h\ lis :• /*W i W\ 1 /\*(l \tSK I 1 V I r ^w I Y 'r v - \s ™\ * /- 1N|, Anvaaii ivnouvn 3N i 3 ios w jo *«y»« n tvno ii v n 3 n i 3 i a aw jo a«v iia i i Library of medicine national library of medicine national library o, 1 i»:o A»v»an IVNOIiVN 3 n i 3 i a 3 w JO All v Ha n 1 v noi i v N 3 n i 3 i a 3W JO All v «a I M/TIIBRARY OF MEDICINE NATIONAL LIBRARY OF MEDICINE NATIONAL LIBRARY ( !|HJO A»V»all TVNOUVN 3NI3IQ3W JO A V V II a II IVNOIiVN 3NI3IQ3W JO A»V«a LIBRARY OF MEDICINE N A T I O N A I L I B R A R Y O F M E D I C I N E N A T I O N A I I I B R A R Y - r%i£k' iJ^y [ IVNOIiVN 3NI3IQ3W JO A II V III MEDICAL CHEMISTRY FOR THE USE OF STUDENTS AND THE PROFESSION: BEING A MANUAL OF THE SCIENCE, WITH ITS APPLICATIONS TO TOXICOLOGY, PHYSIOLOGY, THERiPEUTICS, HYGIENE, &c. BY D. P. GARDNER, M. D., FORMERLY PROFESSOR OF CHEMISTRY IN THE PHILADELPHIA COLLEGE, AND OF CHEMISTRY AND NATURAL PHILOSOPHY IN HAMPDEN SIDNEY COLLEGE, VIRGINIA J CORRESPONDING MEMBER OF THE LYCEUM OF NATUKAL HISTORY, NEW YORK, ETC. ETC. PHILADELPHIA: LEA AND BLANCHARD. 1848. 4 Entered according to the Act of Congress, in the year 1S4S, by LEA AND BLANCHARD, in the Clerk's Office of the District Court for the Eastern District of Pennsylvania. PEIILADELPHIA I T. K. AND P. &. COLLINS, PRINTERS., PREFACE. The Author has felt much embarrassment in the discharge of his duties as a teacher of Chemistry to a medical class, from the want of a suitable text-book. The works on the subject are sufficiently numerous, but they treat the science abstractly, and are for the most part too heavy for the purposes of the medical student. So far as he may judge, there is wanting a book which directs the attention of the novice to the intimate connections between this science and medicine—something which may interest his mind in the subject of Chemistry by pointing out its relations to physiology, therapeutics and practice. The attention of the profession has been excited, within the last few years, by the labors of the German and French chemists, in physiology and the kindred sciences; but these researches are in some measure unappreciated among us, from the want of chemical knowledge, and the apparent difficulty in acquiring it. The author has been desirous of offering a means of dispelling this difficulty, by the preparation of a manual, which may serve as an introduction to more elaborate essays. He does not lay claim to originality, but is more ambitious to be useful; and his highest satisfaction will be found in having contributed something towards the introduction of chemical sci- ence into medicine. D. P. GARDNER, M. D. Philadelphia, July 1848. TABLE OF CONTENTS. Introduction The properties of matter Specific gravity PART I THE CHEMICAL FORCES. Heat The nature of heat ... Expansion .... Radiation .... Conduction .... Specific heat .... Latent heat .... Ebullition .... Vaporization .... Sources and effects of heat Relation of heat to climate Relations of heat to animals and plants Heat and cold as therapeutic agents Light Radiant light .... Reflection and refraction of light The prism .... The undulatory theory ... The nature of the sun's light The chemical and physiological action of light Electricity Common or statical electricity The electrical machine Electrical polarity and the magnet Electrical induction ... Electroscopes and electrometers The Leyden jar and battery 1* CONTENTS. The distribution of electricity The means of electrical excitement Machine electricity in medicine The magnet as a remedial agent Galvanism Cause of galvanism Theory of the galvanic circle Conducting power of metals, &c Ohm's researches - Effects of the galvanic circle Galvanic batteries ... Galvanic effects ... The electro-chemical theory The electrotype The inductive action of galvanism Electro-magnetism The electric telegraph - Galvanometers ... Animal-galvanism Phenomena of the gymnotus and torpedo The effect of the direct and inverse galvanic current on ani mals ..... Action of galvanism on the different nerves Galvanism as a remedial agent The. proper galvanism of animals Galvanism of the muscles ... Induced nervous currents ... Similarity of the galvanic and nervous force Theories of muscular action Affinity Cohesion, capillary attraction, and chemical attraction The phenomena of chemical affinity Allotropism ... Tables of affinity The chemical relations of matter Table of equivalents The atomic theory Symbols of chemical bodies Nomenclature ... Combination by volume Results of the chemical force Crystallization ... Dimorphism and isomorphism - Relations of isomorphism to physiology and therapeutics The production of groups and types ... Catalysis; the propagation of chemical action Relations of catalysis to physiology and therapeutics Page 79 80 82 85 8'.» 92 94 94 95 97 101 103 104 107 108 109 113 115 117 118 121 122 123 124 125 126 128 130 133 134 135 137 138 139 144 145 146 151 157 159 163 166 CONTENTS. PART II THE SIMPLE BODIES OF GREATEST IMPORTANCE. Oxygen Hydrogen ..... Water; oxide of hydrogen; hydric acid Peroxide of hydrogen ... Nitrogen ..... The atmosphere ... Diffusion of gases ... Mechanical properties of the atmosphere The protoxide of nitrogen Nitrous acid and other oxides Nitric acid - Compounds of nitrogen with hydrogen - Ammonia .... Ammonium and oxide of ammonium Sulphur Its characters, properties, and uses Sulphurous and sulphuric acid - Other compounds of sulphur with oxygen Compounds of sulphur with hydrogen - Sulphide of hydrogen; sulphuretted hydrogen Malaria - - - - - Selenium and Tellurium THE HALOID ELEMENTS Chlorine ..... Compounds of chlorine with oxygen Compounds of chlorine with hydrogen - Iodine ..... Binary compounds of iodine Bromine ...... Compounds with hydrogen and oxygen Fluorine ..... THE PHOSPHORUS GROUP Phosphorus - Compounds of phosphorus with oxygen The tribasic phosphates Compounds of phosphorus with hydrogen Arsenic ..... Arsenious acid . - - - Tests for arsenious acid - The copper test Marsh's test . - - - Poisoning by arsenious acid and antidotes Arsenic acid and arseniuretted hydrogen CONTENTS. Other compounds of arsenic Antimony The oxides of antimony Tartar emetic - The chlorides of antimony The sulphurets of antimony Antimoniuretted hydrogen Carbon Carbonic oxide - Page 217 217 21S 218 219 219 220 220 221 * . 222 Carbonic acid - - ' . . .223 Compounds of carbon with hydrogen - _ 224 Cyanogen - 225 Hydrocyanic acid - _ 227 Compounds of cyanogen _ _ .228 Sulphocyanogen - _ 228 Bisulphuret of carbon - Boron and silicon __ . . 228 Boron - 229 Boracic acid and borax - ^ ... 229 Silicon and silicic acid - PART III. ORGANIC CHEMISTRY. Introduction . . 230 Nature of organic bodies • ^ _ .231 Compound radicals - _ 232 Analysis of organic bodies . .".„ . 233 On the production of the primary organic principles - The amylum series _ _ 240 Starch and its varieties - . . 242 Cane sugar - ... 243 Glucose - 243 Other varieties of sugar - - _ 243 Gum and its varieties - " " 244 Lignin and cellulose Bodies produced by the oxydation of the amylum series ^ Oxalic acid and the oxalates - .248 Saccharic acid - __ 248 Mucic acid - - 2. g Other products of oxydation Fermentation 248 The nature of fermentation - - ~* The organic fermentation - The germinative fermentation - - " ^ The viscous fermentation - - " The lactic acid fermentation - - *£j The butyric acid fermentation - - j™> The vinous fermentation CONTENTS. Jx Page Eremacausis Nature and effects of eremacausis .... 259 Compounds of ethyle Alcohol ---..... 261 Ether -----... 263 Etherization - - . . . . -264 Haloid compounds of ethyle ..... 264 Salts of oxide of ethyle -----. 265 Compounds associated with ethyle .... 265 Compounds of acetyle Aldehyde,—Acetylous acid and acetal .... 266 Acetic acid and acetates ..... 266 Compounds derived from the acetyle series ... 269 Products of the distillation of avood The methylic series ...... 270 Derivatives of wood spirit ..... 271 Bodies derived from wood tar - - . - 272 The eremacausis of wood and the amylum series The production of humus and humic acid - - . 274 The preservation of timber ..... 275 Other compound radicals The amyle series ...... 276 Valerianic acid and its salts ..... 277 The benzyle series ...... 278 The salicyle series ...... 280 The cinnamyle series - - - - . -282 The vegetable acids Tartaric acid and its salts ..... 283 Citric acid and its salts - - - . -284 Malic acid ....... 284 Tannic and gallic acids ..... 285 Oils and fats The volatile oils - - - - . - 286 The saponifiable oils and fats ..... 287 The non saponifiable fats ..... 289 Bodies related to the fats ..... 289 The coloring matter Nature of the coloring matters ..... 290 Indigo - ...... 291 Chlorophyll ----... 292 Haematin ....... 293 The vegetable alkaloids and allied substances • - 296 The proteine series Proteine ...... 302 The oxides of proteine ..... 304 Albumen ....... 393 Fibrine ........ 307 Caseine and milk ...... 308 Other proteine bodies ...... 309 X CONTENTS. PART IV. ANIMAL CHEMISTRY. Page Digestion General observations - - - * * -313 The chemical classification of food .... 314 The physiological classification of food - - - - 316 The office of the saliva - - - - -317 The office of the gastric juice .... - 320 The bile and pancreatic secretions .... 322 The chyle ------- 323 Lymph -------- 325 The blood Nature of the blood .----- 326 The chemical history of the blood .... 327 The blood in disease ...--- 330 The effect of venesection - - - * - 332 Respiration ..----- 333 Calorification - - - - - • -338 Changes occurring in the blood ----- 340 Nutrition ....... 342 Secretion ....... 344 Conclusion on the blood - - - - - 347 The capillary force Phenomena and nature of the capillary force ... 349 Penetration of membranes by gases .... 351 Endosmosis and exosmosis . - - . . 352 Cell nutrition --.---- 353 Capillary circulation ...... 353 The urine The varieties of healthy urine - - - - - 356 Urea ---.-.-. 357 Uric or lithic acid - - - - - -358 Derivatives from uric acid ..... 359 Saline matter of the urine ..... 360 Foreign bodies in the urine - - - - - 361 Urinary sediments and calculi ..... 362 Nervous matter Cerebric acid ....... 364 Oleophosphoric acid ...... 364 Bones, hair, horn, &c. ..... 365 CONTENTS. XI PART V. THE METALS. General properties and classification - Metals which decompose water at ordinary temperatures Potassium ..---- Sodium ------- Lithium, Barium, and Strontium ... Calcium ...... Magnesium .----• Metals which decompose water at a red heat Aluminum, Glucinum, Thorium, Yttrium, &c. - Manganese Iron Nickel, Cobalt Zinc Cadmium Tin Metals which cannot decompose water Chromium, Vanadium, Tungsten, Molybdenum, Osmium, Colum bium, Titanium Uranium Copper - Lead Bismuth Mercury Silver Gold Platinum Palladium Rhodium, Iridium Page 366 367 369 370 370 371 372 372 373 375 375 375 376 376 377 377 379 380 381 385 386 387 388 389 MEDICAL CHEMISTRY. INTRODUCTION. Chemistry is the science of atoms; it not only investigates their properties, but their relations to one another, and the influ- ence of certain forces on them. There are, therefore, two capital divisions of the subject, the history of matter and the nature and effects of force. Matter, in this science, is supposed to consist of extremely minute particles or atoms, separated from one an- other by a rare medium called ether, and to possess impenetra- bility, gravity, porosity, inertia, and indestructibility. Force, on the other hand, is convertible, and the result produced by any application of it may be either the motion of a mass, the evolu- tion of heat, light, electricity, or molecular disturbance, these de- pending on the degree and manner of application of the force. Of the chemical forces we know nothing except by their action on matter, which is either that of attraction or repulsion; there- fore for their evolution chemists admit the presence not only of ordinary matter, but also of a rare medium called the luminiferous or universal ether, occupying space, and present in all bodies; in the motion of which the phenomena of heat, light, and electricity are apparent. The atom of the chemist is, therefore, surrounded by an atmosphere or envelope of ether, and is subjected to any action which affects this medium. The term imponderable, formerly employed to designate heat, light and electricity, is not now used, for these are considered forces, and not particular kinds of matter. Definitions.—The terms employed in stating the chemical views of matter require to be defined to obviate any misunder- standing. An atom is the ultimate portion of a body, beyond which fur- ther division is impossible; it is spheroidal, of a known weight called its atomic weight, proportional or combining number; it 2 14 INTRODUCTION. is enveloped by ether, and has inertia. It is said to be elemen- tary or simple when it cannot be changed by heat, light 01 elec- Sty; compound when it can be separated into two or more parts by these forces. It is extremely minute, as may be con- ceived from the fact that a globule of blood is one four-thousand.h part of an inch in diameter, yet consists of three parts-a central nucleus, an envelop of coloring matter, and a proper covering, and that the nucleus, consisting of globulin, contains 1661 atoms Ehrenberg also announces that ten thousand thousand millions ot Baccillari! occupy but one cubic inch. Yet each of these ani- mals consists of many complicated parts. All chemical changes occur among these atoms. . . Matter consists of an aggregation of atoms having extension or occupying space; it is compound or elementary, in a chemical sense, as it is composed of combined or elementary atoms. Its particular form, whether it be a gas, a fluid, or solid, depends upon the condensation or separation of the atoms. In conse- quence of the atoms being separated from one another, there exist spaces occupied by ether between them, which give to the mass the quality of porosity. It also appears to be continually sub- ject to two states of force, attraction and repulsion, the former of which tends to bring the particles together, and the latter acts to disunite them. Porosity.—This term expresses the fact, that all matter, and forms of matter, are full of pores or spaces containing ether, into which bodies can pass under favorable circumstances. The ex- tent of the porosity depends upon the condition of the body, gases and vapors being remarkably porous, and allowing other gases to flow through them with little obstruction, fluids being less por- ous and solids least so. Impenetrability.—The property one portion of matter possesses of occupying space, to the exclusion of all other bodies. It re- fers to the absolute parts, and not to the interstices. Numerous illustrations of this-property are at hand, but a very striking one is as follows:—If a tumbler be inverted into water, it may be pressed down several inches without the water rising into it, be- cause the contained air is impenetrable. On this principle, the diving bell is constructed. Gravity.—All matter has weight, and exerts pressure. This pressure is termed gravity; it is developed to a remarkable extent in bodies of great bulk, as the earth, sun and planets. Inertia.—An indisposition to rest or motion ; incapacity to take on motion, or to stop if in movement. It is necessary that a force be acting to produce motion, and that an equal force or re- sistance be employed to arrest it. The world and planets offer sublime illustrations of the inertia of matter. These being ori- INTRODUCTION. 15 ginally thrown into movement, continue it in the absence of a sufficient impediment to their courses. This property holds for atoms likewise. Indestructibility is a property of atoms. It expresses the fact that an atom of matter cannot be destroyed; it may unite in a variety of ways under the influence of light, heat, or electricity, but it reappears when these forces are removed. Thus the fire does not destroy the atoms of carbon, but merely overcomes their particular combination. If we take means to collect them, they will weigh as much as before combustion. Ether.—This is an extremely rare body, which possesses no appreciable weight, is supposed to envelope every atom, and oc- cupy all space. In it the undulations or movements producing heat, light and electricity, take place. Its existence seems to be more than hypothetical, for it has been shown that the flight of several comets is impeded by an agent which is too rare to dis- turb the movements of the planets. The comets, which are va- porous masses, being more readily influenced by a trifling resist- ance, are soonest affected; in consequence of this action, the comets of Biela and Encke have had their orbits contracted, and their periods lessened each revolution, the former by one, and the latter by two days. The density of a body depends upon the propor- tion of ether to matter, gases containing the greatest amount in- terposed between their particles, and solids the least. Specific Gravity.—All matter has weight or gravity, and this property depends upon the attraction of the earth, but every spe- cies of matter is not equally attracted. An ounce phial of quicksil- ver weighs very much more than the same amount of water, oil, or other fluids. A cubic inch of gold weighs more than twice as much as the same bulk of iron, lead, or zinc. In considering the gravity of a body, it is, therefore, necessary at the same time to remember its bulk, and this is done whenever the specific gravity is given—for the specific gravity (sp. gr.) is the expression of the weight of a body as compared to its bulk. Water is taken as the standard in solids and fluids, air in gases and vapors. The solid or fluid is, therefore, compared to water as unity, and if it be heavier, the proportion as compared to a similar bulk of water is given, and this constitutes the specific gravity. Thus if we wish to ascertain the specific gravity of a fluid, we select a bottle capa- ble 'of containing exactly 1000 grains of water, and this being filled, weigh—then the bulks being the same, the specific gravities will be directly as the weights. If the fluid weigh 1800 grains, its specific gravity will be 1*8 that of water being 1,—or 1800 that of water being 1000. So by this simple means, the thou- sand-grain bottle, the specific gravities of fluids can be taken. We may also employ the buoyant power of liquids, for this is 16 INTRODUCTION. found to be directly as their densities. On this principle the hydrometer and the specific gravity beads are constructed. The hydrometer is a vessel of metal or glass, con- Fig. 1. sisting of a stem, and two ovoidal bulbs, the lower m usually small, and filled with shot or quicksilver, to keep the instrument {Jig. 1) in an upright position in fluids. The stem is graduated, and the whole is of such weight that it floats in most liquids, but in dif- ferent degrees, the stem being more or less sub- merged. When the fluid is light, it sinks lowest, and when heavy, is buoyed up, and we may determine the specific gravity by reading the marks of the scale on the stem. The specific gravity of a solid is readily obtained, by weighing it first in air, then in water, finding the difference, and dividing the first number by this. The difference in this case is the weight of an equal bulk of water. In the case of gases and vapors, a bottle of certain dimensions is taken; this is weighed when full of air, and also weighed after it has been thoroughly emptied under the air-pump; the difference gives the weight of the air irrespective of the glass. If now it be filled with vapor of water, oxygen or any other gas, and weighed, the increase of weight will be due to the gas employed, and by taking air as unity, the specific gravity is readily determined. In all these cases, the temperature is to be considered, for bodies dilate by heat and become of less specific gravity by their enlarge- ment. The temperature adopted as a standard, is 60° F. The foregoing are the essential properties of atoms and matter, but there are others which are particular or dependent. The particular properties, as combustibility, color, malleability, duc- tility, &c.,it is the business of the chemist to discover by experi- ment, and record as a test of the presence of any given sub- stance. The dependent properties arise from peculiar circum- stances; such are elasticity, compressibility, expansibility, cohesion, for the same substance may or may not exhibit these qualities. Water is little elastic, but steam is highly so; the one has cohe- sion, the other little or none. The dependent properties of mat- ter, with the state of combination and other considerations, depend upon the action of the chemical or molecular forces, heat, light, and electricity; hence it is a matter of great importance to under- stand their effects, and this study constitutes a necessary portion of chemistry. PART I. THE CHEMICAL FORCES. HEAT. Heat and Caloric are terms often used indiscriminately, but they were originally employed to designate things entirely differ- ent, caloric being a name given to the agent which produces the phenomena of heat—and heat to some of the effects so produced, as the expansion of bodies, and the sensation of warmth. The cause of heat was formerly attributed to the action of ex- tremely minute imponderable atoms, which had a self-repellent power, and which, intruding between the molecules of matter, caused them to be torn asunder. In the present day, it is attri- buted to movements in the atoms of the ether which occupies the interstices of matter. These movements are similar to the vibra- tions which produce waves, but on a very minute scale. They are also propagated in the same way as waves from a centre, di- minishing in intensity inversely as the squares of the distances. That is to say, the heat which produces an effect equal to 100° degrees of the thermometer at one foot, will produce but |th of this effect at 2 feet, \\h at 3 feet, TVth at 4 feet, &c. This law is true for all central forces, or those in which the effect lessens with distance, as light, gravity, heat. Adopting the ethereal hypothesis of caloric, it will be evident that whilst a substance is heated, and its ether thrown into vibra- tions, the atoms of the body will be forced apart, and the motion will be communicated to all the neighboring ether and matter. In virtue of the first effect, all bodies expand or become enlarged. by heat, and the second effect is termed the radiation or propaga- tion of heat. To these two effects of expansion and radiation, nearly all the phenomena of heat belong. Moreover, the differ- ence in intensity of heat depends upon the strength of the vibra- tions being greater as the temperature rises. Any application of force may throw the calorific ether into vibrations; it is done by pressure, as when gases are suddenly condensed; it is done by friction in filing a piece of metal; it is also produced by electri- cal action, as in the passage of a current of galvanism through a 2* 18 EXPANSION. piece of thin platina, &c, and in a variety of cases, when chemi- cal union occurs, as in the common fire. In these and every other case, there is a force acting upon the ether, and not the introduc- tion of new matter, as according to the corpuscular theory. The effects of Heat.—As we have already remarked, the prin- cipal effects of heat are expansion and radiation. Other conse- quences flow from the undulatory theory; thus as the amount of ether present, in any form of matter, is dependent upon its pecu- liar properties, it is evident that the same force will act unequally upon different kinds of matter, producing different amounts of expansion, and acting in different times. Thus an equal weight of mercury is heated before the same fire, thirteen times sooner than water. In consequence of this difference, bodies are said to have different capacities for heat, or to have different specific heats. When substances are condensed, or pass into a rarer state, it is found that heat is given out, or a sensation of coldness is produced; these phenomena are attributed to effects occurring in a contained or hidden heat, not to be measured except during the act of change; this part of the subject is termed Latent heat. That there is such a state of heat, it is impossible to conceive on the ethereal hypothesis, but as there are many important facts grouped under this head, the term is here preserved. The ac- tions which produce the phenomena of latent heat, will be con- sidered under their proper head. Heat also exerts considerable action in the chemical union of bodies, but this is not now under consideration. The study of heat, therefore, divides itself into four parts: 1. Expansion. 2. Radiation. 3. Specific heat. 4. Latent heat. § 1. EXPANSION. Expansion is the increment in size which elementary bodies undergo by additions of heat; it does not always occur in com- pound bodies, because decomposition, evaporation, or some par- ticular effect may arise to disturb the operation of the agent. The expanded body returns to its original dimension when cooled. It is demonstrated by a number of cases: thus, if we adapt a copper ball to a ring, through which it just passes when cold, and heat it, the ball will expand and become so enlarged that it cannot pass the ring, but on cooling, again returns to its original size. This experiment may be taken as a demonstration of se- veral important facts. It shows that the copper ball does not EXPANSION OF SOLIDS. 19 consist of atoms only, of an unchangeable magnitude, but that it likewise contains between them spaces susceptible of enlargement; the spaces occupied by the ether. The enlargement is not due to the addition of matter, but to the thrusting out of the atoms of the copper by actions taking place in the ether of the spaces. These are of a temporary nature, and the atoms come together again as soon as the vibrations cease. To bring the parts again together, it is generally conceived that a new force of attraction, the reverse of that which separated them, comes into operation. So that the atoms are subject to two forces, and the bulk at any time represents the relation between them. The force of repulsion has been shown to be heat; the force of attraction, or cohesion, is thought to be electricity. The existence of this second force is necessary to return the1 body to its original size; otherwise, the motion commenced in the ether would continue for ever in con- sequence of the inertia of matter. A competent force must there- fore operate to destroy the motion produced by heat, and bring the body to its former state. The volume of a substance always depends upon the relation of these two forces; where cohesion is greatest, the solid is the consequence ; when it is less, the fluid : whilst aeriform bodies possess but little cohesion. In consequence of the different resistance offered by the cohesive force to the disruption of the atoms of bodies, the amount of expansion in objects differs exceedingly. Expansion of Solids.—Solids expand very differently. Thus, between 32° and 212° of Fahrenheit's thermometer, glass expands about TTV77th of its length, iron 8T9tn> gold ej^h' brass 555 th, silver 524th, and lead -g^-i-th. The amount of expansion for high degrees of heat is larger, the rate not being uniform except at low temperatures. Iron at 212° expands soieotn of its length for one degree, but at 572 as much as ^oeTgth. The expansion takes place with immense force, and means have to be taken in the erection of metallic bridges to guard against the consequences. It also affects the length of the pendulum, causing it to beat slower as it becomes heated. For this there is a remedy in the construction of the compensation pendulum. The gridiron pendulum consists of an arrangement of iron and brass rods, such that any increase of length in the iron may be exactly compensated by an expansion in the brass in an opposite direction, the effect of which is that the bob or weight is kept precisely at the same distance from the point of suspension, and the instrument beats with perfect regularity at all temperatures. The expansion of metals is made use of in the arts, as in tir- ing wheels, and for other purposes. The tire being hot when adjusted to the wheel, contracts upon the felloes as it is cooled, 20 EXPANSION OF LIQUIDS. binding them firmly together. Professor Darnell has also em- p oyed it for the construction of a pyrometer to measure high Jer/peratures by the expansion of a platinum bar fitted to a case of plumbago. The heat enlarges the metal, causing it to thrust up a wedge placed above it in the case, and this advance is mea- sured by a gauge, and shows how much the platinum had ex- panded by heat. By this pyrometer it appears that the melting point of copper is 1996° F., gold 2200°, cast iron 2786 F. Expansion\ in Liquids.—All liquids expand by the application of heat, but they do not expand equally, nor does the same liquid dilate regularly for similar increments of heat, but taster as the temperature rises. The unequal expansion of different fluids may be readily de- monstrated by taking three large thermometers, and filling them respectively with alcohol, ether and water. If these be intro- duced into a water bath of the same heat, the ether will rise or expand most rapidly, the alcohol next, and the water least. In this way it has been shown that from 32° to 212° F., or for 180 degrees of heat, water expands ^d of its bulk, olive oil TV-h; alcohol |th; and sulphuric acid T'Tth. In this small amount of heat, the difference in the rate ol ex- pansion is small, but at higher temperatures the rate is very un- equal; thus the absolute expansion of quicksilver from 32 to 212 is Tyh of its bulk; from 212 to 392 = &th and from 392 to 572"= T\d. This applies to all fluids. As fluids cool, they contract steadily until they become solid, except in a few remarkable cases. We find that water contracts only to 39|° F.; it then expands and becomes enlarged by £th its bulk before freezing. The type metal used in casting letters and cast iron has the same property. The temperature at which this anomalous expansion takes place, is called the " point of maximum density." It occurs in fluids which crystalize as they solidify, and is commonly attributed to a change in the molecules when they are about to take on the symmetrical adjustment of a crystal. It is a phenomenon of great importance in nature, for did not water expand in being converted into ice, that body would sink to the beds of rivers and seas, and in consequence of the poor conducting power of water for heat, it could not be thawed during the hottest summers in a deep river, so that the water- courses would be obstructed, life destroyed, and an injurious in- fluence exerted on climate. The expansion of fluids alters their specific gravities. If a measure accurately full at 40° F. contain 1000 grains of water, and it be heated to 100 F., in consequence of expansion, a portion will flow out leaving the vessel fall, but containing only 985 grains; hence the fluid will be lighter than at 40° F. It is, therefore, EXPANSION OF LIQUIDS, 21 necessary, to insure accuracy, that the temperature of a fluid, and especially a gas, should be given when we are treating of its bulk. The principal use made of the expansion of fluids in the arts is in the construction of the thermometer, but it might also be employed as a mechanical force. The thermometer is employed to mark variations in tempera- ture, to determine questions in meteorology and chemistry, and is useful in regulating the temperature of the air in the sick chamber, and of baths. The mercurial thermometer is almost exclusively employed in this climate; its principal advantages are the large range of temperature which may be measured by it, from 39 de- grees below zero to 662° F; the mercury also expands more regularly at high temperatures than other fluids. Thermometers are also filled with colored alcohol and sulphuric acid. This in- strument consists of a glass tube of fine and regular bore, at one end of which is a small bulb. When it is partially filled with mer- cury, the fluid is heated until it rises to the top of the tube, which is then sealed by melting the glass with a blow-pipe flame. It contains only the fluid by the expansion of which we measure temperature, and is free from air. To this is next to be attached a scale for marking the expansion and degree of heat which it cor- responds to, but as there is no rule in nature, any*one may con- trive a scale. The instrument is represented in fig. 2. We have the scales of Fahrenheit, Reaumur, De Lisle and the Centigrade. The Centigrade and Fahrenheit are now almost exclusively employed. To make these, the glass bulbs are first placed in thawing ice, and a mark made at the point where the fluid rests; they are afterwards exposed to boiling water, and a mark made here also. The thawing of ice and boiling of water always take place at fixed temperatures, at the sea level, and are therefore standards. In Fahrenheit's scale, the thawing point is marked 32°, and the boiling 212° F. In the Centi- grade, the first is marked 0° C, or zero Centigrade, and the second 100° C. This scale contains only 100 degrees between the two points. Fahrenheit's scale has 180° between them. The distance between these stationary marks is now divided on a piece of metal, wood, ivory or convenient material, and at- tached to the glass. For degrees above or below these points marks are made of the same value, or, if we are very particular, other stationary points are ascertained and marked on the scale. These are the boiling points of mercury, 662° F., pure ether 96° F., or alcohol 173° F.; and the temperatures of 22 EXPANSION OF GASES. artificial mixtures of snow, and various proportions of salt and other substances are also employed. Authors usually express the scale they allude to by affixing the letters F. for Fahren- heit; C. for Centigrade, and R. for Reaumur; the sign of — (minus) is also employed for temperatures below the 0 or zero, and sometimes -f (plus) for those above. It is often necessary to convert the measures of Centigrade into those of Fahrenheit, and the reverse. To convert Centigrade into Fahrenheit, we multiply by 9 and divide by 5, and add 32, if the degree be above 0. For as 100° C. = 180° F. :: 1° C. = ■f th F. or nearly two degrees. To convert Fahrenheit into Centi- grade, multiply by 5 and divide by 9, subtracting 32 for tempe- ratures above zero. In the scale of Reaumur, there are but 80° R. between the boiling and freezing of water (0°); this scale is therefore converted into Fahrenheit by multiplying by 9, dividing by 4, and adding 32° as before. Expansion in Gases.—Gases and vapors, at temperatures re- mote from their points of liquefaction, expand to a remarkable extent by the application of heat. In consequence of the feeble cohesion they possess, this expansion is nearly the same for all. It is about 4iotn of the volume at 0 F., or j^d of the volume at 32° F. Moreover, the rate of expansion is nearly uniform at all tem- peratures, and whether the body be subject to condensation or not. In consequence of the great expansion of aeriform matter, 460° F. of heat, increasing one cubic inch to two cubic inches, their specific gravity is continually subject to variation. Heated air being lighter, rises as we observe in chimneys. This property of air is the cause of the disturbances in the atmosphere, called winds, and is also the principle whereby ventilation is accom- plished. For this purpose all that is necessary, is to provide egress for the heated air in the upper part of the room, to which it naturally rises, and regulate the supply of fresh air below. Hot air having a great ascensional power from its diminished specific gravity, was first used in balloons, by Montgolfier, in 1782. In consequence of its rapid dilatation, it was employed to form thermometers by Ga- lileo and Sanctorio. Such instruments are of no use from the varying pressure of the air which acts on the volume of the gas also. Hence the rise or fall in the air thermometer, arises both from changes in heat, and in the pressure of the air. Leslie's differential thermometer (fig. 3) having the fluid entirely separated from the atmosphere, FREE RADIATION. 23 is not subject to this disturbance, but can only be made use of in particular cases, not being serviceable as a general thermometer. Liebig conceives that the difference in activity, between the inhabitants of temperate and torrid localities, depends upon the different weights of air, especially oxygen, in equal bulks of the atmosphere. As the capacity of the lungs will be the same, he urges that the quantity of oxygen entering to aerate the blood, will be less in the torrid zone, overlooking the fact that the temperature of the interior of the body will be nearly similar in both situations. § 2. RADIATION. When a hot body is brought into a room, we find that the heat is sent forth in all directions. If a thermometer be employed to measure the heat thus passing out, it will be found that the degree will vary with the distance, being inversely as the square of the distance, and that the temperature will be the same at equal dis- tances around the mass. From these facts we infer that the heated body is a centre of force from which an impression is pro- pagated in spherical waves. The sun is a brilliant instance of this sort of radiation. The word radiation was originally intro- duced in connection with the hypothesis, that heat and light were molecules passing off in straight lines called rays. The influence is not on the particles of air, for radiation takes place through a vacuum, and in the interplanetary spaces which contain no air, it is an affection of the universal ether, the particles of which being thrown into vibrations, produce a wave. This kind of ra- diation, distinguished by the term free radiation, takes place chiefly in gases, and occurs in them without heating their particles. But as ether exists everywhere, a heated body produces undula- tions in fluids and solids also, therefore radiation occurs in these; but it is not a vibration of the ethereal particles only, but of the material atoms also, and the body becomes heated and of less specific gravity. Radiation is divided into three parts: 1. Free Radiation. 2. Interstitial Radiation or Conduction. 3. Convection of heat. Free Radiation.—Every heated body produces free radiation, but substances appear to differ in the rapidity with which the heat is thrown out. It was stated by Leslie, that the facility of radia- tion depended upon the nature of the body, and upon the surface; and that when it was black, or of a dark color, or rough, it radiated faster than when bright, or of a light color. Melloni concludes that hammering a surface alters its emissive 24 REFLECTION OF HEAT. power, but that mere color cannot be said to do so. Scratching a hard surface also hastens radiation, by offering more points ot departure for the radiations, but scratching a soft surface impedes it In connection with this difference, is the reverse quality of absorbing heat, or the facility with which a body becomes warm- ed. As might be inferred, good radiators, as coal, lamp-black, plumbago, are also remarkable absorbers of heat, or become ra- pidly warmed. The radiation is much faster from a substance at a high tem- perature than at a low one, or, in other words, the rate of cooling is much faster at high temperatures than when the substance is but slightly heated. When the least deviation in temperature exists between bodies, the operation of radiation comes into play, and as from a variety of causes, changes of temperature are perpetually occurring, it is customary to admit that interchange of heat by radiation is con- tinually taking place. This position constitutes the ground of the "theory of the exchanges of heat," and offers an explana- tion of the fact that there is a constant effort in bodies and all masses, whether of the earth or planets, to reach an equilibrium of temperature. The formation of dew in the evenings of sum- mer, was explained by Dr. Wells on this hypothesis. It occurs only on clear, calm evenings, for it is necessary that the earth should be chilled by radiation to cause the moisture of the air to fall to its surface; and it does not take place when there are clouds, for these radiating back to the earth, hinder the necessary refrigeration. The propagation of radiant heat is, according to the undulatory theory, accomplished by extremely minute waves set up by the vibrations of the ether, in the same way as the motion of a vio- lin string produces waves in the air, and the phenomenon of sound. These waves do not much exceed those of light in dimensions, for they move with them, and they pass probably with the same velocity of 195,000 miles in a second of time. Nor do these agents resemble one another in such points only, but in nearly all their properties, differing in their effects and relations to matter chiefly. Thus we find that radiant heat, like light, is reflected by some bodies, refracted by others, that it may become absorbed like light falling on a black uneven surface, and that it also ex- hibits the phenomena of polarization. In their origin they are also closely associated, for light is seldom, if ever, emitted by bodies without heat. There is also an intimate relation between the temperature of a body and the color of the light which it throws out, as the heat rises, the light becoming developed. Reflection of Heat.—The undulations of heat or light falling on a polished surface, have their course changed. This may be REFLECTION OF HEAT. 25 demonstrated by holding a mirror before a fire so that the light is reflected on one's face; it will be found that heat passes with it. If the polished surface be plane, the direction is merely changed. The change of direction is according to a simple law, which also applies to light and all kinds of motion; the angle formed by the coming or incident light, or heat with a line per- pendicular to the reflecting surface, is the same as the angle formed by the same line with the receding or reflected ray. In figure 4, a is a plane metallic mirror, b' is a line perpendicular to its face, c is the Fig. 4. direction of the incident ray, and d is the new path of the reflected ray. Now, according to the law, the angle formed between the ray c and the line b', is the same as that between d and b'. This holds true for every reflecting surface. If it be curved as in a b, (Fig. 5,) the light and heat will not be merely dis- persed, but collected into a point; for. let c d be two rays striking the surface, let g z be lines repre- senting perpendiculars at the points Fig. 5. where the rays fall, therefore the di- rection of the reflected rays / in will be such that the incident rays form the same angle with the perpendiculars as these do. If we draw out the di- rection of the rays, under such cir- cumstances, we find that when they are parallel, they will be reflected to a point. When the agent is light, this Fig. 6. rl_ 26 TRANSMISSION OF HEAT. point will be brilliantly illuminated; when heat it will be very hot, because the heat of a number of rays is here condensed. This point is termed the focus of the mirror. If the curve be convex, or the reverse of the foregoing, which is concave, the heat wi'll be dispersed, and not come to any focus. The action of concave mirrors on heat is beautifully illustrated by setting up two mirrors opposite each other, (Fig. 6,) placing in the focal point of one a red hot coal, or ball of iron, and in the focus of the other a little phosphorus, which will be speedily ignited by radiations from the heated matter. The concave mirror, and especially that with a parabolic curve, has been much used in researches on radiation for the purpose of condensing small amounts of heat, and rendering them per- ceptible to the thermometer. Transmission of Heat.—As there are bodies which allow light to pass through them, and others which do not, so some substances transmit the radiations of heat, and others obstruct them. The substances which transmit heat are not necessarily those which are transparent. Hence, the term diathermanous has been used to distinguish those which allow the radiation of heat to pass; and athermanous, for those which are opaque to heat. If we place a piece of glass between a thermometer and the fire, it will obstruct so much heat as to cause a fall in the mercury; but a transparent piece of rock-salt will not cut off any of the radiations. This property of transmitting heat is not dependent on the clear- ness or color of the body, for perfectly transparent alum or ice cuts off nearly all the heat, being opaque to that agent, whilst dark rock salt, and smoky quartz or mica, allow a large amount to pass. Another extraordinary fact has been discovered by M. Melloni in the transmission of heat. He finds that the number of rays, out of a hundred, which pass through a medium, depends upon the temperature of the source. Thus colorless fluor spar allows 78 per cent, of the rays from a heated source, as a fire or oil- flame, to pass, and only 33 from a piece of metal, heated to 212° F. Beryl allows 54 per cent, of the former to pass, and none of the latter. In these experiments, he made use of plates TVth of an inch thick, and heat from the undermentioned sources. His method of detecting heat was novel, and extremely delicate. He employed for this purpose, a thermo-multiplier, consisting of a number of small bars of antimony and bismuth, united in pairs, and from the first and last bars, were copper wires connected with a galvanometer. When one end of the thermo-multiplier was heated, an electric or thermo-electric current was set in motion, which affected the galvanometer, and indicated the degree of heat. The experiments are to be found in Taylor's Scientific Memoirs. The attached table gives the most striking results. CONDUCTION. 27 Transmitted of 100 raj s of heat from .i ■a o SUBSTANCES EMPLOYED. J3 "3. . dfe CI J2 I" fci CO ■^ a a; t^ o D> n c. C,° < & o O Clear rock salt, 92 92 92 92 Colorless fluor spar, 78 69 42 33 Beryl, ..... 54 23 13 0 Iceland spar, .... 39 28 6 0 Plate glass, .... 39 24 6 0 Clear alum, .... 9 2 0 0 Clear ice, .... 6 0 0 .0 From these and other facts, it appears that the radiations of heat, derived from different sources, have unlike properties. Whilst nearly all the heat of the sun's rays penetrates the glass of the window, scarcely any of the heat of the fire passes out of the room through it. While some bodies, as alum, are diather- manous to the waves of heat, propagated by an oil-lamp, they are entirely opaque to those from boiling water or copper, at 734° F. Hence Melloni infers, that there are varieties in heat, as in light; that there are heat waves allied to red, yellow, green, blue, and the other rays of light. This is the basis of the theory of the "Ideal coloration of heat." As a matter of course, the heat rays or heat lints, have not color, but they have different wave lengths, which, in the case of light, is the cause of difference of color. Just as a pure blue glass transmits only light of that color, so ice transmits only heat from a very high temperature, cutting off the rest by absorption or otherwise. This theory is also sustained by the refraction and polarization of heat, which associate this agent completely with light. To study the refraction of heat, clear rock salt is cut into lenses, prisms, &c, and used, as glasses of the same figure are employed in studying the phenomena of light. Polarization is accomplished by the use of plates of doubly refracting minerals. Interstitial Radiation or Conduction.—Conduction has been explained as that case of radiation in which the ether of a solid is not only thrown into undulations, by contact with a heated body, but the material atoms are also acted on. In proof of this view, it may be remarked, that the propagation of the heat is very slow, the resistance being great, and the parts of the solid are warmed, and become expanded. Bodies conduct very unequally, metals being the best conduct- 28 CONVECTION OF HEAT. ors _; moist solids and fluids having but little conducting power, whilst gases do not conduct at all. Metals also differ amongst themselves in this property. Gold, silver and copper, conduct- ing very nearly three times as fast as iron, zinc and tin, whilst porcelain, glass and fine clay have little more than one-tenth the power of gold. The unequal conduct- Fig. 7. ing power of metals is strikingly illus- trated by the following little apparatus (Fig. 7); a is a piece of copper about the size of a cent piece, suspended by a wire or chain and hook to any convenient stand : c, d, e are rods of silver, copper and iron, of the same length and thick- ness, soldered into the central plate; these bear at their ends cup-shaped cavities to hold phosphorus. When a spirit lamp flame is placed under the centre, the heat is conducted with un- equal rapidity to the cups, and the phos- phorus is inflamed in different times. Convection of Heat.—Fluids and aeriform bodies are heated chiefly by currents arising in them. The water occupying the lower portion of a vessel, placed on a fire, becomes heated be- fore the parts above it are warmed; in consequence, it dilates and rises through the fluid; thus a current is set up which conveys the heat. The current of heated water may be made apparent by placing'pieces of amber in the fluid, which rise with the heated portions. As the strata become cooled at the surface, they de- scend, and become again heated; thus the circulation is main- tained. A vessel of water cannot be heated by applying the fire above, or at the side, whereas metals and conductors may be heated by any of these means. In the case of gases, the dila- tation produced by heat is so great that it floats up with consid- erable force. Winds originate in this way ; a bulk of air being heated by contact with the earth, rises, and cold air rushes in to fill the void, and the disturbance is communicated on all sides. The temperature of the air does not arise from the action of radiant heat, but by convection only. This, in a measure, ex- plains the reason of the extreme coldness of mountain tops, and elevations in the air to which the warmed masses scarcely reach. SPECIFIC HEAT. 29 § 3. SPECIFIC HEAT. The term specific heat or capacity for heat is employed to ex- press the singular fact that the rapidity with which equal weights of different substances become heated is very diverse. That is, a pound of quicksilver, of water, and of oil, being placed in simi- lar vessels over the same fire, the first will become heated to 200° F., or any practicable degree, thirty times sooner than the water, and fifteen times sooner than the oil. The specific heats of these bodies are, therefore, to each other as 1-15 and 30, or the specific heat (or capacity for heat) of water is thirty times greater than that of mercury. It follows from this remarkable difference, that if one pound of oil, at 100° F.,be shaken with one pound of water at 40°, instead of the temperature of the two being the mean, it will be but 60° F.; and if the water be the warmer, it will rise to 80° F.; the mean produced by taking two different pounds of water at the same temperatures, being 70° F. In the first case, the oil loses 40 degrees and the water gains 20, or the temperature which imparts 40 degrees of heat to oil is only competent to elevate an equal weight of water 20 degrees. By mixing equal weights of different substances at known temperatures with water, and observing the resulting degrees, the specific heats may be de- termined as referred to water. The length of time during which substances heated to the same point, cool to a given degree, may also be employed to de- termine their capacities, for it is obvious that as water takes thirty times as long as quicksilver to become heated, it will take longer to cool. Lavoisier and Laplace determined the capacities of bodies at the same temperature, by measuring the quantity of ice that they would thaw when introduced into a vessel containing it, called the calorimeter. Water has the highest specific heat of all known substances, and if we take it at 1000, that of alcohol will be 660; sulphuric acid 333 ; ether 520; mercury 33; iron 114; copper 95 ; gold 32 ; glass 179. These numbers are true only below 212° F., the specific heat increasing with the temperature and rarefaction in all classes of bodies. In the case of gases, air is taken as the standard and made 1 or 1000. By the experiments of Apjohn, the specific heat of oxygen is 808; nitrogen 1048; hydrogen 1459; carbonic acid 1195; vapor of water 3172. But the specific heat is much increased if these gases be heated or rarefied by a diminution of pressure. On the other hand, it is diminished under increased pressures. 3* 30 LATENT HEAT. Dr. Black, in explaining the phenomena now under considera- tion, conceived that different substances absorbed unlike quantities of heat, or had different capacities by reason of their porous structure. Such an explanation is not now admissible, but the subject is little understood. There appears to be, however a close connection between the specific heat of a substance and the chemical power of its atoms. For we find that if the specific heat be made the divisor of a constant number for a similar class of substances, a product is obtained that often represents the chemical equivalent of the body. And again we find that in sub- stances of the same chemical class, the specific heats are in an inverse ratio to the equivalents, or to some multiple of them. It is in this relation of heat to the weights of the molecules, that we are to search for the cause of the difference of bodies in their capacities for heat, but too little is known of the subject to permit us to enter upon it in an elementary work. It may, how- ever, be proper to remark that the question refers to the amount of heat operating, rather than to its intensity. § 4. LATENT HEAT. The term latent heat has been introduced into thermotics to signify that, under certain circumstances, the heat applied to a body becomes insensible or latent. Under ordinary circumstances, if we place a substance over a fire, it becomes warm, and the in- crease of temperature can be measured by the thermometer or by the sense of touch; here the added heat is sensible or free : but if a piece of ice be placed in a vessel over the fire, it does not become heated, but merely thaws, remaining at the same tempe- rature so long as any ice is present. The heat in this case was said by Dr. Black and his followers to become latent or hidden in the produced water. It has also been termed the heat of fluid- ity, because it is occupied in producing a remarkable change from the solid to the fluid state. All solids, in passing into the state of liquids, absorb a portion of heat, but not the same amount in every instance. Liquids, in becoming vapors, likewise render heat latent, and this is termed the heat of vaporization, or the "heat of elas- ticity." On the other hand, whenever the vapor returns to the state of a liquid, or is condensed, this heat reappears; ceasing to be hidden, it returns to the sensible state. So when the fluid becomes solidi- fied, the heat of liquefaction is given out, or becomes manifest or free. According to the doctrine of Dr. Black and the molecular theory of heat, these phenomena were readily explained, for it LIQUEFACTION OF SOLIDS. 31 was said that the heat combined chemically with the solid to convert it into a fluid, and was therefore no longer possessed of its ordinary activity; in the same way that caustic potash unit- ing with vinegar, there is produced a mild saline body having none of the acridity of the potash. It is not a simple thing to explain the disappearance of the heat according to the undulatory theory, but it is to be observed that a result is attained requiring the action of considerable force, that is, the production of a vapor from a fluid, or a liquid from a solid. In these cases, the result- ing substance occupies much more space, and the state of its molecules is widely different. To attain these results, the cohe- sive force of the solid or liquid must be overcome, and, in the case of vapors, nearly destroyed; and we presume that the force termed heat is operating as an antagonist to cohesion, and, there- fore, neutralized, and without the power of affecting circumam- bient matter.* The important facts pertaining to this topic will be grouped under three heads: 1st, liquefaction of solids; 2d, ebullition; 3d, vaporization. f Liquefaction of Solids.—The form of a liquid depends upon the heat operating on its molecules, or latent in its texture. Hence all fluids possess latent heat; but the amount and the temperature at which they pass from the solid state differ amongst them. Thus mercury liquefies at —39°; oil of turpentine at -f 14°; sulphuric acid —47°; water -4-32°; phosphorus -f-108° ; sul- phur + 218° ; silver +1872°; gold +2200° F. The number of degrees of latent heat necessary to produce the state of fluidity, is not so well known, but has been determined for water ai 142° ; sulphur 145° ; tin 500° ; bismuth 550° ; zinc 493° F. In these cases the degrees of temperature represent the amounts of heat * Judging from the phenomena of electricity and light, it is also proper to conceive that the difference between the liquid, solid and vaporous states of matter, may consist in the relations of the sides of the molecules constituting them. Thus, adopting the usual hypothesis that these atoms are spherical, it is customary in electricity and light to conceive that they are endowed with axes, the poles or extremities of which have different properties. Thus when unlike poles are opposite, attraction takes place; when like poles, re- pulsion. Now we may conceive that the heat rendered latent is a force em- ployed exclusively in effecting the polar states of these atoms, exercising to- wards them an effect of pressure. And this view is the more plausible, from the fact that the effect ceases if we withdraw the heat, and that an electrical disturbance is always manifest in these cases. According to these remarks, it is inferred that latent heat is not a variety of caloric, but only that agent em- ployed in inducing polarity or a state of pressure, and hence it cannot propa- gate its usual disturbance beyond the limits of the affected bodies, and also that when the external temperature is removed, the particles return to their former state, the disturbance of the molecules affecting the ether, and setting up the undulations which constitute free, sensible, or manifest caloric. 32 HEAT OF FLUIDITY. which would elevate the substances respectively through the mea- sures given. Ice, when becoming water, absorbs 142° of heat before it is completely liquefied, and this amount would serve to raise an equal weight of water from 32° to 174° F. Tin absorbs 500 degrees, or such an amount as would raise that substance, if it were not liquefying, 500° F. without reference to its action on water. The distinction will appear, by referring to the subject of special heat, where it will be found that the amount of heat necessary to warm water and other bodies to the same degree, is very different. The heat of liquefaction measured by that of water, is as follows:—Water 142°; sulphur 27.14 ; bismuth 23.25; zinc 48.3. Hence the latent heat of water is much higher than that of any other known substance. The temperature at which liquefaction takes place, is a fixed point. The thawing of water is rigorously at 32° F., that tem- perature being maintained during the whole period. But the point of freezing or solidification may be slightly varied under certain circumstances. It has been found that water may be cooled to 25° F., if kept perfectly still. The determination of the heat of fluidity in any substance is effected by taking equal weights of the liquid and the solid, at the point of liquefaction, and observing the action of a similar and steady source of heat. Thus if water and ice at 32° F. be taken, it will be found that when the ice is completely thawed, and the resulting liquid at 32° F.,the water will have reached the temperature of 174° F., or have gained 142°, which have been rendered latent in the ice. So an equal weight of sulphur at 218° F., or the point of liquefaction, remained without alteration of temperature, while fluid sulphur had passed from 218 to 363° F., or acquired an increase of 145 degrees ; which, therefore, cor- responds to the latent heat of fluid sulphur. It may also be de- termined by mixing the solid and fluid together at different tem- peratures, and marking the loss of heat. All liquids, in passing into the state of solids, give out their heat of fluidity. Water in freezing throws out 142° F., but this is not suddenly liberated, but produced slowly, for the substance takes a long time to solidify, in consequence of the presence of so much latent heat. The temperature of northern climates is considerably amelio- rated by this property of water, for, on the approach of winter, it is only slowly solidified, throwing out heat in the act. In spring, instead of the frightful inundations which would arise from the instantaneous change of the ice and snow into water, it takes place very gradually, thus regulating the transition from winter to spring which would otherwise be injurious to vegetation. The preparation of refrigerating "mixtures depends upon the EBULLITION. 33 disappearance of heat when solids are suddenly liquefied. Mr. Walker prepared some time since an extensive table, in which are combinations for the purpose of reducing the temperature to— 91° F.* Some of these mixtures are useful in the arts and to the surgeon. One part of snow with two parts by weight of salt, produces a reduction of temperature to 5° F. Equal parts of nitrate of ammonia and water reduce the temperature from 50° to 4° F.; this arises from the rapid solution of the salt, and may be used as an application to the skin when ice is not at hand. The solution of sal ammoniac (chloride of ammonium), or common nitre (nitrate of potash), furnishes a sufficient depression of heat to be useful in surgery. Ebullition.—A fluid urged by heat, at first expands and throws off a considerable amount of vapor, and finally enters into a state of rapid commotion, termed boiling, or ebullition. The disturb- ance in the fluid arises from the rapid passage of bubbles of va- por through it, the heat being expanded in producing vapor, and no longer warming the fluid. The boiling point, under ordinary circumstances, is fixed for the same fluid, but is widely different in various liquids. Water boils at 212° F.; ether 96° ; alcohol 173° ; oil of turpentine 315°; mercury 660°; sulphuric acid 620°; whale oil 630° F. It is remarkably subject to disturbance from pressure. For if we place a vessel containing hot water under the air pump, and exhaust the air, its pressure being diminished, the fluid throws off vapor rapidly and appears to boil at temperatures proportional to the rarefaction, and may even boil at 67° F. or 145° F. below the point at the external pressure of 30 inches of the barometer. This reduction is entirely dependent on the physical impediment presented by the weight of the air ; for alcohol placed in vacuo has its boiling temperature also reduced 145 degrees, or from 173° F. to 28° F.; more volatile fluids flash off into vapor under the same circumstances. As it has been long known that the pressure of the atmosphere diminishes rapidly as we ascend high mountains or in balloons, it became an interesting matter to observe the effect on boiling. It has been found that water boils on the summit of Mont Blanc at 184°, and at Quito at 196° F., the depression of this point being for small elevations equal to one degree for about 530 feet of elevation. The singular expe- riment called the culinary paradox, also demonstrates that the boiling point of fluids is remarkably influenced by diminished pressure. It is thus made: a flask of thin glass is one third filled with water and placed over a spirit lamp, until it boils violently, * These tables are to be found in the larger treatises on chemistry, or in Gardner's Medical Dictionary, article Freezing mixture. 34 VAPORIZATION. so as to fill the upper part of the vessel with steam; it is then well corked If it be now allowed to stand some time, and then the upper part touched with a cold body so as to condense the vapor of water which fills it, this action will reduce the pressure on the liquid, and throw it into ebullition, although the temperature may be reduced below 100° F. The reverse of this position is equally true. Fluids have their boiling points increased by pressure, but the law of increment is unknown; but it becomes less and less as the pressure rises. Water boils at 212° at the ordinary atmospheric pressure ; under the pressure of two atmospheres, it boils at 250°, under 3 atm. 275°; 4 atm. 294°; 12 atm. 374°; and under 50 atmospheres, 510° F. The difference between 1 and 2 being 38 degrees, be- tween 3 and 4 atmospheres but 19 degrees, and between 40 and 50 atmospheres only 24 degrees, or little more than 2 degrees between each atmosphere at this high temperature. As the steam produced is at the pressure to which the water is subjected, it appears that the power of high pressure steam is obtained at a very trifling expense over that necessary to obtain low pressure steam. Vaporization.—Observation teaches us that vapor is rising nearly at all temperatures from fluids, and indeed, in some cases, as ice, from solids also, and that if it were not for the pressure of the atmosphere, most common fluids would be known only as vaporous substances. It has been shown that alcohol would boil at 28° F., and water at 67° F. without this pressure. But with the ordinary pressure, it is notorious that water evaporates when exposed to the air, even at low temperatures, and a slight deposit of snow often disappears without being converted into water. Hence, evaporation, or slow vaporization takes place in sub- stances susceptible of this change, nearly at all temperatures, but the amount rising as vapor is proportional to the temperature when there is no impediment to the process. Heat is, therefore, as completely the cause of vaporization or evaporation at low temperatures, as of boiling, the difference between these being due to the rapidity of the action and degree of heat, and not to any specific causes. The nature of Vapor.—There being some popular errors on this subject, it may be well to state what are the peculiarities of vapors. This class of substances are aeriform, being perfectly clear and like air, when they are without color. They have not the appearance of a fog, as is commonly supposed. They oc- cupy a very much greater space than the liquid, from which they are derived ; thus, at the boiling points, steam occupies 1696 times the bulk of the water, alcohol 519 times, and oil of turpentine 192 times. Vapors differ from gases in returning to the liquid LATENT HEAT OF VAPORS. 35 condition, under the influence of cold and pressure; this is termed their condensation, during which, however, they give out the latent heat they contain. Heat is rendered latent in the production of Vapor.—There is in the case of vapor a molecular state, widely different from that of liquids, and for its production heat must be in every case rendered latent. This is termed the heat of elasticity, from the remarkable elasticity of vapors and aeriform substances. The amount of heat is usually considerable; thus it is found, as com- pared with vapor of water, at 1000°; that of vapor of alcohol will be 376°; of ether 163°; of oil of turpentine 138° F. If the vapor be produced at a point below boiling, the latent heat is greater, being the amount at the boiling point with the difference between it and the observed temperature. In the case of water evaporating at 60° F., the latent heat will be 1000° F. plus the temperature between 60° and 212, or, in all, 1152 degrees. There is not, therefore, any gain of heat by evaporating a fluid at a tem- perature below the boiling point, as was formerly supposed, for all the difference of heat enters the vapor. The amount of latent heat is ascertained by two means; either by observing the length of time during which a given weight of fluid evaporates away over a constant source of heat; or by measuring the heat given out in the condensation of the vapor of a known amount of fluid, in a weighed quantity of water. In the case of water, if we place one pound over such a fire, that it acquires 25 degrees of heat per minute below the boiling point, it will be found, that at this degree, (212° F.,) it becomes station- ary, and that 40 minutes will elapse before it has all evaporated. During this time, it has acquired its former rate of increase, 25 degrees, all of which has been rendered latent. Now the sum of these numbers is 1000 degrees, which therefore represents the heat rendered latent by steam, produced at 212° F. The reverse also holds true, for whenever a vapor passes back into the fluid state, it gives out an amount of heat precisely similar to that necessary to produce the vaporization. In virtue of this fact, vapors exercise a remarkable ameliorating influence on some climates, as on the shores of Newfoundland, and the British Is- lands. In these cases, the vapors of the gulf stream are con- densed on the lands, and giving out their latent heat, warm the air to such an extent, as to elevate the average temperature many degrees. Climates subject to this influence, are not only mild as respects temperature, but are remarkably genial. The condensa- tion of vapor of water is also employed as a means of warming large buildings and conservatories. It is in consequence of the large amounts of heat thrown out in condensation, that we are compelled to resort to various contrivances to liquefy the products 36 evaporation is a cooling process. of distillation. In this process, the fluid is placed over the fire in a vessel of glass, earthenware or metal, and vaporized by the access of heat. The vessels employed are termed stills when of large size, retorts or alembics when of smaller dimensions. To the vessel is adjusted a long tube, curved into the figure of a helix, and called the worm of the still for conveying the vapor, and to secure the refrigeration, this is placed in a large vat through which a current of cold water is continually flowing. This contrivance becomes absolutely necessary where the amount of fluid subject to distillation is large, otherwise a portion of the vapor would issue uncondensed. Liebig has introduced a portable condenser for the laboratory, where the amount of fluid distilled is small. It consists of a cylinder of tin or brass, in the centre of which runs a straight tube b, conveying the warm vapor. The cylinder is closed at both ends in all other respects, and when used, is set at a small angle to the horizon. From the lowest end, arises a long funnel c, by which water can enter the cylinder, and its position is such, that the warmed portions only flow out, as the escape tube d is at the highest part of the condenser. The implement is sustained by a stand, and represented in figure 8. Evaporation is a Cooling Process.—Whenever vapor is pro- duced, heat must be rendered latent, and abstracted from surround- ing matter. If there be not a fire or other source of heat, the abstraction of caloric will produce coldness. If the hand be moistened with ether, which is highly volatile, a sensation of coldness will be perceived in the evaporation. This may be also demonstrated by dropping ether upon the bulk of an air thermo- meter, when the instrument will indicate a considerable fall of temperature. The cryophorus of Dr. Wollaston, is an instrument designed to illustrate this fact in the freezing of water, by its own evapora- tion. A little concentrated prussic acid will solidify, if exposed to the air, in consequence of the cold produced by the vaporization of a part. The cooling effect of evaporation is of considerable influence CIRCUMSTANCES WHICH INFLUENCE EVAPORATION. 37 in regulating climate. The shores of lakes, and moist countries, especially such as abound in forests, being cooler than sandy and dry countries. Advantage is taken of evaporation by the surgeon, in the treatment of fractures and some wounds, lotions being applied to reduce the temperature of the parts by the coldness they produce. The insensible perspiration of the human body is also intended, for the most part, to reduce the animal heat, for we find that it is much increased during the summer, and is also influenced by the state of the moisture in the air. The human epidermis contains an immense number of minute punc- tures, being the mouths of the sudoriparous follicles, from which the perspiration arises. It is calculated that a square inch con- tains 2800 of these, or that there are seven millions over the entire surface. The amount of fluid issuing, varies from U lb. to upwards of 5 lbs. daily, besides about 18 ounces from the lungs. To vaporize this quantity of fluid at the temperature of the body, requires an immense amount of heat. The function of perspira- tion is therefore designed by nature to counterbalance the pro- cess of calorification, and remove the excess of temperature. Hence we find, that, when in the summer season, the animal heat is rendered excessive by the external temperature, evapora- tion or insensible perspiration becomes very active, and on the other hand it is reduced in winter. When the air of any district is hot and full of moisture, evaporation from the skin is impeded, and an extreme sensation of heat and oppression arises, which, if not relieved, is a fertile source of disease, and is by some sup- posed to be the remote cause of bilious and intermittent fevers. Sweat differs from insensible perspiration in being a direct exu- dation of fluid; its production does not refrigerate the body to the same degree, and it commonly occurs as a result of bodily exer- tion, or of some cause which impedes evaporation. The importance of the insensible perspiration to health is scarcely appreciated, and the effect of its diminution in producing disease and death, overlooked. Becquerel and Breschet showed that animals covered with an impermeable coating, speedily died; and M. Mojon has reported a case where a fine child was covered with gold leaf, to make a figure in a pageant, and died in a few hours. . Circumstances which influence Evaporation.—Evaporation taking place from liquids or moist solids in the open atmosphere, is subject to several disturbing causes. The amount of water which rises, depends upon the dryness or moisture of the air. The temperature, action of winds and pressure, also influence the rapidity of evaporation. In air which is calm, and completely saturated with vapor of water, evaporation, from this fluid cannot take place. The same 4 38 THE DEW POINT. holds for all other vapors in a confined space, but the presence of one vapor to saturation, does not influence the ascent of another of a different kind. It is of considerable importance in meteorology, to know the amount of vapor of water in the air at any time, and for this purpose several instruments have been contrived. Those which merely denote the presence of moisture, are called hvgroscopes, those which mark its degree, hygrometers. A sponge moistened with carbonate of potash, a piece of hair or whalebone, serves to indicate the presence of a considerable amount of moisture. The best hygrometers are constructed on two principles: 1st, that the coldness produced by evaporation increases with its rapidity; and, 2d, that whenever a substance is cooled down to the temperature at which the air is saturated with moisture, a de- position of dew takes place. To the first of these belong the wet bulb hygrometer and the psychrometer, and to the second, Daniell's and Bache's hygrometers. But it is not necessary that the student should resort to these for the determination of the dew point, as it can be reached with great expedition, by means of a little ice, a tumbler of water, and a thermometer. A small tumbler or wineglass of thin material and dry exterior is selected, and three quarters filled with water; into this a few pieces of ice (or nitre), are placed, and the whole stirred with the thermometer, the temperature of which is marked at the moment of the first deposition of a dewy mist on the exterior of the glass. This is the dew point, or temperature at which the air is full of moisture, and its capacity to receive more vapor, or drying power, is the number of degrees between this point and the atmospheric tem- perature. When the temperature of the air is 70° F., and the dew point 50° F., the drying power will be 20° F., and vapor will rise freely. As the dew point approximates to the atmo- spheric temperature, the rate of evaporation becomes less, and is finally arrested when they are the same, as this indicates that the air is saturated with moisture. Under such circumstances, espe- cially in the summer, the insensible perspiration of the body be- comes nearly arrested, and a sensation of oppressive heat and languor arises. The probability of rain is also connected with this condition, for when the air is saturated with moisture, a cold wind will condense it, and thus produce a rain storm, whereas this result could not take place if the air were altogether dry. The hyoro- metric state of the atmosphere is also seen in its effects on plants, which appear succulent, and full of vigor in a moist air, but withered when the drying power is great. Winds, or air in motion, influence evaporation mechanically by presenting new portions of matter to the fluid, and thus hin- dering saturation. According to the observations of Dalton a ELASTICITY OF VAPOR. 39 brisk wind increases the amount of evaporation from one-third to one-half. It is in consequence of this effect that wind is so emi- nently refrigerating on the human body, the insensible perspira- tion being considerably increased by its action, the coldness of the surface is rendered greater. The increased evaporation is also apparent in the rapid drying of linen in windy weather. The amount of vapor which can exist in any bulk of air or gas, depends, however, primarily upon the temperature. The drying power and the action of winds influence the rate of eva- poration, but do not affect the amount which any volume of air or space can contain. This depends upon the temperature of the space, and is the same whether it be a vacuum, or filled with gases or other vapors. It is found that 100 cubic inches at 32° F., will contain only .136 grain of vapor of water; at 60°, this rises to •338 grain, and at 100° F., to 1*113 grains. From these num- bers it will be seen that the amount does not only depend upon the temperature, but that the proportion of vapor rises rapidly with the heat, there being not simply double the amount at 60° as compared with 32°, but an excess, so at 100 there is more than three times the quantity at 60°, although the increase of heat is not double. It is found that, as the temperature rises, the weight of vapor increases in a much higher ratio, so that whilst there is but 1'113 grains in a vacuum over water at 100° F., there will be 14-962 grains at 212° F., at little more than double the tem- perature. The elasticity of Vapor.—It has been seen that heat tends to increase the amount of vapor in any space, but each addition is, under ordinary circumstances, opposed by the air or other mat- ters present, and has to overcome this resistance. In a vacuum, vapor forms immediately, but in a volume of air, it has to act by its elastic force, in dilating the gas to find admission ; hence in this case the rise of vapor is impeded. Every accession of vapor enlarges a volume of air, and pushes out a portion, the amount increasing with the temperature. The force exerted by the vapor is termed its elastic force, and it is measured by its power to de- press the column of mercury in the barometer. It is well known that the pressure of the atmosphere is capa- ble of supporting a column of mercury of 30 inches, (see Atmo- spheric Air;) but if we introduce a few drops of water, alcohol, ether, or any other vaporizable substance into the barometer tube, the mercury will be depressed, and no longer stand at 30 inches. The depression arises from the pushing action, or elastic force of the vapor, and increases rapidly with the temperature. If water be introduced above the mercury, at various temperatures, or if heat be applied by means of a hot ring of metal around the barometer tube at the place where the water floats, we find Temperature 32° F. 40° u 60° u 80° u 100° " 120° 1( 150° u 180° u 200° u 212° u 40 MAXIMUM DENSITY. that the mercury descends with each addition of heat, its elas- tic force, or tension increasing with great rapidity. It has been determined by Dr. Dalton that the elastic force of vapor of water is as follows :— Elastic force in depressing the mercurial column. 0.200 of an inch. 0.2 G 3 " 0.524 " 1.000 inch. 1.8G0 " 3.330 " 7.420 " - 15.150 " - 23.640 « - 30.000 " From this we learn that the elasticity or tension rises far more rapidly than the temperature, being but 1*86 inch at 100° F., and 30 inches at 212° F., or the boiling point of water. In all other fluids the tension is equal to 30 inches at their boiling points, the phenomena of rapid vaporization depending upon the force with which the vapor is produced. At the boiling point, the elasticity of vapors is equal to the pressure of the atmosphere, and resist- ance to their formation ceases. This table also puts us in pos- session of the reason why the weight of vapor of water in the air rises so rapidly with the temperature, for as the elasticity in- creases, the impediment offered by the air diminishes, and the amount of vapor rising is enlarged. The amount is always pro- portional to the elasticity, and the latter is as the heat. The elastic force of vapors differs with their volatility; those fluids which have the lowest boiling points, produce the most elastic vapors. Thus, if we introduce ether, water, and alcohol into three barometer tubes at the temperature of 80° F., the water will depress the column 1 inch, the alcohol 1.9 inch, and the ether 20 inches. These numbers 1, 1.9, and 20, therefore, respectively represent their elasticities at the temperature of 80° F. Maximum Density.—The amount of vapor capable of existing in any space, at a given temperature, is fixed, and cannot be ex- ceeded. The term maximum density is employed to signify that this saturation has been reached. If any more vapor is driven into such a place, it does not become diffused into every part, but is condensed on the sides of the vessel, or on the coolest points. On the other hand, the slightest diminution of tempera- ture, or increase in pressure causes a precipitation of some of the vapor; and dew or rain is produced if the operation takes place on a large scale. So, when a cold wind invades a part of the atmosphere saturated with water, or in which the vapor has a maximum density, a portion is precipitated, and a cloud is formed THE ACTION OF PRESSURE ON VAPORS. 41 if it occur in the higher regions of the atmosphere, or a fog if on the surface of the earth. Reducing the pressure of a volume of air saturated with moisture, produces a mist, in consequence of the demand for heat created by the dilatation of the air; for it will be remembered that the specific heat of gases increases with their rarefaction. The nephelescope is an instrument designed to show the production of clouds by the diminution of pressure. It consists of an air pump receiver connected by means of a stop- cock, with a large globe of glass, which is situated superiorly. The globe contains air saturated with vapor of water. The com- munication between the vessels being closed, the air of the lower is removed by the air pump, and then the communication is re- established. By this means, the moist air of the globe is sud- denly dilated, the rarefied air withdraws heat from the glass and vapor, and the point of maximum density being lowered by di- minished temperature, a portion of the vapor becomes visible, and forms a cloud. In nature, clouds often result from the same ope- ration—as when a volume of warm moist air is transported by winds into the elevated regions of the atmosphere, where the pressure being less, the air expands, and vapor is condensed as in the instrument. The action of Pressure on Vapors.—The point in which va- pors differ from gases, is the ready condensation they suffer from the application of pressure or cold. In a space saturated with vapor, the slightest increase of pressure produces liquefac- tion, and the liberation of the latent heat. In the case of gases, the latent heat is also liberated by pressure, but the degree ne- cessary to bring about liquefaction is considerable, and some- times altogether beyond our means, as in oxygen, hydrogen, ni- trogen. The evolution of heat, by the condensation of gases, may be experimentally shown by the fire syringe. This con- sists of a cylinder of brass, closed at one end, in which fits a tight piston, the lower end of which contains a cavity for the ac- commodation of a little tinder or punk. If the piston be driven down sharply, so as to condense the air of the cylinder, with considerable force, the heat evolved will ignite the tinder. But there are gases which are condensible under pressure, as was shown by Mr. Faraday. It appears from his researches, that Sulphurous acid gas is condensed by a pressure of 2 atmospheres at 45° F. Sulphuretted hydrogen " " : Carbonic acid ' Chlorine ; Nitrous oxide Cyanogen Ammonia Hydrochloric acid gas 17 ' 50° li 36 ' 32° " 4 < 60° " 50 45°" 3-6 ' 45° " 6-5 « 50° " 40 • 50° " 42 marriotte's law. As pressure is capable of condensing these gases, cold will produce the same result if sufficiently severe, but the degree is not in most cases at our command. It has been calculated that gaseous ammonia requires a temperature of—63*4° for condensa- tion, whereas carbonic acid requires —230'8°, and nitrous oxide —252*4° degrees. A vapor separated from the fluid whence it rises, cannot resist the slightest pressure, but if the heat be continued, and fresh sup- plies of matter rise, a powerful concentration may be reached. This is termed cumulative pressure from the contained additions of vapor. The pressure of vapors under these circumstances, rises with great rapidity, because the latent heat of such concen- trated vapor does not increase but diminish. If to a stout metal- lic vessel containing water, heat be applied until the whole is 212° F., the vapor or steam will be found capable of sustaining the pressure of the atmosphere, as measured by 30 inches of mer- cury, or 146 pounds on the square inch. This vessel, heated to 250° F., that is, only 28 degrees more, generates steam of double the pressure, such that it is capable of counterbalancing 60 inches of mercury, or 29"2 lbs. on the square inch. At 294° F., the steam has a pressure of 4 atmospheres, or 58'4 lbs.; at 359° F. it equals 10 atmospheres, or 146 lbs. on the square inch. Thus by the application of heat to a fluid, in a confined and strong vessel, the vapor acquires immense elastic force, overcom- ing after a time the most powerful resistance. The high pressure engine is made on this principle. The steam is generated in a strong boiler, and not allowed to pass into the cylinder until under a pressure of four or more atmospheres; it now exerts im- mense force, and drives machinery which steam at the ordinary pressure could not move, but as experience proves, it is often a source of serious accidents. In these engines the steam is allowed to escape from the cylinder into the air, but in the low pressure, or common engine, it is conducted into a tank of cold water, and reduced back into the state of water, by condensation. If, on the other hand, a vapor be separated from its source, and heat is applied, it enlarges its dimensions and increases in elasti- city, but not to the extent pointed out above. The elastic force or pressure is only moderate even at high temperatures. In this action of heat on insulated vapors, they are completely identified with gases, the same law expressing the increase of dimensions in both cases. If we take a cubic inch of any vapor, and of air, place them under similar circumstances, and apply the same heat, they will dilate equally, and acquire elasticity in the same degree. The diminution of pressure is also attended with the same results in both cases, the law of Marriotte being applicable to vapors as well as gases. The law is as follows:— The volume of a gas U SOURCES AND EFFECTS OF HEAT. 43 inversely as the pressure. If we double the pressure on a gas, its volume is diminished one-half, and if, on the other hand, we decrease the pressure one-half, the volume is doubled. Vapors cannot be condensed by pressure without liquefaction, but they dilate according to this law. Hence, diminished atmospheric pressure is conducive to the rapid production of vapor. Cold condenses vapors by removing the heat necessary to im- part to them their peculiar structure, and the degree necessary for this purpose depends upon the amount of latent heat in the par- ticular body. No application of cold can liquefy oxygen gas, for its latent heat is considered very high, and its elastic force great; but in the case of ordinary vapors, the degree of cold is not re- markable. § 6. SOURCES AND EFFECTS OF HEAT. The great source of heat as respects the earth, is the sun, but electrical, chemical, and mechanical actions, tend to develop heat radiations. The earth has also been regarded as a mass whose temperature influences a variety of operations on its surface, but from the extreme coldness of those parts where the sun is absent for a considerable period, its temperature can scarcely be sup- posed to exert any remarkable influence. It is, moreover, appa- rent, according to the law of the equilibrium of temperatures, that if the earth's surface were in those portions in which the sun is absent, warmer than space, rapid radiation would take place, tending to reduce the excess of heat in a short time. The tem- perature of the Arctic regions, measured by navigators, is about __58° F., and this agrees with the temperature of space deduced by Baron Fourier from other considerations. This equilibrium has been stationary for a long time, for we have records of the rate of the diurnal revolutions of the earth for upwards of 2000 years, dur- ing which there has been no alteration. If the earth had cooled during this time, its volume would have contracted, and the revo- lution have become more rapid, and as a consequence, the length of the day shorter. But whilst the crust of the earth has no available degree of heat, the action of the sun makes itself felt to such an extent as to render existence possible. It is known that neither animals nor plants can live below 32° F., or above 212° F., the freezing and boiling points of water, and, in truth, the lim- its' are much more confined. The surface of the earth at—58° F., can sustain no organized being, but the heat of the sun acting unequally, produces the varieties of climate, and is an important cause of the variations in animal and vegetable existence. Over the tropics, where the rays pass almost perpendicularly, and 44 HEAT OF THE EARTH AND AIR. through the least interval of air, their power is most felt; they not only heat the surface, but penetrate the soil, by conduction, to a considerable depth, constituting these portions of the earth a store- house of heat. In northern positions, the rays arrive obliquely; they are dispersed and fall on a curved surface, the same amount being distributed over a much larger space than in the tropics; a greater amount of absorption also occurs in their passage through the increased thickness of the atmosphere; they are, therefore, enfeebled, and neither raise the temperature of the surface, nor penetrate the soil in the same degree. Hence, during winter, the earth freezes, and as we proceed towards the poles, this takes place to increasing depths. The variable inclination of the sun's rays in summer and winter, and the period during which he con- tinues above the horizon, constitute the principal causes of the diversity in the temperature between these periods. The air is likewise unequally affected in different parts of the world; over the tropics it is heated by convection to a great height, the point of perpetual snow or congelation being raised to 15,000 feet, whilst at 40° of N. latitude, it is 9000; at 75° of N. latitude, it is 1000, and at 85° N. latitude, but 117 feet from the earth. If we trace a line through these points, it will represent a curve ris- ing gradually from the surface at the pole, to the equator; below which, the temperature is greater than 32°, as an average for the year; above, it is colder. The curve of perpetual congelation will be similar in the southern hemisphere. Observing the relation between temperature and moisture, it will be apparent, that, under ordinary circumstances, as the atmosphere over a warm latitude contains more moisture than over a cold situation, the rains will be heavier, and of longer duration. Other meteorological pheno- mena will also be regulated chiefly by the temperature of this portion of air. If we pass below the earth's surface, we find that in situations where the sun's action is greatest, the temperature will be affected to a considerable depth. If we dig downwards at the equator, the earth is found to become cooler as we proceed, until a point is reached where the temperature is fixed; beyond this the heat rises again. The temperature below the fixed point, or the stratum of invariable temperature, is due to the heat of the earth. If we examine the temperature at any medium latitude, we find the same phenomena ; the upper crust gradually diminishes in temperature to a certain depth, depending on the location, and beyond this there is an increase. At the latitude of Philadelphia, the depth to be attained before we reach the stratum of fixed temperature, will be about 40 feet; below this the temperature rises at the rate of about one degree Fahrenheit for every additional EFFECTS OF HEAT. 45 42 feet of descent. So far as observations have been made, the increase seems to be nearly uniform. On these grounds it ap- pears, that if we penetrate a mile, the difference will be 120° F.; at the depth of two miles, water cannot exist, being converted into steam; at four miles tin will melt, and at thirty miles depth, iron and most rocks will be in a state of fusion. This deduction, to- gether with the phenomena of volcanoes, constitutes two of the principal grounds of the igneous theory of the earth. It is sup- posed that, in the commencement of time, this globe was in an incandescent state, and that it has cooled down on the surface to a state of equilibrium, but is still occupied interiorly by matter at an intense temperature. The depth of thirty miles is almost as nothing to the radius of the earth; hence the cooled crust is merely a pellicle on the exterior, but of such poor conducting power as to separate us from the central fire. However this may be, the temperature of the globe, on its surface, is now so far re- duced, as to furnish no available supply of heat for the mainten- ance of life. Artificial heat, such as that of the fire, is the product of chemi- cal action. Indeed, with the exception of a few unimportant in- stances of the production of heat by friction and electricity, this agent appears to be in nearly every case set in motion by chemi- cal action. We find that, as the furnace is urged, the heat in- creases, being in all cases proportional to the combustion of fuel. This is a chemical process in which the fuel becomes combined with a constituent of the atmosphere (oxygen), to form regular chemical products. The animal heat was formerly supposed to have a source sui generis, but it is now understood to arise from a slow chemical change analogous to that taking place in combustion. The arte- rialized blood containing free oxygen gas, is constantly acting on the tissues of the body, and especially the fat, and producing by this union carbonic acid and water, the former of which is found in venous blood, and is thrown out by the lungs. These are also the products of combustion in the fire-place, whenever fatty matters, or bodies containing the same elements as fat, are con- sumed. Effects of Heat.—The principal effects of heat on inanimate matter have been detailed—the expansion of bodies; its relation to the forms of matter, whether they be solid, fluid or gaseous, and its tendency to attain an equilibrium. Its influence over chemical operations will be pointed out at length in the course of the work. This force has, however, several important effects on animated objects which it is proper to mention in this place. The chief of these may be considered under the following heads : 46 ISOTHERMAL LINES. 1. The Relation of heat to climate. 2. The Relation of heat to animals and plants. 3. The Relation of heat and cold to man. 4. Heat and cold as therapeutic agents. 1. The Relation of Heat to Climate.—Temperature constitutes the principal, but not the only element of climate. It has already been explained that the difference in intensity of the sun's rays, falling at different latitudes, is chiefly due to their obliquity and the curve of the earth's surface, If heat were the only element, all places on the same latitude would have the same average climate, but such is known not to be the case. Humboldt has determined that if a line be traced on a map, through those places which have the same average temperature during the year, it constitutes a curve altogether different from the line of latitude. The line of 32° F. passes in Europe near Ulea in Lapland at 66° N.lat.,but descends in crossing the Atlantic to 54° N. lat. in Labrador, or 12 degrees south; it then rises in passing through the American continent, reaching its highest point on the western coast, de- scending again to the eastern shore of Asia, and rising to the west of Europe. This constitutes a double curve, the two highest points of which are on the western coasts of America and Eu- rope, and the lowest points on the eastern shores of America and Asia. To this curve the name of the isothermal line has been given. The isothermal lines of 41°, 50°, and 59° F., obey the same general outline, but they do not fall so low on the American coast. Thus the line of 41° F. is found in Stockholm, lat 59| N., and Newfoundland, lat. 48 N., the fall being 111 degrees. The line of 59° F. passes near Rome and Florence, lat. 43° N., and reaches Raleigh, N. C.,lat. 36° N., making a descent of but seven degrees. As the temperatures become higher, the curves correspond to the lower lines of latitude. These lines represent the average temperature, but give no information of the difference of heat be- tween summer and winter. On this point there is less opportu- nity for reaching a useful generalization, for local disturbances operate more completely. It is, however, established that the variation increases as we ascend the continent from the gulf, the deviation being less in Florida and the West Indies than in north- ern latitudes, and becoming greater as we pass through the mid- dle to the northern states, and into Canada. Thus the difference between the hottest and coldest months at Tampa bay, is 22° F., at New York 55° F., at Quebec 60° F. It is not for us to enter upon the causes which produce the wide diversity in climate between western Europe and the United States, but it may be well to point out to the attention of the stu- dent, the influence of prevailing winds, the action of warm vapors CLIMATES FOR INVALIDS. 47 such as those of the Gulf Stream, the neighborhood of exten- sive forests or high mountains, all of which exert an important influence. Forests attract moisture, or condense the vapor of the air to a considerable extent; they also impede the escape of moisture by shading the earth; hence wooded countries are well watered, and their temperature is reduced. Indeed, many portions of the earth have been converted into deserts by the destruction of their forests. To the physician, a knowledge of climate is of considerable importance in the treatment of disease. It is necessary he should discriminate between a dry hot climate, a moist hot climate, an equable climate, and a bracing equable climate. To the con- sumptive an equable moist and warm climate is useful, a dry hot climate would be injurious. Such find great relief at Pensacola, in Florida, and in any other situation on Tampa Bay; where the heat of summer is not much greater than in Philadelphia, being 80° F., and the temperature of winter seldom falls below 58° F., whereas in Philadelphia, it reaches 30° F. Madeira, in the island of Funchal, is another excellent situation ; here the temperature of winter is 60° F. and that of summer 82°, the seasons flowing into one another, so as to produce a remarkable uniformity of climate. To either of these places the consumptive may be sent in the early stages of the disease, as well as patients labor- ing under chronic rheumatism and bronchitis. The West Indian islands are too enervating to most persons ; the eastern coast of Florida is often recommended, but the severe winds here arc very objectionable. There is, however, great advantage to be derived from the amusement of the mind, and for this reason cer- tain places in Europe are frequently selected, as Rome; Florence; Pisa; Undercliff in the Isle of Wight; Torbay in Devonshire, England; where the delights of society can be had as well as a genial climate. Asthma and scrofulous diseases are often much benefited by change of climate. Dyspepsia, hypochondriasis, and the cachexies, often give way to the excitement of travelling, and are especially benefited by a sea voyage. It is to be observed, that the great heat of a tropical climate is seldom useful, and often injurious; it is calculated to develope cerebral and hepatic disease, if there be any tendency to them, and by the great excitement experienced, often shortens the days of the patient laboring under advanced consumption. Exercise is also impeded in such situa- tions, and this is one of the chief curative means. It has been recommended that patients spending a winter in Pensacola, should travel northwards in the summer, so as to add the excitement of a journey, and the pleasures of society in the watering-places, to the benefit of residing in a genial climate. 48 RELATIONS OF HEAT TO ANIMALS AND PLANTS. 2. The Relations of Heat to Animals and Plants.'-The rela- tions of heat to organized objects are numerous, existence being impossible except between a narrow range of temperature. The plants allied to the red snow (protococcus nivalis) are the only living things which can exist at 32° F., and very few are found at a temperature of 120° F., except minute algae ; one of which exists in boiling water, the ulva thermalis. The capacity to manifest the phenomena of life, in the higher animals, ceases far below the boiling point of water, for the disorganization of scald- ing is produced at that temperature. No vegetable product can exist beyond a red heat, all being decomposed at that temperature. The temperatures most conducive to animal and vegetable existence are from 50° to 110°; beyond, in either direction, the operations of existence become impeded. In the larger animals, there is an internal source of heat, which enables them to enjoy a wider range of climate ; but even with this provision, the species rapidly change as we approach the limits of the temperate zone. We observe in the north a great development of hair or fur on the skin, to preserve, by its non-conducting power, the animal heat. On the contrary, in the tropics we discover dogs without hair, and find that the wool of the sheep degenerates into a sparse covering of hair. The range of temperature in which given ani- mals can flourish, is for the most part very limited. The effect of hybernation, and the torpid state in which reptiles pass the hot dry season, are also in a measure attributable to the action of temperature. In the vegetable kingdom, the influence of heat is remarkably apparent. In the arctic region, plants scarcely exist. The first objects which the eye encounters are lichens, and dwarf shrubs; the willows, birches and pines succeed these. In a lower portion of the temperate zone, are found the oaks, elm, and forest trees, with the grain plants, and in the lowest limit of this region are the orange, myrtle, olive and vine, yielding rich stores to the cultivator. In the tropics, the vegetable world ac- quires all its luxuriance; the palm trees, the mahogany and teak, furnish the most graceful and splendid objects of this class. Here the resin-bearing plants, the dye-woods and flowering trees ac- quire a full developement. But in these results the action of light is also powerful. The migrations of birds and fishes are also connected with changes in the seasons. As the winter approaches, the duck and woodcock desert the lakes and woods of the north, to enjoy a more genial climate, and return again with the spring. 3. The Relations of Heat and Cold to Man.—In consequence of the ability man possesses of dissipating the cold of extreme northern positions by artificial heat, his range of habitation is HEAT AND COLD AS RESPECTS DISEASE. 49 much greater than that of other creatures. But whilst this power gives him possession of the globe, it is attended with many in- jurious effects on his health and developement. In the arctic, we find the Esquimaux, Laplanders and Samiodes, scarcely human, living in holes in the ground, with hardly a glimmering of intel- lect. In the other extreme, we find him oppressed by heat, re- duced in longevity, slothful, almost inane. Such are the rewards of the enterprise which distributes our race from the pole to the equator. We do violence to the laws of heat. Many of our diseases depend on climate; witness consumption, leprosy, ele- phantiasis, framboesia, and the hepatic affections of warm regions. Excess of heat or cold continually undermines the system. In the former case, the circulation is fuller, the tissues are rendered lax by dilatation, and man instinctively seeks rest to avoid the dis- tressing heat, and a state of partial congestion occurs in every part of his frame. The brain is enfeebled, the liver gorged, and the system enervated. Slight excesses bring on fatal diseases, in which the recuperative powers of the body are of little avail. Not only are the diseases of hot countries peculiar, but the treatment must also be modified to guard against the enervated state of the patient. The remedial means which would be necessary in the north, if applied to an inhabitant of the tropics, would be altogether improper. Such persons are too much enfeebled by general bleeding, and are to be treated on the anodyne and refrigerant plan, rather than by active depletion. Where the climate is ex- cessively cold, the vital powers are equally depressed, and it is only by severe exercise that the inhabitants are saved from a species of hybernation in the winter, which would extinguish life. Cold acts by depressing the chemical changes in the body essen- tial to existence, and actually reducing the degree of life. During a state of vigor, it is only by the consumption of immense quan- tities of fat and oily matters, that these people are able to resist exterior cold by the animal heat. They are dwarfish, feeble, and short lived. The true habitat of our race is the southern portion of the tem- perate zone, where the variations of temperature scarcely call for change of raiment, and where, under a natural condition of things, everything would appear to minister to temporal happiness and longevity. 4. Heat and Cold as Therapeutic Agents.—That heat and cold should possess extraordinary medicinal powers, will appear, if we consider that the chemical actions of the body, in which we in- clude the cause of the circulation of the blood, are increased by heat and diminished by cold. Under the influence of heat, the circulation becomes fuller, the blood passing freely into the capil- laries of the skin; as a consequence, perspiration and the secre- 5 50 HEAT AS A THERAPEUTIC AGENT. tions are increased, and the whole body is thrown into a state resembling that of fever. If the heat be dry, as that of summer, or of a stove, an abundance of perspiration transudes; if it be moist, as in a vapor bath, (120° F.,) sweat is formed, and the tissues acquire a degree of relaxation that assures us of the diver- sion of a large excess of blood to the skin. In these two states, heat exercises a very different action, being, when dry, stimulating, and attended with less oppression than when applied as vapor or the hot bath, (110° F.) In the latter cases, it is enervating; the activity produced in the functions of the body by these means affect every part, the head, the liver, the intestines, and is followed by a subsequent reduction of action, feebleness and sleep. The hot-bath also differs from the vapor- bath, as regards the function of perspiration, there being little sweat in a bath of 100° F., whereas in the vapor-bath, there is a large amount. If the object be to subdue irregular action over the skin, the vapor-bath is most effectual, but it is more debilitat- ing. Heat, either in the dry state, or as hot water applied locally to the skin, produces a rubefacient, or derivative action, according to its degree. This is often of great service in relieving the lungs or abdominal viscera from irritation, and is applied by means of a poultice, the materials of which, usually corn meal, or linseed meal, retain the heat a long time. Sir A. Carlisle recommended the application of a piece of metal heated by immersion in boiling water to the skin, as a substitute for blistering. The action is the same, the pain is said to be less, and there is no apprehension of strangury. Boiling water produces a partial disorganization of the tissues; it coagulates the albumen of the membranes, destroying its func- tions, and the parts so injured are thrown off by the processes of nature. In treating such accidents, the principal indications ap- pear to be the exclusion of air and the adoption of means to hin- der contractions by the irregular deposition of the new portions of matter. To exclude air, a soap of linseed oil and lime-watet seems to be the best application. Scalds which injure vital organs, or destroy an extensive surface, are necessarily more serious, but the chemical effect is the same in all cases. Burns differ from scalds in the separation of a large amount of the fluid portions of the tissue, as well as the coagulation or destruction of the albumen and animal matters. The actual cautery owes all its power to these chemical effects ; it suddenly dissipates the water of the tissue, which amounts to nine-tenths, and converts the animal matter into a hard solid, capable of obstructing the flow of blood, The hot-bath and other means of employing heat, are contra-in- dicated in general febrile affections, plethora, aneurisms, or hyper COLD AS A THERAPEUTIC AGENT. 51 trophies of the heart, nervous excitability with feebleness, and in every case where it is improper to increase the circulation. Cold acts in a manner precisely the reverse of heat. It drives the circulation from the part, constringing the vessels and diminishing chemical action, in which we also include the cause of the capil- lary circulation. It is therefore operative in directing the blood to the organs of the interior, as well as subduing the circulation. Applied generally, by exposure to a cold air, or to the cold water bath (45° F.), it contracts the skin, and produces a sense of op- pression internally. If this be continued for a considerable time, the circulation becomes so slow that the entire body is chilled, venous congestions occur in the head, chylopoietic viscera and lungs, and death from want of the aeration of the blood, ensues. But when the action is for a short time only, the capillaries of the skin alone are affected, and upon the withdrawal of the agent, the circulation being re-established in these parts, a glowing sensation of heat, or reaction, occurs. Cold water, applied locally and sud- denly, produces a sharp action on the capillaries of the parts, com- municating a sensation to the nervous centres that usually pro- duces spasmodic actions. It is on the nervous centres that cold is most influential as a therapeutic agent. Cold, applied by means of pounded ice, in bladders, to the head, so completely subdues the capillary circulation of the brain, as to arrest incipient inflam- mation, and if continued sufficiently long, destroys the attack. Dashes of cold water, and the cold water shower bath, are equally efficacious in insanity and chronic irritation of the brain. But the application of cold is injurious over the chest or stomach, in in- flammatory affections of the contained organs. The amount of blood circulating in these parts, and the remoteness from the source of cold of many organs, render it impossible to impress every part with this agent. Whilst circulation is diminished on the skin and layers of muscles, it is rendered more active in the deeper seated and affected organs, from the increased quantity of blood diverted to them. In these cases, the derivative action of hot fomentations and poultices is required, and is beneficial. In the treatment of serious accidents, as compound fractures of the limbs, and in averting inflammatory action after wounds, se- vere burns and operations, cold water is the most valuable agent we possess. Applied by irrigation, so that a small stream flows over the part continually for several days, it subdues every approach to inflammatory action, whilst it does not hinder the healthy pro- cesses of restoration, if the temperature be mild. As a morbific agent, cold is of the highest consequence. It is not to be anticipated, that, whilst such remarkable effects arise from its proper application to the healthy body, it is without 52 COLD AS A MORBIFIC AGENT. injurious consequences when long continued. Exposure to cold or draughts of air, by disturbing the circulation locally, produces rheumatisms, catarrhs, and neuralgic affections. Wet feet, by which we mean cold and wet feet, are a prolific source of inflam- matory disturbances, by arresting the capillary circulation of the part. So if the continued action of cold be on the chest, abdo- men, or head, inflammatory actions, which may be local, or affect the entire system, arise. The chilly dews of the autumn, following days of heat, are recognized by some practitioners as the causes of autumnal diarrhoea, bilious and intermittent fever. It is cer- tainly true, that these affections fall mostly upon those exposed to the dews, but it appears that, independently of this, a specific malaria is also necessary to produce some of these diseases. 53 LIGHT. The Nature of Light.—Light, like heat, is now generally thought to be an effect produced by the vibrations of the universal ether. The waves so originating, are propagated with immense velocity, and act upon matter in various ways. Some pass through the structure of bodies by radiation, being bent or refracted in their course; others are reflected, and some are absorbed. This agent is not known to increase the dimensions of bodies like heat, but it is capable of producing numerous molecular changes of a chemi- cal nature. A few substances have the property of absorbing the rays of light, and subsequently emitting them when acted on by chemical, electrical, or other agents. Such are the phospho- rescent substances, of which fluor spar, oyster shells calcined with sulphur, and fused nitrate of lime, are instances. Its intimate connection with heat has been already pointed out; both agents arising simultaneously in the process of combustion, and heat being in nearly every case associated in nature with light. The moon's light, and the phosphorescence of some insects, appear to be nearly without heat. The rapidity of propagation, 195,000 miles per second, is the same, and the diminution of brilliancy follows the same law, being inversely as the squares of the dis- tances. These agents differ, however, in their relations to matter, possessing very different actions on chemical substances, light decomposing many which heat cannot affect, and the reverse. In no instance is this more apparent than on the tissues of the body, heat being perceived nearly in every part, whilst light can only influence the retina. Hence, although they be forces, and closely allied, it is customary to separate them in description, and con- sider them as two agents from the different relations they possess to matter. Light is of much less importance in general chemistry than heat, but in organic chemistry it is the active agent, pro- ducing the compounds of the plant which are necessary to its developement, and the sustenance of animals. This subject be- longs, however, more to physics than chemistry, and we shall introduce only so much as may be necessary to explain its gene- ral properties. . Of Radiant Light.—Light advances in great spherical waves, but any portion striking on a limited surface may be considered a ray, the path of which, from the luminous source, has been a straight line. The ray falling on a hard polished surface, will be 5* 54 THE REFLECTION OF LIGHT. reflected or thrown off according to the same law as the ray of heat, the angle of incidence being equal to the angle of reflection. If the reflecting surface, whether a mirror, or polished metal, be curved, the same effects will ensue as in heat. The concave surface will throw the rays together, causing them to meet in a point, distinguished by its brightness, and called the luminous focus. On the other hand, a convex mirror disperses the light, forming no true focus. But as the rays of light usually reach the eye after having been reflected from objects, they generally communicate an impression of figure and color, called the image. Except light be directly derived from the sun, it always falls on the eye associated with a picture or image, which is produced by the unequal reflecting power of objects, and their relations to color. Hence, although the convex mirror cannot condense light, it yields an image;—the difference between these reflecting sur- faces being, that the concave mirror furnishes a magnified repre- sentation, and the convex a minified image. The plane mir- ror neither enlarges nor diminishes the size of the object. The principle of reflection is employed in medicine, in the catoptric examination of the eye, and the use of the speculum. The catoptric examination of the eye is practised for the detec- tion of cataract, the process being as follows. The iris is dilated by extract of belladonna, and the patient being in a dark room, a lighted candle is held before the pupil, and the images formed by reflection observed. If the eye be sound, or amaurotic, there may be seen three small images of the candle flame, one formed by re- flection from the cornea, another, much feebler, from the anterior surface of the crystalline lens, and the third, which is very feeble, from the posterior surface of the lens. In cataract, both the latter images may be absent, and the innermost will certainly be de- stroyed by the opacity of the crystalline. It is, therefore, a capi- tal means of diagnosis between amaurosis and cataract. The speculum is a conoidal tube of steel, the inner surface of which is highly polished; it is furnished with a handle for facility of introduction. There are various kinds, some being made with a tube of one piece, and others of two or three, so that they may be more readily introduced and expanded afterwards by a screw, or other contrivance. They are employed in the examination of the natural cavities of the body, as the meatus auditorius, the vagina and rectum. When these instruments are to be used, the patient is placed in a convenient position, in a dark room, and the speculum being introduced and dilated, the operator holds a lighted candle in the axis of the instrument, and directing his eye to the polished sides of the tube, adjusts the light and speculum, until he sees a reflected image in the polished metal of such parts of the cavities as he wishes to observe It may be necessary, especially, in examining the rectum, to observe the tube inch by REFRACTION. 55 inch, as we withdraw the instrument. The speculum has been of great service in determining the diseases of the neck of the womb, especially in those cases of protracted leucorrhoea which were formerly considered incurable. It will be perceived that the metal acts as a simple mirror, and the nearer its sides approach to planes, the more natural is the image of the parts, the curved tube distorting them very considerably. Refraction.—When the rays fall on a transparent medium, they are more or less transmitted. If we examine the course of the rays, they are found to be bent out of their direction by this passage, and are said to be refracted. All transparent substances refract light, but the degree of refraction depends upon the sub- stance, and upon the obliquity of the rays. The refracting action of water is readily perceived by holding a rod in this fluid, some- what inclined to its surface; at the point where it touches the water, the rod will appear bent, the immersed portion taking a direction different from the true position of the object. Another fact may be discovered by this simple means. If the rod beheld perpendicularly, the image will be continued through the fluid without bending, or, in other words, when a ray of light passes perpendicularly through a refracting medium, it is not changed in its direction. As glass spectacles and prisms are much employed, it may be useful to under- stand the peculiarities of their refracting action. A piece of plane glass merely bends the ray ; for instance, if r (Fig. .---- x?x 9) be a ray of light falling __________\£ at a upon a piece of plate glass, instead of proceeding in the straight line to b, it is drawn out of this course by the refracting power of the body, and takes the new direction a c, but after emersion, it pro- ceeds onwards in a line parallel with its original route ; for the glass or refracting medium only constrains it so long as the ray remains in its limits. If the glass were convex, (a convex * *%• ll lens,) the rays would be simi- larly refracted ; but the issu- ing rays would be brought together after emersion, as re- presented in Fig. 10. The point of union is remarkably brilliant if the lens be large, and if the eye be placed near it, there will be seen a magnified image of the object from which the rays 56 ACTION OF THE EYE. have passed. This is a magnifying glass, and has the same opti- cal properties as the crystalline lens of the eye. But in the eye, the retina is not placed at the focus of the lens, but beyond ; hence the rays fall upon it after condensation, and depict an inverted image, as will appear from the figure (Fig. 11), in which a b is the image, a c,d e, and b f, rays proceeding to the convex lens of the eye; here c and f are refracted, and issue to meet at the focus g\ subsequently, they diverge again, carrying a picture of the parts they have passed from to the retina h j, which receives the inverted image. For distinct vision, it is necessary that the focal point should bear a certain ratio to the distance between the posterior surface of the lens and the retina, differing with the size of the organ; if this distance be disturbed, vision becomes indistinct; when it approximates to the eye, the individual sees distinctly only when the objects are at a considerable distance. This is the case in the aged, and constitutes the defect called presbyopia, or long-sightedness. The remedy consists in the use of spectacles with convex glasses, which aid the crystalline lens in reducing the focal length. The convexity of the lens in such persons, will be found diminished, and sometimes this will amount to flattening. Where the crystalline lens is removed in the ope- ration for cataract, a magnifying glass is set before the cornea to refract the light and answer its purpose. If the figure of the glass be concave, the reverse effect, or that of minifying, takes place. Such lenses are useful where the defect called myopia, or near-sightedness, occurs. The. crystalline lens in these cases is too convex, and its focus is in advance of the proper point; but by counteracting this, by means of a glass which causes the rays slightly to diverge before entering the eye, the true point is reached, and vision made clear. Myopia is a defect of youth. The most valuable instruments of the optician, as the micro- scope, camera obscura and telescope, are combinations of these two kinds of lenses. The microscope, to which the profession owes so much, is a combination of two or more convex lenses. These are so placed as to observe an object brilliantly illumi- nated by reflection from a small mirror, or by the condensed rays of a large lens. It is the adjustment which gives to the instru- ment its apparent complexity, the principle being very simple. The optical prism is a long piece of glass having three equal sides. If a ray of the sun's light be made to pass through it in Fig. 11. a- c d 7, f / INTERFERENCE OF LIGHT AND SOUND. 57 certain directions, there is produced an elongated image of great brilliancy, and containing all the colors of the rainbow. This is called the sun's spectrum, or the prismatic spectrum. If the prism ab c be arranged as in the figure, (Fig. 12,) the order of colors will be Fig. 12. from above downwards violet, indigo, blue, green, yellow, orange, red. In this experiment, it is apparent that the prism refracts the light, but that in consequence of the difference of length through the glass, along which the upper and lower parts of the beam passes, the different rays are separated. The violet, indigo and blue rays being found at the highest parts of the spectrum, are the most refrangible, the red and orange the least so. But the most remark- able result is that the white or yellowish-light of the sun is by no means a simple emanation, but consists of at least seven parts dis- tinguished by color, refrangibility, and in other respects. If we mix colored powders in such proportions as to represent these seven rays, there will be produced a whitish mixture. Moreover, if a colored light be examined, it will be found to contain only a por- tion of the rays of the spectrum. The prism is by no means the only contrivance by which we can separate the rays of light. Any reflecting substance which is scratched with minute lines of such a depth that they bear a relation to the breadth of the undulations of light, will exhibit the colors of the spectrum. In these cases, as in the prism, the lengths of the paths of the rays are unequal, and their union, which constitutes white light, is disturbed. If, instead of using scratches or plates of unequal thickness, we interpose in the path of a diverging ray of light, a thin opaque body, as a needle, we find that, at a short distance behind it, the shadow ceases, and lines of colored light, like those of the spectrum, but on a minute scale, are perceived. If the light employed in this experiment be of one color only, instead of the bands of various colors, we discern stripes of black, and of the color employed. This constitutes the famous experiment of interference, from the study of which the undulatory theory of light has been proved, and the wave lengths determined. The existence of black bands where there Violet Indigo Blue Green Yellow Orange Hed 58 THE UNDULATIONS OF LIGHT. should be light, arises from the interference of the waves, the paths of which are rendered unequal by the obstruction of the opaque body. The effect arises in this case precisely as in the case of sound, where one wave having a length slightly greater than a second, the two interfere, producing intervals of silence. This experiment is readily made, the means necessary being two tun- ing forks of the same note, and a glass containing water, and vi- brating in unison with the instruments. If the forks be sounded, and held over the glass, they produce a.loud, clear and uniform note, representing the sum of their vibrations. But if we in- crease the weight of one slightly by a drop of sealing wax, and vibrate them, the product is not a uniform note, but a sound which swells and subsides, and in which there are intervals of silence and of increase. By altering the weights of the forks, we have made a difference in their tones, not amounting to a whole note, but less ; hence the undulations in air produced by them, and which constitute sound, are not uniform. Their paths are unequal, and they operate upon the particles of air with different effects, increasing or neutralizing the vibrations and the sounds resulting therefrom. In the interference of light, the causes and effects are similar, but the phenomenon takes place on a very minute scale. The undulations propagated around the opaque object, have paths of different lengths, hence they come in collision, and the result is darkness in the case of a monochromatic light, whenever the paths differ by less than one undulation, or bear the relations of 1 to U, to 2£, to 3s, &c. By varying this experiment, and using differently colored lights, we find that the stripes vary in width, being widest in the red and orange, and narrowest in the violet and indigo. The study of these and similar phenomena furnished Fresnel with the means of measuring the lengths of the waves of different colors. If we divide an inch into ten millions of parts, the wave lengths will be respectively, For the red ray, For the orange ray, For the yellow ray, For the green ray, For the blue ray, For the indigo ray, For the violet ray, 256 parts, 240 227 211 190 185 174 256 10,000,000 ' 240 ____________________(i 10,000,000 227 10,000,000 211 10,O00,U00 196 10,000,000 185 10,000,000 174 __« 10,000.000 DOUBLE REFRACTION. 59 Hence difference of color has a capital and not metaphysical origin, being due to the lengths of the undulations originated by any force. The violet undulations are the most minute, the red the largest. It may be proper to remark, that beyond the least refrangible limit of the spectrum, we find pure heat rays, indicat- ing that the most active undulations of that agent have a greater wave length than red light. The amazing rapidity of the vibra- tions of the ether in the propagation of light will now appear. This impression is communicated at the rate of 195,000 miles in a second of time, and each wave is but a small fraction of the ten- millionth of an inch. From these numbers, it appears that, if a second of time be divided into a million parts, a wave of violet light vibrates 727 millions of times in this interval. The play of colors seen on iridescent minerals, or the feathers of some birds, and on insects, arises from the interference of rays of light. A perfect spectrum may be obtained from a piece of metal regularly marked with close lines, and when it is produced in this way, it is purer than that of the prism. In the interference spectrum, the bands of colors are of equal widths, the yellow rays occupy- ing the centre, whilst in the prismatic spectrum, the bands are very unequal. The colors of ordinary objects depend upon the relations of their surfaces to light, some absorbing one ray and reflecting or transmitting others. Black objects absorb all the rays, polished white surfaces none of them. The colors are seldom pure, but are commonly a mixture, which may be made apparent by dis- persing a beam passing from them by the prism. Many minerals and other transparent objects possess a remark- able action on light, when a ray is passed through them in a par- ticular manner ; it emerges as two beams, one of which is refracted according to the ordinary power of the body, and the other ac- cording to a different force. The first is called the ordinary ray, and the second, the extraordinary ray. Such substances are said to have double refraction. Calcareous spar and quartz offer fa- miliar instances of doubly refracting crystals; if either of these be held over a line of writing in a certain manner, we perceive two images. # The two rays are in all cases changed in the direction of their planes. If the two images be examined by a tourmaline, one is found to disappear, as the crystal is turned around. If a tourmaline be held in a certain direction before a radiant point, light passes through it; but if another tourmaline be now interposed between the eye and emergent beam, and turned about, the light will be found to pass in some directions and be ob- structed, and altogether extinguished in others. So, by reflecting licrht at peculiar angles, (for glass 56° 45', and for water 53° 11,) 60 THE DAGUERREOTYPE. it will be found that a portion is transmitted, and another reflected, which latter, if examined by another reflecting surface of glass, is found to disappear, not being reflected as we turn the second glass, called the analyzer, around. The disappearance takes place in two positions, when the plates differ in their angles by 90° F. and 180 degrees. In these cases, the rays are said to be polarized, and the process is termed polarization. It may be effected by the action of doubly refracting minerals, by the absorbent action of the tourmaline and other bodies, and by reflection. The ef- fects observed in these cases are attributed to the specific action of the mineral particles on the ether in which light is propagated. THE SUN'S LIGHT. The beams of the sun contain, besides light, other forces, dif- fering in their effects on matter. Heat may be discovered in every part of the spectrum, but the hottest portions are in the orange, red, and beyond the luminous parts. We find, also, that in the blue, indigo and violet portions, there exists a degree of chemical activity much greater than elsewhere. If these rays be made to fall upon the chlorides, bromides, or iodides of silver, gold and other metals, they become decomposed. The same rays effect the union of chlorine and hydrogen, frequently with explosive violence. From these effects, they have been termed the Chemical rays, or, more recently, the rays of tithonicity, by Prof. Draper. Indeed, tithonicity has been advanced as a new agent or imponderable ; but this view is opposed to the undulatory theory;—the results being produced by the action of vibrations, conveyed through the ether, on the matter of the chlorides and bodies susceptible of change, and not by a new agent; and depend- ing on tl * state of chemical combination more than on anything else. C emical changes are produced also by other parts of the spectrur The Daguerreotype, and other processes of Photography, for obtaining pictures by the sun's action on metal and paper, depend upon this chemical power of light. The process of the Daguerre- otype consists in acting on a plate of copper covered with silver, by iodine, which yields a rich yellow deposit of iodide of silver. To hasten the sensibility of this covering, the prepared plate is brought in contact for an instant with the vapor of bromine, or the mixed vapors of chlorine and iodine, or otherwise. This is done in a dark place. The plate being ready, is next introduced into a camera obscura, already adjusted to some object, and being inserted in the place of the ground glass of the instrument, it re- ceives the image. The lights of the image impress the sensitive PHYSIOLOGICAL ACTION OF LIGHT. 61 coat of iodide and bromide of silver producing decomposition, and driving the iodine and bromine deeper into the metal, but those portions which are in the shade are little affected. After a minute or two, depending upon the power of the light and pre- paration of the plate, it is removed and placed over a mercury bath, to receive the vapor of this metal heated to 175° F. The mercurial vapor acts upon those parts of the silver which have been rendered free by the action of light, but cannot reach those still in the state of combination. The plate is next washed with hyposulphite of soda to separate the iodide and bromide, and destroy the sensibility of the surface. After this operation the plate pre- sents a picture in white and black, the former of which indicates the parts where the light has acted, and consists of an amalgam of mercury with silver, whilst the black portions present the po- lished silver. In the present day, the silver plate is coated with gold, by means of the chloride of gold, dissolved in hyposulphite of soda, to preserve the picture, and is sometimes colored by dusting different powders on the surface. Other applications of the same principle have been made by Sir John Herschel, Mr. Talbot and Mr. Hunt, for the production of pictures on paper. This department of the art, called Photo- graphy, originated many years since with Mr. Wedgewood, and Sir Humphrey Davy, who employed a solution of nitrate of silver which turns black on paper in the sun's light. Physiological action of Light.—The study of the above facts is of considerable interest to the physiologist. The structure of the human eye has been for a long time compared to a camera ob- scura, and agrees in its parts with this instrument. The cornea npd iris are intended to limit the field of vision, and cut off those lateral rays which would confuse the picture impressed on the re- lina; they have the same function as the tube, which is placed be- fore the lens of the camera. The humors and lens con 'titute a refracting arrangement, answering to the convex lens of th.. instru- ment, and the retina occupies the place of the ground gla. i which receives the image. But the retina cannot be compared to the ground glass of the camera in anything except position; it receives the picture, but not passively. There are changes taking place on •this nervous expansion which are precisely in the degree of the ,light falling, and a communication by undulation is made to the ibrain of the effects which the rays of light are producing on its sensitive surface. This portion of the eye is closely analogous ,\o the Daguerre plate. It consists of a nervous matter which un- dergoes chemical change in proportion to the intensity and color tof the light, being most impressed by the yellow rays, and least ,by the violet; and in these particulars differing from the iodized plate, which is most affected by the indigo and violet rays. That 6 62 THE ACTION OF LIGHT ON PLANTS. the picture is not passively received, will appear, by considering ihe action of intense light, which disorganizes the molecules of the retina, and produces inflammation. In this tissue as in every other of the body, there is provision for waste and repair, and the waste takes place, as in them, under the influence of a chemi- cal cause, which in this case resides in the decomposing action of the sun's rays. That a chemical action occurs, may be proved by the fact, that the retina is incapable of receiving images in rapid succession. There must elapse a space of time amount- ing to about the tenth of a second, between the perfect and con- secutive impression of two objects, and if the time be much less, confusion occurs, and the parts of the two become blended. The luminous appearance of certain insects, as the lampyris, fire fly, and glow worm, has been shown by Matteucci and others to depend upon chemical action, in which oxygen is absorbed, and carbonic acid evolved. The curious instinct of plants, to incline their leaves and stem towards light, and the movements of sensitive plants are connected with the action of the sun's rays. If plants grow in a room lighted only on one side, they will depart from their accustomed upright figure and bend over to the illuminated side.* This effect I have discovered to depend on the action of the indigo ray chiefly, and this fact also furnishes us with an explanation of the upright growth of most vegetables, the blue sky being a radiant to which they naturally direct themselves. But there is no chemical effect of light more important than that taking place in the nutrition of plants. To the leaves of plants there is brought, by the action of the roots and capillary attraction, a store of sap; this consists of water with carbonic acid, saline matters, and a little ammonia. The sun's light acting on the carbonic acid, in the presence of the green matter of the leaf, decomposes it, an effect not otherwise attainable, and by this means brings into existence those compounds of carbon and water which are known as sugar, starch, gum, and which are products destined to sustain the life of man and animals. There is no other means by which these foundation materials of life can be produced, hence it is by no means infrequent in this day, to speak of the sun as the Fountain of life. In the paper referred to, 1 have shown that the green matter of the leaf, called chlorophylle, is brought into existence by the action of the yellow ray of light, which is also operative in decomposing carbonic acid, as Prof. Draper has proved. Being the active agent in the production of * This subject with the action of light generally on plants, was made the subject of a memoir by me, and printed in the London and Edinburgh Philo- sophical Magazine, and Silliman's Journal for 1844, to which the reader is referred for the full particulars. PHYSIOLOGICAL ACTION OF LIGHT. 63 the organic compounds of plants, it is not surprising that the vigor of development in vegetation should depend chiefly on light. We have thus pointed out a difference between the chemical and physical effects of the rays of light. It would appear that, whilst the most refrangible rays, the blue, indigo, and violet, and the space beyond them, are influential in producing changes in the mineral compounds of the daguerreotype, and in the inclina- tion of the stem, and movement of the leaves of plants—the yel- low, green, and orange rays, occupying the central portions of the spectrum, govern organic combinations; producing by their un- dulations, the chemical changes in which existence originates, affecting the retina, and governing the capacity of vision—whilst the least refrangible, the orange and red rays, and the space be- yond them, take on an action allied to heat, being far more active in the production of chemical and physical effects, and as re- gards the human body, awakening the sensation of heat. It was formerly the habit of writers, to speak of the solar spectrum as consisting of three or more agents, and to distinguish between the spectrum of heat, of light, of chemical action, or tithonicity, and of phosphorescence; but we incline to the view of Melloni, Becquerel, and others, that these are effects depending on the con- stitution of the matter, rather than attributable to the independent existence of numerous imponderables. These effects are not confined to the sun's light, but are produced by light, derived from intensely heated sources, or highly phosphorescent sub- stances, as lime, baryta, strontia, or magnesia, heated by the oxy- hydrogen blow-pipe. This, with other facts, point out the na- ture of the sun, and confirm us in the conclusion that he consists of a mass at an intense temperature. Light can scarcely be considered a therapeutic agent, but its action on man is not altogether unimportant. Its absence creates a degree of gloominess in the mind, which is remarkably per- ceptible in the melancholic, whilst its presence excites the senses, and increases the activity of the brain. A cheerful light is of great service to the cachectic, and those suffering from despond- ency, and insolation has been recommended on physiological grounds to those laboring under scrofula, and anaemia; and is highly conducive, according to Edwards, towards removing rickets in young children. It has been demonstrated that the develop- ment of animals, as well as plants, is connected with free expos- ure to light. On the other hand, absence of light acts as a seda- tive, conducing to sleep, and, associated with quietude, is very important in the treatment of irritation of the brain or nerves, after parturition, and severe accidents and operations. In most diseases of the eye, darkness is an essential part of the treatment. 64 PHYSIOLOGICAL ACTION OF LIGHT. The color of the glasses of spectacles, when the eyes are weakly, is also worthy of attention. We find amber, green, and blue glasses used, but these are manifestly different in their effects. The amber-colored and green glasses, allow the active rays of light to pass, and rather exalt the chemical action on the retina; but a light blue, by absorbing the yellow, orange, and green rays, is well calculated to protect the eye. The blue also acts by stop- ping the passage of a portion of the heat rays, which enter through an amber-colored medium. In amaurosis, the defect of vision occasionally arises from want of activity in the retina; and the employment of a strong light has been found by Hufeland to effect a cure, when all other means failed; but this agent is to be used only after a thorough diagnosis. 65 ELECTRICITY. The number of facts in electricity, is extremely numerous but we have, by no means, as good an idea of this agent as of light and heat. There appears to be little doubt, that it is a force propagated by undulations with immense rapidity, and that it produces, like heat and light, both physical and chemical ef- fects, but the difference of its action on matter, makes it more difficult to sustain any theory in electricity. We are also ig- norant of radiant electricity, except in the interstitial variety, (conduction) and this impedes the application of the undulatory hypothesis ; nor do the ideas of Franklin and Dufay, that it is one or two fluids, serve us better. The views of most chemists are, therefore, not matured on this subject, and we believe that Pro- fessor Hare* has been the first, formally to announce his adhe- sion to the polar or undulatory theory, in some degree sustained by the researches of Faraday. The subject divides itself naturally into two parts: 1. Co?n- mon Electricity, 2. Galvanism. § 1. COMMON ELECTRICITY. The term, common or statical electricity is employed to distin- guish the electrical phenomena which result from friction, pressure, or an alteration in the aggregation of the molecules, in non-con- ducting bodies. If a cylinder of glass, resin, sulphur or shell-lac be rubbed with a piece of silk, fur, or woolen cloth, both acquire the pro- perty of attracting light particles of paper, cork, pith and other substances. This affords an illustration of a capital electrical effect called attraction, and is a test of the presence of this agent, every case of molecular attraction being attributable to the action of electricity. But if we suspend a feather, or light pith ball from a stand, and bring any of the above substances excited by friction towards it, two actions will ensue, the object will at first move towards the electric, and subsequently move away, appear- * In his pamphlet, entitled " Objections to the theories severally, of Franklin, Dufay, and Ampere, with an effort to explain electrical phenomena, by statical, or undulatory polarization" Philadelphia, 1848. 6* 66 ELECTRICS AND CONDUCTORS. ing to be repelled. Hence repulsion as well as attraction fol- lows as an electrical effect. It is also worthy of observation that those bodies which have come in contact with one of the excited substances repel one another, but those which have been acted on by the dissimilarly electrified substances attract each other, or like electricities repel, and unlike attract. It is not necessary for the production of electrical excitation, that the bodies be dif- ferent, for one piece of dry silk tissue may be made to excite another, one piece of brown paper another, one glass another. In such cases the two will adhere together. The condition ne- cessary is that the body be not a conductor of electricity, for'in this case the agent would pass off by interstitial radiation as fast as it was excited, and produce none of the local disturbances in which the phenomena of attraction and repulsion arise. Matter is therefore divisible into two classes in electricity.—1. Electrics. —2. Conductors. Electrics are bodies which exhibit excitement by friction, they are also called insulators, because the effects of the electricity are retained on them, and do not pass off. It is also practicable to retain the electrical condition on a conductor, by surrounding it with electrics—this is called insulation. The brass conductor of an electrical machine is supported by glass and surrounded by air, which are non-conductors. Hence it is like an island (insula) cut off from connection with other conductors, and compelled to re- tain its charge. Excitation takes place in conductors or non-elec- trics if they be insulated. The chief electrics are glass, resins, sulphur, amber, animal and vegetable matters when perfectly dry, dry air, hair, feathers, furs. These are nearly incapable of con- ducting any kind of electricity. 2. Conductors or non-electrics are those bodies in which the electricity generated by friction or otherwise is radiated or con- ducted away. These cannot exhibit attraction or repulsion un- less insulated. Bodies differ considerably in conducting power, the metals being best; hard charcoal, fused saline bodies, and strong acids are also fair conductors; whilst water and bodies, whether animal, vegetable, or mineral, moistened with it, are the poorest. The human body is a conductor, although not of the best order. Silver, copper, and gold, are the best of all conductors. The rapidity with which electrical excitement is propagated in a good conductor is equal to the passage of light by radiation, or 195,000 miles in a second; indeed by some the rapidity is thought greater. This rapid passage is demonstrated by the action of the electrical telegraph. The Electrical Machine.—The electrical machine is a contri- vance for obtaining a considerable electrical disturbance, and ob- serving the properties of this agent when developed on a large THE ELECTRICAL MACHINE. 67 scale. It consists of a cylinder or circular plate of glass of con- siderable size, mounted in such a manner as to be capable of rapid rotation. The glass moves with friction between cushions or rubbers of leather, or silk, which are usually anointed with an amalgam of tin, zinc, and mercury, or with mosaic gold (the bisul- phuret of tin). These are the parts which generate the elec- tricity, and the machine is set in action, when the plate or cylin- der is rapidly rotated. But it is necessary that an insulated con- ductor should be placed at some part of the glass to receive the electrical disturbance, and serve as a condenser where the excite- ment may be accumulated. This is usually a cylinder of brass, or of wood covered with tin foil, with rounded ends, and sup- ported on glass legs ; it is called the prime conductor. Connected with the rubbers is also in many machines a second conductor which may be insulated or not. The figure represents a modem plate machine of good construction. Fig. 13. Hence this instrument does not differ in reality from the sim- ple contrivance of rubbing a glass tube with a piece of silk. But when set in action, we perceive several effects which cannot be developed on a smaller scale. Not only are attraction and repulsion made apparent, but sparks are thrown off, and a prickly sensation, sometimes amounting to a sudden spasm, is produced in animals when the excited conductor is touched. Hence the electrical spark, 68 THE ELECTRICAL MACHINE. or where this is not clearly seen, a crackling noise, the phenom- ena of attraction and repulsion, and the shock are capital tests of electrical disturbance when produced by friction. They are said to be the results of electricity of tension, as distinguished from other effects produced by large galvanic batteries, such as the pro- duction of heat, which is said to be an effect of electricity of quart' tity; the term tension or intensity being used to distinguish the effects of the machine, and quantity those of certain galvanic bat- teries. The power of a machine is measured by the length of spark it will give, or the striking distance of the spark. The study of the electrical machine divides itself into two parts, 1st, the cause of the disturbance on the glass and silk, and 2d, the action of the prime conductor. The cause of the electrical disturbance is the friction or mo- tion partly, but where the rubber is smeared with amalgam, this acts likewise, being chemically changed. Confining ourselves to the action of friction, all that it is necessary to explain, is that its operation on the surface of the glass or electric is to produce molecular disturbance. Whether we conceive the atoms to be torn off from the surface, or merely pressed, the physical action must produce a result. It is well known that friction on many bodies produces heat; this is especially the case with the metals, which when filled become rapidly warmed. If then heat and electricity are associated in numerous respects, it will scarcely surprise us that an action which will engender heat, may alto pro- duce electricity. By friction, then, and indeed by every applica- tion of physical force, and in all bodies is electricity disturbed, This disturbance commences in the universal ether, which is in the simplest case thrown into vibrations by the physical force. The vibrations, if there be no interference, will be communicated and create a wave; this is the case in conductors of electricity, a result precisely similar to that occurring in the case of heat. And the connection is closer, for the best conductors of heat are like- wise the best conductors of electricity. But it has been shown that glass and electrics are non-conductors, hence in such cases the vibrations of the ethereal fluid cannot be propagated, and as in the case of heat, electricity acts upon the molecules of the glass, inducing in them a new state. This new state we term the elec- trical condition, and it may be said in a few words, that there is every reason to believe that it consists in a movement of the mole- cules of the matter upon their axes. Conceiving the molecules of matter to be indefinitely small spheres, passive to force, we can understand that whenever union takes place between them to constitute a mass, or when several are combined, there must be some sufficient force to hold them together. This is called co- hesion, simple affinity, or the affinity of aggregation. Whatever ELECTRICAL POLARITY. 69 be the name, it is a force. It cannot be heat, for this expands matter and dissevers particles; it is not light, for the phenomena of attraction are not exhibited by this agent, hence it is now under- stood to be electricity. The atoms are supposed, under the in- fluence of this force, to arrange themselves in determinate direc- tions, each manifesting at one of its sides an attractive influence, and on the opposite side a repulsive or different action, and, ac- cording to the general proposition of electricity, the unlike sides attracting, and the like repelling. Now friction maybe supposed to overcome this affinity, and thus set free the electricity which caused it. Electrical Polarity and the Magnet.—As this is a funda- mental hypothesis in electricity, it may be useful to support it by a little further consideration. Let the spheres a b c, represent atoms of matter, a may be taken to represent the abstract atom; Fig. 14. a b c T P' in this state it merely occupies space, has impenetrability, definite figure, &c.; but it can exert no influence upon any other atom ; it possesses inertia. In nature there exists no such abstract atom. On the contrary, all atoms exhibit attraction or repulsion to other atoms; this satisfies us that there is something operating on every molecule, and that it is a force. Hence the atom, practically, is always associated with force, and this may be represented in figure b, by dividing it by a line, and conceiving that the force operates differently on either side. That on the one side, it renders it attractive to those molecules which are repelled by the opposite side. The force will be dispersed over the surface of the sphere, but more concentrated at two opposite points, (Fig. c.) p p', which are called its poles, and the line between these is termed the axis of the molecule. Such a molecule may be likened to a geometrical globe; the line representing the di- vision between the two parts is the equator, the points of greatest activity are the poles, and the line between them the axis of the globe: to continue the simile, the molecule maybe changed in di- rection by the application of force, and it may revolve around its axis without disturbance of position, as respects the poles; or the axis itself may be made to revolve, causing the poles to change their places with respect to surrounding atoms, or both motions may occur at the same time, under the influence of two forces. The student will now understand what is meant by the polarity of atoms, and by electrical polarization. 70 THEORY OF THE MAGNET. A familiar instance of the polarity of particles is offered in the magnet. There is a natural magnet, which is an ore of iron; the artificial magnet, made by rubbing a piece of steel in certain di- rections with the ore, and also by other processes; and thirdly the magnet formed by the action of electrical induction or the elec- tro-magnet. In each of these we find that one end of the mag- net possesses different properties from the other, and if we bring first one end and then the other, to a magnetic needle, it will be attracted by one and repelled by the other. The ends of the magnet are therefore called by different names, one being the marked end, North, or boreal pole, and the other the south, or austral pole. When like poles are brought together, repulsion occurs ; when unlike, attraction, which is the fact in every case of electrical disturbance. That this is an instance of electrical action, can be shown by the instantaneous production of a magnet, by the action of electricity. Nor is this diversity, or polar action peculiar to masses, for, if we reduce the magnet to the size of a fine needle, it will be apparent, and if this be broken in a number of pieces, each part exhibits a positive and a negative pole. Hence, a magnet is made up of one or more rows of atoms, every one of which Fig. 15. atoms has polarity. The figure (15) represents the the- oretical structure of the mag- net; it consists of atoms, each of which has a positive and negative side and poles, re- presented by the white and black parts; the atoms in the same line or axis, are united by their dissimilar poles, so that the ends of the magnet consist of negative or positive sides only. The power of the N and S poles, depends upon the free ends of the atoms which are not in union, and which exercise at all times attractive or repulsive powers towards certain bodies. The dependence of the polar state upon the action of a force, is made apparent by the fact, that the magnetism of a bar of steel may be destroyed by striking it, applying heat, or passing a strong current of electricity through it, in a" direction opposed to the ar- rangement of the atoms. Indeed one magnet will neutralize another, if they be placed above each other, and in opposite di- rections. The polarities of the magnet affect circumambient matter, as may be seen by dipping either end into fine iron dust, when particles of the iron will adhere. If we place a sheet of paper, or a pane of glass, over a bar-magnet, and sprinkle it with fine iron filings, they arrange themselves in regular lines, (Fig. 16,) each atom of iron acquiring regular polarity. Hence the electrical force of the EFFECTS OF ELECTRICAL POLARITY. 71 magnet is capable of producing effects beyond the steel, and if we measure them, we find that they diminish, as in the case of Fig. 16. •' " :: ... heat and light, inversely as the squares of the distance. The connection between these forces is further increased by the fact that some bodies allow the passage of the magnetic influence, as paper and glass ; whilst others, as iron, and probably cobalt and • nickel, will not let it pass, but retain or absorb it, giving out elec- trical effects. In the same way, then, that blue glass absorbs some rays of light, and becomes colored thereby, iron and steel absorb electricity and become magnetic. The space immediately around a magnet, is called the magnetic atmosphere ; and objects in this space are subjected to a radiant influence, which is of an electrical kind. From the study of the magnet, we therefore arrive at three con- clusions : 1st. That atoms under the influence of the electrical force ex- ; hibit polarity. 2d. That when the force is considerable, the polar influence may reach distant objects, and affect them, producing electrical excitement by induction. 3d. That this radiant influence may be transmitted, or other- wise, according to the nature of the matter ; glass allowing it to pass, whereas iron does not. These facts are important in every portion of electrical or che- mical science, for the latter is but a part of electricity. It has been pointed out, that cohesion, or the simple aggregation of .matter, is the effect of a force which we infer to be the electrical .force ; it will be shown in the sections on chemical action and capillary attraction, that these are likewise cases of electrical ac- tion. Or, in other words, that simple cohesion, complex cohesion, or capillary attraction, and chemical affinity, are cases of elec- trical action, differing principally in degree. \ To return to the electrical machine. The glass, by friction, has its ether thrown into motion; this motion not being propagated, because glass is a non-conductor, affects the molecules of the plate. It is analogous to the action of heat on a non-conductor, ,dSli^ 72 THE PRIME CONDUCTOR. the vibrations not being propagated, the body expands, or even burns, because of the force operating on the matter. Hence, in the machine, the atoms of the glass are put into a new state, by an increase of force; they may be supposed to be thrown into revolution, or to have their polar axes disarranged. The same occurs in the rubbers. The Prime Conductor.—We are now prepared to understand the office of this part of the machine. The forced atomic state of the glass, cannot be equalized, except after some time, in the air ; because air and the glass are non-conductors. But, by placing near to the surface of the plate, the branches of the prime con- ductor, which are usually furnished with numerous metallic spikes, the glass, as each portion passes near the spikes, propagates some of the electrical influence with which it is charged. The atoms of the glass may be supposed to fall back, more or less completely, into their unexcited state. This depends upon the rubber and conduct- or; if both are insulated, electrical phenomena are little developed, and polar effects in each part of the machine arise ; but when the rubbers are put in connection with conductors, so that every disturbance on that side is neutralized by its rapid propagation, the molecules of the glass are nearly relieved in the first turns of the instrument. When both the rubber and prime conductor are insulated, one is found to exhibit positive, and the other negative electricity, and the machine may be likened to a magnet, of which these parts are the poles. We find them, like the poles of the magnet, exhibiting attraction and repulsion dissimilarly, and ex- erting polar effects. To obtain an active electrical state, the rubber must be con- nected by a conductor to some mass, as the earth, which will be scarcely affected by its disturbance, so that its polarity may be neutralized at every turn. The excited glass discharges a portion of its force on the spikes of the conductor; this is propagated to all parts, and polar disturbance soon arises, because the metal is insulated. With each turn, this polar disturbance increases; it is rapidly communicated to the air, and finally it becomes so in- tense, that molecular action occurs in the air; a brush of light darts off the conductor at any projecting part, or a flash of elec- tricity takes place to any conductor within a few inches. This is the discharge of the prime conductor. The flash, or spark, is an effect of the molecular disturbance; it is not the electricity, but is a result of compression and chemical action on the air, arising from electrical force, and attended by the production of light, heat, and chemical effects. The «ound accompanying the spark, is due to the concussion of the air, and is produced in the same way as the thunder which accompanies the flash of lightning. That physical effects are produced by the excited conductor, may be readily shown: for, if we adapt to it a rod ELECTRICAL INDUCTION. 73 terminating in a point, a current of air will issue from the point, when the instrument is in action, which may even blow out a can- dle. Again, if melted sealing-wax be placed on the prime conductor, and the machine set in action, the wax will be spun out in fine threads, being projected to the nearest conductors. Many pretty electrical toys are made to illustrate this fact; such as the elec- trical tree; the electrical orrery. The air around every excited body is disturbed, the molecules being polarized in a direction opposite to the insulated conductor, and serving by pressure to retain the charge on the prime con- ductor. As the excitation increases, the pressure of the air in- creases. This phenomenon is also perceptible in other, if not in all electrics; it takes place in glass, paper, and resins. But as we have seen, in the discharge of the prime conductor; there is a point where a limited stratum of an electric cannot retain a charge. The spark or discharge occurs through air, tearing it asunder ; it also takes place through glass, breaking it in pieces, and will per- forate a piece of card board with great facility. And if we use a card glazed with carbonate of lead, we find that the electrical discharge not only produces the mechanical effect of tearing a hole through it, but the chemical action of decomposing the car- bonate of lead, and producing a black stain. Numerous instances of chemical change may be given, as the combination of oxygen with hydrogen to form water, oxygen with nitrogen to form nitric acid, the burning of cotton, ether, and other bodies. Electrical Induction.—The molecular disturbance giving rise to the phenomena of electricity is propagated in every direc- tion, and induces similar changes in surrounding matter. If the excited parts are in contact with conductors, there is an electrical wave propagated, whatever be their length, and we are not cogni- zant of any action unless the continuity be interrupted, then it will be found that the dissevered ends exhibit polarity. If the con- ductor be poor, as water, or moist animal substances, the propa- gation becomes impeded, and chemical decomposition, disturb- ance of aggregation, or other effects arise. The spasmodic action denominated a shock, takes place if the human body be the con- ductor. On the other hand, if the excited substance, for instance, the prime conductor of the machine, be surrounded with non-con- luctors, or di-electrics, a wave cannot be propagated, but the mole- cules of the body are each affected, and arrange themselves in a nanner similar to the particles of iron acted on by a magnet. 3rofessor Hare, in the memoir before cited, adopts the idea that his difference of conduction, or molecular arrangement, may arise rom the state of the universal ether in the two classes of bodies, n conductors it being condensed, and in dielectrics rare. It would sppear, however, to be also connected with the facility with which 7 74 electrical induction. the polar state is assumed, conductors taking it on readily, whilst non-conductors are more slowly but permanently affected. The propagation of the electric influence through air, glass, resins, sulphur, and dielectrics, affects conductors placed at a dis- tance from the excited body, inducing in them electrical disturb- ance. Hence induction is one of the chief means of producing Fig. 17. free electricity. In the figure (17), m represents the prime con- ductor of an electrical machine; it is powerfully excited, and has the +, plus, positive or vitreous electrical polarity; it is insulated below by a glass stem, and around by air, which is one of the best dielectrics when dry. The atoms of the surrounding air have their polarity so affected, that on the sides towards the conductor they are negative or resinous, and on the remote sides positive. The row of atoms lying between m and c, which is an insulated me- tallic conductor, are affected in this way, all the sides towards m being resinous (r) or positive: c is, therefore, rendered,—, nega- tive on the side nearest these aerial atoms, and its molecules pro- pagating the electrical influence, exhibit polarities in such a direc- tion that all the — sides are towards the end nearest the prime con- ductor, and all the + sides (v) in the opposite end. The ends r, v, not being neutralized by combination, exhibit, like the poles of the magnet, free electricity and the phenomena of attraction and repulsion, as may be seen by suspending light pith balls at these ends, when they will diverge and thereby indicate free elec- tricity. The influence propagated through the air by the prime conductor m, is now propagated by c, and reaches c', where similar effects arise ; thence it may pass to others, through a series depend- ing upon the power of the machine, the interval of dielectric or air, the conducting quality of the insulated conductors, &c, but in every case diminishing from m as the squares of the distances when the same conductors and dielectrics are employed. The molecular arrangement of the dielectric may be rendered evident to the eye by a simple experiment. Take a glass tube furnished at both ends with a brass ball so as to close it, and con> taining oil of turpentine which is a good dielectric, in which a number of short threads of sewing silk, also a dielectric, float; apply one ball near the prime conductor, and let the other touch INDUCTIVE CAPACITY. 75 the table. When the machine is set in action, an influence will be seen to act on the floating filaments of silk; they soon arrange themselves end to end, and become a medium of electrical pro- pagation, lying like threads between the two balls. If the excite- ment be very strong, the molecules of the oil will exhibit rapid currents from one electrified conductor to the other. In this ex- periment, the filaments of silk represent the molecules of air ly- ing between two conductors. The production of currents in the oil is analogous to the production of the electrical brush, and electrical aura or wind from points, which is a physical effect of electricity of high tension, and of the same character as the action on air which produces the snapping report, and flash of the elec- trical discharge. Induction does not take place through all dielectrics in the same degree. Professor Faraday has measured the inductive power " or specific inductive capacity" of the principal dielec- trics, by means of an instrument called the Inductometer. This consists of a contrivance by which sulphur, resins, glass, air, &c, can be placed between two conductors. With the same charge of the prime conductor, the second conductor placed at the same distance in all cases was charged through air 100; through shell- lac 200; through flint glass 176; and through sulphur 224. Hence shell-lac and sulphur have the best inductive capacity. All gases, whether of different density or temperature, appear to have the same inductive capacity. Induction is one of the most common and important of all elec- trical phenomena. If any substance be approached to an excited substance, it is thrown into the electrical state. On this princi- ple are constructed a number of useful and important instruments for testing the presence of electricity called electroscopes, electro- meters, and also the electrophorus and Leyden jar. Many of the supposed cases of electricity by contact, may also arise from in- ductive action. Electroscopes. An electroscope is a contrivance for the detec- tion of electrical disturbance. Two are com- monly employed ; the pith ball electroscope, and Fl=- 18- the gold leaf or Bennet's electroscope. The ^Z^ ^ first consists of two pith balls, connected by a JL linen thread, and suspended on a metallic rod. £3t^L If it be brought near an excited substance, the /fr^f3^^ balls diverge, and the degree of their divergence |j L Wj, is a coarse measure of the amount of excita- A V 1 tion. The gold leaf electroscope is depicted in | ^^ | B figure 18. j l_:----J 1 The cap A is of brass and connected by a me- fPffff j% tallic rod with the gold leaves. The body B is ^^sgggs^ an open glass vessel, on the inside and lower 76 bennet's electrometer. parts of which are pasted strips of tin foil, reaching to the stand and not insulated. When there is no electrical excitement, the gold leaves hang down, side by side, but if an electrified body be brought over the cap A, the leaves immediately diverge, flying apart to the pieces of tin foil. This occurs whether the body exhibit positive or negative polarity. But if the gold leaves are in the act of divergence under the influence of a positive surface, and one that is negative be now brought, they immediately col- lapse. This instrument may be employed to determine the state of the electricity, whether it be positive or negative. For this purpose an excited piece of glass or resin is employed, the for- mer imparting the negative (—) and the latter the -f- condition to the gold leaves. This is accomplished by first bringing the electrified substance to the cap, divergence is produced, then touching the cap with the finger and removing together both the electrified body and finger. The leaves, instead of falling back, as is usually the case, remain apart and changed with the positive or negative influence. If now a body with like excitation be brought, the leaves diverge farther; if with the opposite electri- city, they collapse. If the leaves be positive, a negatively elec- trified substance can be recognized by its power of causing the leaves to come together, and the reverse. Besides these instru- ments, there are two designed to measure quantities of electricity, Coulomb's torsion electrometer, and Harris's balance electrome- ter. The former is a beautiful instrument, and measures the amount of electrical force in the repulsion of a gilt pith ball, by the torsion or twisting of a fibre of silk, or thread of glass. It is employed only in delicate researches, and has been used in the development of the principal facts in the distribution of electri- city. The electrophorus of Volta is a cake of resin, on the upper side of which, is placed a disk of metal, furnished with a glass handle. When used, the resin is excited by a piece of flannel, and exhibits resinous or negative polarity; it therefore induces a change in any neighboring conductor. If the plate be now placed on it, the lower side becomes positive, -f-, and the upper —, ne- gative, by induction, and if now we touch the upper side by a conductor, connected with the earth, its negative polarity is de- stroyed, and the entire surface becomes positive. Upon sepa- rating the plate from the resin, a spark may be obtained by touch- ing it. The electrophorus will retain its excitement under some circumstances for weeks or even months. The Ley den Jar.—This is a wide mouthed jar of glass, stopped with a piece of baked wood, through which runs a brass rod, having above a knob, and terminating below in a chain The THE leyden jar. 77 sides and bottom of the jar are coated, both inside and outside, to within a quarter of the height, with tin foil, as in fig. 19. Fig. 19. Fig. 20. This is one of the most important electrical instruments, for by its means, we are enabled to obtain charges of great power, and by placing twelve or more in a frame in such a manner that all the brass knobs communicate, and all the exterior tin foil is in contact, the most powerful effects of artificial electricity have been procured. Such a contrivance is termed the electrical bat- tery, and is depicted in fig. 20. The jar is charged by placing the knob near the prime con- ductor of the excited machine ; spark after spark passes, and is conveyed to the interior tin coating, by which it is distributed to the glass, there producing the molecular effects observable on dielectrics. That this occurs in the Leyden jar may be readily proved, for if we insulate it, and hold to the exterior coat a con- ductor in contact with the earth, there will pass a spark from this, every time one reaches the inner tin foil. In this case, the disturbance of the interior surface of the glass, is communicated to the exterior by polar arrangement; and the jar cannot be charged to any extent, unless the exterior conducting coat of tin foil will adjust its degree of excitement to that of the glass, which can only be done by placing it in contact with a large mass, as the earth. As the action increases, we discover a peculiar crack- ling or fizzing sound, which warns the operator that the jar is fully charged ; beyond this the glass may be broken by the depth to which the molecular change is propagated, or a spontaneous discharge will take place. This instrument evidently affords us an illustration of inductive action: for the exterior conductor is as actively polarized as the interior, and their condition is the reverse, the exterior being —, negative, when the interior is +, posi- tive. The electric condition of the glass is also certain ; for if in- stead of the jar, we take a large tumbler of glass, and place inside 78 THE leyden jar. and outside a cylinder of tin-ware to represent the coatings, we can remove these parts, allow the two tin cylinders to touch, and, on placing them together again, it will be found that the vessel is still charged. The glass being a non-conductor, has retained its excited state, and it is upon this that the action on the foil depends, the metallic portion serving to equalize the distribution of the force only. Such a contrivance is called the dissected Leyden jar. To discharge the jar, we place a conductor, or a metallic rod between the exterior coat and the brass knob, which forms a part of the interior conducting surface. If this could be effected with so much suddenness that no interval of time existed between the application of the discharging rod to the two parts, simple con- duction would occur along the metal, and a molecular equilibrium be attained, more or less completely, in every part of the jar. But such an application is impossible, for as the metal of the dis- charger, especially if it have a knob, is about to effect the com- munication, a loud snap with the evolution of a bright light and heat is observed. This is no more than an intense spark, which, as from the prime conductor, is more brilliant and has a greater striking distance as the excitement increases. In the case of lightning, it is the discharge of thousands of acres of sur- face, and has a striking distance of miles, a brilliancy equal to the sun's light, and an intense temperature. The heat, light, and sound, are effects produced on matter, and not the electricity. The jar is not completely deprived of excitement by the first discharge, there is usually enough to produce a secondary dis- charge. When the dielectric is of shell-lac, sulphur, &c, the number of discharges, after one application to the prime conduct- or, may be as great as five or six. These subsidiary discharges arise from the presence of a little remaining excitement; this seems to depend upon the degree to which molecular disturbance had been effected ; when it is intense, a portion continues, and still acts, inducing the polar state in the conductors, and this leads to the production of another spark, when connection is again made by a metallic rod. The common discharger in electrical experi- ments is depicted in figure 21 ; the branches are united by a hinge joint, which enables the expen- ds- 21- menter to adapt the distance of the brass knobs to the jar employed. The han- dle is of solid glass. If we discharge the Leyden jar by means of imperfect conductors, a variety of actions are produced. On placing cotton, dusted with powdered rosin, over one of the knobs, it will be inflamed. If we discharge it by a wet string, in the course of which there is a break containing es«Hg<3 LANE'S ELECTROMETER. 79 gun-powder or ether, they will take fire. If the right hand of a man be applied to the exterior tin foil, and the left to the brass knob, a startling shock takes place, increasing in severity with the size of the jar, and degree of the charge. As this shock is sometimes employed in chorea, and other nervous disorders, and the shock to be employed may not be the same in all cases, Mr. Lane has in- vented a machine for regulating its violence. It is called Lane's graduated discharger. The figure (22) exhibits one of these attached to a Leyden jar. It con- Fig. 22. sists of a metallic rod A, furnished with a knob r at either end, or a chain at one end; and sup- ported by a glass upright B. It is capable of motion, and may be brought near to the knob C of the jar, or withdrawn. The violence of the shock depends upon the distance at which it is set from the knob of the jar, for a discharge will take place as soon as the striking distance is equal to the interval. By means of this simple instrument, the physician who desires to increase the activity of the shocks, can do so by regulating the striking distance, his pa- tient touches the exterior with one hand, and holds the chain with the other. The discharge along the conductor takes place through an in- terval of any length, whethes it be feet or miles, and with amazing rapidity. A number of persons, holding each other by the hands, will be simultaneously affected. If there be a choice of objects, the discharge will always take place through the best conductor. It is in consequence of this fact that the passage of electricity appears to be so capricious. Lightning will always strike the best conductors; hence, if we erect metallic rods, of copper or iron, against the side of the house, it will pass along them, if they be well connected with the earth, rather than through the bricks. Trees are very liable to be struck, because they are good conductors.^ What is called the capricious course of the electrical discharge depends, how- ever, upon another fact, namely, that electrical currents produce induction, or induced currents in an opposite direction. Of this we shall treat under the head of galvanism. The Distribution of Electricity.—The excited or polar state, constituting common electricity, is only to be detected on the sur- faces of bodies. The distribution is also dependent on their figure. On a perfect sphere, every portion is equally excited, but on an ellipsoid, the ends evince a greater activity than the cen- tral parts. As the conductor becomes elongated, the electrical excitement accumulates more and more towards the ends, pro- 80 MEANS OF ELECTRICAL EXCITEMENT. ducing a state similar to that of the magnet. If the prime con- ductor be a wire, the length of which is very considerable, in comparison with the breadth, the ends will become active poles, whilst the central parts exhibit little electricity. In such a case, if the ends be pointed, the electric pressure of the air or other dielectric will be so little, that a powerful charge cannot be re- tained, but exerts itself in creating currents in the air, which re- duce the electric excitement of the conductor. By means of a pointed metallic rod, the most powerful charge of a jar may be removed, the electricity producing a stream of air or aura, which destroys the excitement. Hence, the prime conductor of a ma- chine should have no points, except towards the glass plate. And, for this reason, it is preferred to terminate lightning rods with a number of points instead of a sphere. Tke points in this case should be of platinum, a substance that does not rust in the air, and is not fused so readily as iron and most metals. Pieces of thread, hairs, and particles of silk, will also discharge an excited conductor. Means of Electrical Excitement.—Two capital means of exciting electricity, have been considered, friction and induction, but there are others, as change of aggregation, chemical action, contact, and heat. Contact is placed amongst the means, but it only disturbs the electrical state in some cases. If we place a dry piece of plate glass on the surface of pure mercury, the two substances adhere, and with considerable force, constituting a case of heterogeneous affinity or capillary attraction ; on separating them, there will be found considerable electrical excitement, as may be seen by the use of Bennet's electroscope. But a wet glass placed in contact with mercury exhibits no electricity. To develop electricity in such cases, the bodies must have an attraction for one another, the result of which is a polar adjustment of the surfaces coming together, such that electrical polarity ensues. Some authors doubt whether this occurs without the previous preparation of one of the bodies by heat, friction, or other means, but in the case quoted, sue* adventitious assistance does not seem neces- sary. The plate must be merely dry. The numerous instances of capillary attraction, as in all cases where fluids wet a sur- face, or wet one another, seem.to depend upon the production of the polar state by contact. It is not necessary that the bodies be dissimilar, for two pieces of plate glass, two masses of metal will adhere, if brought sufficiently close, and upon separating them, and testing the state of the two surfaces, by proper means, one will be found positive, -f, and the other negative. This is the principle of cohesion. In such cases the action of the force is very feeble, and Sir I. Newton has determined, that for its deve- THERMO-ELECTRICITY. 81 lopment, the surfaces must be brought within at least a millionth part of an inch of each other. Heat produces the electrical state in many minerals, as the tourmaline, boracite, &c, and it indirectly brings it about by de- stroying the aggregation of matter; as in evaporation. If two wires, metals or conductors, having different conducting powers for heat, be brought together at a small surface, and made fast by twisting, soldering or otherwise, and the junction heated, an electric disturbance occurs. Such an instrument is called a Thermo-electric pair, and this kind of electricity, which is not, however, peculiar, thermo-electricity. The best metals for this purpose are bismuth and antimony, or platinum and copper. The degree of disturbance varies with the metals, and does not appear to be proportionate to the heat employed. If a number of small square bars, of one-sixth inch width, and about one and a half to two inches long, of bismuth and antimony, be taken and soldered together in pairs at both ends, so as to esta- blish a communication between the whole number, we have one form of the thermo-electric battery employed by Melloni and Forbes in their researches on heat. The metals may be insu- lated by a film of paper or silk, and bound up in a wooden case. From the terminal bismuth and antimony, proceed copper wires to conduct the polar state of the battery to any desired point. Heat acting on one of its surfaces, so disarranges the molecules of the bars, that they become polarized, and this action being increased by the number of the pairs, a considerable influence is propagated to either terminal wire, one of which forms the posi- tive or +, and the other the —, or negative end of the arrange- ment. Change of Aggregation.—Electricity is evolved when a fluid passes into the state of a vapor, or a solid into a fluid. Common evaporation and the production of steam are, therefore, sources of electrical disturbance. Simple expansion, in some instances, disturbs the electricity, and rupture does so mothers. If a piece of mica be torn in two, the broken ends exhibit different po- larities. The electric state of clouds is supposed to depend upon this action, the vapor rising from the earth, being surrounded by the non-conducting air, retains its excitation until it becomes aggre- gated again into a cloud; here the molecules combine, and their free electricity is destroyed, but the surface of the cloud exhibits powerful polarity. That vapor rising from the earth is in an electric state, may be shown by placing a little metallic vessel con- taining water, on the cap of Bennet's electroscope, and dropping into it a piece of red-hot metal or a live coal; steam is immedi- ately formed and the gold leaves diverge. The remaining water 82 MACHINE ELECTRICITY IN MEDICINE. will, in this case, be found —, negative, and the vapor +, positive, A cloud positively charged is like the prime conductor of the ma- chine, producing induction in all matter near at hand, and throw- ing off a spark or flash, whenever it is sufficiently near, or within striking distance of a tree, mountain, or other conducting body. It appears, from the experiments of Pouillet, that electricity is also produced in ordinary combustion. For, if carbon or hydro- gen be burnt in contact with the cap of the electroscope, the ris- ing vapors are positive, and the residual bodies negative. The production of electricity by chemical action, constitutes the department of the science termed galvanism. MACHINE ELECTRICITY IN MEDICINE. The electrifying machine has been long in use for medical purposes. Its action on the body, in the production of shocks, the prickly sensation of the sparks, and the effects of lightning, induced the profession to expect great results from its employ- ment. These expectations have been, for the most part, disap pointed, but there often occurs cases when the use of the machine may be necessary. Patients sometimes exhibit great faith in its effects, and there is a large number of cases in which it has been supposed to be useful. The agent is applied in a variety of ways,—by shocks from the Leydenjar; bydirecting currents through certain parts; byplacing the patient on an insulated stool and in connection with the prime conductor of the machine; or by directing a brush of electricity from a pointed conductor on some portion of the body. These various ways have received different names, and are employed in diverse affections. Shocks are employed in chorea, and diseases in which a want of nervous activity exists, as nervous deafness, amenorrhoea and partial paralysis. The violence of the shock is to be regulated by Lane's medical electrometer already described. As a general rule, it is best to begin with slight shocks from a pint jar, and increase them as indicated, for there is considerable difference in people as regards the action, some being much affected and pained by shocks which scarcely affect others. The common method of administering the shock is, for the patient to hold in one hand the chain connected with the electrometer, and touch the exterior coating of the jar with the other; in this way the effect is felt in the elbows and across the chest, and may be useful in pleurodynias, or slight muscular or nervous affections of the chest, but can be of no service in diseases of the spine or pelvic viscera. The shock must be directed along or through the parts affected ; thus in cases THE ELECTRIC BATH. 83 of partial paralysis of the legs, it must be passed from the lumbar region over the spine to the foot, and be taken at different points along this course. For this purpose, dischargers of a particular make are used, they consist of a glass handle, supporting a curved brass rod with one brass knob, which may be placed in contact with the Leyden jar by a chain. In using them, the knob of one is placed over the spine or other part, and a connection established by a brass chain with the exterior coating of the jar; the other, which is attached in the same way with the knob of the jar or with Lane's electrometer, is then brought over the other part of the body. The shock is thus driven through any part of the system between the two places of application. In amenorrhoea, one of the dischargers is moved over the lumbar vertebra? and sacrum, and the other placed over the pubis. In this complaint, where it arises from an enfeebled state of the body, the agent seems to be very useful, and is recommended by the highest au- thorities. In the early stages of the paralytic state, arising from nervous debility, some have found shocks driven through the parts from different points of the spine useful. It is necessary to use electricity steadily and for weeks before we abandon it. Whe- ther, in such protracted cases, it be the beneficial agent in the event of cure, cannot be readily determined, but if it does no harm, and the patient desires its use, the physician is not warranted in refus- ing the application. The Electric Bath.—When the patient is placed on an insu- lator, as a stool sustained on glass legs, and put in connection with the prime conductor by a chain or otherwise, he is said to be in the electric bath. By this arrangement he becomes a part of the prime conductor, and the same electric excitement is com- municated to the surface of his body as exists on that part of the machine. In a dark room, the prominent points of the body, especially the hair of the head, will be found to emit a pale elec- trical light. In this situation, some persons experience conside- rable warmth, occasionally copious perspiration occurs, the pulse is quickened, and a sense of formication on the skin is expe- rienced; but, in others, there is little or no effect. The imagina- tion is, probably, more active in all cases than the electricity. If we apply a conductor, as the knuckle to the skin of a per- son in this bath, a spark is seen, and the patient experiences a prickly sensation. It is for the purpose of obtaining such sparks that the insulator is generally employed, and the knuckle, or a brass rod terminating in a knob, held in the hand of the operator, is usually employed. It is found, that if a piece of flannel be placed on the skin, and sparks taken rapidly through it by the conductor, in the direction of the nerves, the effect is more per- manent than if taken simply from the skin. This method is 84 THE MAGNET AS A REMEDIAL AGENT. called electric friction,, and was much recommended by Cavallo, Woodward, and others. Electric sparks are supposed to be bene- ficial in resolving slight tumors, the stiffness of joints, in exciting the organ of hearing in nervous deafness; it has also been em- ployed in atonic amaurosis, numbness, rheumatism, and to excite the biliary function in jaundice. In all these cases, the striking distance of the spark is to be varied, and electric friction employ- ed so as to derive whatever advantage may flow from the use of the agent. Slight shocks may also be used in the above cases, before the electrical treatment is abandoned. The Electric Aura.—The brush, or aura produced on a pointed conductor, has been used in amaurosis, and applied over ulcers. It may be taken from the insulated patient by a pointed conductor, or administered from the prime conductor by a pointed discharger. The current of electricity is also spoken of; in this case the patient merely holds the prime conductor, but no effect is dis- cernible, and it is not worth while to allude to it further as a remedial means. In reviewing the subject, it appears that some advantage does undoubtedly flow from the employment of frictional electricity, and that it is most indicated in diseases connected with a want of nervous power. In such cases, it may excite the secretions, especially those of the liver and uterus. It is also to be consi- dered favorably in those cases where a loss of function arises from nervous prostration, general or partial. Whether it promotes absorption, as was formerly supposed, is doubtful. In chorea, partial paralysis and chronic rheumatism, there is a host of evi- dence in its favor. What the method of cure is, cannot be readily determined, but from its superior efficacy in nervous complaints, it appears to act upon the nerves or their centres. The subject will be resumed under Galvanism. The Magnet as a Remedial Agent.—The native loadstone, a magnetic ore of iron, has been long used for remedial purposes, and is, to this day, employed in some countries. It was formerly sup- posed to be a specific in gout and rheumatism, and to have great powers. Neither this body nor the artificial magnet are em- ployed by the profession in the United States or in Great Britain, but the Germans are zealous in their use. They speak of it as of value in neuralgia, toothache, rheumatic pains, and nearly all nervous ailments, as spasmodic asthma, palpitations, angina pec- toris, gastrodynia. Laennec recommended the use of oval mag- netized plates over the chest in angina pectoris. One of the plates was situated over the precordial region, and the other on the back immediately opposite, and the dissimilar poles were placed next OTHER EFFECTS OF ELECTRICITY. 85 the skin. The magnet, simple or compound, straight or curved, or broad plates magnetized, are employed according to the na- ture of the part. The south and north poles are to be alternately tried, for it is said that one may produce an anodyne effect where the other increases the pain. We know nothing of these effects, but it is very certain that a powerful common magnet produces no impression on the body in health. There is a machine (Fig. 23), invented by Clarke, and another by Saxton, for generating an electrical current by the rotation of Fig. 23. an armature of iron, F G, covered with fine wire, near a permanent magnet D, or the reverse, which has been extensively employed. In this case a feeble current, similar to that of a galvanic battery, is generated, and called the magneto-electrical current. This machine was used in the same cases as the galvanic bat- tery which it has nearly superseded, but has in its turn given place to the galvano-magnetic machine, or elec- trotome, to be described in the next article. It is expensive, loses its power, and produces no peculiar effects. Other Effects of Electricity.—Frictional electricity can be ob- tained only during dry cold weather; if the air be damp, the power of insulation is destroyed, and the effects of the machine become very feeble. It is not, therefore, to be depended on as a force for the production of chemical or other results, and is replaced by the galvanic battery in most cases. It has been remarked that electricity produces chemical union and other effects, and in a few cases, the spark is employed to this day, as in the detona- tion of oxygen and hydrogen, in the analysis of gases. Atmospheric electricity has been supposed to be peculiarly fa- vorable to the development of plants, but of this we have no evi- dence, all attempts made to employ the agent in the cultivation of gardens having failed. In the state of lightning, atmospheric elec- tricity is a powerful and destructive agent, destroying life in- stantly when the stroke is direct, and frequently doing so even at the distance of several feet from the stricken object, by induc- tion. Where life is not extinct, rest, and the removal of all dis- turbing agents, appear to be necessary. Warmth to the skin, coun- ter-irritation, and sometimes artificial respiration, are indicated; but the physician relies on the recuperative powers of the body chiefly, being prepared to meet any secondary effects of inflam- 8 86 OTHER EFFECTS OF ELECTRICITY. mation or debility which may arise. It may be proper to state, that in a thunder storm the safest places are those removed from the neighborhood of elevated or conducting objects, and it is bet- ter to be in the lowest parts of a house than upstairs, and to lay- down on the ground than to stand erect. There is no fear to be apprehended in a storm unless the flash and thunder occur simul- taneously, for as the distance becomes greater, the interval between them increases. 87 GALVANISM. Galvanism owes its name to Galvani, an Italian, but if the true investigator of this form of electricity is to be honored, it should be called Voltaism, from Volta. The distinction between galvanism and electricity is usually said to arise from the impon- derable being in motion in the former case, and stationary in the latter. Hence, frictional electricity is often called statical elec- tricity, and galvanism, with thermo- and magneto-electricity, are said to furnish instances of dynamical electricity. This means, that the phenomena depend upon the conducting powers of the matter affected, and that electricity arises in non-conductors and insulated bodies, but that whenever the force is propagated, it is called galvanism, &c. The distinction not being in the agent, it will scarcely surprise us that galvanism should produce molecu- lar effects in the same way as statical electricity. Indeed, we know little of galvanism, except when the course of the agent is impeded by non-conductors, or inferior conductors, or, in other words, when it produces electrical or molecular effects. The galvanic current must be -interrupted to allow us to see its effects of heat, chemical action, or on the animal. Galvanism appears to differ in another respect. In common electricity, the action is confined to the surfaces of things, and is intense but of little amount; in galvanism, it penetrates into the inner atoms, and is more distinguished for amount or quantity than intensity. The difference between them may be illustrated by reference to heat; the flame of the blowpipe has intensity, and will melt, in an instant, a particle of metal, but it has no quantity, and will not produce anything like the effects of a furnace, although at a lower temperature. In the latter case, we have quantity or amount of force, in the former, intensity. It is practicable to unite these conditions, for if we drive a furnace by bellows, or convert it into a blast furnace, we do not diminish the quantity, whilst the intensity is increased. So, in galvanic arrangements, we are capable of generating amount or intensity at will, and ap- proximating or separating their effects from those of the machine. Whenever the plates of the battery are enlarged, and the fluid increased in activity, amount of galvanism is procured ; on the other hand, if the plates are small and very numerous, galvanism 88 THE GALVANIC CIRCLE. of intensity or tension is obtained, which may closely resemble frictional electricity. Galvanism is electricity produced by chemical action; it takes place in every chemical change, but to be sensible of its presence, it is necessary to introduce, among the bodies undergoing this change, conductors capable of conveying the galvanic influence, so that we may apply the tests of its presence. The most common method of generating galvanism is by immersing a plate of zinc and of copper into a very feeble solution of sulphuric acid and water. We may employ the solution so diluted, that it exerts no action upon either metal. If, now, the metallic plates be par- tially immersed, and brought within a tenth of an inch of each other at their lower ends, and made to touch above, molecular action occurs in the fluid, minute bubbles of gas rise from the copper, and galvanic disturbance takes place. This arrangement constitutes the simple galvanic circle, and of such parts, variously modified, the most powerful batteries are constituted. The simplest variation from this original circle, is where the me- tals, instead of being made directly to touch, can be put in contactor separated by means of two copper wires, one of which is soldered to the zinc, and the other to the copper. The figure may convey a clear idea of such a circle (Fig. 24), which consists of a common tumbler about half filled with the dilute sul- phuric acid, containing Z a zinc plate, C a copper plate; and pp' are the wires called polesx proceeding from the me- tals. The wire of the zinc is called the — or negative pole, the wire of the copper the + or positive pole. The arrows are employed to indicate the supposed course of the galvanic influ- ence or current, from the positive to the negative side. Theory of the Circle.—A little examination will show us that this is none other than an arrangement for the production of internal or molecular electricity. In the first place, it is stated, that the dilute acid would not have acted upon the zinc, without contact of the metals, but if the solution were stronger, the action occurs without this condition, and the reason is, that the acidu- lated fluid is then itself a fair conductor. The action of which we speak, is the union of the zinc with one of the components of the water, oxygen, the other component, hydrogen, rising at the copper surface, in the state of gas. In the circle, there is, there- fore, something present, which produces molecular disturbance, a disturbance analogous to that of heat on the tourmaline or fric- THEORY OF THE GALVANIC CIRCLE. 89 tion on glass. This something is the chemical affinity of zinc for a component of water, oxygen. If we investigate the electri- cal states of the plates, we find that the zinc plate is -f or posi- tive, the copper plate — or negative, and the wires at their ends also + and —, but in a state the reverse of that of the immersed end of either metal. Each metal and wire may, therefore, be compared to a magnet, and the intervening fluid to another; in each case there is a line of particles so arranged as to have their + ends in one direction, and their — ends in another. The three are in connection by dissimilar or attractive poles, and they are also distinct in their electrical relations. In Fig. 25, this state is represented; the part of the arrange- ment represented by the zinc, is one of the Fig. 25. magnets, the atoms of which are polarized in such a way that the + end is in the fluid, and in contact to the — end of the •/ magnetic arrangement representing the / fluid, the positive end of which lies in qo contact with the copper. The copper is ' the third polar arrangement, its immersed end being — and the opposite extremity -f, where it comes in contact with the unlike pole of the zinc. This polarization affects every atom, and occurs only so long as action takes place in the fluid. It is accompanied with a vibra- tory affection of the ether, and the propagation of a wave, which, in a good conductor, may reach hundreds of miles, as in the elec- tric telegraph. The chemical action sets the electricity in action, and is hence called the electromotive source, and it is to the gal- vanic circle what mechanical force is to the common machine. If we change the fluid, we may have action in the reverse direction, or none at all; we may render it more powerful, or diminish it to zero. Let us now consider the reason why action does not occur un- til contact, when the fluid is feeble. On the immersion of the zinc, its atoms become polarized by the action of the oxygen particles of the water, and in the same way, the water and cop- per are polarized; but in every case, the condition is statical; the particles are simply made to arrange themselves conformably to the force present. It is precisely the case of the electrical ma- chine with both the prime conductor and rubber insulated. A few turns produce the polarization of the entire apparatus, one end becomes + and the other—, and no further action can be ob- tained; but if we now connect the two conductors by a metallic rod, equilibrium ensues, and the excited glass disturbs the electricities again. If a rod or chain be made to unite them, the glass will engender electricity without intermission, and the two conductors 8* 90 THE PRODUCTION OF THE CURRENT. will establish an equilibrium at every instant; thus the electrical wave will flow its round incessantly. The Cause of the Current.—These considerations represent the occurrences of the galvanic circle. At first, polar disturbance takes place in virtue of chemical affinity ; nothing more can be ac- complished; everything comes to rest, for every part of the ar- rangement is insulated. We now make the metals touch, or con- nect the conductors, the electrical wave flows, or the forced polar states are neutralized; but as in the turning of the glass, the electromotive source is still present and active, new action occurs between a particle of zinc and oxygen, the wave is regenerated, and a second wave flows. If the surfaces be extensive, this ap- parently intermitting action becomes continuous from the number of particles undergoing union. Several consequences flow from this view of the case. 1st. The amount of galvanism is directly as the rapidity and extent of chemical action, for, as the union between the zinc and oxygen is the source of power, the larger the quantity of these combining, the more galvanism. The truth of this position may be directly proved, for if we weigh the zinc plates, and mea- sure, by its effects, the galvanism, we find that the zinc is changed rigorously in proportion to the galvanism. 2d. The power of a galvanic arrangement is measurably de- pendent upon the facility with which the chemical union of the zinc and oxygen occurs. Hence, whatever assists the chemical action, increases the power of the circle. For this reason, in the common arrangement, sulphuric acid is added to the water; it does not undergo decomposition itself, or participate in the elec- tromotive power, but it dissolves the oxide of zinc, formed by the union of oxygen and zinc, and which, being an insoluble non- conductor, would arrest the excitement. The sulphuric acid re- moves each atom of this compound, forming the soluble sulphate of oxide of zinc, which may be afterwards procured from the so- lution. Thus the acid acts in keeping the metallic surface of the zinc pure, and enabling new atoms of oxygen to act on it. A great improvement has been, of late, made in this part of the gal- vanic apparatus. If the zinc be amalgamated with mercury on its surface, it is presented in such a state of division, that the oxygen acts more freely, the surface is also kept bright by the action of the sulphuric acid as before, and the zinc is less acted on by a feeble acid before contact. As a portion of mercury in the amalgam delivers up its atom of zinc, it retires into the mass of metal, and combines with another portion, and thus molecule after molecule is presented to the active oxygen, under favorable cir- cumstances, for chemical union, The amalgamation of zinc is readily accomplished ; for this pw THE IMPROVEMENT OF THE CIRCLE. 91 pose, it is only necessary that the metal be brought in contact with mercury in a saucer, and the surface rubbed with a pledget of linen or cotton, moistened with dilute sulphuric acid, and used to carry the mercury over the acidulated parts. An amal- gam of a bright lustre is rapidly formed on the surface, and the process is soon completed; it is only necessary to rub it once, for excess of mercury destroys the cohesion of the zinc. Mr. Smee has also determined, that, by employing silver as the negative metal, with the surface roughened by platinum, the power is in- creased by the mechanical assistance given to the hydrogen gas in leaving the surface of the metal. 3d. Another means of increasing galvanic action,is to increase the conducting power of all the parts—of the fluid, of the zinc, and the other metal. This is a condition pointed out by the ana- logy we have drawn; the communication between the two prime conductors being made by a thread, equilibrium would not be brought about so rapidly as by a stout wire. To accomplish these indications, it has been found that the metals should be good conductors ; silver and gold are superior to copper, and these are the only substances which would be so. The amalgamation of the zinc assists its conducting power. But it is in the fluid that this quality may be most increased; for this purpose, the acid must be strong/and in the battery of Mr. Grove, presently to be described, the sulphuric acid is of considerable strength, and the nitric acid concentrated. It will be remembered that the strong acids are pretty good conductors, whereas water is almost a non- conductor. There is also a mechanical method of accomplishing this indi- cation. It is apparent, that the nearer the metals are to each other in the fluid, short of contact, the more readily the conduc- tion takes place. The immersed sections are also favorable to the power, by presenting an immense number of points of action. The doubling of the negative element (copper, silver, or plati- num), about the positive (zinc), also assists, indeed doubles the action, by causing it to occur on both sides of the zinc. Again, as respects the poles, the shorter and thicker they are, and the better they conduct, the more readily does the change of polarity occur; if they be poor conductors, and of small size, the action will be impeded and even stopped. For this reason, stout cop- per wire of the shortest convenient length is to be employed. The influeuce of this part of the apparatus may be readily seen by interposing between the ends of two large copper poles (or electrodes) a secondary wire of small size of platinum, which is an indifferent conductor; it will become red hot, the electric dis- turbance being propagated so imperfectly, that the force is ex- 92 CONDUCTING POWER. Copper " 6 Gold " 9 Zinc " 18 Platinum " 30 Iron " 30 Tin 30 Lead " 72 pended on the molecules producing the specific disturbance termed heat. The comparative conducting powers of different metals belong to this part of our subject. Mr. Harris has found that, if similar wires be made to convey an electric discharge of the same in- tensity, they become unequally heated. The heat, as in the above illustration, arises from the resistance or opposition to the flow of the electricity, and is, therefore, inversely as the conduct- ing power. The following table from him, presents an approxi- mation only, but it undoubtedly gives us something like the order of conducting power, allowing gold and silver a capacity equal to 120. Silver evolved 6 decrees of heat, F., and has 120 conducting power. 120 " " 80 " " 40 24 " " 24 " " 20 " " 12 " " From these numbers we learn that platinum has only one-fifth of the conducting power of silver, and perceive the advantage of using the latter, as in Smee's battery, wherever practicable. In- deed, the only reason that platinum has superseded copper and silver in Grove's battery, is in consequence of the action of the nitric acid, which does not affect platinum, but dissolves the others. M. Pouillct has also determined the conducting powers of the principal bodies for galvanic currents; they are in the following proportion. 5791 5152 3975 3838 855 384 900 200 800 500 600 100 He also measured the conducting power of saline solutions, and arrived at the extraordinary conclusion, that a concentrated solution of sulphate of copper has a power, as compared with copper, of one to sixteen millions; sulphate of zinc, also com- pared with copper, of one to about forty millions. Distilled water lucting power of Palladium " " Sitver ti u Gold " " Copper - " " Platinum u u Bismuth - U li Brass, from. i; " " to c< (( Cast steel, from CC £< " to " " Iron U (C JMurcury - IMPROVED GALVANIC CIRCLES. 93 has, according to the same authority, but one four-hundreth of the conducting power of solution of sulphate of copper, or less than one six-thousandth millionth (f-too-,oVo,7or) of that of me- tallic copper. No galvanic action is perceptible in those cases where the fluid acts on both metals, for the polar disturbance is twofold, and in opposite directions, thus neutralizing one another in the same way as one magnet, reversed over another, destroys its power. To attain the greatest developement of galvanism, the action must be intense, and solely in one direction; if there be two opposed currents, we gain only their difference—for this reason, copper, which stands at the head of Mr. Harris's list, can seldom be em- ployed in the most powerful batteries from the action of numerous fluids on it. Platinum is rarely affected, and where it is possible, silver, covered with platinum, constitutes the best negative ele- ment. 4th. Of Resistance.—Any resistance or impediment occurring in a part of the circle, either by the interposition of a bad con- ductor, lengthening of the polar wires, or otherwise, affects every part of the apparatus simultaneously. The three supposititious magnets, the two representing the metals, and the third repre- senting the fluid, are equally balanced, and of the same power; if, so long as action takes place, we change either of them, we affect the whole. If the exciting fluid be enfeebled by the sepa- ration of the sulphuric acid, the action fails, and is, finally, re- duced to nothing. This was the great difficulty with the old bat- teries of copper and zinc. They could only be charged with feeble acid, and this rapidly disappeared, being converted into sul- phate of zinc by combining with the oxide of zinc; and as the amount of acid diminished, the power of the instrument failed, and, in a few minutes, came to an end. To obtain quantity of gal- vanism, the batteries of Wollaston, Cruickshanks, Children and Hare, were made on an immense scale, offering hundreds of square feet of metallic surface, but they acted only for a short time; and, after a few trials, the metal had to be taken out and scrubbed bright to make them again active. The greatest improvements made of late in galvanism, are in the construction of portable instruments, possessing great power, or the quality of continuing in activity during a long period. To the former, belongs Grove's battery, and to the latter, DanieWs con- stant battery, both of which will be presently described. In the first, the action is maintained for a long time, and by the violence of the chemical changes (there being two fluids polarizing by their action the molecules in the same direction), it is in great amount; in the latter, the object is to keep the action steady, by restoring a fresh particle of sulphuric acid for every one that is removed 94 EFFECTS OF THE SIMPLE CIRCLE. by combination, so as to keep the fluid of equal acidity through- out the time of its employment, which may be prolonged for weeks. Ohm's Researches.—Professor Ohm has studied the conditions necessary to the development of power in the galvanic apparatus, and reduced them to mathematical propositions. They are as fol- lows : 1. The electromotive force varies with the number of the fluids and metals, and with their chemical nature, but does not depend on their amount. 2. The resistance to the galvanic force is directly proportional to the distance between the immersed portions of the plates, the resistance of the fluid itself, and the length of the polar wires— and inversely proportional to the immersed surface of the plates, and the section or thickness of the wires. 3. Therefore, the force of the current is equal to the electro- motive force divided by the sum of the resistances. Effects of the Simple Circle.—By means of a single circle, we are enabled to produce a variety of electrical effects. By break- ing the contact between the polar wires, the electrical spark may be seen, and there is this remarkable difference between the spark of the galvanic arrangement and the electrical machine, that it has scarcely any striking distance even in powerful batteries. If the poles be applied to the tongue, one being placed above and the other below, a slight shock, accompanied with a metallic taste, is perceived. By means of the electroscope, we also discover the presence of electrical disturbance. There is an additional test of great value. It has been known for many years, that a stroke of lightning occasionally destroyed the polarity of the magnetic needle, and (Ersted, in 1819, showed that, when an electrified wire was placed near a magnetic needle, it was disturbed from its true position—hence, this change in direction has become a test of electrical disturbance, and especially in galvanism, which is. therefore, associated with common electricity, in this respect, as well as in the foregoing. It has also been shown, that heat is often produced by electricity, and this is strikingly the case in gal- vanism, heat being developed in great amount wherever the sur- face of the immersed metals is large, and the exciting fluid of great activity. Galvanic Batteries.—The simple circle may satisfy us that galvanism and electricity are the same force, but if we wish to observe the properties of galvanism, it is necessary to combines number of circles, or, in other words, to employ the battery. In the present day, Grove's battery is preferred, but Smee's and Daniell's constant battery are often useful. Of the old batteries,it may be enough to say that they were cumbrous and expensive, grove's battery. 95 and consisted of pairs of zinc and copper plates fastened into a square wooden trough, into which the active fluid was poured, as in'Fig. 26. The zinc plates were all on one side, and the copper on the other, so that each cell contained a copper and zinc plate; the pairs being separated from each other by the fluid. From the last metals, the polar wires proceeded. In batteries in- tended to generate a large quantity of galvanism, the plates were Fig. 26. very large, and either one or very few; when tension or intensity was desired, the plates were small but numerous, amounting, in some experiments, to many thousands. The most important modern instruments are described in the following paragraphs. The voltaic pile, which was the first battery invented, consisted of square pieces of copper and zinc, arranged in pairs, and the pairs were separated by pieces of cloth, moistened with salt and water. Grove's Battery.—This instrument is particularly remarkable for the great amount of heat it sets in motion, even when the re- sistance is moderate. When the number of circles or pairs ex- ceeds twelve, it also exhibits considerable intensity. It is porta- ble, and continues in powerful action for half an hour or more, and in considerable activity for two days. Hence, it is preferred for general purposes to all modern batteries. The circle or pair, Fig. 27, consists of two metals and two fluids, the latter separated from one another by a por- ous vessel of unglazed earthenware. The metals are amalgamated zinc for the positive element, and plati- num for the negative; the poles are of copper usually. The fluids are diluted sulphuric acid, and strong nitric acid. The circle is usually arranged in glazed earthen- ware jars, or stout glass tumblers, the zinc being cast into cylinders with a branch for the purpose of con- necting with the platinum pole of the adjoining pair. The cylinder of zinc is placed in the jar, and within this the porous cylindrical vessel, closed below, but open above, and furnished with a flange to suspend it in the zinc; in the centre of this is the platinum connected with the zinc of the next jar. The sulphuric acid is placed in the outer vessel, and the nitric acid in the porous cylinder. In the bat- Fig. 27. ,t^tk 96 GALVANIC batteries. tery, the jars are placed side by side in one, two or more rows, and connected in the order indicated, the zinc of one with the platinum of the other, the series being uniform throughout, and not anywhere reversed. For if, in any case, the zinc of two cups be united, or two of the platina strips, the order is broken and the battery becomes powerless. The union is commonly made by soldering the platinum, which is usually a strip of one half to one inch wide, and of the length of the porous cylinder, to the branch of the zinc of the adjoining pair. From the last zinc and copper, proceed the poles or electrodes. The size of the jars and zinc cylinders, will depend upon the quantity of galvanism required; but pint vessels, with the metals in proportion, are com- monly selected. Professor Bunsen has modified this battery, by introducing the hard carbon of the gas houses in the place of the platinum. This is called Bunsen's battery. The electromotive source in this battery is the oxydation of zinc by the decomposition of water, but the hydrogen of the water, instead of being liberated at the platinum surface, decom- poses the nitric acid, and again forms water with a portion of its oxygen, whilst the gaseous nitrous oxide is liberated in red fumes of a suffocating odor. By this reunion, the polarity of the whole arrangement is assisted, the water being reformed. The sul- phuric acid employed, may be stronger than that formerly used. Fifty pairs produce the most brilliant results of ignition and che- mical change, but very striking effects may be obtained with twelve. DanieWs constant Battery.—The circle in this case consists of two metals, copper and zinc; and two fluids, dilute sulphuric acid and solution of sulphate of copper, (blue vitriol;) these are separated by a porous earthenware cylinde- by a glass tube, closed below with bladder. The cir- cle is arranged as follows—the cop- per is made of the figure of a jar, with a projecting rod or wire, by which it may be put in connection with the zinc of the adjoining pair; it contains the copper solution; cen- trally the porous vessel is situated; this is nearly filled with dilute sul- phuric acid, and contains a rod of amalgamated zinc, which bears an upright arm or offset, to place it in communication with the copper cup of the next circle. The communicating rods are usually fur- nished with binding screws, whereby the connection can be readily made between the pairs. smee's battery. 97 In this apparatus, the action of oxygen is, as before, the active principle, but the hydrogen is not evolved by the copper surface, for as soon as it encounters the sulphate of copper, chemical decom- position occurs, the copper is set free, its oxygen unites with the hydrogen to form water, and the sulphuric acid entering the zinc cell, serves to restore the strength of the acid there. Hence, for every atom of acid which is removed, by uniting with the oxide of zinc, formed by oxidation, there is an atom restored by the decomposing action of the hydrogen on the sulphate of copper. Therefore, the strength of the sulphuric acid being rigorously maintained, the action is sustained, and would be absolutely con- stant, if the zinc were not dissolved. With a thick zinc rod, the action may be prolonged for weeks. This battery would be of use for medical purposes, but is now partially superseded by the electrotome. It may, however, be recommended as the source of power in this machine. The principal use of Daniell's battery is, in effecting chemical changes which require galvanism of little quantity, but of tension to act for a long time. Figure 28 repre- sents this battery. Smee's Battery.—This variety can scarcely be called a battery, for the circles are ordinarily employed alone. Its chief use is in electro-casting of various kinds, and it is now used extensively in the arts. The circle consists of two stout plates of amalgamated zinc, placed parallel to each other, with a thin sheet of platinized silver between them. The plates are arranged close together, and have strips of wood between them above, and corks below, to secure them in their places. The upper pieces of wood also serve to suspend the plates from the sides of a glass or earthen- ware jar. The platinized silver carries an upright wire with a binding screw to ' ~ble the operater to connect it with the zinc of the adjoining pair, or to sustain the polar wire. The two zinc plates are held firmly together, outside the wood, by a clamp of brass, which also puts them in electrical contact; one of them carries a binding screw for the same purposes as that of the sil- ver. The active fluid is dilute sulphuric acid, and the cell is a glass tumbler, usually of a quart size. Other interesting combinations exist, which are, however, of no practical value. Professor Grove invented a gas battery, con- sisting of tubes, containing hydrogen and oxygen, the electromo- tive source of which was the union of these bodies, by means of spongy platinum. A feeble galvanic action may also be obtained by piling slices of brain and muscle in a regular succession, and keeping the arrangement moist. Galvanic Effects.—When a powerful Grove's battery is employed, the effects are very striking; they are chiefly cases of ignition, the production of light, shocks, and chemical decompo- 9 98 THE EFFECTS OF GALVANISM. sition. But by using a feeble battery, or even a simple^circle, the phenomena of induction may be produced, which are the mosfrema^kable effects of this agent. The action on the human E>dy vdl be considered under the section on Animal Galvanism. One of ^e most important applications of the force is in the casting of metals, or the electrotype. We shall consider these effects in a few paragraphs. The Deflagrating Power.—When the polar wires of a power- ful Grove's battery are gently separated, an intensely brilliant in- terval is perceived, which consists of the action of the galvanic force on the particles of non-conducting air and the metal. 1 lie spark or luminous interval is of different colors, according to the nature of the metals, being green between two copper wires, bluish green between gold, whitish blue when one of the poles terminates in a cup of mercury, and the other nearly touches its surface. If gold, silver or other foil be placed between the poles, it is rapidly volatilized. Iron wire burns with brilliant scintilla- tions. A thin strip of platinum being adjusted to the poles, be- comes white hot, throwing out an intense white light. If the platinum be very fine, it may be heated by a simple circle, or at a considerable distance by a battery; hence it has been made use of as a means of exploding gunpowder in blasting, and for mili- tary purposes. We believe the credit of having first proposed this means of blasting belongs to Professor Hare. By adopting it in mining operations and extensive undertakings, many acci- dents might be avoided, and better results obtained on a large scale. For this purpose, the gunpowder is enclosed in a suitable canister, through which pass two copper wires, insulated from the metal by a coating of silk, Indian rubber, or other non-con- ducting body. The wires proceed to the centre of the combus- tible, and are united at their ends by an exceedingly fine strip of platinum. The polar wires at their tattery ends can be put in connection with the apparatus at will, and the moment the gal- vanic influence acts on them, the platinum is made red hot, and explodes the powder. By this means, a mass of material, amounting to many thousand tons, was removed by a single blast, in the excavations made for the London and Dover railway. Ships may also be blown to pieces at a distance of half a mile and upwards, with a battery on shore, by exploding a water-tight canister, containing several hundred weights of gunpowder, and placed in the channel. This project has, indeed, been looked upon as a means of defence in the case of invasion. The temperature attainable in a small space by a powerful battery, probably exceeds that which can be obtained in any other way, except perhaps Professor Hare's oxy-hydrogen blowpipe. By this means the most refractory metals are fused, and many, as gold, entirely volatilized. GALVANIC EFFECTS. 99 The Production of Light.—-If the poles of the battery be made to terminate in conical pieces of hard charcoal, or the carbona- ceous substance used as luting for coal gas retorts, there is pro- duced the most intense artificial light. It is white, and surrounded by dazzling irradiations, and may be made of considerable amount, by cautiously separating the points. The separation, when a powerful battery is used, may be upwards of an inch, in which case, the flame is arched. But if the points be placed in vacuo, the flame is rectilinear and equally intense. The origin of the flame is not, therefore, due to the combustion of the carbon, but results from the conversion of the electrical disturbance into heat, from resistance to its propagation, and which volatilizes the mole- cules of carbon, and is analogous to the production of heat in those metals which interrupt the current. It has been proposed to use this apparatus for illumination. The intensity of the light is such, that an apparatus, set up in an open place, at a suitable elevation, would illuminate many acres of surface; but in cities, the houses are too crowded to allow of its employment, considering the expense necessary in establishing the light. The batteries would have to be rapidly renewed, and demand constant attention to maintain the brilliancy of the arch of flame. Another similar proposition has been made—to use a spiral coil of platinum for illumination, but the light is less in- tense in this case, demands as much attention, and is equally ex- pensive. Chemical Decompositions.—If the poles of a battery of many pairs, or a battery of intensity, be immersed in acidulated water, the water is decomposed, and if the wires be of platinum, the gases, of which water is composed, are evolved. Numerous so- lutions are acted on in the same way, especially the iodides of po- tassium and sodium, and the bromides, chlorides, or oxides of the same bodies. Mr. Faraday has studied this property of the bat- tery with extraordinary success, and arrived at the following general conclusions. 1st. That only particular substances are susceptible of decom- position; such are, conductors containing two elements, as water, which consists of oxygen and hydrogen. To such bodies he has given the name of electrolytes; the process of decomposition he terms electrolysis; and the poles electrodes. This law is ex- pressed concisely as follows : All compounds, susceptible of pri- mary electrolysis, are of binary composition, containing one atom of each element, and soluble. 2d. Metallic salts, which are soluble in an electrolyte, frequent- ly undergo secondary decomposition. Thus, sulphate of copper dissolved in water, is a metallic salt, containing three elements, (copper, sulphur, and oxygen,) and not electrolyzable, but united 100 CHEMICAL DECOMPOSITION. with water, it becomes decomposed. The action commences in the water, which is an electrolyte; the hydrogen and oxygen are separated, but of these the oxygen only is liberated; the free hy- drogen, said to be in a nascent state, exerts chemical action on the oxygen of the sulphate of copper, removing it from the metal and reforming water. The copper being no longer oxidized, cannot unite with sulphuric acid, and is deposited on the surface of the negative pole. The same is true for metallic iodides, chlorides, cyanides, and bromides, dissolved in suitable solutions, and for metallic salts generally. When alkaline salts are em- ployed, the acid is found at the positive pole, and the alkali at the negative, hydrogen being incapable of reducing the alkaline metals. 3d. The decomposition is perfectly definite. The same cur- rent passing through different electrolytes for the same space of time, will liberate the elements in the rigorous proportion of their atomic weights. Thus, if we submit the electrolytic solutions of iodine, there will always be found the same weight of iodine at the electro-positive, or -f- pole, but the weights at the electro- negative pole will be as the equivalents of the metallic bodies. The atomic weights or equivalents will be found in the next divi- sion of this work. By way of illustration, it may be remarked, that the atomic weight of water is 9; of iodide of potassium, 165*86; of chloride of sodium, 58*78; and that the same current will de- compose in the same time, 9 grains of water, 165*86 grains of iodide of potassium, and 58*78 grains of chloride of sodium. And this is true for every case of primary or secondary decompo- sition, and proves that the chemical force is a galvanic force, and that the atomic theory, which attributes to the atoms of matter definite weights, rests on the basis of experiment. In these cases, the power (galvanic) which held the atoms in combination, is neutralized by the galvanic current, which operates more power- fully in an opposite direction; they, therefore, obey new polar ar- rangements opposed to those acting to produce their union. In virtue of the identity of the galvanic force and chemical affinity, Graham has termed the galvanic current—current affinity. \ So rigid are the chemical relations of the battery, that, if we allow for the losses arising from resistance in the instrument, we shall find, that precisely the same amount of decomposition takes place in the active fluid, and in the decomposing cell. If water, similarly acidulated, be placed in both, there will be decomposed a grain of the fluid for every grain changed in the generating cell. Indeed, in these cases of decomposition, we only modify the gal- vanic circle, for, instead of its containing three parts, or supposi- titious magnets, it now has four—the fluid of the generating cell, which has a + and — end, the metals and the fluid of the de- THE ELECTRO-CHEMICAL THEORY. 101 composing cell, which has also its + and — end—and we"may as conveniently adopt the view that the electromotive force is in one cell, as in the other. This consideration enables us to understand some points, which are almost in dispute among electricians. It was formerly con- ceived, that the poles or electrodes acted as centres of attraction, and that an atom of oxygen was drawn through the thickness of the decomposing fluid by their action. This supposition is unnecessary, for all the action takes place at the surface of the electrodes, which may be points or large surfaces, metallic, solid, or fluid, with equal indifference. The polar states of the elec- trodes are communicated by induction to each particle of the in- tervening fluid; if this be water, the compound molecules arrange themselves with all their oxygen particles turned towards the po- sitive pole, and all their hydrogen towards the negative pole or surface. The fluid magnet is thus formed, and remains stationary, if the force of the electrodes be less, or equal to the chemical at- traction existing between particle and particle of the liquid ; but if it be greater, the ultimate molecules of the line are attracted to the poles, unite with it if their chemical nature permits, or are liberated, if there be no chemical relation. It is to avoid the che- mical combination that platinum poles are employed in the place of copper, which is so superior in conducting power. The ter- minal atoms being liberated, the polar state is restored throughout the fluid, and union occurs along the line of particles, or what Grotthaus calls recombination, takes place particle with particle. The forced or polar state is again reproduced, with a similar re- sult, and thus a succession of waves takes place throughout each line of atoms, and always in the same direction. No disengage- ment of gas, or other product of change, takes place anywhere but at the electrodes, or where the separated molecules can no longer find atoms to recombine with. Electro-Chemical Theory.—The views of Davy, termed the electro-chemical theory, were dependent upon the above facts. It has been modified, in recent times, by Ampere and Berzelius, to clear up hypothetic defects, but otherwise the theory has been approved for upwards of half a century. Some exceptions pre- sent themselves to it, at present, which may, however, be dissi- pated by further study. Whether it stand or fall, this theory has contributed so much to the advancement of chemistry, and is so connected with the subject, that traces of it will remain as long as the science is cultivated. Davy conceived that atoms in the state of rest, have no free electricity, but become excited by contact with certain bodies, and combine in consequence of the attraction arising between the dissimilar electricities of the molecules. He divided matter 9* 102 THE ELECTRO-CHEMICAL THEORY. into two classes, according to the supposed preference for one or the other electricity. Thus oxygen, chlorine and certain other elements, are always found at the positive pole when their com- pounds with metals are decomposed ; hence their electrical pre- ference is for this part of the arrangement, because they are them- selves of a negative electricity under excitement. These bodies were, therefore, termed Electro-negative elements, whilst the metals which selected the — pole, were termed Electro-positive elements. Upon further examination, it was also found that acids were electro-negative, and the oxides or bases, with which they were combined, were electro-positive. Further experience has shown that the electrical condition is not a property of the matter, but depends upon the element or body with which it is in con- tact; for iodine is positive to oxygen and chlorine, but negative to all the metals; so mercury is positive to the haloid bodies, and negative to most metals. Of all the elements, oxygen and potas- sium appear to be the only ones which remain invariably in the same state, in the act of combination oxygen being always elec- tro-negative, and potassium electro-positive. The persistence of a compound often depends upon the intensity of affinity of the elements for different poles. The following table from Professor Kane, exhibits the electri- cal relations of the principal elements. The most powerfully negative bodies are placed in the first, and those most positive in the fourth column—substances intermediate in their electrical ac- tivity are placed in the central columns. Any substance is posi- tive with respect to those towards which the arrows point, and negative towards those bodies placed in the reverse direction. Table showing the Electrical Relations of the Elements to one ANOTHER. Electro-negative. Electro-positive. * Oxygen. Fluorine. Chlorine. Bromine. Iodine. Sulphur. Selenium. Tellurium. Nitrogen. Phosphorus. Arsenic. Antimony. Silicon. Boron. Mercury. Chromium. Vanadium. Iridium. Rhodium. Uranium. Osmium. Platinum. Titanium. Gold. Molybdenum. Tungsten. Columbium. Palladium. Potassium. Silver. Sodium. Copper. t Lithium. Lead. Barium. Tin. Strontium. Bismuth. Calcium. Cobalt. Magnesium. Nickel. Glucinum. Iron. Yttrium. Manganese. Thorium. Cadmium. 1 Aluminum. Zinc. Zirconium. Hydrogen. Lanthanum. Carbon. Cerium. * The substances in Italics are of the greatest importance to the medical chemist. THE ELECTROTYPE. 103 Electro-positive body. Metallic radical. Base. In the case of compound bodies, decomposition is accomplished in a secondary manner, and acids, alkalies, and other substances, deposited at the electrodes. Some compounds, altogether inca- pable of decomposition by galvanism, are still spoken of as con- sisting of an electro-positive and electro-negative part. The fol- lowing scheme represents the electric state of the parts of any compound. Name of substance. Electronegative body. Binary compound - Haloid constituent - Salt......Acid..... Organic compound J Compound Haloid } ComPound radicaL Wasyl*.) The substances called haloid, are oxygen, chlorine, iodine, bromine, cyanogen, and a few others. The Electrotype.—The electrotype is a beautiful application of electro-chemical decomposition. It is intended for the preci- pitation of metals on surfaces of any kind prepared for the pur- pose; when gold is employed, the process is sometimes called electro-gilding, when silver, electro-plating. It is also used for obtaining copies of engravings, by depositing copper on the sur- face of the original; in this case, it is termed electro-engraving. There are other applications for embossing, &c. For these purposes, Smee's battery, or one circle of his arrange- ment, is employed. The generating cell is charged with dilute sul- phuric acid, and the decomposing cell, which may be a tumbler, tureen, or any similar vessel, contains a solution of the desired metal in an electrolyte. For the precipitation of copper, a concen- trated solution of sulphate of copper is employed. To the negative pole of the battery the object to be copied is attached, such parts only as are destined to receive the metallic deposit being exposed, the rest being covered with varnish, wax, or sealing wax, which are non-con- ductors. To the positive pole is at- tached a plate of the metal to be pre- cipitated—copper if we desire a cop- per type, gold if we design gilding the object. Any substance can be coated'with metal if its surface be smeared with plumbago, and contact established with the negative pole. When engravings of coins are used, a coating of plumbago hinders the metal from adhering, rhe figure (Fig 29), represents Smee's instrument in action ; N U is the decomposing cell; Z is the negative polar wire, to which Fig. 29. 104 INDUCED CURRENTS. the coin N is attached; S is the positive polar wire, to which a mass of metal, either copper, gold, silver, &c, according to the operation, is attached at C. In electro-gilding, a concentrated solution of cyanide of potas- sium is used as the solvent of the cyanide of gold, and the nega- tive pole contains gold foil. In plating and platinizing, the same solvent is used. In these processes, a little attention is neces- sary to hinder the metal from being precipitated in the black granu- lar state, which occurs if the solution be too weak. The decom- position in these cases is similar to that described in Daniell's battery, the hydrogen of the water, which is primarily decomposed, causing the separation of the gold or other metal from the cy- anide. The Inductive Action of Galvanism.—In the same way that the electrical disturbance of the prime conductor of the machine, or a magnet, is capable of affecting neighboring conductors, so a galvanic current disturbs the polarity of substances situated near its course. If we place a copper wire, coated with varnish, seal- ing wax, cotton or silk, near the electrodes of a galvanic circle, every time contact is made between the positive and negative poles, an electric wave will pass along the secondary wire. The power of the secondary current will depend upon the thickness and length of the wire, and its approximation to the electrodes. The current of the galvanic battery not having an appreciable striking distance, the wires can be placed very close together, a film of varnish being sufficient to insulate them. The polarities of the secondary wire are the reverse of those of the primary. A third, fourth, fifth, sixth, &c, wire may be employed, and in- duced currents will arise in all, each being in the inverse direction of the one before it, and the intensity diminishing with the dis- tance. Ribbons of metallic foil, covered with silk, may be sub- stituted for the wires with advantage, as several can be packed together. Induced currents take place in all, but are most power- ful in the best conductors. It will be observed, that the current, or molecular change, oc- curs only at the time of forming and breaking the contact between the electrodes. Hence the use of induced currents for giving shocks, producing decomposition, &c, would be unimportant without some contrivance for breaking and forming the galvanic circle with great rapidity. At first, this was accomplished by terminating one of the electrodes in a piece of metal resembling a file, or the surface of which was roughened by fissures; the other pole being moved over this uneven surface, contact was made and broken every time the wire passed from a projection over a fissure. At these points, a spark passed, and the molecu- lar change or current took place backwards and forwards through THE ELECTROTOME. 105 both the primary and secondary wires. When contact was made, the current passed in a given direction, or outwards when broken restoration took place or the wave returned, and thus by rapidly producing impulses of action and reaction, a continuous decom- posing effect, or prolonged nervous shock, could be obtained. At the present day, other contrivances, acting on the same principle, and called rheometers, are employed. The principal of which is, a small temporary magnet, before which is placed a metallic spring that is drawn to the magnet by attraction at one instant, and then reacts, springing away from it, and thus breaks and establishes the current with immense rapidity. One of the best instruments for the purpose of putting persons under the influence of rapid shocks of galvanism (electricity), is constructed on the principle before us, and called the electrotome, or vibrating galvano-magnetic machine. It has superseded the electrical machine, galvanic battery, and magneto-electrical ma- chine, being cheaper, more manageable, and producing effects which may be regulated at will. It can also be intrusted to the care of the patient or his friends, and can scarcely be put out of order. The electrotome (Fig. 30) consists of two parts, a simple cir- Fig. 30. cle, usually Smee's, E, or Daniell's; but a common cell containing a zinc and copper plate, with dilute sulphuric acid, answers very well; and, secondly, an arrangement of wires for producing the induced current. The second part of the machine consists of two wires of great length; one, of copper, to convey the primary current from the generating battery, and the other, of fine iron wire, to convey the induced current. Both are coated with a thin non-conducting material, usually cotton thread. They are wound in a helix A, around a frame of thin card-board, like thread on a spool; the centre of this frame is occupied by a bundle of iron wires, not shown in the figure. One end of the primary wire runs around the small temporary magnet to a small clamp, to which an electrode of the battery can be made fast G—the other terminates in the upright D, which carries a spring and armature; F is a clamp to which the second electrode is attached; it is in 106 THE ELECTROTOME. communication with the brass upright which carries the screw K. As soon as the current passes, the magnet attracts the armature of D, and the connection is broken thereby. The spring, there- fore, reacts, and coming up to the screw K, the current flows again, attraction occurs again, and these phenomena are repeated many times in a second. Each wave in the primary wire creates a wave in the secondary wire and in the bundle of iron rods, and the latter so far reinforces the secondary current of the wire, as to increase its power to a remarkable extent. It acts with the primary current in this respect, so that all the currents are exalted in tension. The longer the secondary wire, and the more numerous the rods, the higher is the tension of the current. The patient receives a shock from the secondary wire, by hold- ing the ends in either hand; for this purpose, convenient handles B C, are provided. The shock of a machine of this kind, set in action by a feeble circle, and consisting of two hundred yards of fine wire, is very intense, transcending many hundred pairs of galvanic plates. The shock can be regulated with the greatest nicety by diminishing the power of the battery, and by diminish- ing the number of wires, or removing them partly from the centre of the helix. By directing the poles of the secondary wire over different parts of the body, as between the spine and extremities, &c, a current can be sent in any desired direction. The poles may also terminate in plates, and be applied over a considerable surface. Moistening the skin of the part with a strong solution of salt, assists the passage of the current in a great degree. Dr. Golding Bird seems to have derived great benefit from an electrotome of a thousand yards of fine wire with a peculiar rheo- meter, such that, the current instead of flowing backwards and forwards, acted only in one direction. With this instrument, a paralytic condition of the body has been produced, amounting, after a few minutes action, to an entire loss of sensation and voluntary motion, the patient being completely enervated. Similar results have been obtained in France, and this modification is worthy of the attention of the profession. I have had one made with eight hundred yards, but whilst it creates a benumbing sensation, and is much less inconvenient to bear than the intermitting current, it has not in healthy persons produced anything but a partial pa- ralysis of the hands and wrists. To observe its effects, currents must be directed from various points of the spine to the parts re- ceiving the nerves, and where the disease of the patient justifies such means, the skin should be previously removed by blisters, and flat polar metals placed over the denuded parts. The poles, in these cases, should be of gold or silver. From European ob- servation, it would appear that the vibrating current produced by the old electrotome creates convulsive action, whilst the constant ELECTRO-MAGNETISM. 107 current induces paralysis or exalted nervous action, according to its direction. The rheometer is depicted in the figure; the wooden cylinder A is furnished with metallic strips at intervals, which break and Fig. 31. form the current by acting on the silver springs B B; the box K contains the electrotome. Electro-Magnetism.—If the primary current passes near to a wire of pure (soft) iron, induction occurs among its molecules, and it exhibits a positive and negative pole, or a north and south pole. This is temporary, and exists only so long as the current flows, or the primary wire is at hand. If the wire be of steel, induction takes place slowly, but becomes permanent—in fact, a true magnetic needle is formed. Either of these wires being sus- pended, will act as a magnetic needle. On the contrary, the polar condition is induced in a wire by the proximity of a per- manent or temporary magnet. If we wind a wire, coated with cotton thread, about a bar, rod, or horse-shoe, of soft iron, and pass a current of electricity along the wire, the iron becomes a magnet, the force of which is dependent on the length of the wire, the battery, and the mass and purity of the iron. Professor Henry put up a temporary or electro-magnet of this kind, which could suspend upwards of two tons attached to its armature. The instant the current of the galvanic battery ceases, the iron loses all its power, and these changes can be pro- duced many hundred times in a second. This offers one of the most striking instances of induction on record, and proves that the action takes place at right angles with the force, as well as in the same plane. It has been shown by M. De la Rive, that if the wires of a small battery be wound into a circle, or prolonged into a helix, the arrangement has the movements of a magnetic needle. Hence a magnetic needle can be made of copper or any conductor, if we provide for the molecular polarities. The Earth's Magnetism.—This brings us to the earth's mag- netism, and the reaction of permanent on teirlporary magnets, 108 THE EARTH'S MAGNETISM. and on galvanic currents, or the subject of Electro-magnetism, which is of great interest, but belongs to Physics rather than to Chemistry. It may suffice for us to allude to the modern theory of the earth's magnetism, which is attributed to thermo-electric currents. The different conducting power of metals (page 27) and other bodies, for heat, is a source of electricity when heat is applied along their points of connection. The surface of the globe consists of land and water, touching at all places; these exercise a very dissimilar conducting power towards the sun's heat, which falls upon them almost incessantly. Thermo-electric, that is to say, electric currents, arise from this source and flow around the earth in curves varying with the arrangement of the land and water, and having two foci, one in the north, in latitude 70° 5' 17", near Hudson's Bay, reached by Sir James Ross in 1831, called the north magnetic pole; the other in the southern hemisphere, called the south magnetic pole. These terrestrial currents induce electrical action in all conductors on the surface, and to discover them, it is only necessary to rotate a disk of cop- per in the plane of the magnetic equator, to generate electrical currents. The magnetic needle arranges itself north and south, under the inductive influence of the terrestrial currents, placing itself at right angles with their course, and reversed, as regards the earth's magnetic pole, for the so called north pole of the mag- netic needle is, in truth, the attracted or south pole, as respects the earth. The terrestrial currents are of the highest interest in the che- mical and geological history of the earth, as well as in the science of electricity. It has been shown by Mr. Fox, of Cornwall, that in mineral veins there is a constant electrical disturbance, and Becquerel, Cross and Bird have pointed out the influence of such currents in producing the crystalization and segregation of mi- nerals, and the stratification of rocks. Hence the production of metallic accumulations in the earth upon which the existence of the metallurgic act depends, is the result of electric currents en- gendered by the heat of the sun. We have no space to devote to a consideration of the numerous cases of the induction of currents, &c, and can only allude to two important instruments, constructed on the principle that a galvanic current induces polarity, viz: the Magnetic Telegraph, and the Galvanometer. The Magnetic Telegraph of Mr. Morse consists essentially of two parts, a galvanic battery with poles of immense extent, "that is, stretching from one city to another, and a temporary or elec- tro-magnet produced by this current. The battery in Baltimore being put in action, the galvanic influence reaches Philadelphia, and there circulating about a large iron horse-shoe, converts it ELECTRIC TELEGRAPHS. 109 into an electro-magnet. This now attracts a piece of soft iron (the armature) placed above it, and at the end of which is a lever carrying a pen ; thus as the iron armature is drawn down, the pen is struck upwards into a piece of paper, and makes a mark. The paper is made to roll by a machine, and thus presents a new surface every second, for the action of the pen. The figure (32) Fig. 32. represents the working portion of this instrument. A message is communicated in the following manner:—The operator at Balti- more, or elsewhere, is provided with • a plan by which he pro- ceeds ; according to this, the different letters of the alphabet are represented by dots or short strokes, and made by breaking, or continuing for a measured time, the connection of the wire with the battery. Every time the current is broken, the electro-mag- net in Philadelphia, or other station, is destroyed, for its action as a magnet depends on the current, hence the pen falls from the paper, but if a new current is now set up, the pen again makes its mark, and it is a dot, a long or short stroke, according as it is more or less continued at the will of the operator at the remote station. Mr. House has a patent for an exceedingly ingenious machine, which prints the message in large type. A wheel, on the circum- ference of which are the raised letters of the alphabet, is made to turn, so long as the current between the stations flows, but stops the moment it is broken; at the same time, a piece of paper is pressed against the letter at which the current is stopped, and an impression made which is inked by a simple contrivance. Galvanometers.—There are two instruments employed for the measurement of galvanic, thermo-electric, and other currents. The Galvanometer is of great service where the influence is fee- ble, and of high tension ; the Voltameter is useful only where the effect is considerable, both as regards quantity and tension, and is employed for the determination of the action of batteries. M. Matteucci has introduced another means of detecting extremely feeble currents, by employing the hind leg of a frog, called by 10 110 THE galvanometer. him the galvanoscopicfrog; it will be described in the next ar- ticle on Animal Galvanism. The Galvanometer.—-This instrument, in its simplest form, consists of a thick brass wire, bent into a parallelogram, and car- rying mercury cups or clamps at the two ends; this encloses a magnetic needle, and is arranged on a stand furnished with a compass card, or a graduated circle to measure the movements of the needle. The instrument of a simple form is represented in Fig. 33. A current of galvanism passing along the wire N, B, S, of this instrument, produces an induced action on the needle, which de- viates from its magnetic position in direction and extent, accord- ing to the nature of the current. Contact is made, with any cir- cle, by placing the polar wires in the cups C, Z, which terminate the wire, and which are charged with mercury. To understand the value of this instrument, and the recent im- provements made in its construction, it will be necessary to ex- plain the action of different currents on the needle. If we place a wire, transmitting a current of galvanism above a magnetic needle, it attempts to arrange itself at right angles with the direc- tion of the current, and will do this if it be strong; but it is cer- tain, that, after the power of the current is sufficient to deflect it to this extent, the needle cannot measure any increase in its force. One of the modern improvements is to enable the expe- rimenter to determine the true amount of force by suspending the needle with a fibre of silk, or a thread of glass, and measuring the deflecting power by forcing back the needle to its old posi- tion ; it is obvious that, in doing this, the silk or glass will be twisted by a force accurately representing the deflecting power, and all that is necessary is, to connect the fibre with an index, traversing a graduated circle, as -in Coulomb's torsion electro- meter. But the needle may range to the east or west, and this depends upon the direction of the current. If the galvanic wire be above, and parallel to the needle, the pole next to the negative end of the battery will move westward ; if the wire be now placed below, it moves eastward; if on either side, the end of the needle will be elevated or depressed. If the current be now reversed, the needle moves to the westward, &c. The parallelogram of wire, there- THE IMPROVED GALVANOMETER. Ill Fig. 34. fore, assists the action of the current, for the force which acts on the upper side to deflect the needle to the west, when the current flows from the positive towards the negative pole, also accom-. plishes a similar effect, when flowing on the lower wire. Hence another improvement of the galvanometer is in the reduplication of the wire, and, instead of one turn, a great number are made, the metal being covered with cotton or varnish to insulate it. The effect is multiplied on the needle, and the instrument made much more sensitive. A third improvement consists in employing two magnetic needles of the same power, and suspended in a reversed direction. When the two are accurately compensated, they lose their direct- ive power north and south, and remain in any position they may be placed ; under such circumstances, they are said to be Astatic. This arrangement is seen in Fig. 34. In this way, the power of the earth's at- traction, which counteracts, in some de- gree, the deflecting force of the current, is neutralized, and the movements are larger and more free. The astatic nee- dles should be suspended by a glass thread in such a manner as to have one situated above the wire of the coil, and the other between its folds ; for this purpose a small space is left in the wires to allow the axis carrying the magnets to pass. The axis is of wood, or ivory. A graduated circle is usually placed under the upper needle. The machine being covered with a glass jar, becomes the im- proved galvanometer. When used, the poles of the battery, thermo-electrie pair, or other electro-motive arrangement, are brought in contact with the termi- nal wires of the coil n. p ; the cur- rent now passes throughout the coil, and thus affects the needle by induc- tion. This delicate instrument was employed by Melloni and Forbes in their researches on Heat, already al- luded to. By means of it, with a thermo-electric pair of brass and tin- ned iron wire, 1 was enabled to dis- cover the law regulating the tempe- rature of plants.* By introducing the point of the pair in the various organs of plants, and measuring their Fig. 35. * London, Edinburgh and Dublin Philosophical Journal. July, 1842 112 THE VOLTAMETER. temperature by the deflecting power of the current, on a delicate galvanometer, I found that the flowers developed the greatest amount of heat, and that the temperature of the vegetable depended upon the ratio of the chemical action going on in a part, and the drying power of the air; so that the function of transpiration in them is equivalent to perspiration in animals, and depends in its variable amount on the hygrometric states of the atmosphere. The Voltameter.-—This is an instrument invented by Profes- sor Faraday for the purpose of determining the action of a battery, by its power to decompose water slightly acidulated with sul- phuric acid. The gases are both collected and measured in a glass tube, graduated in cubic inches and decimal parts. The form employed is various, but the following is simple and con- venient. Take a stout glass bottle of eight ounces capacity, and a wide mouth (Fig. 36); adjust a wooden Fig. 36. stopper to it, perforated so as to allow the bent tube a to pass through it. The tube is sustained in its place by cement or other- wise, and reaches to the upper part of the bottle. In the vessel are introduced the two platinum electrodes to decompose the fluid; these connect by varnished wires with the wooden cap, terminating on the upper surface in separate mercury cups. The voltameter is charged with water slightly acidulated with sulphuric acid. In using this instrument, we bring the positive and negative poles of the battery to the mer- cury cups, whereby the circuit is completed; the gases of the water, being liberated, pass off along the tube a, and are measured in a graduated tube. The power of any two bat- teries will be as the number of cubic inches of gas produced in equal times. n.3 ANIMAL GALVANISM. The extraordinary fact, that there exist several fishes which are capable of producing a shock similar to that of the Leyden jar, has been known for some time. There are five such animals; the electrical Ray or Torpedo (of which there are three varieties, the Torpedo galvani, T. narce and T. nobiliana), inhabiting the Mediterranean Sea; the Gymnotus electricus, or electrical eel, found in large ponds in South America, and from four to five feet in length; and the Silurus electricus, Tetrodon electricus and Trichiurus electricus, which are little known. If the body of either the torpedo or gymnotus be touched,' a slight shock is experienced; but if, in the case of the torpedo, we place one hand on the upper side of the thoracic portion of the body, and the other opposite and under the creature, a power- ful shock is experienced. In the gymnotus, we touch the head and tail to experience the most powerful action of the animal. Confining ourselves to the torpedo, it will be found that there are certain portions of the thoracic regions more active than others, and upon dissecting the part, we discover a cellular structure, called the electrical organ, where the shocks are evidently produced. If we dissect out this part, leaving only its nerves uninjured, it continues to evolve electricity; and, indeed, does so when alto- gether removed from the system. The structure of this organ is peculiar and suggestive of a combination of galvanic piles; it is represented in Fig. 37. Upon a minute inspection of the Fig. 37. organ, it is found to consist of a large number of polygonal cells, regularly superimposed in pris- matic columns. Each cell appears to consist of a cartilaginous wall, over which ramify branches of nerves, and the centre is occupied by a dense albuminous, and slightly saline fluid, like the white of an egg. The nerves sup- plying the organ are very large, and correspond to the eighth pair and a large branch of the trifacial. If one of these nerves be irri- tated, the portion of the organ to which it is distributed produces a current. The nerves of supply terminate in a large lobe of 10* 114 THE POWER OF THE GYMNOTUS IS ELECTRICAL. the brain lying in contact with the medulla oblongata, and form- ing a large portion of the encephalon. An irritant applied to this electrical lobe, or to any portion of the medulla or spinal cord, causes rapid discharges; but this does not occur if the cerebellum, optic lobes, or cerebrum, be touched or even penetrated by a knife. In the gymnotus, the nerves supplying the electrical organs are derived from the dorsal portion of the spinal cord; and in the Silurus, from both the medulla oblongata and spine. By means of the galvanometer we discover that the current producing the shock is from the back to the abdominal side of the fish, or, to speak as an electrician, the dorsal aspect of the organ represents the positive side, and the abdominal the nega- tive side, the current passing from the positive to the negative surface. The shocks of the animal are under the influence of its in- stincts, and can be repeated only a few times before the creature becomes disabled. Indeed, in South America, the gymnotus is caught by irritating and causing it to give a number of shocks, after which it becomes enervated and powerless for some time, and may be taken with the hand. Observe that the electrical power is associated with the deve- lopment of large nerves, influenced by the will, and capable of so far subduing the nervous power of the animal that it loses en- ergy, is incapable of muscular contraction, and entirely enervated. Secondly, if we separate the org«n with its nerves from the body, pinching or irritating the nerves will at first produce electrical cur- rents appreciable by the galvanometer; but this soon ceases, and now the passage of a galvanic current along the nerves arouses the action of the organ again. At the moment of establishing or breaking the galvanic current, the organ responds, but in the in- terval no disturbance occurs. Finally, the cells, separated from all nervous connection, evolve electricity, when pressed or warmed. Matteucci has detected a current from the toes to the head in the frog; Aldini, Donne, and others, musculo-cutaneous currents in many animals, and man. Faraday has shown that a Leyden jar, and indeed a battery, can be intensely charged by the gymnotus; the spark has been seen, needles magnetized, solutions decomposed, and all the phe- nomena of galvanism and electricity produced. Such observa- tions have multiplied, until no doubt exists on the subject, that the nervous energy of the torpedo is convertible into electricity, if it be not that agent. Let us now pass to the influence of electricity and galvanism on the bodies of the higher animals. By the action of this agent, partial or complete paralysis and death may be brought about. Involuntary movement, painful sensations, the manifestation of ACTION OF THE DIRECT AND INVERSE CURRENT. 115 light, sound, taste and odor also occur, when currents are passed through certain nerves. If a current be directed to the brain by a dissevered nerve in a rabbit, pain is produced and muscular contractions result. Here an influence propagated along a sen- sory nerve to the encephalon reacts, or is reflected to a motor nerve, operating in the reflex manner which Dr. Marshall Hall has shown to be the case in the human body with the nervous fluid. If a rabbit be killed by a blow on the head, and then sub- jected to the galvanic current, it is thrown into violent motion every time contact is made or broken, if one of the poles be over the spinal marrow, and the other applied to a muscular surface. If the current pass from the cervical portion of the spinal marrow to the fore legs, they will be convulsed; if from the lumbar por- tion to the hind legs, these are thrown into action. In short, the best results are obtained when the current runs between the nerv- ous accumulations in the spine and the muscles to which they pass. Convulsions occur only when the current is broken, not whilst the circle is closed. If we direct the current through por- tions of the cerebrum or cerebellum, no action occurs, but when it passes through the tubercula quadrigemina, the crura, or the medulla oblongata, violent convulsions occur throughout the en- tire animal, with signs of suffering. It will be observed, that this is similar to the action on the torpedo, the electrical lobe being situated on the medulla oblongata. The difference of effect between a direct and reversed current, is worthy of particular consideration; for the demonstration of this we are indebted to the labors of Professor Matteucci of Pisa. The current is said to be direct when the positive pole of the battery is placed over the spine or nervous centre, and the nega- tive over the ramifications of the nerve. The reverse position gives us the inverse current. Action is greatest when the influ- ence is directed along a specific nerve, and least when it passes across the nerves and muscles. The evidence of pain is much greater at the commencement of the inverse current; the muscu- lar contractions most severe at the beginning of the direct current; but neither effect takes place during the closed state of the circle. If we operate on a living animal, these effects lessen with repetition, and become very feeble, but recur after an interval of rest, so that there is an analogy between the reduction of nervous power under the stimulus of galvanism, and the cessation of ac- tion in the gymnotus and torpedo. It also appears that the gal- vanic influence proceeding from the periphery to the spine, is attended with a reflex nervous current from the centre to the pe- riphery in other nerves ; or that an electrical current of one nerve can set in motion the nervous fluid of another nerve, in the same way that a galvanic current passing along the polar wires, influ- 116 ACTION OF THE DIRECT AND INVERSE CURRENT. ences the electricity of a secondary wire, producing a reversed current therein. There is another intimate relation between the course of the nervous fluid, and the direction of the galvanic current. If we pass a current of galvanism through two legs of a frog connected by a small portion of the lumbar spine, in such a manner that one pole is in contact with the toes of one leg, and the other with the same portion of the other leg, the current will be direct in one limb, and reversed in the other. It will flow from the pe- riphery in one case, and from the spine externally in the other. Now, after some minutes, we will find that the leg conveying the direct current does not contract when the circle is broken, but the other does so for many minutes longer. From this extraor- dinary fact, which is true for living and dead animals, Matteucci draws the important conclusion, that the excitability of a nerve is much more weakened by the passage of the direct (from the spinal marrow to the periphery of the nerve), Man by the inverse current. Again, he has proved by experiments, that the inverse cur- rent, so far from diminishing the excitability of the nerve, exalts it. Thus, if we take the leg and thigh of two frogs, equal in all respects, and pass through one the direct current, contractions of a vigorous kind occur at first, every time the circuit is broken or formed, but these diminish, and are entirely suspended in twenty or thirty minutes; the nervous excitability is now de- stroyed. But the other leg, in which an inverse current flows, is not so affpcted; the convulsions estimated in the first second, are not at all stronger than those occurring three or four hours after the current has been flowing—hours after all trace of ex- citability by the action of this agent has ceased in the limb tra- versed by the direct current. There is a peculiarity in the con- traction which takes place under the influence of the inverse current, after allowing the circuit to remain closed for some time; upon breaking it, the limb is drawn up for some seconds, and not spasmodically affected, a condition resembling tetanus, or permanent contraction being produced. WTe hail in these facts, deduced from numerous and accurate experiments, the first principles calculated to guide us in the ap- plication of the electrical agent to the treatment of disease. Let the student remember : " 1st. That the contraction excited by the electric current, trans- mitted along a nerve in the direction of its ramifications, and which we call direct, is always more energetic than that which the same current produces when passing along the nerves in the opposite direction. "2d. The direct current weakens, and rapidly destroys the ACTION ON THE DIFFERENT NERVES. 117 excitability of a nerve; whilst the passage of the inverse current augments it within certain limits." In respect to the second fact, it is proper to remark that the contraction is stronger after the inverse current has flowed for some time, than at first, whether we excite muscular action by electricity, or the application of any other stimulus, in the dead or in the living subject. Again, if Ave allow the nerve some repose after the passage of the direct current, it recovers part of its ex- citability, and, under the same circumstances, the excess of excite- ment produced by the inverse current soon disappears. The power of the muscular contraction is also proportional to the quantity of electricity which excites it, and the feeblest currents are capable of producing it if properly employed. If we exhaust the nervous power of a limb by the direct current, and then allow the inverse current to flow, it will recover its power of contract- ing, the galvanism serving by its action to bring about a result similar to that of the nervous power itself. The result produced by the current depends upon the function of the nerve along which it traverses. Passing along the nerves of sensation in the direct manner, pain occurs ; in the inverse direction, motion. Passing along the optic nerve, flashes of light are perceived ; sounds heard, when directed through the ear; taste experienced, when flowing through the nerves of the tongue. Experiments made by Humboldt, show that currents transmitted through the ganglionic nerves to the heart and intestines, produce muscular movements in these parts, which are remarkably dif- ferent from those of the ordinary muscles. The movements are slow to appear, but continue during the closed state of the circle, as well as some time after. In the muscles of animal life, they appear only at the interruption, and cease on removing the stimu- lus ; but the heart has been seen to pulsate for some time after the galvanic action had ceased. The influence of a continuous or interrupted current of elec- tricity is also of the first physiological interest. In the cases given, the continuous current was found to destroy nervous power after many minutes when direct, and to exalt it even after hours when reverse. But when interrupted by breaking and forming the communication with rapidity, the nervous power is much more rapidly exhausted, than by the continued application of the direct current. Masson, who first experimented on this subject, succeeded in killing a cat in five minutes by an interrupted cur- rent with a small pile, which would have scarcely affected the animal when continuous. In such cases, the interruptions are not extremely rapid, for Pouillet has remarked that, when the interval between the currents is so small as the 3^0tn °f a second, the effect is similar to that of a continuous current. Matteucci killed 118 GALVANISM AS A REMEDIAL AGENT. a rabbit in a few seconds by the use of an interrupted current passing from the nape of the neck to the mouth. Weber has also remarked that the pulsations of the heart cease when the interrupted current is made to act on its nerves. The electrotome, (page 105,) as usually employed, and the mag- neto-electrical machine, give interrupted currents, and are there- fore to be employed with some care. The electrotome, with Dr. Golding Bird's rheometer, gives an interrupted current, but in one direction only. In this case, the first induced current is felt, but not the return current; hence, by its use, the physician can em- ploy an interrupted current in one direction if he desires, and results widely different from those obtained by using an inter- rupted current in both directions, seem to be obtained. Therapeutic Uses of Galvanism.—The galvanic current from a Cruickshank's battery of fifty pairs of zinc and copper, two and-a-half inches square, charged with salt and water, was formerly employed. In the present day, the electrotome and magneto- electrical machine are almost exclusively employed. These latter are, however, mostly used as contrivances for the production of interrupted currents, but the former may be used for a con- tinuous current by screwing down the armature of the magnet. Cruickshank's battery may be employed for the continuous or interrupted current; this form is, however, objectionable, from the short period during which it is active. For obtaining the con- tinuous cujrent, Daniell's battery is very superior, and much more manageable than it. Current electricity has been recommended in functional amau- rosis and paralysis, in chronic rheumatism, indigestion, asthma, sciatica, neuralgia, nervous deafness, and generally for loss of power in the various parts of the nervous system. It has also been highly spoken of in asphyxia, produced by drowning, suffocation, loss of power in the respiratory muscles, or the heart, or in any other manner. In loss of function of the lungs, brain or other organ from congestion, it has also been recom- mended especially by Dr. Wilson Philip. Reducing the con- sideration of the subject to our limits, and discarding the nume- rous cases which are disputed, we may condense the subject into a few paragraphs. In functional paralysis, arising from want of nervous power, the inverse current from the feet or hands, as the case may be, to the roots of the nerves of supply in the spine, should be used. The contact should be made by broad metallic bands applied to the skin, previously moistened with salt and water, to assist the conducting power, or the connection may be made more complete by introducing acupuncture needles into the part, and bringing the broad polar ends of the electrodes in contact with them. The GALVANISM IN NERVOUS DISEASES. 119 induced current of the electrotome or magneto-electrical machine, with Dr. Bird's rheometer, seems to be serviceable, or the current may be rendered nearly continuous by managing the armature with the finger, or screwing it down on the electro-magnet; or a Daniell's battery may be employed. Experience has shown that, in the commencement, the current must be very feeble, and that it is best to interrupt it some thirty times, during a few minutes, and discontinue the application, recurring to it once or twice daily, at the same hours, for several weeks. During the administration, the patient should be sustained in good general health, the food should be nutritious, and liberal in amount, and the affected limbs used, if possible, or excited by friction, warmth and shampoo- ing. The number of recoveries on record, in these cases, are suf- ficiently great to permit us to expect a favorable issue. An experiment of Matteucci shows that the function of the muscles of a part may be recovered, by the use of galvanism, a long time after the nerves of supply have been cut, whereas it is soon lost if no such means be employed. Divide the two sciatic nerves of a living frog, allow one limb to remain quiet for ten, fifteen, or twenty days, and submit the other, two or three times a clay, to the action of a current—it will be found that the latter contracts, whilst the other leg ceases altogether to be in- fluenced by the galvanic current. Loss of Nervous Power.—In the numerous cases falling under this general head, the nearly continuous and inverse current may be expected to accomplish something when assisted with proper hygienic treatment. As in the case of paralysis, it will be ad- visable to interrupt the current occasionally, and adopt the other adjuvants indicated. Increase of Nervous Power.—Tetanus, hydrophobia, epilep- sy, catalepsy, convulsions, and neuralgias, fall under this head. In tetanus, we have a continued exaltation of nervous power; this is to be treated by the partially continuous direct current, the operation of which is to diminish the nervous power. The elec- trodes are to be placed between the muscles affected, and the roots of their nerves. By this means, a patient laboring under traumatic tetanus, was enabled to open his mouth, and use the affected muscles. A cure was not effected, nor is it to be expected in that variety of the disease arising from wounds; but it would be culpable to discard a remedial means in such cases, even though it may not cure, if it has been found to alleviate suffering. In hydrophobia, the current cannot be readily employed, but if the opportunity offers, it should be continuous and direct. In epi- lepsy, catalepsy, convulsions, and neuralgia, it should also be almost continuous and direct. Experiments on frogs, thrown into convulsions and tetanized 120 GALVANISM IN ASPHYXIA AND ANEURISM. by narcotics, have shown that a continued direct current will overcome these states. In Asphyxia, including congestions of the brain and lungs, the electrical current may be used for the purpose of arousing the muscles of respiration and the heart. For this purpose it should be an inverse current, often interrupted. One pole should be situated high up in the neck, to be as near as possible to the me- dulla oblongata; it should also be brought in contact with the nerves by an incision into the parts, and the other pole must be brought by an incision in contact with the diaphragm, or by acu- puncture needles with the respiratory muscles. In the interrup- tions, which should be frequent, it would be well to bring the pole in contact with all these parts in succession. M. Bourgeois has suggested driving needles into the heart also. In these cases the electrotome is to be preferred. In Aneurism.—Dr. Apjohn suggested, and M. Petrequin of Lyons has practised, the introduction of needles into the anen- rismal sac, put in connection with the poles of a battery, for the purpose of coagulating the blood in the part, and causing the re- moval of the tumor without ligature. M. Petrequin, with several Italian surgeons, have had consi- derable success in this operation. Popliteal and brachial aneu- risms of considerable size, as well as varices, have been completely obliterated by the action of a current from a pile of twenty copper and zinc pairs, two inches square, separated by pieces of cloth moistened with solution of common salt, and used for fifteen mi- nutes. M. Petrequin lays down certain rules essential to success: the force of the circulation should be diminished by compress- ing the vessels of supply, and by diet and other means before the operation—the needles are to be varnished over the parts which are in contact with the integuments and coats of the aneurism, otherwise considerable inflammation arises—four or more nee- dles are to be employed in large aneurisms, and the shocks should be sent through in every direction; the needles are to be plunged obliquely, so that the points approach one another, but do not touch. There is no doubt that, with proper management, this method will be found to supersede the operation of tying the artery in two-thirds of the cases of aneurism. In the cases given, it uniformly succeeded, and the cure was perfect in about eight days. Other Applications.—Prevost and Dumas have proposed gal- vanism for the destruction of the fusible calculus in the bladder. They introduced such a stone into the bladder of a dog, and brought the poles of a Cruickshank battery of one hundred and twenty pairs to bear upon it, in the presence of a large quantity of water—it was entirely disintegrated, being reduced to powder, THE PROPER GALVANISM OF ANIMALS. 121 which was voided. The poles were introduced in a canula by the urethra. In asthma and dyspepsia, Dr. W. Philip used a continuous current; in these cases, the positive pole was placed over the nape of the neck, and the negative to the pit of the sto- mach. In chronic cases, the plan recommended by Dr. Mansford may be found useful. Two plates, one of zinc and the other of silver, of a size and shape depending on the part and gravity of the dis- ease, are provided, and union established between them by a stout silver wire. The plates are adjusted over the roots of the nerves, and the parts affected. To secure their action, both parts are made bare by a blister, and pieces of moistened wash leather placed between the plates and body; the plates are also kept in place by strips of adhesive plaster. The zinc plate should be examined several times a day to remove the oxide by scraping. We should also imagine that frequent interruptions would be serviceable. This plan is empirical, but has been found useful in the hands of Dr. Mansford in epilepsy, and valuable by Dr. Thomas Harris, of Philadelphia, in several cases of neuralgia. The position of the zinc or positive pole must depend on the direction we wish to give the current. Dr. Golding Bird proposes a similar plan for the cauterization of the parts, from which it is to be inferred that the action is severe. He employs discs of metal of the size of a cent piece, and causes the zinc to be frequently cleaned. THE PROPER GALVANISM OF ANIMALS. In considering the electro-motive source in galvanism, we as- sumed the position that in every case of chemical action, electri- city is produced, and its presence may be made evident, whenever conductors are present to convey the influence. By direct expe- riment, Lagave, Buntzen, Prevost and Dumas, Kaemtz and others, have demonstrated that the reaction of blood, saline fluids, and various organic matters, on flesh, nervous matter, brain and the animal solids, produces a galvanic current. Lagave formed a bat- tery of alternate slices of brain and muscle, and conceived that animal electricity arose from the contact of these tissues in all parts of the body, a view somewhat similar to that of Galvani and Aldini. The chemical changes which incessantly take place in the muscles and tissues of animals, produce galvanic disturbance, which has been detected over the whole body by Pfaff, Ahrens and Humboldt, by the divergence of the gold leaves of the elec- trometer, when the subject of experiment was insulated; this is called the proper electricity of the animal. Valli, Donne and Matteucci have found that when the inte- rior of a muscle and the skin, or its cellular envelope, were ex- 11 122 THE GALVANISM OF THE MUSCLES. amined by a delicate galvanoscope, a current of galvanism was always found flowing from within outwardly. Moreover, the intensity and amount of this current depend on the vigor of the animal, and the supply of blood to the part; when blood was partially absent, the current became very feeble. Here, then, we have a demonstration of a galvanic current existing at all times in the muscular tissues, and arising from the changes taking place in the blood and tissue during the functions of nutrition and change, and subject to increase or diminution according to the supply of blood. This is called the muscular current of animals. The nervous system has nothing to do with it, for so long as action takes place between the blood and muscle, the current flows, whe- ther the nerves be divided or entire. It is so far apparent, that a muscular battery may be made by connecting a number of frogs' thighs, in such a manner that the exterior portions of the muscles of one shall be in contact with the interior parts of the next. This may be moistened with a saline mixture or water, and will produce a considerable deviation in the galvanometer, when the ends are brought in contact. It is de- picted in Fig. 38. A is the positive, and R the negative end, and the arrow indicates the direction of the current. Fig. 38. For the detection of the galvanic currents in animals, Galvani, Aldini and Matteucci have introduced the galvanoscopic frog. This consists of a hind limb of a frog, deprived of its skin, with the muscles and bone of the thigh removed, but the crural nerve left entire, and exposed above the knee-joint. The prepared leg may be kept in a glass tube, with the nerve exposed, as in Fig. 39. It will be found that when the nerve is placed on any sub- stance in which galvanic action is occurring, the remaining muscles of the fore-leg and toes will be thrown into contractions, and thus indicate a degree of electrical disturbance too feeble to affect the common electroscopes. Fig. 39. INDUCED NERVOUS CURRENTS. 123 By means of the galvanoscopic frog, it has been proved that electrical currents are produced in all the muscular structures of the body; but such currents have not been discovered in the nerves or glands. Moreover, whatever substances or actions re- duce the vigor of the muscular system, or remove the quantity of blood circulating therein, diminish the force of the current; and, on the contrary, whatever increases its activity, seems to develope a greater electrical action. The galvanoscopic frog is affected, whether the muscle be a part of a living animal, or of one re- cently killed, and especially when the muscle is in the act of con- traction. Again, if a current of galvanism be passed along a nerve, so as to produce muscular contractions in a living or dead ani- mal, the galvanoscopic frog responds to the disturbance. Nay, more, the current induced in one frog may be made to act on a second, third and fourth limb, so that a series of induced currents of the second, third and fourth order, are produced precisely in the same way as in a compoupd helix of wires. The induced currents in these cases do not arise from any direct action of the electrical agent employed in producing the primary effect, for we may surround the nerve of the galvanoscopic frog with varnish or other insulating materials, and yet they occur. Induction occurs, whatever be the cause of muscular contraction, whether the will, mechanical or chemical stimulants, or electricity. But there does not appear to be an induced current when the nerve of the frog lies upon the brain or another nerve, whatever be the measures taken to irritate these parts. If we enter into the consideration of the phenomena of induced contractions, we are led to suspect the existence of a galvanic current in the muscles of animals. We find nearly all the known facts conform to this hypothesis. The amount of the current is so small, and the conductors in which it takes place, so indifferent, that we may fail, in determining some points, more from want of delicate tests than from any distinction between the agents. If we trust to analogy, the hypothesis gathers greater strength, for, anatomically considered, the structure of muscles, and the elec- trical organs of the torpedo and gymnotus, are of the same type, and differ mostly in the size of the cells and the distribu- tion of nerves. The muscles of organic life are remarkably similar, since these receive the same nerves as the electrical organs, as well as possess a similar structure. As galvanism, or any stimulant addressed to the nerves, produces muscular contractions with the evolution of a force, so the same means arouse the organs of the torpedo, and develope an agent identical with electricity. The galvanic action also produces pain, increases the secretions, or induces contractions; it is capable of 124 SIMILARITY OF THE GALVANIC AND NERVOUS FORCE. exalting the nervous power or annihilating it, of causing tetanus, convulsions, or complete prostration. Hence, whatever may be our views of the nervous power, it is apparent that within narrow limits, its place may be temporarily occupied by the galvanic cur- rent, and the results produced will be so similar that no one can distinguish between them. The organic nervous power does not act more rapidly, cannot produce more active movements, nor induce any phenomena of the body different from those brought about by galvanism for a brief period. In the electrical fishes, the nervous power is convertible into galvanism. There are the same laws of induction common to both, and the same necessity for chemical action to develope both. Thus, these agents appear to be, if not identical, modifications of the same force, and by no means so dissimilar as magnetism and electricity appeared to be only a few years ago. All experimenters have failed to obtain an induced current in a magnetic needle, or galvanoscopic frog, from a nerve or the brain. But this does not prove that a cuirent does not pass in them, for we fail even when the nerve is made to transmit galvanism, al- though vigorous contractions are occurring in the muscles. There is another exception taken to the view, that the nervous power and galvanism are identical—that tying a nerve destroys its capa- city to transmit a nervous current. This is to be expected, if we remember that the nerve is an indifferent conductor, which may, like a fluid, convey the force only by a series of decompo- sitions and recompositions among its molecules, and may, there- fore, lose its connection by the action of the ligature. It is said that, under the same circumstances, it can transmit an electrical current which has a striking distance; but Matteucci has shown that it also impedes a galvanic current of very low intensity. This capital objection has, therefore, been removed, and some- thing like a demonstration of the existence of a current passing between the stomach and liver, has been made by Matteucci. It will be remembered that the secretion of the stomach is acid, and that of the liver alkaline, and this has induced many theorists to surmise the existence of such a current. The experimental proof is as follows : a plate of platinum was introduced into the sto- mach of a rabbit, and another placed on the skin over the liver; when these were put in contact by a wire connected with a gal- vanometer, a considerable current was detected, which deflected the needle 20°. This current was found to be connected with the integrity of the pneumogastric nerve, for, on severing it, the deflection became only 3°, and it was entirely connected with the brain, for, on decapitation, it ceased altogether. As we know that chemical action is always occurring in the muscular structure, and Matteucci has shown the muscular or galvanic current derived therefrom to be more intense than that THEORIES OF MUSCULAR ACTION. 125 common to the system, and called the proper electricity of the animal, it is apparent that it must accomplish something. A new theory of muscular action has been based on this fact. It is sup- posed that the galvanism generated in the cells of the muscular tissue, causes them to repel each other, and produces the expand- ed state of the tissue, but that this galvanism is discharged into the nerves of supply at the moment of contraction, causing all the cellules to approximate, by the removal of the cause of re- pulsion. Something of this kind may occur, but the cause of the discharge is not intelligible. Moreover, chemical actions occur in the brain, and are calculated to produce analogous electrical effects. From this we are led to infer that a galvanic (nervous) current may arise from the brain, and another (muscular) from the muscle; but the laws which determine their action, are un- known. It has been objected to such views that muscle and nerve are not good electrical conductors; but this is an unimport- ant matter if it be admitted that they differ in conducting power. The free electricity of the muscle is the product of the chemi- cal changes passing over its parts at all times; but in addition to this, Liebig has found a second source, which, as it throws light on the nutrition of the muscle, we introduce in this place. He has found that the muscular texture is bathed by an acid fluid containing the tribasic phosphate of soda with acid reaction, and lactic acid, whereas, it is well known that the blood and serum, as well as the surfaces of the mucous membranes, the chyle and lymph, possess an alkaline reaction from1, the presence of the tri- basic phosphate with three atoms of base. Now, under these cir- cumstances, a movement will take place in these fluids through the tissues that lie between them, and a galvanic current be generated. Valli, fifty years before, had proposed a view much more in accordance with facts, than either of the foregoing; he con- ceived that the galvanism was set free on the surface of the capillaries which supply the nerves, and that it is constantly con- veyed to the muscular fibres, which continue charged, until a counter influence from the brain neutralizes their exciternent. We close these observations with the remark, that the simi- larity in action of the nervous and galvanic forces is such as to induce us to hope for a more complete investigation of the sub- ject, and even to anticipate that hereafter they may be found identical; but manifested dissimilarly in consequence of the or- ganized structure of the body ; in the same way that electricity and maanetism, although one agent, have few properties exactly similar,°and are apparently opposed in many. One truth is now certain, that galvanism is generated in the body wherever chemi- cal action occurs, as in the changes of nutrition, respiration, and secretion. 11* 126 AFFINITY. Affinity was originally employed to designate a particular force which united the molecules of matter together. There were supposed to be three varieties of this force: that which bound together the similar atoms of bodies, which was called simple affinity or cohesion—that which determined union be- tween dissimilar molecules, termed heterogeneous affinity, or ca- pillary attraction; and lastly, chemical affinity, which served not only to unite dissimilar atoms, but also modified their properties, so that they were no longer to be recognized by physical tests. These varieties of force may be readily illustrated. If we press together two pieces of clean lead, or of plate glass, they will ad- here, and with considerable force; this is an instance of the ope- ration of the cohesive force. If a perfectly clean piece of plate glass be let down to the surface of pure mercury, they attract one another with considerable force in consequence of the heteroge- neous affinity, or capillary attraction, existing between these bo- dies. In neither of the foregoing instances are the substances altered in figure or sensible properties; but if we now bring nitric acid in contact with the quicksilver, union occurs, attended with the evolution of red fumes, and both the acid and metal lose their properties, the mixture becoming a crystalline solid—this is a case of chemical affinity. Formerly, there was supposed to be a radical difference be- tween these forms of affinity, but they are now found to be mo- difications of the same force. Nor is this a new force, sui generis, but an instance of electrical action. This may be readily proved: If we cause two plates of glass to adhere by bringing them in close contact, and then separate them, and carry each to the gold leaf electrometer, one will be found negative, and the other posi- tive. This effect will appear in the case of all solids which are insulated; in fluids, the union is too close to enable us to test the electrical state of the parts, but it will be remembered that Pouil- let has shown that the disintegration of their molecules is attended with electrical disturbance. In cases of capillary attraction, the electrical force is also active; if the glass and mercury be insu- lated, it will be found that on separation both develope electricity. In this case, the attraction is completely under the influence of COHESION, CAPILLARY AND CHEMICAL ATTRACTION. 127 electricity, for if we place a little water on the surface of mercury, no affinity is apparent; the water collects in drops and insulates itself from the mercury, but the instant we bring the negative pole of a galvanic battery in contact with the metal, and let the posi- tive touch the water, union occurs, the water spreading over the quicksilver, and wetting it completely. In chemical affinity, the electrical force controls the action, as we have shown in page 99. The electro-chemical theory is a sufficient evidence of this position. There are circumstances in which these agree, as well as points of difference. In every case of affinity, electrical disturbance arises, but it is most violent in the process of chemical union. The force acts only at insensible distances. Newton came to the conclusion that cohesion did not act at a distance exceeding the millionth of an inch, and it is well known that chemical action rarely occurs, unless one of the bodies be fluid or gaseous. Co- hesion, capillary attraction, and chemical affinity, are all controlled by electricity. If we electrify two pieces of glass similarly, they repel each other; if dissimilarly, cohesion takes place. Water and saline fluids can be made to mingle with quicksilver, when their electrical states are dissimilar. Chemical union of the most intense nature can be overcome by the galvanic current. The question whether capillary attraction, or chemical union, shall take place in any case, depends upon the relation between the force which binds the atoms of either body together, and the degree of disturbance. Capillary attraction is, by no means, a universal result of the action of matter; it takes place only be- tween certain bodies, and differs in intensity. Chemical affinity is equally a special result, occurring only between bodies, the elec- trical relations of which are widely dissimilar; and also differing to a considerable extent in intensity. Clairauthas determined the ratio of the cohesive force to the capillary affinity which produces the rise of fluids in glass tubes, or, what amounts to the same thing, the wetting of a surface by a fluid for which it has an affi- nity; and Professor Draper has added to this estimate the con- dition under which chemical union results. These are expressed in the four following laws: 1st. The force which binds together the atoms of a homoge- neous body, is electricity, and is called the cohesive force; it is very dissimilar in intensity, in different forms and kinds of matter. 2d. If the electrical attraction of a fluid for a solid be less than half the cohesive force, capillary affinity does not occur, the fluid does not wet the solid, and will be depressed in a minute tube made of the solid. 3d. If the electrical attraction of a fluid for a solid exceeds half, 128 CAPILLARY ATTRACTION. but is less than the whole cohesive force, it will wet the solid, and rise through its interstices, or in a capillary tube made of it. 4lh. If the electrical attraction of a solid or fluid for another fluid exceeds the whole cohesive force, chemical union will occur. Cases of solution, of the penetration of gases and vapors into one another, of the ascent of fluids into solids, and the passage of mercury through metals, are instances of capillary affinity. In the relation of mercury to solids, we are presented with instances in which the capillary affinity gradually passes into chemical union. If two globules of mercury be brought near to one an- other, union occurs; this is an instance of cohesion. If iron be brought in contact with this metal, it is in no way affected; the surface is not wetted by the quicksilver, nor does any part of it rise into the interstices of the iron; the cohesive force is greater than the electrical attractions of these substances. But a clean piece of copper or silver brought to the mercury, is instantly affected ; they are wetted, and if exposed sufficiently long, become permeated in all directions; the cohesion of their atoms is over- come, and a compound body is produced. But if we examine the action on the silver more particularly, it will be found that a peculiar substance differing from both of the components, is formed; the amalgam assumes the crystalline figure, and becomes no longer a solution of silver in mercury, but a definite chemical body, composed of a fixed number of atoms, and having a certain figure. In this case, the chemical body is produced without any remarkable disturbance of the electrical force (or ether), and seems to be little more than a case of solution, but in most instances a considerable disturbance of heat, light or electricity occurs during chemical union, and characterizes it. We propose, in this place, to consider chemical affinity, leaving the applications of capillary attraction to the circulation of fluids in animals, to the section on animal chemistry. The subject divides itself into the following sections: § 1. The phenomena of chemical affinity. § 2. The chemical relations of matter. § 3. The effects of the chemical force. § 1. THE PHENOMENA OF CHEMICAL AFFINITY. It has been remarked that the intense electrical affinity which produces chemical union, is usually attended with phenomena that are not perceptible in cases of cohesion and capillary attrac- tion. In chemical union, we commonly observe the evolution of light, heat, electricity, and change of color, density, form, or other sensible properties, and these appearances decide us in referring THE PHENOMENA OF CHEMICAL AFFINITY. 129 the cause to chemical combination. Bodies which are charac- terized by intense causticity, as potash and sulphuric acid, become neutral, possessing little action. Intensely colored substances lose their appearance, fluids become solids, gases are converted into crystalline substances, and every variety of change occurs in chemical union. It is not to be expected that where the active properties, colors, and densities are so altered, the changes should take place without disturbance to the ether contained in the combining substances. This is thrown, in many cases, into intense action; where rapid condensation occurs, great heat is evolved, sometimes gaseous bodies are evolved from solids with explosive violence, or the addition of a fluid throws a solid into intense ignition. Indeed, wherever chemical affinity is considerable, the ether is remarka- bly affected, and light, heat, electricity, change of color, and ex- plosions, often take place. In these cases, the phenomena indicate chemical action. By experience, we have discovered that certain bodies, as oxygen, chlorine, iodine, sulphur, are intensely active, combining with most solids; and reviewing this knowledge, we find that those which are high on the electro-negative scale have the great- est affinity for those high on the electro-positive scale (page 102). Their electrical relations being intense and dissimilar, union occurs between them with great force. Nor does chemical union occur between simple substances only, but between such as are highly complex. Circumstances which assist Chemical Union.—The principal of these are: the fluid form, the nascent state, heat, certain elec- trical states, and light. The fluid state is one of the most essential conditions to the display of chemical action; indeed, formerly it was supposed essential, but we are now acquainted with many instances in which it is not necessary. In the fluid, the cohesive force is con- siderably less than in the solid, and there is a facility of access among the atoms which allows of their juxtaposition. The in- terspaces of fluids are also greater than in most solids, and hence the diffusion of matter is more ready. So considerable is the influence of fluidity, that it is often enough to dry up a mixture to stop chemical union, and this is especially true in organic changes, as in fermentation. The Nascent State.—It is found that when a gaseous sub- stance is first made free from its combinations, it is much more active than when aerial. Oxygen, hydrogen and nitrogen are gaseous bodies, and when in their ordinary state, are not remarka- ble for great activity ; indeed, hydrogen and nitrogen are almost inactive, but when first produced from their compounds, and 130 ALLOTROP1SM. before they have passed into the state of gases, they are the most energetic substances in nature. It is to be supposed that they are fluids in the nascent state, and being much condensed, act with violence, for if we condense them by spongy platinum, artificially, they become energetic. These are not the only instances where a substance displays a great difference in chemical activity. Chlorine, phosphorus, sulphur, carbon, iron, and perhaps nearly every element, has an active and inactive form. Nor are these merely attributable to the state of condensation, for iron, whether active or inactive, has the same appearance. From these facts, it appears that the ability to display chemical affinity is not a property of the atom so much as of the forces by which it is moved, for if inactive chlorine be exposed to the light, it becomes active; again, if active phosphorus be exposed to the same agent, it becomes inactive. Iron thrown into the electrical state, is in- active to agents with which it readily combines under ordinary circumstances. These states of matter are termed allotropic, and the fact of their existence allotropism. Allotropism is not simply the fact that many, if not all, ele- ments exhibit an active and inactive state; for some, as carbon, have three allotropic forms, as the diamond, plumbago, and lamp- black. Hence a necessity has arisen for a descriptive nomen- clature, especially as there is little doubt that the particular state of an element modifies all its compounds. We find in organic chemistry numerous bodies with the same atoms in similar pro- portions, but of very different properties, which are called iso- meric. Such are oil of turpentine and lemons ; carburetted hy- drogen, a fetid gas, and otto of roses. In such cases of isomerism, the difference of properties can only be attributed to the presence of the elements in different allotropic states, or to a difference in the arrangement of the atoms. A new nomenclature, with ap- propriate symbols, has, therefore, been recommended. The ac- tive phase has been designated the alpha (a) state, and, other phases, beta (j3), gamma (y), &c, and the symbols for carbon are written as follows: aC___ 0C..... yC. In this system, the older term, nascent, is rendered alpha, or active; and we say that the alpha or active state of elements is favorable to chemical union. Heat favors chemical combination principally by converting solids into fluids. The alloys furnish excellent illustrations of this fact, for the metals have no action whilst solid, but when fused, the particles run together and union results; this is not, however, always of the chemical kind, but often results from capillary attraction. Certain acids, as the silicic (sand), phosphoric and boracic, act feebly, except at high temperatures, when they CAUSES WHICH RETARD CHEMICAL AFFINITY. 131 become very energetic. In such cases, it is apparent that heat assists chemical action by diminishing the cohesive form. But there are instances where its action is entirely different. For, if we apply heat to some gaseous mixtures (as oxygen and hydro- gen), they unite, and often with explosive violence; in such cases, there is little if any influence exercised on the cohesion of the bodies, and the operation can only be accounted for by reference to the molecular disturbance produced in the mixture, and which is propagated with great rapidity. For, as heat is known to dis- turb the electrical state of many substances, it cannot be doubted that it may act, in this manner, upon a mixture of gases. The electrical state of the matter exerts a complete control over chemical union. This is apparent in the galvanic battery, where, by establishing an electrical state more powerful than that existing between the atoms of a compound, they are dis- severed. It is also apparent in the union produced between gaseous mixtures by the electric spark, which, by disturbing the electrical equilibrium of the mixture, often induces union with explosive violence. Light exerts considerable action, both of union and decompo- sition, among the molecules of matter. In the vegetable, this is most apparent; here it effects the decomposition of carbonic acid gas, and the union of carbon with water, actions which are re- markably different from those of common chemical affinity. A striking instance of its action is in the conversion of inactive, or (3 chlorine into o chlorine, by exposure to the sun's rays for a few seconds. Causes which retard Chemical Action.—The principal causes which impede or arrest chemical action are cohesion, elasticity, and the state of combination. Cohesion acts continually to impede chemical union, where it is considerable, by hindering the apposition of the mole- cules, between which only the force acts. The hammering, or condensing a metal by pressure, by which we increase the cohe- sive force between the atoms, renders the substance less destructi- ble than when porous. Heat, on the other hand, by overcoming the cohesion, nearly always assists chemical union, and fre- quently originates it between bodies which exercise little affinity towards each other. There is another and very important action of cohesion in mo- difying chemical union. It has been said that, as a general rule, the bodies highest on the electro-negative list have the greatest affinity for those highest on the electro-positive class, but this principle is perverted in many cases by the influence of cohesion. For, the two bodies which form a solid compound will unite, although they may be low in the list, in preference to those which 132 CAUSES WHICH RETARD CHEMICAL AFFINITY. are high, but form a fluid by their union. Hence, our measure of affinity is influenced by cohesion as well as the act of chemical union. Elasticity.—A gas is an elastic body, and possesses little chemical activity as compared to a fluid. However great the affinities between substances may be, if one or both are gaseous, they will seldom unite, except under the influence of some dis- turbing force, as heat, light, or electricity. Again, in decomposi- tions, the substances which are elastic will be produced in pre- ference to those which are fluid. So that elasticity, like cohesion, acts by disturbing the affinities of substances as well as by im- peding chemical union. Coldness, by assisting cohesion, diminishes chemical action. This is particularly the case in organic compounds, and in plants and animals. In them the union occurs between numerous atoms, and the product often depends upon the degree of temperature. Fermentations will not take place at temperatures below 40° F., and specific kinds of fermentation arise as we increase the heat, although the bodies present remain the same. State of Combination.—The chemical force is called an elec- tive force, because one body prefers certain others out of a num- ber, and does not enter promiscuously into union with them all. But whilst we know the ordinary appetence of one substance for another, it is not right to conceive that it will elect it under all circumstances. Thus oxygen has a great affinity for hydrogen, and their union forms water; but whether this affinity shall be satisfied, depends not only on the form of the bodies, but their state of combination. If the oxygen be already united with a metal, the hydrogen will scarcely remove it, although abstractly its affinity may be greater; on the other hand, if we present both bodies in the state of combination, they may meet and form water. Let the hydrogen be combined with chlorine, this constitutes the chloride of hydrogen ; let the oxygen be in union with iron, this forms oxide of iron. Bring these together, and decomposition occurs ; the affinity of the oxygen and hydrogen, though they are combined, determines the destruction of the chloride of hydrogen and oxide of iron ; being now separated from their combinations, they unite and form water, the two other substances also com- bining to form chloride of iron. Thus the state of combination influences the play of affinity. The second case presents us with an illustration of double de- composition, and is to be distinguished from single decomposition where the affinity is not controlled, as in the "following case of chloride of copper and iron. The latter metal has a great affinity for chlorine, and finds it already united with copper in the chloride of copper ; this does not destroy its affinity if the salt be in so- TABLES OF AFFINITY. 133 lulion. The iron displaces the copper, which falls in the state of metal, and as this decomposition proceeds, it is ready to unite with every atom of chlorine to form chloride of iron. This is an instance of simple elective affinity, and simple decomposition. In instances of double decomposition, there must be a more powerful chemical affinity between one pair of elements than be- tween the other, or there must be some other disturbing action, as of cohesion or elasticity. Those bodies, which have the greatest action, are said to exhibit divellent affinities, and those which are less active, quiescent affinities; and decomposition will only arise where the divellent affinity much exceeds the quies- cent. Hence the state of combination impedes both simple and com- pound affinities, and is always to be considered in determining the question whether two bodies which are known to have a powerful action on one another under one state of things, shall unite under another phase. Oxygen has the most intense af- finity for potassium, but it cannot, whilst in the gaseous state, decompose the chloride of that metal, nor can it affect this change if combined with hydrogen as water. Tables of Affinity.—The simple law, already expressed, that bodies most intensely negative, unite with those most posi- tive, serves us when the substances are simple and not compound, and in those eases where the disturbing influence of cohesion, &c. does not operate, but in no other cases. Under this restriction, we may prepare tables, exhibiting the preference of oxygen, chlorine, &c, which are curious, but of little praetieal importance. In compounds, containing an acid and base, and called salts, we know one side to be electro-positive, and the other electro- negative ; but cannot determine, by any general law, what the action of another acid or base may be on the salt. In a simple ease, we are aware that soda has an affinity for sulphurie acid, greater than for the nitric, muriatic, acetic, carbonic acids, &c, but this may be modified by very trivial circumstances. A table may be drawn up representing the order of this decomposition for soda, and for sulphuric aeid to show their form; but tables of affinity, as designed by Geoffroy, are of no utility. Soda. Sulphuric Acid. Sulphuric acid, Barytes, Nitric acid, Strontia, Muriatic acid, Potash, Acetic acid, Soda, Carbonic acid. Lime, Magnesia, Oxide o£ silver. 12 134 EQUIVALENTS. The soda or sulphuric acid being alone and without disturb- ance, the order of decomposition given above, will be found cor- rect, but in a compound mixture, it cannot be depended upon. The soda table indicates that the carbonate will be decomposed by the acetic acid, the carbonic acid being driven off—that the acetate in its turn will be decomposed by the muriatic acid, the acetic acid which is volatile escaping: now the muriate may be disturbed by the nitric acid, and this by the sulphuric acid. But if we heat the nitrate of soda in the air, it will lose its acid, and become carbonate of soda. Hence the application of heat de- ranges the chain of affinities. It may be remarked, as a general rule in analysis, that if we mix together a number of active bodies, the order of affinity will not be followed in their combinations, but there will be produced, by preference, compounds which are solid or gaseous. § 2. THE CHEMICAL RELATIONS OF MATTER. There is a striking difference between the union of bodies by the chemical force and under the influence of capillary attraction. If a grain of disulphate of quinine be mixed with a pint of water, every part will be rendered bitter; the medicine will be diffused equally throughout the whole. This will be found true, what- ever the quantity of soluble substance, there being but one limit to solubility, and that is the quantity which can be suspended at a given temperature. But in the case of chemical union, if we add one grain of sulphuric acid to an ounce of potash, the acid will unite with about a grain of this body, leaving the remainder untouched. It will not be found throughout the mass as free sulphuric acid, but as a new substance, sulphate of potash, with properties widely different from the free acid or base. Before we can affect the whole of the potash, a weighed amount of acid must be employed, and we find that their complete union never occurs except in a determinate quantity. If any other acid be used, the quantity will differ before we render the potash neutral. The patient study of the amounts necessary to neutralize, saturate or combine with given bodies, has put us in possession of the equivalent weights, or combining proportions of substances. These numbers also represent the atomic weights, according to the hypothesis that bodies consist of definite atoms. We might prepare a table of the combining weights of bodies, in grains or pounds, for practical purposes, but for the conveni- ence of theory, it is preferable to adopt a standard. Some prefer hydrogen, which is the lightest body in nature for unity; others, THE ELEMENTARY BODIES. 135 for the purpose of facilitating analytical calculations, select oxygen, the most active body, as 100. The former is termed the hydro- gen scale, the latter the oxygen scale. The proportions in which the atoms of bodies combine, are fixed and unalterable; they are true for those which, like the metals and certain gases, have never been decomposed, and are called elementary, and those which are well known to consist of two or more elements in combination. Indeed, if we know the equivalent or combining proportional of the elements of which any compound, as an acid or base, is formed, we also know that of the compound—for it is the sum of the equivalents of the number of atoms present. Thus, sulphuric acid is known to consist of one equivalent or atom of sulphur, the proportional of which is 16.12, and three atoms of oxygen; the number for oxygen being 8, three times will be 24 ; hence the proportional for.the acid is 40.12, which represents its combining number in every case. Again, where union occurs between two salts, or in organic bodies which contain many atoms, it follows the foregoing simple law. Therefore, all that is necessary is a table of the equivalents of the elementary bodies, the rest being deduced by calculation. For convenience, it is customary to employ the initial letters of the English or Latin names of the elementary bodies, instead of writing them in full. These are called the symbols, and when a compound is designated, the symbolical letters are connected by a + sign to indicate their union. Table of the Elementary Bodies of Chemistry asd Combining Proportions according to the I Scales. Names of the elements. Non-metallic and electro- negative bodies. Oxygen Fluorine . Chlorine Bromine Iodine Sulphur Selenium . Tellurium Nitrogen Phosphorus 1 Silicon Boron Carbon Hydrogen . Equiva Symbol. Hydrogen sea 0. 8.01 F. 18.74 CI. 35.47 Br. 78.39 I. . 126.6 S. 16.12 Se. 39.63 Te. 64.25 N. . 14.0 P. . 31.44 Si. 22.22 B. . 10.91 C. . . 6.08 H. . . 1.00 with their Symbols [zdrogen and oxygen ent weights. e. Oxygen scale. 100.0 233.8 442.6 978.3 1579.5 201.17 494.6 801.76 175.0 392.3 277.3 136.2 76.0 12.5 136 THE ELEMENTARY BODIES. Equivalent weights. ______________________» Names of the elements. Metallic, and electro-positive Symbol. Hydrogen scale. Oxygen scale. elements. Potassium . . K. . . 39.26 . . 489.9 Sodium . Ka. . . 23.31 290.9 Lithium . L. . . 6.44 . . 80.3 Barium . . Ba. . . 68.66 . . 856.9 Strontium . . Si. . . 43.85 . . 547.3 Calcium . Ca. . . 20.52 . . 256.0 Magnesium . . Mg. . . 12.69 . . 158.3 Aluminum . . Al. . . 13.7 . . 171.2 Glucinum . . G. . . 26.54 . . 331.3 Yttrium . Y. . . 32.25 402.5 Zirconium . . Z. . . 33.67 . . 420.2 Thorium . Tb. . . 59.83 . . 744.9 Cerium . Ce. . . 46.05 . . 574.7 Lanthanum La. . — — Didymium . D. . .— — Erbium . E. . — — Terbium . Tr. . — — Manganess . Mn. . 27.72 345.9 Iron . Fe. . 27.18 . 339.2 ' Cobah . Co. . 29.57 . 369.0 Nickel . Ni. . . 29.62 . 369.7 Zinc . . Zn. . . 32.31 . 403.2 Cadmium . Cd. . . 55.83 . . 696.8 Lead . . Pb. . . 103.73 . 1294.5 Tin . . Sn. . 58.92 . 735.29 Bismuth . Bi. . . 71.10 . 886.9 Copper . Ca. . . 31.71 . . 395.7 Uranium . U. . . 217.26 . 2711.4 Mercury 1 • Hg. . . 101.43 . . 1264.8 Silver . . • Ag. . . 10S.3 . 1351.6 Palladium . Pd. . . 53.36 . 665.9 Rhodium . R. . 52.20 . 651.4 Iridium . Ir. . . 98.84 . . 1233.5 Platinum . Pt. . . 98.84 . . 1233.5 Gold . . Au. . . 199.21 . . 2486.0 Osmium . Os. . . 99.72 . 1244.5 Titanium . Ti. . . 24.33 . . 303.66 Tantatum . Ta. . . 184.90 . . 2307.4 Tungsten . W. . . 94.80 . . 1183.0 Molybdenui n . Mo. . . 47.96 . . 598.5 Vanadium . V. . . 68.66 . . 856.9 Chromium . Cr. . . 28.19 . . 351.8 Antimony 1 . Sb. . . 129.2 . 1612.9 Arsenic ? . As. . . 75.34 . . 940.1 The substances in this table marked with ? have their com- bining proportionals in some doubt. Several bodies placed in the list of metals are also electro-negative in their characters, espe- cially arsenic and antimony, whilst hydrogen and nitrogen possess THE ATOMIC THEORY. 137 the properties of metals. The substances printed in Italics are of particular interest to the physician. From the above enumeration, it will appear that there are fifty-eight elements known to chemists, but some three or four of these are in doubt; the greater number are also mineralogical curiosities, having little interest and of no known utility. Forty- four are metallic and more or less electro-positive, whilst fourteen, or, according to some authors, ten, are non-metallic and powerfully electro-negative, uniting with most of the former class. Three classes of bodies result from this union, respectively called—acids, bases and salts. Acids are usually of a sour taste, often caustic; they change vegetable blues to red, are electro- negative, and combine with bases to form the common salts. Bases are not distinguished by the foregoing characters; they are also electro-positive, and combine with acids. Salts are the pro- ducts of the union of acids with bases, usually, but there is a class of substances, of which common table salt is an instance, which are very similar to the common salts, but contain neither an acid nor base; such are termed haloid salts. They are com- pounds of the haloid electro-negative substances, chlorine, bro- mine, iodine, fluorine, cyanogen, &c, with metals. We do not, however, confine the term acid to bodies which are sour, and red- den blue infusions, for many have neither of these qualities, but their essential feature is the ability to combine with a base. The Atomic Theory.—The student will now be prepared to understand the beautiful speculation of Dr. Dalton, called the atomic theory. According to this view of matter, it consists of indivisible minute atoms, among which union takes place. These are supposed to be spheroidal and unchangeable, with a fixed weight, and probably of uniform size. Being unalterable and of an invariable weight, called the atomic weight, union can only occur atom to atom and in fixed weight. The equivalents given in the table are supposed to represent the relative densities of the atoms of different elements. Hence it will appear a necessary conse- quence of this view, that compounds should have an equivalent which is the sum of their atomic weights. Another consequence of this theory is, that bodies combine atom to atom, or one atom to two, three, four, or more of another sub- stance, or that the weight of any component must be a simple mul- tiple of its equivalent or atomic number. The atomic weight of oxygen is usually taken as 8, and this body is present in dif- ferent compounds in the weight of 16, 24, 32, 40, 48, but never in other proportions. These, it will appear, are simple multiples of 8, and represent 2, 3, 4, 5, 6 atoms. A second series, in which two atoms of a body combine with three, five or seven of another, is also possible, and such compounds are known in chemistry. 138 SYMBOLS. The laws of combination, therefore, flow from the atomic theory, and are remarkably simple for inorganic or mineral matter, in which there are seldom more than five to seven atoms of any element present. There are but two series in which bodies unite. 1st. 1 atom of A to 1, 2, 3, 4, 5, 6, 7 atoms of B. 2d. 2 atoms of A to 1, 2, 3, 4, 5, 6, 7 atoms of B. The fixedness of the weight, and the equivalent of the com- pound body, result from the hypothesis that the indivisible atoms have certain weights. In organic compounds, these simple numbers do not obtain, for some bodies have several hundred atoms, but with the excep- tion of complexity, there is nothing in their history opposed to the atomic theory. Symbols for Compound Bodies.—The abbreviations employed in treating of the elements, are particularly useful in writing the composition of compound and organic substances. For this purpose several styles are employed. When the substance consists of two elements, or is of a binary form, the electro-positive body (or metal M) is placed on the left hand, and the electro-negative (or radical R) is placed to the right hand. Thus: M. R. If the metal be copper, and the radical oxygen, it is written CuO. In these cases, one atom is always indicated by the capital stand- ing alone ; if there be more, the number must be placed on the right and below, thus : Cu20. In any compound, all the elements present are introduced, with figures to represent the number of each; the elements being placed from the right to the left hand, in the order of their electro-posi- tive power. The following is the formula for starch : . C12H.oOlO- The parenthesis is occasionally used to distinguish the state in which some of the elements are united. In the annexed for- mula, the substance in the parenthesis has the relation of a compound base to that placed exteriorly : (C4H5)0. It represents the structure of ether, which, according to this plan, consists of two distinct parts, a compound base C4H5 = ethyle, united with oxygen, which is neither the only body with which it forms compounds, nor is it immovable from its position. A modification of this is employed when the compound base ex- ists in several proportions : 2(C4H5) and 3(C4HJ; THE STRUCTURE OF FORMULAS. 139 the numbers 2 and 3 here do not affect any term of the formula, except that in the parenthesis. A comma is employed to designate the combination of two compound bodies. Thus: (C4H3)0,HO indicates that the HO (hydrogen and oxygen, or water), is united with the compound base more feebly than the O or oxygen. This formula represents alcohol, or the hydrated oxide of ethyle. If the affinity between the compounds be feeble, we use -f- (plus) between the terms, as S03+HO. A vinculum or band is employed to indicate that the symbol does not belong to the table of elements, but to an organic com- pound. Thus T P7 c represent three well known organic bodies. The T being tartaric acid, the Pr proteine, and the C citric acid. Sometimes we find the same term placed before and after a formula. Thus, 3'HO), P05 CaO , HO. In the first, the HO (water) acts the part of a base to the POs, which is phosphoric acid; in the second, the HO acts the part of an acid to the CaO or lime. The sign = indicates equality: thus, C4H602 = (C4H5)0 , HO indicates that the first is identical with the second, which is the theoretical or rational formula. NOMENCLATURE. Nothing has served to advance the science of chemistry more than an accurate nomenclature. The names of compounds are formed by rule, and not at the option of the discoverer, and make known to every one, the bodies present, and the number of atoms of each ingredient. The laws of nomenclature are exceedingly simple, and are as follows: 1. The names of elementary bodies are those by which the substances are best known, as Copper, Iron, Lead; but when a new body is discovered belonging to this class, it is to be called by a name compounded of two Greek or Latin words, represent- ing its most remarkable properties, or by the name of the mineral from which it is procured. It is wrong to call the new element by the name of a man or country, for, in this way, no informa- 140 THE LAWS OF NOMENCLATURE. lion is imparted, of chemical interest. The most important bodies of chemistry are well named; thus oxygen, formed from Greek words signifying / generate an acid, indicates that, according to the views of the author, it is the principle of acidification. Hy drogen comes from I form water, because it exists in that fluid. 2d. In a substance containing two elements, (binary,) the names of both are introduced; the electro-negative body being written first, and terminating in ide, if it be a base; or, if the com- bination be of two metallic bodies, the most active is put first, and ends in uret. Thus, a basic compound of oxygen with iron, is termed an oxide of iron. Oxygen becomes Oxide Chlorine " Chloride Iodine " Iodide Bromine " Bromide Sulphur " Sulphide Cyanogen " Cyanide. Sulphur is frequently written sulphuret; so is selenium, se/e- nuret; phosphorus, phosphuret; but the terminations should be in ide, as suggested by Dr. Hare. Hydrogen, Carbon, Arsenic, and Antimony, are the principal metallic bodies which combine with other metals, and are ren- dered— Carbon — Carburet Arsenic — Arseniuret Antimony — Antimonuret Hydrogen — Hyduret Nitrogen — Nituret. Compounds of mercury with metals are termed amalgams; com- binations of the common metals alloys. 3d. If the amount of the electro-negative body be more than one atom, and the substance basic, it is designated by the Greek words,protos, first; deuteros, second; tritos, third; as Protoxide of iron, or first oxide of iron, FeO. Deutoxide of manganese, or second oxide of manganese, MnO?. Tritoxide of iron, or third oxide of iron, Fe03. The contraction of the numerals follows the ordinary laws of composition. We write Deutiodide—Tritochloride—Protosulphuret. But, in many cases, it is not certain that the compound con- tains two, three, or more atoms of the electro-negative ; and the comparative terms, per for the highest amount, and sub for the THE LAWS OF NOMENCLATURE. 141 lowest, are used. We have, therefore, the per-oxide, per-chloride, and sub-oxide, sub-chloride. Sesqui (one and a half) is likewise employed to signify that the atoms of the electro-negative bear the ratio of U to 1 of the metal, or of 3 to 2. We have the sesqui-oxide of iron, Fe203; sesqui-sulphuret of arsenic, As2S3. It is to be observed that this law is often violated, and the Latin terms bis, twice; ter, three times, &c, employed in the place of the Greek words. Thus Binoxide is often used for Deutoxide Bichloride " Deutochloride Teroxide " Tritoxide Terchloride " Tritochloride. 4th. When the number of atoms of the metal are in excess over the electro-negative, it is indicated by employing the terms dis, twice; tris, three times; and thus, the Dioxide of Copper is a body in which there are two atoms of copper united with one of oxygen, or Cu20. 5th. When the binary compound has acid properties, the name of the electro-positive element is terminated in ous or ic. The first is used where there are two acids—the other containing more of the electro-negative; if there be but one acid, it is terminated in ic. Thus sulphur forms two strong acids with oxygen—the one con- taining least oxygen is called Sulphurous acid; the second, Sul- phuric acid. We have also Nitrous and Nitric acids; Phos- phorous and Phosphoric acids. Sometimes more than two acids are formed by the union of one electro-positive with an electro-negative body, then the com- parative terms hypo below, and hyper above, are employed. We have a hypo-sulphurous acid, which, as the name indicates, contains less oxygen than the sulphurous acid. We have also the hypermanganic acid, and hyperchloric acid, which severally contain more of the electro-negative body (oxygen) than the man- ganic and chloric acids. Five sets of acids may, therefore, exist: A hypo acid in ous, as the hyposulphurous acid, S202. A hypo acid in ic, as the hyposulphuric acid, S205. An acid in ous, as the nitrous acid, N04. An acid in ic, as the phosphoric acid, P03. An acid in hyper, as the hyperchloric acid, C107. 6th. The compound formed by an acid and base is called a salt. But as there are five acids, there will be five series of salts, and these are distinguished by terminating the acids of ous in ite, and the acids of ic in ate. In writiug the name of the salt, if 142 THE LAWS OF NOMENCLATURE. there be one atom of either component, the acid with its appro- priate termination is placed first, and the metal second, if it be a protoxide. Thus: Sulphate of iron means a compound of sul- phuric acid with protoxide of iron, for there is no such substance as the sulphate of metallic iron. The acids of salts are, therefore, written— Hyposulphite Hyposulpha/e NitrcVe Phosphate Hyperchlora/e. The salts being termed Hyposulphite of Soda, Nitrite of Pot- ash, Phosphate of Iron, Hyperchforite of Potash, $c. Some authors write protosulphate, protophosphate, to indicate that it is the protoxide of the metal which is combined with one atom of the acid. Others, nitrate of the protoxide; but this is not necessary. 7th. If there be more than one atom of the acid, the Latin terms bis, twice; tris, three times, &c, are employed, as Bisul- phate of potash, Bicarbonate of soda, &c. In these cases, the compound is called a supersalt, to distinguish it from the neutral salt in which the acid and base are combined equally, and the subsalt in which the base preponderates. But it is to be remarked, that many acids, especially those of organic chemistry, are polybasic, or have the power of saturating two or more atoms of base. Such are phosphoric, tartaric, citric, and other acids. Those which saturate two atoms, are called bibasic, those which can combine with three atoms, as phosphoric acid, tribasic. 8th. If the oxide of the base be not a protoxide, but a deutox- ide, tritoxide, &c, the terms deutos, tritos, sesqui, &c, are placed before the name of the acid. As Deutosulphate — Tritosulphate Sesquisulphate — Persulphate. Compounds of this kind are not, however, numerous, the pro- toxide being the active base in most cases. Failure of the Nomenclature.—The foregoing nomenclature is all that can be wished for most inorganic compounds, which seldom contain more than five elements, or unite in proportions exceeding five to seven atoms. We are enabled, by means of it, to attain the chemical history of the substance by inspection. Take the nitrate of lead as an illustration ; we discover from the word nitrate that the element nitrogen is the electro-positive constituent of the acid, and that it is* the most oxygenized acid from the ter- mination in ate, or that the nitric acid is present; the other terra FORMULAS FOR ORGANIC BODIES. 143 also informs us that the base is a protoxide of lead, for otherwise it would be called the deutoxide or deutoniirate. But in organic compounds, which contain many hundred atoms, this nomenclature is altogether inapplicable. Fibrine, an import- ant component of plants, and a constituent of blood has the for- mula C4Sn,H36n,N6n,OI40-f-SP or 1042 atoms; it would be impos- sible to describe this by any name which included the elements and their number of atoms. In such cases, a contraction is used for a part of the formula, wherever it can be shown that the elements are not united by the same force. In the above, the -f- sign indi- cates that the P and S (phosphorus and sulphur) are feebly com- bined with the first part of the formula. By distinct researches, the first part is found to unite with other substances in the number of atoms given above, and also in one-tenth these numbers ; or that there is a body consisting of C48,H36,N6,0I4, and this unites with oxygen, chlorine, &c, or 10 times this, or fifteen or other proportions of it combine with sulphur, &c, hence it is called the radical of the compound, and to distinguish it from the ele- mentary radicals, it is called the compound radical, and is fur- nished with a distinct name, proteine, and symbol Pr. The introduction of compound radicals into organic chemistry has done more to advance the science than any other circumstance, by enabling us to trace intimate connections between bodies other- wise widely separated in properties, and in some cases enabling us to produce organic changes of great interest. The compound radi- cals of most interesting bodies are now known, and they are all furnished with symbols, which greatly facilitates the writing and nomenclature of animal and vegetable chemistry. Thus there is no apparent connection between albumen, cheese and fibrine, ex- cept that they are nutritious bodies; if we write out their entire formula, they present great complexity ; but having discovered that the compound radical proteine is present in all, and by analysis that they also contain sulphur or phosphorus in different proportions, we write their formulas as follows: Albumen = 10Pr+S3P Fibrine = lOPr+SP Caseine = lOPr+S and see at once their points of connection and distinction. We discern that all contain 10 atoms of the organic, or compound radical Pr (proteine = C48,H36,014,N6) with specific quantities of sulphur and phosphorus. Therefore in organic chemistry, we do not pretend to employ the nomenclature given for minerals ; but whenever the oppor- tunity occurs, employ a contraction to express a compound body, and call it the compound radical. But if this unites with one, 144 COMBINATION BY VOLUMES. two, or three atoms of an electro-negative, as oxygen, chlorine, iodine, cyanogen, &c, we employ the ordinary terms for bases, and call the substance a protoxide, protochloride, deutoxide, deu- tiodide or tritoxide. Thus we have the deutoxide and tritoxide of proteine. The oxide of ethyle. The nomenclature also fails in isomeric compounds. Thus we may have two or more distinct bodies produced with the same elements in the same proportions; but the above laws direct that we should in the name unite the designation of each element with the number of atoms of each, and thus no difference will appear in the name. Four atoms may be grouped in different ways, thus: A B C -f D, A B + C D; and this may materially affect the sensible properties. In such cases, the method of symbols is the only means of making the difference appear in writing. This subject has already been alluded to in the remarks on Allotropism. Other Theories of Combination.—In the foregoing, it has been assumed that bodies unite atom to atom, but it is true in the case of gases and the vapors of some bodies to assume that they combine by volumes; or that combination results from the mix- ture of substances in certain weights which have no relation to their ultimate parts or atoms. Hence we often find it stated, that the combining volume of a gas is a given quantity, and that it unites in that number or its multiple only. Observation has determined that the combining volume differs for different gases, according to the following table: TABLE OF THE COMBINING VOLUMES OF GASES AND VAPORS, THAT OF HYDROGEN BEING 100. Gas or vapor. Combining volume. Hydrogen.....100 Nitrogen......100 Chlorine......100 Iodine...... 100 Bromine ----.. 100 Carbon (hypothetical) - - - 100 Mercury......200 Oxygen......50 Phosphorus vapor - - . . 25 Arsenic " 25 Sulphur « 16t6Q According to this theory, hydrogen, nitrogen, &c, unite only in quantities representing a volume of 100, 200, 300, 400, and, as we know that these substances combine according to their atomic weights or equivalents, we would infer that the weight of these volumes would be the same as the atomic weights; RESULTS of the chemical force. 145 and such is found to be the case in most instances. This view of combination, therefore, indirectly sustains the atomic theory. The second theory, that bodies combine in fixed weights, called their equivalents or combining numbers, has already been explained, and it differs in nothing from the laws of combination detailed in the preceding pages, except that these weights are supposed to have no relations to the atoms. In the present day, we speak of the union of one atom of sulphur with two atoms of oxygen, which involves a recognition of the atomic theory; for- merly it "would have been said that one prime or combining weight of sulphur united with twice the equivalent of oxygen, which does not indicate an approval of the atomic theory. The numbers are also often written thus: 14 sulphur + 16 oxygen, which does not lead us to infer that oxygen unites in any other number, and therefore is merely an experimental fact distinct from any hypothesis. In the present day, the writings of chemists are all based on the atomic hypothesis, whether it be admitted or otherwise, for without this, the system of symbols would be useless: C2H206 are terms indicating that there are 2, 4, or 6 definite amounts of carbon, hydrogen, and oxygen. If we would write on the view that the compound takes place in given weights only, we should have to express the above differently, as carbon 12 parts -f- hy- drogen 4 parts + oxygen 48 parts, which gives no information of other compounds of these elements. § 3. RESULTS OF THE CHEMICAL FORCE. The chemical force is essentially a molecular force; it acts by setting in motion the atoms or ultimate particles of bodies, and arranging them in a new order. Whether heat, light, &c, be evolved during this process, will be dependent on the resistance and other properties of the matter and ether, and does not flow as a necessary consequence of the operations of this force. Increase of density, the elastic state and other physical changes, are also of a partial nature, and peculiar to certain substances. But a new molecular arrangement is a necessary consequence of chemical action. We do not pretend to know what imparts to substances the sweet, sour, or neutral taste, but may infer with some plausi- bility that these are consequences of the grouping of the atoms. We know that there exists a tasteless and sapid variety of sugar, a soluble and insoluble form of gum, and in both instances the kind and number of atoms are similar; the difference between them being probably due to dissimilarity of grouping, under the in- fluence of the chemical force. So, again, we know that the mole- 13 146 CRYSTALLIZATION. cular arrangements called crystals, sometimes have their figures changed by the presence or absence of heat during their aggrega- tion. The three most remarkable molecular effects of the chemical force, are Determinate crystalline figure ; The production of groups and types ; Catalysis. CRYSTALLIZATION. Those solids which have regular geometrical figures are called crystals, to distinguish them from mere shapeless, or amorphous masses. The crystals may be separate, and their facets and angles apparent, or confused together, or hidden as in ice and several metals. In the latter dases, they may be separated by breaking or cleaving the crystalline mass in the direction of its facets. The crystals, when examined more attentively, are found to be sym- metrical in all their parts, so that the minutest portion as well as the mass presents a certain figure. The crystal is characteristic of the elements present, or of cer- tain groups of elements, and the nature of their union. Hence, in mineralogy, the figure of a substance enables us in many cases to determine its components. To obtain crystals, it is necessary that the solution in which the chemical changes have transpired, be evaporated, or the solv- ent removed, so that the atoms may obey the force which de- termines their aggregation. Otherwise they are solicited by the capillary force, and diffuse themselves in the liquid, producing a solution. Fine crystals are procured by slow evaporation; when- ever they are hurriedly formed, they are imperfect. Besides eva- poration, crystals are formed by long-continued galvanic action, by cooling from fusion or hot solutions, or by the refrigeration of some vapors. The finest crystals in nature are produced by long- continued electrical currents. In determining the form of a crystal, we are not so much in- fluenced by the number of faces as by the angles which they form with one another, and the relations of their axes. Every crystal has three or more axes, one of which is a straight line, passing from above to the lower side, and called the principal axis; and the others, passing from side to side, are called the secondary axes. The figure of the crystal depends upon the lengths of these axes and their angle to one another. There are six systems of crystals recognized in the works on crystallography. CRYSTALLINE SYSTEMS. 147 1. The regular system. 2. The square prismatic system. 3. The right prismatic system. 4. The oblique prismatic system. 5. The doubly oblique prismatic system. 6. The rhombohedral system. 1st. The Regular System.—In this class there are three equal axes, all of which are at right angles to each other. It contains (Fig. 40) the cube, 1; the regular octahedron, 2; and the rhombic dodecahedron, 3. Fig. 40. The letters a—a, in the above figures, represent the points between which the three axes pass. These are very common forms of crystal; the diamond, most metals, alum, fluor spar, com- mon salt and the garnet, furnish instances. 2d. The Square Prismatic System.—The principal or per- pendicular axis a—a, is in this class longer than the other two b—b, which are equal; but the whole are at right angles to each other. The most important forms, are: 1, the right square prism., with the secondary axes b—b, passing from face to face; 2, the right square prism, with the secondary axes passing between the lateral angles; 3, the right square based octahedron, with the axes as in 1; 4, the right square based octahedron, with the secondary axes, as in 2. Fig. 41. 12 3 4 148 CRYSTALLINE SYSTEMS. The zircon, yellow prussiate of potash and native oxide of tin, furnish examples. 3d. The Right Prismatic System.—In this class, there are three axes of unequal lengths a—a, b—b, c—c, but placed at right angles to each other. The chief forms are : the right rectangu- lar prism, 1, Fig. 42; 2, the right rhombic prism ; 3, the right rectangular-based octahedron; and, 4, the right rhombic-based octahedron. Nitrate and sulphate of potash, sulphur crystallized at a low heat, and arsenical sulphuret of iron, furnish illustrations of this system. 4th. The Oblique Prismatic System.—In this class, there are three axes, all of which are sometimes unequal. The two lateral or secondary axes, b—b, c—c, are at right angles to one another, whilst the primary axis a—a is perpendicular to one of them, and oblique to the other. The four figures of Fig. 43 belong to this system: 1 is the oblique rectangular prism; 2, the oblique rhombic prism; 3, the oblique rectangular-based octahedron; 4, the oblique rhombic-based octahedron. Fig. 43. 12 3 4 There are numerous illustrations of this system; the carbonate, CRYSTALLINE SYSTEMS. 149 sulphate and phosphate of soda, biborate of soda, sulphate of iron, and sulphur crystallized by fusion, offer instances. 5th. The Doubly Oblique Prismatic System.—The charac- teristics of this system are, the obliquity of all the three axes, and their difference in length. The crystals have the appearance of great irregularity in consequence of this want of uniformity. The figure represents four species: 1 is the doubly oblique prism, with the secondary axes b—b, c—c, proceeding from the sides; 2, another form of doubly oblique prism, with the secon- dary axes proceeding from the angles; 3 and 4 are correspond- ing doubly oblique octahedra. Fig. 44. 1 2 3 4 a- a, To this system belong the crystals of sulphate of copper or blue vitriol, quadroxalate of potash, and nitrate of bismuth. 6th. The Rhombohedral System.—The characteristics of this class are striking; there are four axes, the three lateral or secondary of which are equal in the same plane, and form an angle of 60° with each other; the fourth, or principal axis, is unequal and per- pendicular to the plane of the other three. To this class belong: 1, the regular six-sided prism; 2, the quartz dodecahedron, or dodecahedron with regular triangular facets; 3, the rhombohe- dron; 4, the triangular faced dodecahedron, with scalene an- gles. Fig. 45. 12 3 4 13* 150 SECONDARY CRYSTALLINE FORMS. This is a very numerous and important system ; quartz, arsenic, antimony, nitrate of soda, ice and calcareous spar, furnish familiar illustrations. Causes disturbing the figure of the Crystal.—In the fore- going illustrations, we have presented the perfect forms belonging to each system. To obtain them in this state of perfection, the deposition of the solid must be very uniform, and it is found that a mild and equable temperature with darkness is conducive to this end. If the density of the solution in which they are forming, or the temperature of its parts, be variable, an excess of deposit will take place on certain facets, and thus the figure may be made to differ considerably from the primary form. But, however complex, the secondary or derived crystal will belong to the same system, the relations of the axes in direction and length being maintained in the case of every departure from the primary. The figure (46) represents a common case of irregular deposition, by which the cube 1 has its angles bevelled or replaced, which action becoming more considerable, converts it into the dodecahedron with rhomboidal facets 2, and becoming excessive, changes it into the octahedron with truncated angles 3. It will be perceived that all of these belong to the regular system of crystallization, and the cube may be often derived by cleavage from the modified solid. Fig. 46. ] 2 3 The series of changes may go so far as to develope only half the crystal, so that a half-sided or hemihedral crystal is produced, the deposition being on alternate facets, instead of taking place on every side. The tetrahedron is in this way derived from the regular octahedron, as represented in the figure (47), in which 1 Fig. 47. 1 2 3 DIMORPHISM AND ISOMORPHISM. 151 represents a modified octahedron, four of the sides being much more developed than the other four; 2 indicates a still further inequality of deposition; and 3 shows the resulting tetrahedron, in which the four small sides are altogether obliterated. The influence of heat, when considerable, even alters the sys- tem to which the crystal belongs. Thus sulphur is found in two forms, as an octahedron with rhombic base when obtained at low temperatures, and as an oblique prism belonging to the fourth class when procured by fusion. Carbonate of lime crystallized at a hxw temperature has the rhombohedral form, but formed at the boiling point of water, it takes the figure of a right rhombic prism. The diamond and other substances evince the same tendency to crystallize in two incompatible forms. Such bodies are termed dimorphous. It is probable that other agents besides heat have considerable influence in altering the crystalline figure, for we know that phosphorus, which is amorphous, becomes beau- tifully crystallized when exposed to the sun's light. Relation between the Crystalline Form anofthe Constitution and Properties of Bodies.—Isomorphism.—Professor Mitscher- lich was the first to point out the close chemical relation often existing between bodies which have a similar crystalline figure. This is especially true with those belonging to the 2d, 3d, 4th and 5th systems, the first and sixth containing so many objects, that it is difficult to trace any chemical connection amongst them. Hence similarity of figure is not necessarily associated with chemical constitution. The relationship discovered by studying the geometrical forms of a number of bodies, was found to subsist between many sub- stances which were not crystalline. Thus it appeared that the substitution of bromine or iodine in a compound could be effected by chlorine, which is a gaseous substance, and the resulting body still retain its crystalline form. Hence many elementary bodies are termed isomorphous which have no direct relationship in their figure, but produce compounds which have a crystalline simi- larity. The doctrine of isomorphism is not limited to the fact that when two crystals belonging to the 2d, 3d, 4th or 5th systems, are examined and found to agree, we are in a measure assured of a similar constitution, or that if the one contain two or three atoms, the second will likewise contain two or three atoms, but it also establishes a relationship between the elements or com- pounds present, which can be traced through numerous instances; and lastly, it leads us to infer that one isomorphous body may replace in part or in whole, another. Hence the crystal is no longer an absolute test of the substances present, for it may be compounded of every isomorphous substance without change of 152 ISOMORPHOUS FORMS OF ALUM. form. The following is a striking instance: common crystalline alum is a double salt, consisting of four atoms of sulphuric acid with one of potash, one of alumina and twenty-four of water, the formula of which is: KO,S03+A1203,3(S03) +24(HO). In this list of substances, the potash (KO) is isomorphous with soda (NaO), with ammonia (oxide of ammonium AmO), and other bodies; the sulphuric acid (S03) is isomorphous with the chromic acid (Cr03), the selenic acid (Se03), and manganic acid (Mn03); the alumina (AlaOs) is also isomorphous with peroxide of iron (Fe203), sesquioxide of manganese (Mn203), aftd sesquioxide of chrome (Cr203). It will be perceived that the bases and acids enumerated have a similarity of constitution, and experimentally they are known to act as substitutes for one an- other. Hence a crystalline body having the figure, and, in most cases, similar properties to alum, may be made up of any or all the above substances. The sulphuric acid may be in part or entirely substituted by the selenic, manganic or chromic acids, or some of each may be present. So the crystal may contain pot- ash, soda, oxide of ammonium, iron, alumina, manganese, &c, for its bases. The following varieties of alum can be made artificially: Potash alum = KO,S03+Al203,3(S03)+24(HO) Soda alum = NaO.SU34-Al2U3,3(SU3)4-24(HO) Ammonia alum = Am6,SU3-r-Al2U3,3(SU3)-I-24(HO) Iron alum = AmO \ ' S03+Fe203,3(S03)+24HO Chrome alum =^m0 i • S03+Cr203,3(S03)-L.24HO. After this it will appear that there is a close connection between figure and chemical history, and that a crystalline form expresses nothing except that its components belong to a certain group of isomorphous bodies, and are combined according to certain laws. Nor is the number of atoms present always similar in the for- mula given for the alums; it will be seen that the bodies which substitute the alumina (A1203) and sulphuric acid (S03) have a similar structure, namely, two atoms of metallic element to three of oxygen in the first, and one atom of sulphur or other element with three of the electro-negative; but the oxide of ar'tnonia, which replaces and is isomorphous with the potash (KO) and soda (NaO), has the structure NH4,0, and contains six atoms, whilst they have but two each. Other cases of this nature occur; thus one atom chlorine (CI) may be replaced by Mn20; two atoms of lime (CaO), or the compound (CaO,HO) hydrate of lime containing four atoms, are isomorphous, and capable of taking ISOMORPHOUS GROUPS. 153 the place of one equivalent of potash (KO) in a crystal, or of oxide of ammonia, which contains six atoms. Another peculiarity of isomorphism is worthy of consideration, and calculated to impress the conviction that the manner and number in which the electro-positive and electro-negative bodies of a compound unite, have much to do with the resulting figure, al- though it does not afford a complete explanation of the mystery. There are a few cases of combination in the proportion of one atom of an electro-negative to seven of an electro-positive ele- ment; they offer a striking group, and are all isomorphous. The perchloric acid (C107); periodic acid (I07) ; and permanganic acid (Mn207) belong to this remarkable family. Iron and some other metals form two basic compounds ; in one, the metal is combined with an equivalent (FeO) ; in the other two, atoms of iron unite with three of oxygen (Fe203) ; now these bases belong to dif- ferent groups, and either with one that has a similar structure. Thus FeO is associated with MgO (magnesia); CuO (oxide of copper); ZnO (oxide of zinc), &c; whilst Fe203 is allied with A1203 (alumina); Cr203 (sesquioxide of chrome), and others of the same kind. In the following table of the most common iso- morphous compounds (acids and bases), this truth will be ren- dered more apparent. TABLE OF ISOMORPHOUS COMPOUNDS. BASES. Names. Symbols. Potash . KO Soda ... NO Oxide of ammonium . AmO Hydrate of lime . CaO,HO Oxide of Silver . . AgO Magnesia . . . MgO Lime (the rhombohedral form) . . . CaO Protoxide of iron . . FeO " r^" manganese MnO " <& zinc . ZnO " t\ cobalt . CoO " ,^; nickel . NiO " " copper . CuO " ** cadmium . CdO The protoxide of lead may also belong to this group PbO ip 1. Remarks. Potash and oxide of ammonium are truly isomorphous, not only in their compounds, but in their action as salts towards other saline bodies, > forming double salts, which are also isomorphous. Oxide of silver is as- sociated with soda to a considerable extent. The hydrate of lime is re- lated to potash. up 2. These bases form salts, which, when in the same degree of satura- tion, and with the same amount of >■ water of crystallization, have the same figure. The sulphates also combine with sulphate of potash, and form double isomorphous salts. 154 Names. Baryta Strontia Lime Oxide of lead ISOMORPHOUS GROUPS. Group 3. Symbols. . BaO . SrO . CaO . PbO Fe„On ALO, Remarks. This is a highly natural group, these oxides occurring frequently as- sociated in minerals. The lime is of the form in which it occurs in arra- gonite. Group 4. Peroxide of iron . . r e2v _ Sesquioxide of manganese Mn203 Sesquioxide of chrome Cro0, Alumina These are all sesquioxides and iso- morphous, replacing one another in whole or in part in the varieties of J alum and other bodies. Sulphuric acid Telluric acid Selenic acid Chromic acid Manganic acid S03 Te03 Se03 Cr03 MnO, Group 1. These acids contain the same pro- portion of base and oxygen, and from > numerous salts which, when con- taining the same amount of water of crystallization, are isomorphous. Phosphoric acid Arsenic acid . Perchloric acid Permanganic acid Periodic acid . PO- AsOs C107 Mn20, 10, Group 2. ") These acids are both tribasic, and j therefore form three sets of salts, all I of which are perfectly isomorphous; | they are also found replacing one another in minerals, and, according J to Orfila, in the bones of animals. Group 3. }This group produces isomorphous salts; it also presents us with an in- stance where two atoms Mn2 may replace one of the other elements. Arsenious acid Oxide of antimony Stannic acid Titanic acid AsOa SbO, Sn02 TiO„ Group 4. ^1 The relations between arsenic and antimony are very intimate, but their I isomorphism is rare. In this case, the arsenious acid is in its unusual crystalline form. These acids do, however, often replace one another, Group 5. These are found combined in the same crystals in minerals. ISOMORPHOUS ELEMENTS. 155 Group 6. Names. Symbols. Remarks. Sulphuret of antimony . SbO, ) _, Sulphuret of arsenic . . AsO, > The first two are sulPhur acids, Sulphuret of bismuth . Bi203 ) and a11 exist united in minerals. Whilst it is sufficiently apparent from the foregoing, which re- present the cases in which compounds are undoubtedly isomor- phous, that one substance may belong to two groups without possessing dimorphism, yet there is such a striking resemblance apparent in the entire combinations of some elements, that many chemists recognize isomorphous groups among elementary sub- stances. Thus we find chlorine, iodine and fluorine, which have no known connection by form, inasmuch as fluorine has never been obtained in the elementary state, and chlorine is known only as a gas, remarkably similar in the numerous compounds they form with other elements. Thus chlorine, with hydrogen, forms an acrid gaseous body ; so do iodine, bromine and fluorine. "With similar proportions of oxygen, they form analogous acids, and those relating to the metals are similar. But we find chlorine in an isomorphous group with manganese, whilst bromine and fluor- ine have no such affinity. So iron is found associated at one time with magnesia and copper, and at another with alumina and manganese. There are, then, great difficulties in arranging the elements in isomorphous groups; but we are to regard the cases of discrepancy adduced rather as exceptions to a law, than throw away the advantages arising from attempting this classification. For, if we can attain it, the study of chemistry is simplified to an inconceivable extent, as we learn by inspection the chemical history of a family of elementary bodies, with their thousands of compounds, instead of having to investigate each separately, and without means to assist us in remembering them by points of con- nection. In the following table, the elements are placed in groups, according to the views of Prof. Graham. The classification is only to be regarded as an approximation ; but imperfect as it may be, it affords one of the most sublime generalizations in science. Thus we find in the same group phosphorus (P), arsenic (As), antimony, (Sb), and nitrogen (N). Let us take a view of these compounds, to see whefher this connection is intimate ; and first with oxygen, they are as follows :— p As Sb N P,0 a a a PO AsO? « NO (( tt 14 N02 P03 As03 Sb03 N03 (( . It combines with the metals, forming phosphuretsor phos- phides. Tests.—Its great inflammability, waxy appearance, and phos- phorescence are characteristic. Compounds—The phosphuret of calcium is employed to ob- tain phosphuretted hydrogen. Several phosphurets exist in nature, but are not employed in the arts or in medicine. Uses.—It is used in the manufacture of friction matches, and sparingly in medicine. For medicinal purposes, the phosphorus should be dissolved in olive or almond oil in preference to ether, which will volatilize, and leave the inflammable solid in contact with the stomach. It has been used in doses of -J^ to TV°fa THE PHOSPHORIC ACIDS. 203 grain, as a nervous stimulant, in which respect it is said to be supe- rior to any known medicine, in the typhoid states which follow some fevers, in nervous debility, paralysis, and diseases arising from an enfeebled state of the body. * It is said to be a powerful aphrodisiac. It should always be given with a large amount of oil or a demulcent body, for the free element is poisonous. Poisoning.—Two or three grains of common phosphorus are said to have produced death, whilst upwards of sixteen have failed to do so. This discrepancy may arise from the condition of the stomach, and the supervention of vomiting. It produces violent inflammation of the stomach and intestines, with purging and vomiting. The treatment should be directed to the evacuation of the poison, and administration of demulcents to defend the mu- cous membrane of the stomach and intestines. Phosphorus with Oxygen.—It forms four compounds with oxygen, of which the phosphoric acid is the only one of import- ance ; they are as follows :— Oxide of phosphorus=P20 Phosphorous acid=P03 Hypophosphorous acid=PO | Phosphoric acid=P05 Oxide of phosphorus is a yellowish-red powder, which may be formed by burning phosphorus in a stream of oxygen under water.—Hypophosphorous acid is formed when phosphorus is boiled in alkaline solutions ; it is little known___Phosphorous acid is obtained by the slow combustion of phosphorus in air, and is a powerfully deoxydizing agent. Phosphoric Acid. Symbol, as usually written, P05; eq. 71.44. —There are four compounds included under the general name of phosphoric acid. These are:— Anhydrous phosphoric acid P05 Monobasic phosphoric acid (metaplwsphoric acid) P05-(-HO or H-j-P06 Bibasic phosphoric acid (pyrophosphoric acid) P05-)-2HO or H-|-P06-|-HO Tribasic phosphoric acid (common phosphoric acid) PO.-|-3HO or H-|-P06, +2HO. The anhydrous phosphoric acid is obtained by burning phos- phorus in an abundance of air or dry oxygen gas. It is a white solid, possessing an intense affinity for water, with which it hisses; it is converted by this union into the tribasic acid. Once formed, no degree of heat is capable of separating all the water; but at less than 400° F., one of the three atoms is driven off, and the bibasic acid is produced;—a full red heat drives off a second atom, and there is formed the monobasic or glacial phosphoric acid. This retains its structure at the highest temperatures, and is the radical compound; hence we prefer writing the formula of these 204 THE TRIBASIC PHOSPHATES. acids H+P06 and H + P06,HO, &c, to making it H4-P06; 2H -f PO ; 3H+P08, as is done by some authors. The anhydrous body, spoken of above, cannot be called an acid, for it does not combine either with metals or metallic oxides. It is fixed, excepting as respects water. Of the three acids, the tribasic is the common product where water is present, the other two being instable, and convertible by boiling into the tribasic form. But monobasic or pyrophosphoric acid is the active body at high temperatures, and exists in minerals. A solution of either of these acids in combination with soda produces a characteristic precipitate with nitrate of silver. The monobasic phosphate throws down a white gelatinous preci- pitate. The bibasic phosphate is white, and contains two atoms of silver, which may be represented in the formula Ag,P06-f AgO. The tribasic phosphate throws down a canary yellow body, which is, according to the above notation, Ag,P06+2AgO. The phosphates of the body, of animals and of plants, are tribasic, and in the ordinary reactions of chemistry, it is the form which is present. It may be obtained by cautious evaporation in deliques- cent crystals, is intensely sour, reddens litmus, is very soluble in water, and is not caustic. In very large amounts, and in the con- centrated state, it is said to be a corrosive poison, and is to be treated by the same means as nitric acid. It forms three series of salts, one in which the hydrogen only is replaced by another metal, another in which an atom of HO is also replaced, and a third in whicK^the hydrogen and both atoms of water are replaced. The bases may be different in these cases. The salts will be as follows:— M,P06+2HO M,P06+MO,HO M,P06+2MO. In which M represents a metal or compound electro-positive radi- cal, as ammonium. Soda presents instances of these three forms. The tribasic phosphate of soda with alkaline reactionNa,P06-|-2NaO The neutral tribasic phosphate=Na,P06-(-NaO-|-HO The tribasic phosphate with acid reaction=Na,P06+2HO. All these precipitate the nitrate of silver of a canary yellow color. These salts are remarkable, and closely connected with the functions of the human body. One of them plays the part of an acid, and is found in the gastric juice, giving to that fluid acidity ; and the alkaline phosphate is present in the saliva, blood, chyle and lymph, and endows these and other fluids of the body with alkalescency. Uses.—The tribasic phosphoric acid is the only one used; it has been recommended as a tonic, refrigerant and febrifuge, in the THE TRIBASIC PHOSPHATES. 205 dose of one to three grains in a weak solution. It does not appear to be superior to the common mineral acids ; but is much milder, and less apt to disagree. It has been also recommended in caries and other diseases of the bones; as a nervous sedative, and for other purposes, but is little employed. Salts.—The tribasic phosphate of soda is employed as a chemical reagent, and the phosphate of soda and oxide "of ammo- nium (microcosmic salt) in blowpipe analysis. The latter is a tribasic phosphate, in which an atom of oxide of ammonium takes the place of an equivalent of water ; its formula is Na,P06,NH40, HO. The tribasic phosphate of soda with alkaline reaction, Na, PO?,2NaO, exists throughout the fluids of the human body, giving them an alkaline reaction. The tribasic phosphate with acid reaction, Na,P06,2HO, exists in the gastric juice, is said also to be present in the fluid derived from the muscles by pres- sure, and to give healthy urine its acid reaction. Bone earth contains two tribasic phosphates of lime, and has the following composition, Ca,P06,2CaO-f-Ca,P06,CaO,HO; in combination with two atoms of water of crystallization, it forms a hard, smooth and pale brown calculus. The ammoniaco-magnesian phosphate of the urine and of cal- culi is a tribasic phosphate, in which an atom of oxide of ammo- nium takes the place of an equivalent of water; its formula is Mg,P06,MgO,NH40, and Avhen crystallized, it contains 19 Aq. The common fusible calculus, so called because it fuses into a clear globule before the blowpipe, is a compound of this body and bone earth ; this form of calculus often attains a great size, and is found in old and exhausted patients. The tribasic phosphates of ammonia and potash are also found in the human body. In plants, the tribasic phosphates, especially of potash, soda, lime and magnesia, play an important part. They are invariably found in the seeds of the cerealia, and no mature grains are pro- duced where phosphates are absent in the soil. Corn, wheat, and the varieties of the bean, contain phosphates almost exclu- sively in their meal, and owe some portion of their nutritiousness to the presence of these salts. For the production of abundant crops of grain, it is necessary the soil should be naturally rich in these salts, or that manures containing them be applied. And as they are but sparingly present, they are soon exhausted by a suc- cession of grain crops ; when bone earth and specimens of lime which contain phosphates are found to be the best amendments. But plants possess an interesting action on the phosphates sup- plied to them from the soil; they decompose them toa limited extent, reducing the phosphorus. This enters into combination with a certain proximate principle (proteine) to form fibrine and albumen. The phosphorus of these nutritious bodies discharges the most 18 206 PHOSPHORUS WITH HYDROGEN. important functions in the frame of animals, being in process of time reconverted into phosphoric acid by oxydation, and servingto increase the amount of phosphates in the urine. All the phos- phates are soluble in the strong acids. Uses.—Phosphorus is procured in the arts from burnt bones which furnish phosphate of lime. Crushed bones are also abund- antly employed in agriculture. The phosphates of soda and micro- cosmic salt are used in analysis. The phosphates of soda and iron have been introduced into medicine ; the former is termed tasteless purging salt, and is an agreeable laxative in doses of two drachms to half an ounce, and an active purge in doses to one ounce or more ; the iron salt is of little importance, being very insoluble, but it is said to be a mild chalybeate. We take this opportunity of turning the attention of the profession to the remarkable properties of the tribasic phosphate of soda with acid reaction (Na,P06,2H0), in endowing the gastric juice with its power to digest animal food, and as a solvent in the urine. It appears to us that it is worthy of trial in cases of dyspepsia, and as a solvent of those varieties of calculus which contain phos- phates. It is readily prepared by digesting common phosphate of soda in a solution of phosphoric acid. Phosphorus with Hydrogen. Symbol H3P.—There are two gases having this composition, one spontaneously inflammable in the air, the other not having this property, but distinguished by a disagreeable odor resembling that of garlic. These are isomeric, and owe their difference to the allotropic state of the phosphorus, the inflammable body being a compound of alpha phosphorus, and the other of /3 phosphorus. They are obtained by warming the phosphuret of calcium with water, when the phosphorus of the calcium unites with the hy- drogen of water forming the gas, and the calcium combining with the oxygen of the decomposed water forms oxide of calcium, or lime. The gas is colorless, and in the alpha form bursts into flame on coming in contact with the air or oxygen. The combustion is attended with the production of beautiful wreaths of white smoke, consisting of phosphoric acid. It is sparingly produced over marshes, and when inflamed, constitutes the ignis fatuus, or " Will- with-the-wisp," spoken of by travellers. elementary arsenic. 207 ARSENIC Symbol, As. Equivalent, 74.34. Arsenic has the appearance of a metal, but forms no basic oxide. It is found in the elementary state as a rare mineral, but is abundant in combination with cobalt, copper, iron, and other metals, forming arseniurets with these bodies. It also exists in the form of native arsenious acid, and as arseniates. The equiva- lent is sometimes taken at half the above number. Characters.—Elementary arsenic, or, as it is called by Profes- sor Pereira, Arsenicum, is a black solid of metallic appearance and lustre, very brittle, crystallizing in rhombohedrons; its sp. gr. is 5.88. It sublimes at 356° F., without previous fusion, into a crystalline mass. Properties.—It possesses all the properties of an electro-nega- tive body, combining with most metals to form arseniurets, which are frequently of a white metallic appearance. Its alloys are brittle. When produced by the action of charcoal upon arsenious acid, it evolves a garlic-like odor, but this does not belong to the metal. It tarnishes in moist air, and becomes slowly oxydized. In the elementary state, arsenic is not poisonous, but the facility with which it changes renders it a disagreeable substance at all times. It is employed in a few alloys. Tests.—Its rich, black and lustrous appearance, high degree of volatility, and capacity of subliming without fusion, are charac- teristic. But it may be advisable to warm it in an open tube, subject to a current of air, by which it is sublimed and converted into a white crystalline powder, arsenious acid. The degree of heat, 356° F., enables us to distinguish it from antimony, which does not sublime short of a white heat, which no glass tube is capable of withstanding without fusion. Compounds.—The most important compounds of arsenic are as follows: The suboxide (fly powder, or black oxide). Arsenious acid (white arsenic), As03. Arsenic acid, As05. Arseniuretted hydrogen, H3As. Bisulphuret of arsenic (Realgar), AsS2. Teisulphuret of arsenic.—Sulpharsenious acid (orpimen'), AsS3. There are also a chloride, iodide, bromide, and fluoride. The Suboxide of Arsenic—This is a black dull powder, into which arsenic resolves itself by long exposure to the air. It has not been analyzed, and many suppose it to be a mixture of arseni- ous acid and the element, because it is resolved into these bodies 208 ARSENIOUS ACID. by sublimation. But the fly-powder of the shops, which is most culpably employed, exposed with water and sugar in saucers, for the purpose of killing flies, is not a uniform product, but usually a mixture containing arsenious acid, sulphur, lamp black, and other bodies. It is often the cause of poisoning, in which cases, the treatment and examination indicated for arsenious acid are necessary, inasmuch as the injurious effects arise from this body. Arsenious Acid—White Oxide of Arsenic—White Arsenic. Symb. As03; eq. 98.34.—It is found as a rare metal in the native state, but is obtained in large quantity for commercial pur- poses, by roasting the ores of iron, and cobalt, which contain it. The arsenious acid is obtained by the action of the oxygen of the air on the metal, and sublimes in flues built for the purpose. This coarse product is next purified by a careful re-sublimation. Characters.—It appears in commerce in two forms, as trans- lucent slabs of a light yellowish tint and glassy appearance, and in opaque white porcelainous lumps, with a conchoidal fracture, and frequently translucent interiorly. The translucent variety passes into the opaque, the difference depending upon crystalline figure, for this acid possesses dimorphism, and the former con- sists of large right rhombic prisms, whilst the white acid is made up of minute octahedrons. There is a slight difference in the solubility and sp. gr. of the two—the transparent having sp. gr. 3.74, and 100 pts. of boiling water dissolving 9.68 parts; whilst the opaque has sp. gr. 3.69, and boiling water takes up 11.47 per cent. A solution of the vitreous acid reddens litmus paper, whilst that of the opaque does so but slightly. The taste of arseni- ous acid is scarcely appreciable, but it leaves an acrid sensation on the tongue. It is volatile, subliming without fusion at 380° F.; its vapour is very dense, inodorous, and is soon condensed. When the sublimation is slow, brilliant octahedrons are obtained, which are very characteristic of this body. The powder of arsenious acid is of a dull white. Properties.—Arsenious acid dissolves in the alkaline solutions, forming soft uncrystallizable arsenites. The acid is readily dis- solved by hydrochloric acid; it is also dissolved by alcohol and oils, and but sparingly by cold water. It is not distinguished for chemical activity, and is readily reduced from its compounds by the action of charcoal and carbonate of soda with heat, being re- solved into elementary arsenic and oxygen. But on organic bodies it possesses considerable activity, combining with them to form indestructible compounds; it is on this quality that its anti- septic and poisonous properties depend. The bodies of persons poisoned have been found almost perfect, but resembling mum- mies, long after their death. It is also destructive to vegetables. Tests.—The powder mixed with three times its weight of re- THE TESTS FOR ARSENIOUS ACID. 209 cently heated, but cold charcoal, and heated over a spirit lamp, in a test tube is reduced—a crust of metallic arsenic appearing about half an inch from the part occupied by the flame. This crust is of a steel-like appearance exteriorly, and readily sublimes bv heat, being converted after two or three'sublimations into a white crys- talline powder of arsenious acid, which occupies the cooler parts of the tube. During the reduction, an odor of garlic is perceived by smelling at the top of the tube. The arsenical powder is also volatile in the open air without fusion. If the arsenious acid be in a clear solution, it may be examined by four means. 1. The ammonio-nitrate of silver test. Hume's test.—This test should be freshly prepared; it is made by cautiously adding solution of ammonia to a fresh and clear solution of nitrate of silver. The precipitate at first formed is to be redissolved by a further addition of ammonia until it is about disappearing. There must not be an excess of either ammonia or nitrate of silver, for in the first case arsenious acid will not be precipitated, and in the second a similar yellow precipitate will be produced with tribasic phosphoric acid or its soluble salts. When the test is properly prepared, it throws down arsenious acid in combination with silver (arsenite of silver) of a canary yellow color. This is a very satisfactory test in a pure solution, but of no value where other acids or saline matters are present. 2. The ammonio-sulphate of copper test. Scheele's test.— Add ammonia cautiously to a weak solution of sulphate of copper, until the precipitate first formed is just redissolved—too much ammonia destroys the test. This throws down a rich green pre- cipitate with solution of arsenious acid, the arsenite of copper. This is a good test, but inapplicable in organic fluids which con- tain tannin, or are colored. 3. The sulphuretted hydrogen lest.—Pass a stream of sul- phuretted hydrogen through the solution, slightly acidulated with hydrochloric acid, and Fig. 52. it will acquire a golden tint, (the ter-sulphu- ret of arsenic,) which may be precipitated by boiling. The simple apparatus depicted in the figure will answer for this purpose; the generating bottle contains sulphuret of iron and dilute sulphuric acid. This test is not of much use by itself, for solutions containing tin, cadmium, antimony and selenic acid, also yield yellow precipi- tates. But the yellow sulphuret of arsenic dissolves in ammonia, forming a colorless solu- tion, which is not the case with the other precipitates. The most decisive test is, however, to collect the yellow precipitate, dry, mix 18* 210 THE COPPER TEST. with charcoal and carbonate of soda, and place in the reducing tube, taking care to have the mixture quite dry. If arsenious acid be present, it will be reduced and form the black shining crust of elementary arsenic. This may be tested by re-sublima- tion, &c. If all the precautions pointed out be adopted, this test, which is, however, tedious, may be employed in detecting the poi- son in organic mixtures, as the contents of the stomach. The copper test.—If strips of bright copper be boiled in pure hydrochloric acid, they are not tarnished, but if arsenic, anti- mony, bismuth, mercury, and a few other metals, be present, the copper is partly dissolved, and these metals precipitated on its surface. This is, perhaps, the most delicate test for the presence of arsenic in muriatic acid, as recommended by M. Runge—less than the 5^„th of a grain having been detected by me in this way. It is to be remarked that both the -nuriatic and sulphuric acids of commerce occasionally contain arsenic, and they must be purified by this means, before use for the detection of this agent. The strip must not be heated too long, or the black scales of arsenic fall off. The color acquired by the copper strip enables us, in some measure, to discriminate between these metals, but is not a safe test. The tarnished strips have to be carefully washed in warm water, dried, and then transferred to a small tube of Bohemian gas, drawn to a point at one end, but open. The flame of a spirit lamp is next made to travel over the tube so as to drive out all moisture. Heat is then to be applied near the pointed end to the metal, and slowly advanced until the metal is made nearly red hot. If any arsenic be present, it will be found about half an inch in advance of the metal, in brilliant octahedral crystals of arsenious acid. These cannot be mistaken for any other substance, but as mer- cury may be present in the contents of the stomach, and would be sublimed, although not as a crystalline white body, it is well to cut the tube with a file below the sublimate, and dissolve it in boiling distilled water. The solution may now be tested by the ammonio-nitrate of silver and the ammonio-sulphate of copper. Or the sublimate may be separated, mixed with freshly burnt charcoal, and reduced for the purpose of obtaining the metallic crust. These manipulations are simple, and may be expeditiously made ; they also enable us to discriminate between any medicines, which may be present in the stomach of the deceased,* and the poison. For this purpose the other fluid tests are useless, and * The reader will find every particular on this subject, in my paper on the introduction of this test into medico-legal inquiries. See The American Journal of Science (Silliman's) for January, 1842. MARSH'S TEST. 211 considering all things, I have more confidence in this test than in any of the preceding, or in Mr. Marsh's, which follows. Hence I proposed its introduction into medico-legal investiga- tions in January, 1842, and find that Professor Christison has adopted it, but without mentioning my communication, which was reprinted in the Edinburgh Philosophical Magazine, and seen by him, for he quotes passages from it. Marsh's test. The arseniuretted hydrogen test.—The suspected fluid is in this case to be placed in a bottle, furnished with a cork and jette tube of glass, and mixed with zinc and dilute sulphuric acid. The dilute acid generates, by contact with the zinc, hydrogen gas, which unites with any arsenic present, and rises as arseniuretted hydrogen. The gas is colorless, has a garlic-like odor, and is readily inflammable, burning with a pale blue flame. It is to be set on fire as it issues- a smoke of arsenious acid is seen to rise from it, and if a clean piece of white porcelain, or a piece of glass, be held in the flame, a stain will be produced, consisting of a central black portion of metallic arsenic, surrounded by a white ring of arsenious acid. If the glass be held entirely above the flame, then the white deposit only is obtained. Identical appear- ances are obtained if antimony, or its compounds, be present in the fluid, but the black crust of metallic antimony does not sub- lime at the low heat at which arsenic is volatilized, and this fur- nishes us with a means of discrimination. The figure (53) represents a simple apparatus for making this test. Fig. 54 represents Marsh's apparatus of the common figure. Fig. 53. Fig. 54. There are several objections to Marsh's test. It is not as deli- cate as the copper test recommended by me, for I have discrimi- 212 IMPROVEMENTS ON MARSH'S TEST. nated a -*-th of a grain of arsenious acid, and Mr. Brett obtained -J-th as*the minimum by Marsh's apparatus. The gases may explode. In organic mixtures, there is so much froth produced as to render the combustion impossible, unless additional manipula- tions be employed. For this purpose the organic matter is to be precipitated by nitrate of silver, or charred by heating with strong sulphuric acid. The products evaporated nearly to dryness, and then redissolved in pure water. Again, the zinc and sulphuric acid both occasionally contain arsenic. Certain improvements have been made in this test by Liebig, Lassaigne, and others. The apparatus represents one of these improvements, Fig. 55. Fig. 55. Description.—The bottle a, or a two or three-necked bottle, is employed to generate the gas, and is preferable to Marsh's tube, for it enables us to operate on larger quantities, without using nitrate of silver or sulphuric acid to destroy the animal matter: fresh dilute sulphuric acid is readily introduced by the funnel b, the end of which passes nearly to the bottom of the gene- rating bottle; c is the escape tube along which the arseniuret- ted hydrogen flows; the bulb is intended to condense any fluid which may rise, and the wide tube d filled with dry chloride of calcium or asbestos, answers a similar purpose, and hinders the passage of bubbles of froth. A small tube e, of hard Bohemian glass, entirely free from lead, is inserted into the condensing tube by a cork; it terminates in a jette. G represents a piece of pla- tinum curved over the tube, and /, a spirit lamp, for the purpose of bringing the tube e to a red heat, and maintaining its tempera- ture; by which any arsenic in the effluent gas is reduced, and collects in a metallic crust a little beyond the heated portion of the tube. The gas may also be inflamed at the jette. H represents another bent tube, which may be attached by a cork to the chloride of calcium tube, so as to conduct the gas into a test glass i. DETERMINATION OF ARSENIC IN POISONING. 213 The above apparatus is for the purpose of testing the effluent gas by heat, which causes any arsenic it contains to be precipi- tated as a metallic crust—but this effect also follows if antimony be present. Or the gas may be conducted through a solution of nitrate of silver, in which, if arsenic be present, a black precipitate falls, and a solution of arsenious acid with nitric acid is obtained. A little hydrochloric acid being added, any free nitrate of silver is precipitated, and the arsenious acid may be tested as before. But, notwithstanding these improvements, Marsh's test is open to serious objections where organic matters are present, for if but a minute quantity of empyreumatic oil rise with the vapor, it will form a black stain at the heated part of the discharging tube. Messrs. Danger and Flandin find, also, that, when the direct test, by holding a vyhite piece of plate or of glass over the flame, is employed, stains may be produced consisting of sulphite and phosphite of ammonia with carbonaceous matter. Conclusion on Testing.—The collection of the arsenic from the body is effected by scraping the coats of the stomach, if any white powder be apparent thereon. Otherwise, the stomach is to be cut up into pieces and boiled with dilute hydrochloric acid, in a glass vessel. The contents of the stomach and matters vomited may also be boiled with the acid. It greatly assists the solubility of the arsenious acid. If the liver, kidney, or other viscus, is to be examined in cases of death from slow poisoning, it is cut up into fine pieces, and treated in the same manner. The clear portions are to be separated by straining with pressure through strong linen, and it will be well to add to the solids, after the first straining, a second or third dose of dilute acid, and this exhausts them of all arsenious acid. The liquid is now evaporated to a small compass. This is all that is necessary if my plan of using copper strips be employed; but if the further examination is to be carried on in Marsh's apparatus, another step is necessary. The concentrated solution is to be mixed with about £th of strong sul- phuric acid, and heated to dryness, care being taken not to elevate the temperature to 300° F. A solution in boiling water is now made and filtered, and this is employed in the generating bottle. The plan recommended by me is to collect the poison with cop- per, using strips three inches long and id of an inch wide, boiling the muriatic acid solution upon them slowly, and removing the cop- per as soon as the exterior becomes black, and before the crust falls off. A number of strips may be used, and thus any amount of arsenic may be collected. These are next to be introduced into suitable subliming tubes, of as small a size as possible, and heated, as stated in the remarks on this test. A part of the arsenious acid may be next reduced with charcoal, and other portions tested with the salts of silver, and of copper, and also by sulphuretted hydro- 214 USES OF ARSENIOUS ACIDS. gen. When the amount of arsenious acid is small, Berzelius's test tube had better be employed in the Fig. 56. reduction. Fig. 56 represents this ves- sel, and the method of using it. Great care must be taken, in all the cases of redaction, that the glass be free from lead, which is stained of a black metallic color by heat, and that no par- ticles of charcoal or empyreumatic matters be mistaken for the arsenical crust. To be certain on these points, the tube must be accurately cleaned with a piece of linen attached to a wire, until it is dry, and free from all stains. If Marsh's test be preferred, the stain on white porcelain or glass is to be obtained, and subsequently examined by heat and solution as heretofore. No one test is suf- ficient, and in the courts of law, in the present day, it is expected that all methods of examination have been made. One further practical observation is necessary before closing this part of the subject. It will be remembered that arsenic acid, which is equally, if not more poisonous, than arsenious acid, is isomorphous with the phosphoric acid. Orfila asserts that the arseniate of lime is occasionally present in the bones and other tissues of the bodies of animals, and the thing is chemically pro- bable, although subsequent and acute observers have not found it. The mass of evidence is against it; moreover, Orfila states that,in these cases, the arsenical substance is not as readily dissolved by hydrochloric acid as the adventitious compounds of arsenious acid. Uses.—It is employed in the arts for making pigments ; in agri- culture, for preparing wheat seed to hinder smut, for which pur- pose it is very inferior to a solution of sulphate of copper or blue vitriol. It is also used to kill rats, vermin and human beings. In medicine it is employed externally as a caustic to malignant growths, especially onychia maligna, but it is often absorbed into the system, and produces dangerous symptoms, and even death. The danger appears to be greater when a small amount is used than a quantity sufficiently large to destroy the ulcerated surface, But the practice is always dangerous. Dilute solutions, especially of arsenite of potash, are used in some obstinate chronic diseases of the skin, as lepra, psoriasis, impetigo. Internally the arsenite of potash (Fowler's solution, or Liquor Potassse arsenitis), is pre- ferred ; it is an admirable medicine in some forms of protracted intermittent, where quinine fails; it is also useful in chronic nervous diseases and cutaneous affections. It is readily absorbed POISONING AND ANTIDOTES. 215 when introduced into the stomach in solution, and fatal effects may arise from a small quantity in this state. This medicine is ex- tremely dangerous for two reasons: that it sometimes appears to produce no effects for a long time, and then suddenly acts with great violence, and secondly, because it produces chronic poison- ing in the smallest doses, if long continued. It is never to be em- ployed after headache, swelling of the eyelids, or other parts of the body, impaired digestion, and a sense of feebleness, are expe- rienced. Poisoning.—So little as four and a half grains of arsenious acid have produced death, but a fatal dose is probably ten grains, and several drachms have failed to do any harm, when received on a full stomach, and soon voided by emesis. Poisoning may occur from the external application of the acid or its soluble com- pounds. The symptoms produced in cases of acute poisoning, are, violent burning at the pit of the stomach, vomiting, thirst, bloody stools, irregular action of the heart, great prostration, clammy sweats, trembling of the limbs, cramps, sometimes deli- rium and death. But there may be little gastro-enteritis, the pa- tient dying as though narcotized, or in convulsions and tetanized. Death occurs more rapidly in the latter cases, and it may lake place in a few hours, or not until three or more days. Antidotes.—Dependence cannot be placed on the antidotes for arsenious acid. The exhibition of the whites of eggs with farina- ceous matters, or large quantities of olive oil, the production of vomiting, and use of the stomach pump, are the best methods of treatment in cases of poisoning. The principal difficulty in these cases arises from the arsenious acid becoming hidden in the folds of the stomach, and enveloped by mucus; hence large quantities of warm water, containing the white of egg, are to be repeatedly thrown into the stomach, and rapidly pumped up, for the worst effects of the poison arise from its absorption. But whilst these are the essential means, it would be culpable, in the present day, to omit the use of the fashionable antidotes. These are lime water and the hydrated peroxide of iron. The first is not of much utility, from the slow action of the arsenious acid on it, and the same objection has been found against the second. The hydrated peroxide ought, however, to be used; it is made by adding solution of ammonia to the peracetate, perni- trate, or any persalt of iron ; the oxide at once falls as a red magma, and is to be thrown on a cotton filter, and washed once or twice with water. It should be fresh, or kept well-stopped, for the dry peroxide is useless. As we do not know how much poison has been taken, the necessary dose cannot be prescribed; but it is a perfectly innocent substance. Hence, give a tablespoonful, suspended in water, every three or four minutes, until the urgent 216 ARSENIC ACID AND ARSENIURETTED HYDROGEN. symptoms are relieved. To a child, a teaspoonful may be given with equal frequency. But do not throw aside the stomach pump to administer this antidote; rather employ it after the free use of that instrument. The hydrated peroxide acts chemically on the poison, neutral- izing it, and forming an arsenite of iron. But it has been clearly proved, that it attacks only the arsenious acid in solution, and has no effect on the solid particles which lie on the mucous mem- brane. It is, therefore, little efficacious, because arsenious acid is but sparingly soluble, and, in most cases, large amounts are introduced into the stomach for the purpose of poisoning. Salts.—The arsenite of potash forms the basis of Fowler's so- lution, and the arsenite of soda of Pearson's solution; they are similar in properties. The arsenite of copper is the fine pigment called Scheele's green. An arsenite of quininehas been recently introduced into medicine as an antiperiodic in protracted inter- mittents. It appears to possess the action of both ingredients, and may be a useful medicine, but in no wise better than an ex- temporaneous combination of arsenious acid and sulphate of quinine. Arsenic Acid. As05?—This is obtained by boili§g a solution of arsenious acid with nitric acid. It is a powerful acid, isomor- phous with the tribasic phosphoric acid, highly poisonous, and somewhat soluble. It is distinguished in the free state, or in its soluble salts by throwing down a brick-red precipitate with nitrate of silver. It is not at present employed. Arseniuretted Hydrogen. H3As ?—This is a violently poison- ous gas ; it may be prepared by putting pieces of zinc in a solu- tion of arsenious acid, and then adding sulphuric acid. The hydrogen formed, reduces the arsenious acid and rises as arseni- uretted hydrogen, more or less mixed with hydrogen. Characters.—It is transparent, has the odor of garlic, sp. gr. 2.695, and is sparingly soluble in water. Properties.—It burns with a pale blue flame in the air, be- coming resolved into water and arsenious acid, when the combus- tion is free; but if this be conducted in a limited supply of air, water and elementary arsenic are produced. It is decomposed by being passed through a red hot tube into elementary arsenic and free hydrogen. It is very poisonous, when inhaled even in small quantity, pro- ducing headache, nervous symptoms, a febrile state with oedema- tous swellings of the eyelids, face and other parts of the body. But as it is not used, poisoning never occurs by it except to the experimental chemist. This gas is generated in Marsh's test for arsenic, and it will be necessary to adopt precautions to escape COMPOUNDS OF ARSENIC. 217 poisoning where the amount of arsenious acid is large, by con- ducting the process in the open air or under a flue. The Sulphurets of Arsenic—Realgar (AsS ) occurs native, and is readily made by heating its components; it is a red vitreous and insoluble body. It is employed in pyrotechny, and is in its commercial form a powerful poison. It is detected by the reduc- tion test. The treatment is similar to that for the arsenious acid except that the antidotes may be dispensed with. Orpiment, or sulph-arsenjous acid, AsS3, is a fine yellow insoluble solid. It occurs native and is used as a pigment, and called King's Yel- low. The commercial body contains arsenious acid, and is a poison. It is detected by the reduction test. In cases of poisoning the treatment is that for arsenious acid. It is employed in certain nostrums as a depilatory, as a paint and by pyrotechnists. Two other sulphurets of the constitution, AsSg and AsS9, are known, but not employed. Realgar, orpiment and the penta- sulphuret (sulph-arsenic acid) AsS5, are sulphur acids, and com- bine with bases like the so called oxygen acids. Other Binary Compounds of Arsenic—The terchloride, As Cl3, is a very instable, oily and dense liquid, intensely poisonous. The iodide, Asl3, is a red volatile and soluble crystalline body. It has been recommended as an external application in a diluted ointment (grs. iij to %i of lard) in tubercular skin diseases, but it does not appear to be superior to arsenious acid. Mr. Donovan strongly recommends the compound iodide of ar- senic and mercury. It is made by rubbing 6.08 grains of metallic arsenic, 15.38 grains of mercury, 50 grains of iodine, with f^i of alcohol, until the mass is dry and of a pale red color. This is then dissolved in half a pint of water, and boiled with half an ounce of hydriodic acid for a few minutes. It is used in solution. The dose is -g\d to T'gth of a grain three times daily, and it is recom- mended in cutaneous affections, fungoid and other diseased growths. ANTIMONY. Symbol (Stibium) Sb. Equiv. 129.2. Antimony is abundant as a sulphuret, which is readily reduced by heat and a flux containing carbon and potash or soda. Characters.—It is a bluish white brittle body, Jamellaled or in rhombohedral crystals, and having considerable metallic bril- liancy. Its sp. gr. is 6.7 to 6.8; it fuses at 797°, and is volatile at a white heat. Properties.—It is a conductor of heat, and burns at a red heat when exposed to the air into an oxide. It is more electro- 19 218 OXIDE OF ANTIMONY. negative in its relations to other bodies than the metals, and strik- ingly isomorphous with arsenic. It is employed in alloying some metals, and the compounds may be termed antimoniurets. Compounds.—The most important compound is the teroxide SbO , which is the basis of tartar emetic. The binary compounds are as follows: Teroxide of antimony (sesquioxide) ... SbOa Antimonious acid......Sb04 Antimonic acid ...... Sb03 Terchloride of antimony ..... SbCl3 Perchloride of antimony ..... SbCl5 Tersulphuret of antimony .... SbS3 Persulphuret of antimony (golden sulphuret) - SbS5 Antimoniuretted hydrogen .... H3Sb Teroxide of Antimony—Sesquioxide—Oxide of Antimony. Sb03; eq. 153.2.—It may be obtained by pouring the solution of antimony in hydrochloric acid (Chloride of Antimony) into water, and digesting the precipitate with solution of carbonate of soda. Characters.—It is a whitish solid, having the same dimorphous crystalline forms as arsenious acid. The precipitated oxide is anhydrous, and fuses into a yellow liquid which concretes into a crystalline mass on cooling. It fuses before the blowpipe, and is volatile. Properties.—It is scarcely a base, although it is found in tartar emetic and some few double salts. It is an active poison, depress- ing the powers of life, and is the active ingredient in the common antimonial preparations. It is used in the preparation of tartar emetic. Tests.—It is dissolved by a solution of cream of tartar, which is converted into the tartrate of potash and antimony, or tartar emetic. Its fusibility into a yellow fluid seems to distinguish it from arsenious acid, which it resembles in most respects. The soluble forms of antimony are precipitated of an orange color by a stream of sulphuretted hydrogen, which does not, however, yield a metalline crust, as in the case of arsenic, by reduction, for antimony is not volatile short of a white heat. Compounds.—It is found in uncertain quantities in the pulvis antimonialis and James' powder, the properties of these medi- cines depending upon its presence. The oxysulphuret, or Kermes mineral, is a compound of tersulphuret with teroxide 2(SbS3) -4-Sb03. This is used as an alterative in doses of gr. i to gr. iij. But the principal compound is tartar emetic, or the tartrate of potash and antimony. Tartar emetic is white, transparent, and crystallizes in rhombic octahedrons. It effloresces in the air. The taste is styptic and metallic, and it dissolves in about 14 parts of water at 60° F., TARTAR EMETIC. 219 and in about 2 parts at a boiling heat. The solution slightly red- dens litmus paper and undergoes spontaneous decomposition by keeping. It is tested by the action of heat, which chars it, and by passing a stream of sulphuretted hydrogen through the solution when the orange red precipitate of tersulphuret is produced, which does not act like the sulphuret of arsenic in the reducing tube. Tartar emetic is a diaphoretic, expectorant and nauseant in small doses (gr. TT2 to gr. j), emetic and purgative in the dose of gr. i, and in doses of gr. ii to gr. iv, often repeated, a powerful arterial sedative. In pneumonitis, it is a valuable medicine administered in doses beginning with gr. ss, and increasing it to gr. ij every two hours until sleep or considerable amelioration of the symptoms occurs. It produces great debility, relaxes the muscular fibres of the body, depresses the vital actions, and reduces the arterial capillary circulation. It seldom acts as a poison, and is not used with that intention, but in cases of accident, vomiting should be encouraged, and tannic acid or astringent solutions administered. A strong oint- ment (Jii to $i of lard) is a powerful vesicant, and diluted is sti- mulant. The medicine is absorbed into the system to a limited extent, and its antimony has been discovered in the viscera by Orfila, Barre and others. It is a dangerous medicine for young children, as it prostrates them too much. Antimonious Acid. Sb04.—A grayish-white powder, infusi- ble, not volatile, insoluble. It combines with the alkalies, but the antimonites are readily decomposed. It is the final result of the action of heat and air on elementary antimony. Antimonic Acid. SbOs.—Procured by the action of strong nitric acid on antimony. It is insoluble; exposed to heat it ac- quires a yellow color, and it combines with the alkalies. It is de- composed by a red heat into antimonious acid and oxygen. Terchloride of Antimony. SbCl3.—A soft butyraceous solid, procured by the distillation of bichloride of mercury and sulphuret of antimony; it is deliquescent, and a solution in hydrochloric acid, dropped into water, produces a bulky precipitate, called the powder of algaroth or oxychloride of antimony (SbCl3-r-3Sb03) + 3Aq. The butter of antimony is caustic, and the oxychloride emetic, but neither is much used except in the manufacture of the teroxide of antimony and tartar emetic. Perchloride of Antimony. SbCl5.—It is made by passing a current of chlorine over hot antimony, and is a heavy fuming liquid, of a bad odor, and readily decomposed. The Sulphurets.—The tersulphuret, SbS3, is an abundant mineral of a brittle texture, and striated dark gray metallic appear- 220 COMPOUNDS OF ANTIMONY. ance. When hydrated, it has an orange color, and is formed when a stream of sulphuretted hydrogen is passed through a solution of tartar emetic. By heating this body in a shallow iron vessel, and stirring until fumes are no longer given off, a gray powder is obtained which may be fused by a red heat, in a closed vessel, into a brown-red glass called the vitrum antimonii. This is a mixture of sulphurets and oxides. When the free oxide is dissolved by acids, there remains an oxysulphuret, Sb03+2(SbS3), called the crocus, or saffron of antimony. By boiling caustic potash on powdered tersulphuret of antimony, a solution is obtained that precipitates, as it cools, an orange red substance called Kermes mineral. This is a mixture of teroxide of antimony and sulphuret. If the hot solution be treated with an acid before its spontaneous decomposition, a brownish oxysul- phuret is thrown down called the orange sulphuret (Hepar an- timonii) or precipitated sulphuret of antimony. It is a good medicine, and employed as an alterative in the compound calomel, or Plummer's pill. The golden sulphuret (SbS5),persulphuret or sulph-antimonic acid, is obtained after the spontaneous pre- cipitation of the kermes, by adding an acid to the antimonial solu- tion in potash. It is of a lighter color than the other two bodies. There is also a sulph-antimonious acid (SbSJ. Antimoniuretted Hydrogen.—This gaseous body is procured by adding zinc and sulphuric acid to a solution of tartar emetic. Its formula is generally supposed to be H3Sb. It burns with a white flame, throwing off a white smoke of oxide of antimony and water. It is reduced by passing through a red hot tube, deposit- ing a metalline crust, at the heated point, which may be readily distinguished from arsenic by its want of volatility at a low red heat. If a white piece of plate be held low down in the flame of this gas, a black crust with a white border like that obtained under the same circumstances from the flame of arseniuretted hydrogen, is obtained, but they differ in the stability of the antimonial crust. CARBON. Symbol, C. Equivalent, 6.0. Carbon is the great organic element, no substance produced by the action of plants being without this body. It exists in nature as the diamond, anthracite and plumbago; and in a compound state in all animal and vegetable substances. It is obtained in an impure state as charcoal and lampblack, by burning vegetable bodies in the absence of air. Characters.—Carbon has three allotropic states. 1. In the dia- the varieties of carbon. 221 mond it is translucent, crystallizes in octahedrons, variously modified and with curved facets. Its sp. gr. is about 3.5, and it is the hardest mineral known. It appears from the researches of Dumas, that it has an organic structure, and is of vegetable ori- gin. It is incombustible except in oxygen, and infusible. 2. Plum- bago is unctuous to the touch, has a metallic lustre, is opaque, and almost incombustible. 3. Anthracite and lampblack are opaque, black, and readily combustible. Properties.—The common or y carbon is readily combustible, becoming converted in a full stream of oxygen into carbonic acid (C02), and in a limited supply into carbonic oxide (CO). It is a good radiator of heat, but a poor conductor of heat or electricity. The diamond possesses a high refractive and dispersive power for light. Charcoal being porous, possesses the property of absorbing gases and also of condensing many times its volume of several, especially ammoniacal and sulphuretted hydrogen gases; this endows it with disinfecting powers, and makes the powder useful in agriculture for the purpose of hindering the escape of many vaporous bodies from the soil. Ivory black, derived from bones burnt in iron retorts, also possesses the power of decolorizing organic solutions, as may be shown by filtering a solution of indigo through it. All the forms of carbon are infusible, and they act as electro-positive bodies in most cases, resembling in this respect the metals, but there are a few compounds of a different character with hydrogen, &c, called carburets. Tests.__The test for carbon is its convertibility into carbonic acid by the action of heat and oxygen gas. Uses.—The above varieties are used in various ways. The dia- mond is used as an ornament and to cut glass. Plumbago is employed in the manufacture of crucibles, for greasing machinery, and the finer sorts constitute the black lead of writing pencils. Ivory black is employed to decolorize solutions, and pounded charcoal to remove the putrescent odor of spoiled provisions or stagnant waters. Anthracite charcoal, &c, as fuel. Compounds.—-The principal binary compounds of carbon are: Carbonic oxide - ~y. Carbonic acid ... - 102^ Light carburetted hydrogen - - H2C. Olefiant gas .... H4C4. Cyanogen (bicarburet of nitrogen) - C2N. Bisulphuret of carbon - - - CS2. Carbonic Oxide. CO; eq. 14.0—This gas is generated when charcoal is burnt in a limited supply of air. Characters.—It is colorless, inodorous, sparingly soluble, sp. gr. 0.972. It has never been liquefied. Properties.—This gas is inflammable, burning with a pale 19* 222 CARBONIC ACID. blue flame into carbonic acid, C02. It is highly poisonous, acting in the same way as carbonic acid. It is by some considered an electro-positive compound radical, and unites, when exposed to light, with chlorine, forming a pungent acid body, called chloro- carbonic acid or phosgene gas. Carbonic oxide is not put to any use. Carbonic Acid. COa; eq. 22.0.—This important gas exists in the air to the extent of 4 to 6 parts in 10.000; it is found in most waters, and is one of the most abundant products of the decomposition and combustion of animal and vegetable sub- stances. It is readily obtained by adding hydrochloric acid to pieces of marble, which is a carbonate of lime; the carbonic acid rises as a gas, and may be collected by displacement. If it be wanted dry, the following apparatus (Fig. 57) will be necessary, in which the long central tube contains fused chloride of calcium, which absorbs any moisture which passes over. Fig. 57. Characters.—It is a colorless gas, of a pungent taste, and little odor. Its sp. gr. is 1.524; 100 cubic inches weighing 47.26 grains. Cold water dissolves about its own volume, but will take up large quantities under pressure; such solutions constitute the soda water of manufacturers. Under a pressure of 28 atmo- spheres, at 32° F., it may be liquefied, and forms a colorless lim- pid fluid; when relieved of pressure, it immediately boils, and, from the cold produced by its rapid evaporation, about £th be- comes solid. Solid carbonic acid has the appearance of snow, and by its evaporation, produces intense cold. Mixed with ether, in vacuo, it depresses the thermometer to —165° F. Properties.—Carbonic acid possesses acid properties ; its solu- tion reddens litmus paper, and it unites with many bases, forming carbonates, which are, however, commonly decomposed by most acids, and also by heat. It is neither inflammable, nor a sup- COMPOUNDS OF CARBON. 223 porter of combustion, and is totally irrespirable, a small amount bringing on narcotism, and destroying life by asphyxiating the animal. Tests.—Its power to extinguish a flame, redden litmus, and cause a white precipitate of carbonate of lime, when passed through clear lime water, enables us to distinguish the gas. The effer- vescence produced by a weak acid on its compounds, with the above tests of the gas, enables us to discriminate the carbonates. Uses.—Carbonic acid dissolved in water is a grateful stimulus to the stomach, especially in nausea. The gas is sometimes em- ployed in the laboratory; also for purposes of suicide, especially amongst the French; and was formerly recommended as a proper medium for the preservation of fruits, &c. Its use in the opera- tions of nature are more important, as it is the chief food of plants, which derive it from the air by their leaves; and, from fertile soils, in solution by their roots. It is also a product of the changes going on in the human body, and is present to the extent of four per cent, in expired air. In cases of asphyxia, by carbonic acid from wells (choke damp), from cesspools, or from the incautious inhalation of the vapor of burning coals, the patient should be freely exposed to the air. The jugular veins should be opened, flannels wrung out of hot water applied to the body and extremities, and artificial respiration esta- blished. The gas introduced into the lungs should contain about one-eighth of protoxide of nitrogen if possible. For this purpose, the bellows should be placed in contact with a large Indian rubber bag, containing the mixed gases. Salts.—The carbonates of potash, of soda, magnesia, lime, prot- oxide of iron, lead, (white lead,) zinc, and copper, are the prin- cipal. Compounds of Carbon with Hydrogen.—Light carburetted hydrogen, CH2, is the common marsh gas, produced by the decay of vegetable matter under water. It is also the explosive gas (fire damp) of bituminous coal mines, and exists in the common gas used for lighting cities. It is colorless, light, so that it is em- ployed in inflating balloons, and combustible, burning with a yel- lowish flame. Olefiant gas. C4H4.—It is made by heating one part of alcohol with four of sulphuric acid, and separating the ether and oil of wine first generated, by passing the products first through a bottle con- taining solution of caustic potash, and secondly, through sulphuric acid. It is a colorless gas, with a slight unpleasant odor, sp. gr. 0.981, is very inflammable, and forms an explosive compound with oxygen. Its combustion is very bright, and it forms the most valua- ble constituent of common gas, and nearly the whole of oil gas. The products of its perfect combustion are water and carbonic 224 CYANOGEN. acid; but, in a common flame, it is only at the outer surface that this result takes place. A flame may, indeed, be divided into three parts, a central, thin, non-luminous cone of unconsumed gas (A, Fig. 58); around this is a shell of partially burnt gas, and then the outer surface. The middle part is called the deoxy- Fig. 58. dizing flame, B, and the exterior the oxydizing . flame, C, in consequence of their action on bodies A c placed respectively in these positions. f/X Flame cannot pass through the close meshes of // AI.—b fine brass or copper wire ; and on this principle [/ A \| Davy's safety lamp is constructed. I /-\-l—-A Mixed with chlorine, it forms an oily, ethereal \J/ liquid, of sweetish taste, called the Dutch liquid, or | chloride of hydrocarbon. Burnt in an atmosphere [Jf_j of chlorine, olefiant gas becomes converted into hy- drochloric acid, and a black deposit of carbon takes place on the sides of the vessel. Coal gas contains the two preceding gases, with numerous impu- rities, especially compounds of ammonia, sulphur, carbonic acid, and tarry bodies. Most of these are separated by condensation, and by passing the gas through a mixture of lime and water. Cyanogen—Bicarburet of Nitrogen. HC2Cy; eq. 26.0.—A gaseous body procured by heating the bicyanide of mercury. Characters.—A colorless gas, of an odor resembling peach blos- soms, readily soluble in water, sp. gr. 1.806. It is converted into a liquid by a pressure of 3.6 atmospheres. Properties.—It is irrespirable and inflammable, burning with a beautiful pink flame. A solution in water rapidly decomposes, yielding ammonia, hydrocyanic acid, a brown inert solid called paracyanogen, isomeric with cyanogen, and other bodies. This substance very closely resembles chlorine in its action, and is hence termed an electro-negative compound radical. Its symbol is Cy. Its compounds with the metals are termed cyanides. Compounds.—With hydrogen it forms the cyanide of hydrogen, HCy, hydrocyanic or prussic acid. With oxygen it forms cyanic, fulminic, and cyanuric acids, which are isomeric. It also unites with iron, forming ferrocyanogen, FeCy3, and ferridcyanogen, FeaCy6, and with sulphur forming another compound radical, S2Cy, termed sulphocyanogen. Other compounds with cobalt, chlorine, &c, exist, which are of little interest. Of the cyanides of metals, the cyanide of potassium, KCy, is much employed to form the insoluble cyanides, in medicine, and in electro-galvanic plating and gilding. The cyanides of mercury, and of gold, have been partially introduced into medicine, but do not merit particular notice, being uncertain in their effects, and inferior to the corrosive sublimate for which they were introduced. The soluble cyanides HYDROCYANIC ACID. 225 of potassium, sodium, and ammonium, are poisonous like prussic acid. The cyanide of silver is used to procure medicinal prussic acid. Cyanide of zinc, in doses of quarter of a grain to one grain, is said to act like medicinal prussic acid, and has been used as a substitute in the same diseases. Hydrocyanic Acid—Cyanide of Hydrogen—Prussic Acid. HCy; eq. 27.0.—This liquid is procured in the pure anhydrous state ; by passing a stream of sulphuretted hydrogen over cyanide of mercury heated to redness, the sulphur of the gas unites with the metal, forming sulphuret of mercury, and the cyanogen and hydrogen combining, produce HCy, or hydrocyanic acid, which must be collected in a vessel refrigerated by ice; the reaction is represented in the formula HgCy and HS=HgS and HCy. Characters.—This is a limpid fluid of great volatility, so that a drop exposed to the air, is partly solidified by the cold produced by the evaporation of a portion. It has a strong odor of peach blossoms, and is readily dissolved by water or alcohol. Its sp. gr. at 45° F., is 0.705, and it boils at 79° F. At zero, or —5° it is a crystalline solid. Properties.—Cyanide of hydrogen has the same general pro- perties, but in a feeble degree as hydrochloric acid. Its hydrogen is readily replaced by metals, and most of the cyanides can be formed by bringing to it a metallic oxide. It is indeed spontane- ously decomposed, especially by the action of light, becoming resolved into an inert black substance called azulmic acid, and ammonia. It is a very feeble acid, scarcely reddening litmus, is not sour, nor able to decompose the carbonates. The vapor burns with a bluish flame. It is an intense poison, one drop having killed a dog in a few seconds of time. Tests.—Cyanide of hydrogen, and the soluble cyanides, are precipitated of a white color, by solution of nitrate of silver. The precipitate does not dissolve in ammonia or cold nitric acid, but does so in the boiling acid. They are also known by adding a solu- tion of potash, then a solution of old sulphate of iron, which con- tains both the protoxide and peroxide of the metal; by this means a greenish blue precipitate is formed which becomes of a rich blue (Prussian blue), by the addition of a little hydrochloric acid. The above procedure, without the final addition of acid, constitutes Messrs. Smith's antidote for this poison. It also serves as a means of recognizing the poison procured from the stomach, or matters vomited, of those who have died under its effects. In Poisoning.—The smell will be a principal test, but this may arise from oil of bitter almonds, cherry laurel water, and other substances which do, however, gradually evolve hydrocyanic acid under certain circumstances. The matters yielding this 226 hydrocyanic acid. odor are to be cut up, if solid, and transferred to a glass retort, with water and sulphuric acid, and submitted to distillation over a water bath. The product is to be received in a refrigerator surrounded by ice, and if it contain hydrocyanic acid, it may be recognized by the odor and the foregoing tests. The principal difficulty which arises in its detection is due to the minute portion which may produce a fatal result, and its great volatility, which causes it to pass off from the body in a few hours, unless very dilute. Uses.—It is used in medicine, being a very valuable remedy as a nervous sedative, and to allay pulmonary and gastric irritation of nervous origin, as in certain forms of gastralgia and asthma. But for this purpose the foregoing anhydrous acid is not employed, nor kept, it being too prone to decomposition. A formula is given in the Pharmacopoeias for a dilute acid which keeps much better; it is as follows:—Take 51 grains of cyanide of silver; 41 grains of strong hydrochloric acid, and a fluidounce of water. Add the salt to the dilute acid,shake and put aside in a dark place. This should be recent, and the dose is from one to ten drops, to be dis- continued when headache or dimness of vision is produced; one drachm may be a poisonous dose. It acts both locally and by absorption; in the former case, it produces numbness, or destroys the sensibility of the nerves, and occasionally it produces vomiting and purging; but its chief action is, when absorbed, on the nervous centres, and especially the respiratory nerves. In poisoning, convulsions, epilepsy, spasmodic breathing, di- lated pupils, diminished pulse, sometimes almost reduced to nothing, occur when the dose is scarcely sufficient to produce death. Recovery occurs in such cases in half an hour, but it may be longer. The treatment is twofold, the nervous system is to be aroused by dashes of cold water over the chest, head and spine, and ammonia or its preparations given as nervous stimulants. Artificial respiration is also to be employed, and it is better to introduce a little chlorine into the air. In addition to these, Messrs. Smith's antidote is to be given as soon as possible, as follows:—first administer solution of car- bonate of potash, and follow it with a dilute solution of old sulphate of iron (containing the protoxide and peroxide); this destroys the hydrocyanic acid, and produces inert Prussian blue. Chlorine should be diffused in the air of the room, which is readily done by pouring some vinegar or other acid on common bleaching salt,— the chloride of lime or soda. But unfortunately death is often produced in an almost imper- ceptible period of time; the unfortunate person falling as if in- stantaneously deprived of life, without struggle or convulsion, except, perhaps, a few gasping efforts of inspiration. The vapor COMPOUNDS OF CYANOGEN AND OXYGEN. 227 of hydrocyanic acid produces this result in minute quantities when inspired. In these cases, the establishment of artificial respiration with chlorinated air, constitutes the only chance of recovery. The blood is often found dark, fluid, and having an oily appear- ance, and the muscles are occasionally insensible to the stimu- lus of electricity. There may also be engorgement of the lungs, brain and spinal marrow, with venous blood, but the arteries are empty. Cyanogen with Oxygen.—Cyanogen produces three isomeric compounds with oxygen: Cyanic acid, CyO; Fulminic acid, Cy202; and Cyanuric acid, Cy303—of which the second has not been in- sulated, and the other two are only known in the hydrated state. Cyanic acid (CyO+HO) is obtained by distilling dry cyanuric acid; it is a colorless acid liquid, like acetic acid, blistering the skin. It is very instable, being converted by water into bicar- bonate of ammonia C2NO,HO+2HO=2(C02)+NH3. But it also spontaneously changes into an inert, white opaque solid, which is insoluble, but convertible by hot sulphuric acid into carbonate of ammonia, offering an extraordinary illustration of isomerism depending upon grouping, for the number of the atoms in this body are the same as in the acid. Cyanic acid is peculiarly interesting, from its being one of the products of the changes taking place on animal food in the body. It exists in the urine in combination with ammonia, another sub- stance produced by the same changes, these forming Urea, which is a hydrated cyanate of ammonia; its formula is C2H4N202, or CyO+NH3+HO. This body may also be obtained by arti- ficial" means, by the action of peroxide of manganese on ferro- cyanide of potassium with heat, and the subsequent addition of sul- phate of ammonia, &c. This salt is remarkably soluble, of a saline taste, and readily crystallizable into four-sided prisms. Fulminic Acid exists in the fulminating powders of mercury, silver and other bodies. It has not been isolated, but is bibasic, and its compounds are remarkably instable. Cyanuric Acid (Cy303+3HO) is obtained by heating urea (cyanate of ammonia) which disengages ammonia; the residue is dissolved in hot sulphuric acid, and nitric acid added until the solution becomes colorless. On mixing with this product water, and cooling, crystals of the above acid fall. It is tribasic, little soluble, and distilled at a red heat yields hydrated cyanic acid only, being, as it were, split into three atoms. Cyanogen with Iron.—The two compounds, Ferrocyanogen or Preussine (FeCy3), and Ferridcyanogen (Fe2Cy6), have not been isolated. They act precisely like electro-negative com- 228 SULPHOCYANOGEN. pound radicals, and are so considered, the former being furnished with the symbol Cfy and the latter with Cfdy. The crystalline substance called yellow prussiate of potash, is much used in the laboratory as a test, and also partially in medi- cine as a mild, nervous and arterial sedative. It is a compound of ferrocyanogen with potash, its formula being 2rv,Oty+«5riU, and it is made on a large scale for the manufacture of Prussian blue, by heating to redness animal matters with potash and iron in iron retorts, washing out the salt and crystallizing. Prussian blue is obtained by adding a solution of this body to a solution of a peroxide of iron. This is not only used as a pigment, but as a substitute for cinchona in intermittent fevers, in doses of four to six grains, and in some neuralgias. The red prussiate of potash, a beautiful salt, contains the ferridcyanogen; it also produces a variety of Prussian blue called Turnbull's blue, and is used as a test. Sulphocyanogen (S2Cy or Csy) has not been isolated, but its potash salt is made by heating powdered yellow prussiate of potash with half its weight of sulphur, and one third of carbonate of potash, and keeping them melted for a short time. Boiling water dissolves the sulphocyanide of potassium, which readily crystallizes. A solution strikes a blood red color with the per salts of iron, and is employed as a valuable test. This substance, in combination with ammonia and other bases exists, in the bodies of animals, and in human saliva. Carbon with Sulphur.—The Bisulphuret of Carbon (UbJ is made by adding pieces of sulphur to charcoal heated to red- ness in a porcelain tube, and receiving the vapors in a vessel containing water and ice. To obtain it pure, it is necessary to re-distill at a low temperature. It is a colorless, transparent, volatile liquid, possessed of great refractive and dispersing power, and was recommended by Brewster for the purpose of filling con- cave shells of glass to answer as lenses. Its specific gr. is 1.272, and it boils at 108° F. It volatilizes with so much rapidity as to produce great cold, but is of so offensive an odor that it can scarcely be employed. It dissolves sulphur and phosphorus. BORON AND SILICON. Symbol, B. Eq., 10.9.—Symbol, Si. Eq., 22.2. These two elements are closely connected, and have some af- finity with carbon, but they are of little interest in medicine. Boron, from its strong affinity for oxygen, is little known; it is a greenish-brown powder, which, when heated, burns in the air into BORON AND SILICON. 229 Boracic acid, B03. This is found in some volcanic waters, and also in combination with soda, forming native borax, or Biborate of Soda. J The acid may be obtained from borax by adding sulphuric acid to a hot solution; on cooling, it falls in small crystalline scales. It melts at a red heat into a glass, and is a feeble acid at ordinary temperatures, but in a strong heat it is one of the most powerful. It was formerly thought to be a sedative, but is not now employed. Borax is a biborate of soda; it is obtained in large prisms or oc- tahedrons, by purifying the native salt. It is saline and cooling in taste, effloresces slightly in the air, and melts in its water of crys- tallization when heated. It is readily soluble, and has the com- position NaO+BO3+10Aq. It is used in the arts, and in the blowpipe analysis of the mineralogist. Its medicinal powers are also said to be considerable, for, according to Vogt, Dr. Copland and others, it throws the uterus into contractions, and may act as an abortive. It is also refrigerant and diuretic, and a large dose produces vomiting. Locally applied, it is a stimulant, and par- ticularly useful as a detergent to aphtha? and ulcerations of the mouth and fauces. The dose internally is from half a drachm to a drachm. Silicon is the basis of sand, rock crystal, and silicious matters generally. It is procured with difficulty, and resembles boron. Its chief compound is Silicic acid, Si03, which is sand or rock crystal. The salts of this body are nearly all insoluble, and make up a large portion of the earth's crust, especially the silicate of alumina which forms slate, and the varieties of clay; and the silicates of iron, lime, potash, &c. But by heating sand with four parts of carbonate of potash or soda, soluble silicates are obtained, from which the hydrated acid may be precipitated as a gelatinous substance by any acid. These salts exist in silicious springs. Glass, porcelain, and common earthenware are silicates. Com- mon table and flint glass contain a silicate of lead, and are unfitted for chemical purposes, from the lead being reduced by heat, and forming a stain like that of arsenic. Hard glass fitted for chemical vessels contains a silicate of lime and potash; it is very infusible and is not stained bv heat. Both boron and silicon combine with Fluorine, forming BF3 (fluoride of boron) and S1F3 (fluoride of silicon), which are gaseous. 20 230 PAET III. ORGANIC CHEMISTRY. The student having passed over the principal elements which make up organic bodies, is now prepared to enter upon their study. It is not our purpose, in this part, to take up every com- pound which the labors of its numerous cultivators have an- nounced within the last few years, but only such as are useful in elucidating the functions of animals and plants, or are of medicinal interest. Organic bodies are of two classes, either the immediate products of the functions of vegetables, as starch, sugar, fibrine, or of a subordinate importance, being produced by chemical changes impressed upon the former; the second class may be termed pseudo-organic. To this belong the acids, ammonia, cyanogen, the vegetable alkaloids, fatty bodies, ether, alcohol, &c. Many of these can be produced by artificial means from the first order, and represent a stage in the passage of organic matter into inorganic or mineral substances. Thus, by the oxydation of fibrine in the body, are formed urea, water and carbonic acid, and ultimately this complex body, which contains upwards of 1000 atoms, is re- duced into water, carbonic acid, and ammonia, passing into inor- ganic matter. So sugar is changed into alcohol, then acetic acid, and finally into carbonic acid and water. The urea, alcohol, and acetic acid, are, in these instances, secondary or pseudo-or- ganic bodies. The true organic bodies, with few exceptions, are produced by plants only ; they consist of carbon, hydrogen, oxygen and nitro- gen chiefly; some, however, contain sulphur and phosphorus, whilst a few present traces of iron, potash, soda, lime, magnesia, and other bodies, either as an intimate ingredient, or as compo- nents necessary to the textures of which they form a part. Thus, it has been found that no cellules or tissue exist without saline matters, and usually with some of the above bodies. On the other hand, a numerous class contain only carbon, hydrogen, and oxygen; and some only carbon and hydrogen, as many essen- tial oils. The number of atoms of each of the principal elements COMPOUND RADICALS. 231 is usually great, and this is one obvious reason for the instability of these compounds. All organic bodies are decomposed by a red heat, and if burnt without access of air, nearly all yield charcoal. Many are changed at a less heat, whilst those which, like fibrine, albumen, casein, &c, contain hundreds of atoms, undergo spontaneous change or fermentation by exposure to oxygen and warmth. The fermentation of one body also communicates change to others, as in the action of yeast, which is decaying fibrine, on a solution of sugar. This catalytic action is not limited to organic compounds', but is a striking peculiarity in them. In nearly all these changes, the oxygen of the atmosphere appears to be the destroying principle, tending, in all cases, to produce inorganic compounds, of which carbonic acid (C02), water (HO), and nitric acid (N05), are the chief; sulphuric and phosphoric acids are also the products of this agent on the sulphur and phosphorus of the organic world. When this oxydation is the principal feature of the decay, it is termed eremacausis, which means slow combustion. The acids and alkalies often determine the products of decom- position; the former, producing substances which, like the oxide of ethyle, are basic; whilst the latter generate acids with which they combine. Nitric acid, by imparting its oxygen, is, however, a most potent agent in their decomposition, oxydizing them, and producing numerous pseudo-organic substances, usually of an acid reaction. Until the last few years, little method existed in this part of chemistry. Each body was separated from the rest, and the ordi- nary laws of affinity were supposed to be at fault; but of late, it has been found that there exist groups or genera amongst organic bodies, which are often very extensive, and which seem to pre- sent a structure similar to those of the mineral world. There are not the simple metals and haloid bodies, but there are compounds distinguished by a striking electro-positive reaction, and others by an equally remarkable electro-negative affinity. These are both called compound radicals; but the terms electro-positive com- pound radical, and electro-negative compound radical, are more definite, ^o that the simple laws of the electro-chemical theory seem to hold for some of the most complex bodies in nature, ten, twenty, or hundreds of atoms, closely united, serving as a nega- tive radical towards either a haloid body as oxygen, chlorine, bromine, or cyanogen, or towards a compound electro-negative radical. By the discovery and extension of the theory of compound radicals, bodies formerly kept separate have been found closely connected, and the extraordinary changes occurring io their oxy- dation or fermentation, become clear and necessary results. A 232 COMPOUND RADICALS. new impetus has also been given to discovery, for no sooner is one of this class suspected than numerous researches are made with the more active agents to investigate the nature of its chlorine, bromine, cyanogen, &c, compounds. The following table con- tains most of the compound radicals at present admitted; many of them have not been isolated; but this is no argument against their existence, for the radical of nitric acid, N05, has never been separated. TABLE OF COMPOUND BADICALS. Electropositive. Symbol. Electro-negative. Symbol. Benzyle . Bz. Cyanogen . Cv. Salicyle . SI. Ferro cyanogen . Cfy. Cinnamyle . Ci. Ferrid cyanogen . Cfly. Ethyle . Ae. Cobalto cyanogen . Ccoy. Acetyle . Ac. Ch romo-cyanogen . Cchy. Cacoilyle . Cd. Platinocyanogen . Cpty. Methyle . Me. Iriiliocyanogen . Ciry. Formyle . Fo. Sulpho-cyanogen . Csy. Cetyle . Ce. Mel lone . Me. Amyle . Ayl. Amiilogene . . Am. Lipyle . Li. Oxalyle . Ox. Allyle . All. Proteine . Pr. Uryle . Ur. Acryle . Acy. Margaryle . Mgl. There are, however, many bodies not yet sufficiently examined for the detection of bases or radicals, as starch, gum, sugar, &c, which, however, present the characters of a natural group. Isomerism is frequent and striking amongst organic compounds, and this will appear a necessary consequence of the grouping of so many atoms by a feeble force ; hence, heat, light, or a cata- lytic action, often produces a new grouping with an entire change of properties. Chemical and mechanical types also prevail in this class of bodies, (see p. 101,) and remarkable substitutions may frequently be made without their destruction. The analysis of organic bodies is rather complex, but the prin- ciple is sufficiently simple. The dry and pure body is mixed with several times its weight of pure, dry black oxide of copper, and heated in a tube of hard glass to a full red heat. By this means all its carbon and hydrogen, taking up the oxygen of the compound of copper, become converted into carbonic acid (C02) and water. These are collected in separate weighed vessels; that for the water contains fused chloride of calcium, which has an intense"affinity for the liquid, and retains all that enters it; by THE NATURE OF ORGANIC BODIES. 233 re-weighing at the end of the operation, its amount is discovered. The carbonic acid is collected in a vessel containing a strong solu- tion of potash, the weight of which, with the glasses known—as all the gas which enters the solution is retained ; by re-weighing at the close of the operation, its amount will be ascertained. By calculation, the amount of hydrogen and carbon in the water and carbonic acid is discovered, and also the quantity of oxygen con- sumed. In this way the carbon, hydrogen and oxygen are ascertained, and if nitrogen be present, it may be collected over mercury as a gas, and its amount directly ascertained, or other means may be employed. The figure represents the apparatus for determining Fig. 59. the carbon, hydrogen and oxygen ; a is the combustion tube set in a charcoal furnace g; b is the chloride of calcium or water tube; c, a connector of India rubber, and m, r, p, Liebig's apparatus of three bulbs to contain the solution of potash and retain the carbonic acid. The above process is not difficult of execution, but requires nice manipulation. It is of no utility to the physician, and, there- fore, not of sufficient importance to occupy the pages of a manual. Those who want to make themselves acquainted with the steps of the analysis will find longer articles in Graham's or Kane's chemistry. ON THE PRODUCTION OF THE PRIMARY ORGANIC PRINCIPLES. We cannot, by bringing the elements oxygen, carbon, and hy- drogen in contact, cause them to unite in such a manner as to produce sugar or any other primary organic body. In such cases, if we employ heat or electricity as the arranging force, there are produced only the first binary compounds of the mineral king- dom. The secondary or pseudo-organic bodies may frequently be produced by certain chemical operations on the primary bodies, or by their partial destruction; but the latter are not generated either in the mineral world, or in the bodies of animals; they appear to 20* 234 LIGHT IS THE ORGANIZING FORCE. be the exclusive products of that tribe of the vegetable kingdom which are of a green color, and require light for their development. The elements concerned in their production, are known to have allotropic states, but have not yet been insulated except in the p (beta) form; they have also an alpha or active state, which is surmised to be fluid, and it is in this, or perhaps some further condition in which they are thrown by the operation of the sun's light, that they combine to form organic bodies. These produc- tions are therefore appropriately considered as the resultants of light, because that agent is essential to their formation, and the substances are totally different from such as would be produced by the operation of electricity or heat. If we plant a seed in a soil perfectly fertile, but in the dark, a young plant is produced, which in a few days has attained its maximum size; here a suitable warmth, a proper soil, and active chemical or electrical conditions are present, but the seedling is of a pale yellow color (etiolated), it is surcharged with moisture, it has not the capacity to increase in size, and after a few days it dies. The nutriment stored up in the seed is converted by heat, moisture, and electrical action into a new arrangement, being partially decomposed—but the ability to group the fluid and saline matters of the soil, and the gases of the air, into new forms capable of supplying more aliment for its growth, and having the capacity of the nutriment of the seed, is absent. To accomplish this, light must be admitted, and if we allow its entrance on one side of a dark room, the young plant instinctively turns to it for succor and support. In the dark, out of pre-existing starch, albumen and other primary organic principles, heat and the chemical force can pro- duce the cellular tissue, oils, fats, resins, acids, alkaloids and other secondary bodies, by a new arrangement of the atoms of the former principles; but these forces are utterly powerless in the creation of starch and albumen out of water, carbonic acid and ammonia which constitute ninety-nine hundredths of the food of plants. We conceive, then, that the changes impressed by the vegetable on its products are peculiar, that their atoms are thrown into new and somewhat instable conditions, and unite by reason of it in groups more complex than in the mineral world, producing results altogether dissimilar, and being by this peculiar cause endowed more or less with the capacity of pro- ducing life, when consumed in an appropriate machine, as the body of an animal. The true organic body is the result of the action of light, and its destruction for the production of inorganic matter is the effect of common electricity, or ordinary affinity. It is, therefore, in an instable state, and in its passage to that which is more perma- THE NATURE OF THE PLANT. 235 nent, extraordinary phenomena arise, such as light, heat, electri- city, and under peculiar circumstances, the motions which we term vital. At least, vital operations take place only during the change of organic matters, under the influence of electrical forces, and cease whenever these are arrested;—life being a resultant of innumerable chemical changes in the body, or in organized mat- ter, derived from the action of plants, and ceasing as soon as a supply of the matter, or a stoppage to the changes, occurs. And these changes are of the nature of oxydation and the conversion of organic, back into mineral matter. The plant, then, is the laboratory in which the true organic principles are created, and the sun's light the agent appointed to mould them into forms capable of sustaining the warmth and energy of animals. Of the agent we have said as much as is consistent with our limits, but it may be well to treat of the nature of the plant and the peculiarities of its action. True plants are to be distinguished from mushrooms, or fungi, which possess functions entirely different, by their green color. They consist internally of cellules either of a hexagonal form or variously elongated for particular purposes. The leaf of a tree presents a specimen of a true plant, but the flowers have the functions of animals; they consume food, throw out heat, and frequently evince motion. The presence of tubes is not essential to the plant, these being provided for the purpose of allowing the fluids of the earth to pass up to the leaf; and another apparatus being also present in trees to carry the sap changed by the action of light, to the roots and other parts of the structure. But without entering into the discussion concerning the ascent and descent of the sap, and the difference of action between the leaves and flowers, it may suffice for us to produce the simplest instance of a true plant, and consider how it is nourished, and what changes are impressed upon its food by light. The simplest vegetable, like the simplest animal, is a single cellule, called the Chlorococcum vulgare. It is found in large numbers on mouldy walls, exposed to the full action of light. Its form is spheroidal, and it consists of a perfect membrane united in all its parts; this is a fine colorless pellicle; in its interior is a green pulverulent matter, with water and other fluids and gases. Exteriorly, the bounding membrane touches the moist wall at one side and' exposes itself to the sun at the other. Here is the entire plant, and the loftiest tree is but an aggregate of such cellules, its leaves possessing no other functions; they differ only in the arrangement of their parts. The young plant is a translucent cellule, its bounding mem- brane is thenliyaline, and it has no green matter in its interior. The membrane consists of cellulose, in combination with a little saline 236 THE POROSITY OF PLANTS. matter; it is the same as that of the cells of all other true plants. Cellulose is a substance almost identical with starch in chemical structure, and is procured from it as well as from sugar and other bodies by chemical changes, as in fermentation, germination and other kinds of sub-decomposition. Cotton, wool, and the hairy down of plants consist of the almost empty cells of cellulose. The chemical nature of this body is altogether different from that of the cell walls of animal substances ; these consist of compounds of albumen with saline matters. The cell wall is everywhere complete, there being no fissures or punctures in it, but it nevertheless allows some bodies to pass through it to the interior, or is porous. Its porosity is not due to palpable apertures, for no microscope can discover them; it is the porosity which belongs to all masses of matter, being due to the spaces which exist between the atoms. Hence it is to be dis- tinguished in its effects from the action of holes which would allow leakage, for through these interstices such bodies alone pass as have an electrical or capillary attraction for the bounding membrane ; and such alone pass into the interior as have a similar relation to the fluid, solid or gases which may occupy it. That the cellules of plants have this interstitial or capillary porosity, I have directly proved by experiments with the epidermis of several species.* The nature of capillary attraction, and the conditions necessary to the entrance of gases or fluids into the interior of cellules, will be fully examined in a subsequent chapter. The cell lies, on one side, in apposition with the earth or moist wall on which it vegetates; from this quarter it is supplied with water, holding in suspension carbonic acid, and a little ammonia, and containing saline matters, of which the phosphates and sul- phates of potash, soda, lime and magnesia are the chief. Some plants, however, demand silica, iron, and other peculiar mineral bodies. The water, with the bodies it contains, is admitted by porosity into the plant, and serves by swelling it out, to advance its development. On the other side, the membrane is in contact with the air, from which it selects carbonic acid, and perhaps, in dry weather, a little carbonate of ammonia. It is now lighted by the sun, and the problem to be resolved is, what changes occur within this petty laboratory ? Such as are the foundation of life, such as shall hereafter furnish means for the support of the physical and mental activity of man himself! The matters which have found entrance through the porous wall of the cellule, constitute the plant food, out of which all organic bodies are directly or indirectly to be generated. This * See my memoir, entitled "The Physical Structure of Plants" in the Ameri- can Journal of Science. "\ ol. ii. 1840. THE PRODUCTION OF ORGANIC BODIES. 237 food, which alone serves to nourish the oak, the weed, or the mildew, consists of water, carbonic acid, ammonia, phosphoric and sulphuric acids, in combination with certain bases of potash, soda, lime and magnesia chiefly, these being in minute quantities, but absolutely essential. Put them together by the electrical force, and we have an impure solution of carbonate of ammonia, and to this they pass upon the final decay of the plant. The result of the chemical force is thus far uniform, but they are now to be grouped by the sun's light. Instead of a simple union in which oxygen gas is the most active element, as in chemical compounds ; instead of a change the great feature of which is oxydation, the light commences organic operations by driving off the oxygen — by a procedure the reverse of that of electricity, and by deoxyda- tion. The yellow ray of light falling on the cellule distended by ca- pillary action with food, commences its digestion by decompos- ing carbonic acid. This body, C02, loses its oxygen, most of which passes out of the cellule into the air, some of which is, how- ever, retained ; this decomposition is the effect of the sun's light, for it does not occur in the plant during darkness. Nascent car- bon is thus produced, and it instantly unites with some of the water present, twelve atoms of carbon combining with ten atoms of water, whereby soluble starch or dextrine is formed, having the form C)2H|0O10. Here is at one effort produced the most im- portant body in organic chemistry. This gives a gummy consist- ence to the water of the cellule, which in the plant constitutes the elaborated sap. By another action of change the green color of the cellule is generated, and thereafter further alterations in the plant food occur. The green matter, termed Chlorophyll, serves the important purpose of decomposing the compound beam of white light; it absorbs the red and allows the yellow and some blue rays to pass during the vigor of the plant; but as soon as it acquires the orange and red tint of autumn, these active rays are more or less cut off, and the functions of the leaf are altered, or cease altogether. , This decomposition of carbonic acid is the starting point of life, and of the activity of the plant. The oxygen'thrown off produces a gaseous current outwards, which is compensated by the substi- tution of a stream of fresh carbonic acid from the air; thus this important aliment is recruited. The thickening of the water by the dextrine, serves to solicit, on the other side, fresh supplies of fluid from the soil, and under the influence of these causes the cellule expands or grows. But chiefly is the effect remarkable in the chemical action of the gummy dextrine itself. The student will learn that sugar, starch, dextrine, cellulose and woody fibre are closely allied, all being compounds of carbon with water, nearly 238 THE PRODUCTION OF ORGANIC MATTER. in the same proportions, and being mutually convertible—they do indeed act as though they were almost isomeric. To have pro- duced dextrine, is, therefore, the same thing as to have generated gum. sugar, &c, as these may be artificially made from it. But the dextrine is still more important, for by its combination with ammonia, present in the cell fluid, there is generated proteine; this process will be explained hereafter. Proteine is the basis or compound radical of fibrine, cheese, albumen, muscles and all the tissues of animals, and the essential component of all food capable of sustaining life. By this simple union, is therefore generated the most important product in nature. But the deoxydizing action of the sunbeam is not confined to carbonic acid ; the phosphoric and sulphuric acids present are re- duced to their elementary forms. The sulphur and phosphorus uniting with proteine give it the structure of fibrine and albumen, and thus the process is completed, whereby the two great classes of organic bodies are produced. To the first class, called the Amylum series, belong the non- azotized bodies, starch, sugar, gum, lignin, and their modifica- tions. By oxydation these yield the vegetable acids, by deoxyda- tion and fermentation they produce alcohol, ether, the oils and allied bodies, and by a high heat volatile and tarry substances. The second class or the Proteine series contains albumen, fibrine, caseine, and their modifications in the blood and animal tissues; by the influence of chemical action these yield ammonia, urea, alloxan, and other secondary animal products, whilst in plants they seem to be connected with the production of the alkaloids and azotized coloring matters. Subordinate to these groups of primary organic bodies, other substances are formed in the texture of plants; some of these are common to all, and many are peculiar to a few. The)' are, more- over, supposed to be produced by catalytic actions, occurring chiefly in the parts of plants removed from the sun's light, and in the roots where there is also a lower temperature than in the leaves. To this secondary class belong the oils and vegetable acids; the former are probably formed in the presence of light, for they are deoxydized, some containing no oxygen, and having a resemblance to the general formula C5H4. The oils are formed from bodies of the amylum series, for they can be produced by fermentation (catalytic action) from them; they also often ap- pear in the Indian corn plant, as the sugar disappears, and are closely connected with its conversion, for carbonic acid is pro- duced at the same time, and, as will appear hereafter, the sepa- ration of this body, with a few equivalents of oxygen, from the amylum compounds, converts them into oily and fatty bodies. As the acids are formed at the same time as the oils, the excess of THE PRODUCTION OF ORGANIC MATTER. 239 oxygen may serve to give them their necessary components, for the equivalents necessary to make up an atom of oil and of vege- table acid, represent two atoms of sugar, with a few atoms of car- bonic acid which are separated. The coloring matters of plants present a resemblance to the proteine bodies, usually contain a considerable amount of nitro- gen, and are most probably secondary products of this radical. The vegetable alkaloids do not present this connection; they con- tain but little nitrogen, and appear to be formed by the action of ammonia on bodies of the amylum series. In entering upon the field of organic chemistry, it may be proper to give some outline of our course. We propose first to present the primary bodies of the amylum series, then the deriva- tives from them produced by the action of fermentation, by oxyda- tion and by heat; this will carry us through the greater part of the non-azotized organic bodies. Special chapters will be de- voted to the oils and fats, alkaloids and coloring matters. The azotized group will next be presented; and we then enter on the subject of food, the process of digestion, the means by which chyle, lymph and the blood are borne through the system, with the nature of these fluids and their offices in the body, including respiration. The nature of secretion, especially of the liver and kidneys, will then be considered. 240 THE AMYLUM SERIES, OR STARCH GROUP. The bodies of this series are not known to have any compound radical, but they all contain 12 atoms of carbon united to from eight to fourteen of water, and if we select C12HsOs, which is lignin, for the primary body, the others will be hydrates of it. This body is also the most stable of the series, and one into which they are resolved in a great measure by plants. The principal bodies are enumerated in the following list, but they present several varieties, some of which have not yet been analyzed. Their formulas are doubled by a few chemists in consequence of some of them forrrting compounds with salt, &c, in the higher number. Those bodies placed in brackets are isomeric. Starch Dextrine - Cellulose - Tragacan thine - Cane sugar - - ) p „ _ Gum Arabic - - 5 ui2Hn^n Sugar of milk - - C12H)20, Sugar of ergot - - C12H1301 Grape sugar (glucose) ~) Sugar of eucalyptus - Sugar of starch Sugar of diabetes Lignin - CI2Hg Os Pectine - - - C„H„ 0, 1 ^C10H,nO, j>Cl2H>4°14 Starch—Fecula. CiaET,0O10.—It is found abundantly in the seeds of plants, and in the tubers, roots and other parts of annuals. It is separated for commercial purposes from wheat and potatoes; the process is as follows: The potatoes are rasped finely by a revolving instrument, and the magma thus produced is kneaded with a large amount of water frequently renewed, upon fine hair sieves, through which the water carries the starch, whilst the cellular and fibrous matters remain behind. The water is at first milky, but soon precipitates its starch, which is altogether inso- luble in cold water, as an adhesive mass, which may now be dried at about 212°, and subsequently splits up into the columnar masses in which it is found in the shops. Potatoes furnish about 23 per cent, of starch, but wheat flour yields upwards of sixty, by a process very similar to the above. The principal substances in commerce abounding jn starch, are arrow-root, tapioca, sago, cassava, rice, barley, and grains gene- STARCH. 241 rally; but the sweet potatoe, many fruits and vegetables, also contain large amounts. Starch is tasteless and inodorous ; it consists of white granules, having a regular organization, but differing in size indifferent plants. It is of soft texture, insoluble in cold water or alcohol, but soluble in boiling water, which appears to rupture the insoluble shell of the cellules, and allow the interior gelatinous body, called amidine, to pass out. The gelatinous starch dries into a yellow transparent body like gum, which afterwards swells in cold water. Starch baked at 400° F. has its cellules broken up, and becomes a clear brownish body called British gum, or leiocome ; it closely resembles common gum, and is used as a substitute in the arts. A cold solution of starch (amidine) is gelatinous in proportion to its concentration; when dilute it is precipitated by solution of lime, baryta, oxide of lead, and other metallic bodies, as well as by alcohol—a few drops of tincture of iodine produce a rich blue color (iodide of starch), which is highly characteristic. This does not act in a boiling solution, and the color is destroyed by heating for some time, the iodine being volatilized. Starch is neutral, but compounds have been formed with oxide of lead, &c. By the action of dilute sulphuric acid and heat, or by diastase, starch is converted first into dextrine, and finally into starch sugar or glu- cose. This is a catalytic action, for a few drops of acid will change almost any amount into dextrine, which is isomeric with starch, and therefore consists of the same atoms differently grouped. There are several varieties of starch—the chief of which are the gelatinous starch of Iceland moss, called lichen starch ; cara- gheenin or the starch of Irish moss; and inuline, which is derived from the root of the dahlia, Jerusalem artichoke, Inula helenium, and other bodies. Inuline is rendered yellow, and not blue, by iodine, and has the formula of C12HMOn, according to Mr. Parnell. Starch is used in the arts for the purpose of giving consistency and polish to textile fabrics; a solution serves also to give card- board splints considerable hardness when dry. In medicine it is used as an absorbent to wounds; and in dietetics as a demul- cent when cooked. Rice, and the bodies already enumerated, consist chiefly of this principle, and are used to an injurious extent in the sick chamber, under a false impression that they are highly nutritious, and easy of digestion. So far from this, it has been found that these aliments are very injurious in cases where there is irritation of the gastro-enteric membrane, especially in children; for, by collecting about the follicles, the granules irritate them, producing or increasing diarrhoea. Indeed, in the H6pitald.es Enfans Trouves, of Paris, it has been found that the diet of rice, to which children suffering from diarrhoea had been condemned, 21 242 CANE SUGAR. was one of the chief causes of mortality in that institution, and light jellies have now been substituted. In these cases it pro- duced follicular inflammation of the intestines, which was the cause of death. The barley-water and farinaceous slops of our sick rooms are equally pernicious, and should be cast aside as a relict of the exploded systems which prescribed indiscriminate purgation, bleeding and sweating as the sheet anchors of the heal- ing art. Iodide of starch has been recommended as a medicine, but possesses little of the activity of iodine, and becomes uncertain in its composition if kept, or exposed to warmth. Sugar.—Under this name are grouped a variety of bodies, hav- ing a sweet taste, and solubility in water, as their characteristics. The principal are cane sugar, glucose, and milk sugar, or lactine, but there are also a sugar of ergot, a sugar of the Eucalyptus, and a variety derived from manna and mushrooms, called mannite, which has the formula CfiH706; this is crystalline and non-fer- mentable. Cane Sugar—Ordinary Sugar.—In the crystallized state its formula is C12HltOu, but two atoms of the water appear to be attached as water of crystallization, and removable by heat, when it melts, and forms the yellowish, transparent barley-sugar. It is obtained from the juice of the sugar cane, beet root, and sugar maple, for commercial purposes, but exists in many other plants. The clear juice is first inspissated by boiling, the scum being continually removed; when it has acquired a certain thick- ness, it is placed in shallow pans to granulate or crystallize. It is then drained from the uncrystallizable syrup or molasses, and con- stitutes raw or Muscovado sugar. This is further refined by re- dissolving, heating with the serum of blood or white of eggs, and removing the scum. The syrup is next filtered through animal charcoal, which decolorizes it, and, being inspissated again to the crystallizing point, it is put into conical moulds. This forms, when dried by a stove, common loaf sugar, which may be further refined by pouring through it in the mould, before drying, some clear syrup. When carefully prepared from syrup, it crystallizes in the fine, large, oblique rhombic crystals of sugar candy. Sugar is deprived of water by a high heat, and resolved into a brown body called caramel, used as a coloring matter. Sugar is neutral in properties, but it forms compounds with common salt, the oxides of lead, barium, calcium, &c. By dilute sulphuric acid it is first converted into glucose, but by long heating it throws down black precipitates called sachulmine and sachuimic acid, nearly resembling common ulmine, the product of the slow decay of woody matter. By the action of caseine fer- ment it is converted into lactic acid. The test will be given under Glucose, THE VARIETIES OF SUGAR. 243 Glucose; C12HI40I4—Fruit Sugar, Grape Sugar, Starch Sugar, Sugar of Honey, Sugar of Diabetes.—As its name implies, it abounds chiefly in fruits, and is readily procured from raisins or honey; it is also the sugar found in the urine of persons afflicted with diabetes mellitus. Cane sugar, starch and lignin are readily converted into it by the action of very dilute sul- phuric acid, assisted by heat in the case of the two latter. It is less sweet and soluble than cane sugar, and crystallizes with dif- ficulty into confused masses. By heat it loses four atoms of water, blackens and becomes decomposed ; it is also blackened by a solution of caustic potash which does not affect cane sugar. On the other hand, it dissolves freely in strong sulphuric acid, and forms sulphosaccharic acid, which yields regular salts with bases. Cane sugar is decomposed and blackened by the strong sulphuric acid. Heated with the alkaline earths, glucose forms glucic acid, and with a boiling solution of the alkalies, the melasinic acid—bodies of no peculiar interest. The principal distinction between glucose and the other sugars is that it is readily fermentable, whilst they have to be convened into it before taking on this change, and some do not ferment under any circumstances—as mannite, and glycyrrhizine, or the sugar of liquorice. It is also distinguished from cane sugar by its action on the oxide of copper. If glucose and cane sugar be mixed in separate tubes with a very dilute solution of sulphate of copper, and a solution of caustic potash be then added until the precipitate first formed is re-dissolved, beautiful blue solutions will be obtained in both vessels; but if they be now heated, the one containing glucose will rapidly change to an opaque green color, then orange, and finally yield a dark red precipitate, leaving the fluid clear; but the fluid containing the cane sugar will remain blue for a long time before it throws down a red precipitate of suboxide of copper. This test is employed also for the purpose of detecting sugar in diabetic urine, the only additional step being the separation of any precipitate Avhich may fall on the introduction of the solution of potash. This is called Trommels test, and is highly satisfactory. Sugar of Milk, Lactine—C12H12012—is present in milk, and obtained by evaporating whey to a syrup, and allowing the sugar to crystallize. It forms white four-sided prisms of considerable hardness, is sparingly soluble, and does not readily ferment, and is converted into lactic acid by caseine ferment. It is used by the homoeopaths to mix with their medicines. Sugar of Diabetes Insipidus.—This curious substance, derived from the urine of persons suffering from insipid diabetes, has all the chemical characters of sugar, but is tasteless. Gum.—Under this head are grouped a number of bodies which 244 THE VARIETIES OF GUM. are more or less acted on by cold water—some, like arabine and dextrine, being very soluble, and forming a thick mucilage ; others, like tragacanthine, merely swelling. They are nearly all taste- less, and when dry, form a more or Jess transparent, brittle or horny mass, without crystalline form. The chief varieties are dextrine, arabine, tragacanthine and pectine. Dextrine.—This is the mucilaginous fluid of vegetables; it is also produced by the action of very dilute sulphuric acid and other catalytic agents on solution of starch, and in germina- tion. Its name is derived from the property a solution possesses of turning a ray of polarized light to the right, whereas gum turns it to the left. It is the great cytoblastema of plants, out of which the various tissues are made by cell growth. It is pro- duced from the starch of seeds and bads by diastase; which is a true ferment derived from the oxydation of albumen. The seed contains albumen or fibrine and starch ; so long as these are kept dry, no change occurs, but on committing it to the soil, moisture and warmth act, and oxygen is absorbed the last, acting on the pro- teine body, produces diastase, and this communicates a change, catalytically, to the starch, which hence becomes a solution of dextrine, and fitted to supply the materials of growth to the cell germs (cytoblasts) of the embryo. Its formula in the dry state is Cl2H]0OI0. Arabine—Gum Arabic; C12HuO„.—It is the produce of seve- ral trees, of the genus Acacia, being thrown out as an exudation from their trunks. The purest is without color, bright, readily soluble, forming a thick mucilage with water. It is employed as a demu' it, and to suspend oily and resinous bodies in pharmacy. Alcohoi -nd a solution of subacetate of lead precipitate it from its solu' ■•11. Tragacanthine, Cerasin, Bassorine, and several other gummy bodies, refuse to dissolve in cold water,but swell and become pulpy. Pectine—Vegetable Jelly.—This substance is found in some fruits, and in the carrot and similar roots; it is sparingly soluble in cold water, but dissolves by heat and gelatinizes as it cools. It is tasteless, and abundant in the currant. By contact with the alkalies it is changed into pectic acid, a substance apparently isomeric with pectine. Its composition is not quite certain, but according to Mulder is C]2H8Ol0. Lignin.—This name is given to the interior insoluble and fixed matter of woody fibre. The fibre itself consists of fusiform cel- lules arranged in bundles, the material of which, like all the cel- lules of the plant, is cellulose (C,2H10Ol0), and these contain the lignin, the structure of which is C12HsOg. Fine linen offers a beautiful illustration of cellular lignin; it is white, tough, taste- less, insoluble and innutritious. Strong sulphuric acid converts LIGNIN AND CELLULOSE. 245 it in the cold into a tough mass resembling a solution of dex- trine; but if the mixture be warmed, the lignin will be charred. If the solution of dextrine obtained in this way be boiled, it be- comes converted into a solution of grape sugar, which may be depurated by neutralizing the acid by chalk, filtering and evapo- rating to dryness. Linen rags may thus be made to yield more than their weight of grape sugar. Cotton fibre presents us with a specimen of nearly pure cellu- lose, and there is not much distinction between the reactions of this body and linen. They have the same general properties; they may both be made into a magma by beating with water, from which preparation paper is made by spreading it over wire frames by rollers. They both dissolve in cold sulphuric acid into dextrine, and they both yield a detonating compound with nitric acid, called gun cotton. Gun Cotton, Nitric Cellulose, Pyroxyline.—When cotton or linen is immersed in a mixture of equal parts of concentrated nitric and sulphuric acids, their texture is scarcely affected, but they combine with two atoms of nitric acid, and when carefully washed and dried at a low heat (130° F.), become more explo- sive than gunpowder. It may be exploded by heat at about 200° F., and by the blow of a hammer. This body was intro- duced by Professor Schonbein as a substitute for gunpowder, but it is too dangerous to be much employed. The Pseudo-organic Bodies derived from the Amylum Series. —The foregoing bodies of the starch group are readily changed into pseudo-organic substances, but with unequal facility. The long-continued action of the alkalies and alkaline eai ' s causes several to become altered into acids, as in the producU a of the glucic and melasinic acids from glucose. Sulphuric id more completely disorganizes many of the series, but its compounds are not of great interest. It is to the action of oxydation that we are indebted for most of these changes. This may be rapid and complete, as when nitric acid is made to act upon starch, sugar, &c, or it may be slow, as in the production of acetic acid from alcohol; in this instance, it is termed eremacausis, or slow combustion. Fermentation and catalytic action are other important means of change. This kind of action is most influential on solutions of glucose; but starch, lactine and other bodies are influenced by it, and highly important bodies result from its action, as alcohol, ether, lactic, acetic and butyric acids. We shall in the following pages confine ourselves to the above sources of change, and adduce the principal products of their action. 21* 246 OXALIC ACID. THE ACTION OF DIRECT OXYDATION ON THE AMYLUM SERIES. All the principal bodies of this series except some of the gums and lactine, are converted into oxalic acid by the action of nitric acid. Gum and sugar of milk yield mucic acid by the same agent. The strength of the acid also influences the process, for the sac- charic or oxalhydric acid is produced when dilute nitric acid acts on sugar. Oxalic Acid.—Formula of the true acid HO+C203 of the crystallized acid HO-f C,03-f-2Aq. To prepare this body take one part of sugar, five of nitric acid of sp. gr. 1.42, diluted with twice its weight of water, place in a retort and warm gently. Much effervescence occurs with the evolution of red fumes, which indicate the decomposition of the acid and oxydation of the sugar. When the action slackens, heat is again applied, and the superfluous acid is distilled off, until the liquid of the retort de- posits crystals on cooling. These are drained, redissolved in a little hot water, and set aside to crystallize. The explanation of the changes is sufficiently simple. 1 atom of cane sugar - - - =CwHnO„ 6 atoms of theoretical nitric acid (N05)= O30N6 Mixture in the retort without the water=C,aHu041N6 This is resolved into 6 atoms of oxalic acid (C203.HO) - =C12H6 024 6 atoms of binoxide of nitrogen(N02) = 013N"6 5 atoms of water - - - - = H5 05 CJ3Hlt041N6 So that one atom of sugar, deriving eighteen atoms of oxygen from the decomposition of the nitric acid, yields six atoms of oxalic acid. But in practice the changes are not so simple, for some further decompositions occur. Oxalic acid is white, intensely sour, more soluble in hot than cold water, and is usually found crystallized in oblique rhombic crystals. These are at a gentle heat deprived of their two atoms of water of crystallization, and then form a white powder which may be sublimed ; but if the ordinary acid be strongly heated, it is decomposed into formic acid, carbonic acid and carbonic oxide without solid residue. It is a powerful acid, the basic HO being replaced by most metallic oxides. It is an active poison, and is occasionally taken by mistake for OXALIC ACID AND OXALATES. 247 Epsom salts, and being abundantly used in the arts for cleaning metals, it may be procured for felonious purposes with facility. In large doses, it acts as a corrosive poison, disorganizing the stomach, but when dilute, it diminishes the heart's action, and acts also on the nervous centres. The antidote, which is to be at once employed, without recourse to emetics or the stomach pump, is pounded chalk mixed up with water. This forms the inert oxalate of lime. The inflammation of the stomach and other symptoms are to be met by the ordinary remedial means, care being taken not to increase by active depletion, the debility of the system too much. Oxalic acid is not now used in medicine; but in dilute doses it is refrigerant, and an arterial sedative; its taste is intensely sour, and it has, therefore, to be mixed with a good deal of water. It is readily recognized in solution or in its soluble salts by producing a white precipitate with lime water, and it is employed for detecting this base in the laboratory. The precipitate of oxalate of lime is soluble in nitric acid. When heated in the open air, it turns black, and is converted into carbonate of lime, or, at a higher temperature in a closed vessel, into caustic lime. The acid is also decomposed by heat. Warmed with strong sulphuric acid, it becomes resolved into water, carbonic acid and carbonic oxide. Compounds.—The oxalates of potash, especially the binoxa- late, occur in many plants, as the sorrel and docks. The quadrox- alate, which is very sour, is sometimes employed to remove ink stains. The oxalate of ammonia is found in some organic sub- stances which are undergoing decay, as guano, and employed in solution as a test of lime. It is a crystalline body of some solubility, and remarkable for the production of oxamide when heated. The salt of ammonia yields several gaseous bodies, and finally a dense white smoke, which may be sublimed, and is the oxamide. This contains the elements of arnidogene with two equivalents of carbonic oxide, or H2N-j-2(CO), and represents a small class of bodies containing arnidogene. The Oxalate of Lime.—This salt has the composition CaO, C203 + 2HO, and it is formed whenever oxalic acid acts on a solution of lime. It exists in many lichens and plants, as the rhubarb; and forms one variety of urinary calculus, the mulberry calculus. It is insoluble in water, but dissolves in nitric acid, and is decomposed by heat, being converted first into the carbonate of lime, and subsequently into caustic lime in a closed vessel. By this means the mulberry calculus is readily distinguished as well as by its rough reddish-brown color. Numerous other oxalates have been formed, but they have been put to no use. 248 OTHER PRODUCTS OF OXYDATION. Saccharic Acid—Oxalhydric Acid, C12H50ll + 5(HO).—This is formed by the action of dilute nitric acid on sugar. It is crystalline, very soluble, sour, and forms soluble salts with lime and baryta, and an insoluble salt with lead. WThen mixed with solution of nitrate of silver, it yields no precipitate, but on adding ammonia, a white body falls, which is decomposed by gently warming the vessel, and metallic silver is precipitated, which, adhering to the glass, gives it a bright mirror-like appearance. This acid is pentabasic, but its compounds are scarcely known. Mucic Acid; Cl2HgO -f2(HO).—This acid is procured by heating gum or sugar of milk with pretty strong nitric acid. It is bibasic, a white, sparingly soluble body of a slightly sour taste; its salts are little known. By heat it is converted into the volatile Pyromucic acid. Other Bodies.—The Suberic acid, obtained by the action of nitric acid on the ligneous matter of cork, is very similar to the mucic,but more soluble; its formula is CgH603-|-HO. Xyloidine (C6H404,N05) is produced by the action of nitric acid sp. gr. 1.5 on starch, which yields a gelatinous body that forms with water a white insoluble substance. Paper dipped for a moment into the acid, and afterwards washed in water, assumes a parchment- like appearance and great inflammability. This is another form of xyloidine. The gun cotton is a direct compound of cellulose with nitric acid, and has been already described in the article on Cellulose. OF FERMENTATION. The word fermentation was originally employed to indicate the movement taking place in wort, when subject to the action of leaven or yeast, but has been greatly extended in its meaning, and now includes several cases of decomposition or change of a catalytic nature, taking place in the bodies of the amylum series, and especially in glucose, and under the influence of a ferment. The ferment consists in every case of a proteinous body, which is in the state of incipient decay, probably suffering oxydation by the access of atmospheric air. Temperature has great influence over this process; thus it will scarcely occur at 40° F., and the resulting body depends consider- ably on the degree of heat maintained during the action; thus at 50° caseine in milk produces lactic acid by fermentation, but at 80° it engenders alcohol, and if carbonate of lime be present, a third substance called butyric acid is formed. The degree of decomposition of the ferment is another important cause of change in the product; thus oxydized albumen, acting as a ferment, converts starch into sugar, and produces the organic OF FERMENTATION. 249 action by which cellulose is formed; when further changed, it converts this sugar (glucose) into lactic acid, and still changing further, at length produces alcohol from the sugar. Thus three or four products arise from the action of the same ferment, which is, however, itself undergoing change, and may be regarded not as one, but as many ferments. That it is the ferment which con- tinues the action, appears from the fact that a given amount of fer- ment will only produce a determined change in sugar or other bodies; but it has the capacity of affecting a large amount. Thus one part of diastase, which is a peculiar ferment produced in the germination of seeds and growth of buds, is capable of converting 2000 parts of starch into sugar. In some kinds of fermentation, as in the brewing of beer, fresh portions of ferment are formed out of proteine bodies present in the wort, so that a double action occurs ; the sugar is changed into alcohol, carbonic acid and water, by one atom of yeast, but the albumen present in the wort is also changed, and forms a new pro- portion of ferment. But nothing of the kind occurs if we add a given weight of yeast to a pure solution of sugar; in this case, there being no albumen to become changed, the first yeast passes through a series of changes, and is finally destroyed, disappearing from the fluid and only affecting a determinate amount of sac- charine matter. This'distinction is important, for it furnishes us with an explana- tion of the different results which attend the action of the same fer- menton different solutions, and it has also been employed by Liebig in his theory of the action of certain contagious poisons. His views are plausible, and worthy of some attention on the part of the pro- fession. Among the contagious poisons adduced, are the small-pox, vaccinia, plague, framboesia, syphilis, dissection virus, measles, scarlet fever, the froth of the mad dog, &c. In all these cases, some- thing called the virus (ferment) is made to act on the body; it may be inhaled by the air, or immediate contact of the ferment may be necessary. This finding its way into the system, produces changes similar to those hereafter to be described, and is also attended by the production of further amounts of the virus, which is formed like new yeast in wort, in consequence of the presence of some suitable proteinous body. This new ferment (virus) may be used in several of the above cases to reproduce the disease in other persons. Another peculiarity exists with respect to the action of some of the above poisons—they act on the body, in most cases only once, as in small-pox, vaccinia, scarlet fever, measles. In these, Liebig "supposes that the matter susceptible of change is destroyed in the body on the first attack, and not again engen- dered. But these are rare in comparison with those cases in which the ferment acts every time it is introduced into the body, 250 THE METHOD IN WHICH FERMENTS ACT. as in syphilis, plague, the dissection virus. Here there is not a peculiar body influenced, but the ordinary principles of the sys- tem. Again, there is a class of diseases which originate in the action of a ferment (virus), but which do not reproduce it—such are bilious remittent, intermittent fevers and similar endemics. It has long been an interesting question to discover the method in which the ferments act. They obviously do not act by any direct affinity, for the yeast added to a solution of sugar, neither unites with it nor with the alcohol produced. If we investigate the matter more closely, we find that the yeast forms no chemical union whatever with the products of decomposition; that it has no affinity to satisfy, and is itself undergoing decay. Berzelius includes the action of fermentation among the cases of catalysis, in which the result produced differs from those of common chemical affinity, and in which the active agent either remains unaffected, acting by its presence, or does not enter into union with the pro- ducts. To this kind of action are also referred the cases where dilute sulphuric acid acting on a solution of starch, converts it into glucose without being affected itself, and numerous cjhanges induced by spongy platinum, platinum black, and other porous media on compound bodies. Many of these cases offer merely illustrations of the fact that, when gaseous bodies are present- ed to one another, or to liquids in a very condensed state, union occurs, the platinum, &c, acting physically or by capillary at- traction to condense. Thus, oxygen and hyrogen are made to unite by spongy platinum, because this substance condenses them so powerfully that they are presented to one another in such a form that the resistance offered to their union by elasticity is overcome. So platinum black, by condensing the oxygen of the air, and bringing it in contact with the vapor of alcohol, oxydizes that body, converting it into acetic acid and water. In some cases of cata- lytic action, the mere act of condensation may be sufficient to pro- duce chemical change, but this does not occur in many instances, and it is also to be remembered that the fact of such powerful condensation argues the presence of a considerable force. Another view of the action of fermentation, which also includes other cases of catalysis, is to the effect that the ferment or other active body disturbs the electrical equilibrium of the bodies pre- sent, or polarizes their particles, and thus sets up new chemical actions. We know that union between atoms is effected by the electrical force, and that decomposition results whenever a new electrical state is produced ; and it may be urged in favor of this view, that the action of fermentation is capable of producing changes out of the fluid in which it is occurring, which are analogous to those of electricity—thus it will cause a mixture of oxygen and hydrogen to unite, and other similar effects. THE RESULTS OF FERMENTATION. 251 Liebig is the author of a third hypothesis, to the effect that the ferment being in a state of decay, molecular movements are trans- piring in its substance, which are communicated to circumjacent bodies of an instable composition. In this view of the case, the cause and effect are molecular movements, and the action of fer- mentation is separated from catalytic actions generally. Prof. Hare objects to this doctrine, on the ground that it is incredible that one molecule of diastase undergoing a slight movement should impart a similar motion to two thousand of starch without being at all checked itself. It may be well to observe that the theory which attributes the effects of fermentation and catalytic actions generally to the influ- ence of electrical disturbance, is that most consonant with the present views of chemists. The results of fermentation are very different. When the ferment is but slightly changed, as in the case of diastase, the pepsin of gastric juice, the ptyalin of saliva, it produces little more than a new grouping of the atoms. Thus diastase converts starch into glucose and cellulose, which scarcely differ in composi- tion. So ptyalin converts sugar into lactic acid which is isomeric. Pepsin renders insoluble albumen, and fibrine soluble. These are all cases of change in grouping;—there is nothing evolved. But the action of yeast is widely different, for it changes the sugar of the wort into alcohol, water and carbonic acid, which are substances in no way similar to the sugar. Hence, the same proteine body, in different stages of decay, constitutes different ferments, and as it departs more and more widely from the consti- tution of proteine, the more power has it to decompose the fer- mentable matters on which it acts. The tendency of fermenta- tion is, moreover, similar to that of all other actions on organic bodies—to reduce them to the inorganic state, the final products being water, carbonic acid, ammonia and cyanogen. But it does not act so rapidly as heat or nitric acid, and produces a great number of intervening changes. Any substances which have the power of hindering the decay of tne ferment, as metallic salts, many spices, alcohol and similar bodies, also stop fermentation. These are termed antiseptics, and the chief are corrosive sublimate, creosote, pyroxalic spirit, sul- phate of copper. Salt and other bodies act by removing the water from the compound. Heat and cold are also antiseptics; the first acts by evaporating the water and hindering that freedom of motion which is essential to chemical change—whilst cold, by solidifying the water, accomplishes the same end. The absence of oxygen, by which the proteine body is first changed, also renders fermen- tation impossible. From the foregoing, the student will be prepared to understand 252 THE ORGANIC FERMENTATION. that there are many kinds of fermentation, or catalytic action, pro- duced by the presence of a ferment. The chief of these are: 1. The organic fermentation. 2. The germinative fermentation. 3. The viscous fermentation. 4. The lactic acid fermentation. 5. The butyric acid fermentation. 6. The vinous fermentation. 1. The Organic Fermentation.—We propose this name for that kind of change which occurs in the solutions of the organic acids and their salts, in mucilage of gum, or paste and other organic bodies in contact with a moderate amount of water. For its manifestation, a temperature from 50° to 80° appears to be most suitable; and, as in all other cases, the presence of a ferment con- taining azote but in the first degree of change. Oxygen is also necessary to its commencement, but the quantity may be ex- tremely small. The chief product of this action is cellulose, which will be found in cells aggregated together in various ways, forming threads in the saccharomyces or torulae, and fleecy masses in the mycoderms, of which the mother of vinegar is an instance. The varieties of mildew and mould belong to this class of organ- ized products, the existence of which is dependent on the first step of decomposition in the amylum or proteine series. Mulder has determined that yeast consists of an organized body, the cells of which contain an oxide of proteine, which continually under- goes change and escapes from the enclosure. In every case of organic fermentation, azotized matter is pre- sent, for if we make a solution of an organic salt in fresh distilled water, taking every precaution that no nitrogen be present, there will appear no mould or mycoderm. Nearly any azotized body will serve to originate this change; fibres of silk will do so, and other bodies which appear to be little acted on themselves. It is probable that the action under consideration is the cause of cell development in all cases; for why should the dextrine of the plant or the albumen of the blood assume the configuration of cells ? There must be for this effect some competent cause, and we can conceive of none so probable as that under consideration. According to this view, when albumen assumes the cellular figure, as it does in yeast and the bodies of animals, there are certain conditions of moisture, temperature and oxygen present constraining it; otherwise it would remain inorganized—there is a change of grouping perfectly analogous to that of starch into sugar, or starch into dextrine. Whilst the organic fermentation appears to act by re-arranging the molecules of organic matter, and forming similar or isomeric compounds, it does not seem to be so restricted in its action as THE GERMINATIVE FERMENTATION. 253 many other kinds of fermentation. In nearly every case, par- ticularly in the germinative, viscous and vinous fermentations, there are produced organized bodies ; these it is presumed re- sult from the first action of the ferment, or express the first alteration in the ferment itself. As the vinous fermentation comes to an end, the torulae become shrivelled and finally subside in the liquid. Torulas, the doubtful objects called vibriones, and a genus called sarcinia, have been found in the diseased gastric juice and urine of man. The first two of these consist of cellules, arranged linearly, the last of four cuboidal cells arranged together. From what has been said, it will be understood that these organized products may be more or less permanent or extremely transient. When the ferment is in minute amount and the action on an organic salt, as citrate or tartrate of potash in solution, the cellular product remains unchanged for months; but in other cases, as in the vinous fermentation, this is a stage in the changes and not a final result. 2. The Germinative Fermentation. Germination.—The changes which occur in the seed under the influence of warmth, moisture and oxygen, constitute a true fermentation, not peculiar to the seed but of common occurrence. It takes place in what has been called the panary fermentation, and according to Bou- chardat, occurs in the stomachs of dyspeptics and those laboring under diabetes mellitus. It is characterized by the production of glucose and cellulose from starch, or, in other words, in germina- tion there are two actions of fermentation, the one producing the conversion of starch, and the other being analogous to the organic fermentation. The temperature most congenial, ranges between 60° and 100° F., the presence of oxygen is indispensable, and water must be supplied in moderate quantities. The chemical phe- nomena are the absorption of oxygen and water by the seed or fermenting body, the evolution of carbonic acid and heat, and the production of sugar (glucose), cellulose, and a particular fer- ment termed diastase. The seed, it will be remembered, contains starch and albumen, from which latter the diastase is produced by the action of oxygen. A reference to the bodies of the amylum series shows that the action of the ferment is little more than to form a new grouping of the atoms of starch. The malting of barley offers an illustration of the germinative fermentation on a large scale. The seed becomes sweet thereby, and throws out a leaf formed of the cellulose engendered by the ferment, and it contains diastase which may be separated in an impure state. It is a white soluble body, resembling the gluten 22 254 DIASTASE, ptyalin and pepsin. of flour. It is capable in the separate state of acting on a solution of starch, and converts it into dextrine and glucose, so that it is an independent ferment. It is not, however, a fixed body when moisture is present, for if malted barley be not dried at a con- siderable temperature, the diastase undergoing further change con- verts the sugar into lactic acid, or it becomes a lactic acid fer- ment. Diastase not only causes germination in seeds, but it also de- termines the growth of buds, and probably all growth in the vegetable kingdom. According to Payen and Persoz, it is found deposited about the eyes of the potato when the tuber is begin- ning to germinate. Mialhe has found a ferment having the characters of diastase in the saliva, being the white substance precipitable by alcohol and formerly called ptyalin. It is an oxydized proteinous body, and has the property of converting a solution of starch into glucose. He calls it diastase. Leuchs had previously observed that saliva has the property of converting starch into sugar. There is but T2oths per cent, of diastase in saliva, but it will be remembered that this ferment is extremely active, one part changing two thousand of starch. Bouchardat announces the existence of diastase in the stomach in diabetes,.and infers that the sugar (glucose) of the urine and blood in that disease arises from its action on the starch of the food. Hence abstinence from amylaceous substances constitutes a principal feature of the treatment, and has been found to answer well. But Barreswil has found that the property of converting starch is also possessed by the pancreatic secretion and the gas- tric juice, and that in all these cases the effect only takes place when the ferments are in contact with alkaline matters, or pos- sess an alkaline reaction in consequence of the presence of the tribasic phosphate of soda (Na,P06,2NaO); for if either the saliva, gastric juice or pancreatic secretion be acidulated, they lose this property but become solvents of albumen and fibrine. This view of the case awakens a suspicion that pepsin or the ferment of the gastric juice is also diastase, or a proteinous body of a very analo- gous character. For the further consideration of this subject, the student is referred to the article on digestion. 3. The Viscous Fermentation.—Vegetable juices, as that of the beet, which contain much sugar when kept at the temperature of 86° to 104° F., undergo fermentation from the changes oc- curring in the albumen they contain. But under the circum- stances prescribed, there is formed mannite, lactic acid, and a viscid body said to be identical with gum arabic, whilst a little car- bonic acid and hydrogen are evolved. There is no alcohol pro- duced, and from the thickening of the fluid, this is distinguished THE LACTIC ACID FERMENTATION. 255 by the name of the viscous fermentation. It can be established in a solution of pure sugar by the action of a ferment prepared by boiling yeast in water, filtering and using the fluid portion. The changes here are those attributable to a new order of group- ing chiefly, for the gum produced belongs to the amylum series. The mannite is a variety of sugar, and the lactic acid is isomeric with milk sugar. Thus one atom of sugar, by the viscous fer- mentation, is split up into 1 atom of lactic acid=C6HB06 1 atom of mannite =C„H.,0, Ci2H13012. The sum represents an atom of glucose, minus one atom of water, and one of oxygen. There are various other means of originating the viscous fermentation, as by animal membranes. The changes in the preparation of sauerkraut also belong to this species of fermentation. In some portions of France they prepare hay by a similar process. 4. Lactic Acid Fermentation.—In the preceding case lactic acid is formed, but in many instances it is generated as the sole or principal product of fermentation ; this is especially true in the souring of milk at moderate temperatures (50° to 70° F.). In this change, the proteine body of milk (caseine) first undergoes a slight decomposition, which may be detected by the altered taste, and acting as a ferment, splits up the atom of lactine into two of acid, C12H°20,2, becoming 2(C6H606), so that this is another case of the re-arrangement of the molecules of the sugar present. This result is also brought about in milk by animal matters, the stomach, or any portion of the mucous membrane of the calf, dog, pig, &c, steeped in water for several days, changes not only milk but solutions of sugar and starch. A solution made from the salted and dried mucous membrane of the calf, called rennet, effects the same result. Diastase kept moist for several days, becoming chano-ed into a new ferment, also brings about the lactic ferment- ation. . ..... This is a very important change, inasmuch as lactic acid is found in nearly every part of the bodies of animals, and food containing it already formed, appears to be easy of digestion, highly nutritious, and especially serviceable in the fattening of animals. To this end it is the custom of some farmers to feed hogs and oxen with a slightly acid mash, which is found to con- tain this acid. , The action of the mucous lining of the stomach on starchy matters, indicates that lactic acid is produced in digestion, and that the lactic fermentation forms a stage in that important process. 256 LACTIC ACID. This acid has been found in the stomach, perspired fluid, the muscular juice, the urine, and in most parts of the body. Lactic acid may be obtained for examination and pharmaceu- tical purposes, by adding sugar of milk to sour milk, and allowing the lactic fermentation to proceed, occasionally neutralizing the acid formed by carbonate of soda. When the transformation is supposed to be complete, the mixture is boiled to coagulate the caseine and then filtered; the filtrate being evaporated at a low heat to the consistence of a syrup, alcohol at 100° F. is next digested on this, and dissolves out the lactate of soda. This alcoholic solution is next decomposed by sulphuric acid, the sul- phate of soda falls, and there remains lactic acid dissolved in the alcohol. Concentrated by cautious evaporation, it forms a thick colorless fluid, sp. gr. 1.215, without smell, and intensely sour. It is very soluble in water, and alcohol, and is a strong acid, uniting with most basic oxides to form lactates. It is monobasic, its formula being H0,C6H505, the HO being replaced by oxides. The acid is pretty permanent, non-volatile, but it is decomposed at a tem- perature of 482° F., being resolved into a crystalline body, having the formula C6H404, with acid properties, and into water and other substances. At a red heat the lactates are converted into car- bonates. The lactates of potash and soda are deliquescent. The lactate of lime is insoluble, and found in nux vomica. The lactate of protoxide of iron is a mild chalybeate, recently introduced into medicine. Lactic acid itself, in the dilute state, has been recom- mended in atonic dyspepsia, at meals, as a promoter of digestion and as a tonic. 5. The Butyric Acid Fermentation.—This is one of the most interesting of the changes produced by ferments, because, in it, an oil is generated from sugar and bodies of the amylum series, and thus great light is thrown on the digestion of this kind of food. It has been decided by the experiments of Liebig, Dumas, Bous- saingault, Edwards, and Payen, that amylaceous matters become converted into fats during digestion; but the process was utterly unintelligible until the discovery of the butyric acid fermentation by M. Pelouze. It is effected by exposing the washed curd of milk (caseine) to a strong solution of sugar, mixed with chalk, at 80° F. The caseine becomes a ferment by decay, producing the character- istic changes of a viscous and lactic acid ferment, and finally ge- nerates butyric acid, which, uniting with the lime of the chalk, forms butyrate of lime—hydrogen and carbonic acid gases are also liberated. An atom of glucose by this fermentation yields an atom of butyric acid, 4 of carbonic acid, 2 of water, and 6 of hydro- gen, or: BUTYRIC ACID. 257 1 atom of glucose .... C,2 Hl4 Ou yields _________ 1 atom of butyric acid - - C8 H8 04 4 atoms of carbonic acid - - C4 08 2 atoms of water .... JJ2 02 4 atoms of hydrogen ... H4 CI2 H14 °11 Butyric acid is found in butter, being the acid of the flavoring substance called butyrin, which is butyrate of oxide of lipyle. It has also been detected by Drs. Ragsky and Percy in fecal matters, by Berzelius in urine, by Gmelin in the juices of the stomach and sweat, and by Lehmann in the kiestein of the urine of pregnant females. It is, therefore, a fat belonging to the system of animals, and its presence in milk leads us to infer, that if this can be pro- duced by fermentation, other fats maybe formed from amylaceous bodies in digestion, especially as lactic acid is resolved into it, and probably other fats. Butyric Acid.—The acid is obtained by decomposing the butyrate of lime formed in the above process, by sulphuric acid; or it may be obtained in minute quantities from butter. It is an oily, slightly yellow fluid, with the odor of rancid butter, and is very soluble in water, alcohol, and ether. Its sp. gr. is 0.963, it is volatile, and boils at 327° F. It is of a caustic, acrid taste, cor- rodes the skin, and the vapor is inflammable. It does not solidify by a cold of 4° F. It forms numerous salts, butyrates, the most interesting of which is that with oxide of lipyle, which is butyrin, a component of butter. Chevreul found that this body could be produced arti- ficially by uniting butyric acid with oxide of glycerine, and that a fat very similar to butter was the product. Fibrine, in its decom- position, also yields butyric acid, and it appears to be formed by the action of potash at 320° F. on this body. It is, therefore, a product of the changes (metamorphoses) of both amylaceous and proteinous bodies. 6. The Vinous Fermentation.—In this case decomposition takes place in the saccharine matter (glucose), and it is resolved into alco- hol, which is a pseudo-organic body,—carbonic acid, and water, neither of which are organic. To produce it, the ferment is more advanced in decay than in the preceding cases, being in the state of yeast. The temperature at which it takes place is about 70° in saccharine juices, wort, must, or a solution of sugar, but in milk it does not occur under 80° F. Water is also essential; indeed, the proteine body could not form yeast without heat and moisture. Oxygen is also necessary to this change. It has been found that fibrine and albumen in the moist state 22* 258 THE VINOUS FERMENTATION. have the property of absorbing oxygen from the air. By this oxy- dation there are first formed oxides of proteine, which combine with water; but if it be pushed farther, the fibrine or albumen becomes disorganized, forming ammonia, carbonic acid, and extractive matters as final results, with the evolution of sulphuretted hydro- gen and other gases. This constitutes the putrefactive decay, or the final destruction of the proteine body. Liebig attributes this proneness to decay to the instability of the nitrogen, and it is true that the most azotized bodies readily suffer decomposition whether organic or inorganic, but the primary action is the property of these bodies to absorb oxygen. In other cases it may be due to the affinity of hydrogen and nitrogen, as in the decomposition of hydrated cyanate of ammonia or urea, and in the explosive fulminates. Mulder has determined that yeast is an oxide of proteine and that it is in the last stage before decomposition. It exists in the form of isolated cellules, the enveloping membrane of which is celhdose, the interior a proteine body, the composition of which is C40H37NsO26=Pr + O8 + 6(HO). This undergoes further decay, but the stage at which it produces the vinous fermenta- tion is now reached. To form alcohol and the other products, it is necessary that the sugar should be in the state of glucose. The changes are, as follows: 1 atom of glucose .... C12 H,4 Ol4 yields --------- 2 atoms of alcohol (C4TT602) - - C8 H]2 04 4 atoms of carbonic acid - - C4 Og 2 atoms of water - - - - H2 02 ^12 H14 014 In this rAange the elements of the yeast do not participate although it is undergoing change at the same time, and finally becomes exhausted, having only a limited capacity to produce fermentation. The alcohol produced in this change is one of an important group of bodies which contain the hypothetical radical ethyle, and will be examined under that head. The vinous fermentation is most common in saccharine fluids, but it may be established in milk. It does not belong to that class of fermentations which occur in living plants or animals, but is destructive in its action. In the case of diabetic urine it has been proposed to test the presence of sugar, especially of the insipid variety (diabetes insipidus), by fermentation, adding yeast and looking for the evolution of carbonic acid and the produc- tion of the cellular objects called toruke which cause ferment- ing fluids to become ropy. But Trommer's test is much more satisfactory. (See Glucose.) A fermentation very similar to the vinous takes place in urine, THE RESULTS OF FERMENTATION. 259 the urea of which is converted into carbonic acid and ammonia under the influence of a ferment formed by the decay of a small amount of mucus (oxydized proteine) voided with it. If the mucus be separated the urea remains unchanged, if it is allowed to ab- sorb oxygen and is moist; this substance is changed, as follows: 1 atom of urea - - - - C2 H4 N2 02 6 atoms of water - - - - H6 06 yield ----.----- 2 atoms of ammonia - - - H6 N2 2 atoms of carbonic acid - C2 04 4 atoms of water H4 04 C2 H10 N2 08 Uric acid and other organic bodies rich in nitrogen are decom- posed in the same way, the products being almost, if not quite, inorganic. Hence the fermentation may produce mere change in group- ing, the products being of a more stable kind, without evolution of gas—this occurs in the bodies of animals and in plants. Or there may be formed pseudo-organic bodies, as lactic acid and alcohol; this also may occur in plants and animals. Lastly, it may entirely disorganize, producing carbonic acid, water and am- monia, from the most organized substances: this does not occur in animals, except in cases of disease. In disease it does occur, for we have urine voided, containing carbonate of ammonia obviously derived from a change in the urea. If the matter were more closely investigated, there is little doubt it would be found that many pathic fluids and products arise from fermenta- tion. In the results of fermentation we perceive a gradual return of the complex organic body, by various graduations, all of which may occur in the same solution, to the inorganic state ; the various products serving only as temporary stopping places. EREMACAUSIS. The formation of vinegar in wines and beer was formerly attributed to a peculiar fermentation, and called the acetous. But it has nothing to do with fermentation being produced not by the action of a ferment, but by the slow absorption of oxy- gen. In this and analogous cases, of which there are a great number, Liebig calls the process Eremacausis, or slow combus- tion, the absorption of oxygen being as essentially a featureof it as in ordinary combustion. By this means organic bodies become oxydized and further approximated to inorganic sub- sttinccs* The conditions necessary are the continuous presence of oxygen, 260 EREMACAUSIS. a limited amount of moisture and a variable temperature. The results will depend upon the supply of oxygen, the temperature and the body subject to change; when the action is rapid, heat is always thrown out. Both azotized and non-azotized bodies are subject to eremacausis. Familiar illustrations of this action are afforded in the formation of vinegar from alcoholic fluids, in the rotting of wood in a moist situa- tion, in the production of nitrates from ammonia in heaps of ma- nure, and in the functions of the human body. The continual introduction of oxygen by respiration, the evolution of oxides, as carbonic acid, water and cyanic acid show that the bodies of animals are the scene of a constant eremacausis by which the fats, muscles and tissues are constantly metamorphosed into effete matters. The function of digestion is, however, a process of fer- mentation. In eremacausis it is not necessary that there be a ferment, but it is essential that there be a means of absorbing and supplying oxygen. This, in the case of the production of vinegar (acetic acid) from beer and wine, is accomplished by the action of the fluid, or it may be accomplished by a piece of platinum; for, if the vapor of alcohol pass over platinum, it becomes oxydized, and forms acetic acid. In the bodies of animals the fibrine of the blood is the substance which absorbs and supplies the oxygen, and the albumen of the serum also does so. Charcoal, the varieties of platinum, fibrine, and other bodies act in these cases catalytically, not being themselves necessarily changed, but yielding oxygen in the active (alpha) state to any instable body. But the decompos- ing body may absorb the gas itself without the intervention of any agent, and the case is not the less one of eremacausis. The oxydation of pseudo-organic bodies, especially alcohol, wood spirit and polatoe spirit, lead to the production of important bodies, and it is an action always resorted to for the purpose of investigating organic bodies. The common means of doing so is, to pass a stream of the vapor over spongy platinum. Heat may also be regarded as an exciting agent of this kind of action, when the organic substances are exposed to the air, from which they derive their oxygen. In these cases, the body may be split into two or more by a new grouping and oxydation, or it may be almost destroyed. We are now prepared to consider the disorganizing effects of fermentation, eremacausis and heat on the amylum series. ALCOHOL AND ITS DERIVATIVES. 261 ALCOHOL AND ITS DERIVATIVES. THE COMPOUNDS OF ETHYLE. Alcohol—Spirit of Wine; Hydrated Oxide of Ethyle (C4H602) is procured by the action of yeast, or fermenting animal matter, on a saccharine solution. One atom of glucose yields two of alcohol, and carbonic acid and water are separated, thus: 1 atom of glucose .... C„ H., O,, •11 1Z 14 14 yields ---------- 2 atoms" alcohol (C4H602) - - C8 H12 04 4 atoms carbonic acid - - - C4 08 2 atoms water -' - - - -^ffe Wk-02 C]2 H14 014 In this change the ferment does not participate by its elements, but the solution becomes thick, and there are produced in it cryp- togamic plants, consisting of strings of cellules, the bounding wall of which is cellulose—these are termed Torulse and Saccharo- myces. The alcohol is separated by distillation. Characters___Alcohol is a transparent, colorless liquid, of a vinous smell, hot taste, and sp. gr., at 60° F., 0.793 when pure, boils at 173° F. It has never been frozen. That in commerce con- tains about 12 per cent, of water and some corn oil, which impairs the odor. The pure anhydrous, or absolute alcohol, is obtained by treating rectified alcohol with carbonate of potash or caustic lime, and redistilling about three-fourths off at a low temperature. The dilute or proof spirit (Spiritus tenuior) contains about 50 per cent, of alcohol. Properties.—It is highly inflammable, burning with a hot, pale flame, much used in the arts from being free from smoke. By this combustion it is resolved into water and carbonic acid, oxygen being absorbed from the air. It has remarkable solvent proper- ties,dissolving many saline bodies, the resins, essential oils, castor oil, the alkalies, most acids, and many vegetable principles, but it does not dissolve the fats, fixed oils (except castor oil), or saline bodies insoluble in water, or which effloresce in the air. With some saline bodies it unites, like water does in its hydrates ; such compounds are termed alcoates by Graham. It is freely soluble in water and ether, indeed its affinity for water is so considerable that it acts as an antiseptic, preserving animal matters by remov- ing the water necessary to establish fermentation in them. Chemically considered, alcohol exhibits all the properties of a hydrated oxide, and if strong acids be brought in contact with it, 262 THE ETHYLE SERIES. assisted by a moderate heat, they separate the water and enter into combination with the oxide, forming sulphates, oxalates, &c. The base here is termed ethyle; it has not been insulated, but we know its oxide, which is ether, and numerous compounds, and they all point to the existence of a powerful electro-positive radical, capable of forming haloid compounds and oxygen salts. The composition of ethyle is inferred to be C4H5, and the follow- ing are its chief compounds: The Ethyle Series. Ethyle, symbol Ae - - C4H. Oxide of ethyle - - - Ae,0 Chloride of ethyle - - Ae,Cl Iodide of ethyle - Ae,I Hydrate of the oxide - - AeO-(-HO Bisulphate of ethyle - - Ae,0-f-2(S03) Phosphate of ethyle - - Ae,0-|-P05 Hyponitrite of ethyle - - Ae,0-j-N03 &c. &c. &c. Of the foregoing bodies, several are of medical interest and will be considered; others, as the iodide with the bromide, sul- phide, cyanide of ethyle, are not put to any use. Of the com- pounds of oxide of ethyle, the acetate, carbonate, oxalate, formate, butyrate and numerous others, are merely objects of curiosity. The enanthic ether forms the bouquet of wines; other compounds with vegetable acids have odors resembling those of the apple, melon and other fruits, so that it is highly probable that these are due to ethereal bodies. Uses and Effects of Alcohol.—It is used as a solvent in the arts, for its hot flame, and for the production of the ethers. In medicine it is an arterial stimulus in small doses, and serves well in cases of debility to arouse the powers of the system, but is transitory in its action. It acts as a local stimulant, and also enters the blood, having been detected in that fluid and in urine; in the circulation it is speedily oxydized, becoming con- verted into carbonic acid and water. The effect of its change in large quantities is to produce stupor, and in fatal cases com- plete asphyxia. These results are due to the separation of the oxygen of arterial blood, which acquires a venous color, and con- sequently the loss of that vital stimulant on the brain and mus- cular apparatus. Respiration therefore becomes labored, the countenance bloated, the lungs and other parts of the system engorged with venous blood, and hence death from a true as- phyxia. We should, therefore, in cases of alarming drunkenness, employ artificial respiration as our sheet anchor, the contents of the stomach and bowels being removed by the stomach pump ETHER. 263 and enemata. In this case an admixture of protoxide of nitrogen with the air may be serviceable ; as well as the interrupted current of galvanism to keep up the motion of the respiratory muscles. The poisoning produced by the Jong-continued use of ardent spirits, one symptom of which is delirium tremens, seems to arise from a direct action of alcohol on the stomach and nervous centres. It is not to be overlooked by the student of medicine, that the ad- ministration of medicines in the form of tincture, or the employ- ment of spirituous potions in convalescence, may awaken a taste for alcohol leading to pernicious habits. The spirituous beverages in use contain different proportions of alcohol, the amount being in brandy, rum and whisky from 50 to 60 per cent. ; in tinctures about 40; in the strong wines, as madeira, port, sherry, malaga, from 21 to 30; in hock, cham- pagne, claret, sauterne and the lighter wines, from 11 to 16 per cent.; in ale, cider and stout 7 to 8.50; in draught porter about 4 per cent. Ether—Sulphuric Ether ; Oxide of Ethyle ; AeO.—Ether is produced by any means which will separate the atom of water from alcohol, or will convert AeO,HO into AeO and water. It was formerly done by distilling dilute sulphovinic acid, which is prepared by warming equal weights of sulphuric acid and alco- hol; this forms a sour syrupy liquid, having the composition AeO,2S03+HO. If this "acid be diluted with water, so that its boiling point be from 260° to 310° F. and distilled, ether and a little water pass over and there remains in the retort hydrated sulphuric acid. But this is an uncertain and expensive process, for below 260° alcohol distills over, and above 310° defiant gas and other bodies pass over. To obviate these difficulties the continu- ous process has been introduced, in which a stream of alcohol is made to enter the still gradually, so that the boiling point of the mixture is retained at about 300° F., and in this way a small quantity of sulphuric acid serves for the change of a large. amount of alcohol. There pass over the vapors of ether and water which are condensed in a Liebig's or other condenser, the two fluids separating spontaneously in the receiver. Characters.-lt is a limpid, colorless fluid o a peculiar and penetrating odor, hot taste, sp. gr. at 60° 0.720, boiling a 96 F. It has not° been frozen, is extremely volatile, slightly soluble in water but very soluble in alcohol. plone^rties.-lt is highly inflammable, burning in contact with oxwennto water and carbonic acid. It is a solvent of many fats, oilfand vegetable principles, and has all the properties of a me- S lie oxkle forming compounds with most acids. The vapor orms an explosive mixture with air and when in contact with it some time is changed into acetic acid by oxydation. 261 ETHERIZATION. Uses.—It is employed in organic analysis as a solvent; and in medicine, being a diffusible stimulus and antispasmodic, and has been found, when inhaled, to destroy sensibility for a time so com- pletely as to allow of the performance of severe surgical opera- tions. The soporific effect is similar to that of alcohol, but pro- duced more rapidly, and it does not cause so much local irritation. The ether entering the blood becomes oxydized, removing the oxygen destined to the metamorphoses of the tissues; hence ven- ous congestion and a partial asphyxia occur. Where its action has been excessive, the same means are to be employed for the restoration of the patient as in the case of drunkenness. In the inhalation, two drachms or more of ether, washed free from alcohol by water, are put on a small sponge, which may be put in a vessel perforated by several holes, and placed over the mouth and nose. The patient inhales through this, each draught of air carrying a large amount of ethereal vapor. Stupefaction occurs in two or more minutes, and lasts five or more minutes. Etherization has been freely practised with little danger, but in cases of hemoptysis it is not safe. There are also irritable states of the brain and spinal centres, in which it is counter-indicated. Chloric ether, or the chloride of ethyle, and chloroform have the same property, and the latter has been freely employed ; it is more active, thirty to fifty drops producing insensibility in the space of one to two and-a-half minutes ; but it appears to be frequently followed by considerable prostration. The therapeutical action is the same, except that the chlorine of these compounds becomes converted into muriatic acid in the blood, and seems to produce the debilitating effects complained of. It would appear that par- turition is accomplished much more favorably under the influence of chloroform than of ether. Its action on the system is more rapid but less persistent, and in consequence of the subsequent prostration, ether is now supposed to be preferable, for the patient recovers from its effects much more completely. Haloid Compounds of Ethyle.—The chloride of ethyle or hydrochloric ether (AeC'l), is made by saturating alcohol with hy- drochloric acid gas, distilling at a low heat, washing the vapor with water, and condensing in an iced refrigeratory. It is highly volatile, limpid, colorless, of a pleasant aroma, sp. gr. 0.874, and boils at 84° F. It has the properties of ether, but is more active; it has been recommended as an anaesthetic agent, but is probably inferior to ether. As an antispasmodic it has been employed in asthma and adynamic diseases of the nervous system, but is not better than ether; the dose is f5ss. Cyanide of ethyle—hydro- cyanic ether, (AeCy) has been recommended by Majendie, in whooping-cough, asthma and convulsive diseases, as a nervous sedative ; the dose is five to ten drops, but it is rarely employed, COMPOUNDS OF ETHYLE. 265 The TodMebl 0 sins^rable odor; it is also an active poison. lhe iodide, bromide and sulphide of ethyle are not employed. Salfs of Oxide of ETHYLE.-Oxide of ethyle (AeO) unites tile ZtTdS^d -K,6 qUaSi-SaltS thuS formed are Cereal, "da- lle, and act as diffusible stimulants. There is a great number of these compounds, but the hyponitrite and acetate are the onTy one used in medicine These ethers are nearly all decomposed by caustic potash and other alkalies, which are, therefore, incom- patioles. The hyponitrite of oxide of ethyle; nitrous ether (AeO,N03) is employed in an impure form in medicine, being dissolved in alcohol in the spiritus a3theris nitrici. It is a pale yellow, volatile liquid, having an agreeable odor of apples ; its density is 0.947, and it boils at 62° F. It is employed, dissolved in alcohol, in medicine as an antispasmodic and diuretic. Acetate of oxide of ethyle; acetic ether (AeO,C4H303) is made by heating, in a retort, three parts of acetate of potash, three of alcohol, and two of sul- phuric acid, washing the vapor with water, digesting the refrige- rated ether with chalk, and afterwards with chloride of calcium and rectifying. It is a highly fragrant, limpid liquid, has a den- sity of 0.890, and boils at 165°. It is a little employed in medi- cine in the same way as common ether. Compounds Connected with Ethyle.—Sulphovinic acid has already been referred to, in the formation of ether. Its composi- tion is AeO,2S03+HO, and it would appear to be a hydrated bi- sulphate of oxide of ethyle, but it has none of the properties of the ethers, being an acid capable of combining with metallic oxides and forming sulphovinates. Its salts are soluble, and all suffer decomposition by heat, as does the acid itself. There is also a phosphovinic acid, (AeO,P05-f-2HO,) and an oxalovinic acid (AeO,2(C203)+HO,) having similar properties. Heavy oil of wine; Oleum sethereum, formerly used as an antispasmodic, when pure is a sulphate of oxide of ethyle and sulphate of etherole (C4H4), a body isomeric with olefiant gas. It is produced by distilling dry sulphovinate of lime; when the heavy oil and alcohol pass over, the latter may be separated by water. It is a yellowish green, oily body with a powerful odor somewhat resembling that of peppermint. Olefiant gas (C4H4) is obtained by heating dilute sulphovinic acid above 320° F. This acts as a true basic compound radical, forming three chlorides, a bromide, iodide, &c. These bodies resemble the ethers, so that, according to some authors, alcohol and the compounds of ethyle, may be reduced to compounds of olefiant gas. Thus, then, is established an intimate relation between all the foregoing bodies and the oils, which are chiefly reducible by heat into olefiant gas. 23 266 COMPOUNDS OF ACETYLE. The chloride of olefiant gas (C4H4,CI2) is the oil of the Dutch chemists, and may be made by mixing equal volumes of chlo- rine and olefiant gas. It is a colorless, fragrant liquid, boiling at 180° F. In this substance is observed the most striking illus- tration of substitutions and the doctrine of types, the whole of the hydrogen being removable by chlorine without altering the number of atoms. The products are as follows : 1 Dutch liquid - - - - C4 H4 Cl2 2 Terchloride of acetyle - - C4 H3 Cl3 3 - - C4H2CI4 4 « C4H Cls 5 Perchloride of carbon C4 Cl6 Many other bodies produced by the action of chlorine, sulphur and similar agents on alcohol, ether, olefiant gas and their com- pounds, are known to chemists, but are not employed in medicine or the arts. COMPOUNDS OF ACETYLE. When alcohol is slowly oxydized, or subjected to eremacausis, acetic acid is produced; this is found to be a hydrated oxide of a hypothetical basic radical of which there are several compounds known; these are included in the adjoined table: Acetyle, symbol Ac C4H3 Hydrated oxide of acetyle (Aldehyde) - Ac,0-(-HO Acetylous acid (Aldehydic Acid) - - Ac024-HO Acetic acid......AC03+HO Terchloride of acetyle - Ac,Cl3 Hydrated Oxide of Acetyle ; Aldehyde has the same relation to acetyle that alcohol has to ethyle. It is an alcoholic fluid of a suffocating odor, sp. gr. 0.79, boiling point 72° F. It undergoes slow eremacausis in the air, or under the influence of platinum black, becoming converted into acetic acid. Acetylous Acid is a peculiarly acrid volatile body and is ob- tained in an impure state by placing a piece of spongy platinum heated to redness in the vapor of ether; the platinum continues incandescent for a long time and an acrid vapor is produced for- merly called lampic acid and containing the acetylous acid. This arrangement constitutes Davy's aphlogistic lamp. Acetal is a colorless aromatic liquid containing the elements of ether and aldehyde (CgHn03); it is procured by a troublesome pro- cess from the result of the action of moist platinum black on the vapor of alcohol. Acetic Acid—Pyroligneous Acid; the Acid of Vinegar (C4H303 + HO).— This acid is common in living plants, and is the product of the eremacausis of all alcoholic fluids. It may be procured very readily and in a state approaching purity ACETIC acid. 267 by what is called the German method. A cask is filled with shavings previously soaked in vinegar ; around the lower parts are holes to allow the access of air, and a stop cock to draw off any liquid from below; in the place of the common top a wooden tray is inserted, the bottom of which is pierced by numerous small punctures, through each of which is drawn a few strands of cotton yarn. Into this tray is poured alcohol diluted with eight parts water, mixed with about TffL_th part of yeast and warmed to 80° F. The dilute alcohol in streaming over the wood shavings is oxydized and partially converted into vinegar ; by sending this product through a second or third time it becomes very strong; and thus vinegar can be obtained in thirty-six hours, superior to that formerly had by exposing wine and cider in half empty casks to air for months. In this process, the shavings be- come quite hot, from the action of the oxygen on the alcohol. The change here is as follows: 1 atom of alcohol - 4 atoms of oxygen yields 1 atom of acetic acid 2 atoms of water - C4 H6 06 It is also found among the products of the destructive distilla- tion of wood, and hence called pyroligneous acid ; but to obtain pure acid it is necessary to distill dried acetate of soda mixed with sulphuric acid. Characters.—Pure acetic acid is a colorless, limpid fluid, of a pungent refreshing odor, volatile; it boils at 248° F., and has the sp. gr. of 1.063. At 50° F. it crystallizes in large plates— this is called glacial acetic acid. Properties.—It is a powerful acid, and its atom of water is basic and replaced by metallic and other oxides. Its true form being HO,C4H303, or according to the hydrogen theory H+C4H3 O , it is monobasic. The vapor is inflammable. It has a strong affinity for water, forming a definite compound with two atoms ; it also mixes with alcohol and ether, and dissolves camphor, the essential oils and many vegetable principles—hence it is em- ployed as a solvent in pharmacy. It is a valuable antiseptic. Uses.__It is chiefly employed as an antiseptic body for the pre- servation of vegetables, and may be used for meats. In the laboratory it is useful as a solvent, and in medicine it is occasion- ally employed as a refrigerant in a diluted state. The strong acid applied to the skin is rubefacient. Pickles are often em- ployed at the table, and seem to do little harm to those in sound health, but are injurious to the dyspeptic and feeble, impeding, in 268 THE ACETATES. some degree, the function of digestion by the antiseptic action of the vinegar; but, as they are usually combined with peppers and stimulants, this may be compensated. It enters the system, and becomes changed by the oxygen of the blood, in common with all the vegetable acids, into carbonic acid and water. Its salts, the acetates, are in the same way converted into carbonates. Salts.—The acetates are readily formed by the action of the acid on metallic oxides or their carbonates, most are soluble, and all such are precipitated by the nitrates of silver or mercury of a white crystalline appearance. But the most characteristic sign of the acid is its odor, which may be produced by warming the acetate with sulphuric acid. Several acetates are used in medi- cine and the arts, the chief of which are the acetates of ammonia, alumina, iron, lead, zinc, copper, and mercury. Acetate of Ammonia (NH40,Ac03) crystallizes in needles, which are very soluble, and have a saline taste. It is readily procured in solution by adding carbonate of ammonia to the dilute acid, and constitutes the spirit of mindererus of pharmacy. It is a well known sudorific and refrigerant in febrile disorders. The old preparation contained empyreumatic bodies, which gave it also antispasmodic properties. Acetate of Alumina and the Peracelate of Iron (Fe203,3(Ac03) are extensively employed in dyeing as mordants ; the latter is also used in medicine as a mild chalybeate. Acetates of Lead.—There are four acetates of lead, the princi- pal of which is the neutral acetate, or sugar of lead. This con- sists of PbO,Ac03-|-3HO; it is common, in bright, colorless rhom- bic prisms, which are soluble, and have a sweet astringent taste. The solution reddens litmus paper. It effloresces in the air, undergoing a partial change into the carbonate. By heat it is resolved into acetone, carbonic acid, and the sesqui-basic acetate of lead 3PbO+2(AcO). Fresh basic acetate of lead is a valuable astringent, and arterial sedative ; there is no remedy so valuable in hemorrhages. It is, however, poisonous in large doses, though much less so than is supposed ; but the old salt, partially converted into carbonate, is highly deleterious. To avoid this effect, it is best to administer it in solution, with sufficient acetic acid to render the mixture clear. Doses of twenty grains have been employed every two or three hours in haemoptysis and dysentery, without injury to the system, and with the best effects on the diseases. Its antidote is sulphate of soda, which forms the insoluble sulphate of lead with the base. Painter's colic (colica pictonum), which is sometimes said to have been produced by this salt, appears to be due to the use of the carbonate chiefly, if not exclusively. It affects painters and those who employ white lead, which is the carbonate. The DERIVATIVES OF THE ACETYLE SERIES. 269 disease is attended with painful colic, tormina, tenesmus, and a par- tial paralysis of the hands; it sometimes ends in introsusception. Previous to the foregoing symptoms, the action of the lead may be recognized by a blue ring around the neck of the teeth. A lemonade containing sulphuric acid is recommended to avert these pernicious effects. The tribasic acetate of lead (3PbO,Ae03) is found in the extractum saturni of pharmacy; it has an alkaline reaction, and is very poisonous. Acetates of Copper. — The principal is purified verdigris, (CuO,AcO,) which forms soluble, green crystals of a metallic taste. It is used as a paint, and is an irritant poison and emetic, similar to the sulphate of copper or blue vitriol. The coarse ver- digris of wine countries, made by exposing old pieces of copper to the action of the husks of grapes, undergoing eremacausis, is a subacetate (2CuO,Ac03+6Aq). This yields the above neutral acetate by solution in acetic acid. Verdigris is a constituent of the met seruginis, a topical application to ulcers, but which is sel- dom employed. Acetate of Zinc crystallizes in very soluble, pearly, oblique, rhomboidal plates: it has the properties of the sulphate, and is used in dilute solution as an injection, and as an astringent wash. Acetate of Mercury (Hg02 + Ac03) is a brilliant, white, crys- talline body, sparingly soluble in water; it was formerly used in medicine, being a constituent of the famous pills of Keyser, and one of the first mercurials employed in Europe. Compounds Derived from the Acetyle Series.—The chief of these are acetone, chloro-acetic acid and chloral. Acetone or pyroacetic spirit (C3H30) is one of the products of the dry dis- tillation of acetate of lead. It is a limpid, colorless fluid, highly volatile, of a peculiar odor, sp. gr. 0.792, and boils at 132° F. It dissolves in water, alcohol and ether, and is very inflammable. This body has been recommended in chronic diseases of the air- passages, and as an antispasmodic. Kane entertains the view that acetone contains a compound base, to which he gives the name of mesityle, and the formula C6H5; he describes several compounds of it. Chloroacetic acid is a white crystalline sub- stance, obtained as one of the products of the action of the sun's rays on a mixture of chlorine and pure acetic acid. It is deli- quescent, with a faint odor, and caustic taste ; the solution is acid, forming 'salts with many bases. Its composition is C4H04C13 or C CI O +HO, or hydrated acetic acid, in which three equivalents of4hydroo-en have been substituted by chlorine. Chloral is some- what analogous, the composition being C4C1302H; this is an oily, colorless liquid, with an acrid vapor. Related to the acetyle series is cacodyle or kacodyle, and its compounds. This compound radical has the formula C4H6As, 270 THE methyle series. which is the same as acetyle -f arseniuretted hydrogen, or C4H3 -r-H3As, and may be regarded as a product of the union of these bodies. It has been isolated by M. Bunsen, and is a colorless, limpid liquid, of a powerful odor of garlic, extremely irritant and poisonous. It is spontaneously inflammable when brought into contact with oxygen or chlorine; the oxides or chlorides of cacodyle resulting. It forms numerous compounds with the haloid bodies, of which none except the oxide is much known ; this is Cadet's fuming liquor. All these bodies are so fearfully poisonous, that they can scarcely be conceived to be useful in the arts or medi- cine. PRODUCTS OF THE DISTILLATION OF WTOOD. When wood is distilled in iron vessels at a red heat, a large number of bodies pass over, including water, inflammable gases, acetic acid, wood spirit and tarry bodies, and there remains be- hind charcoal. The most interesting of these products is wood spirit or Pyroxylic spirit, which resembles alcohol in its chemical relations, and contains a compound radical called methyle; and some of the substances extracted from wood tar. Methyle is a hypothetical body with the chemical peculiarities of ethyle, having the composition C2H3; its principal compounds are as follows: The Methyle Series. Methyle, symbol Me.....CJf3 Oxide of methyle, (wood ether) - - MeO Hydrated oxide of methyle (ivood alcohol) - MeO.HO Chloride of methyle .... MeCl. Oxide of methyle; methylic ether; wood ether, MeO, is made from the hydrated oxide or wood spirit in the same way as ether is produced from alcohol. Sulphuric acid forms with wood spirit the sulp hornet hylic acid, which is the analogue of sulphovinic acid, being a hydrated bisulphate of oxide of methyle MeO, 2S03-f HO, and an aqueous solution is decomposed by heat into oxide of methyle and hydrated sulphuric acid. The oxide is a permanent gas, sp. gr. 1.617, very soluble in water, and burning with a pale flame. The solution has an ethereal odor. Hydrated oxide of methyle—wood spirit; pyroxalic spirit; MeO,HO.—This passes over with the first products of the dis- tillation of wood, there being about one per cent, of it in thepyro- ligneous acid. It is separated from the acid by submitting it to distillation, and receiving only the first portions; this is neutralized THE FORMYLE SERIES. 271 by lime ; the clear liquid is then separated from some oil, which floats on the surface, and the sediment at the bottom of the vessel, and redistilled. It is a volatile liquid nearly colorless, of a peculiar odor, sp.gr. 0.798, boiling at 152° F., of a burning taste and in- 5a—Whatever is oxydized in the body gives out heat, and the amount of change depends exclusively on the proportion of the oxygen. With an increase in the respirations, the propor- tion is augmented. We therefore find that the temperature of animals bears a close relation to the numbers of their respirations. The number of respirations of the pigeon, according to Prevost and Dumas, is 34 in a minute, and its temperature 107.6° F.; in the cat the'heat is 101.3°, and the respirations 24; whereas, in man, it is 98.6° F.,and the respirations average 18 per minute. The amount of oxygen entering the system is subject to per- petual change, it is as the respirations, and these vary from 10 to 40 in a minute. But under ordinary circumstances, it may be allowed that 32 ounces are consumed daily. 29* 342 NUTRITION. We may proceed to calculate how much heat this amount of oxygen would generate in combining with the tissues of the body, and in this way prove that it will be sufficient to sustain the animal heat. For this purpose it is, however, preferable to calculate the amount of heat produced by the combustion of the carbon; as the proportion entering the system has been ascertained more directly, by analyzing the food and excretions. The amount of carbon introduced by food into the circulation daily, at a moderate temperature, in hard working men is equal to 13.9 ounces (Liebig), in men of comparative leisure about 11 ounces, and in those who are of less than ordinary stature, and who use little exertion, especially females, from 8 to 6 oz. Now, according to the experiments of Despetz, the heat yielded in the combustion of one ounce of carbon is capable of elevating 78.15 ounces of water from 32° to 212° F., or 180 degrees ; or 78.15+ 180° equals 14067 degrees of heat. Hence, the 13.9 ounces of carbon consumed in the metamorphoses of the body generate 13.9+14067 or 195531.3 degrees of heat. This, according to Liebig, is sufficient to heat 184.3 lbs. of water from 32° to 98.3° F., or the temperature of the body, and can evaporate 3 lbs. of water, in the form of insensible perspiration, during the day, and allow a large amount of heat to remain to sustain the body from the effects of cooling by radiation. It will be remembered that, besides the amount of carbon, a considerable quantity of hydrogen is also oxydized ; hence this, with the foregoing, will constitute an abundant source of animal heat. Nutrition.—By the introduction of oxygen into" the blood, it becomes capable of repairing the tissues changed by the incessant wear of the machine. Nutrition takes place by the exudation of the albuminous portions of the blood, previously modified by oxygen, through the walls of the capillaries, into the cells of the basement tissue of all parts of the body. By this afflux of blas- tema, new cells are generated and prepared to take the place of those which have been destroyed by chemical action. This is the ordinary process of nutrition in the healthy parts of the body, but in some cases the blastema may be exuded in the amorphous state. In mature life the amount of substance passing out of the blood vessels is exactly counterbalanced by an amount of effete matter returning in the opposite direction. The passage out- wards, or exosmose, is met by a passage inwards, or endosmose, of fluid to the same amount. Thus there is attained an accurate balance between the materials of waste and repair, and the weight of the body remains constant from year to year. But during youth nutrition is in advance of waste, and growth occurs. In THE CHANGES OCCURRING IN NUTRITION. 343 persons of great activity and in disease, waste occasionally ex- ceeds repair. Every muscular or mental effort is accompanied with the oxydation of parts and waste of tissues, and if these be not restored, by rest and generous diet, debility ensues. Ihe matters returning to the blood constitute a portion of its extractive bodies, which are effete forms of proteine; but besides them, urea, carbonic acid and water are probably admitted—for it is scarcely possible that all the changes of oxydation occur in the blood and no portion in the tissues. These currents out of, and into the capillary vessels, are a result of chemical, affinities. The chief of which, according to Liebig, is the acid nature of the fluid external to the blood and the alkaline reaction of the blood itself. Other causes are also calcu- lated to set up such a current, as the difference of density in the inner and outer fluid, the excess of oxygen in the arterial blood, and the amount of carbonic acid in the fluid of the tissues. Hence, the exudation of the blastema, cell-food, or nutriment destined to repair the tissues, is a result of capillary action and obeys its laws. The further consideration of end osmosis and capillary action will be resumed in the next chapter. The following illustration from Liebig sets forth the relations of nutrition to waste in a striking manner. A serpent kept for some time (weeks) without food, and then fed on a goat, rabbit, or bird, expels from the body, apparently unchanged by the intestines, the hair, hoofs, horns, feathers or bones of the devoured animal; exhales carbonic acid and water; and evacuates by the urinary passages urate of ammonia. The urate of ammo- nia answers in serpents to the urea of mammals, and has nearly the same composition. The serpent after a time regains its original weight and no part of the prey is discoverable in its tissues. Let us analyze this simple case of nutrition. The muscles, blood and fatty matters of the prey contained substances in which there were 8 atoms of carbon to 1 of nitrogen. The urate of ammonia con- tainino- all the nitrogen of the food has but 2 equivalents of carbon to 1 of nitrogen; hence there is an excess of 6 atoms of carbon which does not pass off by the urine, but which passes off by the lungs as carbonic acid, having combined with the oxygen admitted by respiration. In the lion and all carnivora the result is the same, but the consumption is more rapid. In man and animals which live on mixed food, the proportion of carbon to the nitrogen changes with the proportion of fatty and amylaceous bodies, but the urea, which contains nearly, if not all the nitrogen of the food, depends rigo- rously on the azotized matters they consume. Under ordinary circumstances a man evacuates 231 grains, or nearly half an 344 SECRETION. ounce of nitrogen in urea and uric acid during the day, and this is the proportion in the meats and proteine bodies he usually consumes. § 3. SECRETION. It has been explained that in the act of nutrition the blood loses a portion of its normal components, and acquires a certain amount of effete matters. These render the circulating fluid impure and unfit to sustain life, and must be thrown out of it. To this end the secretions are necessary, and principally, the urine, the separation of carbonic acid by the lungs and skin, and the bile. The kidneys separate the whole, or nearly the whole, of the effete nitrogen bodies in the form of urea and uric acid, in the carnivora, and urate of ammonia, in birds and reptiles. They remove also the saline matters which are in excess, or which are the products of oxydation and metamorphosis in the body, such as the phosphate of ammonia. This secretion will be ex- amined at length in another part of the work. The secretion from the skin has already been partially treated of, in the chapter on heat, page 37. It consists nearly entirely of water, but carbonic acid, lactic acid and a minute amount of phosphates and urea are also separated. The pure ecretion, the insensible perspiration, is mixed with the sebaceous matter of the sebaceous glands, the office of which is to render the skin soft and pliable. The latter can scarcely be called a secretion, for it is an essential part of the cuticular tissue, and fatty matter scarcely changed, with epithelium scales and a small amount of lactate of lime and soda. The chief office of the insensible perspiration is to equili- brate the heat produced by chemical changes within the body. From the lungs, carbonic acid is excreted ; here also a consi- derable amount of water is evolved in the state of vapor, which serves to refrigerate the system. The secretion of bile is different from the foregoing; this fluid is only partly excrementitious, the greater portion of its solids being returned into the system along with the chyle and serving the same purpose as other fatty matters. The liver is set in the way of the entrance into the blood, of much of the nutritious matter of the food. The portal veins are active in absorbing fatty matters, as well as other substances, from the stomach and intes- tines, which they convey to the liver for assimilation. Hence, this organ not only secretes from the blood, but also assimilates matter for the reparation of this fluid. Portal blood, from which bile is prepared, contains twice as much fat as arterial blood, and this is separated by the liver. THE BILE ; CHOLEATE OF SODA. 345 The tubuh of this organ prepare a mucus, rich in soda, which serves to attract a considerable portion of the fatty matters, from the minute branches of the portal veins. Union occurs between these bodies, and there is formed a compound of a fatty acid (the choleic) with soda, which is the principal constituent of the secretion. But as choleic acid differs from the fats of food, they must undergo in the blood or by the action of the biliary mucus a catalytic change which is of the nature of assimilation. Simultaneously with the formation of this body, cholesterine and coloring matters pass from the blood, and thus the bile is formed. This fluid, therefore, consists of choleic acid combined with the soda (choline-soda, bilate of soda, choleate of soda) of the hepatic mucus, of cholesterine, and coloring matter (biliphsein). Of these the choleate of soda is the characteristic body. Choleic acid (bilic acid, bilifellinic acid) resembles bile, purified by the separation of the coloring matter, by animal charcoal; it is a yellowish, brittle body, resembling gum Arabic, of an intensely bitter taste and soluble in water and alcohol, but not in ether. Artificially combined with soda, it acquires all the characteristics of bile, and forms a yellowish soap, which lathers with water, has an alkaline reaction and a bitter nauseous taste. Its formula, according to Liebig, is C76H66N2022. By the action of strong acids or alkalies, choleic acid is changed into a number of bodies which do not, however, exist in bile; such as the cholic and choloidic acids, &c. The bile in disease often developes a large amount of cholesterine, a non-saponifiable fat, like spermaceti; and a large amount of modified coloring matter called biliverdin, and found by Berzelius to be identical with chlorophyll. These form the two principal ingredients of biliary calculi; and exist separately, or may be combined. They would appear to be products of the mal-assimilation of the liver; for it is probable that choleic acid is a compound of the effete coloring matter of the blood, hEemaphaein, with fatty bodies, which are resolvable into cholesterine. The nitrogen existing in this body shows that some modified proteine body has participated in its formation. The amount of bile produced daily is considerable;1 M. Blondot found that 10 to 12 drachms were discharged daily from the liver of a dog. In this case a fistulous opening into th°, gall-bladder had been made, and the ductus communis choledochus tied. Of this 20 per cent, was solid matter, nine-tenths of which was the choleate of soda (bilin or bilate of soda of authors). This chemist observed that the proportion of bile was increased when fat, sugar, or amylaceous matters were given to the animal. The secretion also served to stimulate the peristaltic action of the 346 THE PRODUCTION OF THE SECRETIONS. bowels, and was carefully licked up by the animal. The ani- mal at first was emaciated, and continued so as long as he licked up the bile, but this being hindered, his bowels became torpid, the stools white, and he grew fat. M. Blondot observed these facts in two dogs, and infers that the bile is excrementitious and of no service in the economy, a view opposed to that of all che- mists and of Schwann, who found in a series of similar experi- ments, that all the animals died from the want of the secretion. Blondot, like other chemists, was unable to detect choleic acid in the faeces of the dogs that licked up the bile, hence there is reason to believe that it was thrown back into the system, probably modi- fied by contact with the chyle. The presence of bile pigment (bilipaein, cholepyrrhin) in the serum, urine or any other fluid, is readily determined by the gradual addition of nitric acid, which produces first a blue, then green, violet, red, and ultimately a yellowish-brown tint. Production of the Secretions.—How are the secretions formed? In the case of the bile and the secretion from mucous surfaces, it arises from the development and separation of cells, but this is not the case with the urine or milk. The milk contains glob- ules, but they are not cells produced by a regular basement tis- sue, but of the same nature as the fat globules of the chyle, or of ordinary emulsions. For if we allow an oily matter to come slowly in contact with a dilute albuminous fluid, there will be formed oil globules, the wall of which is a pellicle of albumen. This is a process altogether distinct from cytogenesis. Urine and milk are secretions which appear to leave the blood without the elaboration of cells; and this is not at all remarkable, since the chyle undoubtedly finds entrance without this mechan- ism. These secretions are merely strained from the blood, and serve to separate matters existing therein. Milk nearly resembles chyle, the principal difference being the presence of caseine in the place of albumen, and the amount of sugar. It is also liable to change from the ingestion of numerous bodies, especially volatile oils and saline matters. The blood always contains a small amount of urea, which is the characteristic component of urine. Indeed, this secretion con- tains nothing which is not pre-existent in the blood, and seems to drain away from that fluid without any considerable preparation. It is remarkably altered by foreign bodies; thus the saline sub- stances with an alkaline base, administered as medicine, are found here unchanged ; so with coloring matters and many volatile oils. Large draughts of water, especially in the winter, increase the amount of the secretion. Secretion, according to this view, is no more than the filtration THE OFFICES OF THE BLOOD. 347 or separation of useless bodies from the blood, and is a result of capillary attraction. wTiie Pnenomenon of vicarious secretion sustains this view. We find that when the action of the liver is diminished or stop- ped, the coloring matter (haemaphaein), which it is the duty of this organ to separate, accumulates in the blood, and is secreted by the kidneys and skin. If the secretion of milk in the female be suddenly stopped, caseine (kiestein) is found in the urine. Urea increases in the blood in diabetes and organic diseases of the kidney, and is discharged by the skin. The menstrual flux is also occasionally discharged in the urine, and sometimes passes off from the mucous membrane of the lungs or stomach. But the capillary action of the glands, whereby the blood is strained of its impurities, and the secretions formed, is like the capillary action of every other part of the body, under the influ- ence of the nerves. The secretion is, therefore, normal only when the body is in health, and disease, affecting the nervous centres, is as influential in changing the relations of the gland- capillaries to the constituents of the blood, as disease in the organ itself. Hence, we have alterations in the urine and other secre- tions, arising from nervous affections and general disease ; and find at one time a suppression of urea, and at another an evacua- tion of albumen. CONCLUSION ON THE BLOOD. From the foregoing, the blood is to be regarded as the great source of nourishment, and the receptacle of the effete matters of the tissues. It is at once the means of sustenance for the body, and the stream into which the substances which have suf- fered decomposition and organic death are cast, to be separated by the liver, lungs, skin and kidneys. The chyle and lymph un- dergoing assimilation in it, and being aerated by respiration, become fitted to repair the tissues, and the muscular and nervous framework. The refuse of the body, which has served its purpose in gene- rating muscular power or nervous activity, returned to it, is sub- jected to further change and prepared to leave the system as urea, carbonic acid and water; substances which become resolved in the air into carbonate of ammonia, carbonic acid and water. Thus the animal machine breaks down the complex amylaceous and pro- teinous bodies of the vegetable, acting on them by eremacausis or oxydation, and restoring them to the mineral world. But the heat and light, which have acted in the plant, to bring together the products of vegetation, are not lost in the body. If 348 THE NATURE OF LIFE AND DEATH. the animal destroys organic matters, and converts them into air and water, with a little saline matter, it economizes their latent forces. Heat is evolved in calorification, and an imponderable closely analogous to electricity, which we call the nervous power, is developed. It has been shown, that the muscular and active man consumes more oxygen, than the spare and inactive; and this that more organic matter may be changed and power produced. As Matteucci (page 122) found, that the activity of the musculo- cutaneous current in animals, depends upon the supply of blood, so we know, that every increase of power, whether of the nervous masses or the muscles, is associated with an increased capillary circulation in the part—with increased oxydation and waste. The power generated is rigorously in proportion to the oxydation of the muscle or brain. Whenever we employ means, as by the inhalation of protoxide of nitrogen, to super-oxydize the blood, excessive action results, and as we diminish the supply of this agent, the powers of life flag, and become extinguished, with the final loss of oxygen. The phenomena, termed by us life, flow from the changes going on in the blood and tissues. Each molecule of fat that is oxydized gives out its proportional of vital heat. Each atom of the fat acid of the brain (cerebric acid) that falls before the affini- ties of oxygen, throws out a force that circulates in the nerves; whilst the muscular tissue responds to the influence of the same element, by the production of movement. Life is the resultant of regulated chemical changes, which owe their peculiarity, to the framework solely. Many of the altera- tions impressed upon the proteine and fat compounds can be imitated in the laboratory, but we perceive heat, light and electricity only as the accompanying phenomena. The evolution of true cellules, which make up the body, is the characteristic of life. It is the laboratory which is peculiar, not the agent of change, for this is purely chemical. Death results, when the generation of cellules comes to an end, or when their food, derived from the blood, is radically altered. If the metamorphoses arising from respiration be not perfected, if the sources of supply be drained, or if disease affects the current, the machine comes to a stand, and its delicate and complicated parts lose their office. The stern laws of the inorganic world rule in the stead of the cellular operations of the organic king- dom, and the body passes to the air and the earth from which it was derived. 349 THE CAPILLARY FORCE. Synonymes. Endosmosis and Exosmosis; Penetration of tissues. Having presented a view of the composition of blood, and the principal nutritious fluids, the question arises how are these con- veyed to the cellules, which they nourish ? Or, in other words, what causes the circulation of the nutritious juices, the penetration of chyle into the system, and the separation of the secretions from the body? We answer that this arises from the capillary force, which is the active cause of the phenomena termed endosmosis and exosmosis, the penetration of tissues, and cell nutrition. The capillary force, or capillary attraction, has been defined in the first part of this book (pp. 12(5 to 123), to be a species of affinity, inferior to the chemical affinity in force, but having the same electrical cause. The wetting of solids by some liquids, cases of solution, the diffusion of gases, and the admixture of liquids, where none of the disturbances characterizing chemical action (p. 128) arise, are instances of capillary affinity. Phenomena of the Capillary Force.—If a piece of dry bladder, or the dry opaque cornea, be placed in water, the fluid penetrates every part, enlarging its bulk, and endowing it with a degree of transparency. This does not arise from leakage, because it takes place in opposition to gravity when the membrane is sus- pended, so as to touch the water at one part only. It arises from the existence of a peculiar affinity between the bodies, and is an illustration of capillary action. All fluids will not rise; if we dip these membranes into mercury, they do not become swollen by its penetration into their parts. The illustrations here presented are not more striking than those occurring continually around us. The ascent of sap in trees, the swelling of wood when immersed in water, the solution of sugar, are all instances of this action. But the nature of capil- lary attraction is best studied with glass tubes. Water and many other fluids wet glass, or have a capillary affinity for it, and will rise between two planes of this material, or in tubes made of it. The height to which water rises in a glass capillary tube, de- pends upon its bore, being inversely as the diameter. A tube of half an inch bore, plunged into water, will scarcely draw the fluid above its common level; but the water within the tube will ex- hibit a concave surface. If the tube be r\ of an inch, the water will rise one inch, if T£otn>tw0 incnes> and s0 forth> according to the above law. 30 350 CAUSE OF CAPILLARY ATTRACTION. Now, if in the place of water, we examine the action of other liquids, we find that they are not attracted in the same degree, but that each fluid rises according to its affinity for the material of the tube. Muschenbroeck determined that a glass capillary tube which would raise sulphuric acid 1.3 inch, would raise alcohol 1.8inch; oil of turpentine, 2.56 inch; water, 3.4 inch; strong solution of ammonia, 3.6 inch ; and solution of carbonate of ammonia, 4.56 inches. It will be observed that the cause of elevation is inde- pendent of specific gravity. Nor is there any chemical action in these cases. The fluids rise because they have different capil- lary affinities for the glass. But all fluids do not rise in capillary arrangements. If a tube of glass or iron be immersed into mercury, the fluid sinks in the interior of the tube, or is repelled. If, however, we change the electrical relations of the tubes and mercury, by putting them in connection with the different poles of a galvanic battery, the fluid rises. So in e.very case we find that the fluid rises when the electrical relations of the two are dissimilar, and is depressed when they are similar. Hence, electricity is the cause of the movements of fluids in solids. This is further established by the fact that the two are always found in different electrical states if separated and examined. (See p. 127.) As there exists so much difference between the affinities of dis- similar fluids, it is apparent that, when a capillary body is brought in contact with two fluids, only one of which exerts an attraction for it, or one of which exerts a greater attraction than the other, it will be affected by the one only. Thus, if water be poured on quicksilver, and a capillary arrangement, consisting of a few strands of cotton yarn let down into it, the wrater will rise, but not the mercury. So if oil be poured on water, and the same sub- stance sunk into them, the oil only rises, for it has a greater af- finity for the yarn than the water. In this way a capillary ar- rangement may be used to effect a partial separation of bodies. If we dip a glass capillary tube into olive oil, a certain amount of the oil will rise, and if we now dip the same tube into water, this will also rise, and push the oil up before it. Thus, movement is effected, the least attractive of two fluids being pushed forward in a tube by the more attractive, and even driven out of it. This law holds in every case where the circumstances are similar. As the advance of the liquid depends on the attraction of the sides of the tube, it cannot rise higher than its upper margin, however minute it may be. If a tube, capable of elevating oil three inches, be broken at one inch above the surface of the fluid, the oil cannot overrun the summit. But if we set fire to the oil, or cause it to be removed from the summit of the tube in this or any other case, fresh quantities will rise from below to take, the CAPILLARY ATTRACTION. 351 place of that carried away or decomposed, and thus a current will be established. This occurs in the common lamp; when unlighted, the wick is saturated with oil, and none overflows, but if we in- flame it, however rapid the consumption, new portions of oil rise to replace those destroyed. Capillary action takes place in every case where the necessary chemical affinities exist.—-It is not necessary that there should be visible vessels or pores, or that there should be a fluid or solid— it occurs between two fluids, between gases, and between gases and solids or fluids. In every case, whether it be a mass of metal, a volume of gas, a fluid, or a membrane, there is an infi- nite number of pores or interstices existing between the ultimate particles, and into these the fluids or gases intrude. To the pas- sage of bodies which have a chemical affinity, no opposing force exists—density, closeness of texture are as nothing; but on the other hand, a tissue, however open, which has no electrical affinity of a fluid, offers an insurmountable obstacle to its pene- tration. Indian rubber, which resists water, is rapidly permeated by carbonic acid, and softened by ether. The intensity of the capillary force is as the electrical rela- tions of the bodies.—When their affinity is slight, the liquid rises in a tube or permeates a tissue, but in a small degree. If it be intense, the fluid rises high in a tube, and may proceed so far as to dissolve or disintegrate the solid. In the highest state of capil- lary attraction, it becomes identical with the chemical force. Applications of the preceding facts.—The preceding facts which are true for membranes, minerals and all bodies whatever, have a special application to the phenomena of the penetration of gases through membranes, to endosmosis and exosmosis, and the capillary circulation in animals and plants. We shall briefly con- sider these applications. The penetration of gases through membranes takes place, however thick they may be, but is more rapid the finer the mem- brane. The passage is through the interstices between the atoms, and not through any obvious pores, and occurs with different rapidi- ties for dissimilar gases. It does not follow the law of diffusion (page 176) in every case, for the membrane sometimes condenses the gas, and may enter into chemical union with it. The pas- sage takes place notwithstanding pressure. Dr. Draper deter- mined that a pressure of 450 lbs. on the square inch, did not hinder the passage of sulphuretted hydrogen through a mem- brane. The introduction of oxygen into the blood, and the exhalation of carbonic acid and vapor of water in the lungs, offer illustrations of penetration in the bodies of animals. There is no difference between the passage occurring through dead or living membrane, 352 THE LAWS OF CAPILLARY MOVEMENTS. or through Indian rubber, water or porous minerals, except so far that these bodies do not condense gases to the same extent. Endosmosis and Exosmosis.—These words were introduced by Dutrochet, to express the fact that when a bladder is filled with alcohol and immersed in water, some portion of the alcohol comes out from the bladder, and is replaced by water, which goes into the bladder. The outward current he termed exosmosis, and the inward, endosmosis. He conceived this to be a peculiar ope- ration, and to depend upon the texture of the membrane, but it is now known to occur through the pores of mineral-bodies. It is a case of the penetration of fluids. It is regulated by a few simple laws, the principal of which are as follows: 1st. The fluids or bodies, on either side the membrane or porous system, must have capillary attraction for it. 2d. They must have an attraction for one another. If we fill a bladder with oil and immerse it in water, the passage inwards and outwards does not occur. The oil penetrates the tissue pass- ing from the inner to the outer surface, but here all capillary at- traction ceases. It cannot advance beyond the limit of the pores or interspaces of the bladder, any more than oil can flow oyer the wick of a lamp. To leave the membrane, it must be solicited by the exterior fluid, and combine with it by capillary action. The same holds for the water from the exterior; this passes through the thickness of the bladder, but being insoluble in oil, cannot mingle with it. Place a solution of potash outside of the bladder of oil, or any substance with which it can combine, or for which it has an affinity, and it will pass out freely. 3d. When the fluids have an attraction for one another, and unequal affinities for the membrane, that which has the greatest passes through most rapidly. If we place strong alcohol in the bladder and water exteriorly, the latter having most affinity for the membrane, enters much more rapidly than the alcohol passes out; hence the bladder becomes distended, and will burst if com- pletely closed. Or if we adjust a graduated tube to it, the excess of fluid rises and may be measured; such an arrangement is termed an endosmometer. A thick solution of gum or sugar, or a concentrated solution of any soluble salt placed within the membrane, solicits the external water, which flows into the bladder in excess. But if the ar- rangement be reversed, the excess of current is in the opposite direction. In all these cases some amount of the denser fluid passes, but in less quantity than the lighter. 4th. The current inwards and outwards flows as long as there is a difference in composition or density between the fluids; the ILLUSTRATIONS OF CAPILLARY ACTION. 353 rate diminishing as the difference lessens. The foregoing laws are also true for gases. Cell Nutrition.—The access of nutriment into the cells of any part is subject to the above laws. Indeed, the growth of the cellule is a consequence of them. The bounding membrane is not an impediment to the passage of nutritious matters, which necessarily possess a considerable capillary affinity for the tissue, any more than the bladder impedes the entrance of water. The current of cell food (cytoblastema) will, as a general rule, flow faster into the cell than its elaborated contents escape—hence, the development of the part and its final destruction by bursting. The basement tissue of a part lying upon the cell food and permeated by it, evolves cells which suck up like a sponge the food, expand by its introduction, and finally burst, yielding their contents as a secretion. Or they may, by absorbing oxygen with their food, as in the muscles, brain and other parts, cause a chano-e thereon, or perform a species of digestion, converting the blas- tema into effete matter, and evolving electricity, or the nervous power. The passage of albumen out of the capillaries, and the intro- duction of the effete fluids of the body, are obviously cases of exosmosis and endosmosis. The ascent of sap in a tree, the introduction of fluid into the veins, lacteals and lymphatics, are other instances, for these are not open vessels. They are charged with a fluid having alkaline reaction, and which has the property of soliciting fatty matters and albumen from the intestines or other parts of the body. Fill a delicate membranous tube, with a dilute solution of carbonate of soda or the alkaline tribasic phosphate of soda, and place it in an oily emulsion, and it will be found that the oil penetrates the membrane by endosmosis. Capillary Circulation.—It is well known that all the functions of the body are carried on in the capillaries and not in the large vessels. The arteries nowhere enter the veins, but between them lie minute vessels or interstices, in which the arterial blood becomes changed into venous. These interstices, whether tubu- lar or intercellular, constitute the capillary system of the body. The diameter of the vessels and spaces varies from 7T'^ to T^5 or less of an inch. The plasma of the blood, the chyle, lymph and muscular fluids move in these interstices, and are altogether independent of the action of any mechanical force. The heart has no influence to control these currents, for it has no connection with the absorbent system, with the portal capillaries, nor with the interstices be- tween the cells. The office of this organ is to regulate the cir- culation in the whole body and to drive the blood into the large 30* 354 CAUSE OF THE CAPILLARY CIRCULATION. arteries. And this it does with a force equal to about one pound to the square inch. The capillary circulation even in the vessels lying between the arteries and veins, is independent of the heat. The movement here is increased or diminished by local means which do not affect the central organ. If the web of a frog's foot be exposed in the field of the microscope, the white blood (plasma) of the capillaries will be seen moving leisurely, from artery to vein, and meandering among the tissues. It all takes a determinate course to the veins. If the web be touched with a drop of strong brine or alcohol, the currents rush to the spot, and a centre of inflammation is established. On the contrary, if an aqueous solution of opium be placed on it, the current becomes more languid and retires from the part affected. Heat also excites the capillary circulation, and cold diminishes it. In these and innumerable similar cases, the heart's action is not in the least affected. The capillary circulation is that essential to nutrition, the presence of the heart being of little importance, except in large animals. The greater number of the inferior animals have no heart, but life cannot exist without a capillary or interstitial cir- culation. The cause of the systemic capillary circulation is the chemical affinity existing betiveen arterial blood and the sides of the vessels or cells among which it flows.—We have seen that the function of nutrition consists in the passage of oxygenized blood through the capillaries. This action demonstrates the existence of a considerable chemical affinity between this fluid and the vessels; in virtue of which it penetrates the basement tissue of the capillaries or moves along their axes. The advance of the arterial blood is a phenomenon analogous to that of the ascent of water in a glass tube; it arises from the attraction of the fluid and solid for each other. This attraction explains the fact that the arteries are always found empty after death, whilst the veins are filled. So long as there is arterial blood, it is attracted by the sides of the capillaries, and hence the vessels which bring it are ultimately emptied. The capillary vessel has arterial blood on one side, and venous blood on the other. The first contains an excess of oxygen, which is lost in the passage, being employed in effecting chemical changes in the capillaries. The question now arises, why is the current invariably in one direction from the arterial to the venous side ? Because arterial blood has a greater affinity for the tissue than the venous blood; hence it not only advances in preference to it, but pushes the venous blood before it;—an effect analogous to the action of water on olive oil, in a capillary tube. This capillary affinity not only is the cause of the circulation, THE CAPILLARY CIRCULATION. 355 but it acts as a force, driving forward the volume of venous blood even to the right auricle, and by distending it, is the cause of the neart s action. In the portal circulation no other force can act, lor the vessels of this system commence in the capillaries of the gastric, intestinal, mesenteric and other veins, and terminate in the porta capillaries of the liver. By the vis a tergo in the arte- rial capillaries, the large abdominal veins are filled, and by the drainage going on by the secretion of bile, a demand for fluid is supported—in the same way that the combustion of oil in a lamp creates a constant demand for more of the fuel. The entrance of fluid from the intestines, and from various parts of the body into the absorbents, is also in virtue of a chemi- cal affinity existing between the entering liquid and the alkaline fluid of these vessels. The venous blood of the pulmonary arteries is driven by the contraction of the right ventricle of the heart, to the extremities of the vessels ramifying on the cells of the lungs. But the heart cannot drive it further. Exclude the oxygen of the air and it stagnates there, and venous congestion is the result. How does the venous congestion of asphyxia arise, if the heart has the power of driving the blood through the capillaries, or if that fabulous operation of contraction and dilation in the capillaries be the cause of its propulsion. Fabulous, for no one has seen it of the thousands of microscopical observers, and there is no mus- cular coat in these vessels. Asphyxia from venous congestion, as in drowning and the inhalation of ether, arises in a few mi- nutes, long before life is extinct, without the nervous power be- ing injured, and is relieved not by causing the heart to beat, and driving forward the blood, but by the establishment of artificial respiration, whereby it may be arterialized. The function of respiration, by oxydizing venous blood, endows it with the power of advancing, by capillary affinity, into the trunks of the pulmonary veins, and filling the left auricle, which is thereby stimulated to contraction. Hence, by the action of the capillary force, the right and left auricles are rilled, and by no power of suction, as is generally conceived. Whatever lessens the supply of oxygen to the body dimin- ishes, and whatever increases it, renders the circulation more rapid. The presence of oxygen in this fluid is therefore the re- mote cause of" the circulation, for it is this agent which gives to arterial blood its affinity for the capillaries and tissues. For the foregoing views, we are chiefly indebted to Professor Draper. Capillary action explains, besides the foregoing, many other operations occurring in the body.—The penetration of liquids into the blood, the evacuation of serous and mucous fluids from 356 CAPILLARY PHENOMENA OF THE BODY. the tissues under the influence of irritants, are instances. If a strong solution of Epsom salts, nitre, or other saline bodies, be in- troduced into the stomach, they produce a diversion of fluid from the tissues by capillary action, in the same way that similar bodies placed in the endosmometer and plunged in water, solicit a current of fluid towards themselves. The purgative or emetic action of many bodies depends on this action. Cold diminishes the capillary circulation, because it diminishes the chemical action between the oxydized blood and the tissues. Heat exercises the opposite effect. Stimulants and epispastics also act by increasing the capillary circulation locally. Saline medicines cannot enter the blood, except when very dilute, because they attract fluid to themselves into the intestines, when concentrated. Numerous medicines act by endowing the blood with a specific quality, which causes an increase or diminution of the affinity existing between it and the capillaries. On this subject, see the section on isomorphism, at page 158. The relation of the capillaries to the circulating fluid, is also under the influence of the nervous system. For Ave find that in- stead of advancing, the blood sometimes becomes stagnant in the parenchymatous tissues, or on the contrary, it may be hurried forward with febrile rapidity. The secretions are dependent on the affinity of certain fluids for the capillary tubes of the glands. URINE. The urine in health is an amber-colored, limpid fluid, with acid reaction. Its sp. gr. is from 1.01 to 1.025, the difference being due to the variable proportion of water. It readily passes into the state of putrefaction, exhaling a urinous or ammoniacal odor. Chemical writers divide the secretion into three parts. 1. The Urina potus, which is produced shortly after drinking; 2. The U. cibi secreted after a meal; 3. The U. sanguinis, morning urine. Of these, the first contains an excess of fluid. The second is mixed with adventitious substances derived from the food, as coloring matters, essential oils, and an excess of saline bodies. The urina sanguinis is that to which the attention of the physician is to be turned, as affording a true indication of the state of the functions of the body. The amount of urine voided in the day averages 2k lbs., and contains about 2| ounces of solid bodies, and rather less than half an ounce of nitrogen. UREA. 357 The normal composition of this important secretion is as fol- lows :— Water,......934.00 Sollds»......66.00 Of the solids there are, in 100 parts, U/ea,......45_10 Uric acid, - 2 50 Extractive matters with ammonia salts ) and chloride of sodium, C 363u Alkaline sulphates - 10.30 Alkaline phosphates - - . 6.88 Phosphates of lime and magnesia - 1.50 From this composition it would appear to be a secretion des- tined to remove from the body effete nitrogenized bodies and saline matters. It is rich in urea and ammoniacal bodies, which are highly nitrogenized, and contains some 16 per cent, of in- organic salts. The principal constituents are urea, ammoniacal salts and the phosphates, and some further observations are neces- sary concerning these bodies. Urea is the characteristic compound of urine; it is the most highly azotized body known, containing 46.7 per cent, of ni- trogen. Its formula isC2H4N202, or the same elements as cyanate of oxide of ammonium (NH4,0 + CyO). It may be procured from concentrated urine, or artificially in the way pointed out at page 227. In the pure state, urea crys- tallizes in four-sided, transparent and colorless prisms, which dissolve in their own weight of water, and are still more soluble in hot alcohol. It has a cooling, saline taste, is inodorous, and permanent in the air. When heated, it melts, and at a higher temperature becomes decomposed into cyanate of oxide of am- monium, cyanuric acid, and ammonia. It is neutral to test paper, but it unites with acids forming salts, of which the nitrate and oxalate are insoluble and characteristic; lime and the alkalies decompose it when assisted by heat, and there is formed a carbonate of the base ; ammonia being evolved. By putrefaction, all the urea of urine disappears, being converted by union with water into carbonate of ammonia, which abounds in old urine, and gives it a pungent odor. This change is brought about by the action of the small amount of mucus voided with the urine, which, becoming oxydized by exposure to the air, acts as a ferment. Urea in the larger animals, is the product of the changes occur- ring in the proteine matters of the body. The nature of this chano-e has been stated to be similar to eremacausis. Carbon is rendered carbonic acid, hydrogen converted into water, and now we find that a portion of the nitrogen is changed into cyanic acid 358 THE AMOUNT OF UREA CHANGES. (C2N,0) by oxydation ; another portion becoming ammonia, and uniting with the cyanic acid to form urea (cyanate of oxide of ammonium). This passes off* by the kidneys chiefly, but a small portion appears to be exuded by the skin. It is generally believed that the urea exists ready formed in the blood, and is merely drained off. In Bright's disease, where there is granular disor- ganization of the kidney, urea accumulates in the blood to a great extent; this also occurs in cholera. The amount of urea depends upon the waste of nitrogenized matters, and the food.—In violent inflammatory fevers its propor- tion rises in fluid urine, from 39 parts in 1000 to 47 parts, whereas it falls to 22 in asthenic diseases, chlorosis and dropsies. Dr. Percy has shown that it increases with exercise, for in these cases there is increased waste of the muscles ; he observed an increase of upwards of one-fifth in the urine of a pedestrian undergoing the process of training. Lehmann and Simon concur in this result. The quantity of urea rises in the urine from infancy to man- hood and declines with age; it is also greater in men than women during the same periods of life. Lehmann has instituted a series of experiments on himself, to determine the connection between the food, and the composition of the urine. The results of his researches are as follows; the num- bers represent the actual amounts of the constituents of urine discharged in a day in grains : Urine. Mixed diet. Animal diet. Vegetable diet. -Die/o/s^rtA. ° sugar and oil. Solid constituents 1044.5 1347.0 912.3 641.8 Urea 499.5 819.3 346.1 237.3 Uric acid 18.0 22.8 15.7 8.0 Extractive and organic matters 203.4 113.5 295.3 272.1 The urine of the herbivora readily becomes alkaline, and contains less urea than that of man and the carnivora, and is also charged with hippuric and other organic acids. But it is a very inte- resting fact, as discovered by Barreswil and Bernard, that the urine of starving herbivorous animals becomes identical with that of the carnivora; abounding in urea, evidently produced from the metamorphoses of their azotized tissues. On the other hand, Scherer has found that a girl living on apples exclusively, voided urine which abounded in hippuric acid, and was turbid and otherwise similar to that of herbivorous animals. Uric Acid is found only in small quantities in the urine of man and the carnivora; it is absent from that of the herbivora, but abounds in the urine of serpents and birds. It becomes less in man under the influence of exercise and vegetable food, and increases in sthenic inflammations and in persons of slothful URIC ACID. 359 habits—hence, its appearance in excess in the urine of those suffering from gout. The normal appears to be about 1.1 in a thousand parts of urine, but it may be increased to 5 or 6 parts. Uric or hthic acid is a glistening white powder, tasteless, ino- dorous, and almost insoluble in cold water, and but slightly soluble in the boiling fluid. Under the microscope, it appears as minute crystalline scales. It is a constituent of the red sediment of the urine, being stained by a red coloring matter (uro-erythrine); of many urinary calculi being either pure or combined with ammo- nia as urate of ammonia; and of gouty concretions, which con- tain urate of soda. It is insoluble in ether and alcohol, but dissolves in dilute nitric acid with the evolution of carbonic acid and nitrogen. This solution, when evaporated, acquires a pink color, which, on the addition of ammonia in excess, changes to a purple-red (murexide, purpurate of ammonia). These changes are characteristic of uric acid. The formula for uric acid is C]nH4N406; but these elements do not appear to be united together with the same force, for the com- pound is readily split up into a variety of products by oxydation, among which urea is often produced. Hence, Liebig regards it as a compound of urea with a compound radical called Uryle (Ur) or cyan-oxalic acid. Or C10H4N4O6=C2H4N2O2+2(C4NO2) or 2 Uryle. When uric acid is boiled with water and the peroxide of lead, it is resolved into one atom of urea, an atom of allantoin and 2 atoms of hydrated oxalate of lead. In this case, the urea of the above formula is set free, and the two atoms of uryle combining with water and oxygen derived from the lead, become divided into allantoin and oxalic acid. The allantoin or allantoic acid thus produced, is identical with the principal ingredient of the allantoic fluid of the calf. It may be obtained in fine rhom- boidal crystals from this excretion, and consists of C4H3N203. Allantoin is converted by heat, and the alkalies or acids into oxalate of ammonia. Hence we perceive a relation between uric acid, urea, and oxalic acid, which last is a product of dis- eased urine. Other interesting bodies are obtained by the oxydation of uric acid, the principal of which are alloxan, parabanic, oxaluric and oxalic acids. The following scheme shows the order of these changes and how uric acid passes into urea by the addition of oxygen and water: Uric acid+4HO+02=2 atoms of urea+3 atoms of oxalic acid Uric acid+2HO+04=2 atoms of mea+parabanic acid+2Coi Uric acid+4HO+04=2 atoms of urea+oxaluric acid +2Co2 Uric acid+4HO+06=2 atoms of urea+6 atoms of carbonic acid 360 HIPPURIC ACID AND THE SALTS OF URINE. Hence, by the addition of water and oxygen, to uric acid, in the functions of the body, oxalic acid may be generated, and it may lay the basis for the mulberry calculus—again, as we have already stated, by vigorous exercise the uric acid of urine diminishes, being converted into urea and carbonic acid by the action of in- spired oxygen. The active beasts of prey void urea only, the inactive tortoise and serpent uric acid alone. These changes are interesting in investigating the origin of stone in the bladder, for, as will be understood, whatever dimin- ishes the supply of oxygen to the blood, as slothfulness or chronic inflammation—in which changes occur too rapidly in a part, and out of proportion to the supply of oxygen—will generate uric acid in the place of urea. On the other hand, excessive exercise, with a deficiency of food, will lead to the production of oxalic acid cal- culus, especially in those parts of the country where water im- pregnated with lime, is ordinarily used. Hippuric Acid is, by Liebig, regarded a normal constituent of human urine, but this is not certain. The quantity is, moreover, small, but in the urine of the herbivora, it is abundant in combi- nation with potash. It is produced in man, by the ingestion of benzoic acid, to which it is allied, and is said to appear when a vegetable diet is persisted in. It occurs in long transparent, four-sided crystals, without odor, and of a faint bitter taste. It is freely soluble in alcohol, less so in ether, and but to a small extent in water. It forms soluble, crystallizable salts, with the alkalies and alkaline earths. It melts into a colorless, oily body, at a moderate heat, but at a higher temperature is decomposed and resolved into benzoic acid, benzoate of ammonia, and a small quantity of an oily body, hav- ing the peculiar odor of the Tonquin bean. The Saline Matters of the Urine.—In healthy urine, two, or according to some authors, three classes of salts exist—the sul- phates, phosphates and lactates; there is also common salt, (chlo- ride of sodium,) in variable proportions. The sulphates are alka- line and soluble, they are derived from metamorphoses going on in the body, for some of the proteine matters contain sulphur; and also directly from the food. Dr. Percy witnessed an increase in the amount of sulphates during active exercise. The phosphates are highly interesting. There are phosphates of ammonia, potash, soda, lime and magnesia belonging to the urine. These are all tribasic, and some are double salts. The acid reaction of urine depends upon the presence of acid tribasic phos- phate of soda, and the phosphate of lime and magnesia therein, are dissolved by this salt in the fresh secretion. But in those dys- peptic and asthenic diseases, in which the urine is alkaline, these FOREIGN BODIES IN THE URINE. 361 bodies are precipitated, and the fluid is voided in a turbid state, or produces a deposit shortly after its separation from the body. Some remarks will be found on the composition of the phos- phates of the urine, at page 205, which renders it unnecessary for us to enter further into the subject. The phosphates are mainly produced by the metamorphosis of the tissues, but some enter the body with the food. The phos- phates of soda and ammonia are peculiarly interesting, as derived from changes transpiring in the muscular and nervous systems. Increased action in the brain and nervous system, produced by excessive application or disease, is attended with an increase of the phosphates of soda and ammonia, and frequently with an abundant deposit of phosphate of lime and magnesia, which are no longer suspended in the urine by the phosphate of soda, in consequence of its loss of acid reaction. Foreign Bodies in the Urine.—As this secretion contains the effete matters of the blood, it is subject to considerable alterations. When the function of the liver is impeded, the coloring matter of the bile or biliphaein, is separated by the kidneys. So when the mammary glands are first excited in pregnancy, and a small amount of milk formed, it re-enters the blood, and is discharged by the kidneys, constituting the substance called kiestien. Kiestien consists of caseous matter; it usually makes its ap- pearance in the urine of pregnant females about the fourth month. It appears as bullae, like the small masses of fat floating on cold mutton broth, from the second to the fifth day after the urine has been voided. Dr. Zimmermann states that it contains vibrios. It is a good test of pregnancy, but may be present whenever there is a vicarious discharge of milk by the urine, owing to any cause. In diabetes, a large quantity of glucose is found in the urine, which may be tested by Trommer's test (page 243) or by fer- mentation. In organic diseases of the kidneys, albumen is often a consti- tuent of the urine. It is recognized by the action of heat and nitric acid, which coagulate the albumen. The precipitate of nitrate of urea formed in urine, which is highly concentrated, is not to be mistaken for coagulated albumen; it differs in color and crystalline appearance. Substances, taken as food and medicines, also change the con- stitution of the secretion. Several essential oils impart to it a peculiar odor, whilst coloring matters, as rhubarb, madder and other bodies, stain it. The vegetable acids appear in the urine, as carbonates of soda and other bases, having become changed in the circulation into the carbonic acid, and entering in combination with 31 362 URINARY SEDIMENTS AND CALCULI. bases found in the stomach and food. The alkaline org? .c salts, as the tartrate of soda, citrate of potash, &c, also appei s in the urine as carbonates of their respective bases. These substances may be taken up to such an extent from food, or as medicines, as to give the urine an alkaline reaction. The alkaline salts with mineral acids, as the sulphate of potash, carbonate of soda, phosphate of soda, &c, appear in the urine without change. The haloid alkaline salts, as the chloride of sodium, ferrocyanide of potassium, iodide of potassium, also ap- pear unchanged in the urine. It is to be remarked, however, that these bodies do not enter the absorbents from the stomach and bowels, except in minute quantities, and if strong solutions of them be administered, they may be voided in the feces, or may produce vomiting or purgation. Besides adventitious saline matters, coloring matters, essential oils and other mineral bodies, the urine may contain abnormal bodies, as a blue coloring matter (cyanourine), resembling indigo, fatty bodies, or it may furnish torulse, and other organized struc- tures. Instead of being acid and limpid, it may be strongly alka- line, turbid, and may even exhale a putrid odor in consequence of the presence of carbonate of ammonia. The Sediments and Concretions of the Urine___Calculi con- sist, for the most part, of the same substances as the sediments so common in urine. They are made up of several kinds of materials, and nucleated about some foreign substance, as a little blood, pus or other body. The principal varieties are : The Uric (or Lithic) Acid Calculus.—The calculus is hard, of a light-yellow brown tint, smooth or warty in appearance, dis- tinctly concentric, and somewhat crystalline. It burns away be- fore the blowpipe, exhaling an ammoniacal odor, is soluble in solution of potash with heat, and yields murexide when warmed with nitric acid, and mixed with a little ammonia. Uric acid forms the principal portion of the brick red or lateri- tious sediment of the urine in fevers; it may be distinguished by its crystalline appearance under the microscope, and by being insoluble when the urine is heated or treated with acetic acid or ammonia. The coloring matter is termed purpurine or uro- erythrine, and is present in very minute quantity. In these cases the steady use of alkaline remedies has served occasionally to dissolve the calculus and remove the gravel. Urate of ammonia forms small calculi, and is common as a sediment. The calculus is made up of concentric layers, and is usually mixed with uric acid ; it is smooth or slightly tuberculated; the fracture is fine and earthy. It decrepitates before the blow- pipe, evolves ammonia when heated in a solution of potash, and URINARY SEDIMENTS AND CALCULI. 363 is soluu.rin solutions of the alkaline carbonates, whilst uric acid is not so. The sediment of urate of ammonia is usually of a light fawn color, amorphous, and dissolved by heating the urine ; in the latter respect it differs from the phosphatic deposits, which are not dis- solved by heat. Phosphate of Lime Calculus.—It is uncommon ; it forms a pale brown, smooth calculus, of separable lamina?. The calculi of the prostate gland are of this kind. It is common as a sedi- ment, and is recognized by being insoluble in hot urine and am- monia, but readily soluble in acetic acid. Phosphate of Ammonia and Magnesia—immoniaco-Magne- sian Phosphate—Triple Phosphate___This calculus is white, and the surface often presents minute crystals ; its texture is hard, somewhat compact and translucent. Heated before the blowpipe, it exhales ammonia, and leaves a white residue. It is readily dis- solved by acids. The phosphate of lime with phosphate of magnesia and ammonia—The fusible calculus.—This is a compound of the preceding two, is very common, and often attains a large size. It is whitish, smooth, earthy and soft. Before the blowpipe it fuses into a bead. It is also readily soluble in acids. Oxalate of Lime calculus—Mulberry calculus.—This is of a brown color, rough and warty, resembling a mulberry. It is very hard and imperfectly crystalline. Before the blowpipe this calculus burns into a white voluminous ash of carbonate of lime. It is easily soluble in nitric acid. Sediments of oxalate of lime are not uncommon; they present minute transparent octahedral crystals under the microscope, are not soluble in ammonia, acetic acid, nor by heat. Their presence indicates a tendency to the formation of urate of ammonia. Cystic Oxide—Cystin.—This is an abnormal body found very rarely in the form of calculus or as a sediment. Its com- position is C6H6N04S2; hence it contains 25.5 percent, of sul- phur. It is neither acid nor alkaline, is combustible, and exhales a peculiar odor. It dissolves both in acids and alkalies. The cal- culus is distinctly crystalline, and presents a waxy appearance externally. The sediment is found under the microscope to consist of six- sided plates, and it is distinguished from other sediments by its solubility in ammonia. Xanthic Oxide—Uric Oxide—Urous Acid.—This is also a peculiar and rare body not present in normal urine. The calcu- lus has a brown surface, scaly fracture, is brown interiorly, and acquires a resinous appearance when rubbed. It is soluble in alkalies, but precipitated from them by carbonic acid. The com- position of xanthic oxide is CJ0H4N4O4, and it differs from uric 364 THE NERVOUS TISSUE. acid in containing two atoms less of oxygen. It also differs from uric acid in being insoluble in the alkaline carbonates. Besides the preceding bodies, carbonate of lime, siliceous mat- ters, and fatty matters, have been found in calcuh. Several of the preceding bodies are often stratified together. THE NERVOUS MATTER. The brain and nervous matter consist of a mixture of albumen and peculiar fats. One hundred parts contain about 20 of solids, of which, according to Fremy, one-third is albumen, one-third fatty matters, and the rest saline and extractive bodies. The fats are cholesterine, common fats, and two which are peculiar—the cerebric acid and oleophosphoric acid. Cerebric acid is a white, crystalline and granular solid; it is slightly soluble in water, to which it imparts a gelatinous appear- ance. It is a true fat acid, and forms compounds which are for the most part insoluble. It is distinguished from other bodies of this class by containing both nitrogen and phosphorus, and is the peculiar component of the brain and nervous system. Its composition per cent., according to Fremy, is as follows: Carbon - - - 66.7 Hydrogen - - - 10.6 Nitrogen ... 2.3 Oxygen ... 19.5 Phosphorus - - 0.9 100. The amount of cerebric acid is much greater in the vesicular portion of the brain than in the nerves or in the fibrous portion. L'Heritier has also determined that the amount of phosphorus, or, what is the same thing, cerebric acid, increases from infancy to manhood, and declines with old age, and that idiots have the least amount. In infancy the amount is about 0.8 per cent, of the brain ; between 15 and 18 it increases to 1.6; in manhood it rises to 1.8 and'2, and in old age falls to 1.0 per cent. In idiots, it seldom exceeds 0.85 per cent. By combustion and the changes of oxydation in the brain, the phosphorus of cerebric acid is converted into phosphoric acid. Oleophosphoric acid is apparently a derivative of the preced- ing, and it has been resolved into phosphoric acid, and a body nearly resembling olein, and termed cerebroleine. It is in the combined state a soft oily body, soluble in alcohol and ether. It disappears very rapidly from the brain, and is hence regarded as a product of the metamorphosis of its constituents, and especially of cerebric acid. BONES, HORN AND HAIR. 365 There is a singular connection between the activitv of the nervous centres, whether in health or as a result of dise'ase, and the proportion of phosphates, especially of soda and ammonia, in the urine. In insanity, myelitis, and great excitement of the brain, the urine is either turbid, or soon precipitates phosphates. It is often alkaline from the presence of the alkaline tribasic phos- phate of soda, and soon becomes ammoniacal after emission, forming the phosphate of magnesia and ammonia. BONES, HORN, ETC. Bones consist of phosphate of lime, a small amount of car- bonate of lime and phosphate of magnesia, and animal matter, principally glutine. The following are the proportions, according to Berzelius, in a specimen of human bone: Glutine......32.17 Vascular substance .... 1.13 Phosphate of lime with a little fluoride ) ,„ n. of calcium $ &J-04 Carbonate of lime .... 11.30 Phosphate of magnesia - - - 1.16 Soda and common salt ... 1.20 100.00 But the bones of the aged contain more mineral matter than those of the young, and the hard bones, especially the enamel of the teeth, than the spongy bones. Horn, hair and feathers are insoluble bodies, consisting of gela- tine, with different amounts of saline matters ; but their constitution is little known. Caustic potash with heat dissolves them all, with the evolution of ammonia, and acids throw down a substance re- sembling proteine. 31* 366 PART V. THE METALS. The metals are those elementary bodies, which are usually electro-positive in their reaction, have a peculiar brilliancy, called the metallic lustre, and are good conductors of heat and elec- tricity. There are from 42 to 45 of these bodies, which are enumerated in the table of equivalents at page 135. They have usually the solid form, and a considerable specific gravity; but potassium, sodium and other metals, are lighter than water, whilst mercury is fluid. Some possess malleability, as iron, copper, gold, silver, whilst others, as antimony and arsenic, are extremely brittle. Most of them possess considerable fixedness in the fire, and a high fusing point, but zinc, arsenic, cadmium, mercury, potassium, sodium and tellurium, are readily distilled. The metals readily unite with oxygen and the haloid bodies, and also with each other. The latter compounds are termed amalgams when mercury is present, and alloys, when this metal is absent. Few metals are found in the native or elementary state in nature, but usually as oxides, sulphurets, arseniurets, carbonates, or in other states of combination. These are called ores, and the processes of metallurgy are chiefly intended to separate the metal from its compounds. Their affinity for oxygen differs widely, and as this is an im- portant feature in the chemical history of the metals, it is custom- ary to group them, according to their action towards this body. There are three groups: 1st. Metals which decompose water, to combine with its oxygen at common temperatures, and are therefore scarcely known in the elementary state ; 2d. Metals which decompose water at a red heat; 3d. Metals which cannot decompose water at all, and have, therefore, but an inferior degree of activity. THE METALS. 367 1st Group. Potassium, Sodium, 3d Group. Lithium, Barium, Strontium, Calcium, Magnesium. Chromium, Vanadium, Tungsten, Molybdenum, Osmium, Columbium, 2d Group. Titanium, Uranium, Aluminum, Copper, Glucinum, Lead, Thorium, Bismuth, Yttrium, Mercury, Zirconium, Silver, Lanthanum, Gold, Cerium, Palladium, Manganese, Platinum, Iron, Rhodium, Nickel, Iridium. Cobalt, Zinc, Cadmium, Tin. Another division is common, but less perfect, into: 1st. Alka- line metals, which includes potassium, sodium and lithium—2d. Alkaline earths, barium, strontium, calcium and magnesium—3d. The true earthy metals, including the five first bodies of the above second group—4th. Imperfect metals; and 5th, the noble metals, which are but little acted on by reagents, and form the last seven bodies of the above third group. In the following pages it is our purpose only to direct the attention of the student to the chief metallic bodies, and not to enter into their chemical history, which is of little importance to the medical man. Nor do we propose to detail all the metallic salts of medicinal value, for these are treated of at length in the works on Materia Medica. POTASSIUM. Potassium, and the metals of the first group, are only obtained in the elementary state by complicated processes, in consequence of their intense affinity for oxygen. It is a bluish-white metal, of a silver-like lustre, brittle at 32° F., but soft at ordinary temperature. It melts at 150 F., and boils at a red heat, yielding a greenish vapor. Its equivalent is 368 COMPOUNDS OF POTASSIUM. 39.26 and symbol K. Its sp. gr. is .865, hence it floats on water; but it decomposes this fluid, and burns with a beautiful pink flame. It is a body of interest in the laboratory as a deoxydizing agent, but of no importance in medicine or the arts. It forms two oxides; KO, the protoxide, which is the basis of caustic potash; and K03, the peroxide, which is scarcely known. It also combines with great facility with sulphur, chlorine, phos- phorus and the haloid bodies generally, forming substances which are often of considerable interest in the arts and medicine. Some of these have been noticed in the articles on the haloid bodies. The hydrated oxide of Potassium—Caustic Potash; KO-f HO.—Although potassium combines with oxygen so readily, the oxide is scarcely known, for if water be present, it instantly unites with it and forms the hydrated oxide or caustic potash. Caustic potash is a white, slightly translucent solid, having an intense affinity for water,, and disorganizing animal tissues to combine with it. It has a soapy feel and is eminently alkaline. It neutralizes the acids, discolors turmeric, and restores the color of reddened litmus. It unites with the carbonic acid of the atmo- sphere, becoming carbonate of potash if left exposed. The source of this body is the ashes of plants, which derive it from the soil. Nearly all its salts are soluble in water, but an excess of tarta- ric acid precipitates it as cream of tartar, or the bitartrate of potash. The bichloride of platinum, and perchloric acid also precipitate it from its compounds, when they are in the concentrated state. Caustic potash is used as an escharotic,and in dilute solution as an antacid, and in irritable states of the gastro-enteric membrane. In the laboratory it is employed as a powerful solvent and cataly- tic agent, especially towards organic bodies. The salts of oxide of potassium ; The salts of potash.—The carbonate of potash is the principal constituent of commercial pearlash; it has a disagreeable alkaline taste, a soapy feel, and is deliquescent. There is a second carbonate, called the bicarbonate, formed by passing a stream of carbonic acid through a solution of the above. The sulphate of potash is anhydrous, saline, and crystallizes in four-sided prisms. There is also an acid sulphate called the bisulphate of potash. Nitrate of potash, or common nitre, is obtained in an impure state, as an exudation on the surface of the earth in India and elsewhere. When pure, it forms anhydrous six-sided prisms, which have a cooling saline taste. It is extensively employed as a refrigerant and diuretic in medicine; and in the arts, for the manufacture of gunpowder, nitric and sulphuric acids. The bitartrate of potash, or cream of tartar, and the citrate and tartrate are employed as refrigerants, and in large doses are laxative. SODIUM AND ITS COMPOUNDS. 369 SODIUM. Sodium nearly resembles potassium, but is of a brighter color, and does not inflame spontaneously on water. If the water be heated, it burns with a rich yellow flame, which is characteristic of this body and its compounds. Its symbol is Na, and equiva- lent 23.3. J » -i Sodium unites with oxygen with great avidity. It forms three compounds, of which NaO, or oxide of sodium or soda, is the most important. But like potash, this is scarcely known, except in the hydrated state. Hydrated Oxide of Sodium—Caustic Soda; NaO-fHO.— This resembles potash, but is milder. It is deliquescent, and ab- sorbs carbonic acid from the air, becoming converted into the carbonate of soda. Soda is derived from sea weeds, and by the decomposition of common salt. The salts of soda may be formed by bringing the acids, &c, in contact with this body, or with the carbonate. They are all soluble, and usually much milder than the corresponding com- pounds of potash. Chloride of Sodium, or common salt (NaCl), is one of the most important saline bodies. It belongs to the class termed haloid salts, being a compound of two elements, and not of an acid and oxydized base. To the same class belong the iodides, bromides, cyanides, &c. It abounds in the sea and saline springs, and is also found in mines, as rock salt. When pure, it crystallizes in translucent cubes, is without water of crystallization, and fuses at a red heat. Its taste is well known. It is not more soluble in hot than cold water, this menstruum dissolving about 33 per cent, of the salt. Its antiseptic properties make it an essential body to the human family; it is also used as food, and in chemical manufactures. Salt is a speedv emetic, acting in doses of half an ounce, and as a laxative in the "dose of a drachm, dissolved in a small quantity of water. Salts of Oxide of Sodium; Salts of Soda.—Carbonate of Soda is obtained from the ashes of sea weeds, and by the de- composition of common salt. It is extensively used as the basis of soaps. In the pure state it forms rhombic octahedrons, efflor- esces in the air, is very soluble, and has an alkaline taste. The bicarbonate, which is used in medicine, is made by transmitting a current of carbonic acid through the solution of the preceding. Sulphate of Soda, or Glauber's salts, forms prismatic crystals; 370 THE ALKALINE METALS. it effloresces in the air, is bitter and purgative. Nitrate of Soda nearly resembles nitre, but is rather deliquescent. LITHIUM. Lithium is a rare metal, resembling both in the elementary state, and in its compounds, sodium. Its compounds yield a red flame, when heated before the blowpipe, and its carbonate is only sparingly soluble. Its symbol is L, and equivalent 6.4. BARIUM. Barium is a metal resembling cast iron in appearance, but not permanent in the air. Its symbol is Ba, and equivalent 68.7. It belongs, along with calcium, strontium, and magnesium, to the alkaline earths, which neutralize bases, and discharge the colors of vegetables, but differ from the alkalies, in the sparing solubility of their oxides and salts. The protoxide (BaO) forms a hydrate, which is termed bary- tes; it is acrid and somewhat caustic. The salts are not used in the arts. The sulphate is a common mineral, called heavy spar, and is employed to adulterate white lead. The soluble salts of barytes are irritant poisons; their antidote is sulphate of soda. The nitrate yields, when burnt, a green flame. STRONTIUM. Strontium is closely allied with barium. Its symbol is Sr, and equivalent 43.8. The sulphate is not so insoluble as the sulphate of barytes, and its nitrate yields, when burnt with charcoal, a rich red flame. CALCIUM. Calcium is scarcely known as a metal. Its symbol is Ca, and equivalent 20.5. It is the basis of lime, which is the protoxide. The Protoxide of Calcium (CaO), or lime, is obtained in large quantities, by burning marble, chalk, and limestone, which are carbonates of lime. The shells of oysters, lobsters, and shell fish, also yield it when burnt. When recent, it is termed quick or caustic lime, and is very active, but by exposure to the air or the action of moisture, it becomes milder, and changes more or less completely into slaked or hydrated lime. Lime is slightly soluble, and the solu- " CALCIUM AND LIME. 371 hon, termed lime-water, has an alkaline taste, and is a good test, and antacid medicine. By exposure to the air, lime absorbs car- bonic acid, whether solid or in solution, and becomes resolved into carbonate of Jime, losing its caustic properties. Solutions of lime, or its salts, are readily known by the action of oxalic acid, or oxalate of ammonia, which throws down the white insoluble oxalate of lime. The Chloride of Calcium, is a very deliquescent body, and employed in the laboratory for the purpose of drying gases, and in organic analysis. The fluoride is the beautiful mineral, called Derbyshire or fluor spa. Salts of the Protoxide of Calcium; Salts of Lime.—The car- bonate is an abundant mineral, being the sole or principal ingre- dient in the varieties of marble, limestone, and chalk. It is in- soluble in pure water, but is slowly dissolved by that which contains carbonic acid. The carbonate yields its carbonic acid, when acted on by most acids, and also by heat. When chalk is prepared by washing, it forms the creta preparata of pharmacy, and is a good antacid. The Sulphate of Lime, gypsum, or plaster of Paris, is a com- mon mineral. It occurs in clear crystals, usually in tables de- rived from the rhombic prism, and also as a white massive body. It is sparingly soluble in water. When calcined it loses water, and becomes plaster of Paris, acquiring the property of setting into a solid with water, and is hence used to obtain casts. It is much employed in agriculture, as a source of sulphates to plants. Phosphate of Lime exists in bones, in the urine, and other anima.1 substances, as well as in the seeds of plants. This is a tribasic phosphate. It is soluble in the acids, but not in water. Bleaching Powder, usually called chloride of lime, is made by bringing hydrate of lime in contact with chlorine. It is a white powder, having a slight odor of the gas, and exhaling it freely when moistened with an acid solution. It is a valuable disin- fecting agent. MAGNESIUM. Magnesium is a white, malleable metal, which melts at a red heat, and readily oxydizes, forming the protoxide or magnesia. Its symbol is Mg, and equivalent 12.7. Protoxide of Magnesia—Calcined Magnesia; MgO.—It is a white, light powder, and sparingly soluble. It is procured by heating the common carbonate to redness. It is slightly alkaline in its reaction, and neutralizes the acids 372 THE SALTS OF MAGNESIUM. perfectly, forming an extensive class of salts, most of which are soluble. It is distinguished by the solubility of its sulphate, and in blow- pipe analysis, by imparting to a small quantity of the chloride of cobalt a pink tint. Salts of the Protoxide; Salts of Magnesia.—The carbonate is a common mineral; it forms a very light, sparingly soluble, white powder. It dissolves freely in a solution of carbonic acid, and may be used in this form in medicine. All the salts of mag- nesia may be obtained by saturating this body. It is much used in medicine, as an antacid and laxative. The Sulphate of Magnesia is common Epsom salts. It is ob- tained by neutralizing the native carbonate by sulphuric acid. It crystallizes in four-sided prisms, which have a disagreeable bit- ter-sweet taste, and dissolve in about their weight of water. The phosphate of magnesia and ammonia is found in decaying urine, and forms a variety of calculus. ALUMINUM. Aluminum has been procured, in small quantity, as a gray powder, which melts below a red heat, and takes fire in the air, burning into the sesquioxide or alumina. Its symbol is Al, and equivalent 13.7. Alumina, or the sesquioxide (AI203), is the basis of clay, and the principal constituent in granite, slate, and the varieties of earthenware. In the pure state, it is a white, insoluble body, which neutralizes acids. Its principal salts are alum, which is a sulphate of alumina and potash, and the acetate, which is employed in dyeing as a mor- dant. Glucinum, Thorium, Yttrium, Zirconium, Lanthanum and Cerium are bodies scarcely known; they are found only in a few rare minerals, and have not been employed in the arts or medi- cine. MANGANESE. This is a white metal, obtained with some difficulty from its ores, and rapidly oxydizing in the air. Its sp. gr. is 8.013, and it is very infusible. Its symbol is Mn, and equivalent 27.7. It forms seven oxides, of which the protoxide (MnO), is of a green color and basic, forming numerous salts—the peroxide (MnOa) is a common black mineral, called in commerce, black oxide of manganese; it is much used in the arts, as a source of oxygen and in the preparation of chlorine. When heated, the IRON. 373 peroxide loses oxygen, and becomes converted in the sesquioxide (Mn203), which is basic, and isomorphous with the sesquioxide •!wvr '?V° °f itS oxides' mar>ganic (Mn206), and permanganic acid (Mn207), have the properties of acids, and unite with the alkalies and other bases. The manganate of potash is termed the mineral chameleon, from the changes in color which its solu- tion undergoes when exposed to the air. It is first green, then purple, blue, and finally red. The salts of the protoxide of manganese have a reddish color usually; they are little known. The protosulphate is used in dyeing, for the production of a brown color. IRON. Iron is found in meteoric stones, and to a small extent, native; but more commonly in the state of oxide, carbonate, and sul- phuret. The most abundant ore is termed the clay iron ore; this is re- duced, by carbonaceous matter and lime, in a smelting furnace. The first product of the reduction is impure or cast iron, which contains silicious and other impurities, and from three to five per cent, of carbon. It is brittle, and much harder than pure or soft iron. Soft or malleable iron is obtained from the preceding by expos- ing it in the melted state for some time to the action of the air of the flue in a reverberatory furnace; by this means the carbon is burnt out. The metal changes in color, loses its crystalline appearance,and becomes exceedingly malleable, ductile and tough. Its sp. gr. is 7.7, and may be slightly increased by hammering. Its symbol is Fe (from ferrum) and equivalent 27.18. Pure iron is obtained as a fine dark powder by passing a stream of hydrogen gas through a solution of the proto-salts. In this state it can be inflamed when dry, by a red heat, and burns with brilliant scintillations. This form has been introduced as a medi- cine, and is exhibited in pills made up with syrup as a mild chalybeate. It is preferable to the old preparation of iron scales from the forge. Steel is made by heating alternate strata of charcoal and plates of iron, or by causing carburetted hydrogen to act on the fused metal. It possesses remarkable elasticity, when cooled suddenly, is more fusible than soft iron, and brittle. It contains about 1.5 per cent, of carbon. Oxides.—Iron soon rusts in moist air, and is otherwise subject to oxydation. There are four oxides, the protoxide (FeO), which is basic and exists in numerous salts of iron—the black oxide, 3Z 374 THE compounds of iron. (Fe304), which is magnetic, and forms the natural loadstone; it is supposed to be a mixture of the protoxide and peroxide; this is also found in the scales of the Smith's forge, and has been used as a chalybeate. The sesquioxide or peroxide (Fe203), which abounds in rust, and may be precipitated from the persalts of iron as a brown magma by the action of the alkalies; this is the hydrated peroxide used as an antidote to arsenious acid. Lastly, ferric acid (Fe03), which is obtained in combination with potash by heating the sesquioxide with nitrate of potash, by which there is formed ferrate of potash; this is instable, and the acid has not been separated. There are also chlorides, iodides, bromides and sulphurets of iron. The protochloride (FeCl) is an exceedingly soluble green- ish-yellow crystalline and deliquescent body, of a styptic taste, and used in medicine as a chalybeate under the name of muriate of iron. The protiodide of iron (Fel) is an esteemed prepara- tion in scrofulous diseases; it is readily made by digesting toge- ther iron wire in tincture of iodine. It is a pale green crystalline body, but very deliquescent and soluble, and becoming changed by exposure in the air to the periodide, which is of a brown color. The protosulphuret of iron (FeS) is a brown brittle solid, made by heating together scraps of iron and sulphur. It is insoluble and used in the preparation of sulphuretted hydrogen. The bisulphuret is an abundant mineral product called iron pyrites. It crystallizes in octahedrons and figures derived from it, and has a rich metallic color like brass. Prussian blue is a ferrocyanide of peroxide of iron. The salts of the oxides of iron.—The protosulphate of iron is the green vitriol or copperas of commerce. It crystallizes in oblique prisms of a green color, which effloresce and become changed into the persulphate by exposure to air and moisture. It is a styptic and emetic body, and is but little used in medicine. In the arts and in dyeing, it is extensively employed. The protocarbonate of iron is a whitish insoluble body pro- cured by the action of potash or soda on a solution of the proto- sulphate. It is a useful chalybeate, but readily changes when exposed to moisture and air. This body is present in ferrugi- nous springs, being suspended by carbonic acid in a solution of which it is soluble. It also abounds in the clay iron ores. The principal persalts are the nitrate, peracetate and persul- phate. These are used in dyeing. Solutions of the protosalts of iron yield a white precipitate with the ferrocyanide of potassium (yellow prussiate of potash), which becomes blue by exposure to the air; in the persalts, this precipitate is blue (Prussian blue) at first. Infusion of galls, and other forms of tannic acid, strike a blue-black color, which is the NICKEL, COBALT AND ZINC. 375 basis of common writing ink. The protosalts in solution or in damp air absorb oxygen, and become converted into persalts, hence there is much difficulty in preserving them ; in pharmacy, this is partially accomplished by the aid of sugar. NICKEL. Nickel is a white malleable metal, requiring a high heat for fusion. It is magnetic, and has a sp. gr. of 8.5. It is little used except as a constituent of German silver. Its symbol is Ni, and equivalent 29.6. Its salts have a characteristic green color. COBALT. Cobalt is a white brittle metal, very infusible, and sp. gr. 8.5. Its symbol is Co, and equivalent 29.5. The pure metal is not used, but its oxide is of value as a blue coloring material for glass and earthenware goods. The chloride yields a pink solution, which may be used as a sympathetic ink; when written on a pinkish paper, it is invisible, but turns of a rich green color as often as it is warmed before the fire. ZINC. Zinc abounds in nature as a sulphuret (zinc blende) and sili- cate. The metal is of a bluish gray; it melts below redness, and burns at a red heat into the white oxide. It distills over in a closed vessel at a high temperature. Its specific gravity is 7.00. It is crystalline and brittle at ordinary temperatures, but becomes malleable, and can be rolled at 300° F. It is much used as an alloy with copper and other metals, and in the metallic state for roofs. Its symbol is Zn, and equivalent 32.3. The oxide (ZnO) is a white insoluble powder; it is basic, and forms colorless salts, of which the sulphate of zinc, white vitriol, is the principal. This crystallizes in colorless prisms with six equivalents of water of crystallization; it is very soluble, has a severe styptic taste, and reddens litmus paper. It is one of the most active emetics known in doses of gr. x to gr. xv. The chloride of zinc is a butyraceous solid; it is used in sol- dering. CADMIUM. Cadmium resembles tin, but is nearly as volatile as mercury. It is not put to any use; its symbol is Cd, and equivalent 55.8. 376 TIN AND CHROMIUM. TIN. It is found in nature somewhat sparingly as an oxide. The metal is white like silver, but less lustrous, and softer. It oxydizes superficially only. Its sp. gr. is 7.2; it melts at about 400, and burns in the open air at a high temperature into an oxide. Its symbol is Sn (from Stannum), and equivalent 58.9. It is used to protect iron from oxydation in the common tin plate, and as an alloy in solders and pewter. There are three oxides of tin : the protoxide (SnO), which is a black powder and combustible, changing into the peroxide; its salts reduce the noble metals, and yields with the chloride of gold a rich blue color called the purple of Cassius;—the sesquioxide (Sn2Os) is scarcely known;—the peroxide (Sn02) has feeble acid properties, and has been termed stannic acid; it is a white pow- der ; fused with glass, it forms common white enamel. There are two chlorides: the protochloride (SnCl), a gray resi- nous-looking body used as a deoxydizing agent—the bichloride (SnCl2), formerly called the fuming liquor of Libavius. It is a thin colorless fluid, yields a colorless vapor, which becomes of a dense white in moist air, and boils at 248° F. It is of great value as a mordant in dyeing. The mosaic gold, or aurum musivum of the electricians, which is of great service in exciting the electrical machine, is an impure bisulphuret of tin. It is prepared by exposing to a low red heat a mixture of 12 parts tin, 6 of mercury, and 7 of sulphur. There remains a brilliant, dark golden body in scales, and of a greasy feel, which is the mosaic gold. CHROMIUM. Chromium is a hard, grayish-white, brittle metal of sp. gr. 5.9, and exceedingly infusible. Its symbol is Cr, and equivalent 28.19. It is not employed in the metallic state, but its oxides are used as colors. The sesquioxide (Cr203) is of a fine green color, and used in staining glass—the second oxide, chromic acid (Cr03), is a pow- erful acid, isomorphous with sulphuric acid. It consists of red crystals, which are very deliquescent, and are readily reduced by organic and other matters into the sesquioxide. Its salts with potash and lead are of a fine orange color; the latter (chromate of lead) is much used as a pigment. The bichromate of potash, which has a deep yellow color, is employed in dyeing. TITANIUM, URANIUM AND COPPER. 377 Vanadium, Tungsten, Molybdenum, Osmium and Columbium are rare metals, scarcely known, and of no practical value. TITANIUM. Titanium is a metal resembling copper in appearance, but it is extremely infusible, and not used in the arts. It is associated with many iron ores in small quantities. Its symbol is Ti, and equivalent 24.3. Its oxide, titanic acid (TiOJ, is a white insoluble substance, employed in coloring enamels. URANIUM. Uranium is scarcely known in the metallic state. Its symbol is U, and equivalent 217.26°. There are three oxides : the protoxide (UO), formerly supposed to be the metal; this is a brown powder, and possesses basic pro- perties ;—the black oxide (U405); this is black, and is used to give a black color to porcelain;—the peroxide (U203) is of a yellow color when hydrated; it forms fine yellow salts, and is used to strike this color in glass and porcelain staining. COPPER. The ores of copper are abundant, especially the oxide, car- bonate and sulphuret; native copper is also common, especially in the north-western territory. In its reduction, the first object is, by roasting in the open air, to convert the copper of the ore into an oxide; this is next mixed with charcoal, and reduced in the furnace. Copper is a reddish-yellow metal, of great tenacity and duc- tility, and very malleable. Its fusing point is about 2000° F., and sp. gr. 8.96. It is one of the best conductors of heat and electricity. Exposed to the air, it becomes coated with oxide, but is not affected to any great depth. Its symbol is Cu (from cuprum), and equivalent 31.7. It forms two oxides. The suboxide or dioxide (Cu02), which forms the red coating on fresh rolled copper. This also occurs in minerals, in beautiful ruby-red crystals. It is used to stain glass of a red color. The protoxide (CuO) is a black powder when dry, but in the hydrated state, is of a pale blue. It is used in organic analysis, to supply oxygen to the substances submitted to heat, for it is reduced with great facility by carbon or hydro- gen, but not by heat alone. This is the basic oxide, most of the salts' of copper containing it. It stains glass of a fine green color. 378 COMPOUNDS OF COPPER. The disulphuret of copper (Cu2S) is an ingredient of copper pyrites, one of the most abundant ores. Chlorine, iodine, bro- mide, and cyanogen, form compounds with copper, but they are not at present employed. Copper is readily detected in solution—ammonia and caustic potash strike a deep purplish blue with it; sulphuretted hydro- gen throws it down as a black precipitate; and yellow prussiate of potash, as a brown precipitate. Some of the solutions yield a precipitate of metallic copper, on a clean piece of iron, placed in them. Its compounds are nearly all of a green or blue color. Its salts stain the flame of a spirit lamp or blow-pipe of a green color. The salts of copper are all more or less poisonous; they are irritants, produce vomiting, purgation and gastro-enteritis. Some are escharotic, and therefore disorganize the stomach. The antidote, which is to be employed at once, and is of more service than even the stomach-pump, is the white of egg. Al- bumen forms with these salts an insoluble body, which, if soon removed from the stomach, exerts no injurious effects. Yellow prussiate of potash has also been recommended, but we prefer albumen. Salts of Copper.—The protoxide of copper unites with nearly every acid, and forms a large number of salts; some of these have already been mentioned in the chapter on acetic acid, and a few remain to be considered. Carbonates of Copper.—Carbonate of soda precipitates a solu- tion of copper, of a light blue color, which, by warming, becomes granular and of a rich green; this has the composition CuO,Co2 + CuO,HO, or is a mixture of the protocarbonate with the hydrated oxide of copper. This is prepared as a pigment, and has the composition of the mineral called malachite. Verditer, made by decomposing nitrate of copper by chalk, is a hydrated dicarbo- nate. No neutral protocarbonate is yet known. The Sulphate of Copper.—This is the blue vitriol of com- merce; it is found in beautiful blue rhomboidal crystals, having the formula CuO,S03-f 3Aq. It is soluble, has a styptic and cupreous taste, and is decomposed at a high temperature. It combines with potash and ammonia, forming deep blue, double salts. That with ammonia, the ammonio-sulphate of copper (cuprum ammoniatum), is of a rich color, and capable of crys- tallizing; it is used as a test for arsenic, and as an antispasmodic and tonic in medicine; the dose is from gr. ss to gr. iv, two or three times a day, and it has been much recommended in func- tional epilepsy. Sulphate of copper is a violent emetic in the dose of gr. x; it is astringent and tonic in less doses, and in the dilute state. But COMPOUNDS OF LEAD. 379 its affinity for albumen is such that it is escharotic, and seldom used except externally. It is employed in the electrotype, and in the arts for various purposes. In contact with metallic copper, it becomes converted into the disulphate. The Nitrate of Copper forms deep blue, deliquescent crystals, which are exceedingly corrosive. The Arsenite of Copper is Scheele's green, formed by bring- ing the ammonio-sulphate of copper in contact with arsenious acid. It is poisonous, and used as a pigment. LEAD. This metal is derived, for the most part, from the sulphuret called Galena, and which abounds in Missouri, and Derbyshire, England. It is reduced by roasting in a reverberatory furnace. Lead is a soft, bluish-gray metal, very ductile and malleable, but of little tenacity or elasticity. Its sp. gr. is 11.45, and its melting point 610° F.; at a white heat it boils and volatilizes. Exposed to the air, it becomes coated with a blackish film of sub- oxide, but it is little acted on by acids, except the nitric acid. Its symbol is Pb (plumbum), and equivalent 103.7. Lead is ex- tensively employed in the arts, and in assaying. Four oxides are known, of which the protoxide only is basic. The suboxide (Pb20) is the black-gray body which forms the tarnish of metallic lead, and the scum on the surface of melted lead. The protoxide (PbO) is litharge; it is prepared by heating lead or the carbonate to a dull red heat in a current of air ; it is of a pale yellow color, heavy, sparingly soluble, and fusible ; it forms colorless salts, with nearly all the acids. The red oxide, or red lead, used as a pigment, and in the manufacture of flint glass, appears to be a mixture of the protoxide and binoxide. The binoxide (PbOJ, called the puce oxide, is a deep brown powder; it is decomposed at a red heat, and not used except in the laboratory to convert sulphurous into sulphuric acid. The iodide of lead is a beautiful yellow substance, of a silky lustre ; it has been recommended by Velpeau in the treatment of scrofulous swellings. The dose is from gr. ss to gr. ij in pill. The soluble salts of lead are readily detected by the action of sulphate of soda, which yields a white heavy precipitate ; by sul- phuretted hydrogen, which throws down a black sulphuret of lead ; by iodide of potassium and by chromate of "potash, which yield rich yellow precipitates. The soluble salts of lead and the carbonate are more or less poisonous. They affect the intestines, producing costiveness, colic, and in severe cases, introsusception ; and also the nervous 380 COMPOUNDS OF LEAD. system, producing partial paralysis. The antidote is dilute sul- phuric acid, or solution of the sulphate of soda. The vapors of white lead factories, and of white paint, are sufficient in some constitutions to induce poisoning; hence this effect has been called painter's colic, or colica pictonum. Salts of the Protoxide of Lead.—The principal compounds of lead used in medicine are the acetates, which have been de- scribed in the article on acetic acid. Carbonate of Lead; PbO,C02.—This is the white lead of the painter; it is a soft, white, insoluble powder, of considerable weight, and readily soluble in acids, and to a limited extent-in water con- taining carbonic acid in solution. It occurs in crystalline needles as a mineral. It is made on an immense scale, in various ways, for the pur- poses of commerce, as a paint, and for the preparation of other salts of lead; but it is little used in medicine. It is powerfully poisonous, producing painter's colic. It has been supposed that this substance is formed in lead cis- terns, which are hence unfit for domestic purposes;—that the carbonate of lead, dissolved by the carbonic acid present in all water, renders the fluid a slow poison. This effect would arise if the water contained carbonic acid only, but this is never the case ; there is nearly always some amount of sulphates, which serve to encrust the cistern with an insoluble coat of sulphate of lead, that protects the metal from all further action by the car- bonic acid of the water. It may be a wise precaution to allow the new cistern to be exposed to the action of water for some weeks before use, or to add a little sulphate of soda to the water first admitted ; but these precautions are scarcely necessary. The nitrate of lead is found in opaque white octahedrons, which are soluble and without water of crystallization. It is used as a reagent in the laboratory. It is converted into a subnitrate by the action of ammonia. The sulphate of lead is a white ponderous amorphous powder, insoluble in water and acids, and inert. BISMUTH. Bismuth is found native; it forms cubic crystals of considerable lustre, a grayish-red color, and very brittle. Its sp. gr. is 9.9, and it melts at about 500° F., and volatilizes at a high temperature. Exposed to the air, it burns with a bluish flame into an oxide. It is easily dissolved by nitric acid. Its symbol is Bi, and equivalent BISMUTH AND MERCURY. 381 There are two oxides of bismuth: the protoxide (BiO), formed I fleatmg the SUDnitrate 5 ^is is an insoluble yellow powder, and the base of the salts of bismuth ;—the peroxide (Bi,OJ is a brown instable body. 3 The chloride of bismuth is a corrosive butyraceous substance. Salts of bismuth.—The only salts of bismuth much known are the nitrate and subnitrate ; the latter is used in medicine. The nitrate is formed by dissolving bismuth in nitric acid ; it forms large, colorless, transparent crystals, which are decomposed by the action of water. The subnitrate is made by pouring the above solution when cold into a large quantity of pure water, when a brilliant white, crys- talline powder is formed, which is the subnitrate. This was for- merly much used as a cosmetic, under the name of pearl powder and magistery of bismuth, but after long use it turns the skin brown, and renders it harsh. It is used in medicine in cases of gastralgia, obstinate vomiting, and as a tonic. The dose is from gr. iv to gr. x, but as much as a scruple has been given three times a day. MERCURY. Mercury or quicksilver is found native, and as a sulphuret. The metal is well known, and distinguished by its fluidity, bril- liant white appearance, permanence in the air, and high sp. gr. of 13.54. It freezes at 39° F., and boils at 620° F., volatilizing without change, so that it can be readily distilled. But if exposed to the air for a long time, at a considerable temperature, it be- comes converted into the red oxide of mercury, but is again re- duced at a red heat. Its symbol is Hg (from hydrargyrum), and equivalent 101.4, but some authors make it 202.0; hence there has arisen much confusion in the nomenclature of its compounds. It is much used in the arts in the preparation of amalgams, sil- vering mirrors, the separation of gold and silver from their ores, and the preparation of the mercurial remedies. It is readily dis- solved by nitric acid even in the dilute state, and in the cold. When mercury is triturated with lard, or with saccharine mat- ters, it is reduced to a fine black powder, which is the active agent in the blue pill, mercurial ointment and hydrargyrum cum creta. In this state it appears to be dissolved by the juices of the sto- mach, and to enter the circulation, being a mild and valuable pre- paration. . The Oxides of Mercury.—There are two oxides, the suboxide, or, according to some, the protoxide—and the protoxide, also called the binoxide, but well known by its characteristic red color. 382 COMPOUNDS OF MERCURY. The suboxide, or gray oxide (Hg20) is readily prepared by adding lime, potash or ammonia to the nitrate. It is a dark gray, heavy powder, insoluble, of basic properties, and slowly decom- posed by the action of light into metallic mercury, and the prot- oxide. It is the substance thrown down when lime water is added to calomel, in the preparation of the black wash. The protoxide of mercury or red oxide, red precipitate, nitric oxide, Hg02, is prepared by heating strong nitric acid on mercury, and evaporating to dryness. Whilst hot, it is of a dark red, but becomes of a lighter red as it cools, and is crystalline ; it is slightly soluble, and has an acrid, caustic, and metallic taste. Indeed, prepared in this way, it is caustic from the presence of an excess of nitric acid, and is used by the surgeon as a dressing to indolent ulcers, and to destroy luxuriant and unhealthy granulations. It is basic, forming salts, but is decomposed by a red heat into mer- cury and oxygen. The yellow precipitate, formed by adding lime water to a solu- tion of corrosive sublimate, in the preparation of the yellow wash or Aqua phagedenica, is a hydrated protoxide. The chlorides of mercury are of considerable medical interest. The subchloride, or mild chloride (Hg2Cl), is calomel. It is a heavy, white, insoluble and tasteless powder, volatilizable at a temperature below redness, and subliming in brilliant yellowish crystals. The powder used in medicine, was formerly prepared by pounding and washing the sublimate, but it is not had by sub- liming the calomel into a chamber filled with steam. This is Howard's calomel, or the hydrosublimate of mercury. It is slightly changed by exposure to the light, acquiring a light brown color, which seems to be due to the formation of a small amount of suboxide. Calomel is readily decomposed, the alkalies yielding a black suboxide ; these preparations are, therefore, incompatible with it. The medicinal powers, both internally, and externally as a desic- calive, are too well known to require further consideration here. The protochloride or corrosive sublimate (HgCl), formerly called the bichloride, is one of the most fearful poisons employed in medicine. It is usually found as white, transparent prismatic crystals, soluble in 16 parts of cold and three of boiling water, and of a powerful metallic taste. It melts at 509° F., and vola- tilizes at a higher temperature, subliming into a crystalline mass. Corrosive sublimate is decomposed by the alkalies and lime; these precipitate a yellow, insoluble body, which we have men- tioned as the hydrated protoxide. It combines with proteinous bodies, and owes its activity as a poison, and as an antiseptic body, to this action—these compounds being insoluble and almost inde- structible. It has a disposition, like the chlorides of platinum and COMPOUNDS OF MERCURY. 383 gold, to form double salts with other chlorides—these are often termed hydrargyro-chlorides. Sal Alembroth is an instance of this kind; this consists of HgCl-r-NH,4Cl + HO, or hydrargyro-chloride of oxide of ammo- nium. The white precipitate of pharmacy, a compound made by adding excess of ammonia to corrosive sublimate, consists of corrosive sublimate with amidide of mercury, or HgCl + Hg,NH2. In poisoning by corrosive sublimate, or any of the preparations of mercury, the white of eggs is the antidote. This acts by form- ing an insoluble compound, which should, however, be removed from the stomach by the stomach pump, as soon as possible. There are two iodides of mercury. The subiodide, Hg2I, is a greenish-yellow, insoluble body; it is readily formed, by adding a solution of iodide of potassium to the sub-nitrate of mercury. It sublimes in red crystals, and is partly decomposed by the action of light. It has been recommended as a remedy, in cases where syphilis and scrofula are conjoined; the dose internally is gr. i; but it is a powerful irritant. The ointment contains one-eighth by weight of the iodide. The iodide of mercury, Hgl, also called the deutiodide and red iodide, is a brilliant scarlet powder, of great weight, sp. gr. 6.32, and insoluble. When rapidly heated, it volatilizes, sublim- ing into yellow crystals, which become red, when scratched by a hard body. When slowly sublimed, the c^stals are of a scarlet color. Like corrosive sublimate, it has a tendency to unite with the alkaline iodides, forming hydrargyro-iodides. It is a powerful irritant and caustic, resembling corrosive sublimate, but not be- ing so active. It has been recommended in cases in which syphilis and scrofula, are combined; the dose internally is gr. T'g. The ointment is a very active, stimulating preparation; it con- tains one-eighth of the iodide. It is particularly recommended in ophthalmia tarsi. There are .two bromides and two cyanides, corresponding to the foregoing bodies, which are, however, but little or not at all employed in°medicine. The cyanide of mercury (HgCy) is the only one of much importance, it forms beautiful, pearly, colorless, square prisms; it is slightly soluble, volatile, and of considerable weight. It closely resembles corrosive sublimate in its proper- ties, and has been mentioned as an antisyphilitic remedy in the dose gr. -1- to gr. } in solution. But it is so poisonous, that it is doubtful whether it should be used. It is employed in the labo- ratory, for the preparation of cyanogen and hydrocyanic acid. The sulphurets of mercury are the black or sub-sulphuret, (Hg S), and the red or protosulphuret (HgS). The former is little used; it is the Ethiop's mineral of the older pharmaco- 384 COMPOUNDS OF MERCURY. pceias; the latter is cinnabar; it is found in nature as the most abundant ore of mercury, and is occasionally used in mercurial fumigations. Cinnabar is a brilliant red, insoluble body, the powder of which forms vermilion; it is of great weight, and readily sublimes. Ac- cording to Orfila, it is inert when pure. Tests for the preparations of Mercury.—The mercurial pre- parations are volatile ; mixed with a little charcoal, or with char- coal and carbonate of soda, and heated in a glass tube, the mercury is readily reduced. The metal is also precipitated from its soluble salts, by a clean plate of copper. Solution of caustic potash, or ammonia, precipitates it from its soluble compounds, as a black or yellow powder, according as it is the suboxide or protoxide. So- lution of albumen is precipitated by all the soluble salts of mer- cury. The Oxygen Salts of Mercury.—The nitrate and sulphate are used in medicine. The acetate was formerly employed in the pills of Keyser. The Neutral Nitrate of Mercury is made by the action of cold dilute nitric acid on mercury. It forms transparent, crystal- line rhombs, which are extremely caustic, and are used as an escharotic to fungous granulations. There is an officinal oint- ment. This is a nitrate of the suboxide, its formula being Hg20, N05-f-2Aq; it is soluble in a small quantity of water, but in a large excess, it becomes decomposed, forming an insoluble sub- nitrate. When a little ammonia is dropped into a solution of the nitrate, a black precipitate falls, which is called Hqjinemanri's soluble mercury; its composition is,accordingtoKane,2Hg20,NO.-f-NH3. If in the preparation of the nitrate an excess of mercury be employed, a crystalline basic salt is deposited after a time; this has the composition Hg20,2N05+3Aq. It is decomposed by water. The neutral nitrate of the protoxide exists only in solution; it is made by dissolving the protoxide (red oxide) in cold nitric acid. If the acid be hot, there is formed a crystalline basic salt, 2HgO, NO--|-2Aq ; this substance yields to cold water a second basic salt which is of a yellow color and insoluble 3HgO,N05-fHO, and to boiling water a red insoluble substance of the formula 6HgO, N05. The yellow insoluble powder above mentioned is some- times called the nitrous turpeth, and. was employed in medicine as an emetic and purgative. The medicine was made by allow- ing water to stand on the yellow powder and decanting it—the fluid and not the insoluble substance was used. The sub sulphate, Hg20,S03, is a white crystalline body formed when sulphuric acid is added to a solution of the neutral subni- COMPOUNDS OF SILVER. 385 trate. The neutral protosulphate of mercury, HgO,SO„ is made by boi ing sulphuric acid with the metal to dryness; it is a white crystalline powder. When the neutral sulphate is mixed with water, it becomes resolved into an acid salt which remains in solution, and there ial s a yellow, acrid, basic compound, 3HgO,SO„, which is the yellow sub-sulphate (hydrargyri sulphas flavus), or turpeth mine- ral ot pharmacy. This body is known as a violent emetic and errhme; in doses of gr. ss, it is alterative, but rapidly produces ptyahsm. It is seldom employed. By long-continued boiling with water, it loses its nitric acid, and becomes resolved into protoxide of mercury. SILVER. Silver is found native, and as a sulphuret and chloride. The ore being reduced, the silver is separated by amalgamation with mercury. The amalgam is next decomposed by distillation. Metallic silver is a white, brilliant substance; it is very mallea- ble and ductile, and one of the best conductors of heat and elec- tricity. Its sp. gr. is 10.5, and its melting point upwards of 1800° F. In the pure state it is so soft that it is alloyed with a small amount of copper to harden it for the purposes of art. Its symbol is Ag (from argentum), and equivalent 108.31. It does not oxydize in the air, but is soon coated with a black crust by sulphuretted hydrogen. Its solvent is strong nitric acid. There are three oxides of silver, all of which are reduced at a red heat; of these the protoxide (AgO) alone is basic. The haloid salts of silver are of some importance in the arts; they are all affected by light, being decomposed. The iodide is the yellow substance employed in the Daguerreotype; it is produced by ex- posing the silver to the vapor of iodine ;—the chloride is a white insoluble body which turns black in the light;—the bromide is a brownish insoluble substance also used in photography. The cyanide is a brown insoluble powder made by precipitating a solu- tion of nitrate of silver by cyanide of potassium; it is used in the preparation of medicinal prussic acid, and also in electro- plating. Silver is readily recognized in solution by the action of a little hydrochloric acid, which throws down the white chloride as a curdy precipitate. This blackens by exposure to the air. It is also thrown down from its solutions in the metallic state by introducing into them a piece of clean iron, copper, or by mercury. The nitrate of silver, AgO,N05, is the only oxygen salt of importance. It is made by the action of strong nitric acid on 33 386 COMPOUNDS OF GOLD. silver. In the pure state, it is crystallized in transparent tables, which are readily soluble in water or alcohol. It fuses when heated, and may be cast into the sticks called lunar caustic, but is decomposed at a red heat. It is a well known caustic and astringent, and has been often recommended in epilepsy. When brought in contact with organic matter in the light, it becomes black; hence it is used to dye the hair of a black color, and to mark linen. The leaden hue acquired by patients who take this medicine for any length of time, is due to the same cause. Am- monia first forms a precipitate in the nitrate, but subsequently re-dissolves the precipitate, producing a clear solution of ammonio- nitrate of silver, which is a valuable test for arsenious acid. GOLD. This metal is always found native, and is separated from mineral impurities by amalgamation. It is a soft, yellow metal, of great lustre, sp. gr. 19.3. It melts at about 2000° F. It is the most malleable and ductile of the metals, and one of the best conductors of heat and electricity. Its symbol is Au (from aurum), and equivalent 199.2. It is unchangeable in the air, even in the finest fibres, and is not acted upon by any pure acid; but a mixture of the nitric and hydrochloric acids (aqua regia), dissolves it. Chlorine acts upon it directly, forming the chloride of gold. In the divided state, gold forms a black powder, like that of platinum, silver and mercury. The preparations of gold are little used. The sesqui-chloride (Au203), formed by the action of nitro-muriatic acid, is a deep yellow, crystalline, and deliquescent salt. This combines with the alkaline chlorides, forming the auro-chlorides. The sesqui-chloride of gold and the auro-chloride of sodium have been employed in medicine as anti-syphilitic remedies, and in cancer. The chloride is said to resemble corrosive sublimate, in its action and power. The dose is gr. TXF to gr. ^, twice a day. The antidote is white of eggs. The auro-chloride of so- dium is employed in gilding Daguerreotype plates. Other preparations of gold, as the iodide, cyanide and oxide, have been mentioned as officinal bodies, but they are inferior to the corresponding salts of mercury, and not used. Indeed, there is some doubt as to their activity, for Velpeau and Bourdeloque have altogether failed to verify the observations of Chrestien, Orfila, and others, concerning their value. The cyanide of gold, a brown, insoluble body, is employed in solution in cyanide of potassium, in the process of electro-gilding. The haloid salts of gold are all changed by light, and decom- PLATINUM. 387 posed by heat. The oxides, of which there are two, do not form salts with the acids. In these respects, gold resembles platinum, indium and rhodium. The presence of gold in a solution, is known by the action of a so ution of the protochloride of tin, which strikes a rich purple color (the purple of Cassius); and also by the sulphate of iron, which throws down a brown precipitate, which is readily fusible before the blowpipe into a bead of gold. PLATINUM. Platinum is always found native, and usually associated with palladium, iridium, and rhodium. It is a white metal, harder, but of less brilliancy, than silver. Its sp. gr. is 21.5, and it is infusible in the furnace; for its preparation, Dr. Hare's blow- pipe is now used, or spongy platinum is alternately heated and pressed, until it becomes solid. It is one of the poorest conduct- ors of heat and electricity amongst the metals. It is malleable and very ductile. Its symbol is Pt, and equivalent 98.84. Platinum is unchangeable in the air, and is not affected by any of the pure acids, but is dissolved by nitro-muriatic acid, and con- verted into the chloride. In consequence of its unchangeability, it is much used for chemical vessels, and is an indispensable metal in the laboratory. It exists in three forms: as the hammered white metal; in a porous state, or spongy platinum; and in fine powder, platinum black. The hammered metal possesses the property of condensing oxygen and some other gases on its surface, especially when red hot, but in an inferior degree. It is, however, capable of effecting catalytic changes in the vapor of many organic bodies. Spongy platinum is prepared by dissolving the metal in nitro- muriatic acid, and then adding chloride of ammonium to the solu- tion ; this forms the insoluble platino-chloride of ammonium, which, heated to redness, leaves a grayish spongy mass of platinum, which is the body in question. Spongy platinum, introduced into a mixture of oxygen and hy- drogen, causes their union, by condensing and bringing the gases together in its pores. In the open air, if a stream of hydrogen be directed on it, the metal becomes red hot. It brings about numerous changes of eremacausis, as the conversion of the vapor of alcohol into acetic acid. Platinum black is the metal in a very finely divided state. It is prepared by mixing a solution of chloride of platinum with an excess of carbonate of soda and sugar, and heating slowly to 212° 388 PALLADIUM AND IRIDIUM. F., with frequent agitation. The black powder formed in this operation, is collected on a filter, washed, and gently dried. It possesses the property of condensing oxygen and other gases, and acts more powerful as a catalytic or oxydizing agent, than spongy platinum. It is used in the manufacture of acetic acid from alcohol in Germany. When formic acid is slowly dropped on it, it becomes converted into carbonic acid by oxydation. Al- cohol and ether dropped on it, are changed into acetic acid with the evolution of so much heat as to cause the inflammation of a portion of these fluids. There are two oxides of platinum, the protoxide, PtO, and bin- oxide, Pt02, which are of little consequence, and form salts of an instable nature, readily decomposed by light and heat. There are also two chlorides, the protochloride, PtCl, and the bichloride, PtCl2. The latter is the common solution of platinum; it is a light-brown, deliquescent solid, exceedingly soluble in water and alcohol. It is most remarkable for the facility with which it is decomposed, and its tendency to unite with the chlo- rides of the alkalies to form platino-chlorides. In virtue of this property, it is employed as a test for potash and ammonia, with which it forms insoluble, crystalline, orange- colored salts. With soda, it forms a soluble crystalline salt. The solution of the bichloride is used in organic analysis for the de- termination of nitrogen, which is first converted into ammonia, and.then forms the platino-chloride of ammonium. It has also been introduced into medicine, as a substitute for corrosive subli- mate, but is inferior, and not now employed. The cyanide of platinum, dissolved in a solution of cyanide of potassium, is employed in the electrotype to coat bodies with pla- tinum. PALLADIUM. Palladium is associated with platinum, and resembles that metal in many respects. It is white, malleable and ductile, al- most infusible, and of sp. gr. 11.5. It does not oxydize in the air, but when heated, acquires a purple tint. The metal is somewhat employed by dentists. Its symbol is Pd, and equivalent 53.36. IRIDIUM. Iridium is a white, brittle metal, almost infusible, and having a sp. gr. of 21.8. Hence it is the heaviest body in nature ; it ia RHODIUM. 389 not dissolved by any acid, but oxydizes by fusion with nitrate of potash. Its symbol is Ir, and equivalent 98.84. RHODIUM. Rhodium is found in the platinum ores. It is a steel white metal, of great hardness and brittleness; its sp. gr. is 11.0, and it is extremely infusible. It is employed to tip metallic pens, and ren- ders them very durable. Its symbol is R, and equivalent 52.20. 33* INDEX. A Absolute alcohol, 261 Acetal, 266 Acetification, 267 Acetone, 269 Acetyle compounds, 266 Acid, acetic, 266 acetylous, 266 aconitic, or equisetic, 2S4 aldehydic, 266 anilic, or indigotic, 292 antimonic, 219 antimonious, 219 apocrenic,274 arsenic, 216 arsenious, 208 arsenic, and poisoning by, tests for, 209 benzoic, 279 bilic, bilifellinic, 345 boracic, 229 butyric, 257 capric and caproic, 286 carbolic, 274 carbonic, 222 cerebric, 364 chloracetic, 269 chloric, 196 chlorohydric, 197 chlorous, 196 choleic, 345 chromic, 376 cinnamic, 282 citric, 284 cyanic, 227 cyanuric, 227 elaic, 288 ellagic, 285 ferric, 374 formic, 271 fulminic, 227 fumaric, 285 gallic, 285 glucic, 243 hippuric, 280, 360 humic, 274 Acid, hydriodic, 200 hydric, 173 hydrochloric, 197 hydrocyanic, 225 hydrofluoric, 201 hydrosalicylic, 281 hydrosulphuric, 191 hyperchloric, 196 hypermanganic, 373 hyponitrous, 182 hyposulphuric, 190 hyposulphurous, 190 isatinic, 292 japonic, 285 lactic, 256 lithic, 358 maleic, 284 malic, 285 manganic, 373 margaric, 288 melasinic,245 metaphosphoric, 203 mucic, 248 muriatic, 197 nitric, 182 nitromuriatic, 197 nitrous, 182 oleic, 288 oleophosphoric, 364 oxalic, 246 oxalhydric, 248 parabanic, 359 pectic, 244 phosphoric, 204 phosphorous, 203 phosphovinic, 265 picric, or carbazotic, 292 purpuric, 359 pyrogallic, 285 pyroligneous, 266 pyrophosphoric, 203 pyrotartaric, 284 racemic, 283 rubinic, 285 saccharic, 24S sacchulmic, 242 salicylic, 281 IND] Acid, sebacic, 289 silicic, 229 stearic, 288 suberic, 248 succinic, 289 sulphindigotic,292 sulphobenzoic, 280 sulphoglyceric, 289 sulphomethylic, 270 sulphosaccharic, 243 sulphovinic, 265 sulphuric, 183 sulphurous, 188 tannic, 285 tartaric, 283 ulmic, 274 urami)ic,359 uric, 358 valerianic, 276 xanthic, 363 Aconitine, 297 Action of presence, 163 Affinity, chemical, 128 Albumen, 306 Alcohol, 261 Aldehyde, 266 Aliments, classification of, 314 and 316 Allantoin, 259 Allotropism, 130 Alloxan, 259 Alloxantine, 259 Alumina, 372 Aluminum, 372 Alums, 152 Amalgams, 381 Amidine, 241 Amidides, 185 Arnidogene, 185 Ammonia liquor, 186 preparation and properties of, 185 Ammoniacal amalgam, 186 Ammonium, 136 Amygdaline, 279 Amyle compounds, 276 Animal chemistry, 313 Animal galvanism, 113 Animal heat, 338 Antiarine, 297 Antimony, 219 chloride, 219 oxide, 218 sulphurets, 219 Aqua regia, 197 Arabine, 2-14 Argol, 283 Aricine, 300 Arsenic, 207 antidotes, 215 i sulphurets, 217 sx. 391 Arterialfzation, 177 Arterial membrane, 311 Asparagine, 297, 317 Atmosphere, composition of, 175 physical constitution of, 176 Atmospheric pressure, 177 Atomic theory, 137 Atomic weights, 135 Atoms, 13 Atropine, 297 Aurum musivum, 376 Azote, 174 B Balsams, 289 Barium, 370 Barometer, 178 Baryta, 370 Bassorine, 244 Batteries, voltaic, 94 Benzamide, 280 Benzoine, 279 Benzyle compounds, 278 Bile, 322, 344 Biliphaein, 295 Biliverdin, 295 Bismuth, 380 Bleaching powder, 371 Blood, normal composition of, 328 action of venesection, 332 globules, 327 in disease, 330 menstrual, 332 Boiling points of fluids, 33 Bone earth, 205 Bones, composition of, 365 Boron, 228 Brain, composition of, 364 British gum, 240 Bromine, 200 Brucia, 297 Buffy coat, 304 Butyrin, 257 C Cadmium, 375 Caffeine, 297 Calcium, 370 chloride, 371 fluoride, 371 Calculi, urinary, 362 Calomel, 382 Calorification, 338 Calorimeter, 29 Camphor, 286 artificial, 287 Caoutchouc, 290 392 INDEX. Capacity for heat, 29 Caramel, 242 Carbon, 220 its compounds with oxygen, 221 sulphuret of, 228 Carbonic oxide, 221 Caseine, 308 Cast iron, 373 Catalysis, 163 Catechin, 285 Cellulose, 245 Cerine, 289 Cerium, 377 Chameleon, mineral, 373 Charcoal, 221 Chinoidine, 289 Chloral, 269 Chloric acid, 196 Chlorine, 194 compounds with oxygen, 196 preparation and properties of, 194 Chloroform, 271 Chlorophyll, 292 Chlorous acid, 296 Cholepyrrhin, 295 Cholesterine, 289 Chondrine, 310 Chrome yellow, 376 Chromic acid, 376 Chromium, 376 Chyle, 324 Chyme, 323 Cinchonine, 300 Cinnabar, 384 Cinnamyle compounds, 282 Circulation of the blood, 353 Coagulation, 327 Coal gas, 224 Cobalt, 375 Codeine, 298 Cohesion, 71, 126 Colchicine, 279 Coloring principles, 290 Colors, 56 Columbium, 377 Combination by volumes, 144 laws of, 138 Combining numbers, 134 table of, 135 Combustion, 169, 224 Compound radicals, 163 and 232 Condensation of vapors, 35 Conicine, or conia, 299 Copper, 377 arsenite, 379 carbonates, 378 nitrate, 379 oxides, 377 sulphate, 378 Corrosive sublimate, 382 Creasote, 273 Cruosin, 293 Cryophorus, 36 Crystallin, 309 Crystallization, crystallography, 146 Curarine, 298 Cyanogen, 224 Cyanourine, 295 Cystic oxide, 363 D Daguerreotype, 60 Daphnine, 298 Daturine, 298 Decomposition of water, 173 Delphinine, 298 Deutoxide of nitrogen, 162 Dew, 24 Dew point, 38 Dextrine, 244 Diamond, 221 Diastase, 253 animal, 318 Differential thermometer, 22 Diffusion of gases, 175 Digestion, 313 Dimorphism, 151 Dispersion, 57 Dutch liquid, 266 E Ebullition, 33 Elaterine, 298 Electricity, action of, on the magnet, 107 animal, 112 conduction of, 92 statical, 65 voltaic, 87 Electro-chemistry, 99 Electrolysis, 99 Electrometers, 75 Electrotome, 105 Electrotype, 103 Electrophorus, 76 Emetine, 299 Emulsine, 279 Enamel, 376 Equivalent, 136 numbers, table of, 135 Eremacausis, 259 Essences, 287 Ethal, 289 Ether, 263 continuous process for, 263 Etherization, 264 . Etherole, 265 INDEX. 393 Ethyle group, 262 Eudiometer, Ure's, 175 Eupione, 273 Evaporation, 34 at low temperatures, 36 Expansion of solids, 19 fluids, 20 gases, 22 F Fatty bodies, 286 Fermentation, vinous, 258 lactic, 255 organic, 252 germinative, 253 viscous, 254 butyric, 256 Ferridcyanogen, 227 Ferrocyanogen, 227 Fibrine, 307 Fixed air, 222 Flame, structure of, 224 Fluorine, 201 Food,314,316 Formomethylal, 272 Freezing of water by evaporation, 38 Freezing mixtures, 32 Fusel oil, 276 G Galvanism, 87 Galvanometer, 110 Gastric juice, 320 Gelatine, 310 Gentianine, 299 Geoffroy's tables, 138 Globulin, 309 Glucinum, 372 Glucose, 243 Glycerine, 289 Gold, 386 Gravity, specific, of gases, determina tion of, 16 Green, Scheele's, 209 Grove's battery, 95 Gum, British, 241 Arabic, 244 Gypsum, 371 H Haematin, Haematosine, 293 Haemacyanin, 295 Haemaphein, 295 Hair, 310 Hare's blow-pipe, 171 Heat, animal, 338 capacity for, 29 Heat, conduction of, 27 exchanges of, 24 latent, 30 radiation, 23, reflection, 24, trans- mission of, 26, varieties of, 27 Hesperidine, 299 Horn, 310 Hydrogen, antimoniuretted, 220 arseniuretted, 216 light carburetted, 223 peroxide of, 173 persulphuret of, 193 phosphuretted, 206 preparation and properties of, 170 sulphuretted, 191 Hygrometer, 38 Hyoscyamine, 299 Hyponitrous acid, 182 Hyposulphurous acid, 190 I Ideal coloration, 27 Indigo, 291 Induction, electrical, 93 galvanic, 104 nervous, 123 Interference, 57 Inuline, 240 Iodine, 198 Iridium, 388 Iron, 373 carbonate, 374 cast, 373 chloride, 374 oxides of, 373 sulphates, 374 Isatine, 292 Isomerism, 144 Isomorphism, 151 K Kacodyle and its compounds, 269 Kermes' mineral, 219 Kiestien, 361 Kreatin, 311 Kreatinine, 312 L Lactine, 243 Lanthanium, 377 Latent heat, 30 Laughing gas, 181 Laws of combination, 138 Lead, 379 action of water on, 380 carbonate, 380 394 Lead, chloride, 379 iodide, 379 nitrate, 380 oxides, 379 Leaven, 249 Leiocome, 241 Leyden jars, 75 Light, cause of, 53 chemical action of, 60 reflection, refraction, 54, 55 wave theory, 58 Lignine, 245 Lignite, 274 Lime, 370 carbonate, 371 chloride, 371 phosphate, 371 sulphate, 371 Lithium, 370 Litmus, 290 Lymph, 325 M Magnesia, 371 carbonate, 372 sulphate, 372 Magnesium, 370 Magnetism, the earth's, 108 Magnets, artificial, 84 Magneto-electrical machine, 85 Magneto-electricity, 107 Malachite, 378 Malaria, 192 Manganese, 372 Margarine, 288 Marriotte, law of, 42 Marsh's test for arsenic, 211 Matter properties of, 13 Maximum density, 40 Meconine, 299 Mercury, 381 chlorides, 382 iodides, 383 nitrates, 384 oxides of, 381 sulphates, 384 Mesite, 273 Metals, general properties of, 365 classification of, 366 Methyle compounds, 270 Microcosmic salt, 205 Milk, composition of, 308 Mindererus spirit, 268 Mineral chameleon, 373 M»lybdenum, 287 Mordants, 290 Morphia, 299 Mosaic gold, 376 Mucilage, 244 Mucus, 309 Murexide, 359 Muscovado sugar, 242 N Naphtha, 275 Narceine, 299 Narcotine, 299 Nervous substance, 364 Nickel, 375 Nitric acid, 182 Nitrogen, 174 its compounds with oxygen, 180 preparation and properties of, 174 Nitrous acid, 182 oxide, 181 Nomenclature, 139 Nutrition, function of, 342 O CEnanthic ether, 362 Ohm's researches, 94 Oils and fats, 286 Oil of bitter almonds, 278 cinnamon, 282 spiraea, 281 vitriol, 188 wine, heavy, 265 Oils, expressed, 287 saponifiable, 287 volatile, 286 Oily acids, 288 Oleine, 288 Olefiant gas, 223, 265 Organic bodies, nature of, 230 analysis of, 232 decomposition of, by heat, 231 general characters of, 231 production of, 233 chemistry, 230 force, 234 Orpiment, 217 Osmium, 377 Oxalates, 247 Oxamide, 247 Oxygen, preparation and properties of, P Palladium, 388 Pancreatic juice, 322 Paracyanogen, 224 Paraffine, 273 INDI Pectine, 244 Pepsin, 321 Perchloric acid, 196 Petroleum, 275 Phloridzine, 281 Phloridzeine, 282 Phosphoric acid,203 Phosphorus, compounds with oxygen, 203 preparation and properties of, 201 Phosphuretted hydrogen, 206 Photography, 60 Picamar, 273 Picrotoxine, 300 Pile, voltaic, 95 Piperine, 300 Pit-coal, 274 Pittakal, 273 Plasma, 307 Platinum, 387 black, 387 chlorides, 388 power of determining union of gases, 387 spongy,387 Plumbago, or graphite, 221 Polarity electrical, 69 Populine, 280 Potassium, 367 oxide of, 368 properties of, 367 Potash, 368 bicarbonate, 368 bisulphate, 368 carbonate, 368 hydrate of, 368 nitrate, 368 sulphate, 368 Potatoe oil and its compounds, 276 Prism, 56 Proteine, 302 Proteine, oxides of, 304 Ptyalin, 318 Pseudomorphine, 368 Purple of Cassius, 376 Pus, 305 Pyroacetic spirit, 269 Pyrometer, Daniell's, 20 Pyroxylic spirit, 270 Q Quicksilver, 381 Quinine, 300 Pv Radiation, 23 Rays of th chem 1, 60 ex. 395 Realgar, 217 Reflection, law of, 25 Refraction, 58 Resins, 289 Respiration, 333 Respiration, changes effected by, 336 consumption of fat in, 338 Rhodium, 389 S Sacchulmine, 248 Safety jet, Hare's, 171 Safety lamp, 224 Salicine, 280 Salicyle compounds, 286 Saliva, 318 Scheele's green, 249 Secretion, 344 Selenium, 193 Silicon, 229 Silver, 385 chloride, 385 iodide, 385 nitrate, 385 Soaps; saponification, 287 Soda, biborate, 229 bicarbonate, 369 carbonate, 369 hydrate of, 369 nitrate of, 370 phosphates of, 205 sulphate, 369 Sodium, chloride, 369 properties of, 369 Solanine, 300 Specific gravity, 15 heat, 29 Spectrum, solar, 60 Spermaceti, 289 Starch, 240 Steam, elastic force of, 42 Stearine, 288 Stearopten, 286 Steel, 373 Strontium, 370 Strychnia, 301 Sublimate, corrosive, 383 Substitution of, 161 Sugar, cane, 242 eucalyptus, 242 from ergot of rye, 242 grape, 243 of diabetes insipidus, 242 of milk, 243 Sulphobenzide, 280 Sulphocyanogen, 228 Sulphur compounds with oxygen, 187 properties of, 187 Sulphuretted hydrogen, 191 396 INDEX. Sulphuric acid, 189 Sulphurous acid, 188 Symbols, 138 table of, 135 Synaptase, 279 Systems, crystallographical, 146 T Tar, varieties of, 273 Tartar, cream of, 283 Tellurium, 103 Thebaine, 301 Theine,301 Theobromine, 301 Thermoelectricity, 81 Thermometer, construction of, 21 differential, 23 Sanctorio's, 22 scales, 21 Thorium, 372 Thousand-grain bottle, 15 Tin, 376 chlorides, 376 Titanium, 377 Tithonic rays, 80 Tungsten, 377 Turmeric, 290 Turpeth mineral, 385 Types, chemical, 162 mechanicals, 162 U Uranium, 377 Urea, 357 Urinary calculi, 362 Urine, composition of, 356 V Vanadium, 377 Vapor, elastic force of, 40 Vapors, nature of, 34 Vaporization at low temperature, laws of, 37 Vegeto-alkalies, 296 Veratria, 301 Verdigris, 269 Vermilion, 384 Vinegar, 266 Vitriol, blue, 378 green, 374 oil of, 188 white, 375 Voltameter, 112 Volumes, combination by, 144 W Water, composition of, 172 of crystallization, 173 Waves, length of light, 58 Wax, 286 Wood-spirit and its compounds, 270 ether, 270 Woody fibre, 245 X Xanthic oxide, 361 Xyloidine, 248 Y Yeast, 248 Yttrium, 372 Z Zinc, oxide of, 375 sulphate, 375 Zirconium, 372 THE END. 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Bolmar, forming, in con- ^ Fr"enTh kngu°agr ' LeV1ZaC'" * C°mplete S6rieS f°r the aCquisiti°n °f A SELECTION OF ONE HUNDRED PERRIN'S FABLES, ACCOMPANIED BY A KEY, Containing the text, a literal and free translation, arranged in such a manner as to point out the difference between the French and English idiom, &x., in 1 vol., 12mo. A COLLECTION OF COLLOQUIAL PHRASES, ON EVERY TOPIC NECESSARY TO MAINTAIN CONVERSATION, Arraneed under different heads, with numerous remarks on the peculiar pronunciation and uses of various words; the whole so disposed as considerably to facilitate Hie acquisition of a correct pronunciation of the French, in 1 vol., 18ino. LES AVENTURES DE TELEJIAQUE PAR FENELON, In 1 vol., 12mo., accompanied by a Key to the first eieht books, in 1 vol., 12mo., con- taining, like the Fables, the text, a literal and free translation, intended as a sequel to the Fables. Either volume sold separately. ALL THE FRENCH VERBS, Doth regular and irregular, in a small volume. n^^LTR7^PHYsrCs7" NEARLY READY. PRINCIPLES OF PHYSICS AND METEOROLOGY. BY J. MULLER, Professor of Physics at the University of Frieburg. nj.rSTRA.TED WITH NEARLY FIVE HUNDRED AND FIFTY ENGRAVINUS OX WOOD, AND TWO COLORED PLATES. In one octavo volume. This Edition is improved by the addition of various articles, and will be found in every respect brought up to tile time of publication. "The Physics of Muller is a work, superb, complete, unique : the greatest want known to Eno lisli Science could not have been better supplied. The work is of surpassing inrerost. The value of this contribution to the scientific records of this country may be duly estimated by the fact, that tiie cost cf the original drawings and engravings alone has exceeded the sum of 2000i."—La?icel, March, 1S4T. jhjTlI^T^ ATT ja.TX*AS OP AETCIESTT GEOGSAPHY, BY SAMUEL BUTLER, D.D., Late Lord Bishop of Litchfield, CONTAINING TWENTY-ONE COLOURED MAPS, AND A. COMPLETE ACCENTUATED INDEX. In one octavo volume, half-bound. butTIFTan^ GSOGSAPHIA CIiiLSSICA, OR THE APPLICATION OF ANCIENT GEOGRAPHY TO THE CLASSICS BY SAMUEL BUTLER, D.D., F.R.S. REVISED BY HIS SON. FIFTH AMERICAN, FROM THE LAST LONDON EDITION, WITH QUESTIONS ON THE MAPS, BY JOHN FR0S1. In one duodecimo volume, half bound, to match the Atlas. LEA AND BLANCHARD'S PUBLICATIONS. SCHOOL BOOKS. WHITE'S UNIVERSAL HISTORY. LATELY PUBLISHED, ELEMS27TS OP UHIVERSAL HISTORY, ON A NEW AND SYSTEMATIC PLAN; FROM THE EARLIEST TMES TO THE TREATY OF VIENNA; TO WHICH IS ADDED, A SUMMARY OF THE LEADING EVENTS SINCE THAT PERIOD, FOR THE USE OF SCHOOLS AND PRIVATE STUDENTS. BY H. WHITE, B.A., TRINITY COLLEGE, CAMBRIDGE. WITH ADDITIONS AND QUESTIONS, BY JOHN S. HART, A.M., Principal of the Philadelphia High School, and Professor of Moral and Mental Science, &c, State of New York. Department of Common Schools. 5 Albany, Oct. \ith, 1&45. Mrssrs. Lea ?^Si?§§S' CLOTHING, BATHING, MINERAL SPRINGS, EXERCISE SLEEP, CORPOREAL AND MENTAL PUR- SUITS, &c, &c, ON HEALTIiY MAN, CONSTITUTING ELEMENTS OF HYGIENE. BY ROBLEY DUNGLISON, M.D.,&c.,&c. In one octavo volume. it Y^M^118 "?i*?e Pursu^1 of £ealth' as wel1 as those who desire l° reti"n LnnriL",0 examine this work. The author states the work has been prepared "to enable the general reader to understand the nature of the actions of various influences on human health, and assist him in adopt- ing such means as may tend to its preservation: hence the author has Usable1"' °mg techmcalities' excePl where they appeared to him indis- REMARKS ON THE INFLUENCE OF MENTAL EXCITEMENT, AND MENTAL CULTIVATION UPON HEALTH. BY A. BRIGHAM, JVT.D. Third edition ; one volume, 18mo. A TREATISE ON CORNS, BT7NZONS, THE DISEASES OF THE NAILS, AND THE GENERAL MANAGEMENT OF THE FEET. BY LEWIS DURLACHER, SUBGEON CHIROPODIST TO THE QUEES. In one duodecimo volume, cloth. BRIEGHWATEE TREATISES. The whole complete in 7 vols. 8vo., various bindings, CONTAINING: ROGET'S ANIMAL AND VEGETABLE PHYSIOLOGY, in 2 vols., with many cuts. KIRBY ON THE HISTORY, HABITS AND INSTINCT OF ANIMALS, 1 vol., with plates. PROUT ON CHEMISTRY—CHALMERS ON THE MORAL CONDITION OF MAN-WHEWELI. 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This is a practical work, and has had a very extended sale. LEA AND BLANCHARD'S PUBLICATIONS. JOHNSON AND LANDRETH ON FRUIT, KITCHEN, AND FLOWER GARDENING. A DICTIONARY OF MODERN GARDENING, BY GEORGE WILLIAM JOHNSON, ESQ. Author of the " Principles of Practical Gardening," " The Gardener's Almanac," Sua. WITH ONE HUNDRED AND EIGHTY WOOD-CUTS. EDITED, WITH NUMEROUS ADDITIONS, BY DAVID LANDRETH, OF PHILADELPHIA. In one large royal duodecimo volume, extra cloth, of nearly Six Hundred and Fifty double columned Pages. This edition has been greatly altered from the originaL Many articles of little interest to Ameri- cans have been curtailed or wholly omitted, and much new matter, with numerous illustrations, added, especially with respect to the varieties of fruit which experience has shown to be peculiarly adapted to our climate. Still, the editor admits that he has only followed in the path so admirably marked out by Mr. Johnson, to whom the chief merit of the work belongs, it has been an object with the editor and publishers to increase its popular character, thereby adapting it to the larger class of horticultural readers in this country, and they trust it will prove what they have desired it to be, an Encyclopaedia of Gardening, if not of Rural Affairs, so condensed and at such a price as to be within reach of nearly all whom those subjects interest. " This is a useful compendium of all that description of information which is valuable to the modern gardener. It quotes largely from the best standard authors, journals, and transactions of societies; and the labours of the American editor have fitted it for the United States, by judicious additions and omissions. The volume is abundantly illustrated with figures in the text, embracing a j udicious selection of those varieties of fruits which experience has shown to be well suited to the United States.—SiUiman's Journal. " This is the most valuable work we have ever seen on the subject of gardening; and no man of taste who can devote even a quarter of an acre to horticulture ought to be without it. Indeed la- dies who merely cultivate flowers vrithin-doors, will find this book an excellent and convenient counsellor. It contains one hundred and eighty wood-cut illustrations, which give a distinct idea of the fruits and garden-arrangements they are intended to represent. " Johnson's Dictionary of Gardening, edited by Landreth, is handsomely printed, well-bound, and sold at a price which puts it witliin the reach of all who would be likely to buy it."—Evergreen. THE COMPLETE FLORIST. A MANUAL OF GARDENING, CONTAINING PRACTICAL INSTRUCTION FOR THE MANAGEMENT OF GREENHOUSE PLANTS, AND FOR THE CULTIVATION OF THE SHRUBBERY—THE FLOWER GARDEN, AND THE LAWN—WITH DESCRIPTIONS OF THOSE PLANTS AND TREES MOST WORTHS OF CULTURE IN EACH DEPARTMENT. WITH ADDITIONS AND AMENDMENTS, ADAPTED TO THE CLIMATE OF THE UNITED STATES. In one small volume. Price only Twenty-five Cents. THE COMPLETE KITCHEN AND FRUIT GARDENER. A SELECT MANUAL OF KITCHEN GARDENING, AND THE CULTURE OF FRUITS, CONTAINTNG FAMILIAR DIRECTIONS FOR THE MOST APPROVED PRACTICE IN EACH DEPARTMENT, DESCRIPTIONS OF MANY VALUABLE FRUITS. AND A CALENDAR OF WORK TO BE PERFORMED EACH MONTH IN THE YEAR. THE WHOLE ADAPTED TO THE CLIMATE OF THE UNITED STATES. In one small volume, paper. Price only Twenty-five Cents. LANDRETKPS RURAL REGISTER AND ALMANAC, FOR 1848, WITH NUMEROUS ILLUSTRATIONS. STILL ON HAND, A TEW COPIES OF THE REGISTER FOR 1847, WITH OVER ONE HUNDRED WOOD-CUTS. This work has 150 lar?e 12mo. pages, double columns. Though published annually, and contain- ing; an almanac, the principal part of the matter is of permanent ntility to the horticulturist and LEA AND BLANCHARD'S PUBLICATIONS. LAW BOOKS. HILLIARD ON REAL ESTATE. NOW READY. THE AMERICAN LAW OP REAL PROPERTY. SECOND EDITION, REVISED, CORRECTED, AND ENLARGED. BY FRANCIS HILLIARD, COUNSELLOR AT LAW. In two large octavo volumes, beautifully printed, and bound in best law sheep. This book is designed as a substitute for Cruise's Digest, occupying the same ground in American law which that work has long covered in the Lnglish law. It embraces all that portion of the English Law of Real Estate which has any applicability in this country; and at the same time it embodies the statutory provisions and adjudged cases of all the States upon the same subject; thereby constituting a complete elementary treatise for American students and practitioners. The plan of the work is such as to render it equally valuable in all the States, embracing, as it does, the pecu- liar modifications of the law alike in Massachusetts and Missouri, New York and Mississippi. In this edition, the statutes and decisions subse- quent to the former one, which are very numerous, have all been incorpo- rated, thus making it one-third larger than the original work, and bringing the view of the law upon the subject treated quite down to the present time. . The book is recommended in the highest terms by distinguished jurists of different States, as will be seen by the subjoined extracts. " The work before us supplies this deficiency in a highly satisfactory manner. It is beyond all question the best work of the kind that we now have, and although we doubt whether this or any other work will be likely to supplant Cruise's Digest, we do not hesitate to say, that of the two, this is the more valuable to the American lawyer. We congratulate the author upon the success- ful accomplishment of the arduous task he undertook, in reducing the vast body of the American Law of Real Property to ' portable size,' and we do not doubt that his labours will be duly appre- ciated by the profession."—Law Reporter, Aug., 1846. Judge Story says:—"I think the work a very valuable addition to our present stock of juridical literature. It embraces all that part of Mr. Cruise's Digest which is most useful to American law- yers. But its higher value is, that it presents in a concise, but dear and exact form, the substance of American Law on the same subject. 1 know no work that we possess, whose practical utility is likely to be so extensively felt." " The wonder is, that the author has been able to bring so great a mass into so condensed a text, at once comprehensive and lucid." Chancellor Kent says of the work (Commentaries, voL ii, p. 635, note, 5th edition):—" It is a work of great labour and intrinsic value." Hon. Rufus Choate says:—" Mr. HiUiard's work has been for three or four years in use, and 1 think that Mr. Justice Story and Chancellor Kent express the general opinion of the Massachusetts Bar." Professor Greenleaf says:—" I had already found the first edition a very convenient book of refe- rence, and do not doubt, from the appearance of the second, that it is greatly improved." Professor J. H. Townsend, of Yale College, says :— " I have been acquainted for several years with the first edition of Mr. Hilliard's Treatise, and have formed a very favourable opinion of it. 1 have no doubt the second edition will be found even more valuable than the first,and I shaU be happy to recommend it as I may have opportunity. I know of no other work on the subject of Real Estate, so comprehensive and so well adapted to the *tate of the law in this country." LEA AND BLANCHARD'S PUBLICATIONS. LAW BOOKS. ADDISON ON CONTRACTS. A TREATISE ON THE LAW OF CONTRACTS AND RIGHTS AND LIABILITIES EX CONTRACTU. BY C. G. ADDISON, ESQ., Of the Inner Temple, Barrister at Law. . In one volume, octavo, handsomely bound in law sheep. In this treatise upon the most constantly and frequently administered branch of law, the author has collected, arranged and developed in an intel- ligible and popular form, the rules and principles of the Law of Contracts, and has supported, illustrated or exemplified them by references to nearly four thousand adjudged cases. It comprises the Rights and Liabilities of Seller and Purchaser ; Landlord and Tenant; Letter and Hirer of Chattels; Borrower and Lender; Workman and Employer; Master, Servant and Ap- prentice ; Principal, Agent and Surety; Husband and Wife; Partners; Joint Stock Companies ; Corporations ; Trustees ; Provisional Committee- men ; Shipowners; Shipmasters; Innkeepers ; Carriers; Infants; Luna- tics, &c. WHEATON'S INTERNATIONAL LAW. ELEMENTS OP INTERNATIONAL LAW. BY HENRY WHEATON, LL. D., Minister of the Unitod States at the Court of Russia, ic. THIRD EDITION, REVISED AND CORRECTED. In one large and beautiful octavo volume of 650 pages, extra cloth, or fine law sheep. " Mr. Wheaton's work is indispensable to every diplomatist, statesman and lawyer, and necessary indeed to all public men. To every philosophic and liberal mind, the study must be an attractive and in the hands of our author it is a delightful one.*—North American. HILL ON TRUSTEES. A PRACTICAL TREATISE ON THE LAW RELATING TO TRUSTEES, THEIR POWERS, DUTIES, PRIVILEGES AND LIABILITIES. BY JAMES HILL, ESQ., Of the Inner Temple, Barrister at Law. EDITED BY FRANCIS J. TROUBAT, Of the Philadelphia Bar. In one large octavo volume, best law sheep, raised bands. " The editor begs leave to iterate the observation made by the author that the work is intended principally for the instruction and guidance of trustees. That single feature very much enhances its practical value." ON THE PRINCIPLES OF CRIMINAL LAW. In one 18mo. volume, paper, price 25 cents. BEING PART 10, OF " SMALL BOOKS ON GREAT SUBJECTS " LEA AND BLANCHARD'S PUBLICATIONS. LAW BOOKS. SPENCE'S EQUITY JURISDICTION. THE EQUITABLE JURISDICTION OF THE COURT OF CHANCERY, COMPRISING ITS RISE, PROGRESS AND FINAL ESTABLISHMENT. T° JECTC^CONC^F¥r%n^ni^SV^0^HE ELUCIDATION OF THE MAIN SUB- UW Sn m ™°rmI0frTnK^ING DOCTRINES OF THE COMMON MON r AW wi™ B%.RASJk^P^,°PEDLRE 1N THE COURTS OP COM- ™XA,Srt ^l,1H REGARD TO CIVIL RIGHTS: WITH AN ATTEMPT T° feS^,IHE1E SOURCES ANDINWHICH 1 HE VARIOUS ALTERATIONS MADE BY THE LEGISLATURE DOWN TO THE PRESENT DAY ARE NOTICED. BY GEORGE SPENCE, ESQ., One of her Majesty's Counsel. IN TWO OCTAVO VOLUMES. Volume I., embracing the Principles, is now ready. Volume II. is rapidly preparing and will appear early in 1818. It is based upon the work of Mr. Maddock, brought down to the present tune, and embracing so much of the practice as counsel are called on to advise upon. A NEW LAW DICTIONARY, ^^TA^'J^0 EXPLANATIONS OF SUCH TECHNICAL TERMS AND PHRASES AS OCCUP ACTION AT LAW AND OF A SUIT IN EQUITY. BY HENRY JAMES HOLTHOUSE, ESQ., Of the Inner Temple, Special Pleader. EDITED FROM THE SECOND AND ENLARGED LONDON EDITION, WITH NUMEROUS ADDITIONS, BY HENRY PENIKGTON, Of the Pliiladelphia Bar. In one large volume, royal 12mo., of about 500 pages, double columns, handsomely hound in law sheep. " This is a considerable improvement upon the former editions, being bound with the usual law binding, and the general execution admirable—the paper excellent, and the printing clear and beautiful. Its peculiar usefulness, however, consists in the valuable additions above referred to, being intelligible and well devised definitions of such phrases and technicalities as are peculiar to the practice in the Courts of this country.—While, therefore, we recommend it especially to the students of law, as a safe guide through the intricacies of their study, it will nevertheless be found a valuable acquisition to the library of the practitioner himself."—Alex. Gazette. " This work is intended rather for the general student, than as a substitute for many abridgments, digests, and dictionaries in use by the professional man. Its object principally is to impress accu- rately and distinctly upon the mind the meaning of the technical terms of the law. and as such can hardly fail to be generally useful. There is much curious information to be found in it in re- gard to the peculiarities of the ancient Saxon law. The additions of the American edition give increased value to the work, and evince much accuracy and care."—Pennsylvania Law Journal. TAYLOR'S MEDICAL JURISPRUDENCE. A PRACTICAL TREATISE ON MEDICAL JURISPRUDENCE. BY ALFRED S. TAYLOR, Lecturer on Medical Jurisprudence and Chemistry at Guy's Hospital, London. With numerous Notes and Additions, and References to American Law, BY R. E. GRIFFITH, M.D. In one volume, octavo, neat law sheep. TAYLOR'S MANUAL OP TOXICOLOGY. IN ONE NEAT OCTAVO VOLUME. A NEW WORK, NOW READY. TRAILL'S OUTLINES OP A COURSE OP LECTURES ON MEDICAL JURISPRUDENC& IN ONE SMALL OCTAVO VOLUME. LEA AND BLANCHARD'S PUBLICATIONS. LAW BOOKS. E A S T'S REPORTS. REPORTS OF CASES ADJUDGED AND DETERMINED IN THE COURT OF KING'S BENCH. WITH TABLES OF THE NAMES OF THE CASES AND PRINCIPAL MATTERS. BY EDWARD HYDE EAST, ESQ., Of the Inner Temple, Barrister at Law. EDITED, WITH NOTES AND REFERENCES, BY G. M. WHARTON, ESQ., Of the Philadelphia Bar. In eight large royal octavo volumes, bound in best law sheep, raised bands and double titles. Price, to subscribers, only twenty-five dollars. In this edition of East, the sixteen volumes of the former edition have been compressed into eight—two volumes in one throughout—but nothing has been omitted; the entire work will be found, with the notes of Mr. Wharton added to those of Mr. Day. The great reduction of price, (from $72, the price of the last edition, to $25, the subscription price of this,) together with the improvement in appearance, will, it is trusted, procure for it a ready sale. A NEW WORK ON COURTS-MARTIAL. A TREATISE ON AMERICAN MILITARY LAW, AND THE PRACTICE OF COURTS-MARTIAL, WITH SUGGESTIONS FOR THEIR IMPROVEMENT. BY JOHN O'BRIEN, LIEUTENANT UNITED STATES ABTILLERY. In one octavo volume, extra cloth, or law sheep. "This work stands relatively to American Military Law in the same position that Blackstone't Commentaries stand to Common Law."— U~. S. Gazette. CAMPBELL'S LORD CHANCELLORS. LIVES OF THE LORD CHANCELLORS AND KEEPERS OP THE GREAT SEAL OF ENGLAND, FROM THE EARLIEST TIMES TO THE REIGN OF KINO GEORGE IV., BY JOHN LORD CAMPBELL, A.M., F.R.S.E. FIRST SERIES, In three neat demy octavo volumes, extra cloth, BRINGING THE WORK TO THE TIME OF JAMES II., JUST ISSUED. PREPARING, SECOND SERIES, In four volumes, to match, CONTAINING FROM JAMES II. TO GEORGE IV. LEA AND BLANCHARD'S PUBLICATIONS. YOUATT AND SKINNER'S STANDARD WORK ON THE HORSE. THE HORSE. BY WILLIAM YOUATT. A NEW EDITION, WITH NUMEROUS ILLUSTRATIONS. TOGETHER WITH A GENERAL HISTORY OF THE HOUSE; A DISSERTATION ON THE AMERICAN TROTTING HORSE; HOW TRAINED AND JOCKEYED. AN ACCOUNT OF HIS REMARKABLE PERFORMANCES; AND AN ESSAl? OCT THE ASS AND THS MULE, BY J. S. SKINNER, Assistant Post-Master-GeneraL and Editor of the Turf Register. This edition of Youatt's well-known and standard work on the Manage- ment, Diseases, and Treatment of the Horse, has already obtained such a wide circulation throughout the country, that the Publishers need say no- thing to attract to it the attention and confidence of all who keep Horses or are interested in their improvement. " In introducing this very neat edition of Youatt's well-known hook, on ' The Horse,' to our readers, it is not necessary, even if we had time, to say anything to convince them of its worth ; it has been highly spoken of, by those most capable of appreciating its merits, and its appearance under the patronage of the 'Society for the Diffusion of Useful Knowledge,' with Lord Brougham at its head, affords a full guaranty for its high character. The book is a very valuable one, and we endorse the recommendation of the editor, that every man who owns the ' hair of a horse,' should have it at his elbow, to be consulted like a family physician,' for mitigating the disorders, and pro- longing the life of the most interesting and useful of all domestic animals.' "—Farmer's Cabinet. " This celebrated work has been completely revised, and much of it almost entirely re-written by its able author, who, from being a practical veterinary surgeon, and withal a great lover and excellent judge of the animal, is particularly well qualified to write the history of the noblest of quadrupeds. Messrs. Lea and Blanchard of Philadelphia have republished the above work, omitting a few of the first pages, and have supplied their place with matter quite as valuable, and perhaps more interesting to the reader in this country ; it being nearly 100 pages of a general history of the horse, a dissertation on the American trotting horse, how trained and jockeyed, an account of his remarkable performances, and an essay on the Ass and Mule, by J. S. Skinner, Esq., Assistant Post- master-General, and late editor of the Turf Register and American Farmer. Mr. Skinner is one of our most pleasing writers, and has been familiar with the subject of the horse from childhood, and we need not add that he has acquitted himself well of the task. He also takes up the import- ant subject, to the American breeder, of the Ass, and the Mule. Tliis he treats at length and con amore. The Philadelphia edition of the Horse is a handsome octavo, with numeroi\s wood-cuts."— American Agriculturist. LEA AND BLANCHARD'S PUBLICATIONS. YOUATT ON THE PIG. THE PIG; A TREATISE ON THE BREEDS, MANAGEMENT, FEEDING, . AND MEDICAL TREATMENT OF SWINE, WITH DIRECTIONS FOR SALTING PORK, AND CURING BACON AND HAMS. BY WILLIAM YOUATT, V.S. Author of " The Horse," " The Dog," " Cattle," " Sheep," das., &c. ILLUSTRATED WITH ENGRAVINGS DRAWN FROM LIFE BY WILLIAM HARVEY. In one handsome duodecimo volume, extra cloth, or in neat paper cover, price 50 cents. This work, on a subject comparatively neglected, must prove of much use to farmers, especially in this country, where the Pig is an animal of more importance than elsewhere. No work has hitherto appeared treating fully of the various breeds of swine, their diseases and cure, breeding, fattening, Sic., and the preparation of bacon, salt pork, hams, dec., while the name of the author of " The Horse," " The Cattle Doctor," Sic, is sufficient authority for all he may state. To render it more accessible to those whom it particularly interests, the publishers have prepared copies in neat illustrated paper covers, suitable for transmission by mail; and which will be sent through the post-office on the receipt of fifty cents, free of postage. CLATER AND YOUATT'S CATTLE DOCTOR. EVERY MAN HIS OWN CATTLE DOCTOR: CONTAINING THE CAUSES, SYMPTOMS AND TREATMENT OP ALL DISEASES INCIDENT TO OXEN, SHEEP AND SWINE; AND A SKETCH OF THE ANATOMY AND PHYSIOLOGY OF NEAT CATTLE. BY FRANCIS CLATER. EDITED, REVISED AND ALMOST RE-WRITTEN, BY WILLIAM YOUATT, AUTHOR OP " THE HORSE." WITH NUMEROUS ADDITIONS, EMBRACING AN ESSAY ON THE USE OF OXEN AND THE IMPROVEMENT LN THE BREED OF SHEEP, BY J. S. SKINNER. WITH NUMEROUS CUTS AND ILLUSTRATIONS. In one 12mo. volume, cloth. " As its title would import, it is a most valuable work, and should be in the hands of every Ame- rican former; and we feel proud in saying, that the value of the work has been greatly enhanced oy the contributions of Mr. Skinner. Clater and Youatt are names treasured by the farming com- munities of Europe as household-gods; nor does that of Skinner deserve to be less esteemed in America,"—American Farmer. CLATER'S FARRIER. EVERY MAN HIS OWN FARRIER: CONTAINING THE CAUSES, SYMPTOMS, AND MOST APPROVED METHODS OF CURB OF THE DISEASES OF HORSES. BT2" FBANCIS CLATER, Author of " Every Man his own Cattle Doctor," AND HIS SON, JOHN CLATER. FIRST AMERICAN FROM THE TWENTY-EIGHTH LONDON EDITION. WITH NOTES AND ADDITIONS, BY J. S. SKINNEL Iii one 12mo. volume, cloth. LEA AND BLANCHARD'S PUBLICATIONS. HAWKER AND PORTER ON SHOOTING. INSTRUCTIONS TO YOUNG SPORTSMEN IN ALL THAT RELATES TO GUNS AND SHOOTING. BY LIEUT. COL. P. HAWKER. FROM THE ENLARGED AND IMPROVED NINTH LONDON EDITION, TO WHICH IS ADDED THE HUNTING AND SHOOTING OF NORTH AMERICA, WITH DESCRIPTIONS OF ANIMALS AND BIRDS, CAREFULLY COLLATED FROM AUTHENTIC SOURCES. BY W. T. PORTER, ESQ,. EDITOR OF THE N. Y. SPIRIT OF THE TIMES. In one large octavo volume, rich extra cloth, with numerous Illustrations. " Here is a book, a hand-book, or rather a text-book—one that contains the whole routine of the science. It is the Primer, the Lexicon, and the Homer. Everything is here, from the minutest portion of a gun-lock, to a dead Buffalo. The sportsman who reads tin's book understanding^, may pass an examination. He will know the science, and may give advice to others. Every sportsman, and sportsmen are plentiful, should own this work. It should be a " vade mecum." He should be examined on its contents, and estimated by his abilities to answer. We have not been without treatises on the art, but hitherto they have not descended into all the minutiae of equipments and qualifications to proceed to the completion. This work supplies deficiencies, and completes the sportsman's library."—U. S. Gazette. "No man in the country that we wot of is so well calculated as our friend of the ' Spirit' for the task he has undertaken, and the result of his labours has been that he has turned out a work which should be in the hands of every man in the land who owns a double-barrelled gun."—N. O. Picayune. " A volume splendidly printed and bound, and embellished with numerous beautiful engravinp, which will doubtless be m great demand. No sportsman, indeed, ought to be without it, while the general reader will find in its pages a fund of curious and useful information."—Richmond Whig. THE BOG, BY WILLIAM YOUATT, Author of " The Horse," Sic. WITH NUMEROUS AND BEAUTIFUL ILLUSTRATIONS. EDITED BY E, J. LEWIS, M.D. &c. &c. In one beautifully printed volume, crown octavo. LIST OF PLATES. Head of Bloodhound—Ancient Greyhounds—The Thibet Dog—The Dingo, or New Holland Dog— The Danish or Dalmatian Dog—The Hare Indian Dog—The Greyhound—The Grecian Greyhound —Blenheims and Cockers—The Water Spaniel—The Poodle—The Alpine Spaniel or Bernardine Dog—The Newfoundland Dog—The Esquimaux Dog—The English Sheep Dog—The Scotch Sheep Dog—The Beagle—The Harrier—The Foxhound—Plan of Goodwood Kennel—The Southern Hound—The Setter—The Pointer—The Bull Dog—The Mastiff—The Terrier—Skeleton of the D0g_Teeth of the Dog at seven different ages. " Mr Youatt's work is invaluable to the student of canine history; it is full of entertaining an J instructive matter for the general reader. To the sportsman it commends itself by the large amount of useful information in reference to his peculiar pursuits wluch it embodies—information which ' he cannot find elsewhere in so convenient and accessible a form, and with so rehable an authority to entitle it to his consideration. The modest preface which Dr. Lewis has made to the American edition of this work scarcely does justice to the additional value he has imparted to it; and the publishers are entitled to great credit for the handsome manner in which they have got it up. — North American. „^______________v^^^^^^^^^^~^^^^^^- THE SPORTSMAN'S LIBRARY, OR HINTS ON HUNTERS, HUNTING, HOUNDS, SHOOTING, GAME, DOGS, GUNS, UJlm* FISHING, COURSING, livelv sketches answer to their title very well. Wherever Nimrod is welcome, there should be cordial -greeting for Harry Hieover. His book is a very clever one, and contains many tastmctive hints, a! well as much light-hearted TeadmS."-Examincr. THE DOG AND THE SPORTSMAN, fa^i?APING THE USES, BREEDING, TRAINING, DISEASES, ETC. OF DOGS AND AN EM ACCOUNT OF TOP DIFFERENT KINDS OF GAME, WITH THEIR HABITS. Also. Hints to Shooters, with various useful Recipes, j f v i ; I BR A R Y OF MEDICINE NATIONAL LIBRARY OF MEDICINE NATIONAL IIBRARY OF ME / > I w>!>a ' » V*SX\X- X ? X. ^•IRARY OF MEDICINE NATIONAL IIBRARY OF MEDICINE NATIONAL IIBRARY OF M TIONAL LIBRARY OF MEDICI IOI1VN 3NI3IQ3W JO ABVaBIl IVNOUVN 3 N I 3 I Q 3 W JO ABVaSM IVNOUVN 3 ir\ i HCINE NATIONAL IIBRARY OF MEDICINE NATIONAL IIBRARY OF MEDICINE N > -l'i,' '1 V;:,'VjK ; ■■•■'!-!>(.•< r?,'rk-:i,» i,. ','A t. \ .f«»iii>!jifi.iiT*lrtinhi^«t '.> !):'•'•