j Sheldon & Company's IN . Henry Senger n Unl Beloi Accept. as Dr ints oj years. ^t C16&] nnd compact statement, the elements of this important brand of science, in their latest aspects and applications. autho: Dn of { process ial, it* itences ution o cism o se. } isburg. Iv&ac^c Jniver Jniver- msand, iu mil arra Sheldon & Company's '2'ext-53ooks. SHAW'S NEW SERIES ON ENGLISH AND AMERICAN LITEEATURE. I. Shaw 9 s Neiv History of English and American Lit' erature. This book ha& been prepared with the greatest care by Prof. TRUMAN J. BACKUS, of Vassar College, using as a basis Shaw's Manual, edited by Dr. WILLIAM SMITH. The following are the leading features of the book : 1. It has been put into the modern, text-book fonn. id. It is printed in larye, clear type. 3. Many parts of the book, which were not very clear, have been entirely rewritten. 4. The history of yreat Authors is marked by the use of larger-sized type, which indicates to the scholar at once the important names iu English and American literature. 5. It also contains diagrams, showing the easiest way to classify and remember the eras in English literature. \Ve believe that this is the best text -book on this important subject ever offered to the American public. II. Shaw's Specimens of American Literature, and Literary Reader. GREATLY ENLARGED. By Prof. BENJ. N. MARTIN, D.D., L.H.D., Professor in the University of the City of New York. 1 vol. 12mo. This book contains specimens from all the chief American writers. Espe- cially tnoee authors who have given tone and character to American literature are so represented that scholars may obtain a just idea of their style. As a LITERARY READER for use in our Higher Seminaries, it is believed that no sriperior book can be found. III. Shaw's Choice Specimens of English Literature. A Uompanion Volume to the New History of Literature. Selected from the chief English writers, and arranged chronologically by THOS. B. SHAW and WM. SMITH, LL.D. Arranged and enlarged for American students by BENJ. N. MARTIN, D.D., L.H.D., Prof, of Philosophy and Logic in the University of the City of New York. 1 vol. large 12mo. We shall still continue to publish Shaw's Complete Manual of English and American Literature. By THOS. B, SHAW, M.A., WM. SMITH, LL.D., author of Smith's Bible and Classical Dictionaries, and Prof. HENRY T. TUCKERMAN. With copious notes and illustrations. 1 vol. large 12mo, 540 pp. '/fff. ELEMENTS OF C H E M ISTRY A TEXT - BOOK I F(M ; ; SCHOOLS. BY ELROY M. AVERY, PH.D., AUTHOR OF ELEMENTS OF NATURAL PHILOSOPHY, ETC. ILLUSTRATED BY NEARLY 200 WOOD ENGRAVINGS. NEW YORK SHELDON & COMPANY, No. 8 MURRAY STREET. 1881. IN MEMORIAL DR. AVERY'S PHYSICAL SCIENCE SERIES. I St. THE ELEMENTS OF NATURAL PHILOSOPHY. - . 9\ TEACHER'S HAHD BOOK. To accompany AVERY'S NATURAL PHILOSOPHY; containing Solutions to Problems, Additional Experiments, Practical Suggestions, etc. THE ELEMENTS OF CHEMISTRY. 4 th. THE HIGH SCHOOL CHEMISTRY. Containing the ELEMENTS OF CHEMISTRY, with additional chapters on Hydrocarbons in Series, or ORGANIC CHEMISTRY. It can be used in the same class with the ELEMENTS. (In preparation^ 5th, TEACHER'S HAND BOOK. To accompany Avery's Chemistries. Copyright, 1881, by Sheldon & Co. Blectrotyped by SMITH & McDotiGAL, 82 Beekman Street, New York. 'T PAVE a room set apart, if possible, expressly for - *- chemical operations. It is generally convenient to have this laboratory on the ground floor, for convenience in supplying water and draining off the waste. This room must be ivell ventilated. Secure a ventilating chamber (App. 22) for the laboratory, and a ventilating hood con- nected with the chimney flue or ventilating shaft for each pupil, if you can. If you can not do this, keep an open fire burning, so that offensive gases and vapors may be removed from the room as well as possible in that manner. Around the walls of the room, provide working benches or tables, about 75 cm. (2-J- feet) wide. Each pupil should be allotted about a meter of working space at these tables, and 7^/6? responsible for its condition. If the building is provided with gas and water, run pipes around the walls, and provide each pupil with a gas cock and a water cock, to which he may attach flexible tubing. Over the benches place narrow shelves, to hold the chemical reagents; be- neath the benches place shelves or drawers, for holding pieces of apparatus, etc, If the building is not connected iv TO TEACHERS. with a regular water supply, see that plenty of water is always at hand in a tank, barrel, or in pails. A small cook stove will be a great convenience. If a room can not be set aside as a laboratory, flat tables may be laid upon the desks, and the reagents', apparatus, etc., kept in a cabinet or cupboard. Of course, a regularly fitted laboratory, w r ith further and better means than those above suggested, is desirable, and should be provided, when means can be secured for the purpose. See Prick's Physical Technics, Chap. I. The chief significance of the foregoing is that, as far as possible, the experiments are to be performed by the pupil rather than for him. Make careful examination of the pupil's notes, seeking to lead him to accurate observation, intelligent discrimination between essential and merely incidental conditions and results of an experiment, as well as to precision and conciseness of statement. Have your pupils habitually pronounce the full name of substances symbolized in this book. For example, " H 2 is composed of H and 0," should be read : " Water is com- posed of hydrogen and oxygen." The author would be glad to receive suggestions from teachers using this book, or to answer any inquiries they mav make. TTAVE a place for everything, and keep everything in 1 its place, when you are not using it. Clean every utensil or piece of apparatus when you have used it ; never put away anything dirty. Cleanliness is a necessity in the chemical laboratory. Ac jiiire the habit of labeling every chemical that you put away or leave for a time, writing the name or the chemical symbol in easily legible char- acters. Before beginning an experiment, look over all of your preparations, be sure that everything is ready and within easy reach, or you may suddenly discover a need for another hand. Be sure that all corks and connections are well fitted. Place your materials and apparatus at your left hand and lay them down at your fight, when you have used them, keeping the middle of your bench clear for operating. Do not waste even inexpensive material. Be sure that you know wliy you do a thing before you do it. Always VI TO THE PVPTL. use the simplest form of apparatus. Do not think that you must have everything just as described by the author. If a Florence flask is called for by the text-book, and you have not one, you may be able to get along with a bottle. A hammer is not wholly necessary for the driving of a nail, although it may be desirable. Make careful notes on all experiments as they proceed. "The scrap of paper well stained with acid is of much greater value than the half worked out, though clean, notes written down after the experiment has passed away." These rough notes should subsequently be neatly copied into a book, the mere copying of the observations being of great help in remembering them. Ever keep in mind the fact that an experiment is in- tended to teach something, and that it can not serve its purpose unless it is accompanied by careful observation of the effects produced, and equally careful study of the rela- tions borne by these effects to the conditions of the exper- iment. Take an early opportunity for a careful reading of the Appendix to this book, so that you may be able to refer to it subsequently, when you need help that it may give. In the folio w.ing pages, the specific gravity of all gases is referred to hydrogen as the standard. All temperatures are recorded in Centigrade degrees. PAGK TO THE TEACHER iii TO THE PUPIL v CHAPTER I. THE DOMAIN OF CHEMISTRY 1 CHAPTER II. WATER AND ITS CONSTITUENTS. SECTION I. ANALYSIS OF WATEK 10 " II. HYDROGEN 14 III. OXYGEN 27 " IV. COMPOUNDS OP HYDROGEN AND OXYGEN . ... 38 CHAPTER III. AIR AND ITS CONSTITUENTS. SECTION I. AIR 45 II. NITROSEN 50 CHAPTER IV. SYMBOLS, NOMENCLATURE, MOLECULAR AND ATOMIC WEIGHTS.. 53 lll CONTENTS. CHAPTER V. COMPOUNDS OF HYDROGEN, OXYGEN AND NITROGEN. PAGE SECTION I. AMMONIA 59 " IT. NITRIC ACID 65 III. NITROGEN OXIDES 68 CHAPTER VI. QUANTIVALENCE, RATIONAL SYMBOLS, RADICALS,.. 74 CHAPTER VII. THE HALOGEN GROUP. SECTION I. CHLORINE 79 II. HYDROCHLORIC ACID 87 " III N OTHER CHLORINE COMPOUNDS 93 " IV. BROMINE, IODINE, FLUORINE 97 CHAPTER VIII. STOICHIOMETRY 104 CHAPTER IX. THE SULPHUR GROUP. SECTION I. SULPHUR 110 " II. HYDROGEN SULPHIDE 117 III. SULPHUR OXIDES AND ACIDS 124 " IV. SELENIUM AND TELLURIUM 187 CHAPTER X. ACIDS, BASES, SALTS. Etc 140 CHAPTER XL BORON 147 CONTESTS. IX CHAPTER XII. PAGE VOLUMETRIC CONSIDERATIONS 151 CHAPTER XIII. THE CARBON GROUP. SECTION I. CARBON 155 " II. SOME CARBON COMPOUNDS 160 '' III. SOME HYDROCARBONS , , 177 " IV. ILLUMINATING GAS 188 " V. SOME ORGANIC COMPOUNDS 194 " VI. SILICON 201 CHAPTER XIV. THE NITROGEN GROUP. SECTION I. PHOSPHORUS 305 " II. PHOSPHORUS COMPOUNDS . . . 211 <; III. ARSENIC AND ITS COMPOUNDS 217 " IV. ANTIMONY, BISMUTH, ETC 222 CHAPTER XV. METALS OF THE ALKALIES. SECTION 1. SODIUM '. 229 " II. POTASSIUM, ETC 237 CHAPTER XVI. METALS OF THE ALKALINE EARTHS 246 CHAPTER XVII. METALS OF THE MAGNESIUM GROUP 252 CHAPTER XVIII. METALS OF THE LEAD GROUP.. . 258 X ' '<>. \TEXT8. CHAPTER XIX. METALS OF THE COPPER GROUP. PAGE SECTION I. COPPER 263 " IL SILVER 267 " III. MERCURY 271 CHAPTER XX. METALS OF THE ALUMINUM AND CERIUM GROUPS.. 275 CHAPTER XXL METALS OF THE IRON GROUP. SECTION I. IRON 279 IL STEEL 290 " III. MANGANESE, COBALT AND NICKEL. 295 CHAPTER XXII. METALS OF THE CKROMIUM GROUP 299 CHAPTER XXIII. METALS OF THE TIN GROUP 802 CHAPTER XXIV. METALS OF THE GOLD GROUP 306 APPENDIX 315 INDEX.. 343 THE DOMAIN OF CHEMISTRY. 1. What is Matter? Mattel 1 is anything that occupies space or "takes up room." Everything discernible by any of our senses is matter. Everything that has weight is matter ; all matter has weight. 2. Divisions of Matter. Matter may be con- sidered as existing in masses, molecules, and atoms. Note. The word molecule is from the diminutive of moles, a Latin word meaning a mass. Etymologically, molecule means a little mas,s. .The word atom is from the Greek, and signifies, etymology cally, a thing that can not be cut or divided. 3. What is a Mass ? A mass is any quantity of matter that contains more than a single molecule, Any quantity of matter that can be appreciated by the senses, even with the aid of modern apparatus, is a mass, while many masses are too minute to be thus appre- ciable. 4. What is a Molecule? A molecule is the smallest particle of matter that can'ejcist l)y itself , separate from other particles of matter ; or it is the smallest quantity of matter into which a mass can be di- vided by any process that does not destroy its identity or change its chemical Mature, Molecules are exceedingly 2 THE DOMAIN OF CHEMISTRY. 4 small, far beyond the reach of vision even when aided by a p-fruverful microscope. /; (,) Acco_rdin to one of the best authorities, a cubic centimeter (Appomlnt 2} eudiometer erect and the water standing at the same level in both tubes. Water may be removed from a, if necsssary to this end, by means of a pipette (App. 5.) Now introduce about 50 cu. cm, of pure H into b, and note the exact amount of gas therein a r ; before. It may prove difficult to introduce exactly 20 and 50 cu. cm. A little variation matters not, provided that you measure accurately the amounts actually introduced, and that the volume of the H is more than twice that of the 0. Suppose that the first measure- ment shows 21 cu. cm. of 0, and that the second shows 75 cu. cm. of mixed gases. Then you have introduced 54 cu. cm. of H. Close the opcm end firmly with the thumb, leaving a cushion of air between it and the surface of the water, as shown in Fig. 26. Pro- duce an electric spark between the ends of the platinum wires in the mixed gases. [Ph., 371 (21), (33), (35), 411.] The spark pro- duces combination between the and part of the H. On removing the thumb and bringing the liquid surfaces to the same level, it will be found that there are only 12 cu. cm. of gas in b. By filling a with water and closing it with the thumb, the gas may be easily passed from b into a, and thence, under water, to a convenient vessel for testing. It will be found to be pure H. The 21 cu. cm. of has united with 42 cu. cm. of H to form a minute quantity of H 2 O, leav- ing the 12 cu. cm. of H because there was no with which it could unite. See 12. If the eudiometer had been kept at a tempera- ture above 100 C., or 212 F., and the gases confined by mercury instead of water, b would have contained 42 cu. cm. of steam and 12 cu. cm. of H. The volume of steam would be the same as that of the H that entered into its composition. The combination was accompanied by a diminution of volume equal to that of the enter- ing into chemical union. In other words, three volumes shrink to two volumes in the process of combination. Representing equal volumes of the gases by equal squares, the volumetric composition of H 2 and the condensation j ust mentioned may be represented to the eye as follows : 42 SYDROGEN AND OX TO EN. 43 As is 16 times as heavy as H [Ph., 253 (3)], the one volume of O weighs 8 times as much as the two volumes of H. Hence, we see that the gravimetric composition of water is 8 parts of to 1 of H, as previously stated. Experiment 54. Support a wide tube of clear glass in a vertical position. A bottomless bottle, the neck of a broken retort, or a lamp- chimney will answer well. Through the perforated cork that closes the upper end, pass a stream of H from the gas holder. When the air has been driven out of the bottle, apply a flame at the lower end and regu- late the flow so that the gas burns slowly at the opening. From another gas holder, pass a current of through a piece of glass tubing drawn out to form a small jet. As the jet passes through the burning gas, the takes fire and burns in an atmosphere of H. 43. Combustibles and Supporters of Com- bustion. Since all ordinary combustion takes place in the air, which furnishes the necessary supply of oxygen, it is customary to speak of oxygen as a supporter of combus- tion, and the hydrogen or other substance that thus unites with the oxygen as a combustible. The experiment just given shows that this distinction has no reason for its con- tinued existence except custom and convenience. When oxygen and hydrogen atoms clash together in chemical union, we have combustion, and it makes no difference whether the hydrogen emerges into an atmosphere of oxygen, or the oxygen emerges into an atmosphere of hydrogen. We shall, however, continue to speak of burn- ing hydrogen and carbon instead of burning oxygen. 44. Hydrogen Dioxide. While water, H 2 O, is the only compound of H and found in nature, another (H 3 2 ), containing 44 HYDROGEN AND OXYGEN. 43 twice ns much 0, may be produced by chemical means. It is a sirupy, colorless liquid, and at 100 C. separates into H 2 and with almost explosive violence. It has no " practical" value, but is of con- siderable theoretical importance. It may be considered as composed of two groups of HO ; thus, (HO) (HO). This group is called hy- droxyl. Hydrogen dioxide, or peroxide, (H0) 2 , is sometimes called free hydroxyl. ( 97.) Ac EXERCISES. 1. What is the difference between a chemical and a physical change ? Make your answer as explicit as you can, and illustrate. 2. (a.) Describe briefly the common method for the preparation of 0, omitting no essential, (b.) Tell what you can of H and its prepa- ration. 3. (a. ) Give the symbol, atomic weight and chemical properties of O. (&.) What is meant by oxidation ? 4. (a.) What is an element ? (&.) How many are known ? (c.) Wliat gases enter into the composition of water? (d.) Prove your answer in two ways, one method being the reverse of the other, (e.) What name do you give to each method ? 5. When a current of steam is passed through an iron tube nearly filled with bright iron turnings or filings, the tube being placed across a furnace and its middle portion heated to redness, large quantities of a combustible gas that may be collected over water are delivered from the tube, (a.) What do you suppose the gas to be ? Why ? (6.) Will the iron turnings in the tube weigh more or less at the end of the experiment than they did at the beginning? Why ? 6. (a.) How many hydrogen oxides are known? Name them. De- fine chemistry. (b.) What is the difference between chemistry and physics ? 7. (a.) What is the distinction between organic and inorganic com- pounds ? (6.) Between a mixture and a compound ? 8. (.) If 240 cu. cm. of H and 120 cu. cm. of be made to com- bine, what will be the name of the product? (b.) If the experiment be performed in a vessel having a temperature above that of boiling water, what will be the name and volume of the product ? 9. If 300 cu. cm. of steam be condensed to water and the water decomposed (Exp. 12), what will be the volume and composition of the product ? * 0. 10. (a.) What weight of His there in 8,064^. of H 2 0? (b.) What volume of H ? (c.) What is a crith ? - b ,. $4 // . 44 BYDROUEX Axn OXYGEX. 44 11. Give a possible explanation for the fact that recently heated but cool platinum sponge will explode a mixture of H and 0. 12. What is meant by the reduction of copper oxide ? 13. How could you tall f ran H ? 14. State tha principal difference between ordinary and its allo- tropic modification. 15. (a.) If a mixtme of 50 cu. cm. of H and 50 cu. cm. of be , exploded in an eudiometer, what will be the name and volume of JjH the remaining gas? (5.) What precaution must be taken in measur- ing the gases ? AIR AND ITS CONSTITUENTS I. AIR. 45. Occurrence. The earth is surrounded by an atmosphere of air extending to a height variously esti- mated at from 50 to 200 miles. Experiment 55. Repeat Experiments 45 and 43, using common air instead of 0. These tests show the presence of free in the air. Experiment 56. When mercury (Hg) is heated in air it is gradually changed into red oxide of mercury (red precipitate). The mercury oxide weighs more than the mercury used, showing that, though it FIG. 28. may have lost something in the process, it has more than made good any such imaginary loss by the gain of something from the air. The process is slow and you would better buy the oxide. Put about 10 g. All?. 45 of this red mercury oxide into an ignition-tube 20 cm. long, provided with a perforated cork and delivery -tube. Close the tube and sup- port it over the lamp-flame in some such way as that shown in Fig. 28. The ignition-tube should be in an oblique position so as to ex- pose at least 3 or 4 cm. of its length to the flame. As the mercury oxide becomes heated, gas will be delivered and may be collected over water in small bottles. The first bottle-full collected should be thrown away, as it contains the air that was in the apparatus at the begin- ning of the experiment. When the gas is no longer delivered freely, remove the delivery-tube from the water, wipe the adhering liquid from it, and then remove the lamp. By testing the gas on hand you will see that it is 0. The came from the mercury oxide, to form which it was given up by the air. At the close of the experi- ment, minute globules of metallic mercury will be found upon the sides of the upper part of the ignition-tube. With proper apparatus, the experiment might be continued until all of the mercury oxide disappeared, leaving behind only metallic mercury. The synthesis of Hg and gave us the oxide; the analysis of the oxide gave us back the identical atoms of Hg and 0. Experiment 57. At one end of the beam of a balance, suspend a long vertical tube, a, containing a taper, and a bent tube, c, con- taining potassium hydrate (caustic potash, KHO). The taper may FIG. 29 45 be supported on a cork, perforated so as to admit air freely to a, which should be about 4 cm. in diameter. Connect the two tubes by a piece of rubber tubing and equipoise them and their contents by weights at w. Instead of equipoising the tubes, they may be weighed carefully, before and after the experiment, as in Exp. 31. Connect the tube, c, with a gas holder, g, filled with H a O, which on being allowed to escape at i produces a current of air through the tubes, and thus maintains the combustion of the taper, which should now be lighted. The head of H 2 in the aspirator, g, and the size of the connecting tubes should be such as to produce a strong current through the apparatus. In addition to lumps of KHO in c, it is well to fill the bend of c with an aqueous solution of KHO, through which the gases will bubble. The H 2 and C0 2 ( 196), formed by the combustion of the H and C of the taper, are absorbed by the KHO. After the taper has burned for a few minutes, the tubes, a and c, are disconnected from the gas holder and allowed to hang freely from the beam. They will be found to be heavier than before the burning of the taper, the added weight being that of the of the air that has entered into combination with the H and the C of the taper. Experiment 58. Provide a cork about 5 cm. in diameter and 2 cm. in thickness. Cover one side with a thin layer of plaster of Paris mixed with H 3 0. The paste may be raised near the edge of the cork so as to produce a concave surface. Dry the cork thoroughly and you have a convenient capsule for floating upon H 2 0. For a single experiment, the cork may be covered with dry powdered chalk or lime. Upon this capsule, p IG Q place a piece of phosphorus that has been dried by wrapping it in blotting or filter paper. Float the capsule upon H 2 0, ignite the phosphorus with a hot wire, and cover it with a bell-glass or other wide-mouthed vessel. While the phosphorus is burning, hold the bell glass down with the hand. The phosphorus combines with the O of the air, forming dense fumes of phosphoric oxide (P 2 5 ). These fumes are soon absorbed by the H 2 O, which rises in the bell-glass to occupy the space vacated by the O. Experiment 59. When the fumes of P 2 5 have been absorbed, slip a glass plate under the mouth of the bell-glass and place it 48 AIR. $J 46 mouth upward, without admitting any air. If the bull-glass be capped, as shown in Fig. 30, it need not be removed from the water- pan ; H 2 should be poured into the pan until the liquid outside the receiver is at the same level as that inside. Test the gaseous contents with a lighted taper. The flame is extinguished, but the gas does not burn. It is neither nor H. It is nitrogen, an element that we shall study in the next section. 46. Composition of Air. Air is composed chiefly of oxygen and nitrogen. Very careful determinations show its volumetric and gravimetric composition to be as follows : By Volume. By Weight. Oxygen . . 20.9 % . . 23.1 % Nitrogen . . . 79.1 76.9 100. 100. This composition of the air is nearly but not quite con- stant at diiferent times and places. The air also contains small quantities of carbon dioxide (C0 2 ). more or less watery vapor, traces of ammonias, etc. 47. Physical Properties. The air, when pure, is transparent, colorless, tasteless, and odorless. Under stand- ard conditions (temperature, 0C. ; barometer, 760 mm.) a liter of it weighs 1.2932 g. or 14.45 criths. It is therefore 14.45 times as heavy as hydrogen. It presses upon the surface of the earth with a force of 1.033 Kg. per sq. cm. or 15 Ib. per sq. in. (Ph., 273, 494.) 48. Chemical Properties. The chemical prop- erties of air are those of its several constituents. Its oxygen supports combustion, the energy of the combus- tion being checked by the diluting nitrogen. Its nitrogen manifests all of the properties of nitrogen. Its watery vapor condenses when the temperature falls, just as any 49 other watery vapor would do. Hence, we have dew and frost. When a stream of air is passed through lime-water, its carbon dioxide renders the clear liquid turbid, just as carbon dioxide always does (Exp. 44). 49. Air is a Mixture. The first sentence in the preceding paragraph intimates that the constituents of our atmosphere are not chemically united but merely mixed ; that each of them is free ( 12). This fact is shown by the following additional considerations : (a.) When the constituents are mixed in the proper proportions they form air, but there is no change of volume or manifestation of heat, light, or electricity. (6.) The composition of air is slightly variable ( 12). (c.) Each gas dissolves in H 2 independently of the other. When H,0 is boiled, it loses the gases it held in solution. Collection and analysis of these gases show that they are 32$ and 68 $> nitro- gen. The H 2 absorbed just as if there was no nitrogen present ; it absorbed nitrogen just as if no was present. This increased richness in is of vital importance to fishes ( 35). If the constit- uent gases were chemically united, they would be absorbed by H 2 in the proportion stated in 46. (d.) The gases do not unite in any simple ratio of their atomic weight. As will be seen subsequently ( 91), this is a very important consideration. 50 NITROGEN. 50 N ITROGEN. Symbol, N specific gravity, 14 ; atomic weight, 14 m. c. ; molecular weight, 2S m. c. ; quantivalence, 3 (or 5). 50. Occurrence. Nitrogen is widely diffused in nature. It is found free in some of the nebulas and in the earth's atmosphere. In combination, it exists in a number of minerals, as the sodium and potassium nitrates (nitre) of Peru and India. It also forms an essential part of most animal and vegetable substances. 51. Preparation. The usual way of preparing nitrogen is to bum out, with phosphorus, the oxygen from a portion of air confined over water, as shown in Experi- ment 58. Instead of the burning phosphorus, a jet of burning hydrogen may be used. The nitrogen thus pre- pared is not perfectly pure, but nearly enough so for ordi- nary purposes. (a.) Any method of getting the of the air to enter into com- bination and form a compound that is easily removed from the residual N will answer. Thus, if a slow stream of air be passed over bright copper turnings, heated to redness in a glass tube, the will unite with the copper, leaving the N to be collected over H 2 0. (&.) Pure N may be obtained by chemical processes, such as heating ammonium nitrite, which decomposes into H 2 and N, as follows : (NH 4 )N0 2 =2H 2 + N 2 . 52. Physical Properties. Nitrogen is a trans- parent, colorless, tasteless, odorless gas. It is a little 54 NITROGEN. 51 lighter than air or oxygen, and 14 times as heavy as hydro- gen, a liter weighing 1.2544 g. } or 14 criths. It is very slightly soluble in water. Experiment 60. Fill a bell-glass with 0, and a stoppered bell-glass of the same size with N. Cover their mouths with glass plates and bring them mouth to mouth, as shown in Fig. 31. Remove the stopper and the glass plates and introduce a lighted taper having a long wick (or a pine splinter). As the taper passes through the N, the flame is extin- guished ; if the wick be still glowing, it will be rekindled in the 0. By moving the taper up and down from one gas to the other, it may be re- kindled repeatedly before the gases become mixed by diffusion. 53. Chemical Properties. The leading charac- teristic of nitrogen is its inertness. Its properties are chiefly negative. It enters into direct combination with but few elements. It is neither a combustible nor a supporter of combustion. It is not poisonous ; we are continually breathing large quantities of it. It kills by suffocation, by cutting off the necessary supply of oxygen, just as hydrogen or water does. Its compounds are generally unstable and energetic. Some of them are decomposed by being lightly brushed with a feather or by a heavy step on the floor ( 113). 54. Uses. The chief use of nitrogen is to dilute the oxygen of the air and thus prevent disastrous chemical activity, especially in the processes of respiration and com- bustion. 52 NITROGEN. 55 55. Tests. Nitrogen may be recognized by its physi- cal properties and its refusal to give any reaction with any known chemical test. EXERCISES. 1. What is meant by allotropism ? Analysis ? Synthesis ? 2. What is the difference between an elementary and a compound molecule ? 3. Why does the burning of alcohol yield steam ? 4. Why does the gas bottle become heated in the preparation of H ? 5. Whatisacrith? 6. Is H poisonous? Can you live long in an atmosphere of H? Why? 7. Is poisonous ? Can you live long in an atmosphere of ? Why? 8. Why is the word " oxygen " a misnomer ? 9. Is the ordinary method of preparing analytic or synthetic? 10. What is the chief characteristic of ? 11. Why is the inner rather than the outer tube of the compound blowpipe used for O ? 12. Name five constituents of ordinary air. 13. State five reasons for holding that the air is a mixture. 14. What is the weight of 1 cu. m. of N ? Of ? 1 U 5 '} 15. How many criths are there in a gram ? SYMBOLS, NOMENCLATURE, MOLECULAR AND ATOMIC WEIGHTS. 56. Atomic Symbols. Chemists have a short- hand way of writing the names of the substances with which they deal. In chemical notation, each element is represented by the initial letter of its Latin name. When the names of two or more elements begin with the- same letter, the initial letter is followed by the first distinctive letter of the name. Thus, C stands for carbon, Ca for calcium, and Cl for chlorine. This use of Latin initials secures uniformity among chemists of all countries. In only a few cases do the Latin and English initials differ. The symbols of all the elements will be found in Appen- dix 1. These symbols of the elements are frequently used to represent their respective substances in general. Thus, we speak of a liter of 0, but in the symbols of compound bodies and in equations representing chemical reactions ( 127), the symbol of an element represents a single atom. To represent several atoms, we use figures placed at the right of the symbol and a little below it. Thus, H 2 means two atoms of hydrogen. (See 165, a.) 57. Molecular Symbols. The symbol of a mole- cule is formed by writing together the symbols of its con- stituent atoms indicating the number of each kind, as just stated. A molecule of water consists of three atoms, two 54 NOMENCLATURE. 57 of hydrogen and one of oxygen; hence, its symbol is H 2 0. Like the atomic symbols of the elements, these symbols of the molecules of compound substances are used to repre- sent their respective substances in the mass. Thus, we speak of a liter of H 2 0, but in the equations representing reactions, each of these symbols represents a single mole- cule. To represent several molecules, we place the proper figure before the symbol. Thus, 3H 2 represents three molecules of water, or six atoms of hydrogen and three of oxygen. Note. The symbol of a molecule is sometimes spoken of as its formula. Chemical notation is the written language of the science. 58. Nomenclature of the Elements. The nomenclature of chemistry is an attempt to represent the composition of a substance by its name. The names of the elements were generally chosen arbitrarily, although some of them allude to sjome prominent property, as chlorine from the Greek cldoros, signifying green, and as has been already stated in the cases of hydrogen and oxygen. Chemical nomenclature is the spoken language of the science. 59. Nomenclature of Binary Compounds. The names of binary compounds (those containing only two elements), have the characteristic termination -ide. .Com- pounds of single elements with oxygen are called oxides ; similar compounds with chlorine are called chlorides; those with sulphur are called sulphides, etc., etc. Thus, we have lead oxide, silver chloride and hydrogen sulphide. When any two elements unite in more than one proportion, one or both of the words constituting the name are modified, as in hydrogen peroxide, carbon disulphide, mercurous chloride and mercuric chloride. 60 NOMENCLATURE. 55 6O. Nomenclature of Ternary Compounds. The most important compounds containing three or more elements are the acids. The most important of these consist of hydrogen and oxygen united to some third element, which is the characteristic one and gives its name to the acid. The terminations -ic and -ous are used with the name of the characteristic element to indicate a greater or less amount of oxygen in the acid. Thus we have : Nitric acid HN0 3 Nilrow* acid. . ..HNO 2 Sulphuric acid H 2 S0 4 Sulphur0ws acid ... . H 2 S 3 The hydrogen of any acid may be replaced with differ- ent metallic elements, giving us the large and important class of compounds called salts. The generic name of the salt is formed by changing the -ic termination of the name of the acid to -ate, or by similarly changing -ous to -ite. Thus, phosphor^ acid furnishes "phosphates, while phosphorous acid furnishes phosphite*. The specific name of the salt is derived from that of the element used to replace the hydrogen of the acid. Thus we have : Nitric acid HN0 3 Nitrous acid. . ..HN0 Potassium nitrate KN0 3 Potassium nitrite KN0 2 Sulphuric acid H 3 S0 4 ! Potassium sulphate. K 2 S0 4 Sulphurows acid H 3 S0 3 ! Potassium sulphite.. K 2 S6 8 (a.} Some chemists prefer to modify the name of the replacing element making it an adjective, e- g., potassic nitrate. In the case of English words that can not be adapted to such adjective forms, the Latin word is used; e. g., plumbic nitrate for lead nitrate. In some cases old forms are still frequently used ; e.g., chlorate of pot- ash for potassium chlorate, or protosulphate of iron for ferrous sul- phate. In some cases, a strict adherence to systematic chemical nomenclature would lead to the use of inconvenient names, as potas- sium aluminum sulphate for common alum. In the so-called organic compounds this inconvenience would frequently be very marked. 56 THE MICROCRITH. 6 1 61. Ampere's Law. The corner-stone of modern chemistry, "as distinguished from the chemistry of the last generation, is a proposition known as Ampere's or Avoga- dro's law, the evidence in support of which can not be satisfactorily presented in this place. It may be stated as follows : Equal volumes of all substances in the gas- eous condition, the temperature and pressure being the same, contain the same number of molecules, 62. The Microcrith. A liter of hydrogen weighs .0896 #., or one crith. It has been estimated that a liter of hydrogen, or of any other gas, contains 10 24 molecules. Then each molecule o'f hydrogen weighs ^^ crith s, and each hydrogen half-molecule weighs ^ritF* crith s. The weight of the hydrogen half-molecule has been called a microcrith (m. c.), and the term is so convenient that we shall use it. It must be remembered that the absolute value of a m. c. is, as yet, unknown, because the number 10 34 , used above, is only an "estimate." When physicists determine accurately the number of molecules in a given volume of a gas, the chemist will know the absolute value of a m. c. It will answer all of our present purposes to remember that umicrocrith is the weight of one atom of hydrogen, and that it is a real unit, measuring a definite quantity of matter, for, as we shall soon see, the hydrogen half-molecule is a hydrogen atom (174). 63. Molecular Weights. The hydrogen molecule weighs 2 m. c. Knowing that oxygen is sixteen times as heavy as hydrogen and remembering Ampere's law, it is evident that the oxygen molecule must weigh 32 m. c. Similarly, we see that the nitrogen molecule weighs 28 m. c., etc. In brief, the molecular weight (in microcriths) 64 ATOMIC WEIGHTS. of a substance is twice the specific gravity (hydrogen standard) of the substance in the aeriform condi- tion. Dry steam being nine times as heavy as hydrogen, its molecular weight is 18 m. c. At the same time, the molecular weight must equal the sum of the weights of the atoms in the molecule. The combining weight of a chemical compound is its molecular weight. (a.) The only known method for determining the molecular weight of a compound with certainty is the determination of its vapor density. The molecular weight of a compound that is not volatile, or volatile only at a temperature so high as to prevent the determina- tion of its vapor density, or that is not volatile without decomposi- tion, must be considered as unknown or, at least, doubtful. 64. Atomic Weights. The chemist is able to analyze any known compound, and to determine the exact proportion of the elements constituting it. We have already seen how he determines the molecular weights. One method of determining the atomic weights will be best understood from an example. (a). Suppose the chemist wishes to determine the atomic weight of O. He begins with steam and finds, from its specific gravity, that its molecular weight is 18 m. c., and, by analysis, that f of this is 0. He proceeds in this way with all of the gaseous or volatile compounds of 0, and tabulates some of the results, as follows : SUBSTANCES. WEIGHT OF MOLECULE. WEIGHT OP O IN MOLE- CULE. Water H 2 CO NO C,H 6 ) or 40 g. of pulverized sodium nitrate (NaN0 3 ,) and 35 cu. cm. of- strong H 8 S0 4 . The mate- rials should be introduced through the tubulure, 8, and care taken that none falls into the neck of the retort. It is well to use a paper funnel for the nitrate and a funnel tube for the acid. Replace the stopper and place the retort upon sand in a shallow sheet iron or pressed tin pan, supported by a ring of the retort stand over the lamp, or upon wire gauze, as shown in the figure. The use of the " sand bath " or gauze lessens the danger of breaking the retort. Place the neck of the retort loose- ly in the mouth of a Florence flask, r, or other convenient re- ceiver, kept cool by H 8 0. It is well to cover the receiver with cloth or bibulous paper ; the H 2 may be brought by a rubber tube siphon (Ph., 298) from a pail of H,0 sufficiently elevated. As the retort is heated, the nitrate 66 NITRIC ACID. 74 liquefies, reddish fumes appear, and HN0 3 condenses in the neck of the retort andjn the receiver. The fumes in the retort will soon dis- appear ; continue the distillation until they reappear. Transfer the HN0 3 to a glass stoppered bottle and save it for future use. After the retort has become thoroughly cool, the solid residue, acid potassium sulphate, should be dissolved by heating with H 2 0, and then removed. (&.) In the arts, the retort is made of cast iron and the distillate is condensed in earthenware receivers. A higher temperature and frequently only half as much H 2 S0 4 are used. 2KN0 3 + H 2 S0 4 = K S0 4 + 2HN0 3) 2NaN0 3 + H a S0 4 = N~a 2 S0 4 + 2HN0 3 . 75. Physical Properties. Nitric acid is a fuming liquid, colorless when pure, but generally slightly tinted with the fumes seen in the retort during its preparation. It has a specific gravity of 1.52, freezes aW>5C., and boils with partial decomposition at 86C. It may be mixed with water in all proportions, the aqua fortis of commerce containing from 40 to 60 per cent, of nitric acid. Experiment 71. Pulverize a few grams of charcoal and heat it. Upon the heated charcoal, pour a little strong HN0 3 . The charcoal is rapidly oxidized to combustion. Experiment 7%. From the end of a meter stick, drop a thin slice of phosphorus into strong HN0 3 . The phosphorus is oxydized to violent combustion. Experiment 73. Into dilute HN0 3 , dip a skein of white sewing silk. In a few minutes, remove and wash it thoroughly with H 2 0. The silk will be permanently colored yellow. Experiment 74- Put a sheet of if Dutch leaf," which may be ob- tained of a sign painter, into a test tube and pour upon it a small quantity of HN0 3 . The metal is instantly dissolved. 76. Chemical Properties. Nitric acid is a power- ful oxidizing agent, and one of the most corrosive known substances. It colors nitrogenous animal substances (e. g., 7$ XITRIC ACID. 67 silk, skin and parchment) yellow, and converts many non-nitrogenous substances (e. g., cotton and glycerine) into violently explosive compounds. It dissolves all of the common metals except gold and platinum, forming nitrates. Experiment 75. Cover a smooth piece of brass or copper with a film of beeswax. With a sharp instrument, write your name upon the metal, being sure to cut through the wax. Cover the writing with strong HN0 3 , In a few moments, the name will appear in a tracery of minute bubbles. A few moments later, wash the acid away with H 3 and remove the wax. The autograph will be etched upon the metal. / 77. Uses. Nitric acid is largely used in the laboratory and in the arts, in the manufacture of gun cotton, nitro- glycerin, etc., and in the preparation of aqua regia ( 114). Engravers use it for etching on copper and steel. Experiment 76. Into a test tube, put a few bits of copper and cover them with HN0 3 . The red fumes of nitric oxide appear, and the liquid is colored blue by the copper nitrate formed. Experiment 77. Into a test tube, put a few cu. cm. of a dilute so- lution of mdigo. Add HN0 3 until the blue solution is bleached. 78. Tests. In testing for nitric acid, first try blue litmus paper. If this test paper be s not reddened when dipped into the liquid in question, the liquid is not an acid. If it be reddened, the liquid is some acid. As the nitrates are all easily soluble, tests for nitric acid yield no precipitates. Free nitric acid may be detected by its bleaching an indigo solution, or by its forming red fumes when added to copper bits or filings. Nitrates show the same effects when heated with sulphuric acid, because of the nitric acid thus set free. The nitrates also deflagrate when thrown upon burning charcoal. 68 NlTBOOEX OXIDES. 79 N ITROGEN OXIDES. Experiment 78. In a small evaporating dish (App. 21), place a few cu. cm. of HN0 3 and add an equal bulk of H 2 0. In another vessel, place a small quantity of NH 4 HO similarly diluted. Into the first liquid, dip a strip of blue litmus paper. The change of color shows an acid. Dip this litmus paper (now red) into the other liquid. The restoration of the blue color shows the presence of an alkali. To the first liquid, add the second, in small quantities at first, and finally drop by drop. Stir the mixture continually with a glass rod, and test with blue litmus paper after each addition of NH 4 HO. At last, it will be found that the mixture will neither redden blue litmus papor nor restore red litmus paper to its original blue. It has neither an acid nor an alkaline reaction. The acid has been " neu- tralized " by the alkali, and we have a solution of a neutral salt. Without boiling the liquid, evaporate it until, when the glass rod is removed, the adhering liquid becomes almost solid upon cooling:. Crystals will now form upon the cooling of the liquid ; these crystals are to be carefully drained and dried. They are ammonium nitrate (NH 4 NO,). 79. Nitrogen Monoxide. Nitrogen monoxide (nitrogen protoxide, nitrous oxide,, laughing gas, N 2 0,) is prepared by decomposing ammonium nitrate by heat. (a.) Into a small Florence flask, /, place a tablespoonful of N H 4 N 3 . Heat gently and carefully over the sand bath or a piece of wire gauze, and collect the gas over warm NH 4 N0 8 = N 2 + 2H 3 0. To show that H 3 is produced, in- terpose, between the Florence flask and the water pan, a condensing bot- tle placed in ice water, as shown at c, in Fig. 38. Test the liquid that col- lects in this bottle by dropping a small piece of potassium into it. The FIG. 38. 82 XITROGKX OXIDES. 69 flask would break before all of the NH^NO-j was decomposed, but by heating a small quantity of the nitrate upon platinum foil, it will be seen that no residue is left. Experiment 79. Repeat Exps. 33, 36, and 37, using N 2 instead of 0. (These are simply combustions in 0, the N 2 being decomposed into its elements.) 80. Properties. Nitrogen monoxide is a colorless, sweet tasting gas, and a good supporter of combustion. One liter of it weighs 22 criths. It may be liquefied and 'solidified by cold and pressure. When the liquid is mixed with carbon disulphide and evaporated in a vacuum, it pro- duces the remarkably ' low temperature of 140 C. (Ph., 526). It is largely soluble in alcohol or water, but less so in warm water. When pure and mixed with one- fourth its volume of oxygen, it may be safely inhaled, pro- ducing the effects that have secured for it the name of laughing gas. If its inhalation is continued, it acts as an anaesthetic. 81. Composition. The composition of nitrogen monoxide is strictly analogous to that of steam (Exp. 53), two volumes of nitrogen uniting with one of oxygen to form two of this compound. 14 m.c. O 16 m.c. 44 m. c. When decomposed by electric sparks, it yields 1 times its own volume of mixed gases, as represented by the typical squares above. 82. Ilypoiiitrous Acid. This acid (H NO) has not yet been prepared, but the corresponding salt, potassium hyponitrite (KNO), is known. We may imagine this reaction : N g O -f H 2 = 2HNO. 70 NITROGEN OXIDES. 83 83. Mtric Oxide. Nitric oxide (nitrosyl, NO,) is prepared by the action of dilute nitric acid upon copper clippings, turnings or filings. The gas may be collected over water. The apparatus is arranged as shown in Fig. 6. The generating bottle is, at first, filled with red fumes ( 87) but the gas collected over water is colorless. Save the blue solution of copper nitrate [Cu(N0 3 ) 2 ]- 3Cu -f 8HN0 3 = 3NO + 3Cu (N0 3 ) 2 + 4H 2 0. Experiment 80, Into a bottle of NO, lower a burning splinter, a burning candle, or sulphur burning in a deflagrating spoon (App. 19). It will not burn in the gas. Experiment 81. Into a bottle of NO, lower a deflagrating spoon containing a bit of vigorously burning phosphorus, the size of a pea. It will continue to burn with great brilliancy. Experiment 82. In a jar of NO, place a few drops of carbon di- sulphide. Close the bottle for a few minutes to allow the liquid to evapo- rate and its vapor to mix with the NO. In a dark room, bring a lighted taper to the open mouth of the jar, as shown in Fig. 39. The mixture burns with a vivid light rich in actinic rays (Ph., 651). Experiment 83. Into a jar of NO, standing in the water pan, pass a stream of from the gas holder. After the red fumes, that are promptly formed have been dissolved by the H 8 0, re- peat the experiment several times, notic- ing the phenomena carefully. FIG. 39. Experiment 84. Fill a large bell glass with NO at the water bath. Cover the mouth under H 2 with a glass plate,. invert the bell glass and remove the plate (Fig. 40). The NO absorbs from the air and forms a cloud of the now familiar red fumes (Exp. 45). 84. Properties. The leading property of nitric oxide is its strong attraction for oxygen. Its relation to 8 7 NITROGEN OXIDES. combustion is peculiar. Ordinary combustibles will not burn in it at all ; phosphorus may be jfo melted in the gas without kindling, but when once well aflame it burns with great energy. The gas is color- less and slightly soluble in water. One liter of it weighs 15 criths. 85. Composition. This is the first compound that we have studied, the gaseous constituents of which unite without condensation. One volume of oxygen unites with one volume of nitrogen to form two volumes of nitric oxide. FIG. 40. 86. Nitrogen Trioxicle. This gas (nitrous anhydride, N 2 3 ,) is an obscure compound that unites with water to form nitrous acid(HN0 2 ). N 2 3 + H 2 = 2HN0 2 . 87. Nitrogen Peroxide. Nitrogen peroxide (ni- tryl, NO 2 ,) is the brownish red gas with which we have so frequently met in our experiments with nitric acid and the nitrogen oxides. It is best prepared by bringing together two volumes of nitric oxide and one volume of oxygen, both constituents being perfectly dry. It is an energetic oxidizing agent ( 152, d). It may be liquefied and solidified. In the presence of water it forms acid com- pounds, probably a mixture of nitric and nitrous acids. Experiment 85. Pass 250 cu. cm. of into a bottle filled with H 2 O, colored with blue litmus. Then pass in 250 cu, cm, of NO. NITROGEN OXIDES. $88 Red fumes of NOo are produced but soon absorbed by the H 2 0. Pass in another 250 cu. cm. of NO. If the and NO are pure, the will be wholly used to form N0._ all of which will be absorbed by the H,0. The acids thus produced turn the colored water from blue to red. 88. Composition. The composition of ni- trogen peroxide, by vol- ume and by weight, may be represented as follows : N0 2 46 m. c. 9. Nitrogen Peiitoxide. Nitrogen pentoxide (nitric anhydride, N 2 5 ) is a crystalline white compound, so unstable that it spontaneously decomposes in a sealed tube into oxygen and nitrogen peroxide. It is particularly interesting on account of its relation to nitric acid. N S 5 + H 2 0=2HN0 3 . 90. Law of Definite Proportions. The truth stated in 12 has been verified by numberless analyses and may be formulated as follows : Any given chemical compound always contains the same elements in the same proportions. 91. Law of Multiple Proportions. // two substances coiribine to form more than one com- pound, the iveight of one substance being considered as constant, the weights of the other vary according to a simple ratio. NITROGEN OXIDES. 73 (a.) This important principle is best illustrated by the nitrogen oxides just studied. BY GRAVIMETRIC BY VOLUMETRIC ANALYSIS. ANALYSIS. a ACTUAL RATIO ACTUAL RATIO NAMES. 1 z z 6 z z o 02 S s -s O S a -a to "Si s a a a 01 the quan- tivalence of potassium is one, that of oxygen is two. (a.) Atoms are classified according to their quantivalence as monads, dyads, triads, tetrads, pentads, hexads and heptads, from the Greek numerals. They are similarly described by the adjectives univalent, bivalent, trivalent, quadrivalent, quinquivalent, sexivalent, and sep- tivalent, from the Latin numerals. Thus, oxygen is a dyad, or it is bivalent ; carbon is a tetrad, or it is quadrivalent. (&.) The quantivalence of an element may be absolute or apparent. Absolute (or true) quantivaleuce is conceived to be a property of 94 SYMBOLS. 75 atoms, invariable for any one atom under like conditions. It is a power that may or may not be exerted to its full extent. With our present limited knowledge, it is impossible to determine the absolute quanti valence of an element with certainty. Apparent quantivalence is the combining power that an atom exhibits in any given compound. It may or may not be the same as its absolute quantivalence. The quantivalence of N apparent in NH 3 is three ; i. e., N there appears to be a triad. Its quantivalence apparent in N H 4 C I is five ; it there appears as a pentad. When atoms of the same element act with different quantivalences, they frequently form compounds as dis- similar as atoms of different kinds would do. A change in the appar- ent quantivalence of an atom implies a change in all of its chemical relations. N 2 is as different from N 2 0- as H 2 is. (c.) The quantivalence of an atom is indicated by Roman numer- als placed above, or minute marks placed above and at the right IV of the symbol, as C or N'". They should not be confounded with the figures below and at the right of the symbol. (d.) Sometimes the words "valence," "equivalence" and "atom- icity " are used in the sense in which we have used the word quan- tivalence. The word " atomicity" more properly refers to the num- ber of atoms in a molecule. (e.) The quantivalence of many common elements is not yet satis- factorily determined. Quantivalence should not be confounded with chemism or affinity. H and Cl have a very great affinity for each other, but each is univalent. 93. Graphic Symbols of Atoms. The graphic symbol of an atom represents its quantivalence by lines or bonds radiating from the symbol, as follows : Monad, Dyad, Triad, Tetrad, Pentad, Hexad. H 0= N= C= =P= =S= The number of bonds is significant ; their direction is not. Thus, the graphic symbol of an atom of oxygen may be written -0-, 0=, 0-, -0, Ck, etc., etc. 94. Empirical and Rational Symbols. Molecular symbols are of two classes, empirical and rational. An empirical symbol is based upon analysis, expresses the 76 SYMBOLS. 94 kind and number of atoms in a molecule, and represents all that we Tcnoiv about the constitution of the molecule. H 2 0, HN0 3 , etc., are empirical symbols. A rational sym- bol attempts to represent, in addition to this, the possible modes of formation and decomposition of substances and are sometimes necessary to enable us to distinguish between substances having the same empirical symbol but endowed with different properties ( 216). Graphic and typical symbols are included under this head. 95. Graphic Symbols. A constitutional or graphic symbol is one that indicates the constitution of a molecule; not, indeed, by showing the arrangement of the atoms in space, for we know nothing at all about that, but by showing which atoms are united with each other in the molecule. It is composed of the graphic symbols of the constituent atoms : (a.) The graphic symbol of H may be written H-O-H ; that of H H 3 N, H-N-H; that of CO 2 , = C=0; that of HN0 8 , H-O-N = and that of S0 , 0=S=0. It will be noticed that each atom has II the number of bonds that represents its quantivalence. 96. Typical Symbols. Chemical symbols are sometimes written in accordance with one of several types, e. g., free hydrogen or hydrochloric acid, water, ammonia and marsh gas. The underlying idea is that the chemical constitution of all known substances is modelled upon a limited number of types. By replacing atomic symbols in the type by others of the same quantivalence, we can obtain the sym- bol for any other member of the class. 97 RADICALS. 77 (a.) Examples of typical symbols are given below : Free Hydrogen. Water. Ammonia. HI H IN H/ Hydrochloric Acid. Sodium Hydrate. Methyl- amine. U ) (CH.)n n ( cif H"} H IN H J Methyl Hydride. Sulphuric Add. Trimethyl- amine. Methyl SUicide. CM CH | N (6.) These typical symbols are not to be considered as suggesting similar properties in the substances referred to any one type. They simply suggest similarity in the supposed grouping of the atoms in the molecule. (c.) It will be noticed, from the examples above, that a compound radical ( 97) may take its proper place in a typical symbol, replacing an atom or more of H according to its quantivalence and that a sub- stance (e. g., H 2 S0 4 ) may be represented as built upon the type of the double molecule of the typical compound. A triple molecule may be thus used, e. g., glycerin = 0. ( every atom has its quantivalence fully satisfied ; i. e., each bond of each atom is engaged. Such atomic groups are said to 78 RADICALS. 97 be saturated. But the group, = S=0, has two free bonds. Such an unsaturated group of atoms is called a compound radical. It may enter into combination like a simple atom, always acting with a quan- tivalence equal to the number of unsatisfied bonds. (a.) The names of compound radicals generally terminate in -yt, as nitrosyl (NO) and nitryl (N0 2 ). Two of these atomic groups may unite, like two atoms, to form a saturated molecule. If, from H-O-H, we remove one atom of H, we have the compound radical H-0-, called hydroxyl. Two of these univalent groups may unite to form H 2 2 ( 44), as follows : (HO)- quantivalence, 1(3,5, or 7), 117. Source. Iodine compounds exist in very mi- nute quantities in the water of the sea and of some saline springs. From sea water, the iodide is absorbed by certain marine plants. The ashes (kelp) of these sea weeds con- tain sodium and magnesium iodides. Iodine is obtained by heating the kelp with sulphuric acid and manganese dioxide. Iodine is thus set free in the form of a beautiful violet colored vapor which soon condenses to a solid. Experiment 119. Put a small piece of I into a dry test tube. Heat the test tube in the flame and notice that the I vaporizes without visible liquefaction (Ph., 509). Notice that the vapor is very heavy as well as very beautiful. If the upper part of the tube be cold, minute I crystals will condense there. Experiment 120. Place some I upon a heated brick and cover the whole with a large bell-glass. This gives a good exhibition of the beautiful vapor. Il8 IODINE. 99 Experiment 121. Prepare some starch paste, as in Exp. 99, and dilute 5 or 6 drops of it with 10 cu. cm. of H 3 0. Dissolve a very small piece of I in alcohol and add a drop of the alcoholic solution to the dilute starch. The starch will be colored blue even when the alcoholic solution is very dilute. The blue color will disappear upon heating the solution and reappear upon cooling it. Experiment 122. Drop a few crystals of I into a large bottle. Dip a strip of white paper into the colorless starch paste and suspend it in the bottle. The paper may be held in place by the stopper of the bottle. As the I sublimes and diffuses through the bottle, it soon comes into contact with the starch and colors the paper blue. Note. A moment's reflection will show that in this experiment the quantity of I that actually comes into contact with the starch and changes its color is almost immeasurably small. Starch will detect the presence of one part of I in 300,000 parts of H 3 0. Experiment 123. Add a few drops of the alcoholic solution pre- pared in Exp. 121 to 10 cu. cm. of H 2 in a test tube. Owing to the sparing solubility of I in H 2 0, most of the I will be precipitated. Pour 5 cu. cm. of this aqueous solution into a test tube, add 8 or 10 drops of carbon disulphide (CS 2 ) and shake the contents of the tube. On standing for a few moments, the CS 2 will settle to the bottom, when it will be seen to be colored purple-red ; the color is due to the I dissolved in the CS 2 . Carbon disulphide will detect the pres- encs of one part of I in 1,000,000 of H 2 0. Experiment 124. Pour 10 cu. cm. of H 2 into each of three tall test glasses. Add a few drops of a solution of potassium iodide to each. To the first, add a few drops of a solution of lead acetate (sugar of lead). Brilliant yellow lead iodide is formed. To the second, add a few drops of a solution of mercurous nitrate. Yellowish-green mercurous iodide is formed. To the third, add a few drops of a solu- tion of mercuric chloride (corrosive sublimate). Scarlet mercuric iodide is formed. 118. Properties, etc. Iodine is a blue-black, crys- talline solid having a metallic lustre. Its vapor has a specific gravity of 127 ; it is the heaviest known vapor. Iodine is very sparingly (1:5500 at 10C.,) soluble in water but readily dissolves in alcohol, ether, chloroform, carbon disulphide or aqueous solutions of the metallic iodides. 100 LUORINE. H8 Its chemical activity is less than that of bromine. It is used in medicine, photography and the manufacture of aniline green. The blue color it forms with starch, its beautifully colored vapor, and the purple-red color it forms with carbon disulphide form delicate tests for free iodine. (a.) I forms acids as follows, hydroiodic, HI; iodic acid, HI0 3 ; periodic acid, H 5 IO 6 . They closely resemble the corresponding C I and Br compounds. (&.) I has no action upon sodium, but when it is heated with potas- sium an explosive combination takes place. Experiment 125. Upon 0.25 g. of pulverized I, placed in a porcelain capsule, pour enough strong ammonia water to cover it and allow it to stand for 15 or 20 minutes. At the end of that time, stir up the powder at the bottom of the liquid and pour a quarter of the contents of the capsule upon each of four small filters (App. 8). Wash the powder well with cold H 3 O, and then remove the filters with their contents from their funnels. Pin the niters to pieces of board and allow them to dry without heating. When the powder is dry, it may be exploded by brushing it with a feather or by jarring it with a blow upon the table. The powder is nitrogen iodide. 119. Nitrogen Iodide. Nitrogen iodide is much less explosive than nitrogen chloride ( 113) but it should not be prepared by the pupil except in very small quanti- ties. Nitrogen forms a similar compound with bromine. LUORINE ; symbol, F ; atomic weight, 19 m. c. ; quantimleme, 1. 120. Source. Fluorine occurs in nature in fluor spar (calcium fluoride, CaF 2 ), and in cryolite (sodium and alu- minum fluorides, 3NaF -f AIF 3 ). It has also been found in minute quantities in the teeth, bones and blood of animals. Note. Fluor spar is a mineral found somewhat abundantly in various parts of the world, especially in Derbyshire and Cornwall, England. Cryolite is found in large quantities in Greenland. 121. Properties. Fluorine is a very remarkable element in that it is the only one that forms no compound 121 FLUORINE. 101 with oxygen and that it has, so far, resisted all of the attempts made to obtain it in the free state. When set free from one compound, it attacks the substance nearest at hand to form a new compound. It surpasses chlorine in its power of combining with hydrogen and the metals, and has a remarkable tendency to .ccxmbine, with silicon^ The difficulties in the way of its prepaia'tionSin-d collection have prevented its satisfactory study by chemists: Cp frequently? but little is known concerning * ire j e fluorine 1 . Its com- pounds closely resemble those of chlorine, bromine and iodine. Note. F has been considered subsequently to Cl, Br and I, because of the comparative lack of knowledge concerning it. There are good reasons why, in grouping them, F should precede Cl, Br and I. Experiment 126. Rub a heated piece of glass with beeswax. If the glass be hot enough to melt the wax, it may easily have one of its surfaces covered with a thin layer of nearly uniform thickness. Let the glass cool. With any pointed instrument, write a name or draw a design, being careful that every stroke cuts through the wax and exposes the glass below. In a small tray made of lead (platinum is better, but a saucer that you are willing to spoil will answer), mix a spoonful of powdered fluor spar or cryolite with enough H 2 S0 4 to make a thin paste. Place the prepared glass (waxed side down) over the tray ; heat the tray gently (not enough to melt the wax) and set it aside in a warm place for two or three hours. (Do not inhale the acid fumes.) Clean the glass by scraping it and rubbing with turpen- tine. The name or design will be seen etched upon the glass. Experiment 127. Upon a pane of glass that will fit the window of your chemical laboratory, or the glass front of one of your laboratory cases, etch the proper designation of the class, the date, and the autographs of the individual members of the class. The " class artist " may add an appropriate border and emblematic designs, ad libitum. Experiment 128. Coat the convex surface of a watch glass with wax, write a name upon it, place it upon a small lead saucer contain- 102 THE HALOGEN GROUP. 122 ing mixed CaF 3 and H 2 S0 4 , fill the watch glass with H 2 to keep the wax from melting, and hold the saucer in the lamp flame. The etching will be finished in a few minutes. 122. Hydrofluoric Acid. This acid (HF) is dis- tinguished from all other substances by its power of cor- roding glass. It evidently corresponds closely to the other hydrides of this .group'. (t& HCI, HBr and HI) but it is more .enorgetic than, any of them. It is readily prepared, as above, by distilling soiwe fluoride with sulphuric acid, e.g., CaF 2 + H 2 S0 4 = CaS0 4 + 2HF. (a.) The reaction is closely analogous to that for the distillation of NaCI with H 2 S0 4 ( 105, a). The solution of HF is also used for etching glass. HF, when dry, does not act on glass, but the slightest trace of H 2 renders it capable of doing so. 123. The Halogen Group. Fluorine, chlorine, bromine and iodine constitute one of the most clearly defined and most remarkable natural groups known to chemistry. They exhibit a marked gradation in proper- ties and close analogies in their elementary condition and in their corresponding compounds. (a.) Concerning their gradation of properties : 1. At the ordinary temperature, F is a gas; Cl is a gas; Br is a liquid and I is a solid. 2. Liquid Cl is transparent ; Br is but slightly so ; I is opaque. 3. C I has a specific gravity of 35.5 ; Br vapor, 80 ; I vapor, 127. 4. F has an atomic weight of 19 m. c. ; Cl, 35.5 m. c ; Br, 80 m. c. ; I, 127 m. c, 5. Generally speaking, their chemical activities are graded in the inverse order, being greatest in the case of F ; less in Cl ; still less in Br and least in I. (In the case of such natural groups the chemi- cal activities frequently vary inversely as the atomic weights.) The atomic weight of Br is nearly the mean of those of Cl and I (35.5 + 127 _ 81.25) and, in general chemical deportment, Br stands half way between the other two elements. (&.) Concerning their analogies : 1. Their binary compounds with potassium and sodium resemble 123 THE HALOGEN GROUP. 103 sea salt. Hence, these compounds are called haloid salts and their elements, halogens (Greek, halos, salt and gennao, I produce). 2. Each of them combines with H, equal volumes of the constitu- ent gases uniting without condensation, to form the haloid acids, HF, HCI, HBrand HI. 3. These haloid acids all have a great attraction for H 2 forming aqueous solutions that have the same chemical properties as the acids themselves. EXERCISES. 1. Give two of the most marked physical properties of H, and two of its distinctive chemical properties. 2. What is a triad ? A pentad? A quadrivalent atom ? A biva- lent compound radical ? Illustrate each. 8. By passing the vapor of I with H over platinum sponge heated to redness, a strongly acid gas is synthetically formed. What is its name, its molecular weight and its specific gravity ? 4. A large jar, about a quarter full of chloride of Ihne had been standing for some time until the upper part contained a gas given off by the chloride. Into this gas, a moistened slip of paper was thrust. The paper was instantly colored deep blue. What was the gas and with what was the test paper moistened ? Explain the phenomenon. 5. What analogies exist between members of the Halogen group ? 6. Symbolize the chlorides, bromides, iodides, chlorates, bromates and iodates of the following: K', Na', Ag', Cu", Zn", Au'", Pt iv , STOICHIOMETRY. 124. Reactions and Reagents. Any change in the composition of a molecule is called a chemi- cal reaction. Substances acting in such a chemical change are called reagents. (a.) Changes in molecular composition are of three kinds : 1. Changes in the kind of the constituent atoms. 2. Changes in the number of the constituent atoms. 3. Changes in the relative positions of the constituent atoms. (6.) When H burns in air, the H and react upon each other ; they are the reagents used to produce a molecular change. 125. Expression of Reactions. In any given substance of homogeneous composition, the molecules are all alike. The nature of the mass depends upon the nature of the molecule. The mass may be fittingly represented by the molecule. Any chemical change in the mass may be represented by a corresponding change in the molecule. Hence, chemical reactions are generally expressed in molecular symbols. 126. Factors and Products. TJie molecules that go into a reaction are called factors; the molecules that come from it are called products. (a.} In the preparation of H ( 23), the factors were Zn nd 2HCI ; the products were ZnCI 8 and H 2 . 128 GRAVIMETRIC COMPUTATIONS. 105 127. Chemical Equations. Chemical reac- tions are very commonly and conveniently repre- sented Inj equations, placing the sum of the factors equal to the sum of the products. (a.) The equality results from the indestructibility of matter (Ph., 37). It indicates that the number of each kind of atoms in the products is equal to the number of the same kind of atoms in the factors. The atoms are differently arranged but not a single one is gained or lost. From this it follows that the symbols in the two members of the equation represent the same number of microcriths. The chemical change does not effect any change in weight. (See Exp. 9.) (b.) Re-examine the equations already given, showing their agree- ment or disagreement with the above statements. (c.) The equation also represents the relative weights of the several substances engaged in the reaction* The equation H 2 + = H Z means, literally, that 2 m. c. of H united with 16 m. c. of yields 18 m. c. of H 2 0, but the relation is equally true for larger quantities of matter. Thus we may learn from it that 2 g. of H unites with 16 g. of to form 18 g. of H 2 0, or that 12 Kg. of H unites with 96 Kg. of to form 108 Kg. of H 2 0. (d.) Strictly speaking, it is not proper to represent a fractional part of a molecule as entering into or resulting from a chemical reac- tion, as we do when we write H 2 + 0:=H 3 0. To obviate the error of representing an atom of free 0, we should indicate twice the quantity of each substance, as follows: 2H 2 + 2 = 2H 2 0. ~Bat,for the sake of convenience, chemists generally, write the equations in the simpler form, as the gravimetric relations expressed are the same. (e.) The equation, written in complete molecules, also represents volumetric relations. Remembering Ampere's law ( 61), we easily see that 2H a + 2 = 2H 2 indicates that two (molecular or other) volumes of H unite with one of O to yield two volumes of dry steam, e. g., 2 I. of H and 1 I. of O unite to form 2 I. of dry steam. 128. Gravimetric Computations. Knowing the equation for any given reaction and the atomic weights of the several elements involved, we are able to solve a great many problems concerning the weight of substances 106 VOLUMETRIC COMPUTATIONS. 128 appearing as factors or products. From the data now known and those given in the problem, make the follow- ing proportion : As the number of microcriths of the given sub- stance is to the number of microcriths of the re- quired substance so is the actual weight of the given substance to the actual weight of the re- quired substance. (a.) The number of microcriths is to be taken, of course, from the equation. A few examples are given : 1. How much H can be obtained from HCI by using 20 g. of Zn (zinc) ? Solution. Write the reaction with the molecular weights of the several reagents. 2(1 + 35.5) 65 + 71 Zn + 2HC! = ZnCI 2 + H 2 . 65 m. c. 73 m. c. 136 m. c. 2 m. c. Form the proportion according to the above rule : 65 m. c. : 2 m. c. : : 20 g. : x g. .-. x = 0.61538 g. or 615.38 mg. of H. Ans. 2. How much HCI will be required? 65 wi. c. : 73 m. c. : : 20 g. : x g. .-. x = 22.46 g. of dry HCI. 4w*. 3. How much ZnCI 2 will be produced? 65 m. c. : 136 m. c.i: 20 g. : x g. .-. x = 41.846 . of ZnClo. Ans. 4. How much Zn is necessary to prepare 1 El of H ? As one liter of H weighs 1 crith or .0896 g., 1000 I. weighs 89.6 g. 65 m. c.:2m.c.:: x g. : 89.6 g. .'. x 2912 g. or 2.912 Kg. of Zn. Ans. 129. Volumetric Computations. Every equa- tion written in the molecular symbols of aeriform sub- stances maybe read by volume. For example 2H 2 -f0 2 = 2H 2 may be read : two volumes of hydrogen unite 130 PERCENTAGE COMPOSITION. 107 with one volume of oxygen to form two volumes of dry steam. We give a few examples. (a.) 1. How much steam is formed by the combustion of 1 1. of H ? Solution. ~By referring to our equation, we see that the volumes of H and of H 2 are equal, because it shows an equal number of molecules for those substances, and we know, from Ampere's law. that equal numbers of gaseous molecules will occupy equal volumes. Hence, the combustion of 1 L of H will give 1 I. of dry steam. 2. How much is needed to burn up 500 cu. cm. of H ? Solution. The equation for the combustion of H shows that the volume of is half that of the H . Hence, it will require half of 500 cu. cm. or 250 cu. cm. of 0. 3. How much H must be burned to form 4 I. of steam ? Solution. The equation shows a relation of equality between the volumes of H and of H 2 (as in the first example). Conse- quently, 4 1. of steam requires 4 I. of H. 4. How much can be obtained from the electrolysis of 3 I. of steam ? Solution. The equation shows that the volume of is half that of aeriform H 8 0. Hence, 3 1. of steam will yield 1.5 I. or 1500 cu. cm. of O. 13O. Percentage Composition. The method of solving problems of this kind will be illustrated by ex- amples, as follows : (1.) What is the percentage composition of HN0 3 ? Solution. The molecular weight of HN0 3 is 1 m. c. + 14m. e. + 48 m. c. 63 m. c. 63 m. c. : 1 m. c. : : 100% : ( 1.59%, the proportion of H. 63 m. c. : 14 m. c. : : 100% : &2.22%, " " N, 63 m. c. :4Sm.c.:: 100% : 76.19% " " O. 100.00% * (2.) The vapor density of a certain compound is 14. Analysis shows that 85.7% of it is O and 14.3% is H. What is its symbol? 108 PERCENTAGE COMPOSITION. 130 Solution. If its vapor density is 14, its molecular weight is 28 m. c. (% 63). 100$ : 85.7/ c : : 28 m. c. : 24 m. c. = C 2 . 100$ : 14.3$ : : 28 m, c. : 4 m. c. H 4 or 2H 2 . Therefore, the symbol is C 2 H 4 . Note. Gaseous volumes will vary witli pressure (Ph., 284) and temperature (Ph., 492). In comparing such volumes, measured under different conditions, the proper correction must be made for this variation (Ph., 494). It is common to refer gaseous volumes to a temperature of 0C. and a pressure of 760 mm. The branch of chemistry that deals with the numerical relations of atoms is called stoichiometry. The gravimetric and volumetric and percentage computations above are stoichiometrical computations. EXERCISES. 1. What do atomic weights express? What weight of can be obtained by decomposing 9 g. of steam ? 2. Give the law of multiple proportions, and illustrate it by the compounds of N and 0. 3. Find the percentage composition of H 2 S0 4 . 4. Upon heating potassium dichromate(K 2 Cr 2 7 ) with a sufficient quantity of HCI, one may obtain Cr 2 CI 6 + 2KCI and water and chlorine. Write the reaction. 5. (a.) How much Zn is needed to obtain 20 g. of H ? (&.) How much, if the Zn contains 5 per cent, impurities ? ^7 t $jtri&-" 6. (a.) How much would be necessary to burn "500 cu. cm. of H ? (&.) If the experiment were performed in an atmosphere at a tempera- , ture of 100C., what would be the name and volume of the product ? (c.) How much would be necessary to burn 5 g. of H ? 7. (a.) What liquid is used in the preparation of HCI? (&.) What is the greatest amount of HCI that can be prepared by using 196 g. of that liquid ? .' .'jt,^ 8. (a.) What is the difference between hydrochloric acid and muri- atic acid ? (&.) What is aqua regia? (c.) Name ^and symbolize the five oxides of N. 9. (a.) Explain the difference between a bivalent and an univalent metal. (6.) What is. quanti valence? 10. When HI gas is passed through a heated glass tube, it is de- composed, and a violet color appears. Account for the appearance of the color. 130 PERCENTAGE COMPOSITION. 109 11. The reaction of Cl upon NH 3 is as follows : 8NH 8 + 3CI 8 = N a +6NH 4 CI. (a.) What weight of Cl is necessary to the production of 12.544 g. of N ? (&.) What volume of Cl ? 12. Marsh gas is 8 times as heavy as H. Analysis shows that f of its weight is C and the rest H. The atomic weight of C is 12 m. c. What is the symbol for marsh gas ? 13. What is the normal volume of a quantity of that measures 1 1. at a barometric reading of 756 mm. 9 . (Ph., 494.) * I 1>N ^' *'# ' THE SULPHUR GROU P. i. SULPHUR. $3JT 'Symbol, S ; specific gravity, 1.9G to 2.07 ; atomic weight, 32 m.c. ; molecular weight, at 1000' 'C., 64 m. c. ; quantivalence, 2 (4 or 6). 131. Occurrence. Both free and combined sulphur are found in nature. Free sulphur is found in certain volcanic regions, especially Sicily, occurring sometimes in the form of transparent yellow crystals, called " virgin sul- phur/' but generally mixed with earthy materials.* It is found in combination with hydrogen or with the metals, as sulphides ; and with oxygen and many metals, as sul- phates. (a.) Among the native sulphides, we may mention hydrogen sul- phide (sulphuretted hydrogen, H 2 S), a gaseous constituent of the waters of "sulphur springs"; lead sulphide (galena, PbS); zinc sul- phide (blende, ZnS) ; copper sulphide (chalcocite, CuS) and iron disul- phide (pyrite, FeS 2 ), etc. (&.) Among the native sulphates we may mention calcium sulphate (gypsum, CaS0 4 ) ; barium sulphate (barite or heavy spar, BaS0 4 ) and sodium sulphate (Glauber salt, Na 2 S0 4 ). (c.) S is found in animal and vegetable tissues. (d.) Nearly all of the S of commerce comes from Sicily. Some of the native crystals here found are 5 or 7 cm. in diameter. 132 SULPHUR. Ill 133. Preparation. Native sulphur is freed from most of its earthy impurities near the place where it is found and thus fitted for purposes of commerce. The process is one of fusion or of distillation. Sulphur is also obtained from pyrite by heat. (a.) One method of obtaining crude sulphur from the native earthy FIG. 56. material is represented in Fig. 56. The earthy material is heated in earthenware pots, a a ; the vaporized S passes over into the similar pots, 6 6, placed. outside the furnace. The S vapor here condenses to a liquid and then runs out into wooden vessels partly filled with H 2 0. It is said that this process is unknown in Sicily. (6.) When the earth is very rich in S, it is sometimes heated in large kettles. The S melts and the earthy matter settles to the bot- tom, leaving the liquid S to be dipped out from above. Sometimes the earth is piled up in a heap and heated, the heat coming from the combustion of a part of the S or of other fuel previously added in proper quantity. The melted S flows, from the heap or settles into a cavity at the bottom. In this latter process, which is largely used in Sicily, two thirds of the S is lost by its combustion. (c.) Pyrite (iron pyrites, FeS 2 ) is. sometimes piled up with fuel, which is then ignited. The heat frees part of the S of the FeS 2 and melts it. The melted S settles into cavities provided for that pur- pose. 112 SULPHUR. 132 (d.) The crude S, provided by the foregoing processes, is then further purified by distillation. It is melted in a tank, a, runs FIG. 57- through a pipe into the iron retort, &, where it is vaporized. The vapor passes from & into the large brick chamber, C, where it con- denses. When the walls of C are cold, the S condenses in the form of a light powder known as " flowers of sulphur " ; when the walls of C are hot, the S condenses to a liquid, and collects on the floor of the chamber, whence it is drawn off and run into moulds to form " roll brimstone." Experiment 129. Put 30 g. of small pieces of S into a test tube of 30 cu. cm . capacity. Hold the test tube in the lamp flame . Notice that it melts, forming a limpid liquid of light yellow color. Heat it hot- ter and notice that it becomes viscid and dark colored. Heat it hotter and notice that it becomes almost black. Invert the test tube and notice that the S has become so viscid that it will not run out from the tube. Heat it hotter and notice that it again becomes fluid. Heat it until it boils and notice that it is converted into a light yel- low vapor. Experiment 130. Pour half of the boiling S of the last experi- 132 SULPHUR. 113 ment, in a fine stream, into a large vessel nearly full of cold H 2 0. The S when taken from the H 2 will be found to have no crystalline structure, to be soft, nearly black and plastic. Allow the S remaining in the test tube to cool slowly and quietly, under close observation. Notice that it repasses through the viscid and limpid states and finally solidifies with a crystalline structure. The needle like crystals may be seen shooting out from the cooling walls of the tube into the liquid. Experiment m Melt 200 Hessian crucible. Allow it to cool until a crust forms over the top. Through a hole pierced in this crust, pour out the remaining liquid S. When the crucible is cool, break it open. It will be found lined FIG. 58. with needle shaped crystals. crucible may be spared by pouring all of the melted S into a pasteboard box or other convenient receptacle and securing the formation of the crystals there. Experiment 132. Dissolve a piece of S in carbon disulphide (CS 2 ). The CS 2 will quickly evaporate, leaving behind crystals of S, that resemble the native crystals. Note. The many forms of crystals have been classified into six systems of crystallization : 1. Isometric axes equal. FIG. 59- 2. Tetragonal) i ater al axes equal. 8. Hexagonal ) 4. Orthorhombic ) 5. Monoclinic > axes unequal. 6. Triclinic ) The crystals of S formed by fusion (Exp. 131) are monoclinic ; the native crystals and those formed by solution and evaporation are orthorhombic. Substances which, like S, crystallize under two sys- tems are called dimorphous (two formed). Sulphur is not only thus dimorphus, but the plastic variety (Exp. 130) is amorphous (without crystalline form). Other substances, like titanium dioxide, crystal- lize in three distinct forms and are said to be trimorphous. A varia- tion in crystalline form is accompanied by differences in other physi- cal properties, as specific gravity, hardness, refractive power, etc. Different substances that crystallize in the same form are said to be isomorphous. Substances that exhibit a double isomorphism are said to be isodimorphous. The trioxides of arsenic and antimony are isodimorphous. 114 SULPHUR. 133 133. Physical Properties. Sulphur manifests remarkable changes when heated. It melts at 115C. ; becomes dark colored and viscid at 230C.; regains its fluidity at above 250C., and boils at 450C. On cooling, these changes occur in inverse order. The specific gravity of its vapor at 500C. is 96, but at 1000C. it is 32. This seems to indicate that at 500C. the molecule is composed of six atoms, which are disassociated at a higher tempera- ture, so that, at 1000C., the molecule is composed of only two atoms. It exists in three distinct forms, orthorhombic, monoclinic and amorphous. (a.) The orthorhombic or natural form of S is brittle and soluble in carbon disulphide, petroleum or turpentine. Its specific gravity is 2.05. (6.) The monoclinic form is brittle and unstable. After exposure to the air for several days, each transparent, needle shaped crystal is converted into a large number of the orthorhombic or permanent crystals, thus becoming opaque. Its specific gravity is 1.96. It is formed as shown in Exp. 131. (c.) The amorphous form is plastic and insoluble in CS 2 . Exposed to the air, it gradually assumes the ordinary brittle form at ordinary temperatures ; heated to 100C., it instantly changes, and evolves enough heat to raise its temperature to 110C. Its specific gravity is 1.96. It is formed by pouring S, heated above 250C., into ^old H 2 0, as shown in Fig. 58. Experiment 183. Mix intimately 4 g. of flowers of S and 8 g. of copper filings. Heat the mixture in an ignition tube (see Exp. 11) until the elements unite with a vivid combustion to form copper sulphide (CuS). Experiment 134. Burn a small piece of S in the air and notice the peculiar blue light and the familiar odor of the suffocat- ing gaseous product ( 144). Chemical Properties. Sulphur unites with oxygen at the FiG.~6o. comparatively low temperature of 136 SULPHUR. 115 about 250C. It enters energetically into union with most of the elements, in many cases with the evolution of light. 135. Uses. Sulphur is largely used in the manufac- ture of sulphuric acid, vulcanized india-rubber, friction matches and gunpowder and in bleaching straw and woolen goods. 136. Tests. Free sulphur is easily recognized by its color and by its odor when burned. Combined sulphur may be detected by mixing the compound with pure sodium carbonate and fusing the mixture before the blowpipe on charcoal. The fused mass contains sodium sulphide. When it is placed on a silver coin and water added, a brown stain of silver sulphide is formed on the coin. Note. Sulphides were formerly called sulphurets. ^8i\ + Pttf*>6* EXERCISES. r 1. Why are the ends of friction matches generally dipped in melted S ? 2. When S is prepared from pyrite, Fe 3 S 4 is formed. Write the reaction. $>/&. - Iffjr:*"*' ^3. By bringing Brand P together in the presence of H 2 0, both * phosphoric (H 3 PO 4 ) and hydrobromic acids are formed, (a.) What yj weight of Br is necessary to yield 5 g. of the colorless gas, HBr? ' (&.) What weight of Br is necessary to yield 10 I. of HBr? . 4. I acts upon KCI0 3 , forming potassium iodate and setting Cl free : 2KCI0 3 + I 3 = 2KI0 3 + CI 2 . (a.) How much Cl by weight may thus be freed by 10 g. of I ? (5.) How much by volume? rfr/J . (a.) How many grams of H may be prepared by the use of - of Zn? (&.) How many liters? (c.) How many grams of HCI are necessary ? 6. (a.) If 20 g. of H be exploded with 0, how many grams of are necessary? (&.) How many grains of dry steam will be produced? 7. (a.) 1 cu.cm. of H 2 will yield, by electrolysis, how many grams of free gases? (&.) How many cu. cm. of 0? (c.) How many : 116 SULPHUR. 136 cu. cm. of H ? (d.) The explosion of thes3 gases will yield how many cu. cm. of dry steam ? 8. (a.) If ozone could be produced from KCI0 3 , how many grams of the former could be produced from 10 g. of the latter ? (6.) How many liters of the former ? ; 9. (a.) Is gunpowder manufacture a chemical or a physical pro- cess ? Why ? (&.) The combustion of gunpowder ? Why ? 10. Calomel and corrosive sublimate are each composed of Hg and Cl atoms. Why do the two substances differ, their atoms being of the same kind? ftfy : 7 **f (> 11. What is the difference between organic and inorganic matter ? 12. State two peculiarities of chemical affinity. 13. The constituents of air are free. Is the air a compound ? 138 HYDROGEN SULPHIDE. 117 HYDROGEN SU LPH IDE. 137. Occurrence. Hydrogen sulphide (hydrogen monosulphide, sulphuretted hydrogen, hydrosulphuric acid, H 2 S) occurs native in certain volcanic gases and is the characteristic constituent of the waters of "sulphur springs." It is generated by the putrefaction of animal matter and causes the peculiar odor of rotten eggs. 138. Preparation. Hydrogen sulphide may be prepared by the direct union of its constituents, but it is generally prepared by the action of dilute sulphuric or hydrochloric acid upon iron sulphide (ferrous sulphide, FeS). (a.) Into a gas bottle, arranged as for the preparation of H ( 20), put about 10 g. of FeS, replace the cork snugly, add enough H 2 to seal the lower end of the funnel tube, and place the bottle out of doors, or in a good draft of air, to carry off any of the offensive H 2 S that may escape. Let the de- livery tube dip 5 or 6 cm. under cold H 2 O, contained in another bottle, e. Add a few cu. cm. of H 2 S0 4 or HCI. Bubbles of gas appear in e and are absorbed by the H 2 0. Add acid in small quantities, as in the preparation of H, until the H 2 ine smells strongly of the gas. Remove the gas bottle and cork tightly. FeS + H 2 S0 4 = FeS0 4 + H 2 S, or FeS + 2HCI = FeCI 2 + H 2 S. (&.) Fig. 63 represents a convenient piece of apparatus for the preparation of H 2 S. It consists of three bulbs of glass, the lower two, & and c, being in a single piece, the tubular prolongation of the upper one, a, being ground to fit gas tight into the neck of & at I and extending downward nearly to the bottom of c. Lumps of FIG. 61. 118 HYDROGEN SULPHIDE. 138 FeS, as large as can be admitted through the tubulure at m, are in- troduced into b, the stricture at e, sur- rounding the prolongation of a, pre- venting them from falling into c. The tubulure at m is then closed by a cork carrying a glass stop-cock. The dilute acid (1 part H 2 S0 4 + 14 parts H 2 0)is poured in through the safety tube, t, passes into c and rises into b, covering the FeS. H 2 S is generated in 5, an? escapes through the stop-cock at m. When this stop-cock is closed, the con- fined gas presses on the surface of the liquid in b and forces it into c and a. When the acid is no longer in contact with the FeS, the generation of H 2 S ceases, and the gas in b is held, under pressure, ready for use. The acid may be removed from the apparatus by the tubulure at n, when it is necessary to renew it. FIG. 62. (0.) Argand lamp chimneys fre- quently break at the neck near the bottom. Into such a broken chimney, put a glass ball of such size that it will not pass through the stricture. Support the chimney by a perforated cork, in a vessel containing dilute acid and pro- vide a delivery tube, as shown in Fig. 63. Place lumps of FeS in the chimney above the glass ball, replace the cork with the de- livery tube, push the chimney down through the large cork into the acid ; the generation of H 2 S begins. When the reaction has continued as long as desired, lift the chimney out of the acid by sliding it up through the large cork. Any member of the class can make this piece of appa- ratus, which is very convenient when only a small quantity of H 2 S is wanted at a time. Of course, it is not necessary that the argand lamp chimney be broken. In the figure, the open vessel is supposed to contain ammonia water, to retain the H 3 S that may escape solu- tion in the H 8 of the middle bottle. 139 HYDROGEN SULPHIDE. 119 (d.) If desirable, the gas may be collected over warm H 2 0. (e.) H 2 S may be prepared by heating a mixture of equal parts of S and paraffiu. By regulating the temperature, the evolution of H 3 S niay be controlled. When the mixture is allowed to cool, the evolu- tion of the gas ceases ; when the mixture is again heated, H 2 S is again given off. This is a very convenient method of preparing H 2 S, but, it is said, that it sometimes leads to explosions. The chemical changes involved in the process are still obscure. 139, Physical Properties. Hydrogen sulphide is a colorless gas, having a sweetish taste and the offensive odor of rotten eggs. It may be liquefied and solidified by cold and pressure. Its specific gravity is 17, it being, thus, a little heavier than air. At ordinary temperatures, water dissolves a little more than three times its volume of the gas. The solution has the peculiar odor of the gas and a slightly acid reaction. Experiment 135. Bring a flame to the open mouth of ajar of H 2 S. The gas will burn with a pale blue flame, forming H 3 and S0 2 and depositing a slight incrustation of S on the inside of the jar. Experiment 136. Fill a Volta's pistol [Ph., 371 (35)] with a mixture composed of three volumes of and two volumes of H 3 S. Pass an electric spark from the electric machine or induction coil through the mixed gases. They will explode violently, com- plete combustion taking place. Experiment 137. Attach, a drying tubs, containing calcium chloride, to the delivery tube of the gas bottle. Provide the dry- glass tubing. When all from the apparatus, and match to the jet. (A mix- plosive.) The gas will Hold a dry bottle over the dense on the sides of the den blue litmus paper. ing tube with a jet made of of the air has been expelled not till then, hold a lighted ture of H 2 S and air is ex- burn with a blue flame, flame. Moisture will con- bottle. This liquid will red- H 2 S + 30 2 = 2H + 2S0, FIG. 64. 120 N TDK G EN S ULPHIDE. 139 Experiment 138. Burn a jet of H 2 S, using the apparatus arranged as described in Exp. 28. Test the liquid that accu- mulates in the bend of d with blue litmus paper. Experiment 139. Inter- pose a glass tube between the drying tube and the jet (Fig. 65). Heat this tube. The H 2 S will be decom- posed and the S be deposited on the cold part of the tube. The product that now accu- FIG. 6s. mulates in the bend of d will not redden blue litmus paper. The analysis of H 2 S is here followed by the synthesis of H 2 0. Experiment 1^0. Fill a glass cylinder with H 2 S and a similar one with Cl. Bring the cylinders together, mouth to mouth. HCI is formed and S deposited. Experiment 14 /.Let a few drops of fuming H N0 3 fall into a globe of H 2 S. The gas will be decomposed with an explosion. Try the experiment with strong H 2 S0 4 or with Nordhausen acid ( 156). Experiment 143. Moisten a bright silver or copper coin and hold it in a stream of H 2 S. The coin will be quickly blackened by the formation of a metallic sulphide. The same effect will follow the dipping of the bright coin into a solution of H 8 S in H 2 (sul- phuretted hydrogen water). See 138, a. Experiment 143. Write your name in a colorless, aqueous solu- tion of lead acetate (sugar of lead). Hold the autograph, before dry- ing, in a stream of H 2 S. The lead sulphide formed renders the in- visible writing legible. Experiment 144. Make a sketch in the same colorless liquid and allow it to dry. At any convenient time, float the paper containing the invisible design upon H 2 S water. The figure will "come out" promptly. Experiment 145. Connect five bottles, as shown in Fig. 66. Put a dilute solution of lead acetate or nitrate into a : an acid solu- tion of arsenic into & ; one of antimony into c ; a dilute solution of zinc sulphate, to which a little NH 4 HO has been added, into d; 141 HYDROGEN SULPHIDE. 121 NH 4 HO into e. Pass a current of H 2 S from tlie generator through the bottles. A black lead sulphide will be precipitated in a ; yellow ar- senic sulphide, in & ; orange anti- mony sulphide, in c ; white zinc sul- phide, in d. The zinc sulphide is _ s , soluble in dilute acids. The NH 3 was % added to the contents of d to destroy the acidity of the solution, to the end that the sulphide might be precipitated, 140. Chemical Properties. Hydrogen sulphide is easily combustible, the products of its combustion being water and sulphur dioxide ( 144). It is readily decom- posed by heat and by certain metals in the presence of moisture and by many oxidizing agents. It precipitates metallic sulphides from .solutions of the compounds of many metals. It may be liquefied by cold and pressure. Its solution reddens blue litmus. The gas is very poison- ous when breathed, and even when much diluted its respiration is very injurious. Under such circumstances, the best antidote is the inhalation of very dilute chlorine obtained by wetting a towel with dilute acetic acid and sprinkling over it a few decigrams or grains of bleaching powder. 141. Composition. The composition of hydrogen sulphide may be ascertained by heating metallic tin in a known volume of the gas. The gas will be decomposed, the sulphur combining with the tin as tin sulphide and the hydrogen being set free. The volume of hydrogen will be the same as that of the hydrogen sulphide decomposed. When a platinum wire spiral is heated red hot in a known volume of hydrogen sulphide by the passage of an electric current (Ph., 387), the gas is decomposed, both of its 6 122 HYDROGEN SULPHIDE. constituents being set free. The volume of the hydrogen will again be the same as that of the hydrogen sulphide. Careful analyses have proved that the gravimetric and volumetric composition of this gas may be expressed by the following diagram : ELS 34 m. c. (a.) The tJtree atoms in the molecule of H 2 S occupy the same vol- ume as the two atoms in the molecule H 2 . In other words, molecular volumes are equal ( 61). 142. Uses and Tests. Hydrogen sulphide is very extensively used in the chemical laboratory as a reagent, forming sulphides that are characteristic (in color, solu- bility or some other easily recognized property) for certain metals or groups of metals. It is easily detected by its odor or by holding in it a strip of paper wet with an aque- ous solution of lead acetate. Note. Hydrogen persulphide (H 2 S 2 ) is known to chemists. It is-- a yellow, transparent, oily liquid. ' EXERCISES. 1. Write the reaction for Exp. 135. ^ y 3 * W : 2. When metallic tin is heated in H 2 S, the gas is decomposed. The S unites with the tin. (a.) Name the solid and gaseous pro- ducts. (6.) How will the volume of this gaseous product compare with that of the H 2 S decomposed? 3. When & spiral of platinum wire is heated in an atmosphere of H 2 S, the gas is decomposed with the deposition of solid S. What volume of H can thus be set free from a liter of H 2 S ? 4. The reaction resulting from passing a current of H 2 S through an aqueous solution of Br is as follows : H 2 S + Br 2 =2HBr + S. (a.} What volume of H 2 S is needed to yield 4 I. of HBr ? (&.) What f*U 142 HYDROGEN SULPHIDE. weight of Br will thus combine with 10 g. of H 2 S? (c.) What weight of Br will yield 25 I. of HBr ? 5. How many grams of NH 4 HO will just neutralize 63 g. of HN0 3 ? /;.-'-- . 6. (a.) How many liters of will unite with 20 I. of NO to form ' N0 2 ? (6.) How many each of and NO to form 30 I. of N0 2 ? 7. Arsenic vapor is 150 times as heavy as H. (a.) What is the molecular weight of As ? Explain. (&.) The atomic weight of As is 75 m. c. How many atoms are there in an As molecule ? 8. (a.} What name would you apply to a substance that has only one kind of atoms ? (&.) One that has two kinds ? (c.) One that has three kinds ? 9. Give Ampere's Law. Define chemistry. Iv 10. Symbolize the sulphides of Na', K', Ag', Ca", Cu", C. 11. What weight of S in 10 I. of S vapor under normal pres- sure at SOOT. ? (ft.) At 1050C. ? ^ , 12. Calculate the percentage composition of cryolite. ( \ 4 r t< \ '& 1 13, ^;;/^ !} ' 124 SULPHUR OXIDES AND ACIDS. 143 SULPHUR OXIDES AND ACIDS. 143. Sulphur Oxitles. Sulphur and oxygen unite to form two acid-forming oxides (or anhydrides) symbol- ized as S0 2 and S0 3 . These unite with water to form the acids symbolized as H 2 S0 3 and H 2 S0 4 , (a.) In addition to these, we are acquainted with sulphur sesqui- oxide (S 3 3 ). which has no corresponding known acid ; with hypo- sulphurous acid (H 3 S0 2 ), which has no corresponding known oxide; with sulphur peroxide (S 2 7 ), and with the thionic acids ( 158). The compound, S 3 3 , is called a sesquioxide because the number of its $) atoms is 1| times the number of its S atoms, the Latin prefix, sesqui, meaning one and a half. 144. Sulphur Dioxide. This oxide of sulphur (sulphurous oxide, sulphurous anhydride, sulphurous acid gas, sulphuryl, S0 2 ) is the sole product of the combustion of sulphur in the air or in oxygen. It is the*only com- pound of sulphur and oxygen that can be formed by direct synthesis (Exps. 36 and 43). 145. Preparation. As ordinarily prepared by burn- ing sulphur in the air, the sulphur dioxide is mixed with nitrogen from the air. When the pure anhydride is wanted, it is generally prepared from strong sulphuric acid by heating it with copper, silver or mercury. (.) Put 20 or 30 g. of small bits of copper and 60 cu. cm. of strong H 2 S0 4 into a flask and apply heat. The gas that is evolved may be purified by passing through H 2 in the wash bottle, b (Fig. 67), and then collected by downward displacement or over mercury or absorbed in H.,0, as shown at c. A solution of copper sulphate, (blue vitriol, CuS0 4 ), remains in the flask. 2H 2 S0 4 + Cu = CuS0 4 + 2H 8 + S0 3 . 145 SULPHUR OXIDES AXD ACIDS. 125 (6.) A solution of S0. z in H S is often wanted in the laboratory. It may be formed by reducing H.,S0 4 with charcoal. 2H 2 S0 4 + C = 2S0 8 +2H 3 + CO,. The mixed gases may be passed through H 2 in a series of Woulffe bottles (Fig, 34); very little of the C0 2 will be ab- sorbed. (c.) It is well to save bits of copper, such as pieces of wire, shells of metallic cartridges, frag- ments of sheet copper, etc., for they will be of frequent US3 in the study of chemistry. p IG Experiment 146. From the generating flask, a (Fig. 67), pass the SO 2 through a bottle or tube packed in ice ; then dry the cool gas with H 2 S0 4 (Exp. 31)*or CaCI 3 (Exp. 28) ; then pass the dry gas through a U-tube packed in salt and pounded ice (Ph. 521). The S0 2 will con- dense to a liquid at the low tempera- ture thus produced. If the U-tube has good glass stop cocks, as shown in the figure, the liquid S0 3 may bs sealed and preserved. Or the two arms of a common U-tube may have been previously drawn out to make a narrow neck upon each ; after the. condensation of the S0 2 , these necks may be fused with the blowpipe flame and the liquid thus sealed for preservation. Caution. The following experiment is hardly safe for performance by the teacher in the class or by the pupil. Such a pressure on the inside of a glass tube of uncertain qualities, as glass tubes generally are, is not to be trifled with. Although less satisfactory, it may be safer to rest the case upon the assertion of the author. Experiment 147. To show the liquefaction of S0 2 by pressure, draw out one end of a strong glass tube (2 cm. in diameter) to a point. Fill the tube with dry SO 2 by displacement. Into the open end, thrust a snugly fitting, greased, caoutchouc stopper. With a stout rod, force the stopper into the tube until the S0 2 occupies about a fifth of its orig- inal volume. Liquid S0 2 will collect at the pointed end of the tube. FIG. 68. 126 SULPHUR OXIDES AND ACIDS. 145 Experiment 148. Pour some of the liquid S0 8 upon the surface of mercury contained in a capsule, and blow a current of air over it by means of a bellows. The mercury will be frozen. Experiment 149. If you have a thick, platinum crucible, heat it red hot and pour some of the liquid S0 2 into it. The S0 2 will as- sume the " spheroidal state," like that of the globules of H 2 O some- times seen upon the top of a hot stove, the temperature of the liquid being below its boiling point. If, now, a little H 2 be poured in, the SO 2 will be instantly vaporized by the heat taken from the H 2 (Ph. 526), which therefore at once becomes ice. By some dexterity, the lump of ice may be thrown out of the red-hot crucible. Experiment 150. Wrap the bulb of an alcohol thermometer in cotton wool and pour some of the liquid S0 2 upon it. The change of sensible into latent heat effected by the vaporization of the SO, produces a diminution of temperature and the thermometer falls, perhaps as low as 60 C. Experiment 151. Pour a quantity of the liquid S0 2 into nearly ice cold H 2 ; a part will evaporate at once, another part will dis- solve in the H 2 0, and a third part of the heavy, oily liquid will sink to the bottom of the vessel. If the part which has thus subsided be stirred with a glass rod, it will boil at once, and the temperature of the H 2 will be so much reduced that some of it will be frozen. Experiment 152. Add a few drops of the aqueous solution of S0 2 to a weak solution of potassium permanganate. The red color will disappear, owing to reduction by S0 2 . Experiment 153. Burn some S under a bell glass within which are some moist, bright colored flowers. The flowers will be bleached. The color may be partly re- stored by dipping some of the flowers into dilute H 2 S0 4 and others into NH 4 HO. Experiment 154. Partly fill each of two glasses with a fresh infusion of purple cabbage. Add a little of the aqueous solution of S0 2 . The bleaching action is not very manifest. To each, add cautiously, drop by drop, a solution of FIG. 69. potassium hydrate (caustic potash, KHO) ; the color will disappear. To the contents of one glass, add a little strong H 2 S0 4 ; a red color appears. To the other add more of the solution of KHO ; a green color appears. 148 SULPHUR OXIDES AND ACIDS. 127 Experiment 155. Suspend a small lighted taper in a lamp chim- ney placed so that a current of air can enter from below. At the lower end of the chimney, place a small capsule containing burn- ing S. Place a piece of window glass over the top of the chimney so as to confine the S0 3 within the chimney. The taper quickly ceases to burn. 146. Properties. Sulphur dioxide is a transparent, colorless, irrespirable, suffocating gas. It has a specific gravity of 32, being nearly 2J times as heavy as air. It condenses to a liquid at 10C., and solidifies when cooled below 76C. The liquid has a specific gravity of 1.49, and vaporizes rapidly in the air at the ordinary temperature, producing great cold. It has a great affinity for oxygen. Under the influence of sunlight, it unites directly with chlorine, acting as a dyad compound radical and forming sulphuryl chloride, (S0 2 )"CI 2 - It bleaches many colors, not by destroying the coloring matter, as chlorine does, but by uniting with it to form unstable, colorless compounds. When, by the action of chemical agents, the sulphur dioxide is set free from the colorless compounds thus formed, the color reappears. It is neither combustible nor a supporter of ordinary combustion. 147. Composition. The composition of sulphur- ous anhydride is represented by the following diagram : 00 SO 2 ,64w.e. 32 m.c.\ 148. Uses and Tests. Sulphur dioxide is largely used in the manufacture of sulphuric acid and for bleach- ing straw, silk and woollen goods. It is also used as an antichlor for the purpose of removing the excess of chlo- rine present in the bleached rags from which paper is 128 SULPHUR OXIDES AND ACIDS. 148 made, and as an antiseptic. When free, it is easily detected by its odor, familiar as that of burning matches, and by its blackening a paper wet with a solution of mercurous nitrate. 149. Sulphurous Acid. Sulphur dioxide is freely soluble in water, forming sulphurous acid (hydrogen sul- phite, H 2 S0 3 ). When this liquid is boiled, it decomposes into water and sulphur dioxide ; when it is cooled below 5C., it yields a crystalline hydrate of sulphurous acid with a composition of H 2 S0 3 + 14H 2 0. On standing, it ab- sorbs oxygen from the air and changes to sulphuric acid (H 2 S0 4 ). As one or both of the hydrogen atoms in its molecule may be replaced by a metal, it gives rise to two series of compounds, called sulphites ( 170). The term " sulphurous acid " is frequently applied to sulphur diox- ide, but such use of the term is seriously confusing and objectionable. 150. Sulphur Trioxide. When dry oxygen and dry sulphurous anhydride are mixed and passed over heated platinum sponge or platinized asbestos, they com- bine, forming dense fumes of sulphur trioxide (sulphuric oxide, sulphuric anhydride, S0 3 ). When these fumes are condensed in a dry, cool receiver, they form white, silky, fiber-like crystals resembling asbestos. Sulphur trioxide may be prepared more easily by gently heating Nordhausen acid ( 156) and condensing the vapor given off, as in the method above described. When perfectly dry, it does not exhibit any acid properties and may be moulded with the fingers without injury to the skin. It has so great an attrac- tion for water that it can be preserved only in vessels her- 152 SULPHUR OXIDES AND ACIDS. 129 metically sealed. It unites with water with a hissing sound and the evolution of much heat, forming sulphuric acid. S0 3 -fH 2 = H 2 S0 4 . 151. Sulphuric Acid. Sulphuric acid (hydrogen sulphate, oil of vitriol, H 2 S0 4 ), occurs free in the waters of certain rivers and mineral springs. It has been esti- mated that one river, the Rio Viuagre, in South America, carries more than 38,000 Kg. of this acid to the sea daily. Sulphuric acid is to the chemical arts what iron is to the mechanical arts, as it enters, directly or indirectly, into the preparation of nearly every substance with which the chemist deals. It has been said that the commercial pros- perity of any country may be well measured by the quan- tity of sulphuric acid that it uses. 152. Preparation. Sulphuric acid is formed by the addition of water to sulphur trioxide. The water may be added at the time of the formation of the anhydride or* subsequently. For this purpose, the sulphuric anhydride is formed by the oxidation of sulphurous anhydride by means of the nitrogen oxides or acids. The direct method of oxidation described in 150 being too expen- sive, the indirect method soon to be described is employed. (a.) In a bottle having a capacity of 1 I. or more, burn a bit of S. In the atmosphere of S0 3 thus formed, place a stick (or a glass rod carrying a tuft of gun cotton) dipped in strong HN0 3 . Red fumes of N0 2 will appear The red fumes show that the HN0 3 has been robbed of part of its 0. 2HN0 3 + SO, =H d S0 4 + 2N0 2 . In the presence of moisture, S0 2 is able to reduco (take from) HN0 2 , HNO ;! , N.,0 3 or N0 2 . In the pro- cess just described, the S0 3 reduced the HNO 3 ; the HN0 3 oxidized the S0 2 . 130 SULPHUR OXtDES AND 152 (&.) The manufacture of H 2 S0 4 may be prettily represented by the following lecture tabJe process: A large glass globe or flask is filled with air or oxygen and provided with five tubes, as shown in FiS0 4 and has a specific gravity of upwards of 1.8. (d) Although we have no reason to think that some of the reac- tions in the manufacture of H 2 S0 4 are not simultaneous, we may, with propriety, trace them as if they were really consecutive ; e. g., (i:> S + 3 = S0 2 . (2.) 2HN0 3 + S0 3 = H 2 S0 4 + 2N0 2 . (3.) S0 3 + N0 2 = S0 3 + NO. (4.) S0 3 + H 2 = H 2 S0 4 . (5.) NO + = N0 2 . In reality, most of the used for the oxidation of the S0 2 comes from the air, admitted to the chambers through the kiln. The part taken in the process by the nitrogen %xide is very interesting, it act- ing as a carrier of O from the air to the S0' 8 . Theoretically, but not practically, a single molecule of HN0 3 or of NO would be sufficient for the manufacture of an unlimited amount of H 2 S0 4 , as maybe seen by repeating the equations above (omitting the second) in a series continued to any extent desired. But, since air is used instead of pure O, the N thus introduced into the chambers has to be re- moved, and, in its passage out, sweeps away much of the nitrogen oxides, which then have to be supplied anew. Experiment 156. Place 27 cu. cm. of H 2 O in a graduated tube. Slowly add 73 cu. cm. of H 2 S0 4 . When the mixture has cooled, notice that its volume is about 92 cu. cm. instead of 100 cu. cm. Caution. In mixing H 2 and H 2 S0 4 , pour the H 2 S0 4 into the H 2 0, not, the H 2 into the H 2 S0 4 . If the lighter liquid be poured on top of the heavier, it will float there and great heat will be de- veloped at the level where they come into contact. This heat might form steam of sufficient tension to burst through the heavier liquid above and do damage by scattering the H 2 S0 4 . When the above directions are followed, the H 2 S0 4 mixes with the H 2 as it falls through it. Experiment 157. Place 30 cu.cm. of H 3 in a beaker glass of about 250 cu. cm. capacity. Into this, pour 70 cu. cm. of concentrated H 2 S0 4 in a fine stream. Stir the mixture with a test tube contain- 153 SULPHUR OXIDES AND ACIDS. 133 ing alcohol or ether, colored with cochineal or other coloring matter. The liquid in the test tube will boil. Holding the test tube in a pair of nippers, ignite the vapor escaping from the test tube. The test tube may be closed with a cork carrying a delivery tube and the jet ignited. It will give a voluminous flame. With a chemical ther- mometer (App. 3), take the temperature of the liquids before and after mixture. If the test tube stirrer contain H 2 O instead of the more volatile liquids mentioned, the H 2 will boil. Expzriment 158. Dip a splinter of wood into H 2 S0 4 . It will be charred as if by fire. Experiment 159. Dissolve 50 g. of crystallized sugar in 20 cu. cm. of hot H 2 0. To this syrup, when cool, add a little H 2 S0 4 and stir the two together. The mixture will become hot and form 'a voluminous, black porous mass. ; 153. Properties. The sulphuric acid of commerce is largely known as oil of vitriol. It has a specific gravity of about 1.82. It generally contains, as impurities, lead sulphate from the chambers and evaporating pans, and arsenic from the pyrite. For most purposes, however, it answers as well as the " H 2 S0 4 , C.P.," or chemically pure acid. The pure acid is a colorless, oily, very corrosive liquid with a specific gravity of 1.842 at the ordinary temperature (1.854 at 0C. and 1.834 at 24C.). It has a very remarkable attraction for water, the combination being marked by a condensation of volume and the evolu- tion of much heat. It may be mixed with water in all proportions. When exposed to the air at ordinary tem- peratures, it does not vaporize but absorbs water from the atmosphere, thus increasing both its weight and vol- ume. On account of this hygroscopic action, it should be kept in well stoppered bottles. Sulphuric acid removes water from many organic sub- stances, completely charring some, like sugar and woody fiber, and breaking others, as alcohol and oxalic acid, into 134 SULPHUR OXIDES AND ACIDS. 153 new compounds (see 213 and 193). It is one of the most energetic acids known. Diluted with 1,000 times its bulk of water, it still reddens blue litmus. It liberates most of the other acids from their salts. 154. Uses. Sulphuric acid is used as a drying agent for gases, in the preparation of most of the other acids, in the manufacture of soda, phosphorus and alum, in the preparation of artificial fertilizers, in the refining of pe- troleum, in the processes of bleaching, dyeing, etc. In fact, there is scarcely an art or trade in which, in some form or other, it is not used, it being employed directly or indirectly in nearly all important chemical processes. It is the most important chemical reagent we have and is made in immense quantities, upwards of 850,000 tons being produced yearly in Great Britain alone. 155. Tests. The most convenient test for free sul- phuric acid is the charring of organic substances. A paper moistened with a natural water containing the free acid, and then dried at 100C. will be completely charred. The acid or solutions of its salts give a white insoluble precip- itate with barium chloride or calcium chloride. 156. Nordhauseii Acid. Nordhausen acid (disul- phuric acid, fuming sulphuric acid, H 2 S 2 7 ), is prepared by the distillation of dried iron sulphate (green vitriol, FeS0 4 ), in earthen retorts. It is a heavy, oily liquid with a specific gravity of 1.89. It fumes strongly in the air and hisses like a hot iron when dropped into water. It is used chiefly for dissolving indigo. (#.) The name, Nordhausen acid, is due to the fact that it was formerly prepared in Nordhausen, Saxony. At the present time, the acid comes almost wholly from Bohemia. The propriety of the 159 SULPHUR OXIDES AND ACIDS. 135 term, disulplmric acid, is shown by tLe equation, 2H 2 S0 4 H 2 O = H 3 S.,0 7 . It may be considered as S0 a dissolved in H.,S0 4 , for, when heated, it separates into those substances, H^SjjOy = S0 3 + H.,S0 4 . 157. Sulphur Scsquioxicle and Hyposiilphuroiis Aciclx. Sulphur sesquioxide (S 2 3 ) is a rare, bluish green com- pound, resembling malachite in appearance. It easily decomposes into sulphur dioxide and sulphur. Hyposulphurous acid (H 2 S0 2 ) is a very unstable, yellow liquid with powerful reducing properties. Its salt, hydrogen sodium hyposulphite (HNaS0 3 ), is used for the re- duction of indigo in dyeing and calico printing. 158. Thioilic Acids. Besides the foregoing, there is a well defined series of sulphur acids, but they are of much less importance. Their corresponding oxides are unknown. (a.) Thiosulphuric acid ................. . . . H 2 S 2 3 Dithionic acid .......................... H 2 S 2 6 Trithionic acid .......................... HgSgOg Tetrathionic acid ........................ H 2 S 4 6 Pentathionic acid ................... .... ,H 2 S 5 C . (&.) The thiosulphuric acid is better known by the misnomer of "hyposulphurous " acid, which properly designates the compound symbolized by H 2 SO. In similar manner, the thiosulphates (e. g., sodium thiosulphate, Na 2 S 2 3 ), are commonly, but improperly, spoken of as " hyposulphites." Note. The word, thionic, comes from the Greek name for S. 159. Sulphur Oxide and Oxyacil. The known sul- phur oxides and oxyacids are symbolized in tabular form below for purposes of convenient study : OxHesj ...... [S a 3 SO, SO, Acids. |H 2 S0 3 .... H a SO, H a S0 1 !H s S a 3 H 3 S z O a H 4 S 3 O a H 2 S 1 O e H 2 S s O, u 136 SULPHUR OXIDES AND ACIDS. 159 - 6fV EXERC jXERCISES. 1. (a.) What is the molecular weight of S0 2 ? (&.) The specific gravity of the gas ? (c.) Its percentage composition ? 2. H 2 Sand S0 3 are often found in volcanic gases. When they v t>'V come into contact, they decompose each* other. Write an equation J0-JiJjl explaining the occurrence of native S in volcanic regions. H-^ f-Wv,*"'< 3. Why can not H 2 S0 4 be used for drying H,S (Exp. 141 ). 4. (a.) How much HN0 3 can be formed from 306 g. of KN0 8 ?" (&.) Haw much H 2 S0 4 will be required ? (c.) What will be the yield of HNaS0 4 ? (d.) If the product be Na 3 S0 4 , what will be the amount thereof? 5. Write the graphic symbol for H 2 S0 4 : (a,) Representing S as a dyad. (&.) As a hexad. tf ~ f ^ ' ' S \ ^'^ ' // / H^ - - h 6. Write the graphic symbol for H 2 S 2 7 , introducing S0 3 twice as a bivalent radical. (H 2 S 2 7 = auhydrosulphuric acid.)#-0- ^v-** 7. The symbol for potassium sulphate is K 2 S0 4 ; that for lead sul- phate is PbS0 4 . (a.) What is the quantivalence of potassium? (&.) Of lead? (See 60.) 8. How would you write the. symbol of a binary compound con- taining a dyad and a triad ? 9. How much JHNO^ will just neutralize 1200 ,#. of ammonium hydrate ? * 0t ft vT ',' ?f ,' ^f * ^ . 10. (a.) How much NH 3 may be formed from 42.8 g. of NH 4 CI ? (&.) How much CaH 2 2 must be used? 11. (a.) What volume of Cl may be obtained from 1 /. of dry HCI ? - (&.) What weight? -/ 3 U / f - / f j ff* 13. When aeriform H 2 and Cl are passed through a porcelain tube heated to redness, HCI and are formed, (a.) Write the reac- tion in molecular symbols. (&.) What volume of O may be thus obtained from 2 1. of steam? (c.) How will the volume of HCI * formed compare with that of the ? (d.) In what simple way may the be freed from mixture with HCI ?' 13. (a.) From 100 g. of KCI0 3 , how many grams of may be ob- tained? (6.) How many liters? 14. H 2 and N are among the products formed when NH^CI and . -, NaN0 2 are heated together in a flask. Write the reaction. "''" '- 15. (ft.) I mix H and Cl, and expose the mixture to sunlight/' K C* What happens? (&.) I add NH 3 to the product just formed. What is the name of this second product ? 16. What is the more common name for oxygen dioxide ? ^ #*J* l6l SELENIUM AND TELLURIUM. 137 SELEN'IUM AND TELLURIUM. SELENIUM ; Symbol, Se ; specific gravity, 4.3 to 4.8 ; atomic weight, 79 m. c. ; molecular weight, 158 in. c. 16O. Selenium. This element is a rare substance, of little industrial importance, but of considerable interest to the chemist. It is occasionally found free, but generally in combination as a selenide. Like^ sulphur, it exists in several allotropic forms. The native form melts at about 217C. and boils with a deep yellow vapor below a red beat. In its leading properties and chemical behavior, it re- sembles sulphur, as will appear in 162. It burns. with an odor resembling that of decaying cabbages. It offers a very great resistance to the passage of the electric current, the resistance being wonderfully diminished by the action of light. The property last mentioned,, has recently been utilized in the construction of the ph otophone and the element thus endowed with added interest and impor- tance. TELLURIUM ; Symbol, Te ; specific gravity, 6.25 ; atomic weight, 128 m. c. ; molecular weight, 256 m. c. 161. Tell urium. This element is even more rare than selenium. It has a metallic lustre and in some of its physical properties, such as the conduction of heat and electricity, it resembles the metals. It melts at about 500C. and volatilizes at a white heat in a current of hy- drogen. Its chemical bel^ 7 ior, however, allies it to sul- phur and selenium. With hydrogen, it forms hydrogen 138 THE SULPHUR GROUP. i6i telluride (H 2 Te), which can not be distinguished by its smell from hydrogen sulphide. Note. The name, xeleidum, is from the Greek word meaning the moon, and the name, tellurium, from the Greek word meaning the earth. 162. The Sulphur Group. Oxygen, sulphur, selenium and tellurium form a natural group. The resem- blances between the last three members of the group are as well marked as those of the chlorine group. As the atomic weight increases, the chemical activity diminishes, selenium being about midway between sulphur and tellu- rium. Their specific gravities, melting and boiling points, show a similar gradation. (a.) Some of the chemical resemblances of the members of this group are easily visible in the following table : Hydrogen oxide. H 3 Hydrogen sulphide. H 2 S Hydrogen selenide. H 2 Se Hydrogen telluride. H 2 Te Iron oxide. FeO Iron sulphide. FeS Iron selenide. FeSe Iron tetturide. FeTe Sulphur dioxide. S0 2 Selenium dioxide. Se0 2 Tellurium dioxide. Te0 2 .... Sulphur trioxide. S0 3 Selenium trioxide. Se0 3 (?) Tellurium trioxide. Te0 3 .... Sulphurous acid. H 2 S0 3 Selenous acid. H 2 Se0 3 Tellurous acid. H 2 Te0 3 Sulphuric acid. H 2 S0 4 Selenic acid. H 2 Se0 4 Telluric acid. H 2 Te0 4 Ethyl oride (ethert. (C 2 H 5 ) 2 Ethyl sulphide. (C 8 H 5 ) 2 S Ethyl selenide. (C 2 H 5 ) 2 Sa Ethyl telluride. (C 2 H 5 ) 2 Te Ethyl hydrate (alcohol}. (C 2 H 5 )HO Ethyl hydrogen sulphide. (C 2 H 5 )HS Ethyl hydrogen selenide. (C 2 H 5 )HSe Ethyl hydrogen telluride. (C 2 H 5 )HTe l62 THE 1. (a.) Give the physical and 'chemical properties of H. (6.) Ex- plain the structure of an oxy-hydrogen blowpipe. 2. What chemical process is illustrated when you prepare H ? 3. (.) State two ways in which the analysis of H 2 may be effected. (&.) Give the composition of H a O by volume and by weight. (c.) What weight of each constituent in a Kg. of H 2 ? /#,'/ 4. A chemist wishes 50 Kg. of H. What substances shall he use ^5" in making it, and how much of each ?/ fa JL f ' jf}*f 5. (0.) H 2 S0 4 is poured upon nitre ; name the two substances that you obtain, (b.) Write the reaction, hf v^^i W#j -WS^ + ft / .j. 6. (a.) What is the least amount of H g S0 4 that will completely /^4 < '.'/react with 4 Ib. of KNO 8 ? (6.) How much will the liquid product -/' '' r weigh I . '&&C fi*QL"V- ^^ ^ 7. (.) From 8 ^ ofTCNOi, how much HN0 3 can be liberated fl^*?/ How much H 2 S0 4 is the least that would be required? (a.) Give the names and symbols for the oxides of N. (6.) Give the law of multiple proportion. 9. (a.) What is the difference between air and water, chemically considered? (&.) Give one chemical and one physical property of and of NH 3 . 10. Write the reactions for the preparation of Cl, HF, S0 2 , H 2 S, and state at least one leading property of each. 11. When a hot metallic wire is plunged into a certain binary acid gas, violet fumes are seen. What is the gas? H j 12. (a.) How is Cl obtained? (&) Explain the reaction, (c.) Give the most remarkable chemical properties of the substance. 13. (a.} What is the most common compound of Cl ? (b.) Find its percentage composition. ^. 7$'' 14. (a.) Give the atomic weight of each of the elements that you have studied. (&.) What is meant by atomic weight ? ACIDS, BASES, SALTS, ETC. 163. Acids. -The word acid is difficult of satisfactory definition. The term signifies a class of compounds that generally have a sour taste, a peculiar action upon vegeta- ble colors (e. g., the reddening of blue litmus), and that unite with other compounds (bases) of an opposite quality to form a third class of compounds (salts) possessing the characteristics of neither of the first two classes. Tlie only constituent common to all acids is hydrogen which is replaceable with an electro-positive or metallic element. (a.) The term, acid, is sometimes used to designate certain com- pounds that contain no H, as S0 2 , C0 2 , etc. Such use of the term is incorrect and seriously confusing. (&.) The binary acids consist, almost exclusively, of H Combined with some member of the halogen group (123). Their names all have the termination -ic. (c.) We may suppose the ternary acids to be formed of hydroxyl (HO, 44), and a negative radical, as : .0 HNO, H 2 S0 4 (HOHN0 2 ) ; H-0-(N0 2 ) ; H-0-f/ (HO) 3 =(S0 3 ); H-0-(S0 2 )-0-H H 3 P0 4 ; (HO) 3 E(PO); H-0-(PO)-0-H ; Phosphoric acid. II H-0-S-O-H. II o II H-0-P-O-H. The atom of " saturating " shown in each case in the fourth column becomes a part of the negative radical as shown in the second 1 64 ACIDS, BASES, SALTS, ETC. 141 and third columns. Similarly, the '-linking " oxygen becomes a part of the hydroxyl. ((Z.) Acids take their names from their non-metallic or negative radicals. If only two ternary acids of a non-metallic element are known, the one in which the molecule contains the greater number of O atoms takes the termination -ic ; the other takes the termina- tion -ous. Sometimes the radical forms three or even four ternary acids. The acid in which the molecule contains a number of atoms greater than that of the -ic acid takes the prefix per- ; the one in which the number is less than that of the -ous acid takes the prefix, hypo-. The use of these prefixes and suffixes will be made clear by a study of the following examples : HCI0 4 ...... .perchloric acid. I HCI0 3 .......... chlone acid. I H 2 S0 4 ........ sulphun'c acid. HCI0 3 ....... chlor0ws acid. H 2 S0 3 ...... sulphmws acid. HCIO .... hypoch\owus acid. | H 2 S0 2 . .hyposvdphuwus acid. Unfortunately, there is a lack of uniformity among chemists in the nomenclature of acids and salts ; hence, a certain amount of con- fusion in the literature of the science. (See 60.) 164. Basicity of Acids. The hydrogen of an, acid that may be replaced by a metal is called basic hydro- gen. If the acid molecule has one atom of basic hydro- gen, the acid is called a mono-basic acid. If it has two such atoms, the acid is called a di-basic acid. Similarly, we have tri-basic and tetra-basic acids. ( .) The basicity of an acid molecule depends upon the number of its directly exchangeable H atoms and may generally be represented by the number of hydroxyl groups it contains. For example : HN0 3 is a mono-basic acid .................. (HO) (N0 8 )'. H 2 S0 4 is a di-basic acid ....... (HO) H 3 P0 4 is a tri-basic acid .................... (HO) (PO)'". Be it remembered, however, that the basicity of an acid molecule depends, not upon the total number of its H atoms, but upon the number of them that are endowed with this peculiar power of direct exchange from metallic atoms. H 3 P0 4 is called tribasic, not be- cause it has three H atoms but because it may form three distinct salts with one metal ( 170). 142 ACIDS, BASES, SALTS, ETC. 165 .165. Anhydrides. An oxide of a non-metallic (or electro-negative) element, which, with the elements of water, forms an acid, is called an anhydride. Nitrogen peroxide (N 2 5 ) and sulphunc and sulphurous oxides are anhydrides. Acid oxide is a better name. 166. Bases. The word base indicates a very impor- tant class of ternary compounds, opposed in chemical properties to the acids. The bases restore most colors that have been reddened by an acid. Like the acids, they may be considered hydroxyl compounds ; unlike the acids, their hydroxyl is united with a metallic (or electro-positive) radical. The chief characteristic of a base is its power of reacting with an acid to form water and a salt. The characteristic difference between an acid and a base is that the hydrogen of the former may be replaced by a metallic atom ; that of the latter by a non-metallic atom. (a.) The term, base, is frequently, but ill-advisedly, used to desig- nate certain compounds that neutralize acids and form salts but that contain no H, as CaO ( 290), etc. Basic oxide is a better name. (6.) The H of a base that may be replaced by a non-metallic ele- ment is called acid hydrogen. We have mon-acid, di-acid, tri-acid bases, etc. KHO, Ca(HO) 2 , AI(HO) 3 and Ti(HO) 4 represent bases. (c.) "The hydroxyl compounds of the elements that have a markedly metallic character are bases. The hydroxyl compounds of the elements that have a markedly non-metallic character are acids. The hydroxyl compounds of the elements that are neither mark- edly metallic nor non-metallic sometimes act as bases and some- times as acids. Thus, SbO(HO), antimonyl hydroxide, is a weak base or a weak acid, exhibiting one character or the other according to the nature of the compound with which it is brought into con- tact." 167. Hydrates. The basic oxides unite with water to form hydrates or hydroxides. Thus, K 2 -f H 2 2KHO, potassium hydrate or caustic potash. In similar l6p ACIDS, BASES, SALTS, ETC. 143 manner, we may produce Na'HO, sodium hydrate ; Ca"(HO) 2 or Ca"H 2 2 , calcium hydrate, etc. The hydrates are bases. (a.) A hydrate may be considered as a metallic compound of hydroxyl. (&.) Some of tlie hydrates yield solutions that corrode the skin and convert the fats into soaps. They are called alkalies. Potassium and sodium hydrates are alkalies. 168. Basic Ammonia. Ammonia water, in its physical relations, resembles a simple aqueous solution of a gas, while, in its chemical relations, it acts like an alka- line hydrate. On this account, its symbol is often written on the water ty^oe, thus : ( NH *)' I 0, or (NH 4 )HO. This symbol assumes the existence of a univalent compound radical, NH 4 . This purely hypothetical radical is called ammonium, and is considered a metal. The grottpiJNxf frequent occurrence in combination. Ammonium hydrate, (NH 4 HO) has been termed the^ volatile alkali." Experiment 160. Repeat Effj. 78. The ammonium nitrate thus produced is the substance we used in the preparation of nitrous oxide (N 2 0). HN0 3 + (NH 4 )HO = (NH 4 )N0 3 + H 2 0. Experiment 161. Repeat Exp. 160 using a dilute solution of potassium hydrate (caustic potash, KHO) instead of NH 4 HO. The crystals thus produced are KN0 3 , the substance used in preparing HN0 3 (74, a). A HN0 3 + KHO = KN0 3 + H 2 0. '169. Salts. In the experiments just given, the pro- ducts of the metathesis were water and a new class of com- pounds called salts, so named on account of their general resemblance to common salt (NaCI), a type of this class of compounds. A salt is a compound formed (1.) By replacing one or more of the hydrogen atoms of an acid with electro- positive (metallic) atoms or radicals. Compare HN0 3 and KN0 3 . 144 ACIDS, BASES, SALTS, ETC. (2.) By replacing one or more of the hydrogen atoms of a base with electro-negative (non-metallic) atoms or compound radicals. Compare KHO and K(N0 2 )0 or KN0 3 . (3.) By the direct union of an anhydride and a basic oxide. Thus, calcium sulphate results from the direct union Of sulphuric anhy- dride and calcium oxide (quicklime): S0 3 + CaO = CaS0 4 . Note.Qi these three views of the formation of a salt, the first is the one most frequently taken, but occasionally the other two are convenient. An acid is sometimes called a " hydrogen salt ;" e. g., hydrogen nitrate (HN0 3 ). 17O. Classification of Salts. -Salts may be nor- mal (or neutral), double, acid or basic. (a.) A normal salt is one that contains neither basic nor acid H. All of the basic H of the acid or acid H of the base from which it was formed has been replaced as stated in the last paragraph. K 2 S0 4 and CuSO^ are normal salts. (&.) A double salt is one in which H of the acid from which it was formed has been replaced by metallic (or positive) atoms of dif- ferent kinds. Forexample, common alum, AI 2 '"K 2 '(S0 4 ) 4 , is a double salt. (c.) An acid or hydrogen salt is one that contains basic H. Only part of the H of the acid from which it was formed has been re- placed, on account of which, in most cases, it still acts like an acid, reddening blue litmus. The hydrogen potassium sulphate, HKS0 4 , mentioned in 74 (a.) is an acid or hydrogen salt. (d.) A basic salt is one that contains acid H. Only part of the H of the base from which it was formed has been replaced, on account of which, in many cases, it still acts like a base, turning reddened litmus to blue. For example, lead hydrate is a base with the sym- bol, Pb"H 2 O 2 or H 2 Pb0 2 . Replacing half of this H with the acid radical, N0 2 , we have H(N0 2 )PbOo, the symbol for lead hydro- nitrate, a basic salt. (e.) A binary acid will yield a binary salt when its H is replaced. Thus, HCI yields NaCI. 171. Siilplnir Salts. In the ternary compounds (acids, bases, and salts) so far studied, the molecules have been bound or linked together by bivalent oxygen. But there is another distinct class of ternary molecules in which the constituent atoms are linked together 171 ACIDS, BASES, SALTS, ETC. 145 by bivalent sulphur. In these molecules, the sulphur may be " linking," "saturating," or both. The compounds are named and symbolized in the same way as the corresponding* oxygen compounds. Thus : The type H H has its analogue in H S H or H 2 S. KHOorK H " " K S H. KoC0 3 orK, = 2 = (CO)" " K 3 = S 2 = (CS)or K 2 CS 3 . In nomenclature, these "sulphur salts," (in which term, acids and bases are included) are distinguished from the corresponding " oxy- gen salts" by prefixing sulpha-. Thus, the analogue of potassium hydrate is called potassium sulphohydrate ; that of potassium car- bonate is called potassium sulphocarbonate. The "sulphur salts" are not so numerous or so well know* as the " oxygen salts," EXEECISES. 1. (a.) What is the difference between an atom and a molecule ? (b.) Between a physical and a chemical property? (c f ) Define and illustrate base, acid, salt. - (d.) State the differences between an -jc, an -ous, and an -ate compound. 2. (a.) Why is sulphurous acid said to be dibasic? (&.) What is the difference between an acid sulphite and a normal sulphite ? (c.) Between an acid sulphite and a hydrogen sulphite ? 3. (a.) Write the empirical symbol for the hydrate of the monad radical, nitryl. (&.) For the hydrate of (S0 8 )". 4. Why are there no acid nitrates ? 5. (a.) Write the symbols of the most common oxygen and hydro- gen compounds with elements of the chlorine group. (&.) Give the quantivalence of each element, (c.) State the gradation of physical and chemical properties among these elements, (d.) Give easy tests for Cl and I. 6. (a.) Give the usual mode of liberating C I , and write out the reaction. (&.) Find what per cent, the Cl is of the substance that furnishes it. , 7. Write the reactions expressing the preparation of at least 5H a S0 4 , using not more than two molecules of HN0 3 . '"' 8. When mercuric oxide (HgO) is heated, it decomposes. Write the reaction. (Owing to the high price of HgO, this reaction is sel- dom employed.) 9. State 7 the composition of water, both volumetric and gravi- m( ' tric 146 ACIDS, BASES, SALTS, ETC. I?I 10. When is prepared from Mn0 2 , Mn 3 4 is formed. Write the reaction. 11. When a current of H a S is passed through a solution of a cer- tain salt, copper sulphide (Cu"S) is precipitated with the formation of H 8 S0 4 . Write the reaction. 12. You are given NaCI and H 2 S0 4 and required to fill ajar with HCI. Describe the process and sketch the apparatus you would use. 13. Complete the following equation with the symbol for a single molecule: Ba0 8 + 2HCI = BaCI 8 +.t_ > : -u W 6/sT ^ BORON. Symbol, B; specific gravity, 2.68; atomic weight, llm. c.; quantkalence, 3. 172. Boron. This element may be obtained in the crystalline form with a specific gravity as given above. These crystals are nearly as hard, lustrous and highly re- fractive as the diamond. It may also be obtained in the amorphous form as a soft brown powder, or in scales with a graphite-like lustre. It is not found free in nature. It has one oxide (boron trioxide, boric or boracic anhydride, B 2 3 ). Its most important compound is borax (sodium pyroborate, Na 2 B 4 7 ), large quantities of which are found in California. Boron is the only non-metallic element that forms no compound with hydrogen. It is remarkable for its direct union ( 53) with nitrogen, the union being attended by the evolution of light and the product having the composition, BN. (a.} It forms BCI 3 , BF 3 , etc. Experiment 162. Heat some boric acid crystals ( 173) in a clean iron spoon. The heated crystals first melt and then become viscous as the H 2 is driven off. Touch this mass with a glass rod and draw out the adhering mass into long threads. This viscous substance is B,0 8 . 2H 3 B0 3 = B 8 3 + 3H 2 0. Experiment 163. Dissolve 6 g. of powdered Na 2 B 4 O 7 in 15 or 20 cu. cm. of boiling H 2 0. Add 3 or 4 cu. cm. of HCI or 2 cu. cm. of H 2 S0 4 ; stir and allow to cool. Crystals of boric acid (H 3 B0 3 ) will be formed. 148 BORON. 173 Experiment 164- Dissolve a few crystals of H 3 B0 3 in alcohol. Upon igniting the alcohol and stirring the solution, the flame will be of a beautiful green color; or add a little C 2 H 6 and H 2 S0 4 to a solution of Na 2 B 4 7 . Heat the materials and ignite the vapor ; the flame will be tipped with green. 173. Boric Acid. Boric acid (orthoboric acid, bo- racic acid, H 3 B0 3 ) may be freed from any borate by the action of almost any other acid, in consequence of which it is considered a very feeble acid. It may be formed by the union of the oxide with water : B 2 3 + 3H 2 0=2H 3 B0 3 . (a.) Upon heating H 3 B0 3 to 100C. it is changed to metaboric acid: H 3 B0 3 H 2 = HB0 2 . (6.) Upon further heating at 140'C. for a longtime, this is changed to pyroboric acid : 4HB0 2 H 2 = H 2 B 4 O 7 , or, 4H 3 B0 3 5H 2 = H 2 B 4 7 . (c.) The characteristic green color which the acid gives to the alcohol flame affords a convenient test for its presence. (d.) Native H 3 B0 3 is found free in the volcanic regions of Tuscany whence nearly all that is brought into commerce is obtained. Vol- canic jets of steam, charged with H 3 B0 3 issue into natural or arti- ficial ponds or lagoons, the water of which condenses the steam and becomes charged with the acid. (Fig. 73.) Upon evaporation, these waters yield pearly crystals of H S B0 3 . These steam jets are called suffioni. Deep borings into the earth have been made, constituting successful artificial suffioni. Basins of masonry are built at different levels on a hill side, each of which surrounds two or three wffioni. Water from a spring or lagoon is conducted into the upper basin and is charged by the sujfioni for twenty-four hours. This water is then conducted by a wooden pipe to a second basin, where it is further charged, and so on through six or eight basins, when the H 2 contains two or three per cent, of H 3 B0 3 . From the last basin, a thin sheet of the liquid is run over a corrugated sheet of lead, 125 m. long and 2 m. wide. This lead sheet is heated by the suffioni below it ; the liquid is thus eco- nomically concentrated by evaporation. The liquid is further con- centrated by evaporation in lead pans until the acid begins to crys- tallize. These lagoons produce about 1,500 Kg. of H 3 BO 8 daily. L, EXERCISES. 1. What is the molecular weight of boron trioxide? ^J y$. What per cent, of B in orthoboric acid ? / 7 "^ 3. Write the symbol of cal- cium (Ca") pyroborate.^ fty I 4. (a.) What is the basicity ofH 8 B0 3 ? (&.) IsMg 3 (B0 3 ) 3 an acid or a double salt ? 5. (a.) What results from heating H 3 S0 4 with Cu, NaCI and Mn0 2 respectively? (&.) If the latter two are acted upon together, what results ? 6. How much Zn must be used to generate sufficient H to raise in the air, by its buoy- ancy, a balloon weighing 7. By strongly heating Mn0 2 , it is reduced to a lower oxide, thus : 3Mn0 3 = Mn 3 4 + 3 . (a.) What weight and (&.) what volume of can be thus prepared from 50 g. of 8. State the method of pre- paring HN0 3 and the amount of each substance needed for 10 Ib. of the acid./ ;.A ^ / 9. \Vrite a graphic symbol for HP' /r 3 ; for HP0 3 . (10.) (a.) What is a salt? How is it formed? (6.) How does a chloride differ from a chlorate ? Illustrate by potas sium compounds. 11. (a.) What is the weight FIG. 73- "*' SI73 of the C I in 5 Ib. of common salt ? (6.) What per cent, of is there in potassium chlorate ? 12. Give the economic properties of chlorine, and show on what they depend. 13. Give two of the most useful compounds of HN0 3 with some use of each. /i/yi 14. Sulphur trioxide may be obtained by heating concentrated H 8 SO 4 with P 8 6 . Write the reaction. XII. VOLUMETRIC. 174. A Deduction. Let us imagine such a fraction- al part (about -, see 62) of a liter of hydrogen, that it shall contain 1,000 hydrogen molecules. By Ampere's law, the same volume of chlorine will contain 1,000 chlorine molecules. By the direct union of these ( 108), we shall have formed two such volumes (about ~ I.) of hydro- chloric acid gas, which, according to Ampere's law, must contain 2,000 molecules. 1000 H 2 + 1000 CI 2 = 2000 HCI. But each molecule of hydrochloric acid (HCI) contains one hydrogen atom and one chlorine atom. Consequently, the 2,000 acid molecules will contain 2,000 Jiydrogen atoms and 2,000 chlorine atoms. Since these 2,000 hydrogen atoms of the product are identical with the 1,000 hydrogen molecules of the factor, it follows that each hydrogen mole- cule contains two atoms or that the hydrogen molecule is diatomic. In the same way we see that the chlorine molecule is diatomic. 175. The Unit Volume. As the weight of the hydrogen atom is taken as the standard of atomic weight and called a microcrith, so the volume of the hydrogen atom is taken as the standard of atomic volume and called the unit volume. At present, the absolute value of the 152 VOLUMETRIC. 1 75 unit volume is as unknown as the absolute value of the microcrith. The accurate determination of the one will carry with it the determination of the other ( 62). The unit volume is the volume of one atom of hydro- gen; it is a real unit measuring a definite quan- tity of matter. The (gaseous) molecular volume is al- ways two unit volumes. (a.} The symbols of the diatomic elements ( 65) represent one unit volume and the respective atomic weights of the several substances ; < *' = 1 1 u 6 nit Volume \ of ox ^ en ' The s ^ mbols of tlie mo "- atomic elements represent two unit volumes and the respective atomic weights of those substances ; e.g. , Hg = j g ^^i'uSis } of mer - cury. The symbols of the tetratomic elements represent one-half unit volume and the respective atomic weights of these substances ; < *-> ? - | i 8 un?t' volume} of phosphorus. See 240, e. 176. Law of Gay-Lussac. The ratio in which gases combine by volume is. always a simple one ; the volume of the resulting gaseous product bears a simple ratio to the volumes of its constituents (see 91). (a.} The following modes of volumetric combination illustrate the truth and meaning of the law. (1.) 1 unit volume + 1 unit volume = 2 unit volumes. E.g., HCI; HBr; HI; NO. Condensation = 0. (2.) 2 unit volumes + 1 unit volume = 2 unit volumes. E.g., H 2 0; H 2 S; N 2 0; N0 2 . Condensation = i. (3.) 3 unit volumes + 1 unit volume = 2 unit volumes. Kg., H,N ; S0 3 . Condensation = . 176 VOLUMETRIC. 153 / 00- A EXERCISES. // 1. (a.) What is a unit volume? (ft.) A microcritli ? (c.) What is the relation of specific gravity ta combining weight? (d.} Give the specific gravity ofHCI,NH 3 ,CI, and C0 2 . - 2. How could you prove from a molecule of steam that the mole- cules of and H have each two atoms ? 3. (a.) How is prepared in large quantities? (6.) Give the reac- tion. 4. (a.) Name three physical properties of 0. (&.) Two chemical properties, (c.) How can these chemical properties be shown ? (d.) Mention one use of in the arts, (e.) One use in the natural world, (/.) Mention three of its most important compounds. 5. (a.) Explain what is meant by the atomic weights of H and 0. (&.) Explain the terms atom and molecule as applied to H 2 0. 6. (a.) If 180 cu. cm. of NH 3 be decomposed by electric sparks into/'' its elements, what will be the volume of each of these elements? (&.) If then 130 cu. cm. of be introduced and another electric spark produced in the containing vessel, the temperature being 16C., what will be the volume of the remaining gaseous contents of the vessel ? 7. (a.) Name two chemical properties of H that are the reverse of two of 0. 8. (a.) How is HN0 3 prepared on a large scale? (&.) How can you show that an acid is an acid ? (c.) What are alkalies ? (d.) What is " laughing gas"? (e.) Name three oxides of N. 9. (a.) What are bases? (6.) What class of elements forms acids? (c.) What class of elements forms bases ? (d.) What is a salt ? 10. (a.} What is the combining weight of a chemical compound ? (&.) HN.O S + KhfO = KN0 3 + H 2 0. What is the relative amount of the substances used ? 11. Give the most remarkable chemical properties of Cl and I and their industrial applications. 12. (a.} Where is S found? (&.) How is H 2 S made, and what are its properties ? (c.) What is meant by oxidizing agents and what by reducing agents? 13. When a thin stream of H 2 S0 4 flows into a retort filled with broken bricks hjeated to redness, the following reaction takes place : $$&. ' H,S0 4 = SO. + H.O + 0. (a.) What weight and (&.) what volume of can be thus prepared from 50 g. of H 2 $0 4> C. P.I (C. P. = chemically pure,) 14. Mn0 3 and HCI are heated together. Give the properties of the gas evolved. 154 VOLUMETRIC. 15, Write the symbol for the hydrate of sulphuryl. 16. (a.) A small quantity of H 2 S0 4 is poured upon Zn in a flask. Give the chemical reaction. (6.) Substitute HCI for the hLSO^ ; in- dicate the resultant change, if any. (c.) If iron be substituted for Zn, what change ? 17. How many liters of Cl may be prepared from 87. G g. of HCI ? 18. What weight of each substance must be used to prepare 120 *.ofH 2 S?J^,fy/ . F$ 19. How much H 2 S0 4 will dissolve 120 g. of Zn? 7f# f 20. Describe the preparation of HCI, NH 3 , and N 2 O. "'Give the re- action in each caso. Name a chemical property of each. 21. (a.) What is the difference between chemical and physical properties ? (&.) What is an element ? (c.) What is a chemical com- pound ? 22. (a.) What is the composition of air ? (6.) Is the air a chemical compound? 'V ~f ; /f i - . / /W V * / - / f*A J i H-Jfy / f) * c^yC.' ' X THE CARBON GROUP. I. CARBON. Symbol, C ; atomic weight, 12 m. c. ; quantivalence, 4. 177. Occurrence. Two allotropic modifications of carbon, the diamond and graphite, are found free in nature. Carbon is also found free in an impure form, as mineral coal. Combined with hydrogen, it occurs in pe- troleum, bitumen, etc. Combined with oxygen, it forms a constituent of the atmosphere upon which all vegetable life is directly dependent. United with oxygen and cal- cium, it is found as limestone, chalk and marble. All organic bodies contain carbon and when any of these is heated out of contact with oxygen there remains a third allotropic variety, amorphous carbon or charcoal. Cer- tainly, carbon is a very abundant and important element. (a.) The chemical identity of these several allotropic forms is shown by the fact that, when highly heated with 0, they all form the same compound, C0 2 , 12 parts of any variety of C uniting with 32 parts of to form 44. parts of the oxide. Experiment 165. Arrange the apparatus as shown in Fig. 74. Two thick copper wires pass through a caoutchouc stopper that closes the mouth of a cylinder filled with 0. The enclosed ends of the copper wire are joined by a spiral of fine platinum wira. Place 156 CARBON. 178 a small diamond, if you have one to spare, in the spiral at a, and pass the electric current from a battery of eight Grove's cells through the wires. The platinum is heated to whiteness and the dia- mond takes fire. On breaking the circuit, you will see a brilliant combustion result- ing in the complete disappearance of your diamond. If a small quantity of clear lime water has been previously placed in the cylinder, it will remain clear until the dia- mond has burned. Upon agitating the lime water, at the close of the combustion, it will be rendered milky in appearance, thus showing the formation of C0 2 . See Exp. 44. FIG. 74. 178. The Diamond. Diamond is a crystalline solid, brilliant, transparent and generally colorless. Dia- monds are most frequently found in the form of rounded pebbles and cut into the desirable forms by pressing the sur- face of the stone against a revolving metal wheel covered with a mixture of diamond dust and oil, diamond being the only substance hard enough to cut the gem. Thus, we see that it is the hardest known substance. It does not conduct heat or electricity and, when polished, has a magnificent lustre and high refractive power upon light (Ph., 613, a.). These properties, together with its perma- nence and rarity, make it the most precious of gems. Its specific gravity is 3.5. One of the long standing prob- lems of chemistry has recently been solved by the produc- tion of artificial diamonds. (a.) The diamond undergoes no change at the ordinary tempera- ture, but, when heated between the carbon electrodes of a strong electric current, it softens, swells up and is changed to a black mass resembling coke. When heated in 0, it burns to C0 2 , as explained in Exp. 165. In hydrogen or any atmosphere that has no chemical l8l CARBON. 157 action upon it, the diamond may be heated to the highest furnace temperature without change. " The Regent " diamond is valued at 125,000. 179. Graphite. Graphite or plumbago is familiarly known as the " black-lead" of the common " lead pencil." It is found abundantly in nature in the crystalline and amorphous forms, the crystals being wholly unlike those of the diamond. It is opaque, nearly black, and has a semi -metallic lustre. It is very friable and has an unctu- ous feel. It is a good conductor of heat and electricity. It is unalterable in the air at ordinary temperatures. Its specific gravity varies from 2 to 2.5. It is used in making pencils, lubricating machinery, in making crucibles es- pecially for the manufacture of steel, as a stove polish and in electro typing (Ph., 400). (a.) For many years, graphite was supposed to contain lead ; whence the names plumbago and black-lead. The name, graphite, is from the Greek word, grapho, ( = I write). 1O. Intermediate Forms. Intermediate between graph- ite and charcoal are the forms of carbon known as mineral coal, coke and gas carbon. 181. Mineral Coal. Mineral coal consists of the remains of the vegetation of the carboniferous era in the earth's geologic history. The woody fibre has undergone a wonderful transformation through the means of heat and pressure. When a considerable part of the hydrogen, oxygen and nitrogen of the original woody material re- mains in this product, the coal is called soft or bituminous. These elements may be largely removed from bituminous coal by distillation. Soft coal generally contains sulphur impurities and cakes in burning. When the coal has been subjected to a sort of natural distillation, so that it has 158 CARBON. l8l been deprived of nearly all of its hydrogen, oxygen and nitrogen, it is called hard coal or anthracite. There is a somewhat complete gradation of coals from anthracite down to lignite and peat, in which the wood is but little changed. Experiment 166. Half fill a good sized ignition tube (one about 15 cm. long will answer well) with coarsely powdered bituminous coal. Close its mouth with a cork carrying a delivery tube made of FIG. 75. good sized glass tubing that terminates in a water bath. Support the ignition tube in a sloping position and heat the coal. Collect the gas in small bottles as it is delivered in the water bath. The gas will burn as if it were ordinary illuminating gas. When the igni- tion tube has cooled, break it and examine the coke that it contains. 182. Coke. When bituminous coal is distilled, it yields a variety of volatile hydrogen-carbon compounds (hydrocarbons) and a solid, porous residue called coke. The latter is an incidental product of the manufacture of illuminating gas but is also made on a large scale for use in iron smelting, the volatile constituents of the coal being allowed to escape. ( 221, #.) 183. Gas Carbon. Gas carbon is a very hard, com- pact substance that is formed as a crust on the inner sur- 184 CARBON. 159 face of the retorts at gas works. It is a good conductor of heat and electricity and is largely used in the manu- facture of galvanic batteries (Ph., 383, 385) and of the carbon electrodes of electrie lamps (Ph., 389.). Experiment 167. Repeat Exp. 166, using splinters or shavings of wood instead of soft coal. When the gas is no longer evolved, re- move the end of the delivery tube from the water pan and imbed it in a thick paste of plaster of Paris to prevent the entrance of air to the ignition tube. When the apparatus has cooled, the charcoal may be removed without breaking the tube. Experiment 1GS. Heat a piece of charcoal upon platinum foil and notice tliat it burns with a simple glow, i.e., without any flame. 184:. Charcoal. Charcoal is generally prepared by the distillation or incomplete combustion of wood. In England, where wood is scarce, small wood and saw-dust are distilled in cast iron retorts, the volatile products being collected. In this country, where wood is yet abundant, the process is more primitive, the volatile products gener- ally going to waste. (d.) The common method of burning charcoal is to pile up sticks of wood in a large heap around a central flue, covering it with turf a FIG. 76. and earth, leaving holes at the bottom for the admission of air and a hole at the top of the central flue. The fire is kindled at the hot- 160 CARBON 184 torn of the central flue, and the rate of combustion controlled by regulating the supply of air, the process often requiring several weeks. At the proper time, all of the openings are closed and the fire thus suffocated. The method depends upon the fact that the volatile constituents of the wood are more easily combustible than the C and thus unite with the limited supply of 0. In some parts of the country, charcoal is burned in permanent kilns, instead of turf covered heaps. (6.) The charcoal retains the form of the wood from which it was made, the shape of the knots and even the concentric rings being plainly visible. Its volume is about 65 or 70 per cent, and its weight about 25 per cent, of the wood from which it was formed. Experiment 169. Set fire to a lump of rosin and hold a cold plate over the flame. Soot will be deposited upon the plate. Experiment 170. Press a spoon or plate down upon a candle flame so as nearly to extinguish the flame. Soot will be deposited upon the spoon. Experiment 171. Partly fill a spirit lamp with turpentine, light the wick and cover the lamp with a bell glass or wide mouthed jar. Thrust a pencil or chalk crayon under one edge of the bell glass so as to raise it from the table and admit a small supply of air to the flame. Soot will collect upon the sides of the bell glass. 185. Lampblack. When a FIG. 77. hydrocarbon, like rosin, turpentine, wax, petroleum, etc., is burned, the hydrogen is first oxidized. If the supply of oxygen be insufficient for the complete combustion, the carbon set free by the decomposition of the compound will be left in a finely divided, amorphous state, as soot or lamp-black. The same effect will appear if the temperature of the flame be reduced below that at which carbon burns, as was the case in Exp. 1G9. Lamp- black is manufactured on the large scale by burning tar. 187 CARBON. 161 rosin, turpentine, petroleum, or the natural gases of petro- leum (gas wells) in a supply of air insufficient for complete combustion and leading the smoky products into large chambers, where they are deposited. It is largely used as a pigment and in the manufacture of india and printer's inks. 186. Bone-black. Bone-black, which is the most important variety of "animal charcoal," is prepared by charring powdered bones in iron retorts. The calcium phosphate of the bone remains and ; forms about 90 per cent, of the black porous mass. The charcoal is conse- quently left in a very finely divided or porous condition, spread over the particles of the phosphate or distrib- uted among them. For this reason, it has greater ab- sorptive and decolorizing power than vegetable charcoal (Exp. 180). Experiment 172 . Mix 2.5 g. of black copperoxide (CuO) with 0.25 #. of powdered charcoal. With some of the mixture, partly fill a small ignition tube and heat it strongly. Metallic copper will remain in the tube while the C will unite with the of the CuO and escape as a gas. The C has reduced the CuO and the CuO has oxidized the C. 187. Charcoal as a Reducing Agent. Owing to the energetic union of carbon and oxygen at high temperatures, charcoal is largely used as a reducing agent. Anthracite and coke are also used for the same purpose. The preparation of metals from their ores (metallurgy) de- pends in a very large degree upon this property of carbon. Experiment 173. Break a piece of charcoal into two. Attach a sinkei to one of the fragments and immerse it in H.,0. Notice the bubbles rise as the H 2 enters the pores of the charcoal and forces out the air previously absorbed. The experiment may be improved by placing the beaker glass containing the H 2 and the C under the receiver of an air pump and exhausting the air. Experiment 174. Place the other fragment of the charcoal on the 162 CARBON. 188 fire, and when it has been heated to full redness for some time, plunge it quickly into H 2 0. Notice that it needs no sinker to keep it under H 2 and that very few bubbles escape from it through the liquid. Experiment 175. Fill a long glass tube with dry NH 3 at the mer- cury bath (Exp. 61). Heat a piece of char- coal to redness to remove the air from its pores and plunge it into mercury. When the charcoal is cool, thrust it into the mouth of the cylinder. The gas will be absorbed by the charcoal and mercury will rise in the tube (Ph., g 275). Experiment 176. Repeat the last experi- ment, using dry HCI instead of NH 3 . 188. Charcoal as an Absorbent. The porous nature of charcoal gives it a remarkable power of absorb- ing gases. Beech wood charcoal has been known to ab- sorb 170 times its own volume of dry ammonia. Other gases, liquefiable with comparative readiness (e. g., HCI, S0 2 , H 2 S, N 2 0, CC>2) are absorbed in large but variable proportions, while gases that are coercible only with diffi- culty (e.g., 0, H and N) are absorbed much more spar- ingly. This power depends upon the fact that all gases condense in greater or less degree upon the surface of solid bodies with which they come into contact. It is said that 1 cu. cm. of compact (boxwood) charcoal exposes a surface of 0.5 sq. m. The more easily the gas is liquefied the more largely is it absorbed by charcoal, which, at least, points toward the conclusion that in such absorption it is, at least, partly liquefied. Experiment 177. Into a bottle of H,S put some powdered char- coal . Shake the bottle for a moment . The offensive odor of the H 2 S will have disappeared. Experiment 178. Into the neck of a funnel, thrust a bit of cotton igo CARBON. 163 woo] and cover it to the depth of 2 or 3 cm. with powdered charcoal. Through this solution, pass a quantity of H 2 O charged with H 2 S ( 138, .) The filtered liquid will be free from offensive odor. Experiment 179. Place a small crucible filled with freshly ignited and nearly cold powdered charcoal into ajar kept supplied with H 2 S. When the charcoal is saturated with the gas, quickly transfer it to a jar of 0. The charcoal will burst into vivid combustion. 189. Charcoal as a Disinfectant. By condens- ing offensive and injurious gases and bringing them into intimate contact with condensed oxygen, charcoal acts as an energetic disinfectant. The fetid products of animal and vegetable decay are not only gathered in but actually burned up. This property is retained by the charcoal for a long time and, when lost, may be restored by ignition. A dead animal may be buried under a thin covering of charcoal and waste away without giving off any offensive odor. This oxidizing power of charcoal fits it for use as a disinfectant in hospitals, dissecting rooms and elsewhere, and forms the foundation of much of the utility of charcoal filters for water for drinking purposes. Experiment 180. Place a dilute solu- tion of the blue compound of iodine and starch (Exp. 121), of indigo dis- solved in H 2 S 3 7 ( 156), of cochineal and of potassium permanganate in each of four flasks To each , add recently ignited bone-black. Cork the flasks, shako their contents vigorously, and pour each liquid upon a separate filter. The sev- eral filtrates will be colorless. If the first part of any filtrate be colored, pour it back upon the filter for refiltration. FIG. 79. 190. Charcoal as a Decolorizer. As illustrated in the above experiment, charcoal, and especially animal 164 CARBON. IQO charcoal or bone-black, is able to remove the color as well as odor from many solutions. This power seems to de- pend more upon the adhesion between the carbon and the particles of coloring matter than upon oxidation. Brown sugar is purified, by filtering its colored solution through layers of bone-black. If ale or beer be thus treated, it loses both its color and bitter taste. Thus we see that charcoal can remove other substances than coloring matter from solutions. Sulphate of quinine and strychnine may be thus removed. This property of charcoal (and bone- black) is utilized in the preparation or purification of many chemical or pharmaceutical compounds. 191. Other Properties of Carbon. Carbon, in all of its forms, is practically infusible and non-volatile, but it may be slightly fusible and volatile at the high tem- perature of the voltaic arc. Although it has great chemi- cal activity at high temperatures, it seems to be unalter- able at the ordinary temperature of the air. The lower ends of stakes and fence posts are often charred before embedding them in the earth to render them more durable. Charred piles driven in the River Thames by the ancient Britons in their resistance to the invasion of their country by Julius Caesar, about 54 B. C., are still well preserved. Wheat, charred at the destruction of Herculaneum and Pompeii, in 79 A.D., still appears as fresh as if recently prepared. Perfectly legible manuscripts, written in ink made of lamp-black, have been exhumed with Egyptian mummies. Carbon is unique, in that it forms a very large number of volatile hydrogen compounds. These com- pounds are called hydrocarbons. Note. Binary compounds of carbon were formerly called car- burets. IQI CARBON. 165 EXEECISES. 1. Is charcoal lighter or heavier than H 2 ? 2. (a.) I burn a piece of wood in the open air ; what becomes of it? (b.) What volume of steam will result from burning 100 g. of H ? 3. (a.) State the useful properties of charcoal. (&.) How much is needed to burn 500 g. of charcoal ? (c.) How many liters of CO., will be produced? /3 ^ 4. Give the characteristics of three allotropic modifications of car- bon, and give a leading property of each. 5. How would you prepare a solution of HCI ? 6. Write the symbol for sulphuryl oxide. ^ 7. Write the typical and empirical symbols ?or nitrosyl hydrate and nitryl hydrate. 8. Write the reaction for the combustion of turpentine in Exp. 93. 9. Give proof of the fact that diamond is carbon. 10. In what way does the disinfecting power of C differ from that of Cl ? 11. Is C a bleaching agent ? Why? 12. Would it not be a great improvement in quinine to filter it through charcoal and thus remove its intensely bitter taste ? Why ? 13. Symbolize compounds of C with L', M" Q,'" R and X, these last letters symbolizing hypothetical elements. , iv iv 14. Write graphic symbols for H 8 S0 3 and H 3 S0 3 , $\\ ' ^ 166 SOME CARBON COMPOUNDS. SOME CARBON COMPOUNDS. 192. Carbon Oxides. There are two oxides of carbon, having the molecular symbols CO and C0 2 - The first may be considered the product of incomplete combus- tion of carbon ; the second, that of complete combustion. Both of them are gaseous. 193. Carbon Monoxide. Carbon monoxide (car- bon protoxide, carbonic oxide, carbonous oxide, carbo- nyl, CO) yields, when burned, the characteristic blue flame often seen playing over a freshly fed coke or anthracite fire. It may be prepared in many ways, only two of which will be given here. Experiment 181. Pulverize 5 g. of potassium ferrocyanide and place it in a quarter liter Florence flask. Add 25 cu. cm. of strong H 2 S0 4 and heat gently, removing the lamp as soon as the gas begins to come off rapidly. The gas may be passed through a solution of potassium hydrate (KHO) and collected over H 2 0. Experiment 1S2. Place a small quantity of oxalic acid (H 2 C 2 4 ) in a small Florence flask, add enough strong H 2 S0 4 to cover it, place upon a sand bath and heat gently. The H,S0 4 removes H 2 from the H 2 C 2 O 4 and leaves a mixture of CO and C0 2 . The C0 g may be removed by passing the mixed gases through a solution of KHO, as in the last experiment, or by collecting over H 3 rendered alka- line by such a solution. 194. Properties. Carbon monoxide is a colorless, odorless, poisonous gas. It is a little lighter than air, having a specific gravity of 14 (sp. gr. = .967, air stand- ard). It is scarcely soluble in water, but is wholly ab- sorbed by an acid or ammoniacal solution of cuprous Ip5 SOME CARBON COMPOUNDS. 167 chloride (Cu 2 CI 2 ). It is liquefiable only with extreme difficulty. Like hydrogen, it does not support combus- tion but is combustible. It burns with a pale blue flame and yields carbon dioxide (C0 2 ) as the sole product of its combustion. It is an active pouon and doubly dangerous on account of its lack of odor. One per cent, of it in the air is fatal to life, which it destroys, not merely by exclud- ing oxygen (suffocation), as hydrogen, nitrogen, etc., do, but by direct action as a true poison. As this gas is formed in charcoal and anthracite fires, and as it secures an easy passage through faulty joints and even through cast iron plates heated to redness, it is the frequent cause of oppression, headache and danger in stove or furnace- heated and ill-ventilated rooms. Carbon monoxide is rightly chargeable with many of the ill effects usually at- tributed to the less dangerous carbon dioxide. (a.) CO is readily oxidized to C0 2 and C0 2 is easily reduced to CO. Thus, when air enters at the bottom of an anthracite fire, the unites with the C to form C0 2 . As the C0 3 rises through the glowing coals above, it is reduced to CO. CO 2 + C = SCO. When this heated CO comes into contact with the air above the coals, it burns with its characteristic blue flame and forms C0 2 . (&.) Under the influence of sunlight, two volumes of CO unite 'directly with two volumes of Cl, forming two volumes of carbonyl chloride or phosgene gas (COCU). It will be noticed that here, CO acts as a dyad compound radical. 195. Uses. Carbon monoxide is an important agent in many metallurgical operations, on account of its power to reduce metallic oxides. It may be used instead of hy- drogen in Exp. 31. In the reverberatory furnace, the air supply is regulated so that the fuel burns to carbon mon- oxide, which, in a highly heated condition, plays over the metallic oxides on the hearth and, by abstracting oxygen 168 SOME CARBON COMPOUNDS. 195 from them for its own combustion to carbon dioxide, re- duces them to the metallic condition. 196. Carbon Dioxide. Carbon dioxide (carbonic anhydride, C0 2 , often improperly called carbonic acid or carbonic acid gas) is always formed when carbon or any carbon compound is burned under conditions that afford an abundant supply of oxygen. It may be easily obtained by the decomposition of carbonates, such as marble, chalk, or limestone. It is a product of animal respiration, of fermentation and of the decay and putrefaction of all ani- mal and vegetable matter. It is produced in large quan- tities in burning limestone to quicklime. CaC0 3 = CaO+ C0 2 . Experiment 183. Repeat Exps. 42 and 44. The white precipitate that causes the turbidity is calcium carbonate (CaC0 3 ). CaH 2 2 + C0 3 = CaC0 3 + H 2 0. Experiment 1S4. Mix 11 g. of red oxide of mercury and 0.3 g. of powdered charcoal. Heat the mixture and collect over H 2 O the gas that is given off. Test the gas with lime water. The that FIG. 80. united with the C came from the mercury oxide. 2HgO + C CO 2 + 2Hg. Examine the ignition tube carefully for traces of metallic mercury. In similar manner, many solid, liquid and gaseous bodies that are rich in give it up readily to unite with C and form C0 2 . In other words, such bodies are " reduced " by the C- I 9 6 SOME CARBON COMPOUNDS. 169 Experiment 185. Into a bottle, arranged as described in 20, put a handful of small lumps of marble or chalk (CaC0 3 ). Prepared crayons mil not answer. Cover the lumps with H 2 O and add small quantities of HCI from time to time as may be needed to secure a continued evolution of gas. Collect several bottles of the gas over FIG. 81. H 2 0. Replace the tube d by one bent downward at right angles near c. Insert the vertical part of this tube in a bottle. As this gas is heavier than air, it may be collected thus by " downward displace- ment." CaC0 3 + 2HCI = CaCI 2 + H 2 + C0 2 . Note. HCI is better than H 2 S0 4 in preparing CO 2 from CaC0 3 because CaCI 2 is more easily soluble than CaS0 4 . Old mortar, powdered oyster shells, coral or limestone will answer instead of marble or chalk, but marble is preferable as there is less frothing. Experiment 186. Arrange two flasks containing lime water, as shown in Fig. 83. Apply the lips to the tube and inhale and exhale air through the apparatus. In a few moments, the lime water in C, through which the air passes from the lungs, will b3comemilky,while that in B, through which the air passes to the lungs, remains clear. See Exp. 44. Unrespired air forced through lime water by means of a small bellows or other means will not produce such turbidity. Experiment 1S7. Dissolve 50 8 FIG. 82. 170 SOME CARBON COMPOUNDS. 196 cu. cm. of molasses in about 400 cu. cm. of H 2 and place the liquid in a half liter flask. Add a few spoon- fuls of yeast, cork the flask and con- nect its delivery tube with a small bot- tle, b, filled with H 2 0. A delivery tube should extend from the bottom of b into a cup, c. Put the apparatus into a warm place and fermentation will soon begin. As the liquid in F fer- ments, bubbles of gas will rise through it and pass over into &, forcing a cor- responding quantity of H 2 0intoc. When b is nearly full of this gas, remove its stopper and test its contents with a flame and with lime water. The gas is C0 2 ( 200). Let the liquid in ^remain in a warm place for two or three days. Cork and save for future use. The sugar (C 6 H 12 6 ) of the molasses was decomposed into alcohol (C a H 6 0) and C0 2 . The C 2 H 6 remains dissolved in the liquid in F. FIG. 83. FIG. 84. Experiment 188. Suspend a light glass or paper jar from one end of a scale beam and counterpoise it with weights placed in the scale 197 SOME CARBON COMPOUNDS. 171 pan at the opposite end. Pour C0 2 into the jar and it will descend. Experiment 189. Partly fill a wide mouthed jar with C0 2 . Throw an ordinary soap bubble into the jar. It will float on the sur- face of the heavy gas. Experiment 190. Fill a long necked Florence flask with C0 2 . Pour in a little H 2 0, close the mouth with cork or finger, shake the bot- tle and then open the mouth under water. Part of the C0 2 will have been dissolved in the H 3 0, and more H 2 will enter the flask to fill the partial vacuum. Close the mouth, shake again, and once more open the mouth underwater, More H 2 will enter. In this way, all of the C0 2 may be dissolved in H 2 0. After agitating C0 2 and H 2 in a test tube closed by the thumb or palm of the hand, the tube and contents may be held hanging from the hand, supported by atmospheric pressure. (Ph., 293.) 197. Physical Properties. Carbon dioxide is a colorless gas, so heavy that it may easily be poured from one vessel to another. Its specific gravity is 22, it being 1 times as heavy as air. In consequence of its high specific gravity, it diffuses but slowly and often accumu- lates in wells, mines and caverns (see article, " Grotto del Cane," in any encyclopaedia). Under a pressure of 50 atmospheres at the ordinary temperature, it condenses to a liquid whose specific gravity is 0.83. The rapid expan- sion of this liquid, when released from pressure, produces a temperature low enough to freeze part of itself to a white, snow-like mass. This solid carbon dioxide, when mixed with ether, produces a degreo of cold that quickly freezes mercury, and in a vacuum, yields a temperature of HO^C. The gas is soluble in water, volume for volume at ordinary temperatures and pressures; more largely, at lower tem- peratures or higher pressures. Experiment 191. From a large vessel filled with C0 8 , dip a turn- 172 SOME CARBON COMPOUNDS. 198 blerful of the gas and pour it, as if it were H 2 0, upon the flame of a taper burning at the bottom of another tumbler. The flame will be extinguished. Experiment 192. Fasten a tuft of " cot- ton wool" to the end of a wire or glass rod, dip it into alcohol, ignits and quickly thrust the large flame into a bottle of C0 2 . The flame will be instantly extin- FIG. 85. guished. Experiment 193. Fasten a piece of magnesium ribbon, 15 or '20 cm. (6 or 8 in.) long to a wire, ignite the ribbon and quickly plunge it into a jar of C0 2 . It will continue to burn, leaving white flakes of magnesium oxide (MgO) mixed with small particles of black C. Rinse the jar with a little distilled H 2 0, pour the H 2 into an evaporating dish, add a few drops of HCI and heat. The MgO will dissolve, leaving the black particles floating in the clear liquid. 198. Chemical Properties. Carbon dioxide, being the product of complete combustion, is incombusti- ble. It is a non-supporter of ordinary combustion. Its solution in water is often considered true carbonic acid (H 2 C0 3 ). The gas may be completely absorbed by a solu- tion of potassium hydrate (KHO). Experiment 194 . Pass a stream of C0 2 through lime water. Notice that the formation of CaCO 3 soon renders the water turbid but that, the current being continued, the turbidity soon disappears. When the water has thus lost its milky appearance, boil it. The excess of C0 2 will escape in bubbles ; the liquid will become turbid again and deposit a precipitate of CaC0 3 . 199. Uses, etc, Carbon dioxide has been successfully used for extinguishing fires in coal mines, even when the fires had raged for years and defied all other attempts at putting them out. The efficiency of the common, porta- ble " fire extinguishers" depends upon this same property of carbon dioxide. Water charged with large quantities of the gas is sold under the meaningless name of " soda 201 SOME CARBON COMPOUNDS. 173 water." While we thus see that it is not poisonous when taken into the stomach, it is injurious when breathed into the lungs. When largely diluted with air, it has a narcotic effect and its presence to the extent of nine or ten per cent, of the atmosphere is sufficient to cause suffocation and death. When we remember that the processes of respiration and combustion (e.g., the combustion of illumi- nants) are robbing the atmosphere of occupied rooms of the invigorating oxygen and yielding immense quantities of injurious carbon dioxide, we see that it is not easy to over- estimate the importance of systematic school and house- hold ventilation, even ignoring the many other causes for its necessity. While thus destructive of animal life it is essential to vegetable existence. Water containing carbon dioxide in solution is capable of dissolving calcium carbonate and other substances that are insoluble in pure water. In this way, many rocks are disintegrated, stalagmites and stalactites formed, or the soil fitted for the needs of plants. It is also used in "cor- roding " lead for use as a paint (lead carbonate) and in the preparation of sodium and other carbonates. 200. Test. The precipitation of calcium carbonate when carbon dioxide is passed through lime water or shaken with it, is the most common test for the gas. Its power of extinguishing flame is often a convenient but not a definite means of detecting its presence. 201. Carbon Bisulphide. Carbon disulphide (CS 2 ) is prepared synthetically on a large scale by passing sulphur vapor over glowing coke or charcoal. C 2 + 2S 2 = 2CS 2 . 174 SOME CARBON COMPOUNDS. 202 Caution. Li performing experiments with CS.,, see that there is no flame near. Experiment 195. Put a few drops of CS 3 into each of four small test tubes. Into the first tube put a little powdered S ; into the second, a few crystals of I ; into the third, a very small piece of P into the fourth, a little H 2 0. Notice the solubility of the S, I and P in CS 2 and the insolubility of CS 2 in H 2 0. Experiment 196. Wet a block of wood and place a watch crystal upon it. A film of H 2 may be seen under the central part of the glass. Half fill the crystal with CS 2 and rapidly evaporate it by blowing over its surface a stream of air from the luugs or a small bellows. So much heat is rendered latent in the vaporization that the watch crystal is firmly frozen to the wooden block. (Ph., g 526, 527.) Experiment 197. Into a glass cylinder, pour a few drops of CS 2 . In a few moments the cylinder will be filled with the heavy vapor of CS 2 . Thrust the end of a glass rod, heated not quite to redness, into the cylinder. The vapor will be ignited. See Exp. 82. 30 2 + CS 2 = C0 2 + 2S0 2 . 2O2. Properties. Ordinary carbon disulphide is a liquid of light yellow color and offensive odor. Its vapor is injurious to animal and vegetable life and exceedingly inflammable. As it is heavier than water and insoluble therein, it is easily preserved under water. It is diathermanons, has a highly refractive effect upon light (Ph., 552, 553, 613), evaporates rapidly at ordinary temperatures and boils at about FIG. 86. 46^0., yielding a heavy vapor that ignites at about 150 C., and that forms an explosive mixture with air. (a.) When pure, CS 2 is colorless and has an agreeable odor re- sembling that of chloroform. 2O3. Uses. Carbon disulphide is used as a solvent for phosphorus^ iodine, sulphur, and many resins and oils. 205 SOME CARBON COMPOUNDS. 175 It is used largely in the extraction of fats and oils and in the cold process of vulcanizing caoutchouc. 204, Cyanogen. This compound of carbon and nitrogen (CN or Cy) is a univalent radical (-C=N). It was the first compound radical isolated. It will be noticed that it has two symbols, the first of which indicates its chemical composition. It is generally prepared by heating the cyanide of gold, silver or mercury, and collecting over mercury. Hg"Cy 2 = Hg + Cy 2 or Hg"(CN) 2 = Hg + (CN) 2 . Cyanogen is a colorless, poisonous, inflammable gas. It acts like a monad element, forming compounds corre- sponding to the chlorides, e. g. : Free chlorine CI 2 Free cyanogen Cy 3 or C 2 N 2 Potassium chloride KCI Potassium cyanide.. . . KCy or KCN Hydrochloric acid HCI | Hydrocyanic acid. . . HCy or HCN Some of the cyanides will be subsequently noticed. 205. Hydrocyanic Acid. Hydrocyanic acid (cyan- hydric acid, HCN or HCy) may be prepared by passing hy- drogen sulphide over mercury cyanide heated to about 3GC. HgCy 2 + H 2 S = 2HCy + HgS. It is a volatile, inflammable, intensely poisonous liquid. Its aqueous solution is well known as prussic acid. Caution. Potassium cyanide is intensely poisonous, not only when taken internally, but also when brought into contact with an abrasion of the skin, a cut or scratch. Experiment 198. Place a small quantity of powdered potassium cyanide in a test tube and add a few drops of strong H 2 S0 4 . The escaping HCy produces effervescence and may be detected by its peculiar odor, like that of bitter almonds. The reaction is similar to that between NaCI and H 2 S0 4 in the preparation of HCI. v> ' / 176 SOME CARBON COMPOUNDS. 205 EXERCISES. 1. In Exp. 181, the potassium ferrocyanide (K 4 FeC 6 N 6 ) contains 3H 2 as " water of crystallization," Additional H 3 is furnished by the commercial H 2 SO 4 . Among the products are to be found potas- sium sulphate (K 2 S0 4 ), iron sulphate (FeS0 4 ) and ammonium sul- phate [lNH 4 )._,S0 4 ]. Write the reaction for that experiment. 2. Write the graphic symbols and the names of H.,COo, Na 2 C0 3 and HNaC0 3 . 3. Write an equation showing what becomes of the CO., removed from the CO in Exp. 182. ^~ 4. Write the reaction for Exp. 182. /b --; CkJ+n }$ fa^&C ^Wj 5. When free cyanogen is mixed with an excess of and an elec- tric spark passed through the mixture, an explosion occurs. On cooling, the residual gases, one of which is N, have the same volume as the original mixed gases. Write the reaction. # y i 6. What is the weight of a liter of cyanogen gas ? t \,\^(/ 7. How would you prove the solubility of HCI, NH 3 and C0 2 ? ' 8. (a.) What weight of C0 g would be produced by burning 5 g. r ofC? (6.) What volume? ; < '>& . 9. (a.) What weight of C0 2 may be obtained from 100 g. of CaC0 3 by the action of HCI ? (6.) What volume? -I l 10. What is the weight of 10 I. of CO 3 ?yf ftf' 11. (a.) If 20 cu. cm. of CO and 10 cu. cm.' of 6 be mixed in an eudiometer and an electric spark passed through, what will be the name and volum3 of the product? (6.) Write the reaction, (c.) If this product be agitated with a solution of KHO, what will be the effect upon the gaseous volume ? 12. Write the empirical symbols for nitrosyl chloride and sulphuryl chloride. f/& &l f$0}&1*^ 13. Give the laboratory mode of liberating COo, with the reaction, 9?'' and the per centage composition of the source of the C0 2 . 14. (a). How many liters of C0 2 can, be obtained from 200^. of CaCO { ? (&.) Howmanv, if the carbonate contains 3 percent, of ilica? /;; : fjUH -JJ^JSS 1 .^. If sulphuryl chloride be poured into H 2 O, we have the follow- ing reaction: SO 2 CI 2 + 2H. 2 = H 2 SO 4 + 2HCI. How milch dry HCI may be thus prepared from 135 g. of S0 2 CI 2 ? J '$ 16. Describe a method of preparing 0, and express, by symbols, the changes that take p^ce. X/ft^J* 3- 17. How is HNO 3 prepared? Express, by symbols, the changes. 18. Explain and illustrate what you understand by quantivalence. 19. Give the specific gravity of C0 2 , NH 3 , HCI, and H 2 , with the principle by which it is easily determined. 207 SOME HYDROCARBONS. 177 SOME HYDROCARBONS. 206. Hydrocarbons. The compounds of hydrogen and carbon are called hydrocarbons. They are so very numerous that any attempt at even naming them would carry us beyond the proper limits of an elementary text book. They are capable of classification into series, each one differing but little in composition and properties from its neighbors in its series. (See 220.) 207. Marsh Gas. Marsh gas (methyl hydride, hy- drogen monocarbide, methane, CH 4 ) occurs free in nature, being a. product of the decay of vegetable matter confined under water. In warm sum- mer weather, bubbles often rise to the surface of stagnant pools. If the vegetable mat- ter at the bottom of the pond be stirred, the gas bubbles will rise rapidly. The gas may be collected by filling a bottle with water, tying a funnel to its mouth, as shown in Fig. 87, and inverting it over the ascending bubbles. Of this gas, about 75 per cent, is marsh gas; the rest is chiefly carbon dioxide with some nitrogen. The carbon dioxide may be removed by agita- ting the mixed gases with lime-water. Marsh gas also escapes from seams in some coal mines and forms the dreaded " fire damp " of the miner. It also escapes in FIG. 87. 178 SOME HYDROCARBONS. 207 large quantities from " gas wells " in petroleum producing regions. It is the first of a homologous hydrocarbon series known as " The Marsh Gas Series." Experiment 190. Into a gas pipe retort (App. 22) 15 or 20 cm. long, put an intimate mixture of 3g. sodium ac-tate, 3 g. sodium hydrate, (caustic soda, NaHO) and 6 g, quicklime. Place the retort in a stove, heat to redness and collect the gas over H 2 O. Experiment 200. The levity and inflammability of CH 4 maybe shown as in the case of H, by introduc. ing a lighted taper into an inverted jar of it. The gas will burn at the mouth of the jar, and the candle flame, as it passes up into it, will be extinguished. Experiment 201. Fill a tall bottle of at least one liter capacity with warm H 3 0, invert it over tha water pan, and pass CH 4 into it, until a little more than one-third of the H 2 is displaced ; cover the bottle with a towel, to exclude the light, and then fill the rest of the bot- IG ' 88 ' tie with Cl. Cork the bottle tightly, and shake it vigorously, to mix the gases together, keeping the bot- tle covered with the towel. Then open the bottle and apply a flame to the mixture. HCI will be produced, and the sides aud mouth of the bottle become coated with solid C in the form of lamp- black. Test for HCI with moistened blue litmus paper and with a rod wet with NH^HO. 2O8. Properties. Marsh gas is a colorless, odorless, tasteless gas, but slightly soluble in water. With the ex- ception of hydrogen, it is the lightest known substance. It is combustible, burning with a feebly luminous, bluish- fellow flame. Its calorific power is very great (Ph., 569). It forms an explosive mixture with air or oxygen and has been the cause of many terribly fatal explosions in ill- ventilated coal mines. When decomposed by electric sparks, it yields twice its volume of hydrogen. It may be 210 SOME HYDROCAEBOXS. 179 considered a hydride of the univalent compound radical, methyl (CH 3 ). (a.) A mixture of CH 4 with twice its volume of is more violently explosive than a similar mixture of H and 0. 2O9. Chloroform. When chlorine is allowed to act on methyl hydride, the hydrogen of the latter is gradually replaced, forming successively CH 3 CI, CH 2 Ci 2 , CHC1 3 and CCI 4 . Chloroform (CHCI 3 ) may be considered as marsh gas in which three hydrogen atoms have been replaced by three chlorine atoms! It is a colorless, volatile liquid, much used as an anaesthetic in surgical operations. It is manufactured by distilling dilute alcohol with chloride of lime. Marsh Gas. Chloroform. > H-t-H Cl-t-CI 21O. Alcohol. When the juices of plants and fruits that contain sugar/e.0., the juice of the grape or apple, stand for some time in a warm place, they begin to fer- ment. The fermentation may be aided by the action of yeast. The fermented liquid has lost the sweet taste of the sugar because the sugar (C 6 H, 2 6 ) has been decomposed into carbon dioxide and alcohol (C 2 H 6 0). See Exp. 187. The preparation of alcohol is illustrated by Exp. 202. (a.) The chief peculiarity of the hydrocarbons arises from the facil- ity with which the C atoms unite themselves one to another and thus constitute the framework of the various molecules. For exam- V pie, we have the methane molecule, H-C-H. By replacing one atom HI 180 SOME HYDROCARBONS. 210 of H with the univalent radical methyl (CH 3 ), we have H-C-C-H, H H or ethane (ethyl hydride). By substituting the univalent radical, H H HO, for one atom of the H in ethane, we have (HO)-C-C-H, or ordinary HH alcohol (ethyl hydrate). By successive substitutions of (CH 3 yfor H, H H H H we may pass from CH 4 to C 3 H 6 , C 3 H 8 , C 4 H io or H-C-C-C-C-H, etc. HH H^ Experiment 202. Pour half of the fermented liquid of Exp. 187 into a flask, F, placed on the ring of a retort stand. Connect Fwith an empty flask or bottle, b, having a capacity of about 100 cu. cm., and placed in a water bath. Connect 6 with a flask or bottle, c, im- FIG. 89. mersed in cold H 2 0, as shown in Fig. 89. Boil the liquid in F; the vapors of C 3 H 6 O and of H 2 pass into b, the temperature of which is a little below the boiling point of H 2 O (100~C.) because its water bath is kept barely boiling [Ph., 502 (2), 513.] Here, most of the steam is condensed while the vapor of C 2 H C passes on to c, and is there condensed. The distillate condensed in c is dilute alcohol. If it is not strong enough to burn when a flame is brought into contact with it, it may be distilled again, or a second bottle and water bath, 6', may be interposed between b and c. The experiment should not be continued after a quarter of the liquid in F has been vaporized. 213 SOME HYDROCARBONS. 181 Instead of condensing the C 2 H 6 in the flask, c, the Liebig con- denser (Ph., 512, a.}, shown in Fig. 90, may be used. Some H 2 O will remain in the C 2 H 6 even after re-distillation. This may be removed by quicklime. 211. Properties. Al- cohol is a colorless, volatile, inflammable liquid. Its spe- cific gravity is 0.8 and its boiling point 78C. It ab- sorbs moisture from the at- mosphere and is capable of mixing with water in all proportions. Alcohol that contains no water is called ab- solute alcohol. Alcohol that is " 90 per cent, proof" is con- sidered to be of good quality. As marsh gas is considered to be a hydride of methyl, so ordinary- alcohol is consid- ered to be a hydrate ( 167) of the univalent compound radical, ethyl (C 2 H 5 ). 212. Uses. Alcohol is largely used in the chemical laboratory, in pharmacy and in the arts. It affords a smokeless fuel and is an indispensable solvent for many substances (such as resins and oils) that are insoluble in water. It is the fundamental principle of all fermented and distilled liquors. 213. Ether. Ether [ sulphuric ether," ethyl ether, ethyl oxide, (C 2 H 5 ) 2 0] is prepared by distilling a mixture of strong sulphuric acid and alcohol. The distillate, which is a mixture of ether and water, is condensed in a cold re- ceiver and separates into two layers, water below and ether above. The ether is drawn off and wholly freed from water by standing over quicklime and redistillation. 182 SOME HYDROCARBONS. 213 (a.) The chemical reaction may be represented as follows : Alcohol. Hydrogen Ethyl Sulphate (C 2 H 5 )HO + H,S0 4 = H 2 + H(C 2 H-)S0 4 . H(C 2 H 5 )S0 4 + (C a H 5 )HO = (C 8 H 8 ) 8 + H 8 S0 4 . It will be noticed that the full amount of H 2 S0 4 engaged remains at the end of the reaction. C 3 H 6 is supplied in an uninterrupted stream, and thus the distillation goes on continuously. Caution. Owing to the danger arising from the extreme volatility and inflammability of (C 2 H 5 ) 2 O, the pupil should deal with only minute quantities of this compound. Experiment 203. Put 10 or 12 drops of C 2 H 6 O and an equal quantity of H 2 S0 4 into a test tube and heat gently. The peculiar odor of (C 2 H 5 ) 2 may be recognized. Experiment 26 1. Pour a small quantity of (C 2 H 5 ) 3 O into the palm of the hand and notice its rapid evaporation and absorption of sensible heat (Ph., 517). Experiment 205. Put a few drops of (C 2 H 5 ) 2 into a tumbler, cover loosely and, after the lapse of a minute, bring a flame to the edge of the tumbler. .The heavy vapor of (C 2 H 5 ) 3 will ignite with a sudden flash. 214. Properties. Ether is a colorless, volatile,, in- flammable liquid, having a specific gravity of 0.72. It is almost insoluble in water and has a strong and peculiar odor. It is largely used as an anaesthetic ( 80, 2C9) in surgical operations. Its common name, "sulphuric ether," is a misnomer as ether contains no sulphur. Ether may be considered as ethyl oxide. Note. The relations of C 2 H C and (C 2 H 5 ) 2 to each other and to their compound radical, ethyl, may be made more evident by the following typical symbols ( 96) : Water Type. Alcohol. Ether. 215. Acetic Acid. If the half of the fermented liquid of Exp. 187 remaining after Exp. 202 be tasted. 2l6 SOME HYDROCARBONS. 183 after standing for a few days, it will be found to be sour. If allowed to stand long enough, it will be changed to vin- egar. By a process of oxidation, the alcohol is changed to acetic acid (" pyroligneous acid," C 2 H 4 2 ,) and water. Vinegar is a dilute solution of acetic acid with coloring matter and other impurities from the juice of the fruit from which it is generally made. (a.) If two atoms of H in the compound radical C 2 H. be replaced by we shall have the oxygenated radical C 3 H a O, called acetyl. This radical has not yet been isolated. It is, consequently, a " hypothetical, oxygenated, compound radical." Acetyl hydride (C 2 H,0,H), a volatile, unstable and easily oxidizable compound, is called aldehyde; acetyl hydrate (C 2 H 3 0,HO) is called acetic acid. This acid is monobasic. (b.) The conversion of C 2 H 6 to C 2 H 4 3 is represented by the fol- lowing equations : Alcohol. Aldehyde. (C 2 H 5 )HO + = H 3 + (C 2 H 3 0)H. Acetic add. (C 2 H 3 0)H + = (C 2 H 3 0)HO = C 8 H 4 2 . (c.) Pure C 2 H 4 2 is prepared by distilling a mixture of H 2 S0 4 and some acetate, such as sodium acetate. Lead acetate is commonly called by the dangerous name, "sugar of lead;" copper acetate is called " verdigris." (d.) We have already noticed the relation between ethyl, alcohol and ether. The relations of acetic acid to these may be shown as follows : Ethyl (C 2 H 5 ), when oxygenated, becomes acetyl (C 2 H 3 0). Acetyl (C 2 H 3 0) with hydroxyl becomes acetic acid or acetyl hy- drate (C 2 H 4 2 ). 216. Isomerism. Acetic acid and methyl formate are two distinct substances, having different properties, but represented by the same molecular symbol, C 2 H 4 2 . Dif- ferent substances having the same percentage com- position are said to1}& isomeric ; the substances are 184 SOME HYDROCARBONS. 2l6 called isomers; the peculiar phenomenon is called isomerism. Isomers that have the same molecular sym- bol, like acetic acid and methyl formate, are said to be metameric. Isomers that have different molecular sym- bols are said to be polymeric. Acetylene (C 2 H 2 ) and benzene (C 6 H 6 ) are polymers. (a.) There are at least seven distinct substances having the symbol Ci H 6 CI 2 , differing from each other in solubility, fusibility and chemical behavior. We can only imagine that the difference be- tween metameric substances is due to a difference in -the arrange- ment of the atoms in the molecule. (&.) Isomeric substances bring clearly to view the value of rational symbols ( 94). Formic acid (CH 2 3 ) is a hydrate of the univalent radical, formyl : CH ^ j 0. Replacing the H in this typical sym- bol for formic acid by methyl (CH 3 )', we have ^ j- as the typical symbol for methyl formate. Acetic acid is a hydrate of the univalent radical, acetyl : C a H 3^ ? Q While, therefore, the empiri- cal symbol,C 2 H 4 O 2 affords no means of distinguishing between acetic acid and methyl formate, the typical symbols, ^ 3 j- and ^ j- represent clearly, to eye and mind, two distinct substances. Simi- larly, C 2 H 6 represents common alcohol or methyl ether. The C H ) former is ethvl hydrate, 2 u !- ; the latter is methyl oxide, iS:l- (c.) Isomerism is a peculiarity of the hydrocarbons. The several members of the olefiant gas series ( 220) are polymers. 217. Olefiant Gas. Olefiant gas (ethene, ethylene, hydrogen dicarbide, C 2 H 4 ) is prepared by removing the elements of water from alcohol. It is the first of a homol- ogous hydrocarbon series, known as " The Olefiant Gas Series." Experiment 206. In a large beaker glass, mix 120 cu. cm. of H 2 S0 4 and 30 cu. cm. of C 2 H 6 0, with caution and constant stirring. Half fill a liter flask with coarse sand and pour the mixed liquids upon the sand. Close the flask with cork and delivery tube, and 219 SOME HTDROCARBOXS. 185 heat it gently upon the sand bath. The gas will be delivered mixed with aeriform C,H 6 O, (C 2 H 5 ) 2 0, C0 2 and S0 2 , and maybe collected over water. If pure C 3 H 4 be desired, two wash bottles,* one contain- ing strong Ho SO 4 and the other, a solution of NaHO may be inter- posed between the flask and the water bath. The purpose of using the sand is to lessen the frothing in the flask. C 3 H 6 0-H 2 = C 2 H 4 . Experiment 207. Apply a flame to the mouth of a bottle of C,H t and force out the gas by pour- ing in H 2 0. The C 2 H 4 burns with a brilliant white flame. C 2 H 4 + 30 2 = 2C0 2 + 2H 2 0. Experiment 208. Fill ascda water bottle with one volume of C S H 4 and three volumes of 0. Wrap a towel about the bottle and apply a flame to the mouth of the bottle. A vio- lent explosion will take place. Experiment 209. Half fill a liter flask over the. water bath under H 2 0, half a liter of Cl FIG. 91. into the flask, and place a small cup under the mouth of the flask. The 1,000 cu. cm. of mixed gases will rapidly decrease in volume, H 2 will rise in the flask and oily drops will be formed and fall through the H 2 into the cup beneath. There has been a direct synthesis of the two gases to form ethylene chloride, (" Dutch liquid," or u oil of the Dutch chemists," C 2 H 4 CI 2 ). Hence the name, " olefi- ant gas." By agitating the C 2 H 4 C1 2 with a solution of sodium car- bonate, the former may be purified and its agreeable odor obtained. (See Note following Exp. 94.) 218. Properties. Olefiant gas is colorless, com- bustible and irrespirable. It is slightly soluble in water, and forms an explosive mixture with three times its vol- ume of oxygen. It may be decomposed by electric sparks, giving twice its volume of hydrogen. 319. Acetylene. Acetylene (ethine, C 2 H 2 ) is a 186 SOME HYDROCARBONS. 2IQ transparent, colorless gas, that burns with a strongly lu- minous, smoky flame. It acts as a poison when it comes into contact with the blood. It may be formed by direct synthesis of its constituents at very high temperatures. It is one of the ingredients of illuminating gas. (a.) Carbon electrodes may be fitted to pass through apertures in a globular glass flask, through which a slow current of pure H is flow- ing. By passing a powerful electric current through the carbons and then separating them, the electric arc is produced in an atmosphere of H. This process results in the synthesis of C 2 H 2 . 22O. Homologous Series. Methane, ethene and ethine represent each a series of hydrocarbons. In each series, the addition of CH 2 to the symbol of one member, gives the symbol of the next member. Hydrocarbons that differ thus from one another are said to belong to homologous series. (a.) Each series has its general formula or symbol : Series. General Formula. Symbols of Members. Marsh gas C n H 2n + 9 CH 4 ; C 3 H 6 ; C 8 H 8 ; C 4 H 10 ; C 5 H 12 Olefiantgas C n H 2n C 2 H 4 ; C 3 H 6 ; C 4 H 8 ; C 5 H 10 Acetylene C n H2 n -2 EXERCISES. 1. (a.} What is the specific gravity of marsh gas, on the hydrogen standard ? (b.) On the air standard ? (c.) What will a molecule of it weigh ? (d.) What will a liter of it weigh ? 2. (a.) What are the products of the combustion of methyl hy-^^ dride ? (6.) When a liter of it is burned, what is the weight of th-^y dioxide produced ? (c.) Of the monoxide produced ?/ t y . w y 3. (a.) What volume of is necessary to the complete combustion of a liter of CH 4 ? (&.) What weight of ? 4. Find the percentage composition of alcohol. 5. (a.} What is the weight of a molecule of ethyl oxide? (&.) Of a liter of ether vapor ? (c.) Of a liter of liquid (C 2 H 5 ) 2 ? 220 SOME HYDROCARBONS. 187 6. (a.) What volume of H may be obtained by the decomposition of 500 en. cm. of olefiant gas ? (&.) By the decomposition of 10.5 criths of ethylene? 7. Which is the heavier, C 2 H 4 or N 2 ? 8. (a.) Give a short statement of the process for making- sulphuric acid. (&.) Which is the most interesting action in the process? (c.) What is the specific gravity of the acid and how is this specific grav- ity secured ? 9. When a mixture of H and CO is exposed to the action of a ', '/2. Aeries of electric sparks the following reaction takes place : 3H 2 + CO = CH 4 + H 8 0. ?f6j- - What volume of methane can thus be produced from 12 544 g. of carbon monoxide ? 10. (a.) Show that the specific gravity of a compound gas is one half its combining weight. (&.) How many atoms are there in a molecule of P? 11. The composition of a compound gas is 85 f per cent, of C and 14| of H ; its density is 14 ; what is is symbol ? ^ - 12. Account for the fact that 23 #. of C 2 H f) will, without any addi- tion of material by the manufacturer, yield about 30 g. of C 2 H 4 2 . 13. Find the symbol of a substance whose vapor density is 23 and whose analysis shows the following percentage composition : C,52.2; H, 13; 0, 34.8. ^> ' 14. Write the empirical and graphic symbols for ethyl. H ' 15. What word more fully descriptive than isomeric may be plied to substances that have the same percentage composition and molecular weight ? 16. Symbolize the acetates of Na', K', Ca" and (NH 4 )'. 188 ILLUMINATING GAS. 221 ILLUMINATING GAS. Experiment 210. Into a gas pipe retnrt, put some fragments of bituminous (soft) coal. To the delivery tube, attach a piece of glass tubing drawn out to a jet. Place the retort in a hot fire and, as the illuminating gas is delivered, ignite it at the jet. 21. Illuminating Gas. Illuminating gas is pre- pared by distilling sub- stances consisting in whole or in part of hydrogen and carbon. For this purpose, wood, resin, or petroleum is sometimes used but, far more commonly, a mixture of cannel and caking bitu- minous coals furnishes the desired products. A section- al view of the apparatus used is shown in Fig. 93. The coal is placed in Q shaped FIG. 92. retorts, six or seven feet long, made of fire clay. The charge is about 200 Ib. of coal to each retort. The retorts, C, are arranged in groups or " benches " of from three to seven, as shown in Fig. 92. All the retorts of a bench are heated to a temperature of about 1200C. or 2200F. by a single coke fire. After charging the retorts, their mouths are quickly closed by heavy iron plates. 221 ILLUMINATING GAS. 189 FIG. 93. 190 ILLUMINATING GAS. 221 (a.) The products of the distillation, when cooled to the ordinary temperature, are solid, liquid and gaseous. The liquid products are volatile at the high temperature of the retort. (&.) The solid products are coke and gas carbon. The coke is coal from which the volatile constituents have been removed by intense heat. It, is largely used as a fuel for domestic, metallurgical and other purposes. The gas carbon is an incrustation that gradually forms on the inside of the retorts. It is used for making plates for galvanic batteries and "carbons" or " candles " for electric lamps (Ph., 383, 385, 389). (c.) The liquid portion of the distillate is chiefly an aqueous solu- tion of ammonium compounds, certain hydrocarbons like benzol and toluol, and a viscous coal tar which is complex in its composi- tion. (d.) The gases of the distillate are very numerous. One writer mentions nineteen light producing constituents, including benzol and toluol vapors, C 2 H 2 and C 2 H 4 ; three diluents, viz., H, CO and CH 4 ; and fourteen impurities, including N, 0, H 8 0, H 2 S, C0 2 , S0 2 and CS 2 . (e.} When the volatile products leave the retort, they pass up through the ascension pipes, i, down the dip pipes and bubble through the seal of tar and water already collected in the long, horizontal iron tube, mm, called the hydraulic main. From this point forward, cooling ensues, accompanied by the condensation of vapors "and the falling of the tar particles mechanically carried along in the hot rush of the gas from the retorts." The gas is loaded with impuri- ties from which it must be freed before it is in a salable condition. ( f.) From the hydraulic main, where it left much of its tar and H 8 O, the gas passes through the vertical cooling pipes, D, called the condensers. Here it is cooled to 20C. or 25C. and largely freed from its tar, oils and ammonium compounds. The gas now assumes a condition less thickened and turbid and more favorable to chemical treatment. In large gas works, there are many sets of these con- densers. In the Cleveland works, each set measures 840 linear feet. Every particle of gas has to pass the whole length of one of these sets of condensers. (g.} In large works, an "exhauster" is placed between the hy- draulic main and the condensers. By this means, the gas is pumped from the retorts and forced through the condensers, thus reducing the pressure in the retorts. 221 ILLUMINATING GAS. 191 (7i.) Chief among the impurities still remaining, are ammonium compounds, CO* and H a S. These ammonium compounds are easily soluble in H a O. Therefore, the gas is next washed in the tower or " scrubber," 0. Here the gas, in a finely divided state, rises through a shower of minute particles of H.>0 and, thus, has its easily soluble impurities washed out by the spray. To prevent the ascent of the g.is in large bubbles, of which only the surfaces would come into contact with the H 2 0, the scrubber is filled with coke, brush, or lat- tice work for " breaking up" both gas and H 3 into minute particles. This scrubbing also cools the gas still more and removes some of the CO 2 and HoS. The tower is generally three or four feet in diameter and thirty or forty feet high. More than one are used in some works. (i.) The gas next passes through the purifiers, M, the object of which is to remove the remaining C0 2 and H 2 S. The purifier con- sists of boxes containing trays with perforated bottoms. These trays contain the material which removes the impurities as the gas filters through. Some works use slaked lira 3 in the purifiers, others a mixture of copperas (iron sulphate, FeS0 4 ,) saw-dust and slaked lime. At manufacturing establishments where iron and steel arti- cles are polished, the grindstone dust is intimately mixed with minute particles of the metal. This inexpensive mixture of grind- stone dust and iron or steel is used in the purifiers of the Cleveland Gas Light and Coke Co. (j.) From the purifiers, the gas is conducted to the gasholders, Q. These gas holders are sometimes sixty feet high and more than 100 feet in diameter. (&.) The gas, as delivered to the consumer, consists chiefly of the three diluents mentioned above, the CH 4 constituting -about a third - of the gas sold. These feebly luminous gases, H, CO and CH 4 , serve as carriers of the six or seven per cent, of more highly luminous con- stituents, while the combustion of the former furnishes much of the heat needed for the decomposition of the latter and the raising of its carbon particles to the temperature of incandescence. (I.) Other conditions being the same, and .within certain limits, the higher the temperature, the greater the quantity of gas produced ; the lower the temperature, the richer the quality. Similarly, the longer the time of the charge, the greater the quantity; the shorter the time, the richer the quality. A skillful mixture of grades of coal and regulation of temperature and time of charge enables the gas engineer to vary the products of the chemical processes in the retort 192 ILLUMINATING GAS. 221 and furnish an article that is attractive and satisfactory to the con- sumer, or .profitable to the proprietors, or to compromise between these conflicting interests. Experiment 211. Heat some pieces of bituminous coal in the gas pipe or other retort and pass the gas as it is evolved through the apparatus shown in Fig. 94. The volatile liquid products will condense in the re- ceiver, m, or "hydraulic main." Thence, the gas 94- passes through the first arm of the U-tube and changes the color of a moistened strip of red litmus paper to blue, thus showing the presence of NH,j. In the second arm, it is tested for H 2 S ( 142). In the bend of the second tube, is placed lime water, which becomes milky, thus showing the presence of C0 2 . The gas is then collected over H 3 O. By lowering the capped receiver into the H 2 or by pouring more H 2 into the water bath and opening the stop-cock, the gas may be forced out and burned as it issues. EXERCISES. 1. See App. 1. Read the following symbols, thus : N 2 represents one molecule of nitrogen consisting of two atoms : O, , O 3 , H 2 0, 2H 2 0, H 2 , 2P 4 , CI 2 , NH 3 , H,S0 4 , FeS0 4 , AI 2 (S0 4 ) 3 , ~4AI 2 (SOJ S , C0 2 , CO. 2. Write down the weights represented by each of the following expressions: 2Rf6; 10H 2 0, 2CS 2 , 12CH 4 , K 2 AI 3 (S0 4 ) 4 , 24H 2 0. 3. Name the compounds symbolized as follows : CaO, MgO, ZnS, KCI, NaBr, AgF, H 2 S, HI, KCN, SSe, PH 3 . 4. If two volumes of C 2 H 4 and four of Cl be mixed, a black smoke and HCI are formed. Write the reaction. < { ~-#// 5. How much NH ;5 will just neutralize 10 g. of HCI ? 6. How many liters of O are necessary to combine (complete com- bustion) with (a.) 12 criths of C ? (&.) 2 g. of S ? (c}. 10 g. of C ? 7. How many liters of Cl are necessary to decompose 12 I. of HI? 8. (a.) Distinguish between the properties of CO and those of C0 2 . (&.) How does each destroy life? (c.) Give a test for each. 221 ILLUMINATING GAS. 193 9. Steam and Cl are passed through a porcelain tube heated to redness. What takes place ? 10. (a.} What is meant by the basicity of an acid? (6.) By the acidity of a base ? (c.) How is the name of a salt derived from that of an acid ? 11. Explain the significance of each of the following symbols for potassium sulphate : K 2 S0 4 ; K 2 0,S0 3 ; E8}sO a and K v ' A j/-L\y%: J 4i?J >- y * ' '"fit* -} . 194 SOME ORGANIC COMPOUNDS. S 222 SOME ORGANIC COMPOUNDS. 222. Organic Compounds. There are known to the chemist many substances formed by the subtle pro- cesses of animal and vegetable life. These were formerly supposed to be incapable of production in any other way and their consideration formed a distinct branch of study known as Organic Chemistry. But within the last few years, many of these organic compounds have been pro- duced in the chemical laboratory from "dead matter." Each of these triumphs of modern chemistry removes a stone from the wall dividing the realms of organic and in- organic chemistry. In fact, the wall, as a wall, is already ruined. In this section, we shall consider a few of the almost innumerable known organic compounds. The molecular structure of most of them is very complicated. Experiment 21%. Place a teaspoon ful of the white of an egg in a test tube ; add 25 cu. cm. of C 2 H 6 0. Notice the coagulation. Experiment 213. Place the remainder of the white of the egg in a test tube ; place the test tube and a thermometer in a vessel of H 2 ; heat the H 3 O ; notice that at the temperature of about 60C. the white of the egg coagulates. 223. Albumen. Albumen is a substance of very complicated structure. It is typical of a group of bodies (histogenetic) that are essential to the building up of the animal organism, of which group the leading members are albumen, fibrin and casein. These differ but little, if 224 SOME ORGANIC COMPOUNDS. 195 any. in their chemical composition, but widely in their properties. They all exist in two conditions, the soluble and the insoluble. (a.) The white of the eggs of birds is the most familiar instance of albumen. It is soluble in H 2 and coagulated by heat or C 2 H 6 0. The albumen of plants is found chiefly in the seed. The formula, C 72 H, 18 N 18 S0 2 ,, has been given for albumen, but its chemical composition has not yet been satisfactorily determined. (&.) Soluble fibrin is found in the blood. It hardens on exposure to the air and, entangling the corpuscles of the blood, forms the clot. By washing the clot with H 3 0, fibrin is left as a white, stringy mass. Insoluble fibrin constitutes muscular fibre. (c.) Casein is found in the milk of animals. It is not coagulated by heat but is coagulable by rennet, the inner membrane of the stomach of the calf, This property is utilized in cheese making. (d.) All of the albuminoids " are amorphous, and may be kept, when dry, for any length of time, but, when moist, they rapidly putrefy and produce a sickening odor." Experiment 214* Dilute a quantity of HCI with about six times its volume of. H 3 0. Place a clean bone (e.g., the femur of a chicken) in the dilute acid and allow it to remain for three or four days. The mineral part of the bone will gradually dissolve, and there will be left a flexible substance which preserves the shape of the bone, and which, when dry, has a translucent, horny appearance. Experiment 215. Place the flexible substance left from the last experiment in H 2 and boil it for three or four hours. It will dis- solve and, when the liquid cools, will assume a jelly-like condition. 224:. Gelatin. The bones and skins of animals contain a substance called ossein. The product of Exp. 214 was ossein. When this substance is boiled in water, gelatin is produced. The product of Exp. 215 was gelatin. Glue is an inferior quality of gelatin. Isinglass is nearly pure gelatin ; it is made from the swimming bladder of the sturgeon. The thin plates of mica used in stoves are sometimes, with gross impropriety, called isinglass. 196 SOME' ORGANIC COMPOUNDS. 225 225. Sugar. There are several varieties of sugar, among which the most important are sucrose, dextrose and levulose. 226. Sucrose. Sucrose (cane sugar, C 12 H 2 20,|) is found in the juice of certain plants, as sugar cane, sugar maple and beet root. In the manufacture of cane sugar, the juice is pressed from the canes by passing them be- tween rollers. The juice is treated with milk of lime and heated. The lime neutralizes the acids and the heat coag- ulates the albumen in the juice. The coagulated albu- men rises and mechanically carries with it many of the impurities, some of which have combined with the lime. The scum thus formed is removed, and the liquid evapo- rated until it is of such a consistency that sugar crystals will form when the liquid is cooled. The crystals, when drained, are " brown " or " muscovado " sugar. The liquid remaining is molasses. (a.) Brown sugar is refined by dissolving it in H 2 0, filtering the solu- tion through layers of animal charcoal and evaporating the H 2 O from the filtrate. When C^H^O^ is boiled, part of it is changed to a mixture of dextrose and levulose, the proportion thus changed de- pending upon the temperature and time of boiling. To lessen this loss of sucrose, the filtered solution is evaporated in large " vacuum pans" from which the air and steam are exhausted. The degree of concentration desired is thus secured more quickly and at a lower temperature (Ph., 503-505,) thus lessening the loss and obviating the risk of burning. When the "mother-liquor" drains from the crystals in moulds, loaf-sugar is left ; when it is driven off by a cen- trifugal machine, granulated sugar is left. (&.) The sugar from the sap of the sugar maple or from the juice of the beet root is identical with cane sugar. As the impurities of maple sugar are agreeable to the taste of many persons, the sugar is not refined. Beet sugar is always refined, as its impurities are offensive to all. (c.) When sucrose is melted and allowed to cool rapidly, barley 227 SOME ORGANIC COMPOUNDS. 197 sugar is formed. When it is heated to about 215C., H 2 is expelled and caramel remains. ( ' /^ 4J- U Oxygen.. ; = 27.58 per cent, /"t Vapor density, 4. 04, on the Carbon. . . = 62.07 per cent, Hydrogen., = 10.35 air standard. What is the molecular symbol of the compound ? 7. (a.} Find the percentage composition of marsh gas. (&.) Of olefiant gas. 8. What weight of KCI0 3 is necessary to the preparation of 35,000 cu. cm. of ? (?& '.' V f 9. On completely decomposing, by heat, a certain weight of KCI0 3 ; I obtain 20.246 g. of KCI. (a.) What weight of KCIO, did I use ? (b.) What volume of did I obtain ? 10. To inflate a certain balloon properly requires 132.74 Kg. of H. What weight of Zn and of H 8 S0 4 will be needed to prepare this quantity of H. 11. Write the name and a graphic symbol-for H 2 S 2 3 , introducing dyad S and hexad S. A &L<\ 232 SILICON. 201 SILICON. %Or Symbol, Si ; atomic weight, 28 m. c. ; quantivalence, 4. 231. Silicon. Although this element does not occur free in nature, it is the most abundant and widely diffused of all the elements except oxygen. Combined with oxygen alone, as silica or quartz, or with oxygen and potassium or sodium, etc., as metallic silicates, it forms a large part of the earth's crust. (a.) Free Si may be prepared by the action of sodium upon potas- sium silico-fluoride. K 2 SiF 6 + 2Na 2 = 2KF + 4NaF + Si. (&,) Si exists, like C, in three allotropic forms ; as a soft, brown, amorphous powder which burns easily in air or 0, forming Si0 2 ; as hexagonal plates, corresponding to graphite in lustre and electric conductivity; as needle shaped octahedral crystals, corresponding to diamond in hardness. These octahedra are hard enough to scratch glass. (c.) The only acid that attacks crystallized Si, is a mixture of HN0 3 and HF. (d.) There is a compound of H and Si known as hy- drogen silicide (SiH 4 ) that is somewhat analogous to CH 4 . Similar compounds are formed with members of the halogen group, as SiCI 4 , etc. 232. Silicon Dioxide. Silicon has only one oxide (silica, silicic anhydride, Si0 2 ) It is very abundant in nature. Its purest form is quartz or rock crystal, which is found in beauti- ful hexagonal prisms terminated by hexagonal 202 SILICON. 232 pyramids. Quartz has a specific gravity of 2.6, and is hard enough to scratch glass. (.) Amethyst, cairngorm-stone and rose quartz are nearly pure crystallized Si0 2 . Agate, carnelian, chalcedony, flint, jasper, onyx and opal are nearly pure amorphous Si0 2 . White sand and sand- stone are generally nearly pure Si0 2 . Silicious sand and sand-stone are often colored yellow by an iron oxide. (&.) Si0 2 is insoluble in H 2 or in any acid except HF, but it may be dissolved in a boiling solution of potassium or sodium hydrate. The potassium or sodium silicate thus formed is called " soluble glass" or " water glass." Si0 2 is dissolved in the waters of some thermal springs. The Geysers of Iceland contain dissolved Si0 2 , which is deposited by the cooling waters upon objects immersed in them. Si0 2 melts in the oxyhydrogen flame to a colorless glass that remains transparent when cold. (c.) Si0 2 from the soil is found in certain plants, especially grains and rushes. The outer coat of rattan contains much Si0 2 , as does the leafless plant, horse tail, which is, consequently, used for polish- ing and scouring. (d.) Si0 2 is also found in animal substances. The feathers of cer- tain birds are said to contain 40 per cent, of SiCX. Experiment 217. Place a few cu. cm. of concentrated soluble glass in a small evaporating dish and add strong HCI until the mixture shows an acid reaction. A thick jelly like mass will be formed in the liquid. Place the dish on a water bath and evaporate its contents to dryness. Heat this solid residue gently over the lamp. It will di- minish in volume. Add H 2 and filter. The insoluble powder left upon the filter is precipitated Si0 23 one of the lightest known pow- ders. This jelly like mass formed in this experiment probably is silicic acid (H 4 SI0 4 ). 233. Natural Silicates. Silica unites with many metallic oxides to form silicates. The natural silicates are very numerous and many of them are of a very complex composition. Thus, clay is a silicate of aluminum ; feld- spar is a double silicate of aluminum and potassium; mica is a triple silicate of aluminum, potassium and iron. 234 SILICON. 203 Experiment 218. Add some HCI to a dilute solution of water glass. NaCI or KCI will be formed with H 4 Si0 4 . Pour the liquid mixture into a dialyser, made of parchment paper stretched over a wooden ring and floated on the surface of pure H 2 0. The chloride solution passes through the membrane while the H 4 Si0 4 remains dissolved in the dialyser. Crystallizable substances, like NaCI and KCI are sometimes called crystalloids, and uncrystallizable substances, colloids. Crystalloids and colloids may be separated as in this experiment. The process is called dialysis. 234:. Artificial Silicates. Sodium and potassium silicates (water or soluble glass) are largely used in the arts. But by far the most important of the artificial silicates is glass, which is a mixture of a silicate of sodium or of potassium, or of both, with a silicate of one or more other metals. The composition is determined by the desired infusibility, insolubility, transparency or color of the glass. (a.) Bohemian glass is a silicate of potassium and calcium. It is fusible only with difficulty and is but little acted upon by chemical reagents. It is free from color and is largely used in chemical appa- ratus, especially in ignition tubes. (5.) Window, crown or plate glass is a silicate of sodium and cal- cium. It is harder than Bohemian glass, but more easily fusible and more readily acted upon by chemical reagents. (c.) Bottle glass, or common green glass, is a silicate of sodium, calcium, aluminum and iron. Its color is due to the iron oxide pres- ent as an impurity in the cheap materials used. It is harder and more infusible than window glass, but more easily acted upon by acids. ( 10. Soft, Hard. 11. Flexible, Brittle. 12. Poisonous, Not poisonous. 239. Uses. Phosphorus is extensively used in the manufacture of friction matches, the match tips generally being a mixture of phosphorus, glue and potassium chlo- rate. " Safety matches " are tipped with an timonous sul- phide and potassium chlorate. These ignite, not by simple friction, but by rubbing on a prepared surface containing red phosphorus, manganese dioxide and sand. Ordinary phosphorus mixed with flour paste is a " rat poison " that has probably led to the burning of many houses. Phos- phorus is used in medicine ; many of the phosphates are important remedial agents. Phosphorus fumes produce, in the workmen in match factories, "phosphorus-necrosis, a disease in which the bones of the jaw are destroyed." (.) About 1200 tons are said to be made yearly, nearly all of it at two establishments, one near Birmingham, England, and the other at Lyons, France. The manufacture is dangerous, on account of the easy inflammability of the product. . 210 PHOSPHORUS. 239 EXERCISES. 1. (a.) Symbolize two molecules of pentad phosphorus. Three mole- vi cules of quadrivalent sulphur. (&.) What do S 2 and 60" 2 represent ? 2. (a.) What is a binary molecule ? (6.) A ternary molecule ? (c.) How are binary molecules named ? Illustrate. 3. How much P is contained in 120 Kg. of bone ash, of which _ ^88.5 # is Ca 3 (P0 4 ) 2 and the rest CaC0 3 ? '1 / X^//- 4. (a.) Find the percentage composition of carbon monoxide. (6.) Find the symbol of a gas having the composition 27.27% C ; 72.73$ O, and weighing 1.9712 g. to the liter. 5. Red oxide of copper contains 88.8 parts of Cu and 11.2 parts of 0, by weight. Black oxide of copper contains 79.87 of Cu and 20.13 of 0. The symbol for the black oxide is CuO ; what is the symbol for the red oxide? 6. What is the meaning of the following : we take H 3 0, 0<$g|] will remain. 7. Can S 2 and S 6 exist at the same temperature ? Explain. 8. Write the name and full graphic symbol for (HO) -(SO,) -(SO,) -(HO). ' +/-J-' ' 240 PHOSPHOR US COMP UNDS. 211 PHOSPHORUS COMPOUNDS. 24O. Hydrogen Phosphide. This colorless, poisonous, ill-smelling gas, (phosphuretted hydrogen, phosphine, PH 3 ;) is generally prepared by heating phos- phorus in a strong alkaline solution. (a.) Dissolve 40 g. of potassium hydrate (caustic potash) or 60 g. of freshly slaked lime in 110 cu. cm. of H 2 0. Place it in a flask of not more than 200 cu. cm. capacity ; add 1 g. of P in thin slices, and 5 or 6 drops of (C 2 H 5 ) 2 0; close the flask with a cork carrying a long glass delivery tube that terminates beneath H 2 as shown in Fig 98. The volatile (C. 2 H 3 ) 2 is added that its heavy vapor may force the of the air from the flask. When the contents of the flask are boiled, gas escapes from the delivery tube and bubbles up through the H 2 0. As each bubble of gas comes into contact with the air, it bursts into flame with a bright light. If the air of the room be still, beautiful expanding rings of white smoke (P 8 5 ) will rise, with vortex motion, to the ceiling. 3KHO + P 4 + 3H 2 = 3KP(HO) 2 + PH 3 . (6.) PH 3 is easily formed by placing calcium phosphide in H 2 0. (c.) Two other compounds of H and P are known, of which one is liquid and the other solid at the ordinary temperature. Their proper symbols have not yet been definitely ascertained, but the liquid is generally represented by PH 3 or PgH^ and the solid by P 2 H or P 4 H 8 . FIG. 212 PHOSPHOR US COMP UNDS. 240 ( C J ,H 5 )' 3 P0 3 . (c.) H 3 P0 4 may be prepared by tho direct union of P 2 5 and boil- ing H B 0, but the usual process is to oxidize red P with strong HN0 3 or ordinary P with dilute HNO 3 . When heated, it changes to H 4 P B O 7 or H P0 3> as explained below. It is tribasic, and yields normal, double and acid phosphates in great variety. This acid is sometimes, with questionable propriety, called orthophosphoric acid. It and its salts arc the most important of the phosphoric series. (d.) H 4 P S T is formed by heating H 3 P0 4 to 215T., thus depriving it of H 2 : 2H 3 P0 4 H 8 = H 4 P 2 O 7 . It is tetrabasic and yields normal, double and acid pyrophosphates in great variety. The group, PO (phosphoryl) acts as a trivalent compound radical. The equation above may be written graphically as follows : From Xw tuke H -- H and ^O remains (PO> /OH < P phosphoric acid. 242 ruosp nours COMPOUNDS. 215 EXERCISES. &T For List of Elements and their Symbols see Appendix 1. 1. What is the apparent quanti valence of P in P 2 5 ? Represent this molecule by its graphic symbol. 2. (a.) What is the name of Ca" 3 (P0 4 )o V (b.) Why may not the symbol be written CaP0 4 ? 3. Choose between HNa'P0 4 and HNa 2 P0 4 . Give a reason for your choice. // "^2^ i^A^T ^'^'tV;J' EXERCISES. ^ / 1. The practical yield being half the theoretical, how much potas- sium may be prepared from 138 Kg. of potassium carbonate?,/ \ M ^A 2. What is the percentage composition of KCI0 3 ? 7~ ?^ H 3. What is the radical of potash ? ' 4. Give at least one reason in favor of each of the following sym- bols for salammoniac : NH 3 HCI and NH 4 CI. 5. Complete the following equations': ' A/J|C*/V (a.) HNCX + NH 3 = WH S0 4 + KHO=/f< (c.gHN0 8 + PbO = 6. What is the molecular weight of caustic potash ? 7. I explode a mixture of 4 I. of H and 5 I. of Cl. (a.) What volume of HCI is produced ? (b.) Which gas, and how much of it remains uncombined ? 8. (a.) What volume of N 2 0maybe formed by heating 30j7.,of' NH 4 N0 3 ? (b.) What will the volume be at 15C. and 740 mm. '(? 9. Assuming that H 2 O will absorb half its weight of NH 8 , calcu- late the amount of NH 4 CI necessary to the production of 3 Kg. of NH 4 HO. (3,/^f 10. What substances do the following symbols represent : CH 4 ; C 2 H 5 CI ; CHCI 3 ; ^ 2 ^( 5 \ 0; H-O-O-H ? 11. (a.) Write the empirical symbols and the systematic names for the following : a H 5 j- and pu 3 j- 0. (b.) What is the common ) 3 / name for the former ? 12. What is the object of having the room " warm " for Exp. 254 ? 13. Give the names and graphic symbols for PCI 3 and PCI 6 . - , i METALS OF THE ALKALINE EARTHS. CALCIUM: symbol, Ca ; specific gravity, 1.58; atomic weight, 39,9 m. c. ; quantivalence 2 and 4. 289. Calcium. Calcium compounds occur largely diffused in nature, especially the carbonate in the forms of calcite, chalk, marble, limestone, coral, etc. They are found in all animal and vegetable bodies. The metal was first obtained by Davy in 1808, by the electrolysis of its chloride. Calcium is a light yellow, ductile, malleable metal about as hard as gold. It is scarcely oxidizable in dry air. easily oxidizable in moist air, burns vividly with a very bright yellow light when heated to redness in the air and decom- poses water with evolution of hy- drogen. Note. The name, calcium, is from calx, the Latin name for lime. 290. Calci- um Oxides. Calcium monox- ide (lime, quick- lime, CaO) is pre- pared by igniting FIG. no. calcium carbo- nate. On the large scale, lime is " burned " from limestone 2QI METALS OF THE ALKALINE EARTHS. 24? placed in a kiln of rude masonry often built in the side of a hill, the process requiring several days. Lime is a white, amorphous substance about three times as heavy as water. It is infusible in even the oxy-hydrogen flame ( 397) but when so heated emits an intense light, known as the lime or calcium light (Exp. 49). It is largely used in making mortars and cements and, in the laboratory, for drying gases and liquids and for other purposes. (a.) In the lime-kiln, a limestone arch is built above the fire and the remaining limestone placed upon this arch from above. When the CaO has been burned, the kiln is allowed to cool, the CaO is re- moved and a new charge introduced. Improved kilns also are used in which the process is continuous, the charge being introduced from above and the CaO withdrawn from below. (&.) Pure CaO may be prepared by igniting crystallized calcite in a crucible with a perforated bottom, so that the C0 2 may be swept away as it is evolved. (c.) When CaO is exposed to the air, it absorbs H.0.and C0 2 and falls to a powder known as air slaked lime. (d.) Calcium dioxide (Ca0 2 ) has been prepared by precipitation from lime water with H 2 2 . 291. Calcium Chloride. Calcium chloride (CaCI 2 ) is easily prepared by the action of hydrochloric acid upon marble, and evaporation of the solution. It has a strong attraction for water, is deliquescent and is used for drying gases. (.) CaCI 2 may be crystallized from a saturated solution. These crystals (CaCI 2 , 6H 2 0), when mixed with snow, produce a tempera- ture of 48C. (Ph., 521). Experiment 2G3. Add a few drops of H 2 O to a small quantity of slaked CaO and rub it to a paste between the fingers. Its action can be felt as it actually dissolves or destroys a little of the skin. Experiment 864. Put 30 g. of recently burned CaO upon a saucer, hold the saucer in the palm of the hand and pour 20 cu. cm. of H 2 248 METALS OF THE ALKALINE EARTHS. upoii it. Notice the increase of bulk and the rise of temperature. Thrust a friction match iiito the crumbling mass. It will be heated to the point of ignition. Sprinkle a little gunpowder upon the slak- ing lime ; perhaps it will take fire. Experiment 265. Dip a piece of colored cambric or calico into a half ht3r of H 2 into which 15 g. of chloride of lime have been stirred. Notice the effect upon the color of the cloth. Then dip the cloth into very dilute HCI or H 2 S0 4 . Notice the effect on the color of the cloth. Wash the cloth thoroughly in H 2 0. 292. Calcium Hydrate. When fresh, well burned lime is treated with one-third its weight of water, the di- rect synthesis yields calcium hydrate [calcium hydroxide, caustic lime, slaked lime, Ca(HO) 2 > CaH 2 2 ] with the evolution of great heat (Ph., 524, 5). Calcium hydrate is a white, alkaline, caustic powder. It dissolves more easily in cold than in hot water, yielding an alkaline, feebly caustic liquid called lime water. Lime water readily absorbs carbon dioxide. Lime water containing solid particles of calcium hydrate in suspension is called milk of lime or cream of lime according to the consistency of the mixture. (a.) The power of absorbing C0 2 and H 2 S leads to the use of CaH 2 2 in the purifiers of gas works. Its caustic action leads to its use (as milk of lime) in removing the hair from hides for tanning. Its alkaline properties fit it for use in making an insoluble " lime soap" for stearine candle manufacture. Mixed with sand and H 2 0, it forms mortar, which absorbs CO 2 from the air and becomes a mix- ture of calcium hydrate and carbonate and sand that firmly binds together the bricks or stones between which it has been placed. (6.) When CaH 2 2 is exposed to the action of Cl, it forms " bleach- ing powder" or " chloride of lime " which is made in immense quan- tities. This substance may be considered a mixture of calcium chloride and calcium hypochlorite (CaCL + CaCI 2 2 ) or a double salt, CaOCI 2 , at once a chloride and a hypochlorite of calcium, ClOf ^ a ' (11^') ** * s sometimes called calcium chloro-hypo- chlorite, and graphically symbolized as follows : CI-Ca-0-CI. 2Q4 METALS OF THE ALKALINE EARTHS. 249 Experiment 2GG. Place a little lime water in a test tube and pass through it a stream of C0 2 . Notice the precipitation of CaC0 3 that renders the liquid turbid. Notice also that as the passage of C0 2 into the liquid continues, the latter becomes clear again, the precipi- tate being dissolved. Boil the clear liquid to expel some of the ab- sorbed CO 2> and the precipitate again appears. Test the liquid at each step of the experiment with litmus paper to determine whether it gives an acid or an alkaline reaction. 293. Calcium Carbonate. Calcium carbonate (CaC0 3 ) occurs in many forms, both crystallized and amorphous. The shells of oysters, clams and other mol- lusks are almost wholly calcium carbonate. .It forms the greater part of egg shells and is found in bones. It is found in enormous masses forming whole mountain ranges. It is barely soluble in water but more easily soluble in water charged with carbon dioxide. When cal- careous mineral waters are exposed to the air, they lose part of their carbon dioxide and, consequently, precipitate the calcium carbonate previously held in solution. Hence, the formation of stalactites, stalagmites, tufa, travertine, etc. All of the forms of calcium carbonate are easily acted upon by even dilute acids, the action being attended by effervescence due to the escape of the expelled carbon dioxide. > 294. Calcium Sulphate. Calcium sulphate (CaS0 4 ) is found in nature as the mineral anhydrite. The hydrated sulphate (CaS0 4 , 2H 2 0) is gypsum, which, when in the crystalline form, is called selenite. By heat- ing gypsum to about 120C., it parts with its water of crys- tallization forming plaster of Paris. When this plaster is mixed to a paste with water, it again unites with the water and becomes hard or " sets." Hence, its use as a cement and for making casts of various objects. Calcium sulphate 250 METALS OF THE ALKALINE EARTHS. 2Q4 is sparingly soluble in water. Water containing calcium sulphate or carbonate in solution is called " hard/' Ala- baster is a variety of gypsum. (a.) When soap (sodium or potassium stearate) is added to hard water, there is a metathetical reaction, resulting in the formation of an insoluble calcium or " lime soap " (calcium stearate), which rises as a scum upon the surface of the liquid. The soap can not perform its proper office until it has precipitated the calcium salt. Other agents are often used to precipitate the calcium compound and thus "soften" the water. 295. Calcium Phosphate. There are several calcium phosphates ( 242), the most important of which is bone-phosphate, Ca 3 P 2 8 . It is the chief inorganic constituent of the bones of animals. It is important as a source of phosphorus, and valuable, when ground to a powder, as a fertilizer. STRONTIUM: symbol, Sr ; specific gravity, 2.5 ; atomic weight, 873 m. c. ; quantivalence, 2 and 4. 296. Strontium. This rare metal closely resembles calcium in appearance and properties. It has two oxides (SrO and Sr0 2 ). It chiefly occurs in the sulphate (celestine, SrS0 4 ) and in the carbonate (strontianite, SrC0 3 ). BARIUM : symbol, Ba ; specific gravity, 4 ; atomic weight, 136.8 m. c. ; quantivalence, 2 and 4. 297. Barium. This rare metal closely resembles calcium in appearance and properties. Its melting point appears to be higher than that of cast iron. It has two oxides (baryta, BaO; and Ba0 2 ), occurs in nature as a sulphate (heavy spar, BaS0 4 ) and decomposes cold water. 297 METALS OF THE ALKALINE EARTHS. 251 EXERCISES. 1. Write the reaction for the burning of CaO. 2. Write the reaction for the preparation of CaCI^/J^fT 3. Write the reaction for preparing calcium hydroxide.^^W^* 4. Why is the formula for calcium hypochlorite CaCI 3 3 instead of CaCIO, the formula for hypochlorous acid being HCIO ? 5. When a current of C0 2 is passed through an aqueous solution of Ba0 2 , hydroxyl and BaCO 3 are formed. Write the reaction.^'? - 6. How much KN0 3 and H 2 S0 4 shall I need to prepare enough * HN0 3 to neutralize 5 Kg. of chalk? (!) 7. What is the property that chiefly distinguishes Cl and the ele- ments most like it from K and the elements most like it V 8. What is meant by the statement that caustic soda is formed upon the water type? 9. What are the characteristic properties of C 1 10. Write the empirical, typical and graphic symbols for common salt, caustic potash, baryta, sulphuric acid, acetic acid and marsh gas. 11. (a.) What is the weight of 1 I. of Ql? (b.) Of H g S? (c.) of co? /* vy,>-; hf 131 & }>9$#tf- 12. Compare and contrast P and As respecting their physical and 'chemical properties. 13. Symbolize the sulphates, nitrates, chlorides, chlorates, acetates, *&- bromides and bromates of Ca, Ba and Sr. 14. How much of each of Na ; NH 4 ; Sr and K is equivalent to one * ^JL atom of Ca? I 4fc- &. - -v- ^K-//-~ *c * t - // H- METALS OF THE MAGNESIUM GROUP. MAGNESIUM : symbol, Mg ; specific gravity, 1.75 ; atomic weight, 24 m. c. ; quantivalence, 2. 298. Magnesium. Magnesium compounds are widely and abundantly distributed but the metal is not found free in nature. It is prepared in considerable quan- tities by fusing together magnesium chloride (MgCl 2 ) and sodium, or from the double chloride of potassium and mag- nesium, called carnallite, a mineral found abundantly in the Stassfurt deposits ( 276). It has a silver white ap- pearance, preserves its lustre in dry air and tarnishes in moist air. It is readily acted upon by most acids with the evolution of hydrogen and, as it is perfectly free from arsenic, is often used, instead of zinc, in Marsh's test ( 246). It is found in commerce, usually in the form of ribbon. This ribbon, when ignited, burns with a bril- liant light of high actinic (Ph., 651) power. The mag- nesium light has been seen from a distance of twenty-eight miles at sea and has been used for photographic purposes. Experiment 267. Coil 15 cm. of Mg ribbon around a lead pencil. Change the pencil for a knitting needle or iron wire, hold the wire horizontal and ignite one end of the ribbon. The coil of Mg will burn to an imperfect coil of MgO. 299. Magnesium Oxide. Magnesium oxide (magnesia, MgO) is formed when the metal is burned in air. It may be prepared by the ignition of the magnesium salt of any volatile acid; e. g., the carbonate, nitrate or 302 METALS OF THE MAGNESIUM GROUP. 253 chloride. It is used in medicine and for making infusible crucibles, as it does not melt below the temperature of the oxyhydrogen flame. 30O. Magnesium Salts. Magnesium Chloride (MgCI 2 )is found in sea water, in many saline springs and as a constituent of carnallite. It is largely used in dressing cotton goods. Magnesium sulphate (MgS0 4 ) is found in nature as kieserite. The hydrated sait (MgS0 4 ,7H 2 0) is called Epsom salt, and is found in many mineral waters. It is used as a purgative and in dressing cotton goods. Magnesium carbonate (MgC0 3 ) occurs as native magnesite. A mix- ture of the carbonate and the hydrate (MgH 2 2 ) prepared by adding Na 2 C0 3 to a solution of MgCI 2 or of Epsom salt, is called magnesia ZINC : symbol, Zn ; specific gravity, 6.9 ; atomic weight, 65 rn.c.; quantivalence,2. 301. Sources of Zinc. Metallic zinc is not found in nature. The carbonate (smithsonite, zinc spar, ZnC0 3 ); the silicate (calamine, Zn 2 Si0 4 ); the sulphide (sphalerite, blende, ZnS) and the oxide (red zinc ore, zincite, ZnOj are found native in paying quantities. 302. Preparation. The zinc ore is first roasted and thereby converted to an oxide. This oxide is then smelted with half its weight of coal and the distilled zinc vapor condensed and purified. (tf.) There are several processes of smelting Zn, including the Eng- lish, Belgian and Silesian. In the English process, the roasted ore and coal are put into iron crucibles covered at the top and having an iron tube fitting into the bottom. The crucibles are heated in conical furnaces. The vaporized metal passes down the tube and is col- lected in vessels. This process is less economical than the others. (6.) In tlie Belgian process, fire clay cylindrical retorts, 1 m. long and 20 cm. in internal diameter are used. About 50 of these retorts are set in one furnace, slanting slightly from a horizontal direction so that the metal may run out. Each retort is provided with a taper- ing neck and a sheet iron condenser. The smelting is completed in eleven hours, two charges being worked per day. 254: METALS OF THE MAGNESIUM GROUP. 302 (O In the Silesian process, now generally adopted, fire day mufflers, M, M, about 1 m. long, are arranged side by side on the FIG. in. floor of a reverberatory furnace. The vaporized Zn passes out by the bent clay tube, A, and is received, as it condenses, in a vessel placed in the closed recess, 0. Metallic Zn, in the form of fine dust, mixed with ZnO, is also obtained. The mixture is called zinc dust ; it is a valuable reducing agent. (d.) The Zn is then remelted, cast into slabs or cakes and sent into the market under the name of Experiment 268. Mix 20 g. of zinc dust and 40 g. of powdered KN0 3 . (If you cannot get the zinc dust, pulverize granulated zinc, 21). Heat a small Hessian crucible to redness, remove it from the fire and place it in the ventilating closet or where the fumes that may be formed will be drawn into the chimney. By means of a ladle with a handle about 1 m. long, drop the mixed Zn and KNO 3 into the red hot crucible. . The Zn will burn with great energy at the expense of the of the KNO S . Experiment 269. Put a pinch of finely powdered blue indigo into a test tube, add half a teaspoonful of zinc dust or fine Zn filings and two teaspoonfuls of a strong solution of NaHO. Heat the mixture. The nascent H evolved changes the blue indigo (C 8 H 5 NO) to- white indigo (C 8 H 8 NO). 304 METALS OF THE MAGNESIUM GROUP. 255 Experiment 370. Dip a piece of \vliite cloth into the solution of white indigo. When it is exposed to the air, the reduced indigo is oxidized to the blue variety and the cloth is permanently colored. The color is " fast." Experiment 271. Dissolve 10 g. of lead acetate (sugar of lead) in 250 cu. cm. of H 3 and add a few drops of C 2 H 4 2 . In this solution, suspend a strip of Zn. The Zn and Pb will change places, leaving a solution of zinc acetate and a metallic " lead tree." The tree will be more beautiful if the ends of the Zn be slit into branches before immersion. The weights of the dissolved Zn and the precipitated Pb will be in the FIG. 112. ratio of their atomic weights. 3O3. Properties. Zinc is a bluish white, crystal- line metal. It is ductile and malleable at about 130C. or 140 P C., under which circumstances it may be drawn into wire or rolled into sheets or plates. At the ordinary tem- perature and at temperatures above 200C., it is brittle. The commercial article is seldom pure, generally contain- ing lead, iron and carbon, while traces of arsenic and an- timony are often found. Zinc dust is a valuable reducing agent. Zinc is readily acted upon by a boiling solution of sodium and potassium hydrates and by most acids, with the evolution of hydrogen. (Ph., 373, 374.) It melts at 410C., and distils at about 1000C. Pure zinc is not easily soluble in dilute sulphuric acid while impure zinc is thus soluble (Ph., 386.) Zinc is not much affected by air, either dry or moist. It readily precipitates most metals from solutions of their salts. (a.) Brass is an alloy of Zn and Cu. German silver is an alloy of Zn, Cu and Ni. (6.) Galvanized iron is simply iron coated with Zn. The term is a gross misnomer, as galvanic action is not involved in the process. 304L Zinc Compounds. Zinc oxide (ZnO) is 256 METALS OF TBE MAGNESIUM GROUP. 304 found as an ore in New Jersey. Its color is due to the presence of red oxide of manganese. Zinc oxide is known in commerce as zinc ivliite, and is prepared on a large scale for use as a paint. Zinc chloride (ZnCI 2 ) is formed by dissolving zinc in hydrochloric acid. It is nsed for pre- serving timber, as a caustic in surgery, in cleansing the surfaces of metals for soldering and, very largely, for the fraudulent purpose of weighting cotton goods. It is solu- ble in alcohol and very deliquescent. Zinc sulphate (white vitriol, ZnS0 4 , 7H 2 0) is used in medicine, in dyeing, and in galvanic batteries. GLUCINTJM: symbol, Gl ; specific gravity ,2.1; atomic weight, 9 m. c. ; quantivalence, 2. 305. Gin rill u m. This rare metal is also known as glucinium and as beryllium (symbol, Be). Its oxide is found in the mineral beryl. By fusing its chloride with potassium or sodium, the metal is formed as a dark gray powder which acquires a metallic lustre by burnishing. The metal may be made coherent by fusing this powder under sodium chloride. It has a silver white color and melts at a lower temperature than silver does. CADMIUM ; symbol, Cd ; specific gravity, 8.6 ; atomic weight, 112 m. c. ; molecular weight, 112 m. c. ; quantivalence, 2. 3O6. Cadmium. This rare metal occurs in nature associated with zinc ores. As it is more volatile than zinc, its vapor comes over with the first portions of the zinc dis- tilled. It forms compounds very similar to the corre- sponding zinc compounds. It has a tin white color, is susceptible of a high polish and gives a crackling sound when bent, as tin does. As its vapor density is 56, we con- clude that its molecule contains but a single atom. (a.) The statement that the vapor density of Cd is 56, means that the vapor is 56 times as heavy as H. Consequently (% 61) its mole- 307 METALS OF THE MAGNESIUM GROUP. 257 cule weighs 56 times as much as the H molecule or 112 m. c. But this molecular weight is the same as its atomic weight. Hence, the inference above stated. 3O7. The Magnesium Group. The metals of this group decompose water only at a high temperature and glucinum, probably, not at all. They are volatile and burn with a bright flame when heated in the air. Each mem- ber of the group forms only one oxide and one sulphide. ' EXERCISES. 1. (a.) In the preparation of Mg from magnesium chloride and so- dium, what is the other product of the reaction? (&.) How may it be separated from the metal ? (c.) What is the other product when it is prepared from carnallite ? 2. How much ZnO can be obtained by oxydizing 100 g. of Zn ? What weight of C0 a is yielded by the burning cf 1 I. of CH 4 ? If 150 cu. cm. of and 400 cu. cm. of H are mixed and ex- ploded, (a.} what volume of steam is produced ? (&.) Which gas, and now much of it, remains in excess? , '& 5. By a series of electric sparks, I decompose 100 cu. cm. of NH 3 , add 90 cu. cm. of and explode the mixture. Give the name and volume of each of the remaining gases. 6. Write the name and full graphic symbol for S-(S0 2 )-(HO) - S-(S0 8 )-(HO)' 'u- >-o-$-0-V-d'~tf-C METALS OF THE LEAD GROUP. LEAD: symbol, Pb ; specific gravity, 11.37; atomic weight, 206.4 m. c. ; quanticalence, 2 (and 4). SOS. Source of Lead. Lead is seldom found free in nature but its sulphide (galena, galenite, PbS) is quite abundant and is, by far, its commonest ore. The lead sul- phide is generally associated with silver sulphide. 309. Preparation. The smelting of lead from its ore is a simple process. The ore is first heated in an open reverberatory furnace, in which one part of the sulphide is oxidized yielding lead oxide (PbO) and sulphur dioxide while another part is oxidized to lead sulphate. The furnace is then closed and heated to a higher temperature when the oxide and sulphate just formed act each upon a part of the still undecomposed ore, yielding metallic lead and sulphur dioxide. 310. Properties. Lead is a metal so soft as to be easily cut with a knife or indented with a finger nail and to leave a streak when rubbed upon paper. It has con- siderable malleability and little ductility. Eepeated fusion renders it hard and brittle, probably by oxidation. When freshly cut, it has a bluish gray color and a bright lustre which is quickly dulled by oxidation. It melts at 334C. and may be crystallized by slowly cooling a large quantity of the melted metal and pouring out the still liquid por- 313 METALS OF THE LEAD GROUP. 259 tion. It is very slightly acted upon by cold sulphuric or hydrochloric acid ; its best solvent is nitric acid. (a.} Potable waters in general and especially well waters contain- ing ammoniacal salts, often due to decaying organic matter, act upon lead with the formation of compounds that act as cumulative poisons. In many cases, the use of lead water pipes is very dangerous for this reason. If, upon examining the inner surface of a lead pipe that has been thus used, it is found to be bright it may be known that danger- ous soluble salts have been formed and carried away with the water. " A word to the wise is sufficient." (6.) In the presence of air and moisture, lead is attacked by even feeble acids like acetic or carbonic acid. Hence, the use of cooking utensils that are made of lead or that contain lead even in the form of solder or as an adulteration of otherwise harmless substances ( 388, &.) sometimes leads to the formation of poisonous lead com- pounds. When these are taken into the system, they unite with cer- tain tissues of the body and may accumulate until the quantity is sufficient to produce poisoning ( 315). 311. Uses. Lead is largely used for many purposes on account of its softness, pliability, easy fusibility and its comparative freedom from chemical action with water and most of the acids. 312. Lead Oxides, Lead suboxide (Pb 2 0) is also' called plumbous oxide. Lead monoxide (PbO) is also called plumbic oxide but more frequently, litharge. It is prepared on the large scale by highly heating me 1 ! ted lead in a current of air. It is used in the manufacture of glass. Lead sesquioxide (Pb 2 3 ) is considered to be a compound of the monoxide and dioxide. Eed lend or minium (Pb 3 4 ) is largely used as a paint and in the manufacture of flint glass. Lead dioxide (Pb0 2 ) or plumbic peroxide is most easily pro- duced by treating red lead with nitric acid. 313. JLeatl Sulphide. Lead sulphide (PbS) occurs native as galenite or galena and may be prepared artificially by passing hy- drogen sulphide into any solution of a lead sa?t. The precipitate thus formed is of a deep but varying color. This color, together with the insolubility of the precipitate is of use in detecting the presence of lead. 260 METALS OF THE LEAD GROUP. 314 314. Some L.ca V f w 327 SILVER. tW* '-v- SILVER. Symbol, Ag ; specie gravity, 10.5 ; atomic weight, 107.6 m. c. ; guantivalence, 1 and 3. 325. Source. Silver is a widely diffused and some- what abundant element and lias been known from the earliest times. It is found native, sometimes in masses weighing several hundred pounds and often alloyed with copper, mercury and gold. It more commonly is found as a sulphide, mixed with other metallic sulphides. Its most abundant source is argentiferous galena although the car- bonates have been found in richly paying quantities, especially in the Leadville (Colorado) mining region. 326. Preparation. The processes of preparing metallic silver from its ores are numerous and widely different, depending largely, in any given case, upon the nature of the ore, the position of the mine, the price of labor, fuel, etc. 327. Properties. Silver is a beautiful, brilliant white metal, harder than gold, softer than copper, exceed- ingly malleable and ductile and the best known conductor of heat and electricity. It melts at 1040C. and then ab- sorbs 22 times its volume of oxygen. When the melted silver cools quickly, the oxygen escaping from the interior of the mass breaks through the hardening crust driving out some of the molten metal and giving the phenomenon known as "spitting" of silver. The metal is unaltered in the air and resists the action of hydrochloric and cold sul- phuric acid but dissolves readily in nitric acid. {a.) Ag is so malleable that it may be formed into leaves so thin 268 SILVER. 327 that 4000 measure only 1 mm. in thickness ; so ductile that 1 g. of it may make 1800 m. of wire and so tenacious that a wire 2 mm. thick will sustain a weight of more than 80 Kg. (b.) Ag unites slowly with the halogen elements and more readily with S and P. The tarnishing of Ag is generally due to the formation of a silver sulphide by the action of H 2 S present in the atmosphere. 328. Uses. Owing to its susceptibility of high polish, its permanency and other properties, silver is much used for jewelry, plate and coin. Owing to its softness, it is generally hardened with copper. American and French coin contain ten per cent, and English coin 7.5 per cent, of copper. It is used for chemical utensils as it is not acted upon by the fused hydrates of the alkali metals as glass and platinum are. 329. Oxides. There are three oxides of silver ; silver tetrant- oxide or argentous oxide (Ag 4 0) ; silver hemioxide or silver oxide (Ag 2 0) and silver peroxide or dioxide (Ag 2 2 ). When silver oxide (Ag 3 0) is digested with ammonia, it forms a very explosive, black powder, known as fulminating silver. Its composition has not yet been satisfactorily determined. Experiment 276. Fill three test tubes one-third full of H,0 and pour into each a few drops of a strong solution of AgN0 3 . Add 2 or 3 cu. cm. of a solution of NaCI to the contents of the first tube and shake it vigorously, AgCI will be precipitated as a dense, white curdy mass. Add 2 or 3 cu. cm. of a solution of KBr to the contents of the second tube and shake as before; a yellowish precipitate of AgBr will be thrown down. Add 1 or 2 cu. cm. of a solution of KI to the con- tents of the third tube and shake as before ; yellowish, flocculent Agl will be formed. Experiment 277. Try to dissolve one-third of each of these pre- cipitates separately in HNO 3 . They will not thus dissolve. Experiment 218. Treat a second third of each precipitate with (NH 4 )HO. Determine which dissolves most easily and which least easily. Experiment 279. Treat the last third of each precipitate with a strong solution of sodium thiosulphate ( 158, &). Each of the halo- gen salts is quickly dissolved. 332 SILVER. 269 Experiment 280. Precipitate more AgCI from a solution of AgN0 3 by HCI or a solution of NaCI. Filter the solution and wash the pre- cipitate retained upon the filter thoroughly with H 2 0. Open the filter, spread the curdy AgCI evenly over it and expose it to the direct rays of the sun. (Ph., 651.) The white precipitate quickly changes to violet, the color deepening with continued exposure. Note. The last five experiments illustrate the principal processes of photography. 330. The Silver Haloids. Silver chloride (AgCI) is found native in semi- transparent masses, called horn silver. It may be prepared by precipitation from a solution of any silver salt by a solution of hydrochloric acid or any other chloride. It is insoluble in water and acids but easily soluble in ammonia water. Silver iodide or bromide is precipitated from a similar solution by a solution of an iodide or bromide. These compounds are much used in photography. 331. Silver Sulphide and Cyanide. Silver sulphide (Ag 2 S) is an important silver ore and is formed artificially by the action of sulphur or hydrogen sulphide upon the metal. Silver cyanide (AgCN) is a white curdy precipitate, insoluble in dilute nitric acid but soluble in ammonia water or in solutions of the cyanides of the alkali or alkaline earth metals. It is used in electro-plating (Ph., 399, a). (a.) When a silver spoon is left for a time in an egg or in mustard it becomes blackened by the formation of silver sulphide. Hence, silver egg-spoons are often gilded. 332. Silver Nitrate. Silver nitrate (AgN0 3 ) is prepared on a large scale by dissolving silver in dilute nitric acid and evaporating to crystallization. It is found in commerce in crystals. When fused and cast into sticks, it is called lunar caustic. In this form, it is used in surgery, 270 SILVER. 332 acting as a powerful cautery. Pure silver nitrate is not altered by exposure to sunlight, but when in contact with organic substances it blackens, forming insoluble com- pounds of great stability. It is, consequently, used in making indelible inks and hair dyes. It is also used in medicine and in photography. Like all of the other solu- ble silver salts, it is poisonous. 333. Other ilver Salt. Silver sulphate (Ag 2 S0 4 ); silver phosphate (Ag 3 P0 4 ) and silver carbonate (Ag 8 C0 3 ) are among the many important silver salts. iWiWMwUb EXERCISES. 1. Why do silver coins become blackened when carried in the pocket with common friction matches ? 2. 564 Kg. of lead sulphife will yield how much Fb ? 3. At a very high temperature, AgoO may be decomposed much as2^4 J the HgO was in Exp. 56. Write the reaction in molecular symbols. 4. What action have the alkalies upon Ag ? /> i { ic&'^- 5. If recently precipitated and moist AgC I be placed upon a sheet of Zn, a dark color will soon appear at the edge of the salt. The chloride will soon be converted into a dark gray powder of finely divided Ag. Explain. 4 5 d ' t"**^ ^ "' * 6. The change mentioned in Exercise 5^ will be much more rapid if the AgCI be moistened with HCI. Why? 7. When AgCI is fused with an alkaline hydrate, the chloride is reduced to a metal, a non combustible gas is set free and an alkaline chloride is formed. What is the gas? S. If a silver dime be dissolved in HNO$, the solution will be blue. A solution of AgM0 3 is colorless. Whence the blue <- f 10. (a.} How many cu. cm. of VI may be obtainecf firom 1 1. of NH 3 ? (&.) Of N ? (c.) How may the elementary grases be obtained from the compound ? (d.) How may the eudiometer be used to free . the N from the H ? 11. If HCI be used instead of cream of tartar with HNaC0 8 , what residue would remain in the biscuit '** 337 MERCURY. 271 ME RCU RY. Symbol, Hg ; specific gravity, 13.6 atomic weight, 200 m. c. ; molecular weight, 200 m. c ; quant ivalence, 2. 334. Source. Mercury, or quicksilver, is found native in small quantities but chiefly as a sulphide (HgS) called cinnabar. The best known deposits of cinnabar are at Idria in Austria, Almaden in Spain, and New Almaden in California. Mercury is also brought from China and Japan. 335. Preparation. The sulphide is generally mixed with quicklime or iron turnings and distilled. The sulphur unites with the lime or iron and the mercury vapor is condensed by being brought into contact with water. 336. Properties. Mercury is a silver white metal, liquid at the ordinary temperature. It vaporizes slowly at ordinary temperatures, boils at about 357C. and freezes at 39. 4C., becoming a ductile, malleable, white solid which can be cut with a knife. The liquid is scarcely affected by exposure to the air but, when heated for a long time in the air, it oxidizes. It is soluble in strong, boiling sul- phuric acid but its best solvent is nitric acid. (a.) The vapor density of Hg is 100. We, consequently, conclude that the molecule of this element contains but a single atom ( 806, a). 337. Uses. Mercury is largely used in the construc- tion of thermometers, barometers and other physical and chemical apparatus, for the collection of gases that are 272 MERCURY, ETC. 337 soluble in water, for the preparation of mirrors, for the ex- traction of gold and silver from their ores, and for the preparation of various mercurial compounds. Expcrimen^ SSL Prepare an amalgam by adding bits of Na to Hg slightly warmed in an evaporating dish. 338. Amalgams, Compounds or mixtures of the metals with mercury are called amalgams. They are. generally formed by the direct union of the two metals. Many of these amalgams, or mercury alloys, are largely used in the arts. Tin amalgam is used in " silvering " mirrors ; cadmium amalgam, which gradually hardens, has been used for filling teeth ; zinc and tin amalgam is used for coating the rubbers of electric machines (Ph., 322, 345). 339. Mercury Oxides. Mercury forms two oxides, mercurous oxide (suboxide of mercury, gray oxide of mercury, Hg 2 0) and mercuric oxide (red oxide of mercury, red precipitate, HgO). The latter is a powerful poison. It is prepared by heating mercury for a long time in air or, on the large scale, by heating an intimate mixture of mer- cury and mercuric nitrate. It decomposes, at a red heat, into its elementary constituents (Exp. 56). 340. Mercury Sulphide. This compound (HgS) is largely found native as cinnabar. When prepared artificially, it is called vermillion. It is of a brilliant red color and is used as an oil and water-color paint, in lithographers' and printers' inks and in coloring sealing-wax. 341. Mercury Salts. Mercury forms two series of salts, corresponding to the two oxides, viz., the mercurous salts and the mercuric salts. The members of the two series are widely different in their properties. The mer* 343 MERCURY, ETC. 273 curie compounds are more powerfully poisonous than are the mercurous. (a.) Mercury is generally considered a dyad, even in the mercurous compounds. In such cases, the quantivalence is explained by assum- ing that the double atom (Hg.,)" partly saturates itself as is shown Hg-CI by the graphic symbol, | . A similar explanation may be made Hg Cl concerning the quantivalence of Cu. (6.) Mercury may be detected in almost any soluble mercurous or mercuric salt by placing a piece of clean Cu into a solution of the salt. 343. Mercurous Salts. The most important mer- curous salt is mercurous chloride (calomel, Hg 2 CI 2 ). It is tasteless, odorless and insoluble in water and is, even now. largely used in medicine. It is commonly prepared by sublimation from an intimate mixture of mercury and mercuric chloride. (a.) Mercurous nitrate [Hgo(N0 3 ) 2 ] is formed by the action of cold, dilute HN0 3 on Hg. Mercurous sulphate (Hg 2 S0 4 ) is formed by heating concentrated H 2 S0 4 with an excess of Hg or by precipitat- ing Hg 3 (N0 3 ) 2 with H 2 S0 4 . (&) Hg 2 Br 2 may be precipitated by adding HBror KBr to a solution of Hg 2 (N0 3 ) 2 . Similarly, Hg 2 I 2 may be precipitated by adding KI to a solution of Hg 2 (N0 3 ) 2 . It is also formed when iodine is rubbed with the right proportion of Hg, a small quantity of C 2 H 6 being added. It is a green powder and gradually decomposes into HgI 2 and Hg. Experiment 282. Place a drop of a solution of Hg 2 (N0 8 ) 2 or of corrosive sublimate upon a clean copper coin. Rub the drop over the coin and Hg will be deposited upon the Cu. 343. Mercuric Salts. Mercuric chloride (corro- sive sublimate, HgCb) is a powerful poison. It coagulates albumen, forming an insoluble compound, in consequence of which the white of eggs ( 223) furnishes the best an- tidote in case of poisoning by this salt. It unites with many other organic substances to form insoluble, stable 274 MERCURF, ETC. 343 compounds and is used in preserving animal and vegetable tissues from decay. It is somewhat soluble in cold water and easily soluble in hot water. It is prepared by sublim- ing a mixture of mercuric sulphate and sodium chloride. (a.) Botanical and zoological specimens are preserved from decay and from the attacks of insects by brushing over them a solution of HgCI 2 in C 2 H 6 0. (&.) Mercuric nitrate [Hg( NO 3 ) 2 ] is prepared by boiling Hgin HN0 3 until a portion of the liquid no longer gives a precipitate with NaCI. Mercuric sulphate (HgS0 4 ) is prepared by heating Hg with at least V s times its weight of H 2 S0 4 . It is decomposed by heat into Hg 3 S0 4 , S0 2 , O and Hg. (c.) Hg combines directly with Br, forming HgBr 2 and evolving heat. When Hg is rubbed in a mortar with I and a small quantity of CoH 6 0, it forms HgI 2 and evolves heat. It may be precipitated by adding KI to a solution of HgCL. It is a, scarlet powder. (See E 5 ,,8.) v/9r.*f./.il.*}m .? j 1. An old process of preparing Hg 3 CI 2 was to sublime a mixture that gave this reaction : HgS0 4 + Hg + 2NaCI = Na 2 S0 4 +Hg 2 CI 2 . (a.) Write this equation in full molecular symbols. (&.) What weight of metallic Hg is needed thus to combine with 1 Kg. of NaC! ? 2. Is Hg(CN) 2 a mercurous or a mercuric compound? What is its name ? 3. Is cinnabar a mercurous or a mercuric compound ? 4. Zinc nitrate and potassium carbonate react as follows : Zn(N0 3 ) 2 + K 2 C0 3 = ZnC0 3 + 2KN0 3 . ow much Zn(N0 3 ) 2 is required to give 103.17 g. of ZnC0 3 ? 5. How much ZnC0 3 may be obtained from 156 g. of Zn(N0 3 ) 2 ? How much KoC0 3 is needed to decompose 75 g. of Zn(N 7. Wliat quantity of KN0 3 will result? f 8. How much K 2 C0 3 must be used to obtain 54 g. of ZnC _ 9. How much KN0 3 will be produced?/^^f / Mfaft+j 10. It is said that 1 sq. m. of leaf in sunlight will decompose 1 of CO 2 per hour, (a.) What weight of C will be assimilated in an hour by 1,000,000 trees, each of which has 100,000 leaves, each leaf measuring 25 sq. cm.? (&.) What will be the volume of the carbon assimilated, assuming that its specific gravity is 1 *4 i leaf arbon . \i METALS OF THE ALUMINUM AND CERIUM GROUPS. ALUMINUM: symbol, Al ; specific gravity, Z. 6 ; atomic weight, 27.3 m. c,; quantivalence of the double atom (AI 2 ), 6. 344. Source. Aluminum (or aluminium) ranks third among the elements and first among the metals in quantity and extent of distribution. It is not found native; its oxide is found in the minerals emery and corundum, among the purer varieties of which are the ruby and the sapphire ; its fluoride, in cryolite; its silicates, in the feldspars and micas, the disintegration of which, by weathering, gives rise to the several kinds of clay. It is also found in the topaz, emerald and garnet. It consti- tutes about one-twelfth of the earth's crust, and is contained in all fertile soils but is not taken up by any plants except a few cryptogams. 345. Preparation. Notwithstanding the abundance of aluminum compounds, no cheap method of preparing the metal has yet been found. It is generally prepared by fusing together, in a reverberatory furnace, 100 Kg. of an artificial double chloride of aluminum and sodium with 35 Kg. of sodium, adding 40 Kg. of cry- olite to act as a flux. 346. Properties. Aluminum is a remarkably light and sonorous metal. It is of a bluish white color and susceptible of a bright polish. It .is tenacious and very malleable and ductile. It is best worked at a temperature of from 100C. to 150C. It does not readily oxidize in air, is insoluble in nitric acid and is not easily soluble in 276 ALUMINUM, ETC. 346 sulphuric acid. Its best solvent is hydrochloric acid al- though it dissolves easily in boiling solutions of the alkali hydrates. 347. Uses. The lightness, lustre, strength, unalter- ability in air and hydrogen sulphide, ease of working, sonorous and non-poisonous qualities of aluminum would lead to an extensive use of the metal were it not for its high price. It is used chiefly in making delicate balances, light weights, opera glasses and other instruments calling especially for lightness and moderate strength. Aluminum bronze (90 per cent. Cu + 10 per cent. A!) is very hard and malleable, yields fine castings, lias the tenacity of steel, the color of gold and takes a high polish. 3 18, Aluminum O\icle. Aluminum oxide (alumina, AI 2 3 ) occurs native in corundum, ruby, sapphire, etc. Its crystals are second in hardness only to the diamond. An impure, granular variety is called emery. 349. Other Aluminum Compounds The most im- portant of the aluminum compounds are the silicates, some of which have been mentioned. Common alum is a double sulphate of alu- minum and potassium [AI 2 (S0 4 ) t , + K 2 S0 4 + 24H 2 0]. Ammonium alum, now becoming common, differs in composition by having am- monium sulphate [(NH 4 ) 3 S0 4 ] in place of the potassium sulphate. Cryolite is a double fluoride of aluminum and sodium (AI 2 F 6 + 6NaF). A deposit 80 feet thick and 300 feet long is known on the west coast of Greenland. INDIUM: symbol. In; specific gravity, 7.4 ; atomic weight, 1134 m. c. 35O. Indium. Indium is a rare metal discovered in blende by means of the spectroscope in the year 18C3. It is white, non-crystalline, easily malleable and softer than lead. It dissolves slowly in hydrochloric or dilute sul- phuric acid but easily in nitric acid. 353 GALLIUM, ETC. 277 GALLIUM: symbol, Ga; specif c gravity, 5.9; atomic iceijht, 69.8 m. c. 351. Gallium. Gallium is a rare metal, discovered in blende by means of the spectroscope in the year 1875. It is bluish white, tough, may be cut with a knife and fuses at the remarkably low temperature of about 30C. It is not easily soluble in nitric acid but dissolves readily in dilute hydrochloric acid or an alkaline hydrate solution with the evolution of hydrogen. 353. The Aluminum Group. The metals of this group form feebly basic sesquioxides. Their sulphates form double salts with the sulphates of the alkali metals. Common alum is a familiar example of these double salts. They crystallize in regular octohedrons. (a.) The apparent quantivalence of these elements may be seen in the symbols of their compounds, in which the double atom of each metal acts as a hexacl. Some of these known compounds are sym- bolized thus : A! 2 3 AI 3 S 3 AI 3 CI 6 AI 2 (S0 4 ) 3 AI 2 (N0 3 ) 6 In 2 3 In 2 S 3 In 2 CI 6 In 2 (SO 4 ) 3 In 3 (N0 3 ) 6 Ga 2 3 Ga 2 S 3 Ga 2 Cl a Ga 2 (S0 4 ) 3 Ga 2 (N0 3 ) 6 V 353. The Cerium Group. This group consists of six rare metals, the separation of which, one from the other, is very difficult. Two of them, erbium and terbium, have not yet been isolated. The metals of this group are contained, chiefly as silicates, in several rare minerals found in Scandinavia, Siberia and Greenland. Cerium is the best known. It is malleable and ductile and, when it is scraped with a knife or struck with a piece of flint, the metallic particles struck off burn with great brilliancy. Cerium burns in a flame with a light more brilliant than that of magnesium. It forms both cerous and eerie com- 278 THE CERIUM GROUP. 353 pounds. When these metals are present, they are easily distinguished by means of the spectroscope. (a.) The following table exhibits the leading known properties and compounds of these metals : If ! Elements. g *i 7. Write the 'g a tetrad. f'H in 10 #. of be t: METALS OF THE IRON GROUP. r. IRON. Symbol, Fe ; specific gravity, 7.8 ; atomic weight, 56 m. c.; quan- ticalen.ce, 2, 4 and 6. 354. Occurrence. Iron, the most important of all the metals, is seldom found native. Metallic iron of me- teoric origin has been found. This element is widely dis- tributed, traces of it being found in the blood of animals, in the ashes of most plants, in spring, river and ocean waters, and, in fact, in nearly all natural substances. Its ores are numerous, abundant and comparatively pure. (a.) The most important iron ores are specular iron or hematite (Fe 3 3 ); limonite or brown hematite [Fe 4 3 (HO) G ] : magnetite or magnetic iron (Fe 3 4 ) ; spathic iron (FeC0 3 ) and clay iron-stone or black-band iron-stone, which is a spathic iron containing clay or sand with other substances and generally found as nodules or bands in the coal measures. (&.) The value of an iron ore often depends more upon the nature of its impurities than upon its percentage of Fe. 355. Calcination. The hydrate, the carbonate and the " black-band " iron ores are generally prepared for smelting by roasting them. In this way the water and carbon dioxide are expelled, the ores are oxidized and rendered more porous, while any sulphides that may be present are oxidized and the sulphur driven off. 280 IB ON. 356 356. Preparation ; Direct Process, The na- tive or artificial oxides, are sometimes reduced in " bloomery forges " of simple construction. The broken ore is heated with charcoal, the fire being supplied with a hot-air blast. The charcoal deoxidizes the ore, the reduced iron collects as a pasty mass called " the bloom" which separates from the fusible mass called " slag." The "bloom " needs only to be hammered to yield a good quality of wrought iron. The process is simple and time-honored but expensive on account of the quantity of fuel consumed and of iron lost in the slag. 357. Preparation; Indirect Process. The indirect process of forming wrought or malleable iron con- sists of two distinct stages : 1st, the production of cast iron from the ore ; 2d, the production of wrought iron from the cast iron. 358. Cast Iron. This is a carbonized, fusible pro- duct of the blast furnace, which will soon be described. The preparation of cast iron involves four steps. The first is the preliminary calcination of the ore for the pur- poses mentioned in 355. With some ores, this step is not necessary ; in other cases, it is effected in the upper part of the blast furnace. The second step is the reduction of the oxide to the metallic state by heating it with carbon. The third step is the separation of the silicious or calcare- ous impurities of the ore by fusion with some other sub- stance, called a flux, to form a fusible slag. The fourth step is the carbonizing and melting of the iron. This ad- dition of the carbon renders the product more easily fusi- ble. The melted iron is finally run into rough moulds and forms semi-cylindrical masses, known as pig-iron. 359. The Blast Furnace. The blast furnace 359 IRON. 281 (Fig. 113) is a shaft of fire-brick and masonry, often cased in iron plate. It is from 50 to 90 feet in height and from 14 to 18 feet in diameter at the "belly" or widest part. Alternate layers of coal, coke, flux and ore are introduced from above as the heated mass settles in the furnace and FIG. 113. the molten iron and slag are drawn off below. With ores that contain siliceous impurities, the flux is limestone; with ores that contain calcareous impurities, the flux is clay or of a siliceous character. The fusible silicate formed by the union of the flux and the impurities of the ore con- 2S2 IRON. 359 stitnte the slag. A blast of hot air is forced in at the hearth, through pipes, t t called tuyeres (pronounced tiveers) and the combustion thus sustained and invigorated. The melted iron settles to the crucible or lowest part of the hearth while the melted slag floats upon its surface and overflows a dam in an almost continuous stream. When the crucible is full of molten metal, the latter is drawn off through a tapping hole which is, at other times, stopped with sand. (a.) The throat of tlie blast furnace is closed with a cup and cone arrangement, as shown in Fig. 113. The cone, b, is lowered by a chain when a charge is to be introduced. When & is raised against the cup, a, the throat of the furnace is closed and the escape of the blast furnace gases into the air is prevented. These gases consist of very hot hydrocarbons with H, CO, C0 2 , \\,etc. These heated gases, some of which are combustible, are conveyed by pipes from the throat of the furnace and utilized for heating the tuyeres and the boilers for steam power purposes. (&.) The chemical changes that take place in the blast furnace are of great interest and have been carefully studied, but our knowledge of them is still far from complete. At the lower part, where the temperature is highest, the fuel burns to C0 2 ; in the widest part of the furnace, the C0 3 is reduced by the glowing C to CO ; at a point still further up, where the temperature is from GOO'C. to 900C. the CO reduces the ore to a spongy mass of metallic iron. As the spongy metal descends to the bottom part of the furnace, near the bolly where the temperature is from 1000C. to 1400C., it takes up C, becoming thus more fusible, melts completely and runs down into the crucible below the level of the mouth of the tuyeres. In the meantime, the fusible slag has been formed and melted. It then floats on the surface of the heavier iron in the crucible and thus pro- tects the metal from the oxidizing action of the blast. (c.) Cast iron is generally contaminated with S, Si, P, and fre- quently with Mn, and contains from two to six per cent, of C. (d.) Pig iron includes while cast iron, gray cast iron and several in- termediate varieties called mottled cast iron. White cast iron con- tains all of its C in chemical union. When it is dissolved in HCI or H 2 S0 4 , various hydrocarbons are formed that give a disagreeable odor to the H evolved. In gray cast iron, part of the C crystallizes IRON. 283 out in cooling, forming graphite, which is left in the form of black scales when the iron is dissolved in an acid. White cast iron con- tracts on solidifying ; gray ca&t iron expands on solidifying and is, therefore, the better adapted for foundry use although it is less easily melted. Spiegeleisen is a variety of white cast iron very rich in C, and containing Mn. It is very hard and crystalline and is used in the Bessemer process of steel manufacture. When it contains 25 per cent . or more of Mn it becomes granular and is called ferro- manganetz. 36O. Wrought Iron. Cast iron is changed to wrought iron by a process called puddling, in which most of the carbon, silicon, sulphur and phosphorus of the cast iron is burned out. Wrought iron contains less than half of one per cent, of carbon, its malleability increasing and its fusibility decreasing as the quantity of carbon di- minishes. It may be welded at a red heat. (a.) A puddling furnace is shown in elevation in Fig. 114 and in FIG. 114. section in Fig. 115. The charge of pig iron and, generally, a quan- 284 IRON. 360 tity of iron scale or other iron oxide, are placed in the bed, h, sepa- rated from the fire grate by the fire bridge, &, and from the chimney by the flue bridge, d. A strong draft is furnished by the chimney and controlled by a damper at the top of the chimney, which dam] er may be opened or closed by the workman. After the charge has FIG. 115. been melted, it is vigorously stirred or puddled, and the C, S, Si and P thus removed The iron becomes less easily fusible by the ' decarbonizing. The pasty mass is then carried from the furnace, the fusible slag removed and the porous Fe welded into a solid mass by hammering or squeezing. Experiment 283. Place about 15 g. of pulverized Fe 2 3 in the bulb of the tube, c, Fig. 116. Pass a current of dry H through the bul b tube. FIG. 116. When all of the air has been driven from the apparatus, heat the oxide to redness. When it has been reduced to a black powder of 362 IRON. 285 metallic Fe, remove the lamp and allow the contents of the bulb to cool in a current of H. Fe 3 3 + 3H 2 = Fe 2 + 3H 2 0. This black powder may be set on fire by a lighted splinter. It oxidizes so easily, that it will take fire if emptied from the bulb tube into the air while it is still hot. 361. Properties of Iron. Iron may be prepared in a pure state by reducing the oxide with hydrogen or car- bon monoxide. In the compact state, it is ductile, malle- able, tenacious and highly magnetic. It does not oxidize in dry air at ordinary temperatures. When heated in air, an oxide forms. This " scale oxide" is beaten off by ham- mering and may be found in considerable quantities about a blacksmith's anvil. Iron oxidizes or rusts rapidly in moist air. It is readily acted upon by dilute hydrochloric, nitric or sulphuric acid. It fuses at a white heat but soft- ens before it melts. In this softened state it may be welded. Sand or borax is sprinkled upon the heated sur- faces that are to be united and a fusible slag is thus formed with the coating film of oxide. When the two pieces of iron are then hammered together, the slag is driven out leaving clean surfaces of iron in contact. The blows of the hammer bring the metallic particles within the range of molecular attraction (Ph., 46, a), cohesion binds them fast and the iron is welded. (a.) Commercial iron is never pure. If P is present as an impurity, the iron is brittle when cold and is said to be " cold-short." The presence of S renders the iron brittle when hot ; the iron is then said to be " red short." 362. Oxides of Iron. Iron forms three well- known oxides; ferrous oxide (iron monoxide, FeO), ferric oxide (iron sesquioxide, Fe 2 3 ) and ferroso-ferric oxide 286 IRON. 362 (magnetic oxide of iron, Fe 3 4 ). The ferric and mag- netic oxides are found native as iron ores. (a.) FeO may be prepared by heating ferrous oxalate in a close ves- seXor by passing H over Fe 8 3 heated to 300C. If exposed to the air within a few hours after its preparation, it oxidizes so rapidly as to take fire. (&.) Fe 2 :} is one of the most important iron ores. This oxide is prepared artificially for use as a paint. A fine variety is known as jeweller's rouge, and is used for polishing glass and metals. Another artificial variety is called crocus, and is also used for polishing metals. (c.) Fe 3 4 is found in large quantities as the richest of iron ores. Many specimens attract iron and are called loadstones (Ph., 302). Scale oxide is chiefly Fe 3 4 . We may consider Fe 3 4 as a mixture or compound of FeO and Fe 3 s . Experiment 284. Cover a teaspoonful of fine iron filings with three or four times its volume of dilute H 2 S0 4 . When the evolution of H ceases, pour off the clear liquor, add a few drops of strong HN0 3 and boil the liquid. The yellowish-red color is due to the presence of ferric sulphate. Add N H 4 H to the solution and shake the liquids together. A red precipitate of ferric hydrate will be formed ; it may be collected upon a filter. 363. Iron Hydrates. -Fm-o^s hydrate (FeH 2 2 ) is obtained by treating a solution of a pure ferrous salt with potassium or sodium hydrate in absence of air. The precipitate thus formed is an unstable, white powder, which rapidly oxidizes with change of color, evolution of heat and, sometimes, incandescence when exposed to the air. Ferric hydrate (Fe 2 H 6 6 ) is prepared by precipi- tating a moderately dilute solution of a ferric salt(e.#., Fe 2 CI 6 ) with an excess of ammonia water. When freshly jprepared, it is one of the best antidotes for arsenic ( 247). f\ 364. Iron Sulphides. Iron and sulphur form two well-known compounds, iron monosulphide (FeS) and iron disulphide (FeS 2 ). Iron monosulphide is formed by di- 366 IRON. 287 rect union of its constituents. A roll of brimstone may be made to penetrate a red hot plate of steel or wrought iron with formation of melted sulphide. It is generally prepared by gradually throwing a mixture of three parts of iron filings and two parts of sulphur into a red hot cru- cible. It is the cheapest source of hydrogen sulphide and, hence, very important. Iron disulphide occurs widely dis- tributed in nature as pyrite (or iron pyrites). It is largely used in the manufacture of sulphuric acid and ferrous sulphate. 365. Iron Salts. Iron forms two well defined series of salts. In the ferrous series, the iron atom acts as a dyad as it does in ferrous oxide. In the ferric series, the iron double atom (Fe 2 ) VI acts as a hexad as it does in ferric oxide. (See also Ex. 2, page 289.) (a.) Solutions of ferrous salts readily absorb and precipitate ferric salts unless an excess of acid is present. They, therefore, act as powerful reducing agents and are largely used as such in the labora- tory and the arts. (6.) The ferric salts are readily reduced to the corresponding ferrous compounds. 366. Iron Chlorides. The halogen elements form, with iron, both ferrous and ferric compounds. These series are well typi- fied by ferrous and ferric chlorides. Ferrous chloride (FeCI 2 ) is best prepared by passing a current of hydrochloric acid gas over an ex- cess of red hot iron filings or wire. Ferric chloride (Fe 2 CI 6 ) may be prepared by passing a current of chlorine through a solution of fer- rous chloride until the solution smells strongly of the gas and then displacing the excess of chlorine by passing a current of carbon di- oxide through the warm liquid. This solution, when concentrated, has a dark brown color and an oily consistency. Experiment %85. Dip a piece of cotton cloth into a solution of nut galls and allow it to dry; dip it into a solution of green vitriol and hang it up in a moist atmosphere. It will be permanently colored by the precipitation of an insoluble iron tannate. 288 IRON. 367 367. Iron Sulphates, etc. Ferrous sulphate (green -vitriol, FeS0 4 , 7H 2 0) is made in immense quan- tities by exposing pyrite (FeS 2 ) to the action of the at- mosphere, as an incidental product in the manufacture of copper sulphate or by dissolving iron in dilute sul- phuric acid. It is largely used in the arts. Ferric sulphate [Fe 2 (S04) 3 ] is prepared by the action of nitric acid upon an acidulated solution of ferrous sulphate: 6FeS0 4 + 3H 2 S0 4 + 2HN0 3 = 3Feo(S0 4 ) 3 + 2NO + 4H 3 0. (a.) Ferrous nitrate [Fe(N0 3 ) 2 ] is a very soluble, unstable com- pound. Ferric nitrate [Fe 3 (N0 3 ) 6 ] is prepared by dissolving Fein H N 3 . It is largely used as a mordant in dyeing and calico printing. Ferrous carbonate (FeC0 3 ) is found as an iron ore. 36 . Iron Cyanides. Iron unites with cyanogen to form ferrous and ferric cyanides. The most important iron cyanides, how- ever, are double compounds. When crude potash (K 2 C0 3 ) is fused with nitrogenous organic matter, such as horn, feathers, dried blood, leather clippings, etc., in the presence of iron filings, the fused mass leached with water and the liquid evaporated, large yellow crystals are formed. These crystals are potassium ferrocyanide [K 8 (CN) 12 Fe 2 , 3H 2 0], better known as yellow prussiate of potash. This compound is important as it serves as the point of departure for the preparation of nearly all the cyanogen compounds. It may also be formed by the additiou of a ferrous salt to an aqueous solution of potassium cyanide. 12KCN + 2FeS0 4 = K 8 (CN) 18 Fe 3 + 2K 2 S0 4 . The tendency to form this salt is so great that metallic iron is rapidly dissolved when heated in such a solution of potassium cyanide. When a current of chlorine is passed into a solution of potassium ferrocyanide, the reac- tion \\Q\fapotassmmferricyanide [K 6 (CN) 13 Fe 2 ] or red prussiate of potash. The class of compounds known as Prussian-blues are chiefly compounds of ferrous and ferric cyanides, generally united with potassium. Experiment S86. Half fill each of two test glasses with a very di- lute solution of FeS0 4 and each of two other glasses with a similar solution of Fe 2 (SO 4 ) 3 . Prepare a dilute solution of K 8 Cy 12 Fe., and one of K 6 Cy 12 Fe,. Add a drop of K 8 Cy 12 Fe 2 to one of the glasses of Fe 2 (S0 4 ) 3 ; a blue precipitate will be formed and color the liquid. In similar manner, add K 8 Cy 18 Fe 2 to FeS0 4 ; no color will 368 IRON. 289 appear. In similar manner, add K 6 Cy 12 Fe 2 to FeS0 4 ; the blue color will appear. In similar manner, add K G Cy 12 Fe 2 to Fe 2 (S0 4 ) 3 ; no color will appear. In the name of K 8 Cy 12 Fe 2 , the pupil will notice a contraction for ferrous ; a similar contraction for ferric appears in the name of K G Cy ]2 Fe 2 . When, in this experiment, we brought two -OILS or two -ic compounds together, no color was produced. When an -ous compound and an -ic compound were brought together, a blue color was formed. Potassium ferro- and ferricyanides act thus with all ferrous and ferric salts and may, consequently, be used as tests to detect the presence of these salts in any solution or to dis- tinguish between them. Experiment 387. Soak a piece of cotton cloth in a solution of Fe 2 (S0 4 ) 3 and then dip it into an acidulated solution of K 8 Cy 12 Fe 2 . Prussian blue is precipitated upon the cloth which is thus colored. K EXERCISES. 1. Name the compounds symbolized as follows: FeBr 2 ; Fe 2 Br C 12 N ]2 Fe 2 Fe 2 (S0 4 ) ft 2. State two things indicated by the following graphic symbol : Cl Cl CI Fe-Fe-CI. 0 3 and heat gently. A brisk effervescence takes place. Test the gas evolved with a glowing splinter. The calcium hypochlorite contained in the bleaching powder is, under the catalytic influence of the sesquioxide, decomposed. Write the reaction. Experiment 293. Prepare an aqueous solution of CoC 1 3 by dis- solving CoO or Co 3 3 in HCI. Make a drawing with this nearly colorless solution. Heat the sketch to about 150C. ; it will appear blue. Breathe upon it ; the blue color will disappear. Experiment 294. To 2 cit. cm. of the pink solution of CoCI 3 in a test glass, add an equal quantity of sodium silicate or " water glass," well diluted so as to be thin. A blue precipitate appears. CoCI 2 + Na 3 Si0 3 =2NaCI + CoSi0 3 , or 2CoCI 3 + Na 4 Si 5 12 = 4NaCI + Co 2 Si 5 12 . NICKEL; symbol, Ni ; specific gravity, 8.9; atomic weight, 58.6 m. c. 379. Nickel. Mckel is almost always associated with cobalt in either terrestrial or extra-terrestrial matter. It is a lustrous, white metal, ductile, malleable, magnetic, very hard and susceptible of a high polish. It can be welded. It is largely used for plating articles of iron and steel to protect them from rusting. It is also used in coinage and for making alloys. German silver is an alloy of nickel, copper and zinc. 298 NICKEL. 379 (a.) The oxides of Ni are the monoxide (nickel oxide, NiO) and the sesquioxide (nickel peroxide, Ni a O s ). Nickel salts are derived from the monoxide. The inoit important salt is the nitrate. 38O. The Iron Group. The metals of this group form basic monoxides; they also form sesquioxides and corresponding series of salts. Cobalt and nickel have the same atomic weight and are seldom separated in nature. EXEECISES. 1. Pyrolusite may be reduced to Mn 3 4 by intense, li eat. Write the reaction. , 2. Write a graphic symbol for K s Mn0 4 . A 3. Write two graphic symbols for K 8 Mrio0 8 . 4. Write a graphic symbol for manganese sesquioxide, represent- ing the metal as a dyad. ^ ~ . 5. Write a graphic symbol for nickel sesquioxide, representing the metal as a tetrad. / * A ** ^ 6. Write a graphic symbol for Mn"0 3 . * .".. ;/ ' ' 7. Which is the correct symbol for nickel hydrate, NiHO or NiH 2 3 V Give a reason for your answer. . 8. (a.) Write the symbol for jpobaltous hydrate. (&.) For cobaltic. hydrate. * ' &>M>K 9. (a.) Write the equation representing the reaction for Exp. 289. (b.) For Exp. 290. 10. Write the symbol for the potassium salt of the, hydrate of manganese heptoxi^e. What is the name of the salt ? f\iA\#\ ! ^ O+H^iM^^i^W^t W ^^ ">* METALS OF THE CHROMIUM GROUP. CHROMIUM: symbol, Cr; specific gravity, 4.78 ; atomic weight, 52,4 m. c. 381. Chromium. Chromium is a rather rare, almost sil ver white metal and is not found free in nature. Its chief ore is chromite or chrome iron ore (FeCr 2 4 ). It forms the green coloring matter of emerald, serpentine and other minerals. The fused metal is almost as hard as the diamond and melts less easily than platinum. At a white heat, it combines directly with oxygen or nitrogen, forming, with the latter, a brown chromium nitride. It is a good con- ductor of electricity and is magnetic. The presence of 0.5 to 0.75 per cent, of this metal renders steel (" chromium steel ") harder than carbon alone can do. Several chro- mium compounds are somewhat extensively used in the arts. (a.) Chromium forms three oxides ; the monoxide (chromous oxide, CrO) ; the sesquioxide (chromic oxide, green oxide of chromium, Cr 2 3 ) and the trioxide (chromic anhydride, Cr0 3 ). (&.) Chromic trioxide may be obtained by treating potassium di- chromate with H 2 S0 4 . The red crystals thus formed may be dis. solved in H 2 forming chromic acid (H 2 Cr0 4 ). (c.) Potassium chromate (yellow chromate of potash, K 2 Cr0 4 ) is used in the arts, but the potassium dichromate (bichromate of potash, K 2 Cr 2 7 ) is, by far, the most important of the Cr compounds, as it serves as the starting point in the preparation of nearly all of the others. It crystallizes in beautiful garnet red prisms and is prepared in large quantities from FeCr 3 4 . Chrome yellow is a lead chromate (PbCr0 4 ). It is largely used as a pigment. (d.) Chrome alum [K 2 S0 4 , Cr 2 (S0 4 ) s , 24H 2 0] is used in dyeing, calico printing and tanning. 300 MOLYBDENUM. 382 Experiment 295. Dissolve 15 g. of pulverized K 2 Cr 2 7 in 100 cu.cm. of warm H 3 0. When the solution has cooled, add 15 cu. cm. of strong H 2 S0 4 , and pour it into a porcelaiu dish placed in cold t-LO. When the liquid is cool, slowly stir in 8 cu. cm. of C 2 H 6 and set the whole aside for a day. At the end of that time, crystals of K 2 S0 4 , Cr 2 (S0 4 ) 3 , 24H 2 will cover the bottom of the dish. MOLYBDENUM ; symbol, Mo ; specific gravity, 8.6 ; atomic weight, 95.8 m. c. 382. Molybdenum. This metal is rare and has been but imperfectly studied. It is prepared by heating its trioxide or one of its chlorides to redness in a current of hydrogen. It has a silver white color, and is highly infusible. Molybdenum has four known oxides : MoO ; *Mo.,0 3 ; Mo0 2 ; Mo0 3 , Molybdic acid has the com- position, H 2 Mo0 4 . TUNGSTEN : symbol, W ; specific gravity, 19.1 (?) ; atomic weight, 183.5 m. c. 33. Tungsten. Tungsten is a rare metal, being found in only a few minerals, the most important of which is wolfram, a tungstate of iron and manganese. It is said that the addition of tungsten to steel improves the hardness and tenacity of the latter. Tungsten forms two oxides, W0 2 and W0 3 . Tungstic.acid has the composi- tion, H 8 W0 4 . URANIUM : symbol, U ; specific gravity, 18.33; atomic weight, 240 m. c. 3 I. I r; ni II in. This is a rare metal, the chief ore of which is pitch blende, an impure uranium oxide (U 3 8 ). The metal is mal- leable and hard and has a color resembling that of nickel. It has two well known oxides, the dioxide (uranyl, uranous oxide, U0 3 ) and the trioxide (uranyl oxide, uranic oxide, U0 3 ). These oxides mix to form the intermediate oxides, U 2 5 (black oxide of uranium = U0 3 + U0 3 ) and U 3 8 (f6 $L 7. A certain Compound has a molecular weight of CO m. c. Its centesimal composition is as follows : 40 o C ; 53.4 of and 6.6 of H. What is the com pound & <} f^^ $ . C S. Indicate the quantivalence of each of the following radicals : S, 0, Cl, HO, NH 4 , PO, S0 2 . 9. Write the graphic symbol for phosphoryl trichloride. ' V ^/ /; **K : '. * TTT^. /. / ItjM'MU \' M;fo(f*h , (J wM^w %ffa i "vi METALS OF THE GOLD GROUP. |3fGoLD: symbol, Au ; specific gravity, 19.265; atomic weight, 106.2 m. c. ; quantivalence, 1 and 3. 393. Occurrence. Gold is widely distributed in nature but in only a few places is it found in quantities sufficient to repay the cost of obtaining it. It is generally found in the native state alloyed with silver. Native gold is found in the quartz veins that intersect metamorphic rocks and in the alluvial deposits, called placers, formed by the disintegration of gold bearing rocks. (a.) The richest deposits of Au are in California, Colorado, Nevada and Australia. Native Au is found in crystals, nuggets, grains and scales. While the particles are sometimes so small as to be invisible in even " paving " quartz, a single nugget, weighing 184 pounds and valued at 8376, 10s. 6d., was found in Australia. Gold compounds are also found in nature. Two mines in Nevada produced in 1877, $15,597,263 in Au and $17,061,587 in Ag. 394. Preparation. In quartz mining, the ore is first pulverized. The gold is then extracted from the powdered mineral by means of mercury. The gold amal- gam thus formed is subjected to distillation. In " placer digging," the lighter constituents of the alluvial deposit are washed away, the heavier gold remaining in the " wash- pan" or "cradle." In "hydraulic mining," immense streams of water are directed, under great pressure, against the surface of the auriferous deposit. In this way, great 396 GOLD. 307 quantities of sand, clay and gravel are disintegrated and hurried forward in a turbid torrent, from which the heavy gold particles settle into interstices previously prepared in the tunnel, through which the muddy mass is caused to flow. The amount of labor and capital expended in Cali- fornia upon canals, aqueducts, shafts and tunnels for hydraulic mining is very great. Experiment 299. Add a few drops of a strong solution of AuCI 3 to a liter of H 2 0. Into this dilute solution, drop one or two pieces of P, the size of a mustard-seed, and place the whole in the sunlight. In the course of a few hours, the water will have a distinct purplish tint, This will deepen in color until finally, if the solution has the proper strength, a beautiful ruby-red liquid will be obtained. The color of this liquid is due to finely divided metallic gold. 395. Properties. Gold is a brilliant, beautiful, orange-yellow metal. It is the most malleable and ductile of the metals. It may be beaten into leaves not more than 0.0001 mm. thick ; 1 g. of it may be drawn into 3240 m. of wire. It is softer than silver, nearly as soft as lead. It fuses at about 1100C., and volatilizes at very high temperatures. It is not attacked by oxygen or water at any temperature. It does not dissolve in any simple acid except selenic but dissolves readily in aqua regia or in any other acid liquid that evolves chlorine. (d.} One ounce of Au leaf may be made to cover 189 sq. ft. , while 280,000 leaves placed one upon another measure only one inch in thickness. One grain of Au will gild two miles of fine Ag wire, the deposit of Au being about 0.000002 mm. thick. Ordinary gold leaf transmits green light. Au may be precipitated in so fine a state that it remains suspended in the liquid, causing it to appear ruby -red by reflected light or blue by transmitted light. The red color of ruby glass is due to the presence of Au in a finely divided state. Au is sometimes called the "king of metals." 396. Uses. Gold is used for coinage, jewels, gilding 308 PLATINUM. 396 and other purposes, for which, it is well adapted by its beautiful color and lustre, its unalterability and compara- tive rarity. Pure gold is so soft that coins and jewels made of it would soon wear out. It is, therefore, hardened by alloying with copper. American and French gold coins contain one-tenth copper ; British gold coins, one-twelfth. (a.) The purity of Au in jewels is estimated in carats, pure Au being " 24 carats fine." An alloy containing f gold is " 16 carats fine." (&.) The compounds of Au are of little chemical interest. There are two oxides, the monoxide (aurous oxide, Au 8 0) and the trioxide (auric oxide, gold sesquioxide (Au 2 3 ). There are two chlorides, AuCI and AuCI 3 . Aurous cyanide (AuCN) dissolved in a solution of KCN is used in electro gilding (Ph., 399, a). PLATINUM : symbol, Pt ; specific gravity, 21.5 ; atomic, iceiyht, 196.7 m. c. 397. Occurrence, etc. Platinum is found only in the native state, but very seldom pure. The so called " platinum ore " is an alloy of the metals of this group, with iron, copper, etc. It is found in the Ural mountains, in Brazil, Borneo, California and other places. The preparation of pure pla- tinum is a matter of great difficulty. For fusing the metal on the large scale, a crucible made of two pieces of lime is used with a compound blowpipe (Fig. 119). The upper part of the blowpipe is made of copper ; the lower part, of platinum. Coal gas is gener- ally used instead of hydrogen. The lime of the crucible successfully resists FIG. the high temperature produced and absorbs the slags formed during the operation. 397 PLATINUM. 309 Experiment 300. Boil 0.5 g. of Pt in small fragments in a tea- spoonful of aqua regia as long as the metal seems to be acted upon. Pour the liquid into an evaporating dish, add aqua regia to the re- maining Pt and proceed as before, continuing thus until all of the Pt has been dissolved. Evaporate the solution to dryness upon the water bath. Dissolve this residue (PtC I 4 ) in H 2 0. Experiment 301. Heat a few drops of the solution of PtCI 4 in a test-tube. Notice the odor of the gas evolved. Hold a strip of mois- tened litmus at the mouth of the test tube. It will be bleached. 2PtCI 4 = Pt 2 + 4CI 2 . ' Experiment 302. Pour a teaspoonful of a solution of NH 4 CI into a test tube, acidulate it with HCI, and to it add a drop of the solution of the PtCI 4 just prepared. A yellow, insoluble powder (2NH 4 CI,PtCI 4 ) will soon be precipitated. Repeat the experiment, taking enough of the solutions to make half a teaspoonful of the yellow precipitate, being careful that at last there shall be a slight excess of free NH 4 CI rather than of PtCI 4 in the overlying liquid. Allow the precipitate to settle, separate it from the clear liquor by decantation and partly dry it at a gentle heat. When the precipitate has acquired the con- sistence of slightly moistened earth, transfer it to a cup-shaped piece of Pt foil, and heat it to redness in the gas flame, until fumes of NH 4 CI are no longer driven off. A gray, loosely-coherent, sponge-like mass of metallic platinum will remain in the cup ; it is platinum sponge. Experiment 303. Repeat Exp. 30, using either illuminating gas or H*. Experiment 304- Fill a spirit lamp with a mixture of C 2 H 6 and (C 2 H 5 ).jO. Suspend a spiral of Pt wire over the wick (Fig. 120) and light the lamp. When the wire is red hot, blow out the flame. The mixed vapors rising from the wick are oxidized by the heated Pt; the spiral is thus kept brightly incandes- cent. This is Davy's glow lamp. The experiment may be varied by suspend- ing the spiral in a loosely covered test glass contain- ing (C 2 H 5 ) 2 0, as shown in Fig. 121, or by heating a bit of Pt foil in a Bunsen flame and blowing out the flame. The foil will glow and may reignite the gas if held near enough to the burner. FIG 120. FIG. 121. 310 PLATINUM. 398 398. Properties. Platinum is a heavy, soft metal of tin-white color. It is infusible at the highest tempera- ture of the blast furnace but yields before the oxyhydrogen flame. Its melting point has heen estimated at 2000C. It is very malleable and so ductile that it may be drawn into a wire less than 0.001 mm. in diameter. Like gold, it has little affinity for the other elements. It is not oxi- dized by oxygen, water, nitric or sulphuric acid at any temperature. It dissolves in aqua regia more slowly than gold does. It also dissolves in chlorine water. Like iron, it may be welded at a white heat. (a.) Red hot Pt absorbs 3.8 volumes of H, which it gives off when heated in a vacuum, the surface of the Pt becoming then covered with hubbies. Similarly, H is absorbed by Pt, at the negative electrode in the electrolysis of H 2 (Exp. 12), the occluded H being given off when the current is reversed so as to make the Pt the positive electrode. (&.) is not absorbed by Pt but it is condensed on a clean surface of the metal. Thus, mixtures of or air with H, CO, C 2 H 4 , C 2 H 6 or (C 2 H 5 ) 2 vapor, and other easily inflammable gases or vapors may be made to combine, sometimes slowly, sometimes quickly, some- times with explosion (Exps.. 30 and 52). (0.) The preparation of platinum sponge has been illustrated in Exps. 300 and 302. Owing to its large surface, compared with its volume, it is able to condense large quantities of 0. (d.) Platinum-black is a form of metallic Pt, even more finely di- vided than platinum-sponge. It is a soft, dull, black powder. It can absorb more than 800 times its volume of 0. When boiled in H 2 and dried in a vacuum over H 3 S0 4 , it absorbs from the air so rapidly that the mass becomes red hot. If upon the powder, when cooled after such absorption of 0, some C 2 H 6 or* (C 2 H 5 ) 2 be dropped, the oxidation of the liquids will heat the metal red hot. (e.) Pt unites readily with other metals forming alloys which are generally more easily fusible than the element. 400 PALLADIUM. 311 399. Uses. On account of its infusibility and its chemical inertness, platinum is invaluable to the chemist. In the laboratory, it is used for crucibles, evaporating dishes, stills, tubes, spatulas, forceps, wire, blowpipe tips, etc. In sulphuric acid manufacture, large platinum stills and siphons ( 152, c) are used for concentrating the acid. As its rate of expansion is nearly equal to that of glass (Ph., 485, a), it is used in the manufacture of eudiom- eters, Geissler tubes, incandescent electric lamps, etc. (a.) On account of Pt forming easily fusible alloys, care should be had not to heat Pt utensils with an easily fusible metal, e.g., Pb, Bl, Sn or Sb, or any easily reducible compound of a metal. They should not be used for fusion with nitre, the alkalies, or alkaline cyanides. They should not be heated in contact with P or As nor brought into direct contact with burning charcoal. (&.) " Without Pt, it would be impossible, in many cases, to make the analysis of a mineral. The mineral must be dissolved. Vessels of glass and all non-metallic substances are destroyed by the means we use for that purpose. Crucibles of Au and Ag would melt at high temperatures. But Pt is cheaper than Au, harder and more durable than Ag, infusible at all temperatures of our furnaces nnd is left intact by acicls and alkaline carbonates. Pt unites all the valuable properties of Au and of porcelain, resisting the action of heat and of almost all chemical agents. Without Pt, the composition of most minerals would have yet remained unknown." Liebig. ALLADIUM : symbol, Pd ; specific gravity, 11.4 > atomic icciyhl, 106.3 m. c. 4OO. Palladium. This metal is contained in most platinum " ores," and is found native. Is has a color re- sem-bling that of platinum. Its melting point is about that of wrought iron, the lowest of any of the metals of this group. It possesses the power of absorbing hydrogen in a greater degree than any other metal ( 24, d). It has not been largely employed in the arts although its silver- 312 RHODIUM IRIDIUM RUTHENIUM. 400 white color and unalterability in the air have led to its use in preparing the graduated surfaces of astronomical instru- ments. It does not tarnish on exposure to hydrogen sul- phide and has been, therefore, used for coating silver arti- cles and by dentists as a substitute for gold. RHODIUM : symbol, Rh; specific gravity, 12.1 ; atomic weight, 104.1 m. c. 401. Rhodium. This metal is found in platinum " ore." It has the color and lustre of aluminum. It is melted with greater difficulty than platinum. It is almost insoluble in acids, but is more easily acted upon by chlorine than any other of the platinum metals. IRIDIUM; symbol, IT; specific gravity, 22. 38 ; atomic weight, 192.7 m.c. 402. Iritlium. This metal also is found in platinum " ore." It has a white lustre, resembling that of polished steel. It is very brittle when cold but slightly malleable at a white heat. Pure, massive iridium is not attacked by aqua regia. An alloy of one part of iridium and nine parts of platinum is extremely hard, as elastic as steel, more difficultly fusible than platinum, unalterable in the air and susceptible of a beautiful polish. This alloy was adopted by the International Commission at Paris in 1872 for the standard metric measures. Iridium is the most -difficultly fusible of the platinum metals except ruthenium and osmium. It has been used for the negative electrodes in electric lamps. ^ RUTHENIUM* : symbol, Ru ; specific gravity, 12.26-, atomic weight, 103.5 m. c. 403. Riitlienimii, This metal is found in platinum and other ores. It combines with oxygen more readily than any of the other platinum metals except osmium, It is hard and brittle, and, 404 OSMIUM. 313 next to osmium, the most difficultly fusible metal of this group. It is only slightly acted upon by aqua regia. It combines with chlorine nt a white heat. OSMIUM: symbol, Os; specific gravity, 22477 ; atomic weight, 198.6 m. c. l()l. Osmium. This metal is found in platinum "ore, "from the other constituents of which it is easily separated, as it unites directly with oxygen to form a very volatile compound, OsO 4 . Osmium crystals have a bluish white color and are harder than glass. Osmium is the heaviest known substance and has not yet been fused. It is not used in the arts but its alloy with iridium (osmiridium) is used for tipping gold pens as it is not attacked by acids, and for the bear- ings of the mariner's compass as it does not oxidize and is non-mag- netic. Note. Gold, silver, platinum, palladium, rhodium and iridium ate sometimes called " the noble metals." H - * - \ EXERCISES. -' 1. What takes place when Na is thrown into H 8 ? 2. Describe an experiment showing the difference between a mix- ture and a compound.. --vy^ 3. State the effect of heat upon Mn0 2 , KCI0 3 , NH 4 CI, NH 4 N0 3 , P and S respectively. 4. You are given Zn, H 2 S0 4 , KHO and H 2 and required to prepare H from them by two distinct processes. Describe the processes and write the reaction for each. ^ ^ j^frj "V {/ at/j^-5^" 5. I have two cylindrical jars or H, one of which 1 hold mouth upward, the other mouth downward. At the end of 30 seconds, I plunge a lighted taper into each jar. Tell what you would expect to take place in each case. *)}-{ tf 6. What are the products of the combustion of f-f 2 S in the,air. 7. How can you make H 2 S0 4 from S, H 2 and HN0 3 ? 5r^T? S. What elements can be obtained from HCI, NH 3 and H 2 0? How^; would you obtain them in each case ? 9. (a.) When H is burned in air, what is the product? (&.) When burned in Cl ? 10. An electric spark is produced in a mixture of 120 CM. cm. of. H and 60 cu. cm. of O. How would you conduct the experiment so as to show the gaseous condensation ? 314 OSMIUM. 404 , 11. You are required to prepare from Cl and H 2 0. How would you do it ? 12. You are given some Hg, a glass flask, a lamp, some glass tub- ing and required to make pure 0. How will you do it under ordi- nary barometric conditions V ' 13. When HN0 3 is .poured on Cu. how does the action differ from" a simple solution ? (J 14. You are given ammonium carbonate and nitric acid and re- quired Jo prepare laughing gas from the materials. How will you doit? nt 9 J^ / iov.x ^^^^fej^f^t. 15. What is the fineness of British gold coin in carats? 2. Q_ 16. When a positive monad radical replaces an atom of H in NH 3 , / the compound ammonia is called an amine. See 96, a. k Write the typical symbol for_di-ethylamine ; for potassamine. L /v/. 17. When a negative (or acid) monad radical replaces fc'n atom of H in NH 3 , the compound ammonia is called an amide. Write the symbol for di-iodamide. The symbol for acetyl is given on p. 183. Write the symbol for acetamide. 18. Write the symbols for potassium sulphite ; hydrogen potassiuin sulphite ; calcium sulphite and hydrogen calcium sulphite. 0%^ Jvf #? ' 19. Write the name and full graphic symbol for ^-(S0 2 )-(HO) ' -' 20. Which of the graphic symbols called for in Ex. 5, p. 227, is preferable? Why? See 164, a. 21. Write the graphic symbol for phosphorus tetricdide (P 2 I 4 ) in- dicating trivalent P. 22. Write the graphic symbol for pyrophosplioric chloride, ao r\ \ J ' / /? />^\ ^ v &,\ 23. (a.) Write *the graphic symbol for H 3 P0 3 $4!(&.) Does t bol indicate a dibasic or a tribasic acid ? 4? -*- ' 24. Explain the fact that when new flannel is first was alkaline soap, it becomes yellow. 25. What weight of is needed to burn 9 g. of CS 8 ?'- / 7- / - / ' ^C" 26. How would you distinguish between Pt and Ag? Between ^.Pt and Sn ? Between Ag and Sn ? *h 1. Table of the Elements. An alphabetical list of the elements with their symbols and atomic weights is given below. In the body of the work some of the atomic weights were given in ap- proximate numbers, for greater ease in memorizing and computation. In the table below, the atomic weights are given according to the most accurate determinations yet made. The less important ele- ments are printed in italic. Name. Aluminum. . Sym- bol. Alicro- criths. 27.3 AL, ^Antimony (stibium).. .Sb . .122 Arsenic As... 74.9 Barium Ba...l36.8 Beryllium Be (See Glucinum.) Bismuth Bi. .210 Boron B.... 11 Bromine Br. ...79.75 Cadmium. Cd...lll.6 Ccesium Cs...l32.5 ^ Calcium Ca... 39.9 * Carbon. ., . .C. ... 11.97 Cerium . ,Ce.. .141.2 - -Chlorine Cl... 35.37 Chromium Cr.... 52.4 Cobalt Co... 58.6 Columbium Cb . 94 Copper (cuprum) Cu.. , 63 . 1 Davyum Da.. 153 Decipium De. .157 Didymium Di . . 147 Erbium Er ..169 Fluorine F... 19.1 Gallium Ga... 69.8 Glucinium (See Glucinum.) Glucinum Gl.. . 92 Sym- Micro* ool. criths. Name. Qold(aurum) Aul96.2 -Hydrogen H . . 1 Indium In. 113.4 Iodine I. .126.53 Iridium Ir 192.7 Hron Fe..55.9 Lanthanum. La 139 Lead (plumbum) : Pb 206.4 Lithium Li . . 7.01 Magnesium Mg. 23.98 Manganese Mn..54.8 Mercury (Jiydrargyrum). Hgl99.8 Molybdenum Mo. 95.8 Nickel Ni. 58.6 Niobium (S ee Columbium). Mb "Nitrogen N . . 14.01 Norwegium No. 72. Osmium Os 198 6 Oxygen ..15.96 Palladium Pd 106.2 -.Phosphorus P . .30.96 Platinum Pt.196.7 4 Potassium (tedium). ... K .. 39.04 j Rhodium Rh.104.1 I Rubidium Rb..85.2 ! Ruthenium Ru.103.5 Selenium Se.-79 .. (See Silicon.)... SI 316 APPENDIX. Micro- Silicon ................ Si ____ 28 Silver (argentum) ...... Agl07.66 K Sodium (natrium) ...... N a. 22. 29 Strontium ............. Sr . .87.2 ^Sulphur ............... S. ..31.98 Tantalum .............. Tal82 Tellurium ............ Te 128 Terbium .............. Tr..99 Thallium. . .Tl.203.6 Thorium Th.231.5 Tin (stannum) Sn.117.8 Titanium Ti . .48.15 Tungsten (wolframium) W. 183.5 Uranium U r.240 Vanadium V.. 51.2 Yttrium Yt...92.5 Zinc Zn...64.9 Zirconium Zr. . 90 2. Iflctric Pleasures. For a fuller consideration of tlie international or metric measures, the pupil is referred to Avery's Natural Philosophy, 24-30 and 35-36. Chemists of all countries use these units, almost exclusively. The deci- meter rule (Fig. 122) is shown as being divided into ten cen- timeters, each of which is divided into ten millimeters. The cubic decimeter measures a volume called a liter (pronounced leeter). The cubic centimeter (cu. cm) is 0.001 of a liter (I). The weight of one cu. cm. of water at the freezing tempera- ture is a gram (g). These three units, the liter, the cubic centimeter and the gram are the ones of most frequent occur- rence in chemical works. The actual weights and measures should be habitually used in every school laboratory. 1 cu. in. =16.386 cu.cm. I grain =0.0648 g. jf x ,*,_ w.v^, ,. 1 liquid qt.=0.946 I. loz. Troy =31.1035.?. | 1 yard=0.9144wJl fl'd oz.= 29.562 ^.m.|llb.Av.= 0.4535^. J 3. Thermometers. Chemists use the cen- a tigrade thermometer almost exclusively. One or 2- more centigrade thermometers (chemical), having s. the scale marked on the glass tube, and having no Z frame like that of the ordinary hous3 thermometer, j] should be in every school laboratory. In this book fi temperatures are always given in centigrade do- "5- grees. To change centigrade readings to Fahren- heit readings, multiply the number of centigrade - w degrees by f and add 32. To change Fahrenheit readings to centigrade readings, subtract 32 from the number of Fahrenheit degrees and multiply the remainder by f. (See Ph., 480, 481.) The best thermometers are straight glass tubes, of uniform diameter, with cylindrical instead of spherical bulbs ; such instruments can be passed tightly ^ ** through a cork, and are free from many liabilities to error FIG. 123 to which thermometers with paper or metal scales are APPENDIX. 317 always exposed. A cheaper kind of thermometer, having a paper scale enclosed in a glass envelope, will answer for most experiments. 4. Gla Working. Much of the chemist's apparatus is made of glass which softens and becomes plastic when heated. Skill- ful workers in wood or metal may be found in almost any town, but glass working will generally devolve upon the teacher and pupil. It is, therefore, discussed at some length in this place. (a.) Glass Tubing. Glass tubes bent into various shapes are con- stantly needed. The pupil should acquire dexterity in preparing these for himself. Glass tubing is of two qualities, hard and soft. The former softens with difficulty and is desirable only for ignition or combustion tubes. (Fig. 18.) But little of it will be needed. It is generally better to buy the ignition tubes required. Soft glass tubing will be needed in larger quantities. In purchasing, it is re- commended that the greater part be of a single size. Fig. 124 shows desirable sizes and the proper thickness of the glass for each size. By using, habitually, one given size of tubing, the various articles made therefrom are more easily interchangeable than FIG. 124. they would otherwise be. (&.) Cutting and Bending Tubes. Glass tubing and rods must gen- erally be cut the desired length. For this purpose, lay the tube or rod upon the table and make a scratch at the required dis- tance from one end with a three-cornered file. Hold P the tubing in both hands, as shown in Fig. 125, with the scratch away from you and the two thumbs opposite the mark. With a sharp jerk, push out the thumbs and pull back the fingers. The glass will snap squarely off at the desired place. The best flame for bending ordinary tubes is that of a fish-tail gas burner, but that of a spirit lamp will do. Be sure that the tube is dry ; do not breathe into it before heating it. Bring the part of the tube where the bend is desired into the hot air above the flame ; when it is thoroughly warm, bring it into the flame itself. Heat about an inch of the tube, holding it with both hands and turning it constantly that it may be heated uniformly on all sides. The tube should be held between the thumb and first two fingers of each hand, the hands being below the tube, palms upward and the lamp between the hands. The desired yielding condition of the glass will be detected by feel- 318 APPENDIX. ing better than by seeing, i. ., the fingers will detect the yielding of the glass before the eye notices any change of color or form. i When the glass yields easily, remove it from the flame and gently bend the ends from you. If the concave side of the g'*ass be too hot, it, will " buckle ; " if the .convex side be too hot, the curve will be flattened and its chan- nel contracted. Practice, and practice only, will enable you to bend a tube neatly. When a tube or rod is to be bent or drawn near its end, a temporary handle may be attached to FIG. 126. it by softening the end of the tube or rod, and pressing against the soft glass a fragment of glass tube, which will adhere strongly to the softened end. This handle may subsequently be removed by a slight blow or by the aid of a file. If a considerable bend is to be made, so that the angle between the arms will be very small or nothing, as in a siphon, the curvature can not be well produced at one place in the tube, but should be made by heating, progressively, several cm. of the tube, and banding continuously from one end of the heated portion to the other (Fig. 127). The several parts of such a bent tube should all lie in the same plane so that the finished tube may lie flat on a level surface. It is difficult to bend tubing large enough for TJ-tubes (Fig. 14). They would better be bought. When the end of a tube or rod is to be heated, it is best to begin heating the glass about 2 cm. from the end, as cracks start easily from an edge. Smooth the sharp edges at the ends of the tube by heating them to redness. Anneal the bent tube by with- drawing it very gradually from the flame so as not to let it cool suddenly. Never lay a hot tube on the bench but put it on some poor conductor of heat until it is cool. Gradual heating and gradual cooling are alike necessary. Glass tubing may be advantageously united by rubber or caoutchouc tubing when the substance to be conducted will not corrode the latter, or when the temperature em- ployed is not too high. Short pieces of rubber tubing are much used APPENDIX. 319 as connectors to make flexible joints in apparatus. Gas delivery tubes, etc. (Fig. 6), are generally made in several pieces joined with caoutchouc connectors, which, by their flexibility, add much to the durability of the apparatus. Long glass tubes bent several times and connecting heavier pieces of apparatus are almost sure to break, even with careful use. The internal diameter of the connector should be a little less than the external diameter of the glass tubing. The connection may be made more easily by wetting the (c.) Drawing Tubes. In order to draw a glass tube down to a finer bore, thoroughly soften it on all sides uniformly for 1 or 2 cm. of its length and then, taking the glass from the flame, pull the parts asunder by a cautious movement* of the hands. The length and fineness of the drawn out tube will depend upon the length of tube heated and the rapidity of motion of the hands. If the drawn out part of the tube is to have thicker walls in proportion to its bore FIG. 128. than the original tube, keep the heated portion soft for two or three minutes before drawing out the tube, pressing the parts slightly together the while. By this process the glass will be thickened at the hot ring. By cutting the neck at a, with a file, jets are formed such as are needed for Exps. 21, 26, etc. (d.) Closing Tubes. Take a piece of tubing long enough to make two closed tubes of the desired length. Heat a narrow ring at the middle of the tube and draw it out slightly. Direct the point of the flame upon the point c (Fig. 128) which is to become the bottom of one tube, draw out the heated part and melt it off. Each half of the original tube is now closed at one end but they are of different forms. (Fig. 129.) You can not close both ends satisfactorily at the same time. A superfluous knob of glass generally remains upon the end. If FIG. 129. small, it may be removed by heating the whole end of the tube, and blowing moderately into the open end. The knob being hotter than any other part, yields to the pres- sure from within and disappears. If the knob is large, it may be drawn off by sticking to it a fragment of tube, and then softening the glass above the junction. The same process may be applied to 320 APPENDIX. the too pointed end of the right hand half of the original tube, or to any bit of tube that is too short to make two closed tubes. When the closed end of a tube is too thin, it may bs strengthened by keep- ing the whole end at a red heat for two or three minutes, turning the tube constantly between the fingers. In all of these processes, keep the tube in constant rotation that it may be heated on all sides alike. It will be difficult for the pupil satisfactorily to work tubing large enough for test tubes (Fig. 7). They would better be bought. They come in nests of assorted sizes. (e.) Blowing Bulbs. This is a more delicate operation than any yet described. It requires considerable practice to secure even moderate success. If the bulb is to be large compared with the size of the tube carrying it, the glass must be thiqjiened before the bulb can be blown. If the bulb is to be at the middle of a piece of tubing, the tube is to be heated red hot at that place, removed from the flame, and the ends gently pressed toward each other. If the glass " wrinkles " in thick- ening, as it may do if tooliighly heated, a good bulb cannot be blown there. If the bulb is to be at the end of the tube, the end is closed and the glass then thickened by holding the closed end in the flame, keeping it in constant rotation. When the glass is so soft that it bends from its own weight, the end of the tube is placed between the lips, the other end, if open, is closed with the finger, and air is steadily pressed into the tube by the mouth rather than by the lungs, the tube being kept in rotation. This must be done quickly but cautiously, the eye being kept upon the heated part. Practice will soon enable you to determine when to stop the pressure. If the bulb thus obtained be not large enough, it may be reheated and again ex- panded, provided the glass be thick enough. The pressure must not be too strong or sudden and never applied while the glass is in the flame. It is better, as a general thing, to buy funnel. tubes (Fig. 6) and bulb tubes (Fig. 16) than to make them. (/.) Welding Glass Tubes. The well fitted ends of two pieces of glass tubing may be joined by heating them to redness and press- ing them together while in a plastic condition. Practice is necessary to good results, but the skill should be acquired as funnel tubes and other pieces of apparatus often need mending. If necessary, the end of one tube may be enlarged by rapidly turning the glass in the flame until it is highly heated, and then, while it is still in the flame, flaring it outward with an iron rod. Hold the ends together and heat them well with a pointed flame, until they are united all around. Force air in at one end to swell out the joint a little, heat it again until the swelling sinks in, blow it out again, and repeat the process until the APPENDIX. 321 joint is smooth and the pieces well fused into each other. Without this repeated heating and blowing out, the joint is likely to crack open when cooled. (g. ) Piercing Tubes. A hole may be made in the side of a tube or other thin glass apparatus by directing a pointed blowpipe flame upon the glass until a spot is red hot, closing the other end, if open, with the finger and bio wing forcibly into the open end. The glass is blown out at the heated spot. The edge may be strengthened by laying on a thread of glass around it, and fusing the thread to the tube in the blowpipe flame. (h.) Glass Cutting and Cracking, etc. For cutting glass plates, a glazier's diamond is desirable but efficient and cheap" glass-cutters," made of hardened steal have been put upon the market within a few years. For shaping broken flasks, retorts and other pieces of thin glassware, cracking is more satisfactory. A scratch is made with a file, preferably at the edge of the glass. Apply a pointed piece of glowing charcoal, a fine pointed flame or a heated glass or metal rod to this scratch. The sudden expansion by heat will generally pro- duce a crack. If the heat does not make one, touch the hot spot with a wet stick. A crack thus started may be led in any desired direc- tion by keeping the heated rod or fine flame moving slowly a few mm. in front of it as it advances. A flask or retort neck may sometimes be cracked round by tying a string soaked in aloohol or turpentine round the place, setting fire to the string and keeping the flask turning. When the string has burnt out, invert the flask and plunge it into water up to the heated circle. It will generally crack as desired. The lower ends of glass funnels, and the ends of gas delivery tubes that enter the generating bottle or flask should be ground off obliquely on a wet grindstone, or shaped thus with a file wet with a solution of camphor in turpentine, to facilitate the dropping of liquids from such extremities. With a little care and patience, a hole may be drilled through glass by using a file kept wet with the solution mentioned. Such a hole may easily be enlarged or given any desired shape with a file thus wet. FIG. 130. The lips of bottles may be ground flat by rubbing them on a flat surface sprinkled with emery powder kept wet. The bottle should be grasped by the neck and rubbed around with a gyratory motion, 322 APPENDIX. pains being taken to prevent a rocking motion whereby first one side of the lip shall be ground and then another, thus leaving the bottle in as bad a condition at the end of the work as at the beginning. The work may be finished by rubbing with fine emery powder on a piece of plate or window glass, until all parts of the ground surface lie in the same plane. See F rick's Physical Technics [17]. FIG. 131. FIG. 132. FIG. 133. 5. Pipettes and Graduates. Tubes drawn out to a small opening at one end and used to remove a small quantity of a liquid from a vessel without dis- turbing the bulk of its contents, are called pipettes. They often carry a bulb or cylindrical enlargement, as appears in the forms shown in Fig. 131. The manner of using them is shown in Fig. 132. They are often graduated. A cylindrical measuring glass, graduated to cubic centimeters (Fig. 133) is almost indispensable in the laboratory. 6. W oil life Bottles. A very conven- ient substitute for Woulffe bottles may be made by perforating the glass cover of a fruit jar ac- cording to directions given in App. 4, h. The holes carry cork or caoutchouc stoppers through which the several tubes pass, as shown in FIG. ,34. Fi ' 134 APPENDIX. 323 7. Thin Bottomed Glassware. Glass vessels are largely used for heating liquids ID the laboratory. All such vessels have uniformly thin bottoms that they may not be broken by unequal ex- pansion when heated. If moisture from the atmosphere or other source accumulates on the outer surface, it should be carefully wiped off before or during the heating. Retorts are often used. Those that have tubulures (Fig. 37, a) are preferable to those that have not (Fig. 43). v Florence Flasks are now much used instead of retorts as they cost much less. They may be bought in any size desired and with the bottom rounded or flattened. (See Figs. 13, 32, 37?-, 50, etc.) Heated retorts and flasks should not be placed on the table as the sudden cooling may break them. They may better be placed on rings covered with listing or made of straw or other poor conductor of heat, as shown in Figs. 43 and 71. Beakers are thin, flat-bottomed glasses with slightly flaring rims, as shown in Figs, 9, 58, etc. They are conveniently used for heating liquids when it is desirable to reach every part of the vessel as with a stirring rod. They are generally sold in nests of different sizes. Beakers of more than a liter's capacity are too fragile to be desirable. Test Tubes are thin glass cylinders, closed at one end and having lips slightly flared. The mouth should be of such a size that it may be closed by the ball of the thumb. The tube may be held in the flame with the fingers, with wooden nippers, as in Fig. 2, or by a band of folded paper around the upper end. A test tube rack, some- what similar to the one shown in Fig. 135, should be made or bought, to hold the tubes upright when in use and to hold them inverted when not in use. Test tubes may be held in an inverted position, as at the pneu- matic trough or water pan, by weighting them with lead rings cut with a saw from lead pipe. The ring should be of such a size that it will easily slip over the tube but not over the lip of the tube. Test tubes may be easily cleaned with little cylindrical brushes made of bristles held between twisted wires. They cost but a few cents each. The chief danger in clean- ing a test tube is that the bottom may be broken out. The brush should, therefore, have a tuft of bristles at its end. When the upper end of a tube is held in the fingers during the heating, the tube should be rolled or turned in the flame so that all sides may be'equally heated. 324 APPENDIX. 8. Filtering. Funnels that have an angle of exactly 60 should be chosen. The circular piece of filter paper should be folded first on its diameter, then again at right-angles to the first fold and then opened out so as to leave three folds on one side and one on the other, as shown in Fig. 136. It is then to be placed in a funnel, the funnel placed in proper position and the liquid to be fil- tered carefully poured upon the paper. If the first filtration does not clear the liquid, the filtrate should be poured back upon the same filter for refiltration. Another way of folding the filter paper is to make the first fold as above. Then a fold equal to a quarter of the semicircle is made upon each side of the paper. Each of these smaller folds is then folded back upon itself. The sheet is then opened, as shown in Fig. 137, and thus placed in the fun- ^* ^X^. Rapid filtration may be secured by making a rib- bed filter as follows : Fold * i ^L |/ the paper as before on two diameters at right- angles to each other. FIG. 136. FIG. 137. FIG. 138. Open at the last fold and spread out the paper, ace, which will have a crease, co. Bring the corners a and e to the point c and make the creased lines, bo and do, so that the paper shall be creased in the same way at bo, co and do. Open the paper as shown in Fig. 138, and fold the corner a upon b, creasing the paper in the opposite di- rection. Make similar creases midway between 6 and c, between c and d, and between d and e. The last four folds leave creases op- posite in direction to those made at bo, co and do. On opening the paper and putting it into the funnel, it will stand out from the glass, touching it only at several of the edges of the folds. Filters may be folded at leisure moments and kept ready for use. For coarse and rapid filtering, the neck of the funnel may be plugged with tow or cotton. For filtering solutions that would destroy the texture of the filter paper, a plug of asbestos or of gun cotton is placed in the neck of the funnel. The funnel may be supported in any convenient way. Sometimes it may be placed in the neck of the bottle (Fig. 79), care being had that it does not fit air tight. It may often be supported from, the retort stand or other independent support. When convenient, the APPENDIX. 325 lower end of the funnel should touch the side of the vessel that re- ceives the filtrate so that the latter shall fall quietly rather than in splashing drops. The end of the funnel neck should be ground off obliquely, as stated in A pp. 4, h. When a precipitate has been collected upon a filter, it may be washed by filling the filter two or three times with distilled water and allowing it to run through. A washing bottle (Fig. 139) is of great convenience, the stream of water being driven out at c by air from the lungs forced in at a. The stream of water is directed so as to wash the precipitate from the sides of the filter toward its apex. The jet may be carried by a piece of flexible tubing attached to c, so that it may be turned in any direction without moving the bottle. When a precipitate is very heavy, it may be washed by shaking it up with successive quantities of water in a test tube, and pouring off the water when the precipitate has settled down. A wet glass rod held against the lip- of the test tube greatly assists in pouring off the liquid without dis- turbing the precipitate. 9. Cork*, etc. It is not always easy to obtain corks of good quality and considerable size. Many experiments have failed through defects in corks used. Use bottles with small mouths when you can. Choose corks cut across the grain rather than those cut with the grain, as the latter often provide continuous channels for the escape of gases. Select those that are as fine grained as you can get. They will generally need to be softened before use. This may be done by rolling on the floor with the foot, on the table with a board or with a cork squeezer made for that purpose. Corks may be made less porous by holding them, for a few minutes, under the surface of melted paraffine wax. FIG. 139. FIG. 140. In boring holes through corks, a small knife blade or rat-tail file 326 APPENDIX. may be used, but a set of brass cylinders, made for the purpose, is more convenient. Such a set of cork borers and the way of using them are shown in Fig. 140. Use a borer with a diameter a little less than that of the glass tubing to be used. When the borer be- comes dull, grind or file the outer bevelled edge and. with a sharp knife blade, pare off the rough metal on the inside of the edge. Caoutchouc stoppers are more durable than cork and much to be preferred. They may be bored as above described. If they harden, they may be softened by being kept for a time in a closed flask con- taining a few drops of turpentine. If the glass tube enters the bored stopper with much difficulty, wet the outside of the tube with tur- pentine. In passing glass tubes through stoppers of cork or caoutchouc, see that the end of the tube is smooth (see App. 4, &), hold the tube as near as possible to the stopper and force it in with a slow, steady, rotary, onward motion. Do not hold a funnel tube by the funnel, or a bent tube at the bend if you can avoid doing so. If the glass tube enters the bored cork with much difficulty, smear the outside of the tube with soap and water. Test all joints made, in the manner de- scribed in 21. The sticking of glass stoppers is a frequent source of trouble in the laboratory. Many methods of loosening them have been suggested. When one fails another must be tried. Under such circumstances, patience and persistence are necessary. It is hardly ever necessary to break the bottle. Generally, the stopper may be started by tap- ping it lightly on opposite sides alternately with a block of soft wood. The expansion of the bottle neck by heat will often loosen the stopper. The heat may be applied by friction with the fingers or a piece of tape, by a flame or by hot water. If the application of heat be continued too Ion 5 79, a, and for many other purposes. By the addition of a per- forated cylinder carrying strong wire netting to the ' ' Evaporating Burner," we produce a " Hot Air Bath," convenient for many labora- tory purposes. It is shown in Fig. 154. The ' ' Solid Flame Burner " is shown at one-fourth actual size in Fig. 155. It will boil 2 I. of water in six or seven minutes, and may be used for melting zinc in an iron ladle, as directed in 21. Other pieces of the " Fletcher " apparatus will be mentioned. 17. Blowers and Blowpipes. For working tubes of considerable size, a blower and blast lamp are necessary. The blower FIG. 156. FIG. 157. may easily be made. Fig. 156 shows it in perspective, and Fig. 157 in section. The sides of the bellows, m, and of the reservoir, n, are FIG. 158. FIG. 159. made of leather nailed to the boards at top and bottom. The ar- rangement of valves is evident from Fig. 157. A spring keeps a con- . stant pressure on the air in n. Air is delivered through the tube, t, and conducted to the blast lamp by flexible tubing. The length, ab, 336 APPENDIX. may be about 60 cm. A more desirable form, made by the Buffalo (N. Y.) Dental Manufacturing Co., is shown in Fig. 158. A Bunsen blast lamp is shown in Fig. 159. Gas enters by the tube at the right. The other tube is connected with the blower. It may be had of James W. Queen & Co., Philadelphia. The temperature may be increased by placing the glass to be heated before a piece of charcoal upon which the flame plays. Fig. 160 shows a " Hot Blast Blowpipe " furnished by the Buffalo Dental Manufacturing Co. The upright jet may be used for light or for a moderate heat for bending tub- ing, etc. It is arranged so that it may be bent down to ignite the blowpipe jet at c, as shown by the dotted lines. The air pipe is coiled around the gas pipe and both are heated by a small Bunsen burner beneath. This blow- pipe gives a pointed flame that will melt a fine platinum wire. When gas can not be had, alcohol, naphtha or oil may be used with the mouth or blast ..... ^. \ WICK HOLDER TURNED HALF A. REVOLUTION* .;' blowpipe for many pur- poses. A large wick is essential which, with its holder, should be cut obliquely, so that the flame may be directed downward when neces- sary. The lamp should be of such a form that the work may be held close to the wick. A desir- able lamp for such pur- poses, furnished by the Buffalo Dental Manu- facturing Co., is shown in Fig. 161, The wick holder may be adjusted at any angle desired by turning it in its collar. The cut is half the size of the actual lamp. Any such lamp may be used with a common mouth blowpipe, FIG. 161. APPENDIX. 337 such as is shown in Fig. 162, or with the blast from the blower. An attachment, similar to that shown in Fig. 150, may be added to the Bunsen burner for blowpipe purposes. A blowpipe, suf- ficient for many purposes, may be made from glass tub- FlG - l62 - ing. Blowpipes may ba bought in a great variety of forms. In using the mouth blowpipe, air should be forced through it by the action of the cheeks rather than by the action of the lungs. A little practice will enable teacher or pupil thus to maintain a continuous current of air from the nozzle, breathing naturally in the meantime. See the Tinner's Soldering Lamp, App. 18. 18. Soldering. The teacher or pupil will often find it very convenient to be able to solder together two pieces of metal. A bit of soft solder, the size of a hazlenut, may be had gratis of any good natured tinsmith or plumber. Cut this into bits the size of a grain of wheat. Dissolve a teaspoonful of zinc chloride in water and bot- tle it. It may be labelled " soldering fluid." Having bought or made an alcohol lamp (Ph., App. B), you are ready for work. For example, suppose you are to solder a bit of wire to a piece of tinned ware. If the ivire be rusty, scrape or file it clean at the place of joining. By pincers or in any convenient way hold the wire and tin together. Put a few drops of " soldering fluid " on the joint, hold the tin in the flame so that the wire shall be on the upper side, place a bit of solder on the joint and hold in position until the solder melts. Remove from the flame holding the tin and wire together until the solder has cooled. The work is done. The mouth or blast blowpipe, previously mentioned, will be a convenient substitute, in many cases, for the alcohol lamp. Where gas can not be had, the " tin- ner's soldering lamp " is convenient. It may also be used in working glass. At the base of a perforated sheet iron cylinder, M, is a metal alco- hol lamp. The cylinder supports a strong metal cup, C, beaten into shape. The opening by which the alcohol is introduced into this cup may be closed by a cork, which will then act as a safety valve. A bent tube passes from the upper part of the cup and terminates in a nozzle of 1 mm. aperture, midway between the wick of the lamp, a, and the bot- tom of the cup, C, The flame of a vaporizes part of the alcohol in C. This vapor escapes under pressure at the nozzle, where it ignites, forming a pointed, horizontal and very hot flame, which protrudes through the opening in front. The bent tube may pass through a slit in the back side of the cylinder. If you have a "soldering 338 APPENDIX. FIG. 163. iron," you can do a wider range of work, as many pieces of work cannot be held in the lamp flame. Fig. 163 shows a convenient form of heater for such soldering irons. It burns gas. 19. Deflagration Spoon. A deflagrating spoon for burning phosphorus, sulphur, etc., in oxygen may be bought for a few cents of any apparatus dealer. One may be made by soldering the bowl of any ordinary metal spoon or any other metal cup to a long wire handle and bending the wire upward at a right angle near the cup. A cup may be hollowed in the side of a piece of chalk or lime and then fastened to a wire handle. If a metal cup be used for combus- tions in oxygen, it is well to line it with some infusible materinllike clay, powdered chalk, lime or plaster of Paris. . A coated cork cap- sule, smaller than the one mentioned in Exp. 58, may be provided with a wire handle and used as a deflagrating spoon. In any case, the upper part of the wire handle should be straight so that it may be thrust through the cover of the jar. 20. Cocks. Whenever flexible tubing is used, pinch cocks furnish cheap substitutes for stop cocks. Fig. 164 shows one form ; other forms may be found represented in catalogues of dealers in chemical wares. When the gas is to flow, the pinch cock is placed so that the tub- FlG. 164. i n g passes through the open space, o ; when the supply is to be cut off, the tubing is compressed between the arms at c. A s^op cock may be made as follows : Provide two glass tubes, one of which slides easily into the other. Close one end of the smaller tubs (App. 4, d,) and with a rat-tail file wet with a solution of cam- phor in turpentine, make a hole in the side 2 or 3 cm. from the closed APPENDIX. 339 end. Connect the tubes by a piece of rubber tubing that snugly fits the smaller tube. When the smaller tube is pushed into the larger one until the hole in the side is visible (Fig. 165) the cock is open ; when the smaller tube is drawn back (Fig. 166), the hole is closed by the rubber tubing FIG. 165. and the cock is closed. A very simple valve for controlling the flow I of fluids may be made by placing a glass ball in a piece of soft rubber tubing. The ball should be larger than the opening in the tubing. By pinching the rubber at the side of the ball, a little channel is made through which the liquid or gas may pass. FIG. 166. 21. Evaporating Dishes, Crucibles and Fur- naces. Evaporating dishes may be had made of porcelain and pro- FIG. 167. FIG. 168. vided with a projecting lip and glazed on both sides or only en the inside. The latter are the cheaper but the former are the more desirable. Sizes from 8 to 15 cm, in diameter are best adapted to the needs of most classes. They should be supported upon wire gauze, the sand or water bath and never exposed to the naked flame. For granulating zinc ( 21) or fusing salt ( 99), Hessian crucibles are cheap and largely used. They will endure a very high temperature but should be heated somewhat gradually. They may be heated in a coal or coke fire in any ordinary stove. Heated crucibles may be handled conven- FIG. 160. iently with crucible tongs, two common 340 APPENDIX. forms of which are represented in Fig. 168. They may be had of Bullock & Crenshaw, Philadelphia. Small clay crucibles and cap- sules are very valuable pieces of apparatus. With the Fletcher " Blowpipe Furnace " and the clay crucible shown in Fig. 169, several grams of cast iron may be melted in a very few minutes. For melting iron, brass, copper, etc., up to quantities of five or six pounds, the " Injector Gas Furnace," shown in Fig. 170, and a plumbago crucible, AIR CHECK FIG. 170. are convenient and efficient. The plumbago crucible must be heated slowly the first time it is used. Smaller quantities (about 1 Kg.\ of such metals may be melted in a plumbago crucible, by the Fletcher FIG. 171. " Crucible Furnace for Petroleum," shown in Fig. 171. These three Fletcher Furnaces require the aid of the " Blower," shown in Fig. 156 or 158. 2*2. Uletal Retorts. Oxygen maybe prepared by carefully heating the materials in a Florence flask or glass retort, but for this APPENDIX. 341 and other processes, where high temperatures are used, as in the prepa- ration of illuminating and marsh gases, an iron or copper retort is very desirable. Such retorts may be had in a variety of forms, made of iron, sheet iron or copper, of dealers in chemical or philosophical apparatus, at prices ranging from $1 upwards. The author has made a very cheap and wholly efficient retort as follows : Cut a thread on each end of a piece of inch or f-inch gas pipe, a, 6 or 8 inches long/ Screw an iron cap, k, over one end. For the other end, provide an iron ! "reducer," t, carrying a piece of f-inch gas pipe, e, about 15 or 18 FIG. 172. inches long. The materials being placed in the capped tube, the re- ducer with its pipe is screwed on the open end of the tube. The closed retort may then be thrust into the coals of any ordinarystove. A piece of glass tubing maybe sealed, with plaster of Paris, into the end of the small iron tube. This affords a good means for connect- ing the retort with rubber tubing and protects the latter from burn- ing. If desirable, the inner surface of k may be smeared with wet plaster of Paris before screwing it upon a. If, at the end of the ex- periment, t is not easily removed from a, a few blows will generally start it. The parts of this retort may be had of any gas or steam fitter. A sheet iron retort may be made by any tinner as follows : the conical piece, ia, has a horizontal flange turned around its lower edge at a. The circular bottom piece has its edge turned over this flange, as shown in the sectional figure, and hammered down. The joint on the sloping side, ia, is lapped and hammered, as is generally done in making , stove pipe. The mouth at i is made slightly flaring FIG. 173. by hammering, to admit a cork carrying a glass de- livery tube. The joints may be sealed by washing them on the inside with a thin paste of plaster of Paiis. The cork may be protected from over heating by providing a cup, cc, which may be filled with water or a wet cloth. A good retort may be made by luting on the cover of a small iron kettle and connecting a delivery tube with its nose. 23. Ventilating Chamber, etc. A chamber, 50 cm. by 75 cm. or larger, with glass sides and provided with a ventilating flue that has a good draft, is important for experiments with chlorine, hydrogen sulphide, etc. The ventilating flue may, in some cases, be advantageously connected with the chimney. It may be built against the chimney and provided with two or three narrow slits 342 APPENDIX. through the brick work from top to bottom of the closet. At least one side of the chamber should be made so that it may be opened, but when shut, it should fit closely. Openings that may ba closed, should be made in the bottom of the chamber for the admission of air so that a current may be obtained. A lamp burning in the cham- ber will aid in keeping up the current and carrying off the offensive gases. 24. Test Papcr, etc. Litmus paper, both blue and red, should be kept on hand for the detection of acids and alkalies. Lit- mus is a blue coloring matter prepared from certain lichens and found in commerce in small cubical masses somewhat soluble in water. White, unsized paper is stained with an infusion of 30 g. of litmus in 250 cu. cm. of boiling water. Such a paper is reddened by an acid (Exps. 41, 106, etc.). The blue litmus paper may be faintly reddened by immersion in vinegar or any other dilute acid. This reddened paper is colored blue by the action of an alkali (Exp. 64). A purple liquid may be prepared by steeping red cabbage leaves in water and filtering. Such a cabbage solution will be colored red by an acid, or green by an alkali.^ Prepare such, a solution. To a part of it, add a few drops of sulphuric acid ; it will become red. To another part, add a few drops of a solution of potassium hydrate ; it will become green. With constant stirring, cautiously pour the red liquid into the green. At first, the red color will disappear and the compound appear green, but, by continued addition of the red liquid, a point will be reached when the compound will be blue instead of green. The acid and alkali are then mutually neutralized. Com- pare Exp. 78. A ruby red tincture of cochineal may be prepared by digesting 3#. of cochineal in a mixture of 50 cu. cm. of alcohol and 200 cu. cm. of water at the ordinary temperature for several days. Acids will change the color of such a tincture to orange ; alkalies will change it to violet carmine. Turmeric paper, prepared by staining unsized paper with a tincture (alcoholic solution) of turmeric root (curcuma), is sometimes used as a test for alkalies which turn it from yellow to brown (Exp 64). See also Exps. 99 and 100. FIGURES REFER TO PARAGRAPHS, UNLESS OTHERWISE SPECIFIED, Acetic acid, 215. Acetyl, 2150:. " hydrate, 215, a. " hydride, 215, a. Acetylene, 219. Acid, Acetic, 215. " Anhydrosulphuric, Ex. 6, p. 136. " Arsenic, etc., 249. " Basicity of an,i64. " Binary, 163, b. " Boracic, 173. " Boric, 173. " Bromic, etc., 116. " Carbonic, 198. " Chamber, 152, c. " Chlorhydric, 104. " Chloric, etc'., 112. u Chromic, 381, &. " Cyanhydric, 205. " Definition of, 163. " Disulphuric, 156. " Fluorhydric, 122. " Fuming sulphuric, 156. " Glacial phosphoric, 242, e. " Haloid, 123, b. " Hydrochloric, 104. " Hydrocyanic, 205. " Hydrofluoric, 122. " hydrogen, 166, b. " Hydrosulphuric, 137. " Hyponitrous, 82. " lodic, etc., 118. " Manganic, 376, e. '* Metaphosphoric, see Phosphoric. u Molybdic, 382. " Muriatic, 104. 41 Nitric, 73. Acid, Nitro-hydrochloric, 114. " Nitro-murialic, 114. " Nitrous, 86. " Nordhausen, 156. " Oxalic, Exp. 289. " oxides, 165. " Permanganic, 376, f. Phosphoric, etc., 242. " Prussic, 205. " Pyroboric, 173, b. Pyroligneous, 215. Pyrophosphoric, 242. " salts, 170. " Silicic, Exp. 217. " Stannic, 389. " Sulphuric, etc., 149, 151, 157, 158. " Ternaty, 163, c. " Thionic, 158. " Tungstic, 383, Acidity of bases, 166, b. Acids, Nomenclature of, 163. Affinity, Chemical, 8, 9. Agate, 232, . Air, 45-49. " slaked lime, 290, c. Alabaster, 294. Albumen, 223. Alcohol, 210. Aldehyde, 215, a. Alkali, 167, b. " The volatile, 168. Allotropism, 39. Alloys, 322 ; 303, a. Alum, 349. Alumina, 348. Aluminium, see Aluminum. Aluminum, 344. " bronze, 347. 344 INDEX. Figures refer to Paragraphs, unless otherwise specified. Aluminum, group, 352. " oxide, 348. sulphate, 349. Amalgam, 338. Amethyst, 232, a. Amide, Ex. 17. p. 314. Amine, 96, a ; Ex. 16, p. 314. Ammonia, 66, 168. type, 96. Ammonium, 168, 286. chloride, 287. nitrate, 288. Amorphous, Note, p. 113. Amp' re's law, 61. Analysis defined, 18. " of water, 14. " Quantitative, Note, p. 296. Anhydride, 165. Anhydrite, 294. Anhydrosulphuric acid, Ex. 6, p. 136. Animal charcoal, 186. Anthracite, 181. Antimoniuretted hydrogen, 253,0. Antimony, 251, 44 chlorides, 253,^. 44 glance, 251. 44 hydride, 253, a. " oxides, 253, b. 44 sulphides, 253, c. Antozone, 38, a. Aqua fortis, 73. " regia, 114. Argentum, etc., see Silver. Arrow root, 228. Arsenic, 243. acid, 249. 44 hydride, 245. 41 oxides, 247, 248. 44 sulphides, 250. White, 247. Arsemuret, Note, p. 217. Arseniuretted hydrogen, 253, a. Arsine, 245. Aspirator, App. 13. Atom defined, 5. Atomic attraction, 8, 9. 41 symbols, 56, 93. 44 volume, 175, a ; 240. e. " weight, 64. Atomicity, 65 ; 92, d ; 174. Attraction, Forms of, 8. Auric, see Gold. Aurous, see Gold. Avogadro's law, 61. Azurite, 319, a. Barley sugar, 226, c. Barite, 131, b. Barium, 297. Baryta, 297. Base defined, 166. Bases, Acidity of, 166, b. Basic ammonia, 168. " hydrogen, 164. 44 oxides, 166, a. 44 salts, 170. Basicity of acids, 164. Bauxite, Beakers, App. 7. Beet sugar, 226, b, Bell metal, 322, 388. Benzol, 221, c. Beryllium, 305. Bessemer steel, 371. Bicarbonate of sodium, 269. 41 of potassium, 279. Bichromate of potassium, 381, c. Binary acids, 123, b. 44 compounds, 59. Bismuth, 254. Bisulphide of carbon, 201. Bisulphate of sodium, 267, c. Bituminous coal, 181. Bivalent, 92, a. Black ash, 268, a. Black-band iron stone, 354, a. Black lead, 179. Black oxide of manganese, 376, d. Blast furnace, 359. Bleaching powder, 292, b. Blende, 131, a ; 301. Blister steel, 370. Bloom, 356. Blower, App. 17. Blowpipes, App. 17. Blowpipe, The compound, 41. Blue vitriol, 324. Bohemian glass, 234, a. Bone-black, 186. INDEX. 345 Figures refer to Paragraphs^ unless otherwise specified. Bone phosphate, 295. Boracic acid, 173. Borax, 172, 271. Boric acid, 173. Boron, 172. Bottle glass, 234, c. Brass, 303, a \ 322. Braunite, 375. Bread making, 229. Brimstone, 132, d. Britannia metal, 388, a. Bromine, 115. Bronze. 322, 347, 388. Brown sugar, 226. Bulbs, Blowing, App. 4, e. Bunsen burner, App. 15. Butter of antimony, 253, d. " of tin, 389. Cadmium, 306. Caesium, 285. Cairngorm-stone, 232, a. Calamine, 301. Calcareous waters, 293. Calcic, see Calcium. Calcite, 289. , Calcium, 289. " carbonate, 293. " chloride, 291. " chloro-hypochlorite, 292, b. " hydrate, 292, " tiypochlorite, 292, b. " light, Exp. 49 ; 290. " oxides, 290. " phosphate, 295. " stearate, 294, a. " sulphate, 294. Calomel, 342. Calx, Note, p. 246. Cane sugar, 226. Caoutchouc stoppers, App. 8r Caramel, 226, c. Carbon, 177. " disulphide, 201. " dioxide, 196. " group, p. 155. " monoxide, 193. " oxides, 192. Carbonic acid, 198. Carbonic anhydride, 196. Carbonyl, 194, b. Carburet, Note, p. 164. Carnallite, 276. Carnelian, 232, a. Casein, 223. Casserite, 385. Cast iron, 358. Catalysis, 31. Caustic lime, 292. " lunar, 332. " potash, 280. " soda, 270. Celestine, 296. * Cellulose, 230. Cementation steel, 370. Centesimal computations, 130. Ceric, see Cerium. Cerium, 353. Cerous, see Cerium. Chalcedony, 232, a. Chalcocite, 131, a ; 319, a. Chalcopyrite, 319, a. Chalk, 289. Chamber acid, 152, c. Charcoal, 184-191. Chemical action, TI. " affinity, 8. " changes, 10. " equations, 127. Chemism, 8. Chemistry defined, 13. Chili nitre or saltpeter, 271, b. Chlorate of potash, 281. " of potassium, 281. Chlorohydric acid, 104. Chloride of antimonj', 253, d. u of ethylene, Exp. 209. " of hydrogen, 104. " of lime, 292, b. " of methyl, 209. " of nitrogen, 113. - Chlorine, 98. " acids, 112. " Diatomic, 174. " group, 123. " oxides, in. Chloroform, 209. Chrome alum, 381, d. " iron ore, 381. 346 INDEX. Figures refer to Paragraphs, unless otherwise specified. Chrome, yellow, 316, b \ 381, c. Chromic acid, 38:, b Chromite, 381. Chromium, 381. " steel, 381. Cinnabar, 334, 340. Clay, 233, 344. " iron-stone, 354, a. Coal, 181, 184, 186. " gas, 221. " tar, 221, c, Cobalt, 378. Cocks, App. 20. Coin, 328, 379; 396. Coke, 182. Collection of gases, 21 ; Exps. 15, 185. Colloid, Exp. 218. Colored glass, 234, h. Columbium, 260. Combining weight of compounds, 63. " " of elements, 64, a. Combustion, 33. Combustible, 43. Composition of elementary molecules, 65- Computations, 128-130. Compound blowpipe, 41. " radicals, 97. Compounds, 6, 12. Concentrated lye, 270. Constitutional symbols, 95. Cooking soda, 269. Copper, 319. " acetate, 215, c ; 324. " arsenite, 324. " carbonate, 324. " glance, 319, a. " nitrate, 324. " oxides, 323. pyrites, 319, a. " Ruby, 323. " snlphate, 324. Coral, 289. Corks, App. 9. Corrosive sublimate, 343. Corundum, 348. Cream of lime, 292. Crith defined, 24. Crocus, 362, b. Crown glass, 234, b. Crucibles, App. 21. Crucible steel, 373. Cryolite, 120, 349. Crystal, 234, d. Crystals, Classes of, Note, p. 113. Crystallization, 268, b. " water of, 268, c. Crystalloid, Exp. 218. Cupric, see Copper. Cuprite, 319, a. Cuprous, see Copper. Cyanhydric acid, 205. Cyanogen, 204. D Davy's glow lamp, Exp. 304. Davyum, App. i. Decipium, App. i. Definite proportions, Law of, 90. Deflagrating spoon, App. 19. Deliquescence, 280, a. Dextrin, 228. Dextrose, 22% Dialyser, Exp. 218. Dialysis, Exp. 218. Diamond, 178. Di , see bi . Dicarbonate, see Bicarbonate. Dichromate, see Bichromate. Didymium, 353. Dimorphous, Note, p. 113. Disulphate, see Bisulphate. Disulphide of carbon, 201. Double salts, 170. Drummond light, Exp. 49, 290. Drying gases, Exps. 61, 88 ; App. 14. Dutch leaf, Exp. 74. u liquid, Exp. 209. Dyad, 92, a. E Efflorescence. 268, c. Egg shells, 293. Element defined, 6. Elements, Molecular composition 05,65. " Nomenclature of, 58. u Electro-negative, 166. " Electro-positive, 163. " Table of, App. i . Emerald, 344, 381. Emery, 348. INDEX. 347 Figures refer to Paragraphs^ Empirical symbols, 94. Epsom salt, 300. Equations, Chemical, 127. Equivalence, 92, d. Erbium, 353. Etched glass. 234, /. Etching, 77, Exps. 126-8. Ethene, 217. Ether, 213. Ethine, 219. Ethyl, 211. " hydrate, 211. " oxide, 213. Ethylene, 217. u chloride, Exp. 209. Eudiometer, 42. Evaporating dishes, App. 21. Factors, 126. Feldspar, 233, 344. Fermentation, 210, Exp. 187. Ferric, see Iron. Ferrous, see Iron. Fibrin, 223. Filtering, App. 8. Flasks, App. 7. Flint, 232, a. " glass, 234, d. Florence flasks, App. 7. Flowers of sulphur, 132, d. Flue dust, 317. Fluorhydric acid, 122. Fluorine, 120. Fluor spar, 120. Flux, 359. Formulas, Molecular, Note, p. 54. Fruit sugar, 227. Fulminating silver, 329. Fuming sulphuric acid, 156. Funnels, App. 8. Funnel tubes, App. 4, e. Furnaces, App. 16 and 21. Fusible metals, 256. Galena, 131, a ; 308, 313. Galenite, 308, 313. Gallium, 351. Galvanized iron, 303, b. unless otherwise specified. Garnet, 344. Gas carbon, 183. " holders, App. 13. u Illuminating, 221. Gases, Collection of, 21, Exps. 15, 185. " Drying, Exps. 61, 88 ; App. 14. Gay-Lussac's law, 176. tower, 152, c. Gelatin, 224. German silver, 303, a 379. Glacial phosphoric acid, 242, e. Glass, 234. " stoppers, App. 9. " Ruby, 395, a. u tubing, App. 4, a. " Uranium, 384. " working, App. 4. Glauber's salt, 267, b. Glucinum, 305. Glucose, 227. Glow lamp, Davy's, Exp. 304. Glover tower, 152, c. Glue, 224. Gold, 393. Graduates, App. 5. Grape sugar, 227. Graphic symbols, 95. Graphite, 179. Gravimetric computations, 128. Green vitriol, 367. Gray antimony, 251. " oxide of mercury, 339. Gun cotton, 230, b. Gypsum, 131, ; 294. H Haematite, 354, a. Halogen group, 123. Haloids, 123, b. Hard coal, 181. " soap, 270 ; 278, b. " water, 294. Hartshorn, 66. Hausmanite, 375 Heavy spar, 131, b \ 297. Hematite, 354, a. Hemioxide, 323, 329. Heptad, 92, a. Hexad, 92, a. Hexivalent, 92, a. 348 INDEX. Figures refer to Paragraphs^ unless otherwise specified. Homologous series, 220. Horn silver, 330. Hydrargillite, Hydrates, 167. Hydraulic main, 221, e. Hydrocarbons, 206. Hydrochloric acid, 104. " " type, 96. Hydrocyanic acid, 205. Hydrofluoric acid, 122. Hydrogen, 15. 19. Acid, 166, b. " antimonide, 253, a. " arsenide, 245. " Basic, 164. " carbide, 207. H chloride, 104. " Collection of, 22. " Combustion of, 40. " Diatomic, 174. " dicarbide, 217. " dioxide, 44. " oxides, 44. " peroxide, 44. " persulphide, Note, p. 122. a phosphide, 240. " pistol, Note, p. 40. " potassium carbonate, 279. *' preparation of, 21. " properties of, 24, 25. " purification of, 26. " salts, 170, c, Note, p. 144. " silicide, 231, d. " sodium carbonate, 269. " sodium sulphate, 267, c. " sulphate, 151. " sulphide, 137. " Tests of, 28. " tones, Exp. 29. type, 96. " Uses of, 27. Hydrosulphites, Ex. 4, p. 305. Hydroxides, 167. Hydroxyl, 44. Hyponitrous acid, 82. Hyposulphites, 157 ; 158, b. Illuminating gas, 221. Indigo, Exps. 269 and 270. Indium, 330. Inorganic substances, 7. International measures, A pp. a. Inulin, 228. Inverted sugar, 227. Iodide of nitrogen, 119. Iodine, 117. Iridiutn, 402. Iron, 354. " carbonate, 367, a. " Cast, 358. * chloride, 366. " cyanide, 368. " Galvanized, 303, b. " group, 380. " hydrates, 363. " Malleable, 374. " nitrate, 367, a. " ores, 354, a. " oxides, 362. " Pig, 358. ;4 pyrites, 132, c : 364. " salts, 365. " spathic, 354, a. '' specular, 354, a. " sulphate, 367. " sulphide, 364. u Wrought, 360. Isinglass, 224. Isomerism, 216. Isomorphism, Note, p. 113. Jasper, 232, a. Jeweller's rouge, 362, b. K Kieserite, 300. King of metals, 395, a. Lactose, 226, d. Lagoon, 173, d. Lamp-black, 185. Lamps, App. 15 and 16. Lanthanum, 353. Laughing gas, 79. Law, Ampere's or Avogadro's, 61. " Gay-Lussac's, 176. " of definite proportions, 90. INDEX. 340 Figures refer to Paragraphs, unless otherwise specified. Law of multiple proportions, 9: Lead, 308. " acetate, 215, c \ 314. " Black, 179. u carbonate, 314. " chloride, 314 ; 316, b. " chromate, 316 b. " group, 318. " iodide, 316, b. i; oxides, 312. " pencils, 179. '' poisoning, 315. " Red, 312. " Sugar of, 314. ' sulphide, 313. " Tests for, 316. " tree, Exp. 271. " White, 314. Leblanc, 268. Levulose, 227. Lichtenberg's metal, 256. Liebig condenser, Exp. 202. Lignite, 181. Lime, 290. " Air slaked, 290, c. " Caustic, 192. M Chloride of, 292, b. " Cream of, 292. u light, 290. " Milk of, 292. " Slaked, 292. " soap, 292, a ; 294, a. " stone, 289, 293. *' water, 292. Limestone, 289, 293. Limonite, 354, a. Litharge, 312. Lithium, 283. Litmus paper, App. 24. Loadstone, 362, c. Lunar caustic, 332. Lye, 270, 278. M Matter defined, i. u Divisions of, 2. Mass defined, 3. Magnesia, 299. " alba, 300. Magnesite, 300. Magnesium, 298. " carbonate, 300. chloride, 300. group, 307. oxide, 299. sulphate, 300. Magnetite, 354, a. Malachite, 319, a ; 324. Malleable iron, 374. Maltose, 226, d. Manganese, 375. salts, 377. oxides, 376. Manganic acid, 376, e. " anhydride, 376, e. Manganite, 376, c. Maple sugar, 226, b. Marble, 289. Marsh gas, 207. " type, 96. Marsh's test, 246. Mercury, 334. " bromides, 342, b ; 343, c. chlorides, 342, 343. " iodides, 342, b ; 343, U Unit volume, 175. Univalent, 92, a. Uranium, 384. Uranyl, 384. U-tubes, App. 4, b. Valence, 92, d. Vanadium, 258. Vegetable parchment, Exp. 216. Ventilating chamber, App. 23. Ventilation, 194, 199. Verdigris, 215, c ; 324. Vermillion, 340. Vinegar, 215. Vital air, 35. Vitriol, Blue, 324. " Green, 367. " Oil of, 151. " White, 304. Volatile alkali, 168. Volumetric combination. Law of, 176. " computations, 129. W Wash bottle, App. 8. Washing soda, 268, b. Water, Analysis of, 14. " bath, App. 10. " composition of, 14, 17, 40, " glass, 234. Hard and soft, 294. u of crystallization, 268, c. " synthesis of, 17. " type, 96. White arsenic, 247. " lead, 314. " vitriol, 304. Window-glass, 234, b. Wood's metal, 256. Woulffe bottle, Note, p. 23 ; App. 6. Yellow chromate of potash, 381, c. 354 INDEX. Figures refer to Paragraphs, unless otherwise specified. Yellow prussiate of potash, 368. Yttrium, 353. Zinc, 301. " carbonate, 301. u chloride, 304. '' dust, 302, c. " ore, 301. Zinc oxide, 304. " silicate, 301. " spar, 301. " sulphate, 304. " sulphide, 301. " white, 304. Zincite, 301. Zirconia, 391. Zirconium, 391. NEW AX1> VALVBLE TEXT-BOOKS. A V E R Y ' S ELEMENTS OF NATURAL PHILOSOPHY. It is the most elegantly illustrated text-book on Natural Philosophy that has been published for Schools. 1st. It is well known that thoroughly good text-books on the Natural Sciences are the most difficult to obtain. 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