0L- LIBRARY OF THE UNIVERSITY OF CALIFORNIA. PACIFIC THEOLOGICAL SEMINARY. .84529 Class Book Accession No.' LIBRARY GIFT OF _, '\ "\ ^ FIEST PEINCIPLES or CHE1ISTEY, FOB THE Is* 0f BENJAMIN SILLIMAN. JR.. M.A.. M.D. niOFKSSOR IN TALE COLLEGE OF CHEMISTRY AS APPLIED TO THE ARTS, AND OF MEDIOAC CHEMISTRY AD TOXltJOLOGF IN LOUISVILLE ONITKRSITY. ttf) JTour !3jtg>U.| HUTI'gUjMi^tlirrf Illustrations. \ OF THE UNIVERSITY O. OF S^LiCViE FORTY-EIGHTH EDITION. REWRITTEN AND ENLARGED. PHILADELPHIA: H. C. PECK & THEO. BLISS. 1860. In preparation by Professor Silliman, An Elementary Treatise on Natural Philosophy, for Colleges and Schools. Entered according to the Act of Congress, in the year 1852, by H. G PECK & TIIEO. BLISS, in the Clerk's Office of the District Court of the Eastern Pfotrict ot I'eiinsylvani*. UTOIEOTYPED BT L. JOHNSON A*D OOu PULXTED BT 0. SHMUM. TO FOB IWTY YEARS PROFESSOR OF CHEMISTRY IN YALE COLLEOB, BB8IGNED TO PROMOTE THAT SCIENCE, Tfl WHICH HE HAS DEVOTED HIS LIFE, RESPECTFULLY DEDICATED, THK AUTHOR. ^84529 PREFACE TO THE THIRD REVISED EDITION. DURING the five years -which have passed since the second edition of this work was prepared, intense activity has prevailed in all depart- ments of chemical research. Any attempt to preserve the stereotype plates of that edition in the present was found to he quite impracti- cable. The whole work has been entirely revised, rewritten, and so far rearranged, as experience has shown to he desirable. Some parts have been enlarged, and some have been contracted, so that on the whole the size of the volume remains much as before. A great number of new illustrations have been added, more than doubling the number in the former editions. A considerable number of wood cuts have been taken fromKegnault's excellent Court de Chimie, and many new ones have been drawn from the author's apparatus. Every important fact, formula, and number in the work has been carefully compared with the most recent and valued authorities. The changes made in the atomic weights of element- ary substances, during the last five years, have been numerous and im- portant; and in most cases these changes have added simplicity to the science. The new facts and principles gleaned in no inconsiderable num- bers for this edition, have been woven into the text in suc'a a manner as to present, it is hoped, an uniformity of design. In the Organic Chemistry, greater simplicity and unity has been giver. U> the principles involved in the almost unwieldy mass of facts which have accumulated so rapidly during the last ten years. The author has again to acknowledge his obligations to his friend and former associate, Mr. HUNT, for his lucid and original exposition of this part of the subject. The adoption of this work by many of the first seminaries of learning in this country, is a gratifying evidence to the author that his design has been appreciated ; and he trusts that those who gave their confi- dence to the two first editions, will find the present one, in many import- ant respects, superior to them. NEW HAVEN, September 30, 1852. FROM THE PREFACED THE FIRST EDITION. THE object of this work is sufficiently indicated by its title. It hal grown out of the exigencies of teaching, and has been received as the text-book in the public lectures at Yale College. It is important that a work of this kind should contain only such matter as is actually taught to a class by recitations and lectures. All fulness beyond this is unavailable to either teacher or pupil, and serves often to embarrass the one and discourage the other. This is, perhaps, the reason why several works, otherwise excellent, have failed to answer the purpose for which they were written. The science of Chemistry has now reached the point where its first principles can be presented by the teacher with almost mathematical precision. Chemistry has attractions of an economical and experimental charac- ter, which will always secure for it a place in every system of educa- tion. Without wishing to diminish its claims to attention on these grounds, the author urges the paramount advantages possessed by his favourite science, as a study peculiarly fitted to train the mind to a me- thodized and logical habit of thought. If nothing more is to be derived from its study than the entertainment offered by brilliant phenomena, and a knowledge of convenient economical processes, the pupil will fail of its most important advantage. The beautiful philosophy, the perspi- cuous nomenclature, and lucid method of modern chemistry, are so ob- vious that they cannot fail to awaken the attention of every intelligent pupil, and carry him on his course of intellectual culture with rapid progress. The author has consulted all tha best authorities within his reach, both in the standard systems of England and France, and in the scien- tific journals of this country and Europe. The works of Daniell, Gra- ham, Brande, Kane, Fownes, Gregory, Faraday, Mitscherlich, Berzelius, Dumas, Liebig, and Gerhardt, have all been used, as also the treatises of Dr. Hare and Prof. Silliman. The Organic Chemistry is presented mainly in the order of Liebig in his Traite de Chimie Organique. The author takes pleasure in ac- knowledging the important aid derived in this portion of the work from his friend and professional assistant, Mr. THOMAS S. HUNT, whose familiarity with the philosophy and details of Chemistry, will not fail to make him one of its ablest followers. The labour of compiling the Or- ganic Chemistry has fallen almost solely upon him. If it shall be found to meet the wants of both teachers and pupils, and to promote the progress of Scientific Chemistry in this country, the author will feel that he has not laboured in vain. NEW HAYEK, December 30, 1846. TABLE OF CONTENTS. PART I. PHYSICS. INTRODUCTION Sources of Natural Know- ledge 13 Observation 14 Divisions of Natural Science. 15 MATTER. General Properties of Matter 16 Mechanical Attraction 17 Molecules 18 Three States of Matter Co- hesion 19 Capillary Attraction 21 Exosmose and Endosmose 23 Mechanical Properties of the Atmosphere 23 Air-pumps 24 Law of Mariotte 26 Barometer 28 Weight of Atmosphere 30 Weight and Specific Gravity 31 Hydrometer 33 CRYSTALLIZATION. Nature of Crystallization 36 Polarity of Molecules 37 Crystalline Forms 38 Measurement of Crystals 41 LIGHT. Sources and Nature... 43 Undulations 44 Properties of Light 46 Reflection 47 Simple Refraction 48 Analysis of Light 50 Double Refraction 52 Polarization 53 Chemical Rays 55 Phosphorescence 56 HEAT. Sources 57 Properties 58 Communication of Heat 59 Radiation 60 Conduction 61 Vibrations 62 Convection 65 Transmission of Heat 66 Expansion 69 Thermometer 75 Pyrometer 78 Capacity for Heat 79 Change of State produced by Heat 81 Liquefaction, Latent Heat... 82 Vaporization 85 Boiling 86 Spheroidal State 87 Boiling in vacuo 89 Elevation of Boiling-points by Pressure 90 Steam Engine 92 Evaporation 93 Density of Vapors 94 Dew-point 95 Hygrometers 96 Diffusion and Effusion of Gases 97 Liquefaction and Solidifica- tion of Gases 98 ELECTRICITY 100 Magnetic Electricity, Mag- netism 101 Electrical Machines 107 Statical Electricity 108 Electroscopes 108 CONTENTS. PAGE Theories of Electricity 110 Leyden Jar Ill Electrophorus 113 Galvanism 114 Voltaic Pile 115 Ohm's Law 118 Batteries 120 Smee's Battery 121 Daniell's Battery 122 Grove's Battery 123 Bunsen's Battery 124 Electrical Light 125 PAfll Electro-Magnetism 127 Amperes Theory 128 Electro-Magnets 130 Electromagnetic Telegraph.. 131 Prof. Henry's Discoveries.... 134 Magneto-Electricity 137 Therm^Electricity 139 Animal Electricity 140 Electrochemical Decomposi- tions 142 Faraday's Researches 143 Electrotype 148 PART II. CHEMICAL PHILOSOPHY. ELEMENTS AND THEIR LAWS OP COMBINATION 150 Table of Elementary Bodies 152 Laws of Combination 153 Chemical Nomenclature and Symbols 155 Combination by Volume 161 Specific Heat of Atoms 162 Isomorphism and Dimorph- ism 162 Chemical Affinity 164 PART III. INORGANIC CHEMISTRY. CLASSIFICATION OF ELEMENTS 169 Oxygen 169 Management of Gases 174 Chlorine 176 Compounds of Chlorine with Oxygen 180 Bromine 183 Iodine 184 Fluorine 186 Sulphur 187 Sulphurous Acid 190 Sulphuric Acid 192 Chlorids of Sulphur 187 Selenium 198 Tellurium 199 Nitrogen 199 The Atmosphere 201 Compounds of Oxygen and Nitrogen 203 Nitric Acid 204 Protoxyd of Nitrogen 206 Nitric Oxyd 208 Phosphorus 210 Compounds of Phosphorus with Oxygen 213 Carbon 216 CONTENTS. 9 PA(JE Carbonic Acid 220 Carbonic Oxyd 223 Bisulphuret of Carbon 224 Cyanogen 225 Silicon 227 Silica 228 Fluorid of Silicon 229 Boron 229 Boracic Acid 230 Hydrogen 231 Water 236 Eudiometry 239 Action of Platinum with Hy- drogen and Oxygen 242 Oxybydrogen Blowpipe 244 History of Water 246 Peroxy d of Hydrogen 249 Hydracids 250 Chlorohydric Acid 251 Bromohydric Acid 255 lodohydrio Acid 256 Fluohydric Acid 257 Sulphydric Acid 258 Compounds of Hydrogen with class III 261 Ammonia 262 Phosphuretted Hydrogen 265 Compounds of Hydrogen with the Carbon group 266 Marsh Gas 267 Olefiant Gas 268 Combustion and Structure of Flame 272 Safety Lamp 276 METALLIC ELEMENTS General Properties of Metals 278 Metallic Veins 278 Physical Properties of Metals 280 Chemical Relations of the Metals 283 Salts 285 Potassium 288 Compounds of Potassium 291 Potash 292 Salts of Potash 295 Sodium 300 Caustic Soda, Common Salt.. 301 Sulphate of Soda 302 Carbonate of Soda 304 Nitrate of Soda 305 PAGB Phosphates of St da 306 Borax 307 Lithium 307 Ammonium 308 Compounds of Ammonium... 309 Barium 311 Strontium 313 Calcium 314 Gypsum 316 Carbonate of Lime 317 Magnesium 319 Sulphate of Magnesia 320 Aluminum 321 Alums 322 Silicates of Alumina 323 Manufacture of Glass 323 Pottery 327 Glucinum, Yttrium, Zirco- nium, Thoria 328 Manganese 328 Iron 330 Reduction of. 334 Chromium 336 Nickel 339 Cobalt 340 Zinc 341 Cadmium 342 Lead 343 Uranium 345 Copper 345 Vanadium, Tungsten, Colum- bium, Titanium, and Mo- lybdenum 348 Tin 349 Bismuth 350 Antimony 352 Arsenic 354 Detection of Arsenic in poi- soning 357 Mercury 361 Calomel 364 Salts of Mercury 366 Silver 366 Cupellation 368 Gold 371 Palladium 372 Platinum 373 Iridium, Osmium 375 Rhodium, Ruthenium 376 10 CONTENTS. PART IV. ORGANIC CHEMISTRY. PAGE INTRODUCTION 377 Nature of Organic Bodies.... 377 Laws of Chemical Trans- formations 379 Equivalent Substitution 380 Substitutions by residues 384 Sesqui-salts, Direct Union... 385 On Combination by Volumes 386 Density of Carbon Vapor 386 On the Law of the Divisibility of Formulas 387 On Isomerism 388 On Chemical Homologues.... 389 Temperature of Ebullition... 390 ANALYSIS OP ORGANIC SUB- STANCES 390 Density of Vapors 395 Water 396 Ammonia 397 Carbonic Acid 400 SUGAR, STARCH, AND ALLIED SUBSTANCES 401 Cane, Grape Sugars 401 Sugar of Milk, Mannite 402 Products of the Decomposi- tion of the Sugars 403 The Vinous Fermentation... 403 Lactic Acid 405 Gum 407 Starch 407 Woody Fibre 409 Xyloidine, Pyroxyline, Guri- cotton 411 Transformation of Woody Fibre 412 Destructive Distillation of Wood 413 Kreasote 413 Wood-tar, Paraffin, Coal-tar 414 Petroleum 415 ALCOHOLS, VINOL 415 Action of Acids upon Alcohol 417 Ethers 419 Nitric, Nitrous, Perchloric Ethers 420 Sulphovinic Acid 420 Silicic Ethers, Olefiant Gas... 425 Products of the Oxydation of Alcohol.... .. 426 Chloral, Sulphur Aldehyd 428 Acetic Acid 429 Acetates, Acetate of Potash... 430 Acetate of Lead 431 Acetate of Copper, Chlorace- ticAcid 432 Acetic Ether 433 METHOL 434 Wood-spirit, Pyroxylio Spi- rit, Methylio Alcohol 434 Sulphomethylic Acid 435 Oxydation of Methol 437 AMYLOL, Amylic Alcohol 438 Oxydation of Amylol 439 Spermaceti, Wax 440 GLYCERIDS 441 Soaps, Butyric Acid 442 Phocenine, Enanthylic and Pelargonic Acids 443 Oleine, Palmatine, Marga- rine, Stearine 444 Fatty Acids 446 ALKALOIDS OP ALCOHOL SERIES 448 Ethamine, Methamine, Amy- lamine 449 Triethamine 450 BITTER-ALMOND OIL 452 Benzoilol 452 Chlorinized Benzoilol, Hy- drobenzamide 453 Benzoic Acid 454 Benzen 455 SALIC YLOL 458 OTHER ESSENTIAL OILS 459 Oil of Cinnamon 459 Oil of Turpentine 459 Oils of Juniper, Pepper, Ca- raway, Parsley, meeting at the proper interval, (a,) will produce a beam of double intensity ; but if they meet at the half interval of vibration, darkness results. This j, io . 56 is interference of light. In mo- ther of pearl and many other natural bodies, a beautiful play of colors is seen. The microscope reveals on such sur- When are waves made double, and when set at rest? 58. Illustrate the interference of waves of sound in figs. 54 and 55. What of thermo- electricity ? 59. Describe the interference of light from fig. 56. 46 LIGHT. faces delicate grooves and ridges, and these are at such dis- tances as to produce interference in the light-waves, result- ing in partial obscuration and partial decomposition. The same effect is artificially produced in medal-ruling. This irised effect can be transferred by pressure or copied by the electrotype, or even on wax. 60. The transverse vibrations of a ray of light distinguish this from all other modes of undulation or vibration. Dr. Bird illustrates this by fig. 57, which represents a spherical particle of ether alternately extended and depressed at its poles and equator, oscilla- ting, or trembling, rather than undulating. Thus, each particle in turn communicates the Fig. 57. i m p u l s e which it receives, and yet the centre of each may remain unmoved from its place ; as motion in a series of ivory balls causes only the termi- nal one to swing, the intermediate ones remaining unmoved. In light-waves, the vibration or pendulation of each particle is perpendicular to the path of the ray ; and yet the alternate effect of the movements of contiguous particles will produce a progressive vibration. Thus, in fig. WaQ(Q\O) ' 58 > A B C D may represent particles of A" B c ii ether in the path of a ray of light, the Fig. 58. phases of elevation in A and C and those of depression in B and D being coincident. The fact of the vibrations of light-ether being transverse to the path of the ray was first observed by Fres- nel. These vibrations are conceived to occur in any or every transverse plane. Leaving these interesting generalizations, we must briefly recapitulate the well-established 61. Properties of Light. 1st. Light is sent forth in rays in all directions from all luminous bodies. 2d. Bodies not themselves luminous become visible by the light falling on them from other luminous bodies. 3d. The light which pro- ceeds from all bodies has the color of the body from which it comes, although the sun sends forth only white light. 4th. Light consists of separate parts independent of each other. 5th. Rays of light proceed in straight lines. 6th. Light moves with a wonderful velocity, which has been computed What instances are named from nature ? 60. What are transverse vi- brations in light? How is the undulation thus produced? What i? said of progressive motion ? 61. Enumerate six properties of light. REFLECTION. 47 by astronomical observations to be at least one hundred and ninety-five thousands of miles in a second of time. This velocity is so wonderful as to surpass our comprehension, Herschel says of it, that a wink of the eye, or a single motion of the leg of a swift runner, or flap of the wing of the swiftest bird, occupies more time than the passage of a ray of light around the globe. A cannon-ball at its utmost speed would require at least seventeen years to reach the sun, while light comes over the same distance in about eight minutes. 62. When a ray of light falls on the surface of any body, several things may happen. 1st. It may be absorbed and disappear altogether, as is the case when it falls on a black and dull surface. 2d. It may be nearly all reflected, as from some polished surfaces. 3d. It may pass through or be trans- mitted ; and, 4th. It may be partly absorbed, partly reflected, and partly transmitted. All bodies are either luminous, transparent, or opake. Bodies are said to be opake when they intercept all light, and transparent when they permit it to pass through them. But no body is either perfectly opake or entirely transparent, and we see these properties in every possible degree of difference. Metals, which are among the most opake bodies, become partly transparent when rnado very thin, as may be seen in gold-leaf on glass, which trans- mits a greenish-purple light, and in quicksilver, which gives by transmitted light a blue color slightly tinged with purple. On the other hand, glass and all other transparent bodies arrest the progress of more or less light. 63. Reflection. Light is reflected according to a very simple law. In fig. 59, if the ray of light fall from P' to P, it is thrown directly back to , P'; for this reason, a person looking into a common mirror sees himself correctly, but his image appears to be as far behind the mirror as he is in front of it. The line P P' is called the normal. If the ray fall from R to P, it will be reflected to R', and if from r, then it will go in the line /, and so for any other point, Illustrate its velocity. 62. What happens to incident light ? How are bodies divided in respect to light? Give illustrations of imperfect opacity. 63. What is the law of reflection ? What is the normal ? 48 LIGHT. [f we measure the angles RPP' and P'PR', we shall find them equal to each other, and so also the angles r P P' and P' P /. These angles are called respectively the angles of incidence and reflection. We therefore state that the angle of incidence is equal to the angle of reflection, which is the law of simple reflection. This law is as true of curved sur- faces as it is of planes ; for a curved surface (as a concave metallic mirror) is considered as made up of an infinite number of small planes. 64. Simple Refraction. If a ray of light falls perpendi- cularly on any transparent or uncrystallized surface, as glass or water, it is partiy reflected, partly scattered in all direc- tions, (which part renders the object visible,) and partly trans- mitted in the same direction from - ^ ___^i which it comes. If, however, the '^V llf light come in any other than a ^ = ~ 1T ~^ ^ perpendicular or vertical direction, as from R to A, on the surface of a thick slip of glass, as in fig. 60, it will not pass the glass in the line RAB, but will be bent or refracted at A, to C. As it leaves the glass at C, it again travels in Fig. 60. a direction parallel to R A, its first course. Refraction, then, is the change of direction which a ray of light suffers on passing from a rarer to a denser medium, and the reverse. In passing from a rarer to a denser medium, (as from air to glass or water,) the ray is bent or refracted toward a line perpendicular to that point of the surface on which the light falls; and from a denser to a rarer medium the law is reversed. A common experiment, in illustration of this law, is to place a coin in the bottom of a bowl, so situated that the observer cannot see the coin until water is poured into the vessel ] the coin then becomes visible, because the ray of light passing out of the water from the coin is bent toward What is the angle of incidence ? What of reflection ? What is true of curved surfaces? 64. What is refraction? Demonstrate the law by fig. 60. Which way is the ray bent ? Give a familiar illustration of refraction. THE PRISM. 49 the eye. In the same manner, a straight stick thrust into water appears bent at an angle where it enters the water. 65. Index of Refraction. The obliquity of the ray to, the refracting medium determines the amount of refraction. The more obliquely the ray falls on the surface, the greater the amount of refraction. A little modification of the last figure will make this clear. Let R A (fig. 61) be a beam of light falling on a refracting medium : it is bent as before to E/. If we draw a circle about A as a centre, and let fall the line a a, from the point a, where the circle cuts the ray R, and at right angles to the normal A' A, the line a a is called the sine of the angle of incidence ; while the line a! a' is called the sine of Fig. 61. the anyle of refraction. If a more oblique ray r cuts the circle at b, the line b b will be longer than the line a a, inasmuch as the angle b A a is greater than the angle a A a. The line measuring the obliquity before refraction, when the ray passes into a denser medium, is always greater than that which measures it after. The ratio of these lines ex- presses the refractive power of the medium. This is called the index of refraction. In rain water the ratio of these lines is as 529 : 396 or 1-31 ; in crown glass it is as 31 : 20 or 1-55; in flint glass 1-616, and in the diamond 243. 66. Substances of an inflammable nature, or rich in carbon, and those which are dense, have, as a general thing, a higher refracting power than others. Sir Isaac Newton observed that the diamond and water had both high refracting powers, and he sagaciously foretold the fact, which chemis- try has since proved, that both these substances had a com- bustible base, or were of an inflammable nature. 67. Prism. In the cases of simple refraction just ex- plained, the ray, after leaving the refracting medium, goes on in a course parallel to its original direction, because the 65. What is the index of refraction ? Demonstrate this from fig. 61. 66. What substances have highest refraction ? What was Newton'^ sug- gestion about the diamond ? 50 LIGHT. Fig. 62. ,R' two surfaces of the medium are pa- rallel. If, however, the surfaces of the refracting medium are not parallel, the ray, on leaving the second sur- face, will be permanently diverted from its original path. , The com- mon triangular glass prism (fig. 62) illustrates this. As already explained, the ray R is bent toward the normal in media more dense than air. But in tho prism the emergent ray R is, by the same law, still farther refracted in the direction R'. By altering the form of the surfaces, we may thus send the ray in almost any direction, as in the common multiplying-glass, which gives as many images as it has surfaces of reflection. In this way it is that concave metallic mirrors concentrate, and convex ones disperse a beam of light. Fig. 63 shows the prism conveniently mounted for use. __ Analysis of Light. By means of the prism, p- 63 Sir Isaac Newton demonstrated the compound na- ture of white light, such as reaches us in the ordi- nary sunbeam. In fig. 64 a pencil of rays from R, fall- ing from a small circular aperture in the shutter of a darkened room on a common trian- gular prism, is refracted twice, and bent upward toward the white screen R', placed at some distance from the prism, where it forms an oblong colored image, composed of seven colors. This image is called the prismatic or solar spectrum. The spectrum has the same width as the aperture admit- ting the beam of light, but its length is greatly increased be- yond its diameter, the ends retaining the rounded form of the opening. This image or spectrum presents the most beautiful series of colors, exquisitely blended, and each pos- sessing a degree of intensity, splendor, and purity far ex- ceedingly the colors of the most brilliant natural bodies. These colors are not separated by distinct lines, but seem to 64 - 67. How is light refracted by surfaces not parallel. What is tho prism 1 PRISMATIC COLORS. 51 SOLAR SPECTRUM. melt into one another, so that it is impossible to say where one ends and the next begins. The light from flames of all kinds, the oxy-hydrogen blowpipe, and the electric spark, or galvanic light, is also compound in its nature, like that of the sun and other ce- lestial bodies. 69. Prismatic Colors. The colors of the solar spectrum are in the following order, reading upward : red, orange, yel- low, green, blue, indigo, violet. These colors are of very different refrangibility, and for this reason are presented in a broad and blended surface, the red being the least refracted, and the violet the most. The seven colors of Newton, it is believed, are really composed of the three primitive ones, red, yellow, and blue. This idea is well expressed in the following diagram, (fig. 65.) The three primitive colors each attain their greatest intensity in the spectrum at the points marked at the summit of the curves; while the four other co- lors, violet, indigo, green, and orange, are the result of a mixture, in the spectrum, of the first three. A portion of proper white light is also found in all parts of the spectrum, which cannot be separated by refraction. We may hence infer that there is a portion of each color in every part of the spectrum, but that each is most intense at the points where it appears strongest. The light is most intense in the yellow portion, and fades toward each end of the spectrum. Sir John Herschel has detected rays of greater refrangibi- lity than the violet of the spectrum and are beyond it, which have a lavender color. They have this color after concen- tration, and are therefore not merely, as might be supposed, dilute violet rays. If the spectrum is formed by a beam of light passing through a slit not over -Mh of an inch in width, the image 65 ' 68. Describe the analysis of light. What is the image called ? What is the form of the spectrum? How are the colors arranged? Describe the blending of the colors from fig. 65. What is lavender light? 52 LIOIIT. will be crossed by a great number of dark lines, which al- ways appear in the same relative position. They are called the fixed lines of the spectrum, and are much referred to as boundary lines in optical descriptions. 70. Each of the prismatic colors has some other, which blended with it produces white light, and hence is called its complementary color. Let indigo be regarded as a deeper blue, and each of the three primary colors has its secondary colors. Fig. 65 shows the three primary tints blending to Fig.65(4i.) f orm w hite light at the centre: at the other parts the complementary colors are opposite to each other, c. g. red and green, blue and yellow. 71. Double refraction of light is a phenomenon ob- served in many crystalline transparent bodies, and is due to their peculiar structure. It is also seen in bone, shell, horn, and other similar substances. The beam of light in passing through such bodies is split into two portions, each of which gives its own image of any object seen through the doubly refracting substance. In calcite, carbonate of lime, or Ice- land-spar, this phenomenon is beautifully seen. A sharp line, like p q, fig. 66, when seen through a rhomb of calc- spar, in the direction of the ray 11 r, will seem to be double, a second parallel line m n, being seen at a short distance from it, and the dot o will have its fellow e. In this 66m case the light is represented as com- ing from II to TJ and, passing through the crystal, it is split and emerges in two beams at e and o. The same effect would be produced if the light fell so as to strike any part of the imaginary plane A C B D, which divides the crystal diagonally and is called its principal section. The axis or line drawn from A to B is contained in this plane. But if we look through the crystal in a direction parallel to this plane (A C B D) there is only simple refraction, and only one line is seen. One of these beams is called the ordinary and the other the extraordinary ray. In the case of crys- tallized minerals, this result is due to the naturally unequal What lines are seen in the spectrum? 70. What of the colors of na- tural bodies ? 71. What is double refraction ? Describe fig. 66. What is the ordinary ray? Which the extraordinary? What relation has this phenomenon to crystallization? POLARIZATION. 53 elasticities of the molecules in the crystals and it is ob- served only in those minerals whose molecules are ellipsoidal and is wanting in those, like fluor-spar, &c., which belong to the cube and its derivatives, in which the molecules are spherical. In well annealed glass, by mechanical pressure, a sufficient separation of the two rays may be produced to cause color by interference, though not enough to cause two images 72. Polarization. The light which has passed one crys- tal of Iceland-spar by extraordinary refraction is no longer affected like common light. If we attempt to pass it through another crystal of the same substance, there will be no fur- ther subdivision, and only a greater separation of the two beams. This peculiarity of the extraordinary ray is called polarization. This interesting phenomenon was accident- ally discovered in 1808 by Malus, while looking through a doubly-refracting prism at the light of the setting sun, reflected from the surface of a glazed door standing at an angle of about 56 45', which is the angle at which glass polarizes light by reflection. It is the peculiarity of light which has been polarized that it will no longer pass through certain substances which are transparent to common light. Many crystalline sub- stances possess the power of polarizing light. The mineral called tourmaline has this property in a remarkable degree. The internal structure of this mineral is such that a ray of light which has passed through a thin plate of it cannot puss through a second, if it is placed in a position at right angles with the first. For example, in the annexed figure (67) we have two R thin plates of tour- maline placed pa- rallel to each other in the same direc- tion. A ray of Fig. 67. light passes through both, in the direction of R R/, and apparently suffers no change : if, however, these plates are so placed as to cross each other at right angles, as in fig. 68, the ray of light 72. What is polarization ? Who discovered this phenomenon ? What ia the peculiarity of jiolarized light? Illustrate this from tho tourmaline. 54 LIGHT, is totally extinguished ; and two such points may be found in revolving one of the plates about the ray as an axis. 73. For illustration, we may suppose the structure of this mineral to be such that a ray of light can pass between the ranges of particles in jne direction only, as a flat blade may pass - between the wires of a bird- \ cage, fig. 69, if placed pa- \ rallel to them; but will be Fig. 69. ^ \ arrested by the bars, if presented at right angles to the wires. Light is polarized in many ways, as, for example, by passing through a bundle of plates of thin glass or of mica, as in fig. 70, by reflection from the surface of unsilvered glass, of a polished table and of most polished non-metallic surfaces, and at a particular angle for each. This is plane polarized light. 74. The beautiful phe- nomenon of circular and elliptic polarization is seen in many crystalline bodies. Plates of quartz, a mineral having one axis, show the prismatic co- lors, when viewed by po- larized light, arranged in circles and a cross, as in fig. 71; and by the revolution of the plane of polarization through 90, the colors are changed, and a light cross (fig. 71) occupies the plane of the dark one. Nitre gives two axes of polarization, which in the revolution of the plane show the changes seen in figures 73 and 74. Uniaxial crystals uniformly give circular, and binaxial ones Fig. 72. ^ Fig. 73. elliptical figures Fig. 74. When is the ray extinguished ? 73. How is this phenomenon explained in reference to the structure of the crystal? In what ways is light po- larized? 74. What crystalline bodies give circular, and what elliptical polarization? Illustrate this from quartz and nitre. LIGHT. 55 75. The chemical power of the sun's rays is seen in the blackening of chlorid of silver, which Scheele long ago observed to take place much more rapidly in the violet ray than in any other part of the solar spectrum. It was afterward observed by Hitter that this blackening likewise occurred beyond the violet ray, apparently in the dark. The researches of Neipce, Daguerre, and others, have greatly enlarged the boundaries of our knowledge on thia subject, and given to the world the elegant arts of the daguerreotype and photography. The darkening of metallic salts by light is owing to a peculiar class of rays in the spectrum, called by Dr. Herschel the chemical rays, which are diffused indeed in all parts of the spectrum, but which are concentrated with more power beyond the violet. This influence has also been variously denominated actinism, energia, and tithonicity. 76. The accompanying diagram (fig. 75) will enable the student to comprehend this subject as at present understood. From A to B we have the solar spectrum, with the colors in the same order as already described. The cl emical power is greatest at the violet, and the greatest heat at the red ray. At b another red ray is discovered, and at a is the lavender light. The luminous effects are shown IXDIG0 by the curved line C, the maxi- BLUE, '. . mum of light being found at GREEN, . the yellow ray. The point of greatest heat is at D, beyond the red ray, and it gradually declines to the violet end, where it is entirely wanting, the other limit of heat being at c. The chemical powers are greatest about E, in the limits of the violet, and gra- dually extend to d, where they arc lost. They disappear also LAVENDER, EXTREME RE1>, 6 : ~i- Fig. 75. 75. What is the chemical power of the sunbeam ? 76. Ulustrata th relations of the chemical and other rays, from fig. 75. 56 PHOSPHORESCENCE. entirely at C ; the yellow ray, which is neutral in this re- spect, attains another point of considerable power at F, in the red ray, which gives its own color to photographic pic- tures, and disappears entirely at e. The points D, C, E, there- fore represent respectively the three distinct phenomena of Heat, Light, and Chemical Power. This last is. believed to be quite independent of the other powers; for all light may be removed from the spectrum by passing it through blue solutions, and yet the chemical power remains unaltered. 77. It will readily be perceived that these phenomena connected with the sunbeam exert no inconsiderable or unimportant influence in the order of events, whether as connected with the development of life on our planet, or with those great physical changes which depend on the calorific and magnetic agencies that seem inseparably con- nected with the light and heat of the sun. Plants can decompose carbonic acid and carry on the functions of nutrition only under the power of solar light; and the yellow ray has been shown by Dr. Draper to be the one by whose agency this change is effected in the vegetable kingdom. 78. Phosphorescence is a property possessed by some bodies of emitting a feeble light, often at ordinary temperatures. The diamond and some other substances, after being exposed to the rays of the sun, will emit light for some time in the dark. Fluor-spar, feld-spar, and some other minerals, give out a fine light of varied hues, when gently heated or scratched. Oyster-shells which have been calcined with sulphur and exposed to the sunlight, will shine in a dark place for a considerable time afterward, and even an electrical spark will renew this emanation. The glow-worm, the fire- fly, rotten wood, decaying fish, and various marine animals possess the same power, although in these cases the cause is probably different from that which excites the same pheno- menon in crystallized bodies. 77. What consequences follow the phenomena described? 78. What il phosphorescence ? HEAT. 57 III. HEAT. Sources and Properties of Heat. 79. THE phenomena of Heat, or Caloric, are eminenly interesting to the chemical student. They may be discussed under two general divisions: 1. The Physical; and, 2. The Chemical. Under the first head are included the communi- cation of heat, by radiation, by conduction, and convection; the transmission of heat by various substances, and the phenomena of expansion, including thermometers and pyro- meters ; and lastly, specific heat. Under the second head are placed the changes produced by heat in the states of bodies ; for example, liquefaction and latent heat of liquids, vapor- ization and latent heat of vapors, liquefaction of gases, natural evaporation and congelation, density of vapors, and so forth. 80. The sources of licat are chiefly the sun, combustion, and chemical changes; friction, electricity, vitality; and, lastly, terrestrial radiation. Solar heat, as is well known, accompanies the sun's light, and it unquestionably results from the intensely high tem- perature of the sun itself. It is believed that the sun's rays do not heat the regions of space, and the earth's atmosphere is heated almost entirely by contact with the surface of the heated earth. A portion of the sun's heat is however taken up by the air before the rays reach the earth. Combustion and chemical change, including vital heat, are sources of heat, limited by the quantity of matter suffer- ing change, and to the time in which the change takes place. The stores of fossil fuel laid up in the coal formations and the vegetable combustibles now on the earth's surface may be considered as a result of the sun's action through the powers of vegetable life. Friction causes heat, as a result of mechanical motion. The heat of friction continues as long as the mechanical power required to produce motion is maintained. No change of state or loss of weight is necessarily experienced 79. What is said of heat? How is the subject discussed? 80. What arc the sources of heat ? What of solar heat ? What of combustion ? What of friction? 58 HEAT. ill the substances employed. Count Rumford showed that in the boring of cannon under water, the heat evolved was so considerable as to bring the water, in a short time, to the boiling-point. The same observer succeeded in warming a large building by the heat evolved from the constant move- ment of large plates of cast-iron upon each other. Friction- heat may be regarded as the equivalent of the motion pro- ducing it. The heat of the electrical spark and of the galvanic current will be considered elsewhere. 81. Terrestrial radiation is a constant source of heat, escaping from the interior of the earth, and has doubtless some effect in modifying the climate of our globe. Geolo- gists consider it proved that the earth has cooled to its pre- sent condition from a state of intense ignition, and that this state still remains in the interior, at no very considerable distance from the surface. All deep mines and Artesian wells show a constant and progressive increase of temperature in going down, and below the line of atmospheric influence. The Artesian well in the yard of the great Grenelle slaughter- house, in Paris, is 2000 feet deep, and the water rises with a temperature of 85 degrees Fahrenheit. At Neusalzwerke, in Westphalia, is a well 2200 feet deep, and its water has a temperature of 91. The average increase of temperature from this cause is estimated to be 18, for every hundred feet of descent. Assuming this ratio, we shall have at two miles the boiling-point of water ; and at about twenty-three miles, or only T g^th of the earth's radius, there must be a temperature of near 2200 degrees of Fahrenheit. At this heat, cast-iron melts, and trap, basalt, obsidian, and other rocks are perfectly fluid. The geological importance of these facts is self-evident ; and we cannot fail to remark here an efficient cause for all hot-springs. 82. Properties of Heat. Heat is invisible and impon- derable. It proceeds, like light, in rays, with great but hitherto undetermined velocity. The intensity of heat-rays varies inversely as the square of the distance . from the source of heat. Rays of heat, like those of light, may be concentrated from a metallic mirror, but not from those of glass, as this substance absorbs heat very largely. They are 81. What is said of terrestrial radiation? What is determined in deep wells? What is the rate of increase ? At what depth would iron rnelt? S2. What are the properties of heat? How is it like light? COMMUNICATION OF HEAT. 59 also of various refrangibility, and capable of double refrac- tion and polarization. Therefore, they move in waves 01 undulations. Heat is self-repellant, as two bodies heated in vacuo repel each other. It is communicated by conduction and by convection as well as by radiation. It is variously absorbed and transmitted by various substances, and pro- duces different degrees of expansion, varying with the nature of matter affected. Lastly, it determines the phenomena of congelation, liquefaction, and vaporization. The physio- logical sensation of cold and heat experienced in our per- sons is not to be confounded with the physical and chemical phenomena of heat now to be discussed. This sensation is, within certain limits, entirely relative. For example, if one hand is plunged in a vessel of iced-water and the other into moderately warm water, a strong contrast is evident imme- diately ; but if we suddenly transfer both hands to a third vessel of water, at the common temperature, our sensations are instantly reversed. The third vessel is warm as com- pared with ice-water, and cold compared with the tepid water. Communication of Heat. 83. Heat is communicated from a hot body, 1. By radia- tion, or transmission of rays of heat in all directions ; 2. By contact of the atmosphere conveying it away, (convec- tion;) and, 3. By communication to the substance support- ing it, (conduction.) By one or all these modes, a body placed in vacuo or in the air, and differing in temperature from surrounding bodies, gradually regains the equilibrium of temperature. If hot, it loses, and surrounding bodies gain ; if cold, it gains at the expense of those substances having a higher temperature. 84. Radiation takes place from all bodies wherever there is a disturbance of equilibrium, but in very various degrees, according to the nature of the body and of its surface. All bodies have a specific radiating and absorbing power in respect to heat. To these the retaining and reflecting powers are strictly opposed. Radiation takes place in a vacuum more easily than in air, and is, therefore, quite What is said of the sense of heat and cold ? Give an illustration. 83. How is boat communicated ? 84. How does radiation happen ? 60 HEAT. Fig. 76. independent of any conducting medium. Rays of heat may be concentrated by the parabolic metallic mirror. All rays of heat or light falling on this form of mirror are collected at F, the focus, (fig. 76,) and a hot body placed there will have its rays sent forth in parallel straight lines, as shown in the figure. A second and similar mirror may be so placed as to receive and collect in a focus all the rays proceeding from any body in the focus of the other, where they will become evident by their effect on the thermometer. If the hot body be a red-hot cannon-ball, and the mirrors are carefully adjusted, so as to be exactly opposite each other in the same line, the accumu- lation of heat in the focus of the second mirror is such as to inflame dry tinder, or gunpowder, even at many feet distance. 85. This striking experiment is shown by the conjugate mirrors, arranged as in fig. 77. Ice placed in the focus of one of the mirrors will de- press a thermometer in the other focus, not because cold is ^^^ radiated, (as cold is o mere negation,) but because in this case the thermometer is the hot body and parts with its heat to fuse the ice. A thermometer sus- pended midway between the two mirrors is not affected. A plate of glass held between the mirrors will cut off the calorific rays thus proving a difference of penetrating power be- tween the rays of heat and of those of light. As soon aa the screen is raised the phosphorus in the focus is inflamed. 86. Radiation and Absorption of heat are exactly equal to each other in a given ' surface, but, as before stated, the nature of the substance and of the surface have much influence in these respects. All black and dull surfaces ab- sorb heat very rapidly when exposed to its action, and part How does a metallic mirror affect heat? 85. Describe the experiment in fig. 77. 86. What of absorption? Hovr does color affect it? CONDUCTION OF HEAT 61 with it again by secondary radiation. The sun shining on a person dressed in black is felt with much more power than if he were dressed in white. The former color rapidly absorbs heat, while from the latter a considerable part of it is reflected. The color of bodies has, however, nothing to do with their radiating powers, and one colored cloth is as warm in winter as another, as regards the emission of heat. (Bache.) If the radiating power of a surface covered with lamp- black be assumed as 100, that of a surface covered with Indian ink will be 88, with ice 85, with graphite 75, with dull lead 45, with polished lead 19, with polished iron 15, with polished tin, copper, silver, or gold, 12. (Leslie.) Hence the polished metallic vessel, which is so well adapted to retain the heat of boiling water, is the very worst vessel in which to attempt to boil it. The sooty surface next the fire, however, transmits heat with the greatest rapidity. In the experiment with the mirrors just described, the polished surfaces remain cool, reflecting nearly all the heat which falls upon them. A glass mirror in the same experiment would be useless, as glass absorbs nearly all the heat, of low intensity, which falls upon it. 87. The formation of dew is owing to radiation, cooling the surface of the earth so rapidly, that the moisture of the air, which is always abundant in summer, is condensed upon it : as we see it on the outside of a tumbler of iced-water in a hot day. Radiation takes place more rapidly from the surface of grass and vegetation than from dry stones or dusty roads : for this reason, plants receive abundant dew, while the barren sand has none. 88. Conduction of heat. A metallic bar placed by one end in the fire, slowly becomes hot, the heat being trans- mitted by conduction from particle to particle. Each so- lid has its own peculiar rate of conducting heat, but in all it is a progressive operation, the heat seeming to travel with greater or less rapidity, according to the nature of the solid. If we hold a pipe-stem or glass rod in the flame of a spirit-lamp or candle, we can heat it to redness within an inch of our fingers without inconvenience ; but a wire of silver or copper held in the same manner soon be- Give some results of radiation from different substances. 87. How U dew formed ? 88. What is conduction ? Why does it fall on plants ? 62 HEAT. comes too hot to hold. This is owing to an inherent dif- ference in these solids, which we call conducting power. The . ] progress of conducted 6 heat in a solid is easi- ly shown, as in fig. 78, representing a rod of copper, to which are stuck by wax several marbles at equal distances ; one end is held over a lamp, and the marbles drop off, one by one, as the heat melts the wax; that nearest the lamp falling first, and so on. If the rod is of copper, they all fall off very soon ; but if a rod of lead or platinum is used, the heat is conveyed much more slowly. Little cones of various metals and other substances may be tipped with wax or bits of phosphorus, as shown in fig. 79, and placed on a hot surface. The wax will melt, or the phosphorus inflame, at different times, according to the conducting ' power of the various solids. A screen is needed to cut off the radiant heat, which would otherwise in- flame the phosphorus prematurely. Accurate experiments have been made, which have enabled us to arrange most so- lids in a table showing their conducting powers. The metals, as a class, are good conductors, while wood, charcoal, fire-clay, and similar bodies are bad ones. Thus gold is the best con- ductor, and may be represented by the number 1000 ; then marble will be 23-5, porcelain 12, and fire-clay 11. Metals, compared with each other, are very different in conducting power. Thus Gold 1000 Silver 973 Copper 898 Platinum 381 Iron 375 Zinc 363 Tin 304 Lead ... ,...180 89. Vibrations occur in masses of metals and other sub- stances when conducting heat, which seem to indicate the production of waves or undulations among the particles. Mr. Trevellyan has remarked that if a mass of warm brass is placed on a support of cold lead, the rounded surface of What is its rate in different substances ? 89. How is an undulation proved to exist in heated bodies ? Mention Trevellyan and Page's ex- periments. CONDUCTION OF HEAT. 63 the brass resting on the flat surface of the lead, the brass bar is thrown into a series of vibrations, accompanied by a distinct sound and a rocking motion, of the brass, until equilibrium is restored. Dr. Page has shown that a current of galvanic electricity passed through a similar apparatus produces the same results. Fig. 80 shows Page's apparatus, in which a feeble current of electri- city produces a rocking motion of the metallic masses resting on the bars of brass. The best effects are Fig. 80. produced between good and bad conductors of heat, the former being the hot bodies. 90. Heat is conducted in crystallized bodies, in curves springing from the sources of heat. In plates of homoge- neous substances these curves are circles ; in those of a crys- talline texture, belonging to the rhombohedral system, the curves are ellipses of very exact form, whose longer axes are in the direction of the major crystalline axis proving the conducting power of such bodies to be greatest in that direc- tion. The mode of experimenting in such cases is to cover the surface of the crystalline plate with wax, heat very gra- dually, and watch the lines of fusion on the surface. 91. The sense of touch gives us a good idea of the dif- ferent conducting power of various solids. All the articles in an apartment have nearly the same temperature ; but if we lay our hand on a wooden table, the sensation is very dif- ferent from that which we feel on touching the marble mantel or the metal door-knob. The carpet will give us still a different sensation. The marble feels cold, because it rapidly conducts away the heat from the hand ; while the carpet, being a very bad conductor, retains and accumulates the heat, and thus feels warm. Clothing is not itself warm, but, being a bad conductor, retains the heat of the body. A film of confined air, is one of the worst conductors; loose clothes are therefore warmer than those which fit closely. For the same reason, porous bodies, like charcoal, are bad conductors ; and a wooden handle enables us to manage hot bodies with ease. 92. The conducting power of fluids is very small. A 90. How is heat conducted in crystals? 91. What does touch inform us of ? 92. What of the conducting power of fluids ? 64 HEAT, simple and instructive experiment will prove this satis- factorily. A glass, like that in fig. SI, is filled nearly to the brim with water. A thermometer-tube, with a large ball, is so arranged within it that the ball is just covered with the water : the stem passes out at the bottom through a tight cork, and has a little colored fluid, L, in it, which will, of course, move with any change of bulk in the air contained in the ball. Thus arranged, a pointer I marks exactly the position of one of the drops of enclosed fluid, when a little ether is poured on the surface of the water, and set on fire. The flame is intensely hot, and rests on the surface of the water j the column of fluid at I is, however, unmoved, which would not be the case if any sensible quantity of heat had been imparted to the water. The warmth of the hand touching the ball will at once move the fluid at I, by expanding the air within. By heat- ing a vessel of water on the top, then, , we should never succeed in creating any thing more than a superficial elevation of temperature : at a small depth the Fig. 81. water would remain cold. Liquids do possess a very low conducting power, contrary to the opinion of Count llumford, and heat appears to be propagated in them by the same law as in solids, when care is taken to avoid the production of currents. 93. The conducting power of gases is also very small. Heat travels with extreme slowness through a confined portion of air. This is a very different thing from the con- vection of heat in gases, which we will presently explain. Double windows and doors, and furring (so called) of plas- tered walls, afford excellent illustrations of the slow con- duction of heat through confined air. We have no proof that heat can be conducted in any degree by gases and va Explain the experiment, fig. 81. What of the conducting power of gases? CONVECTION OF HEAT. 65 pors. To illustrate the relative conducting powers of solids, fluids, and gases : if we touch a rod of metal heated to 120, we shall be severely burned ; water at 150 will not scald, if we keep the hand still, and the heat is gradually raised ; while air at 300 has been often endured without injury. The oven-girls of Germany, clad in thick socks of woollen, to protect the feet, enter ovens without inconvenience whero all kinds of culinary operations are going on, at a tempera- ture above 300 ; although the touch of any metallic article while there would severely burn them. 94. Convection of heat is its transportation, as in liquids and gases, by the power of currents. Heat applied from beneath to a vessel containing water, warms the layer or film of particles in contact with the vessel. These expand with the heat, and consequently, becoming lighter, rise, and colder particles supply their place, which also rise in turn, and so the whole contents of the vessel come in quick succession into con- tact with the source of heat, and convey it through the mass. This is well illustrated in fig. 82, which shows how water acts in a vessel of glass, when heated at a point be- neath by a spirit-lamp. Each par- ticle in turn comes under the in- fluence of heat, because of the per- fect mobility of the fluid. A series of such currents exists in every vessel in which water is boiled, and they are rendered more evident by throwing into it a few grains of some solid (like amber) so nearly of the same gravity of water that it will rise and fall with the currents. 95. In the air, and in all gases and vapors, the same thing happens. The earth is heated by the sun's rays, and the film of air resting on the heated surface rises, to be re- placed by cold air. The rarefied air may be easily seen, on a hot day, rising from the surface of the earth, being made Fig. 82. 94, What is convection ? Illustrate it in water. 95. How is heat distri outed in air. 5 66 HEAT. visible \>'j its different refractive power. Hence arise many aerial currents and winds. The currents of the ocean aro also influenced by the same cause. Transmission of Seat. 96. Light passes through all transparent bodies alike, from what source soever it may come. The rays of heat from the sun also, like the rays of light from the same lu- minary, pass through transparent substances with little change or loss. Radiant heat, however, from terrestrial sources, whether luminous or not, is in a great measure ar- rested by many transparent substances. If the sun's rays be concentrated by a metallic mirror, the heat accompanying them is so intense at the focus as to fuse copper and silver with ease. A pane of colorless window-glass interposed between the mirror and the fpcus, will not stop any considerable part of the heat. If the same mirror is presented to any other source of heat, however, (as, for example, to the red-hot ball, 85,) the glass plate will stop nearly all the heat, although the light is undiminished. We thus distinguish two sorts of calorific rays, which are sometimes called Solar and Culinary Heat; and we discover that substances transparent to light are not, so to speak, transparent to heat in a like degree. This property is distinguished from transparency by the term Diathermancy, (meaning the easy transmission of heat.) It appears that many substances are eminently diathermous, which are almost opake to light; like smoky quartz, for example. The temperature of the source of heat has the greatest influence on the number of rays of heat which are transmitted by a given screen ; as in the case of the glass plate, which permits nearly all the sun's rays to pass, but arrests over 65 per cent, of the rays from a lamp-flame. 97. Our knowledge on this subject has been derived almost entirely from the researches of M. Melloni, of Naples. This philosopher, by the use of a peculiar apparatus, called the thermo-electric pile, was able to detect differences of tempera- ture altogether inappreciable by common thermometers. This instrument is an arrangement of little bars of the two metals, 96. Distinguish transmission of heat from that Qf light. What ij diathermancy ? What was Melloni's research ? TRANSMISSION OP HEAT. 67 Fig. 83. antimony and bismuth, about fifty of which are sol- dered together by their alternate ends, the whole being, with its case, not more than 2 inches long, by to i of an inch in diameter. The least differ- ence of heat between the opposite ends of this little battery will produce an electrical current capable of influenc- ing a magnetic needle in an instrument called a galvanome- ter, (202.) The needle of the galvanometer will move in exact accordance to the intensity of the heat. This is so delicate an instrument, that the radiant heat of the hand held near the battery will cause the needle to move some 10 over its graduated circle. In fig. 84, a is the source of heat, (an oil- Fig. 84. lamp in this case,) & a screen having a hole to admit the passage of a bundle of rays; c is the substance on which the heat is to fall ; d the thermo-multiplier, or battery, which is to receive the rays after they have passed through the substance c. Two wires connect the opposite members of this battery with the galvanometer e, which, for steadiness, is placed on a bracket attached to the wall. Thus arranged, and with various delicate aids which we cannot here explain, a vast number of most instructive experiments have been made on radiant heat from different sources, and its effect ascertained on various substances. Four different sources of heat were employed : 1. The naked flame of an oil-lamp ; 2. A coil of platinum wire heated to redness by an alcohol-lamp; 3. A surface of blackened copper heated to 734; and, 4. The game heated to 212 by boiling water. The first two of these are luminous sources of heat, the last two non-luminous. 98. As already stated, the temperature of the source 97. What are Melloni's researches ? Describe the arrangement in figs. 83 and Si. 8 HEAT. greatly influences the number of rays transmitted. That which has passed through one plate of rock-salt has less liability to be arrested by a second ; still less by a third, and so on. The following table will show a few of the principal re- sults : Names of interposed substances, common thickness, 0.102 inch. Transmission of 100 rays of heat from A 1 92 36 39 38 37 9 8 6 ll I'-s 92 28 24 28 28 2 Copper at 734. F 92 6 6 6 6 92 Iceland-spar . ... Plate-glass Rock-crystal Alum, transparent Ice, pure and transparent Thus it appears that rock-salt is the only substance which permits an equal amount of heat from all sources to pass. In other cases, the number of rays passing seem proportioned to the intensity of the source. M. Melloni has called rock- salt the glass of heat, as it permits heat to pass with the same ease that glass does light. It is supposed that the difference found by experiment in the diathermancy of bodies is owing to a peculiar relation which the various rays of heat sustain to these bodies, analogous to that difference in the rays of light which we call color. Thus all other bodies, except salt, act on heat as colored glasses act on light, entirely absorbing some of the colors, and allowing others to pass. In this view, rock-salt may be said to be colorless as respects heat, while alum and ice are in the same sense almost back. Opake bodies, like wood and metals, entirely prevent the transmission of heat ; but dark-colored quartz crystal is seen, by the table, to differ only 1 from white crystal, and even perfectly black glass does not entirely stop all heat. 99. By cutting rock-salt into prisms and lenses, the heat from radiant bodies may be reflected, refracted, and concen- 98. What substance transmits heat most readily? Which least so? What is rock-salt called ? 99. How is heat polarized, fcc. ? EXPANSION. 69 trated. like light, and doubly refracting minerals, like Ice- land-spar, will polarize it. Expansion of Bodies lyy Heat. 100. All bodies expand with an increase of heat, and diminish with its loss. The expansion of a solid may be shown by a bar of metal which, as in the fig. 85, is provided with a handle, which at ordinary temperatures ex- actly fits the gauge. On heating this over a spirit-lamp, or by plunging it into hot water, it will be so much expanded in all its dimensions as no longer to enter the gauge. On cool- ing it with ice, it will again not only enter freely, but with room to spare. The same fact is shown by a ball, to which, when cold, a ring with a han- dle will exactly fit; but on heating the ball, the ring will no longer encircle it. The expansion of a fluid may be shown by filling the bulb , of a large tube (fig. 86) with coloured water to a mark on the stem. On plunging the bulb into hot water, the fluid is seen to rise rapidly in the stem. If it be cooled by a mix- ture of ice and water, it is seen to sink considerably below the line. A similar bulb (fig. 87) filled with air, and hav- ing its lower end under water, is ar- ranged as in the figure, to show the [ expansion of air by heat. The warmth of the hand applied to the naked ball will be sufficient to cause bubbles of air to escape from the open end through the water ; and on removing the hand, the contraction of the air in the ball, Fi S- 86> from the cooling of the surface, will cause a rise of the fluid in the stem, corresponding to the volume of air expelled, as 100. What is expansion ? Illustrate it for a solid. For a liquid. Foi a gas. 70 HEAT. shown in the figure. The slightest change of temperature will cause this column of fluid to move, as the air expands or contracts. In fact, it is the old air-thermometer. 101. Expansion of JSolids. Expansion by heat varies greatly: 1. According to the nature of the substance ; and, 2. Not in degree only, but also in the law which it follows. In solids, between the freezing and boiling of water, the rate of expansion in the same solid is equal for each additional degree. In experiments on this subject, rods of equal length are used, composed of the various subjects of experiment, whose expansion in length is accurately measured. In fig. 88, the rod t is confined by a, so that its free end bears against b. Heat- ed by an alcohol lamp, or other _LLL LLO7 a S source of heat, it expands and car- ries forward the Fig. 88. index g over the graduated arc c. On cooling, it contracts, and the spring a moves the index back again to the starting point. This linear expansion, multiplied by 3, gives the expansion in volume very nearly. Thus, for example, in the following solids, when heated from 32 to 212 Fahrenheit, the ex- pansion is In Length. In Bulk. 339 parl 349 s of zinc = 340 c lead = 350 r 11 2 parts = 113 116 " =117 523 silver = 524 174 = 175 583 643 810 copper = 584 gold = 644 iron = 811 194 " = 195 217 " = 218 270 " =271 921 1006 1113 2831 antimony = 922 platinum =1007 white glass = 1114 black marble =2832 < 307 " =308 335 " = 336 371 " =372 943 " =944 102. The expansion of fluids is ether apparent or absolute, according as the dilatation of the containing vessel is or is not 101. What is the rate of expansion in solids ? examples from table, in length and bulk. Describe fig. 88. Give EXPANSION. 71 taken into account. This fact may be illustrated in the annexed apparatus, (fig. 89,) where a tube of glass is bent twice at right angles, the open ends a and b upper- most; a larger tube surrounds each, leaving two cells, in which water of different tem- peratures may be poured. The inner tube is filled, for example, with colored water, of the ordinary temperature, to the level P; hot water is now poured into the outer cell of 6, when an immediate elevation of level in the colored fluid is seen to m. This is on the principle that the heights of columns of liquids in equilibrium are inverse to their densities. In this manner it has been de- termined that in heating from 33 to 212, 9 measures of alcohol becomes 10 ; of water, 23 measures becomes 24 ; and of mercury, 55 measures becomes 56. Thus it happens that in the com- mon changes of the seasons the bulk of spirits varies about 5 per centum. It has been determined, also, that liquids are progressively more expansible at higher than at lower temperatures. The liquefied gases illustrate this law in a remarkable manner, for fluid carbonic acid, as observed by M. Thilorier, has a dilatation four times greater than is ob- served in common air at the same temperatures. The law of expansion in liquids is not yet well made out. 103. Unequal Expansion of Water. The general law of expansion for nearly all solids and fluids, especially within the limits of the freezing and boiling points of water, is, that each solid or fluid expands, or contracts, an equal amount for every like increase, and reduction of, temperature, each body having its own rate of dilatation. There are, how- ever, some exceptions to this law, of which water offers a remarkable example. As the comfort, and even habitability of our globe, are in a great degree dependent on this excep- tion to the ordinary laws of nature, it is worthy of special notice. If we fill a large thermometer-tube or bulbed glass (fig. 90) with water, and place it in a freezing mixture, where wo 102. Describe the apparatus fig. 89. "What is the expansion of water? Of alcohol? 103. What inequality in the expansion of water? 72 HEAT. can observe the fall of the temperature by the thermometer, we shall see the column descend regularly with the temperature, until it reaches 39 -1 F., when the contrary effect will take place : the water then begins suddenly to rise in the tube, by a regular expansion, until the temperature falls to 32, when so sudden a dilatation takes place as to throw the water in a jet from the open orifice. If, on the other hand, we heat water in such an apparatus, commencing at 32, we shall find that, until the temperature rises to 40, the fluid, in place of expanding as we might expect, Fig. 90. will actually contract. Water has, therefore, its greatest density at 39 -5, and its density is the same for equal temperatures above and below this point ; thus we shall find it having a similar density at 34 and 45. 104. Beneficial Results. Let us now observe what useful end this curious irregularity in the expansion of water sub- serves. When winter approaches, the lakes and rivers, by the contact of the cold air, begin to lose their heat on the surface; the colder water, being more dense, falls to the bot- tom, and its place is supplied by warmer water rising from below. A system of circulation is thus set in motion, and its tendency, if the mass of water is not too large, is to reduce the whole gradually to the same temperature throughout. When, however, the water has cooled to 39 -5, this circula- tion is arrested by the operation of the law just explained ; below this point the water no longer contracts by cooling, and of course does not sink ; but on the contrary expanding, as before explained, it becomes relatively lighter, and remains on the surface : the temperature of this layer or upper stratum gradually falls, until the freezing point is reached, and a film of ice is formed. But as ice is a very bad conductor, the heat now escapes with extreme slowness; all currents tending to convey away the cooler parts of the water are arrested, and the thickness of the ice can increase only by the slow conduction through the film already formed : the consequence is, that our most severe winters fail to make ice of any great thickness. Other causes, also, which we shall What is its maximum density ? 104. What beneficial result follows ? Why is freezing a slow process ? Describe the mode of freezing of lake* aud rivers. EXPANSION. 7iJ presently explain, co-operate at all times to render the freez- ing of water a very slow process. We cannot fail to be im- pressed by the wisdom of that Power, which not only frames great general laws for the government of matter, but also makes exceptions to them, when the welfare of His creatures requires them. 105. The expansion of all gases and vapours is the same for an equal degree of heat, and equal increments of heat produce equal amounts of expansion. The rate of expansion amounts to 4-^th part of the volume of the gas at Q for each degree of Fahrenheit's scale, or between 32 and 212 to 0-366, or more than of the initial volume of the gas. When gases are near the point of compression at which they become liquid, this law becomes irregular, and is not strictly true for all gases ; but the departures from the law are so small that we need not mention them here. 106. Practical application of the laws of expansion in solids are frequently made with great advantage in the arts. The rivets which hold together the plates of iron in steam- boilers are put in and secured while red-hot, and on cooling draw together the opposite edges of the plates with great power. The wheelwright secures the parts of a carriage- wheel by a red-hot tire, or belt of iron, which being quickly quenched, before it chars the wood, binds the whole fabric together with wonderful firmness. The walls of the Con- servatory of Arts, in Paris, after they had bulged badly, were safely drawn into a vertical position, by the alternate con- traction and expansion of large rods of iron passed across it, and so secured by screw-nuts and heated by Argand lamps as to draw the walls inward. Towers of churches and other buildings have been thrown down or otherwise injured by the expansion of large iron rods (anchors) built into the masonry with the design of strengthening them. The Bun- ker Hill monument is daily bent out of a perfect vertical by the heat of the sun expanding the granite of which it is built. The mechanical arts are, in fact, full of beautiful applications of the principles of expansion. Among these we may mention 107. The Compensation Pendulum, adapted to regulating the rate of time-pieces. The length of the pendulum is 105. What is the law of expansion in gases ? How much does air dilate for each degree ? 106. Mention some instances of expansion in the arts. HEAT. altered by variations of temperature, and of course the rate of the clock is disturbed. A perfect compensation for this g error is obtained by the use of a compound pendulum of brass and iron, or other two metals, arranged as is shown in fig. 92, in such a manner that the expansion of one metal downward will exactly counteract that of the other metal upward; thus keeping the ball of the pendulum at a uniform dis- tance from the point of suspension. The shaded bars represent the iron, and the light ones the brass. The same object is accom- plished by using mercury, as shown in fig. 91, contained in a glass or steel vessel at the end of the pendulum-rod. The expansion which lengthens the rod also increases the volume of the mercury; this increase of bulk in the mercury raises the centre of gravity to an exactly compensating amount, and the Fig 91. Fi 92 c ^ oc ^ remains unaltered in rate. Watches and ' chronometers are regulated by a like beautiful contrivance. The balance-wheel, (fig. 93,) on whose uniform motion the regularity of the watch or chronometer depends, is liable to a change of dimensions from heat or cold. If made smaller, it will move faster, and if larger, slower. To avoid this error, the outside of the wheel is made of brass, the inside of steel, and cut at two opposite points; one end of each part is screwed to the arm, and the loose ends of the rim, being united by a Fig. 93. screw, are drawn in or thrown out by the changes of temperature, in precise proportion to the amount of change ; thus perfectly adapting the revolution of the wheel to the force of the spring. The principle of this wheel, it will be seen, is the same as in the compound bars, (107.) A pendulum of pine-wood is sometimes em- ployed for clocks, because it is so little changed by varia- tions of temperature. 108. The unequal expansion of solids is well shown by 107. What is the compensation pendulum? What the mercurial? What is the compensation balance ? THE THERMOMETER. 75 joining firmly, by rivets, two bars, one of iron and one of brass, as in fig. 94. When Fio . 94> they are heated, the brass / expanding most, will cause ~ the compound bar to bend, as shown in the fig. 95. ^^~^~^ ' ' ' : ^ r ~~^ = ~^^^, If they are cooled by ice, ^^"^ ""-^ the brass contracting most, lg ' ' will bend the united metals in an opposite direction, The Thermometer. 109. The Thermometer is an instrument for measuring heat by the expansion of various liquids and solids. This in- strument was invented by Sanctorio, an Italian, in A. D. 1590. His was an air-thermometer, such as is figured in the context. A bulb of glass with a long stem is placed with its ^-^ mouth downward, in a vessel containing a portion of colored water, (fig. 96.) A part of the air r being first expelled from the ball by expansion, the fluid rises to a convenient point in the stem, to which is attached a scale of equal parts, with degrees or divisions marked by some arbitrary rule. Thus arranged, the instrument indicates with great deli- cacy any limited change of temperature in the sur- rounding air. The portion of air confined in the ball, when heated, expands, and pressing on the column of fluid in the stem, drives it down, accord- ing to the amount of expansion or the degree of heat; and the reverse results from a decrease of temperature. The air thermometer has given place to 110. The Common Thermometer. This instrument indi- cates changes of temperature by the expansion of mercury or of alcohol contained in the bulb blown upon the end of a very fine glass tube. Mercury possesses very remarkable properties fitting it for a thermometric fluid : it may easily be obtained pure ; its rate of expansion is singularly uniform between its boiling and freezing points, and the range of temperature between these points is greater than in any other fluid, (about 660 Fahr.) For very low temperatures alcohol is preferred, as it has never yet been solidified, even with the intensest 108. Describe figs. 94 and 95. 109. What is the thermometer? De- ncribe Sanctorio's thermometer. 110. Describe the common thermometer. HEAT. artificial cold of the carbonic acid bath (151,) or of the arctio regions. The precautions needed to make a thermometer, such as will meet the demands of modern science, are too numerous to be fully described here. Suffice it to say, that by expanding the air in the empty ball, while the open end of the tube is covered with mercury, a portion of it is carried in by the pressure of the atmosphere, and by boiling this, all air is expelled and the tube entirely filled with mercury. The quantity is so adjusted by trial that it will stand at a convenient height in the tube. Finally, the tube is sealed by the lamp, while the contained mercury is expanded to completely fill it. The empty space in a good thermometer is therefore a torricellian vacuum. 111. Graduation of Thermometers. The scales adapted to the thermometer in various countries are divided into arbitrary degrees, and, unfortunately for science, the scales differ widely. There are, however, two fixed points in all, which are determined by direct ex- periment. These are the boiling and freezing points of water, or, more accurately, the melt- ing point of ice. The space between these two points is divided into a certain number of equal parts, according to the scale to be employed. In France, and on the continent of Europe generally, the scale of Celsius, or Centigrade, is employed, which divides this space into 100 degrees. In England and America the scale of Fahrenheit, a Hollan- der, is adopted. This scale adopts for its zero point the cold produced by a freezing mixture of snow and salt; which its author assumed to be the greatest possible cold. The word zero signifies nothing, but we know that as cold is the mere absence of heat, it is hope- less to expect an absolute zero. The scale of Reaumur, adopting the melting of ice as zero, divides the space between that point and the boiling of water into 80 degrees. The 130- 100 90- 1 : 50- H Fig. 97. 111. How are thermometers graduated ? What are fixed points ? THE THERMOMETER. 77 Bcalc of De Lisle, which is no longer used, read downward from zero at boiling water to 150, the freezing of the same. Annexed, in fig. 97, we have these four scales compared. It will be seen that zero Centigrade is zero Reaumur and 32 Fahrenheit; while 100 ,0- = 80 R. =212 F. In other words, these three scales divide the space between the two fixed points respectively into 100 0., 80 K, and 180 F. ; or, reducing to smallest terms, 5 C. = 4 R, .= 9 F. To reduce Centigrade to Fahrenheit, we can multiply by 9 and divide by 5, and add 32 to the quotient, and vice versa. Suppose we wish to know what 70 C. is on Fahrenheit's scale; we have the proportion 5 : 9 : : 70 : 126. If we add 32, which is the difference between zero of F. and C., we have 126 -f- 32 = 158, which is the number required, for 70 C. = 158 F. In stating thermometrical degrees, the sign -f- is used for points above zero, and for those below. Fahren- heit's scale is the one employed in this work. 112. The Self-Registering Thermometer is a form of the instrument contrived for the purpose of ascertaining the extremes of variations which may occur, as, for instance, during the night. It consists of two horizontal thermometers attached to one frame, as in fig. 98 ; b is a mercurial ther- Fig. 98. mometer, and measures the maximum temperature, by push- ing forward, with the expansion of the column, a short piece of steel wire, of such size as to move easily in the bore of the tube ; it is left by the mercury at the remotest point reached by the expansion ; a is a spirit-of-wine thermometer, and measures the minimum temperature. It contains a short cylinder of porcelain, shown in the figure, which retires with the alcohol on the contraction of the column of fluid, but does not advance on its expansion. Name the three scales. What is boiling water in each ? What freez- ing? Convert Centigrade 70 to Fahrenheit. 112. What is the self- registering thermometer ? 78 HEAT. o Fig. 99. 113. The Differential Thermometer is a form of air-ther- mometer, so named because it denotes only differences of temperature. It consists of two bulbs on one tube, bent twice at right angles^ and supported, as shown in fig. 99. A little sulphuric acid, water, or other fluid partly fills the stem only. When the bulbs of this instrument are heated or cooled alike, no change is seen in the position of the column ; but the instant any inequality of temperature exists between them, as from the bringing the hand near one of them, the column of fluid moves rapidly over the scale. A modification of this instrument, of great delicacy, was con- trived by Dr. Howard of Baltimore, in which sulphuric ether was the fluid used, the bulbs being vacuous of air. 114. A Pyrometer is an instrument for measuring liiyh temperatures. As mercury boils at about 660, we can estimate the temperature of fused metals, and the like, only by the expansion of solids. The only instrument of this sort which we need mention, as it is the only one susceptible of accuracy, is Daniell's Register Pyrometer. It consists of a hollow case of black-lead, or plumbago, into which is dropped a bar of platinum, secured to its place by a strap of platinum and a wedge of porcelain. The whole is then heated, as, for instance, by placing it in a pot of molten silver, whose temperature we wish to ascertain. The metal bar expands much more than the case of black- lead, and being confined from moving in any but an upward direction, drives forward the arm of a lever, as shown in fig. 100, over a graduated arc, on which we read the degrees of Fahren- heit's scale : (this graduation has been determined beforehand with great care.) This instrument gives very accurate results; by Fig. 100. it the melting point of cast iron 113. What the differential? 114. What are pyrometers? Describe Daniell's. SPECIFIC HEAT. 79 has been found to be 2786 F., and of silver I860 F. The highest heat of a good wind-furnace is probably not much above 3300. Fig. 88 (101) is a pyrometer of ordi- nary construction. 115. Breguet's thermometer is constructed upon the principle of the unequal expansion of metals, (107.) A compound piece of me- tal is formed by soldering together two equal masses of silver and platina two metals whose expansion is very unequal. This is rolled thin and coiled into a spiral as shown in a b, (fig. 101.) It is suspended from a fixed point p, while its lower end is free and carries an index i. Variations of temperature cause this spiral to un- wind or wind up, and these motions are indicated by the motion of the pointer. This is a more delicate thermometer than any mercurial or spirit one. A beautiful modification of Breguet's thermometer has been contrived by Mr. Saxton, to measure the temperature of the sea in deep soundings. 116. All thermometers for accurate research are divided on the glass stem by aid of a graduating engine and mi- crometer } each instrument being, according to the plan of Regnault, graduated by an arbitrary scale. Capacity for Heat, or Specific Heat. 117. Different bodies have different capacities for heat. If equal measures of mercury and of water, for example, are exposed to the same source of heat, the mercury will reach a given temperature more than twice as soon as the water, and it will cool again in half the time. Mercury is said, therefore, to have only half the capacity for heat which water has. We learn by trial that each substance in like manner has its own relations to heat as respects capacity. This is called also specific heat, a term synonymous with capacity. Water is adopted as the standard of comparison for this property, and the trial is usually made upon equal weights rather than upon equal measures of the substances compared. Specific heat connects itself curiously with the atomic constitution of matter. Several modes may be em- 115. What is the metallic thermometer? 116. How are thermometers accurately graduated ? 117. What is capacity for heat ? Give examples. What is specific heat? 80 HEAT. ployed to determine it; as by mixture, by melting, by warming, or by cooling. The determination of this property is called calorimetry, and the modes of experiment most usual are either by mixture or by the fusion of ice. 118. The Method of Mixtures. If a pint measure of water, at 150, be mixed quickly with an equal measure of the same fluid at 50, the two measures of fluid will have the temperature of 100, or the arithmetical mean of the two temperatures before mixture. If, however, we rapidly mingle a measure of water at 150, and an equal measure of mercury at 50, we shall find that they will have the tem- perature of 118. The mercury has gained 68, and the water lost about half as much, or only 32. Hence we infer that the same quantity of heat can raise the tempera- ture of mercury through twice as many degrees as that of water, and that the specific heat of water will be to that of mercury as 1 : 047, when compared by measure. But if we divide this number (0-47) by the density of mercury (13-5) we obtain the number 0.035, which expresses the specific heat by a comparison of weights. Water has then more than 30 times the capacity for heat which is found in mercury ; and in this peculiarity we find an important rea- son of the singular fitness of this fluid metal for the con- struction of thermometers. 119. El/ the melting of ice in the calorimeter of Lavoisier, is in fig. 102, the capacity of most substances for heat has een determined. A set of metallic vessels abc are so arranged that when a warm body is placed in c, all the heat it gives off in cooling will go to melt the lumps? of ice surrounding it. The water of fusion escapes at the cock s, and is measured in the graduated glass beneath. To cut off the heat of the surrounding air, the space between a and b is also filled with ice. The water which melts from this portion is carried away by r. In this apparatus the relative capacities . 102 of all solid and fluid substances may, with proper precautions, be accurately What is calorimetry ? 118. Describe the method of mixtures. 119. What is Lavoisier's calorimeter ? CHANGES PRODUCED BY HEAT. 81 determined by the respective measures of water which flow from s during the experiment, in which each body cools from an agreed temperature, (e. g. 212) to 32 , the constant temperature of c. The same result may be reached in some cases more simply by employing a large lump of solid ice a (fig. 103) in which a well W has jj been scooped out, and covered by a lid of ice b. Any solid substance, or a fluid contained in a glass flask, may be placed in W, and, when the | temperature has fallen to 32, the water con- tained in W may be measured as before. To es- timate the capacity of heat in gases, atmospheric air is chosen as unity and the method of melting is adopted by passing a certain volume of gas through a tube refrigerated by ice. 120. It is plain, from what has been said, that the capa- city of bodies for heat is a phenomenon not indicated by the thermometer. In the foregoing experiments, water and mercury have been each heated to 212, and yet the result demonstrates that an equal weight of water contains at that temperature about 30 times as much heat as the mercury. The thermometer can indicate only actual intensity of heat, and not its volume or quantity. In the following table of specific heats, it will be seen that this property has much connection with the physical condition of bodies as respects fluidity or crystalline ar- rangements, as is evident by comparing the capacity of water and ice, and of the various forms of carbon : Water 1000 Ice 513 Turpentine 468 Carbon (charcoal) 241 Anthracite (Pa.) 201 Graphite 201 Diamond 146 Steel 116 Sulphur 177 Sulphur lately fused 184 Ether 520 Alcohol 660 Mercury 33 Iron. Copper 114 Zinc 95 Brass 94 Silver 57 Antimony 51 Gold 32 Lead 31 Phosphorus 118 95 ! Glass 197 Changes produced Tjy Heat in the, State of Bodies. 121. Fluidity \s a result of temperature, as is seen in the familiar case of water, which is either ice, water, or steam, What simpler one is described ? 120. What does the thermometer lail in indicating? Give examples from table. 121. What is fluidity ? 6 82 HEAT. according to the temperature to which it is subjected. Many solids can be melted by an increase of temperature, and the melting point is always the same for a given solid. Some substances pass at once to the fluid state, while others, as wax, assume an intermediate pasty condition, and others, like ice, fuse very slowly indeed. The degree of heat at which bodies melt varies exceedingly. Thus platinum is not melted at 3280. Iron melts at about 2800 ; gold, at 2016; silver, 1873; zinc, 773; lead, 612; tin, 442; Newton's alloy, 212; potassium, 136 ; phosphorus, 108; wax, 142; tallow, 92; olive oil, 36; ice, 32; milk, 30; wines, 20; mercury, 39; fluid ammonia, 46; ether, 47; while pure alcohol is not solid at 175 below Fahrenheit's zero. 122. Liquefaction is attended by a remarkable absorption of heat. We have already seen that two equal measures of water at different temperatures assume when mingled the mean of their previous temperatures, (118.) If, however, we take a pound of ice at 32, and a pound of water at 212, we shall find, when the ice is melted, that the two pounds of water have the temperature of only 52 ; the ice gains only 20, while the water has lost 160. There are, then, 140 of heat lost in producing this change. We can take another mode of trial. Let us expose a pound of ice and a pound of water, each at 32, to a constant source of heat, in two vessels every way alike, and note the changes of temperature by the thermometer. The same quantity of heat is flowing into each vessel. When the ice is all melted, we shall find that the water into which it is con- verted has still only the temperature of 32, while the other pound of water has risen from 32 to 172 : here again we see the loss of 140 of heat used in converting the ice into water. We may reverse the last experiment, and take equal weights of ice at 32 and water at 172 and mix them : when the ice is all melted the mixture will still have the temperature of only 32 ; so that, in whatever way we may make the trial, we constantly observe the loss of 140 of heat. This is called the heat of fluidity, it being necessary to the existence of the water in a fluid state ] and it is also designated latent heat, because it is lost, absorbed, or con- Name the fluidity-points of several bodies. 122. What phenomenon attends liquefaction? Give an example. How is this reversed ? What is latent heat? CHANGES PRODUCED BY HEAT. 83 cealed, as it were, and no indication of it can be found by the thermometer. 123. This law is equally illustrated by the slow freezing of water. If a vessel filled with water at 52 be placed in an atmosphere of 32, it will rapidly cool down to 32 by the loss of 20 of temperature. After this, it will, as may be seen by the thermometer, remain at 32, until it is all converted to solid ice ; although we cannot doubt that it is all the while giving out a quantity of heat, which had before been insensible or latent. If the water had been ten minutes in cooling from 52 to 32, (or in losing 20,) then it would require one hour and ten minutes, or seven times as long, for it to become completely frozen. If, then, in equal times it lost equal degrees of heat, its latent heat will be 20 X 7 = 140, which is the same result as before. Thus we arrive at the seeming paradox that freezing is a warming process. By experiment we may show that water may be cooled some 8 or 9 degrees below its freezing point and still remain liquid, if its surface be covered with a thin film of oil, or if it is a thin smooth vessel, kept quite still; but the least disturbance will cause it, when in this situa- tion, to become solid at once, and the temperature will im- mediately rise from 23 or 24 to 32. The freezing of a part has therefore given out heat enough to raise the tem- perature of the whole from 24 to 32, or through 8. Our domestic experience in cold climates often supplies examples of this fact. The solidification of a saturated solution of sul- phate of soda is also an example of the same nature ; the ves- sel containing the solution becomes sensibly warm. In like manner, it is true that melting is a cooling process. A solid can melt only by absorbing heat from surrounding bodies, which must, of course, become cooler. Hence, in part, the cooling influence of an iceberg, which is often felt for many leagues, or of a large body of snow on a distant mountain ; and the chill felt in the air on a bright day in spring, when snow is rapidly melting on the ground. It is a wise order of nature that makes the freezing and thawing of snow and ice extremely slow and gradual pro- 123. Illustrate it by the freezing of water. How may water remain liquid below 32? How is freezing a warming process? What proof of design is here indicated ? 84 HEAT. cesses. If water became solid at once on reaching 32, it would be suddenly frozen to a great depth ; and if ico melted as quickly on reaching the same temperature, the most sudden and dreadful floods would accompany these events, and the common changes of the seasons would bo calamitous to human comfort and life. 124. Freezing mixtures owe their powers, to the principles just explained. Ice-cream is frozen by a mixture of snow or pounded ice with common salt. In this case, the two solids are rapidly changed to fluids ; the ice is melted by the salt, and the salt is dissolved by the water from the melting ice. Both these operations absorb a large quantity of heat. The surrounding bodies are called on to supply the heat required, and the cream in a thin metallic vessel cools so rapidly as to be soon turned to ice. The thermometer will fall in this operation to F. ; and this was the very experiment by which Fahrenheit (111) assumed that he had attained to a true zen.. of cold. Nitrate of ammonia dissolved in water at 46 will sink the temperature to zer">, ami the exterior of the vessel becomes at once thickly covered with hoar-frost. Common saltpetre, (nitrate of potassa,) dissolved in water, lowers its tempera- ture about 15 or 18, and is therefore much used in the hot regions of Asia, where it abounds, for cooling wine. Mer- cury may be frozen by using a mixture of three parts of chlorid of calcium and two of dry snow ; this mixture will sink the temperature from -{-32 to 50. Five parts of finely-powdered sal ammoniac and five of nitre, dissolved in nineteen of water, will reduce the temperature from 50 to 10 j and a little powdered sulphate of soda, drenched with strong hydrochloric acid, will sink the thermometer from 50 to 0. But the most intense cold is that which results from the volatilization of liquefied carbonic acid and nitrous oxyd gases, by which the enormously low temperatures of 175 and even 220 are reached. 125. Diminution of volume causes a portion of latent heat to become sensible. Air suddenly compressed into a email space, as in the fire-syringe, (fig. 104,) evolves heat enough to fire a portion of dry punk on the end of the piston. Metals rapidly struck, as on an anvil, become hot 124. What are freezing mixtures ? Give their theory. What is the most intense artificial cold ? 125. What ignites tinder in the fire-syringe ? VAPORIZATION. 85 enough to enable the smith to light his fire. "Wa- ter poured on quicklime combines with it, with the evolution of much heat; the water in this case taking on the solid form. Sulphuric acid and water, when mingled, give out great heat, and the bulk of the mixture is less than that of the two before mixing. Liquefaction is always a cooling process, and solidification or condensation a heat- ing one. A certain quantity of heat may be con- Fig. 104. sidered as necessary to preserve each body in its natural condition : if it be condensed, less is required, and it gives out the excess ; and if expanded, it absorbs more. Vaporization. The Boiling Points of Bodies. 126. A continuance of the heat which melted the ice into water, will turn the water into vapor or steam. The phe- nomena which attend this physical change are not less curious or instructive than the last. If we place a known quantity of water over a steady source of heat, we shall see the thermometer indicating each mo- ment a higher temperature, until, at 212, the fluid boils; after which the thermometer indicates no further change, but remains steady at the same point until all the water is boiled away. Let us suppose that, at the commencement of the experiment, the temperature of the water was 62, and that it boiled in six minutes after it was first exposed to the heat : then the quantity of heat which entered into it each minute was 25, because 212, the boiling point, less 62, leaves 150 of heat accumulated in six minutes, or 25 each minute. Now if the source of heat continue uniform, we shall find that in forty minutes all the water will be boiled away; and hence there must have passed into the water, to convert it into steam, 25 X 40 1000. One thousand degrees of heat, therefore, have been absorbed in the process, and this constitutes the latent heat of steam. So much heat, indeed, was imparted to the water, that if it had been a fixed solid, it would have been heated to redness; and yet the steam from it, and the fluid itself, had during the whole time a temperature of only 212. 125. Give examples of heat evolved from condensation. 126. What is vaporization ? What is the latent heat of water ? How is it observed ? 86 HEAT. 127. The capacity of water for heat is greater than that of any other body known; and in vapor it preserves the same distinction. The latent heat of steam has been vari- ously stated by different experimenters at 940, 956, 960, $72, and 1000. The latest, and probably the most accurate determination, is that of Brix, viz. 972. The latent heat of vapors has no relation to their points of boiling. The supe- riority of vapor of water in respect to latent heat will be seen by a comparison with that of several other bodies, viz. latent heat of vapor of water =972, of ammonia 837, of alcohol 386, of ether 162, of oil turpentine 133. The large amount of latent heat contained in steam becomes again sensible on its condensation to water; thus enabling us to make great use of it as a means of conveying heat. The steam, so to speak, takes up a large quantity of heat, and transports it to the point where we wish it applied. One gallon of water converted into steam, at the ordinary pressure of the atmo- sphere, will raise five gallons and a half of ice-cold water to the boiling point. In this way we can boil water in wooden tanks, heat large buildings by steam-pipes, and make numberless other useful applications of steam-heat in the arts. It is found in practice that to heat buildings by steam, every 2000 feet of space to be heated to 75 requires one cubic foot of boiler capacity, and that every square foot of radiat- ing surface on the conducting pipes will heat 200 cubic feet of space. 128. The boiling point of each fluid is constant, other things being equal, but is peculiar to itself; thus, ether boils at 96, ammonia at 140, alcohol at 173, water at 212, nitric acid 250, oil turpentine 314, phosphorus 554, sul- phuric acid 620, whale-oil 630, and mercury at 662. 129. Boiling is the mechanical agitation of a fluid by its own vapor. This happens whenever the liquid becomes so hot that its vapor can rise in bubbles to the surface, uncou- denscd by atmospheric pressure or by the temperature of the fluid. ' The elasticity or tension of the vapor then be- comes greater than the united pressure of the fluid and the air. When the boiling is vigorous, a great number of these bubbles of uncondensed vapor rise to the surface at the same 127. What capacity has water for heat ? Give other latent heats. Why +he superiority of water for steam piy-poses ? 128. What of the boiling points of fluids? 129. What is boiling? VAPORIZATION. 87 instant, and the liquid is thrown into violent agitation. If a vessel containing cold water be heated suddenly, the lowei surface receives the most heat ; bubbles of vapor are formed, and rise a little way, when, meeting the colder water, the vapor is at once condensed, and the liquid, before sustained by the elastic vapor, falls with a blow on the bottom of the vessel, often destroying it, if of glass. 130. The boiling point is much affected by the nature and condition of the vessel. In a metallic vessel, water boils at 210 and 211. If a glass vessel be coated inside with shel- lac, water boils in it at 211; but if it be thoroughly cleaned with sulphuric acid, water in it may be heated to 221 or more, without the escape of bubbles. A few grains of sand, a little fragment of wire, or a small piece of charcoal will, however, at once equalize these differences, and cause the water to boil steadily at 212. This simple means will prevent the unpleasant jar from sudden escape of vapor, and frequent fracture of the glass vessel. The boiling point is more re- markably affected by variations in atmospheric pressure than by any other cause, and we shall presently advert more in detail to the phenomena connected with it. 131. Spheroidal State of Liquids. If drops of water are let fall on a metallic plate heated considerably above the boiling point, it is observed that they do not evaporate very rapidly, and that there is no hiss- ing sound, while the globules of water roll about quietly, floating, as it were, over the hot surface. Thus situated, water is said to be in the " spheroidal state," a term employed by M. Boutigny, who has made many curious and in- structive experiments on this subject. Water passes into this condition at 340, and may at- tain it even at 288. A grain and a half of water in this state at 392 requires 3-30 minutes to evaporate; at a dull red-heat, the same quantity will last 1-13 minutes, and at a bright red, 0-50, the rate of evaporation increasing with the tem- perature. The water, in these experiments, does not touch or wet the hot surface, but is kept at a sensible distance from it by the elas- Fi S- 105 - 130. What affects the boiling point? 131. What is the spheroidal state ? Describe the experiment in fig. 105. 88 HEAT. 106 tic force of an atmosphere of its own vapor, as well also as by the repulsive action of hot surfaces. The vapor is a non-conductor, and its formation abstracts the sensible heat from the fluid ; so that, notwithstanding the proximity of the red-hot metal, the temperature of the fluid is found to be always lower than its boiling point, being, for water, 205 0< 7; for alcohol, 168 ; for ether, 93-6 ; for hydrochloric ether, 50 0< 9, and for sulphurous acid 13-1. The temperature is estimated as shown in fig. 105, where the liquid is contained in a metallic capsule in the flame of a good eolipile. 182. If a thick and heavy silver capsule is heated to full whiteness over the eolipile, it may by an adroit movement be filled entirely with wa- ter, and set upon a stand, some seconds before the heat declines to the point when contact can occur between the liquid and the metal. When this happens, the water, be- fore quiet, bursts into steam with almost explosive violence, and is projected in all directions, as shown in fig. 106. On the principle explained, the hand may be bathed in a vase of molten iron, or passed through a stream of melted metal unharmed ; and we find here an explanation of the success of some instances of magic. 133. The pressure of the atmosphere determines the boiling point of fluids. It follows, therefore, that by a di- minution of pressure, water may be made to boil at a much lower temperature than 212. If we place some warm water in a glass under the air- pump bell (fig. 107) and exhaust the air, the water will boil vigorously, although the temperature, as note d by tne thermometer, is observed to fall con- stantly. So, in ascending high mountains, the boiling point falls with the elevation, from the diminished pressure of the air. On this account, a difficulty is expe- rienced at the hospice of Saint Bernard, on the Swiss Alps, in cooking eggs and other viands in boiling water. This place is 8400 feet above the sea, and water boils there at 196 : on the summit of Mount Blanc, it boils at 184. We 107 132. Describe fig. 106. Why can the hand be safely plunged in fluid on? 13.3. What determines the boiling point of fluids ? How is it OB iron ? mountains ? VAPORIZATION. 89 learn that it is the temperature, and not the boiling which performs the cooking. The Rev. Dr. Wollaston proposed to determine the height of mountains by the boiling point. He found an ascent of 530 feet to be equal to a decrease of 1 in the boiling point ; and with a thermometer having large spaces considerable accuracy may be attained. In deep pita (as in mines) the boiling point rises. 134. The culinary paradox gives a very good illustration of the phenomena of boiling under diminished pressure. A small quantity of water is boiled in a glass vessel, as in the figure : when the water is actively boiling, a good cork is firmly inserted, and the vessel removed from the heat. It may now be supported in an inverted position, with the mouth under water, as seen in the figure. The boiling will still continue, even more rapidly than before ; and if we at- tempt to check it by affusion of cold water, we shall only cause it to boil more vehemently. A little hot water will, however, at once arrest the ebullition. In this case, the air is driven out of the vessel on the first boiling of the water; and, as we close the orifice while the steam is still issuing, there is only the vapor of water in the cavity. As this condenses from cooling, the pressure on the water diminishes, and it boils more easily from the heat it still contains: the affu- sion of cold water, by producing a more per- fect condensation, occasions a more violent ebullition. Hot water, however, increases the elasticity of the uncondensed vapor, and re- presses the boiling. These alternations can be produced as long as the water in the vessel is warmer than the cold water poured on it. When cold, the space. over the water will be a good vacuum, and if we turn the water from the ball into the neck, it will fall like a solid body, with a smart blow and rattling sound. This is sometimes called the water -hammer. The perfection of the vacuum can be tested by withdrawing the cork under water : the pressure of the atmosphere will then drive in Fig. 108. a quantity of water equal to the vacuum produced by the first expulsion of the air. 134. What is the culinary paradox ? Explain the continued boiling. 90 HEAT. 135. The Pulse Glass of Dr. Franklin is a very good illustration, F . also, of boiling under diminished pressure ; and the cool sensation felt by the hand at the instant when the fluid boils most violently, is proof of the heat absorbed in converting a part of the fluid into vapor. Practical application of these facts is made in the arts on a large scale, as in manufacturing sugar. The boiling of the syrup is performed in vacuo, in large pans of copper, holding several hundred gallons, the air and vapor being removed from the vessels by the air pump of a steam-engine : the syrup is thus rapidly boiled down at a temperature of 150 to 180, without any danger of burning. Vegetable extracts are frequently made, and saline solutions boiled, in the same way. Nothing in the arts shows more clearly the value and beauty of scientific principles. 136. Elevation of the Boiling Point by Pressure. In Papin's digester, (fig. 110,) a strong iron vessel with a safety- valve, water may be heated under the pres- sure of its own vapor to 400, or higher. This apparatus may be so arranged with a thermometer and pressure gauge, (fig. Ill,) that we can note the relations of pressure and temperature (Marcet's apparatus) : the ther- mometer-ball is in the steam cavity; the gauge descends into some mercury in the bottom. It is supported by a tripod /over a lamp e, and a stopcock d cuts off the ex- Fig. 110. ternal air, when the boiling has commenced. As the steam accumulates, it, pressing on the mercury, forces it up the tube, against the imprisoned air in the gauge I. When the gauge shows double the pressure of the air, the thermometer will indicate a temperature of 250-5. 3 at- mospheres of pressure raise the temperature to 275, 4 to 293-7, 5 to 307, 10 to 358, 15 to 392-5, 20 to 418-5, 25 to 439, 30^0457, 40 to 486, and 50 atmospheres raise it to 510. Perkins heated steam so highly that a jet of it set fire to combustible bodies. 135. Explain the pulse-glass. What practical application is made of these principles? 136. What is Papin's digester? What Marcet'd? What relation is there between boiling points and pressure ? VAPORIZATION. 91 The clastic power of steam in con- tact with water is limited only by the strength of the containing ves- sel ; but if steam alone be heated without water, then its elastic or expansive power is exactly like that of other gases or vapors. M. de la Tour has shown that many liquids may be entirely converted into va- por in a space but little greater than their own volume. 137. The increase of volume in changing from a liquid to a gaseous state is such, that 1 cubic foot of water becomes nearly 1700 cubic feet of steam; or, in whole num- bers, a cubic inch of water becomes nearly a cubic foot of steam ; while 1 cubic foot of alcohol and ether yield respectively 493 and 212 cubic feet of vapor. The latent heat of steam diminishes as the sensible heat rises, so that the heating power of steam at 400 is no greater than that of an equal volume at 212. On the other hand, the latent heat of steam produced at low tempera- tures, as in a partial vacuum, in- creases as the sensible heat falls. Hence there is no fuel saved by dis- ~; tilling in vacuo. There is a con- stant ratio between the "latent and Flg> 11L sensible heat of steam; the two added together always give the same sum. Thus, steam at 212 has latent heat = 972; giving the sum 1184. Subtract the sensible heat of steam at any temperature from the constant number 1184, and we have the latent heat for that temperature, e. g. steam at 280 has a latent heat of 904. So, also, at 100, steam has 1084 of latent heat. 138. Equal volumes of different vapors contain equal quan- tities of latent heat. By iceiylit, water vapor has about twice What was DC la Tour's observation? 137. What is the dilatation of eteain ? What relation between sensible and latent heat? 92 HE,\T. Fig. 112. and a half more latent heat than alcohol vapor, (972 : 385;) but the specific gravity of alcohol vapor is about 2-5 times greater than that of water-vapor, (1590 : 622.) Consequently, if the same expenditure of heat produces from all vapors the same bulk of vapor having equal quantities of latent heat, there can be no advantage in substituting any other fluid for water as a source of vapor in the steam-engine. 139. The Steam- Engine. The principle of this apparatus is simple, and easily illus- trated by the little instrument contrived by Dr. Wollaston, (fig. 112.) A glass tube, with a bulb to hold a little water, is fitted with a piston. A hole passes from the under side through the rod, and is closed by a screw at a. This screw is loosened to admit the escape of the air, and the water is boiled over a lamp : as soon as the steam issues freely from the open end of the rod, the screw is tightened, and the pressure of the steam then raises the piston to the top of the tube ; the experimenter withdraws it from the lamp, the steam is condensed, and the air pressing freely on the top of the piston forces it down again; when the operation may be repeated by again bringing it over the lamp. In the common condensing en- gine (fig. 113) a cylinder a is fitted with a solid piston, the rod of which moves through a tight packing in the cover, and to it the machinery is attached. A pipe d brings the steam from a boiler to the valve arrangement c by which the steam is admitted, alter- nately, to the top and bottom of Fig. 113. 138. What of equal volumes of different vapors? Compare alcohol and water. 139. What is Wollaston's toy? Give the principle of thi Btearu-engine in fig. 112. VAPORIZATION 93 the cylinder ; and also an alternate communication is opened with the condenser b. Thus, when the steam enters at the top, (in the direction of the arrow,) that at the bottom of the piston is driven through the lower opening to 6, where it is condensed. The valves are moved at the proper time by the machinery. 140. Evaporation from the surface of liquids takes place at all temperatures. Even snow and ice waste by evapora tion, at temperatures much below 32. Mercury rises in vapor even at the temperature of 60. Faraday found at that temperature that a slip of gold-leaf suspended in a vacuum over mercury was, in a few hours, whitened by amal- gamation with the vapor of that metal. The state of the atmosphere as to dryness and pressure influences natural evaporation, which is greatly increased by heat and a rapid wind. It must be remembered that all the water which falls to the earth in snow and rain has arisen in evaporation. That natural evaporation takes place only from the surface is proved, by its being entirely prevented by. a film of oil on the fluid. 141. Influence of Pressure on Evaporation. If we introduce a few drops of water into the vacuum above the mercury in a barometer tube, a part of it will be vaporized, and the level of the mer- cury will be correspondingly reduced. The tension of the vapor is increased by an elevation of tem- perature. A larger tube may be placed over the barometer tube, the lower end of which dips under the mercury, and we may then fill the intervening space with hot water, (fig. 114.) The vapor of the confined water will force down the column of mercury in direct proportion to the temperature ; and, by means of a thermometer and a scale of inches, we can tell exactly the tension of the vapor of water for every temperature under 212. 142. Maximum Density of Vapors. Into the torricellian vacuum introduce a portion of sulphuric ether: a part of it is instantly converted into vapor, and the mercury depressed thereby to s ' 114: * 140. What of natural evaporation? 141. What influence has pressui* on evaporation? 94 HEAT. about 14 inches. If we have a deep cistern, as in fig. 115, in which we can depress the tube by the pressure of the hand, it will be seen that the film of liquid on the surface of the mercury increases as the tube descends, until the vapor of ether is at last entirely converted to the fluid state. On withdrawing the hand, the ether again flashes into vapor. There is then, it is plain, a point of density (or pressure) for the vapor of ether, which cannot be passed without again converting it to a liquid. This is true of all volatile liquids; and this point is called the maximum density of vapors. The weight of 100 cubic inches of water vapor at 212 is 14-962 grains, while, at 32, the same volume of vapor of water is only 0-136. The point of maximum density of a vapor is lowered by cold as well as by pressure, and when these two effects are united, we can convert many gases, which are quite permanent at the com- mon pressure and temperature of the air, into liquids, and even to solids. 143. The cold produced by evaporation is owing to the assumption of heat by the newly formed vapor. Availing ourselves of this prin- ciple, water may be frozen by the evaporation of ether, even in the open air. Leslie showed that water might be frozen by its own evapo- ration, as in the experiment figured in the mar- gin, (fig. 116.) Water is contained in a shal- low capsule supported by a tripod of wire over a dish containing sulphuric acid, and the whole is covered by a low air-jar. On working the pump, the water eva- porates so rapidly in the vacuum as to boil even at 72 : its vapor is instantly absorbed by the sul- phuric acid, and in this way both Fig. 116. the sensible and latent heat are removed so rapidly that the water is frozen, while still ap- parently boiling. Fig. 115. 142. What is meant by maximum density of vapors ? 143. Whence iho cold of evaporation ? What is Leslie's experiment ? VAPORIZATION. 95 The Cryophorus, or frost-bearer, offers another illustration of the same principles. This instrument, invented by Dr. "Wollaston, consists of two glass bulbs blown upon the same tube(fig.H7): one of them contains a lit- tle water; the space over the water is a va- l S- ' cuum, the tube having been sealed when the water was boiling. On placing the empty bulb in a freezing mix- ture, the vapor of water is so rapidly condensed as to freeze the fluid in the ball which is remote from the freezing mixture, and which is usually protected by an envelope of muslin. 144. Dew- Point. If we drop bits of ice into a tumbler of water (one of polished silver is best) having the same temperature with the air, and watch the fall of a thermo- meter placed in it, we can denote with accuracy the temper- ature of the water, when it has cooled so far that moisture begins to be deposited on the clean surface of the glass. This temperature is called the dew-point; and the number of degrees between it and the temperature of the air is an accurate indication of the actual dryness of the air. In this climate, in summer, this difference amounts often to 40 or more, and in India it has been known to be as much as 61 ; that is, with an external temperature of 90, the dew-point has been seen as low as 29. The amount of moisture in the air has an influence on the indications of the barometer, and it is always requisite, in making baro- metrical observations, to make a correction for the tension of the vapor of water in the air. Several common facts are explained by a reference to these principles. When the air is highly charged with humidity, it deposits dew on any substance colder than itself. A glass of iced water in summer is immediately covered with a coat of condensed vapor; when a warm humid morning succeeds a cool night, we see the pavements and walls of the houses reeking with deposited water, as if they had been drenched with rain. The fall of dew (as has been already explained) Describe the cryophorus. 144. What is the dew-point ? How observed ? What common facts are explained by it ? HEAT. occurs in consequence of the radiation from the earth re ducing its temperature below the " dew-point." 145. Hygrometers are instruments to determine the amount of moisture in the air. One much used is called the wet lulb hygrometer, (fig. 118,) or psychro- meter, and consists of two similar delicate mer- curial thermometers, the bulb of one of which is covered with muslin and is kept constantly wet by water, led on to it by a string from a tube in the centre. The evaporation of the water from the wet bulb reduces the temperature of that thermometer to which it is attached, in propor- tion to the dryness of the air, and consequent rapidity of evaporation. The other thermometer indicates the actual temperature ; and the differ- ence being noted, a mathematical formula ena- bles us to determine the dew-point. 146. But a much more delicate instrument for this use is that of Mr. Daniell, which is con- structed on the principle of the cryophorus, (143.) It is represented in fig. 119. The long limb ends in a bulb, which is made of black glass, 1 that Fig. 118. ^he condensed vapor may be more easily seen on it. It contains a portion of ether, into which dips the 6all of a small and delicate thermometer contained in the cavity of the tube. The whole instrument contains only the vapor of ether, air having been removed. The short limb carries an empty bulb, which is covered with muslin. On the support is another thermometer, by which we can observe the temperature of the air. When an observation is to be made by this in- strument, a little ether is poured on the muslin : this evaporates rapidly, and of course reduces the temperature of the other ball. As soon as this has fallen to the dew-point, the moisture collects and is easily seen on the black glass. At this instant, the temperature indicated Fig. 119. j^ t h e t w o thermometers is noted, and 145. "What are hygrometers ? Describe the wet bulb. 146. Describe Daniell's. What is the principle of Daniell's? Which is the best? VAPORIZATION. 97 tb, difference gives us the true dew-point. The latest and most improved form of hygrometer is that of Ilegnault : it involves the principle of Daniell's, with important means of additional accuracy. 147. Diffusion and Effusion of Gases and Vapors. The vapor of water will rise and fill a confined vessel of air, and have the same tension as if no air were present. It will take a longer time to do it, but as much will ultimately rise as if the space were a vacuum. The air seems to be an impediment only to the rapid rise of the vapor. On the same principle, probably, is explained the curious and important fact, that, when different gases are in contact, they will not remain separate, but will soon mingle uniformly, even against the force of gravity. Our atmosphere, for instance, is composed of two gases, the specific gravities of which are as 976 to 1130, and we might suppose that the heavier would be at the bottom, as would be the case in two such liquids as water and oil. But they are found to be in a state of uniform mixture. If we connect together by a narrow tube two bottles, (fig. 120,) containing, one a light gas, hydrogen, and the other a heavier gas, oxygen, and place the heavy one uppermost, in a few hours we shall find them per- fectly commingled; as may be proved by the fact that the mixture will explode violently on touching Fi - 12 - a match to the open mouth of one of the vessels, which we know a mixture of these two gases will always do. 148. If we fill the end of a glass tube (fig. 121) of moderate size with a plug of plaster of Paris, we form what is called Graham's diffusion tube. When the plaster is dry, if the tube be filled, for example, with hydrogen gas, and its open end intro- duced into a vessel of water, this liquid is seen to rise rapidly, owing to the escape of the light gas into the air. At the same time the air enters the tube, and renders the mix- ture explosive ; but nearly four volumes of Fig. 121. 147. What is meant by diffusion of gases ? Give an illcutration. 148. A'hat is the diffusion tube ? In what proportion does the air enter? 98 HEAT. hydrogen escape for one of air which enters, and these are called the diffusion volumes of hydrogen and air. Every gas has its own diffusion volume depending on its density, these being inversely as the square root of the densities of the gases. The same law pertains to the rapidity with which gases rush into a vacuum through a minute orifice. 149. The passage of gases through moist membranes is connected with this subject, but involves also another con- dition, viz. the solubility of certain gases in water. For example, a bladder partly full of air, and tied tightly at the neck, is introduced into an air-jar full of carbonic acid ; after some hours the bladder is found much distended, and may finally burst, from the passage of the carbonic acid gas into it. This is effected by the solubility of this gas in water : it thus passes the pores of the membrane, and is rapidly diffused again in the air of the bladder. Dr. Mitchell found that the time required to pass the same volume of several gases through the same membrane was 1 minute for ammonia, 2 minutes for sulphuretted hydrogen, 3i for cyanogen, 5 for carbonic acid, 6J for nitrous acid, 28 for olefiant gas, 37 J for hydrogen, 113 for oxygen, and 160 for carbonic oxyd. For nitrogen the time was much greater. 150. Liquefaction and Solidification of Gases. In 1823, Faraday first demonstrated the possibility, by united cold and pressure, of reducing several gases to the liquid and even solid state. The apparatus originally employed in these interesting but hazardous experiments, was simply a stout glass tube, bent as in figure 122, containing the materials to evolve the gas, and heated at both ends. If cyanogen 122. is to be liquefied, dry cyanid of mercury is placed in one end of the tube, and heated, while the empty end is cooled in a freezing mixture : the gas, accumulating in a narrow space, is liquefied by the force of its own elasticity. Some hazard attends these experiments, and the operator should be protected by gloves and a mask of wire-gauze. In this way, chlorine, cyanogen, What is the law of diffusion ? 149. What of the passage of gases through membranes ? Give an example. What are Mitchell's results ? lot) Who first liquefied gases ? What was the means? VAPORIZATION. carbonic acid, nitrous oxyd, and several other gases have seen reduced to the liquid state, and some to the solid con- dition. Several of these gases as ammonia, cyanogen, and sulphurous acid may be liquefied by cold alone, without additional pressure. 151. M. Thitorier's apparatus for liquefaction of carbonic acid involves the same principle. In fig. 123, g is the gene- rator of the gas, a strong cast- iron vessel, hung by centres on a frame f\ in it is put the requisite quantity of carbonate of soda and water, and a tube a of copper, holding an equivalent amount of strong sulphuric acid ; the cap of red metal is strongly screwed in, the valve closed, and the position of the appa- ratus inverted, by turning it over on its centres; the acid then runs out among the car- bonate of soda, and an enor- mous pressure is generated by the successive portions of gas evolved. After a time, when the action is complete, the generator is connected by a metallic tube with the receiver r] stopcocks, simple screw-plugs having a conical point, confine the gas, and being opened, the liquefied gas collects in r, which is cooled by a freezing mixture for the purpose of condensing it. In this way, several successive quarts of the liquid carbonic acid gas are accumulated in r. A por- tion of this liquid may be safely drawn off into a strong glass tube refrigerated. It can then be drawn off by a jet j secured to the top, which enters a metallic box b with perforated wooden handles. The rapid evaporation of a part of the liquid gas absorbs so much heat from the rest, that a considerable portion is converted to a fine white solid, like dry snow, which fills the box. When once solidified, it wastes away very slowly, and may be handled and moulded with ease. If suffered to rest on the hand, how- ever, it destroys the vitality of the flesh, like a hot iron. It is now in a condition analogous to bodies in the spheroidal Fig. 123. What gases have been liquefied ? Describe Thilorier's apparah 100 ELECTRICITY. state (131 ;) being surrounded by an atmosphere of its own vapor, the radiation of heat to it from surrounding bodies is cut off, and it acquires the very low temperature of 140, If it is wet with ether in a capsule containing mercury, the latter is frozen solid, and can then be hammered with a wooden mallet, and drawn out like lead. When moistened with ether in vacuo, with certain precautions, the very low temperature of 166 is produced. Carbonic acid at has a tension of nearly 23 atmospheres ; at 32 its tension is 38 atmospheres; at 84, 12 J; at 75, 4.60; and at 111, 1-14 atmospheres. It becomes at 71 a clear transparent solid, sinking in the surrounding fluid. This apparatus once exploded in Paris, killing the assist- ant in a frightful manner. It is, however, due to Mr. Chamberlain, of Boston, to say that the author has re- peatedly used several of these instruments of his construc- tion with entire safety. 152. By the use of mechanical pressure, and the enor- mously low temperature of the bath of carbonic acid and ether in vacuo, Faraday has succeeded in reducing several other gases to the liquid or solid state. These facts will be mentioned under the history of the several substances. The greatest artificial cold hitherto observed is 220 below zero of Fahrenheit, and was obtained by Natterer, with the aid of a bath of liquid nitrous oxyd and sulphuret of carbon in vacuo. The greatest natural cold recorded is 76 below zero. Several gases have resisted all attempts to reduce them to a liquid state, viz. hydrogen at 27 atmospheres; oxygen at 58 ; nitrogen, nitric oxyd, and carbonic oxyd at 50, and coal gas at 32 atmospheres, aided by the greatest artificial cold. IV. ELECTRICITY. 153. More than 600 years B. c. the ancients observed in amber a remarkable power of excitation by friction. Mo- dern science has conferred on this power the name of elec- tricity, from the Greek word for amber, (electron.'] This force, or power, has various modes of existence or manifesta- 152. How has Faraday reduced other gases ? What is the lowest temperature observed ? What in nature ? What gases have resisted liquefaction? 153. What was the first electrical observation? MAGNETIC ELECTRICITY. 101 tion, which are chiefly, 1. Magnetic electricity; 2. Erie- tioual, or statical electricity; 3. Dynamical, voltaic, or gal- vanic electricity, (from chemical action;) 4. Thermo-elec- tricity; and, 5. Animal electricity. Magnetic Electricity, or Magnetism. 154. Lode-stone. A kind of iron-ore has been know* from remote antiquity, that has the property of attractir, to itself small particles of iron; this is called the lode-stone. By contact, it can impart its virtues to iron and steel, and also, to a consider- able degree, to cobalt and nickel. As it abounded in Magnesia, it w called by Pliny magnes, and hence the name magnet. This ore mounted in a frame of soft iron II, (fig. 124,) constituted the original magnet : pp' are the poles. A bar, or needle of steel, which has received the magnetic influence, when suspended on a point, ^ will be found to have a directive tendency, by which one end turns invariably to the north. The needle, therefore, has polarity, and the end turning north is called the north pole, and the other end the south pole. 155. Polarity. If we bring the north end of a magnetic bar near to the similar end of the suspended needle, the latter will move away, as indi- cated by the arrows, being repelled by the similar power of the bar. If, however, we bring the end N - toward the opposite end of the needle S, it |s ^ """"'iimniiBp will be attracted to the bar, and strive to move Flg " 126 ' as near to it as possible. The reverse is, of course, true of the opposite end of the bar. If, in place of a magnetic bar, we had used a bar of unmagnetic iron, we should have found both ends of the suspended needle equally, but less power- fully, attracted by it. We thus learn (1) that the magnet has polarity ; and (2) that poles of the same name repel, and those of opposite names attract each other. 156. Induction of Magnetism. The manner in which a magnet, or lode-stone, imparts its own power to surrounding "What modes of electricity are named ? 154. What is the lode-stone ? What is the needle? 155. What is polarity? What is the law of rfr pulsion? 156. What is induction ? It32 ELECTRICITY. substances, is called induction, and thoso bodies capable of manifesting this power are said to be magnetized by the in- ductive influence. Thus, a series of bars of soft iron laid about a magnetic bar, as in the figure, will all become temporarily magnetic by induction ; and in obedience to the law just stated, their ends next the N are all S, and their remote ends all N. Every mag- Fig. 127. nc ^ go j- S p e ak, is surrounded by an atmosphere of influence, which has its centre in the poles of the magnet, and diminishes in intensity inversely as the square of the distance. This decrease of force is prettily illustrated by an experiment shown in the annexed cut. The bar magnet holds a large key ; this can hold a second smaller than itself; this, a nail ; the nail, a tack-nail ; and lastly, a few iron- filings are held by the tack-nail; and the whole re- ceive their magnetism by induction from the bar, and each article has its own separate polarity. In- duction takes place through a glass-plate, or any similar substance. 157. Permanent, magnets can be made only of hardened steel. Soft iron and steel become mag- nets only while under the influence of other magnets, and lose their own power as soon as removed from them. Magnetism is imparted by { touch,' as it is technically called, from a previously existing mag- net. An unmagnetic bar of hardened steel, when properly rubbed by the poles of a magnet, will itself soon acquire polarity and magnetic power. Mag- Fig. 128. netism is thought to rest mostly on the surface of the metal. Every magnet is regarded as made up of a great number of small magnets, so to speak, each particle of steel having its own polarity. We cannot conceive of one n * n s n s n * n s n s n s v s sort of polarity existing cj*a cjg rgra CM c^ma r^w cca r^sa g Without the Other. Thus, aS^i^Si^ESEi i fig urc 129, we see a p }o . 129 magnified representation Explain figs. 127 and 128. 157. What are permanent magnets ? What \s attraction and ' touch' ? How are the forces in a magnet distributed ? MAGNETIC ELECTRICITY. 103 of this condition. Each little magnet has its own n and *. Those which occupy the middle of the bar, being acted on alike in all directions, can show no power ; but the force accumulates toward each end, until we find the greatest power in the last range of particles, which we term the poles. If we dip a magnetic bar in iron-filings, we shall find only the ends attracting a tuft of the metallic particles, while the middle is free. If two magnetic bars, however, like the figure, are placed together, (-f- and ,) and a sheet of paper laid over them, they will attract iron-filings scattered on the paper, in the way represented in the figure : here a pair of central poles have power to attract the iron, which the middle part of the simple bar had Fig. 130. not. The particles of iron arrange themselves in what are called magnetic curves. These curves represent very nearly the lines of magnetic force which always environ a magnet, and tend to impart magnetic properties to all bodies solid, liquid, or gaseous which come within their range. 158. Artificial Magnets are made of all forms, the most common being the so-called horse-shoe magnet, shaped like figure 131. It is found that the power of magnets is much increased by uniting several thin plates of V hardened steel, each of which is separately magnet- Fl - 131 - ized. A bar of soft iron, called the keeper, is placed across the poles of the horse-shoe magnet, to prevent it from losing power; and if it be made to hold a weight nearly equal to the power of the magnet, it will be found to gain strength daily up to a certain point, and in like manner to lose its magnet- ism if unemployed. Artificial magnets, weighing one pound, have been made to sustain 28 times their own weight. 159. The Earth's Magnetism. The earth is regarded as a great magnet. Its power is equal, according to Gauss, to that which would be conferred if every cubic yard of it con- tained six one-pound magnets. The sum of the force is equal to 8,464,000,000,000,000,000,000 such magnets. The magnetism which we see in bars of steel and the lode- Illustrate this as in fig. 129. 158. How kre magnets formed and pre- served ? What is terrestrial magnetism ? What its force in a cubic yard? 104 ELECTRICITY. stone is the result of induction from the earth. Magnetism from the earth is induced in all bars of steel or iron which stand long in a vertical position. Tongs and blacksmiths' tools are often found to be magnetized. A bar of iron held in the magnetic meridian, and at the proper inclination, becomes immediately magnetic from the induction of the earth ; and the effect may be hastened by striking it on the end with a hammer : the vibration seems to aid in inducing the magnetic force. The tools used in boring and cutting iron are also generally found to be magnets. The magnetic poles of the earth are not in the same points with the poles of revolution or the axis of the earth, and for this reason the magnetic needle does not point to the true north and south, but varies from it more or less, and differs at different times, as the magnetic pole alters its position. This is called the variation of the needle. 160. Dipping Needle. The magnetism of the earth is beautifully shown by the dipping needle, represented in the annexed figure. The needle n is sus- pended on the horizontal bar a, so as to move in a vertical plane, instead of horizontally, as in the compass-needle. The graduated vertical circle c is placed in the magnetic meridian, and the needle then assumes, in this latitude, (41 18',) the position shown in the figure, dipping Fig. 132. at an angle of 73 27'. Over the mag- netic equator it would stand horizontal, being equally at- tracted in both directions. At either magnetic pole it would be vertical. The horizontal variation of the needle, its dip, and the intensity of the polar attraction, are subject to daily and local changes, from the fluctuations of temperature in- fluencing the magnetic conditions of the atmosphere, as shown by the late results of Faraday. 161. Magnetics and Diamagnetics. Dr. Faraday, in 1845, made the important discovery that all solid and liquid sub- stances, and many gases, were subject to the magnetic in- fluence. According to his results, confirmed by numerous subsequent observers, all bodies may be subdivided into two great classes the magnetic and diamagnetic. To the first How are objects affected by it? Where are the magnetic poles ? 160. What is the dipping needle ? What is said of variations in dip, or positive, and that in the air , or ne- gative ; the copper has the reverse signs. These relations are expressed in the figures by the signs -j- and , and by the direction of the arrows showing the -f- electricity of the zinc passing to the of the copper in the acid; while the bubbles of gas (hydrogen) set free at the -f- end of the zinc Describe the pile, fig. 152. 183. What are the conditions of a voltaio circuit? How is its action suspended? What are the electrical states of the immersed metals ? Illustrate by figs. 153, 154. ELECTRICITY OF CHEMICAL ACTION. 117 are delivered at the of the copper. Fig. 154 shows how the current may be established by wires, without the direct contact of the slips. In this case the wires (as in the pile) carry the influence in the direction of the arrows, and the existence of the current and its positive and negative characters may be shown by the effect produced by it on a small mag- netic needle, which will be influenced by the wires carrying the current, just as by the magnet being attracted or repelled according as it is above or below the wire, Fig. 154. and in either case endeavoring to place itself at right angles to the conducting wire, (201.) The direction of the voltaic current (and of course the -f- or qualities of the metals from which it is evolved) depends entirely on the nature of the chemical action produced. Thus, if, in the arrangement just described, strong ammonia were used in place of the dilute acid, all the relations of the metals and the fluid would be reversed, since the action would then be upon the copper. 184. Thus is electricity the result of chemical action ; and conversely we see that, under the arrangement described, chemical action is controlled by the electrical condition of the metals. This is electricity in motion, or dynamic elec- tricity; and frictional electricity may be regarded as stag- nant or statical electricity. Let us attend somewhat further to the theory of the voltaic circle. 185. In the compound voltaic circuit, composed of two or more members, connection is formed, not between members of the same cell, but between those of opposite names in contiguous cells. This is seen by in- specting the arrows and signs -(- and in figure 155. The electricity always flows, both in simple and compound cir- cles, from the zinc to the copper, in the Fig. 155. 184. How is this mode of electricity regarded ? 185. What are the con- ditions of a compound voltaic series ? Describe it in fig. 155. 118 ELECTRICITY. fluid of the battery; and from the copper to the zinc, out of the battery. This is important to be remembered, since the zinc is called the electro-positive element of the voltaic series, although out of the fluid it is negative ; and conse- quently, in voltaic decomposition, that element which goes to the zinc-pole is called the electro-positive element, being attracted by its opposite force; while the element going to the copper is called, for the same reason, the electro- negative. The compound circle, reduced to the simplest form of expression, would be Copper zinc -fluid copper zinc. Here the copper end is negative and the zinc positive, but the two terminal plates are in no way concerned in the effect ; so that, throwing them out of the question, we bring it to the state of the simple circle, which is simply Zinc -fluid copper ; and here we find the zinc end negative, and the copper end positive. 186. A certain resistance to the passage of a voltaic cir- cuit is offered by every element used in its construction. New properties are thus acquired by the compound circuit, which are never seen in the single couple, while the latter possesses certain attributes not seen so well in the compound series. For example, no single pair of plates, however large, will afford a current capable of decomposing water or of affording an electrical shock, although a maximum of mag- netic effect may thus be produced. These differences were formerly ascribed, rather vaguely, to what has been called quantify and intensity. Thus, in the compound circuit, supposing each -j- and in the circuit to neutralize each other, then only the final quantities -j- and remain as expressed in the poles; and it was argued that the quantify of electricity was no greater than would be afforded by a single couple, while its intensity, owing to the resistance over- come in each cell, was greatly increased. This matter has been placed on the basis of mathematical demonstration by 187. Ohm's Law.Qhrn, of Berlin, in 1827 first de- monstrated that, as the voltaic apparatus itself is composed 186. What effect is due to each element ? "What new properties clooa the current thus acquire? What was meant by quantity and intensity ? 187. What law expresses the conditions of a voltaic circuit? ELECTRICITY OF CHEMICAL ACTION. 119 solely of conductors, the electric current must proceed, not only along the connecting wire, from pole to pole, but also through the whole apparatus ; that the resistance offered to the passage of the current consisted therefore of two parts, one exterior to, and one within, the apparatus. This expla- nation cleared up at once the difficulties which had previously beset this subject when regarded only in view of the exterior resistance. Let the ring a b c in fig. 156 represent a homo- geneous conductor, and let a source of electricity exist at A. From this source the electricity will / \ diffuse itself over both halves of the ring, the I I positive passing in the direction a, the negative \^^/ in b, and both fluids meeting at c. Now it fol- lows, if the ring is homogeneous, that equal quan- Fis< 156 * tities of electricity pass through all cross sections of the ring in the same time. Assuming that the passage of the fluid from one cross section of the ring to another is due to the difference of electrical tension at these points, and that the quantity which passes is proportional to this difference of tension, the consequence is that the two fluids proceeding from A must decrease in tension the farther they recede from the starting point. 188. This decreasing tension may be represented by a diagram. Suppose the ring in fig. 156 to be stretched out to the line A A'. Let the ordinate A B represent the tension of positive electricity at A, and A' B' that of the negative fluid ; then the line B B' will express the tension for all parts of the circuit, by the varying lengths of A B, A' B' at every point of A c or c A'. Hence Ohm's celebrated formula, F = -|, where F represents the strength of the current, E the electro-motive force of the battery, and B, the resistance. Therefore the greater the length of the circuit, the less will be the amount of electricity which passes through any cross section in a given time. In exact terms, this law states that the strength Demonstrate fig. 156. 188. How do you express the decreasing ten . ion ? What is Ohm's formula ? Give the meaning of each expression. What is the la^r as stated? 120 ELECTRICITY. of the current is inversely proportional to the resistance of the circuit, and directly as the electro-motive force. 189. But in the simplest voltaic circuit we have not a homogeneous conductor, but several of various powers in this respect. To illustrate this, let the conductor A A' (fig. 158) consist of two portions having different cross sections. For example, let the cross section of A d be n times that of d A' j then if equal quantities pass through all sections in equal times, if through a given length of the thicker wire no more fluid passes than through the thinner wire, the difference of tension at both ends of this unit of length of the thicker wire must be only -th of what it is in the latter. Thus, " the electric fall," as Ohm calls it, will be less in the case of the thick wire than of the thinner, as shown by the line B a in the figure. The result is expressed in the law that the "electric fall" is directly as the specific resistances of the conductors, and in- versely as their cross sections. Hence, the greater the resist- ance offered by the conductor, the greater the fall. The very simplest circuit must therefore present a series of gra- dients expressive of the tension of its various points as one for the connecting wire, one for the zinc, one for the fluid, and one for the copper. The electro-motive force of a voltaic couple (" E" of Ohm's formula) may be experi- mentally determined, and it is proportional to the electric tension at the ends of the newly broken circuit. 190. Galvanic Batteries are constructed of various forms, according to the purpose for which they are to be used. One of the earliest forms contrived was the Cruickshauk's trough, (tig. 159,) in which the plates of copper and zinc soldered together are secured in grooves by cement, water-tight, all the zincs facing in one direction. The acid was poured into the 189. How does it apply to conductors not homogeneous ? What is the electric fall ? Give the law. Describe the course of the current in and out of the fluid. What is the simplest expression of tho compound circle ? 190. What was Cruickshank's battery ? ELECTRICITY OF CHEMICAL ACTION. 121 trough until the cells were filled. To avoid the incon- venience arising from loss of power, (which in this form of instrument is greatest at the first moment of contact be- tween the plates and the acid,) Dr. Hare contrived his revolving deflagrators. These were so constructed, that by a quarter revolution of the trough, the acid could at plea- sure, and without disturbing the arrangements of the operator, be thrown off or on the plates, and the maximum effects of this kind of the battery be obtained. But recent improvements in the construction of the battery have supplied us with several superior forms of the instrument, suited to various purposes, and possessing the valuable qua- lity of constancy of action. 191. Amalgamation. In the original form of the gal- vanic battery, made of copper and of unamalgamated zinc, there is a great amount of local action in each cell, arising from the impurity of the zinc. When the surface of the zinc is amalgamated with mercury, the local action ceases ; and the amalgamated surface, being reduced to one uniform electrical condition, will remain for any length of time in the acid fluid unacted on, until connected with the electro- negative element. All improved batteries are therefore now constructed with amalgamated zinc. It should be remarked that the local action in a battery cell, arising from the cause named, not only consumes the power of that member, but reduces the energy of the whole series. In order to have a constant voltaic circuit of equal power, not only the evils arising from local action must be avoided, but also, as far as possible, the exhaustion of the fluid of excitation. Batteries so constructed as to meet these difficulties are called sustaining batteries, or constant batteries. Some of the more important of these we will briefly describe. 192. Since 's Battery is formed of zinc and silver, and needs but one cell, and one fluid to excite it. The silver plate (S, fig. 160) is prepared by coating its surface with platinum, thrown down on it by a voltaic current, in the state of fine division, which is known as platinum-black. The object of this is to prevent the adhesion of the liberated hydrogen to the polished silver. Any polished smooth sur- face of metal will hold bubbles of gas with great obstinacy, What was Hare's improvement? 191. What is amalgamation ? What Us use ? What is said of local action ? 192. What is Smee's battery ? 122 ELECTRICITY. thus preventing in a measure the contact between the fluid and the plate by the in- terposition of a film of air-bubbles. Tho roughened surface produced from the de- posit of platinum-black entirely prevents this. The zinc plates z z in this battery arc well amalgamated, and face both sides of the silver. The three plates are held in position by a clamp at top b, and the interposition of a bar of dry wood w prevents the passage of a current from plate to plate. Water, acidulated with one-seventh its bulk of oil of vitriol, or, for less activity, with one-sixteenth, is the exciting fluid. The quantity of electricity excited in this battery is very great, but the intensity is not so great as in those compound batteries to be described. This battery is perfectly constant, does not act until the poles are joined, and, without any attention, will maintain a uniform flow of power for days together. A plate of lead, well silvered, and then coated with platinum-black, will answer equally as well, and indeed better than a thin plate of pure silver This battery is recommended over every other for the stu- Fig. 160. Fig. 161. dent, as comprising the great requisites of cheapness, ease of management, and constancy. A form of it, well calcu- lated for the student's laboratory, is shown in fig. 161, which is a porcelain trough with six cells. This battery is the one universally employed in electro-metallurgy. 193. DanieWs Constant Battery. This truly philosophi- cal instrument (fig. 162) is made up of an exterior circular What are the advantages of Smce's battery ? ELECTRICITY OF CHEMICAL ACTION. 123 cell of copper C, three and a half inches in diameter, which serves both as a containing vessel and as a negative element ; a porous cylindrical cup of earthenware P (or the gullet of an ox tied into a bag) is placed within the copper cell, and a solid cylinder of amalgamated zinc Z within the porous cup. The outer cell C is charged by a mixture of eight parts of water and one of oil of vitriol, saturated with blue vitriol, (sulphate of copper.) Some of the solid sulphate is also suspended on a perforated shelf, or in a gauze bag, to keep up the saturation. The inner cell is filled with the same acid water, but without the copper salt. Any num- ber of cells so arranged are easily connected together by binding screws, the C of one pair -p- ^ to the Z of the next, and so on. This instru- ment, when arranged and charged as here described, will give out no gas. The hydrogen from the decomposed water is not given off in bubbles on the copper -side, as in all forms of the simple circuit of zinc and copper ; because the sulphate of copper there present is decomposed by the circuit, atom for atom, with the decomposed water, and the hydrogen takes the atom of oxyd of copper, appropriating its oxygen to form water again, and metallic copper is deposited on the outer cell. No action of any sort results in this battery, when properly arranged, until the poles are joined. Ten or twelve such cells form a very active, constant, and econo- mical battery. 194. In the common sulphate of copper battery (fig. 163) only the acid solution of sulphate of copper is used. The surface of zinc becomes soon en- cumbered by the metallic copper in a state of fine division thrown down upon its surface. It is a very useful battery for electro-mag- I netic purposes. 195. Groves Battery. Mr. Grove, of Lon- don, has contrived a compound sustaining battery, of great power and most remarkable intensity of action. The metals used are platinum and amalgamated 193. What is Daniell's battery ? 194. What is the sulphate of coppe? battery ? What is Grove's battery ? 124 ELECTRICITY. Fig. 164. zinc. A vertical section of this battery is shown in fig. 164. The platinum -f- is placed in a porous cell of earthenware, containing strong nitric acid. This is surrounded by the amalga- mated zinc in an outer vessel of dilute sul- phuric acid, (six to ten parts water to one of acid, by measure.) The platinum, being the most costly metal, is here surrounded by the zinc, in order to economize its surface as much as possible. In this battery the hydrogen of the decomposed water on the zinc side enters the nitric acid cell, decomposes an equivalent of the acid, forming water with one equivalent of its oxygen, while the deutoxyd of nitrogen is given out as a gas, and, coming in contact with the air, is converted into hyponitric acid fumes. No other form of battery can be com- pared with this for intensity of action. A scries of four cells (the platinum foil being only three inches long and half an inch wide) will decompose water with great rapidity; and twenty such cells will evolve a very splendid arch of light from points of prepared charcoal, and deflagrate all the metals very powerfully. It is rather costly, and trouble- some to manage, as are all batteries with double cells and porous cups. 196. Bunscn's carbon lattery is a valuable addition to our resources in this department. It employs a cylinder of car- bon for the negative element, in place of the platinum in Grove's battery. The carbon is that of the gas-works, pulverized and mould- ed with flour, and afterward baked like pot- tery into compact cylinders. This battery (fig. 165) has the advantage of large mem- bers and great cheapness of construction. Fifty large-sized members, 10 inches high, the outer cups 5 inches in diameter, cost about fifty-five dollars in Paris, made by Deleuil, Rue du Pont-de-Lodi, No. 8. The author has found this, on the whole, the most efficient and economical of all batteries suited to show the more splendid and intense effects of voltaic electricity. Fig. 165. 196. What is Bunsen's battery? What is the reaction in these com- pound batteries ? ELECTRICITY OF CHEMICAL ACTION. 125 197. The effects of voltaic electricity are, 1. Physical; 2. Chemical; and, 3. Physio- logical. Under the first head are included the electrical, luminous, calorific, and elec- tro-magnetic phenomena of the circuit. 198. Deflagration. When the current from a series of 20 or 50 pairs of Grove's or Bunsen's battery is passed through points of prepared charcoal, as in the dis- charger, (fig. 166), a most brilliant light and intense heat are produced. No effect is seen until contact is made between the poles p and n, when, on withdrawing them, the arch of light elongates, and connects the separated poles, in the manner shown in fig. 167. This arch is in a powerful pile some inches in length. It is accompanied with an elongation of the pole on the -- or carbon side of the battery, and a depression or hollow- ing out of the -J- or zinc side. This flame is a conductor of electricity, and is attracted and repelled by the magnet, as shown in fig. 168. By holding a magnet in a certain position the flame may be made to revolve, accompanied at the same time with a loud sound. In the small capsule of carbon S, (fig. 169,) gold, platinum, steel, mercury, and other sub- stances are speedily fused and deflagrated, with various colored lights and volatilization. The easy fusion of platinum by the pile is a proof of the intensity of the heat, as this effect can be pro- duced by no other source of heat known, except that of the oxyhydrogen blowpipe. By the union of the currents from several hundred carbon cells, M. Despretz has lately volatilized the diamond. The ingenuity of the teacher will vary the ex- periments, always so surprising and instructive. Fig. 166. Fi s- 168 Fig. 169. Fig. 170. 197. Classify the effects of voltaic electricity. of deflagration. Which pole elongates ? 198. Describe the effects 126 ELECTRICITY. 199. The electrical light of the voltaic circuit is in no degree dependent on com- bustion, as may be proved by establishing connection between the poles in a vacuum in a glass vessel exhausted by the air-pump, and containing the poles conveniently ar- ranged, as in fig. 170. No less brilliancy is perceived in this case than in the air. 200. A constant light is produced from the battery of Grove or Bunsen, by an in- genious mechanical arrangement of the poles. Fig. 171 shows that of M. Du- boscq, of Paris. The poles S and I are preserved at the same distance by the ac- tion of an electro-magnet in the foot E, upon a soft-iron bar F F in connection with an endless screw V, moving the pullies P P', which are connected by cords with the poles S and I. The contact of S and I induces magnetism in the electro-magnet E, while the springs R L regulate the mo- tion of the machinery. The apparatus is simple and portable, and its effect is to make the electrical light so steady and con- stant that it may be used for all optical ex- periments. The author has also shown that good daguerreotypes may be taken with it in a few seconds. For this pur- pose the light is concentrated by a large parabolic mirror, so placed that the poles meet in its focus. The positive pole con- sumes much more rapidly than the nega- tive, both from a more intense action upon it and because its particles are carried over and deposited on the negative pole, elon- gating the point of the latter. To provide for this difference, the pulley P' is variable, and carries the pole I up propor- tionably faster, so that the focal position of the light remains unchanged. How docs a magnet affect the arc of flame ? 199. How does a vacuum affect the electrical light? Describe fig. 170. 200. What is the arrange- ment for rendering the light constant ? Describe fig. 171. Fig. 171. ELECTRO-MAGNETISM. Electro- Magn etism. 201. Prof. CErsted, of Copenhagen, in 1819 first made known the law of electro-magnetic attraction and repulsion. If a wire conveying a voltaic current is brought above and parallel to a magnetic needle, (as shown in ^ fig, 172,) the latter is invariably affected, as if influenced by the poles of another magnet. If the current is flowing, as in- dicated by the arrow on the wire, say to the north, then the north pole of the needle will turn to the east ; if the current is flowing south, it will turn to the west. If the wire carrying the current is placed beneath the needle, the same effect is produced as if the current had been reversed ; the needle turns in the opposite way to what it does when the wire is above. The effort of the needle is to place itself at right angles to the wire, as if influenced by a tangential force. That the wire conveying a voltaic current is itself magnetic, is proved by this experi- ment. If the wire is bent in a rect- angle, as in fig. 173, and wound with Fig. 173. silk or cotton, to prevent metallic contact, and the lateral passage of the power from wire to wire, then it is evident that a current flowing over the wire will have to paiss many times completely around the needle, and the effect which is produced will be nearly in proportion to the number of turns made by the wire. In this way we can make a very feeble current give decided indications. Such an arrangement is called a galvanoscope or galvanometer. 202. In delicate galvanoscopes, in order to free the magnetic needle from the di- Fig. 174. rective tendency which it receives from the earth's magnetism, two needles are used, with their unlike poles placed opposite to each other, (fig. 174,) one 201. Who discovered electro-magnetism ? What effect has a current on, a wire ? What is meant by a tangential force ? What is a galvanometer ? 128 ELECTRICITY. within and the other above the coil. They will then hang suspended by the silk fibre which supports them, with nc tendency to swing in any direction, since they are wholly occupied with their own attractions and repulsions, and their directive power is neutralized. Consequently, they are free to move with the slight- est influence of any current passing through the coil. Such an arrange- ment is called an astatic needle. To give it greater delicacy, and prevent the currents of air from moving it, a glass shade (fig. 175) is placed over it, and the movements of the needle are read on the graduated circle. By means of a screw provided for that purpose, the coil is revolved until it is Fig 175 parallel with the needle, as the point of greatest sensitiveness. The ten- dency of the galvanometer needle, it will be remembered, is always to place itself at right angles to the direction of the electrical current, that position being the equator of the attracting and repelling powers, and consequently a point of equilibrium. 203. Ampere's Theory. In 1820, while the original dis- covery of (Ersted was attracting the greatest attention, M. Ampere, of Paris, proposed to account for the phenomena of terrestrial magnetism by supposing a series of electrical currents circulating about the earth from east to west, in spirals nearly at right angles to its magnetic axis. The sun's rays impinging on the surface of the earth, encircle it, so to speak, with an unending series of spiral lines, pro- ducing, by thermo-electricity, the phenomena of magnetic in- duction. Arago found, in accordance with these views, that if iron-filings were brought near a connecting wire while a voltaic current was passing, that they adhered to it in concentric rings. These fell off the moment the circuit was broken. Hence it was inferred that if a voltaic current was made to pass in a spiral about any conductor, it would become magnetic. This inference was verified by the 202. What is an astatic needle ? How is it freed from the influence of terrestrial magnetism? 203. What was Ampere's theory ? What de- monstration did M. Arago devise ? ELECTRO-MAGNETISM. 129 Fig. 176. 204. Helix. A wire coiled as in fig. 176, made the me- dium of communication for a voltaic current, becomes ca- pable of manifesting very strong magnetic influence on any con- ductor placed in its axis. A delicate steel needle, laid in the helix, will be drawn to the centre and held suspended there, without material support, like Mahomet's fabled coffin. If the needle is of steel, the mag- netism it thus receives will be retained by it ; but if it be of soft iron, it is a magnet only while the current is passing Brass, lead, copper, or any other metallic conductor, can by galvanism be made to manifest temporary magnetic power. The polarity of the needle in the helix will depend on the di- rection in which the current is carried; if from right to left, the south pole will be at the zinc end ; if from left to right, this polarity is reversed. If the spiral is reversed in the middle, then a pair of poles will be found at the point of reversal, and this as often as the reversal may happen. A steel needle placed in such a helix receives the same reversals. Such an arrangement is shown in fig. 177. 205. The polarity of the helix is well shown by the arrangement represented in fig. 178, called De la Rive's ring. A small wire helix, whose ends are attached to the little battery of zinc and copper con- tained in a glass tube, floats on the surface of a basin of water, by means of a large cork, through which the glass tube is thrust. On exciting this small battery by a little dilute acid, poured into the tube, and placing the apparatus on the water, it will at once assume a polar direc- tion, as if it were a compass-needle, Fig. 177. Fig. 178. the axis of the helix being in the magnetic meridian and it will then obey the influence of any other magnet brought near it, manifesting the ordinary attractions and repulsions 204. What is the helix? How is a needle in it affected? What po- larity has it ? What does fig. 177 illustrate ? Why are the poles reversed at N ? 205. What shows the polarity of the wire itself? Describe fig. 178. 130 ELECTRICITY. Fig. 179. 206. The helix is placed as in figure 179, its lower end dipping into a cup of mercury p, in connection with one pole k, while it is held by its upper end n in connection with the other pole. In this situation, when the cur- rent passes, the separate turns of the helix attract each other, thus shorten- ing the spiral and raising the point out of the mercury, with a vivid spark. This breaks the connection the un- magnetized helix falls the point again touches the mercury, when a fresh contraction happens. These effects are made very striking by holding one end of an iron rod, or of a bar magnet, within the spiral. If a magnetic bar is used, the vibrations obey the ordinary law of polarity, ceasing entirely when a pole of like name is introduced. 207. Electro- Magnets. The induction of magnetism in soft iron by the voltaic current, furnishes us the means of producing magnets of astonishing power. Let a b (fig. 180) be a cylinder of soft iron, fitting the opening of a helix. If the cur- rent from several Grove's batteries be passed through the wires m n, sufficient magnetic power will be developed to sustain a I, oscil- lating in a vertical line, even should it weigh eight or ten pounds. This is one of the most surprising of all experimental demonstrations. By the use of this arrangement on a large scale, and with a battery of 100 members of platina, a foot square, Dr. Page sustained a mass of soft iron 600 pounds in weight, with a vertical movement of eighteen inches. On this principle he has propelled a magnetic engine on a railway at considerable speed, and sought to apply the power to other mechanical uses. 208. Professor Henry first demonstrated the fact that the power of an electro-magnet with a given voltaic current was greatly increased when the helix wire was divided into 206. Explain the action of the helix in fig. 179. 207. What is an electro- magnet? What remarkable result is mentioned? 208. What did Pro- fessor Henry iirst show ? Fig. 180. ELECTRO-MAGNETISM. 131 coils of limited length. Availing himself of this principle, he constructed electro- magnets lifting over two thousand pounds, with a single cylinder battery of small size. All the corresponding ends of the helices are carried to their appropriate poles. 209. The ring helix (fig. 182) is a striking mode of exhibiting the inducing effect of a voltaic current. Here two semicircles of soft iron, fitted with han- dles, are magnetized by the current passing in R, the ends a b being in con- nection with a battery. The rings of iron and of wire are quite separate, and, when the current passes, the iron (about f inch diameter) becomes so strongly magnetic as to sustain, easily, 50 pounds. Small electro-magnets have been made to sustain 420 times their own weight. 210. Electro-magnetic Motions. Faraday first produced motion by the mutual action of magnets and conductors, and Prof. Hen- ry, in this country, about the same time. By various combinations of the principles already explained, a great number of inge- nious pieces of electro-magnetic apparatus have been contrived for showing motion; by wires attracting and repelling by circles and rectangles of wires revolving the one within the other by armatures revolving before the poles of permanent or electro- magnets, and these adapted to carry various forms of machinery. But as these illus- trate no new principles, we refer the student to the excellent manual of magnetism by Daniel Davis, Boston, where the whole subject will be found very ably discussed. 211. The Electro-magnetic Telegraph is Fig. 181. Fig. 182. a contrivance which very happily illustrates the application of abstract 209. What does fig. 182 show? 210. Who first observed eleetro-i netic motions ? 132 ELECTRICITY. scientific principles and discovery to the wants of society. The inconceivably rapid passage of an electrical current ove! a metallic conductor was discovered by Watson in 1747/and thi^ discovery gave the first hint of the possibility of using electricity as a means of telegraphic communication. Nume- rous attempts were made, very early after this discovery, to construct a telegraph to be worked by ordinary electricity ; but from difficulties inherent in the mode, these attempts were attended with only very partial success. The discovery of electro-magnetism by GErsted, in 1820, supplied the neces- sary means of successful construction. Superior to all other contrivances in the essential conditions of simplicity, in con- struction and notation, is the beautiful contrivance patented by Professor Morse in 1837. In the accompanying figure (183) Fig. 183. we have a view of the most essential parts of Morse's tele- graphic register. A simple electro-magnet m m, with its poles upward, receives its induced magnetism from a cur- rent of electricity conducted by the wires W W from the distant station. As soon as the circuit is completed, m m becomes a magnet, and draws to its poles an armature or bar of soft iron a on the lever I. The motion of this lever starts a spring which sets in motion the clock arrangement c. This clock machinery, in consequence of the weight attached to 211. Explain the principles of the electro-magnetic telegraph and its operations. ELECTRO-MAGNETISM. 133 It, will, when once set in motion, continue to move. The immediate object of the clock machinery is to draw forward a narrow ribbon of paper p p in the direction of the arrows, and to cause it to advance with a regular motion. The paper ribbon passes by the end of the pen-lever ?, in which is a steel point s, that indents the paper whenever this end of the lever is thrown upward by the attraction of the armature a to the magnet m. If m m were constantly magnetized, the mark made by the point s would be a continuous line. But we can make and discharge an electro-magnet as often and as fast as we please ; the instant, therefore, the circuit W W is broken, m m ceases to be a magnet, and lets go the iron armature a, when the point s of the lever falls, so as no longer to mark the paper. The circuit being renewed, the point marks again ; and this may be repeated as often as the operator pleases. The length of time that the circuit is closed will be exactly registered in the corresponding length of the mark made by s. The completing of the cir- cuit is performed by touching a spring on the operator's table, which establishes a metallic communication between the poles of the battery. A touch will produce a dot, a con- tinued pressure a long line, and intermitting repeated touches a series of dots and short lines. These easily form an alpha- bet. To complete the arrangement, each operator must have his own battery in connection with the register at the dis- tant station. In practice, only one wire is used with each register, the circuit being completed by connecting the other pole of the battery with the moist earth by means of a buried metallic plate and a wire. The remarkable observation that the earth could be used in this manner as a part of the cir- cuit, was made by Steinheil, in G-ermany, in 1837. Such is a brief account of one of the most remarkable discoveries of modern times. In Bain's telegraph, the circuit decomposes a salt of iron, staining a paper with the marks of the con- ductor, and no magnet is employed. 212. The telegraph has become an important auxiliary in astronomical observations, by furnishing an exact means of determining longitudes. For this purpose the principal astronomical observatories in the United States are connected by telegraphic wires, and such is the velocity of the electrical wave that any communication made from one station will bo 212. How is the telegraph auxiliary to astronomy? 134 ELECTRICITY. received at all the others at almost the same instant. The velocity of the wave has been determined by the experiments of the Coast Survey to be about 15,000 miles in a minute. Wheatstone asserts that the wave of electricity moves as rapidly at least as that of light. Other very ingenious and important applications have been made of the telegraph for regulating time-pieces and for signalizing fires. The city of Boston is provided with such a system, a detailed descrip- tion of which may be found in the American Journal of Science for January, 1852. One curious fact connected with the operation of the tele- graph is the induction of atmospheric electricity upon the wires to such an extent as often to cause the machines at the several stations to record the approach of a thunder-storm. This induction occasions a serious inconvenience in working the telegraph, not unattended with danger to the operators. 213. Professor Henry observed that when the current from a single pair of plates was passed through a long con- ducting wire, a vivid spark appeared at the instant of breaking contact between the conductor and the battery ; accompanied, also, by a feeble shock. A long conductor, then, supplies the place of; an increased number of plates in a voltaic scries, and to some degree imparts the quality of intensity to a current of quantity. A flat spiral of copper ribbon, one hundred feet long, wound with cotton, and var- nished, shows these effects well. The magnetic needle indicates the direction of the current, (fig. 184.) The opposite sides of the spiral of course produce opposite effects on the needle. The magnetism pro- duced is, however, to be distin- guished from the new effects ex- cited by the passage of the feeble Fig 184 current through the coiled con- ductor, on breaking contact, i. e. the vivid spark and the shock. The latter is feeble with 100 feet of copper ribbon, and becomes more intense if the length of the conductor be increased, the battery remaining the same ; but the sparks are diminished by lengthening What other facts are mentioned regarding the telegraph ? 213. What was Henry's observation on the spiral ? ELECTRO-MAGNETISM. 135 the conductor beyond a certain point. The increase of in- tensity in the shock is also limited by the increased resistance or diminished conduction of the wire, which finally counter- acts the influence of the increasing length of the current. On the other hand, if the battery power be increased, the coil remaining the same, these actions diminish. 214. These effects Prof. Henry ascribed to the generation of a secondary current at the moment of breaking contact. This secondary current moves in a direction opposite to that of the battery current. If a long coil of fine, insulated wire be brought within a small distance of the flat spiral, this new current will be detected in the second coil. The ar- rangement used by Prof. Henry is seen in the annexed figure. A small battery L is connected with the flat spiral of copper ribbon A by wires from the battery cups Z and C. This communication is broken at will, by drawing the end of one of the battery wires Z over the rasp. When the coil of fine wire W is in the position indicated in fig. 185, and the hands Fig. 185. grasp the conductors, a violent shock is felt as often as the circuit is broken by the passage of the wire over the rasp. When the coil W contains several thousand feet of wiro, and is brought near A, the shocks are too intense to be borne. As this induction takes place through a distance of many inches, we can, by placing the spiral A against a division wall, or the door of a room, give shocks to a person in another room, who grasps the conductors of the wire coil W, and brings it near to the wall on the side opposite to A. A screen or disc of metal introduced between the two coils will cut off this inductive influence. But if it be slit by a cut 214. What were these currents called ? How do they move ? What cf the spark and shock ? 136 ELECTRICITY. from the centre to the circumference, as a & in fig. 186, the induction of an intense current in W is the same as if no screen were present. Fig. 186. Discs or screens of wood, glass, paper, or other non-conductors, offer no impediment to this induction. 215. Induced Currents of the third, fourth, and fifth order. If the wires from W be connected with another flat spiral, and it with a second coil of fine wire, and so on, (fig. 187,) a series of currents will be induced in each alternation of coils. The secondary intense current in B will induce a quantity current in the second flat spiral C ; and a second fine wire coil W will induce a tertiary intense current, and so on. These currents have been carried to the ninth order, decreasing each time in energy by every removal from the original battery current. The polarity, or direction of these secondary currents, alternates, commencing with the second- ary. Thus the current of the battery is -}- ; and the secondary current is -}- ; the current of the third order is ; the cur- reut of the fourth order is -j- ; and the current of the fifth order is . These alternations are marked in the figure above, and were also determined by Prof. Henry. 216. Compound Electro-magnetic Machine. By combin- ing the results just briefly enumerated, a great number of ingenious electro-magnetic machines have been produced, adapted to medical use, and illustrative of the induction of magnetism and secondary currents. One of these, contrived by Dr. Page, is seen in fig. 188. In this little machine, a short coil of stout insulated copper wire forms a helix, within which some straight soft-iron wires M are placed. The 215. To what degree have they been carried ? ELECTttO-MAflNETTRM. 137 battery current is made to pass through this stout wire, by which means mag- netism is induced in the soft iron. The conducting wires are so arranged beneath the board that the glass cup C contain- ing some mercury is in connection with the battery. The bent wire W dips into this mercury, and also by a branch into B, and when in the position shown in the figure, the current from the battery will flow uninterruptedly. As soon, however, as the battery connection is completed, M becomes strongly magnetic, and draws to itself a small ball of iron on the end of P; this moves the whole wire P W and raises the point out of the mercury C; as the wire leaves the mercury, a brilliant spark is seen on its surface, the contact being thus broken with the battery, M ceases to receive induced magnetism, and the ball P being consequently no longer attracted to M, the wire W falls by its gravity to the position in the figure. This again establishes the battery connection, and the same effects just described recur; thus the bent wire W receives a vibratory motion, and at each vibration a brilliant spark is seen at C, and M becomes magnetic. It remains only to mention that the short quantity wire is surrounded by a fine intensity wire, 2000 to 3000 feet long, having no metallic connection with the battery or quantity wire, with its ends terminating in two binding screws on the left of the board, The fine wire receives a secondary induced cur- rent like the coil W, (185,) which, if touched, produces the most intense shocks at each vibration of the wire. These shocks are graduated by withdrawing part or all of the soft- iron wires M. 217. Magneto-Electricity. As we have seen effects pro- duced from galvanism which exactly resemble those of ordi- nary machine electricity and the magnetic influence, so, conversely, we might expect the production of electrical effects from the magnet. The electrical current from a single 216. Explain the apparatus, fig. 188. 138 ELECTRICITY galvanic pair, we have seen, produces magnetism in a spiral wire at right angles with its own course ; so the induction of magnetism in soft iron from a permanent magnet, in like manner, produces an electrical current at right angles to itself in the wire coiled on the armature. This class of phenomena was discovered by Faraday in 1831, and our countryman, Mr. J. Saxton, soon contrived a machine very similar to the one in fig. 189, called a magneto-electrical Fig. 189. machine. This consists of a powerful magnet S, secured to a board, with its poles so situated that an armature, formed of two large bundles of insulated copper wire W, wound on soft-iron axes, may be revolved on an axis before its poles, by the multiplying wheel M. A current of electricity is thus induced in W, just as in the flat coils, the permanent magnet here taking the place of the flat spiral. The cur- rent excited in "W is led off by conductors to the binding screws p and n, the continuity of the current being broken (in imitation of the rasp in 185) by a contrivance at 6 on the axis, called a break-piece, (fig. 190,) which is made by alternate ribs of metal c and ivory i, the current is broken by the ivory and Fig. 190. renewed by the metal, and at every break, the person whose hands grasp the conductors, secured to p and n, feels a sharp shock, which may be graduated at will by the rapidity of the revolutions of M, and by the adjustment of the break b. A long and fine wire say 217. What is magneto-electricity ? Explain fig. 189. THERMO-ELECTRICITY. 139 3000 feet of wire -^ of an : ;_h in diameter is required to produce shocks and chemical decompositions. A shorter and stouter wire, as 250 feet of wire y 1 ^ or inch in dia- meter will produce no shock, but will deflagrate the metals powerfully, and produce a secondary current of induction in soft iron. We thus imitate in magnetism the effects produced from a voltaic current, the short and stout wire of the armature is the simple circuit of large plates; the long and fine wire is like the compound circuit of smaller plates. Thermo-Electricity, or the Electrical Current excited ly Heat. 218. If two metals unlike in crystalline structure and conducting power are united by solder, and the point of their union is heated or cooled, an electrical current will be excited, which will flow from the heated point to the metal which is the poorer conductor. Bismuth and antimony are such metals, being bad conductors, and unlike in crystalline structure. If two bars of these metals are united, as in fig. 191, and the point c is warmed by a lamp, a current will be set Fig. 191. in motion, which will flow from b to a, as in the figure. The compass-needle may be thus affected, as by the voltaic current. For this purpose two bars may be mounted as in tig. 192, and their junction being heated by a lamp, the needle will swing, in conse- quence of the electrical current excited by the heat. When several Fig. 192. such are joined, we have a greatly increased effect, as in the thermo-electric pile in Melloni's apparatus, (fig. 193.) 219. Thermo-electric effects are not confined to metals, for they may be produced from other Flg ' 193> solids, and even from fluids ; and a single metal, as an iron wire, which has been twisted or bent abruptly, will originate a thermo-electric current when the distorted part is greatly 218. What is thermo-electricity ? How does the current move ? 140 ELECTRICITY. heated. The rank of the p* r i)cipal metals in the thermo- electric series is as follows, beginning with the positive : Bismuth, mercury, platinum, tin, lead, gold, silver, zinc, iron, antimony. When the junction of any pair of these ia heated, the current passes from that which is highest to that which is lowest in the list, the extremes affording the most powerful combination. If we pass a feeble current of electricity through a pair of antimony and bismuth, the temperature of the system rises, if the current passes from the former to the latter ; but if from the bismuth to the antimony, cold is produced in the compound bar. If the reduction of temperature is slightly aided artificially, water contained in a cavity in one of the bars may be frozen. Thus we see that as change of temperature disturbs the electrical equilibrium, so conversely the disturbance of the latter produces the former. Animal Electricity. 220. The existence of free electricity in the animal body is proved by the results of Aldiui and Matteucci. In some animals we see a special apparatus for the purpose of exciting at will intense currents of electricity. There are also such currents in all animals. For example, when the lumbar nerves of a frog, held in the manner shown in fig. 194, are touched to the tongue of an ox lately killed, and at the same in- stant the operator grasps with the other hand, well wetted in salt water, an ear of the ox, a con- vulsion of the frog's legs indicates Fig. 194. the passage of an electric current. 221. The same delicate electroscope also shows similar excitement when its pendulous ischiatic nerves touch the human tongue, the toe of the frog being held between the 219. What range have these effects ? How is a fall of temperature ob- served in a compound bar of antimony and bismuth ? 220. What is animal electricity? Explain the experiment in iig. 194. 221. How else is the same fact shown ? How does the cunoat circulate ? ANIMAL ELECTRICITY. 141 moistoned thumb and finger of the experimenter. This is what Donne" calls the musculo-cutaneous current; passing from the external, or cutaneous, to the internal, or mucous, covering of the body. This current may be de- tected, as was shown by Aldini, in the frog's legs above. For this purpose he prepared the lower extremities of a vigorous frog, (fig. 195,) and, by bending up the leg, brought the muscles of the thigh in contact with the lumbar nerves : contractions immediately ensued. Thus it ap- pears from experiments made by Matteucci, that a current of positive electricity is always circu- lating from the interior to the exterior of a muscle, and that although the quantity is ex- g> 95 ' ceedingly small, yet by arranging a series of muscles, having their exterior and interior surfaces alternately connected, he produced sufficient elec- ( ^ ~~~\ tricity to cause decided I 4-\ effects. By a series of half thighs of frogs, arranged as ^ nnWm in fig. 196, he decomposed Fig. 196. the iodid of potassium, deflected a galvanometer needle to 90, and by a condenser caused the gold-leaves of au elec- troscope to diverge. The irritable muscles of the frog's legs form an electroscope 56,000 times more delicate than the most delicate gold-leaf electro- meter. Professor Matteucci's frog-gal van oscope (fig. 197) is therefore far the most sensitive test of electricity that can be employed. When the pendulous nerve is touched simultaneously in the places where electrical excitement is suspected, the muscles in the tube are instantly convulsed. 222. The electrical eel of South America men- tioned by Humboldt, and the torpedo a flat fish found on our own coast are remarkable examples Ig ' 7 ' of those animals having a special electrical apparatus of nervous matter and cellular tissue arranged in the manner of the pile. The student is referred to the lectures of Pro- What has Donne called it ? How is it shown in the legs of the frog alone ? How does this current circulate ? How does fig. 196 prove it ? What is the delicacy of the frog-galvan oscope ? 222. What animals have a special electric apparatus ? 142 ELECTRICITY. fessor Matteucci on living beings for further details on this very interesting subject. We can only add, that the shock from these animals is sufficient to charge a Ley den jar, to produce chemical decompositions, and to paralyze vigorous animals. The legs of the common grasshopper are, it is said, equally sensitive electroscopes as those of the frog. Electro- Chemical Decomposition. 223. By far the most interesting chemical result of Volta's pile was the new power it placed in the hands of chemists, of unfolding the secrets of combination, and of assigning their relative positions to the several elements. Indeed, the electro-chemical theory has been carried so far by some chemists, that every chemical decomposition has been referred to the play of electrical forces. 224. The decomposition of water is the finest possible illustration of this power. Water is a compound of oxygen and hydrogen gases, in the proportions of one measure of the former to two of the latter. When two gold or platinum wires are connected with the opposite ends of the battery, and held a short distance asunder in a cup of water, a train of gas-bubbles will be seen rising from each and escaping at the surface. With two glass tubes placed over the plati- num poles, (fig. 198,) we can collect these bubbles as they rise, and shall soon find that the gas given off from the plate is twice the volume of that obtained from the -f- plate. When the tubes are of the same size, this difference of volume becomes at once evi- dent to the eye. By examining these gases, we shall find them, respectively, pure hydro- Fig. 198. g en and pure oxygen, in the exact proportion of two volumes of the former to one of the latter. The rapidity of the decomposition is greater when the water is made a better conductor, by adding a few drops of sulphuric acid. 223. What was the most interesting result of Volta's pile ? 224. Hovf is water decomposed by it ? Describe fig. 198. ELECTRO-CHEMICAL DECOMPOSITION. 143 If we employ a decomposing cell with only one tube over the conductors, it will be found that the gaseous contents will explode by the electric spark or by a lighted taper ; and if this is done over water the perfection of the vacuum re- sulting from the explosion will be seen by the height of the column which rises in the tube, (fig. 199.) 225. We learn from this most in- structive experiment, that the voltaic current has power to decompose chemi- cal compounds, that this decomposition takes place in definite proportions of ^ the constituents and that these consti- tuents appear invariably at opposite poles of the battery. Fig- 199. 226. A decomposing cell interposed in the circuit will give us an exact account of the amount of electricity flowing. Such an in- strument has been called by Faraday a voltameter, (fig. 200.) It differs from the common decomposing cell, in having a ground-glass tube at top bent twice, so as to deliver the accu- mulating gases into a graduated air- vessel, in which their volume is mea- sured. A more simple form of the apparatus is easily constructed, as in figure 201, (page 144,) of two glass Fig. 200. tubes, two corks, and the conductors p p. 227. The experimental researches in electricity by Dr. Faraday, which are the basis of modern science on this subject, required the introduction of certain new terms, some of which require explanation. Tho termi- nal wires or conductors of a battery are often termed the poles, as if they possessed some attractive power by which they draw bodies to themselves, as a magnet attracts iron. Faraday has shown that this notion is a mistake, and that the terminal wires act merely as a path or door 225. What does this experiment teach? 226. What other cells are named ? 227. What is said of Faraday's researches ? What did they re- quire? W r hat does he call the poles, and why? 144 ELECTRICITY. PO Fig. 201. TO to the currents, and he therefore calls them electrodes, from electron and odos, a way. The electrodes are any surfaces which convey an electric current into and out of a decom- posable liquid. The term electrolysis, from electron, and the Greek verb luo, to unloose, is used to express decomposition ; and the substances suffering decomposition are termed electrolytes. Thus, the experiment mentioned in the last section is a case of electrolysis, in which water is the electrolyte. The elements of an electrolyte are called ions, from the Greek particle ion, going, since the elements go to the -j- or electrode. The electrodes are distinguished as the anode and the cathode, from ana, upward, and odos, way, or the way in which the sun rises; and kata, downward, and odos, or the way in which the sun sets ' } the anode is -f-> and the cathode . We will now briefly consider the 228. Conditions of Electro- Chemical Decomposition. (1.) All compounds are not electrolytes, that is, they are not directly decomposable by the voltaic current. Many bodies, however, not themselves electrolytes, are decomposed by a secondary action. Thus, nitric acid is decomposed in the electrical circuit by the secondary action of the nas- cent hydrogen, which, uniting with one equivalent of the oxygen, again forms water and nitrous acid. Sulphuric acid is not an electrolyte, while hydrochloric acid is ; and the nascent chlorine from the latter attacks the -(- electrode, if it be of gold. (2.) Electrolysis cannot happen unless the fluid be a conductor of electricity ; and no solid body, however good a conductor, has ever been thus decomposed. A plate of ice, however thin, interposed between the elec- trodes, will entirely prevent the passage of the power; but the electrolysis will proceed as soon as the least hole melts in the ice, through which the power can pass. Fluidity is therefore a very essential condition of electrolysis. The fluidity may be that of heat, or of solution; thus, the Explain the terras electrode, electrolysis, and electrolyte. What are ions? 228. Are all compounds electrolytes? Give examples. What is the second condition of electrolysis ? Give examples. ELECTRO-CHEMICAL DECOMPOSITION. 145 chlorids of lead, silver, and tin are not electrolysed in a solid state, but when fused they are decomposed with ease. (3.) The ease of electro-chemical decomposition seems in a good degree propoitioned to the conducting power of the fluid. Thus, pure water is by no means a good conductor, and its electrolysis is difficult; but the addition to it of a few drops of sulphuric acid, or of some other soluble con- ductor, greatly promotes the ease with which it is decom- posed. (4.) The amount of electrolysis is directly propor- tioned to the quantity of electricity which passes the elec- trodes. (5.) The binary compounds of the elements, as a class, are the best electrolytes. Water and iodid of potassium are instances; while sulphuric acid, which has three equivalents of base to one of acid, is not an electro- lyte. No two elements seem capable of forming more than one electrolyte. (6.) Most of the salts are resolvable into acid and base. Thus, sulphate of soda is resolved into sul- phuric acid, which appears at the -|- electrode, and will there redden a vegetable blue; and the soda which appears at the electrode will restore the previously reddened blue ; so that by reversing the direction of the current, these striking effects are also reversed, 229. (7.) A single ion, as bromine, for instance, has no disposition to pass to either of the electrodes, and the cur- rent has no effect upon it. There can be no electrolysis except when a separation of ions takes place, and the se- parated elements go one to each electrode. (8.) There is no such thing, in fact, (as has been often supposed,) as an actual transfer of ions from one part of the fluid to cither electrode. In the case of water, for example, oxygen is given out on one side, and hydrogen on the other. In order that this may be the case, there must be water be- tween the electrodes. We cannot believe that the separa- tion of the elements takes place at the electrode where one ele- . -I T 1 , 1 i , 1 nient is evolved, and that the other travels over unseen to the opposite electrode. We may, Fio . 9Q9 (3.) To what is the ease of the electrolysis proportioned? (4.) TG what is its amount owing ? (5.) What class of compounds are the best electrolytes? Give examples. (6.) What of salts? Give examples. 229. (7.) What is said of a single ion? (8.) What of the transfer of ions ? Give the explanation offered of the decomposition of water. 10 146 ELECTRICITY. however, conceive of water in its quiet state, as represented by the diagram, (fig. 202,) each molecule being firmly united lay polar attractions (218) to every other, and that the electrolytic force of the electric current has power to disturb this polar equilibrium, each molecule being simi- larly affected. In this case the electrolysis will proceed from particle to particle through the whole chain of affini- ties, decomposing and recomposing, until the ultimate parti- cle on each side, having no polar force to neutralize ^ esca P es at that ele - trode which has a polarity ._. opposite to itself. This explanation may be better understood, perhaps, by inspecting the second diagram, (fig. 203,) which represents a series of compound molecules of water undergoing electrolysis, the H and being eliminated at the opposite extremities. The same explanation will be found to serve for all other cases of electrolysis, both simple and secondary. 230. (9.) A surface of water, and even of air, has been shown capable of acting as an electrode, proving that the contact of a metallic conductor with the decomposing fluid is not essential. The discharge from a powerful electrical machine was made to pass from a sharp point through air to a pointed piece of litmus paper moistened with sul- phate of soda, and then to a second piece of turmeric paper similarly moistened. This discharge had power to effect a true electrolysis; the blue litmus was reddened by the sul- phuric acid set free from the sulphate of soda, while the yellow turmeric was turned brown by the alkaline soda from the same salt. 231. (10.) Electrolysis takes place in a series of com- pounds in the precise order of their equivalents. Thus, if wine-glasses are arranged in a series, and in one is placed sulphate of soda, in another acidulated water, in another iodid of potassium, and in another hydrochloric acid, and if the whole series be connected together by siphon tubes, or moistened lampwick, passing from glass to glass, and a 230. (9.) What is said of electrolysis without metallic conductors? Explain the experiment of the electrolysis of sulphate of soda by the electrical machinfc. 231. How does electrolysis occur in a series of com- pounds ? ELECTRO-CHEMICAL DECOMPOSITION. 147 powerful galvanic current be then passed through them, electrolysis will occur in all, but unequally. It has been proved by acccurate experiment, that the decomposition which ensues is in exact proportion to the equivalents of each substance. In other words, we may say it requires one equivalent of electricity to decompose one equivalent of an electrolyte formed from the union of an equivalent of acid and another of base. Conversely, from the fact that an equivalent of electricity is required to de- compose any compound, it is proved that the opposite ele- ments of this compound, in uniting, will disengage the same equivalent of electricity. 232. (11.) The passage of a current within the cells of a voltaic battery depends also upon the decomposition in each cell, equally with that between the platinum electrodes. The same phenomena which we notice in the decomposing cell (224) take place also in each battery cell. Water is decomposed, and the hydrogen is given off from the positive plate, while the oxygen combines with the zinc, and thus escapes detection. Therefore, no fluid not an electrolyte is suitable to excite a battery. Acid water acts, for this pur- pose, only by the decomposition of the water and oxydation of the zinc. The presence of the acid is useful only so far as it combines with the oxyd of zinc constantly accumulating on the zinc plate, which must be removed as fast as formed, in order to keep up a steady flow of electricity. 233. The theories which have been proposed to account for electro-chemical decomposition and the action of the voltaic circuit, we cannot discuss here, any further than to say that the chemical theory first proposed by Dr. Wollaston is now generally accepted. Volta argued that the contact of different metals was essential to the production of a cur- rent. The researches of Faraday, however, in confirming the chemical view of Wollaston, have completely disproved the contact theory. A very simple experiment by Faraday illustrates this statement. A slip of amalgamated sheet zinc bent at a right angle is hung in a glass of dilute acid; on it is laid a folded piece of bibulous paper moistened with In other words, what do we say ? Conversely, what ? 232. How does a current pass in the cells of a battery ? What happens in each cell ? What is requisite in the fluid used to excite a battery ? How does acid water act in the battery? 233. What two theories have been proposed to account for the electrical phenomena of electrolysis? What tjitnple experiment disproves the contact theory ? 148 ELECTRICITY. iodid of potassum. A .platinum plate, with an attached wire of the same metal, is now placed in the acid water, but not in contact with the zinc; the sharpened end of the wire is bent, so as to touch the moistened paper, and very soon it is discolored by a brown spot made by the freo iodine, liberated from the electro-chemical de- composition of the iodid of potassium, with which the paper is moistened. There is no contact of metals, and the current is excited only from the Fig. 204, decomposition of the iodid out of the cell, and of the water in it. A very strong argument in favor of the chemical theory has been before mentioned, that the di- rection of the current is always determined by the nature of the chemical action the metals most acted on being always positive. 234. The electrotype, or deposition of metals from their solution by the voltaic current, seems to have been suggested by Daniell's battery. It has been remarked, that the cop- per of the sulphate of copper in the outer cell of that battery is deposited in a metallic state. The procuring of a pure metal in a perfectly malleable state, by means of a current of electricity, is a most important fact, and has given rise to a new and valuable art, which has become wonderfully extended in its applications. We thus accomplish, in fact, a cold casting of copper, silver, gold, zinc, and many other metals; and a new field of great extent has been thus opened for the application of metallurgic processes. The tinting of metals of various hues by metallic oxyds, and the coloring of their surfaces by palladium, are among the most surprising of its effects. The very simple apparatus required to show these re- sults experimentally, is represented in the figure, (205.) It is nothing, in fact, but a single cell of Daniell's battery. A glass tumbler S, a common lamp-chimney P, with a bladder-skin tied over the lower end and filled with dilute acid, is all the appara- lg ' ' tus required. A strong solution of sulphate of copper is put in the tumbler, and a zinc rod Z in P, 234. What is the electrotype? Explain its uses. ELECTRO-CHEMICAL DECOMPOSITION. 149 the moulds, or casts, m m are seen suspended by wires attached to the binding screw of Z. Thus arranged, the copper solution is slowly decomposed, and the metal is evenly and firmly deposited on m, m. A perfect reverse copy of m is thus obtained in solid, malleable copper. The back of m is protected by varnish, to prevent the ad- hesion of the metallic copper to it. In this manner the most elaborate and costly medals are easily multiplied, and in the most accurate manner. In practice, casts are made in fusible metal of the object to be copied, and the operation is conducted in a separate cell, containing only the sulphate of copper, one of Smee's batteries supplying the power. The art is also now extensively applied to plating in gold and silver from their solutions ; the metals thus deposited adhering perfectly to the metallic surface on which they are deposited, provided these be quite clean and bright All the copper-plates of the charts of the Coast Survey are reproduced by the electrotype the originals are never used in the press, but only the copies, and any required number of these may be produced at small expense. 150 PART II. CHEMICAL PHILOSOPHY. ELEMENTS AND THEIR LAWS OF COMBINATION. 235. THE number of elements, (or simple substances,) as DOW recognized, is sixty-two, forty-nine of which are metals The elements are usually divided into metals and metalloids, or non-metallic substances. This convenient distinction is not strictly accurate, since there are several elements, as tellurium, carbon, arsenic, silicium, and others, which seem to possess an intermediate character. The term metalloid is therefore preferable. Only fourteen of the elementary bodies are of common occurrence, and of these the atmo sphere, water, and the great bulk of the planet are com- posed. The remainder are comparatively rare, and are known only to the chemist. Of these, twenty-one, marked in the table with an asterisk (*), will not be discussed in this work, or will be very briefly considered, because of their great rarity, and the difficulty of procuring the substances containing them. 23G. At common temperatures, and when set free from combination, nearly all the elements are solids. Two, mer- cury and bromine, are fluids, and five are gases, namely, chlorine, fluorine, hydrogen, oxygen, and nitrogen. A few only of the elements are found naturally in a free or un- combined state, among which we may name oxygen, nitro- gen, carbon, sulphur, and nine or ten metals. All the rest exist in combination with each other, and so completely disguised as to manifest none of their properties. 237. The names of the elements are arbitrary or conven- tional, while the nomenclature of their compounds is sub- ject to the strictest laws. Some of the elementary bodies have been known from the remotest antiquity, and were in common use long before the science of chemistry was heard of. Thus several metals, as Copper, (Cuprum,) Gold, (Aurum,) Iron, (Ferrumf) Mercury, (Hydrargyrum^) Sil- 235. What is the number of elements? How divided? What occupy an intermediate position ? 236. What is the physical condition of the elements ? Which are fluid ? Which gaseous ? Which found uncom- bined ? 237. What of the names of elements ? Which have been long known ? ELEMENTS LAWS OP COMBINATION. 151 ver, (Argentum,) Lead, (Plumbum,} Tin, (Stannum,) have long been known either by the names we now give them, or by those Latin terms of which our English names are trans- lations. The alchemists named the metals after the various planets. Thus, Gold was called Sol, the Sun ; Silver, Luna, the Moon; Iron, Mars; Lead, Saturn; Tin, Jupiter; Quick- silver, Mercury ; and Copper, Venus. Hence, formerly the astronomical signs or symbols of these planets were employed to represent the names of these metals, and they are still in use in some countries. Several of the elements have been named from some prominent or distinguishing physical property of color, taste, or smell, which they possess : thus, Bromine is so called from the Greek word bromos, fetor; Chlorine, from chloros, green, in allusion to its greenish color; Chromium, from chroma, color, because it makes highly-colored compounds, as chrome-yellow; Glucinum, from glukus, sweet, from the sweet taste of its salts ; Iodine, from ion, a violet, and eidos, in the likeness of. Another class of names has been con- trived from what was supposed to be the characteristic at- tribute of the body in combination. Thus, Oxygen was so named because many of its compounds are acids, from the Greek, oxus, acid, and gennao, I produce. Hydrogen is from hudor, water, and gennao, I produce. 238. It has been discovered that the elements, in corn- Dining among themselves, unite always in certain weights, in- variable in each case, and supposed to have an immediate re- lation to the atomic constitution of the substance. These weights represent respectively the quantities in which the elements unite with each other, and they are called equiva- lent atomic weights or combining numbers. In the follow- ing table, the equivalent or combining numbers of all the elementary bodies are given in accordance with the latest and best authorities. Because hydrogen enters into combi- nation with other bodies in a smaller weight than any other known element, it has generally been used in Great Britain and in this country as the basis of the scale of equivalent numbers. It is supposed also, by some good chemists, that the numbers expressing the combining weights of all bodies What of astronomical signs ? Whence such names as bromine, Hy- drogen ? Iodine, &c. ? 238. How do the elements unite ? What do the weights represent ? What are they called ? Why is hydrogen unity ? 152 ELEMENTS LAWS OF COMBINATION. would be found, on more accurate research, to be simple multiples of the unit of hydrogen. If this view were cor- rect, it would give us the great convenience of avoiding fractional numbers. The latest investigations have so far confirmed this idea, that in the present edition of this work a largely increased number of elements stand with simple numbers. Berzelius determined more atomic numbers than any other chemist, and his labors have in most cases stood the severest review, and deserve the everlasting gratitude of chemists. Most chemists of continental Europe assume oxygen as 100; therefore, to convert the numbers of the fol- lowing table to the oxygen scale, multiply them by 12*5. TABLE OF ELEMENTARY SUBSTANCES, WITH THEIR SYMBOLS AND ATOMIC WEIGHTS OR EQUIVALENTS. Name. Svra- 1 bo!. II =: I. Name. Svm- bol. Nl H=l- 29-6 Al Sb As Lin Be Hi B Br CJ Ca Ce Cl Cr Co Cm,Ta Cu D B Fl Au U I Ir Fe La Pb Li Mg Mn Hg 13-7 12'.)- 75' 68-50 47 208' 10-9 80' 56' 20- 6- 47' 35.50 26-7 29-5 184- 31-7 Ki- rn- 1- 127- 99- 28- 36* 103-5 6-5 12-2 27-6 100- Niokol Antimony (Stibium) Molybdenum *Xiobium Mo Nb N Xo <)s O Pd Pe P Pt K Jt 11 u Se Si Ag Na Sr ^ To Tli Th Su Ti W II V Y Zn Zr 46- 14- 90-6 8- 53-3 98-7 52 - 2 52-2 40- 21-3 108- 44- 16- 64- iV.rtj r ) ! ,t- yo- no- 68-0 32-5 22-4 Bari um Nitrogen *Bery Ilium (Gluciuum)... Bismuth Boron Oxygen *Pniladiuin | Cadmium Calcium *Ccrium Potassium (Kalium) : *Hhodium Cobalt *Co! u mbi u m (Tan! al um) ' Silieium I Silver (Argon turn) Folium (Natrium) * Did vmium #Erbium Strontium : Sulphur Fluorine Gold (Auruni) I *Terbium Iodine *Thorium i Tin (Stannum) i *Titanium 'Lantaniuni Load (Plumbum) Lithium *Tungsten(^Yolfrarnium) *Vana/lium WuKiicsinni *Yttrium 7inc *Zirconium i Combination by Weight. 239. The laws by which the elements unite to form com- pounds, are included in the four following propositions : What of its multiple relations ? Who determined most atomic weights ? COMBINATION BY WEIGHT. 153 1st. The law of definite proportions, or, a compound of two or more elements, is always formed by the union of certain definite and unalterable proportions of its constituent elements. 2d. The law of multiple proportions, which requires that when two bodies unite in more proportions than one, these proportions bear some simple relation to each other. 3d. The law of equivalent proportions, according to which when a body (A) unites with other bodies, (B, C, D, &c.,) the proportions in which B, C, and D unite with A shall represent in numbers the proportions in which they will unite among themselves, in case such union takes place. 4th. The law of the combining numbers of compounds, by which the combining proportion of a compound body is the sum of the combining weights of its several elements. 240. These general laws of combination are subject to some modifications, which will be explained as they arise. The first of the laws above given is the result of chemical analysis, and is proved by synthesis. Thus, from nine grains of water we obtain eight grains of oxygen and one of hydro- gen, and by the union of the like weights of these two sub- stances we obtain nine grains of water. Constancy of com- position is the essential feature of chemical compounds. By the law of multiple proportions, we learn that if a body (A) unites with a body (B) in more proportions than one, these proportions bear a simple relation to each other. Thus, we may have the series of compounds A -f- B : A -j- 2B : A -}- 3B : A -f- 4B : A -f- 5B, as in the case of nitrogen and oxygen, between which this very series occurs, forming five distinct compounds, in which one, two, three, four, and five, parts by weight (atoms) of oxygen unite with one of nitrogen. (2.) In place of this simple ratio we may have one intermediate : thus, the expressions 2 A -j- 3B : 2A -j- 5B : 2A-J-7B represent a series of compounds which are equal to the fractional ratios 1 : 1, 1 : 2J, 1 : 3i. 241. As by chemical analysis the law of definite proportions is established, so by the same direct experimental method do we prove the law of equivalent proportions. Oxygen is an element forming at least one definite compound with every 239. What is the 1st law of combination ? The 2d ? The 3d ? The 4th ? 240. Whence is law 1st derived? Give an example ? What of the law of multiple proportions? Give examples of the 2d modification? 241. How is the law of equivalent proportions demonstrated ? What is said of oxygen ? 154 ELEMENTS LAWS OF COMBINATION. other element known except fluorine. These compounds are termed oxyds, (246.) By analysis we find that water always contains in 100 parts 11-11 parts of hydrogen and 88-89 parts of oxygen. If we ask how much oxygen is proportional, or equivalent to a unit of hydrogen, we state the simple proportion 11-11 : 100 : : 88-89 : x in which x = 8, which is therefore the equivalent of oxygen. In like manner, we might go on making analyses of all the compounds of oxygen until we had completed the whole list, when we should have a table of equivalents for all the elements, hydrogen being unity. Thus, 16 parts of sulphur, 6 parts of carbon, 1 part of hydrogen, 8 parts of oxygen unite with -j 35-5 parts of chlorine, 100 parts of mercury, 28 parts of iron, 14 parts of nitrogen. Of course, 16, 6, 1, 35.5, 100, 28, and 14, are respec- tively the equivalents of sulphur, carbon, hydrogen, chlo- rine, mercury, iron, and nitrogen. Chemical equivalent and atomic weight have the same meaning in this work. 242. If any of those bodies unite to form compounds, the union will always happen in quantities by weight exactly proportional to those numbers. Thus, hydrogen (1) unites with chlorine (35-5) to form chlorohydric or muriatic acid. In 36-5 pounds, therefore, of this acid, there Avill be 1 pound of hydrogen and 35-5 pounds of chlorine. If sulphur com- bines with mercury, it will require 16 parts of sulphur and 100 parts of mercury, and there will be 116 parts of sul- phuret formed; or it may require 32 parts of sulphur to 100 parts of mercury, when we should have a bisulphurct. If oxygen is assumed as the standard of comparison for atomic weights, then, calling it 100, hydrogen will be 12-5, and all the other elements will have numbers just twelve and a half times as large as their equivalents on the hydrogen scale. It follows, as a necessary result of this law of equivalent proportions, that the combining numbers of a compound should be the sum of the equivalents of its constituents. Give the mode of determining atomic weights ? Give some examples ? What is the meaning of chemical equivalent? Of atomic weight? 242. What is tho relation among elements in combination? How is it in chlorohydric acid ? In sulphurct. of mercury ? What of tho combining numbers of compounds ? NOMENCLATURE AND SYMBOLS. 155 Chemical Nomenclature and Symbols. 243. It would have been a hopeless task for the strongest memory to retain all the names of chemical compounds, if they had like the names of the elements been bestowed by the caprice of those who first discovered, or described them. A committee of the French Academy, with Lavoi- sier at their head, in 1787, settled the principles of chemi- cal nomenclature, which endure to this day, although the actual state of the science requires great changes in them. All chemical compounds are made to derive their names from one or more of their constituents. Before stating the rules of nomenclature, we must define certain general terms of common occurrence. 244. Bodies are divided into acids, bases, and salts. Salts result from the union of acids with bases. By the voltaic pile salts are decomposed (228 [6]) into acids and bases the acids go to the positive pole, the bases to the negative. We therefore call the acid, in reference to electrical law, the electro-negative constituent, and the base the electro-positive. This is equally true of those compounds which render up their elements in electrolysis as of salts which are simply separated into acids and bases: c. like any of the preceding, and has analogies J with the succeeding group of metals. CLASS ir. CLASS in. CLASS iv. CLASS v. CLASS vi. 2. Chlorine.... 3. Bromine.... 4. Iodine 5. Fluorine.... 6. Sulphur.... 7. Selenium.. 8. Tellurium. 9. Nitrogen 10. Phosphorus , 272. How are the elements divided? What of the accuracy of this division? How many classes are named for 1st division? Name the 1st class, the 2d, the 3d, the 4th. What other elements belong to this group? What is the formula of the hydrogen compounds of this group ? What is class 3 ? Class 6 ? OXFGEN. 160 273 We will consider these several classes separately. The compounds which each element forms with those before it, will be taken up in order ; and we shall then be better able to understand the relation of each element to its asso- ciates in the same group. The several classes, too, will then be better understood in the analogies which unite, and the differences which separate them. CLASS I. OXYGEN. Equivalent, 8. Symbol, 0. Density, 1-106. 274. Dr. Priestley discovered oxygen in 1774. It was also rediscovered by Scheele, of Sweden, immediately after, and without a knowledge Of Priestley's discovery. Before this time, all gaseous bodies were considered to be only modes of common air, and oxygen was first called vital air, and, in allusion to the then existing theories, dephlogi&ticated air. It was the illustrious Lavoisier, author of the present nomenclature of chemistry, who proposed the name oxygen, (from oxus, acid, and gennao, I form.) Lavoisier had also rediscovered oxygen in 1775. At that time it was supposed that all acids contained oxygen. Oxygen is the most widely diffused and important of the elements. It forms over one-fifth part of the atmosphere by weight, eight-ninths of the waters of the globe, and pro- bably one-third part of its solid crust. It has also the widest range of affinities of all known substances, and by its im- mediate agency combustion and life are alone sustained. 275. Preparation. Oxygen gas is procured by heating the oxyds of lead, mercury, or of manganese, or the salts, nitrate of potassa, chlorate of potassa, or nitrate of soda. Chlorate of potassa is, however, the salt generally em- ployed, as yielding a large volume of pure oxygen with a gentle heat. This salt contains six equivalents of oxygen, and parts with them all at a moderate heat, leaving a residue of chlorid of potassium. Thus C10 5 KO = ClK-f 60- One ounce of chlorate of potassa yields 543 cubic inches of pure oxygen, or over a gallon and a half. The arrangement of 273. In what order are they discussed ? 274. Who discovered oxygon, and when ? How were gases formerly considered ? Who named oxygen ? Whence the name ? What of the importance and diffusion of oxygen ? 275. How is it prepared ? 170 NON-METALLIC ELEMENTS. apparatus for this purpose is shown in fig. 206. A con- venient portion of chlorate of potassa is pulverized and mixed with its own weight of manganese, or better with the black oxyd of copper. The dry mixture is placed in the flask a of hard glass, where it is heated by the lamp below. A bent tube fitted to a by a cork, conveys the gas to the air-bell 6, previously Fig. 206. filled with water and inverted in the water-trough. The heat of the lamp decom- poses the salt, and pure oxygen is freely given off, displacing the water in the air-jar. By aid of the oxyds of manganese or copper the decomposition of the chlorate of potassa is rendered gradual and safe. Without this precaution the operation proceeds with almost ungovernable energy; the whole volume of gas being given off almost at the same instant, when the point of decomposition is reached. The metallic oxyd seems to act by distributing the heat, and by the me- chanical distribution of the salt: clean sand may be used with nearly equal success. The glass may be protected from fusion by a thin metallic cup c employed as a sand-bath. 276. When large volumes of oxygen gas are required, a more economical plan is to heat the peroxyd of man- ganese strongly in an iron retort ar- ranged in a rever- beratory furnace, (fig. 207.) One pound of good oxyd t 207. of manganese will Give the way by chlorate of potassium. Why is oxyd of manganese used ? How does it act? 276. What is the process by fig. 207 ? OXYGEN. 171 E'eld seven gallons of oxygen, with some carbonic acid. This st is removed by passing the gas through t^e wash-bottle 10 containing solution of potash, which absorbs carbonic acid. In this process Mn0 3 becomes MnO-f-0; about twelve per cent, of the weight of oxyd employed being obtained as oxygen. Oxygen gas may also be procured from oxyd of manganese by aid of strong sulphuric acid and a moderate heat. The mixture is placed in a balloon d, (fig. 208,) and heat applied. Sulphate of manganese is formed, and half the quan- tity of oxygen in the original oxyd, or one equivalent, is given off. Car- bonic acid is removed by the potash so- lution in w. Bichromate of potash may be substituted for the oxyd of manganese in this case with good results. Both should be in fine powder. 277. Properties and Experiments. Oxygen, when pure, is a transparent, colorless gas, which no degree of cold or pressure has ever reduced to a liquid state. It is a < little heavier than the atmosphere, its density being, compared to air, as 1-1057 : 1-000. One hundred cubic inches of the dry gas weigh 34-19 grains. It is without taste or smell. It is very slightly dissolved in water, one hundred volumes of water dissolving only about four and a half of the gas. Its most remarkable pro- perty is the energy with which it supports combustion. Any body which will burn in common air, burns with . greatly increased splendor in oxygen gas. A newly | extinguished candle or taper, (fig. 209,) which has the i least fire on the wick, will instantly be rekindled in Q* oxygen, and burn in it with great beauty. A quart Fig^oo, How is gas of this source purified ? What is the reaction of heat on manganese ? How is procured by sulphuric acid as in fig. 208 ? 277. What are the properties of ? How does it act on. combustibles? 172 NON-METALLIC ELEMENTS. JL'ig. 210. of this gas in a narrow-mouthed bottle, will easily relight a candle fifty times. A bit of charcoal bark (fig. 210) with only a spark of ignition on it, attached to a wire and lowered into a jar of this gas, will burn with intense brilliancy, producing carbonic acid. A steel watch-spring dipped in melted sulphur and ig- nited, when lowered into a jar of pure oxygen gas ; bursts into the most magnificent combus- tion, (fig. 211.) The oxyd of iron which is formed falls down in burn- ing globules, like glowing meteors, which fuse themselves into the glazed surface of an earthen plate, although covered with an inch of water. If, as often happens, a motion of the spring throws a globule of this fused oxyd against the side of the glass vessel, it melts itself into the sub- stance of the glass, or, if that is thin, goes through it. This is one of the most brilliant and instructive expe- riments in chemistry. If the ori- fice at top is closed air-tight, and water is poured into the plate, we shall find, as the experiment proceeds, that the water will rise in the jar as the gas is consumed. If we could collect and weigh the globules of oxyd of iron, we should find in them an increase of weight equal to the weight of the oxygen consumed. If the watch-spring or wire is coiled into a helix, as in fig. 212, then the com- bustion proceeds in a most beautiful series of revolutions, greatly heightening the splendor of the experiment. These experiments should be conducted in a dark room to have the full effect of their brilliancy. If the flame of a lamp, (Fig. 213,) is supplied by a jet of oxygen, the tempe- rature of combustion is so much elevated Fig. 211. Fig. 212. Explain the experiments in figs. 210, 211, and 212. OXYGEN, 173 that a platina wire may be fused in it. We thus imitate the oxyhydrogen blow-pipe to be described further on, (385.) 278. Oxygen, when inhaled, affects life by quickening the circulation of the blood, and causing an excitement, which, if continued, would result in general inflammatory symp- ^^JT ~ ^ toms and death. In an atmosphere of pure oxygen we would live too fast, exactly as combustion is too rapid in an atmosphere of this gas. It exerts, how- ever, no specific poisonous influence, being, when used in moderation, altogether salutary, and often resorted to, to inflate the lungs of drowned persons, and not unfrequently with the most beneficial results. The blood is constantly brought into contact with the air in the lungs, and it is the oxygen in the air which is the active agent in render- ing it fit to sustain life. Pure oxygen is constantly supplied to the atmosphere by the processes of vegetable life. 279. Ozone, the allotropic or double condition of oxygen. When a stream of electrical sparks is passed through a tube in which a current of dry pure oxygen is flowing, the gas assumes new properties. The same result is obtained also where water is electrolysed, (224,) when phosphorus slowly consumes in a globe of moist air, or when a Leyden battery is discharged. In all these cases there is a peculiar odor, perceived also after a powerful discharge of electricity from the clouds. Hence the name ozone, from ozumi, to smell. However this result may be obtained, it is observed that oxygen in this condition, or air containing it, presents much more powerful oxydizing powers than ordinary oxygen. It will turn strips of white paper dipped in protosulphate of manganese to brown from the production of peroxyd of man- ganese. It will decolorize solution of indigo as promptly as nitric acid, and it bleaches even more powerfully than chlorine. This body, Schonbeiu, its discoverer, regards now as an allotropic condition of oxygen, (as suggested by Berze- lius.) Its presence in the air is shown by the discoloration of papers dipped in iodid of starch solution. It has been argued, but on insufficient grounds, that this body in the 278. How is the lamp flame affected ? How does it act on life ? How on the blood ? 279. What of ozone ? How obtained ? What ita cha- racters '{ 174 NON-METALLIC ELEMENTS. Fig. 214. sir was a miasmatic agent. A few words will be in place here, upon the Management of Gases. 280. Pneumatic Troughs. Gases not absorbed by water, are always collected in a vessel of water, called a pneumatic trough. Figure 214 shows a small neat one, made of glass, proper for the lecture-table ; but, for general purposes, they are usually made, like the one below, (fig. 215,) of japanned cop- per, of tin plate, or of wood, to hold several gallons of water. The essential parts are the well W, in which the air-jars are filled, and a shelf S, covered with about an inch of water. A groove or channel d is made in the shelf, to allow the end of the gas-pipe to dip under the air-jar. If nothing better is at hand, a common wooden tub or water-pail, with a per- forated shelf and invert- ed funnel, will answer for small operations. Learners are sometimes puzzled to tell why the water stands in an air- jar above the level of the cistern. A moment's thought, however, on the principles of atmospheric pressure (27) already explained, will make this clear. We must remem- ber, too, that gases are only light fluids, and must be pour- ed upward in water, by the same laws which require fluids heavier than air to be poured downward. 281. To store large quantities of gases, capacious vessels 215. 280. What is a pneumatic trough ? How are gases managed ? poured ? 281. How are they stored ? How OXYGEN. 175 of copper or tinned iron are used, which are called gas- holders. These vessels are made frequently to hold 30 to 50 gallons. The simplest form is that of a large air-jar, pro- vided with stopcocks at the top for the entrance and escape of the gas, and contained in an exterior cylindrical vessel of water. A more con- venient gas-holder for some purposes is that contrived by Mr.Pepys, a view and section of which are shown in the annexed figures, (216 and 217.) It is a tight cylinder of copper or tin g, with a shallow pan of the same metal, supported above it by Fig. 216. several props, two of Fi S- 217 - which are tubes with stopcocks, a b. Near the bottom is a large orifice o, for receiving the gas. To use this instru- ment, it is first filled with water by closing the lower orifice o with a large cork, and opening all the upper ones a b s. Water is then poured into the shallow pan ' p, until it runs out at s, which is then closed; the remain- der of the air escapes through b', when it is full, the cocks a b are shut, and the lower orifice being then opened, the water, sustained by the pressure of the air, cannot escape except as it is driven out by the entrance of the gas at o, from which it runs as fast as the gas enters. When used, arrangements must be made to provide for the water driven out by the gas entering at o. The gas is obtained for use by drawing it off from the orifice s or b at the same time that the shallow pan p is full of water, and the cock a open. The tube to which this cock is attached goes nearly to the bottom of the vessel. An air-jar is easily filled with gas from the holder by placing it full of water in the upper Fig. 218. Explain figures 216 and 217. How is gas drawn from the cas holder? Explain figure 218. 176 NON-METALLIC ELEMENTS. pan, (see fig. 218,) over the orifice b ; on turning the twc stopcocks a by the gas issues from b and fills the jar, while the water of the jar runs down the pipe a to supply the place of the gas. In collecting gas, the precaution should never bo neglected of first allowing all the atmospheric air to escape from the vessels, before any of the gas is saved for use. Bags of vulcanized India-rubber cloth are prepared by the instrument-makers as gas-holders, which can be used without the inconvenience of employing water. They are filled by the flexible pipe p and stop- cock c, (fig. 219,) which also serve for the exit of the gas Gases which are absorbed by water may be collected over mercury; the high price of mercury makes, however, F . this an expensive method ; moreover, some gases as chlorine, for instance act chemically on the mercury. "We may better collect the absorbable gases in clean dry vessels, by displacement of air, as is explained in the next section. CLASS II. CHLORINE. Equivalent, 35-50. Symbol, Cl. Density, 244. 282. History and Preparation. This very remarkable element was first noticed by Scheele, in 1774, while examin- ing the action of chlorohydric acid on peroxyd of manga- nese. For a long time it was believed to be a compound body. It was called chlorine by Davy, who established its elementary character. It is easily obtained from chlorohydric acid HC1, by its action upon pulverized oxyd of manganese, in an apparatus similar to figure 220. The acid is poured in at pleasure by the safety tube s, after the manganese has been made into a paste with the first portions. The heat of a lamp or a pan of coals evolves the gas freely. It is rapidly absorbed by cold water; but if the vessels are filled with water of What of India-rubber bags ? What of absorbable gases ? 282. When and by whom was chlorine discovered ? How is it obtained ? How is it collected 2 CHLORINE. 177 Fig. 220. Fig. 221. 100 to 150 temperature, it is collected with little loss. Any acid vapors are washed out in w. A strong solution of common salt (brine) does not absorb chlorine, and may be usefully employed in some cases to collect this gas in a small porcelain or other trough. Owing to its great weight, it may also be very conveniently collected by displacement of air in dry vessels, using an apparatus like figure 221. The fluc- tuations of the air are prevented by a bit of card-board with a slit on one side, and the greenish color of the gas enables the operator to see when the vessel is full. The vessels must have glass stoppers or covers of glass ground tight; in such, the gas may be preserved at pleasure. The opera- tion should be performed in a well-ventilated apartment, to avoid injury from the corrosive and irritating gas. 283. In this process the affinities are between the man- ganese, for one equivalent of the chlorine in the acid, form- ing chlorid of manganese, and between the oxygen of the manganese and the hydrogen of the acid, forming water The following symbols will render this more clear : we take Mn0 2 and 2HC1, and obtain MnCl, 2HO, and CI. How by figure 221 ? What precaution is advised ? 283. What are the affinities in this process ? Give the equation. 12 178 NON-METALLIC ELEMENTS. I The last equivalent of chlorine, having nothing to detain it, is given off. Pure chlorine is also easily obtained by acting on one part of powdered bichromate of potash, in a small retort, with six parts of strong hydrochloric acid. A gentle lamp- heat is required to begin the process, which then goes on without further application of heat, yielding abundance of gas. Dry chlorine is obtained by using an apparatus, figure 222, attached to the evolution flask fig. 220 by o' f any acid vapors are washed out in the bottle 10, and all moisture is removed by the chlorid of Fig- 222. calcium tube a b, the dry gas being collected by displacement in /. 284. Properties. Chlorine is a greenish-yellow gas, (whence its name, from cliloros, green,) with a powerful and suffocating odor. It is wholly irrespirable and poisonous. Even when much diluted with air, it produces the most annoying irritation of the throat, with stricture of the chest, and a severe cough, which continues for hours, with the discharge of much thick mucus. The attempt to breathe the undiluted gas would be fatal ; yet, in a very small quantity, and dis- solved in water, it is used with benefit by pa- tients suffering under pulmonary consumption. For this purpose an inhalation apparatus is used, like fig. 223. The mouth is applied at o, the air enters at a, and, passing through the dilute solution, becomes more or less charged with chlorine. Cold water recently boiled ab- sorbs about twice its bulk of chlorine gas, Fig. 223. acquiring its color and characteristic pro- perties. This solution is much used in the laboratory in How is it obtained dry ? 284. What are its properties ? How does it affect respiration ? How is it safely inhaled ? CHLORINE. 179 preference to the gas. It should be preserved in a blue bottle, or in one covered by black paper, to avoid decompo- sition, (228.) The moist gas exposed to a cold of 32 yields beautiful yellow crystals, which are a definite compound of one equivalent of chlorine and ten of water, (C1,10HO.) If these crystals are hermetically sealed up in a glass tube, (fig. 224,) they will, on melting, exert a pressure of five atmo- spheres, so as to liquefy a portion of the gas, which is distinctly seen as a yellow Fi S- 224 - fluid, of density 1-33, not miscible with the water which is present. It does not solidify at zero. Chlorine is one of the heaviest of the gases, its density being 2-44, and 100 cubic inches weighing 76'5 grains. 285. Chlorine solution readily dissolves gold-leaf, forming chlorid of gold : silver solution produces in it a dense pre- cipitate of chlorid of silver, which ammonia re- dissolves. A rod a, (fig. 225,) moistened in ammonia water, and held over chlorine solution, produces a dense cloud of chlorid of ammonium. A crystal of green vitriol dropped into a test- tube containing chlorine water, gives a dark so- lution at bottom of perchlorid of iron. Fi S- 225 - 286. The bleaching power of chlorine is one of its most remarkable and valuable properties. The solution of chlo- rine immediately discharges the color of calico rags or of writing-ink. The moist gas does the same, but the dry gas does not bleach. Chlorine is evolved in the arts from a mixture of salt, sulphuric acid, and manganese, for the bleaching of paper and rags, and of all manner of cotton or linen stuifs. It does not bleach woollens, nor printers' ink, probably because of its indifference to carbon, which forms the basis of printers' ink. The bleaching power is probably due to its affinity for hydrogen. 287. Chlorine spontaneously inflames- phosphorus, and powdered metallic arsenic, or antimony, forming chlorids of those substances. A rag or bit of paper, wet with oil of turpentine and held in a bottle of chlorine, is inflamed, and What of its solution? How crystallized? How liquefied? How dense? 285. What are tests for chlorine? 286. What valuable pro- perty of Cl is named ? How if dry gas is used ? How is it evolved in the arts ? What exceptions to its bleaching ? Whence this property ? 287. How does Cl act on phosphorus, y fig. 227. 182 NON-METALLIC ELEMENTS. the U tube, refrigerated by means of ico and salt in the outer vessel. Chlorid of mercury is formed, and oxyd of chlorine CIO. Hypochlorous acid is a light-yellow gas, much resembling chlorine; condensed, it is a reddish- yellow corrosive liquid, boiling at 68, and sparingly soluble in water. The vapor detonates with a hot iron : water absorbs 200 times its volume of it, and gains a beautiful yellow color and powerful bleaching properties. Its aqueous solution is very unstable, being decomposed by light, and even by agitation with irregular bodies, as broken glass. Hypochlorous acid is one of the most powerful oxydizing agents known, raising sulphur and phosphorus to their highest state of oxydation a result which only strong nitric acid can accomplish. It is formed from two volumes of chlorine and one of oxygen condensed into two volumes. Thus, 2 volumes of chlorine weigh 4-880 1 " oxygen " 1-105 5-985-5-2 = 2-992 while experiment gives us 2-977 for the density of this sub- stance. The ciichlorine of Davy is a mixture of chlorine and chloro-chlorous acid, and not a protoxyd of chlorine, as was supposed. It is obtained when chlorohydric acid acts on chlorate of potassa, is a greenish-yellow gas, darker than chlorine, of a very pungent and persistent odor. It explodes with a hot iron. 292. Chlorous, liy- pochloric, and per- chloric acids are all procured from the' decomposition of chloric acid. When fused chlorate of potassa is acted on by sulphuric acid, in the vessel b, (fig. 229,) a very explo- sive, yellow gas Fig. 229. collects in a. Thia What ore its characters? What is its volume, constitution, and den- flity ? What is euchlorine? What of chlorous and hyperchlorous acids ? BROMINE. 183 experiment demands great precautions to avoid accident. The vessel b may be secured by setting it into an outer vessel of warm water. The gas explodes by a warm iron, by pressure, and sometimes without any apparent cause. 293. If strong sulphuric acid is poured upon a small quantity of crystals of chlorate of potash in a wine glass, a violent crackling is heard, and the glass is soon filled with the heavy yellow vapors of the chlorous acid gas, which at once inflame a rag held over it wet with turpentine, with a smart explosion. If chlorate of potash is mixed with sugar, (both separately pulverized and mingled with caution,) a drop of sulphuric acid will inflame the mixture with a brilliant com- bustion. Phosphorus burns spontaneously in chlorous acid gas : if some small fragments of phosphorus are added to a glass of water at the bottom of which a few crystals of chlorate of potash have been placed, (fig. 230,) and sulphuric acid is introduced by means of a long-tubed funnel to the bottom of the vessel, the salt is decomposed, and the phosphorus flashes under water in the chlorous acid which is set at liberty. Fig. 230. BROMINE. Equivalent, 80. Symbol, Br. Density, in vapor, 5-39. 294. History. This element was discovered in 1826, by M. Balard, in the mother-liquor, or residue of the evapora- tion of sea-water, and by him named from its offensive odor, (bromos, bad odor.) It is widely diffused in nature, exist- ing in minute quantities in combination with various bases in the salt-water of the ocean, of the Dead Sea, and of nearly all salt-springs. It is also found in a few minerals. The salines of our Western States are many of them rich in bromids. It has been largely prepared at Freeport, Pennsylvania, on the Ohio, for use in pharmacy. 295. Bromine is a dense red fluid, exhaling at common temperatures a deep reddish-brown vapor. It is one of the heaviest non-metallic fluids known, its density being from 2-97 to 3-187. Sulphuric acid floats on its surface, and is What precaution is given ? 293. What of sulphuric acid on chlorato of potassa ? What is the action on phosphorus ? 294. Give the history of bromine. Where is it found ? 295. Give its characters. 184 NON-METALLIC ELEMENTS. used to prevent its evaporation. At zero it freezes into a brittle solid. It boils at 116-5. A few drops in a large flask will fill the whole vessel, when slightly warmed, with blood-red vapors, which have a density of 5-39. It is a non-conductor of electricity, and Buffers no change of pro- perties from heat or electricity. It dissolves slightly in water, forming a bleaching solution; and at 32, if left in contact with water, it forms a crystalline hydrate with it, of a red bronze color, analogous to the hydrate of chlorine. It is a corrosive and deadly poison, disorganizing organic struc- tures with great energy. One drop on the beak of a bird produced instant death. It has even been used for suicide. Its odor resembles chlorine, but is more offensive and per- sistent. It has bleaching properties. In a word, bromine in all its properties and combinations, has the greatest ana- logy to chlorine, but is less energetic in its affinities, being displaced by chlorine from its combinations. Bromine acts with explosive violence on phosphorus, po- tassium, antimony, and other similar substances, forming bromids. 296. Bromine is used in photography, and its compounds also in medicine. It is detected in the mother-liquor of salt-water by chlorine gas, or solution of chlorine, which sets it free, when it is recognized by its peculiar color. Ether added to this solution takes up the liberated bromine on agitation, and floats on the surface in a reddish-brown stratum. It is prepared in the arts by distilling a mixture of bromid of sodium, manganese, and dilute sulphuric acid, and collecting the product in a cold receiver. Bromic acid BrO- is similar in all its reactions to chloric acid, and forms salts with alkaline bases, called bromates. The chloride of bromine BrCl 5 is soluble in water and de- composed by alkalies. IODINE. Equivalent, 127. Symbol, I. Density in vapor, 8*7. 297. History. Like chlorine and bromine, this substance has its origin in the sea, being secreted by nearly all sea- weeds from the waters of the ocean. It was discovered in What smell has it ? How does it act on combustibles ? 296. How used? How detected' What compounds does it form ? 297. What is ihc history of iodine? IODINE. 185 1811, by M. Courtois, of Paris, in the kelp, or ashes of sea- weeds. The common bladder sea-weed, (Jfucus vesiculosus,') and many other sea- weeds of our own coasts, abound in salts of iodine. It has been found in mineral springs associated with bromine, but less abundantly, and also in one or two minerals. In the arts its chief uses are for the photographic pictures, and in the process of dyeing. In medicine it is of great value, in glandular and other diseases. 298. Preparation. ^Kelp is treated with water, which washes out all the soluble salts, and the filtered solution is evaporated until nearly all the carbonate of soda and other saline matters have crystallized out. The remaining liquor, which contains the iodine, as iodid of magnesium, &c., is mixed with successive portions of sulphuric acid in a leaden retort, and after standing some days to allow the sulphu- retted hydrogen, &c., to escape, peroxyd of manganese is added, and the whole gently heated. Iodine distils over in a purple vapor, and is condensed in a receiver, or in a series of two-necked globes. 299. Properties. Iodine crystallizes in brilliant blue- black scales of a metallic lustre, somewhat resembling plum- bago. When slowly cooled from a state of dense vapor in a glass-tube hermetically sealed, it crystallizes in acute octa- hedrons with a rhombic base, (46.) The density of iodine is 4-95, it melts at 235, and boils at 247, forming a superb violet vapor of unequalled beauty; (hence its name, iodes, like a violet.) For this purpose a few grains of it may be vola- tilized in a bolt-head, or from a hot surface under a bell, as in fig. 231, when on cooling it is deposited in brilliant crystals lining the glass. It assumes the sphreoidal state in a red-hot crucible, forming a splendid experiment, (131.) It is almost insoluble, one part dis- solving in 7000 parts of water. Alcohol dissolves it largely, forming tincture of - 231 iodine. Sal-ammoniac, nitrate of ammonia, and soluble iodids also dissolve it. It tem- porarily stains the skin deep brown, and its odor reminds us somewhat of chlorine. 300. Chlorine and bromine both decompose the corn- In what is it found ? How pTepared ? 299. What are its characters? What of its vapor ? How soluble ? What dissolves it? 186 NON-METALLIC ELEMENTS. pounds of iodine. Iodine is an energetic poison. Iodine forms a beautiful deep-blue compound with a cold solution of common starch. By this test a millionth part of iodine can be detected. In combination it is detected by the same agent, if a little nitric acid or chlorine water is previously added to the fluid supposed to contain an iodid, whereby the iodine is set free. Acetate of lead added to solutions of salts of iodine produces a yellow crystalline precipitate. The iodid of potassium is the salt most familiarly known of all the iodine compounds, and is the usual form in which this substance is administered medicinally. Compounds of Iodine with Oxygen. 301. Iodine unites with oxygen, forming hypoiodic, iodic, and hi/periodic acids. Their constitution is seen in the fol- lowing formula) : Hypoiodic acid I0 t lodicacid 10. Hyperiodic acid I0t These acids are analogous to the hypochloric, chloric, and perchloric acids. lodic acid is formed by the action of strong nitric acid on iodine, and subsequent evaporation, to expel the free nitric acid remaining. It is a very soluble substance, and crystallizes in six-sided tables. Chlorine unites with iodine, forming two, and possibly three distinct chlorids, (Id, IC1 3 , and IC1 5 .) These are formed by the direct action of chlorine on dry iodine. There are also bro- mids of iodine of uncertain composition. FLUORINE. Equivalent, 19. Symbol, F. Density, (hypothetical,) 1-292 302. This element is known entirely by its compounds Its remarkable energy of combination with other elements, and especially with silicon, which is a constituent of all glass, has rendered its isolation very difficult. It is a yel- lowish-brown gas, having the smell and bleaching proper- ties of chlorine. It does not act on glass, (as its compound with hydrogen does,) but unites directly with gold. Its specific gravity is 1-292. Fluorine forms no compound with oxygen, and probably 300. Give tests for iodine. Give its oxygen compounds? S02. What Crf fluorine ? Why is it difficult to isolate ? SULPHUR. 187 holds a place intermediate between oxygen and chlorine. Its most remarkable compound, fluohydric acid, we shall mention in the section on hydrogen. Its power of etching glass was known long before fluorine was suspected to exist. 303. When a mixture of fluor-spar with peroxyd of man- ganese and sulphuric acid is heated, a reaction takes place, by which fluorine in an impure form is disengaged. If the gas thus produced is passed through water having iodine sus- pended in it, combination takes place, and a fluorid of iodine is formed, which crystallizes in yellow scales. A fluorid of bromine is formed by a similar process, which has been used hvthe photographic art with success. It is not crystallizable. The precise composition of these bodies is not known The atomic weight of fluorine is very nearly an aliquot part of the equivalents of chlorine, bromine, and iodine, and these four bodies form a well-marked natural family, closely related by many similar properties. CLASS III. SULPHUR. Equivalent, 16'0. Symbol, S. Density in vapor, 6-654. 304. History. Sulphur is one of those elements which, occurring abundantly in nature, have been known from the remotest antiquity. It is found in many volcanic regions, as in the Island of Sicily, the vicinity of Naples, in Cuba, and many islands of the Pacific. Recent volcanic regions producing sulphur are called solfataras. It is also found in beds of gypsum, as a rock, near Cadiz in Spain, and at Cracow in Poland. Sulphurets of iron, copper, and other metals are widely diffused in the earth and in combination as sulphuric acid, sulphur forms nearly half of the weight of 'common gypsum, or plaster of Paris. 305. Properties. It is a straw-yellow, brittle solid at common temperatures, having a gravity of 1-98. It is tasteless, and without odor until rubbed. By warmth and friction it acquires its well-known brimstone odor. It is a non-conductor of heat and electricity. By friction it gives How is fluorine disengaged ? What of its atomic weight ? 304. What is the history of sulphur ? 305. What are its equivalent and characters 1 188 NON-METALLIC ELEMENTS. negative electricity abundantly. It is very volatile, sublim- ing in "flowers of sulphur" minute crystals even below the melting point, or 226. By this means it is freed from earthy and other impurities. When fused below 280 it is an amber-colored mobile fluid, lighter than solid sulphur, which sinks in it. It is cast in moulds, giving roll sulphur. On cooling, it shrinks so as to fall from the mould, (fig. 232.) The roll sulphur held for a moment in the hand gives a peculiar crackling sound, from the disturb- ance of its particles by heat, and it often breaks when so held. It is insoluble in water, and nearly so in alcohol and ether. In oil of turpentine and some other oils, it is partly soluble, and largely so in bisulphid of carbon. Vapor of alcohol also dis- solves sulphur vapor. Sulphur is very combustible, burning with a blue flame and the familiar odor of a match, due to the production of sulphurous add. It combines energetically with metals, forming sulphurets or sulphids, supporting combustion like oxygen. Fig. 232. Thus, a bundle of iron wires, as shown by Dr. Hare, Fig. 233. Fig. 234. Fig. 235. (fig. 233,) is rapidly burned with scintillations, when held in the jet of sulphur vapor is. uing from a gun-barrel, the end of which has been heated to redness, bits of roll sul- phur thrown in, and the muzzle stopped with a cork. 306. Sulphur occurs in two distinct crystalline forms, one of which is the right rhombic octohedron and the other is the oblique rhombic prism. Figures 234 and 235 give its usual form as found in nature or as crystallizing from solution. When slowly cooled from fusion, as in a crucible, if the crust formed on the surface be pierced while the interior is How is it purified ? How does heat affect it ? What solubility has it ? How does it act on combustibles? What is Hare's experiment? 306. What of the form of sulphur? SULPHUR. 189 still fluid, and the liquid part turned out, the interior will present, as in fig. 236, long, slender, compressed prisms. These belong to the second form of sulphur. This was one of the first instances of dimorphism noticed by Mitscherlich. 307. The fusion of sulphur at different temperatures presents remarkable facts. At 226-280 it is a clear, straw-yel- low fluid; before reaching 280 it begins to grow darker ; from that point to 300 it assumes a deep yellow color; at 374 it has an orange tint and becomes somewhat viscid ; at 500 it becomes dull-brown, and at this high temperature its viscidity is such that the vessel containing it may be turned over without the sulphur falling out. Above this last temperature it begins to grow more fluid. If at this moment it is thrown into cold water, it remains pasty, trans- parent, preserves its brown color, and may be drawn out into long threads which have almost the elasticity of caoutchouc. It regains its original brittleness only after many hours. In this pasty state, sulphur may be moulded by the hands, and is used to copy medallions and other works of art. At 600 it is volatilized in a deep red-brown vapor, resembling the vapor of bromine. The density of its vapor is 6-654. 308. In its chemical relations, sulphur much resembles oxygen. It forms sulphurets with most of the elements that form oxyds, and these sulphurets often unite to form bodies analogous to salts, as the oxyds do. Berzelius insists, very properly, that its binary combinations, from their analogy to the oxyds, should be called sulphids, and not sulphurets. Its uses are well known. It is one of the essential ingre- dients of gunpowder, and is the basis of matches of all kinds. Nearly all the sulphuric acid used in the arts is made from it. The gas arising from its combustion is em- ployed in bleaching straw and woollen goods ; and in medi- cine it has a specific power in certain obstinate cutaneous diseases. The flowers of sulphur of commerce nearly always have an acid reaction, due to the sulphurous acid formed in sublima- H S 3 5 , S 4 5 > S 5 5 . 310. Sulphurous Acid, S0 2 . Preparation. This is the sole product of the combustion of sulphur in oxygen, as in the experiment figured in fig. 237, where burning sulphur Fig. 237. Fig. 238. in a spoon is lowered into a jar of oxygen gas. Other methods are used however in the laboratory to procure this gas. One of the best is to heat in a retort or flask (fig. 238) an intimate mixture of six parts of peroxyd of manga- nese and 1 of flowers of sulphur, in fine powder. The sul- phur is burned at the expense of one portion of the oxygen of the peroxyd of manganese. The sulphurous acid gas is given off abundantly, and may be freed of a little vo- latilized sulphur, by a wash-bottle. Mercury and copper also decompose sulphuric acid, yielding sulphurous acid, by aid of heat ; but the first method is much preferable on every account. It must be collected in dry vessels or over mercury. 309. What are its oxygen compounds ? prepared in fig. 237 ? How collected ? 510. What is SO,? How SULPHUR. 191 311. Properties. Sulphurous acid is a colorless acid gas, with a pungent, suffocating odor, recognized as that of a burning match. It extinguishes flame. A lighted candle lowered into a jar containing it is extinguished, and the edges of the flame, as it expires, are tinged with green. A solution of blue litmus or purple cabbage turned into a jar of the gas is at first reddened by the acid, and then bleached. Articles bleached by it, after a time regain their previous color. Water at 60 absorbs nearly fifty times its volume of sulphurous acid, forming a strongly acid fluid. Hence the necessity for collecting this gas over mercury, or by displacement of air in dry vessels. Its avidity for mois- ture is so great that it forms an acid fog with the water in the atmosphere, and a bit of ice slipped under a jar of it on the mercurial cistern is instantly melted; the water ab- sorbs the gas, and the mercury rises to fill the jar. 312. Sulphurous acid is easily liquefied under ordinary pressures at 14 and below, using a tube with a bulb E, like fig. 239, placed in a refrigerating vessel F. The gas is first dried by chlorid of calcium before passing into E. The liquid gas is easily preserved by turn- ing it into a tube drawn out like A B, (fig. 240,) and previously refrigerated. The part A serves for a funnel. The blowpipe flame seals it hermetically at or, and it may be then preserved for future use. Under a pressure of two atmospheres, this gas is condensed at a temperature Fig- 240. of 59. It is a colorless mobile fluid of a density of 1-42. Its evaporation produces intense cold. If the ball of a mercury thermometer is enveloped in cotton and moistened by liquid sulphurous acid, the mercury is frozen, and a spirit of wine thermometer indicates a temperature as low as 60. By its evaporation water is frozen in a red-hot cru- cible. It is a crystalline solid, transparent and colorless, at 105, sinking in the liquid gas. 313. The volume of sulphurous acid is the same as that of the oxygen employed in producing it. In other words, sul- 311. Give its properties. What of its bleaching? Of its avidity for moisture? 312. How and at what temperature liquefied ? How collected and preserved ? AVhat of its sudden evaporation ? What temperature ? 313. What of the volume of SOj? Give the calculation. 192 NON-METALLIC ELEMENTS. phurous acid contains 1 volume of oxygen and ^ voiume of sulphur vapor (258) condensed into 1 volume. Thus, One volume of sulphurous acid density ........................ 2'247 Substract the weight of 1 volume of oxygen ................. 1*106 Leaving ................................................................. 1*141 Which represents very nearly Jth volume of sulphur 1-109 6 By weight, sulphurous acid contains sulphur 50-87, oxygen 49-13=100. One hundred cubic inches of it weigh 68-70 grains. 3 14. Besides its use in bleaching straw and woollen goods, sulphurous acid is employed as a bath for diseases of the skin, and is a powerful disinfectant, even arresting putrefac- tion and fermentation. Sulphites are salts containing sulphurous acid. Their solutions are gradually changed to sulphates by absorbing oxygen. 315. Sulphuric acid, S0 3 .HO. This acid is one of the most important compounds known; its affinities are very powerful, and no class of bodies is better understood by chemists than the sulphates. In the arts great use is made of sulphuric acid, many millions of pounds of it being an- nually consumed in manufacturing nitric and muriatic acids, the sulphates of copper and alum, in the process of dyeing, and more than all, in the manufacture of carbonate of soda from sea-salt. It is not formed by the direct union of its elements, since we have seen that only sulphurous acid can result from the combustion of sulphur in oxygen. Sulphurous acid must be oxydized to form sulphuric acid. 316. This may be done by passing a mixture of sulphur- ous acid with common air over spongy platinum, heated to redness in a tube, when there will issue from the open end of the tube a mixture of sulphuric acid in vapor, with ni- trogen from the air. In the arts, however, this process cannot be used \ but sulphuric acid is made on a large scale by bringing together sulphurous acid S0 3 , hyponitric acid N0 4 , and water HO, all in a state of vapor, in a large chamber, or series of chambers, lined with lead, when sul- What of its density ? 314. What of the uses of sulphurous acid ? 31 5. What of SO, ? What it? use ? 316. How is SO, formed ? SULPHUR - 193 phmous acid S0 3 passes to a higher state of oxydation S0 3 at the expense of one-half the oxygen of the hypo- nitric acid N0 4 , which thus becomes reduced to the state of the deutoxyd ofnitrogen,(N0 2 -) The arrangement employed is repre- sented in fig. 241. A A is a chamber, fifty feet or more long, lined on all sides with sheet- lead. A very large leaden tube B, opening into one end of the cham- , . ber, communicates with a furnace. Its lower end rests in a gutter o o of dilute acid, to prevent the effects of too much heat and the escape of the vapors. The sulphur is introduced by a door c to an iron pan; and a fire built beneath, n. The heat melts the sulphur, which burns in a current of air passing over it, and the sulphurous acid thus formed enters the chamber, in company with air, and the vapors of nitric and hyponitric acids set free from small iron pans standing over the sulphur, and containing the materials to evolve nitric acid, (sulphuric acid and saltpetre.) A small steam-boiler e furnishes a jet of steam x as required, and a quantity of water covers the floor, which is inclined so as to be deepest at k. A chimney with a valve or damper p allows the escape of spent and useless gases. Things being thus ar- ranged, the chamber receives a constant supply of sulphur- ous acid, common air. nitric acid vapor, and steam. 317. These compounds react with each other in such a manner that the oxygen of the air is constantly transferred to the sulphurous acid, to form sulphuric acid. Deutoxyd of nitrogen N0 3 in contact with air becomes hyponitric acid N0 4 , and this last in presence of a large quantity of water is transformed into nitric acid N0 5 and deutoxyd of nitrogen. Thus, GNO^HO^NO.+wHO-f-^NO,,. Now, sulphur- ous acid, in presence of hydrated nitric acid (N0 5 -(-wHO) Explain the fig. 241. 317. Whence the oxygen to form S0 ? Giv the reactions by the formulae 13 194 NON-METALLIC ELEMENTS. is changed into sulphuric acid, and transforms the nitric acid into hyponitrac acid, thus renewing the reaction continually. Thus, S0 3 +N0 5 -}-?iHO = S0 3 +7*HO-f N0 4 . In this way a small quantity of nitric acid can be made to oxydize an indefinite amount of sulphurous acid ; serving the purpose, as it were, of a carrier of oxygen from the atmospheric air to the sulphurous acid. Meanwhile the water on the floor of the chamber grows rapidly acid ; and when it has attained a specific gravity of about 1-5, it is drawn off and concen- trated by boiling, first in open pans of lead until it becomes strong enough to corrode the lead, and afterward in stills of platinum until it has a density of about 1-8, in which stato it is sold in carboys, or large bottles, packed in boxes. 318. The process of forming sulphuric acid is easily illustrated in the class-room by an arrangement of apparatus like that shown in fig. 242. Two flasks o e are so connected Fig. 242. by bent tubes with a large balloon, that from one b sulphurous acid, and from the other e deutoxyd of nitrogen are supplied to the large balloon r. A third flask w furnishes steam as it is wanted. Fresh air must be occasionally blown in at the open tube t, the effete products escaping at o. Thus arranged, the reactions above described take place. If but little vapor of water is present, the sides of the globe are soon covered What is the density of SO, in the chambers ? 318. Explain the figur* and process 242. SULPHUR 195 with a white crystalline solid, which appears to be a compound of sulphurous and of nitrous acids (SO a ,N0 4 .) This sub- stance is decomposed by a larger quantity of water into sul- phuric acid and hyponitric acid, and as it is known to be formed in the leaden chambers in large quantities, it is sup- posed to have an important influence in the production of sul- phuric acid. 319. This process by the leaden chambers is known in the arts as the English process for sulphuric acid. Formerly sulphuric acid was procured by distilling dry sulphate of iron (green vitriol) in earthenware retorts, at a high tem- perature. The oily fluid thus obtained was hence vulgarly called oil of vitriol. This old process is still in use at Nord- hausen, in the Hartz Mountains, producing an acid which is commonly known as Nordhausen acid. It is the most con- centrated form possible for fluid sulphuric acid. Sulphuric acid unites with water in four proportions, forming definite compounds, namely : Nordhausen acid, sp. gr. 1-9 2(SO)HO Oil of vitriol, " l'S3 SO,,HO Acid of " 1-78 S0 3 ,HO-f-HO Acid of " 1-63 S0 8 ,HO-j-2H 320. Nordhausen acid is a dark-brown, oily fluid, fum- ing when exposed to air, and hissing like a hot iron when water is let fall into it drop by drop. To mingle the two rapidly in any quantity is unsafe. Cautiously heated in a retort protected by a hood of earthenware A, as in fig. 243, 319. What is this process called ? What was the old one ? Whence the vulgar name ? What is the most concentrated S0 3 ? What hydrates of SO, ? What of Nordhausen S0 3 ? 196 NON-METALLIC ELEMENTS. a white, crystalline, silky product distils over and is col lected in the cool receiver. This is anhydrous sulphuric acid S0 3 . It does not possess acid properties by itself, but by contact with water or moisture it is changed to common sulphuric acid. It must be preserved in tubes hermetically sealed. It has therefore been inferred that sulphuric acid cannot exist without water, or that water is essential to the acid property. In this case it is supposed that the oxygen of the water joins that already with the sulphur, (forming S0 4 ,) while the new compound thus produced unites with hydrogen, forming S0 4 H. 321. When exposed to a temperature of 29, sulphuric acid freezes; and acid of 1*78 exposed to a temperature of 32 freezes in large crystals. One hundred parts of concen- trated sulphuric acid contain 81-64 real acid, 18-36 water, SO ? HO. At 620 it boils, giving off a dense, white, and very suffocating vapor. It is intensely acid to the taste, and deadly, if by any accident it is swallowed, corroding and burning the organs with intense heat. It blackens nearly all inorganic matters, charring or burning them like fire. Its strong disposition for water enables us to employ it in desiccation, and in the absorption of aqueous vapor; using for this purpose a shallow pan (fig. 243) containing Fig. 244. S0 3 HO, while the substance to be dried is placed above it, and the whole then covered with a low bell-jar or a tight-fitting plate. 322. Great heat is generated from the mixture of 4 parts by weight of strong sulphuric acid and 1 of water, and a diminution of bulk attends the mixing. The temperature rises as high as 200. So that water in a test tube b (fig. 245) may be made to boil when placed in the mixture contained in the beaker-glass a. If common sulphuric acid is used for this purpose, it becomes milky when water is added to it, from the precipitation of sulphate of lead, derived from the ls ' 4 ' boilers in which it was made. This salt is soluble in strong sulphuric acid, but is precipitated by addition of water. How is crystalline SO, obtained? What formula is given? 321. When does SO, freeze ? What of sp. gr. 1-78 ? Give other traits of SO,. 322. What if water and S0 3 are mingled ? Why is the mixture milky ? SULPHUR. 197 323. Sulphuric acid forms sulphates, a class of salts most minutely known to chemists, and many of which are fami- liarly known in common life. Chloride of barium, added to sulphuric acid, or to a soluble sulphate, throws down an abundant precipitate of sulphate of baryta, a salt insoluble in all menstrua. The same test gives a precipitate also with sulphurous acid, (sulphite of baryta,) but the latter is soluble in chlorohydric acid. 324. There are several chlorids of sulphur. The apparatus figured in fig. 245 shows the manner of preparing one of Pig. 246. them ClS a . Sulphur is placed in the small retort P and fused by the lamp beneath, while a current of chlorine libe- rated from the ballon c, and dried over the chloride of cal- cium tube a, is delivered gently by the descending tube almost in contact with the fused sulphur in P. Combination en- sues, chloride of sulphur distils over and is condensed in the receiver r, kept cool by water from the fountain. This chlorid of sulphur is a reddish-yellow fluid, of a disagreeable odor. It boils at 280, giving a vapor of density 4-668. The density of the liquid is 1'68. Water decomposes it, forming sulphur and chlorohydric acid. One volume of this substance in vapor is formed of 1 vol. chlorine 2-440 J " sulphur G -f* 2-218 Giving the theoretical density 4-658 While experiment gives 4-668 323. What salts does SO, form? What tests for SO,? 324. ETow is CIS, formed? Describe fig. 245. What are its characters? Give iti volume and density. 198 NON-METALLIC ELEMENTS The bromids and iodids of sulphur possess very little interest. SELENIUM. Equivalent, 40. Symbol, Se. Density, 4-3. 325. History and Properties. This element was dis- covered by Berzelius, in 1818, and named by him from sdcne, the moon. It is associated in nature with sulphur in some kinds of iron pyrites, and in a lead ore from Saxony, and also at the Lipari Islands combined with sul- phur and accompanied by other volcanic products. It closely resembles sulphur in most of its properties, as well as in its natural associations. At common tempera- tures it is a brittle solid, opake, and having a metallic lustre like lead, but in powder it is of a deep red color. Its specific gravity is 4'28 for the vitreous, and 4-80 for the granular variety from slow cooling. It softens at 212, and may then be drawn out into red-colored threads } at a little higher temperature it melts completely, and boils at 650, giving a deep yellow vapor without odor. It passes through the same changes of state by heat as sulphur. It is insoluble. When heated in the air, it combines with oxygen, and gives out a disagreeable and strong odor, like putrid horse-radish. Before the blowpipe, on charcoal, it burns with a pale blue flame, and 5 ^ of a grain, so heated, will fill a large apartment with its odor. It is a non-con- ductor of heat and of electricity, and excites resinous elec- tricity. 326. The compounds of selenium with oxygen are three, two of which are acids, analogous to sulphurous and sul- phuric acids. They are Oxyd of selenium SeO Selenious acid SeO Selenic acid SeO f Oxyd of selenium is formed when selenium is heated in the air. It is a colorless gas, and possesses the strong odor before mentioned. 327. Selenious acid is formed when selenium is burned 325. What of selenium? Give its characters. Its equivalent. 326 What compounds of has it? SELENIUM. TELLURIUM NITROGEN. 199 in a current of oxygen gas, as in the tube a, (fig. 247.) A small portion of selenium is placed at b, and fused by a lamp ; at this temperature, oxygen flowing, from a reservoir, in at a, combines with the selenium, forming Se0 3 , which is a white crystalline body, very so- luble in water, and sublimed by heat un- changed. Selenic acid is formed when sele- nium is burned by nitrate of potash, forming selenate of potash. It resembles sulphuric acid in its properties. Both selenious and selenic acids form salts with the alkalies and bases, every way similar to the sulphites and sulphates. Selenid of sulphur is found native among volcanic products. TELLURIUM. Equivalent, 64. Symbol, Te. 328. This rare substance is related to selenium and sul- phur. It forms compounds with gold and bismuth, found native as minerals. Pure tellurium is a tin-white, brittle substance, with a metallic lustre, and density of 6-26. It- melts at low redness, and takes fire in the air, forming tel- lurous acid, Te0 3 . With hydrogen it forms a compound, analogous to arseniuretted hydrogen, and sulphuretted nydrogen. CLASS IV. NITROGEN, OR AZOTE. Equivalent, 14. Symbol, N. Density, -972. 329. Preparation and History. This gas forms four- fifths of the air, and is an essential constituent of most organic substances. It was first described by Rutherford, in 1772. It is only mingled mechanically with oxygen in our atmosphere, which is not a chemical compound. It is most easily procured for purposes of experiment from the atmosphere, by withdrawing the oxygen of the air 327. What of selenious acid ? 328. What of tellurium ? 329. Give ihe history of nitrogen. 200 NON-METALLIC ELEMENTS. by phosphorus. This is easily done by burning some phos- phorus in a floating capsule, under an air-jar, upon the pneu- matic cistern, (fig. '248.) The strong affinity of phosphorus foi oxygen enables it to withdraw ^_ every trace of this element, i leaving behind nitrogen nearly __ pure, containing about ^th of phosphorus. The water soon ab- sorbs the snow-white phosphoric acid. The first combustion of the phosphorus expels a portion of the air by expansion ; but as the combustion pro- ceeds, the water rises in the jar, until it occupies about Jth of its space. When this experiment is performed over mercury, the white phosphoric acid remains unchanged. Nitrogen may be procured pure by passing a current of air over copper turnings in a tube of hard glass heated to redness : the oxygen is all retained by the copper, while nitrogen is given off. Nitrogen can also be obtained, by decomposing strong water of ammonia, by chlorine gas : the ammonia yields its hydrogen to the chlorine, and the nitrogen is given off. The apparatus (fig. 249) may be used for this purpose, in which p is an evolution- flask for chlo- rine, and the strong am- monia water is in 10. Great care should be taken to prevent all the ammonia becoming sa- turated, as in Fig. 249. that case a How prepared ? How from ammonia ? What precaution is notei ? is the reaction ? WITROGEN. 201 very dangerous compound (chloride of nitrogen) will be formed by the action of the chlorine, on the chlorid of am- monia produced in the process. The nitrogen collects in n. 3Cl-fNH 3 =3HCL-fN. 330. The properties of nitrogen are mostly negative. It is a colorless, tasteless, odorless, permanent gas. It has not been liquefied. It combines directly with no element, but indirectly it enters into most powerful combinations. In the atmosphere it appears to act chiefly as a diluent of oxygen. Its density is 0-972, or a little less than air. A taper immersed in it (fig. 250) is extinguished im- mediately. An animal placed in nitrogen dies from want of oxygen, and not because of any poisonous character in the gas, as might be inferred from its abundance in our atmosphere. Hence its name azote, from a privative, and the Greek zoe, life, to deprive of life. Nitrogen is derived from Latin nitriuniy nitre, and gennao, I form. One hundred g ' ' volumes of water dissolve about two and a half volumes of nitrogen. The Atmosphere. 331. The mechanical properties of the atmosphere have already been considered, (20.) The number and propor- tion of the constituents of the atmosphere are constant, although their union is only mechanical. Repeated analyses have shown that atmospheric air is always formed of nitro- gen, oxygen, watery vapor, a little carbonic acid, traces of carburetted hydrogen, and a small quantity of ammo- nia. The air on Mount Blanc, or that taken in a bal- loon by Gay-Lussac from 21,735 feet above the earth, had the same chemical composition as that on the surface, or at the bottom of the deepest mines. The carbonic acid, being liable to changes in quantity from local causes, is found to vary slightly. To the constituents already named, we may add the aroma of flowers and other volatile odors, and those unknown, mysterious agencies, which affect health, and are called mias- mata. From the results of numerous analyses, we state the composition of the atmosphere in 100 parts, to be 330. What its properties? What its function in air? How affects life? Hence, what name has it? Define the word nitrogen. 331. What of air? How are its constituents ? What of its purity ? What aro its constituents ? 202 NON-METALLIC ELEMENTS. By weight. Nitrogen 76-90 .. Oxygen 23-10 .. By measure. .... 79-10 .... 20-90 100-00 100-00 To this we must add from 3 to 5 measures of carbonic acid in 10,000 of air, about the same quantity of carburetted hydrogen, a variable quantity of aqueous vapor, and a trace of ammonia. Nitric acid is also sometimes found in small quantity in rain-water, formed in the air by the electrical discharges of thunder-clouds, and washed out by the rains. 100 cubic inches of dry air weigh 31-011 grains. In 10,000 volumes the constitution of the air will be, therefore Nitrogen 7901 Oxygen 2091 Carbonic acid 4 Carburetted hydrogen 4 Ammonia trace 10,000 332. The analysis of air is accomplished by any sub- stance which will remove the oxygen. But the accurate performance of this process requires numerous minute pre- cautions, any notice of which is out of place here. Eu- diometry is the term applied to the common method of analysis for air. This term is derived from Greek words signifying a good condition of the air, and was employed because it was formerly thought that an analysis of the air would show if it was in a salutary condition. One of the simplest means of analyzing the atmosphere, consists in removing the oxygen by the slow combustion of phos- phorus. For this purpose a stick of phosphorus is sustained on a plati- num wire (fig. 251)inaconfinedpor- tion of air, contained in a graduated glass tube, whose open end is be- neath water. A gradual absorption takes place, and in about twenty- four hours the water ceases to rise in the tube, by which we know that the phosphorus has removed all Fig. 251. Give analyses of air? What is its composition in 10,000 volumes" 2. How analyzed? What is eucliometry ? NITROGEN. 203 the oxygen. The water absorbs the resulting phosphorous acid, and we may read off, by the graduation on the tube, the amount of oxygen removed. A narrow-necked bolt-head shows this result in a more striking manner in the class-room, the large volume of air in the ball causing a very apprecia- ble rise of water in the stem during the course of a lecture, (fig. 252.) When speaking of hydrogen, we will mention another method of eudiometry. The agency of the air in combustion and respiration will also be explained under the appropriate heads. The air dissolved in water, and on which water-breathing animals live, is found to be decidedly more rich in oxygen than the atmospheric air. This is owing to the fact that oxygen is much more abun- dantly absorbed by water than nitrogen, in the proportion of -0-iG to -025. These numbers express, respectively, the ratio of solubility of the two gases in water. The air in water has the constitution By analysis. By theory. Oxygen 32 31-5 Nitrogen 68 68-5 100 100-0 Compounds of Oxygen and Nitrogen. 333. Nitrogen unites with oxygen, forming five com- pounds, three of which are acids. Their names and consti- tution are thus expressed : Symbol. Protoxyd of nitrogen (nitrous oxyd) NO Deutoxyd of nitrogen (nitric oxyd) N0 a Nitrous acid NO, Hyponi trie acid N0 4 Nitric acid N0 As nitric acid is the source whence all the other com- pounds of nitrogen are obtained, we will commence with the history of that compound : This important compound was known in the earliest days of alchemy, but it was Cavendish who, in 1785, first made known its constitution. He formed it by direct union of its elements over a solution of potash, by aid of a series of electrical sparks continually passed through a mixture of the two gases N and 0, for several successive days, What of air dissolved in water ? 333. What are the oxygen com- pounds of nitrogen? Give the series. What is the source of other ni- trogen compounds ? 204 NON-METALLIC ELEMENTS. in a close tube, (fig 253 ) The ends of the tube, con- taining the gases and pot ash solution, dipped into and contained mercury as a conducting medium for the electricity. Nitre was, Fig. 253. subsequently, found in the eolution, thus giving the strongest evidence of a union of the two gases. 334. Nitric Acid, "Aqua Fortis," N0 5 HO. This power- ful acid is obtained by heating saltpetre (nitrate of potassa) or nitrate of soda with strong sulphuric acid. The nitric acid is displaced by the sulphuric, and distils over, being much more volatile than the sulphuric acid. 335. The arrangement of apparatus required is seen in figure 254. The retort R contains the nitre in small crystals, and should be supported in a sand-bath ; or, if the quantity of nitre does not exceed a pound or two, a naked fire answers very well. An equal weight of sulphuric acid is then added, with care not to soil the interior neck of the retort. Heat is gradu ally applied, and the re- Fig. 254. ceiver kept cold by a con- stant stream of water distributed over its surface by a piece of filtering paper. No corks or luting of any kind can be used about the apparatus, as the vapors of concen- trated nitric acid attack all organic substances with energy, as also the alumina and other bases of clay-lute. In the first moments of the operation the vessels are filled with deep-red vapors of hyponitrous acid, due to the decomposi- tion of the first formed portions of nitric acid by the great 334. What is the history of NO,? What was the experiment of Ca- vendish ? What is the process, fig. 254 ? What precautions are given ? NITROGEN. 205 excess of sulphuric acid. As the distillation proceeds, the vessels become colorless and the distillate very nearly so. The red vapors appear again at the close of the opera- tion, and furnish a signal when to arrest the process and change the recipient. This is because the temperature rises toward the close, to the decomposing point of nitric acid. The bisulphate of potash in the retort remains some time after the heat is withdrawn in a state of quiet fusion, having a temperature of about 600. When reduced to about 250, hot water may be added in small portions at a time, and with care the retort may be saved, although it is often sacrificed from the crystallization of the sulphate of potassa. In the arts this process is conducted in large vessels of iron set in brick furnaces. 336. Properties. Nitric acid is a mobile fluid, nearly colorless, fuming, intensely acid, staining the skin instantly yellow, and acting with great energy on most metals and organic substances. It has usually a reddish color, due to the presence of hyponitric acid. When most concentrated it has a density of 1-51 1'52, and contains 86 parts in 100, real acid. It boils at 187. It is decomposed by light, evolving red fumes of hyponitric acid and free oxygen, which sometimes forcibly expels the stopper. It should, therefore, be kept in a dark place, or in black bottles. Poured on pulverized charcoal which has recently been ignited, it deflagrates it with energy ; warm oil of turpentine is immediately fired by it; and its action on phosphorus is too violent to be a safe experiment, without great precau- tion. The concentrated acid freezes at 40; but if diluted with half its weight of water, it freezes at about 1$. The green hydrous acid (343) freezes to a bluish-white solid. The dilute acid yields by distillation a product, at first more concentrated, but when it has a boiling point of 250 the product is of uniform strength, and contains 40 parts real acid in 100. Like sulphuric acid, it forms several definite hydrates, of which the highest is the strong acid described above. Anhydrous nitric acid N0 5 has been lately obtained by decomposing dry nitrate of silver by perfectly dry chlorine. Anhydrous ntric acid crystallizes in colorless rhombs, which fuse at 30; and it boils at 50 with decoin- 336. What are the properties of NO,? How does it act on combusti- bles ? What of its hydrates ? Of anhydrous NO, ? 206 NON-METALLIC ELEMENTS. position. It is soluble in water, evolving much heat, and yielding colorless, hydrous nitric acid 337. Nitric acid is a powerful solvent of the metals, and carries them to their highest state of oxydation. This action is always attended with the production of binoxyd of nitrogen N0 3 and hyponitric acid. The nitrates are all soluble in water. When fused with carbon they are de- composed with brilliant deflagration of the charcoal. Nitrio acid decolorizes a solution of sulphate of indigo, and with a few drops of chlorohydric acid it dissolves gold-leaf. Passed in vapor through a porcelain tube heated white- hot it is decomposed, yielding nitrogen and oxygen. 338. Protoxyd of Nitrogen NO, Nitrous Oxyd, or Laugh- ing Gas. This gaseous compound of nitrogen is prepared by heating nitrate of ammonia NH 4 O.N0 5 in a glass flask ; (fig. 255,) by the aid of a spiritrlamp. The gas is given off at about 400 to 500, and is delivered by the bent tube to an air-jar on the pneumatic trough. The iiitrate of ammonia, which is a crystalline white salt formed by neu- tralizing dilute nitric acid by carbonate of ammonia, is so constituted as to be resolved by heat alone into nitrous oxyd and water; thus, NH 4 O.N0 5 become by heat 4HO -f 2NO Con- sequently, the equivalents of these ele- ments show us, that 80 grains of nitrate of ammonia, will yield 44 grains of Fig. 255. nitrous oxyd, and 36 grains of water. Care must be taken not to heat this salt too highly, as it then yields nitric oxyd and hyponitric acid. If a red cloud is seen during any part of the operation, the heat must be abated. 339. Properties. Protoxyd of nitrogen is a colorless gas, with a faint, agreeable odor, and a sweetish taste. With a pressure of fifty atmospheres at 45 F. it becomes a clear liquid, and at about 150 degrees below zero freezes into a beautiful clear crystalline solid. By the evaporation of this solid, a degree of cold may be produced far below that of the carbonic acid bath (151) in vacuo, (or lower than 174 337. How does it affect metals ? What of nitrates ? 338. How is NO prepared ? Give the reaction ? What precaution is noted ? 339. What ,ire its properties ? What of its liquid ? What temperature ? NITROGEN. 207 F.) It evaporates slowly, and does not freeze, like carbonic acid, by its own evaporation. The specific gravity of nitrous oxyd is 1-527; 100 cubic inches of it weigh 47-20 grains. Cold water absorbs about its own volume of this gas. It cannot, therefore, be long kept over water, but may be collected over the water-trough in vessels filled with warm water. It supports the combustion of a candle, (fig. 256,) and sometimes relights its red wick with almost the same promptness as pure oxygen. Phosphorus burns in it with great splendor. With an equal bulk of hydrogen, it forms a mix- ture that explodes with violence by the electric spark or a match : the residue is pure nitrogen, the oxygen forming water with the hydrogen. Passed through a red-hot porcelain tube it is re- Flg> 256> solved into its constituent gases. One volume of protoxyd of nitrogen contains 1 volume of nitrogen 0-972 ^ volume of oxygen 0-552 Theoretical density 1-524 340. It may be breathed without injury, but it produces a remarkable excitement in the system, amounting to in- toxication, and, if carried far, even to insensibility. To pro- duce these effects without injury, it should be quite pure, and especially free fiom chlorine, and inhaled through a wide tube, from a gas-holder or bag. The presence of chlorid of ammonium in the nitrate employed should be especially avoided, as producing chlorine. There is a sweetish taste, and a sensation of giddiness, followed by joyous or boisterous exhilaration. This is shown by a disposition to laughter, a flow of vivid ideas and poetic imagery, and often by a strong disposition to muscular exertion. These sensations are usually quite transient, and pass away without any resulting languor or depression. In a few cases, dangerous conse- quences have followed its use, and it should always be em- ployed with great caution. In at least one case, in the labo- ratory of Yale College, it produced a joyous exhilaration of spirits, which continued for months, and permanent restora- tion of health. Its effects, however, on different individuals, are various. How does it act on combustibles ? What is its volume ? 340. What its effect if breathed ? 208 NON-METALLIC ELEMENTS. 341 Deutoxi/d or E'moxyd of Nitrogen, Nitric Oxyd. This gas is easily prepared by adding strong nitric acid to clippings of sheet-copper, contained in a bottle arranged with two tubes, (fig. 257.) A little water is first put with the copper cuttings, and the nitric acid poured in at the tall funnel-tube until brisk effervescence comes on. In this case the copper is oxydized by a part of the oxygen of the acid, and the oxyd thus formed is dissolved by another portion of acid. The nitrogen, in union with the two equivalents of oxygen, is given off as nitric oxyd, which, not being ab- sorbed by water, may be collected over Fig. 257. the pneumatic-trough. Many other metals have the same action with nitric acid. The action is renewed by continued additions of nitric acid. It is also obtained very pure by heating nitrate of potash KO.N0 5 with a solution of protochlorid of iron Fed, in an excess of chlorohydric acid. 342. Properties. Nitric oxyd is a transparent, colorless gas, tasteless and inodorous, but excites a violent spasm in the throat when an attempt is made to breathe it. It has never been condensed into a liquid. Its specific gravity is 1-039, and 100 cubic inches weigh 32-22 grains. It con- tains equal measures of oxygen and nitrogen uncondensed. A lighted taper is usually extinguished when immersed in it, but phosphorus previously well inflamed will burn in it with great splendor. When this gas comes into contact with the air, deep-red fumes are produced, by its union with the oxygen of the air to form hyponitric ncid. If to a tall jar, nearly filled with nitric oxyd, standing over the well of the cistern, pure oxygen gas be turned up, deep blood- red fumes instantly fill the vessel, much heat is generated, and a rapid absorption results from the solution of the red nitrous acid vapors in the water of the cistern. 343. Nitric oxyd is rapidly absorbed by solution of green sulphate of iron, forming a deep-brown solution of sulphate of peroxyd of iron. Colorless nitric acid also absorbs nitric 341. What of NO,? How evolved ? 342. Give its properties. Why irrespirable ? How affects combustibles ? In contact with air produces what ? Give an illustration. 343. What absorbs it ? NITROGEN. 209 oxyd, and acquires first a yellow, then an orange-red, and finally a lively green color. This operation is best con- ducted in an apparatus of bottles arranged as in fig. 258, and called Woulf's apparatus. The gas generated in a passes Fig. 258. in succession into the fluid of each vessel. The central tubes serve as safety-tubes. The colors named above are beauti- fully seen in the several bottles, the first becoming green before the last has gained an orange tint. By carefully heating the green acid, the hyponitric acid contained in it may be expelled. The deutoxyd of nitrogen decomposes the nitric acid, forming hyponitric acid, (345.) 344. Nitrous Acid, N0 3 . This is a thin, mobile liquid, formed from the mixture of four measures of deutoxyd of nitrogen with one measure of oxygen, both perfectly dry, and exposed after mixture to a temperature below zero of Fahrenheit. It has an orange-red vapor : the liquid at common temperatures is green, but at zero is colorless. Water decomposes it, forming nitric acid and deutoxyd of nitrogen. It forms salts, called nitrites. 345. Hyponitric Acid, N0 4 . When the green nitric acid obtained in the process just described (fig. 258) is cautiously distilled, hyponitric acid in notable quantity is collected in the refrigerated receiver. The apparatus is ar- ranged as in fig. 259. The green acid is heated in the retort r, by means of a water-bath w, over the lamp 2fi3 dry white powder. Con- tact of humid air converts it into the above form, which always contains some phosphoric acid. It is one of the less powerful acids. By heat it decomposes the oxyds of mer- cury and silver. It forms salts called phosphites. 354. Phosphoric Acid, P0 5 . This acid is formed by the action of strong nitric acid on phosphorus, as well as from bones, by the action of sulphuric acid, as in the process for obtaining phosphorus, (347.) ^Iien phosphorus is burned in a full supply of oxygen ,gtts^ this acid is the product. For this purpose, an arrangement like fig. 264 is adopted. Fig. 262. Fig. 264. The large globe is filled by displacement with oxygen, dried by the chlorid of calcium vessel c. The phosphorus is burned in a capsule, supported at the bottom of the globe on a bed of dry gypsum, and is dropped in at pleasure by the porcelain tube t, whose orifice is closed by a cork. The Describe the arrangement, fig. 262. What are its properties ? 354. How is P0 formed ? PHOSPHORUS. 215 bottle with two necks receives the vapors of phosphoric acid, a draft being kept up by the porcelain tube p, which is made to act as a chimney, by the alcohol flame from the cup a. In this way the combustion is kept up at pleasure, as fresh oxygen is supplied by the hose p. In a dark room this experiment forms a most magnificent display of mellow light. Such is its avidity for water, that phosphoric acid hisses like a hot iron when added to it. It makes an intensely acid solution, which, evaporated to dryness and ignited, yields on cooling a transparent glassy solid, called glacial phos- phoric acid. 355. Phosphoric acid forms three distinct hydrates with water, and three classes of salts. These salts give a beauti- ful example of the substitution of a metal for hydrogen in the production of salts. Let M represent a metal in the following formulae, and we have Acids. Salts. Monobasic or metaphosphoric acid IIO.P0 5 , giving metaphosphate MO.POj Bibasic or pyrophosphoric acid 2HO.PO&, " pyrophosphate 2MO.PO* Tribasic or common phosphoric acid 3IIO.PO, " phosphate SMO.POs For a full account of these interesting modifications of phosphoric acid, the student is referred to Dr. Graham's excellent Elements of Chemistry. The compounds of phosphorus, especially the phosphates of lime and of magnesia, are very widely distributed in nature, and enjoy an important function in the economy of life. The tribasic phosphates produce with nitrate of silver a yel- low precipitate ; with solutions of magnesia and ammonia a fine granular one, (ammonio-phosphate of magnesia;) and the molybdate of ammonia detects the smallest trace of this acid even in the fluids of the body. 356. Chlorids of Phosphorus. Of these there are two, the perchlorid PC1 5 , and the terchlorid PC1 3 . The first is formed when phosphorus is introduced into a jar of dry chlorine. It inflames and lines the sides of the vessel with a white matter, which is the perchlorid of phosphorus. This compound is very unstable, and when put in water both it and the water suffer decomposition, and hydrochloric and phosphoric acids result. To form the other, PC1 3 , the appa- ratus used for the chlorid of sulphur may be employed, sub- stituting phosphorus for sulphur in the retort P, (fig. 245.) How from bones ? What are its properties ? What is glacial P0 8 ? 355. What of its hydrates ? What tests for PO S ? 356. What chloridi of phosphorus are there ? How is PC1 3 formed ? 216 NON-METALLIC ELEMENTS. The bromids, iodids, and sulphurets of phosphorus have the same constitution as the chlorids, and are formed by contact of the elements. They are unimportant, and the eulphuret is a very violent and dangerous compound to form. CLASS V. THE CARBON GROUP. CARBON. Equivalent, 6. Symbol, C. Specific gravity in vapor, 0-829. 357. History. Carbon is an element found in all three kingdoms of nature. Charcoal and mineral coal, which are the two common forms of carbon, have been known from the remotest times of history. Its great importance in the daily wants of society makes it one of the most interesting of the elementary bodies, and our interest in it is not dimin- ished from the fact that the charcoal and mineral coal which we use as fuel and the black-lead of our pencils are, essen- tially, the same thing with that rare and costly gem, the diamond. The three distinct and very dissimilar forms of existence which this element assumes, give us one of the best examples known of the allotropism of bodies. We will very briefly mention the principal characters of the three forms of carbon: 1. The diamond; 2. Graphite or plum- bago ; 3. Mineral coal and charcoal. 358. The diamond is pure carbon crystallized. It takes the forms of the regular system, or first crystalline class, (44,) of which the annexed figures are some of the common modifications. Its crystalline faces are often curved, as in fig. 266. The diamond is the hardest of all known sub- stances, and can be scratched or cut only by its own dust. Fig. 266. Fig. 267. Fig. 268. Fig. 269. The solid angles of this mineral, formed by the union of curved planes, are much used, when properly set, for cutting glass, What of the bromids and sulphurets ? 357. Give the history of carbon. What is its equivalent ? What of its allotropism ? 358. What of the diamond ? CARBON. 217 which it does with great ease and precision. It has a specific gravity of 3'52, and the highest value of any kind of treasure. The most esteemed diamonds are colorless, and of an inde- scribable brilliancy, described as the " adamantine lustre. " They are often slightly colored, of a yellowish, rose, blue, or green, and even black tint. The largest known dia- mond formerly belonged to the Great Mogul, and when found weighed 2769-3 grains, or nearly six ounces: it had the form of half ahen's-egg. The Pitt,or Regent diamond, was sold to the Duke of Orleans for 130,000. It weighs less than an ounce. This was the gem which Napoleon mounted in the hilt of his sword of state. The Koh-i-noor, or mountain of light, (the Great Mogul diamond,) which now belongs to Queen Victoria, was valued to the British government at two million pounds sterling, but its com- mercial value is about three millions of dollars, or 622,000. It weighed before its recent cutting, 1108 grains, or 277 carats. This gem was found at Golconda. The diamond is usually found in the loose sands of rivers, and is gene- rally accompanied by gold and platinum. Its native rock is supposed to be a peculiar flexible kind of sandstone, called itacolumite; and it is sometimes found loosely imbedded in a ferruginous conglomerate in Brazil. A few diamonds have been found in the United States; chiefly in North Carolina. 359. From its high refractive power the diamond is sup posed to be of vegetable origin. The sun's light seems to be absorbed by the diamond, since it phosphoresces beautifully for some time in a dark place, after it has been exposed to the sun. It is a non-conductor of heat and electricity, and is very unalterable by chemical means. It is infusible, and not attacked by acids or alkalies. But heated to redness in the air, it is totally consumed, and the sole product of its combustion is carbonic acid gas. 360. (2.) Graphite or Plumbago. This form of carbon is sometimes improperly called "black-lead," but it does not contain a trace of lead in its composition, and bears no re- semblance to it, except that both have been used to mark upon paper. This peculiar mineral is found in the most ancient rocks, Give its form and characters. What is its lustre ? What are some of the highly valued diamonds ? What of Koh-i-noor ? Where is the diamond found? 359. What of its supposed origin? 360. What is plumbago? 218 NON-METALLIC ELEMENTS. as well as with those of a more modern era. It is also fre- quently found in company with coal, and is sometimes formed artificially, as in the fusion of cast-iron. It almost always contains a trace, and sometimes several per cent, of iron, which is, however, foreign to it; otherwise it is pure carbon. It is very much used for making pencils, and the coarser sorts are manufactured into very useful and refractory melt- ing pots. The most valued plumbago for the finest drawing pencils has been brought chiefly from the Borrowdale mine, in Cumberland, England; but it is a common mineral in this country, as, for instance, at Sturbridge in Massachusetts, St. John in New Brunswick, and many other places. It is found crystallized in flat, six-sided prisms, a form altogether incompatible with that of the diamond. It is soft, flexible, and easily cut; its density is 2-20; feels greasy, and marks paper. It is quite incombustible by all ordinary means, but burns in oxygen gas, forming only carbonic acid gas, and leaving a red ash of oxyd of iron. 361. (3.) Coal. The vast beds of mineral carbon, known as anthracite, bituminous coal, brown coal, and lignite, are all of them nearly pure carbon. Of the first two of these, no country has such abundant and excellent supplies as the United States. These accumulations of fuel are the remains of the ancient vegetation of the planet, which, long anterior to the creation of man, a bountiful Providence laid away in the bowels of the earth for his future use. Bituminous coal differs from anthracite only in having a quantity of volatile hydro- carbon united with it, which is wanting in the anthracite. This opake combustible mineral is entirely a non-conductor of electricity, and some of its varieties excite resinous electricity. 362. Charcoal from wood is the carbonized skeleton of the woody fibre which is found in all plants. The best charcoal is made by heating sticks of wood in tight iron vessels, without contact of air, until all gases and vapors cease to be given off. A great quantity of acetic acid, tar, and oily matters, with water, are given out, and a jetty black, brittle, hard charcoal is left behind, which is a per- fect copy of the form of the original wood. It is a non-con- ductor of heat, but conducts electricity almost as well as a metal. It is a very unchangeable substance, insoluble in Where found? What its character? 361. What of coal? What its origin ? What difference between anthracite and bituminous ? What of its electrical character? 362. What is charcoal ? What its characters ? CARBON. 219 water, acids, or alkalies, suffers little change from long ex- posure to air and moisture, and does not yield to the most intense heat to which it can be subjected, if air is excluded. 363. Charcoal has the property of absorbing gases to a most remarkable degree, at common temperatures. A frag- ment of recently heated charcoal, of a convenient size to be introduced under a small air-jar over the mercurial cistern, will soon take up many times its own volume of air, as will appear by the rise of the mercury in the air-jar. In this case it absorbs more oxygen than nitrogen, the residual air having only eight per cent, of oxygen in it. On heating, it again parts with the gas it has absorbed. The power of absorption seems to depend entirely on the natural elasticity of the gas, and not at all on its affinity for carbon. Those gases that are most easily reduced to a fluid condition by cold and pressure, are most abundantly absorbed by char- coal. Charcoal from hard wood with fine pores has this property in the highest degree. Thus, charcoal from box- wood freshly prepared, will absorb of ammoniacal gas 90 times its own volume ; of muriatic-acid gas, 85 times ; of sulphuretted hydrogen, 81 times ; of nitrous oxyd, 40 times; of carbonic acid, 32 times ; of oxygen, 9*25 times; of nitro- gen, 1-5 times; and of hydrogen, 1-75 times its own volume. 364. Charcoal also has the power of absorbing the bad odors and coloring principles of most animal and vegetable substances. Tainted meat is made sweet by burying it in powdered charcoal, and foul water is purified by being strained through it. The highly colored sugar-syrups are completely decolorized by being passed through sacks of animal charcoal, (bone-black,) prepared by igniting bones. It also precipitates bitter principles, resins, and astringent substances from solution. Common ale or porter becomes not only colorless, but also in a good degree deprived of its bitter principles, by being heated with and filtered through animal charcoal. This property is lost by use, and regained by heating it afresh. Its power of absorption seems similar to that possessed by spongy platinum, (251.) Hydrogen, in small quantity, is very obstinately retained in the pores of charcoal, and water is consequently always produced from 363. What of its absorbing power? What regulates its power with carious gases ? 364. What of its disinfecting and decolorizing powers ? 220 NON-METALLIC ELEMENTS. the combustion of carbon in pure oxygen gas. Carbon has a greater affinity for oxygen at high temperatures than any other known substance, and for this reason it is useful in reducing the oxyds of iron and other oxyds to the metallic state. Lamp-black is a pulverulent variety of carbon, pro- duced from the imperfect combustion of oils and resins. Compounds of Carbon with Oxygen. 365. The compounds of carbon, oxygen, and hydrogen embrace a majority of the bodies described in the organic chemistry; which is therefore not improperly termed the chemistry of the carbon series. We will consider at pre- sent, however, only carbonic acid and carbonic oxyd. 366. Carbonic Add, C0 a . History. This is the sole product of the combustion of the diamond or any pure carbon in the air, or in oxygen gas. It was first recognized and described by. Dr. Black, in 1757, under the name of fixed air. This philosopher proved that limestone and magne- sian rocks contained a large quantity of this gas in a stato of solid combination with the earths, and also that it was freely given out in the processes of fermentation, respira- tion, and combustion. 367. Preparation. Carbonic acid is easily procured by treating any car- bonate with a di- lute acid. Car- bonate of lime, in the form of mar- ble powder, is usually employed for this purpose : it is put with a little water into a two- mouthed bottle A, (fig. 270 ;) dilute chlorohydric acid is turned in at the tube-funnel b t when the gas is Fig. 270. What is lamp-black? 365. What of the compounds of C with hydrogen, Ac.? 366. What is C0 a ? What was Black's discovery? ?67. How is C0 3 prepared? CARBON. 221 set free with effervescence, and escapes through the bent tube at a. Its weight enables us to collect it in dry bottles, by displacement of air, as in the case of chlorine. It may also be collected over water. No heat is required, and the acid is added in small successive portions, the gas being freely evolved at each addition. When obtained by the action of monohydrated nitric acid on bicarbonate of am- monia, the carbonic acid evolved retains a cloudy appear- ance, even after passing through water, which renders it visible a point of some importance in experiments with this gas. 368. Properties. At the common temperature and pres- sure, carbonic acid is a colorless, transparent gas, with a pungent and rather pleasant taste and odor. At a tem- perature of 32, and a pressure of 30 to 36 atmospheres, it is condensed into a clear limpid liquid, not as heavy as water, which freezes by its own evaporation into a white, snow-like substance. We have already described (151) the apparatus and process by which this interesting experiment is per- formed. Carbonic acid is about once and a half as heavy as common air, having a specific gravity of 1-529 ; and 100 cubic inches therefore weigh 47-26 grains. Owing to its weight, it may be poured from one vessel to another, (fig. 271.) Car- bonic acid instantly extinguishes a burning taper lowered into it, even when mingled with twice or three times its bulk of air. Burning sulphur and phosphorus are also immediately extinguished in this gas. Potassium, however, quite clean, may be burned in a Florence flask filled with dried carbonic acid; the potassium is ignited by application of heat, and Fi s- 2n - the carbon is then deposited on the glass vessel. Fresh lime-water agitated with this gas, rapidly absorbs it, becoming at the same time milky, from the production of the insoluble carbonate of lime; soluble, however, in excess of carbonic acid. In this way the pre- 368. What its properties? What its density ? How does it affect eom- bustion ? How is it decomposed ? 222 NON-METALLIC ELEMENTS sence of carbonic acid in the atmosphere is easily detected, and this gas is distinguished from nitrogen by the same test. 369. Cold water recently boiled absorbs rather more than its own volume of carbonic acid gas, but with pressure more will be taken up, in quantity exactly proportioned to the pressure exerted. The solution has a pleasant acid taste, and temporarily reddens blue litmus paper. The "soda water," so much used as a beverage, is usually only water strongly impregnated with carbonic acid, the soda being generally omitted in its preparation. The efferves- cence of this, as well as of small beer and sparkling wines, is due to the escape of this gas. Natural waters have usually more or less of this gas dissolved in them ; and some mineral springs, like the Saratoga and Ballston springs, and the Seltzer water, are highly charged with carbonic acid. 370. DeatJi follows the inspiration of carbonic acid, even when largely diluted with air. It kills by a specific poisonous influence on the system, resembling some narco- tics, and is unlike nitrogen in this particular, which kills only by exclusion of air. Instances of death from sleeping in a close room where a charcoal fire is burning, and from descending into wells which contain carbonic acid, are lamentably frequent. The latter accident may be avoided by taking the obvious precaution to lower a burning candle into the well before going into it, when if the candle burns with undiminished flame, all may be considered safe, but its being extinguished is certain evidence that the well is unsafe. Wells containing carbonic acid may often be freed from it by lowering a pan of recently-heated charcoal into the well, which will soon absorb thirty-five times its bulk of this gas, (363,) thus removing the evil. Even so small a quantity of carbonic acid as 1 or 2 per cent, produces, after eome time, grave effects on respiration. Small animals thrown into a vessel full of this gas, may be recovered by im- mersion in cold water. The so-called Black Hole of Calcutta is a noted instance of the fatal effects of respiring an atmo- sphere overcharged with carbonic acid. 369. What of its solution in water? 370. What is its effect on life ? Where do accidents often happen? How prevented? What quantity is injurious ? CARBON. 223 371. Numerous natural sources evolve large quantities of carbonic acid, particularly in volcanic districts. The Grotto del Cane, in Italy, (dog's grotto,) is a well-known example of the natural occurrence of this gas. But the quantity evolved there is trifling compared to that, which escapes constantly from Lake Solfatara, near Tivoli, whose surface is violently agitated with the gases boiling through it. It is always present in the air, being given off by the respiration of all animals; and, besides the other sources already named, is an invariable product of all common cases of combustion. All the carbon which plants secrete in the process of their development, is derived either from the carbonic acid of the atmosphere, which they decompose by the aid of sunlight and their green leaves, retaining the carbon and returning the pure oxygen to the air; or it is absorbed by their rootlets, and then decomposed by the sun's light at the surface of the leaf. 372. Carbonic acid is formed of equal volumes of its two constituent gases, condensed into one. For this rea- son the air suffers no change of bulk from the enormous quantities of this gas which are hourly formed and decom- posed on the earth. This acid unites with alkaline bases, forming an important class of salts, (the carbonates,) which are decomposed by even the vegetable acids, with the escape of carbonic acid. 373. Carbonic Oxyd, CO. Preparation. Tjhls )gas is most easily obtained from oxalic acid. This acid, when treated with five or six times its volume of sulphuric acid, in the flask a, (fig. 272), is decomposed, yielding equal volumes of car- Fig. 272. 371. What sources are named for it? How in the air? Whence the car- bon of plants ? 372. What is its constitution ? What are its salts called ? 373. How is CO prepared? What of oxalic acid ? ' 224 NON-METALLIC ELEMENTS. bonic acid and carbonic oxyd. Thus, C 3 3 +HO=CO a +CO, the water remaining with the sulphuric acid. The carbonic acid is easily removed by a solution of caustic potash in the wash-bottle o. Dry, finely-powdered, yellow prussiate of potash, when decomposed by ten times its weight of sulphuric acid, in a very capacious vessel, yields an abundant volume of pure oxyd of carbon. 374. Properties. This is a colorless, almost inodorous gas, burning with a beautiful pale-blue flame, such as is often seen on a freshly-fed anthracite fire. Its specific gravity is a little less than that of air, or -967 ; and 100 cubic inches of it weigh 30-20 grains. Water absorbs about J 9 of its volume of itj it does not render lime-water milky, and explodes feebly with oxygen. It is not respirable, but is even more poisonous than carbonic acid, producing a state of the system resembling profound apoplexy. This gas is very largely produced in the process of reducing iron from its ores in the high furnace. Carbonic oxyd is formed of half a volume of oxygen, and one volume of carbon, or two volumes of carbon and one of oxygen, condensed into two volumes. 375. Chloro-carbonic oxyd is formed of equal volumes of chlorine and oxyd of carbon. This union with chlorine is produced by the influence of light, and hence the product was called phosgene gas. This is a pungent, highly odorous, suffocating body, possessing acid properties, and decomposed by water. Its formula is CO.C1, or carbonic acid in which chlorine occupies the place of an atom of oxygen. Its density is 3407. Compounds of Carbon with the CJilorine Group. The chlorids of carbon will be described in the organic chemistry. 376. Bisulphuret of Carbon, C.S a . This remarkable product is formed by the direct union of its elements. In a retort of fire-clay C, (fig. 273,) fragments of charcoal are placed. A porcelain tube b descends nearly to the bottom of the retort, being luted with clay at a. Whon the retort is red hot, small bits of roll sulphur are from 374. What are the^ properties of CO ? 375. What is chloro-carbonic oxyd ? 376. How is bisulphuret of carbon prepared in fig. 273 ? CARBON. 225 Fig. 273. Fig. 274. time to time dropped in at 6, and this orifice immediately closed by a cork. The vapor of sulphur rising among; the ignited carbon combines with it, and bisulphuret of carbon distills, is con- densed by a refrigerating tube,(fig.274,) and collected in the bottle surrounded by cold water, o. The first pro- duct is yellow, from free sulphur, and is purified by a second distillation. When pure, bisulphuret of carbon isacolorless, very mobile and volatile fluid, with a disgusting odor, altogether peculiar. Its density at 32 is 1-293 ; at 60, 1-271. It boils at 110, and its vapor has a density of 2-68. Its power of refracting light is very remark- able. It dissolves sulphur, phosphorus, and iodine, these bodies being deposited again in beautiful crystals by the evapora- tion of the sulphuret of carbon. Gutta percha and India- rubber are also soluble in it. It burns in the air at about 600, with a pale blue flame, producing carbonic and sul- phurous acids. It forms an explosive mixture with oxygen, and a combustible one with binoxyd of nitrogen. It dis- solves easily in alcohol and ether, and is precipitated again by water. Carbon with Nitrogen. 377. Cyanogen, C 3 N or Cy. This important and in- teresting compound of carbon and nitrogen belongs appro- priately to the organic chemistry ; but it deports itself so much like an elementary substance and its compound with hydrogen, (cyanhydric or prussic acid,) and its metallic compounds also, are of so much general interest, that it is proper to mention this compound-radical here. What are its properties? What its solvent powers? 377. What. of cyanogen ? Give its formula. 16 226 NON-METALLIC ELEMENTS. Carbon and nitrogen combine only indirectly. If car- bonate of potassa and carbon are heated together in a por- celain tube, while nitrogen is passing over them, oxyd of carbon escapes, and cyanid of potassium in considerable quantity remains in the tube, and may be dissolved out by water. Cyanogen is usually prepared in the laboratory, by decomposing cyanid of mercury (CyHg) in a small retort by heat, and collecting the gas over mercury. It is more economically and abundantly prepared, however, by heating a mixture of 6 parts of dried ferrocyanid of potassium, and 9 parts of bichlorid of mercury in a flask of hard glass. The cyanid of mercury formed is decomposed immediately into mercury and cyanogen. 378. Properties. Cyanogen is a colorless gas, of a strong and remarkable odor, resembling peach-pits. Its density is 1-86. At a temperature of 4, it is liquefied, and at common temperatures, with a pressure of 4 or 5 atmo- spheres. Liquid cyanogen is a colorless, very mobile fluid, whose density is about 0-9. By keeping a short time, it undergoes a change, becomes brown, and deposits a brown powder in the glass. This is paracyanogen, an isomeric form of cyanogen, a portion of which is always seen as a residue in the retort after decomposing cyanid of mercury. Cyanogen burns with a magnificent and characteristic purple flame, giving carbonic acid and free nitrogen. For this purpose a large vessel may be filled with the gas, by displacement. Water dissolves 4 or 5 times its volume of cyanogen, and alcohol 24 or 25 times its volume. Cyanogen forms cyanids compounds almost exactly analogous to the chlorids of the same metals, and in which cyanogen com- ports itself like an element. Cyanogen is formed from 1 volume of carbon vapor, weighing 0-8290 and 1 volume of nitrogen " 0-9713 1-8003 which is a close approximation to 1-86, the result of ex- periment. How do C and N unite ? How is Cy usually prepared ? How from bichlorid of mercury and ferrocyanid of potassium ? 378. What are its properties ? How liquefied ? How does the liquid change ? How does Cy burn ? What compounds does it form ? Analogous to what ? What is its volume composition ? SILICON. 227 SILICON. Equivalent. 21-3. Symbol, Si. Density in vapor, (hypo- thetical,} 15-29. 379. Silicon combined with oxygen, forming silica, is abundantly distributed throughout the earth. It is said to form th part of the crust of the globe. Silicon is prepared by decomposing the double fluorid of silicon and potassium by metallic potas- sium. The potassium, in small pieces, is mingled with th its weight of the dry white powder of the double fluorid, in a test-tube, (fig. 275,) which is then heated. Reaction occurs as soon as the bottom of the tube is red, and spreads through the whole mass. The cool residue is treated with water, which dissolves the fluorid of potas- sium, and leaves silicon. Thus, 3KF.2SiF 3 -f 6K = 9KF+2Si. 380. Properties. Silicon is a nut-brown powder, and a non-conductor of electricity. Heated in air or oxygen it burns, forming silica. If heated in a close vessel, it shrinks, and becomes more dense. Before ignition it is soluble in hydro- fluoric acid, but after this it is insoluble, and is incombustible in the air or oxygen gas. It seems then to resemble the graphite variety of carbon. These two diverse conditions of silicon are probably connected with the two states in which silica occurs. 381. Silicic acid, or silica, Si0 3 , is far the most import- ant of all the compounds of silicon. It exists abundantly in nature, in the form of rock crystal, agate, common un- crystallized quartz, silicious sand, &c. ; it also enters largely into combination with other substances to form the rock masses of the globe. It is a very hard substance, easily scratching glass, and is difficult to reduce to a powder ; its specific gravity is 2 -66. Its usual crystalline form (fig. 276) is a six-sided prism, with two similar pyramids. It is infusible 379. What of silicon ? Give its equivalent. How is it prepared ? Give the reaction. 380. What are its properties? What two States? 381. What is silica? 228 NON-METALLIC ELEMENTS. alone, except by the power of the compound blow- pipe. It dissolves with effervescence in fluohydric acid and in fused carbonate of soda or potash. No acid, except the hydrofluoric, has any effect on silica. When in its finest state of division it is still harsh Fig. 276. and gritty to the touch or between the teeth. 382. When silica is fused in 4 or 6 times its weight of car- bonate of soda or potassa, and this mass is treated with a large volume of dilute chlorohydric acid until it manifests a decidedly acid reaction, the silica after some time separates as a transparent, tremulous jelly. This is soluble hydrated silica. If dried, it again becomes gritty and insoluble as before. Most natural waters contain some small portion of soluble silica; it has often been seen in this state in mines; and on breaking open silicious pebbles, the central parts are sometimes semifluid and gelatinous. The hot waters of the great geysers in Iceland, and of other hot springs, also dis- solve large quantities of silica, probably aided by alkaline matter. Agates, chalcedony, carnelian, onyx, and similar modifications of silica have been deposited from the soluble state. It is in this condition, no doubt, that silica enters the substance of many vegetables, as, for instance, the reeds and grasses, which have often a thick crust of silica on their bark. It is in this form also that silica acts as the agent of petrifaction. 383. The acid powers of silica are seen only at high tem- peratures, when it saturates the most powerful alkalies and displaces other acids, forming silicates. Hence its great use in the art of glass-making, as it is the basis of all vitreous fabrics, including porcelain and potters' ware, which are all silicates. Soluble glass is formed when an excess of alkali is employed; and liquor of flints is an old term applied to a solution of silicate of potassa or soda. 384. Chlorine, bromine, fluorine, and sulphur, all form compounds with silicon, having the formula SiR 3 , or exactly the formula for silica. The chlorid of silicon is formed by passing dry chlorine over a mixture of fine silicious sand and charcoal in a porcelain tube heated to redness. It is a colorless, mobile liquid, having a density of 1-52, and boil- ing at 138. It is decomposed by water into silica and What its forms in nature ? 382. When fused with alkali, how is it separated ? How does it exist in water and plants ? 383. What of it* acid powers ? 384. What does S form with class II ? What of ita chlorid ? BORON. 229 ehlorohydri j acid. Bromid of silicon is formed in a similar manner. 385. Fluorid of Silicon, (flno-silicic acid,') may be pre- pared by heating sulphuric acid with fluor-spar in powder, to which is added twice its own weight of fine silica or powdered glass. The apparatus should be quite dry : Fluor-spar. Silica. Sul. Acid. Sul. Lime. Water. Flue-rid Silicon. 3CaF -f SiO, -f 3(SO,.HO) = 3(CaO.SO,) -f 3HO + SiF,. Fluorid of silicon is a colorless gas, irrespirable, and de- composed by water. Its density is 3-57. It forms dense white vapors in contact with the moisture of the air. Passed into water it is immediately decomposed, gelatinous silica is precipitated, and the water becomes a solution of hydro-fluo- silicic acid. The reaction is 3SiF 3 -f 3HO = 3HF.2SiF 3 -f Si0 3 . The fluorid of silicon should not pass directly into the water from the gas tube, but into some mercury on which the water rests, as in fig. 277. If this precaution be neglected the open end of the gas tube will become plugged with deposited sili- ca. The silica obtained in this operation, when well washed, is quite pure. The hydro-fluosilicic acid forms an insoluble salt with potas- sium 3KF.2SiF 3 . Fig. 277. BORON. Equivalent, 10'90. Symbol, B. Density in vapor, (hypo- thetical,} -751. 386. Boron is known chiefly by its compounds, borax and boracic acid. Boracic acid is found in nature, either free or combined with various bases ', but it is rather a rare sub- stance. Boron is prepared by heating the double fluorid of 385. What is its fluorid ? Give the reaction by which it is produced ? What its characters ? How does water affect it ? What is hydro-fluosili- cic acid ? Explain its production as in fig. 277. 386. What is boron ? How distributed in nature ? What its equivalent ? 230 NON-METALLIC ELEMENTS. boron and potassium in an iron vessel, with potassium, an in case of silicon. Boron is a dark olive-green powder. Heated to 600 in air it burns brilliantly, forming boracic acid. It does not conduct electricity, and is insoluble in water. Heated out of contact of air it suffers no change. 387. Boracic Acid, B0 3 , is exhaled from volcanic vents, as in Yulcano, one of the Lipari Islands, and also more abundantly in the Tuscan maremma, not far from Leghorn. There it issues, accompanied by jets of steam, from the soil. These jets have been carried into lagoons of water constructed around them, where the boracic acid is taken up by the water. The heat of the earth affords the means of evapo- rating the water. Figure 278 shows one of these masonry basins, 0, built around the jets, (stvjffbni.) A series of these, four or five in number, are arranged one above the other : the least concentrated solutions occupy the upper basin, and are in turn, once in twenty-four hours, drawn off to the lower, and finally to the evaporating pans E F, also heated by the escaping steam from the earth. In this man- ner the solution is brought to crystallize, and is purified by repeated crystallization. The production of boracic acid from this source equals two millions and a half pounds per year. Fig. 278. 388. In the laboratory, boracic acid is obtained by de- composing borax of commerce. For this purpose, one part of borax is dissolved in two and a half parts of boiling water, and chlorohydric acid added until the liquid is strongly acid. On cooling, the boracic acid crystallizes in elegant tufts of scaly crystals, and is purified by a second crystallization. Boracic acid is a white pearly substance in thin scales : these have a feeling like spermaceti, are feebly acid to the taste, and soluble in twelve parts of boiling and in fifty parts of 387. How is B0 3 found? Describe the Tuscany lagoons. How are they heated? Whence the B0 3 ? 388. How is BO, prepared in the laboratory ? What are its properties ? HYDROGEN. % 231 cold water. A boiling saturated solution deposits f ths of its acid on cooling. The crystals contain 43 per cent, of water. By heat it fuses in its crystallization-water, which is finally expelled, and the acid, when heated to redness, fuses to a clear glass, which may be drawn out in fine threads. This glassy acid loses its transparency by keeping for some time. Boracic acid is a feeble acid in solution, but it expels sul- phuric acid from the sulphates at a red heat and forms glass with oxyds of lead and bismuth, of very high refractive powers. Alcohol dissolves boracic acid, and the solution, when set on fire, burns with a peculiar green flame, charac- teristic of boracic acid. Hydrous boracic acid is volatile by vapor of water, but the glassy acid is quite fixed at the highest temperatures. Borac'ic acid and the borates are much used as fluxes, to promote the fusion of other bodies. 389. Chlorid of Boron, BC1 3 , is formed in the same man- ner as chlorid of silicon. It is a colorless gas of a specific gravity of 4-09, decomposed by water into chlorohydric and boracic acids. 390. Fluorid of Boron, BF 3 . This gas is obtained when we heat together 2 parts of fluor-spar and 1 part of fused boracic acid in a vessel of porcelain at redness. 7B0 3 -f- 3CaF=3(Ca02B0 3 )-|-BF 3 . It is a colorless, suffocating gas, strongly acid, very soluble in water, and exceedingly greedy of it, so that it even carbonizes organic substances to obtain it, in the manner of sulphuric acid. Water dissolves 700 or 800 times its volume of this gas. If fluor-spar, boracic acid, and concentrated sulphuric acid are heated together in a glass retort, a gas of a brownish color, very acid, and breaking on the air in white fumes, ia obtained : this is hydro-fluoboracic acid. It must be collected over mercury. CLASS VI. HYDROGEN. Equivalent, 1. Symbol, H. Density, 0-0692. 391. History. Hydrogen was first described as a dis- tinct substance by the English chemist Cavendish, in 1766, and was called by him inflammable air. It had previously What dissolves it? What is characteristic of BO,? How does heat affect it ? 389. What of BC1, ? 390. What of fluorid of boron ? What of its properties ? 391. What is the history of hydrogen ? Its equivalent? 232 NON-METALLIC ELEMENTS. been confounded with other combustible gases, several of which had been long known. Hydrogen exists abundantly in nature as a constituent of water, and also of nearly all animal and vegetable substances, in such proportions as to form water when these bodies are burned. It is named from the Greek hudor, water, and yennao, I form. 392. Preparation. This gas is generally prepared by the action of dilute sulphuric acid on zinc or iron. Zinc ia usually preferred. The acid is diluted with four or five times its bulk of water, and the operation may be conducted Fig. 279. in a glass retort, or more conveniently by using a gas- bottle a, (fig. 279,) containing the zinc in small fragments, to which the dilute acid is turned through the tube-funnel 6. The shorter tube /, with a flexible joint, conveys the gas to the air-jar standing in the cistern g. No heat is re- quired in this operation. An ounce of zinc yields 615 cubic inches of hydro- gen gas. Zinc is readily granulated, by being turned, when melted, into cold water. When hydrogen is re- quired in large quantity, a leaden pot or stone jar, properly fitted, and hold-- Fig. 280. j n g a g a ]i on or more, is used to contain the requisite charge of materials, and the gas is stored for use in a gas-holder, or India-rubber bag, (fig. 280,) (281.) 393. The reaction in this case is between the zinc and How does it exist ? 392. How is it prepared and stored ? 393. What Is the reaction ? HYDROGEN. 283 the sulphuric acid, the hydrogen of the latter being replaced by the zinc, thus : S0 3 .HO-j-Zn == S0 3 .ZnO+H. If chlorohydric acid had been used, the reaction is still more simple, thus: HCl-f Zn r=ZnCl-j-H. Water is essential to the rapidity of the action, by dissofv ing the sulphate of zinc, which is insoluble in strong sulphu- ric acid, and unless removed, immediately arrests the process. 394. Hydrogen gas, when obtained from iron, has a peculiar and offensive odor, due to the presence of a vola- tile oil formed from the carbon always pre- sent in iron. That pro- cured from zinc is also somewhat impure. Traces of sulphuretted 11 i i hydrogen and carbonic acid are usually found in hydrogen, from impurity in the metals employed ; and also a trace of both iron and zinc is raised in vapor, and gives color to the flame of common hydrogen. Most of these impurities are removed by pass- ing the gas through a second bottle d, (fig. 281,) containing an alcoholic solution of caustic potash. Water only, in d, removes the vapor of acid found usually in the gas. 395. Properties. Hydrogen is a colorless, inflammable gas : it has never been liquefied. It refracts light very pow- erfully, and has the highest capacity for heat of any known gas. It is, when quite pure, inodorous and tasteless, and may be breathed without inconvenience when mingled with a large quantity of common air. The voice of a person who has breathed it acquires for a time a peculiar shrill squeak. It cannot, however, support respiration alone, and an animal plunged in it soon dies from want of oxygen. Water ab- sorbs only about one and a half per cent, of its bulk of pure hydrogen gas. Sounds are propagated in hydrogen with but little more power than in a vacuum. Hydrogen is the lightest of all known forms of matter, How is water necessary to it ? 394. What renders it impure ? How is it purified ? 395. What are the properties of hydrogen ? How as re- spects respiration ? 234 NON-METALLIC ELEMENTS. being sixteen times lighter than oxygen, and fourteen times and a half lighter than common air. 100 cubic inches of it weigh only 2-14 grains. Soap-bubbles blown with it rise rapidly in the air ; and it is often employed to fill balloons in absence of the cheaper coal gas. A turkey's crop, well cleansed, makes a good balloon on a small scale, for the class-room, and very beautiful small balloons (from l to 5 feet diameter) are prepared in Paris of gold-beaters' skin. 396. Hydrogen is the most attenuated as well as the lightest form of matter with which we are acquainted. We have reason to suppose the molecules of this body to be smaller than those of any other now known to us. Dr. Faraday, in his attempts to liquefy hydrogen, found that it would leak freely with a pressure of 27 or 28 atmospheres, through stopcocks that were perfectly tight with nitrogen at 50 or 60 atmospheres. This extreme tenuity, together with the remarkable law of diffusion of gases already explained, (147,) renders it unsafe to keep this gas in any but perfectly tight ves- sels. A small crack in a bell-jar, quite too narrow to leak with water, will soon render the hydrogen with which it may be filled ex- plosive. The superiority in diffusive power which hydrogen has over common air, is well seen in what is called Mr. Graham's diffusion tube, of which a figure is annexed. A glass tube, 11 or 12 inches long, (fig. 282,) and of convenient size, has a tight plug of dry plaster of Paris at the upper end, and being filled with dry hydrogen by displacement of air, and its lower end put into a glass of water, the hydrogen escapes so ra>idly through the plaster plug, that the water is seen to rise in the tube, so as in a few mo- ments to replace a considerable portion of the hydrogen, and the remaining portion of gas is found to be explosive. Hydrogen also enters into combination in a smaller propor- tionate weight than any known body, (238,) and consequent- ly has been chosen as the unit of the scale of equivalents. What of its density ? What the weight of 100 cubic inches ? What use is made of its levity ? 396. What is the tenuity of hydrogen ? Give illustrations from Faraday ? What is Graham's diffusion tube ? What of the atomic weight of hydrogen ? Why has it been adopted as unity ? HYDROGEN. 235 897. Hydrogen is a most eminently combustible gas, tak- ing fire from a lighted taper, which is instantly extinguished by being plunged into the gas. It burns with a bluish-white flame and a very faint light. A dr} bottle with its mouth downward (fig. 283) is well suited to collect this gas by dis- placement of air, as the heavier gases are collected by the reverse position. When lighted, the gas burns quietly at the mouth of the bottle; and the extinguished taper may be relighted by the flame at the mouth. If the bottle is suddenly re- versed after the gas has burned awhile, the remain- ing gas, being mixed with common air, will burn rapidly with a slight explosion. Three of the most remarkable properties of hydrogen are thus shown by one experiment, viz. its extreme levity, its combustibility, and its explosive union with oxygen. If this gas is incautiously mingled with common air, or much more, with pure oxygen, a severe ex- plosion results when the mixture is fired. The ^ eyes or limbs of inexperienced operators have thus too often paid the forfeit of carelessness by the explosion of glass ves- sels. Particular caution is required not to employ any gas until all the common air is expelled, as well from the gene- rator, as from the receiving-vessel or gas- holder. 398. Water is the sole product of the combustion of hydrogen. The production of water from this combustion, and cer- tain musical tones, are neatly shown by an arrangement like fig. 284. The gas is generated in the bottle a, and a perforated cork at the mouth has a small glass tube, from the narrow end of which the stream of hydrogen is lighted. An open glass tube IS ' ' b, about two feet long, held over this flame, is at once bedewed by the water produced in the combustion, and a musical tone is also generally heard. This arises from the interruption which the flame suffers from the rapid current of air ascending Flg * 285 ' 397. Give illustrations of its combustibility. What happens if it ia mixed with air? What caution is required? 398. What is the product of its combustion ? What happens if it is burned from a jet in a tube ? 236 NON-METALLIC ELEMENTS. through the tube, causing it to flicker, and being moment- arily extinguished, there occur a series of little explosions, so rapid as to give a tone. The pitch of the note produced, depends on the length and size of the glass chimney (fig. 285) and the size of the jet of hydrogen, which should bo small. If the jet is fitted to the gas-holder, we can modulate the tone by regulating the supply of gas with the stopcock. The little gas bottle (fig. 284) is often called the " philoso- pher's lamp." Compounds of Hydrogen with Oxygen. 399. There are two known compounds of hydrogen with oxygen, viz. : Water (the oxyd of hydrogen) HO Binoxyd of hydrogen H0 The first of these is the most remarkable compound known, whether we contemplate it in its purely chemical relations, or in reference to the wants of man and the present condition of the globe. 400. Water. The student has already become familiar with the composition of water, as formed by the union of two volumes of hydrogen and one of oxygen. In examining the compounds of hydrogen and oxygen, as in all other chemical investigations, we can pursue the subject either analytically or synthetically ; that is, we can either form the compounds by the direct union of the elements, or we can decompose these compounds, and thus gain a knowledge of their constitution. The simplest case of the decomposition of water is that where metallic potassium, or sodium, is employed. The P tass i um > fr m i ts great affinity for oxygen, takes it from the water, (fig. 286,) and the hydrogen escaping, is burned. If sodium is introduced into an inverted test-tube under water, the hydrogen is collected. The reac- tion is K+ HO = KO+ H. 401. The voltaic decomposition of water (224) is, however, by far the most satisfactory experiment to this point which How is this explained? 399. What compounds does hydrogen form with oxygen ? 400. What of the constitution of water ? What is the simplest case of its decomposition ? Hew does potassium effect this ? COMPOUNDS OF HYDROGEN. 237 we possess, since both 'ele- ments of the water are evolved in a pure form and in exact atomic pro- portions by volume and weight, (fig. 287.) In fact, this is a complete experi- mentum crucis, being both analysis and synthesis; for fwe may so arrange the single tube apparatus (fig. 288) that the mixed gases Fig. 287. f rom the electrolysis of water may be fired by an electric spark, as soon as a sufficient volume of the mixture has been collected. A complete absorption follows the explosion, and ri &* 288> the gases again go on collecting. Platinum, heated very hot, decomposes water, and both gases are evolved: this happens when vapor of water is passed through a tube of platinum heated .to intense whiteness. 402. What potassium and sodium accomplish at ordinary temperatures, is accomplished by iron, only at a red heat. The experiment figured in fig. 289 was devised by Lavoisier : an iron tube, (as a gun- barrel,) or better a tube of porcelain, protected by an exterior tube of iron, heated in a furnace to full redness. The tube contains \ clean turnings of iron, or better a bundle of clean iron wire of known weight. A small retort a, holding a Fig. 289. Iktle water, is boiled by a spirit-lamp at the moment when the tube is at a full red-heat : the vapor of the water coming into contact with the heated iron is decomposed, the oxygen is retained by the iron, forming oxyd of iron, and the hydro- gen is given off from the tube /, which may be made to conduct it to the pneumatic trough. For every eight 401. What of the voltaic decomposition of water ? How does platinum decompose water ? 402. Describe Lavoisier's experiment, fig. 289. What becomes of the oxygen ? 238 NON-METALLIC ELEMENTS. grains of weight acquired by the iron, 46 cubic inches of hydrogen, weighing one grain, have been evolved. 403. The iron in this case is evidently substituted for the hydrogen, taking its place with the oxygen to form the oxyd of iron, while the hydrogen is set free. The oxyd of iron resulting from this action, is the same black oxyd which the smith strikes off in scales under the hammer, being a mix- ture of protoxyd and peroxyd. This case of affinity is an interesting one, because it is seemingly reversed when, under the same circumstances, we pass a stream of hydrogen over oxyd of iron. The iron is then reduced to the metallic state, and water is produced. It will be remembered that we cited this instance (270) while speaking of the influence of quantity of matter in determining the nature of the chemical changes which might take place among bodies. Referring to the case (393) of sulphuric or chlorohydric acids and zinc, we cannot fail to observe the similarity of the two cases of decomposition. That water, or the oxyda- tion of a base, is not essential to the evolution of hydrogen is conclusively shown in the case of dry chlorohydric acid (HC1) and zinc, which evolve hydrogen, when no compound containing oxygen is present: HCl-{-Zn ZnCl-|-H. 404. Zinc and iron do decompose water even without the aid of an acid, but only with great slowness, and the action ceases as soon as the metal is covered by the coating of the oxyd thus formed, which protects it from further corrosion. A dilute acid removes this coating of oxyd, and also aids, no doubt, in establishing such electrical relations as to make the zinc highly electro-positive. That this is the fact seems quite probable, because pure zinc is hardly affected by dilute acids, and we have already noticed the effects of amalgama- tion (191) in rendering the zinc incapable of decomposing water. Much mystery formerly hung over this case of chemical action, which, is quite cleared away by the view now pre- sented. It was formerly said that the presence of an acid in water with zinc disposed the zinc to decompose the water. This is what was meant by " disposing affinity ." But there can be no oxyd of zinc to exert this influence on the acid, 403. What is the theory of the process? Why is this an interesting case of affinity ? What similarity is noticed with a previous case ? 404. What of the slow decomposition of water by zinc ? What view was held formerly? What of disposing affinity? COMPOUNDS OF HYDROGEN. 239 until the water is decomposed ; so that the idea that the acid disposed the zinc to decompose the water is quite futile. 405. The real nature of hydrogen was for a long time not well understood. It was associated with oxygen and chlorine, because it was supposed to bear the same relations to chlorohydric acid, that oxygen bears to sulphuric and chloric acids. It is now known that hydrogen is most closely allied to the metals, particularly to zinc and copper; that the chlorids, iodids, and fluorids of hydrogen, although they possess the characters which we assign to acids, resemble in many respects the chlorids, iodids, &c., of the same metals; that in fact, hydrogen is a metal exceedingly volatile, proba- bly standing in that respect in the same relation to mercury, that mercury does to platinum, but still possessed of all truly chemical peculiarities of the metallic state, and no more deprived of the commonplace qualities of lustre, hardness, or brilliancy, than is the mercurial atmosphere which fills the apparently empty space in the barometer tube. (Dr. Kane.) The vapor of mercury, and of other volatile metals, is, like hydrogen, a non-conductor of heat and electricity; but we cannot on this account deny their metallic character. We must not forget, moreover, that hydrogen may yet, by suffi- cient cold and pressure, be made fluid or solid, when doubt- less we shall see its resemblance in physical, as well as we now do in chemical characters, to the metals. The propriety of assigning to hydrogen the place in our classification which it occupies, will thus be more apparent to those who have usually seen it placed next to oxygen. 406. 'A mixture of oxygen and hydrogen gases will never unite under ordinary circumstances of temperature and pres- sure ; but the passage of an electric spark through them, or the application of red-hot flame, or an intensely heated wire, will produce an explosive union, destructive to the contain ing vessel, unless the gas is in extremely small quantities. The re-composition or synthesis of water, was proved in the experiment in the-single cell decomposing apparatus, (fig. 288.) If that explosion had taken place in a dry vessel over mercury, the interior would have been bedewed with moisture from the regenerated water. This may be done, as in fig. 405. What is said of the real nature of hydrogen ? What reasons exist for supposing it a metal ? 406. How is the union of hydrogen and oxygon effected ? 240 NON-METALLIC ELEMENTS. 290, where a strong glass tube t is divided into equal parts, for convenience of measuring, and supported firmly in the mercury vase v. An electrical spark from the Leyden vial I is made to pass through the gas- eous mixture by means of the platinum wires p soldered into the walls of the upper part of the tube. Such an arrange- ment is an eudiometer, some allusion to which was made in 332. Hydrogen furnishes us the most convenient means of analysis of gases containing oxygen, by combining with it to form water. In eudiometri- cal analysis it is always from the volume that the result of the analysis is deduced, and not, as in case of solids, from the weight. A very good form of eudiometrical tube is that of Dr. Ure, (fig. 291.) It is a graduated tube, closed as before at one end, and bent on itself. When used, it is filled with dry mercury, by placing it horizontally in the mercury trough. A portion of the gaseous mixture to be de- tonated is then introduced, the thumb placed over the open end, and all the mix- ture adroitly transferred to the closed limb. The mercury is made to stand at the same level in both limbs, by forcing out a por- tion with a glass rod thrust in at the full side. These adjustments being made, the whole bulk of the mixture is read on the graduation, and while the thumb is firmly held over the open end of the tube, an electrical spark is made to explode the Fig. 291. gases. The air between the thumb and Describe fig. 290. How is hydrogen useful in gas analysis ? What U Ure's eudiometer? How is it used? COMPOUNDS OP HYDROGEN. 241 the mercury acts like a spring to break the force of the ex- plosion and afterward, on removing the thumb, the weight of the atmosphere forces the mercury into the shorter leg, to supply the partial vacuum occasioned by the union of the gases. Proper allowances being made for temperature and pressure, the quantity of residual gas is read on the gradua- tion, and a calculation can then be made of the amount of oxygen present. If the gas contains carbon, carbonic acid would be formed, and must be absorbed by potash solution. 407. Yalta's eudiometer, represented in fig. 292, is a very complete instrument for gas analyses over the pneumatic-trough. In this instrument the explosion is made in a thick glass tube A B, into which the electrical spark is passed by t. The graduated measure p screws into the funnel D, and is used to measure the portion of gas to be deto- nated, which is poured in by the funnel C at bottom. Before use, the tube P is removed, the cocks R and S are both opened, and the whole in- strument sunk in the cistern until it is entirely full of water. The cock R is then shut, the portion of gas measured in P and introduced by C, the cock S closed, and explosion made. If any residue re- mains, its quantity is measured by opening R, when it rises into P, previously filled with water, and its quantity is read off on the graduation. The metallic strap p serves as a communication for the electric circuit, and also as a scale of equal parts for ruder measurements of gas. This instru- ment is well adapted for rapid class illustration, in the lecture room, and is applicable in all eu- diometrical experiments in which gaseous analysis is to be performed by oxygen and hydrogen. For accurate research, the beautiful eudiometer of Regnault is the most reliable instrument. 408. The explosion of oxygen and hydrogen gases, when mingled in atomic proportions, is very severe, and can be performed safely only on very small volumes of the gases, or in strong vessels of metal. The ingenuity of the demon- strator will devise many instructive and amusing experi- llow is the carbonic acid removed? 407. What is Volta's eudiometer? How is it used ? 408. What illustrations are given of the severity of th explosion of oxygen and hydrogen ? 242 NON-METALLIC ELEMENTS. ments depending on the explosion of this mixture. The gas-pistol, and hydrogen-gun, (fig. 293,) a blad- der filled and fired from a pin-hole or by an electric spark, soap-bubbles, and other familiar illustrations, all give evidence of the energy of the action by which water is formed from the union of its elements. The explosion is probably due to the rush of air consequent on the sudden expansion and immediate condensation of a vo- Fig. 293. lume of steam formed at the most intense heat which can be produced by art. The union of oxygen and hydrogen can, however, be ef- fected slowly and quietly, without any explosion or visible combustion. This is accomplished by passing the mixed gases through a tube heated below redness ; and at a still lower temperature, if the tube contains coarsely powdered glass or sand. We see in this case an instance of that re- markable phenomenon called "surface action," (251) be- fore alluded to. 409. Professor Dbbereiner, of Jena, observed, in 1824, that platinum in the state of fine division, known as spongy platinum, would cause an immediate union of these gases. A drop of strong chlorid of platinum evaporated on writing paper, and the paper burned, gives platinum in that state, and such a pellet of paper may be prepared in an instant and used to fire hydrogen. The common instrument employed for lighting tapers is made by taking advantage of this principle. A little spongy platinum is formed into a ball, and mounted on a ring of wire (fig. 294) which slips within the cup d on the top of gas- holder a (fig. 295.) The gas is generated by the action of dilute acid in the outer vessel a on a lump of zinc z hanging in the inner vessel /, and Fig. 294. j g j e j. ou j. a j. pi easure by the cock c, issuing in a stream on the spongy platinum. The latter is at once heated to redness by the stream of hydrogen, which is con- densed within its pores to such a degree that it combines with a portion of oxygen, always present in the sponge by atmospheric absorption. The union of these gases is attended by intense heat, and, as a consequence, the platinum at once glows with redness, and the hydrogen is inflamed. After How is this union effected slowly ? 409. What was the observation of Dobereiner ? Describe the hydrogen lamp ? COMPOUNDS OF HYDROGEN. 243 some time the sponge loses this property to a certain extent, but it is again restored by being well ignited. When the spongy pla- tinum is mixed with clay and sal-ammoniac made into balls and baked, its effects are less intense, and such balls are often used in analy- sis to cause the gradual combination of gases. Faraday has shown that clean slips of pla- tinum foil, and even of gold and palla- dium, qan effect the silent union of hydro- gen and oxygen. For this purpose the pla- tinum is cleaned in hot sulphuric acid, washed thoroughly with pure water, and hung in a jar of the mixed gases. Combination then takes place so ra- pidly as to cause at every instant a sensible elevation of the water in the jar. If the metal is very thin, it sometimes becomes hot enough during the process of combination to glow, and even to explode the gases. 410. The same effect of platinum in causing combination is seen in other bodies besides oxygen and hydrogen. Seve- ral mixtures of carbon gases will act with platinum in the same way ; and the vapors of alcohol or ether may be oxydized by a coil of platinum wire hung from a card in a wineglass (fig. 296) containing a few drops of either of these fluids. The coil of wire is heated to red- ness in a lamp, and, while still hot, is hung in the glass ; it then, if air has free access, retains its red-hot condition as long as any vapor of ether or alcohol remains. In this case, only the hydrogen of the ether, or al- cohol, is oxydized, and the carbon is unaf- Fig. 296. fected; a peculiar irritating acid vapor is given off, which affects the nose and eyes unpleasantly. Little balls of pla- tinum sponge suspended over the wick of an al- cohol lamp will, in like manner, glow for hours after the lamp is extinguished. A spirit-lamp fed with alcoholic ether will cause the coil of plati- num wire (fig. 297) to glow for hours in the same way, constituting what has been called the aphlo- gistic lamp. What has Faraday shown on this point ? 410. How does platinum act on vapors ? What is the aphlogistic lamp ? 244 NON-METALLIC ELEMENTS. 411. The oxyliydrogcn blowpipe of Hare enables the chemist to use safely the intense heat produced by the com- bustion of oxygen and hydrogen. In Dr. Hare's instru- ment the two gases were brought from separate gas-bolderb and mingled only in the moment of contact. The flame of the oxyhydrogen blowpipe differs from the flame of a lamp or candle by being, so to speak, a cone of aerial matter en- tirely ignited in every part, while the flame of a candle is ignited only on the outside, (460.) The structure of the jet contrived by Profes- sor Daniell illustrates this, where the oxygen tube o is seen (figure 298) to pass through that carrying the hydrogen, H. Thus the combus- tible gas is in contact with the oxygen to burn it both from the air and from the instrument. The jet may be pro- vided with a cock (fig. 299) and connected with the gas- holders by two flexible pipes attached at and H. The o Fig. 293. Fig. 299. Fig. 301. Fig. 300. gas-holders may conveniently be made of impervious caoutchouc cloth, arranged with pressure boards, and weights as in fig. 300, an arrange- ment which admits of convenient transportation and dispenses with the use of water. The gas is ad- mitted and expelled by the flexible pipes p and controlled by the cocks c . The effects of the compound blow- pipe may also be safely produced by passing a stream of oxygen from a gas-holder (fig. 301) through the 411. What is Hare's blowpipe ? How does its flame differ from common flames? How is the jet fig. 298 constructed? How are the gases disposed ? COMPOUNDS OF HYDROGEN. 245 flame of a spirit-lump w. The jet is regulated by the cock I, while the lamp-flame supplies the hydrogen. 412. The mixed gases, in atomic proportions, are some- times forced by a condensing syringe into a very strong metallic box, from which they issue by their own elasticity. To prevent the danger of explosion, a contrivance is employed called " Hemming' s safety tube." This is a brass tube, six or eight inches long, filled with fine brass wire, closely packed, and having a coni- cal rod of brass forcibly driven into their centre, by which the wires are very closely crowded together. This forms in fact a great number of small metallic tubes, through which the gas must pass. It is a property of such small tubes entirely to arrest the progress of flame as we shall presently see. (Safety lamp of Davy, 464.) The jet is screwed to one end of this tube, and the other end is connected with the holder of the mixed gases. Fig. 302. Several severe explosions, it is said, have occurred, even with all these precautions ; so that if the mixed gases are used at all, it should only be in a bag or bladder, the bursting of which can be attended with no danger. 413. The effects of the compound blowpipe are very remarkable. In the heat of its focus the most refractory metals and earths are fused, or dissipated in vapor. Plati- num, which does not melt in the most intense furnace of the arts, here fuses with the rapidity of wax, and is even vola- tilized. Even those metallic oxyds, as lime, magnesia, and alumina, which are entirely infusible in any other artificial heat, yield to this focus. By the adroit management of the keys, which a little practice soon teaches, we can either re- duce metallic oxyds, or oxydize substances still more highly. The flame of the mixed gases falling on a cylinder of pre- pared lime, adjusted to the focus of a parabolic mirror, pro- duces the most intense artificial light known. This is what is called the Drummond light. It is extensively employed in distant night-signals, and can be seen farther at sea than any 412. How are the mixed gases burned safely? What is Hemming's safety jet ? 413. What are the effects of the compound blowpipe ' What it the Drummond ligLt ? 246 NON-METALLIC ELEMENTS. other light. It is also used as a substitute for the sun's light in optical experiments. The galvanic focus alone, among artificial sources of light, surpasses it ; (200.)* History of Water. 414. "Water, when pure, is a colorless, inodorous, tasteless fluid, which conducts heat and electricity very imperfectly, refracts light powerfully, and is almost incapable of com- pression. We have already made so much use of water, in illustration of the laws of heat and of chemical combina- tion, in the former part of this volume, that the student must already be familiar with many of its attributes. Its greatest density, it will be remembered, (103,) is found to be at 39-5, or, more exactly, 39 -83. It is the standard of comparison (33), for all densities of solids and liquids. In the form of ice, its density is 0-94, and at 32 it freezes. One imperial gallon of water weighs 70,000 grains, or just ten pounds. The American standard gallon holds, at 39-83 Fahr., 58,372 American troy grains of pure distilled water. One cubic inch, at 60 and 30 inches barometer, weighs 252 j 4 5 8 248 NON-METALLIC ELEMENTS. The solvent powers of pure water are generally greater than those of common water. Gases are nearly all absorbed or dissolved in cold water, and some of them to a very great extent, while others, as hydrogen and common air, very slightly. Hot water dis- solves many bodies which are quite insoluble in cold, especially when aided by small portions of alkaline matter. The waters of the hot springs in Iceland and Arkansas de- posit much silicious matter before held in solution ; and Dr. Turner found that common glass was dissolved in the cham- ber of a steam-boiler at 300, and stalactites of silica were formed from the wire basket in which the glass was sus- pended. 418. Water always absorbs the same volume of a given gas, whatever may be its density : thus, of carbonic acid, of ordinary tension, it dissolves its own volume j it would do no more if the gas were reduced to half its first density ; and it dissolves the same volume when the pressure is at 80 atmospheres. Hence water which has absorbed gases under pressure, parts with them in effervescence when that pressure is removed. Ag.-iin, if a mixture of gases is present at a given tension, water absorbs of each the same volume as it would take up if only that one was present. Such, it will be remembered, is the fact with regard to the gases of the atmosphere, (382.) Gases dissolved in water are all ex- pelled by boiling. If, therefore, we would know what- volume of a given gas was dissolved in water, the fact is accurately determined by boiling a measured quantity in a flask quite full, as in figure 306, aud conveying the escap- ing gas by a bent tube (also previously filled with water) to a gra- duated jar on the Pig. 306. What of the action of hot water!' 418. What volume of gases does water absorb? How does pressure affect this ? How of mixed gases ? How is the volume of gases contained in water determined? Describe tig. 306. COMPOUNDS OP HYDROGEN. 249 mercurial cistern. We then measure the volume of gas ex pelled directly. 419. The powers of water as a chemical agent are very various and important. From its neutral, mild, and salu- tary character, we are accustomed to regard it only as a negative substance, possessed of little energy, while it is in fact one of the most important chemical agents in our pos- session. Besides its solvent powers, we know that it com- bines with many substances, forming a large class of hy- drates : hydrate of lime and potash are examples. It is also, as we have seen, (320,) essential to the acid properties of common sulphuric, phosphoric, and nitric acids, acting here the part of a much more energetic base than in the hy- drates. It forms an essential part in the composition of many neutral salts, and can be replaced in composition by other neutral saline bodies; while as water of crystallization it discharges still another important and distinct function, the crystalline forms of many salts being quite dependent on its presence in atomic proportions. Of organic struc- tures, both animal and vegetable, it forms by far the most considerable constituent. Its vapor at high temperatures displaces some of the most powerful acids, as Tilghmann has shown, in his patent process for procuring the alkaline bases by decomposing their sulphates, chlorids, and even, to some extent, silicates, by vapor of water at a high temperature. Sulphate of lime, for example, so treated, has all its sul- phuric acid driven off as S0 3 , and caustic lime is left behind. The geological importance of these facts can hardly be over- estimated. 420. Peroxyd or Binoxyd of Hydrogen, This curious compound was discovered in 1818, by M. Thenard. It is obtained in decomposing the peroxyd of barium by as much very cold solution of hydrofluoric acid (fluosilicic or phos- phoric acid may be used as well) as will exactly saturate the base, the whole being precipitated as fluorid of barium. The reaction may be expressed thus : Poroxyd of barium. Fluohydric add. Fluorid of barium. Peroxyd of hydrogen. Ba0 2 + HF = BaF + H0 3 . The peroxyd of hydrogen remains dissolved in the water, which is freed ,from the insoluble fluorid of barium by filtra- 419. What are the chemical powers of water ? What is crystallization, water ? What are Tilghmann's experiments ? 420. What is tho per- oxyil of hydrogen ? How procured ? Give the reaction. ii50 NON-METALLIC ELEMENTS. tion, and then evaporated in the vacuum of an air-pump by the aid of the absorbing power of sulphuric acid. 421. Properties. The properties of this body are very remarkable. When as free from water as possible, it is a syrupy liquid, colorless, almost inodorous, transparent, and possessed of a very nauseous, astringent, and disgusting taste. Its specific gravity is 1453, and no degree of cold has ever reduced it to the solid form. Heat decomposes it with effer- vescence and the escape of oxygen gas. It can be preserved only at a temperature below 50. The contact of carbon and many metallic oxyds decomposes it, often explosively, and with evolution of light. No change is suffered by many bodies which decompose it; but several oxyds, as those of iron, tin, manganese, and others, pass to a higher state of oxydation. Oxyd of silver, and generally those oxyds which lose their oxygen at a high temperature, are reduced to a metallic state by this decomposition. When diluted, and especially when acidulated, the peroxyd of hydrogen is more stable. It is dissolved by water in all proportions, bleaches litmus paper, and whitens the skin. None of its compounds are known, nor does it seem to have any ten- dency to combine with other bodies. Compounds of Hydrogen with the II. and III. Classes. 422. The eminently electro-positive character of hydrogen causes it to form well-characterized and analogous com- pounds with all the members of the oxygen group. These binary compounds have frequently been called the hydracids, in distinction from those acid bodies already considered, which, in parity of language, have been called the oxacids. It is, however, more in accordance with facts and the principles of a philosophic classification, to look upon these bodies as having in reality the same essential characters as the chlorids, bromids, iodids, &c., of other electro-positive bases. The principles of our nomenclature require these compounds to be called after their electro-negative elements, t. e. chlorohydric acid, bromohydric acid. Their general formula is HR. The compounds of hydrogen to be con- sidered under this head are 421. "What are its properties ? 422. What are the hydracids ? What riew is taken of their constitution? What compounds are enumerated under this head ? What is their general formula ? COMPOUNDS OF HYDROGEN. 251 Chlorohydric acid HOI Bromohydric acid HBr lodohydric acid HI Sulphydric acid HS Selenhydric acid HSe Tellurhydric acid HTe Fluohydric acid HF 423. Hydrogen and chlorine, mingled in the gaseous state, combine with explosion by the touch of a match, forming chlorohydric acid. The rays of the sun effect the same result instantaneously, while in diffuse light combina- tion follows in a gradual manner and quietly. In the dark, no union occurs, showing that light in this case plays the part of heat, and impresses, as we shall see, a peculiar con- dition on chlorine. If two vessels of equal capacity (fig. 307) are filled, the one, A, with dry hydrogen, the other, B, with dry chlo- rine, by displacement, and are then united, as seen in the figure, on exposing them with precaution to the sun's direct rays, an im- mediate explosion follows. Dr. Draper has shown that chlorine gas which had been ex- posed alone and dry to the sun's light ac- quired the power of forming this explosive union with hydrogen, even in the dark, and retained it for some time; while, on the other hand, chlorine prepared in the dark manifests no avidity for hydrogen un- less exposed to the light. This fact was before mentioned (288) when speaking of the active and passive conditions of chlorine. In its passive state, (as prepared in the dark,) it actually replaces hydrogen in the constitution of many organic bodies, or, in other words, assumes an electro-posi- tive condition. The effect of the sun's light is to confer a new state upon it, probably by a new arrangement of its molecules, by which its character is completely changed. It then apparently becomes highly electro-negative. The decomposition of water by chlorine (288) evinces its strong affinity for hydrogen. Chlorine thus becomes one of the most powerful oxydizing agents known, since the nascent oxygen given off during the decomposition of water attacks with energy any third body which may be present that is capable of combining with it. 424. Chlorohydric Acid, HC1. If the experiment (fig. 423. How do chlorine and hydrogen act when mingled ? Describe fig. 307. What has Draper shown ? What is the passive state of chlo- rine ? What relation has it in this state to organic bodies ? On what dues the decomposition of water by chlorine depend ? 252 NON-METALLIC ELEMENTS. 307) is placed in diffuse light, the green color of the gas is seen gradually to diminish and finally to disappear alto- gether; and, on opening the junction beneath mercury, no ab- sorption occurs, and the vessels are found to be filled with chlorohydric acid gas. It appears therefore that this acid is formed by the union of equal volumes of the constituent gases without condensation Its density is consequently equal to half the sum of the united densities of chlorine and hydro- gen, i.e.244+ -069=2-509 -f-2 = 1-254, theoretical den- sity of chlorohydric acid gas. Experiment gives 1-2474. 425. Chlorohydric acid is a colorless, acid, irrespirable gas. It forms copious clouds of acid vapor with the moist- ure of the air, very suffocating, and irritating the eyes. It extinguishes a lighted candle, and is not decomposed by electricity. It is very soluble in water, which at 32 takes up about 500 times its volume and acquires a density of 1-21. At a higher temperature it absorbs less. This gas is therefore collected over mercury. A bit of ice passed up to a jar of it on the mercury cistern, is fused immediately by its avidity for water, a dilute solution of chlorohydrio acid results, and the mercury rises to fill the jar. With a pressure of over 26 atmospheres it becomes a colorless liquid, which has never been frozen. 426. Preparation. For experimental purposes in the laboratory it is sufficient to warm the wtrong commercial liquid acid, which parts with a large portion of gas at a gentle heat. This may be dried by passing it through a chlorid of calcium tube. The apparatus thus ai- ranged is shown in figure 308. The concentrated acid is placed in c and its moisture is removed by -the chlorid of calcium apparatus a. The weight Fi - 308 - of the gas enables us to collect it by displacement of air in dry vessels b. For this purpose it is not usually requisite to dry it. In the arts it is always obtained from the decomposition 424. What is the constitution of chlorohydric acid? What is its theo- retical composition and density ? Its experimental ? 425. What are its properties ? How soluble in water ? How collected ? 426. How is it pi-epared for experiment in the laboratory ? Describe fig. 308. COMPOUNDS OF HYDROGEN. 253 of common salt, (chlorid of sodium, NaCl,) by sulphuric acid. The reaction is sufficiently simple : NaCl -f- S0 3 . HO = (NaO.S0 3 ) -f HC1. The apparatus employed in this process is shown in fig. 309. Common salt is placed in the flask a, provided with a safety tube / and an eduction tube I. The sulphuric acid for decomposing the salt is introduced at pleasure through f. The action is aided by a gen- tle heat from the fur- nace below. The chloro- hydric acid is rapidly evolved and passes into c, where it is washed by a little warm water and thence by e to the last ^ bottle dj where it is ab- \ sorbed by the ice-cold water which it contains. In the middle bottle is a tube g, of large size and open at both ends, its lower extremity dips into the wash-water. This contrivance prevents the accident which is otherwise likely to happen should a partial vacuum occur in a, from a cessation of the action ; when the pressure of the air on the fluid in d would carry it back into c, and finally into a. The safety tube (fig. 310) at- tached to the flask a also serves to prevent this acci- dent as well as to introduce the acid. When a liquid is poured in at the funnel-top, it must rise as high as the turn, "before it can pass down into the flask, and a portion of the fluid is therefore always left behind in the bend, which serves as a valve against the entrance of air, and also effectually pre- vents an explosion of the flask in case the tube of . delivery should become stopped. This simple con- Flg ' 310 * How is it procured in the arts ? Give the reaction. Describe the appa^ rntus, fig. 309. What is a safety tube ? Describe fig. 310. Fig. 309. 254 NON-METALLIC ELEMENTS. trivance we have often employed but have not before ex plained its action. This same apparatus may be employed in making solutions of all the absorbable gases, and is so simple as to be within the means of the humblest laboratory ; the essential parts being only wide-mouthed bottles, glass tubes, a gas bottle or flask, and corks. 427. Pure chlorohydric acid is procured by distilling the commercial acid. The distilling apparatus employed for this purpose is seen in fig. 311. The heat is applied by a sand-bath beneath the retort. The gas given off is absorbed by a little water placed in the last bottle, which is connected by a bent tube with the two-necked receiver. If the com- Fig. 311. mercial acid is diluted by water until it has the specific gra- vity I'll, it no longer evolves acid fumes when heated, and the fluid distilled has the same density as that in the retort, retaining 16 equivalents of water. 428. Properties. Liquid chlorohydric acid is a colorless, highly acid, fuming liquid, having when saturated a speciBc gravity of 1'247 : it then contains 42 parts in a hundred of real acid. Its purity is tested by its leaving no residue on evaporating a drop or two on clean platinum, and by its giving no milkiness when a solution of chlorid of barium is added to it, (due to sulphuric acid.) Neutralized by ammonia, it ought not to become black when hydrosul- 427. How obtained pure? Describe fig. 311. At what density does it distill unchanged? 428. What are the properties of the liquid acid? What ars tests of its purity ? COMPOUNDS OP HYDROGEN. 255 phuret of ammonium is added, (due to iron.) This acid is an electrolyte, and is also decomposed by ordinary elec- tricity. A mixture of muriatic acid gas with oxygen, passed through a red-hot tube, produces water and chlorine. The commercial acid is always impure, and colored yellow by free chlorine, iron, and organic matters. ^ests. A solution of nitrate of silver detects the pre- sence of a soluble chlorid, or of chlorohydric a,cid, by forming with it a whito curdy precipitate of chlorid of silver, which is soluble in ammonia, but insoluble in acids or water. A rod a, if dip- ped in ammonia and held over a glass containing chlorohydric acid, gives off a dense white cloud of chlorid of ammonium. 429. The uses of chlorohydic acid are very numerous. Its decomposition by oxyd of manganese affords the easiest mode of procuring chlorine, (282.) It dissolves a great number of metals and oxyds, forming chlorids, from which these metals may be obtained in their lowest state of oxydation. In chemical analysis and the daily operations of the laboratory it is of indispensable use. Chlorohydric acid is made in the arts in immense quanti- ties, especially in England, where the carbonate of soda is largely made from common salt (chlorid of sodium) by the action of sulphuric acid. Mingled with half its own volume of strong nitric acid, it makes the deeply colored, fuming, and corrosive aqua-regia. This mixed acid evolves much free chlorine, which in its nascent state has power to dissolve gold, platinum, &c., forming chlorids of those metals, and not nitromuriates as was formerly supposed. As soon as all the chlorine is evolved, this peculiar power of the aqua-regia is lost. 430. Bromohydric Acid, HBr, Bromid of Hydrogen. Hydrogen and bromine do not act upon each other in the gase- ous state, even by the aid of the sun's light; but a red heat or the electric spark causes union only among those parti- cles, however, which are in immediate contact with the heat, the action not being general. Bromohydric acid may be prepared by the reaction of moist phosphorus on bromine in a glass tube (fig. 313.) The gas given off must be collected What tests are named? 429. "What are its uses? What is aqua-regia ? 430. What is bromohydrie acid ? How prepared? 256 NON-METALLIC ELEMENTS. over mercury. It is composed, like chlorohydric acid, of equal volumes of its elements not condensed. Its specific gravity is 2-731, and it is condensed by cold and pressure into a liquid. In its sensible properties it bears a close re- semblance to chlorohydric acid. With the nitrates of silver, lead, and mercury, it gives white precipitates similar to the chlorids. It has a strong avidity for water, and dissolves largely in it, giving out much heat during the absorption. The saturated aqueous solution has the same reactions as the dry acid, and fumes with a white cloud in contact with air. It dissolves a large quantity of free bromine, acquiring thereby a red tint. 431. lodohydric Add. This body may be formed by the direct union of its elements at a red-heat, but is more easily prepared by acting on iodine and water with phosphorus, by which means the gas is formed in large quantities. The action of phosphorus and iodine is violent and dangerous, but may be regulated and made safe by putting a little powdered glass between each layer of phos- phorus and iodine, (fig. 313.) Phos- phoric acid is formed and remains in solution, while the iodohydric acid gas is given out, and may be col- lected over mercury, or dissolved in water. The dry gas has a great avidity for water. Its specific gravity is 4443, being formed, like the last two compounds, of one vo- 313 lume of each element uncondensed. Cold and pressure reduce it to a clear liquid,which,at 60 Fahr., freezes into a colorless solid, having fissures running through it like ice. It forms a very acid fluid by solution in water, which has, when saturated, a specific gravity of !?, and emits white fumes. The aqueous solution is also prepared by transmitting a current of hydro- sulphuric acid through water in which free iodine is sus- pended. The gas is decomposed, sulphur set free, and hydriodic itcid produced, which is purified from free hydro- sulphuric acid by boiling, and from sulphur by filtration. 432. Properties. The aqueous iodohydric acid is easily 431. How is iodohydric acid prepared? What are its properties? How to its aqueous solution prepared ? COMPOUNDS OP HYDROGEN. 257 decomposed by exposure to the air, iodine being set free. It forms characteristic, highly colored precipitates with most of the metals, particularly with lead, silver, and mercury. Bromine decomposes it, and chlorine decomposes both hydrobromic and hydriodic acids, thus showing the relative affinities of these bodies for hydrogen. This acid is a valuable reagent; its presence in solution is easily detected by a cold solution of starch, which, with a few drops of strong nitric or sulphuric acid, instantly gives the fine characteristic blue of the iodid of starch. 433. Fluohydric acid is obtained from the decomposition of fluor-spar by strong sulphuric acid. The operation must be performed in a* retort of pure lead, silver, or platinum, and requires a gentle heat. Fig. 814 shows 'the form of retort used for this purpose, the junction of the head and body is made tight by a lute of gypsum and water, a^ as any lute containing silica will be attacked by the fluohy- dric acid. The sulphate of Fig. 314. j- me resu iting from the action forms a solid insoluble mass in the body of the retort : hence the necessity of so large an opening. The fluohydric acid resulting is condensed in a large tube of lead, bent as in Fig. 315. fig. 315, so as to enter a refrigerant apparatus : at one end it is luted to the beak of the retort, at the other is narrowed to a small aperture. The reaction is expressed as follows : CaF -f S0 3 .HO = S0 3 .CaO -f HF The fluor-spar employed should be quite free from silica and sulphur. 434. Properties. Concentrated fluohydrie acid is a gas which at 32 is condensed into a colorless fluid, with a den- sity of 1-069. Its avidity for water is extreme, and when brought in contact with it, the acid hisses like red-hot iron. Its aqueous solution, as well as the vapor of the acid, attack glass and all compounds containing silica very powerfully. It 482. What are its characters? 433. How is fluohydric acid pre- pared ? Describe the apparatus, fig. 314. What is the rsaction ? 434. What are its properties ? 17 258 NON-METALLIC ELEMENTS. is often used in the laboratory for marking test-bottles or gra- duated measures, or biting in designs traced in wax on the surface of glass plates. It is a powerful acid, with a very sour taste, neutralizes alkalies, and permanently reddens blue litmus. On some of the metals its action is very powerful; it unites explosively with potassium, evolving heat and light. It attacks and dissolves, with the evolution of hydrogen, cer- tain bodies which no other acid can affect, such as silicon, zir- conium, and columbium. Silicic, titanic, columbic, and mo- lybdic acids are also dissolved by it. Fluohydric acid, in its most concentrated form, is a most dangerous substance. It attacks all forms of animal matter with wonderful energy. The smallest cfrop of the concen- trated acid produces ulceration and death, when applied to the tongue of a dog. Its vapor floating in the air is very corrosive, and should be carefully avoided. If it falls, even in small spray, on the skin, it produces an ulcer, which it is very difficult to cure. For this reason it is quite inexpe- dient for unexperienced persons to attempt its preparation. By using a weaker sulphuric acid, however, or by having water in the condenser, no risk is incurred. As before re- marked, it attacks -silica more powerfully than any other body. This fact puts us in possession of an admirable mode of analyzing silicious minerals, when we do not wish to fuse them with an alkali. 435. Sulphydric Acid, Sulphuretted Hydrogen. When the protosulphuret of iron or the sul- phuret of antimony is treated with a dilute acid, effervescence occurs, and a gas is given out having a most disgusting, fetid odor, which at once reminds us of the nauseous smell of bad eggs. This process is performed in the evo- lution-bottle A, (fig. What its uses? What of its safety ? How does it act on the organs? What is its great affinity ? 435. What is hydro-sulphuric acid ? What is its common name ? COMPOUNDS OF HYDROGEN. 259 310) in which a portion of sulphuret of iron is acted on by dilute sulphuric acid turned in at the funnel-tube b. The es- caping gas is led by a to the inverted bottle. This operation should be performed in a well-drawing flue or in the open The reaction is FeS-fS0 8 -f HO=FeO.S0 8 +HS. air. If sulphuret of antimony is used, heat is needed; and we must employ the apparatus fig. 317, and chlorohydric in- Fig. 317. stead of sulphuric acid. This mode evolves no free hydro- gen, which is present in small quantities when protosul- phuret of iron is used. This is sulphuretted hydrogen gas, one of the most useful reagents to the chemist, especially in relation to the metallic bodies. 436. Properties. Sulphydric acid is a colorless gas, of a disgusting odor, like that of putrid eggs. Its density is 1-191, or a little heavier than air. It is liquefied at 50 by a pressure of 15 or 16 atmospheres, and at 122 Fahrenheit it freezes into a white confused crystalline solid, not transparent, and which is much heavier than the fluid, sinking in it readily. Heat partially decomposes it. It burns with a blue flame, depositing sulphur on the interior of the bottle. Sulphurous acid and water are its products of combustion. Mingled with 1 volumes of oxygen the combustion is complete, no sulphur is deposited, and there How prepared ? Give the reaction. Why is sulphuret of antimony sometimes preferred? 436. What are its properties? Is it combustible ? How is it decomposed ? How much oxygen burns it ? What are the pro- du-jtg of combustion ? 260 NON-METALLIC ELEMENTS. is a shrill explosion. Strong nitric acid also inflamos and burns it. Chlorine, bromine, and iodine also decompose it. Mingled with a considerable volume of air in contact with organic matter, it slowly forms sulphuric acid. It is a true but feeble acid. Water, if cold, and recently boiled, dissolves 2$ or 3 times its volume of sulphydric acid. Woulf 's apparatus (fig. 321) is best adapted for this purpose. The solution has the characteristic smell and taste of the gas and all its pro- perties. If boiled it loses all its gas, and if kept a short time it becomes troubled from precipitation of sulphur : this is due to oxygen dissolved in the water. The solution of sulphydric acid should therefore be kept in well-stopped bot- tles, quite full. This solution is much used in the labora- tory. Added to solutions of metallic salts it throws down characteristic precipitates, offering to the chemist an easy mode of distinguishing substances or of separating them from one another. The gas passed directly into solutions of metals as in fig. 318, answers the same purpose. Such an Fig. 318. apparatus is conveniently kept for use, and should be always at hand. 437. It occurs in nature in many mineral springs, giv- ing the water highly valuable medicinal characters. Many such springs in this country are much resorted to, as at Sha- ron and Avon, N. Y., and the sulphur springs of Virginia. At Lake Solfatara, near Home, this gas is given off copi- ously with carbonic acid. The disgust at first felt at drink- ing these nauseous waters is soon overcome, and those patients who take them in large quantity soon observe the gas to penetrate their whole system and exude in their perspiration. Silver coin, and other silver articles in the pockets of such persons, are soon completely blackened by the coating of sulphuret of silver formed on their surface. Although salutary when taken into the stomach, it is, even when present in the air in only a small quantity, a deadly poison to the more delicate animals. Numerous deaths are also recorded of those who have attempted to work in vaults and sewers where it abounds. How soluble is it? Will the solution remain unchanged? Why not? 437. What is its natural history ? IIow does it affect life ? COMPOUNDS OF HYDROGEN. 261 438. When sulphurous acid and sulphuretted hy- % drogen gas are brought together in a common receiving vessel, mutual decomposition ensues, and the sulphur of both is thrown down, which attaches itself to the sides of the vessel in a thick yellow pellicle. The sul- phurous acid is evolved in a, (fig. 319,) (310,) and sulphydric acic in b, and both are carried to the bottom of the middle bottle at a b. Sulphydric acid is formed from 1 volume of hydrogen= 0-0692 And J volume of sulphuric vapor 6 -^2 = 1*1090 Giving for the theoretical density of the gas 1/1782 While experiment gives 1*1912 There is a bisulphydric acid, HS a , but no further men- tion will be made of it. 439. Selenhydric and tellurhydric acids are exactly analo- gous to the last-named compound, and their general interest is so small that we pass them without further notice. Compounds of Hydrogen with Class III. 440. The compounds which hydrogen forms with the nitro- gen group are strongly contrasted in chemical and physical characters with the remarkable natural family which has just engaged our attention. The latter are all acid, and gene- rally in an eminent degree. The compounds of hydrogen with the nitrogen group are, on the contrary, either neutral or strongly basic, forming a series of salts or peculiar com- pounds with the hydracids before named. The compounds named under this head are Ammonia NHj Phosphuretted hydrogen PH, We might add in the same connection the hydrogen com- pounds of arsenic and antimony, AsH 3 and SbH u , sub- 438. What is the experiment in fig. 319 ? What is the composition of this gas? What its theoretical and experimental isnsity? 439. What compounds are used in this section ? Give the ftrmulae. What other similar compounds are named ? 262 NON-METALLIC ELEMENTS. stances quite similar to PH., in many of their attributes, but convenience refers these to the metallic bodies. 441. Or'ujiii of Ammonia. Hydrogen and nitrogen do not unite in mixture, nor by the aid of heat. A series of electrical sparks, as in the case of nitrogen and oxygen, (333,) passed through a mixture of hydrogen and nitrogen, will produce a limited quantity of ammonia. But it is only when these gases come together at the moment of their evolution from previous combination, (nascent state, 269,) and while, so to speak, they still have the impression of change upon them, that they unite with freedom. Ammonia is there- fore a constant product in the decomposition of those organic substances which contain nitrogen. It is in fact from the destructive distillation of horns, hoofs, and other highly ni- trogenized forms of animal matter, that the ammonia of commerce is in great measure derived. This nascent union also occurs without the aid of the products of life. A fragment of metallic iron in moist air soon contracts a film of oxyd of iron, which, like other porous bodies, absorbs the atmospheric gases, while the electrical influence of the oxyd of iron with water and metallic iron, forming in fact a voltaic circuit, effects a slow decomposition of water, whose hydrogen unites in its nascent state with atmospheric nitrogen to form ammonia. Thus we reach an explanation of the well-known fact, that oxyd of iron often contains a notable proportion of ammonia. 442. Again : Hydrogen is evolved, as all know, by the action of dilute sulphuric acid on zinc. Nitric acid effects the same end, if of a certain concentration. But if nitric acid be added drop by drop to dilute sulphuric acid, while hydrogen is being evolved by its action on zinc, the effer- vescence from escaping hydrogen is checked, and, if the ad- dition of nitric acid is cautiously made, a point is reached when the evolution of hydrogen ceases entirely. The zinc is still dissolving, but the hydrogen is immediately seized as fast as it is evolved, by the nitrogen from the decomposed nitric acid, ammonia is formed, and the fluid is found to con- tain a notable quantity of nitrate and sulphate of ammonia. 441. What is the origin of ammonia? How do the two gases unite? How does this happen from the dung of animal matters ? How without their aid? 442. How is ammonia formed by the solution of zinc? Describe the process. COMPOUNDS OF HYDROGEN. 263 443. Ammonia was known to the ancients, and bears proof of its antiquity in its very name. They obtained sal-ammo- niac by burning the dried dung of camels in the desert, whence the name, ammonia, from ammos, sand, in allusion to the desert, which was also called Ammon, one of the names of Jupiter. The sal-ammoniac, sulphate of ammonia, and am- monia-alum, are found among the products of volcanos. Free ammonia is exhaled from the foliage and found in the juices of certain plants, in the perspiration of animals, in iron rust, and absorbent earths. Rain water also contains a small quantity of ammoniacal salts, washed out of the atmo- sphere j and the guano so much valued as a manure, is rich in various ammoniacal compounds. 444. Preparation. Ammonia is prepared by decompos- ing sal-ammoniac, by dry lime and heat. For this purpose equal parts of dry powdered sal-ammoniac and freshly slaked dry lime are well mingled and heated in a glass, or, if the quantity is considerable, in an iron vessel. The lime takes the chlorohydric acid, forming chlorid of calcium, and am- monia is given out as a gas. Fig. 320 shows the arrange- ment for the purpose. The ammonia is col- lected over mercury. In the laboratory it is more convenient to employ in the flask e strong solution of am- monia, which yields a large volume of gas at a gentle heat. If it is required to dry the gas, it cannot be done by chlorid of calcium, which ab- sorbs it largely in the Fig. 320. cold, but dry caustic lime or potassa must be used. 445. Properties. The dry gas is colorless, having the very pungent smell so well known as that of "hartshorn," (because it was procured formerly from the horns of the hart.) 443. What of the antiquity of ammonia? What natural sources are named for it? 444. How is it prepared? Describe the process, tig. 320. 445. What are its properties? 264 NON-METALLIC ELEMENTS. It is, when undiluted, quite irrespirable, and attacks tha eyes, mouth, and nose powerfully. It is strongly alkaline, and is often called the volatile alkali. It restores the blue of reddened litmus, turns green the blue of cabbage and dahlia, and neutralizes the most powerful acids. Its density is about half that of air, or 0-597. It does not support combustion, but the flame of a candle as it expires in the gas is slightly enlarged, and surrounded with a yellowish fringe. A small jet of ammoniacal gas may also be burned in an atmosphere of oxygen. With its own volume of oxygen it explodes by the electric spark, and produces water and free nitrogen. Passed through a tube tilled with iron wire, and heated to redness, dry ammonia is entirely decomposed; yielding for every 200 measures of ammonia, 300 measures of hydrogen, and 100 of nitrogen. The metal in the tube acts to decompose the ammonia solely by its presence, (271.) At a temperature of 50 it is liquefied with a pressure of 6 atmospheres, and with the ordinary pressure it is liquid at 40, producing a white, translucent, crystalline solid, heavier than the liquid. 446. Ammonia is instantly absorbed by water. A frag- ment of ice slipped under the lip of an air-jar filled with dry ammonia over the mercury cistern is melted at once, and the mercury rapidly rises to supply the place of the absorbed gas. This forms a weak solution of ammonia, as may be shown by its action with reddened litmus. Cold water dissolves 500 times its volume of ammonia, all of which is How does it act with other bodies? How is it classed? What its density? How as respects combustion? How is it decomposed? What is the product? 446. How absorbablc is it? COMPOUNDS OF HYDROGEN. 265 expelled by heat. . This solution is called aqua ammonia?,. It is prepared in a "Woulf ' s apparatus b, c, d, (fig. 321,) and is evolved from dry lime and sal-ammoniac in a. The tubes i dip to the bottom of the water in each bottle, and slight pressure may be made by causing the last i to dip into mer- cury. The fluid is seen to mount in o, o } o, indicating tho pressure, which of course is greatest in b. 447. Solution of ammonia, if saturated in the cold, is lighter than water, being sp. gr. 0-870, containing 32 J parts in 100 of real ammonia. Its odor is overpowering, causing suffusion of the eyes and a strong alkaline taste. It boils at 130, and freezes only at 40. It saturates acids, and forms definite salts. Ammonia is always recog- nized by its odor and its restoring the blue of reddened litmus, carrying other vegetable blues to green, and browning yellow turmeric. Its salts are decomposed by dry lime or caustic potassa, evolving the characteristic ammomacal odor. A rod moistened in chlorohydric acid brought near a vessel evolving ammonia causes an imme- diate cloud of chlorid of ammonium, (fig. 322.) It must be preserved in well-stopped bottles in a cool place, as the heat of summer or of a warm room causes gas enough to be evolved to blow out the stopper of the bottle. Fig. 322. 448. Hydrogen and Phosphorus. Phosphurettcd Hydro- gen. This gaseous body is conveniently prepared by em- ploying quicklime recently slacked, water, and a few sticks of phosphorus, in a small retort, (fig. 323,) the ball of which Fig. 323. is nearly filled with the mixture. A gentle heat generates How is aqua ammoniae formed ? Describe Wottlf ' s apparatus. 447. What are the properties of the solution ? How are its salts decomposed ? 448. How is phosphuretted hydrogen obtained ? 266 NON-METALLIC ELEMENTS. the gas, which breaks from the surface of the water (beneath which the beak of the retort dips very slightly) in bubbles, that inflame spontaneously as they reach the air, rising in beautiful wreaths of smoke, which float in concentric, expanding rings. Phos- phuret of calcium thrown into a glass of water (fig. 324) is instantly decomposed, and evolves the spontaneously inflammable gas. Fig. 324. Chlorohydric acid evolves from this com- pound the variety of this gas which is not spontaneously inflammable. 449. Properties. This gas has a digusting, heavy odor, like putrid fish, which is far more annoying than that of sulphuretted hydrogen. It is transparent and colorless, has a bitter taste, and, if dry, may be kept unchanged either in the light or dark. It loses its spontaneous inflammability by standing a time over water, a body being deposited which is probably phosphorus, in its red modification. It is deadly when breathed. It acts very violently with oxygen gas. If bubbles of it are allowed to enter ajar of oxygen, each bubble burns with a most brilliant light and a sharp explosion. The mixture of even a very small quantity with oxygen would be quite hazardous, destroying the vessels. Its property of spontaneous inflammability is undoubtedly owing to a portion of free vapor of phosphorus. In its chemical relations phosphuretted hydrogen is nearly neutral, but is in some respects a base, as it forms crystalline salts with bromohydric and iodehydric acids, which are decom- posed again by water. There are three phosphurets of hydrogen, P a H, PH 2 , and PH 3 . The second of these is a liquid, the third is the sub- stance described above. Compounds of Hydrogen with the Carbon Group. 450. Carbon and Hydrogen form a vast number of compounds in the organic kingdom, many of which will come under our consideration in the organic chemistry. 449. What are its properties? What is its most remarkable pro- perty ? What its constitution ? 450. What compounds of hydrogen and tarbon are named ? COMPOUNDS OF HYDROGEN. 267 There are two gases, marsh gas and olefiant gas, or the light and heavy carburetted hydrogens, which are found in the inorganic kingdom, although they are derived from the destruction of organic bodies. These two compounds we will now consider. They are Light carburetted hydrogen gas CH a or C S H 4 Olefiant, or heavy carburetted hydrogen gas... C a II a " C 4 H 4 451. Liglit Carburetted Hydrogen Gas; Marsh Gas; Fire Damp. This gas occurs abundantly in nature, being formed nearly pure by the decomposition of vegetable mat- ter under water, (marsh gas.) The bubbles which rise when the leaves and mud of a stagnant pool or lake are stirred, are light carburetted hydrogen, with some nitrogen and car- bonic acid. It may be collected in such situations by means of an inverted funnel and bottle, as in figure 325. In coal mines it is copiously evolved in company with heavy carburetted hydrogen and carbonic acid, (fire damp.) In the | salt region of Kanawha, it flows =] so abundantly from the artesian wells with the salt water, as to fur- nish heat enough by its combustion for evaporating the salt water. The village of Fredonia, in New York, Fi s- 325 - . has for many years been illuminated with this gas, derived from the saliferous deposits. 452. Preparation. Marsh gas is prepared by treating equal parts of acetate of soda and solid hydrate of potash with one and a half parts of quicklime. The materials are ground separately, well mingled, and strongly heated in a retort of hard glass protected by a thin sand-bath of sheet- iron. The acetic acid C 4 H 4 4 of the acetate is decomposed by the potash, which removes from it 2 equivalents of car- bonic acid, and marsh gas is evolved, thus: Acetic acid C 4 H 4 4 = Carbonic acid, 2 equivalents C a 4 Marsh gas GjIU C 4 H 4 4 CII 4 4 Give their composition. 451. What is marsh gas ? How may it bt collected ? What other natural sources are named ? 452. How is it pre- pared ? Give the reaction. '268 NON-METALLIC ELEMENTS. The lime preserves the glass of the retort from the action of the potash. 453. Properties. Marsh gas is colorless, inodorous, slightly absorbed by water, and is respirable when mingled with common air. Its weight is about half that of air, or 559, and 100 cubic inches weigh 1741 grains. It burns with a yellow flame, giving as the products of combustion water and carbonic acid. Mingled with common air, it forms an explosive mixture, which collects in large quantities in the upper part of the galleries of coal-mines, giving origin to fearful explosions and the destruction of many lives of miners. Twice its volume of oxygen burns it completely. It has never been liquefied. In a tube of porcelain, at full redness, it is decomposed, carbon is deposited, and hydrogen evolved. With moist chlorine in the sunlight, it forms carbonic and chlorohydric acids, but is not affected by it in the dark. It is composed in 100 parts, of hydrogen 25, vapor of carbon 75 ; or by volume, of 2 volumes of hydrogen = 0-696X2= 0-1392 and i volume of carbon vapor = -829 -r- 2 = 0-4145 Theoretical density of marsh gas 0-5537 454. Olrfiant Gas, or heavy Citrluretted Hydrogen Gas. This gas was discovered in 1796, bv an association of Dutch chemists, who gave it the name of olefiant, because it forms a peculiar oil-like body with chlorine. It is prepared by mixing strong alcohol with five or six times its weight of oil of vitriol in a capacious retort, and applying heat to the mixture. The action is complicated, and cannot be well explained at this time. The gaseous products are olefiant gas, carbonic acid, and sulphurous acid. The alcohol is 453. What are its properties? What danger arises from it in coal- mines ? How is it composed by volume ? 454. How is it prepared ? COMPOUNDS OF HYDROGEN. 269 charred, and at the end of the operation froths up very much. The gas can be purified by passing it first through a wash- bottle containing a solution of potash, and then through oil of vitriol ; the potash removes the acid vapors, and the oil of vitriol retains the ether, (fig. 326.) 455. Properties. Olefiant gas is a neutral, colorless, tasteless gas, nearly inodorous, and having a density of 0-9784; 100 cubic inches of it weighing 30 57 grains. It burns with a most brilliant white light and evolves much free carbon. With three volumes of oxygen gas it burns completely, with a tremendous detonation, which is too severe even for very strong glass vessels. Bubbles of the mix- ture may be exploded by a burning paper, as they rise from beneath the surface of water. Water and carbonic acid are the sole products of this combustion. It is partially decom- posed by passing through tubes heated to redness, and much carbon is deposited. This effect happens in the iron retorts of city gas-works, in which crusts of pure carbon, sometimes of great thickness, accumulate from the decomposition of the gas. 100 parts of olefiant gas contain 200 hydrogen and 100 vapor of carbon. Thus, 2 volumes of hydrogen weigh 0-1392 14-29 1 volume of carbon vapor 0-8290 85-71 0-9672 100-00 Its formula is thence C 4 H 4 , and the experimental density (0-9784) is a near approach to the theoretical. 456. The chlorine compound will be described in the organic kingdom. It burns with chlorine, forming chloro- hydric acid, and depositing its carbon in a dense cloud. Illuminating gas is formed of a union of marsh gas and of olefiant with some free hydrogen. The power of illumination is derived from the olefiant gas. Ammonia, its sulphuret, carbonic acid, tar, and resinous pyrogenic compounds require to be removed from coal gas before it is fit for use ; and this is accomplished by passing it through water, cooling it in con- densers, and transmitting it through dry lime purifiers, and through dilute solution of sulphate of iron to remove HS and C0 3 . The other compounds of hydrogen with boron, &c., are too little known to require description now. 455. What its properties ? How much oxygen burns it ? What are the products ? How decomposed ? What is its composition ? 456. Whenco its name ? What is illuminating gas ? 270 COMBUSTION. Combustion , and the Structure of Flame. 457. Combustion. This familiar phenomenon is the dis- engagement of light and heat which accompanies some cases of chemical union. Nearly all our operations being per- formed in the atmosphere, the term combustion has come to be restricted, in a popular sense, to the union of bodies with oxygen, with development of light and heat. Thus, carbon, sulphur, phosphorus, &c., are familiar examples of elementary combustibles, while oil, tar, coal, wood, &c., are compound ones. The products of the combustion of organic bodies are all gases or vapors, and are no longer combustible; while the products of the combustion of iron, phosphorus, potassium &c., are oxyds, bases, or acids, and generally are incapable of further change from similar action. Thus, iron burns brilliantly in oxygen gas, (277,) forming a com- pound, capable of no further change in oxygen. Iron also burns in vapor of sulphur, (fig. 232,) but the protosulphuret of iron so formed is still capable of burning in oxygen. For such reasons as these, bodies were for a long time di- vided by chemists into two classes, of combustibles and supporters of combustion. This mode of arrangement is now for the most part abandoned. It was radically defective as a philosophical classification of elements, since it seized on a single phenomenon accompanying chemical union, and disregarded all those natural analogies which group the ele- ments into distinct classes. 458. In all cases of combustion the action is reciprocal. Hydrogen burns in common air ; but if a stream of oxygen is thrown into a jar of hydrogen, through a small aperture at the top, when the latter is burning, the flame is carried down into the body of the jar, and the oxygen will continue to burn in the hydrogen, as it issues from the jet. In this case the oxygen may be said to be the combustible, and the hydrogen the supporter. The simple statement in both cases is, that oxygen and hydrogen combine, and combus- tion that is, the disengagement of light and heat is the consequence. (Daniell.) The diamond burns in oxygen gas, but the latter is as much altered by the union as the former ; 457. What is combustion ? How is the term restricted ? What division of elements was founded on this phenomenon? 458. What of ^he re- ciprocal nature of combustion ? What of light and heat evolved ? COMBUSTION. 271 and wo cannot therefore say whether the oxygen or the carbon is the most burnt. Heat and light attend this union : but the carbon of the human body is as truly burnt in the lungs by the atmospheric oxygen, as is the fuel on our fires. The product of this combustion, the carbonic acid, thrown out by the lungs at every exhalation, is the same thing as the carbonic acid which is discharged at the mouth of a furnace. In the case of the animal body, the combustion is so slow that no light is evolved, and only that degree of heat (98 to 100) which is essential to vitality. The term combustion must have, then, a chemical sense vastly more comprehensive than its popular meaning. The rust which slowly corrodes and destroys our strongest fixtures of iron, and the gradual process of decay which reduces all structures of wood to a black mould, are to the chemist as truly cases of combustion as those more rapid combinations with oxy- gen which are accompanied by the splendid evolution of light and heat. The heat produced by combustion has received no satis- factory explanation. We know that any change of state in a body is accompanied by an alteration of temperature. When two liquids become solid, we can better understand why heat should be produced, (124.) But why the union of carbon and oxygen, or of oxygen with hydrogen, to form a gas, should evolve such intense heat as to fuse the most refractory bodies, is as yet unexplained. 459. Bodies become visible in the dark at about 1000 of heat. This fact has been lately confirmed by the re- searches of Draper, on the shining by heat of a strip of platinum in the dark, when heated by a current of voltaic electricity. It is true of all bodies capable of being heated, whether solids, or fluids, as melted metals. It is impossible by any means to render a gaseous body visibly red. A coil of platinum wire suspended in the current of air escap- ing from an argand-lamp chimney is at once heated to red- ness, while, as every one knows, the hot air itself is entirely invisible. Combustible gases heated to a certain point in the air, take fire and burn, as when we apply to our gas- burner the flame of a match. The color of red-hot bodies de- pends on the temperature. Yellow light begins to be evolved What chemical extension is given to the term ? Whence the heat evolved in combustion ? 459. At what temperature do bodies become visible in the dark? 272 NON-METALLIC ELEMENTS. at about 1325, and at 2130 all the colors of the spec trum were- observed by Draper in the light viewed by a prism as it came from incandescent platinum. A full white heat, seen by day-light, is supposed to be at least 3000. The increase of brilliancy in the light from hot bodies is at a much higher ratio than the temperature. Thus, the same observer found the "brilliancy of light at 2590 more than thirty-six times as great as it was at 1900. Of Flame. 460. The structure and nature of flame deserve particu- lar notice. If we look attentively at the flame of a candle, (fig. 327,) we see that it is formed of several distinct parts, wrapped, so to speak, conically about each other. 1st. There is the interior cone a a', form- ed entirely of combustible gases, and giving no light. 2d. The cone efg, which is very brilliant, and where the gaseous contents of the first portion become mingled with atmospheric oxygen ; the hydrogen is burned, and the carbon, precipitated in minute parti- cles, reflects light powerfully. And 3d. We see the thin outer envelope c d b, where the combustion is completed, but where there is much less brilliancy of illumination than incfy. In the flame of a gas jet A, Fig. 327. (fig. 328,) the same parts are recognized, similarly let- i What was Draper's experiment? What, is the temperature of yellow light? What the brilliancy as compared with temperature? What is noticed in the structure of flame? Describe fig. 327. What are the parts of th ) flame ? Define flame. FLAME. 273 Fig. 330. an interior unignited mass of inflammable gas. This is easily demonstrated by introducing a small tube of glass Z>, fig. 330, into the cone H, by which a portion of the inflammable gas is led out and may be burnt at the open end of the tube. In like man- ner, by bringing a sheet of platinum foil over the flame of a large spirit- lamp, it will be heated to redness in a ring on the outer circle, while the centre remains black, showing that the interior is comparatively cold. Phos- phorus fully ignited in a metallic spoon, is at once extinguished by im- mersion in the interior of a volumin- ous flame, like that from alcohol, burn- ing in a small capsule. The air is shut out by the screen of flame : the phosphorus, finding no oxy- gen, goes out, but may be seen fused in the spoon : bringing it again to the air, it is rekindled, and so on. 461. A high temperature, it will be easily seen, is an indispensable condition for a perfect and brilliant combus- tion, as the light reflected from the ignited carbon is vastly greater at 3000 than at 2500, (459.) A plentiful supply of oxygen is of course the antecedent of a perfect combus- tion. The candle or lamp becomes smoky whenever these conditions are imperfectly fulfilled as when the wick of a candle becomes too long and reduces the temperature of the flame below the point of bril- liant combustion, supplying at the same time a superabundance of material. The candle must then be snuffed; or it may be provided with a fiat plaited wick, as in fig. 331, which bends out- ward as it burns, and coming in contact with the air, consumes as fast as it protrudes. In all flames like that of the candle, when the air has contact only on one side, combustion is very imperfect. A more rapid and abundant supply of oxygen is the object in the construction of the argand and solar lamps and all similar contrivances. Fig. 331. 462. This is accomplished in the argand burner by How is it demonstrated by fig. 330 ? What other experiments are given ? 461. What are the conditions of perfect combustion? Why is a candle an imperi'ect illumination ? What is the principle of the argand burners ? 18 274 NON-METALLIC ELEMENTS. Fig. 332. employing a circular wick a I c d (fig. 332) arranged between the metallic tubea through the centre of which g h a draft of air rises, as shown by the central arrows. The draft is made more powerful by using a glass chimney, contracted at D so as to deflect the ascending outer cur- rent of air strongly against the flame. Thus, at the same instant, fresh supplies c of oxygen are brought in contact with the inner and outer surfaces of flame, which still retains the same relation of parts as before. The heat of combus- tion is enormously increased by these means; and with the same amount of fuel, a much more brilliant light is pro- duced. In the common double-current spirit-lamp, employed in the laboratory for high heats, the construction is similar, a metallic chimney replacing the glass. A section of this lamp is seen in fig. 333. Dr. C. T. Jackson has described a modi- fication of the double-current spirit- lamp, in which a blast of air from a bellows is introduced within the inner tube. The arrangement is such chat the blast issues in a narrow ring, con- centric with the wick and in close contact with it. Properly manage^, this lamp forms the most powerful lamp-furnace in use. The invention in fact ap- plies the principle of the mouth blowpipe to the argand lamp. In places where gas is used,, the gas-lamp, (fig. 334,) fed 1 Fig. 334. by a flexible pipe and supplied with a metallic or mica chimney, leaves nothing to be desired for a powerful and economical Describe fig. 332. Why is the heat increased? lamp ? What the gas-lamps ? What is Jackson-, FLAME. 275 heat. A small glass spirit-lamp, with a close cover, (fig. 335,) to prevent evaporation, is an indispensable convenience in even the humblest laboratory. 463. The Mouth Blowpipe (fig. 336) converts the flame of a common lamp or candle into a powerful furnace. By the blast from the jet of the blowpipe, the operator turns the Fig. 336. flame in a horizontal direction upon the object of experi- ment, at the same time that he supplies to the interior cone of combustible matter a further quantity of oxygen. The flame suffers a remarkable change of appearance as soon as the blast strikes it, and the inner blue point b has very different chemi- cal effects from the exterior or yellow point c, (fig. 337.) Immediately before the exterior flame is a stream of intensely heated air, which is capable of pow- erfully oxydizing a body held in it, and this point is therefore called the oxydizing flame. The inner or blue point 6 a is called the reducing flame, and in it all metallic oxyds capable of reduction are easily brought to the metallic state or to a lower degree of oxydation. Be- tween the outer and inner flames is a point of most intense heat, where refractory bodies are easily melted. Charcoal is generally employed to support bodies before the blow- pipe flame, when we would heat them in contact with car- bon. Forceps of platinum are used to hold the substance when it is to be heated alone. If the substance is to be submitted to the action of borax, 463. What is the principle of the mouth blow pipe ? What parts are noted in the flame before the jet,fig. 337 ? What is the reducing and what the oxydizing flame ? 276 NON-METALLIC ELEMENTS. or of carbonate of soda, or any similar reagent, a small platinum wire, bent into a loop at one end, is used to hold the fused globule, as seen in fig. 338. Then, by varying Fig. 338. its position in the flame as above described, we may submit it successively to the reducing agency of carbon vapor, and oxyd of carbon at J, to the intense heat of burning carbon at c, or to the power- ful oxydizing influence of the current of hot air immediately in front of the point c. The art of blowing an unintermit- ting stream is soon acquired, by breathing at the same time through the mouth and nostrils ; and an experienced opera- tor will blow a long time without fatigue. No instrument is more useful to the chemist and mineralogist than the mouth blowpipe. By its means we may in a few moments submit a body to all the changes of heat, or the action of reagents, which can be accomplished with a powerful furnace. Sufcty Lamp. 464. The temperature of flame may be so reduced by bringing cold metallic bodies near it as to be extin- guished. Davy also observed that a mixture of explosive gases, could not be fired through a long narrow orifice like a small tube. On these simple facts rests the power of the " safety lamp" of Sir Humphry Davy to protect the life of the miner. If a narrow coil of copper wire, (fig. 339,) be ^ brought over a candle or lamp so as to encircle it, the flame will be extin- Fig. 339. guished; but if the wire be previously heated to redness, the flame continues to burn. The same effect will be produced by a small metallic tube. A wire held in the flame is seen to be surrounded with a ring of non-lu- minous matter. If many wires, in the form of a gauze, are brought near the flame of a candle, it will be cut off and extinguished above ; only a current of heated air and smoko will be seen ascending, (fig. 340,) while the flame continues to burn beneath, and heats the wire gauze red-hot in a ring, marking the limits of the flame. The flame may be relighted 464. What is the effect of a cold body on flame ? What was Davy'a observation ? FLAME. 277 above the gauze, and will then burn as usual, as seen in fig. 341. Sir Humphry Davy found that a wire gauze would in all cases arrest the progress of flame, and that a mixture of explosive gases could not be fired through it. A wire gauze is only a series of very short square tubes, and their power to arrest flame comes Fig. 340. Fig. 341. from the fact that they cool the gases below their point of ignition. Happily, the heat required to ignite the carbon gases is much higher than that which causes the union of oxygen and hydrogen. 465. The fire damp or explosive atmosphere of coal- mines, is a mixture of light and heavy carburetted hydro- gen, with many times their volume of common air. These gases, being lighter than the air, are found especially in the upper part of the galleries of mines, and when the naked flame of the miner's lamp meets such an atmosphere, a terrible explosion often follows. These explosions in coal-mines b.vo destroyed thousands of those whose duties requir- ed them to submit to the exposure. To avoid these lamentable accidents, Davy invented the safety lamp. This is only a common lamp surrounded by a cage of wire gauze, completely enclosing the flame, (fig. 342.) When this lamp is placed in an explosive atmosphere, the gas enters the cage, enlarges the flame on the wick, and burns quietly, the gauze effectually preventing the passage of the flame outward. We thus enter the camp of the enemy, disarm him, and make him labor for us. The miner is not only protected by this in- strument, but ig rendered conscious of the danger by the enlargement of the flame. As long as the lamp can burn, it is safe to stay, as an irrespira- ble atmosphere would extinguish the flame. The powerful blast of wind which sometimes sweeps Fig. 3*2. Explain figs. 340 and 841. What is the application ? What peculiari- ty is noticed of the carbohydrogen gases? 465. What is the fire damp ? Where does it chiefly collect? How was Davy's lamp constructed? What is its action? 278 METALLIC ELEMENTS. through the mines may render the lamp unsafe, by forcing the flame against the gauze, until it is heated so hot as to inflame the external atmosphere. This accident is prevented by the addition of a glass to cover the sides, the air being admitted from below through flat gauze discs. II. METALLIC ELEMENTS. General Properties of Metals. 466. The number of the metals is forty-eight, of which about half are entirely unknown, except in the laboratory, and as the rarest minerals in our cabinets. Of the other half, only fourteen or fifteen are familiarly known, or pos- sess in a remarkable degree those qualities of ductility, lustre, and malleability, which are inseparable from our common notions of the metallic character. A metal is an opaque body, of a peculiar brilliancy, de- scribed as the metallic lustre. It conducts heat and elec- tricity, and in electrolysis it goes to the negative pole of the voltaic battery, and is therefore an electro-positive body. These are the chief characters peculiar to the class. Metallic Veins. 467. In nature, the metals exist commonly in union with sulphur, oxygen, and arsenic. A few, as gold, copper, pla- tinum, and mercury, are found native, or uncombined, or are occasionally alloyed with each other, as native gold nearly always contains a portion of silver. When the metals are combined with sulphur, or other mineralizing agents, by which their proper metallic characters are masked or con- cealed, they are called ores. The native metals, gold, cop- per, platinum, &c., are not properly denominated ores, being obtained in a metallic state from the sands. The discovery and extraction of the ores of the metals constitutes the art of milting. The separation of the metals from their ores, by heat or other means, is a separate branch of chemical art, known as metallurgy. Mining demands a minute knowledge of the. mineralogical character of the ores of metals and of 466. What is the number of metals ? How many are commonly known ? What is a metal? 467. How do the metals exist in nature? What are ores? What is mining? What is metallurgy ? What does mining re- quire ? METALLIC VEINS. 279 the earthy minerals with which these are associated ; as well as the mode of occurrence of mineral veins and ore beds, and the mechanical methods adopted for the raising of the ores from the earth, their separation from foreign substances, and their preparation for market. 468. The ores of metals are seldom scattered through the rocks in a diffused manner, but are usually collected in veins or lodes, accompanied by quartz, carbonate of lime, and various other minerals, called the vein-stone, or gangue. The metal-bearing veins occur more frequently in regions where primitive rocks abound, as in granite and its associates. Often, however, they extend from these rocks to those which rest above them, and are stratified ; showing that the veins fill fissures in the earth, occasioned by the cooling of its heated mass, and into which the minerals now filling them came by injection or infiltration. These fissures usually occur together, in a degree of order, the veins being more or less parallel, as seen in c,c,c,&c.,(fig.343,) which is an ideal sec- tion of a metallic deposit, (the veins are here seen to reach from the gra- nite c to the stratifi- ed rocks a, a.) Cross veins, or courses, often intersect in a different direction, as d, e, &c. , and these have usually a mi- neral character entirely distinct, and showing a different age and origin. At the intersection of veins there is usually an enlargement of the lode, and often a more abundant deposit of the metallic ore. It is very rare, if ever, that the metallic ore fills the vein entirely. It usually forms small threads running through the vein-stone, now expanding, and again contracting, as seen in the vertical section of a vein in fig. 344, where a, b, c show the rocky gangue surrounding 468. How are ores found? What is a vein-stone or gangue? Wnere do veins most frequently occur? Describe fig. 343. Where are veins enlarged ? How is the ore usually distributed in mineral veins ? '280 METALLIC ELEMENTS. the metallic ore d, e, f, g. Often the ore dies out entirely, as at b, c, and is again renewed farther on. A few minerals only are found in beds re- gularly stratified between layers of other rocks. Some of the ores of iron are so found, as well as coal and rock-salt. But the mode of origin of these last is quite distinct from that of the ores of the metals. Fig. 345 shows the mode of occurrence Fig. 345. of rock-salt in masses, filling cavities formed probably by the solution of minerals previously existing there. Physical Properties of Metals. 469. The physical properties of the metals include their den- sit}', lustre, color, opacity, malleability,ductility, laminability, tenacity, crystallization, fusibility, and conducting power. In density, metals present every variety, from potassium (865) and sodium, (-972,) floating on water, to gold (19-26) and platiua, (21-5,) the heaviest bodies known. In lustre they range from the splendor of gold and of burnished silver, to the dulness of manganese and of chromium. This property often depends on the mechanical condition of the metal ; thus, gold and platinum, as thrown down from solution in fine powder, are dull yellowish-brown, and black powders, which show the lustre and color appropriate to the metals only under the burnisher. The color of most of the metals is dull white or gray. Silver is nearly pure white ; gold, yel- Describe fig. 344. What substances arc found in beds ? What is .sluivrr, in fig. 345 ? 469. What are the physical properties of metals ? What of density? What of lustre? How do mechanical conditions affect lustre? PHYSICAL PROPERTIES OF METALS. 281 low; and copper and titanium are red. Copper is the basis of all colored alloys; being fused with tin and zinc to form bell and gun metal and yellow brass. To determine the color of a polished metal accurately, the light must be reflected many times from its surface, as may be done by placing two polished surfaces of the same metal opposite each other, and examining with a prism the light reflected at an angle of 90 from them. In this way it is found that the proper color of copper is orange-red ; of gold, after ten reflections, a beautiful red ; of silver, a reddish-white ; of zinc, a delicate indigo-blue; of bronze, an intense red; of steel, a feeble violet, &c. In looking into a deep vase of polished metal, or into a highly polished bronze cannon, or the bore of a new steel rifle, these tints of color by reflection are seen. Opacity is not absolute in metals, as is proved in the case of gold-leaf on glass, through which a beautiful violet-green light is seen. This light is found by optical experiments to be truly transmitted light, and not a color caused by the mi- nute fissures of the gold-leaf. It is worthy of remark that this greenish color is complementary to the red, which is the reflected color of the gold. 470. Malleability, or the capability of being beaten by blows into thin leaves, is found in the highest perfection in gold, and in a good degree in many other metals. Some metals are perfectly malleable when cold, as silver, gold, lead, and tin; others are malleable when hot, as iron, plati- num, &c., and are not without this property, though in a much less degree, even when cold. Some, like zinc, are lami- nable at a moderate heat, but brittle above and below it; others, like antimony, are brittle at all temperatures short of fusion. Gold leaf has been beaten so thin as to require 250,000 leaves to equal one inch in thickness, or 1,365 such leaves would about equal in thickness one leaf of this book. Ductility and laminability are properties closely allied to mallea'bility. Iron, for instance, unless heated, can not be beaten like gold, but it may be drawn into fine wire, (ductility,) and plated by rollers into thin sheets, (laminability). "What of color ? Enumerate colored metals and alloys ? How are metallic colors accurately determined? What are thus found to be the colors of gold, of copper, of silver, zinc, and bronze ? Is opacity absolute ? Why not? What is proved of the green color of gold? To what is it complementary? 470. What of malleability, ductility or cor- responding to chlorohydric acid C1H. One principal objec- tion to this view is, that these hypothetical radicals have in general never been isolated. It is, however, true that those acids which are capable of existing dry and in a separate state, as sulphuric, (S0 3 ,) phosphoric, (P0 5 ,) nitric, (N0 5 .) and carbonic, (C0 3 ,) are not acids as long as they remain dry; and although they form compounds with dry ammonia, that these compounds are not salts. Sir Humphry Davy long ago suggested that hydrogen was the real acidifying principle in all acids. 482. If the salt-radical theory is finally adopted, all acids must be considered as hydrogen acids, and all salts as haloid salts. For example, let us take two common saline bodies and present them according to these two views. Old view. New view. Sulphate of zinc ZnO 4- S0 3 Zn-J-SO^ Nitrate of soda Na04-N0 5 Na-J-N0 6 According to the new view, when an acid dissolves a metal, there is no necessity for supposing water to be decom- posed. The metal takes the place of the hydrogen, and the latter is given off in a gaseous form ; or if the oxyd of the metal is used, the oxygen and hydrogen unite to form water, and no effervescence ensues. The apparent simplicity of this view renders it attractive, and it has been most warmly supported by Profs. Graham and Liebig, while in this country it has found an able op- ponent in Dr. Hare. 481. What is said of theformulaof SO,? What view of acids is suggested? What objection is urged? What is true of dry S0 3 russian - Sulphur ............. 11-9 ...... 12-5 ...... 11-5 ...... 10 ......... 9 ......... 9-9 Charcoal ............ 13-5 ...... 12-5 ...... 13'5 ...... 15... ...... 16 ......... 14-4 Nitre ................ 74-6 ...... 75- ...... 75- ...... 75 ......... 75 ......... 75-7 Much of the explosive energy of gunpowder depends on its granulation ; a fine dust, of the same composition with powerful powder, burns with a rapid deflagration, but with- out explosion. The constitution of gunpowder is varied according to the use for which it is intended. Thus, 20 sulphur, 18 charcoal, and 62 nitre, are used for blasting- powder in mines, and its combustion may be rendered still slower by mixing it with several times its bulk of sawdust. The effect then is more powerful in moving large masses of rocks. The gases formed in the combustion of gunpowder are carbonic acid and nitrogen, while sulphuret of potassium remains as a solid residue. The combustion of a squib, or moist gunpowder, gives a much more complicated result; nitric oxyd, sulphuretted hydrogen, carbonic acid, carbonic oxyd, nitrogen, and other products being formed. 502. Chlorate of Potash, KO.C10 5 . This salt is the salt already named (275) as the best source of pure oxygen gas. It is formed by passing chlorine gas through a strong solution of carbonate of potash, chlorate of potash and chlorid of po- tassium being formed, the chlorate being easily crystallized out by its less solubility. The carbonic acid escapes. The reaction is between 6KO.C0 3 +601 = 5KC1 -j- KO.C1CK + 6C0 3 . 503. Properties. Chlorate of potash crystallizes in flat, pearly tables, referable to the oblique rhombic prism. Water at 32 dissolves only 3-3 parts in 100; at 60 only 6 parts, while boiling water dissolves nearly 60 parts; it is therefore much more soluble in hot than in cold water. It is insolu- ble in alcohol. Its taste is cooling and disagreeable, resem- bling nitre. It fuses at 750 ; above that heat, oxygen is given off, and chlorid of potassium left behind. It is a most What is the constitution of gunpowder in different countries ? On what does its explosive energy depend ? What are the products of its combus- tion ? If wet, what are they? How is blasting-powder made more effi- cient ? 502. What is chlorate of potassa, and how formed ? 503. What are its properties ? ?>00 METALLIC ELEMENTS. energetic oxydizing agent. It forms explosive mixtures with Dearly all combustible bodies. 504. With sulphur and charcoal it forms a compound that explodes by friction, or by a drop of sulphuric acid, and was formerly much used in the preparation of friction matches. With sulphur alone, it detonates powerfully when wrapped in a paper and struck by a hammer. With phosphorus its reaction is extremely violent ; a deafening explosion follows the slightest compression of the ingredients, and burning phosphorus is projected in all directions. Its large con- sumption in the preparation of matches has rendered it a cheap salt. All attempts to form a gunpowder of chlorate of potash have failed, the action of the mixture being so violent as to rend asunder the arms employed. A mixture of sugar and chlorate of potash is instantly inflamed by a drop of sulphu- ric acid, and burns with the violet color which belongs to all the salts of potassium. The characters of the salts of potash are the same with reagents as those of potassa before given, (490.) The salts of the alkalies are distinguished from all other metallic salts by yielding no precipitate to an alkaline carbonate. All the potash salts form with sulphate of alumina a crystalline double sulphate of potassa and alumina common alum crystallizing in octahedrons. SODIUM. Equivalent, 23. Symbol, Na. Density, -972. 505. Sodium wag discovered by Davy soon after the dis- covery of potassium, and in the same way. It is now pre- pared by a process quite similar to that already described (484) for potassium ; the carbonate of soda being used in place of the carbonate of potassa. This metal forms more than 40 parts in 100 of common salt, and is also frequent in various combinations in the mineral kingdom. The ashes of sea-plants afford crude What its solubility? What is its reaction with combustibles? 504. Why not fit for gunpowder? What color does it burn with? What are the characters of potash salts ? What compound do they form with alumina? 505. Give the history and distribution of sodium. How procured ? SODIUM. 301 carbonate of soda, in place of the carbonate of potash pro- cured from land-plants. 506. Sodium is a white metal, with a silvery brilliancy, and much resembles potassium in its general properties. Ita color is much whiter than that of potassium, and its dis- position to tarnish less. Its density is '972, and it melts at 194. At common temperatures it is harder than potas- eium, but is easily moulded in the fingers. It does not in- flame on cold water, unless in masses of considerable size, but moves about rapidly, fused into a brilliant sphere, until it is all consumed. It may be alloyed with potassium by simple pressure, and is then inflamed on water, or alone on hot water, burning with a bright yellow light, characteristic of sodium, and strongly contrasted with the violet color of the potassium flame. The same color is seen when a piece of soda-glass, or any mineral containing soda, is held in the flame of the blowpipe; the flame is instantly tinged yellow. Exposed to the air, sodium soon falls to a white powder of oxyd of sodium. The compounds of sodium are so similar to those of potas- sium that we can pass them with a brief notice. The oxyds of sodium and their hydrates are the same in composition as those of potassa. 507. The hydrate of soda, or caustic soda, NaO.HO, is procured by decomposing the carbonate by quicklime, in the same manner as has already been described for caustic potash, (488.) It is a powerful alkaline base, very soluble in water, and deliquescent in moist air. It forms a white crystalline cake, resembling potassa. It is a corrosive and energetic poison. All its salts are soluble, which renders it somewhat difficult to detect its presence in solution. 508. Chlorid of Sodium, or Common Salt, NaCL This familiar and abundant substance is too well known to need much description. It is formed when sodium burns in chlorine gas, as well as when soda, or its carbonate, is neu- tralized by chlorohydric acid. In Poland, Austria, Spain, Sicily, and Switzerland, extensive beds of pure rock-salt are found, which are regularly mined. Common salt forms about 27 of every 1000 parts of sea-water, and in warm 506. What its properties? What is the color of its flame? What of its compounds ? 507. What is NaO.HO ? How procured ? Give its pro- perties. What of its salts? 508. What is NaCl? How artificially formed ? How found in nature ? 302 METALLIC ELEMENTS. climates, especially In the West Indies, sea-water is evapo- rated in large quantities by the sun's heat, to obtain salt. Numerous saline springs are found in New York, Ohio, Kentucky, and other places in this country, which afford vast quantities of salt by evaporation. The brine springs iu Onondaga county, New York, are among the most valuable, and have been worked since 1789. Their water contains one- seventh part of dry salt. The water of the Great Salt Lake, in Deseret, contains 200 parts of salt in 1000, or over Jth of its weight. This salt is nearly pure. The Dead Sea has a still greater concentration, ( 544.) Common salt crystallizes in cubes, which are anhydrous, and crackle, or decrepitate, when heated, owing to water mechanically entangled in them. Salt forms singular hopper-shaped crystals, (fig. 352.) These are produced on the surface of the evaporating brine, and grow by increase of the outer edges, as gravity sinks them constantly, a trifle below the surface of the fluid, each ad- ditional row of particles being built upon Fig. 352. the upper and outer edge of the last. It requires 2*7 parts of water for its solution, and it is equally soluble in hot and cold water. In pure alcohol it is scarcely at all soluble. Its density is 2-557. It fuses at redness, and sublimes in vapor at a higher temperature. It is em- ployed for this reason to glaze earthenware, since its vapor is decomposed by the oxyd of iron of the clay, chlorid of iron being driven off, while soda unites with the silica of the clay to form the glaze. The bromid, iodid, and sulpJiurcts of sodium resemble the corresponding compounds of potassium, and the two former likewise crystallize in cubes. 509. Neutral Sulphate of Soda, Glauber's Salt, NaO. S0 3 -f-(10HO). This familiar salt is found abundantly in commerce in large crystals, which contain more than half their weight of crystallization water, viz : "I eq. anhydrous sulphate of soda 71 44*10 10 " water 90 55-90 1 " crystallized sulphate of soda 161 100*00 How much in sea water ? in salines ? in the Great Salt Lake ? What of its crystallization ? How are the hoppers formed ? How soluble ? Its density ? Why used to glaze pottery ? 509. Give the formula for Glauber's salt. What is its composition ? COMPOUNDS OP SODIUM. 303 210 It fuses at a moderate temperature in its own water leaves, on heating, anhydrous sulphate of soda. to air, the crystals of Glauber's salt efflo- 93 resce, and fall to powder, from loss of 322 water. If its solution is heated above 93, anhydrous sulphate of soda is thrown down. The solubility of sul- phate of soda presents very remarkable anomalies. Below 32 it is slightly soluble. At 32, 12 parts dissolve in 100 parts of water : the quantity dissolved increases very rapidly with the tempe- rature up to 93, which presents the maximum of solubility of the salt, being 322 parts in 100 of water. Above that point the solubility diminishes rapidly with each increment of temperature, until at 218 it has diminished to 210 parts in 100 of water. The line ABC 32 o 218 on the diagram (fig. 353) illustrates Fig. 353. the relations of solubility and temperature in this salt at a glance. The vertical divisions to 0' register the range of temperature from 32 to 218; the horizontal ones (Vindi- cate the degree of solubility, which reaches 322 parts at 93. The curve of solubility then descends from B to C, when 210 parts are dissolved at 218. The cause of this sud- den diminution of solubility, is the decomposition of the hydrous salt in solution at that heat, and the precipi- tation of a portion of anhydrous sulphate of soda. A solu- tion of Glauber's salts saturated at boiling heat in a vessel capable of being corked while boiling, and suifered to cool, will often crystallize completely on withdrawing the cork, a change from the fluid to the solid state occasioned by the concussion of the air. The same thing happens if a small crystal is dropped into a saturated solution of the salt, (41.) Sulphate of soda is a familiar aperient. In the arts, its chief use is in the preparation of carbonate of soda, as will be presently described. It is a result, on a large scale, of How does it fuse ? How if exposed ? How does it dissolve in water at different temperatures ? What is its curve of solubility ? Describe the diagram 353. How is its solution in vacuo crystallized ? What is its use in the arts ? SOI METALLIC ELEMENTS. the preparation of chlorohydric acid, (426.) The other sulphates of soda require no mention at present. The solu- tion of sulphate of soda (12 parts) in strong chlorohydric acid (10 parts) produces cold enough to freeze a considerable quantity of water in summer. 510. Carbonate of Soda, NaO.C0 3 . Soda replaces in the ashes of sea-plants the potash found in those of land- plants. Hence, formerly, the carbonate of soda of com- merce was procured, almost exclusively, from the ashes of sea-weeds. This salt is now obtained entirely from common salt by the process of Leblanc, which will be briefly described. This process depends on the fact that when sulphate of soda, carbonate of lime, and carbon are heated together, carbonate of soda, oxysulphate of lime, and oxyd of carbon are the products. The reaction is between 2 eq. of sulphate of soda, 3 of carbonate of lime, and 9 of carVon; thus, 2(NaO.S0 3 ) -f 3 (CaO.C0 2 ) + 90 = 2 (NaO.C0 3 ) + (2CaS.CaO)-flOCO. The oxysulphuret of calcium is wholly insoluble in water, which takes out from the pulve- rized mass only carbonate of soda. This operation is pre- pared in a reverberatory furnace constructed like the section seen in fig. 354. The parts A and B receive the mingled Fig. 354. materials, (1000 parts of anhydrous sulphate of soda, 1040 of chalk, and 530 of charcoal powder.) The fire on the grate F plays upon the charge on the sole of A, and completes the chemical reaction which was begun in B, where the charge is first placed: a bridge-wall separates the two. The workman judges, by the appearance and consistency of a What freezing mixture does it form ? 510. Give the formula for car- bonate of soda. How was it procured formerly ? Describe Leblanc's pro- cess ? What is the reaction ? Describe fig. 354. What gas is formed ? How is the progress of the operation determined? SODIUM. 305 portion withdrawn from time to time, of the progress of tho operation. The oxyd of carbon forms a blue flame over the surface, which disappears when the reaction is over. The heat following the arrow, next plays upon solution of car- bonate of soda in the boiler C, the lixivium of a previous charge, and evaporates it to dry ness, while at the same time the more dilute solution of carbonate is heated in D, to be drawn from time to time into C. The steam and pro- ducts of combustion escape by the chimney 0. Carbonate of soda crystallizes in great crystals of an ob- lique form and containing 10 atoms of water, viz. NaO. C0 3 -f 10HO, equal to 63 parts water in 100 of the salt. It fuses in its own water of crystallization. The anhydrous carbonate, as it comes from the furnace, is called soda-ash. Bicarbonate of soda is procured by exposing soda-ash to carbonic acid from fermenting grain, as in distilleries, or by passing this acid into solution of carbonate. It is, so to speak, a carbonate of soda plus a carbonate of water, or NaO.C0 3 -fHO.CO a . It is not a very solute salt : 100 parts of water take up 8 of bicarbonate. Boiling water expels one of the equivalents of carbonic acid. This is the salt used in preparing effervescent draughts. The sesquicarlonate of soda, Trcma, 2Na0.3C0 2 +4HO is found native in certain lakes in Africa and South America. It crystallizes in right rhomboidal prisms, unchanged in air, and little soluble in water. / 511. Nitrate of Soda, Soda Saltpetre, NaO.N0 5 . This salt is found in India and South America, where extensive plains are covered by it, as at Tarapaca in Chili, and Iquique in Peru. It resembles nitrate of potassa, but cannot be used to replace that salt in gunpowder, on account of its strong disposition to attract water from the air. It is much em- ployed, however, in procuring nitric acid, and also as a fer- tilizer in agriculture. It is a white salt, crystallizing in rhombs, specific gravity 2-09, very soluable, with .a cooling taste, and deflagrates on burning coals with a strong yellow light. By carbonate of potassa in solution it is immediately transformed into nitrate of potassa and carbonate of soda. How is the solution evaporated ? How does the salt crystallize ? How much water has it? How is the bicarbonate formed? How soluble ? What is the sesquicarbonate. 511. What is the history of nitrate of soda ? What does it resemble ? What its use ? How does it act with com- bustibles ? 20 306 METALLIC ELEMENTS. 512 The phosphates of soda correspond to the three con< ditions of phosphoric acid (355) before noticed : they are 1. Phosphate of Soda (tribasic) H0.2NaO.P0 5 -f 24HO. The common phosphate of soda of pharmacy is prepared by precipitating the acid phosphate of lime (347) with a slight excess of carbonate of soda. It crystallizes in oblique rhombic prisms, which are efflorescent. The crystals dissolve in four parts of cold water, and undergo the aqueous fusion when heated. The salt has a pleasant saline taste, and is purgative; its solution is alkaline to test-paper. When evaporated above 90 it crystallizes in another form, with 14 instead of 24 atoms of water. 2. Subphosphate of soda 3NaO.P0 5 -|-24HO is obtained by adding solution of caustic soda to the preceding salt. The crystals are slender six-sided prisms, soluble in 5 parts of cold water. It is decomposed by acids, even the carbonic, but suffers no change by heat, except the loss of its water of crystallization. Its solution is strongly alkaline. The study of these salts by Prof. Graham has greatly enlarged our views of chemical philosophy. 3. Biphosphate' of Soda, or Superphosphate, 2HO.NaO. P0 5 -j-HO. This salt may be obtained by adding phos- phoric acid to the ordinary phosphate, until it ceases to pre- cipitate chlorid of barium, and exposing the concentrated solution to cold. The crystals are prismatic, very soluble, and have an acid reaction. When strongly heated, the salt becomes changed into monobasic phosphate of soda. 513. Microcosmic salt, or phosphate of soda and am- monia, (HO.NH 4 O.NaO.P0 5 -|-8HO,) is much used in blow- pipe operations as a flux. It is formed by dissolving with a gentle heat, 1 part of chlorid of ammonium and 6 or 7 parts of phosphate of soda, in 2 of water. Chlorid of sodium is formed, and the microcosmic salt crystallizes out in rhombic prisms, which lose 8 HO by heat. Its fanciful name was derived from its supposed virtues in promoting fertility in the impotent. 514. Bibasic Phosphate of Soda, Pyrophosphate of Soda, 2NaO.P0 5 -j-10HO. Prepared by strongly heating com- 512. What phosphates are named ? What is the formula of the tribasic ? Give its properties. What is the subphosphate ? What the superphos- phate ? What of Graham's researches ? What is the biphosphate of eoda ? 513. What is microcosmic salt ? How formed ? 514. What in bibasic phosphate ? Give its formula. LITHIUM. 307 mon phosphate of soda, dissolving the residue in water, and recrystallizing. The crystals are very brilliant, permanent in the air, and less soluble than the original phosphate : their solution is alkaline. A bibasic phosphate, containing an equivalent of basic water, has been obtained ; it does not, however, crystallize. 515. Monobasic Phosphate of Soda, MetapliospJiate of Soda, NaO.P0 3 . Obtained by heating either the acid tri- basic phosphate, or microcosmic salt. It is a transparent, glassy substance, fusible at a dull red-heat, deliquescent, and very soluble in water. It refuses to crystallize, and dries up in a gum-like mass. The tribasic phosphates give a bright yellow precipitate with a solution of nitrate of silver, and with molybdate of ammonia : the bibasic and monobasic phosphates afford white precipitates with the same substances. The salts of the two latter classes, fused with excess of carbonate of soda, yield the tribasic modification of the acid. 516. Borax ; Bibomte of Soda; Tincal ; Na0.2B0 3 + 10HO. Borax crystallizes in right rhomboidal prisms, which are soluble in 15 or 16 parts of water : the solution has an alkaline reaction and sweetish alkaline taste. It loses its water by heat, and being very fusible, is much used as a flux in metallurgic processes and as a blowpipe reagent. It is entirely procured from natural sources of boracic acid already mentioned, and from the waters of several lakes iu Thibet, in which it is dissolved. LITHIUM. Equivalent, 6-5. Symbol, L. 517. This very rare metal is a constituent of several minerals, as spodumene, petalite, lithia-inica : hence its name, from lithos, a stone. The electrolysis of the hydrate afforded Davy a white oxydizable metal analogous to sodium. Ita small atomic weight is remarkable. The oxyd LO is an alkali, but much less soluble than 515. What is the monobasic phosphate ? What are the tests for tribasic phosphates ? Of the bibasic ? How are the bibasic, &G., con- verted to the tribasic form ? 516. What is borax ? What its source and uses ? 517. What is lithium ? What of LO ? What use for its salts ? 308 METALLIC ELEMENTS. potash arid soda. Its sulphate is a beautiful salt, and givea a rosy flame to alcohol. The lithia compounds all give this tint to the outer flame of the blowpipe. Some of its salts ftave been used internally with advantage in cases of urio *cid calculus. AMMONIUM. Equivalent, 18. Symbol, NH 4 , (hypothetical.') 518. Ammonium, NH 4 . The compound metallic radical ol ammonia has never been isolated, although we have reason to laelieve in its existence. When a solution of ammonia, or of sal-ammoniac, is electrolyzed, nitrogen escapes at the -\- side _ 4. and hydrogen at the side, fig. 355 ; but if the latter pole is made by using a portion of mercury in the bend of the tube I, no hydrogen is evolved, but the mercury swells up, loses its fluidity, becomes like soft butter, and gradually Fig. 355. attains many times its original bulk, having the lustre and general character of an amalgam. A more simple mode of forming this amalgam, consists in making a little potassium or sodium combine by heat with about 100 times its weight of metallic mercury. This alloy, when placed in a strong solution of sal-ammoniac, begins at once to increase in volume by the formation of the ammo- niacal amalgam, until it has attained very many times its original bulk, and has a pasty, butter-like consistence. When the alloy of potassium is placed in hydrochloric acid, the alkaline metal decomposes the acid, forming chlorid of potassium and evolving hydrogen. If we subsitute for the acid (chlorid of hydrogen) a solution of chlorid of zino ZnCl, a like decomposition ensues ; but the zinc, instead of being set free like the hydrogen, combines with mercury to form an amalgam. The present reaction is precisely similar ; chlorid of ammonium NH 4 C1 being substituted for the 518. What is ammonium? Give its history. How obtained more simply than by electrolysis ? What is the appearance of the amal- gam ? What illustration is given from the alloy in HC1 and in ZnCl ? What is the reaction in the present case ? COMPOUNDS OF AMMONIA. 309 chlorid of zinc : the ammonium which is liberated com- bines with the mercury and forms the light pasty amalgam. It crystallizes in cubes at 32, whereas pure mercury is fluid even at a temperature of 39 F. It is evident that it has combined with something which has given it new properties. This is supposed to be the metallic radical ammonium. The spongy mass, as soon as the electric action ceases, rapidly suffers decomposition. Ammonia and hydrogen are set free in the proportion of 1 to 2, and the mercury regains its original state, unaltered. Berzelius and other able chemists explain this reaction, on the ground that the ammonia, by gaining an additional equivalent of hydrogen, assumes the peculiar character of a metal, and unites with mercury, forming an amalgam. This hypothetical metal can replace potassium and sodium perfectly in combination, and is there- fore isomorphous with them. All the salts of ammonia are, on this view, derived from this radical, and its union with the second class gives us a series of bodies analogous to the chlorids, bromids, &c., of the other electro-positive bases. Compounds of Ammonium. 519. Chlorid of Ammonium ; Sal- Ammoniac, NH 4 C1. This salt occurs in nature, sometimes quite pure, as at De- ception Island, and in volcanic districts generally. It was originally prepared, in Egypt, (443,) by sublimation from the soot of the burnt camel's dung. This is done in large flasks of glass, (fig. 356,) the sal- ammoniac collects in the upper part, and the cake is removed by breaking the bottle. It is always contaminated by organic matters. It is also obtained largely from the ammo- niacal waters of the gas-works. It is purified by evaporating the crude solutions to dryness, after treating them with a slight excess of chlorohydric acid to neutralize tha free am- monia, and subliming the dry mass in iron Fi< vessels. What is the product of its decomposition ? What is the explanation of Berzelius? How are the ammoniacal salts viewed? 519. What if sal- ammoniac ? How prepared ? 310 METALLIC ELEMENTS. It has a sharp saline taste, corrodes metals powerfully, if soluble in three parts of cold water, and crystallizes from its solution in octahedrons. The sublimed salt has a fibrous texture, and is very tough and difficult to pulverize. The formation of this compound is easily shown by using the apparatus already figured, (438,) with hydrochloric acid in one flask and strong ammonia water in other ; the commingling of the dry gases, driven over by heat to the central bottle, fills it with a white cloud of sal-ammoniac, HCl-f NH 3 = NH 4 C1. The preparation and properties of ammonia have already been explained, (444.) 520. Sulphydret of Ammonium, (^Ilydrosulpliurct of Am- monia,} NH 4 S-{-HS. This very useful reagent is formed by passing a long-continued, slow current of sulphuretted hydrogen from the gas-bottle a, (fig. 357,) through the bottles d, ,/, g, filled with strong water of ammonia. This arrangement is a simple form of Woulfe's appara- tus, (fig. 257.) A single bottle of ammonia (as cT) ia sufficient for all common pur- poses. It should be kept cold. The ammonia absorbs Fig. 357. an enormous quan- tity of the gas, and the resulting sulphuret, which has the strong odor of the gas, is colorless at first, but gradually assumes a yellow color. It forms numerous salts with electro-negative sul- phurets, being itself a powerful sulphur base. It is an invaluable reagent as a precipitant of the metals, and is also used in medicine. There are several simple sulphurets of ammonium, but they are of no particular interest. 521. Sulphate of Ammonia, or Sulphate of Oxyd of What its properties ? How formed artificially ? 520. What is sulphydret of ammonium ? Describe fig. 357. What is the chemical character of this body ? What its uses ? COMPOUNDS OP AMMONIA. 311 Ammonium , NH 4 O.S0 3 -|-HO. This salt, which is a pow- erful fertilizer, is procured in the large way by neutralizing the ammoniacal liquor of the gas-works by sulphuric acid : or it may be easily obtained pure by neutralizing dilute sul- phuric acid with carbonate of ammonia. 522. There are several carbonates of ammonia. The common sal-volatile of the shops, with a pungent smell and alkaline reaction, is nearly a sesquicarbonate 2NH 4 0.3CO a . Exposed to the air, this salt becomes a white inodorous powder, which is the bicarbonate. The sesquicarbonate is a very valuable salt to the chemist. It forms the basis of the smelling-bottles so much in use. The dry white powder formed by the contact of dry carbonic acid and ammonia in an apparatus like figure 319, is a neutral anhydrous carbonate NH 3 .C0 3 , very pungent and volatile, dissolving readily in water. 523. Nitrate of Ammonia, or Nitrate of Oxyd of Am monium, NH 4 O.N0 5 -]-HO. This salt has already been noticed (338) under the description of nitrous oxyd. Its crystals resemble nitre, deliquesce in moist air, and dissolve in 2 parts of cold water, the solution sinking the thermo- meter to zero, (124.) It deflagrates on burning coals like nitre, and hence received the old name of nitrum flammens . 524. All the ammoniacal salts are volatilized by a high temperature, and yield the ammoniacal odor by trituration with caustic potassa or lime, or by boiling with solutions of potash. They are all soluble, and give a sparingly soluble, yellow, crystalline precipitate with chlorid of platinum. 521. What is sulphate of ammonia ? 522. What carbonates are named ? What one is formed, from the union of the gases ? 523. What is nitrate of ammonia? Give its formula. How decomposed by heat? What id its frigorific powr ? What name had it ? 524. What are tests for am- moniacal salts " 312 METALLIC ELEMENTS. CLASS II. METALS OF THE ALKALINE EARTHS. 525. This class includes barium, strontium, calcium, and magnesium, the bases of the alkaline earths, baryta, strontia, lime, and magnesia : these are all soluble to some extent in water, with an alkaline reaction, but differ very much in the eolubility and other properties of their various salts. BARIUM. Equivalent 68-5. Symbol, Ba. 526. Barium is a silver-white malleable metal, easily oxydized, and melts at a red heat. It was procured by Davy by a process similar to that which yielded potassium, &c. It is better obtained by passing vapor of potassium over baryta (oxyd of barium) heated to redness in an iron tube. Mercury dissolves out the reduced metal, and the amalgam is then distilled. It is named, from the striking weight of its salts, from bar us, heavy. 527. Baryta, or Protoxyd of Barium, BaO. Baryta is best obtained by decomposing the nitrate at a red heat. It is a dry, gray powder, which combines with water to form a hydrate, slaking with the evolution of great heat and even light. Its density is 545. The hydrate dissolves in two parts of hot water, or twenty of cold, and crystallizes in flat tables. The aqueous solution is a valuable test for carbonic acid. Sulphate of baryta, or heavy spar, is found abundantly, as an associate of other minerals, in veins ; and from it, or the native carbonate of baryta, ail the artificial compounds of barium are formed. 528. The peroxyd of barium BaO., is formed by pass- ing pure oxygen gas over the oxyd heated to dull redness in a porcelain tube. It is chiefly interesting as being the means of procuring the peroxyd of hydrogen, (420.) 525. What are the metals of the alkaline earths ? 526. What is the equi- valent of barium? Give its properties. Whence its name? 527. What is baryta? How docs it act with Avater? What its density? 528. How is peroxyd of barium formed, and for what used ? STRONTIUM. 313 Chlorid of Barium, BaCl + 2HO. This salt occurs in white tabular crystals, containing two equivalents of water, which are expelled by heat. It dissolves in a little more than twice its weight of cold water, and the solution is a valuable reagent for detecting the presence of sulphuric acid. 529. The nitrate of baryta BaO.N0 5 -fHO is also a soluble white salt, which crystallizes in anhydrous octahedrons, and dissolves in eight parts of cold or three parts of hot water. Both it and the chlorid are prepared by dissolving the native or artificial carbonate in the proper acid. Sulphate of baryta, heavy spar, BaO.S0 3 , is a mineral found abundantly in many places in this country, as at Cheshire, Connecticut. It crystallizes in tabular modifica- tions of the rhombic prism, often very beautiful. It is also found massive at Pillar Point, New York. Its specific gra- vity (4-3 to 4-7) gives it the name of heavy spar. It is quite insoluble in water or acids, and not easily decomposed. When strongly heated with charcoal powder, however, it suffers decomposition, BaO.S0 3 -f 4C = BaS -f 4CO ; carbonic oxyd is given off, and the soluble sulphuret of barium may be dissolved out from the coaly mass. Sulphate of baryta is extensively ground up for a pigment, being mixed with white-lead as an adulteration. 530. Carbonate of Baryta , BaO.C0 3 , or the wither ite of mineralogists, is a mineral of some interest, and useful as the chief source of the various compounds of baryta. All the soluble baryta salts are poisonous, and their presence may always be detected by sulphuric acid, or a soluble sul- phate, with which they form the insoluble sulphate of baryta. The compounds of barium give a peculiar yellow color to the flame of the blowpipe, different from the yellow flame of soda. STRONTIUM. Equivalent, 44. Symbol, Sr. 531. Strontium is obtained from its oxyd in the same manner as barium, and, like it, is a white metal, oxydized Give the characters of the chlorid of barium. For what is it a test? 529. How is the nitrate of baryta characterized? How is heavy spaf found in nature ? Give its formula and properties. 530. What is car- bonate of baryta ? What character have the soluble salts of baryta ? How is their presence detected ? 531. How is strontium obtained, and how characterized ? 314 METALLIC ELEMENTS. easily in the air, and decomposing water at common tempera- tures. There are two oxyds, the protoxyd and the peroxyd of strontium, similar in properties to the like oxyds of barium. The sulphate of strontia (celestine) is a rather abundant mineral, and the carbonate (strontia nite) is much esteemed by mineralogists. They are very similar in properties to the sulphate and carbonate of baryta. 532. The chlorid of strontium SrCl -f OHO is a deli- quescent salt, soluble in two parts of cold water. It loses its water of crystallization by heat. Both it and the nitrate of strontia SrO.N0 5 are much employed by pyrotechnists in forming the red fire of theatres and fireworks. All the compounds of strontium give a peculiar red tint to the flame of the blowpipe, while the barytic salts do not. The salts of strontia are not poisonous. CALCIUM. Equivalent, 20. Symbol, Ca. 533. Calcium is a yellowish-white metal, obtained like barium, and has so strong a disposition to combine with oxygen that it is difficult to observe its properties. 534. Protoxyd of Calcium, Lime, CaO. This most valu- able substance, so well known as quicklime, is procured in a state of great purity by heating the stalactites from caverns, or the purest statuary marble, for some hours to full redness in an open crucible. The carbonic acid and organic coloring matter are driven off, and oxyd of calcium (lime) nearly pure remains. Pure lime is a white, very infusible, and rather hard body, having a density of 3-18. It has a great affinity for carbonic acid, taking it from the air and falling to powder, (air- slaking.) It also combines with water to form a hydrate, evolving great heat, (slak- ing.) When this operation is performed under a glass bell, (fig. 358,) the vapor of water at first condensed on the walls of _____ the jar soon forms a transparent atmosphere > 358. of steam, which, when the bell is raised, What familiar salts of this ratal are found native ? 532. Describe the chlorid of strontium. What is it used for? 533. What is calcium, and how is it obtained ? Give its equivalent? 534. What is lime? How procured? What its density ? What is air-slaking? What slaking by water ? CALCIUM. 315 breaks on the air in a dense cloud of vapor. The heat is greatest when the water is about half the weight of lime employed. Is sufficiently high often to inflame gunpow- der. The hydrate CaO.HO is a dry, bulky powder, soluble in 1000 parts of water, to form lime-water. With water it forms a milk of lime; a corrosive paste used to re- move hair from hides. Lime-water is a valuable reagent and antacid ; it has a disagreeable alkaline taste ; blues reddened litmus, and absorbs carbonic acid from the air, by which it becomes milky from precipitation of carbonate of lime soluble in excess of carbonic acid. 535. Common lime is prepared by heating limestone (car- bonate of lime) in large stone furnaces, filled from the top with the limestone and fuel ; the fire is kept up constantly, by renewed charges of the materials at top, while the pre- pared caustic lime is drawn out at the bottom. The carbonic acid is much more rapidly expelled when the vapor of water and other products of combustion come in contact with the heated limestone. Indeed, it is hardly possible by heat alone in close vessels to expel the C0 3 , since carbonate of lime is fusible under those circumstances without decomposition. Mortar acts as a cement by the slow formation of carbon- ate of lime, which binds together the grains of sand that .make up the greater part of the mixture. The smaller the portion of lime used, and the sharper the silicious sand employed, the more firm will be the cement at last; but it is then so much more difficult to work, that an excess of lime is usually employed. The presence of oxyd of iron and manganese, of alumina, magnesin, silica, and other like substances in a limestone, gives the lime prepared from it the property of hardening under water, when it is called hydraulic lime. Lime is much used in improved agriculture, as a manure. It acts to decompose vegetable matters, to neutralize acids, dissolve silica, and* retain carbonic acid. It is always present naturally in every fertile soil, and is a constant ingredient in the ashes of most plants. 536. Clilorid of Calcium, CaCl. The solution of lime, What heat is given out in this operation ? Where greatest ? How soluble is the hydrate ? 535. How is common lime prepared ? Why is vapor of water useful in the process ? How does mortar act as a cement? What is hydraulic lime ? 536. What is the chlorid of calcium ? 816 METALLIC ELEMENTS. or of its carbonate, in hydrochloric acid to saturation, gives us this chlorid. It is when fused a white crystalline solid, with a great avidity for moisture, and for this reason it is used in the desiccation of gases, &c. It is soluble in alcohol, with which it forms a definite crystallizable compound. It forms a powerful freezing mixture with ice, (124.) The sulphurets and phosphurets of calcium have little in- terest. The phosphuret being decomposed by water, is an available source of the spontaneously inflammable phosphu- retted hydrogen, (fig. 326.) 537. Sulphate of Lime Gypsum Selenite, CaO.S0 3 * This salt, in the form of hydrate CaO.S0 3 -f 2HO, is abundant in nature, and is much used in agriculture as a manure, being ground to powder; and, after expelling the water by heat, as a material for stucco and plaster casts. It is then commonly known as " plaster of Paris." The varie- gated and fine white varieties are called alabaster. When crystallized in transparent flexible plates, it is called selenite. These crystals are sometimes compound in such a manner as to present an arrow-head form, like fig. 359. Such crystals are called hemitropes. Anhydrous gypsum CaO.S0 3 also is found native, and is known by the minera- logical name of anhydrite. Gypsum is frequently associated with rock- salt. It is soluble in about 500 parts of water, and is present in most natural waters. By a heat of 250 to 270 it loses its water of composition: when the anhydrous powder is moistened, the lost water is regained, and it becomes solid ; but if heated, even to 330, it no longer regains its water of composition. It fuses at a red heat to a crystalline anhydrous mass. This power of resolidification, when mixed with water, gives gypsum its value in copying works of art, and in forming stucco ornaments. By using solution of common alum in place of water, gypsum becomes very hard, and is thus treated for producing pavements. Fig. 359. For what is it used ? What is the phosphuret of calcium used for? 537. Give the common names of sulphate of lime. For what is it used ? Give its properties. What is fig. 359 ? How is gypsum hardened ? On what docs its use in stucco depend ? What is anhydrite ? CALCIUM. 317 538. Fluorid of Calcium, Fluor-spar, CaF. This is a rather abundant mineral, being found beautifully crystallized, of various colors, in the cube and its modifications. It is the principal source from which we obtain the fluohydric acid (433) by decomposition with sulphuric acid. It often phos- phoresces very beautifully with heat, emitting a green, yellow, or purple light, at a temperature below redness. 539. Phosphates of Lime. There are several phosphates of lime corresponding to the several phosphoric acids, (355.) The earth of bones is a tribasic phosphate of lime, and the mineral known as apatite is also a phosphate of lime. The phosphates of lime are insoluble in water, but dissolve in dilute acids. All cereal grains, and many other vegetables, contain phosphate of lime in their ashes, and this salt is therefore an indispensable ingredient of all fertile soils, and the form in which phosphorus is introduced into the animal structure. 540. Carbonate of Lime Marble Calcareous Spar, CaO.C0 3 . This is one of the most abundant minerals of the earth, forming in limestone vast mountains and wide- spread geological deposites. It oc- curs most superbly crystallized in rhombohedral forms, which consti- tute brilliant ornaments in mineralo- gical collections. The transparent double refracting Iceland spar, (fig. 360,) and the dimorphous form, arragonite, are examples of this salt. Fig. 360. It is soluble in dilute acids, with escape of carbonic acid, and is also decomposed by heat, leaving quicklime. Water aided by carbonic acid, and perhaps by the organic acids of the soil also, dissolves carbonate of lime, and again deposits it in stalactites and stalagmites, on exposure to the air. These phenomena are beautifully seen in Mammoth Cave, Schoharie Cave, and many similar situations. The stalactites depend from the roof, growing by the deposit of freshly precipitated portions of carbonate of lime on their 538. What is fluor-spar ? How is it found ? For what used ? What beautiful property has it ? 539. What phosphates of lime are known ? In what do we find phosphate of lime ? How does phosphorus enter tho system ? 540. What is the formula of carbonate of lime ? What other names has it ? What is formed from it ? What optical property has it? How does water dissolve it ? What are stalactites and stalagmites ? METALLIC ELEMENTS. surfaces, which are kept moist by the trickling of water con- taining the salt in solution. The water which falls to the floor from the point of each stalactite slowly builds up a coni- cal mass called a stalagmite, and when these meet they form a column. All these stages are well shown in fig. 361, Fig. 3d. from Regnault. Before these fairy-like creations of nature's architecture are darkened by torches, their beauty is en- chanting. 541. Hypochlorite of Lime, CaO.CIO, Bleaching- Pow- der. This valuable compound is formed when chlorine gas is gradually admitted to hydrate of lime slightly moist and kept cool. The chlorine is absorbed largely, and the Ueuch- ing-powder of the arts is formed. Bleaching- powders con- tain a mixture of hypochlorite of lime, chlorid of calcium, and hydrate of lime. It is a soft white powder, easily soluble in about 10 parts of water, giving a highly alkaline solution, which bleaches feebly. It is employed by dipping the goods in the weak solution, and then in very dilute acid water. The chlorine is thus evolved and does its work. Several repetitions are needed to complete the process, and the acid is washed out with care. This compound emits a strong smell, which is similar to chlorine, but is due t& Describe their formation as in fig. 361. What is bleachLng-powder ? How formed ? How employed ? MAGNESIUM. 3 19 hypochlorous acid ; it is very useful for disinfecting offen- sive apartments, and its energy is increased by the addition of a little 'acid water. The disinfecting liquid of Labarraque is a compound of chlorine with soda, similar in composition to solution of bleaching-powder. The best bleaching-powders contain 39 parts of available chlorine, and 2 parts, in combination, as chlorid of calcium. If one equivalent of each ingredient were present they would be in the proportion of 48 -57 chlorine and 5143 parts hydrate of lime. Ordinary bleaching-powders contain only about 30 per cent, of chlorine. The mode of determining the amount of chlorine present is called chlorimetry, and is based on the quantity of sulphate of indigo which is decolorized by a standard solution of chlorine. The salts of lime are not precipitated by ammonia, but form an entirely insoluble oxalate, with oxalic acid or oxalate of ammonia. MAGNESIUM. Equivalent, 12 -2. Symbolj Mg. 542. Magnesium is obtained by decomposing the chlorid of that metal heated to redness in a glass tube, by passing over it the vapor of potassium or sodium. Chlorid of po- tassium or sodium is formed, and the metallic magnesium is separated by dissolving out the soluble chlorid. It is a white metal, malleable and brilliant. It fuses with a red heat, and if heated to redness in the air, burns with a brilliant light, producing oxyd of magnesium. It does not tarnish in dry air, and does not decompose water even at 212, but dissolves in acids with escape of hydrogen. 543. Oxyd of Magnesium, Calcined Magnesia , MgO. This substance is left when the carbonate of magnesia is heated to redness/ It is a white, very light, earthy powder, insoluble in water, but readily soluble in weak acids. It occurs in nature crystallized in regular octahedrons, form- ing the mineral periclase. It is much used in medicine as a mild and efficient aperient. The hydrate of magnesia "What is Labarraque's liquor ? What is the composition of bleaching- powder ? What is chloriinetry ? What precipitates the salts of lime ? 542. Give the equivalent and preparation of magnesium. What are its Soperties? 543. What is the oxyd of magnesium? How is it used? Dvr found in nature ? 320 METALLIC ELEMENTS. MgO.HO is formed wnen magnesia is precipitated from its solutions by an alkali. Heat expels the equivalent of water, leaving calcined magnesia. Tho hydrate is found beau- tifully crystallized in thin pearly plates at Hoboken, New Jersey. 544. Chlorid of Magnesium, MgCl. This chlorid is best prepared by neutralizing equal portions of chlorohydric acid, ona with magnesia and the other with ammonia, mixing the two portions and evaporating to dryness. The dry mass is heated in a covered crucible as long as sal-ammoniac is given off, when pure chlorid of magnesium is left. It is a very deli- quescent salt, and supplies the means of procuring metallic magnesium. When magnesia is dissolved in hydrochloric acid, a hydrated chlorid of magnesium results. By heat the water is expelled, carrying with it chlorohydric acid, and leaving pure magnesia behind. The bittern of salt springs is chlorid of magnesium ; it exists in sea-water, and is the largest ingredient in the waters of the Dead Sea. The iodid and bromid of magnesium are also soluble salts, but the fluorid is insoluble. 545. Sulphate of Magnesia, Epsom Salts, MgO.SO ? -f- 7HO. This well-known salt is easily formed by dissolving magnesia, or its carbonate, in sulphuric acid. It is also found native at Corydon, Illinois. In the waters of Epsom Spa, in England, and in numerous mineral waters, it is a large constituent. It is made on a large scale by dissolving serpentine rock in strong sulphuric acid. It is very soluble, and, like all the soluble salts of magnesia, has a peculiar bitter taste. 546. The carbonate of magnesia, magnesite, MgO.CO a/ is found native in magnesian rocks, and is formed artificially by decomposing any of the soluble salts of magnesia by an alkaline carbonate, giving the magnesia alba of pharmacy. It is insoluble in water; but a solution of carbonic acid dissolves it, and forms the celebrated Murray's solution of magnesia. It is decomposed by contact of air, carbonic acid escapes, and carbonate of magnesia is thrown down. The double carbonate of magnesia and lime is found as an ex- What is calcined magnesia? 544. How is the chlorid of magnesium prepared? Describe it. When magnesia is dissolved in chlorohydric acid, what happens ? 545. What is the composition of sulphate of mag- nesia? How is it made in the large way ? In what waters is it found? 646. What is carbonate of magnesia? What is Murray's solution? ALUMINUM. 321 tensive rock formation, called dolomite, and when crystal lized, pearl spar. Phosphate of soda with ammonia throws down a crys talline insoluble salt from magnesian solutions, which is the double phosphate of magnesia and ammonia. This is the most ready mode of testing for the presence of magnesia. 547. Magnesia occurs abundantly in nature as a con- stituent of many minerals, as well as in the form of hydrate and carbonate. The silicates of magnesia form a very im- portant class of minerals, of which talc, soap-stone, pyroxene, hornblende, serpentine, &c., are examples. Magnesia is also found in the ashes of most plants, in union with phosphorio acid. CLASS III. METALS OF THE EARTHS. ALUMINUM. Al. 13-69. 548. Aluminum is best obtained, like magnesium, by the action of sodium or potassium on its chlorid. It is a gray powder, not easily melted, has a metallic lustre, and burns, when heated in the air, with a bright light, forming alumina. 549. Alumina; Sesquioxyd of Aluminum ; Corundum, A1 2 3 . Pure alumina is found crystallized in those precious gems, the oriental ruby and sapphire, which are next in hardness and value to the diamond. Emery (cornudum) ig also nearly pure alumina. Alumina is an abundant ingre- dient in many other minerals, and forms a large part of many slaty rocks, from whose decomposition clays are produced. Pure alumina is a fine white powder, not rough and gritty like silica. Its density is 4-154. It is infusible except under the oxyhydrogen blowpipe. After ignition it is al- most or entirely insoluble. Hydrate of alumina Al 2 3 -f-3HO exists in the minerals diaspore and gibbsiie. Alumina is precipitated as a hydrate from solution, by either potash, soda, or ammonia, and their carbonates; an excess of the first two will redissolve the precipitate. The hydrate is very bulky, and shrinks very What test have we for magnesia ? 547. How does magnesia occur in uature ? Mention some of its silicates. 548. How is aluminum obtained? What are its properties and density? 549. What is the formula of alu- mina ? In what is it found pure ? How arc the hydrous and anhydroua alumina distinguished? What precipitates and Avhat redissolves it? * 322 METALLIC ELEMENTS. much on drying. Hydrosulphuret of ammonium throws down alumina. The anhydrous alumina is almost insoluble in acids, while the hydrate is readily dissolved, forming salts of a peculiar astringent taste, familiarly known in common alum. The chlorid of aluminum has no particular interest except as a means of procuring the metal. Aluminate of potassa KO. A1 3 3 is formed when a solution of alumina in potassa is gently evaporated : it appears in crystalline grains. IJaryta an( ^ magnesia afford similar examples. Spinel, a mineral species, is an aluminate of magnesia MgO.Al 3 3 . These are instances of the double function which alumina possesses of acting the part both of acid and base, (474, 3.) 550. Sulphate of Alumina, A1 3 3 .3S0 3 +1SHO. This salt is prepared by saturating dilute sulphuric acid with alumina : it has a sweetish astringent taste, is soluble in 2 parts of water, and crystallizes in thin plates. Alums. Sulphate of alumina forms, with potash., soda, and ammonia, double salts of much interest, called alums. They are all soluble salts, with a sweetish astringent taste, and crystallize in the regular system, or first class, (44,) usually as modified octahedrons, which have uniformly 24 equivalents of water of crystallization. Common potash- alum has the formula Al a 3 .3S0 3 +KO.S0 3 +24HO, (256;) it dissolves in 18 parts of cold water, and the solution has an acid reaction. The water of crystallization of the alums is expelled by heat : the salt first suffers watery fusion, and then swells up into a light porous mass, many times the volume of the salt em- ployed, and protruding beyond the vessel employed, as in fig. 362. This is called burnt- alum. All the basic sesquioxyds isomorphous with alumina may replace it in the constitu- tion of an alum. Alum and acetate of alumina are largely employed in the arts of dyeing and tanning. Fig. 362. Alumina combines with coloring matters, and seems to form a bond of union between the fibre of the cloth What salts does it form? What is aluminate of potassa? What ij spinel? Give the formula of alum. 550. What is burnt alum? What is the use of alums ? ALUMINUM, o23 and the color. In this it is said to act the part of a mor- dant. When alum is added to the solution of a coloring matter, and the alumina is then precipitated with an alkali, all the coloring matter is thrown down with it, and forma what is called lake. The common lake used in water-color- ing is derived from madder treated in this way. Carmine is a lake made from cochineal. 551. Silicates of Alumina. This is the most extensive &nd important class of the aluminous salts, and comprises a great number of interesting minerals. Feldspar, A1 3 3 . SSiOg-j-KO.SiOg, which is one of the chief components of granite and granitic rocks, is of this class, and has the com position of an anhydrous alum, the sulphuric acid being replaced by the silicic. Albite is a salt having soda in place of the potash in feldspar, while spodumene and pctalite are similar compounds, with a portion of the soda replaced by litliia. Kyanite and andalusite are simple basic silicates of alumina. Many other similarly constituted compounds are found among minerals, some of which are hydrous and others anhydrous, and varied by frequent substitution of peroxyd of iron, manganese, or other isoniorphous bases, for the alumina. Plants do not take up alumina, and it is not yet proved that their ashes ever contain it. Its value in the soil seems to be in retaining moisture, ammonia, and carbonic acid, and in giving firmness to the other incoherent components of the soil. The decomposition of these silicates gives origin to clay, whose peculiar qualities derived from the alumina fit it for the purpose of the potter. This is the place to say a few words upon the two import- ant arts of glass-blowing and pottery. Manufacture of Glass. 552. Silicates of Soda. Both soda and potash unite by fusion with silicic acid to form silicates of variable compo- sition. If 3 parts of the alkali are used to 1 of the silica, thn glass is soluble in water, but whatever may be the pro- What is a mordant ? What a lake ? 551. What is the most important class of alumina compounds ? What is the formula of feldspar ? What silicates are named? What is the function of alumina in soils? What ar.e clays ? 552. How do the alkalies unite with silica. What is the cha- racter of the compounds so obtained? 324 METALLIC ELEMENTS. portions used, the resulting silicate is always an uncrystal- line, homogeneous, transparent mass. The "soluble glass" formed by fusing together 8 parts of carbonate of soda (or 10 of carbonate of potash) with 15 parts of pure sand and 1 of charcoal, is insoluble in cold, but dissolves in 4 or 5 parts of hot water, forming a sort of varnish, which may be applied to wood or manufactured stuffs, which are to a good degree protected from it by the action of fire. 553. Glass is a variable compound of the silicates of potash, soda, lime, and alumina, with oxyds of lead and iron, fused together by a very high and long-continued heat, in proportions suited to the object for which the glass is to be used. The relation between the oxygen in the base and that in the silica determines the degree of fusibility of the glass : thus, the greater the proportion of silica the less the fusibility of glass. The principal varieties of glass are these, viz : Window glass, a silicate of soda and lime, which re- quires an intense heat for its fusion, and forms a very hard and brilliant glass. Plate glass, such as is used for mirrors, crown glass employed for glazing, and the beauti- ful Bohemian glass, are all silicates of potash and lime. Crystal glass is formed by fusing together 120 parts of fine sand, 40 of purified potash, 36 of litharge or minium, (oxyd of lead,) and 12 of nitre. This forms a very fusible glass easily worked, and so soft as to be cut and polished with comparative ease. The oxyd of lead greatly increases its brilliancy. Green bottle-glass is usually a silicate of lime and alumina, with oxyds of iron and manganese, and potash or soda. It is formed of the cheapest refuse of the soap-boiler's waste, and lime which has been used to make caustic potash or soda. 554. The processes of the glass-house are all exceedingly interesting and instructive the tools few and simple the results dependent on the adroit manipulations of the work- man. The materials are fused in clay pots, of which seve- ral are heated in one circular reverberatory furnace, their What is soluble glass ? 553. What is glass ? What determines the fusibility of glass ? What sorts are named ? What is the composition of window and plate ? What of crystal ? What of green bottle-glass ? 654. How are the materials fused ? ALUMINUM. 325 mouths outward. Fig. 363 shows a section of one of them. After two days and nights, the metal, or fused glass, is brought to a homogeneous condition and the consistence of honey. The chief instrument of the glass- blower is his punta rod, which is simply an iron tube a b, fig 364, open at both ends and covered by a wooden collar c d to protect the hands from the heat. This rod is thrust into the pot of molten glass while it is turned in the hand, a portion of the fluid i A rod is withdrawn, and Fi s- 364 ' if enough has not adhered to meet the wants of the work- man, he takes up a second portion. This he first fashions into a cylindrical form upon a slab of iron, rolling the rod over and over in his hand, (fig. 365.) Suppose it is required to make a glass tube, such as is so much used in the laboratory. He ap- plies his mouth to the end of the punta-rod and blows. The cylinder of glass is inflated, .and assumes .^^^^k a pear shape, as in fig. 366. An assistant now ^^^ applies his tube, containing also a small rigt 366 ' portion of hot glass, to the opposite extremity of the first mass, (fig. 367,) and drawing against the other, the ellipti- Fig. 365. Fig. 367. Fig. 368. cal mass is elongated and assumes the form seen in fig. 368. The two workmen now walk rapidly away from each other in opposite directions, drawing their tubes in the same line, ~ving the ductile, glass the form of a tube, as seen in fig. A few inches from each punta-tube the glass becomes of a uniform size, the small cavity originally blown in the What are the instruments used? How is a glass tube formed? Ulus. trate the process from figs. 363-369. What is pressed glass ? 326 METALLIC ELEMENTS. mass (fig. 3G6) is elongated to a smooth cylindrical bore, and however small the glass tube may be drawn out, this bore always remains circular and entire through its whole length. To fashion a bottle, the operation is commenced in the same manner, but the adroitness of the workman enables him to elongate it by centrifugal force, wheeling the molten mass over his head while he inflates it; and the bottom is drawn in by revolving the rod rapidly on a crotch while he applies the surface of an iron instrument to the revolving flexible glass to fashion it at his will. Most of the cheap glass vessels now manufactured are formed by blowing the glass in a metallic mould opening in two parts. This is called pressed glass. In the laboratory a flat lamp, like fig. 370, fed with tallow, is employed to fashion tubes into the various forms re- quired for the construction of the apparatus. The flame is driven by a bellows under the table worked by the foot. With a little practice, the operator soon acquires suf- ficient skill to make from plain tubes such forms of glass apparatus as are figured^in this work. All glass must be carefully annealed after it is made, by slow cooling, or it will break in pieces with the least scratch or jar. Slow cooling of heated glass for many hours, or even days, is required for heavy articles. Prince Rupert's /"" drops (fig. 371) are little tears of glass dropped / into water when fused. The outer surface becom- // ing solid while the inner parts are still flexible, |A there comes to be an enormous strain on the ex- ^f terior, due to the contraction at the centre. If the Fig. 371. little end of this tear is broken, the whole sud- denly and with an explosion flies into dust. Unannealed glass is to a certain degree under the same conditions of unequal tension. Hence the necessity of annealing or slow cooling to give time for the* particles to rearrange them- selves without strain. Glass is colored red by the oxyds of copper and gold, blue by oxyds of cobalt, white by tin, How is glass worked in the laboratory ? What is annealing? How is this illustrated by Prince Rupert's drops ? Explain the illustration. How is glass colored ? ALUMINUM. 827 arsenic and antimony, yellow by uranium, purple and violet by manganese, and green by chromium, iron, nickel, &c. By the skilful use of these oxyds, with a heavy and highly refracting glass, the various gems are very beautifully imi- tated. Such imitations are called pastes. Pottery. 555. One of the oldest of human inventions is the fashioning of vessels of use and ornament out of clay. The bricks of Babylon and Nineveh, covered with arrow-head inscriptions, are among the most ancient memorials of history. The decomposition of feldspar and other aluminous mine- rals and rocks gives origin to the clays which are so import- ant in the art of pottery. Decomposed feldspar forms porcelain clay, commonly called kaojin. The undecom- posed mineral is often ground up to mix with the materials for porcelain. The difference between porcelain and earthen- ware consists in the partial fusion of the materials of the former by the heat of the furnace, which gives it the semi- transparency and great beauty for which it is so highly prized. Common earthenware is often glazed with oxyd of lead, an unsafe mode for culinary vessels : common salt (508) is also used, being raised in vapor by the heat of the kiln. The soda unites with silica, while the chlorine escapes as chlorid of iron. The glaze in porcelain is formed of a more fusible mixture of the same materials, put over the articles as a wash, after they have been once through the furnace, (in which state they are called biscuit ware;) they are then baked again at a heat which fuses the glaze, but which does not soften the body of the ware. All porcelain is twice fired and sometimes thrice. If painted, the design is laid upon the surface in colors formed from metallic oxyds, which develop th'eir appropriate tints only after fusion with the ingredients of the glaze. Metallic gold is put on in the form of an oxyd, and the steel lustre is produced by metal- lic platinum. This beautiful art is carried to a wonderful How made refractive? 555. What is one of the most ancient arts? Whence is potter's clay derived ? What is kaolin ? What is the difference between porcelain and earthenware ? How is pottery glazed ? How porcelain ? How painted ? 328 METALLIC ELEMENTS. perfection in the royal establishments of France and Prus- Bia, where the first talent is employed in modelling and paint- ing. Any further detail of these interesting branches of applied chemistry would be out of place here, and the stu- dent is referred to larger works for a fuller description. 556. There are six other metals belonging to this class, which are so rare and comparatively unimportant that we pass them with the most cursory enumeration : Glucinum is the base of a sesquioxyd G 3 S , (glucina,) which is the characteristic earth of the emerald, beryl, and chrysoberyl, It is very like alumina, and is named in allusion to tho sweet taste of its salts. Yttrium is the metal of the earth yttria YO, found in the minerals yttrocerite, &c. Zir- conium is found as a sesquioxyd of zirconia Zr^ in zircon. Thoria was found by Berzelius in the rarest of all minerals, the thorite, of Sweden. Thorium has the highest specific gravity (9) of any eftrth. Cerium and lantanium are in- variably associated, and with them another rare metal, didy- mium. The minerals ccritc, allanite, and monazite contain them. CLASS IV. HEAVY METALS, WHOSE OXYDS FORM POWERFUL BASES. MANGANESE. Equivalent, 2 7 -6. Symbol, Mn. Density, 8. 557. Manganese is never found as a metal in nature, but may be produced from its black oxyd by a high heat with charcoal. Metallic manganese is a gray, brittle metal, not magnetic, and resembles some varieties of cast-iron. It dis- solves rapidly in sulphuric acid with escape of hydrogen. Manganese, in the form of the black oxyd, is an important and pretty common metal. Its great use is for producing chlorine (282) and in the manufacture of glass, where it acts by its oxygen to decolorize the compound. 558. We enumerate five compounds of manganese, viz. protoxyd MnO ; sesquioxyd (or braunite) Mn 3 0., ; peroxyd, or deutoxyd, (pyrolusite,) Mn0 2 ; manganic acid Mn0 3 ; hypermanganic acid Mn 3 7 . 656. Enumerate the other earthy metals named in this section. 557. What are the equivalent and properties of manganese ? What form of it ia most common ? For what is it used ? 558. How many and what oxydi yf manganese are named? MANGANESE. 329 The protoxyd is a green-colored powder, formed from heating the carbonate of manganese in an atmosphere of hydrogen. It is a powerful base, attracts oxygen from the air, and is the base of the beautiful rose-colored salts of manganese. The sesquioxyd or Iraunite occurs crystallized in octahe- drons and forms belonging to the dimetric system. The hydra ted sesquioxyd Mn 3 3 +H0 (manganite) is a finely crystallized mineral, in long black prisms, found in superb specimens at Ilfeld, in the Hartz. In powder the sesquioxyd is brown ; it is decomposed by chlorohydric acid with the evolution of chlorine, but sulphuric acid combines with it to form a sesquisulphate, which yields a purple double salt with sulphate of potash, (manganese alum,) iso- morphous with the corresponding salt of alumina. 559. The peroxyd Mn0 2 is the most common and most valuable ore of manganese. From it we' obtain oxygen, and, by the decomposition of chlorohydric acid, chlorine. It is found abundantly at Bennington, Vermont, and other places in this country. When crystallized it is called pyrolusite. Beautiful specimens of this mineral have been observed at Salisbury and Kent, Connecticut, among the iron ores. 560. Manganic acid is known only in combination, espe- cially as manganate of potash. This is best formed by mix- ing equal parts of finely powdered black oxyd of manganese and chlorate of potash with rather more than one part of hydrate of potash dissolved in a very little water. This mixture, when evaporated, is heated to a point short of red- ness, and a dark green mass is formed which contains man- ganate of potash. In this case the manganese obtains oxygen from the chlorate of potash, and the manganic acid thus formed combines with potash, giving a salt in green crystals. This salt, dissolved in water, gives a brilliant emerald-green solution, which almost immediately changes color, being in quick succession green, blue, purple, and finally crimson- red, and has thence been called chameleon mineral. This last color is due to the presence of permanganic acidj which, however, cannot be separated from its combinations, but Which is the base of the rose-colored salts ? What is the sesquioxyd ? Give the formula of the hydrated sesquioxyd? What is said of the sul- phate of the sesquioxyd? 559. Which is the most common ore of man- ganese? Where and how is it found? 560. Describe manganic acid and the salt it forms with potash. What is the changeable compound called? 330 METALLIC ELEMENTS. forms a salt with potash in beautiful purple crystals. The compounds of permanganic acid are more stable than the manganates. The salts of these acids are respectively iso- morphous with sulphates and perchloratcs S0 3 and Cl a O r 561. The clilorids of manganese MnCl and Mn 3 Cl 3 cor- respond to the protoxyd and sesquioxyd. The chlorid is formed abundantly in acting on black oxyd of manganese (282) with hydrochloric acid. The mixed solution of chlo- rids of iron and manganese is evaporated to dryness, and then heated to dull redness. The chlorid of manganese is then dissolved out from the dry mass, leaving the insoluble protoxyd of iron behind. It has a beautiful pink tint, and deposits tabular rose-colored crystals on evaporation. It is soluble in alcohol, and fusible by heat. 562. The salts of manganese are numerous, and in a chemical view quite important. Sulphate of manganese MnO.S0 3 -f-7HO is a very beautiful rose-colored salt, iso- morphous with sulphate of magnesia. It is used to give a fine brown dye to cloth, being decomposed by a solution of bleaching-powder, which forms the brown peroxyd in the fibre of the stuflfe. It is also used in medicine. Potassa and soda throw down the oxyd of manganese as a white powder, which immediately turns brown from the forma- tion of a higher oxyd. The carbonates of the alkalies throw down carbonate of manganese from their soluble salts. Any compound of manganese fused upon a slip of platina with carbonate of soda, gives a powerfully characteristic green salt, the permanganate of soda. IRON. Equivalent, 28. Symbol, Fe. Density, 7-8. 563. Iron is found malleable, and alloyed with nickel, in large masses of meteoric origin. One of these, discovered in Texas, weighs 1635 pounds, and is now in Yale College cabinet. It is not certain that malleable iron of terrestrial origin has yet been discovered in nature. Iron is the most abundant and most useful metal known to man. Its ores What is said of the salts of manganic and permanganic acid? 561. Describe the chlorids of manganese ? 562. What is said in general of the salts of manganese? What tests are named for manganese and it,s salts? 563. What is the equivalent of iron? How is malleable iron found ? What is said of its abundance and value ? IRON. odl are found everywhere, and often in immediate connection with the coal and limestone necessary to reduce them to the metallic state. There is no soil, and scarcely any mineral, which does not contain some proportion of the oxyd of iron. We know iron as malleable iron, steel, and cast iron. 564. To obtain pure iron is not easy, and the best iron of commerce is always contaminated with carbon and silicon. Small quantities of iron are prepared absolutely pure, in the laboratory, by reducing the pure oxyd of iron in a bulb of hard Fig. 372. glass a b (fig. 372) by a current of dry hydrogen. The bulb A is heated by the flame of a spirit-lamp. This apparatus serves for numerous reductions of metallic oxyds, as, for example, the oxyds of cobalt, nickel, zinc, &c. The bulbed tube a b is drawn down at c (fig. 373) to a narrow neck, so that while the tube is yet A full of hydrogen it may be seal- ed by the blowpipe both at c and b: otherwise the pulverulent Fig. 373. metallic iron, from its strong afiinity for oxygen, will take fire on contact of air, and be carried back again to its original condition of oxyd. If this operation is conducted in a por- celain tube at a high heat, the iron formed assumes a metallic lustre, and does not oxydize ; and if protochlorid of iron is used in place of the oxyd, the metal rises in vapor, lining the tube with a brilliant crystalline crust. 565. When quite pure, it is nearly white, quite soft, per fcctly malleable, and the m*st tenacious of all metals, (471.) Its density is 7-8, which may be a little increased by ham- 564. How is pure iron obtained? Describe fig. 372. What happens if the iron so obtained is exposed to air ? How is it obtained more dense 1 665. What are its properties ? S32 METALLIC ELEMENTS naering. It crystallizes in forms of the first class, a:> is* beautifully shown in the crystalline structure of the meteoric iron, and sometimes in the crust produced in the reduction of the protochlorid. It fuses with extreme difficulty, first becom- ing soft or pasty, in which state it is welded. When intensely heated in air or oxygen gas it combines with oxygen, burning with brilliant light and numerous scintillations, and is converted into oxyd of iron, (fig. 374.) Iron also attracts oxygen from the air at common tempera- tures, forming rust. This does not happen in dry air, but the presence of moisture, and particularly of a little acid vapor, very much promotes its formation. Iron decomposes water very rapidly at a red-heat, hydrogen being evolved. Its magnetic relations have already been fully explained. Cobalt and nickel are the only other magnetic metals. 566. The oxyds of iron arc three, viz : 1. Protoxyd, FeO; 2. Sesquioxyd, commonly called peroxyd, Fe 3 3 ; 3. Ferric acid, Fe0 3 . The magnetic oxyd Fe 3 4 is regarded as a compound of protoxyd and sesquioxyd FeO.Fe 3 3 , in which the sesquioxyd plays the part of a base, (475.) 1. The protoxyd of iron FeO is a powerful base which is unknown in nature except in combination. It saturates acids completely and is isomorphous with a lar^e class of bodies, of which zinc and magnesia are examples, (263.) This oxyd is thrown down from its solutions by potash, as a whitish bulky hydrate, that soon gains another portion of oxygen from the air, becoming brown, and finally red. Its salts, when soluble, have a styptic taste like ink, and a greenish color, of which the most familiar example is green vitriol, or sulphate of protoxyd of iron. 2. The peroxyd of iron Fe 2 3 is found native in the beautiful specular iron of Elba, and also in the red and brown hematites. Limonite 2(Fe 2 3 )-(-3HO is a hydrous sesquioxyd. It is slightly acted on by the magnet, and after ignition is almost insolublesn strong acids. It is iso- morphous with alumina, and is generally associated with it in soils and many minerals. It is often of a brilliant red, What is welding? 566. What oxyds are named ? Give their formulas. Describe the protoxyd and its salts. How is the peroxyd known ? IRON. 833 and, as ochre of various tints, is much used as a pigment. Ammonia, potassa, or soda precipitates it from its solutions as a bulky red hydrate, which, in its moist condition, is esteemed an antidote to poisoning by arsenic. Colcothar, or rouge, is this oxyd prepared by calcining the sulphate : it is much used in polishing metals. Magnetic oxyd of iron Fe 3 4 is familiarly known in the common magnetic iron ore and native lode-stone. It crys- tallizes in octahedrons. It forms no salts, and, as has al- ready been remarked, is regarded as a salt of FeO-}-Fe 3 3 . The finery cinders or scales thrown off under the smith's hammer are this oxyd. 3. Ferric Add, Fe0 3 . This compound, discovered by M. Fremy, corresponds to manganic acid. Ferrate of potash is formed when one part of peroxyd of iron and four parts of nitre are heated to full redness in a covered crucible for an hour. The ferrate of potash is dissolved out of the porous mass by ice-cold water. The solution has a deep amethyst- ine color, and is easily decomposed by heat. A soluble salt of baryta precipitates ferric acid as a beautiful red fer- rate of baryta, which is permanent. 567. The chlorids of iron Fed and Fe 3 Cl 3 correspond to the protoxyd and sesquioxyd of the same base. The per- chlorid is often used in medicine, and may be formed by saturating hydrochloric acid with freshly prepared peroxyd of iron. The protiodid of iron is also a valuable medicine. The sulphurets of iron are found in nature, and are known under the mineralogical names of pyrites and marcasite FeS 3 , and magnetic pyrites Fe 7 S s . The protosulphuret FeS is easily formed artificially, by fusing sulphur with iron filings : they ignite with a vivid combustion, and proto- sulphuret of iron is formed, which is much used in pre- paring sulphuretted hydrogen. Yellow iron pyrites and white iron pyrites (marcasite) are dimorphous forms of the bisulphuret FeS 3 : the first is one of the most common of crystallized minerals. 568. Of the salts of iron, green vitriol, or copperas, a pro- What is colcothar ? Give the formula of the black oxyd. How is it found in nature ? What is ferric acid ? 567. What chlorids of iron are named ? What oxyds do they correspond to ? What are the sulphurets of iron ? For what is the protosulphuret used ? What is the name of the ordinary sulphuret ? What two forms of it are found in nature ? 334 METALLIC ELEMENTS. tosulphate FeO.S0 3 -f-7HO, is the most important. It is made in immense quantities, as at Stafford, Vt , from the fermentation of iron pyrites, which furnishes both the acid and the base. This salt crystallizes beautifully, and is much used as the basis of all black dyes and of ink, and in the manufacture of prussian blue. Persulphate of iron is a sulphate of the peroxyd Fe 3 3 -f-3S0 3 . Carbonate of iron occurs in nature as spathic iron ore, which is isomorphous with carbonate of lime. A variety of steel is made directly from this ore without cementation, (570.) It is formed artificially by precipitating a solution of protosulphate by an alkaline carbonate. It is used in medicine. Water containing carbonic acid dissolves protoxyd of iron and acquires the well-known flavor of chalybeate waters : exposure to air permits the escape of the carbonic acid, when the iron falls as red peroxyd. Phosphate of iron FeO.P0 5 -j-8HO is formed as a green- ish-white gelatinous precipitate when solution of tribasic phosphate of soda is added to solution of protosulphate of iron. It is an article of the materia medica. Vivianite is a mineral having the same formula, found both massive and crystallized, of a beautiful indigo-blue color. The cyanogen compounds of iron will be described in the organic chemistry. The presence of a salt of iron is easily detected by the fine blue (prussian blue) formed on adding prussiate of potash to the solution : an infusion of galls gives a black color (ink) to solutions of iron salts. 569. The chief ores of iron are, 1. The specular iron or peroxyd, including red and brown hematite; 2. Limonite, or hydrous peroxyd, from which the best iron is made (bog iron also comes under this head;) 3. Clay iron-stone, which is an impure carbonate of iron, or carbonate of iron with carbonate of lime and magnesia this is the nodular ore and band ore of the coal formations ; 4. Black or magnetic oxyd of iron, which is the ore of the iron mountains of Missouri and of Sweden. The reduction of the ores of iron to the metallic state is usually performed in large furnaces called hujh or blast fur- 568. Which of the salts of iron is of great importance? How and where is it made in this country? What is the carbonate and for what used? What of the phosphate? What tests are named for iron ? 569. What ores of iron are enumerated? How is the reduction of iron effected? IRON. 335 naces. These are built of stone, in a conical form, 30 to 50 feet high, and lined internally with the most refractory fire-bricks. The furnace is divided into the throat, the fire-room b, the boshes e y (that portion sloping inward,) the crucible t, and the hearth h. The blast of air supplied from very large blowing cylinders is intro- duced by two or three tuyere . pipes a a, near the bottom. In the most improved furnaces, the air-blast is heated by causing a it to pass through a series of pipes in the upper portion of the furnace, so as to have a temper- Fig. 375. ature of 500 or more when it enters the furnace. When the furnace is brought into action, it is first heated with coal only, for about 24 hours, to raise it to the proper tem- perature \ and then is charged alternately with proper pro- portions of coal, roasted ore, and lime for flux, until it is quite full. When once brought into action, the blast is kept up for months or even years, until the furnace requires repairing. The ore is reduced on the boshes, and in the upper part of the crucible, where the oxyd of carbon is found almost pure in presence of an excess of white-hot carbon and ore previously dried and in part reduced in the higher parts of the furnace. The melted metal collects on the hearth, where it rests, covered by the molten flux, which is a glass, formed by the fusion of the lime used, with the earthy parts of the ore. From time to time, the iron is drawn off by an opening level with the hearth, previously stopped with clay, and run into rude open moulds in sand. This is cast iron, and is of various qualities, according to the various charac- ter of the ore and the working of the furnace. If malle- able bar iron is wanted, the cast iron is again melted, in what is called the puddling furnace, where it is stirred Describe the high furnace. What is the hot blast? What is the ope- ration of the furnace ? What is cast iron ? How is malleable iron made from cast iron ? 336 METALLIC ELEMENTS. about by an iron rod, in contact with oxyd of iron, and a current of heated carbonic oxyd from burning wood or coal. It gradually becomes stiff and pasty from the burning out of the carbon, and from some molecular change not well understood. This pasty condition increases until the iron is finally raised in a rude ball and placed under the blows of a huge tilt-hammer, when the scoria is pressed out and the particles made to cohere. It grows tenacious by a repe- tition of this process, being cut up and piled or faggoted and reheated several times, until it is finally rolled in the roll- ing-mill into tough and fibrous metal. 570. Steel is formed from, refined iron by heating it for days in succession in contact with charcoal in close vessels, (called cementation.) It gains from one to two per cent of carbon, becomes fusible, and can be tempered according to the use for which it is designed. The Catalan forge is a furnace formed like a smith's forge on a large scale, and in which the circumstances of the high and puddling furnace are combined, so that malleable iron is produced from the ore the cast iron being brought to the ductile state in the same fire where it is reduced from the ore charcoal is the fuel of the Catalan forge. The best iron is always produced when charcoal is the fuel, being free from sulphur and phosphorus, the two worst enemies of good iron. CHROMIUM. Equivalent, 264. Symbol, Cr. Density, 6. 571. Chromium in combination with iron is rather an abundant substance, particularly in this country, being found as chromic iron at Barehills, near Baltimore ; Lancaster Co., Pa., and in several other places. The beautiful red chro- mate of lead is also a natural product in Siberia. The metal, from its great affinity for oxygen, is very difficult to procure. It is a hard, almost infusible substance, resem- bling cast iron, nearly insoluble in acids, and does not decompose water. It may be oxydized by fusion with nitre, but does not change in the air. 570. What is steel? What is the Catalan forge? What fuel makes the best iron ? 571. What are the symbol and properties of chromium ? How distributed in nature ? CHROMIUM. 337 572. The oxyds of chromium are exactly the same as those of manganese. Chromium bears the strongest analogy in its chemical character to manganese and iron. The pa- rallelism of constitution in the oxyds of these three metals is shown in the following tabular arrangement : Acids. Protoxyd. Sesqxiioxyd. Black oxyd. Peroxyd. , * > Manganese forms.. MnO ... Mn a 3 ... Mn,0 4 ... MnO a MnO, Mn,0 t Iron forms FeO ... Fe,0 3 ... Fe 3 4 ... FeO, Chromium forms... CrO ... Cr a 3 ... Cr,0 4 ... CrO a CrO, Cr.O, The protoxyd of chromium is a strong base, acting in combination like the protoxyd of iron, with which it is iso- morphous. 573. Sesquioxyd of chromium Cr 2 3 may be obtained in little rhornbohedral crystals by passing the vapor of chlo- rochromic acid through a heated tube, 2Cr0 3 Cl = Cr 3 3 -f- 201-j-O. The crystals are deposited on the walls of the tube in a brilliant deep-green crust. They are as hard as ruby. Their density is 5-21. The hydrated sesquioxyd of chromium Cr a 3 -j-HO is easily prepared by treating a boiling and rather dilute solu- tion of bichromate of potash with an excess of chlorohydric acid, and then wi^h successive portions of alcohol or sugar until it assumes a fine emerald tint. Ammonia throws down a bulky, pale-green precipitate, soluble in acids and shrink- ing very much in drying this is the hydrate. On ignition it undergoes vivid incandescence and becomes deep green. The sesquioxyd of chromium is a feeble base like those of iron and alumina, and may replace them in combination, as in the formation of chrome alum with sulphate of potash. Sesquioxyd of chromium forms an alum also with the sul- phates of soda and ammonia. All the salts of this oxyd are either emerald green or bluish purple. It imparts a rich tint of green to glass and porcelain, and is the cause of the color of the emerald. Chrome iron is composed of this oxyd and protoxyd of iron FeO.Cr 2 3 , isomorphous with magnetic iron FeO.Fe 3 3 , and with spinel MgO.Al 2 3 . The chrome iron of Pennsylvania contains a little nickel. 574. Chromic acid Cr0 3 is readily formed by treating 572. What strong analogies has it ? Give the parallel oxyds of Mn, Fe, and Cr. 573. How is sesquioxyd of Cr obtained ? How is its hydrate ? What are its properties ? What salts does it form ? What is chrome iron ? 574. How is chromic acid formed? 22 338 METALLIC ELEMENTS. a cold and concentrated solution of bichromate of potash with one and a half parts of sulphuric acid. The mixture, when cold, deposits brilliant ruby-red prisms of chromic acid. The sulphato of potash in solution above, may be turned off, and the chromic acid dried on a porous brick, being carefully covered with a glass to prevent access of organic matters, which at once decompose it. If a little of this acid be thrown into alcohol or ether, the violence of the action is such as to set fire to the mixture. Chromic acid forms numerous salts, which are highly colored. The protochlorid of chromium CrCl is obtained as a white and very soluble substance by the action of dry hy- drogen gas on the sesquichlorid. The sesquichlorid Cr 3 Cl 8 is prepared by passing chlorine gas over an ignited mixture of the sesquioxyd and charcoal. It forms a crystalline sublimate of a peach-blossom color, which is insoluble in water. The sesquioxyd dissolves in chlorohydric acid, but the hydrated chlorid thus obtained is decomposed by heat. Chlorochromic acid Cr0 3 Cl is a deep-red volatile liquid, much resembling bromine in its appearance. It is formed when 10 parts of common salt and 17 of bichromate of potash are intimately mixed, and heated in a retort with 30 parts of concentrated sulphuric acid. The chlorochromic acid distils over, filling the receiver with a superb ruby-red vapor. Its density is 1-71, and it boils at 248. Water decomposes it, forming chromic and hydrochloric acids. It may be preserved in tubes hermetically sealed. 575. The chromate and the bichromate of potash are both familiar compounds of chromic acid. The first, KO.Cr0 3 , is formed on a very large scale, by decomposing the native chromic iron with nitrate of potash, by aid of heat. Chro- mate of potash is dissolved out from the ignited mass, and crystallizes in anhydrous yellow crystals. It is isomorphous with sulphate of potash, dissolves in two parts of cold water, and is the source of all the preparations of chromium. Bichromate of potash K0.2Cr0 3 is formed by adding sulphuric acid to a solution of the yellow chromate, when half the potash is removed, and the bichromate crystallizes Give its properties. Describe the chlorids of chromium. Describe chlo. rochromic acid. 575. How is chromate of potash formed ? How is bi- chromate of potash formed ? NICKEL. 339 by slow evaporation in brilliant red crystals of a rhombic form, which are soluble in ten parts of cold water. 576. ChromateofLeadChromeYdlow (PbO.Cr0 3 ) is the well-known pigment prepared by precipitating the nitrate or acetate of lead by a solution of chromate or bichromate of potash. Chrome Green is the oxyd of chrome, prepared in a particular way. NICKEL. Equivalent, 29-6. Symbol, Ni. 577. Nickel is rather a rare metal. It is prepared from the speiss or crude nickel of commerce. It is white and malleable, having a density of 8 to 8 '8, and fuses above 3000. Reduced from its oxyd by hydrogen (fig. 373) at a low temperature, it takes fire in the air. The compact metal is not easily oxydized. It is the only metal beside iron and cobalt which is magnetic. This property it loses when heated to 700. Meteoric iron almost invariably contains nickel, sometimes as much as 10 per cent. Its chief ores are cop- per-nickel and speisa-cobalt. Arseniuret of nickel and cobalt is found at Chatham, Conn., and oxyd of cobalt and manganese in Mine-la-Motte, Mo. The emerald nickel, a beautiful green hydrous car- bonate described by the author, is found in Lancaster Co., Pa. Its formula is 3(NiO)C0 2 +6HO. 578. There are two oxyds of nickel. The protoxyd NiO is prepared by precipitating a solution of nickel by caustic potash : this is soluble in ammonia. It gives a grass-green hydrated oxyd, which, by heat, loses its water and becomes gray. The oxyd of nickel is isomorphous with magnesia, and has been obtained crystallized in regular octahedrons. The salts of this oxyd have a fine green color, which they impart to their solutions. The peroxyd of nickel NiO a is a dull black powder, of no particular interest. 579. The sulphate of nickel NiO.S0 3 +7HO is a finely crystallized salt, occurring in green prisms, which lose their 576. What is chrome yellow? What chrome green? 577. In what Btate does nickel occur in nature ? Describe its properties. What of ita magnetic property ? 578. What are oxyds ? In what form does the proL- oxyd crystallize ? 579. Describe the sulphate and oxalate of nickel. 340 METALLIC ELEMENTS. water of crystallization by heat. It forms beautiful, well crystallized double salts, with the sulphates of potash and ammonia. Oxalic acid precipitates an insoluble oxalate of nickel from the solution of the sulphate, and the metallic nickel is easily obtained from the oxalate by heat. Nickel is chiefly employed in making German silver, a white malleable alloy, composed of copper 100, zinc 60, and nickel 40 parts. COBALT. Equivalent, 29-5. Symbol, Co. 580. Cobalt is a metal almost always associated with nickel, and closely resembling it in many of its reactions. When pure it is a brittle, reddish-white metal, with a density of 8 '53, and melts only at very high temperatures. It is nearly as magnetic as iron. It dissolves with difficulty in strong sulphuric acid, and is not oxydized in air. It forms two oxyds every way analogous to those of nickel. Its prot- oxyd is a grayish-pink powder, very soluble in chlorohydric acid. It forms pink salts. This oxyd occurs native. The chlorid of cobalt CoCl is formed by dissolving the oxyd in hydrochloric acid. The solution is pink, and when very dilute may be used as a blue sympathetic ink, which may be made green by mixing a little chlorid of nickel. Writing made with this on paper is colorless when cold, but becomes of a fine blue or green when gently warmed, and loses its color again on cooling. The salts of cobalt and nickel are isomorphous with those of magnesia. They are not thrown down by sulphuretted hydrogen, but give blue or green precipitates with potash, soda, and their carbonates. The same precipitates with ammonia are soluble in excess of that reagent. Oxyd of cobalt imparts a splendid blue to glass, and the pulverized glass of this color is called smalt and powder blue. Zaffre is an impure oxyd of cobalt, used to give the blue color to common earthenware. What is the composition of German silver? 580. What are the charac- ters of cobalt? What interesting experiment is mentioned with the chlorid ? With what oxyd are the oxyd of cobalt and its salts isomor- phous ? What use is made of the oxyd of cobalt ? ZINC. 341 ZINC. Equivalent, S2-.5. Symbol, Zn. Density, 6-86 to 7-20. 581. Zinc is an important and rather common metal. It is not found native, but a peculiar red oxyd of zinc abounds at Sterling, New Jersey, and calamine or carbonate of zino is found abundantly in many places. The ores of zinc are reduced by heat and charcoal, in large crucibles closed at top, but having a clay tube a b descending from near the top, as in fig. 376, through the crucible and its support B, to a vessel of water C. The cover is luted on and the heat raised. The metal, being volatile, rises in vapor, which descending through the tube, is condensed in the water below. This is called distillation per descensinn. 582. Zinc is a bluish-white metal, easily oxydized in the air, and crys- tallizes in broad foliated laminae, TjV Q'Tft well seen in the fracture of an ingot of the commercial metal. It is called spelter in the arts, and is largely used to alloy copper in forming brass, to form sheet zinc, and also for the protection of iron in what is called galvanized iron. Zinc is not a malleable metal at ordinary temperatures, but at a temperature of between 250 and 300 it becomes quite malleable, and is then rolled into sheet zinc. At about 390 it is again quite brittle, and may be granulated by blows of the hammer : at 773 it melts, and if air has access to it, it takes fire, and burns rapidly with a brilliant whitish-green flame, giving off flakes of white oxyd of zinc, anciently called lana philosophica and pompTiolix. It is completely volatile at a red heat. We constantly em- ploy zinc in the laboratory to procure hydrogen, and granu- late it by turning it slowly into cold water from some height. It dissolves in solutions of soda and of potassa, with evolu- tion of hydrogen and formation of zincate of the alkali employed. 583. The oxyd of zinc ZnO is formed when zinc burns 581. Hew is zinc reduced from its ores? How distilled ? 582. What are its properties ? At what temperature is it malleable ? 342 METALLIC ELEMENTS. in air. Only one oxyd is known. It is, when pure, a white powder ; yellowish while hot. It contains zinc 80-26, oxygen 19-74. It is insoluble in water, but forms a hydrate with it. The anhydrous oxyd mingled with drying- oils forms a valu- able paint, now coming into use in place of white-lead. It has the advantage of not changing by sulphuretted hydro- gen and of not being deleterious to the health of the work- men. It is now largely manufactured from the red zinc of New Jersey, and from the franklinite of the same region, which contains a large quantity of zinc. Calaminc is a native carbonate of zinc ZnO.C0 3 , and is its most valuable ore. Electric calcimine is a silicate 3(ZnO)Si0 8 +HHO. Chloric? of zinc ZnCl is a valuable escarotic, and has been much used in dilute solution to preserve anatomical subjects for dissection. Sulphuret of zinc, Blende, ZnS, is one of the mostcommon of the ores of zinc. It occurs in beautiful brilliant crystals, modi- fications of the first system, called by the miners Hack-jack. Sulphate of Zinc, or White Vitriol, ZnO.S0 3 +7HO. This salt has the same form as the sulphate of magnesia, and looks extremely like it. It dissolves in 2 parts of cold water, at 60, but at 212 is indefinitely soluble, as it then fuses in its own crystallization water. It forms double salts with the sulphates of ammonia and potash. It is a powerful and very rapid emetic. Sulphuret of ammonia throws down a characteristic white precipitate of sulphuretted zinc from its neutral solutions CADMIUM. Equivalent, 56. Symbol, Cd. Density, 8'7. 584. Cadmium is generally found associated with zinc. It is quite malleable, white, and harder than tin. It fuses at 442, and volatilizes completely at a temperature a little above this. It is not easily oxydized, and is but slightly soluble in chlorohydric or sulphuric acid. Nitric acid dis- solves it with ease, forming a salt from which sulphuretted hydrogen throws down a very characteristic orange-yellow sulphuret. This compound is also found native and crys- tallized, 583. Describe the oxyd ZnO. What large use is being made of it? What is calamine ? Blende ? Sulphate of zinc ? What of its solubility ? 584. What are the properties of cadmium ? LEAD. 343 Its oxyd CdO is a bronze powder, formed by igniting tho nitrate or carbonate, and rises in a brown vapor when cad- mium is placed in the focus of the oxyhydrogen blowpipe. LEAD. Equivalent, 103-5. Symbol, Pb. Density, 1145. 585. This useful and familiar metal occurs in boundless profusion in this country. Its chief ore is galena, or sul- phuret of lead, from which the metal is easily obtained by smelting with a limited amount of fuel at a low heat. The carbonate, phosphate, chromate, and arseniate are also na- tural salts of lead, much prized by the mineralogist. Lead is a bluish-gray metal, very soft and ductile, but not very tenacious, (471 ;) it oxydizes in the air quite rapidly, forming a coat of oxyd, or carbonate, which usually protects it from further corrosion. Its destiny is 11-45, and it fuses at about 630; when melted it combines rapidly with oxygen from the air, forming either protoxyd, or red oxyd, accord- ing to the degree of heat employed. It is somewhat volatile above a red heat. Lead is acted upon by distilled water and by rain water. Water, by reason of its affinity for the oxyd of lead, acts like an acid upon metallic lead. A bright slip of pure lead is tarnished almost immediately in pure water, and after a short time becomes covered with a pellicle of carbonate of lead ; while the water yields a dark cloud to sulphuretted hydrogen, showing the presence of oxyd of lead dissolved in it. It is, therefore, unsafe to use water-pipes of lead, unless it has been proved by experiment that the particular water in question does not act on this metal. The carbonate, which is the salt generally produced under these circumstances, is an energetic poison. The presence of a very small quantity of foreign mattej* in water, and especially of the sulphate of lime, usually arrests this action, and renders the use of lead- pipes in a majority of cases not hazardous. Lead does not easily dissolve in strong acids, except in nitric, with which it forms a soluble salt : strong sulphuric acid dissolves it only when heated, forming nearly insoluble sulphate of lead. 585. What is the chief ore of lead ? What are the properties of lead ? Its density and fusion point? Is it volatile ? What acts on lead ? What salt of lead is most poisonous ? What arrests the action of water on 1<^ .* 344 METALLIC ELEMENTS. Th >re are three oxyds of lead, viz. suboxyd Pb 3 0, prot- oxyd PbO, and peroxyd, or plumbic oxyd Pb0 2 . 586. Protoxyd of Lead, Litharge, Massicot, PbO. This oxyd is a yellow powder, formed by slowly oxydizing lead with heat. It is slightly soluble in water, and the solution is alkaline : in solution of sugar it is largely soluble. It fuses easily, and dissolves silica with great rapidity ; hence its use in glazing pottery (555) and in the manufacture of glass, (553.) It forms a large class of definite salts, which have often a sweet takte, as is seen in the acetate, or sugar of lead. The peroxyd Pb0 3 is prepared by acting on the red-lead with dilute cold nitric acid : it is a puce-colored body, which plays the part of an acid, forming salts with bases. The oxyd of lead forms insoluble salts with the fatty acids, of which the well-known diachylon plaster is an example. There are several intermediate oxyds of lead, called miniums which are of variable composition, according to the tempera- ture at which they are prepared. Red-lead is a familiar ex- ample of these. Its formula is Pb 3 4 or 2PbO.Pb0 2 . It has a fine orange-red color when well prepared, and is some- times found crystallized in the fissures of the furnaces. It is prepared by exposing lead to a constant temperature of about 700. Acted on by hydrochloric acid, it evolves chlorine, and, with sulphuric acid, oxygen is given off. It is preferred to litharge for glass-making. The chlorid and iodid of lead possess no particular inte- rest ; the latter crystallizes in beautiful yellow scales from its solution in hot water. The chlorid, iodid, and sulphate are all very insoluble compounds. Sulphuretted hydrogen throws down a black sulphuret from all soluble salts of lead, being the best test of its presence. 587. Zinc precipitates it from its solutions by voltaic action, in beautiful crystalline plates of metallic lead, which assume a branching form, often an inch or two in length, and hence called the lead-tree, or arbor saturni, from the alche- m i s ti c nalll e of this metal. The acetate is usually employed : an ounce of the salt is dissolved in two quarts of What oxyds of lead are there ? 586. What names has PbO ? Give its properties. What is PbO a ? What is diachylon piaster? What are the miniums? What use is made of minium? What test LB named for lead salts ? 587. How is metallic lead precipitated from its solution ? COPPER. 345 distilled water, and a piece of clean zinc suspended in it by a thread : the precipitation is gradual, and occupies one or two days. The arrangement is seen in the fig. 377. 588. Carbonate of Lead, White-lead, Ceruse, PbO.C0 3 . This salt is found beautifully crystallized in nature, but is prepared artificially in very large quantities, for the pur- poses of a paint. This pigment is obtained by casting lead in very thin sheets, which are then rolled up into a loose Bcroll Z (fig. 378) and placed in a pot over a small quantity of vinegar u, supported on the ledge b b, so as not to project above the pot, nor touch the vinegar. The vinegar is obtained from the fermentation of potatos. Many thousands of these pots are arranged in successive layers over each other, with covers n' m between, and the interstices filled with spent tan, or ferment- ing stable-dung, which gives a gentle heat to the acid. After a time the lead is completely Ig ' ' converted into an opake white crust of carbonate. The theory of this process will be explained when we describe the ace- tates of lead, (Organic Chemistry.) White-lead is now largely adulterated by sulphate of baryta, but the fraud may be easily detected by dissolving the carbonate in an acid, when the sulphate of baryta will be left behind. Carbonate of lead is highly poisonous. 589. URANIUM, (equivalent 60.) This rare metal is found only in a few very rare minerals, of which the best known are pitch blende, an impure oxyd of uranium, and uranite, one of the most beautiful of mineral species, which is a phos- phate of uranium. The metal is of a silver color, a little malleable, and has so great an affinity for oxygen as to burn in the air. It forms two oxyds, UO and U 2 3 . The salts of uranium possess considerable chemical interest. COPPER. Equivalent, 31-7. Symbol, Cu. Density, 8-87. 590. Copper has been in familiar use since the times of Tubal Cain, and is one of the most important metals to the 588. How is the carbonate prepared, and for what is it used ? 589. In what minerals is uranium found? What oxyd does it form? 590. What is the history of copper ? 346 METALLIC ELEMENTS. wants of society. It is often found in the metallic state. The metallic copper of Lake Superior is found in irregular veins, filling fissures, from which it is cut by chisels, and by drills in huge blocks of great purity. Small masses of silver are also often found adherent to the copper. One mass from this region, now at Washington, weighs over 3000 pounds, and such masses are frequent. The most usual ores of copper are the red oxyd of copper, copper pyrites, and copper glance, a pure sulphuret, or sulphuret of copper and iron. The blue and green malachites, or carbonates of copper, phosphate and arseniate of copper, and many other salts of this metal, are also found in the mineral kingdom. Copper is very malleable, and is the only red metal except titanium. It fuses at 1996, and has a density of 8-78, which may be increased to 8-96 by hammering. It does not change in dry air, but in moist air becomes covered with a green coat of carbonate, known as verdigris, (corruption of the French vert de gris.) It is stiffened by hammering or rolling, and softened again by heating and quenching in water. It may be drawn into very fine wire of good tenacity, which is an excellent conductor of heat and electricity, and is much used in electro-magnetism and for the telegraphic conductors. Nitric acid is the proper solvent of copper, sulphuric and hydrochloric acids scarcely acting upon it. 591. There are four oxyds of copper, suboxyd Cu a O, protoxyd CuO, binoxyd Cu0 3 , and an acid oxyd whose composition is unknown. The protoxyd, or black oxyd of copper, CuO, is the base of all the blue and green salts of copper. It is formed by decomposing the nitrate with heat. It is black and very dense, quite soluble in acids, and forms many important salts which are isomorphous with those of mag- nesia. It yields all its oxygen to organic matters at a red heat, and for this purpose is much used in their analysis. The suboxyd, or red oxyd of copper, Cu 3 0, is found native in beautiful octahedral crystals, and is also formed when copper is oxydized by heat. This oxyd communicates How found at Lake Superior ? What copper ores are named ? Give its equivalent and characters. What is the solvent of copper? 591. What oxyds of copper are known ? What relative to the black oxyd of copper ? Describe the suboxyd. COPPER. 347 to glass a magnificent ruby-red color. The chlorids and iodids of copper are of no great importance. 592. Sulphate of copper, blue vitriol, CuO.S0 3 -f-5HO, is an important salt, crystallizing in large, beautiful blue rhombs, which are soluble in four parts of cold and two parts of hot water. It loses its water by a gentle heat and falls to a white powder. It is much used in dyeing and for exciting galvanic batteries. With ammonia it forms a dark- blue crystallizable compound. 593. Nitrate of copper CuO.N0 5 -f-3HO is formed by dissolving copper in nitric acid to saturation, and is a deep- blue, crystallizable, deliquescent salt, very corrosive, and easily decomposed : a paper moistened with a strong solu- tion of this salt cannot be rapidly dried without taking fire, from the decomposition of nitric acid. The residues of operations for obtaining deutoxyd of nitrogen (341) afford an abundant supply of this salt in the laboratory. Ammonia detects the smallest traces of this metal in solution, by the deep violet-blue of the ammoniacal salt of copper which is formed. Iron precipitates it from its acid solution as a brilliant red coating. Copper is a metal most readily obtained in a metallic form from its solutions by voltaic decomposition. The sulphate is usually employed for this purpose in the electro- type, the arrangement be ing made like fig. 379, the operation of which has been already explained in section 234. The alloys of copper are much prized for their various useful applications in the arts. Brass is zinc , copper f . Dutch metal, of which thin leaves are made, contains Fig. 379. 10 to 14 of zinc. 592. Describe the sulphate of copper. 593. What is the nitrate ? How does it affect organic matter? How is copper detected? Why is cop- per used in electrotyping ? What of its alloys ? 848 METALLIC ELEMENTS. CLASS V. METALS WHOSE OXYDS ARE WEAK BASES OR ACIDS. 594. The five first metals in this class are so rare that we may pass them with a very brief mention. They are VANADIUM, TUNGSTEN, COLUMBIUM, TITANIUM, and MOLYBDENUM. Vanadium appears to be closely allied to chromium. The vanadic acid V0 3 forn^s salts with lead and copper, found native as vanadinite, and volborthite CuO.V0 3 . Tungsten , so named from its great weight, (12*11,) exists as tungstic acid W0 3 in wolfram and scheeletine CaO.W0 3 or tungstate of lime. Native tungstic acid has been observed in Monroe, Conn. : it is a yellow powder, soluble in ammo- nia, but insoluble in acids. Columbium, or tantalum, is the metal of a mineral called columbitc, (in allusion to its American origin, by Hatchett, its discoverer,) or tantalite, a salt of iron in which this metal is the acid. It forms two oxyds, Ta0 3 and Ta0 3 , both acids. It is with the columbite of Haddam that the two new metals, pelopium and niobium, are found, as described by Rose. Titanium is a copper-red metal, crystallizing in cubes. It forms with oxygen titanic acid Ti0 2 , a substance found pure in three distinct minerals, viz. rutile, anatase, and Brookite, an interesting case of trimorphism. This acid is soluble in strong chlorohydric acid, but precipitates, on di- lution and boiling, a white, insoluble powder, much resem- bling silica. It is used to give a yellowish tint to porcelain in preparing artificial teeth. Molybdenum is a white, slightly malleable, infusible metal, density 8-6. The sulpliuret is a common mineral distributed in primitive rocks: it resembles graphite. It forms with oxygen oxyd of molybdenum MoO, binoxyd Mo0 3 , and mo- lybdic acid Mo0 3 , which is its most important compound. Molybdic acid forms soluble salts with the alkalies, of which the molybdate of ammonia is the most valuable, being the 594. What is vanadium ? What is tungsten ? In what minerals found ? What is colurnbiurn? In what mineral found? What new metals have been found with it? What is titanium? What is titanic acid? What natural forms has it? How is molybdenum found in nature? What im- portant salt does it form ? TIN. 349 most delicate test known for phosphoric acid. Molybdate of lead is a beautiful native salt of this acid. Heat converts the sulphuret into the impure acid, and it is also oxydized directly by monohydrated nitric acid. TIN. ( Equivalent, 59. Symbol, Sn, (Stnanum.*) Density, 7 -29. 595. Tin is one of those metals which have been known from the most remote antiquity. The mines of Cornwall have been worked for the oxyd of tin since the times of the Phoenicians and Greeks. It has been found in this country only at Jackson, N. H., in small quantities. Tin is a white metal with a brilliant lustre, not easily tarnished, and resist- ing the action of acids to a remarkable degree. It is soft, very ductile, laminable, malleable, but of feeble tenacity. Tin foil is made of one-thousandth of an inch in thickness, or even much thinner. A bar of tin when bent gives a pe- culiar crackling sound, familiarly called the cry of tin, due to the disturbance of its crystalline structure. It is one of the best conductors of heat and electricity. 596. Tin has a density of 7*29, and fuses at 442. Its alloys are very valuable ; gun-metal (copper 90, tin 10) is one of the strongest alloys known, of a reddish-yellow; bell- metal (copper 78, tin 22) is a very sonorous and brittle alloy, of a pale yellow ', and speculum-metal (copper 70 to 75, and tin 25 to 30) is a hard, brilliant, almost white, aad ex- cessively brittle alloy. Pewter is a mixture of tin and anti- mony or lead. Tin-plate is only sheet-iron coated with tin. Chlorohydric acid dissolves tin with escape of hydrogen, forming SnCl. Strong nitric acid does not dissolve tin, but the addition of a little water to the acid causes a violent action, and the tin is speedily converted to stannic acid Sn0 3 . 597. There are two oxyds of tin : 1. The protoxyd SnO; and 2. The peroxyd Sn0 2 . There are numerous intermediate oxyds formed of these two. 1. This is obtained by preci- pitating a solution of protochlorid of tin with an alkaline 595. What history is given of tin ? What are its equivalent and genera* properties? 596. Give its density and fusibility? What is said of its alloys with copper? What is tin-plate and pewter? How does nitric acid affect it ? 597. What oxyds of tin are there ? What is the nrot- oxyd. 350 METALLIC ELEMENTS. carbonate, which yields a bulky hydrate ot the protoxyd It is a very unstable compound, passing into the peroxyd at a very moderate heat. 2. The peroxyd is found native in the beautiful crystallized tin stone. It may be obtained in a soluble and an insoluble condition. When the perchlorid is precipitated by an alkali, the bulky white precipitate of hydrated peroxyd which appears is easily soluble in acids; but if tin is acted on by an excess of moderately strong nitric acid, a white insoluble powder is formed, which is not acted on by the strongest acids. Heat converts both into a lemon-yellow powder, which dissolves in alkalies, but not in acids, and which is known as stannic acid : it reddens test-paper, and forms salts. The putty used to polish stone and glass is the peroxyd of tin 598. Protochlorid of tin SnCl which is prepared by dissolving tin in hot chlorohydric acid, is a powerful de- oxydizing agent, and reduces the salts of silver, mercury, platinum, &c., to the metallic state. The anhydrous proto- chlorid is formed by heating protochlorid of mercury with powdered tin. 599. Perchlorid of tin SnCl 3 is a dense fuming liquid, long known as the fuming liquor of Labavius. It is formed by distilling a mixture of 1 part of powdered tin and 5 of corrosive sublimate. The tin mordant used by the dyers is formed by dissolving tin in chlorohydric acid, with a little nitric acid, at a low temperature, or by passing chlorine gas through the protochlorid. The sulphurets of tin correspond to the chlorids. The bisulphuret (aurum musivum) is used as a bronze color for imitating gold in ornamental painting and printing, and also to excite electricity in the electrical machine, (166.) The alchemistic name for this metal was Jove, and the medicinal preparations of tin are still called jovial prepa- rations. BISMUTH. Equivalent, 208. Symbol, Bi. Density, 9-8. 600. Bismuthia found native, and also in combination with Describe the peroxyd. What two modifications of it are named ? How does heat affect them? What is "putty?" 598. How is protochlorid of tin employed as a reagent? 599. What is perchlorid of tin, and how prepared ? What is the tin mordant ? What sulphurets of tin are there ? What was its alchemistic name ? BISMUTH. 551 other substances. Native bismuth is found in the United States, at Monroe, Conn. It is a brittle, highly crystalline metal, of a reddish-white color, with a density of 9-8, and fuses at 507. It is obtained in large and beautiful obtuse .rhombic crystals, by fusing several pounds of bismuth in an earthen pot, purifying by successive portions of nitre, and leaving it to cool until a crust is formed on its surface, which is pierced by a hot coal and the still fluid interior turned out. The vessel will be lined with a multitude of brilliant crystals. It dissolves in nitric acid, but, like other metals of this class, does not decompose water under any circumstances. 601. Two oxyds of bismuth are known. The protoxyd Bi0 3 is formed by gently igniting the subnitrate. It is a yellowish powder, easily soluble in acids, and is the base of all the salts of bismuth. It is, however, a very feeble base, since even water decomposes its salts. The peroxyd Bi0 5 is not of much interest. 602. The nitrate of bismuth Bi0 3 .N0 5 -f 3HO is the most interesting of its salts. It may be obtained from a strong solution in large transparent crystals, which are decomposed by water. The solution of the nitrate of bismuth turned into a large quantity of water is immediately decomposed, with the production of a copious white precipitate of subni- trate of bismuth. This is owing to the superior basic power of the water, which takes a part of the nitric acid. The white precipitate is a basic nitrate Bi0 3 .N0 5 -f-3Bi0 3 HO. This white oxyd has been much used as a cosmetic. It blackens by sulphuretted hydrogen. 603. The alloy of bismuth, known as Newton's fusible metal, is formed of 8 parts bismuth, 5 parts lead, and 3 parts tin, and melts at about 208, (473.) It is much used in taking casts of medals. An alloy of 1 lead, 1 tin, and 2 bismuth, fuses at 200-75. The expansion of bismuth in cooling renders it a valuable constituent of alloys where sharpness of impression in casting is important. 600. What is the color and fusibility of bismuth ? Describe its crys- tals, and the mode of obtaining them. 601. How many oxyds has this metal? 602. What is the most interesting property of the nitrate ? What use is made of the subnirate? 603. What its the composition of Newton'fc fusible metal ? What more fusible alloy is named ? (552 METALLIC ELEMENTS. ANTIMONY. Equivalent, 129. Symbol, Sb, (Stibium.'} Density, 67. 604. This metal is derived chiefly from its native sul- phuret, which is a rather abundant mineral. The metal is obtained by fusing the sulphuret with iron-filings, or car- bonate of potash, which combine with the sulphur and set free the metal. It is a white, brilliant metal with a blue tint, forming broad rhomboidal crystalline plates in the com- mercial article, but fine granular if purified from foreign metals, which cause it to assume a coarse crystallization. It is very brittle, and, like bismuth, may be reduced to a fine powder. It fuses at about 842, and lower if quite pure : a high fusion point is a sign of its impurity. It is, in a cur- rent of hydrogen, entirely volatile, but alone and covered very slightly so. It dissolves in hot chlorohydric acid, but nitric acid converts it into the insoluble white antimonic acid. Its alloy with lead is type-metal, which, like the alloys of bismuth, gives very sharp casts, by reason of the expan- sion it undergoes at the moment of solidification, which forces the metal into all the fine lines of the mould. It is remarkable that both of the constituent metals shrink when cast separately. Finely powdered antimony is inflamed in, chlorine gas, forming the percblorid. 605. Two oxyds of antimony are known, viz : 1. Antimonic Oxyd, Sb0 3 . This oxyd may be obtained by digesting the precipitate from chlorid of antimony by water, with carbonate of potash or soda, or by burning anti- mony in a red-hot crucible; and also by subliming it from the surface of fused antimony in a current of air. It is a fawn-colored insoluble powder, anhydrous, and volatile when highly heated in a close vessel. Boiled with cream of tartar, (acid tartrate of potash,) it forms the well-known tartar emetic, which may be obtained in crystals from the solution. The glass of antimony is an impure fused oxyd, pre- 604. How is antimony obtained ? What are its properties? What of it? grain? Its fusion? Its alloys? C05. How many compounds does antimony form with oxygen ? What important salt does the oxyd form wit) ?otash? ANTIMONY. 353 pared for the purpose of making tartar emetic. Heated iu air, this oxyd gains another equivalent of oxygen, and forms 2. Antimonic acid Sb0 5 is formed, as already stated, when antimony is digested in an excess of strong nitric acid, or better in aqua-regia with nitric acid in excess. It dissolves in alkalies, with which it forms definite salts, that are again decomposed by acids, hydrate of antimonic acid being thrown down. The hydrate loses its water below a red heat, becoming a crystalline fawn-colored powder; and by a higher heat one equivalent of oxygen is expelled, anti- monious acid being formed. 606. There are chlorids and sulplmrets of antimony cor- responding to the oxyd and to antimonic acid. The terchlorid, butter of antimony, SbCl 3 , is made by distilling the residue of the solution of sulphuret of anti- mony in strong hydrochloric acid, (fig. 317.) When a drop of the distilled liquid forms a copious white precipitate on falling into water, the receiver is changed, and the pure chlorid is collected. It is a highly corrosive fuming fluid, and by cooling forms a crystalline deliquescent solid. It is used in medicine as a caustic. Water decomposes it, but it dissolves in hydrochloric acid unchanged : water poured into the solution throws down a bulky precipitate, which is a mixture of oxyd and chlorid of antimony, and has long been known by the name of powder of algaroth, SbCl 3 . 2Sb0 3 . The bromid of antimony is a crystalline volatile com- pound. 607. The tersulphuret of antimony SbS 3 constitutes the common commercial sulphuret, and the beautiful crystal- lized native mineral, antimony glance. The pentasulphuret of antimony SbS 5 is formed by boil- ing the tersulphuret with potash and sulphur, and throwing down the compound in question by an acid, as a golden yel- low sulphuret, known by the name of sulphur auratum t or golden sulphur of antimony. More generally, however, the decomposition on adding an acid, as above, gives us the oxysulphuret of antimony SbS 3 -|-Sb0 3 , which is a What is antimonic acid? 606. Describe the terchlorid? How de- decomposed ? 607. What is said of the sulphurets ? What are the golden sulphuret and kermes mineral ? 354 METALLIC ELEMENTS. characteristic reddish-orange precipitate. This is the sub- stance known as Jcermes mineral, and is an article of the older medical practice. The solution of sulphuret of anti- mony in caustic potash and sulphur is a case in which eulphuret of potassium is a sulphur base, and sulphuret of antimony a sulphur acid. The formation of tartar emetic with tartaric acid, and the production of the characteristic reddish-yellow sulphu- ret of antimony with sulphydric acid are the most signal tests of antimony. The sulphydrate of ammonia produces the same colored precipitate, but this is soluble in excess of the precipitant, as the former also is in the solution of al- kalies. The blowpipe also furnishes good evidence : when a bit of metallic antimony is fused under the oxyhydrogen blowpipe it volatilizes and burns, and if it be thrown on the floor or an inclined board, it scatters in numerous burning globules, whose path is marked by a white stain of oxyd of antimony. We will, under arsenic, mention how anti- mony is to be distinguished in cases of poisoning. ARSENIC. Equivalent) 75. Symbol, As. Density, 5*8. 608. Metallic arsenic is found native in thick crusts, called testaceous arsenic, evidently deposited by sublimation. It is, however, more usually obtained in the form of arseni- ous acid As0 3 , from roasting the ores of cobalt, nickel, and iron, with which metals it is often combined. Mispickel, a double sulphuret of iron and arsenic, is a great source for this metal. The vapors of arsenious acid given out in the roasting are condensed in a long horizontal chimney, or in a dome constructed for the purpose ; the first product being purified by a second sublimation. Arsenic is a brilliant crystalline steel-gray metal, brittle, and easily pulverized. In vessels free from air it may be sublimed unchanged at a temperature of dull redness. Its vapor is colorless, very dense, (10-37,) and has a remarkable odor, resembling garlic. The garlic odor is well perceived on subliming a fragment of What is the nature of this salt? What are the best tests of antimony? How does it act under the blowpipe? 608. How is arsenic found, and in what minerals? What are its properties? How is it sublimed un- changed? What is the density and odor of its vapor? ARSENIC. 355 arsenio or of arsenious acid from a live coal. It sublimes without fusion. It may, however, be fused in tight vessels under pressure of its own vapor. Metallic arsenic soon tarnishes in air and assumes a dull cast-iron look. It is sold by druggists under the absurd names of fly-powder, cobalt, and mercury names intended to deceive and likely to mislead, involving obvious danger. Metallic arsenic is easily obtained in distinct crystals by subliming the commercial metal, or arsenious acid, mingled with charcoal and carbonate of soda, or black flux, (484,) in a tube of hard glass, or, if a larger quantity is required, in a small retort. The mixture is put in a b, (fig. 380,) and heated to redness while the air is shut out. The metal rises and is deposited in a black metallic mirror in the cool part of the tube just above. Metallic arsenic is an active poison. It burns in the air with a blue flame, and it is also inflamed in chlorine gas. Fi s- 38 - 609. The oxyds of arsenic are, 1. Arsenious acid As0 3 , and 2. Arsenic acid As0 5 . 1. Arsenious Acid White Arsenic Ras-l>ane, As0 3 j This well-known and fearful poison is formed, as just stated, when metallic arsenic is sublimed in air, or when any of the ores of arsenic are roasted. This oxyd is what is usually meant when the term arsenic is used in commerce. When newly sublimed, it is a hard transparent glass, brittle, and with a density of 3*7. It slowly changes to a white opake enamel, resembling porcelain. This change is gradual, the vitreous portions being still found in the centre of the opake masses. As sold in commerce, it is usually reduced to a white powder, rarely found without adulteration. It sublimes at 380, without change, and crystallizes in bril- liant octahedrons, as may be well seen by slowly subliming a small quantity in a glass tube. Its vapor is inodorous, but if sublimed from charcoal it gives the peculiar garlic odor of metallic arsenic, being reduced to that state. It is soluble in about 10 parts of hot water, and is almost taste- less, with a faint sweetish flavor, which renders it the more How may it be fused? How does air affect it? What names has it? How obtained crystallized? 609. What oxyds does it form? Give formu- las. What is arsenious acid? What are its common names ? What are its characters ? What change does it suffer ? How does it crystallize ? How soluble ? What of its taste ? 356 METALLIC ELEMENTS. dangerous poison, since no warning is given to the victim who takes it, as in case of most other metallic poisons. The vitreous acid is three times as soluble as the opake. The solution in water is acid to test-paper, and deposits nearly all its arsenic in crystals on cooling, retaining 1 part to 30 of water. Chlorohydric acid dissolves arsenic, and if a solution of 4 parts As0 3 in 6 of HC1 and 2 of water is slowly cooled from boiling, the As0 3 is deposited in trans- parent octahedrons, and if in the dark, the formation of each crystal is accompanied by a spark, and sometimes the light produced is such as to illuminate a dark room. The alka- lies dissolve arsenic, but do not form crystallizable salts with it. Arsenious acid contains As 75-75, 24-25. 610. Arsenic Acid, As0 5 . This acid is formed by adding nitric acid to the solution of white arsenic in hydrochloric acid, as long as any red vapors of nitrous acid show them- selves, and then carefully evaporating the solution to entire dryness : a white porous subcrystalline mass remains, which is slowly soluble in water. Its solution is a powerful acid, quite similar in chemical characters to phosphoric acid. The analogy is so great that there is a complete similarity in con- stitution, and even in external appearance, between all the salts of these two acids. For every tribasic phosphate we have an arseniate, not only similar in constitution, but iso- morphous, and so resembling it in all its external properties as not to be distinguished by the eye. Thus the tribasic phosphate of soda (512) and the tribasic arseniate of soda, are Phosphate of soda H02NaO.PO l -f-24Aq. Arseniate of soda H02NaO.AsO-f-24Aq. These, and many other facts, lead to the opinion that the elements are themselves isomorphous; and in fact arsenic has no claim to the metallic character but its lustre, being in chemical properties and natural affinities associated with phosphorus. 611. The clilorid of arsenic AsCl 3 is a fuming volatile liquid, decomposed by water, and very poisonous. The bromid and iodid are both crystallizable solids, also decom- posed by water. What is said of its chlorohydric solution ? 610. How is AsO formed? What are its properties? What analogy has it with P0 ? To what opinion do these facts lead ? 611. What of chlorid of arsenic ? ARSENIC. 357 The sulphurets of arsenic are natural compounds, used as pigments, and also in pyrotechny. The first, AsS 2 , is a red transparent body, called realgar, and AsS 2 is the golden- yellow orpiment. Both these substances are found native^ and are usually associated. They are brought from Koor- distan in Persia, and from China. The Mohammedans use the yellow orpiment as a depilatory in their ceremonial puri- fications. Two higher sulphurets may be formed, which are AsO s and As0 9 : the former is the product thrown down by sulphuretted hydrogen in a solution of arsenic. The sulphurets are soluble in alkalies and in sulphydrate of am- monia. 612. Arseniuretted Hydrogen, AsH 3 . This is a gas pro- duced by the action of dilute sulphuric acid on an alloy of zinc and arsenic, or by the evolution of hydrogen in presence of arsenic or arsenious acid. Figure 381 shows the ordinary gas evolution bottle A, in which are the materials for producing hydrogen. An arsenical solution poured in at n m, immediately changes the color of the flame at 6; before colorless, it now becomes of a peculiar blue, and evolves a cloud of arsenious acid, Fig. 381. or deposits metallic arsenic on a cold surface. Marsh's test for arsenic depends on the generation of this gas. It is a virulent poison of the most active description. This gas is readily absorbed by a solution of sulphate of copper, and precipitates an arseniuret of that metal. Its density is 2-69 : it has a peculiar disgusting odor, and is decomposed by heat alone with deposition of metallic arsenic. It is liquid at 22F. : water dissolves it slightly, and chlorine completely decomposes it with- flame. Detection of Arsenic in Poisoning. 613. The too frequent use of arsenic as a means of destroy- ing human life renders it of the greatest moment to know certain processes for its detection. Arsenic is almost always What are the sulphurets ? 612. What is arseniuretted hydrogen ? How produced? What of its flame? What are its properties? 613. What of arsenical poisoning ? S58 METALLIC ELEMENTS. fatal when it lias time to become absorbed by the circulation in sufficient quantity. The most reliable antidotes which have been proposed are the moist hydrates of sesquioxyd of iron and of caustic magnesia. With both these arsenic forms insoluble salts. The alkalies, being solvents of arsenic, only increase the danger by favoring absorption. We enumerate a few of the tests for arsenious and arsenic acids : 1. Sulphydric acid produces in acid or neutral solutions of As0 3 and As0 5 a rich orange-yellow precipitate, (orpi- ment,) soluble in ammonia and alkalies, and in sulphydrate of ammonia, but precipitated again by acids. 2. Nitrate of silver and ammonia-nitrate of silver pro- duce in solutions of arsenious acid a lemon-yellow precipitate, (arsenite of silver,) soluble in nitric acid. In solutions of arsenic acid they produce a brick-red precipitate. 3. Ammonia-sulphate of copper gives a brilliant green precipitate (Sdieelds green) in alkaline or neutral solutions of arsenious acid, which precipitate (arsenite of copper) is soluble in excess of ammonia. 4. A slip of Iriyht metallic copper, placed in a boiling solution of arsenic or arsenious acid made acid by chloro- hydric acid, is soon coated with a gray deposit of metallic arsenic. This is called Reinsch's test, and is applicable even in presence of organic matters which vitiate, partially or wholly, the previous tests. 5. Reduction of the metal from the oxyds or sulphurets is justly esteemed in judicial investigations as the most reli- able of all- tests. This is accomplished by several modes. The oxyds or sulphurets are min- gled with finely-powdered charcoal and carbonate of soda or cyanid $T^ of potassium and placed in a small tube a d (fig. 382) of hard glass. The part a b is heated red hot, Fl S- 3S2 when, if arsenic is present, it is sublimed in a black metallic mirror at c. A small tube is used, because in many cases very minute portions are ope- What are antidotes, and why ? How does sulpbydric acid act as a test of arsenic ? How nitrate of silver and ammonia ? How ammonia-sul- phate of copper? What is Reinsch's test? What of the reduction pre- ferred? Describe from fig. 382. ARSENIC. 859 Fig. 383. rated on. In order to prove the character of this ring, the tube is broken off at b, (fig. 383,) and the flame of a spirit-lamp applied cautiously while the tube is gently inclined. A current of air passing over the ring of metal converts it to arsenious acid, which lines the cooler parts of the tube with email brilliant octahedrons of a size visible by a magnifier. If further proof were required, a current of sulphydric acid will convert the white crust into yellow orpiment, wholly soluble in ammonia, precipitated by chlorohydric acid, and insoluble in that menstruum. 6. Marsh's test, by means of arseniuretted hydrogen, gives unequivocal testimony when arsenic is present. Fig. 384 shows a convenient form of the apparatus used for this purpose, which is more simply arranged as in fig. 381. This apparatus has the conve- nience of a cock to regulate the escape of the gas. The zinc is in the lower bulb the acid water and suspected substance are introduced by the upper bulb. The zinc and all the materials employed must be scrupulously ex- amined as to freedom from arsenic. For this purpose the flame of hydrogen muse not give the least spot upon clean porcelain. On adding the arsenical solution, however, the flame be- comes livid, larger, gives off white vapors, and deposits a tache or spot, in the form of brown- Flg> 384> black mirror, on the surface of porcelain, as in fig. 385. Antimony gives a similar spot, which is liable to be con- founded with that from arsenic. It is, however, more sooty- black. Exposed to vapor of iodine in a small capsule, anti- mony spots turn reddish orange, while arsenic spots appear orange yellow, and soon vanish entirely. Exposed for a moment to vapor of chlorine given off from bleaching-pow- ders in a capsule, the spots being on the underside of the cover of the same, the spots disappear. If a drop of nitrate of silver be then let fall on the flat surface, if arsenic was How is itoxydizedin fig. 383 ? What further proof may be had? What is Marsh's test ? Describe fig. 384. What care is required ? What eft'ect is seen on introducing an arsenic solution ? What gives a similar spot ? How are the spots distinguished ? How by chlorine and nitrate of silver ? 360 METALLIC ELEMENTS. present there will be a brick-red stain visible, amounting to a precipitate if much of the metal existed while antimony does no such thing. These distinctions are conclusive. The arrangement of Marsh's apparatus recommended by the commission of the Paris Academy, in cases of judicial investigation, is shown in fig. 385. The evolution bottle A Fig. 385. is provided with a bulb-tube a I, to retain moisture, which is more effectually removed by the chlorid of calcium tube c d. The gas is conducted through the horizontal tube f y, ter- minating in a jet-point, where the taclie of the flame can be received upon a clean porcelain surface C. As heat decom- poses the arseniuretted hydrogen, means are provided to heat the tube while the gas is passing, the radiant heat being cut off by a screen c. In this case the metallic arsenic appears in a ring at /, while the flame loses its peculiar character, and no taclie is seen at y. The ring so obtained may be subsequently tested as before indicated, as well also as the tache. The cause of the tache will appear on a moment's attention. Calling to mind what was said on the structure of flame, (460,) it is obvious, by reference to fig. 386, showing a larger view of the jet <7, (fig. 385,) that . the part d c' must contain ' the reduced arsenic in hot hydrogen gas, surrounded by the burning envelope a c I. Now the porcelain Pig - 386 ' surface is held in the line Des'cribe fig. 385. What does the heat accomplish ? How is the tache btained in fig. 385 ? MERCURY. 361 z x, and must receive the metallic mirror, if any arsenic is present. 614. In most cases of arsenical poisoning it is required to search for proof in the mass of organic matters ejected by the patient, or in the tissues of the body itself; and either case requires all organic matters to be destroyed before tests can be applied. This may be done in a great majority of cases by oxydizing and charring the whole mass to be treated, cut small, in a porcelain capsule, with a mixture of strong nitric acid and oil of vitriol. These are added in small quantity, and gentle heat applied until the coaly mass is nearly dry. Water is then added, and the whole thrown upon a filter and washed : the filtrate contains all the arsenic and other metals. Marsh's, Reinsch's, or any of the other tests just enumerated may then be applied. Such is a very brief ac- count of the most valuable modes of examination in cases of poisoning by arsenic. Further details would be out of place here. CLASS IV. NOBLE METALS: WHOSE OXYDS ARE RE- DUCED BY HEAT ALONE. MERCURY. Equivalent, 100. Symbol, Hg, (Hydrargyrum?) Density, 13-596. 615. This is the only metal which is fluid at ordinary temperatures. It is found as native, or running mercury, in Spain and Carniola, and also as cinnabar, or sulphuret of mercury. In Upper California a very large deposite of cin- nabar has lately been opened. It is also found both in Mexico and Peru. The alchemists supposed it to be silver enchant- ed, (quicksilver,*) and made many efforts to obtain from it the solid silver it was supposed to contain. Pure mercury is* a silver-white, fluid metal, unchanged by air, and very brilliant. Cooled below 3944, as by car- bonic acid, (150,) it solidifies, and is then as malleable as lead. It crystallizes in cubes. It boils at 662, and forms a colorless vapor, of the density 6-976. Even at 32, a 614. How is proof obtained in case of organic matters being present? What agent of oxydation is used? How is the testing carried on ? What are noble metals? 615. What of mercury? How found? Why called quicksilver ? What arc its properties ? 362 METALLIC ELEMENTS. very rare vapor rises from it, as is evident from the effect on claguerrian plates. If heated in the air at or above 600, it slowly passes to the condition of red oxyd of mercury, which is its highest combination with oxygen. By this ex- periment Lavoisier proved the composition of air, and per- formed the first recorded chemical analysis. 616. The uses of mercury are numerous and important in the arts, and also in medicine. It forms alloys (amalgams) with many other metals ; with tin it constitutes the brilliant coating of glass mirrors, (called silvering,) and it is of indis- pensable importance in procuring gold and silver from their ores, and in gilding by the old process. Its use in filling thermometers and barometers has already been noticed. It expands by each degree of Fahr. 37^ of its bulk, in heat- ing from 32 to 212, and at nearly the same ratio for the whole scale of 662. 617. The purity of mercury is roughly judged of by its forming no film on glass, and by its breaking into small globules, which should preserve their spherical form, when they run from an inclined surface. If they form a queue, or drag a tail, as the workmen express it, it is owing to the presence of lead or some other similar impurity. It may be purified from all non-volatile ingredients by Fig. 387. distillation in an iron bottle A, (fig. 387,) formed of one of the iron flasks in which quicksilver is imported. This is What of its volatility? 616. What are its uses? What fits it spe- cially for thermometers ? What is its rate of expansion ? 617. How it its purity judged of? How is it purified ? Describe fig. 387. MERCURY. 363 completely enclosed in the furnace, and the tube 5 c con- nects with a bag of leather or caoutchouc, reaching to a basin of water, and kept cool by a stream of water from the cock r. The tension of its vapor is very small, so that it quickly returns to the fluid state, thus producing a great commotion in the process of boiling. The distilled mercury is only partly purified, and the process must be completed by the action of dilute nitric acid at a gentle heat, which unites to form nitrate of mercury with a part of the mercury. This salt reacts with the other portion of the mercury to form nitrates of all other metals which may be present. After a day or two, with frequent agitation, the action is complete, the water is evaporated at a gentle heat, and the crust of nitrate of mercury removed. The remaining mercury, now quite pure, is washed with much water and dried. Mercury may be so finely divided by agitation and other mechanical means, as to lose its metallic appearance entirely, as in blue pill, mercurialized chalk, (creta cum hydrargyrof) and mercurial ointment, which do not, as has sometimes been stated, contain the suboxyd of mercury, but only mercury in a state of very minute mechanical division. Nitric acid dissolves mercury very rapidly even in the cold : hydrochloric acid scarcely acts on it, and sulphuric only by the aid of heat, when it forms an insoluble sul- phate of mercury, evolving sulphurous acid. The equiva- lent of mercury is often stated at 200, on the supposition that the gray oxyd is the protoxyd ; but this seems to be more properly considered as a suboxyd, and the real pro- toxyd as the red oxyd. On this view the equivalent is stated at 100. 618. The gray, or suboxyd of mercury, Hg 3 0, is formed by digesting calomel in caustic potash, or by adding the same reagent to a solution of the nitrate of the suboxyd of mercury. It is an insoluble, dark gray powder, which is easily decomposed into metallic mercury and the red oxyd, Hg 9 6 = HgO+Hg. The red oxyd, or protoxyd, red precipitate, HgO, is prepared in the large way by heating the nitrate very cau- tiously until it is quite decomposed, and a brilliant red How is the purification completed ? How does mechanical action af- fect it? Give examples. What dissolves it? How does S0 3 affect it? What of its equivalent ? 618. How is suboxyd formed ? How decom- posed ? How is the red oxyd formed ? What is precipitate per se ? 364 METALLIC ELEMENTS. crystalline powder produced. It may also be formed bj heating metallic mercury for a long time in a glass vessel nearly closed, and in this form is the preparation to which the old name of red precipitate per se was applied. Heat decomposes this oxyd, into oxygen and metallic mercury. It is, like the oxyd of lead, slightly soluble in water, and gives to it an alkaline reaction. It is a poison, and is used externally as an irritant and escharotic. 619. The chlorids of mercury correspond to the oxyds, and are both very important compounds. 1. Subcklorid of Mercury, (Calomel,) Hg 3 CL This well- known medicine is formed by precipitating a solution of sub- nitrate of mercury with common salt. A white, insoluble, taste- less powder falls, which is the calomel. Even strong acids, when cold, do not affect it ; but it is instantly decomposed by alkalies, and the suboxyd produced. Heat sublimes it unchanged. Its complete insolubility at once distinguishes this safe and mild substance from the highly poisonous corrosive sublimate. It should be in very tine powder for medical use, as then the presence of corrosive sublimate is easily detected in it by imparting its taste to water. Its freedom from adulteration may be determined by heating it on the surface of a clean spatula, when it should volatilize unchanged without leaving any residue. It is obtained by slow sublimation, in beautiful transparent crystals square prisms with octahedral summits. Its density is 6-5, and in vapor 8-2. Vapor of calomel is composed of 1 volume of mercury vapor 6 4 976 i volume of chlorine 1*220 1 volume of calomel vapor.. Hg a Cl 8'196 Calomel is decomposed by nitric acid, forming corrosive sublimate and nitrate of protoxyd of mercury. Ammonia turns it to a gray powder, which is an amid and chlorid of mercury Hg ? Cl.HgNH 3 . 2. Corrosive Sublimate, or Chlorid of Mercury, HgCl. This salt is most economically prepared by the decompo- sition of sulphate of mercury, by common salt, whose How does heat affect it? How is it used? 619. What of the chlo- rids? What is the name of the subchlorid ? How formed ? What are its properties ? What of its state and purity ? Its density ? What is the constitution of its vapor? What decomposes it? What is corrosive sublimate ? MERCURY. 365 simple interchange gives corrosive sublimate and sulphate of soda, HgO.S0 8 +NaGl = HgCl-|-NaO.S0 8; The chlo* rid is also formed by dissolving the red precipitate in hot chlorohydric acid. Corrosive sublimate is a very heavy crystalline body, soluble in about 16 parts of cold water, and in two or three parts of hot, giving a solution which possesses the most distressing and nauseous metallic taste, and is a deadly poison. It is soluble in alcohol and ether. It melts at 509 and sublimes at about 563. Its vapor has a density of 942, and contains 1 volume of vapor of mercury 6-967 1 volume of chlorine 2-440 1 volume HgCl 9-407 Albumen completely precipitates it, and the whites of eggs or milk are therefore antidotes for this poison. For the same reason it is, doubtless, that timber and animal sub- stances are preserved from decay, as in the kyanizing pro- cess, by steeping in solution of corrosive sublimate. The albuminous portions of wood suffer decay sooner than the vegetable fibre, and these are rendered completely inde- structible in the process of Mr. Kyan, which is now in use in our national shipyards. Ammonia produces in solution of corrosive sublimate (and also in those of other salts of protoxyd of mercury) a white bulky precipitate of uncertain composition, and long known as white precipitate. It is regarded as a double amid and chlorid of mercury Hg 3 Cl.NH a . 620. There are two iodids of mercury, Hg 3 I and Hgl. The second is a brilliant scarlet-red precipitate, formed by adding solution of iodid of potassium or hydriodic acid to a solution of corrosive sublimate. The iodid is at first yellow, but soon passes by molecular change into the splen- did scarlet crystalline powder before noticed. It cannot be used as a pigment on account of its instability. Two sulphurets of mercury exist Hg 2 S and HgS, the first of which is a black powder, formed when sulphuretted hy- drogen is passed through a solution of subnitrate of mercury. The sulphuret HgS, or cinnabar, is formed when the nitrate How procured? Give the formula. Give its properties. What is the density of its vapor? What is an antidote for it ? What is kyanizing? What is white precipitate ? 620. What iodids of mercury are there ? What sulphurets ? 366 METALLIC ELEMENTS. of mercury (nitrate of the red oxyd) is treated with sulphu- retted hydrogen. It is a black precipitate, but turns red when sublimed, and forms the familiar pigment, vermillion. This is the common ore of the quicksilver mines. Salts of Mercury. 621. The salts of protoxyd of mercury HgO are colorless, but the basic salts are yellow. The Nitrates of Mercury. The action of nitric acid on mercury varies with the temperature and the strength of the acid. In the cold, dilute nitric acid dissolves mercury, forming a neutral nitrate of the suboxyd ; but if the mercury is in excess, a salt is deposited in large and transparent white crystals, which is a nitrate with excess of base. If hot and strong, the nitrate of the red oxyd is formed, which is a very soluble salt, not crystallizable. A basic salt of this oxyd may also be formed, which is decomposed by water. Sulphate of mercury HgO.S0 3 results as an insoluble white subcrystalline powder, by the action of the strong acid on metallic mercury, sulphurous acid being evolved. Boil- ing water decomposes this salt, removing a part of its acid, by which a yellow basic sulphate is formed, known as tur- peth mineral. Its composition is 3HgO.S0 3 . The sulphate of the gray oxyd Hg a O.S0 3 is formed as a crystalline white powder, by treating a solution of subnitrate of mercury with sulphuric acid. It is slightly soluble in water. Fulminat- ing mercury and other cyanids are described in the organic chemistry. All the compounds of mercury are volatile at a red heat ; and those which are soluble whiten a slip of clean copper, by depositing metallic mercury on its surface. SILVER. Equivalent^ 108. Symbol, Ag. (Argentum.} Density, 10-5. 622. The mines of Mexico and of the Southern Andes furnish most of the silver of commerce, although many mines of this metal are found in Spain, Saxony, and the Hartz Mountains. Galena, or the native sulphuret of lead, is also What is vermilion? 621. How are the nitrates of mercury obtained? What is the nature of the nitrate of the red oxyd ? How is the sulphate formed? What are the characteristics of mercurial compounds? 622. From what sources is silver obtained ? SILVER. 367 a constant source of silver, as it is never quite free from this precious metal. Silver is often found native. It is more usually in combination with sulphur and antimony. The brilliant lustre and white color of this valuable metal are familiar to all. It is perfectly ductile and malleable, and in hardness stands between gold and copper. For the pur- poses of economy and in coinage it is essential to alloy it with about T ^ part of copper, to render it sufficiently stiff and hard. It is one of the best conductors of heat and electricity, and its surface reflects light and heat more per- fectly than any other metal. It is used for this reason in reflectors ; and hot fluids longer retain their heat in vessels of silver than in any other. It remains untarnished in air free from sulphur gases ; from these it gains a brown-black sur- face of sulphuret of silver. It does not combine with oxygen when heated in it ; but fused silver absorbs even twenty times its volume of oxygen, parting with it again on cooling. It is slightly volatile even in the furnace, but in the carbon crucible of the galvanic focus (fig. 169) it volatilizes com- pletely. It crystallizes in cubes often very beautifully modified. It fuses at 1873; and, owing to its absorption of oxygen and disposition to contract in the mould, it is a difficult metal to cast. Nitric acid dissolves silver in the cold with great rapidity, and if it contains any gold, this is left undissolved as a brown powder. Solution of coin alloy appears green, from the copper it contains. Hydrochloric acid scarcely acts on silver, and sulphuric acid only when hot, forming the sparingly soluble sulphate. Silver is obtained pure from its solution in nitric acid by precipitation with metallic copper, as a finely-divided crys- talline powder ; also by decomposing its chlorid by fusion with two parts of dry carbonate of potash. 623. Silver is parted from alloys of copper and from argen- tiferous lead by the process of cupdlation. This depends on the oxydation of* the base metal in a current of heated air, and the absorption of these oxyds by the cupel. This is made of bone-ashes, and compacted in a mould into the form of fig. 388 ; seen in Fig. 3SS. What are the properties of silver? What does fused silver absorb? How volatile? What of coin ? What dissolves it? What separates me- tallic silver from its solution? 623. What is cupellatiori ? Describe thy cupel. 368 METALLIC ELEMENTS. section in fig. 389. The bone-ash does not fuse at tne most intense heat of the cupellation furnace. The cupels are of various sizes, according to the weight of the assay. In metallurgic art they are employed Fig. 389. in the final purification of silver-lead, of immense size, constructed on a hearth of bricks. Those here figured are small, and are heated in a muffle, or low oven-shaped ves- sel, (fig. 390,) set in the cupellation furnace, as shown in section A, (fig. 392.) Several cupels are accommodated on its hearth, Fig. 390. while the air entering its mouth D, partly closed by E, draws over the surface of the fused assay, and out at the lateral slits A in the muffle, thus oxydizing the Fig. 392. Fig. 391. lead. Fig. 391 is a general view of the cupellation furnace, which is formed of three parts, united where the bands are shown. The sectional drawing (fig. 392) indicates more clearly the relations of the parts. Small charcoal is fed to the fire Or at F, and the- ignited coal finds its way to B, where it rests on the hearth E. To aid this descent, an iron rod What is the muffle? Describe the process and figs. 391 and 392. SILVER. 369 is introduced from time to time at o o, (fig. 391.) The opening I H regulates the draft, which is suspended by open- ing F G. The muffle is thus heated very intensely, and the condition of the assay is observed from time to time by re- moving E. M is the draft-pipe, and N a sheet-iron shelf to receive the hot cupels. Pure metallic lead is usually added to the alloy to be cupelled, to several times its weight. The oxyd of lead is absorbed as fast as it is formed, carrying with it oxyd of copper and other impurities into the porous bone-ash. Finally, at the close of the process, the globule of silver flashes into a perfectly polished sphere or button of a white color. This is one of the most ancient and valu- able of metallurgical operations, and is equally applicable to gold and its alloys as to silver. By this process all the currency of the world is regulated, in connection with the process of solution in nitric acid, and precipitation by a stand- ard solution of salt, which is known as Gay-Lussac's wet assay in distinction from cupellation, which is called the dry method. 624. Much of the lead of commerce contains too little silver to allow an economical use of the process of cupellation. The silver is then separated by Pattinson's process, as it is called, founded on the fact that the alloy of silver and lead is more fusible than pure lead; and the latter, on cooling, separates in small crystals, which can be skimmed out of the richer lead by an iron cullender. This process enables the metallurgist to remove with profit even so small a proportion as six ounces of silver from a ton of lead. The small portion of rich lead is then cupelled. 625. Three oxyds of silver are known by chemists : the suboxyd Ag 2 ; the protoxyd AgO ; and the peroxyd AgO a . We will now notice only the protoxyd. This is formed when the solution of silver in nitric acid is saturated with caustic potash, or when the chlorid of silver, recently pre- cipitated, is digested in a solution of caustic potash of den- sity 1-3. It is a dark-brown or black powder, if prepared by the first mode, or quite black and dense by the second process. It is a base, forming well-defined salts. Ammonia How does the button appear at the consummation of the process? What is the wet and what the dry assay ? 624. What is Pattinson's pro- BOSS ? 625. What oxyds of silver are there ? How is AgO formed ? What are its properties ? 24 370 METALLIC ELEMENTS. dissolves it readily, and it is also somewhat soluble in water, to which it gives an alkaline reaction. The solution of oxyd of silver in cyanid of potassium forms the silver-plating so- lution in this branch of electro-plating. The oxyd is easily reduced by heat alone, and by the contact of organic matter. 626. Chlorid of silver AgCl is formed when any soluble salt of silver is treated with a soluble chlorid or with chlo- rohydric acid. This substance fuses at a moderate red heat into a transparent pale-yellow fluid, which is horny and tough when solid, and hence called horn silver, a form in which this metal is sometimes found in mines. It is very sensitive to light, turning dark and finally black, especially in contact with organic matter in sunlight. It is easily reduced to the metallic state by the nascent hydrogen gene- rated when zinc is acted on by dilute sulphuric acid in con- tact with the chlorid. Pure silver and chlorid of zinc result ; or it may be reduced by fusion with twice its weight of car- bonate of soda or potash, (622.) The iodid and bromid of silver are, like the chlorid, inso- luble in water, and very sensitive to light. The daguerreo- type and calotype are both dependent on the sensitiveness of these compounds to light, for the accuracy and beauty of their results. The sulphurets of silver are found native, and the tarnish which blackens silver articles on long exposure, is formed by sulphuretted hydrogen in the air. 627. The nitrate of silver AgO.N0 5 is a salt which crys- tallizes in beautiful flattened tables of an hexagonal form, soluble in half their weight of hot water. By heat it fuses, and, when cast in cylindrical moulds, forms the slender sticks called lunar caustic, so much used by the surgeon. Its solution has a disgusting metallic taste, even when very dilute. It is a most delicate test of the presence of chlorine or of any of its compounds. It blackens rapidly in contact with organic matter when exposed to the light, and forms an indelible ink, which is much used in marking linen. Solution of cyanid of potassium will remove the stain pro- duced by nitrate of silver. Metallic copper at once throws down metallic silver from the nitrate, and solution of nitrate 626. Describe the chlorid. How can it be reduced? What are tho relations of the silver compounds to light? What is the action of sul- phuretted hydrogen on silver ? 627. Describe the nitrate. What is lunar caustic ? What are its reactions ? GOLD. 37i of copper is formed. Mercury precipitates metallic silver from a dilute solution, in beautiful tree-like forms, called arlor Diance. Ammonia, by acting on precipitated oxyd of silver, forms a fulminating compound. It is extremely hazardous to deal with, as it explodes even when wet. The fulminating silver produced by the reaction of alco- hol, nitric acid, and silver, will be described in the Organic Chemistry. GOLD. Equivalent, 98-7. Symbol, Au. Density, 19-26. 628. This valuable metal is found only in the metallic or native state, being very widely diffused in small quantities in the older rocks. From these, by the action of various causes, it finds its way into the sand of rivers, and is dis- tributed in small quantities, in many widespread deposits of coarse gravel or shingle, as in Alta California, Australia, on the eastern flanks of the Ural mountains, and over a wide belt of country in Virginia, the Carolinas, Georgia, and Ala- bama. These diluvial deposits furnish nearly all the gold of commerce, by the process of washing and amalgamation with mercury. Large masses of gold sometimes occur, as one of twenty-eight pounds in North Carolina. In Si- beria a mass was found, now in the Imperial Cabinet of St. Petersburg, weighing nearly eighty English pounds. Several of still greater size, mingled with quartz, have been found in California. Generally, however, it occurs only in minute rounded and flattened grains or scales. It is also found in veins of quartz, in compact limestone, and distributed in iron pyrites. Native gold is usually alloyed with from 5 to 15 per cent, of silver. Since the discovery of gold in California, in March 1847, it is estimated that at least fifty millions of dollars have been annually obtained there, chiefly from the auriferous sands of those regions. 629. Gold is distinguished by its splendid yellow color, its brilliancy, and freedom from oxidation, by its extreme malleability and ductility, by its high specific gravity, (19-26 to 19-5,) and by its indifference to nearly all reagents. It What is the arlor Diance ? 628. How does gold occur in nature ? How t& it obtained? What of California ? 629. Describe this metal ? 372 METALLIC ELEMENTS. fuses at 2016 F., and is dissolved only by aqua regia, (420,) chlorine, nascent cyanogen, and by selenic acid. The first is the solvent commonly known, and yields perchlorid of gold. 630. Gold forms two very unstable oxyds, Au 2 and Au 3 3 , which are decomposed even by light. Two corre- sponding chlorids exist. The perchlorid is a very deliques- cent salt, forming a red crystalline mass, soluble in ether, alcohol, and water. Metallic gold is deposited in elegant crystalline crusts from the ethereal solution of the chlorid. Ammonia throws down from solutions of gold an olive- brown powder, fulminating gold, which, when dry, explodes with heat, or by percussion. 631. The solution of protosulphate of iron throws down gold from its solutions in a very fine brown powder, which, when diffused in water, is green, as seen by transmitted light. The protochlorid of tin forms a characteristic purple preci- pitate in gold solution, called the purple of 'Cassius, which is used in porcelain-painting, and is probably a compound of the oxyds of tin and gold. Gilding of ornamental work is usually performed by gold-leaf; but other metals are gilded, either by applying it as an amalgam with mercury, the mercury being afterward expelled by heat, or preferably by the new process of galvanic gilding from a solution of the double cyanid of gold and potassium. Gold wash, as it is called, is applied by a mixture of carbonate of soda or potash in excess, with oxyd of gold, in which small articles cleansed in nitric acid are boiled, and thus become perfectly covered with a very thin film of gold. 632. PALLADIUM, Pd. This very rare metal is usually as- sociated with gold, being found in a native alloy of gold and silver from Brazil. It is a white metal, more brilliant than platinum, very infusible, malleable, and ductile. It is, how- ever, fused by the compound blowpipe. It gains a blue tarnish, like steel, by heating in the air, which it loses by a white heat. In hardness it is equal to fine steel, and it does not lose its elasticity and stiffness by a red heat. Its density varies from 10-5 to 11-8. It suffers no change by exposure What is its usual solvent ? 630. How many oxyds of gold are there ? Describe the perchlorid. 031. What tests distinguish gold? How ia gilding effected ? 632. What of palladium ? What peculiar properties Us it? PLATINUM. 373 in the air. It gives a peculiar and beautiful color to the surface of brass when applied in the electro-metallurgical process. Its equivalent is 53-3. Its qualities would render it a vety valuable metal if it could be obtained in a sufficient quantity. Nitric acid dissolves it slowly, but aqua regia more rapidly. It forms two oxyds and two correspond- ing chlorids. PLATINUM. Equivalent, 98-7. Symbol, PL Density, 19*70 to 21-23. 633. Platinum is a very remarkable metal, and, if abun- dant, would be extensively useful in domestic economy. It is found native in the gold-workings in South America, and in Siberia on the eastern slope of the Urals. No ore of platinum is known except its alloy with gold, and those with iridium, osmium, and rhodium. Platinum is a white metal, between tin and steel in color, but harder than gold or silver, and, unless quite pure, is, when unannealed, nearly as hard as palladium. A very little rhodium or iridium renders it more gray in color and much harder. If pure it is very malleable, especially when hot, and can then be imperfectly welded. Its ductility and tenacity are remarkable ; but its most valuable property is its infusibility, which is so great that the thinnest platinum foil may be safely exposed to the most intense heat of a wind furnace. It is soluble only by aqua regia. It alloys readily with lead, iron, and other base metals, so that great care is needed in using platinum vessels, not to heat them in contact with any metal or metallic oxyd with which they combine. Caustic potash, and phosphoric acid, in contact with carbon, will also act upon platinum at a red heat. This is a most useful metal to the chemist, and vessels of plati- num are quite indispensable in the operations of analysis. Large retorts or boilers are made of it for the use of manu- facturers of sulphuric acid, holding sometimes sixty or more gallons. In Russia it has been employed in coinage, for which by its great density and hardness it is well suited. When recently fused by the compound blowpipe or the gal- 633. What is the history of platinum ? Describe its characters and ics ? What of its density ? 374 METALLIC ELEMENTS. vanic focus, its density is about 19-9, which is increased to 21*5 by pressure and heat. 634. Platinum is obtained pure by digesting crude plati- num in aqua regia, and adding to the deep- brown liquid a solution of chlorid of ammo- nium : this throws down an orange-colored precipitate, which is a double chlorid of plati- num and ammonium. This precipitate is reduced by heat to the metallic state, a porous dull-brown mass, commonly known as platinum sponge. All the platinum of com- merce is treated in this way. The sponge is condensed in steel moulds, like fig. 393, by heat and pressure, and when compact enough to bear the blows of the hammer, is heated and forged until it is perfectly tough and homogeneous. The follower K is driven down by the hammer upon the platinum sponge confined in the steel seat c b. Spongy platinum is a very remarkable sub- stance, having, as already noticed, (409,) power Fig. 393. ^0 cause the combination of hydrogen and oxygen, and to effect other chemical changes without being itself altered. Platinum black is a still more curious form of this metal. It is formed by electrolyzing a weak solution of chlorid of platinum, when the black powder appears on the negative electrode. The silver plates in Smee's battery (192) are prepared in this way. It is also prepared by adding an excess of carbonate of soda, with sugar, to a solution of chlorid of platinum, and gradually heating the mixture to near 212, stirring it meanwhile. The black powder which falls is afterward collected and dried. This powder has the property of causing union among gaseous bodies as, for example, the elements of water to a greater degree than the spongy platinum. 635. Platinum forms two oxyds, and two chlorids, viz. P10; P10 3 and P1C1; P1C1 2 . The oxyds are prepared from the chlorids by precipitation with alkalies, and are very 634. How is it obtained from its ores ? How is it condensed ? What Is platinum black, and what arc its properties ? C35. How is the bi- ehlorid prepared ? OSMIUM. 375 unstable. The protochlorid is prepared by heating the bichlorid to 460, when chlorine is evolved and P1C1 is left as a greenish-gray insoluble powder. The bichlorid of platinum is the usual soluble form of platinum, and is always formed when platinum is digested in aqua regia. It is prepared pure by dissolving spongy platinum in this menstruum, and cautiously expelling the acid by evaporation, at the temperature of a water-bath. It gives a rich orange colored solution both in alcohol and water; and forms insoluble salts of much interest, with many metallic chlorids. Those with the alkaline metals are the most im- portant. The double chlorid of platinum and potassium is a very sparingly soluble salt, (P1C1 2 KC1,) which falls as a yellow, highly-crystalline precipitate, when chlorid of plati- num is added to a solution of chlorid of potassium. The double chlorid of sodium and platinum (PlCl 3 NaCl-|-6HO) is, on the other hand, very soluble, and forms large beautiful yellowish-red crystals in a dense solution. Potash and soda are most easily separated, by the different solubility of their double platino-chlorids. The double chlorid of am- monium and platinum (P1C1 3 NH 4 C1) is the orange precipi- tate before named, and is the best test to determine the presence of platinum in a solution. Associated with platinum are iridium, osmium, rhodium, and ruthenium metals whose rarity permits us to pass them with a very brief mention. 636. IRIDIUM (Eq. 99) is found alloyed with osmium, forming the mineral iridosmine, IrOs 3 , in flat scales, mal- leable with difficulty. It is the hardest alloy known, being as hard as quartz. It is very infusible. It is true tin- white, crystallizes in hexagonal forms, and its density is from 19 -3 to 21-12 being the densest body known. This mineral is much used to point gold pens. It is unacted on by aqua regia. It forms four oxyds. OSMIUM (Eq. 99-6) has a density of 10, of a bluish-white color, is neither fusible nor volatile, and forms, by its com- bustion in air, the very volatile and poisonous osmic acid Os 4 . It forms five oxyds, OsO, Os 2 3 , Os 2 0, Os 3 0, and Os 4 0. Fused with nitre, osmium forms osmiate of potassa. Describe the double chlorids of platinum and the alkalies, their prepa- tion and characteristics. What metals are associated with platinum ? 636. What of iridiurn? What use has iridosmine? What is the density of iridium? What of osmium? Its oxyds? 376 METALLIC ELEMENTS. RHODIUM (Eq. 52-2) is so named from the rose color of its salts. It is a reddish-white metal, density about 10-5, and resembles iridium in hardness, fusibility, and malleability, as well as in resisting the action of acids. It forms two oxyds, RhO and Rh 2 r RUTHENIUM (Eq. 52-2) is another metal observed, lately, to the extent of 5 or 6 per cent., in the iridosmine. Its den- sity is about 8-6. It is very like iridium in all its charac- ters, and has until lately been confounded with it. What of rhodium? Its color and density? Its oxyds? What o! rutheniu m ? Where found ? What relations has it ? 877 PART IV. ORGANIC CHEMISTRY. [THE last edition of this work was written about five years since, and having been desired to prepare this portion of the book for a new edition, it was thought proper to re-write it almost entirely. The views of chemical theory here adopted, have been in part advanced in the pages of the "Ame- rican Journal of Science" during the last four years. I have there at- tempted to point out what I conceive to be true in the respective systems of Giessen and Montpellier; and have laid down certain principles, which, in the present work, have been applied to the elucidation of a variety of questions. I have refrained from here developing at full length my own theoretical views, as being from their novelty unsuited to the cha- racter of an elementary treatise. It has been my plan to select from the great amount of matter which the chemistry of the carbon series now embraces, those subjects whose his- tory is well known and best fitted to illustrate the theory of the science, and at the same time to include the matters most interesting, in a practical view, to the medical and general student. Both these classes will, how- ever, find it necessary to resort to more extended works for the history of many series of compounds, which have been omitted or very briefly noticed in these pages; while, on the other hand, it is hoped that the more advanced student will not find the work unworthy of a perusal. I have not thought it necessary in an elementary treatise to cite authorities ; but I may remark that I have availed myself of the works of Liebig, Gerhardt, and Gregory, and of the various chemical memoirs which have appeared in the different scientific periodicals for the last few years. The most recent discoveries in organic chemistry are here em- bodied. T. STEBEY HUNT. MONTREAL, CANADA EAST, July, 1852.] INTRODUCTION. Nature of Organic Bodies. 637. Definition. The name of Organic Chemistry is used to designate that branch of the science which investigates the phenomena and results of organic life, examines the che- mical relations of animals and plants, and the properties and 378 ORGANIC CHEMISTRY. transformations of the peculiar bodies which they afford. The constituents of organic bodies are comparatively few in number. Carbon with oxygen, hydrogen, and nitrogen, form all the combinations peculiar to organic substances. In addition to these, however, sulphur, phosphorus, and iron sometimes occur in small quantities in organic products; and the results of their decompositions and transforma- tions under the influence of different reagents, give rise to an immense number of compounds, in which, with the four organic elements already mentioned, are often united sul- phur, phosphorus, arsenic, antimony, chlorine, bromine, iodine, and the metals. 638. It was formerly supposed that the production of the so-called organic substances was exclusively the prerogative of life. But later discoveries have shown that it is possible so to combine the organic elements as to form many of the products which were formerly obtained only through the medium of plants and animals. Hence the distinction be- tween organic and inorganic chemistry is no longer so well denned as before. But as in organic bodies carbon is always present, and is the only constant element, we may define or- ganic chemistry as the chemistry of the compounds of carbon. We may distinguish in mineral chemistry many such classes of compounds; as the nitrogen series, in which nitrogen is a constant and characteristic element; the silicon series, in- cluding all the silicious compounds : so in studying the chemistry of organic bodies, we find that they may all be re- duced to one, the carbon series. 639. Among the organic matters which make up the structure of living beings, we must distinguish two classes : first, organized substances, which show either to the naked eye, or under the microscope, a peculiar structure, entirely different from that of crystallization, and never exhibited except in those matters which have been formed under the influence of the vital force: such are the woody and muscular fibres, the cellular and vascular tissues, the globules of blood and of starch (which see). These are not always homogeneous chemical compounds, and art, even could it imitate their chemical constitution, will never succeed in giving them their organized forms. The power which effects this must ever remain one of the secrets of life. The second class of organic substances includes those which are either produced by the destruction of organized LAWS OF CHEMICAL TRANSFORMATIONS. 379 bodies, or are the secretions or excretions of organized beings. They are subject to the same laws of form as in- organic bodies, and are liquid, solid, or gaseous, crystallized or amorphous. It is this second class of organic substances which we are able to form artificially, and which are pro- perly in the domain of the chemist ; among these are in- cluded the various alcohols, oils, acids, resins, sugars, gums, alkaloids, and coloring matters. 640. The immediate effect of chemical agencies upon or- ganized bodies is to produce disorganization, and to convert them into substances which belong to the second class. Hence the study of organized structures belongs to the phy- siologist, and it is only where he leaves them that the chemist begins. The effect of strong heat upon organic bodies is peculiar. They are completely decomposed into a variety of products, among which are water, carbonic acid gas, carburets of hydrogen, and, if nitrogen be present, am- monia. The carbon, which is generally present in larger quantity than is required to form these compounds, remains in the form of charcoal; hence organic bodies are always more or less combustible, and, unless volatile,. generally char or blacken by heat. 641. In addition to the bodies of the carbon series, both animals and vegetables contain salts of potash, soda, lime, magnesia, and iron, with sulphuric, phosphoric, and silicic acids, chlorine and fluorine. Animals also secrete phosphate and carbonate of lime to form their bones, as in vertebrates, and their external coverings, as in the mollusca. These salts have been already described under their proper heads, in the Inorganic Chemistry, and their relations to life will be considered in the section on the nutrition of animals and Dlants. Laws of Chemical Transformations. 642. The various changes met with in the study of or- ganic substances, resulting in the destruction of existing combinations, and the formation of new ones, may conve- niently be reduced to two classes; first, equivalent substitu- tions) and second, direct union. It will be shown that, in the first case, decomposition and recomposition are reciprocal and simultaneous, so that the one implies the other, and we investigate at once the laws of both. In the second case, this relation apparently does not exist; but there is a direct 830 ORGANIC CHEMISTRY. decomposition, which is the converse of direct union, and consists in the partition or dissection of a compound into two or more compounds having a lower equivalent. JEJq uit'a len t Su. Ijstitu tio n . 643. The law of substitution is, that one or more atoms of an element in a compound may be replaced by any other element, or group of elements, which are equivalent in their chemical relations ; and the chemical constitution of the compound remain unchanged. Thus acetic acid C 4 H 4 O 4 may lose three atoms of hydrogen and take in their place three equivalents of chlorine, which last are substituted for the hydrogen, without changing the acid constitution of the body j the new compound, cliloracetic acid, C 4 (HC1 3 )0 4 closely resembles acetic acid in its properties. Here 85-5 parts of chlorine are equivalent to 1 of hydrogen, and C1 3 is equivalent to H 3 , and may be substituted for it without altering the 1ypc of the compound. Bromine and iodine, and perhaps fluorine, may replace hydrogen in a similar manner. 644. In the foregoing reaction C 4 H 4 4 and Cl fi are con- cerned, and C 4 (HCl 3 )0 4 and 3(ClH) are the results. We shall show farther on, from a consideration of their combining volumes, that as the equivalent volume of chlorohydric acid is (HC1), that of hydrogen is (HH), and that of chlorine (C1C1). In the reaction between acetic acid and chlorine, there are then but three equivalents or volumes of chlo- rine, 3(C1C1), and each successive volume exchanges one* of its atoms for one of hydrogen: thus, (C 4 H 4 4 )-f(ClCl) =(C 4 H 3 Cl0 4 )-f (C1H) and so on with a second and third volume of chlorine. In many instances we can trace the successive steps by which atom after atom of hydrogen is replaced by chlorine, a corresponding equivalent of hydro- chloric acid being simultaneously formed. The law of equi- valent substitution is then reducible to that which has been called double elective affinity, and always supposes the reaction of two complex bodies, which give rise to two new ones. 645. As hydrogen is replaceable by Cl, Br, and I, so oxygen is capable of being replaced by sulphur, selenium, and tellurium. This can seldom be effected directly, as in the case of chlorine and hydrogen, but it is obtained by in- direct decompositions. Alcohol, which is C 4 H 6 2 , gives sul- EQUIVALENT SUBSTITUTION. 381 pkur alcohol, C 4 H 8 S a , and the selenium compound will bo C 4 H 6 Se 2 . Mineral chemistry affords similar instances; sulphate of soda is 2S0 3 -f-2NaO, or S 2 Na 3 8 , while the hypo- sulphite of soda is S 2 Na 3 (0 2 S 6 ), and another salt is S Na f (O 4 S 4 ). These different sulphates crystallize with the same amount of water, have the same form, and the same solu- bility. Nitrogen, phosphorus, arsenic, and antimony, which form a natural group, may also replace each other, equivalent for equivalent; thus, ylycocoll, which is C 4 H 5 N0 4 , has a corre- sponding arsenical compound, alkargene, C 4 H 5 As0 4 . 646. When any acid, like chlorohydric or acetic acid, acts upon a metal such as zinc, hydrogen is evolved, and a chlo- rid or acetate of zinc is formed, in which Zn has replaced the hydrogen, HCl-f Zn=H-f ZnCl, and C 4 H 4 4 -|-Zn= = C 4 H 3 ZnO 4 -f-H. If chlorine (C1C1) acts upon zinc, we ob- tain the same chlorid as with chlorohydric acid, (ClCl)-j-Zn 2 2(ZnCl), and when chlorine combines with hydrogen, it is (ClCl)-f (HH)=2(HCi). Now as the action of HC1 upon zinc evolves hydrogen (HH), all these analogies lead us to conclude that the equivalent of zinc is Zn 2 =(ZnZn), and hence that in the case of acetic or chlorohydric acids, an equivalent of zinc reacts with two equivalents of the acid. Acetic acid C 4 H 4 O 4 -f ZnZn=C 4 (H 3 Zn)0 4 + (ZnH), but ZnH with an- other equivalent of C 4 H 4 4 yields a second equivalent of acetate and one of hydrogen (HH). The hydrates of metals like ZnH are seldom stable, and as they decompose water .and acids very readily, are difficult to be isolated. The re- placement of the hydrogen in acids by a metal is then ana- logous to that of its substitution by chlorine. 647. When an acid is brought in contact with a metallic oxyd, double decomposition ensues in the same manner, but with the formation of an oxyd of hydrogen; acetic acid C 4 H 4 4 -fZnO:=C 4 H 3 Zn0 4 -f HO. But with the equiva- lents here proposed, the composition of oxyd of zinc must be written Zn a 2 , and that of water H 2 2 , so that as in the reaction with metallic zinc, two equivalents of the acetic acid react with Zn 3 3 . If we represent the actions as consecutive, the first result will be (ZnH)0 2 , or the hydrated oxyd of zinc, corresponding to ZnH, which with another equivalent of acid exchanges its Zn for H, forming water, (H 9 a ). 648. All the metals proper are capable of replacing in this 382 ORGANIC CHEMISTRY. manner a portion of the hydrogen of acids to form salts. A great number, like acetic acid, have only one atom of hydrogen which can be replaced by a metal, but in others two and three atoms may be in a similar manner replaced. These are called bibasic and tribasic acids ; while such as acetic acid are said to be monobasic. Tartaric acid is bibasic; its composition is represented C 8 H 6 12 , or C 8 H 4 (H 2 )0 12 ; the two equivalents of hydrogen may be replaced by two equivalents of some metal as C s H 4 Zn 2 12 ; by two dif- ferent metals as in C s H 4 (KNa)O ia , or but one equivalent may be replaced as in C 8 H 4 (HK)0 12 . The latter still retains acid properties, and is called an acid salt. The salts of tribasic acids may contain either one, two, or three equiva- lents of hydrogen replaced by a metal; the first two of these salts will be acid, and the last neutral. The monobasic acids are almost always volatile, while the bibasic and tribasic acids are never volatile without decomposition. 649. The sesquioxyds, which have been represented in treating of mineral chemistry as composed of two equivalents of a metal combined with three of oxygen, offer a peculiar case in the formation of salts. If we take, for example, the peroxyd of iron, Fe a 3 , we find that it saturates, not twc equivalents of acetic acid, but three, and that while in the acetate of the protoxyd of iron FeO replaces H, in the acetate of the peroxyd two-thirds of an equivalent of iron sustain the same relation ; if then we would represent the acetate of the peroxyd, we must write it C 4 H 3 Fef0 4 . In other words Fe 2 3 has reacted as if it were 3(Fef 0). But if we ex- amine these two salts still farther, we find that in their che- mical reactions they differ from each other as widely as tho salts of two distinct metals, and that we have in the salts of the peroxyd, iron with two-thirds its ordinary equivalent, and with peculiar and distinct properties. We may designate the iron in the proto-salts as ferrosum, with an atomic weigh! of 28 and the symbol Fe, and the iron in the persalts as ferricum, with an atomic weight of 18*6, and write its symbol, fe. The sesquioxyd of iron, Fe 2 3 , is then 3(feO) and the corresponding acetate of ferricum C 4 H 3 fe0 4 . This same view is to be extended to the proto and ses qui-salts of chromium and manganese, and to the salts of alumina, which is a sesquioxyd; also to the salts of mercury and of tin, in which the equivalents of the two forms are to EQUIVALENT SUBSTITUTION. 383 each other as 1 : 2. We have ckromosum and cJiromicum } aluminicum, stannosum and stannicum, mercurosum and mercuricum; the second form of the metal is distinguished by writing its symbol with a small letter as Cr, cr, al, Su, sn, Hg, hg, &c. 650. We have seen that acetic acid may exchange three equivalents of hydrogen for chlorine, and but one equiva- lent for a metal, so that in chloracetate of silver, C 4 C1 3 Ag0 4 , all the hydrogen is replaced. There are many acids in which we cannot effect the substitution, by chlorine, nor can the fourth atom of hydrogen in acetic acid be thus replaced; it can be removed only by substituting a inetal. Thus the hydrogen which is replaceable by chlorine is distinct from that which is equivalent to a metal. It will be shown far- ther on, however, that there are some bodies in which this distinction appears to be lost, and in which all the hydrogen may be replaced either by chlorine or a metal. 651. In treating of the action of chlorine upon acetic acid, we have considered the process only with reference to the acid ; but the substitution is reciprocal, and there is mutual decomposition. To make the question more simple, we will select a case where but one atom of hydrogen is replaced. The essence of bitter almonds, benzoilol, has the composition C 14 H 8 O a ; by the action of chlorine, hydrochlo- ric acid is formed, and one atom of hydrogen is replaced by chlorine, C 14 H 8 3 +(ClCl)=C 14 H 5 Clp 3 -hHCl. Now if we consider only the oil, it will be said that an equivalent substitution has taken place of Cl for H ; but it is equally correct to say, that the benzoilol minus H has replaced Cl in. the equivalent of chlorine (C1C1) ; in other words, that the essence has ceded H to form hydrochloric with Cl, and that the residue has replaced the eliminated atom of chlorine. When the constitution of the bodies becomes more com- plex, the action is still the same; benzoilol reacts with nitric acid, which is NHO 40 * The products of its combustion are estimated as before. 394 ORGANIC CHEMISTRY. 671. Fatty bodies, and others which contain much carbon and a small quantity of hydrogen, are more perfectly burned by employing chromate of lead instead of copper. This sub- stance does not readily attract moisture from the atmosphere, like oxyd of copper, and is consequently better when the hy- drogen is to be determined accurately. The chromate of lead is prepared for use by heating it until it begins to fuse, and when cool reducing it to powder. 672. When nitrogen is a constituent of organic bodies, it is determined by placing in one end of the combustion tube about three inches of carbonate of copper, secured in its place by a plug of asbestus ; and then the nitrogenous body is introduced, mixed with oxyd of copper. The re- maining space in the combustion tube is filled with turnings of metallic copper. The air is then withdrawn by an air- pump, and a gentle heat applied to the carbonate of copper, which evolves carbonic acid, and drives out all remaining traces of common air. The tube is now heated as usual, and the gases evolved are collected in a graduated air-jar, over mercury. When the combustion is finished, heat is again applied to the carbonate of copper, and another portion of carbonic acid expelled, which drives out all the nitrogen from the tube. The use of the copper turnings is to decom- pose any traces of nitric oxyd which may be formed in the process. The carbonic acid is removed from the air-jar by a strong solution of potash, and pure nitrogen remains, which is measured with the usual precautions, and from its volume the weight is easily determined. 673. Another and a preferable mode of determining nitro- gen, is that of Will and Varrentrapp, which is founded on the fact that when a body containing nitrogen is heated with an excess of caustic potash, or soda, all the nitrogen is evolved in the form of ammonia, and may be thus estimated, by con- ducting it into hydrochloric acid, and forming, with chlorid of platinum, the double chlorid of platinum and ammonium. 674. Chlorine is determined in the analysis of organic compounds, by passing the vapor over quicklime heated to redness in a combustion tube; chlorid of calcium is formed, which is afterward dissolved in water, and the chlorine precipitated by nitrate of silver. From the weight of the chlorid of silver, the amount of chlorine is calculated. 675. Sulphur is a rare constituted of organic compounds. tts presence is detected by fusion with nitre and carbonate DENSITY OF VAPORS. 395 of soda, or by digestion with nitric acid. Sulphuric acid is thus formed, and is precipitated as sulphate of baryta, from the weight of which that of the sulphur is determined. In the analysis with oxyd of copper, a small tube of peroxyd of lead is introduced between the chlorid of calcium tube ind the potash apparatus, to absorb the sulphurous acid rrhich is evolved. Density of Vapors. 676. The determination of the destiny of vapors is of great importance ; in the case of some volatile organic com- pounds which form no combinations with other substances, it is the only means of ascertaining their constitution and equi- valent. The process is very simple, and the method employed in the case of gases has been already described, (49.) When the substance is a liquid or solid, it is introduced into a narrow- necked glass globe, of the form represented in fig. 401, the weight of which is carefully ascertained. The globe is held by means of a handle firmly attached by a wire, beneath the surface of an oil or water-bath, and then heated to some degrees above the boiling-point of the sub- stance. When this is all volatilized and the globe is filled with the vapor, the open and projecting end of the globe's neck is sealed by the flame of a spirit-lamp : at the same time the temperature of the bath is noted. When the globe is cooled it is again weighed, and the end of the neck broken off beneath the surface of mercury, which rushes up and fills the empty vessel. The mercury is then ^. carefully measured. The capacity of the vessel and its weight being thus ascertained, we can find the weight of a volume of vapor at the observed tempera- ture, and by an easy calculation can determine what would be its volume at the ordinary temperature, (88:) its weight he same volume of specific gravity required. / A / \ / o compared with that of the same volume of air gives the 677. It is proposed, before commencing the study of those bodies of the carbon series which we have included under the head of Organic Chemistry, to consider briefly the prin- cipal products of the ultimate decomposition of this class of substances. These are water, ammonia, and carbonio 396 ORGANIC CHEMISTRY. acid gas. The latter only strictly comes within our limits, and all of them have been described in the first part of this work ; but we shall bring them up again to illustrate certain laws of substitution, which will help to explain the history of the more complex organic compounds. We shall then treat of starch and sugar, and some other bodies of high equivalents, whose history is comparatively simple, and proceed to the products of their decomposition by fermentation and other means, among which are different alcohols and acids. Water. 678. In the first part of this volume, water has been de- scribed as having the formula HO, and as composed of two volumes of hydrogen and one of oxygen, condensed into two volumes of vapor of water ; we have already given the rea- sons which lead us to adopt four volumes as its equivalent, and to write its formula H a 3 . We shall now speak of the products of substitution de- rived from water. If the oxygen be replaced by sulphur we have sulphuretted hydrogen : the selenium and tellu- rium compounds have a similar composition. One or both atoms of the hydrogen may be replaced by a metal. Hy- drate of potash KO.HO is water in which one equivalent of H is replaced by potassium : it is (KH)0 3 , and anhy- drous potash will be K 2 3 . The hydrated oxyds result from the replacement of one equivalent of hydrogen by a metal, while in the anhydrous oxyds both are thus replaced. Water thus resembles a bibasic acid, and the hydrated oxyds may be compared to acid salts, while the anhydrous oxyds are like neutral salts. 679. The so-called suboxyds are illustrations of the change of equivalent upon which we have insisted. The red oxyd of copper is Cu 2 0, or rather Cu 4 2 , but copper here unites in twice its ordinary equivalent weight, and in this form, which we may designate as cuprosum, with the symbol cu, is strictly equivalent to H and to Cu, so that tho red oxyd is cu 2 2 . The peroxyds, like those of hydrogen or barium, may be either oxyds which have combined with an additional amount of oxygen, and thus increased their equivalent weight, being H 2 4 and Ba 3 4 , or they may be regarded as sustaining to the ordinary oxyds the same re- lation that the black oxyd of copper does to the red oxyd, AMMONIA. 897 being compounds in which barium and hydrogen unite in one-half their ordinary equivalent : thus, (Bai) 3 3 , &c. The same views apply to the persulphuret of hydrogen and other persulphurets. From the volumes of the correspond- ing bodies of the carbon series, the first view is probably the true one. 680. We have shown that in the group H 3 , chlorine may replace H to form chlorohydric acid, and we may here refer to an example in which an atom of the hydrogen is replaced by a metal. It is a product of the action of hypo-phosphorous acid upon a salt of copper, and is a yellow powder contain- ing Cu 2 H, which corresponds to cuH. Chlorohydric acid dissolves it with the evolution of hydrogen and the forma- tion of a chlorid of duprosum, cuH-f-HCl cuCl-f-HH, the hydrogen of both being evolved. It has already been remarked that there are examples of bodies in which all of the hydrogen may be replaced either by chlorine or by a metal, and water is such a body; hydrated hypochlorous acid CIO, HO is (ClH)O a , or water in which Cl replaces H : the second equivalent of hydrogen may be replaced by a metal to form a hypochlorite, as in C10.KO, which is (C1K)0 3 . But this second equivalent may also be replaced by chlorine, and we have the so-called anhydrous hypochlorous acid, which is C1 3 2 , or water in which chlo- rine has been substituted for the whole of the hydrogen. Ammonia. 681. Ammonia is composed of six volumes of hydrogen and two of nitrogen (0 being represented by one volume,) condensed to one-half, or to four volumes : its formula is then NH 3 . Its properties have already been described, and we have only to notice some of its derivatives. Like water, the whole of its hydrogen may be replaced either by chlo- rine or by a metal. The direct action of chlorine decom- poses it; the hydrogen forms hydrochloric acid, and the nitrogen is set free in the form of gas ; but with a solution of a salt of ammonia, like the muriate or sal-ammonia, the action is different ; the chlorine is slowly absorbed and a heavy yellow oil separates, which is a most dangerous com- pound, exploding with great violence by a gentle heat, by the contact of phosphorus, fat oils, and many other sub- stances. It is composed of NC1 3 , and by the explosion is resolved into these elements. The name of chlorid ofnitto- 398 ORGANIC CHEMISTRY. gen has been given to it, but it is ammonia in which the hydrogen has been replaced by chlorine, and may be called trichloric ammonia. The action of iodine upon ammonia is more moderate than that of chlorine : if it is triturated with a solution of ammonia or mixed in an alcoholic solution, a black powder is obtained which explodes when dry by the slightest friction, but less violently than the chlorid. Its composition is NI 2 H, and it is therefore liniodic ammonia. The chlorine compound is indifferent to acids, but the iodic species still exhibits feebly basic properties : it is dissolved by dilute acids and precipitated again by a solu- tion of potash. 682. When potassium is heated in ammoniacal gas, one equivalent of hydrogen is displaced, and an olive-green com- pound is obtained, which is N(H 2 K), and is decomposed by water into, hydrate of potash and ammonia N(H 3 K)-{-H 3 3 =(HK)0 2 -f-NH 3 . When ammonia is passed over heated oxyd of copper, water is formed, and a compound which con- tains Cu 6 N. It corresponds to the red oxyd of copper, or oxyd of cuprosum cu 2 2 , and is Ncu 3 , or ammonia in which all the hydrogen has been replaced by cuprosum. It is formed at a temperature of 480 F., and is decomposed into its ele- ments with evolution of light at 540 F. 683. The salts of ammonia next claim our notice. Their characters and preparation, and the theory of ammonium have already been described, (518.) The mode of their formation is different from that of ordinary salts of metals : these, we have shown, whether the metals or their oxyds are employed, are produced by an equivalent substitution with the elimination of hydrogen or water, while ammonia and the acids unite directly to form salts, without the pro- duction of any second body. Thus ammonia and chlo- rohydric acid NH 3 -j-HCl yield sal-ammoniac NH 4 C1; and sulphuric acid, which is bibasic and must be written 2S0 3 .H 2 2 =S 2 H 2 8 , fixes directly 2NH 3 to form sulphate of ammonia. But these salts, notwithstanding their differ- ent mode of formation, are closely analogous to the salts of potassium and even isomorphous with them ; and while chlorid of potassium is KC1, the NH 4 in sal-ammoniac i& perfectly similar in its relations to K ; and hence sal-ammo- niac is often regarded, not as the hydrochlorate of ammonia NH 3 .IJC1, but as the chlorid of a quasi-metal, ammonium, which unites with Cl like potassium, and, like this metal, AMMONIA. 899 may even form an amalgam with mercury ; for (NII 4 )Hg evidently corresponds to KHg, and Zntlg. Ammonium,NH 4 , is then a group which, although it cannot be isolated, may replace hydrogen, and is equivalent to it. The neutral sulphate of ammonia is S 8 (NH 4 ) a O s , as sulphate of potash is S 3 (K 3 )0 8 , and the acid sulphate S 3 (H.NH 4 )0 8 , corresponding to S a (HK)0 8 . The group NH 4 may be represented by the symbol Am. 684. The compound corresponding to a metallic oxyd in which NH 4 replaces H, like (KH)0 2 , probably exists in the aqueous solution of ammonia : it will be (NH 4 . H)0 2 or (AmH)0 2 ; but the ammonia is readily evolved by heat, the compound being like some salts of ammonia, very unstable. We shall see hereafter that there are homologues of ammo- nia which form more fixed combinations. A compound of (NH 4 ) 3 2 , or Am 2 2 , corresponding to an anhydrous oxyd, is also possible ; like oxyd of zinc, (Zn 2 3 ,) it would evolve an equivalent of water in combining with an acid. 685. In the same way that ammonia combines directly with acids it may unite with metallic salts ; for example, with chlorid of copper CuCl-f-NH 3 = (NH 3 Cu)Cl, and with sulphate of silver S 3 Ag 2 O s -f-2NH 3 =S 2 (NH 3 Ag) 2 3 : in these compounds one equivalent of hydrogen in the ammonia is replaced by copper and silver, and the groups may be designated cuprammonium and argentammonium. The white precipitate of mercury obtained by adding am- monia to a solution of chlorid of mercury is a body of this class, and is represented by (NH 2 Hg 3 )Cl : when this is boiled in a solution of sal-ammoniac, another compound is obtained, which is (NH 3 Hg)Cl. Here one and two equiva- lents of hydrogen are replaced by mercury. With the chlorid of platinum a similar chlorid is obtain- ed, which is known as the green salt of Magnus, and is (NH 3 Pt)Cl. But the group NH 4 may replace an equivalent of H in the last, and we have a salt described by Gros and Ileiset, which is N(AmH 2 Pt)Cl or (N 3 H 6 Pt)Cl. Still another one has an equivalent of hydrogen replaced by 01, and is (N 3 H 5 ClPt)Cl. All of these correspond to chlorid of ammo- nium, and it will be observed that the sum of their atoms is always divisible by two. They combine with the oxygen acids like ammonia, and their sulphates, when decomposed by- baryta, give the hydrated oxyds corresponding to (KH)O i; 400 ORGANIC CHEMISTRY. and, like it, caustic and alkaline. Cobalt and some other metals yields analogous compounds. 686. The decomposition of ammoniacal salts to form water and amids has already been alluded to, (654.) An ammo- niacal salt eliminates one equivalent of water for each equi- valent of ammonia which it contains, and the salt, if neutral, yields a neutral amid ; but if the salt is acid, that is, if a bibasic acid has combined with one equivalent of ammonia, and has still an atom of hydrogen replaceable by a metal, this is preserved in the amid, which is then a monobasic acid. These compounds are often directly formed by the action of heat upon the several salts, and sometimes by distilling them with anhydrous phosphoric acid, which combines with the water. Amids may sometimes lose the elements of another equivalent of water, and form a class of bodies known as anhydrid amids, or nitryls. Acetate of ammonia C 4 H 4 4 +NH 3 =C 4 H 7 N0 4 H 2 2 = C 4 H 5 N0 2 , or acetamid, from which if H 2 3 be again abstracted, there remains acetonitryl C 4 H 3 N. 687. Nitrous oxyd, which is NO, or rather N 2 2 , is formed from nitrate of ammonia NH0 6 .NH 3 , by the abstraction of 2H 2 2 , and is a true nitryl. Like all the other bodies of this class, it can reassume the elements of water and regenerate the acid and ammonia ; when passed over heated hydrate of potash, a nitrate is formed, ammonia escaping. Phosphoric acid forms not less than three anhydrid amids, corresponding to different salts of the different modifications of the acid. They are all white insoluble powders, which, under the influence of strong acids or alkalies, yield phos- phoric acid and ammonia. The one corresponding to nitrous oxyd is (PN)O a =P0 5 .NH 4 p-2H a O a . The points of interest with regard to the amids of the organic acids will be considered in their proper places. Carbonic Acid. 688. This compound has already been described, but we again refer to it to speak of its equivalent, which, to corre- spond to those adopted for organic substances, must be writ- ten C 3 4 in its anhydrous state. The gas fixes H 2 2 when it takes the acid form ; and carbonic acid, such as it exists in solution, is consequently C 2 H 2 6 , in which one or both equivalents of hydrogen may be replaced by a metal, form- SUGAR, STARCH, ETC. 401 ing neutral and acid carbonates, or bicarbonates, as they are often called. . Carbonic acid is very readily separated from its aqueous solution, or decomposed into carbonic acid gas and water, in which it differs from more fixed bibasic acids, which some- times require a high temperature to effect such a division. 689. Carbonic oxyd, which we write C a 2 , is interesting from its action with chlorine in the formation of phosgene gas. It directly fixes 2C1 to form C 3 C1 3 3 , which evidently corresponds to an hydrogen compound C 3 H 3 0. This group, of which phosgene is the chlorinized species, is the prototype of an important class of organic compounds, the aldehydes SUGAR, STARCH, AND ALLIED SUBSTANCES. 690. Under this head is included a class of substances of vegetable origin, which agree in containing carbon with oxy- gen and hydrogen in the proportions which form water. When soluble, they are insipid, or have a sweet taste, and are generally nutritious. They are not volatile, and are readily decomposed by heat and many other agents. 691. Sugars. These bodies are soluble in water, have a sweet taste, and most of them by the process of fermentation yield alcohol and carbonic acid. Cane Sugar, C M H 3a O S3 . This occurs in the juices of many plants, as the sugar-cane, maple, beet-root, and Indian corn. It is obtained by evaporating the juice to a syrup, when the sugar crystallizes in grains of a brownish color, and is rendered pure and white by redissolving it, and filter- ing the solution through animal charcoal, (337.) By the slow evaporation of a concentrated solution, it is obtained in fine transparent crystals, which are derived from an oblique rhombic prism ; in this state it constitutes rock-candy. It fuses at 356, and forms, on cooling, a vitreous mass well known as barley sugar : this gradually becomes opaque and changes into a mass of small crystals of ordinary sugar. Sugar is soluble in about one-third its weight of water, form- ing a thick syrup. It is insoluble in pure alcohol. 692. Grape Sugar; Glucose, C^H^O^ -f 2H 8 3 . This sugar is found in the grape and many other fruits, and in honey. It is formed when cane sugar or starch is boiled with dilute sulphuric acid, and is a product in many other trans- 26 402 ORGANIC CHEMISTRY. formations. The urine in the disease called diabetes meUituz contains a large quantity of grape sugar, which is formed from the starch and similar substances taken as food. Grape sugar is generally obtained as a white granular mass, which requires one and a half parts of cold water to dissolve it : it is less sweet to the taste than cane sugar, and about two and a half times as much are required to give an equal sweetness to the same volume of water. When heated to 212, the two equivalents of water are expelled. With sulphuric acid, grape sugar forms a coupled acid, the sul- pbosaccharic. It forms with chlorid of sodium, a crystal- line compound, which is C^H^O^-NaCl.!!,^. The water is lost by heat. If a solution of grape sugar is mixed with a solution of potash, and then with a little sulphate of copper, the liquid becomes dark, and soon deposits suboxyd of copper in the form of a red powder ; cane sugar yields no precipi- tate until the solution is boiled. This test enables us to detect the Yflflss part of grape sugar in a liquid. Honey is a mix- ture of crystallizable grape sugar, with an uncrystallizable syrup identical with it in composition. 693. Sugar of Milk; Lactose, C W H 2? 20 +2H 3 3 . This is found only in the whey of milk, and is obtained by evapo- rating it, and purifying the product by crystallization. Lactose forms semi-transparent prisms, soluble in six parts of cold water, and two and a half of boiling water ; it is much less sweet than cane or grape sugar. By a heat of 212 its water is expelled ; when boiled with dilute sulphuric acid, it combines with the elements of two equivalents of water, and is converted into grape sugar. Mannite, C 13 H 14 la . This substance is not properly a sugar, as it does not contain oxygen and hydrogen in the proportions to form water, and is not susceptible of fermenta- tion. It exists in the juice of celery and many sea-weeds, and constitutes the principal part of the manna of the shops, which is the concreted juice of a species of ash-tree. When this is dissolved in hot alcohol, mannite is deposited oa cooling in delicate silky crystals, which are sweet, and very soluble in water and alcohol. Mannite dissolves in a mixture of fuming nitric and sul- phuric acids, and water precipitates from the mixture a white matter, insoluble in water, which may be crystallized by dissolving in hot alcohol. It is formed by the fixation of the elements of nitric acid and the elimination of those of VINOUS FERMENTATION. 403 water, and is represented by C 12 H 8 N" ( .0 3(i . We may repre- sent N0 4 as replacing hydrogen, and designate it by X The new compound, which is called nilro-mannite, will be then C 12 H S (N0 4 ) 6 12 C 13 H 8 X 6 13 . This mode of notation is convenient, but, agreeably to the views laid down in the introduction, we must suppose successive substitutions, in the first of which C 13 H t4 13 H0 a replaces H in nitric acid NH0 6 , yielding N(C 13 H 13 10 )O n and H 3 a ; this product then reacts with a new equivalent of nitric acid, and so on. From the large portion of oxygen which it contains, nitro- mannite is very combustible, and it explodes spontaneously when struck with a hammer. Products of the Decomposition of the Sugars. 694. The Vinous Fermentation. When the juice of grapea or other fruits containing sugar is exposed to the air, a pecu- liar decomposition ensues, in which the sugar is resolved into carbonic acid gas and alcohol. A solution of pure sugar is not changed by exposure to the air ; but if there is added to it a little yeast, or the juice of any fruit in the state of fermentation, decomposition takes place, and carbonic acid and alcohol are formed. Many substances besides yeast will effect this change, as blood, albumen, or flour paste in a state of decomposition. It appears that the influence of a fer- ment depends on the condition rather than on the kind of matter. Any nitrogenized substance capable of undergoing putrefaction produces the same effect, and we are to attribute this change in the juice of fruits, to a small portion of albu- minous matter present. The mode in which these substances act is not understood, but it is supposed that when in a state of decomposition, they are able to induce a similar state in other substances with which they are in contact; the equi- librium of the atoms in the compound is thus disturbed, and the elements arrange themselves in new forms. It is interesting to know that the fermentation of sugar takes place only in immediate contact with the ferment. This is readily shown, as in figure 402, by placing a solution of sugar in the bottle A, and some beer yeast in the tube ab } the lower end of which is covered with porous paper. The sugar solution passes through the paper into the tube, where an active fermentation is set up with an abundant Fig. 402. 404 ORGANIC CHEMISTRY. evolution of carbonic acid. Meanwhile no change occurs in the solution in the bottle, which may be preserved unaltered for any length of time. G95. The act of fermentation is always accompanied by the appearance of a peculiar microscopic vegetation, which is formed when solutions containing albuminous matters are abandoned to putrefaction. The solution becomes tur- bid, and a gray deposit is gradually formed in it, consisting of ovoidal bodies variously grouped, whose development has been carefully studied under the microscope. Figures 403 to 407 show the various stages of this fungus growth. The >* C -W 3 Fig. 403. Fig. 40i. Fig. 405. Fig. 406. Fig. 407. original globule (1) A, fig. 403, in about six hours produces another, (2,) fig. 404, 13, like itself; the two again each germinate a third, as seen at 3, C and D, fig. 405; and in like manner the germination proceeds, as in E, (4,) fig. 406, until, in about throe days, thirty globules are formed about the original cell. The development then ceases. The se- veral globules are coherent, but appear to be distinct and complete in themselves. 696. The conversion of grape sugar into alcohol and car- bonic acid is very simple : one equivalent of dry grape sugar C^H^O.^ divides so as to form four equivalents of alcohol and four of carbonic acid gas. 4 equivalents of alcohol 4XC 4 H B 2 = C^II^O, 4 " of carbonic acid gas 4 X C a 4 = C g 0,, 1 " of grape sugar Grape sugar is the only kind which is capable of this fer- mentation ; and, although the others readily yield alcohol and carbonic acid, it is found that the first effect of the fer- ment is to transform them into grape sugar, by the assimila- tion of the elements of water. 697. Weak alcoholic liquors often become acid when exposed to the air, from oxydation of the alcohol and the formation of acetic acid ; but this acid is sometimes directly LACTIC ACID. \C formed from the decomposition of the sugar, independent of the action of the air, and is the cause of the souring of such wines as contain considerable sugar, but are very weak in alcohol. If a solution of sugar is mixed with cheese curd and exposed for some weeks to a temperature of about 68 F., the air being excluded, it becomes acid, and a portion of the sugar is converted into acetic acid C 4 H 4 4 . An equivalent of grape sugar contains the elements of six equivalents of this acid. The presence of cheese curd under condi- tions modified by temperature and the presence of earthy bases, causes other fermentations and different results. At a temperature of from 95 to 104 F. the products are lactic acid C 13 H 12 12 , and a viscous substance analogous in composition to sugar. Such a decomposition takes place in the juices of beets and carrots at a high temperature, and has been called the viscous fermentation. Mannite some- times appears as a secondary product. If carbonate of lime is added to saturate the lactic acid as soon as formed, the decomposition proceeds at a lower temperature, and the lactate of lime is almost the only product. An equivalent of grape sugar C^II^O^. breaks up into two equivalents of lactic acid C 12 Hj 3 12 . 698. The action of the curd of milk in a more advanced state of decomposition gives rise to the vinous fermentation : milk at the ordinary temperature becomes sour from the conversion of its sugar into lactic acid, but when kept at about 100 the grape sugar at first formed is converted into alcohol and carbonic acid gas. In this way the Tartars pre- pare a spirit from mare's milk; an elevated temperature promotes the decomposition of the curd and enables it to effect this transformation. 699. Lactic Acid, C la H 12 13 . This acid may be obtained from sour milk, but is more easily prepared by the fermenta- tion of sugar with caseine. Fourteen parts of cane sugar are dissolved in sixty of water ; to the solution is then added four parts of the curd from milk, and five parts of chalk to neutralize the acid as it is formed. This mixture is kept at a temperature of 80 to 95 F. for eight or ten days, or until it becomes a crystalline paste of lactate of lime. This ' t s pressed in a cloth, dissolved in hot water, and filtered ; the solution is then concentrated by evaporation. On cool- ing, it deposits the salt in crystals, which may be purified by recrystallization. The lactate of lime may be V>CGIU- 406 ORGANIC CHEMISTRY. posed by the careful addition of oxalic acid, which precipi- tates the lime, and the solution of lactic acid thus obtained is concentrated by evaporation, and puri6ed by solution in ther. It is a syrupy liquid, of specific gravity 1-215, and is strongly acid to the taste. 700. When lactic acid is heated to 482, a white crystal- line substance sublimes, which is called lactide: it is derived from the acid by the abstraction of the elements of two equi- valents of water, and has the formula C 13 II S S . It is soluble in alcohol, but scarcely soluble in water : by long continued boiling with it, however, it is converted into lactic acid. This acid is bibasic, and its salts are generally soluble and crystallizablc. The lactate of lime C 13 H 10 Ca 3 13 crystallizes in fine prisms, with six equivalents of water. The lactate of zinc is obtained by decomposing a hot concentrated solu- tion of lactate of lime by chlorid of zinc : the salt crystallizes in cooling in beautiful colorless prisms. The lactate of iron C ia H 10 Fc a O ia is sparingly soluble in cold water, and may be prepared by a similar process : it is employed in medicine. A double lactate of lime and potash, and acid lactates of lime and baryta have been obtained ; the latter is C ia (H 11 Ba)0 ls . If the crystalline paste of caseine and lactate of lime is kept for some time at a temperature of about 95, the salt gradually redissolves, hydrogen and carbonic acid gases escape, and when, after a few weeks, this new fermentation has sub- sided, there remains only a solution of the lime salt of a new acid, butyric acid, C 8 H S 4 . In this butyric fermentation, the lactic acid is decomposed into carbonic acid, hydrogen and the new acid, C 13 H I3 13 = 2C 3 4 + 2H 3 +C 8 H 8 4 . 701. Under certain circumstances not well understood, there appears as an accessory product to the vinous ferment- ation, an oily liquid, which is homologous with alcohol and has been named amylol. It is represented by C 10 H 13 3 , and is supposed to be formed from sugar by a process which may be called the amylic fermentation, in which, as in the butyric, hydrogen and carbonic acid will be disengaged. The action of dilute nitric acid with cane or grape sugar yields saccharic acid C^H^O^, which is bibasic : strong nitric acid converts sugar into oxalic acid, and chromic acid into formic acid. All of these derivatives will be described in their proper places. 702. When sugar is added to a concentrated solution of three times its weight of hydrate of potash, and heated, the STARCH. 407 mixture becomes brown, and hydrogen gas is evolved. When the action ceases and the mass is cooled, dissolved in water> and distilled with dilute sulphuric acid, it yields formic and acetic acids, with a new acid, the metacetonic, which is obtained as a volatile liquid, with a pungent acid odor. It is monobasic, and has the formula C 6 H 6 4 . A mixture of sugar and quicklime, when distilled, affords acetone and an oily liquid called metacetone which yields metacetonic acid when distilled with a mixture of bichromate of potash and sulphuric acid. Mannite, starch, and gum afford the same results with hydrate of potash and lime. 703. Gum, C^H^O,^. This substance is best known in gum arable : the gums which exude from the cherry and plum, the mucilage of flaxseed, and of many other plants, are identical with it. Gum is soluble in water, and forms a viscid solution, from which alcohol precipitates it unchanged. When boiled with dilute sulphuric acid, it is converted into grape sugar. With nitric acid, gum and lactose yield the rnucic acid, which distinguishes them from all the other bodies of this class. The mucic acid is a white crystalline powder, which is sparingly soluble in water : it is bibasic, and is represented by the formula C 13 H 10 16 . It is conse- quently metameric with the saccharic acid, although quite different in its properties. 704. The pectic acid, which is extracted from many fruits, appears to be nothing but a modified form of gum, and yields grape sugar with dilute acids. It combines with lime and some other bases to form compounds, which have been described as pectates. Both gum and sugar have also the property of exchanging one or two equivalents of hy- drogen for lead, barium, or calcium, to form similar com- binations. 705. Starch, C^H^O^. This substance exists in a great variety of vegetables. It is found in all the cereal grains, in the roots and tubers of many plants, as the potato, and in the bark and pith of various trees. It is obtained by bruising wheat and washing it in cold water, which holds the starch in suspension, and deposits it on standing. Potatoes furnish a large portion of starch by a similar process. The substances known as arrow-root, salep, sago, and tapioca, are varieties of starch, obtained from different plants, and sometimes altered by the heat employed in drying. When examined by the naked eye it is a white shining 408 ORGANIC CHEMISTRY. powder, but under the micro- scope is seen to consist of irregu lar grains, which have a rounded outline, and are composed of concentric layers, covered with an external membrane. The diameter of the grains of potato starch is about 2 ^ D of an inch. Starch is insoluble in cold water, but if the mixture is heated, the globules swell, burst their envelopes, and form a transparent jelly, which is cha- racterized by producing a deep blue color with a solution of iodine. When the solution of starch is mixed with a little acid, or an infusion of malt, and gently heated, it becomes very fluid, and is changed into dextrine.* This has the same com- position as starch, but is very soluble in cold water, and is not colored blue by iodine. If starch is heated to 300 or 400, it is rendered soluble in water, and possesses all the properties of dextrine. In this state it is used in the arts as a substitute for gum, under the names of British yum and Iciocomt'. When dextrine is boiled for some time with dilute sulphuric acid, it is converted into grape sugar. It has been mentioned that grape sugar i.s formed in this way from starch; but its formation is always preceded by that of dextrine. One part of starch may he dissolved in foui parts of water, with about one-twentieth of sulphuric acid, and the mixture boiled for thirty-six or forty hours. The liquid is then mixed with chalk to separate the acid, and by evaporation and cooling affords pure grape sugar. Oxalic acid may be substituted for the sulphuric, with the same result. Starch sugar is extensively manufactured in Europe, and is often used to adulterate cane sugar. In this process the starch combines with the elements of two equivalents of water, C a4 H so 20 -j-2H a O s =C S4 H w O, M : the acid is obtained at the end of the process quite unaltered, and one part of acid will saccharify one hundred of starch by long continued boiling. Starch or dextrine unites with sulphuric acid to #So named, because when a beam of polarized light is passed through the solution, it causes the plane of polarization to deviate to the riyht hand. WOODY FIBRE. 409 form a coupled acid; and it is probable that this is first formed and then destroyed by boiling : at the moment of decomposition, the liberated dextrine takes up the elements of water necessary for the formation of sugar. A small portion of the coupled acid is always found in the solution. 706. The action of an infusion of malt upon sugar is peculiar : this substance is prepared from barley, by moistening the grain with water, and exposing it to a gentle heat till germination takes place, when it is dried in an oven at such a temperature as to destroy its vitality. The grain now contains a portion of starch sugar, and a small portion of a substance called diastase* to which its peculiar proper- ties are due. It is precipitated by alcohol from a concen- trated infusion of malt, as a white flaky substance, which contains nitrogen, and is very prone to decomposition. When a little diastase is added to a mixture of starch and water, at a temperature of from 130 to 140, the starch is soon converted into dextrine, and in a few hours into grape sugar. The action of an infusion of malt is due solely to the presence of a minute portion of this substance, one part of which will convert two thousand parts of starch into sugar. This effect appears to be due to a peculiar state of the diastase, which is a portion of the azotized matter of the grain in a modified form, and is analogous to the ferments, already alluded to. 707. Woody Filrc; Cellulose, C 24 H 30 20 . This substance is the solid insoluble part of vege- tables, and remains when water, alcohol, ether, dilute acids, and al- kalies have extracted from wood all its soluble portions. It is nearly pure in cotton, paper or old linen. The tissue of vegetables is formed principally of cellu- lose. The cellular tissue is seen almost pure, constituting the cell walls of young plants. These cells arc sometimes spherical, or rounded in form. In other cases the woody tissue forms oblong cells, communicating by their extre*ni- Fig. 409. #From the Greek diistemi, to separate, because it separates the insoluble envelopes of the starch globules. 410 ORGANIC CHEMISTRY. ties, as seen in figure 409, which is a section of aspara- gus, and also in figure 410, which shows a fibre of flax much magnified. The cellulose in this form receives Jie name of vascular tissue. In the course of time the walla of the cells become lined with an incrusting matter, which grows thicker with the age of the plant, finally leaving only minute pores or con- duits for the circulation of the sap. This incrusting matter which forms a part of ordinary wood, is named lignin. It is chemically . different from cellulose, but has been little studied. Figure 411 shows the structure of wood as seen in the transverse section of a piece of oak, under the microscope. The black spaces are the ducts, for the circulation of the sap, of which a a a are re- markable examples. The white lines mark the outline and comparative thickness of the original cells, such as are seen in the vertical sec- tion of asparagus, fig. 409. These have been filled with lignin, which is more dense and hard near the centre of the tree than at the exterior. The albuminous matters, Fig. 411. which are the principal cause of the decay of wood, are also more abundant in the outer than in the inner cells. The coloring and resinous matters are deposited with the incrusting material. Cellulose is identical in composition with starch and dex- trine, and by the action of strong sulphuric acid is dissolved and converted into that substance. This experiment is easily made with unsized paper or cotton : to two parts of this, one part of the acid is very slowly added, taking care to prevent an elevation of temperature, which would char the mixture. In a few hours the whole is converted into a soft mass, which is soluble in water, and is principally dextrine. If the mixture is now diluted with water and boiled for throe or four hours, the dextrine is completely converted into GUN-COTTON. 411 grape sugar, which is obtained by neutralizing the acid with chalk, and evaporation. By this process paper or rags will yield more than their weight of crystallizable sugar. 708 The mutual convertibility of these different sub- stances is interesting in relation to many of the phenomena of vegetable life. The starch in the germinating seed is changed by the action of diastase into sugar, in which so- luble form it seems better fitted for the nourishment of the embryo plant. In the growth of this, we have an example of the formation of cellulose from sugar, in which this substance assumes a structural form under the action of the vital force. This is a transformation from the unorganized to the organized, which mere chemical affinity can never effect. 709. Many unripe fruits, as the apple, contain a large quantity of starch, but no sugar. After the fruit is fully grown, the starch gradually disappears, and in its place we find grape sugar. This change constitutes the ripening of fruits, and, as is well known, will take place after they are gathered. In this process we have clearly a conversion of the starch into sugar, by the agency of the vegetable acids present in the fruit a change which is the reverse of the previous one, and is probably independent of life. 710. Xyloidine, Pyroxyline. The action of strong nitric acid upon starch yields a compound very similar to nitro- mannite, which is insoluble in water and very combustible : if we represent N0 4 by X, the formula of this body, to which the name of xyloidine has been given, will be C 34 H 1S X 2 20 = C 3 . t H 18 N 2 38 . With sugar a similar sub- stance may be formed. The action of strong nitric acid, or a mixture of nitric and sulphuric acids, upon woody fibre, such as paper, cotton, or sawdust, gives rise to an interesting substance, which has been named pyroxyline, or gun-cotton, as that form of cellu- lose yields the purest product. The following is an outline of the process: one hundred grains of clean cotton are im- mersed for five minutes in a mixture of an ounce and a half of nitric acid of specific gravity 145 to 1-5, with the same measure of strong sulphuric acid; it is then removed, care- fully washed in cold water from every trace of acid, and dried at a temperature which should not exceed 120. As thus prepared, it preserves the form of the cotton unaltered, but has Iftss strength than the original fibre. Jt inflames 412 ORGANIC CHEMISTRY. by a very gentle heat : sometimes, under circumstances not well understood, it has been observed to take fire at 212 F. Its combustion is instantaneous, accompanied by an immense volume of fiame, and it leaves not the slightest residue. When ignited in a confined space it explodes with great violence : one-tenth of a grain is sufficient to shatter the strongest glass tube. Its power in propelling balls is about eight times greater than that of gunpowder; its tremendous energy depends upon the fact that it is completely resolved, by its combustion, into aqueous vapor and permanent gases, which are carbonic oxyd, carbonic acid, and nitrogen. As these arc much less noxious than the gases resulting from the combustion of gunpowder, the gun-cotton will be found of great use in mining. Its composition is analogous to that of nitro-mannite. There appear to be two species, one of which is soluble in a mixture of alcohol and ether, and the other insoluble ; both are generally present in gun- cotton. They are substitution products from cellulose, and, representing N0 4 by X, the insoluble form is C^HjgX^Ogo, and the soluble C^H^X^ = C M II 14 N 8 0. It will be seen that they are formed from the action of nitric acid with the elimination of H 3 0,, for each equivalent of the acid. Thus, C^H 20 20 -h 6NH0 8 = C a4 H M N i 44 +6H.O r The ethereal solution dries rapidly and leaves a tenacious transparent film of pyroxyline : it is used in surgery for covering wounds and abraded surfaces from the air, and is known by the name of collodion. Transformation of Woody Fibre. 711. By the action of atmospheric air and moisture, wood undergoes a slow decay, dependent on the absorption of oxy- gen, to which Liebig has applied the term eremacausis.* The carbon is converted into carbonic acid, while the oxygen and hydrogen of the lignine unite to form water. The re- sidue is still found to contain oxygen and hydrogen in the original proportions, but the relative amount of carbon is continually increasing. For each equivalent of carbonic acid two of water are evolved. The final result of this pro- cess is a brown or black residue, which constitutes vegetable * From erema, slow, and kausis, combustion, a term by which that chemist denotes those changes which take place in organic bodies from the gradual action of oxygen. DESTRUCTIVE DISTILLATION OP WOOD. 413 mould. Different products of this decomposition have been described under the names of humus, yeine, ulmine, humic and ulmic acids. Nearly all of these bodies contain ammonia, for which they have a strong affinity : this is in part absorbed from the air, but the experiments of Mulder seem to show that they have the power of forming ammonia from the nitrogen of the atmosphere. Pure humic acid moistened and placed in a close vessel filled with air, is found after some months to contain a considerable quantity of ammonia. The hydro- gen, evolved by a slow decomposition of the water, is brought into contact with nitrogen under such conditions that they combine and produce the alkali. 712. The decomposition of wood, when buried in the ground and excluded from the action of the air, is very dif- ferent. The oxygen which it contains gradually combines with the carbon to form carbonic acid, and substances are obtained in which the proportion of carbon and hydrogen is greater than in the original fibre. Peat, lignite, and bitu- minous coal are products of this decomposition. The car- bon and hydrogen in coal combine in various ways, and often generate vast quantities of gaseous carburets of hydro- gen, (450.) Anthracite has resulted from the action of heat on bituminous coal, which has expelled all the volatile in- gredients, and left a residue of nearly pure carbon. Destructive Distillation of Wood. 713. The principal products of the decomposition of wood by heat are carbonic acid gas, water, and gaseous carburets of hydrogen. With the water are mixed several other bodies, among which are acetic acid and pyroxylic spirit, presently to be described, and a quantity of oily, tar-like substance, containing several interesting bodies, which we shall mention. These products are .obtained on a large scale by distilling wood in iron cylinders ; the quantity of acetic acid is so considerable that the process has become important in the arts. Kreasote. This substance occurs dissolved in the crude acetic acid from wood, and is separated and purified by a complicated process. It is a colorless oily fluid, which boils at 397, and has a specific gravity of 1-037. It 1ms a peculiar and very persistent odor, resembling that of smoke, and a powerful burning taste. It is soluble in about 100 414 ORGANIC CHEMISTRY. parts of water, and the solution possesses powerful antiseptic qualities. Meat which has been soaked in it is incapable of putrefaction,* and acquires a delicate flavoi of smoke. The power of wood-smoke to preserve flesh is due to the presence of kreasote. It is a corrosive poison when taken in any quantity, but a dilute solution is used medicinally, both internally and externally, as a styptic and antiseptic. The composition of kreasote is C 14 H 8 3 . It combines with the alkalies to form crystalline compounds. 714. Wood-tar contains several carburets of hydrogen, one of which, called eupion, is an oily, fragrant liquid, of the specific gravity -655, being the lightest liquid known. Its formula is, probably, C 6 H 6 . Paraffin. This is a white crystalline substance, obtained from the less volatile portions of wood-tar. It crystallizes in delicate needles, which fuse at 110 ; it is soluble in alco- hol and ether. Its formula is C 43 II 50 . Paraffin is obtained in large quantities by the dry distillation of beeswax. 715. Coal-tar consists principally of a mixture of various hydrocarbons; some of these are liquid and very volatile, constituting what is called gas naphtha. Among the less volatile products are two solid carburets of hydrogen, naph- thalen, and paranaphtJialen, or anthracen. The first of these is formed by the decomposition of many organic matters by heat. Its formula is C 20 H 8 : it is volatile, and forms beautiful pearly crystals of a fragrant odor. The action of chlorine, bromine, and nitric acid on naphthalen, gives rise to a great number of compounds. They are formed by suc- cessive substitutions of the hydrogen by one or more of these substances, and many metameric modifications of these bodies exist. Thus, the bichlorinized naphthalen C 20 H 6 C1 3 occurs in seven modifications, which are perfectly distinct in their characters. We are led to suppose that these compounds owe their different properties to a different arrangement of their constituent atoms, and it is easy to see that, in this way, the number of possible combinations will be immense. More than twenty substances have been described, in which chlorine is in part substituted for the hydrogen of the naph- thalen. The final product of the action of chlorine is C 20 C1 8 , being a chlorid of carbon, which preserves the type of naph- thalen. In addition to these, coal-tar contains a consider- * Hence the name, from the Greek kreas, flesh, and soto, I preserve. ALCOHOLS. 415 able proportion of a body named phenol, and several organic alkaloids. The watery products of the distillation of coal hold a large quantity of ammonia in solution, often combined with hydrosulphuric and hydrocyanic acids. 716. Petroleum. In many parts of the world an oily matter exudes from the rocks, or floats on the surface of springs. The principal sources of this substance are Amiano in Italy, Ava, and Persia, but it is found in many places in our own country. The well-known Seneca oil is an instance of this kind. Petroleum is a variable mixture of several bodies. By distillation, it yields a colorless liquid, called naphtha, which is very light, volatile, and combustible. Its formula is, probably, C 13 H 10 . Naphtha occurs nearly pure in Italy and Persia, and is used for illumination. Petroleum contains a variety of other bodies, among which are paraffin, and several resinous matters, formed, perhaps, by the oxydation of naphtha. These substances are pro- bably derived from coal or other matters of vegetable origin. ALCOHOLS. 717. This series of compounds has already been alluded to in explaining the principle of homology. The alcohols may be represented by C n H w 4_ 3 3 , n being a number divisible by two : all of them by oxydizing agents lose H 3 and combine with 3 to form monobasic acids, whose general formula is C^H n 4 . Of these acids we have now nearly a complete series up to the stearic acid, in which n = 38. But a few of the corresponding alcohols are known j the principal are methol C 3 H 4 3 , wine alcohol C 4 H G 3 , amylic alcohol oramylol C 10 H 13 3 , and cctic alcohol or cetol C 33 H 34 3 . We shall first describe the alcohol of wine, to which we may conveniently give the name of vinol : it is the best known and most important of the series, and will serve to illustrate the history of the others. VINOL COMMON ALCOHOL, C 4 H 6 3 . This substance has long been known under the name of alcohol, or spirits of wine. We have already explained the manner in which it is obtained as a result of the fer- mentation of sugar. The vinous fermentation in the juice of the grape and -other fruits, in an infusion of malt, or in the 416 ORGANIC CHEMISTRY. syrup of the sugar-cane, always results in the conversion of the sugar which it contains, into alcohol and carbonic acid gas. When the fermentation is arrested before all of the Bugar is decomposed, tho wine is sweet; if the liquor is bottled before the action is finished, the excess of carbonic acid remains in solution, and gives an effervescent and spark- ling property, as in bottled beer and champagne. When these fermented liquors are distilled, the alcohol, boiling at a lower temperature than water, passes over first. By repeated distillation in this way, a liquid is obtained which contains 85 parts of alcohol in 100. To obtain it free from water, it is digested with quicklime, or better with fused chlorid of calcium, which combines with the water. The mixture is then distilled in a water-bath, and pure alcohol passes over. A convenient apparatus for condensing the vapor of alcohol, ethers, and other volatile substances, is shown in figure 412. Fig. 412. The retort r is connected with a glass condensing tube t, about which a metallic tube ra is secured by corks at the ends, leaving a water-tight space between the two. A funnel tube / conducts cold water from the tank w to the lower end of the condenser. This escapes at the upper orifice o, thus maintaining a constant current of cold water, by means of which the vapors of even very volatile liquids are easily condensed. 718. Pure or absolute alcohol is a colorless fluid, with a specific gravity of about -800, and boils at 173 F. Its den- ACTION OF ACIDS UPON ALCOHOL. 417 sity varies very much with its temperature, (102 ;) thus at 82 it is 0-815 ; at 50, -8065 ; at 59, -8021 ; at 68, -7978 ; and at 77, -7933. It has a pungent and agreeable taste and a fragrant odor. It is very combustible, and burns with a pale blue flame without smoke, which renders it very useful as a source of heat in chemical processes. The action of alcohol on the system is well known as that of a power- ful and dangerous stimulant. It is largely used in the operations of the arts, the preparation of medicines, and the processes of chemistry. Its solvent powers are very great : the volatile oils and resins are dissolved by it, as well as many acids and salts, the caustic alkalies, and a large num- ber of other substances. The density of alcohol vapor is 1589-4, and its equivalent is represented by four volumes, oxygen being one volume ; thus 4 volumes of carbon vapor ............. 4X 829. = 3316'0 12 " hydrogen .................. 12 X 69-2 = 830-4 2 oxygen .................... 2 X 1105-6 = 2211-2 6357 7 6 Equal 4 volumes alcohol vapor, of which 1 volume weighs.... 1598-4 719. Pure alcohol dissolves several salts, as the chlorid of calcium and the nitrates of lime and magnesia, and forms with them crystalline compounds, in which the alcohol takes the place of the water of crystallization, by virtue of the homologous relation which it sustains to water. When potas- sium is added to alcohol free from water, hydrogen is evolved and a crystalline compound formed, in which the metal replaces hydrogen. It is C 4 H.K0 2 , and by the action of water is decomposed into alcohol and hydrate of potash, C 4 ELK0 3 -f H 3 2 = C 4 H 6 O 2 -f (KH)0 3 . By an indirect pro- cess, a compound is obtained in which the oxygen of alcohol is replaced by sulphur, and which is C 4 H 6 S 2 . It is a colorless very volatile liquid, having a strong odor resembling that of onions. Like the oxygen species, it may exchange H for a metal ; with oxyd of mercury it forms water and a crystal- line compound C^H 5 HgS a : from the violence of the action it has received the fanciful name of mercaptan, (from mer- Action of Acids upon Akohol. 720. It has been shown that when n in the general formula of the alcohols becomes equal to zero } we have 27 418 ORGANIC CHEMISTRY. water H 3 2 , which may be regarded as their homologuc and prototype. We have farther pointed out the fact that a group of elements is often found to be equivalent to an atom of hydrogen, and capable of replacing it in combination : such is NH 4 in the ammonia salts; and in the compounds of vinic alcohol, the group C 4 H 5 will be found to sustain simi- lar relations. In water, which is (HH)O a , one atom of hydrogen may be replaced by this group, and we have then (C 4 H 5 .H)O a , which is alcohol. In the potassium compound just described, the second atom of hydrogen is replaced by a metal, and we shall presently describe a compound in which both atoms of the hydrogen are replaced by the organic group: it is (C 4 H 5 .C 4 H 5 )0 3 ==C 8 H 10 3 . This same group may also replace the hydrogen in acids; a monobasic acid reacts with one equivalent of alcohol and eliminates an equivalent of water, forming a compound in which C 4 H 5 replaces H in the acid, and renders it neutral. Such compounds are called ethers of the various acids. With bibasic and tribasic acids, two and three equivalents of alcohol combine to form neutral ethers, and eliminate two and three equivalents of water. But when a bibasic acid re- acts with but one equivalent of alcohol, only one atom of its hydrogen is replaced, and the second atom remains as be- fore, capable of being exchanged for a metal. Such com- pounds are acid ethers or vinic acids. 721. Although the ethers are thus analogous to salts in their constitution, they are less readily decomposed than the corresponding metallic salts ; they frequently require the aid of heat to effect the breaking up of the combination, and are generally more stable as their equivalent is more elevated. The neutral ether containing sulphuric acid, for example, does not precipitate salts of baryta, and the corresponding vinic acid forms a soluble s&t with that base. In these, and many other instances, the properties of the acids seem masked in their ethers, but similar cases are met with in the salts of inorganic bodies. 722. The action of chlorohydric acid, and other acids containing no oxygen, upon alcohol, requires a little explana- tion. We have seen that when HC1 acts upon a metal, the compound eliminated is of the type H a ; but when the hy- dracid acts upon a hydrated oxyd, as (KII)0 3 , the same chlorid is formed, and H 3 2 is evolved; so it is with al- cohol, which with hydrochloric acid yields water and a body ETHERS. 419 C 4 H S 01. As C 4 H 5 is equivalent to H, the new ether repre- sents chlorohydric acid, and is evidently the chlorinized species of a hydrocarbon C 4 H 6 , which should yield with (Cl a ) the same product, as a result of direct substitution. As water H 3 a is the prototype of the alcohols, so (H a ) is the prototype and homologue of the carbohydrogens like C 4 H 8 , whose formula is C J! n+2 C M H n -fH 3 ; and chlorohydrio acid HC1 is the type of the chlorohydric ethers. As the ethers of alcohol contain 4 H 5 , replacing H in the acids, and consequently differ from the latter by (C 2 H 2 ) 3 , it follows that the ethers are always homologous with their parent acids. In describing these compounds, we shall often designate the group C 4 H 5 by the symbol Et, and write alcohol (EtH)O a . Ethers. 723. Chlorohydric Ether, CJIl==fttCl. When alcohol is saturated with chlorohydric acid gas, and heated, it is con- verted into water and this ether, (EtH)0 3 +HCl = EtCl -f- H 2 a . By distillation it is obtained as a pungent aromatic liquid, slightly soluble in water, and boiling at 52 F. : at a temperature of 4 it crystallizes in cubes: its specific gravity is '873. By distilling alcohol with hydrobromic acid, or a mixture of phosphorus and bromine, which evolves the acid, hydro- bromic ether EtBr, is obtained as a volatile liquid heavier than water; and by substituting iodine for bromine, liydriodic ether EtI is found. It is a colorless liquid, with a specific gravity of 1-920, and a boiling point of 160 F. These ethers are all decomposed by an alcoholic solution of hydrate of potash into alcohol and a potassium salt, EtCl-f-(KH)0, 1 , = (EtH)0 2 -|-KCl. By the action of potassium upon chlo- rohydric ether, a compound is obtained in which K replaces Cl. It is C 4 H 5 K orEtK : this is decomposed by water into hydrate of potash and a volatile oily substance C 4 II 6 , to which the name of acetene has been given. It is the hydro- carbon corresponding to H a , and may be written EtII. Another product has been formed, which is C 8 H 10 , in which the second atom of hydrogen is replaced by C 4 H. : it is EtEt, and has a density corresponding to four volumes of vapor. The binary grouping which prevails throughout all com- pounds is such as to forbid the isolation of the elements C 4 H 5 , which are always grouped with a metal, chlorine, or 420 ORGANIC CHEMISTRY. even another equivalent of themselves, so that the law of divisibility is never violated. 724. Nitric Ether N(Et)0 B = N(C 4 H 5 )0 6 . The action of alcohol and nitric acid is violent and irregular, the alcohol being oxydized at the expense of the oxygen of the acid, and several compounds formed ; but the addition of a little urea or nitrate of ammonia to the mixture of the acid and alcohol prevents this, and the ether is then formed and distilled over by the aid of heat ; water being the only other product. Nitric acid N0 5 HO = NH0 6 +(EtH)O a =NEt0 6 H-H a O a . It is a colorless liquid of a sweet taste, is heavier than water, in which it is insoluble, and boils at 185 F. Its vapor explodes by heat. 725. Nitrous Ether, or Hyponitric Ether, N(Et)0 4 = C 4 H 5 N0 4 . When nitric acid acts upon starch, copious red vapors are evolved, which are anhydrous hyponitric acid N0 3 : they are rapidly absorbed by dilute alcohol, with the produc- tion of sufficient heat to cause the new ether to distil over, when it is condensed by means of ice. Hyponitric acid N0 3 HO = NH0 4 +(EtH)0 3 =N(Et)0 4 +H 8 O a . The hyponitric ether is a pale yellow liquid, having a fragrant odor of apples : it boils at 62, and has a specific gravity of -947. It is one of the pro- ducts of the action of nitric acid with alcohol, when urea is not added; and a solution of the impure product in alcohol, obtained by distilling alcohol with nitre and sulphuric acid, constitutes the sweet spirits of nitre of the old chemists, which is still used in medicine. If a mixture of nitric acid and alco- hol is distilled with the addition of turnings of metallic cop- per, pure nitrous ether may be obtained. Nitrous ether undergoes a remarkable decomposition by the action of sulphuretted hydrogen : the gas is rapidly absorbed, with the separation of sulphur, and alcohol, water, and ammonia are formed ; C 4 H 6 N0 4 +3H .S fl = S 6 +H 2 3 -|-C 4 H 6 0+NH 3 . Perchloric ether is obtained by an indirect process as an oily liquid, heavier than water, having a sweet, pungent taste, like oil of cinnamon. It explodes by slight friction, heat, or percussion, with fearful violence. Perchloric acid being C10 7 HO = C1H0 8 , the ether is C1(C 4 IL)0 8 . Like the nitric and hyponitric ethers, it is decomposed by an alcoholic solu- tion of hydrate of potash into alcohol and a perchlorate. Sulphovinic Acid. . 726. When sulphuric acid, mixed with its weight of alcohol, is heated to boiling, combination ensues with the SULPHOVINIC ACID. 421 elimination of water, and sulphovinic acid is formed; sul- phuric acid S ? H 3 8 +(EtH)O a =S 2 (EtH)0 8 +H a 3 . By diluting the mixture with water and saturating it with car- bonate of lime, the free sulphuric acid is converted into insoluble sulphate of lime, and the soluble sulphovinate is obtained by evaporating at a gentle heat and cooling, in colorless prisms. As the carbohydrogen elements have re- placed one equivalent of hydrogen in the sulphuric acid, the new acid is monobasic, and the lime salt is S 3 (EtCa)O a -f-H fl O a : this water of crystallization is lost in a dry atmo- sphere. By substituting carbonate of baryta for lime, the baryta salt S 3 (EtBa)0 8 is obtained in fine crystals; from this salt, by double decomposition, the sulphovinates of other bases may be obtained. Dilute sulphuric acid preci- pitates all the baryta from the baryta salt, and sulpho- vinic acid, S 2 (EtH)0 8 is obtained in solution : when concen- trated in vacuo it forms a syrupy liquid, which is decomposed by heat into alcohol and sulphuric acid, by taking up the elements of water. The lime and baryta salts undergo, in part, a similar decomposition by boiling, and after several years, even at the ordinary temperature, are changed into sulphates and alcohol. With hydrate of potash a similar change takes place by heat, and alcohol and a sulphate are formed. Sulphovinate of potash S 3 (KEt)0 8 -f(KH)0 3 =S 2 K 3 8 -h(EtH)0 3 ; or neutral sulphate of potash and alcohol. If the hydro-sul- phuret of potash KS.HS = (KH)S fl is employed, sulphur- alcohol (EtH)S 3 is formed by a similar reaction ; and with any salt, like the acetate of potash C 4 H 3 K0 4 , a compound is ob- tained, in which Et replaces K : it is C 4 H 3 (Et)0 4 , or acetic ether. In this way the perchloric and many other ethers are formed by double decomposition. 727. When carefuHy dried sulphovinate of potash is dis- tilled with a mixture of potassic alcohol (EtK)0 2 , sulphate of potash is formed, and a volatile liquid distils over, in which the second atom of H is replaced by the elements C 4 H 5 . S 3 (EtK)0 8 -f-(EtK)0 3 r=S 3 K 3 8 +(EtEt)0 3 . This compound is also obtained when, within certain limits of tem- perature, sulphovinic acid acts upon alcohol; S B (EtH)O 8 -|-(EtH)0 3 ==S 3 H 3 8 -f (EtEt)0 3 being the products. The result of this complete substitution may be conveniently designated as hydrovinic ether, precisely as alcohol is hydro- vinic acid. It has long been known in the history of tho 422 ORGANIC CHEMISTRY. science under the simple name of ether, which has since beec extended to a great number of allied products, and has become a generic term. It is a colorless, limpid, volatile liquid, and as its vapor is very combustible, should never be brought near a flame. It has a specific gravity of -725, and boils under the ordinary pressure of the atmosphere at 96 F. : by its rapid spontaneous evaporation it produces great cold. It is sparingly soluble in water, and the ether of the shops, which often contains alcohol, may be purified by agitation with its volume of water, which dissolves the alcohol, while the ether floats upon the surface. Although in the liquid state it is lighter than alcohol, its vapor is much heavier. The density of ether vapor is 2556-3 ; four volumes then equal 10227*2, and contain two equivalents, or eight volumes of alcohol, minus one equivalent, or four vo- lumes of water : 2 equivalents of alcohol vapor, 2 X 6357*6 = 12715-2 1 equivalent of water H a O a 2488-0 1 equivalent, or four volumes of ether vapor = 10227*2 1 volume of ether vapor 2556-3 Its equivalent is therefore 2C 4 H 3 = C 8 H 13 4 H 3 3 = C 8 H 10 2 , or Et a 3 . 728. Ether is used in the arts and in many chemical pro- cesses as a solvent; and in medicine, internally as a stimu- lant, and externally as a refrigerant, from the cold produced by its evaporation. An important application was some years since pointed out by Dr. Charles T. Jackson, of Boston, and introduced into practice by Mr. Morton, a dentist of that city : it depends upon the fact that the vapor of ether, when mixed with atmospheric air and inhaled, produces a kind of intoxication, followed by a state of stupor, in which it was found by these gentlemen that the subject is so far insensi- ble to external impressions, as to undergo the most difficult surgical operations without pain. This important discovery has been very extensively applied both in this country and in Europe ;* and the vapor of several other liquids has been found to produce similar effects. 729. In the manufacture of ether on a large scale, the reaction of sulphovinic acid and alcohol is employed. When * The French government, in token of the high importance of the dis- covery, has bestowed upon Dr. Jackson the Cross of the Legion of Honor. ETHERS. 423 the mixture of alcohol and sulphuric, acid containing sul- phovinic acid and water, is diluted, so as to boil much below 300 F., it is, as we have already shown, decomposed again into sulphuric acid and alcohol ; but at about 300 F., the sulphovinic acid reacts upon a second equivalent of alcohol instead of an equivalent of water, and yields sul- phuric acid and ether. By an ingenious method, the alter- nate formation and decomposition of sulphovinic acid may be made to furnish an unlimited supply of the new pro- duct. The arrangement is represented in the fig. 413. A mixture of five parts of alcohol of 90 per cent, and Fig. 413. eight parts of ordinary sulphuric acid is placed in the flask e, through the cork of which passes a thermometer t, and two tubes, one of which d, conveys the vapors away to a condenser B, while the other a, which dips below the surface of the liquid, is arranged to supply pure alcohol from a reservoir E. The mixture is now raised to its boil- ing point, which is about 300 F., and carefully maintained at that temperature, so as to be in constant ebullition. Al- cohol is slowly admitted through the cock /, in sufficient quantity to preserve the original level of the liquid in the flask. In this way, as the sulphovinic acid meets with tho 424 ORGANIC CHEMISTRl alcohol, it is decomposed into ether and sulphuric acij, but this reacting upon another portion of alcohol, forms water, which is volatilized, and a new portion of sulphovinic acid, to be decomposed in its turn. The ether and water distil over and are condensed together; and the same portion of sulphuric acid will serve to convert an indefinite quantity of alcohol into water and ether; a trace only of the sul- phuric acid passes over. The ether is decanted from the water, and purified by distilling from, a small quantity of hydrate of potash. 730. As it has long been obtained by the distillation of sulphuric acid with alcohol, it was formerly called sulphu- ric ether, a name which is still sometimes retained. The true sulphuric ether, which corresponds to the other neutral ethers, is obtained by the action of anhydrous sulphuric acid upon hydric ether. It is a neutral, dense, oily fluid, and differs from sulphovinic acid in having the second equiva- lent of II replaced by Et, its formula being S 2 (Et 3 )0 8 . By heat it is decomposed, in the presence of water, into sul- phovinic acid and alcohol. 731. Compounds have been obtained which correspond to ether in which 3 is replaced by sulphur, selenium, and tellurium. The sulphur compound is C 8 H 10 S 3 or Et 3 S 3 , and is obtained by the action of hydrochloric ether upon sul- phuret of potassium 2EtCl+K fl S 8 = 2KCl-j-Et 9 S s : with bisulphuret of potassium, a compound is obtained which is Et 3 S 4 , and corresponds to persulphuret of hydrogen H a S 4 . These are volatile liquids, insoluble in water, and having a strong odor like garlic. 732. Phosphoric acid yields several compounds contain- ing the elements of alcohol. The tribasic acid is P0 5 .3HO = PII 3 8 , and the neutral phosphoric ether is P(Et 3 )0 8 . The other two compounds are P(Et 3 H)0 8 and P(EtH 3 )0 8 , and are respectively monobasic and bibasic vinic acids. Cart ovinate of potash is obtained when carbonic acid gas is passed into a solution of hydrate of potash in pure alcohol. The acid being C fl H fl 6 , the new salt is C 2 (EtK)0 B . The acid has not been isolated. The true carbonic ether is C a (Et a )0 6 =C 10 H 10 6 . By substituting bisulphuret of car- bon for carbonic acid gas in the above process, carbovinatea are obtained iu which the oxygen is in part replaced by sulphur. The acid is obtained in a separate form, and ia OIEFJANT GAS. 425 O a (EtH)(O a S 4 ); from the yellow color of some of its salts, it has been called xantliic add. 733. Silicic Ethers. The action of chlorid of silicon upon alcohol yields two silicic ethers. They are odorous, pungent, and volatile liquids, which are rapidly decomposed by alkalies, like the other ethers, and slowly by water alone ; when exposed to moist air, in imperfectly closed vessels, they evolve alcohol and are gradually decomposed, leaving hy drated silicic acid in beautiful transparent masses, resem- bling rock crystal. The formula of one is represented by C 13 H 15 Si0 6 which corresponds to a tribasic silicic acid Si0 3 .8HO = SiH 3 6 , and is Si(Et 3 )0 6 . The other is C 8 H 10 Si 4 14 , which represents a bibasic acid 4Si0 3 4-H 3 O a =Si 4 H 3 14 ; the ether being Si 4 Et a 14 . Chlorid of boron with alcohol yields two similar ethers : they burn with the fine green flame characteristic of boracic acid. Boracic ether is formed when alcohol is distilled from boracic acid, and is the cause of the green flame of an alco- holic solution of the acid. 734. Olefiant Gas, C 4 H 4 . When alcohol is mixed with so much sulphuric acid that the mixture does not boil below 320 F., the sulphovinic acid which is formed, undergoes a decomposition different from those already de- scribed ; it breaks up directly into sulphuric acid and ole fiant gas, S 2 (C 4 H 5 H)0 8 = S 2 (H 2 )0 8 +C 4 H 4 . A more elegant way of preparing it is by an arrange- ment similar to that used for pro- ducing ether. Sulphuric acid is diluted with nearly one-half its weight of water, so that its boil- ing point is between 320 and 330, and being heated in the flask a (fig. 414) to ebullition, the vapor of boiling alcohol is' introduced from the flask d by the tube 6, which dips a little way in the acid. In this process, we may suppose that sulphovinw acid is formed with the escape of an equivalent of water in vapor, and is then im- mediately decomposed into sul- phuric acid and olefiant gas; an equivalent of alcohol yields C 4 lI 4 -fII fl O a . The gas is thus Fig. 414. 426 ORGANIC CHEMISTRY. obtained quite pure, and the process may be continued for any length of time. This compound is a product of the destructive distillation of many organic substances, and is abundant in the gases for illumination prepared by the decomposition of coal and the fat oils. 735. When mingled with its own volume of chlorine combination ensues, and the product condenses as a heavy oily liquid of a sweet pungent taste. It was discovered by an association of Dutch chemists, who, from this reaction, gave to the carbohydrogen the name of olefiant gas. It is C 4 H 4 C1 3 , and corresponds to a carbohydrogen C 4 H 6 , identical in composition with aceten. By the action of chlorine a series of compounds is formed by successive substitutions ; we have C 4 H 3 C1 ? , C 4 H 2 C1 4 , C 2 HC1 5 and C 4 C1 8; A similar series of com- pounds is obtained from chlorohydric ether, which, though re- presented by the same formulas, are unlike in their properties : the two series afford an interesting case of metamerism. The final product of the action of chlorine upon both series of compounds is the chlorid of carbon C 4 C1 6 . This is a white crystalline solid, with an aromatic odor, like cam- phor; it melts at 320, and, at a temperature a little above this, may be distilled unaltered. It is scarcely combustible, and is unchanged by acids or alkalies. When its vapor is pas- sed through a porcelain tube heated to redness, it is resolved into chlorine gas and a new compound C 4 C1 4 , which is a volatile liquid, of the specific gravity of 1-55. If the vapor of this compound is passed repeatedly through a tube at a bright red heat, it is decomposed into chlorine and C 4 C1 8 . This body forms soft, silky crystals, which are vola- tile and combustible. The name of etlicrilen has been applied to the type C 4 H , metameric with aceten, and etheren to olefiant gas. The derivatives will be monochloricj bichloric etheren, &c. Bichloric etherilen, by the action of an alcoholic solution of hydrate of potash, yields chlorid of potassium and mono- chloric etheren C 4 H 3 C1 : the same way, trichloric etherilen gives C 3 H 2 C1 3 ; and sexchloric aceten C 4 C1 6 , with hydrosul- phuret of potassium, yields C 4 C1 4 . Products of the Oxydation of Alcohol. 736. Aldehyd or Acetol, C 4 H 4 O a . The action of oxyd- izing substances removes H a from alcohol and yields PRODUCTS OP OXYDATTON OP ALCOHOL. 427 aldehyd.* It is formed, together with nitrous ether, when nitric acid acts upon alcohol. One equivalent of nitric acid NH0 6 +C 4 H 6 3 =:H 2 3 -fNH0 4 -|-C 4 H 4 2 ; besides aldehyd, water and nitrous acid are the products, the latter of which forms an ether with another portion of alcohol. Aldehyd is best obtained by the aid of chromic acid act- ing upon alcohol. For this purpose an apparatus may be constructed like fig. 41 5 ; entirely of glass, which will bo Fig. 415. found very useful for the distillation of numerous volatile products in organic chemistry. Equal weights of pow- dered bichromate of potash and strong alcohol are introduced into the flask a, and 1 parts of sulphuric acid are gradu- ally added by the safety tube s. Much heat is produced by the mixture, and the distillation commences at once, but is continued by a gentle lamp-heat under the sand-bath of a. . The condensing tube t is of glass, and iced water from, the reservoir n enters and escapes by the two glass tubes i, v, the former of which has a funnel mouth. The impure product is mixed with ether and satu- * Whence its name, from alcohol deliydrogcnatu*. 428 ORGANIC CHEMISTRY. rated with ammonia, when a compound of aldchyd and ammonia separates in fine crystals. This, decomposed by dilute sulphuric acid, affords pure aldehyd, as a colorlesa liquid having a suffocating ethereal odor. It boils at 70 F., and has a specific gravity of -790 : it mixes readily with water, and, when heated with a solution of potash, becomes brown and deposits a resinous substance. The abstraction of H 2 seems to have been made from the group C 4 H 5 , and C 2 H 3 appears in acetol to play the same part as C 4 H 5 in alcohol. Thus, with potassium a com- pound is formed which is (C 4 H 3 .K)0 2 , and the crystalline compound with ammonia is C 4 H 4 6 2 4-NH 3 = (C 4 H 3 .NH 4 )O a , in which NH 4 replaces II. When a solution of aldehyd is added to one of ammoniacal nitrate of silver, the metal is reduced and lines the vessel with a brilliant film of sil- ver. A similar process has been successfully applied to the manufacture of mirrors. 737. Aldehyd cannot be preserved unchanged, even in sealed tubes, but is slowly changed into two polymeric com- pounds. One of these, claldchyd, is a dense oily fluid, which has none of the properties of aldehyd. The density of its vapor is three times that of aldehyd ; and its formula is 3C 4 H 4 2 = C 12 H 13 O q . The other body, meta Idcliyd, forms hard white prisms ; it is formed by the union of four equiva- lents of aldehyd, and is C lfl H 16 O s . Aldehyd is also ob- tained as a product of the decomposition of lactic acid or lactate of copper by heat, and is formed in large quantity when a lactate is distilled with binoxyd of manganese and sulphuric acid. When the isomerism of lactic acid with glucose is considered, it is easy to understand that while the latter is decomposed by fermentation into carbonic acid and alcohol, lactic acid by oxy elation may yield carbonic acid and aldehyd. We shall see, farther on, that it is possible to reproduce lactic acid from aldehyd. 738. Chloral* By the prolonged action of chlorine upon alcohol a liquid is obtained, to which the name of chloral has been given. It is aldehyd in which chlorine replacca II 3 , and is represented by C 4 (HC1 3 )0 2 . Sulphur aldehyd C 4 H 4 S 3 has also been obtained, and both the trichloric and sulphuretted species yield polyme- ric modifications similar to those of normal aldehyd. The action of sulphuretted hydrogen upon an aqueous solution of aldchydate of ammonia produces large transparent crys- PRODUCTS OP OXYDATION OP ALCOHOL. 429 tals of an organic base, named thialdine. It is slightly soluble in water, but dissolves readily in alcohol and ether : the crystals are very fusible and volatile, and may be dis- tilled with the vapor of boiling water. The formula of thialdine a C 13 H 13 NS 4 : it corresponds to an amid of the trimeric modification of sulphuretted aldehyd C 13 H 13 S 6 . This base has no alkaline reaction, but forms beautifully crystalline salts. A corresponding compound, in which selenium replaces sulphur, has been formed, but is very unstable. A mixture of bisulphuret of carbon with an alcoholic solution of aldehydate of ammonia deposits sparingly soluble crystals of a new base, called carbo-tJiialdine, which is represented by C 10 H 10 N 3 S 4 . It contains the elements of two equivalents of aldehyd, and its formation is thus re- presented : 2C 4 H 7 N0 9 +0 9 S 4 =2H 9 9 +C 10 H 10 N 9 S 4 . 739. Acetic Add, C 4 H 4 4 . When aldehyd is exposed to the air it absorbs 3 and is converted into acetic acid C 4 H 4 3 -f-0 2 =C 4 H 4 4 . If a mixture of hydrate of potash and linie be moistened with alcohol and exposed to heat, hydrogen gas is evolved, and an acetate formed, C 4 H 6 O a -|- KH0 3 =C 4 H 3 K0 4 +H 4 . 740. Pure alcohol undergoes no change when exposed to the air alone ; but if its vapor mixed with air is brought into contact with platinum-black, it slowly unites with oxygen to form aldehyd, which readily absorbs another portion of oxygen and produces acetic acid. The oxydating power of finely-divided platinum has been before alluded to ; it ab- sorbs or condenses great quantities of gases and vapors in its pores, where they appear to be brought together in such a state that they readily react upon each other. 741. The formation of acetic acid may be beautifully shown by placing a little platinum -black in a watch-glass, by the side of a small vessel of alcohol, covering the whole with a bell-glass, and setting it in the sunlight. In a short time the vapor of acetic acid will condense on the sides of the glass, and run down in drops; and if we occasionally admit fresh air by raising the bell-jar, the whole of the alcohol will be acidified in a few hours. In the ordinary process for vinegar, alcoholic liquors, as wine and cider, are exposed to the air in open vessels. Although a mixture of pure alcohol and water does not absorb oxygen from the air, a small portion of any ferment, 430 ORGANIC CHEMISTRY. as vinegar, already form ed, or the fun gus plan t called mother of vinegar, enables it to com- bine with oxygen. In this process the essen- tial thing is a free supply of air and a propel temperature. In the manufacture of vine- gar on the large scale, this is secured by causing the liquor (b, fig. 416) to trickle from threads of cotton drawn through holes, over shavings of beech-wood previously soaked in Fig. 416. vinegar, and contained in a large cask with holes in its sides, (c c c c,) so as to admit a free circulation of air. In this way a vast surface is exposed, and the ab- sorption of oxygen is very rapid, causing an elevation of 20 or 30 in the temperature. The liquid is passed through this apparatus four or five times in the course of twenty-four hours, in which time the change of the alcohol into vinegar is generally complete. The product is collected in the vessel a. 742. Acetic acid is also obtained by distilling wood in close vessels, (712,) a process employed on a large scale for the preparation of the acid. The products are, besides car- bonic acid and carburetted hydrogen, a large quantity of acetic acid mixed with oily and tarry matters, from which it is separated mechanically. The acid thus prepared is known as pyroliyneous acid, and is largely used in the arts of dyeing and calico-printing ; but being contaminated by cmpyreumatic oils, is not fit for the purposes of domestic economy. By combining it with bases, salts are obtained, which, when decomposed, afford a pure acid. 743. By distilling dried acetate of soda with strong sul- phuric acid, a very concentrated acid is obtained, which, when exposed to cold, deposits crystals of pure acetic acid C 4 H 4 4 . The pure acid is solid below 60 F. ; when liquid, it has a specific gravity of 1-063, and boils at 248. It is perfectly soluble in water, alcohol, and ether ; it has a pun- gent fragrant odor and a very acid taste, and, when applied to the skin, is highly corrosive. The acid is monobasic ; all its salts are soluble in water. Acetates. 744. Acetate of potash C 4 H 3 (K)0 4 is easily prepared by neutralizing acetic acid with carbonate of potash. It is a very soluble deliquescent salt, and is employed in medicine. ACETATES. 431 Acetate of soda C 4 H 3 (Na)0 4 forms large crystals with six equivalents of water. It is prepared in large quantities from pyroligneous acid; the salt is heated to destroy the oily matters, and then affords by its decomposition a pure acid. Acetate of ammonia C 4 H 4 4 +NH 3 == C 4 H 3 (NH 4 )0 4 is used in medicine by the name of the spirit of Mmdereus. It is prepared by saturating acetic acid with ammonia, and is exceedingly soluble and volatile. The acetate of zinc is a beautiful white salt, and is employed as a tonic and astrin- gent. The acetate of alumina C 4 H 3 (al)0 4 is much used in dyeing; it is obtained by decomposing a solution of alum by one of acetate of lead ; sulphate of lead precipitates, and acetate of alumina with acetate of potash remains in solu- tion. The protacetate and pcracetate of iron are prepared in a similar manner, and are largely employed in calico-print- ing and dyeing. They are represented by C 4 (H 3 Fe)0 4 , and C 4 H 3 fe0 4 . (See 649.) 745. Acetate of Lead, C 4 H 3 (Pb)0 4 . This salt is well known under the name of sugar of lead. It is prepared by dissolving oxyd of lead (litharge) in acetic acid, and crystal- lizes with three equivalents of water, which are expelled by gentle heat. It is a white salt, with a very sweet and astrin- gent taste, and is often employed as a medicine ; but is poi- sonous, and should be used internally with caution. The acetate of lead has a great tendency to combine with oxyd of lead, with which it forms several definite compounds. These are generally designated as basic salts, but should be carefully distinguished from the salts containing more than one equivalent of base, which are formed by bibasic and tribasic acids. In these last, the metal replaces the hydro- gen of the acid, but in the basic acetates the neutral salt com- bines directly with the oxyd. To distinguish them, the term surlasic is applied, and the compound of the acetate with an equivalent of oxyd of lead is called the surbasic acetate of lead. Three of these compounds are known, in which the acetate is combined with one-fourth, one, and two and a half equivalents of oxyd. The second is the only one of importance. 746. Surbasic Acetate of Lead, C 4 H 3 Pb0 4 -fPb 3 O a This salt, commonly called the tribasic acetate, is obtained by digesting a solution of six parts of the acetate with seven of litharge ; the oxyd is dissolved, and the liquid affords, by evaporation, a salt crystallizing in long needles. It is also 432 ORGANIC CHEMISTRY. slowly formed when metallic lead is digested in an open vessel with a solution of the acetate, oxygen being absorbed from the air. The salt is very soluble in water, and its solution has an alkaline reaction ; it is known in pharmacy as Goulard's extract, or solution of lead. When exposed to the air, it absorbs carbonic acid, and the equivalent of oxyd of lead is precipitated as a carbonate. This reaction enables us to explain the formation of white-lead. 747. A process frequently employed is to mix litharge and about ^3 of sugar of lead into a thin paste with water? the mixture is gently heated, and a current of carbonic acid is passed through it. The acetate of lead dissolves a portion of the oxyd to form the tribasic salt ; this is immediately decomposed by the carbonic acid, which precipitates car- bonate of lead, and leaves the acetate free to dissolve a new portion of oxyd. In this way the smallest quantity of the acetate is able to convert a large portion of the oxyd into carbonate, and at the end of the process to remain unaltered. 748. In the ordinary process, the plates of lead are ex- posed to the action of acetic acid, moisture, air, and the car- bonic acid from fermenting tan, (588.) The lead immedi- ately becomes covered with a film of oxyd by the action of the air. This is dissolved by the vapor of the acetic acid, and forms a solution of neutral acetate, which moistens the plates and gradually acts upon them, forming, by the aid of the atmospheric oxygen, the basic acetate, which is decomposed by the carbonic acid, in the same manner as in the last process, and the neutral acetate is again set free to act upon the me- tallic lead ; the process goes on until all the lead is carbon- ated. In this way a small quantity of acetic acid will, under favorable circumstances, convert a hundred times its weight of lead into carbonate in a few weeks. 749. Acetate of Copper, C 4 H 3 (Cu)0 4 . This salt is very soluble, and forms beautiful green crystals of the monoclinic system, containing one equivalent of water. The acetate of copper forms several surbasic salts which are insoluble in water. The fine green pigment called verdigris is a mix- ture of two or more of these : all of these copper salts are very poisonous. The acetate of silver C 4 H 3 (Ag)0 4 crystal- lizes in white scales, and is the least soluble of the acetates. 750. Chlomcetic AdJ, C t Cl 3 (H)0 4 . We have already mentioned this product of the action of chlorine upon crystallizable acetic acid ; one equivalent of the acid and ACETATES. 43,3 three of chlorine yield three of chloroliydrie acid and one of the new compound, C 4 H 4 4 -f 3C1 3 ==C 4 C1 8 (H)0 4 -f-3HCl. The chloracetic acid is very soluble, but may bo obtained in fine rhombohedral crystals ; its salts resemble the ordinary acetates. When an amalgam of potassium is added to a solution of chloracetate of potash, chlorid of potassium, hydrate of potash, and the normal acetate of potash are formed. In this reaction water intervenes, and we may suppose that the alkaline metal, decomposing water, forms 3(KH)O a and 3KH, which last, reacting with the chloracetate, would form chlorid of potassium, leaving H 3 in place of the chlorine. Acetic Ether, C 4 H 8 (Et)0 4 = CgH 8 4 . -This ether is form- ed by the direct action of acetic acid upon alcohol, but is best obtained by distilling a mixture of five parts of acetate of soda, eight of sulphuric acid, and three of alcohol. It is a very fragrant and volatile liquid, soluble in seven parts of water. The odor of wine- vinegar is due to the presence of a little acetic ether. It contains, like the ethers of other mo- nobasic acids, the elements of the acid and the alcohol minus an equivalent of water H 3 2 . The ethers like this, formed by the acids of the type C n ll w 4 with their respective alcohols, are polymeric of the corresponding aldeydes ; acetic ether equals 2 XC 4 H 4 3 .. Acetic ether is dissolved by a concentrated solution of am- monia, and the solution affords by evaporation a white crys- talline substance, very volatile and fusible, to which the name of acetamid has been given ; it is the amid of acetic acid, and contains the elements of acetate of ammonia less an equivalent of water : C 4 H 3 (NH 4 )0 4 = C 4 H ? N0 4 = H 3 2 -f- C 4 H 5 NO a , which is the formula for acetamid. In its form- ation from the ether, alcohol is set free ; acetic ether C 8 H 8 O 4 -hNH 8 =C 4 H 8 O a +C 4 H 5 NO fl . The ethers of almost all acids yield amids by a similar reaction. When heated gently with potassium, acetamid evolves a gas and yields cyanid of potassium C 3 KN. If acetamid is distilled with anhydrous phosphoric acid, the elements II 3 3 are abstracted from it, and a volatile liquid is obtained, which is C 4 H 5 N0 3 II 2 2 = C 4 H 3 N. It has received the name of acetonitryl. By the action of strong acids and alkalies both of these compounds regenerate ammonia and acetic acid. 751. When an acetate is heated with an excess of hydrate 434 ORGANIC CHEMISTRY. of potash, it breaks up into carbonate of potash and a sarbo- hy drogen C 3 H 4 . Acetate of potash C 4 H 8 K0 4 + (KH)O fl r= C a K 3 6 -|-C 3 H 4 . It has already been described under the name of marsh gas, from its occurrence in marshes, as a product of the decomposition of vegetable matter. To indi- cate its relations in the organic series, the name of formen has been given to it. The chloracetates undergo a similar decomposition, and yield trichloric formen C 3 C1 3 H, in which C1 3 replaces H 3 . The chloracetate of ammonia is decom- posed by boiling with an excess of ammonia, into carbonate and this chlorinized species. 752. When an acetate is decomposed by heat, or when the vapor of acetic acid is passed through a red-hot tube, the acid undergoes a peculiar decomposition; two equivalents of it unite with the elimination of one equivalent of carbonic acid, C 3 H 3 .2 XC 4 H 4 4 =C 8 H 8 8 C a H a O B = C 8 H 6 O a To this liquid the name of aceton has been given ; by oxyd- izing agents, like chromic acid, it yields acetic acid. We have already mentioned aceton as a product of the distilla- tion of sugar with lime : it is accompanied with an analogous compound, to which the name of metaceton has been given, and which corresponds to a new acid homologous with acetic acid, to which the name of metacetonic or propionic acid has been given. It is C 6 H 6 O 4 r=C 4 H 4 4 -t-C 2 H 2 , and is very much like acetic acid in its properties. When a paste of wheat flour is fermented with fragments of white leather and a quantity of chalk, propionate of lime is formed in large quantity. The fermentation is probably analogous to that which yields butyric acid. The decomposition of the salts of propionic acid by heat furnishes directly propion or metaceton, in the same way as butyric acid furnishes the homologue butyron. By the action of nitric acid upon butyron, a coupled acid is obtained, which is nitropropionio acid C 6 (H 5 N0 4 )0 4 =: C 8 H 5 N0 8 . METHOL, C a H 4 O a . 753. Wood-spirit , Pyroxylic Spirit, Metliylic Alcohol* This substance has already been mentioned as a product of * Pyroxylic spirit, from pur, fire, and xulon, wood. Methylic alcohol, from methu, wine, and hide, wood; signifying the wine or alcohol of wood. In names like kakodyl, and the terms ethyle, amyle, in the language of the compound radical theory, the same syllable is derived from hule, in its more extended sense of matter or principle. METHOL. 435 the destructive distillation of wood. The acetic acid of the crude product being saturated with lime, impure methol is obtained by distillation, and is afterward purified by re- peated rectifications. It is a colorless liquid, of a peculiar and somewhat unpleasant odor, and a hot, pungent taste. It has a specific gravity of -798, and boils at 152 ; it ia very combustible, and burns with a pale blue flame. Like alcohol, it mixes in all proportions with water. It is occa- sionally used in the arts for dissolving resins and making varnishes, and the pure wood-spirit has lately acquired some celebrity in the treatment of phthisis, under the name of wood-naplitha. Like vinic alcohol, methol forms crystal- line compounds with several salts and with baryta. It furnishes derivatives in which H is replaced by K, and O 3 by S fl . The nitric ether of methol is obtained by the direct action of the acid upon the alcohol, and resembles the vinic compound. The chlorohydric ether C a H 3 Cl is a colorless gas. The hydrobromic and hydriodic methylic ethers, ob- tained by processes similar to those described for the corre- sponding vinol compounds, are liquids at the ordinary tem- perature. In the bodies of this series, which is homologous with that of vinic alcohol, C 3 H 3 plays the same part that we have assigned to C 4 H 5 . This group may be designated by Me, and wood-spirit will be (MeH)0 3 , while the chlorid is MeCl and the nitrate N(Me)O fl . These ethers are decom- posed by a solution of hydrate of potash, with the formation of potash salts and methol. 754. The sulpliometliylic acid is prepared in the same manner as the sulphovinic; and like it, is an acid ether. It is S 2 (MeH)0 3 . It is more stable than the sulphovinic acid, and may be obtained in crystals. The neutral sulphuric ether is prepared by distilling wood-spirit and sulphuric acid, and is S fl (Me a )O s ; by boiling water it is converted into sulphomethylic acid and methol; S s (^Me a )0 8 -f-H a 8 = S 2 (MeH)0 8 -f (Mell) O a . With ammonia it undergoes a partial decomposition, and yields sulphametliane and wood- spirit; S 3 (Me 3 )0 8 -fNH 3 --=C 3 H 4 3 +S 3 (C 2 H 5 N)0 6 . The nature of the action will be understood by referring to what has been said of acetamid ; it is the amid of sulphoniethylio acid, and by hydrate of potash is decomposed into a sulphate, methol, and ammonia. When sulphomethylic acid is decomposed by heat, methylia 436 ORGANIC CHEMISTRY. ether is obtained as a colorless gas. The principles involved in its formation are the same as those which have already been explained in speaking of the ether of spirits of wine. Its formula is C 4 II 6 O a = Me a O a , and it is consequently metameric with vinic alcohol. 755. The chlorohydric ether of alcohol has been shown to correspond to a carbo'hydrogen aceten, C 4 H a = (C 3 H a ) 3 H 3 ; in the same manner the methol compounds are derivatives of a homologous hydrocarbon (C 3 H 3 ) H 3 = C a H 4 , which is formen or marsh gas, already described as a result of the decomposition of the acetates. By the action of chlorine the atoms of hydrogen may be successively replaced, and the final result is C 2 C1 4 , a chlorid of carbon. The trichloric Bpecies C 2 HC1 3 is of some interest, and is commonly known by the name of cMoro/brm. Its formation by the decompo- sition of chloracetate of ammonia has already been mentioned, but it occurs as a product of the action of chlorine or hypo- chlorites upon many organic substances. When alcohol or wood-spirit is distilled with a solution of two or three parts of chlorid of lime in twenty of water, chloroform is the prin- cipal product; it is a dense oily liquid, having a specific gravity of 1480, boils at 141 F., and is nearly insoluble in water. It has a pleasant aromatic odor and a very sweet pungent taste. An alcoholic solution of it, prepared by dis- tilling chlorid of lime with an excess of alcohol, has long been known in medicine by the incorrect name of chloric ether. Its vapor, when mixed with atmospheric air and in- haled like ether, produces insensibility; as it is more agree- able to the senses and more potent in its operation, chloro- form has, to a considerable extent, replaced ether as an anaesthetic agent in surgical practice. The action of potash upon an alcoholic solution of iodine produces a yellow crystalline substance, which is iodoform, the iodine compound corresponding to chloroform, and is C a HI 3 . These compounds with an alcoholic solution of hydrate of potash are decomposed into formate, with chlorid or iodid of potassium, and water; C 9 HCl 8 -+-4(HK)O t =C - (HK)0 4 +3KC1+2H 3 3 . The hydrocarbon C 3 H 3 , corre- sponding to olefiant gas, is not known in this series, but the final action of chlorine upon chloroform produces C 3 C1 4 , which is a dense liquid; at a red heat it loses C1 3 and is converted into a crystalline chlorid C 3 C1 3 which is the perchloric spe- cies of the unknown C a H a , or perhaps polymeric of it. METHOL. 4f7 Oxydation of MetJiol. 756. When the vapor of methol mixed with air, is exposed to the action of platinum black, oxygen is absorbed, and water is formed with a new acid, which is homologous with acetic acid, C 3 H 4 3 -f 4 = H 2 2 -f C 3 H 3 4 . The inter- mediate product C 3 H 3 2 , corresponding to aldehyd, has never been obtained. The action of heated hydrate of potash upon wood-spirit evolv 7 es hydrogen, and forms a salt of the new acid, to which the name of formic acid is given. It is Becreted by a species of ant, (Formica rufa^) from whence it derives its name, and by the stinging nettle, (Urtica urens ;) it is also the result of the action of oxydizing agents, upon many organic substances, as sugar and alcohol, and may be advantageously prepared by the following process : 800 grains of bichromate of potash and 300 of sugar are dissolved in seven ounces of water. The mixture is placed in a retort, and one measured ounce of sulphuric acid very gradually added ; it is then distilled (tig. 415) with a gentle heat, until three ounces of liquid are obtained. This is dilute formic acid, and may be used to form salts, which, when decomposed, afford a strong acid. The pure acid is obtained by passing sulphuretted hydrogen gas over dry formate of lead ; sulphuret of lead and formic acid are produced. The action is aided by a gentle heat, and the acid distils over. It is a colorless liquid, of specific gravity 1-168, which boils at 212, and at 32 crystallizes, like acetic acid, in shining plates. It fumes in the air, and has a very pungent odor, resembling that of ants; it is powerfully acid and corrosive, instantly blistering the skin. When this acid or its salts are heated with strong sulphuric acid, it is decomposed with the evolution of pure carbonic oxyd gas : C 3 H 3 4 = C 3 3 +H 3 3 . The formates resemble the acetates. The formate of silver C 3 (HAg)0 4 is decom- posed when its solution is boiled ; the silver is precipitated, while carbonic acid and carbonic oxyd gases escape, 2C 2 (HAg)0 4 = Ag 3 +H 3 3 +C 2 4 +C 3 3 . 757. Formic acid yields with alcohol an ether which is C 3 (HEt)O 4 =0 8 HgO 4 . The acetic ether of methol has the same composition C 4 (H 3 Me)0 4 C 6 H 6 4 - These two ethers are similar in their general physical characters, but by the action of hydrate of potash, one yields a formate and alcohol, and the other an acetate and methol. The formic 438 ORGANIC CHEMISTRY. ether of methoi is C^HMe^ = C 4 TI 4 4 : it is metameric with acetic acid. All of these ethers by the action of chlorine exchange their hydrogen in whole or in part for that ele- ment. The final result of the substitution in formo-methylic ether is C 4 C1 4 4 . We have already shown that such ethers are polymeric of the corresponding aldehyds. The chlorin- ized ether by heat is resolved into two equivalents of phos- gene gas C 4 C1 4 4 = 2C 3 C1 2 2 ; phosgene gas is, in fact, the chlorinizcd derivative of methylic aldehyd, which will be C a H 9 9 . AMYLOL, C 10 H 13 O a . 758. Ami/lie Alcohol. We have already alluded to this compound as a product of fermentation under certain circum- stances. In the rectification of the crude spirit obtained by the fermentation of potatoes, it separates as an oil, which comes over with the last portions of the spirit, and is inso- luble iu water : the distillers give to it the name of fouscl oil, or potato oil : it is sometimes observed in the spirit from other sources, and seems to be a product of the trans- formation of starch or sugar, under conditions not well understood. When pure, it is a colorless liquid, which is insoluble in water, has a specific gravity of '818, and boils at *2()\) F. It has a burning taste, and a pungent odor which excites coughing and often nausea. In its chemical relations it is precisely similar to alcohol, and methoi, with which it is homologous ; its formula is C 10 H 13 3 =(C 10 H U .H)0 3 ; it forms ethers in which C 10 H M , corresponding to C 2 II 3 , to C 4 II 5 , and to II, replaces hydrogen; we shall represent this group by the symbol Ayl. The chlorohydric amylic ether is formed by the action of the acid upon amylol, and is C^II^Cl = AylCl. The bromine smJ iodine compounds are similar, as also the nitrous and nitric ethers, the latter being N(C 10 II 11 )0 6 , or nitric acid in which Ayl replaces hydrogen ; as in all similar reactions, H 2 3 is eliminated in its formation, and it rege- nerates a nitrate and amylol by the action of an alcoholic solution of hydrate of potash. * With sulphuric acid, sulpha- mylic acid, corresponding to the sulphovinic, is formed, which is monobasic; by its decomposition, amylic ether C^H^Og is obtained, which corresponds to the hydric ether of alcoho 1 , and is Ayl 2 2 , or water in which the group C^II^ has re- placed both equivalents of hydrogen. By tin action of an AMYLOL. 439 excess of sulphuric acid, the carbohydrogen C^H^, corre- sponding to olefiant gas, is obtained : the alcohol breaks up into C 10 H 10 and H a 3 . 759. Oxydation of Amylol. By the action of platinum black, amylol combines with oxygen and is converted into an acid homologous with the acetic and formic acids : when heated with hydrate of potash, hydrogen is evolved, and a salt of the same acid is formed, C 10 H 13 3 -j-(KH)0 3 = C 10 (H 9 K)0 4 -|-H 3 . By distilling the potash salt with sul- phuric acid, the new acid C 10 H 10 4 is obtained. It is iden- tical with that previously known to exist in the root of the Valeria na officinalis, and hence called valeric or valerianic add. It is also found in several other plants, and decay- ing cheese sometimes owes its peculiar flavor to a proportion of valeric acid. It is a colorless oily liquid, which is solu- ble in a large quantity of water, is strongly acid and caustic, and has the characteristic odor of valerian root j it boils at 347, and has a specific gravity of -937. Its salts are all soluble in water and monobasic ; they have a slight odor like the acid. The valerate of zinc crystallizes in white scales, and is employed in medicine as a substitute for vale- rian, the medicinal properties of which it possesses in a high degree. The action of chlorine upon the acid alfords a pro- duct similar to chloracetic acid. The valeric acid yields with amylic alcohol an ether which has, when pure, an agreeable flavor, like apples. The acetic ether of amylol has a no less striking resemblance in its odor to jargonelle pears ; the flavors are not however deve- loped until the ethers have been diluted with alcohol. These ethers are obtained by distilling mixtures of amylol and acetic or valeric acid with sulphuric acid, and are used to give the peculiar flavors of the fruits in perfumery and con- fectionery. 760. In ascending the series of alcohols, in proportion as the amount of carbon and hydrogen is greater, the bodies become more insoluble in water, and assimilated to the oils and fats and to the different species of wax, to which they have intimate relations. These bodies are generally ethers of acids, which are for the most part homologous with acetic and valeric acids; or glycerids, a class of compounds analo- gous to ethers in their composition. From them several new alcohols are obtained, and a still greater number of 440 ORGANIC CHEMISTRY. acids pertaining to the alcohol series. We shall first notice those which belong to the class of compound ethers. Spermaceti. This substance occurs mixed with oil, fill- ing large cavities in the head of the sperm whale, (Physeter macrocephalus.) The oil is removed by pressure, and finally by washing in a dilute solution of potash, and the sperma- ceti is obtained as a white solid, which fuses at 120, and crystallizes on cooling in beautiful broad pearly plates. It is soluble in alcohol and ether, but insoluble in water, and is used in pharmacy and in the fabrication of candles. Spermaceti has the composition of a compound ether, and, when gently heated with hydrate of potash, is decomposed into the potash salt of a new acid C 10 (H 15 K)0 4 , and the alcohol of that acid C l6 H 13 3 . The acid has been called ethalic add, and the alcohol ethal or ethol ; spermaceti cor- responds to the acetic acid of vinic alcohol, and contains the elements of the acid, and the alcohol minus H 3 O a . Both of these are white crystalline volatile substances, analogous in physical properties to spermaceti. Ethalic acid melts at 131; it yields with other alcohols, ethers which are fusi- ble and crystalline. Ethal forms with sulphuric acid the sulphethalic acid, corresponding to the sulpho vinic, and when heated with hydrate of potash to 400, evolves hydrogen, and is converted into ethalate of potash. 761. Wax. This substance has been supposed to be a vegetable production, and to be collected by bees from the plants upon which they feed ; but experiments have shown that they yield wax even when fed upon pure sugar or honey, and that it is a secretion of the insects themselves. A species of wax brought from China IK very analogous to spermaceti in its composition, and when decomposed by hydrate of potash, yields the salt of a new acid, called the cerotic, acid, and the corresponding alcohol ccrotoL The acid has the formula C^H^Oj and the alcohol is C^IT^O^ These compounds are less soluble and fusible 1 than the ethalic series; the wax fuses at 18'2F., and the alcohol at 174. The alcohol yields with sulphuric acid a coupled monobasic acid, and with chlorine a product which corre- eponds to a chlorinized aldehyd. Heated with hydrate of potash, cerotol evolves hydrogen and is converted into cero- tate of potash. It cannot be distilled without partial change, being converted into water and carbohydrogens polymeric with olefiant gas. GLYCERIDS. 441 Common beeswax is separated by boiling alcohol into a soluble portion, and a residue comparatively insoluble. The soluble part consists principally of cerotic acid in a free state. The insoluble part is decomposed by potash into ethalic acid, and a new alcohol, mellisol, which is repre- sented by C 8o H 62 3 : it is crystallizable, and melts at 185. When fused with potash it yields mellisic acid C 60 H 60 4 . GLYCERIDS. 762. Under this title may be included a number of neutral fats and oils, which, by the action of bases, are converted into salts of fatty acids, with the separation of a substance to which the name of glycerin has been given, in allusion to its sweet taste, (from glufcw, sweet.) Glycerin is pre- pared by heating a mixture of olive-oil, oxyd of lead, and water. The oil is decomposed, and the acids form insoluble salts with the lead, while the glycerin is dissolved in the water; the solution is treated with sulphuretted hydrogen to precipitate a little dissolved oxyd of lead, and evaporated in a water-bath. It is formed in large quantities as a pro- duct of the saponification of fats by boiling with hydrate of lime and water. The liquid which separates from the insoluble lime salts is a watery solution of glycerin con- taining a little lime; this may be separated by carbonic acid, and the glycerin is then obtained by evaporation. The formula of glycerin is JC 6 H 8 6 . It is a colorless, syrupy liquid, with a specific gravity of 1-280, of a very sweet taste, and is readily soluble in water and alcohol; it is not volatile, but when strongly heated is decomposed, evolving acetic acid and other products, the most important of which is acrolein. 763. Acrolein is also produced when the glycerids are decomposed by heat; and is best obtained by distilling gly- cerin with anhydrous phosphoric acid. The glycerin losea the elements of two equivalents of water : C 8 H 8 6 2H 2 3 = 6 H 4 3 , which is the formula of acrolein. It is a colorless, very volatile liquid, with a peculiar acrid, penetrating odor, which is perceived when the fat oils are strongly heated ; it is lighter than water, and sparingly soluble iu that liquid. With potash it reacts liko aldehyd, and it reduces oxyd of 442 ORGANIC CHEMISTRY. silver with the formation of a new acid, the acrylic, which is C 6 H 4 4 . It resembles the acetic acid in its properties, and under the influence of alkalies is converted with oxy- dation into a mixture of formic and acetic acids ; C 6 H 4 4 -{- 2(HK)0 9 +O a =C 4 (H 3 K)0 4 +C s (HK)C) 4 +H 9 3 . 764. The constitution of the glycerids is such, that in de composition they combine with the elements of 3H 2 2 , and produce two equivalents of a fatty acid and one of glycerin. All of them undergo this change when heated with a solution of hydrate of potash or soda, or with oxyds, like oxyd of lead and lime. The salts thus formed are soaps; and different kinds of soaps are produced, according to the nature of the fatty acid and the alkali. Those of potash are very soluble and remain mixed with the water, glycerin, and excess of alkali employed in their preparation ; they form soft soaps, while those of soda are less soluble and more easily sepa- rated from the liquid, and constitute hard soaps. Those of lime, lead, and other bases are insoluble in water, and the lead-plaster or diachylon of surgeons is a lead soap. When a solution of a soap with an alkaline base is mixed with a salt of any other base, double decomposition ensues, and an insoluble earthy or metallic salt is precipitated ; it is the presence of salts of lime or magnesia in natural waters; which gives them the power of decomposing soaps, and con- stitutes what is called hardness in water. Strong acids in the same way decompose soaps, and separate the fatty acid in an oily form. Strong sulphuric acid decomposes the glycerids like an alkali, and liberates the fatty acids, form- ing with the glycerin an acid analogous to the sulphovinic, to which the name of sulpliogty 'eerie acid is given. Butter consists of several glycerids which are difficult of separation. When saponified, and the soap decomposed by distillation with sulphuric acid, it yields four volatile acids, homologous with the acetic. They are called the butyric, caproic, caprylic, and capric acids. Of these the first is best known : the others are separated from it, and from one another, by the different solubility of their baryta salts. Butyric acid is more easily obtained by the fermentation of sugar under certain conditions, which have already boen explained, (700.) The butyrate of lime is decomposed by a solution of car- bonate of soda, and the soda salt being concentrated by cva- GLYCERIDS. 443 poration is mixed with an excess of sulphuric acid, when the butyric acid rises to the surface as an oily layer, which is separated and purified by distillation. It is a colorless liquid, which boils at 327 F., and is lighter than water. It mixes with pure water and alcohol in all proportions. The odor of butyric acid is strong and disagreeable, resembling that of vi- negar and rancid butter ; it is powerfully acid and caustic. The salts of butyric acid are all soluble in water; the buty- rate of lime C s (H 7 Ca)0 4 is less soluble in hot water than in cold, and separates almost entirely by boiling, in transpa- rent prisms, which redissolve as the liquid cools. 765. By mixing together alcohol, butyric acid, and strong sulphuric acid, the heat evolved is sufficient to cause the formation of butyric ether, which is precipitated on adding water to the mixture, being insoluble in it. It is a colorless liquid, soluble in alcohol, to which it gives the flavor of pine apples; the solution is used by confectioners to flavor syrups, and by distillers in the fabrication of spirits. 766. When a mixture of glycerin and butyric acid is heated with sulphuric acid, an oily liquid is obtained, which is supposed to be the butyric glyccrid, to which butter owes its peculiar flavor. It is the only glycerid which has been formed artificially ; by alkalies it yields glycerin and a buty- rate like the natural glycerids ; its composition, agreeably to the rule which we have stated, will be 2C S H S 4 +C 6 H 8 6 The distillation of butyrate of lime affords butyron corre- sponding to aceton, and a volatile liquid, butyral C 8 H 8 2 ; it absorbs oxygen from the air, yielding butyric acid, and is the aldehyd of the butyric series. The oil of the porpoise (Delphinus phoca) contains a gly- cerid, to which the name of phocenin has been given : it is the glycerid of valeric acid, which has been described by the name of phocenic acid. The action of nitric acid upon castor- oil yields a volatile oily acid with a fragrant odor, to which the name of enanthylic acid has been given; it is C 14 H 14 4 ; and the distilled water of the rose-geranium (^Pelargonium roseuni) contains another, pelargonic acid, 1S H 18 4 . The peculiar flavor or bouquet of wine is due to a small portion of a peculiar ether, which is obtained when great quantities of wine are distilled, and possesses, in a high degree, the vinous flavor. By hydrate of potash it is do- composed into alcohol and a volatile acid, which has the 444 ORGANIC CHEMISTRY. composition of pelargonic acid, and is probably identical with it. The foregoing acids are all odorous, more or less soluble in water, and may be distilled over with its vapor; their boiling points, however, become gradually higher, and their lime and baryta salt less and less soluble. Beyond caprio acid C 2/) H 20 4 , they are solid at the ordinary temperature, no longer volatile with the vapor of water, and yield with lime and baryta insoluble salts, and with the alkalies proper soaps. Among these the cthalic, cerotic, and melissic have already been mentioned. We shall notice a few of the more important ones remaining. 767. The palm-oil which is expressed from the nuts of the Elais gurncnsis is composed of a fluid fat, olcin, and a solid crystalline substance to which the name of palmatin has been given ; it is the glycerid of ethalic acid, which is sometimes named palmitic acid. The fat of animals is composed in like manner of a liquid fat and a solid crystal- line material. By careful pressure in the cold, this separa- tion may be in part effected, and if the fats have been kept for a long time in fusion, the solid portions crystallize out more or less perfectly on cooling. It is by taking advantage of this property that lard-oil is made. The solid portion may be purified by crystallization from ether. That ob- tained from beef and mutton consists principally of two substances, to which the names of maryarin and stearin have been given. The former is readily soluble in ether, and fuses at 116 F. ; stearin, on the contrary, is very little soluble in cold ether, and melts at 130. By saponi- fication they yield maryaric and stearic acids, one fusing at 140, and the other at 168. Although thus distinguished, these bodies have the same composition : they are both mo- nobasic and have the formula C 34 H 34 4 . The rnargaric has been distinguished by the name cf para-stcaric acid. The action of heat and of acids under certain conditions converts stearic acid into this isomeric modification. While marga- rin and stearin are mingled in beef and mutton fats, the oils, like olive-oil, consist of margarin and olein. Human fat yields by saponification a large amount of palmitic acid, with some margaric, and a new acid, which is probably C S6 H 36 4 - 768. The olein of lard, of olive-oil, and of almond-oil, yields by saponification an acid which is called oleic itcid, OLYCERIDS. 445 and, like olein itself, is a colorless liquid, insoluble in water. It has a slightly acrid taste, and its alcoholic solution has an acid reaction. Its composition is represented by C 3 gH 34 4 . Oleic acid does not therefore belong to the series of homo- logous acids already described, but is one of a new series, of which acrylic acid C 6 H 4 4 is also a member; in this series the number of equivalents of oxygen is four, and that of the equivalents of carbon is always two more than the number of the hydrogen. 769. When the vapor of nitrous acid is passed through oleic acid, this is rapidly transformed into a crystalline sub- stance, which is elaidic acid, and is an isomeric modifica- tion of the oleic acid. The action of the nitrous vapor upon olein produces a corresponding modification of the glycerid. Elaidic acid, like oleic, is monobasic, and forms beautiful crystals, which melt at 112. When these acids are fused with hydrate of potash they undergo a remarkable trans- formation j their homologue, acrylic acid, gives acetic and formic acids, while the oleic and elaidic yield acetic and ethalic acids with the evolution of hydrogen : C 36 H 34 4 -{- 2(KH)0 3 = C 32 (H 31 K)0 4 +C 4 (H 3 K)0 4 +H 3 . The acid from the saponification of a variety of whale-oil has been found to have the formula C 38 H 36 4 , and another from the vegetable oil of the Moringia aptera C 30 H 38 4 , while the olein from human fat has yielded anthropic add C 34 H 33 4 . All of these are monobasic and are homologues of acrylic acid and oleic acid. Their decomposition by hydrate of potash will probably yield corresponding acids of the acetic series. Thus, C 38 H 36 4 , to which the name of dceglic acid ha? been given, should yield stearic and acetic acids. 770. Castor-oil from the seeds of Ricinus communis is distinguished from other fixed oils by its ready solubility in alcohol. The solid fatty acids which it yields, appear to be margaric and palmitic ; the olein affords by its sapo- nification an oily acid, which, while containing carbon and hydrogen in the same proportion as in the last series, has six equivalents of oxygen. Different experimenters have apparently obtained from different specimens of oil two homologous acids, to which they have ascribed the formulas C 38 H 36 6 and C 36 H 34 6 . To both of these the name of ricinoleic acid has been given. With nitrous vapor, castor- oil yields a crystalline glycerid like olive-oil. 446 ORGANIC CHEMISTRY. 771. We have then three homologous series among che fatty acids ; the first and most complete is that homologous with acetic and ethalic acids; the second is that of oleio acid ; the third that of ricinoleic acid. The first has the general formula C w H n 4 , the second C.H n _ 2 4 , and the third C n H M _ a 6 . The series of the first, as far as known, is here given : 1. Formic CJI a 4 2. Acetic C 4 H 4 4 3. Propionic C 6 H 6 4 4. Butyric C 8 H 8 4 5. Valoric C 10 H 10 4 6. Cnproic C w H, a 4 7. Enanthylic C M H I4 4 8. Caprylic C IS II IS 4 9. Pclargonic C I8 II I() 4 10. Capric C.^II^O, 11. Margaritic C^H^O, 12. Laurie C 24 II a ,0 4 13. Cocinic C.Ha.0. 14. Myristic C^H^O, 15. Benic CIIO 16. Ethalic C M TI M 4 17. Stearic C 34 II 34 4 18. Bassic C 3( .H 3K 4 19. Balenic C^II^O, 20. 21. 22. Behcnic C^II^O, 23. 24. 25. 26. 27. Ccrotic C M II H 4 28. 29. 30. Melissic C 60 II go 4 772. We have already described the alcohols of the 1st, 2d, 5th, 16th, 27th, and 30th acids, and we have to add that of the 16th. In this group there is a regular transition r rom formic acid, through the propionic, butyric, and other paringly soluble oily acids, to the insoluble ethalic and stearic. In the first ten, which arc liquid at ordinary tem- peratures, and distil without any change, there is a progres- sive increase of about 36 F. in the boiling point of each acid. Thus, the formic boils at 212, the acetic at 212-f- 36 = 248, and the propionic at 248-f 36 = 284. The fusing point of the solid acids rises in a similar manner, but with less apparent regularity. The fact that the acids are less fusible than their glycerids has led to their use in the manufacture of candles, which are sold under the name of stearine, adamantine, or Belmont sperm. The tallow is commonly saponified by heating it in vats by steam, with a mixture of lime and water ; an insolu- ble lime salt is formed, and the glycerin remains dissolved in the water. This salt is decomposed by diluted sulphuric or chlorohydric acid, with the aid of heat, and the mixed acids, which rise to the surface, are, when cold, submitted to pressure, by which the oleic acid is removed, and the stearic and margaric acids are obtained nearly pure. The crystalline tendency of the fused acid is corrected by adding GLYCERIDS. 447 a little pulverized gypsum to tlie mass for the fabrication of candles. The decomposition of the glycerids by sulphuric acid, already described, is sometimes employed for this purpose. The higher acids of the series may be distilled without change in vacua or in a current of steam, but undergo a partial de- composition when distilled in the ordinary manner. These acids may be distinguished from stearin, from wax, and spermaceti, for which they are often substituted, and with which the latter are frequently adulterated, by their ready solubility in alcohol, and in a heated solution of carbonate of soda. 773. The action of nitric upon oleic acid yields the volatile acids of the above series, from the acetic to the capric inclu- sive; the other fatty acids yield similar results, and the stearic acid is the first product of the action of nitric upon oleic acid. The residue of the action of nitric acid contains four soluble crystallizable bibasic acids the succinic, C S H 8 , adipicj C 13 H 10 8 , pimelic, C 14 H la 8 , and suberic, C 10 H 14 8 ; they correspond to homologues of oleic acid, which have fixed 4 , and are represented by C B H,^_ a O a . The succinic acid was originally obtained by distilling amber, a fossil resin which occurs in recent geological formations. Succinic acid is soluble in water and alcohol ; when heated it fuses, and is decomposed into water and a neutral crystalline substance called succinid C 8 H 4 6 , which, when boiled with water, is gradually reconverted into succinic acid. The other acids are of but little importance ; the suberic is a product of the action of nitric acid upon cork. When olein or oleic acid is distilled, selacic acid is obtained ; it is crystallizable, vola- tile, and soluble in water, and has the formula C^H^O,,, being homologous with those just mentioned. When fused with hydrate of potash, these acids are decomposed, and yield members of the acetic series. Thus, the pimelic forms valerate of potash, and, instead of the acetic acid and hydro- gen which the homologues of oleic acid would yield, carbonic acid and water are obtained. 774. Castor-oil and ricinoleic acid, like olein, yield sebacio acid by distillation. When ricinoleic acid is distilled with an excess of a strong solution of hydrate of potash, sebacate of potash is formed, and hydrogen is evolved, with a peculiar oily liquid, having the formula C 16 H 18 2 . The reaction may be thus represented : C 36 H 34 6 + 2(KH)0 3 448 ORGANIC CHEMISTRY. -hC 16 H 18 ? -j-H a . The new volatile product is the alcohol corresponding to caprylic acid, and may be named caprylol. It is insoluble in water, has an agreeable aromatic odor, a specific gravity of -823, and boils at 356 E. With sul- phuric acid it forms a vinic acid, and with acetic and chloro- hydric acids, ethers similar to those of ordinary alcohol; by oxydation it yields caprylic acid C 10 H 1G 4 . 775. The different animal fats generally yield, by saponi- fication, small portions of one or more of the volatile acids already described, and many of them are met with in the distilled water of various plants. Many glycerids appear to undergo a slow, spontaneous decomposition when moist; glycerin is liberated and may be removed by water, while the acids are found in a free state. The alcoholic ethers of all these fatty acids may be obtained by passing chlorohydric acid gas through their alcoholic solutions, or by heating the same solutions with sulphuric acid : they are, like the gly- cerids, neutral, fusible, fatty bodies, and have the same constitution as their homologue, acetic ether. When a gly- cerid is dissolved in alcohol and treated with chlorohydric acid, the ether is formed in the same way, and may be pre- cipitated by adding water, which will be found to retain glycerin in solution. The action of ammonia alike upon the ethers and glycerids enables us to obtain the amids of the fatty acids with the separation of alcohol or glycerin. They have the same constitution as acetamid, and are all decomposed by hydrate of potash, with the formation of a salt of the acid and ammonia. Those of the higher acids are solid insoluble fatty bodies. ALKALOIDS or THE ALCOHOL SERIES. 776. The relations between hydrogen represented as H 3 , water, and ammonia have already been considered, and we have shown that the alcohols may be viewed as compounds in which the groups C 2 H 3 , C 4 H 5 , C 10 H. UJ &c. replace H in water. These same groups may replace the successive equivalents of hydrogen in ammonia and oxyd of ammonium, giving rise to an interesting class of bodies which are perfectly analo- gous to ammonia in their chemical relations, and are called organic alkalies or alkaloids. Besides these obtained from the alcohols, there are many other alkaloids, products of dif- ALKALOIDS OF THE ALCOHOL SERIES. 449 ferent transformations of organic bodies 5 others exist ready formed in plants. We shall in this place consider only the first class. 777. When chlorohydric, or better bromohydric ether, is digested with a concentrated solution of ammonia, it slowly dissolves. This operation is accelerated by heat, and is best effected by exposing the ether and ammonia hermetically sealed in glass tubes, to the heat of boiling water. The solu- tion is soon effected, and the mixture, on cooling, is found to contain a salt of the new ether-ammonia : hydrobromic ether, EtBr-f NH 3 =NH 3 Et.Br, bromid of ethammonium, or NH 3 Et.HBr. When decomposed by lime or potash in the same way as sal-ammoniac, the new alkaloid NH 3 Et, which is named ethamine, is obtained as a very volatile liquid, with a specific gravity of -696. It has a powerful odor resembling that of ammonia, and its solution is very caustic, acting like a strong alkali with acids and metallic gaits. It is soluble in all proportions in water and alcohol. 778. If a hydracid ether of methol be substituted for the vinic ether, a corresponding methylic ammonia, or metha- mine, may be obtained, which is NH 3 (C a H 3 ) or NH a Me. It is a colorless gas, which at a low temperature may be condensed into a liquid, and is very soluble in water, which dissolves in the cold 1154 times its own volume of the gas. The solution is powerfully acrid and caustic, and in its odor and chemical properties closely resembles am- monia; the gas is combustible. The salts of these new bases are like those of ammonia, but are more soluble. When placed in contact with a new equivalent of the ether, these alkalies react with it precisely like ammonia itself, and salts of new alkaloids are obtained, in which two and three atoms of hydrogen are successively replaced by the carbohydrogen elements. In this way NHEt 3 and NEt 3 = NC 13 H 15 arQ obtained; and by using successive dif- ferent ethers, mixed alkaloids may be formed, such as NHEtMe and NMe 3 Et. The amylic and cetylic ethers yield perfectly analogous compounds. Amylamine is NH 3 Ayl NH fi (C 10 H 11 ). It is a very mobile liquid, having a specific gravity of -750, and boiling at 203 ; it has at the same time the odor of ammonia and of the amylic compounds, and is very caustic and alkaline. We may even have N(Me.Et.Ayl), in which the elements of three different alcohols are united. These higher alkaloids are liquids, which have still the ch- 29 450 ORGANIC CHEMISTRY. racters of ammonia, but are less volatile and caustic than those of lower equivalents. 779. When triethamine NEfc 3 is brought in contact with another equivalent of hydriodic ether, it no longer decom- poses it, but unites directly with it to form a salt. This ether EtI, as we have already shown, corresponds to HI, and the ammonia unites with it as it would with the acid: in the latter case a simple ammonia would form iodid of ammonium NH 4 I, and the trivinic ammonia N(Et,H)I; but with the ether it forms NEt 3 .EtI = NEt 4 I, or the iodid of vinic ammonium NEt 4 . The new iodid forms fine crystals, which have all the reactions of an ordinary iodid with me- tallic salts. With recently precipitated oxyd of silver, double decomposition ensues, giving rise to iodid of silver and oxyd of vinic ammonium: 2NEt 4 I-fAg s O a ==2AgI+(NEt 4 ) 9 9 j but as anhydrous lime with water produces a hydrate (CaH)0 3 , so the new oxyd forms with it two equivalents of a hydrate (NEt 4 .H)0,,, which corresponds to (KH)0 2 . It is obtained by evaporation as a very soluble, deliquescent substance, alkaline and corrosive like hydrate of potash, which it closely resembles in its chemical reactions. As we have supposed ammonia to unite with water and form a hydroxyd of ammonium, so in this compound the trivinic ammonia is united with vinic water or alcohol. The aqueous compound of ammonia is readily decomposed by heat; and in like manner, if the new oxyd is exposed to the heat of boiling water, it is decomposed into trivinic ammonia, and alcohol, which latter breaks up into olefiant gas and water; C 4 H 4 -f-H 3 3 . 780. The methylic compound is quite similar to the last. When the hydriodic ether of methol is digested with ammo- nia, the hydriodate of methamineisfor the most part trans- formed into the iodid of ammonium, and the iodid of niethic ammonium; 4N(H 3 Me)I=3NH 4 I-f N(Me 4 )L The new iodid forms sparingly soluble crystals, which yield a hy- droxyd very alkaline and caustic. The amylic and complex ammonium salts are analogous in their characters. Ethamine andmethamine have \ een obtained by several other processes, and are found in the products of animal decomposition. 781. By the action of an alloy of potassium and antimony upon the hydriodic ethers, compounds are obtained represent- ing ammonias, in which aiitimony replaces nitrogen, (645.) ALKALOIDS OP THE ALCOHOL SERIES. 451 They are SbMe a =SbC B H 9 and SbEt 3 = SbC 13 H J5 . By oxydizing agents they lose H 2 , and the resulting compounds constitute alkaloids which form a class of salts. Stibethic ammonia unites with hydriodic ether to form SbEt 4 .I, analogous to the nitrogen compound, and this, with oxyd of silver, yields a hydroxyd which is a strongly alka- line base. In like manner, SbMe 4 I and Sb(Me 3 Et)I may be obtained ; all corresponding to the iodids of ammonium and potassium. The action of chlorine or nitric acid upon sti- bethic ammonia removes H 2 and gives rise to salts of a new alkaloid SbC 12 H 13 , which is called stibethine. 782. When a mixture of acetate of potash and arsenious acid is distilled at a low red heat, there is obtained, among other products, a volatile liquid, somewhat soluble in water, to which the name of alkarsine has been given. It is an organic base, related to those just described, in which arsenic replaces nitrogen. It contains C s H 13 As 2 2 , and corresponds to the oxyd of an arsenic ethamine, from which H 2 has been eliminated, as in stibethine ; As(EtH 2 ) = AsC 4 H 7 H 2 = As C 4 H 5 , which combines with chlorohydric acid like ammonia : the anhydrous oxyd (AsC 2 H 5 ) 2 .H 2 3 = (AsC 3 H fl ) 2 3 is al- karsine, or oxyd of arsinum. With chlorohydric acid it yields a liquid chlorid (As0 3 H 6 )Cl, to which the name of chlorarsine, or chlorohydrate of arsine, has been given. It is a true salt, like chlorid of ammonium, and by double decomposition yields different salts, which are also formed by the action of acids upon alkarsine. The chlorid is decomposed by metallic zinc; chlorid of zinc is formed, and the organic elements are set free ; but two equivalents of arsinum unite to form a com- pound, which is C 8 H lj .As a =(AsC a H 6 ) fl . It is a compound quasi-metal, and corresponds to Zn 2 and H 2 . It combines directly with chlorine to form anew the chlorid \ like alkar- sine, it is a volatile liquid, which, when exposed to the air, fumes and takes fire even at the ordinary temperature. All of these compounds have a disgusting odor, and are fear- fully poisonous. The oxyd, alkarsine, is like an alkali, acrid and corrosive. M. Bunsen, to whom we are indebted for a knowledge of these bodies,, gave to the compound quasi- metal the name of Italwdyl, (from kakosj evil, and huh, principle.) 783. When kakodyl is covered with water, it slowly ab- sorbs oxygen from the air and yields alkarsine : if to the 452 ORGANIC CHEMISTRY. alkarsine/oxyd of mercury is added under water, the metallic oxyd is reduced, and a new compound remains in solution, formed by the oxydation of the alkaloid arsine, which com- bines with the oxygen and forms AsC 4 H 5 4 , which is the formula of the new body, alkargen. The solution yields by evaporation large rhombic prisms of the new substance, which is inodorous, has but little taste, and is not at all poisonous. Deoxydizing agents, like sulphurous acid, converts it into alkarsine. Alkargen combines with acids to form crystalline compounds like arsine; but by its combination with oxygen the alkaloid seems to have become more feebly basic than before ; as in ammonia, one atom of hydrogen in alkargen or its salts is replaceable by a metal, so that we may have a compound like AsC 4 (H 4 Cu)0 4 .HCl, or chloro- hydrate of cupric alkargen. By the action of sulphuretted hydrogen, the oxygen in this alkaloid is replaced by sulphur, and crystals obtained which are AsC 4 H.S 4 . 784. Succeeding the alcohols and their derivations may be considered a class of volatile liquids, many of them essential oils, which have analogies with alcohols or aldehyds, although not homologous with the preceding series. We shall men- tion briefly some of the more important. Their history is now nearly as complete as the alcohols, and scarcely less in- teresting, but the limits of this work will not permit us to speak of them at length. BITTER-ALMOND OIL, C 14 H B 3 . 785. Bcnzoilol, Essential Oil of Bitter Almonds. This oil does not exist ready formed in the almonds, but is pro- duced by the reaction of certain principles contained in the kernel, when aided by the presence of water. It is obtained by bruising bitter almonds into a paste with water, and dis- tilling the mixture, when the oil passes over, with hydro- cyanic acid and other impurities- It is purified by redistil- ling it from a mixture of protochlorid of iron and lime, and is a colorless oily liquid, of a pungent burning taste, and very fragrant odor, like that of bruised bitter almonds. It boils at 356, but its vapor distils over with that of water at 212 : its specific gravity is 1-073. It is often used in flavoring articles of food, but the crude oil which is sold for BENZOILOL. 453 this purpose is exceedingly poisonous ; the pure oil is com- paratively harmless. By the action of hydrosulphuret of ammonia upon bit- ter-almond oil, its oxygen is replaced by sulphur, and an insoluble powder is obtained of the formula C 14 H 6 S 3 . Its decomposition by heat gives rise to a variety of new and curious products. 786. Vhlorinized Benzoilol, C 14 H 5 C10 2 . This is obtained by the action of dry chlorine gas upon the oil of bitter almonds. It is a colorless liquid, which is decomposed by alkalies, yielding a chlorid and a benzoate. By distilling this with bromid or iodid of potassium, similar compounds are obtained, in which bromine or iodine replaces an equiva- lent of hydrogen. The action of dry ammonia upon the chlorinized ben- zoilol yields chlorohydric acid, and a new substance, benza- mid, C 14 H 5 C10 3 +NH 3 ^C 14 H 7 N0 3 +HC1. It is soluble in water, and crystallizes in beautiful prisms. 787. Hydrobenzamid. When bitter-almond oil is placed in a concentrated solution of ammonia, it is gradually con- verted into a white crystalline mass of this substance. It is formed from three equivalents of benzoilol and two of ammonia by the abstraction of the elements of three equivalents of ^ water; _ 3(C 14 H 6 O 2 )-f 2NH 3 = C 43 H 18 N 2 + 3H 3 O a . In this reaction the ammonia loses the whole of its hydrogen, which unites with the oxygen of the oil, and the residue (N a ) is substituted for 6 . By the action of chlorohydric acid it takes up the elements of water, and regenerates the oil and ammonia ; the latter combines with the acid to form sal-ammoniac. When boiled in a solution of potash, it is converted into a metameric modification, which is no longer decomposed by acids, but unites directly with them and neutralizes them. This substance, which is an alkaloid, is also formed when ammo- nia is passed through an alcoholic solution of the oil of bitter almonds ; it is called benzoline or amarine. When the crude oil of bitter almonds is mixed with an alcoholic solution of potash, it is gradually converted into a white crystalline substance, which is called benzoine. It is polymeric of the oil, and is formed by the union of two equivalents of it; its formula is consequently C 2S H 12 4 . When the vapor of benzoine is passed through a red-hot 454 ORGANIC CHEMISTRY. tube, it is reconverted into bitter-almond oil. By the action of chlorine upon fused benzoine, H 3 is removed in the form of 2HC1, and a crystalline compound remains, which is called benzile, and is C 28 H 10 4 . 788. When bitter-almond oil is exposed to the air, it rapidly absorbs oxygen, and is converted into a white crys- talline substance, which is benzoic acid ; this is formed by the combination of two atoms of oxygen ; the oil is the aldehyd of the acid. The same effect is produced when the oil is heated with hydrate of potash ; hydrogen gas is evolved, and benzoate of potash formed. A more abun- dant source of benzoic acid is found in benzoin, a fragrant resinous substance which is obtained from the Laurus ben- zoin. This contains a large quantity of the acid, which may be procured by exposure to a gentle heat, when the acid is volatilized, and condenses as a white sublimate. It is also obtained by boiling the benzoin with lime, which forms benzoate of lime j chlorohydric acid added to the previously concentrated solution, precipitates the pure acid in crystal- line plates. Benzoic acid forms light silky crystals of a pearly whiteness, and has a pleasant aromatic taste, very slightly acid. When pure it is inodorous, but generally has a little volatile oil adhering to it, which gives it a fra- grant odor, like vanilla. It is volatile at a gentle heat, evolving a suffocating vapor, which condenses unchanged. It is very slightly soluble in cold, but more easily in hot water. The formula of benzoic acid is C 14 H 4 : it is monoba- sic, and forms a large class of salts, which are of but little importance. The benzoic vinic ether is obtained by pass- ing chlorohydric acid gas through an alcoholic solution of beuzoic acid, and is C 14 (H 5 Et)0 4 C 1? H 10 4 . It is a fra- grant volatile liquid, which in its chemical reactions resem- bles the other ethers j with ammonia, it affords benzainid and alcohol. Benzamid is the amid of benzoic acid, and with H 2 3 yields benzoic acid and ammonia. It is vola- tile, but at a high temperature loses a second equivalent of H 2 a and becomes C 14 H 5 N. This is a liquid to which the name of benzonitryl is given with 2H 2 3 it regenerates benzoic acid and ammonia. With strong nitric acid, benzoic acid yields a crystalline compound, with the elimination of H 3 2 ; it is the nitro- benzoic acid which has already been alluded to, (652,) and from its mode of formation is monobasic. When heated PHENOL. 455 with a mixture of nitric and sulphuric acids, a second equivalent of nitric acid is fixed, and binitrobenzoic acid is formed. The atom of hydrogen in each case is eliminated from the nitric acid, and its saline capacity destroyed, but the benzoic elements still retain the original atom of H, replaceable by a metal, and thus each of the new acids is monobasic. The decompositions of the ethers and amids of these acids yield a variety of curious compounds. 789- Benzen. The vapor of benzoic acid passed through a red-hot gun-barrel, is decomposed into carbonic acid and a new substance named benzen, benzol, or phene, which is C 13 H 6 . C 14 H fl 4 =C 3 4 -}-C 13 H 8 . Benzen is more easily obtained by distilling benzoic acid with slaked lime, which combines with the carbonic acid. It is a colorless, fragrant liquid, which boils at 187, and has a specific gravity of 830 ; at .32 F. it forms a white crystalline mass. Ben- zen is formed when the fat oils are decomposed at a red heat, and is obtained in the manufacture of oil-gas for illu- mination. With fuming sulphuric acid, benzen yields a monobasic acid, the sulphobenzenic, and a neutral crystalline body, mlplwbenzid. They are analogous to sulphovinic acid and sulphuric ether. The phenic alcohol or phenol C 13 H 6 3 is obtained by the decomposition of salicylic acid, which contains two atoms more of oxygen than benzoic acid. The name of carbolic acid is also given to it, and it occurs as a natural product in the secretion of the beaver, called castor enm, which owes its peculiar odor and probably its medicinal properties to a small portion of phenol j it is also contained in the oil of coal-tar. Phenol forms colorless crystals, which are liqui- fied by moisture, although but slightly soluble in water. Its aqueous solution has an acrid taste, and an odor like wood-smoke or cfeasote, which it also resembles in being poisonous, and a powerful antiseptic. Kreasote is probably an homologue of phenol. 790. The derivatives of phene and phenol may be repre- sented as compounds in which C 13 H 5 replaces H, precisely as the group C 4 H S in those of vinic alcohol. With sulphu- ric acid, phenol yields phenosulphuric acid S a (C 13 H 5 .H)O g! That formed by benzen is S 3 (C 13 H S .H)0 B , and is pheno- sulphurous acid: sulphurous "acid", 2(SO a .HO) = S 3 H 3 . With nitric acid, phenol yields three successive products, in 456 ORGANIC CHEMISTRY. which one, two, and three equivalents of N0 4 may oe r3 presented as replacing hydrogen. The view of tbo con- stitution of such bodies, given under nitrobenzoic acid, is, however, to be preferred. Phenol has, like abohol, an atom of hydrogen, replaceable by a metal, and all these derived compounds have acid characters and are mono- basic. The trinitric phenol is interesting as the final re- sult of the action of nitric acid upon many organic sub- stances, and has been described under the names of picric, nitropicricj carbazotic, and nitrophenisic acids. It 18 C ia H 3 (NOJ 3 O a ==C 18 H 8 N 3 p 14 , and forms yellowish-white crystalline scales, which dissolve in a large quantity of water, yielding a deep-yellow solution, with an intensely bitter taste. Its salts are yellow, and explode when heated. That of potash C 12 (H 2 K)N 3 14 is a crystalline salt, very sparingly soluble in water. 791. The action of nitric acid upon benzen yields a dense oily liquid, which has a very sweet taste, and an odor like the essence of bitter almonds, for wbich it is substituted in per- fumery. It contains C 12 H 5 N0 4 , and, by the further action of a mixture of nitric and sulphuric acid, fixes a second equivalent of the nitrous elements, and yields C 13 H 4 N 3 8 . Nitrobenzen is to nitrophenol what nitrous ether is to nitric ether, and is the nitrous ether of phenol, or N(C 13 H 5 )0 4 = C 13 H 5 N0 4 , and the second product may be regarded as N(C ia H 5 .N0 4 )0 4 , still corresponding to N(H)O 4 . 79*2. Phenol combines with ammonia and forms C 13 H 6 2 , NH 3 . When this compound is heated in a sealed tube, it is converted into water, and a new alkaloid: C ?3 H 6 02-f- NH 3 ==H 3 3 4-C 13 H 7 N. This is an ammonia in which C 13 H 5 replaces H, and is N(C 12 H 5 .H 2 ). The same group may replace an atom of hydrogen in the alcohol-ammonias, and mixed ammonias containing the different alcoholic and phenic carbohydrogens, are thus obtained. To this new alkaloid the name of aniline is given : it is a colorless, oily liquid, with a pleasant vinous odor, a burning taste, and is poisonous : it boils at 328, and has a specific gravity of 1 - 028. Aniline is slightly soluble in water; it decomposes metallic solutions, and with acids acts the part of a strong alkali, forming crystalline salts. These salts by heat yield compounds analogous to the amids, which are called aniluh. They are amids in which C 12 H 5 replaces H. The presence of aniline is readily detected by a solution of hypochlorito ANILINE. 457 of lime or bleaching-powder, which produces a beautiful violet-blue with a solution of the alkaloid. It occurs as a product of the destructive distillation of many organic matters, and is associated with phenol in coal-tar. When an alcoholic solution of nitrobenzen is mixed with sulphuric acid and a fragment of zinc, the hydrogen evolved by the decomposition of the acid reacts with the nitrobenzen to form aniline and water, C 12 H 5 N0 4 -{-3H a = C 12 H 7 N-|-2H 3 3 . Sulphuretted hydrogen produces a similar effect, sulphur being separated. When binitric benzen is thus treated, an alkaloid is obtained, which is nitric aniline, in which one equivalent of the nitric elements enters into the alkaloid; it is C 12 H 6 (N0 4 )N. By indirect processes, alkaloids are obtained which corre- spond to aniline, in which H and H 2 are replaced by chlorine and bromine. Their basic powers are less strong than the normal aniline, and the trichloric species C 13 H 4 C1 3 N is no longer an alkaloid. When by double decomposition we endeavor to obtain a hyponitrite of aniline, the salt is at once decomposed into phenol, nitrogen gas, and water, 798. When benzoate of lime is submitted to distillation, the principal product is a body corresponding to the aceton of acetic acid j two equivalents of benzoate 2C 14 (H 5 Ca)0 4 = CaCa^Og-f-CagH^Oa. The new compound is fusible, volatile, and crystallizes in large prisms, which are soluble in alco- hol and ether ; fused with hydrate of potash, it is decom- posed into benzoate and benzen, C 30 H 10 O a -f (KH)0 2 == C 14 (H 6 K)0 4 -|-C 12 H 6 . From this relation to benzoates and benzen or phene, it has received the name of benzophenon : with chemical agents it affords several new and curious compounds. Benzoilol is one of a group of aldehyds which are repre- sented by the general formula C W H,,_ 8 2 , and yield volatile monobasic acids with 4 , decomposable into C 2 4 and car- bohydrogens C n H n _ B , which form alkaloids C n H n _ 5 N. The essence of the seeds of cumin (Cuminum cyminum) consists of such an ildehyd, cuminol C 30 H 12 3 , and a carbohydrogen homologous with benzen, cymen C 20 H 14 . The distillation of cuminic acid with baryta affords another homologue, cu- mcn C 1S H 18 . This with strong nitric acid yields nitro- cumen, but, by long boiling with dilute acid, it is converted into benzoio acid In the same way cymen gives rise to a 458 ORGANIC CHEMISTRY. new acid, called lolulic ac/t7, which is C 16 H S 4 , and homo logous with benzoic and cuminic acids ; with baryta it yields toluen C 14 H S , which is also obtained by the distillation of tolu balsam. Alkaloids homologous with aniline have been formed from all these hydrocarbons. The action of nitric acid upon benzen has failed to yield an acid lower in the series than the benzoic. Phenol belongs to another group of what may be termed alcohols, which are represented by the general formula C n H H _ 6 2 . There is still another class of aldehyds, repre- sented by C n H n _ s 4 , which are consequently metameric with the acids of the benzoic group, and which form acid with 6 . Such is salicylol, the essential oil of Spirea ulmaria, (queen of the meadow.) SALICYLOL, C 14 H 6 4 . 794. This is obtained by distilling the flowers of spirea with water ; the oil does not pre-exist in the plant, but is formed during the process, like benzoilol, by the reaction of principles in the plant which have not yet been examined. It may also be formed fromsah'cme, a vegetable principle ex- tracted from several species of Salix, to which both substances owe their name. Salicylol is a colorless liquid, heavier than water, in which it is somewhat soluble, and has the fragrant odor which is perceived when the flowers of spirea are bruised. Its composition C J4 II 6 4 is identical with that of benzoic acid. One atom of hydrogen in it may be replaced by chlorine or bromine, and an atom of hydrogen is also re- placeable by a metal yielding compounds like C 14 H 5 K0 4 . It forms a crystalline compound with ammonia, which soon changes into an amid like hydrobenzamid. Heated with hydrate of potash, hydrogen is evolved and a salt of salicylic acid is formed. The acid is C 14 H 8 4 . It crystallizes in delicate white prisms, and is volatile and sparingly soluble in water. Salicylic acid is monobasic, a/id has considerable resemblance to the benzoic ; it forms a coupled acid with nitric acid. 795. The ethers of salicylic acid are easily formed : that of methol is interesting, because it constitutes the principal part of the fragrant essential oil of winter-green, Gaultheria t>rocumbenSj obtained by distilling that plant with water. The ether is readily decomposed by an alcoholic solution ESSENTIAL OILS. of hydrate of potash, and yields wood-spirit and salicylato of potash. If to the hot solution of the salt an excess of chlorohydric acid is added, the salicylic acid crystallizes on cooling. Ammonia converts the ether into a crystalline mass of salicylamid, which has the composition of salicylate of ammonia minus H 2 3 . When the salicylic acid is rapidly distilled, it is decomposed into carbonic acid and phenol C 14 H 6 4 C 2 4 -f C 13 H 6 3 . If strong nitric acid is added to the oil of winter-green or salicylic acid, and the mixture boiled so long as red vapors appear, a large quantity of trinitric phenol, nitropicric acid, is obtained on cooling. The essences of anise, fennel, and some other plants, con- sist principally of an oil, to which the name of anethol has been given. It is C^H^Oa : by oxydizing agents, such as nitric acid, it is converted into oxalic acid, and a new acid resembling the salicylic and homologous with it, which is called anisic acid C 16 H 8 6 . Its decomposition yields car- bonic acid and anisol C 14 H 8 2 , a homologue of phenol. OTHER ESSENTIAL OILS. 796. The essences just described are types of a large Dumber of essential oils, which, although not all homologous with the classes named, sustain the relation of aldehyds or alcohols to corresponding acids. Such is the oil of cinna- mon, which is G 1S H S 3 , and yields by oxydation cinnamic acid C 1S H 8 4 . This acid is associated with the benzoic, which it resembles, in its properties, in the balsam of tolu : by nitric acid it is oxydized and yields benzoic acid. When distilled with baryta it is decomposed into carbonic acid and a carbohydrogen, cinnamen C 16 H 8 . Both cinnamol and cinnamen appear to exist in the bal- sams, such as styraXj benzoin, tolu, and the balsam of Peru. These consist of resinous matters, apparently formed by the oxydation of essential oils, and mixed with cinnamic or benzoic acids, or with both. 797. The oxygenized essences already described are, as in the case of cuminal, often associated with other oils, which, like cymen, contain no oxygen, and these carbohydrogen oils sometimes constitute the only product of the distillation. The most important of this class has the formula G 80 H 8 , and is best known under the form of oil of turpentine. It is obtained by distillation from the crude turpentine which 460 ORGANIC CIIEMISTR*. exudes from many species of PI'HUH, and is a mixture of the volatile oil and a resin. Its taste and odor are well known ; it has a specific gravity of -8(35, and boils at 312. It is insoluble in water, but soluble in alcohol. Oil of turpentine is of great use in the arts, for the preparation of varnishea and paints, and is used for illumination, under the names of camphcne and pine-oil. The liquids sold for the same pur- pose, under the names of burning-fluid and Kpirit-yas, are solutions of camphene in highly rectified alcohol, and, from their great volatility and inflammability, are very liable to explosion and dangerous accidents. 798. The oils of juniper, pepper, caraway, parsley, citron, lemon, oranye, and bcryamot are carbohydrogens, identical in composition, density, and boiling point with oil of turpentine, and may be included under the general name of camphen. They absorb chlorohydric acid gas, and yield a crystalline compound, which is C 2 JI 10 .IIC1 C 20 H 17 C1, and has all the characters of a substitution product from 20 II 18 . The liquid portion of the oil which has been treated with the gas has the same composition as the solid. This is crystalline and volatile, and has an odor like ordinary camphor. The essence of citron, unlike the others, fixes 2HC1, and yields a compound C 20 II 18 Cl a . These chlorinizcd bodies are decom- posed when distilled with lime, arid yield modifications of camphen, distinguishable principally by their odors and their different action upon polarized light. 799. When moist oil of turpentine is exposed to cold, it often deposits a crystalline compound : a similar substance is slowly separated from a mixture of the oil with alcohol and nitric acid. It crystallizes in beautiful prisms, and is volatile, very soluble in alcohol, and sparingly soluble in water. The composition of this new body is represented by C/ 20 H 20 O 4 , and it is therefore formed by the fixation of 2EI a 3 ; it crystallizes with an additional equivalent of water, which is expelled by heat : the name of terebol is given to it. When dissolved by boiling, in water acidulated with sulphuric or chlorohydric acid, it is completely decom- posed into water and a volatile liquid, terpinol, which is obtained by distillation and has an odor of hyacinths : it is C 40 H. 14 O a . Chlorohydric acid gas expels water from fused tcrol/ol, and yields O fl0 H 18 Cl fl , a crystalline body identical iu composition with that obtained from lemon camphen. The odors of these different varieties of the same carbo ESSENTIAL OILS. 461 hydrogen depend upon differences in constitution not yet understood; they are apparently independent of the pre- sence of any oxygenized compound, as the different essences may be distilled from hydrate of potash or potassium, with no other effect than that of refining their odors. The oil of roses is a carbohydrogen of different composition, probably (AjQlljjjy 800. Many of the oxygenated volatile oils deposit, by cold, crystalline compounds which are often isorneric with the oils themselves, and are distinguished by the general name of stcaroptcns, or camphors of their respective oils, from their resemblance to common camphor. This substance is obtained by distilling the wood of the Lauras camphora with water, and is crystalline, very volatile, fragrant, and soluble in alcohol, but insoluble in water. Its formula is C ao H lfl 3 ; heated with hydrate of potash under pressure, it combines directly with it and forms a salt, campholate of potash C ao (H 17 K)0 4 . With strong nitric acid it yields camphoric acid C 30 H lfl 8 , which is bibasic. 801. The Drybalanops camphora of Borneo yields a solid fragrant essence, which is known as Borneo camphor, and is much valued in the East: it also exists in the essential oil of valerian. This camphor has the formula C 20 FI 18 3 , and, when heated with nitric acid, loses H a and yields laurel camphor. When distilled with anhydrous phosphoric acid, it yields a form of camphen which exists with the camphor in the plant, and fixes H a O a to form it. When laurel camphor is thus distilled, a carbohydrogen O fl0 H 14 is obtained, which is ci/men. 802. The essential oil of black mustard-seed Sinapia niyra, is obtained by distilling the bruised seeds with water. It is heavier than water, pungent and acrid, and contains sulphur. It is represented by the formula C 8 H 5 NS a . With ammonia it combines and forms a crystalline alkaloid, thioxi- namine, C 3 H 8 N a S 2 , which, when heated with oxyd of lead, loses H 3 S a and forms sulphuret of lead and water, together with a new alkaloid C 9 H N 9 , called sinamine, which is crys- talline, and is a strong base. The essential oil of horse-radish, Oochlcaria, ojjlcinaluj is identical with that of mustard. The oil of asafootida con tains carbon, hydrogen, and sulphur: it is probably C 19 H 13 S $ , and seems allied to a sulphuretted ether or alcohol : with chlorid of mercury it forms a crystalline compound which 462 ORGANIC CHEMISTRY. contains the elements of the oil with those of the mercurial salt. When mixed with sulphocyanid of potassium, a decomposition ensues which gives rise to the essential oil of mustard. The oil of garlic belongs to the same series, which is very interesting from its curious and as yet imperfectly known relations. The odorous secretion of the polecat, Mephitis putorius, contains sulphur, and perhaps belongs to the same class. 803. Resins. These substances are vegetable products, and seem to have been generally formed by the oxydation of essential oils ; they are insoluble in water, but soluble in alcohol and ether, and many of them are used in pharmacy and in the arts. Among them are copal) mastic, clemi, guiacum, and colophony or pine resin. In their crude state they are often mixed with volatile oils, which may be sepa- rated by distillation with water, as those of turpentine and elemi, or with soluble acids, like the benzoic and cinnamic, as in the balsams, and often with gums and other principles soluble in water, constituting what are called in the materia medica, yum resins, like asafoetida and gamboge. The true resins are many of them acids, and form distinct salts with bases. The resin of the pine may be obtained by care- ful management from its alcoholic solution, in crystalline crusts, very soluble in ether and sparingly soluble in alcohol. Exposed to heat, it distils over and condenses in an isomeric modification, distinguished in its crystallization and solu- bility. Under certain circumstances, both varieties may be converted into an amorphous form. They have been denominated pimaric and sylvic acids, and are both mono- basic, and represented by C 40 H 30 4 . Two equivalents of oil of turpentine and 6 , yield H 3 a and an equivalent of pimaric acid. The resins of copaiva, elemi, and anime be- long to one or another of the modifications of this acid. 804. Caoutchouc, Gum-Elastic. This curious substance in found in the juices of many plants, but is principally obtained from the Hcvea guianesis, and latropha elastica. Its ordi- nary properties are well known : it is insoluble in water and alcohol, but dissolves in ether and many volatile hydrocar- bons : when softened by these solvents, it is wrought into a great variety of curious and useful articles. Small tubes of gum-elastic are very useful in the laboratory, to join glass tubes and form flexible joints. They are easily made from sheet caoutchouc by cutting the folded edges of the VEGETAL ACIDS. 463 with clean scissors over a glass tube, as seen in figure 417. Caout- chouc is very com- bustible, and burns with a bright smoky flame. It contains Fig. 417. carbon and hydrogen only, and probably in equal equivalents; but it furnishes no reactions by which we may fix its formula or even determine whether it is chemically homogeneous. When exposed to heat it is decomposed, and yields several volatile hydrocarbons homologous with olefiant gas : among them are said to be C S H 8 , C 10 H 10 , and C 40 H 40 . These mixed liquids are used as a solvent for caoutchouc } the volatile oils from coal4ar are also employed for the same purpose. When caoutchouc is immersed in a bath of melted sulphur, or when sulphur is added to its substance and the mate- rial afterward exposed to a considerable heat, (280,) the caoutchouc undergoes a peculiar change. It becomes much firmer and stronger, and less liable to be softened by heat or rendered rigid by cold; in this form it is known as vulcanized gum-elastic, and is extensively used in the arts, in preference to the unaltered caoutchouc. This is Goodyear' s patent. 805. Gutta Percha. This substance exudes from the Isonandra gutta, a tree common in the Malaccan peninsula, and forms a tough and elastic mass at ordinary temperatures, which becomes ductile and plastic when warmed by immer- sion in hot water. Gutta percha (pronounced pertcha) is a mixture of several resins, which are separable from each other by means of their different solubility in alcohol and ether. The greater portion of it consists of a resin which softens at 104 F., and is but little soluble in cold ether when pure. It contains a greater amount of oxygen than pimaric acid. Gutta percha is readily dissolved by chloro- form and sulphuret of carbon, which deposit it unchanged by evaporation. It is capable of being moulded into a great many articles of utility and ornament. VEGETAL ACIDS. 806. Besides the acids which we have described as derived from bodies of the alcohol group, or from the various essen- tial oils, and which are generally monobasic, volatile, and. 164 ORGANIC CHEMISTRY. when of high equivalents, sparingly soluble in water, there remains to be described a class of acids of high equivalents, which are bibasic or tribasic, very soluble in water, and contain a large amount of oxygen, having analogies with the lactic acid. Such are the oxalic, citric, tartaric, and malic acids, and some others of less consequence. 807 Oxalic Add, C 4 H 2 8 . The salts of this acid exist in many vegetables : the agreeably sour taste of the wood- Borrel, Oxalis acetosella, of the common sorrel, a species of RumeXj and many other plants, is due to the acid oxalate of potash which they contain, and from which the acid may be extracted. It is also a product of the action of nitric acid upon alcohol, upon sugar, starch, lignin, and many other organic substances. To prepare it, one part of sugar is heated with eight parts of nitric acid, specific gravity 1-25. A violent action ensues, and much nitrous acid is evolved; when this ceases, the solution is concentrated by evaporation, and on cooling yields a large quantity of crystals of oxalic acid, which are purified by washing in a little cold water and recrystallization. 808. Oxalic acid forms colorless* crystals, which are C 4 H 2 8 -f-2H a 2 ; by a gentle heat the water is expelled, and the dry acid remains as a white powder, which, at a higher temperature, is in part sublimed unchanged, and partly decomposed into formic acid, water, carbonic acid and carbonic oxyd gases. The acid is very soluble in water, has a strongly acid taste, and is poisonous. When the acid or one of its salts is heated with strong sulphuric acid, it is decomposed without blackening, a character by which it is distinguished from the succeeding acids, and evolves equal volumes of carbonic acid and carbonic oxyd gases j Oxalic acid is bibasic ; the neutral oxalate of potash is a very soluble salt, and is C 4 (K 3 )0 S ; the acid oxalate C 4 (KH)0 8 is less soluble, and has a pleasant acid taste. It is known under the name of bmoxatatc, and as it was for- merly obtained from the wood-sorrel, is often sold as salt of sorrel, for the purpose of removing iron-stains from linen, which it does by forming a soluble salt with the iron oxyd. The acid oxalate crystallizes with another equivalent of oxalic acid to form a salt which is called a quadroxalate, and contains C 4 H ? O s -j-C 4 (HK)0 8 , or one-fourth the amount of potash that is in the neutral oxalate. The acid might OXALIC ACID. 466 hence be regarded as quadribasic, and be 8 H 4 16 , but its other reactions lead to the conclusion that it is properly bibasic. The second equivalent of acid may be regarded as holding a place analogous to that of the crystal-water in other salts. The oxalate of ammonia C 4 (NH 4 ) 3 8 crystal- lizes in fine prisms ; when decomposed by heat it loses 2H 2 3 , and yields the amid of oxalic acid, oxamid, which is C 4 H 4 N 2 4 . It is a neutral insoluble body, and by the action of acids is reconverted into oxalate. The acid oxa- late of ammonia yields in like manner an acid amid, oxa- mic add, C^IA+^HS^^H.NO, H a 2 -=C 4 H s N0 6 . It is monobasic, and forms a series of salts : when its solution is boiled it is changed into acid oxalate of ammonia. The oxalate o.f lime crystallizes with 2H 3 3 ; it is a very insoluble salt, and occupies an important part in the vegetable economy, being secreted by a large number of plants, in the cells of which the microscope reveals a great number of beautiful crystals of this substance ; this appearance is represented in figure 418, of a vessel from the bark of Torreya taxifolia. In many of the lichens, the oxalate of lime appears to replace the woody fibre, and to be Fig- 418. somewhat allied in its functions to the carbonates and phos- phates of lime in the animal kingdom. The oxalates of the inctals are generally insoluble. With two equivalents of the alcohols, oxalic acid forms neutral ethers ; and with one, vinic acids. The oxalic ether of wood-spirit is obtained in fine crystals ; it is C 4 (Me 2 )O s : mixed ethers of tlie different alcohols may be obtained, such as C 4 (EtMe)0 8 . When ammonia in excess is added to oxalic ether, oxamid is obtained ; but if the ammonia is cautiously added, a beautiful crystalline substance is formed, which is named oxamethane, and regenerates an oxalate, alcohol and ammonia, by fixing 2H a 2 . It corresponds to sulphamethane, and is at once the amid of oxalovinic acid, and the ether of oxamic acid. Oxalic acid pertains to the series already described under oleic acid, including succinic and suberic acids, and represented by CH,*_ 2 8 ; when fused with hydrate of potash it yields a formate. 809. Tartaric Acid, C 8 .H 8 13 . This acid exists in the juices of many fruits,, particularly that of the grape, as an acid fcartrate of potash. As this salt is almost insoluble in dilute Xi 466 ORGANIC CHEMISTRY. alcohol, it is deposited, during the fermentation of wine, in crystalline crusts, known as crude tartar, or anjol. It is decomposed by chalk to form a tartrate of lime ; this is mixed with an equivalent of sulphuric acid, which forms a sulphate, and liberates the tartaric acid. From a concen- trated solution it crystallizes in fine rhombic prisms, very soluble in water and alcohol, and having a pleasant acid taste. Tartaric acid is bibasic. The acid tartrate of potash C S (H 5 K)0 13 is prepared by refining the crude tartar by crystallization, and generally appears as a crystalline powder, sparingly soluble in water, and feebly acid to the taste. It is known in pharmacy as cream of tartar. The neutral tartrate is mu h more soluble in water, and is commonly called soluble tartar. It is C s (H 4 K a )0 13 . By saturating cream of tartar with carbonate of soda, a double salt is ob- tained which is C s (H 4 KNa)0 13 : it forms very large transpa- rent prismatic crystals, and is known as Rochelle salt. 810. When cream of tartar and oxyd of antimony are boiled together in water, solution takes place, and, on cool- ing, transparent crystals of a double salt are deposited, which is known in medicine by the name of tartar emetic. The part which the oxyd of antimony plays in this com- pound is peculiar. We may represent two equivalents of oxyd of antimony 2Sb0 3 = Sb 3 6 as (SbO a ) 3 3 , correspond- ing to H 3 3 , and the group SbO a will then be equivalent to H, and may replace it in combination. The salt in ques- tion is such a compound, and the acid tartrate being C 8 H 4 (HK)0 13 , tartar emetic dried at 212 is C 8 H 4 (Sb0 9 .K) O 13 . The crystals at the ordinary temperature contain H 3 a as water of crystallization, but lose it by a gentle heat. If the dried salt is heated to 428, it breaks up into water H a O a , and a salt which is C 8 H a (SbK)O ia : in this compound antimony in one-third its ordinary equivalent may be sup- posed to replace hydrogen as in the analogous compounds of the sesqui-oxyds : if we call this Sbj, stibicum, and repre- sent it by sb, the dried salt then becomes C 8 H fl (sb.K)O ia : it is then, however, quadribasic. Oxyd of uranium UO S may in the same way replace H in a tartrate, and by heat Uj, corresponding to sb, and represented by ur may be obtained in combination, replacing H : in this way all the hydrogen is removed and a compound obtained which is C 8 (ur a sb 3 )0 ia . Arsenious acid As0 3 and boracic acid BoO a VEGETAL ACIDS. 467 rifford, with bitartrate of potash, compounds analogous to these salts of oxyd of antimony. Tartaric acid dissolves peroxyd of iron and forms a very soluble salt : in this, as in the preceding compounds, the metal is not precipitated by solutions of potash or ammonia. The decomposition of tartaric acid by heat produces several new acids, which have not yet been thoroughly studied. 811. The crude tartar obtained from the wine of the Vosges some years since, was found to contain an isomerio modification of tartaric acid, which is less soluble than the ordinary acid, and crystallizes with an equivalent of water, while the common form is anhydrous : the new acid precipi- tates solution of the salts of lime, and in the chemical cha- racters of several of its salts is distinguished from the ordi- nary tartaric acid, with which however it is metameric : it has received the name of racemic acid. The replacements of the crystals of tartaric acid and of its salts are upon alter- nate angles, constituting what is called a hemihedral modi- fication, and the order of the replacements is from left to right : a solution of tartaric acid or of any tartrate acts upon polarized light, and causes the ray to rotate in the same direction. Racemic acid and its salts are not hemi- hedral, and do not affect in any way the ray of polarized light. When, however, a solution of the double racemate of potash and ammonia is crystallized, two sets of crystals are obtained in equal quantities : the one are hemihedric to the right, and identical in all respects with the ordinary tartrate of these bases : the others have left-handed hemihedrism, and cause the beam of polarized light to deviate to the left ; and these two salts contain two tartaric acids which are distinguish- ed from each other only by their opposite hemihedral modi- fications and their action upon polarized light. The right- handed acid is ordinary tartaric acid, and the left-handed a new and a distinct modification ; and these two are not by any known means convertible into one another. The forma of the two crystals are to each other as the image in a mirror is to the object. When saturated solutions of the two acids are mixed, they become warm, and deposit crystals of the racemic acid, in which their mutual influence upon polarized light is neutralized. 812. Malic Acid, C S H,.0 10 . This acid exists in the juices of many sour fruits, particularly in the apple and the ber- ries of the mountain ash, Sorlus aucuparia : the stems of 4GS ORGANIC CIIEMTST11V. the garden rhubarb also contain a large quantity of it tt is very soluble in water and alcohol, and crystallizes with difficulty ; its solution has a pleasant sour taste. The malic acid is bibasic, and the malates of the alkaline bases are very soluble. The acid malate of ammonia C S (H.NH 4 )0 10 forms large transparent crystals. The neutral rnalate of lead C 8 (H 4 Pb 2 )0 10 is obtained as a white readily fusible precipitate, which in an acid liquid slowly changes into delicate crystals. Malic acid is not volatile, but is decom- posed by heat into water and new acids, which are described in the larger works. 813. When tartaric and malic acids are heated with anhy- drous alcohol, vinic acids are obtained corresponding to the sulphovinic. The neutral ethers are more difficult of prepa- ration, as they are soluble in water and not volatile : by passing hydrochloric acid gas, however, through the alco- holic solutions of the acids, neutralizing the excess of acid with carbonate of soda, and agitating the mixture with hydric ether, the ethers of the acids are dissolved out, and may be obtained by evaporating the solution at a gentle heat. They are converted by ammonia into amids and ethers of amidic acids : in this way tartramic acid and tar- tramid may be obtained. 814. Malic ether yields malamid, which has the compo- sition of and appears to be identical with asparagine, a peculiar nitrogenized principle found in the juices of the asparagus, mallows, and particularly in the young shoots of vetches which have vegetated in the dark. It forms large crystals, sparingly soluble in cold water, and contains C 8 H 8 N 3 6 , corresponding to malate of ammonia from which the elements of water have been abstracted, C S H 4 (NH 4 ) 3 10 2H 3 2 = C 8 H 8 N a O ? : by the action of alkalies or acids i* loses ammonia and yields aspartic acid C 8 H 7 N0 8 , which is now found to be identical with tnalamic acid, and to be formed from acid malate of ammonia as oxarnic acid is from the acid oxalate. The ordinary action of acids or alkalies does not further decompose this acid ; but when nitric oxyd is passed into a solution of asparagine or aspartic acid in nitric acid, the hyponitrous acid formed, decomposes the aspartic, yielding malic acid, nitrogen, and water, by a decomposition similar to that described under aniline : C S H N0 8 +NH0 4 = C 8 H a 1Q VEGETAL ACIDS. 4G9 Citric Acid, C 13 H 8 14 . This acid exists in the juices of many fruits, often associated with the tartaric and malic, and is the acid of lemons. It is obtained by saturating lemon-juice with chalk, by which an insoluble citrate of lime is formed ; this is decomposed with an equivalent of sulphuric acid, which forms sulphate of lime, and the citric acid is obtained by evaporation and crystallization. It forms large crystals belonging to the trimetric system ; it is very soluble in water, and has a strong but agreeable acid taste. The citric acid is tribasic, and forms with potash three salts, in which one, two and three atoms of hydrogen are replaced by potassium : the first two salts are acid, and the last, which is C 13 (H 5 K 3 )0 14 , is neutral. In the same way it yields a neutral ether with three equivalents of alcohol, and vinic acids with one and two equivalents. When exposed to heat, citric acid is decomposed into H 2 2 and C 12 H 6 13 ; this is a new acid, which is also found combined with lime in the Aconitum napellus, and is hence called aconitic acid ; it is tribasic and very soluble in water: when the action of heat is carried still further, the acoui- tic acid is decomposed into C 3 4 and C 10 H S ; this last ia called citraconic acid, and is bibasic, soluble, and by heat distils in part unchanged : a higher temperature decomposes it into water, and a neutral liquid C ao H 4 6 . This sub- stance, which is called citraconid, slowly dissolves in water, and combines with H a 3 to form an acid isomeric with citra- conic acid. 815. Tannic Acid, Tannin. Many plants contain a peculiar principle, characterized by an astringent taste, and by precipitating animal gelatine from its solutions, forming with it an insoluble compound, upon the production of which depends the prosess of tanning leather. The barks of oak and hemlock, and gall-nuts, which are excrescences resulting from the puncture' of insects upon the branches of a species of oak, contain a large portion of this principle, which ia named tannic acid, and are used in the preparation of leather : they are also employed with persalts of iron in dyeing black, and in the formation of writing-ink. The vegetable extracts called kino and catechu, and many other vegetable substances, contain a principle analogous to the tannin of the oak. Tannic acid is obtained in a pure state from gall-nuts, which yield about one-third of their weight, by the following process: They are reduced to a coarse pow- 470 ORGANIC CHEMISTRY. der, and placed in the upper part of a vessel like that repre- sented in the figure, the mouth of which is previously stopped with a piece of linen, and a quantity of hydric ether is then poured over them, which slowly filters through, and collects in the lower vessel, where it separates into two layers. Ordinary ether contains about one- twelfth of water, which dissolves the tannic acid to the exclusion of all other substances, and forms a solution that does not mix with the ether, which dissolves a portion of coloring matter from the gall-nut. The dense aqueous solution is separated, washed with a little ether, and finally evaporated in shallow vessels by a gentle heat. It forms a brilliant porous mass, which has gene- rally a light yellow tint; it is very soluble in water and has a purely astringent taste. Sul- jjj phuric, nitric, chlorohydric and phosphoric acids give copious precipitates with its solution, which ng. 419. are combinations of the two acids. The tannic is a feeble acid, and is bibasic or polybasic. The alkaline tan- nates are soluble ; those of the metals are generally insoluble, and often colored. The pertannate of iron is the basis of black dyes; and of writing-ink : it is insoluble in water, but when the solutions are dilute, the precipitate remains a long time suspended, especially if a little gum is added, as in the fabrication of ink. When a solution of tannic acid in potash is heated, a salt of gallic acid is formed, with the production of a brown matter. Similar results are obtained when strong acids act upon tannin, and the powder of nut- galls mixed with water undergoes a sort of fermentation, which also yields gallic acid. When boiled for some time with dilute sulphuric acid, tannin is converted into gallic acid and grape sugar. The brown products obtained with strong acids and alkalies, result from the decomposition of the sugar which is produced. The probable formula of tannic acid is C 52 H 24 32 ; two equivalents of it with 6H 3 2 yield one of glucose, C^H^O^, and two of gallic acid, Gallic Acid, C 14 H 6 10 . This acid exists ready formed in the seeds of the mango : it is most easily prepared by the process of fermentation already described ; it is dissolved out. of the mixture by boiling water, and separates on cool- VEGETAL ALKALOIDS. 471 ing in small silky crystals, which require 100 parts of cold water for their solution, and have an acid and astringent taste. Gallic acid does not precipitate gelatine, and the black color of the pergallate of iron is destroyed by boil- ing. Gallic acid is bibasic : its salts have been but little studied. When carefully heated, it is decomposed into C a 4 and a crystalline sublimate, which is pyrogallic acid, and is C 13 H 6 . It is very soluble in water and alcohol, and when dissolved in a solution of hydrate of potash, absorbs oxygen so rapidly from the air as to be employed in eudiometry. Both gallic and pyrogallic acids reduce the salts of plati- num, gold, and silver. An application of this is made for the purpose of coloring the human hair, which is first wet with a solution of gallic acid, and then, after drying, moist- ened with an ammoniacal solution of a salt of silver. The reduced metal imparts a fine black or brown color to the hair, which is permanent. For a large number of other vegetable acids, many of which are yet but imperfectly known, the student is refer- red to more extended treatises. VEGETAL ALKALOIDS. 816. The artificial organic alkaloids which we have de- scribed under different heads in the preceding pages, have been considered as derivatives of ammonia in which one or more atoms of hydrogen are replaced by the elements of some carburet of hydrogen j such are aniline and metha- mine. We have pointed out how these, like ammonia, may fix the elements of water, and form compounds analogous to hydrate of potash, such as the hydroxyd of vinic ammo- nium (NEt 4 .H)0 3 ; but when these combine with an acid, the oxygen is eliminated in the equivalent of water which is formed, and it is but the group NEt 4 , which replaces hydro- gen in the acid. There are, however, a large number of organic bases occurring in different vegetable substances, which, like aniline and ammonia, combine directly with acids without the formation of water, and which contain oxygen. All of these alkaloids contain one and sometimes two atoms of nitrogen, and may be regarded as derivatives of ammonia in which the group of elements replacing hydrogen contains oxygen. They are commonly crystalline and not volatile 472 ORGANIC CHEMISTRY. without decomposition, and generally possess active medi* cinal powers. Those of opium, cinchona, hellebore, and many others constitute the active principles of these drugs. When exposed to heat, especially in the presence of caus- tic alkalies, they are decomposed, and generally evolve volatile alkaloids without oxygen ; among these, methamine and aniline are met with. Several other volatile alkaloids obtained by the action of a solution of hydrate of potash upon plants, are supposed to be the result of a similar decomposition. 817. Many of the vegetal alkaloids are strong bases, and completely neutralize acids ; others are comparatively feeble, and their salts are even decomposed by a gentle heat. They combine with chlorid of platinum to form double salts, which are generally sparingly soluble, and analogous to the chlorid of platinum and ammonium : some of them unite with one, and others with two equivalents of the chlo- rid, and in like manner they frequently form two chloro- hydrates by fixing one and two equivalents of chlorohydric acid, thus giving rise to neutral and acid salts. The alkaloids combine with metallic salts in the same way as ammonia, and yield compounds with nitric acid, and with nitrate of silver. They generally form combinations with chlorid of mercury, which have a similar composition with the ammonia salts. We shall first describe some of the more important of the oxygenized alkaloids, and then pro- ceed to speak of those amilogous to aniline. 818. Alkaloids of Cinchona, or Peruvian Bark. The barks of several species of cinchona owe their medicinal properties to the presence of two alkaloids, which are named quinine and cinckonme. They are extracted by digesting the bark in a dilute acid, and adding to the infusion a solution of carbonate of soda, which precipitates the alkaloids in an impure state. The precipitate is washed 'and dissolved in boiling alcohol ; a little animal charcoal is added to remove some coloring matter, and the filtered liquid, on cooling, deposits crystals of cinchonine, while the more soluble quinine is obtained by evaporation. Quinine is a white crys- talline substance, sparingly soluble in water, but readily so in alcohol and ether. The formula of this alkaloid is C SS H 33 N 2 4 . It is readily soluble in acids, forming crystallizable safts ; which have a very VEGETAL ALKALOIDS. 473 bitter taste. These are two chlorohydrates, one C 38 H 33 N 3 4 HC1, which if we would compare it with chlorid of ammo- nia, must be written (C 3S H 23 N 3 4 )C1 = QuCl, and a second acid salt QuOl.HCl, or C 3S H 33 N 3 4 .2HC1 ; the platinum double salt corresponds to this acid chlorohydrate : there exists, in like manner, two sulphates of quinine, which with several other salts of this base are employed in medicine. Cinchonine is represented by C 33 H 22 N 3 3 ; it differs from quinine only by 3 , and resembles that base in its charac- ters, but is less soluble in alcohol and ether. Its salts are similar to those of quinine, and are often substituted for the latter in medical practice. 819. In the preparation of these alkaloids, a portion of quinine is often obtained as an uncrystallizable resinous mass, which is, however, identical in chemical composition and medicinal properties with the crystalline base. It is called quinoidine. The cinchona known in commerce as pale bark contains principally cinchonine; the yellow bark qui- nine, and the red bark, a mixture of both. Different varie- ties of cinchona have furnished two or three other bases very similar to these; to which the names of aricine, chinova- tine, and quinidine have been given. These bases are accompanied with a peculiar acid, called quinic or kinic acid ; it forms large crystals resembling tar- taric acid, and is bi basic : its composition is represented by C 14 H 13 12 . The results of its decomposition form a very interesting series. By the action of chlorine and bromine upon solutions of chlorohydrate of cinchonine the hydrogen of the alkaloid is in part replaced, and blchloric and bibromic cinchonine are obtained ; the former is C 3g H 30 Cl a N a 3 , and is isomorphous with the normal alkaloid. When cinchonine is distilled with hydrate of potash, a carbonate is formed and hydrogen gas escapes, with a new volatile base named' chinoline or qninolt'ne, which is an oily liquid and resembles aniline in its properties. Its compo- sition is represented by C 18 H 7 N : C 35 H 33 N 3 2 -f-2(KH)0 3 = 2C 18 H 7 N-f-C a K 3 -f 5H fl . Quinine and strychnine yield chinoline by a similar process. Alkaloids of Opium. This substance is the inspissated juice of the capsules of a species of poppy, Papaver somni- ferum, and contains several organic bases. The most im- portant of these, and the one to which it owes its power aa 474 ORGANIC CHEMISTRY. an anodyne, is morphine. It is prepared by precipitating a solution of op : 'im by carbonate of soda, as in the process for quinine ; the impure morphine is digested in cold alcohol to remove some other alkaloids present, and finally dissolved in dilute acetic acid. The cautious addition of ammonia to the acetate thus formed, precipitates the morphine, which is dissolved in hot alcohol, and crystallizes on cooling. It forms brilliant rectangular prisms, which are sparingly soluble in water, readily so in hot alcohol, and insoluble in ether; it has a persistent bitter taste. Its formula is C 34 H 19 N0 6 . Morphine forms crystalline salts, some of which, as the chlorohydrate, sulphate, and acetate, are employed in medi- cine. The best opium contains six or eight per cent, of this alkaloid. 820. Codeine is a base which occurs in small quantities with morphine ; it is more soluble in water than that alka- loid, and dissolves readily in ether : it seems allied to mor- phine in its effects upon the animal system. The formula for codeine is C 3G H 31 N0 8 . When heated with sulphuric acid, codeine yields a compound which is derived from the sulphate by the elimination of 2H 3 2 , and corresponds to an amid: morphine and some other alkaloids yield similar compounds. Bases have been obtained from it in which portions of the hydrogen are replaced by chlorine, bromine, and the nitric elements. When heated with potash it evolves volatile bases, among which are ammonia and methamine. Nareotine is another alkaloid, which occurs in consider- able quantity in opium, and is separated from the morphine by being very soluble in ether and insoluble in water. It forms brilliant transparent crystals, and has the formula C^HjggNO,^ Nareotine is but a feeble base : by oxydizing agents it is decomposed, and yields a peculiar acid called the opianic C 20 H 10 10 , and a new alkaloid, cotarnine C 26 H 13 N0 8 . In addition to these there have been observed several other bases in smaller quantities in opium : such are narceine, papaverine, and theuaine ; they are but little known. Opium contains also a peculiar tribasic acid, the meconic C 14 H 4 14 . It is not improbable that in certain seasons and conditions of soil and climate, different alkaloids may be formed in the same plant, and to an extent replace each other ; that such is the case with different species of a genus is shown by the history of cinchona and some other pjants. VEGETAL ALKALOIDS. 475 821. Strychnine. This alkaloid is found in the StryJinoa fiux-vomica, and several other plants of the same genus. It is prepared by digesting the nux-vomica with water acidu- lated by sulphuric acid, and precipitating the solution by caustic lime. The impure precipitate is boiled with alcohol and animal charcoal, and the liquid on cooling deposits the strychnine in crystals. It is almost insoluble in water, abso- lute alcohol, and ether, but dissolves in dilute alcohol : its salts are crystallizable, intensely bitter, and highly poisonous. Strychnine and its compounds produce a spasmodic affection of ,the muscles of voluntary motion; they are used in minute doses in cases of paralysis. The poison of the celebrated upas is the product of the Stryclmos tieute, and owes its activity to strychnine. The formula for strychnine is CH M N a 4 ; Brucme is another organic base, which is associated with the last, in several species of StrycJinos. It resembles strych- nine but is more soluble in water and alcohol, and although similar in its action upon the animal system, is less potent. Its formula is C 46 H 20 N 2 8 . Both of these bases yield pro- ducts in which the hydrogen is in part replaced by chlorine and bromine. 822. Pipermeis a crystalline alkaloid extracted from black pepper, and is a feeble base : the formula C 70 H 36 N 3 10 is assigned to it. When heated with a mixture of hydrate of potash and quick-lime it disengages two volatile bases, one of which appears to be picoline, an alkaloid which is meta- meric with aniline, and is obtained as a product of the dis- tillation of bones. The other, to which the name of piperi- dine is given, has the formula C 10 H 1 N : it boils at 212 F., is soluble in water, caustic, and has a strong odor of am- monia. Piperidine is homologous with arsine and stibethine, having the general formula CJH^^N; N being replaceable by As or Sb. These are alcoholic ammonias which have lost H 2 , and may have one, two, or three atoms of the hydro- gen in NH 3 replaced by the alcoholic elements. Thus arsine has but one, and stibethine three equivalents of the carbo- hydrogen, while the new base has two, which may corre- spond to the vinic and propionic, C 4 and C 6 ; or to the butyric and methylic, C 8 and C 3 . Piperdine, with one equivalent of hydriodic ether, exchanges H for C 4 H 5 , to form a new base ; but with a second yields an iodid, which 476 ORGANIC CHEMISTRY isNC 10 H 10 Et 2 .I, and corresponds to the iodid of vinic am- monium. 823. Theme; Caffeine, C 16 H 10 N 4 4 . This organic base is found in coffee, tea, the fruit of the Paullnia sorbalis, and the Ilex paraguayensis, which affords the matte, or Paraguay tea. It is most abundant in green tea, which contains from two to five per cent. ; the best coffee does not yield one per cent. To obtain it, a strong decoction of tea is mixed with a solution of the surbasic acetate of lead, as long as a pre- cipitate is formed; to the clear solution a little ammonia is added to precipitate the excess of lead, and the liquid by evaporation furnishes theine in delicate silky crystals. It is readily soluble in hot water and alcohol, and may be volatilized without decomposition ; its taste is slightly bitter, Theine is a feeble base, and its salts* are easily decomposed . the chlorohydrate crystallizes beautifully. With nitrate of silver it yields a salt in fine crystalline groups, which is It is worthy of notice, that the plants which furnish this alkaloid are used by different nations to prepare a grateful and gently stimulating beverage. As these substances resemble each other only in containing theine, it is probable that they owe their common properties to the presence of this principle, and that, in some unknown manner, it pro- motes digestion and the other vital functions. The Bra- zilians prepare from the fruit of the Pauluiia sorbalis an extract called by them yuurana, which is much esteemed as a remedy in dysentery and nephritic complaints; it con- tains a considerable quantity of tbeine. 824. The seeds of the 2 hcobroma cacao, from which cho- colate is prepared, yield an alkaloid thcobrominc, which re- sembles caffeine and is homologous with it : it is C 14 H S N 4 4 , and the common formula of the two is therefore C n H n _ 6 . N 4 4 . With chlorine and oxydizing agents these alkaloids yield a series of interesting bodies, to which we shall again advert. 825. Sola-nine, from the Solanum nigrum,B.Did several other species, hyoscyamine, from Hyoscyamus niyer, atropine, from Atropa belladonna, and daturine, from Datura stramo- nium, are alkaline principles which possess in great perfection the poisonous properties of the plants from which they are derived. They are obtained by somewhat complicated pro- cesses, and are crystalline and volatile. Their salts are VEGETAL ALKALOIDS. 477 employed in medicine. Veratrine is found in the Veratrum album, or white hellebore; it forms a white crystalline powder, which is insoluble in water, but soluble in alcohol. It is a powerful acrid poison, but is used medicinally in neuralgia with beneficial results. Aconitine is obtained from the Aconitum napettus, and resembles veratrine in its properties. Sanguinarine is an alkaloid which exists in the blood-root, Sanguinaria canadensis, and to which this plant owes its active properties. Emetine, the emetic principle of ipecacuanha, is also an organic alkaloid. There are many other oxygenized bases which have been artificially formed. Such are benzoline, which has been described as an isomeric modification of hydrobenzamid, and many more, which the limits of this treatise will not permit us to notice. 826. Of the volatile bases analogous to aniline and chino- line, obtained from plants, but two have been much studied, nicotine and conine. Nicotine is the alkaloid of tobacco, and is obtained by distilling a concentrated infusion of the plant with lime or hydrate of potash. The recent plant contains a peculiar crystalline body, called nicotianine, which affords nicotine by the action of caustic potash ; but in the prepared tobacco, nicotine exists ready formed, and can be extracted by the action of ether to which a little ammonia has been added. When tobacco is smoked in a German pipe, the liquid which condenses in the well contains a large quantity of this alkaloid. The strongest Virginia tobacco affords, when dry, six or seven per cent, of the alkaloid, and mild Havanna tobacco no more than two per cent. The formula of nicotine is C 20 H 14 N 3 . It is an oily liquid heavier than water, in which it is somewhat soluble. It distils at a high temperature unchanged. The taste of nicotine is very acrid, and its odor recalls that of tobacco ; it is extremely poisonous. This base is strongly alkaline and forms very sojuble salts ; it fixes 2HC1 to form a deli- quescent chlorohydrate. 827. Conine is obtained from the hemlock, Conium macu- latum, by distilling any part of the plant with a dilute solution of hydrate of potash. Like the last, it is an oily liquid, which is slightly soluble in water, and possesses in a high degree the smell, taste, and poisonous properties of the hemlock. It is strongly alkaline, and yields a series of deliquescent salts ; the formula of conine is C 16 H 15 N. There still remain to be described a number of other 478 ORGANIC CHEMISTRY. vegetable substances which are not included under any of the previous classes. Among them are some neutral bodies, like araygdaline, salicine, and populine, which are inte- resting from the peculiar metamorphoses of which they are susceptible ; and besides these, several substances used in coloring, among the most important of which, in regard ta its chemical history, is indigo. 828. Amygdaline. This substance exists in the propor- tion of four or five per cent, in bitter almonds ; it is also met with in the kernels of peaches and cherries, and in the leaves and young shoots of many species of Sorbus, Prunus, and others of the Pomacece. It is obtained from bitter almonds from which the fat oil has been removed by pressure between heated plates, by boiling the residue in strong alcohol. The alcohol is then distilled off in a water-bath, and the syrupy residue, mixed with a little yeast, is set aside to ferment : by this treatment a portion of sugar which the almonds contain is destroyed. The clear liquid is again evaporated to a syrup and mixed with ether, which precipi- tates the amygdaline in a crystalline powder. It is readily soluble in alcohol and water, and crystallizes from the latter in large prisms, with three equivalents of water; it has a bitter taste. The formula of araygdaline is C^H^NO^ : when boiled with solution of baryta, it takes up the elements of one equivalent of water, and is converted into ammonia and amygdalic acid, which remains dissolved as amygdalate of baryta. Amygdaline may be regarded as the amid of this peculiar acid, which is C^H^O^. Bitter almonds contain, besides amygdaline and a fat oil, a large portion of a nitrogenous substance, to which the name of emulsine is given ; it constitutes the principal part of sweet almonds, which contain no amygdaline. When bitter almonds are bruised with water, or when an aqueous solution of amygdaline is mixed with a small portion of emulsine from sweet almonds, a peculiar decomposition ensues. The solution acquires the odor of the essence of bitter almonds, and the amygdaline is found to be converted into prussic acid, benzoilol, and grape sugar. Amygdalme, with two equivalents of water, contains the elements of these three compounds; C 40 H a7 N0 2a +2H 2 2 = C 3 NH+C 14 H 6 O v I" ^24^34^24- Amygdalic acid, when distilled with sulphuric acid and peroxyd of manganese, yields also bitter-almond essence, with carbonic and formic acids. The action of SALICINE. 479 emulsine in producing this curious change may he compared to that of diastase, to which emulsine has a certain resem- blance. If its solution is heated to 212 F., it is precipi- tated in an insoluble form, and has no longer any action on amygdaline. 829. Salicine. This principle exists in the bark of those species of willow which have a bitter taste. The decoction of the bark is mixed with the surbasic acetate of lead as long as a precipitate is formed ; to the filtered liquid dilute sul- phuric acid is added to precipitate the dissolved lead, care- fully avoiding an excess. The solution is then decolorized by animal charcoal, and, by evaporation and cooling, deposits pure salicine. It is so abundant in the bark of some willows as to separate in crystals when a concentrated decoction is cooled. Salicine forms small white crystals, readily soluble in alcohol and water ; it has a very bitter taste, and is em- ployed in medicine as a febrifuge and tonic. Its formula is ^52^36^38' When a solution of salicine is mixed with a small portion of the emulsine of sweet almonds, and heated for some hours to 105 F., it is completely decomposed into grape sugar, and a new compound which separates in fine rhombohedral crystals, and is named saligenine. It contains C 14 H 8 4 , and its formation from salicine is thus represented : C 53 H 36 2g -f- 2H 3 O a rr=C 24 H 24 24 -f2C 14 H 8 O s . Saligenine is readily soluble in water, alcohol, and ether ; by the action of dilute acids it loses H 2 3 , and is changed into a white substance insoluble in water, called saliretine. When a solution of salicine is heated with dilute chlorohydric or sulphuric acid, it is at first decomposed into grape sugar and saligenine, but the further action of the acid converts the latter into saliretine, which separates in white flakes. When a solution of salige- nine is mixed with chromic acid or oxyd of silver, these are reduced, and the oxygen combining with the saligenine forms salicylol and water; C 14 H 8 4 -(-Ag a 3 = C 14 H 6 4 -f H 2 3 -{-Ag 2 . Salicine, when distilled with a solution of bichromate of potash and dilute sulphuric acid, yields a large amount of salicylol, identical with the essence of spirea ulmaria. 830. Dilute nitric acid by heat decomposes salicine with oxydation into grape sugar and salicylol, which, by oxyda- tion, yields salicylic and nitrosalicylic acids; the final pro- duct, with a concentrated acid, is nitropicric acid. If sail- 480 ORGANIC CHEMISTRY. cine is dissolved in dilute cold nitric acid, a new compound is obtained, which is formed from salicine by the fixation of oxygen and the separation of water; C 52 H 36 2S +0 4 = C 52 H 34 O 30 -j-H 3 3 . This substance, which separates from the solution in crystals, is called lielicine, and, by the action of emulsine or dilute acids, is decomposed into grape sugar and salicylol, C a ,H 34 M +H,0,==0 M H M !! .+2C M H,0 4 . 831. Populine. This is a crystalline substance which ia obtained from the leaves and bark of the aspen-tree, Populus tremula. It resembles salicine, but is less soluble, and has a sweetish taste. With acids it yields benzoic acid, grape sugar arid saligenine, and when boiled with a solution of baryta, is completely decomposed into saliciue, and benzoic acid, which combines with the baryta. Populine is repre- sented by CgolI^O^, and by fixing H 2 3 is converted into salicine and benzoic acid, C 80 H 8a +2H 9 O a =C 5a H 88 O ?8 -j- 2C 14 H 6 4 . To indicate this relation, the name of bmzosalicine has been proposed for the principle. When dissolved in cold nitric acid, a new substance is obtained, which is termed benzohelicine, and by boiling with magnesia is decomposed into a benzoate and helicine. Neither of these compounds is affected by emulsine, but the action of acids and alkalies converts benzohelicine into grape sugar, and the mctameric bodies, benzoic acid and salicylol. 832. Phloridzine. This substance is contained in the root- bark of the apple, pear, cherry, and some other trees. When a concentrated decoction of the bark is cooled, it is deposited in a crystalline powder, which, when purified, forms delicate silky crystals, sparingly soluble in cold water, but readily in alcohol. It has a slightly bitter taste, and is supposed to possess febrifuge properties. The probable formula of phlo- ridzine is C^H^O^, but it crystallizes with 2H 2 0, r When boiled with dilute acids, it is decomposed like salicine into glucose and a crystalline insoluble substance called pldorc- tine C 34 H 13 8 . When exposed to the action of moist air and ammoniacal vapors, phloridzine is converted into a dark-blue mass, very soluble in water, from which acetic acid precipitates a red powder that dissolves in ammonia with a magnificent blue color. It is called phlorizeine, C 4S H 23 24 -fO s -h2NH 3 == C 48 H 33 N 3 30 -j-H 2 2 . The ammo- niacal solution of phlorizeine is rendered colorless by proto- salts of tin, sulphuretted hydrogen, and other deoxydizing agents, but on exposure to the air reassumes its color by COLORING MATTERS. 431 tne absorption of oxygen. This substance acts the part of a feeble monobasic acid, and gives splendid colored precipi- tates with metallic salts. If a salt of alumina or hydrated alumina is added to the ammoniacal solution, it combines with all the coloring matter and forms a blue precipitate, leaving the solution colorless. The action of phlorizeine with alumina is analogous to that of many dye-stuffs, which form with oxyd of tin or alumina insoluble colored compounds. This property of alumina has alrea/iy been alluded to ; when a tissue of cotton is first im- pregnated with a solution of the acetate of this base, then dried and immersed in a hot solution of a coloring matter like phlorizeine, this is precipitated, and the insoluble co- lored compound is fixed in the tissue. 833. There are several other principles obtained from plants or animals, which are characterized by this property of forming insoluble colored compounds with metallic oxyds, like oxyd of tin or alumina, and are hence employed in the art of dyeing as coloring matters. We shall briefly notice the more important of those which have already been in- vestigated. In some instances, the plants contain principles which generate the coloring matters by decompositions, such as we have seen in the case of phloridzine. Such is the origin of the colors of the lichens and of madder. 834. Several species of lichen, as the Roccella tinctoria of South America and the Cape of Good Hope, the Lecanora tartarea of Northern Europe, and some others, are used for the fabrication of a blue or purple dye-stuff, known by the different names of archil, litmus, cudbear, and tournsol. When these lichens are digested in the cold with milk of lime, the solution yields with acids a white precipitate, which may be crystallized from alcohol and from its solu- tion in boiling water. It is an acid, and forms crystal- lizable salts. The names of lecanorine, lecanoric acid, and orscllic acid have been applied to it by different investigators ; fits composition is represented by C 32 H 14 14 . When a solu- tion of lecanoric acid is heated to ebullition with an excess of lime or baryta, a new acid is formed by the fixation of the elements of water; C 33 H 14 14 -f H 2 3 =:2C 18 H S 8 , which is the formula of the new acid, to which the name of orsel- linic or lecanorinic has been given. It is crystalline and more soluble than the lecanoric acid ; when its alcoholic solu- tion is treated with chlorohydric acid, or even when simply 31 482 ORGANIC CHEMISTRY. boiled, the crystallizable ether of the acid, C 16 H 7 (C 4 H J0 8 is obtained, which has also been described under the names of pseud erytlirine and lecanoric etlicr. When this ether is boiled for some time with baryta water, it is decomposed with the evolution of alcohol, into carbonic acid and a new substance, orcine ; the same body is obtained by a similar process from the two acids, and by the dry dis- tillation of lecanorine. The lecanorinic acid breaks up into carbonic acid and orcine ; C 10 H 8 8 C 3 4 -|-C 14 H 8 4 , which is the formula of orcine. It forms large colorless prismatic crystals of a sweet taste, which are very soluble in water, and volatile without decomposition. When orcine is moist- ened with ammonia and exposed to the air, it absorbs oxygen, and is converted into a splendid purple coloring substance, which resembles the analogous product from phloridzine, and is named orccinc. Its probable formula is C 14 H 9 N0 6 : orsellic and orsellinic acids also yield orceine when their ammouiacal solutions are exposed to the air. 835. The lichen, called Ecernia prunastri, yields cvernic acid, which appears to be homologous with lecanoric acid, and to be C 34 H 1(i 14 : when boiled with an alkali it is de- composed into orcine, and a new acid homologous with lecanorinic, which is called cverm'nic acid C 1S H 10 S . The Gi/rophora 2^ustulata, known in Canada as tripe, de rochc, and many other species, contain analogous substances, all of which are available for the manufacture of archil. For this purpose the lichens are ground to a paste with water, a solution of ammonia and sometimes urine is added, and the whole frequently stirred, until, by the action of the air } the whole of the orsellic acid is converted into orceine, when the mixture assumes a magnificent purple color. Further exposure to the air turns it blue, and forms what is known in commerce as litmus. When the proper colors have been developed, lime and plaster of Paris are added to the mass, to give it bulk and consistency, and the whole is dried. Archil is used with solution of tin, especially in the dyeing of silks. Litmus colors the common test-paper for acids, which, decomposing the blue compound with lime or am- monia, set free the red orceine. Many salts which are capable of decomposing this feeble combination, restore the red color of litmus, and are thus said to possess an aciJ reaction. 836. The roots of madder, Rulia tinctoria, contain in theii COLORING MATTERS. 48? recent state, according to the latest investigations, a yellow crystalline substance, called xanthine or ruberythric acid r which, when boiled with acids or alkalies, is decomposed into glucose and an orange-red volatile crystalline substance, sparingly soluble in water, to which the name of alizarine is given. The formula C 30 H 10 10 has been assigned to it. Se- veral other compounds have been described as obtained from madder, but alizarine appears to be the true coloring prin- ciple. Madder is used in giving to cotton the much valued Turkey-red dye, which is produced by the conjoined action of a salt of tin, alumina, and alizarine : the combination of the coloring principle with alumina forms the red pigment called madder lake. 887. The red coloring matters of alkanet or anchusa, of sandal-wood, and of carthamus are insoluble in water, but soluble in alkalies, and appear to possess acid properties. The latter, carthamine, is the coloring principle of the pink saucers used in dyeing flowers and feathers. On the addi- tion of acetic acid to its alkaline solution, it is precipitated 111 an insoluble form, and then fixes itself on the tissue without the intermedium of a metallic oxyd. Hematoxy- line is obtained from logwood ; it is very soluble and forms yellow crystals : its solutions are rendered blue by alkalies and red by acids, and give a violet color with alum, and a black with salts of iron. The coloring principle of the cochineal insect is a purple body, very soluble in water and alcohol ; it forms beautiful lakes and scarlet dyes with salts of tin and alumina, and has been called carminic acid ; the formula C 28 H 14 1(5 is assigned to it. The pigment known as carmine is a lake obtained from cochineal with alumina. 838. The yellow coloring matters of plants are generally non-azotized substances. Among the most important are quer- citrine } the coloring principle of the Quercus tinctoria t and luteoline, from the wood, Reseda luteola, both of which are soluble and crystalline. The yellows of turmeric and gam- loge are of a resinous nature. Others employed in dyeing are marine, from the Morus tinctoria, and annatto. The leaves of plants contain a green resinous matter, which is soluble in alcohol and ether, and seems to possess acid properties ; it is called chlorophyll. The blue and red colors of flowers are very perishable, and have not been accu- rately examined. Those of the violet, iris, dahlia, and many 484 ORGANIC CHEMISTRY. other flowers, are turned red by acids and green by alkalies. A most delicate test-paper is prepared with an alcoholic in- fusion of the petals of purple dahlias. 839. Indiyo. This important coloring substance is ob- tained from a great number of plants, the principal of which are the Indigofera tinctoria and I. anil, with some species of the genera Isatis, Nerium y and Polygonum. The juices of these contain a peculiar colorless principle in solution, which, when exposed to the air, absorbs oxygen, and is con- verted into indigo. In the manufacture of this substance, the plants are steeped in water, and made to undergo a kind of fermentation ; the clear liquid is then exposed to the air, and frequently agitated to facilitate the absorption of oxy- gen j by this process it gradually becomes blue, and deposits the insoluble indigo. 840. Indigo is obtained in strongly cohering masses of a deep blue, which assume, when rubbed, a coppery metallic lustre. That of commerce is never pure, but is mixed with various foreign matters. Indigo is insoluble in water, alco- hol, oils, dilute alkalies, and chlorohydric acid : when cau- tiously heated it is volatilized as a purple vapor, which condenses in delicate crystals. The composition of indigo is expressed by C 16 H 5 N0 2 . In contact with water and de-oxydizing agents, indigo is converted into a colorless substance, which is soluble in alkaline liquids j this is generally effected by a mixture of lime and sulphate of iron : one part of indigo in fine powder, four parts of quicklime, and three of protosulphate of iron are digested with a large quantity of water. The protoxyd of iron formed by the action of the lime, reduces the indigo, which in this form is dissolved by the alkaline solution, forming a yellow liquid. If this is exposed to the air, oxy- gen is absorbed, and the indigo is separated in its original color and insolubility. It is by impregnating cloth with this solution, and precipitating the indigo in its texture by the action of the air, that the fine indigo-blue colors are produced. 841. Chlorohydric acid added to this yellow solution, precipitates the dissolved substance as a gray crystalline powder, which, when moist, rapidly becomes blue by absorb- ing oxygen, and is converted into indigo. It is called indigogen, and has the formula C 33 H 13 N 3 4 : exposed to the air it fixes 2 , and is converted into H a O a COLORING MATTERS. 485 and 2C 10 H 5 NO a . When indigo is boiled with an alcoholic solution of caustic soda and grape sugar, it is converted into indigogen, while formic acid is produced by the oxydation of the sugar. This alcoholic solution, exposed to the air, deposits pure indigo in crystals. 842. Concentrated sulphuric acid dissolves indigo by the aid of a gentle heat, and forms two acids, (652,) which are produced by the union of one and two equivalents of indigo with one of sulphuric acid, the elements of water being eliminated. They are named the sulphindigotic and sulplio- purpuric acids, and, like their salts, are intensely blue. The first named is the most important : when a solution of sulph- indigotic acid is boiled with woollen cloth, it is completely decolorized, the acid being taken up by the cloth ; in this way the color called Saxon blue is obtained. It resists completely the action of water, but is easily dissolved out by a solution of the carbonate of ammonia, which distinguishes it from the blue color obtained with solutions of indigogen. 843. If powdered indigo is heated with a solution of chromic acid or dilute nitric acid, it dissolves and forms a yellow solution ; this, on cooling, deposits beautiful orange- red prisms of a new substance, called isatine, which is formed from indigo by the combination of 3 , and is C 16 H 5 N0 4 : with potash it forms a salt of isatmic acid, which, when sepa- rated from the alkaline base, is decomposed by a gentle heat into isatine and water. Isatine forms several amids with ammonia. When it or indigo is distilled with caustic potash, a large quantity of aniline is obtained : the intermediate product is formed when indigo is dissolved in a solution of potash ; a yellow solution is obtained, which appears to contain reduced indigo, and a salt of isatinic acid, but on evaporating to dryness and fusing the mass, hydrogen is evolved, and carbonic and anthranilic acids are formed. An- thranilic acid contains C 14 H 7 N0 4 . It is soluble, crystalliza- ble, and volatile, but, when mixed with sand and rapidly distilled, is completely decomposed into carbonic acid gaa and aniline : C 14 H 7 N0 4 = C 2 4 +9 13 H 7 N. The action of chlorine upon indigo destroys its blue color, and transforms it into a species of isatine in which one and two equivalents of hydrogen are replaced by chlorine. These resemble normal isatine, and, when distilled with potash, yield species of aniline in which the same substitu- tion exists. Dilute nitric acid 3 inverts indigo by long boil- 486 ORGANIC CHEMISTRY. ing into ammonia, carbonic, and nitrosalicylic acids ; with stronger nitric acid it forms nitropicric acid. THE CYANIC COMPOUNDS. 844. The bodies of this series are obtained as products of a great number of reactions, and are very important in their relations to organic chemtstry. A cyanid was first recognised in a product of the action of potash upon dried blood, which was employed for producing, with a salt of iron, a fine blue pigment, known as Prussian or Berlin blue : hence the name, from the Greek, kuanos, blue. The ammoniacal salts of the acids C n H n 4 yield, as we have shown, nitryls by the loss of 2H 2 2 , which regenerate the ammoniacal salt by again assimilating the elements of water. The general formula of these bodies is C n H^_jN. The nitryl of formic acid ^ ^HN", and is formed when the vapor of formate of ammonia is passed through a red-hot tube j C,(H.NH 4 )0 4 ^C 2 H 5 N0 4 2H 2 2 == C 2 HN. This nitryl is the parent of the cyanic series, and is commonly known as prussic or hydrocyanic acid. The equivalent of hydrogen which it contains may be replaced by a metal, and the salts called cyanids thus obtained. The cyauid of potassium is formed when nitrogen gas is passed over a mixture of char- coal and carbonate of potash, heated to the temperature at which potassium is evolved. It is sometimes found as a pro- duct in furnaces from the action of atmospheric nitrogen upon the intensely heated mixture of carbon and alkali resulting from combustion : the potassium in this case unites directly with carbon and nitrogen. Cyanid of potassium is also obtained when animal substances, like leather, horn, or dried blood, or the charcoal obtained from them, which contains several per cent, of nitrogen, are heated with carbonate of potash ; its separation and purification will be described farther on. 845. Hydrocyanic acid, is easily obtained by distilling cyanid of potassium with dilute sulphuric acid, or by decom- posing cyanid of mercury at a gentle heat by sulphuretted hydrogen ; 20JHgN+H&=2C a HN+Hg r To procure the anhydrous acid, the best arrangement is shown in fig. 420. Cyauid of mercury in coarse powder is placed in the tube a b, and decomposed by a gentle cur- Tent of sulphydric acid, evolved from sulphid of iron and CYANIC COMPOUNDS. 487 diluted sulphuric acid. The sulphydric acid is dried by passing it over chlorid of calcium in the tube c d, and the product of the action is collected in the bent tube contained in the freezing mixture C. The operation may be conducted with- out danger in the open air. Pure hydrocyanic acid is a color- less limpid liquid, which boils at 80 F., and has a specific gravity of -697 ; a drop of it let fall upon paper, produces so much cold by its partial evaporation, as to freeze the remain- der. Hydrocyanic acid is combustible, and burns with a white flame; it is scarcely acid in its reaction with test-papers : its taste is pungent and aromatic, and its odor very powerful, both recall those of peach blossoms or bitter almonds ; the distilled waters of these substances and of the cherry-laurel, owe a part of their flavor to the presence of the acid, which is one of the products of the decomposition of amygdaline by emulsirie. When hydrocyanic acid is mixed with an. excess of strong chlorohydric acid, it is completely decom- posed into sal-ammoniac and formic acid ; boiled with hydrate of potash, it is decomposed in a similar manner, and yields ammonia and formate of potash : C 3 HN-j-H 2 3 -f (KH)O a = C a HK0 4 +NH 3 . 846. Hydrocyanic acid is a most fatal poison; a single drop of -the concentrated acid placed upon the tongue of a large dog produces immediate death, and the diluted acid even in very small doses causes giddiness and nausea. It appears to act as a sedative to the arterial system, and the suspension of animation following a large dose of it, does not always result in death, if proper remedies are employed. Ammonia and brandy are considered the most efficient anti- dotes to its effects. The vapor of the acid is also poisonous when inhaled; but workmen constantly exposed to it in a diluted state appear to become accustomed to it, so as to 488 ORGANIC CHEMISTRY. experience no deleterious effects. The dilute acid is em ployed in medicine ; when pure, it readily undergoes sponta- neous decomposition, yielding ammonia and a brown inso luble matter; but if it is diluted, and a trace of sulphuri* acid is present, the acid may be preserved for a long time; especially if secluded from the light. The cyanid of potassium C S KN is deliquescent and verj soluble in water and alcohol ; it forms cubic crystals, and has the taste, smell, and medicinal properties of hydrocyanic acid: it is strongly alkaline in its reactions. Cyanid of ammonium C 3 AmN = C a H 4 N 3 is obtained by saturating hy- drocyanic acid with ammonia, and is volatile and very poison- ous. Hydrocyanic acid dissolves red oxyd of mercury, and the solution yields colorless crystals of a cyanid C a HgN, which are soluble in water and alcohol, and are poisonous. Hydrocyanic acid and soluble cyanids throw down from solutions of silver a white curdy precipitate insoluble in acids, and resembling the chlorid; it is cyanid of silver, and is insoluble in ammonia. Salts of palladium decompose even the cyanid of mercury, and form an insoluble precipitate of cyanid of palladium. The other cyanids are obtained by double decomposition : they are generally insoluble in water, but soluble in cyanid of potassium, forming salts, which will presently be described. The action of chlorine upon hydrocyanic acid or cyanid of mercury, yields a compound in which chlorine replaces the hydrogen of the acid ; it is a gas of a very strong odor, and at a low temperature crystallizes in colorless needles : it dissolves in water without decomposition, for the solution does not precipitate salts of silver. Its formula is C a ClN : the bromic and iodic species are crystalline and very volatile. These compounds are commonly called chlorid and iodid of cyanogen ; the name of cyanogen being applied to the group C 2 N, which plays the same part in the saline combina- tions as Cl does in the chlorids, and is often represented by the symbol Cy, the hydrocyanic acid being CyH. 847. When the carefully dried cyanid of mercury is heated nearly to redness, it is decomposed into metallic mer- cury, and a colorless gas which is liquefied by a pressure of four atmospheres. It has a pungent odor, resembling that of prussic acid, and burns with a beautiful violet purple, yielding nitrogen and carbonic acid gas; it is soluble in water and alcohol, and must therefore be collected over mercury. This gas is called CYANIC COMPOUNDS. 489 cyanogen : the formula of its equivalent of four volumes ia C 4 N 2 . It is therefore not the hypothetical compound repre- sented by Cy, but sustains the same relation to it that the equivalent of four volumes of chlorine, C1 2 does to the atom Cl which enters into the composition of a cblorid. In its formation, two equivalents of cyanid of mercury react upon each other, CyHg+CyHg==Hg s +Cy a ==C 4 N fl . When heat- ed with potassium, combination ensues with combustion, and cyanid of potassium is formed. Cyanogen corresponds to the nitryl of oxalic acid ; oxalate of ammonia, C 4 H a 8 .2NH a =C 4 H 8 N a 8 4H 9 9 ==C 4 N r Its aqueous solution decomposes by keeping, and a variety of products are obtained, among which is oxalate of ammonia, regenerated by a combination of cyanogen with the elements of water. When one volume of cyanogen and two of sulphu- retted hydrogen gas are mixed in the presence of water or alcohol, direct combination ensues, and the compound C 4 N a .H 4 S 4 is obtained, which corresponds to sulphuretted oxamid : it forms orange-red crystals, soluble in alcohol, but sparingly soluble in water. When boiled with a dilute solution of potash, it evolves ammonia, and is completely converted into oxalate and hydrosulphate of potash, C 4 H 4 NA+4(KH)O a =2NH 8 +0 4 K 8 8 +2(KH)S 8 . By boiling with chlorohydric acid, the crystals are converted into oxalic acid, ammonia, and sulphuretted hydrogen. 848. Cyanates. The cyanids combine with oxygen to form a new class of salts, called cyanates. Fused cyanid of potassium absorbs oxygen from the air, and reduces oxyd of copper and other metals with ignition, at a tem- perature below redness. By adding oxyd of lead, in small quantities, so long as reduction takes place, the cyanid ia completely converted into cyanate, and the lead separates in a metallic state. The fused mass may be crystallized by solu- tion in boiling alcohol, and is deposited in pearly plates, very soluble in water; C 2 KN-f-Pb 3 3 = C fl KNO fl -j-Pb a . Strong acids liberate the cyanic acid, but decompose it immediately into carbonic acid and ammonia. Cyanic acid may be con- sidered as the acid nitryl of carbonic acid, derived from bi- carbonate of ammonia by the loss of 2H a 3 . C 3 H 3 6 .NH 3 = 2H 3 O s -{-C a HNO a . Its aqueous solution is readily decom- posed, especially in the presence of strong acids and alkalies, into a carbonate and ammonia, and the crystals of cyanate of potash in a moist atmosphere attract water, and, evolving 490 ORGANIC CHEMISTRY. ammonia, are converted into bicarbonate of potash. Cyanic acid is obtained in a pure form by the distillation of cyanuric acid : it is a colorless, volatile liquid, with an odor like acetic acid, and is very caustic, blistering the skin. It may be pre- served in a freezing mixture, but at the ordinary temperature changes very rapidly into a white, solid, insoluble, isomerio modification, called cyamdid, which by heat is reconverted into cyanic acid. 849. Cyanic acid combines directly with two equivalents of ammonia, and forms a soluble salt having the reactions of a cyanate of ammonia ; but if its solution is boiled, am- monia is evolved, and a substance having the composition of neutral cyanate of ammonia remains in solution j it is an alkaloid, and combines directly with acids. The same com- pound is obtained as a product of the spontaneous decompo- sition of an aqueous solution of cyanogen or cyanic acid ; the ammonia formed from one portion of cyanic acid, uniting with undecomposed acid, yields C 3 HN0 3 .NH 3 = C 3 H 4 N 3 3 . This alkaloid exists in human urine, and has hence been named urea. When fresh urine is evaporated by a gentle heat to a small bulk, and mixed with an excess of nitric acid, the nitrate, of urea C 2 H 4 N 3 2 .NH0 6 , which is spar- ingly soluble in the dilute acid, separates in large brilliant plates; these may be washed with iced water and decom- posed with carbonate of potash : the urea is then separated from the nitre by alcohol, in which the former alone is soluble. 850. A better process for its formation is by cyanate of potash : the salt known as the yellow prussiate of potash con- tains the elements of cyan id of potassium and cyanid of iron. It is dried at 212 F., and eight parts of it are mixed with three of dry carbonate of potash, and the mixture fused at a low red heat in an iron crucible : the iron separates in a spongy metallic form, and a white crystalline mass is ob- tained, which is cyanid of potassium, mixed with about one- fourth of cyanate, and is known in the arts as Liebig's cyanid of potassium. If to this mass, still in fusion, fifteen parts of red-lead are gradually added, the whole is converted into pure cyanate of potash. It is to be dissolved in cold water, mixed with a solution of eight parts of sulphate of ammonia, and evaporated to dryness. The cyanate of am- monia, formed by double decomposition, is thus converted into urea, which is separated from the accompanying sul- CYANIC COMPOUNDS. 491 phate by boiling the residue in alcohol. It crystallizes, on cooling, in transparent, colorless prisms, readily soluble in water and alcohol, and having a fresh, sharp taste, like nitre. It is a weak base, but forms compounds with oxalic and chlorohydric as well as with nitric acid ; concentrated sulphuric acid and hydrate of potash, by the aid of heat, convert it into carbonate and ammonia. When urea ia evaporated to dryness with a solution of nitrate of silver, the elements arrange themselves so as to form nitrate of ammonia and an insoluble crystalline cyanate of silver, which explodes by heat. A solution of urea heated in a sealed tube to 284 F. is converted into carbonate of am- monia C 2 H 4 N 3 4 +2H 3 3 := C 3 H 3 6 .2NH 3 . The urea in urine undergoes the same change by boiling or by putre- faction. Nitrous acid at once decomposes it into water, nitrogen, and carbonic acid gases, 2NH0 4 +C 2 H 4 N 2 O a 3H 9 O a +C 2 4 +N 4 . 851. Sulphocyanates. Fused cyanid of potassium reduces sulphurets in the same way as oxyds, and combines directly with sulphur to form a cyanate C 2 KNS 3 , in which sulphur replaces oxygen. If a mixture of dried prussiate of potash is fused with sulphur and carbonate of potash in a covered crucible, and the heat gradually raised to redness, until the mass is in quiet fusion, there is obtained a mixture of sulpho- cyanate of potash and sulphuret of iron. The salt is dis- solved out by boiling water, and crystallizes on cooling. The best proportions are 46 parts of the dried prussiate, 17 of dry carbonate of potash, and 32 of sulphur. Sulpho- cyanate of potash forms colorless prismatic crystals, having a taste like nitre ; they are deliquescent, and soluble both in water and alcohol. The sulphocyanic acid C 2 HNS 3 is obtained in solution when the lead salt is decomposed by dilute sulphuric acid, and is a colorless liquid acid, with an odor like vinegar. These compounds are all more stable than the oxycyanates. Sulphocyanate of ammonia C 2 (NH 4 )NS 3 is obtained by a peculiar reaction ; a solution of cyanid of ammonium separates the excess of sulphur from persulphuret of ammonium, and if a mixture of the two salts in solution is digested with finely divided sulphur, the sulphur is dis- solved by the sulphuret and transferred to the cyanid, which is wholly converted into sulphocyanate : by boiling the solu- tion, the volatile sulphuret of ammonium may then be ex- pelled, and the sulphocyanate obtained in crystals. Tho 492 ORGANIC CHEMISTRY. soluble sulphocyanates are characterized by forming a deep blood-red liquid with persalts of iron, which is due to the formation of a persulphocyanate of that metal ; this reaction affords a very delicate test both for salts of iron and sulpho- cyanates. 852. When a solution of sulphocyanate of potash is heated with nitric acid, or when chlorine is passed through its solu- tion, a yellow substance separates, which contains the ele- ments of cyanogen, sulphur, oxygen, and hydrogen, and has been called cyanoxsulphid ; its nature is not well understood. Exposed to heat, it yields sulphur and sulphuret of carbon among other products, and leaves a yellow residue named mellon, which is probably C 12 H 3 N D , and by a strong red heat is decomposed into cyanogen, nitrogen, and hydrogen gases. Mellon decomposes fused sulphocyanate of potassa, and yields a salt called mdhnid of potassium^ 2 HK 3 N g . When this salt or mellon is boiled with a solution of hydrate of potash, ammonia is evolved and a salt obtained, to which the name of cyamellurate of potash is given; it isC 12 HK 3 N 8 O a : the corresponding acid is sparingly soluble in water. Polycyanids. 853. The cyanids exhibit a great tendency to polymerism, and form compounds in which two, three, and six molecules of simple cyanid are condensed into one. The mellon series is an instance of such a polymerism. When cyanogen is ob- tained by the decomposition of cyanid of mercury, a portion of a black carbon-like body is always formed, which is repre- sented by C 13 N 6 , and is named paracyanogen. It contains the elements of three equivalents of cyanogen, and is entirely converted into it when heated in a current of carbonic acid gas; C 12 Ng 3C 4 N 3 . Heated in hydrogen gas, it yields hydrocyanic acid, ammonia, and carbon; C 13 N 6 -|- H 12 = 3C 3 HN-|-3NH 3 -f-C 6 . The brown substance formed by the spontaneous decomposition of an aqueous solution of cyano- gen or of hydrocyanic acid, is similar in its nature. 854. When boracic acid or a borate is heated with a cya- nid, a compound of boron and nitrogen is obtained : it is, how- ever, best prepared by igniting calcined borax with twice its weight of sal-ammoniac ; the mass washed with water and dilute acids, leaves a white insoluble powder, which burns at a high temperature with a green flame, and when heated CYANIC COMPOUNDS. 493 with hydrate of potash or strong sulphuric acid, is decom- posed into a borate and ammonia : the same decomposition is produced when it is heated in aqueous vapor. It reduces oxyds of lead, copper, or mercury, at a temperature below redness, with the evolution of nitric oxyd gas. The pro- portions of its elements are represented by B 4 N 2 , but, from its fixed nature, it is probable that it has a higher equivalent, corresponding perhaps to paracyanogen. 855. The action of chlorine upon an aqueous solution of hydrocyanic acid, the latter being in excess, yields a volatile liquid, which is C HC1 2 N 3 , and corresponds to a triple mole- cule of cyanid in which two atoms of hydrogen are replaced. By the further action of chlorine the third atom is removed, and the perchloric tricyanid C 6 C1 3 N 3 is obtained : this is also formed when dry chlorine acts upon paracyanogen, or upon the cyanid of mercury, with the aid of sunlight, and, unlike the monocyanid, is a crystalline solid, which is vola- tile at above 300 F. When the bichloric tricyanid above mentioned is digested with oxyd of mercury, cyanid of mer- cury and water are formed, with a pungent volatile liquid, boiling at 61 F., which is C 4 C1 2 N 3 , or & perchloric dicyanid, containing the elements of two equivalents of the mono- cyanid. It is not decomposed by water, but with hydrate of potash yields chlorid of potassium, and the products of the decomposition of cyanic acid, ammonia, and a carbonate. 856. The solid tricyanid is decomposed by water into chlo- rohydric acid, and cyanuric acid, which is polymeric of the cyanic, and is C 6 H 3 N 3 6 . The same acid is formed when a solution of cyanate of potash is mixed with a small quantity of acetic or nitric acid insufficient for its complete decompo- sition ; cyanurate of potash is deposited. When the com- pound of chlorohydric acid and urea is heated, sal-ammoniac sublimes and cyanuric acid remains; 3C 4 H 4 N 3 O a .HCl 3HCl.NH 3 -f C 6 H 3 N 3 6 ; and urea, when heated alone until it ceases to evolve ammonia, is converted into a grayish mass, which is an amid of cyanuric acid. This is dissolved in concentrated sulphuric acid, the solution decolorized by a little nitric acid, and mixed with its bulk of water; the cyanuric acid separates, on cooling, in prismatic crystals, feebly acid to the taste. It may be crystallized unchanged from a boiling solution in nitric or chlorohydric acid, but by long continued ebullition with them, is slowly decomposed like cyanic acid ; into carbonic acid and ammonia. When 494 ORGANIC CHEMISTRY. exposed to a strong heat it is decomposed into cyanic acid, which is thus obtained pure, C H 3 N 3 (1 ==3C a HNO a . 857. Cyanuric acid is tribasic, and forms both neutral and acid salts. The cyanuric ether of alcohol, obtained by distilling a sulphovinate with alkaline cyanurate of potash, forms beautiful crystals sparingly soluble in water, which are fusible, volatile, and have the formula C (C 4 H a ) 3 N a 6 . When sulphocyanate of ammonia is decomposed by heat, a residue is obtained consisting of mellon and an amid of cyanuric acid, to which the name of melamine is given. It is dissolved from the crude product by a dilute boiling solu- tion of hydrate of potash, and separates, on cooling, in color- less rhombic octahedrons. It is C 6 H fl N 6 , and differs by 3H a O a from the neutral cyanurate of ammonia. Melamine is a strong organic base, and forms crystalline salts. When boiled with strong acids or alkalies, it is slowly decomposed into ammonia and a cyanurate. The intermediate steps in the decomposition are the amids, corresponding to cyanu- rates with one and two equivalents of ammonia, and are called ammdid and ammeline. The latter is C 6 H 5 N 5 O a and is a weak base. By heat melamine is decomposed into mel- lon and ammonia; 2C 8 H 6 N B =C la H 8 N 9 -f3NH 8 . 858. Fulminates. The salts which from their explosive character have received this name, correspond to the dicya- nid C 4 C1 2 N 2 already described, and contain the elements of two atoms of cyanate. When nitrous vapour is passed into a solution of nitrate of silver in alcohol, the fulmi- nate of silver C 4 Ag a N a 4 is deposited. The same salt is formed when a solution of silver in a large excess of nitric acid, is added to alcohol ; the action is complex; besiies the fulminate, aldehyd, acetic and formic ethers are formed by the oxydizing power of the acid, and by a polyinerism of the alcoholic molecule, an acid which is homologous with lactic acid and is C 8 H 8 13 . The action of nitric acid upon alcohol yields aldehyd and nitrous ether, and the deoxyda- tion of another portion of the acid giving rise to nitrous acid, this may react with the ether and form fulminic acid and water, NH0 4 +C 4 H 5 N0 4 =C JI 2 N 3 4 +2H 2 O a . The sil- ver salt is sparingly soluble in water, and forms delicate white crystals, which explode with terrible violence by fric- tion with any hard body, even under water. The products of the decomposition are carbonic acid and nitrogen gases, and a mixture of cyanid with metallic silver. The fulminate CYANIC COMPOUNDS. 495 of mercury is less explosive than the silver salt, and is the material used in the preparation of percussion caps. To pre- pare it, one ounce of mercury is dissolved by a gentle heat in eight and a-half ounces by measure of nitric acid, of spe- cific gravity 1*4, and the solution is poured into ten mea- sured ounces of alcohol, specific gravity '830 ; action soon ensues, with the evolution of copious white fumes, and the fulminate is deposited in white crystalline grains, which are washed with cold water, and dried at a very gentle heat. The salt is somewhat soluble in boiling water, and crys- tallizes on cooling; it explodes violently by a heat of 390 F., by friction, 'percussion, and by contact with strong acids. Its formula is C 4 Hg 3 N 3 4 . When fulminate of silver is dissolved in nitric acid, one-half of the silver is removed and an acid salt separates, which is C 4 HAgN 3 4 ; chlorid of potassium precipitates only one-half the silver and yields C 4 KAgN e H 4 . Metallic copper separates the whole, and forms a copper salt. The double fulminate of copper and ammonia is decomposed by sulphuretted hydrogen into urea, sulphocyanic acid, water, and sulphuret of copper. It may be said to separate into cyanate of ammonia, which changes to urea, and cyanate of copper, which yields sulphuret of copper and cyanic acid ; this, with an equivalent of H 3 S 2 , is converted into water and sulphocyanic acid. 859. The relations of the cyanids to the bodies of the series of alcohols are full of interest. When a sulphoviimte is distilled with cyanid of potassium, hydrocyanic ether is obtained as a liquid sparingly soluble in water and boiling at 176 F. It is C 3 (C 4 H 5 )N or C 6 H 5 N, and is homologous with hydrocyanic acid. When heated with hydrate of pot- ash, it is not decomposed like other ethers, but evolves ammonia, and produces a salt of propionic acid C 6 H 6 4 homologous with formic acid. The hydrocyanic ether of wood-spirit C 4 H 3 N yields in the same way acetic acid, C 4 H 3 N+2H 2 3 r=NH 3 -f C 4 H 4 4 . These ethers are identical with the nitryls obtained by distilling the ammoniacal salts of these acids with anhydrous phosphoric acid ; the amy- lic ether is the nitryl of caproic acid, C 13 H 13 4 . The vinic cyanic ether, with potassium, evolves a gas which is C 4 H 6 , and the residue yields to water cyanid of potassium. A ^ub- etance remains which may be crystallized from boiling water, and is an organic base to which the name of cyane- thine has been given. Its formula is C 18 H 15 N 3 corresp.ond- 496 ORGANIC CHEMISTRY. ing to three atoms of hydrocyanic ether, and it pertains to the type of the trieyanids. 860. When the crystalline compound of aldehyd and ammonia is dissolved in water with a mixture of hydrocyanic and chlorohydric acids, and evaporated to dryness, sal-am- moniac is obtained, and the chlorohydrate of a new base, which is formed from the elements of aldehyd, hydrocya- nic acid and water, C 4 H 4 3 -f C 3 HN+H S 2 = C H 7 N0 4 . The name of alanine is given to this new substance, which is crystalline, soluble in water and dilute alcohol, and has a sweet taste ; an atom of hydrogen in it may be replaced by a metal, so that, like ammonia, it combines both with acids and metallic salts. By the action of nitrous acid, alanine is converted into lactic acid, nitrogen and water, 2C 6 H 7 N0 4 -{- 2NH0 4 - C 12 H 13 12 -f 2H.O.+ N 4 . 861. A cyanic ether is obtained by distilling a sulpho- vinate with cyanateof potash; it is C 2 (Et)NO a = C 6 H 5 N0 3 , and is a very volatile liquid, which combines with ammonia and forms a body crystallizing in beautiful prisms, and solu- ble in water and alcohol. It is C 6 H S N 3 3 , and is vinic urea, differing from ordinary urea by 2C 3 H 3 ; when decom- posed by hydrate of potash, it yields carbonic acid, and one equivalent of ammonia, with one of ethamine, or vinic ammonia, NEI 2 (C 4 H 5 ). In the same way vinic cyanic ether, which is homologous with cyanic acid, is decomposed, car- bonic acid and ethamine being the only products. The cyanic ethers of the other alcohols yield similar results. 862. When the vapor of cyanic acid from the distilla- tion of cyanuric acid is passed into alcohol, crystals are deposited which contain the elements of one equivalent of alcohol and two of the acid, C 4 H 6 3 +2C 2 HN0 3 :=C 8 H s N a 6 . This compound is decomposed by distillation into alcohol and cyanuric acid, but with a solution of baryta, alcohol is set free and the baryta salt of a new acid is formed, which is called allophanic arid, and contains the elements of two equiva- lents of a cyanate with one of water, being C 4 H 4 N a ; it differs from fulminicacid by H a 2 , and is monobasic. When acids are added to its salts, or when a solution of its baryta gait is boiled, it is decomposed into a carbonate and urea; allophanic acid contains the elements of urea and carbonic eld, C 4 H 4 N 2 6 -C 2 H 4 N 3 3 +C S 4 - The vapors of cyanic acid are absorbed by aldehyd CYANIC COMPOUNDS. 497 and a sparingly soluble crystalline compound is formed, to which the name of irigenic acid is given. The formula C 9 H 7 N S 4 , representing a monobasic acid, is assigned to it, but its equivalent is probably more elevated. 863. When cyanogen gas is passed into an alcoholic solution of aniline, sparingly soluble crystals of a new base separate. It has received the name of cy aniline, and is formed by the combination of one equivalent of cyanogen and two of aniline, C 4 N a +2C 18 H,N = C 28 H 14 N 4 . Its salt* readily separate into aniline, and products of the decompo- sition of cyanogen. Aniline absorbs the gaseous chlorid of cyanogen, and the chlorohydrate of a new base is formed, C/31NJ-20 u H 7 N = ClH.CJH u N a . The new alkaloid is called melaniline; it is crystalline, and its salts are more stable than those of cyaniline. It combines directly with cyanogen to form a base analogous to cyaniline, to which the name of cyamelaniline is given ; it is C 30 H 13 N S . These bodies are derived from a compound of two equivalents of aniline, C M H 14 N a ; melaniline is formed from it by the sub- stitution of C 3 N for H : and the fixing of C 4 N 2 = (C 2 N) a or (Jy 3 , is analogous to the direct combination of Cl a and C1H. A reaction similar to the last, in which C 2 HN or CyH com- bines directly, is found in the vegetal alkaloid harmaline C 28 I! 14 N 3 2 ; when this base is mixed with hydrocyanic acid or its salts with a cyanid, it combines with C 2 HN to form a new crystalline base, cyanharmaline, C 23 C 14 H 3 3 -}-C a HN = C 30 H 15 N 3 3 . This combination is decomposed by heat into prussic acid and harmaline, but forms with acids, salts which are permanent. Many other alkaloids, besides ani- line, form compounds with cyanogen and cyanids. 864. By the action of chlorine gas in sunlight upon a hot saturated solution of cyanid of mercury, chlorohydric acid, chlorid of mercury, and sal-ammoniac are fonned, together with carbonic acid, nitrogen, and the chloric cyanid, which escape in the gaseous form, while a yellow oily liquid separates, which is heavier than water, and has a pungent odor and caustic taste. The formula C 13 N 4 G1 14 is assigned to it; it is soluble in alcohol and ether, but in- soluble in water, which however decomposes it into nitro- gen, and carbonic and chlorohydric acids. By keeping, it is spontaneously decomposed, with the separation of per- chloric acetene C 4 C1 8 . This compound is probably derived 498 ORGANIC CHEMISTRY. from a combination of six molecules of cyanid, of which the normal species will be C 12 H 6 N 6 , a group which is the type of a large and important class of polybasic salts, ranch more stable than the ordinary cyanids.* The six atoms of hydrogen are all replaceable by a metal, but two or three atoms of the metallic elements are combined in such a way as not to be recognized by the ordinary reagents, and like the three atoms of hydrogen or chlorine in the acetic acids, form a constant part of the acid. The second atom of sil- ver in the fulminates, and the condition of the metals in some of the tartrates, present analogous instances. 865. Ferrocyanids. These salts may be represented by C 13 (Fe 2 M 4 )N 8 ; M being hydrogen or any metal. The two atoms of Fe are so combined as not to be precipitated by alkalies or sulphurets. The ferrocyanid of potassium is formed with the separation of hydrate of potash, when metallic iron or its oxyd is digested with a solution of cyanid of potassium, hydrogen being evolved in the former case: Fe 9 8 -f 2C fl KN = 20,FeN-fK 9 O fl , which, with H 2 3 , gives 2(tiK)O a . The cyanid of iron unites with another portion of cyanid of potassium, to form the new salt C 13 (Fe a K 4 )N This is the ordinary source of all the cyanic compounds. It is prepared on a large scale from the impure cyanid, formed by the calcination of animal matters with carbonate of potash, or by passing heated atmospheric nitrogen over fragments of intensely ignited charcoal, impregnated with the carbonate. 'In both processes cyanid of potassium is obtained, mixed with excess of the carbonate of potash. It is dissolved in water and digested with oxyd of iron, or a solution of protosulphate of iron is added, until the precipitate at first formed is no longer dissolved by the cyanid. The * Perchloric acetene is decomposed at a red heat into Cla, and C 4 C1 4 , or perchloric etherene. When this substance is exposed to the com- bined action of chlorine and water, with exposure to the sun's rays, the compound C^lg is regenerated ; at the same time, a portion of it forma with the elements of water, chlorohydric and chloracetic acids; C Cl s -f- 2H,O a ^=3HCl^-C 4 Cl 3 H04. We have seen that by the aid of an amal- gam of potassium, the chlorine of a chloracetate may be removed, and the normal acetic acid formed. It has lately been found that when the vapor of acetic acid is decomposed at a red heat, there are obtained, besides carbonic acid gas and acetene, small portions of benzene, phenol, and napthaline. These carbon compounds, high in the organic series, may now by these reactions, be formed, from charcoal, through the cyanid* FERROCYANIDS. 499 filtered liquid is then evaporated, when the ferrocyawd of potassium separates in large translucent lemon-yellow tabular crystals, containing 3H 2 2 , which is expelled by a gentle heat. It is very soluble in water, but insoluble in alcohol, and is not poisonous. This salt is known in the arts as tho yellow prussiate of potash, and is employed in dyeing, in the manufacture of prussian blue, and the fabrication of the various cyanids. The preparation of Liebig's cyanid of potassium, of the cyanates and sulphocyanates, by means of this salt, has been already described. When it is carefully dried and fused in a close iron vessel, the cyanid of iron is decomposed into nitrogen and a carburet, and pure cyanid of potassium is obtained, which may be crystallized by dis- solving it in boiling alcohol of specific gravity -900. When two parts of the dried ferrocyanid are heated with one of chlorid of mercury, pure cyanogen gas is evolved, and by boiling two parts of the crystallized salt with three of per- sulphate of mercury and fifteen of water for a few minutes, cyanid of mercury crystallizes on cooling. Distilled with dilute sulphuric acid, the ferrocyanid yields hydrocyanic acid, which is best prepared by this process.* Heated with an excess of concentrated sulphuric acid, the ferrocyanid under- goes a peculiar decomposition; the hydrocyanic acid evolved in the presence of a strong acid takes up the elements of water and yields ammonia and formic acid; but this last, by concentrated sulphuric acid, is decomposed into carbonic * A dilute acid is readily prepared by distilling a mixture of two parts of ferrocyanid of potassium, one of sulphuric acid, and two of water, and collecting the product in a receiver containing two parts of water, until the liquid amounts to four parts. For this purpose the apparatus shown in figure 415 is well calculated. This acid, from the presence of a trace of sulphuric acid, is not liable to decomposition; it contains fifteen or twenty per cent, of pure acid. To determine the amount of real acid present, a weighed quantity of the distilled acid is added to a solution of nitrate of silver, which should be in excess ; the precipitate of syanid of silver is collected on a filter, dried at 212, and weighed. Its weight divided by 5 gives the amount of real acid in the specimen. Let us euppose that 70 grains of the acid yield 80 of cyanid of silver, equal to 16 of real acid, 70 : 16 : : 1UO : x, which equals 22-85 ; it then contains 22-85 per cent, of real acid. But if it is required to reduce it to any standard, as one of three per cent., which is the ordinary medicinal acid, then as this will consist of 97 of water and 3 of real acid, 3 : 97 : : 16 : x, and x = 5j.7'3 grains of water, which must be added to 16 of anhydrous acid to reduce it to the standard. But as 70 grains of this acid contain already 54 of water, it is obvious that we have to add 517'3 54 = 463-3 grains of water to 70 grains of acid to reduce it to the required standard. 500 ORGANIC CHEMISTRY. oxyd gas and water, and the result is a copious evolution of this gas in a pure state ; the residue contains bisulphate of potash, and a double sulphate of ammonia and iron. 866. When a saturated solution of the ferrocyanid is mixed with strong chlorohydric acid and agitated with ether, a white crystalline matter separates, being insoluble in the ethereal mixture; it is washed with ether and dried in vacua, and is ferrocyanic acid, C 12 (Fe ? H 4 )N 6 . Its taste is acid and astringent : it is very soluble in water, and is decomposed by exposure to the air, into hydrocyanic acid and a cyanid of iron. When the potash salt is mixed with solutions of salts of lime, baryta, and zinc, insoluble or sparingly soluble salts are obtained, which are C I2 (Fe a KCa 3 )N 6 , &c. The copper salt is analogous in composition; it is insoluble in water, and has an intense red-brown color, which makes ferrocyanid of potassium a delicate test for that metal. With a protosalt of iron a similar compound is obtained, which is greenish-white, and rapidly becomes blue by exposure to the air. With a persalt of iron a characteristic deep blue precipitate is obtained, which is the pigment prussian blue. It is C 13 (Fe 2 fe 4 )N 6 , the replaceable iron being in the form offerricum. The iron salt should be added in excess, or the precipitate will contain a portion of potassium, like the pre- ceding compounds. Prussian blue forms a light porous mass of a deep violet-blue color, with a copper-red reflection : it is insoluble in water and dilute acids, but when recently precipitated is very soluble in solutions of oxalic acid and tart-rate of ammonia, forming deep blue solutions which are used as writing-inks. Boiled with a solution of hydrate of potash, peroxyd of iron separates, and ferrocyauid of potas- sium is formed. 867. Ferricyanids. When chlorine is passed into a dilute solution of ferrocyanid of potassium, the gas is absorbed, and the liquid loses the power of precipitating persalts of iron. On evaporating the yellow solution, a new salt is obtained in beautiful deep red transparent prisms, which is known as red prussiate of potash or f&rrwyanid of potassium. This Bait contains C la (Fe a K 3 )N fl , one atom of K having been separated to form chlorid of potassium with the chlorine; but the iron being in the state of ferricum, the salt becomes C 19 (fe 3 K 3 )N 6 , and the acid is C 12 (fe 3 H 3 )N 6 , and is tribasic. It is obtained by decomposing the lead salt with- dilute sul- phuric acid. The ferricyanid of potassium does not affect NITROPRUSSIDS. 501 the persalts of iron, but gives with protosalts, a blue pre- cipitate which is C 13 (fe 3 Fe 3 )N 6 ; it has a finer hue than Lhe ferrocyanid, and is known as Turnbull's blue. When a solution of the red prussiate is mixed with one of potash, in the presence of organic matters, ferroeyanid is formed, and the organic substance is oxydized by the oxygen set free. This process is employed in calico-printing for discharging colors. 2C 12 (fe 3 K 3 )N 6 = 2C 12 (Fe 3 K 3 )N 6 + 2(KH)O a = 2C 13 (Fe 3 K 4 )N 6 +H 3 4 = H 3 3 +0 a . Peroxyd of hydrogen appears thus to be the oxydizing agent in this reaction, which is very energetic; oxalates are converted by it into carbonates, and a solution of chromic oxyd in potash, into chrornate of potash. The same view may be extended to oxydation by chlorine: 2Cl+2H a O a = 2HCl+ H 3 4 . 868. Nitroprmsids. "When a current of nitric oxyd gas (N0 3 , or rather N 3 4 ,) is passed through a heated solution of ferricyanic acid, a reaction ensues which may be thus reprc- sented : 2C 18 (fe 8 H 8 )N 8 =20 13 (Fe,H 8 )N 8 +N 3 4 = 2C 9 HN -f-2C 10 Fe 3 H 3 N 6 O s ; the products being hydrocyanic acid, and a new substance to which the name of nitroprmsic acid has been given. When either the red or yellow prussiate of potash is heated with nitric acid so much diluted that no nitric oxyd is evolved, nitroprussic acid may be obtained. For this purpose 844 grains of crystallized yellow prussiate are pulverized, and mixed in a capacious vessel with six fluid-ounces of dilute nitric acid, of specific gravity 1-12; the heat of a water-bath is applied until action commences, and is then removed; the salt dissolves, and the liquid as- sumes a dark coffee color, with a copious evolution of gas, consisting of hydrocyanic acid and cyanogen, with some nitrogen, resulting from a secondary decomposition. When the solution is complete, the heat of a water-bath is again applied until the liquid gives a dark green or slate-colored precipitate with a protosalt of iron. On cooling, nitrate of potash crystallizes, and the liquid is neutralized with car- bonate of soda, and boiled; a copious precipitate is formed, and the filtered liquid is of a clear deep-red color, and con- tains only nitrates of potash and soda, with the nitroprussid of sodium. The nitrates are in part separated by concen- tration and cooling, and on evaporating the remaining liquid at a gentle heat, the new salt separates in ruby-red prisms, resembling in appearance the red prussiate : its formula is C, (Fe 2 Na 2 )N 6 2 ; the crystals contain, besides, 2H 2 2 , 502 ORGANIC CHEMISTRY. The potash salt is obtained by substituting carbonate OK potash for the soda, but is more soluble. The nitroprussids do not precipitate the persalts of iron, but yield with proto- salts a salmon-colored precipitate which is C 10 (Fe 2 Fe a )N 6 O s , and with copper salts a pale green insoluble nitroprussid of copper. This is decomposed by a solution of baryta, and gives a soluble baryta salt, which may be decomposed by sulphuric acid, and the nitroprussic acid obtained in dark *ed crystals, very soluble in water.* If a solution of a nitroprussid is mixed with one of an alkaline sulphuret, a magnificent purple liquid is obtained; this reaction is so delicate as to detect the smallest trace of a soluble sulphuret. The color soon fades by standing, and the solution then contains ferrocyanid, sulphocyanid, and a nitrite, while nitrogen, hydrocyanic acid, oxyd of iron, and sulphur are set free. Nitroprussid of sodium forms a crys- talline compound with hydrate of soda which is decomposed by boiling; nitrogen gas and peroxyd of iron, with ferro- cyanid, nitrite and oxalate are the products. 869. The action of cyanid of potassium upon salts of chromium, manganese, and cobalt, gives rise to salts which correspond to the ferricyanids, the metals being in the same equivalent as in the sesquisalts. The compounds corre- sponding to ferrocyanid have not been obtained : when pro- tocyanid of cobalt is dissolved in cyanid of potassium, Bcsquicyauid of cobalt, cyanid ofcdbalticum C a coN is formed, and potassium is liberated, which, decomposing the water, forms hydrate of potash, evolving hydrogen gas, 4C 3 CoN + 2C a KN=CC 3 coN-j-K 2 . The cobaltic cyanid with another * The formula here given for the nitroprussids is that proposed by M. Gerhardt, and corresponds best with the original analyses of the dis- coverer, Dr. Play fair, and even with the subsequent results of Mr. Kyd, whose proposed formula for the soda salt, Cy Fe a Na.,NO, is not admissible unless it is doubled. There are many reasons for believing that carbon replaces sulphur and oxygen, somewhat as nitrogen does hydrogen, and then 4 N a and 4X3 become equivalent to each other, while peroxyd of hydrogen H,,0 4 and nitrous acid NH0 4 correspond to cyanic acid, NII(C 2 2 ), and hydrocyanic acid C 2 IIN, to C 2 Hy and to water O a H 3 . The nitroprussids are then ferrocyanida which have lost IIj, becoming bibasic, and under the influence of 4 N 2 have exchanged Cy=C 2 N for its equivalent 2 N. The formula will then be written (Cy 5 .O i N)Fe a Na a = (^loOzXFe^NaJXg. A similar view may be extended to a great number of compounds ; nitrobenzene, for example, is benzoilol in which N replaces H and O a replaces C 2 ; thus, (C 13 O a )(H i N)O a , corresponding to C u H 6 O a . ACIDS OF THE URINE AND BILE. 503 portion of cyanid of potassium forms the cobalticyanid of potassium C 13 (co 3 K 3 )N 6 . Platinum has a great tendency to form a platinocyanid, and when the metal in its spongy form is heated to redness with ferrocyanid of potassium, the mass yields to water the new salt, which crystallizes in long transparent rhomboidal prisms, yellow by reflected and blue by transmitted light : it is C 13 (Pt 3 K 3 )N". By decomposing the mercurial salt with sulphuretted hydrogen, platinocyanic acid C ia (Pt 3 H 3 )N 8 is obtained ; it is very soluble, and crystallizes in golden-yel- low prisms, with a copper-red reflection. The baryta salt forms short lemon-yellow prisms, which are greenish by reflected light. 870. The other complex cyanids have been but little studied : one containing silver is obtained when the oxyd, chlorid, or cyanid of silver is added to a solution of cyanid of potassium. The arcjentocyanid of potassium is very soluble, and forms colorless tabular crystals; its composition is represented by C 13 (Ag 3 K 3 )N 6 . It is much less stable than the previous compounds ; the silver is not precipitated by chlorids, but strong acids throw down insoluble cyanid of silver, and set free hydrocyanic acid. With a salt of lead, "a precipitate is obtained in which lead replaces the potassium. The silver salt is used in electro-plating, and is generally prepared by dissolving oxyd or chlorid of silver in a solution of cyanid of potassium, hydrate of potash or chlorid of potassium being formed at the same time. Oxyd of silver decomposes even the ferrocyanid to form the new double salt. In the process of electro-silvering, the silver being liberated at one pole, the potassium and cyanic elements are set free at the other, and this pole being terminated by a plate of silver, the metal is dissolved as fast as it is deposited at the other pole, thus preserving the strength of the solution. Oxyd'of gold is readily soluble in cyanid of potassium, and yields a double salt which is used in a similar manner to the last for the process of electro-gilding. A solution of cyauid of potassium may be used to remove from the.skin or from linen, the stains produced by salts of silver, gold or mercury. ACIDS OF THE URINE AND BILE. 871. These animal secretions contain several peculiar azotized acids, which are very interesting from their meta- 504 ORGANIC CHEMISTRY. morphoses : those of urine are named the uric and Jiippnnt. acids. The hippuric acid is found principally in the urine of herbi- Torous animals; that of stall-fed horses and cows containa a considerable quantity. To obtain it, the fresh urine may be mixed with chlorohydric acid in the proportion of four ounces of the acid to a gallon, and allowed to stand for some hours in a cool place. A crystalline matter which is deposited is impure hippuric acid : it is separated, redis- solved by boiling in water with excess of milk of lime, and a little animal charcoal to decolorize it : the filtered hot solution of hippurate of lime is then mixed with a slight excess of chlorohydric acid, and hippuric acid separates on cooling in beautiful white prisms. The fresh urine may also be heated to ebullition with milk of lime, and after separating the precipitate thus formed, boiled down to one-tenth, and then precipitated by chlorohydric acid : in this way a larger portion is obtained, (from forty to fifty grains from a pound.) Hippuric acid is very soluble in boiling water, but requires about 400 parts of cold water for its solution. It is monobasic and is represented by C 1S H NO B ; when boiled with peroxyd of lead it is converted by oxydation into benzamid, carbonic acid and water: C 18 H ( ,N0 +0 6 = C 14 H ? N0 3 + 2C 3 4 + II 3 2 - % the action of nitrous acid, hippuric acid is decomposed like aspartic acid, and yields water, nitrogen, and a new acid called ben- zoylycollic acid: it is C 38 H 1B 16 , two equivalents of hippu- ric acid being concerned in the reaction. Benzoglycollic acid is bibasic ; it is sparingly soluble in cold water, but dissolves readily in boiling water, alcohol, and ether. It fuses below 212 F., and at a higher temperature is decom- posed, benzoic acid subliming. When boiled with dilute sulphuric acid, it is decomposed into benzoic acid, and a new bibasic acid called the glycollic, C 8 II S 13 . This is homo- logous with lactic acid, to which it bears a vciy close re- semblance, and appears to be identical with the acid formed in the preparation of the fulminates. Beuzo^lycollic acid yields two equivalents of benzoic, and one of glycollic acid : C 36 H 18 18 +^H 8 S = 2C H H 6 4 +C s H s O la . 872. When hippuric acid is boiled with a strong acid, it is decomposed into benzoic acid and a sweet crystalline substance, which was first obtained by the action of sulphuric acid upon glue or gelatine; it has hence received the name URIC ACID. 505 of suga r of gelatine , glycycoll, or glycocine, (from glukus sweet, and kolla glue.) It is best obtained by boiling hippuric acid for half an hour, in ten parts of a mixture of sulphuric acid diluted with twice its volume of water. On cooling, ben zoic acid separates, and after removing the sulphuric acid by saturating it with carbonate of lime, glycocine re- mains in solution, and may be purified by crystallization from dilute alcohol. Glycocine forms colorless prismatic crystals which are soluble in four or fiv r e parts of water, but are in- soluble in pure alcohol ; its taste is sweet, like grape sugar. Its formula is C 4 H 5 N0 4 , and its formation from hippuric acid is thus represented; C u H^O B +H fl O a =CH O 4 -f C 4 H 5 N0 4 . It is homologous with alanine, and is, like it, an organic base, forming salts which crystallize beautifully. An atom of hydrogen in it may be replaced by a metal, and species like C 4 (H 4 Cu)N0 4 are obtained, whnh saturate acids, like the normal glycocine. Alkargen, C 4 H 5 As0 4 , the product of the oxydation of alkarsine, is glycocine, in which arsenic replaces nitrogen. By the action of nitrous acid, glycocine is decomposed and yields glycollic acid : 2C 4 H a N0 4 +2NHO,= N 9 +2H a O a +C a H 9 O ia . Benzoglycollic acid may be viewed as a coupled acid, in which two equivalents of the monobasic benzoic have re- placed H 2 in the bibasic glycollic acid, with the elimination of 2H 3 3 ; it is therefore itself bibasic. When a mixture of benzoic and lactic acids is fused together, water is evolved and the homologue of benzoglycollic acid, corresponding to lactic acid, is obtained : it is C 40 H 20 16 , and is readily decom- posed by strong acids into benzoic and lactic acids. 873. Uric or lithic add exists in the urine of carnivo- rous animals, and in that of man in the last associated with hippuric acid. The solid white urinary excretions of birds and serpents are composed almost entirely of urate of am- monia. The urine of the boa or other serpents is dissolved by boiling in a solution of hydrate of potash, ammonia being evolved. A current of carbonic acid gas is then passed through the liquid, which throws down a sparingly soluble acid urate of potash. This is washed with cold water to remove impurities, and redissolved in a hot dilute solution of potash : from the warm liquid chlorohydric acid separates a gelatinous precipitate, which soon changes into a white crystalline powder of pure uric acid. The uric cid may be separated from the dung of pigeons or other 506 ORGANIC CHEMISTRY. birds by a solution of borax in 100 parts of boiling water: the acid is thrown down from this by chlorohydric acid, and may be dissolved in potash, and purified by the process already described. Uric acid is soluble in 2000 parts of hot water, and has feeble acid characters : it is represented by C 10 H 4 N 4 6 , and is bibasic; the urates, like the acid itself, are sparingly soluble. The products of the decomposition of uric acid arc numerous and interesting. When boiled with water and peroxyd of lead, carbonic acid gas is formed, and a substance called allantotn, which exists in the amniotic liquid of the cow, and in the urine of young calves. Its formula is C S H 6 N 4 6 ; allantoin forms brilliant, colorless prisms, soluble in 160 parts of cold water. The further action of peroxyd of lead decomposes it into an oxalate and two equivalents of urea, C 8 H 8 N,O fl +2H a O a +0 8 =C 4 H 3 8 +2C B H 4 N a 1> , Boiled with acids it fixes the elements of one equivalent of water, and forms one equivalent of urea, and allanturic acid C H 4 N 2 6 ; this is very soluble and deliquescent. When boiled with baryta-water, allantoin is completely decomposed into an oxalate and ammonia; C 8 H 6 N 4 6 -f4(BaH)0 3 + H fl O fl =2C 4 Ba a 8 +4NH ? . 874. When uric acid is mixed with warm chlorohydric acid and chlorate of potash is gradually added, the acid is dissolved and oxydized at the expense of the oxygen of the chloric acid. It is converted by this process into urea and a new compound, alloxan C 8 H 4 N 3 10 . This substance is also formed when uric acid is added in small portions to nitric acid of specific gravity 1-43; it dissolves with the evolution of nitrous fumes, mixed with nitrogen and carbonic acid from a partial decomposition of the urea, and on cooling, alloxanis deposited; C^HAOp+SHA+O^C.HAO.-r- C S H 4 N 2 10 . Alloxan crystallizes in small colorless brilliant rhomboidal crystals, with a vitreous lustre, which are an- hydrous; or in large prisms which contain water, and are efflorescent. It is very soluble in water, and its solution gives to the skin, after some time, a purple stain and a nauseous odor. In contact with bases, alloxan combines with H 3 2 to form a feeble bibasic acid, called the alloxanic acid. Boiled with a solution of baryta or with acetate of lead, alloxan fixes the elements of water and yields urea and a salt of niesoxalic add, which is soluble, quadribasic, and represented by C 6 H 4 13 . If a solution of alloxan is gently URIC ACID. 507 heated with peroxyd of lead, carbonic acid gas is disengaged, and urea remains in the solution, mixed with insoluble oxa- late and carbonate of lead. Alloxan, with water and oxygen, yields urea, carbonic acid, and oxalic acid ; C 8 H 4 N 3 10 -f- H a 3 -f 9 = C a H 4 N a O a +C fl 4 +C 4 H.,0 8 . The carbonate of lead in the residue results from a further oxydation of a portion of the oxalate by the peroxyd. 875. When sulphuretted hydrogen is passed through a solu- tion of alloxan, sulphur is deposited, together with a white crystalline substance named alloxantine; it is C 16 H 10 N 4 O ao , and is formed by the combination of two equivalents of alloxan, which fix at the same time H 3 . When a solution of alloxan is mixed with chlorohydric acid, and a fragment of zinc is added, the hydrogen from the decomposition of the acid is not evolved, but unites with the alloxan to form alloxantine, which crystallizes upon the zinc. Alloxantine is also formed when a solution of alloxan is boiled with dilute sulphuric or chlorohydric acid, and is deposited on cooling ; an equivalent of water is decomposed, and H 3 unites with two equivalents of alloxan to form alloxantine, while the 3 oxydizes another equivalent of alloxan, as in the case of peroxyd of lead, and forms oxalic and carbonic acids and urea, which last in presence of the acid, is decomposed into ammonia and car- bonic acid. The decomposition of water in this reaction is analogous to that of sulphuretted hydrogen in the previous process. This substance is sparingly soluble in water : it appears to possess feeble acid properties, but is at once de- composed in contact with bases. When alloxantine is warmed with twice its volume of water, and a little nitric acid is added, solution takes place, with the evolution of nitric oxyd ; the filtered liquid mixed with a few drops of the acid, to oxydize any excess of alloxantine in solution, deposits on cooling pure alloxan; C l6 H 10 N 4 20 -|-0 3 2C 8 H 4 N a 10 -j-H 3 3 . The most advantageous way of preparing alloxan is to dissolve uric acid in warm, somewhat dilute chlorohydric acid, with the aid of one-fourth its weight of chlorate of potash, to precipitate alloxantine by passing sulphuretted hydrogen through the diluted solution, and convert it into alloxan by the above process. 876. A boiling aqueous solution of alloxantine is still further decomposed by sulphuretted hydrogen ; sulphur separates, and dialuric acid is formed ; this is C S H 4 N 2 S , and is monobasic; its ammonia salt is colorless, but becomes 508 ORGANIC CHEMISTRY. blood-red on drying. Dialuric acid differs from alloxan by 8 , and its potash salt is formed by a process of de-oxydation when cyanid of potassium is added to a solution of alloxan. By exposure to the air, this acid absorbs water and oxygen, and is changed into a dimorphous form of alloxantine. Alloxantine contains the elements of alloxan, dialuric acid, and an equivalent of water; when its solution is mixed with one of sal-ammoniac, alloxan is formed, chlorohydric acid set free, and an insoluble crystalline substance separates, to which the name of uramile is given ; it is the amid of dia- luric acid, being C 8 H S N 3 6 . An equivalent of alloxantine, C 16 H 10 N 4 O ao +HCl.N H 3 = C.H 4 N,0 M +C.H.N,0,+HC1+ 2H a 3 . When a solution of alloxan is heated to boiling with sulphite of ammonia, it deposits, on cooling, brilliant plates of a new salt, the thionurate of ammonia. Thionuric acid is bibasic, and contains the elements of alloxan, am- monia, and sulphurous acid; it is C s H 7 N 3 S fl 14 . When its solution is heated to boiling, it is completely decomposed into uramile and sulphuric acid, C 8 H 5 N 3 8 -{-S a H a 8 ; but if previously mixed with sulphuric acid and evaporated in a water-bath, dialuric acid and sulphate of ammonia are obtained. 877. The solutions of uric acid in nitric acid are colored of a beautiful purple by ammonia; and alloxautine in an ammoniacal atmosphere, or solutions of uramile in ammonia or hydrate of potash, absorb oxygen from the air, and assume the same purple color. If, to a nearly boiling solution of alloxan, one of carbonate of ammonia is added in slight excess, there is a violent effervescence from the escape of carbonic acid gas, and the liquid assumes so deep a purple hue as to be almost opaque. As it cools, delicate square prisms are deposited, which are garnet-red by transmitted, and golden-green by reflected light; their powder, under a burnisher, assumes a green metallic brilliancy. This beautiful substance is named murexid, in allusion to the murcx which furnished the purple dye of the ancients; it is slightly soluble in cold water, and colors it purple. Crys- tals of it are also obtained when uramile arid oxyd of silver are boiled with water containing a little ammonia; the silver is reduced, and the filtered purple solution deposits murexid on cooling. The probable formula of murexid is C 8 H 4 N 4 4 , corresponding to the amid, or rather nitryl of alloxauic acid. Alloxanate of ammonia, C 8 H N 3 O ia .2NH 3 4H 2 O a ^C 3 H 4 CHOLIC ACID. 509 N 4 4 . A solution of murexid in hot water gives a red precipitate with nitrate of silver; its solution heated to boiling with sulphuric acid, yields a precipitate of uramile and alloxan, while alloxantine and sulphate of ammonia re- main in solution. When uric acid or alloxan is boiled with an excess of strong nitric acid, carbonic acid gas is evolved and para- banic acid formed j it is C 8 H a N 3 6 , and is bibasic and very soluble. When its ammonia salt is heated to boiling, it fixes H 3 3 , and is converted into oxalurate of ammonia. The addition of chlorohydric acid to a solution of the new salt separates the oxaluric acid as a sparingly soluble powder, which is represented by C 6 H 4 N 3 8 . When its aqueous solution is boiled, it is converted into oxalic acid and urea, O fl H 4 N 3 8 +H 3 3 = C 4 H 3 8 +C 3 H 4 N 3 3 . 878. The action of chlorine upon the alkaloid caffeine, produces, among other products, a feebly acid crystalline substance, sparingly soluble in water, to which the name of amalic acid has been given. It closely resembles allox- antine, and is homologous with it, being C 24 H 1S N 4 30 ; the two differ by 4C 3 H 3 . When amalic acid is moistened with water and exposed to the action of air and ammonia, it is converted into a reddish-brown substance, which, by solution in hot water, yields red crystals, scarcely distin- guished from murexid by their characters. They are named murexoine, and are probably the murexid of this series, of which the other members have not yet been studied. 879. Cholic Acid. The bile of animals is a solution of the soda or potash salts of two azotized acids, one of which contains sulphur. When ox-bile is evaporated to dryness and dissolved in alcohol, the careful addition of ether pre- cipitates first the salt of the sulphur acid, and by a further addition of ether, aided by cold, the soda salt of the dis- solved cholic acid may be obtained in crystals. On adding sulphuric acid to their aqueous solution, the acid separates after some time in delicate white silky crystals, which have a bitterish sweet taste, and are very sparingly soluble in water. Cholic acid is monobasic, and is represented by C 5fl H 43 N0 13 . When boiled with a solution of baryta, it is decomposed like hippuric acid into glycocine and a new acid, containing no nitrogen, which is called cholalic acid, ojByjo !f +H jl o,===o f Hyiro 4 +c - H 40 o Mf which is the formula of cholalic acid. It forms colorless octahedral 510 ORGANIC CHEMISTRY. crystals, which require 4000 parts of cold water for then solution, but are very soluble in alcohol. When exposed to heat, or when boiled with strong chlorohydric acid, it is converted successively into clioloidic acid and an almost insoluble resinous body, dyslysine, both of which are formed by the loss of the elements of water ; dyslysine is C 48 H 36 O a . When cholic acid is heated with a dilute acid, it loses H fl O s , and yields cliolonic acid, C 5a H 41 N0 10 , which, by boiling, is decomposed into glycocine, and choloidic acid or dyslysine. 880. Acetate of lead precipitates the cholic acid from bile which has been purified by solution in alcohol, but leaves in solution the sulphuretted acid, to which the name of choleic acid is given ; the bile of sheep, and of some fishes is almost entirely composed of choleates, and that of the dog is pure choleate of soda. Choleic acid resembles the cholic acid, but both it and its salts are more soluble in water. Its formula is C 5a H 43 N0 14 S 2 ; when boiled with a solution of baryta, it is decomposed like the cholic acid, and yields cholalic acid ; and in place of glycocine, a neutral body named taurine^ which is crystalline, soluble in water and alcohol, and contains C 4 H 7 NO & S a . The action of acids yields taurine and cholalic acid, and the spontaneous putre- faction of recent ox-bile, which is mixed with the mucus of the gall-bladder, affords similar results; acetic and allied acids, probably froin the decomposition of glycocine, accom- pany the taurine, which is itself decomposed at a later stage of the process, sulphurous and sulphuric acids being formed. 88 i. The bile of pigs contains a peculiar acid to which the name of hyocholic acid is given : it is C M H 43 N0 10 , and is homologous, not with cholic, but with cholonic acid, dif- fering from this by C 3 H 9 : boiled with baryta water, it yields glycocine and hyochotaiic acid, homologous with cholalic acid : by chlorohydric acid it is converted into glycociue and a homologous species of dyslysine: C 54 H 43 N0 10 = C 4 H 5 N0 4 Bile contains, besides these salts, a portion of fat, a yel- low coloring matter, and a neutral crystalline body resem- bling spermaceti in appearance, to which the name of c/wlesterine is given : it often forms concretions in the gall- bladder, known as biliary calculi. The formula C^H^O, is assigned to it. NITROGENOUS NUTRITIVE SUBSTANCES. 511 NUTRITIVE SUBSTANCES CONTAINING NITROGEN. 882. Under this head may be described a class of sub- stances which are common to plants and animals, and sustain a very important part in the economy of nutrition. The seeds and juices of all plants, in addition to the starch, sugar and lignine always present, contain peculiar substances which, although unlike in form and solubility, have a general similarity of composition with each other, and with the muscular tissue of animals. The relations between these bodies may be said to be analogous to those between starch, gum, dextrine, and lignine. In both, the differences are to be considered as in part depending upon organization, and in part upon that molecular arrangement, which constitutes a species of isomerism. As lignine and starch may be con- verted into dextrine, and as both dextrine and gum, by acids, yield glucose, so these diiferent azotized substances may be converted one into another. To these bodies the general name of protein compounds has been given, from proteuo, I take the pre-eminence, in allusion to their import- ance in the vital economy. 883. The muscle or flesh of animals is called fibrin, and is an organized form of protein ; fibrin also separates from the blood during coagulation, and is, when pure, a white tasieless mass, insoluble in water, and becomes horny and translu- cent by drying. It dissolves in acetic and dilute chloro- hydric acids, in warm solution of sal-ammoniac, nitre, and several other salts, and is separated from them by heat in an insoluble amorphous form. The serum of the blood and the white of eggs contain in solution a large quantity of a protein compound, which is similar in its characters to dissolved fibrin, and coagulates by a heat of 158 F. : it is called albumin, and is nearly pure in the white of eggs. Albumin when coagulated by heat is insoluble in water, and resembles fibrin in its chemi- cal properties j milk contains another soluble form of pro- tein, which is not coagulated by heat, but is at once sepa- rated in an insoluble condition by a dilute acid; it has received the name of casein, and is nearly pure in the curd of skimmed milk. Casein appears to be insoluble in water when pure, and to be held in solution in milk by a small portion of soda : the albumin of the blood is by the action of a solution of potash converted into a form resembling casein 512 ORGANIC CHEMISTRY. 884. When a paste of wheat flour is washed with water until all the starch is removed, a tenacious gray substance remains, which dries into a horny mass, and which, though not possessed of the organized structure of muscular fibre, is soluble in acetic acid, and is chemically identical with fibrin : it is called glutin. The water from the washing of the paste, from which the starch has separated by repose, and the juices of many vegetables, yield by heat an insoluble protein body, which is vegetable albumin. When beans or peas are bruised witli water, a large quantity of protein \L dissolved, and may be precipitated by the addition of ail acid. It is called legiimin, or vegetable casein. 885. When any one of these substances is dissolved in a moderately strong solution of hydrate of potash, and heated for some time to 120 F., the addition of acetic acid in slight excess, separates a white flocculent matter, which when washed with water and dried, is a yellowish brittle mass, soluble in acetic acid, but insoluble in water a-nd alcohol. It is pro- tein in a state of comparative purity, and has nearly the same composition, from whatever source it is obtained. In their natural state, the protein bodies contain variable and often considerable quantities of mineral matter in a state of combination or intimate mixture. The curd of milk yields, when burnt, several per cent, of ashes, consisting principally of phosphate of lime. The different protein compounds also contain small, but variable proportions of sulphur and phosphorus in combination with the organic elements, pro- bably replacing oxygen and nitrogen in a portion of the protein, and the sulphur remains after solution in potash and precipitation by acetic acid. If to a solution of any protein body in potash, a little acetate of lead is added, and the solution is heated to boiling, it becomes black from the formation of sulphuret of lead; but even by ebullition it is difficult to decompose the whole of the sulphur compound. The amount of sulphur generally varies from 1 to 1-5 per cent., but the protein from cows' horns and hoofs contains, according to Mulder, from 3*4 to 4-6 per cent, of that element. The proportion of phosphorus in the different forms of protein also varies from a trace, to -8 per cent., and in vegetable casein it rises to 2-4 per cent: it is sometimes absent. 886. The facility with which the protein bodies are altered by spontaneous decomposition, and by different reagents, renders it very difficult to fix their exact composition. If PROTEIN. 513 we suppose the sulphur to replace a portion of the oxygen, the formula C^H^NgOg may be assigned as expressing very closely the composition of protein. The greatest amount of sulphur present in any variety of protein, scarcely amounts to one equivalent : the normal protein appears to be inti- mately mixed with a sulphuretted compound, which has probably the same equivalent composition in other respects as protein itself: an analogous case occurs in the two acids of the bile, which can scarcely be separated from each other by any known difference in properties. The phosphorus which is sometimes present, may belong to a body in which that element replaces nitrogen, wholly or in part. There are other organic matters in the brain and the blood, which contain phosphorus in a similar combination ; but it is more probable that in the protein bodies, it exists as phosphate of lime. 887. The following numbers give the proportions of carbon, hydrogen, nitrogen, and oxygen, required by the above formula, and the results of an analysis of the protein from albumin, and one of fibrin. The amount of oxygen equivalent to the sulphur present, is given on one side, and added to the quantity of oxygen, for the purpose of com- parison : .Analyses by Mulder. Calculated. Protein. Fibrin. Carbon ........... 53-93 53-7 52-7 Hydrogen ....... 6-36 6-9 6-9 Nitrogen ......... 15.73 14-4 15-4 Oxygen ........... 23'98 23-6 1 . , 23-5 ) 24 ., Sulphur ........... 1-4=0-7 | 24 3 l-2=0-6 J 2 * * Phosphorus ...... 100-00 100-0 100-0 The results of different analyses of protein from other sources, show still greater variations in composition, one reason of which is the want of definite chemical characters by which we may be able to separate it from any admixture of foreign bodies. The above formula, however, coincides better than any other, with the analyses of the purest forms of protein : protein is, according to it, an amid, or rather a nitryl, of cellulose; C M H w O M +3NH a = 6H a O +0 H wN. 8 . It should therefore under proper conditions assimilate water, and yield ammonia, and a body belonging to the series of cellulose, dextrine, or glucose ; in fact, when proteia 33 514 ORGANIC CHEMISTRY. is dissolved in strong heated chlorohydric acid, it is com- pletely decomposed into ammonia, which forms sal-ammoniac, and a brown insoluble matter identical with that produced by the slow decay of woody fibre, and derived from cellulose by the loss of the elements of water. A similar body is produced from grape sugar by the action of chlorohydric acid. The muscular tissue is insoluble protein in an organized condition, and sustains a similar rank in the animal structure to that of cellulose in the vegetal, while albumin and casein are soluble unorganized forms of protein, and may be com- pared to dextrin and gum. 888. The action of hydrate of potash aided by heat, upon the different forms of protein, evolves a great deal of ammonia mixed with hydrogen, and probably several vola- tile bases, and the residue contains, among other substances, salts of acetic, butyric, and valeric acids, and two crystal- line azotized bodies, named leucine and tyrosine. The former has the formula C 13 H 13 N0 4 ; it is homologous with glyco- cine and alanine, and is an organic base resembling these in its characters. Tyrosine is C^H^NOg. These two bodies arc also obtained as products of the action of sulphuric acid upon protein. The protein bodies when mixed with water and kept in a warm place, readily undergo spontaneous decomposition, and evolve a disagreeable odor, becoming putrid. Fibrin is at first converted into a soluble form resembling albumin, hydrogen gas and ammonia are evolved, and there remain in solution ammoniacal salts of butyric and valeric acids, besides leucine and tyrosin, and a portion of undecomposed protein. 889. When any form of protein is distilled with a mix- ture of bichromate of potash and sulphuric acid, the latter not being in excess, the protein is oxydized by the chromic acid, and a great variety of volatile products are obtained; among them are prussic acid, or formic nitryl, and the nitryl of valeric acid, together with bitter-almond oil, benzoic acid, and the formic, propionic, butyric, and valeric acids. When peroxyd of manganese is substituted for the bichromate, with an excess of sulphuric acid, the nitryls are not obtained, but besides bitter-almond oil, and the acids already mentioned, the acetic and caproic acids, together with the acetic, pro- pionic, butyric, and valeric aldehyds. In the latter process the residue contains salts of ammonia, and the acids may result from the decomposition of previously formed bodies PROTEIN. 515 liko leuclne : this, when distilled with a mixture of oxyd of manganese and sulphuric acid, yields carbonic acid and valero-nitryl, and the latter by an excess of acid is con- verted into valeric acid ancl ammonia. The destructive distillation of the protein bodies yields a large amount of carbonate of ammonia, and a number of volatile oily bases, some of which are homologous with ammonia, besides water and inflammable gases, and leaves a bulky charcoal very difficult of combustion, which con- tains several per cent, of nitrogen, and is perhaps a mixture of carbon with something analogous to paracyanogen. 890. When fibrin or casein is kept for some time in a cool, dark, and moist place, it undergoes a decomposition which results in its partial or entire conversion into a fusible fat, resembling butter and easily saponified, which has not yet been minutely examined. It is said to have a sweet taste, and to be readily volatile; if such is the case, it is not improbable that the product is an ether of some fatty acid or acids. This change is observed in the preparation of some kinds of cheese, and may be supposed to consist in the fixing of the elements of water, the separation of the nitro- gen in the form of ammonia, and a great portion of the oxygen with some of the carbon, in the form of carbonic acid gas. It is accompanied with the development of a great number of mycodermic plants, or moulds, which appear to be nourished by the evolved gases. 891. The protein bodies not only undergo spontaneous decomposition themselves with great facility, but, under cer- tain conditions, induce changes in a great variety of organic substances. The action of casein in converting sugar into acetic and lactic acids, and this latter into butyric and car- bonic acids and hydrogen, and the conversion of sugar into alcohol and carbonic acid have already been described. Diastase which changes starch into sugar, and emulsine which effects the decomposition of salicine and amygdaline, are forms of protein or an allied substance. If a minute portion of putrefying fibrin is added to a solu- tion of leucine, this substance is decomposed and valerate of ammonia remains dissolved : the spontaneous decomposition of urea, hippuric acids, and the acids of the bile, in the pre- sence of the putrescent animal matters of the secretions, are similar instances. These phenomena may be included under the general name of fermentations ; although the term should 516 ORGANIC CHEMISTRY. be perhaps more restricted in its signification, and exclude those processes in which diastase and emulsine are the agents. 892. The alcoholic fermentation has heen the one most carefully studied; it is produced by decomposing casein or fibrin, as well as by yeast. Yeast, when obtained from fer- menting beer, has a chemical composition allied to protein, and resembles it in its properties ; it is found under the microscope to be completely organized, and to consist of two minute species of fungus, which seem to be always produced and propagated in a solution of sugar, when undergoing the vinous fermentation : the presence of decomposing protein in a sugar solution, appears to excite fermentation by afford- ing the conditions necessary to the development and nutri- tion of these fungi. These bodies are figured in 695. One of the species in yeast appears to be more especially connected with the vinous fermentation, and, being much greater in size, may be separated by filtration from the other, which is regard- ed as the fungus of the lactic and butyric fermentations; this last also appears in the conversion of casein into fat, and it pro- duces the decomposition of urea into carbonic acid and ammo- nia, a change which is rapidly effected in the presence of yeast. The acetic fermentation is characterized by a distinct fungus. The power of yeast or any form of protein to produce these organic changes, is destroyed by boiling water, by chlorid of mercury, arsenious acid, salts of iron, zinc, alka- lies, mineral acids, or by oil of turpentine or kreasote. Yeast may be dried at a gentle heat, and regain its activity when moistened with water, but if when dried, it is finely divided by trituration, so as to destroy the fungi, it is inert. It may be said that whatever is fatal to the vitality of the fungi, destroys at the same time the activity of the fer- ment. The bodies just mentioned are known to act as antiseptics, preventing putrescence, but it is not improbable that all cases of putrefaction belong to the same class of phenomena as these fermentations. 893. From the constant connection between the develop- ment of certain fungi and different chemical changes, it is supposed by many chemists that they are the agents in the process of fermentation, which is one essentially vital, and that the fungi decompose the organic bodies, perhaps by a sort of absorption and subsequent excretion. The action of boiling water and of antiseptics, destroys the power of diastase and emulsine to act upon starch and GELATIN. 617 amygdaline. I am not aware whether in these reactions, the development of fungi has been noticed. The phenomena most analogous to fermentations ope such as those in which a small portion of sulphuric acid converts a large amount of alcohol into ether, or olefiant gas, and water, or where the same acid converts dextrine into sugar, or to the spontaneous decomposition of a solution of urea at an elevated tempera- ture : in all these cases, the influence of vitality is evidently excluded. Our knowledge of chemical dynamics appears as yet inadequate to explain the part which fungi play in many processes, or to draw the distinction between those changes which appear to be effected through their agency, and those which are purely chemical. 894. Gelatin. This substance exists in many animal tis- sues, as the skin, cellular membranes, tendons, and ligaments, and forms the frame-work of the bones ; in this organized form it is insoluble in cold water, but by boiling it dissolves, and the solut::B forms on cooling a firm jelly, which is very characteristic of gelatin; this, when dried, constitutes ordinary glue. The substance known as isinglass, is the dried air-bladder of certain fishes, and is a nearly pure gela- tinous tissue, which is soluble in boiling water. A so- lution of gelatin is precipitated by salts of mercury, and yields a copious insoluble precipitate with an infusion of nutgalls, or a solution of tannic acid ; the insoluble tissues absorb tannic acid from its solutions to form the same com- pound, which constitutes leather. The process of tanning consists essentially in immersing the prepared skin in an infusion of oak or hemlock bark, by which it is saturated with tannin, and becomes incapable of putrefaction, insoluble in boiling water, firm, elastic, and, to an extent, water-proof. 895. Gelatin undergoes putrefaction like protein, and is susceptible of exciting fermentation ; the products of its decomposition by oxydation, and by the action of acids and alkalies, are the same with those of protein. It however yields, in addition to leucine, its homologue, glycocine C 4 H 5 N0 4 , which was first described by the name of sugar of gelatin. When a solution of gelatin is boiled for many hours with dilute sulphuric acid, a large quantity of sulphate of ammonia is formed, and the liquid contains sugar, which yields alcohol and carbonic acid by fermentation. This reaction leads to the supposition that, like protein, it is nearly allied to dextrin or glucose, and the formula 518 ORGANIC CHEMISTRY. CjuH^NjOg, which accords closely with the results of various analyses of soluble and insoluble gelatin, makes it corre- spond to an amid formed from one equivalent of glucose and four of ammonia by the loss of eight of water. C^H^O^-L 4NH 3 = C^H 20 N 4 6 8 -|-8H a p 2 . The decomposition by sul- phuric acid will then consist in the assimilation of water, and the regeneration of glucose and ammonia. The gelatinous substance obtained from cartilage differs somewhat in its composition and properties from ordinary gelatin, and has been distinguished by the name of chondrin. THE BLOOD. 896. This substance when recent is a homogeneous, slightly viscid, red fluid, of a saltish taste and a peculiar odor. When examined under a microscope it is found to consist of a transparent and nearly colorless liquid, in which are floating an immense number of small red bodies, (blood corpuscles,) varying in form and size in different animals, also a small and variable proportion of colorless globules, less in size than the red corpuscles, to which the name of lymph ylobulcs is given ; their real nature is not well understood. Very soon after the blood is taken from the body, it separates into a red mass, called the cruor or clot, and a yellowish liquid, the serum. This change is due to the separation from the liquid of a portion of fibrin, which involves, as in a net, the blood corpuscles, and forms a soft mass distended with serum. If the blood, as soon as drawn, is stirred with a branched stick, the fibrin which separates, adheres in the form of white silky filaments, and the coagulation of the blood is prevented. The same result is obtained if the recent blood is mixed with three or four volumes of a saturated solution of sulphate of soda; this holds the fibrin in solu- tion, and the red corpuscles separate unaltered; they may be separated by a linen filter, and washed from the serum with a solution of sulphate of soda, provided a current of air is kept up through the mix- Fig. 421. hire , These bodies in the blood of most mammiferous ani- BLOOD. 519 lg> mais are red circular discs, with a depressed centre and color less exterior; those of birds, reptiles, and fishes are elliptical. Figure 4'^1 shows the blood discs of the common frog, as they appear under the microscope. The corpuscles in man are very small, being not more than from -g^ 1 ^ to ffoW f an * nc k i n diameter; those of frogs are three or four times greater in their longer diameter. Figure 422 is a microscopic view of the red globules in the blood of man; they are very similar to those of other mammals; the cen- tral portions are less brilliant than the borders. The discs are often seen resting upon each other flatwise, as they are represented at a a a, and more frequently edgewise, as at bb. 897. When placed in pure water, the corpuscles swell, burst, and dissolve into a deep red liquid, which is coagulated by heat, and contains a large portion of protein, analogous to albumin. The coloring mat- ter is separated from this by ammoniacal alcohol, in which it sdone is soluble, and is obtained by evaporation as a dark red- brown mass, which is insoluble in pure water, but dissolves with the aid of alkalies, forming a blood-red solution. It constitutes but four or five-hundredths of the dried blood- globules, and is called liematosine. It contains a large portion of iron ; chlorine separates the iron and renders the matter colorless; an alkaline sulphuret or sulphuretted hydrogen renders it greenish-black, probably from the sepa- ration of a metallic sulphuret, and strong sulphuric acid is said to remove the iron, forming a protosalt, and leaving the red color unaltered. The condition of the iron is analogous to that of this metal in some salts, as in the tartrates, in which it is not precipitated by the ordinary reagents. The coloring matter, according to Mulder, affords by analysis, Carbon.... 66-49 Hydrogen 5-30 Nitrogen 10-50 Oxygen H'05 - o a& Iron o'oo 100-00 520 ORGANIC CHEMISTRY. 898. The serum of the blood is alkaline, and ' ) .tains a large amount of dissolved albumen, which is coagulated by heat ; besides this, it holds in solution a considerable amount of salts, which are chlorid of sodium, with sulphates, phos- phates, and carbonates of potash and soda, phosphates of lime and magnesia, and peroxyd of iron. The blood con- tains besides about 1-6 parts in 1000 of fatty substances, consisting in part of ordinary saponifiable fats, and in part of a peculiar fatty acid containing phosphorus, besides cholesterine, and a fat named seroline. The following table is by Becquerel and Ilodier, and represents the average composition of healthy human blood of both sexes: Man. Woman. Density of the defibrinated blood 1-0602 1-0575 Density of the serum 1-0280 1-0275 Water 779-000 791-100 141-100 127-200 Albumin. . 69-400 70-500 Fibrin 2-200 2-200 Extractive matters ) 6-800 7-400 Salts J " 1-600 1-620 Serolino 020 020 Phosphuretted fatty matter 488 464 Cholesterine. 088 090 Saponifiable fat 1-004 1-046 Chlorid of sodium 3-100 3-900 Other soluble salts 2-500 2-900 Insoluble phosphates 334 354 Oxyd of iron . ... 566 -541 The existence of alkaline carbonates in the blood has been denied by some chemists, who assert that its alkalinity is due to the presence of tri basic phosphate of soda. Traces of fluorid of calcium, oxyds of manganese, lead, and copper have been detected in the blood of different animals, and silica in that of fowls. Besides these, urea and hippurio acid are found, and uric acid is said to have been detected ; in certain cases of disease, the coloring matter of the bile, and its fatty acids, with an increased quantity of cholesterine appear in the blood. After the ingestion of vegetable food, the blood also contains a portion of sugar. BLOOD. 521 899. The color of arterial blood is bright scarlet, and that of the venous blood is dark red. The blood of the veing acquires the bright red tint in the lungs, and loses it again in the capillary vessels. These variations in color depend upon changes in the form and condition of the blood cor- puscles, producing a difference in the reflection of light; those in arterial blood being convex and transparent, while those in the veins have become flattened and semi-opaque. These changes depend upon the action of oxygen ; this gas is much more readily and more copiously absorbed by the blood than by water; the arterial blood of a horse contains in a state of solution from J to T \j its volume of gas, which contains about four parts of oxygen to one of nitrogen; this oxygen disappears in the capillary vessels, and is replaced in the venous blood, by carbonic acid gas. When venous blood is agitated in contact with atmospheric air or with oxygen, it absorbs this gas, and acquires the bright red color of arterial blood; on the contrary, the corpuscles separated from arterial blood and washed with a solution of sulphate of soda, assume the dark red color of venous blood and become disintegrated, dissolving and passing through the filter, unless supplied with oxygen. If, how- ever, a current of atmospheric air is passed through the mixture upon the filter, the corpuscles preserve their scarlet tint, and remain entire. 900. The globules of the blood appear to be living organ- isms, which are capable of resisting the dissolving action of a solution of sulphate of soda, so long as life remains, but almost immediately become asphyxiated when deprived of air, and at once lose their bright color, and yield to the dis- solving action of the saline solution. The solutions of some salts, as sal-ammoniac and the chlorid of potassium, prevent the aeration of the blood, even in oxygen gas. The vitality of the blood, a doctrine as ancient as the time of Moses, is thus sustained by these facts. The sponta- neous coagulation of the blood, when removed from the body, or in the veins after death, is caused by the separa- tion in an insoluble organized form of a portion of dissolved protein, and seems, like the organization of effused lymph, to be dependent upon an inherent vitality of the fluid, exte- rior to, and perhaps independent of the blood corpuscles. The proportion of fibrin which thus separates is intimately connected with the state of the vital powers, and affords an 522 ORGANIC CHEMISTRY. index to the state of the system in health or disease. In scrofula and other maladies connected with an asthenic con- dition of the system, the blood coagulates but feebly, and the amount of fibrin which separates is much less than ordinary ; while in inflammatory diseases, where the action of the system is unduly heightened, the blood coagulates firmly and rapidly, and the proportion of fibrin formed is much greater than in healthy blood : fibrin constitutes the so-called huffy coat of the blood in inflammatory diseases. The normal quantity of fibrin in healthy blood may be stated at from 2-2 to 2-5 parts in 1000; while in cases of phlegmasia it rises to 6 and 7, and in scrofula and the latter stages of typhus is not above 1-2 or 2. In cases of death by lightning, and by certain poisons, or from a blow upon the stomach, or even from sudden mental emotions, like violent anger, the blood is found to have lost the power of coagulation. The blood corpuscles are found to diminish with the proportion of fibrin, and in some cases of scrofula amount to no more than 64 to 70 parts in 1000; they are at the same time, small, pale, and irregular in shape. The pro- portion of globules is also diminished after blood-letting or hemorrhages, and while in acute diseases generally, it remains unaltered, is increased in plethoric patients. The propor- tion of albumin and fibrin taken together, generally remains unchanged, except in what is called Bright' s disease, when the amount of albumin is notably diminished, a change de- pendent upon its excretion in the urine. The mean com- position of the blood in the two sexes is seen, by the table already given, to be somewhat different, ( 898.) 901. The Flesh Fluid. The recent muscular fibre from which the blood has been drained, contains about 80 per cent, of watery fluid, which may be removed by chopping the flesh and washing it with cold water. The liquid thus obtained, un- like the blood, has an acid reaction ; when heated, a form of pro- tein resembling albumin coagulates; if the acid liquid is then neutralized by baryta-water, phosphate of baryta and phos- phate of magnesia separate, and by evaporation, sparingly soluble, colorless crystals of creatin C 8 H 9 N 3 4 , are deposit- ed. This substance is neutral, but when its solution is evaporated with an acid, it loses H 2 3 and is converted into a crystalline, strongly alkaline, organic base, creatinine (XH 7 N 8 2 , which under certain circumstances unites with and regenerates creatin. When boiled with an excess THE FLESH-FLUID. 523 of caustic baryta, creatin is decomposed, ammonia is evolved, and a carbonate formed, from the decomposition of urea; the liquid affords crystals of sarcosine C 8 ELN0 4 . Creatin with water yields urea and sarcosine, C 8 H g N 3 4 -{-H fl 3 = C 3 H 4 N s 3 -f-C 6 H 7 N0 4 . Sarcosine is metameric with alanine, which it very much resembles in its general characters, and is like it an organic base, but is distinguished from alanineand its homologues, by subliming unchanged at a heat of 212 F. There are evidently two metameric series of bases of the type C n H n _j_ 1 N0 4 , which are represented by alanineand sarcosine ; glycocine and leucine appear to pertain to the same series as alanine, while the sulphuretted base thialdine, C 13 H 13 NS 4 would seem from its ready volatility to belong to the series of sarcosine. 902. The flesh-fluid also affords a peculiar acid, called ino- sinic acid, which is very soluble in water, and has the peculiar flavor of broth. Its probable formula is C 30 H 14 N 4 22 , repre- senting a bibasic acid. The salts of inosinic acid crystallize beautifully ; that of baryta is sparingly soluble ; and those of potash and soda evolve, when decomposed by heat, a strong and agreeable odor of roasted meat. Besides this, an acid, which appears to be a modification of lactic acid, is obtained from the flesh-fluid. Creatin has been found alike in the flesh of birds, beasts, reptiles, and fishes. Fowls, which con- tain the largest quantity, furnish about y^ 3 ^ of creatin, and about half as much of the inosinate of baryta. Creatin and creatinine are also found in the urine, and uric acid has been detected in the muscle of an alligator. The flesh-fluid contains a considerable amount of salts, principally alkaline phosphates and chlorids ; the salts of potassium here predominate, while those of sodium are more abundant in the blood. 903. Saliva. This fluid in its normal state is slightly alkaline, and contains, besides animal matter, small por- tions of salts, principally chlorids and phosphates of alka- line bases ; in that of man a small portion of a soluble sulphocyanate is found. The pancreatic juice is also alkaline, and analogous to the ealiva in its composition ; both of these secretions contain in solution an azotized organic substance, which may be preci- pitated by alcohol, and like diastase possesses the power of rapidly transforming a solution of starch into dextrine and glucose, They are supposed in this manner to exercise an 524 ORGANIC CHEMISTRY. important part in preparing these substances for assimila. tion. The serum of the blood has a similar action upon starch. 904. The secretion of the stomach, called the gastric juice, is acid in its reaction, and contains portions of alkaline chlo- rids, free lactic acid, and an azotized substance similar to that of the saliva. It has the power of dissolving, at the temperature of the body, fibrin, coagulated albumin, and other forms of protein, but has no solvent action upon starch ; if however the gastric fluid is rendered feebly alkaline, it no longer dissolves protein, but acts upon starch like the saliva and pancreatic juice. In the same way these, when rendered acid, acquire the power of dissolving protein. The tissue of the pancreas from a dead animal, when cut in pieces and mixed with water, still exerts a solvent power upon starch, and the lining membrane of the stomach, when digested with water slightly acidulated with chlorohydric acid, forms an artificial gastric juice. The animal matter of the gastric juice, which is apparently identical with that of the saliva, has been named pepsin, (from pepto, I digest,) and like diastase is at once rendered inactive by a boiling heat, and by various antiseptics. It is analogous to the protein bodies in its composition, and like them has, under certain condi- tions, the power of converting sugar into lactic acid, and thus changing its reaction, so as to become capable of dis- solving protein. 905. The bile has already been shown (879) to consist essen- tially of the soda-salts of two azotized acids : besides these, there are small portions of alkaline chlorids and phosphates, and some mucus, the azotized secretion of the mucous surfaces. The substance of the liver generally contains a small portion of sugar. The bile is alkaline in its reactions, and has the power of rendering fats and oils soluble, acting like a soap, and apparently fitting them for the process of assimilation. The same power is possessed by the saliva and pancreatic juice, which with the bile and gastric juice are brought in contact with the food in different parts of the alimentary canal, and by their combined action render the amylaceous, fatty, and proteinaceous portions of the food soluble, and ready to be elaborated in the form of chyle. Such, in the present state of our knowledge, seems to be the nature and result of the process of digestion. CHYLE. URINE. 525 . 306. Cliyle. This fluid in the human body, as taken up by the lacteals from the small intestines, is white and opake, and contains dissolved protein in a form resembling albumen, with small globules of fat, to which its milkiness is due, and a portion of sugar, besides various salts and a portion of iron in a soluble form ; when first taken up from the intestines, it yields but very little fibrin, but the chyle from the thoracic duct coagulates like blood, yielding a clot which contains fibrin, and the clear liquid resembles the serum of the blood, to which this liquid is already as it were in a state of transformation, wanting only the red corpuscles. The solid excrements of animals contain portions of the food, insoluble or unfit for assimilation ; those of the herbi- vora are made up in part of ligneous matter, and those of carnivora contain a portion of an azotized substance, and yield ammonia by their decomposition ; phosphates and other salts are present in considerable quantity, in the excrements, and render these substances valuable as manures. 907. Urine. This excreinentitious substance is separated from the blood by the kidneys, and removes from the body various salts and azotized matters. The latter are urea and hippuric and uric acids, which have already been described. The urine of birds and reptiles, which is white and solid, is principally urate of ammonia. That of herbi- vorous mammals is alkaline, and contains in solution, besides urea, a large amount of hippuric acid; while in carnivora this acid is wanting, and a large amount of urea is found, with a little uric acid. This is nearly the composition of the urine of man subsisting upon a mixed diet : the average quantity of urea in healthy human urine is about 3 per cent., and that of uric acid about y^ou ^ a ^ so contains a little hippuric acid. When benzoic acid is taken into the stomach,, the urine a few hours afterward is found to con- tain a large amount of hippuric acid, apparently formed in some way from the benzoic acid. Creatin and creatinine are also found in urine, and that of young .salves contains in addition to a considerable quantity of creatinine, a notable amount of allantoin. The saline matters of the urine general- ly amount to two or three per cent., and consist of chlorid of sodium, with sulphates and phosphates of potash and soda, And traces of ammoniacal salts, besides phosphates of lime and 526 ORGANIC CHEMISTRY. magnesia. Urine also contains a peculiar organic coloring matter, and a portion of mucus from the blidder, which in a few hours excites a decomposition of the urea, the liquid becoming alkaline from the carbonate of ammonia formed. If this mucus be removed by filtration, the urine may be preserved a long time without change. When putrescent urine is evaporated, the ammoniacal salt forms with the phosphate of soda, the double phosphate of soda and ammo- nia, which was formerly known as the essential salt of urine, or microcosmic salt* If the residue is evaporated to dryness and distilled at a red heat, the acid of a portion of phos- phate of ammonia is decomposed by the organic matter present, and a small quantity of phosphorus is obtained; it was by this process that this curious element was first prepared. The fresh urine of man and the carnivora has an acid re- action, which is ascribed to the uric acid held in solution by phosphate of soda : on adding a little chlorohydric acid to the urine, the uric acid separates after a few hours in small but distinct crystals. 908. In disease the composition of this fluid is sometimes altered, and the elements of the chyle and blood find their way into the urine : in some forms of dropsy and diseases of the kidneys, it contains albumin, while the urea is deficient, and is found in the blood and other fluids of the body. In other cases, all the sugar contained in the food, or formed in the digestive process from starch, is excreted in the urine, under the form of glucose, and constitutes the disease called diabetes mellitus : in this disease the urine still contains urea in large quantity. In some states of the system, the uric acid increasing in quantity, or the solvent power of urine being diminished, this acid is deposited in the form of gravel or calculus. Urio acid or urate of ammonia constitutes the most common form of calculus; but phosphate of -lime, and the phosphate of magnesia and ammonia, besides oxalate and more rarely carbonate of lime, are also found as urinaiy concretions. * So named by the older chemists as it was then supposed to be a gait peculiar to man. Man was called the microcosm, because in hi three-fold nature is repeated in miniature the order of the universe, the great koumos or macrocosm. MILK. 527 909. Milk. This secretion of the female contains in a soluble form all the substances necessary for the nutrition of the young, protein, fat, su- gar, and various salts. When viewed under the microscope, milk is seen (fig. 423) to con- tain numerous globules of fat suspended in a clear liquid ; these globules are butter, and give to milk its opacity. The proportions of its ingredients vary, but the following analy- sis of cow's milk may be taken as an example : 1000 parts contain, Water 873-0 Butter 30-0 Casein, and a little albumin 48-2 Milk-sugar, or lactose 43.9 Phosphate of lime, with a little fluorid of calcium 2-3 Chlorids of potassium and sodium 1'7 Phosphate of iron and magnesia, with a little soda com- bined with casein *9 1000-0 Woman's milk contains proportionably more sugar and less casein, and in these respects it resembles asses milk, which also contains but little butter : the milk of carnivora like wise contains a considerable proportion of sugar, even when the animals have been fed for a long time exclusively on flesh. It is in this case probably derived from the transformation of gelatin or protein, in the manner already pointed out; and the lactic acid in the flesh-fluid of carnivora must have a similar origin. 910. When milk is saturated with common salt and filtered, a clear liquid is obtained, which holds in solution the casein, sugar, and salts; while the butter rests upon the filter in tho form of globules, which are enclosed in an albuminous mem- brane, and are insoluble in ether. If, however, the milk is first boiled, the albuminous coating appears to be dissolved, and the whole of the butter is dissolved by agitation with ether, leaving the milk transparent. After a few hours' repose the greater part of the globules rise to the surface in the form of cream. In describing casein, (875,) the effect of acids ia 628 ORGANIC CHEMISTRY. producing the coagulation of milk has been already noticed : *he whey contains all the sugar, and the soluble salts. Th spontaneous coagulation of milk depends upon the forma- tion of a little lactic acid from the sugar : in the prepara- tion of cheese, an infusion of the lining membrane of a calf's stomach, called rennet, is added, which causes an almost immediate separation of the casein in an insoluble form ; this reaction does not depend upon the formation of lactic acid, but may take place in the presence of an excess of alkali ; milk in its recent state has an alkaline reaction. In cheese which has been long kept, there are found seve- ral products of the decomposition of casein, among which are salts of butyric and valeric acids, and probably leucine j besides butter from the milk, cheese often contains a portion of fat, from the transformation of the casein already described. 911. Eyys. The white part of the eggs of fowls con- sists of a solution of albumin, with small quantities of soda and various salts : on boiling eggs, a portion of sul- phur, from the albumin, combines with soda to form a sul- phuret of sodium, which is recognized by the blackening of a piece of bright silver. The yolk of eggs contains, besides a protein compound, a large portion of oil which consists principally of oleine and margarine, and a peculiar viscous matter which contains ammonia, and yields, by the action of acids, oleic and margaric acids, and a soluble acid which appears to contain the elements of phosphoric acid and glycerine. Besides these, lactic acid and the salts which are found in the blood and flesh-fluid, are present. 912. The brain and nervous substance are similar in their chemical nature, and the white and gray portions of the brain differ chiefly in their structure ; they contain about 80 per cent, of water. The solid matter consists in part of a protein body, and in part of a substance which, by the action of acids, yields products similar to the viscous matter of the yolk of eggs. Besides these there is present fatty crystalline acid, which contains nitrogen and about one per cent, of phosphorus, and has been named cerebric jLcid. It is but little known, but is probably somewhat analogous to the acids of the bile. It appears to be identi- cal with the phosphurettcd fat of the blood j cholesterine is also present in the substance of the brain, besides an BONES. 529 oily fat acid, which appears to contain the elements of phos- phoric and oleic acids. The solid matter of the brain con- tains about four per cent, of phosphorus. 913. Bones. The bones consist of a tissue of insoluble gelatine enveloping a large amount of earthy salts. The bones of young animals contain but a small portion of mine- ral matter, which increases with their growth. A deficiency of the solid ingredients occurs in rickets, and other diseases connected with defective nutrition. The dried bones of adults contain from 30 to 40 per cent, of organic matter, which is almost entirely soluble in boiling water ; water also removes small quantities of salts of soda. The remainder, is principally tribasic phosphate of lime P0 5 .3CaO, with small portions of phosphate of magnesia, carbonate of lime, and fluorid of calcium. The two analyses which follow are of a human femur and the femur of an ox : Man. Ox. Phosphate of lime 58-30 59-67 Phosphate of magnesia......' 2-09 1-21 Carbonate of lime 7'07 G-39 Fluorid of calcium 2-73 2-05 Organic matter 30-58 31-11 10CW 100-43 When a bone is immersed in a dilute acid, as the chloro- hydric, the earthy salts are entirely removed, and the bone becomes translucent and flexible. It then dissolves in boil- ing water, leaving only a small portion of insoluble tissue, consisting of the blood-vessels which penetrated its sub- stance, and which are composed of protein. The horns of the deer are analogous to bones in composition ; the tusks of the elephant, which constitute ivory, and the teeth, are very similar : the latter contain less organic matter than bones, and in the enamel of the teeth, which contains a considera- ble amount of fluorid of calcium, the animal matter is absent. 914. The horns of cattle, which, unlike those of the deer, are flexible and softened by heat, are, like the hoofs of ani- mals, composed of a protein body containing a large amount of sulphur. The skeletons of zoophytes and the shells of mollusks contain a small quantity of animal matter, with carbonate of lime and small portions of phosphates of lime and magnesia and fluorid of calcium. Those of many crustaceans consist principally of phosphate of lime with a little magnesia and carbonate of lime. 34 530 ORGANIC CHEMISTRY. When the leather-like coating of the salpce and some other tunicate mollusks is digested with a solution of potash, the nervous and muscular portions are dissolved, and the in- soluble residue contains no nitrogen, and appears identical in composition to the cellulose of plants. NUTRITION OF PLANTS AND OF ANIMALS. 915. IN the order of nature, the animal creation derives its support from the vegetable, whose products are directly or indirectly the food of the former. A large number of animals subsist upon herbs or grains, and the flesh of these vegetable feeders is the food of carnivorous animals. Plants have the power of forming from carbonic acid, water, and ammonia, those bodies of the carbon series which are neces- sary for the support of animals. The nutrition of plants may then be properly considered first in order. 916. The organic substances essential to plants are cellu- lose and protein, to which we may perhaps add starch; these go to make up the simplest vegetable structure, and neither of them are probably ever wanting. In addition to these are sugar, gum, oils, resins, acids, alkaloids, and many other substances, some one or more of which are gene- rally present in different parts of plants. The history of the related series of cellulose, starch, sugar, and gum, and of the protein compounds, has been already given. These bodies in their organized forms always contain small and variable portions of salts of potash, soda, lime, and magnesia, with chlorine, phosphoric, sulphuric, and silicic acids. The juices of plants contain these same salts in solution, some- times with the addition of those of ammonia, and various vegetable acids, either free or in the form of salts. Theso mineral ingredients appear essential to healthy development; they perform, however, but a secondary part in the nutrition of plants, whose food consists essentially of water, carbonic acid, and ammonia, from which, as has been already said, they form the various organic substances, by the combina- tion of certain molecules and the elimination of certain others, in a manner similar to that which we have so often illustrated in the preceding pages. NUTRITION OP PLANTS AND ANIMALS. 531 917. Cellulose and the allied substances contain pre- cisely the elements of carbon and water, and may be formed from the elements of carbonic acid gas and water, cr rather from hydrated carbonic acid C 3 H a 6 , by the separation of oxygen; 12dX0 8 =0 JW H fl0 O fl0 +0 4S . Protein, which we have shown may be regarded as the amid of cellulose, is formed with the concurrence of the elements of ammonia, in a manner which will be at once understood. Sugar and gum differ from cellulose only by the elements of water, and the various vegetable acids and other matters contain- ing oxygen, hydrogen, and carbon, may be formed in a manner analogous to cellulose from carbonic acid and water, by the separation of oxygen. It is probable that the saline and alkaline matters in the juices exercise peculiar influences upon these processes, and conduce to the formation of the various products. 918. The oxygen set free in all these processes is evolved in the form of gas. If a branch of a green healthy plant is exposed, under an inverted bell-glass filled with water, to the sun's rays, minute bubbles of gas appear upon the leaves, and rise to the top of the vessel. They are pure oxygen, which is constantly evolved by all healthy plants when exposed to the influence of light. In darkness, the action is suspended or imperfectly performed, and the carbonic acid which is absorbed by the roots, is given off from the leaves instead of oxygen ; the leaves of plants also exhale large quantities of water. Although it is principally through the roots that carbonic acid, water, and ammonia are taken up, the leaves have also the power of absorbing water and gases for the support of the plant. If a plant is made to grow in a mixture of oxygen and carbonic acid gases, the latter is gradually absorbed and replaced by pure oxygen. Flowers and fruits, during the period. of their growth, however, reverse this process, and absorb oxygen from the atmosphere, while they evolve car- bonic acid gas. 919. The atmospheric waters falling upon the earth, con- tain in solution a portion of carbonic acid and a minute quantity of carbonate of ammonia, two ingredients which are always present in the atmosphere. The water dissolves from the soil a minute portion of earthy and alkaline salts, which are in part set free by the disintegration of the earthy minerals under the influence of water and carbonic acid 532 ORGANIC CHEMISTRY. In this form the different elements are taken up by tho rootlets of the plant, and while the carbonic acid and am- monia are assimilated in the way that we have seen, tho sulphates and phosphates furnish the portions of sulphur and phosphorus contained in vegetable protein, while their alkaline bases with the vegetable acids, form salts, which, being decomposed by heat, are the source of the alkaline carbonates, always found in the ashes of vegetables. The bitartrate of potash in the juice of grapes is an example of the occurrence of an organic potash salt. 920. Careful analyses of their ashes have shown that the nature and proportions of saline matters differ greatly in different plants, and that the long-continued cultivation of any species of plant upon the same soil may so far exhaust the soluble mineral matter as to render the soil unfruitful. In such circumstances, its fertility may be restored by the application of mineral manures, such as bone-dust, gypsum, and wood-ashes. A soil which has become unfitted for the growth of one plant may still contain the mineral substances necessary for the support of another, and hence the utility of an alternation of crops in agriculture. The ashes of tobacco contain, for example, a large amount of potash salts, and those of wheat and other cereal grains abound in phos- phate of lime, and contain but little potash ; so that a soil unfitted for tobacco may still produce good wheat, and vice versa. Many plants which grow in the vicinity of the sea contain a large amount of salts of soda; such are those that afford the impure alkali kelp or barilla. The amount of mineral matter in many of the fucoids or sea-weeds is very large, and the quantity of potash which they contain some- times exceeds that of the soda ; a fact which shows the curious power of plants to choose certain elements in preference to others, for the proportion of potash salts in sea-water is very small. The ashes of marine plants are also remarkable for containing salts of iodine, an element which cannot be detected in sea-water, but is contained in considerable quan- tity in the plants growing therein, and is even present in traces in many fresh-water plants. 921. Fertile soils generally contain a portion of organic matter, derived from the decomposition of roots, leaves, and other vegetable substances, and approaching to what hag been named humus or humic acid. This substance by its slow decomposition constantly evolves carbonic acid, and is NUTRITION OP PLANTS AND ANIMALS. 533 thus a source of carbon to the roots of plants. This organic matter also contains in its substance the various salts neces- sary for plants, and during its decay, sets them free in a soluble form. It is still further efficient by the power which it possesses, in common with charcoal, clay, and other poroua substances, of absorbing the ammonia contained in the air or evolved from the decomposition of azotized matters, and holding it in such a form that it is dissolved out by atmo- spheric waters, and brought to the roots of plants. It would also appear, from the experiments of Mulder, that humus possesses the power of forming ammonia with the nitrogen of the air. 922. Some chemists maintain that soluble forms of humus are directly absorbed by the roots, and thus constitute their food : there are however no proofs of such an absorption, and many arguments against it. It is well established that, if supplied with atmospheric waters and the proper mineral ingredients, plants will flourish and mature their seeds in a soil destitute of organic matter. Many plants are para- sitic, and grow without any connection with the soil ; they may be suspended in the air, and will continue to grow for years, absorbing food through their leaves, and generating cellulose, protein, and other organic bodies. The small portion of mineral matter which these plants contain, may be derived from the solution and absorption of the dust floating in the air. In the process of germination, the albumin of the moisten- ed seed becomes soluble, and its starch is converted jnto sugar : these substances serve to nourish the embryo plants, but when the roots and leaves are fully formed, the plant begins a new mode of life. Its carbon is derived from carbonic acid, and the decomposing organic matters of the soil serve only as sources of carbonic acid, ammonia, and salts. -We have seen how some of the fungi excite the decomposition of protein and sugar solutions, apparently assimilating a portion of the evolved carbonic acid and ammo- nia, and it is not improbable that the rootlets of the higher orders of plants may act in a like manner upon the organic matters in the soil, thus accelerating their decomposition. 923. Animal matters act beneficially as manures, by the ammonia which they evolve with the carbonic acid, in the pro- cess of decay. Bone-dust in addition, affords phosphates; and urine, besides its ammonia, contains a great variety of 534 ORGANIC CHEMISTRY. earthy and alkaline phosphates, and chlorids. Dilute solu- tions of sulphate, or other salts of ammonia, act as powerful stimulants to vegetation, and the efficacy of guano, which is the decomposing excrement of sea-birds, is due in great part to the ammonia which it yields. In its recent state it con- tains besides inorganic salts a large portion of urate of ammonia, from which, during decomposition, oxalate and other salts of ammonia are formed. Wheat manured with guano is said to contain a larger proportion of protein than that grown upon the same soil without the manure. The efficacy of gypsum depends in part upon its furnishing lime and sulphates to plants, and in part apparently from its power of condensing and retaining in the form of sulphate, the ammonia from the air and other sources. The ammo- nia contained as carbonate in atmospheric waters being brought in contact with earthy salts in the soil, must always be brought to the roots of the plants, in the form of sulphate or chlorid, or as a soluble ammonia-magnesian salt. 924. The food of animals, whether they feed upon flesh, or upon vegetable substances, consists of protein in its vari- ous forms, starch, sugar, gum, and fat, to which, in the case of carnivorous animals, gelatine is to be added. The vege- table feeders convert the protein bodies of their food into muscular fibre, which is afterward the food of the carnivora. These protein compounds, which can alone form blood and muscle, are to be distinguished from the non-azotized por- tions of the food, and have been called the plastic elements of nutrition, in distinction from the- latter, which are named the plastic elements of respiration, being consumed in that process. Gelatine probably belongs to the latter class ; it has never been found in the blood, and is supposed to be converted into sugar and ammoniacal salts. 925. The power of producing from simpler bodies, the complex organic products, does not belong to the animal system. The process of digestion has already been briefly described ; the saliva, bile, gastric and pancreatic juices exert upon the food an essentially disorganizing, destroying action, which reduces it to a soluble plastic form, fit for assimila- tion, in which process the protein assumes an organic struc- ture, and forms blood and muscular fibre, while gelatine is probably formed from a portion of it, by a reaction not well understood. The sugar contained in the food or formed from the starch, appears to be in great part absorbed by NUTRITION OP PLANTS AND ANIMALS. 535 the coats of the stomach and small intestines, in the same way as water and saline fluids, and thus finds its way into tne veins, without passing through the chyle-duct. It is directly oxydized in the circulation, and in a few hours after its ingestion disappears entirely from the blood. Alco- hol is absorbed in the same way, and oxydized in the circu- lation, being converted into water and carbonic acid. Ace- tic acid has been found in the blood as an intermediate product of the oxydation of alcohol, and formic acid is said to have been detected after the ingestion of sugar. The fat, which, with the protein, passes through the chyle into the blood, is deposited in the adipose tissues : besides that contained in the food, it is probable that fat is formed by some process from the other aliments; its spontaneous production from protein has been already described, and we have seen how fatty acids, like the butyric, valeric, and capric, may be formed from sugar, and by the oxydation of protein. To these considerations may be added some ex- periments which seem to show that geese, in the process of fattening, secrete a greater amount of fat than is contained in the food which they consume. 926. It has been shown that the blood in the lungs dis- solves a large portion of oxygen gas. The cells of that organ are filled with air in the process of respiration, and the minute branches of the pulmonic artery are spread over the walls of the cells. The delicate arterial membrane being permeable to gases, oxygen is absorbed and carbonic acid gas given off through it. The use of the oxygen in the oxydation of sugar and alcohol has already been shown ; the whole of the oxygen absorbed, is not given out in the form of carbonic gas, but is in part exhaled as aqueous vapor from the lungs, and from the skin. There is, in addition to this oxydizing process, a constant action- going on in the tissues, which results in their disor- ganization and conversion into simpler forms. This is effected in the capillary vessels with the concurrence of the dissolved oxygen of the arterial blood; protein is decomposed, with the addition of oxygen, into a set of highly carbonized bodies, the fatty acids of the bile ; and of highly azotized sub- stances, urea and uric acid, which are carried by the veins to the liver and kidneys, and are separated from the blood; in the one case to be voided in the urine, and in the other to be returned to the alimentary canal ; and there to perform 536 ORGANIC CHEMISTRY. gome part in the nutritive process. It is not improbable that the acids of the bile may be converted into ordinary fats, which are thus indirectly formed from the protein tissues. Lactic acid on the one hand, and creatin and in- osinic acid on the other, are also products of this metamor- phosis, which has been called the destructive assimilation. Its relation to the matter of the brain and nerves is not yet well understood. 927. The oxydation of fat, by which it is converted ulti- mately into carbonic acid and water, does not probably take place in the circulation, as in the case of sugar, but is effected through the capillary vessels, in the tissues where the fat has previously been deposited. When the amount of sugar, and farinaceous food is great, animals grow fat, for the glu- cose preserves the fatty tissues from the influence of the oxygen, which is consumed in the oxydation of the sugar and the change of the protein tissues. If, however, the supply of farinaceous food is diminished, the fat is removed by oxydation faster than it is deposited, and finally dis- appears. 928. The object of nutrition, in its wider sense, is to supply the waste of the tissues, and satisfy the demands of the respiratory process, thus preserving the balance of the system. In those animals that feed upon flesh, the fat con- tained in their food or formed from protein, supplies the wants of the latter process; while in those animals which live upon vegetables, or like man upon a mixed diet, the sugar, alcohol, and farinaceous portions of the food supply more or less completely the demands of the respiratory process, and, if these be in excess, the fat contained in the food often accumulates in the system. The waste of the muscular, and probably also of the nervous substances, appears to sustain an intimate relation to the amount of muscular and nervous activity of the system,* while the oxydation of the respiratory elements is related to animal heat. Respiration is essential to life, and even in those animals which do not breathe air, the process is ef- fected through oxygen dissolved in the water. We have * The condition of sleep, in which the muscular and nervous energies are to a great degree suspended, probably sustains an important relation t,c the nutritive process, particularly as related to the brain and nerves. The different functions of plants in light and darkness suggest an analog^ in this connection, which is worthy of consideration. NUTRITION OP PLANTS AND ANIMALS. 537 shown that oxygen is necessary to preserve the life of the blood corpuscles out of the body ; and it is the deprivation of air which causes the death of animals, by preventing the aeration of the corpuscles, and destroying the vitality of the blood. The introduction of large quantities of alcohol into the system produces a similar asphyxia, by rapidly con- suming the oxygen, and thus preventing the proper aeration of the blood. The presence of phosphuretted fat, mentioned in the analyses of the blood before given, is said to be confined to the venous blood, which contains no soluble phosphates ; in the arterial blood the fat is freed from phosphorus, which is found in the form of phosphates in the serum. 929. The oxydation of carbon and hydrogen compounds, converting them into carbonic acid and water, is supposed to be the source of vital heat in animals ; the amount of carbon thus thrown off from the lungs of a full-grown man is equal to about seven ounces in twenty-four hours. In some instances of disease, however, where the respiratory function has been suspended for many hours, the heat of the body has remained undiminished. Plants have equally to a certain extent, the power of maintaining a temperature above that of the atmosphere : this is most evident in the leaves and young shoots, where vegetation is most active; but in plants the vital process is accompanied with a con- stant evolution of oxygen, from an action the very reverse of that which goes on in animals. Heat is a common result of chemical changes, even where oxygen is not absorbed, and there is no difficulty in understanding its production in any of the processes of assimilation. It is, however, probably true, that in healthy animals the oxydation of carbon sustains a direct relation to the heat evolved. Hence it is that in warm climates, where the loss of animal heat is small, farinaceous matters, containing a large amount of oxygen, and as it were, partly oxydized, are the food of the people, and are found most congenial to the taste j while the inhabitants of arctic regions consume large quantities of fat and oil, less oxygenized species of food, which are found not only agreeable, but necessary to support the demands of the respiratory process, and to resist the intense cold. 930. The elements of the food of plants are taken from the air, earth, and waters, and by the forces of the living organism are formed into woody fibre,, starch, sugar, and 538 ORGANIC CHEMISTRY. protein, which serve for fuel and for the nourishment 01 animals. By the processes of life, by combustion and decay, these elements are again set free in the forms of water, carbonic acid, and ammonia, and enter once more into the current of organic life. In this way, the results of the decomposition of organic matters are removed from the atmosphere, which would otherwise be vitiated by them, and the carbonic gas which is taken up by plants, is re- placed by an equal volume of oxygen gas, so that the purity of the air is preserved. In the mutual dependence of the great processes of animal and vegetable life and decay, there is seen a system in which no one process is its own end, but is implicated in every other, and can be understood only in its relation to tho Universe, and to that Being who is at once the efficient and final Cause of all creation. APPENDIX, CONTAINING TABLES OP WEIGHTS AND MEASURES, OP CORRESPOND- ING THERMOMETRICAL DEGREES, HYDROMETER TABLES, STRENGTH OF ALCOHOL, AND ANALYSES OF WATERS. WEIGHTS AND MEASURES. AVOIRDUPOIS, OR IMPERIAL WEIGHT. 1 drachm 16= 1 ounce 256= 16= 1 pound 3584= 224= 14= 1 stone 28672= 1792= 112= 8= 1 hundred weight... Equivalents in Troy grains. 27-34 437-5 7000- 98000- 784000- 473440=35840=2240=160=20=1 ton 15680000- TROT WEIGHT. 1 grain. 24 " = 1 pennyweight. 480 " = 20 " = 1 ounce. 6760 " =240 " =12 " : :1 pound. APOTHECARIES' WEIGHT. 1 grain, gr. 20 " =1 scruple, 9 60 " =3 " =1 drachm, 3. 480 " = 24 " = 8 " =1 ounce, %. 6760 " =288 " =96 " =12 " =1 pound, Ib. 539 540 APPENDIX. APOTHECARIES', OR WINE MEASURE. Adopted in the United States and Dublin Pharmacopoeias. Troy grains of pure water, Cubic inches. at 6QO F. 1 minim, trg -00376 = 0-95 60= 1 fluid-drachm, f 3 -2256 = 56-95 480= 8= 1 fluid-ounce, f g..-.. 1-8047 = 455.607 7680= 128= 16=1 pint, 28-8750 = 7289-724 61440=1024=128=8=1 cong 231-000 =58317-798 The imperial gallon contains of water, at 60 70,000- grains. The pint (^th gallon) 8,760- " The fluid-ounce (^th of pint) 437-5 The pint equals 34-66 cubic inches. The American standard gallon contains of pure water, at 39 -83, 68-372 Troy grains. The French kilogramme= 15434- grains, or 2-679 Ibs. Troy, or 2-205 Ibs. avoirdupoids. The gramme =15-4340 grains. " decigramme = 1-5434 " " centigramme = -1543 " " miligramme = -0154 " The metre of France =39-37 inches. " decimetre = 3-937 " " centimetre = -394 " " millimetre = -0394 " TABLE OP THE CORRESPONDING DEGREES ON THE SCALES OF FAHRENHEIT, REAUMUR, AND CENTIGRADE, OR CELSIUS. Fahr. Reaum. Cent. 212 203 194 185 176 167 158 80 76 72 68 64 60 56 100 95 90 85 80 75 70 Fahr. Reaum. Cent. Fahr. Reaum. Cent 149 140 131 122 113 104 95 86 77 68 69 52 48 44 40 36 32 28 24 20 16 12 65 60 55 50 45 40 35 30 25 20 15 50 41 32 23 14 5 4 13 22 31 40 8 4 4 8 12 16 20 24 28 32 10 5 5 10 15 20 25 30 35 40 APPENDIX. 541 HYDROMETER TABLES. COMPARISON OF THE DEGREES OP BATTM^'s HYDROMETER, WITH THB REAL SPECIFIC GRAVITY. 1. For Liquids Heavier than Water. Osg tea. Specific gravity. Degrees. Specific gravity. Degrees. Specific gravity. Degrees. Specific grarity. 1-000 20 1-152 40 1-357 60 1-652 1 1.0*7 21 1-160 41 369 61 1-670 2 1-013 22 1-169 42 381 62 1-689 3 1-020 23 1-178 43 395 63 1-708 4 1-027 24 1-188 44 407 64 1-727 5 1-034 25 1-197 45 420 65 1-747 6 1-041 26 1-206 46 1-434 66 1-767 7 1-048 27 1-216 47 1-448 67 1-788 8 1-056 28 1-225 48 1-462 68 1-809 9 1-063 29 1-235 49 1-476 69 1-831 10 1-070 80 1-245 50 1-490 70 1-854 11 1-078 31 1-256 51 1-495 71 1-877 12 1-085 32 1-267 52 1-520 72 1-900 13 1-094 33 1-277 53 1-535 73 1-924 14 1-101 34 1-288 54 1-551 74 1-949 15 1-109 35 1-299 55 1-567 75 1-974 16 1-118 36 1-310 56 1-583 76 2-000 17 1-126 37 1-321 57 1-600 18 1-134 38 1-333 58 1-617 19 1-143 39 1-345 69 1-634 2. Baume's Hydrometer for Liquids Lighter than Water. Degrees. Specific gravity. Degrees. Specific gravity. Degrees. Specific gravity. Degrees. Specific gravity. 10 1-000 23 918 36 849 49 789 11 993 24 913 37 844 50 785 12 986 25 907 38 839 51 781 13 980 26 901 39 834 52 777 14 973 27 896 40 830 53 773 15 967 28 890 41 825 54 768 16 960 29 885 42 820 55 764 17 954 30 880 43 816 56 760 18 948 31 874 44 811 57 757 19 942 32 869 45 807 58 753 20 936 33 864 46 802 59 749 21 930 34 859 47 798 60 745 22 924 35 854 48 794 642 APPENDIX. TABLES OF ANALYSES Nos. 1 to 6, inclusive, show the ingredients in 1 American standard and Nos. 9 and (1) (2) (3) (4) Ingredients. Schuylkill River. Croton River. Charles River. Spot Pond. 1 2 3 4 6 6 7 8 9 Chlorid of Potassium... Chlorid of Sodium Chlorid of Ammonium. Chlorid of Calcium Chlorid of Magnesium. Chlorid of Aluminum... Bromid of Sodium Bromid of Magnesium. 1470 0094 167 372 166 1547 0420 3969 10 11 Sulphate of Potash Sulphate of Soda ... 153 3816 2276 1*> Sulphate of Lime 235 2624 13 14 15 16 17 18 Sulphate of Magnesia.. Sulphate of Alumina... Nitrate of Magnesia.... Phosphate of Lime Phosphate of Alumina. Alumina 0570 832 0973 and iron. 1081 19 Silicic Acid 0800 077 traces traces 20 21 22 23 24 25 26 27 28 Carbonate of Soda Carbonate of Baryta... Carbonate of Strontia.. Carbonate of Lime Carbonate of Magnesia Carbon, of Manganese. Carbonate of Iron Fluorid of Calcium Salts of Soda with the ") Nitric and Organic L Acids j 1-8720 3510 1-6436 2.131 662 traces 1-865 1610 0399 5291 3722 1420 Total 4-2600 6-660 1-6680 1-2468 Carbonic Acid Gas in \ cubic inches / Analyzed by 3879 Author 17-418 Author 0464 Author 38-79 Author NOTE. No. 1 is the supply for the city of Philadelphia, No. 2 for New York, and No. 5 for Boston ; Nos. 4 and 6 are small lakes in the vicinity of Boston, and No. 3 is a river in Massachusetts, emptying near Boston. APPENDIX. 543 OF NATURAL WATERS. gallon, (or 58-372 grains.) Nos. 7, 8, and 9 are in one pound Troy, 10 in 1000 parts. (5) (6) (7) (8) (9) (10) Long Pond. Mystic Pond. Saratoga C. Spring. Seltzer Spring. Sea Water Brit. Chan. "Water of Dead Sea. 1 .-0380 1590 1-6256 2685 7660 traces 2 0323 27-911 19-6653 12-9690 27-9590 78-650 3 ... ... 0326 traces ... 4 0308 1544 ... 28-220 6 0764 ... ... ... 3-666 60-950 7 ... 1613 ... * 8 ... ... ... ... 0290 7-950 9 ... ... 0046 traces ... 10 ... ... 1379" 2978 ... ... 11 ... ... ... ... ... ... 12 ... 1-2190 ... 1 1-4060 traces 13 1020 1-9768 ... ... 2-2960 ... 14 ... 4478 ... ... ... ... 15 ... ... 1004 ... 16 ... ... ... 0007 ... ... 17 ... 2810 ... 0020 ... ... 18 0800 ... 0069 ... ... 19 0300 5559 1112 2265 ... ... 20 ... ... 8261 4-6162 ... ... 21 ... ... ... 0014 ... 22 ... ... 0672 0144 ... 23 2380 9894 5-8531 1-4004 0330 M 24 0630 1698 4-1155 1-5000 ... 25 ... ... 0202 ... ... 26 ... 0173 ... 27 ... ... ... 0013 ... ... 28 ^ -5295 ... ... ... ... ... 1-2220 32-7671 34-7452 21-2982 35-255 165-770 in 100 c. in. 10-719 10-313 114- 126- Author. Author. Schweitzer. Struve. Schweitzer. Author. No. 7 is the well-known "Congress Spring." No. 8 is a cele- brated German Spa. No. 10 was collected by J. D. Sherwood, Esq., April, 1843, near the mouth of the Jordan. 544 APPENDIX. ABSTRACT Of the Table of Lowitz, showing the proportion by weight of absoiuU or real alcohol in spirits of different densities. Sp, gr. at 60. Per cent, of real alcohol. Sp.gr. at 60. Per cent, of real alcohol. Sp. gr. at 60. Per cent, of real alcohol. 0-796 100 0-881 66 0-955 32 0-798 99 0-883 65 0-957 31 0-801 98 0-886 64 0-958 30 0-804 97 0-889 63 0-960 29 0-807 96 0-891 62 0-962 28 0-809 95 0-893 61 0-963 27 0-812 94 0-896 60 0-965 26 0-815 93 0-898 59 0-967 25 0-817 92 0-900 58 0-968 24 0-820 91 0-902 57 0-970 23 0-822 90 0-904 56 0-972 22 0-825 89 0-906 55 0-973 21 0-827 88 0-908 54 0974 20 0-830 87 0-910 63 0-975 19 0-832 86 0-912 52 0-977 18 0-835 85 0-916 61 0-978 17 0-838 84 0-917 60 0-979 16 0-840 83 0-920 49 0-981 15 0-843 82 0-922 48 0-982 14 0-846 81 0-924 47 0-984 13 0-848 80 0-926 46 0-986 12 0-851 79 0-928 46 0-987 11 0-853 78 0-930 44 0-988 10 0-855 77 0-933 43 0-989 9 0-857 76 0-935 42 0-990 8 0-860 75 0-937 41 0-991 7 0-863 74 0-939 40 0-992 6 0-865 73 0-941 39 0-867 72 0-943 38 0-870 71 0-945 37 0-872 70 0-947 36 0-874 69 0-949 35 0-875 68 0-951 34 0-879 67 0-053 33 OF THE UNIVERSITY INDEX. The references are to the number* of the sections. ACETOL, 736. Acetamid, 750. Acetates, 744. Acetonitryl, 750. Acetene, 723. Acetene, perchloric, 725, Aceton, 752. Acetic acid, quick process for, 741. Acetic ether, 750. Acetic amylic ether, 759. Acetamid, 686. Acid, acetic, 739 ; benzoic, 788; aco- nitic, 814; acrylic, 763; adipic, 773; allophanic, 862; allanturic, 873; alloxanic, 874; anthropic, 769 ; anisic, 795 ; antimonic, 605 ; anthranilic, 843; amygdalic, 828; amalic, 878; arsenic, 610; arseni- ous, 609; aspartic, 814; benzo- glycollic, 872; boraeic, 387; bro- mic, 296; bromohydric, 430; butyric, 764; camphoric, 800; capric, caproic, caprylie, 764; carbazotic, 790; carbonic, 366, 688 ; carminic, 837; cerebric, 912 ; cerotic, 761 ; chloracetic, 750 ; chloric, 290 ; chlorochromic, 574 ; chlorohydric, 424; chlorus, 292; cholic, 879; cholalic, choloidic, cholonic, 879 ; cholelc, 880; chro- mic, 574; cinn&mic, 796; citra- conic, 814; citric, 814; columbic, 594; cuminic, 793; cyanuric, 856,-dialuric, 876; elaidic, 769; enanthylic, 766; ethalic, 760; evernic, 835; ferric, 566; ferro- cyanic, 866 ; fluoboric, 390 ; fluo- hydric, 433 ; fluosilicic, 385 ; for- mic, 756; fulminic, 858; gallic, 815 ; glycollic, 871; hippuric, 871; humic, 921; hydrioclic, 431; hydrobromic, 430; hydrochloric, 424 ; hydrocyanic, 844 ; hydro- fluoric, 433; hydroselenic, 439; hydrosulphuric, 435; hyperiodic, 301; hyocholic and hyocholalic, 881 ; hypochlorous, 291 ; hypocula- ric, 292; hydrotelluric, 439; hypo- nitric, 345 ; hypophosphorous, 352; iodic, 301; inosinic, 902; iodohy- dric,431; isatinic, 843; kinic, 819; lactic, 699 ; leoanoric and lecano- rinic, 834; lithic, 873; malic, 812; manganic, 560; margaric, 767; meconic, 820 ; metacetonic, 752 ; mellisic, 761 ; malamic, 814 ; mesoxalic, 874; molybdic, 594; nitric, 334 ; nitromuriatic, 429 ; nitrophenisic, 790 ; nitropicric, 790; nitroprussic, 868; nitrosali- cylio, 830; nitrous, 344; oleic, 768; opianic, 820; orselinic, or- sellic, 834; oxalic, 807; oxamic, 808; palmitic, 767; parabonic, 877; para-stearic, 767; pectic, 704; pelargonic, 766; perman- ganic, 560; phocenic, 766; pyro- gallic, 815; phosphorus, 353; phosphoric, 354; picric, 790; pimelie, 773; pimaric, 803; pla- tinocyanic, 869; propionic, 752; prussic, 844; pyroligneous, 742; quinic, 819; racemic, 811; mec- onic, 820 ; ricinoleic, 770 ; rubery- thric, 836 ; saccharic, 701 ; sali- cylic, 794 and 830 ; sebacic, 773; selenic, 327 ; selenhydric, 439 ; selenious, 327 ; silicic, 381 ; stan- nic, 597 ; stearic, 767 ; suberic, succinic, 773 ; sulphamylic, 758 ; sulphomethylic, 754; sulphotha- lic, 760 ; sulphovinic, 726 ; sul- phindigotic, 842 ; chloracetic, 750 ; sulphocyanic, 851 ; sulpho- benzenic, 789; sulphydric, 435; sulphoglyceric, 764; sulphurous, 310 ; sulphuric, 315 ; sulphopur- puric, 842; sylvic, 803; tannic, 815; tartaric, 809; tartramic, 813; toluylic, 793 ; telluhydric, 439 ; tellurous, 328; thionuric, 876; titanic, 594; trigenic, 862; 545 546 INDEX. tungstic, 594 ; ulmic, 711 ; uric, 871, 873; valeric (valerianic), 759; xanthic, 732. Acids, fatty, list of, 771 ; vegetable, 806; vinic, 720; monobasic, bi- basic and tribasic, 648; cou- pled, 652; named, 249; of the urine and of bile, 871 ; theory of, 481, 646. Aconitine, 825. Acrolin, 762. Affinity, chemical, 265 ; circumstan- ces which influence, 268. Agriculture, chemistry of, 920. Air-pump, 22; syringe, 125. Air, analysis of, 332. Alabaster, 537. Alanine, 860. Albumin, animal, 883; vegetable, 884. Alcohols, 717 ; products of its oxy- dation, 736; amylic, 758; me- thylic, 753 ; sulphur, 719. Alcohols and acids, relations of, 720. Aldehyd, 736; sulphur aldehyd, 738. Algaroth, powder of, 606. Alizarine, 836. Alkanet, 837. Alkalimetry, 497. Alkaloids, of the alcohol series, 776 ; vegetal, 816; of ammonia, 817; of cinchona, 818; of opium, 819. Alcargen, 783 ; alcarsine, 782. Allantoine, 873. Alazarine, 836. Alloxan and Alloxantine, 875. Alloys, 473. Almonds, essential oil of bitter, 785. Alumina, 549 ; acetate of, 744 ; sili- cates of, 551 ; sulphate of, 550. Aluminum, 548. Alums, 550. Amalgams, 473; Amalgamation, 191. Amarine, 787. Ammeline and ammelid, 857. Amids, anhydrid, 686. Ammonia, 440, 681 ; origin of, 441 ; acetate of, 744 ; bin-iodized, 681 ; hydrosulphuret of, 520; oxalu- rate of, 877; present in the at- mosphere, 331; stibethic, 781; trichlorinized, 681 ; salts of am- monia, 519 ; water of, 446 ; thio- nurate of, 876 ; salts of, 683. Ammonium, 518; compounds of, 519 ; cyanid, 846 ; chlorid of, 519 ; sulphuret of, 520. Ampere's theory, 203. Amygdaline, 828. Amylic ether, 758. Amylic alcohol, products of its oxyd- ation, 759. Amylol, 701, 758. Amylamine, 778. Analysis of organic bodies, 664. Anhydrous sulphuric acid, 320, Aniline, 792 ; nitric, 792. Aneroid Barometer, 30. Anilids, 792. Anethol, 795. Animal electricity, 220. Animals, nutrition of, 915 : food of. 924. Anthracite, 712. Anthracen, 715. Antimony, 604; oxyds of, 605; chlorids of, 606; glass of, 605; sulphurets of, 607; tartrate of, and potash, 607. Aphlogistic lamp, 410. Aqua regia, 429; ammonise, 446; fortis, 334. Arbor Dianse, 627 ; Saturni, 587. Argol, 809. Archil, 834. Aricine, 819. Aragonite, 540. Arrowroot, 705. Arsenic, 608 ; as a poison, detection of, 613; chlorid of, 611; oxyds of, 609 ; Marsh's test for, 6)3 ; re- duction of, 608; metallic, 608; arsenic acid, 610; Reinsch's test, 613; sulphurets of, 611. Arseniuretted hydrogen, 612. Arsine, 782. Artesian wells, temperature of, 81. Ashes of plants, 920. Asparagine, 814. Atmosphere, chemical history of, 331 ; analysis of, 332 ; mechanical properties of, 20 ; weight of, 26, 26, 27, 31 ; determination, den- sity of, 39 ; limits of, 32. Atomic weights, table of, 238 ; vo- lumes, 260. Atoms, 13; specific heat of, 261; polarity of, 42. Atropine, 825. Attraction of gravitation, 10; che- mical, 8 ; mechanical, 8 ; capilla- ry, 16. INDEX. 5-17 Aurum Musivum, 599. Azote, see Nitrogen, 329. Balsams, 796. Barium, 526. Barometer, 27, 29 ; Aneroid, 30. Barley-sugar, 691. Baryta, 527; carbonate of, 530; nitrate of, 529; sulphate of, 529. Batteries, galvanic, 190; Groves', 195; Bunsen's, 196; frog, 221; Daniels', 193 ; Smee's, 192. Beeswax, 761. Benzamide, 786 ; Benzoine, 787. Benzene, or Benzole, 789. Benzoline, 787, 825. Benzile, 787 ; Benzonitryl, 788. Benzophenon, 793. Benzosalicine, 831. Benzohelicine, 831. Benzoilol, 651, 785; chlorinized, 786. Bile, 905 ; acids of, 879. Biliary calculi, 881. Bibasic acids, 648. Bizmuth, 600 ; oxyd of, 601 ; nitrate of, 602 ; fusible alloy, 603. Bituminous coal, 711. Bleaching powders, 541. Blood, 896; color and globules of, 900. Blowpipe, compound, 411; mouth, 463. Blue pill, 617. Boiling, phenomena of, 129 ; in va- cuo, 133 ; boiling-point, 128 ; ele- vated by pressure, 136. Bones, 913. Bouquet of wine, 766. Boron, 386; com 387; with hydrogen, 388 ; chlorid of, 389 ; fluorid of, 390. Borax, 516. Brain and nervous matter, 912. Bright's disease, 900. British gum, 705. Bromine, history of, 294 ; properties of, 295. Bromic ether, 723. Brucine, 821. Butter and butyrine, butyror e 764; butter of antimony, 606. Buffy coafe of blood, 900. Burning oil, 797. Cadmium, 584. Caffeine, 823. Calcareous spar, 540. Calcium, properties of, 533 ; chlorid of, 536; fluorid of, 538; oxyd of, 534. Caloric, 79 ; Calorimetry, 117. Calculi, urinary, 908. Calomel, 619. Camphene, 797. Camphor, 800 ; Borneo, 801. Cane sugar, 691. Candles, stearine, 772. Calculi, biliary, 881. Caoutchouc, 804; Capacity for heat, 117. Capillary attraction, 16. Caprylol, 774. Caustic potash, 489. Carbonic acid, 688 and 366; lique. faction and solidification of, 151; how removed from wells, 370 ; of atmosphere, 371; constitution of, 372 ; theoretical density of, 657. Carbonic oxyd, 373 and 689. Carthamus and carthamine, 837. Caprylol, 774. Carburetted hydrogen, heavy, 450. " " light, 450. Carbon, 357; bisulphuret of, 376; compounds with hydrogen, 450 ; nitrogen, 377; compounds with oxygen, 365 ; oxyd of, 373 ; den- sity of vapor of, 657 ; series, che- mistry of, 638. Cartesian devil, 38. Castor oil, 770. Casein, 883 ; vegetable, 884 j chan- ges to a peculiar fat, 890. Cathode, 227. Catalysis, 271. Catalan forge, 570. Catechu, 815. Cassius, purple of, 631. Cellulose, 707. Cerium, 556. Ceruse, 588. Cerotal, 761. Chameleon mineral, 560. Charcoal, 362 ; absorbs gases, 563 ; and odors, 364. Change of state by heat, 121. Chemical transformations, 642, Chloral, 738. Chlorimetry, 541. Chlorophyle, 838. Chemical affinity, 265 ; attraction, 8 ; nomenclature, 243 ; philoso^ phy, 235. Cinchona bark, 818. 48 INDEX. Cinchonine, 818 ; bichloric and bi- bromic, 819. Chinovatine, 819. Chlorine, preparation, 282 ; and pro- perties, 284 ; allotropism of, 288 ; compounds with oxygen, 289 ; passive condition, 423. Chloroform, 755. Chlorocarbonic oxyd, 375. Chlorarsine, 782. Cholesterine, 881. Chromium, 571; oxyd of, compared, 572; chloridof, 574; compounds with salts of, 575. Citric acid, 814. Citraconid, 814. Cinchona, alkaloids of, 818. Chyle, 906. Classification of elements, 272. Cleavage of crystals, 51. Coal, 361 ; gas from, 456 ; products of its distillation, 715. Coal tar, 715. Cold, greatest natural, 152. Cobalt, 580 ; chlorid of, 580. Cobaltocyanids, 869. Codeine, 820. Cohesion, 11 and 14; of fluids, 15; of gases, 19. Colors, complementary, 70. Colomb's electrometer, 168. Collodion, 710. . Coloring matters described, 833; red, 836; from lichens, 834; yel- low, 838. Columbium and Columbite, 594. Compounds, how named, 243. Combination, mode of, in organic bodies, 642. Combination, laws of, 239 ; by vo- lume, 257 and 656; by direct union, 654. Combustion, a source of heat, 80 ; nature of, 457 ; heat of, 458 ; and structure of flame, 457 and 460. Complementary colors, 70. Congelation, 123. Conine, 827. Conduction of heat, 88. " " in curves, 90. Convection of heat, 94. Copper, 590 ; acetate of, 749 ; al- loys of, 593; nitrate of, 593; oxyds of, 591 ; sulphate of, 592. Cornudum, 549. Copal, 803. Corpuscles of blood in frogs and man, 896. Cotarnine, 820. Corrosive sublimate, 619. Cream, 910. Cream of tartar, 809. Creatine and creatinine, 901. Cryophorus, 143. Crystallization, circumstances Influ- encing it, 41 ; nature of, 40. Crystalline forms, 43. Crystals, measurement of, 52. Culinary paradox, 134. Cupellation, 623. Cyanates, 848. Cyanids, 844 ; complex, 866 ; double, 853 ; relations to alcohol series, 859. Cyanid of potassium, 846. Current, passage of in cells of a bat- tery, 185 ; strength of, 186 ; se- condary, 214. Cuminal, 793; Cumene, 793. Cudbear, 833. Cyamelid, 848. Cyanoxosulphid, 851. Cyanogen, 377, 847. Cyanic compounds, 844. Cyanates, 848. Cyanethene, 859. Cyaniline, Cyamelaniline, and Cy- anharmaline, 863. Cyamellurate of potash, 852. Cymen, 793, 801. Daniell's battery, 193. Davy's safety lamp, 464. Decomposition of water, 224, 400. Deflagration, 198. De La Rive's ring, 205. Density of vapours,142,656, and 676. Desiccation, 321. Daturine, 825. Destructive distillation of wood, 713. Dew, formation of, 144; point, 144, Daniels' hygrometer, 146. Dextrine, 705. Diabetes mellitus, 692, 908. Diabetic sugar, 908. Diamond, history and forms of, 358. Diachylon, plaster, 586, 764. Diastase, 706. Dicyanid, perchloric, 855. Didymium, 556. Diffusion of gases and vapours, 147 Digestive process, nature of, 904, Dimorphism, 264. INDEX. 549 Dipping needle, 160. Distillation of alcohol, 717. Dyslysine, 879. Dobereiner's observation, 409. Du Fay's hypothesis, 172. Dutch liquid, 454 and 735. Earth's magnetism, 159. Eel, electrical, 222. Eggs, 911. Elasticity of air, 21. Electrical machines, 166. Electrical excitement, 164; eel, 222; polarity, 165. Electricity, 153 ; conductors of, 169; of high steam, 178 ; statical, 163 ; distribution of, 170; magneto, 217; thermo, 218 ; animal, 220 ; theo- ries of, 172. Electricity of chemical action, 179 ; effects of, 197; constant light from, 200. Electro - chemical decomposition, 223 ; conditions of, 228 ; theory of, 233 ; magnetism, 201 ; mag- netic telegraph, 211 ; metallurgy, 234 ; plating, 870. Electro-magnetic motions, 210, 216. Electro-magnets, 207. Electrolysis, 227 ; order of, 231. Electrophorus, 177. Electroscopes, 167. Electrotype, 234. Elements, denned, 13 ; table of, 238; laws of combination, 235, 239; non-metallic, classified, 272. Emetic, tartar, 607 and 810. Emetine, 825. Emulsine, 828. Endosmose and exosmose, 18. Epsom salts, 545. Equivalents, table of, 238. Equivalent proportions, 239. Equivalent substitution, 643. Etna], ethol, 760. Ethammonium, 777. Ethamine, 777. Ether, amylic, 758 ; acetic amylic, 759; butyric, 765; chloric, 755; hydrobromic, 723; chlorohydric, 723 ; hydriodic, 723 ; hyponitric, 725 ; hydrovinic, 727 ; himinife- rous, 55; lecanoric, 834; nitric, nitrous, 724-5; oxalic, 808; per- chloric, 725 ; silicic, 733 ; sulphu- ric, 730. Ethers, 723. Etherilene and etherine, 735. Euchlorine, 291. Eudiometry. 332; by hydrogen. 405, 407. Eupion, 714. Evaporation, 140; influence of pres- sure on, 141 j cold produced by. 143. Expansion by heat, 100 ; of solids, 101; of liquids, 100, 102; of gases, 105; of water, 103; beneficial re* suits of, 104. Faraday's researches in magnetism, 161 ; in liquefaction, 150; in elec- tricity, 227. Fats, and substances derived from them, 775. Feldspar, 551. Fermentation by proteine bodies, 891 and 694; butyric, 700; vis- cous, 697. Ferricum and ferrosum, 649. Ferrocyanids, 865. Ferricyanids, 867. Fibre, woody, 707. Fibrin, animal and vegetable, 882, 883 ; change of, by potash, 889 ; by moisture, Ac., 890. Flame, structure of, 460; of the mouth blowpipe, 463; effects of wire gauze on, 464. Flesh fluid, 901. Fluidity, 121 ; heat of, 122. Fluorine, 302. Fluor-spar, 538. Fluids, properties of, 15 ; conduction of heat in, 92. . Food of animals, 924. Formene, tri-chlorinized, 755. Formulas, divisibility of, 659. Franklinian hypothesis, 172. Freezing mixtures, 124. Friction, a source of heat, 80. Frog's legs, 179, 180, 221. Fulminates, 858. Fungi in fermentation, 695 and 893 Fousel oil, 758. Fusible metal, 603. Galena, 585. Gall-nuts, 815. Galvanism, 179; quantity and in tensity in, 186. Galvanic batteries, 190-6. Galvanoscopes, 202. Gases, laws of the conduction of heat in, 93 ; diffusion and efiusioL, 147; passage of through mem- b ranee, 149 ; liquefaction of, 150 ; 550 INDEX. management of, 280 ; combine by volume, 257. Gasholders, 281. Gastric juice, 904. Gay Lussac's silver assay, 623. Geine, 711. Gelatine, sugar of, 895. Germination of seeds, 900. German silver, 579. Glass, 552; manufacture of, 554. Glauber's salt, 509. Glucinum, 556. Glucose, 692. Gluten, 884. Glycerides, 762. Glycerine, 762. Glycocoll and glycooine, 872. Gold, 628; oxyds and chlorids of, 630 j wash, 631. Goniometer, common, 52; Wollas- ton's, 53. Goulard's extract, 746. Grape sugar, 692. Graphite, 360. Grove's battery, 195. Guano, 923. Guarana, 823. Gum, 703; elastic, 804 j resins, 803; Gun cotton, 710. Gunpowder, composition of, 501. Gutta percha, 805. Gypsum, 537. Hardness, 14. Hare's blowpipe, 411. Harmaline, 863. Hartshorn, 445. Heat, 79; communication of, 83, absorption of, 86 ; convection of, 94 ; conduction of, 88 ; expansion by, 100 ; properties of, 82 ; radiant, 84, 97 ; solar, 80 ; sources of, 80 ; specific, 117; transmission of, 96; latent, 122. Heavy spar, 529. Helicine, 830. Helix, 204; contracting, 206. Hematosine, 897. Hematite, red and brown, 569. Hematoxyiine, 837. Hemming's safety tube, 412. Henry's coils, magnets, 208, 213. Homologous bodies, 661. Honey, 692. Horns, 914. Humus, 921. Hydrobenzamide, 787. Hydraulic line, 535. Hydrogen, 391; properties, 395; nature of, 405 ; acids, 422 ; action with chlorine, 423 ; arseniuretted, 612; bromine, 430; carbon, 450; chlorid, 423; fluorine, 433 ; iodine, 431 ; nitrogen, 440 ; oxygen, 399 ; phosphorus, 448 ; binoxyd of, 420; selenium, 439; sulphur, 435; per- oxyd of, 420 ; specific gravity of, 295. Hydrometer, 37. Hydrosulphuret of ammonium, 520. Hygrometers, 145, 146. Hypochlorite of lime, 541. Hyoscyamine, 825. Imponderable agents, 11. indigo, 839. Indigogene, 840. Induction of magnetism, 156 ; of a secondary current, 214; of elec- tricity on telegraphic wires, 212. Ink, black, 815 ; sympathetic, 580. Insulators of electricity, 169. Intensity, quantity, 186. Interference of waves, 58, 59. lodoform, 755. Iodine, 297 ; compounds with oxy- gen, 301. Ions, 227. Iridium, 636. Iron, 563; ferrocyanid, 867; ores of, 569; pure, 564; chlorids, 567; pyrites, 567; phosphate, 568; acetates, 744; lactate of, 700; oxyds of, 566; reduction of ita ores, 569; salts of, 568 ; specular, 566 ; sulphurets of, 567. Isatine, 843. Isinglass, 894. Isomerism, 660. Isomorphism, 262. Kakodyle, 782 ; protoxyd of, 783. Kermes mineral, 607. Kino, 815. Kreasote, 713. Kyanite, 551. Kyanizing process, 619. Lactates, lac tide, 700. Lactose, 693. Lakes, 550, 836. Lamp,Davy's safety,464;Argand,462. Lantanium, 556. Lard oil, 768. Laughing gas, 338. Law of divisibility of formulas, 659. Law of chemical transformations, 642. INDEX. 551 Lead, 585; acetates of, 745, 746; carbonate of, 588 ; oxyds of, 586 ; plaster or diachylon, 586 ; preci- pitated by zinc,587; sulphuret, 585. Leather, 894. Lecanorine, 834. Legumen, 884. Leiocome, 705. Leyden jar, 173 ; dissected, 175. Leucine, 888. Light, 54 ; interference of, 59 ; po- larization of, 72; properties of, 61 ; sources and nature of, 55 ; analysis of, 68 ; chemical rays of, 75, 76 ; vibrations of, 60. Lignin, 707. Lignite, 712. Lime, 534 ; carbonate of, 540 ; hypo- chlorid of, 541 ; lactate of, 700 ; phosphate of, 539; sulphate of, 537. Liquefaction, 122 ; and solidification of gases, 150. Liquids, properties of, 15, 92. Litharge, 586. Lithium and lithia, 517. Litmus, 835. Lodestone, 154. Logwood, 837. Lunar caustic, 627. Luteoline, 838. Lymph globules, 896. Madder, 836. Magnesia, 543 ; carbonate of, 546 ; calcined, 543 ; sulphate of, 545. Magnesian minerals, 547. Magnesium, 542; chlorid of, 544; oxyd of, 543. Magnetism, 154; induction of, 156; of the earth, 159. Magnetics and diamagnetics, 161. Magnets, 157. Magnets, electro, 207. Magneto-electricity, 217. Magnus, green salt of, 685. Malachite, green and blue, 590. Malamid, 814. Malt, action of on sugar, 706. Malates, 812. Malleability of metals, 470. Manganese, 557; chlorids of, 561; oxyds of, 558; salts of, 562. Mannite, 693. Manures, 920. Marble, 540. Margarine, 767. Mariotte's law, 24. Marsh's test for arsenic, 613. Massicot, 586. Matter, general properties of, 6; divisibility of, 12. Matteucci's researches, 220. Melting-points, 121. Mellisol, 761. Mellon, 852. Melloni's researches, 97. Melam, 852. Melamine, 857. Melaniline, 863. Mercaptan, 719. Mercury, 615; double amide of, 619; chlorids of, 619; fulminate of, 858; iodids of, 620; nitrates of, 621 ; oxyds of, 618 ; sulphate of, 621 ; sulphurets of, 620. Metacetone, 752. Metameric bodies, 660. Metaldehyde, 737. Metallurgy, electro, 234. Metals, general properties of, 466 ; physical properties, 469 ; fusi- bility, 121 ; oxyds of, 474 ; che- mical relations of, 474 ; tenacity of, 471. Metallic veins, 467. Methol, 753 ; oxydation of, 756. Methylic alcohol, 753. Methylic ether, 754. Methamine, 778. Microscomic salt, 513. Milk, 909 ; sugar of, 693. Mindereus, spirit of, 744. Miniums, 586. Molecules, 13 ; polarity of, 42. Molybdenum, 594. Monobasic acids, 648. Mordants, 550. Morine, 838. Morphine, 819. Mortar, 535. Mouth blowpipe, 463. Murexid, 877 ; murexoine, 878. Muriatic acid, 428. Murray's solution, 546. Muscular tissue, 887. Names of elements, 237. Nascent state, 269. Naphtha, 716 ; naphthaline, 715. Narcotine and narceine, 820. Nervous matter, 912. Neutrality of salts, 479. Newton's fusible metal, 603. Nickel and its oxyds, 577, 578- sulphate, 579. 552 INDEX. Nicotine and nicotianine, 826. Nitre, 499 ; sweet spirits of, 725. Nitro-prussids, 868. Nitrogen, 329 ; compounds with oxygen, 333 ; determined in or- ganic compounds, 672 ; chlorid of, 681. Nitrous oxyd, 338. Nitric oxyd, 341. Nitryls, 686. Nomenclature and symbols, 243. Nordhausen acid, 320. Nutritive substances containing nitrogen, 882. Nutrition of plants and animals, 915 ; elements of, 930. (Ersted's law, 201. Ohm's law, 187. - apparatus for compressibility of water, 15. Oil of bitter almonds, 785; of fousel, 758 ; of castor, 770 ; of mustard, 802; of roses, 799; of lard, 767, 797; of palm, 767; of potato, 758 ; of cumin, 793 ; of cinnamon, 796 ; of the Dutch chemists, 735; of spirea, 793; of caraway, citron, bergamot, juni- per, lemon, parsley, 798 ; of tur- pentine, 797 ; of winter-green, 795; of vitriol, 319; of horse- radish, 802. Oils, volatile or essential, 796. Olefiant gas, 734, 658; with chlo- rine, 735. Oleine, 767. Opium, alkaloids of, 819. Orcin and orceine, 834. Ores, how distributed, 468. Organic bases or alkaloids, 816. Organic bodies characterized, 637- 639 ; general properties of, 638 ; analysis of, 664; modes of com- bination in, 643 and following. Orpiment, 611. Osmium, 636. Oxygen, 274 ; properties and ex- periments, 277; allotropic state, 279. Oxyhydrogen blowpipe, 411. Oxamethane, 808. Ozone, 279. Palm oil, palmatine, 767. Palladium, 632. Pancreatic fluid, 903. Papaverine, 820. Paracyanogen, 853. Paranaphthalene, 715. Paraffine, 714. Pascal's experiment, 27. Pattinson's process for silver, 624. Peat, 712. Pendulums, 107. Peru balsam, 796. Peruvian bark, 818. Pepsin, 904. Petalite, 517. Petroleum, 716. Phene, 789. Phenol, 716, 789; trinitric, 790. Phloretine, phloridzuae, phlorizein^ 832. Phocenine, 766. Phosgene gas, 689. Phosphorescence, 78. Phosphoric acid, hydrates of, 355. Phosphorus, 346; red or amor- phous, 349 ; chlorids, bromids, 356; compounds with oxygen, 350. Phosphuretted hydrogen, 448. Piperin, picoline, and piperidine, 822. Plants, their nutrition, 915. Platinocyanids, 869. Platinum, 633 ; chlorids and oxyds, 635 ; power to cause the union of gases, 409 ; sponge and black, 634. Plumbago, 360. Polarization of light, 72. Polarity, electrical, 155, 165; of molecules, 42 ; magnetic, 155. Polecat, secretion of, 802. Populine, 831. Polycyanids, 853. Polymeric bodies, 600. Potash, 488 ; acetate of, 744 ; aluiui- nato of, 549 ; carbonates of, 495, 496 ; chlorate, 502 ; chroraate of, 575; argentocyanid of, 870; cy- anate, 850; nitrate, 499 ; salts of, 494 ; sulphates of, 498 ; tartrate of, 809 ; yellow prussiate, 865 j red prussiate, 867. Potassium, 483; properties, 485; per- oxydof, 487; tests for, 490; sulphu- rets, 492 ; chlorid, bromid, and io- did, 491 ; cyanid, 844, 846 ; ferri- cyanid of, 867 ; ferrocyanid, 865 j mellonid of, 852 ; oxyds of, 487, Potato oil, 758. v Pottery, art of, 555. Pneumatic trough, 280. INDEX. 553 Presence of a third body, 271. Prussian blue, 866. Pruseic acid, 844. Prussiate of potash, 865. Prism, its action on light, 67. Prismatic colors, 69. Proteine, 882 ; relation to albumen, fibrin, and casein, 883 ; analyses and constitution of, 887; changes of, 888, 890. Pulse glass, 135. Purple of Casaius, 631. Pyrometer, 114. Pyroxylic spirit, 753. Pyroxyline, 710. Pyrophorus, 492. Quantity and intensity, 186. Quercitrine, 838. Quicksilver, 615. Quinine, 818 j Quinidine, 819. Quinoline, 819. Racemic acid, relations to light, 811. Radiation, terrestrial, 81; of heat, 84. Radicals, salt, 480. Ratsbane, 609 ; realgar, 611. Red lead, 586. Red precipitate, 618. [63, 64. Reflection and refraction of light, Refraction, index of, 65 ; double, 71. Rennet, 910. Repulsion, 8. Residues of substitution, 653. Resins, 803. Reinsch's arsenic test, 613. Respiration, 926 ; elements of, 924. Rhodium and its compounds, 636. Rochelle salt, 809. Ruthenium, 636. Sago and salep, 705. Safety lamp, 465. Sal-ammoniac, 443. Salicine, 794, 829. Salicylol and its derivatives, 794, 829. Salicylamid, 795. Saligenine, saliretine, 829. Saliva, 903. Salts, theory of, 477 ; haloid, 480 ; neutrality of, 479. Salt, common, 508 ; of sorrel, 808. Salt-radical, 481. Saltpetre, 499. Sarcosine, 901. Sandal wood, 837. Sanguinarine, 825. Saxon blue, 842. Secondary currents, 214. Selenium, 325 ; oxyd of, 326. Selenite, 537. Serum and seroline, 898. Sesqui-oxyds and salts, 649. Silica, 381. Silicic ethers, 733. Silicon, 379; chlorid of, 384; fluo- rid of, 385. Silver, 622 ; oxyds of, 625 ; chlorid of, 626 ; nitrate of, 627; fulminate of, 858. Sinamine, 802. Smee's battery, 192. Soaps, 764. Soda, 507 ; acetate of, 744 ; biborate of, 516; carbonates of, 510 ; nitrate of, 511 ; phosphates of, 512 ; sili- cates of, 552 ; sulphate of, 509. Sodium, 505 ; chlorid of, 508. Soils, relation of to plants, 920. Solanine, 825. Solids, properties of, 14 ; expansion of, 101. Solidification of gases, 150. Solubility of sal soda, 509. Soluble tartar, 809. Solution, 267. Spathic iron, 568. Specific gravity, 33 ; rule for, 34; of gases, 39. Specific heat of bodies, 117. Spectrum, prismatic, 68 ; fixed linei in, 69. Spermaceti, 760. Spheroidal state of bodies, 131. Spirea ulmaria, oil of, 793. Spodumene, 517. Spirits of wine, 717; of nitre, 725. Spinel, 549. Starch, 705. Stalactites, 540. Stibethine, 781. Steam, 126; latent heat of, 138; elastic force of, 136 ; engine, 139. Stearin, 767 ; candles, 772. Stearoptens, 800. Steel, 570. Stibium, 411. Strontium, 531 ; chlorid of, 532. Strychnin, 821. Styrax balsam, 796. Substitution, equivalent, 643. Substitution by residues, 653. Sugar of lead, 745 ; of gelatin, 895. Sugar of milk, 693. Sugars, 691 ; products of the'j de- composition, 694. 554 INDEX. Sulphainetbone, 754. Bulphamethane, 808. Sulphovinie acid, 726. Sulphocyanates, 851. Sulphur, 304 ; compounds with oxy- gen, 309 ; chlorid of, 324. Sulphobenzid, 789. Sulphur auratum, 607. Sulphuric acid manufacture, 318. Sulphuretted hydrogen, 435. Surbasic and bisurbasio acetate of lead, 745, 746. Sustaining batteries, 192. Symbols, chemical, 253. Tanning, 815. Table of chemical equivalents, 238. Tannin, 815. Tartar emetic, 810 ; tartrates, 810 ; crude tartar, 809. Tartramid, 813. Tapioca, 705. Taurine, 880. Telegraph, electro-magnetic, 211. Tellurium, 328. Temperature of flame, 461 ; of in- candescence, 459. Terebol, 799. Terpinol, 799. Tenacity of metals, 471. Thebaine, 820. Theine, 823 ; theobromine, 824. Thilorier's apparatus, 151. Theories of electro-chemical decom- position, 233 ; of substitution, 643. Thermo-electricity, 218. Thermometers, 109 ; Bregnet's, 115; graduation, 111 ; thermo-electric, 97 ; self-registering, 112. Thialdin, 793. Thorium, 556. Thiosinamine, 802. Tin, 595 ; alloys of, 596 ; oxyds of, 597 ; chlorids of, 598, 599. Tissues, waste of the animal, 926 ; cellular and vascular, 707. Titanium, 594. Tobacco, alkaloids of, 825. Tolu, balsam, 793. Toluen, 738. Triethamine, 779. Tricyanid, 855. Touch, sense of, 91. Tournsol, 834, Turmeric, 838. TurnbulTs blue, 867. Transmission of radiant heat, 98. Tungsten, 594. Turpeth mineral. 621. Turpentine, oil of, 796. Tyrosin, 888. Types, 643. Ulmine, 711. Undulations, 56. Upas, poison of the, 821. Uramile, 876. Uranium, uranite, 589. Urea, 849 ; vinic, 861 ; urine, 90* ; acids of, 907. Ure's eudiometer, 405. Urinary calculi, 908. Vacuum, 23 ; Torricellian, 27. Valerianates, 759. Vanadium, 594. Vapor of alcohol, density of, 718. Vaporization, 126. Vapors, maximum density of, 142 ; density of determined, 676. Vegetal acids, 806. Vegetable mould, 711. Vegetables, nutrition of, 915. Vegetal alkaloids, 816. Veratrine, 825. Verdigris, 590. Vermilion, 620. Vibrations of light, 60 ; of heat. 89. Vinegar, quick process for, 741. Vinic acids, 720. Vinol, 717. Viacns fermentation, 694. Viscous fermentation, 697. Visible redness, 459. Vitality, 8. Vital heat, 929 ; force, 639. Vitriol, blue, 592; green, 568; oil of, 319 ; white, 583. Volatile alkali, 445. Volatile oils, 796. Volta, his discoveries, 180. Voltaic pile, 182 ; circle, 183, 184. Voltameter, 226. Volume of sulphydric acid, 438; combination by, 257, 656. Vulcanized gum-elastic, 804. Waves, 57, 58. Water, history of, 414, 678 ; as a chemical agent, 419 ; compressi- bility of, 15 ; capacity for heat, 127; crystalline forms of, 415; air in, 416; solvent powers of, 417; decomposition of, 400 ; vol- taic, 224; formation of, 397, 401; unequal expansion of, 103; bal- loon, 38. INDEX. 555 Water-hammer, 134. Wax, 761. Weight and specific gravity, 33. Wells, Artesian, 81. White arsenic, 609 ; lead, 588. White precipitate, 619. Wollaston's goniometer, 53. Wood, destructive distillation 713 ; tar, 714. Wood naphtha, 753. Wood spirit, 753. of, Woody fibre, 707; transformation of, 711. Xanthine, 836. Xyloidine, 710. Yeast, action of, 892. Yellow prussiate of potash, 865. Yttrium, 556. Zaffre, 580. Zinc, 581; oxyd of, 583 ; chlorid and sulphate of, 583; lactate of, 700 Zirconium, 556. OF THE UNIVERSITY THS END. THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW AN INITIAL FINE OF 25 CENTS WILL BE ASSESSED FOR FAILURE TO RETURN THIS BOOK ON THE DATE DUE. THE PENALTY WILL INCREASE TO SO CENTS ON THE FOURTH DAY AND TO $1.OO ON THE SEVENTH DAY OVERDUE. MAR 18 1941 LD 21-95m-7,'37 YB 1 7055 _84529 if