UC-NRLF hlfl 575 THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA PRESENTED BY PROF. CHARLES A. KOFOID AND MRS. PRUDENCE W. KOFOID ELEMENTS CHEMISTRY, WITH PRACTICAL, EXERCISES, ILLUSTRATED BY on USE OF SCHOOLS BY FRAXCIS J. GRUXD, Author of " Elements of Natural Philosophy," " Elements of Plane and Solid Geometry," " Popular Lessons in Astronomy," ' Exercises in Algebra," " Arithmetic," etc. tion and object of Chemistry. BOSTON: CARTER, HENDEE AND CO, 1833. (hi Entered according to act of Congress, in the year 1833, BY FRANCIS J. GRUND, in the clerk's office of the District Court of Massachusetts. 75* PREFACE. IN preparing the following Elementary Treatise of Chemistry, it has been the author's particular study to form a proper scientific arrangement, which shall enable the learner to see the connexions which exist between the different branches of the natural sciences, and to conduct him gradually from a knowledge of the sim- ple bodies, or elements of nature, to a correct under- standing of their more complex combinations. The divisions of the work, it is believed, will be found natural, and such as will prove a strong assistance to the memory. The Introduction contains the outlines of General Chemistry, treating separately, I. Of the definition and object of Chemistry. II. Of Chemical action. III. Of the Chemical apparatus, and Of the Chemical composition of bodies. The first four chapters may be considered as contain- ing the elements of inorganic chemistry. The first treats iv PREFACE. of the gaseous elements and their binary combinations ; the second, of the thirteen non-metallic elements and their binary combinations ; the third chapter treats sep- arately of the metals, and the fourth of the salts. To the description of each element is annexed a short table, exhibiting its principal combinations with other substances, and each chapter is followed by questions for recapitulation, which are numbered to correspond with the sections of the book. The fifth and sixth chapters treat respectively of vegetable and organic chemistry, and the seventh chap- ter explains the three principal processes of fermentation, or the spontaneous decomposition of organized matter. Each of these chapters is again followed by questions for review, numbered to correspond with the sections of the text. The appendix contains a brief description of the steam engine, with questions for the learner. Nu- merous engravings are introduced for illustrating the ex- periments, and indeed no expense and labor spared to render the work intelligible even to ordinary capacities. It is hardly necessary to add that on his tour to Europe the author has had an opportunity to embody in his work the latest discoveries in chemistry, and that it may therefore be reasonable in him to hope that in this respect his book is not inferior to any similar work published in this country. BOSTON, OCTOBER 1st, 1833. TABLE OF CONTENTS. INTRODUCTION. page. I. Definition and Object of Chemistry, . /'_ II. Chemical Action, 4 III. Chemical Apparatus, . . . IV. Chemical Composition of Bodies, . . " . . . 36 RECAPITULATION. I. Questions on Definitions, "Mr." . . <( . j. 42 II. do. on Chemical Action, 43 III. do. on Chemical Apparatus, .... 46 IV. do. on the Chemical Composition of Bodies, . 48 CHAPTER I. Of the Properties and Combinations of the Four Gaseous Elements, Oxygen, Hydrogen, Nitrogen, and Chlorine. A. Oxygen, tV/--^: *i;n ^. 50 Theory of Combustion, . . . r. ;,,; . 52 B. Hydrogen, . . . . . # .j^^ 59 Properties of Hydrogen gas, 61 Combination of Hydrogens with Oxygen Water, . 73 C. Nitrogen or Azote, 87 Combinations of Nitrogen with Oxygen, ^ -^ u'* " \ 93 do. Nitrogen with Hydrogen, . . . 101 D. Chlorine, . . .- 103 Combinations of Chlorine with Oxygen, ' / '-* 104 do. do. with Hydrogen, . : .' 106 do. do. with Nitrogen, .i^i^i^P . 109 RECAPITULATION. Questions for Reviewing some of the most important Principles contained in the 1st Chapter. A. Questions on Oxygen, . . v^I'l j*> i^sfiV~:^. 1^ B. do. on Hydrogen, . . ' T ; ~ . 112 # vi CONTENTS, C. Questions on Nitrogen, . . . . . . 116 D. do. on Chlorine, 120 CHAPTER II. Of the remaining nine Non-metallic Elements, and their combinations, 122 A. Carbon, 122 Combinations of Carbon with Oxygen, . 125 do. do. do. Hydrogen, 129 do. do. do. Nitrogen, . 134 do. of Cyanogen with Oxygen, 135 do. do. do. Hydrogen, . . 135 Other combinations of Cyanogen, 138 Combinations of Carbon with Chlorine, . 138 do. do. do. Sulphur, 139 B. Sulphur, . 141 Combination of Sulphur with Oxygen, 142 do. do. do. Hydrogen, . . 147 C. Silenium, ...... 149 D. Phosphorus, . 149 Combinations of Phosphorus with Oxygen, do. do. do. Hydrogen, 151 . 152 E. Boron, 155 . 155 F. Iodine, . . . . . ".'../' '.'*:?. 156 Combination of Iodine with Oxygen, 157 do. do. do. Hydrogen, . 157 G. Bromine, ....... 158 Combinations of Bromine, .... . 159 H. Silicon, ....... 159 Combinations of Silicon with Oxygen, . . 160 Properties of Silex, 160 I. Fluorine, .^ . 162 -i'-T V. 162 Other combinations of Fluorine, 163 RECAPITULATION. Questions for Reviewing the most important Principles contained in Chapter II. A. Questions on Carbon, 164 B. Questions on Sulphur, ...... 167 C. Questions on Silenium, ...... 169 D. Questions on Phosphorus, 169 E. Questions on Boron, 171 . F. Questions on Iodine, . . 171 G. Questions on Bromine, 172 H. Questions on Silicon, . 172 I. Questions on Fluorine, , . . . . ' 173 . CONTENTS. Vll CHAPTER III. OF THE METALS. Preliminary remarks, . . . . . . 174 Jj. Of the six Alkaline Metals, Potassium, Sodium, Lithium, Calcium, Barium, and Strontium, . . 180 1. Potassium, 180 Combinations of Potassium, 183 2. Sodium, 185 Combinations of Sodium, 185 3. Lithium, 186 Combinations of Lithium, 187 4. Calcium, 187 Combinations of Calcium, 187 5. Barium, 188 Combinations of Barium, 188 6. Strontium, 189 Combinations of Strontium, ..... 189 B. Of the six Earthy Metals, Magnesium, Yttrium, JLlumi- um, Glucinum, Zirconium, and Thorium. . . 190 1. Magnesium 190 Combinations of Magnesium, 191 2. Glucinum, 192 Combinations of Glucinum, ..... 192 3. Yttrium, 193 Combinations of Yttrium, ..... 193 4. Alumium, 193 Combinations of Alumium, 193 5. Zirconium 194 Combinations of Zirconium, 194 6. Thorium, 195 Combinations of Thorium, 195 C. Of the nine Noble Metals, Mercury, Silver, Gold, Plati- num, Palladium, Rhodium, Iridium, Osmium., and Nickel, 195 1. Mercury, 195 Combinations of Mercury with Oxygen, . . . 196 do. do. do. Chlorine, . . 197 do. do. do. Sulphur, . . . 199 2. Silver, 200 Combinations of Silver, 200 3. Gold, 202 Combinations 6f Gold, 203 4. Platinum, . . ,:f ; 204 5. Palladium, . *'.?:>'.. "/ ; 206 6. Rhodium, 207 7. Iridium, , 207 8. Osmium, . 207 9. Nickel, . 208 X CONTENTS. 7. Carbonate of Lead, . . . . . . 283 8. do. Iron, 284 9. do. Copper, 284 G. Phosphates, 234 1. Phosphate of Ammonia, 285 2. do. Soda, 285 3. do. Lime, 286 H. Chromates, 286 1. Chromate of Potash, 287 2. do. Lead, 287 3. do. Mercury, . 287 I. Jlrseniates and JLrsenites, 287 1. Arsenite of Potash, 288 2. do. Cobalt, 288 J5f. Cyanites and Fulminates, 288 RECAPITULATION. Questions for Reviewing the most important Principles contained in Chapter IV. I. Questions on the General Remarks on the salts and acids, 289 Questions on Crystalography, 291 A. Questions on the Nitrates, 292 B. Questions on the Chlorates, 293 C. Questions on the Chlorides, 294 E. Questions on the Sulphates, 295 F. Questions on tiie Carbonates, 296 G. Questions on the Phosphates, 298 H. Questions on the Chromates, 298 I. Questions on the A rseniates and A rsenites, . . . 299 K. Questions on the Fulminates, 299 CHAPTER V. VEGETABLE CHEMISTRY. General Remarks on the Difference between Organic and In- organic matter, . . 300 I. UNSALIFIABLE VEGETABLE SUBSTANCES, . . 303 A. Neutral Unsaleable Vegetable Substances, , 304 1. Woody Fibre, ... ; ... 304 2. Starch, 304 3. Gum, or Mucilage, 305 4. Sugar, 305 B. Watery, Unsaleable Vegetable Substances, . . 306 1. Volatile or essential oils, 306 2. Fat or fixed oils, 307 3. Resins, 308 4. Wax, . 309 5. Alcohol, .... '"V . -'. 309 6. Ether and Naphta, . . . .: . .,* . 310 . CONTENTS. XI II. SALIFIABLE VEGETABLE BASES, ... 311 III. VEGETABLE ACIDS, . 312 A. Fixed Vegetable Acids, 312 1. Tartaric acid, 312 2. Citric acid, ...;... 313 3. Malic acid, . . . . . . . .313 4. Oxalic acid, 314 5. Gallic acid, 314 6. Vegetable Jelly, or Pectic acid, . . . 314 7. Bitumous acid, 315 B. Vegetable Acids capable of Sublimation, , . 315 1. Benzoic acid, 315 2. Succinic acid, 316 3. Boletic acid, . . . . . , . .316 C. Liquid Vegetable Acids (capable of Distillation), 316 1., Acetic acid, 316 2. Prussia acid, . . .. . . . .318 3. Cyanic acid, 318 IV. VEGETABLE SUBSTANCES OF AN UNDETERMINED NATURE, '. f . \. 318 1. Coloring matters, . .' , -. ;v --'.. 318 2. Vegetable extracts, . :/v r v.r5. :,:<- ;"';. N 3. Fennentous principles, . . . * ; 320 a. Lees (dregs), 320 b. Vegetable albumen, 321 . c. Gluten, 321 RECAPITULATION. Questions for Reviewing the most important Principles Contained in Chapter V. A. Questions on the general remarks on the difference between organic and inorganic bodies, v c. , . 322 Questions on the unsalifiable vegetable substances, . . 323 Questions on the salifiable vegetable substances, . . 325 Questions on the vegetable acids, . . . . . 325 Questions on vegetable substances of aji undetermined nature, 327 CHAPTER VI. ANIMAL CHEMISTRY, . ri** or -: . . . 329 1. Animal Jelly (Glue), .... *-;,,:.%; 331 2. Albumen, . 331 3. Blood, 332 Chemical changes in the nature of Blood, occasioned by Respiration, 333 4. Of the Milk, 333 5. Butter, . 334 6. Cheese, 334 7. Sugar of milk, . , , ... , . ,. f . 335 XII CONTENTS. 8. Animal mucus, 335 9. Animal oils and fats, 335 10. Animal acids, 336 a. Olific acid, 336 6. Lactic acid, 337 d. Mucous acid, : e. Formic acid, . 337 11. Of the different liquids employed in the process of digestion, 338 a. Saliva, 338 6. Gastric juice 338 c. Bile, 338 12. Of the Chyle, 339 13. Substance of the Brain and Nerves, . . . .340 14. Fibrin, 341 15. Of the Bones, Teeth, and Cartilage, . . . .341 16. Of the Marrow, 342 17. Of the Muscles, Membranes, Ligaments and Tendons, . 342 18. Coverings of animals, 343 a. Of the skin, . . . . . . . .343 6. Nails, Claws, Horns, Hoofs, Scales, &c, . . 343 e. Hair, Bristles, Feathers, Wool, and Silk, . . 344 RECAPITULATION. Questions for Reviewing the most important Principles con- tained in Chapter VI, . . . ,v ... 845 CHAPTER VII. Of the Chemical Process accompanying the Development, Life, and Death of Organized Bodies. A. Germination of seeds. . 351 B. Process of Nutrition necessary to life, . . . 351 C. Of the spontaneous decomposition of Organic substances, 352 1. Vinous Fermentation, . 352 Phenomena accompanying vinous fermentation, . 353 2. Acetous Fermentation, 354 3. Of the process of Putrefaction, .... 355 Putrefaction with free access of air, . . . 356 Putrefaction with little or no access of air, . . 356 RECAPITULATION. Containing Questions for Reviewing Chapter VII. . . 357 APPENDIX. On the steam engine, 360 Questions on the steam engine, 371 CHEMISTRY. INTRODUCTION. I. DEFINITION AND OBJECT OF CHEMISTRY. I. ALL natural sciences, that is, all human knowledge about created nature, may be divided into two great classes Natural History, and Natural Philosophy. II. Natural History has for its object the systematic description of animate and inanimate (living and lifeless) bodies, and is again divided into Zoology, Botany, and Mineralogy ; : according as the bodies described are Ani- mals, Plants, or Minerals. III. The object of Natural Philosophy is to explain the various phenomena which occur in the material world, by finding out their mutual relation and connection with certain invariable principles, called Laws of Nature. The phenomena, themselves, may have their origin in the general properties of matter ; such as gravity, attraction, elasticity, &c,* and consist, then, principally in motion ; or they may be occasioned also by certain powers which are inherent in bodies, by virtue of which one body changes the form and properties of another with which it comes in contact. On this account Natural Philosophy has been divided into two great branches ; one which treats of the Mechanical properties of matter Natural Philosophy * See Grund's Elements of Natural Philosophy. 1 CHEMICAL ACTION. This double composition is exhibited by the following *ki~ table. Saltpetre. nitric acid, alkali. nitrogen, oxygen, potassium, oxygen. Query. Which, in this example, are the nearer, and which the more remote ingredients of saltpetre ? J)ns. In this ex- ample nitric acid and alkali are the nearer ; nitrogen, potassium, and oxygen, the more remote ingredients of saltpetre. VIII . Those substances which have not as yet been decomposed by any means in our power are called Ele- ments ; but it does not follow that all substances which are now considered as elements, are really incapable of chem- ical analysis. Query. What then does the word Element express in chemistry ? Ans. The word Element indicates only the degree of our knowledge with regard to a certain substance, and shows that we have not, as yet, been capable to decom- pose this substance. II. CHEMICAL ACTION. IX. It has been observed that each chemical composi- tion or decomposition, in other words, all chemical action, is effected by a peculiar kind of attraction, called affinity. This, therefore must be considered as the principal cause of all chemical phenomena. The changes produced on bodies which are subjected to it, are principally the following. a. A change in temperature. EXAMPLE. Oil of vitriol and water suddenly mixed, pro- duce a temperature of 212 Fahrenheit: Again, Salammo- niac and snow mixed together, produce a cold equal to zero of Fahrenheit's thermometer. Hence chemical affinity changes the capacity for heat, or the specific caloric of bodies. (Nat. Phil. Chap. VI.) C.HEMICAL ACTION. 5 b. A change in the physical properties of bodies. EXAMPLE. Sulphur and oxygen are both destitute of smell, taste, or action on vegetable color ; but when combined to- gether they form a powerful acid, of a strong smell, which changes blue vegetable colors into red. ANOTHER EXAMPLE. Quicksilver, which is of a bright tin- color, unites with sulphur, which is yellow, and forms a sub- stance called cinnaber, distinguished by its beautiful red color. c. Change in the aggregate form of bodies* EXAMPLE. Oxygen and hydrogen are both aeriform,f or gaseous, but when combined in the ratio of about 1 to 8, form the well-known liquid, water. It is not unfrequent to see chemical action accompanied by light. The intensity of this light increases with the degree of affinity which exists between the two combining bodies, and the circumstances which favor their combination. This phe- nomenon will be explained in Chap. I, when treating of oxy- gen. X. It becomes us to speak separately of the great influ- ence which heat has upon all chemical phenomena. And this is not only so far true, that no chemical action takes place without a change of temperature ; but is founded also on the fact that some combinations or decompositions are. effected only through the influence of higher degrees of tem- perature (when one or the other body has previously been heated.) Heat, therefore is a powerful chemical agent, which, in most cases, favors the chemical affinity of one body for another ; although there are instances in which heat seems to produce a different effect. EXAMPLE. The process of fermentation and putrefaction (see Chapter VII) requires at least 32 degrees Fahrenheit. dgain Quicksilver combines with oxygen only when heated to 2 12 degrees; and the result of this combination, which is the oxide of quicksilver, separates again into quicksil- ver and oxygen, when submitted to a red heat. ANOTHER EXAMPLE. The Chloratts, a class of salts with which we shall hereafter become acquainted, are decomposed * See Natural Philosophy, Chapter I, t See Natural Philosophy, 1* 6 C.HE MI CAL ACTION. and give off the oxygen which they contain, when thrown upon live coals. XI. The greatest obstacle to chemical action is the co- hesive attraction of bodies ; that is, (as has been ex- plained in Natural Philosophy) the attraction by which their particles are kept together and in their relative positions.* This is the reason why bodies combine readiest with each other, when one or the other has been reduced to the fluid state ; because the cohesive attraction is less in liquids than in solid substances. It also explains why heat in- creases the action of chemical affinity ; because heat, by expanding all bodies (Natural' Philosophy, Chap. VI,) lessens their cohesive attraction, and predisposes them for the fluid state. From this the general inference has been drawn, that no chemical action takes place, except one of the two bodies is in the fluid state. This rule, however, is not without exceptions. Query What would take place if there were no cohesive attraction to counteract the chemical affinities of bodies ? Ans. Without the cohesive attraction of the particles of bodies, all substances would combine and unite with each oth- er to one huge mass. Query How, then, must chemical affinity and cohesive at- traction be considered in reference to each other ? Ans. They must be considered as two opposite powers in nature whose effects, by a wise distribution of Providence, are won- derfully balanced. XII. Bodies frequently combine with each other in such a way that each of them loses its physical properties in the combination. They are then said to be neutralized. In the above example, the oxygen and the sulphur are neutralized in sulphuric acid. ANOTHER EXAMPLE. Alkali (potash) and sulphuric acid are each distinguished by a peculiar taste ; potash changes blue vegetable colors into green, and sulphuric acid turns them into red. By mixing these substances in the proper proportion, we obtain a salt destitute of either acid or alka- line qualities ; its taste being bitter, and the salt itself be- ing without any effect on vegetable colors. * See Natural Philosophy, Chapter I. CHEMICAL ACTION. 7 Query In what state are the potash and the sulphuric acid, in this case, contained in the salt? JJns. They are neutralized in it. It may be well to observe here, that in order to effect a complete neutralization, the two bodies must combine in a certain fixed proportion, before or beyond which no such phe- nomenon takes place. XIII. Some bodies combine with each other in all pro- portions, and preserve still a portion of their original properties. Such a combination is more properly called a mixture. EXAMPLE. If wine and water be poured together, a mix- ture is obtained in which the fluidity of both liquids, as well as some of the taste and color of the wine is preserved. The same is the case when vinegar and water, alcohol and water, alcohol and wine, &c, are poured together. XIV. Whenever we wish to decompose a chemical com- pound into its constituent parts, we must have recourse to a third substance, with which one of these parts is to com- bine, by which means the other becomes disengaged or free. This kind of chemical attraction, in consequence of which a body quits a combination already existing, for the sake of forming a new one, is called Elective affinity; because the body seems, as it were, to elect one combination in preference to another, which it has already formed. EXAMPLE. Muriate of lirne is a compound of muriatic acid and lime ; but when potash is added to the solution the muri- atic acid combines with the potash, and the lime being now- disengaged falls to the bottom, and forms what is called a precipitate. This process may be represented to the eye by the following figure. Muriate of Potash. C Muriatic acid. Potash, Muriate of Lime. < (| Lime. The original compound (Muriate of Lime) is composed of Muriatic acid and lime. As soon as potash is added, the mu- riatic acid combines with the potash, and forms muriate of pot- ash ; and the lime becomes free, CHEMICAL ACTION. Query What substance, in this example, shows an elect- ive affinity for Potash ? Jlns. The muriatic acid. Query Why ? Ans. Because it quits its combination with lime, and unites, as it were, in preference with the potash. XV. When a solid body combines with a fluid, the product is called a solution. In this case the affinity be- tween the two substances continues to act only to a certain point, that is, the liquid is only capable to dissolve a cer- tain portion of the solid so that if we wished to have a greater quantity of the solid dissolved, we should have to add more of the liquid. The point beyond which the affin- ity of the liquid ceases to act upon the solid, is called the point of saturation ; and the solution itself, when arrived at this point, is said to be saturated. EXAMPLE Water will dissolve only a certain quantity of sugar or salt, until it becomes saturated. A fresh quantity of sugar or salt being then added will remain unchanged at the bottom of the vessel. But if a new quantity of water be added to the solution, then a new quantity of sugar or salt will be dissolved. XVI. The saturation of liquids depends principally 1. Upon the temperature of the liquid. 2. Upon the degree of affinity which exists between the liquid and the solid ; and 3. Upon the purity of the liquid. The warmer the liquid is, the more can it generally dis- solve of a given solid. To this rule, however, there are several exceptions. EXAMPLE. Water of the temperature of 212 Fahrenheit, will dissolve no more common salt, than water of the tempera- ture near the freezing point. Water of the temperature of 212 dissolves even less magnesia, than water of the common temperature of the atmosphere. But with regard to most salts the solving power of water increases with the tempera* ture. XVII. It frequently occurs that a compound of two substances cannot be decomposed without the assistance of a third and fourth substance. The affinity of the third substance for any one of the constituent parts of the CHEMICAL ACTION. 9 compound, is then, of itself, not sufficient to produce a sep- aration. This kind of affinity is called Double or Complex affinity. It will be best understood from the following EXAMPLE. Zinc decomposes water (which is a compound of oxygen and hydrogen) only when an acid is added. The hydro- gen of the water then becomes free, while the zinc and oxygen combine together with the acid to form a salt. The zinc, of itself, is not capable of separating the oxygen from the hydrogen ; but the acid having a strong affinity for a combination of zinc and oxygen, predisposes the oxy- gen to quit its combination with water and to combine with the zinc. For an illustration, see the following table : ( hydrogen, Water, J ( oxygen, >xygen, } > oxide of zinc, 1 zinc, ) \ salt, acid ) Zinc alone does not separate the oxygen from the hy- drogen; but when the acid is added, which has a strong affinity for the oxide of zinc, this latter substance (oxide of zinc) is formed, and combines with the acid to salt. Some philosophers ascribe these phenomena to a predispos- ing affinity ; because the acid, in our first example, seems to predispose the oxygen for a combination with the zinc. Query What substance, in this example, has exercised a predisposing affinity upon oxygen? Jlns. The acid. Query Why ? Jlns. Because it has disposed it for a combination with the zinc. Query But by what means doea the acid predispose the oxygen for a combination with the zinc ? Jlns. By the strong affinity which it has for the oxide of zinc, which is a combination of the oxygen with zinc. XVIII. If two compounds be brought together in a state of solution, it frequently happens that a double de- composition, and two new compositions take place. Both the original compounds are then decomposed, and two new compositions are formed by a mutual interchange of in- gredients. Such a compound action is said to be caused by double elective affinity. 10 CHEMICAL ACTION. EXAMPLE. The well known substance, sugar of lead, (which is used as a paint) is composed of acetic acid (vinegar) and lead. White vitriol is a compound of sulphuric acid and zinc. Now if a solution of sugar of lead be mixed with a so- lution of white vitriol, the acetic acid will quit its combination with lead, and unite with the zinc ; while, at the same time, the sulphuric acid which is set free, unites with the lead and forms an insoluble hard powder (sulphate of lead) which is precipitated. For an illustration see the following dia- gram. Acetate of zinc, C Acetic acid, Zinc, } Sugar of Lead, 3 V White Vitriol, ( Lead, Sulphuric acid, ) Sulphate of lead. The original compounds, sugar of lead and white vitriol, are placed at the extremities of the two brackets ; their respective ingredients, acetic acid and lead, and zinc and sulphuric acid, are placed inside of the brackets ; the new compounds, ace- tate of zinc, which is formed by the combination of the acetic acid with the zinc is placed above the upper, and the second compound, sulphate of lead, formed by the combination of the lead with the sulphuric acid, is placed under the lower bracket. Query Which substance does the acetic acid, in this ex- ample elect in preference to the lead with which it was com- bined ? Ans. The zinc, with which it combines, setting lead free. Query And which substance does the sulphuric acid elect in preference to the zinc ? ./7ns. The Lead, giv- ing off the zinc with which it was united. Query And why is this action called double elective affinity ? Jlns. Be- cause two distinct elections took place, viz. the acetic acid elects the zinc, and the sulphuric acid the lead, for a new combination. This kind of affinity often effects the decomposition of a substance which would have resisted the action of single elective or predisposing affinity. XIX. It has been said that while some bodies combine with each other in all proportions and form mixtures, others have a limit to their combination, which is the point of SATURATION. But there are substances which combine with each other only in certain Jixed proportions, that is, CHEMICAL ACTION. 11 so many parts or weights of one substance, with a definite number of parts or weights of another. The product of such a combination is always a compound in which the properties of the constituent parts are completely neutral- ized. (See XII.) EXAMPLE. Sulphur and oxygen are apparently heteroge- neous substances ; oxygen is a gas, and sulphur a solid body. These two substances however unite with each other in the proportion of 16 weights of sulphur with 24 weights of oxygen, in which case they form a compound which is known by the name of sulphuric acid ; and whose properties are totally dif- ferent from those of the sulphur or oxygen ; these are therefore neutralized by the combination. Some bodies combine with each other only in one pro- portion ; others combine in two, three, four and more fix- ed ratios. EXAMPLE. Zinc and oxygen combine with each other only in one proportion, forming what is called oxide of zinc ; but the two gases, known by the name of oxygen and nitrogen, com- bine with each other in five distinct ratios, viz. I volume of nitrogen with 1 volume of oxygen, 1 u it it it O tt it it j it tl tl it 3 it ti it J tl tt it it ti ti n and 1 " " " " 5 " " " the five resulting combinations being two oxides and three acids of nitrogen, and there are no other combinations of these two substances known. Similar fixed ratios have been discovered in the com- bination of other bodies to definite compounds, and it has been observed that in these combinations the original prop- erties of the ingredients are always completely neutralized, so that we are able to lay down the general principle : No two bodies combine with each other to neutralization, except in ajixed determined proportion, which remains always the same, for the same two substances. Now it has been remarked and proved by numerous ex- periments, that if a body, A, combines with another body, B, for instance, in the ratio of 1 weight of A with 2 weights of B ; and the same body A , combines with a third body, C, in the ratio, say of I weight of A, to 3 of C, then the body, B, will, if it have any neutralizing affinity for 12 CHEMICAL ACTION. the body C, combine with it in the ratio of 2 to 3, or at least in a multiple of this ratio by a whole number ; that is in 2, 3, 4, 5 or 6 times this ratio ; so that the ratio in which one and the same body, A, combines to neutralization with different bodies, B, C, D, 4*c, being once known, the neutralizing ratio in which these bodies combine with each other are also determined This will be better understood by the following EXAMPLE. (2 Ibs. ofB, Supposing 1 Ib. of a substance A. combines with ( ^ ^ ^ p' [ 5 Ibs. of E; then the relation of the substance, A, to the bodies, B, C, D, E, determines also that of the bodies B, C, D, and E to each other ; viz. if the body, B, has a neutralizing affinity for C, D, and E, it will combine with them in the ratio of ( with 3 Ibs. of C, 2 Ibs of B { with 4 Ibs. of D, ( with 5 Ibs. of E. Further, if C, has any neutralizing affinity for C, D, and E, it will combine with them in the ratio of !2 Ibs. of B, 4 Ibs. of D, 5 Ibs. of E. If D have any such affinity for B, C, and E, it will combine with them in the ratio of ( 2 Ibs. of B, 4 Ibs. of D with { 3 Ibs. of C, ( 5 Ibs. of E, And lastly if E have this affinity for B, C, and D, it will combine with them in the ratio of r 2 Ibs. of B, 5 Ibs. of E with ! 3 Ibs. of C, ( 4 Ibs. of D. Thus a single table expressing the fixed proportions in which the body A, combines respectively with B, C, D and E, has given us at once the fixed proportions in which B, C, D, and E combine with each other. CHEMICAL ACTION. 13 The learner will now be able to understand the follow- ing example, which is taken from nature : We know from experience that 37 weights of Muriatic acid combine with 28 of Lime, 40 " " Sulphuric acid " " 48 " Potass, 54 " " Nitric acid " " 32 " Soda, 28 " {< Phosphoric acid ' " 17 " Ammonia. These ratios give not only the proportions in which each of these substances combines with that which is placed on the same line with it ; but also the proportion in which each of these substances combines with all others. Thus, 28 weights of Lime, with 37 weights of muri- atic acid combine to saturation 40 weights of Sul- phuric acid combine to saturation 54 weights of Nitric acid combine to sat- uration with with 48 32 17 Potass. " Soda, " Ammonia, 28 weights of Lime, 48 " " Potass, 32 " Soda, 17 " " Ammonia, 28 weights of Lime, 48 " " Potass, 32 " " Soda, 17 " " Ammonia. Or we could also take any of the four substances, Lime, Potass, Soda, or Ammonia ; say soda, and write the four acid substances after it, viz. 37 weights of Muriatic acid, 40 " " Sulphuric acid, 54 28 Nitric acid, Phosphoric acid, 32 weights of / Soda combine to / with saturation \ and so on. Now as 37 weights of muriatic acid combine in the same proportions with Lime, Potass, Soda, and Ammonia, in which 40 weights of sulphuric acid combine with these substances, 37 weights of the first acid are said to be equivalent to 40 weights of the second; and accordingly, also to 54 weights of Nitric, and to 28 weights of Phospho- ric acid. In like manner are 28 weights of lime equiva- 2 14 CHEMICAL ACTION. lent to 48 weights of potass, 32 of Soda, 17 of ammonia. Or we may also say that 37 weights of muriatic acid are equivalent to 28 weights of lime, 48 of potass, 32 of soda, &c, or that 28 weights of lime are equivalent to 37 weights of muriatic, 40 of sulphuric, 54 of nitric, and 28 of phos- phoric acid, and so on. We shall show in the body of the following work that similar equivalent numbers have been found for a great many substances in the chemical catalogue ; and it is by these numbers that we are able to express the definite pro- portions in which one substance combines tvith all others, for which it has a strong chemical affinity. The smallest number of weights of one substance which in this manner combines with other substances, is said to be a CHEMICAL EQUIVALENT for all other substances with which it is ca- pable of entering into combination. Now it has been found by experiments that in all cases where a body is composed of two elements, the sum of the equivalents of the elements is equal to the equivalent of the body itself. Knowing therefore the equivalent of the elements of a body, we also know that of the com- pound ; and the reverse, if the equivalent of the compound and the elements of its composition are known, the equiv- alents of its elements may be inferred from it. This will be better understood from the following EXAMPLE. 1 weight of hydrogen combines with about 8 weights of oxygen to water. Consequently if 1 weight of hydrogen gas is taken for unity of comparison, the equivalent of oxygen will be 8 ; whence that of water will be 1 added to 8, equal to 9. And the reverse ; suppose we know that the chemical equivalent, of water is 9 ; and that it is composed of I equivalent of water and 1 of oxygen. Knowing the equivalent of water to be = 9, we should at once infer that of the oxygen, which must be equal to 8. ANOTHER EXAMPLE. One weight of hydrogen com- bines with 16 weights of sulphur, to sulphuretted hydrogen ; consequently the weight of hydrogen taken for unity, the chemical equivalent of sulphur is 16. Now the chemical equivalent of oxygen being 8, it is known that 2 equiva- lents of oxygen combine with 1 equivalent of sulphur to CHEMICAL ACTION. 15 sulphurous acid. Query What is the equivalent num- ber of sulphurous acid ? Ans. 32. Query Why ? Ans. Because it is composed of 1 equivalent of sulphur = 16 and of 2 equivalents of oxygen (each equal to 8) = 16 Consequently, Chemical equivalent of sulphurous acid = 32 Jigain Supposing we know the chemical equivalents of sulphurous acid = 32, and also that it is composed of 1 equivalent of sulphur, and 2 equivalents of oxygen, (each equal to 8.) Required the chemical equivalent of sulphur. Ans. The equivalent of sulphurous acid being = 32 Subtract from it 2 equivalents of oxygen (each equal to 8) = 16 The remainder will be the equivalent of sulphur = 16. These few examples will be sufficient to show the beau- ty and harmony of the theory of chemical equivalents ; as well as the advantages which the practical chemist may derive from it. Were the chemical equivalents of all bodies unchangeable, and as correctly determined as those we have mentioned in our last examples, then it would indeed be possible to intro- duce mathematical precision and certainty into the science of chemistry, which would then in no respect yield to any of the exact sciences. A single experiment which should show the relation of an unknown substance to one with whose proper- ties we are already acquainted, would suffice to determine the relation of that substance to all other bodies ; which relation would, in most cases, be found by a mere addition or subtrac- tion, as has been shown in the last two examples. But this is far from being universally true. The same limits with which the human understanding invariably meets in all sciences, await us also in chemistry. For the proportion in which bodies combine are not always as definitely pronounced as we could wish them to be. In some bodies they are less percep- tible than in others, and there are substances whose composi- tion is so vague and indefinite that thus far, it has been impos- sible, even by the nicest experiments, to fix upon any of their supposed definite equivalents. We know farther, from expe- rience, that 1 equivalent of one body, does not always combine again with 1 equivalent of another ; on the contrary it has 16 CHEMICAL ACTION. been found that 1 equivalent of one body frequently combines with 1, li, 2, 3, or 5 equivalents of another ; and there are ex- periments and facts, which have induced some of the best chemists now living to suppose that one equivalent of one sub- stance may also combine with 4-, ^, f ;, ^ and even equivalent of another substance. Hence the universal advan- tage which it was hoped would be obtained from a numerical computation of chemical equivalents has, thus far, not been realized. For although we may be able to investigate by experiment the proportion of matter or weight in which two substances combine with each other, yet will this investigation not always lead us to a precise result as regards the chemical equivalent of the compound ; because we do not always know whether 1, , 2, or one fourth, one third, two thirds, one eighth, or one sixth equivalent of either substance is combined with one equivalent of the other. But as far as the whole theory of Chemical proportions is supported by actual experiments, it not only serves to facilitate the labors and to assist the memory of the practical chemist; but deserves also, on account of its harmony with other laws of nature, to be ranked among the most brilliant discoveries of the human mind. The chemical equivalents of a great number of substan- ces, as far as we have been able to determine them by ac- tual experiments (but in most cases unfortunately only by arithmetical computation), have been arranged in tables, of which one is attached to the end of the book. From what we have said it will easily be seen that they are not in all cases to be relied upon with mathematical certainty, although many authors speak of them as established facts, or consider the whole theory established beyond any rea- sonable doubt. In most of these tables the weight of t equivalent of hydrogen gas is taken for unity of compar- ison. The same is done in our table, for reasons which we shall explain hereafter when treating of hydrogen gas. The full development of the theory of chemical equiva- lent cannot be given here (in the introduction to chemis- try) ; nor can it be expected that the pupil shall have an adequate idea of it from the few statements of facts which we have made in this section. But we shall revert to this subject again, and give a more complete exposition of it, as we go along, treating separately of the most important substances of the chemical catalogue. CHEMICAL APPARATUS. 17 III. CHEMICAL APPARATUS. [It is to be understood that only the most useful and essen- tial apparatus, which may be easily procured, can find a place in an elementary treatise for schools. A complete description of it is found in Berzelius's Chemistry, Vol. 1.] XX. a. Apparatus for dividing bodies. Fig. I. These consist of mortars and pestle, (Fig. I.) hammer and anvil, (Fig. II.) Fig. III. Fig. IV. knives, (Figs. Ill, IV and V.) 18 CHEMICAL APPARATUS. Fig. VI. Jiles, (Fig. VI,) &c, the construc- tion of which is sufficiently plain from the diagrams. b. Apparatus for separating liquids from solids. Fig. VII. To these belong sieves, (Fig. VII.) Fig. VIII. cullenders, (Fig VIII.) Fig. IX. straining cloths, (Fig. IX.) CHEMICAL APPARATUS. Fig. X, Fig. XI. Fig. XII- 19 Fig. XIII. Fig. XIV. funnels, (Fig. X, XI, and XII.); &c. The decanting jar is repre- sented in Figs. XIII and XIV. Its shape is sufficiently plain from the figure, and its applica- tion in the pouring of liquids, easily understood. Fig. XV. Fig. XVI. Fig. XVII. A spherical or common glass bottle, (Figs. XV and XVI,) with a small cylindrical tube, fixed air-tight in the cork, serves to separate a liquid from a solid by the process of evapora- tion (explained in Natural Phi- losophy). To separate a lighter rluid from a specific heavier one, the separatory funnel (Fig. XVII) is used, which opens upwards and downwards. When the lighter fluid is de- canted through the upper aperture the spe- cific heavier descends through the lower. 20 CHEMICAL APPARATUS. Fig. XVIII. The operations of the syphon has already been described in Natural Philosophy, Chapter V. c. Apparatus for the liquefaction of solids. Fig. XIX. Fig. XX. These consist of melting pots, (Fig. XIX,) or cru- cibles, (Fig. XX,) made of earthen ware, silver or platinum ; of glass vessels called matrasses, of which one is represented in Fig. XXI. of porcelain saucers and spoons, (Figs. XXII,) for stirring acids which would effect metal or glass, &c. Fig. XXL CHEMICAL APPARATUS. 21 d. Apparatus for evaporation and crystalization. Both processes have been described in Natural Philosophy. XXI. For this purpose we make use of what are called Fig. XXIII. Fig. XXIV. evaporating dishes, made of porcelain, glass, or silver. (See Fig. XXIII.) Their form must be flat, to present the greatest possible surface to the atmos- phere. When the process of evaporation takes place under the influence of heat it is called a steam-bath. For this purpose a flat vessel, made of wedgewood ware, is bedded in hot sand or ashes. (See Fig. XXIV.) e. Apparatus for distillation. XXII. This is a contrivance for collecting the volatile Fig. XXV. portion of a body which es- capes through the process of evaporation. The most com- mon is an alembic, (Fij XXV,) composed of a flasl (which may be bedded in sand) the head of which fits air-tight in the neck of the pipe, which is destined to carry the rising gas from the flask into the receiver. 22 CHEMICAL APPARATUS. Fig. XXVI. The common still, (Fig. XXVI,) an instrument 7 sim- ilar in its construction to an alembic, is made of cop- per. It is shaped like a kettle, A, and has a hollow mov- able head, B, to which a pipe, C, is attached, leading to a spirally formed tube, commonly called the worm, which for the purpose of cooling, may be immersed in water. The vapours then contained in it are, by this means, con- densed, and descend in drops when the cock, E, is opened. Fig. XXVII. The" instrument more gen- erally employed for distillation is a retort. It may be made of glass, porcelain, or metal ; and is either as shaped in Fig. XXVII, or as represented in Fig. XXVIII. There is al- ways a receiver, R, con- nected with it, which in some instances is again provided with a pipe and stop-cock, to let off the distilled liquid at differ- ent periods. The ope- ration of this apparatus is easily understood. When the liquid which is heated in the retort, A, evaporates, the volatile parts are collected by the receiver, R. CHEMICAL APPARATUS Fig. XXIX. A Florence flask (Fig. XXIX,) with a pipe fixed air-tight through its cork, is a cheap apparatus, answering most purposes for which retorts are used. The pipe, A, may be connected with a receiver, as in Figs. XXV [I, and XXVIJI. f. Apparatus for heating Chemical substances. X XIII. These consist in lamps and furnaces. Fig. XXX. Fig. XXXI. The latter are either portable air furnaces with crucible stands (Figs. XXX, and XXXI) ; or they are fixed wind- furnaces of which one is represented in Fig. XXXII. Fig. XXXII. 24 CHEMICAL APPARATUS. Both kinds of furnaces are so constructed that the air has free access to the fire from below. By this means a continued draught is created, which, as we shall see here- after, is necessary for a brisk flame or free combustion. For the heated air in the furnace becomes specifically lighter and escapes through the upper opening, while the outer air rushes from below in its place. (See Natural Philosophy, Chap. V.) Fig. XXXIII. Figs. XXXIII, XXXIV, and XXXV, represent the three principal kinds of lamps used for chemical purposes. Fig. XXXIII represents the common lamp. A combustible substance, usually made of cotton, called the wick, is immersed in oil, with which the whole apparatus is filled, and is then lighted. The flame, nourished by the oil, which as- cends through the wick and is gradually consumed, throws out heat and light at the same time. Fig. XXXIV. Fig. XXXIV represents a spirit lamp. The main difference be- tween this lamp and the one just described, consists in spirit of wine being employed instead of oil, the heat of the flame of this sub- stance being much more intense than that produced by the flame of a common oil lamp. Fig. XXXV. Fig. XXXV represents an Argand lamp, with its stand. This is as great an improvement upon common lamps as the wind-furnace upon a common fire-place. Its principal advantage over a common lamp consists in a round hollow wick through which the air is admitted by an opening from below, causing thereby a much more perfect combustion, and throwing out much more light and heat than is done by a common lamp, CH.EMICAL APPARATUSj. 25 where the air comes only in contact with the exterior part of the flame. The flame of the Argand lamp is moreover covered by a round open glass, which serves it in the office of a chimney, through which the heated air ascends and is replaced by the air which enters from be- low ; the draft thereby created tending not a little to in- crease the intensity and heat of the flame. Fig. XXXVI. A convenient contrivance for heating bodies in a retort, is Guiton's Lamp-furnace. It consists of an iron or brass rod, O P, with several slid- ing sockets, which serve to support the lamp, A, and the arms, LF, OG, of which there may be as many as may be thought expedient. The arms terminate in iron or brass rings for the sake of supporting retorts and receivers, (see the figure) |T or in small forceps to hold the body which is to be ex- posed to the heat of the lamp. These arms may, by means of sockets, be moved up and down the rod, O P, or turned sideways, and then screwed fast to any particular part of it, as the experiment may require ; and the same may be done with the lamp, in order to regulate the heat. The whole apparatus is best fastened to a table, T, by means of a screw, B, in or- der to give more steadiness and security to the experiment. Fig. XXXVII. For the sake of producing a very intense heat with a common oil or spirit-lamp, an instrument is used which is called a common blow-pipe. It con- sists of a bent brass tube, whose upper end is from one third to one half inch in diameter ; but is grad- ually tapering to a point, as is represented in figure XXXVII. When the lower (bent) end is placed in the flame of the lamp and the upper is applied CHEMICAL APPARATUS. to the mouth or nostrils, a stream of air may be applied to the jet of the flame for the double purpose of giv- ing it a horizontal direction, and making it gradually taper to a point, to which the body that is to be heat- ed must then be exposed. The body must be placed upon a piece of charcoal, which may be held by small forceps. (See fig. L. page 32.) Fig. XXXVIII. An improvement upon the common blow-pipe, is Gahn's blow-pipe, (Fig. XXXVIII.) which instead of the bent tube is provided with the chamber A, to which the smaller orificed pipe, B, is attached. The advantage of this apparatus consists in the chamber, A, retaining the mois- ture from the breath, which, when the common blow-pipe is used, often stops the process, or diminishes the flame. Fig. XXXIX. A more convenient contrivance than either is that rep- resented in Fig. XXXIX. where the blow pipe C, commu- nicates with a bellows A, which may be moved with the foot by placing it upon the board, B, and by which means CHEMICAL APPARATUS. 27 a constant stream of air is sent through the jet of the flame, D. This apparatus is particularly used for closing the tubes of barometers and thermometers, and such similar purposes. g. Apparatus for compressing bodies, or extracting liquids from bodies in which they are contained. Fig. XL. XXIV. For the purpose of extract- ing liquids from solids in which they are contained, two kinds of presses are used ; one with one screw only, (Fig. XL.) and the other with two, (Fig. XLI.) The press with one screw consists chiefly of an iron arch, A, fas- tened to a block of wood, B, and con- taining in C the nut through which the screw, D, moves up and down. The substances contained in the basin, E, are by this screw compressed, and the liquid descends through the nose, F. Fig. XLI. The press with two screws (Fig. XLI.) consists of two boards, A and B, which are brought together by the two screws, C, C, and by this means compress the substances which are placed between them. The remainder of the construction is similar to the press with one screw. 28 CHEMICAL APPARATUS. Fig. XLI1. When a solid substance is to be dis- solved in a liquid, an instrument is often used, which is called the hydrostatic, or, from its inventor, Count Real's press. It consists of a strong tin barrel, A B, which in C is provided with a fine sieve, and in D, with a discharging spout. The upper part screws into a metallic cover E, which terminates in a long narrow tube, and is, in I, provided with a stop- cock. The solid substance from which an extract is to be made, is first put in the barrel and placed upon the sieve C ; on top of it is placed a tin plate, K, which like the sieve, C, is provided with a great many fine holes ; the cover is then screw- ed upon the barrel, and the narrow tube, G H, filled with the liquid which is to be employed for the solution of the solid. The solving power of the liquid is pro- digiously increased by the hydrostatic pressure of the liquid, (see Natural Philosophy, Chapter VI) which by this means forces its way through the solid substance between K and C, and collects in the lower part, B, of the barrel, whence it may be drawn off by the discharging spout, D. CHEMICAL APPARATUS. 29 Fig. XLIII. The pressure of liquids is also taken advantage of in the construction of Brahma's hydraulic press. It consists of a large pump barrel, A, B, C, D, which communicates with a small forcing pump, M N. The two pistons, P, P, work water tight in their respective barrels. The whole space between the two pistons is filled with water. The substance to be pressed is placed upon the top, A B, of the large piston, above which a strong fixed surface, F G, is made to meet the pressure. When the small piston is forced down by means of the lever, E, the water exercises a pressure upon the lower end, C D, of the large piston, P, which will be as many times greater than the force with which the small piston is worked down, as the surface of the larger piston is larger than the surface of the smaller one. Thus, if the surface of the smaller piston be one square inch, and that of the larger one square foot, then the pressure on the upper piston will be 144 times greater than the force which pressed the smaller piston down* Hence one man working on the lever, E, may exercise pressure upon the piston, P, equal to that which it would take 1 44 men of the same strength to produce, if directly working upon C D. If the surface of the smaller piston were only one fourth of a square inch, then the pressure upon C D upwards would be 4 times 144, or 576 times greater ; and so on. Now it is easily seen that the greater the power is, which presses the piston P, upwards, the 3* 30 CHEMICAL APPARATUS. greater will be the pressure exercised upon the body which is placed between the two surfaces, A B, and F G ; whence the utility of this apparatus follows of course. 7i. Apparatus for collecting gases. XXV. For collecting gases an apparatus called the Pneumatic tub, water, or quicksilver bath, is employ- ed. It consists of a tub, A, (see the figure) in which a Fig. XLIV. shelf is fixed in such a manner, that the liquid, common- ly water or quicksilver, may rise two or three inches above it. Ajar or receiver, B, filled with the same liquid is placed upon this shelf, (which for this purpose must be provided with several holes) with its mouth downward. The pipe, C, conducts the gas which is forming in the retort, D, to the jar, B, in which it rises in little bubbles, expelling thereby the liquid of which it takes the place. Fig. XLV. Another apparatus for collecting gases is Priestley's bell-glass. (Fig. XLV.) This useful apparatus consists of a bell glass, A, the neck, B, of which may be closed or opened by means of the stop-cock, C. This con- trivance is very convenient for the collect- ing of gases, because in order to fill it with water or quicksilver, it is only necessary to open the stop-cock, C, and immerse the glass perpendicularly in the liquid. As the glass fills with the liquid, the air escapes through the neck, B D. Its principal use however consists in transferring gases CHEMICAL APPARATUS. 31 from one vessel to another ; for which purpose the gas which escapes through the neck, B D, need only be col- lected by a receiver. Fig. XLVI. Another application of this apparatus is made by filling a bladder (Fig. XLVI.) with a particular gas that may be contained in the bell-glass. This, as we shall see hereafter, is very desirable for the sake of certain experiments. The bladder, L, (Fig. XLVI.) must for this purpose be tied air-tight to a brass tube, G H, which by means of the stop-cock, F, may be clos- ed or opened at pleasure, and in G is made to screw to the extremity, D, of the neck of the bell-glass. When this is done, and the two cocks, G and F, are opened, the bell-glass (Fig. XLV.) needs only be perpendicularly immersed in quicksilver or water, and the gas will escape through the neck into the bladder. When the bladder is rilled, the stop- cock F, is closed, and the barrel G H, unscrewed from the bell-glass. It is also common to provide the bell, A, with a scale S, (see the last figure) in order to estimate the volume of gas which escapes by the rise of the quick- silver or water in the bell-glass. i. Apparatus necessary for various chemical purposes. Fig. XLVII. XXVI. To these we reckon stands, (Fig. XLVII.) 32 CHEMICAL APPARATUS. Fig. XLVIII. Fig. XLIX. Fig. L. Fig. LI. Fig. LII. Fig. LIII. Fig. LIV. shears, (Fig. XLIII.) pincers, (Fig. XLIX.) forceps, (Fig. L.) plates, (Fig. LI.) cylindrical glasses, (Fig. LII.) glass tubes, (Fig. LIII.) tubs, (Fig. LIV.) UHEMI|CAL APPARATUS. Fig. LV. bellows, (Fig. LV. ) and especially accurate beams and scales (Figs. LVI, LVII, and LVIII.) The principle of the common balance, (Fig. LVI1I.) has already been described in Natural Philosophy. It remains for us to say a few words on the construction of beams, or portable balances (Figs. LVI and LVII.) These are insturments of great utility to the practical chemist, and serve either for the determination of the specific gravi- ty of substances, or to show at once the proportion of their chemical compositions. In the latter case they are called per-cent balances. Fig. LVI represents Nicholson's porta- ble balance. It consists of a hollow body, , made of silver or tinned iron, to which is fastened a piece of thin wire, b, which at its upper extremity supports a small plate or cup, d. To the lower extremity of the body, a, is attached an- other piece of wire,/, stronger than the one above, carry- ing a metallic cone, g, the lower point of which is filled out with lead to give the apparatus a perpendicular direction, 34 CHEMICAL APPARATUS. when immersed in water. The weight of the whole must be less than the water which it displaces, in order that it may swim, (see Natural Philosophy, Hydrostatics,) and be able to bear a small additional weight upon the cup, d, before it sinks to the point, e, marked upon the upper wire. The use of this apparatus in determining the specific gravities of bodies is exceedingly simple. When the body whose specific gravity is to be determined is a liquid, then immerse the apparatus first in water, and then in the pro- posed liquid ; placing in each case as many weights in the cup, d, as is necessary to make it sink to the point, e. The weight of the apparatus added to the weight placed in the cup, d, will in each case give the weight of equal volumes of both liquids, which, divided by one another, will give the specific gravity of the liquid in question. To give an EXAMPLE : Suppose the weight of the apparatus is 180 grains, and the weight required to make it sink in water to the point, e, equal to 42 grains more. Suppose 80 grains were necessary to make it sink to the point, e, in the oth- er fluid ; then 42 added to 180 gives 222 grains for the weight of the water ; and 80 added to 180 gives 260 grains for the weight of the liquid ; and dividing 260 by 222, we obtain 1, 17 for the specific gravity of the liquid. If the body whose specific gravity we wish to know is a solid, then place it in the cup, d, and add to it as many weights as will sink the apparatus to the point, e. By this means you find the absolute weight of the body. For if the apparatus requires 42 grains of itself to sink to the point e, and now that the body is in the cup, d, it re- quires but 30 grains, the body itself must evidently weigh 12 grains. Hence the absolute weight of a body is found by subtracting the weights added to it when in the cup, d t from the weight which is required to sink the balance alone to the point e. Remove the body now from the cup, d } to the hollow cone, g% and the apparatus will immediately rise ; for it will lose as much of its weight as the water weighs, which the body now displaces. (Natural Philosophy.) Adding therefore as many weights to the cup, d } as will make the apparatus again sink to the point e, we determine the abso- lute weight of an equal volume of water ; and dividing the absolute weight of the body by the weight of an equal vol- CHEMICHL APPARATUS. 35 ume of water, we obtain its specific gravity. To give an EXAMPLE : Suppose the balance requires of itself 42 grains to sink to the point e, but when the body is in the cup it requires but 12 grains ; and if the body be now removed from the cup, d, to the cone, g, 5 further grains are necessa- ry to sink the apparatus to the point, e; required the spe- cific gravity of the body 1 Ans. By the first supposition it is evident that the body must weigh 30 grains ; and by the second it is plain that an equal volume of water weighs 5 grains ; hence 30 divided by 5, equal to 6, is the specific gravity of the body. (See Natural Philosophy, Chap. IV.) The per cent balance Fig. LVII, is an instrument by which the degree of mixture of two liquids, or of a liquid with a solid substance is ascertained. It consists of a hol- low body, , made of silver or tinned iron, bearing upon its upper extremity a scale, a b, and on its lower end some heavy substance to give the apparatus a perpendicular di- rection when immersed in the liquid. The scale is gen- erally divided into 100 degrees, each degree marking the existence of 1 portion of one liquid in another, or of a solid substance in a liquid. But such a scale will only serve for one particular kind of mixture, and must be altered or changed if applied to another. Such are the beer, bran- dy or spirit scales, which by the degree of their immersion in these respective liquids, show the quantity of alcohol contained in them. The deeper they immerse, the less water, and consequently the more alcohol is contained in these liquids ; alcohol being specifically lighter than water. (See Natural Philosophy, Chap. IV.) But the scale used for brandy would not answer for beer or wine, and vice versa. Tc. Lutes. XXVII. These are employed to join together the parts of vessels which are used in distillation, to prevent the es- cape of vapors. A mixture of China clay with a solu- tion of borax will do for metallic vessels. When the liquid which is to be distilled is not corrosive, slips of bladder or paper spread with gum arabic or flour-paste will answer the purpose; 8 parts of yellow wax mixed with one part of turpentine oil, forms a very good resinous lute. 36 CHEMICAL COMPOSITION OF BODIES. TV. CHEMICAL COMPOSITION OF BODIES. XXVIII. All bodies in nature are either animate or in- animate. The former, to which belong the plants and an- imals, are composed of a variety of exceedingly delicate vessels, filled with liquids, of which each has a particular office, and the assemblage of which forms what is called their organization. Hence it is also customary to call plants and animals organized or organic bodies, in opposi- tion to dead or inanimate substances, which being merely composed of particles kept together by the power of cohe- sion, are said to be unorganized or inorganic. XXIX. With regard to chemistry, all unorganized or inorganic bodies are, I. Either simple or compound ; that is, either as yet not known to contain other ingredients, or composed of two or more heterogeneous substances. 2- The compounds of unorganized bodies are most al- ways formed by a binary combination (combinations of two and two substances). Thus water is composed of two el- ements, oxygen and hydrogen ; Saltpetre of two substan- ces, nitric acid and alkali, of which each is again a com- pound of two other substances : (nitric acid is a compound of nitrogen and oxygen, and alkali a compound of Potas- sium and oxygen.) See introduction, VII. 3. The compounds of unorganized bodies can, in most cases, be produced by the combination of their elements. Thus, water may be produced, as we shall see hereafter, by combining oxygen and hydrogen in the proper propor- tions; saltpetre may be produced by a combination of nitric acid and alkali, &c. Organized bodies, on the contrary, are 1. Generally composed of more than two elements. 2. They cannot be produced by art, through a combi- nation of their chemical ingredients ; because they all con- tain a certain vivifying principle, totally unknown to us ; and which will probably forever escape all our anatomical and chemical researches. XXX. A vast number of organized and unorgan- CHEMICAL COMPOSITION OF BODIES. 37 ized bodies have been subjected to chemical analysis, and, by means of art, been decomposed into their ingredients ; but there are fiftyfour substances, which, thus far, have resisted all attempts to decompose them, and, on that account, are called elements. Of these, 4 are gaseous or aeriform bodies ; 9 are solid, non-metallic substances ; and 41 are metals. We shall here annex their names, and propose to treat separately of the properties and com- binations of each in the course of this book. NOMENCLATURE OF ELEMENTS. a. Gaseous Elements. 1. Oxygen, 3. Nitrogen, 2. Hydrogen, 4. Chlorine. b. Solid Substances. 5. Carbon, 10. Iodine, 6. Sulphur, 1L Bromine, 7. Selenium, 12. Silicon, 8. Phosphorus, 13. Fluorine. 9. Boron, c. Metals. 14. Potassium, 32. Iridium, 15. Sodium, 33. Osmium, 16. Lithium, 34. Nickel, 17. Calcium, 35. Iron, 18. Barium, 36. Lead, 19. Strontium, 37. Tin, 20. Magnesium, 38. Copper, 21. Glacinum,or Berillium, 39. Zinc, 22. Yttrium, 40. Bismuth, 23. Allumium, "41. Cobalt, 24. Zirconium, 42. Antimony, 25. Thorium, 43. Arsenic, 26. Mercury, 44. Manganese, 27. Silver, 45. Tellurium, 28. Gold, 46. Titanium, 29. Platinum, 47. Cerium, 30. Palladium, 48. Uranium, 31. Rhodium, 49. Columbium, 4 38 CHEMICAL COMPOSITION OF BODIES. 50. Tungsten, (Wolfram,) 53. Molybdenum, 51. Cadmium, 54. Vanadium. 52. Chromium, And of these 54 elements the whole infinite variety of bodies is composed ! ! XXXI. The various chemical compositions arising from the combination of these elements may again be arranged under six different heads : 1. Oxides. This name is applied to all combinations of oxygen with another element. Thus, the combination of oxygen with iron is called oxide of iron ; that of oxygen with manganese, oxide of manganese, &c. 2. Adds. These are combinations of certain substan- ces with acidifying (acid-producing) principles, common- ly oxygen or hydrogen, and distinguish themselves by the following properties : a. They have generally (not always) a sour taste. b. Most of them are soluble in water ; and change blue vegetable colors into red. c. They are all negatively electric; (Natural Philoso- phy, Chap. IX.) that zs, they adhere to the positive or zinc pole of the voltaic pile. (To understand this more com- pletely see the remark on the following page.) d. Combined with solid substances they form salts, or at least substances which bear a great resemblance to salts. The last mentioned properties are, by modern chemists, considered the most characterizing and essential qualities of acids. 3. Bases. To this class belong all substances remark- able for the following two properties : a. When combined with acids they form salts ; and b. When separated from a combination with an acid by the action of a voltaic battery, they adhere to the negative pole. They are consequently positively electric. * Not all acids have a sour taste ; neither do all acids necessarily contain oxygen, as it was once believed. Prussic acid, for instance, has a bitter taste, and contains no oxygen in its composition. CHEMICAL COMPOSITION OF BODIES 39 The learner ought to direct his attention particularly to the distinguishing characteristic between acids and salts ; viz. that the acids are negatively, and the bases positively electric. 4. Salts. So are termed the almost innumerable com- binations of the bases with the acids. 5. Sulphides and Chlorides. These are combinations of sulphur or chlorine with an element, commonly a metal. 6. Alloys of Metals. These are combinations of one metal with another. The combinations of quicksilver with other metals have received the special name of Amal- gams. The theory of Galvanic electricity, as well as that of the voltaic pile or battery, has already been given in the ninth chapter of Natural Philosophy. It has there been stated, that the most important experiments which can be made with the galvanic battery belong to chemistry. This is so far true that it may well be said that the theory of Galvanic electricity has changed the face of the science of Chemistry. Its influence upon the chemical decomposition of bodies stands unrivalled by any other agent in nature, and is truly universal. There is hardly a substance in nature, upon which galvanic electricity does not more or less exercise its influence ; and by its agency the most difficult chemical decompositions have been effected with comparative ease and facility. EXAMPLE. The fixed alkalies, a class of bodies with whose properties we shall become acquainted in the 3d chapter, were believed to be elements, and resisted every attempt to decom- pose thenr, until the brilliant discoveries of Davy and Berze- lius, who dissolved them into their elements by means of pow- erful Galvanic Batteries. Nor is this decomposing power of Galvanic electricity confined to a few chemical compounds ; for nearly all the acids, and the class of bodies we have dis- tinguished by the name of salts, yield their elements when ex- posed to the action of this universal agent. It is on this ac- count, Galvanic Electricity has become a criterion (and indeed, as we have said before, the best criterion we have) of the basic or acid nature of a chemical substance. For whenever a salt is decomposed into its two principal constituents, the acid and the basis, the acid adheres invariably to the positive, and the basis to the negative pole of the galvanic battery. Now as the positive or zinc pole of the battery attracts only nega- tive electric bodies, (see Natural Philosophy, Chap. IX.) and the negative or copper pole attracts positively electric sub- 40 CHEMICAL COMPOSITION OF BODIES. stances, we conclude that all acids are in reference to the class of bodies which are called bases, negatively, and all bases in reference to the acids, positively electric substances. But it does not follow from this that a basis cannot of itself be attracted by either of the two poles, or that an acid cannot be composed of two elements, which evince again opposite elec- tricities to each other. This as we shall soon see, occurs frequently enough ; but it is sufficient for us at present, to understand the difference between an acid and a basis, as we shall revert to this subject again in the fourth Chapter. We shall now describe the manner in which the combina- tions of the almost innumerable class of bodies which are characterized by the names of salts and acids, is effected by galvanic electricity. (See Natural Philosophy, Chapter IX.) Fig. LIX. If the trough apparatus (Fig. LIX.) is used, then the cells, A, are filled with water, which contains in solution a quan- tity of common salt, or which is mixed with a small portion of muriatic or sulphuric acid. The plates, B, which are fit- ted to these cells and connected by a slip of wood, are then let down into the cells, and the two conducting wires, Z and C, (of which Z is connected with the positive, or zinc pole, and C with the negative or copper pole) are brought in contact with the substance, S, which is to be submitted to the agency of the battery. Now if this happens to be a salt, it has been found that the acid of which it is composed ad- CHEMICAL COMPOSITION OP BODIES. 41 heres invariably to the positive or zinc pole, Z, and the basis to the negative, or copper pole, C, of the battery. A very convenient apparatus of this kind, which may be at pleasure increased or diminished, is Count Stadion's Couronne Fig. LX. des Tasses, or cup-battery. It consists of a number of cups of glass or wedgewood, (see Fig. LX.) In each cup is placed a plate of zinc, and another of copper, in such a manner that the metals do not touch each other in the cups ; but are without connected with each other by slips of metal. The same order of plates zinc, copper, zinc, copper, &c, is of course preserved throughout the apparatus. When the cups are filled with a solution of salt or muriatic acid, then the effect is the same as that produced by the trough-battery. It is easily perceived that the strength of such an apparatus may be increased or di- minished by employing a greater or smaller number of cups. To account for the chemical decomposition of bodies by Galvanic Electricity, several ingenious theories have been invented, among which that of Sir Humphrey Davy deserves decidedly the preference. He supposes the ele- ments of all chemical compounds to be originally possess- ed of opposite electricities. These opposite electricities are, by the chemical affinity which these elements have for one another, kept in a perfect state of equilibrium. But when such a compound is exposed to the agency of a gal- vanic battery, then the attractive and repulsive force of the two opposite poles, effect a separation of its elements ; the negatively electric element flies to the positive or zinc pole, and the positively electric ingredient, to the negative pole of the battery. Those substances which adhere to the neg- ative pole are then said to be positively electric ; and those which adhere to the positive pole of the battery are called negatively electric bodies. Thus according to what 4* 42 RECAPITULATION. we have said all acids are, in reference to those substances which we call bases, negatively electric ; and all bases are, in reference to the acids, positively electric substances. This theory, although there are several objections to it, is strongly corroborated by some very prominent phenom- ena, which accompany the decomposition of salts by gal- vanic Electricity ; and of which we shall have an oppor- tunity to speak hereafter when treating of salts. RECAPITULATION. [The preceding Introduction, contains the outlines of Gene- ral Chemistry. It will therefore be well for the teacher to go over it a number of times until he is perfectly satisfied that his pupils have understood the definition of chemistry, andean give a tolerably good account of the laws of affinity and chem- ical action. Not until then ought they to commence the study of the first chapter.] I. QUESTIONS ON DEFINITIONS. [I.] Into how many classes are all natural sciences di- vided 1 What are these ? [II.] What is the object of Natural History 1 Which are the three great branches of Natural History 1 [III.] What is the object of Natural Philosophy ? Into what two branches has Natural Philosophy been divided ? How do you define Chemistry 1 [IV.] What do you call the peculiar kind of attraction which is only manifest in contact, and which is the cause of a change in the properties of bodies ? Give an example. [V.] In how many different ways does the chemical affinity which one body has for another manifest itself ? What are these two ways 1 What is the first of these processes called 1 What the second ? Give an example of chemical composition or synthesis. Give an example of chemical analysis. RECAPITULATION. 43 What is the difference between mechanical and chemical separation ? Give instances of mechanical and chemical di- vision. [VF.] What are the parts obtained by a chemical sep- aration or analysis called? What is the body called from which they are derived ? Give an example. [VII.] When do you call a body composed of nearer and more remote ingredients 1 Give an example. Which, in your example are the nearer, and which the more remote ingredients ? [VIII.] What are those substances called which are not, as yet, decomposed by any means in our power 1 Does it follow from this that all substances which are now con- sidered as elements are really incapable of analysis ? What then does the word element express in chemistry ? II. QUESTIONS ON CHEMICAL ACTION. [IX.] What kind of attraction must be considered as the principal cause of all chemical phenomena? What changes does chemical affinity produce on bodies which are subjected to its action ? [In the answerto this question the pupil ought only to enu- merate the three principal changes, a, &, c, printed in italics.] Give examples of changes produced in the temperature ; of changes produced in the physical properties of bodies ; and of changes produced in aggregate form of bodies. [X.] Does chemical action ever take place without a change of temperature ? What important fact do you know respecting it ? Does heat generally favor or coun- teract chemical affinity 1 Give examples. [XI.] What is the greatest obstacle to chemical affin- ity 1 Why do bodies combine readiest with each other, when one or the other has been reduced to the fluid state ? Why does heat increase the action of chemical affinity? 44 RECAPITULATION. What general inference has been drawn from this ? Is this rule without exception ? What would take place if there were no cohesive attraction to counteract the chemical affinities of bodies ? How must chemical affinity and cohesive attraction be considered in ref- erence to each other? [XII.] When are two bodies said to be neutralized ? Give examples of neutralization. In what state are potash and sulphuric acid contained in the salt which is formed by their combination ? What is neces- sary in order to effect a complete neutralization ? [XIII.] What are those combinations called, in which the ingredients still preserve a portion of their original properties ? Give an example of such a combination. [XIV.] To what must we have recourse in order to decompose a chemical compound into its constituent parts ? What is that kind of chemical attraction called, in con- sequence of which a body quits a combination already ex- isting, for the sake of forming a new one ? Why is this attraction called elective affinity 1 Give an example of the action of elective affinity. (Ex- plain the figure, page 7.) What substance, in your example, shows an elective affinity for potash ? Why ? [XV.] What is the product of the combination of a solid body with a flujd called ? Does the affinity between a solid and a liquid substance continue forever, or is it limited to a certain point? How is that point called, beyond which the solving power of the liquid ceases to operate upon the solid 1 What is the solution itself said to be, when arrived at this point 1 Give an example. [XVI.] Upon what three things does the saturation of liquids principally depend ? Is there no exception to the general rule, that heat increases the solving power of liquids'? Give examples. RECAPITULATION. 45 [XVII.] What do some compounds of two substances require for their decomposition ? When is this the case 1 What do you call this kind of affinity 1 Give an example. (Explain the table on page 9.) To what do some philosophers ascribe these phenomena ? Why? What substance in your example (page 9) exercises a pre- disposing affinity upon oxygen ? Why ? By what means does the acid predispose the oxygen for a combination with the zinc ? [XVIII.] What does frequently happen when two compounds are brought together in a state of solution ? What is this compound action said to be caused by ? Give an example. (Explain the table on page 10.) Which substance, in your example, does the acetic acid elect in preference to the lead, with which it was combined ? Which substance does the sulphuric acid elect in preference to the zinc ? And why is this action called double elective affinity ? [XIX.] In what other manner do bodies combine, be- sides forming mixtures, or dissolving others to saturation ? What sort of compound do we always obtain from a com- bination in fixed proportions ? Give an example. Do bodies always combine with each other in only one fixed proportion 1 Give an example where one substance combines .with another in several fixed proportions ? Have similar fixed substances been discovered in the combinations of other bodies ? And what has been ob- served in reference to these combinations 1 What general principle are we enabled to lay down, from these observa- tions ? If the remainder of this section should be found too diffi- cult for the beginner, it may be omitted until reviewing the first four chapters of the book. But it would be better for him if he could explain the example on page 12. If he has understood it well, let him take the substance B, in reference to A, C, D, E, and F. and determine from that the relation of A to C, to D, E, and F, &c. The better he understands this example, the better will he be able to comprehend the one which is taken from nature, and which consists of larger pro- portions. 46 RECAPITULATION. Let the pupils now explain the table on page 13. The teacher may also let them copy that table, and then ask the following questions : Ques. Why are 37 weights of mu- riatic acid said to be an equivalent to 40 weights of sulphuric acid ? Why are 40 weights of sulphuric acid an equivalent to 54 of nitric acid, or to 28 of phosphoric acid ? Why are 28 weights of lime equivalent to 48 weights of Potass, or to 32 of soda ? What is the smallest number of weights of one sub- stance called which combines to saturation with all other substances for which it has a strong chemical affinity ? By what means is the chemical equivalent of a compound substance found, when the chemical equivalents of its elements are known 1 Explain example I. Explain example II. Explain example III. III. QUESTIONS ON CHEMICAL APPARATUS. [XX. J a. What instruments are principally used for dividing bodies ? b. What instruments are used for separating liquids from solids. Explain the separatory funnel, (Fig. XVII, page 19) and its operation. c. What apparatus is used for the liquefaction of solids. [XXI ] d. What apparatus is used for evaporation and crystallization 1 Why must the form of evaporating dish- es be flat 1 What is the process of evaporation called, when it takes place under the influence of heat 1 What apparatus is used for this purpose 1 [XXII.] e. What is the most common apparatus used for collecting the volatile portion of a body which escapes through the process of evaporation ? Describe Fig. XXV. Describe the common still, (Fig. XXVI.) What is the name of the instrument most commonly employed in distil- lation ? Explain Figs. XX VII and XXVIII. What other apparatus answers most purposes for which retorts are used ? f. In what consists the apparatus for heating chemical substances 1 On what principle are both, the portable air- RECAPITULATION. 47 furnace with crucible stands, and the fixed wind-furnace constructed ? What is the construction of the common lamp? What is the difference between a common lamp and a spirit lamp 1 In what consists the principal advan- tage of an Argand's lamp over a common lamp ? For what purpose is the flame of an Argand's lamp covered with a cylindrical open glass ? How is Guiton's lamp furnace constructed 1 (Explain Fig. XXXVI, page 25.) What is the name of the instrument which is used for producing a very intense heat with a common oil or spirit lamp? Of what does it consist? Explain its operation and the manner in which it is used. What is the difference between Gahn's blow-pipe and the common blow-pipe ? Explain Fig. XXXVIII. In what does the advantage of this apparatus consist? What other still more convenient contrivance is there, than either the common or Gahn's blow-pipe. Explain Fig. XXXIX. [XXIII. ] How many different kinds of presses are used for extracting liquids from solid substances. Explain Fig. XL. Explain Fig. XLI. What apparatus is frequently used when a solid sub- stance is to be dissolved in a liquid ? Describe Fig. XLII. How is Brahma's Hydraulic press constructed ? Ex- plain Fig. XL1II. [XXIV.] What apparatus is used for collecting gases ? Describe Fig. XLIV. What other apparatus is used for collecting gases? Explain Fig. XLV. What applica- tion is made of Priestley's bell glass ? Explain Fig. XLVI. [XXV.] What other apparatus is used for various other chemical purposes ? Explain Nicholson's portable balance Fig LVII. How is the specific gravity of a liquid deter- mined by means of Nicholson's portable balance? (Ex- plain the example, page 34.) How is Nicholson's balance to be used when the body whose specific gravity we wish to determine is a solid ? (Explain the example on page 35.) 48 RECAPITULATION. What sort of an instrument is the per-cent balance ? How is it constructed 1 (explain Fig. LVII.) Can the scale which is used for one mixture of liquids be employ- ed also for another ? [XXVI.] For what purpose are lutes employed ? What kind of lute will answer for metallic vessels ? What sort of lute will answer for liquids which are not corrosive ? What composition makes a good resinous lute ? IV. QUESTIONS ON THE CHEMICAL COMPOSITION OF BODIES. [XXVII.] To what class of bodies belong plants and animals ? Of what are plants and animals composed ? What are all inanimate substances merely composed of? [XXVIII.] What characterizing properties have all inanimate bodies in reference to chemistry 1 (The answer to this question consists in the recitation of the three heads, 1, 2, 3, printed in italics.) Give an example of binary combinations of bodies. What characteristics, on the contrary, distinguish all organized bodies ? How many different substances are there, which have thus far resisted all attempts to decompose them ? What are they there- fore called ? How many of these elements are gaseous ? How many are non-metallic solid substances ? How many are metals 1 If the teacher thinks fit, the pupils might now commit their namevS to memory, or they may also omit this, until the review- ing of the book. [XXIX.] Under how many different heads may the va- rious chemical compositions, arising from the combination of these elements be arranged 1 What are they ? (The answer to this question consists in the enumeration of the six heads, Oxides, Acids, Bases, &>c. What substances are called oxides? Give examples. What substances are called acids ? What are the char- acterizing properties of the Acids ? By what properties are those bodies distinguished which are called Bases 1 RECAPITULATION. 49 What are salts? What are sulphides and chlorides ? What do you understand by alloys of metals I [Upon the remainder of this section the teacher need ask but a few questions, as the same subject occurs again in the 4th chapter.] What becomes of all salts when exposed to the action of Galvanic Electricity ? Why is galvanic electricity the best criterion of a salt or an acid 1 Describe the manner in which salts are decomposed by galvanic electricity ? (Explain Fig. LIX.) Of what does Count Stadion's Cup-battery (Couronne des Tasses) consist? (Explain Fig. LX.) What is Sir Humphrey Davy's theory with regard to the electrical phenomena exhibited by all chemical coin- pounds? What, according to this theory, are all those substances called which adhere to the negative pole of the galvanic pile ? What, those which adhere to the positive pole? What are all acids in reference to that class of bodies, which are called bases ? What, all bases with regard to those substances called acids ? CHAPTER I. OP THE PROPERTIES AND COMBINATIONS OF THE FOUR GASEOUS ELEMENTS, OXYGEN, HYDROGEN, NITROGEN, AND CHLORINE. A. Oxygen* 1. Properties of oxygen. By the name of oxygen we distinguish a gas contained in our atmosphere, of which it constitutes about 21 per cent ; (being the T 2 ^ part of the whole atmosphere). It is also a component part of water, forming nearly T 8 ^j of its whole weight. It is colorless, a litile heavier than atmospheric air, and insol- uble in water, and is destitute of either smell or taste. Its presence is absolutely necessary to the continuance of animal life ; but breathed in its pure state it is injurious, because it affects the lungs. 2. Mode of obtaining ozyg'.-n. Oxygen is obtained in a variety of ways, of which "it will suffice to mention the following four : 1. From a substance called Chlorate of potash ; by heating it in a retort and collecting the gas which is giv- en off by means of the pneumatic tub. Fig. LXI. * From a Greek word, signify it g formation of acid. OXYGEN. 51 When the Chlorate of Potash is heated it fuses, and gives off the oxygen in a very pure state, which is then, through the pipe, conveyed to the receiver, in the manner explained in the Introduction, page 30, Fig. XLIV. 2. From a substance called Red Oxide of quicksil- ver. The process is nearly the same as that just de- scribed. 3. From a substance called Black Oxide of manga- nese. 4. From a variety of growing vegetables when exposed to solar light, and from the green matter formed in stag- nant pools, when immersed in water. This is an experi- ment requiring no other apparatus than a tumbler filled with water ; if at hand, Priestley's bell-glass is best adapt- ed for it, having a contrivance at the neck, by which means the gas may be introduced into another vessel or a bladder. (See Fig. XLV, page 30.) 3. Combinations of oxygen. Oxygen combines with nearly all simple and compound bodies. The process by which this combination is effected is called the oxygena- tion of bodies. This oxygen ation is sometimes accompani- ed by the phenomenon of fire, (by light and heat) in which case it is termed combustion. The products of the differ- ent combinations of oxygen with other elements are either oxides or acids ; according to the different proportions in which the oxygen combines with them. EXAMPLE. Carbon combined with oxygen gives 1 oxide and 3 different acids. Sulphur combined with oxygen gives 4 different acids. Iron forms with it 2 different oxides, &c. 4. The different oxides and acids arising from the va- rious combinations of oxygen with other substances, have each received a particular name, indicative of the proportion of oxygen contained in the combination. The oxides are termed Protoxides, Deutoxidcs and Peroxides. The name of Protoxide is given to the smallest quantity of oxygen com- bined with another substance ; that of Deutoxide denotes the next greater quantity of oxygen combined with it ; and the name of Peroxide is applied to the greatest proportion 52 OXY'GEN. of oxygen which an oxide is capable of holding. With regard to the acids, we are in the habit of distinguishing them by iheir terminations, in ic or ous ; or by putting the Greek preposition hypo (signifying under) before the name of the acid. The name of the acid ending in ic in- dicates the highest degree of oxygenation ; that termin- ating in ous indicates the next lower degree ; a still lower degree, if there be any, is expressed by the preposition hypo. EXAMPLE. The gas called nitrogen forms with oxgyen three different acids, which, according to the degree of oxygen- ation (the quantity of oxygen contained in their composition) are called nitric acid ; nitrous acid, and hypo -nitrous acid. Ni- tric acid indicates the highest degree of oxygenation ; nitrous acid the next lower, and hypo-nitrous acid the lowest degree. Theory of Combustion. 5. It has been said before ( 3) that the combination of some bodies with oxygen is accompanied by fire in which case it is called the combustion, or burning of bodies. The combustion or burning of bodies, therefore consists in their sudden combination with oxygen.* Every body capa- ble of such a combination is called a combustible sub- stance. Phlogiston of the ancients. The ancient chemists ascribed the process of combustion, or the phenomenon of fire, to a par- ticular substance which they called phlogiston. But this the- ory has long ago been exploded ; and it is now generally taken as an established fact that this phenomenon is produced, as we have said before, by the sudden union of oxygen with a com- bustible body. 6. Degree of temperature necessary for combustion. There are bodies which combine with oxygen to combus- tion without being previously heated (as is, for instance, the case with a substance called sulphuretted hydrogen) ; most bodies, however, require for this purpose a certain high degree of temperature. * We su.ill se.3 hero.ifter that the gas termed chlorine is in a cer- tain measure capable of producing similar phenomena. OXYGEN. 53 EXAMPLE. Sulphur, wood, coal, phosphorus, &c, must first be heated to a certain degree of temperature before they ex- hibit the phenomenon of fire. But when these bodies are once heated, they generally give out sufficient heat to keep up the degree of temperature necessary for their combustion. Fig. LXII. Fig. LXHL The chemical process of a burn- ing candle (Fig. LXII,) or lamp, (Fig. LXIII,) is this : The wick a, is lighted by a piece of burning paper or wood. By this means the surrounding particles of fat or oil are heated to the boiling point, (Natural Philosophy, Chap. VI,) and thereby decomposed as all an- imal substances, into inflammable gases. These combine with the oxygen of the atmosphere and pro- duce the phenomenon of light, commonly called the^ame of the candle. This flame gives out sufficient heat to keep the degree of temperature necessary for the decomposition of another portion of the fat or oil ; and so does this process continue until the whole candle or oil is exhausted. 7. Light given out by the combustion of bodies, The light which is given out by different substances during the process of combustion is subject to variation in intensity and color. EXAMPLES. Phosphorus, zinc, and arsenic give out a white light ; the flame of sulphur is blue ; that of selenium azure / &c The color of the flame does not only depend on the burning substance, but also upon the degree of heat pro- duced by its combustion. Most combustible bodies when moderately heated burn with a yellow or blue flame ; par- ticularly if there be no draft to supply the flame with fresh quantities of oxygen. 8. Combustion in oxygen. All combustible bodies burn in oxygen with increased splendor. 5* 54 OXYGEN. Fig. LXIV. EXAMPLE. A small piece of wax taper with its flame blown out, but its snuff still red hot, when immers- ed into a vessel filled with oxygen, is instantly rekindled, and throws out a most vivid light. -(See Fig. LXIV.) Fig. LXV. A piece of sulphur or phosphorus, let down into a jar filled with the same gas will burn with indescribable brilliancy. (See Fig. LXV.) In order to perform these experiments a common bottle or jar may be filled with the gas by means of the pneumatic tub. (Intr. page 30.) Through the cork of the bottle a piece of wire may be made to pass, containing at its lower end the body which is to be immersed. (See the next figure.) ANOTHER EXAMPLE. Iron, which only burns at very ele- vated temperatures, needs but a red heat to burn in oxygen gas with a light which is almost as dazzling and insufferable to the eye as the sun itself. Fig. LXV I. A faint representation of it is given in Fig. LXIV. A piece of piano-wire spirally twisted, is in- troduced air-tight through the cork, a, of a bell-glass or receiv- er filled with oxygen gas. To the lower end of this wire is at- tached a piece of thread, touch- ed with sulphur or wax, to ignite the wire in the first instance. As the gas is a little heavier than atmospheric air, its escape or mixing with the atmosphere is prevented by placing the receiv- er in a basin filled with water. If we were to employ a com- OXYGEN. 55 mon jar for the same experiment, then the little globulse of melted wire which drop during the process of combustion, would melt the glass, or if the bottom of the vessel be thin, fuse a hole through it, without breaking the glass. Query What do all these examples prove, in reference to the heat produced by the burning of substances in oxygen gas ? Ans. These examples prove that the heat given out by the combustion in oxygen gas is incomparably more intense than that thrown out by combustion of the same substances in atmos- pheric air. Query And what would become of our grates, stoves, or iron forges, in short, of all the labors of the black- smith, if our globe was surrounded by pure oxygen ? Ans. Our grates and stoves would burn and melt the moment they would get red hot ; and as to the labors of the black smith, they would be entirely out of the question ; for in order to shape iron, it must first be made red hot (it being exceedingly hard in its natural state); and the moment it would get red hot it would begin to burn and melt into balls. 9. If the whole product of combustion is weighed it is always found to be heavier than the substance was before the combustion. Thus, when a piece of wire is .burnt in oxygen its weight is found to increase by 40 per cent, that is, 100 grains of iron before the combustion, weigh 140 grains after it. The reason of this change in the weightofiron, is because 40 grains of oxygen gas combined with it during the combustion. A similar increase of weight is noticed in all bodies which are burnt in oxygen gas, and corresponding changes take place at every com- bustion in atmospheric air. To this general rule it can- not be objected that the ashes obtained from burning wood, straw or other substances weigh generally much less than these substances did before they were burned ; because when these bodies are burnt in the open air, we do not obtain the whole product of their combustion. A great quantity of inflammable gas which is always given off dur- ing their combustion, escapes through the chimney or in the air. But when these are collected and their weight added to that of the ashes, then the sum of these united weights is always greater than that of the wood, straw, or other substance before the combustion. 10. No combustion can take place without the pres- 56 O X Y G E M . etice of oxygen;* the process of combustion , therefore, can only be continued as long as there is a sufficient quantity of oxygen to support it. This follows immediately from what we have said in 5. For if every combustion consists in the combination of oxygen with a combustible substance, it is self-evident that no such process can take place un- less a sufficient quantity of oxygen is present. Moreover we can mark the actual consumption of oxygen gas during combustion by a very easy Fig. LX VII. EXPERIMENT. Take a common bell-glass or receiver, through the cork of which introduce a piece of bent wire, supporting at its lower end a small lighted candle, a, and place the whole over a basin of water. As the candle is burning, the water of the basin will rise in the receiver, so that if a small scale be introduced into the latter, the rising of the water will indicate the quantity of oxygen consumed. Query What does the rising of the water in the receiver prove ? Jlns. It proves that a portion of the gas in the re- ceiver is consumed by the flame of the candle. Query Why ? Ans. Because without such a consumption of the gas no vacuum could be created in the receiver, into which the water could be forced by the external air. ANOTHER EXPERIMENT. Instead of oxygen, fill the re- ceiver (in the last figure) only with common atmospheric air. The burning of the candle, although less vivid, will still consume a portion of air ; the water will still rise in the receiver, although not so rapidly nor so high as when pure oxygen is employed ; and the candle, after burning more and more faint, will finally become extinguished. When the quantity of air then remaining in the receiver is examinedj it is found to have lost just y 2 ^ of its volume, which is ex- actly the proportion in which oxygen is contained in atmos. * We shall see in future that a few substances burn faintly in chlorine ; but this can hardly be considered an exception to the genera! rule. OXYGEN. 57 phericair. (See 1.) A burning candle now introduced into this air is instantly extinguished ; small animals, birds, frogs, &c, introduced into it speedily die ; in short, the remainder of the air in the receiver is totally unfit either to support combustion or the process of respiration of liv- ing animals. Query What does the slower burning of the candle in common atmospheric air prove ? Jlns. It proves that the vividness and splendor of the combustion depend on the great- er or less quantity of oxygen which is consumed ? Ques. But why does not the water rise as high in the receiver as when pure oxygen is employed ? *Qns. Because the whole quantity of air in the receiver is not consumed by the burning of the candle ; but only that portion of it which is pure oxygen. Ques. And why does the candle become extin- guished, when -j- 2 ^ of the whole air originally contained in the receiver are consumed? Jlns. Because the air which then remains in the receiver is destitute of oxygen gas, and is on that account incapable of supporting either combustion or res- piration. Ques. What, therefore, is necessary in order that a complete combustion of bodies shall take place in at- mospheric air or oxygen ? Ans. It is necessary that a fresh quantity of atmospheric air or oxygen should be supplied, while the process of combustion is going on. Fig. LXVIII. ^^ ANOTHER EXAMPLE. A burning candle introduced into the receiver of an air- ( pump (Fig. LXVIII,) burns 'slower and slower as the air in the receiver becomes more and more exhausted, (Natural Philosophy, Chap. V,) until finally it becomes wholly ex- tinguished. A small animal or a bird introduced instead' of the candle will be thrown into convulsions and expire. Gunpowder, phosphorus, and sulphur will cease to burn in the vacuum. An improper mixture of gases, in which the oxygen is not contained in a sufficient proportion, produces the same effect ; because it is then unfit to support the pro- cess of combustion or respiration. 58 OXYGEN. What remarkable coincidence do you here observe between the process of respiration and combustion ? Jins. That oxygen is alike indispensable to the one and the oth- er ; for whenever the process of combustion discontinues from want of oxygen, that of respiration ceases also. Ques. What mode, therefore, may be devised for finding out wheth- er a certain mixture of gases is respirable or not? Jlns. A burning candle may be introduced in it; when it continues to burn the gas will be respirable ; when it is extinguished, or burns but dimly, then the gas will not be fit for respiration. This is a convenient way for trying the air in old wells or in caverns, and cannot be too urgently recommended ; many lives having been lost by omitting this caution. 11. The quantity of air or oxygen necessary for the continuance of the process of combustion is supplied ei- ther by a draft or by means of bellows. We know from Natural Philosophy, (Chap. V,) that when a body is burning, the heated air which surrounds it becomes spe- cific, lighter, and ascends, while a fresh portion of exter- nal air rushes in its place. This is called a draft. To facilitate it we build fire-places and chimneys. The high- er the chimney is, or the greater the difference between the temperature of the air ascending in the chimney, and that of the surrounding atmosphere, the greater is the draft, and the better therefore will the fire burn. Query Could you now devise a means for improving smok- ing fire-places? */2ns. Yes. Smoking fire-places might be improved by heightening the chimneys. Ques. Why? Jlns. Because this would create a better draft, adding there- by continually a new quantity of oxygen to the fire, and caus- ing by that means a more perfect combustion. Query And can you now explain the reason why an Argand's lamp (see Fig. XXXV, page 24,) burns brighter when the glass is put on, than without it ? Ans. Because the glass serves in this in- stance as a sort of chimney, which increases the draft, 12. Extinguishing of Jire. Fire is extinguished, as we have seen, by abstracting the oxygen from the burning substance, or, which amounts to the same thing, by ex- cluding the atmosphere from the burning substance. This is effected by covering the combustible substance with an- other substance, through which the oxygen of the atmos- OXYGEN. 59 phere cannot penetrate. For this purpose we commonly employ water, merely because it is readiest procured ; but then it is necessary to use a sufficient quantity to cover the whole surface of the burning body. Small quantities of water are of little or no use in confla- grations ; but, on the contrary, rather contribute to increase them ; because red hot coal, as we shall see hereafter, decom- poses water into hydrogen and oxygen ; the latter of which substances adds necessarily to the rapidity of the flames. ( 7.) It is for this reason blacksmiths are in the habit of wet- ting their coal before using it. 13. It has already been observed that some sub- stances combined with oxygen without the phenomenon of fire. This is the case when the combination takes place very slowly. It is in this manner many of the metals combine with oxy- gen at the mean temperature of the atmosphere. Sodium, potassium, iron, lead, tin and manganese are oxidized with- out giving out any observable degree of heat or light. Another substance, (which we shall become acquainted with in the course of this work) termed nitric oxid, combines with oxygen at the greatest cold ; while carbon unites with it at a temperature exceeding (556 degrees Fahrenheit, without the phenomenon of fire. 14. It remains for us to speak of the process of desoxidation, which consists in separating the oxygen from a body with which it is combined. It is effected two ways : 1. By Jicat. This is the case with the oxides of the precious metals, silver, gold, platinum, &c. 2. By the admixture of a third substance, commonly potassium, for which oxygen has a great affinity. (See Art. Potassium, Chap. III.) The different combinations of oxygen with other substances will be spoken of when treating of these substances. 75. Hydrogen. 15. When water is subjected to the action of Gal- vanic Electricity, it is, as we have had occasion to remark 60 HYDROGEN. before, decomposed into two distinct gases, whose proper- ties are in every respect directly opposite to each other. These two gases are Hydrogen* and Oxygen. Fig. LXIX. The experiment may be made either by means of a voltaic pile, (Fig. LXIX,) or by a trough bat- tery (see Fig. L1X, page 40). When the voltaic pile is employ- ed, the apparatus represented in Fig. LXIX, in which the two poles A, B, are introduced into a cylin- drical tube filled with water, is very convenient. Fig. LXX. When the trough-battery is used, the two poles of the battery are introduced into a bent glass tube, shaped like a V,(see Fig. LXX.) This tube is first filled with water and then inverted and held over a basin filled with the game liquid, which in this case answers the purpose as a pneumatic tub. The two gases, hydrogen and oxygen, inio which the water is decomposed, rise in little bubbles to the top, but are in both instances obtained in a state of mixture. Fig. LXXL To obviate this we make use of an ap- paratus represented in Fig. LXXL The two poles of the galvanic battery are brought in contact with two brass knobs, A and B, which by means of thin platina wires melt into the glass, communicate with the water in the bent tube. Each of the extremities of the tube is fitted to a small jar, closed with a stopper, and the whole apparatus is filled with water. When the battery is set in motion, the water in the tube becomes decomposed * From a Gteek word, signifying formation of water. HYDROGEN. 61 and forms two distinct gases ; but by a fixed law of elec- trical attraction (mentioned before in Intr. page 41,) one of these gases, the hydrogen, always collects about the nega- tive or copper pole, and on that account rises in little bub- bles in the jar which is connected with that pole ; while the oxygen follows the electric attraction of the positive or zinc pole, and collects in the other jar. By tho aid of this apparatus the two gases are obtained separately, and may be examined for the sake of various chemical purposes. What is most remarkable about this decomposition of wa- ter is, that the volume of hydrogen gas thence obtained, is always exactly double that of the oxygen, from which we infer that in water two volumes of hydrogen are combined with one volume of oxygen. But about this we shall soon have occasion to say more. Properties of Hydrogen Gas. 16. When hydrogen gas is examined in its pure state (as obtained from the decomposition of water by gal- vanic electricity), it is found to be destitute of color, taste, or smell. It is much lighter than atmospheric air, only one sixteenth as heavy as oxygen and indeed the light- est ponderable substance in nature.* It is highly com- bustible ( 5), and when ignited (kindled) by a burning substance, or an electric spark, burns with a yellowish flame and gives out great heat. It is unfit for respiration, although it may be breathed for a short time with impuni- ty. It is equally unfit to support the process of combus- tion, although it is, itself, a highly combustible substance. A burning substance immersed in it, is instantly extin- guished. * In speaking of the speci6c gravity of bodies, we always suppose the pressure of the atmosphere equal to 30 inches of quicksilver, and its temperature equal to 60 degrees of Fahrenheit's thermometer.- - (See Grund's Natural Philosophy, article Gravity.) 6 HYDROGEN. Fig. LXXII. EXPERIMENT. If a lighted candle or wax taper is brought near the mouth of a bottle or jar filled with hydrogen gas, the gas will instantly ignite at the mouth of the bottle ; but the taper itself, when deeper immersed, will be extinguished. When the taper is drawn out, it will again be ignited by the burning hydrogen at the mouth of the bottle. This experi- ment may be repeated a number of times, until the gas is entirely exhausted. Query What does the inflammation (ignition) of the gas at the mouth of the bottle prove ? Jlns. It proves that hydrogen is a highly com- bustible substance. Query And what does the extinguish- ing of the candle when immersed in hydrogen, show ? Ans. It shows that although hydrogen is, itself, a highly inflamma- ble gas, it is not capable to support the combustion of other substances. Fig. LXXIH. ANOTHER EXPKRIMENT, which shows that the specific gravity of hydrogen is much less than that of atmospheric air, may be performed by lAfilling two common beer or wine glasses (Fig. LXXIII,) with this gas, and placing them, one with its open mouth up, and the other down. In a few minutes the gas will have entirely es- caped from the glass B, which is placed with its mouth up but it will still be found in the one, A, which has its mouth turned downwards. This may be easily ascertained by applying the flame of a can- dle to the mouth of each glass. The hydrogen contained in the glass, A, will burn ; but in B there will be nothing but at- mospheric air, which of course will not ignite. Query Why has the gas escaped from the glass which has its'mouth up? Jlns. Because hydrogen being much lighter than atmospheric air, would naturally ascend as a piece of wood does, when placed under water. Query But why does the gas remain in the glass with its mouth down ? Ans. Because a vessel filled with hydrogen, having its mouth turned downwards, may be considered as closed ; for the escape of the gas is prevented from above, and the pressure of the heavier atmosphere does not permit it to descend below. HYDROGEN. 63 Fig. LXXIV. Query In what manner then can you transfer hydrogen gas from one vessel to another ? Ans. It is only necessary to place the mouth of an open vessel or receiver, B, (Fig. LXXIV,) over the open neck or mouth of another vessel or jar, A, rilled with the gas. The gas will, on account of its levity, escape thrrough the neck of the vessel, A (through which, for convenience sake, an open tube may be made to pass), and ascend in the receiver B, from which it will expel the atmospheric air. ANOTHER EXPERIMENT, which shows the levity of hydrogen gas, and at the same time enables us to find its specific grav- ity is the following. LXXV. Take an open jar or phial, C, which attach to one scale of a common balance with its mouth downwards, and set the whole apparatus in equilibrium by add- ing as much weight to the scale B, s is necessary for that pur- pose. Conduct hydrogen from a Florence flask, F, into the jar. In proportion as the hydrogen ascends through the pipe, P, and expels the atmospheric air from C, the scale B will sink ; and by marking the weight which it is finally necessary to place upon A, in order to restore the equilibrium, we determine the difference between the weight of atmospheric air previously contained in it, and that of an equal volume of hydrogen gas. This will enable us to find the specific gravity of hydro- gen. For when the weight of the atmospheric air in the jar A is known, (which may be easily obtained by finding what the jar weighs when the air is exhausted from it) it is only necessary to find the weight of an equal volume of hydrogen ; which we obtain by subtracting the loss of the jar when filled with that gas, from the weight of the 64 HYDROGEN. atmospheric air contained in it. The weight of the gas thus found, divided by that of atmospheric air, gives the specific gravity of hydrogen. This you will probably bet- ter understand from an EXAMPLE. Supposing the jar, when the air is exhausted from it, loses 14 T 4 o- grains ; supposing further, that by intro- ducing the hydrogen, instead of the atmospheric air, the jar loses 13 T 4 , w;,must be cemented in such a manner that their points nearly touch each other on the inside. Provide a mixture of pure hydrogen and oxygen in the proportion of two volumes of the former to one volume of the latter, with which fill a jar, I, fitted with a stop-cock, PI, to which the cock of the tube may be screwed, in a manner similar to Priest- ley's bell glass and bladder (Introduction, pages 30 and 31). Extract the air from the tube by an exhausting syringe or an air-pump, and screw it tight to the jar. When the two cocks are opened a portion of the mixed gases will rush into the tube ; this it is best to extract again from the tube to make sure of the exhaustion of any remaining air. Place the tube again upon the jar, and by opening again both cocks, fill it another time with the mixture of the gases ; and take great care to close both stop-cocks. Now pass an electric spark through the wires, and the gases in the tube will explode (2 0, page, 69). Allow the tubes to cool; after which let in a fresh portion of the mixture, whicn, when the cocks are closed may again be inflamed and continue this process until a strong dew is seen upon the interior of the tube This upon examination you will find to be pure water. If the two gases are mixed in the exact proportion ot two HYDROGEN. 75 volumes of hydrogen to one volume of oxygen, then the whole mixture will be consumed; but if the mixture be made in any other proportion, the excess of either gas will be left; because they combine in no other. Query Why must the glass tube in this experiment be stronger than in others ? Jlns. Because it must resist the explosion of the gases when an electric spark is applied to them. Query Why must the two stop-cocks be carefully closed before the electric spark is passed through the wire ? Jlns. Because one volume of oxygen and two volumes of hy- drogen form a highly explosive mixture ( 20, page 69); consequently if the cocks were not closed the inflammation of the gases in the tube would communicate itself to the jar, and cause an explosion which would destroy the jar, and endanger the safety of the experimenter. Query And what fact does this experiment tend to establish ? Jlns. It establishes the indisputable fact that water consists of two volumes of hydrogen combined with one volume of oxygen, and that these gases com- bine in no other proportion to water than in that of two vol- umes of hydrogen with one volume of oxygen, 25. The law which we have just found respecting the combination of hydrogen and oxygen corroborates what we have stated in the Introduction {page 11) in ref- erence to the composition of all definite compounds. Now as hydrogen is the lightest ponderable substance in nature, it will combine in the smallest proportion by weight with all other substances ; consequently, if the weight of hy- drogen which combines with oxygen is taken for unity of comparison, the chemical equivalent of oxygen is 8 ; be- cause 1 volume of oxygen weighs 8 times as much as the two volumes of hydrogen with which it combines ; hydro- gen being 16 times lighter than oxygen.* But the chem- ical equivalent of oxygen and hydrogen being known, that of water follows of course. This is composed of I equivalent of hydrogen equal to 1 and 1 equivalent of oxygen, equal to 8 consequently chemical equivalent of water equal to 9. * Two sixteenths is the same as one eighth ; consequently the weight of the two volumes of hydrogen is only one eighth of the weight of one volume of oxygen; or, which is the same, the weight of the hydrogen employed is to that of the oxygen as I to 8. 76 HYDROGEN. In a similar manner have the chemical equivalents of oth- er substances been determined in reference to hydrogen ; and we shall make it a rule for the remainder of this trea- tise, to write at the head of each substance, its equiva- lent number ; and if the body we treat of is a compound, then we shall besides this, affix the chemical equivalents of its elements. Some philosophers have assumed oxygen as the standard of comparison, which being supposed equal to 100, the chem- ical equivalent of hydrogen is one eighth part of ICO, or 12,5. Most English and American chemists however prefer the for- mer method, on which account we have adopted it throughout this treatise. 26. The composition and decomposition of gases follow a still more simple law, which is that of combining in definite volumes, instead of definite weights. Thus, when one gas combines with another, 1 volume of the one, combines always with 1, 2, 3, 4, &.c, volumes of the oth- er, and in no intermediate proportions. 27. Properties of water. Water, in its pure state, is destitute of color, taste, or smell, and is on this ac- count most admirably fit to be the natural drink of man. It is the most universal solvent in nature, (dissolves most solid substances) and absorbs many of the gases, such as hydrogen, oxygen, nitrogen, &c. A cubic inch of dis- tilled (purified) water weighs about 252 grains. Its great- est density is at the temperature of 40 degrees ; it freezes at 32, and becomes converted into stearn at the tempera- ture of 212 Fahrenheit. According to the nicest exper- iments, it is composed of 28 T f 2 ; so that the condensation of these gases in the act of forming water, is nearly 2000 volumes into one ! Query From what has just been observed respecting the enormous condensation of the volumes of the gases which are employed in the formation of water, can you now account for the great heat given off during the cornhustion of hydro- gen? JJns. When hydrogen is burnt nearly 2CCO volumes of gas (hydrogen and oxygen) are condensed into one ; by HYDROGEN. 77 which means the heat which was hidden in the gas becomes sensible, and produces the astonishing effects of the compound blow-pipe, and the explosive mixture of hydrogen and oxygen. We have said that the greatest density of water is at about 40 of Fahrenheit's thermometer. In this respect it makes an exception to all other liquids, which are known to contract as they cool down to their freezing points. (Natural Philoso- phy, Chap. VI.) This peculiarity of water is of the greatest influence upon the economy of nature. The water which nearly covers one third of the earth, becomes a most efficient means of equalizing its temperature, making those parts hab- itable which would otherwise be buried in perpetual frost, or scorched with insufferable heat. The cold air from the polar regions absorbs the heat from the great waters or lakes until they are cooled down to 40 degrees Fahrenheit. At this point the refrigerating influence of the atmosphere nearly ceases ; because the uppermost stratum of water, by further cooling, becomes lighter (loses its density) and instead of sinking to the bottom, remains in a cake of ice suspended at the surface, preventing thereby the water below from being further expos- ed to the influence of the colder air. Without, this peculiar property of water, the cold air would continue to rob it of its heat until the whole should be cooled down to 32 degrees, when it would at once settle into a solid mass. Every living creature in it would perish ; the ice in the northern regions would never be liquefied, and navigation finally made impossi- ble.* 28. Jce. Water in the act of freezing or congeal- ing (see Natural Philosophy, Chap. VI,) expands by nearly J of its volume, and so great and violent is this expansion, that it bursts tubs, casks, water-pipes, &c, in which water is suffered to freeze. It also explains why trees and plants are destroyed in hard frosts, and such similar phenomena. The specific gravity of ice is less than that of water, viz, only T 9 ^, or 0.92, that of water being I. This is the reason why the ice remains at the surface of the water, and explains the phenomena alluded to in the preceding paragraph. * Library of Useful Knowledge, treatise on Chemistry. 7* 78 HYDROGEN. 29. Rain, River, and Pump-water. We distin- guish yet between Rain, River, and Pump water. The purest of these is rain-water, because descending through the atmosphere, it is least exposed to the influence of other substances. JVext to it comes River water, which however is often known to contain certain salts of soda, lime, and magnesia, of which we shall speak in the 4th Chapter. These two kinds of water are called soft water, in oppo- sition to the hard pump-water, which contains always a greater or less quantity of carbonic acid. Mineral waters contain gases and salts in such proportions that they are only used as physics in medicine. Sea water contains a variety of salts. Among these are common salt, Glau- ber's salt, muriate of lime and of magnesia. The two last-mentioned ingredients give it that disagreeable taste and smell, which causes nausea and vomiting when taken into the stomach. 30. AH kinds of water contain atmospheric air (generally from 3 to 4 per cent), not indeed as a chemical ingredient^ but mechanically mingled with their particles. From this water may be freed either by the air-pump, or by boiling. The latter method is preferable. When water is brought under the receiver of an air-pump and the air is exhausted in the receiver, the particles of atmos- pheric air which are mechanically intangled in the water, rise in little bubbles to the surface and expand themselves in the vacu- um created over the water, according to the laws of elastic fluids (Natural Philosophy, Chap. IV). The boiling of water consists in heating it until it becomes converted into steam. Just before this takes place the water is thrown into a violent agitation, partly occasioned by the expansion of the atmospheric air contained in it ; little bubbles of air rise to the surface and escape along with the steam which is forming during the pro- cess of ebullition. 31. Water, although a tolerably good conducter of Electricity, (Natural Philosophy, Chap. VIII), is a very bad conductor of heat. Of this we can easily convince ourselves by the following HYDROGEN. 79 Fig. LXXXVIII. EXPERIMENT. Place a small air-thermometer capable of showing very minute alteration of tem- perature, in a jar filled with water, so that the bulb of the thermometer may be a little below the sur- face. Upon this pour a small quantity of ether, which being specifically lighter than water, will remain on top and may be inflamed. The ether will burn for a considerable time without affecting the thermometer in any sensible degree. It will indeed be quite a different case when the heat is applied to the water from below. In this case the ther- mometer is soon affected. But then it is not the conduct- ing power of water which transfers the heat from the bot- tom of the jar to the surface and the thermometer ; it is because the heated particles of water themselves are ex- Fig, LXXXIX. panded and rise to the surface, while another por- tion of colder water sinks from the surface to the bottom and occupies their place. This motion can actually be observed by boiling water in which some particles of amber or of some other light sub- stance are diffused, in a glass tube applying the heat from below. The particles of amber will be seen to rise from the bottom of the tube, being car- ried along by the particles of water to which they adhere, while those near the surface will be ob- served to descend with the colder particles of water. The same experiment may be made with other liquids, all of them being bad conducters of heat, and capable of being heated only in conse- quence of the mobility of their particles. (See Natural Philosophy, Chap. VI.) Query Could water be very well heated without the mobility of its particles, which enables those which are heated to ascend, making thereby room for the colder ones to 80 HYDROGEN. descend and become heated ? dns. No ; because the con- ducting power of water in itself is very bad, as we have seen from the experiment described in Fig. LXXXV1II. Ques. And what is the reason that the burning ether on the surface of the water in that experiment, does not materially affect the thermometer? Ans. Because the heated particles on the surface of water, becoming specifically lighter, must of course, from hydrostatic principles, remain on top, and prevent thereby the next lower particles from ascending. And in this consists the whole difference between heating a liquid from below and above (applying the heat at the bottom or at the surface). 32. It has been stated in Natural Philosophy, Chap. VI, that the pressure of the atmosphere, or of steam, is an obstacle to the boiling of liquids and consequently also to the boiling of water. This has been stated as a reason why water boils sooner under the receiver of an air-pump, from which the air has been exhausted, or on the top of high mountains, where the pressure of the atmosphere is less than on the plain, &c ; but we can illustrate this law still more strikingly and satisfactorily by the following Fie XC EXPERIMENT Adapt a cork covered with a thick coating of sealing wax, to a glass flask, into which put water to the depth of about one inch. Place it over a lamp until it boils, and suffer the boiling to continue for a short time, after which introduce the cork air-tight and re- move the flask from the lamp. The water will boil a little while after the heat ceases to be ap- plied ; but on plunging the flask into ajar filled with cold water or ice, the boiling recommences with great violence and continues until the wa- ter in the flask is nearly cold. Jf the flask is ta- ken out before the boiling ceases, and is plunged into hot water, the boiling immediately stops ; but upon being again introduced into cold water the boiling recommences with violence. Qutry. Why is the cork in this experiment introduced during the boiling of the water in the flask? Ans. It is done in order to exclude the atmospheric air, and to prevent the escape of the steam with which the flask becomes filled when the water boils in it. Ques. Why does the water con tinue to boil for a little while after the heat ceases to be ap- HYDROGEN. 81 plied to it? Ans. Because when the flask is removed from the lamp, its sides come in contact with the cold atmospheric air, which condenses part of the steam, and by this means lessens the pressure on the surface of the water ; this enables the water to boil for a short time, although its temperature is re- duced. Qites. But why does the water recommence boiling when the flask is plunged into cold water or ice ? Jlns. Be- cause the steam in the flask becomes then suddenly conden- sed, removing thereby the whole pressure from the water, and by that means throws it into a state of violent ebullition. Ques. And why does the boiling cease when the flask is introduced into hot water ? JJns. Because this leads to the formation of afresh quantity of steam in the flask, whose pressure pre- vents the boiling of the water. Qucs. And what inference should you draw from the experiment you have just explained ? Jlns. That water (and all other liquids) require higher degrees of temperature to boil under a heavy pressure of air or steam ; and considerably lower degrees of temperature to boil token this pressure is removed from them. 33. Water absorbs constantly a portion of heat, with which it either combines, or through the medium of which it becomes converted into vapor. The quantities of heat or caloric thus absorbed by the large waters on our globe, tend in no small degree to moderate the tem- perature of the torrid regions, and to create an agreeable freshness near the banks of rivers and on the seacoast. This continued formation of vapors from the surface of wa- ter is called the process of evaporation, and it serves some of the most important purposes of nature. The vapors of water contained in the atmosphere form mists or clouds, which when brought in contact with the higher, and consequently colder strata of air, are condensed and de- scend again as dew, rain, or snow, to moisten our fields in summer, or to protect them during the winter ; assisting thereby the vegetation of trees and plants, without which animal life itself would soon become extinct. (See Natu- ral Philosophy, Chap. VI.) The refrigerating influence of forming vapors of liquids may be illustrated on a small scale by the following fcYDROGEN. Fig. XCJ. EXPERIMENT. Pro- vide a watch-glass filled with water and place it over a shallow vessel filled with sulphuric acid, and bring the whole under the receiver of an air-pump. As the air is exhausted from the receiver vapors will abundantly rise from the water, which being speedily absorbed by the sulphuric acid (which has a great affinity for water) creates such a degree of cold as to freeze the water in a very short time. If instead of sulphuric acid we employ ether, the same effect will be produced ; but in this case the ether becomes vaporized, and absorbs such a quantity of heat from the water as to con- geal it. A still better illustration of the cold produced by the rapid process of evaporation may be given by means of an instrument invented by Dr Wollaston, and which has received the name of Cryophorus or Frust-bearcr. Fi