LIBRARY OF THE UNIVERSITY OF CALIFORNIA. Class PRINCIPLES OF CHEMISTRY; EMBRACING THK MOST RECENT DISCOVERIES IN THE SCIENCE, AND THE OUTLINES OF ITS APPLICATION TO AGRICULTURE AND THE ARTS. X ILLUSTRATED BY NUMEROUS EXPERIMENTS, NWWLY ADAPTED TO THE SIMPLEST APPARATUS. BY JOHN A. PORTER, M.A., M.D. PROFESSOR OF AGRICULTURAL AND ORGANIC CHEMISTRY IN YALE COLLEGE. NEW YORK: A. S. BARNES & CO., 51 & 53 JOHN-STREET, I860. * Entered according to Act of Congress in the year 1856, by JOHN A. PORTER, in the Clerk's Office of the District Court for the District of Con- necticut. IN the preparation of this text-book on Chemistry, it has been the design of the author to disencumber the subject of much detail, which is only of interest to the professional chemist, and at the same time to bring the illustration of the more important phenomena of the science within the reach of every school and every individual student. The most distinguished philosophers have not deemed it beneath their dignity to employ the simplest means of inves- tigation. The teacher will not be loth to take advantage of similar means in illustrating their discoveries. An important design of this work is to show how this object may be ac- complished, by the simple addition of a few test-tubes and a spirit lamp, to a list of chemical apparatus which may be found in every house. Among the other distinctive features of the work, are a more complete classification than usual according to chemi- cal analogies, the explanation of chemical phenomena in ordinary language, as well as symbols, and the addition of a complete set of formulae in the Appendix. A number of recent and important discoveries are introduced, and the relations of Chemistry to the Arts and Agriculture, are es- pecially considered. The method adopted for the explanation of chemical phe- nomena, while it is believed to be more effectual in imparting the leading idea of all chemical reactions, leaves to the 1 11 PREFACE. student the useful exercise of constructing formulae. He is at the same time supplied in the Appendix with a com- plete control of his results. This part of the work contains in addition, numerous tables, and other supplementary mat- ter for the use of the more advanced student The language of the atomic theory has been rigorously adhered to throughout the work, as the best expression of our present knowledge of the constitution of matter. While it is liable to no objection which does not hold against the language of every department of Physics, its uniform employment has the great advantage of accustoming the mind to a conception which furnishes a probable explanation of the most obscure portions of the science. Several topics introduced in the chapters on Physics, are designed simply as introductory to other subjects, and are very briefly treated, in accordance with this design. Among the numerous authorities consulted in the prepa- ration of this work, the author would especially mention the works of Berzelius, Liebig, Gmelin, Gregory, Regnault, Payen, Graham, Silliman and Stockhardt. He would also take this opportunity of acknowledging the important aid extended by his able professional assistant, DR. ROBERT A. FISHER, both in the execution of his design for a simplified course of experiment, and for valuable information in rela- tion to several processes of applied chemistry. Boxes containing apparatus and materials neatly put up to accom- pany this work, may be ordered of J. R LTJHME, & Co., dealers in Chemical Apparatus and Pure Chemicals, No. 556 Broadway, New York. Price $6.00. The list embraces all the articles named on the last page of the work, with the exception of those marked with an asterisk, which may be procured of any druggist. TABLE OF CONTENTS. PART I. PHYSICS. PAGE ATOMS AND ATTRACTION, ... 11 LIGHT. Chemical action of Light, 15 Theories, 15 Laws, ...... 17 Analysis of Light, . . 22 HEAT. Nature and Sources, 25 Communication of Heat, 30 Changes effected by Heat, 48 HEAT. Expansion, PAGE .... 50 .... 61 Vaporization, .... 66 Boiling, ...... 77 ELECTRICITY AND MAGNETISM, . 99 Galvanism, ..... 103 Batteries, ...... 114 Galvanic Decomposition, 117 Magnetic Telegraph, . .124 PART II. CHEMICAL PHILOSOPHY. ELEMENTS, . MIC CONSTITUTION, . EXPLANATION OF SYMBOLS, LAWS OF COMBINATION, . , PAGE . 129 129 . 132 134 PAGE PROPERTIES OF ACIDS AND BASES, 137 EFFECT OF SOLUTION, . . . 138 ELECTRICAL CONDITION OF THE ELEMENTS, 138 IV CONTENTS. PART III. INORGANIC CHEMISTRY. FAQE METALLOIDS. Oxygen, 141 ^.Ghlorine, 149 /Modine, 156 Bromine, 158 -^'.--Fluorine, 158 / Sulphur, 159 Nitrogen, 169 Phosphorus, . . . .176 Arsenic, 179 Carbon, 185 Boron, 197 METALS. Classification, . .231 CLASS I. Potassium, &c. 233 CLASS II. Barium, be cause they are such poor con- ductors, and beside, because they contain air shut in between their fibres, which is a non-con- ductor. as will be hereafter shown. The object of clothing is not to impart heat, but to prevent its escape CONDUCTION. 33 from the body. It -escapes more or less through all substances, but less rapidly through the fibrous materi- als just mentioned, and therefore their superiority for winter clothing. If we lived in an atmosphere hotter than our bodies, the object of clothing would be to ex- clude heat, and the same non-conducting materials now used would be best adapted for this purpose also. Sometimes it is actually the object of clothing to keep out heat ; as, when workmen enter hot furnaces in cer- tain manufacturing processes. Thick clothing, of non- conducting materials, is obviously best in this case also. In summer, coarser fibre of linen, which is a better conductor than cotton or wool, is more used, because it conveys away the heat of the body more rapidly, as is desirable in the warmer season. 63. FURS OF ANIMALS. We see, in Why has the , . , , . Deity varied what has been stated, the reason why the ninuffl 9 * Deity has clothed animals inhabiting cold climates with fine furs. While the elephant of the torrid zone has but a few straggling hairs, the polar bear has a thick coat of fine fur to keep in his vi- tal heat, and enable him to endure the extreme rigor of a northern climate. So the sea-fowl has a thick covering of soft down to protect him from the cold of the ocean, while the ostrich has an open coat of scanty feathers. ,, r , , 64. WARMTH OF SNOW. Snow keeps Why does snow r tend to keep the earth warmer in winter than it would otherwise be, not because of any heat it imparts, but because, by reason of its low conducting power, and that of the air which it con- 2* 34 HEAT. tains, it prevents the escape of the heat which is stored in the earth from the previous summer. But for this indirect warming effect of the snow, the cold of a sin- gle winter would be sufficient to kill whole races of plants. Thus, the cold of the winter weaves a garment to protect the earth from its own influence. How do the ^' BUILDING. In building, the same principles of principles apply as in the case of clothing. C piyinthtcas~e Bad conductors, when suitable in other of buildings? respects, are the best materials for walls, making a house cooler in summer and warmer in winter. Wood and brick, for example, are in this respect better than iron. They keep out the heat in summer, and, though they have the same effect to exclude the heat of the sun's rays in winter, they more than make up for this by preventing the escape of the larger quantity of heat produced by the fires in- side. The inhabitants of the Arctic regions build their winter huts of snow, and thus make practical use of its low conducting power. Double doors and windows have more than a double effect in preventing the escape of heat in winter, because of the non-conducting wall of air between them. ,, . . , 66. REFRIGERATORS. These are double- What is the principle in- walled wooden box- es > sed to refrigerators ? articles of food from the heat of the summer. The space between the double walls and top is filled with pulverized charcoal, which has in itself very little conducting CONDUCTION. 35 power, and again is non-conducting because of the air between the particles. 67. FIRE-PROOF SAFES. These are constructed on the same principle, the space be- tween the double walls being filled with gypsum, or some other non-conducting material. They are used as repositories of valuable papers and other property, for greater security in case of fire. 68. WHY BODIES FEEL COLD OR HOT. Why do bodies . feel cold or A metallic door-knob feels colder than the kot ? wood to which it is fastened, although it cannot actually be so. It is because the metal is the best conductor, and carries off the heat of the hand more rapidly. If a piece of metal and wood be placed in a hot oven till both become equally hot, as they must by long exposure to the same heat, the metal will feel hotter than the wood. It is because the metal, by its greater conducting power, supplies heat more rapidly to its own surface to be taken away by the hand. 69. SIMPLE TEST OF CONDUCTING POWER. Give a simple test for deter- Among bodies equally hot, the colder a Inducting 6 bod y feels j the better conductor it is. That power of 'a body this is generally the case is evident from the last paragraph. On applying this test, we find the metallic lamp-stand, cooler, and therefore a better con- ductor than the table cover on which it stands. In an oven, or other place where the heat is greater than that of our bodies, the test would be reversed. For 36 HEAT. the flow of heat would be in this case into the hand, from this highly heated object, and the body that brought it fastest, or felt hottest, would be thereby proved to be the best conductor. 70. LIQUIDS NON-CONDUCTORS. Water it in a test-tube may be boiled at the top 'quids are non- w h jj e j ce frozen into the bottom will re- conditctors ? _ main unmelted. If a bar of metal with a cavity at the bottom for the ice were heated in the same way, the heat would be conducted downward so rapidly that the ice would soon disappear. Explain the ?!. FlRE ON WATER. Fire may be experiment kindled on water by pouring a little ether with ether to / prove that li- upon its surface and inflaming the flame will be found heat. t have slight effect on the temperature of the water. And, what lit- tle effect it has, is principally due to the fact that the glass or metal of the containing vessel carries the heat downward and distributes it to the liquid. When water is heated by a fire beneath it, it is not by conduction, but by another process, explained in a subsequent paragraph. The above experiment may be made in a tin cup very nearly filled with water. A tea-spoonful of ether having been poured on the water, the bottle is to be corked and set away, for fear of ex- plosion, from the kindling of the ether which it con- tains. The experiment, as described, is not in the least degree dangerous. CONVECTION. 37 CONVECTION. 72. It has been already shown that Explain how liquids become liquids and gases are non-conductors. This implies that they cannot be heated, like a mass of metal or other solid, by communi- cation of heat from particle to particle. Each parti- cle, on the contrary, receives its heat directly from the source of heat, and conveys it away, making room for others. Hence the term convection. In the process of boiling water, for example, the first effect of the fire is to heat the lower layer of liquid, and thereby to expand and make it lighter. It then rises as a cork would in water, and gives place to another portion, which be- comes heated and rises in. its turn. Thus a circula- tion is commenced, the warmer portions ascending and the cooler descending, which continues until the water boils. Before this happens, each particle will have made many circuits, accumulating heat with each re- turn, but not communicating it to others. Air and gases become heated in the same way. 73. CONVECTION MADE VISIBLE. The How can the ., , , circulation in circulation above described may be ren- dered visible b addin s a little of the " flow ~ berenderedvis- erS of Slllphlir" to Water , iblc? . . and then heating it in a test-tube over a spirit lamp. The suspended particles will be found to move in the direction indicated by the arrows, showing that the water has the same motion. The 38 HEAT. upward current is not, it is to be remembered, because of any tendency of heat to rise. Heat, on the con- trary, travels in one direction as well as another. But it is, -as before explained, because hot water is lighter than cold. Dust of bituminous c.oal answers the purpose in this experiment still better than " flowers of sulphur." It is necessary to have something that will neither sink or swim, but remain suspended in the water. 74. HEATING ROOMS. A room becomes How does a . room become heated by a stove in the same manner. heated? rp ne ^ T ^ R i mme( ji a te contact with the hot surface becomes heated and rises. Cooler air comes in from all sides to take its place, and be heated and less in turn. A circulation is thus established pre- cisely similar to that which occurs in the flask, as rep- resented in the figure. Any light object, as a feather, or a flock of cotton-wool, held over a stove or an open flame, will prove by its ascent the existence of the up- ward current. How rapidly heat thus passes upward by convection, may be proved by holding the finger above the flame of a lamp, and then at an equal distance at its side, and comparing the effect. How is the at- ^' CONVECTION IN THE HEATING OF THE mosphere heat- ATMOSPHERE. Heat is distributed through the earth's atmosphere in the same manner. At the equator, where the surface is hottest, the air heated by contact with it rises and flows off toward the poles, while colder air from the polar regions flows in to take its place, to be heated and rise in turn, contin- uing the circulation. But for this arrangement, the RADIATION. 39 equatorial regions, which are constantly receiving ex- cess of heat from the sun, would soon become unin- habitable by reason of its accumulation, and the polar regions, from extreme cold. The currents or winds thus produced are subject to great irregularities, which are considered in works on natural philosophy. RADIATIOK 76. The general laws of radiation What are the laws of the are the same for heat as for light. Rays eat? i0n f of heat divei 'g e constantly from all points of the surface of all bodies, in straight lines and in every direction ; and the intensity of heat varies inversely as the square of the distance. The latter point is explained in the chapter on light. 77. HEAT is RADIATED FROM ALL BODIES. Illustrate the . . fact that heat It is to be observed that while light pro- in alW radiatl~d cee( * s onlv ^ roni certain bodies, heat pro- from bodies, ceeds from all points of all bodies without exception. If the mercury in a thermometer were fro- zen by extreme cold, and then hung in a cavity made for the purpose in a block of ice, radiation of heat from the ice would melt it, even if there were no air in the cavity to help melt it by conduction. 78. PROPORTION OF RADIATION TO TEM- What can be said of the pro- PERATURE. The hotter a stove is the more heat il S lves Ollt ' This is obvious, and we might naturally suppose that a stove twice as hot as another stove, compared with other objects about it, would give out heat just twice as fast. It 40 HEAT. gives out heat,- in fact, more than twice as fast, the ra- pidity of radiation being more than in proportion to the temperature. 79. POLISH is UNFAVORABLE TO RADIA- What are the . effects of rough TioN. A coffee-pot oi well brightened metal will keep its contents hot much bet-. diation? t er than a dingy, blackened one, thus re- warding the housewife for her pains. The brightness is not the cause of this effect. It is owing to the fact that polished surfaces are more dense, and dense sur- faces do not allow heat to pass readily. But if the pol- ished coffee-pot be covered with muslin so as to give it a less dense surface, radiation and consequent cooling will proceed more rapidly again. One would think that the polished surface beneath the cloth would have the same effect in retaining the heat as before, and that the cloth would still further retard its escape ; but ex- periment proves that this is not the case. Radiation depends on the surface, without regard to what is be- neath it, and the superiority of the cloth as a radiator is more than sufficient to make up for its non-conduct- ing influence. Rough uncompact surfaces, generally, radiate well. High polish being unfavorable to radia- tion, stoves should not be too highly polished. The high polish of soldiers' helmets makes them much cooler than if they were made of dull metal. ,. r , . 80. COLOR DOES NOT AFFECT RADIATION.-^ What effect has color on A black coat wastes no more of the heat of the body by radiation than a white one. Except in the direct rays of the sun, one is just as warm as the other. But the former absorbs and imparts REFLECTION. 41 to the body more of the heat which comes to it asso- ciated with intense light, as is the case with the heat of the sun, and therefore its advantage as an article of winter clothing. Ti r , . . 81. TRANSMISSION OF HEAT. The heat What is said of the of the sun passes with its light through transmission ,, , -r i / of heat thro' a U transparent substances. But heat from bodies ? j ess m t ense sources is absorbed, and in large part stopped by many substances which allow light to pass : such are water, and alum, and glass to a less extent. A glass plate held between one's face and the sun will not protect it, but held before the fire will intercept a large part of the heat. So a glass lens or burning-glass will stop the heat of a fire, instead of transmitting and con- centrating its raysj as it does those of the sun. It is a singular fact, on the other hand, that many substances which allow heat to pass, effectually stop the light. Such are black glass and smoked quartz crystal. Rock salt allows heat to pass so perfectly that it has been called the glass of heat. 82. REFLECTION OF HEAT. Polished What bodies are the best re- metallic surfaces are the best reflectors. S53***gJ Coffee takes lon s er to boil in a bri s ht cof- subject. fee-pot, because the heat is reflected from the bright surface and does not enter the liquid. If it were desired to heat a liquid as rapidly as possible, and keep it hot as long as possible in the same vessel, it would be wise to take a dingy one for the rapid heat- ing of the liquid, and then to polish it in order to fasten the heat in. Glass mirrors do not reflect heat so well as those of uncovered metal, because of the absorbing 42 HEAT. power of the glass, mentioned in the last paragraph. But this absorbing power is very slight for heat which comes from an intense source like the sun, so that such mirrors reflect the solar heat quite perfectly. 82. ABSORPTION OF HEAT. Surfaces are What bodies absorb heat good absorbers, in proportion as they are poor reflectors. All the heat that falls on any surface, must be either reflected or absorbed. In proportion, therefore, as little is reflected much is ab- sorbed. 83. ABSORPTION CONTINUED. Dark cloth- What effect /-,, > r has color on ing is warmer than that of light color, for the warmth of ^ reason t fr a t heat associated with light clothing ? seems to follow the laws of the latter and undergo absorption or reflection with it. Now we know that dark objects owe their dark color to the fact that they absorb much light, and reflect but little to the eye. Ex- periment shows that they absorb much heat also, if the heat be associated with light. The absorbed light must show the way, as it were, for the entrance of the heat. Dr. Franklin proved what has been stated, by the ob- servation that when different colored cloths are spread upon snow, it melts most rapidly under those which are darkest. 84. EQUILIBRIUM OF TEMPERATURE. How is equili- brium of tem- It has before been stated that heat is con- ^11^ Stantl 7 radiated from all bodies. Absorp- tion of heat, is also universal. If any num- ber of bodies are equally hot, they remain so, each ac- cording to its surface, imparting to the rest and receiv- ing from all the rest, taken together, the same quantity RADIATION. 43 of heat. If one is hotter than the rest, it gives faster than it receives, until the equilibrium is reached. And if, while they are thus coming to the same temperature, one is a good reflector, and therefore slow to receive the heat which comes to it, it is also slow to part with what it gets ; thus the difference of reflecting power is without influence. 85. COOLING OF THE EARTH. Were it slid** of the not f r the SU11 > tne heat f tne eart h wolll d cooling of the waste away very rapidly into space. It is, in fact, radiated into space now, as truly as if there were no sun or stars, but these make tip for the loss. At night, when the sun is below the horizon, the waste by radiation takes place very rapidly, and the earth and air grow colder in consequence. It is not simply because of the absence of the direct heat of the sun, for this is removed at once when the sun sets, while the cooling proceeds until morning. As the earth, being solid, is a better radiator than the air, it cools most rapidly, sending out its heat through the air into space. In this way the earth often becomes cooled from ten to twenty degrees lower than the air above it. 86. ICE IN THE TROPICS. Advantage How is ice pro- ... duccd in the is taken of the cooling which occurs by ra- trojncs? diation, to produce ice, in countries where the temperature of the air does not fall to the freezing point. Water contained in shallow vessels, placed in trenches dug in the ground, to protect it from currents of warm air, becomes covered with ice by a night's ex- 44 HEAT. posure. That the water is not frozen by evaporation, is evident from the fact that it does not freeze in windy nights, when evaporation is greatest. 87. THE FORMATION OF DEW. Dew formation of does not "fall." Its deposition is an- other consequence of the cooling of the earth by radiation. The air, however transparent, al- ways contains moisture, absorbed and invisible. Cold, causes the air, like every thing else, to contract, and presses out of it, as it were, the water which it con- tains. Now, when at night the earth has become cooled by radiation, the warmer air which comes in contact with it is cooled, and thus made to deposit its moisture in the form of dew. When the temperature is sufficiently low, the dew takes the form of frost. 88. WHY CLOUDS PREVENT DEW. Clouds prevent he send back the heat radiated from the earth, formation of -fry a new ra di a tion, and thus prevent the cooling which is essential to the produc- tion of dew. No dew is found therefore, on cloudy nights, ' when, if it came from above, like rain and snow, we should expect most. 89. ARTIFICIAL PREVENTION OF DEW How can the . formation of AND FROST. It is only necessary to sub- stitute for clouds the artificial canopy of a muslin handkerchief, or any other cover- ing, at a little distance from the earth, to prevent the deposition of dew and frost. Gardeners practised this method of protecting their tender plants from frost, long before philosophers explained it. RADIATION. 45 90. ABSENCE OF DEW ON POLISHED SUR- "Why is dew not ' deposited FACES. Dew does not form on polished surfaces because they are poor radiators, or, in other words, do not allow their heat to escap'e, and thereby produce the degree of cold which is required to form dew. Leaves and grass receive most dew, because they are the best radiators. 91. SUPPOSED RADIATION OF COLD. Why does the . thermometer li a piece oi ice be held before a ther- broucht "near mometer > ^ wn "l cause the mercury to sink. ice? It is not because cold has been radiated from the ice, but because the thermometer, in common with all other bodies, is constantly giving out heat, and when the ice is near, it does not get its due portion in return. The ice cuts off the heat that would have come to it from other objects behind it, and gives it but little in its place. 92. REFRACTION OF HEAT. Rays of How arc rays of heat re- heat from the sun and other objects, are refracted or bent out of their course, on passing from one medium to another, similarly to rays of light. By ordinary glass prisms most of the heat rays are refracted in a less degree. 93. HEAT RAYS AND CHEMICAL RAYS. The light which proceeds from the sun, is rays and che- accompanied by rays of heat and others mical rays ? . called chemical or actinic rays. In the analysis of light by a prism, the chemical rays accu- mulate principally in the region of the violet color of 46 HEAT. the spectrum, while the most of the heat rays are thrown into the region of the red, and below it. Nei- ther the place of the heat rays nor the chemical rays is visible to the eye, but a delicate thermometer proves that there is most heat just below the red, and a piece of paper covered with chloride of silver, (a substance very sensitive to the chemical rays of light,) grows black most rapidly in the region of the violet. The place of the chemical and heat rays is thus shown, al- though neither can be seen. It is not to be understood that they are confined to the points indicated, but only that they are accumulated there in largest proportion. 94. BURNING GLASSES. The collection action th of of ra Y s of heat from the sun b y ordinary burning glass- burning glasses, depends on the fact that they are refracted, or bent out of their course on passing from one medium to another, pre- cisely as in the case of light. A lens made of two watch-glasses, filled with water, answers for heat as well as light, and may be used as a burning glass. 95. DIFFERENT HEAT RAYS. There are ray* of heat different kinds of heat rays, as there are of light rays ; some will pass through one substance best, and some through another. Thus, a piece of smoked rock salt allows the blue heat ray of the spectrum to pass, while alum lets the lower or red heat ray pass. 96. ANALYSIS OF HEAT. The analysis How is the analysis of ot neat is enected. by the same means as keate/eeteJf are through a prism just as if light were to be analyzed, RADIATION. 47 but a dark colored glass is previously placed before the prism, to absorb the light and allow the heat only to pass. Emerging from the prism, it forms an invisible spectrum of rays beyond. These rays correspond to the different colored rays of light, and have different capacities of passing through different substances, as before stated. But, strictly speaking, they have no color ; they were called blue and red, simply to de- signate their relative position. Heat from very intense sources is mostly violet, and violet heat passes more readily than the other rays through most substances. This accounts for the fact that the heat of the sun is not stopped by glass, and many other substances which stop the heat of a fire. 97. EFFECT OF DIFFERENT HEAT RATS xrid of the IN MELTING SNOW. Snow melts compara- meiting of tively slowly in the heat of the sun, for snow? J J the reason mentioned in the last paragraph. Being from a highly heated source, it passes through the snow instead of stopping to melt it. But near a fallen tree melting proceeds more rapidly, because the heat absorbed as violet, is radiated again from the mod- erately heated source as red heat, which, falling on the snow in- its vicinity, is readily absorbed, instead of be- ing transmitted. 98. BURNING GLASS OF ICE. A lens How can gun- powder be iff- sufficiently powerful to ignite gunpowder may even be made of ice. In using any lens, it is first to be placed near the object to be ignited, and then withdrawn till the spot of light which it casts is round and very small. The focus to which 48 HEAT. all the rays of light converge is thus found. The heat focus is a little beyond, but so near that the difference need not be taken into account. Section 3. Changes effected by Heat. 99. EXPANSION, MELTING, AND VAPORIZA- TION are the principal changes effected by heat? heat, while contraction, freezing, and con- densation of vapor are produced by its withdrawal. But before these changes are explained, it will be well to consider certain remarkable differences in the heat- ing effects of heat, in the case of different substances. 100. THE HEATING EFFECT OF HEAT IS Are the effects DIFFERENT FOR DIFFERENT SUBSTANCES. of neat equal in different It might naturally be supposed that the same quantity of heat actually imparted to different substances would make them equally hot ; but this is not the case. If two cannon balls of the same size, and at the same temperature, are quenched, the one in mercury and the other in water, the mer- cury will be made much hotter than the water, by the reception of the same amount of heat. It does not simply feel hotter, as it might do if it were not really so, from the superior conducting power of the mercury, but it is actually so, as may be ascertained by testing the temperature by the thermometer. What is sped- 101- SPECIFIC HEAT. If the above ex- fic heat ? periment were varied, by quenching in mercury a bullet of one-thirtieth the size of that used SPECIFIC HEAT. 49 for the water, the two would be brought to the same temperature. In other words, mercury requires but one-thirtieth as much heating as water, to make it equally hot. It fills up, as it were, with heat, more rapidly. The comparative quantity required by each substance is called its specific heat. 102. Taking water as the standard, and callin g its specific heat one, that of mer- mercury? Of C ury is about one-thirtieth. That of iron is about one-tenth. The specific heat of other substances is given in decimals in a table con- tained in the appendix. What is capa- 103. CAPACITY FOR HEAT. - If We COm- dty for heat ? p are e q ua i {mlks of water and' mercury, instead of equal weights, AVC make out the specific heat of mercury to be one-half instead of one-thirtieth. The comparison is sometimes made in this way, but the term capacity for heat, instead of specific heat is always employed in such cases. Thus, we say that water has twice the capacity of mercury for heat. ,, . . .. 104. RELATION OF HEAT AND DENSITY. W liat relation exists between If water were suddenly converted into density and , , -i -i -i capacity for niercury, much heat would be given out, heat? as j s evident from what has already been stated. So when a metal is hammered, the capacity of the denser metal for heat being less, the surplus goes to make it sensibly hotter. In other words, in proportion as density is increased in any substance, its capacity for heat is diminished, and vice versa. It is not, however, to be understood that the comparative capacity for heat in different substances is always in 3 50 HEAT. proportion to their density ; this is by no means uni- versally the case. 105. THE OCEAN A RESERVOIR AND How does the ocean serve as REGULATOR OF HEAT. In hot Weather the a reservoir -L -L >i i c -\ if and regulator ocean absorbs the heat of the air. If it of heat? were an ocean of mercury, it would soon grow as hot as the air, and therefore cease absorbing but its capacity for heat is so much greater that this does not occur. Again, in cold weather, it is con- stantly giving out the large quantity it has absorbed, but at the same time itself grows cool, though very slowly. It is thus a reservoir of heat and a regulator of climate. 106. FIRE BY COMPRESSION. The fire principle of svr i n g e > represented in the figure, is an the Fire Sy- instrument designed to produce fire by the compression of air. On forcing the piston suddenly down, the tinder below it is ignited. This takes place on the principle already explained. The specific heat of compressed air is less than that of air uncompressed. When the com- pression takes place, the surplus elevates the tempera- ture and inflames the tinder. EXPANSION. 107. EXPANSION UNIVERSAL. All bodies, ha* at hea/ e on solid > liquid, and gaseous, expand by heat, dun"?* ^ b ~ and contract to tneir original dimensions on cooling. An iron wire lengthens by heat : the mercury in a thermometer expands and rises by EXPANSION. 51 heating ; air partially filling a bladder expands and fills it by the operation of the same cause. 108. HOW HEAT EXPANDS BODIES. - Heat How does heat operate to ex- operates to produce expansion, by insinua- pand bodies? tmg itsel f between the particles of Sllb- stances and increasing their distance from one another. The cooling process is simply a removal of heat, which allows the particles to assume their original dis- tances from one another, in obedience to the attraction of cohesion. 109. EXPANSION OF SOLIDS. The ex- Among solids, . . which expand pansion of solids by heat is comparatively the most? smalL Among S olids, the metals expand the most ; but an iron wire increases only ^^2 in length on being heated from zero up to 212. Ex- pansion in general bulk is about three times as great as in length. Thus, a cannon ball heated to 212 would occupy about zj-o niore space than when cooled down to zero. 110. ILLUSTRATION. The expansio-n of metals be U- "be lllustra- lustrated ? , ted by ar- ranging a brick, a knit- tirig-needle. and a shin- gle, as in the figure. On heating the needle with a spirit lamp, the shingle, if before carefully poised, will be overturned. What appli- 11L WHEEL-TIRES, RIVETS, ETC cation of this Important application of even this small expansion ts . . made in the degree of expansion is made in the arts. t | reg Q carr j a g e w heels, for example, 52 HEAT. are made originally too small for the frames they are to surround.. They are' then heated red hot and ap- plied in a state of expansion. The contraction which afterward takes place, on sudden cooling hy cold wa- ter, binds the wooden frame-work together with the greatest firmness. So in making steam-boilers, the rivets are fastened while hot, that they may by subse- quent contraction unite the plates more firmly. 112. HOT-WATER PIPES. In certain What disad- . . . ^ vantages arise uses to which iron is applied, the conse- ^ansion. 6 o/*~ ( l uences ^ expansion have to be carefully metals? guarded against. A cast-iron pipe for the conveyance of steam or hot water, must not be so laid that its ends touch two opposite walls, lest by its ex- pansion when heated, the walls should be overturned. 113. CLAMPS IN WALLS. If the two ends of a P iece of metal are fixed so that clamps in they cannot move, and contraction takes walls ? place by cold, the metal must break. Cast- iron clamps in walls are frequently thus broken. If they are of wrought iron, they often crush the stone, and thus loosen themselves in their sockets. 114. LIFTING WALLS. Walls of build- Mow are walls straightened ings in danger of falling, have been restored b ,, qucnces remit OF VERY COLD WATER. But lOI the 16- from the ex- mar k a bl e fact that more cold makes very pansion of wa- ter by cold ? cold water lighter, and not heavier, and thus enables it to exert the protecting influence just explained, the cold of a single winter would be suffi- cient to kill all the fishes inhabiting our lakes and rivers. Another consequence would be change of cli- mate, as a necessary result of the formation of im- mense masses of ice, which the heat of the summer would be insufficient to melt. The temperate regions of the earth would thus become uninhabitable. Such are the consequences which are obviated by this remarkable exception to a general law of expansion. The whole realm of nature furnishes no more remark- able evidence of design on the part of the CREATOR. 124. SOME LIQUIDS EXPAND MORE THAN In what pro- portion do spi- OTHERS. Some liquids expand more by T oil,ald water heat than others. Spirits of wine, on be- expand? j ng heated from 32 to 212, increases one- ninth in bulk ; oil expands about one-twelfth, and wa- ter, as has before been stated, one-twenty-third. It is much to the advantage of the dealer in spirits to buy in winter and sell in summer. Twenty gallons bought in January, will have become, by expansion, twenty-one in July. The difference between the cold- est and warmest weather of the year, is sufficient to make about this difference in bulk. How do gases 125 ' GASES EXPAND M R E THAN EITHER compare with SOLIDS OR LIQUIDS. Gases expand more solids and li- , . , quids in ex. tnan either solids or liquids by heat. The t reason is, that in gases there is no co- EXPANSION. 57 hesion to overcome, as in the two other states of matter. While iron increases in general bulk ^y^th. and water about ^Vd, on being heated from the freez- ing to the boiling point of the latter, air expands more than Jd by the same increase of temperature. 126. LAW OF EXPANSION FOR GASES. State the law of expansion Gases expand ^oth of the bulk which they for gases. possess at 32, for every degree above that point, and contract in the same proportion for every de- gree below it. Thus, 490 cubic inches at 32 would so expand as to occupy an inch more space at 3-3, still another inch at 34, and at the same rate for higher temperatures. And the same quantity would contract by cold, or withdrawal of heat, so as to oo cupy an inch less space at 31, and two inches less at 30, and so on for lower temperatures. The law is the same for steam and other vapors. What is a 127. THE THERMOMETER. The ther- thermometer ? niometer is an instrument in which ex- pansion is made use of to show changes of tem- perature. A straight wire, which would grow regu- larly and perceptibly longer in proportion to the increase of temperature, would form the most conve- nient thermometer. But solids do not expand enough, or with sufficient regularity, for this purpose. The liquid metal mercury, is therefore employed instead, being inclosed in a glass tube and bulb. 128. MANUFACTURE OF THERMOME- How are ther- mometcrsman- TERs. In making thermometers, the mercury being first introduced into the bulb, is boiled, so as to expel all air and moisture, 3* 58 HEAT. and fill the tube with its own vapor. As the metal cools, it contracts and collects in the "bulb and lower part of the tube, leaving a vacuum above. The end of the tube being then closed by fusion, the instrument is complete, with the exception of grad- uation. Used in this condition, the mercury would be observed to rise and fall with changes of tempe- perature, but we should not be able to say how much or how little. 129. GRADUATION OF THERMOMETERS. thermometers To obtain a fixed point from which to graduated/ count, the instrument is immersed in melt- ing ice, and the point to which the mercury sinks scratched on the glass. This point is called zero. Another fixed point is obtained by immersing the thermometer in boiling water, and when the mercury has risen, noting this height also on the glass, and marking it 100. The space be- tween the two points is next divided into one hundred equal parts, by scratches on the glass, and numbered from one up to a hundred. The upper and lower portions of the tube are marked off into divisions of the same length, for very high and low temperatures. CENTIGRADE THERMOMETER. Describe the Centigrade A thermometer graduated as above is called a centigrade thermometer, from th e fact that the space between < ' boiling ' ' and ^ " freezing" is divided into one hundred degrees. This is by far the most rational method of graduating, and these thermometers are in general use on the THE THERMOMETER. 59 continent of Europe, and by scientific men all over the world. 131. FAHRENHEIT THERMOMETER. This Describe the . Fahrenheit is the thermometer in common use in this thermometer. country . The i ristr ument itself is pre- cisely the same as the centigrade. The difference is only in the graduation. In graduating it, the space between the freezing and boiling points having been marked on the glass, is divided into one hundred and eighty parts, and the rest of the tube, above and below, into similar spaces. The zero, or starting point, is fixed lower down than in the centigrade, where nothing especial happens, instead of where water freezes. The consequence is, that in counting up and affixing the numbers? the freezing point comes at 32, and the boiling point at 212. There is no good rea- son for placing the zero there, or for qhoosing such a number as 180 for the number of de- grees between freezing and boiling. The centigrade graduation is, therefore, much to be preferred. If a thermometer of each kind were immersed in boiling water, the mercury would rise in the centigrade to the point marked 100, and in the Fahrenheit *^ ^^ to the point marked 212. In the same way,^ero cen- tigrade corresponds to 32 Fahrenheit. The two ther- mometers are compared in the figure. ff oio is extreme 132. EXTREME COLD, HOW MEASURED. coidmeasurcd? AS the temperature is lowered, the mer- cury of the Fahrenheit thermometer sinks, until by 60 HEAT. sufficient cold it reaches 39 degrees below zero. There, intense cold has no effect upon it, for at this point the mercury freezes. How much colder it is than 39 cannot be told, therefore, by the mercurial thermometer. Thermometers containing alcohol in- stead of mercury are used for this purpose, because al- cohol never freezes, and will continue to sink further and further in the tube the colder it grows. 133. EXTREME HEAT, HOW MEASURED. How is extreme heat meas- If a Fahrenheit thermometer is heated, the mercury in it rises, till it reaches 662, and then begins to boil. A little more heat forms suf- ficient vapor of mercury to burst the tube. For this reason, a mercurial thermometer cannot be used to measure extreme heat. A platinum bar inclosed in a black lead tube shut at the bottom, is common- ly employed for this purpose. Tube and bar are placed on the fire, or in the melted metal, whose heat it is desired to measure, one end being left out, so that it can be seen. The consequence is that the platinum bar expands, and projects from the earthen tube. The tube itself expands but little. The further the bar projects, the greater is the heat. As it pushes out, it is made to move an index hand, and point to the number indicating the tempera- ture, on a graduated arc. This arc is first graduated by repeated trials, observing how much the bar projects and moves the hand by the same heat which raises the mercury one degree in the Fahrenheit thermometer. n ., ., 134. THE AIR THERMOMETER. A col- Describe the , air thermome.- umn of air confined in a glass tube over ***' colored water, was the first thermometer LIQUEFACTION. 61 used. Heat expands the air and lengthens the column downward, pushing the water before it, while cold has the contrary effect. The temperature is thus indicated by the height at which the water stands. 135. ILLUSTRATION. The principle of ^incTll *o/ the air thermometer may be illustrated as the air ther- represented in the figure. A mometer. ^ , . , ,,, -. , , test-tube is half filled, and then inverted in a glass of water without allowing the water which it contains to flow out. Heat applied to the tube will lengthen the column of air by expansion. LIQUEFACTION. 136. SOLIDS BECOME LIQUIDS BY HEAT. flow do sohds become li- m On being heated up to a certain point, solids quids? are jilted, or converted into liquids. Thus, at all temperatures below 32, water is solid ice, but the moment it is warmed up to this point, by change of weather or other means, it begins to melt. The temperature at which this change occurs is called the melting point. 32 is therefore the melt- ing point of ice. The melting point of sulphur is 226, and of lead, 612. 137. ALL SUBSTANCES ARE FUSIBLE. Are all sub- stances fusi- All substances are fusible, or, in other words, may be melted ; but the melting point of all is not definitely known. Thus carbon has been fused by the heat of the galvanic battery, but it is impossible to state the melting point in degrees. 62 HEAT. Under great pressure, increased heat is required to ef- fect fusion. Thus the melting point of sulphur is raised from 226 to 285, by a pressure of 11,880 Ibs. to the square inch. nrj . 138. DISAPPEARANCE OF HEAT IN MELT- Wtiat remark- able drcum- TNG . Melting or fusing is effected by heat, stance attends the melting of and a remarkable circumstance attending it, is the disappearance of the heat which has effected the change. Thus, if a thermometer be applied to ice or snow which has just begun to melt, it will be found to stand at 32. Let the ice be then introduced into a tumbler, and placed on a stove, and the temperature again tested at the moment when the conversion into water is completed. The thermometer will be found again to stand at 32. The water produced is no hotter than the original ice, yet heat has been pour- ing into it, through the bottom of the ves- sel,during the whole process of melting. If a piece of glass of the same size had been subjected to the same heat, it would have grown constantly hotter. It fol- lows that in the case of the ice there has been a disappearance of heat. This disappearance always occurs whenever a solid is converted into a liquid. What other ^9. ANALOGOUS DISAPPEARANCE OF { appTarance ACIDITY - Chemistry furnishes other in- does chemistry stances of disappearance, which may help us in understanding this one. If vinegar be poured upon chalk it loses its sourness. It is be- cause a combination has taken place between the acid FREEZING POINT. 63 vinegar and the lime which the chalk contains, and a new substance, called a salt, has been formed out of both. So in the present case, we may suppose that heat and the solid have combined to form a liquid, and the property of heat to effect the senses and the ther- mometer, has at the same time disappeared. Any liquid may therefore be regarded as a compound of solid and heat. The heat which thus disappears is called com- bined, or latent heat. Mention some 140. FREEZING MIXTURES. - When Solids feezing mix- ta k e a liquid f orm by other means, as. for tures. How do ** ;. they produce example, when salt dissolves in water, the temperature is generally much reduced. Nitre, for example, reduces the temperature of water in which it is dissolved from 15 to 18 degrees, and is there- fore much used in the East, where it is abundant, for cooling wines. Mixed nitre and sal-ammoniac have a still greater effect. Sulphate of soda drenched with strong muriatic acid, will reduce the temperature from 50 to zero. 141. When two solids, on being mixed, Mention other . . freezing mix- become both liquid, still greater cold is often roduced - Tnis is the case witn a duce greater mixture of snow with common salt, or with chloride of calcium. By the former mix- ture, used as shown in paragraph 121, ice cream is frozen. By the latter mixture, a cold sufficient to freeze mercury may readily be produced. For this purpose, three parts of the salt are to be mixed with two of dry snow. 64 HEAT. 142. THE MELTING OF SNOW COOLS THE How docs the Whenever ice is converted into wa- inelting of snoiv affect the ter, whether rapidly by fire or slowly by change of weather, the disappearance of heat, above mentioned, occurs. Thus, when the snow melts in spring, heat is drawn off from the air and made latent, or combined in the water which re- sults from the melting. This makes the weather cooler than it would otherwise be, and retards in a measure the advance of spring. How do liquids 143. FREEZING. Liquids become solids become solids? ^y t } ie rem oval of their combined heat. Thus, if molten lead be allowed to stand awhile, the heat which it contains passes away into other objects, warming them ; and the metal itself, having lost its heat, becomes solid. So in winter, the combined heat which is contained in water, is conveyed away by the colder air, and the water, having lost its heat, is con- verted into ice. 144. FREEZING POINT. The tempera- What is the L freezing point ture at which a substance passes from the of a liquid? liquid into the golid gtate ig called the freezing point. Thus, 32 is the freezing point of wa- ter. The freezing point of any substance is, as might be supposed, the same as the melting point. Water, for example, becomes ice in process of cooling, at the same temperature that ice becomes water in process of heating. 145. ALL LIQUIDS HAVE THEIR FREEZ- Can .all liquids be frozen? ING POINTS. There is good reason to be- Give examples. ^ Q ^ ^ ^.^ without exception> L AT E NT U R AT. 65 have their freezing points, but the reduction of tem- perature requisite has not in the case of all been at- tained. Alcohol and ether, for example, have never been frozen. 146. IN FREEZING, LATENT HEAT BE- what fr becomes COMES SENSIBLE HEAT. If Water, in Sllffi- of the latent cient quantity, be taken into an apartment whose temperature is several degrees be- low the freezing point, and then allowed to become ice, it will be found that the freezing process has ac- tually warmed the apartment several degrees. The latent heat has been drawn off by the colder air of the room, raising its own temperature, and leaving the water in the condition of ice. 147. CELLARS WARMED BY ICE. In ac- How can cel- lars be warmed cordance with the principle above stated, tubs of water are sometimes set to freeze in cellars, thereby to prevent excessive cold. And even in the coldest climates a sufficient supply of wa- ter might thus be made to secure an apartment against extreme cold. 148. EFFECT ON CLIMATE. The milder ha% a fhe free*- climate of the vicinity of lakes which are ing of water accustomed to freeze in winter, and the on climate ? ~ . , . moderation of the weather during a snow storm, are accounted for on the same principle. As the melting of snow retards in a certain degree the ad- vance of spring by the heat it abstracts from the at- mosphere, so the formation of ice tends to make the advance of winter less rapid, by the heat which it evolves. 66 HEAT. CHAPTER VII. VAPORIZATION. 149. FORMATION OF VAPORS. While Do vapors . . form at all melting, or the conversion of a solid into temperatures? a liquid) occurs on ly w hen the solid is heated up to a certain fixed point, the conversion of a liquid into a vapor takes place at all temperatures. Thus water is always passing off into vapor from the surface of the ocean, and from the moist earth. 150. VAPORS TRANSPARENT. All vapors What is the appearance of are perfectly transparent, like the atmo- sphere. If water be boiled in a flask, it will be found that the steam within the flask is as transparent as air. The steam thrown from a locomo- tive would be invisible if it remained steam We should hear its roar, but see nothing. 151. DENSITY OF VAPORS. Vapors are / the density of vapors uni- of all degrees of density. The vapor of water may be as thin as air, or, again, al- most as dense as water itself. 152. ELASTICITY OF VAPORS. All va- lllustrate the elasticity of pors are elastic, like air. Steam, like air, vapors. ft compressed in a cylinder, with a close fitting piston, by a heavy weight, would expand again, and force the piston out, as soon as the weight were removed. The force with which a vapor expands, or strives to expand supposing the weight not removed, is called its elastic force or tension. VAPOR. 67 153. DENSITY DEPENDS ON TEMPERA- How does tern- perature a/ect TURE. If water is boiled in a flask, the density? latter Decomes filled with steam> But? although full, more steam can be crowded into the same space. On corking the flask and continuing the heat, the temperature of the water will be raised. Then, forced as it were, by the additional heat, its par- ticles have the power of crowding into the steam be- fore produced, and making it more dense. But after a time, no more can be forced in until the temperature is still further increased. In other words, there is a maximum density corresponding to every temperature. And what is here said of steam, is true of vapor of water produced at lower temperature, and also of other vapors. The higher the temperature, the greater is the density of all vapors, provided a surplus of material is present. But if this is not the case, heat has simply the effect of expanding the vapor as it would an equal quantity of air. In the case of a partial supply of water, the vapor grows more dense, but does not reach the highest density which it would have at the same temperature with a full supply. TI , , 154. DISAPPEARANCE OF HEAT IN VA- What remark- able drcum- TORS. The same disappearance of heat stance attends , . . 1-1- j the formation which occurs when a solid is converted oj- vapors? ^ Q a jjquj^ occurs also when a liquid is converted into a vapor or gas. Thus, if we wish to cool a room in summer, we sprinkle the floor. As the water evaporates, much of the heat of the room dis- appears. It has entered into combination with water to produce vapor, and has no longer the power of af- 68 HEAT. fecting the senses and the thermometer. In the same manner, our bodies are cooled in summer by perspira- tion, and the evaporation which accompanies it. All vapors may, indeed, be regarded as combinations of heat with the liquids from which they are formed. And in this case, also, the heat which becomes latent in thus combining, is called latent heat. 155. FREEZING BY EVAPORATION. The How can ether be made to more rapidly a substance evaporates, the ^Explain* ^its niore heat does it require for the evapora- action. tioii. This it obtains from objects in con- tact with it. Ether may be made to evaporate so rapidly as to freeze water, even in summer. This is best accomplished by covering the bottom of a test- tube with a cotton rag, or several layers of porous f p paper, as represented in the figure, dipping it into ether, and then waving it to and fro in the air, or spinning it between the palms of the hands. By repeating this process several times, a few drops of water, previously placed in the tube, may be frozen. A mixture of liquefied carbonic acid and nitrous oxide gases, previously liquefied, produce on evaporation a temperature of 220 degrees below zero. 156. PROTECTION FROM HEAT BY EVA- How does eva- poration pro- PORATION. By previously moistening the tect from heat? fingerS; they m&y bu dipped unharmedj f or an instant, into molten lead, or passed through a stream of white-hot iron as it flows from the furnace. A cloak of comparatively cool vapor is formed from the moisture upon the fingers, and keeps them from con- tact with the molten metal. VAPOR. 69 pp> 157. RELATIONS OF AIR AND VAPOR. Does vapor rp^ Q earth is surrounded by air to the displace air ? depth of fifty miles. It is also surrounded by vapor occupying the same space which the air oc- cupies. But they are independent of each other. Each contracts for itself, and expands for itself, accord- ing to the temperature. When more vapor is produced by evaporation from the sea, or other sources, it rises into the air without displacing it or pushing it aside, only rendering the vapor which it before contained more dense. 158. QUANTITY OF VAPOR IN THE AT- ^ vapor M S P HERE - The air is always full of va- in the por ; that is, where there is a cubic inch of air, there is a cubic inch of vapor with it, occupying the same space. Upon what 159 ' QUANTITY OF WATER THE AIR MAY does the quan- CONTAIN AS VAPOR. The quantity of wa- tity of water . , * . . in the air de- ter present in the air, in the form of trans- P end? parent vapor, depends on the density of the vapor, and this differs, as has been shown, according to heat and the abundance of water. In summer, and over the sea, it is commonly most dense. At a me- dium summer temperature of 75 degrees, the vapor in the air is sometimes so dense that every cubic yard of air contains a cubic inch of water, in this form. But it can never at this temperature contain more. It is then said to be " saturated," and also that its capacity for water is filled. 70 HEAT. CAPACITY OF THE AIR FOR WA- What effect has heat upon TER INCREASED BY HEAT. - But, as the the quantity of vapor present weather grows warmer, the capacity of the air for moisture is increased, so that at 100, it can contain twice as much as at 75, or two cubic inches. On the other hand, as the weather grows cooler, its capacity is diminished, so that at 50 it can hold scarcely more than half a cubic inch, and is saturated by this comparatively small quantity. And, in general, the capacity of the air for moisture is in- creased by the elevation of its temperature. 161. EFFECT OF WIND. Wind causes evaporation to proceed more rapidly, not tity of vapor because the air in motion has any greater in the air ? r . , . capacity for moisture, but because new portions of air are brought successively into contact with the wet surface. As fast as one portion has im- bibed a certain amount of moisture, another portion of drier and more thirsty air takes its place. 162. DEPOSITION OF MOISTURE. It fol- Explain the deposition of lows that air that is saturated, or, in other words, has its full portion of moisture in the form of vapor, must deposit a portion of it in the form of water in cooling. Thus a cubic yard of sat- urated air at 75, on being cooled down to 50, would yield half a cubic inch of water, or half of the whole quantity which it originally contained. If we sup- pose the experiment to be performed in a glass vessel where the eifect of cooling could be observed, we should first see a mist or dew within the box, consist- ing of the particles of water which the colder air can VAPOR. 71 no longer retain. This mist would gradually deposit and collect in the form of water, and if measured, would be found to make more than half a cubic inch. Something less than half a cubic inch would remain as invisible vapor in the cooled air. If the air were cooled further, part of this would be condensed to water. What is 163. UNSATURATED AIR. Air that does said of unsat- not con tain its complement of water will urated air and its moisture ? not yield any by slight cooling. It would be like slightly compressing a half-filled sponge. But as the cooling proceeds, the vapor becomes so dense that further cooling will cause a deposition of moisture. A cubic yard of air at 75, containing only half a cubic inch of water in the form of vapor, would yield none on being cooled down to 50. At this point the formation would commence. If it contained originally less than half a cubic inch, it would have to be cooled still lower before any moisture made its appearance. The less the moisture, in short, the more cold it would require to wring it out. Is the quantity 164. QUANTITY OF VAPOR IN THE AT- MOSPHERE As has been already stated, ways propor- the capacity of air for vapor is in propor- tioned to its . m , r . - warmth? tion to its warmth. The air of summer can therefore contain more than that of winter ; and it frequently does so. But this is not necessarily the case, for the capacity for moisture is not always filled. Hot air over a desert, for example, contains less mois- ture than cold air over the sea. And in the same lo- cality, and during the same season, the quantity of 72 HEAT. moisture in the air will differ from day to day, and from hour to hour. This will depend a good deal on the wind, whether it blows from the land or from the sea. Sometimes it contains a cubic inch of water in the form of vapor in every square yard, but generally less. 165. MIST AND FOG. These are What is the 1 . cause of mists aqueous vapor, rendered visible by the and fogs? cooling of the air, as before explained. When the air is saturated, the least cooling will pro- duce a fog, as in the case supposed in paragraph 129. When it is not saturated, more cooling will be required, as in the case supposed in the subsequent paragraph. The beautiful veil of mist, which forms in summer nights over low places, is owing to the cooling of the air below its point of saturation, which takes place after sunset. 166. MIXED CURRENTS OF AIR. The *" p henomena of mist > f g' clouds > and con - fogs by mixed sequently of rain, are more commonly currents of air . . . ., , , , owing to the mixture of cold and warm winds or currents of air. When this admixture takes place, the warm air becomes colder, and tends to de- posit its moisture, and the cold air warmer ; and it might be at first supposed that those two influences would counteract each other. For example, if a cubic yard of air at 100 mixes with a cubic yard at 50, they both become 75, and it might be thought, that the warming of the colder cubic yard would increase its capacity for moisture, as much as the cooling of the warmer cubic yard would diminish its capacity, and FOG. 73 that consequently no mist would be produced. But, as before stated, it has been ascertained by experiment that hot air at 100 will contain about two cubic inches, and air at 50, about half a cubic inch of water. The two would therefore contain two and a half cubic inches. But air at 75 can hold but one cubic inch, and consequently the two cubic yards would hold but two cubic inches. The surplus half inch would con- sequently take the form of visible moisture, called cloud, fog, or mist, according to circumstances. It is not to be understood, from what is above stated, that half a cubic inch of water is always yielded by every two cubic yards of air at 50 and 100 which come to- gether ; if they are not totally saturated, the quantity will be less. 167. FOGS ON THE SEA COAST. The Why are fogs produced on sea is cooler than the land in summer, and the sea coast? warmer m w i n t e r. As a consequence, the air above the sea is cooler in summer and warmer in winter, than that above the land. The admixture of these bodies of air, which takes place along the coast, produces fogs on the principle above stated. 168. FOGS ON RTVERS. When land and Why do fogs form on riv- water have the same temperature, as may be the case with small lakes and rivers, the difference of radiation during a single night often produces fogs. The land cools more rapidly than the water. As a consequence, the air above the land is cooler than that above the water. As the two bodies of air mingle, fog is produced, and is seen following 4 74 HEAT. the devious course of the river, or brooding over the lake in the morning. 169. NEWFOUNDLAND FOGS. The fogs What causes __ ,, , the Newfound- on the banks of Newfoundland are owing land fogs? ^ Q ^ mixture of cold winds from the north, with the warm air of the gulf stream, which passes along that part of the ocean. 170. CLOUD-CAPPED MOUNTAINS. The 402? ro- temperature of the air at high elevations duced on high is always lower than at the general level mountains? of the earth. As the warm breeze comes up from the warmer valleys, the two currents min- gling, produce clouds. A clear atmosphere through- out a whole day is rare, on high mountains. 171. DEW POINT. It has been already What is the geen ^^ a j r ^as to be cooled more or less dew point ? before it yields moisture, according to the amount which it contains. If it contains about one cubic inch to the cubic yard, or, in other words, is satu- rated, the least cooling will cause the appearance of visible moisture. If it contains half as much, it must be cooled down to 50 P. If it contains less than half as much, still more refrigeration is required. The temperature at which the deposition be- gins in any case is called the dew point. 172. HOW TO FIND THE How can the dew point be DEW POINT. - It is Common- ly found by adding ice, lit- tle by little, to a glass of water con- taining a thermometer. As the water grows cool, the glass cools also, and as a DEW. 75 consequence, the exterior air immediately in contact with it. After a time, moisture begins to deposit. The temperature at which this occurs is noted, and is the dew point. 173. DEW. The earth cools, as has Explain the . formation of been before stated, every clear night, by radiation. The air in immediate contact with it, becomes thereby so much cooler, that it cannot retain all its water in the form of invisible vapor, and the deposition of the surplus in the form of dew is the consequence. 174. Grass and foliage receive most dew because they are good radiators, and losing the most their own heat most rapidly, cool down the air sufficiently to cause a deposition of its moisture. The soil itself, and stones, receive less, or none at all, because they do not, by their own ra- diation, become sufficiently cool to produce the same effect. Dew does not form on a cloudy night, because the clouds radiate heat to the earth and thus prevent the requisite cooling. 175. CAPACITY FOR VAPOR : EXPANSION How is it -r. . -, -i known thatthe NOT THE CA USE. It must not be Supposed increased ca- that the increased capacity of air for va- pacity of air . for moisture por, which results from heating, is owing * to its ex P a nsion. Air does indeed expand about one-twentieth between 50 and 100, but its capacity for moisture is quadrupled by the same rise of temperature. 76 HEAT. 176. ABSORPTION NOT THE CAUSE. It MM* allorp- is not uncommonly supposed that the air tion is not, the acts to absorb vapor as a sponge does to draw up water. The term " saturated" used for convenience in scientific works is calculated to give this impression. But vapor rises just as well, and even more rapidly, into a vacuum, or space from which all the air has been removed. WJiat then is 177. INCREASED DENSITY OF VAPOR THE the cause? CAUSE. The air absorbs any vapor that may be formed, whether more or less dense. At higher temperatures, denser vapor is produced. It follows that the air will contain more water, in proportion to the elevation of its temperature. 178. REMOVAL OF AIR DOES NOT IN- Does the remo- . val of air in- CREASE THE QUANTITY. It might be SUD- "formation *o/ P ose( ^ tnat more water would rise into a vapor ? vacuum in the form of vapor, than into a space filled with air, on the ground that the removal of the air would make more room for something else. But this is not the fact. The presence or absence of air makes no difference. 179. SEVERAL GASES AND VAPORS MAY Do vapors and _ ., 1 , ,, gases exclude OCCUPY THE SAME SPACE. It follows from each other ? the lagt p ara g rap h t h at vap ors do not dis- place the air ; they penetrate it instead. And it is a remarkable fact, that a number of vapors may occupy the same space without interfering with one another ; and each in the same quantity as if the rest were ab- sent. VAPOR. 77 Give the exam- 180. Thus, as much water will rise in P les - vapor into a jar of air as if it were a va- cuum. And, in addition to this, as much alcohol and ether successively, as if the jar were entirely empty. The tension or pressure from within, outward, is, of course, increased by each additional vapor. 181. MOIST AIR LIGHTER THAN DRY. Why is moist air lighter It would naturally be supposed that air than dry air ? conta j n j n g moisture, would be heavier than air containing none. And it would be so, but for the fact that the presence of vapor causes the air to ex- pand slightly, and grow lighter, and this to an extent more than sufficient to compensate for the increase of weight. BOILING. 182. WEIGHT OF THE ATMOSPHERE. lt As an introduction to the subject of boil- atmosphere ing^ jt will be necessary to consider the has weight ? - pressure of the atmosphere. The earth is surrounded by an atmosphere, estimated to be fifty miles high. It is very light compared with the earth itself, or with water. But it has weight, as may be proved by weighing a bottle full of air, and then pumping out the air and weighing it again. The empty bottle will be found to weigh less than the bottle full of air. 183. ANOTHER PROOF OF THE WEIGHT Give another proof that air OF THE AIR. That the air has weight, is has weight. a g a i n proved by tying a piece of bladder 78 HEAT. over a glass cylinder, open at both ends, placing the open end air-tight on the plate of an air pump, and then exhausting the air. The pressure of the column of air that stands on the bladder is sufficient to break it, and the air settles in, as effectually as if it were a col- umn of iron. The atmosphere exerts such pressure, amounting to about fifteen pounds to every square inch, on all parts of the surface of the earth. 184. A SIMPLE MEANS OF PROOF. - Describe a simple means Wind a stick with cotton and press thatair l * has it; to the bottom of a test-tube, con- wight. taining enough water thoroughly to moisten it. It will be found difficult to withdraw the piston. The difficulty arises from the fact that the column of air which rests upon it, must be lifted at the same time. Having raised it a little way and released it, the piston flies with force to the bot- tom, owing to the weight of the same column of air. 185. ELASTIC FORCE OF THE ATMOSPHERE. Every cubic inch of air at the surface of its elastic the earth, may be likened to a piece of in- dia-rubber, which has been compressed into the space of a cubic inch, by a heavy weight placed on it. If we suppose a piece of rubber, while thus com- pressed, to be confined in a strong metallic box, it would evidently exert an elastic force in all directions, equal to the force which compressed it. So the lower por- tions of air, which are kept compressed by the air above, exert elastic force. And it is better to regard the pressure of fifteen pounds on every square inch of PRESSURE OF THE ATMOSPHERE. 79 the surface of the earth, as a consequence of the elastic force of the lower portions of air, rather than the direct effect of the weight of the whole air. The weight of the whole atmosphere produces the elastic force of the lower portions by compressing them, and the elastic force of the lower portions exerts the pressure. Why are we 186. WHY THE PRESSURE OF THE AIR notcrushedby DOES NOT CRUSH US. If a thin glaSS V6S- the pressure of '- . -, -, -, . , the atmo- sel were turned upside down, and air-tight, sphere? upon a table, it would collapse but for the fact that it is filled with air, which, according to the last paragraph, has elastic force equal to that of the air without. So our bodies would collapse, but for the fact that our lungs, and all of the cavities of the body, are filled with air, possessing the same elastic force as the external air ; a force which it had acquired by compres- sion, before it was taken into our bodies. 187. QUANTITY OF WATER THE PRES- What sustains the water in SURE OF THE AIR WILL SUSTAIN. If a ^uM^rfre- tumD ^ er be filled under water, and then sentcd in the lifted OUt bottom Up- figure ? 1 ward, as shown in the figure, it is well known that the wa- ter will not run out. The pressure of the atmosphere on the surface of the water outside, keeps the water forced up on the in- side. 188. The effect would be the same if What quanti- , tu of water the tumbler were twice as tall, or if we * i *^ . i suppose it lengthened into a tube thirty- three feet long. If a still longer tube 80 HEAT. were used, it would be found that the level of the water inside, would never be more than thirty- three feet above the level outside. The remainder of the tube wonld be empty, as re- presented in the figure. In other words, the pressure of the atmosphere will sustain a col- umn of water thirty-three feet high. Water rises in a pump from this cause. 189. QUANTITY OF MERCURY THE incheTofnier- PRESSURE OF THE AIR CAN SUSTAIN. cury will the i n performing the experiment of air sustain? the last paragraph with mercury, it will be found that the level within the tube, will be thirty inches above the external level. In other words, the pressure of the atmosphere will sustain a column of mercury thirty inches high. 190. If a long tube is used, there is, of Explain the __ . . Toricdlian course, an empty space above. This is vacuum. ca ii e d the Toricellian vacuum, from the fact that a vacuum was first produced in this manner by an Italian philosopher, named Toricelli. It is not an absolute vacuum, a small portion of mercury being al- ways present in the space in the form of transparent vapor. 191. BOILING. Thus far we have con- Whatismeant ,-,,,,,, . /, f by the term sidered solely the formation of vapors from boiling? the surfaces of liquids< But where any liquid is heated up to a certain point, vapor forms in bubbles below its surface. The production of vapor with ebullition is called boiling. BOILING. 81 192. Water begins to boil when it is What is the boiling point heated up to 212 ; alcohol, at 173 ; and Of W ethcr ' ? ether, at 96. As the proper temperature is Of alcohol ? fi rst reached at the bottom of the vessel, near the fire, the formation of bubbles begins there ; and as the surplus heat comes in below, they continue to be formed at this point. Every liquid has its own boil- ing point. How much 193. EXPAN- stcam do cubic SION m BOIL ING. inches of wa- ter, alcohol, A cubic inch of and ether re- , ., -, . spcctiveiy pro- water boiled in dnce? an O p en vessel, produces 1696 cubic inches of steam. A drop one-tenth of an inch in diameter, would make enough to fill a vessel of the diameter of one and a fifth inches. A cubic inch of alcohol produces about 500 cubic inches of alcohol vapor ; one of ether about 250. The ether vapor is most dense, that of alcohol next, and the steam least so. 194. DISAPPEARANCE OF HEAT IN BOILING. If a thermometer be held in boiling water, it indicates a temperature of 212 F. Continue the fire, and although heat constantly passes up into the water through the bottom of the vessel, it grows no hot- ter. The steam which is produced has 4* What is said of the disap- pearance of heat in boiling? 82 HEAT. also precisely the same temperature. Neither water or steam are hotter, although both have been con- stantly taking in heat. But the heat has not been without effect, any more than in the conversion of a solid into a liquid. It has combined with the liquid to form the steam. In this case, also, the heat which disappears is called latent heat. 195. RELATION OF PRESSURE TO BOIL- Howdoespres- ING. In order that a bubble of steam may sure oppose f . . boiling ? form, it is necessary that a small portion of water, shall expand into a comparatively large portion of steam to form it. But the atmosphere is constantly pressing on the surface of the water, and acting through the water, in all parts of the vessel, to prevent any separation of particles or expansion. The case is similar to that of a piece of india-rubber com- pressed beneath a mass of iron : it cannot expand ow- ing to the weight of the iron. 196. HEAT OVERCOMES PRESSURE. But Explain how heat overcomes if we could by some means increase the pressure. elasticity of the india-rubber, it would ex- pand and lift the iron. So, if we can in any way in- crease the tendency of the particles of water to sepa- rate, it will finally be strong enough to overcome the pressure of the atmosphere above arid affect separation. Heat has this effect. As the water becomes hotter, the tendency of its particles to fly apart becomes greater and greater, till, at last, it is sufficient to over- come the pressure which has before crowded them to- gether, and a bubble of steam is formed. Others im- mediately follow, and boiling thus commences. This BOILING. 83 takes place at 212 Fahrenheit, which is therefore called the boiling point of water. 197. EFFECT OF HEIGHT ON BOILING. What effect . ... has height on At great elevations, the atmosphere is, m boiling? factj lighterj and there is i ess o f j t above us, and the consequence is that water boils on moun- tains, at a lower temperature than in the valleys below. It is found, by careful observation, that an elevation of five hundred and fifty feet above the level of the sea, makes the difference of one degree in the boiling point. 198. MEASUREMENT OF ALTITUDES. the This fact once established, a tea-kettle and mountains be a thermometer are the only requisites for determined? . . . . r . mi taking the height of a mountain. The summit being reached, the tea-kettle is boiled, and the heat of the water tested by the thermometer. If the mercury stands at 211, it is known that the height is 550 feet ; if at 210, the height is 1100 feet ; and at whatever point it stands, it is only necessary to multiply 550 by the number of degrees depression of the mercury below 212, to ascertain the elevation. On the top of Mont Blanc, water was observed by Saus- sure to boil at 184. This gives us the means of calcu- lating very closely the height of that mountain. 199. EFFECT OF DEPTH ON BOILING. What effect kas depth on In mines the atmosphere is heavier, and oihng? there is, beside, more of it above us, than at the surface of the earth. Water must, in consequence, be more highly heated before it will boil. 550 feet makes, as before, a difference of one degree. We are thus provided with a simple means of determining the 84 HEAT. depth of mines. Owing to various causes, the atmo- sphere at the same elevation is a little heavier some days than others, so that the height of a mountain or the depth of a mine, as thus measured, would not be always precisely correct. 200. ARTIFICIAL CHANGE OF BOILING POINT - I* is obvious, from what has already of liquids be been stated, that all it is necessary to do to changed? , ... change the boiling point, is to change the pressure of the atmosphere, on the surface of the water to be boiled. To produce this change of pressure, it is not necessary to ascend mountains, or to descend into mines ; it may be done by removing the atmosphere by artificial means. This would be done by attaching a tube, air-tight, to the mouth of a test-tube or flask and drawing off the air by means of an J^ air pump. Cold water may thus be caused to boil. So by pumping more air into the flask, the pressure would be increased, and the boiling point elevated ; and by this means boiling water would be prevented from further boiling. This subject is further considered in paragraph 204. 201. CULINARY PARADOX. Boil some wa- Descnbe the , . . culinary par- ter m a test-tube, and then cork it tightly, while steam is still issuing from its mouth. Though removed from the fire, the wa- ter will still continue to boil. This will behest observed by inverting the tube, as the bubbles of steam form more rapidly from the cork surface than from the glass. A few drops of cold water sprinkled on the tube will occasion a more violent STEAM. 85 ebullition ; while on the other hand, boiling water, or the application of flame, will cause the boiling to cease. 202. EXPLANATION. The principle is e^ tne same as m tne experiment of the last the culinary paragraph. As the steam condenses, by paradox. r . . . J the cooling influence of the air, a partial vacuum is produced, and a diminished pressure, which enables the water to boil with less heat. Cold water, by condensing the steam and removing the pressure more perfectly, increases the ebullition, while boiling water or flame renews the steam, and consequent pres- sure, and therefore checks boiling. 203. WATER HAMMER. The test-tube " Water Ham- prepared as above, is a simple form of the " water hammer." If very thoroughly cooled, and then sjiaken with the kind of motion which would be required to make a bullet rise half way in the tube and fall again, the water will strike like lead on the bottom. It is because there is no air and but little vapor present to break its fall. 204. SUGAR BOILING. When syrup Now may sy- .,.,,, , ,. rup be boiled is boiled down under the ordinary pres- z. gure Q f tne atmosphere, it is apt to be browned or injured in flavor. By boiling it in a pan with an air-tight lid, and pumping off the air, and the vapor as fast as formed, boiling may be easily effected at a temperature as low as 150. This method is put in practice by sugar boilers, and the disadvantages above mentioned are thus avoided. 86 HEAT. 205. In cooking, this method could Can food be cooked by the not be employed. The water might, in- same method ? ^^ be made tQ boil ftt lgOOj bm the boi l ing water, owing to its less heat, would not have the effect of water boiling at 212. Many vegetable juices and infusions which are used for medicines, and would be injured by a high temperature, are boiled down, like sugar syrup, under diminished pressure. 206. SlNQING OF THE TEA-KETTLE. ringing of the The singing sound which precedes boiling , tea-kettle. ^ owing to the collapse of the first bubbles of steam, as they rise into the colder water above. The very first bubbles that form are not steam, but air which the heat expels. Steam bubbles are then formed, which rise a little way, and, being reconverted into water, contract, and finally collapse. If the heat is continued and the water made hotter, the next are able to rise further. Finally, when the water becomes as hot as the bubbles, they make their way through, and boiling is thus commenced. What is a 207. STEAM BOILERS. The boiler is the steam boiler? vessel in which steam is formed. From the boiler it passes to other parts of the apparatus to move the machinery. Steam boilers are of various forms, but are always made of great strength, to resist the internal pressure to which they are subjected. Explain the 208. The figure repre- sents an or( ji nar y ste am boiler, with STEAM. 87 the pipe which conveys the steam to the engine. A safety-valve is also represented, which will be more fully explained in another paragraph. 209. ELASTIC FORCE OF STEAM. Under How great is . the elastic ordinary circumstances, the elastic force of force of steam? steam is obviously equal to the elastic force or pressure of the atmosphere. A man who rises from a chair with a fifty-six pound weight on his shoulder, must exert an extra muscular force, equivalent to fifty- six pounds, in rising ; and he must continue to exert it while he stands. So every bubble of steam must have an elastic force equal to that of the air which it lifts, or it cannot be formed under the pressure of the atmo- sphere, or continue to exist when once formed. 210. ELASTIC FORCE, HOW INCREASED. As lon S as the vessel > in which steam is steam 'incrcas- made, is open, the pressure is as stated in the last paragraph. But if the boiler be closed steam-tight, and the heat continued, more steam forms, and, crowding into the same space above the water increases the pressure. In other words, the space becomes filled with denser steam, of greater elastic force ; and the force is finally sufficient to burst the boiler, unless it can find some vent. 211. INCREASED TEMPERATURE ACCOM- panies in PONIES INCREASED PRESSURE. - Steam of creased pres- high elastic force can only be made in a sure of steam ? close vessel. But in proportion to the increase of elastic force, is the increase of pressure on the surface of the water. Therefore, the boiling point becomes higher and higher, or, in other words, the wa- 88 HEAT. ter has to grow constantly hotter, in order that steam may form ; and as steam always has the temperature of the water with which it is in contact, the steam grows constantly hotter also. 212. THE EXACT RELATION OF TEMPE- How can the exact relations RATURE TO PRESSURE. It is desirable to iLr^STpre*- know tne increase of pressure for each ele- sure be deter- vation of temperature. A steam boiler sup- mined? ,. . . . _ r plied with a barometer guage and a thermo- meter affords the means of ascertaining this rela- tion. Or it may be done by a very small boiler, made for the purpose. The barometer guage is nothing more than a bent tube fitted into the boiler, open to the air at the top, and containing quicksilver in the lower part of the bend. We will suppose all the air to have been expelled from the boiler, the stop- cock through which it made its escape closed, and the whole interior to be filled with steam. As more steam is produced, pressure is increased, and the temperature of both water and steam rise, as before explained. What pressure 213. Where the temperature has has steam at rea ched 250, it is found that the pres- 2oO . at / dis- sists in converting a liquid into vapor, and recondensing the vapor. The apparatus represented in the figure, suffices for illustration. Water being boiled in the test-tube, the steam con- denses in the cooler vial. If the latter be covered with wet paper, the con- "~ densation is more perfect. The apparatus commonly used in distillation, consisting of retort and receiver, is represented in the appendix. 236. OBJECT OF DISTILLATION. The ob- object*} *&%> J ect f distillation is commonly to purify, tiilationf O r, in other words, to separate the liquid distilled, from other substances with which it may be mixed. Thus, sea water is distilled to sepa- rate the pure water from salt. The water becomes steam, and is condensed as pure water, while the salt remains behind. So alcohol is distilled, or converted into vapor, and recondensed, to separate it from water, and the various refuse matters which are mixed with it after fermentation. But the separation is not per- 5 HEAT. feet, for, althougn alcohol is more volatile, and distils more rapidly, a portion of water always distils with it. Distilled liquors, therefore, always contain a certain proportion of water. MAGNETISM. 99 CHAPTER IV. ELECTRICITY AND MAGXETISM. 237. NATIVE MAGNETS. The native mag- What proper- ties has the na- net, or loadstone, is a mineral which has tive magnet? the remar j c able property of attracting me- tallic iron to itself, and of taking north and south di- rection, when suspended and free to move. Particles of iron brought near, rush toward it, and remain at- tached to its surface, without any visible cause. It ex- erts this attractive force just as well through wood, stone, or any other material, as through the air. 23$. ARTIFICIAL MAGNET. The same Describe an . 1-1 artificial mag- properties may be imparted to a piece of steel, by a process to be hereafter described. Such a piece of steel thereby becomes itself a magnet. Magnets are often made of a shape approaching that of a horse-shoe, the two poles being brought near to each other. A piece of soft iron, called an armature, is placed across the end to prevent the loss of magnetic power, which is found otherwise to occur. 239. MAGNETIC NEEDLE. If a steel bar What is the magnetic nee- be made into a magnet, and then balanced on a pivot, it will turn, until one end points north and the other south. That which ^ moves toward the north is called the north pole, and the other end the south pole. A small bar thus balanced is called a mag- too MAGNETISM. netic needle, and is the essential part of the mariner's compass. 240. ATTRACTION OF MAGNETS FOR EACH How do the . poles of mag- OTHER. The law of attraction between 'each^tter? magnets is, that unlike poles attract, and like poles repel. The north pole of one magnet, therefore, attracts, and is attracted by the south pole of another. 241. WHY THE MAGNETIC NEEDLE POINTS In^gneriT nee- N RT H. In accordance with the law stated die point in the last paragraph, the tendency of the noTth ? magnetic needle to point north, may be ac- counted for by supposing the south pole of an enor- mous magnet, to exist somewhere near the north pole of the earth. If we call the end of the needle which points north its north pole, it is evident that the sup- posed pole at the north must be a south pole. For the same reason, xve might suppose the north pole of an enormous magnet to exist near the south pole of the earth. Connecting these poles, we should accordingly have an immense magnet running through the earth from north to south. This supposition will account for many of the phenomena of magnetism ; but it is not supposed to be the true one. Another theory is presented in a subsequent paragraph. 242. INDUCED MAGNETISM. When a Sio;To/~ P iece f * ron is brought near to a magnet, magnetism, in the iron receives magnetism, by induction, soft iron. ., . . ., ., and becomes itself, temporarily, a magnet. If approached to the south pole, its adjacent end ac- MAGNETISM. 101 quires north, and the remote one south polarity, and mutual attraction results. By virtue of its ac- quired or induced magnetism, it will attract an- other piece of iron, as is represented in the figure, and affect it in all respects similarly. From the second key, another smaller one may be sus- pended, and from this another, and so on. It is only necessary, that each successive object shall be smaller than the one to which it is attached. The magnetism thus acquired is only temporary in the case of iron, but in the case of steel it is, in some degree permanent, and may, by the proper means, be rendered entirely so. 243. DIAMAGNETISM. If a needle of What is said j ron be hung, by a thread, between the of diamagnet- J ism? poles of a horse-shoe magnet, it immedi- ately turns, so that one of its ends points to the north pole, and the other to the south. This is also a consequence of induced magnetism, as ex- plained in the preceding paragraph. The metal nickel, oxygen gas, and many other substances, both solid, liquid, and gaseous, are similarly attracted by the poles of a magnet, though in a much less degree. All bodies which are not attracted are repelled, and if sus- pended between the poles, turn so as to bring their ex- tremities as far away from the poles as is possible. The former class are called magnetic, and the latter diamagnetic bodies. To show the phenomena of at- traction and repulsion with gases and liquids, the mate- rials are inclosed in tubes or bulbs. In the case of most substances, excepting iron, these effects can only be at- 102 ELECTRICITY. tained by means of powerful magnets and delicate ap- paratus. ELECTRICITY. 244. FRICTIONAL ELECTRICITY. If a tional dectri- glass tube be rubbed with silk, it will after- cit y ? ward attract to itself filaments of the silk, as a magnet attracts iron. Or, if the knuckle be ap- proached to the tube, a spark may be drawn from it. These phenomena are called electrical. Both glass and silk are said to be electrically excited. The same ex- periment may be made with a stick of sealing-wax. State the theory 245. THEORY OF ELECTRICITY. AcCOrd- of electricity. j D g to fa e v j ew CO mmonly entertained of these phenomena, both glass and silk contain two electri- cal fluids in a state of combination, which are so sepa- rated by friction, that the positive fluid of both ac- cumulates in the glass, and the negative in the silk. The positive sustains the same relation to the negative, that the north polarity of a magnet does to the south ; and, in consequence of the difference of the separated fluids, the two bodies containing them attract like op- posite poles of a magnet. It is also true, that similarly electrified bodies repel like similar poles of magnets. As in the case of heat and light, we know nothing of the electrical fluid, save by its effects. Illustrate by ^46. The human body may also be elec- examples. tricially excited, so as to yield a spark, by rapid sliding over a carpet. Gas may be lighted by the spark. The gas in certain manufactories is instantane- GALVANIC ELECTRICITY. 103 ously lighted throughout the whole establishment by electricity developed by the friction of the machinery. 247. CONDUCTION OF ELECTRICITY. Like Explain the . . conduction of heat or caloric, electricity may be conducted electricity. ^ Qm Qne body tQ another< ThuSj if ft piece of metal be electrically excited, or, in other words, charged with a quantity of either the positive or nega- tive fluid, another piece of metal will immediately be- come so on connecting it with the first by a metallic wire. The connection being formed, it will attract or repel filaments of silk or other material, precisely as the first one does. The fluid is supposed to flow from one piece of metal to the other, through the wire, and we therefore speak of a current of electricity. But it is not certain that any thing actually passes, any more than in the case of light and heat before considered; 248. GALVANIC ELECTRICITY. It is also What is gal- vanic electri- found that electricity is developed when Clty ? two metals are placed in contact with each other, and with an acid at the same time, < as is represented in the figure. This is called galvanic electricity, from the name of an early experimenter in the science. The acid acts on the zinc, arid the cur- rent flows continuously in the direction indicated by the arrows. This apparatus is the sim- plest form of the galvanic battery. ,, . . 249. ELECTRODES. For convenience in What is an electrode ? certain experiments, it is customary to at- tach platinum wires, to the exterior portions of the me- tallic slips. These are called electrodes. The wire con- 104 GALVANIC ELECTRICITY. nected with the copper forms the positive electrode, and the one attached to the zinc, the negative. 250. Platinum wire is chosen, because Why is plati- num used for there is frequent occasion to immerse the electrodes ? electrodes in corrosive liquids, and this me- tal, for the most part, withstands their action. For many experiments, it is found best to flatten the ends of the wires forming the electrodes, so as to produce a larger surface. The same object may also be effected by terminating them with strips of platinum. 251. ELECTRICAL CONDITION OF ATOMS. What is the ,, .. , . . electrical con- All atoms of matter are regarded as origi- d atoms^ nally charged with either positive or nega- tive electricity. Hydrogen and the metals are electro-positive ; oxygen, chlorine, and cyanogen, and other substances, to be described hereafter, are ne- gative. A molecule of water is made up of a positive atom of hydrogen, and a negative atom of oxygen ; hydrochloric acid, of positive hydrogen and negative chlorine ; oxide of silver, of positive silver and nega- tive oxygen. The figure, in which +' represents positive and negative, may represent a mole- cule of either of the compounds named. 252. QUANTITY OF ELECTRICITY. The What quanti- . ty of electrid- quantity of electricity thus combined or Z i war t ? ned neutralized, in almost all kinds of matter, is enormous. Faraday has shown that a drop of water, contains more than is discharged in the most violent flash of lightning. The terms atom t and molecule, .ire synonymous. But "molecule" is limited, in the present work, to the'particle of a compound. GALVANIC ELECTRICITY. 105 253. DECOMPOSITION OF WATER. If the Describe the .. . decomposition electrodes are immersed in water, as repre- of water. ^^ in the figur ^ the water is decomposed, and separated into its elements. Bubbles of hydro- gen collect on the negative electrode, and bubbles of oxygen on the posi- tive, and finally disengage themselves, and rise through the water. 254. It is to be observed that positive Why does hy- . , -1-1 drogen appear hydrogen is liberated at the negative pole, as if the latter had a P ower analogous to that of the magnet for iron, to draw the hydrogen out of the water, in which it exists combined. On the other hand, negative oxygen is liberated at the positive pole, as though the latter had the same attrac- tive power for oxygen. The above figure is given solely for the purpose of illustration. The actual form of apparatus for decomposing water, by the galvanic current, is described in a subsequent paragraph. 255. THEORY OF THE DECOMPOSITION OF Give the theo- . ry of the de- WATER. It is a remarkable circumstance, %! sition f in the decomposition just described, that it continues to occur even when the elec- trodes are quite widely separated from each other. Now, a molecule of water is extremely small, and cannot occupy the space between the electrodes, if they are separated to any considerable ex- tent. The space must be occu- pied by many such particles, which, 5* 106 GALVANIC ELECTRICITY. for the sake of definiteness, we will conceive of as ar- ranged in straight lines, between the two electrodes. The circles iiUhe figure, inscribed H and O, represent one of these lines of molecules. The difficulty now arises, to account for the fact, that when the hydrogen is liberated at the negative pole, the oxygen, combined with it a moment before, is not also liberated at the same point. The view to be taken of it is as follows : that as soon as the atom of oxygen loses its hydrogen, it combines with the hydrogen of the next molecule of water. The oxygen of this second one being thereby liberated, combines with the hydrogen of the next ; and this decomposition and recomposition continues throughout the series. The end of the series being reached, the last oxygen atom escapes in the form of gas. The action being simultaneous throughout the series, this evolution occurs at the instant that the hydrogen is set at liberty at the negative electrode. It is, therefore, quite as proper to give the explanation of the diffi- culty first stated, by beginning with the liberation of oxygen at the positive electrode, and supposing the hydrogen to combine with the oxygen of the next molecule of water in the series, and so on to the nega- tive electrode, where hydrogen is evolved. The ac- tion is, in fact, as before stated, simultaneous. 256. DEPOSITION OF METALS. The me- Explain the . . . deposition of tals are electro-positive. Oxygen, chlorine, niL bygal ' &c '' on the other hand > are negative. If, therefore, oxides, chlorides, or cyanides of the metals are subjected to the action of the electrodes, they are decomposed, while the metal ELECTRO-PLATING. 107 goes to the negative, and the oxygen, chlorine, or cyanogen, to the positive. But the metals, when sepa- rated from their combinations, being solid bodies, can- not escape. They collect on the negative electrode, in- stead. If this be attached to a brass spoon or fork, or any other object it is desired to plate, the spoon be- comes itself the electrode, and the metal is deposited upon it as long as the action of the battery continues. At the same time, the oxygen, or other negative ele- ment, goes to the positive electrode, generally cor- roding it, instead of passing off as gas. 257 . SILVERING APPARATUS. The re- W hat appara- . tue is required quirements for electro-silvering or gilding, are first > a batter Y of somewhat different form from that already described, though precisely the same in principle ; second, an acid to ex- cite it ; and third, a solution containing gold or silver. These will be described in turn. 258. A convenient form of the apparatus is represented in the fig'i are, and may be prepared from sheet zinc and copper in a few mo- -^ ments. It consists of a bent strip of the former metal, with a strip of copper thc fastened between the two portions. The metals should be within an eighth of an inch of each other, but without contact. To secure this, they are tied together with thread, bits of wood or cotton cloth being previously interposed. Copper wires being attached to the zinc and copper, as rep- resented in the figure, the apparatus is placed in a com- mon tumbler, and the battery is complete. 108 GALVANIC ELECTRICITY. 259. Before combining the battery as How and why ...... is the zinc above described, it is best to wash the zinc with soa P and water > and afterward with dilute sulphuric acid, and then to immerse it for half a minute or so in a solution of ni- trate of mercury. By this process, the zinc acquires a thin film of quicksilver, which afterward protects it from the action of the acid used to excite the battery, excepting when the current is completed. When the battery is in operation, it also has the effect of making the action, more equal and constant. It is then to be again washed, and newly immersed in the acid solu- tion. This solution is prepared by dissolving quicksil- ver, of the bulk of two peas, in nitric acid, and pouring the clear liquid into a tumbler of water. 260. THE EXCITING ACID. The exci- How is the ex- . . citing acid ting liquid is dilute sulphuric acid, consist- preparc . .^ ^ Qne p art Q .J ^ vitriol, to ten parts of water. The acid is poured into the proper quantity of water, and set aside to cool. 261. THE SILVERING SOLUTION. To How is the sil- . . vering solution make a half pint of the solution, a dime is prepared? placed in a test-tube and dissolved in ni- tric acid, the solution being diluted with water. Muri- atic acid is then added, which precipitates the silver, in the form of a white curd. This is allowed to settle, and the green liquid, which contains the copper of the coin, is poured off. Water is again added, and the curd al- lowed to settle ; this cleansing process is several times repeated. The test-tube is then half filled with water, and heated, and bits of cyanide of potassium ad- ded, until a transparent solution is obtained. ELECTRO-PLATING. 109 262. A solution for gilding, is prepared How is the so- " _ lutionfor , by drying a solution of gold, at a moderate heat > and dissolving it in cyanide of po- tassium, as above described. The process for gilding, is in all respects the same as that for the deposition of silver. 263. THE PROCESS. The battery and How is the sil- .... veriny process silvering solution being prepared, the cop- conducted? ^ CQ ^ or ^j^ object to be silvered, is cleansed with potash, rubbed with chalk or rotten- stone, and then attached to the wire proceeding from the zinc. A silver coin is fastened to the other wire, and immersed in the silvering solution ; acid is then added to excite the battery, and the object to be silvered is lastly immersed. It should be hung face to face with the silver coin, and quite near to it, the two being kept in their places by blocks placed across the tumbler, as represented in the figure. The coin will receive a per- ceptible coatingwithin a few minutes, and will be more thickly covered, according to the time of immersion. The deposit is hastened by keeping the solution mode- rately warm. This is especially advantageous in the commencement of the process. The newly plated sur- face is without lustre, and requires burnishing after re- moval from the solution. 264. OBJECT OF THE SILVER COIN. The What is the object of the piece of silver is attached to the positive wire, to maintain the strength of the solu- tion. It is eaten away, and dissolved as fast as silver is deposited on the objects connected with the negative wire. The reason of this is, that the cyanogen of the 110 GALVANIC ELECTRICITY. solution, when it goes to the positive pole, as before ex- plained, combines with silver, forming new cyanide of silver, which dissolves and mixes with the rest. Thus, the strength of the solution is always maintained. The coin is attached to the negative wire, by flattening the latter, laying it on the back of the coin, and covering the whole with sealing wax ; the coin and wire should be previously slightly warmed, and the wax used at a moderate heat, so that it shall not run between the wire and the coin, and prevent their perfect contact. How are med- 265. COPYING OF MEDALS. If it IS de- ais copied? sired to copy the face of a medal or a coin, the same apparatus suffices. The reverse and edges of the coin are very slightly oiled, to prevent the adhesion of the copy about to be made. It is then placed in the solution. The metal deposits upon it, copying perfectly every elevation and depression. When the crust is suffi- ciently thick, which will be after the lapse of twelve hours, the coin, with its shell of metal, is removed, and the whole process repeated with the mould. The de- posit which now forms in the shell, is an exact copy of the face of the original coin. Moulds are also made by stamping the coin into soft metal, and using the impres- sion thus produced instead of the copper shell. Copper plates, for engravings, may be copied so perfectly by this method, as to be fully equal to the original. How are wood 266. COPYING OF WOOD CUTS. The diffi- cuts copied? culty of copying other than metallic ob- jects, by the processes, that they are not generally good conductors. Thus, when a wood cut is attached to the negative wire, it does not itself receive a nega- ELECTRIC LIGHT. Ill live character from the wire, and will not, therefore, take positive metal from the solution. This is obvia- ted by covering the block with a fine powder of plum- bago or black lead, which has high conducting power. 267. This process is very extensively It what cases r / is the process practised. Where a large number of cuts pra of the same kind are wanted, as for exam- ple, to print labels for dry goods, only one engraving on wood is made, and numerous copies are taken by the above process, which is much less costly. 268. HEATING EFFECTS OF THE CUR- Descrtbe the heating e/ect RENT. If the electrodes are connected of Recurrent? while the b attery j s j n actlO n, the wire be- comes heated more or less strongly, according to the size of the plates. If the plates are very large, the wire melts, even though it be of platinum, the most infusible of metals. Gold may even be converted in- to vapor by the same means. Carbon, supposed a few years since to be entirely infusible may be also super- ficially fused, and even volatalized between the electro- des. It condenses again at a little distance, in the form of microscopic crystals. Imperfect diamonds have been thus artificially produced. With such a battery as has been described the elevation of temperature would be scarcely perceptible. 269. THE ELECTRIC LIGHT. If the current How is the . electric light be allowed to pass between two points of produced ? prepared charcoal, an exceedingly intense light is produced, accompanied by great heat. Char- coal is employed because it is a comparatively infu- sible, and inferior in conducting power. A metallic 112 GAI VANIC ELECTRICITY. wire, under the same circumstances, would melt, or if too large to undergo fusion, would allow the current to flow readily through it, without that detention which is essential to the production of the above effects, in their highest degree. 270. If the charcoal points be with- How ts the ' , , . -, electric flame drawn from each other, a splendid electric produced? flame is p ro d u ced between them. This flame is not the result of combustion, for the char- coal is extremely dense, and wastes away but slow- ly. It is purely electric. Metals melt in it, and are dissipated in vapor. A much larger battery than that here described, is requisite fox the production of ei- ther the light or flame. In experimenting with the compound battery, hereafter described, a slight spark will be observed, on separating the electrodes. 271. DECOMPOSITION IN THE BATTERY. A decomposition, similar to that of wa- in the battery ter and metallic compounds, as above de- scribed, takes place in the battery itself, and seems to be the source of its power. Suppose, for example, the acid with which the zinc and copper are in contact, to be hydrochloric, each molecule of which is composed of an atom of hydrogen and an atom of chlorine. The zinc becomes positive where it is in contact with the acid, and negative at the other end, the extremities assuming different states, as in the case of a piece of soft iron suspended from a magnet. The outer portion of the copper being in con- tact with the negative end of the zinc, is, itself, nega- tive, while the end immersed is positive. The atoms GALVANIC ELECTRICITY. 113 composing the acid, are supposed to be arranged as rep- resented in the figure. The alternation of positive and negative, in copper, zinc, and the line of acid molecules is analogous to the case of the sus- pended keys. As long as the metals are immersed, and made to touch, an atom of zinc constantly combines with an adjacent atom of chlorine. It follows, that no chlorine is set at liberty. As fast as each atom unites with the zinc, its hydrogen combines with the next chlorine, the hydrogen of this, with the next, and so on, as before explained, in the de- composition of water. Hydrogen is therefore con- stantly given off at the surface of the copper. But when the two metals are not in contact above the li- quid, and the circuit is, consequently, not completed, there is no negative influence exerted at the extremity of the copper, and the series of decompositions, before described, does not occur. 272. A SALT EMPLOYED AS EXCITANT Explain how . -,, -iini a battery can It is not essential, that an acid shall be used b amit? ed by as tlie excitm g liquid iii the galvanic bat- tery. A metallic salt is sometimes em- ployed. This may be best illustrated, by supposing chloride of copper to be employed instead of hydrochlo- ric acid, which is chloride of hydrogen. The chlo- rine goes to the zinc, as in the previous case, and the copper of the salt, to the strip of copper, placed in the solution. Being a solid, it remains there, and en- crusts the copper, instead of being evolved, as in the case of hydrogen. 114 GALVANIC ELECTRICITY. 273. DIFFERENT KINDS OF BATTERIES. What is said . .. . o/ the differ- There are different kinds 01 galvanic bat- britertef teries, but the principle in all is the same. Two of the forms in most common use are described in the Appendix. Smee's battery is especially recommended to the student, for its cheap- ness, simplicity, and efficiency. It is very similar, as will be seen, to the simple one which has been already described. 274. COMPOUND CIRCUIT. For the sake What is said f . ,. . . f of the com- ot simplicity, all the foregoing decomposi- pound circuit? tions have been described, as a result of the action of a simple voltaic circle, consisting of an acid, and two metals. But, it is found that in many decom- positions, the power of such a battery is insufficient. The efficiency is increased by employing several single batteries together, and bringing them all to bear upon the same electrode. How are heat- 275. The heating and magnetic effects ing and mag- f fa b attery are very ^cft increased by netic effects J J J produced? uniting the plates, as in the preceding fig- ure, where all the zinc plates are joined together, so as virtually to form one. The quantity of the current is thus increased. Power of decomposition, and to give shocks, such as are taken from an electrical machine, GALVANIC ELECTRICITY. 115 are increased by uniting them as in the figure which follows. The intensity of the current is thus increased. What is the meaning of in- tensity ? Of quantity ? 276. MEANING OF INTENSITY AND QUAN- TiTY. The terms intensity and quantity are rather vaguely used, and do not de- scribe as definitely as may be desired, the different properties of the current. The student must associate the term quantity with increased heating and magnetic effects, and the term intensity, with power of decomposition. 277. DECOMPOSITION BY THE COMPOUND Explain the ... apparatus for CIRCUIT. Jb or the decomposition oi water, a S6rieS f Slx CU P S > Sllch aS haVG beetl al- ready described for use in plating, will suf- fice. They are to be united according to the second ar- rangement. The zinc of each cup is to be connected with the copper of the next in order, by a copper wire, forming a good metallic contact. This being done, another long wire is fastened to the first copper plate, and one, also, to the last zinc, and bits of platinum wire or foil are attached to their ends. A small test-tube is then filled with acidulated water, and inverted in a cup, also containing water and acid. The wires are bent upward into the cup, as represented in the figure. The battery being now set in operation, by dilute acid, as before described, 116 GALVANIC ELECTRICITY. the evolution of gas immediately commences from the the platinum wires. This compound battery will be found rather slow in its operation, and has been de- scribed only for the purpose of illustrating the use of the more powerful galvanic batteries of similar con- struction. The student is advised to substitute for it the Voltaic pile, as hereafter described. 278. AN EXPLOSIVE MIXTURE. A mix- What proper- , , ty has the ture of hydrogen and oxygen gases, in the US proportion m which they are here evolved, is explosive. This property is the evi- dence that the gases are really oxygen and hydrogen, in due proportion. A sufficient quantity being col- lected, the mouth of the tube is covered with the finger, the tube inverted, and a match applied at the mouth. A slight puff is all the evidence that will be obtained from a small quantity of the mixture. A test-tube full will give a sharp report. 279. SEPARATE COLLECTION OF THE How may the , . , gate* be col- GASES. By using two test-tubes, instead lected*cpa- o f before described, and introduc- rately ? ing an electrode into each, the gases may be separately collected and tested by the methods give in the section which treats of those gases. 280. The water is acidulated in the ex- Wky is the . water to be de- penment, to make it a better conductor of "dilated? the mmience which must pass through it, from one electrode to the other, in order that the decomposition may take place. The reason for using platinum electrodes has already been given. In the present case, if the copper wires themselves GALVANIC ELECTRICITY. 117 were introduced, the negative electrode would appro- priate all the oxygen to itself, thereby becoming grad- ually converted into oxide of copper, and nothing but hydrogen gas would be obtained. 281. DECOMPOSITION OF A SALT. The Describe the decomposition effected by the galvanic decomposition * of a salt. current, may be more strikingly illustrated by introducing the electrodes into a dilute solution of sal-ammoniac, previously colored by litmus, or red cabbage. Chlorine is liberated at the positive pole, and bleaches the solution in its vicinity, while ammonia is evolved with hydrogen, at the negative pole, and changes the color of the solution from blue to red. That of the cabbage is changed by the same means, from red to green. By employing a glass box with two compartments, such as is represented in the figure, the two portions of the liquid may be kept distinct. It is essential, for reasons that will be understood from the preceding paragraph, that there be an unbroken chain of molecules of the electrolyte, or substance to be de- composed, between the electrodes. This is effected by making the partition quite loose, and keeping it in its place by strips of paper, placed along the edge. All the communication that is essential, then takes place through the pores of the paper, while the partition at the same time prevents the mixing of the contents of the sepa- rate cells. The same object may be accomplished by the employment of two tea-cups, holding the liquids, and connected by moistened lamp-wick ; a larger pile, 118 GALVANIC ELECTRICITY. and a longer time, is in this case required to effect the decomposition. The glass box may be made according to the directions given in paragraph 33 for making a prism. Describe the 282. THE VOLTAIC PILE. The first Voltaic pile, form of galvanic battery ever produced is represented in the figure, and is called the Voltaic pile, from the name of its inventor. It consists of a succession of discs of zinc, copper, and cloth, moistened with acid, al- ternating with each other, as represented in the figure. Each series forms a simple battery, and the whole pile is a compound battery, essentially the same as that before described. Wires to serve as electrodes are to be at- tached to the extreme copper and zinc. 283. The enlarged form of the Voltaic What is said ., .... of the en- pile represented in the next figure will be Voltaic found a mogt efficient apparatus for ef- fecting decomposition. It is composed of sixteen plates of each metal, each having a surface of twelve square inches. The zinc should be amalga.- mated, as before explained. Flannel, or any similar material may be employed to separate the plates. With this piece of apparatus, the spark is readily obtained, and slight shocks may be taken by bringing the two hands into contact at the same moment with the top and bottom of the pile. On terminating the electrodes with fine iron wire, and frequently uni- ting and separating them, scintil- ELECTRO-MAGNETISM. 119 lations of the burning metal may also be readily pro- duced. By increasing the number of the plates still more striking effects are obtained. With a pile con- sisting of six or eight plates a foot square, platinum wire connecting the electrodes may be readily fused. Such a battery is also more effectual in the electro- magnetic experiments which follow. Describe the 284. MAGNETIC PROPERTIES OF THE CUR- magnetic pro- RENT> jf t h e w i re connecting the zinc perties of the galvanic cur- and copper of the galvanic battery be wound in a spiral, as represented in the figure, the coil, or helix, as it is termed, be- comes possessed of magnetic properties. Like a magnet, it attracts iron, and other magnets, and according to the same laws. How may a 285. THE SUSPENDED BAR. A rod of iron ^ endedln e Drou g nt near one f tne extremities of the the air ? coil, is not only attracted, but actually lifted up into the centre of the coil, where it re- mains suspended without contact, or visible sup- port, as long as the battery continues in action. Science has thus realized the fable of Mahomet's coffin, which was said to have been miraculously suspended in the air. The helix, for this and similar experiments, is wound closer than is rep- resented in the figure, and is composed of several layers of wire. A powerful battery is also essential to success in this experiment. 286. POLARITY OF THE COIL. That What is the ', i action of a such a coil has polarity, may be proved, precisely as with a magnet. One end of it attracts the north pole of a magnet, and 120 GALVANIC ELECTRICITY. is therefore a south pole. The other end attracts the south pole of a magnetic nee- dle, and is therefore, itself, a north pole- But the direction in which the current moves round in the helix, determines which shall be north, and which south.. As the current is represented to move in the first of the two coils in the figure, the up- per end of the coil is north, and the lower end south. If it is made to move in the other direction, as in the second figure, the poles are reversed. 287. CONSEQUENT MOTION or A sus- Hoio may we obtain motion FENDED COIL. To obtain motion of the /eif ke C d li ~ coil itself > as a consequence of its magne- tism, it is necessary to suspend it ; and in order to suspend it with perfect freedom of motion, it is necessary to suspend the battery with it. Such a suspended coil and battery is represented in the figure. In preparing it, the wire is wound forty or fifty times round a test-tube, (which is afterward removed,) and copper and zinc plates then attached to the ends. The plates are tied together with several layers of paper between them, then dipped in acid, and the apparatus carefully suspended by an untwisted silk fibre. The acid absorbed by the paper, suffices to maintain for some time the action of the battery. On approaching a magnet to either pole of the suspended coil, it is at- tracted or repelled precisely as if it were a magnet. In- stead of suspending the apparatus by a thread, it may ELECTRO-MAGNETISM. 121 be floated on acidulated water, by means of a cork, and submitted to the same experiment. In this con- struction, the wires proceeding from the end of the coil, pass through the cork, before connecting with the metallic plates. The first described method of suspen- sion is regarded as the best. 288. THE COIL A MAGNETIC NEEDLE. How may the coil be conver- On floating a coil with extreme deli- <=acy upon water, and protecting it from all currents of air and water, it assumes north and south direction, and becomes, in fact, a mag- netic needle. This can only be accomplished by means of a light glass cup, blown for the especial pur- pose, and prolonged into a cone below, to give it stead- iness in the water. This cup is filled with dilute acid, in which the plates are immersed, and is then floated in a larger vessel. 289. MUTUAL ACTION OF COILS. Two Describe the . mutual action helices, or coils, such as are described in the last paragraph, floating near each other, attract or repel, precisely as if they were magnets, according as like or unlike poles are brought together. They finally attach themselves to each other in the position represented in the figure, lying parallel and with opposite poles in contact. In this position, it will be observed, that at thepoint of con- tact, the currents are moving in the same direction. The attraction of the unlike poles, may be regarded, then, as a consequence of the attraction of like cur- rents. For it is found to be universally true, that 6 122 GALVANIC ELECTRICITY. currents moving in the same general direction, attract each other, while those moving in opposite directions, repel. What is the 290. MUTUAL ACTION OF COIL AND MAG- mutual action NET jf a floating magnet be substituted of a coil and magnet? for one of the coils, in the above ex- periment, the result is not in the least affected. They act toward each other precisely as if both were magnets, or both, coils. 291. ACTION OF A SINGLE WIRE ON What is the . , action of sin- A COIL. A single wire, carrying a cur- yle wire on a rent actg Qn & fl oatm cr co il in the same magnetic coil r manner. Stretched above it, as in- dicated in the figure, the north pole of the coil will move to the right. The motion is such as to bring adjacent currents, in the wire, and in the coil, to co- incide in direction. 292. POLARITY OF THE COIL IMPARTED What effect f has the mag- TO IRON. A bar of soft iron placed in neticcoil upon t k Q -i b ecornes itself a magnet, and re- metals ? ceives the name of electro-magnet. Great- er power is acquired if the metal is, closely wound with copper wire, covered with cotton 3 to prevent any lateral passage of the current. The horse-shoe shape, in which the poles are brought round near to each other, is the more common. The power of such magnets contin-' tinues only while the current is passing. Electro- p magnets have been constructed capable of lifting a ton, or even more. They are sometimes employed in dress- ing iron ores, to separate, by their attraction, the work- ELECTRO-MAGNETISM. 123 able ore from the refuse earth with which it is mixed. A steel bar introduced into the helix while the current is passing, becomes permanently magnetic. Permanent magnets, are now commonly made in this manner. 293. PERMANENT MAGNETISM OF STEEL. What effect has the mag- It appears, from the last paragraph, that "ted I 11 1 * a bar f S ft ir011 1S a ma g net > as lon g a S an electrical current circulates around it. But the steel, if once magnetic, remains so permanent- ly. This is accounted for, by supposing that the cur- rent, in the wire, excites a current in the surface of the steel itself, which continues to flow, without interrup- tion, after the wire is removed. 294. ACTION OF A SINGLE WIRE ON What is the action of a A MAGNET. ^-A wire, carrying a cur- t magnet? * rent in the direction shown in the figure, acts on a magnet, precisely as on a floating coil. The north pole of the mag- net is made to deviate to the east. The mo- tion is such as to bring adjacent currents in wire and magnet to coincide. 295. ELECTRICAL THEORY OF MAG- Explain the . electrical theo- NETisM. According to this theory, all mag- T tlm? magne ' netism ? including that of the load-stone, the magnetic needle, and that of the earth itself, is a consequence of the circulation of electrical currents. In the earth, such currents are known to be excited, and kept in motion, by the sun, heating in turn successive portions of its surface. They flow from east to west, making of the earth, as it were, an im- mense coil, or helix. In magnets they are also in con- 124 GALVANIC ELECTRICITY. Explain the figure. stant circulation, the direction being dependent on the position in which the magnet is held. In the case of a magnet whose north pole is directed north, the di- rection is from west to east across the upper surface, and of course, in the contrary direction on the under side. The earth acts on a magnet, or a floating coil, as one helix acts on another. The north and south direction of the magnetic needle is a consequence of this action. 296. THE THEORY ILLUSTRATED. In illustration of this theory, let a globe be coiled with a wire, carrying a current, as indicated in the figure. Let the current flow from east to west through the coil. A small magnetic needle placed at different points on the surface of the globe, however the po- sition of the latter may be changed, will always point to "its north pole. It is under- stood, in this experiment, that the current is strong enough to overcome the influence of the earth itself on the mag- net. A freely movable coil through which a current was passing, would, in this case also, act precisely like a magnet. 297. MAGNETIC TELEGRAPH. The ex- Explain the . . principle of planation of the mechanism of the mag- netic tele g, ra P h belongs to Natural Philoso- phy. The principle of its operation may MAGNETIC TELEGRAPH. 125 be here given. It has already been stated, that a piece of soft iron becomes a magnet, when a current of elec- tricity circulates in a coil surrounding it. Now, sup- pose the two ends of such a coil, situated in a distant city, to be made long enough to reach a battery in the place where the reader resides, and to be stretched along over posts, and connected with the poles of the battery. The current occupies no perceptible time in its passage. Therefore, as soon as the battery is set in operation, it circulates through the whole extent of the wire, and, of course, through the coil in the distant city. The piece of iron which it incloses is made a magnet, and will immdiately lift its arma- ture. If the current is stopped, the piece of iron ceases to be a magnet, and drops its armature. But the operator at the battery can send or stop the current at will, by simply disconnecting one of the wires, and thereby lift or let fall the armature a hundred or a thou- sand miles off, as often as he pleases. He can have an understanding, also, with the person in the distant city, who sees the motion of the armature, as to what it shall mean. One lift may indicate the letter A ; two lifts, the letter B ; and so on. So any thing may be spelled out, and it thus becomes possible to commu- nicate ideas by electricity. If these lifts of the arma- ture can be made to record themselves on a slip of paper, the further advantage of writing at the distant station is gained. And this is precisely what is realized in Morse's telegraph, and more particularly described in all recent works on Natural Philosophy. 126 GALVANIC ELECTRICITY. 298. THE EARTH, USED AS A CONDUCTOR. What ^s said of the earth It would seem requisite to extend both ends as^conduc- of the wire f orming the coil through all the intervening distance, and then to con- nect them with the opposite poles of the battery ; but it is found, in practice, that one is sufficient, and that all the middle portion of the second wire may be dis- pensed with. The remaining ends, one connected with the helix, and the other with the battery, being made to terminate in large plates, and buried in the ground, the earth between them is found to take the place of the second wire, and complete the circuit. Mention some 299. APPLICATIONS OF THE TELEGRAPH. remarkable There are many applications of the tele- applications t of the tele- graph beside the one of transmitting intel- graph. ligence to distant places. In the city of Boston, an alarm of fire is instantaneously communi- cated throughout the city, and the bells rung by tele- graphic apparatus. In Marseilles, France, a single clock is made by sim- ilar means to indicate the time on dials, placed in the street lamps of the city. Electro-magnetic apparatus has also been employed with the most remarkable suc- cess in increasing the dispatch and accuracy of astro- nomical observations ; making it possible to accomplish during a single night in the study of the heavens, what formerly cost a month of labor. 300. PHYSIOLOGICAL EFFECTS OF GAL- Describe the physiological VANisM. The nerves of animals are ex- fanism f ? ff to increase their affin- ity for oxygen. Take carbon, as an exam- ple. Before heating, its affinity for oxygen is not suf- ficient to bring about the requisite combustion. In this condition it may, therefore, lie for any length of time, in the air, or oxygen gas, without uniting with it. But heat stimulates the tendency to combination, and the bit of charcoal previously ignited, goes on burning, until it is consumed. The first particles obtain the necessary stimulus of heat, from the previous igni- tion, the next from the burning of the first, and so on. 343. UNCOMBINED OXYGEN REQUISITE. What kind of __ '. oxygen is re- Mere presence of oxygen is not sufficient amlnrtion? for. combustion. It must be free, or un- combined oxygen. After burning char- choal in oxygen gas, the vial contains just as much oxygen as before, but being already combined, it has no affinity, or appetite, for more carbon, and there- fore will not produce a new combustion. 344. EACH PARTICLE IN TURN MUST BE, If each parti- cle is not heat- HEATED. If the first particles that com- bme ' do llot communicate sufficient heat to the next, then the combustion stops. This may be illustrated by lighting a tightly wound roll of paper, and holding the flame upward. It is soon extinguished, because the heat that is produced OXYGEN. 147 by the combustion of one portion of the paper, is not communicated to the next, but passes off into the air. But if the taper be held with the flame downward, each particle in turn receives the stimulus of heat ne- cessary to combination, and the whole is consumed. 345. DECAY OF LEAVES AND WOOD. What causes the decay of The decay of leaves and wood, is a sort of slow combustion, but not sufficiently vigorous to produce light and heat. In this case, as in the ordinary combustion of wood or coal, the particles which have combined with oxygen, pass off into the air, in an invisible form. 346. BLEACHING. Bleaching may also How may . * bleaching be be regarded as a kind of slow combustion. On exposing cloth to sun and air, its color- ing matter is gradually burned up, by the atmospheric oxygen. 347. OXYGEN A PURVEYOR TOR PLANTS. oxygen\ a ^ nas been seen that both in combustion purveyor for an( j d ecaVj the oxygen of the air combines with the particles of leaves, and wood, and coal, and passes off with them in an invisible form. It flies off with them into the air, and yields them again to living plants, to produce new leaves and flowers, and fruits. Indeed, they are entirely dependent, for their support, on what they thus obtain from the death and decay of their predecessors, through the agency of this ever active purveyor, the oxygen of the air. But for the fact that the particles of vegetable and animal mat- ter, can thus be used again and again, the supply would 148 METALLOIDS. soon be exhausted, and vegetation cease upon the face of the earth. 348. OZONE. By passing an electrical How is * ne current, continually, through oxygen gas, for some time, it becomes mysteriously changed in its proportions. In this changed condition it is called ozone. It is, as it were, intensified in its affin- ities by the current, so that like chlorine, it will attack silver, and exhibit many other of the properties of the latter gas. The electricity of the air has similar effects on the oxygen which it contains, and, in consequence of its varying electrical condition, the proportion of ozone is, also, from time to time, extremely varied. There is reason to believe that this substance has important influ- ence upon health, and that either its deficiency or excess, is injurious. In cholera seasons, it has been observed to be present in comparatively small quantity, while, during the prevalence of a species of influenza called " grippe," it is said to be more abundant. These obser- vations need confirmation, by further experiments, before the facts can be regarded as fully established. The pres- ence of ozone, is indicated by the discoloration, through the influence of a current of air, of a test paper, de- scribed in the section on chlorides. Tir , 349. RELATIONS TO LIFE. Oxygen is What relation to life does ox- as essential to life, as it is to combustion. ygen sustain! The ^^ oxygen of the ^ ig better adapted to breathing, than pure air, but that which con- tains much less than its due proportion, is no longer fitted to support life. Respiration consumes oxygen, so that the air of a close room is constantly being depri- CHLORINE. 149 ved of this essential constituent, without obtaining any new supply. As a consequence, it soon becomes unfit to breathe. The case is similar to that of a taper burned in a bottle. The oxygen of the air in the bot- tle, is gradually consumed, and the flame grows grad- ually more and more dim, till it goes out. So life grows fainter and fainter, in a close, unventilated room. What is said 350. Oxygen has been used, with great of oxygen as success, as a means of resuscitation, in cases a means of ' resuscitation ? of suffocatio.ii and drowning, when similar use of air was without effect. In such cases, it is forced into the lungs through a tube, from a jar or bladder. CHLORINE. What is chlo- 351. DESCRIPTION. Chlorine is a yel- T wLreisit lowish green gas, of peculiar odor, about found"! %\ times as heavy as the air. More than one half of common salt is chlorine. Salt mines and the ocean, therefore, contain it in immense quantities. 352. PREPARATION. Chlo- How is chlo- rineprepar- nne is prepared from muriat- ic acid, which is composed of, chlorine and hydrogen, by using some agent to retain the latter, and liberate the former. Black oxide of manganese is 1 such a substance. Give the com- 353. The oxide is well covered with mu- picte proceeds. r j a ti c acid, and kept warm, as the evolution of the gas proceeds. This is best effected by a cup of hot water, as represented in the figure. Chlorine gas soon displaces the air in the second vial. It should be corked as soon as filled. 150 METALLOIDS. Explain the 354. It will be remembered that black process. oxide of manganese, is a substance con- taining a double portion of oxygen, part of which is feebly held, and very willing to go. Its use in making chlorine, depends on this fact. The loosely held oxygen, seizes upon the hydrogen of the muri- atic acid, remaining with it as water, and at the same time setting its chlorine at liberty. 355. A SIMPLER METHOD. Acids expel Describe an- . - , , . , , other method chlorine from many bases which have of preparing prev iously been made to absorb it. chlorine f Lime is one of these bases. Bring into a wide-mouthed, half-pint vial, a table spoonful of dilute sulphuric acid, and add rather more than the same bulk of chlo- ride of lime, or bleaching powder. It is best to add it in small portions, covering the vial with a cork or bit of glass, after each addition. The vial will soon be filled with faintly green chlorine gas. More of the materials will be required, if the chloride of lime is deteriorated by exposure to the air, as is often the case. The gas thus produced, may be used for most of the experiments which follow, with- out transferring it to another vessel. 356. CHLORINE, HEAVIER THAN that chlorine AIR. This is already imperfectly lhan *af P roved ; in the first method of col- lecting chlorine, but the follow- ing proof is more satisfactory. The gas pro- duced in the last experiment, may be slowly poured 'from the vessel containing it, into CHLORINE. 151 another wide-mouthed vial. The second vial, if the smaller of the two, may be thus filled without re- ceiving any acid from the first. In small quantities the gas cannot be seen to flow, but will actually pass from one vessel into the other. Its presence may be proved by the methods given in the following experi- ments. 357. CHLORINE DISSOLVES IN WATER. that chlorine Having filled a vial with chlorine, by the " first of the methods above described, cork it, and open it under water, contained in a bowl. As the gas dissolves in the water, the latter will rise to take its place. When it has risen a little way, cork, and shake the vial, and open it again below the surface. The water will then rise and dissolve still more of this gas. The so- lution is to be set aside for a subsequent experiment. Gas produced by the second method above described, may also be used in this experiment, if previously transferred to another vial. 358. ACTION OF CHLORINE ON METALS. Describe the action of chlo- Chlorine gas combines with many metals, rine on metals. convertmg tnem into chlorides. Their ac- tion may be illustrated by sprinkling, finely pulverized antimony, into a bottle of chlorine. Each particle of metal ignites as it falls through the gas, and a minia- ture shower of fire is thus produced. The white smoke which is produced in this experiment, is composed of minute particles of chloride of antimony. 152 METALLOIDS. 359. NASCENT CHLORINE. Nascent chlo- What ts the . action of nas- rme, in its action on the metals, is the most cent chlorine* powerful agent known. Even the noble metals yield to its power, and waste away in the liquid which contains it. The term nascent signifies being born, or in the act of formation. What is the 360< A11 ases are most ener getic, in general fact their action at the first moment of their in relation to . nascent bo- separation from compounds which contain them, and while they may be regarded as still retaining the solid form themselves. The subse- quent expansion into the gaseous form, diminishes their energy. 36.1. Nascent chlorine is best obtained How is nas- .. , * i i i i i / . cent chlorine by mixing hydrochloric acid with half its best obtained? bu j k of strong n i tr [ c aci( j. g uch a mix _ ture is called aqua regia. The latter acid compels the former to yield a constant supply of its own chlorine in the nascent condition. It does this, by means of its oxy- gen, which seizes upon the hydrogen of the hydrochlo- rine acid, forming water, and sets its chlorine at liberty. The remnant of the nitric acid escapes, as in the case of its action on metals hereafter described. 362. CHLORINE DECOMPOSES WATER. Does chlorine . decompose wa- 11 chlorine water be exposed to the sun for some days, it loses its green color. The chlorine combines with the hy- drogen of the water, forming hydro- chloric acid, and sets its oxygen at liberty. If the experiment be made in a bottle, inverted in water, so that the CHLORINE. 153 oxygen may collect, bubbles of this gas will be found above the liquid. This experiment proves the pow- erful affinity of chlorine for hydrogen. 363. BLEACHING BY CHLORINE. Intro- How is calico _ bleached by duce bits of calico into the solution 01 chlorine ? c hl or ine before obtained. Most colors will soon disappear. If the solution is weak, the bleaching effect will be better shown, with infusion of litmus or red cabbage. Color may also be removed from cloth or paper by hanging the article to be bleached, pre- viously moistened with water, in a vial of gaseous chlorine. 364. Chlorine water may be prepared How ts chlo- rine water best in larger quantity, by leading the gas di- preparcd? rect iy j nto wa ter. The first of the two methods before described, will be found the most ad- vantageous. 365. OXYGEN THE REAL BLEACHING Explain how chlorine AGENT. The real bleaching agent in this bleaches. me thod of bleaching, is the same as that mentioned in paragraph 346. It is oxygen, always present during the process, as an element of the water which moistens the material. The chlorine simply acts to bring nascent oxygen into activity. It does this by depriving it of the hydrogen with which it is combined. The oxygen having thus lost its com- panion, looks about, as it were, for something else with which to combine. The coloring matter of the cloth being the first thing at hand, is destroyed by the extreme energy of its affinity. 7* METALLOIDS. 366. ACTION OF NASCENT OXYGEN. The Show the ad- vantage of superior force of an element in its nascent nascent oxy- con( ji t i on j s strikingly shewn in the above experiment. A piece of calico, hung in a bottle of oxygen gas, would not lose its color. But the nascent oxygen which chlorine liberates, be- gins to destroy the coloring matter on the first instant of its liberation. 367. CHLORINE AND TURPENTINE. Im- JJescnoe the inflaming of merse a rag wet with camphene or spirits of turpentine in a vial of chlorine gas. It is immediately inflamed, with the production of dense black smoke. Spirits of turpentine is composed of hydro- gen and carbon. The former combines energetically with chlorine, as to produce flame in the above experiment, while the latter is separated in the form of black particles, which con- stitute the smoke. 368. USE AS A DISINFECTANT. As chlo- Is chlorine a disinfectant ? rine destroys color, when used as a bleach- ing agent, so it destroys noxious vapors in the air. Its minute atoms fly forth like birds of prey, seizing on the impurities of the atmosphere, and de- vouring them. Chloride of lime is commonly substi- tuted for chlorine for this use. A little of this salt is placed in a saucer, and moistened, when it gradually yields chlorine through the action of the carbonic acid of the air. Stronger acids evolve it abundantly. CHLORINE. 155 369. CHLORINE A DESTRUCTIVE AGENT. What is said . . of chlorine as Chlorine, as has been seen, is one of the a destructive mogt destructive of all substances. It not agent only destroys colors and odors, but any kind of vegetable or animal matter, long submitted to its action, wastes away, and is destroyed. It does this partly by its own direct action, and partly by letting loose the atoms of nascent oxygen, as before described. 370. IN WHAT SENSE DESTRUCTIVE. It In what sense is it destruct- is always to be borne in mind that the term destruction is used in chemistry in an entirely figurative sense. Thus, neither oxygen nor chlorine, strictly speaking, destroy. They only com- bine with the particles of the substances they seem to destroy, forming new, and often invisible compounds. Many of these will be hereafter mentioned. 371. RELATIONS TO ANIMAL LIFE. Chlo- G-ive the rcla- . . tions of Mo- rine is a poisonous gas. No danger, how- rmcto animal ever? ig to be appre h e nded from the escape of small portions into the air, during the preceding experiments. The diluted gas, however, is apt to produce irritation of the throat, and consequent coughing, In what re- 372. RESEMBLANCE TO OXYGEN. In chTorinTre many respects chlorine is similar to oxy- semble oxy- gen, as has already been shown. It com- bines with almost all of the elements, and with many compounds. This combination is often attended with light and heat, and is therefore com- bustion. The metal antimony, for example, as has 166 METTALLOIDS. already been shown, will burn, in chlorine gas, even without kindling. Mention some 373. COMPOUNDS OF CHLORINE AND OXY- compounds of GEN Chlorine combines with five atoms chlorine and oxygen- of oxygen to form chloric acid. This acid is of importance, principally, as a constituent of the chlorate of potash, to be hereafter mentioned in con- nection with Nitrates. Hypoclorous acid a constitu- ent of bleaching powders is another compound of chlo- rine with oxygen. It is again mentioned in the section on Chlorides. IODINE. v/ 374. DESCRIPTION. Iodine is commonly dine? WJiere seen in the form of brilliant blue-black is it found? scales, somewhat similar to plumbago in appearance. In odor it resembles chlorine. It is found in the water of the ocean, in sea-weeds, sponges, &c., but always in combination with sodium, or some other metal. Minute traces of it are found to exist in the atmosphere, and thence are transferred to the bodies of animals. 375. PREPARATION. For the preparation Explain the . . manufacture oi iodine, a lye of iodine? made fj . om the ashes of certain sea-weeds, is heated with oil of vitriol and black oxide of manga- nese. The liberated oxy- gen of the latter expels va- IODINE. 157 pors of iodine from the mixture. These being led into a receiver, crystallize in brilliant scales. A retort and receiver are commonly used in the process. The ashes of sea- weed, employed for the purpose, are called kelp, and are prepared in great quantities on the coast of Scotland. VIOLET VAPORS or IODINE. violetlapors Introduce a few scales of iodine into of iodine pro- a test-tube or vial, and heat it for duced? a moment over the spirit lamp. The solid iodine is immediately converted into a beautiful violet vapor, which fills the vial. As the latter cools, the iodine becomes again solid, in the form of minute crystals. On warming these crystals, thejeolbr re-appears. ^^077. COLORING EFFECT ON STARCH. - Describe the jj eat a |j u i e i O( J me i n a ^ive effect produ- ced by iodine stem, and as soon as vapors ap- paste? C pear, blow them against a sheet of paper, covered with figures made with thin starch paste. The iodine vapor imme- diately colors them blue. The paste may be made in a test-tube, over a spirit lamp. 378. ENGRAVINGS COPIED BY IODINE.- How are en- gravings copi- A transient copy of an engraving, or other ed by iodine ? p rm t ec j ma tter, may be made, by exposing it to faint fumes of iodine, and then pressing it down upon paper moistened with vinegar, or dilute nitric acid. The vapors, adhere to the ink only, and are transferred by pressure ; producing, with the starch contained in ordinary letter paper, a blue impression. 158 METTALLOIDS. BROMIDE. 379. Bromine is a dense reddish-brown of bromine? fluid, exhaling at ordinary temperatures, a deep orange-colored vapor. It is similar, in its chemical properties, to chlorine, but the latter is the stronger of the two, and expels bromine from its compounds. Thus, if chlorine be passed into one end of a heated tube containing bromide of silver, the va- pors of bromine will be seen to pass out at the other end, and escape, while the chlorine remains, and takes possession of the metal. Bromine, like chlorine, is found in sea- water, and in the water of mineral springs, combined with sodium, or some other metal. The power of chlorine to expel it from its compounds, is made use of in manufacturing bromine. This sub- stance is used in photography, but is otherwise of little general interest. Although widely distributed, it ex- ists in nature, in comparatively small quantities. Bro- mine vapors have the effect of imparting to starch a beautiful orange color. FLUORINE. '^What is said 380. Fluorine is yellowish-brown gas, of fluorine? O f stron g odor, somewhat similar to that of chlorine. It is one of the elements of the beautiful mineral, fluor spar. It is prepared from the fluoride of potassium, by means of the galvanic current. Its isola- tion has been attended with great difficulties, and the SULPHUR. 159 gas is therefore imperfectly known. Its principal com- pounds, are hydrofluoric acid, and fluor spar, to be here- after described.* S.ULPHUR. 381. DESCRIPTION. Sulphur is a brittle W/iatissul- phur? Where yellow solid, burning with a peculiar odor, it occur? ma( j e familiar in the ignition of common friction matches. With the metals, it forms sulphides or sulphurets. In Sicily, and certain other volcanic regions, it occurs in beautiful, yellow crystals. Gyp- sum, and iron pyrites, or fools gold, represent the two principal classes of minerals that contain it. It also enters in small proportion into the composition of all animal and vegetable substances. It is the sulphur in eggs that blackens the silver spoon with which they are eaten. 382. PREPARATION. In preparing com- Describe the manufacture mercial sulphur, the impure material of of suphur ? vo i can i c regions, is highly heated, and thus made to fly off as vapor, leaving its earthy impurities behind. The vapors are condensed as flowers of sulphur. The process by which a solid is thus vap- orized, and re-converted into a solid, is called sublima- tion. Native sulphur may also be partially purified by simple fusion. Its earthy impurities having settled, it is poured off into moulds, and thus converted into roll brimstone. * Many compounds of chlorine, bromine, iodine and fluorine, with each other and with oxygen, are known to the chemist,/but they are without interest to the general student V 160 METTALLOIDS. 383. SUBLIMATION OF SULPHUR. SlZlf The sublimation of sulphur may be of sulphur be shown by heating a small bit of the \ shown ? substance in a test-tube. Flowers of sulphur will deposit in the upper portion of the tube. 384. COMBUSTION OF SULPHUR.- What is said ,__ . . of the com- Melt some flowers of sulphur upon ^afphur{ the 6nd f a wire wound with thread, and hang them after ignition in a vial of oxygen gas. The oxygen gas com- bines with the sulphur, forming a new com- pound gas, called sulphurous acid. A bril- liant blue flame accompanies the combina- tion. It thus appears that acids may be gase- ous, as well as liquid. The acidity may be proved, as usual, by blue litmus paper. 385. BLEACHING BY SULPHUR. Intro- Descnbe the process of duce a red rose, or other flower, into a vial mTans n of b L. filled with sulphurous acid. It will soon phur ? lose its color. Wash it with dilute sulphu- ric acid, and the color re-appears This experiment may also be made in a bottle, in which sulphur has been burned in common air. 386. EXPLANATION. Sulphurous acid Why docs sul- -, , , , , phurous acid lorms a white compound with the red color- bieach? - n g matter O f the rose ft mav seem incom- prehensible, that a colorless gas, and red coloring matter should unite to form white, and it would be so, were the case one of mere mixture. But it is an SULPHUR. 161 instance of chemical combination, in which as is often the case the properties of the constituents entirely /dis- appear. When sulphuric acid is afterward used, the co- lor re-appears, because the stronger acid has expelled the weaker, and has itself no inclination to form with the coloring matter a similar combination. 387. STRAW BLEACHING. The bleach- proccL If ie m f straw goods is always effected by straw bleach- su lphurous acid. They are first moistened, and then exposed to the fumes of burning sulphur. An inverted barrel is often made to serve the purpose of a bleaching chamber. Articles thus bleached by sulphurous acid, after a time, regain their color. This is not the case in chlorine bleaching, be- cause the coloring matter is not merely changed, but destroyed. The agent is not applicable to straw, on account of a faint brown tinge which it imparts to the material. 388. COPYING MEDAL- ? LIONS. Sulphur melts, medallions by readily, by application of sulphur? *\ , :*. heat. At a higher temper- ature, it thickens again. Still further heating, makes it again fluid. In this second period of fluidity, it has the remarkable property of assuming a waxy consistence, on being poured into water. In this condition, it is used for copying seals, coins, and medals. The copy acquires, in a few hours, the original hardness of sulphur. The plastic material may be obtained in the form of elastic 162 METTALLOIDS. strings, by pouring molten sulphur from a test-tube, into cold water. 389. SULPHUR CRYSTALS. Sulphur may How may crys- talsof sul- be obtained in a crystalline form, by melt- *tained? * n ^ * n a P^P 6 bowl, at a gentle heat, and then allowing it to cool. A crust soon forms on the top, which is broken, and a portion of the liquid sulphur below, poured out. On breaking the pipe, it. is found filled with crystals, shooting across the interior, from the encrusted walls. SULPHURIC ACID. Describe sul- 390. DESCRIPTION. Sulphuric acid is a phuric acid. colorless, oily fluid, of intensely acid taste, known in commerce as oil of vitriol. It is composed of sulphur and oxygen, in the proportion of one atom of the former, to three of the latter. It also contains Water, with which it is chemically combined. As it is among the most important of all chemical products, the process of its manufacture will be given with some detail. 391. PREPARATION. Sulphuric acid may How may sul- . . phuric acid be be made directly, from its elements, by ig- prepai nithig a mixture of air and vapor of sul- phur, with a red-hot 'iron. In quantity, it is always made from sulphurous acid, by imparting to the latter additional oxygen. Take a bottle in which sulphur has been burned, and which, therefore, contains sulphur- ous acid, and hold in it, for a short time, a rod or stick ,. SULPHURIC ACID. 163 moistened with nitric acid. The gaseous sulphurous acid obtains oxygen from the nitric acid, which is rich in this element, and very liberal of it, and thereby be- comes sulphuric acid. A little water, previously placed in the bottom of the vial, absorbs the acid thus formed. To acidify the water to any considerable extent, it will be necessary to burn sulphur, and introduce the moistened rod repeatedly. That the acid is not the sulphu- rous or the nitric acid, employed in the pro- cess, may be proved by using it to make hy- drogen gas. 392. REMARK. The red fumes which What causes . the red fumes nil the vial m the last experiment, consist of the changed nitric acid, (nitric oxide,) which has just given up part of its oxy- gen, and is now resuming part of it from the air. It thereby becomes a third substance, of a red color, to be again mentioned in the section on nitric acid. 393. MANUFACTURE OF OIL OF VITRIOL. Explain how . sulphuric acid The method of the production of oil lurcd^ ^ v i tr il on a l ar ge scale, is essentially the same as that above given. Fumes of burning sulphur, and vapor of nitric acid, with air and steam, are introduced into a leaden chamber, when the process proceeds, as before described. 394. Comparatively little nitric acid is Why is but little nitric needed in the process, for it is found that acid required wn jj e ft y^ids oxygen to the sulphurous fumes, the changed acid greedily seizes oxygen from the air of the chamber, arid imparts it again, to keep up 164 METALLOIDS. the process. The air is, therefore, the real oxidizer, while the changed nitric acid only acts to transfer it to the sulphurous fumes. Describe the 395. DESCRIPTION OF ACID CHAMBERS. acid chambers, rp ne fjg ure represents one form of the leaden chambers employed in the above manufac- ture. Connect- ed with them are a steam boiler and two furnaces, in one of which sulphur is burned, and converted into sulphurous acid. Over the sulphur is another vessel, containing the materials for making nitric acid, the formation of which commences as soon as the sulphur flame has imparted the requisite heat. The vapors thus produced, are mingled with air and steam in the leaden chamber. How they act together to produce sulphuric acid, has been already explained. The space is divided by a partition, in order that all the materials may be more thoroughly mixed, as they pass through the narrow opening below it. The acid, as it forms, dissolves in water which covers the bottom of the chamber, and is thus collected. Lead is used as a lining for the cham- bers, because the acid woul-d destroy almost any other material that might be employed. 396. The dilute acid obtained from the How is the chamber acid chambers, is concentrated first in leaden concentrated? vessels? and afterward) when it hag become strong enough to corrode the lead, in retorts of platinum. The metal platinum, being of about half the value of SULPHURIC ACID. 165 gold, the vessels in which the evaporation is carried on, are extremely expensive. Some manufactories de- liver tens of thousands of pounds of sulphuric acid per day. 397. COMPARATIVE STRENGTH OF SUL- Hov) is the strength of PHURIC ACID. SulphUHC acid JS the S shmvn? iC cid stron g est of a11 acids - This ma 7 be shown by bringing it to a direct 'trial of strength with other strong acids. If poured, for example, on nitrate of potassa, which is, as its name implies, a com- pound of nitric acid and potassa, it takes sole possession of the base, and expels the nitric acid in the form of vapor. It expels muriatic acid from its compounds in the same manner. This is the method by which nitric and muriatic acids are always obtained. Whatever they can accomplish when free, may therefore be traced back to the power of sulphuric acid, which gave them their liberty. The latter is the king among the acids, who accomplishes indirectly, what he cannot ef- fect in person. The solution of the noble metals by aqua regia is one among these indirect results. 398. Sulphuric acid is volatile at high Is it strongest at high tenipe- temperatures. Phosphoric, and other non- volatile acids, are, therefore, under certain circumstances, superior to it. This is illustrated in cer- tain crucible operations, where compounds containing sulphuric acid are heated with such acids. The sul- phuric acid is then easily dispossessed, and compelled to take refuge in flight. What is the 399. ACTION OF SULPHURIC ACID ON action of sul- METALS . Sulphuric acid attacks all metals, jjliunc acid on metals. with the exception of platinum and gold. 166 METALLOIDS. Even the dilute acid acts on all the metals hereafter named, as far as manganese. 400. The action of the dilute acid may Illustrate the . . action of the be illustrated, by placing a few bits of zinc dilute acid. in a tumbler? with a i itt i e waterj an d ad- ding a small portion of oil of vitriol. The metal dis- solves with the evolution of hydrogen gas. The rea- son of the evolution of this gas has been already given. 401. The action of the strong acid may Illustrate the J action of the be illustrated, by heating a little copper, strong acid. w{ih Q[{ of vitriol> in a test-tube. The metal dissolves with the evolution of sulphurous acid fumes. The reason of the appearance of sulphurous acid will be given in the next section. 402. AFFINITY FOR WATER. The affin- liffinlt *ofwl- ity f sulphuric acid for water is so strong phurtc add that it lays hold on every particle of the for water? . / f , invisible aqueous vapor of the atmosphere. It finds it, in what seems the driest air ; and every par- ticle which it catches, it retains. It grows in bulk by what it thus drinks, as will be seen if a little oil of vitriol is left exposed to the air, for a few days, in an open vessel. It is sometimes necessary, in chemical operations, to free gases from all the aqueous vapor which is mixed with them. This is done completely, by causing them to bubble through oil of vitriol, and again collecting them. 403. HEAT BY DILUTION. When sul- What takes . place whensui- phuric acid and water are mixed, conden- U sat i n ta ^ es place, accompanied by eleva- tion of temperature. Fiftv cubic inches of SULPHUROUS ACID. 167 sulphuric acid, and fifty cubic inches of water, when mixed, do not fill a vessel of the capacity of one hun- dred cubic inches, but fall about three inches short. Condensation has, therefore, taken place to the amount of three inches. Heat is, as it were, pressed out in such cases, as explained in the early part of this work. 404. WOOD CHARRED BY SULPHURIC Why does sul- phuric acid ACID. Wood dipped in oil of vitriol is soon charred. Wood is composed of car- bon, hydrogen, and oxygen. The last two together form water. The affinity of sulphuric acid for water has been mentioned above. The acid and the wood being in contact, it would seem that the hydrogen and the oxygen of the latter agree to combine and satisfy this demand. The carbon being at the same time isolated, appears in its natural black color. Sulphuric acid ex- erts a similar action on other vegetable substances. 405. IMPORTANT USES. Sulphuric acid What are the . uses of sul- is largely employed for dissolving indigo, pkuric add? for use in dyeing and calico p r i nt i n g . a i so? for converting common salt into sulphate of soda, as a preparatory step to the manufacture of carbonate of soda. It is also essential in the manufacture of super- phosphate of lime, an article now so extensively used in agriculture. Nitric and muriatic acids are pro- duced through its agency from nitre and common salt. SULPHUROUS ACID. What is sul- 406. DESCRIPTION. Sulphurous acid is phurous acid? a gaSj having the smell of a burning match. 168 METALLOIDS. It is composed of sulphur and oxygen, in the proportion of one atom of the former to two of the latter. The ter- mination " ous" indicates, as in other cases, a smaller proportion of oxygen than is contained in some other acid composed of the same elements. 407. PREPARATION. It has already been How is sul- phurous acid shown that this acid may be prepared, by prepared? burning sulphur in oxygen. Another, and better method, is to heat, oil of vitriol, with bits of cop- per. The oil of vitriol is thus deprived of part of its oxygen, and converted into sulphurous acid. The process may be con- ducted in a test-tube. By lead- ing the gas through a smaller tube, into a vial partly filled with water, a solution of sulphurous acid may be obtained, possessed of the same bleaching and other properties as the gas itself. When the evolu- tion of the gas commences, the heat of the lamp is no longer required. Explain the 408. EXPLANATION. Copper has a very process. strong affinity for oxygen, and takes it from the oil of vitriol, which possesses it in large pro- portion. The oil of vitriol, thus deprived of part of its oxygen, is converted into sulphurous acid gas. 409. USE IN PRESERVING WINES. Slll- W ny ^.? sul- phurous acid phurous acid, in small quantities, is some- 7eTtowlnes d ? times added to wine > to prevent its sour- ing. This change is owing to the absorp- tion of oxygen from the air. Sulphurous acid is a NITROGEN. 169 substance possessed of an excessive appetite, or affinity, for oxygen. A small portion of it in a wine cask, will seize on what little oxygen finds admission, and so prevent the deterioration of the wine. It destroys it- self in this act of protection, and is converted into sul- puric acid. How is sul- ^' ^ SE 1N SUGAR MANUFACTURING. phurous acid The oxygen of the air so modifies the employed in . . ~ ,, .. . . , , manufactur- juice of the sugar-cane, that it cannot be ing sugar ? made to yield its due proportion of sugar. Sulphurous acid, by appropriating the oxygen to itself, prevents this effect, and is said to double the product. It is generally used in the form of its lime compound, called sulphite of lime. The objection to its use con- sists in the slight sulphurous taste which it imparts to the sugar. But this is said to be removed by clarifi- cation, at a loss of ten per cent., leaving still a large gain from the employment of the process. The bleach- ing effects of sulphurous acid have already been illus- trated. NITROGEN. 411. DESCRIPTION. Nitrogen is a trans- trogen ? parent gas, without taste or odor. It forms Where is it about f our _fif t h s of the air we breathe. It found ? occurs also in combination with other ele- ments in a solid form. One-fifth of the weight of the dried flesh of animals is nitrogen. It also enters into the composition of nitre and other salts. 170 METALLOIDS. Howisnitro- ^- PREPARATION. Nitrogen is pre- gen prepared? p are d from ordinary air by removing its oxygen. For this purpose a small portion of phospho- rus is floated on a slice of cork upon water, and then kindled, and a vial inverted over it. As it burns, it abstracts the oxygen ; the water rises to take its place, and what is left of the air is nitrogen. The cork should be a little hol- lowed out, and chalk scraped into the cavity. Water must be poured into the saucer as the first portion rises into the bottle. The bottle is then cooled, either by water or long standing, and co-rked while yet inverted It is then shaken, to wash the gas. A piece of phosphorus, of the size of a large pea, is sufficient for the preparation of half a pint of gas. Explain the 413. EXPLANATION. The burning phos- process. phorus selects all of the oxygen atoms in the air, and, by combining with them, converts them into solid particles of a certain oxide of phosphorus, called phosphoric acid. These particles at first ap- pear as a white smoke, and are afterward dissolved in the water. 414. NITROGEN EXTINGUISHES FLAME. If Does nitrogen extinguish a burning taper be lowered into the bottle of flame? y. n j trO g enj as above prepared, it will be im- mediately extinguished. Flame is the brightness which accompanies active chemical combination, but here is nothing to combine. Nitrogen is a sloth among the elements, possessing no degree of chemical activity. THE ATMOSPHERE. 171 415. PRINCIPAL OFFICE OF NITROGEN.- What is the principal of- The principal office of the nitrogen of the ficeofnitro- air is to dilute its oxygen. The latter, if pure, would soon consume our bodies, as it hastens the combustion of a taper, or other combus- tible. 416. THE ATMOSPHERE. The air we What is the composition breathe, and which, to the depth of fifty of the air? miles or more; f orms t h e crystal shell, or envelope of the globe we inhabit, is a mixture of nitro- gen and oxygen gases, with aqueous vapor. It also contains small and varying proportions of carbonic acid, and ammonia. 417. PROOF THAT AIR is A MIXTURE. How is it proved to be a That it is a mixture, and not a chemical compound, is sufficiently evident from the fact that it possesses no new and peculiar properties different from those of its constituents. It is further proved to be a mixture, from the fact that heat, which is the usual attendant on chemical combination, is never occasioned when air is artificially produced by the ad- mixture of its constituents. yse 418. USE OF CARBONIC ACID AND AMMONIA served by IN THE AIR Carbonic acid and ammonia. its carbonic acid and aw although present in the air in extremely small quantity, subserve the most impor- tant purposes in administering to the growth of plants. They constitute the gaseous food of all forms of vege- table life, as will be more fully explained in succeeding chapters of this work. 172 METALLOIDS. 419. ANALYSIS OF THE AIR. The me- proportion of thod b Y which the relative amount of ox- nitrogen deter- ygen and nitrogen in the air is determined has been already given. On burning phos- phorus under a glass jar, as there described, the water is found to rise and fill a little more than one-fifth of the vessel, thereby indica- ting that one-fifth of the air which it contained was oxygen gas. The remaining fths is nearly all nitro- gen. In accurate experiments, a graduated tube is employed, instead of a jar or tumbler. It is not es- sential that the phosphorus should be ignited. With- out ignition, it will gradually combine with all the oxygen, and remove it from the air contained in the tube. 420. In order to determine the amount How is the . . amount of car- of aqueous vapor and carbonic acid in the atmosphere, a gallon, or other measured nia deter- quantity of air, is drawn through tubes containing materials to absorb these sub- stances. This quantity is known by the increased weight of the tubes after the experiment is completed. 421. THE APPARATUS DESCRIBED. The Describe the . f . apparatus apparatus used in the experiment is repre- wfedinthis sen ted in the last figure. It consists of a analysis. bottle, or small cask, filled with water, and provided with a cock below. The cock is turned, and as the water no ws out, air flows in through the tube to take its place. The quantity of air that has passed NITRIC ACID. 173 through the tubes is known by the quantity of water that has flowed out from the cask. The materials em- ployed in the tubes are pumice stone drenched with oil of vitriol, in the first, to absorb the water ; and caus- tic potassa, in the second, to retain the carbonic acid. The method for determining the amount of ammonia in the atmosphere is essentially the same, muriatic acid being used as the absorbant. 422. PROPORTIONAL COMPOSITION OF What are the proportions of THE AIR. The proportions of the four fousfttwnteof constituents of the air above mentioned, the atmo- as obtained by the method just described, are, about 21 per cent, of oxygen, 79 of nitrogen, arWth of carbonic acid, and t?4fofcrvtb of ammonia. The proportion of aqueous vapor is ex- tremely variable. That of carbonic acid and ammo- nia is also variable to a considerable extent. NITRIC ACID. What is nitric 423. DESCRIPTION. Nitric acid is a thin. acid? colorless, and intensely acid fluid. It cor- rodes metals instantaneously, with the evolution of deep red vapor. It is composed of nitrogen and oxygen, in the proportion of one atom of the former to five of the latter. It contains, in addition, water, with which it is chemically combined. It is possible to make it an- hydrous, or free from water, but such an acid is never used. How is nitric 424. PREPARATION. Nitric acid exists add prepared? m a dormant state in ordinary saltpetre. 174 METALLOIDS. Its affinities being entirely satisfied by the potassa with which it is combined in that substance, it lies there per- fectly inactive. Sulphuric acid being stronger, has the power of taking its base, and expelling the acid in the form of vapor. In or- der to collect and condense the acid fumes, the mixture may be made in a test-tube, the mouth of which opens into a vial or flask. It is necessary to keep the vial covered with porous paper or cloth, and to moisten it frequently in order to maintain its coolness. Wher e larger quantities are prepared, a retort and well-cooled receiver are employed, as represented in the Appendix. 425. OXIDATION OF METALS. If a little What effect has nitric acid nitric acid is poured upon a copper coin, placed in a capsule or saucer, the coin will immediately begin to dissolve. It is not, strictly speaking, the metal which dissolves. One portion of the acid first converts the metal into oxide, by giving it part of its own oxygen. It thereby destroys itself, while another portion of undecomposed acid dissolves the oxide which is formed. One portion, in reality, sacrifices itself to satisfy the appetite of the other. Most other metals are similarly acted on by nitric acid. What is nitric 426. NITRIC OXIDE.* The vapors which oxide? are gj ven off m the j ast experiment are * It will be observed that the term oxide is sometimes applied to compounds of the metalloids with oxygen. (See chap, iii., Inorg. Chem.) NITRIC ACID. 175 nitric oxide, changed by the air into which they rise. The nitric oxide is, so to speak, the fragment of nitric acid, which is left after three atoms of its oxygen are abstracted. Rising into the air, it combines with oxy- gen enough partly to supply the place of that it has just lost, and is thus converted into red fumes of per- oxide of nitrogen, containing four atoms of oxygen. This compound is also called hyponitric acid. Still another compound of nitrogen with oxygen is de- scribed in the section on nitrates. 427. Repeat the experiment of the last JJeecrioe ano- . >--, ther method of paragraph, placing the coin and acid in a rld d fum/ s Ule sma11 vial or test - tube > instead of a saucer, and collect the nitric oxide produced, as shown in the figure. The collec- tion should not be commenced until a colorless gas is produced. It will be best to fill the vial to only two-thirds of its capa- city. Then lift it from the bowl, and let the remaining water run out. The air will immediately rush in, and change the colorless ni- tric oxide to red vapors of the peroxide of nitrogen. How does ni- 428. OXIDATION WITHOUT SOLUTION. tnc acid act Nitric acid oxidizes tin and antimony, but on tin { J ' does not dissolve them. The experiment will be best made with tin-foil. After the action of the acid, it will be found converted into a white pow- der. Gold and platinum are neither dissolved nor ox- idized by nitric acid. 176 METALLOIDS. 429. COMBUSTION BY NITRIC ACID. As How may com- bustion be nitric acid contains much oxygen, combus- effectedby ni- j. j on ^y fa means would seem to be a probable result. To prove that it has this effect, boil strong nitric acid in a test-tube, the mouth of which is filled with hair. As the vapors pass through they will cause it to smoke, and, if the acid is sufficiently strong, produce ignition. 430. COMBUSTION OF Describe the . experiment Phosphorus is readily withphospho- ignited by throwing it upon nitric acid. If the acid is not very strong, it must be previously heated. Particles of phosphorus, scarcely larger than mustard seed, should be used in this experiment. PHOSPHORUS.- Whatisphos phorus ? Where does i occur? phosphate portion. flow is it pre- pared ? PHOSPHORUS. 431. DESCRIPTION. Phosphorus is a wax-like, and nearly colorless, solid, read- t ily ignited by heat or friction.* 1 It forms part of the mineral apatite, which is a of lime. Bones also contain it in large pro- It is never found umcombined. 432. PREPARATION. Phosphorus is made from bones. These are composed, * When phosphorus is cut, it should always be under water, and every particle not used should be immediately returned to a bottle containing water. PHOSPHORUS. 177 principally, of gelatine and phosphate of lime. The individual constituents are gelatine, lime, oxygen, and phosphorus. To obtain the phosphorus, all the rest are to be first removed. Fire removes the gelatine, oil of vitriol the lime, and charcoal, the oxygen. Give the com- 433. The bones, having been previously piete process, burned, the ground ash is mixed with di- lute sulphuric acid and water, and, after several hours, filtered. Sulphuric acid unites with the lime, forming an insoluble sulphate, and at the same time sets the phosphoric acid at liberty, The solution containing phosphoric acid is then mixed with charcoal, and heated in an earthen or iron retort. The carbon takes the oxygen, and passes out of the retort with it, as gaseous carbonic oxide. The phosphorus which is left, being vaporized by the heat, is also expelled, but is reconverted into solid phosphorus by the cold water into which it passes. The figure will give some idea of the arrangement. The neck of the earthen retort passes into a copper tube, which leads into water. The gas produced by the process bubbles through the water and escapes, while the phosphorus is hardened by it, and remains. The mass thus obtained is melted under water, and run into moulds. 434. PHOSPHORESCENCE. This term is phorescence?~ applied to the luminous appearance of sea- water when agitated, and to other faint light, unaccompanied by perceptible heat. It is ob- served when an ordinary friction match is rubbed upon the hand in the dark. The light is owing to a slow 8* 178 METALLOIDS. combustion of phosphorous, which takes place without kindling. The product of the combustion, is a white powder, called phosphorous acid, which soon becomes liquid, by absorbing moisture from the air. 435. A HARMLESS FIRE. By agitating How may a . harmless fire phosphorus with ether, a small portion of be produced 9 the f ormer su bstance is dissolved. This solution, if rubbed upon the face and hands, makes them luminous, in the dark. This is another case of phosphorescence. A piece of phosphorous of the size of a pea is amply sufficient for the experiment. 436. COMBUSTION UNDER WATER. Phos- How may phosphorus be phorus may be burned under water, by the ^te??*** hel P of substances ricn in oxygen. Chlo- rate of potassa is such a substance. Place a few scales of this salt, and a bit of phospho- rous of the size of a pea, at the bottom of a wine glass previously filled with water. Par- tially fill the bowl of a pipe with oil of vitriol, and drop it in small portions on the mixture, bringing the pipe stem, each time, close to the bottom of the glass. As soon as the stronger acid is applied, chloric acid, containing much oxygen, is liberated and decomposed, and the phosphorus inflamed. A similar combustion of phosphorus, by means of nitric acid, has already been described. 437. FRICTION MATCHES. Ordinary What is said of friction phosphorus is too inflammable to be em- ployed in the manufacture of friction match- es. By heating it under carbonic acid for a long time, it becomes changed in color, and also less fusible and in- ARSENIC. 179 flammable. In this form of red phosphorus, it is used in the manufacture of friction matches. ARSENIC. 438. DESCRIPTION. Arsenic is a grey Why is arsen- / . ic introduced substance, of metallic lustre, and for this metalloids? reason, commonly classed among the met- als. On the other hand, in view of the compounds which it forms, and especially in view of the fact that its oxygen compounds are acids, and not oxides, it is more properly classed among the metal- loids. Its analogies to phosphorus are most striking, and it is for this reason here introduced, in immediate connection with that element. In what re 439. ANALOGIES TO PHOSPHORUS. Ar- spccts do pkos- sem ' c unites with oxygen in the same pro- phorus and . J ... arsenic resem- portions as phosphorus, forming similar acids. These in turn form salts resembling each other most perfectly, in external appearance and in crystalline form. It also combines with three atoms of hydrogen, to form arseniuretted hydrogen, a gas analogous to phosphuretted hydrogen, to be hereafter described. Of the two principal oxygen compounds of phosphorus, the higher, or phosphoric acid, is the more important, and was therefore more particularly consid- ered. On the other hand, the lower orarsenious acid, is the more important of the acids of arsenic. How is arsenic 440. PREPARATION. Metallic arsenic is prepared ? found native. It may also be prepared 180 METALLOIDS. from arsenious acid, by heating with a large proportion of carbon, as in the Case of phosphorus, before described. Beside mixing with carbon, it is best, also, to cover with the same material, and heat from above, downwards. The metal passes off as vapor, and condenses in the cooler part of the tube, or other vessel in which the experiment is per- formed, as a steel grey incrustation. ARSENIOUS ACID. 441. RATSBANE. The ordinary white What are the , J properties of arsenic of the shops, also known as rats- arscnious bane, is a white and nearly insoluble sub- stance, possessed of a slightly sweetish taste. It is not properly arsenic, but arsenious acid. It contains three atoms of oxygen, to one of metal. Al- though sweet, it is called an acid, because it possesses the chemical characteristic of an acid, viz : the ca- pacity of uniting with bases to form salts. Howisitpre- 442. PREPARATION. Arsenious acid is pared? prepared from metallic sulphurets, many of which contain a certain proportion of arsenic, by roasting in the air, and thus burning out their arsenic, in the form of arsenious acid. The fumes are condensed in high chimneys, from which the incrustation of the solid acid is afterward removed. Mispickel, which is a double sulphuret of iron and arsenic, and certain ores of nickel and cobalt, are much employed for the production of arsenious acid. ARSENIC. 181 443. POISONOUS PROPERTIES OF ARSENIC. What is said of arsenic as White arsenic or arsenious acid is a fearful a poison? poison, and more frequently employed than any other substance, for the destruction of life. But its detection, and the entire demonstration of its pres- ence in the body, after death, or in materials which have previously been ejected from the stomach, is cer- tain. 444. No one but a professional chemist What is said of its detec- should undertake such an investigation, tijon ? involving, as it does, the issues of life and death. No one else, indeed, can, be qualified to guard, with certainty, against the presence of arsenic in the chemicals which are used in the process, or in other res- pects, to bring the inquiry to that point of absolute de- monstration, which is always required in judicial inves- tigations. But the methods of detection, being simple, and a subject of interesting and instructive experiment to the student, will be briefly described in the paragraphs which follow. Many other compounds of arsenic, be- side arsenious acid, are highly poisonous. How arsenic i* ^45. DETECTION OF ARSENIC. If a few detected? drops of a solution of chloride of arsenic* be added to the liquid from which hydrogen is being evolved from a vial, by the ordinary process, the nascent hydrogen decomposes the chloride of arsenic and carries off the metal, in the form of a gas. On sub- sequently kindling the hydrogen jet, and bringing * Such a solution is prepared, by dissolving white arsenic in hydro- chloric acid. 182 METALLOIDS. down upon it a cold white surface, like that of a plate or saucer, the metal is again given up, and reveals itself as a brownish black and high- ly lustrous stain. The process may be con- ducted in an ordinary vial, to which a pipe stem, or glass tube has been fitted, by the method before described. The above method of detection is called Marsh's test. In a case of suspected murder by poison, the moment of the in- troduction of the pure porcelain into the flame, be- comes one of the most intense interest. The gather- ing stain, is at once the emblem of guilt and sentence of ignominious death. 446. EXPLANATION. The decomposi- Sxplainthe t j on O f arsen i ous ac {d by hydrogen, in the above process. J J above experiment, and the reason of the deposition of the metallic mirror, still remains to be ex- plained. The nascent hydrogen affects the decompo- sition of the acid, by a double action ; on the one hand uniting with the metal to form arseniuretted hydrogen, which escapes, and on the other hand, with its chlorine to form hydrochloric acid, which remains behind. The mirror of metal is deposited upon the plate or saucer, because the introduction of the cold body into the flame, so lowers its temperature that the metal itself can- not burn. If the jet of gas is left to burn without in- terference, both of its constituents are consumed to- gether, and the flame assumes a blue color, from the presence of the arsenic. ARSENIC. 183 How are ar- ' DISTINCTION BETWEEN ARSENIC AND tenicandan- ANTIMONY STAINS. If in testing for arsen- Smguish i c > by the method above described, a metallic cd - spot is obtained, the evidence of the pres- ence of arsenic is not entirely conclusive. A solution of antimony, if substituted for arsenic in the experi- ment, will give rise to the production of somewhat sim- ilar stains. But the experimenter will find, on com- paring the two kinds of spots, that they are of quite different appearance. Those of antimony are of deep- er black, and fainter lustre. Again, those of arsenic are much more readily removed by heat. " Chloride of soda," is a still more conclusive means of distinguish- ing them. A solution of this substance will dissolve the arsenic stains, while it leaves those of antimony unaffected. The " chloride of soda," to be used in the experiment, is prepared by adding an excess of car- bonate of soda, to a solution of " chloride of lime," and then filtering the liquid. 448. ADDITIONAL TESTS FOR ARSENIC. Mention some . .. , additional A second test has already been given in l^ t c s / or arse ' the paragraph on the preparation of me- tallic arsenic, to which the student is re- ferred. The formation of a yellow precipitate, on the addition of hydro-sulphuric acid to a solution, also renders it highly probable that arsenic is present. If on drying the precipitate, and heating it with a mixture of cyanide of potassium and carbonate of soda, a metallic mirror is obtained, the inference of the pres- ence of arsenic is confirmed. The process is to be conducted as directed in paragraph 440. In this exper- 184 METALLOIDS. iment, the cyanide of potassium has the effect of retain- ing the sulphur, while it allows the volatile arsenic to pass and deposit above. 449. Still another evidence of the pres- What is said of the garlic ence of arsenic, is afforded in the charac- teristic garlic odor which is emitted by the flame produced by burning arsenic, in the experi- ment previously described, called Marsh's test. The same odor is also obtained on sprinkling a little ar- senious acid upon burning charcoal. Mention the 450. PREPARATIONS FOR THE ARSENIC preparations TEST> Before proceeding with the che- for the ar- senic test? mical experiments for the detection of ar- senic, some preliminary labor is com- monly required, to bring the material to be tested into proper form. It com- monly consists of matters which have been ejected from the stomach, or of the contents of the stomach itself. If the student wishes to begin at this point, in his experi- ments, he may add a small portion of arsenic to some bread and water, and proceed with this paste, in his investigation. This mixture is to be diluted with water, and saturated with chlorine, as in the process for preparing a solution of this gas. Chlorine has the effect of destroying a certain portion of the organic matter, and rendering the rest floculent, so that the liquid may be easily separated from it by filtration. It also brings the arsenic perfectly into solution, as a chloride. This solution is then filtered, and treated as directed in the preceding paragraphs. CARBON. 185 What is the ^^* A NTIDOTE TO ARSENIC. The hy- antidotefor drated sesquoxide of iron is regarded as the best antidote to arsenic. (See Oxides.) Its action depends on the formation of a compound, with the poison in the stomach, which is insoluble, and therefore inactive. Milk, sugar, and white of eggs, are also given with advantage, as in most other cases of poisoning. 452. ARSENIC EATERS OF AUSTRIA. What is said _ . . ., . of the arsenic In the mountainous portions of Austria, tria r ?^ AuS ~ bordering on Hungary, the peasantry are given to the strange habit of eating arse- nic. It is said to impart a fresh, healthy appearance to the skin, and also to make respiration freer when as- cending mountains. Those who indulge in its use commence with half a grain, and gradually increase the dose to four grains. If this habit is regularly in- dulged, its injurious effects are said to be long retarded. But as soon as the dose is suspended, the symptoms of poisoning by arsenic immediately manifest themselves. CARBON. 453. DESCRIPTION. Carbon in the form Describe the . different of coal, is a black, brittle, solid. As forms of car- pi umDa go, and coke, it is grey, with me- tallic lustre ; as the diamond, it is trans- parent, and the hardest of known substan- ces. Plumbago is commonly called black lead, but it contains no lead whatever. The figure in the margin represents the more common crystalline form of the diamond. 186 METALLOIDS. 454. OCCURRENCE. In the form of bi- carbon occur? tuminous and anthracite coals, carbon ex- ists in immense quantities, buried in the earth, in various countries ; as graphite, or plumbago, it is also quite a common mineral ; as the diamond, it is the rarest of all gems. It is one of the elements in limestones, marbles and chalk, which are all carbonate of lime. It forms nearly one half of all dried veget- able matter, and more than half of all dried animal matter. One two-thousandth of the air, also, is car- bonic acid, of which carbon is a constituent. 455. CHARCOAL. The Illustrate the preparation preparation of charcoal, one of charcoal. Qf the forms Qf carboilj may be illustrated by heating a small por- tion of wood or cork, in a test-tube. The other constituents of the wood, and part of the carbon, are converted into water, gases, and tan, and the larg- est part of the carbon ramains behind, in the form of charcoal. 456. PREPARATION. In quantity, it is coal made? commonly made by burning wood in large heaps, previously covered with earth and sod. It is necessary to admit a little air, through open- ings in the heap, to maintain a partial combustion. If too much air is admitted, the wood is entirely consumed, and no charcoal is produced. Coke is made from bituminous coal, by a similar process, and is also obtained as a residue in the manufacture of coal gas. CARBON. 187 457. LAMP BLACK. Lamp black, still an- other form of carbon, is made by conducting the smoke of rosiri into chambers, construct- ed for the purpose. It consists of unburned particles of carbon. It is used, extensively, in making paint. Bone black is made by heating bones in closed vessels. It is a sort of charcoal produced from the gelatine of the bones. 458. PURIFYING PROPERTIES OF CHAR- Dcscribe the purifying COAL. Charcoal absorbs gases, and retains Ztoal S f them iri its P ores ' in lar e qualities. Tainted meat, and musty grain, intimately mixed with it, become sweet. The charcoal has re- moved the unpleasant gases, proceeding from them. The absorbent power of charcoal may be illustrated, by holding a paper moistened with ammonia, in a vial, until the air within it has acquired a strong ammo- niacal odor. On afterward introducing some pow- dered charcoal, and shaking the vial, the odor will be removed. 459. PRESERVATIVE PROPERTIES OF Illustrate the , , preservative CHARCOAL. Charcoal may be used as a properties of preventive, as well as a corrective of de- charcoal f cay. Posts, if charred at the bottom, be- fore they are set, are rendered more durable. Water will keep longer in charred vessels than in those which have not thus been prepared. The decay of meats and vegetables is retarded by packing them in charcoal. Charcoal is itself, one of the most unchangeable of sub- stances. Wheat and rye charred at Herculaneum 1800 years ago, still retain their perfect shape. 188 METALLOIDS. 460. DECOLORIZING EFFECTS OF CHAR- Describe its decolorizing COAL. Charcoal has, also, the effect of power. removing coloring matters, and bitter and astringent flavors from liquids. Thus, ale and porter lose both color and fla- vor by being filtered through sugar. Sugar refiners take advantage of this property, in decolorizing their brown syrups. Animal charcoal, or bone black, is best adapted to these uses. As an illustration of the decolorizing effect of char- coal, let water colored with a few drops of ink, be filtered through bone black. The color will be found to disappear, in the process. 461. COMBUSTION OF CARBON. All of of the . . bonic acid be One oi the most interesting of all chemical solidified? experiments, is the solidification of car- bonic acid. By combined cold and pres'sure, this trans- parent gas, which, under ordinary circumstances, is so 9 194 METALLOIDS. thin that the hand, passed through it, does not recog- nize its presence, can be converted into a solid snow. This is done by bringing into a strong iron cylinder, connected by a tube with a second similar receptacle, the material for making more of the gas than there is room for in the two vessels. The cylinders being closed, and the gas produced by the agitation of the materials, it is evident -that they must burst, or the gas must pack itself away in some more condensed form. The second vessel is surrounded by ice, and kept extremely cold, during the process. In this colder vessel, the gas assumes a liquid form. Being removed in this condition, one portion of the liquid evaporates so rapidly as to freeze the rest. An explosive expan- sion of the liquid into gas would naturally be antici- pated, but this does not occur. The materials used in the process are sulphuric acid and carbonate of soda. 478. CARBONIC OXIDE. When carbonic How is car- -i bonic oxide acid is passed through hot coals, it loses half of its oxygen, and becomes carbonic oxide. This takes place in coal fires. The coal in the lower part of the grate, where air is plenty, receives its full supply of oxygen, and becomes car- bonic acid. The hot coals above, where the supply of air is limited, take half of the oxygen from the carbonic acid, and reduce it to this oxide, convert- ing themselves partially into carbonic oxide at the same time. The new gas passes on to the top of the fire, and there, where air is again abundant, it burns with a blue flame, and reconverts itself into carbonic acid. This gas is much more poisonous than carbonic CARBONIC OXIDE. 195 acid, and is one source of the danger which arises from open fires in close rooms. One-two-hundredth of it makes the air, if inhaled for any considerable time, a fatal poison. 479. COMBUSTION OF CARBONIC OXIDE. How is car- ionic oxide For small experiments, the gas is best pre- best prepared? ^^ by coyermg ft half tea -spOOnful of oxalic acid* with oil of vitriol, and heating them to- gether in a test-tube. The gas, on being kindled at the mouth of the tube, burns with a beautiful blue flame. The experiment is re-ndered more striking, by producing a jet, as represented in the figure. The gas thus obtained is really a mixture of carbonic oxide with carbonic acid, but the admixture does not mate- rially affect the experiment. 480. EXPLANATION. Each molecule of Explain the . formation of oxalic acid contains carbon, oxygen, and carbonic oxide. hydrogerij in the proportion to form one molecule each, of water, carbonic oxide, and carbonic acid. Through the agency of sulphuric acid, this de- composition is accomplished. The water remains with the acid while the gases are evolved. 481. IT PRODUCES METALS FROM OXIDES. effect on me- With the help of a high temperature, car- talhc oxides? bon j c ox [^ e takes oxygen from oxides, and converts them into metals. It contains oxygen * This acid has the appearance of a salt, and is poisonous. 196 METALLOIDS. already, but its chemical appetite is only half satisfied with that element. It is this gas, produced in the fire, as before described, which converts iron ores into metal, in the smelting furnace. It is itself converted into car- bonic acid at the same time. SILICON. What is sili- 482. DESCRIPTION. Silicon is a dark con ? gray substance, possessed of metallic lustre, but classed with the metalloids, because it resembles them in its compounds. It is also called silicium. It is prepared from silica, by the method hereafter de- scribed for the production of calcium from lime. 483. SILICIC ACID OR SILICA. Quartz *icaf ^ Sll ~ or roc ^ crvsta lj i s nearly pure silica. Sea- sand, opal, jasper, agate, cornelian, and chalcedony, are other forms of the same substance. It forms also part of a very abundant class of rocks, called silicates, and probably forms one-sixth of the mass of the earth. 484. SOLUBLE SILICA. Silica may be How can silica be made solu- dissolved in water, by first fusing it with a large proportion of potash. On then ad- ding acid, to neutralize the potash, the silica precipitates in the form a jelly. By this circuitous process, the most gritty sand is converted into a soft jelly. A sin- gular application of this rock-jelly, in the adulteration of butter, has recently been detected in England. Dis- solved silica also occurs in nature, and hardens into agates, onyx, and other precious stones. BORON. 197 485. PETRIFACTIONS. As wood wastes What is the cause of pet- away in certain sihcious waters, the par- rifaction? of the departing atoms, and thus copy the wood in stone. Such copies are called petrifactions. BORON. What is 60- 486. DESCRIPTION. Boron is a brown ron ? powder, never seen except in the chemists laboratory, and of no practical value. It occurs in nature, combined with other elements, as borax arid boracic acid. 487. BORACIC ACID. This acid is com- Hoio 'is bora- cic acid form- monly seen in the form of white pearly scales. It exhales with volcanic vapors which issue from the earth in Tuscany. These va- pors are condensed in water, and the solid acid is obtained by evaporating the solution. The acid is used like borax, as a flux. It is bitter, rather than sour, to the taste, but is called an acid because it forms salts. HYDROGEN. 488. DESCRIPTION AND OCCURRENCE. What is hy- i i AS drogen? Hydrogen is a colorless gas, about one fif- occurl dOCS U teenth aS heaV y aS the air ' li 1S f SUch extreme tenuity, that it may be blown through gold leaf, and kindled on the opposite side. One-ninth part of the ocean, and the same proportion of all water in existence, is hydrogen gas. It enters, 198 HYDROGEN. also, largely into the composition of all animal and vegetable matter, and forms the basis of most liquids. 489. PREPARATION. Introduce a few Describe the method of pre- bits of iron or zinc paring iff ^ ft yial one _ t hird filled with water. Add a tea- spoon-full or more of common sulphuric acid, and attach to the vial a bent tube or a clay pipe, as represented in the figure. The evolution of the gas immediately commences. The first portions, which contain an admixture of air, are allowed to escape ; the pipe-stem is then brought under the mouth of the vial, and the gas collected.* 590. EXPLANATION. Water is compos- Explain the formation of ed of oxygen and hydrogen gases. Each hydrogen? WQuld be & ag but for holds it in the liquid form. In the above process for preparing hydrogen, the zinc is, as it were, the ransom paid for its liberation. The oxygen combines with the zinc and the hydrogen escapes. 491. Pure water will not suffice in the What purpose is served by process. It must contain acid, to unite the acid? with the Qxide of zinc? as fagt ag f ormecl> The presence of an acid, for which the oxide has great affinity, seems to stimulate its formation. It may, * When a taper can be applied at the mouth of the pipe-stem without explosion, it may be certainly known that an unmixed gas is in pro- cess of evolution. A cloth should be thrown over the vial and this test made before commencing the collection. The connection of the ap- paratus in the above experiment is made with a paper stopper, formed on a bit of pipe-stem or glass tube. HYDROGEN. 199 indeed, be regarded as a general law, that the pres- ence of acids promotes the formation of oxides, and vice versa. 492. ANOTHER METHOD. Hydrogen Give another J method ofpre- may also be made, by passing steam through a heated gun-barrel, containing bits of iron. Bundles of knitting needles are commonly em- ployed for the purpose. The steam leaves its oxygen, combined with the iron, and escapes as hydrogen gas. 493. COMBUSTION OF HYDROGEN. Bring What i* pro- , , duced by the a dry, cold tumbler, over a burning jet of combustion of hydrogen. The vessel will soon become hydrogen f moistened on the interior. The water thus produced, is a result of the combination of hydro- gen with oxygen of the air. But for the cold surface, with which it is brought into contact, it would have escaped into the air as vapor. The composition of water was shown in Part 1., (> 277,) by galvanic de- composition. It is here demonstrated by combining its elements, and thus reproducing it. Water is also formed in the combustion of any substance containing hydrogen as one of its constituents. The above expe- riment may therefore be made with a lighted lamp or candle, as well as with the jet of pure hydrogen. 494. EXPLOSION OF MIXED OXYGEN AND How is an ex- plosive mix- HYDROGEN. Allow oxygen to flow into an turcprepared? i nverte( i ^ as directed in para- graph 330, until it is one-third full. Fill it up with hydrogen, collected as shown in Par. 489. Cork the vial under water. It is now filled with an explosive mixture, which may be fired by the 200 METALLOIDS. application of a taper. To secure against accident, the precaution should invariably be observed, of winding the vial with a towel, before the discharge. 495. EXPLANATION. The explosion re- Why does this mixture ex- suits from the fact that all of the hydrogen plode? ^ n t j ie v - a j k urns at oncej causing great heat, and sudden expansion of vapor. The combus- tion is thus simultaneous, because oxygen, the sup- porter of combustion, is present at every point. When, on the other hand, a jet of hydrogen is kindled, no explosion occurs, because the combination is gradual. Combustible hydrogen meets with oxygen in this case, only on the surface of the jet. n , -i th 496. THE HYDROGEN GUN. The expe- hydrogen gun, riment for the explosion of mixed hydro- and the me- -, . -, -, thodofcharg- gen and oxygen gases, may be made in a ing it. strong tin tube, provided with a vent near the closed end. Such a tube, about an inch in diame ter, and eight inches in length, is called the hydrogen gun. In loading it, the vent is stopped with wax, the tube filled with water, and the gases, previ- ously mixed in the right proportion, poured upward into it, as indicated in the figure. The gun, being thus loaded, is tightly corked, under water, and afterward fired at the vent. The explosion is sufficient to expel the cork with vio- lence, accompanied by a loud report. The vial from which the tube is loaded must not be too large, or it will not be practicable to turn it and pour upward, as desired. This difficulty HYDROGEN. 201 may also be obviated, by the substitution of a water- pail, for the bowl represented in the figure. 497. CHARGE OF AIR AND HYDROGEN. Describe an- other explosive As air contains uncombmed oxygen, a mixture of air and hydrogen also forms an explosive mixture. But, as air is only one-fifth oxy- gen, five times as much of it must be used ; in other words, five parts of air are required, for every two parts of hydrogen. To make the mixture, hydrogen may be led, as before, into an inverted vial, a little more than two-thirds full of air. The exact propor- tion is not essential in this, or any similar case of ex- plosive mixture. 498. A SIMPLER METHOD. A simpler Give a sim- ,-/., pier method method of loading the gun, or charging ^ adin9the the vial with the explosive mixture, is to invert it over a jet of hydrogen, as repre- sented in the figure. The pipe-stem, or tube, which conveys the gas, is previously wound with paper, till it occupies about two-thirds of the inner space of the gun. Escaping hydrogen fills the remainder. On withdrawing the tube, air enters to take its place, and the gun is thus charged with mixed air and hydrogen, in the right proportions. It is then corked and fired. This experiment may also be made with a test-tube, discharging it at the mouth. Explosions with mixed air and hydrogen, are, of course, less violent than where pure oxygen is used instead of the diluted oxy- gen of the air. Docs hydrogen 499. HYDROGEN WILL NOT SUPPORT COM- support com- ' % . J .: ; bustion? BTTSTION. Flame is extinguished in hy- 9* 202 METALLOIDS. drogen, as it would be in water. Re-charge the gas bottle, if necessary, and hang a second large-mouthed vial above it, as represented in the figure. Af- ter a few minutes, it may be presumed that the tipper vial is filled with hydrogen. Apply a lighted match to its mouth, and the gas will inflame, and continue to burn with a faint light. Introduce a second taper, as represent- ed in the figure. It will be kindled at the mouth of the bottle, and again extinguished above. The match is extinguished, because, a little abo've the mouth of the vial, there is no oxygen to sup- port the combustion of the carbon and hydrogen, of which it is composed. 500. HYDROGEN MADE BY THE METAL Describe the ./*,-, preparation SODIUM. Another very beautiful, but more expensive method of making hydrogen gas, is as follows. Fasten a piece of me- tallic sodium, of the size of a pep- per-corn, upon the end of a wire, and thrust it suddenly under the end of a test-tube filled with water, and held very near the surface, as represented in the figure. The metal melts as soon as it touches the water, and rises to the top of the tube. Hydrogen is immediately formed, and displaces the water, fill- ing the tube rapidly with the liberated gas. Explain the 501. EXPLANATION. Sufficient heat is process. evolved by the action of sodium on water to fuse it at once. The metal is lighter than water, and therefore rises to the top of the tuba. At this WATER. 203 point the chemical process begins. Sodium has the most intense affinity for oxygen, and therefore com- bines with this element of the water, setting its hydro- gen at liberty. No acid is required as in the case of zinc. Metallic potassium may also be used in this experiment. To avoid its ignition by contact with the water, it is to be wrapped in paper, and the twisted end of the wrapper used as a holder, with which to thrust it under the mouth of the tube. WATER. 502. COMPOSITION. Many important Of what is , J _ water com- properties of water have already been il- posed lustrated in the chapter on Vaporization. Others will be mentioned below. It is composed of oxygen and hydrogen, as has already been proved both by analysis and synthesis. These gases are condensed in combination to about a^Vo- of their original volume. It remains to show how the exact proportion in which they enter into the composition of water is as- certained. 503. FIRST METHOD OF PROOF. One Describe the . method by gal- method is to decompose water by the gal- vanic P rocess > and collect and weigh the gases obtained. The oxygen is found to weigh eight times as much as the hydrogen. Water is thus shown to be composed of eight parts of oxygen, by weight, to one part of hydrogen. In other words, nine pounds of water contain eight pounds of oxygen and one pound of hydrogen. 204 METALLOIDS. 504. SECOND METHOD. Another method Show how com- . -,->-> .position by is to measure the gases obtained by the 7al 9 culated y ^ same method of decomposition. Two from measure, measures of hydrogen are thus obtained for every single measure of oxygen. The chemist then pro- ceeds to calculate the relative weight. Knowing before- hand that hydrogen is the lighter gas, weighing but one-sixteenth as much as the same quantity of oxygen, he infers that the double volume obtained in the above experiment, weighs but one-eighth as much as the oxygen obtained in the same decomposition. The result of this indirect process is the same as that stated at the conclusion of the last paragraph. Describe the Q5- THIRD METHOD. A third method third method, consists in the reproduction of water from mixed hydrogen and oxygen, observing at the same time the quantities in which they combine. This may be readily effected in a test-tube. The gases being introduced into the tube in about the right proportion, and in small quantity, its extremity is then intensely heated. A slight explo- sion and combination of the gases is the result, and the water rises to take their place, mingling with the small quantity of water produced in the experiment. Any excess of either gas remains uncombined. Whether this surplus is oxygen or hydrogen, may be readily proved by methods previously given. This excess being sub- tracted from the quantity of the same gas originally used, shows the proportion in which the combina- tion has occurred. WATER. 205 506. The explosion may be avoided, How may the . ' explosion be and a gradual combination of the gases ef- fected, by evaporating a few drops of pla- tinum solution in the test-tube, and igniting the residue previous to the commencement of the above experi- ment. A ball of fine iron wire is then crowded into the end of the tube. The mixture of gases being finally introduced, the least touch of flame upon the end of the tube is sufficient to effect a gradual combi- nation. For an explanation of the agency of plati- num in the above experiment, the student is referred to the chapter on metals. The iron wire serves to prevent ignition, and consequent explosion, by appro- priating part of the heat produced by the combination of the gases. The form of the experiment last de- scribed, is the only one that can be recommended to the student. With the security against explosion which it affords, a test-tube filled with the mixed gases may be submitted to experiment. Where very accu- rate results are sought, the process must be conducted in a carefully graduated tube. By employing mercury instead of water, the water produced in the experiment may be seen. 507. FOURTH METHOD. Still another Give the meth- . . od by oxide of method is illustrated in the figure. It con- essential- ly, in the production of water from its elements as before ; furnishing, at the same time, the means of as- certaining the proportional weight of the gases, which have taken part in its formation. The tube most 206 METALLOIDS. distant from the aspirator* is first filled with oxide of copper, and then heated while a current of hydrogen gas is drawn over its surface. The heated hydrogen carries with it the oxygen of the copper, and passes into the second tube, as vapor of water. Here it is re- tained by potassa, or some substance of similar proper- ties. Both tubes are afterward weighed, and their gain or loss determined, by comparison with their weight before the commencement of the process. 508. The loss of weight in the one tube. How are the results calcu- expresses the weight of the oxygen which it has furnished for the formation of water ; the gain in the second tube, gives the weight of the water thus formed. The difference of the two, gives the weight of the hydrogen which has been appropriated in its passage, and now makes part of the newly formed water. For every nine grains of water thus produced, it is found that eight grains of oxygen, and one of hy- drogen have been consumed. Its precise composition is thus demonstated, by another and quite distinct pro- cess. What is said 5$> SOLUTION. Water is a very gene- of solution ? ra i so i ven t. The disappearance of salt, or sugar, in water, is an example.f Transparency is es- sential to a solution. Where the particles of a solid are distributed throughout a liquid, as when chalk is * A vessel employed, as in the present instance, to produce a current of air or gas, is called an aspirator. t Water also di-solves many gases. The ammonia of the shops is prepared by passing gaseous ammonia in water. WATER. 207 stirred with water, it is said to be diffused, instead of dissolved. The solvent action of water plays a most important part in nature, as will be seen in the conclu- ding chapter of this work. The subjects of solution, and precipitation, are more fully considered in the chapter on Salts. Wkatispre- ^10. PRECIPITATION. Where a substance dpitation ? which has been dissolved, is re-converted into a solid form, it is said to be precipitated. Thus, when air from the lungs is blown through a quill or pipe-stem into water, the lime combines with the carbonic acid from the lungs, and falls to the bottom of the vessel, in the form of solid particles of chalk. The solid thus produced, is called a precipitate. 511. FILTRATION. Filtration is What is filtra- tion, and hoio the separation of a precipitate is it effected? from the Uquid m which it j g con- tained. This is effected by throwing the mix- ture into a paper cone, which retains the solid, while the liquid passes through its pores. Such a filter is prepared by folding unsized paper into the shape of a quadrant, which is then opened, so as to form a cone, commonly supported in a glass funnel. It is possible, in small experiments to dispense with the funnel, as is done in the figure, and even to use ordi- nary newspaper, in the place of that especially pre- pared for the purpose. 208 METALLOIDS. 5 12. CRYSTALLIZATION. Dissolve Howmaycrys- ir i r i ^ ta^s of alum be hall a pound oi alum in a pint of obtained? boiling water, and hang a cotton cord in the vial. As the water cools, crystals will form on the thread. Bonnet wire may be bent into the shape of baskets, miniature ships, &c., and cov- ered, by this means, with a beautiful crystalliza- tion. Explain the 513. EXPLANATION. Hot water has for process. most substances greater solvent power than cold water. In the case of alum, for example, water slightly warmed, will dissolve twice as much as cold water. It follows, that as the hot water becomes cold, part of the alum must become solid again. In so doing, the particles, in obedience to their mutual at- traction, arrange themselves in crystals, as described in the first Chapter III. 514. SNOW CRYSTALS. Snow flakes are What is said 1-1 of snow crys- always either grouped or single crystals, and their form may often be distinctly seen with the naked eye. They are best observed by catching them upon a hat, or other dark object, and inspecting them in the open air. 515. CHEMICAL COMBINATIONS. Water What is said of the combi- unites with both bases and acids, to form nations of wa- hydrate ^ Thus? ^^ lim ^ ^ formg hy _ drate of lime ; with sulphuric acid, hy- drated sulphuric acid. Most of. the oxygen acids, in the form in which we employ them, contain water in a state of combination, and are therefore hydrated WATER. 209 acids. They may also be regarded as salts, of which oxide of hydrogen or water is the base. What is said 516. RELATIONS TO LIFE. Water forms, feiatioLfo US by far ' the S reater P art of a11 animal and life? vegetable matter, as will be more fully seen in the portion of this work which treats of or- ganic chemistry. To water, the leaf of the vegetable and the muscle of the animal, owe, in a great degree, their pliancy and freedom of motion. In view of these and other relations to life, the negative properties of water are not the least important. Had it taste, 01 odor, however exquisite, we should soon weary of them. And but for its mild and neutral character, it would irritate the delicate nerves and fibres which it bathes. 517. At very high temperatures the va- Whnt is the J effect of water por of water decomposes many minerals, rature k sf mp ' and ex P els stron g acids from their com- pounds. Under the stimulating influence of heat, this neutral liquid becomes a chemical agent of extreme energy. Such decompositions as are here referred to, are without doubt, constantly going on be- neath the surface of the earth. COMPOUNDS OF HYDROGEN, WITH CHLORINE, BROMINE, IODINE, FLUORINE, AND SULPHUR. Under this head are to be described a new series of acids, distinguished by the absence of oxygen from all which have hitherto been mentioned The molecules of each, like those of water, are composed of single atoms of their constituents. 210 METALLOIDS. They are all gaseous, and are sometimes called hy- dracids, from the hydrogen which enters into their com- position. Their salts are described in Chap. III. HYDROCHLORIC ACID. 518. DESCRIPTION. Hydrochloric acid * s a c l r l ess g as j fuming, by contact with add? What the air. It sometimes issues from volca- is said of its , . ,, . . ,, . , occurrence? noes, but is, tor the most part, an artificial product. Its solution in water is known as muriatic acid. 519. PREPARATION. Gaseous hydro- prepa'ratlon. chloric acid, may be produced, like water, by the direct combination of its elements. For this purpose, equal volumes of the two gases are mixed by candle-light, or in carefully covered bottles, and then exposed to the direct rays of the sun. The action of the light is so intense, that on throwing a bottle, thus filled, from shadow into sunlight, it imme- diately explodes. The explosion is a consequence of the energetic union of the two gases, under the influ- ence of the chemical rays of the sun. The acid pro- duced is at once dissipated in the air. Great caution should be used in this experiment, for even the diffused light of day has been known, in some instances, to occasion explosion. 520. ANOTHER METHOD. Hydrochloric Describe an- other mode of acid may also be made from common salt, preparing it ? which f um i s h es the chlorine, and ordinary hydrated sulphuric acid , which furnishes the hydrogen. HYDROCHLORIC ACID. 211 A tea-spoonfull of common salt is introduced into a test-tube, with about the same bulk of water. Half as much acid is added, then the mixture gently heated, and the acid gas led into water, as shown in the figure. Water absorbs, at ordi- nary temperatures, 480 times its own volume, of the gas. There is no occasion, for the purpose of experiment, to carry on the process till it is thus saturated. A few minutes will suffice to make an acid strong enough to dissolve zinc. Explain the 52 1. EXPLANATION. Hydrated sulphu- process. r j c %(,[& fr as always a strong tendency to form metallic salts. In this case it takes the metal, sodium, from the common salt, and thereby converts itself into sulphate of soda. At the same time it gives back hydrogen to the salt, in place of its lost sodium, converting it, by the exchange, into hydrochloric acid. The process just described, is the one always employed in the manufacture of hydrochloric acid. 522. ACTION OF HYDROCHLORIC ACID ON What metals ,, , . , -IT i does hydro- METALS. Hydrochloric acid dissolves tm> chloric dis- an( j a ]j o f fa e meta | s w hich precede it in solve ? the chapter upon metals. For tin, a hot and concentrated acid must be employed. 523. The solution depends on the fact On what does the solution that the metals take chlorine, from the depend? hydrochloric acid, thereby converting themselves into soluble chlorides. The hydrogen then 212 METALLOIDS. assumes the gaseous form, and escapes with lively ef- fervescence. An experiment may best be made with zinc, to which a little dilute acid is added. What is aqua 524. AQUA REGiA. On mixing muriatic regia? ac {^ w ith half of its bulk of strong hydro- chloric acid, aqua regia is produced ; so called, from its regal power over the noble metals. Gold and platinum, which are not effected by either acid alone, dissolve readily in aqua regia. The solvent power of aqua re- gia depends, as before explained, on the nascent chlo- rine which it supplies. 525. HYDROBROMIC AND HYDRIODTC ACIDS. ^lobromicand These acids are of interest to the chemist hydriodie only. They resemble hydrochloric acid, acids ? . . in being colorless gases, strongly acid, soluble in water, and capable of dissolving many metals. HYDROFLUORIC ACID. 526. DESCRIPTION. Hydrofluoric acid What is hy- drofluoric is a colorless, corrosive gas, acting on glass, and many minerals which other acids do not affect. It condenses into a liquid, at the freezing point of water. It is not known to occur ready formed in nature. 527. PREPARATION. Hydrofluoric acid How is hydro- fluoric acid is made Irom a mineral called fluor spar, prtpar by ttie game meai)S employed to make hy- dochloric acid. On account of its corrosive action on glass, vessels of lead or platinum are employed in the HYDROFLUORIC ACID. 213 process. This gas is so poisonous, when inhaled, and its solution so corrosive to the skin, that its prepara- tion, in any considerable quantity, should be left to the experienced chemist. Explain the ^28. EXPLANATION. In the above pro- process ? cess, the fluor spar, which is a fluoride of calcium, furnishes the fluorine, and hydrated sulphuric acid, the hydrogen. The remaining constituents unite to form sulphate of lime, which remains in solution. 529. ETCHING ON GLASS. It has already cess for etch- been stated that hydrofluoric acid attacks wg glass. glass, and many minerals. By covering with wax, they may be protected against the corrosion. Advantage is taken of these two facts in etching upon glass. The surface is first slight- ly warmed and rubbed with beeswax, and then warmed again, to produce an even coating. Figures, or letters, are then drawn upon the glass, through the wax, with a pen-knife, or other pointed instrument. The plate, being now exposed for a few minutes, to the fumes of hydrofluoric acid, and the wax subsequently re- moved, is found to be deeply etched. Fumes of hy- drofluoric acid, for the purpose, are best obtained by placing a half tea-spoonful of pulverized fluor spar, in a warm tea-cup, and covering the powder with oil of vitriol. A little ether, or potash, will be found of use in removing the last portions of wax from the plate. Explain the 530. EXPLANATION. As OXygeil COm- above process, bines with carbon to form carbonic acid, so 214 METALLOIDS. the hydrofluoric acid eats out the silicon of the glass, where it is exposed, and passes off with it, in the form of a new and more complex gas. A solution of the gas may be prepared by the process employed for hy- drochloric acid. Bottles of vulcanized India rubber, or gutta purcha, may be used in keeping the solution. HYDROSULPHURIC ACID. 531. DESCRIPTION Hydrosulphuric acid What is hy- . dromlphuric is a colorless gas, also known as sulphu- retted hydrogen. It has a putrid odor and feeble acid properties. Like the rest of the series, it is soluble in water. It occurs in many natural waters, called sulphur springs. It is one of the products of the decomposition of animal matter, and the source of much of the disgusting odor which they emit during putrefaction. Howisitpre- ^32. PREPARATION. It is made from pared? sulphuret of iron, as hydrochloric acid is made from common salt ; and hydrofluoric acid from fluor spar. In the above process, sulphuret of iron furnishes the sulphur, and hydrated sul- phuric acid, the hydrogen. The remaining elements unite to form sulphate of iron, which remains in solu- tion. On account of the disgusting smell of the gas, it is best to prepare it only in small quantities. 533. DISCOLORATION OF METALS AND What effect has it on met- PAINTS. The blackening of silver watches als, &c. ? an( j co i ngj i n t j ae v i c i n ity O f Sulphur HYDROSULPHURIC ACID. 215 springs, is an effect of hydro-sulphuric acid gas. Its discoloring effect may be illustrated, by pouring a little dilute sulphuric acid upon a few grains of sulphuret of iron, in a tea-cup, and holding a bright moist coin in the fumes. Its effect on paints may be shown by exposing a piece of paper, moistened with solution of sugar of lead, in the same manner. The white paper immedi- ately assumes a dark metallic stain. Paper moistened with a solution of tartar emetic, takes a deep orange hue. This experiment is often varied, by drawing amusing figures on paper, with lead solution, and bringing them out by exposure to the gas. 534. EXPLANATION. The change of Explain the , cause of the color in each case, is owing to the forma- toior 9e f tion of a metallic sulphide, having a diffe- rent, and generally a darker color. Zinc is not blackened, because its sulphide happens to be white. For this reason, chemical laboratories, and other places where hydrosulphuric acid is likely to be evolved, should be painted with zinc paints, instead of those containing lead. 535. RELATIONS TO LIFE. Sulphuretted What is the effect of ml- hydrogen, if inhaled in any considerable ?f on ow- quantity, acts as a poison. Caution should therefore be observed, in experiments with this gas. The mixture of gases which is given off from recently ignited coal, contains sulphuretted hy- drogen acid, in large proportion, and owes its deleterious qualities, in considerable part, to this admixture. 216 METALLOIDS. AMMONIA. 536. DESCRIPTION. Ammonia is a col- WTiat is am- monia? orless gas, of pungent smell, and alkaline P r P erties -. It is exhaled from vdlcanoes, and is a product of the decomposition of all vegetable and animal matter. Its molecule contains one atom of nitrogen to three of hydrogen. mi . . .j 537. PRODUCTION FROM ITS ELEMENTS. What ^s said of its produc- Although nitrogen and hydrogen gases are trogenandhy- the sole elements of ammonia, they cannot, drogent under ordinary circumstances, be made to unite directly, and form it. Heat does not stimulate their affinities sufficiently to bring about this result. Electrical sparks passed, for a long time, through a mixture of the gases, cause them to combine to a lim- ited extent. 538. PRODUCTION FROM NASCENT ELE- Production from its nas- MENTs. Iron, at a high temperature, ex- cent elements. pelg hydrogen from or dinary hydrate of potassa, and nitrogen from nitre. If heated with both together, it expels both nitrogen and hydrogen, and the two nascent elements unite, to form ammonia. The experiment may be performed by covering bits of potash and nitre with iron filings, and heating them in a test- tube. Another method of producing ammonia, through the agency of platinum sponge, is described under the head of Platinum. How is ammo- 539t PREPARATION. Ammonia is com- ma common- monly made from salts that contain it, by ly prepared ? using some strong base to retain the acid, AMMONIA. 217 and set the gas at liberty. Potash or lime may be used for this purpose. Introduce into a test- tube about half an inch of a stick of fused potash, and covered it with powdered sal-ammoniac. On the addition of water to dissolve them, am- monia will be immediately evolved. Rest the tube on the table, and place a wide-mouthed vial over it to collect the gas. 540. SOLUTION IN WATER. AQUA AMVIO- How is its so- lubility in wa- NIA. Bring the mouth of the vial filled with ter proved? ammoniacal gas, quickly, into a bowl of water. The water will swallow up the gas so rapidly as to rise and fill the vial, producing a weak solution of ammonia, or hartshorn. If only a small portion of water be allowed to enter, and the vial be then re- moved from the bowl and shaken, the hartshorn ob- tained will be comparatively strong. For the prepira- tion of the solution in large quantity, the method given in the section on Chlorine is to be preferred. The vial should be previously warmed. Newly slaked lime may be substituted for potash. How ma,, the 54L A MINIATURE FOUNTAIN. Fill a ammonia be pi n t v ial with ammonia, by employed to produce a jet the method above given, and of water ? immediately introduce, air- tight, into its mouth, a moist paper stopper, with a bit of pipe-stem run through it. Then invert the bottle into O a bowl of water. The absorption by the first portions of water that enter will be so com- 10 21$ METTALLOIPS. plete as to produce a vacuum, into which more wa- ter will rise, in a jet, as represented in' the. figure. 542. ALKALINE PROPERTIES. Bring the Explain its action on material for making ammonia into a tea- acids ' cup, or similar open vessel. Hold a strip of litmus paper, previously reddened by an acid, in the gas, as it is evolved. The acid will be neutralized by the ammonia, and the paper restored to its original color. Any substance which is very soluble, and neutralizes strong acids, is called an alkali. As ammonia has this property, arid is also volatile, it is therefore called a vol- atile alkali. The same experiment with litmus paper, may be also made with the hartshorn obtained in the last experiment. 543. JT FUMES WITH ACID VAPORS. Describe its . , effect on acid Moisten a piece of paper with strong mu- vapors. riatic acid, and wave it to and fro through the gas. White fumes are produced, by the union of the muriatic acid and the ammonia. In uniting, they produce small particles of mu- riate of ammonia, or sal-ammoniac, in the air. It is of these that the fumes consist. It will be observed, that in this experiment the ma- j|| terial from which the ammonia was originally pre- pared is reproduced. The same fumes are formed, on waving a paper moistened with muriatic acid through the atmosphere of a stable. Ammonia is constantly evolved in such places, from the decomposition of ani- mal matter. PHOSPHURETTED HYDROGEN. 219 PHOSPHURETTED HYDROGEN". 544. DESCRIPTION. Phosphuretted hy- Whatisphos- . r J pkurettedky- drogen is a colorless gas, of an odor that drogen? hag been compare( i to t h at Q f p utr id fish. It is spontaneously inflammable by contact with the air. In the relative proportion of its elements, it cor- responds with ammonia. This gas is sometimes pro- duced in the decay of vegetable and animal matters. The jack-o-lantern, or will-o-t he-wisp, sometimes seen in swamps and grave-yards, is supposed to have its origin in the spontaneous production and combustion of this gas. How is it pre- 545. PREPARATION. Phosphuretted hy- pared? drogen is made from phosphorus, with the help of water and an alkali. Water furnishes the requi- site hydrogen, if lime or potash is at the same time present. Introduce into a small vial two-thirds full of water, a stick of ordinary fused potash, broken in pieces, and a bit of phosphorus of the size of a pea. On the application of heat, this gas is evolved. It is carried through a pipe-stem, and al- lowed to bubble up through water contained in a tea-cup or bowl, as represented in the figure. If the atmosphere is still, the bubbles, as they burst and inflame, form beautiful white rings, which rise in succession into the air. These rings consist of particles of phosphoric acid, produced by the combustion of the phosphorus which 220 METTALLOIDS. is contained in the gas. In order that the gas may be safely evolved, it is best to heat the vial in a tea-cup containing salt, dissolved in three times its bulk of water. The addition of salt has the effect of raising the boiling point. The comparatively high tempera- ture required, may thus be obtained without exposure of the vial to the direct flame of a lamp. Explain the 546. EXPLANATION. In the action which above process, occurs in making phosphuretted hydrogen from potash, water, and phosphorus, the latter plays the part of an extremely rapacious element. It makes no distinction in the objects of its appetite, but seizes upon both oxygen and hydrogen of the water, two substances as widely different from each other as pos- sible. It forms with the one, phosphuretted hydrogen, and with the other, what might be called phosphuret- ted oxygen, but is, in fact, an acid. Potash is em- ployed in the process, to promote the formation of this acid. In its absence, water resists the affinities of the phosphorus, and neither acid or phosphuretted hydro- gen are obtained. COMPOUNDS OF HYDROGEN WITH CARBON. 547. Most of the compounds of carbon and hydro- gen belong to the vegetable world, and will therefore be more properly considered in the chapter on organic chemistry. Only two of them, which exist ready formed in nature, will be here mentioned. CARBURETTED HYDROGEN. LIGHT CARBURETTED HYDROGEN. What is u kt ' ^ ESCRIPTION - Light carburetted carburctted hydrogen is a colorless, inodorous, in- Whcre does it flammable gas, about half as heavy as occur? a j r j ts mo iecule contains two atoms of carbon to four of hydrogen. It is produced in ponds and marshes, by the decomposition of vegetable matter under water, as will be more fully explained in Part III. From this circumstance it is also called marsh gas. Mixed with other gases, it issues from fissures in coal mines, forming the fire damp, formerly so much dreaded, on ac- count of its explosive properties. As coal is of vegeta- ble origin, the gas of the mines which proceeds from it is also traceable to the vegetable world. In some districts, and more particularly in regions where borings are made for salt, it issues from the earth in sufficient quantity to form the fuel which is required to boil down the brine, or even to illuminate villages. How is it pre- 549. PREPARATION. - An pared? impure, light, carburetted hy- drogen, is obtained from wood, by simple heating. For this purpose, saw-dust, or bits of shavings are heated in a test-tube. The gas may be burned in a jet as fast as formed. The product thus obtained is not pure, but mixed with olefiant, and other gases, which make the flame more luminous. The pure gas, may be made from strong vinegar, (acetic acid,) by the agency of heat and potash, as will be explained in the latter part of this work. 222 METTALLOIDS. 550. EXPLOSIONS IN MINES. Marsh gas Explain the . , . cause of explo- forms, with air, an explosive mixture be- *ion in mines? fore alluded ^ w hich is often the occa- sion of fearful accidents in mines. The experiment may be made with olefiant gas, which has the same explosive property. This property belongs, indeed, to most gases and vapors which contain hydrogen ; as for example, to the vapors of ether, alcohol, camphene, and " burning fluid/' 551. DAVY'S SAFETY LAMP. The dis- Descnbe Da- . . -.-i t i r-v -i i vy's safety tinguished English chemist, Davy, devised lamp. a method O f security against these explo- sions. It consists in surrounding the miners' lamp with wire gauze, which will admit air through its insterstices, but will not let out flame to ignite the explosive atmosphere of the mine. This effect may be illustrated, by holding down a piece of wire gauze upon the flame of a candle. If the gauze is fine, the flame will not pass through it. This effect is owing to the reduc- tion of temperature which the wire occasions. The subject will be better understood by reference to the paragraphs which follow, on the nature of flame. HEAVY CARBURETTED HYDROGEN. 552. DESCRIPTION. Heavy carburetted What are the { properties of hydrogen is a colorless gas, of peculiar defiant gas? ^ezl\$\\ odor, also known as olefiant gas. CARBURETTED HYDROGEN. 223 It is nearly twice as heavy as the light carburetted hy- drogen just described, and contains twice the quantity of carbon. It forms a small proportion of the Jire damp, of mines, and salt borings, before described. How is it pre- 553. PREPARATION. Heavy carburetted pared? hydrogen is made from alcohol, by the de- composing action of sulphuric acid. Bring into a test- tube a tea-spoonful of alcohol, with a little sand, and add four times as much oil of vitriol. On heating over a spirit lamp, the gas is evolved, and may be burned like the gas just described, at the mouth of the tube. The acid employed, has the effect of retaining part of the elements of the alcohol, and allows the rest, to escape as olefiant gas. The reaction* is more fully ex- plained under the head of organic chemistry. 554. ILLUMINATING GAS. Gas for illu- How is illu- minating gas mination, is commonly prepared from bitu- minous coal. Such coal is principally composed of carbon and hydrogen. A portion of these elements, pass off under the influence of a high temperature, in the form of gas. The product, is rather, a mixture of gases, among which light and heavy carburetted hydrogen are the principal. The process may be illustrated, by heating a little pulver- ized bituminous coal in a test-tube. If the heat is in- tense, coal tar will be produced at the same time. The illuminating power of gas is principally derived from heavy carburetted hydrogen. Its quality, within cer- tain limits, depends on the relative proportion of this constituent. * The term reaction, signifies, in chemistry, the mutual action ot chemical 224 METALLOIDS. How is it pu- 555. PURIFICATION. The gas as it rises, rifled f contains ammonia and sulphuretted hydro- gen, two impurities which it is desirable to remove. The first may be stopped in its passage, by a loose wad of moist- ened paper ; the last, by a similar wad, moistened with solution of sugar of lead. The papers having been introduced, the pipe-stem is fitted to the tube with a pa- per stopper, and the tube heated over the alcohol flame, with the help of a blow-pipe. When the coal has become red hot, the gas will pass off in sufficient quantity to be ignited, at the extremity of the tube. How ore the ' ^ ^ conclusion of the process, impurities the upper wad contained in the tube, will be found blackened by the sulphuretted hydrogen which it has retained. On removing the second one, it will be found to smell of ammonia. The presence of this body may also be shown, by the fumes which it yields with muriatic acid. 557. ARRANGEMENTS IN GAS WORKS. Describe the process in gas The process in gas works is essentially the same, as that above described. The coal is heated in iron retorts. The tar collects in pipes lead- ing from it. Carbonate of ammonia is washed out by a jet of water, which plays in an enlargement of the pipe. Lastly, sulphuretted hydrogen is removed by the retentive power of a metallic base, lime being gen- erally substituted for lead. FLAME. 225 558. COLLECTION AND DISTRIBUTION. After purification, the gas is collected in lectedand dis- } e n . on holders, called easrmeters. tributed ? Tiiese may be represented by the inverted tumbler of the figure. Gas pouring in from below would lift and fill it. <^TS^ If an orifice were made in the top, the tumbler would immediately set- tle into the water. The air would, at the same time, escape through the orifice. The distribution of illumina- ting gas, from public gas works, is effected on the same principle. The weight of the sinking gas- ometer, is sufficient to press it through pipes, to all parts of a large city. 559. GAS FROM WOOD. Gas may be How may gas be made from made from wood, by the same means above given. Only a moderate heat is re- quired, in this case, to produce tar at the same time. Gas of higher illuminating power than that prepared from wood or coal may also be made from oil fat or rosin. Even refuse vegetable substance may be em- ployed. A pound of dried grape skins have been found to yield 350 quarts of excellent illuminating gas. The dried flesh of animals has sometimes been employed for its manufacture. FLAME. What is said 560. FLAME. Nothing in nature is, to of flame ? t j ie un i ns t rilc ted eye, more mysterious than flame. It is, seemingly, body without substance, and 10* 226 METALLOIDS. shape, without coherence. It is created by a spark, and annihilated by a breath. Invulnerable itself, it destroys whatever it touches. Divided and subdivided, it is still the same, yet endowed with the power of re- solving other materials into their elements. Chemistry resolves this mystery, and gives us the satisfaction of definite knowledge in its place. But, as in all similar case, while satisfying the understanding, it opens new fields to the imagination. The subject of combustion, as involved in flame, introduces us, for example, to a knowledge of the grand system of circulation of mat- ter as set forth in the last chapter of this work. 561. STRUCTURE OF FLAME. EXPLANA- J5sfain the nifitdnre of TioN. Every lamp or candle, is a gas factory, in which gas is k first produced out of oil or fat, by the fire which kindles it, and afterward by heat the of its own flame. A flame, if carefully ob- served, will be found to consist of three distinct parts ; a dark centre, a luminous body, and a faint blue envelop. The dark centre, is unburned gas. The body of the flame consists of particles of carbon or lamp- black, heated white hot, by the combustion of hydrogen. In the exterior blue envelop, the carbon particles are consumed as they are crowded outwards, by the flow of newly-formed gas. 562. EFFECT OF FLAME ON METALS. What is the effect of flame If a tarnished penny be held perpendicu- larly in the flame of a lamp or candle, the on metals ? FLAME. 227 portion within the flame will lose its coating of oxide, while the exterior portions at the same time become more deeply oxidized, and consequently, darker colored. It is because there is an excess of carbon arid hydro- gen in the interior of the flame, to take oxygen from the metal, by their superior affinity, and pass off with it as gas or vapor. In the outside, on the other hand, there is an abundant supply of air to impart oxygen, or, in other words, to oxidize. By moving the coin to and fro after it is once thoroughly heated, the instanta- neous conversion of metal into oxide, and oxide into metal, may be readily observed. A beautiful play of colors, like those upon a soap bubble, will be found to attend the transformation. The flame of a spirit lamp is, in some respects, preferable for this experiment. 563. OXIDIZING FLAME. The blue en- What is the oxidizing velop of the flame, which, with the hot air adjacent, has the property of oxidizing metals, is called the oxidizing flame. 564. REDUCING FLAME. The body of What ift the _ J reducing the flame, which, with the heated gas flame ? within it, has deoxidizing effects, and re- duces oxides again to the metallic form, is called the reducing flame. The process of deoxidizing is called reduction. 565. THE BLOW-PIPE. The peculiar effects of both the oxidizing and reducing simple con- flame, may be still better obtained, by help ftructton. of the simple mouth blow-pipe. In want of a metallic tube, a common tobacco-pipe, to the bowl 228 METALLOIDS. of which a piece of a second stem is fitted, as represented in the figure, may be made to answer the purpose. With its aid, a lamp or candle flame is converted into a miniature blast furnace. The mouth is ap- plied at the end of the long stem, while the shorter one carries the blast to the flame. The orifice of the latter should be extremely small. It may be so rendered, by filling with clay, and then piercing it with a needle. 566. OXIDIZING BLOW-PIPE FLAME. To d oxidize with the blow-pipe, the flame, for oxidation? mixed with a large proportion of oxygen, Give an ex- . _ . . .. ample. is blown forward upon the metal, or other material, subjected to experiment. This is effected by introducing the extremityof the blow-pipe, a little within the flame. The air of the lungs be- comes thus mixed with the rising gases. The result is, a slender, blue flame, at the point of which, within its fainter blue envelop, the metal is to be held. A piece of lead, of the size of a grain of wheat, placed on charcoal, hollowed out for the purpose, and exposed to the flame, will soon bo converted into litharge. The oxide will be recognized by the yellow incrustation which it forms upon the charcoal support 567. REDUCING BLOW-PIPE FLAME. To How is the blow-pipe used convert oxides into metals, or in other blow-pipe, the gases of the flames are FLAME. 229 blown forward, upon the substance, mixed with little air. The extremity of the blow-pipe is placed against the outer wall of the flame, a little higher than in the previous case. The flame thus produced is yellow, and of the shape represented in the figure. The oxide to be reduced, is to be placed within the yellow body of the flame, but near its termination. The litharge produced in the last experiment, may be re-converted, by this means, into metallic lead. 568. OXYHYDHOGEN BLOW-PIPE. The Describe the compound or oxhydrogen blow-pipe, as oxyhydrogc* blow-pipe. commonly constructed, consists of two gasometers, containing, the one, oxygen, and the other hy- drogen gas. Tubes leading from these, are brought together at their extremity, and the two gases are burned in a single jet. The heat thus pro- duced, is the most in- tense that has ever been realized except by galvanic means. Iron, copper, zinc, and other metals, melt and bum in it readily ; the former, with beau- tiful scintillations, and the latter, with characteristic colored flames. With a sufficiently constant flame 10* 230 METALLOIDS. platinum also may be readily fused. The apparatus represented in the figure, furnishes a simpler means of obtaining similar results/ An abundant flow of hy- drogen is required, and a pint bottle should, therefore, be employed in its preparation. To retain it free from water, which would tend to reduce the heat of the flame, a little cotton may be introduced into the bowl of the pipe through which it passes. In evolving the oxygen, only a part of the tube should be heated at a time, lest the gas should be too rapidly evolved. FLAME CONTINUED. The student will ture of flame already have found abundant evidence that {rairf UlU8 ~ air or ox yg en * s essential to combustion. A still more striking illustration of the sub- ject remains to be given. A phosphorus match, if suddenly introduced into the interior of a flame, notwithstanding the high temperature in its vicinity, is not ignited. The wood burns off, but the phosphorus of the match does not un- dergo combustion. The same principle may be illustrated by holding a match for a moment through the body of the flame. It is consumed at the sides, while the centre remains unburned. CLASSIFICATION OF METAI-3. 231 CHAPTER II. METALS. 569. CLASSIFICATION. The metals may How may the metals be das- be arranged in groups, or classes, according to their affinity for oxygen. Those which tarnish, or rust most readily, come first in order, while the last group is made up of the noble metals, which retain their brilliancy, unimpaired. 570. CLASS i. POTASSIUM AND SODIUM. Describe the metal* of These two metals combine with oxygen so eagerly, as to tarnish instantaneously, on exposure to the air. They even seize on that which is contained in water and expel its hydrogen. The hypothetical metal, ammonium, is described in connec- tion with this group, because of the similar properties of its compounds. Describe Class 571. CLASS II. BARIUM, STRONTIUM, CALCI- IL UM, MAGNESIUM. The metals of this class show their affinity for oxygen, in the same manner as those of Class I. But they are inferior, in this respect, to both potassium and sodium. Either of these metals can deprive them of the oxygen with which they may have combined. Describe Class 572. CLASS III. MANGANESE, ALUMINIUM, IIL IRON, CHROMIUM, COBALT, NICKEL. The metals of this class tarnish less rapidly than the fore- going, by exposure to the air. In order that they may decompose water, and appropriate its oxygen, they re- 232 METALS. quire the stimulus of an acid, or of heat. Except in the case of manganese, the heat must be sufficient to convert the water into steam. Strictly speaking, there- fore, they do not decompose water, but steam. Describe Class 5 ?3. CLASS IV. TlN AND ANTIMONY.- IV - Tin and antimony tarnish less readily than the metals of the previous class. To enable them to decompose water, and appropriate its oxygen, they re- quire the stimulus of a red heat. An acid, or mode- rate heat will not suffice. Describe Class ^74. CLASS V. COPPER, BISMUTH, AND LEAD. Although copper and lead become tarnished, or covered with a thin film of oxide, rather more readily than the metals of the last two groups, their affinity for oxygen under other circumstances is less. This is evident in the fact that a red heat ena- bles them to decompose water and appropriate its oxy- gen, but feebly. Acids will not suffice. Bismuth does not tarnish so readily as copper or lead. Describe Class 5 ?5. CLASS VI. MERCURY, SILVER, PLA- VL TINUM, AND GOLD. The metals of this class do not tarnish, and do not decompose water under any circumstances. Even if made to combine with oxygen by other means, they yield it again very readily, and return to the condition of metals. They are called the noble metals. POTASSIUM. 233 CLASS I. POTASSIUM. 576. DESCRIPTION. Potassium is a bluish White metal > H g hter than Water > solvents; and soft, like bees-wax. Like wax. it is occurrence? also converted by the heat of an ordinary fire into vapor. Water and acids dissolve it readily. The metals of this and the folloAving groups, were dis- covered by Sir Humphrey Davy, early in the present century. They were first produced by the galvanic process. Potassium is a constituent of many rocks, of all fertile soils, and of the ashes of plants. The more important minerals which contain it, are men- tioned in Chapter III. 577. PREPARATION. Potassium is made flow is potas- sium pre- from carbonate of potassa, by removing pared? j tg car b olu ' c acid and ox- ygen. This is accomplished by heating intensely with charcoal, which removes both in the form of carbonic oxide. The metal which accompanies the gas, in the form of vapor, is condensed by naptha, instead of water. The process is essentially the same as that for preparing phosphorus, but requires apparatus beyond the reach of the ordinary experimenter. Cream of tartar, if heated, is converted into a nearly suitable mixture of carbonate of potassa, and pure carbon, for this purpose. A small quantity of charcoal, in fragments, is added, and the whole heated intensely in an iron retort. 234 METALS. Explain the 578. COMBUSTION ON WATER. PotaS- actionofpo- gmm jf thrown UDOll tassium on r water. water, is immediately ignited and burns with a beautiful violet flame. Strictly speaking, it is not potassium which burns, but the hydrogen which it sets at liberty, Owing to its strong affinity for oxygen, it takes this element from water, liberating, and at the same time kindling, the hydrogen with which it was before combined. The color of the flame is due to a small portion of vaporized potassium which burns with this gas, as it is evolved. The globule of metal used in this experiment, gradually disappears, because the potassa which it forms by uniting with oxygen, is soluble in water. 579. USES OF POTASSIUM. Potassium State the uses of potassi- has not been applied to important uses in the arts, but is a valuable agent in the hands of the chemist. It is a key which unlocks many substances from the prison in which nature has confined them. Through its agency, brilliant metals may be obtained from lime, magnesia, and common clay. 580. This effect depends on the supe- On what does its action dc- nor affinities of potassium, which enable pcnd? - t to a pp r0 p r { a t e oxygen, chlorine, and other substances, with which the above, and several other metals are combined in nature, and to isolate the metals themselves. The potassium is, at the same time, converted into oxide, or chloride of potassium, SODIUM. 235 which is soluble in water, and may be washed away from the metal which has been produced. SODIUM. 581. PROPERTIES. The metal sodium is Sodium de- scription, similar in its properties to potassium. It ^dvni^and * s P re P are d by similar means, from carbo- occurrcnce? nate of soda, and may be employed by the chemist, for the same purpose. It occurs, principally, in nature, in the form of common salt. Thrown upon water, it decomposes it, without however igniting the hydrogen which is evolved.* Sodium is readily sol- uble either in water or acids. 582. USES OF SODIUM. Sodium is now .For K'hat pur- . pose is it prepared in large quantities, in France, as a material to be used in the manu- acture of the metal aluminiu n. Its cost, a few years since, was ten dollars an ounce. It can now be pro- cured for less than a dollar per pound. AMMONIUM. 583. Ammonium is a compound of ni- Wkat is said . . of ammoni- trogen and hydrogen, which is presumed um ' to be a metal. Its molecule contains one atom of nitrogen, to four of hydrogen. If a metal, it differs from all others, in being a compound, and not a simple element. There are, however, good grounds * If sodium is wrapped in paper, to prevent waste of heat, it burns with flame, like potassium, upon water. 236 METALS* for believing in the existence of such a compound gaseous metal. The chloride of ammonium is named in accordance with this view. Judging from the prop- erties of the salt, we might reasonably expect, by re- moval of its chlorine, to obtain from it a substance with metallic properties, as well as from chloride of sodium or common salt. But the experiment does not justify the expectation. As soon as the chlorine is re- moved, the metal also decomposes, and a mixture of gases is the result. The principal ground for attribu- ting a metallic character to the combination of nitrogen and hydrogen gases, in the preparations above stated, has been already indicated. They supply, in certain salts, the place which known metals fill in the other and similar compounds. A confirmatory experiment is described in the succeeding paragraphs. 584. AMMONIUM AMALGAM. Another Slate another ...., . ~ reason for be- ground for believing in the existence of l exSce l of e a ammonium, with true metallic properties, metal ammo- i s found in the following experiment : If nium. . i i chloride of ammonium be mixed with an amalgam of sodium and mercury, a double decomposition ensues. The chlorine and sodium unite to form common salt, while the mercury combines with the ammonium with- out losing its metallic lustre. But there is no instance of this retention of metallic properties in the combination of mercury or any other metal with any non-metallic substance. The inference is that ammo- nium is a metal. But any attempt to isolate it by re- BARIUM. 237 moval of the mercury from the amalgam, is ineffectual. As soon as this is done the ammonium is resolved into gaseous ammonia and hydrogen. This change takes place, indeed, spontaneously. 585. In performing the above experiment, How is the amalgam ex- a small globule of potassium or sodium is formldl peT ~ heated with a thimble full of mercury in a test-tube, and a strong solution of sal am- moniac added. The mercury increases in bulk without losing its lustre, and continues to expand till it fills the tube or glass with a light pasty amalgam. CLASS II. BARIUM, STRONTIUM, CALCIUM, MAGNESIUM. 586. BARIUM. Barium is a soft silvery pro- metal, easily tarnished in the air. It is ami m ade from baryta, by the process already described under the head of potassium. Its compounds, including baryta, from which it is pre- pared, are hereafter described. Barium is soluble in water and most acids. 587. STRONTIUM. Strontium is very Strontium . description, similar to barium, but darker in color. It is absolvents? P roduced from strontia by a similar process. Its solvents are also the same. 588. CALCIUM. The metal calcium is Calcium de- . . pro- similar to barium, and is made from lime b >" the use of Potassium, as before de- scribed. Its solvents are the same as those of the metals above-named. 238 METALS. Magnesium- 589 ' MAGNESIUM. Magnesium is a Soft description, white metal, prepared from its chloride preparation, , . . solvents and instead oi the oxide, by similar means. None of the metals of this class have as yet been applied to any useful purpose in the arts. Water oxidizes magnesium as it does the other metals of the class, but converts it into an insoluble white powder. Most acids dissolve it. CLASS III. ALUMINIUM 590. DESCRIPTION. Aluminium is a bluish white metal, made from common currence, and c j a y. It is about one-third as heavy as solvents ? * y iron. It fuses at the same temperature as silver, and preserves an untarnished surface in the air. It does not decompose water, even with the aid of boiling heat. Alloyed with iron, it protects the latter from the action of the air. This metal is a con- stituent of common clay, and therefore a part of all fer- tile soils and the rocks that produce them. It is also a constituent of numerous minerals. By its discovery every clay bank is converted into a mine of precious metal. How is it pre- 591. PREPARATION. Aluminium is pre- pared? pared like magnesium, from its chloride, by fusion with potassium or sodium. The latter rnetal is commonly employed. The fluoride may also be used in the process, or the mineral cryolite, which MANGANESE. 239 is a compound of fluoride of aluminium with fluoride of potassium. The latter constituent interferes in no wise with the process. The method of preparing the chlo- ride, as a material for the production of the metal, is given in the section on Chlorides. 592. ACTION OF ACIDS. Muriatic acid What is the . action of acids is its proper solvent, and forms with it a colorless solution. Nitric acid whitens it, if previously dipped into strong potash or soda. Dilute sulphuric acid is without action. Aluminium may be poured from one vessel to another in a fused condition without oxidation. Like silver it may be deposited by the galvanic process. 593. It is highly sonorous, and therefore other proper- adapted to manufacture of bells. This metal is now prepared in France at less than three dollars per pound. The French government propose to use it for helmets and cuirasses, for which it is especially fitted by its lightness and tenacity. 594. MANGANESE. Manganese is a description, grey brittle metal, produced from its oxide production, b heatnig w j t h charcoal. It is found in occurrence, solvents and nature as black oxide of manganese and as a constituent of many other minerals. It enters also in small proportions into the composition of soils. Diluted sulphuric or muriatic acid are its proper solvents, forming with it pale rose-colored solutions. The black oxide serves as a source of oxygen, and is also employed in the preparation of chlorine gas. It is also used in the production of artificial amethysts, and also to impart to glass the same violet tint. 240 METALS. CLASS III. IRON. 595. DESCRIPTION. Pare iron is nearly Mention some properties of white, quite soft, exceedingly malleable and highly tenacious. It may be rolled into leaves so thin that a bound book containing forty- four such leaves shall be only one-fifteenth part of an inch in thicknesss. In the condition of perfect purity it is never seen except in the chemist's laboratory. Even the purest iron of commerce contains traces of other substances. Dilute sulphuric or muriatic acids are its proper solvents, form- ing with it green solutions. The addition of nitric acid, or chlorine, changes the color to red. Iron may be readily burned, as has al- ready been shown in the section on Oxygen. 596. OCCURRENCE. Iron is a most Does metallic . iron occur in abundant metal, but is rarely or never nature? found in the metallic form, excepting as meteoric iron. In this condition it is always alloyed with nickel. The latter metal being uniformly com- bined with it in masses known to have fallen to the earth as meteors, its presence in similar masses dis- covered on the surface of the earth, is regarded as evi- dence of their meteoric origin. Iron is a constituent of a great variety of minerals, of all soils and plants, and even of the blood of animals. The peroxide of iron, the magnetic oxide, and clay iron stone, are its principal ores. Whole mountains of the magnetic oxide exist in Missouri, and in Sweden. IRON. 241 How is iron produced ? 597. PRODUCTION. Iron is produced from its ores, which are impure oxides, by heating with lime, to remove the impurity ; and at the same time with coal, and the gases proceeding from it, to remove the oxygen. A smelting furnace, such as is represented in the figure, being previously heated, is charged with the material in layers, and the heat main- tained by the coal of the mixture. In the upper part of the furnace the materials are thoroughly dried. As they gradually settle, they become more thoroughly heated, and meet carbonic oxide from the coal below, which robs the iron of its oxygen, and converts it into particles of metal. Still lower down, the lime combines with the earthy por- tions of the ore, forming a liquid glass. The re- duced iron thus liberated, collects, fuses, arid sinks to the bottom of the furnace. Prom this point it is run off into channels of sand, where it hardens into pig iron. How is the 598. EXPLANATION. The ordinary im- slag formed? purities of the ore- are clay and quartz, or For what uses r j T. ? may it be em- silica. Lime has the property of forming, p oye with both of these, a fusible glass, or slag, which floats upon the melted iron. This material is 11 242 METALS. of a light green color. But it may be otherwise col- ored to suit the taste, and cast into slabs, columns, ar- chitectural and parlor ornaments of great beauty. The process by which its brittleness is removed, and the slag adapted to the above uses, has not been made public. 599. CAST IRON The pig or cast iron, Give the com- . . position and as it is called, which is thus obtained from P c r aTiron f the furnace > is not P ure iron > but a con > pound of iron with carbon. It has ob- tained four or five per cent, of this element from the coal with which it was reduced. The addition of carbon to its composition causes iron to melt more readily. But for its absorption, the metal would not have become sufficiently soft to flow from the fur- nace. Carbon has also the opposite property of mak- ing iron harder and more brittle when cold. Castings of agricultural implements and other objects, are made by remelting the pig iron, and pouring it into moulds of the required shape. 600. WROUGHT IRON. Wrought iron is How is wrought iron made from cast iron, by burning out its made? carbon. This done in what is called a reverberatory furnace, such as is represented in the fig- ure. The carbon is burned out by the surplus air of the flame, which is made to play upon the molten iron. Prom the constant stirring which is essential, such a furnace for refining iron is called a puddling furnace. The IRON. 243 metal becomes stiffer as it loses carbon, and is then hammered and rolled into bars. 601. IRON WIRE. The bar. or wrought Mention an important iron thus produced, is highly malleable and wrought iL. ductile > aild ma 7 be rolled into she ets, or How i$ iron drawn into the finest wire. Wire is made wire made ? by drawing a wrought iron bar, by ma- chinery, through a hole of less than its own diameter, and repeating the process until the required degree of fineness is attained. Wrought iron loses its tenacity, and becomes granular and brittle, like cast iron, by long jarring. This effect sometimes occurs in the wheels and axles of railway carriages, and is the occasion of serious accidents. 602. WELDING. Wrought iron becomes How is wrought iron soft at a certain heat, without melting. This property, which adds greatly to its usefulness, belongs to no other metal excepting plati- num. In the soft state, two pieces may be united by hammering. This process is called welding. The surfaces to be welded are sprinkled with borax, to pro- tect them from the air, which would form a crust of oxide of iron, and prevent a perfect contact. Its fur- ther action is explained in the chapter on Salts. Beside borax, other materials having a similar effect are fre- quently employed. How is steel 603. STEEL. Steel may be made from made ? cast i ron by burning out half its carbon. Or it may be made from wrought iron, by return- ing half of the carbon which was removed in its preparation. The latter is the process generally pur- 244 METALS. sued. It consists in burying the wrought metal in iron boxes containing charcoal, and heating it for several days, till combination with a certain portion of the carbon is effected. 604. ANNEALING. The hardness of How is steel . ..... made soft or steel depends upon the rate at which it is cooled. By heating it to redness, and cooling it slowly, it is rendered as soft and malleable as wrought iron. This process is called annealing. By cooling it very suddenly, it becomes as hard and brittle as cast iron. Steel instruments are commonly ham- mered out of the soft steel, and subsequently hardened. How is steel 605. TEMPERING STEEL. Steel hardened tempered? as above described is too hard and brittle for most uses. Any portion of its original softness and tenacity may be returned to it, by reheating and slow cooling. To restore the whole, a red heat would be required. To give back part, and make a steel so tough as not to break readily, yet sufficiently hard for cutting, a lower temperature is employed. This process is called tempering. The sort of temper imparted de- pends upon the degree of heat which has been em- ployed. 606. The proper temperature is ascertained How is the , . , , , proper heat by the color which the steel assumes when ascertained? heated< Toolg for cutting metal are heate d till they become a pale yellow ; planes and knives, to a darker yellow ; chisels and hatchets, to a purplish yellow ; springs, till they become purple, or blue. In each case they are afterward slowly cooled. These colors are owing to a film of oxide of iron, which is CHROMIUM. 245 formed upon the steel under the influence of heat. The tint is different, according to the thickness of the film. All these colors may be seen by heating a knit- ting-needle in the flame of a spirit lamp. Where it is hottest it becomes blue, and this color shades off into pale yellow on either side, like the colors of the solar spectrum. Chromium CHROMIUM. 607. DESCRIPTION. Chromium is a grey . * description, metal, not readily tarnished, and so hard P of"so!nts, aS t0 SCratch g lass ' Jt is of no use in the and uses? arts in the metallic form. It is found in combination with iron, as chromic iron, and also in beautiful Crystals, as red chromate of lead. It may be prepared from its oxide, like iron, by heating with charcoal. Its compounds are much used as paints. Chrome green and chrome yellow are among the number. Its proper solvents are the same as those of iron. The solutions of this metal are green. COBALT 608. DESCRIPTION. Cobalt is another grey metal, tarnishing but slightly in the air. It is somewhat malleable. It is found combined with arsenic, as arsenical cobalt, and in some other minerals. As metal, it is without useful application in the arts. It may be produced like iron, by heating with charcoal, Cobalt de- scription, pro- duction, oc- currence, sol- vents, and uses ? 246 METALS. but is more readily reduced by hydrogen. A cur- rent of this gas being made to pass through a hot tube containing the oxide, it combines with oxygen, and passes off with it as water, leaving the metal in the form of a fine powder. Its proper solvents are the same as those of iron and chromium. The solutions of cobalt are pink. The oxide is employed for im- parting a blue color to glass. NICKEL. Nickel 609. Nickel is still another grey metal, ' l[ 8 hiQ * in color and more malleable than ores, solvents, cobalt, and not much affected by the air. and uses? * * i i " It is round in combination with copper, in the mineral called copper nickel. It may be prepared by either of the methods used for cobalt. Its proper sol- vents are the same as those of the last four metals. The solutions of this metal are green. Nickel is principally used in the preparation of the alloy called German sil- ver. This imitation of silver is brass rendered white by the proportion of nickel which it contains. The alloy is composed of one hundred parts of copper, six- ty of zinc, and forty of nickel. ZINC. 610. DESCRIPTION. Zinc is a bluish- de- scription, white metal, readily tarnished in the air. Jt is brittle at ordinary temperatures, and converted into vapor at a red heat. If ZINC. 247 heated somewhat above the temperature of boiling wa- ter, it can be rolled into sheets. At a higher tempera- ture it again becomes brittle. Sulphuric and muriatic acids dissolve it readily, forming colorless solutions. It is not found native. The red oxide, and the carbon- ate, called calamine, are among its more important ores. 611. PRODUCTION. Zinc is produced produced? from its oxide by heating with charcoal to remove tne ox yg en ? or > m other words, to reduce it. When made from the carbonate, the ore is previously roasted, to expel its carbonic acid and bring it to the state of oxide. As the metal is volatile at the heat required in its reduction, an ordinary furnace, such as is used for making iron, can- not be employed in the process : the metal would be lost in vapor. A clay retort, or muffle, such as is re- presented in the figure, is used instead. The zinc va- por condenses in the cool neck, and falls, in drops of melted metaLinto a vessel of water placed to receive it. The carbonic oxide produced in the process at the same time, escapes into the air. It will be observed, that the process is essentially the same as that for pro- ducing potassium and phosphorus, as before described. Acids dissolve zinc, forming colorless solutions. 612. ACTION OF HEAT AND AIR. Zinc How may zinc - : - be burned? may be burned by heating it on charcoal, in the blow-pipe flame. It melts, and con- verts itself rapidly in the process into white oxide of zinc. If an intense heat is employed, the vapors of the metal burst through the crust and burn 248 METALS. to oxide, with a brilliant greenish flame. When zinc is burned in considerable quantity, in a highly heated crucible, the oxide forms flakes in the air, to which the name of lana philosophica, or philosophers' wool, was given by the alchemists. The metal may be melted over a spirit lamp, in an iron spoon. Mention the 613. USES OF ZINC. Zinc is principal- uscs of zinc. \y employed in the form of sheet zinc, for roofing and similar purposes. It is also used, like tin, as a coating to protect iron chains and other objects from rust. The coating is effected by plunging the iron into molten zinc, which forms an alloy upon its surface. The iron thus coated is sometimes called gal- van' zed iron, though without reason, as is evident from the above process. Solutions of zinc are sometimes used to prevent the decay of wood, and to render it less combustible. It has also been employed with success, as a substitute for copper, in sheathing vessels. CLASS IV. TIN. x 614. DESCRIPTION. Tin is a brilliant Describe the . .. .. . _ metal Tin. white metal, very soft and malleable, and From what t easily tarnished. When a bar of tin ore is it made? * is bent, it gives a peculiar grating sound, fancifully called the cry of tin. This is a consequence of the friction of the minute crystals of tin of which it is composed. Its only ore is an oxide, called tin TIN. 249 stone, of which Cornwall, England, is the principal locality. How is tin 615. PRODUCTION. Tin is produced, produced ? \fa e j ron an( j mos t other metals, by heating its oxide with carbon. The materials are heated in a small blast furnace. The carbonic oxide produced in the fire, as before explained, is the reducing agent. It takes the oxygen from the ore, and passes off with it as carbonic acid, while the metal fuses, and runs to the bottom of the furnace. By heating tin before the blow-pipe, it is rapidly converted into white oxide. How do adds 616. ACTION OF ACIDS. Tin resists act on tin ? we ak acids remarkably. Dilute muria- tic and sulphuric acids, which dissolve most of the metals before described, act upon it but feebly. The concentrated acids dissolve it with comparative ease. Its solution, although less poisonous than those of lead, are still injurious to health. Acid food should, therefore, never be allowed to stand for a long time in tin vessels. The solutions of tin are colorless. 617. Nitric acid acts upon tin with en- Whatisthe action of ni- ergy ; but, like a ferocious animal that de- tnc acid? stroys without devouring its prey, leaves it undissolved. It converts it into a white insoluble powder of oxide of tin, with the evolution of the usual red fumes. This case is an exception to the usual action of nitric acid. One portion of the acid commonly acts to produce oxide, while another portion dissolves the oxide formed. The experiment for the solution 11* 250 METALS. of tin may be made with tin-foil, in a tea-cup or test- tube. 618. Aqua-regia,) it will be remembered. What is the action of aqua- is a mixture of nitric and muriatic acids. regia on tin ? Jn most caseg they ^ &g before degcribedj in concert, to dissolve metals that neither can dissolve alone. They act thus, also, upon tin, in small por- tions. But if larger quantities are employed, the mix- ture grows warm, and the nitric acid, as if stimulated beyond restraint, attacks the metal for itself, and con- verts it, as when it acts alone, into a white powder. 619. COATING PINS. Common brass pins How are pins coated with are coated, by boiling with cream of tartar tin? and tin-foil, or bits of tin. The acid of the tartar acts as solvent. Tin is then deposited on the mere electro-positive brass, as in cases of galvanic decomposition. At every point where brass, tin, and the liquid are in contact, a small galvanic battery is, in fact, produced. How is tin 620. TIN WARE. Tin is cast in va- plate made ? r i ous forms, for culinary and chemical uten- sils. A little lead is added to give it greater tough- ness. Common tin ware is made of sheet-iron, coated with tin. The coating of the metal is effected by dipping well cleaned sheet-iron into molten tin. 621. CRYSTALLINE TIN. Tin has a great How may the " crystalline tendency to assume a crystalline form. *tin C bele.en? The stmct ure may be observed on wash- ing the surface of ordinary tin plate with aqua-regia, to remove the thin coating of oxide. It may be still better seen if a tin plate is heated over a ANTIMONY. 251 lamp till the coating melts, then suddenly cooled, and afterward cleaned as above directed. The whole sur- face is then found to be covered with beautiful crys- talline forms. AOTIMONY. Describe the 622. DESCRIPTION. Antimony is a blu- ish white and hi hl y crystalline metal what ore is it which does not tarnish in the air. It is obtained? 1-11 so brittle that it may be readily reduced to powder. The ore from which the metal is produced is the grey sulphuret, or antimony glance. 623. PRODUCTION. Antimony may be How is anti- . . monypro- obtained from its oxide, by the usual pro- cess of reduction. The sulphuret is first partially converted into oxide by roasting, and still fur- ther by carbonate of soda, which is added in the sub- sequent process. It is then mixed with charcoal, and intensely heated in crucibles. At a white heat the metal fuses, and sinks to the bottom. The soda added in the process exchanges its oxygen for the remaining sulphur of the ore. 624. ACTION OF HEAT AND AIR. If heated How may an- ... , , 4 timony be before the blow-pipe, antimony soon melts, and burns with a white flame. It is at the same time converted into oxide. A portion of the oxide escapes into the air, while the rest forms a white coating upon the charcoal sup- port. At the high temperature which is here produced, the affinity of the 252 METALS. metal for oxygen is so stimulated, that the molten globule will continue to burn, even if removed from the flame. By directing a stream of air upon it, from a pipe-stem, the combustion may be maintained till the globule is entirely consumed. 625. If the molten globule be allowed Describe an P ,, ,, n experiment to fall upon the floor, it im- . with the mol- mediately divides into hun- x ten globule? '"^ > dreds of smaller globules, which jjjs&Z... radiate in all directions, leaving each a dis- - '//', I V\\ tinct track of white oxide behind it. What is the 626. ACTION OF CHLORINE. A shower rinelnanti-' of fire ma y be P roduced ^Y sprinkling fine many ? powder of antimony into a vial containing chlorine gas. The metal is hereby converted into a white smoke of chloride of antimony. In its rela- tions to the principal acids, antimony resembles tin. Its solutions are colorless. 627. USES OF ANTIMONY. The principal What are the f . . principal uses use of antimony is in the preparation of of antimony? alloySj io ^ Q hereafter described. Among these, type metal is the most important. Many of the compounds of antimony, like other poisonous sub- stances, are used with advantage in medicine. Tartar emetic is one of these medicinal compounds contain- ing antimony. BISMUTH 253 CLASS V. BISMUTH. Bismuth -de- ^^' DESCRIPTION. Bismuth is a brittle, script-fan, sol- crystalline metal, of a reddish white color. vents, and oc- . . currence in It is used in making certain alloys. Like antimony, it can be readily ground to pow- der. Crystals of bismuth may be obtained by the method described in the section on sulphur, as represented in the figure. Nitric acid is its proper solvent, and forms with it a colorless solution. Bismuth is found native, forming threads of metal in quartz rock. Its most productive localities are in S axony. 629. PRODUCTION. The metal is pro- How is bis- . muthprodu- cured from the rock which contains it, by simple heating, in inclined tubes. At a comparatively moderate temperature the bismuth fuses and runs down into vessels placed to receive it. 630. EFFECT OF HEAT AND AIR. The What is its action before same experiments before the blow-pipe, thcbloiv-pipc? and with mo i ten globules, which were described in the case of antimony, may be made with bismuth. The only difference is, that the metal does not burn with flame, and that the coat- ing of oxide on the charcoal is yellow, instead of white. 631. USES OF BISMUTH. Its principal What are the uses of bis- use is in the preparation of alloys, to be muth? described hereafter. One of them has the 254 METALS. remarkable property of fusing in boiling water. Seve- ral compounds of bismuth are used in medicine ; the sub-nitrate, is also employed as a cosmetic. This use of it is quite hazardous, as certain gases which are often present in the air., have the effect, as will be here- after seen, of changing its color to a deep brown or black. Copper de- scription, ores, solvents? COPPER. 632. DESCRIPTION. Copper is a red, malleable, and highly tenacious metal. It tam i shes in the ^ but ig ] ess i n j ure( } fty rust than iron, and therefore more durable. Nitric acid is its proper solvent, and forms with it a green solution. Copper is found in abundance, in the metallic condi- tion, on the southern shore of Lake Superior. It is chiseled out, in masses, from the rocks which contain it. The metal is more commonly obtained from a mineral, called copper pyrites, which is a double sul- phuret of iron and copper. It is also found as pure sulphuret, red oxide, and carbonate. Minute traces of copper are found in human blood. 633. PRODUCTION. Copper is prepared State briefly the mode of from the impure production. sulphuretj by first burning out the sulphur, in the air ; and secondly, heating with charcoal, to remove the oxygen which has taken its place. Sand is at the same time added, to form a floating slag with the oxide of iron, and thus remove it from the molten copper. COPPER. 255 The oxide of iron thus removed, is derived from the sulphuret of iron, which is a usual constituent of cop- per ores. 634. Both of the above processes of State further particulars of roasting and heating with charcoal, and epro sand, must be several times repeated before pure metallic copper is obtained. It is to be remarked that the formation of a slag, which shall remove this iron, depends on the fact that its oxide is by no means so easily reduced as copper. Being once brought into the state of oxide, it remains in this con- dition and unites with the silicic acid of the sand. 635. ACTION OF HEAT AND AIR. Copper What is the , .,..,. effect of heat is readily oxidized m the air, at a high temperature. Its oxidation may be ob- served, by holding a copper coin in the flame of a spirit lamp, as described in the section on Flame. The iri- descent hues observed in the experiment, are owing to the varying depth of oxide on different portions of the coin. By long continuation of the process, the whole surface is converted into black oxide. If it be sooner suspended, and the coin plunged into cold water, a coating of red oxide containing less oxygen is obtained. 636. USES OF COPPER. Copper is used Mention some . . . , . of the uses of ior a variety of purposes, for which iron copper. would be less suitable, on account of its rapid oxidation. Its employment in sheathing ships, is an example. It is also a constituent of various alloys, to be hereafter described. Among these, all gold and silver coins, and the metal of gold and silver plate, are included. 256 METALS. LEAD. 637. DESCRIPTION. Lead is a bluish scription, ores grey metal, extremely malleable, and read- and solvents? ^ tarnished in the air. It is heavier than any other of the metals mentioned in this work, except mercury, gold, and platinum. Nitric acid is its proper solvent, forming with it, a colorless solution. The principal ore of this metal, is galena, or sulphuret of lead. Lead is also found as carbonate, sulphate, and phosphate of lead. How is lead 638. PRODUCTION. Lead is obtained obtained? from the sulphuret, by heating it with iron, to remove the sulphur. A mixture of metallic lead and sulphuret of iron are thus produced, from which the lead separates by its greater specific gravity. If the oxide of lead could be readily obtained, the reduc- tion by charcoal would be as applicable here, as in the case of other metals. 639. A SECOND METHOD. Another method, is to heat the sulphuret with a portion of sulphate. The sulphate has a large supply of oxygen, while the sulphuret is destitute of this ele- ment. The two may be mixed in such proportions that they will together contain just enough oxygen to carry off all the sulphur, as sulphurous acid. This result having been accomplished by heat, the pure metal of both remains behind. As a preparation for JSxplain an- other method. LEAD. 257 this process, a portion of sulphuret is converted into sulphate, by heating in a reverbaratory furnace. Both parts of the process are in practice united ; a moderate heat with abundant air being first supplied, a portion of sulphate is produced. This is afterwards more highly heated, with the undecomposed sulphuret which remains. 640. ACTION OF AIR AND HEAT. If What occurs i-i-i i i c .1-11 .1 when lead is ^ ea( i is heated before the blow-pipe, in the heated before oxidizing flame, it melts and disappears. the blow-pipe ? The charcoal support becomes at the same time covered with yellow oxide of lead or litharge. The grey coating which at first forms upon the lead, is an oxide containing less oxgen. If, on the other hand, litharge is heated in the reducing flame, it is converted into metal. 641. ACTION OF WATER. Water, with Wh,at is the r . . action of water the help of the air which it always con- on lead. tains, acts sensibly upon lead and becomes in consequence poisonous. This action of water is most decided when it contains no foreign matter. On being conducted through leaden pipes it becomes therefore more impure as a consequence of its very purity. Whatprevents 642. The presence of sulphates and cer- this action? tanl otner salts, such as are usually con- tained in spring water, prevents this effect. The very substances, whose presence in water we are accustomed to regret as impurities, thus become our most efficient protectors against the poisonous effects of lead. 258 METALS. 643. But this rule is not without ex- Do impurities always pro- ception. Certain substances seem to in- crease the action. It is therefore always prudent where it is proposed to conduct water through leaden pipes, to ascertain by direct experiment, whether the particular water in question acts upon the lead or not. 644. ILLUSTRATION. The difference in Describe the . experiment the action of pure water upon lead, and ithlead and that which contains foreign substances in distil Lea water. solution, may be readily proved by exper- iment. For this purpose, bright slips of lead may be placed in two tumblers, the one containing rain water, and the other well or spring water. The former will soon become turbid while the latter remains unaffected. 645. The presence of lead in the former How may the presence of case may be still more strikingly shown, fawn*/ ^ eUeT ky adding to the water a few drops of a solution of hydrosulpluric acid. The for- mation of a dark cloud will show the presence of lead, and indicate the danger to be apprehended. 646. LEAD TREE. Dissolve some crys- Describe the lead tree and tals of sugar of lead, in thirty or forty Us" production. timeS theif bulk f Wat6r > and fil1 a vial with the solution. A strip of zinc, hung in the vial, will branch out in a beautiful ar- borescence of metallic lead. It may be neces- sary to clarify the solution by the addition of a little clear vinegar or acetic acid. A day or two will be required for the completion of the experiment. The effect depends on the MERCURY. 259 superior affinities of zinc for acetic acid. The zinc takes away acid and oxygen from successive portions of the sugar of lead, and leaves the particles of lead subject to the laws of crystallization. At the same time, the zinc having acquired possession of the acid and oxygen, comes into solution as acetate of zinc. A similar arborescence is produced in a solution of silver by metallic mercury. How are shot ^47. MANUFACTURE OF SHOT. Shot are made? prepared by pouring melted lead through perforated iron vessels. The drops are made to fall from a great height that they may become cooled and solidified in their descent. They are caught in water that their shape may not be impaired. Having been assorted by means of seives, they are" polished in revolving casks, containing a small portion of black lead or plumbago. Mention other ^48. OTHER USES OF LEAD. In the uses of lead. form of sheet lead this metal is applied to a variety of familiar uses. It is also largely em- ployed in the manufacture of lead tubing. It is a constituent of various alloys, among which pewter and type metal are the more important. CLASS VI. MERCURY. 649. DESCRIPTION. Mercury is a white Mercury de- - . , i / i i i scription, sol- fluid metal of high lustre and beauty. It "discover? retains the fluid condition at all ordinary temperatures,and is only rendered solid by 260 METALS. extreme cold. Nitric acid is its proper solvent. Mer- cury is sometimes found in the metallic form, but more commonly as the sulphuret or cinnabar, which is its principal ore. It is said that the mines in Mexico were accidentally discovered by a native hunting among the mountains. Laying hold of a shrub to assist him in his ascent, he tore it up by the roots, and a stream of what he supposed to be liquid silver flowed from the broken ground. How is mer- 650. PRODUCTION. Mercury is prepared cury obtained ? f rom t h e sulphuret, by simple roasting in a current of heated air. This metal yields its sulphur so readily to the oxygen of the air that no other agent is essential in its production. The mercurial vapors pass along with the gas, into tubes or chambers where the temperature is lower, and are there condensed to the liquid form. Mention other 651. Mercury may also be produced from methods. fa e sulphuret by the employment of iron filings to remove the sulphur, as in the case of lead. Burned lime may also be used. Its calcium combines with the sulphur and uses its own oxygen for the partial conversion of the sulphuret thus formed into sulphate of lime. 652. ACTION OF HEAT AND AIR. Mercury, What is the J7 action of heat like water, may be boiled away and con- verted into vapor, by the application of heat. At 39 below zero it freezes. It is always to be borne in mind in experiments with this metal arid its compounds, that its fumes as well as its salts, are extremely poisonous. By free access of air and MERCURY. 261 moderate heat, mercury may be gradually converted into red oxide, but a higher temperature expels the oxygen thus absorbed, and the oxide is again converted into metal. This production of a metal from an oxide, by heat alone, is characteristic of the noble metals. They are loth to obscure their splendor in rust ; if it is forced upon them, they need but little assistance of heat to throw it off and re-assume their original beauty. 653. AMALGAMS GLASS MIRRORS. What are amalgams? Mercury combines with many metals form- n?rs sUvered? * n & com P oun ds which are called amalgams. When the mercury is in large proportion they are fluid. Gold, silver, and lead, for example, may be dissolved in mercury. This solvent power of mercury is usefully applied in extracting gold from the rocks which contain it. The beautiful silvering of mirrors consist of an alloy of tin and mercury. Tin foil is applied to the glass, and being afterward drenched with mercury, the excess is removed by pressure. The tin has thus absorbed about one-fourth of its own weight of mercury. 654. A copper coin may be similarly coppercoin be silvered, by rubbing with metallic mer- cur Y> or keeping it well moistened for some time with a solution of mercury in nitric acid. If the solution is quite acid, it must first be nearly neutralized by ammonia. The coin is to be af- terward polished. The chemical action which takes place in this case is similar to that explained in the case of the lead tree. By drawing a line across a thin brass plate, with a pen dipped in solution of mercury, METALS. the plate will be so weakened that it may afterward be readily broken. 655. OTHER USES OF MERCURY. The Mention^ some compounds of mercury are extensively mercury. used in medicine. Corrosive sublimate, a poisonous chloride of mercury, is employed for the destruction of vermin. It is also used in what is called the kyanizing process, to impregnate wood and other vegetable and animal substance, and thus prevent their decay. Another important use of mer- cury is found in the manufacture of barometers and thermometers. It is especially adapted to the measure- ment of heat, by its fluidity at low temperatures, and its ready and equable expansion. SILVER. 656. DESCRIPTION. Silver is a lustrous scription, ores white metal of perfect ductility and malle- and solvents? abil j tVi Itg 1 QSS Q f ] ustre QJ1 exposure, is owing to the presence of a small proportion of sulphur- etted hydrogen in the air. Nitric acid is its proper sol- vent, though for certain purposes oil of vitriol is pre- ferred. Silver is often found native, but moro fre- quently combined with sulphur as silver glance. Galena or sulphuret of lead always contains it in small proportion, and sometimes to the amount of one or two per cent. How is silver && PRODUCTION. Silver is prepared obtained? f rom t h e sulphuret, by first roasting the ore SILVER. 263 with common salt, in order to convert it into chloride. Iron is subsequently employed to remove the chlorine, and isolate the metallic silver. Give the com- 658. Mercury is added with the iron, in piete process. orc j er ^^ j t ma y dj sso i ve the silver from the mass of roasted ore and iron, as fast as it is formed' The materials are agitated with water for many hours together. At the end of the process the mercury, with its load of silver, is drawn off from the bottom of the cask. The solution of silver in mercury is afterward filtered through buckskin or closely woven cloth, which allows a large part of the liquid metal to pass, while the silver with a small portion of mercury is detained. The silver is then freed of its remaining mercury by heat. The above process is called amalgamation. 659. SILVER OBTAINED FROM LEAD. Describe the process for Almost all lead, as produced from galena and its other ores ' contains a certain pro- portion of silver. The latter metal may be freed from a large part of the lead by melting the alloy and then allowing it to cool slowly. Most of the lead solidifies in small crystals, and may be skim- med out with an iron cullender. An alloy containing silver in large proportion remains in the liquid condi- tion. It is afterwards solidified by further cooling. The above is called Pattinson's process. 660. CUPELLATION. The remainder of How is the re- j eac [ j s separated from the silver by con- maimng lead separated? verting it into oxide, in a current of heated air. The silver does not oxidize under these circumstances, but retains the metallic form. 264 METALS. The mass of metal grows smaller as the process pro- ceeds, till finally pure silver remains. The moment of its production is indicated by a beautiful play of colors and a sudden brightening of the metal. The above process is carried on upon a hollowed and com- pacted mass of bone-ash, called a cupel. The object of the cupel is not alone to support the metal, but to ab- sorb the hot and fused oxide of lead as fast as it is formed. If a. little copper is present, it is also absorbed with the lead. The process is called cupellation. 661. It may be illustrated on a small How mcf/ the process be u~ scale, by making an excavation in a piece lustrated? Q f c [ iarcoa ] ) an( j pressing into it a lining of well burned and moistened bone ash. A globule of lead, to which a little silver has been added, is to be heated, on the support, in the oxidizing flame. For separating a small quantity of lead from silver, the bone ash is not essential. The process may be conducted before the blowpipe, upon the naked char- coal. A small portion of silver may often be obtained from the lead of commerce by this means. What is said 662. SILVER COIN. The standard sil- of silver coins? ver o f t h e United States is an alloy con- taining ten per cent, of copper. Silver plate should have the same composition. The object of alloying with copper, is to impart greater hardness to the metal, and secure against the gradual loss from attrition, which would otherwise occur. Spanish silver often contains a small proportion of gold. The gold is left as a black SILVER. 265 powder, in dissolving such coins in nitric acid. Its color and lustre may be brought out by rubbing. 663. THE SILVER ASSAY. Assaying is What is as- , n ,, . laying, and tne process by which the proportion of met- why necessa- a i s j n an a }} oy j s ascertained. In all estab- lishments where money is coined, assaying is an important part of the work of the establishment. The precious metals, as received at the mint, commonly contain a certain proportion of other metals. But it may be too much or too little. It is the business of the assayer to ascertain its precise composition, that the metal may be rendered purer, if necessary, or be fur- ther alloyed, if found purer than the standard. 664. As a preparation for the silver as- Descmbc the process of as- say, a sample, containing an ounce, or other definite weight of the impure metal, is dis- solved in nitric acid. The dissolved silver has the pro- perty of becoming solid again, and sinking to the bottom of the clear solution as a white curd, just in proportion as common salt is fur- nished to it. But the other metals which may be present, as impurities, have no such effect. It follows, that the amount of silver present, is just in proportion to the amount of salt it is necessary to supply, before the pre- cipitation, or formation of the curd, ceases. Now, the assayer knows beforehand, how much salt he must supply to the solution of an ounce of metal, if it be all silver. If he finds that an ounce of the sample, re- quires to be supplied with the same quantity, before the precipitation ceases, he knows that the metal is all silver ; 12 266 METALS. if but half as much is required, he knows that it is but half silver. Having ascertained the true proportion, the assay is completed. The salt required in the pro- cess is employed in the form of a solution, and the quantity used is known by pouring it from a graduated vessel. 665. EXPLANATION. The curd, which Explain the chemical ac- forms in the above process, is insoluble abovTprocess. chloride of silver, formed from the silver of * the solution, and the chlorine of the salt. The nitric acid and oxygen, which were combined with the silver, at the same time unite with the sodium, forming nitrate of soda, which remains in solution. 666. SILVER SEPARATED FROM COPPER. Describe the ,/. method of ex- Copper, obtained from certain ores, con- tams so mucn silver as to make their separa- tion an object of importance. The method pursued is, to fuse the copper with lead. As the lead flows out again by subsequent fusion, it brings with it all the silver, and the copper remains behind as a spongy mass. This process is called liquation. The silver is then freed from lead by the process of cupellation al- ready described. Mention some ^67. IfsES OF SILVER. Most US6S of uses of silver, silver are so familiar that they need not be here mentioned. Its employment for daguerreotype plates depends on the fact that the color of many of its compounds is readily changed by light. This sub- ject is more fully considered in the section on chlo- rides. The nitrate of silver, or lunar caustic, is used in surgical operations, to burn or cauterize the flesh. GOLD. 267 In solution, it is also employed as a hair dye, and in the production of indelible ink. GOLD. Mention some 668. DESCRIPTION. Gold is a yellow properties of meta i o f brilliant and permanent lustre. gold? Its sol- vent? and Its extreme malleability is strikingly illus- occurrence? into a leaf but little more than ^J of an inch in thickness. As the fact may be otherwise stated, a cube of gold, five inches on a side, could be so extended as to cover more than an acre of ground. Such gold leaf is permeable to hydrogen. A jet of this gas may be blown through it and kindled on the opposite side. Gold is proof against all ordinary acids, excepting aqua- regia. It is found only in the metallic state, and com- monly either in quartz rock or in the sands of rivers. Native gold contains from five to fifteen per cent, of silver. How is pure ^69. PRODUCTION. - THE REFINING PRO- goid produced? CESS . Native gold may be freed from the silver which it contains, by the agency of concentrated sulphuric, or nitric acid. A difficulty in accomplishing this result arises from the fact that every particle of silver is so perfectly surrounded by gold, that the acid does not readily reach it. This difficulty is overcome by fusing more silver into the gold, and thus opening a passage for the solvent. This being done, both the original silver and that which has been added, are read- ily removed. The above is the process at present pur- sued in France for refining gold. 268 METALS. Describe an- 670. ANOTHER METHOD. The SGCOIld other method. me thod is essentially the same as that al- ready described, with the substitution of nitric for sul- phuric acid. The addition of silver, as a preliminary step, is found necessary in this process also. So much silver is added, that the gold forms but a quarter of the mass exposed to the action of the acid. The method is hence called quartation. * The process involves a previous knowledge of the approximate composition of the mixed metal. This may be obtained by the touchstone, as hereafter described. Whatisamal- 671. AMALGAMATION. Gold may be ob- gamation? tained from any material which contains it, even in small proportion, by the process of amalga- mation. This process consists in agitating the finely divided material with mercury, until the latter has ex- tracted all of the precious metal. It is then obtained from its solution in mercury, by the same means em- ployed in the case of silver. This method is employed in the case of the gold-bearing quartz of California. The dust of jewelers shops is similarly treated, in order to save the small proportions of gold which it contains. 672. GOLD FROM LEAD AND COPPER. How is gold . separated Certain ores of lead and copper contain so much old that it; is Profitable to extract it from the metal which they yield. This is done by the processes of liquation and cupellation be- fore described. * In the practice of the United States Mint, the addition of less silver has been found sufficient. The proportion of gold is there reduced to one-third. Nitric acid is then employed in the refining process. GOLD. 269 673. GOLD FROM STJLPHURETS OF IRON, How is qold ci i i f e obtained from &c. Sulphurets of iron, copper, dec., certain ml- sometimes contain gold, in small quantity, and so completely disseminated that it can- not be readily extracted by mercury. It has been found advantageous to heat such ores with nitrate of soda, previous to amalgamation. The sulphurets are thus partially converted into sulphates, which can be washed out. What remains of the pulverized material is at the same time thoroughly opened to the action of mer- cury. Describe the 674. THE GOLD ASSAY. Gold to be as- method of 'as- sa y e( j contains commonly, only silver and saying gold ? . . . ' ' / Why is siher copper, as impurities. By msing the sam- ple with lead, and then removing this metal by cupel! ation, it carries with it the copper, into the cupel. A globule, containing only gold and silver, remains. The silver is then dissolved out by nitric acid. The remaining sponge of pure gold being weighed, and its weight compared with that of the orig- inal sample, the assay is completed. More silver is added in the process, for reasons stated in a. previous paragraph. What is the 675. ASSAY OF GOLD BY THE TOUCH- touckstone? STONE. Any hard and somewhat gritty and how ts it J J used in assay- stone, of a dark color, which is not acted on by acids answers the purpose of a touch- stone. The assay consists in marking upon the stone with the alloy, and judging of the purity of the metal from the color of the mark, and the degree in which it is affected by an acid. Nitric acid, to which a very 270 METALS. small quantity of muriatic acid has been added, is em- ployed in this test. Gold alone is proof against its action. In proportion to the permanence of the mark, is the purity of the gold which has been submitted to the assay. What is said 676. GOLD COIN. The gold employed of gold coin ? f or CQ ^ plate and j e we i ry j s a ] wa y s alloyed with a certain portion of copper or silver, to give it greater hardness. The standard gold of the United States is nine-tenths pure gold, the remaining tenth being an alloy of copper and silver. 677. PURITY OF GOLD. The purity of How is the de- . gree of purity gold is expressed in carats , a carat signify- mwMdr ing ' P racticall 7> one twenty-fourth. Thus, when gold is said to be sixteen carats fine, it is meant, that two-thirds of it is pure gold. Gold eighteen carats fine is three-fourths pure gold, and one- fourth alloy. 678. GILDING. Gilding by the galvanic How is copper jewelry gild- battery has been already described. This method is, in most cases, preferable to all others. Copper jewelry is thinly gilded by boiling in a solution of gold in carbonate of soda or potash. The solution is prepared by first dissolving the gold in aqua regia, and afterward precipitating and re-dissolving it, by means of the carbonate above named. 679. Gildine may also be effected by an Describe the J method of gild- amalgam of gold and mercury. The amal- omof am/ am ^ em applied, the mercury is expelled by heat and the gold remains. This me- thod is very frequently employed. A coating of pure PLATINUM. 271 gold is produced upon articles of jewelry, made of im- pure metal, by first heating them, and then dissolving out the copper by means of nitric acid. PLATLNTJM. 680. DESCRIPTION. Platinum is the Platinum Description, last of the noble metals. It resembles ^sofoentsT' Stee ^ m c l r > anc ^ possesses a high degree of malleability. It is the heaviest and the most infusible of all metals. At a white heat it may be welded, like iron. Like gold, it resists the action of any single acid, but may be dissolved in aqua-regia. It is commonly found, like gold, in small flattened grains, in the sand of certain rivers. Its pecuniary value is about half that of the more precious metal. 681. PLATINUM CONDENSES GASES. The Mention a re- markable ef- metal platinum has the remarkable pro- P eri Y of condensing gases upon its surface, and thereby increasing their affinities. This effect is in proportion to the surface exposed. It may be prepared for this experi- ment by burning paper, previously moistened with a solution of this metal. Such an ash, by simple exposure to the air, condenses and retains a large quantity of oxygen within its pores. On holding it in a jet of hydrogen, the condensed oxygen immediately unites with the latter gas so energetically as to inflame it. 682. Platinum is employed for similar Give another illustration of purposes, in the form of a sponge, and as a this effect. powder, called p latinum black. A mixture 272 METALS. of nitric oxide and hydrogen, passed through a tube con- taining heated platinum black, issues from the tube as ammonia and water. The hydrogen has entered into combination with both of the elements of the nitric oxide, producing two new compounds. Why isplati- 683. OTHER USES OF PLATINUM. The num. superior m0 st important use to which platinum is to ot her metals _ . for chemical applied in the arts, is in the manufacture apparatus? o ^ ^Q^^I apparatus. Its extreme in- fusibility and resistance to acids, adapt it especially to this purpose. In the manufacture of oil of vitriol, for example, no other material excepting gold could well take the place of the platinum vessels, in which con- centration is effected. Platinum crucibles are also in- valuable, as they may be exposed to the fire of a blast furnace without injury. Nothing less than the most intense heat of the oxyhydrogen blow-pipe, or galvanic battery, is sufficient to fuse this metal. ALLOYS. . 684. The compounds of metals with alloy? Give metals are called alloys. The following fiontf P bras S are amon g the more important. and other al- Brass is copper, lightened in color by the addition of one-fourth its weight of zinc. German silver is a kind of brass, still further whitened by nickel. Its exact composition has been given in another place. An alloy of 30 parts silver, 25 of nickel, and 55 of copper forms a nearly perfect substitute for silver for all ornamental purposes. ALLOYS. 273 Bronze is copper, containing ten per cent, of tin. Bell metal is a kind of bronze, containing tin in larger proportion. Pewter is an alloy of tin with variable proportions of antimony or lead. Britannia ware, so called, is a sort of pewter. Type metal is an alloy of lead, containing twenty- five per cent, of copper. By the use of tin, instead of lead, a better, but more expensive type metal may be produced. Zinc, with a few per cent, of copper, lead, and tin, has also been recently employed. Fine and coarse solders are alloys of tin and lead the former being two-thirds, and the latter one-fourth, tin. Hard solder is a variety of brass. Newton's fusible metal, which has the remarkable property of melting in boiling water, is composed of 8 parts of bismuth, 5 of lead, and 3 of tin. Many of the above alloys are slightly varied in their character by the addition of other metals in small quantity. 274 SALTS. CHAPTER III. SALTS. SOLUTION AND CRYSTALLIZATION. , 685. DEFINITION. Under the general What com- pounds are head of salts, are included all compounds of acids and bases, and beside these, the compounds of chlorine, bromine, iodine, sulphur, &c. with the metals. Sulphate of soda, or blue vitriol, is an example of the first class, and chloride of sodium, a common salt, of the latter. 686. PREPARATION or SALTS. The salts Mention some methodsofpre- of most acids may be produced, by sim- paring salts ? ^ b rmgmg tne ac id an d ox id e together. Sulphate of potassa is thus produced, from sulphuric acid and potassa. Heat is sometimes required, to bring about the combination. They may also be prepared from the carbonates. Thus acetate of lime, is pro- duced by pouring strong vinegar on chalk, or carbo- nate of lime. Carbonic acid is, in such cases, expelled by the stronger acid which is employed. Other meth- ods of preparing individual salts, will be hereafter given. Explain solu- 687. SOLUTION. The particles of all tion. bodies are held together, as before ex- plained, by the attraction of cohesion. But water has SOLUTION. 275 also an attraction for these particles. In the case of many substances, it overcomes the force of cohesion and distributes them throughout its own volume. Such a distribution, in which the solid form of the solid is entirely lost, is called solution. Different liquids are employed, as solvents for different sub- stances. A solution is said to be saturated when no more of the solid will dissolve in it. 688. PRECIPITATION. In solution, the Have the par- ticles lost their particles of bodies have not lost their TractionThoio property of cohesive attraction. It is only may they be overcome by a superior force. As soon as precipitated ? this is weakened, they unite again to form a solid. The solvent power of alcohol for camphor, is thus diminished when water is added to the solution. As a consequence, the camphor immediately re- assumes the solid form. When a solid is thus re-produced as a liquid, it is called a precipit- ate. The above experiment is made, by ad- ding water to an ordinary solution of camphor. 689. One case of precipitation is men- Mention two . i i T general mcth- tioned m the preceding paragraph. But it ods of precip- mav ^ e effected by various methods. All ttation f * of these may be arranged under two heads ; precipitation by changing the character or quantity of the solvent, and precipitation by changing the sub- stance dissolved. Mention three 690. CHANGE OF SOLVENT. The three 'b' cases in whic h precipitation is effected by ye of sol- changes in the solvent, are, mixing, cooling, and evaporation. The first has just been 276 SALTS. described. The second is illustrated in the production of alum crystals, by cooling a hot solution. The third consists in dissolving a solid in some liquid, and then boiling away the latter. The experiment may be tried with a saturated solution of salt and water. As fast as the water is boiled away, the portion which has lost its solvent, re-assumes the solid form. 691. CHANGE OF SUBSTANCE DISSOLVED. Describe two , . , , . cases by The change in the substance dissolved, is Stance' ^ mb ' effected ? in some cases > by addition, and in others by subtraction. Carbonic acid, blown through lime water, precipitates it, by addition. The precipitate is chalk, or carbonate of lime. Pot- ash, added to a solution of sulphate of copper, precip- itates it by subtraction ; the precipitate is oxide of copper, deprived of its acid by the potash. 692. EXPLANATION. The above cases State the cause f . . , ~ of predpita- of precipitation, demand some further ex- hon. m the planation. As fast as carbonic acid is blown above cases. into the lime water, in the first case, the new substance, chalk, or carbonate of lime, is produced throughout the liquid. We may suppose that innume- rable particles are first formed, before they unite to form a precipitate. But the cohesive attraction put forth by the particles of this new compound is so great that the opposing attraction of the water is overcome, they rush together, and assume the solid form of a pre- cipitate. This did not happen in the case of lime alone, because the cohesive attraction between its particles is inferior to the opposing attraction of the water. The second case is to be similarly explained. COHESION. 277 693. RELATION OF COHESION AND AFFIN- What is said of the relation iTY. The chemical affinity of potassa for "/ndaffinit ? carbonic acicl , is evidently greater than that of lime. The former base retains the acid so firmly, that no degree of heat can effect it, while the latter gives up its acid with readiness, under the influence of a high temperature. Notwithstanding the superior affinity of potassa, lime will take from it, its carbonic acid, if added to a solution of carbonate of potassa, in water. The mixture being made, the par- ticles in this and in all similar cases, tend to re-arrange themselves in the solid form. They seem to do this without reference to their chemical affinities, in such a manner as best to resist the solvent action of the water, or other liquid. Carbonate of lime resists such action better than carbonate of potassa. The former is there- fore produced. The cohesion of carbonate of lime, using the term, in the sense of capacity to resist the separating power of water, has therefore determined the production of this substance, in opposition to or- dinary chemical affinities, 694. The above case illustrates a gene- Statc and il- lustrate the ral law. Two substances, which when general law? Qn it e( j form an insoluble compound, gen- erally unite and produce it, when they meet in so- lution. To illustrate by another example : phos- phate of lime, or bone ash, is insoluble. Then we may be sure that phosphoric acid and lime, if brought together by mixing two solutions, will de- sert any substances with which they were before combined, and unite to form insoluble phosphate of 12* 278 SALTS. lime. This rule is not without exceptions, but it enables the chemist to determine beforehand innume- rable cases of precipitation. 695. SOLUTION AND CHEMICAL COMBINA- tion differ TioN. Solution differs from chemical com- bination in tne varying proportions in which it occurs according to tempera- ture, and in the absence of any change of chemical properties. Nitre, for example, dissolves in water, at 100, in nearly double the quantity which will dis- solve at 70. At the same time, it forms a solution to which it has imparted its own chemical properties unchanged. 596. Another important distinction is State another , important found in the following fact. While chem- twn ' ical combination is most active between bodies whose properties are most opposed, such as fat and resins, solution occurs most readily in the case of similar substances. The metals dissolve in mer- cury. Salts dissolve in water. Fats and resins dissolve in alcohol and ether, which, like themselves, contain much hydrogen. 697. CRYSTALLIZATION. In passing from What is said , r o/ crystalline the liquid to the solid condition, the par- arrangement? ^^ Qf mogt bodieg assume a crystalline arrangement. Their mutual attraction is more than a mere force which draws and binds them together. It groups them in regular forms. The crystals thus produced are often too small to be separately seen. But even where this is the case, the crystalline structure is readily observed. Surfaces of zinc, or cast iron, ex- CRYSTALS. 279 How may ' posed by recent fracture, are familiar examples. But where the circumstances are favorable for the forma- tion of individual and separate crystals, the most beau- tiful and symmetrical forms are often the result. 698. PRODUCTION OF CRYSTALS. Most . of the salts to be described in this cnap- produced? ter may be 0^^ j n tne form of crys- tals, by evaporating or cooling their saturated solutions. The method by cooling, has already been described, in the Chapter on Water. In obtaining crystals by evaporation, the solution is to be moderately heated, in a saucer or other vessel. The crystals formed by either method, commonly contain water, which becomes part of the solid crystal, and is called water of crystalliza- tion. 699. VARIETY OF CRYSTALS. The forms of leaves and flowers are scarcely more va- rious than those of crystals. The latter are, as it were, the flowers of the mineral world, as distinctly characterized in their peculiar beauty as the flowers that bloom in the air above them. Even where color fails, the eye of science distinguishes pe- culiar features which often enable it to determine the nature of a substance, from the external crystalline form which it assumes. 1234 5 How may the variety of crystals be il- lustrated ? 280 SALTS. What is said 700 ' FoRMS OF CRYSTALS.AS every of the variety flower has its own distinctive form of of forms in a . , . single sub- leaves and petals, so every substance has its own form or set of forms from which it never essentially varies. Among these, or its combi- nations, it is, as it were, left free to choose in every crystal which it builds. The mineral quartz, which caps its prismatic palace with a hexagonal pyramid, is an example. Its common form represented in Fig. 4, is a combination of the prism and double six-sided py- ramid, which commence the series. 701. A form similar to the double six- D escribe some forms of a sided pyramid, with faces corresponding to single set. -^ twe j ve converging edges, belongs to the same set. Double pyramids similar to each of these, but of one-half or one-third their relative height, or differing from them by some other simple ratio, also belong to the same set of forms. Fig. 3 represents a form com- posed of two of these pyramids. Fig. 5 represents another form in which one of them is modified by two faces of a prism. To all of these and certain other in- timately related forms, the imaginary privilege of se- lection and combination, above referred to, extends. But most substances, like quartz, as above described, affect some particular shape or combination in which they usually appear. 702. MODIFICATIONS OF CRYSTALS. What modifi- _ ... cations of the Whatever the form or combination may be, may occur? ^ * s su 806 ?^ 6 of variation, in any degree, so long as its angles correspond to those of the perfect shape. Thus the mineral quartz, in its CRYSTALS. 281 commonly occurring combination, is not restricted to a perfectly symmetrical shape, like that above presented. It may develop one surface and diminish the others to any extent. Forms such as are represented in the margin result. Different as they seem, it will be observed that they agree precisely with the per- fect shape in the angles be- tween the surfaces of the prism and pyramid, and the different surfaces of each. In this their identity as crystalline forms consists. It would thus seem that nature pays exclusive attention to the corners and an- gles in her various systems of crystalline architecture. 703. The least variation of the relative What consti- ..... , tutes a new length of the vertical axis that is not by some simple ratio, constitutes a new and distinct form. This has its related forms as before, the whole making a new and distinct set, to which the choice of any substance that enters it, is limited. 704. SYSTEMS OF CRYSTAL FORMS. It Define ano- ther system of will be obvious to the student that the sub- C forms liUe stitution of an octahedron, such as is re- presented in the accompanying figure, for the double six-sided pyramid, would be the starting point, of an entirely distinct system of forms. Within its limits there might be in- numerable sets as before. It would be, as it were, the type of a new order of crystalline architec- ture, susceptible of variations consistent with the ge- neral style. 282 SALTS. Define the 705. A third system is characterized by fourth^ inequality in three principal dimensions. systems. The axis or lines connecting the solid an- gles in the octahedron, and joining the faces in the prism, are all unequal. As each axes may be indefi- nitely varied in this system, there is room wthin its limits for still greater variety than before. The fourth system differs from the third in an oblique position of some one of the unequal axes. The student will readily imagine certain oblique forms which it in- cludes. The fifth system is characterized by an ob- lique position of three unequal axes.* 706. The regular system, which is pro- What are the f characteristics perly the first, has all its axes equal, and all /yst k emT Ular its an g les ri g ht angles.f The figures which precede this paragraph, represent some of its simpler forms. Those which follow, are among its most interesting combinations. In the last, the student will be able to select three distinct kinds of surfaces. One of these sets, if enlarged to the exclusion of the others, would produce a cube, * The variations of length and inclination of axis which correspond to the different systems, may be beautifully illustrated to the eye by a wooden frame work movable at the centre with threads connecting the arms. f The first and sixth systems are made to change places in the above ai'rangement, for the convenience of illustration, from the quartz crystal. CRYSTALS. 283 another a regular octahedron, and a third a dodecahe- dron ; forms corresponding to those of the preceding line. In view of its simplicity, the regular system may be regarded as a sort of primitive architecture, yielding, however, to no other system in the beauty of its forms. Under one or the other of these systems all forms of crystals are included. To each of them, with the ex- ception of the last, belong innumerable sets of forms according to the degree of inequality or inclination of the axes. Equality and rectangular position of the axes being characteristic of the first system, it is not suscep- tible of the sort of variation which is essential to pro- duce different sets of figures. But in this, as in other systems, the modification of surfaces may occur to any extent. , , ,, 707. As the architect is able, from some bn.ow now trie formofacrys- relic of a broken column, to build up in ferr^ifrom, imagination the temple of which it formed its angles. a p art . as the comparative anatomist knows how, from the fragment of a single bone to reconstruct in imagination the perfect animal which possessed it ; so, from the merest point of a crystal, its complete form may often be readily inferred. In proportion as a dou- ble pyramid is lengthened out, the angles above arid below are rendered more acute. Prom an accurate admeasurement of this angle its whole shape may there- fore be inferred. Such admeasurement of various an- 284 SALTS. gles is employed not alone as a means of inference of perfect from imperfect shapes, but as the simplest means of accurate description. For, as before stated, it is the size of the corresponding angles of a crystal which form its characteristic. Have different 70S. ISOMORPHISM. Many substances substances ever whi(jh are aljke in ^ , mmber and arrange . Iflv SGL-iflv CTlj& m ^ tallineform? ment of their atoms, although these atoms are different in kind, have the same crystalline form. This is the case with common alum, and other alums to be hereafter mentioned. The similar arrangement of atoms will be best seen by inspecting the formulas which represent them. These are given in the appendix. The term expresses their likeness in form. Besides this series there are many other isomorphous groups. Give the pro- 709. It is to be regarded as probable, babie reason. t h at fa Q sna pe and size of the molecules thus similarly composed, is exactly the same, and that it is for this reason that they may be used in building up crystals of the same form. The different alums will even unite when they crystallize, in building up one and the same crystal. Substances which are thus si- milar in composition, and crystallize in the same form, are called isomorphous. There are many cases of simi- lar crystalline form in substances which are not thus related in other respects. Such bodies are not called isomorphous, notwithstanding their identity of crys- talline form. Certain substances crystallize in forms belonging to two or even three different systems, ac- cording to the temperature, or other circumstances under which their crystallization occurs. Such sub- stances are called dimorphous or trimorphous. OXIDES. 285 OXIDES. Define an ox- 710. The compounds of the metals with terms ere- ox yg en j wit h tne exception of those which ferent oxides have decided Iv acid properties, are called distinguished? _ J oxides. When a metal unites with oxy- gen in several different proportions, forming different oxides, these a"re distinguished as protoxide, deutoxide or binoxide, tritoxidc or teroxide : terms signifying first, second, and third ^oxides. The highest oxide is also called peroxide. An oxide containing three atoms of oxygen to two atoms of metal, is called a sesquiox- ide. The names of chlorides, sulphurets, &c. are simi- larly modified, to indicate the proportion of chlorine, sulphur, &c. which they respectively contain. Com- pounds of non-metallic substances with oxygen which do not possess acid properties, are also called oxides. There are, for example, oxides of nitrogen and phos- phorus. 711. PROPERTIES OF OXIDES. The What is said of add and lower oxides are generally strong bases, basic proper- w ^{\ e tne higher oxides exhibit basic or tics in oxides ? acid properties, according to circumstances. Binoxide of tin, for example, described in a previous chapter, acts as a base in combining with sulphuric acid to form 'a sulphate, while, if fused with potassa, it acts as an acid, and forms a stannate. On account of its acid property, the binoxide of tin is also called stan- nic acid. The name is derived from Stannum, which is the Latin word for Tin. 286 OXIDES. 712. FORMATION OF OXIDES. Oxides How are ox- ides formed? may be formed directly by the union of Give exam- oxygen and metal, or, indirectly, by sepa- rating them from some salts which con- tain them. Thus oxide of copper may be produced by simply heating copper in the air ; or, by precipita- tion from the nitrate, through the agency of potassa, or, thirdly, by simply heating the nitrate till all the acid is expelled. The oxides of tin and antimony are also directly produced, by the action of nitric acid on the metals. What is a hy- 713. HYDRATES, OR HYDRATED OXIDES. drated oxide? Oxides commonly combine in the act of precipitation with a certain proportion of water. The compound thus formed, are called hydrated oxides, or simply hydrates. The water may, in most cases, be separated from them by heat, and the uncombined oxide thus obtained. 714. CONVERSION OF OXIDES. When What is said . of the conver- oxides are converted into chlorides, sul- sionof oxides? phuretgj ^ by double decompositions, to be hereafter described, the chlorides, sulphurets, &c., correspond to the oxides from which they are formed. Thus, protoxide of iron yields protochloride, while ses- quioxide yields sesquichloride. 715. THE ALKALIES. The oxides of po- Give some . properties of tassmm and sodium are called alkalies. the alkalies. They are known as pot assa and soda, and are commonly obtained as hydrates. They are white infusible substances, from which the water cannot be expelled by heat. They are soluble in water, POTASSA. 287 and are the strongest of all bases. From their destruc- tive action on animal matter, they are called caustic alkalies, and are often distinguished, by this term, from the carbonates of potassa and soda. POTASSA. 716. Potassa is prepared from wood What is the source of po- ashes. The ley obtained from these be- ing evaporated to dryness, the mass which remains is the crude potash of commerce. This, when purified, becomes pearlash. How is potassa 717. CAUSTIC POTASSA. Commercial prepared? potash and pearlash are both carbonates of potash, from which the carbonic acid must be removed, in order to produce potassa itself. This is done by a milk of slaked lime. A solution of potash, in at least ten parts of hot water, or a hot ley, made directly from wood ashes, should be employed in the experiment. To this, the milk of lime is added, little by little, the solution boiled up after each addition, and then allowed to settle. If, after settling, a por- tion of the clear liquid is found no longer to effervesce on the addition of an acid, it is sufficient evidence that all the carbonic acid has been removed by the lime, and the process is completed. This must be as- certained by trial. About half as much lime as pot- ash will be required in the process. Caustic soda is similarly made from the carbonate of soda. 718. The boiling in the above process Give a modi- fication of the may be omitted, if the mixture be fre- above method. quent]y sha ken up, during several days. 288 OXIDES. This modification of the method is much the most convenient for the production of caustic al- kalies in small quantities. Solutions, useful for a variety of chemical purposes, are thus obtained, and should be preserved for use. They may be converted into solids, by evaporation, and the solid thus obtained fused and run into moulds. The commercial caustic potassa, occurring in slender sticks of white or grey color, is thus produced. 719. AFFINITY OF POTASSA FOR WATER. How can the affinity of po- Ordinary potassa, as before stated, is a h y drate - But its affinit y for water, is by no means yet satis- fied in this form. If exposed in an open vessel, it rapidly attracts moisture from the air. It often dissolves, in the course of a few days, in the water thus obtained. 720. DECOMPOSITION BY POTASSA. Po- What is said . of the decom- tassa added to the solution of almost P saitsTyp f o- an y salt > occasions a precipitate. The tassa? potassa takes the acid, and precipitates the insoluble base. If the experiment be made with an ammonia salt, the base being volatile, passes off into the air. Experiments may also be made with green, blue, and white vitriols, which are, respectively, sul- phates of iron, copper, and zinc. , 721. CLEANSING AND CAUSTIC PROPER- EB OF PoxAssA.-If soiled rags be boiled perties of po- w i t h a dilute solution of potassa, they will be thoroughly cleansed by the process. POTASSA. 289 The potassa unites with the acid of the grease con- tained in the cloth, and thus makes it soluble in water. 722. ACTION OF POTASSA ON ANIMAL What is the action of po- MATTER. Potassa is extremely destructive ^al matter />" of animal matter. It readily dissolves the skin, as may be proved by rubbing a little between the fingers. If applied in sufficient quantity. it destroys the vitality of the flesh. It is often used for this purpose by surgeons. 723. EFFECT ON VEGETABLE COLORS. How does po- tassa affect vc- Vegetable blues which have been pre- getabie colors? viously re ddened by acid, are restored to their original color by the action of potash and other alkalies. The blue pigment called litmus is the one most readily obtained. In preparation for the exper- iment it is infused in hot water The transformation from blue to red, and vice versa, may be repeated as often as desired, by the alternate addition of acid and alkali. Paper soaked in the red and blue liquids forms the test-paper of the chemist. It is used to in- dicate the presence of smaller quantities of acid and alkali than could be recognized by the taste. An extract of purple cabbage leaves, or the leaf itself, may be used in the above experiment. In this case, the change of color by alkalies is from red to green. 724. PROPERTIES OF SODA. The prop- of erties of soda, are very similar to those of potassa, as above described. 13 290 OXIDES. OXIDE OF AMMONIUM. 725. FORMATION. When hydrated WJiatissaid . . of oxide of sulphuric acid combines with ammonia, ammonium? tne wa ter which it contains is regarded as converting the ammonia into oxide of ammonium, with which the acid then combines. The action of other hydrated acids is the same. In naming the cor- responding salts, the oxide of ammonium is called ammonia. Thus, the compound with sulphuric acid, is called sulphate of ammonia. It is to be borne in mind, that oxide of ammonium of such salts, contains an atom of water, in addition to the constituents of ammoniacal gas. OXIDE OF CALCIUM. How is lime 726. LIME. Lime or oxide of calcium obtained? is best obtained by heating chalk, marble or limestone. These are all carbonates of lime. Under the influence of a high temperature, the tendency of the carbonic acid to assume the gaseous form is so increased, that the chemical affinities of the base are overcome. The carbonic acid escapes, leaving the caus- tic lime behind. This is the process of the ordinary lime kiln. The superior strength of potassa and soda, as bases, is illustrated by the fact that the carbonic acid cannot be removed from them through the agency of heat. TO* , , ^27. HYDRATE OF LIME. SLAKED LIME. What is hy- drate of * When water is added to lime, one equiva- ^^me? j ent j mme( ji ate ]y combines with it, and LIME. 291 forms a hydrate. The hydrate, like that of potassa, is dry, although it contains a large portion of combined water. As the water thus becomes solid in the com- pound, its latent heat is given off to the air or sur- rounding objects. The employment of heat thus pro- duced for culinary operations has been recently sug- gested. If the process of slaking be conducted under a tumbler, with a slight surplus of water, steam will be produced. On lifting the tumbler, it will be- come visible by its condensation into vapor. 728. IGNITION BY LIME. The heat How may gun- powder be iff- thus produced, is often sufficient to ignite Ik^en^of gun-powder. It should be sprinkled on lime? the mass, and kept dry while the slaking proceeds. Warm water and well-burned lime should be employed in the experiment. 729. ACTION OF THE AIR. If lime is What is the action of the exposed to the action of the air, it gradu- aironlime? cart)On i c acid and water, and becomes converted into a mixture of hydrate and carbonate. It is then called air-slaked lime. By sufficiently long exposure the conversion into carbo- nate is complete. 730. LIME IN MORTAR. Ordinary mortar mortar har- is a mixture of sand and lime. It hardens not simply by drying, but by the absorp- tion of carbonic acid from the air. A compound of hydrate and carbonate of lime, possessed of great hard- ness, is thus produced. A gradual combination, also takes place between the silica and the lime, which binds the two constituents still more firmly together. 292 OXIDES. 731. HYDRAULIC CEMENT. If, in the WJiat is liy- drauic ce- preparation of lime, a limestone is used which contains a certain proportion of clay, a double silicate of alumina and lime is produced. The compound has not alone the property of combi- ning with water, like ordinary lime, but of becoming extremely hard and insoluble in the process. Such a lime is called hydraulic cement, and is used for building under water. Silica, magnesia, and some other sub- stances impart the same property to lime. ALUMINA, MAGNESIA, (fee. Whatisalu- 732. ALUMINA, &c. Alumina, so named mina ' from the corresponding metal, is insoluble, and is called an earth. It is, like the peroxide of iron, a sesquoxide, containing three atoms of oxygen to two of metal. Natural alumina, colored blue, is called sap- phire. Colored red, it forms the oriental ruby. The topaz and the emerald are also compounds containing the same oxide. Baryta, strontia, lime and magnesia, are regarded as standing midway between the earth alumina and the alkalies, and are called alkaline earths. They are more or less soluble, and possess the general properties of the alkalies, in a diminished degree. Magnesia is sometimes classed as an earth. 733. OTHER METALLIC OXIDES. The What are the properties of remaining metallic oxides are powders of lalhfoxiL% differ ent colors. Most of them are insol- uble. The more important have been already noticed, in the Chapter on Metals. Their OXIDES. 293 hydrates may be obtained by precipitating solutions of their salts with potassa, soda, or ammonia. The hy- drate of the oxide of copper, and peroxide of iron, may serve as examples. The former is blue and the latter a reddish brown. 734. The hydrated oxides of nickel, co- ted oxid dis- bait, tin and copper, produced from soliu soiveinam- tion o f these meta i s b y t h e addition of moma ? J ammonia, are again re-dissolved in an excess of ammonia. That of copper dissolves with a beautiful blue color, which is conclusive evidence that the liquid with which the experiment is made contains copper in solution. 735. USES. Oxide of magnesium or Give the uses of some of the magnesia, and mercury, among others, are oxide* ? used in medicine, and white oxide of zinc, as a paint. Litharge or protoxide of lead is employed in making flint-glass and varnishes. Red lead is used as a paint. Oxide of bismuth is employed as a cos- metic. 736. Oxide of manganese is used to C lor laSS U1 ' le aild Vi let Oxide f glass by the cobalt, to color it blue : oxides of copper, oxide of man- ganese, cobalt, and chromium, to impart a green color to C dx pC &c 7 n ' lass and P orcelaitl j peroxide of iron, to give it a yellowish red, and protoxide, a bottle-green. Sub-oxide of copper gives to glass a beautiful ruby red. Silver and antimony are employed to produce different shades of yellow and orange. Vi- olet and rose color, are obtained by means of the purple of cassius, a beautiful purple precipitate, containing 294 CHLORIDES. tin and gold, and obtained by adding protochloride of tin to a gold solution. 737. GLASS STAINING. The effect of effects be illua- oxides, above mentioned, in coloring glass, trated? mav ^ Q jn us t ra ted by fusing them into a borax bead. The bead is to be formed with the aid of the blow-pipe, in a loop of platinum wire. In the absence of such wire, the borax glass may be made upon the surface of a pipe bowl. In- stead of employing the oxide, it is generally more convenient to moisten the bead with a very small quantity of a solution of the metal. In order to obtain good colors, the quantity of coloring material employed must be very small. 738. For staining glass and porcelain su- and porcelain perficialiy, a colored and easily fusible S laSS 1S fil>St P re P ared with borax Or S0me analogous material. This being ground up and applied as a paint, is afterward baked into the surface. Several of the oxides mentioned in a pre- ceding paragraph are thus employed. CHLORIDES. 739. DESCRIPTION. The chlorides are, Describe some of the proper- for the most part, soluble salts, of colors corresponding to the solutions of the metals from which they are produced. Common salt may stand as a type of the class. The chloride of silver, subchloride of mercury or calomel, are insoluble, and the chloride of lead but slightly soluble in water. CHLORIDES. 295 740. PREPARATION. Chlorides may be How are chlo- , , . . ., , , . , rides made made by the action of chlorine or hydro- chloric acid on the metals. The combus- tion of antimony in chlorine gas, the solu- tion of gold in aqua regia, and that of zinc in hydro- chloric acid are examples. The chemical action in each of these cases has been explained in previous chapters. The solutions being evaporated, the chlorides are ob- tained in the solid form. The solution of zinc in hy- drochloric acid is a case of single elective affinity: the metal elects or chooses the chlorine. 741. Chlorides may also be formed by How are chlo- rides produced the action of hydrochloric acid on oxides. from oxide*? Thug common salt or chloride of sodium may be made by mixing hydrochloric acid and soda. The hydrogen of the acid and the oxygen of the soda unite to form water, while the chlorine of the acid and the metal sodium unite, to form the chloride. This is a case of double decomposition, resulting from double elective affinity. The chloride commonly corresponds to the oxide from which it is produced. Thus soda, which is a protoxide, yields common salt, which is a protochloride. Again, sesquioxide of iron, containing three atoms of oxygen to one of metal, yields susqui- chloride of iron containing the same proportion of chlo- rine. How are the ^2. The insoluble chlorides may be ob- insolubie chlo- tained directly in a solid form by a similar rides obtained directly in a, double decomposition. Thus, chloride of solid form? so dium and oxide of silver in solution, 296 CHLORIDES. yield, when mixed, a precipitate of chloride of silver ; newly-formed oxide of sodium or soda remains in solution. The latter unites with the acid originally employed to dissolve the oxide of silver. This is commonly nitric acid. 743. CHLORIDE OF SODIUM. COMMON From what _. i / i sources is com- SALT. Common salt is found in great Obtained? abundance in Poland and other countries, as Rock salt, which is regularly mined like coal. It is also obtained by evaporating the water of the sea or salt springs, in the sun or by artificial heat. When the salt water is boiled down, the salt separates in crystals, while the impurities remain in the small portion of liquid which is not evaporated. These con- sist principally of chloride of magnesium and other salts. Contrary to the general rule, salt is equally solu- ble in cold and hot water. 744. When salt is to be made from How is salt , . . . produced from water which contains it in very small pro- portion, it is a frequent practice in Europe, to pump the weak brine to the top of large heaps of brush, and allow it to trickle through them. The object of the method is to produce a large evapo- rating surface. The air, as it passes through the heaps, carries away a large part of the water, and leaves the salt behind. The strong brine which is collected below, is then boiled down, as before described. The annual produce of the salt spring at Syracuse, New York, ex- ceeds 5,000,000 bushels. CHLORINE. 297 745. Beautiful crystals of common salt How may crys- . . .. ' , .. tals of salt be may be obtained by gradually evaporating obtained? a saturale( j solution. This will be accom- plished by keeping it for some time moderately warm, on a stove or in the sun. The crys- tals are shaped as represented in the figure, and are made of innumerable smaller cubes, which build them- selves regularly upon the edges as the larger crystals sinks little by little into the solution. 746. USES OF COMMON SALT. The use How does salt act to preserve of common salt in preserving the flesh of fl esh? animals from decay, depends in part on the fact that it extracts from the flesh a large propor- tion of water. It thus, to a certain extent, dries them. This action will be immediately observed if a little salt be sprinkled upon flesh. It will speedily draw out the juices of the meat, and itself disappear, by dis- solving in them. ffowmucksait 747 ' SEA WATER. Every pound of sea is contained in water contains from one-half to five- sea water ? in the water of eighths of an ounce of salt. The greater theDeadSea? part of thig is c hl or ide of sodium or com- mon salt. The water of the Dead Sea contains a much larger proportion, and is more than an eighth part heavier than pure water. Owing to its greater density, a muscular man floats breast high in it without the least exertion. Fresh eggs, which sink in sea water, float in that of the Dead Sea, with one-third of their length above the surface. 13* 298 CHLORIDES. 748. CHLORIDE OF LIME. BLEACHING On what does the value of POWDER. The commercial article of this ? name is P re P ared b Y passing chlorine gas over lirne. It is a white powder, with an odor similar to that of .chlorine gas. Its value depends on the fact that the gas is thus brought into a solid form, and made capable of transportation. It may be released again by the simplest means, to be used as a bleaching and disaffecting agent. The addition of an acid, as has been seen in the chapter on chlorine, is all that is necessary to effect this object. It occurs, in- deed, spontaneously in the moistened powder, through the action of the carbonic acid of the air. 749. ILLUSTRATION. To illustrate its How may its properties be bleaching power, a strip of calico may be illustrated? soa ked in a solution of the chloride, and then in acid water. Nascent chlorine is thus liberated in the fibre of the cloth, and is more effectual than if otherwise applied. 750. FORM OF COMBINATION. The che- How are its ... i -, elements com- mical action which occurs in the formation lined? of chloride of lime is as follows. The chlorine combines with both constituents of the lime forming with its metal chloride of calcium, and with its oxygen, hypochlorous acid. This acid combines as it is produced, with another portion of lime, forming a salt. Bleaching powder is therefore a mixture of chloride of calcium and hypochlorite of lime, with a certain pro- portion of lime still uncombined. The name chloride of lime has no chemical propriety. The mixture is, practically, chlorine and lime, for as soon as an acid is CHLORIDE OF ALUMINIUM. 299 added, all of the original lime is re-formed and chlorine is evolved. 751. CHLORIDE OF ALUMINIUM. This How is chlo- ride of alumi- salt is of peculiar interest and importance, "pared*? *' * n v * ew ^ * ts employment in the prepara- tion of the new metal aluminium. It is prepared by heating alumina at the same time with car- bon and chlorine. The alumina is torn asunder, as it were, by the affinities which are thus brought into play. The carbon takes its oxygen and passes off with it as car- bonic oxide, while the chlorine takes the metal and es- capes with it as volatile chloride of aluminium. The carbon in the process is supplied by coal tar. The process is conducted in iron retorts, the materials hav- ing been previously ignited together before their intro- duction. How is it pu- 75%- The chloride is impure, from the rifted? presence of volatile sesquichloride of iron. This is separated by leading the uncondensed vapors over highly heated points of iron. The iron has the effect of removing part of the chlorine from the ses- quichloride of iron and reducing it to a non-volatile protochloride. It is thus stopped in its course, while the chloride of aluminium passes on unaffected. It con- denses in the cooler part of the apparatus, in the form of colorless transparent crystals. 753. COLORED FLAMES. A series of What is said . of colored beautiful name experiments may be made flames? assumes different colors according to the chloride em- ployed. Chloride of sodium or common salt, gives 300 SALTS. a yellow ; chloride of potassium, violet ; chloride of calcium, orange ; chloride of barium, yellow ; chloride of copper, blue. Instead of the chlorides, other soluble salts may be employed with the addition of a little hy- drochloric acid. , beautiful green may be obtained from a copper coin moistened with strong nitric acid, with the use of alcohol as before. The colors of fire- works are similarly produced by the addition of the above and certain other salts. 754. OTHER CHLORIDES. The other What is said i i j / of other ckio- chlorides are not of sufficient general in- terest to be here particularly described. Cor- rosive sublimate, the uses of which are mentioned in the chapter on Mercury, is a chloride of this metal. Calomel is a subchloride of the same metal. IODIDES, BROMIDES AND FLUORIDES. 755. The iodides and bromides are What is said of the iodides classes of salts analogous to the chlorides. andbromides? Those o f potassium, used in medicine and in photography, are the most important. 756. DETECTION OF T r pkateof soda, SALT. This is a white salt, forming crys- and itsprcpa- ta } s belonging to the third system, such as ration. J are represented in the fig- ure. It is used to some extent in medi- cine, and in large quantities for the pro- duction of carbonate of soda. It is prepared by pour- ing oil of vitriol upon common salt. A double decom- position takes place between the salt and the water of the acid ; hydrochloric acid is formed, which passes off, and soda, which remains combined with the sulphuric SULPHATES. 307 acid. It is to be understood that this reaction between water and common salt, takes place only when sulphuric acid is present. The method of making the experi- ment is given in the paragraph on the preparation of hydrochloric acid. What is said 115. Sulphate of soda may be obtained of its crystals? m cr y s tals, by evaporation. These crys- tals, like those of many other salts, lose their combined water, on exposure to the air, and become converted into a white powder. This change is called efflores- cence, and the salt which experiences it is called efflo- rescent. In preparing the salt on a large scale, for conversion into carbonate of soda, large quantities of hydrochloric or muriatic acid are incidentally pro- duced. Whatissul- 77^' SULPHATE OF BARYTA. The sul- pkate of ba- phate of baryta is a white insoluble sub- ryta? How . / prepared? stance, which may be obtained, as a pre- cipitate, by double decomposition of any soluble baryta salt with a soluble sulphate. It is a mineral of frequent occurrence, known as heavy spar. It is used for the adulteration of white lead, in which it may be easily detected as a residue, on dissolving the white lead in dilute nitric acid. The sulphate of lead is another of the few insoluble sulphates. 777. ALUM. Ordinary alum is a double Describe \ alum, and its sulphate of alumina and potassa. Solu- prcparation. ^^ of the tWQ ^^ when mixed? CQm _ bine to form the double salt. The sulphate of alu- mina required in the process may be obtained by dis- solving alumina from common clay by sulphuric acid. 308 SALTS. Or it may be produced by exposing cer- tain clays or slates, which contain sul- phuret of iron to the action of the air. Under these circumstances, the sulphur becomes converted into sulphuric acid, which unites with both oxide of iron and alumina. From this mixture the protosulphate of iron is sepa- rated by crystallization, leaving a solution of sulphate of alumina to be used in the preparation of alum. What is burnt ^8. On heating alum in a crucible or alum ? pipe-bowl, it swells up into a light porous mass, and is converted into burnt alum. At the same time it loses its water of crystalliza- tion, of which it contains twenty-four molecules to each molecule of the double sulphate. 779. OTHER ALUMS. The name, alum, What is said of other is appplied to a number of salts of analo- gous composition to the common alum al- ready described. In one of these, sesquioxide of chro- mium, and in another, sesquioxide of iron, takes the place of the alumina or sesquioxide of alumina. In a third kind of alum, oxide of ammonium replaces the potassa. All of these alums contain the same number of molecules of water of crystallization. They have all the same crystalline form, and. if mixed in solu- tion will crystallize together. They are, therefore, isomorphous salts. Their perfect analogy of composi- tion will be best seen by the inspection of their formu' Ise, given in the Appendix. What is said 780. OTHER SULPHATES. VlTRIOLS. of vitriols? Several of the sulphates have received the NITRATES. 309 common name of vitriols. Sulphates of zinc, copper, and iron are called respectively white, blue, and green vitriol. Green vitriol readily absorbs oxygen from the air, and becomes brown, from the accumula- tion of peroxide of iron upon its surface. A solution of it is changed to a yellowish-red color, by the oxidizing action of either nitric acid or chlorine. A crystal of blue vitriol is represented in the figure. The form belongs to the fifth system. NITRATES. How are ni- 781. The nitrates are formed by transformed? fa^ act ion of nitric acid on metals, as already explained, and also by the action of the acid on oxides previously formed. In the latter case, the metallic oxide takes the place of the water of hydration, which always belongs to the acid. They are also produced by double decomposition. The figure represents a crystal of salt- petre. The form belongs to third system. This latter method is illustrated below, in the preparation of nitrate of potassa from the nitrate of lime. 782. NITRATE OF LIME. This salt is How is nitrate . of lime, pro- of considerable interest, from the fact that it is employed in the production of salt- petre or nitre. It is formed in the so called, nitre beds, by mixing together refuse animal matter with earth and lime. In the gradual putrefaction of the animal mat- ter which follows, its nitrogen takes oxygen from the 310 SALTS. air, and is converted into nitric acid. The acid then combines with the lime to form the nitrate. The salt is afterward extracted by water. The formation of nitric acid, above mentioned, takes place only in the pre- sence of alkaline substances. In their absence the ni- trogen passes off, combined with hydrogen, as am- monia. Even in the presence of lime, there is reason to believe that ammonia is first formed, and its consti- tuents afterwards converted into nitric acid and water. 783. NITRATE OF POTASSA. NITRE, OR Explain the formation of SALTPETRE. This salt is a constituent of certain soils, especially in warm climates. These soils always contain lime, and are said to be never entirely destitute of vegetable or animal matter. It is obvious, therefore, that nitrate of potassa may be formed in them, as the same salt of lime is formed in the nitre beds just described. A small proportion of nitric acid exists in the atmosphere, combined with am- monia. This, also, may be a source of part of the nitric acid of the nitrous soils. Again, it is probable that nitric acid is slowly formed from the atmosphere by the direct combination of its elements in the porous soil. Nitre, on being highly heated, yields a third of its oxygen in the form of gas. 784. Nitre is obtained from nitrous soils Hew ^s nitre obtained from, by lixiviation with water, and subsequent nitron soils? crystallizatioiL From nitrate o f Iim6j it is produced by double decomposition with carbonate of potassa. Carbonate of lime precipitates, while nitrate of lime remains in solution. This may be afterward poured off, evaporated, and crystallized. NITRATES. 311 785. USES OF NITRE. Nitre is exten- Mention some of the uses sively employed by the chemist and in the arts, as an oxidizing agent. A few grains of it introduced into a solution of green vitriol, or sul- phate of iron, to which some free sulphuric acid has been added, will immediately change its color. The sulphuric acid sets nitric acid at liberty, to which the oxidation and change of color are to be attributed. Nitre, when heated, yields part of its oxygen, as before stated. If heated with metals, it converts them into oxides. The principal use of nitre, is in the manufac- ture of gun-powder. Howareni- - NlTRATE OF AMMONIA. - LAUGHING trate of am- GAS. Nitrate of ammonia may be prepared monia and ,, laughing gas irom the carbonate, by evaporation with produced? nitric acid When heatedj the hydrogen of the ammonia, and an equivalent quantity of the ox- ygen of the nitric acid, unite to form water, and the residue of both passes off as protoxide of nitrogen, or nitrous oxide. The compound is also called laughing gas, from the exhilarating effects which it occasions, when breathed in considerable quantity. Impurity of material or excess of heat occasion the production of an impure and deleterious gas. In view of these facts, the preparation, and inhalation of laughing gas is not to be recommended to the student. Ex lain the ^^ ' GUN-POWDER. Gun-powder is a action of the mixture of nitre, charcoal, and sulphur. o/ When ignited, the carbon burns instanta- neO usly, by help of the oxygen of the nitre, thus producing a large volume of carbonic acid gas. To 312 SALTS. this gas, together with the nitrogen which is also set at liberty at the same moment, the force of the explosion is due. The sulphur, at the same time, combines with the potassium of the nitre, and remains with it as a sulphuret of potassium. Three equivalents of carbon to one of nitre, and one of sulphur, expresses very nearly the composition of gun-powder. It varies, how- ever, according to the uses for which it is intended, and the country in which it is manufactured. From the proportion, by equivalents, the relative weight of the constituents can readily be calculated. 788. COLLECTION OF THE GASES. For How arc the . -in- / gases col- the production and collection of the gases evolved in the combustion of gun-powder, the fuses of ordinary "firecrack- ers" may be employed. Several of them are to be ignited at the same time, in an ordinary test- tube. The mouth of the latter being then brought under a filled and inverted vial, the gases are collected as fast as they are evolved. 789. NITRATE OF SILVER. Nitrate of Describe ni- ., . i j trate of silver, silver, or Lunar caustic, is employed, in What are its sur g erVj for cauterizing wounds. A solu- tion of the salt in which the oxide has been precipitated by ammonia, and re-dissolved by a slight excess, is extensively employed as an indelible ink. The black color comes from oxide of silver, and finely divided metal, precipitated in the cloth. It may be removed by soaking in solution of common CARBONATES. 313 salt, and thus converting the silver of the mark into chloride of silver. This is soluble in ammonia, and may be afterward extracted by that agent. Nitrate of silver is also the basis of most dyes for the hair. Describe the 790. OTHER NITRATES. Nitrate of soda other nitrates. j s a wn it e salt, found native in South America. It is used in the manufacture of nitric acid, and, to some extent, as a fertilizer of the soil. The remaining nitrates are soluble salts, of colors corres- ponding to the solutions of the metals, as already de- scribed. The uses of the nitrates of silver and bismuth have already been mentioned. CARBONATES. Describe the 791. CARBONATES. The carbonates are, carbonates. f or tne most part) wn ite or light colored salts, of which chalk may serve as an example. The carbonate of copper is found native, both as blue and green malachite. All of the carbonates, excepting those of the alkalies, may be decomposed by heat. The latter are sol- uble, and retain their acid at the highest temperatures. The figure represents a crystal of carbonate of lime or calc spar. 792. PREPARATION. The insoluble car- How are the ... insoluble car- boiiates may be produced by precipitating solutions of the metals or their salts, by carbonic acid or solutions of the alkaline carbonates. In the latter case, a double decomposition occurs, with exchange of acids and bases. 14* 314 SALTS. What is said of carbonate of potassa ? Describe car- bonate of soda. 793. CARBONATE OF POTASSA. POTASH. The method of preparing potash and pearlash, from wood ashes, has already been considered in the paragraph on Potassa. Saleratus is a carbonate containing a large proportion of carbonic acid. Its use, for u raising" bread and cake, is familiar. The acid employed with it, sets the carbonic acid gas at liberty and thus puffs up the " sponge." 794. CARBONATE or SODA. SODA. Carbonate of soda is commonly known under the name of soda. It is a white soluble salt, familiar from its use in Seidlitz and soda powders. Its carbonic acid is the source of the effer- vescence in these preparations. 795. Carbonate of soda is prepared from flow i.s carbo- . . note of soda the sulphate of soda. 1 his salt being prepared? heated with charcoal is converted into sulphide of sodium. On heating the latter with car- bonate of lime, a double de- composition occurs, and car- bonate of soda is produced, with sulphide of calcium as an incidental product. Both parts of the process are com- bined in practice. Sulphate of soda, chalk, and coal, are heated together in a rever- beratory furnace, the carbonate of soda is then dissolved out from the fused mass, dried, purified, and subse- quently crystallized. The sulphide of calcium would dissolve at the same time, and thus defeat the process, were it not rendered insoluble by combination with a certain quantity of lime. CARBONATES. 315 Describe an- 796. Another method of manufacturing other method, carbonate of soda, consists, essentially, in separating sulphur from the sulphate, by means of oxide of iron, and substituting carbon in its place. In this process also, the materials are heated with charcoal, in a reverberatory furnace, and the carbonate afterward extracted by water. The impure uncrystallized carbo- nate of soda, is known in commerce, as soda ash, and is largely employed in the manufacture of hard soap, and in other processes. What is sal 797. CARBONATE OF AMMONIA. SAL VOL- volatile? ATILE. The ordinary sal volatile of the shops, used as smelling salts, is a carbonate containing three equivalents of acid to two of base. It wastes away gradually in the air, and passes off in a gaseous form. 798. PREPARATION. Sal volatile is pre- How is sal . volatile pre- pared by heating together carbonate of pared \ime and chloride of ammonium. Carbo- nate of ammonia immediately passes off', while chloride of calcium remains behind. The carbonate is led into a cold pipe or chamber, where it takes the solid form. The mixture of chalk and sal ammoniac is sometimes used as smelling salts. The production of sal volatile from the mixture is very gradual if heat is not applied. 799. The property from which How is it proved to be the salt receives its name, may volatile f be illustratedj by holding in its vicinity a rod or roll of paper, moistened with strong muriatic acid. A dense cloud of sal ammoniac is immediately produced in the air, from the union of the two vapors. The 316 SALTS. experiment is more striking, if the sal volatile is warmed in a cup or other vessel. This salt is sometimes used by bakers for making bread and cakes light and spongy. 800. CARBONATE OF LIME. Carbonate of carbonate of lime, in the form of chalk, marble, arid of ime? ordinary limestone, is a most abundant mineral. Whole mountain chains consist of the latter rock. The shells of shell-fish are principally carbon- ate of lime. There is good reason, indeed, to believe that all limestones have their origin in accumulations of such shells, which have been consolidated in the course of ages. 801. SOLUBILITY IN CARBONIC ACID. The solubility of carbonate of lime in carbonic acid is readily shown, by passing a current of the gas through water clouded with pulver- ized chalk or marble. Other mineral substances which form the food of plants are dissolved by the same means, and then find their way into the roots, to 5 subserve the purposes of vegetable life. 802. INCRUSTATIONS IN BOILERS. Car- What is said of incrusta- bonate of lime dissolved in carbonated twns m boil- water j s a g a i n precipitated on boiling the solution. This is owing to the escape of the acid. Incrustations in tea-kettles and steam-boilers, in limestone districts, owe their origin to the same cause. In some cases, the crust is formed of gypsum, or other earthy matters contained in the water. One method of avoiding this inconvenience in steam-boilers, is by How is the solubility of carbonate of lime in car- bonic acid shown ? PHOSPHATES. 3l7 the addition of a smaller boiler, in which the water is first heated, arid its sediment deposited. Give the sta- 803. STALACTITES. The masses of car- lactites. bonate of lime which hang like mineral icicles from the roofs of caverns are called stalactites. The water that penetrates the soil is the architect of these curious forms. Impregnated with carbonic acid, derived from decaying vegetation, it takes up its load of carbonate of lime as it settles through the rock, and deposits it again on exposure to the air of the cavern, in various and often fantastic shapes. Another portion of water, dripping to the floor of trje cavern, builds up similar forms, called stalagmites, from below. 804. ARTIFICIAL MARBLE. The surface How ts artifi- rial marble of wood or stone may be marbled by cov- produccd? ering it with successive coats milk of lime, and allowing each in turn to dry before the next is ap- plied. The surface is then smoothed and polished, and carbonic acid finally applied, by which it is converted into marble. The milk of lime is simply a mixture of slaked lime and water, and may be so colored as to produce a variegated surface. PHOSPHATES Describe the 805. PHOSPHATES. The phosphates, phosphates. w j th the exception of those of the alka- lies, are, for the most part, white insoluble salts. Phosphate of lime may be taken as an ex- ample. The white residue which is obtained on heating the bones of animals, until all the animal matter is destroyed and expelled, is principally phosphate of lime. 318 SALTS. 806. Ordinary phosphoric acid has the Why is ordi- ,, , . . naryphospho- property of combining with and neutrah- edtrTba ticT~ zing tnree e( l uivalents f Dase j instead of one, as is the case with most other acids. It is therefore called a tribasic acid. The hyd rated acid contains, also, three equivalents of water, and may be regarded as a salt in which the water acts the part of base. Arsenic acid is similar in this respect, as well as in the amount of oxygen which it contains, and in the salts which it forms with bases. Two other kinds of phosphoric acid may be prepared from that above mentioned ; the first combines with one, and the second with two equivalents of base. 807. PREPARATION. The phosphates of How are the . f J phosphates the alkalies may be produced by the ac- preparcd? tion of phosphoric acid on the proper car- bonates. The remaining phosphates may be precipi- tated by solution of phosphate of soda, from solutions of the metals or their salts. As in other cases of pre- cipitation, there is here a double decomposition, with exchange of acids and bases. 808. SUPERPHOSPHATE OF LIME. A Describe the . - preparation mixture bearing this name, formed by the action of dilute sulphuric acid on burned bones, is extensively used as a fertilizer of the soil. The sulphuric acid, when added, appropri- ates part of the lime of the bones, forming with it gypsum ; at the same time, it leaves the phosphoric acid which it displaces, free to combine with another portion of phosphate of lime and thereby to render it soluble. The commercial article is a mixture of this SILICATES. 319 soluble substance with the gypsum and animal char- coal produced in its formation. Other materials are often added, increasing or diminishing, according to their nature, its agricultural value. The basis of the manufacture, is commonly the refuse bone black of the sugar refineries employed in the process. 809. OTHER PHOSPHATES. The phos- Whatis mid . of other phos- phate of soda is used in medicine phates? and j^ tne cnem i stj to produce other phosphates. The phosphate of silver is a beautiful yellow precipitate, obtained by pre- cipitating salts of silver with phosphate of soda or any other salt containing phosphoric acid. SILICATES What is said 810. The silicates form an exceedingly of silicates? i ar g e c | ass o f salts. They are, for the most part, insoluble, and are variously colored. Mica and feldspar, two of the constituents of granite, may serve as examples. As com- ponents of this and other rocks, the silicates make up a very considerable portion of the mass of the earth. 811. PREPARATION. Most silicates may How are sili- . f _ catespre- be artificially formed by fusing together pared? quartz sand, with the proper oxide. This is done in the manufacture of glass, to be hereafter described. Silicates may also be formed by precipita- ting solutions of metals or their salts by the solution of an alkaline silicate. 320 SALTS. .812. CLAY. Clay is a silicate of alu- composition mina, commonly containing silicate of po- tassa and other materials in small pro- portion. The best kaolin or porcelain clay is perfectly white, and is nearly pure silicate of alumina. How is soluble 813. SOLUBLE GLASS. Soluble glass is glass made? made by fusing sand with potassa or soda. Its production may be illustrated in a soda bead, by subsequently re-fusing it, with addition of sand. As the silicic acid combines with the soda, carbonic acid is expelled, as will be evident from an efferves- cence on the surface of the bead. Soluble glass is sometimes used as a sort of varnish for rendering wood fire proof. 814. WINDOW GLASS. Common window manufacture glass is a silicate of lime and soda. To f la W ss nd W f rm il > Chalk > S da > q uartz salld and ld glass are fused together until the mass be- comes fluid. The molten glass is then blown, by means of an iron tube, as soap bubbles are blown with a pipe. The first form of the bubble is that represented in the figure. The glass blower next contrives to lengthen out the bubble, as he blows it, to a larger size, and finally to blow out the end by a strong blast from his lungs. It is then trimmed with a pair of shears, and the other end cracked off by winding round it a thread of red hot glass. Such a thread is readily produced by cfipping an iron rod into the pot of molten glass, and then withdrawing it. The bubble of glass is thus GLASS. 321 brought to the form of a cylinder, such as is represented in the figure. The cylinder is then cracked longitudinally, by letting a drop of water run down its length, and following it by a hot iron. It is subsequently reheated, opened, and flattened out into a sheet, which is then cut into paries of smaller size, if required. How are glass 815. GLASS TUBES. To make a glass tubes made? tube, a bulb is first blown, such as is repre- sented on the previous page. An assistant then at- taches his tube to the hot bulb at the opposite side, and moves backward. The glass is thus drawn out, as if it were wax, and the cavity within it is elongated to a smooth and perfect bore. 816. GLASS BOTTLES Bottles and a Glass bottles? . f . great variety of other objects of glass, are made by the enlargement of similar bulbs within a mould of the required shape. Bottle glass is usually made of cheaper and less pure materials than window glass, and contains, in addition to the materials before mentioned, alumina and oxides of iron and manganese. It owes its green color to the protoxide of iron. Glass mir- 817. GLASS MIRRORS. Plate glass, such rors? as is used for mirrors, instead of being blown, is cast in metallic tables of the required shape, and then rolled out and polished. Wha.n*crys~ 818. CRYSTAL GLASS. This name is tal glass ? given to a highly brilliant glass, contain- ing potassa and litharge as bases. It is used for prisms, lenses, lustres, and the finer qualities of cut glass ware. 14* SALTS. With the addition of borax, it is also employed for im- itations of precious stones. What is ena- 819. ENAMEL. Enamel is an opaque md? glass, produced by the addition of some material which does not dissolve in the fused mass. Binoxide of tin is the material commonly employed. Various tints may be imparted to enamel, as to ordi- nary glass, by the addition of small quantities of me- tallic oxides. A thin surface of enamel is often baked on to a metallic surface, as in the case of watch dials, and various objects of jewelry. How is glass 82 0. COLORED GLASS. Glass is colored colored? an( j stained by the addition of various me- tallic oxides. The peculiar coloring effects of these substances have already been mentioned, in the sec- tion on Oxides. EARTHENWARE. What is the 821. Clay is the basis of all earthenware, basis of all from the finest porcelain to the coarsest earthenware? How is porce- brick. Being first fashioned by moulds or lain made? ^_ means j nto t h e proper form, it is dried, baked, and subsequently glazed, to render it impervious to water. In the man- ufacture of porcelain, glazing is not essential. Sand and chalk are ad- ded to the original material, and the heat is carried so high as to bring the whole mass into a semi- vitreous condition. This is also the case in certain kinds of stone- BORATES. 323 ware. Porcelain is, however, commonly glazed to add to its beauty. 822. GLAZING. Earthenware after its Describe tlie process of first baking is porous, and therefore unfit glazing. ^ mogt useg ^ or W j 1 ' c j 1 ^ j s intended. It is subsequently covered with a thin paste formed of the constituents of glass. Being then subjcted a second time to the heat of the furnace, a thin glass or glaze is formed upon the surface. The glazing of certain wares is effected by exposure at a high temperature to vapors of common salt. A double de- composition ensues with the oxide of iron which the ware contains, by which soda is formed. This imme- diately fuses with the silica and other materials to form the glaze. The chloride of iron which is formed at the same time passes off as vapor. A paste of pounded feldspar and quartz, to which borax is sometimes added, is employed in glazing porcelain. 823. PORCELAIN PAINTING. Metallic of 'porcdTin oxides form the basis of the pigments used painting? n p a j n t m g upon porcelain. The color- ing effect of the different pigments is mentioned in the chapter on metallic oxides. The patterns on ordinary .earthenware are first printed on paper, and then trans- ferred, by pressure, to the unglazed ware. The paper is afterwards removed by a wet sponge. BORATES. What is 824. BORAX. Borax is the only impor- lorax? tant salt among the compounds of boracic 324 SALTS. acid. The salt contains two atoms of acid to one of base, and is therefore a biborate. It is a white soluble salt, which swells up when heat- ed, in consequence of the escape of its water of crystallization. How is borax 825. PREPARATION. Borax is found in prepared? solution in the water of certain shallow lakes in India. It remains as an incrustation in the beds of these lakes when they dry up in summer. It is also prepared by the action of a solution of boracic acid on carbonate of soda. What is said 826. BORAX GLASS. The light spongy of borax glass? mass which is produced on heating borax, may be melted down by greater heat and converted into borax glass. This glass has the property of dissolving metallic oxides, and receiving from them peculiar colors, as described in a former paragraph. The chemist often determines the metal which a salt or oxide contains, by the color which it thus imparts to glass. The method of making the experiment has already been given. 827. SOLDERING, WELDING, ETC. Borax Why is borax . . \ . employed in is employed in soldering metals, to keep soldering? ^ metallic sur f aces clean. It does this by dissolving the coating of oxide which forms upon them, and forming with it a glass which is fluid at a high temperature, and easily pushed aside by the melted solder. Its use in welding iron depends on the same property. Borax is employed, to some extent, in medicine. It is also a constituent of the glass called CHROMATES. 325 jewellers paste, which is used in producing imitations of precious stones. CHROMATES. 828. CHROME YELLOW. To prepare this How is chrome . ., . , yellow pre- pigment, a solution of the commercial pared? bichromate of potassa is added to a solution of sugar of lead. A double decomposition ensues ; the result of which is the production of a beautiful yellow precipitate, known as chrome yellow. The precipitate is a chromate of lead. The bichromate of potassa used in the experiment, is made from the mineral chrome iron, which has been mentioned in a previous chapter. The acid itself, which is without practical applications, may be made from the salt. It contains, like sulphuric acid, three atoms of oxygen. How is chrome ^^' CHROME ORANGE. Chrome yellow yellow con- ma y be converted into chrome orange, by verted into . . , , . chrome digestion with carbonate of potassa. Cloth dyed yellow by dipping it alternately into a solution of bichromate of potassa and sugar of lead, is instantaneously changed to orange by immersion in boiling milk of lime. This action of the lime, as well as that of carbonate of potassa, depends upon its ab- stracting a. certain portion of the chromic acid, leav- ing thereby a chromate of lead of different composi- tion and color. 326 SALTS. 830. CHROME GREEN. On adding sul- Dcscribe the . . preparation phuric acid and a few drops of alcohol to a solution of bichromate of potassa, the solu- tion is immediately changed from red to green. The alcohol has taken oxygen from the chro- mic acid, and converted it into oxide, which remains in solution, as a soluble sulphate. Part of the sulphu- ric acid has at the same time combined with the potassa, to form sulphate of potassa. It is to the presence of the sulphate of chromium in solution that the color of the liquid is due. By adding an alkali to the solution, a green precipitate of the hydrated oxide is produced. This oxide forms a kind of " chrome green." App. 830. MAKGANATES. 831. CHAMELEON MINERAL. By fusion What is cha- ... , meleon miner- with nitre, the black oxide of manganese may be still further oxidized, and converted into an acid. The new acid at the same time com- bines with the potassa of the nitre to form manga nate of potassa. This salt has been called chameleon min- eral, from the spontaneous change of color which takes place in its solutions. 832. PREPARATION. The experiment How is chame- leon mineral may be made by filling a pipe stem with prepare . a m j xture o f tne materials, and thrusting it into burning coals. It may be made on a still smaller scale before the blow-pipe, using a broken pipe-bowl to support the materials. The compound dissolves in water, forming a green solution, which on standing is gradually changed to a beautiful red. THE DAGUERREOTYPE. 327 833. EXPLANATION. The addition of a Explain the action of sul- few drops of sulphuric acid, produces the above-mentioned change instantaneously. This acid combines with the potassa, setting the manganic acid at liberty. One portion of manganic acid then appropriates part of the oxygen of the other part, and converts itself into hypermanganic acid, which still remains combined with potassa, im- parting the red color to the solution. The deoxydized portion of the acid precipitates, at the same time, as bin- per oxide. The remaining manganates are not of especial interest or importance. THE DAGUERREOTYPE. 834. THE DAGUERREOTYPE. The da- Explain the guerreotype may be regarded as a painting i n mercury, upon a silver surface. The employment of mercury is preceded by what may be called an invisible painting upon the silver. This is ac- complished, like the production of an image in a mirror, by mere presentation of the picture, or other object to be copied, before the prepared plate. The mercury, afterward used in the form of vapor, adheres to the plate, and forms its white amalgam, just in proportion to the lights and shades of the previous image thrown upon the plate. Describe the 835. THE DAGUERREOTYPE PROCESS. - process of ta- j n or( j er to p re p are the plate for what has King daguer- reotypes. above been called the invisible painting, it is exposed to vapors of iodine, and thereby covered 328 SALTS. with a coating of iodide of silver.* A picture or face to be copied being presented before the prepared plate, the light which proceeds from it acts chemically upon the iodide of silver. It decomposes it, to a certain extent, and separates the iodine, thus open- ing the way for the mercurial vapor, which is afterward to be employed. The light has this effect, just in pro- portion to its intensity. That which proceeds from the lighter portions of the face, or dress, has most effect ; that from the black portions, none at all, and that from the intermediate shades, an effect in exact proportion to their brightness. When the plate is afterward ex- posed to the action of the mercurial vapors, they find their way to the silver surface and paint it white, just in proportion as this chemical effect upon the iodine has been produced, and the way has been opened for their admission. The darker portions of the plate are pure silver. They appear dark in contrast with the white amalgam.! 836. USE OF THE LENS. In taking da- What is the object of the guerreotypes, a lens is placed between the object to be copied and the plate, in order that the light which proceeds from the former may be concentrated, and its effect thus increased. * Bromide and chloride of iodine, are employed to give additional sensitiveness to the plate. The iodide is thus made to contain a por- tion of bromide and chloride of silver. f The art of taking portraits from the life by the Daguerreotpe pro- cess, was invented by Dr. J. W. Draper, of the University of New York. PHOTOGRAPHS. 329 837. CHEMICAL ACTION OF LIGHT. The What is said . . . . of theckemi- chemical action or light, on which the t production of daguerreotypes depends, is rays possess one o f tne mO st interesting and remarkable this power ? of chemical phenomena. The rays of the sun are so subtle, that they pass through solid crys- tal and leave no trace of their passage. Yet with them comes a power that can overcome the strongest chemical affinities, and resolve the compounds which it has pro- duced into their original elements. This power resides in what are called the chemical, act wic, or tit/ionic rays. These are mingled, under ordinary circumstances, with those of light, but are capable of separation by certain media. What are pho- $38. PHOTOGRAPHS. - Pictures produced tographs ? through the agency of light, whether upon silver, or paper, are, properly, photographs, or light pic- tares ; the name, however, is especially appropriated to the latter. For the purpose of illustration, a method of producing negative pictures, as they are called, will be here given. H is scnsi- 839 - The sensitive paper required in tive paper the process, is prepared by floating a slip of letter-paper, for two or three minutes, upon salt water ; and then for double the time, with the same side down, on a solution of nitrate of silver. Chlo- ride of silver forms within the fibres, and renders the paper sensitive to light. After each immersion, the slip should be dried off by blotting paper. When finished, it should be immediately laid away between the leaves of a book, for protection against the light. 330 SALTS. 840. Such paper, if placed in direct What effect has direct sun- sun light, becomes violet, and then dark l s?n*itivepa- brown, in the course of a few minutes. per? The change is owing to the partial decom- position of the chloride of silver. A new substance, of darker color, is then produced ; whether a lower chloride of different shade, or a mixture of metal and chloride, or a compound of oxide and chloride, is not very certainly known. 841. If a cross or other device cut How may cop- be pro- irom dark paper, be pressed down upon of sen- sensitive paper, by means of a glass plate, sitive paper ? an d be left to cover it during the exposure to light, the paper will be pro- tected beneath it, and an exact copy of the device thus ob- tained. The most delicate lace may be copied hy the same method. In reproducing engravings by this means, they must be previously rendered translucent, so that the imprinted portions will allow the light to pass. This may he accomplished by waxing them, with the help of a hot iron, or by simple oiling. The dark parts of the engraving appear light, and the light portions dark, in the picture. By copying the copy, a true representation of the original device, called a " positive picture," is obtained. Both the " pos- itive" and " negative" are soon destroyed by the action of light upon the whole sensitive surface. But the means exist for rendering them entirely permanent in any exposure. H X Y COUNTERFEITING. 331 842. THE SILVER SOLUTIONS. To prepare How is the sil- ver solution the silver solution, above required, put a prepai three cent piece into a test-tube, having a diameter a little larger than the coin itself. Then fill the tube to the depth of an inch, with a mixture of equal parts of nitric acid and water. The solution of the coin commences immediately. When it is completed, fill up the tube with water, mix well by shaking, and the solution is ready for use. For the same quantity of salt solution, enough common salt to fill about two- thirds of an inch of the tube, may be used. 843. ANASTATIC PRINTING. This name Describe briefly the is given to a process by which any kind astatic print- ^ Panted matter, may itself be converted ill O ? into a plate, from which new copies may be printed. It consists, essentially, in the transfer of the letters, or other design, to zinc, by pressure, the paper having been previously moistened by dilute acid. The oil of the ink remains, and the paper is re- moved. The zinc plate is then used, like an ordi- nary lithographic stone. When the inked roller is passed over it, the ink only adheres to the design, from which an impression may then be taken by the ordi- nary process. What is said of 844 COUNTERFEITING. Bank notes may counterfeiting fa counterfeited by either of the above by the above process? processes. Great apprehension has been felt, test they should render the use of paper money en- tirely insecure. An effectual means of protection against such counterfeiting, has recently been devised.* * Serop van's patent. 332 SALTS. Copying by the anastatic process, obviously depends upon the absence of oil from the back ground of the picture. The employment of an oil tint, instead of blank paper, for the back ground, is therefore a perfect security against it. Counterfeiting by the photographic process depends on the fact, that the light which falls on a picture is intercepted by the dark letters. If they are printed in a transparent blue, the chemical rays are permitted to pass through the printed as well as the imprinted portions. A copy with the contrasts of the original picture is thereby rendered impossible. By printing with blue ink, on a back ground of some other color, both of the securities against counterfeiting above mentioned, are combined. CHEMICAL ANALYSIS. 845. DIRECT METHOD. In the process Describe anal- ysis by sol- of analysis, advantage is taken of the dis- tinguishing properties of different sub- stances, to effect their detection and separation. They may sometimes be separated by the employment of a solvent which acts upon one, and leaves the other mi- dissolved. The separation of silver from gold in the process of assaying, is a case in point. Describe di- 846. A more common method is to bring rect analysis tne wno le substance into solution, and oy precipita- tion, afterward separately to precipitate its sev- eral constituents, by agents which have no effect upon the rest. The separation of alumina from lime may serve as an example. A mixture of the two being dis- CHEMICAL ANALYSIS. 333 solved in acid, the former may be precipitated by am- monia. The latter remains in solution and may be afterward removed by some other agent. 847. INDIRECT METHODS. Indirect me- II lust rate the , , - indirect mcth- thods of analysis are much more frequently od - employed than either of the above. The detection of silver in a copper alloy may serve as an example. The alloy being first dissolved, hydrochloric acid is added to the solution, as a test. The appearance of a white insoluble curd, is taken as conclusive evi- dence of the presence of silver. No other metal of an alloy ever combines with the chlorine of hydrochloric acid to form such a precipitate. The evidence is quite as satisfactory to the chemist as that which would be obtained by the separation of the silver in the metallic form. 848. Neither is separation necessary, in How is the . weight calcu- order to ascertain the exact weight of the lated? metal which has been precipitated. Ad- vantage is here taken of the well-established law of combination by definite proportions. The chloride of silver produced in the experiment, is invariably of the same proportional composition. It is made up of an atom of silver, to every atom of chlorine. Its weight being ascertained by the balance, the amount of silver which it contains may be calculated with absolute pre- cision, by help of the table of atomic weights. This weight being compared with that of the original alloy, gives, by a simple calculation, the per centage propor- tion of silver which the alloy contains. The nature and quantity of other constituents, whether of compounds 334 CHEMICAL ANALYSIS. r or mixtures, is determined by processes analogous to these which have above been described. 849. SEPARATION INTO GROUPS. In the Nation into 1 analysis of substances containing many con- groups effect- stituents, a separation into groups, precedes the isolation of the individual constituents. This is effected by the use of certain agents, in suc- cession, which have the property of precipitating whole groups. These being again dissolved, are commonly subdivided into smaller groups by similar means. The detection and separation of the individual constituents is finally accomplished by means already described. Some general idea of the process of inorganic analysis may be obtained from the foregoing. Particulars upon this subject must be sought in works on analytical chemistry. 335 TV. ORGANIC CHEMISTRY. CHAPTER I. GENERAL VIEWS. 850. DEFINITION. Organic chemistry is Of what does . . . organic chem- that division of the science which treats istry treat ? Q f su b s t a nces o f animal or vegetable ori- gin. Starch, wood, gums, and resins ; the juices, colo- ring matters, and fragrant principles of plants; the blood and flesh of animals ; all come under its conside- ration. The process of germination, in which the plant first comes to be a living thing ; the processes of decay and putrefaction, in which it returns again to the earth and atmosphere, are also to be treated under this division of the subject. Most organic forms of matter experience peculiar changes, and are converted into new substances by chemical means. The products of such transformations belong also to organic chemistry.* 851. VARIETY OF ORGANIC MATTER. Illustrate the . f . variety of or- The variety of organic matter is almost garde matter. w j t hout limit. Every color of every dye, every flavor of every sweet or bitter herb, every gum, * Carbonic acid, water, bone ash, and some other substances, are ex- ceptions to the above rule, and are commonly treated under the head of inorganic chemistry. Though often produced from animal and vegetable substances, they also exist, ready formed, in nature, or may be readily made from organic or mineral matter. 336 ORGANIC CHEMISTRY. and every resin, is a distinct organic substance. In the animal body, also, there is scarcely less variety. The fluids which dissolve the food, the blood which distributes it throughout the body, the color which tints the skin aiid hair, and the milk "which nourishes the young, are a few of the substances which it includes. 852. MATERIALS OF VEGETABLE GROWTH. What arc the -..,' - . materials of With the exception of the small proportion ^ mmera l matter which is derived from the earth, the materials out of which all animal and vegetable matter is formed, are but few in number. Carbonic acid, ammonia, and water, are all. These are partly obtained from the air, and partly from the earth. Carbon, hydrogen, oxygen, and nitrogen, are the four elements which enter into their compo- sition. What is re.- 853. CONVERSION OF THE MATERIALS. - workable in A vital force slumbers within the seed, the new pro- , . ,, parties which which in germination wakes to life. Call- result ? j ng to - tg a j^ fa Q ijgj lt an( j Warmt l 1 O f t h e sun, it weaves, as it were, out of the scanty mate- rials which have been mentioned, all of the varied forms of vegetable matter. Among the materials, one is a tasteless solid ; the rest are tasteless gases. Yet sweet, sour and bitter flavors result from their combi- nation, with all the other boundless variety of the or- ganic world. 854. SIMILARITY OF COMPOSITION. Yet Give some in- , stances of aim- more remarkable than the limited number il ^olidth of elemeilts > fr m which so great a variety di/f rent pro- of organic substances is formed, is the per similarity of composition in many sub- GENERAL VIEWS. 337 stances, which are yet so widely different in their pro- perties. Vinegar differs from alcohol, for example, in containing a little more oxygen and a little less hydro- gen, while the proportion of carbon in each is the same. Ether, also, contains the same amount of carbon as the alcohol from which it is formed, with a little less hydro- gen and oxygen. Yet these substances are all widely different in their properties. Mention some 855. IDENTITY OF COMPOSITION. Most hichr*difi remarkaole f all > and at first view incred- ferent in pro- ible, is the fact that many organic sub- tdenticaHn stances which are as widely different in composition. properties as any which have been named, are still precisely the same in their composition ; not alone containing the same elements, but containing them in precisely the same proportion. The most careful chemical investigation finds no difference of composition in wood, gum, and starch. The sugar which sweet milk furnishes, arid the acid which exists in the sour, contain identically the same proportions of the same constituents. The oils of turpentine, lemon and pepper, so different in their taste, contain an equal quantity of carbon and hydrogen, without the addition of any third substance to either, to account for the difference. Truly, organic chemistry has brought us to results as strange as the dream of the alchemist, who believed that lead might be converted into silver, and copper into gold. All such substances, possessing the same composition with different properties, are called iso- meric bodies a term signifying their similarity of com- position. 15 338 ORGANIC CHEMISTRY. 856. ARRANGEMENT OF ATOMS. At a loss How are the above facts ac- for any other way of accounting for such counted for? difference o f properties, we are compelled to believe that it is because of difference of atomic arrangement. We have seen, in the case of iodide of mercury, mentioned in a former chapter, that a mere touch, which produces motion and re-arrange- ment of its atoms in smaller groups, at the same time changes the color of the compound from yellow to red. Now the molecule of lactic acid, although containing the same relative proportion of all of its constituents, is smaller than the molecule of sugar of milk. It con- tains six atoms of carbon, six of hydrogen, and six of oxygen. The molecule of sugar of milk contains twelve of each, and can therefore furnish material to make two of acid, as it does in the souring of milk. And we may suppose that the change from sweet to sour is owing to this subdivision of the molecules. 857. There are other cases of identical How is diver- . , . -, -, T rr sity of prop- composition, in which there is no difference countedfor whatever in the size of the molecule, or the when there is number of atoms which enter into its corn- no difference . . . ., ., of compost- position. This is the case with the oils of tionor size? turpentine, lemon, and pepper, and perhaps with wood, starch, and sugar. The molecules of each are composed, not alone of the same proportion of the elements which enter into its composition, but, as there is reason to believe, of the same number of atoms of each. We are therefore compelled to look for the differ- ence which shall account for their peculiar property, in a different arrangement of atoms, inside of the mole- GENERAL VIEWS. 339 cules themselves. A more satisfactory idea of this sub- ject can be obtained after reading what follows, on the subject of organic radicals. Give an in- 858. SUBSTITUTION. A still more re- stance of sub- ma rkable evidence of the influence of ar- stitution titat does not affect rangement or grouping of atoms, remains P 10 P C ^ to be mentioned. The internal arrange- ment of a molecule remaining the same, it seems to matter little, in many cases, of what it is composed. Hydrogen may even be replaced by chlorine, a body as widely different from it as anything which nature affords. By this means, ordinary acetic acid is con- verted into chloracetic acid, a body remarkably anal- ogous in its properties to the acid from which it is formed. From this, again, by withdrawing the chlo- rine and restoring the hydrogen, the original acetic acid is reproduced. 859 TYPES. The last example will What in said . , of the doctrine serve as an illustration of the doctrine of cnem i ca l types and substitution, which cer- tain chemists have endeavored to extend to all organic bodies. It has been maintained that the properties of these bodies depend solely upon arrange- ment, without any reference to the nature of the ele- ments combined. The fact is, that while there are many cases of such substitution without essential change of properties, it is always attended by more or less modification of the original substance. The properties of a compound are therefore to be regarded as depending neither upon the nature or arrangement of atoms alone, but upon both causes combined. The 340 ORGANIC CHEMISTRY. type, is the group which remains permanent, while the individual atoms which compose it are changed. 860. COMPOUND RADICALS. Many or- Ilhistrate the ' subject of com- game bodies, although compounds, com- P cah d Tadl ' P ort themselves as if they were elementary substances. Some of these are, as it were, metals ; forming oxides, chlorides, and salts, like the true metals, which have already been considered. Others correspond more nearly to the metalloids. Each being organic, and like a metalloid, the root of a whole series of compounds, is called an organic radical. The term radical is sometimes applied, for similar reasons, to chlorine, bromine, and other elementary substances. As the organic substances above referred to, are com- posed of different elements, they are called compound radicals. 861. ILLUSTRATION. A molecule of or- ple of acom- dinary ether is composed of four atoms of poundradical carborij fi ve o f hydrogen, and one of oxy- gen. But the carbon and hydrogen atoms are grouped together, forming a compound radical called ethyle, with which the oxygen is then com- bined to form ether or oxide of ethyle. Alcohol, as illustrated in the figure, is the hydrated oxide of this radical. Al- dehyde, a substance to be hereafter more particularly described, has the same composition as alcohol, with the exception that two atoms of hydrogen have been removed from the radical. Acetic acid is formed from aldehyde by the re-placement of the removed hydrogen by the same number of atoms of oxygen. Ethyle itself may be prepared indirectly from the oxide, as potassium HOMOLOGOUS SERIES. 341 is obtained from potassa or oxide of potassium, although by a different process. What were the 862. It is but a few years since the grounds of be- met f 10( i o f producing ethyle was discovered, hef vn the ex- & J of but chemists believed in its existence al- most as confidently before, as now. They co-eery? reasoned that ether, which possesses the properties of an oxide, must have its radical, as Sir Humphrey Davy reasoned that potassa, soda and lime, must each contain its metal. 863. HOMOLOGOUS SERIES. Certain of What are ho- .<>'' moiogous these compound radicals sustain to each other a curious numerical relation. They form a series in arithmetical progression, differing from each other in composition, by a common difference. Two atoms of carbon with two of hydrogen forms the common difference of the series referred to. Methyl, the radical of wood spirit, begins the list with two atoms of carbon and three of hydrogen. Ethyle follows its composition being expressed by the addition of the common difference to the last. Margaryl, a radical contained in certain fats, is the seventeenth member of the series. Each of these radicals has, like ethyle, its own oxide or ether, its hydrated oxide or alcohol ; also its aldehyde and its acid. A series of radicals, ethers, alcohols, aldehydes and acids, each in arithmetical pro- gression, is thus produced. Such series are called ho- mologous. 864. PRODUCTION. There are many saps How are the * *- different mem- in most of the series, but the law of their bersproduccd? progression is so we]1 established, that no 342 ORGANIC CHEMISTRY. doubt can exist as to the probable production of the missing members. The most complete of the series is given in the Appendix. Several of its more simple members may be produced by the action of nitric acid upon those higher in the scale. The acid has the effect of burning out part of their carbon and hydrogen, and thus reducing the relative proportion of their constitu- ents. 865. PROGRESSION OF PROPERTIES. What is said of the relation There is also a similar progression of pro- ~ P ertieS in the SerieS ' The earlier men l- bers of the alcohol series are highly vol- atile liquids; the later are solids at ordinary tempera- tures. Each increase of the relative properties of car- bon and hydrogen produces a substance which is more fixed. In other words, the boiling point is higher for each successive member. The difference for each is about 34 F. The density of the vapors increases by a similar law. It is thus possible to predict, with accu- racy, the boiling point and density of vapor in members of the series which have not yet been discovered. 866. RADICALS NOT ISOLATED. The Have all or- . ganic radicals larger part of the organic radicals have not been isolated? yet ^een isolated. They are only known in their compounds, and the belief in their existence rests on the reasoning which has been given in a previ- ous paragraph. This is regarded by chemists as abun- dantly sufficient for giving them names and places among chemical compounds. It is still, however, to be borne in mind, that the reasoning is not of the nature of absolute demonstration. SUBSTITUTIONS. 343 Mention some > SUBSTITUTION COMPOUNDS. It Was instances of stated, in a previous paragraph, that there the substitu- ., , ,, . . - tionofradi- are many cases of substitution of the ele- cals ' ments for each other, without material change of properties. Certain cases of substitution of organic radicals for the elements remain to be men- tioned. Theoretically considered, they form, perhaps, the most important discoveries which have for years been made in organic chemistry. Ammonia, as the student is already informed, is a volatile base whose molecules consists of one atom of nitrogen and three atoms of hydrogen. For one of these atoms of hydro- gen, a molecule of the radical ethyle may be substituted, without very materially affecting its properties. The new ammonia thus formed is, like the first, a volatile base resembling the first so nearly in odor that it must have been repeatedly mistaken for it when accidentally produced. It is, however, a liquid at ordinary temper- atures. This body has received the name of etliyla- mine. Methylamine is another body of the same series, produced by the replacement of two of the atoms of am- monia by the radical ethyl. Triethylamine is a third. By a similar substitution of hydrogen in ammonia by the radical methyl, another series is produced. Other radicals yield other series. 868. OTHER SUBSTITUTIONS. There are Mention other cases of sub- other bodies which result from the substi- stitution. tution of different radicals or the metal pla- tinum, for the different atoms of hydrogen. Substitu- tions may even exist in the substituting radicals. All of these bodies retain the type of ammonia, and all of 344 ORGANIC CHEMISTY. them have basic properties. Many of them are strikingly similar to ammonia in odor and other properties. These substitution compounds afford still further evidence of the influence of arrangement of atoms and molecules in determining the character of chemical compounds. Many of these bodies differ very widely in their com- position, and are yet closely allied in their properties. The methods of producing the substitutions above mentioned, are not of interest to the general student. A general notion of substitutions may be obtained from the double decompositions with which the student is already familiar. ORGANIC CHEMISTRY. 345 CHAPTER II. VEGETABLE CHEMISTRY. What is mid 869. GERMINATION. Before the process- of germination es of transformation of the materials of the and the chan- ... ges which at- earth and atmosphere into the innume- rable products of the vegetable world can commence, a rudimental plant must be developed from the seed. The seed itself contains the materials for its production. These are principally starch, and gluten,* or the other substances analogous to each, which have already been described. The first stage in the process is the absorption of moisture and oxygen from the air, and the conse- quent production of diastase^ This sub- stance has the remarkable property of con- verting starch into sugar, and rendering soluble all of the remaining gluten of the seed. By the appropria- tion of these materials, which have been stored up for it in the seed, the germ is developed into a perfect plant. It lets down its root into the soil in search of * Gluten is the stringy substance which remains on removing the starch from dough by long continued kneading. It is further described in a subsequent paragraph. f Diastase is an oxydized gluten, which is always produced from gluten in germination. 15* 346 ORGANIC CHEMISTRY. mineral food, and lifts its leaves into the atmosphere, from which it is to derive its principal nourishment. At this point, the true vegetative process commences. 870. VEGETABLE NUTRITION. Every What is the office of leaves leaf is a net to catch the fertilizing con- ^ p a stituents of the air, and appropriate them to the uses of the plant. It drinks them in through its countless pores, while the root supplies the remaining material and sends it upward in the rising sap. All of these materials meet in the leaf, which is the labora- tory in which their conversion into vegetable matter is to be accomplished. The light and heat of the sun co-operate with the vital forces of the plant, in the transformation which succeeds. 871. Whatever proportion of carbonic evohed from acid and water may be employed as the plants? raw ma terial, it is obvious, by comparison of their composition with that of vegetable substances, as hereafter given, that the oxygen is furnished in larger quantity than is required. Water alone supplies a sufficient quantity of this element, and more than enough for most substances that are to be formed. As the process of transformation proceeds, this gas is there- fore constantly thrown off into the air. It is the refuse of the manufacture. Inasmuch as the evolution takes place from the leaf and other green parts of the plant, it is reasonable to suppose that this is the point where the process of transformation is principally conducted. The gum, sugar, or other materials produced, are dis- solved in the descending sap, and transformed into other products, in the course of their circulation. OFFICE OF THE ROOT. 347 872. The agency of the leaves of the , of plants in absorbing and decomposing car- ro- bonic acid > ma y be illustrated by the simple ved by experi- means represented in the figure. A glass funnel being filled with leaves, and slightly carbonated water, is exposed to the sun. Oxygen gas is gradually evolved from the absorption and decomposition of the carbonic acid, and collects in the tube of the funnel. The oxygen may be tested by the usual means. The inversion of the fun- nel without loss of its contents, is easily effected, by covering it with a saucer and turning it in a pail of water. 873. For certain transformations of ma- What trans- . . . formations oc- terial in plants, the evidence is entirely con- purin plant*? clusiye> The sugar beet and tumip are sweetest in the earlier stages of their growth. Later in the year they become hard and fibrous. This change is undoubtedly owing to the conversion of the sugar, contained in the sap, into woody fibre. In the ripening of grain, the sweet and milky juice of the young plant is converted into starch. Both hay and grain, which are harvested too late, are deteriorated by the conver- sion of a portion of their starch and sugar into wood. In the ripening of fruits a portion of their acid is con- verted into sugar, as is evident from their change of flavor. 874. OFFICE OF THE ROOT. The agency How w the ac- o f fa e roo t s m supplying the plant with its tion of the roots'illus- mineral food, may be illustrated by the apparatus represented in the figure. In preparation for the experiment, a glass fun- 348 ORGANIC CHEMISTRY. nel is tightly covered with a piece of blad- der, and then filled with a solution of sugar or salt. A tube is then fitted, air tight, to its extremity. A glass vial, from which the bottom has been removed, may be sub- stituted for the funnel in this experiment. On placing the apparatus, thus arranged, in a vessel of water, the latter penetrates the ani- mal membrane, and adds itself to the con- tents of the funnel. The flow of the water is called endosmose, and is made apprecia- ble to the eye by the rise of liquid in the tube. An cxosmose, or flow of a small portion of the contents of the funnel outward, takes place at the same time. 875. The phenomenon exhibited in the Explain the . phenomenon above experiment, is to be accounted for of endosmose. by the difference of cap il] a ry attraction in the bladder for the two liquids. The spongioles, with which the extremities of the roots are provided, being filled with solutions of gum and sugar, act similarly upon the liquids of the soil. The endosmotic action, above described, is not confined to the roots of plants, but occurs in all their organs, through the walls of the minute cells of which they are composed. In connec- tion with the transpiration of water from the leaves, it is probably the principal cause of the circulation of the sap. The relation of the plant and soil is further considered in a subsequent chapter. 876. CONSTITUENTS OF PLANTS. Amoner Mention some of the more the more important of vegetable substances ffSe a ^ Ve ' are wood, starch, sugar and gluten. Woody stances. fibre forms the mass of the plant ; starch WOOD. 349 and gluten collect in the seed j while sugar and gum exist principally in the sap and fruit, or exude from the bark. WOOD. Mention dif- S77 ' W ODY FIBRE. Woody fibre, of ferent forms which the fibrous threads of cotton or flax of ivoody fibre , j /r ^-its com- ma Y serve as an example, is composed of position. carbon, hydrogen and oxygen. Its mole- cule contains twelve atoms of carbon, to ten of hydro- gen and ten of oxygen. It constitutes the solid mass of all vegetable organs, whether hard and firm, like the fibre of the oak ; soft, like the pulp of fruits ; or fibrous, like cotton and flax. In one or the other of its forms it therefore serves us for shelter, clothing and food. It forms in plants the cells in which the vege- table juices are contained, and the veins or pores through which they circulate ; and has thence received its name of cellulose. In wood, these cells are often lined or filled with a substance of similar composition, to which the name of lignin has been given. 878. CHANGE BY HEAT GAS, CHAR- changed by COAL, ETC. Under the influence of heat? a high temperature, without access of air, wood is converted into charcoal, water, gases, wood vinegar, and tar. It is to be observed that this change is the simple result of a re-ar- rangement of the atoms of the wood itself, with- out the help of additional oxygen or other ele- ments. It is a most remarkable instance of va- 350 ORGANIC CHEMISTRY. riety as produced by varied arrangement. The new substances are, as it were, different patterns, woven from the same colored threads. The gases, of which carbonic acid, light and heavy carburetted hydrogen are the principal, have been already described. Wood vinegar and wood tar form the subjects of subsequent paragraphs. An excess of carbon remains behind as charcoal. The process is called dry distillation. The decomposition may be illustrated with saw-dust, in a test tube, as previously described. 879. SIMILAR CHANGE IN NATURE PEAT. Mention a si- . milar change Peat is formed by the decay of vegeta- tn nature. j } j e matter un( } er wa ter. The green slime which forms, in the summer, upon stagnant water, is composed of minute plants. These die, each season, and sink to the bottom, until, in the course of years or ages, vast accumulations of vegetable matter are the result. By their partial decay or putrefaction under water, they are converted into peat. The process is analogous to that of dry distillation, and the products similar. Carbonic acid and carburetted hydrogen gases are evolved, while a solid residue of peat remains be- hind. It may be regarded as a half-formed charcoal. Peat contains, in addition to its carbon, a little hydro- gen and a still smaller proportion of oxygen. The carbonic acid evolved in the above process, often makes its way to the surface, at some neighboring locality, in the form of mineral springs. 880. BITUMINOUS COAL. The formation How is bitutm- . , . , . nous coal 01 bituminous and anthracite coal is a con- formed? sequence of a similar decay of vast accu- WOOD. 351 mulations of vegetable matter, which have been buried in the earth during previous ages of its existence. As a consequence of pressure, the material takes a different form from that already described, and is found, after ages have elapsed, as bituminous coal. Howisanthra- 881. ANTHRACITE COAL. Where bitu- dte formed? mous coa i has been subjected to great heat, more carbon and hydrogen are expelled, and anthracite coal remains. A similar change takes place where bi- tuminous coal is heated by artificial means. The coke which remains, is, like anthracite coal, nearly pure car- bon. 882. PRODUCTION OF HUMUS. Humus, What is hu- mus? How is or the vegetable mould of forests, is formed it produced? by the decay of wood Qr yegetable matter in the air. Such decay is a species of slow combus- tion. The carbon is more slowly consumed than the other constituents. The vegetable mould or humus which remains after the partial decay, is, therefore, like peat, much richer in carbon than the material from which it was produced. It is variable in composition, according to the progress of the decay. The access of oxygen from without being unlimited, it is found to remain in equal atomic proportion with the hydrogen. What is the 883. WHITE ROTTEN WOOD. White composition of roUe n wood, which forms in stumps and wliite rotten wood? the interior of trees where there is abun- dant moisture and deficient access of air, has a different composition. The water present becomes chemically combined, and the product may be regarded as differ- ing from the former, somewhat as a hydrated oxide differs from the oxide itself. 352 ORGANIC CHEMISTRY. 8$4. PREVENTIVES OF DECAY. The ten- How may the decay of wood dency of wood to decay is checked by be prevented? ^ and ^ Q b certain salts> p or this purpose, corrosive sublimate and chloride of zinc have been chiefly used. The process of impreg- nation with metallic salts is called kyanizing. 885. INCOMBUSTIBLE CLOTH. Cotton How is cloth IT- T ^ i rendered in- cloth immersed in a solution or phosphate combustible? Q f ma g nesia j s thereby rendered incombus- tible. Silicate of potassa is also used on wood for the same purpose. 886. EFFECT OF SULPHURIC ACID ON What is the effect of sul- WOOD. Sulphuric acid chars or blackens P wood? aCid n wood b y abstracting a portion of the dxygen and hydrogen which it contains. The carbon is then left in excess, with its characteris- tic color. This action of sulphuric acid is a conse- quence of its strong affinity for water, the elements of which it appropriates from most organic substances. Dilute sulphuric acid has another remarkable effect, to be hereafter mentioned. 887. EFFECT OF NITRIC ACID. Nitric What is the -11,, effect of nitric ac id gradually consumes wood and other add on wood? organic matter> as effectually as if they were burned by fire. The final products of its action are also the same as those of ordinary combustion. This action is accompanied with the evolution of orange fumes, as when the same acid acts on metals. The first effect of nitric acid is to stain wood yellow ; for which purpose it is sometimes employed. Nitric acid may also be made to combine with woody fibre, form- ing gun cotton. WOOD. 353 What is the 888. EFFECT OF MURIATIC ACID. This acid aci ^ has no very strik i n g effect on wood on wood? or other organic substances. But chlorine decomposes and destroys them ; principally, in conse- quence of its affinity for hydrogen, as before explained. What effect ^89. EFFECT OF ALKALIES. - Alkalies have alkalies have the effect of hastening the decompo- on wood and . . similar sub- sition of organic substances. This effect is, in part, due to the fact that they promote the absorption of oxygen from the air. Paper or cloth in contact with lime or potash, is found to lose its strength speedily, and finally to crumble away. The theory of this action has already been given in the paragraph on nitrate of lime. Where the atmosphere is excluded, it would seem, from certain experiments, that lime has an opposite effect, and rather retards than promotes the decomposition of organic matter. What differ- 890. W OD VINEGAR. The acid pro- cnt substances duct, as obtained in the dry distillation are contained . , . , . . , , in wood vine- of wood, contains, beside acetic acid and gar? water, a sort of alcohol, called wood- spirit, and an oily, colorless fluid called kreosote. The latter has the odor of smoke, and has the same effect in preventing the putrefaction of animal sub- stances. The effect of smoke is owing, indeed, to the kreosote which it contains. A dilute solution of this oil in water, is used in medicine and for curing meats. 891. WOOD TAR. Wood tar is a mix- cl?are Sl con an ' ture of various oils, and volatile crystalline tained in wood solids composed principally of carbon and hydrogen. Kreosote, which is also ob- 354 ORGANIC CHEMISTRY. tained from wood vinegar, is one of the oils. Another of them, called eupion, has a pleasant odor, somewhat similar to that of the flower called narcissus. Pittacal, a beautiful blue coloring matter, resembling indigo, and paraffine, resembling spermacetti, are also obtained from tar. 892. COAL TAR. Coal tar Jances^r'e is produced from bituminous contained in coal, in the process of mak- coal tar ? ... . ing illuminating gas. It con- sists of numerous liquid and solid hydro- carbons, produced by the decomposition of the coal from which it was formed. Among them is napthaline, like camphor in appearance, and dissipated, like this sub- stance, by exposure to the air. Others are mentioned in the next paragraph. Coal tar, mixed with chalk, or other material, is used as a cement, and also as a material for covering roofs. 893. USEFUL PRODUCTS FROM COAL useful pro- ' TAR - The first product of its distillation, ducts of coal i s a light oil, commonly known as benzole. This may be substituted for spirits of tur- pentine, for a great variety of uses. Another heavier oil, which is obtained from it, is used as a solvent of india-rubber, and also for lubrication and illumination. In Europe, the pitchy mass, which remains on dis- tillation, is employed in moulding refuse coal dust into cakes, to be used as fuel. The light oil is also con- verted by the action of nitric acid, into an artificial es- sence, similar to that of bitter almonds, used exten- WOOD. 355 sively for scenting soap. -Its vapor, mixed with air, is also burned as gas. The heavy oil may be converted by a different action of the same acid, into beautiful lemon-colored crystals of carbazotic acid, a substance now used in France as a yellow dye for silks and wool. 894. OILS FROM COAL. The oils may How are oils ,,';"", produced from be directly produced from bituminous coal itself, and in much larger quantities than from tar, by avoiding the high temperature to which coal is subjected in the production of tar and gas. The production of oils by this means promises to be a very important branch of industry. 895. GUN-COTTON. This material, so How is gun- cotton pre- entirely harmless in appearance, has an pared? explosive energy superior to that of gun- powder. It may be prepared by immersing ordinary cotton, for the space of five minutes, in the strongest nitric acid. It is then to be washed thoroughly, and dried at a moderate heat, for fear of explosion. The material is found to have lost a certain portion of its oxygen and hydrogen, in the form of water, and to have assumed nitric acid, in its place. It is not how- ever changed in its appearance. A mixture of nitric acid with two-thirds of its volume of oil of vitriol, is found to be preferable to pure nitric acid, in the above experiment. The oil of vitriol assists in abstracting from the cotton the water which it is desired to replace by nitric acid. Gun-gotton is also called pyroxyline. Similar compounds, which are less explosive, may be prepared from sugar and starch. 356 ORGANIC CHEMISTRY. 896. USE OP GUN-COTTON, Gun-cotton. What is said of Us proper- is not likely, for several reasons, to super- cede gun-powder, for use in fire-arms. It is much more expensive, and so suddenly explosive as often to burst the barrels in which it is fired. Its ex- plosive force depends, like that of gun-powder, on a sudden combustion throughout its whole substance, and consequent evolution of a large volume of mixed gases and vapor. Of these, carbonic acid, nitrogen, and aqueous vapor are the principal. 897. GUN-COTTON SOLUTION COLLODI- What in collo- dion ? How is ON. Gun-cotton dissolves in ether, form- ing a syrupy liquid, which, on evapora- tion, leaves behind a transparent, tenacious film. It is used, to some extent, in place of ordinary court-plaster, for covering wounds and protecting them from the air. Howmay W ood 898 ' W D CONVERTED INTO SUGAR. be converted Wood may be converted into sugar, by caus- ing it to combine, chemically, with four ad- ditional molecules of water. This addition gives it the precise composition and properties of grape sugar, and, in fact, converts it into that substance. Poplar wood is found best suited for the purpose, and can be made to yield four-fifths its weight. To effect the conversion, the wood is first reduced to saw-dust, then moistened with somewhat more than its own weight of oil of vit- riol, and left to stand for twelve hours. Being subse- quently pounded in a mortar, the nearly dry material becomes liquid. It is then boiled with addition of water, and the transformation is completed. It only remains to remove the sulphuric acid, and evaporate STARCH. 357 the syrup. The former object is effected by the addi- tion of chalk and subsequent nitration, and the latter, as usual, by boiling TT 899. WOOD CONVERTED INTO GUM. How is wood converted into If the boiling be omitted in the above pro- cess, the woody film takes the form of a gum, called dextrine, of the same composition as the. wood itself, but soluble in water. Linen, or cotton rags, or paper, may be converted into sugar, or gum, by the same process. The sugar obtained is the same as that contained in grapes, and is therefore called grape sugar, and also glucose. It differs, somewhat, from ordinary cane sugar, as will be hereafter explained. STARCH. WJiatissaid ^00. DESCRIPTION. Starch is identical of the compo- i n composition with wood and gum. It sitlon and i -i structure of consists of minute enveloped grains, which burst and discharge their contents when swollen by warm water. Where is 901. OCCURRENCE. Starch isfoiuid starch found? j n abundance in most grains and other seeds ; in the tubers of the potatoe plant ; in many fruits, and in the pith of certain trees. In greater or less quantity, it is contained in all substances of vege- table origin which are used as food. Horse chestnuts contain 12 per cent, of starch, and have been used in Europe for the production of flour. 902. STARCH FROM POTATOES. Starch How is starch . prepared from is prepared from rasped potatoes, by wash- potass/ ing them Qn a seiye> Th water becomes 358 ORGANIC CHEMISTRY. % milky, as it passes through, from the fine starch grains which it carries with it. These are allowed to settle, and being collected and dried, are brought into com- merce as potatoe starch. A cotton-cloth may be sub- stituted for the seive in this experiment. 903. STARCH FROM WHEAT. If wheat How is starch made from, flour is moistened with water, and exposed to the air, it enters into a putrefaction which destroys, in the course of a few days, the other constituents, and leaves the starch un- affected. The residue being then washed and dried, the manufacture is completed. Io- dine may be used as a test for starch, as described under the head of iodides. Gums and woody fibre, although of the same composition, are not similarly affected. 904. CONVERSION OF STARCH INTO How is starch ... 1 converted into SUGAR. Starch, like woody fibre, may be converted into sugar through the agency of sulphuric acid. A dilute acid containing only j\ of its volume of oil of vitriol, is brought to the boiling point, and the starch then added by degrees while the boiling continues. A half hour or a little more suffices for the conversion. An infusion of brewer's malt has the same effect as the dilute acid. The sulphuric acid is then to be removed, and the syrup concentrated as before described. The sugar in this case also is grape, and not cane sugar. Such sugar is manufactured largely in Europe for adulterating cane sugar. In England its manufacture is prohibited by law. 905. CONVERSION OF STARCH INTO GUM. How is starch ,-,--. , , transformed By keeping the liquid near to the boiling into gum? point, without actual boiling, the gum SUGAR. 359 called dextrine, is obtained in the above process, instead of sugar. It may also be prepared by roasting starch, carefully, with constant stirring, until it acquires a brownish yellow color. This gum is used largely in calico printing, for thickening colors. It is also used in making the so-called " fig-paste," and certain other kinds of confectionery. The composition of starch and gum is precisely the same. 906. GUM. Gum arabic. and the sum What is said . . . . . of natural of fruit trees generally, is identical in com- gum*l position with woody fibre and starch. They are either soluble, like gum arable, in water, or swell up with it to form a thick paste, like gum traga- canth. The substance called pectine, which causes the juice of currants, and other fruits to stiffen with sugar into a jelly, is also similar to the above sub- stances in composition. All of these bodies, like wood and starch, are convertible into sugar by the action of sulphuric acid. SUGAR. GRAPE SUGAR - The production grape sugar of this substance from wood and starch has already been described. It does not exist in the juice of grapes, as its name would imply. The sugar of the grape and other acid fruits, contains two molecules less of water. It is spontaneously converted into true grape sugar or glucose, and found in incrus* tat.ons upon the surface of the dried fruit. Those fruits and trees which have but little acid in their 360 ORGANIC CHEMISTRY. juice or sap, commonly contain cane sugar. The sweetness of honey is due to grape sugar. This va- riety is much Jess valuable than that of the cane, from the fact that it has but little more than one-third of its sweetening effect. 908. CANE SUGAR. The sugar in com- Whot is said . . . . ' , of the compo- nion use is principally derived from the su g ar cane > an( l thence receives its distinc- trndMt artifidal pro- tive name. It differs in its composition duction f f -i -i from starch, wood, and gum, in containing a single additional molecule of water, while grape sugar contains four. It would seem from this com- position, that it would be more easily produced by artificial means, from starch and similar substances. But this is not the fact. No modification of the process above described, has as yet been devised by which starch and wood can be induced to take one additional atom of water, in- stead of four. Such a process would be a discovery of the greatest importance, as it would enable us to con- vert our potatoe and grain fields at will, into sugar plantations, and make us independent of foreign sup- plies. The figure represents a crystal of cane sugar. The form belongs to the fourth system. 909. OCCURRENCE. Cane sugar is What are the . . principal principally produced from the sugar cane, from beets ' and the American maple. But it is contained in smaller quantity in the sap of most plants, and in all fruits and vegetables which are not acid to the taste. The production of beet sugar in Europe, in 1850, was estimated at 190,000 SUGAR. 361 tons. That of cane sugar in cane growing countries is incomparably greater. 910. PRODUCTION. In manufacturing How is cane , . sugar pro- sugar from the cane, the juice is first pressed out, between heavy iron rollers ; then clar- ified, and finally boiled down until it will crystalize on cooling. The granular crystals form the raw sugar ; the drainings, molasses. Lime is the principal agent in clarification. Its first effect is to neutralize the acid of the juice, which, as before seen, would gradually con- vert the cane sugar into grape sugar, and thus injure its quality. It also precipitates, with other impurities, the gluten, which, as will be hereafter seen, tends to produce more acid. The methods of producing sugar from the beet and maple are essentially the same. The final purification of sugar by bone black has already been described. 911. MOLASSES. A large portion of How may mo- . . lasses be con- sugar is ordinarily lost in the form of mo- vertedinto lasses, from which it cannot be made to sugar f separate by crystallization. This is owing to the presence of impurities not separated by clarifica- tion, which interfere with the process, in a way not per- fectly understood. A method has recently been con- trived of avoiding the loss, and thus largely increasing the product of the beet and cane. Baryta added to the syrup, combines with the sugar, and takes it to the bottom of the vessel, as a solid compound of sugar and baryta, while the impurities remain behind. This pre- cipitate is then removed and diffused in water. Car- bonic acid being added, combines with the baryta, and 16 362 ORGANIC CHEMISTRY. leaves the sugar to form a pure and crystallizable syrup. Another method of increasing the product of sugar has been described in the section on sulphurous acid. How is alcohol produced from ALCOHOL. 912. PRODUCTION FROM SUGAR. By i - the addition of brewers' yeast or some si- milar ferment to sugar, it is gradually con- verted into alcohol. Two molecules of water are sepa- rated in the process. One-third of the carbon and two- thirds of the oxygen which remain, pass off as carbonic acid gas, while alcohol remains. The yeast enters into no combination, and furnishes no material in the pro- cess. It acts merely by its presence to effect the de- composition, as will be hereafter explained. Explain the 913. In this process of conversion, each diagram. molecule of sugar makes two of alcohol, and four of the acid. The figure repre- sents a molecule of grape sugar, after the removal of two molecules of water. An arbitrary arrangement is given to the atoms for convenience of illustration. On striking off enough carbon and oxygen from the corners to make the required amount of carbonic acid, the residue may be supposed to fall apart into two molecules of alcohol. Alcohol is also produced from cane sugar by fermentation. The first stage in the process is its conversion, by yeast, into ALCOHOL. 363 grape sugar. The latter is then changed into alcohol and carbonic acid, as above described. 914. COMPOSITION. The composition What is the composition of of alcohol appears sufficiently from the mid- dle groups of the preceding figure. Accord- ing to the theory of compound radicals it is a hydrated oxide of ethyle. The principal group of the annexed cut, represents a molecule of the radical ; the remaining circles stand for the oxygen and water with which it is combined in alcohol. 915. PRODUCTION FROM POTATOES AND How is aico/iol made from po- GRAIN. Wliei'6 molasSCS Or Solution of sugar is the material used, alcohol is pro- duced as already shown. But when potatoes and grain are employed as the material, a previous process is necessary by which the starch is converted into sugar. This consists in the addition of bruised malt to the mashed potatoes or grain. The diastase of the malt, has the effect of gradually transforming starch into sugar by its presence, as yeast converts sugar into alcohol. The mixture being kept at a temperature of about 140, in a few hours the transformation is complete. The starchy mixture has become sweet, and receives the name of wort. Brewers' yeast and water being then added to the wort, the conversion into alcohol commences. This is afterward separated from the water and refuse fibre of the potatoe or grain by the process of distillation, described in a subsequent paragraph. 364 ORGANIC CHEMISTRY. What is said 916. PRODUCTION FROM ILLUMINATING of the produc- GAS Alcohol may also be produced from tion of alcohol from olefiant heavy carburetted hydrogen, one of the con- gas ' stituents of ordinary illuminating gas. This is one of the most remarkable results of modern science. Most of the processes of organic chemistry consist in taking apart the complex molecules of organic matter and reducing them to a simpler form, as was illustrated in the production of alcohol and carbonic acid from sugar. Na- ture, for the most part, jealously withholds from man the power so to direct her forces as to build up arid produce more complex organic substances by the com- bination of those of simpler nature. This takes place as a general rule only under the influence of the vital forces of vegetable and animal existence, as when the plant produces sugar from the elements of the atmos- phere. The case is an exception to the general rule. Explain its 917. By reference to the central group production. o f tne fig ure which represents a molecule of heavy carburetted hydrogen, it will be seen that all that is necessary to effect its conver- sion into alcohol, is the addition of two molecules of water. By long agitation of the gas with strong sul- phuric acid, the transference of part of the water which it holds combined is effected. On subsequent dilution and distillation, alcohol is obtained from the mixture. Carbonate of potassa is added in the process of distil- lation, to diminish the proportion of water which would otherwise pass off with the alcohol. After repeated dis- tillation, strong alcohol is thus obtained. ALCOHOL. 365 918. DISTILLATION OF ALCOHOL. The What ^,<< said of fae presence process of distillation may be illustrated of distillation? with the simple appals ^presented in the figure. On heating wine, cider or beer in the test- tube, its alcohol will be ex- pelled as vapor and re-con- densed as a colorless liquid. The cooler the vial is kept the more perfect is the condensation. The apparatus commonly employed in the distillation of alcohol, con- sists of a large copper vessel in which the fermented wort is heated, and a long tube called the worm, in which the vapors are condensed. The worm is made to wind in a spiral, through a tub of cold water, that the condensation may be more completely effected. The spirit pours out at the lower end of the worm, where it emerges from the tub. It may be strength- ened by repeated distillation. In order to obtain it entirely free from water, a highly rectified spirit is mixed with lime, or chloride of calcium, and re-dis- tilled. These substances have such affinity for water, that they prevent its escape as vapor, while they in no wise effect the distillation of the alcohol. By this means pure alcohol, or absolute alcohol, is ob- tained. Wimtis spir- ^19. USES OF ALCOHOL. Ordinary it* of wine? spirits of wine is a dilute alcohol contain- Mention some . uses of aico- ing but about seventy per cent. 01 absolute hol? alcohol. The taste and odor of alcohol its combustible character, and action as a stimulus, are too familiar to need further mention. Its density, and 366 ORGANIC CHEMISTRY. boiling point, are given in the Appendix. It is largely used in medicine, and as a solvent of oils and resins, and many other substances which water does not dis- solve. Medicinal extracts of many roots and herbs, "cologne," and other perfumed liquids are thus pro- duced. What is the ^20. SPIRITUOUS LIQUORS. - SpiritUOUS source of the liquors contain alcohol in large but varying different spir- J ituousli- proportion. They differ in their flavor according to the material from which they are produced. Brandy is distilled from wine, rum from molasses, and whiskey from malt liquors. The latter name is also given, in this country, to the liquor made from potatoes, corn, and rye. In Europe, the latter are more commonly called brandies. How are wines 921. WINES. Wines are produced by produced? the fermentation of the juice of the grape. On exposure to the air, the gluten of the juice becomes a ferment, and causes the conversion of the sugar into alcohol. The addition of yeast is therefore unneces- sary. This is also true of the juice of the apple, pear, and other fruits from which fermented liquors are sim- ilarly prepared. How is cham- 922. CHAMPAGNE. Champagne and pagnemade? o ther sparkling wines owe their peculiar- ity to the presence of carbonic acid, in large propor- tion. This is secured by allowing the last stages of fermentation to proceed in firmly corked bottles, so that all the gas which is evolved is retained. Or an or- nary wine is first produced by the usual process, and sugar and yeast are then added, to excite a new fer- mentation in the bottled liquid. MALT LIQUORS. 367 What is said ^23. ALCOHOL IN WINES. Wines differ of the pro- i n the amount of alcohol which they portion of al- . coholin tain; from five per cent., in the weakest champagne, to twenty-five, in the strongest sherry. Those of southern climates are strongest, be- cause the grapes of those regions contain more sugar to undergo conversion into alcohol. Most wines also contain more or less acid and urifermented sugar. What is said 924. TARTAR. The acid of wine is of acid in . ., , . . . ^ . . \tines? tartanc acid, which exists in combina- tion with potash in the juice of the grape. It grad- ually deposits in wine casks in the form of acid tar- tra'te of potash or cream of tartar. This separaton of tartar is one source of the improvement of wines, and more particularly of the rhenish wines, by age. 925. FLAVOR OF WINES. The wine What is said . of the flavors flavor which belongs to all wines, is owing to the presence, in extremely small portion, of an etherial liquid called aenanthic ether. Tliis substance does not exist ready formed in the grape, but is produced in the re-arrangement of atoms which takes place in fermentation. Its vinous odor, when separated from the wine, is most intense. It is prepared in Europe from grain spirit or cheap wines, and is used in this and other countries for producing imi- tations of wines of higher price. Potatoe whiskey is commonly the basis of these manufactured wines. Beside the general vinous flavor, different wines, like flowers, have an aroma, or bouquet, peculiar to them- selves. These are owing, to other and different flavor- ing substances, present in still smaller proportion, than the aenanthic ether. 368 ORGANIC CHEMISTRY. 926. BEER AND ALE. Beer is the fer- tfow are malt liquors pre- merited extract of malted grain. The malt pare ' is prepared by softening barley in water, and then allowing it to sprout or germinate. Diastase, which is formed in the process of germination, con- verts the starch of the grain into sugar, and thus pre- pares it for the subsequent process of fermentation. Yeast and hops are added to the extract of malt, which is called the wort, to bring about fermentation and help to give the product flavor. Ale is a similar malt liquor of different color. Porter is a darker variety of beer, made from malt which has been browned by roasting. 927. CONVERSION OF ALCOHOL INTO How is alcohol . , , , . , . converted into ETHER. Alcohol is converted into ether ether ? ky h eat i n g w i tn o {\ o f vitriol. To illus- trate its preparation, equal volumes of strong alcohol and oil of vitriol may be thoroughly mixed in a test- tube, and the vapors con- densed in a cool vial, as J represented in the figure. A little sand may be added to the mixture with advant- age. The vial should be kept cool by means of paper repeatedly moistened, during the process. The space between the tube and the neck of the vial should also be loosely closed with wet paper. 928. EXPLANATION. Alcohol is, as Explain the -,*/ above re-ac- above stated, the hydrate of the oxide of tl011 ' ethyl. Sulphuric acid combines with tho ETHYL. 369 oxide itself, on heating, forming a bi- sulphate, and at a little higher tem- perature, yields it up again, as gaseous ether or oxide of ethyl. The change in the alcohol consists, simply, in the loss of an atom of water. The whole figure represents a molecule of alcohol ; the lower portion one of ether. 929. PRODUCTION OF ETHYL. The How is the -i i 11 radical ethyl radical ethyl cannot, like many metals, be procured? directly produced from its oxide. Heat, or other means, applied to accomplish this object, destroys the radical itself. But the end may be reached by a circuitous process. This consists in first producing from the oxide, an iodide of ethyl, and then removing the iodine by a metal. A colorless gas, of the composition indicated by the hydrogen and carbon at- oms of the figure, is thus evolved. 930. CONVERSION OF ALCOHOL INTO How is alcohol convertedinto OLEFIANT GAS. The production of alcO- olefiantgas? ^ fr()m olefiant gag hag been described in the section on hydrogen. The subject is again in- troduced, for the purpose of illustrating the change, by reference to the atomic composition of the two sub- stances. Representing the atom of alcohol as before, it is converted by the removal of two atoms of oxy- gen, and two of hydrogen, into olefi- ant gas. The composition of this gas is indicated by the central group of the annexed figure. The ab- straction of oxygen and hydrogen is effected through 16* 370 ORGANIC CHEMISTRY. the agency of the sulphuric acid used in the process. It will be observed that the radical ethyl, which has re- mained permanent in the changes before described, is here destroyed, by the abstraction of a part of its hy- drogen. What is aide- 931. CONVERSION OF ALCOHOL INTO ALDE- hyde? HYDE. Aldehyde is a clear colorless liquid of a peculiar ethereal odor, produced by the action of the air or oxygen on alcohol. It is the product of a partial, slow combustion, or ereme- causis of the alcohol, and forms the middle point in the conversion of alcohol into vinegar. It is for this reason that it is here introduced. 932. The two atoms of hydrogen, How is alcohol , . .. , , . converted into which are burned out m the process, are aldehyde ? indicated in the figure by smaller inscribed letters. By the removal, the radical ethyl is converted into the radical acetyl. Aldehyde is therefore a hy- drated oxide of acetyl. The characteristic odor of the substance is often perceived, in the process for making vinegar. It may also be produced by depressing a wire gauze upon an alcohol flame, and thereby making the combustion incomplete. 933. CONVERSION OF ALCOHOL INTO VIN- ZSZZ&f If dll te alcoho1 ; s exposed to the alcohol into a i r? it is converted, by oxidation, into ace- tic acid. Part of its hydrogen having been burned out to form aldehyde, the oxy- gen acts further to oxidize the alde- hyde which has been produced. The composition of each molecule is such VINEGAR. 371 as is represented in the preceding figure. It will be ob- served that the oxygen added is just sufficient to sup- ply the place of the hydrogen removed in the formation of aldehyde. The latter substance being a hydrate of the protoxide of acetyl, acetic acid is a hydrated terox- ide of the same radical. The presence of yeast or some other similar ferment, is essential in the produc- tion of vinegar, as well as in that of alcohol. Describe the 934. PROCESS OF MANUFACTURE. A process. f ew y ears since, vinegar was exclusively produced by the souring of .wine or cider. At pres- ent, large quantities are made from alcohol, by diluting it with water, adding a little yeast, and then exposing it to the action of the air. This is best accomplished by allowing the diluted alcohol to trickle through shav- ings, packed in well ventilated casks. A few passages through the cask suffices to convert the liquid into vinegar. The addition of yeast is unnecessary in pro- ducing vinegar from cider or wine, as these liquids con- tain a substance which acts as a ferment. The vapor of alcohol may be readily converted into acetic acid by contact with platinum black. The property of pla- tinum to produce oxidation in similar cases, has been already explained. 935. CHLOROFORM. Chloroform is best Howischloro- . ...... formprepar- obtained by distilling pure alcohol with water and bleachin g powder. Its mole- cule consists of two atoms of carbon, and one of hydrogen, combined with three of chlorine. The carbon and hydrogen atoms are regarded as more inti- mately combined to form the radical formyl. Chloro- 372 ORGANIC CHEMISTRY. form is therefore a terchloride of this radical. It is a colorless and volatile liquid, of a peculiar, sweetish smell. The inhalation of its vapor, produces insensi- bility to pain, and is much employed in surgical ope- rations, for this purpose. Ether has the same effect, in a less degree. A mixture of the two, is more com- monly employed in this country. 936. FUSEL OIL. Fusel oil is a peculiar What is fusel ,.,-.,, f . oil? Mention kind of alcohol, of extremely nauseous its properties. Q ^ an( j p O j sonous properties, which ac- companies ordinary alcohol in its production from potatoes and grain. It may he separated by nitration through charcoal. But this process of purification is often neglected, and the fusel oil left to add its poison to the deleterious effects of the alcohol itself. It is this doubly poisonous alcohol which forms the basis of numerous manufactured liquors, wines, and cordials. Fusel oil is the hydrated oxide of amyl. This radical contains ten atoms of carbon, to eleven of hydrogen. It belongs to the series of alcohols mentioned in the first chapter of organic chemistry. ORGANIC ACIDS. mat is said 937 - ACETIC ACID. Ordinary vinegar of theproduc- j s a dilute acetic acid. It cannot be con- tion and prop- erties of acetic centrated by evaporation, as the acid is volatile, as well as the water which dilutes it. To obtain the strong acid, recourse is had to the salts of acetic acid, from which it is prepared by the method used for nitric and muriatic acids. The pure TANN1C ACID. 373 acid is a solid. It mixes with water at low tempera- ture, in all proportions, and is commonly seen in its dis- solved state. Its compounds with metallic oxides are called acetates. The sugar of lead, so called, is an acetate, formed by dissolving litharge in acetic acid. 938. TANNIC ACID. Tannin, or tannic e acid > exists in nut-galls and in the bark properties of and leaves of many trees. It is the prin- tannic acid ? . . .... . , . ciple which imparts to them their astrin- gent taste, and gives to the tan liquor the property of converting hides into leather. When separated from the other substances with which it is combined in nature, it is a yellowish, gummy mass. It is soluble in water, and possesses the property of precipitating glue or gelatin, and many other metallic oxides. 939. WRITING INK. Common writing What is the . coloring mat- ink is prepared from nut-galls and proto- ter^of writing sulphate of iron> W hen first made, it is principally a tannate of the protoxide of iron, and forms a very pale solution. Before it is fit for use, it must be exposed for a time to the air, and thereby converted, partially, into tannate of the peroxide. This is a bluish black precipitate, and imparts to it the requisite color. It is essential to the permanence of ink, that the change should take place, in part, in the fibre of the paper itself. Too long exposure should, therefore, be avoided in the manufacture. The pale ink thus produced, which blackens further in using, is much more permanent than a thicker, darker ink, produced when this caution is not observed. 374 ORGANIC CHEMISTRY. 940. Six parts of nut-galls to four of Give the pro- cess of its copperas, are found to be the best propor- preparation. tiong for prO( } U cing a permanent ink. The galls are to be boiled with water, the decoction strained, and mixed with copperas solution. Gum and cloves are added, the former to keep the coloring matter of the ink from settling, and the latter to prevent its moulding. After a ripening of a month or more the liquid is strained. The coloring matter of ink is immediately produced in a solution of copperas, as a bulky precipi- tate, by the addition of tincture of galls, and a little nitric acid. HYDROCYANIC ACID. 941. CYANOGEN. Before proceeding Mention the . . composition with the description of hydrocyanic, or P mssic acid > the production of cyanogen, which enters into its composition, will be briefly consid- ered. Cyanogen is a colorless gas, with a peculiar odor, resembling that of peach pits. It is nearly twice as heavy as atmospheric air. It burns with a beautiful purple flame. Cyanogen is a compound radical, posssessed of important analogies to chlorine, and the other electro-neg- ative elements. Its molecule contains one atom of ni- trogen and two of carbon. How is cyano- 942. PRODUCTION. Cyanogen may be gen prepared? expelled from the cyanide of mercury, by CYANIDES. 375 the agency of heat. This metal retains cyanogen as it does oxygen, but feebly. A method more commonly employed is to produce and decompose the cyanide of mercury at the same moment. This is effected by mixing chloride of mercury, to furnish the metal, with the double cyanide of iron and potassium, which fur- nishes the cyanogen. The other elements unite to form chlorides of iron and potassium, while the cyanide of mercury is decomposed as fast as it is formed. The double cyanide of iron and potassium, above referred to, is the commercial yellow prussiate of potash. Two parts of this salt are to be heated with one of bi-chloride of mercury, in the above process. The prussiate cannot be used alone for the production of cyanogen, on ac- count of the firm retention of this radical by the highly electro-positive metals which enter into the com- position of the salt. How isc a- ^^* CYANIDE OF POTASSIUM. Cyanide nide of potas- of potassium is a white substance, resem- siumprepar- , .. ... , ed? Mention bling porcelain m appearance, and quite soluble in water arid Alcohol. It is largely employed in preparing solutions of the precious metals, for galvanic gilding and silvering. It is produced on a large scale, by fusing together carbonate of potash and refuse animal matter. The latter furnishes the carbon and nitrogen required for the production of cyangen, while the carbonic acid and oxygen of the salt, are principally evolved as oxide of carbon. The cyanide of potassium is best extracted from this residue by alco- hol, which leaves the other material undissolved. ORGANIC CHEMISTRY. 376 How is yellow 944 P^ssiATE OF POTASH. Cyanide prussiate of of iron is always incidentally formed from potash pre- . pared? Men- the iron of the vessel in the above process. tion its uses, j f Wftter ig added t() th cyanides dissolve ; although the latter, when alone, is entirely insoluble. From the solution, the double cy- anide of potassium and iron, mentioned in a preceding paragraph, is obtained, by evaporation, in splendid yel- low crystals. It is known in commerce as yellow prussiate of potash, and is largely used in the arts for the production of prussian blue and cyanide of potas- sium. Prussian blue is obtained by adding its solution to a salt of the peroxide of iron. As any solution of iron is readily peroxydized by the addition of a little nitric acid, the yellow prussiate may be employed as a test for this metal. 945. FERROCYANIDES. The yellow What is said 3 of ferrocya.no- prussiate of potash, produced as above de- scribed, is not properly a double cyanide of iron and potassium. There is reason to believe that the cyanogen is more intimately combined with the iron than such a name would imply. It seems to have lost its ordinary properties, in the compound. Neither the alkalies, or sulphide of ammonium, which usually precipitate iron from its solutions, have any power to precipitate it from this salt. The three mole- cules of cyanogen, which enter into its composition, seem to have hidden and absorbed it. They have formed with it, indeed, a new compound radical, called ferrocyanogen. The double salt above mentioned is therefore more properly a ferrocyanide of potassium. PRUSSIC ACID. 377 Ferrocyanogen, like all other compound radicals, con- ducts itself, under ordinary circumstances, as an ele- mentary substance. WJiatisfcrri- 946. On tne removal of one atom of cyanogen? potassium from two molecules of this salt, a coalescence of the ferrocyanogen of the two mole- cules seems to be the result, and a new compound radi- cal is formed. This radical is called ferricyanogen. It combines with the three remaining atoms of potas- sium, to form ferricyanide of potassium. Give the ro - ^^ ' P RUSSIC ACID. Hydrocyanic acid erties of prus- i s made from cyanide of potassium, by the its mode of same method employed for producing hy- preparation. drochloric ac id f rom common salt. The ferrocyanide of potassium is more commonly employed in the process. Prussic acid is intensely poisonous. A drop or two of the concentrated liquid, placed upon the tongue of a dog, produces immediate death. On ac- count of its extremely dangerous properties, the prepa- ration of the acid should never be attempted except by a professional chemist. The odor of the acid is somewhat similar to that of cyanogen, and may be fre- quently detected in the vicinity of establishments where galvanic gilding is conducted. Ferrocyanogen and fer- ricyanogen, like simple cyanogen, have their hydrogen acids and series of salts. The acid of the former is bibasic, and that of the latter tribasic, as already shown by the composition of their potassium compounds. What is said ^48. OTHER ORGANIC ACIDS. Tartaric of citric, ma- acid, before mentioned, is found in the lie, lactic, ox- alic, and for- grape. The acid tartrate of potassa or mie acids ? crea m of tartar, which deposits in wine 378 ORGANIC CHEMISTRY. casks, is one of its most important salts. Another has been mentioned under the head of antimony. Oxalic acid is found in wood sorrel and in certain lichens. It is also prepared by the action of nitric acid on wood, sugar, and starch. When these substances are burned in the air, their carbon is converted into carbonic acid. Oxalic acid contains half the proportional quantity of oxygen, and may be regarded as the product of a less perfect combustion by the oxygen of nitric acid. It is a white crystalline solid and a most dangerous poison. The effect of heat on oxalic acid, with its precise com- position, is given in the section on carbonic oxide. Citric acid is the acid of lemons, malic acid, that of the apple, and formic acid that of the red ant. The latter may also be formed from wood spirit, by oxida- tion, through the agency of platinum black, as acetic acid is formed from ordinary spirit or alcohol. Lactic acid will be again mentioned under the head of animal chemistry. 949. THEIR COMPOSITION. All of these What is the composition of acids differ in taste and in various chem- *acids? Ve * ca ^ P r P ert i es ? as do those of inorganic chemistry. Yet all of them contain the same three elements which are also contained in wood, gum, and starch. They contain these elements in various proportion, but their peculiarities are not to be ascribed to this cause alone. They may be regarded as in part, at least, the consequence of a difference of arrangement of the atoms, as has already been ex- plained ESSENTIAL OILS. 379 ESSENTIAL OILS. What is said ^50. V LATIL E, OR ESSENTIAL OILS. of the compa- Oils of turpentine and lemon, and otto of rative compo- sition of es- roses, are examples of essential oils. They sential oils ? are a i most as var i ous as plants themselves. Yet the composition of those that differ most widely is often the same. This is the case with the oils of orange, lemon, pepper, turpentine, juniper, parsley, citron and bergamot. They contain carbon and hy- drogen alone, and in the same proportion; twenty atoms of the former to eight of the latter. Those of bitter almonds, cinnamon, cloves, and anise-seed, con- tain oxygen beside. Those of mustard, and onions, contain oxygen, and sulphur, in addition, and are char- acterized, like all sulphuretted oils, by a peculiar, pun- gent smell, and acrid, burning taste. 951. OCCURRENCE AND PREPARATION. How are the . essential oils Essentials oils are oftenest found in the prepared? fl owe rs, seeds, and fruits of plants, but sometimes in the stalks and roots. From these they are obtained by distillation with water. The volatile oil passes over with the steam, and floats upon the con- densed liquid in the receiver. Oil of turpentine is thus made, from the common turpentine, or pitch as it is sometimes called, which exudes from the pine ; ordi- nary rosin remains behind. The delicate perfume of violets, and other flowers which contain but a small portion of essential oil, is extracted by mingling the flowers with lard. This substance has the property of absorbing the oil, and yielding it again by distillation. co 380 ORGANIC CHEMISTRY. 952. USE OF THE ESSENTIAL OILS. - What are the . . uses of the es- 1 he essential oils are extensively em- senttal oils ? ployed in the manufacture of essences, per- fumes, and cordials. All of these liquids are solutions of the oils in alcohol, with the addition, in the case of cordials, of a portion of sugar. The oil of turpentine is used in the manufacture of varnishes and burning fluid, to be hereafter described. 953. BURNING FLUID. " Burning fluid," What is the position of so called, is a solution of camphene or rectified turpentine in alcohol. The sole object of the camphene is to increase the proportion of carbon, and thus render the flame more luminous. Unmixed camphene may also be burned in lamps provided with tall chimneys. The effect of the chimney is to make a strong draft, and thus provide a liberal supply of oxygen in proportion to the large amount of carbon which the liquid contains. With- out this provision, camphene burns like camphor, with much smoke, depositing a large part of its carbon in the form of soot or lamp-black. What is said 954 BURNING FLUID, "EXPLOSIVE." of the expio- The mixture of alcohol and camphene, sibility of ./,.-, i " burning- known as burning fluid, is commonly spoken of as explosive. That this is not the fact, may be readily shown by pouring a little in a saucer, and inflaming it. It burns, under these circumstances, as quietly as from the wick of a lamp. But if a can, containing burning fluid, be shaken up and then emptied of its liquid con- tents, it is found to contain an explosive atmos- phere. To prove this, it may be tightly corked BURNING FLUID. 381 and fired through a small hole punched in the side. On applying a lighted taper to the opening, the can explodes with a loud report, and is torn to pieces by the force of the escaping gases. The small proportion of fluid remaining in the can, after every drop that can be poured out is removed, is sufficient to produce this effect. 955. EXPLANATION. The principle of What is the cause of the the explosion is precisely the same as that explosion? involved in the same experiment with hy- drogen and air. The only variation consists in the sub- stitution of the combustible vapor of alcohol and cam- phene, for hydrogen gas. It is the mixture of alcohol vapor, and air, to which the effect is to be principally ascribed ; the experiment may be made, indeed, as well with unmixed alcohol, or ether, as with burning- fluid. It may also be made with camphene, but in this case the vessel must be warmed, in order to vaporize the liquid in sufficient quantity. 956. The above experiment may be Describe an- /. j .-, c , i -u other form of performed with safety, in an open vial, by the expert- vaporizing a drop or two of either of the above liquids within it, and then apply- ing a lighted taper to the mouth. In this case, the ap- pearance of flame at the mouth of the vial, and a rushing noise, is all that is observed. This experiment will enable the student to disprove the alleged unex- plosive character of certain fluids in use for purposes of illumination. In moderately warm weather it is sufficient to fill the vial, and then to empty it, in order to form the explosive atmosphere. 382 ORGANIC CHEMISTRY. 957. ARTIFICIAL ESSENCES. Many of What * naid of artificial the essentials oils are compounds of organic acids and bases. Several of them may be artificially produced. Pine apple oil is a compound butyric acid with ether or oxide of ethyl. The bu- tyric acid of the compound may be prepared from rancid butter or by fermenting sugar with putrid cheese. Bergamit pear oil is an alcoholic solution of acetates of the oxide of ethyl, with acetate of oxide of amyl. The latter is the ether of the nauseous and poisonous fusel oil, which has before been mentioned. What is arti- 958. Apple oil is a compound of vale- fdal apple rianic acid with the same ether. The oil? Artifi- cial oil of bit- valenanic acid of the compound is also ter almonds? ^^ from fugel Q ^ Oil of grapes, and oil of cognac, used to impart the flavor of French brandy to common alcohol, come from the same source. Oil of winter-green may be prepared from willow bark and wood vinegar. Oil of bitter almonds is prepared from coal tar. These artifical essences, although pro- duced in several cases from poisonous substances, may be used as flavors with perfect safety. It is highly probable and in many cases certain, that the flavor of the fruits themselves, is owing to the presence of these precise compounds, in small quantities. , jr , , 959. EMPYREUMATIC OILS. The vola- What are em- pyreumatic tile oils which are produced by the de- structive distillation of vegetable and ani- mal substances receive this general name. The oils of wood and coal tar are examples. Another em- pyreumatic oil is produced in the combustion of to- RESINS. 383 bacco in ordinary pipes. This oil is extremely poison- ous. It is to be understood that these oils do not exist ready formed in the substances from which they are obtained, but are produced in the re-arrangement of atoms, which takes place when organic bodies are sub- jected to a high temperature. 960. CAMPHORS. Several of the oxy- What is the . J origin of the genated essential oils deposit white crystal- wnphonf line solids by cold These are frequently isomeric with the oils themselves, and are called cam- phors. Ordinary gum camphor is obtained like the es- sential oils, by the distillation of the leaves of the Lau- rus Camphor i with water. Its volatile character is the occasion of a singular appearance, when small bits of the substance are thrown upon warm water. The par- ticles are seen to sail about as if they were possessed of life, owing to the propelling effect of the vapor which escapes beneath them. ,/A How are re- 961. RESINS. The resins, of which sins formed? ordinary pine rosin may serve as an exam- ple, are formed by the action of oxygen upon the essen- tial oils. Oil of turpentine may be thus partially con- verted into resin, by long exposure to the air. On sub- sequently heating it, only a portion is found to be vola- tile, while a resinous mass remains behind. Turpen- tine, or pitch of pine trees, is thus formed in nature, from the oil of turpentine, as it exudes from the trees. But the conversion is only partial, so that the turpentine yields, on distillation, a portion of oil, while rosin remains behind. Resins are easily distinguished from gums by their insolubility in water ; they are, on 384 ORGANIC CHEMISTRY. the other hand, readily soluble in alcohol or ether. They are not liable to decay, like most other substan- ces of vegetable origin. Copal, shellac, mastic, and amber, are all resins. The latter is found in certain coal mines, and at the bottom of the sea, and has probably had its origin in the forests of some primeval age. 962. EXPLANATION. The action of Explain the ~ , ... , above trans- the oxygen of the air, m the above case, formation? ^ similar to that which occurs in the con- version of alcohol into vinegar. A portion of the hy- drogen is burned out, as it were, and removed in the form of water, while another portion of oxygen takes its place. 963. USE OF THE RESIN VARNISHES. what use is made of the The resins are principally employed for the T arT varnishes production of varnishes. These are simply made? solutions of resins in alcohol, ether, or spirits of turpentine ; or an intimate mixture of the latter with fused resin and oil. In preparing copal var- nish, which is the most brilliant and durable, the resin is first fused, then incorporated with heated oil, and afterward diluted with spirits of turpentine. A com- mon varnish for maps, engravings, and similar objects, is made by dissolving mastic with a little Venice tur- pentine and camphor, in spirits of turpentine. Pounded glass is added to the pulverized material during the process of solution. The object is covered with a so- lution of isinglass before using this varnish, to prevent its absorption. Shellac, in alcohol, is employed to impart to wood or other material a resinous coating^ RESINS. 385 which is afterward polished with rotten stone. Copal varnish is also similarly used. Shellac, dissolved in soda or potash, is sometimes used to give body to paints, as a substitute for part of the more expensive material. What i rosin 964. ROSIN SOAP. The resins possess soap? an ac id character, and like fats, form soap with the alkalies. Common rosin is largely consumed, with fat and potash, in the manufacture of common brown soap. The greater hardness which it imparts depends on the formation of a certain portion of rosin soap, in the mixture. 965. SIZING. The soap which is How is rosin used in sizing formed on boiling rosin with strong potash paper? - g uge( j m s j zni g p a p er . Being mixed with the material from which paper is to be made, a solution of alum is afterward added to the pulp, and a compound of rosin and alumina thus produced in every portion of the mass. The pores of paper made from this mate- rial are thus completely filled, and the spreading of the ink prevented. A surface sizing which is less ef- fectual, is also given to paper by a solution of glue, applied after the paper is formed. When this is de- stroyed by erasure, its place may be supplied, and the spreading of ink prevented, by rubbing powdered rosin upon the spot from which the sizing has been removed. 966. SEALING-WAX. Sealing-wax con- What is the tionof sists, principally, of shellac. Venice tur- pentine is added to make it more inflam- mable and fusible, and vermilion or lamp-black to color it. Ship pitch is resin changed and partially decom- 17 cotnposi sealing-icax ? 386 ORGANIC CHEMISTRY. posed by heat. Shoemakers wax is made by a similar process. What are the ^67. ROSIN OIL AND GAS. Rosin is products of partially converted by dry distilla- te dry distil- \ . . . , . lation of tion into an oil, which is largely used for adulterating other oils, and also for purposes of illumination. A black pitch remains in the retort. The oil has the advan- tage of extreme cheapness, but owing to its large proportion of carbon, can only be burned in lamps furnished with tall chimneys. At a still higher temperature rosin is converted into gas, with a residue of carbon. What is as- 968. AspHALTUM. Asphaltuni or bi- phaltum? tumen is a mineral resin, similar to the black pitch which remains from the distillation of coal tar. This material is found on the shores of the Dead Sea, in the island of Trinidad, and in several European localities. It is extensively employed for hydraulic cements, roofing, and pavements. 969. PETROLEUM. Petroleum is a liquid What is said . of the source, hydrocarbon, also known as rock oil. It is often found u P on standing water, in bitu- ofpetrole- minous coal districts. Pits are also dug for the purpose of collecting it. These become filled with water, upon which the oil rises, more or less abundantly. The rectified petroleum is called naptha, and is a nearly colorless and highly volatile fluid. The entire absence of oxygen in its composi- tion, adapts it perfectly to the preservation of the metals potassium, and sodium, in their metallic condition. CAOUTCHOUC. 387 It is also used as a solvent of sulphur, phosphorus, fats, resins, and caoutchouc. Both asphaltum and petroleum have been, probably, produced by the action of vol- canic fires upon bituminous coal. 970. GUM RESINS. The dried juices what is said . , of gum re- of certain plants consist of mixtures of gum and resin. These mixtures are called gum resins. Water dissolves the gum, and holds the resin in suspension, thus forming what is called an emulsion. Alcohol, on the other hand extracts the re- sin from their mixtures. Assafoetida, gamboge, and opium, are a few examples of gum resins. 971. CAOUTCHOUC. GUM ELASTIC. Mention the i i ' sources and Caoutchouc is a hydrocarbon, obtained from outchouc{ tne milk y J uice f certain trees in Asia, Africa, and South America. This constit- uent of the juice hardens, on exposure to the air, while the remainder is removed by evaporation. By the ad- dition of a little ammonia, the milk may be retained in its liquid condition. Caoutchouc is soluble in ether, spirits of turpentine, oil of coal tar, and many other hydrocarbons. Sulphuret of carbon, a volatile liquid obtained by passing sulphur vapors over ignited char- coal, is also a complete solvent of India-rubber and gutta percha. 972. VULCANIZED RUBBER. Heated for How is caout- chouc vulcani- a snort time with sulphur, at 280, or Z ave the^rl - somewnat above this point, caoutchouc ertiesof mil- becomes remarkably changed in its nature, canized " rub- -, . ~ , . , , ,, ber ? and is no longer stiffened by cold, or soft- ened by heat. It is then called vulcanized 388 ORGANIC CHEMISTRY. rubber, and constitutes the material out - of which most India-rubber goods are now made. The hard rubber which is extensively employed for the manu- facture of cornbs, knife-handles, pencil-cases, &c., is composed of pitch, India-rubber, sulphur, and mag- nesia. The mixture is softened at about 270, then pressed into moulds to give it the required shape. It is afterward wrought like ivory. Whatisgutta 973 ' G UTTA PERCHA. Gutta percha is percha? identical in composition with gum elastic, Mention some , , _. of its proper- but possessed of quite different properties. ties and uses, ^mong them is its extreme toughness, and comparatively slight elasticity. It is rendered soft and plastic by immersion in boiling water, and in this pasty condition may be moulded into any required shape. It can be vulcanized, like caoutchouc, and is then proof against elevation of temperature. It is employed as a substitute for caoutchouc where great elasticity is not required. Both of the above substances approach more nearly in their composition to the essential oils, than to any other class of compounds. PROTEIN BODIES PUTREFACTION". Stated com- 974 ' VEGETABLE FIBRIN. The glutin- position and ous mass which remains when dough is properties of . . vegetable kneaded in water until all the starch is fibnn. removed, is called gluten or vegetable fibrin. It diners from all the organic matter hitherto described, in containing nitrogen, with small quantities VEGETABLE ALBUMEN. 389 of sulphur, and phosphorus. Its exact composition is given in the Appendix. It is a grey substance, and is the material which gives its cohesion to bread. 975. VEGETABLE ALBUMEN AND CASEIN. What is said . -i r. of vegetable Vegetable albumen is a similar substance, contained, ni smaller quantity, in the juices of fruits and vegetables. It is coagulated by heat, like the white of egg, when the juices are boiled. Vegetable casein is another substance of very similar composition and properties, found principally in the seeds of leguminous plants. It precipitates like the curd in sour milk, when a little acid is added to an aqueous extract of the seeds. These substances derive their names from their resemblance to animal fibrin, albumen, and casein. Vegetable casein is also called legumine. All of these substances were at one time supposed to be compounds of a single substance, called protein, itself free from both sulphur and phos- phorus. Later experimenters have not succeeded in isolating such a substance, and the theory is therefore abandoned. The name is retained in this work as a convenient designation of the class of substances here considered. 976. OCCURRENCE. One or more of Where are the above subxtan- these substances is present in greater or cesfuund? legs quant i t y in a u parts o f p i ants . They are found accumulated with starch, in the fruit and seed. The seeds of cereals, such as wheat and rye, and those of leguminous plants, such as peas and beans, contain them in large proportion. 390 ORGANIC CHEMISTRY. , r , 977. CHARACTERISTICS. If a bit of Mention a pe- culiarity of gluten be placed on the end of a wire and burned, a very different odor is produced pounds. from that of burning starch or wood. The smell approaches that of burning wool, and is a means of distinguishing organic matter which contains nitrogen. If boiled with potassa, the sulphur of gluten is extracted, and the solution will blacken paper moist- ened with sugar of lead. This reaction furnishes an- other means of detecting nitrogenous substances. 978. PUTREFACTION. A still more im- Describethe . *.'. i_ process of pu- portant distinction of nitrogenous substan- trefaction. ceg f rom those which contain no nitrogen, is their spontaneous putrefaction. Left to themselves, they are resolved, like blood and flesh to which they are allied in composition, into a variety of other pro- ducts. It is not strictly correct to say that this decom- position is spontaneous. The substance must first have been exposed to the air. An oxidation or slow combustion is then commenced, which, although en- tirely imperceptible in its effects, and checked at once by exclusion of air, ensures the subsequent putrefac- tion. It burns out a small portion of carbon and hy- drogen, and thus removes, as it were, the key-stone of the arch in every molecule. The atoms may then be supposed to fall together and re-arrange themselves as is required by the known products of their decompo- sition. 979. PRODUCTS OF PUTREFACTION. The Mention some ^. 'L- % > ' r products of re-arrangement which occurs m putrefac- ef action. cons i stSj essentially, in the combustion FERMENTATION. 391 of the carbon of the substance with oxygen, while the hydrogen divides itself between the nitrogen, phospho- rus, and sulphur, forming ammonia, phosphuretted and sulphuretted hydrogen. It is to these gases that the offensive smell which is given off in putrefaction is principally to be ascribed. 980. FERMENTATION. Any one of the What substan- . , ce* are capable nitrogenous substances above mentioned, of producing hi j undergoing the change which is jermentation ? D called putrefaction, is capable, by its mere presence, of acting as a ferment. A little putrefying gluten, for example, added to a solution of sugar, will convert it into alcohol and carbonic acid. Here again the key-stone of the molecule is removed, or rather in this case moved. The motion of the atoms of the putrefying substance would seem to be the cause. The effect is analogous to that of heat, through whose agency, also, complex organic bodies are resolved into others of simpler constitution. 981. YEAST. The first stage in the What is the first stage in formation of yeast is the production of a the process? microscopic vegetation, which consumes all the protein, converting it in.to the substance of a microscopic plant. Ordinary brewers' yeast is such a mi- croscopic vegetation. Being produced, it passes imme- diately into the putrefaction above described, effecting, at the same time, the conversion of any sugar which may be present into alcohol and carbonic acid. By some, the growth of the microscopic plant itself, instead of its subsequent change, is supposed to be the cause of fermentation. 392 ORGANIC CHEMISTRY. Holds yeast 98 2. PRODUCTION OF YEAST. - Yeast has produced? no t on jy fa e p Ower o f converting sugar into alcohol, but it at the same time occasions the production of more yeast from dissolved protein. In the ordinary process of beer brewing, the newly formed yeast collects on the surface of the fermenting vats. It is thence removed, to serve as the excitant of a new fermentation, or to be employed in the production of bread, which is, chemically considered, an analogous process. 983. DIFFERENT KINDS OF FERMENTA- Mention seve- ral kinds of TioN. The products of fermentation are fermentation. Different, according to temperature and other circumstances. Thus the same sugar which at 40, to 86, with cheese used as a ferment, yields car- bonic acid and alcohol, at a temperature of 86, to 95 is converted into lactic acid. The latter, by the further action of the curd, with slight elevation of tempera- ture, is converted into butyric and carbonic acids. By the same ferment, at a still higher temperature, a portion of gum is produced with the lactic acid. These diffe- rent processes of transformation have received, respec- tively, the names of the vinous, lactic, butyric, and viscous fermentations. The conversion of starch into sugar by diastase may be regarded as a species of fer- mentation. This substance is a slightly changed glu- ten. It is always produced in germination, and may be precipitated by alcohol in the form of white flakes, from a concentrated infusion of malt. One part of it is sufficient to convert two thousand parts of starch into sugar. BREAD. 393 What is said 984 FLOUR. Fine flour makes less of the nutri- nutritious bread than the coarser varieties. tious proper- .!**>* ties of fine because it contains a smaller proportion of gluten. Gluten being tougher than the starch, is not reduced to so fine a powder, and is par- tially separated in the process of bolting. All grains contain sugar in small proportion. Sugar is therefore one of the constituents of flour. Whatchemi- ^85. BREAD. The " raising" of bread cat principles i s a process of fermentation. The yeast are involved in making employed in the process converts a portion of the starch of the flour into sugar, and subsequently into alcohol and carbonic acid. The sponge is made light and porous, by the gas bubbles which become entangled within it. A large part of the alcohol produced in the process escapes into the oven, and thence into the exterior air. It may be condensed and converted into spirits by the proper apparatus. This has been successfully done in large bakeries in Europe, but the process has not been found to be of any considerable economical importance. In the process of baking a portion of starch is converted into gum. By moistening the baked loaf with water the gum is dissolved, and by a new heating, hardens into the shining surface which is often observed on bakers' bread. What materi- 986 - YEAST POWDERS. The gas which ais are some- i s needed to make bread lia:ht, may be times substi- tuted for produced by other means than the process yeast / of fermentation. If carbonate of soda, for example, is kneaded into the dough, and tartaric acid 17* 394 ORGANIC CHEMISTRY. subsequently added in proper proportion, the weaker carbonic acid is expelled. A light sponge is produced by its escape, without the loss of the starch and sugar which are consumed in the process of fermentation. Soda and tartaric acid prepared for this purpose are known under the name of yeast powders. Carbonate of ammonia being entirely volatile by heat, may be employed alone for the same purpose. A portion of the salt probably remains in the bread, and is more or less injurious, on account of its alkaline character. 987. TEST FOR YEAST POWDERS. The What is the . . f , objection to great objection to the use of these pow- *fa U inlfreadf ^ GYS * u the P re P aration f bread, consists in their liability to contain soda or acid in undue proportion. Whether this is the case, may be ascertained by dissolving the powders in water, and mixing the solutions. If the product is neutral to the taste and does not effervesce on the addition of either soda or acid, this fact will be evidence of their proper preparation. If otherwise, more or less injury is to be anticipated from their use. Excess of the al- kalies especially interferes with the process of diges- tion, by neutralizing the acids which accomplish it. The use of soda and saleratus with sour milk is liable to the same objections. What is said, ^88. THEIR EFFECT ON HEALTH. It Ihe^rfffe^'on ma ^ wel1 be tlie most dreadful of poisons, are are they so examples of the alkaloids. They are white crystalline bodies, but slightly solu- ble in water. Most of them, like the protein bodies above mentioned, contain the four organic elements ; but they differ widely from these substances, in possess- ing a positive chemical character. They are called alkaloids from their resemblance, in certain properties, to the alkalies of inorganic chemistry. Their action upon vegetable colors is the same ; like the alkalies, they also form salts with both organic and inorganic acids. They are, in fact, true alkalies. Their alkaline property does not, however, seem to depend on the oxygen which they contain. Some of them, indeed, do riot contain this element. It is highly probable that certain of the alkaloids belong to the class of compound ammonias mentioned in the first chapter of Organic Chemistry. What is their 990. Their action on the human body action on the does no t depend upon their alkaline char- human body ? Thdr anti- acter, but on other and peculiar properties ***' belonging to each. The salts of the alka- 396 ORGANIC CHEMISTRY. loids are generally preferred in medicine, in view of their ready solubility. In large doses they are all poisonous. The tincture of nut-galls is employed as an antidote, because of the property of the tannic acid which it contains, to form with most of the alkaloids insoluble precipitates. 991. OCCURRENCE. Morphine is con- Wfiat is the . r source of the tamed in opium, qmmne is extracted from alkaloids ? Peruvian bark, and strychnine, from the nux vomica. The latter is also the poison of the celebrated upas. Theine and nicotine are other alkaloids, the former of which is found in tea and coffee, and the latter in tobacco. Theine may be obtained, as a sublimate of silky crystals, by moderately heating tea in an iron pot covered with a paper cone. 992. PREPARATION. Most of the alka- How are the alkaloids ex- loids may be extracted from the material which contains them by means of acidu- lated water. A salt of the alkaloid is thus obtained in solution. From this salt the alkaloid may be precipi- tated, like oxide of iron or any other base, by. am- monia. Nicotine is a most energetic poison, falling scarcely below prussic acid in its destructive properties. COLORING MATTERS. What is said 993. INDIGO. The vegetable dye-stuffs of indigo? are extremely numerous. Indigo, madder, and logwood are among the more important. Indigo is deposited from the colorless juice of certain plants by simple exposure to the air. It may be sublimed in DYEING. 397 purple crystals, by rapid heating. By removing the oxygen absorbed in its production, the original color- less juice may be, as it were, reproduced from commer- cial indigo. This object is effected by the use of pro- tosulphate of iron, which is converted into sulphate of the peroxide in the process. Caustic lime is at the same time added to dissolve the deoxidized indigo. The colorless solution is employed in dyeing ; cloth im- pregnated with it becomes blue on exposure to the air. A solution of indigo in concentrated sulphuric acid is also employed in dyeing. Wh,at is mad- 994. MADDER. Madder is the ground der? roo t O f t^ rulia tinctoriutn. This plant is cultivated extensively in India and Europe. It con- tains a red dye, produced by the action of the 'air or certain chemical agents, upon the juices of the recent plant. This body is called alizarine, and may be ob- tained in beautiful crystals. An infusion of the root in hot water contains a portion of this substance in solution. What is log- 995. LOGWOOD. This is a red wood, wood? obtained from Spanish America and much employed in dyeing. Its coloring matter is called he- matoxyline. By evaporating a decoction of the wood and re-dissolving in alcohol, this substance may be ob- tained, on a second evaporation, in the form of yellow crystals. DYEING. 996. DYEING. Few dves can be per- Explain the * theory of dye- manently imparted to cloth without the in- ing fast colors. tervention Q f some third su bstance, which 398 ORGANIC CHEMISTRY. shall, as it were, hold them together. Such a substance, with strong affinity for the coloring matter of the dye, and also for the fibre of the cloth, is called a mor- dant. The fabric to be dyed being first impregnated with the mordant, is then introduced into the dyer's vat to receive its permanent color. What is said 997. MORDANTS. Alumina and oxide of of mordants? j ron are fa e p r i nc ip a i mordants employed. They may be " fixed " in the cloth by immersion in the acetates of these oxides. A subsequent exposure for several days to the air is essential, in order that the acetic acid may in part be expelled. A portion of it, however, remains, so that the oxides are, strictly speak- ing, in the condition of basic acetates. After this ex- posure, and subsequent washing in hot water, the fabric may be immersed in the dye. An ounce of madder heated with a pint of water will be sufficient for an experiment. The fabric is to be boiled for an hour or more with the unstrained decoction. 998. PREPARATION OF THE MORDANT. How is the alu- . minous mor- The solution of acetate of alumina is most conveniently prepared from alum, by the substitution of acetic for its sulphuric acid. This is accomplished by the addition of acetate of lead. Sulphate of lead is at the same time precipi- tated, and may be filtered off from the acetate which is formed. Three pounds of alum and two of sugar of lead, to three gallons of water, are the proportions to be employed. This mordant produces a red color. How are vari- 999. VARIOUS COLORS BY THE SAME ous colors pro- DYE g y fa Q use o f different mordants. ducedfrom one dye? various colors may be produced from the MINERAL DYES. 399 same dye. Substitute four pounds of green vitriol for the alum used in. the previous case, and the madder gives a deep black. Add four ounces of arsenic with the green vitriol, and a mordant is produced with which the dye will yield a beautiful purple. In the latter case, the solution must be reduced to one-tenth of its original strength by the addition of water. 1000. DYEING WITH LOGWOOD. By the briefly the pro- employment of the last two mordants, with lo d wood 9 ? m i xe d m equal proportions and diluted with an equal quantity of water, a mordant for dyeing black with logwood is obtained. For dyeing purple with the same material, a tin mordant is used. It may be prepared by dissolving tin in muriatic acid, with the gradual addition of nitric acid, then precipi- tating and re-dissolving with potassa. The cloth being impregnated with this mordant and thoroughly dried, is passed through dilute sulphuric acid, to remove the potassa and leave the oxide of tin. After subsequent drying and exposure to the air, the fabric is ready for the dye. What are 1001. MINERAL DYES. The dyes de- minerai dyes? scr i De d in the following paragraphs, are distinguished from those before mentioned, by contain- ing no organic matter. They consist of colored salts or oxides, precipitated in the fibre of the cloth. Although these substances belong, strictly speaking, to inorganic chemistry, they are here introduced to complete the survey of the subject of dyeing and calico printing. 1002. PRUSSIAN BLUE. A mineral blue How is a min- eral blue ob- may be produced by impregnating cloth tamed? ^^ ^ so i ut i on o f ace tate of iron, before 400 ORGANIC CHEMISTRY. described as a mordant, and then immersing it in an acidified solution of prussiate of potash. Prussian blue is thus precipitated in the cloth. This blue is found to be brightened by passing it through a solution of sugar of lead. 1003. MINERAL GREEN. A mineral green How is a min- .*-.., eraigreenpro- is produced in the same manner by the em- duced? ployment of sesquichloride of chromium, and subsequent immersion in potassa. The color con- sists of sesquioxide of chromium, precipitated from the chromium salt by the action of the alkali. The so- lution of sesquioxide of chromium is prepared by the addition of sugar to a solution of bichromate of potassa in dilute sulphuric acid. A part of the oxygen of the chromic acid being abstracted by the organic matter, it is converted into an oxide, which remains in solution. 1004. CHROME YELLOW. To produce a How is a min- . . eral yellow mineral yellow, the cloth may be impreg- produced? nated with acetate or nitrate of lead, then dried and passed through sulphate of soda, to fix the lead as sulphate in the cloth. On finally immersing it in bichromate of potassa, the cloth becomes dyed with yellow chromate of lead. The above process modified by printing instead of saturating with acetate of lead, gives yellow figures on a white ground. CALICO PRINTING. How is a white 1005. WHITE FIGURES. If it is desired ^oods ro dyed t0 obtain a desi g n in white, on goods dyed duced? with either of the above madder colors, CALICO PRINTING. 401 HXY the design is printed with a paste of tartaric acid upon the colored cloth. On subsequently immersing the goods in a bath of chloride of lime, chlorine is evolved in the tissue, and the color discharged only where the acid is printed. The white thus produced is of course in exact cor- respondence with the printed design. Howareyellow 1006 - PANTED YELLOW AND BLUE. To and blue de- produce yellows on madder red and purple signs obtained ' on dyed grounds, before described, tartaric acid is grounds t printed with the nitrate of lead, and the cloth immersed in bleaching liquid. The color of the printed portions is discharged by the combined action of the acid and bleaching liquor ; the lead is at the same time fixed in the cloth, as chloride of lead. On subsequent immersion in bichromate of potassa, the yellow figures of ehromate of lead are produced as be- fore. For blues on the same colored grounds, a mix- ture of Prussian blue, dissolved in bichloride of tin, with tartaric acid, is printed on the cloth. The dis- charge of the ground color beneath the figure, is effected, as before, by chloride of lime. 1007. VARIEGATED PATTERNS. All of How are varie- ._ gated patterns the madder colors which have been men- produccd ? tioned, may be produced upon a single piece of white goods, by printing the different figures of the pattern with different mordants. This is accomplished by passing the fabric between different sets of rollers, each of which is supplied with a paste of the proper mordant, and so engraved that it yields the desired im- 402 ORGANIC CHEMISTRY. pression. On subsequently introducing the goods into the madder bath, the various colors are developed. The whole piece is at the same time transiently colored ; but the dye may be readily removed from the imprinted portion by thorough washing. A white ground for the colors is thus obtained. RELATION OF PLANTS TO THE SOIL. AGRICULTURAL CHEMISTRY. 1008. The mineral substances which What mineral , , _, . ,. . ., , , substances do plants obtain from the soil, are known by plants obtain ana iy s i s o f the ashes which they yield on from the soil ? J J combustion. They consist of acids and bases, which enter into the composition of all fertile soils. The bases are potassa, lime, magnesia, and oxides of manganese and iron. These are found com- bined in the ashes with silicic, sulphuric and phosphoric acids, and are accompanied by small proportions of common salt. The carbonic acid which is found in certain ashes is produced in the combustion of the plant. The ashes of all cultivated plants contain the above substances ; but in different proportions accord- ing to the nature of the plant. The phosphates pre- dominate in grains ; lime exists in large proportion in grasses ; potash in edible roots ; and silica in straw. The approximate composition of the ash of different plants is given in a table in the Appendix. In estimating the relative proportions of the different constituents which are abstracted from the soil by different crops, the quan- tity of the crop, as well as the composition of its ash, is of course to be brought into this account. CONSTITUENTS OF SOILS. 403 1009. COMPOSITION OF SOILS. Many of Of what are J soils com- the above substances are contained in the pose ' soil in extremely small proportion. Soils are principally composed of vegetable matter in a state of decay, with clay, sand, and carbonate of lime. The vegetable matter consists of the remains of plants of previous years, and the clay, lime, and sand, are the product of the gradual crumbling and decomposition of rocky crust of the earth. 1010. USE OF VEGETABLE MATTER IN State the uses of vegetable SOILS. The wood, leaves, and twigs of oih T m which vegetable matter is composed, fur- nish, in their gradual decay, the potash, silica, and other constituents of their own skeletons to form the framework of new plants. The organic mat- ter is, at the same time, converted into ammonia and carbonic acid ; these constitute the gaseous food on which all vegetable life is sustained. 1011. ADDITION OF VEGETABLE AND ANI- K$Zd -AL MATTER._The addition of more of by the addi- this material to the soil, in the form of peat tion of vegeta- - / bh and animal or muck from swamps, is of great advan- ta S e ? because it increases the supply of the two important classes of materials which have been mentioned. Animal matter of all kinds, whether decomposed, as in stable manure and guano, or in its original condition in the form of flesh, wool, and bones, is a still more valuable addition to the soil. The reason of its higher value, consists in the fact that while it yields most of the other substances which decaying vegetable matter supplies, it furnishes ammo- 404 ORGANIC CHEMISTRY. nia, which is the rarest and most expensive one, in much larger proportion. 1012. USE OF THE CLAY. The clay in What purpose . does day sub- soils serves to retain the ammonia and e certam otner valuable materials, which would, otherwise, be washed away by descending rains. It seizes not only upon that which comes from the decaying humus, but finds particles in the drops of every shower, which it stores safely away for the future use of the plant. It serves also to retain moisture in the soil, and to impart to it the tenacity by which the roots are enabled to gain a firm hold upon the earth. Soils which contain but a small proportion of clay are for these reasons improved by its addition. 1013. USES OF THE SAND. Sand, where What is the office of sand it exists in due proportion, gives the proper tn wist degree of porosity to the soil, and thus ensures the entrance of the air and fertilizing liquids, and the draining away of all excess of water. Access of air is important, because it brings with it fertilizing ammonia and carbonic acid, and by accelerating the decay of vegetable matter, produces more of these valuable substances. 1014. USES OF THE LIME. The lime in What is the -, . , , -, -, office of lime soils, beside serving directly as building on the soil? mater ial for all forms of vegetation, is the key which unlocks other treasures of the soil and sup- plies them, also, to the growing plant. The building material which is furnished, as before explained, by the decay of previous plants, is not sufficient. A por- tion of it never reaches the fields from which it was ACTION OF LIME. 405 originally derived. Exported in the form of grain, or milk, or beef, it returns to the soil in some distant re- gion or is poured into the rivers and the sea through the drains of populous cities. New supplies of potash and other material, are, therefore, demanded by the vegetation of every successive year. 1015. A large part of the materials re- How docs it . accomplish the ferred to are locked up in hard grains of object ? granite, or other silicates which are found in the soils. Being insoluble in water and the other solvents of the soil, they are inaccessible to the plant. Lime has the property of forcing itself into the rocky prison of every such insoluble grain, and setting part of its inmates at liberty. At the same time it opens the door to the action of other agencies which liberate the rest. They are then floated away in the water which penetrates the soil, and being in due season ab- sorbed, are built into the substance of the plant. 1016. ACTION OF LIME ON MINERAL MATTER Give the chem- ......,, , ... . ical explana- EXPLAINED. The actlOll of lime, Which tfon US a ~ nas J ust b een mentioned, is a simple conse- quence of its basic properties. It takes possession of part of the silicic acid of the alkaline silicate in the rocky grains. Their potassa and soda being now combined with this acid in small proportion, are soluble in the water which penetrates the soil. 10 17. The water of the soil always con- What other . . /--. j decomposing tains a certain proportion 01 carbonic acid. a s % s t / xist ' sin This acid being itself material for vege- table nutrition, has also the property of dissolving those mineral substances which the plant --P 406 ORGANIC CHEMISTRY. needs for its support. By the joint action of carbonic acid and water, this transfer is constantly going on even without the aid of lime. But the latter substance very much accelerates the action, arid thus adds greatly to the fertility of the soil. 1018. ACTION OF LIME ON ORGANIC MAT- Mention an- . . other use of TER. Lime has another important enect l soil nihe on so ^ s ' m hastening the decomposition of their organic matter, and thus, indi- rectly, supplying in large quantity, valuable materials, before mentioned, which these are adapted to furnish. As this decomposition proceeds in the presence of lime, part of the nitrogen of the organic matter takes the form of ammonia, and part is converted into nitrates, as will be remembered from the chapter on Salts. But the proportion of either is practically immaterial, as both are found to subserve a similar purpose in building up the plant. 1019. All of the effects which have * been mentioned, may be regarded as grad- tioned effects ually produced in every soil which contains increased ? Mention an- carbonate of lime as a constituent. When it; is deficient in quantity, they are, of course, increased by its addition in the form of chalk or marl, or limestone. These substances have also the effect of sweetening peaty and marshy soils, which are rendered sour from the presence of too large a proportion of vegetable matter, and thus ren- dering them fit for cultivation. 1020. BURNED LIME. Burned or caustic In what form has lime the lime has all these effects in a much greater degree, and therefore its extensive use as a fertilizer of the soil. It should be used GUANO. 407 cautiously on soils which contain but a small propor- tion of vegetable matter, for fear that in the more rapid decomposition which it stimulates, it may entirely exhaust the soil of this material. If employed in such cases it should be with admixture of vegetable matter, that the loss which it occasions may be completely replaced. 1021. EFFECT OF ASHES ON SOILS. What other _ . . substances act Potassa or soda applied in the caustic state, similarly? Qr ag car b ona t es have entirely analogous What caution is to be observ- effects on the soil. They render the in- edin their use? , , , .' soluble silicates soluble, by increasing in them the proportion of base, and also hasten the decay and conversion of vegetable matter. The admixture of lime or ashes with guano or decomposed manure, is to be avoided, because of their effect to expel the ammonia which these substances contain. This may be avoided by previously incorporating the material with a large proportion of clay or vegetable mould, which shall serve as an absorbent of the liberated gas. What is said 1022. COMPOSTS. CompOStS COllsist of of composts? vegetable and other matter, heaped to- gether for fermentation and partial decay, in order to prepare them for application to the soil. In such mix- tures, all alkaline materials, including lime, have an effect similar to that which they produce upon the organic matter of the soil. Whatisgua- 1023. GUANO. Guano consists of the no? accumulated droppings of birds, and is principally obtained from certain rocky islands on the 408 ORGANIC CHEMISTRY. coast of South America. In these haunts of the heron flamandj and other sea-fowl, it is accumulated, in some instances, to the depth of a hundred feet. The de- posit is usually in smaller quantity, but amounts in the aggregate to millions of tons. The material was em- ployed as a fertilizer by the natives of Peru and Chili, long before its introduction into England or the United States for the same purpose. 1024. DIFFERENT VARiETiES.-The qual- Whatiisaid ... ... of different ity of guano differs materially, according to tlie source fr m which it is derived. The ammoniacal salts, on which its agency as a fertilizer principally depends, being soluble in water, the product of moist climates is of comparatively little value. The best is obtained from the coast of Peru, where rain seldom or never falls. The African, Patagonian and other varieties, are much inferior. In what does 1025 ' AGRICULTURAL VALUE. The ag- theagricui- ricultural value of guano lies principally tural value . . of guana m the ammonia and phosphate of lime depend? which it is capable of yielding to plants. These constitute, in the best varieties, about one-third of the whole weight. Part of the ammonia is ready formed, and part is produced in the subsequent change which the nitrogenous matter of the guano experiences in the soil. The latter may be produced immediately by a chemical process, and its quantity accurately determined. In estimating the value of guano, it is customary to record the quantity of this potential am- monia, as if it were an existing constituent. SOILS. 409 What is said 1026. ARTIFICIAL AMMONIA. The COI1- of the artifi- stituents of the ammonia which we pur- cial produc- .. ~ tionofammo- chase, in the form of guano, at so great expense and bring from distant regions of the earth, exist in unbounded quantity at our very doors. Four-fifths of the atmosphere are nitrogen gas, and the ocean is an exhaustless reservoir of hydrogen. But, strange to say, the chemist with all his skill, cannot, except by circuitous and expensive methods, effect their combination. The discovery of some cheap and ready means of accomplishing this object, would transform the face of the earth, by the unlimited quan- tity of fertilizing material which it would supply. This result may, perhaps, be reached by patient investiga- tion. But no sudden triumph over nature need be anticipated. Improvements in Agriculture will, as a general thing, be only realized by the earnest co-opera- tion of scientific and practical men, in laborious and oft-repeated experiment. 1027. EXHAUSTION OF SOILS. When What is said i * , of the exhaus- soils become exhausted 01 those substances tion of soils? which form the mineral food of plants, the growth of vegetation ceases. It is never absolute, but consists in a great reduction of that portion of their material which is in a condition to be appropri- ated by the growing plant. Such soils are gradually restored by rest. A gradual decomposition of their insoluble material occurs by means of agencies which have before been mentioned, and the soil is thus re- stored to its original condition. These effects are very much hastened by plowing in such a growth as can 18 410 ORGANIC CHEMISTRY. be obtained. Rye, buckwheat, and clover are among the plants best adapted to the purpose. Vegetable mat- ter is thus added to the soil, which, in its decay, hastens the decomposition of the soil itself. What is said 1028. DEFICIENCY OF ONE OR MORE CON- of defitien- sTiTUENTs. The comparative exhaustion ties in partic- ular constitu- of some one or more of the constituents of the soil, is a much more frequent oc- currence. It is commonly the result of the cultiva- tion of the same crop during many successive seasons, and the consequent reduction of those materials which the particular plant requires in largest proportion. De- terioration of soils from this cause, is repaired by an artificial supply of the failing ingredients. It is more wisely guarded against by such a rotation of crops as shall make different demands upon the soil in succes- sive years. What is said 1029. MAINTENANCE OF FERTILITY. - f the e / ect f The effect of decomposing animal matters decomposing animal matter on the soil, has been already considered. the soil ? return the very material which was abstracted from the soil, with the addition of nitro- genous matter, originally derived from the air by the growing plant. In an enlightened system of rural economy, the production of these materials in large quantity and their careful preservation, is therefore an object of paramount importance. The addition of gypsum or dilute sulphuric acid to fermenting ma- nures, is of great advantage in retaining their ammonia in the form of sulphate, and preventing its escape into the air. When additional ammonia is required, it is 411 most cheaply obtained in the form of guano. The phosphates, whose quantity may be often increased with advantage, are best supplied in the form of " super- phosphate of lime." Other materials are less frequently required. For further information on the subject of the present section, the student is referred to works which treat especially of Agricultural Chemistry. 1030. " SUPERPHOSPHATE OF LIME." What is said of superphos- 1 he method employed in the manufacture phateofiime? of supe rphosphate of lime," has been al- ready given in the chapter on Salts. As in the case of guano, its agricultural value depends on actual or potential ammonia, and phosphate of lime. In propor- tion as the phosphoric acid is in a soluble form, the value is much increased. Additional information on this subject is given in the Appendix. ANIMAL NUTRITION. 41.3 .'. --^-. ,.-!-, ..'. CHAPTER III. ANIMAL CHEMISTRY. ANIMAL NUTRITION. 1031. RELATIONS OF ANIMAL AND VEGE- How is the life of am- TABLE LIFE. The life of animals is sus- mah sustain. tained by the consumption of material compounded and prepared by the plant, and converted into its own substance, out of the mate- rials of the earth and air. This is virtually true even of the carniverous species, for the animals on which they feed have derived their support from the vege- table world. When they yield their own flesh as food, it is only a changed vegetable matter which they thus supply. All animal matter may therefore be regarded as vegetable matter, more or less modified, or entirely transformed by the processes of the animal body. 1032. FORMATION OF BLOOD. The blood tion of the material required for animal growth is blood? - , . * . mi V floated to its destination. This complex fluid will therefore first engage our attention. The food having been ground up by the teeth, and moist- ened by the saliva, is conveyed to the stomach, and 414 ORGANIC CHEMISTRY. submitted to the action of the gastric juice. Here it is converted into a uniform greyish semi-fluid mass, called chyme. The chyme is pushed forward by sponta- neous contraction of the stomach. It yields its nutri- tious matter, in the form of a milky liquid called chyle, to minute absorbent vessels, distributed upon the surface of the intestines. Through these absorb- ent vessels it passes into the general circulation, and is converted into blood. What are the 1033. TRANSFORMATION OF THE FOOD. offices of the The transformation of the nutritious por- qastricand . ,, . . . , T . ~, 1 pancreatic tion of the chyme into chyle, is effected, juices? j n p artj j^ the g as t r i c juice, and in part by the secretion of the pancreas. The latter organ lies back of the right end of the stomach, and pours its secretions into the duodenum, or first of the small in- testines. The gastric juice dissolves the protein com- pounds of the food, while the secretion of the pan- creas transforms the sugar and starch of the food into grape sugar. The chyle is thus perfected, and pre- pared to be drawn off from the refuse portions of the food. As sugar forms no part of healthy blood, we must suppose that it undergoes immediate transforma- tion with fat or other material, as soon as it enters the circulation. The office of the bile which is secreted by the liver, and poured into the intestines, is not tho- roughly understood. 1034. THE GASTRIC JUICE. The saliva To what is the ..... ..... -11 * * solvent agency which is mingled with the loocl in masti- of the gastric cat i on has an effect similar to that of the juice due ? secretion of the pancreas. Another of its THE BLOOD. 415 probable agencies is to introduce air into the stomach, to act upon its lining membrane and produce from it one of the constituents of the gastric juice. The solvent agency of this fluid is in part owing to the ferment thus formed, and in part to the free acids which it con- tains in solution. The latter are phosphoric, hydro- chloric, butyric, and lactic acids, in part free, and partly in the form of salts. 1035. COMPOSITION OF THE BLOOD. Give the com- position of the If fresh blood is beaten with a branched blood ' stick, it is separated into a slightly alka- line liquid, called the serum, a fibrous material called fibrine, and red globules, which sink, after a time, to the bottom of the vessel. The fibrine adheres in threads to the stick with which the operation is performed. It is analogous, in composition and properties, to the vege- table gluten from which it is formed. The serum con- tains albumen, and resembles the white of egg. The globules are also principally albumen, with a small proportion of a red coloring matter called hematosine. Albumen and fibrine both contain phosphate of lime or bone earth. The serum contains, also, certain salts, and a small proportion of fat. All of these substances together form but about one-fifth of the blood ; the remaining four-fifths are water. When blood is left to stand, after being drawn from the body, the fibrine coag- ulates spontaneously, entangling and taking with it the red globules, and thus separating them from the serum. 1036. ANIMAL NUTRITION. It is evident What niateri- /. , -, . 1,1 -u ah arc. found irom the preceding paragraph that much ready formed O f the mater j a i required to build up the in the blood ? r body, is found ready formed in the blood. 416 ORGANIC CHEMISTRY. It has been transferred to it from the vegetable world without material change in composition. Thus the fibre which is required for muscle and fat to fill out the tissues, require only to be built into their places in the animal frame, as a mason lays up a wall from materials provided to his hand. For the production of other animal substances, essential changes are required. The power of selection and appropriation of the proper ma- terials for every organ and every secretion, is found to reside in innumerable minute cells, which are distributed in every part of the body, and are endowed with pecu- liar powers, according to the offices they are designed to fulfill. BONES, FLESH, &c. 1037. BONES. Bones consist of earthy What is the J composition of matter, and a cartilagenous material com- itThLnr iS monl y known a s gelatine. The bone earth, or mineral matter, is principally phosphate of lime, arid forms in mammiferous animals about two-thirds of the whole weight. The remaining third is cartilage. Either of these constituents may be removed from the bone without effecting its shape. By removal of the cartilage, a brittle, earthy frame- work remains. By removal of the earthy material, a perfectly flexible mass is obtained, of a form entirely similar to that of the original bone. The first change may be effected by long digestion in dilute muriatic acid, and the latter by fire. If in the second process the car- tilaginous matter is not entirely consumed, bone black FLESH. 417 or animal charcoal is produced, the uses of which have been already described. Of what does 1038. FLESH. Lean flesh or animal flesh consist ? muscle is composed of fibrine, penetrated by a liquid which forms four-fifths of the whole, and is called flesh fluid, or juice of the flesh. It contains a peculiar organic acid, possessing the flavor of broth, crystalline substances called creatine and creatinine, and certain salts. Being extracted by cold water and then heated, it forms a nourishing and highly flavored soup. Hot water coagulates its albumen, and prevents its escape from the flesh. Gradual heating is on this ground to be recommended in the preparation of soups, while sudden exposure to a high temperature, both in boiling and roasting, yield more nutritious and highly flavored meats. The salts of potash prevail in the flesh fluid, while those of soda are more abundant in the blood. Unlike the blood, this fluid is acid in its re- action. 1039. SKIN, TENDONS, LIGAMENTS. The What is said of tendons and cartilaginous material above mentioned as ligaments ? a const j tuent o f bones, is transformed by boiling water, without change of composition, into gelatine or glue. The skin, cellular membrane, tendons and ligaments of the body undergo the same change, and yield the same product. Gelatine may even be prepared from refuse leather, by first extracting the tannin, and thus reducing it to the condition of the original hide. The tannin obtained in the process may also be em- ployed for tanning new hides. Hoofs, hair, horn, and feathers, although very similar substances, are not thus affected by boiling. 18* 418 ORGANIC CHEMISTY. Wliat isgela- 1040. GELATINE. Gelatine is soluble in tine? water, and yields a stiff jelly on cooling from a hot solution. On this property is based its use in the preparation of jellies for the table. The com- mercial article employed for this purpose and ordinary glue are essentially the same. 1041. The substance known as isin- Crive the com- 7 ., -I--I--II-IT < position and glass, is the dried air bladder of a species ^ stur o eon 5 au & forms m its natural con- dition, a soluble gelatine. Gelatine contains the four principal organic elements ; nitrogen and oxy- gen being in somewhat larger proportion than in the protein bodies. Hoofs, hair, and the other substances above mentioned, contain sulphur in addition. Gelatine is susceptible, like the protein bodies, of putrefaction, and also of exciting fermentation. As starch is changed into sugar by the action of dilute sulphuric acid, so by the action of oil of vitriol, gelatine may be converted into a sweet crystalline substance, called glycocoll or sugar of gelatine. 1042. HIDES, TANNING. A solution of What chemical combination gelatin forms, with tannin or tanmc acid, tan ~ a tenacious insoluble precipitate. The tanning of leather depends on the forma- tion of this insoluble compound in the hides which are submitted to the process. They are im- mersed for this purpose in an infusion of oak and hemlock bark, until the combination has taken place throughout the whole thickness. They are thus secured against putrefaction and converted into firm, elastic leather. Hides may FATS. 419 also be preserved by soaking them in alum and after- ward in oil. Soft chamois' leather is prepared by working the skin with fat alone. FATS. 1043. COMPOSITION. We have already What is said * of the consti- seen that there are both acids and bases of tutton of fats? p ure iy organic origin, and that these may combine like the similar compounds of inorganic chem- istry, to form salts. The animal fats and oils are mix- tures of such compounds in different proportions. The principal of these organic salts are stearine, margarine, and oleine. Stearine is solid, oleine fluid, and marga- rine occupies a middle position between the two. The difference of consistence in butter, lard, and tallow, is owing to varied proportions of these three substances which enter into their composition. Beside the fats contained in other parts of the body, the brain and nerves of animals contain, with albumen and water, certain peculiar acids and fats. 1044. SEPARATION OF FATS IN OIL. How may the . IT- / constituents of The steariiie and oleine of whale oil sep- rated? Cpa ' arate spontaneously in cold weather. The cold which i sufficient to harden the for- mer, leaves the latter in a fluid condition. This effect is often observed in lamps during winter weather. The case is quite analogous to the separation of cider into alcohol and water, by freezing. The water congeals, and leaves the alcohol fluid. Both separations are im- perfect. As the alcohol produced by the above process 420 ORGANIC CHEMISTRY. is diluted to a large extent with water, so the oleine retains a considerable portion of stearine in solution. 1045. SEPARATION OF FATS IN TALLOW How may the . . , . , f . , different fats AND LARD. Stearuie is obtained from lard and tallow on a similar principle. It har- dens on partially cooling the melted fat, forming a mass from which the fluid oleine may be sep- arated by pressure. Stearine thus obtained is used in the manufacture of candles, while the oleine forms lard or tallow oil. The former has, of late years, given place to stearic acid, procured from the same sources, by means to be hereafter described. Margarine may be separated from butter by similar heating and slow cooling. It is regarded by some chemists as a simple mixture of stearine and oleine. and not a distinct sub- stance. 1046. GLYCERINE. Glycerine is the base cer'me? How of all the fatty salts which have been is it made? mentioned. It is a viscid, sweetish liquid containing the same elements as grape sugar, and in nearly the same proportion. On removing the stearic, and oleic acids from melted stearine, or oleine, it re- mains in the liquid form. This removal may be ef- fected by lime. The white lime compound floats upon the water which is used in the process while glycerine is dissolved. How is stearic 1047. STEARIC ACID. The compound acid made? formed by lime, as described in the last paragraph, if tallow has been used in the process, is a mixture of oleate and stcrate of lime. From these, stearic and oleic acids are liberated by the agency of SOAPS. 421 diluted oil of vitriol. The material floats on the dilute acid, gradually losing lime, and becoming transparent by its action. Sulphate of lime or gypsum is formed at the same time and sinks to the bottom of the vessel. The stearic and oleic acids are drawn off while yet warm, and run into cubical moulds. The latter is sub- sequently removed from the mixture by gentle heat and pressure. The remaining stearic acid is then re- melted and allowed to cool slowly. It is thus ob- tained in a brilliant white mass, of crystalline texture, with the lustre of mother of pearl. This material is principally employed in the manufacture of candles. Its superiority to stearine for this purpose, consists in the fact that it is less softened by heat. The two sub- stances differ in their melting point about ten degrees. 1048. SOAPS. Soaps are compounds of How are pot- . ' . ash and soda stearic and oleic acids with caustic potash ~ or soda '* The y are P roduced b y boiling fats with either of the alkalies, till the mixture becomes nearly or quite transparent. The glycerine which is expelled from the fats in the process, remains mixed with the soap which is produced. Pot- ash soaps are soft. Soda soaps may be converted into a floating coagulum, and separated from the water used in their preparation by means of common salt. This method is employed to give them their hardness. The action depends on the insolubility of the soap in salt water. Salt added to potash soap seems to have the * In the ordinary preparation for soap making, the lye is made to pass through lime in the leach tub, that its carbonic acid may be par- tially removed. 422 ORGANIC CHEMISTRY. same effect. But its action in this case is due to a double decomposition, in which a floating soda soap is formed, chloride of potassium remaining in solution. Soaps may be also made without the use of water, by combining oil or fat with melted potash. 1049. LINIMENTS, &c. Soaps are soluble How are trans- parent soaps in alcohol, forming the tincture of soap which is used for bruises. With the ad- dition of camphor, this tincture forms opo- deldoc. Transparency is imparted to soap by the evap- oration of an alcoholic solution of the well dried mate- rial. Liniments are soaps prepared from ammonia and oil by the simple agitation of the materials. 1050. PROPERTIES OF SOAPS. Soaps Explain the cleansing ac- which are prepared, as above seen, from tion of soap. ^ &nd ^ haye the property Q f dissol- ving more of the same material. On this property their cleansing effect principally depends. When they are dissolved, a portion of the alkali becomes free by the substitution of water as base. This free alkali adds to the cleansing effect, by its own affinity for the oils and other organic matter. Alkalies alone are not equally effectual ; they tend to shrink the fibre of cloth, and thus protect it against a perfect purification. The strength of the tissue is at the same time gradually im- paired. MILK, BUTTER, &c. 1051. MILK. Milk is analogous to What is the . T i , composition of blood in compositon, as is implied in the milk? office which it fulfills in the nutriment of 423 the young animal. But casein takes the place of the fibrin of the blood, and fat is also found in milk, in much larger proportion. This fluid also contains sugar ? which is peculiar in its character and has therefore received the name of sugar of milk. Butter is pro- duced by the coalescence of the small particles of oil which are suspended in milk, and partially separated in the cream. Chemically considered, it is a mixture of oleine and margarine. On partially cooling melted butter, the latter collects at the bottom of the liquid oleine, which forms the other constituent ; a portion at the same time remains in solution. Beside the above substance, butter contains phosphates and other salts, with certain neutral fats, from which it derives its flavor. 1052. CHEESE. On exposure to the air Why is the . . , curd separated for a considerable time, the sugar contained by exposure? ^ R m jjj . - g p art i a iiy converted in lactic acid, and the casein is precipitated. One reason of this pre- cipitation is to be found in the neutralization of the free alkali of the milk. The casein having thus lost its solvent, assumes the solid form. The coagulation of milk may also be effected by rennet, which con- sists of an infusion of the lining membrane of the stomach of the calf. Its mode of action is not well understood. 1053. SOLID MILK. Milk may be brought into the solid form by careful pared? evaporation, with a moderate heat. It must be constantly stirred during the process. A ma- chine has been recently patented which secures all of 424 ORGANIC CHEMISTRY. these objects. With the addition of a little soda and gum, milk may be thus kept sweet in the solid condition for many months. The addition of water is all that is necessary to reproduce it in its original form. CHEMICAL CHANGES IN THE ANIMAL BODY. 1054. Certain important changes which What is said of changes in are constantly occurring in the animal body ^animal remain to be considered. The body is not the same in any two successive mo- ments of its existence. Every breath exhales a por- tion of its substance into the atmosphere, and every effort, whether of brain or muscle, is accompanied by some transformation in the material of which it is composed. 1055. CHANGES IN THE BLOOD. By com- Mention cer- tain changes paring the blood of animals with their in the blood? foodj it win be evident that certain mate- rials have been not only modified, but entirely trans- formed in its production. Starch and sugar are impor- tant constituents of the food, but. they form no part of healthy blood. They are transformed into fat or other material as soon as they enter the circulation, and in this new form constitute the fuel from which the heat of the animal body is derived. Other changes which occur in the blood will be mentioned in subsecuient paragraphs. 1056. ANIMAL HEAT. The oxygen What is the source of an- which is necessary for the slow combustion imalheat? Q f ^ mater i a i aDove mentioned, is taken into the blood in the course of its passage through RESPIRATION. 425 the lungs. It passes on with them, through the ar- teries, into the minute capillary vessels which are distributed throughout the body. In these vessels their combination takes place, with the same produc- tion of carbonic acid and evolution of heat, as if the material were burnt in air or oxygen gas. The carbonic acid thus formed is carried back to the lungs in the venous blood, and there exhaled, through the thin membrane of the air cells, and exchanged for a new supply of oxygen gas. In view of the relations of starch and sugar to the process of respiration, as above shown, they have been termed the respiratory constituents of the food. 1057. RESPIRATION. In cold weather What is said . . further of res- a larger amount of oxygen is inhaled with piratwn ? every breath, in consequence of the greater density of the air. Respiration is also involuntarily hastened, and the blood, from the two causes combined, becomes more thoroughly impregnated with oxygen gas. The transformation or combustion of the respi- ratory constituents of the blood, proceeds more rap- idly in consequence, and more internal heat is pro- duced to oppose the external cold. This is one of the provisions of nature by which the animal body is ena- bled to resist the influence of the seasons and of cli- mate. Labor has the same effect as cold in hastening respiration and necessitating a larger supply of food. What change 1058. CHANGE IN COLOR OF THE BLOOD. of color does F rO m the fact that the globules of the the blood ex- perience in the blood undergo a change of color in the lun s s - lungs, where oxygen is absorbed, it is pre- sumed that they serve, by absorption of the gas, as the 426 ORGANIC CHEMISTRY. medium for its conveyance through the body. As a consequence of the changed color of the globules, arterial blood is of a bright scarlet, while venous blood is dark red. The same change of color which takes place in the lungs, may be readily produced by agitating blood drawn from the veins with air or ox- ygen gas. What is said 1059. RELATIONS OF FOOD AND TEM- of therein- PERATURE. In proportion as the draft of tions of food . . n . and tempera- & furnace is increased, more fuel must be tore? supplied for its combustion. For the same reason more respiratory food must be taken into the system, in proportion as more atmospheric oxygen is inhaled. The fact that a larger quantity is required in northern climates thus receives a scientific explanation. The preference entertained in arctic regions for cer- tain kinds of food, is also accounted for by the same necessity for increased resistance to the external cold. The train oil and fat which the Greenlander con- sumes with avidity, are a better fuel in the animal body than the starch which form a principal part of the food consumed in warmer climates. The chemical reason of this difference is found in the fact, that starch and allied substances contains oxygen in larger proportion. They are, as it were, in their natural con- dition, partially burned or oxidized substances. 1060. CHANGE OF THE ANIMAL TISSUES. What change takes place in In proportion to the muscular or nervous lhlbodyT f activity of the animal, the substance of the body is disorganized and returned to the blood from which it was produced. From the UREA. 427 blood it is finally removed by the kidneys, principally in the form of urea and uric acid, and thrown off as waste material from the system. These substances, although organic, may be figuratively regarded as the ashes of the consumed muscle and other nitrogenous constitu- ents of the body. A portion of the carbon and hy- drogen of the animal organs has at the same time dis- appeared, like the elements of respiratory food, in the form of water and carbonic acid. What is 1061. UREA. Urea, when " separated said of Urea ? f rO m its solution, is obtained as a white crystalline solid. Its molecule contains four atoms of hydrogen, to two each of carbon, nitrogen, and oxygen. When left in contact with the mucus with which it is accompanied in the secretion of the kidneys, it is speedily converted, by combination with four molecules of water, into carbonate of ammonia. Urea may also be artificially produced from cyanic acid arid ammonia. This cyanate is identical with urea in composition, and is converted into urea by solution in water and evaporation. It was among the first of organic bodies artificially produced. Uric acid con- tains the same elements with a larger proportion of oxygen, and also yields ammonia by its decomposition. Besides the above substances, the secretion of the kid- neys contains various soluble salts, which have formed part of the body. The insoluble salts are removed from the system by other means. 1062. DISAPPEARANCE OF FAT. STARVA- What is said of the disap- TioN. Vv hen the supply oi respiratory P nce f food is deficient, nature avails herself of the fat previously stored in the animal 428 ORGANIC CHEMISTRY. body, as fuel to sustain tjhe animal heat. It is taken up by the blood, and burned in the capillary vessels, as before described. This happens in the case of the bear and other hybernating animals. Lying dormant during the winter season, their fat is consumed, and they emerge lean from their dens in the spring. Where food is deficient and there is no accumulation of fat to supply its place, the muscle and other portions of the body are consumed, and death by starvation is the con- sequence. 1063. REPAIR OF THE TISSUES. As fast How are the tissues repair- as the worn out matter of the muscles and other organs is removed, its place is supplied in the healthy body by new material from the blood. Through it, also, the phosphates of the soil and the vegetable world are transferred to the skeleton of the animal, and in smaller proportion to other parts of the frame. The blood is itself renewed by the materials of the food. 1064. VARIETIES OF FOOD. It is implied Mention two classes of in the foregoing, that the two classes of f ood ' substances which enter into the compo- sition of the food of animals, subserve very diiferent purposes in the animal economy. The first class, of which starch and sugar are the principal, serve, by their gradual combustion, to sustain the animal heat. They are included, as above stated, under the general name of respiratory food. The protein bodies, on the other hand, all of which contain nitrogen, are appropriated in the formation of blood and muscle ; they make up the sanguineous or plastic food. In view of the fact FOOD. 429 that the respiratory food enters also, in a changed form, into the composition of the blood, the former term can scarcely be regarded- as distinctive. The latter, which designates the office of the protein bodies in furnishing material to build up the organs of the body, is much to be preferred. 1065. PROPORTIONS OF FOOD. For the What is said . ,,.,..,, of the import- economical sustenance of animals, it is of Proportion of i m Pr tance tnat a proper relation of quanti- thetwo kinds ty should be maintained between these two varieties of food. Respiratory food alone, provides no material for supplying the waste of the or- ganized tissues. Plastic food, on the other hand, is es- pecially adapted to this end, but is poor fuel for sus- taining the heat of the body. Yet in lack of other material, it is diverted from its natural use, and thus appropriated at great economical disadvantage. 1066. Nature teaches us something on What does na- ture teach on this subject, in the composition of milk this subject? am j tnose g ra i ns which constitute the principal food of man. It will be found by reference to the table in the Appendix, that the quantity of respiratory matter in these substances, is from three to six times greater than that of the plastic material. When the object is to fatten an animal, the proportion of respiratory matter may be considerably increased by the use of potatoes, rice, and other farinaceous food. Being furnished in excess, it accumulates in the body in the form of fat. Working animals, on the other hand, must be supplied with nitrogenous or plastic 430 ORGANIC CHEMISTRY. food in large proportion. The use of bacon, with peas, beans, and eggs, and many other popular mix- tures of food, are accounted for on the principle above stated. For the development of most of the views presented in this chapter, the world is indebted to the distinguished Liebig. ORGANIC ANALYSIS 1067. ULTIMATE ANALYSIS. CARBON AND How are car- bon and hy- HYDROGEN. The proportions of carbon 'mined ? deter ~ an( ^ hydrogen in organic substances, is ascertained from the quantity of carbonic acid and water which they yield on combustion. The combustion is effected in a glass tube, by means of oxide of copper, and the products are collected by means similar to those described in the process for an- alyzing the air. 1068. NITROGEN AND OXYGEN. Thepro- How are nitro- .... . , gen and oxy- portion of nitrogen m an organic substance gendetermin- is usua n y determined by the quantity of ammonia it will yield by combination with hydrogen. This combination is effected by heating the organic substance with hydrate of potassa or soda. The quantity of the ammonia produced in the process is estimated by the amount of acid it will neutralize. From the weight of this compound, that of the nitrogen it contains is readily calculated. The amount of oxygen in an organic substance is ascer- tained by subtracting the total weight of all the other constituents. PROXIMATE ANALYSIS. 431 How are or- 1069. PROXIMATE ANALYSIS. When it ganic bodies j s desired to separate organic bodies from fromlach each other, and determine their relative other? proportion without reference to their ele- mentary composition, the methods are analogous to those of inorganic chemistry. Distillation, and the analysis of the fats, which have been already described, may be taken as examples. CIRCULATION OF MATTER. 433 CHAPTER III. CIRCULATION OF MATTER. 1070. The relations of the three king- What proves ,.."*' . , . the relation doms of nature have been already mciden- tall y considered in former parts of this nature? work. It remains to present the subject in a single view. It is obvious, at a glance, that the soil does not furnish all the material which is required for the wants of vegetable life. The level of our meadows is not lowered by removal of successive crops, nor does the forest dig its own grave at its roots as it lifts its ponderous trunks into the air. The atmosphere, as well as the soil, contributes to the increase of mass, whether of wood or grain, and indirectly feeds all races of animal existence. The relation of the three kingdoms of nature is thus established. 1071. Water is one of the principal How does wa- . ter serve in agents in the system of circulation of a/matte?/ matter > which constitutes the life of the globe we inhabit. In the fulfillment of its office, it passes incessantly from sky to earth, now mingling with the currents of the atmosphere, and anon with those which form the arteries and veins of the great world of waters. Lifted into the atmos- 19 434 ORGANIC CHEMISTRY. phere by the sun, it descends again in dew and rain, corroding and dissolving the rocks on which it falls, and distributing them widely over land and sea. 1072. It settles through the stony crust What distinct , . . . , , , office does it of the earth, into the dark recesses of the fulfil? rocks where crystals blossom out of the formless stone, and supplies them with the material for their wonderful architecture. It penetrates the soil, and supplies the same material to the roots of plants for the still more wonderful creations of leaf, and fruit, and flower. Again it hastens through brooks and rivers on its course, and pours its burden into the sea, for the use of the innumerable forms of vegetable and animal life which inhabit its waters. The coral insect builds up solid islands out of the mat- ter it provides. Countless shell-fish clothe themselves in the same rocky garments, and finally cast them aside, to be buried under the slime of the sea and harden, in the course of ages, into stone. The water which has served these various offices, climbs anew into the heavens upon the solar rays, and again descends in the rain, repeating forever its round of service to the earth. 1073. The further relations of the three How may the n L , . further reia- kingdoms of nature may be presented in fhrll king- a sm gl e picture. Imagine a giant tree, the doms be i'llus- representative of all the vegetation of the earth, spreading wide its branches as a shel- ter for man and beast. Let us suppose them to subsist entirely upon its fruit, and to warm themselves by fires made from its branches. The tree, through its leaves, CIRCULATION OF MATTER. 435 draws its supply of gaseous food from the atmosphere, and through its roots, its mineral sustenance from the soil. It has purified the air in the process, of gases which would become noxious by accumulation, and returned to it the oxygen which is the vitalizing breath of the animal world. The mingled material of its food, worse than worthless to animals, has, at the same time, been transformed into wood and fruit, and other forms of vegetable matter. 1074. At this point, without interruption Explain the . return of mat- m the circuit, commences the return of m r oshere "*' material to tne atmosphere from which it was derived. Animals that feed upon the fruit of the tree, already breathe much of it back again to the air, while they live, and the rest is re- stored by their death and subsequent decay. Leaves that fall and moulder, and branches that are burned as fuel, make the same return of the elements of which they are composed, to the great reservoirs of the at- mosphere and earth. And what happens thus to leaf and fruit, happens also at last to the parent tree itself. One by one its giant branches fall and moulder, and melting again into the air, add to its inexhaustible stores of fertility, and provide the material for a new round in the grand system of circulation. 1075. What happens beneath the single Illustrate the extent of these tree, occurs also in every flower that lifts relations. ^ petals to the sun, and is a thousand times repeated in every forest upon the face of the earth. No limits of distance or of size, restrict the mutual rela- tions and dependencies of nature. The exhaled carbon 436 ORGANIC CHEMISTRY. of the polar bear feeds the lotus of Egyptian plains, and the breath of the southern lion is redistilled in the fragrance of the Norwegian pine. The particle of mat- ter that once burned in the fire of the poet's brain, and floated with his song upon the air, now blooms in the mountain flower and anon lies buried in its mould. 1076. According to the view thus pre- What is the material sour- sented, it will be seen that the sun is the If the ^orlf? reat material source of the life of the world. He wings the vapors that rise from the sea, and fall again to make their ministering circuit in the earth. The solar rays are the agents also, in the transformation of matter, which takes place in every leaf and blossom, and provide the animal kingdom with its food. 1077. No less is the sun the source of Show how it is , ., , , t i -, the source of all the mechanical power which is known U P n the earth ' The fallin g fl d f N1 ~ agara is but the recoil of the spring which is bent in evaporation from the sea and earth. All force which is derived from the fall of water, is thus traceable to the sun, which lifted it in the form of cloud and vapor. The energies of fire and steam, are only other forms of the force inherent in the solar rays, originally exercised in the organization of the vegetable matter which serves as fuel. Immediately produced by oxidation, and the heat which it evolves, they find their ultimate source, as well as their precise equivalent, in the deoxidizing influence of the solar rays. The forces of the human body are fed by consumption of similar materials, and may therefore be traced to the same source. CIRCULATION OF MATTER. 437 1078. Every planet that surrounds with What further influence has its orbit the great centre of our system, is equally dependent upon his influence. Held in their courses by his attraction, and encircling him in ceaseless revolution, they draw from the parent orb the strength and beauty which clothes their lesser spheres. What wonder, that in vague acknowl- edgement of his influence, heathen have acknowledged the sun as their God, and worshipped at his shrine. How natural that Christian nations should find in his life-giving power, a fitting emblem of the glory and beneficence of the great Father of the Universe, by whom all suns and systems, are, and were created. APPENDIX. 439 APPENDIX, IN this Appendix are included formulae descriptive of chem- ical reactions of the text, and other matter no less important, whose introduction into the text would have interfered in a measure with the plan of the work. The formulae constitute a precise statement, in the lan- guage of the symbolical nomenclature, of the reactions al- ready described in more general terms. It is not to be understood from the formulae that the materials concerned in any process must always be brought together in the pre- cise proportions indicated in the first member of the equation. One or the other may be in excess ; if so, the excess is null, and not considered in the formula. The latter regards and indi- cates only the relative quantities which are actually concerned in each reaction the first member having reference to the materials employed, and the latter to the products. Interpreted according to the atomic theory, each formula gives on the one side of the equation, the nature and rela- tive number of the atoms or molecules which take part in any reaction, and on the other, the nature and relative num- ber of those which result. The student will do well, as an occasional exercise, to cal- culate from the formulae the relative quantities of materi- als required in a reaction, and of products resulting from it in pounds and ounces. A T in the tables stand respectively for acetic and tartaric acids. 440 APPENDIX. 160. The numbers given in the text are only approximations. The exact quantities may be readily calculated by the law of expansion and contraction of gases, and vapors previously given, taking the volume of steam at 212 ( 232,) as a start- ing point. 232. According to the most recent determination, by Regnault, the latent heat of steam is 966'6. According to the same experimenter the sum of the latent and sensible heat is not rigorously constant. 235. The apparatus commonly employed in the laboratory for distillation, consists of a retort and receiver, as represented in the figure. In Liebig's ap- paratus, for the same purpose, the vapors are made to pass from the retort or flask through a long inclined tube. The latter is enclosed in a second tube, which is constantly supplied with cold water. A more per- fect condensation is thus effected. 248. ACTIVE FORCE or THE GALVANIC CURRENT. The active force of the galvanic current, is directly as the whole electro- motive force in operation, and inversely as the sum of all the APPENDIX. 441 impediments to conduction. The above is Ohm's law. By the electro-motive force, is to be understood the whole force generated by the chemical action in the battery. The im- pediments are found in the imperfect conducting power of the bodies, whether liquid or solid, which enter into the cir- cuit, and the resistance which the current encounters in passing from one to another. 273. (1.) SMEE'S BATTERY. Of all the batteries in common use, Smee's, which is represented in the figure, is the simplest. It consists of a plate of silver, with plates of zinc hanging near it on either side. The two zinc plates com- municate with each other by a metallic connection, and are, therefore, but one plate. It is found best to roughen the silver with platinum black. Smees' bat-j teries are commonly sold in this condition. The clamp and bar are simply to keep the plates in place. Water acidulated with from one-seventh to one-sixteenth of its bulk of oil of vitriol, is employed in this battery. It is generally used in plating, and is recommended to the student on account of its cheap- ness, simplicity, and efficiency. 273. (2.) GROVES' BATTERY. In Groves' battery the metal plati- num is used, instead of copper or silver. It is placed by itself, in a porous earthern cup containing nitric acid. The vessel is placed in a larger one, containing zinc and sulphuric acid. The two acids mix to some extent through the pores of the inner cup, so as to complete the circuit by their con- 19* 442 APPENDIX. tact. Without this the battery could not ope- rate. The figure represents Groves' battery, with the thumb screws by which the wires are connected with the platinum and zinc. The outer dark portion within the cup is the zinc, divided from top to bottom, that the acid may flow freely, and come into contact with both sides. 307. THE ATOMIC THEORY. That combination takes place in definite and multiple proportions, is directly proved by exper- iment. Oxygen, for example, unites with hydrogen in the proportion of 8, 16, 32 and 40, to one of the latter element, and refuses to combine in any other proportion. If matter were infinitely divisible, no reason can be assigned for this fact. Each infinitesimal portion of oxygen possessing the same affinities, we should expect to find combination in exact proportion to the quantity supplied. Dalton's atomic theory, the truth of which is assumed in the text, affords a luminous explanation of the facts under consid- eration. According to this theory, oxygen combines with hy- drogen in no smaller proportion than that of 8 to 1, because this is the ratio of weight in the least existent particles of the two substances. It combines in the proportion of 16, 24, 32 and 40, by uniting 2, 3, 4 or 5 of its atoms to one of Hydro- gen. It refuses to combine in any intermediate ratio, be- cause its atoms are indivisible. The same view of the con- stitution of matter is essential to the explanation of innumer- able facts in organic chemistry. The value of a table of atomic weights does not depend in the least degree upon the reception of the atomic theory. It is a list of combining proportions, determined by careful APPENDIX. 443 analysis, and reduced to a simple standard of comparison. Its truth is independent of all theory. RELATIONS OF ATOMIC WEIGHT AND DENSITY. The com- parative weight of equal measures or masses of different sub- stances is not necessarily the same as the comparative weight of their atoms. The mass of iron, for example, is heavier, while the atom of iron is lighter than that of potassium. To account for the fact, we must suppose the lighter atoms of iron so closely arranged that they thus more than make up by their larger number, for their inferior weight. In solids generally, there is no correspondence between atomic weight and specific gravity ; but in the case of many elements which exist in the gaseous state, or are capable of assuming it, the correspondence is complete, as shown in the following para- graph. COMBINING MEASURES OR EQUIVALENT VOLUMES. A cubic foot of nitrogen, weighs just fourteen times as much as the same measure of hydrogen, and the relation of the atomic weight is the same. In combining by atomic weights or equivalents, they therefore combine in equal measures. Chlorine, and the vapors of bromine, and iodine, belong to the same class. Taking hydrogen 1 as the standard, their combining measures are all 1. In the case of oxygen the correspondence referred to does not exist. It is sixteen times as Iieavy as hydrogen, while its atom weighs but eight times as much ; here again we are under the necessity of supposing a closer arrangement of the atoms. Those of oxygen are not only heavier, but twice as closely approxi- mated. Taking hydrogen as the standard, the combining measure of oxygen is therefore . That of phosphorus arid arsenic is the same, and that of sulphur^-. In the case of most other substances the ratio is not so simple. In the comparison of combining measures it is more customary to adopt oxygen as the standard of unity. The 444 APPENDIX. combining measure of hydrogen, chlorine, etc., becomes 2, as a consequence, and that of other gases or vapors is proportionally changed. In the production of compound gases, the elements either suffer no condensation or experi- ence a very simple change of volume. Thus hydrochloric acid gas, formed by the combustion of hydrogen and chlo- rine, possesses the united volumes of its constituents. EQUIVALENT VOLUMES OF COMPOUND GASES. As the equivalent, or combining proportion of a compound, is equal to the sum of the equivalents of its constituents, it follows that the combining measure of hydrochloric acid, is equal to the sum of the combining measures of hydro- gen and chlorine, 2+2 = 4. Ammonia is formed by the union of three volumes of hydrogen, and one of nitrogen. Condensation takes place to the amount of of the whole volume of their mixed gases. The combining measure is therefore equal to the sum of the combining measures of the constituents divided by 2. The sum of the combining measures is 8. 8-7-2=4. Steam is composed of one com- bining measure (two volumes) of hydrogen, united with one combining measure or volume of oxygen, and condensed to two volumes in combination. Its combining measure is therefore 2. The above instances may serve as examples of the interesting relations of atomic weights, specific quan- tity, and combining measures. CALCULATION OP SPECIFIC GRAVITY. The density or spe- cific gravity of a compound vapor or gas of known propor- tional composition, may be readily calculated from that of its constituents, supposing the amount of condensation which takes place in their combination to be known. The results thus obtained, are more accurate than any results of experi- ment. In like manner the proportional composition of a compound may be calculated from a knowledge of its ele- ments and density. The density of the vapor of carbon and APPENDIX. 445 other solids which are not known in the gaseous form, may be calculated from the density of their compounds with ele- mentary gases of known density. That of carbon, for ex- ample, may be deduced from that of carbonic acid. The calculation involves an assumption as to the equivalent vol- ume of carbon. Assuming it to be the same as that of hy- drogen, the density of carbon vapor is 423 '4. If its equiva- lent volume is the same as that of oxygen or that of hydro- gen, the density is doubled. ATOMIC VOLUMES. It is obvious that the number of atoms of a given weight in any mass, must be in proportion to the density of the mass. The size of the same atoms must be less in the same proportion. The atomic volume of any substance is therefore obtained by dividing the atomic weight by the density or specific gravity of the body. The subject of atomic volumes has important relations to the science of crystallography. In comparing atomic volumes it is assumed that the space which a body occupies is com- pletely filled by the atoms, without intervening space. ATOMIC HEAT. The numbers 28, 32, 103, represent, in the order in which they are given, the atomic weights of iron, copper, and lead. It is a remarkable fact that if the three metals be taken in these relative proportions, it will require the same expenditure of heat to make them equally hot. 103 pounds pounds of lead can be heated up to 212, for example, by burning the same amount of alcohol which will heat 32 pounds of copper, or 28 Ibs. of iron, to the same degree. Most other metals, and the non-metallic element, sulphur, come into the same class, or in other words, have the same atomic heat. The atomic heat of arse- nic and silver is double that of the elements above men- tioned. Other elements are different in this respect, but commonly by some simple ratio of difference. The cor- respondence is never absolute, but so close as to have lead 446 AXPENDIX. many chemists to attribute the variations to errors of exper- iment, and to regard the law of correspondence of atomic weights as universal. 313. CALCULATION OF FORMULAE. The student interested in the subject will readily devise for himself the reverse pro- cess of calculating formulae from the per centage results of analysis. The formulae obtained must obviously be such, that if reconverted into per cents, the numbers obtained will agree very nearly with the results of analysis. There may sometimes be a doubt whether the simplest formula which will express the composition, or some multiple of it is the true one. This can only be decided by the analysis of one of the compounds of the substance in which the formula of the second constituent is established. The reasoning will be best illustrated by an example. It being assumed that neutral salts contain one equivalent of base to one of acid, the analysis of the neutral sulphate of potassa would establish the formula for sulphuric acid, SO, instead of SaOe. KO,SO3 would express correctly the com- position of the salt, while the substitution of SsOe for SsOa in the same formula, would give a double proportion of acid. 323. When the same element unites with oxygen in different proportions to form different acids, these are distinguished by prefixes and terminations, which indicate the order in which they stand to each other, with respect to the quantity of oxygen. The first acid of such a series discovered, generally receives the termination " ic." Chloric acid may serve as an exam- pie. Another acid compound of chlorine since discovered, " IlvS'l^' ^* APPENDIX. 447 and containing more oxygen, is called hyperchloric, signify- ing higher than chloric. The other names of the list indi- cate, by their prefixes and terminations, the order of oxy- geriation of the several acids. The same means of distinc- tion are employed in other series. Hypochlorous acid, - - - Vv CIO. Chlorous acid, ''" - : V - - ClOa. Hypochloric acid, (peroxide of chlorine,) C1O4. Chloric acid, ' lTi - ; H ClOs. Hyperchloric acid, ... *v r < ClOr. 332. KO,C1O 5 =KC1+6O. 334. 338. 340. C+2O=CO 2 . 354. 2HCl+MnOa=2HO+MnCl+Cl. 355. (CaCl+CaO,ClO)+2SO 3 =2(CaO,SO 3 )+2Cl. 358. Sb+5Cl=SbCls. 362. It will be observed, on comparing 362 with those which precede, that chlorine sometimes expels oxygen, and is sometimes expelled by it. In relation to the apparent in- consistency of these facts, litrle more can be said than that chemical affinities are modified by circumstances, the action of which is not perfectly understood. 365. HO+C1-HC1+O. I 375. NaI+2SO3+MnO 2 =NaO 3 SO 3 +MnO,SO3+I 384. S+2O=SOa. 400. Zn+HO,SO 3 = ZnO, SOs+H. 408. Cu+2SO 3 =CuO, SOa 448 APPENDIX. 411. IODIDE OP NITROGEN. Iodide of Nitrogen, a very explo- sive compound, is formed when an alcoholic solution of iodine is added to aqua ammonia. It precipitates in the form of a black powder. The precipitate should be thrown upon a filter, washed, and while still moist, divided into small por- tions for the purpose of experiment. When dry it explodes violently by simple touch, and sometimes even spontaneously. CHLORIDE OF NITROGEN. Chloride of nitrogen is a still more dangerous compound than the above. To prepare it ajar filled with chlorine gas is suspended over a solution of sal ammoniac, contained in a leaden saucer. After the lapse of a few hours, an oily liquid forms and falls to the bottom of the solution. This is the chloride of nitrogen. Mere contact with a combustible material, such as fat, oil, phos- phorus, &c., is sufficient to cause its explosion. A single drop of the liquid explodes so violently as to shatter to pieces any earthen or glass vessel upon which the explosion takes place. The preparation of this compound cannot be recom- mended ; in the hands of the ablest experimenters it has been the occasion of the most dangerous accidents. 413. P+5O=POs. 424. KO, N0 5 +HO, S0 3 =KO, SCh+HO, NO 5 . 425. 3Cu+4N0 5 =3(CuO, NO 5 )+NO 2 . 426. NO 2 +2O=NO4. 428. 3Sn+2NO 5 =3SnO 3 +2NO 3 . 430. 3P+5NO 5 =3PO 5 +5NO 2 . 433. 5C+PO 5 =5CO+P. 446. AsCls +6Zn + 6(HO, SQ 3 ) = 6(ZnO, SOs + 3HCl+AsH 3 . 464. C+2O=CO 2 . 465. HCl+CaO,CO 2 :=HO+CaCl+CO 2 . APPENDIX. 449 478. C 480. CaOs, HO+SO 3 =HOSO 3 +CO 2 +CO. 490. Zn-{-SO3+HO 2 =ZnO, SO 3 +H. 492. 3Fe+4HO=Fe 3 O4+4H. 496. H+O=HO. 501. Na+HO=NaO+H. 519. H+C1=HC1. 521. HO,SOa+NaCl=NaO, SOs+HCl. 530. SiO 3 +3HF=3HO+SiF 3 . 537. N+3H=NH 3 . 539. CaO+NH 4 Cl=HO+CaCl+NH 3 . 543. NH 3 +HC1=NH4C1. 546. KO+3HO+2P=KO,PO 3 +PH 3 . 553. 2SO 3 +C4H 5 O 2 =2(HO, SO 3 )+C4H 4 . 577. 2C+KO,CO 2 =3CO+K. 585. Na+NH4Cl + Hg 626. Sb+5Cl=SbCl5. 680. The other elements not mentioned in the text are glucinum, cadmium, cerium, colnmbium or tantalum, didymium, erbi- um, indium, lanthanum, molybdenum, niobium, norium, osmium, palladium, pelopium, rhodinm, ruthenium, seleni- um. tellurium, terbium, thorium, titanium, tungsten or wol- framium, vanadium, ytrium, and zirconium. With the ex- ception of selenium and tellurium, which are analogous in their properties to sulphur, they may be classed with the metals. They are of rare occurrence, and may be regarded as sustaining the same relation to the other elements as do the asteroids and satellites to the more important members of the solar system. 646. Zn+PbO, A=ZnO, A+Pb. 665. NaCl+AgO, NO 5 =NaO, 450 APPENDIX. 685. NEUTRAL, ACID, AND BASIC SALTS. In general, salts con- taining an equivalent of base to an equivalent of acid are called neutral. The composition fixes the name, whether ex- actly neutral to the taste and in their action or vegetable colors, or not. Salts containing more acid in proportion are called super-salts or acid salts, and those containing mere base, sub-salts or basic salts. There are two exceptions to the above rules. The first is that of certain classes of acids which have double and treble neutralizing power, and require, therefore, the first two atoms, and the latter three atoms of base, to make them neutral salts. Such acids are bibasic and tribasic, in contra. distinction from the mono-basic or ordinary salts. Phospho- ric acid is one of the latter class of tribasic acids, and the neutral phosphates have therefore three atoms of base and is called a tribasic phosphate. Phosphates containing more acid or base than their proportion, are acid or basic accord- ing 1 y- The second exception is that of salts or bases which con- tain more than one atom of oxygen to an atom of metal. In proportion as they contain more, they neutralize more acid. Alumina or oxide of aluminium, for example, contains three atoms of oxygen. Its neutral sulphate, therefore, is a salt containining 3 atoms of acid. A salt of aluminium containing more or less than their proportion, is acid or basic accord. DOUBLE SALTS. There are also double salts or compounds of salts with each other. They are generally of the same acid. Thus alum is a double sulphate of potassa and alu- mina and the bisulphate of potassa may be regared as a double sulphate of potassa and water. Such double salts APPENDIX. 451 are not mere mixtures. They have their own crystalline form, and each particle of their crystals contanis all the ele- ments of both. BINARY THEORY OP SALTS. Sulphate of potassa, and other similar salts, are commonly regarded as ternary com- pounds. But many chemists are of the opinion that they are constituted after the plan of the binary salts, and their acids on the plan of a hydrogen acid. They would write sulphuric acid, SO4,H, instead of HO,SOs, thus indicating that the hydrated acid is composed of the radical, S(X (a compound playing the part of an element,) with hydrogen. Sulphate of potassa would, according to this view, be writ- ten K,SO4, instead of KO,SO3. The acid and salt are thus represented as analogous in constitution to a hydracid and a binary salt; thus, (SO4)H corresponds with C1H, and K(SO4) with KC1. The advantage of this view is that it makes but one great class of acids, and one of salts, associ- ating substances which are analogous in their properties. Hydrogen thus becomes characteristic of an acid. This view also simplifies the subject of the production of salts from acids, making it to consist simply in the replacement of the hydrogen of the acid by a metal. Thus in the action of sul- phuric acid (HO.SOa) on zinc, sulphate of zinc (ZnO,SOs) is formed by the simple replacement of the hydrogen of the acid by the metal zinc. As will be seen more clearly in the introduction to Organic Chemistry, it is no conclusive objection against the view, that the radical SO4 has not been isolated. There is the best reason for believing in the exist- ence of many such hypothetical radicals. A similar objection has indeed been urged against the ordinary view, according to which SOs neutralizes potassa in the sulphate of this base. The objection lies in the fact that anhydrous sulphuric acid is not possessed of acid properties, and can therefore be scarcely regarded as an acid, in its anhydrous condition. 452 APPENDIX. 717. CaO, HO+KO, CO 2 =CaO, COa+KOHO. 725. NH 3 +HO,SO 3 =NH 4 O, SOs. 726. CaO, CO 2 =CO 2 +CaO. 727. CaO+HO=CaO, HO. 741. HCl+NaO=HO+NaCL 742. NaCl+AgO, NO 5 =NaO, NO^+AgCl. 748. (CaCl+CaO,ClO)+2CO 2 =2(CaO, CO)+2C1. 750. 2CaO+2Cl=(CaCl+CaO, CIO). 751. 3C+3Cl-fAl 2 O 3 =3CO+Al 2 Cl 3 . 760. HO, SO 3 +CaF=CaO, SOs+HF. 762. PbO, A+HS=HO, A+PbS. 769. NaO+SO 3 =NaO, SO. Vide 400. 770. (CaO, SO 3 +2HO)=2HO-fCaO, SOs. 772. 2HO+CuO, SOs = (CaO, SOs+2HO). 774. HO, SO 3 +NaCl=HCl+NaO, 80s. 775. Glauber's Salt=(NaO, SOs + lOHO). 777. Alum=(KO, SOa+AlaOa, 3SO+24HO). 778. (KO, SOa + AlaOs, 3SOs+24HO)=24HO + (KO, SOs+AhOs, 3SOs). c 77Q (ChromeAlum=(KO,SO3+Cr 2 O 3 ,3SO3+24HO. '< Ammonia Alum=(NH40, SOa+AlaOs, 3S03+24HO). f Sulphate of Zinc =(ZnO, SOa+7HO). 780.-! Sulphate of Copper^ (CuO, SOs+5HO). [Sulphate of Iron=(FeO, SO 3 +7HO). 783. Nitrate of Potash (Nitre) =KO, NO 5 . 784. CaO,NO 5 +KO,CO 2 =CaO,CO 2 +KO, NO 5 . 786. NH 4 0, N0 5 =4HO+2NO. 787. S+KO, NO7+3C=KS + N+3CO 2 . 789. Nitrate of Silver (Lunar Caustic)=AgO, NO*. 790. Nitrate of Soda^NaO, NO*. 792. KO, CO 2 +CaO, NO 5 =KO, NO 5 +CaO,CO 2 . 795. CaO, CO 3 +NaS=CaS+NaO, C0 2 . 797. Sesqui-carbonate of Ammoma=2NH40, 3CO 2 . APPENDIX. 453 804. CaO+C0 2 =CaO, CO*. 809. (2NaO, HO, P0 5 + 24HO) + 3(AgO, NO 5 = 2(NaO,NO 5 ) + HO,NO 5 +24HO+3AgO,PO 5 . 824. Biborate of Soda=(NaO, 2BO 3 + 10HO). 828. Chromate of Lead (Chrome yellow) = PbO, CrO 3 . 829. KO, C0 2 + 2(PbO, Cr0 3 )=KO, Cr0 3 +CO 2 + 2PbO, CrOs. 830. Commercial chrome green is a mixture of Prussian blue and chrome yellow. 833. 3(KO, MnO 3 )+2S0 3 =2(KO, S0 3 )+MnO 2 -f KO, Mn 2 O 7 . 845. 4NO 5 +3Ag+Au=3(AgO, NOs)+NO 2 +Au. 846. 3NH 4 O + CaO, NO 5 + A1 2 Q 3 , 3NO 5 = 3(NH 4 O, NO 5 )+CaO,NO 5 +Al 2 O 3 . 847. CuO, NO 5 + AgO, NO 5 + HC1 = CuO, NO 5 + HO, NO+AgCl. 877. Woody Fibre = CiaHioOio. 890. Kreosote==Ci4H80 2 . Carbazotic 894. Gun Cotton (Pyroxalme)=Ci 2 H 8 08, 4NOs. ? 898. C J2 HioOio+4HO=Ci 2 Hi 900. Starch=Ci 2 HioOio. 904. Ci 2 HioOio+4HO=Ci 2 Hi 907. Grape Sugar=Ci 2 Hi 4 Oi4. 908. Cane Sugar=CiaHnOii. 913. (Ci 2 Hi 2 4CO 2 . 914. Alcohol=C4HeOa. 917. C4 454 APPENDIX. 919. FULMINATES. This name has been given to a class of highly explosive salts, obtained by the action of alcohol upon certain nitrates. The most important are the fulmi- nates of mercury and silver. Fulminating mercury is pre- pared by dissolving 1 part of mercury in 12 parts of nitric acid, sp. grav. 1.36, and subsequently adding 11 parts of 80 per cent, alcohol. Upon warming the mixture a compli- cated reaction takes place, dense white vapors are given off, and the fulminate is thrown down as a crystalline powder. This is to be washed with cold water and afterwards dried at a moderate temperature. This salt explodes violently by heat, friction, or percussion, and sometimes even without any apparent cause. It is largely employed in the manufac- ture of percussion caps, torpedoes, &c., &c. Fulminating silver detonates still more violently than the mercury salt. By friction with a hard body, it explodes even under water. It is prepared as above, using 10 parts of nitric acid and 20 parts of alcohol. Too much caution cannot be observed in manipulating with these highly dangerous compounds. They should be prepared only in quantities of a few grains. Fulminate of Silver=2AgO, CyaOa. 927. Ether=C 4 H 5 O. Alcohol =C 4 HeO 2 or (C 4 H 5 O+HO). 928. 929. 930. C 4 H 6 O 2 +2S0 3 =2(HO, 931. 932. 933. 935. Chloroform- C 2 HCFs. 938. Tannic Acid=Ci 8H 5 O 9 , 3HO=Qt, 3HO. APPENDIX. 455 941. Cyanogen=C 2 N=Cy. An arbitrary symbol. 942. FeCy, 2KCy+HgCl 2 =FeCy,2KCl + Hg+2Cy. 943. Cyanide of Potassium==KC 2 N=KCy. 944. Prussian Blue = Ci 8 N 9 Fe7 = Fe 4 Cfy 3 . fFerrocyanogen=3Cy, Fe=Cfy. 945.j Ferrocyanide of Potassium = (3Cy, Fe+2K) = I Cfy,2K. 946. 2(3Cy, Fe + 2K) - K = (2(3Cy, Fe) + 3K) = 2Cfy, 3K. 947. KCy+HO, SO 3 =KO, SOs+HCy. fTartaric Acid=CsH4Oi o, 2HO=T, 2HO. Oxalic Acid=C 2 O 3 , HO=O, HO.^ .Citric Acid^CisHsOn, 3HO=Ci, 3HO. 49>1 Malic Acid=C 8 H40 8 , 2HO-M, 2HO. Formic Acid =C 2 HO 3, HO. LLactic Acid=C 6 H 5 O5, HO. 975. In the present state of our knowledge in respect to the protein bodies, we must abandon every formula by which their atomic constitution is said to be expressed. Generally, they contain in 100 parts : 55.16 carbon, 7.05 hydrogen, 21.81 oxygen, 16.96 nitrogen, with to 1 per cent, sulphur and phosphorus in an unknown form. Morphine^CssHaoNOe. C44H 2 3N 2 O8 or |Quinine=C 2 oHi 2 N0 2 . [Theine and Caffeine=Ci aHi oN 4 0. 993. Indigo=Ci6H 5 NO 2 . 994. Alizarine = C 2 o H i o O i o . 995. Hematoxyline C4oHi ?0i s. 1002. Vide 994. 456 APPENDIX. 1003. (KO, SOs + Cr 2 O 3 , 3S0 3 ) + 3KO = 4(KO ; SO 3 )+Cr 2 O 3 . 1025. MODE OF ESTIMATING THE VALUE OP GUANO, &C. In estimating the money value of guano for agricultural pur- poses, ammonia may be set down at 16 cents per pound, potash at 4 cents, and phosphoric acid at 1 to 2 cents. As far as the latter exists in a soluble form, its value is doubled. Other substances are of so little comparative value that they need not be taken into the account. These valuations are based, not alone on their relative value as fertilizers, but on the cost of the different substances when obtained from other sources. They are somewhat arbitrary, but may serve as a means of approximate estimation of the value of guano and other fertilizers. As an average of the composition of thirteen samples of Peruvian guano, Prof. Way obtained the following results : ammonia, 17*41 pgr cent.; phosphoric acid, 11-13; potash, 3*50. This would seem to be considerably above the or- dinary average. The pecuniary value of such an article, according to the above valuation, would be $63.00 per ton, of which 855.60 would lie in the ammonia. No distinc- tion is made in the potential and actual ammonia of guano, because the conversion of the former into actual ammonia, takes place so rapidly in the soil. But the potential ammo- nia of most nitrogenous substances, as of clippings of hides and other similar refuse, is to be estimated at least 25 per cent, lower, in view of their comparatively slow conversion. In all analyses of concentrated fertilizers excepting guano, in which the first distinction may be neglected, the amount of actual and potential ammonia, of soluble and insoluble phosphoric acid, and of potassa, should be separately stated. APPENDIX. 457 The latter constituent is, however, of comparatively little importance. The farmer who purchases his artificial fer- tilizers without a skillful and well attested analysis, is at the mercy of the ignorant or unscrupulous dealer. 1 046. Glycerine = C 6 H e O c . fStearic Acid^CesHeeOe, 2HO=St, 2HO. 1047.<{Margaric Acid^Cs^ssOs, HO. [Oleic Acid^CseHssOa, HO. $Urea=C 2 N 2 H 4 3 . I Uric Acid=CioN4H 3 5 +HO. APPENDIX. 459 TABLE L TABLE OF THB DISCOVERY OF OKRTAEf ELEMENTS. Authors of the discovery. Dates. Known to the ancients. Names of Elements. Gold, . Silver, . Iron, Copper, . Mercury, Lead, . Tin,. . Sulphur, Carbon, Antimony, . . . Described by Basil "Valentine, 1490 Bismuth, . . . Described by Agricola, 1530 Zinc, ..... First noted by Paracelsus, .... 16th centur} r . Phosphorus, . . Brand, , 1660 Arsenic, . . . ) grant 1733 Hydrogen, . . Cavendish, 1766 Chlorine, . . , Scheele, 1774 Oxygen, . . . Priestly, 1774 Manganese, . . Gahn and Scheele, 1774 Chromium,. . . Vauquelin, 1797 Potassium, Sodium, . Sir Humphrey Davy, 1807 Calcium, Boron, . Iodine, .... Courtois, 1811 Silicon, .... Berzelius, 1823 Bromine, . . . Ballard, 1826 Aluminium, . . "Wohler, . 1828 Magnesium, . . Bussy, 1829 460 APPENDIX. TABLE IL ATOMIC WEIGHTS.* Hydrogen=1.00. Aluminium Al 13.63 Lead Pb 103.57 Antimony Sb 129.00 Lithium Li 6.64 Arsenic As 75.00 Magnesium Mg 12.00 Barium. Ba 68.59 Manganese Mn 27.57 Bismuth Bi 208.00 Mercury Hg 100.05 Boron B 11.04 Nickel Ni 29.55 Bromine Br 79.97 Nitrogen N 14.00 Calcium Ca 20.00 Oxygen O 8.00 Carbon C 6.00 Phosphorus P 31.36 Chlorine Cl 35.46 Platinum Pt 98.94 Chromium Cr 26.78 Potassium K 39.11 Cobalt Co 29.49 Silicon Si 14,81 Copper Cu 31.68 Silver Ag . 107.97 Fluorine Fl 19.00 Sodium Na 23.00 Gold An 196.67 Strontium Sr 43.67 Hydrogen H 1.00 Sulphur S 16.00 Iodine I 126.88 Tin Sw 58.82 Iron Fe 28.00 Zine Zn 32.53 * These atomic weights are calculated fro-ni the best and most pre- cise investigations; some of them have not yet been established by recent experiment, but are calculated from others eo determined. FRESEMUS. APPENDIX. 461 TABLE III. SPECIFIC GRAVITY OF SOLIDS, Pure water at 60 F=1.000 Platinum >"'' 20 98 Tin . . . 7 29 Gold 19 26 Zinc 7 03 13 60 Antimony . . . 6 70 Lead , . 11 45 . . 6.65 Silver . . . . . . 10.50 . . . 6.00 Bismuth. . 9 80 . . 5.80 8 87 Iodine . . 495 Cobalt 8 54 . . . 2 60 Nickel . . . . . 8.28 . . . 1.86 8 00 Sodum ... . . . 97 Iron . . -. . 7.80 . . . 0.86 TABLE IV. SPECIFIC GRAVITY OF LIQUIDS, Pure water at 60 F=1.000 Mercury 13.596 Bromine . . . 2.79 to 3.19 Sulphuric Acid . . . . 1.800 Nitric Acid 1.515 Ammonia . Turpentine Alcohol . . Ether . . 0.870 0.865 0.800 0.720 TABLE V. SPECIFIC GRAVITY OF GASES. Dry air at 60 F=1.000 Chlorine 454 Oxygen 1 109 Nitrous Oxide .... Carbonic Acid . .525 525 Carbonic Oxide Nitrogen . . . . 0.970 . . . 970 Fluorine 296 . . . 0.069 Hydrochloric Ac. gas . . .261 Ammoniacal gas . . . 0.589 462 APPENDIX. TABLE VI. LINEAR EXPANSION OF SOLIDS ON BEING HEATED FROM 32 TO 212 F. Zinc (cast) expands ~z%~% Iron expands _,_ Zinc (sheet) 30 Steel (tempered) a!* Lead sir Steel (untempered) " J~2j Silver " *i* Platinum " TiVT Copper " yir Flint Glass T2T Gold *** Black Marble 2"83"1T TABLE VIL SPECIFIC HEAT. Water=1.000 Alcohol 0.660 Ether 0.520 Nitric Acid 0.442 Oil of Turpentine . . . 0.425 Sulphuric Acid .... 0.833 Carbon 0.241 Common Salt 0.225 Lime 0.205 Sulphur 0.202 Glass . ,0.197 Phosphorus 0.187 Iron 0.113 Zinc 0.099 Arsenic 0.081 Tin 0.056 Iodine 0.054 Silver 0.050 Mercury 0.033 Platinum 0.032 Gold , . 0.032 TABLE VIII. MELTING POINTS OF SOLIDS. Cast Iron ne/^ at 3479 Potassium melts at 154 Cobalt 2800 Wax 142 Silver 2283 Spermaceti 112 Gold 2016 Phosphorus 108 Copper Lead 1996 612 Tallow Olive Oil 92 8G Bismuth 497 Ice 32 Tin 442 Oil of Turpentine 14 Sulphur 226 Mercury 39 Newton's Alloy 208 Liquid Ammonia, 40 Sodium 194 Ether i 47 APPENDIX. 463 TABLE IX. BOILING POINTS OF LIQUIDS. Mercury boils at 662 Nitric Acid boils at 248 Whale Oil " it 630 Water ' ' 212 Sulphuric Acid " 620 Alcohol ' ' 173 Sulphur " tt 600 Bromine < < 116 Phosphorus Oil of Turpentine M it tt 551 312 Ether Sulphurous Acid ' ' 96 14 TABLE X. COMPOSITION OF HUMAN BLOOD ACCORDING TO LfiCANU. Water 78.015 Fibrin . . . . . . 210 6509 13.300 Crystallizable fat 0.243 Oily fat 0.131 Salts of the alldlies 837 0.210 545 100.000 TABLE XL COMPOSITION OF COW'S MILK. Water 873.0 Casein, and a little albumen 48.2 Butter 30.0 Sugar of milk 43.9 Phosphate of lime with a little chloride of calcium .... 2.3 Phosphate of iron and magnesia, and a little soda .... 0.9 Chlorides of sodium and potassium 1.7 1000.00 464 APPENDIX. TABLE XII. RELATIVE PROPORTIONS OF THE SANGUIGENOUS TO THE RESPIRATORY CONSTI- TUENTS IN DIFFERENT KINDS OF FOOD. Sanguigenous. Respiratory. Cow's milk contains, for 10 30= -S 8 ' 8 fat and ( 10.4 milk sugar Human milk 10 40 Horse beans " 10 22 Peas 10 23 Fat mutton " 10 27=11.25 fat Fat pork 10 30=12.5 " Beef 10 17=7.08 " Veal 10 1=0.41 " Wheat flour " 10 46 Oatmeal 10 50 Rye flour " 10 57 Barley 10 57 Potatoes (white) " 10 86 Potatoes (blue) " 10 115 Rice 10 123 Buckwheat " 10 130 Starch is the principal constituent of respiratory food in the sub- stances mentioned in the table. When sugar and fat take its place, the fact is separately indicated, while their equivalent in starch is given in the principal column for convenience of comparison. The above table is taken from Liebig's Letters on Chemistry. TABLE XIIL PER CENT BY MEASURE OF ALCOHOL IN SPIRITOUS LIQUORS AT 62 F. Rum contains 72 to 77 per cent. Cognac " Whiskey 50 " 54 59 Geneva 50 Port wine " 21 to 23 Sherry 15 " 25 Madeira " " 18 " 22 Malmsey " " 16 Claret " " 9 to 15 Burgundy " " 7 " 13 Rhenish 8 " 13 Moselle 8 " 9 Tokay 9 Champagne " 5 to 15 " APPENDIX. 465 TABLE XIV. HOMOLOGOUS SERIES OF ORGANIC ACIDS. 1. Formic .... CaHaCM 16. Ethalic . . . . C32H3204 2. Acetic .... CiHiOi 17. Stearic . . . . C34H34O4 3. Propiouic . . . CSH604 18. Bassic . . . . C3SH3&O4 4. Butyric .... CsHsOi 19. 5. Valeric .... CicHicCM 20. 6. Caproic .... Cl2Hl204 21. 7. Enanthylic . . . Cl4Hl404 22. Behenic . . . C44H4404 8. Caprylic .... CieHieO4 23. 9. Pelargonic . . . CisHisCh 24. 10. Capric .... CsoHsoCh 25. 11. Margaritic . . . C22H2204 26. 12. Laurie .... C24H2104 27. Cerotic . . . . C54H3404 13. Cocinic .... C26H2S04 28. 14. Myristic .... GssHttOl 29. 15. Benic .... C3oHscO4 30. Melissic . . . . CsoHsi04 TABLE XV. COMPOSITION OF THE ASHES OF COMMON CROPS. ndian Corn. Wheat Wheat Straw. Rye. Oats. Pota- toes. Tur- nips. Hay. Carbonic acid, trace. 10-4 Sulphuric acid, 0-5 i-o i-o 1-5 10-5 7-1 13.6 2-7 Phosphoric acid, 49-2 47-0 31 47-3 43-8 11-3 7-6 6-0 Chlorine, . . 0-3 :race. 0-6 0-3 2-7 3-5 2-6 0-1 2'9 85 2-9 4-9 1*8 13-6 22 -9 Magnesia, . . 17-5 15'9 5-0 10-1 9-9 5-4 5-3 5-7 Potash, . . . Soda, .... 23-2 3-8 29-5 trace. 7'2 0-3 32-8 4-4 j- 27-2 51-5 trace. 42-0 5-2 18-2 2-3 Silica, .... 0-8 1-3 67-6 0-2 2-7 8-6 7-9 37-9 Iron, .... 0.1 trace. 1-0 0-8 0-4 0-5 1-3 1-7 Charcoal in ash, ) and loss, . ) 4'5 2'4 5-7 0-3 0-7 lOO'O 100-0 lOO'O lOO'O lOO'O 100-0 100-0 100-0 Lbs. of material } 6000 12500 1000 requir'd to yield > 100 Ibs. of ashes. j 10000 5000 2000 5000 2500 to 13000 to 20000 to 2000 20' 466 APPENDIX. TABLE XVI. SOLUBILITY OF SUBSTANCES KG NaO NH 4 BaO SrC CaO MgC AbO MnO FeO NIC 1 1 1 1 1 12 2 2 2 2 2 s 1 1 1 1 1 i2 2 2 2 Cl 1 1 1 1 1 1 1 1 1 1 1 I 1 1 1 1 1 1 1 1 1 SO3 1 1 1 3 3 1*8 1 1 1 1 1 NOo I 1 1 1 1 1 1 1 1 1 1 POs 1 1 1 2 2 2 2 2 2 2 COa 1 1 1 2 2 2 2 2 2 2 CaOs 1 1 1 2 2 2 2 2 2 i 2 BOa 1 1 1 2 2 2 2 2 2 2 2 A 1 1 1 1 1 1 1 1 1 1 1 "T 1 1 1 2 2 2 12 1 i2 i2 AsOs 1 1 1 2 2 2 2 2 2 2 2 AsOa 1 1 1 2 2 2 2 2 CrOs 1 1 1 2 2 2 1 2 1 2 EXPLANATION OF THE TABLE. To ascertain the solubility or insolubility of a salt from tbe above table, its acid is sought in the left hand column, and its base in the upper line. The square, which is in line APPENDIX. 467 TABLE XVI. (CONTINUED.) IN WATER AM) ACIDS. ZnO PbO SnO SnO BiOa CuO Hg20 HgO AgC PtO SbO 2 2 2 23 2 2 2 2 2 2 s 2 2 2 3 3 2 Cl 1 11 1 1 1 1 2 1 3 1 I 1 2 2 1 2 2 3 SO3 1 2 1 1 1 i2 1 1 2 1 2 NOo 1 1 1 1 1 1 1 1 POs 2 2 2 2 2 2 CO2 2 2 2 2 2 2 2 CaOs 2 2 2 1 2 2 2 2 2 12 BOs 2 2 2 2 2 1 A 1 1 1 1 1 1 12 1 1 1 f 2 2 12 2 1 i2 2 2 1 AsOs 2 2 2 2 2 2 2 AsOs 2 2 2 2 2 2 CrOa 1 2 2 2 2 2 i2 2 2 with both, contains the desired information. The numeral 1, indicates solubility in water ; 2, solubility in either nitric or hydrochloric acid, and 3, insolubility in either. The smaller numerals indicate a low degree of solubility. INDEX. Acetic Acid, 372. Acid, Arsenious, 180. Antidote to, 185. Marsh's Test for, 181. Poisonous properties of, 181. Boracic, 197. Carbonic, 189. Hydrochloric, 210. Action of, on Metals, 211. Hydrocyanic, 374. Hydrofluoric, 212. Hydrosulphuric, 214. Muriatic, 210. Nitric, 173. Oxalic, 378. Prussic, 377. Stearic, 420. Sulphuric, 162. Sulphurous, 167. Stannic, 285. Tannic, 373. Acids. Formation of, 136. Organic, 372. Properties of, 137. Affinity, Relation of cohesion and, 277. Air, Analysis of the, 172 Proportional Composition of the, 173. TJnsaturated, 71. Albumen, Vegetable, 389. Alcohol, 362. Aldehyde, Conversion of Alcohol into, 370. Alkali, Volatile, 218. Alkalies, The, 286. Effects of, on Wood, 353. Vegetable, 395, Alkaloids, Alloys, 272 Alum, 307. Different kinds of, 308. Alumina, 292. Aluminium, 238. Amalgams, 261. Ammonia, 216. Carbonate of, 815. Nitrate of, 311. Ammonium, 235. Oxide of, 290. Analysis, Chemical, 332. Organic, 430. Anastatic printing, 331. Animal Body, Chemical changes in the, 424. Heat, 424. Tissues, Changes of, 426. Antimony, 251. Apparatus for silvering and gild- ing, 107. Aqua Regia, 212. Arsenic, 179. INDEX. 469 Arsenic, Eaters of Austria, 185. Marsh's Test for, 181. Artificial Essences, 382. Ashes, Effect of, on Soils, 407. Asphaltum, 386. Assay of Gold, 269. Silver, 265. Atmosphere, Elastic Force of the, 78. Quantity of vapor in the, 71. Weight of the, 77. Atomic Weights, Table of, App. Atoms and Attraction, 1 1. Attraction, Chemical, 12. Distance of, 13. of Cohesion, 12. of Gravitation, 12. B. Barium, 237. Barometer Guage. 90. Baryta, Sulphate of, 307. Bases, Organic, 395. Properties of, 137. Batteries, Different kinds of, 114. Batten 7 , Decomposition in the, 112. Bismuth, 253. Bleaching, by Oxygen, 147. Sulphur, 160. Powder, 298. Blood, Composition of the, 415. Changes in the, 424. Color of the, 425. Table of the Composition of the, App. Transformation of the, 414. Blowpipe, 227. Oxhydrogen, 229. Boiling, 77-80! Disappearance of Heat in, 81. Effect of Depth on, 83. Height on, 83. Expansion in, 81. Point, Artificial Change of, 84. Height measured by, 83. Bones, 416. Boracic Acid, 197. Borates, 323. Boron, 197. Bread, Raising of, 393. Bromine, 158. Burning Fluid, 380. 46. of Ice, 47. C. Calcium, 237. Oxide of, 290. Camphors, 383. Caoutchouc, 387. Carbon, 185. Combustion of, 188. Carbonates, 313. Carbonic Acid, 189. Oxide, 194. Carburetted Hydrogen, Heavy,222. Light, 221. Casein, 389. Cellars warmed by Ice, 65. Cement, Hydraulic, 292. Chamelion Mineral, 326. Charcoal, Combustion of, in Oxy- gen, 145. Decoloring effects of, 188. Preparation of, 186-349. Preservative properties of, 187. Purifying properties of, 187. Reduction of Ores by, 188. Cheese, 423. Chemical Analysis, 332. Chemistry, Organic, General views of, 335. Chloride of Lime, 298. Sodium, 296. Chlorides, 294. Chlorine, 149. a Disinfectant, 154. Bleaching by, 153. Compounds of, with Oxygen, 156. Relations to Animal Life, 155. Resemblance to Oxygen, 155 Test for, 301. Chloroform, 371. Chromates, 325. Chromium, 245. Circulation of Matter, 433. Clay, 320. 470 INDEX. Cloth, Incombustible, 352. Coal, Anthracite, 851. Oils from, 355. Cobalt, 245. Cohesion, 12. Relation of, and Affinity, 277. Cold, Definition of, 27. Extreme, how measured, 59. Supposed Radiation of, 45. Water, Lightness of, 55. Collodion, 356. Color, Change of, by Touch, 301. Coloring Matters, 396. Combustion, Definition of, 145. under Water, 178. Composts, 407. Compound Blowpipe, 229. Circuit, Decomposition by the, 115. Galvanic Circuit, 114. Radicals, 340. Concave Lens, Action of, 22. Mirrors, Theory of, 19. Conducting Power, Simple Test of, 35. Copper, 254. Counterfeiting, Prevention of, 331. Crystal Forms, Systems of, 281. Glass, 321. Crystallization, 208. Culinary Paradox, 84. Cupellation, 263. Cyanides, 374. Cyanogen, 374. D. Daguerreotype, The, 327. Davy's Safety Lamp, 222. Decay, Preventives of, 352. Definite Proportions, Law of, 134. Dew, 75. Absence of, on Polished Sur- faces, 45. Artificial prevention of, 44. Formation of, 44. Point, 74. how to find the, 74. Distillation, 97. Dyeing, 397. Dyes, Mineral, 399. E. Earth, Cooling of the, 43. Earthen-ware, 322. Effervescent Drinks, 191. Elastic Force of Vapors, 89 Electric Light, 111. Electricity and Magnetism, 99. Conduction of, 103. Decomposition of water by. 105. Frictional, 102. Galvanic, 103. Quantity of, in Matter, 104. Theory of, 102. Electrodes, 103. Elements, Electrical Relations"of 138. Number of, 11. Table of, App. Empyreumatic Oils, 382. Enamel, 322. Engine, The Steam, 91. Equivalents, Chemical, 134 Table of, App. Essences, Artificial, 382. Essentials Oils, 379. Etching on Glass, 213. Ether, Conversion of Alcohol into, 368. Ethyl, Production of, 369. Evaporation, Economy in, 97. Effect of Wind on, 70. Freezing by, 68. Protection from Heat by, 68. Expansion, 50. Fracture of Glass Vessels by, 53. Law of, for Gases, 57. Lifting Walls by, 52. of Cold Water by Cold, 54. Gases, 56. Liquids, 54-56. Solids, 51. Wood and Marble, 53. INfJEX. 471 F. Fats, Composition of, 419. Separation of, in Oil, 419. Tallow and Lard, 420. Fermentation, 391. Ferrocyanides, 376. Fibre, Woody, 349. Filtration, 207. Fire by Compression, 50. on Water, 36. Proof Safes, 35. Flame, 225. Effect of, on Metals, 226. Flesh, 417. Fluorides, 302. Fluorine, 158. Fogs, 72. Food and Temperature, Kelations of, 426. Proportions of, 429. Transformation of the, 414. Varieties of, 428. Freezing, 64. by Evaporation, 68. Mixtures, 63. Fusel Oil, 372. O. Galvanic Coil, Motion of a sus- pended, 120. Polarity of, imparted to Metals. 122. Polarity of the, 119. The, a magnetic needle, 121. Coils, Mutual Action of, 121. Current, Heating Effects of the, 111. Magnetic Effects of the, 119. Galvanism, Discovery of, 127. Physiological Effects of, 126. Gas from Wood, 225. Illuminating, 223-349. Gastric Juice, The, 414. Gelatine, 418. ermination, 345. Gilding, 270. Galvanic, 107. lass, Colored, 322. Crystal, 321. cut by Hot Wire, 53. Etching on, 213. Soluble, 320. Staining, 294. Window, 320. Glauber's Salt, 306. Glycerine, 420. Gold, 267. Gravitation, 12. Green, Chrome, 326. Mineral, 400. Guano, 407. Gum from Wood, 357. Resins, 387. Gun Cotton, 355. Gunpowder, 311. Gutta Percha, 388. Gypsum, 305. II. Heat, Absorption of, 42. Analysis of, 46. Animal, 424. Capacity for, 49. Changes effected by, 48. Communication of, 30. Conduction of, 30. Convection of, 37. Disappearance of, in Boiling, 81. Melting, 62. Vapors, 67. Extreme, how measured, 60. Latent, 65. Nature of, 25. of Chemical Action and Elec- tricity, 29. the Fixed Stars, 29. Protection from, by evapora- tion, 68. Quantity of, given out by tha Sun, 28. Radiation of, 39. 472 INDEX. Heat, Rays of, 45. Effect of different, 47. Reflection of, 41. Refraction of, 45. Relation of, to Density, 49. Specific, 48. the Ocean a Reservoir of, 50. Theories of, 25. Transmission of, 41. Heavy Carburetted Hydrogen, 222. Hides, Tanning, 418. Homologous Series, 341. Table of the, of Organic Acids, App. Humus, Production of, 351. Hydrates, 286. Hydraulic Cement, 292. Hydrochloric Acid, 210. Hydrocyanic Acid, 374. Hydrofluoric Acid, 212. Hydrogen, 197. Phosphuretted, 219. Sulphuretted, 214. I. Ice in the Tropics, 43. Ignition by Lime, 291. Illuminating Gas, 223. Incrustations in Boilers, 316. Indigo, 396. Induction, Magnetic, without Con- tact, 101. Ink, Writing, 373. Intensity of Electricity, Meaning of, 115 Iodine, 156. Iron, 240. Combustion of, in Oxygen, 143. Isomorphism, 284. EN Lamp Black, Preparation of, 187. Latent Heat, Proof that Boiling is effected by, 96. Latent Heat, Quantity of, in Steam, 96. Sum of, and Sensible Heat always the same, 96. Laughing Gas, 311. Lead, 256. Chromate of, 325. Light, 15. Analysis of, 22. Chemical Action of, 15-329. Laws of, 17. Medium, Definition of, 17. Ray, Definition of, 17. Reflection of, 18. Refraction of, 20. Theories of, 15. Light Carburetted Hydrogen, 221. Lime, Action of, in Soils, 405. Ignition by, 291. Nitrate of, 309. Sulphate of, 305. Liniments, 422. Liquefaction, 61. Liquids, Conversion of vapors into, 95. Nonconductors of Heat, 36. Logwood, 397. Dyeing with, 399. Lunar Caustic, 312. Madder, 397. Magnesium, 237. Magnet, Artificial, 99. Magnetic Induction without Con- tact, 101. Needle, 99. Telegraph, 124. Magnets, Attraction of, for each other, 100. Native, 99. Magnetism, Electrical Theory of, 126. Induced, 100. Mahomet's Coffin, 119. Manganates, 326. Manganese, 239. Marble, Artificial, 317. Marsh's Test for Arsenic, 181. INDEX. 473 Matches, Friction, 178. Mercury, 259. Quantity of, the Air can Sus tain, 80. Metals, 231. Classification of, 231. Deposition of, by Electricity, 106. Effect of flame on, 106. Milk, 422. Solid, 423. Table of the Composition of, Cow's, A pp. Human, App. Mineral Dyes, 399. Moisture, Deposition of, 70. Molasses, 361. Mordants, 398. Multiple Proportions, Laws of, 134. Muriatic Acid, 210. Effect of, on Wood, 354. Nickel, 246. Nitrate of Silver, 312. Nitrates, 309. Nitre, 310. Nitric Acid, 173. Effects of, on Wood, 352. Nitrogen, 169. Nutrition, Vegetable, 346. O. Oil of Vitriol, Manufacture of, 163. Oils, Empyreumatic, 382. Essential, 379. from Coal, 355. Olefiant Gas, Conversion of Alco- hol into, 369. Organic Acids, 372. Analysis, 430. Bases, 395. Chemistry, General Views of, 335. Oxalic Acid, 378. Oxides, 285 Oxides, Formation of, 136. Names of, 135. reduced by Carbonic Oxide, 195. Uses of, 293. Oxygen, 141. a Purveyor for Plants, 147. Bleaching by, 147. Compounds of, with Chlorine, 156. Oxhydrogen Blowpipe, 229. Ozone, 148. P. Peat, 350. Petroleum, 386. Phosphates, 317. Phosphorescence, 177. Phosphorus, 176. Combustion of, by Nitric Acid, 176. Combustion of, in Oxygen, 144. Phosphuretted Hydrogen, 219. Photographs, 329. Plants, Constituents of, 348. Relation of, to the Soil, 402. Plaster, Aluminated, 306. of Paris, 305. Platinum, 271. Porcelain Painting, 323. Potassa, 287. Carbonate of, 314. Nitrate of, 310. Potassium, 233. Cyanide of, 375. Precipitation, 207-275. Pressure, Actual, in different En- gines, 90. of the Atmosphere, 79. The Exact Relation of Temper- ature to, 88. Printing, Anastatic, 331. Calico, 400. Prism, construction of, 21. Effect of, on Rays, 21. Prussic Acid, 377. Putrefaction, 390. 474 INDEX. Quantity of Electricity, Meaning of, 115. R. Radiation of Heat, 39. Color not effected by, 40. Polish unfavorable to, 40. Proportion of, to Temperature; 39. Radicals, Compound, 340. Rays, Heat and Chemical, 45. Refraction of Heat, 45. Light, 20. ^ Refrigerators, Construction of, 34. Resins, 383. Gum, 387. Respiration, 425. Roots, Office of the, 347. Rosin Oil, 386. Soap, 385. S. Safety Lamp, Davy's, 222. Sal- Ammoniac, 218. Volatile, 315. Salt, Common, 296. Decomposition of a, by Gal- vanism, 117. Glauber's, 306. Saltpetre, 310. Salts, 274. Formation of, 136. Names of, 135. Sealing Wax, 385. Shot, Manufacture of, 259. Silicates, 319. Silicon, 196. Silver, 262. Assay, 265. Nitrate of, 312. obtained from Lead, 263. Silvering, Galvanic, 107. Sizing for Paper, 875. Skin," Tendons and Ligiments, 417. Soaps, 421. Properties of, 422. Soda, Carbonate of, 314. Sulphate of, 306. Sodium, 235. Chloride of, 296. Soils, 402. Soldering, 324. Soluble Glass, 320. Solution, 206-274. Effect of, on Chemical Affinity, 138. Spirituous Liquors, 366. Stalactites, 317. Stalagmites, 317. Starch, 357. Starvation, 427. Steam Boilers, 86. Elastic Force of, 87. Engine, 91. Guages, 90. Heating Houses by, 95. Safety Valve, 91. Water Heated by, 95. Stearic Acid. 420. Steel, 243. Permanent Magnetism of, 123. Tempering, 244. Strontium, 237. Substitution, Equivalent, 339. Substitutions, 343. Sugar, Boiling in Vacuo, 85. Cane, 360. Grape, 359. from Starch, 358. Wood, 356. Manufacturing, Use of Sul- phurous Acid in, 159. Sulphates, 305. Sulphur, 159. Liver of, 303. Milk of, 304. Sulphurets, 302. Sulphuretted Hydrogen, 214. Sulphuric Acid, 16.2. Effect of, on Wood, 352. Sulphurous Acid, 167. Superphosphate of lime, 318-411. INDEX. 475 Symbols, Calculation of Weights from, 133. Explanation of, 132. T. Tannic Acid, 373. Tanning, Hides, 418. Tar, Wood, 353. Tartar, 367. Tea Kettle, Singing of the, 86. Temperature and Food, Relations of, 426. Equilibrium of, 42. The exact Relation of Pres- sure to, 88. Thermometers, Graduation of, 58. Manufacture of, 57. The Air, 60. Tin, 248. Tissues, Repair of the, 428. Types, Chemical, 339. T. Vaporization, 66. Vapor, Capacity of the Air for, 75. Quantity of, in the Atmos- phere, 69. Quantity of water the Air may contain as, 69. Relations of Air and, 69. Vapors, Conversion of Liquids in- to, 95. Density of, 66. depends on Tem- perature, 67. Elasticity of, 66. Formation of, 66. Transparent, 66. Varnishes, 384. Vegetable Chemistry, 345. Vinegar, Conversion of Alcohol into, 370. Process of Manufacture, 371. Wood, 353. Voltaic Pile, 118. Vulcanized Rubber, 387. W. "Water, Action of, on Lead, 257. Affinity of Potassa for, 288. Capacity of Air for, increased by Heat, 70. Chemical Combinations of, 208. Decomposition of, by Electri- city, 105-115. Hammer, 85. heated by Steam, 95. Proof of the Composition of, 203-204. Quantity of, the Air may con- tain as Vapor, 69. Quantity of, the Pressure of the Air will Sustain, 79. Sea, 297. Theory of the Decomposition of, 105. \ Welding Iron, 243. White Rotten Wood, 351. Window Glass, 320. Wines, 366. Wood, 349. Charred by Sulphuric Acid, 167. Conversion into Gum, 357. Sugar, 356. Y. Yeast, 391, Powders, 393. Yellow, Chrome, 325-400. Z. Zinc, 246. 476 APPARATUS AND MATERIALS. LIST OP CHEMICALS AND APPARATUS REQUIRED FOR THE EX- PERIMENTS DESCRIBED IN THIS WORK. 1 lb. Black Oxide of Manganese J " Bleaching Powders. " Chlorate of Potassa. J Alum. " Sulphur. J " Common Caustic Potash, in Sticks. I " Acetate of Lead, (Sugar of Lead.) 1 " Sulphate of Copper, (Blue Vitriol.) J " Carbonate of Ammonia, (Sal Volatile.) 2 oz. Bichromate of Potash. 2 " Bone Black. 2 " Sulphuret of Iron. 2 " Nitrate of Potash, (Salt Petre.) " Chloride of Ammonium, (Sal Ammoniac.) " Yellow Prussiate of Potash. " Cyanide of Potassium. 14 Oxalic Acid. " Ground Nut Galls. 1 " Phosphorus. 1 " Fluor Spar. 1 " Borax. 1 " Chloride of Barium. 1 " Chloride of Strontium. 1 " Chloride of Mercury, (Corrosive Sublimate.) 1 " Beeswax. 1 " Metallic Antimony 1 " Block Tin. 1 " Bismuth. 2 Mercury, (Quicksilver.) 1 " Arsenious Acid, (Ratsbane.) APPARATUS AND MATERIALS. 477 \ oz. Tartar Emetic. \ " Iodide of Potassium. J " Iodine. " Potassium. J " Solution of Chloride of Platinum. 1 Glass, (4 oz.) Spirit Lamp. Fine platinum foil and wire. 1 doz. assorted test-tubes. ^ sheet blue Litmus Paper. \ " red Litmus Paper. Fine Iron Wire. * Sheet Zinc. * Sheet Copper. * Sulphuric Acid, (Oil of Vitriol.) * Hydrochloric Acid, (Muriatic Acid.) * Nitric Acid, (aqua fortis.) * Alcohol. * Ether. * Clay Pipes and Vials. * Bowls, Tumblers, &c. * Not contained in the box of apparatus and materials put up to accompany this work. XiVKKSITY OF CALIFORNIA LIBRARY THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW DEC NOV 3 1915 JUL 2 MAY IB JAN 30m-6,'14