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Edited by Spencer. l2mo.................. 125 BOISE'S Exercises in Greek Prose Composition. i2mo........................ 75 Continued in the end of this volume. -~^^^il «.v*^**^ \V*W\ • ^%vx v.. ^%\N THE HAND-BOOK OF HOUSEHOLD SCIENCE. A New Worhfor Schools and Families, BY EDWARD L. YOUMANS AND ELIZA A. YOUMANS, NOW m PEESS BY D. Appleton & Oo. ----w---- The object of this work is to offer a clear and popular scientific account of the facts, principles, and laws which influence our life, health, and comfort, as dwellers in houses. It will have an immediate practical bearing upon the management of domestic affairs, and the course of domestic life; and is also designed to aid in awakening an intelligent and increasing interest in the place of family concourse. The work is the result of much study, thought, and experiment, and will afford a more entertaining and useful view of this important subject than any other book yet offered to the public. It will embrace several departments, viz: 1. Heat.—Extent of its"influence—its various kinds of movement —its physiological effects—its sources—properties and values of fuel —various modes of producing and diffusing heat. 2. Light.—Properties and motions—supposed nature—source and composition of colors—laws of their harmonious arrangement—how they affect the eye—how they influence each other—artificial light, its various sources—mechanism of tne eye—how it is affected by arti- ficial light—diseases resulting—management of artificial light. 3. Air.—Composition—influence of each of its elements upon man —various sources of its impurity in the dwelling—rate of its contam- ination there—diseases resulting from impure air—its removal- ventilation. 4. Aliment.—Composition and properties of the various alimentary substances—culinary implements—culinary changes of food—its pre- servation—physiological effects of food—its course of digestion—how it contributes to warmth—how it produces strength—its final desti- nation—influence of special aliments—nutritive value of food—the vegetarian question—considerations of diet, 5. Cleansing.—Agents employed for the purpose—their properties and effects—cleansing by mechanical and chemical means—air, water, and various household objects. The Hand-book of Household Science will be copiously illus- trated with new and original designs, and will be adapted to follow the present class-book, and also for universal reading. YOUMANS' CHEMICAL CHART. Published byJ). Appleton & Co., 346 & 348 Broadway, New Tori. New Edition, enlarged and improved. This chart, which is adapted to the Author's Class-Book, accom- plishes for the first time, for chemistry, what maps and charts have long done'for geography, geology, astronomy, &c, by presenting a new and valuable method of illustration. Its plan is to represent chemical composition to the eye by colored diagrams, 60 that the numerous facts of proportion, structure, and relation, which are the most difficult in the science, are presented to the^mind through the medium of vision, and may thus be easily acquired and long retained. The want of such an aid has been long felt by the thoi ghtful teacher, and no other scientific publication that has ever emanated from the American press has met with the universal favor that has been accorded to this chart. It is invaluable as an assistant to public lecturers, to teachers in class-room recitation, and for refer- ence in families. The new edition is five feet by six in size, on beautiful paper, and represents more than a hundred of the most important chemical substances, by means of nearly a thousand dia- grams in sixteen different colors. That it may be Drought within the reach of schools, it is sold at the low price of Five Dollars, being the cheapes1 chart, considering its cost, that is published in the United States. , YOUMANS' ATLAS OF CHEMISTRY. Peice $2. The Atlas employs the same mode of illustration (in book form) as is employed in the " Chemical Chart." The application of the diagrams is here much extended, occupying thirteen plates in six- teen colors, and accompanied by 100 quarto pages of beautifully printed explanatory letter-press. It is a chart in a portable and con- venient form, containing many of the latest views of the science which are not found in the text-books. It is designed as an additional aid to teachers and pupils, to be used in connection with the author's class-book, or as a review, and for individuals who are studying alone. A CLASS-BOQJTfV ••• \ / C \ ' ;/ \\ . ~:*i s ^p^-e »-■-, CHEMISTR T, THE PRINCIPLES OF THE SCIENCE ARE FAMILIARLY EXPLAliTEE AND APPLIED TO THE ARTS, AGRICULTURE, PHYSIOLOGY, DIETETICS, VENTILATION, AND THE MOST IMPOR- TANT PHENOMENA OF NATURE. DESIGNED FOR THE USE OF ACADEMIES AND SCHOOLS" ■JZ^H^ AND FOB POPULAR BEADING. VV^ l * "v/7/SS BY EDWARD L. YOUMANS, \Ov m ^*"•.-*• * AUTHOR OF "A NEW CHABTT OF CHEMIST*Y.* "v!^* V> (,/ ^\ *^^"* / ----- To know That which before us lies in daily life Is the prime wisdom. Miltoh. NEW-YOft^T D. APPLETON ,.<&^c6MPANYi 34 6 & 3| 6 BEO^|TA"Y. Mj.DCOO.LTHI. Entered according to Act of Congress, in the year IB51, By D. APPLETON & CO., ;j» the Clerk's ow* of the District Court of the United States for the Southern Dieq definite, and always the same. If several similar atoms unite, as each is indivisible, they must be multiples of each other {multiple proportions) ; and as one atom may replace another in a compound, their relation must be that of equivalents. This theoiy has been so universally received by chemists, that its terms have become incorpora- ted with the language of the science ; so that to say an atom of iron combines with an atom of oxygen, is as common as to say that a proportion or equivalent of iron combines with an equivalent proportion of oxygen. 33. Of the form or figure of atoms nothing whatever is known. It is therefore no matter in what shape they are represented, as the object is net to indicate their figure, but their relations. 34. If each square upon the Chart is considered to represent Upon what assumed grounds is the atomic theory based ? Do the laws ol combination result from these propositions ? What is said of Jhe reception oi this theory by chemists ? Is any thing known of the form of atoms ? How does the Chart give a clear idea of 'ie atomic theory ? THE ATOMIC THEORY---CRYSTALLIZATION. 37 an atom, we shall then have a clear view of the atomic theory. Single atoms are seen to combine to form compound atoms: thus an atom of water contains two elementary atoms, of silica four, and an atom of gluten eighty-four simple atoms. Until the announcement of the atomic theory, we had no adequate explanation of the uniformity of the proportions of chemical combination, or of the nature of the cause which renders combination in other proportions impossible. 35. Crystallization.—When certain solid substance are dissolved in liquids or melted, so that their particles are free to move among each other, upon the evaporation of the liquid, or the cooling of the melted mass, the atoms arrange them- selves together in certain regular geometrical forms, called crystals. The process by which crystals are formed is called crystallization. Thus, when common salt crystallizes, its at- oms arrange themselves in the form of dice or cubes. Alum assumes the form of a double pyramid placed base to base. 36. Attraction, in causing atoms to cohere so as to form solid masses, seems not to act equally all around each atom, but between certain sides or parts of one atom, and corre- sponding parts of another; so that when allowed to unite ac- cording to their natural tendencies, they always assume a certain definite arrangement. This property of atoms has been called their polarity, because in these circumstances they seem to resemble magnets, which attract each other only by their poles. When the arrangement of its atoms is not crystalline, a body is said to be amorphous. Any change which tends to permit freedom of motion among the atoms of amorphous bodies, favors the reaction of the polar forces, and promotes crystallization. What are crystals? What is crystallization? What form do the crystals ol common salt assume ? What those of alum? What is said of the polarity, of atoms ? In this property, what do they resemble ! What is an amorphous body ? 38 INORGANIC CHEMISTRY. 37. The power with which atoms arrange themselves in the crystalline order is seen in the freezing of water; as the particles assume their new position, the water expands with a force sufficient to burst the strongest iron vessels, or to rend solid rocks. 38. Blows, continued vibration, friction, and variations of temperature produce changes in the molecular arrangement of metals; and it is thought that the axles of railroad-cars, though at first constructed of tough and fibrous wrought- iron, may from these causes acquire that crystalline and brittle structure which they often exhibit upon breaking. Crystals of the salts often contain water, called the water of crystalli- zation. These, when exposed to the air or to heat, part with this water, lose their transparency, turn white, and fall to powder: this is called efflorescence. Others attract water from the air, and this is known as deliquescence. 39. The primitive geometrical forms which crystals assume are divided into six classes or systems, and in each of these classes there is a vast number of secondaiy forms. Thus in carbonate of lime, 680 modifications of crystalline form have been described. As the subject of crystalline forms, to be made interesting, requires full details, we must refer the in- quiring student to the complete treatises upon Mineralogy and Crystalography. 40. When the same body possesses the property of being crystallized in two different systems, it is said to be dimor- phous. Isomorphous bodies are such as have the property What is said of the force with which atoms arrange themselves in the crystalline form ? Give an example. What is said of the effect of blows, friction, and vibration of the axles of rail-cars ? What is efflorescence ? What is deliquescence ? How many primitive geometrical forms do crystals possess ? How many secon- lary forms of carbonate of lime have been enumerated ? What is a dimorphous body ? What aro isomorphous bodies ? CRYSTALLIZATION—ALLOTROFISM. 39 of replacing each other in crystals, without giving rise to new figures. Ten groups of isomorphous bodies have been discovered. 41. Isomeric compounds ire such as contain the same elements, in the same proportions, and yet have different properties. Formerly it was supposed that compounds hav- ing the same chemical constitution must necessarily have the same qualities, but such is now proved not to be the fact. Spirits of turpentine, the oil of lemons, oil of juniper, oil of black pepper, and oil of bergamot, as is seen upon the Chart, contain equal amounts of carbon and hydrogen, yet their properties are very different. Oil of roses and illumi- nating gas are also identical in composition. The difference of properties in isomeric bodies is accounted for by supposing that the atoms or molecules are differently arranged in the different cases, as is represented by the Chart. 42. Allotropism.—Chemists have lately shown that many of the elements may exist under two or more different con- ditions, called allotropic states. In one state they readily exert their usual active properties; in the other they seem passive, and as it were torpid. Thus the diamond is the passive foim of carbon, and it can hardly be made to burn in oxygen gas ; while lamp-black, which is one of its active forms, is so highly combustible that it often takes fire spon- taneously in the open air. It has been suggested that these conditions of the elements are retained when they enter into combination. What are isomeric compounds ? Give examples. How is the difference of pron> wties in these compounds accounted for ? What are allotropic states ? What examples are offered ? 40 INORGANIC CHEMISTRY. THE NOMENCLATURE. 43. The chemical nomenclature is a system of naming, in which the structure of the terms employed expresses the composition of the substances to which they are applied. This nomenclature is the most perfect to be found in any of the sciences. It is very simple, and gives the mind great power over the subject. 44. In the case of simple bodies, the rule is to retain the old established terms; but when a new element is discovered, to give it a name expressive of some leading property. Thus, chlorine takes its name from its greenish color, and iodine from its purple vapor. All the lately discovered metals are distinguished by a common termination, as potassium, sodium, platinum, &c. 45. Compound bodies are of three kinds, acids, bases, and neutral bodies, or those which possess neither acid nor basic properties. Acids are usually known by the following prop- erties : a sour taste, a power of altering vegetable colors. (changing blues to red), and the property of combining with and neutralizing or destroying the properties of the bases or alkalies. 46. A large number of the acids are formed by the union of oxygen with other bodies; they are then named from the element with which the oxygen unites. Thus, sulphur with oxygen gives sulphuric acid, carbon with oxygen gives car- bonic acid, phosphorus with oxygen forms phosphoric acid. Acids in which there is no oxygen are named from both their What is the chemical nomenclature ? What is said of it ? What is the rule in the case of simple bodies ? Give examples. How are compound bodies divided ? What are acids ? How are a large number of the acids formed? How are these named? •xamples. How are acids named which contain no oxygen? Whoa tho NOMENCLATURE. 41 elements: thus, hydrogen and chlorine form hydrochloric acid, hydrogen and. fluorine hydrofluoric acid. When differ- ent acids are formed by the union of the same elements in different proportions, they are distinguished by terminations and prefixes. The termination ic describes the strongest, ous a weaker, and the prefix hypo, which means under, a still weaker acid. Thus nitric acid contains a higher proportion of oxygen than nitrows acid, and this more than Ay^onitrous acid (see Chart). The prefix hyper means more, as per- chloric acid, or more commonly perchloric, which contains more oxygen than chloric acid. 47. Bases are distinguished by their power of combining with and neutralizing acids. They include the alkalies, which have a peculiar acrid taste, as lime, called the alkaline taste; and have also the power of restoring vegetable blues when destroyed by an acid. Besides the alkalies, bases also com- prehend those metallic oxides which do not exhibit these alkaline properties, but yet unite with acids. 48. Most of the bases are formed by the union of oxygen with another element, commonly a metal; as oxygen with iron, termed oxide of iron, oxygen with potassium, oxide of potassium, &c. When oxygen combines with the same ele- ment in different proportions, forming several oxides, its quan- tity is indicated by the use of prefixes. Thus proto indicates one equivalent or the lowest proportion of oxygen; deuto, twJ, and trito, three, equivalents of oxygen. Per is used to express the highest degree of oxidation, and is often applied elements form different acids, how are they distinguished ? What is the meaning of ic, of ous, of hypo, of hyper, or per 1 How are bases distinguished? What bodies are comprehended by the term Bases? ., How are most of the bases formed ? How is the quantity of oxygen m an oxiaa denoted? What does proto indicate? Beutol Trito7 How is per used 1 What are suJoxides ? What are sesouioxidcs 1 42 INORGANIC CHEMISTRY. to the deutoxide and tritoxide. Some oxides, which have such inferior basic properties as not to combine with acids, are termed sw&oxides. jBmoxide is equivalent to deutoxide; and sesquioxides are those in which the oxygen is in the pro- portion of one and a half to one, of the element with which it is combined. (See Chart, Binary Compounds.) 49. The acids and alkalies, although possessing opposite properties, have a powerful attraction for each other, and combine to form salts. By this union the properties of both the acids and bases are completely lost, and a neutral salt is the result. If, however, there is not sufficient base com- pletely to saturate the acid, an acid-salt, or super-salt, results; while if the base is in excess, a basic-salt, or sub-salt, is formed. Salts are named after both their elements, as phosphate of Hme, from phosphoric acid and hme. But as several acids of the same general name may combine with one base, the salts are distinguished by turning the ic of the acid into ate of the salt, and ous into ite: thus nitric acid forms nitrates, nitrous acid nitrites, and hyposulphurous acid hyposulphites. The basic element of a salt is indicated by its usual prefixes; thus, protosulphate of iron is a sulphate of the protoxide of iron. (See Chart.) Salts formed from elements containing oxygen are termed oxygen-acid salts; those containing no oxygen are named haloid salts, from their resemblance to sea-salt— chloride of sodium (291). 50. As oxygen forms oxides, so chlorine forms chlorides, bromine bromides, iodine iodides, fluorine fluorides, sulphur sulphides, phosphorus phosphides, and carbon carbides. The When acids and alkalies unite, what is the result ? What is a nperult? What a mtolt ? How are salts named ? Example ? When several acids of the same general name combine with one base, how are the salts distinguished ? Examples 7 How is the degree of oxidation of the base of a salt represented ? What are oxy gen-acid salts? What are haloid salts? To what compounds are ide and uret attached? THE NOMENCLATURE—SYMBOLS. 43 compounds of these last three substances are known most generally by the termination uret, as sulphuret of iron, car- buretted hydrogen. 51. Chemical Symbols.—-In the case of most organic com- pounds the nomenclature fails, and cannot be made to express composition. Another expedient has been happily resorted to, which meets the difficulty: it is the use of what are known as chemical symbols. For the symbol of an elementary sub- stance we take the first letter of its name; but as several sub- stances may have the same initial letter, to distinguish be- tween them, we either employ the first letter of their Lathi names, or add a second small letter. Thus, C stands for carbon, CI for chlorine; and as P is taken for phosphorus, K, from kalium, the Latin for potash, is taken for potassium. A symbolic letter represents not only an element, but one atom or proportion of that element. Thus, N 0 stands for one atom of nitrogen and one of oxygen, which forms nitrous oxide. If more proportions than one are to be expressed, a small figure is added in the same manner as the powers of roots are expressed arithmetically by exponents. Thus, N Os represents nitric acid, which contains five equivalents of oxy- gen. A large figure placed before a parenthesis indicates that all included within it is to be multiplied; thus, 3(S 03 + HO) represents three atoms of hydrated sulphuric acid. Some writers dispense with the parenthesis. A collection of symbols is called a formula. 52. Equations and Diagrams.—Chemical changes are shown by means of formulae arranged in the manner of an equation. The separation of carbonic acid, and the formation What takes the place of the nomenclature in Organic Chemistry ? What is^cn as the symbol of an element? When two elements have the same initial letter, how do we distinguish between them ? Give some examples. How is the pro- portion of an element expressed? Examples. What are formulae 1 44 INORGANIC CHEMISTRY. of plaster of Paris, when sulphuric is added to carbonate ol hme, is thus represented: Ca 0 C 02 + S 03 = Ca0 SO, 4- C 02. The substances to be changed, carbonate of lime and sulphuric acid, are placed at the left; the products of the change, sulphate of lime and free carbonic acid, are seen at the right. A still better way of illustrating decomposition is by means of fines, such as are shown upon the Chart. By this method the foregoing changes appear as in the above diagram. Here the substances to be changed and the products of change are not only arranged opposite each other, as in the equation, but the character of the change is exhibited more clearly. The plain lines show that one of the products is a sohd, and the dotted line that the other escapes as a gas (16). As there is nothing lost during the change, the equivalents upon each side, if added together, will produce equal amounts. 53. It is very important that the nomenclature and the use of symbols should be well learned; and as the common way of teaching this part of the subject is difficult, tedious, and unattractive, it is desirable that beginners should have the Chart constantly before them while attending to it. Much time and labor will thus be saved, while clear, and therefore the most lasting ideas are acquired. MANIPULATION, OR THE OPERATIONS OF CHEMISTRY. 54. Manipulation means hand-work: it is a term applied to all the practical operations of Chemistry. To become an How are chemical changes shown ? How are the substances arranged ? U said to be a still better way of illustrating chemical changes ? What is chemical manipulation ? Wh»* MANIPULATION. 45 expert manipulator requires great experience, tact, and a high perfection of bodily senses; but many useful operations may be executed with but slight practice and few instru- ments. The object of all chemical investigation is to ascer- tain something unknown in reference to the properties of , bodies, and this is done in various ways. 55. We determine by taste if bodies are sweet, like sugar; sour, like vinegar; bitter, as epsom salts; saline, as common salt; burning, as alcohol; insipid, as water which has just been boiled, or entirely tasteless. The properties of many substances are revealed by the odors they emit. Thus the peculiar smell of burnt feathers, woollen rags, &c, indicates animal substances. C olor is an important property of bodies, and should always be noticed. Some experience is necessary to identify different shades from description; and the pupil will do well to procure slips of paper of a large variety of tints, and paste them in a book with the name of the color opposite each. 56. The property of hardness, which is very important in reference to minerals, is determined in a comparative way, by rubbing or rasping one body against another, and observ- ing which is scratched. Thus talc is scratched by gypsum, and gypsum by calcareous spar. The diamond scratches all bodies and is itself scratched by none. The finger nail also affords a good indication in this way; soapstone and plaster of Paris yield readily to it, while limestone is but slightly affected. 57. Weight is a fundamental property of all bodies; to ascertain it accurately is therefore a matter of great impor- How are tho properties of many bodies easily determined ? What is color? How do wo ascertain tho comparative hardness of bodies? What is said of weight ? Hew is weighing performed ? 46 INORGANIC CHEMISTRY. tance. When we take a piece of wood in one hand, and a piece of lead of the same size in the other, we say that one is heavy and the other light. We mean that they are heavy and fight compared one with the other; these terms, then, always express the comparative weight of equal bulks of different substances. We have standards or units of weight with which all bodies may be compared, as troy weight, apothecaries' weight, &c. Weighing is performed by means of an instrument called the balance or scales. No balance should be used, even for the roughest chemical work, that will not turn with the tenth of a grain. 58. Specific Gravity.—The specific gravity of a body is its weight compared with either water or air. Solids and liquids are usually compared with distilled water, gases with common air. A cubic foot of water weighs about 1000 ounces; a cubic foot of iron weighs 7800 ounces; it is there- fore 7 and ^ times heavier than water, hence we say its specific gravity is 7-8. Gold is 19J times heavier than water; its specific gravity is 19*5. The specific gravity of a solid is obtained by first weighing the body out of the water, and then weighing it suspended in the water, when it will be found to weigh less. The weight in air is divided by the loss in water, and the quotient gives the specific gravity of the substance. The specific gravity of a liquid may be ob- tained by filling with it a bottle which will hold just 1000 grains of pure water, and then weighing it. Such a bottle will hold just 1340 grains of molasses, 1840 grains of oil of vitriol, 13,500 grains of quicksilver, and only 840 grains of alcohol: these numbers, divided by 1000, give the specific gravities of these several substances. What is meant by th3 specific gravity of a body ? What are solids and liauids compared with? Gases? How da we determine the specific gravity of a soUd? How of a liquid ? CHEMICAL OPERATIONS. 47 59. Pulverization, trituration, or comminution is the break- ing or grinding down of hard substances into powder. It is effected usually in a strong vessel termed a mortar, made of Wedgwood's ware, or porcelain, Fig. 1. This operation must be performed upon most solid bodies before they can be dissolved. 60. Solution.—The act of dissolving, by which a solid substance, when placed in a liquid, disappears, leaving the liquid clear, as sugar or common salt in water. A gas may also be said to dissolve in a liquid when it is absorbed by it. The liquid which effects solution is called the solvent. Infusion and digestion consist in steeping or soaking substances in liquids in order to dissolve some portion of them. 61. Precipitation consists in the separation of a dissolved substance from the liquid solvent. Spirits of camphor is a solution of camphor in alcohol. If water be added to it, the camphor separates from the alcohol as a white cloud, which soon settles to the bottom : it is precipitated. The substance separated from the solution is called the precipitate, the sub- stance added the precipitant. 62. Filtering.—The act of straining, by which solid sub- stances (usually precipitates) are separated from liquids. Coarse sand or cloth is sometimes used to form a filter, but most commonly porous or unsized paper (blotting paper). The paper is cut into pieces of a circular form, Fig. 2, and folded over, as the cross lines represent. It then readily assumes the form Fig. 3, when it is placed within a funnel How is trituration performed ? What is meant by solution ? What by infusion and digestion ? What is precipitation ? Give an example. Which is the precipitate 1 Which the precipitant? What is filtering? What substances are used as filters ? J 48 INORGANIC CHEMISTRY. which rests upon a stand,* Fig. 4. The filtered liquid is called the filtrate. Fig. 4. Fig. 2. * ill- ^^ 63. Decantation is the act of gently pouring off a liquid from its sediment, as when a precipitate has settled to the bottom. Mix some chalk and water in a tumbler, let it rest until the chalk is deposited, carefully cant the tumbler over to one side, and you will decant the water. 64. Distillation is the process by which a liquid is evapo- rated in one vessel by heat, the vapor conveyed to another Fig. 5. vessel by means of a tube or otherwise, and there condensed by cold into its original liquid form. Fig. 5 represents the 'For minute directions in experimenting, see "Griffin's Chemical Recreations," or •' Faraday's Manipulations of Chemistry." What is decantation ? What is distillation ? What is dry distillation ? Destructive distillation ? MEASUREMEN1 OF HEAT. 49 retort and receiver which are commonly used for distillation. The object may be either to separate a liquid from substan- ces dissolved in it which will not evaporate; or to separate two liquids which evaporate at different temperatures, as alcohol and water (380). Dry distillation is the distillation of substances without the addition of water. Destructive distillation is the distillation of substances at a high tem- perature, so that their elements are separated and form new combinations. 65. Heat is the great agent made use of by the chemist to produce changes in matter, hence Chemistry has been de- fined as " philosophy by fire." The spirit-lamp is the most convenient means of producing heat, as alcohol when burn- ing produces a very high temperature, but little light and no smoke. In the absence of the common spirit-lamp, the stu- dent may make one by inserting the tin or brass tubes of an oil-lamp through a cork, and fitting the cork tightly to a wide-mouthed vial. A common cotton wick is employed, but when not in use it should be closely capped to prevent evaporation. MEASUREMENT OF HEAT. 66. Variations of temperature are shown by an instrument called a thermometer or heat-measurer. It acts upon the general principle that heat expands all bodies and cold con- tracts them. A narrow tube of glass terminating at its lower extremity in a bulb, filled with colored alcohol, or most commonly with quicksilver, is attached to a frame or case. The bulb being dipped into water in which ice is Wh -■ is tho spirit-lamp the best means of producing hest for the chemist? Wj at !b the principle of the thermometer? How is the freezing point obtained? How tho boilt * point ? 5 50 INORGANIC CHEMISTRY. melting, the position of the mercury is marked, and called the freezing point, or, more properly, the point of melting ice. The bulb is then dipped into boiling water, the mercury ex- pands, and the height to which it rises is marked as the boil- ing point. 67. In the centigrade thermometer, which is used in France, the space upon the scale that intervenes between the freezing and boiling points is marked into 100 equal divisions, called degrees. The zero, or cipher from which we begin to count, is therefore the freezing point, and 100° the boiling point. This is the most natural and perfect scale. Reau- mer's thermometer, used in the east of Europe, has the same space upon the scale divided into 80°; and Fahrenheit's ther- mometer, the one used in this country and England, has the same portion of the scale divided into 180°; but what is very singular, it has the zero, or point at which we commence count- ing, fixed at 32° below the freezing point; so that from zero to the boil- ing point we have 180°+ 32°= 212°. The centigrade thermometer is repre- sented by the letter (C), Reaumer's by (R.), and Fahrenheit's by (F.). The degrees above zero are marked with the sign ( + ), those below with the sign ( — ) : see Fig. 6. The following table exhibits several interesting facts in re- gard to temperature: How are the spaces between those two points divided in different thermome- ters ? Which is the most natural scale ? How are degrees abeve and below thi toro point distinguished ? Fig. 6. C F £&-- 0-- imf- fr- O 5.O.-—t 212 122 MEASUREMENT OF HEAT. 51 Greatest artificial cold measured (Faraday).........—166° F. Greatest natural cold observed by a "verified" ther- mometer (Sabine).............................. 58° Estimated temperature of the planetary spaces (Fourier)...................................... 58° Mercury (quicksilver) freezes...................... 39° A mixture of equal parts of alcohol and water freezes 7° Ice melts........................................+ 82° Greatest density of water......................... 39-8° Mean temperature at the equator.................. 81-5° Heat of human blood............................. 98° Highest natural temperature observed (of a hot wind in Upper Egypt.—Burkhardt)................... 117-3° Alconol boils..................................... 172-94° Water boils...................................... 212° Tin melts........................................ 442° Lead melts...................................... 612° Mercury boils.................................... 660° Red heat (Daniel)................................ 980° Heat of a common fire (Daniel).................... 1141° Brass melts...................................... 1869° Silver melts...................................... 2283° Cast-iron melts................................... 3479° 68. Thermometers should never be suddenly plunged into very cold or very hot water, as the glass is liable to crack; and the indications of thermometers bought at the shops oi instrument-makers ought not to be trusted, unless they are at first carefully compared with some well-known standard instrument. The mercurial thermometer is capable of meas- of sohd bodies. What precautions should be observed in using thermometers ? In buying them ? What is the limit of the indications of the mercurial thermometer? How ar« higher temperatures measured ? 52 INORGANIC CHEMISTRY. OF THE CHEMICAL ELEMENTS, AND THEIR COMPOUNDS. OXYGEN. Symbol 0, equivalent 8. 69. This is the most important of the elements. It is in some way concerned in nearly all chemical changes, and in most of them it takes a very prominent share. As we shall be much in its company in the following pages, it will be well to make its acquaintance first. 70. Properties.—The condition of oxygen is that of a gas; that is, it resembles common air, which is a mixture of sev- eral gases. Some gases when exposed to great cold are brought down to the liquid, and even the solid state (168), and others are condensed into liquids by pressure: but no degree of cold or pressure ever yet applied has been able to overcome or destroy the gaseous properties of oxygen; chem- ical force alone can do this. Oxygen is transparent, coiorless, tasteless, and inodorous, like oommon air; it is about one- tenth heavier than that body, and possesses the same me- chanical properties. It acts neither as an acid nor an al- kali, and is dissolved sparingly by water, 100 gallons ab- sorbing about 4i of the gas. The term oxygen signifies acid-former. It was applied by Lavoisier, who supposed it to be the active principle of all acids, an opinion now known to be false. There is reason to believe that oxygen is capable of existing in two allotropic states (42), a passive or quies- cent state, and an active condition, in which its affinities are What is said of oxygen ? '^2JSZn "I8'' What f°rCe a,°De Can Chaj*e il "»to a liquid r roit1 condition / What aro its Dronertip* 9 What ;„ .u ■ W? Why wasit8onamed?PWhat"0z0r? ° ^^ °f ^ '^ OXYGEN. 53 greatly exalted. The ozone, discovered in the atmosphere by Prof. Schonbein, concerning which much has been said, is supposed to be the active form of oxygen. 71. Preparation.—"We prepare the purest oxygen, and in the readiest way, from chlorate of potash. A portion of this salt is powdered, dried, and mixed with about one-fourth its weight of black oxide of manganese, or oxide of copper, and heated in a flask, retort, or tube, over a spirit-lamp. The gas comes off copiously, and is collected in jars over water. The pneumatic trough, which is used for this purpose, may be any convenient vessel, containing a shelf, and holding suf- ficient water readily to fill a jar placed within it, which is then inverted and put upon the shelf. The water in the trough must cover the mouth of the jar. The gas is deliv- ered by the tube at the open end of the jar, through which it rises, displacing the water, and gradually fill- ing the vessel. This ar- rangement is shown in Fig. 7. The oxide of manganese or copper is not in any way changed ; it acts by catalysis (31), promoting in a very high degree the decomposition of the chlorate. Chlo- rate of potash costs about one dollar per pound, and one ounce will yield about two gallons of the gas. Oxygen may also be prepared by exposing a mixture of bichromate of potash and sulphuric acid, or peroxide of manganese and How is pure oxygen gas best obtained? What is a pneumatic trough ? How is the oxygen collected? How does the manganese act in promoting decompo- sition? 54. INORGANIC CHEMISTRY. sulphuric acid, to heat. When chlorate of potash is used, the decomposition may be thus expressed. 72. Extent of its Diffusion.—Oxygen is by far the most widely diffused of all the elements. It constitutes one-fifth by weight of the atmosphere, eight-ninths of the ocean and all other waters, nearly one-half of the solid rocks that com- pose the crust of the globe,—of every solid substance we see around us, the houses in which we live, the stones and soils upon which we tread, and much more than one-half of the bodies of all living animals and plants. This is shown by the predominance of the red color upon the Chart. 73. The discovery of oxygen was made by Dr. Priestley, in 1774, and it has been justly pronounced "the capital dis- covery of the last century, rivalling in importance the great discovery of gravitation by Newton in the preceding cen- tury." It disclosed the phenomena of nature in an entirely new aspect, exploded the old theories, and laid the founda- tions of modern chemical science. A glance at the Chart shows that oxygen has a very wide range of combination. It unites with all the elements except fluorine, forming com- pounds termed oxides. The act of combination is called oxi- dation ; the separation of oxygen from a compound is termed deoxidation. 74. Oxygen a Sustainer of Combustion.—The leading property of oxygen is the intense energy with which it unites What is said of the diffusion of oxygen? What effect did the discovery of this gas produce upon science ? What striking S^ESLHT ^ a ^^ *"»<»«*—» What is oxidation? combustion? Why are they less intense'when 001^^3^illS OXYGEN. 55 with other substances. So vehement is this action that fire is produced, and hence oxygen is the great supporter of com- bustion. All substances which burn in the air, burn in pure oxygen gas with greatly increased brilliancy. An extinguish- ed candle plunged into it is instantly relighted if the least spark of fire remain upon the wick. Iron wire burns in it with vivid scintillations, and phosphorus with a fight so bril- liant that the eyes cannot endure it. In all these cases the light and heat are produced by the chemical union of the oxygen with the burning body, the weight of which is in- creased exactly in proportion to the amount of oxygen con- sumed. All the common cases of combustion which take place in the air are due to the same cause—the combination of its oxygen with combustible substances. It here proceeds in a more subdued and regulated way, because atmospheric oxygen is diluted with four times its bulk of another gas, which if taken alone extinguishes fire altogether. 75. Illumination.—Two conditions are necessary for illumination: a sufficiently high temperature, and the pres- ence of sohd matter within the heated space. Neither of these conditions alone answers the purpose. The burning of pure oxygen and hydrogen gases together produces intense heat, bat is without sufficient light to be even visible in the daytime; and a fire of charcoal which contains no gas, also yields very little light. But if solid carbon be placed within the oxy-hydrogen flame, a brilliant illumination at once ensues. The elements of oil, tallow, wood, &c, with which oxygen unites in ordinary burning are chiefly hydrogen and carbon; the hydrogen it burns to water (90), and the carbon to car- bonic acid (167), both escaping away into the atmosphere. What two conditions are essential for illumination? What is said of the burn- ing of hydrogen and charcoal ? How can the oxy-hydrogen flame be made to give a brilliant light ? In the ordinary burning of oil, Sec, what takes place ? 56 INORGANIC CHEMISTRY. 76. The affinity of oxygen for hydrogen is superior to its af. finity for carbon. It therefore seizes upon the hydrogen first, where it is present in sufficient quantity, burning it with the production of intense heat. The solid carbon is at the same time set free, and its particles being heated to a luminous whiteness, produce the light which is emitted from the flame. The luminous particles of carbon, floating forward as they are liberated to the surface of the flame, come in contact with atmospheric oxygen, and are there consumed. When the burning body contains both elements, but a disproportionate amount of carbon, as in spirits of turpentine, more of it is set free than can be consumed by the oxygen, and the flame smokes. When the hydrogen is in excess, as with alcohol, there is much heat, but little light, and no smoke; when mingled, these liquids correct each other's defects, and form the basis of " burning mixtures." 77. Structure of Flame.—Common flame is not, as it ap- pears, a solid cone of fire, but a hollow luminous shell, as is shown by holding a piece of metallic wire gauze over the flame of a common lamp, Fig. 8. Fi 8 In the centre there appears a dark space, surrounded by a ring of light. This dark central portion is constant- ly filled with gases, formed from the tallow or oil by heat, in precisely the same manner that they are distilled from coal and resin by the gas-manu- facturer. The inclosed gases generated at b, \rvr 9 c.ln. not^of course, be burned up until they pass to the surfice' of Why is the hydrogen burned first? What produces the iw,*? m. •., flame smoke? When will the light be deficient ? T„L, , I ■ When w,n formed ? uencieut / How are burning mixtures How is common flame shown to be hollow ? WW ia ™„f • .... ^e? Whatissaidoftheargandiamp? "Jn^tS^*"™" OXYGEN. 57 the flame at a, for want of oxygen. In argand lamps the wick is circular and hollow, and a stream of air is admitted to the interior of the flame, which thus has a double burning sur- face. A tall glass chimney is placed over the flame, which secures a strong upward current; and hence an abundant supply of oxygen to tho flame. The conical or pointed form of the flame is caused by the rising currents of heated air. 78. Despritz has shown that the heat evolved in all com- mon cases of combustion, depends upon the quantity of oxygen consumed, and not upon the amount of the combus- tible with which it unites. Thus a pound of oxygen com- bining with hydrogen, charcoal, and alcohol, gives in each case very nearly the same quantity of heat; each raising 29 pounds of water from the freezing to the boiling point. The amount of heat produced by equal weights of different combustibles, combining with oxygen, he found to be as follows: 1 pound of charcoal . . raised from 32° to 212°, 78 lbs. of water. " wood holding 20 pr. ct.) ,, it ? „ of water i " alcohol " "68 " " oilorwax " "90 " " hydrogen . . . . " " 236 " The quantity of oxygen consumed in these cases varies greatly. 79. Oxidation at Low Temperatures.—But the affinity of Upon what does the heat of combustion depend ? What is the example offered ? How much water does 1 lb. of charcoal by union with oxygen raise from the freez- ing to the boiling point ? Of wood holding 20 per cent, of water ? Of alcohol ? Of oil or wax ? Of hydrogen ? Does oxidation take place at low temperatures ? Does oxygen ever combine with bodies without the production of sensible heat ? Is the heat produced the Same, whether the iron is burned in oxygen gas or rusted in the air? 58 INORGANIC CHEMISTRY. oxygen is exerted at low temperatures as well as at high ones its activity never ceases. It exists in a free state throughout the atmosphere which envelops the globe, and is in constant contact with all forms of matter; attacking every thing with which it is not already combined. This slow combustion, though unaccompanied by light, is always attended with heat, although it may not be in sufficint quantity to be meas- ured. An ounce of iron rusted in the air, or burnt in oxyo-en gas, produces exactly the same amount of heat in both cases; the difference being, that in the former instance the heat is developed so slowly as to take years, while in the latter case the same effect is produced in as many minutes. 80. The cause of decay in vegetable and animal substan- ces is the action of oxygen upon the elements of which they consist. They are oxidized, or undergo a slow combustion, called by Liebig eremacausis, which breaks them up into simpler and more permanent compounds. Oxidation is also the grand process by which air, earth, and sea are cleansed and purified from innumerable contaminations. Putrid va- pors and pestilential effluvia are destroyed by a process of burning, more slow, indeed, but as really as if it were done in a furnace. The offensive impurities which constantly pour into rivers, lakes, and oceans are perpetually oxidized by the dissolved gas, and the water is thus kept pure and sweet. This is the reason why waters that have become foul and putrid by absence of air, are sweetened and purified when freely exposed to its action. 81. Relation of Oxygen to Life.—But the most interesting relations of oxygen are to the animal kingdom. It is the universal supporter of respiration; and, as this is a vital pro- cess, it is a supporter of life. The lungs of land animals What is the cause of decay? What is the great cause of purification in air earth, and sea ? How is this process effected ? OXYGEN. 59 (565) and the gills of fish (559) are both adapted to the same purpose—to absorb oxygen ; the one from the air, the other from water. An animal confined in a given bulk of air, having consumed its oxygen, dies. If confined in the same bulk of free oxygen, it fives about thrice as long, and more than ten times as fast. A mouse placed in a jar of oxy- gen breathes very quick, becomes highly excited, and springs about with the greatest activity. But the effect is too power- ful : over-action, fever, and in a short time death, are the result. 82. The chemical action that here takes place is simple oxi- dation, the same that occurs in the open combustion of fuel, except in a less intense degree. The oxygen combines with the elements of the body, oxidizing or burning them, and the products of the combustion pass from the system by the various channels. Its action upon the living system is the same as upon dead matter, purely destructive. It enters the lungs, is absorbed by the blood, and carried to every part where blood-vessels are to be found. Every organ, tissue, muscle, nerve, and membrane is wasted away, burnt to poi- sonous gases and ashes, and thrown from the system as dead and useless matter; and if these constant losses are not repaired by the due supply of food, emaciation ensues. The fat being most combustible, is burnt first; the muscles then soften, shrink, and decay; and lastly, the brain is attacked, delirium results, and life ceases. This is called starvation: it is oxidation, absolute burning to death. 83. Such is the relation of oxygen to all the animal races which inhabit the earth. Its action is essentially and always How is oxygen related to the animal kingdom ? If an animal is confined in a given bulk of air, what results ? If in the same bulk of oxygen gas, what ensues ? Describe the effects of placing a mouse in a jar of oxygen. What Is the nature of the action of oxygen in this case V How does it affect the system ? If food be not taken to repair the waste, what follows ? What, then, il starvation? 60 INORGANIC CHEMISTRY. destructive ; and yet it is the sustainer of life—the mainspring of all vital activity. But if this agent enshrouds the globe, and its office be thus only to burn and destroy, it may be asked why it does not speedily reduce all combustible thino-g to ashes, and the earth to desolation. This question Avill be more properly answered when we come to the chemistry of light and vegetation (337). 84. Oxidation a Source of Mechanical Power.—The chem- ical properties of oxygen are a source of power, which is made use of to produce the greatest mechanical effects. When we say that the affinities of oxygen are energetic, it is meant that, in combining with bodies, it gives rise to vast force. A bushel of coals properly consumed in a steam- engine, produces a power sufficient to raise 70 millions of pounds weight a foot high (J. Herschel). The origin of this prodigious force is the chemical union of almost 200 pounds of oxygen with the carbon of the coal. Oxidation, or the affinity of oxygen for the elements of fuel, is thus the ulti- mate source of all steam power. Electric current* and the force of electro-magnetism are caused by the combination of oxygen with the metals of the galvanic battery; and in pro- portion to the activity of this chemical action is the intensity of the effect. In hke manner, all macular force in animals is produced by the oxidation of carbon and hydrogen within the hving system (582). Every stroke of the piston-every tele- graphic transmission—every motion of the hand-is an exhi- bition of force which began in chemical changes. Cut off the supply of oxygen, and the steam-engine comes to rest, the galvanic battery cease^toaet^ndthe animal dies. Are the chemical properties of oxygen a source ofnnw«r9 n T produced by the combustion of a busheVoGoals' Whl How much power J. force ? What, then, is the ultimate sourct of a.l 1J! ", * °ngin °f ** forces of electricity and electro-magnetism owmg Tcf™Z?- T° Wh* are the »>ao duo? Remove the oxygen, and what follows? " m"8CUlar *™ HYDROGEN. 61 HYDROGEN. Symbol H, equivalent 1. 85. Properties.—Hydrogen is a transparent, tasteless gas, the lightest of all known substances, having about Jjth the weight of common air. When pure it is devoid of smell, al- though, as commonly prepared, it contains impurities, which give to it a disagreeable odor. Hydrogen is never found free in nature, but exists in water, constituting ith of its weight. It is an essential constituent of all organized substances, vege- table and animal, and is abundantly supplied to plants in water, which they possess the power of decomposing. From its extreme lightness, hydrogen is better fitted than any other substance to inflate balloons, though for this purpose coal- gas, from its greater cheapness, is generally used. 86. Preparation.—It is best prepared by the action of dilute sulphuric acid upon bits of zinc. These are placed in a bottle, Fig. 10, to which a cork is Fig. 10. tightly fitted. The cork has two tubes inserted. The one for admitting the acid dips beneath the water; the other leads to a pneumatic trough, where the gas is collected in tumblers or jars, in the same manner as oxygen (71). In this case the zinc decomposes the water, and unites with its oxygen, while the hydrogen is set free and escapes. The sulphuric acid dissolves the oxide of zinc as fast as it is formed—thus main- taining a clear metallic surface con- What are the properties of hydrogen ? Where is it found ? How is it best prepared ? State the changes that take place. How can it b« tbtained from steam ? How does water applied to the forge-fire increase the heat J 6 62 INORGANIC CHEMISTRY. HO\ ZoAZnO SOs----------^-ZnOSOa tinually in contact with the water. The diagram exhibits these changes. The portions first collect- ed are not to be used, as when mixed with air, hydrogen gas is always explo- sive. Hydrogen is also obtained by passing vapor of water (steam) through a red-hot gun-barrel, when the oxygen unites with the iron, and the hydrogen is set free. In the same manner, when a blacksmith sprinkles water upon his forge- fire, the red-hot coals decompose it, forming carbonic acid with its oxygen, while the liberated hydrogen burns with the production of increased heat (88). 87. From its extreme tenuity, hydrogen passes through crevices and pores with greater facility than any other sub- stance. Dr. Faraday, in his attempts to liquefy it by pres- sure, found that it would leak and escape through apertures that were quite tight to other gases; its atoms must therefore be comparatively much smaller. A bell rung in hydrogen is scarcely audible, and when breathed (which, without pre- caution, is a dangerous experiment) the voice becomes re- markably shrill. Although a gas, and the lightest of all bodies, hydrogen is inferred, from its chemical relationships, to be a metal. Its gaseous form is no objection to this idea, as metallic mercury takes the form of invisible vapor at com- mon temperatures, and other metals may be vaporized by heat. 88. A burning body plunged into hydrogen is extin- guished ; it is, therefore, a non-supporter of combustion; but, in contact with oxygen, it burns, emits a feeble blue h>ht, and produces an intense degree of heat. The oxy-hydrogen What was the result of Dr. Faradav's nffpm«*0 *~ v <• t , disprove? Whyishydrogen'Sf^ ^-'-PPortcombustion? What issaidoftheoxy-hydrogen blow-pipe? Ho. HYDROGEN. 63 blow-pipe is a contrivance for mingling a continuous stream of these gases in an inflamed jet; the light produced by this flame is faint, but the heat is very great. Substances that do not fuse in the hottest blast-furnaces melt in this heat like wax. A small bit of lime of the size of a pea placed within the oxy-hydrogen jet glows with extraordinary intensity (75), producing what is called the Drummond light. This is the light made use of, as a substitute for the sun's rays, in the solar microscope; it is also employed in coast surveys fov night-signals. In one case the light emitted by the ball o lime was distinctly visible at a distance of 96 miles (D. B. Reid). The heating power of the oxy-hydrogen flame is ac- counted for by the fact that it is solid, and not hollow like ordinary flame (77), and also that a larger amount of oxygen is condensed by union with hydrogen than with any other element (78). 89. Soap-bubbles blown with hydrogen rise in the air, and may be set on fire with a candle. With a mixture of three parts air and one of hydrogen, when fired, they explode with a loud report; if two parts of hydrogen is mixed with one of pure oxygen, the explosion is very violent and deafening. 90. The term hydrogen signifies water-former. If a jet of Hydrogen be set fire to, and a cold dry tumbler be held over the flame, the inside of the glass will be instantly covered with a film of dew, which rapidly increases, and at last con- denses into drops of water. In all cases where hydrogen is burned with oxygen, water is the product. lathe Drummond light produced? For what is it used? How far has it beon »eea ? How is the heating power of the oxy-hydrogen flame accounted for ? In what condition does hydrogen explode? What is the meaning of the term hydrogen ? Describe the experiment with tho lumblor. 6'4 INORGANIC CHEMISTRY. OXYGEN AND HYDROGEN—WATER. HO =9 91. Properties.—This substance, though familiar to all possesses very remarkable properties, and should be care- fully studied. Water is composed of the tvro gases, oxy- gen and hydrogen, in the proportion by weight of 8 parts oxygen to one part hydrogen; or by measure, 1 part oxygen to 2 of hydrogen. When pure, it is a tasteless, inodorous liquid ; colorless in small quantities, but in large quantities of a splendid ultramarine blue, as when it forms lakes from the melting of Alpine glaciers, and as seen by Parry in the polar regions. It is the most abundant and widely diffused of all chemical compounds. It readily as- sumes either the solid, liquid, or vaporous state; and with equal facility becomes sweet, sour, salt, astringent, bitter, nauseous, or poisonous, as the substances which it dissolves possess any of these properties. The importance of water, both in the laboratory of the chemist and of Nature, is due to this universal solvent power. 92. Hydrates.—Water unites with acids and bases, form- ing a class of compounds called hydrates. These combina- tions are often attended with heat; water combining with lime develops sufficient heat to ignite wood. Ships at sea have been fired by the accidental wetting of lime in their holds. This heat is caused by the passage of the water from a liquid to a solid state. 93. The Water-Atmosphere.—All natural water contains dissolved a certain amount of various gases, which may be expelled by boiling. It thenjia^ninsipid, disagreeable Why should water be carefully studied ? Of what is it composed? In whal PTt10D8lfhatiSitSC°,0r? Whati^ of its solvent power? How ifirifedf w, T^1 ^Tl°f the heatr'oduce4 by these combinations? How is it caused ? U hat is said to be dissolved in all natural waters ? What !• WATER. 65 taste; but upon being exposed to the air a sufficient length of time, the gases are redissolved, and the water regains its palatable flavor. Oxygen gas is thus absorbed to the ex- tent of about four per cent., and the respiratory apparatus of fish (branchea, or gills) is so arranged (559) that a cur- rent of water is constantly flowing in contact with a network of delicate vascular membranes, by which the gas is im- bibed : hence, strictly speaking, aquatic as well as land ani- mals breathe air. On the summits of high mountains, where the air is rarer and more attenuated, less oxygen is absorbed, and hence the lakes in the mountainous valleys of Switzer- land and the Andes are destitute of fish.—(Brande.) 94. A small quantity of air dissolved in water greatly diminishes its power of dissolving other gases. If water, already saturated with one gas, be exposed to another, the second is absorbed only in proportion as the first escapes. The proportion of different gases taken up by pure water is very variable. Of ammonia it absorbs 780 times its bulk, of hydrochloric acid gas 480, and of carbonic acid an amount only equal to its own volume. Of olefiant gas it dissolves 12-5 per cent., and of nitrogen and hydrogen but 1-6 per cent, of its volume. 95. Constituents of Common Water.—Water which has fallen from the clouds as rain, in the country, away from cities and large towns, is the purest we meet with, being contaminated only with the gases which exist in air. But when filtering through the soil and crevices of the rocky strata, it dissolves various earthy salts, which, in many cases, modify its properties very much. River and creek the effect of boiling ? How much oxygen gas does water contain ? Do fish breathe this gas? Why are lakes on high mountains destitute of fish? When water con- tains one gas and absorbs another, what takes place ? What is the purest water ? How does it become impure ?. What water contains most of these salts? 6* C6 INORGANIC CHEMISTRY. waters usually contain the least of these salts, spring anrj well water more, and sea-water and mineral waters tho largest quantity. 90. Hard Water.—Water derives its quality of hardness from the presence of these substances, chiefly salts of lima (the carbonate and sulphate). A single grain of sulphate of lime will convert 2000 grains of soft into hard water. When common soap is put into hard water, instead of dissolv- ing in it as it does in soft water, it curdles, or is decomposed, and a new soap is formed, which contains lime instead of pot- ash or soda. This new soap will not dissolve, and may often be seen upon the surface in the form of a greasy scum. It adheres to whatever is washed in it, and gives that unpleasant sensation called hardness when we wash our hands. To test this quality of water, dissolve a little soap in alcohol, and place a few drops of it in the water which it is wished to examine. If it remains clear, the water is perfectly soft; if it becomes muddy or opaque, the water is ranked as hard. 97. Hard Water for Kitchen Use.—Hard water is a much less perfect solvent than soft water; that is, being already partially saturated, it dissolves additional substances but im- perfectly. It is therefore inferior to it for all domestic uses, as tea and coffee making, where solution is to be effected. 98. Its Effects as a Drink.—The use of hard water as a drink is unfavorable in dyspeptic affections.—(Pereira.) The bad effects of hard water upon the animal system are also seen in the horse. " Hard water drawn fresh from the well will assuredly make the coat of a horse unaccustomed to it stare, and it will not unfrequently gripe and otherwise in- jure him."—{Touatt.) To what does water owe its hardness ? What is the effect when soap is put into hard water ? How may we test this quality ? Why is hard water inferior to soft for domestic purposes? WATER. 67 99. Sea- Water.—The solid constituents of sea-water amount to about 3£ per cent, of its weight, or nearly half an ounce to the pound. Its saltness may be considered as a necessary result of the present order of things. Rivers which are constantly flowing into the ocean contain salts varying in amount from 10 to 50 and even 100 grains per gallon. They are chiefly common salt, sulphate and car- bonate of lime, magnesia, soda, potasji, and iron; and these are found to be the main constituents of sea-water. The water which evaporates from the sea is nearly pure, con- taining but very minute traces of salts. Falling as rain upon the land it washes the soil, percolates through the rocky layers, and becomes charged with saline substances which are borne seaward by the returning currents. The ocean, therefore, is the great depository of every thing that water can dissolve and carry down from the surface of the continents ; and as there is no channel for their escape, they of course constantly accumulate. 100. The continuance of this process for numberless ages must inevitably have produced a highly saline condition of the ocean. " The case of the sea is but a magnified repre- sentation of what occurs in every lake into which rivers flow, but from which there is no outlet except by evaporation. Such a lake is invariably a salt lake. It is impossible that it can be otherwise ; and it is curious to observe that this condition disappears when an artificial outlet is produced for the waters."—{Fownes.) 101. The waters of the Dead Sea are much more salt than those of the ocean. It is situated at the bottom of an What proportion of solid matter is contained in sea-water ? From whence is it derived? What are these salts chiefly? Why do these salts accumulate in the sea? What is the condition of lakes that have no outlet but by evaporation? What is the effect of creating an artificial outlet ? What is said of the Dead Soa ? 68 INORGANIC CHEMISTRY. immense basm or valley several hundred feet lower than the Mediterranean Sea, and has no outlet. The streams of water which flow into it do not raise its level, in consequence of excessive evaporation. Its condition is well described by a recent traveller. "When bathing in its waters I floated upon the surface like a log of wood, without stirring hand or foot. With much exertion I could dive sufficiently deep to cover all my body, when I was thrown out again to the surface, in spite of all my efforts to descend lower. On coming out of the water, I found my body covered ovei with an incrustation of salt the thickness of a sixpence." 102. Mineral Waters.—These are such as contain saline substances in the largest proportion. Those which abound in the salts of iron (carbonates and sulphates of iron) are called chalybeate or ferruginous waters. If the waters are brisk and sparkling, carbonic acid gas is present, and they are called carbonated or acidulous waters. If the active in- gredient be sulphur, the spring is termed sulphurous. If the odor of decayed eggs, or the scourings of a foul gun- barrel is exhaled, the waters are charged with sulphuretted hydrogen. The water of the celebrated Congress Spring, at Saratoga, contains, according to Allen's analysis, the fol- lowing ingredients in a gallon : Chloride of sodium......................... Hydriodate of soda and bromide of potassium Carbonate of soda......................... Carbonate of magnesia.................. Carbonate of lime......................... Carbonate of iron..................... Bilex and alumina..................... Total solid contents........... What are chalybeate waters? What are acidulous ? What sulphurous? What *re the main constituents of Congress water? 390,246 grs. 6,000 " 9,213 " 100,941 " 103,416 " 1,000 " 1,036 " 611,852 grs. WATER. 69 Carbonic acid......................................386,188 gre. Atmospheric air................................... 3,261 Total gaseous contents.................389,449 grs. 103. Organic Impurities in Water.—All natural waters, even those which fall from the clouds according to Liebig, contain traces of decomposing organic matters in variable quantity. To this they owe the quality of becoming putrid when kept. In many cases, it is present in such quantity as to injure health, derange the bowels, and often produce vio- tent dysentery. Stagnant waters, abounding in putrescent Aiatter, 2ontain numberless minute animals {animalcula), which are sometimes exhibited by means of the solar micro- scope ; they are not found in the waters commonly used for drink. 104. Purification of Water.—The best method of purify- ing water is by distillation (64). This is effected by passing the steam from one vessel into another, which, being kept cool, condenses it: to render it perfectly pure, it must be redistilled at a low temperature in silver vessels. By filtra- tion through sand, or other closely porous media, water may be deprived of suspended impurities, and of all living beings. Boiling kills all animals and vegetables, expels the gases, and precipitates carbonate of lime, which constitutes the fur or crust often seen lining tea-kettles and boilers. Alum (two or three grains to the quart) cleanses turbid or muddy water. The alum is decomposed by carbonate of lime, and the alu- mina set free, carries down the impurities mechanically; but the sulphuric acid of the alum, combining with the lime, forms sulphate of lime, and makes the water harder than What is said of the organic matters contained in water ? Does comm.cn drinking water contain animalcula? How is water best purified ? What is the effect of filtration ? Of li oiling ? Of alum? Of the alkalies potash and soda' 70 INORGANIC CHEMISTRY. before. The alkalies, potash or soda, soften water. They decompose and precipitate the earthy salts, leaving in solu- tion an alkaline salt, which does not harden it. 105. Effect of Leaden Vessels upon Water.—Water some- times becomes poisonous by contact with lead, as when lead pipes, cisterns, roofs, gutters, &c, are used. The purer the water, the more liable it is to become impregnated with lead, as the presence of earthy salts in solution exerts a protecting influence. Spring and well waters are, therefore, less liable to this contamination than rain-water, which is purer. Water which tarnishes polished lead, when left at rest upon it in a glass vessel for a few hours, or which contains less than about FoS ota its weight of salts in solution, cannot be safely trans- mitted through lead pipes without certain precautions. The best remedy, where there is danger, is to leave the pipes full of water at rest for three or four months, or to substitute for the water a weak solution of phosphate of soda.—( Christison.) 106. Necessity of Water to Organized Beings.—To the or- ganic kingdom water is an agent of the first necessity, as its abundance and scarcity regulate the distribution of animals and plants over the globe. Its properties seem to mark out the plan of animated nature. From the highest animal, to the meanest vegetable that can grow on a bare rock, this ingredient is absolutely required. It is an essential constit- uent of all parts of living bodies, forming upwards of one- half the weight of all newly gathered vegetable substances cultivated by man. FTnwP, 7? • Cr m°St Uab'e '° beCome P°isoned by intact with lead! How can we determine whether lead will be acted on by water? What is the best remedy where there is danger ? Y What is said of the importance of water to the organic kingdom ? In what two states does water exist in organic bodies ? *^Z*Z°mZtZTintheBrowflIofplants? Whatisthe*«»««-- WATER. 71 107. Water exists in most organized bodies in two separate Btates. In one it may be regarded as an essential portion of the substance, as of sugar or starch in their dryest state (349), from which it cannot be separated without breaking up the compound. In the other state, it is associated with bodies so loosely that it may be removed by drying. The quantity that may be thus separated from various articles of diet, without injury to the compound, is as follows: Wheat 14-5 per cent., rye 16-6, oats 20-8, barley 13-2, Indian corn 18, peas 16, beans 14*11, potatoes 75'9, turnips 92*5, carrots 87*6, beet-root 87*8, white cabbage 92*3, blood 80, muscle of beef 74, of veal 75, of mutton 71, of pork 76, of chicken 73, trout 80*5 per cent.—(Pereira.) 108. Both gases and the mineral elements of soils enter the roots of plants dissolved in water. As sap, this watei circulates through the various organs, carrying and deposit- ing the newly formed substances, yielding up its own ele- ments, and ministering perpetually to the growth of the plant. 109. In animal systems the use of water is equally im- portant (495). It is the natural drink of all adults, being the liquid employed in the body to dissolve and distribute the food. Eighty per cent, of the blood (Liebig) and seventy-four per cent, of flesh (Brande) consist of water; while, to repair the constant waste and loss from the system, an adult man requires about three-fourths of a ton per year {Draper). The softness, pliancy, and symmetrical fulness of the animal body, is produced by the liquids of which it is chiefly composed. The tendency of flesh or fresh meat to putrefaction, is" caused by the large quantity of watery How much does a man consume annually? What gives symmetry and fulness lo tho animal form? How does water cause putrefaction in flesh? How U it chcckod ? 72 INORGANIC CHEMISTRY. juices it contains. As solution favors chemical action (29), putrefactive changes readily set in; but are checked if the flesh be dried, as is often done for the preservation of meats. 110. Under ordinary circumstances, water freezes at 32°, and boils at 212°; it retains its liquid condition, therefore, through a range of 180°; and, as in this state only it can exist in animals and plants, these limits mark the thermal conditions upon which living beings can continue on the earth. 111. A cubic inch of water forms very nearly a cubic foot of steam. Water occupies the smallest space, or is most dense at 39-83° F.; if its temperature varies from this point, in either direction, it expands in bulk; this is called the point of maximum density of water. In freezing, water expands very much, and exerts so great a force as to burst the strongest vessels in which it is contained. It is thus that the surface of the hardest rocks is crumbled down into soil fit for the support o'f vegetable life; the water, per- colating into minute crevices and fissures in summer, freezes in winter, and expands with a force which breaks the solid stone. 112. Snow does not quench thirst, but rather increases it; and the natives of the arctic regions " prefer enduring the utmost extremity of this feeling, rather than attempt to remove it by the eating of snow."—(Capt. Ross.) 113. The specific gravity of ice is 0-92 (Silliman); it therefore floats upon the surface of water. If it sank as fast as it is formed, whole bodies of water would be con- n™"1 7^! Ii?itf.,d°eS Wat6r maiDtain Us humidUy ? What relation has this property of water to life ? ieiTVT °f7ater fTS h°W mUCU Steam ? At What temperature is it most Hnw 1 ti! fP?d m fiee2iDg? At what temperature is it most dense ? How does this property of water affect rocks ? ■ What is the specific gravity of ice ? If it were heavier than water, what wouM NITROGEN. 73 verted into solid ice. During freezing the substances dis- solved in water are expelled, hence the ice of sea-water (as is well known to sailors), when melted, forms fresh water. Water from melted snow, for the same reason, contains no air or gas; hence fish cannot live in it (Pereira). One impe- rial gallon of water weighs 70,000 grains, or just ten pounds. The American standard gallon holds 58,372 American Troy grains of pure distilled water, at the maximum density. One cubic inch weighs 252*458 grains, which is 815 times as much as an equal bulk of atmospheric air (Silliman). A cubic foot of water weighs veiy nearly 1000 ounces avoir- dupois (998'2 oz. Brande). DEUTOXIDE OP HYDROGEN. H 02 = 17. 114. This curious compound is formed by chemists, with difficulty, by adding to water another equivalent of oxygen. It is a syrupy liquid, of a disagreeable odor, a nauseous, bitter, astringent taste, and is not frozen by intense cold. It is easily decomposed, often with an explosion, and sometimes with a flash of light. As yet, it is of no use. NITROGEN {Azote) Symbol N, equivalent 14 115. Properties and Sources.—Nitrogen is a perma- nently elastic gas, destitute of either taste, smell, or color; Blightly lighter than the air, and remarkable for its negative be the result? What is said of the ice of sea-water ? Of water from melted snow ? What is the weight of a gallon of water? Of a cubic inch ? A cubic foot? What is the composition of deutoxide of hydrogen ? Its properties ? U«es ? 7 74 INORGANIC CHEMISTRY. properties, entering reluctantly into union, and, from its proneness to escape, forming very unstable compounds. It supports neither combustion nor respiration; a lighted taper introduced into it is instantly quenched, and animals placed within it immediately die. It Fi„ ,, has from the latter circumstance been called azote (life-destroyer). The term nitrogen refers to its origin from nitre. It constitutes nearly four-fifths of the air (see Chart). It is best obtained by burning phosphorus in a confined portion of air over water (Fig. 11); the phosphorus takes the oxygen forming phos- phoric acid, which is soon removed by the water, and nitrogen is left. The accompanying diagram illustrates the change. 116. Nitrogen is not found in any of the mineral forma- tions of the earth's crust, except in some varieties of coal which are of vegetable origin. It is an important element of the vegetable kingdom, to which it is probably supplied by ammonia and nitric acid, which contain it, and exert a very favorable effect upon plants (123). It exists in the tissues or muscle of the animal body to the amount of 17 per cent. Whether plants derive their nitrogen directly from the air through their leaves, or dissolved in water through their roots, and whether the animal system Las the power of using or assimilating it when absorbed from the air by the lungs, are questions not yet settled by chemists. rhat are the properties of nitrogen ? Why has it been called azote ? Whal the origin of its present name ? How is it best obtained ? it found in minerals ? How is it supplied to vegetables ? PROTOXIDE OF NITROGEN. 75 OXYGEN AND NITROGEN.—NITROUS OXIDE. {Protoxide of Nitrogen, Laughing Gas, Exhilarating Gas.) NO = 22. 117. Properties and Preparation.—Oxygen combines with nitrogen to form a series of five compounds (see Chart, Binary Compounds), remarkable as illustrating in a perfect manner the law of multiple combination (21). The first in the series is protoxide of nitrogen or nitrous oxide, called also, from its peculiar effects when inspired, laughing gas, or exhilarating gas. It is prepared from nitrate of ammonia, by heating it in a flask, at a moderately low temperature. The gas escapes through a tube, and is collected in jars, over water in the pneumatic trough. Four ounces of the salt produce one cubic foot of the gas. It should be al- lowed to stand for some time over water, to absorb any nitrous acid that may happen to be formed. The change that takes place is shown in the diagram^one atom of ni- trate of ammonia yield- ing two atoms of pro- toxide of nitrogen and three of water. Pro- toxide of nitrogen is a colorless, transparent gas, of a sweetish taste, and very solu- ble in water; cold water taking up about three-fourths of its volume of the gas. Its specific gravity is 1-52 ; it sup- ports combustion actively, and may be condensed into a liquid by a pressure equal to fifty atmospheres. • 118. Physiological Effects.—The effect of nitrous oxide upon the system, when taken into the lungs, is peculiar, and For what is the nitrogen group of compounds remarkable ? What is the first 9t these? How is it obtained? Explain the changes. What are its properties ? HVN • NOa...........---~- r.-,2 N O ;^.-:^3!; o 76 INORGANIC CHEMISTRY. very remarkable. The best method of breathing it is to use a bladder which has been softened in water, or an India- rubber bag filled from the pneumatic trough. A wooden mouth-piece attached to the bladder is placed between the teeth (Fig. 12), the nostrils are closed Fig. 12i by the fore-finger and thumb, and the gas inhaled as in common breath- ing. Its effects are different upon different constitutions: on some it produces symptoms of stupor, which last for a few seconds. Some fall senseless, but recover with confused ideas and headache. The pugnacity of some is excited ; all articles which are lia- ble to injury from the violence of the inhaler should there- fore be removed. But the most are affected with pleasura- ble sensations—they laugh and skip about as if intoxicated, " A feverish glow overspreads the system, a thousand de- lightful visions pass before the mind, the man lives a year in a minute, and* that year is in the seventh heavens." 119. The celebrated Mr. Wedgwood, "after breathing the gas for some time, threw the bag from him, and kept breathing on laboriously with an open mouth, holding his nose with his fingers, without power to remove them, although aware of the ludicrousness of his situation; he had a violent inclination to jump over the chairs and tables, and seemed so light that he thought he was going to fly." 120. Mode in which Nitrous Oxide acts upon the Sys- tem.—" These effects are undoubtedly due to the oxidizing Does it produce peculiar effects upon the system? What is the best method ol breathing it ? What effect does it produce upon different constitutions 1 What does Mr. Wedgwood say of its effects upon himself? To what are these effects owing? Why is it moro active when breathed than •xygen ? NITRIC ACID. 77 action which the protoxide establishes in the system. In this respect it is far more active than even pure oxygen gas, and the reason is obvious: oxygen is but slightly absorbed by watery fluids, but this gas is taken up by them to a very great extent. When it is introduced into the lungs it is rapidly dissolved in the blood, and carried by the circulation to every part of the body, oxidizing whatever is in its path, producing a febrile warmth and an unusual mental disturb- ance.' '—(Draper) 121. Deutoxide of nitrogen, N02, hyponitrous acid, N03, and nitrous acid, N04, are compounds of no general mterest, except as illustrating the laws of chemical union; I therefore omit them. NITRIC ACID (Azotic Acid, Aqua Forth). NOs = 54. 122. Preparation and Uses.—This is the most important of the chemical compounds of oxygen and nitrogen. It is prepared by distilling equal weights of sulphuric acid and nitrate of potash; when on a large scale, retorts of iron or stone-ware are used. The reactions are seen in the diagram. Pure nitric acid is a colorless liquid, of sp. gr. 1-521. It smokes when exposed to the air, and is partially decomposed by the action of light, nitrous acid being formed, which gives it a yellow or orange color. It has an intensely acid taste, and reddens vegetable blues. It stains the skin and nails, and many other animal substances, of a permanent yellow color; How is nitric acid prepared ? Explain the reactions which take place. Whal are its properties ? What its chief uses? Why does it rust the metals so power- fully? 7* KONOs-----^v-HONOs 2ffo S03-_^KOH02SOs 78 INORGANIC CHEMISTRY. and is hence used to produce yellow patterns upon colored woollen fabrics. It is used for etching on copper, for assay- ing or testing metals, and as a solvent for tin by dyers and calico-printers. It is also used in medicine, as a caustic, to cleanse and purify foul ulcers. In consequence of its large proportion of oxygen, it con-odes or rusts the metals with great energy, and hence is the most powerful of oxidizing agents. 123. Nitric acid occurs, in small quantity in rain-water, especially after thunder-storms, and is hence supposed by some to be produced in the air by lightning, which com- bines the gaseous nitrogen and oxygen ; others suppose it to be produced by the oxidation of ammonia in the air. It is found in nature in combination with the alkalies and earths, in the soil of various localities. Combined with potash or soda, nitric acid is a very valuable fertilizer. Applied to young grass, or to the sprouting shoots of grain, it hastens and increases their growth. It also occasions a larger produce of grain, and this grain, as when ammonia is employed, is richer in gluten, and more nutritious in its quality.—(John- stoti.) 124. Aqua Regia.—A mixture of nitric and muriatic acids is called aqua regia, or royal water, because it alone is capa- ble of dissolving the royal or noble metals, as they are termed, gold, platinum, &c. The explosive preparation contained in percussion caps (fulminating mercury) is formed by dissolv- ing mercury in nitric acid and adding alcohol. From what source is it thought to be furnished to rain-water ? What is said ol its use in agriculture ? What is aqua regia ? Whence does it derive its name ? How is the explosirt ""■teparation of percussion caps formed ? AMMONIA. 79 NITROGEN AND HYDROGEN—AMMONIA (Volatile Alkali). H3N=17. 125. Properties and Preparation.—Ammonia is a gas formed by the union of nitrogen and hydrogen. It is colorless, irrespirable, of a pungent, caustic taste, lighter than the air, sp. gr. 0-59, and possesses strong alkaline properties; neutralizing acids, and changing vegetable yellows to brown. Being a gas, it is called volatile alkali, to distinguish it from those that are fixed or solid. It is obtained by heating in a flask equal quantities of slaked lime and muriate of ammonia; and as it is lighter than the air, it may be collected, by what is termed the method of dis- placement, in an inverted vessel (Fig. 13). As the gas accumulates in the upper portion of the inverted jar it displaces the air, expelling it downwards. The decom- position is shown in the di- agram. The great source of ammonia in commerce is the liquor of the gas- works. Ammonia has a strong affinity for water, which absorbs 780 times its bulk of the gas. This solution is called aqua ammonia, and is the common form in which it is sold and used. 126. Uses.—Ammonia is used medicinally in various ways. It is administered internally as a powerful stim- ulant, and applied externally as a counter-irritant, and for blistering the skin. It is mixed with olive oil (1 part ammo- What is ammonia? What are its properties? How is it obtained? By what method is it collected ? What Is its chief commercial source ? What proportion of ammonia does water absorb ? What are its uses in medicine? •HsN CaC12HO 80 INORGANIC CHEMISTRY. nia to 2 of oil), and applied externally in sore throat, undei the name of volatile liniment. It is apphed to the nostrils to recover from fainting, and, if procured in time, is the best antidote to prussic acid. Aqua ammonia, in large doses, is poisonous ; the readiest remedy is vinegar. 127. Ammonia is one of the most active elements of ma- nure ; it is produced by the putrefaction of all organic sub- stances containing nitrogen, and as it is highly volatile, it con- stantly tends to escape into the ah, where it is lost. The fluid excretions of animals evolve it in large quantities: if these are collected in tanks, and sulphuric acid added, fixed sulphate of ammonia is formed in the liquid, and all the am- monia is thus saved for farm use. Sulphate of lime (plaster) and sulphate of iron (green vitriol) also serve to fix ammonia. Those circumstances of decomposition which give rise to am- monia, produce at the same time carbonic acid, which unites with it, forming carbonate of ammonia. It is in this form that it exists in the atmosphere. The application of ammo- nia increases the luxuriance of vegetation. It enters the roote of plants dissolved in water, and, according to Liebig, is ab- sorbed by their leaves from the air. THE ATMOSPHERE. 128. Its Composition.—The atmosphere is the thin, trans- parent, elastic medium which surrounds the globe, extend- ing above its surface to the height of about forty-five miles. It was supposed by the ancients to be a simple body, the different properties which it manifested being caused by ex- What is said of its use in agriculture ? Does it naturally tend to waste ? How may it be saved ? In what form does it exist in the atmosphere? What are its effects upon plants ? What is the atmosphere ? How high does it extend ? Of what does it consist' In what proportions? THE ATMOSPHERE. 81 halations fiom the ground ; and this opinion prevailed until within about a century. The air is now known to be a compound, consisting, by bulk, of 79 per cent, of nitrogen, and 21 per cent, of oxygen; or by weight, of 77 per cent. of nitrogen, and 23 of oxygen. (See Chart.) It also con- tains about -j^o its bulk of carbonic acid, and a minute proportion of watery vapor. 129. Relative Quantities of its Elements.—A very clear idea of these quantities may be gained, by supposing the air throughout to be of the same density, and its elements sep- arated into strata in the order of their specific gravities. In such a case the air would extend to a height of about five miles.—(Graham.) Its greatest quantity of watery vapor, if condensed, would form a stratum of water about five inches deep ; the layer of carbonic acid would be about thirteen feet deep ; that of oxygen about one mile; and that of nitrogen about four miles in depth. 130. Constituents and Properties of the Air.—The chem- ical properties of the air are chiefly those of the oxygen it contains, this gas being diluted and weakened by four times its bulk of the negative element, nitrogen (115). As at- mospheric oxygen is the universal sustainer of animal life (81), its proportion has been admirably adjusted to this ob- ject ; or rather, the organization of animals may be said to conform to the constitution of the air, because if this were changed, disturbance throughout all the orders of living beings would inevitably ensue. Were the atmosphere wholly composed of nitrogen, life could never have existed, animal How may we gain a clear idea of tho proportion of its elements ? What would be the thickness of each stratum ? To What does the air chiefly owe its chemical properties ? If the proportion ol oxygen in the air were changed, what would follow ? If it were all nitrogen, whaC would be the result ? What, were it to consist wholly of oxygen ? 82 INORGANIC CHEMISTRY. or vegetable: were it wholly to consist of oxygen, othei things remaining as they are, the world would run through its career with fearful rapidity; combustion, once excited, would proceed with ungovernable violence; animals would live with hundred-fold intensity, and perish in a few hours. But duly attempered by a large admixture of nitrogen, the grand functions of the animal races, of which it is the main- spring, are carried forward at a measured rate, and within regulated limits. 131. Carbonic Acid of the Air.—The proportion of car- bonic acid diffused through the air, always minute, varies slightly in different situations. There is less in the air of the country than in that of cities; less over the sea than over the land; less over a moist soil than over a dry one, because it is rapidly absorbed by water. It is furnished to the air by animals, which continually exhale it from their lungs (595). It is produced in vast quantities by combus- tion, by putrefaction and decay; and it escapes in immense volumes from volcanoes, both active and extinct.—(Fownes.) On the other hand, it is absorbed by the leaves of all plants, and is necessary to their growth. 132. Watery Vapor of the Air.—The atmosphere also contains more or less of watery vapor, which seems to be essential to both animals and plants, as neither of them can live in perfectly dry air. The proportion of moisture in the air depends upon the temperature; the hotter the air, the more it will hold; the cooler, the less : 100 cubic inches of air at 57° contains -35 of a grain of watery vapor.—(Brande) When the atmosphere is saturated with moisture, that is, contains all it can hold, if its temperature falls, a portion of What is said of the proportion of carbonic acid ? From whence is it derived ? Does watery vapor in the air perform any useful office ? Upon what does its proportion in the air depend ? What is the cause of dew ? THE ATMOSPHERE. * 83 its water will fall, or be deposited. It is thus cooled at night, which causes the deposit of dew. 133. When two currents of air of different temperatures, saturated with moisture, meet and mingle, the resulting mean temperature falls below the point necessary to hold all the water in a state of vapor; a portion of it, therefore, must fall. This is supposed to be a cause of clouds and rain. Thus south- erly winds saturated with humidity, loming in contact with the colder air of northern latitudes, usually give rain. For the same reason, the contact of air in motion with the cold surface of the earth must cause the precipitation of water. This explains the differences in the quantity of rain collected at different elevations in the same place. Thus the annual fall of rain in London, as measured by a rain-gage, was ascertained to be, at a height of 242 feet, 15-9 inches; at 73 feet, 20-4 inches; and upon the ground, 24*4 inches; showing that the air is more cooled near the ground, and, consequently, deposits more rain. The annual fall of rain is greatest at the equator, and diminishes towards the poles. At Granada (lat. 12° north), it falls to the depth of 126 inches ; at New York (lat. 40° north), its depth is 40 inches. 134. Snow-flakes.—When clouds form, at a temperature below 32°, the vapor freezes into an infinity of delicate needle-like crystals, which deviate from each other at angles of 30°, 60°, or 120°, giving rise to beautiful hexagonal and star-like figures. This is the crystalline structure of the snow-flake, shown in Fig. 14. Snow differs very much in the arrangement of these spiculae; but the flakes are all of the same configuration in the same storm. What is the cause of clouds and rain ? What is said of the difference in the fall of rain at different elevations ? What at different latitudes ? What is the origin of snow-flakes ? What their crystalline structure ? Have they always the same figure ? 84 INORGANIC CHEMISTRY. Fig. 14. 135. Additional Substances in the Air.—Liebig has showe that the air also contains minute traces of ammonia, which are washed down, and may be detected in rain-water. In- deed, as the sea contains a little of every thing that is soluble in water (99), so the atmosphere may be conceived to contain a little of every thing that is capable of assuming the gaseous form. The odorous emanations of plants, the miasms of marshes, and principles of contagion, though all producing effects upon the human body, cannot be collected from the air, nor even their presence detected by chemical tests. It is supposed that these substances do not exist in the true gaseous state, but are composed of fixed organized particles, which float about suspended in the atmosphere, like the pollen of flowers. They are all, however, oxidized and destroyed, as the air contains within itself the means of its own purification. 136. The Law of Gaseous Diffusion.—The oxygen and What other substances naturally find their way into the atmosphere ? In whal form are many of these substances supposed to exist ? Is the atmosphere a chemical compound ? By what law is the intermixture ol te gases rogulated ? How is its operation illustrated ? THE ATMOSPHERE. 85 nitrogen gases, of which the air is chiefly composed, are not chemically united with each other, but only mixed to- gether mechanically. If we mmgle them in a vessel in the same proportions, we get an artificial air, having the same properties as the natural air. This uniform intermingling of the gaseous elements is brought about by what is called the law of gaseous diffusion. Its operation may be thus shown : two vessels are to be placed one above the other, Fjg 15 and connected by a narrow tube of any convenient length (Fig. 15). The lower vessel may be filled with carbonic acid gas, and the upper vessel with hydrogen gas. After a short time the carbonic acid, although twenty times heavier than the hydrogen, will be found to have ascended into the upper ves- sel ; while hydrogen will have descended into the lower one,—a complete intermixture of the two gases in equal proportions having taken place against the action of gravity. 137. This effect will be produced even though a barrier, as a membrane of India-rubber, intervene. The force with which gases thus diffuse into each other is very great. Dr. Draper has proved that sulphuretted hydrogen will dif- fuse into atmospheric air, though resisted by a pressure of fifty atmospheres, equal to the weight of a column of water more than 1500 feet in height. In like manner, all gases possess the power of diffusing into each other, although at different rates of velocity, depending upon their density: the lighter the gas, the more rapid is the diffusion. 138. This principle is of the utmost importance in rela- tion to the air, because if either of its constituent elements were to separate from the mass, the extinction of life would What is said of the force with which gases diffuse into each other ? Why is this principle of the greatest importance ? 8 86 INORGANIC CHEMISTRY. follow. Dr. D. B. Reed assumes that the exhalations from the lungs and skin of a single human body vitiate, or spoil for breathing, ten cubic feet of air per mmute, or about 90,000 gallons per day. This foul air, with that formed by innumerable other sources of contamination, is perpetu- ally removed by diffusion, and the atmosphere is thus pre- served respirable and pure. 139. Relations of the Atmosphere to the Living World.— But it is in its relations to living beings that the atmos- phere appears of the highest interest. The vegetable world is derived from the air. It consists of condensed gases that have been reduced from the atmosphere to the solid form, through the agency of the sun's fight (329.) On the other hand, animals which derive all the material of their struc- ture from plants, destroy these substances while living, by respiration, and when dead, by putrefaction; thus returning them again, in the gaseous form, to the air from whence they came. In respect to air, the offices of plants and ani- mals antagonize. What the former derives from the air, the latter restores to it. It is the great link between the two worlds of organization. From the atmosphere all liv- ing beings came, and to it they must all return. " It is the cradle of vegetable and the coffin of animal life." We shall study this matter further in Organic Chemistry. 140. Weight of the Air.—A column of air one inch square, and extending upward to the limit of tne atmosphere, weighs about fifteen pounds; it therefore exerts a pressure on every square inch (at the level of the sea) equal to this weight; but as we pass upward the air expands, becoming more thin From whence is the vegetable world derived ? What does it consist of? What is said of animals ? What, then, is the relation of plants and animals ? What is the weight of a column of air, one inch high, extending to the top 0i Ums atmosphere ? What do we find as we pass upward ? How far must a gal THE ATMOSPHERE—CHLORINE. 87 and light as the elevation increases. A gallon of air, removed from the ground to the height of 11,556 feet, would expand into two (Brande) ; at twice this height its density would be again diminished one-half, and so on. This rarefaction in- creases so rapidly, that a cubic inch of air at the surface of the earth, if raised to a height of 500 miles, would expand so as to fill a space equal in diameter to the orbit of Saturn. 141. Curve of Congelation.—The temperature of the air decreases one degree for every 350 feet of elevation; there is, therefore, over all places, and at all seasons, an altitude at which it falls to the freezing point. At the equator this point is located 15,000 feet above the level of the sea. At latitude 40° it is 9000 feet, at 75° 1000, while at the poles it sinks into the ground. This forms what is called the line or curve of perpetual congelation. Air expands Tf„ of its bulk for every degree of temperature through which it rises. One hundred cubic inches of pure air weigh 30-829 grains.— (Regnault.) Air, assumed as 1, is taken as the standard of the specific gravity of gases—temperature 60°, barometer 30 inches. (For an account of the physical properties of air, the pupil is referred to the Natural Philosophy.) CHLORINE. Symbol CI, equivalent 355. 142. Source and Preparation.—Chlorine is a gas of a greenish color, as its name implies, and is about two and a half times heavier than air. It supports combustion, though Ion of air be taken upward from the ground to double its bulk? What is said of the expansion of a cubic inch of air? In what ratio does the temperature of the air decrease as we ascend? What is meant by the curve of perpetual congelation ? What is its height at the equator 1 At lat. 40" i What is the rate of expansion of air as we ascend ? 88 INORGANIC CHEMISTRY. Fig. 16. less perfectly than oxygen, and combines directly with the metals, forming a class of bodies called chlorides. It is found abundantly in nature, existing in common salt to the amount of 65 per cent, in union with sodium. Chlorine is best prepared by the action of three parts of hydrochloric acid upon 1 part of black oxide of manganese, in a flask, by the aid of heat. The decomposition may be traced in the accompa- nying diagram. It may be collected in the pneu- matic trough over hot water or strong brine, but is absorbed by cold water. It may also be collected by carrying the tube to the bottom of an open vessel; the chlorine rises and expels or dis- places the air (Fig. 16). 143. Bleaching Properties of Chlo- rine.—It is easily dissolved in cold water, and in this state exerts a re- markable bleaching power over vegeta- ble colors. It is principally used in bleaching cotton cloth and paper. The bleaching-powder of commerce is chloride of lime. Chlorine is also a powerful disinfectant, and is used to destroy the bad effluvia of sick rooms; but in these cases it requires to he used with caution, as it is excessively irritating to the lungs. Its bleaching and disinfecting properties are due to its strong affinity for hydrogen, which it takes away from coloring and putrescent substances, thus decomposing them entirely. xb> ■ N O4 AS STEAM,2 H 0 FROM THE FURNACE, 2 SOj^^^S^ 2S02 2(SO»HO) 188. When this acid is procured by the distillation of green vitriol, it comes off in a very dry state, and attracts moisture so rapidly as to cause a fuming ; it is hence called fuming oil of vitriol, or Nordhausen acid, because it was largely manufactured in a city of this name in Saxony. Com- mon or hydrated sulphuric acid contains a larger proportion of water. The former kind dissolves indigo. 189. Properties.—Sulphuric acid has a thick, oily appear- ance, with at first a greasy or soapy feel; but it speedily cor- rodes the skin, and causes an intense burning sensation. It has a powerful affinity for water; when a splinter of wood is dipped into it for a short time, it turns black (chars), the acid taking away from it the elements of water, and leaving the carbon. In like manner, it chars and decomposes the skin, and most organic substances, by removing their water. When water and sulphuric acid are mixed, the two liquids shrink into less space, and heat is produced. Pure oil of vitriol is colorless; but slight traces of organic matter, as dust or straws, turn it of a dark shade, as it is usually seen in commerce. It is an active poison, the best antidote being copious draughts of chalk and water, or carbonate of soda or magnesia. What is the fuming or Nordhausen acid ? What are the properties of sulpb'wws scid? Why does it char and blacken organic bodies? What is the appearance of the sulphuric acid of commerce ? Is it poisonous ? What is the antidote ? 10 110 INORGANIC CHEMISTRY. 190. Uses.—Sulphuric acid is extensively used in the manufacture of soda from common salt; also in the manufac- ture of chlorine for bleaching; of citric, tartaric, acetic, nitric, and muriatic acids ; sulphate of soda, sulphate of magnesia, blacking, soda-water, and various paints; also in dyeing, calico-pi-inting, gold and silver refining, and in purifying oil and tallow. Its chemical uses are innumerable. It is the Hercules of the acids. 191. This acid unites with bases forming the sulphates, and exists in nature both combined, as with lime in gypsum, and free, as in some streams the water of which it renders sour. S Os is nearly twice as heavy as water (specific grav- ity 1-8), a gallon weighing about 18 pounds. The test for sulphuric acid is chloride of barium, with which it forms an insoluble salt. The remaining compounds of sulphur and oxygen are not of general interest. SULPHURETTED HYDROGEN. {Hydrosulphuric Acid) HS = 17. 192. When sulphur and hydrogen are set free together, hey unite to form a colorless, transparent gas, having he well-known smell of decaying eggs. It is produced *y the putrefaction of all organic substances containing mlphur, as flesh, blood, hair, excrements, albumen of eggs, kc. It is this gas which gives the putrid odor to sul- phurous waters. A rotten pump-log standing in a well of hard water (containing gypsum) may render it nauseous by setting free sulphuretted hydrogen. If the well is puri- fied, and a new log introduced, the water may be restored to What are the uses of sulphuric acid? In what form does it exist in nature ? What is its test ? What is the composition of sulphuretted hydrogen ? From what substances l« U derived ? What is said of its odor ? What is its effect upon animals ? PHOSPHORUS. Ill sweetness. Sulphuretted hydrogen is very deleterious when respired. A small bud dies immediately in air containing TsVo °f ^^ g3® '• Fo~o kine(i a middle-sized dog, and y| 6 a horse.—(Brande.) PHOSPHORUS. Symbol P, equivalent 32. 193. Its Discovery.—This remarkable substance,was first obtained about 200 years ago, by one of the alchemists, while trying to discover the art of making gold. Its mysterious properties were regarded with wonder and awe, and it was shown around among the initiated under the name of the " Son of Satan." 194. Properties.—Phosphorus is a solid, of a waxy ap- pearance, easily cut, colorless and transparent, but turning yellow by exposure to the light. It possesses the singular quality of shining in the dark, and is hence called phosphorus, or light-bearer. It is highly combustible, often taking fire in the air upon the slightest touch, and burning furiously; it is therefore always kept under water. Great caution is re- quired in experimenting with it. It is a poison. 195. Source of Phosphorus.—Bones contain phosphorus— they consist of gelatine, lime, and phosphoric acid. To ob- tain it, the bones are first burned, which drives off the gela- tine. The lime is then separated by adding oil of vitriol, and the oxygen of the remaining phosphoric acid is removed by the action of charcoal at a high heat. The phosphorus distils over by means of a suitable apparatus, and is collected What Is stated of the discovery of phosphorus? What are its properties ? From what source and how is phosphorus obtained ? How much may bo ex> u-actod from the human skeleton ? 112 INORGANIC CHEMISTRY. under water. The skeleton of a man weighs from 10 to 12 pounds, and contains from l£ to 2 pounds of phosphorus. 196. Its Use in Matches.—Phosphorus takes fire at a temperature of about 120°; and as this may be produced by slight friction, it is well adapted to tip the ends of friction matches. As the phosphorus would be liable to take fire if exposed to the air, it is kneaded with water and gum, or glue, into a paste, which, when dried, serves as a protecting varnish. • Chlorate of potash, nitre, red-lead, or some other substance rich in oxygen, is worked into the paste to insure prompt combustion. The points of the matches being first coated with sulphur, are dipped into this preparation, and then cautiously dried in a stove. When the surface is broken by friction, the phosphorus takes fire first, the sulphur next ignites, and then the wood of the match:—200,000 pounds of phosphorus are used annually in London alone for the manufacture of matches. 197. Its Physiological Relations.—Phosphorus not onlj exists as phosphate of lime in the bones of animals, but in n free or unoxidized state it is an essential constituent of the brain and nervous matter. It is also an ingredient of albumen and fibrin. The uncombined phosphorus is burned by the oxygen of respiration, forming phosphoric acid, which, united with soda or ammonia, passes from the system by the route of the kidneys. The uncombined phosphorus of the nervous and cerebral tissue is not in its ordinary form. It is capable of existing in two allotropic states (42). In one of these conditions its active properties are suspended. It passes into this torpid state in plants, is consumed by animals in food, passes unchanged through their circulating fluids, and is How are matches made ? Is much used for this purpose? In what other part of the animal body is phosphorus found ? In what condl ilon does it here exist ? PHOSPHORIC ACID. thrown into the active state, and oxidized under the influence of the vital force. 198. Phosphorescence.—That shining, self-luminous ap- pearance which is sometimes exhibited by putrefying fish, which is also occasionally seen in decaying wood, in the fire- fly and glow-worm, is termed phosphorescence, and is thought to be due to the slow oxidation of phosphorus at low tem- peratures. It is supposed that the beautiful luminous ap- pearance of the inter-tropical seas is due to the decay of small jelly-fish, or blubber, so abundant in the ocean, and which contain phosphorus. PHOSPHORIC ACID. POs= 7202. 199. Phosphorus has an intense affinity for oxygen. Place a bit of phosphorus, of the size of a pea, in a wine- glass, cover it with hot water, and direct against it a current of oxygen gas, it bursts into a violent combustion beneath the surface of the water. When a match is burned, the white smoke that appears is phosphoric acid; it is always produced when phosphorus is burned in dry air or oxygen gas. This acid condenses into solid white flakes of a snowy appearance, and possesses a powerful affinity for water, hissing like a red-hot iron when brought in contact with it. In small quantities it is not poisonous; and when taken me- dicinally, it must be sucked through a quill or glass tube, as it corrodes the teeth. Phosphoric acid is of great importance in agriculture, as it is»principally from its presence in bones that they are so useful as a manure (286). There are What luminous appearances are supposed to be due to phosphorus ? State the composition of phosphoric acid. How may it be formed ? What aw tta properties ? To what is the value of bones in'agriculture due ? 114 INORGANIC CHEMISTRY. three other compounds of phosphorus and oxygen, but they are of interest only to the scientific chemist. PHOSPHURETTED HYDROGEN. (Phosphide of Hydrogen.) PHj= 34-02. 200. This is a colorless, transparent gas, of a disgusting odor, to which the nauseous smell of putrefying animal sub- stances is partially due. It is more offensive than sulphu- retted hydrogen. It may be prepared by boiling phosphorus with a strong solution of potash in a glass retort, the extrem- ity of which dips beneath the surface of water. The bubbles of gas, as they escape into the air, inflame spontaneously, and burn with a bright yellow light. Each bubble, as it explodes, produces a wreath of gray smoke, which dilates, as it rises, with curious rotatory movements of its parts. The singular phenomenon of Will-o'-the-wisp, or Jack-'o-lantern, where a flame or light is said to move at night over marshy places, is supposed to be due to the presence of this self-in- flammable phosphuretted hydrogen. OF THE METALS. 201. The metals are a numerous class of bodies, distin- guished by a peculiar brilliancy called the metallic lustre, and as being good conductors of both heat and electricity. They, however, exhibit great variations in these, as well as other properties. Authors are not agreed jn their classification of the metals. Give the composition and properties of phosphuretted hydrogen. How ia il prepared? What effect takes place when it comes in contact with air? How il the Jack-o'-lantern accounted for ? What are the metals ? POTASSIUM AND 0X1 GEN. 115 METALS OF THE ALKALIES. POTASSIUM. {Latin, Kalium) Sym. K, equiv. 39; sp. gr. -869. 202. Properties.—Potassium is a silver-white metal, at common temperatures so soft that it may be moulded in the fingers like wax. It is never found free in nature, but oc- curs abundantly in rocks and soils combined with oxygen, as potash. It is produced in the metallic state by the action of charcoal upon potash at a very high tempera- ture, which withdraws its oxygen. Davy first separated potassium by means of an electrical current in 1807. It is the lightest of all the metals. POTASSIUM AND OXYGEN—POTASH. KO = 47. 203. The affinity of potassium for oxygen is very strong; when exposed to the air, it becomes immediately incrusted with a film of oxide, and can only be preserved under naphtha, a liquid containing no oxygen. Thrown upon the surface of water, it decomposes it, removing its oxygen, and burning with a beautiful pink flame. The same phenomenon appears if the metal be placed in contact with ice, when it instantly bursts into flame. This shows how gunpowder is fired by touching it with an icicle. There is potassium mingled with Hie powder. When potassium is burned in dry oxygen, pure potash, K 0, is formed. This has a very powerful affinity What is potassium ? How did Davy first obtain it ? How is the strength of its affinity for oxygen shown ? What is stated of its affinity for water ? 116 INORGANIC CHEMISTRY. for water, which it imbibes as soon as it is exposed to the air, forming the hydrated oxide of potassium, K 0, H 0, or caustit potash. 204. Caustic potash is procured from carbonate of potash, by the action of hme, which deprives it of carbonic acid. It is a white powder, having a powerful affinity for water, which it takes rapidly from the air, and runs into a liquid. Potash possesses all the properties of the alkalies in a pre- eminent degree: it is the type of that class of bodies. It saturates the most powerful acids, changes vegetable yel- lows to brown, and restores the blues discharged by acids; and also decomposes animal and vegetable substances, whether living or dead. It is used in medicine in the form of small sticks, to cauterize or cleanse ulcers and foul sores; it is hence called caustic potash. If a solution of potash be shaken in a bottle with olive oil, or any other fixed oil (404), it will be found to convert it into a soap. This accounts for the soft, greasy feel it has when touched by the finger, as it decomposes the skin, and forms a soap with its oily elements, Its uses in agriculture will be stated when we come to the salts (272). Alkalimetry is the art of measuring the propor- tion of alkali in an impure mixture or compound. SODIUM (Latin, Natrium.) Symbol Na, equivalent 22-97. 205. This is a brilliant white metal, very much resembling potassium both in appearance and properties. It has a strong affinity for oxygen, and must be preserved in naphtha. If What is potash? What position does it hold among the alkalies? How is il obtained ? What are its properties ? How is it used in medicino ? Why docs it feel greasy to the fingers? What is alkalimetry? Describe tho properties of sodium. What is said of its abundance ? SODA—LIME. 117 thrown upon the surface of hot water, it bursts into a beau- tiful yellow flame, and is converted into the oxide of sodium, jr soda. It is prepared in the same way as potassium, but tvith less difficulty. It is perhaps the most abundant metal npon the globe, as it constitutes two-fifths of sea-salt, and is a large ingredient of rocks and soils.—(Gregory.) SODIUM AND OXYGEN—SODA. Na 0 = 30-97. 206. This alkali was long confounded with potash, which it greatly resembles, although its properties are less marked. For commercial purposes, it is chiefly derived from sea-salt, and is extensively employed in the manufacture of soap and glass. It is always present in the bodies of animals. METALS OF THE ALKALINE EARTHS. CALCIUM. Symbol Ca, equivalent 20. 207. Calcium is a metal but little known. It is obtained with difficulty, and is put to no use. Its name is derived from calx, the Latin term for lime; hence also the English word calcareous. Calcium combined with oxygen forms lime. CALCIUM AND OXYGEN—LIME. CaO=28. 208. Lime is produced by burning limestone (carbonate of limo) in large masses, in kilns. The carbonic acid is driven off into the air by the heat, and a white stony substance re- Whence is it derived ? Describe the metal calcium. How is lime obtained ? What is the effect of the burning ? What Is quick' limo, or caustic lime ? 118 INORGANIC CHEMISTRY. mains, called quicklime, or caustic lime. It is porous, and sufficiently hard to be transported without falling to pieces. One ton of good limestone yields 11 cwt. of lime. 209. Hydrate of Lime.—When water is poured upon quicklime, it absorbs it (every 28 pounds of lime taking 9 pounds of water), swells to thrice its original bulk, crumbles to a fine white powder, and is converted into a hydrate of lime, Ca 0 HO; this process is called slaking. During slaking, heat is produced, often sufficient to ignite wood (92). If water is added too rapidly in slaking, it seems to chill ihe lime, and produces gritty lumps, which impair its value for building and agricultural purposes. 210. When quicklime is exposed to the air, it first rapidly imbibes moisture, and crumbles to powder; it then gradu- ally absorbs carbonic acid, becoming more and more mild, 'ess and less caustic, and finally regains the neutral condition of the carbonate. Lime exhibits the properties of a strong alkali, decomposing organic tissues, and saturating the strong- est acids. It is more soluble in cold than in hot water; 778 pounds of cold water, or 127t> oounds of hot water, are re- quired to dissolve 1 pound of lime. Hence, when a cold saturated solution of lime-water is boiled, a portion of the lime is deposited, which accounts for the crust or fur which lines the interior of tea-kettles and boilers in localities where the water is impregnated with lime. Lime-water is a satu rated solution of lime in water; it is used to counteract acid- ity of the stomach. Cream or milk of lime is a thick mix- ture of the hydrate with water, such as is used for -white- washing. In tanneries, the hides are immersed in milk of What is the effect of water upon quicklime ? What is the effect of adding water too rapidly in slaking ? How is caustic lime changed to the carbonate ? What is stated of its solublt't)' For what is lime-water used ? What is milk of lime ? Its use ? LIME. 119 lime, which partially decomposes them, so that the hair may be easily rubbed off. 211. Mortar and Cement.—Lime mixed with sand forms mortar, employed by builders to cement stones and bricks together, as glue is used to join pieces of wood. To make the best mortar, the lime should be perfectly caustic, and the sand sharp and coarse-grained; the presence of clay, even in small proportions, is injurious. The nature of the changes by which the mortar becomes hardened is not satis- factorily explained. Hydraulic cement possesses the prop- erty of solidifying under water, which ordinary mortar will not do. This property is owing to the presence of sand and clay (silicate of alumina) in the lime of which it is made. 212. Lime exists in Organized Structures.—The mineral portion of the skeletons of the higher animals consists of lime combined with phosphoric acid. The shells of the lower animals contain lime, combined chiefly with carbonic acid ; and as all parts of animals are derived from the vege- table world, lime must be an essential constituent of plants. Its most extensive use is in agriculture. 213. Lime in Crops.—Some soils contain an abundant natural supply of lime ; to such its addition is of course use- less. Where it does not exist, it must be applied, to enter into the systems of plants. The following table exhibits the amount of lime removed from an acre of land in the fol- lowing crops; tops, straw, and grain are included. Lime. Lime Wheat, 25 bushels, 8-7 lbs. Turnips, 25 tons, 138-8 lbs. Barley, 88 " 15"0 " Potatoes, 9 " 266-0 " ' Oats, 50 " 8-2 " Red Clover, 2 " 126-0 " (Johnston.) How is the best mortar made ? In what part of animal structures does lime exist? Why should hme be added to soils which do not possess it? 120 INORGANIC CHEMISTRY. These quantities are not always the same ; wheat, especially, contains much more lime than is here stated, when grown upon land to which it has been copiously applied. 214. Effect of Lime upon the Soil and Plants.—Lime exerts a very favorable action upon clay soils, by loosening and rendering them less adhesive, and also by setting free the alkalies which are locked up in clay. Soils abound- rng in vegetable matter are often improved by liming. It thanges inert substances in the soil, so as gradually to ren- der them useful to vegetation, decomposes noxious corn- sounds, neutralizes baneful acids, sweetens vegetation, and improves the quality of almost every cultivatable crop. Strain grown upon well-limed land, it is said, has a thinner ,\kin, is heavier, yields more flour, and that richer in gluten than if grown on unlimed land. On flax alone it is said to be injurious, diminishing the strength of the fibre of the stem. Hence in Belgium flax is not grown upon land until seven years after the lime has been applied.—(Johnston) 215. Compounds formed by lime in the soil are in- soluble ; its action is therefore slow, often requiring from three to six years to produce the best effect. At first it often diminishes the crops, and always does this in over- doses. The hydrate acts most speedily, but good effects may be exp*ected from the carbonate after a longer time. " The more dry, shallow, light, and sandy the soil, the less abundant in vegetable matter; the milder and warmer the climate in which it is situated, the less the quantity of lime which the prudent farmer will venture to mix with it." Lime should never be mixed with fermenting farm-yard What effect has lime upon clay soils? How does it act upon soils rich in vege- table matter? What is said of grain grown on limed land ? What of flax? Why is its beneficial action so slow? What is the effect of an overdose? Under what circumstances should lime be used with caution ? Why should lime never be mixed with farm-yard manure ? MAGNESIUM—ALUMINUM. 121 manure, as it expels ammonia, a most valuable element of fertility. MAGNESIUM. Symbol Mg, equivalent 12-67. 216. Magnesium is a silver-white metal, like the three preceding. It is of no use, and is prepared only as a curi- osity. It unites with oxygen, forming oxide of magnesium, or common magnesia, Mg 0. Magnesia was first distin- guished from lime by Dr. Black, about a hundred years ago. It is a white powder, possessing feeble alkaline prop- erties, and dissolving in about 55,000 times it? weight of water.—(Fresinius) Magnesia is found united, with acids ; as a sulphate in mineral waters, as a carbonate in magnesian limestone, as a silicate in talc, serpentine, &c. It is pre- pared by igniting the carbonate. It is used as a mild aperient and corrector of acidity. Magnesia is found in the ash of nearly all plants, but its action upon soils is obscure. Specific gravity, 3'61. METALS OF THE EARTHS. ALUMINUM Symbol A], equivalent 13-69. 217. This metal never occurs free in nature, but always in union with oxygen, forming a sesquioxide of aluminum, Al2 03. It absorbs moisture with great avidity. Alumina can neither be pronounced an acid nor an alkali, and yet it seems to possess the properties of both ; towards acids it sometimes What fire the properties of magnesia? How is alumina obtained? What are its properties? In what forms loes it exist puro? 11 122 INORGANIC CHEMISTRY. plays the part of a base, while towards bases it behaves at an acid__forming combinations with either. Pure alumina is found crystallized in those precious gems, the ruby and sapphire, which are next in hardness and value to the dia- mond ; also in a more massive form, as corundum or emery. 218. Used to fix Colors.—Alumina has a powerful at- traction, both for vegetable coloring matter and the fibre of cloth ; it is hence used by dyers to fix the color upon their fabrics. It is then said to act as a mordant (479). When a solution of alum is mixed with an alkali, the coloring mat- ter is carried down, and forms what is called a lake. Car- mine is a lake of cochineal. Alumina also absorbs and combines with oily matters; hence a certain kind of clay called fullers' earth is used to extract grease-spots from wood, paper, &c. 219. Composition of Soils.—Alumina is the basis of clay in soils; but it is always mixed with more or less silica or sand. To determine the relative amount of clay and sand in a specimen of soil, agitate it thoroughly with a consider- able quantity of water, and pour the mixture into a tall glass vessel or wide tube. When left at rest, the coarser particles of sand will first fall to the bottom, then the finer sand, and lastly the clay. By observing the relative thick- nesses of the different layers, we get a tolerably correct idea of their proportional quantities. By pouring off the turbid water, after the sand has settled, the clay may be separated from it. It is, however, to be remembered that the purest clay we can obtain by repeated washings and separations, still contains from four to six per cent, of very fine sand, Upon what property does the use of alumina as a mordant depend ? What il E lake ? How does alumina act to extract grease-spots ? How can we determine the relative amount of it in soils ? How dooi Profesaoi lohnston classifj soils ? CLAY—SILICON. 123 which can only be removed from it by the refined processes of chemistry. Professor Johnston classifies soils as follows : pure clay, or pipe clay, that which will allow nothing to sub- side or separate when diffused through water. The strongest clay soil parts with 10 to 15 per cent, of sand by boiling with water and decantation. A clay loam loses from 15 to 30 per cent, by the same process. A loamy soil deposits from 30 to 60 per cent., a sandy loam from 60 to 90 per cent., while a sandy soil contains no more than 10 per cent. of pure clay. 220. Clay exhibits in a high degree the power of absorb- ing and retaining water; hence soils in which clay abounds, after heavy rains suffer the water to evaporate but slowly, and are therefore wet and cold. It is also adhesive, and so compact as to prevent the free extension of the roots. On the contrary, in dry weather it shrinks, hardens, and cracks. Sand possesses the opposite qualities: it retains water but feebly, yields it readily by evaporation, and so completely lacks adhesion that its particles are blown about by the winds. A due admixture of theseearths corrects their mutual faults, and forms a productive soil. Clay possesses the valuable property of condensing carbonic acid and ammonia from the atmosphere Porcelain, pottery, bricks, &c, are chemical combinations of alumina with silica, and will be noticed among the silicates (209). SILICON. Symbol Si, equivalent 21-35. 221. This is a brown powder which does not occur in na- ture. It is difficult to produce, and is of no importance ex- Why are strong clay soils wet and cold ? What effect has dry weather upoa Biem ? U hat are tho disadvantages of a sandy sod ? What is said of silicon? What is stated of the abundance of silica upon the 124 INORGANIC CHEMISTRY. cept to the scientific chemist. It holds an equivocal positioj in systems of classification. Brande ranks it among the met- als ; and although it may have affinities elsewhere, I adopt his arrangement in this respect, and associate it with aluminum: these form the bases of the two principal earths. Silica, or oxide of silicon, is estimated to form one-sixth part of the sur- face of the globe.—(Silliman). In extent it seems to occupy a similar place in the mineral world with carbon in the or- ganic world. (See Chart). SILICA. (Silicic Acid—Silex—Sand.) Si 03 = 45-35. 222. Preparation and Varieties.—This abundant com- pound may be prepared by heating rock-crystal (quartz) to redness, and quenching it in water, when it may be easily reduced to a fine, white, tasteless, gritty powder, which is nearly pure silica. In some of its forms this mineral is found everywhere. It constitutes a large portion of the rocks in many mountain ranges, the sand and gravel of soils, and the pebbles upon the sea-shore. It forms gun-flints, grindstones, and the porous burr-stones used in flouring-mills for grind- ing grain. Crystallized silica, when colorless, forms quarta or rock-crystal; when violet-colored, it is the amethyst; when green, chrysoprase ; when red, rose-quartz ; when pos- sessing red veins or spots, blood-stone ; when of a flesh-color, carnelian ; when deposited from water, chalcedony. Sard is a reddish-brown variety of chalcedony. ' Onyx is a milk-white variety. Sardonyx consists of the two in plates or layers, giving rise to a beautiful arrangement of colors, and when cut forms cameos. Agate, jasper, and opal are also forms of How may pure silica be obtained ? What further is said of its diffusion ? What we the names of tho various substances formed of silica ? SILICA. 125 iilica. Silica, as it occurs in all these forms, is contaminated with certain impurities, usually oxides of iron. Quartz is so hard as to give fire with steel, and scratch glass; and so pure, as to be often used for the eyes of spectacles, under the name of pebbles. 223. Silica an Acid.—However strange it may seem that such substances as sand and flint should be ranked among acids, yet such is the fact.- At high temperatures, silica ex- hibits powerful acid properties, and neutralizes numerous bases, forming a class of salts—the silicates. Glass, porce- lain, and pottery-ware are all salts—silicates of various bases formed at a high heat (303). Most rocks and minerals are also silicates. (See Chart.) 224. Silica is dissolved by but one acid, the hydrofluoric, which is hence often used for etching glass. Although common quartz and sand are totally insoluble in water, yet they are rendered soluble by the action of the alkalies ; hence one reason of applying potash to soils, is to dissolve their silica. When liberated from its combinations by the agency of the air (302), it is soluble in water, and hence is always present in springs, the waters of which trickle through soils and the fissures of rocks. Silica is necessary to the growth of vegetation, and exists abundantly in many plants ; particu- larly in the stalks of the grains and grasses. It is this which communicates stiffness and strength to their stems, as the skeleton does to the bodies of animals. If there is a defi- ciency of soluble silica in the soil, the grain-stalk will be weak, and liable to break down, or lodge. It is silica which gives their quality to scouring-mshes. When does silica exhibit acid properties? What salts of silica are in com- moil use ? What acid dissolves silica? Under what circumstances docs silica becoroa soluble ? What office does it perform in plants ? 11* 126 INORGANIC CHEMISTRY. METALS EMPLOYED IN THE ARTS. IRON. (Latin, Ferrum.) Symbol Fe, equivalent 28. 225. Were we to seek for that circumstance which might best illustrate the peculiarities of ancient and modern civili- zation, we should perhaps find it in the history of this metal. The ancients, imbued with a martial spirit and passion for conquest, regarded iron as the symbol of war, and gave it the emblem of Mars. And if it were required also to sym- bolize the pacific tendencies of modern society—its triumphs of industry and victories of mind over matter, its artistic achievements and scientific discoveries—we should be com- pelled to make use of the same metal, iron. As gold and jewels have long been the type of ignorant and empty pomp, so iron may now be well regarded as the emblem of benefi- cent and intelligent industry. 226. Uses of Iron.—Iron, in some of its innumerable forms, ministers to the benefit of all. The implements of the miner, the farmer, the carpenter, the mason, the smith, the shipwright, are made of iron, and with iron. Roads of iron, travelled by " iron steeds," which drag whole townships after them, and outstrip the birds, have become our commonest highways. Ponderous iron ships are afloat upon the ocean, with massive iron engines to propel them; iron anchors to stay them in storms; iron needles to guide them; and springs of iron in chronometers, by which they measure the time. Ink, pens, and printing-presses, by which knowledge is scattered over the world, are alike made of iron. It warms us in our apartments; relieves our jolts in the car- riage ; ministers to our ailments in the chalybeate mineral How did the ancients regard iron ? Of what may it now become the symbol! Enumerate some of tho uses that are made of iron. IRON. 127 waters, or the medicinal dose; it gives variety of color to rocks and soils, nourishment to vegetation, and vigor to the blood of man. Such are the powers of a substance which chemists extract from an otherwise worthless stone. 227. Properties of Iron.—Iron is of a grayish-white color, and of a perfect lustre when polished. It may be thrown into many conditions, in which it exhibits remarkably differ- ent properties. It is malleable, as in bar or wrought iron; and may be forged into any form under the hammer. It is very ductile, and may be drawn out into the finest wire, which is extremely tenacious (tough); an iron wire ■£§ of an inch in diameter bearing a weight of sixty pounds. 228. Welding of Iron.—When wrought-iron is heated to whiteness, it becomes soft, pasty, and adhesive, and two pieces in this condition may be incorporated or hammered together into one. This is called welding. During the heating, a film of oxide is formed upon the surface of the metal, which would obstruct the ready cohesion of the sep- arate masses. To prevent this, the smith sprinkles a little sand upon the hot iron, which combines with the oxide, forming a fusible silicate of iron, which is easily forced out by pressure, leaving clean surfaces that unite without diffi- culty. This important quality is enjoyed only by iron, pla- tinum, and sodium. All the other metals pass suddenly from the solid to the fiquid state at their respective meltmg points, as ice is changed to water. 229. Wrought and Cast Iron.—Wrought-iron possesses what is called a fibrous texture; that is, it seems to consist of compacted threads, running parallel to each other like the fibres of flax. Another state of the metal is cast-iron, which, What is the appearance of iron ? Name some of the conditions it may assume. What is welding ? Have all metals this property ? What is the texture of wrought-iron ? What Of cast-iron ? What is said of tlm 128 INORGANIC CHEMISTRY. on the contrary, has a granular texture (consists of grains) it is brittle, cannot be forged, but may be melted and cast in moulds, which wrought-iron cannot. Cast-iron expands when first poured into a mould, so as to copy it perfectly; but it subsequently contracts, so as to be less in size than the original pattern. The expansion is caused by the particles assuming a crystalline arrangement while consolidating; the contraction by the cooling of the metallic mass, after it has solidified. Wrought-iron is said to lose its tough, fibrous character, by the effect of blows or constant jarring, and to 'become crystalline. 230. Ores of Iron—The Per Centage Scale.—Iron occurs in nature almost universally in a state of combination. The mineral masses which it forms with oxygen, carbon, sulphur, and the metals, and from which it is extracted, are called its ores. They are quite numerous, but are not all equally valu- able as sources of the metal. The five principal ores that are wrought for the production of iron, are exhibited upon the Chart by means of a scale marked off into a hundred divisions. The proportions per cent, of iron, and the elements with which it is combined in the ore, are shown in a very clear manner. This method of expressing chemical compo- sition, by proportions per cent., was in general use before the introduction of atomic proportions: it is still much employed. 231. One of the richest ores of iron is loadstone, or the magnetic black oxide. It contains seventy-two per cent, of iron to twenty-eight per cent, of oxygen, and is a mixture of the protoxide and the peroxide. It is of a grayish color, and when rubbed gives a black powder, and is strongly magnetic. This is one of the most valuable ores; it is very widely dif- changes which cast-iron undergoes after being poured into the mould? What sauses its expansion and contraction ? What are ores of iron? How is their composition represented upon the Chart? IRON. 129 fused, and furnishes iron of the best quality. The superior iron from Russia, Germany, and Sweden is produced from it. Specular iron (red iron ore).—This is very hard, and some- times resembles polished steel. When coarse, the oxide is of a brown color; but its powder is always red, thus distin- guishing it from the magnetic oxide. This oxide contains sixty-three per cent, of iron to thirty-seven of oxygen. It exists in all the red clays, which are termed ores when they yield twenty per cent, of the metal. Hematite (hydrated oxide of iron).—Brown iron-stone is very abundant all over the world, and particularly in the United States, and is the chief source of the iron of commerce. It usually affords a yellow powder, and is not attracted by the magnet unless it has been burnt or roasted. It contains fifty-nine per cent, of iron, twenty-seven of oxygen, and fourteen of water. 232. Pyrites, which signifies fire-stone, is so named be- cause it was used in firelocks, before the introduction of gun- flints, to produce sparks with steel. It is a sulphuret of iron, of which there are two principal varieties, the red and white. Yellow pyrites, when it occurs in minute brilliant scales, is sometimes mistaken for gold (fool's gold). It is tested at once by heating it, when it gives off a sulphurous smell. Pyrites is chiefly prized as a source of copperas, alum, Span- ish brown, sulphur, and sulphuric acid. Yellow pyrites con- tains forty-seven per cent, of iron and fifty-three of sulphur. Sparry iron (steel ore) is of a yellowish-gray or brownish- red color. It is a carbonate of iron, and effervesces slightly with nitric acid. This ore contains sixty-three per cent, of oxide of iron, thirty-four per cent, of carbonic acid, with a What is said of loadstone? What is its color? What of its powder? What are the properties of specular iron or red ore ? Of hematite ? What is the meaning of the term pyrites? Its origin? Composition? What Is it often mistaken for? What are its chief uses? What is stated concerning (parry iron ? What does it produce ? 130 INORGANIC CHEMISTRY. small quantity of lime, magnesia, and manganese. A variety of steel is made dhectly from this ore, without cementation (236). The cheap German steel is derived from this ore. 233. Obtaining the Metal.—The process of separating this metal from its ores is called reducing or reviving it, and the ores are said to be smelted. The operation is conducted in tall chimney-like structures, termed blast-furnaces. They are constructed of the most refractory fire-proof bricks, and are from thirty to sixty feet high, and about sixteen feet in internal diameter in the largest place, having the form seen in Fig. 18. The top or mouth of the furnace serves both for charg- ing it and for the escape of smoke: it is both door and chimney. The tubes serve to supply the air, which is driven in by means of a steam- engine and an air-pump, or fanners. A single blast apparatus, connect- ed with an English fur- nace, propelled 12,588 cubic feet of air per minute.—( Ure.) Formerly the air was used at the ordinary temperature (cold blast), but within a few years an immense improvement has been effected by heating the air before it enters the furnace (hot blast). 234. In some cases, the materials are drawn up an in- clined plane, to the mouth of the shaft, by means of the What is reducing or reviving ? In what is the operation of smelting conducted ? Describe the blast-furnace. What is the hot blast? The cold blast? IRON. 131 same Steam-engine that impels the blast mechanism. The furnace is supplied with ore, coal, and limestone, broken into small fragments. When the heat is sufficiently intense, the carbon of the fuel deoxidizes the iron, and carbonic acid is also expelled from the lime, leaving it caustic. Sand and clay, in greater or less quantities, now remain combined with the iron. The lime, acting as a flux, unites with these, form- ing the slag or scoria, a crude semi-vitreous product. The melted iron, falling to the bottom of the furnace, accumulates, and is drawn off by taking out a tap or plug. It is allowed to run into a bed of sand, containing straight channels, and furrows running at right angles. The former are termed by the workmen the sow, and the latter the pigs, and hence the origin of the term pig-iron. As the contents of the furnace are removed from below, crude ore is constantly supplied above, and the operation goes on day and night uninterrupt- edly for years, or until the fabric demands repair. 235. The product of the smelting-furnace is cast-iron. Its peculiar properties of brittleness and fusibility are due to the presence of a considerable quantity of carbon and some other impurities, the removal of which converts it into wrought- iron. This is done in an oven-shaped furnace (reverberatory furnace), in which the fuel is not mingled with the metal, as in the case of smelting, but heats it by the flame reflected from the low roof. A workman, with a long oar-shaped implement of iron, stirs (puddles) the melted mass until the carbon is burned away, and the metal becomes thick and pasty: this is called puddling. The puddler then rolls it up In what form are the materials introduced ? What are the first changes which take place ? What part does the lime play ? What is the origin of the term pig- iron? What is the product of the smelting-furnace ? What impurities does it contain ? How is it changed into wrought-iron? Describe the puddling process. How is the iron greatly improved ? 132 INORGANIC CHEMISTRY. into balls, which he transfers to the tilting-hammer, where it is beaten by heavy blows into a rude bar, the liquid impu- rities, consisting principally of silica and alumina, being squeezed out, as water is driven from a compressed sponge. The metal, still hot, is then passed between grooved cylin- ders, and rolled out into bar-iron. The quality of the metal is greatly improved when these bars are broken up, bound together, reheated to the welding point, and put through the same process repeatedly: this is called piling or fagoting. In malleable iron there is still retained a small portion of carbon, about \ per cent. 236. Steel.—This remarkable modification of iron is a compound of iron with about one and a half per cent, oi carbon. It is made by imbedding bars of the best wrought- iron in powdered charcoal, in boxes or sand-furnaces which exclude the air, and heating it intensely for a week or ten days. The chemical changes that take place are obscure; probably carbonic oxide penetrates the heated metal, is de- composed, surrenders part of its carbon, and escapes as cai ■ bonic acid. The steel, when withdrawn, has -a peculi.v, rough, blistered appearance, and is hence known as blistered steel. This method of making steel is called the process of cementation. When blistered steel is drawn into smaller bars, under the tilting-hammer, it forms tilted steel; and this, broken up, heated, and again drawn out, forms shear steel, so called because it was originally thus prepared for making shears to dress woollen cloth. English cast-steel is prepared by melting blistered steel, casting it into moulds, and draw- ing it out into bars. Case-hardening consists in forming the surface of iron into steel, by heating it with charcoal for a short time. What is steel ? How is it made ? What change occurs ? What is tilted steel J What is shear steel ? What is case-hardening ? IRON. 133 237. In its properties steel combines the fusibility of cast- iron with the malleability of bar-iron. Its value for cutting instruments, springs, &c, depends upon its quality of being tempered. When heated to redness, and suddenly quenched in cold water, it becomes so hard as to scratch glass. If again heated, and cooled slowly, it becomes as soft as ordi- nary iron ; and, between these two conditions, any required degree of hardness can be obtained. As the metal declines in temperature, the thin film of oxide upon its surface con- stantly changes its color. The workmen are guided by these tints. Thus a straw yellow indicates the degree of hardness for razors, a deep blue for sword-blades, saws, and watch- springs. Steel receives a higher polish than iron, and has a less tendency to rust. 238. Nitric acid, placed upon steel, corrodes the metal, and leaves the carbon as a dark-gray stain; writing and orna- mental shading is thus often produced upon it. A good quality of steel, when its clean surface is washed with dilute nitric acid, should give a uniform tint. If it exhibits a fibrous, streaked, or mottled appearance, we may infer that it has been unequally carbonized, and is not the best. A drop of nitric acid leaves upon iron a whitish-green stain (oxide) ; it may thus be distinguished from steel. Steel may be made magnetic, and retains its magnetism permanently; but soft iron may be charged with magnetism, and deprived of it, at will. Upon this property of iron depends the action of the electro-magnetic telegraph. 239. Oxides of Iron.—Iron has a strong affinity for oxy- gen (74), and unites with it, forming oxides. When metallic Upon what does its value for cutting instruments depend ? What is said of pol- tiling and rusting? What effect has nitric acid upon steel ? What is the test of good steel? How may iron be distinguished from steel ? What is said of the magnetic propertiel of iron and steel ? 12 134 INORGANIC CHEMISTRY. iron is exposed to moist air, it soon becomes covered with a red crust, which is the sesquioxide of iron, Fe2 03; it is also called the peroxide. This oxide gradually absorbs water, turns of a yellowish color, and forms rust, which is hydrated peroxide of iron. These colors are well shown in bricks, which before burning are of a yellow color, owing to the hydrated peroxide of iron in the clay. Heat expels the water from the peroxide, which colors the bricks red. 240. These compounds of iron are the most abundant ox- ides in nature, existing in numerous stones, rocks, and soils, and are the cause of their red and yellow colors. Protoxide of iron, Fe 0, cannot be produced in a separate state, as it attracts oxygen and rapidly passes into the peroxide. In a state of combination it is widely diffused in nature, existing chiefly in those rocks having a greenish or dark tint. The iron in min- eral waters (chalybeate springs) usually rises to the surface in the form of a protoxide; after a brief exposure to the air more oxygen is absorbed, and a reddish scum is formed upon the surface, which gradually falls to the bottom of the current as a reddish sediment of insoluble peroxide. 241. When iron is heated in the smith's forge, and then beat on the anvil, a scale flies off which is of a black color, and when crushed gives a black powder: this is the black oxide, and is supposed to be a combination of the two other oxides, Fe 0 + Fe2 03. Gallic acid, Avith Fe2 Oa, gives a black precipitate (writing-ink); chlorine water and oxalic acid remove it. 242. Iron rusts rapidly in water containing air (oxygen), What gives to brick their yellow color before being burned ? Why are they red liter they are burned ? What is said of the abundance of these oxides ? Why cannot the protoxide ol Iron be easily obtained in a separate state? Of what is the reddish sediment in chalybeate springs composed ? What is black oxide of iron ? What is ink composed of? MANGANESE. 135 or the slightest trace of acidity. But in water which has been deprived of air by boiling, or rendered alkaline by lime, ammonia, potash, or soda, it is not rusted, but retains its polish for years.—(Brande) Galvanized iron is made by dipping iron, the surface of which has been cleaned, into a bath of melted zinc, and then into another of melted tin. The coating thus given p re vents rust. When cast-iron, as cannon, for ex- ample, has been long buried in the sea, it becomes lighter, and Ls changed into a substance resembling black-lead. The iron in this case has probably been dissolved by chlorine from the sea-salt. Cast-iron is rendered malleable by heating it for a considerable time with iron scales or oxide. It is thrown into the market under the name of malleable iron. MANGANESE. Symbol Mn, equivalent 27-67. 243. Manganese is a hard, brittle metal, of a grayish-white appearance, much like cast-iron. It never occurs pure in nature, but its oxides are found combined with many ores of iron, a metal which it resembles in many of its properties. Manganese is prepared by making its oxide into a paste with oil and lamp-black, and heating it to whiteness in a covered crucible. It rapidly oxidizes when exposed to the air, and is best preserved in naphtha. 244. It forms no less than seven different compounds with oxygen. Its oxides are diffused in small quantities through nearly all soils, and traces of them may be detected in the ashes of most plants. Protoxide of manganese is of a pale- green color, is a powerful base, giving rise to rose-colored How is galvanized iron made? What is said of iron long buried in the sea How is cast-iron rendered malleable ? What is manganese ? What metal does it resemble ? How is it prepared ? 136 INORGANIC CHEMISTRY. salts. The peroxide, or black oxide, Mn 02, is employed as a cheap method of procuring oxygen gas on a large scale, and for the manufacture of chlorine. It is also used under the name of glass-maker's soap, to destroy the green tinge given to glass by protoxide of iron, and to oxidize carbonaceous impurities. If added to glass in large quantiV.es, it gives it an amethyst or purple color. It has also beer reentry made use of in the manufacture of steel. ZINC. Symbol Zn, equivalent 32*52, 245. Zinc is a brilliant, bluish-white meta , sp. gr. 7, found abundantly in nature in the state of sulplnL.et (zinc blende), and as carbonate, or calamine. It exists is: immense quan- tities in the State of New Jersey. At common temperatures it is brittle, but when heated from 212° F. to 300° it may be roiled out into thin sheets, and retains its malleability when cold. At 400° it becomes again quite brittle, at 770° it melts, and when air has access to it, it takes fire, burning with a whitish-green flame. It soon tarnishes in moist air, forming a thin film of oxide, which resists change. Zinc ia extensively used for roofing, gas-pipes, gasometers, gutters, the lining of refrigerators, for preparing hydrogen, and in galvanic batteries. It is lighter than lead, cheaper than copper, and less liable than iron to be affected by oxidation. COPPER. (Latin, Cuprum) Symbol Cu, equivalent 31-66, sp. gr. 8-95. 246. Copper is a tough, malleable metal, of a red color, and often found native in masses cf great magnitude. It is What is said of the oxides of manganese ? What are their uses ? What ia zinc? What are its properties? Its uses? LEAD. 137 stiffened by hammering, and softened by heating and quench- ing in water; the reverse of the effect produced upon steel (237). In moderately dry air copper slowly acquires a superficial brown tarnish, consisting of a thin film of sub- oxide, Cu, 0. In damp air it acquires a green crust, from the formation of the carbonate. Vegetable acids dissolve copper in the cold state and not in the hot state. Sauces containing vinegar, and preserved fruits or jellies, should, therefore, not be allowed to remain in copper vessels, as the Baits produced are poisonous. Being little affected by the air, copper is better adapted for culinary and many other utensils than iron. LEAD. (Latin, Plumbum.) Symbol Pb, equivalent 103-56, sp. gr. 11-35. 247. This useful and familiar metal occurs under various mineral forms, but the most valuable one is galena, a sulphu- ret. Lead is a soft, blue metal, easily scratched by the nail, and leaving a stain when rubbed upon paper. It is highly malleable, but not very ductile. In the air a film of oxide is rapidly formed, which protects it from further corrosion. It melts at about 612°, and on the surface of the melted mass an oxide (dross) rapidly forms. It contracts upon solidify- ing, which renders it unfit for castings. Litharge is a pro- toxide of lead, PbO. Minium, or red-lead, consists of Pb, 04. White-lead is a carbonate of the protoxide of lead; it is the most important salt of lead, being extensively used as a white paint, and also to give body to other paints. What is copper? What effect has air upon it? What precautions should be rtwerved in the use of copper utensils? What is lead? Give itaproperties. What is litharge? Red-lead? White tad? 12* 138 INORGANIC CHEMISTRY. ANTIMONY. (Latin, Stibium.) Symbol Sb, equivalent 129-03. 248. Antimony occurs in nature united with sulphur. It is a brittle, bluish-white metal, and is but little affected by exposure to the air. The compounds of antimony are used in medicine, the most important being the tartrate of anti- mony and potash, or tartar emetic. ARSENIC. Symbol As, equivalent 75. 249. Arsenic is a brilliant, brittle, steel-gray metal, usually occurring united to iron and sulphur, from which it is sep- arated by heat. The coarse gray powder sold as fly-poison, under the name of cobalt, consists of metallic arsenic. Common arsenic, or arsenious acid, As 03, is formed by a union of the metal with oxygen. This is white arsenic, or ratsbane, the well-known poison. Its antidote is iron-rust (hydrated sesquioxide of iron), with which it combines, forming the insoluble arseniate of iron. If this is not at hand, milk, the whites of eggs, soap-suds, or sugar, should be swallowed; and the same observation may be applied to other cases of poisoning. Arsenious acid prevents the decay of organized substances, and it is therefore rubbed on the flesh side of the skins of animals that are to be preserved. When exposed to heat it volatilizes before melting, and its vapor has the odor of garlic. What are the properties and uses of antimony ? What is tartar emetic? What is arsenic ? What is said of it ? What is the antidote ? What is Ihi •Sect of common arsenic upon flesh ? iIXN—MERCURY. 139 TIN. (Latin, Stannum.) Symbol Sn, equivalent 58-82. 250. Tin is a brilliant, silver-white metal, which occurs most abundantly in Cornwall, England. It has been found in this country only at Jackson, N. H., in small quantities. It is softer than gold, slightly ductile, and very malleable, common tin-leaf or foil being often not more than y^ „ of an inch in thickness. It melts at 442°. When a bar of tin is bent it gives a peculiar crackling sound, due to the dis- turbance of its crystalline structure. It tarnishes but slightly upon exposure to the air, and is therefore very suit- able for cooking-vessels. Sheet-iron coated with tin consti- tutes the common tin-ware, MERCURY. (Latin, Hydrargyrum.) Symbol Hg, equivalent lOO'Ol. 251. Mercury is sometimes found in the metallic state, but is principally obtained from the bisulphuret (cinnabar), by distillation with lime or iron filings in iron retorts. It has a silvery-white color, a brilliant lustre, and is distin- guished from all other metals by being liquid at ordinary temperatures. It solidifies only when cooled to —40° F., and is then soft and malleable, but if reduced to a much lower temperature it becomes brittle. It boils at about 6C0°, and emits vapors at all temperatures above —40° F. Its sp. gr. is 13-568. 252. Mercury is extensively used in the construction of What ia the appearance of tin? What are its properties? What is common tin-ware ? Give an account of mercury. 14:0 INORGANIC CHEMISTRY. barometers, thermometers, mirrors, &c. When heated nearh to its boiling point, and exposed to the action of air, it ab- sorbs oxygen, and is converted into the peroxide of mercury (red oxide), which, when heated, evolves oxygen, and is re- duced to a metallic state. It was from this source that Priestley first obtained oxygen gas. Mercury combines with chlorine in two proportions, forming the protochloride of mercury, Hg CI (calomel), and the bichloride, Hg CI, (cor- rosive sublimate). The latter has a disagreeable, acrid, me- tallic taste, and is very poisonous. The proper antidote is white of egg, which forms with it an insoluble, inert com- pound. SILVER. (Latin, Argentum.) Symbol Ag, equivalent 108. 253. Silver occurs native, both uncombined and as a sul- phuret and chloride. It is the whitest of the metals, and has a bright, beautiful lustre. It is very malleable and duc- tile. It may be extended into leaves not exceeding r„ of an inch in thickness, and one grain may be drawn out into 400 feet of wire. It is used chiefly for coinage and silver plate. Silver does not tarnish in air or water. It forms compounds with oxygen, sulphur, chlorine, iodine, and bromine, all of which are darkened by the action of light, a property which is made use of in the daguerreotype process. PLATINUM. Symbol Pt, equivalent 98'68, 254. This very valuable metal is of a whitish-gray color, somewhat resembling silver. When pure, it scarcely yields For what is mercury used ? What is the composition of calomel ? What ia thl composition of corrosive sublimate ? Describe silver. What is said of its compounds ? What are the qualities of platinum ? GOLD—ALLOYS. 141 in malleability to gold and silver. It is very ductile, and takes a good polish. But the qualities which render it so useful, and in some cases indispensable to the chemist, are its extreme difficulty of fusion, being unaffected by any fur- nace heat, and the perfect manner with which it resists the action of almost all acids. It is acted on by chlorine and aqua regia, but less easily than gold, and is not affected by air. Platinum is about half as valuable as gold. Sp. gr. 22'5. GOLD. (Latin, Aurum.) Symbol Au, equivalent 98'33. 255. This is one of the most widely diffused of the metals, being found native in every country, generally in the form of minute grains, though sometimes in masses weighmg several pounds. It has a brilliant yellow color and great density. It is so very malleable that it may be extended into leaves yraVotf °f an mcn m thickness, and so ductile that a single grain may be drawn into 500 feet of wire. It does not tarnish or oxidize when exposed to the air or heat, is af- fected by nr single acid, and dissolved only by aqua regia (124). Its specific gravity is 19"2. METALS COMBINED WITH EACH OTHER—ALLOYS. 25G. Metals combine with metals to form alloys—an im- portant class of bodies, as each compound thus produced may be looked upon, for all practical purposes, as a new metal. 257. Brass is an alloy of copper and zinc : four parts of the former to three of the latter. When the proportion of tine is increased we have pinchbeck, or Dutch gold. What is said of gold? What are its properties? What are alloys ? How may they be considered ? What Ubrass? Pinchbeck? 142 INORGANIC CHEMISTRY. 258. German silver is an alloy of copper, zinc, and nickel, the finer kinds containing most nickel. Bronze consists of 90 parts of copper to 10 of tin ; gun-metal, 92 copper to 8 of tin ; bell-metal and gong-metal of 80 parts of copper to 20 of tin. Britannia consists of about 100 parts of tin, 8 of an- timony, 2 of bismuth, and 2 of copper. 259. The speculum of Lord Rosse's celebrated telescope is composed of 126-4 of copper to 58-9 of tin. 260. Type-metal is an alloy of 3 parts of lead and 1 of antimony. Pewter is composed of tin, with a little antimony, copper, and bismuth. The inferior kinds contain a good deal of lead. 261. Alloys which contain mercury are called amalgams. An amalgam of tin is used for silvering the backs of mirrors; and an amalgam of tin and zinc for exciting electrical ma- chines. Gold and silver coin is alloyed with from fe t° fe of copper, by which its hardness and wearing quality is greatly improved. SALTS. 262. Salts are combinations of acids with bases (49). They are a very numerous class of bodies. We can here notice but few of them, and those very briefly. The common idea of a salt is that it must have a saline taste, like ordinary kitchen salt, and dissolve in water; but this notion is erro- neous, as many salts have no taste at all, and are insoluble in any quantity of water, either cold or hot. There are two ways of classifying or grouping the salts—either by placing What is German silver ? Bell-metal ? Bronze ? Britannia ? Type-metal ? Pewter ? What are amalgams ? What is said of coin ? What is a salt? What is the common idea of a salt? How is this wrong 1 Bow are the salts classified? SALTS—SULPHATE OF LIME. 143 together those which have a common acid, or those which have a common base. I have adopted the arrangement of Dr. Gregory, and classed together those derived from a common acid. The salts contain variable proportions of water, which are represented upon the Chart by the usual symbolic letters (H 0), instead of diagrams. SULPHATES. PROTOSULPHATE OF IRON. (Copperas, Green Vitriol.) Fe 0, S 03 + 7 H 0.-(Silliman.) 263. This salt, composed of sulphuric acid and protoxide of iron, is largely manufactured at Stafford, Vt., by the de- composition of iron pyrites, which furnishes, by oxidation, both the acid and the base (see Chart). It is used for dye- ing dark colors, for making ink, and in medicine as a tonic in nervous diseases, and where the blood is supposed to be deficient in iron. It often exists in soils to a pernicious ex- tent, but is decomposed by lime; gypsum or plaster being formed. SULPHATE OF LIME. (Plaster of Paris, Gypsum., Alabaster) Ca 0, S 0 3 + 2 H 0 = 86. Sp. gr. 2*.-(Graham.) 2G4. This salt is easily made artifieially, by dropping sul- phuric acid upon lime. It occurs in many parts of the world, forming extensive rocky beds. It is so soft as to be scratched with the nail. The white varieties are turned in lathes, and worked with edge tools into various ornamental What is the composition of protosulphate of iron ? For what is it used ? \ hat is the composition of sulphate of lime ? What are its common names? ,'T " " found? Wnat ia alabaster? What property adapts it for taking cu*t*? What is stucco-work ? ^^ 144 INORGANIC CHEMISTRY. forms, constituting the common alabaster. When powdered gypsum is heated to nearly 300° F., it parts with its water of crystallization. If now it is made into a liquid paste with water, it again combines with it, and speedily hardens or sets, resuming its stony aspect. Owing to this property, it is used to take impressions and make casts, by being run into hollow moulds. It is also used in architecture for making orna- mental figures and designs upon walls and ceilings, called stucco-work. 265. Ground gypsum is of extensive use in agriculture. It is supposed to act by furnishing lime and sulphur to plants, and by absorbing carbonate of ammonia from the air and rain-water. It is said to fix the ammonia, that is, it is de- composed, forming sulphate of ammonia and carbonate of lime. It dissolves in 468 times its weight of water, and is a constituent of most springs, the water of which it renders hard (96). SULPHATE OF MAGNESIA. (Epsom Salts.) Mg0, S Oa + 7 H0— (Graham) 266. This well-known salt is made by dissolving magnesian limestone or serpentine rock in strong sulphuric acid. It exists in some natural waters, as in the Epsom springs, whence its name. It is used in medicine as an aperient, and as an antidote to the salts of lead, which are poisonous. SULPHATE OF SODA. (Glauber'«Salt) Na 0, S Os -f 10 H 0 = 71 + 90.—(Graham) 267. This salt is made by the action of sulphuric acid upon soda or common salt. It was introduced into medicine by What is said of the use of gypsum in agriculture? Give the composition and uses of Epsom salts. Of Glauber's salt. SALTS—THE CARBONATES. 145 Glauber, and is therefore called Glauber's salt. Its chief use is as a cathartic for horses and cattle. SULPHATE OF ALUMINA AND POTASH. (Alum) KO SO3 + AI2O3 3S03 + 24HO. 268. Alum is a double salt, consisting of two bases united to one acid. It has a sweetish, astringent taste, and is dis- solved in 18 times its weight of cold water, and in its weight of boiling water.—(Fownes.) It is extensively used in dyeing, the alumina it contains being the active agent (218). It is also used in tanning, and in clarifying liquors, &c. The potash of alum may be replaced by soda (soda alum) and ammonia (ammonia alum), without altering the form of its crystals. THE CARBONATES. 269. These are very abundant in nature. Carbonic acid, being always present in the air and in natural waters, is ever ready to seize upon free bases. The union of carbonic acid in salts is very weak, owing to its elastic property, by which it constantly tends to escape into the condition of a gas. It is expelled from its combinations by most other acids, and always with effervescence, a property which distinguishes the carbonates. What are the properties of alum ? Why aro carbonates so abundant? Why are they easily decomposed? Ho^» ire they distinguished? 13 146 INORGANIC CHEMISTRT. CARBONATE OF SODA. Na 0, C Oa +10 H 0 = 53 + 90.—(Graham.) 270. The form of the soda of commerce is soda-ash. It was formerly procured by leaching the ashes of marine plants. It is now chiefly made from sea-salt, by the action of sulphuric acid; sulphate of soda is formed, which is con- verted into the carbonate by means of lime and sawdust, under the influence of heat. The discovery of this process by Leblanc, of France, at the close of the last century, pro- duced immense results upon the manufactures and commerce of the world. (See Liebig's Letters on Chemistry.) Car- bonate of soda, being both cheaper and purer than ordi- nary potash, is largely employed in the manufacture of soap and glass. It is also much used by washerwomen as a detergent, and to render hard water soft. Soda replaces potash in the ashes of plants grown near the sea. 271. Bicarbonate of soda is formed by passing a stream of carbonic acid through a saturated solution of the carbon- ate of soda, which unites with a second equivalent of the acid. It forms the effervescing soda-powders, and is used in bread-making instead of yeast, to render the dough light and spongy. CARBONATE OF POTASH. KOCOa = 69. 272. This is a highly alkaline and very soluble salt. It is prepared on a large scale by leaching wood-ashes, and ,Give the composition of carbonate of soda. Howls it obtained ? What «i» its properties ? What are its uses ? How is the bicarbonate formed ? For what is it used ? What is the equivalent of carbonate of potash ? How is it prepared ? WhU is said of the ashes of different plants ? SALTS—THE CARBONATES. 147 evaporating the solution in hon pots; the product is hence called potash. When this crude potash is heated to red- ness, its carbonaceous impurities burn away, and pearlash is formed. Potash, or pearlash, therefore, represents the readily soluble portion of wood-ashes, and consists chiefly of carbonate of potash, with small amounts of carbonate of soda and common salt. Ashes are said usually to yield about fe their weight of potash ( Watson); but different plants, and even different parts of the same plant, yield ashes of a very different composition. Thus the ashes from one ton of pine wood give of pure potash, 0'90 lbs.; beech, 2-90 lbs.; oak, 3-6 lbs.; common wheat straw, 7'80 lbs.; dry straw of wheat before earing, 34 lbs.; bean-stalks, 40 lbs.; stalks of Indian corn, 35 lbs.; thistles in full growth, 70 lbs.; wormwood, 146 lbs.—(Ure.) 273. This explains at once the great value of potash in agriculture. It is carried away by crops, and must be re- stored to the soil, or the land will be exhausted. Certain plants, as Indian corn, potatoes, the grape-vine, lS.-(Brande.) 289. These salts are of no interest, being used only in the daguerreotype process, to decompose the salts of silver upon the surface of the plates. How aro phosphates apphed to the soil ? discovery has recently been made ? What is said of the hypo-eulphitea ? How are the bones prepared ? Wnat 154 INORGANIC CHEMISTRT. OF THE HALOID SALTS. 290. The compounds that we have been considering be- long to the class of oxygen acid salts. There is another group called the haloid salts, from their resemblance to common salt (chloride of sodium). They consist of simple bodies, as chlorine, fluorine, &c, united directly with the metals. CHLORIDE OF SODIUM. (Common salt, Sea-salt, Rock-salt, Kitchen-salt) Na CI = 58-47, sp.gr. 2-5. 291. This well-known substance crystallizes in the form of cubes, which dissolve in 2-7 times their weight of water, alike hot or cold. Salt is obtained either from the earth, in the form of blocks (rock-salt); or, if it occurs impure, by digging holes in the salt-beds, and filling them with water, which, when it will dissolve no more, is pumped out and evaporated in shallow pans. It is also largely produced from brine springs, and by the evaporation of sea-water; the latter, however, has a bitter taste, from the salts of magnesia, which also exist in the sea. Sea-water contains about one-thirtieth its weight of salt (about 5 oz. to the gallon). Estimating the ocean at an average depth of two miles (Lyell), the salt it holds in solution, if separated, would form a solid stratum 140 feet thick. 292. Salt exists in plants in small quantities, and some- times promotes their growth by being applied to the soil. It is also an ingredient of animal bodies; it exists in the blood, What of the haloid salts ? How is common salt obtained ? What amount of salt is contained in sea-waie SALTS—CHLORIDES. 155 and is eaten with relish by both man and beast. It has been calculated that the average annual consumption of salt by an adult amounts to sixteen pounds, or about five ounces per week.—(Pereira) Salt is used for packing and preserv- ing meat; it prevents putrefaction by absorbing water from the flesh (504). CHLORIDE OF CALCIUM Ca CI = 55-5. 293. This is a substance having a strong affinity for water. Chemists use it for drying gases. 294. Chlorine combines with iron, forming two com- pounds, the protochloride, Fe CI, and the sesquichloride, or perchloride, Fe2 Cl3, which are seen to correspond with the axides of iron. FLUORIDE OF CALCIUM (Fluor Spar.) CaFl = S9. 295. This salt is found in minute quantity in the teeth and bones of animals.—(Berzelius.) The native fluor spar is used as a source of hydrofluoric acid. It is so soft as to be readily cut into various forms; and from its beautiful variety of colors it is employed for ornamental articles. Is salt useful to plants ? How much salt is consumed by an adult annually ? What is chloride of calcium ? What is said of the compounds of chlorine and iron I What of fluoride of calcium ? 156 INORGANIC CHEMISTRY. MINERALS. QUARTZ. SiOs. 296. Quartz is silica crystallized. When broken down mto fine grains, it forms sand, and this, consolidated or ce- mented with oxides of iron, constitutes sandstones. The United States Capitol is built of sandstone; it is called free- stone, because it is easily wrought. When silica is fused with bases it unites with them, playing the part of an acid (223), and forming salts—the silicates. Most rock formations consist of minerals which are composed of these silicates. Their constitution is represented upon the Chart in the same manner as the other salts: figures placed above the diagrams signify that the compound atoms with which they are connected are to be multiplied by them. Thus feldspar is seen to contain three atoms of alumina and three of silica. TALC. MgO,SiOs. 297. Talc is a silicate of magnesia. French chalk and soapstone are varieties of talc, and are so soft as to be worked ■with the same tools as wood. Soapstone does not fracture in the fire, and is used as lining for fireplaces, grates, U ? ACTION OF SOLAR LIGHT. 169 balanced in the economy of nature, that the constitution of the atmosphere remains unchanged from age to age. How wonderful, that a few gases condensed from the invisible air, translated from the systems of plants to those of animals, and then restored again to the air, should give rise to all the grand and awful phenomena of life and death upon this planet! 320. Light controls Vegetable Growth.—The motive power of the vegetable machine is the light of the sun. The chem- ical changes which take place in the leaf are brought about by the action of this force. None can fail to have observed that light exerts a most favorable influence upon vegetation. Plants made to grow in the dark are white, watery, and sickly. Their products are diseased, and often poisonous, and they cannot mature or bear seeds. If but a single beam of light is admitted, the leaves and branches turn and bend towards it with eagerness. Even in the shade they are feeble and unhealthy; but when exposed to sunlight, they speedily acquire a bright green tint, and become thrifty and vigorous. A plant was discovered in a mine, which, from its singular appearance, was supposed to be a new variety. It was taken up into the light, when in a few days it turned out to be common tansy. 330. The nature of the compounds produced in leaves depends upon the quantity or intensity of the light. Tropi- cal plants secrete powerful medicinal, aromatic, and coloring substances which they cannot be made to yield in the less brilliant light of higher latitudes, although the temperature is maintained artificially at the point to which they have been h/th'ehl^?emeCn9ffChanSe3i"P,antS? What^».eaPPealanceofplan^roTn 51i£ unoT^. ZTthe "hade' are they viS°r0U9 ? Wh J, is the effect SSl^n'^"jat have grown in the dark? Give an example. hat uaaid of tropical plants? How ia this fact applied ? 15 170 VEGETABLE CHEMISTRY. accustomed. This circumstance is taken iulvant;x'e of in cultivating vegetables for the table ; for many, if raised un- der diminished light, may be used for food which are natu- rally unpleasant, and quite obnoxious to the taste. Thus celery, which is naturally rank, tough, and stringy, if its stems are blanched or made to grow in the absence of light, becomes esculent and palatable. The sides of fruits exposed to the sunlight are of a ruddy color, and of a sweeter taste than those parts that are shaded; while some leaves are acid in the morning, tasteless at noon, and bitter at night. 331. Compound Nature of Light.—A ray of light comino from the sun produces a threefold effect—an ifiuminating, a heating, and a chemical effect. It is therefore said to be composed of a luminous ray which impresses the eye, a calo- rific ray which affects the thermometer, and a chemical ray which acts neither upon the thermometer nor the eye, but produces chemical changes, as upon the plate in the daguer- reotype process. By passing a ray of light through a prism (see Natural Philosophy), it is decomposed into a series ol seven colors—violet, indigo, blue, green, yellow, orange, and red—which are thrown in this order upon an oblong space called the spectrum. If passed through a second prism, these rays are united again, and form simple white light. Dr. Draper has determined that the ethereal force which pro- duces changes among chemical atous, controlling the decom- positions and combinations which take place in the leaf, re- sides in the yellow region of the spectrum. 332. Mode in which Light acts upon the Leaves.—The science of optics teaches us that light consists of vibratory, Does a ray of light contain any other than the luminous principle? What are they ? What is the effect of passing light through a prism ? In what part of tin spectrum does the force affecting chemical atoms reside ? Of what does light consist ? To what are the different colors owing 1 How maj r landscape or a bunch of flowers be seen to bear an analogy to a plecs of muiic. ACTION OF SOLAR LIGHT. 171 wave-like movements or undulations in an ethereal medium which exists throughout all space, just as sound is the result of "undulations propagated by vibrating bodies through the air; and as the different tones of sound are occasioned by variations in the size and rapidity of the aerial undulations which fall upon the ear, so the different colors are also due to diversity in the magnitude of the ethereal waves which impress the eye. And to carry the analogy still further, as a melodious piece of music may be regarded as the result of innumerable air-vibrations of various degrees of intensity, skilfully arranged by the composer to produce a harmonious impression upon the ear; so also a bunch of flowers, or a beautiful landscape, must be looked upon as produced by countless myriads of luminiferous wavelets, originating in the sun, and sent across the abyss of space to act upon chemical atoms, and arrange them into combinations of most exquisite symmetry and beauty. 333. Wonderful Nature of'the Ethereal Action.— " A forest- tree, from its magnitude, rising perhaps a hundred feet from the ground, and spreading its branches over hundreds of square yards, may impress us with a sense of sublimity. A section of its stem might assure us that it had lived for a thousand years, and its total weight could only be expressed by tons. An object like this may indeed call forth our ad- miration, but that admiration is expanded into astonishment when we consider minutely the circumstances which have been involved in producing the result. If we conceive a single second of time, the beat of a pendulum, divided into a milhon of equal parts, and each one of these inconceivably bnef periods divided again into a million of other equal parts, awave^llowlight, during one of the last small intervals, fcrSJiTT°f the BUbJeC' ad^«^8ublimityVthe contemplation^ 172 VEGETABLE CHEMISTRY. has vibrated 535 times; and now that yellow light is the agent which has been mainly involved in building up the parts of the tree, in fabricating its various structures, and during every one of a thousand summers, from sunrise to 6unset, the busy rays have been carrying on their operation. Who, then, can conceive, when in the billionth of a second such enormous numbers of movements are accomplished, how many have been spent in erecting an aged forest oak! Who also can conceive the total amount of force employed, from century to century, in arranging the vegetation of the surface of the globe !" 334. Relation of the Sun to Vegetation.—" Look also at the sun! Even the magnificent views of the astronomer are here surpassed, and that gigantic star no longer appears as a centre or focus of mere mechanical force, who draws up comets from the abysses of space, and with an inexpressible velocity precipitates them headlong back again—who afar off watches the revolving planet glide on its elliptic path, or makes the tide ebb and flow in the seas ; but he appears as the fountain of light and of life, who spreads in the torrid zone a luxuriant vegetation, and in autumn ripens the har- vests for our use—whose many-colored rays, during the re- volving seasons, are occupied in fashioning and forming food for us, or evaporating pure water from the sea, or condensing clouds in the sky, which give an air of change and life to those regions of eternal repose."—(Draper.) 335. The Sun's Rays a Source of Incalculable Power.— All force is estimated by the effect it is capable of producing. The power of the solar beams may thus be definitely meas- ured, and it appears almost incredible. They decompose lu what relationships does the sun appear ? What examples are given of the chemical power of the sun'g rays ? Can forca be created or destroyed ? SOLAR LIGHT A SOURCE OF POWER. 173 carbonic acid at common temperatures—an effect which all the resources of the chemist cannot enable him to imitate. It has been seen (84) that the affinity of oxygen for carbon and hydrogen, the power with which they unite, is very great. The solar beams, in separating them, must neces- sarily expend an equal amount of force. It is in the chem- ical union of oxygen with carbon and hydrogen that the muscular power of animals arises. The power of the steam- engine is also due to the combination of atmospheric oxygen with the carbon and hydrogen of wood and coal. But be- fore these elements can unite for the production of power, an equal quantity of force is exerted by the sun's light to separate and arrange them. In nature, it is no more pos- sible to create or destroy force than matter. It passes from state to state ; but its total amount, when we take the uni- verse into the estimate, is unchangeable. Power, which emanated from the sun, and was expended in the formation of vegetable structures, where it remained for a time latent or hidden, reappears through the admirable contrivance of the steam-engine, or the thousand-fold more wonderful mechanism of the human body. 336. Sourc; of the Power obtained from Coal.—The great deposits of coal which are scattered over various parts of the earth consist of the carbonized remains of a vegetation which flourished long before man appeared upon the globe, perhaps thousands of centuries ago. The trees of that period were vastly larger than those now upon the earth, and must have been condensed from an atmosphere richer in carbonic acid than ours, and perhaps by a more brilliant sun. And yet this coal, having slumbered in its ancient beds until layer after layer of rocks has been formed above it, now What is said about the great deposits of coal ? Whence was the coal originally derived ? Whence canv? the power by which it was condensed from the air ? 15* 174 VEGETABLE CHEMISTRY. comes forth as from a reservoir of power and beneficence, to surrender again its ethereal agents, light and heat, for the use of man, and return as carbonic acid to the air from whence it came. The power which we now derive from it was expended by the sun, millions of years ago, in separating it from the carbonic acid of the ancient atmosphere. 337. The Solar Rays are the Antagonists of Oxygen.—- We have seen that oxygen gas (82) is the foe of organization and life; its affinity for the other organic elements being such, that it perpetually rends them from their combinations, thus inducing constant decay and dissolution. We now per- ceive that the solar rays are the great antagonists of oxygen. Under their influence, the mineral elements are changed to living forms. Under the influence of oxygen, they are re- turned again to the inorganic world. If oxygen dilapidates, they renovate; if that decomposes and breaks down, they construct and build up ; if that is seen in the falling leaf of autumn, they are proclaimed in the exuberant foliage and blossoms of spring. If oxygen is the mainspring of destruc- tion upon the globe—wasting, burning, consuming, and hastening the dissolution of all things—the solar rays con- stitute the mighty force of counteraction. They reunite the dissevered elements, substitute development for decay, call forth a glory from desolation, and life and beauty from the very bosom of death. 338. Nature of the Plant—We may therefore regard the green, growing plant as the grand factory of organic nature. It is a machine driven by the power of solar light, whose office is to form and construct the compounds which are to be consumed by animals, for the production of force, loco- Wha/, is said of the relations of oxygen and the solar rays ? How may we look upon the growing plant ? What two kinds of compounds ara fcahioned in plants ? WOODY FIBRE. 175 motion, and sensation. It obtains carbon from carbonic acid, hydrogen from water, nitrogen from ammonia or nitric acid, and various earthy and alkaline salts from the soil. With these elementary or mineral substances it fabricates organic compounds, which are deposited in its tissues. We pass now to an examination of some of the more important substances produced by plants. PRODUCTS OF VEGETABLE GROWTH. WOODY FIBRE. (Lignin) Cw Hio do. 339. Structure of Wood.—The substance of wood which abounds in the trunk and branches of trees, giving them firmness and strength, is the most abundant product of vegetation. Besides forming the bulk of all trees, it also exists in the straw and stalks of grain, in the membrane which envelops the kernel (bran), in the husk and skin of seeds, and in the rinds, cores, and stones of fruit. It con- sists of slender fibres or tubes, closely packed together. When first formed, these tubes are hollow, and serve to convey the sap or vegetable juices; but in the heart-wood of trees (duramen) they become filled up and consolidated, the circulation of fluids taking place in the white external sap-wood (alburnum). 340. In most trees of temperate climates these woody tubes are deposited in external layers or rings, one every year; so that by cutting the trunk across, and counting the What is the most abundant product of vegetables? Where is it found? Oi what does it consist? What purposes do these tubes serve when first formed? What is the duramen ? What is the alburnum ? How may we determine the age of a tree ? What trees have these layers most dense ? Upon what does the hardness of wood depend ? R 176 VEGETABLE CHEMISTRY. rings, we can determine the age of the tree. Those tree* which grow on a poor soil, in high situations, exposed to the wind, have these layers of fibres more dense and closely packed together than if grown in a protected spot, or upon a moist, rich soil. Upon the density with which the fibres are imbedded together depends the property which different kinds of wood possess, of hardness or softness, by which they are worked with ease or difficulty. 341. Value of Wood as Fuel.—Equal weights of differ- ent kinds of wood give out the same amount of heat in burning if they are equally dry. But wood varies greatly in the amount of moisture it contains, and upon this circum- stance mainly depends the economy of different samples for fuel. The proportion of water contained in wood may be ascertained by drying the shavings in an oven at 140°, and determining the amount of loss by weighing. Green wood contains from 20 to 50 per cent, of water (sap); birch has 30, oak 35, beach and pine 39, elm 44, and poplar 50 per cent. Wood dried in the air (seasoned) for a year, still contains from 20 to 25 per cent, of water. If dried at a strong heat (kiln-dried), it yet retains 10 per cent, of moist- ure, and begins to carbonize (char) before parting with it all. Thoroughly kiln-dried wood afterwards absorbs from the air 10 or 12 per cent, of water. 342. The presence of water diminishes the value of wood for fuel, by absorbing and carrying off the heat during its conversion into steam, and by causing slow and imperfect combustion. One pound of artificially dried wood will raise Upon what circumstance does the economy of different kinds of wood for fuel depend? How is the proportion of water contained in wood ascertained? Give the per centage in different specimens of green wood. How much water does eeasor»3d wood contain ? When kiln-dried, how much ? How does water diminish the value of wood for fuel ? What amount of heal •Fill a pound of dried wood produce ? How much oxygen will it consume ? WOODY FIBRE. 177 35 pounds of water from the freezing to the boiling point, and consume the oxygen from 148 cubic feet of air. 343. The Chemical Properties of Fuel adapted to the Wants of Man.—" Next to his food, man's most pressing want, even in the rudest state of society, is protection against cold. He employs fire for this purpose ; that is to say, he takes means for developing violent chemical action between the elements of certain combustible substances and the oxygen of the air, and of availing himself of the heat thus disengaged. But does one man in a thousand, while enjoying the warmth of his fire, reflect for a single moment upon the combination of circumstances to which his pleasure is due ? Does he reflect on the very peculiar nature of the fuel provided for him in the forest or the field, or in the black bituminous coal, the relic of a vegetation now passed away ? Does he pause for a moment to consider that the character- istic components of his blazing log, the carbon and the hy- drogen, are the only elementary substances in existence fit- ted for the purpose; the only bodies, whose products of combustion are of such a kind as to pass off in invisible and odorless forms, to mingle in the air, and eventually to return again into the very same condition as that which has just been destroyed ? It is most wonderful, when we reflect on these things, to observe how much our physical happiness depends upon what some will call accidental circumstances. Is it by accident that carbonic acid is odorless and harmless unless in considerable quantity, while the oxides of all other combustible substances capable of existing in a gaseous state are pungent and irritating, and insufferable in the smallest doses ?"—(Fownes) 344. Preservation of Wood from Decay.—The decay ol wood is caused by the action of moisture and oxygen upon How are wood and coal especially adapted for fuel? 178 VEGETABLE CHEMISTRY. its outer surface and within its pores, and also by albumen (374), a putrefiable substance contained within its sap. It is therefore preserved by covering it with a coating of paint or other preparation, which protects it from air and moisture, and also by expelling the sap and filling its pores with un- changeable substances, as solutions of mineral salt. Kyan- ized wood is such as has been thus impregnated with cor- rosive sublimate (bichloride of mercury), which precipitates the albumen, rendering it insoluble and harmless. 345. Boucherie, of France, impregnated wood with com- mon salt and pyrolignite of iron, by felling the trees in sum- mer, and immersing the lower ends of their trunks in the saline solution; as the water evaporated from the foliage the liquid was drawn up into the trunk, and at length made its appearance in the leaves. He found that green wood required about one-fortieth its weight of the preserving (an- tiseptic) liquid, and became harder, tougher, more durable, and less combustible than by natural seasoning. Steaming wood, or soaking it in water when newly cut, tends to pre- serve it by dissolving out its sap. 346. Cloth and paper are composed of wood. Linen and cotton consist of woody fibre nearly pure. Flax contains a gray coloring matter, which is removed by bleaching and boiling in ley; it is then perfectly white. The fibres of cotton are white when they come from the pod (except the yellow nankeen cotton), and the goods are bleached only to remove the soil which they have acquired by manufacturing. Paper, as well as the clothing we wear, is therefore com- posed of woody fibre, being made chiefly from waste cotton What causes the decay of wood ? How does paint preserve it ? What is kyan> ized wood? Describe Boucherie's method of preparing wood for preservation. What are linen and cotton composed of? What is said of flax? Of cotton Ibres ? Of paper ? Describe the process of paper-making. WOODY FIBRE. 179 and linen rags; for the coarser kinds, old ropes and cut straw are used. In this process, the rags, after being bleached by chlorme, are boiled in alkali, and reduced to pulp by means of a beating-engine. The pulp, formed into sheets and dried, is blotting paper. To convert it into writ- ing paper it is soaked in a preparation of glue and alum, or of rosin and alumina (sized), and then pressed between hot iron plates. 347. Wood may be made explosive—Gun-cotton. When raw cotton is steeped for a few minutes in equal quantities of nitric and sulphuric acids, and then carefully washed with water and dried, it becomes explosive, like gunpowder, and forms gun-cotton. Flax, tow, and even purified sawdust, may also be made similarly explosive. The change that takes place consists in separating the elements of water from the woody fibre by sulphuric acid, and their replacement by nitric acid, which is also a large element of gunpowder. The explosive power of gun-cotton is eight times greater than that of gunpowder (Silliman), but it is very dangerous, being liable to inflame at low temperatures. It ignites at 350° F. 348. Collodion is a solution of gun-cotton in ether. It is applied to wounds; the ether evaporates, leaving a film which excludes the air and favors healing. 349. Composition of Pure Wood.—Pure woody fibre is white, tasteless, insoluble in water and alcohol, and has a specific gravity of 1 -5 ; hence all wood, when deprived of the air within its pores, sinks in water. It belongs to a class of bodies called the ternary group—starch, sugar, How is gun-cotton formed ? What change takes place ? How does It compare with gunpowder in explosive power ? Why is it dangerous? What is coUodion ? For what is it used ? Whatarethe properties of pure wood? To what class of bodies does it belong' for what are they remarkable ? How do they differ ? 180 VEGETABLE CHEMISTRY. and gum (see Chart)—which are remarkable for containing an equal number of oxygen and hydrogen atoms ; their composition is therefore simply charcoal and water (hydrate of carbon). They all contain the same quantity of carbon, differing only in the proportions of water; they are thus readily transformed one into another, and may all be pro- duced by plants out of simple carbonic acid and water. The formula for woody fibre, obtained from Dr. Prout's analy- sis, gives C12 H8 08. Cellulose, a substance associated with woody fibre, has the composition C12 H]0 O]0. We have no unobjectionable data from which the atomic equiv- alent of lignin can be inferred.—(Brande.) 350. Heat changes Woody Fibre into Starch.—When fine sawdust is boiled in water to separate every thing soluble, and then dried and several times heated in an oven, it be- comes hard and crisp, and may be ground into a fine meal, which has a taste and smell similar to that of ground wheat; it ferments when made into a paste with yeast, and produces a uniform spongy, nutritious bread.—(Autenrieth) 351. Wood may be converted into Sugar and Starch.— Wood, when dipped in strong sulphuric acid, is charred; that is, the acid attracts from it the elements of water, while the carbon remains. If shreds of old cotton or linen, which con- sist of nearly pure woody fibre, are boiled for several hours in diluted sulphuric acid, they are converted first into gum, ana then into grape-sugar (368). By this process the rags will yield more than their weight of crystallizable sugar. Woody fibre is also converted into starch, by boiling with caustic potash. 352. Distillation of Wood.—When wood is burned in How may woody fibre be converted into starch ? How may it be changed to sugar? What is the result of the distillation of wood ? WOODY FIBRE. 181 close vessels (destructive distillation), or with but a partial access of air, it gives rise to a large number of compounds, depending upon the nature of the various substances con- tained in its tissue. Among.these are carbon, defiant gas, and ammonia, which have already been noticed, and we can glance at but one or two others of the most important. 353. Pyroligneous Acid is <& crude vinegar distilled from wood: nearly half a pound may be produced from a pound of beech-wood. It is a brown, acid liquid, having a strong, smoky taste and odor. It is cheap, and contains acetic acid. It is extensively employed to manufacture salts, the acetates used by dyers as mordants. 354. Creosote is a brown oily liquid, obtained from wood- tar and pyroligneous acid. It has a powerful, smoky, burn- ing taste, corrodes the skin, and mixed with alcohol and oil of cloves, it is used as a remedy for toothache. The term creosote means flesh-preserver. Meat steeped for a few hours in a solution of 1 part creosote to 100 water remains sweet, and will not putrefy. It preserves the flesh by coagulating its albumen (374). The same effect is produced by vapor of creosote which exists in smoke. Meat and fish, exposed to the smoke of green wood, undergo a like change. It is this vapor in smoke which renders it so irritating to the eyes, causing the flow of tears. 355. Slow Decay of Wood.—When wood, straw, or leaves are exposed to the air, they turn of a brown or black color, and undergo a slow burning, or decay (eremacausis). The change that, here occurs is the same as in active combustion, the only difference being, that in the first case it takes years, What is pyroligneous acid ? For what is it used? What is the meaning of the word creosote? How does it preserve flesh ? Doei it exist in smoke ? What is the difference between slow decay and active combustion? To what il Ifce dark color of rich soils owing? 182 VEGETABLE CHEMISTRY. while in the latter it is done in mmutes. The hydrogen a oxidized first (76), and most rapidly; the residue, of course, contains an increased and constantly increasing proportion of carbon, which gives it a darker color. It is thus that veg- etable matter in different stages of decomposition (humus, ulmine, geine, vegetable mould, &c.) impart a black, rich ap- pearance to soils. 356. Carbonaceous matter constantly accumulates in the soil of forests, which proves that it must be derived from the atmosphere. It is removed from soils by cropping, and may be restored by adding vegetable and animal manures, by ploughing in fresh plants (green-manuring), or by cultiva- ting those which leave many roots in the earth. A crop of clover was found to leave in the soil several thousand pounds weight of roots, while wheat did not leave \ this quantity. 357. Mineral Coal derived from Vegetation.—Mineral coal was formed in the earth from an ancient vegetation, by a kind of smouldering decomposition, such as moist vegeta- ble matters, straw, and manure undergo when placed in compost heaps. The trees were collected in basins by floods and covered with mud, where they were gradually carbonized. In anthracite coal, which consists of nearly pure carbon, this decay has reached its last stage; in the bituminous coal it is less advanced, much hydrogen siill remaining; the bituminous variety, therefore, burns with flame, while anthracite does not. How is it shown to be derived from the atmosphere ? When removed by crop- ping, how may it be restored ? How was mineral coal formed ? What is the difference between anthracite ana bituminous coal ? STARCH. 183 STARCH. (Fecula) C12 Hio Oio. 358. Proportion of Starch in different Grains.—Starch is an abundant vegetable product. It is deposited in the grains, seeds, roots, stems, and fruits of many plants. Po- tatoes (different varieties) contain from 10 to 20 per cent, of starch; buckwheat, 52 per cent.; barley-meal, 67; oatmeal, 59 ; rye flour, 61; wheat flour, 56 to 72 ; Indian corn, 80 ; rice, 82 ; peas, 32 ; and beans, 35 per cent.—(Pereira) 359. Appearance of Starch Grains.—Pure starch is a snow-white powder of a glistening aspect, which makes a crackling noise when pressed with the finger. It is composed of trans- parent rounded grains, the size of which varies in different plants from Fig. 19. Wheat. freaetfiW 3"0 0 to inch in diam- >vP0Q eter ; being largest in the potato, and smallest in wheat. Examined by a microscope, the whole surface of the grain appears covered by parallel rings, which seem depressed or cut Beans. egar to give it strength. The presence of these substancei may be ascertained by saturating the acid with an alkali; the acrid taste of the substances will then become sensible. ETHER. 391. Organic Radicals.—When equal weights of oil of vitriol and alcohol are heated in a retort, a vapor passes over, which may be condensed into a colorless, limpid fluid, known as ether, or sulphuric ether, because sulphuric acid is employed to obtain it. The composition is C4 H5 0 ; differing from alcohol in the absence of the elements of one atom of water, which has been taken away by the sulphuric acid (see Chart). In a theoretical point of view, ether is looked upon as the oxide of an organic radical, ethyle, which is represented by the formula C4 H5. Ether, according to this view, would be oxide of ethyle, and alcohol a hydrated oxide of ethyle. The ethyle is looked upon as a radical, or root, from which springs a series of compounds, just as potassium may be regarded as the radical or root of potash, hydrate of potash, sulphate of potash, &c. Potassium is a simple radi- cal, and as ethyle appears to comport itself in a similar man- ner, it is called a compound radical. 392. Properties of Ether.—Ether has a hot, pungent taste, and a fragrant odor. It is extremely volatile, disap- pearing even when poured through the air from one vessel into another. It evaporates so rapidly that when poured upon the hand it produces cold; hence it is used in cooling lotions in surgery. It boils at 96°, or when exposed to the sun in summer, and is very combustible, burning with more light than alcohol, and some smoke. It. is used to relieve How is sulphuric ether obtained ? What is a compound radical ? Enumerate the properties of ether. For what is it used ? CHEMISTRY OF BREAD-MAKING. 201 and prevent spasms in asthma, in doses of half a tea-spooaful mixed with water. Vapor of ether, mixed with ah and re- spired, produces an intoxicating effect like laughing-gas, and also insensibility to pain, like chloroform. It dissolves the fats and oils, and is hence of great importance in Organic Chemistry. 393. Chloroform.—This is made by distilling alcohol with chloride of lime in a capacious retort. Its composition is C, H Cl3. It is a dense, limpid fluid, half as heavy again as water, and very volatile. Its vapor, when breathed, produces insensibility, so that severe surgical operations are experienced without pain. CHEMISTRY OF BREAD-MAKING. 394. Grain and Flour.—The grain of which bread is made consists mostly of starch, gluten, and sugar: these are to be so changed from their raw state as to become agree- able to the taste and easily digested. The grain is pulverized, or ground in mills, and separated by sifting, or bolting, into different qualities of flour or meal. The ligneous husk of grain produces the bran, while the flour is formed by the interior white portions. The gluten is tougher and more difficult to grind than the starch, hence the finest and whitest flour, obtained by repeated siftings, contains a larger propor- tion of starch, the darker colored flour being richer in gluten; and as the nutritive properties of flour are in proportion to the quantity of the nitrogenized element (gluten), the latter kind will make the most nutritious bread. How is chloroform made ? What effect does it produce when breathed ? What are the chief substances in grain ? What is the first process to which tho grain is subjected? From what part of the grain is the bran derived ? From what is the flour formed? What flour contains most starch? What kinds are richest in gluten ? Which wili make the most nutritious bread ? 202 VEGETABLE CHEMISTRY 395. Adulterations of Wheaten Flour. — The flour of wheat, Avhich is most generally employed for bread, is some- times adulterated with potato starch. It may be detected by adding nitric acid, which changes the flour to a fine orange yellow, whereas it does not affect the color of the starch.—( Ure.) It is also often mixed with chalk, lime, and gypsum, which is shown by the increased specific gravity of the flour, and by the excessive quantity of ashes left upon burning. 396. Rising of the Dough.—When flour is mixed with water, kneaded into a dough, and baked, if it be in a thick mass it will be tough and clammy; if spread out thin it will be hard and horny, and in both cases it will be very indigestible. To avoid these properties of bread, and form a light, spongy dough, various methods are employed. If a paste of flour and water be set aside for some days, in a warm place, it putrefies and turns sour; and if a portion of this be incor- porated into fresh dough, it excites the vinous fermentation. The decomposing gluten acts upon the sugar (379) of the flour, resolving it into alcohol and carbonic acid. The car- bonic acid is liberated, in the form of minute bubbles of gas, throughout the whole substance of the dough; and being caught, as it were, by the adhesive gluten, it causes the mass to swell and rise. These bubbles form the pores or vesicles, which, in the best bread, are small and uniform, but some- times constitute large, irregular cavities, or holes, in the heart of the loaf. This is liable to take place if the dough is too watery, or not sufficiently kneaded, or if the flour is too finely ground, or the heat of the oven is insufficient. How may the adulterations of flour be detected? How may the vinous fermentation be excited in bread 1 What is the effect ol the liberation of carbonic acid? How do these vesicles appear in good bread? How in indifferent qualities? When will this be likely to occur? CHEMISTRY OF BREAD-MAKING. 203 397. Ferment used in Bread-making.—The putrefying dough used to excite fermentation is called leaven. Brew- er's yeast, formed by the fermenting action of malt, in the process of making beer, is the most prompt and active of all the alcohol ferments; for making bread its use is regarded as much superior to common leaven. If the fermentation proceeds too far, the dough becomes sour; that is, the vinous passes into the acetous fermentation, the alcohol changes to vinegar. When this has occurred, the evil is readily corrected by the addition of a little carbonate of soda, or magnesia, which neutralizes the acid. The acetate of soda, or magnesia, thus formed, gives to the bread no disa- greeable taste, and acts upon the system only as a mild aperient; it is therefore unobjectionable. 398. Dough raised without Ferment. — By fermentation the bread is raised at the expense of the sugar contained in the flour; but any method, by which a gas may be set free throughout the doughy mass, answers the same purpose. If bicarbonate of soda be mingled with the flour, and dilute muriatic acid afterwards added, the acid and soda combine, forming common salt, and carbonic acid is rapidly disen- gaged, forming a very light sponge. It must be kneaded immediately. Carbonate of ammonia (smelling-salts) is also used for the same purpose, particularly for making sponge- cake and light biscuit: the salt is volatilized by the heat of baking. Water, impregnated with carbonic acid, is some- times used to raise bread. 399. Effect of Baking upon Bread.—In the process of baking, the elements of the dough are changed by heat. Whnt is the best leaven for bread-making? If the vinous fermentation passes Into tho acetous, how may the evil be remedied? Is there any method of making bread light, except at tho expense of the flour? What is it Y 204 VEGETABLE CHEMISTRY. The alcohol formed by fermentation is expelled as vapor Attempts have been made in very large bakeries to con- dense and save it, and a weak spirit was obtained, but it seems not to have paid for the trouble of collecting it. Tho effect of heat upon the gluten and the starch is to destroy their distinctive characters ; they form a chemical compound, and cannot be separated, as before, by a stream of water. In consequence of this change, and also because of its light- ness, bread is readily soluble in the juices of the stomach, or, in other words, is easy of digestion. We have seen that starch (363) by the action of heat is transformed into solu- ble dextrine, or gum ; a part of the starch also undergoes this change in the oven, especially on the surface of the baked bread, which receives the strongest heat from the roof of the oven. If the crust of the hot bread is rubbed over with water, and restored for a few minutes to the oven, some of the dextrine dissolves, forming that smooth, shining surface which we see on loaves of bread and rolls. The water added to the flour forms about one-third the weight of the bread. A small portion has evaporated by the heat of baking, but most of it becomes fixed, that is, enters into chemical union with the substance of the bread. 400. Nutritive Value of Bread from Wheat.—The expe- rience of all civilized people agrees with the results of Chemistry in indicating wheat as the first of the bread-pro- ducing grains. The following comparison of its composition with that of milk and blood will show its high nutritive powers. It will be remembered that milk constitutes the sole food from which all the parts of the young animal are What is the effect of baking upon bread ? How does the heat affect the gluten and starch ? How is the shining surface seen on the crust of broad and rolls form- ed ? How much water is contained in the bread ? How is wheat classed among breaa-producing grains? CHEMISTRY OF BREAD-MAKING. 205 formed; while blood, which supplies the whole body with its elements of nutrition, must necessarily represent the whole body in its chemical constitution. Flour. Fibrine, Afbumen, Caseine, Gluten, Oil and starch, Sugar, Chloride of potassium, Chloride of sodium, Phosphate of soda, " " lime, " " magnesia, " " iron. Blood. Fibrine, Albumen, Caseine, Coloring matter, Fats and oils, Sugar, Ditto. Milk. Albumen. Caseine. Butter. Milk-sugar. Ditto. J The analogy in this case does not extend to the relative quantities of each element. 401. Dyspepsia, or Graham Bread, is formed from wheat- en flour which retains its bran. With weak stomachs, it agrees better than the finer kinds, and is probably healthful for all. Rye forms a nutritive bread, although inferior in this respect to wheat. It is more retentive of water than wheat, and hence remains longer moist. Its effect upon the bowels is laxative. Rice has the opposite tendency. It ia said that a mixture of 75 per cent, of rye with 25 of rice forms a good bread, free from the defects of both. Indian corn makes an excellent species of bread. It contains a much larger proportion of oil than the other grains. The proportion of the oily element varies from 8 to 10 per cent., the yellow variety containing more than the white. Corn-meal deteriorates in the air more quickly than wheat or other flour; this is caused by the rapid oxidation of From what is Graham bread made ■> "*at is said of it ? What is said of rya bread ? Wb at are the properties ot bread made of Indian corn ? 18 206 VEGETABLE CHEMISTRY. the oil (423), and does not take place when the grain is un- ground. The oily matter which resides in a certain portion of the seed-grain, by baking, is diffused throughout the starchy and glutinous matter of the meal, communicating that pecu- liar taste and aroma which distinguishes corn-bread. 402. Alum is extensively used by bakers to improve the appearance of bread. It augments its firmness and hard- ness, rendering it less liable to crumble when cut, and ena- bling the baker to separate the loaves more readily after their removal from the oven. It also increases its whiteness, so that inferior kinds of flour can be made into bread of the best aspect. Several other saline substances are also some- times introduced into baker's bread for dishonest purposes. Their presence is easily detected. 2000 grains of pure bread will not yield more than from 15 to 25 grains of ashes; if more than this is found, they have been added fraudulently. OLEAGINOUS PRODUCTS OF PLANTS. FATS AND OILS. 403. Identity of the Oils and Fats.—The oils and fats possess the same chemical qualities, the only difference be- ing in their consistency, which depends upon the tempera- ture. An oil may be called a liquid fat, or a fat, a solid oil. The same body, as tallow or lard, by a slight alteration of temperature, changes from a solid to a liquid, without alter- ing its essential properties. What the Africans call palm- oil, and know only as a liquid, we call palm-butter, because in this country it is a solid. Oily substances are found in For what purpose is alum used in bread ? How may impurities in bread be &*■ tected ? What is the difference between an oil and a fat? In what parts of plants doei vdl occur ? What are the hard oils caUed? THE DELS. 207 considerable quantities in plants. They occur in many seeds, as that of flax; also in nuts, as the walnut and almond, from which they are obtained by pressure. They are of various degrees of consistence, from thin almond or spermaceti oil, to solid tallow. The hard oils of vegetables are frequently termed vegetable butters, as nutmeg-butter, palm-butter. The animal fats, in strictness, require to be considered among animal products in the third division of the work; but in properties and composition they are identical with the vege- table oils, and therefore cannot be conveniently separated from them. 404. Volatile and Fixed Oils.—The oils are of two kinds, fixed and volatile. The fixed oils are highly inflammable, do not unite with or dissolve in water, are slippery and unctu- ous, and do not evaporate in the air ; if placed upon paper, they communicate to it a permanent stain. They are usually bland and mild to the taste, and are decomposed by the action of heat. The volatile oils are also inflammable and nearly insoluble in water, but they are hot and pungent to the taste, and evaporate in the air. A drop left upon paper passes away, leaving no stain. They occasion the peculiar odor emitted by many plants. 405. Amount of Oily Product from different Sources.— The oily substances of vegetation are principally accumula- ted in the fruit, and particularly in the seed. In herbace- ous plants they are less abundant, although existing in con- siderable proportion in the straw and stalks of grain. The proportion of oil in various substances, by the most recent determinations, is as follows : In Indian corn, 9 per cent., oats 3*3, fine wheat flour 1-4, bran from the same 4-65, rice How are the oils divided? Give the properties of the fixed oils. What is th« lharacter of the volatile oils? How is the oil from plants obtained ? 208 VEGETABLE CHEMISTRY. 1, dry hay 3 to 4, straw of wheat 3% oat-straw 5'1, olivo seeds 54, finseed 22, white mustard 36, black mustard 18, almonds 46, cocoanut 47, walnuts 50, yolk of eggs 28*75, cow's milk 3'13 per cent. They are obtained by mechanical pressure, as linseed oil, by the agency of heat, as in the animal fats, by distillation, and by solution in ether. 406. Proximate Principles of the Oils.—Chemists havo shown that fats and oils have a true saline composition; that is, they consist of acids in combination with a base. The proximate principle of the oils, which plays the part of a base, neutralizing acids, is called glycerine, so named from its sweetish taste. When pure it is a thick, syrupy, inodor- ous liquid, soluble in all proportions in water and alcohol, and has the composition C6 H8 06. It is expelled from its combination by the ordinary alkalies. Glycerine is united in the oils with three acid substances: Stearic acid (C3, H38 04), margaric acid (C34 H34 04), and oleic acid (C,6 HM 04).—(Silliman) With stearic acid it forms stearate of glycerine, or stearine: with margaric acid it forms margarate of glycerine, or margarine ; and with oleic acid it forms oleate of glycerine, or oleine. Stearine, margarine, and oleine are therefore distinct oily or proximate principles. They are each a combination of a fatty acid with a base. They have different properties, and may be readily separated from the oily bodies in which they are combined together. 407. Oleine is that portion of oil which causes its fluidity. The thinner and more liquid an oil or fat, the more oleine does it contain. Olive oil, and vegetable oils generally, . contain a large portion of oleine. The hard fats contain less What have chemists shown to be the composition of the oils ? What is glyce« tine ? With what is it united ? What does it form ? What are these three sub Itances ? What is oleine ? In what substances is it found abundantly ? PROXIMATE PRINCIPLES OF THE OILS. 209 of it in proportion to their hardness, hence it exists in greater quantity in the fat of the swine than in the harder tallow of the sheep or ox. It is expressed on a great scale from lard, for burning in lamps, and for other uses. 408. Stearine and Margarine.—Stearine gives to certain fats and oils the opposite property of solidity. It is most abundant in tallow and suet. It is obtained by subjecting the solid fats to great pressure, in flannel or hair bags, be- tween hot iron plates; the oleine is separated, and flows away. The solid stearine thus procured is used for the manufacture of stearine candles, which very much resemble those of wax. Oils which are liquid at common temperatures contain a small proportion of stearine in solution, as may be shown by exposing them to the action of snow or ice, when the stearine is deposited and the oleine floats above : hence in winter olive and castor oils deposit solid stearine, and be- come thick. A pound of tallow contains about three-fourths of a pound of stearine, of olive oil not more than one-fourth. Margarine resembles stearine in its property of hardness; it exists in human fat, butter, goose-fat, and olive oil. 409. Variation in the Proportion of these Elements.— The solid and fluid parts are mixed together in different pro- portions in the oily substances of different plants and ani- mals, and in different parts of the same animal. They are also modified by feeding, and other circumstances. Thus the tallow from animals fed upon dry, ripe fodder, is more solid than when they are fed upon grains. The superior hardness of Russian tallow is due to this chcumstance, their animals being fed upon dry fodder eight months in the year. What property does stearine give to substances ? Where is it most abundant 1 How is it obtained ? For what is it used ? Why do olive and castor oils become Ihick in winter? What is said of margarine? Where is it found? What effect does the food of animals have upon their oily parts ? How may fata ind oils be bleached ? Upon what does the odor of oils depend ? 18* 210 VEGETABLE CHEMISTRY. Fats and oils are generally either colorless or slightly yellow, but may be bleached by the protracted action of light. Tho stearic, margaric, and oleic acids which they contain are without smell, but some of them have peculiar odors de- pendent upon the presence of certain volatile acids; thus, butter contains butyric acid, goats' fat hircic acid, whale oil phocenic acid, &c. 410. Why Oily Bodies are Inflammable.—By reference to the Chart, or the formula we have just given (406) for their proximate principles, it will be seen that the oil group consists almost entirely of carbon and hydrogen, with but a very small proportion of oxygen. They are thus composed of two elements, which have a most powerful affinity for oxygen ; we should, therefore, conclude that they must be exceedingly combustible, and such is the fact. Every one is aware of the violence with which they burn when set on fire ; and being rich in hydrogen, they produce a large flame. So strong is this attraction for oxygen, that when cotton, tow, straw, and cloth, which present an extended surface to the action of the atmosphere, are imbued with oil, they often take fire spontaneously (spontaneous combustion), and thus frequently occasion conflagrations. In consequence of their combustibility, and the large quantity of light which they emit in burning, oleaginous bodies are universally used as a source of illumination. Some of them are converted into gas (oil gas), several of them are consumed in lamps in the liquid state, while the solid fats are formed into candles. 411. Way in which a Candle Bums.—In burning gas no wicks are used, and yet their use in lamps and candles seems to be to bring their materials into a gaseous form. In a burn- How does the composition of the oils account for their exceeding combustibility? Tor what are the oils universally employed ? In what forms ? THE OILS AS A SOURCE OF LIGHT. 211 ing candle, the fat below is melted by the heat Fis-20- into the form of a hollow cup, b d, Fig. 20, which may be considered a reservoir of oil. The wick, consisting of parallel cotton fibres, acts as a sys- tem of capillary vessels, drawing or sucking up the liquid as fast as it is consumed above. The liquid oil is thus carried into the hollow interior of the flame (77), where it is exposed to a high temperature without being able to come in con- tact with air; it is in the same position as if it were inclosed in an iron retort between red-hot coals. It is here immediately converted into gaseous and vaporous combustible products, which form the inner dark portion of the flame. The office of the wick is to maintain a steady supply of oil to be distilled or vaporized b the flame ; but as the candle burns down the wick of course extends upward in the centre of the flame, where it remains charred and unconsumed, the access of air beinar prevented by the surrounding cone of fire. As the charred wick increases in size, it impedes the activity of combustion, and consequently causes a deposit of unburnt carbon, in the form of a spongy, sooty snuff at the top, which darkens the flame. 412. Plaited Wicks.—In. some of the finer candles, as wax, sperm, and stearine, this evil has been avoided by plaiting or twisting the wicks. By this means the free ends of the fibres constantly bend out of the flame, as at c, Fig. 20, and are reduced to ashes. The symmetry of the flame is injured by this arrangement, as it follows the direction of the inclining wick fibres. The rim of the cup is also apt to be melted down on one side, so that the liquid fat gutters What is the oflBce of the wick in candles ? Why does the candle want snuffing ? What is the advantage of plaited wicks? Why arc they not used for tallow 212 VEGETABLE CHEMISTRY. over the edge. This evil is so serious as to prevent the use of plaited wicks in common tallow candles, which suffer more than the harder and more infusible kinds. The power of the common wick to influence the quantity of light emitted by a candle flame, is thus shown by the experiments of Peclet. The intensity of the light from a freshly snuffed candle (six to the pound) being represented by 100, it becomes in 4 minutes 92, in 8 minutes 50, in 10 minutes 41, in 12 min- utes 38, in 15 minutes 34, in 20 minutes 32, in 22 minutes 25, in 24 minutes 20, in 28 minutes 19, in 30 minutes 17, and in 40 minutes 14. Less than half an hour, therefore, is sufficient to reduce the light of an unsnuffed candle to one- seventh its original brilliancy. 413. Different Candles Compared.—It has been found that the quantity of material consumed per hour in burning, by different candles, is as follows : they were six to the pound, and occasionally snuffed, so as to maintain as nearly as possible an equable flame. Stearine consumed per hour 164 grains, spermaceti 143, wax 134, tallow (moulds) 128, The relative proportions of light produced were, for the spermaceti 10, the stearine 7-4, the wax 6-6, and the tallow 4*7. The consumption of sperm oil by a well-trimmed ar- gand lamp of the ordinary dimensions (wick one inch in di- ameter) was about 800 grains, per hour; it gave a light equal to 10 or 11 spermaceti candles of six to the pound. 414. Oil as a Preservative.—Oily bodies are lighter than water, and will not mix with it; they therefore float upon its surface, and are sometimes employed to protect substances from the action of the air. Thus fresh lemon-juice, if exposed candles ? In what time is the light from a freshly snuffed candle diminished "h* half? Does a stearine or tallow candle consume most rapidly ? How does oil protect substances from the action of air ? What is its effect ity«a our shoes ? Upon iron ? Upon wood ? THE DRYING OILS. 213 to the air, speedily moulds, but if covered with oil it does not. Preserved fruits also keep much longer when melted butter is poured over them. Having no affinity for water, sub- stances which are imbued with it are impenetrable to that liquid; hence by greasing our shoes they are protected from absorbing moisture. Oiled iron does not rust in damp air, while wood or fabrics which are charged with oil are preserved from decay by the exclusion of water, which is an active agent of decomposition. DRYING OILS. 415. Oily bodies, if protected from the air, undergc little change ; if exposed to it, they absorb its oxygen, gradually thicken, and some finally become quite hard and solid. These are termed drying oils, and are used in paints and for the manufacture of varnishes. 416. Linseed Oil.—This is the most important of the drying oils, and is obtained by expression from the seeds of common flax, which yield from 20 to 25 per cent, of their weight. When the seeds are submitted to pressure at com- mon temperatures (cold drawing, or cold pressure), the oil is of a pale-yellow color and of the greatest purity, but if at a steam heat a larger quantity may be obtained ; it is then of an amber color, and more liable to become rancid (423). It is slowly bleached by sunlight, and when long kept in a half-filled bottle it thickens, and does not dry well. It has a specific gravity of 0-93. The drying properties of linseed oil, which adapt it to the painter's use, are greatly increased by boiling for several hours with the addition of a little htharge (protoxide of lead)—two to four ounces of litharge What are drying oils? For what are they used? How is linseed oU obtained? What is its appearance? How are lta drying 214 VEGETABLE CHEMISTRY. to every gallon of oil; a little acetate of lead and sulphate of zinc are also sometimes introduced with benefit. The product is known as boiled oil, purified oil, and drying oil. It acquires by boiling a brownish-red color, and hence when white-lead is to be made into a paint with linseed oil it is prepared in the unboiled state, in consequence of its paler color. The change wrought in the oil by boiling, consists in depriving it of certain gummy, mucilaginous matters which are dissolved in it, and greatly retard the drying. The compounds of lead combine with this mucilage, forming an insoluble body, which is precipitated as a white sediment. If, after boiling for a time, the oil is set fire to and permitted to burn for half an hour, and the flame then extinguished by placing a cover upon the vessel (burning oil or fat should never be quenched with water), it acquires a viscid, tenacious consistency, and forms printers' ink by the addition of a due quantity of lamp-black; 417. Oil-silk consists of silk cloth to which several coat- ings of purified linseed oil have been successively applied. Oil-cloth is cotton cloth which has been treated in a similar manner. Mixed or ground with various coloring matters, chiefly metallic oxides, linseed oil forms numerous paints, which are smeared upon wood to preserve it and give it color. 418. Walnut Oil is obtained by pressure from walnuts; it is of a pale yellowish-green color, and of a peculiar odor. When fresh it is sometimes used for culinary purposes, but when rancid it is purgative. It is more drying than linseed oil, and possesses less color, which renders it a valuable in- properties increased ? What is it then called ? Why is it not boiled when white- lead is to be used with it? What is the effect of boiling? How is printers' wk . made? What is oil-silk ? What is oil-cloth ? What ia said of walnut oil ? THE UNCTUOUS OILS. 215 gredient of many paints. It is sometimes used for burning in lamps, and as a basis for varnish. 419. Hemp-seed Oil is of a greenish-yellow color, has a disagreeable smell, and a mawkish taste. It is extensively used for making paints, varnishes, and soft soaps. 420. Poppy Oil, expressed from the seed of the poppy, is of a pale-yellow color, inodorous, and of a slightly agreeable flavor, much resembling olive oil, which is sometimes adul- terated with it. It makes a clear varnish, and is used at the table as a substitute for olive oil. It has none of the nar- cotic properties of the poppy-juice. 421. Croton Oil is expressed from the seeds of a plant which grows in India. It is a thick, brown oil, of a peculiar odor, and acrid taste. It is powerfully purgative. 422. Castor Oil is obtained from the seeds, or beans, of the castor-oil plant. It is of a pale straw color, and has a bland, but somewhat nauseous flavor. Its principal use is in medicine, as a mild laxative. It is also used for printing-ink, and in perfumery as an application to the hair. THE UNCTUOUS OILS. 423. The Unctuous Oils are such as do not dry up when exposed to the air, but continue soft and sticky. This prop- erty renders them very valuable for diminishing the friction of rubbing surfaces, as the axles of carriages and other ma- chines, a purpose to which the drying oils are not adapted. For the same reason, the unctuous oils are worked into leather to maintain it in a soft and pliable condition. The unctuous oils and fats are liable, by long exposm-e to the air, to turn rancid; that is, they absorb oxygen and generate What is said of hemp-seed oil ? Of poppy oil ? Of croton oil ? Of castor oil ? 216 VEGETABLE CHEMISTRY. peculiar acids, which emit a disagreeable odor. This change appears to result principally from minute quantities of nitro- genized organic tissues, which remain diffused through the fats. The rancidity of oleaginous bodies may be in a great measure removed by boiling them with water and a little magnesia, until it has lost the property of reddening litmus. 424. How Unctuous Oils are Purified.—As the drying oils are purified by oxide of lead, so the same change is pro- duced in unctuous oils by sulphuric acid. We have seen (189) that this acid possesses the property of charring or- ganic substances, but it does not act with equal energy upon all. When added to oil, it first attacks its nitrogenized and mucilaginous impurities : these are decomposed and precipi- tated. When just sufficient acid is used to effect this object, the mucilage alone is charred ; if too much, the oil itself is decomposed. 425. Olive Oil, or Sweet Oil.—This oil is obtained by pressure from the fleshy or pulpy part of the fruit of the olive-tree. The finest kind is of a yellowish color, has a thin consistence, a slight odor, an agreeable taste, and when swal- lowed leaves a very slight sense of acrimony in the throat. When pure it has less tendency to change than almost any other of the fat oils, but the inferior qualities soon become rancid. It contains 72 per cent, of oleine and 28 of marga- rine, the latter of which congeals in cold weather. Being less apt than most other oils to thicken by exposure to air, it is preferred for greasing delicate machinery, especially watch and clock work. It is used at table as a condiment for salads, and is hence termed salad oil. In Spain it is used as What are the unctuous oils? For what are they used? What is rancid oil? What causes the change ? How may it be removed ? What is the effect of sulphuric acid upon the unctuous oils? How is olive oil obtained ? What aro its properties ? For what Is it used ? ANIMAL FATS. 217 a substitute for butter. Taken in large quantities, it acts as a mild laxative. 426. Palm Oil is a solid butter-like oil, of an orange- yellow color, obtained by pressure from the fruit of the palm- tree. It is readily blanched by heat, or the joint action of air, hght, and moisture, and also by chlorine. It contains 70 per cent, of oleine and 30 of stearine, and is used in the man- ufacture of soap and candles. Oil of almonds is expressed from sweet almonds; also from bitter almonds by cold pres- sure, as if heat is employed the oil contains prussic acid. It is mainly used in liniments, ointments, and soap. Unctu- ous oils are also obtained from rape-seed, beech-nuts, hazel- nuts, and the stones of fruits. ANIMAL FATS. 427. These are contained in the bodies of animals, in what is termed cellular tissue or adipose membrane. They are obtained by a beat sufficient to liquefy the fat, and burst the including cell, or sack. The more solid portion of the fat (stearine) forms a layer next to the inner surface of the cell-membrane, the softer part (oleine) being inclosed with- in. Fat forms about one-twentieth the weight of a healthy animal. 428. Mutton Tallow.—This is a very white and solid fat. It has little odor when fresh, but acquires a peculiar, rancid smell, when exposed for some time to air. 429. Beef Tallow is of a yellowish-white color, firm, and yields 75 per cent, of stearine to 25 of oleine. 430. Neat's-foot Oil is obtained from the feet of oxen, by What is palm oil ? What is said of the oil of almonds ? In what part of animals is the fat deposited ? How is it obtained ? What is said of mutton tallow ? Beef tallow ? 19 218 VEGETABLE CHEMISTRY. first divesting them of the hoof and hair, and then boiling them with water. This oil remains liquid below 32°, and is not liable to change or rancidity. It is used for oilinp- leather and greasing machinery ; particularly steeple-clocks, which require, in consequence of the cold to which they are often exposed, an oil not liable to solidify. 431. Hog's Lard is a white, inodorous, soft fat, which, when long exposed to the air, grows yellow, rancid, and sour. It yields 38 per cent, of stearine, which has been used for the manufacture of candles, and 62 per cent, of oleine, which is considerably used for burning in lamps. Goose-fat consists of 68 oleine and 32 stearine 432. Change of the Human Body inio Adipocere.—Hu- man fat is soft, yellowish, without odor, varying little in different parts of the system. The bodies of persons that have been for years buried in church-yards are sometimes found to have been changed into a peculiar substance, resem- bling fat, and termed adipocere. The same kind of fatty matter is formed in the vats which collect the offal from dissecting-rooms and slaughter-houses; it is also found when the bodies of animals are exposed to running water till the muscular and membranous parts have been washed away. It has been shown that this substance is the original fat of the body, which has resisted decomposition, and is partly in the state of a fatty acid, and partly saturated by ammonia, with traces of lime and magnesia.—(Brande) ' 433. Train Oil (Whale Oil).—Oil is obtained from the fat of various fishes, as the whale, the dolphin, the seal. It is of a yellow color, and not of a disagreeable odor, unless the fish were putrid, or the oil was expressed by a strong What is said of neat's-foot oil ? Hog's lard ? Goose-fat ? What is adipocere ? When is it formed ? What ia said of whale oil? WAX. 219 heat. Whale oil is used for illumination, to grease leather, in medicine, and in soap-making. 434. Spermaceti Oil is extracted from cavities in the head of the sperm whale, and is superior to common whale oil for burning in lamps. When cooled, after the death of the animal, it deposits a white, sparkling, crystalline, fatty sub- stance, so hard that, when rubbed, it crumbles to powder. When purified, it is used for candles. WAX. 435. Some plants produce a considerable quantity of a substance resembling beeswax, and which, in some of its properties, approaches the fatty bodies. The glossy coating, or varnish, which is observed upon the surface of leaves, fruit, and bark, rendering them impermeable to water, con- sists of vegetable wax. It occurs in large quantities in the common cabbage. 436. Beeswax, a secretion of the honey-bee, is the most important of these bodies. In its ordinary state it is yellow, but is bleached white by exposing it for some time in thin ribands, to the joint action of air, light, and moisture. Com- mercial beeswax is very commonly adulterated with the flour of peas and beans, with starch, and even brick-dust. These may be readily detected by sphits of turpentine, which takes up the wax, but leaves the impurities undissolved. Resin, too, is often used: it may be separated by cold alcohol, which dissolves it. Wax is much used for candles, but is not adapted to be either dipped or moulded. The wax can- dles are made either by applying wax, softened in hot water, Spermaceti oil ? For what is it used ? Is wax a vegetable product ? Upon what pgjts is it found ? How may impurities in beeswax be detected? How are wax candles made? What are the uses of beeswax ? 220 VEGETABLE CHEMISTRY. little by little, to the wick, by the hand, or by pouring melted wax upon the suspended wick with a ladle. When the candles have thus grown sufficiently large, they are rolled upon a table to give them the exact form. Beeswax is used for smoothing sewing-thread, and when dissolved in potash-ley it forms a pecuhar soap, used for polishing floors. 437. Point at which Oils Solidify.—The temperatures at which various oily substances pass from the liquid to the solid state are thus compared: Beef tallow about 100° F.; mutton tallow 100° to 106°, stearine from tallow 131°, palm oil 85°, stearine from palm 120°, hog's lard 81°, stea- rine from hog's lard 110°, spermaceti 112°, beeswax 150°, almond oil 30° ; olive oil deposits 28 per cent, of stearine at 22°, margarine of butter 118°, oleine of butter 32°. 438. Oily Bodies as Food.—As the oily bodies are found diffused in considerable quantities in those vegetable sub- stances which form the natural diet of man, there can be no doubt of their healthfulness as food. Yet it is equally certain that when separated and consumed as they :>ften are in large quantities, they prove highly injurious. " Fixed oil or fat," says Dr. Pereira, " is more difficult of di- gestion, and more obnoxious to the stomach, than any other alimentary principle. Indeed, in some more or less obvious or concealed form, I believe it will be found the offending ingredient in. nine-tenths of the dishes which disturb weak stomachs. Many dyspeptics who have most religiously avoided the use of oil or fat in its obvious or ordinary state (as fat meat, marrow, butter, and oil), unwittingly employ it in some more concealed form." Much of the bad effects of oily substances upon the stomach is probably caused by Give the temperatures at which oily bodies solidify. What is said of oily bodies as food ? Why is frying the most objectionable -node of preparing oil for food ? Will fatty bodies taken as food sustain life ? DIETETIC PROPERTIES OF THE FATS. 221 the way in which they are frequently cooked. The fats, by heating, give off, with other voaltile oils and fatty acids, a peculiar acrid substance called acroleine. In the process of frying, which is carried on at a high temperature, they are liable to this decomposition, and when taken into the stom- ach turn sour and rancid, producing heartburn. For this reason, frying is the most objectionable of all the methods by which oily substances are prepared for the table. Fatty bodies are ranked among the heat-producing foods (574) or elements of respiration, for which they are remarkably adapted. They cannot support nutrition nor sustain life. Animals which have been fed entirely upon butter and lard, refuse to take it after some time, and ultimately die of inanition. ACTION OF ALKALIES UPON THE FIXED OILS. 439. Saponification, or Production of Soap.—It was sta- ted that the proximate principle of the oils and fats, stearine, margarine, and oleine, are saline bodies ; that is, they consist of fatty acids combined with a common base, glycerine. When other bases, as potash, soda, or ammonia, are made to act upon the fatty substances, they expel the glycerine from its combination, and take its place, uniting with the fatty acids, and forming soaps. Soaps are therefore regular salts, combinations of margaric, stearic, and oleic acids, with potash, soda, ammonia or lime. The change by which they re produced is called saponification. The capability of being saponified is one of the most important properties of the oil family, and they are hence divided into two classes, the saponifiable and the non-saponifiable oils. The fixed oils belong to the former class. How are soaps formed ? What are they ? What is saponification ? How are the oils divided ? 19* 222 VEGETABLE CHEMISTRY. 440. Process of Soap-making.—The alkalies in general use for soap-making are potash and soda. They require to be in a caustic state, which is produced by dissolving them, and passing the solution (ley) through newly slaked lime, which takes away their carbonic acid. In this caustic ley the fats are boiled, their glycerine is set free, and the fatty acids combining with the alkali form soap, which exists as a solution in the water. In order to obtain the soap in a solid form, the solution is boiled down to a certain degree of concentration, when the soap ceases to be soluble, and rises to the surface in a soft, half-melted state. This being drawn off into moulds, cools and forms hard soap. If soda ley is used, the soap may be separated from the water in which it is dissolved by adding common salt which forms a brine, and at once coagulates the soap ; if potash ley is used, the addition of salt decomposes the potash soap, and forms a soap of soda. 441. Hard and Soft Soaps.—The consistence of soaps depends chiefly upon its alkalies, soda giving rise to hard soap, and potash to soft soap, the latter alkali being the more deliquescent. The consistence of the oil also somewhat influences the quality of hardness. The stearate of soda, therefore, forms the most sohd soap, and the oleate of pot- ash the softest. Between these two extremes, any required degree of firmness can be obtained by selecting the proper materials, and stopping the evaporation at any desirable point. 442. Composition of different Kinds of Soap.—Common yellow hard soap consists of soda with oil or fat and resin. Describe the process of soap-making. Upon what does the consistence of soap depend? Of wkat is common hard soap composed ? White or curd aoop ? Castile eoap ? Windsor soap ? Fine toilet soap ? VARIETIES OF SOAP—ITS VALUE. 223 The latter element will not form a good soap with alkali alone, but requires to be worked with at least an equal weight of oil. The acid powers of resin are very feeble; it neutralizes the soda less completely than oil, and the soap is therefore very alkaline, acting too powerfully upon woollen fabrics and all other animal fibres to which it is applied. Common white soap or curd soap consists of tallow and soda. Castile soap is composed of olive oil and soda colored with metallic oxides, chiefly oxides of iron, in such a way as to give 't the desired mottled appearance. Green and black soap, employed in factories for cleansing colored cotton fabrics, is made of fish oil and potash. Windsor soap consists of tallow, a small proportion of olive oil and soda. Cocoanut oil gives to soap the property of forming a strong lather. Fine soft toilet soap is made with purified hog's lard and potash, colored and perfumed. Fancy soaps are essentially common soaps, mixed with different aromatic oils and color- ing substances, and diversified in form so as to suit the fashion of the day. 443. Value of Soaps.—Soap has a powerful affinity for water, and may retain from 50 to 60 per cent, of it and still remain in the solid state. Even when dry and hard it holds from 25 to 30 per cent, of water. There is hence an advan- tage to the consumer in purchasing dry and old soap, while the vender is interested in selling it with as large an amount of combined water as possible. To effect this, it is often kept in damp cellars and an atmosphere saturated with moisture to prevent it from drying. The quantity of mois- ture is easily determined by cutting the soap into thin slices, weighing and drying at a temperature not exceeding 212° ; the loss of weight shows the proportion of water. The How mid why is soap often saturated with moisture ? How is a good soap known? 224 VEGETABLE CHEMISTRY. value of soap thus mainly depends upon it3 dryness, but it should also possess the proper degree of solubility. Some dissolve too freely in washing, and hence waste very rapidly when used, while others possess the opposite quality; as, for example, " the small cubic mass of white, waxy, stubborn substance generally met with on the washing-stands of bed- rooms in hotels, and which for an indefinite period passes on from traveller to traveller, each in turn unsuccessfully attempting by various manoeuvres and divers cunning immer- sions in water to coax it into a lather." A good soap should dissolve quite freely, feel very soft and pleasant upon the skin, and afford a thick, copious lather. 444. Properties of Soap.—Soap is soluble in fresh water, but remains insoluble in salt water, except that made from cocoanut oil, which dissolves in weak brine, and is therefore used for washing with sea-water. Acids, as acetic and sulphuric, decompose soap, uniting with its bases and set- ting free the fatty acids. Soaps of soda and potash are decomposed by the salts of lime, a lime-soap being formed which is insoluble in water; hence waters which contain sulphate or carbonate of lime wash badly (96). Hard wa- ter, when an alkaline soap is added, decomposes it, form- ing a rough, sticky, disagreeable, earthy soap, having no detergent properties, and being therefore unfit for washing. Soaps of metallic oxides, as oxide of lead, are employed medicinally for plasters. Soap is soluble in alcohol, form- ing tincture of soap, which is an excellent liniment for bruises. Soap dissolved in spirits of camphor forms opodel- doc. Volatile liniment is an ammoniacal soap. 445. Mode in which Soaps act in cleansing.—As water Give the properties of soap. How is soap affected by hard water? Howie M smployed medicinally ? What is opodeldoc? Volatile liniment? CLEANSING ACTION OF SOAP. 225 has no affinity for oily substances, and will not dissolve them, of course it cannot alone remove them from any surfaces to which they may adhere. The skin is perpetually bedewed with oily matters which exude from the glands, and, uniting with dust and dirt, form a film or coating all over the body. Soap being always alkaline, acts upon the oil during ablu- tion, partially saponifies it, and renders the unctuous com- pound freely miscible with water, so as to be easily removed. The cuticle or outer layer of the skin is composed of albu- men, which is soluble in the alkalies (373). A portion of the excess of alkali which exists in soap must soften and dis- solve a part of the cuticle, which, when rubbed off, carries with it the dirt. Thus every washing with soap iemoves the old face of the scarf-skin, and leaves a new one. If the hands are too long exposed to the action of a very alkaline soap, they become tender, that is, the cuticle is dissolved away, and becomes so thin as not to protect the inner or sensitive skin. On the contrary, where the scarf-skin and dirt are rarely disturbed by soap, the sensibility of the skin is necessarily benumbed. The action of soap in cleansing textile fabrics is of a similar nature ; the alkali not only acts upon greasy matter, but, as is well known, dissolves all or- ganic substances. Being partly neutralized, its solvent power is less active than if it were in a free condition. The oily nature of the soap also increases the pliancy of the articles with which it is washed. It is said that woollen fabrics, if washed with a weak solution of carbonate of soda, will not shrink as when washed with soap. What is the action of soap in cleansing clothes ? What is its effect upon tho ikin ? If the skin is long exposed to the action of soap, what is the rosidt ? Ii •oap is seldom applied, what follows ? What is said of washing woollen fabrics ? 226 VEGETABLE CHEMISTRY. OF THE VOLATILE PRINCIPLES OF PLANW. VOLATILE OILS. 446. Their Sources and Preparation.—The volatile or ethereal oils take their name from the property of readily evaporating in the air. They dissolve in alcohol, and their solutions are called essences. From this circumstance they are also known as essential oils. They are met with in all parts of plants—in the leaves, bark, and root, but principally in the flower. Sometimes different parts of the same plant contain different oils, as, for instance, the orange-tree, which fur- nishes one from its leaves, another from its flower, and a third from the rind of its fruit. Essential oils are not so volatile as water; nevertheless, they rise with the vapor of water; and it is by this means that they are generally ex- tracted. The plant is put into a still, or alembic, containing water, and heat is applied. The vapor rises, passes over, and condenses in the receiver, carrying with it the oil which is found swimming upon the surface of the distilled water. When flowers or leaves are used, they are suspended in a cage in the centre of the still, in order to be acted on by the vapor only, because if they come in contact with the sides of the vessel the heat would injure them. 447. Properties and Uses of the Ethereal Oils.—The vol- atile principles of plants are generally limpid and lighter than water, yet some are heavier, and others, as camphor, solid. They have not the greasy feel of the fat oils, but What are volatile oils ? Why are they called essential oils ? Whence are thej obtained ? How are they separated from the plant ? Give the properties of the essential oils. What is stearopten ? Elaopten ? How are medicated waters formed ? Perfumed waters ? Perfumed vinegar ? Poma- tum? THE VOLATILE OILS. 227 are rather rough to the fingers,, causing a cork moistened by them to squeak when twisted into a vial. They are in- flammable at lower temperatures than the fixed oils, and burn with a smoky flame. The more solid portion of the essential oils is called stearopten, the fiquid part elaopten. Exposed to the air, they imbibe oxygen, and are either con- verted into acids or dry up, and are changed to resins (453). A small portion of these oils is dissolved by water, sufficient to communicate to it their peculiar taste and smell. These solutions are sold by apothecaries under the name of med- icated waters. Various oils, as bergamot, lavender, rose- mary, &c, dissolved in alcohol, form perfumed waters, as Cologne water (eau de Cologne). They dissolve in strong acetic acid, forming perfumed vinegar, and when mixed with lard and other fixed oils form pomatum, hair-oil, &c. 448. Composition of the Volatile Oils.—As respects com- position, the volatile oils are of two kinds. The first class consists of but two elements, carbon and hydrogen; and a large number of them, as oil of turpentine, oil of lemons, oil of juniper, oil of black pepper, oil of citron, oil of parsley, are isomeric, ad having the composition CSH4, or 2 (C5H4). These are, therefore, vegetable hydro-carbons. The second class contains, in addition to carbon and hydrogen, a small proportion of oxygen, and sometimes sulphur and nitrogen. These are distinguished by their pungent, acrid properties, irritating tne eyes, provoking tears, and, when placed upon the skin, blistering it. The oils of mustard, onions, garlic, horse-radish, hops, and asafcetida, are the most common ex- amples of this class. How are the volatile oils divided ? Of what does the first class consist ? What ire they called ? What is the composition and properties of the second class ? 223 VEGETABLE CHEMISTRY. ESSENTIAL OILS WHICH CONTAIN ONLY HYDROGEM AND CARBON. 449. Oil of Turpentine, commonly called spirits of tur- pentine, is obtained by distilling with water the thick semi- fluid turpentine, which flows from the wounded bark of cer- tain species of the pine, and is the cheapest, most abundant, and most useful of all the volatile oils. It is a limpid, color- less liquid of a peculiar odor. It boils at 314°, and has a sp. gr. of 0-87. It burns with a very luminous flame, and is extensively used as a source of light; but in its common or crude state, it deposits a resinous substance, and soon clogs the lamp. To prevent this, it is redistilled, or rec- tified, and then goes under the name of camphene. The lamp must be so constructed as to furnish a copious supply of air, or the turpentine will smoke. Mixing with it a por- tion of alcohol also corrects this evil. A pint of good oil of turpentine burns in an argand lamp about ten hours, giv- ing a light equal to about twelve spermaceti candles. It is largely employed in the manufacture of varnish to dissolve the resins, also in the preparation of paints, to remove grease- spots from cloth, dissolve India-rubber, and in medicine. 450. Oil of Lemons is obtained from the rind of the lemon, both by expression and by distillation. It is very fluid, colorless, of an agreeable lemon odor, a pleasant, pungent flavor, and is often used by cooks as a substitute for lemon- peel. Oil of lemons is sold under the name of scouring- drops, and used to remove grease stains from silk, as the fixed oils all dissolve in the ethereal oils. Oil of black pep- How is spirits of turpentine obtained ? What are its properties ? What is cam phene ? With what should the lamps be furnished ? For what other purpose! It spirits of turpentine employed ? What is said of the oil of lemons ? Oil of black pepper ? THE VOLATILE OILS. 229 per is limpid and colorless, but by keeping, it becomes yel- low. In odor it resembles pepper, but is devoid of its hot taste. 451. Oil of Juniper is obtained by distilling bruised juni- per-berries with water. It is limpid, of a faint yellow color, and used for flavoring gin. Oil of orange-peel closely re- sembles the oil of lemons. Oil of bergamot is a thin yel- low liquid from the rind of the bergamot orange. Oil of roses, attar or otto of roses (C4 H4), condensed, is olefiant gas, obtained by distilling rose-flowers, or, in the East Indies, by stratifying them with a certain kind of seed which imbibes the oil, and then yields it by expression. The roses cf this climate do not furnish sufficient oil to be worth procuring, and even in the East (Asia) the produce is very small, one hundred pounds of the roses yielding about three drams of oil. It is of a pale-yellow tint, and of a strong odor, re- sembling the fresh flower. ESSENTIAL OILS CONTAINING THREE OR MORE ELE- MENTS. 452. Oil of Peppermint, obtained from the peppermint plant by distillation, is of a pale-yellow color, which deepens by age. It has a strong odor of the herb, and a hot, aro- matic flavor, succeeded by a sense of coldness upon the tongue. Oil of lavender is at first colorless, but acquires an amber tint. It is highly pungent, and is much employed as an article of perfumery. Common camphor, C10 H8 0.-—■ This concrete or solid essential oil is extracted from the roots and wood of the camphor-tree, which are chopped up and boiled with water in an iron vessel, with an earthen head containing straw, upon which the camphor condenses What is said of oil of juniper ? Oil of orange-peel ? Oil of roses ? Oil trf pep- permint ? Oil of lavender ? Camphor ? 20 230 VEGETABLE CHEMISTRY. after sublimation. Camphor is a white, half-transparent crystalline substance, having a warm, pungent, and some- what bitter taste. It evaporates in the air at ordinary tem- peratures, and sublimes in close vessels, attaching itself to the surface most exposed to light. It is soluble in alcohol, and is used in medicine both internally and externally. THE RESINOUS PRODUCTS OF PLANTS. 453. Source and Properties of the Resins.—Resinous sub- stances are very common in vegetables, and are found as piox- imate constituents of most plants; they are obtained from two sources. The balsams which exude from the bark of certain trees consist of resins dissolved in essential oils; when the oil has been dissipated by evaporation, the resin remains in the solid state. The volatile oils also, by sufficient expo- sure to the air, absorb oxygen, thicken, and are themselves converted into resm. The resins are, therefore, oxidized es- sential oils. This explains why volatile oils thicken and lose their odor and properties when kept and exposed to the air, and why old spirits of turpentine is not good for re- moving grease-spots from clothing, as it leaves a resinous stain. They are non-volatile solids, fusible, and highly in- flammable. When pure, they are inodorous, and usually of a pale yellow or brown color; but as commonly met with, they are odorous from traces of essential oil, and variously colored by foreign substances. They are insoluble, or but partially soluble in water, but dissolve in alcohol, ether, and the essential oils, and form varnish. They are feebly acid, combining with alkalies, and forming resinous soaps, which are capable of producing lather, and possess a low detergent power (442). How are resins obtained? What are they? Give their properties. RESINS—COLOPHONY—LAC. 231 454. Colophony (Common Resin), C40 H30 04.—This is the residue left after distilling turpentine from pine-trees to obtain its oil. 250 lbs. of turpentine yield about 30 lbs. of oil of turpentine and 220 of resin. Resin is a brittle, taste- less, almost inodorous substance, of a smooth, shining frac- ture, easily reduced to powder when cold, softening at 160°, and melting at 275° F. It produces a contrary effect to oil as regards friction, rendering a surface which is covered with it rough, uneven, and adhesive. It is hence applied to the bow of the violin, and the cords of clock-weights, and belts of machinery, to increase their adhesion and prevent them from slipping. If resin is set on fire in the open ah, and after a sufficient time the flame is extinguished, a soft, black, pitchy substance remains, known as shoemaker's wax. 455. Lac.—This is a resinous substance flowing from several plants, in the East Indies, through punctures made in their branches by insects. The twig becomes incrusted with a reddish substance, which consists of the juice of the plant, hardened and imbued with coloring matter, derived from the insect. These twigs, broken off, constitute the stick-lac of commerce; when removed from the twigs it is seed-lac; when melted, strained, and poured upon a smooth surface, so as to spread ou+ into thin plates, it forms shellac. The coloring matter of lac is used as a scarlet dyestuff, in two forms, under the names of lac-lake and lac-dye. The best shellac is of an orange color, the inferior kinds of a dark brown. Being hard and tough, it is used to make sealing- wax. For this purpose, turpentine is added to increase its inflammability, and various coloring matters to give it the What is common wsin? What are its properties? Why is it used on violin- hows and the belts of machinery ? How is shoemaker's wax obtained ? How is lac obtained? What is stick-lac? Seed-lac? SheUac? Lac-lake! Wol- ish is an alcoholic solution of shellac with a small quantity of oil. It is laid on by a ball of cotton, and then rapidly rubbed in the direction of the fibres of the wood. The finer articles of furniture are usually polished, the more ordinary ones varnished. Oil of turpentine is a leading solvent of varnish. Japan, or black varnish, contains asphaltum, and elastic varnish India-rubber. 460. Gum-resins.—Many plants, particularly in hot cli- mates, produce compounds which contain both the resinous and gummy principles. Their gummy portion is soluble in water, and the resinous portion in alcohol. Opium, asafcetida, aloes, gamboge, myrrh, and frankincense are vegetable prod- ucts- of this nature. 461. Caoutchouc (India-rubber, Gum Elastic).—This well- known substance is obtained by making incisions through the bark of certain trees, of the fig or banian species, which grow in South America and the East Indies: a milky juice flows out, which, upon evaporation, yields about 32 per cent, of caout- chouc. The poppy, the lettuce, and other plants, having vis- cid, milky sap, seem also to contain it. Caoutchouc, when pure, is white and transparent; its dark color being due to the blackening effect of the smoke in drying. It is highly elastic, and the freshly cut surfaces adhere strongly, if pressed together. It is insoluble in water, alcohol, and acids; but dissolves in ether, naphtha, sphits of turpentine, and other essential oils. The solutions in ether and naph- tha leave the caoutchouc in an elastic state. It is,a sim- ple hydro-carbon, containing no oxygen, and burning with a nish ? How is a spirit varnish made ? What is oil varnish ? What is Frencn polish ? How is it applied ? Mention some of the gum-resins. How is India-rubber obtained? What aro its properties ? What are its usee? THE ORGANIC ACIDS. 235 luminous, sooty flame. Its uses are very various. Dissolved, and applied to fabrics, t forms water-proof cloth: it is also used for shoes; and when cut into thin shreds, and boiled with linseed oil (4 oz. caoutchouc to 2 lbs. of oil), it forms a mixture used for making boots water-tight. It forms gas- bags, flexible tubes, and connectors for the laboratory. India- rubber is vulcanized by impregnating it intimately with sul- phur, whereby its elasticity is increased at low temperatures, and other useful properties added to it. 462. Gutta Percha is obtained from the milky juice of certain East Indian trees, in the same way as caoutchouc. When pure it is of a dirty-white color, of a greasy feel, and has a peculiar leathery smell. At ordinary temperatures it is non-elastic, tough, and as hard as wood; but when im- mersed in hot water it softens, so as to admit of being moulded into any shape, and again hardens when cooled. It melts at 250°, is highly inflammable, and bums in a manner similar to sealing-wax. It dissolves in boiling spirits of tur- pentine, but not in alcohol or the fixed oils. It is applied to many uses in the arts. THE ACID PRODUCTS OF PLANTS. 463. The Organic or Vegetable Acids.—These substances are numerous in the vegetable kingdom, occurring largely in fruits, and sometimes in the leaves and roots. They exist in a free state, and combined with bases, forming acid salts both soluble and insoluble. They are composed of carbon, hydrogen, and oxygen, with the exception of oxahc acid, which contains only carbon and oxygen. In general, the oxygen is greatly in excess; in acetic acid only is it in the What are the properties of gutta percha ? What is Raid of vegetable acids ? Of what are they composed ? 236 VEGETABLE CHEMISTRY. proportion with hydrogen to form water. The hydroges and oxygen, shown upon the Chart at the left of the organic acids, represent the basic water with which the acid is com- bined, and Avhich cannot be separated from it without de- stroying also the organic acid. 464. Tartaric Acid, C8 H4 O10 + 2 H 0—(Brande).— This acid is found abundantly in grapes and tamarinds. It exists also in rhubarb, the potato, and in the roots of wheat, madder, and the dandelion. When new wine is decanted from the lees, and set aside in vats or casks, it gradually de- posits a hard crust or tartar on the sides of the vessel. This is a compound of tartaric acid with potash, familiarly known as cream of tartar. From this tartaric acid is produced, by the action of chalk and sulphuric acid. It is used in calico- printing and in medicine. It has an agreeable acid taste, dissolves readily in water, and causes a violent effervescence when mixed with a solution of carbonate of potash or of soda. It is extensively used in artificial soda-powders and effervescing draughts. 465. Citric Acid (Acid of Lemons), Cu H5 On -f- 3 H 0. —This acid gives their sourness to the lemon, the orange, the cranberry. It also exists, mixed with much malic acid, in the currant, cherry, gooseberry, raspberry, strawberry, and whortleberry. It is obtained chiefly from the juice of the lemon, and is used, like tartaric acid, for effervescing draughts. Malic Acid, C8 H4 08 + 2 H 0—(Brande).— This is the principal acid of unripe apples (hence its name, from malus, apple). It also exists in the free state in pears, peaches, quinces, plums, apricots, cherries, gooseberries, raspberries, strawberries, grapes, blackberries, currants, elder- Where is tartaric acid found? What is cream of tartar? What are the uses of tartaric acid ? What is said of citric acid ? Whence does malic acid derive its name ? When is it found ? THE ORGANIC ACIDS—TANNIC--GALLIC. 23T berries, and several other fruits. It has a very sour taste, but is not used in a separate state. 466. Tannic Acid (Tannin), C18 H5 09 -f 3 H 0— (Lie- big).—This substance is found in the leaves and bark of cer- tain trees, and imparts to them a puckering taste. It is nearly colorless, soluble in water, and has a powerfully astringent taste. Nut-galls contain of tannic acid 2 7-4 per cent.; oak bark, 6*3; chestnut bark, 4-3; elm bark, 2-7; sumach, 16-2 ; green tea, 8'5 ; Souchong tea, 10. The astrin- gent quality of tea is due to the tannin it contains. Tannic acid combines with the peroxide of iron, forming a blue- black precipitate (pertannate of iron), which is used for coloring gray and black, and also for making writing-ink. Gum is added to the ink to retain the coloring matter in suspension, and to prevent excessive fluidity. 467. Tannic acid also possesses the peculiar property of combining with gelatine, and forming a compound insoluble in water. Upon this property depends its extensive appli- cation in the manufacture of leather, by uniting with the gelatine of which the skins of animals are chiefly composed (535). The skins are packed in vats with layers of ground bark, and the whole is immersed in water. The tannin dis- solved out of the bark gradually unites with the skin. The process is quickened if conducted under pressure (quick tan- ning), by which the solution is made to penetrate the tissue more rapidly. 468. Gallic Acid, C7 H 03 + 2 H 0—(Liebig).—This acid is found associated with tannin in bark, and is formed from tannic acid, by exposing a solution of it to the air for What are the properties of tannic acid? Where is it found? How is writing- ink made from it ? What effect does it produce upon the skins of animals? How are the skins tanned ? What is said of gallic acid ? 238 VEGETABLE CHEMISTRY. some time. Like tannic acid, it yields a precipitate with protosalts of iron, but a deep blue-black with a persalt. It does not precipitate gelatine. 469. Pectic Acid (Pectine, vegetable jelly), C12 H8 O10— (Mulder).—Pectic acid exists in the juice of most pulpy fruits, and is extracted, for dietetical purposes, chiefly from currants, apples, quinces, strawberries, and raspberries. Pectic acid and pectine have the same composition. They have an insipid taste when pure, and are somewhat allied in properties to the gums. Fruit jellies prepared with sugar form agreeable cooling articles of food in febrile and inflam- matory complaints. It is but slightly nutritive. 470. Oxalic Acid, C2 03 + H 0.—This acid imparts the sour taste to common sorrel and the rhubarb plant, in which it exists combined with potash and lime. It is obtained in crystals, which are intensely sour and poisonous, chalk or magnesia being the antidote. It may be made artificially by the action of nitric acid upon sugar or starch, which yield about half their weight of the oxalic acid. Oxalic acid is the test for lime, and forms with it an insoluble salt, oxalate of lime. It removes ink and iron stains from linen. BASIC PRODUCTS OF PLANTS. 471. Vegetable Alkalies.—Most plants give rise to pecu« liar substances, usually in very small quantity, which exhibit alkaline properties ; they are much less abundant than the vegetable acids, and are generally sparingly soluble in water, of a bitter taste, and always contain nitrogen. They form the active medicinal agents of the plants in which they occur, and are generally very poisonous. These bodies are of in» What is said of pectic acid ? Oxalic acid ? For what is it used ? What is said of the vegetable alkalies ? For what are they used ? COLORING MATTERS—INDIGO. 239 fcerest only to physicians and chemists, andtherefore cannot be described in this place. COLORING MATTERS PRODUCED BY PLANTS. 472. Different Kinds of Coloring Matter.—As a class, vegetable coloring matters do not possess many chemical characters in common, and are associated together on account of their common application in the arts. Most of them are acids, but some are neutral: some are ternary and others quaternary. The most vivid and brilliant of vegetable colors, those of flowers, are fugitive, small in quantity, and very difficult to separate. The coloring matters in the interior of plants, where they are not exposed to light, are less brilliant but more durable. The most common color of the vegetable kingdom is green, but the substance which gives rise to this color (chlorophyl) is of an oily nature, and cannot be easily applied to cloth. Nearly all the coloring matters of plants which are capable of being separated are blue, yellow, and red. No genuine black coloring substance has ever been obtained from plants. Acids and alkalies act so remarkably upon vegetable coloring matters, that the latter are em- ployed as tests for these substances (45, 47). BLUE COLORING MATTERS. 473. Indigo.—This well-known dye-stuff is obtained from the juice of several plants which grow in hot climates. The juice is colorless, but when exposed to the air it absorbs oxy- gen and deposits a blue sediment, which is thrown into mar- ket, in the form of a powder, often cohering in cakes, as How do the vegetable coloring matters differ in character ? What is said of the most brilliant colors? What color is most abundant in vegetables? Why can U not bo separated ? What coloring mattere can be separated from plants ? uo VEGETABLE CHEMISTRY. commercial indigo. It is tasteless, without odor, insoluble in water, and nearly so in all other liquids except sulphuric acid. When placed in situations which deprive it of oxygen in- digo loses its blue tint, becomes colorless, and soluble in water. On exposure to the air, the deoxidized indigo absorbs oxygen again, and acquires its deep blue color and insolubility. Fab- rics may, therefore, be steeped in a solution of colorless or white indigo, as it is called, and by subsequent exposure to the air the color is developed. Indigo affords a bright tint, and adheres to textile fibres with great permanence. 474. Litmus.—This coloring substance is extracted from certain species of moss which grow upon rocks. They yield at first a purple or red coloring matter, which is changed to blue by the action of the alkalies. The cubes of fitmus used for making test-paper are thus prepared. RED COLORING MATTERS. 475. Madder.—The roots of the madder-plant, ground to powder, furnish this valuable dye-stuff. The powder is at first yellow, but reddens by exposure to air and absorption of oxygen. Besides red, madder furnishes a purple, a yel- low, an orange, and a brown. 476. Brazil-wood and sandal-wood, the former yielding a coloring substance soluble in water and the latter a resinous body insoluble in water, are used for dyeing red. Carmine is of animal origin, being derived from the cochineal, a dried insect of Mexico. It affords an intense red. Lac-dye is also of animal origin. Whence is indigo obtained ? What are its properties ? To what is its blue color owing ? What is said of its permanence ? How is litmus obtained ? For what is it used ? What colors are obtained from madder.? What is Brazil-wood ? Sandal-wood ? Carmine ? COLORING MATTERS—CHLOROPHYL. 241 YELLOW" COLORING MATTERS. 477. These are obtained from the bark of-the black oak (durecitron), from the wood of the West Indian mulberry (fustic), and from the green berries of the buckthorn. Anat- to, extracted from the pulp of certain seeds grown in South America, is much used to color butter and cheese. It is also employed to give an orange color to milk. Turmeric is derived from the roots of an East Indian plant, and saf- fron from the flowers of an herb growing in the temperate climates. GREEN COLORING MATTERS. 478. Chlorophyl (Leaf-green).—This is the substance to which the vegetable world owes its uniform green color. Il is of a waxy nature, soluble in alcohol and acids, but insol- uble in water, as is shown by the fact that rain falling ovei leaves is not turned green. Berzelius asserts that chloro- phyl exists only in very small quantity in plants, the leaves of a large tree not containing perhaps more than 100 grains. This substance appears to be a direct, and perhaps the first product, of the action of light upon vegetation, as it never appears except in those parts exposed to the luminous agent. Thus plants removed from a dark cellar into the sunlight turn rapidly of a green color, and every one may have re- marked in spring, when the foliage begins to start, how quickly, after a few days of cloudy weather, the color of the leaves is changed to a deep green by the rays of the sun. A writer mentions a forest upon which the sun had not shone for twenty days. " The leaves during this period were ex- From what are yellow coloring matters obtained ? What are the uses of anatto ? Whence is turmeric obtained ? Saffron ? What is chlorophyl ? How is it shown to be insoluble? Is it ever formed in 21 242 VEGETABLE CHEMISTRY. panded to their full size, but were almost white. One fore- noon the sun began to shine in full brightness; the color of the forest absolutely changed so fast that we could perceive its progress. By the middle of the afternoon the whole of this extensive forest, many miles in length, presented its usual summer dress." The vegetable green is changed to yellow in autumn, probably by oxidation. It has been re- marked that all trees and shrubs the leaves of which redden in autumn bear red fruit or berries; the nature of this red coloring matter is not known. Sap-green is an extract pre- pared from the juice of the buckthorn berries. 479. Principles involved in Dyeing.—The art of the dyei consists in impregnating textile fabrics with the various col- oring matters in such a manner that they will remain perma- nent or fast, and not change by wear or washing. Some coloring substances, as indigo, for example, unite directly with the fibres, forming fixed colors. Others, those chiefly that are soluble in water, if applied to the goods do not of themselves adhere, but are discharged by washing. These require some intermediate substance which has an affinity both for the coloring matter and the fibre, and will link them together in one insoluble compound; such a substance is called a mordant (from mordeo, I bite), because it is said to bite the color into the cloth. The principal mordants are salts of tin, iron, and alumina (218). In calico-printing the mordants are first fixed upon the cloth, either uniformly or in spots, and the color subsequently applied by means of blocks or revolving cylinders. The cylinder machines com- municate colors very rapidly, the cloth passing through them at the rate of a hundred feet per minute, or a mile in the the dark ? What striking occurrence is mentioned illustrating this point? What b sap-green ? In what does the art of the dyer consist? In what respect do colors differ 1 What is a mordant? How are -qordants used? EXTRACTIVE MATTER. 24:3 hour. The textile fibres consist of hollow tubes (Figs. 21, 22), which the mordants are supposed to enter, filling them like bags, and remaining there to receive the coloring matter. Fig. 21. Fig< 22 Cotton Fibres. Linon Fibres. Woollen Fibres. EXTRACTIVE MATTER. 480. This term has been applied to numerous substances which have been extracted by chemists, chiefly from vege- tables, by the action of various solvents, and which have not yet been accurately examined. The number of known plants exceeds a hundred thousand, and each possesses peculiar principles in small quantity, to which its flavor and medicinal properties are due. Of this vast number, but few compara- tively have been studied by the chemists, and whatever they meet with of this kind that is unknown is designated as ex- tractive matter. CULTIVATION OF PLANTS. 481. Its Relations to the Air.—When a vegetable sub- stance is burned, the mass of it disappears, taking the form What is meant by extractive matter ? 244 VEGETABLE CHEMISTRY. of gases and escaping into the air, and a small residue re« mains, termed ashes. Now when plants grow, they draw back again from the atmosphere all those gases which escape into it by combustion, and obtain from the soil only those mineral solids which form its ashes. Thus the great bulk of vegetable matter is derived from the air, and as the atmos- phere is uniform in composition, that portion of the nutrition of plants which depends upon this source may go forward in all places with nearly equal facility. The air contains an exhaustless store of elements for the use of vegetation, and so far as it is concerned, all plants may be grown with equal success in all places. 482. Relations to Heat and Light.—But it is not so with the agencies of heat and fight which radiate from the sun. In consequence of the globular figure of the earth, these fall unequally upon its different parts. At the equator, where the rays are perpendicular, the heat and light are most in- tense, while as we pass towards the poles, the rays strike the surface more obliquely, and the effect is diminished in inten- sity. Now to these variations plants are adapted. Equato- rial vegetation, requiring large quantities of heat and light, cannot flourish in temperate climates, for although the atmos- phere and soil may contain all the chemical elements neces sary to its composition and nourishment, one of the condi tions essential to its growth is wanting. 483. Relations to the Composition of Soils.—In addition to the part played by the atmosphere and climate, which may be regarded as independent of human control, there is a third condition of the growth of plants which relates to the How does the burning of a vegetable substance divide its elements? What becomes of the part that escapes into the air ? Are these matters abundant in he air ? Are the agencies of heat and light equally distributed over the earth ? Why can not equatorial plants be grown in temperate regions ? CULTIVATION OF PLANTS. 245 composition of soils. If there is a want of elements derived from this source, growth is impossible; but if they are abun- dantly supplied, nutrition is rapid, and growth luxuriant. To ascertain and regulate the adaptations of soils to plants, to find out what elements are necessary for their develop- ment, and the most economical method cf supplying them, is the great problem of Agriculture. 484. Effect of Organic Manures.—It has been stated (139) that the source of the organic elements of vegetation— carbon, hydrogen, oxygen, and nitrogen—is the air. This is proved by the slow and gradual accumulation of organic substances in the soil of forests and of meadows, where it could not have been added artificially. But in growing cul- tivated plants, we do not depend entirely upon this source. A plant supplied with all the necessary inorganic substances, and allowed sufficient time, will extract the necessary gases from the ah- and attain a vigorous development. But if it is deshed to hasten the maturity of a plant, as is frequently necessary in certain climates, or to stimulate it to excessive development, then organized substances, vegetable or animal, are added to the soil, winch by decay and putrefaction gen- erate large quantities of carbonic acid and ammonia in the immediate neighborhood of the roots, by which they are taken up, dissolved in water. 485. Inorganic Elements of Soils.—The inorganic elements of plants (ashes), though small in quantity, are nevertheless of the highest importance. Unlike the organic elements, which are the same in all plants, these vary in different vari- eties of vegetation. Consequently, as one kind of plant takes What condition besides the climate and atmosphere is necessary for the growth of plants ? What is the great problem of Agriculture ? If we wish to stimulate the growth of plants, what plan is to be adopted? Why do farmers change the kind of crop upon a soil instead of growing one 21* 246 VEGETABLE CHEMISTRY. one mineral from the soil, and others take other kinds, the farmer finds it advantageous to cultivate in succession dif- ferent varieties of plants upon the same ground (rotation of crops). If a soil yields good crops of one vegetable and not of another, it must be wanting in the characteristic mineral elements of the latter, which should then be supplied. And if any particular plant, cultivated or wild, flourishes in any given spot, an examination of its ashes indicates at once the capabilities of the soil, by showing what soluble salts it fur- nishes. 486. Substitution of Elements.—Although the ashes of certain plants are distinguished by the prevalence of certain bases, as those of potatoes and turnips by potash, and those of peas and beans by lime, yet to a certain extent one base may be substituted for another, as soda for potash, or mag- nesia for lime. This can only be done, however, by forcmg nature, as it were, out of her regular course. 487. The best Manure for a Plant.—Decaying vegetable and animal substances applied to crops, act not only by sup- plying carbonic acid and ammonia, but also by furnishing such inorganic salts as the decomposing substance may hap- pen to contain; hence, for any particular crop, as hay, grain, or potatoes, there is no manure so good as the same kind of vegetable in a state of decay, or its ashes, or the manure of animals fed upon it; but in the latter case, it is of the first importance to make use of the whole manure of the animal, as its fiquid excretions, the part most liable to be lost, are by far the richest in soluble salts. 488. The Golden Rule of Agriculture.—The great rule kind constantly ? If a plant flourish upon a soil, what information do we gain by examining its ashes ? What is said of the substitution of one element for another? What is the best manure for a plant ? CULTIVATION OF PLANTS. 24.7 (O be followed in this branch of agriculture, is to restore to the soil, in the shape of manure, exactly what it has lost in the crop; as by this means alone the fertility of the soil can be maintained, and the vocation of the farmer be sus- tained upon a remunerative basis. By failing to heed this rule, millions of acres of the finest land in this country have been already so exhausted as not to be worth cultivating, and millions more are now undergoing the same ruinous process. No one who contemplates for a moment the de- plorable waste of manure (especially human excreta, the richest of all) which is so prevalent both in our cities and large towns, and also among the generality of farmers, can be at a loss to account for this gradual decline in the fruitfulness of land. Manure is the raw material which is to be worked up into sustenance for human beings; but in our seaboard cities it is thrown into the ocean, and in other cities it is cast into rivers and borne seaward, as if it possessed no value whatever. Every consideration, therefore, as well of public beneficence as of private thrift, demands that all fer- tilizers, every kind of manure, both liquid and solid, shall be saved with the most rigid economy. It is the farmer's mo- tive power: with it he can do every thing, without it, nothing. What is the golden rule of agriculture ? What is the result of neglecting this •ule ? What, then, should demand the first consideration of the farmer ? ORGANIC CHEMISTRY. ANIMAL CHEMISTRY. GENERAL NATURE OF THE ANIMAL FUNCTIONS. 489. Animal Chemistry instructs us in the composition and chemical properties of the several parts of the animal body, and throws light upon many of the changes to which they are constantly subjected in the living being. Very much, however, that transpires within the vital mechanism is still wrapped in mystery which Chemistry at present is unable to penetrate. Physiology ha* but recently consented to avail herself of the assistance of this science in solving her prob- lems, and already many beautiful and highly important re- sults have been obtained. The rapid advance lately made in this interesting and most useful department of knowledge, justifies the expectation that the animal system will continue still further to surrender its secrets, until the whole field of legitimate investigation shall have been explored. 400. The Exercise of Power produces Waste of Matter.— It is an established law of nature, that the exercise of all force is attended by a waste of matter. No action, however trifling, can take place but at the expense of the materia] engaged in its performance. Every breeze that sweeps What does Animal Chemistry teach ? Does il explain aU the chemical changes that occur in animals ? What has recently been done ? What law is here given? In obedience to this law, what course is pursued bj mechanics ? FORCE EXERTED AT THE COST OE MATTER. 249 over the ground alters somewhat its surface. The rain that falls upon a naked rock bears away some portion of it to the sea. So well is it understood that motion can only occur at the cost of material, that mechanics resort to every contri- vance which can diminish the amount of this loss; they con- struct machines of the hardest and most lasting substances, they execute the nicest adjustments, apply oil or other lubri- cating bodies to all rubbing surfaces, yet, notwithstanding these precautions, the mechanism finally falls a prey to its own activity, or in other words, it becomes worn out. 491. Waste of Matter in Organized Structures. — But it is not alone in the department of mechanics or the inor- ganic world that we observe the operation of this law ; it is displayed on a vastly more imposing scale in the organic kingdom of nature. The vital actions of plants, then growth, and the development of their various parts and products, can only take place by means of an enormous waste of matter, as we have seen when speaking of evapo- ration from the surface of the leaves (324). In the animal system, every motion which it performs, voluntary or invol- untary, every movement of a limb, and indeed every exer- tion of the mind, is accompanied by a destruction or waste of the material of which the animal fabric is composed Throuo-h the lungs, the kidneys, the bowels, and the whole surface of the body, the worn-out, and, as it were, used- up atoms, are rejected from the system to the extent of several pounds each day. It is an error to suppose that decay and decomposition begin only after the death of the body. They proceed during every moment of life, from the first kindling of the vital spark to its extinction in death. What examples of the operation of this law are seen in the vegetable and ani- mal kingdoms ? Upon what does the maintenance of life dt^end ? What i3 tho distinction between living and dead matter ? 250 ANIMAL CHEMISTRY. Indeed, the maintenance of animal fife is only possible by the perpetual waste and destruction of the organism by which it is manifested. In the passage of constituent par- ticles from the living to the dead state, consists the life and power of the individual. Were this process of dying by atoms, in a measured and regulated way, suddenly to cease, the death of the whole system would be the consequence. It is usually said that dead animal matter is marked by its necessary tendency to decay, while the living body is dis- tinguished by its power of resisting decay. But so far is this from being true, that the very opposite is the fact. The fixed condition of the continuance of life in an animal is the decomposition which all its parts constantly suffer, while dead animal matter may be preserved, it is well known, for almost any length of time unchanged. Meat, by partially cooking and sealing up free from air, may be kept sweet even in the moist state for years. Cold also arrests decay. In Russia, animals are long kept in the market in a frozen state, and their flesh, when thawed, is as good as ever. 492. Reparative Power of the Living Being.—But in one very important respect the living mechanism differs from the inanimate machine ; the latter has no ability to repair the destruction it suffers by use. There is no inherent power in a watch or a steam-engine to restore its wasted parts ; action goes forward until checked by loss of sub- stance and consequent derangement, when the combination is handed over to the mechanic for" reconstruction. The living body, on the contrary, is endowed with a capacity of self- renovation. It can repair its failing tissues, and counteract its own constant tendency to ruin. The process by which this renewal takes place is called nutrition, and the sub- stances employed to carry it on constitute food or nutriment. In what respect does the living body differ from the inanimate machine ? MODE OF THE SUPPLY OF MATTER. 251 By means of food, therefore, the living organism can com- pensate the rapid expenditure of its own substance, restore its losses, and maintain its power. 493. Supply of Matter to the Plant.—This process of nutrition is accomplished by different methods in the two great departments of organic life. The plant is fixed to one spot, and has no power of changing its locality. Its roots penetrate the soil to a limited distance, and its leaves are spread through the air. Within this narrow space it finds the elements necessary to its growth. Water, with mineral salts, and gases extracted from the earth and atmosphere, constitute its food. If these happen to abound, the plant exhibits a condition of high activity, a rapid and luxuriant growth; if this supply is deficient, development is corre- spondingly feeble and imperfect. The simple object of the plant is to grow, and form various proximate substances. It is hence found in immediate connection with the sources of its nourishment, and there remains throughout the whole term of its life. 494. Mode in which Animals are supplied with Matter.— The case is different with animals, especially the higher classes. They are organized for the accomplishment of other purposes besides bare vegetative development, and the nutritive operations are so carried on as not to interfere with the higher functions. Having the power of locomotion, by which it is capable of moving from place to place, the ani- mal is supplied with a cavity (stomach), into which it receives a store of food sufficient to last it for a considerable time, in- dependent of a supply from any external sources. From this cavity the system is gradually supplied with nutritive mat- To what conditions is the plant confined ? How do the conditions of nutrition in animals differ from those ol plants? What constitutes a fundamental distinction between animals and plants? 252 ANIMAL CHEMISTRY. ter until its contents are exhausted, when the store is again renewed as occasion may require. The presence of this di- gestive cavity or stomach, for the reception of a stock of nourishment, is peculiar to animals, and it may be looked upon as a fundamental feature of distinction between tho animal and vegetable races. 495. Office of Water in the Animal Economy. — The constant and rapid changes of which the living body is the theatre, require that it should be so organized as to permit the greatest possible freedom of motion among its elements. This could only be done by making use of a perfect liquid as a medium and vehicle of that incessant transportation of particles which takes place within the organism. Water is the instrument chosen for this purpose. Its complete liquidity within a considerable range of temperature, togethei with its numerous other properties (91), adapt it in a won- derful degree to this office, and it is therefore found to be the leading and fundamental constituent of all organized fabrics, existing to the extent of 75 per cent, throughout the animal system. Whatever is to take part in the processes of the living body must first be reduced to a state of solu- bility, so as to be carried to its appointed stations by the liquid currents which are constantly flowing to all parts of the organization. To effect this purpose is one of the chief objects of digestion. 496. Operations to which Food is subjected in the Body.— In a comprehensive sense, digestion may be regarded as the conversion of food into blood. But this act consists of sev- eral steps or stages which are commonly distinguished as, 1st, mastication and insalivation, or chewing the food and Why must a large portion of the animal system be in a liquid condition ? How is water adapted for this purpose ? What is digestion ? What are the several stages of digestion ? RELATION OF CULINARY PROCESSES TO DIGESTION. 253 mixing it with the saliva of the mouth; 2d, chymification, or digestion proper, solution in the stomach ; 3d, chylifica- Hon, or the production of chyle by further digestion in the intestines ; and 4th, sanguification, or the conversion of chyle into blood. We shall gain the clearest idea of the subject, in the hasty glance to which we are confined, by following this natural order, and tracing the food through the series of interesting and remarkable changes which are successively impressed upon it, until it becomes part of the fabric of the animal system, and by then inquiring in what manner and for what purposes it is separated and thrown back again to the inorganic world, from whence it was first derived by plants. CULINARY PREPARATION OF FOOD. 497. The changes which food undergoes by the various operations of cooking may be considered as preparatory to digestion; and as they greatly influence this process by either aiding or obstructing it, it is proper at this point briefly to notice them. 498. Effect of Cooking upon Vegetables.—The general effect of cooking upon vegetable substances is more or less completely to destroy then organization by means of the de- composing agency of heat. By boiling, the grains of starch which constitute a large portion of most vegetable foods are ruptured or disorganized, and partially dissolved. Vege- table albumen is coagulated or solidified by boiling (373). When potatoes are boiled, the starch of which they mainly consist does not form a mucilage or jelly, such as is pro- duced by boiling pure starch. This is probably due to the What is the general effect of cooking upon vegetables ? What is the effect 91 boiling upon starch ? Upon albumen ? Why does not the starch of potatoes form mucilage upon boiling ? What other results are produced by boiling vegetaolea ? What is said of roasting and baking ? 22 254 ANIMAL CHEMISTRY. effect ti Jxv albumen which exists in the tuber in ine form of a filmy envelope around the starch grains, and thus par- tially cuts them off from the solvent action of the water. The hard parts of vegetables become softened, and the tis- sues, which are more or less tough, as the leafy portions of greens, &c, by sufficient boiling become tender, and are easily dissolved in the stomach. Sugar, gum, and various other mbstances are dissolved, and volatile oils dissipated by boiling. A quite similar effect is also produced upon the starch and albu- men of vegetables by the processes of roasting and baking. 499. Animal Food.—The changes produced upon animal tood differ in some respects from those upon vegetable sub- stances, the nutritive value of flesh depending greatly upon the manner in which the cooking operations are conducted. The flesh of the lower animals which is used as food pos- sesses the same constituents and properties as that of man, and therefore the fewer changes it undergoes by culinary preparation, the easier and more complete will be its trans- formation in the system. If flesh employed as food is again to become flesh in the body, it is clear that none of its ele- ments should be withdrawn from it by any preliminary oper- ations to which it may be submitted. 500. Effect of Boiling upon Flesh.—The muscular fibre of meat, in the natural state, is everywhere surrounded by liquid albumen, and when this is removed, the fibre which re- mains is the-same in all animals. The effect of boiling upon free muscular fibre, which constitutes the basis of lean meat, is to render it hard and tough in proportion to the briskness and duration of'the process. But this effect is, to a certain Upon what does the nutritive value of flesh depend ? Why should flesh be changed as little as possible in cooking ? What is said of muscular fibre ? What is the effect of boiling upon it ? Why is the flesh of young animals mm* toiadi.tr than that of old ones ? CULINARY PREPARATION OF FOOD. 255 extent, prevented by the coagulation of the albumen, which envelops the fibres, and protects them from the full effect of ebullition. Hence the flesh of young animals, which is richer in albumen, is more tender than that of old ones, which con- tains much less. The albumen, by protracted boiling, becomes hard, but not tough. 501. Nutritious Juices of Flesh.—The juices of flesh con- tain not only its dissolved albumen, but also other soluble substances to which the agreeable taste and flavor of meat, as well as its nutritive effect, are due. Hence, if flesh is chopped fine and soaked in cold water, these substances will be all dissolved out, so that the fibrinous residue, when boiled, proves perfectly tasteless. If the watery solution is concen- trated by evaporation, and poured over the meat from which it was removed, it restores the natural flavor. All sorts of flesh are alike in this respect, their peculiar odorous and sapid principles existing in the soluble state. Hence, if a cold aqueous solution of venison or fowl is added to boiled beef and the whole warmed together, the beef acquires the taste of the venison or fowl. The common practice of boil- ing meat and vegetables in large quantities of water, which is thrown away and with it nearly the whole of the soluble matter, is thus seen to be wasteful and injurious in a high degree. We also see that the plan of stewing, in which all the soluble matter is retained in the sauce or juice and served with the meat, has decided advantage over boiling. Liebig, who has lately investigated this subject, suggests the follow- ing application of these principles : 502. Best Method of boiling Meat.—" If the flesh intended to be eaten be introduced into the boiler when the water is in To what is the flavor of meat due ? How may the fibre be rendered tasteless ? How is the flavor restored ? What conclusions are drawn from this? What is the best method of boding meat ? Describe the effect of this process 256 ANIMAL CHEMISTRY. a state of brisk ebullition, and if the boiling be kept up foi some minutes, then so much cold water added as to reduce the temperature to 165° F., or 158°, and the whole kept at this temperature for some hours, all the conditions are united which give to the flesh the quality best adapted to its use as food. When it is introduced into boiling water, the albu- men immediately coagulates from the surface inwards, and in this state forms 'a crust or shell, which no longer permits the external water to penetrate into the interior mass of flesh. But the temperature is gradually transmitted to the interior, and there effects the conversion of the raw flesh into the state of boiled or roasted meat. The flesh retains its juices, and is quite as agreeable to the taste as it can be made by roast- ing ; for the chief part of the sapid constituents of the mass is retained under these circumstances in the flesh." 503. Best Method of preparing Soup.—" Soups which are to contain the soluble portions of meat are not best ob- tained by long boiling the flesh. The boiling water coagu- lates and renders insoluble that which should be dissolved in the soup, and which may be extracted by cold water. When one pound of lean beef, free of fat, and separated from the bones, in the finely divided state in which it is used for beef-sausages or mince-meat, is uniformly mixed with its own weight of cold water, slowly heated to boiling, and the liquid, after boiling briskly for a minute or two, is strained through a towel from the coagulated albumen and fibrine, now become hard and horny, we obtain an equal weight of the most aromatic soup, of such strength as cannot be ob- tained, even by boiling for hours, from a piece of flesh. When mixed with salt and the other usual additions by which soup is seasoned, and tinged somewhat darker by means of roast- Why should not the flesh be long boiled, in making soup ? What process is tecommended ? CULINARY PREPARATION OF FOOD. 257 ed onions and burnt sugar, it forms the very best soup which can in any way be prepared from one pound of flesh." 504. Effect of Salting upon Meat.—"It is universally known that, in the salting of meat, the flesh is rubbed and sprinkled with dry salt, and that where the salt and meat are in contact, a brine is formed, amounting in bulk to one- third of the fluid contained in the raw flesh. I have ascer- tained that this brine contains the chief constituents of a con- centrated soup or infusion of meat, and that, therefore, in the process of salting, the composition of the flesh is changed, and this, too, in a much greater degree than occurs in boil- ing. In boiling, the highly nutritious albumen remains in the coagulated state in the mass of the flesh; but in salting, the albumen is separated from the flesh; for when the brine from salted meat is heated to boiling, a large quantity of albumen separates as a coagulum. It is now easy to under- stand that in the salting of meat, where this is pushed so far as to produce the brine above mentioned, a number of substances are withdrawn from the flesh which are essential to its constitution, and that it therefore loses in nutritive qualities in proportion to this abstraction."—(Liebig) 505. Other Methods of preparing Meat.—In roasting, meat parts with a considerable portion of its water by evap- oration ; the albumen it contains is coagulated; the mus- cular fibre is hardened, especially upon the outside, where it is often partially carbonized before the interior is suffi- ciently done. Broiling and baking produce similar effects to roasting. Frying is the most injurious method of cook- ing meat, as the heat is applied by means of boiling oil or fat. By the high temperature these are so changed as to What is the effect of salting upon meat? How is it shown that the albumen is separated from the flesh ? How is meat affected by roasting ? Broiling ? Baking ? Frying ? •22* 258 ANIMAL CHEMISTRY. become very indigestible, and this property is also, in a degree, communicated to the meat. The flesh of animals is rendered harder and more indigestible by drying, smoking, pickling, as well as by salting. MASTICATION. 506. Instruments of Mastication in Man.—The instru- ments of mastication, by which the food is crushed and re- duced to fineness, are chiefly the teeth. The form of the teeth varies in different animals, according to the nature of then food. Thus in the carnivora (flesh-eaters) they have cutting-edges, and work against each other like the blades of a pair of scissors. In the graminivora (grain-eaters) they are terminated by large, flat, rough surfaces, adapted for grinding. The roughness of these surfaces is preserved by the unequal wear of the teeth, as they are composed of alter- nate vertical plates of substances having unequal degrees of hardness. Human teeth are of both these forms; they are 32 in number. The four front teeth in each jaw are termed incisors (cutting-teeth), the next tooth on each side the cuspid (canine or eye tooth), the next two bicuspids (small grinders), the next three molars (mill-like, or grinders). 507. Mode of reducing Food by Birds.—In birds, the office of reducing food is performed by the gizzard, a hollow muscle, furnished with a hard, tendinous lining, which in the grain-eating birds is strong and thick. The mechanical powers of the gizzard have been tested by causing the birds to swallow with their food balls of glass, which were soon ground to powder; and the points of needles and of lancets, What is the form of the teeth in the carnivora ? In the graminivora ? How aro they kept rough? What is said of human teeth? How many are there of each kind, and what are they termed? What is the oflice of the gizzard in birds? What instances are mentioned MASTICATION. 259 Fig. 23. fixed in a ball of lead, were blunted and broken off, whilst its own coat was not injured. In some of the lowest species of animals, the place of the gizzard is occupied by a curious pair of jaws, armed with teeth, by the working of which the food is effectually crushed. 508. Structure and Decay of the Teeth.—The teeth of man and the higher animals are composed of three very different substances—the enamel (a), (Fig. 23), which covers the whole crown of the tooth; the cement (d), which covers the fangs; and the ivory, or dentine (b), which constitutes the body of the tooth. The enamel is formed of fibres, or tubes, laid parallel to each other. It is composed almost entirely of mineral matter (phosphate of lime and fluoride of calcium), and con- tains not above two per cent, of animal matter, and is generally so hard as to strike fire with steel. The cement resembles bone (539), contain- ing about 40 per cent, of animal matter. The body of the tooth contains about 25 per cent, of animal matter, its min- eral matter being phosphate and carbonate of lime, in the form of very minute tubes. When teeth decay, the enamel is first worn off so as to expose the ivory, which is gradually dissolved by the acid of the unhealthy mucous membrane and saliva. The decay is thus deepened, until it reaches the nerve (c), when toothache occurs. The teeth are not sup- plied with nourishment, and hence have little or no power of restoring lost portions. Bhowing the mechanical powers of this organ? What is found in some of the lower animals? Describe the teeth of man. What are the composition and properties of enamel ? Uomcnt ? Dentine ? How does the process of decay proceed in teeth ? 260 ANLMAL CHEMISTRY. 509. Tartar of the Teeth.—This term is applied to a de- posit formed upon those parts of the teeth which are not protected from the cleansing action of the tongue. It is most abundant in the mouths of persons who speak much, and keep the mouth open, so as to allow the evaporation of the saliva. It consists of the earthy phosphates contained in the saliva, together with about 20 per cent, of animal matter. 510. Importance of complete Mastication of Food.—It is the office of the teeth to destroy the cohesion and mechanical texture of food, and separate its particles, so as to expose the largest possible surface to the chemical solvents in the diges- tive process. The chemist well understands the importance of thorough mechanical pulverization as a preliminary to sol- vent action. It is important, for the same reason, and to the same extent, that food should be well masticated before swallowing. The necessity of finely dividing food, in order to extract from it the fullest nutritive effect, has been shown by experiment. Cows fed upon ground barley yielded a larger product of milk than when fed upon an equal quantity of whole grain.—(R. D. Thompson.) INSALIVATION. 511. Properties of the Saliva.—Saliva, or spittle, is the fluid which moistens the mouth. It is separated from the blood by three pahs of glands, two beneath the tongue, and one in the cheeks, each pouring out its secretion by a separate canal. It is a transparent, viscid fluid, containing about one per cent, of earthy and alkaline salts, with a little mucus, and 99 per cent, of water. It has the property of entangling a large quantity of air, the oxygen of which, being swallowed What is said of the tartar of the teeth ? Why is thorough mastication necessary ? What examr le illustrates its advantage' What is saliva? What organs supply it? What are its properties? THE SALIVA—CHYMTFICATION. 261 with the food, is probably essential to digestion. The secre- tion of saliva is commonly just sufficient to lubricate the mouth, but during chewing it is poured out copiously. The amount has been estimated at from 15 to 30 ounces per day in a healthy adult. According to Mitscherlich, the saliva is commonly acid, but is alkaline during a meal. In some dis- eases, as intermittent fever, it is very sour. 512. Use of the Saliva.—The principal purpose of the saliva appears to be, when mixed with the food during mas- tication, to begin the chemical work of digestion. It has the power of converting starch into sugar, and sugar into lactic acid, and, when acidulated, of dissolving flesh and albuminous substances. " In general, the benefit derived from this process of insalivation is just that which is obtained by the chemist when he bruises in a mortar with a small quan- tity of fluid the substances which he is about to dissolve in a large amount. If the preliminary operations of mastica- tion and insalivation be neglected, the stomach has to do the whole of the work of preparation, as well as to accomplish the digestion; thus more is thrown upon it than it is adapted to bear; it becomes overworked, and manifests its fatigue by not being able to discharge its own proper duty." CHYMIFICATION-DIGESTION. 513. The Stomach: its Form and Size.—-The masticated food is carried by the act of swallowing (deglutition) into the oesophagus (gullet), which conducts it downward into the stomach. This organ is a large membranous bag, placed across the upper part of the abdomen. Its form is exhib- Where does the process of digestion commence ? What changes are effected bv the saliva ? If the process of insalivation is neglected, what effect follows ? Vv^hati the course of the food when swallowed? Describe the stomach. In whIt animals is it largest? In what is it smallest ? What is the size of the hu« man stomach ? 262 ANTMAA. CHEMISTRY. ited in Fig. 24, the large end being situated on the left side of the body, as is there seen. In different animals the size of the stomach varies exceedingly, according to the concen- tration of the food upon which they live. Thus in the flesh- bating animals it is very small, only a slight enlargement of the oesophagus; while in those which feed upon herbage, it is distended into an enormous cavity, or rather into sev- eral, as in the cow and sheep. The capacity oi the human stomach is about three pints. As a general rule, it is larger among those that live upon coarse, bulky diet. 514. Structure of the Stomach.—It consists of three mem- branous layers or coats, traversed by numerous blood-vessels and nerves. The outer layer is a smooth, glistening, whitish membrane, such as lines the abdomen, and covers all the in- ternal organs. Its use is to strengthen these organs, and by its smoothness and constant moisture, to permit them to move upon each other without irritation. The middle coat consists of two layers of muscular fibres, one of which runs length- ways and the other crossways, or around the stomach. By means of these muscles, it is enabled to contract its dimensions in all directions, so as to adapt its capacity to the amount of its contents ; they also play an important part ia giving mo- tion to the organ. The third layer of the stomach lines its inter- nal surface. It is a soft, velvet-like membrane, of a pale pink color in health, and of much greater extent than the outer coats, by which it is thrown into numerous folds or wrinkles. It is constantly covered with a thin, transparent, viscid mucus. 515. Properties of the Gastric Juice of the Stomach.— From the blood-vessels, which are distributed thickly over the stomach, there is separated, or poured out upon its in- What is the appearance and use of the outer coat of the stomach ? Tho mid Jl« layer ? The inner coat ? What are the properties of the gastric juice ? PROPERTIES OF THE GASTRIC JUICE. 263 ner surface, a pure, limpid, colorless, inodorous, slightly viscid, and always distinctly acid fluid, known as the gastric juice. It is readily diffusible in water or spirits, and effer- vesces slightly with alkalies. It is never obtained pure, but always mixed with another secretion of the stomach—a vis- cid, semi-opaque substance, salt to the taste, and without acid properties. The gastric juice, when taken from the stomach, may be kept for many months, if excluded from the air, without becoming foetid. It is powerfully antisep- tic, checking the progress of putrefaction in meat. 516. Composition of the Gastric Juice, and Mode of its Ac- tion.—The acid properties of the gastric juice are due to free hydrochloric, acetic, and lactic acids, which have been discov- ered in it by different chemists. Its solvent power over food depends upon the action of these acids (some suppose chiefly the hydrochloric), and also upon a peculiar animal principle, called pepsin, which is probably derived from the coats of the stomach, and is supposed by Liebig to act in the same way as ferment (379). It seems to affect nitrogenous aliments in the same way that diastase does starch (363), converting them into a state of solubility. The gastric juice also contains salts, muriates, and acetates of potash, soda, magnesia, and lime, although it may be observed that its composition varies in different animals, and seems adapted to different kinds of food. 517. The Power of Digestion is limited.—The gastric juice is not secreted constantly or regularly by the walls of the stomach, so as to accumulate and be in readiness for the food when it is introduced. It is poured out only when What acids are found iu the gastric juice ? To what does it owe its solvent power? How is it supposed to act upon the food? What salts are found in it ? Is it alike in all animals ? What causes the flow of the gastric juice ? How is the amount produced regu- lated ? Why should not the food taken exceed a fixed amount ? If food is taken in excess, what is the consequence ? 264 ANIMAL CHEMISTRY. food or some other substance is brought in contact with its interior surface, by which its secreting vessels are stimu- lated or aroused to action. When the stomach is empty, any solid substance taken into it will start the flow of the juice; but if the substance be not of a nutritive character, the secreting vessels speedily discover the cheat, and with- hold the secretion. It is an important fact, also, that the amount of gastric juice which the stomach is capable of pro- ducing is not in proportion to the quantity of food taken into it, but in proportion to the amount of food that the system requires for healthful nutrition. A definite proportion of food only can be digested in a given quantity of the fluid, as its action, like that of other chemical solvents, ceases after having been exercised on a fixed amount of matter. When the juice has become saturated, it will dissolve no more, and if an excess of food has been taken it rests as a burden upon the stomach, or passes half digested into the bowels, producing irritation, pain, and disease. 518. Effect of the Motions of the Stomach.—The food, as it enters the stomach through the cardiac orifice (Fig. 24), is immediately subjected to a peculiar movement by which it is thoroughly intermixed with the gastric fluid. This motion is produced by the alternate contraction and relaxation of the muscular bands (514), which produce a constant agi- tation or churning of the alimentary mass. The muscular contractions appear to take place in a kind of succession, by which the contents of the stomach are made to revolve or pass around the interior of the stomach in a circuit. This route is traversed by the food in from one to three minutes, but as chymification advances, the rapidity of the motions increases. The combined effect of this agitation and of the What is the first action of the stomach upon the food ? How is this motion pro- duced ? How long does it continue ? What is chyme ? Describe its appearance. EXPERIMENTS ON DIGESTION. 265 Mingled solvent is to reduce the sohd food to a uniform, pulpy, semi-fluid condition, in which it is known as chyme. It is of a grayish color and creamy aspect when the aliment used is rich ; and when otherwise, of a gruelly appearance. 519. Results of Dr. Beaumont's Experiments.—We are indebted for many interesting particulars concerning diges- tion to the observations of Dr. Beaumont, made upon the stomach of a young man named Alexis St. Martin, who had a hole perforated in his stomach by a gun-shot wound. It healed, leaving a permanent orifice of such size that the finger could be readily introduced, substances transferred, and va- rious observations made upon the nat;u-e of the processes which went forward within. Dr. Beaumont availed himself of the opportunity thus afforded to study the operations of digestion, and the results he obtained have added greatly to our knowledge of the subject. Among the conclusions to which he arrived are the following : That the presence in the stomach of any substance which is difficult of digestion inter- feres with the solution of food that would otherwise soon be reduced; that bulk is as necessary for healthy digestion as nutritious matter itself, a fact which explains vhe custom of the Kamschatkans, of mixing earth or sawdust with the train- oil ; that soup and fluid diet are not, alone, fit for the sup- port of the system, and are not more easily digested than solid afiment; that moderate exercise facifitates digestion (except, perhaps, immediately after a full meal); and that temperature controls digestion. This was shown by adding the gastric juice to finely divided food in vials, and frequently agitating it. At 100°, which is about that of the stomach, the solution proceeded with considerable rapidity; while in To* hat circumstance are we indebted for the experiments of Dr. Beaumont? Vhat is the first of his conclusions? The second ? What custom does this ex- -.lain? What is his next conclusion ? How was this shown ? What substancei Hid he find to require most time for digestion ? What the least ? 23 266 ANIMAL CHEMISTRY. the cold air the food was scarcely affected. A gill of watei at 50°, injected into the stomach, lowered its temperature up- wards of 30°; the natural heat was not fully restored again for more than half an hour; the habit of drinking ice-water freely during or after a meal must therefore retard digestion. Dr. Beaumont also made numerous experiments to determme the time required for different articles of diet to digest in the stomach, a summary of which is given in the following table : Rice............... Pig's feet, soused... Tripe, soused....... Trout, salmon, fresh. it a a Apples,sweet, mellow Venison, steak... Apples, sour, mellow Cabbage,with vinegar Codfish, cured, dry. Ejrgs, fresh........ Liver, beef's, fresh. Milk.............. Tapioca........... Milk............. Turkey, wild...... " domesticated Potatoes, Irish..... Parsnips.......... Pig, sucking....... Meat hashed with / , vegetables......\ Warmed Lamb, fresh.........Broiled.. Goose..............Roasted Cake, sponge........Baked Cabbage-head.......Raw Beans, pod..........Boiled.. Custard.............Baked___ Chicken, full-grown Fricasseed Apples, sour, hard... Raw Oysters, fresh.......Raw Bass, striped, fresh.. Broiled Beef, fresh, lean, rare Roasted " steak..........Broiled... Cori. cake.___......Baked.... Dumpling, apple.....Boiled.... Eggs, fresh......>#.. Boiled soft Mutton, fresh........Broiled •.. " " ........Boiled.... Preparation. Time. Boiled.... Boiled.... Boiled.... Boiled.... Fried..... Raw...... Broiled... Boiled.... Raw...... Raw...... Boiled___ Raw..... Broiled- • • Boiled.... Boiled.... Raw..... Roasted .. Boiled.... Roasted .. Baked.... Boiled.... Roasted .. b. m. 1 — 1 — 1 — 1 30 1 30 1 30 1 35 1 45 2 — 2 — 2 — 2 _ 2 — 2 — 2 — 2 15 2 18 2 25 2 30 2 30 2 30 2 30 2 30 2 30 2 30 2 30 2 30 2 30 2 45 2 45 2 50 2 55 3 — 3 — 3 — 3 — 3 — 3 — 3 — 3 — Pork, recently salted, Soup, chicken....... Oysters, fresh....... Pork, recently salted. Pork steak.......... Corn bread......... Mutton, fresh......., Carrot, orange....... Sausage, fresh...... Beef, fresh, lean, dry. Bread, wheat, fresh.. Butter.............. Cheese, old, strong... Eggs, fresh.......... Flounder, fresh...... Oysters, fresh........ Potatoes, Irish....... Soup, mutton....... " oyster......... Turnip, flat.......... Beets............... Corn, green, & beans. Beef, fresh, lean..... Fowls, domestic..... Preparation. Time Veal, fresh.......... Soup, beef, vege- ( tables, and bread ) Salmon, salted...... Heart, animal....... Beef, old, hard, salted Pork, recently salted. Cabbage, with vinegar Ducks, wild......... Pork, recently salted. Suet, mutton........ Veal, fresh.......... Pork, fat and lean___ Suet, beef, fresh..... Tendon ............ Raw..... Boiled.... Roasted.. Broiled... Broiled... Baked.... Roasted • • Boiled.... Broiled... Roasted .. Baked.... Melted ... Raw...... Hardboil'd Fried.... Fried.... Stewed . Boiled... Boiled... Boiled... Boiled... Boiled... Boiled... Fried.... Boiled.... Roasted . Broiled- ■. Boiled.... Boiled.... Fried..... Boiled-... Flied..... Boiled.... Roasted .. Boiled-... Boiled.... Fried..... Roasted • • Boiled.... Boiled.... h. m. 3 — 3 — 3 15 3 15 3 20 3 30 3 30 3 30 3 30 3 30 3 30 3 30 3 30 3 30 3 30 3 38 3 30 3 45 3 45 4 — 4 — 4 __ 4 — 4 — 4 — 4 — 4 13 4 15 4 30 4 30 4 30 4 30 4 30 5 15 5 30 5 30 DIGESTION IN THE STOMACH. 267 520. A part of the food only is dissolved in the stomach.— The act of digestion is but partially performed in the stom- ach. The gastric juice possesses the power of dissolving only the nitrogenized elements of foods (372)—albumen, fibrine, gluten, caseine. The ternary compounds, starch, sugar, and the oily bodies, are unaltered. Indeed, the incip- ient changes begun in the starchy principles by intermixture with the saliva are arrested in the stomach. Chyme, there- fore, is food out of which the nitrogenized principles have been dissolved by the gastric fluid, leaving its remaining proximate elements, starch, sugar, and oily matters, without essential change. A portion of the nitrogenized substances dissolved is supposed to be absorbed dhectly into the blood, by the veins which are distributed throughout the coats of the stomach. A portion of the water, also, which is taken mto the stomach to allay thirst is taken up in the same man- ner by the coats of the stomach, and carried by the veins mto the general circulation. As this stage of digestion is completed, the chyme gradually passes out of the stomach, through the pyloric orifice (situated at its small extremity, see Fig. 24), into the intestines. 521. The intestinal tube or alimentary canal, into which the chyme flows from the stomach, is divided into two parts— the small intestine, and the large intestine, or colon. In man the former is estimated to be about twenty-six feet in length, and the latter about six feet.—(Bell.) The small intestine is disposed in a convoluted or twisted manner, so that a great extent of it may be packed within a small compass: the larger portion is arranged very much as is represented Does the gastric juice dissolve all the food? How does it affect the ternary group of bodies ? What becomes of the dissolved albuminous substance ? Into what does the chyme pass from the stomach ? What is tho duodenum ? What substances flow into the duodenum near the pyloric orifice? 268 ANIMAL CHEMISTRf". in Fig. 24. The first portion* of the small intestine con« nected with the stomach is slightly larger than the rest, and is called the duodenum. A few inches from the pyloric Spleen Gail-Bladder. Large Intestine — Coecum Small Intestine. Fig. 24.—Dioestive Apparatus of Man. orifice there opens into the intestine two passages or ducts, through which the bile from the liver, and the pancreatia juice from the pancreas, are emptied into the duodenum. DIGESTION IN THE DUODENUM. 269 522. The Pancreatic Juice.—Through the pancreatic duct a liquid is poured which is secreted by the pancreas, and known as the pancreatic juice. In its properties it closely resembles the saliva, but contains from 8 to 9 per cent, of solid matter. It is generally considered to be alkaline, but when rendered acid it possesses the properties of gastric juice, and is more powerful (524). 523. The Bile.—This liquid is separated from the venous blood by the liver, and flows into the gall-bladder, whence it is poured into the duodenum at a point a little below the entrance of the pancreatic duct. It is a viscid, oily substance, of a greenish-yellow color, a nauseously bitter taste, and mixes in all proportions with water. Bile is alkaline, from the presence of soda. It gives 12 per cent, of ash, 11 of which are carbonate of soda. It also contains a peculiar substance of feebly acid properties called choleic acid, or bilic acid. This acid neutralizes a portion of the soda in the same manner as the fatty or resinous acids, forming choleate of soda. In consequence of this soapy property, it is used, as in the case of ox-gall, to remove greasy spots from cloth, and the bile of the sea-wolf is ordinarily employed as a soap by the Icelanders. Although the bile is looked upon as an excretion from the blood (581), yet it performs an important office in digestion. CHYLIFICATION. 524. Duodenal Digestion.—'the chyme is mingled with the biliary and pancreatic secretions as it passes into the duodenum. Their intermixture is effected, as in the case of What me the composition and properties of the P°™f 1C-^1 ^ We produced? What are its properties ? For what,is *™"T*™ ^ the_ With what is the chyle mixed in the duodenum? By what means are the, 23* 270 ANIMAL CHEMISTRY. the stomach, by the contraction of the muscular walls of the intestine (peristaltic motion), which serves at the same time to propel the mass along the alimentary tube. The chemical action begun by the saliva during mastication, and suspended in the stomach, is here resumed. The starch is converted into dextrine and sugar, and a part of the sugar still further changed to lactic acid. It is probable, however, that a por- tion of the sugar is converted into fat, as the recent experi- ments of Meckel appear to show that bile possesses the power of effecting this transformation. He found that when bile was mingled with grape-sugar, and allowed to remain in contact with it for some time, a much larger quantity of fatty matter existed in the mixture than could have been present in the bile. The oily substances of the chyme are dissolved, or reduced to the state of an emulsion, so as to be readily absorbed. This change was formerly supposed to be produced exclusively by the bile. The late researches of Bernard, however, have proved that this is the function of the pancreatic juice. When this secretion is mixed with oily or fatty matters out of the body, it effects this change on them at once, although neither saliva, gastric juice, nor bile are able to perform it. The product of these changes is a whitish, opaque* milky-looking liquid, termed chyle. Its appearance is due to innumerable oily globules which are diffused through it. 525. Effect of the Different Juices.—The gastric juice of the stomach is charged with the office of bringing the nitro- genized elements of food into a state of solution, while the saliva of the mouth, the bile, and pancreatic juice effect the mingled together ? What chemical changes now occur ? What appears from the experiments of Meckel ? What is the office of the pancreatic juice ? What is Bhyle ? By what are the nitrogenized elements dissolved? Tho non-nitrogemz«d ? U CHEMICAL NATURE OP DIGESTION. 271 same change upon the non-nitrogenized principles. If the acid of the gastric juice is neutralized, as by the introduc- tion of bile into the stomach, it loses its power of dissolving albuminous substances, and attacks oily bodies; on the other hand, if the bile and pancreatic fluid are rendered acid, they cease to affect the ternary compounds, but act upon those which are nitrogenized. The methods thus employed to bring the food into a state of solution are purely of a chem- ical nature, in all respects analogous to those adopted by the chemist in attaining a similar object. The analogy is complete in the following particulars: first, in both cases the solids are brought to a state of fine division; second, they are agitated and completely intermixed with the sol- vents ; third, a fixed quantity of liquid can act only upon a definite proportion of solid matter; fourth, heat influences the process; fifth, the same solvent acts differently upon different solid substances. SANGUIFICATION. 526. Mode in which the Chyle is removed from the In- testines.—So long as the alimentary matter remains in the intestinal cavity, it can no more minister to the wants of the system than if it were in contact with the external surface of the body; indeed, strictly speaking, it has not yet been taken into the system. It is absorbed by a peculiar set of vessels called the lacteals, which commence in the intestinal tube by a multitude of little rootlets that unite at first into minute trunks, then into larger ones, and at length deliver the gastric juice is made alkaline, what foUows ? If the bile be made acid, What is the result ? In what respect do these processes resemble the operations of the chemist? What is the office of the lacteals? What do they consist of? Where do they 272 ANIMAL CHEMISTRY. their contents into a kind of common reservoir, the thoracic duct, which empties into a large vein near the shoulder. In' their course the lacteal tubes are convoluted, or twisted to- gether, into peculiar knot-like bodies, by which they are greatly prolonged; these knotty masses, or ganglia, are called mesenteric glands, because they are inclosed between two layers of a membrane or fold called the mesentery (Fig. Origin of Lacteal Vessels Intestine. Mesentery. Lymphatic Vessels. 25). The lacteals do not open by distinct apertures into the intestinal tube, but terminate in numberless minute pro- jections, called villi, which form a loose tissue upon the mucous membrane of the intestinal wall. It has been found that the act of lacteal absorption is carried on by means of ompty ? What are the mesenteric glands ? Why are they so called ? What an villi ? How is lacteal absorption carried on ? Are these cells always present 1 SANGUIFICATION---OFFICE OF THE LACTEALS. 273 vast numbers of exceedingly minute cells or sacs, which are formed within the villous tissue. In the intervals, when there is no chyle to be absorbed, these cells cannot be seen; but every time digestion takes place, a new crop springs up. Their growth is very rapid and their life transitory. In growing, they absorb into themselves part of the fluid that surrounds them ; and it is probable that when they are ma ture, they either burst or dissolve and deliver the fluid to the absorbent vessels. That it is the special office of the lacteals to absorb the chyle, is shown by the fact that they are not distributed upon the stomach, or upon that portion of the intestinal tube above the point where the bile and pancreatic juice enter the duodenum. They are abundant upon the small intestine, but less numerous upon the large one. 527. Selecting Power of the Lacteals.—The lacteals pos- sess the power of absorbing only that portion of the contents of the intestinal canal which is capable of being used by the system; and as the food which is eaten contains other sub- stances, these, of course, are left as a residue in the intes- tines. This solid residue (excreta), which remains to be ex- cluded from the alimentary passage, must be looked upon, not as having taken any part in the grand processes of the system, but as mainly composed of matters incapable of any such service. It however contains a_ small proportion of the waste matters of the system, as the brown coloring mat- ter of the bile, mucus, and some salts, chiefly insoluble phos- phates of lime and magnesia. 528. Changes which occur in the Lacteals.—h\ its course through the lacteals, the chyle undergoes a change, by which What is said of their growth? Of their disappearance ? From what do we infer that the lacteals absorb chyle? Do the lacteals take up all the contents of the alimentary canal? What is said ° WhaUhi?e takes place in the chyle during its passage through the lacteals? 274 ANIMAL CHEMISTRY. it is brought mto a closer relationship with blood. If exam« bed at its first entrance into these vessels, before it has pass- ed through the glands, it is entirely destitute of that power of spontaneously coagulating, or clotting, which is so remarka- ble in blood. It consists, in 100 parts, of 90 water, 3^ albu men, the same of oils, and about 3 parts of other animal and saline matter. But the chyle drawn from the lacteals, after it has passed through the mesenteric glands, possesses the power of coagulating slightly; this is caused by the trans- formation of a portion of" the albumen into fibrine, by which the fluid begins to assume the properties of blood. When the chyle has reached the thoracic receptacle, its proportion of albumen is still further diminished, while the fibrine is correspondingly increased; and it now separates promptly, like blood, into clot and serum, in which state it is mingled with the venous current of the great circulation. Thus the prominent chemical change occurring in the lacteal vessels consists in the conversion of albumen into fibrine. Other transformations take place, but they are not so well under- stood, and cannot be detailed here. THE BLOOD. 529. The series of changes which have just been described have for their object to prepare from the food a nutritious fluid which shall supply materials of renovation and growth to all parts of the body. This fluid is called blood, and the apparatus of tubes and channels (blood-vessels) by which it is conveyed into all parts of the body is termed the circulatory system. 530. Properties of the Blood.—In man and the higher What is the objsct of the changes just described ? What is the circulatory sys- tem? What are the properties of blood ? Of what two parts does it consist ? What Is the form of blood-disks in man ? What do they consist of? COMPOSITION OF THE BLOOD. 275 orders of animals, the blood is of a red color; florid and ap- proaching to scarlet when drawn from the arteries, and of a deep purple when taken from the veins. It has an unctu- ous or soapy feel, a slightly nauseous odor, a saline taste, and an alkaline reaction. When first removed from the body, the blood appears to the naked eye a uniform red liquid; but when examined by a microscope, it is seen to consist of two distinct parts—a clear and nearly colorless fluid, called the plasma or liquor sanguinis, and of an immense number of mmute, rounded, red particles floating in this fluid, which are known as blood-globules, blood-disks, or blood-cor- puscles. They vary greatly in size and form in different animals. In man they are flat disks resembling pieces of money, but usually exhibiting a slight depression towards the centre, and having a diameter from about the -^ToXi to 4000 of an inch. The corpuscles consist of a thin membrane or sac (globuline), a nitrogenized substance, filled with a red coloring matter (hematine), in which hon is a large element. 531. Coagulation.—After the blood has been removed from the body for a short time, it spontaneously coagulates, or separates into a dark-red jelly, or clot (crassamentum), and a pale-colored, slimy liquid (serum). Coagulation is caused by the change of soluble fibrine contained in blood to the insoluble state. It was formerly supposed that the blood was alive, and that this change consisted in its death; but the same event is constantly taking place within the body, as the liquid fibrine of the blood is deposited to form solid flesh. As the fibrine coagulates, it forms a fine net-work or jelly throughout the liquid, which entangles and mcloses the red corpuscles. It also contains a portion of the serum, which What is coagulation of the blood? What is its cause? What was once ^ Bosedtobethecause? Of what does the clot consist? The serum/ ttitution of the blood always the same ? 276 ANIMAL CHEMISTRY. may be removed by pressure. The serum consists of waterj albumen, fatty matter, and various salts. Gregory state? that the healthy proportions of serum and clot are 87 per cent, of the former, to 13 of the latter; but it is obvious that these proportions must vary in the healthy individual, from a great variety of causes. Thus the mere swallowing of a draught of water must alter the composition of blood, and thus effect its analysis. The general constitution of the blood is here given, from Lecanu: Water,................780-145 Crystalline fatty matter,___ 2-430 Fibrine,............... 2-100 Oily matter,.............. 1*310 Coloring matter,.......133-000 Extractive matter,......... 1-790 Albumen,............. 65-090 Salts and bases,.......... 14-135 1000-000 NUTRITION, 532. The formation of the various parts of a living body from a single homogeneous liquid—the blood—the nourish- ment and growth of a young animal upon milk, and the development of a chicken from the liquid contents of an egg, are phenomena alike wonderful and mysterious. Of the vital force, by which these changes are guided, we compre- hend nothing; something is however known of the trans- formations which occur, and more of the chemical nature of the products which are formed. The process by which the various organs and tissues of the system are elaborated from the blood is called nutrition. 533. Source of the Animal Tissues.—We have observed that woody fibre, of which the fabric of plants is almost en- tirely constructed, is composed only of three elements—car- What is nutrition ? How does the composition of animal tissue compare with that of woody fibre ? Oi rrtiat are the animal tissues formed ? What bodies are aU alike in (composition ? NUTRITION OF ANIMAL TISSUES. 277 bon, hydrogen, and oxygen. The fundamental tissue of the animal fabric is equally uniform in its chemical constitution, containing the same elements as woody fibre, with the addi- tion of a large proportion of nitrogen. Vegetable tissue is thus totally incapable of conversion into animal tissue; but the nitrogenized products of plants are adapted to this pur- pose, and it is from these that they are wholly constructed. The areolar tissue, which is composed of membranous cells, diffused throughout all parts of the body, the muscular fibres which constitute flesh, together with the various blood- vessels and membranes which form the groundwork of the animal system and the chief portion of its solids, all have the same chemical composition as the nitrogenized com- pounds of plants,—gluten, vegetable albumen, and caseine. They all contain nitrogen to the extent of 17 per cent. 534. Nutrition of the Tissues.—The nutrition of the ani- mal tissues is therefore, in a chemical point of view, a very simple process; consisting essentially in the coagulation or solidification of fibrine, which has its origin in plants. When albumen is changed from the fiquid to the solid state, it exhibits no traces of organization; that is, the particles arrange themselves into a brittle mass, instead of tough, thready fibres, and it has not the qualities which would adapt it for muscular tissue: fibrine, on the contrary, presents these qualities in an eminent degree, coagulating into fibres or filaments, so that blood in which fibrine is dissolved has been very properly termed liquid flesh. The relations of albumen, fibrine, and flesh have been very justly compared to those of raw cotton, the spun yarn, and the woven fabric. The conversion of albumen into fibrine which has been noticed What is the difference between coagulated albumen and coagulated fibrine ? To what are the relations of albumen, fibrine, and flesh compared? What is said to be the result of late researches? How does the nutrition of carnivorous and he* bivorous an'-""!* differ ? 24 278 ANIMAL CHEMISTRY. as occurring in the lacteals (528), and which is also constant* ly taking place in the blood, is therefore a simple flesh- forming process, the product necessarily remaining in a liquid state, that it may be distributed by the circulation into all parts of the system, while it gradually coagulates into fib'rous and muscular tissue. Late microscopical dis- coveries render it probable that ihe process of nutrition is carried on by means of the growth of innumerable cells, which are developed and extended upon the sohd surfaces. The nutrition of the grain and herb-eating animals is of the same nature as in those which subsist upon flesh, the con- stituents of their blood being in both cases of vegetable origin. The only difference is, that carnivorous animals ap- propriate those elements of nutrition (blood and flesh), which have already served a similar purpose in animals which live upon vegetation. 535. Consumption.—If the conversion of albumen into fibrine is incomplete, the tissues are imperfectly nourished, and the strength and vigor of the body are impaired. The formation of tubercles in the lungs, which give rise to con- sumption, is due to this cause—the imperfect elaboration of the fibrine. Tubercular matter consists of half-formed cells, fibres, &c, and coagulated albumen, deposited in the tissue of the lungs, which consequently impairs respiration, and produces irritation and inflammation, like any other for- eign matter. The only manner in which any curative means can be brought to bear upon this terrible scourge is by at- tention to the constitutional states from which it results. This is sometimes hereditary, and sometimes induced by in- sufficient nutrition, habitual exposure to cold and damp, What it the cause of tubercles in the lungs? Of what does tubercular matte- consist ? What effect does it produce ? What circumstances will induce tuber •Hilar disease ? What treatment is recommended ? PROPERTIES OF GELATINE. 279 long-continued mental depression, &c. The treatment must be directed to the invigoration of the system, by good food, active exercise, pure air, warm clothing, and cheerful occu- pations ; and by a due employment of these means, at a suf- ficiently early period, many lives might be saved, which would otherwise fall a sacrifice to tubercular disease.—(Car- penter) PRODUCTS OF NUTRITION. 536. Gelatine.—When the tendons, ligaments, cartilages, skin and bones of animals are for some time boiled in water, a substance is extracted, which gelatinizes, or forms a jelly, on cooling. It is a nitrogenized compound, having the for- mula C13 H10 05 N2 (Mulder); but, unlike the albuminous substances, it is not formed by plants, nor is it found in the blood: it must, therefore, be looked upon as a secretion, although some chemists maintain that it is formed by the process which is employed to obtain it, and has no real ex- istence in the animal organism. The gelatine from car- tilage is termed chondrine. Pure gelatine is colorless, transparent, inodorous, and insipid. In cold water it gradu- ally softens and swells, but does not dissolve until heated. The cooled solution remains as a more or less firm jelly. Gelatine is insoluble in alcohol, ether, and the fixed and vol- atile oils. Isinglass is the name given to a commercial form of gelatine, which is obtamed chiefly from the ah-bladder of fish, as the sturgeon and cod. When the membranes are cleansed, dried, and scraped, they form leaf isinglass; when folded into packages they constitute book isinglass. It is ex- " From what substances is gelatine obtained? How does it.difler from_ the.albu- minous substances? How do some chemists regard it? What^ ehondrme What are the properties of pure gelatine? What is isinglass? Leaf isinglass? Book isinglass ? For what is it used ? How may it be preserved ? 280 ANIMAL CHEMISTRY. tensively employed as an article of diet, in the form of jelly*. one part of isinglass dissolves in 100 of hot water, forming a thick, tremulous jelly, when cooled. Jelly may be kept in close vessels for some days without change, but in open vessels it soon becomes mouldy, especially in the vicinity of blossoming plants (Brande) : it then putrefies, although this change, it is said, may be arrested by a little acetic acid, without much affecting the jelly. 537. Glue is a form of gelatine extracted from bones, the parings of hides, and the hoofs and ears of cattle, by boiling in water, or by steam pressure. The solution obtained cools into a stiff jelly, which is cut by wires into thin slices, and dried upon netting, to which its peculiar grooved appearance is due. Good glue is hard, brittle, translucent, and of a brown- ish color. By immersion in cold water, it absorbs three or four times its weight without dissolving. Where less water is absorbed, or where the glue loses its viscid aspect in cold water, it is unfit for use. The employment of glue, in uniting or binding substances together, is well known. Its adhesive power is increased by adding to it white-lead or borax—an ounce of the salt to a pound of glue. 538. Court-plaster is silk cloth, varnished over with a solution of gelatine. Transparent wafers are also made of gelatine; common wafers being made from flour-paste, col- ored with various substances. 539. Bones, their composition.-—Bones consist of gelatinous tissue, into which mineral matter has been deposited, until it possesses a stony hardness. The mineral substances are phos- phate and carbonate of lime. The phosphate predominates in the higher animals; in the lower, the carbonate. The amount What is glue? What are the qualities of good glue ? How is poor glue known? How may the adhesive power of glue be increased? What is court-plaster ? Of what are wafers made ? What do bones consist of? What is said of the mineral matter of bones ? CONSTITUENTS OF BONES. 281 of mineral matter in bones increases with age : thus in the child it forms about half the weight of the bone, in the adult four-fifths, and in the old person seven-eighths. 540. Mineral and Organic Elements of Bones.—If a bone is soaked in diluted muriatic acid, the mineral salts are dis- solved out, the animal matter remaining as tough, flexible, nearly transparent gelatine, having the same form as the bone. If, on the other hand, we submit a bone to strong heat, the animal portion is burned out, and the earthy part remains. The bone is then brittle, and falls to pieces at the slightest touch. Hence bony structures owe then tenacity to the organic element, and their hardness and stiffness to the mineral substances of which they consist. In the disease called rickets there is a deficiency of the inorganic constitu- ents, and the bones, therefore, become twisted and distorted. A solution of phosphate of lime, in phosphoric acid, has been prescribed as a remedy. There is also a malady of an oppo- site nature, in which there is less than a healthy supply of animal matter. In this case the bones are exceedingly liable to fracture. The nails, claws, and horns of animals, are anal- ogous in composition to the bones. 541. Mode in which the Shells of Crustacea are produced. __In some of the lower species of animals, as crabs and lob- sters (crustacea), the bony skeleton, instead of traversing the interior of the body, exists in the form of an external cover- ing, or shell. This shell is periodically thrown off, and re- newed again in a very speedy and curious manner. There is, laid up in the walls of their stomach, a supply of carbonate of lime, in the form of fittle concretions, known as " crab's How may we separate the animal from the earthy portion of bones ? To what Is the tenacity of bones due ? To what do they owe their hardness ? What is the cause of rickets ? 71e remedy ? What other disease of the bones is mentioned ? In the crustacea, where is the bony skeleton found ? When this sheU is cast oS by the animal, how is a new one formed ? 24* 282 ANIMAL CHEMISTRY. eyes." When the shell is cast off this matter is taken up by the blood-vessels, and carried out to the surface of her body, where a new shell is formed in a day or two. 542. Hair, its Composition.—The basis of hair is a nitro- genized animal tissue, containing deposits of lime, magnesia, and salts of hon, together with a considerable quantity of sulphur, to which much of its disagreeable odor in burning is due. The various colors of hair are due to the differences in its chemical composition. Thus, according to Wilson, red hair contains a reddish-colored oil, a large proportion of sul- phur, and a small quantity of hon; fair hah a white oil, with phosphate of lime, and the white hair of the aged a consid- erable quantity of the phosphate. 543. Fat.—The properties of fat have been already de- scribed (427). It is separated from the blood, and deposited in the adipose tissue, throughout all parts of the body, in the shape of small globules, from the -^q to -g-^g of an inch in diameter. This deposit forms a layer, of various degrees of thickness, which gives roundness and symmetry to the animal form, and at the same time furnishes a kind of pad, or cushion, for the support of movable parts. It has been an earnest question among chemists whether the fat of animals is exclusively derived from vegetables, or in part generated within the organism from the non-nitrogenized elements of food. It is at present thought that the animal does possess such a power, while it is known that fat exists in plants to a much larger extent than was formerly supposed. 544. Nervous Matter.—The nerves are minute threads or cords, which in man extend into all parts of the body, and Of what is hair composed? To what are its various colors owing? What does ted hair contain ? Fair hair ? Gray hair ? From what is the fat of the system derived ? What are some of its uses ? What question concerning its production has been discussed by chemists ? THE NERVES—SECRETIONS. 283 which perform a twofold object: one class or set transmits sensations to the brain, the seat of the mind, while another set conveys the mandate of the will from the brain to the muscles, by which it is executed. 545. Composition of the Nerves.—The chemical compo- sition of the nerves is the same as that of the brain. The nervous matter of an adult gives, upon analysis in 100 parts: Of Water,............................................72-51 Albumen,............................................ 9-40 Fat,................................................. 610 Osmazome and Salts,................................10-19 Phosphorus,......................................... I'80 100-00 The structure of the nerves is tubular, the wall being com- posed of albumen; within it is contained minute fat glob- ules, and with these the phosphorus is associated. This element, as will be shown in another place (592), is es- sentially connected with the operations of the mind. The amount of phosphorus in the nervous matter of infants was found upon analysis to be 0-80, in aged persons TOO, in adults 1-80, and in idiots 0*85 per cent.—but half that which is found at the adult period, or condition of greatest mental A-igor. Osmazome is an ill-defined compound, to which the aromatic flavor of soup has been attributed. It is lately shown to be a mixture of several substances. SECRETIONS. 546. Those substances which are separated from the blood, not for the purpose of purifying it, but to answer some pur- What are nerves? What is their office ? What is the composition of the nerves ? What the structure ? How does tho amount of phosphorus vary ? What is osmazome ? 284 ANIMAL CHEMISTRY. pose in the animal economy, are termed secretions. The saliva, gastric juice, and pancreatic juice, already described, are examples. To these may be added mucus, which is se- creted from the surface of membranes (mucous m,embranes), and lymph, which is poured out from the lymphatic vessels; neither of which have been satisfactorily examined. The tears (lachrymal secretion) consist of water, rendered slightly saline by common salt, and containing also a little albumen, combined with soda. MILK 547. Its Source and Composition.—This fluid is secreted from the blood of females, of the class mammalia, for the nourishment of then young. It is the only substance com- pletely prepared by nature as an article of food; and it is so constituted as to furnish materials for the development of all the various organs and compounds of the young animal: its composition must, therefore, be a matter of interest. It is a white liquid, of a sweetish taste, a peculiar odor, and contains, dissolved, sugar, caseine, and salts; also a fatty substance, butter, which is diffused throughout it in the form of minute globules, that are visible with the microscope, while at the same time the liquid appears transparent. The composition of fresh cow's milk is as follows: Water,.............................................. 88-30 Caseine, ............................................ 4-82 Milk-sugar,......................................... 3*39 Butter,............................................. 3-00 Salts,............................,.................. 0-49 100-00 Solid matter,........................................ 11-07 What are secretions ? Give examples. What do tears consist of? What is said of milk as food ? State its properties. What is it3 composition t MTLK—PRODUCTION OF BUTTER. 28 J 548. The Lactometer, or Milk-measurer.—When freshly drawn milk is permitted to stand, the butter-globules rise to the surface and form cream. The proportion of cream in milk may be determined by means of an instrument called the lactometer, which consists simply of a glass tube, six or seven inches long, which is marked off into a hundred equal divisions. It is filled with a sample of milk and allowed to stand, when the per cent, of cream which forms upon the surface is read off upon the scale. 549. Production of Butter. — Butter is obtained either from cream or from milk, by agitating it in various ways (churning). This is necessary, because the oil-globules are invested by a delicate membrane, which requires to be rup- tured before the butter will cohere into a solid mass. Heat also bursts the globules and causes them to unite, but the butter thus produced is of a poorer quality. The best temperature for churning is, for cream, 55° to 58°, and for milk 65°.—(Johnston) During the process the tempera- ture rises from 4° to 10°, and the milk or cream, if sweet, turns sour, oxygen is absorbed, and acid formed, which seems to aid in the coalescence of the oil-globules. From a great variety of causes, butter is liable to changes by which its quality is impaired; among these may be mentioned the absorption of bad odors by cream, if not kept in a perfectly clean place with a frequent renewal of fresh air; washing with water containing much lime Or organic matter, and packing with impure salt. But the chief source of injurious changes in butter is the putrefaction of cheesy matter, ca- seine (375), of which it always contains a small portion. What is cream? What is the lactometer ? How is it used? How is butter obtained ? Why is churning necessary ? What is said of butter produced by heat ? What is the best for churning ? What changes occur during Hie process t How does butter sometimes become deteriorated in quality ? 286 ANIMAL CHEMISTRY. The caseine converts the sugar of milk into lactic acid, and that into butyric acid, to wliich the disagreeable smell of rancid butter is mainly due. 550. Milk-sugar (Lactine), C12H,0O10 + 2 H 0.—This ia the substance which gives to milk its slightly sweet taste. It is obtained by evaporating clarified whey until it crystallizes. It is much less soluble than cane or grape sugar, and there- fore much less sweet: it is also hard and gritty. 551. Caseine, or the curd of milk, has the same composi- tion and properties as vegetable caseine (375): it exists in milk in a state of solution, but is very insoluble in water, one pound of caseine requiring 400 pounds of that liquid to dis- solve it. Caseine is held in solution in milk by means of a small quantity of soda; if this is neutralized by an acid the caseine is at once precipitated, as insoluble curd, and an ad- dition of a little carbonate of soda or potash, so as to form a weak alkaline solution, redissolves it. 552. Natural Curdling of Milk.—When milk is exposed to the ah for a certain length of time, it becomes sour and curdles; that is, its caseine is precipitated. The curd, how- ever, does not readily separate from the liquid part (whey), unless a gentle heat be applied, when it contracts in bulk and rises to the surface. The souring and cm-dling process proceeds slowly in the cold, but quickens as the temperature is elevated; and is observed to take place first at the surface of the milk, where it is in contact with the ah. The changes that here occur are begun by the oxygen of the air, which induces decomposition in the nitrogenized caseine; this de- composition is propagated to the sugar of milk, which is What is said of milk-sugar? What is said of caseine? How is it held in solution? What precipitates it How may it be redissolved? How is milk curdled ? How is the curd separated from the whey ? When doei MILK—THE CURDLING PROCESS. 287 changed to lactic acid, probably by being first converted into grape-sugar; but this is not precisely known. The lactic acid gives to milk its sourness, and by neutralizing its soda precipitates the caseine. 553. Artificial Curdling of Milk. — It seems to matter nothing whether the acid is generated spontaneously by the elements of milk, or is added artificially, the effect being the same. Almost any acid substance possesses the power of curdling milk. In Holland, muriatic acid is said to be exten- sively employed for this purpose in the cheese manufacture. In Switzerland they add a little sour milk to produce the curd; while in other countries vinegar, tartaric acid, lemon-juice, cream of tartar, and salt of sorrel, are also employed. But the substance most generally used for this purpose usually consists of the lining membrane of the stomach of a calf, prepared by salting and drying. The rennet is soaked in water or whey, which being added to the milk, and the temperature raised to 95°, coagulates it promptly. It has been hitherto considered that the coagulating action of rennet is due to a portion of gastric juice which it retains; but late researches show that it acts in the same manner as caseine (552), by changing milk-sugar into lactic acid, through its decompo- sition. Gastric juice, it is true, cm-dies milk rapidly; but the thorough and repeated washings and dryings to which rennet may be subjected without destroying its efficacy, ren- ders it impossible to ascribe its action to that solvent, while it is well known that other membranes besides that of the stomach, in a state of decomposition, convert sugar of milk into lactic acid. it curdle most rapidly ? Where does the process begin? State the changes that occur. How may milk be artificially curdled? What substances are employed for this purpose ? How does rennet act in the curdling of milk ? How does it appear thai gastric juice is not the agent in producing the change ? 2(8 ANIMAL CHEMISTRY. 554. Experiment of Berzelius. — The small quantity of rennet which takes part in the process is well illustrated by an experiment of Berzelius. He took a bit of the lining of a calf's stomach, washed it completely, dried and weighed it carefully, and put it into 1800 times its weight of milk. He then heated it 120°, and when coagulation was complete withdrew the membrane, washed, dried, and again weighed it: the loss was T^- of its entire weight. But one part of the membrane, therefore, was used in coagulating thirty thousand of milk. 555. Preservation of Milk.—Milk or cream may be pre- served, or restored to a state of sweetness when it has begun to sour, by adding to it a small quantity of soda, pearlash, or magnesia, which neutralizes the lactic acid: the lactates thus formed are not unwholesome. The action of curd, in decom- posing sugar of milk, is arrested or prevented by heating it to the boiling temperature. Hence if milk be introduced into bottles, well corked, put into a pan with cold water and gradually raised to the boiling point, and after cooling be taken out and set away in a cool place, the milk may be pre- served perfectly sweet for half a year.—(Johnston) If the bottle in this case be uncorked, and the milk exposed to the ah, the caseine, after a few days, resumes its property of de- composing milk-sugar and forming lactic acid. By evapora- ting milk at a moderate heat, with constant stirring, its solid constituents are left as a dry mass, which may be kept for any length of time, and wliich, when dissolved in water, is said to possess all the properties of the most excellent milk. 556. Adaptation for Food.—Milk contains all the saline substances which are found in the blood (400), or which the Describe the experiment of Berzelius. How may sour milk be restored to sweetness? How may milk be prepared sc as to remain swer t for months ? What is the effect of uncorking the bottle ? RESPIRATION. 289 growing animal requires, phosphate of lime in large quan- tity (40 gallons contain 1 lb.) for the development of bones, common salt to furnish by its decomposition the hydro- chloric acid of the gastric juice and the soda of the bile, and also a trace of iron, which reappears in the coloring matter of the blood. The other constituents of milk perform equally important offices in nutrition; the butter yields fat, the sugar is burned for the production of heat, the caseine forms flesh, and the large proportion of water supplies this necessary element to the system. RESPIRATION. 557. Destructive Force in the System.—Thus far the changes that have been noticed as occurring in the animal body are of a formative nature, their object being to build up the system by constant additions of matter to all its parts. The amount of food taken for this purpose of course varies very much in different individuals and different cir- cumstances, but it may be stated as an average that an adult man consumes each day two pounds and a half of solid food, and from four to five pounds of liquid, besides taking into his system two pounds of oxygen gas from the air. And yet his body does not increase in its weight, but in health remains of a uniform bulk and weight from year to year. A destructive process must therefore be constantly going on in the system, sufficiently active to use up and carry away the same amount of matter that is supplied How does the composition of milk compare with that of blood? What offices do its different constituents perform in nutrition? How much food does an adult consume daily ? How much oxygen ? Why does ■ot His body increase in weight ? What is the channel of this waste ? 25 290 ANIMAL CHOUSTKY. through the channels of nutrition. The source of this per- petual waste and destruction is the act of respiration, by which common air is brought into contact with every por- tion of the animal organization. 558. Nature of Respiration always the same, its Modes different.—The relation of animals to the atmosphere is of a most direct and vital nature. All the peculiar actions which take place in the animal structure, and which taken collectively we call life, are set in motion and kept in motion by atmospheric oxygen. Its effect is exerted upon the body through the medium of the respiratory organs. The action of oxygen is exactly of the same nature in all animals, buf the structure and arrangement of the respiratory mechan- ism differ according as they are destined to be acted upon by oxygen in the condition of a gas, or in a state of solution in water. Animals low in the scale of nature, whose struc- ture is simple, and the composition of their bodies porous, have no separate breathing apparatus; their respiration is what is called cutaneous, that is, air contained in the water in which they live penetrates all parts of their body, and acts upon the blood. Those animals which inhabit the water have special organs for breathing, termed branchia, or gills, which are composed of feathery filaments, or tufts of blood-vessels, situated externally upon the body, and de- signed to be acted upon by the air which is contained in water. The higher animals respire by lungs, which consist of membranous bags lodged within the body, and which are directly acted upon by the air. 559. Respiration of Fishes.—The branchia, or gills of Does oxygen act in the same manner upon all animals? Is the respiratory ap- paratus of all animals alike ? How is the respiration of the lowest animals per- formed? What is the breathing apparatus of fish called? What organs have the higher animals for this purpose ? AQUATIC RESPIRATION. 291 fish consist of a mass of blood-vessels in the form of deli- cate comb-like fringes, arranged in rows on each side of the throat. The branchia are hence situated on the outside of the body, but they are overlaid by a large valve-like flap, which is termed the gill-cover, and which is seen in constant motion when the fish is in its native element. A continual current of water is made to pass over the gills by the action of the mouth, which takes in a large quantity, and com- pressingnt by muscular contraction, the gill-cover opens, the fibrils spread, and the water is forced out through openings between the rows of fringes. Each fibril consists of two ves- sels, a vein and artery, one of which brings the blood, while the other returns it again to the system. As the water flows over the surface of these vessels an interchange takes place, the carbonic acid of the impure blood escapes outwardly, while the oxygen of the water-atmosphere (93) is absorbed into the blood, which is thus purified. 560. The art of drowning fishes under water, which is practised by anglers, consists in keeping their mouths open by means of the hook, which makes it impossible for the animal to breathe, and thus produces suffocation. 561. Why Fish die when removed from the Water. — When a fish is withdrawn from the water, the fringes of its gills speedily mat or clog together and dry up, so that the air cannot exert any action upon them, and respiration there- fore ceases; but if the gills are kept constantly moist, they will continue to perform their office of absorbing oxygen, and thus maintain life. There are certain fishes which pos- sess the means of securing this condition. The gill-filaments Describe the breathing organs of fishes ? How are the gills supplied with oxy- gen ? Of what does each fibril consist ? What chemical change takes place I Bv what means are fish drowned in water ? How may fishes be kept alive when out of water? What contrivances have son* fksh, enabling them to live for some time upon land? 292 ANIMAL CHEMISTRY. are so arranged that they do not clog together, and by means of little reservoirs of water, which are provided for the purpose, they may be kept moist for some time. These contrivances are said to enable some species of fish to re- main sufficiently long upon land to migrate from lake to lake. 562. Respiration of Whales.—Many marine animals, as whales, seals, porpoises, &c, breathe atmospheric air, and are therefore compelled frequently to rise to the* surface. Some possess the means of carrying with them a temporary supply of air; others, as the whale, have reservoirs in which the arterial blood can be accumulated : as it is rendered im- oure in the body, it passes into another reservoir connected with the veins, and the animal is thus enabled to remain for a considerable time beneath the surface. 563. Respiration of Insects.—The organs of respiration in insects are internal—within the system. The air is admit- ted through minute orifices called spiracles, arranged along the side of the body, which open into a system of tubes (trachea). These air-tubes ramify and extend into all parts of the body. 564. Respiration of Reptiles.—The low form of respira- tion which takes place in reptiles is carried on by means of air-sacs contained within the body, and which may be re- garded as the rudest form of lungs. The air enters through the mouth; but reptiles have no power of filling their lungs by a process resembling our inspiration, or drawing in of air: they are obliged to swallow it by mouthfuls, as we do Why are some marine animals often compelled to rise to the surface of the wa- ter ? What arrangement has the whale which enables it to stay some Ume under the water ? Describe the respiratory organs of insects ? By what means is the respiration of reptiles carried on ? How ia air taken into their bodies ? How miy they be strangled ? RESPIRATION IN THE HIGHER ANIMALS. 293 Fig. 26. food, forcing or pushing it down by muscular contraction Reptiles, as well as fishes, may therefore be suffocated 01 strangled by keeping their mouths constantly open. 565. Respiration by Lungs.—The higher animals breathe by means of true lungs. In man, these consist of a pair of large, pouch-shaped organs, situated in the upper cavity of the body (thorax), one on each side of the heart. The windpipe (trachea), which passes from the mouth to the chest, there separates into two bronchia, one of which enters each lung. These cL'vide into smaller bronchial tubes, which again subdivide, and finally terminate in minute cavi- ties called air-cells. The whole arrangement has been com- pared to an inverted tree, the trunk representing the wind- pipe, the branches and twigs the subdivisions of the bron- chia, and the expanding buds the air-cells. The air-cells are about T^o of an inch in di- ameter, and then number in a person of average size has been estimated by Weber at 600,000,000. They are all composed of one continuous membrane, which is computed to have a surface thirty times greater than the exterior of the body. Fig. 20 represents one side of the lung present- ing its natural appearance, and Describe the lungs in man ? What is said of the size and number of these air eeS:? WhS of the membrane composing them ? By what means are the lung* constantly supplied with fresh air? 294 ANIMAL CHEMISTRY. the other the branchings of the air-passages, or bronchia] tubes, by which the air is conveyed to every part of the lungs. The lungs completely fill the cavity of the chest, so that by the alternate expansion and contraction of the surrounding walls and floor, they are correspondingly enlarged and dimin- ished in size; the contractile pressure of the chest driving the air out (expiration), and the the external pressure of the atmosphere forcing it back again (inspiration). By this means the constant renewal of the air in the lungs is secured. 566. Circulatory Apparatus in Mm.—As the perpetual renovation of the vital fluid of the body takes place within the lungs alone, there must obviously be a provision for its constant passage through these organs ; they are therefore included in the route of the general circulation of the blood. The higher animals possess two hearts, which, although lo- cated together (double heart), have yet no direct communica- tion with each other. Each heart has two openings or cav- ities : the upper one being termed the auricle, or receiving cavity, and the lower one the ventricle, or propelling cavity, which connect with each other by means of orifices guarded by valves. In man, the blood which has been used in his system, and can be of no further service until purified, is all gathered into a large vein (vena cava), and poured into the auricle of his right-side heart. From this it passes to the ventricle, and is there driven through another large vessel (pulmonary artery) to the lungs. Having been properly changed here, it passes by another vessel (pulmonary vein) to the left-heart auricle, thence to the left ventricle, from which it is distributed through the aorta all over the body The large trunks, both arteries and veins, as they pass from Describe the heart of the higher animals ? At what point is all the impure blood collected ? Where does it then pass ? After its purification in the lungs where is it again collected ? By what vessels is it then distributed through the body? Whal CIRCULATION IN MAN. 295 the central heart, divide into smaller branches, and these are still further divided until they become no larger than a hair, and are hence called capillaries (from capillus, a hair). The I-esser or Pulmonary Circulation ■ymt. Fig. 27. Greater or Systemic Circulation. air-cells of the lungs are covered with these minute vessels, called pulmonary capillaries, and it is through these that the blood flows from the right to tbe left heart in the lesser are the minute divisions of the arteries and veins called? What arc pulmonarj capillaries ? Wh at a re systemic capillaries ? 296 ANIMAL CHEMISTRY. or pulmonary circulation. Besides these, other mmute blood-vessels are distributed throughout all parts of the sys- tem ; they are therefore termed systemic capillaries. It is through these that the blood flows from the left to the right heart (systemic or greater circulation), the capillary arteries being continuous with the capillary vems. An ideal representation of the circulation in man is given in Fig. 27. 567. Changes which take place in the Lungs.—The blood which has been passed through the" systemic capillaries and been returned by the veins to the heart is called venous blood. It is of a dark purple color; but Avhen it reaches the lungs, and is submitted to the action of the air, it changes to a bright crimson, and is then known as arterial blood. Accompanying this alteration of color there is also a chemi- cal change. Oxygen, from the air contained in the lungs, passes inward, or is absorbed through the cell-membrane, and combines with the blood; while at the same time car- bonic acid and water from the venous blood escape through the membrane in the opposite direction, mingle with the air, and are thrown from the lungs by expiration. The power of membranes to condense and transmit gases has been noticed before (137). 568. Oxidation occurs chiefly in the Systemic Capillaries.— It was formerly supposed that the carbonic acid and water * were formed in the lungs by the direct union of the oxygen with the carbon and hydrogen of the blood. But this idea has been abandoned, as it is shown that animals respiring pure hydrogen or nitrogen continue for some time to exhale carbonic acid, which would not be the case if it were only formed immediately by oxidation in the lungs. On the con- What is venous blood ? What is its color? What color does it acquire in the lungs ? What is it then called ? What chemical change also occurs ? How is it shown that the carbonic acid and water are not formed in tho lungs? USES OF IRON IN THE BLOOD. 297 trary, it is at the opposite extremity of the circulation, in the systemic capillaries, where the arterial system passes into the venous, that the oxidation of carbon and hydrogen takes place. It is here that the blood loses its florid arterial aspect and acquires a dark or venous tint, parts with its oxy- gen, and becomes charged with carbonic acid. These capil- laries, therefore, which are diffused throughout all the body, perform exactly the opposite office to .those of the lungs. 569. Supposed Use of Iron in the Blood-Disks.—The oxy- gen, when absorbed, combines not with the mass of the blood, but with its red disks only, and its union with them seems to be of a peculiarly loose nature, as it is surrendered up at all points of the organism to enter into other combina- tions. Liebig has thrown out a suggestion that the iron which exists in the coloring matter of the disks, and which is found nowhere else in the human body, has for its special office to carry oxygen and carbonic acid. He supposes the iron when it arrives at the lungs to be in the condition of a protoxide, but to be rapidly converted into a peroxide by the absorbed oxygen. In this state it is distributed to the caoillaries of the system, where, coming in contact with the tissues which have a higher affinity for its oxygen, it yields it up, and is reduced to the condition of a protoxide. It then unites with carbonic acid, forming the protocarbonate of iron, and returns through the venous channels to the lungs, where its carbonic acid is discharged into the air, when it is again freighted with oxygen, to continue the round perpetually. This hypothesis is plausible, but is not yet accepted as a physiological fact. In what part of the body are these substances formed ? What is said of the sys- ''wththaTdoL the absorbed oxygen combine ? What offices does Liebig aV tribute to the iron of the blood ? 298 ANIMAL CHEMISTRY. 570. The Change of the Blood is Chemical.—That the change of the venous blood effected in the lungs is of a purely chemical nature, is shown by the fact that the same changes will take place when it is exposed to the air out of the body, even through the medium of a thick membrane, such as a bladder. In this experiment, the surface of the blood only is changed, as the air has no access to the interior of the mass; but in the lungs, as it flows through a multi- tude of little vessels so minute as to admit but one tier of disks, and as these vessels are scattered over a vast surface, a large quantity of blood is readily and completely acted upon. 571. Again, that the changes of the blood are entirely of a chemical nature and dependent upon chemical causes, is shown by the effect of excessive chemical action. When an animal which has been killed by the respiration of pure oxy- gen (81) is examined after death, the blood in the veins is found to have the same florid color as in the arteries. 572. Rate of this Chemical Action.—The activity with which the respiratory process in man is carried forward, and the changes impressed both upon the air and the blood, is very surprising In a healthy adult man the pulsations number, upon an average, 75 in a minute, and physiologists are very generally agreed that two ounces of blood are driven by each contraction (pulsation) from the heart to the lungs, or 9 lbs. 6 oz. in a minute. The quantity of bleod in the entire system is estimated by the best authorities to be about one-fifth the weight of the entire body, or 28 pounds in a person weighing 140 pounds. All the blood in the body will, therefore, flow through the lungs in the short period of What are the proofs that the changes occurring in the blood are purely chemical ? What is the number of pulsations in a minute in a healthy adult man? How much blood is driven from tbe heart to th^ lungs in the same time What is tho OXIDATION IN THE ANIMAL SYSTEM. 299 three minutes, or the prodigious amount of 13,500 pounds every 24 hours. As to the quantity of air taken into the lungs by respiration experimenters are less perfectly agreed, probably on account of the extreme variation to which it is liable in different circumstances. Coathupe fixes the aver- age number of inspirations at 20 in the minute, and the average bulk of each inspiration at 16 cubic inches, which gives 266 cubic feet in 24 hours, but this is considered too low. Valentin estimates it at 398^ cubic feet per day (about 2500 gallons), and Agassiz as high as 700 cubic feet. 573. The Great Event of the Animal Economy.—From what has been seen of the properties of oxygen, we shall be prepared to conclude that the introduction of this remark- able body into the animal system by means of special con- trivances, which serve to diffuse it in the most rapid manner to all parts of the organization, is an affair of the utmost import in its connection with the phenomena of animal life. The elements of which the organism is chiefly composed are those for which this gas has the most powerful affinity. It enters the system in a free state, it leaves it in a state of combination; oxidation has therefore occurred within, and we are to find that this is the fundamental and characteristic process in the animal economy. SOURCE OF ANIMAL HEAT. 574. The stiffening, benumbing, stupefying, and fatal effects of cold upon the living body, are well known. The performance of the vital functions requires a certain degree estimated amount of blood in the entire system ? According to this estimate what amount of blood passes through the lungs in 24 hours? What estimates of the amount of air inspired are given ? What is said of the introduction of oxygen into the system T 300 ANIMAL CHEMISTRY. of heat, and this amount, which varies in different animal^ is generated within the system. The temperature of the human body in a state of health, and in all climates, is con- stantly maintained at 98°. The extreme variations from this point are in scarlet fever and locked-jaw, when it has been known to run up to 110f°, and Asiatic cholera and asthma, in which it has sunk to 20° below the healthy standard. The source of this heat is the chemical union of carbon and hydrogen with oxygen, a true combustion wliich goes on in the capillary system, and which is supplied on the one hand with fuel from the food which is eaten, and on the other with oxygen which is furnished by respiration. The use of the non-nitrogenized principles of food may now be perfectly understood; they are destined to be consumed by respiration—to be burnt in the capillary furnace of the system for the production of animal heat. The starch, sugar, gum, and oily substances contained in food, whatever intermediate changes they may undergo, are finally converted into carbonic acid and water by oxidation; and in whatever manner the combination takes place, heat must be developed. 575. Conditions of its Development.—The heat of the an- imal body being due to the chemical union of oxygen with the elements of food, it follows that the amount of heat pro- duced must be in proportion to the amount of chemical ac- tion, and this depends upon two conditions : first, the quan- tity of oxygen supplied by respiration; and second, the quantity of carbon and hydrogen furnished in the fcod. In other words, the heat of the human body having the same What is the constant, healthy temperature of the human body ? What extreme variations are mentioned? What is the source of this heat? What purpose da the non-nitrogenized principles of food serve in the system ? What are they all ultimately converted into ? Upon what two conditions does the heat of the animal body depend? How ** then may it be regulated? RELATION OF RESPIRATION TO HEAT. 301 source as that of a furnace, may be regulated in two ways— either by controlling the draught of ah or the supply of fuel 576. Effect of the Rate of Respiration.—The amount of heat generated in an animal is strictly related to its rate of respiration, and the amount of oxygen it absorbs. In reptiles and fishes, the structure of the respiratory organs (559, 564) is such that but a small proportion of oxygen is taken into the system; the quantity of heat which this produces is there- fore small; their temperature rises and falls with that of the surrounding medium, and is never but a little above it; they are hence called cold-blooded animals. On the contrary, the resphatory mechanism of bhds is on a most perfect plan: it works rapidly, and their temperature is consequently main- tained at a high point, 100° to 112°. Infants breathe more rapidly than adults, and the temperature of their bodies is several degrees higher. But the most striking illustration of the control of the respiration over the bodily heat is seen in the case of those animals which pass the winter season in a state of profound sleep or torpor (hybernation). In this condi- tion the breathing becomes very slow, the imperfectly oxygen- ated blood flows sluggishly through the heart, and the heat of the animal falls, it may be, almost to the freezing point. The animal becomes motionless, cold, and senseless, and " its entry into Death's chamber is prevented only by its being brought to his very door." The marmot in summer is a warm-blooded animal, but as it passes into hybernation the number of respirations falls from 500 to 14 in an hour, the pulse at the same time sinking from 150 to 15 per minute. Small as is the amount of oxygen which thus enters the sys- What is said of the respiration of reptiles and fishes? Why are they cold blooded? How does the respiration and temperature of birds differ from hese Why is the temperature of infants above that of adults? What is the condition ol animals in a state of hybernation ? Give an account of the marmot 26 302 ANIMAL CHEMISTRY. tern, it must be neutralized, and the animal accordingly, be- fore entering into winter-quarters, lays up a copious supply of resphatory food in its tissues in the form of fat, wliich slowly combines with the oxygen, producmg a small amount of heat, and protecting the vital structure from being de- stroyed. These animals are consequently observed to come forth in the spring in a very lean condition. 577. Influence of different Kinds ;(/" Food in producing Heat. — The influence of food (fuel) in modifying animal temperature is admirably exhibited in the provision made by nature for obtaining a uniform degree of he&t in men of all climates. In tropical countries, where the temperature of the surrounding ah- rises nearly, or quite to blood-heat (98°), it is obvious that the body will receive caloric, or be heated from without to nearly the full extent of its require- ment, and therefore have little need for generating it within. But in the polar regions, where the prevailing temperature is 100°, or often 150° lower, a powerful demand is necessarily made upon the heat-producing process. Accordingly, we find that the food, under these circumstances, is adapted to the wants of the case. Where little heat is to be disen- gaged, the amount of carbon and hydrogen in the food is in a correspondingly small proportion; when the calorifying energy of the system is to be powerfully taxed, they con- stitute the chief element of diet. The inhabitant of the tropic, with a high external temperature, finds ample suste- nance in fresh vegetables and fruits, which contain, according to Liebig, no more than 12 per cent, of carbon; while, on the other hand, the residents of the arctic regions, subjected to intense cold, live habitually upon train-oil and other fatty substances, which consist almost entirely of hydrogen and Why is there little need for generating heat within the body in tropical climatesl iVhy is it highly necessary in the polar regions ? How does the food of the Lap- SOURCE OF ANIMAL HEAT. 303 carbon. The West Indian disrelishes food which is rich in grease; and while the Laplander would dine comfortably upon tallow candles, he would be but ill satisfied with a meal of oranges or pineapples. To burn so large a propor- tion of combustible material, more oxygen is introduced into the lungs in frigid climates, in consequence of the greater condensation of the air by cold, while, at the same time, the respiration is greatly quickened by the greater amount of muscular exercise (584) which must be put forth to secure a supply of food. 578. Quantity of Carbon consumed. — The quantity of carbon burned in the system of an adult man daily, in a temperate climate, has been variously estimated, but is prob- ably about 10 oz.; seven of which are supposed to escape as carbonic acid, through the lungs, and three through the skin, which is also charged in a limited degree with the function of excreting carbon from the system. According to the ex- periments which have been made, the heat produced by the oxidation of this amount of carbon is less than the quantity generated within the body. But it must be remarked that much hydrogen, as well as sulphur and phosphorus, are also oxidized with the evolution of heat, while the results of ex- periments upon the living body to determine this point, from their extreme liability to error, must be received with caution. 579. Nervous Agency.—It has been assumed that vital heat is to be ascribed not to chemical, but to nervous agency; but this idea seems to be clearly set aside by observing what takes place in plants. There are two marked periodsmthe landerTffer'frwn'thai of the West Indian ? Why is it that the arctic inhabitant consumes more oxygen than those living in milder climates? What quantity of carbon is estimated to be burned daily in the "3**™*** adult man? Through what organs does its products pass from the system? What -rther substances are also burned-to produce heat? To what other cause has the production of animal heat been ascribed? How is 304 ANIMAL CHEMISTRY, life of a plant, in which it exercises the heat-evolving function; and becomes independent of surrounding temperature. In the germination of seeds, as we have seen (320), there is a development of heat, and the same thing occurs during the act of flowering. Thus a thermometer, placed in a bunch of flowers of the Arum, rose to 121°, when the temperature of the ah was but 66°. Now in both these cases there is an absorption of oxygen, which unites with the sugar of the flower and the oil of the seed, and a liberation of carbonic acid in exact proportion; and that the heat is simply due to oxidation, is proved by the fact that, if the presence of oxygen is prevented, no heat is evolved; whereas if pure oxygen gas is employed, the liberation of heat is more rapid than usual. The effect, in this' case, cannot be due to nervous action, for plants have no nervous system. The production of heat in the animal body is under the control of the nervous system, probably in the same manner that the fire which drives a steam-engine is under the control of the stoker or fireman; but he certainly cannot be considered as the source of the fire—as producing the heat—but only as its regulator; he may extinguish the fire, or increase it, and in the same man- ner the nervous system influences animal heat. 580. Animal Temperature regulated by Evaporation.—It has been stated that the temperature in man, except in cases of disease, never rises higher than about 98° F. It is kep< down to this point by the cooling effect of evaporation, which takes place from the surface of the skin. This organ is pen- etrated by a vast number of minute tubes (about 700 inches of tubing to each square inch of skin-surface), by which wa- this shown to be erroneous? At what two periods is heat evolved by plants? What chemical changes occur? How is it proved that the heat is due to oxida- tion? Why can it not be ascribed to nervous agency? In what sense may the production of heat in the body be controlled by the nervous system? By what means is the heat of the system kept down to 98° ? How is the skin RELATION OF THE LIVER AND LUNGS. 305 ter (perspiration) is poured out and evaporated, thus carrying away the surplus heat from the body. The amount of fluid which escapes from the skin, as insensible perspiration, is estimated at 11 grains, and that from the lungs seven grains pei minute. The power which men have exhibited of en- during excessive heat, for a short time, is due to the increased activity of surface-evaporation. 581. Office of the Liver.—If more resphatory food is taken into the system than is consumed by respiration or deposited as fat, it is separated from the blood by the fiver. A special channel (portal circulation) carries the venous blood through this organ, where its surplus hydro-carbon (fatty matter, bile) is strained out. If too much work is thrown upon the fiver it becomes disordered, and the substances which it should draw off accumulate in the blood, producing various symptoms, generally known as bilious. This is quite liable to happen in warm climates, when the elevation of the ex- ternal temperature, combined with the want of sufficient ex- ercise to stimulate respiration, leaves the non-nitrogenized elements of food unconsumed in the system. A similar disor- dered condition of the liver sometimes results from a diseased state of the lungs, by which they are rendered incapable of furnishing the due amount of oxygen for the combustion of the respiratory food. The office of both lungs and fiver is to relieve the blood of excessive carbon: then functions are thus complementary; that is, when the action of one increases, the other diminishes. It is observed that, throughout the whole animal series, the development and activity of the res- phatory organs stands in an inverse proportion to that of the adapted for this process ? What is the amount of insensible perspiration ? How have men been enabled to endure excessive heat for a short time ? What is the office of tho liver? How are bilious symptoms produced? Where are they the most frequeut? What other cause sometimes produces disease of 26* 306 ANIMAL CHEMISTRY. liver. Thus the resphatory system of insects is very exten- sive, while the fiver is so small that for a long time it was not recognized as such. In bhds and mammalia also, which breathe by lungs, the size of the liver is much less in pro- portion to that of the body than in reptiles and fishes, whose respiration is feeble. In the lower aquatic animals, in which respiration is least perfect, the liver is developed to an enor- mous size, often making up a large part of the bulk of the body. SOURCE OF ANIMAL POWER. 582. It depends upon Oxidation. — As the existence A heat in animals has been shown to depend upon respiration, and its quantity upon the activity of that process; so we are now to find that animal power or muscular force has precisely the same source, and that the degree of its manifestation depends also upon the rate at which oxygen is introduced into the system. It is now, however, the solid muscular tissues which are oxidized, instead of the respiratory food. The body can exert no power, perform no act, produce no motion, but at the cost of a portion of the muscular system by which these efforts are manifested. The power of a mus- cle to contract, and thus exercise force, originates only in the orocess of its own destruction, in the separation and loss of its constituent particles, which pass from the organized to the inorganic state by the act of oxidation. This combination of oxygen with the muscular tissues, for the production of force, we shall also find to be an additional source of animal heat. 583. Power of Exertion sustained by the Respiration of the liver? In what relation do the lungs and liver stand in regard to each other? state some examples of this. In what docs muscular power originate ? OXIDATION A SOURCE OF ANIMAL POWER. 307 Oxygen.—Eveiy one must have observed that active exercise produces rapid breathing. When the body is in a state of complete repose, as in sound sleep, the respirations are slow- est ; by moderate exertion they become more frequent, and violent effort, as in running, produces panting, or a quick succession of inspirations and expirations. That it is the oxygen in this case, which, by acting upon the system, sus- tains its power of exertion, is proved by the experience of those who have ascended high mountains. When they have attained such a height that the atmosphere becomes consid- erably rarefied, there is less oxygen taken into the system by the same number of inspirations than under ordinary circum- stances. The result is, that they are fatigued by the slight- est effort. 584. Examples.—The amount of oxygen which different classes of animals respire determines their energy or activity. We find, for example, that in bhds and insects whose res- piration is the highest, the muscular power is greater in proportion to their size than in any other animals, while in cold-blooded reptiles and fishes it is in a very great degree inferior: thus it has been ascertained that a butterfly, not- withstanding its comparatively diminutive size, consumes more oxygen than a toad. In those birds which are ever upon the wing, as swallows and eagles, the respiration is most active, their temperature rising to 112° F.; while in those birds which rarely fly it stands at 100° F. Insects, when in a state of rest, are cold-blooded; their respiration being feeble, and their temperature rising and falling with that of the surrounding air: but when in motion they are very active, consume much Upon what does the rapidity of breathing depend ? How is it shown to be tho action of oxygen which enables the system to sustain exertion? What is said of birds? Of reptiles? How does the consumption of oxygen in t butterfly compare with that in a toad?. How does the temperature rf insects vary? Givo tho example of the humble-bee. Of the nursing-bees. 308 ANIMAL CHEMISTRY. oxygen, and generate a proportionate amount of heat. Thus a humble-bee was found to consume more oxygen, and pro- duce more carbonic acid in a single hour after its capture., during which its body was in constant action, than in the whole succeeding twenty-four hours, when it was at rest. Another, in a state of violent excitement, communicated to three cubic inches of air 4° of heat in five minutes, its own temperature being raised 7° in the same time. The " nursing-bees" of the hive maintain the temperature neces- sary for hatching the larvae by means of an incessant motion of then limbs, by which quickened respiration is induced, and consequently heat; while they are seen crowding upon the cells, and clinging to them, for the purpose of communi- cating to them their warmth. 585. Case of Carnivorous Animals.—Animals which feed upon vegetation constantly consume the respiratory elements of their food, and lay up chiefly the nitrogenized portions in their tissues. In consuming then- flesh, therefore, the car- nivorous animals find a deficiency of respiratory food, and must depend for the maintenance of their heat upon the car- bon and hydrogen set free from their muscular system by exercise. This necessity compels them to increasing activity, as is well illustrated by the restlessness of the tigers and hy- enas seen at menageries, which keep moving instinctively from side to side of their narrow cages. By this means there is a constant and sufficient waste of the muscular tissue to support the respiratory process. 586. Necessity of Sleep.—As the waste or oxidation of the tissues corresponds with their exercise, so, if they are kept in a healthy or natural state, their nutrition or renova- Why have carnivorous animals a deficiency of respiratory food? How is their ntal boat sustained ? What example have we of their constant activity ? If the tissues of the animal are to be kept in a healthy state, what condition is NECESSITY OF SLEEP. 309 tion must in like manner correspond to their waste, or, in other words, the quantity of food eaten must, as everybody knows, be in proportion to the amount of exertion performed or of force expended. In the involuntary muscles, as those of the heart, which are constantly in play, the repair is as constant as the waste, and they are perpetually preserved in working order. But in the voluntary muscles, those which are controlled by the will and exercised in all kinds of labor, the exact balance between the nutritive and destructive op- erations is not maintained ; waste exceeds supply, the mus- cular parts fail in power, and they must periodically cease their activity, that the waste matters may be replaced, and the nutritive operations recover their equilibrium. This pe- riodical rest is afforded by sleep. 587. Why the Demand for Sleep is not Uniform.—In in- fancy, the nutritive process is more active than that of waste, and the body increases in mass, or grows. Accordingly, infants sleep much the largest share of the time. In adult manhood, waste and supply are equal, the sleep being just sufficient to recruit the loss of strength. But in old age the destructive process predominates over that of nutrition, the body wastes away, and but a small amount of sleep is required to effect the imperfect renewal, of which the failing- tissues are only capable. The decay and decline of the aged results from unchecked oxidation going on throughout the system, the activity of the nutritive process not being suffi- cient to counteract the destructive agency of oxygen. 588. Estimate of Human Force.—The muscular force which may be exerted by a healthy adult man is estimated, necessary ? How is it with, the involuntary muscles ? With the voluntary muscles ? How is the equilibrium restored ? Why do infants sleep more than adults ? Why does the time required for Bleep by adults and aged people differ? What oauses the decline of the aged ? 310 ANIMAL CHEMISTRY. in mechanics, as equal to moving one-fifth of his own weight with a velocity of 2£ feet per second, during eight hours of the day. Thus, if the weight of a man be 150 lbs., he is capable of carrying 30 lbs. a distance of 72,000 feet in eight hours, or of exerting a force equal to this in other directions. For the production of this force, there is consumed by oxi- dation a certain definite amount of muscular tissue, and this must be restored again if the same effect is to be produced on the succeeding day. Liebig states that this restoration is accomplished and the waste matter renewed in seven hours' sleep. 589. The Art of Fattening Animals consists in placing them in certain conditions in which the power of nutrition, or the formative process, most completely prevails in the system. All causes which tend to depress the action of the destructive force, and exalt the nutritive or constructive force, favor the increase of the bulk of the animal. Animals, to fatten most rapidly, should be kept at an elevated tempera- ture, so as to consume as little food as possible in the pro- duction of internal heat. They should also be maintained in complete repose, and not disturbed or excited in any way, in order to prevent the waste consequent upon muscular ac- tion. This state is most favored by darkness. Oily or starchy foods contribute to the formation of fat, and nitro- genized substances to the development of muscle or lean meat. What is the estimated force of a healthy adult man ? Example. How much sleep is required to restore the waste produced by this expenditure ? In what does the art of fattening animals consist 1 What course should be pur BU Catalysis,.......................... ■» Cellulose,..........................*"^ Chart, mode of representing the ele- ments, ........................ 29 n 338 GENERAL INDEX. PAQE Chart, definite prorxirtions,.......... 30 " multiple proportions,.........30 " atomic theory,............... 36 * affinity,...................... 28 Chlorine,.......................... 87 Chloride of Sodium,................154 " ofCalcium,...............155 Chloroform,.......................201 Chlorophyl,........................241 Jhymification,.....................261 Uhyliflcation,......................269 Coal, source of the power of,........173 " Mineral,......................182 Circulation in Man,.................294 Cohesion,......................... 34 Coke,............................. 97 Copper,...........................136 Copperas,.........................143 Collodion,.........................179 Copal,.............................232 Consumption,......................278 Cooking, of Vegetables,............253 " ofFlesh,..................254 Congelation, curve of,..............87 Combustion,-•••...................54 Combining Numbers,...............29 Court-plaster,......................280 Creosote,..........................181 Crystallization,..................... 37 Cultivation of Plants,...............243 Cyanogen,.........................105 Decantation,....................... 48 Deliquescence,..................... 38 Diagrams,......................... 43 Diamond,..........,.............. 91 Digestion,.........................261 " Experiments of Dr. Beaumont upon,....................265 Dimorphism,...................... 38 Distillation,........................ 48 Drummond Light,.................. 63 Dyeing, principles of,..............242 Efflorescence,...................... 38 Electricity,........................ 34 Elements, organic,..............27, 162 " table of,................. 25 " number of,............... 25 Epsom Salts,......................144 Ether,.............................200 Ethyle,............................200 Equations,........................ 43 Excretion by the Lungs,........___314 " by the Kidneys,___......312 Fats, animal,..................217, 282 Fermentation, vinous,..............194 " Lactic Acid,..........197 <* Acetous " ..........198 PAO« Feldspar,..........................157 Fibrine, vegetable,.................193 Fireworks,........................151 Filtering,.......................... 47 Flame,............................ 56 Fluorine,.......................... 90 Fluoride ofCalcium,................155 Gaseous Diffusion, Law of,..........84 Gastric Juice,......................262 Gelatine,..........................279 Germination,......................164 German Silver,....................142 Glass,.............................158 Glauber Salt,......................144 Glue,..............................280 Glycerine,.........................208 Gold..............................141 Graham Bread,....................205 Gum, Arabic^ Senegal,.............187 Gun-Cotton,.......................179 Gunpowder,.......................150 Gutta Percha,......................235 Gypsum,..........................143 Haloid Salts,.......................154 Heat,........................33,49, 57 Hornblende,.......................157 Hydrogen,.....'.................... 61 " Deutoxide of,............. 73 Hydrates,.......................... 64 Hyposulphites,.....................153 Illumination, • ■ • •..................55 Indigo,............................239 India-rubber,......................234 Insalivation,.......................260 Iodine,............................ 90 Isinglass,..........................279 Iron,..............................126 " Pig,...........................131 " welding of,....................127 " Wrought and Cast,.............127 " Ores of,.......................128 " in Blood,......................297 Isomerism,........................ 3c Isomorphism,...................... 39 Lac,..............................231 Lactic Acid,.......................197 Lactometer,......................"285 Lard,...........................[.'218 Laughing Gas,..................... 75 Lead,.............................137 Leaf, office of,.....................165 Litmus........................\\,'.240 Light,.............................! 34 " controls vegetable growth,.....169 " nature of,....................170 GENERAL INDEX. 339 Lignt, power of,....................172 " mode of action upon the Leaf,. 172 Lime,.............................117 " Hydrate of,...................118 " in Mortar,....................119 " in Soils,......................120 Madder,...........................240 Magnesium,.......................121 Magnesia,.........................121 Manganese,........................135 Margarine,........................209 Mastication,.......................258 Mercury,..........................139 Mica,..............................157 MUk,..............................284 " curdling of,.................. " preservation of,.............. Milk-sugar,...................... Minerals,..........................116 Nascent State,...................... 35 Nitrogen,.......................... 73 Nitrous Oxide,..................... 75 Nitrate of Potash,..................150 " ofSoda,....................151 Nomenclature,..................... 40 Nutrition,.........................276 Oils, fixed and volatile,.............207 " why inflammable,.............210 " as a preservative,.............212 m '* drying,.......................213 u unctuous,.....................215 Oil, Castor,........................215 " Croton,........................215 « Hempseed,....................215 " Linseed,.......................213 « Neat's-foot,....................217 " Olive,.........................216 « Palm,.........................217 ■ Poppy,........................215 « Spermaceti,....................219 « Train,.........................218 « Walnut,.......................214 Oils, volatile,......................226 Oil of Bergamot,...................-«9 " Black Pepper,...............-go « Lavender,...................229 « Lemons,....................228 « Juniper,.....................229 « Orange-peel,.................229 « Peppermint,.................229 « Turpentine,..................228 « Roses,.......................229 Oil-ailk............................214 uu*llK' .................208 Oleine,. 103 Oleflant Gas........ ••••••...........«« « mode of burning,.......104 Organic Chemistry,...............161 PAGK Organic Radicals,..................200 Oxygen,........................... 52 Oxy-hydrogen Blowpipe,........... 63 Oxidation,......................54, 58 Oxides of Iron,....................133 Phosphorus,.......................Ill Phosphoresence,...................113 Phosphuretted Hydrogen,..........114 Platinum,.........................140 Phosphate of Soda,................152 " ofLime,................152 Poisons, action of upon the System,. .324 Polarity of Atoms,.................. 37 Potassium,........................115 Potash,...........................115 Precipitation,...................... 47 Proportions, definite,............... 29 « multiple,.............. 30 Proximate Principles,..............162 Quartz,...........................-156 Resins,............................230 Respiration,.......................289 « ofFishes,...............290 « ofWhales,.............292 « of Insects,..............292 « ofReptiles,.............292 u by Lungs,...............293 Safety Lamp,......................102 Sago,.............................185 Salt, effect of upon Meat,...........257 Salts,.............................142 Sanguification,.....................271 Secretions,........................283 Serpentine,........................156 Silica,.............................124 Silicon,............................123 Silicates, artificial,..................15a Silver,............................140 Sleep, necessity of,.................308 Snow-flakes,......................83 Soda,.............................»7 Soap, production of,................221 " composition of,...............222 " valueof,................... -223 " properties of,................224 " action of in cleansing,.........224 Sodium............................116 Solution,...........................47 Soup, best method of preparmg,.....256 Specific Gravity,................... 46 Starch,............................183 Stearine,..........................■??* Steel,...........-,-•.••••;..........Hi Stomach, form and size of,..........£>i « structure of,.»............263 « motions of,...............264 840 GENERAL INDEX. PAGE Sulphur,.........................106 Sulphate of Iron,...................1« " of Lime,..................I43 " of Magnesia,..............144 « ofSoda,..................144 « of Alumina and Potash,---145 Sulphuretted Hydrogen,............110 Sugar,............................187 " Cane and Grape,..............188 " mode of obtaining,............188 " uses of,.......................189 Sugar-Candy,......................190 Symbols,.......................... 43 Synthesis.......................... 24 Talc,..............................156 Tallow, Mutton,....................217 « Beef,......................217 Tapioca,...........................185 Thermometer —................. 50 PAGE Tin,..............................."9 Type Metal,........................142 Varnish,..........................233 Ventilation, .......................315 Vinegar,...........................198 " putrefaction of,.............199 " adulteration of,.............199 Water,............................ 64 " constituents of,............... 6o " impurities of,................ 69 " hard,........................ 66 « sea,.........................67 " mineral,..................... 68 « purification of,...............69 " importance of to living beings, 70 " office in the animal economy,. .252 Wax,.............................219 Woody Fibre,......................"* TESTIMONIALS. OF THE CLASS-BOOK OF CHEMISTRY. From the 2sT. T. Commercial Advertiser. Either for schools or for general reading we know of no elementary work on Chemistry which in every respect pleases us 60 much as this. From the Albion. A remarkably interesting and thoroughly popular work on Chemistry, re- commended to the general reader by the clearness of its style, and its freedom from technicalities. From the Boston Common School Journal. We consider this Chart a great simplification of a somewhat confused {ob- ject ; and wo welcome it as another successful attempt, not only to simplify truth, but to fix it in the mind by the assistance of the eye. If we were called to teach the elements of chemistry in a school-room, we should be very unwilling to lose the valuable assistance of this ingenious chart. From the National Intelligencer. Besides the fulness with which this work treats of the chemistry of agri- culture and the arts, we regard it as chiefly valuable for the clear account it gives of the action of chemical agents upon the greatly varied functions of life. It is very elementary and practical; and whether for the use of schools or of private libraries, it is an appropriate because an instructive and entertaining From the Scientific American. Such a book in the present state of chemical science was demanded, but to present the subject in such a clear, comprehensive manner, in a work of the size before us, is more than we expected. The author ^s happily succeeded in clothing his ideas in plain language-true eloquence-so as to render the subiect both interesting and easily comprehended. The number of men who can write on science, and write clearly, Iff small; but our author is among that n umber. From the Farmer ami Mechanic. A Class-Book of Chemistry for the use of beginners and young students, which^Culdbe oTvested as much as possible of its tedious technicalities and T™ rpn-nMvenes^) so oftenattending their first efforts in this important study, ^3^. 'desideratum To supply this need, the present volume is «„S ItfsdesiSas apopular introduction to the study.of this engage the interest OF THE CHEMICAL CHART. From Hoeaob MLann, President ofAntioch College. mmmmim TESTIMONIALS. ing form and color, can learn a hundred things by inspection, while the ear is learning one by description, so, when material objects, too minute to be sees, or too intimately combined to be distinguished, can be represented by form and color, the same great advantage is obtained. The power of the learner is multiplied, simply by an exhibition of the object, or its representative, to a superior sense. . , I think Mr. Toumans is entitled to great credit for the preparation of his Chart, because its use will not only facilitate acquisition, but, what is of far greater importance, will increase the exactness and precision of the student's elementary ideas. From Dr. John W. Dbafeb, Professor of Chemistry in the University of New York. Mr. Youmans' Chart seems to me well adapted to communicate to begin- ners a knowledge of the definite combinations of chemical substances, and as preliminary to the use of symbols, to aid them very much in recollecting the examples it contains. It deserves to be introduced into the schools. From James B. Rogebs, Professor of Chemistry in the University of Penn- sylvania. We cordially subscribe to the opinion of Professor Draper concerning the value to beginners of Mr. Youman's Chemical Chart. John Tobeey, Professor of Chemistry in the College of Physicians and Surgeons, New York. William H. Ellet, Late Professor of Chemistry in Columbia College, S. C. James B. Rodgebs. Professor of Chemistry in the University of Pennsylvania. From Alonzo Pottee, LL.D., Philadelphia. The conception embodied in Mr. Youman's Chemical Chart strikes me as a very happy and useful one, and the execution is evidently the fruit of much care and skill. I should think its introduction into schools, in connection with the study of the first principles of Chemistry, was much to be desired. From Dr. Robeet Haee. I concur in thinking favorably of Mr. Youmans' Chemical Chart. The design is excellent, and as far as I have had time to examine the execution, I entertain the impression that it is well done. From Benjamin Silliman, LL.D., Prof, of Chemistry at Yale College. I have hastily examined Mr. Youmans' new Chemical Diagrams, or Chart of chemical combinations by the union of the elements in atomic proportions. The design appears to be an excellent one. From W. F. Hopkins, Professor of Natural and Experimental Philosophy in the U. S. Naval Academy, Annapolis, Md. Mr. Youmans' Chemical Chart is admirably adapted to assist the teacher in communicating, and the learner in receiving, correct notions of the laws of chemical combination. I commend it to the patronage of schools and acade- mies where chemistry is taught, and shall immediately introduce it into the institution with which I am connected. From Pbop. Gkat, Author of Text-Books on Natural Philosophy, Chemistry .and Geology. Mr. Youmans' Chart presents to the eye a clearer view of the manner in which the atoms of chemical compounds are united, than could be rained bv the most labored description. * * * * ' It would be especially useful to institutions not furnished with chemical apparatus. TESTIMONIALS. From Joseph McKeen, Superintendent of Common Schools in New York. I have been greatly pleased with an examination of a Chart of elementary Chemistry, by Mr. Youmans. It seems to me that it so simplifies the subject, that pupils in the best classes in our common schools may acquire from a few lessons, with its aid, more knowledge of the laws and principles of this science, than from months of study without such means of illustration. I know of no other chart like this; and as by its means Chemistry may now be taught with the same facility as geography or astronomy, I would earnestly commend it to the attention of school committees, teachers, and learners. From Jas. R. Chilton, M.D., Chemist. I have examined the Chemical Chart of Mr. E. L. Youmans, and am much pleased to say that it is a valuable means of readily imparting a correct know- ledge of the nature of chemical combinations. A variety of compounds are dissected, so as to show at a glance their ultimate atomic constitution, in such a way as to impress it more forcibly upon the mind than could be effected by any other method with which I am acquainted. To those who are studying to obtain a knowledge of elementary and agricultural chemistry, as well as to all learners of chemical science, Mr. Youmans' Chart will render easily understood what might otherwise appear very difficult From Dr. Thomas Antisell, Prof, of Chemistry in the Vermont Medical College. Mr. Youmans' Chart is got up in a style which renders it a neat apppend- age to the lecture-room, and wherever Chemistry is taught in schools and public institutions, it will be found an invaluable assistant to both teacher and pupil. OF THE ATLAS OF CHEMISTRY. Every one who has studied Chemistry, will remember the many perplex- ine hours spent in trying to fix in the memory the component parts of various compounds. To us, it was a most irksome and disagreeable task. Had Mr. Youmans' book been placed in our hands, we are certain that we could have mastered our lessons with much less than one fourth of the labor we were obliged to bestow. We call this in all respects a model \>ook.—Cleveland Plavndealer. Here we have science in pictures—chemistry in diagrams—eye-dissections of all the common forms of matter around us; the chemical composition and properties of all familiar objects illustrated to the most impressible of our senses by the aid of colors. This is a beautiful book, and as useful as it is beautiful Mr. Youmans has hit upon a happy method of simplifymg and bringing out the profoundest abstractions of science, so that they fall within the clear comprehension of children.—Home Journal. The author was lead to the construction of his plan by noticing the defects nf the abstract method by which the science is usually taught in books. Laboring under Se disability of blindness, whUe pursuing his own studies he ^Sueeply impressed with the importance of visual demonstration in ob- tetato^a knowledge of physical phenomena. We do not hesitate to say that ncmethod halcome unoe/ our notice, by which the beginner in Chemistry c2rXe,so effectual!? «nd so agreeably initiated into the rudiments of the stfence as bytheprocess madeSuse of in this yolume.-Harpers' Magaeme An excellent idea, well carried out. The style is lucid and happy, the defltftions concle and clear, and the illustrations felicitous and appropriate. __fflica Morning Herald. We have devoted some little time in looking over this Atlas, and compar- i™irrelativeTmerits with similar treatises heretofore published, and feel bolnd to accordtoM'the highest degree of approbation an* b.yor.-Lawrence Sentinel TESTIMONIALS. This method of using the eye in education, though not the royal road i» knowledge, is really the people's railroad—a means of saving both time anj labor. This work is worth for actual instruction in common sohools far more than a set of apparatus, which the teacher might not be able to use, while every one can teach from the Atlas. We pronounce it, without exception, the best popular work on Chemistry in the English language.—Life Illus- trated. Mr. Youmans is not a mere routine teacher of his favorite science; he has hit upon novel and effective methods for the illustration of its principles. In his writings, as well as his lectures, he is distinguished for the comprehensive order of his statements, his symmetrical arrangement of scientific facts, and the happy manner in which he addresses the intellect through the medium of ocular demonstration. In this last respect, his method is both original and singularly ingenious.—N. Y. Tribune. With this plan a vast amount of information is attainable by mere inspec- tion. In a manufacturing community like ours, chemistry should be studied by young and old, and in the works of Mr. Youmans "the science is presented in its most attractive and useful form.—Newark Daily Advertiser. Mr. Youmans handles his subject in a simple, yet masterly style, and we consider his Atlas unequalled in its simplicity and adaptation to the wants of both teacher and pupil.—N. Y. Sun. If we were asked by a young lover of science what work we would recom- mend as an introduction to the interesting science of Chemistry, we would most confidently name this of Mr. Youmans. Among all the works upon this part of natural science which have of late years been published, we do not know of one which presents its principles so briefly and yet so clearly. It ia also a happy idea to apply to Chemistry the method of diagrams, which has succeeded so well in tho cognate sciences, and it is a wonder that some of our great ones did not sooner think of it. We are not at all surprised that so many professors and principals of academies should have spoken so favorably of it, for were we a professor, we would discard every other class-book on the subject in order to adopt this without delay. * * If there be any thing, however, that should please us as religious reviewers more than all the rest we could easily find in it the spirit that continually, without any effort, raise.' the author's mind "from Nature up to Nature's God." It is exceedinglj gratifying to see this manifested by one who is certainly no ignoramus, and the contrast it affords to the conduct of so many of our scientific men who are beginning to ape the skepticism and philosophism of Europe, is an honor to Mr. Youmans, of which he may be prouder than even his great chemical knowl alge.—Metropolitan Magazine, {Baltimore.) D. APPLETON f CO., PUBLISHERS. HAND-BOOK OF THE ENGLISH LANGUAGE. BY G. R. LATHAM, M. D., F. R. 8. 12mo. 400 pages. Price $1 25. This work is designed for the use of students in the University and High School* " His work is rigidly cclentiflc, and hence posseses a rare value. With the wide- ipreadlng growth of the A^glo-Saxon dialect, the immense present and prospectiv* power of those with whom this is their ' mother tongue,' such a treatise must be counted ■like interesting and useful."— Watchman and Reflector. "A work of great research, much learning, and to every thinking scholar it will be i •ook of study. The Germanic origin of the English language, the affinities of the Eng- toh with other languages, a sketch of the alphabet, a minute investigation of the etymo. ogy of the language, &c, of great value to every philologist"— Observer. HISTOKY OF ENGLISH LITERATURE. BY WILLIAM SPALDING, A. M YBOFK80B OF LOGIC, BHBTOBIO, AND MBTAPHT8I08, IN THE UNIVERSITY OF BT. ANBBKW. 12mo. 418 pages. Price $1 00. The above work, which is just published, is offered as a Text-book for the use of advanced Schools and Academies. It traces the literary nrocress of the nation from its dawn in Anglo-Saxon times, down to L present day. Commencing at this early period, it is so constructed as to introduce the reader gradually and easily to studies of this kind Comparatively little speculation is presented, and those literary^nu- ments of the earlier dates, which were thought most worthy of at en tioT are described with considerable fulness and in an attractive manner In the subsequent pages, more frequent and sustained effort aTmad* to arouse reflection, both by occasional remarks on the rek- HoJbetween intellectual culture and the other elements of society, Id by bints as to the theoretical laws on which cntxcism should U founded. The characteristics of the most celebrated modern works ar« •nulvzed at considerable length. The manner of the author is remarkably plain and mterestrng^ .imort compiling the reader to linger over his pages with tuweaned attention. ^ D. APPLETON f CO^ PUBLISHERS. CLASS-BOOK OF CHEMISTRY. BY EDWABD L. YOUMANS. 12mo. 340 Pages. Price 75 Cents. Every page of this book bears evidence of the aithor's supeiioi ■bility of perfectly conforming his style to the capacity of youth. Thii is a merit rarely possessed by the authors of scientific school-books. and will be appreciated by every discriminating teacher. It is espe eially commended by the eminently practical manner in which each subject is presented. Its illustrations are drawn largely from the phe- nomena of daily experience, and the interest of the pupil is speedily awakened by the consideration that Chemistry is not a matter belong- ing exclusively to physicians and professors. From Peof. Wm. H. Bigelow, Principal of Clinton Street Academy. " The eminontly practical character of the Qiass-Book treating of the familiar ap- plications of the science, is in my opinion its chief excellence, and gives it a value fai superior to any other work now before the public." From David Stme, A. M., formerly Principal of the Mathematical Department, and Lecturer in Natural Philosophy, Chemistry and Physiology, in Columbia Col " Me. Youmans : Dear Bib,—I have carefully examined your Class-Book on Chem Istry, and, in my opinion, it is better adapted for use in schools and academies than any other work on the subject that has fallen under my observation. " I hope that the success of your Class-Book will be proportionate to its merits, and that your efforts to diffuse the knowledge of Chemistry will b« duly appreciated by th« friends of education." "Either for Schools or for general reading, we know of no elementary work o» Chemistry which n svery respect pleases us so much as this."—Com. Advertiser. CHART OF CHEMISTRY. BY EDWABD L. YOUMANS. Youmans' Chart of Chemistry" accomplishes for the first time, for chemistry, what maps and charts have for geography, astronomy, geo- logy, and the other natural sciences, by presenting a new and admir able method of illustrating this highly interesting and beautiful science. Its plan is to represent chemical compositions to the eye by colored diagrams, the areas of which express proportional quantities. ABOVE, IN ATLAS FORM 18 D. APPLETON §■ CO., PUBLISHERS. CLASS-BOOK OF PHYSIOLOGY. BY B. N. COMINGS, M D. 12mo. 2*70 pages. Price 90 Cents. This volume, which is well adapted to the wants of schools and academies, has been prepared from the "Principles of Physiology, by Comings and Comstock, and is brought out in "ts present form a< the urgent request of numerous friends of education who have highlj eommended that work, which was found too expensive for general us* in the school-room. It will be found to explain and illustrate fully and clearly as many principles of physiology as can be expected in a work of its limit That human physiology can be made more easy of comprehension, more profitable, and more attractive to the beginner of the study, by appro- priate references to the comparative physiology of the inferior animals, than by any other method, is an established fact in the mind of the author, which he has made eminently available in the preparation of this work, thus giving to this work peculiar claims to the attention of teachers. The work is illustrated by 24 plates and numerous wood-engrav- ings, comprising in all over 200 figures. COMPANION TO ABOVE. (In Press.) Containing illustrations' and Questions. COMMON SCHOOL PHYSIOLOGY. Dr. Comings. (Nearly Ready.) From Abeaham PowELSON,.Jr., Teacher, No.- 204 Schermerhom Street, Brooklyn, New York. » After a very careful examination of the Class-Book of Physiology, by Comings, I can freely say that I consider it a performance of superior excellence. It embodies a fund of information surpassing in imporUnce and variety that of any other work of the kind which has come under my n^Uce." Frvm Andbew J. Welles, Glastonbury, Conn. «It appears to me to be admirably adapted to the purpose for which it was designed and I think will readily be admitted into our schools." "The illustrations are more complete, and in a style superior to any I have ovei ■een in a school-book, making it really attractive to tho eye." From Wm. D. SniPMAN, East Haddam, Ct. "Please accept my thanks for a copy of your ' Class-Book of Physiology, by m Comings' I have given the work a somewhat careful examination, and am very strongl tennressed with its value as an elementary work for schools and families. It oontai. 4 rimple and lucid exhibition of the subject upon which it treats, and illustrates th« «iences by a great amount of instructive and curious information, which cannot fail U MAke it an attrflctivebook fbr ingenious young persons." 19 D. APPLETON 9 CO,, PUBLISHERS. MANUAL 0 F ELEMENTARY GEOLOGY BY SIB CHABLES LYELL, M A., P. E. S. 1 VoL 8vo. 512 pages. Price $1 76. This is a reprint of the fourth London edition of a work of distil* guished reputation, beautifully illustrated by Five Hundred Woodcuto Being the production of a writer who stands at the head of the depart- ment of knowledge which he has undertaken to expkin, is sufficient guaranty for the invaluable character of the work for the scientific rtaader and observer, as well as for general use in our seminaries of learning. "There is no branch of natural science whero there is a more quickly recurring ne- cessity for new editions of elementary books, than Geology. It is itself but the germ et a science, dally gathering fresh facts and extending its jurisdiction over rew fields of ob- servation. What was a satisfactory account of its discoveries a few years ago, is now ob- solete. And among the scholars and observers who have done most to advance th« science, and are most competent to elucidate its present condition, is the author of th« volume before us."—Charleston Mercury. PRINCIPLES OF GEOLOGY. BY BIB CHAKLES LYELL, A. M, F. B. & 1 Vol. 8vo. 834 pages. Price $2 25. " This is a noblo volume of over 800 pages, 8vo., on fan* paper, in clear type, and abundantly illustrated with maps, engravings and woodcuts—an honor to the publishers who have issued it, and speaking well for the progress in scientific studies in this coun- try—inasmuch as it would not be re-published, without a fair j-rospect of a remunerat- ing sale. It is a book that we cannot pretend to review; but we take pleasure in an- nouncing its appearance as a work which those of our readers interested in the growing, and in many respects very practical science of geology, will be glad to see. The author stands among the foremost of those who have devoted themselves to reading tbe history of the earth as written in and upon its own bosom."—Christian Register. "ItwfJ only be necessary to announce this new and handsome edition of Lyell's itandard work on geology, to induce all lovers of this most instructive science, to securs aeopyof the work, if possible; for every successive edition of such a work has rs value which none of its predecessors had, inasmuch as new discoveries are being constantly B»