatic acid on copper filings, yields by evaporation crystals of a grass- green colour, in the form of rectangular pa- rallelopipeds. Their sp. gr. is 1.68. They are caustic, very deliquescent, and of course very soluble in water. According to Berzelius, it consists of acid, 40.2 Deutoxide, 59.8 folio The ammonia-nitrate evaporated, yields a fulminating copper. Crystals of nitrate, mixed with phosphorus, and struek with a hammer, detonate. When pulverized, then slightly moistened, and suddenly wrapt up firm, in tin-foil, the nitrate produces an explosive combustion. The nitrate seems to consist of a prime of acid -+- a prime of deutoxide, besides water of crystallization. Snbnitrute of copper is the blue precipi- tate, occasioned by adding a little potash to the neutral nitric solution. JVitrite of copper is formed by mixing ni- trite of lead with sulphate of copper. The sulphate or blue vitriol of commerce is a bisulphate. Its sp. gr. is 2.2. It con- sists of Acid, 31.38 2 primes, 10.0 32.0 Oxide, 3232 1 do. 10.0 32.0 Water, 36.30 10 do. 1125 36.0 10000 31.25 100.0 A mixed solution of this sulphate and sal ammoniac, forms an ink, whose traces are invisible in the cold, but become yellow when heated; and vanish again as the paper cools. A neutral sulphate of copper may be formed by saturating the excess of acid with oxide of copper. It crystallizes in four-sided pyramids, separated by qua- drangular prisms. Mr. Proust formed a subsulphate by ad- ding a little pure potash to a solution of the last salt. A green-coloured precipitate falls. Protosulpkite of copper is formed by pass- ing a current of sulphurous acid gas through the deutoxide of copper diffused in water. It is deprived of a part of its oxygen, and combines with the acid. The sulphate, si- multaneously produced, dissolves in the water; while the sulphite forms small red crystals, from which merely long ebulli- tion in water expels the acid. Sulphite of potash and copper is made by adding the sulphite of potasli to nitrate of copper. A yellow flocculent precipitate, consisting of minute crystals, falls. Ammonia-sulphate of copper is the salt formed by adding water of ammonia to solution of the bisulphate. It consists, ac- cording to Berzelius, of 1 prime of the cupreous, and 1 of the ammoniacal sul- phate, combined together; or 20.0 -f- 7.13 -+- 14.625 of water. Subsulphate of ammonia and copper is formed by adding alcohol to the solution of the preceding salt, which precipitates the subsulphate. It is the cuprum ammoni- acum of the pharmacopoeia. According to Berzelius, it consists of Acid, 32.25 or nearly 2 primes, Deutox. of copper, 34.00 1 do. Ammonia, 26.40 4 do. Water, 7.35 2 do. 100.00 Sulphate of potash and copper is formed by digesting bisulphate of potash on the deutoxide or carbonate of copper. Its crystals are greenish-coloured, flat paral- lelopipedons. It seems to consist of 2 primes of sulphate of potash -j- 1 prime of bisulphate of copper -f- 12 of water. The following acids, antimonic, anti- monious, boracic, chromic, molybdic, phos- phoric, tungstic, form insoluble salts with deutoxide of copper. The first two are green, the third is brown, the fourth and fifth green, and the sixth white. The benzoate is in green crystals, sparingly so- luble. The oxalate is also green. The binoxalates of potash and soda, with ox- ide of copper, give triple salts, in green needle-form crystals. There are also am- monia-oxalates in different varieties. Tar- trate of copper forms dark bluish-green crystals. Cream-tartrate of copper is a bluish-green powder, commonly called Brunswick Green. To obtain pure copper for experiments, COP COP we precipitate it in the metallic state, by immersing a plate of iron in a solution of the deutomuriate. The pulverulent copper must be washed with dilute muriatic acid.* In the wet way Brunswick or Friezland green is prepared by pouring a saturated solution of muriate of ammonia over cop- per filings or shreds in a close vessel, keep- ing the mixture in a warm place, and ad- ding more of the solution from time to time, till three parts of muriate and two of copper have been used. After standing a few weeks, the pigment is to be separated from the unoxidized copper, by washing through a sieve; and then it is to be well washed, and dried slowly in the shade. This green is almost always adulterated with ceruse. This metal combines very readily with gold, silver, and mercury. It unites im- perfectly with iron in the way of fusion. Tin combines with copper, at a tempera- ture much lower than is necessary to fuse the copper alone. On this is grounded the method of tinning copper vessels. For this purpose, they are first scraped or scoured; after which they are rubbed with sal am- moniac. They are then heated, and sprink- led with powdered resin, which defends the clean surface of the copper from ac- quiring the slight film of oxide, that would prevent the adhesion of the tin to its sur- face. The melted tin is then poured in, and spread about. An extremely small quantity adheres to the copper, which may perhaps be supposed insufficient to prevent the noxious effects of the copper, as per- fectly as might be wished. When tin is melted with copper, it com- poses tbe compound called bronze. In this metal the specific gravity is always greater than would be deduced by computation from the quantities and specific gravities of its component parts. The uses of this hard, sonorous, and durable composition, in the fabrication of cannon, bells, statues, and other articles, are well known. Bronzes and bell-metals are not usually made of copper and tin only, but have other admix- tures, consisting of lead, zinc, or arsenic, according to the motives of profit, or other inducements of the artist. But the atten- tion of the philosopher is more particularly directed to the mixture of copper and tin, on account of its being the substance of which the speculums of reflecting tele- scopes are made. See Speculum. The ancients made cutting instruments of this alloy. A dagger analyzed by Mr. Hielm consisted of 83^ copper, and 16^ tin. Copper unites with bismuth, and forms a reddish-white alloy. With arsenic it forms a white brittle compound, called tombac. With zinc it forms the compound called brass, and distinguished by various other Vol.. I. names, according to the proportions of the two ingredients. It is not easy to unite these two metals in considerable propor- tions by fusion, because the zinc is burnt or volatilized at a heat inferior to that which is required to melt copper; but they unite very well in the way of cementation. In the brass works, copper is granulated by pouring it through a plate of iron, per- forated with small holes and luted with clay, into a quantity of water about four feet deep, and continually renewed: to pre- vent the dangerous explosions of this me- tal, it is necessary to pour but a small quan- tity at a time. There are various methods of combining this granulated copper, or other small pieces of copper, with the va- pour of zinc. Calamine, which is an ore of zinc, is pounded, calcined, and mixed with the divided copper, together with a portion of charcoal. These being exposed to the heat of a wind furnace, the zinc be- comes revived, rises in vapour, and com- bines with the copper, which it converts into brass. The heat must be continued for a greater or less number of hours, ac- cording to the thickness of the pieces of copper, and other circumstances; and at the end of the process, the heat being sud- denly raised, causes the brass to melt, and occupy the lower part ofthe crucible. The most scientific method of making brass seems to be that mentioned by Cramer. The powdered calamine, being mixed with an equal quantity of charcoal and a portion of clay, is to be rammed into a melting ves- sel, and a quantity of copper, amounting to two-thirds of the weight of calamine, must be placed on the top, and covered with char- coal. By this management the volatile zinc ascends, and converts the copper into brass, which flows into the rammed clay; conse- quently, if the calamine contain lead, or any other metal, it will not enter into the brass, the zinc alone being raised by the heat. A fine kind of brass, which is supposed to be made by cementation of copper plates with calamine, is hammered out into leaves in Germany; and is sold very cheap in this country, under the name of Dutch gold, or Dutch metal. It is about fivo times as thick as gold leaf; that is to say, it is about one sixty-thousandth of an inch thick. Copper unites readily with antimony, and affords a compound of a beautiful violet colour. It does not readily unite with man- ganese. With tungsten it forms a dark brown spongy alloy, which is somewhat ductile. Seen Ores of ''opper. * Verdigris, and other preparations of copper, act as virulent poisons, when intro- duced in very small quantities into the sto- machs of animals. A few grains are suf- ficient for this eff'ect. Death is commonly preceded by very decided nervous disor- 43 COR CRI ders, such as convulsive movements, te- tanus, general insensibility, or a palsy of the lower extremites. This event happens frequently so soon, that it could not be oc- casioned by inflammation or erosion of the primae vix; and indeed, where these parts are apparently sound. It is probable that the poison is absorbed, and through the circulation, acts on the brain and nerves. The cupreous preparations are no doubt very acrid, and if death do not follow their immediate impression on the sentient sys- tem, they will certainly inflame the intes- tinal canal. The symptoms produced by a dangerous dose of copper are exactly similar to those which are enumerated un- der arsenic, only the taste of copper is strongly felt. The only chemical antidote to cupreous solutions whose operation is well understood, is water strongly impreg- nated with sulphuretted hydrogen. The alkaline hydrosulphurets are acrid, and ought not to be prescribed. But we possess in sugar, an antidote to this poison of undoubted efficacy, though its mode of action be obscure. M. Duval introduced into the stomach of a dog, by means of a caoutchouc tube, a solution in acetic acid, of four French drachms of ox- ide of copper. Some minutes afterwards he injected into it four ounces of strong sirup. He repeated this injection every half-hour, and employed altogether 12 ounces of sirup. The animal experien- ced some tremblings and convulsive move- ments. But the last injection was follow- ed by a perfect calm. The animal fell asleep, and awakened free from any ail- ment. Orfila relates several cases of individuals who had by accident or intention swallow- ed poisonous doses of acetate of copper, and who recovered by getting large doses of sugar. He uniformly found, that a dose of verdigris which would kill a dog in the course of an hour or two, might be swal- lowed with impunity, provided it was mix- ed with a considerable quantity of sugar. As alcohol has the power of completely neutralizing, in the ethers, the strongest muriatic and hydriodic acids, so it would appear, that sugar can neutralize the ox- ides of copper and lead. The neutral sac- charate of lead, indeed, was employed by Berzelius in his experiments, to determine the prime equivalent of sugar. If we boil for half an hour, in a flask, an ounce of white sugar, an ounce of water, and 10 grains of verdigris, we obtain a green li- quid, which is not affected by the nicest tests of copper, such as ferroprussiate of potash, ammonia, and the hydrosulphurets. An insoluble green carbonate of copper re- mains at the bottom of the flask.* Copperas. Sulphate of iron. * Corals seem to consist of carbonate of lime and animal matter, in equal pro- portions.* Cork is the bark of a tree of the oak kind, very common in Spain and the other southern parts of Europe. By the action of the nitric acid it was found to be acidified. See Acid (Sube- ric). * Cork has been recently analyzed by Chevreul by digestion, first in water and then in alcohol. By distillation there came over an aromatic principle, and a little ace- tic acid. The watery extract contained a yellow and a red colouring matter, an un- determined acid, gallic acid, an astringent substance, a substance containing azote, a substance soluble in water and insoluble in alcohol, gallate of iron, lime, and traces of magnesia. 20 parts of cork treated in this way, left 17.15 of insoluble matter. The undissolved residue being treated a sufficient number of times with alcohol, yielded a variety of bodies, but which seem reducible to three; namely, cerin, resin, and an oil. The ligneous portion of the cork still weighed 14 parts, which is called suber.* Cork (Fossil). See Asbestos. Corrosive Sublimate. See Mercu- ry. •Corundum. According to Professor Jameson, this mineral genus contains 3 spe- cies, viz. octohedral corundum, rhomboidal corundum, and prismatic corundum. 1. Octohedral, is subdivided into 3 sub- species, viz. automalite, ceylanite, and spi- nel. 2. Rhomboidal corundum, contains 4 sub- species, viz. salamstone, sapphire, emery, and corundum, or adamantine spar. 3. Prismatic, or chrysoberyl. See the several sub-species, under their titles m the Dictionary.* * Cotton. This vegetable fibre is solu- ble in strong alkaline leys. It has a strong affinity for some earths, particularly alu- mina, several metallic oxides, and tannin. Nitric acid, aided by heat, converts cotton into oxalic acid.* * Couch. The heap of moist barley about 16 inches deep on the malt-floor.* * Cream. The oily part of milk, which rises to the surface of that liquid, mixed with a little curd and serum. When churn- ed, butter is obtained. Heat separates the oily part, but injures its flavour.* Cream of Tartar. See Acid (Tar- taric). * Crichtonite. A mineral so called in honour of Dr. Crichton, physician to the Emperor of Russia, an eminent mineralo- gist. It has a velvet-black colour, and crys- tallizes in very acute small rhomboids. Lustre splendent, inclining to metallic; fracture conchoidal; opaque; scratches fluor spar, but not glass. Infusible before CRU CRY the blow-pipe. It occurs in primitive rocks along with octahedrite. Professor Jame- son thinks it may probably be a new spe- cies of titanium-ore.* Crocus. The yellow or saffron-colour- ed oxides or iron and copper were former- ly called crocus martis and crocus veneris. That of iron is still called crocus simply, by the workers in metal who use it. * Cross-stone. Harmotome, or pyra- midal zeolite. Its colour is grayish-white, passing into smoke-gray, sometimes mas- sive, but usually crystallized. Primitive form, a double four-sided pyramid, of 121° 58' and 86° 36'. Its principal secondary forms are, a broad rectangular four-sided prism, rather acutely acuminated on the extremities with 4 planes, which are set on the lateral edges; the preceding figure, in which the edges formed by the meeting of the acuminating planes, that rest on the broader lateral planes, are truncated; twin crystals ofthe first form, intersecting each other, in such a manner that a common axis and acumination are formed, and the broad- er lateral planes make four re-entering an- gles. The crystals are not large. The surface of the smaller lateral planes is double-plumosely streaked. Lustre glis- tening, between vitreous and pearly. Of the cleavage, 2 folia are oblique, and 1 pa- rallel to the axis. Fracture perfect con- choidal. Translucent and semi-transparent. Harder than fluor spar, but not so hard as apatite. Easily frangible. Sp. gr. 2.35. It fuses with intumescence and phosphores- cence, into a colourless glass. Its consti- tuents are 49 silica, 16 alumina, 18 bary- tes, and 15 water, by Klaproth. It has hitherto been found only in mineral veins and agate-balls. It occurs at Andreasberg in the Hartz, at Kongsberg in Norway, at Oberstein, Strontian in Argyllshire, and also near Old Kilpatrick in Scotland. Jameson* • Croton Eleutheria. Cascanlla bark. The following is Trommsdorfs ana- lysis of this substance, characterized by its emitting the smell of musk when burn- ed. Mucilage and bitter principle 864 parts, resin 688, volatile matter 72, water 48, woody fibres 3024; in 4696 parts.* • Crusts, the bony coverings of crabs, lobsters, &c. Mr. Hatchett found them to be composed of a cartilaginous substance, like coagulated albumen, carbonate of lime, and phosphate of lime. The great excess of the second, above the third ingredient, distinguishes them from bones; while the quantity of the third, distinguishes them from shells. Egg-shells and sna.l-she Is belong to crusts in composition; but the animal matter is in smaller quantity. By Merat-Guillot, 100 parts of lobster crust, consist of 60 carbonate of lime, 14 phos- phate of lime, and 26 cartilaginous matter. 100 of hen's egg-shells, consist of 89.6 car- bonate of lime, 5.7 phosphate of lime, 4.7 animal matter.* * Cryolite. A mineral which occurs massive, disseminated, and in thick lamel- lar concretions. Its colours are white and yellowish-brown. Lustre vitreous, inclin- ing to pearly. Cleavage fourfold, in which the folia are parallel with an equiangular four-sided pyramid. Fracture uneven. Translucent. Haider than gypsum. Easily frangible. Sp. gr. 2.95. It becomes more translucent in water. It melts in the heat of a candle. Before the blow-pipe, it be- comes first very liquid, and then assumes a slaggy appearance. It consists, by Klap- roth, of 24 alumina, 36 soda, and 40 fluoric acid and water." It is therefore a soda- fluate of alumina. If we regard it as com- posed of definite proportions, we may have 1 prime alumina, 3.2 26.33 1 do. soda, 3.95 32.51 2 do. acid, 2.75 22.63 2 do. water, 2.25 18.53 S}« 16. 12.15 100.00 Vauquelin's analysis ofthe same miner- al gives 47 acid and water, 32 soda, and 21 alumina. This curious and rare mineral has hitherto been found only in West Green- land, at the arm of the sea named Arksut, 30 leagues from the colony of Juliana Hope. It occurs in gneiss. Mr. Allan of Edin- burgh had the merit of recognizing a large quantity of this mineral, in a neglected heap brought into Leith, from a captured Danish vessel. It had been collected in Greenland by that indefatigable mineralo- gist M. Giesekc* * Cryophorus. The frost-bearer or carrier of cold, an elegant instrument in- vented by Dr. Wollaston, to demonstrate the relation between evaporation at low temperatures, and the production of cold. If 32 grains of water, says this profound philosopher, were taken at the tempera- ture of 62°, and if one grain of this were converted into vapour by absorbing 960°, • ,., , 960° then the whole quantity would lose -j— = 30°, and thus be reduced to the tem- perature of 32°. If from the 31 grains which still remain in the state of water, four grains more were converted into va- pour by absorbing 960°, then the remain. ing 27 grains must have lost ?T of 960* = 142°, which is rather more than suffi- cient to convert the whole into ice. In an experiment conducted upon a small scale, the proportional quantity evaporated did not differ much from this estimate. If it be also true that water, in assuming the gaseous state, even at a low tempera ture, expands to 1800 times its former bulk, CRY CRY then in attempting to freeze tbe small quantity of water above mentioned, it would be requisite to have a dry vacuum with the capacity of 5X1800=9000 grains of water. But let a glass tube be taken, having its internal diameter about one- eighth of an inch, with a ball at each ex- tremity of about one inch diameter, and let the tube be bent to a right angle at the distance of half an inch from each ball. One of these balls should be somewhat less than half full of water, and the remaining cavity should be as perfect a vacuum as can readily be obtained; which is effected by making the water boil briskly in the one ball, before sealing up the capillary opening left in the other. If the empty ball be immersed in a freezing mixture of snow and salt, the water in the other ball, though at the distance of two or three feet, will be frozen solid in the course of a very few minutes. The vapour contained in the empty ball is condensed by the common operation of cold, and the vacuum produ- ced by this condensation gives opportunity for a fresh quantity to arise from the oppo- site ball, with proportional reduction of its temperature.* * Crystal. When fluid substances are suffered to pass with adequate slowness to the solid state, the attractive forces fre- quently arrange their ultimate particles, so as to form regular polyhedral figures, or geometrical solids, to which the name of crystals has been given. Most of the so- lids which compose the mineral crust of the earth, are found in the crystallized state. Thus granite consists of crystals of quartz, feldspar, and mica. Even moun- tain masses like clay-slate, have a regular tabulated form. Perfect mobility among the corpuscles is essential to crystalliza- tion. The chemist produces it either by igneous fusion, or by solution in a liquid. When the temperature is slowly lowered in the former case, or the liquid slowly ab- stracted by evaporation in the latter, the attractive forces resume the ascendancy, and arrange the particles in symmetrical forms. Mere approximation of the parti- cles, however, is not alone sufficient for crystallization. A hot saturated saline so- lution, when screened, from all agitation, will contract by cooling into a volume much smaller, than what it occupies in the solid state, without crystallizing. Hence the molecules must not only be brought within a certain limit of each other, for their concreting into crystals; but they must also change the direction of their poles, from the fluid collocation, to their position in the solid state. This reversion of the poles may be ef- fected, 1st, By contact of" any part of the fluid, with a point of a solid, of similar composition previously formed. 2d, Vi- bratory motions, communicated either from the atmosphere, or any other moving body, by deranging, however slightly, the fluid polar direction, will instantly determine the solid polar arrangement, when the bal- ance had been rendered nearly even, by previous removal of the interstitial fluid. On this principle we explain the regular figures wiiich particles of dust or iron as- sume, when they are placed on a vibrating plane, in the neighbourhood of electrized or magnetized bodies. 3d, Negative or resinous voltaic electricity instantly deter- mines the crystalline arrangement, while positive voltaic electricity counteracts it. On this subject, I beg to refer the reader to an experimental paper, which I publish- ed in the fourth volume of the Journal of Science, p. 106. Light also favours crys- tallization, as is exemplified with camphor dissolved in spirits, which crystallizes in bright, and re-dissolves in gloomy weather. It might be imagined, that the same bo- dy would always concrete in the same, or at least in a similar crystalline form. This position is true, in general, for the salts crystallized in the laboratory; and on this uniformity of figure, one of the principal criteria between different salts depends. But even these forms are liable to many modifications, from causes apparently slight; and in nature, we find frequently the same chemical substance, crystallized in forms apparently very dissimilar. Thus, carbonate of lime assumes the form of a rhomboid, of a regular hexahedral prism, of a solid terminated by 12 scalene trian- gles, or of a dodecahedron with pentago- nal faces, &c. Bisulphuret of iron or mar- tial pyrites produces sometimes cubes and sometimes regular octohedrons, at one time dodecahedrons with pentagonal faces, at another icosahedrons with triangular faces, &c. While one and the same substance lends itself to so many transformations, we meet with very different substances, which pre- sent absolutely the same form. Thus fluate of lime, muriate of soda, sulphuret of iron, sulphuret of lead, &c. crystallize in cubes, under certain circumstances; and in other cases, the same minerals, as well as sulphate of alumina and the diamond, assume the form of a regular octohedron- Rome' de ITsle first referred the study of crystallization, to principles conforma- ble to observation. He arranged together, as far as possible, crystals of the same na- ture. Among the different forms relative to each species, he chose one as the most proper, from its simplicity, to be regarded as the primitive form; and by supposing it truncated in different ways, he deduced the other forms from it, and determined a gradation, a series of transitions between this same form, and that of polyhedrons, CRY which seemed to be still further removed from it. To the descriptions and figures which he gave of the crystalline forms, he added the results of the mechanical mea- surement of their principal angles, and showed that these angles were constant in each variety. The illustrious Bergmann, by endeavour- ing to penetrate to the mechanism of the structure of crystals, considered the differ- ent forms relative to one and the same sub- stance, as produced by a superposition of planes, sometimes constant and sometimes variable, and decreasing around one and the same primitive form. He applied this primary idea to a small number of crystal- line forms, and verified it with respect to a variety of calcareous spar§ by fractures, which enabled him to ascertain the posi- tion of the nucleus, or of the primitive form, and the successive order of the la- minae covering this nucleus. Bergmann, however, stopped here, and did not trou- ble himself either with determining the laws of structure, or applying calculation to it. It was a simple sketch, of the most prominent point of view in mineralogy, but in which we see the hand of the same mas- ter who so successfully filled up the out- lines of chemistry. In the researches which M. Haiiy under- took, about the same period, on the struc- ture of crystals, he proposed combining the form and dimensions of integrant mo- lecules with simple and regular laws of ar- rangement, and submitting these laws to calculation. This work produced a ma- thematical theory, which he reduced to analytical formulae, representing every pos- sible case, and the application of which to known forms leads to valuations of angles, constantly agreeing with observation. Theory ofthe structure of Crystals. Primitive forms.—The idea of referring to one of the same primitive forms, all the forms which may be assumed by a mineral substance, of which the rest may be re- garded as being modifications only, has frequently suggested itself to various phi- losophers, who have made crystallography their study. The mechanical division of minerals, which is the only method of ascertaining their true primitive form, proves that this form is invariable while we operate upon the same substance, however diversified or dis- similar the forms ofthe crystals belonging to this substance may be. Two or three examples will serve to place this truth in its proper light. Take a regular hexahedral prism of car- bonate of hme (PI. XIII. figs. 1 and 2). $ This is what lias been called dent de tochon, but which M. Haiiy calls metastatic. CRY If we try to divide it parallel to the edges. from the contours of the bases, we shall find, that three of these edges taken alter- nately in the upper part, for instance, the edges If, c d, b m, may be referred to this division: and in order to succeed in the same way with respect to the inferior base, we must chuse.not the edges lff',c,d,' b' m', which correspond with the preceding, but the intermediate edges if f, b' c', ( m'. The six sections will uncover an equal number of trapeziums. Three of the lat- ter are represented upon fig. 2. viz. the two which intercept the edges If, c d, and are designated by p p o o, a a k k, and that which intercepts the lower edge df f, and which is marked by the letters n n i i. Each of these trapeziums will have a lustre and polish, from which we may easily ascertain, t'uit it coincides with one ofthe natural joints of which the prism is the assemblage. We shall attempt in vain to divide the prism in any other direction. But if we continue the division parallel to the first sections, it will happen that on one hand the surfaces of the bases will always become narrower, while on the other hand, the altitudes of the lateral planes will de- crease; and at the term at which the bases have disappeared, the prism will be chang- ed into a dodecahedron (fig. 3.), with pen- tagonal faces, six of which, such as o o i O e, o I k i i, &c. will be the residues of the planes of the prism; and the six others E A I o o, O A' K ii, &c. will be the imme- diate result ofthe mechanical division. Beyond this same term,the extreme face9 will preserve their figure and dimensions, while the lateral faces will incessantly di- minish in height, until the points o, k, of the pentagon o\ k i i, coming to be con- founded with the points i, i, and so on with the other points similarly situated, each pentagon will be reduced to a simple tri- angle, as we see in fig. 4.§ Lastly, when new sections have oblitera- ted these triangles, so that no vestige of the surface of the prism remains (fig. 1.), we shall have the nucleus or the primitive form, which will be an obtuse rhomboid (fig. 5.), the grand angle of which E A I or E O I, is 101° 32' 13". * § The points which are confounded, two and two, upon this figure, are each marked with the two letters which served to desig- nate them when they were separated, as in fig. 3. 4 It is observed, that each trapezium, such as p p o o (fig. 2.) uncovered by the first sections, is very sensibly inclined from the same quantity, as well upon the resi- due p p d e b m of the base, as upon the residue o of' l' of the adjacent plane. Set- ting out from this equality of inclinations, we deduce from it, by calculation, the va- CRY If we try to divide a crystal of another species, we shall have a different nucleus. For instance, a cube of fluate of lime will give a regular octohedron, which we suc- ceed in extracting by dividing the cube upon its eight solid angles, which will in the first place discover eight equilateral triangles, and we may pursue the division, always parallel to the first sections, until nothing more remains of the faces of the cube. The nucleus of the crystals of sul- phate of barytes will be a straight prism with rhombous bases; that of the crystals of phosphate of lime, a regular hexahedral prism; that of sulphuretted lead, a cube, &c; and each of these forms will be con- stant relative to the entire species, in such a manner, that its angles will not undergo any appreciable variation. Having adopted the word primitive form in order to designate the nucleus of crys- tals, M Haiiy calls secondary forms, such varieties as differ from the primitive form. In certain species, crystallization also produces this last form immediately We may define the primitive form, a so- lid of a constant form, engaged symmetri- cally in all the crystals of one and the same species, and the faces of which follow the directions of the laminae which form these crystals. The primitive forms hitherto observed, are reduced to six, viz. the parallelopipe- don, the octohedron, the tetrahedron, the regular hexahedral prism, the dodecahe- dron with rhombous planes, all equal and similar, and the dodecahedron with trian- gular planes, composed of two straight py- ramids joined base to base. Forms of integrant Molecules.—The nu- cleus of a crystal is not the last term of of its mechanical division. It may always be subdivided parallel to its different-faces, and sometimes in other directions also. The whole of the surrounding substance is capable of being divided by strokes pa- rallel to those which take place with re- spect to the primitive form. If the nucleus be a parallelopipedon, which cannot be subdivided except by blows parallel to its faces, like that which takes place with respect to carbonated lime, it is evident that the integrant mole- cule will be similar to this nucleus itself. But it may happen that the parallelopipe- don admits of further sections in other di- rections than the former. We may reduce the forms of the inte- grant molecules of all crystals to three, which are, the tetrahedron, or the simplest of tiie pyramids; the triangular prism, or the simplest of all the prisms; and the pa- lue of the angles with the precision of mi- nutes and seconds, which mechanical mea- surements are not capable of attaining. CRY rallelopipedon, or the simplest among the solids, which have their faces parallel two and two. And since four planes at least are necessary for circumscribing a space, it is evident that the three forms in ques- tion, in which the number of faces is suc- cessively four,five,and six.have btill, in this respect, the greatest possible simplicity. Laws to which the Structure is subjected. —After having determined the primitive forms, and those ofthe integrant molecules, it remains to inquire into the laws pursued by these molecules in their arrangement, in order to produce these regular kinds of envelopes, which disguise one and the same primitive form in so many different ways. Now, observation shows, that this sur- rounding matter is an assemblage of lami- nae, which, setting out from the primitive form, decrease in extent, both on all sides at once, and sometimes in certain particu- lar parts only. This decrement i effected by regular subtractions of one jr more rows of integrant molecules; and the the- ory, in determining the number of these rows by means of calculation, succeeds in representing all the known results of crys- tallization, and even anticipates future dis- coveries, indicating forms which, being still hypothetical only, may one day be present- ed to the inquiries ofthe philosopher. Decrements on the Edges.—Let s s' (fig. 6. PI. XIII.) be a dodecahedron with rhom- bic planes. This solid, which is one of the six primitive forms of crystals, also pre- sents itself occasionally as a secondary form, and in this case it has as a nucleus, sometimes a cube, and sometimes an octo- hedron. Supposing the nucleus to be a cube:— In order to extract this nucleus, it is sufficient successively to remove the sis solid angles composed of four planes, such as s, r, t, &c. by sections adapted to the direction of the small diagonals. These sections will display as many squaresA E O I, BOO'E',10 O' I' (fig. 7.), &c. which will be the faces of the cube. Let us conceive that each of these faces is subjected to a series of decreasing la- mina: solely composed of cubic molecules, and that every one of these laminae exceeds the succeeding one, towards its four edges, by a quantity equal to one course of these same molecules. Afterwards we shall de- signate the decreasing laminae which enve- lope the mucleus, by the name of laminte of superposition. Now, it is easy to con- ceive that the different series will produce six quadrangular pyramids, similar in some respects to the quadrangular steps of a co- lumn, which will rest on the faces of the cube. Three of these pyramids are repre- sented in fig. 8. and have their summits in s, t, r. Now, as there are six quadrangular py- CRY CRY ramids, we shall therefore have twenty-four triangles; such as O s I, O 11, &c. But because the decrement is uniform from s to t, and so on with the rest; the triangles taken two and two are on a level, and form a rhomb • O 11. The surface of the solid will therefore be composed of twelve equal and similar rhombs; *. e. this solid will have the same form with that which is the subject of the problem. This structure takes place, although imperfectly, with re- spect to the crystals called boracic spars. The dodecahedron now under conside- ration, is represented by fig. 8. in such a way that the progress of the decrement may be perceived by the eye. On examin- ing the figure attentively, we shall find that it has been traced on the supposition, that the cubic nucleus has on each of its edges 17 ridges of molecules; whence it follows, that each of its faces is composed of 289 facets of molecules, and that the whole solid is equal to 4913 molecules. On this hypothesis, there are eight laminx of superposition, the last of which is reduced to a simple cube, whose edges determine the numbers of molecules which form the series 15,13, 11, 9, 7, 5, 3, 1, the differ- ence being 2, because there is one course subtracted from each extremity. Now, if instead of this coarse kind of masonry, which has the advantage of speak- ing to the eye, we substitute in our ima- gination the infinitely delicate architecture of nature, we must conceive the nucleus as being composed of an incomparably greater number of imperceptible cubes. In this case, the number of laminae of su- perposition will also be beyond comparison greater than on the preceding hypothesis. By a necessary consequence, the furrows which form these laminae by the alternate projecting and re-entering of their edges, will not be cognizable by our senses; and this is what takes place in the polyhedra which crystallization has produced at lei- sure, without being disturbed in its pro- gress. M. Haiiy calls decrements in breadth, those in which each lamina has only the height of a molecule, so that their whole effect, by one, two, three, &c. courses, is in the way of breadth. Decrements in height are those in which each lamina, exceeding only the following one by a single course in the direction of the breadth, may have a height double, triple, quadruple, &c. to that of a molecule: this is expressed by saying that the decrement takes place by two courses, three courses, &c. in height. We are indebted to Dr. Wollaston for ideas on the ultimate cause of crystalline forms, equally ingenious and profound. They were communicated to the Royal So- ciety, and published in their transactions for the year 1813. Among the known forms of crystallized bodies, there is no one common to a greater number of substances than the regular oc- tohedron, and no one in which a corres- ponding difficulty has occurred with re- gard to determining which modification of its form is to be considered as primitive; since in all these substances the tetrahe- dron appears to have equal claim to be re- ceived as the original from which all their other modifications are to be derived. The relation of these solids to each other is most distinctly exhibited to those who are not much conversant with crystallo- graphy, by assuming the tetrahedron as primitive, for this may immediately be converted into an octohedron by the re- moval of four smaller tetrahedrons from its solid angles. (Plate XIV. fig. 1.) The substance which most readily admits of division by fracture into these forms, is fluor spar; and there is no difficulty in ob- taining a sufficient quantity for such expe- riments. But it is not, in fact, either the tetrahedron or the octohedron, which first presents itself as the apparent primitive form obtained by fracture. If we form a plate of uniform thickness by two successive divisions of the spar, pa- rallel to each other, we shall find the plate divisible into prismatic rods, the section of which is a rhomb of 70° 32' and 109° 28' nearly; and if we again split these rods transversely, we shall obtain a number of regular acute rhomboids, all similar to each other, having their superficial angles 60° and 120° and presenting an appearance of primitive molecule, from which all the other modifications of such crystals might very simply be derived. And we find, moreover, that the whole mass of fluor might be divided into, and conceived to consist of, these acute rhomboids alone, which may be put together so as to fit each other without any intervening vacuity. But, since the solid thus obtained (as re- presented fig. 2.) may be again split by na- tural fractures at right angles to its axis (fig. 3.), so that a regular tetrahedron may be detached from each extremity, while the remaining portion assumes the form of a regular octohedron; and since every rhom- boid that can be obtained, must admit of the same division into one octohedron and two tetrahedrons, the rhomboid can no longer be regarded as the primitive form; and since the parts into which it is divi- sible are dissimilar, we are left in doubt which of them is to have precedence as primitive. In the examination of this question, whether we adopt the octohedron or the tetrahedron as the primitive form, since neither of them can fill space without leav- ing vacuities, there is a difficulty in con- ceiving any arrangement in which the par- CRY CRY tides will remain at rest: for, whether we suppose, with the Abbe Haiiy, that the par- ticles are tetrahedral with octohedral cavi- ties, or, on the contrary, octohedral parti- cles regularly arranged with tetrahedral cavities, in each case the mutual contact of adjacent particles is only at their edges; and, although in such an arrangement it must be admitted that there may be an equilibrium, it is evidently unstable, and ill adapted to form the basis of any per- manent crystal. With respect to fluor spar and such other substances as assume the octohedral and tetrahedral forms, all difficulty is removed, says Dr. Wollaston, by supposing tiie ele- mentary particles to be perfect spheres, which, by mutual attraction, have assum- ed that arrangement which brings them as near to each other as possible. The relative position of any number of equal balls in the same plane, when gently pressed together, forming equilateral tri- angles with each other (as represented perspeclively in fig. 4.), is familiar to every one; and it is evident that, if balls so plac- ed were cemented together, and the stra- tum thus formed were afterwards broken, the straight lines in which they would be disposed to separate would form angles of 60° with each other. If a single ball were placed any where at rest upon the preceding stratum, it is evi- dent that it would be in contact with three of the lower balls (as in fig. 5.), and that the lines joining the centres of four balls so in contact, or the planes touching their surfaces, would include a regular tetrahe- dron, having all its equilateral triangles. The construction of an octohedron, by means of spheres alone, is as simple as that of the tetrahedron. For, if four balls be placed in contact on the same plane, in form of a square, then a single ball resting upon them in the centre, being in contact with each pair of balls, will present a triangular face rising from each side of the square, and the whole together will represent the superior apex of an octohedron; so that a sixth ball similarly placed underneath the square will complete the octohedral group, fig. 6. There is one observation with regard to these forms that will appear paradoxical, namely that a structure, which, in this case, was begun upon a square foundation, is really intrinsically the same as that which is begun upon the triangular basis. But if we lay the octohedral group, which con- sists of six balls, on one of its triangular sides, and, consequently, with an opposite triangular face uppermost, the two groups, consisting of three balls each, are then si- tuated precisely as they would be found in two adjacent strata of' the triangular ar- rangement. Hence, in this position, we may readily convert the octohedron into a regular tetrahedron, by addition of four more balls (fig. 7.). One placed on the top of the three that are uppermost forms the apex; and if the triangular base, on which it rests, be enlarged by addition of three more balls, regularly disposed around it, the entire group of ten balls will then be found to represent a regular tetrahedron. For the purpose of representing the acute rhomboid, two balls must be appli- ed at opposite sides of the smallest octo- hedral group, as in fig. 9. And if a greater number of balls be placed together, fig. 10. and 11. in the same form, then a com- plete tetrahedral group may be removed from each extremity, leaving a central oc- tohedron, as may be seen in fig. 11. which corresponds to fig. 3. We have seen, that by due application of spheres to each other, all the most sim- ple forms of one species of crystal will be produced, and it is needless to pursue any other modifications of the same form, which must result from a series of decre- ments produced according to known laws. Since then the simplest arrangement of the most simple solid that can be imagined, affords so complete a solution of one of tbe most difficult questions in crystallography, we are naturally led to inquire what forms would probably occur from the union of other solids most nearly allied to the sphere. And it will appear that by the supposition of elementary particles that are spheroidi- cal, we may frame conjectures as to the origin of other angular solids well known to crystallographers. The obtuse Rhomboid. If we suppose the axis of our elementary speroid to be its shortest dimension, a class of solids will be formed which are nu- merous in crystallography. It has been re- marked above, that by the natural group- ing of spherical particles, fig. 10. one re- sulting solid is an acute rhomboid, similar to that of fig. 2. having certain determin- ate angles, and its greatest dimension in the direction of its axis. Now, if other particles having the same relative arrange- ment be supposed to have the form of ob- late spheroids, the resulting solid, fig. 12. will still be a regular rhomboid; but the measures of its angles will be different from those of the former, and will be more or less obtuse according to the degree of oblateness of the primitive spheroid. It is at least possible that carbonate of lime and other substances, of which the forms are derived from regular rhomboids as their primitive form, may, in fact, con- sist of oblate spheroids as elementary par- ticles. Hexagonal Prisms. If our elementary Spheroid be on (he CRY CRY contrary oblong, instead of oblate, it is evident that, by mutual attraction, their centres will approach nearest to each other when their axes are parallel, and their shortest diameters in the same plane (fig. 13.). The manifest consequence of this structure would be, that a solid so formed would be liable to split into plates at right angles to the axes, and the plates would divide into prisms of three or six sides with all their angles equal, as occurs in phosphate of lime, beryl, &c. It may farther be observed, that the proportion of the height to the base of such a prism, must depend on the ratio between the axes of the elementary sphe- roid. The Cube. Let a mass of matter be supposed to consist of spherical particles all of the same size, but of two different kinds in equal numbers, represented by black and white balls; and let it be required that, in their perfect intermixture, every black ball shall be equally distant from all surround- ing white balls, and that all adjacent balls of the same denomination shall also be equidistant from each other. The Doctor shows, that these conditions will be fulfil- led, if the arrangement be cubical, and that the particles will be in equilibrio. ¥\g. 14. represents a cube so constituted of balls, alternately black and white through- out. The four black balls are in view. The distances of their centres being every way a superficial diagonal of the cube, they are equidistant, and their configura- tion represents a regular tetrahedron; and the same is the relative situation of the four white balls. The distances of dissi- milar adjacent balls are likewise evidently equal; so that the conditions of their union are complete, as far as appears in the small group: and this is a correct representative of the entire mass, that would be compo- sed of equal and similar cubes. There remains one observation with re- gard to the spherical form of elementary particles, whether actual or virtual, that must be regarded as favourable to the fore- going hypothesis, namely, that many of those substances, which we have most rea- son to think simple bodies, as among the class of metals, exhibit this further evi- dence of their simple nature, that they crystallize in the octohedral form, as they would do if their particles were spherical. But it must, on the contrary, be acknow- ledged, that we can at present assign no reason why the same appearance of simpli- city should take place in fluor spar, which is presumed to contain at least two ele- ments; and it is evident that any attempts to trace a general correspondence between Vol. T. the crystallographical and supposed che- mical elements of bodies, must in the present state of these sciences, be prema- ture. Any sphere when not compressed wril be surrounded by twelve others, and, con- sequently, by a slight degree of" compres- sion, will be converted into a dodecahe- dron, according to the most probable hy- pothesis of simple compression The instrument for measuring the angles of crystals is called a goniometer, of which there are two kinds 1. The goniometer of M. Carangeau, used by M. Haiiy, con- sists of two parallel blades, jointed like those of scissars, and capable of being ap- plied to a graduated semicircular sector, which give:* the angle to which the joint is opened, in consequence of the previous apposition of the two blades to the angle of the crystal. 2. The reflective goniome- ter of Dr. Wollaston, an admirable inven- tion, which measures the angles of the minutest possible crystals with the utmost precision. An account of this beautiful in- strument may be found in the Phil. Trans. for 1809, and in Tilloch's Magazine for February 1810, vol. 35. Mr. William Phil- lips published, in the 2d volume of the Geological Transactions, an elaborate se- ries of measurements with this goniometer. A striking example of the power of this instrument in detecting the minutest forms with precision was afforded, by its appli- cation to a crystalline jet-black sand, which Dr. Clarke got from the island Jean Mayen, in the Greenland seas. " Having there- fore," says Dr. Clarke, " selected a crystal of this form, but so exceedingly minute as scarcely to be discernible to the naked eye, I fixed it upon the moveable plane of Dr. Wollaston's reflecting goniometer. A dou- ble image was reflected by one of the planes of the crystal, but the image re- flected by the contiguous plane was clear and perfectly perceptible, by which I was enabled to measure the angle of inclina- tion; and after repeating the observation several times, I found i' equal to 92° or 92$°. Hence it is evident that these crys- tals are not zircons, although they possess a degree of lustre quite equal to that of zircon. In this uncertainty, I sent a small portion of the sand to Dr. Wollaston, and requested that he would himself measure the a?ij>-/e of the particles exhibiting splen- dant surfaces. Dr. Wollaston pronounced the substance to be pyroxene; having an angle, according to his observation, of'92i°. He also informed me that the sand was similar to that of Bolsenna in Italy." Such a ready means of minute research forms a delightful aid to the chemical philosopher, as well as the mineralogist. M. Haiiy, by a too rigid adherence to the principle of 44 CRY CRY geometrical simplicity, obtained an erro- neous determination of the angles in the primary form of carbonate of lime, amount- ing to 36 minutes of a degree. And by as- signing to the magnesian and ferriferous carbonates of lime the same angle as to the simple carbonate, the error became still greater, as will appear from the follow- ing comparative measurements. Observed angle by Dr. Wollaston's Theoretic angle. Error. goniometer. Carbonate of lime, 105° 5' 104° 28' 40" 0° 36' 20" Magnesian carbonate, 106° 15' 104° 28' 40" 1° 46' 20" Ferriferous carbonate, 107° 0' 104° 28' 40" 2° 31' 20" M. Haiiy will no doubt accommodate his results to these indications of Dr. Wollas- ton's goniometer, and give his theory all the perfection which its scientific value and elegance deserve. M. Beudant has lately made many ex- periments to discover, why a saline prin- ciple of a certain kind sometimes im- presses its crystalline form upon a mixture, in which it does not, by any means, form the greatest part; and also with the view of determining, why one saline substance may have such an astonishing number of secondary forms, as we sometimes meet with. The presence of urea makes common salt take an octohedral form although in pure water it crystallizes in cubes, similar to its primitive molecules. Sal ammo- niac, which crystallizes in pure water in octohedrons, by means of urea crystallizes in cubes. A very slight excess or defi- ciency of base in alum, causes it to assume either cubical or octohedral secondary forms; and these forms are so truly se- condary, that an octohedral crystal of alum, immerged in a solution which is richer in respect to its basis, becomes en- veloped with crystalline layers, which give it at length the form of a cube. The crystalline form in muddy solutions acquires greater simplicity, losing all those additional facets which would otherwise modify their predominant form. In a gelatinous deposite, crystals are rarely found in groups, but almost always single, and of a remarkable sharpness and regularity of form, and they do not under- go any variations, but those which may re- sult from the chemical action of the sub- stance forming the deposite. Common salt crystallized in a solution of borax, ac- quires truncations at the solid angles of its cubes; and alum crystallized in muriatic acid, takes a form which M. Beudant has never been able to obtain in any other manner. 30 or 40 per cent of sulphate of copper may be united to the rhomboidal crystal- lization of sulphate of iron, but it reduces this sulphate to a pure rhomboid, without any truncation either of the angles or the edges. A small portion of acetate of cop- per reduces sulphate of iron to the same simple rhomboidal form, notwithstanding that this form is disposed to become com- plicated with additional surfaces. Sulphate of alumina brings sulphate of iron to a rhomboid, with the lateral angles only truncated, or what M. Haiiy calls his va- rieli unitaire; and whenever this variety of green vitriol is found in the market, where it is very common, we may be sure, according to M. Beudant, that it contains alumina. Natural crystals mixed with foreign substances, are in general more simple than others, as is shown in a specimen of axinite or violet schorl of Datiphine, one extremity of which being mixed with chlo- rite, is reduced to its, primitive form; while the other end, which is pure, is va- ried by many facets produced by different decrements. In a mingled solution of two or more salts, of nearly equal solubility, the crys- tallization of one of them may be some- times determined, by laying or suspending in the liquid, a crystal of that particular salt. M. Le Blanc states, that on putting in- to a tall and narrow cylinder, crystals at different heights, in the midst of their sa-. turated saline solution, the crystals at the bottom increase faster than those at the surface, and that there arrives a period when those at the bottom continue to en- large, while those at the surface diminish and dissolve. Those salts which are apt to give up their water of crystallization to the atmos- phere, and of course become efflorescent, may be preserved by immersion in oil, and subsequent wiping of their surface. In the Wernerian language of crystalli- zation, the following terms are employed: When a secondary form differs from the cube, the octohedron, &c. only in having several of its angles or edges replaced by a face, this change of the geometrical form is called a truncation. The alteration in the principal form produced by two new faces inclined to one another, and which re- place by a kind of bevel, an angle, or an edge, is called a bevelment. When these new faces are to the number of three or CRY more, they produce what Werner termed a pointing, or acumination. When two faces unite by an edge in the manner of a roof, they have been called culmination. Replace- ment is occasionally used for bevelment. The reader will find some curious ob- servations on crystallization, by Mr. J. F. Daniell, in the 1st volume of the Journal of Science. Professor Mohs, successor to Werner in Freyberg, Dr. Weiss, professor of miner- alogy, in Berlin, and M. Brochant, profes- sor of mineralogy in Paris, have each re- cently published systems of mineralogy. Pretty copious details, relative to the first, are given in the 3d volume of the Edin- burgh Philosophical Journal.* In a paper in the Journal de Physique, M. Le Blanc gives instructions for obtain- ing crystals of large size. His method is to employ flat glass or china vessels: to pour into these the solutions boiled down to the point of crystallization: to select the neatest of the small crystals formed, and put them into vessels with more of the mo- ther-water of a solution that has been brought to crystallize confusedly: to turn the crystals at least once a day; and to supply them from time to time with fresh mother-water. If the crystals be laid on their sides they will increase most in length; if on their ends, most in breadth. When they have ceased to grow larger, they must be taken out of the liquor, or they will soon begin to diminish. It may be observed in general, that very large crystals are less transparent than those that are small. The crystals of metals may be obtained by fusing them in a crucible with a hole in its bottom, closed by a stopper, which is to be drawn out after the vessel has been removed from the fire, and the sur- face of the metal has begun to congeal. The same effect may be observed if the metal be poured into a plate or dish, a lit- tle inclined, which is to be suddenly inclin- ed in the opposite direction, as soon as the metal begins to congeal round its edges. In the first method, the fluid part of the metal runs out of the hole, leaving a kind of cup lined with crystals: in the latter way, the superior part, which is fluid, runs off, and leaves a plate of metal studded over with crystals. The operation of crystallizing, or crys- tallization, is of great utility in the purify- ing of various saline substances. Most salts are suspended in water in greater quantities at more elevated temperatures, and separate more or less by cooling. In this property, and likewise in the quantity of salt capable of being suspended in a eiven quantity of water, they differ greatly from each other. It is therefore practica- ble in general to separate salts by due man- CUR agement of the temperature and evapora- tion. For example, if a solution of nitre and common salt be evaporated over the fire, and a small quantity be now and then taken out for trial, it will be found, at a certain period of the concentration, that a considerable portion of salt will separate by cooling, and that this salt is for the most part pure nitre. When this is seen, the whole fluid may be cooled to separate part of the nitre, after which, eva- poration may be proceeded upon as before. This manipulation depends upon the diffe- rent properties of the two salts with regard to their solubility and crystallizat on in like circumstances. For nitre is considerably more soluble in hot than in cold water, while common salt is scarcely more soluble in the one case than in the other. The com- mon salt consequently separates in crystals as the evaporation of the heated fluid goes on, and is taken out with a ladle from time to time, whereas the nitre is separated by successive coolings at proper periods. * Cube Ore. Hexahedral Olivenite. Wur- felerz. Wern. This mineral has a pistacio- green colour, of various shades. It occurs massive, and crystallized in the perfect cube; in a cube with four diagonally op- posite angles truncated; or in one trun- cated on all its angles; or finally, both on its edges and angles. The crystals are small, with planes smooth and splendent. Lustre glistening. Cleavage parallel with the truncations of the angles. Translucent. Streak straw-yel- low. Harder than gypsum. Easily fran- gible. Sp. gr. 3.0. Fuses with disengage- ment of arsenical vapours. Its constitu- ents are, 31 arsenic acid, 45.5 oxide of iron, 9 oxide of copper, 4 silica, and 10.5 water, by Chenevix. Vauquelin's analysis gives no copper nor silica, but 48 iron, 18 arsenic acid, 2 to 3 carbonate of lime, and 32 wa- ter. It is found in veins, acornpanied with iron-shot quartz, in Tincroft and va- rious other mines of Cornwall, and at St. Leonard in tbe Haut-Vienne in France. As an arseniate of iron, it might be ranked among tbe ores of either this metal or ar- senic.—Jameson* Cupel. A shallow earthen vessel, some- what resembling a cup, from which it de- rives its name. It is made of phosphate of lime, or the residue of burned bones ram- med into a mould, which gives it its figure. This vessel is used in assays wherein the precious metals are fused with lead, which becomes converted into glass, and carries the impure alloy with it. See Assay. Cupellation. The refining of gold by scorificution with lead upon the cupel, is called cupellation. See Assay. Curd. The coagulum which separates from milk upon the addition of acid, or other substances. See Milk. DAT DEC • Ctanite, or Kyanite. Disthene of Haiiy. Its principal colour is Berlin-blue, which passes into gray and green It oc- curs massive and disseminated, also in dis- tinct concretions. The primitive form of its crystals is an oblique four-sided prism; and the secondary forms are, an oblique four- sided prism, truncated on the lateral edges, and a twin crystal. The planes are streak- ed, splendent, and pearly. Cleavage three- fold. Translucent or transparent. Surface of the broader lateral planes as hard as apatite; that of the angles, as quartz. Ea- sily frangible. Sp. gr. 3.5. When pure it is idio-electric. Some crystals by friction ac- quire negative, others positive electricity; hence HaUy's name. It is infusible before the blow-pipe. It consists, by Klaproth, of 43 silica, 55.5 alumina, 0.5*0 iron, and a trace of potash. It occurs in the granite and mica slate of primitive mountains. It is found near Banchory in Aberdeenshire, and Bocharm in Banffshire; at Airolo on St. Gothard, and in various countries ot Europe, as well as in Asia and America. It is cut and polished in India as an infe- rior sort of sapphire.—Jameson.* * Cyanogen. The compound base of prussic acid. See Prussine.* * Cymophane of Haiiy. The Chryso- beryl.* D DAMPS. The permanently elastic fluids which are extricated in mines, and re destructive to animal life, are called damps by the miners. The chief distinc- tions made by the miners, are choak-damp, which extinguishes their candles, hovers about the bottom of the mine, and consists for the most part of carbonic acid gas; and fire-damp, or hydrogen gas, which occupies the superior spaces, and does great mis- chief by exploding whenever it comes in contact with their lights. See Gas, Com- bustion, & Lamp. * Daoubite. A variety of red schorl from Siberia.* * Daphnin. The bitter principle of Daphne Alpina, discovered by M. Vauque- lin. From the alcoholic infusion of this bark, the resin was separated by its con- centration. On diluting the tincture with water, filtering, and adding acetate of lead, a yellow daphnate of lead fell, from which sulphuretted hydrogen separated the lead, and left the daphnin in small transparent crystals. They are hard, of a grayish co- lour, a bitter taste when heated, evaporate in acrid acid vapours, sparingly soluble in cold, but moderately in boiling water. It is stated, that its solution is not precipita- ted by acetate of lead; yet acetate of lead is employed in the first process to throw it down * •Datolite. Datholit of Werner. This species is divided into two sub-species, viz. Common Datolite, and Botrioidal Datolite. 1. Common Datolite. Colour white of various shades, and greenish-gray, inclin- ing to celadine-green. It occurs in large coarse, and small granular distinct concre- tions, and crystatLzed. Primitive form, an oblique four-sided prism of 109° 28' and 70° 3^.'. The principal secondary forms, are the low oblique four-sided prism, and the rectangular four-sided prism, flatly acuminated on the extremities, with four planes which are set on the lateral planes. The crystals are small and in druses. Lus- tre shining and resinous. Cleavage imper- fect, parallel with the lateral planes ofthe prism. Fracture fine grained, uneven, or imperfect conchoidal. Translucent or transparent. Fully as hard as apatite. Very brittle, and difficultly frangible. Sp. gr. 2.9. When exposed to the flame of a candle it becomes opaque, and may then be rubbed down between the fingers. Before the blow- pipe it intumesces into a milk-white co- loured mass, and then melts into a globule of a pale rose colour. Its constituents are, by Klaproth, silica 36.5, lime 35.5, boracic acid 24.0, water 4, trace of iron and man- ganese. It is associated with large folia- ted granular calcareous spar, at the mine of Nodebroe, near Arendal in Norway. It re- sembles prehnite, but is distinguished by its resinous lustre, compact fracture, infe- rior hardness, and not becoming electric by heating.—Jameson* * 2. Botrioidal Datolite, See Bot- RYOr.I IE.* * Datura. A vegeto-alkali obtained from Datura Stramonium.* * Dead-Sea Water. See Water.* Decantation. The action of pouring oft'the clearer part of a fluid by gently in- clining the vessel after the grosser parts have been suffered to subside. Decoction. The operation of boiling. This term is likewise used to denote the fluid itself which has been made to take up certain soluble principles by boiling. Thus we say a decoction of the bark, or other parts of vegetables, of flesh, &c. Decomposition is now understood to imply the separation of the component parts or principles of bodies from each other. The decomposition of bodies forms a very large part of chemical science. It seems probable from the operations we are DEL DEL acquainted with, that it seldom takes place but in consequence of some combination or composition having been effected. It would be difficult to point out an instance of the separation of any of the principles of bodies which has been effected, unless in consequence of some new combination. The only exceptions seem to consist in those separations which are made by heat, and voltaic electricity. See Analysis, Gas, Metals, Ores, Salts, Mineral Waters. * Decrepitation. The crackling noise which several salts make when sud- denly heated, accompanied by a violent ex- foliation of their particles. This pheno- menon has been ascribed by Dr. Thomson, and other chemical compilers, to the " sud- den conversion of the water which they contain into steam." Bat the very example, sulphate of barytes, to which these words are applied, is the strongest evidence of the falseness of the explanation; for abso- lutely dry sulphate of barytei decrepitates furiously, without any possible formation of steam, or any loss of weight. The same thing holds with regard to common salt, calcareous spars, and sulphate of potash, which contain no water. In fact, it is the salts which are anhydrous, or destitute of water, which decrepitate most powerfully; those that contain water, generally enter into tranquil liquefaction on being heated. Salts decrepitate, for the same reason that glass, quartz, and cast-iron crack, with an explosive force, when very suddenly heat- ed; namely, from the unequal expansion of the laminae which compose them, in conse- quence of their being imperfect conduc- tors of heat. The true cleavage of mine- rals may often be detected in this way, for they fly asunder at their natural fissures.* f Deflagratiow. This word is used by electricians and chemists, to denote that kind of combustion, which takes place in metallic wires, or leaves, when subject- ed to galvanic or electric discharges. See Galvanic Deflagrator/}- • Delphinite. See Pistacite.* • Delphinia. A new vegetable alkali, recently discovered by MM. Lasseigne and Feneulle, in the Delphinium staphysagria, or Stavesacre. It is thus obtained: The seeds, deprived of their husks, and ground, are to be boiled in a small quanti- ty of distilled water, and then pressed in a cloth. The decoction is to be filtered, and boiled for a few minutes with pure mag- nesia. It must then be re-filtered, and the residuum left on the filter is to be well washed, and then boiled with highly recti- fied alcohol, which dissolves out the alkali. By evaporation, a white pulverulent sub- stance, presenting a few crystalline points, is obtained. It may also be procured by the action of dilute sulphuric acid, on the bruised but unshelled seeds. The solution of sulphate thus formed, is precipitated by subcarbo- nate of potash. Alcohol separates from this precipitate the vegetable alkali in an impure state Pure delphini;< obtained by the first pro- cess, is crvst Uine while wet, but becomes opaque on exposure to air. Its taste is bit- ter and acrid. Win n heated it melts; and on cooling becomes hard and brittle like resin. If more highly heated, it blackens and is decomposed. Water dissolves a very small portion of it. Alcohol and ether dissolve it very readily. The alco- holic solution renders sirup of violets green, and restores the blue tint of litmus reddened by an acid. It forms soluble neutral salts with acids. Alkalis precipi- tate the delphinia in a white gelatinous state, like alumina. Sulphate of delphinia evaporates in the air, does not crystallize, but becomes a transparent mass like gum. It dissolves in alcohol and water, and its solution has a bitter acrid taste. In the voltaic circuit it is decomposed, giving up its alkali at the negative pole. Nitrate of delphinia, when evaporated to dryness, is a yellow crystalline mass. If treated with excess of nitric acid, it be- comes converted into a yellow matter, little soluble in water, but soluble in boiling al- cohol. This solution is bitter, is not pre- cipitated by potash, ammonia, or lime-wa- ter, and appears to contain no nitric acid, though itself is not alkaline. It is not de- stroyed by further quantities of acid, nor does it form oxalic acid. Strychnia and morphia take a red colour from nitric acid, but delphinia never does. The muriate is very soluble in water. The acetate of delphinia does not crys- tallize, but forms a hard transparent mass, bitter and acrid, and readily decomposed by cold sulphuric acid. The oxalate forms small white plates, resembling in taste the preceding salts. Delphinia, calcined with oxide of copper, gave no other gas than carbonic acid. It exists in the seeds ofthe stavesacre, in com- bination with malic acid, and associated with the following principles: 1. A brown bitter principle, precipitable by acetate of lead. 2. Volatile oil. 3. Fixed oil 4. Albu- men. 5. Animalized matter. 6. Mucus. 7. Saccharin" mucus. 8. Yellow bitter princi- ple, not p ec ipilable by acetate of lead. 9. Mineral salts.—Annates de Chimie et Phy- sique, vol. xii p. 358 * Deliquescence. The spontaneous as- sumption of the fluid slate by certain sa- line substances, when left exposed to the air, in consequence of the water they attract from it. DEW DEW Depmlegmation. Any method by Which bodies are deprived of water. Dephlogisticated. A termoftheold chemistry, implying deprived ofphlogiston, or the inflammable principle, and nearly synonymous with what is now expressed by •xygenated, or oxidized. Dephlogisticated Air. The same with oxygen gas. Derbyshire Spar. A combination of calcareous earth with a peculiar acid called the Fluoric, which see. •Desiccation is most elegantly accom- plished, by means of the air-pump and sul- phuric acid, as is explained under Conge- lation * Destructive Distillation. When organized substances, or their products, are exposed to distillation, until the whole has suffered all that the furnace can effect, the process is called destructive distilla- tion. Detonation. A sudden combustion and explosion. See Combustion, Fulmi- nating Powders, and Gunpowder. * Dew. The moisture insensibly depo- sited from the atmosphere on the surface ofthe earth. The first facts which could lead to the just explanation of this interesting, and, till very lately, inexplicable natural phenome- non, are due to the late Mr. A. Wilson, professor of astronomy in Glasgow, and his son. The first stated, in the Phil. Trans, for 1771, that on a winter night, during which the atmosphere was several times misty and clear alternately, he observed a thermome- ter, suspended in the air, always to rise from a half to a whole degree, whenever the for- mer state began, and to fall as much as soon as the weather became serene. Dr. Patrick Wilson communicated, in 1786, to the Royal Society of Edinburgh, a valuable paper on hoar-frost, which was published in the first volume of their Transactions. It is replete with new and valuable obser- vations, whose minute accuracy subsequent experience has confirmed. Dr. Wilson had previously, in 1781, described the surface of snow, during a clear and calm night, to be 16° colder than air 2 feet above it; and in the above paper he shows, that the depo- sition of dew and hoar-frost is uniformly accompanied with the production of cold. He was the first among philosophical ob- servers who noticed this conjunction. But the diff'erent force with which different sur- faces project or radiate heat being then un- known, Dr Wilson could not trace the phe- nomena of dew up to their ultimate source. This important contribution to science has been lately made by Dr. Wells, in his very ingenious and masterly essay on dew. 1. Phenomena of Dew. Aristotle justly remarked, that dew ap- pears only on calm and clear nights. Dr. Wells shows that very little is ever dcpo- sited in opposite circumstances; and that little only when the clouds are very high. It is never seen on nights both cloudy and windy; and if in the course of the night the weather, from being serene, should become dark and stormy, dew which had been de- posited will disappear. In calm weather, if the sky be partially covered with clouds, more dew will appear than if it were en- tirely uncovered. Dew probably begins in the country to appear upon grass, in places shaded from the sun, during clear and calm weather, soon after the heat of the atmosphere has declined, and continues to be deposited through the whole night, and for a little after sunrise. Its quantity will depend in some measure on the proportion of mois- ture in the atmosphere, and is consequently greater after rain than after a long tract of dry weather; and in Europe, with southerly and westerly winds, than with those which blow from the north and the east. The di- rection of the sea determines this relation of the winds to dew. For in Egypt, dew is scarcely ever observed except while the northerly or Etesian winds prevail. Hence also, dew is generally more abundant in spring and autumn, than in summer. And it is always very copious on those clear nights which are followed by misty morn- ings, which show the air to be loaded with moisture. And a clear morning, following a cloudy night, determines a plentiful depo- sition of the retained vapour. When warmth of atmosphere is compatible with clearness, as is the case in southern latitudes, though seldom in our country, the dew becomes much more copious, because the air then contains more moisture. Dew continues to form with increased copiousness as the night advances, from the increased refri- geration ofthe ground. 2. On the cause of dew. Dew, according to Aristotle, is a species of rain, formed in the lower atmosphere, in consequence of its moisture being con- densed by the cold of the night into minute drops. Opinions of this kind, says Dr. Wells, are still entertained by many per- sons, among whom is the very ingenious Professor Leslie. (Relat. of Heat and Mois- ture, p. 37. and 132.) A fact, however, first taken notice of by Gerstin, who published his treatise on dew in 1773, proves them to be erroneous; for he found that bodies a little elevated in the air, often become moist with dew, while similar bodies, lying on the ground, remain dry, though neces- sarily, from their position, as liable to be wetted, by whatever falls from the heavens, as the former. The above notion is perfect- ly refuted, by what will presently appear relative to metallic surfaces exposed to the air in a horizontal position, which remain DEW DEW dry, while every thing around them is co- vered with dew. After a long period of drought, when the air was very still and the sfcy serene, Dr. Wells exposed to the sky, 28 minutes be- fore sunset, previously weighed parcels of wool and swandown, upon a smooth, un- painted, and perfectly dry fir table, 5 feet long, 3 broad, and nearly 3 in height, which had been placed an hour before, in the sun- shine, in a large level grass field. The wool, 12 minutes after sunset, was found to be 14° colder than the air, and to have ac- quired no weight. The swandown, the quantity of which was much greater than that of the wool, was at the same time 13° colder than the air, and was also without any additional weight. In 20 minutes more, the swandown was 14$ colder than the neighbouring air, and was still without any increase of its weight. At the same time the grass was 15° colder than the air four feet above the ground. Dr. Wells, by a copious induction of facts derived from observation and experiment, establishes the proposition, that bodies be- come colder than the neighbouring air be- fore they are dewed. The cold therefore which Dr. Wilson and Mr. Six conjectured to be the effect of dew, now appears to be its cause. But what makes the terrestrial surface colder than the atmosphere? The radiation or projection of heat into free space. Now the researches of Professor Leslie and Count Rumford have demonstra- ted, that different bodies project heat with very different degrees of force. In the operation of this principle, there- fore, conjoined with the power of a concave mirror of cloud or any other awning, to re- flect or throw down again those calorific emanations which would be dissipated in a clear sky, we shall find a solution of the most mysterious phenomena of dew. Two circumstances must here be considered:— 1. The exposure ofthe particular surface to be dewed, to the free aspect of the sky. 2. The peculiar radiating power of the surface. 1. Whatever diminishes the view of the sky, as seen from the exposed body, obstructs the depression of its tempera- ture, and occasions the quantity of dew formed upon it, to be less than would have occurred, if the exposure to the sky had been complete. Dr. Wells bent a sheet of pasteboard into the shape of a penthouse, making the angle of flexure 90 degrees, and leaving both ends open. This was placed one evening with its ridge uppermost, upon a grass-plat in the direction of the wind, as well as this could be ascertained. He then laid 10 grains of white, and moderately fine wool, not artificially dried, on the middle part of that spot of the grass which was sheltered by the roof, and the same quantity on ano- ther part ofthe grass-plat, fully exposed to the sky. In the morning the sheltered wool was found to have increased in weight only 2 grains, but that which had been exposed to the sky 16 grains. He varied the expe- riment on the same night, by placing up- right on the grass-plat a hollow cylinder of baked clay, 1 foot diameter, and 2$ feet high. On the grass round the outer edge ofthe cylinder, were laid 10 grains of wool, which in this situation, as there was not the least wind, would have received as much rain, as a like quantity of wool, fully exposed to the sky. But the quantity of moisture acquired by the wool, partially screened by the cylinder from the aspect of the sky was only about 2 grains, while that acquired by the same quantity fully exposed, was 16 grains. Repose of a body seems necessary to its acquiring its utmost coolness, and a full deposite of dew. Gravel walks and pavements project heat, and ac- quire dew, less readily than a grassy sur- face. Hence wool placed on the former has its temperature less depressed than on the latter, and therefore is less bedewed. Nor does the wool here attract moisture by ca- pillary action on the grass, for the same ef- fect happens if it be placed in a saucer. Nor is it by hygrometric attraction, for in a cloudy night, wool placed on an elevated board acquired scarcely any increase of weight. If wool be insulated a few feet from the ground on a bad conductor of heat, as a board, it will become still colder than when in contact with the earth, and acquire fully more dew, than on the grass. At the wind- ward end of the board, it is less bedewed than at the sheltered end, because in the former case, its temperature is nearer to that of the atmosphere. Rough and porous surfaces, as shavings of wood, take more dew than smooth and solid wood; and raw silk and fine cotton are more powerful in this respect than even wool. Glass projects heat rapidly, and is as rapidly coated with dew. But bright metals attract dew much less powerfully than other bodies. If we coat a piece of glass, partially, with bright tin-foil, or silver leaf, the uncovered portion of the glass quickly becomes cold by radiation, on exposure to a clear nocturnal sky, and ac- quires moisture; which beginning on those parts most remote from the metal, gradu- ally approaches it. Thus also, if we coat outwardly a portion of a window pane with tin-foil, in a clear night, then moisture will be deposited inside, on every part except opposite to the metal. But if the metal be inside, then the glass under and beyond it will be sooner, or most copiously bedewed. In the first case, the tin-foil prevents the glass under it from dissipating its heat, and therefore it can receive no dew; in the second case, the tin-foil prevents the glass DEW DEW which it coats, from receiving the calorific influence of the apartment, and hence it is sooner refrigerated by external radiation, than the rest of the pane. Gold, silver, copper, and tin, bad radiators of heat, and excellent conductors, acquire dew with greater difficulty tlian platina, which is a more imperfect conductor; or than lead, zinc, and steel, which are better radiators. Hence dew which has formed upon a metal will often disappear, while other substances in the neighbourhood remain wet; and a metal purposely moistened, will become dry, while neighbouring bodies are acquiring moisture. This repulsion of dew is communicated by metals to bodies in contact with, or near them. Wool laid on metal acquires less dew, than wool laid on the contiguous grass. If the night becomes cloudy, after having been very clear, though there be no change with respect to calmness, a considerable alteration in the temperature of the grass always ensues. Upon one such night, the grass, after having been 1^° colder than the air, became only 2° colder; the atmos- pheric temperature being the same at both observations. On a second night, grass be- came 9° warmer in the space of an hour and a half; on a third night, in less than 45 minutes, the temperature ofthe grass rose 15°, while that ofthe neighbouring air in- creased only 3$°. During a fourth night, the temperature of the grass at half past 9 o'clock was 32°. In 20 minutes after- wards, it was found to be 39°, the sky in the mean time having become cloudy. At J Heat of the air 4 feet above the grass, ------ wool on a raised board, - - ------ swandown on the same, - - ------ surface of the raised board, - ------ grass-plat,....... The temperature always falls in clear nights, but the deposition of dew, depend- ing on the moisture of the air, may occur or not. Now, if cold were the effect of dew, the cold connected with dew ought to be always proportional to the quantity of that fluid; but this is contradicted by experience. On the other hand, if it be granted that dew is water precipitated from the atmosphere, by the cold of the body on which it appears, the same degree of cold in the precipitating body may be attended with much, with little, or with no dew, according to the existing state of the air in regard to moisture, all of which circumstances are found really to take place. The actual precipitation of dew, indeed, ought to evolve heat. A very few degrees of difference of tern- the end of 20 minutes more, the sky being clear, the temperature of the grass was again 32°. A thermometer lying on a grass- plat, will sometimes rise several degrees, when a cloud comes to occupy the zenith of a clear sky. Wher, during a clear and still night, different thermometers, placed in different situations, were examined, at the same time, those which were situated where most dew was formed, were always found to be the lowest. On dewy nights the tem- perature of the earth, half an inch or an inch beneath the surface, is always found much warmer than the grass upon it, or the air above it. The differences on five such nights, were from 12 to 16 degrees. In making experiments with thermome- ters it is necessary to coat their bulbs with silver or gold leaf, otherwise their glassy surface indicates a lower temperature than that of the air, or the metallic plate it touches. Swandown seems to exhibit great- er cold, on exposure to the aspect of a clear sky, than any thing else. AVhen grass is 14° below the atmospheric temperature, swandown is commonly 15°. Fresh un- broken straw and shreds of paper, rank in this respect with swandown. Charcoal, lampblack, and rust of iron, are also very productive of cold. Snow stands 4° or 5° higher than swandown laid upon it in a clear night. The following tabular view of observa- tions by Dr. Wells, is peculiarly instruc- tive:— 6A. 45' 7h. 7h. 20' 7h. 40' 8/». 45' 604° 60$° 59« 5.3« 54° 53 $ 54$ 51$ 48$ *** 54$ 53 51 47$ 42$ 58 57 55$ — — 53 51 49$ 49 42 perature between the grass and the atmos- phere is sufficient to determine the forma- tion of dew, when the air is in a proper state. But a difference of even 30°, or more, sometimes exists, by the radiation of heat from the earth to the heavens. And hence, the air near the refrigerated sur- face must be colder than that somewhat elevated. Agreeably to Mr. Six's observa- tions, the atmc sphere, at the height of 220 feet, is often, upon such nights, 10° warmer than what it is seven feet above the ground. And had not the lower air thus imparted some of its heat to the surface, the latter would have been probably 40° under the temperature of the air. Insulated bodies, or prominent points, are sooner covered with hoar-frost and dew than others; because tiie equilibrium of DEW DEW their temperature is more difficult to be restored. As ae.ial stillness is oecessary to the cooling effect of radiation, we can understand why the hurtful effects of cold, heavy fogs, and dews, occur chiefly in hol- low and confined places, and less frequently on hills. In like manner, the leaves of trees often remain dry throughout the the night, while the blades of grass are covered with dew. No direct experiments can be made to ascertain the manner in which clouds pre- vent or lessen the appearance of a cold at night, upon the surface ofthe earth, greater than that of the atmosphere. But it may be concluded from the preceding observa- tions, that they produce this eff'ect almost entirely by radiating heat to the earth, in return for that which they intercept in its progress from the earth towards the hea- vens. The heat extricated by the- conden- sation of transparent vapour into cloud must soon be dissipated; whereas, the ef- fect of greatly lessening or preventing al- together tbe appearance of a greater cold on the earth than that of the air, will be produced by a cloudy sky during the whole of a long night. We can thus explain, in a more satisfac- tory manner than lias usually been done, the sudden warmth that is felt in winter, when a fleece of clouds supervenes in clear frosty weather. Chemists ascribed this sud- den and powerful change to the disengage- ment of the latent heat of the condensed vapours; but Dr. Wells's thermometric ob- servations on the sudden alternations of temperature by cloud and clearness, ren- der that opinion untenable. We find the atmosphere itself, indeed, at moderate ele- vations, of pretty uniform temperature, while bodies at the surface of the ground suffer great variations in their temperature. This single fact is fatal to the hypothesis derived from the doctrines of latent heat. "I had often," says Dr. Wells, " smiled, in the pride of half knowledge, at the means frequently employed by gardeners, to protect tender plants from cold, as it appeared to me impossible that a thin mat, or any such flimsy substance, could prevent them'from attaining the temperature of the atmosphere, bv which alone 1 thought them liable to be injured. But when I had learn- ed, that bodies on the surface of the earth become, during a still and serene night, colder than the atmosphere, by radiating their heat to the heavens, I perceived im- mediately a just reason for the practice, which I had before deemed useless. Be- ing desirous, however, of acquiring some precise in formation on this subject, I fixed perpendicularly, in the earth of a gras plat, four smal'l sticks, and over their up- per extremities, which were six niches Vol.. I. above the grass, and formed the corners of a square whose sides were two feet long, I drew tightly a very thin cambric handkerchief. In this disposition of things, therefore, nothing existed to prevent the free passage of air from the exposed grass to that which was sheltered, except the four small sticks, and there was no sub- stance to radiate downwards to the latter grass except the cambric handkerchief." The sheltered grass, however, was found nearly of the same temperature as the air, while the unsheltered was _>* or more cold- er. One night the fully exposed grass was 11" colder than the air; but the sheltered grass was only 3° colder, lience we see the power of a vi-ry slight awning, to avert or lessen the injurious coldness of the ground. To have the full advantage of such protection from the chill aspect of the sky, the covering should not touch the subjacent bodies. Garden walls act partly on the same principle. Snow screens plants from this chilling radiation. In warm cli- mates, the deposition of dewy moisture on animal substances hastens their putrefac- tion. As this is apt to happen only in clear nights, it was anciently supposed that bright moonshine favoured animal corruption. From this rapid emission of heat from the surface of the ground, we can now ex- plain the formation of ice during the night in Bengal, while the temperature of the air is above 32°. The nights most favourable for this effect, are those which are the calmest and most serene, and on which the air is so dry as to deposite little dew after midnight. Clouds and frequent changes of wind are certain preventives of conge- lation. 310 persons are employed in this operation at one place. The enclosures formed on the ground are four or five feet wide, and have walls only four inches high. In these enclosures, previously bedded with dry straw, broad, shallow, unglazed earthen pans are set, containing unboiled pump-wa- ter. Wind, which so greatly promotes eva- poration, prevents the freezing altogether, and dew forms in a greater or less degree during the whole of the nights most pro. ductivc of ice. If evaporation were con cerned in the congelation, wetting the straw would promote it. But Mr. Williams, in the 83d vol. of the Phil. Trans, says, that it is necessary to the success ofthe process that the straw be dry. In proof of this he mentions, that when the straw becomes wet by accident it is renewed; and that, when he purposely wetted it in some of the in- closures, the formation of ice there was al- ways prevented. Moist straw both conducts heat and raises vapour from the ground, so as to obstruct the congelation. According to Mr. Leslie, water stands at the head oi' radiating siib.-^nnces. See Caloric* 4:5 DIA DIA * Diallasx. A species ofthe genus Schil- ler spar. Diallage has a grass-green colour. It occurs massave or disseminated. Lustre glistening and pearly. Cleavage imperfect double. Translucent. Harder than fluor spar. Brittle. Sp.gr. 5.1. It melts before the blow-pipe into a gray or greenish ena- mel. Its constituents are 50 silica, 11 alu- mina, 6 magnesia, 13 lime, 5 3 oxide of iron, 1.5 oxide of copper, 7.5 oxide of chrome.— Vauquelin It occurs in the island of Corsi- ca, and in Mont Rosa in Switzerland, along with saussurite. It is the verde di Corsica ditro of artists, by whom it is fashioned into ring-stones and snuff-boxes. It is the sma- ragdite of Saussure. The diallage in the rock is called gabbro* * Diamond. Colours w hite and gray, also red, brown, yellow, green, blue, and black. The two last are rare. When cut it exhi- bits a beautiful play of colours in the sunbeam. It occurs in rolled pieces, and also crystal- lized : 1st, In the octohedron, in which each plane is inclined to the adjacent, at an angle of 109° 28' 16". The faces are usually cur- vilinear. This is the fundamental figure.— 2d, A simple three-sided pyramid, truncated on all the angles. 3d, A segment ofthe oc- tohedron. 4th, Twin crystal. 5th, Octohe- dron, with all the edges truncated. 6th, Octohedron, flatly bevelled on all the edges. 7th, Rhomboidal dodecahedron. 8th, Octo- hedron with convex faces, in which each is divided into three triangular ones, forming altogether 24 faces. 9th, Octohedron, in which each convex face is divided into six planes, forming 48 in all. 10th, Rhomboi- dal dodecahedron, with diagonally broken planes. 11th, A flat double three-sided py- ramid. 12th, Very flat double three-sided pyramid, with cylindrical convex faces. 13th, Very flat double six-sided pyramid. 14th, Cube truncated on the edges. Crystal small. Surface rough, uneven, or streaked. Lustre splendent,and internally perfect adamantine. Cleavage octohedral, or parallel to the sides of an octohedron. Foliated structure. F'rag- ments octohedral or tetrahedral. Semi-trans- parent. Refracts single. Scratches all known minerals. Rather easily frangible. Streak gray. Sp. gr. 3.4 to 3.6. It consists of pure carbon, as we shall presently demonstrate. When rubbed, whether in the rough or po- lished state, it shows positive electricity; whereas rough quartz affords negative. It becomes phosphorescent on exposure to the sun, or the electric spark, and shines with a fiery light. In its power of refracting light it is exceeded only by red lead-ore, and or- piment. It reflects all the light falling on its posterior surface at an angle of incidence greater than 24° 13', whence its great lustre is derived. Artificial gems reflect the half of this light. It occurs in imbedded grains and crystals in a sandstone in Brazil, which rests oo chlorite and clay-slate. In India the diamond bed of clay is underneath beds of red or bluish-black clay; and also in allu- vial tracts both in India and Brazil. For the mode of working diamond mines, and cutting and polishing diamonds, consult Jameson's Mineralogy, vol. i. p. 11. The diamond is (lie most valued of all mi- nerals. Dr. Wollaston has explained the cutting principle of glaziers' diamonds, with his accustomed sagacity, in the Phil. Trans. for 1816. The weight, and consequently the value of diamonds, is estimated in carats, one of which is equal to four grains, and the price of one diamond, compared to that of another of equal colour, transparency, purity, form, SLc.isasthe squaresof the respective weights. The average price of rough diamonds that are worth working, is about L. 2 for the first carat. The value of a cut diamond being equal to that of a rough diamond of double weight, exclusive of the price of workman- ship, the cost of a wrought diamond of 1 carat is L.8 2 do. is 2a X L-8, «=, 32 3 do. is 32 X L-8, _ 72 4 do is 4» X l-8> — 128 100 do. is 1008 x L.8, =80000. This rule, however, is not extended t© diamonds of more than 20 carats. The lar- ger ones are disposed of at prices inferior to their value by that computation. The snow- white diamond is most highly prized by the jeweller. If transparent and pure, it is said to be of the first water. The carat grain is different from the Troy grain. 156 carats make up the weight of one oz. troy; or 612 diamond grains are con- tained in the Troy ounce. From the high refractive power of the diamond, MM. Biot and Arago supposed that it might contain hydrogen. Sir H. Da- vy, from the action of potassium on it, and its non-conduction of electricity, suggested in his third Bakerian lecture that a minute portion of oxygen might exist in it; and in his new experiments on the fluoric com- pounds, he threw out the idea, that it might be the carbonaceous principle, combined with some new, light, and subtle element, of the oxygenous and chlorine class. This unrivalled chemist, during his resi- dence at Florence in March 1814, made several experiments on the combustion of the diamond and of plumbago by means of the great lens in the cabinet of natural his- tory, the same instrument as that employed in the first trials on the action of the solar heat on the diamond, instituted in 1684 by Cosmo HI. Grand Duke of Tuscany. He snbsequently made a series of researches on DIA DIG tiie combustion of different kinds of char- the water is formed by the combustion of Goal at Rome. His mode of investigation hydrogen existing in strongly ignited char- was peculiarly elegant, and led to the most coal. As the charcoal from oil of turpen- decisive results. *" tine left no residuum, no other cause but the He found that diamond, when strongly presence of hydrogen can be assigned for ignited bv the lens, in a thin capsule of pla- the diminution occasioned in the volume ot tinum, perforated with many orifices, so as to the gas during its combustion. admit a free circulation of air, continued to The only chemical difference perceptible burn with a steady brilliant red light, visible between diamond and the purest cnarcoal is, in the brightest sunshine, after it was with- that the last contains a minute portion ot drawn from ihe focus. Some time after the hydrogen; but can a quantity of an element, diamonds were removed out of the focus, less in some cases than l-50,U00tli part 01 indeed, a wire of platina that attached them the weight of the substance, occasion so to the tray was fused, though their weight great a difference in physical and chemical was only 1.84 grains. His apparatus con- characters? The opinion of Mr. Tennant, sisted of clear glass globes of the capacity of that the difference depends on crystalhza- from 14 to 40 cubic inches, having single a- tion, seems to be correct. Iransnarent so- pTrtures to which stop-cocks werlattached. lid bodies are in ge^non^ictors of A small hollow cylinder of platinum was at- electricity ; and ,t isjp,.obab UvJ^t £e same ta^hed to one end ofthe stop-cock, and was corpuscular arrangements which giveto mat- mo^ ^^3? JerLtfed* capsule ter?he power of tra=itt,ng and^poanzing for containing the diamond. When the ex- light, are likewise connected with its lela periment was to be made, the globe con- taining the capsule and the substance to be burned was exhausted by an excellent air pump, and pure oxygen, from chlorate of potash, was then introduced. The change of volume in the gas after combustion was tions' to electricity. Thus water, the hy- drates of the alkalis, and a number of other bodies which are conductors of electricity when fluid, become non-conductors in their crystallized form. That charcoal is more inflammable than with , stopiock, "^X^TfteT rnTcoma £ b" ft^ d "nld up'pears to the stop-cock of the globe, and the ab- gen it co <" . f Uit sorption was judged of by the quantity of to burn in ^f^X^edUiu^on mercury that entered the tube, which af- Plumb^0's°S'bet^en the diamond and forded a measure so exact, that no altera- supposed £ ««tbetw «n ^ is donQ tion however minute could be overlooked. «omm°n .£i°^^eV?he power pos- He had previously satisfied himself*: . away by the- -S^ceous suLtaneis of quanbty ot moisture, less than l-100th ota sessea y and separating colouring grain, is rendered evident by deposit on on ^«rbinf fn flmd is probably niechanical, a polished surface of gass; for a pieceat matters n ^ j ^ paper weighing one grain was mtroduced and depenogit n 5 ^ into a tubeV about ^^«^SS^ S^ ^**and'lnimal clJcoal, and t^rr^wZ^^^T^l ITdoesnofexistin Plumbago,coak, or an- tible on the inside _ of ^ g^thouS^the *»££; rf^ chemical m e be. paper, when weighed in a balance «"™nB diamond and other carbonaceous wi&i 1-lOOth of a grain, indicated no appre- ^nts,ry be demonstrated by ignit.ng ciable diminution. , ; chlorine, when muriatic acid is pro- The diamonds were always heated to rea i former— ness before they were introduced into.he ^«^ J"^ '„ ^ owing to lhe mo». cansule. During their combustion, the glass liie visiui I ^ t0 tha est. *" u ^ w,* HlffV-rent experi- This circumstance is in favour of the opi- From the results of his f1^™ e^" nion> that the minute quantity of hydrogen ments, conducted with the most unexcep , difference be- diamond in oxygen, withou [ »^h»n*ea£ hJ been given for a diamond. njygen, there is every reason to believe Wat DIG DIG * Digestion. The conversion of food into chyme in the stomach of animals by the solvent power of the gastric juice. Stune interesting researches have been lately made on this subject by Dr. Wilson Philip and Dr. Prout Phenomena, &c. of digestion in a rabbit.— A rabbit which had been kept without food for twelve hours, was fed upon a mixture of bran and oats. About two hours afterwards it was killed, and examined immediately while still warm, when the following cir- cumstances were noticed: The stomach was moderately distended, with a pulpy mass, which consisted ofthe food in a minute stale of division, and so intimately mixed, that the different articles of which it was composed could be barely recognized. 1 he digestive process, however, did not appear to have taken place equally throughout the mass, but seemed to be confined principally to tiie superficies, or where it was in contact vvieh the btomach. The smell of this mass was pecu- liar, and difficult to be described. It might be denominated fatuous and disagreeade. On being wrapped up in a piece of linen, and subjected to moderate pressure, it yield- ed upwards of halt a fluid ounce of an opaque reddish-brown fluid, which instantly red- dened litmus paper very strongly. It in- stantly coagulated milk, and, moreover, seemed to possess the property oi redis- solvingthecurd and converting it intoa fluid, very similar to itself in appearance. It \v; s not coagulated by heat or acids; and, in short, did not exhibit any evidence of mi. al- buminous principle. On being evaporated to dryness, and burned, it yielded very copious traces of an alkaline muriate, with slight traces of an alkaline phospiiutc and sulphate; also of various earthy salts, as the sulphate, phosphate, and carbonate of lime. "The first thing," says Dr. P. "which strikes the eye on inspecting the stoms.chs of rabbits which have lately eaten, is, that the new is never mix-.-d with tbe old tbod. I'he former is always I mind in the centre sur- rounded on all sides by the old food, except that on the upper part between the new food and the s>iialler curvature ofthe stom- ach, there is sometimes littie or no old tbod. If the old and the new food are of difi'erent kinds, and the animal be killed alter taking the latter, unless a great length of time has elapsed after taking it, tlie line of separation is perfectly evident, so that the old may be removed without disturbing the new tbod. " It appears that in proportion as the food is digtsied, it is moved along tiie great cur- vature, when tiie change in it is rendered more perfect, to the pyloric portion. The layer of food lying next the surface of the stomach, is first digested. In proportion as this undergoes the t roper change, it is moved fj.t bj the luusc.a.a lcJ:mi of the btomach, and that next in turn succeeds to undergo the same change. Thus a continual motion is going on; that part of the food which lies next the surface of the stomach passing to- wards the pylorus, and the more central parts approaching the surface." Dr. Philip has" remarked, that the great end of the stomach is the part most usually found acted upon by the digestive fluids after death. The following phenomena were observed by Dr. Front:— Comparative examination of the contents of the duodena of hvo dogs, one of which had been fed on vegetable food, the other on animal food only. The chymous mass from vegeta- ble food (principally bread) was composed of a semi fluid, opaque, yellowish-white part, containing another portion of a similar co- lour, but firmer consistence, mixed with it. Its specific gravity was l.u56. It showed no traces of a free acid, or alkali; but coagu- lated milk completely, when assisted by a gentle heat. That from animal food was more thick and viscid than that from vegetable food, and its colour was more inclined to red. its sp. i;r. was 1.022. It showed no traces of a tree acid or alkali; nor did it coagulate milk even when assisted by the most favour- able circumstances. On being subjected to analysis, these two specimens were found to consist of Chyme from Chyme from vegetable food, animal tood. Water, 66.5 60.U Gastric principle, united with the alimentary matters, and apparent- ly constituting the • chyme, mixed with excrementitious mat- ter, ... 6.0 15.8 Albuminous matter, part- ly consisting of fibrin, derived from the flesh on which the animal had been fed, - — Biliary principle, - 1.6 Vegetable gluten? - 5.0 Saline matters, - 0.7 Insoluble residuum, 0.2 100.0 1.5 1.7 07 0.5 100.0 Very similar phenomena were observed in other instances. Hut when the animal was opened at a longer period after feeding, Dr. Prout generally found much stronger evi- dences of albuminous matter, not only in the duodenum, but nearly throughout the whole of the small intestines. The quantity, however, was generally veiy minute in the ileum; aud where it enters the ccccum, no DIS DIS traces of this principle could be perceived See Sanguification.* Digestive Salt. Muriate of potash. Dioestkr. The digester is an instrument invented by Mr. Papin about the beginning of the last century. It is a strong vessel of copper or iron, with a cover adapted to screv/ on with pieces of felt or paper inter- posed. A valve with a small aperture is made in the cover, the stopper of which valve may be more or less loaded either by actual weights, or by pressure from an ap- paratus on the principle of the steelyard. The purpose of this vessel is to prevent the loss of heat by evaporation. The solvent power of water when heated in this vessel is greatly increased. * DiorsiDE. A sub-species of oblique edg- ed augite. Its colour is greenish-white. It occurs massive, disseminated, and crystalliz- ed: 1. In low oblique four-sided prisms. 2. The same, truncated on the acute lateral edges, bevelled on the obtuse edges, and the edge of the bevelment truncated. 3. Eight-sided prisms. The broader lateral planes are deeply longitudinally streaked, the others are smooth. Lustre shining and pearly. Fracture uneven. Translucent.— As hard as augite. Sp. gr. 3. 3 It melts with difficulty before the blow-pipe. It consists of 57.5. silica, 18.25 magnesia 16.5 lime, 6 iron and manganese.—Luugicr. It is found in the hili Ciarmetta in Piedmont; also in the black rock at Mussa, near the town of Ala, in veins along with epidote or pistacite, and hyacinth-red garnets. It is the Alalite and Mussite of Bonvoisin.* * Dioptase. Emerald copper-ore.* * Dippel's animal oil, an oily matter ob- tained in the igneous decomposition of horns in a retort. Rectified, it becomes colourless, aromatic, and as fight and volatile as ether. It changes sirup of violets to a green from its holding a little ammonia in solution.* * Dipvre. Schmelszstein. This mineral is distinguished by two char- acters; it is fusible with intumescence by the blow-pipe, and it emits on coals a faint phosphorescence. It is found in small prisms. united in bundles, of a grayish or reddish- white. These crystals are splendent, hard enough to scratch glass; their longitudinal fracture is lamellar, and their cross fracture conchoidal. Its sp. gr. is 2.63. The primi- tive form appears to be the regular six-sided prism. It consists of 60 silica, 24 alumina, 10 hme, 2 water, and 4 loss.— Vauquelin. It occurs in a white or reddish steatite, mingled with sulphuret of iron, on the right bank of the torrent of Mauleon in the western Py- renees.* * Distillation. The vaporization and subsequent condensation of a liquid, by means of an alembic, or still and refrigera- tory, or of a retort and a receiver. The old distinctions of distillatio per lalus, per ascen- sum, and per decensum, are now discarded. Under Laboratory, a drawing and de- scription of a large stiff of an ingenious con- struction is given. The late celebrated Mr. Walt having ascertained, that liquids boiled in vacuo at much lower temperatures than under the pressure ofthe atmosphere, appli- ed this fact to distillation; but he seems, ac- cording to Dr. Black's report ofthe experi- ment, to have found no economy of fuel in this elegant process; for the latent heat of the vapour raised in vacuo, appeared to be considerably greater than that raised in or- dinary circumstances. Mr. Henry Tritton has lately contrived a very simple apparatus for performing this operation in vacuo; and though no s'\ing of fuel should be made, yet superior flavour nay be s cured to the dis- tilled spin's and esseniial oils, in conse- quence ofthe moderation of the heal. The still is of the common form; but instead of being placed immediately over a fire, it is immersed in a vessel containing hot water. The pipe from the capital bends down and terminates in a cylinder or barrel of metal plunged in a c;stern of cold liquid. From tiie bottom of this barrel, a pipe proceeds to another of somewhat larger dimensions, which is surrounded with cold water, and furnished at its top with an exhausting syringe. Ihe pipe from the bottom of the still, for emptying it, and that from the bottom of each barrel, are provided with stop-cocks. Hence, on exhausting the air, the liquid will distil rapidly, when the body ofthe alembic is surrounded with boiling water. When it is wished to withdraw a portion of the dis- tilled liquor, the stop-cock at the bottom of the first receiver is shut, so that on opening that at the second* in order to empty it, the vacuum is maintained in the still. It is evi- dent that the first receiver may be surround- ed with a portion of the liquid to be distil- led, as L have already explained in treating of alcohol. By this means the utmost econ- omy of fuel may be observed. The term distillation, is often applied i.i this country, to the whole process of con- verting malt or other saccharine matter, into spirits or alcohol. In making malt whiskey, one part of bruis- ed malt, with from four to nine parts of bar- ley meal, and a proportion of seeds of oats, corresponding to that ofthe raw grain, is in- fused in a mash-tun of cast iron, with from 12 to 13 wine gallons of water, at 150° Fahr. for every bushel of the mixed farina- ceous matter. The agitation then given by manual labour or machinery to break down and equally diffuse the lumps of meal, con- stitutes the process of mas/ung. This opera- tion continues two hours or upwards, accord- ing to the proportion of unmalted barley; DIS DIS during which the temperature is kept up, by the effusion of seven or eight additional gal- lons of water, a few degrees under the boil- ing temperature. The infusion termed wort having become progressively sweeter, is al- lowed to settle for two hours, and is run off from the top, to the amount of about one- third the bulk of water employed. About eight gallons more of water, a little under 200° F. are now admitted to the residuum, infused for nearly half an hour with agita- tion, and then left to subside for an hour and a half, when it is drawn off. Some- times a third affusion of boiling water, equal to the first quantity, is made, and this infu- sion is generally reserved to be poured on new farina-, or it is concentrated by boiling and added to the former liquors. In Scot- land, the distiller is supposed by law, to ex- tract per cent 14 gallons of spirits, sp. gr. 0.91917, or 1 to 10 over proof, and must pay duly accord,ngly. Hence, his wort must have at least the strength of 55$ pounds of saccharine matter, per barrel, previous te letting it down into the fermenting tun; and the law does not permit it to be stronger than 75 pounds. Every gallon of the above spirits contains 4.6 pounds of alcohol, sp.gr. 0.825, and requires for its production the complete decomposition of twice 4.6 pounds of sugar = 9.2 pounds. But since we can never count on decomposing above four- fifths of the saccharine matter of wort, we must add one-fifth to 9.2 pounds, when we shall have 11£ pounds for the weight of saccharine matter, equivalent in practice to one gallon of the legal spirits. Hence, the distiller is compelled to raise the strength of his wort up to nearly 70 pounds per barr e as indicated by his saccharometer. This concentration is to be regretted, as it mate- rially injures the flavour ofthe spirit. The thinner worts of the Dutch, give a decided superiority to their alcohols. At 62 pounds per barrel, we should have about 12 per cent of spirits of the legal standard. To prevent acetification, it is necessary to cool the worts down to the proper fer- menting temperature of 70°, or 65°, as ra- pidly a« possible. Hence, they are pumped immediately from the mash-tun into exten- sive wooden troughs, two or three inches deep, exposed in open sheds to the cool air; or they are made to traverse tiie convolu- tions of a pipe, immersed in cold water.— The wort being now run into the ferment- ing tun, yeast is introduced and added in nearly equal successive portions, during three days; amounting in all to about one gallon, for every two bushels offarinaceous matter. The temperature rises in three or four days, to its maximum of 80°; and at the end of 10 or 12 day s the fermentation is completed; the tuns being closed up during the last half of the period. The distillers do' not collect the yeast from their fermenting tuns, but allow it to fall down, on the supposition that it en- hances the quantity of alcohol. The specific gravity of the liquid has now probably sunk from 1.060, that of wort equivalent to about 56 pounds per ba-rel, to 1.005, or 1.000; and consists of alcohol mix- ed with undecomposed saccharine and fari- naceous matter. The larger the proportion of alcohol, the more sugar will be preserved unchanged; and hence the impolicy of the present laws on distillation. Some years ago, when the manufacturer paid a duty for the season, merely according to the measurement of his still, it was ms in- terest to work it off with the utmost possible speed. Hence the form of still and furnace described under Laboratory, w.is contrived by some ingenious Scolcn d stillers, by w Inch means they could work off m less than t"iir minutes, and recharge, an 80 gallon stm; an operation which bad a few years before last- ed several days, and which the vigiiant fra- mers of the law, after recent investigation, deemed possible only in eight minutes. The waste of fuel was however great. The du- ties beuig now levied on the product ot spi- rit, the above contest against time no longer exists. It has been supposed, but 1 i.i.:iik on insufficient grounds, that quick distn.a- tion injures the flavour of spirits. This I believe to depend, almost entirely, on the mode of conducting tiie previous fermenta- tion. In distilliDg off the spirit from the ferment- ed wort or wasii, a hydrometer is used to as- certain its progressive diminution of strength, and when it acquires a certain weakness, the process is stopped by opening the stop- cock of the pipe, w Inch issues from the bot- tom of the still, and the spent wash is re- moved. There is generally introduced into the still, a bit of soap, whose oily principle spreading on the surface of the boiling li- quor, breaks the large bubbles, and of course checks the tendency to froth up. The spirits of the first distillation, called in Scotland low wines, are about 0.975 sp. gravity, and contain nearly 20 per cent of alcohol of 0.825. Redistillation of the low wines, or doubling, gives at first the fiery spirit called first-shot, milky and crude, from the presence of a lit- tle oil. This portion is returned into the low wines, What flows next is clear spirit, and is received in one vessel, till its density di- minish to a certain degree. The remain- ing spirituous liquor, called faints, is mixed with low wines, and subjected to another dis- tillation. The manufacturer is hindered by law from sending out of his distillery, stronger spirits than 1 to 10 over hydrometer proof, equivalent to sp. gr. 0.90917; or weaker spi- rits than 1 in 6 mider proof, whose sp. gr. is 0.9385. DIS DOL The following is said to be the Dutch mode of making Geneva:— One cwt. of barley malt and two cwts. of rye meal are mashed with 460 gallons of water, heated to 162°F. After the faring have been infused for a sufficient time, cold water is added, till the wort becomes equiva- lent to 45 pounds of saccharine matter per barrel. Into a vessel of 500 gallons capa- city, the wort is now put at the temperature of 80°, with half a gallon of yeast. The fermentation instantly begins, and is finished in 48 hours, during which the heat rises to 90°. The wash, not reduced lower than 12 or 15 pounds per barrel, is put into the still along with the grains. Three distilla- tions are required; and at the last, a few juniper berries and hops are introduced to communicate flavour. The attenuation of 45 pounds in the wort, to only 15 in the wash shows that the fermentation is here very imperfect and uneconomical; as indeed we "might infer from the small proportion of yeast, and the precipitancy of the process of fermentation. On the other hand, the very large proportion of porter yeast in a cor- rupting state, used by the Scotch distillers, cannot fail to injure the flavour of their spirits. Rum is obtained from the fermentation of the coarsest sugar and molasses in the West Indies, dissolved in water in the proportion of.nearly a pound to the gallon. The yeast is procured chiefly from the rum wort. The preceding details give sufficient instruction for the conduct of this modification of the process. Sykes' hydrometer is now universally used in thepcollection of the spirit revenue in Great Britain. It consists, first of a flat stem, 3.4 inches long, which is divided^ both sides into 11 equal parts, each of which is subdivided into two, the scale being num- bered from 0 to 11. This stem is soldered into a brass ball 1.6 inch in diameter, into the under part of which is fixed a small co- nical stem 1.13 inch long, at whose end is a pear-shaped loaded bulb, half an inch in diameter. The whole instrument, which is made of brass, is 6.7 inches long The in- strument is accompanied with 8 circular weights, numbered 10, 20, 30,40,50,60,70, 80, and another weight ofthe form of a paral- lelopiped. Each of the circular weights is cut into its centre, so that it can be placed on the inferior conical stem, and slid down to the bulb; but in consequence of the enlargement ofthe cone, they cannot slip oft'at the bottom, but must be drawn up to the thin part for this purpose. The square weight ofthe form of a parallelopiped, has a square notch in one of its sides, by which it can be placed on the summit of the stem. In using this instru- ment, it is immersed in the spirit, and press- ed down by the hand to O, till the. whole di- vided part ofthe stem be wet. The force of the hand required to sink it, will be a guide in selecting the proper weight. Having taken one ofthe circular weights, which is necessary for this purpose, it is slipped on the conical stem. The instrument is again immersed and pressed down as before to O, and is then allowed to rise and settle, at any point of the scale. The eye is then brought to the level of the surface of the spirit, and the part of the stem cut by the surface, as seenfom below, is marked. The number thus indicated by the stem is added to the number of the weight employed, and with this sum at the side, and the temperature of the spirits at the top, the strength per cent is found in a table of 6 quarto pages. " The strength is expressed in numbers denoting the excess or deficiency per cent of proof- spirit in any sample, and the number itself (having its decimal point removed two places to the left) becomes a factor, whereby the gauged content of a cask or vessel of such spirit being multiplied, and the product be- ing added to the gauged content, if over proof, or deducted from it if under proof, the result will be the actual quantity of proof spirit contained in such cask or ves- sel."* •Disthkxe. See Cyastte.* * Distinct Concretions. A term in Mineralogy.* Docimastic Art. This name is given to the art of assaying. See Assay, Blow- riFB, Analysis, and the several metals. ♦Dolomitr. Of this calcareo-magnesian carbonate, we have three sub-species. 1. Dolomite, of which there are two kinds* § 1st. Granular Dolomite. White granular. It occurs massive, and in fine granular distinct concretions, loosely aggregated. Lustre glimmering and pearly. Fracture in the large, imperfect slaty. Faint- ly translucent. As hard as fluor. Brittle Sp. gr. 2.83. It effervesces feebly with acids. Phosphorescent on heated iron, or by friction. Its constituents are 46.5 car- bonate of magnesia, 52.08 carbonate of lime, 0.25 oxide of manganese, and 0.5 oxide of iron. Klaproth. Beds of dolomite, con- taining tremolite, occur in the island of Iona, in the mountain group of St. Gothard, in the Appenines, and in Carinthia. A beautiful white variety used by ancient sculptors, is found in the Isle of Tenedos. Jameson. The flexible variety was first noticed in the Borghese palace at Rome; but the other varieties of dolomite, and also common gra- nular limestone, may be rendered flexible, by exposing them in thin and long slabs to a heat of 480° Fahr. for 6 hours. § 2d, Brown Dolomite, or magnesian lime stone of Tennant. Colour, yellowish-gray and yellowish- brown. Massive, and in minute granular DRA DYE concretions. Lustre internally glistening. Fracture splintery. Translucent on the edges. Harder than calcareous spar. Brittle. Sp. gr. of crystals, 2.8. It dissolves slowly, and with feeble effervescence; and when calcined, it is long in re-absorbing carbonic acid from the air. lis constituents are, lime 29.5, magnesia 20.3, carbonic acid 472. Aiununa and iron 0.8. Tennant. In the north of England it occurs in beds of considerable thickness, and great extent, resting on the Newcastle coal formation. In the Isle of Man, it occurs in a linK-stone which rests on gray-wacke. It occurs in trap-rocks in Fifesiiire. When Lid on iand after being calcned, it prevents vegetation, unless the quantity be snialll To the pivceeding- vanity we must refer a flexible dolomite found ne.u Tuunouth Cas- tle, it is yellow,sh-,m.iy, passing into cream- yellow. Ma&sive. Dull. Fracture earthy. Opaque. Yields readily to the knife. In thin plates, very flexible. bj>. gr. 2.54, but the stone is porous. It dissolves in acids as readily as common carbonate of lime. Its constituents are said to be 62 carbonate of lime, and 36 carbonate of magnesia. AVhen made moderately dry, it loses its flexibility; but when either very moist or very dry, it is very flexible. 2d Columnar Dolomite. Colour pale gray- ish-white. Massive, and in thin prismatic concretions- Cleavage imperfect. Fncture uneven. Lustre vitreous, inclining to pearly. Breaks into acicular fragments. Feebly translucent. Brittle. Sp. gr. 2.76. Its con- stituents are 51 carbonate of lime, 47 car- bonate of magnesia, 1 carbonated hydrate of iron. It occurs in serpentine in Russia. 3d, Compact Dolomite, or Gurhofite. Co- lour snow-white. Massive. Dull. Fracture flat conchoidal. Slightly translucent on the edges. Semi-hard. Difficultly frangible. Sp. gr. 2.76. When pulverized, it dissolves with eff'ervescence in hot nitric acid. It consists of 70.5 carbonate ot lime, and 29.5 carbonate of magnesia. It occurs in veins in serpentine rocks, near Gurhoff", in Lower Austria.* Draco-Mitigatcs. Calomel. See Mer- cury.* * Dragon's Blood. A brittle dark red coloured resin, imported from the East In- dies, the product ofpterocarpus draco, anddra- ctena draco. It is insoluble in water, but soluble in a great measure in alcohol. The solution imparts a beautiful red stain to hot marble. It dissolves in oils. It contains a little benzoic acid.* ♦Drawing Slate. Black chalk. Co- lour grayish black. Massive. Lustre of the principal fracture, glimmering; of the cross fracture, dull. Fracture of the former slaty, ot the latter, tine earthy. Opaque. ft writes. Streak same colour, ana glis- tening. Vety soft. Sectile. Easily fran- gible. It adheres slightly to the tongue,— Feels fine, but meagre. Sp. gr. 2 11 It is infusible. Its constituents are, silica 64 06, alumina 11, carbon 11, water 7.2, iron 2.75 It occurs in beds in primitive and transition clay-slate, also in secondary formations. It is found in the coal formation of Scotland, and in most countries. It is used in crayon- painting. I'he trace of bituminous shale is brownish and irregular; that of black chalk is regular and black. The best kind is found in Spain, Italy, and France.* Dcctility. That property or texture of bodies, which renders it practicable to draw them out in length, while their thickness is diminished without any actual fracture of their parts. This term is almost exclusively applied to metals. Most authors confound the words malle- ability, laminability, and ductility together, and use them in a loose indiscriminate ways but they are very diff'erent. Malleability is the property of a body which enlarges one or two of its three dimensions, by a blow or pressure very suddenly applied. Lamina- bility belongs to bodies extensible in dimen- sion by a gradually applied pressure. And ductility is properly to be attributed to such bodies as can be rendered longer and thin- ner by drawing them through a hole of less area than the transverse section of the body so drawn. Dyeing. The art of dyeing consists in fixing upon cloths of various kinds any co- lour which may be required, in such a man- ner as that they shall not be easily altered by those agents, to which the cloth w ill most probably be exposed. As there can be no cause by which any colouring matter can adhere to any cloth, except an attraction subsisting between the two substances, it must follow, that there will be few tinging matters capable of in- delibly or strongly attaching themselves by simple application. Dyeing is tlierefore a chemical art. The most remarkable general fact in the art of Dyeing, consists in the diff'erent de- grees of facility, with which animal and vegetable substances attract and retain co- louring matter, or rather the degree of faci- lity with which the dyer finds he can tinge them with any intended colour. The chief materials of stuff' to be dyed are wool, silk, cotton, and linen, of which the former two are more easily dyed than the latter. This has been usually attributed to their greater attraction to the tinging matter. Wool is naturally so much disposed to combine with colouring matter, that it re- quires but little preparation for the imme- diate process of dyeing; nothing more being required than to cleanse it, by scour- ing, from a fatty substance, called the yolk, DYE DYE which is contained in the fleece. For this purpose an alkaline liquor is necessary; but as alkalis injure the texture of the wool, a very weak solution may be used. For if more alkali were present than is sufficient to convert the yolk into soap, it would at- tack the wool itself. Putrid urine is there- fore generally used, as being cheap, and containing a volatile alkali, which, uniting with the grease, renders it soluble in water. Silk, when taken from the cocoon, is co- vered with a kind of varnish, which, be- cause it does not easily yield either to wa- ter or alcohol, is usually said to be soluble in neither. It is therefore usual to boil the silk with an alkali, to disengage this mat- ter. Much care is necessary in this opera- tion, because the silk itself is easily cor- roded or discoloured. Fine soap is com- monly used, but even this is said to be de- trimental; and the white China silk, which is supposed to be prepared without soap, has a lustre superior to that of Europe. Silk loses about one-fourth of its weight by be- ing deprived of its varnish. See Bleach- ing. The intention of the previous prepara- tions seems to be of two kinds. The first to render the stuff' or material to be dyed as clear as possible, in order that the aque- ous fluid to be afterward applied, may be imbibed, and its contents adhere to the mi- nute internal surfaces. The second is, that the stuff may be rendered whiter and more capable of reflecting the light, and conse- quently enabling the colouring matter to exhibit more brilliant tints. Some ofthe preparations, however, though considered merely as preparative, do real- ly constitute part of the dyeing processes themselves. In many instances a material is applied to the stuff, to which it adheres; and when another suitable material is ap- plied, the result is some colour desired. Thus we might dye a piece of cotton black, by immersing it in ink; but the colour would be neither good nor durable, because the particles of precipitated matter, formed of the oxide of iron and acid of galls, are al- ready concreted in masses too gross either to enter the cotton, or to adhere to it with any considerable degree of strength. But if the cotton be soaked in an infusion of galls, then dried, and afterward immersed in a solution of sulphate of iron (or other ferruginous salt), the acid of galls being every where diffused through the body of the cotton, will receive the particles of ox- ide of iron, at the very instant of their transmission from the fluid, or dissolved to the precipitated or solid state, by which means a perfect covering of the black inky matter will be applied in close contact with the surface of the most minute fibres of the cotton. This dve will therefore not Vot. I. only be more intense, but likewise more adherent and durable. The French dyers, and after them the English, have given the name of mordant to those substances which are previously applied to piece goods, in order that they may afterward take a required tinge or dye. It is evident, that if the mordant be uni- versally applied over the whole of a piece of goods, and this be afterward immersed in the dye, it will receive a tinge over all its surface; but if it be applied only in parts, tbe dye will strike in those parts only. The former process constitutes the art of dyeing, properly so called; and the latter, the art of printing woollens, cot- tons, or linens, called calico-printing. In the art of printing piece goods, the mordant is usually mixed with gum or starch, and applied by means of blocks or wooden engravings in relief, or from cop- per plates, and the colours are brought out by immersion in vessels filled with suitable compositions. Dyers call the latter fluid the bath The art of printing affords many processes, in which ihe eff'ect of mordants, both simple and compound, is exhibited. The following is taken from Berthollet. The mordant employed for linens, in- tended to receive different shades of red, is prepared by dissolving in eight pounds of hot water, three pounds of alum, and one pound of acetate of lead, to which two ounces of potash, and afterward two ounces of powdered chalk, are added. In this mixture the sulphuric acid com- bines with the lead of the acetate and falls down, because insoluble, while the argilla- ceous earth of the alum unites with the acetic acid disengaged from the acetate of lead. The mordant therefore consists of of an argillaceous acetic salt, and the small quantities of alkali and chalk serve to neu- tralize any disengaged acid, which might be contained in the liquid. Several advantages are obtained by thus changing the acid of the alum. First, the argillaceous earth is more easily disen- gaged from the acetic acid, in the subse- quent processes, than it would have been from the sulphuric. Secondly, this weak acid does less harm when it comes to be disengaged by depriving it of its earth. And thirdly, the acetate of alumina not being crystallizable like the sulphate, does not separate or curdle by drying on the face of the blocks for printing, when it is mixed with gum or starch. When the design has been impressed by transferring the mordant from the face of the wooden blocks to the cloth, it is then put into a bath of madder, with proper attention, that the whole shall be equally exposed to this fluid. Here the piece be- ^ DYE comes of a red colour, but deeper in those places where the mordant was applied. For some of the argillaceous earth had be- fore quitted the acetic acid, to combine with the cloth; and this serves as an inter- medium to fix the colouring matter of the madder, in the same manner as the acid of galls, in the former instance, fixed the par- ticles of oxide of iron. With the piece in this state, the calico-printer has only there- fore to avail himself of the difference be- tween a fixed and a fugitive colour. He therefore boils the piece with bran, and spreads it on the grass. The fecula of the bran takes up part of the colour, and the action of the sun and air renders more of it combinable with the same substance. In other cases, the elective attraction of the stuff to be dyed has a more marked agency. A very common mordant for woollens is made by dissolving alum and tartar together; neither of which is decom- posed, but may be recovered by crystalli- zation upon evaporating the liquor. Wool is found to be capable of decomposing a solution of alum, and combining with its earth; but it seems as if the presence of disengaged sulphuric acid served to injure the wool, which is rendered harsh by this method of treatment, though cottons and linens are not, which have less attraction for the earth. AVool also decomposes the alum, in a mixture of alum and tartar; but in this case there can be no disengagement of sulphuric acid, as it is immediately neu- tralized by the alkali of the tartar. Metallic oxides have so great an attrac- tion for many colouring substances, that they quit the acids in which they were dis- solved, and are precipitated in combination with them. These oxides are also found by experiment to be strongly disposed to combine with animal substances; whence in many instances they serve as mordants, or the medium of union between the co- louring particles and animal bodies. The colours which the compounds of metallic oxides and colouring particles as- sume, then, are the product of the colour peculiar to the colouring particles, and of that peculiar to the metallic oxide. * The following are the dye-stuffs used by the calico-printers for producing fast colours. The mordants are thickened with gum, or calcined starch, and applied with the block, roller, plates, or pencil. 1. Black. The cloth is impregnated with acetate of iron (iron liquor), and dyed in a bath of madder and logwood. 2. Purple. The preceding mordant of iron, diluted; with the same dyeing bath. 3 Crimson. The mordant for purple, united with a portion of acetate of alumi- na, or red mordant, and the above bath. 4. Red. Acetate of alumina is the mor- DYE dant, (sec Alumina), and madder is the dye-stuff. 5. Pale red of different shades. The preceding mordant diluted with water, and a weak madder bath. 6. Brown or Pompadour. A mixed mor- dant, containing a somewhat larger pro- portion of the red than of the black; and the dye of madder. 7. Orange. The red mordant; and a bath first of madder, and then of quercitron. 8. Yellow. A strong red mordant; and the quercitron bath, whose temperature should be considerably under the boiling point of water. 9. Blue. Indigo, rendered soluble and greenish-yellow coloured, by potash and orpiment. It recovers its blue colour, by exposure to air, and thereby also fixes firm- ly on the cloth. An indigo vat is also made, with that blue substance, diffused in water with quicklime and copperas. These sub- stances are supposed to deoxidize indigo, and at the same time to render it soluble. Golden-dye. The cloth is immersed al- ternately in a solution of copperas and lime- water. The protoxide of iron precipitated on the fibre, soon passes by absorption of atmospherical oxygen, into the golden-co- loured deutoxide. Buff. The preceding substances, in a more dilute state. Blue vat, in which white spots are left on a blue ground of cloth, is made, by ap- plying to these points a paste composed of a solution of sulphate of copper and pipe- clay; and after they are dried, immersing it stretched on frames for a definite number of minutes, in the yellowish-green vat, of 1 part of indigo, 2 of copperas, and 2 of lime, with water. Green. Cloth dyed blue, and well wash- ed, is imbued with the aluminous acetate, dried, and subjected to the quercitron bath. In the above cases, the cloth, after re- ceiving the mordant paste, is dried, and put through a mixture of cow dung and warm water. It is then put into the dye- ing vat or copper. Fugitive Colours. All the above colours are given, by ma- king decoctions of the different colouring woods; and receive the slight degree of fixity they possess, as well as great brillian- cy, in consequence of their combination or admixture with the nitro-muriate of tin. 1. Red is frequently made from Brazil and Peachwood. 2. Black. A strong extract of galls, and deuto-nitrate of iron. 3. Purple. Extract of logwood and the deuto-nitrate. 4. Yellow. Extract of quercitron bark, or French berries, and the tin solution. 5. Blue. Prussian blue and solution of tin. i J 9+ & s«*SS; —.,#• - •>• ■-'A ^^' _- ♦.«.—'-. .. 3*£ '^■Pr^S? • Bit--SAro>f3