THE COMPLETE C H EM I STRY A TEXT BOOK FOR HIGH SCHOOLS AND ACADEMIES. BY ELROY M. AVERY, PH.D., AUTHOR OF A SERIES OF TEXT BOOKS ON PHYSICAL SCIENCE. ILLUSTRATED BY NEARLY 2OO WOOD ENGRAVINGS. SHELDON & COMPANY, NEW YORK AND CHICAGO. DR. AVERY'S PHYSICAL SCIENCE SERIES. I St. FIRST PRINCIPLES OF NATURAL PHILOSOPHY. ad. THE ELEMENTS OF NATURAL PHILOSOPHY. 3 d. THE ELEMENTS OF CHEMISTRY. 4 th. THE COMPLETE CHEMISTRY. This contains the ELEMENTS OF CHEMISTRY, with an additional chapter on Hydrocarbons in Series or Organic Chemistry. It can be used in the same class with THE ELEMENTS OF CHEMISTKY. Copyright^ 1881, 1883, by Sheldon &> Co. Electrotyped by SMITH A McDouGAL, 82 Beekman St., New York. HTTTAVE 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 musf 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 feet) wide. Each pupil should be allotted about a meter of working space at these tables, and held 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 237483 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, with further and better means than those above suggested, is desirable, and should be provided, when means can be secured for the purpose. See Frick'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 may make. He gratefully acknowledges the aid given him by many of his fellow-teachers. Especial mention is due Mr. John Bolton, Instructor in Physical Science in the West High School of Cleveland, 0., for great help in the preparation of Chapter XXV. 1 PAVE a place for everything, and keep everything in " 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. Acquire 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 right, 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 why you do a thing before you do it. Always VI TO THE PUPIL. 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 following pages, the specific gravity of all gases is referred to hydrogen as the standard. All temperatures are recorded in Centigrade degrees. ^ .._.-- PAGE TO THE TEACHER iii TO THE PUPIL v CHAPTEK I. THE DOMAIN OF CHEMISTRY 1 CHAPTEE II. WATER AND ITS CONSTITUENTS. SECTION I. ANALYSTS OP WATER 10 " II. HYDROGEN 14 III. OXYGEN 27 IV. COMPOUNDS OF HYDROGEN AND OXYGEN. ... 88 CHAPTEE III. AIR AND ITS CONSTITUENTS. SECTION I.-)tAiR 45 IL NITROGEN 50 CHAPTEE IV. SYMBOLS, NOMENCLATURE, MOLECULAR AND ATOMIC WEIGHTS.. 53 Vlll CONTENTS. CHAPTER V. COMPOUNDS OF HYDROGEN, OXYGEN AND NITROGEN. PAGE SECTION I. AMMONIA 59 " II. 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. OTHER CHLORINE COMPOUNDS 93 " IV. BROMINE, IODINE, FLUORINE 97 CHAPTER VIII. STOICH IOMETRY 104 CHAPTER IX. THE SULPHUR GROUP. SECTION I. SULPHUR 110 " II. HYDROGEN SULPHIDE 117 " III. SULPHUR OXIDES AND ACIDS 124 " IV. SELENIUM AND TELLURIUM 137 CHAPTER X. ACIDS, BASES, SALTS, Etc 140 CHAPTER XI. BORON .147 CONTENTS. IX CHAPTER XII. PAGE VOLUMETRIC CONSIDERATIONS 151 CHAPTER XIII. THE CARBON GROUP. SECTION I. CARBON 155 " II. SOME CARBON COMPOUNDS 166 III. SOME HYDROCARBONS 177 " IV. ILLUMINATING GAS 188 V. SOME ORGANIC COMPOUNDS 194 VL 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 CONTENTS. CHAPTER XIX. METALS OF THE COPPER GROUP. PAGE SECTION I. COPPER. 263 II SILVER 267 " III. MERCURY 271 CHAPTER XX. METALS OF THE ALUMINUM AND CERIUM GROUPS.. 275 CHAPTER XXI. METALS OF THE IRON GROUP. SECTION I. IRON 279 II. STEEL 290 " III. MANGANESE, COBALT AND NICKEL 295 CHAPTER XXII. METALS OF THE CHROMIUM GROUP 299 CHAPTER XXIII. METALS OF THE TIN GROUP 302 CHAPTER XXIV. METALS OF THE GOLD GROUP 306 CHAPTER XXV. ORGANIC CHEMISTRY. SECTION I. THE PARAFFINS 315 II. THE OLEFINES 342 " III. THE BENZENE SERIES 352 M IV. TERPENES, ALKALOIDS, ETC 373 APPENDIX 381 INDEX.. . 409 V. THE DOMAIN OF CHEMISTRY. 1. What is Matter? Matter is anything that occupies space or "takes up room." 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 mass. The word atom is from the Greek, and signifies, etymologi- 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 exist by itself t 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 nature. Molecules are exceedingly 2 THE DOMAIN OF CHEMISTRY. 4 small, far beyond the reach of vision even when aided by a powerful microscope. (a.) According to one of the best authorities, a cubic decimeter (Appendix 2) of gas, at the ordinary atmospheric pressure, contains about 1,000,000,000,000,000,000,000,000 (=10 24 ) molecules. (6.) Natural Philosophy teaches us that heat is one kind of energy resulting from motion (Ph. 473). But this motion of a hot body, constituting the heat of the body, is wholly invisible. The motion pertains to " parts of the body too minute to be seen separately and within limits so narrow that we cannot detect the absence of any part from its original place. We are to have the conception of a body consisting of a great many small parts, each of which is in motion. We shall call any one of these parts a molecule of the sub- stance. A molecule may, therefore, be denned as a small mass of matter, the parts of which do not part company during the excur- sions which the molecule makes when the body to which it belongs is hot." (c.) The molecules of any given substance are held to be exactly aiike, but different from the molecules of any other substance. For example, one copper molecule is exactly like every other copper molecule, but different from every molecule of any substance that is not copper. The nature of the substance, therefore, depends upon the nature of its molecule. 5. What is ail Atom ? An atom is the small*, est particle of matter that can exist even in com- bination. (a.} Nearly every molecule is composed of two or more atoms. As we shall see, some molecules are very complex. The common sugar molecule contains forty-five atoms. (&.) An atom may also be denned as the smallest quantity of an element that exists in any molecule. 6. Elementary and Compound Substances, All substances are classified as being either elementary or compound. Any substance that can not be sep- arated, by any known means, into two or more essentially different kinds of matter, is called an THE DOMALV OF CHEMISTRY. 3 dement. Any substance that can be thus separated is called a compound. Compounds consist of two or more elements in chemical combination. The atoms of any given element are of the same kind ; those of a compound are of two or more kinds. There are as many kinds of atoms as there are elements. Sixty-six elements have been already recognized (see Appendix 1). Some of these are very abundant and widely distributed ; others have been found only in such minute quantities that even their properties have not yet been satisfactorily determined. Other elements will doubtless be discovered and it is possible that some substances now considered ele- mentary will be found to be compound. In fact, nearly every improvement in our methods of examination (see Ph., 638, b) leads to the detection of elements previously unknown. Silver and gold are elements ; wood and water are compounds. 7. Organic and Inorganic Substances. - Substances that have been formed by animal or vegetable life are called organic substances ; those that have not been thus formed are called inor- ganic. Flesh and bone, oak and cotton are organic sub- stances; metals, air, water, etc., are inorganic. (a.} This distinction is less important than formerly. Of late years, chemists have succeeded in producing several " organic " sub- stances from "inorganic" materials. The old barrier between or- ganic and inorganic chemistry is being broken down, and many chemists now look forward, not hopelessly, to a future when even food may be made in the chemical laboratory as well as in the fields and pastures. 8. Forms of Attraction. Each of the three di- 4 THE DOMAIN OF CHEMISTRY. 8 visions of matter has its peculiar form of attraction. The attractions of masses and molecules pertain more particu- larly to natural philosophy ; the attraction existing be- tween atoms pertains chiefly to chemistry. Atomic at- traction is called chemism or chemical affinity. Experiment 1, Pulverize separately a teaspoonful each of loaf- sugar and potassium chlorate (chlorate of potash) and mix them together upon a porcelain plate. Dip a glass rod (Appendix 4, a) into strong sulphuric acid and hold the rod in a horizontal position over the mixture and close to it but so as not to touch it. Notice that there is no peculiar action visible. Now hold the rod in a vertical position, so that a drop of acid will fall upon the mixture. The mixture is immediately ignited. Experiment 2. Into a mortar, put a bit of potassium chlorate the size of a grain of wheat, and cover it with powdered sulphur. Notice that there is no peculiar action visible. Now rub them to- gether vigorously with the pestle. A sharp explosion or a succes- sion of minute explosions will take place. Jgg" See the Caution following Experiment 36. Experiment 3. Cover a bit of phosphorus, the size of a pin head, with pulverized potassium chlorate and wrap the materials in a bit of soft paper, so as to form a minute torpedo. The phosphorus and the particles of potassium chlorate lie close together, but no action takes place. Now place the torpedo on a small anvil or other smooth, hard surface and force the phosphorus and potassium chlorate closer together by a blow with a hammer. A violent explosion takes place. 9. Peculiarities of Chemical Affinity. The foregoing experiments illustrate the fact that atomic at- traction is effective at insensible distances only. In only a few cases is it possible by mechanical means to bring solid particles sufficiently near each other for the desired chemical action. The necessary freedom of molecular motion (Ph., 54, 55, 57), is generally secured by solution, fusion or vaporization of one or more of the 10 THE DOMAIN OF CHEMISTRY. 5 materials used Hence solvents and heat are important agents in the chemical laboratory. Another peculiarity is that dtoitiic attraction is most energetic between dissimilar substances. (a.) A body is dissolved or " in solution" when it is so finely di- vided and its particles are so completely dispersed through the water or other solvent that they can neither be seen nor separated from the liquid by filtering. 1O. Physical and Chemical Changes. A physical change is one that does not change the composition of the molecule, and, therefore, does not change the nature of the substance acted upon. A chemical change is one that does change the composition of the molecule and, therefore, does change the nature of the substance. (a.) A piece of marble may be ground to powder, but each grain is marble still. Ice may change to water and water to steam, yet the nature of the substance is unchanged. Such as these are physical changes. But if the piece of marble be acted upon by sulphuric acid, a brisk effervescence takes place, caused by the escape of carbon dioxide, which was a constituent of the marble ; calcium sulphate (gypsum), not marble, will remain. (Experiment 185.) The water may, by the action of electricity, be decomposed into hydrogen and oxygen. (Experiment 12.) Such as these are chemical changes. Experiment 4- Rub together in a mortar 4 g. of sodium sulphate crystals and 2 g. of potassium carbonate. The two solids form a liquid. Repeat the experiment with ice and salt. Experiment 5. Saturate 4 cu. cm. of water with calcium chloride ( 291). Add slowly 0.5 cu. cm. of sulphuric acid. The two trans- parent liquids form a white, opaque solid. [Ph., 524 (4).] Experiment 6. Moisten the inner surface of a beaker glass, or clear tumbler, with strong ammonia water, and place a few drops of the liquid in the glass. Cover it with a glass plate (or piece of writing paper). Moisten the inner surface of a similar clear glass THE DOMAIN OF CHEMISTRY. 10 vessel with hydrochloric (muriatic) acid. Invert the second vessel over the first, mouth to mouth, so that the contents of the two vessels shall be sep- arated only by the glass plate. Each vessel is filled with an invisible gas. Now remove the glass plate. The in- visible gases diffuse into each other and form a dense cloud that slowly settles in the form of a white powder. rIG. I. Experiment 7. Dissolve five or six lumps of loaf-sugar in a beaker glass or a tea-cup with as little warm water as possible. Place the beaker glass upon a large plate and into the syrup slowly pour strong sulphuric acid, stirring the contents of the beaker glass at the same time. A black, porous solid will fill the glass, and probably overflow upon the plate. Experiment 8. In a conical test-glass, or a test-tube, dissolve a few crystals (0.5 g.) of silver nitrate in 10 cu. cm. of water. In a second test-glass, place a similar solution of lead nitrate ; in a third, a solu- tion of mercuric chloride (corrosive sublimate) ; in a fourth, 10 cu. cm. of chlorine water (Exp. 86), to which a few drops of a freshly prepared dilute solution of starch have been added. Each solution will be as clear as water. To each, add a few drops of the colorless solution of potassium iodide, and notice the colors produced, yellow, orange, scarlet and blue. Experiment 9. Into a glass tube 2 cm. in diameter, and 15 or 20 cm. in length, having one end closed and rounded like a test-tube, place 20 mg. of freshly burnt char- coal. Draw the upper part of the tube out to a narrow neck. Fill the tube with dry oxygen and seal the tube by fusing the neck. Weigh the tube and its contents very care- FIG. 2. II TEE DOMAIN OF OffEMlSTRT. 7 fully. By gradually heating the rounded end of the tube, the char- coal may be ignited and, with sufficient care, entirely burned without breaking the tube. When the charcoal has disappeared, weigh the tube and its contents again. The chemical changes that led to the disappearance of the charcoal have caused no change in the weight of the materials used. See App. 4, c and d. Experiment 10. Put a few small pieces of zinc into a test-tube and pour some strong nitric acid upon them. Reddish fumes appear, and the tube becomes warm. 11. Characteristics of Chemical Action. From the preceding pages we learn that atomic attraction is a very powerful agent in its own field, but that it acts only upon the minutest divisions of matter (atoms) and at dis- tances too small to be perceptible. The resulting action leads to a general change of properties, physical and chemical, always excepting weight. This exception is the direct result of the indestructibility of matter (Ph., 37). Every atom of matter has a certain definite weight, and as, in these changes, the atoms are merely rearranged but none destroyed or created, the sum total of the weights of these atoms must remain unchanged. Whenever these atoms rush together (synthesis, 18) they develop heat, which is thus a frequent result of chemical action (Ph., 568). As will be seen from the next paragraph, chemi- cal action takes place between definite quantities of mat- ter only. Experiment 11. Fine iron filings and powdered sulphur may be mixed in any proportion. From such a mixture the iron may be re- moved by a magnet ; the sulphur may be removed by solution in carbon disulphide ( 201), filtration and subsequent evaporation of the filtrate. The iron is still iron, the sulphur is still sulphur. In the mixture the free iron or sulphur particles may be detected with a microscope. Now mix thoroughly 4 g. of the powdered sul- phur with 7 g. of the iron filings, and place the mixture in an igni- tion stituent of the mixture. The ferrous sul- phide, which contains the iron and the sul- phur, differs from both in appearance and properties. It always consists of 7 parts of iron to 4 parts of sulphur by weight (or 56 : 32), however or wherever obtained. Instead of using the ignition-tube represented in Fig. 3, the mixed iron and sulphur may be placed in a small Hessian crucible (Appen- dix 21), covered with a similar inverted p IG crucible and heated in a coal fire. 12. Mixtures and Compounds. Mixtures of two or more substances may be formed by mingling them in all conceivable proportions, but a compound formed by chemical action consists of certain invariable proportions of its constituents. Thus, oxygen and hydrogen may be mixed in any desired proportion, but they will unite to form water only in the ratio of eight parts to one by weight, or one part to two by volume. When iron rusts, the oxygen of the air combines with the metal at the rate of 3 grams or ounces of oxygen to 7 grams or ounces of iron. No chemist can make 3 grams of oxygen unite with G grams of iron. In a mixture, the constituents are said to be free ; in a compound, they are said to be combined or in combination. (a.) Gunpowder is composed of charcoal, sulphur and potassium nitrate (nitre or saltpeter) mechanically mixed. The potassium nitrate may be washed out by water and, by evaporating the water, may be secured in the solid form. The sulphur may then be removed from 13 THE DOMAIX OF CHEMISTRY. the mixture, as in Experiment 11. The charcoal will be left alone. The constituents of gunpowder could not be thus separated if they were in chemical union. When gunpowder is ignited, the constit- uents ctsmbine to form enormous volumes of gaseous products. 13. Chemistry Defined. Chemistry is the branch of science that examines the elements and their compounds experimentally, and investigates the laws that regulate their combination. (a.) The experimental examination above mentioned has to do with the properties and composition of substances and the known or pos- sible chemical changes they may undergo. (6.) Such changes as we have seen in the foregoing experiments can not be foretold ; they can be ascertained only by experiment ; i. e., by placing the substances in question under circumstances that the chemist can control and vary. Hence, chemistry is called an experimental science. WATER AND ITS CONSTITUENTS. ECTION I. ANALYSI S OF WATER. 14. The First Question. One of the most famil- iar substances in nature is water. Its appearance, uses, occurrence, and many of its valuable properties are mat- ters of common observation and every day application. We know that it furnishes the units of weight (Ph., 36), of specific gravity (Ph., 24fc), and of specific heat (Ph., 532). We know that it may assume the solid, liquid and gaseous forms in succession. While these and many others are well-known facts, the healthy mind still asks, " Of what is it made ? " This very question, "Of what is it made ?" which thus confronts the young chemist at the threshold of the science, will force itself upon his attention at every step of his progress. It, therefore, deserves careful con- sideration. Working together, we shall find an answer. Experiment 12. The apparatus represented in Fig. 4 consists of a vessel containing water (to which a little acid has been added to increase its conductivity) in which are immersed two platinum strips which constitute the two electrodes of a galvanic battery. Glass tubes containing acidulated water are inverted over the plati- num electrodes. A battery of three or four Grove cells will answer very well for our present purpose (Ph., 384). When the WATER. 11 FIG. 4. circuit is closed and the current passed through the water between the electrodes, bubbles will be noticed rising in the glass tubes and gradually displacing the water therefrom. Gas will accumulate about twice as rapidly in the tube covering the negative electrode (Ph., 377) as in the other. 15. Another Question. By the time the water has been displaced from one of the tubes, we shall, per- haps, be wondering what is in the tube. This question, " Wlicit is it?" is also continually recurring to the chemist. Lift the tube carefully, holding it mouth downward, and gently cover its mouth with the thumb. It looks like air; is it air? To obtain our answer, we must, as usual, make an ex- periment. Experiment 13. Light a taper or dry splinter of wood, and thrust it into the tube, as shown in Fig. 5. The taper flame will be extinguished and the gas will burn at the mouth of the tube. Notice the appearance of the flame. The taper may be withdrawn and re- lighted at the mouth of the tube and the experiment repeated. Was it air in t/te tube ? FIG. 5. 12 WATER. 15 We have now interrogated Nature, conversing with her in her own language. The question being properly put, she answered that it was not air. The answer was intelli- gible and satisfactory. As a matter of present convenience, we shall call this gas hydrogen. 16. What is in the other Tube ? By this time the other tube is probably full of gas, generated at the positive electrode. If so, break the circuit (Ph., 376) and remove the tube, closing its mouth as before. Is it air ? Is it hydrogen ? Experiment 14. To put these questions in proper form, light the taper and let it burn until a spark will remain upon the wick when the flame is blown out. Thrust the glowing taper (or a glowing splinter) into the tube. The taper is rekindled and burns with un- usual vigor and brilliancy. The answer is as prompt and unmistakable as before. It was not air ; it was not hydrogen. For purposes of present convenience, we shall call this gas oxygen. 17. The Synthesis of Water. So far, we have seen that water is composed of oxygen and hydrogen, there being twice as great a volume of the latter as of the former. We have also learned that these gases look like common air, but that, in their action upon burning sub- stances, they are very different from air and from each other. If we wish to know whether water has any other constituent, or suspect that these gases came from the small quantity of acid used to increase the water's con- ductivity for the electric current, it would be natural to try to unite these gases and see what the product is. For such an experiment we are not quite ready. By the anal- ysis of something we have secured separated oxygen and 18 WATER. 13 hydrogen ; for their synthesis, it is desirable that we know more about them (Exps. 28 and 53). 18. Analysis, Synthesis, and Metathesis. By chemical analysis, we mean the breaking up of a com- pound into its constituent parts (Exp. 12) ; by chemical synthesis, we mean the union of two or more substances to form one, different from any of its constituents (Exp. 27). Synthesis is chiefly used to prove the results of analysis. Metathesis consists in the interchange of dissimilar atoms or groups of atoms between two sets of molecules, and implies that the structure of these molecules is not other- wise altered ( 74 a). It may almost be regarded as a con- currence of analysis and synthesis. HYDROGEN. 19 HYDROGEN Symbol, H ; specific gravity, 1 ; atomic, weight, 1 m. c. ( 62) ; molecular weight, 2 m. c. ; quantivalence, 1 ( 92). 19. Occurrence. It was long thought that hydro- gen did not occur free in nature, but it has been found uncombined in meteors, volcanic gases, and the solar and stellar atmospheres. In combination, it is almost every- where, being found in water, in petroleum, and in all animal and vegetable substances. Note. The word hydrogen is derived from the Greek hudor ( = water) and yennao ( I produce). FIG. O. The Apparatus. Provide a good bottle, about 20 cm. (8 in.) high, and having a mouth about 2.5 cm. (1 in.) in diameter. See that the edges of the bottle are smooth, so that they will not cut the cork. Get a caout- chouc stopper or fine grained cork (App. 9) that will fit 5 21 HYDROGEN. 15 the mouth of the bottle snugly, and furnish it with a funnel tube, , and a delivery tube, b, (App. 4, b) as shown in Fig. 6. The funnel tube should be of such a length that, when the cork is in its place, the tube will reach within 1 cm. ( in.) of the bottom of the bottle To the delivery tube, b, connect a piece of glass tubing, rf, bent near each end. The connection may be made by a short piece of snugly fitting rubber tubing, c. If desira- ble, c and d may be replaced by a piece of rubber tubing of suitable length. The lower end of d terminates beneath the inverted saucer or tin plate, e, placed in the pan, /. The saucer has a notch in its edge for the admission of d, and a hole in the middle of its bottom ; this hole should be a little larger than the delivery tube. Into the pan, pour enough water to cover the saucer. Fill a bottle, g, with water and invert it over the hole in the bottom of e. Atmospheric pressure will keep the water in g. (Ph., 275). 21. The Preparation. Granulate some zinc by melting about 250 g. (-J- Ib.) in a Hessian crucible or iron ladle, and slowly pouring it, while very hot, into a pail or tub of water, from as great a height as you can conven- iently reach. Put about 25 g. (1 oz. ) of this granulated zinc (clippings of ordinary sheet zinc will answer, but not so well) into the gas bottle, B, pour in water until the bottle is about a quarter full and replace the cork. Be sure that all of the joints about the mouth of the bottle are tight. To test this, place the delivery tube between the lips and force air into the bottle until water rises in the funnel tube and nearly fills the funnel. Place the end of the tongue against the end of the delivery tube to prevent the escape 16 HYDROGEN. 21 of air from the bottle. If the water retains its elevation in a, the joints are tight. If the water falls in a to the level of that in B, the apparatus leaks and must be put into satisfactory condition before going on. Pour sulphuric or hydrochloric acid through the funnel tube, a, in small quantities, not more than a thimble full at a time. Gas will be generated with lively effervescence in B and bubble up in y, displacing the water therefrom. This method of collecting a gas, by the displacement of water, is called " collecting over water." It will be thus briefly indicated hereafter. 22. The Collection. The gas first delivered will be mixed with the air that was in the apparatus at the beginning of the experiment. This should be thrown away, as it is dangerously explosive. When a quantity of gas about equal to the contents of the gas bottle has thus been allowed to escape, fill a test tube or small wide- mouthed bottle with the gas, remove it from the water pan, being careful to hold it mouth downward, and bring a lighted match, or other flame, to the mouth. If the gas burns with a puff, or slight explosion, it is not yet free from air. In this way continue to test the gas, as it is de- livered, until it burns quietly at the mouth of the tube and within it. Keep the end of the delivery tube, d, under water until you are sure that the hydrogen is unmixed with air. Do not, at any time, bring a flame into contact with any considerable quantity of hydrogen until you have established its non-explosive character by testing a small quantity as just described. For such tests, bottles are not so good as test tubes or cylinders (App. 7), as they confine the gas more and thus increase the danger in case 23 HYDROGEN. 17 of an explosion. Add acid through the funnel tube from time to time, as may be necessary to keep up a brisk effer- vescence in the gas bottle. Fill several bottles with the unmixed gas, slipping the mouth of each, as it is filled, into a saucer containing enough water to seal the mouth of the bottle and prevent the cscupe of the hydrogen. If you have used the pneumatic trough (App. 12) instead of the water pan, the bottles may be left upon the shelf of the trough, which should be a little below the surface of the water. At your earliest convenience, fill one of the gas holders (App. 13) with hydrogen. Note. There are several other ways of preparing hydrogen. Some of them will be considered subsequently. 23. The Reaction. The hydrogen just prepared resulted from the action of the zinc upon the acid, water being used to dissolve the solid compound thus formed. Resulting from this action, we have the hydrogen gas and a chemical compound called zinc chloride if hydrochloric acid was used, or zinc sulphate if sulphuric acid was used. This compound remains dissolved in the water of the gas bottle. The zinc chloride or sulphate may be obtained separate by filtering and evaporating the solution. We may represent hydrogen by the symbol H, and zinc by the symbol Zn. Hydrochloric acid is composed of hydrogen and chlorine (an element which we shall soon study 104) and may be represented by HCI. The zinc chloride is composed of zinc and chlorine and may be represented by ZnCI 2 - In fact, chemists of all nations represent these substances by these convenient abbreviations and other substances by similar symbols, as will be explained soon ( 56). The chemical changes that took place in the gas 18 HYDROGEN. 23 bottle may be represented by the following equation (127): ' Zn + 2HCI=ZnCI 2 + H 2 . The free zinc united with the chlorine of the acid to form the zinc chloride, thus setting free the hydrogen of the acid. As hydrogen is a gas, it bubbled through the water causing the effervescence. As zinc chloride is a soluble solid, it was dissolved by the water. From the clashing together of atoms in this reaction, much heat was developed (Ph., 674, 676). At the close of the experi- ment, small black particles are sometimes to be seen float- ing in the solution in the gas bottle. These are bits of carbon that were present, as impurities, in the zinc. Experiment 15. Instead of ' ' collecting over water," collect the gas by " upward displacement," : s follows : Bring the delivery tube, d, of the gas bottle (Fig. 6) or gas holder into a vertical position. Hold over it a test tube, or small bottle, as shown in Fig. 7, and cause the H to flow rapidly through the tube, d. In a few moments the air will be driven from the test tube and replaced with H. That this gas is not mixed with air (after allowing the H to i'ow a sufficient length of time) may be shown by testing it in the manner described in 22. What does this experiment teach ? Experiment Id. Refill the bottle with H, cover the mouth, turn the bottle right side up, remove the cover and quickly apply a flame. How does the H flame differ from those previously seen ? Why ? Experiment 17. Take two cylinders or large test tubes of equal size. Fill one of them, a, with H. Bring the mouth of a to that of &, gradually turn a, from its inverted position, as shown in Fig. S, until it is upright below b. Place a upon a table and in half a minute test the two tubes with a flame. If the experiment has been neatly performed, it will be found that &, which had air, now has H, FIG. 7. FIG. 8 HYDROGEN. 19 and that a, which had H, now has air. The H was poured upward from n to b. This is called " upward decantation," and is possible because of the extreme levity of this gas as compared with the sur- rounding air. Experiment IS. Equipoise two beaker glasses, as shown in Fig. 9. Fill the inverted beaker with H, by upward decantation. The equi librium will be destroyed, and the glass containing H will rise. FIG. 9. Experiment 19. To the flexible rubber delivery tube of a gas holder containing H, attach the stem of an ordinary clay pipe, or a small glass funnel. With the gas flowing slowly (the flow being controlled by the stop-cock), dip the pipe into a saucer of soap-suds, and, when a film is formed over the mouth of the pipe, turn its mouth upward and open the stop-cock wider. The bubble soon Irraks away from the pipe and rises like a balloon. Note. The last experiment will be more satisfactory if the soap solution be prepared by making a strong solution of white caetile snap in warm soft water that has been recently boiled, and adding half its volume of glycerin. Shake the mixture thoroughly, and it is ready for use. Experiment 20. Over a vertical tube delivering H, hold a HYDROGEN. sheet of gold leaf or unglazed paper. The gas will pass through the gold or paper, and may be lighted on the upper side of the sheet. Experiment 21. The remarkably rapid diffusion of H may be shown as follows: Cement with sealing-wax the porous cup of a Grove cell to a glass funnel, mouth to mouth. Pro- long the stem of the funnel, s, with a glass tube passing snugly through the cork of the bottle B. The funnel may be supported by the retort stand, B, and connected to the glass tube by a piece of rubber tubing. The bottle is to be half full of water and provided with a delivery tube, d, drawn out to a jet above and dipping into the water below. When a bell glass, , contain- ing H is placed over the porous cell, the H diffuses inward so much more rapidly than the air can diffuse out- ward that an increased pressure is exerted on the surface of the water in B. If all of the joints are tight, water will be thrown from the jet, as shown in Fig. 10. The experiment may be simplified by allowing the tube, s, to dip into water in an open vessel. Bub- bles will rise through the water. FIG. 10. Experiment 22. The diffusion of H may be shown more easily but less prettily by closing one end of a glass tube 3 or 4 cm. (1^ in.) in diameter and about 30 cm. (12 in.) long, with a plug of plaster of Paris 1 or 2 cm. thick, filling it with H by upward displacement and placing the mouth of the tube in a tumbler of water. The outward diffusion of the gas through the porous septum reduces the pressure on the water in the tube, which is then forced upward by atmospheric pressure. An argand lamp chimney answers well for the experiment. The plug may be inserted by spreading a stiff paste of the plaster and water in a layer of the desired thickness upon a piece of writing-paper and pressing one end of the chimney down into it. In an hour or two the plaster will have set. The paper may then be easily removed and the plaster outside the tube broken off. Allow it to dry over night before using. In filling the tube 24 HYDROGEN. 21 with gas, hold it so that the septum will be covered with the fleshy part of the hand to prevent premature diffusion. The water may be colored with cochineal or indigo or ink. Experiment 23. To show the effect of H upon sounds produced in it, fill a large bell glass with the gas, suspend it mouth downward, and strike a bell in it, as shown in Fig. 11. Instead of the bell, one of the small squeaking toys well known to chil- dren may be sounded in the H. When the gas has been purified ( 36), the pupil may with safety inhale it once or twice and try to speak or to sing bass with his lungs filled with it (Ph., 434). 24, Physical Properties. Hydrogen is a transparent, color- less, tasteless, odorless gas, as may be seen by direct inspection. It is the lightest known substance. One FlG - II liter of it weighs 0.0896 grams, which iveight is called a crith ; 100 cu. in. weighs 2.14 grains. It refracts light much more powerfully than air (Ph., 612), and is often taken as the standard of specific gravity for aeriform bodies. It has recently been liquefied by subjecting it to a very great pressure (Ph., 58, 59, 277), at a very low temperature. Because of its extreme lightness, it diifuses more rapidly than any other known substance, and has a peculiar effect upon sounds produced in it (Ph., 426). It is only sparingly soluble in water, 100 volumes of the liquid absorbing only one or two of the gas. (a.) H is about 14 times as light as air, 11,000 times as light as water, 150,000 times as light as mercury, and 240,000 times as light as platinum. (6.) That H is not very soluble in water is shown by the fact that it may be collected over water But the metal palladium absorbs or " occludes " several hundred times its volume of H, forming what HYDROGEN. 24 seems to be a true alloy. For this and other reasons it is thought by some that H is the vapor of a highly volatile metal. (c.) We have many metallic solids and one metallic liquid ( 334) which may be solidified by cold Why may we not, it is asked, have a metallic gas? H has been liquefied ; it may be solidified. In fact, it is claimed that H has been solidified. Mercury vapor is present in the " vacuum " of every thermometer and barometer. As we know a metal that is liquid under ordinary circumstances and solid or gaseous under peculiar conditions, it is not difficult to conceive a metal that is gaseous under ordinary circum- stances and liquid or solid under peculiar conditions. The metallic nature of H has not yet been generally admitted. (d.) Palladium, at a red heat, occludes 935 times its volume of H and 376 times its volume at the ordinary temperature. After absorb- ing the gas, the tenacity, specific gravity, thermal and electric con- ductivity of the metal are diminished. Platinum, at a red heat, absorbs 3.8 times its volume of H. Experiment 24. Repeat Exp. 13, and describe the phenomena ally. What two chemical properties of H does this experiment illustrate? Experiment 25. Repeat Exp. 19, and while the bubble is in the air, touch it quickly with a lighted taper. Be sure to see all that the experiment shows, and then tell t what you see. Experiment 26. Replace the bent delivery tube of the gas bottle with a straight one having the upper part drawn out to form a jet. After the H has been escaping for some time, test small quanti- ties of it until you are sure that it is unmixed with air. Then, and not until then, apply flame to the jet. This is the " Philoso- pher's candle." Hold a small coil of fine wire in the upper FIG 12. P art f tne flame. Describe fully the flame of the " Philoso pher's candle "(Fig. 13). FIG. 13. Experiment 27. Over the flame of the "Philosopher's candle,' hold a clear, dry, cold tumbler. In a few moments the clear glass HYDROGEtf. FIG. 14. will become dimmed with a sort of dew, evidently caused by the condensation of some vapor farmed by the lurning of H in air. Expt rime nt As'. Pass a stream of H from the gas holder through a IT-tube, a, (Fig. 14), containing calcium chloride, which will retain diiy aqueous vapor that may be mixed with the gas. To the further end of this dry- ing tube attach a piece of glass tubing, b, drawn out to form a jet. Over the jet, place the bulb of a thistle or funnel-tube, e, which is bent and connected by a perforated cork to one leg of the U-tube, d. In the other leg of this U-tube, place a loosely fitting test tube, e, nearly filled with ice- water. The hydrogen flame should be 13 or 14 mm. (i in.) long. The size of the flame may be largely controlled by regulating the pressure at the gas holder. In four or five minutes, an appreciable quantity of liquid will be found in the bend of d ; by keeping the flame steadily burning for half an hour, a considerable quantity of the liquid will be secured. This liquid is water. Why was the gas passed through the drying tube? Why was the test tube of cold water placed in the leg of d ? Note. The leg of d that contains e would better be connected by rubber tubing with an aspirator (App. 13), and the flow of steam and air through c and d thus increased. Experiment 29. Over the flame of the " Philosopher's candle," hold a glass tube, t, 30 or 40 cm. (12 or 15 in.) long, as shown in Fig. 15. By moving the tube up and down, a position will be found in which the apparatus gives forth a musical tone. If the experiment does not work at first, vary the size of the flame or change the tube, t, for a larger or smaller one. The current of air drawn upward into t (Ph., 541) gives rise to a series of minute explosions which follow in such rapid succession that a continuous sound is produced (Ph., 429, 469, a.}. See Fig. 15. Note. The two-necked bottle, w, shown in Fig. 15 (p. 24), is called a Woulflfe bottle. Such bottles are also made with three necks. As the mouths are smaller than that of the gas bottle pre- viously described, tight joints are more easily secured Woulffe bot- tles are very convenient for many purposes. See App. 6. FIG. 15. Experiment 30. If you have a piece of platinum sponge, the size of a pea, make for it a support by winding a fine wire spirally into the form of a little cup. Heat the sponge to redness in the lamp, and when cold, hold it 2 or 3 cm. above a small jet of dry H, The cold gas soon heats the cold sponge to redness ; the sponge in turn ignites the gas. In repeating the experiment, the preliminary heating of the sponge, probably, will not be neces- sary. ( 398, 6.) Note. The heating of the sponge drives off traces of certain absorbable gases, such as ammonia, which inter- fere with the inflaming power of the platinum. This property of platinum has been explained by saying that the metal condenses or even liquefies a film of H and one of oxygen on its surface, and that the two condensed elements when brought together, under circumstances of such inti- mate contact, chemically unite at the ordinary temperature, the heat of such union exciting the combination of the rest of the gases. 25. Chemical Properties. Hydrogen is an ele- ment, combustible at about 500 0. (App. 3), i. e., it combines chemically with the oxygen of the air at that temperature. Its flame is pale (almost non-luminous under ordinary atmospheric pressure) but intensely hot. The burning of a given weight of it, as 1 e readily dissipated with characteristic luminous effects. A fine wire of platinum, an exceedingly refractory metal, is readily melted, and silver can be thus distilled. A piece of lime or chalk, freshly scraped to a point and held in the flame, is heated to such a high degree of incandescence that it produces a light of remarkable intensity. This is essentially the Drummoud or calcium light. The temperature of the oxy hydrogen flame has been estimated to be above 2800" C. Experiment 50. Over the jet, a, of the com- pound blowpipe, slip a piece of rubber tubing. Allow both gases to flow through the apparatus, and dip the tubing into a metallic dish full of soap- suds until a mass of foam FIG. 25. lias formed, as shown in Fig. 25. Close the stop-cocks at the gas holders or the blowpipe, remove the tuHng from the soap suds, and then touch the foam with a flame carried at the end of a stick about a meter in length. A violent explosion will take place. (See 22 and the Note following Exp. 19.) Note. If you have no compound blowpipe, introduce one volume of and two of H into a gas bag or small gas holder (App. 13). The gases will soon become thoroughly mixed by diffusion, when they may be passed into the soap suds through the rubber tubing. Remember that this mixture is dangerously explosive ; be sure that there is no possibility of flame coming into contact with the contents of the gas bag or the connected tubing. The explosion just described was free from danger, because the restraining wall of the explosive mixture was only a thin film of H.,0, the flying fragments of which could do no harm. If the contents of your gas holder should ex- plode, the flying fragments would probably do serious damage. It 40 HYDROGEN AND OXYGEN. 42 is advisable to throw away the mixed gases that may remain at the close of the experiments with them. Any attempt to burn these gases previously mixed, even as they issue from the jet of the com- pound blowpipe, will result in an explosion. Experiment 51. Repeat Experiment 19, using the mixed gases instead of H and guarding carefully against an accidental explo- sion. The bubble, or a mass of bubbles, dipped from the dish shown in Fig. 25, may be safely exploded while resting in the palm of the hand. Note.K hydrogen pistol may be made of a tin tube 3 or 4 cm. in diameter and 15 or 20 cm. in length, closed at one end. The open end is to be fitted with a cork, and the closed end provided with a small opening the size of a pin hole. By placing the thumb over the pin hole, the pistol may be filled over water with the mixed gases, the cork put into place, and the pin hole presented to a candle or lamp flame. The cork is the bullet of this pistol. The pistol may be partly filled with H by upward displacement, thus providing a mixture of H and air, that is less violently explosive because of the dilution of the O of the atmosphere. Experiment 52. A tall tin cup filled with a detonating mixture of H and may be inverted over a piece of platinum sponge. The sponge may be supported a few inches above the table by the wire used in Exp. 30. In a few moments the mixed gases will be ex- ploded. 42. The Eudiometer. The eudiometer is an in- strument for determining the propor- tions in which gases unite. It consists of a strong glass tube with two plati- num wires fused into the sides, near the closed end. The wires nearly touch within the tube. One of the most common forms, devised by Ure, FIG 26 consists of a U-tube with the closed arm, Z>, graduated to cubic centimeters. It is represented in Fig. 26. 42 HYDROGEN AND OXYGEN. 41 Experiment 53. Fill the eudiometer with water and hold it with the open arm, a, horizontal, under water and under the closed arm, b. By means of a rubber tube carrying a short piece of glass tubing drawn out to a fine jet, pass about 20 cu. cm. of pure O from the gas holder into b. Be sure that the air had been previously driven out of the delivery tube ; make the measurement with the eudiometer erect and the water standing at the same level in both tubes. Water may be removed from a, if necessary 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 as t>efore. 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 O. Suppose that the first measure- ment shows 21 cu. cm. of O, and that the second shows 75 cu. cm. of mixed gases. Then you have introduced 54 cu. cm. of H. Close the open 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 6. 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 0, leav- ing the 12 cu. cm. of H because there was no O 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 just mentioned may be represented to the eye as follows : 42 HYDROGEN AND OXYGEN. 43 As O is 16 times as heavy as H [Ph., 253 (3)], the one volume of O weighs 8 times us much as the two volumes of H. Hence, we see that the gravimetric composition of water is 8 parts of O 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 FlG - 2 7- gas, the takes fire and burns in as atmosphere of H. 43. Combustibles aud 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 I)i oxide. While water, H 2 0, is the only compound of H and O found in nature, another (H 2 2 ), containing 44 HYDROGEN AND OXYGEN. 43 twice as much 0, may be produced by chemical means. It is a sirupy, colorless liquid, and at 100 C 1 . separates into H.,0 and with almost explosive violence. It Las 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 hydrox'yl. ( 97.) 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. (&.) Tell what you can of H and its prepa- ration. 3. (.) Give the symbol, atomic weight and chemical properties of 0. (6.) What is meant by oxidation ? 4. (a.) What is an element? (6.) How many are known? (c) What 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? (&.) 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. (&.) What is the difference between chemistry and physics ? 7. (a.) What is the distinction between organic and inorganic com- pounds ? (&.) Between a mixture and a compound? 8. (".) If 240 cu, cm. of H and 120 cu. cm. of O be made to com- bine, what will be the name of the product ? (6,) 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. c*n. of steam be condensed to water and the water decomposed (Exp. 12), what will be the volume and composition of the product? 10. (a.) What weight of H is there in 8,064 g. of H 2 O ? (&.) What volume of H ? (c.) What is a crith ? 44 HYDROGEN AND OXYGEN. 44 11. Give a possible explanation for the fact that recently heated but cool platinum sponge will explode a mixture of H and O. 12. What is meant by the reduction of copper oxide ? 13. How could you tell from H ? 14. State the principal difference between ordinary and its allo- tropic modification. 15. (#.) If a mixture of 50 cu. cm. of H and 50 cu. cm. of be exploded in an eudiometer, what will be the name and volume of the remaining gas? (6.) What precaution must be taken in measur- ing the gases ? AIR AND ITS CONSTITUENTS. 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 46, using common air instead of 0. These tests show the presence of free O 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. 46 AIR. 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 O 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 O. 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 , 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 2 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 O and CO 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 O of the air that has entered into combination with the H and the C of the taper. Experiment 5S. 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 8 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, FIG 30^ place a piece of phosphorus that lias been dried by wrapping it in blotting or filter paper. Float the capsule upon H 2 O, 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 0. Experiment 59. When the fumes of P 2 O 5 have been absorbed, slip a glass plate under the mouth of the bell-glass and place it 48 AIR. 46 mouth upward, without admitting any air. If the bell-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 different times and places. The air also contains small quantities of carbon dioxide (C0 2 )> more or less watery vapor, traces of ammonia, 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 1.29472 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 AIR - 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 O independently of the other. When H 2 is boiled, it loses the gases it held in solution. Collection and analysis of these gases show that they are 32 % O and 68 % nitro- gen. The H 2 absorbed O just as if there was no nitrogen present ; it absorbed nitrogen just as if no O 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 8 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 NITROGEN. Symbol, N; specific gravity, 14; atomic weight, 14 m. c. ; molecular weight, 28 m. c. ; quantivalence, 3 (or 5}. 50. Occurrence, Nitrogen is widely diffused in nature. It is found free in some of the nebulae 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 burn 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 O 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 8 0. (6.) 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 O, 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. FIG. 31. 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. What is a crith ? 6. Is H poisonous ? Can you live long in an atmosphere of H ? Why? 7. Is O 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 O ? 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 O ? 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. g 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 some prominent property, as chlorine from the Greek chloros, 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 -out 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 Nitrow* acid HN0 2 Sulphuric acid H a S0 4 Sulphurow* acid. . ..H 2 S0 3 The hydrogen of any acid may .he 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, phosphoric acid furnishes phosphates, while phosphorous acid furnishes phosphides. 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 Nitron acid HNO 2 Sulphuric acid H 2 S0 4 Sulphutws acid H 2 S0 3 Potassium nitrate. ..KNO 3 Potassium nitrite. . .KNO 8 Potassium sulphate. K 2 SO 4 Potassium sulplute. K 2 SO s (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 T&E ffiCROCRlTH. 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 - C 2 HO a so, (CH,),B0 5 (C,H S ) 3 B0 3 (C,H s ),Si0 4 OsO, o. 18 m.c. 28 " 30 " 46 74 44 46 64 60 80 104 146 208 263 32 " 16 m. c. 16 " 16 " 16 16 32 32 32 32 48 48 48 64 " 64 " 32 " 16 m.c. x 1. M tl 16 m.c. x 2. M 16 m. c. x 3. 16 m. c. x 4. 16 m. c. x 2. Carbon monoxide Nitric oxide Alcohol Ether Carbon dioxide Nitrogen peroxide Sulphur dioxide. ... Acotic acid Sulphur trioxide Methyl borate Ethyl borate Ethyl silicate Osmium oxide Etc., etc. Oxygen 58 ATOMIC WEIGHTS. 64 He notices that the smallest weight of in any of these com- pounds is 16 m. c., and that all the others are simple multiples of this. He cannot believe that this is mere chance, especially as he finds similar results in determining other atomic weights. The only ex- planation possible is that this 16 m. c. is the weight of a definite quantity of 0, and that it represents the least quantity of O that can enter into combination ( 5). Hence, 16 m. c. is the atomic weight of O, and the substances analyzed contain respectively one, two, three and four atoms of to the molecule. Of course, the symbols in the second column of the table above can not be determined until after the determination of the atomic weights of the elements involved. The table also shows that the O molecule consists of two atoms. The combining weight of an element is its atomic weight. 65. Composition of Elementary Molecules. Chemists have ascertained that hydrogen, oxygen, nitro- gen, chlorine, bromine, iodine, sulphur, selenium, tellu- rium and potassium have two atoms to the molecule ; that cadmium and mercury have one, and that phosphorus and arsenic have four. Nothing is yet known concerning the composition of the other elementary molecules. When the specific gravity of the vapor of any of the other ele- ments is accurately determined, the molecular weight of that element becomes a matter of knowledge ( 63). Then, knowing both the molecular and the atomic weight, the composition of the molecule is at once removed from the region of hypothesis to that of fact. EXERCISES. 1. Which will, under similar conditions, occupy the more space, 100 molecules of H or 100 molecules of N ? 2. (a.} From what acid may we consider that sodium sulphate is formed ? (6.) Sodium sulphite ? 3. (a.) Write the symbol for hydrogen monoxide. (&.) For hydro gen dioxide. 4. What is the molecular weight of a vapor that is 23 times as heavy as H ? 5. How many microcriths are there in a gram ? COMPOUNDS OF HYDROGEN, OXYGEN AND NITROGEN. SECTION r. AM MON IA. 66. Occurrence. Ammonia (NH 3 ) exists in small quantities in the air, whence it is brought down to the earth by rain and dew. It is formed by the putrefaction of animal and vegetable matter. The ammonia of com- merce is chiefly obtained from ammoniacal salts incident- ally produced in the manufacture of coal gas. Ammonia is familiar to many under the name of hartshorn. 67. Preparation. The preparation of ammonia is sufficiently illustrated by the next three experiments. Experiment 61. Into a half liter flask, pour about 200 cu. cm. of strong ammonia water ( N H 4 H 0). Close the flask, a, with a cork carrying a fun- nel tube and a delivery tube, as shown in Fig. 32. The delivery tube should pass to the bottom of a tall drying bottle, b, containing about a liter of quicklime broken into small Gently heat the liquid in a. FIG. 32. 60 AMMONIA. 6? and NH 3 (which is a gas) will be given off. After passing through 8 it may be collected by upward displacement or over mercury. If collected over mercury, the funnel tube in a must have a consider- able length. Experiment 63. In a mortar, or the palm of the hand, rub together equal weights of pulverized ammonium chloride (sal-ammoniac, NH 4 CI) and quicklime (CaO). Notice the smell before and after rub- bing. 2NH 4 CI + CaO = CaCI 2 + H 2 O + 2NH 3 . Experiment 63. Mix 25 or 30 g. of pulverized ammonium chloride with 50 to 60 g. of freshly slaked lime (CaO + H 2 = CaH 2 2 ), that has been allowed to cool. Place the mixture in a half liter flask and add enough H 3 to cause it to aggregate in lumps when stirred with a rod. When the mixture is gently heated, NH 3 is produced in accordance with the reaction. 2NH 4 CI + CaH 2 2 = CaCI 2 + 2H 2 +2NH S The gas, after being dried, may be collected in bottles by upward displacement and the bottles corked. This is the most common way of preparing NH 3 in the laboratory. Experiment 64. Fill a liter bottle, a, with N H 3 by upward displacement. By holding at the mouth of the inverted bottle a moistened strip of turmeric paper or red litmus paper, the experi- menter will be able to tell when the bottle is filled ; the turmeric will turn brown or the litmus blue. Close the bottle with a cork (a rubber stopper is preferable) through which passes a small .glass tube. Place the end of this tube in H 2 O, colored with red litmus solution (App. 24) The H 2 O will, in a moment, rush into the bottle with violence, changing from red to blue as it enters (see Exp. 106). FIG. 33. Experiment 65. From the- flask of Experi- ment 63, pass the gas through a series of Woulffe bottles, partly filled with H 2 O, as shown in Fig. 34. The delivery tube of one bottle terminates under H 2 in the next. A safety tube, s, (open at both ends) passes through the cork in the middle eck of each bottle. The delivery tube of the generating flask should not dip into the H 2 of the first bottle. This precaution prevents the possibility of H 2 O being forced back into the heated 68 AJfJIONIA. ttt FIG. 34. flask and breaking it. It is well to keep the Woulffe bottles in vessels containing cold H 2 0, as heat is evolved in the condensation of the NH 3 . At the end of the experiment, put the ammonia water just prepared into convenient bottles, cork tightly, and save for future use. 68. Physical Properties. Ammonia is a color- less, irrespirable gas and has a pungent odor. It is much lighter than air, its specific gravity being &J-, i. e., a liter of it weighs 8.5 criths (.7616 #.). It liquefies under a pressure of 6^ atmospheres at 10C., 4 atmospheres at 0C., or 1 atmosphere at 40C. The liquid solidifies at 75C. Under ordinary conditions, the liquid rapidly evaporates, producing intense cold (Ph., 526). It is re- markably soluble in water, one volume of which absorbs 803 volumes of the gas at 14C., H ^ a or 1148 at 0C. This saturated solution (aqua ammonia) has a specific gravity of .85. Experiment 66. From a gas holder containing five volumes of H and two volumes of nitric oxide (NO, 83), pass a stream of the mixed p IG g gases through a bulb tube contain- AMMONIA. 69 FIG. 36. ing platinized asbestos, as indicated in Fig. 35. The gases escap ing at a will redden moistened blue litmus paper. Heat the bulb ; the H and N combine, N H 3 is formed, and, as it escapes at a, turns the reddened paper blue again. Experiment 67. From the drying-bottle of Experi- ment 61, lead the delivery tube, d, through a narrow glass cylinder to its upper end, as shown in Fig. 36. As the NH 3 issues at a, try to light it ; it will refuse to burn. Through the flexible tube, b, pass a current of O into the cylinder. The jet of NH 3 being now sur- rounded by an atmosphere of 0, may be lighted ; it will burn with a yellowish flame. Experiment 68.-Pa.ss a stream of from the gas holder through a strong aqueous solution of NH 3 in a flask. Heat the flask and bring a flame into contact with the mixed gases as they issue from the neck of the flask. They will burn with a large yellow flame. Experiment 69 Upon a piece of broadcloth or dark colored calico, let fall a few drops of dilute sulphuric acid. The acid will produce red spots. Apply ammonia water to the spots and they will disap- pear. This is a familiar experiment in most laboratories. 69. Chemical Properties. Ammonia and its aqueous solution have strong alkaline properties ( 168), neutralizing acids and restoring vegetable colors changed by acids. The gas is combustible only when mixed with oxygen. 70. Composition. Analysis of ammonia shows that it is composed of fourteen weights of nitrogen to three weights of hydrogen, or of one volume of nitrogen to three of hydrogen, the four volumes of the constituents being condensed to two volumes of the compound. Thig may be represented to the eye as follows : 1 m. c. m.c. 14 m.c, 71 AMMONIA. 63 In other words, when ammonia gas is decomposed, it doubles its volume, yielding half its volume of nitrogen, and one and a hall' times its volume of hydrogen. (a.) Suppose 100 cu. cm. of NH 3 to be confined over mercury in a eudiometer. By producing electric sparks in it, the gas is decom- posed and increases its volume to 200 cu. cm. Add, say 100 cu. cm. of and produce a spark in the mixed gases. There is a shrinkage of 225 cu. cm., the gases now measuring 75 cu. cm. The shrinkage was due, of course, to the formation of H 2 Hence, two-thirds of the 225 cu. cm., or 150 cu. cm., was H, and the other 75 cu. cm. was 0. But, as we introduced 100 cu. cm. of 0, and only 75 cu. cm. of it has combined, the other 25 cu. cm. must be in the eudiometer as part of the residual 75 cu. cm. Consequently, we have left 50 cu. cm. of N, and 25 cu. cm. of 0. The 50 cu. cm. of N and the 150 cu. cm. of H came from the 100 cu. cm. of NH 3 . 71. Uses. Ammonia water is largely used in the laboratory and as a detergent. It is also largely used in the preparation of sodium carbonate, in the production of aniline colors and in the manufacture of indigo. Liquid ammonia is used in the freezing of artificial ice. Experiment 70. Prepare 100 cu. cm. of the " Nessler re-agent," as follows: into 80 cu. cm. of H 2 put 3.5 g. of potassium iodide, and 1.3 g. of mercuric chloride (corrosive sublimate, HgCI 2 , a deadly poison). Heat to the boiling point and stir until the solids are dis- solved. Add a saturated solution of HgCI 2 in H 2 O, drop by drop, until the color of the red mercuric iodide is just perceptibly per- manent. Then add 16 g. of potassium hydrate (caustic potash), or 12 g. of sodium hydrate (caustic soda), and add H 2 until the solution measures 100 cu. cm. The reagent should be of a slightly yellowish tint. If it be colorless, add a little more of the HgCI 2 solution, until the permanent tint is just perceptible. Place the liquid in a well-stoppered bottle. Drop about 2 cu. cm. of the Nessler reagent into 50 cu. cm. of a very weak solution of NH 3 and stir the mixture, which will be changed to a brown color; the more NH 3 in the solution, the deeper the brown. Save the rest of the reagent in carefully stoppered bottles. 64 AMMONIA. 72 72. Tests, The tests for ammonia are its pungent odor, its turning moistened red litmus paper blue, the fumes of ammonium chloride it produces with hydro- chloric acid (Exp. 6), and the test with the Nessler reagent. The ammonia of ammoniacal compounds may be generally set free by heating the compound with potas- sium hydrate and then detected by the above means. Ammonia tests play an important part in the analysis of potable waters the development of ammonia indicating contamination by organic matter. EXERCISES. 1. (a.) What weight of H is contained in 11 g. of NH 3 ? (6.) What volume of H ? 2. (a.) What volume of H can be produced by the decomposition of 2 I. of NH 3 ? (6.) What weight of H ? 3. (a.) What weight of H can be united with 28 g. of N to form ammonia ? (&.) What volume of H ? 4. (a.) What weight of N can be united with 9 g. of H to form NH 3 ? (&*.) What will be the weight of the product ? 5. (a.) If 100 cu. cm. of NH 3 be decomposed in a eudiometer, 100 cu. cm. of added, and an electric spark passed through the mixed gases, what gases will remain ? (&.) What will be the volume of each? 6. Why were the safety tubes used in Exp. 65 ? 74 NITRIC ACID. 65 II. NITRIC ACID. 73. Sources. The chief sources of nitric acid, V (aquafortis, HN0 3 ,) are potassium nitrate (saltpetre or nitre,) which is obtained in abundance in India, and so- dium nitrate (Chili saltpetre or soda nitre), which is found as an efflorescence on the soil of a sterile region in Chili and Peru, and exported in large quantities from those countries. 74. Preparation. Nitric acid is always prepared from a nitrate by distillation with sulphuric acid (H 2 S0 4 ). (a.) Into a quarter liter retort, a, having a glass stopper, put 50 g. of pulverized potassium nitrate (KN0 3 ,)or 40^. of pulverized sodium nitrate (NaNO 3 ,) and 35 cu. cm. of strong H 2 SO 4 . The mate- rials should be introduced through the tubulure, *, 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, cr other convenient re- ceiver, kept cool by H ., . It is well to cover the receiver with cloth or bibulous paper; tl.e H 2 O may be brought by a rubber tube siphon (Ph., 298) from a pail of H a O 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 and in the receiver. The fumes in the retort will soon dis- appear ; continue the distillation until they reappear. KN0 3 + H 2 S0 4 = HKS0 4 + HN0 3 . 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. (b.) 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 a SO 4 are used. 2KN0 3 + H a S0 4 = K 2 S0 4 + 2HN0 3 , 2NaN0 3 + H 3 SO 4 = Na 2 SO 4 + 2HN0 3 . 75. Physical Properties. Nitric acid is a fuming liquid, colorless when pure, but generally slightly tinted w.'tb the fumes seen in the retort during its preparation. It has a specific gravity of 1.52, freezes at 550., and boils with partial decomposition at 86C. It may be mixed w th 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. U,Km the heated charcoal, pour a little strong HNO ;J . The charcoal is rapidly oxidized to combustion. Experiment 72. 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 siik. In a few minutes, remove and wash it thoroughly with H 2 O. The silk will be permanently colored yellow. Experiment 74 Put a sheet of " 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. 3 78 NITRIC 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 2 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 indigo. 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 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, orby 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 NITROGEN OXIDES. 79 NITROGEN OXIDES. Experiment 78. In a small evaporating dish (App. 21), place a fe\^ eu. 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 paper 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 :j ). 79. Mtrogen 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 H 8 0. NH 4 NO 3 = N 8 + 2H 8 0. To show that H 2 O 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 NITROGEN OXIDES. 69 flask would break before all of the NH 4 N0 3 was decomposed, but by In -at ing a small quantity of the nitrate upon platinum foil, it will be seen that no residue is left. Experiment 7.9. Repeat Exps. 33, 36, and 37, using N 2 O instead of 0. (These are simply combustions in O, the N 2 O 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. N 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. 2. Hypoiiitrous Arid. This acid (H NO) has not yet been prepared, but the corresponding salt, potassium hyponitrite (KNO), is known. We may imagine this reaction : N 2 + H 2 = 2HNO. 70 NITROGEN OXIDES. 83 83. Nitric 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 + 8HN0 3 = 2NO + 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 3 0, re- peat the experiment several times, notic- ; ng 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. n combustion is peculiar. Ordinary combustibles will not burn in it at all ; phosphorus may be 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 Trioxide. This gas (nitrous anhydride, N.,0 3 ,) is an obscure compound that unites with water to form nitrous acid(HN0 2 ). N 8 3 + H 8 = 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 S5. Pass 250 en. 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 N0 3 are produced but soon absorbed by the H 2 0. Pass in another 250 CM. cm. of NO. If the and NO are pure, the O will be wholly used to form NO 2 , all of which will be absorbed by the H 3 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 : N O 16 m.c. 9. Nitrogen Pciitoxide. 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 2 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. // tivo substances combine to form more than one com- pound, the weight of one substance being considered as constant, the weights of the other vary according to a simple ratio. 91 NITROGEN OXIDES. 73 (a.) This important principle is best illustrated by the nitrogen oxides just studied. BY GRAVIMETRIC BY VOLUMETRIC ANALYSIS. ANALYSIS. d ACTUAL RATIO ACTUAL RATIO NAMES. 9 z d z 6 Z z o B 4-1 Nitrogen monoxide N 2 28 : 16 If :1 2 : 1 2 : 1 Nitric oxide NO 14 : 16 n:2 1 1 2 2 Nicrogentrioxide. . N 2 3 28 : 48 lf:3 2 : 3 2 : 3 Nitrogen peroxide. N0 2 14 : 32 1|:4 1 : 2 2 : 4 Nitrogen pentoxide N 2 5 28 : 80 lf:5 2 : 5 2 : 5 Attention is called to the consecutive numbers, 1, 2, 3, 4, and 5, in the columns headed " Ratio." (6.) This law necessarily results from the definition of an atom ( 5). Since the atoms can not be divided, the elements can combine only atom by atom and, consequently, either in the ratio of their atomic weights or some simple multiple of that ratio. EXERCISES. 1. Is the air a mixture or a compound ? Why ? 2. State the points of resemblance and difference between O and N. 3. (a.) Is the process of preparing O analytic or synthetic? (6.) Of preparing N0 2 ? (c.) N 2 O ? 4. How could you prove the presence of in air ? 5. If two liters of N and one of O be combined, what will be the name and volume of the product ? 6. (a.) How is ammonia water prepared ? (6.) How is liquid am- monia prepared ? (c.) What will result from the decomposition of a liter of laughing gas into its constituent elements ? (d.) Write tho reaction for the preparation of NH 3 . 7. When N 2 is mixed with H and the mixture exploded, N and a compound vapor are formed. Write the reaction. V, QUANTIVALENCE, RATIONAL SYMBOLS, RADICALS. 92. Quaiiti valence. In hydrochloric acid (HCI), one atom of chlorine unites with one of hydrogen. In water, one atom of oxygen unites with two of hydrogen. In ammonia, one atom of nitrogen unites with three of hydrogen. In marsh gas (CH 4 ), one atom of carbon unites with four of hydrogen. One atom of potassium may replace one atom of hydrogen in nitric acid (HN0 3 ) yielding potassium nitrate (KN0 3 ,) while one atom of copper replaces two atoms of hydrogen in sulphuric acid (H 2 S0 4 ) forming copper sulphate (CuSO^.). One atom of potassium can replace one atom of hydrogen, but no more ; one atom of copper can replace two atoms of hydrogen, but no less. The quantivalence of an atom or group of atoms ( 97) expresses the num- ber of hydrogen atoms with which it can combine or for which it may be exchanged ; e. g., 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. (6.) The quantivalence of an element may be absolute or apparent. Absolute (or true) quantivalence 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 quantivalence 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 NH 4 CI is five ; it there appears as a pentad. When atoms of the same element act with different quanti valences, 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 5 as H 2 is. (e.) The quantivalence of an atom is indicated by Roman numer- als placed above, or minute marks placed above and at the right 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 chernism 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=E =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-, -Q, 0<, 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 knoiv 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 2 may be written H-O-H ; that of H O H 3 N, H-N-H ; that of C0 2 , 0=C=0 ; that of HN0 3 , H-O-N = VI and that of SO o, 0=S=O. 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 modeled 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. H| Ammonia. H N H' Hydrochloric Add. Methyl Hydride. Sodium Hydrate. Na H Sulphuric Acid. H H 1 Methyl- amine. Trimethyl- amine. CH 3 CH 3 Lead Methyl. (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 SO 4 ) may be represented as built upon the type of the double molecule of the typical compound. A triple molecule (C H V" ) may be thus used, e. g., glycerin = v 3 ^ 5; j- 3 . (d.) Typical symbols are of great assistance in classification, es- pecially in the case of the carbon compounds. 97. Simple and Compound Radicals. An atom or group of atoms that seems to determine the char- acter of a molecule is called a radical. Such an atom is called a simple radical ; such a group of atoms is called a compound radical. In the graphic symbols given above, it will be noticed that, in each case but one (S0 2 ), 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 -yl, as uitrosyl (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 23 ( 44), as follows : (HO)-(HO) or H-O-O-H. EXERCISES. 1. Considering C I to be a monad, write the graphic symbols for CI 2 0, CI 2 3 , HCIO and HCI0 3 . 2. What quantivalence for Cl is indicated by the symbol H-O-CI = ? II 3. Write three graphic symbols for S0 2 , two of which shall rep- resent i' as a compound radical (sulphuryl) and all of which shall represent S aS a dyad. 4. Write two graphic symbols for S0 3 , one of them representing S as a dyad, the other representing S as a hexad. 5. Name the substances, symbolized as follows, indicating the sym- bols for compound radicals : N = N O = N\ \/ , -N = 0; -0-N = 0; /> ; O O = N / -<&' State the difference between the indications given by the last two symbols. VII. THE HALOGEN GROUP ECTfON I. CH LORI NE. ^, Symbol, Cl ; specific gravity, 35.5 ; atomic weight, 35.5 m. c. ; molecular weight, 71 m. c. ; quantivalence, 1, (3, 5 or 7). 98. Occurrence. Chlorine does not occur free in nature, but it is very abundant and widely diffused, being a constituent of common salt (sodium chloride, NaCI), and of potassium chloride (KCI). Every liter of sea-water may be made to yield about five times its volume of chlorine. Note. The name comes from the Greek chloros, meaning green. The elementary character of chlorine is seriously questioned, but the gas has not yet been shown to be compound. 99. Preparation. Chlorine is generally prepared, directly or indirectly, from common salt (NaCI). (a.) Melt a small quantity of NaCI in a Hessian crucible over a coal fire, and pour the fused salt upon a stone slab or brick floor. When the NaCI is cool, put about 30 g. of it into a liter Florence flask, add 30 g. of manganese dioxide (Mn0 2 ) and 35 cu. cm. of strong sulphuric acid ( H 2 SO 4 ), previously diluted with an equal bulk of H 2 0. The stopper of the flask should have a delivery tube passing to the bottom of a tall, dry, glass cylinder. It is well to provide a safety tube (App. 12) for the flask. Shake the flask to mix the materials, place it upon a sand bath and heat gently. Cl is evolved and is collected in the cylinder by downward displacement. When the cylinder is full, 80 CHLORINE. 99 close the mouth with a greased glass plate. The yellowish green color of the gas enables the ex- perimenter to see when the cylin- der is full. Be careful not to in- hale the gas. Perform all experi- ments with Cl in a draught of air or in a ventilating closet (App. 23) if you have one. 2NaCI + Mn0 3 +3H 2 S0 4 ^ MnSO 4 + 2HNaSO 4 + 2H 2 + CU. (6.) Another way of preparing Cl is to use 12 g. of MnO 2 and 25 cu. cm. of hydrochloric (mu- FIG. 42. riatic) acid instead of the NaCI, Mn0 2 and H 2 S0 4 . The gas may be collected, although with loss, over hot water or strong brine. 4HCI + MnO = MnCI CI (c.) The easiest way of preparing Cl is to put a small bottle of chloride of lime, bleaching powder (CaOC 1 2 ), say 15 or 20 g., into the bottom of a glass vessel of several liters capacity, and then, by means of a funnel tube passing through the pasteboard cover of the large jar, to pour dilute H 2 S0 4 upon the CaOCI 2 . Experiment 86. Prepare some chlorine water by passing a current of Cl through H 2 0, in a series of Woulffe bottles, arranged as in Exp. 65, ex- cept that the tubes should not dip so far under the sur- face of the H 2 0. The solu- tion formed is heavier than H 2 0. The chlorine water may be' preserved for a con- siderable time by placing it in bottles wrapped in opaque paper and closed with greased stoppers. If we wish to absorb the whole of a small quantity of Cl, we may pass it into an inverted ' 43- retort filled with H 8 0, as shown in Fig. 43. 100 CHLORINE. 81 Experiment 67. Into a jar filled with Cl, pour H a O until the jar is a third full of. the liquid. Close the mouth of the bottle with the hand and shake the bottle. The gas will be ab- sorbed, a vacuum formed and the bottle held against the hand by atmospheric pres- sure (Fig. 44). 1OO. Physical Properties.- l| Chlorine is a yellowish green, irres- pirable gas with a suffocating odor FlG - 44- and astringent taste. Even a very small quantity of it in the air produces violent coughing and irritation of the air passages, when it is inhaled. Any attempt to breathe it undiluted would doubtless prove fatal. It is about 2J times as heavy as air, one liter weighing 35.5 criths. It may be liquefied by pressure or cold. It is largely soluble in water, one volume of which, at 10C., dissolves 2 vol- wmes of the gas. The solution has most of the proper- ties of the gas, and, when saturated, gives off the gas freely on exposure to the air. Experiment 88. Fill a tall bottle or cylinder holding 500 cu. cm er more with Cl. The gas may well be dried by passing it over cal- cium chloride, as in Exp. 28, or by passing it over fragments of pumice saturated with sulphuric acid (H 8 S0 4 ), as in Exp. 31, or by allowing the gas to bubble through H 2 S0 4 . Slowly sift freshly prepared filings of metallic antimony into the bottle. The two elements will combine with the evolution of heat and light. Filings of metallic arsenic or bismuth give similar effects. Experiment 89. Place a thin slice of dry phosphorus in a deflagrat- ing spoon and place it in a jar of Cl. The gas and the solid com- bine directly with a pale flame. Experiment 90. Burn a jet of H, or illuminating gas, in an atmos phere of Cl, as represented in Fig. 45. Reverse the conditions and burn a jet of Cl in H (see Fig. 27). Try to burn a jet of Cl in O, and a jet of in Cl. 100 FIG. 45. Experiment 91. Pour chlorine water into a solution of hydrogen sulphide (H 2 S, 137). The Cl robs the H 2 S of its H to form HCI, while the S is precipitated. Experiment 92. In a dark- ened room, mix equal volumes of H and Cl, previously prepared in the light. With the mixture, fill three stout soda bottles. Wrap one of the bottles with a towel, remove the cork and ap- ply a flame to the mouth of the bottle. The mixed gases com- bine with an explosion. The towel will protect the experi- menter if the explosion break the bottle. Wrap the second bottle with a towel to which a string, two or three meters loner, has been attached. Carry the covered bottle into a sunny place FIG. 40. and, by means of the string, re- ioo CHLORINE. 83 move the towel. The sun's direct rays cause the mixed gases to ex plode. This experiment succeeds best with a thin glass bulb filled with a gaseous mixture obtained by the electrolysis of hydrochloric acid. On exposing one of these bulbs to bright day light, or to the electric : FIG. 47. or magnesium (Fig. 47) light, a sharp explosion occurs, produced by the synthesis of the gases prepared by electrolytic analysis. Place the third bottle in diffused sun light. The two gases will unite gradually and quietly. Allow the bottle to remain for future use. Experiment 93. Fill five wide-mouthed bottles with dry Cl and close their mouths with greased glass plates. Heat some oil of turpentine (C 10 H ]6 ) over the water bath (App. 10). Fasten a tuft of shredded tissue paper or of cotton to a wire or splinter, dip it into the hot turpentine, and quickly plunge it into the first bottle of Cl. The paper or cotton will generally take fire and burn with a very dense smoke (Fig. 48). Into the second bottle, thrust a burning dry FIG. 48. wood splinter ; into the third, FiG-49. 84 CHLORINE. 101 thrust a burning piece of paper ; into the fourth, a burning wax or tallow taper (Fig. 49) ; into the fifth, a deflagrating spoon containing burning petroleum. Note the effect in each case. Note. The combustibles used in the last experiment contain H and carbon (C). This H combines with the Cl and sets the C free, as smoke. Experiment 94. Fill a tall tube with Cl and invert it over a cup of H 2 0. Place the tube in a sunny place. After a few days, test the gaseous contents of the tube for 0, and the water for an acid. Seek for the odor of Cl. Note. If two volumes of olefiant gas (C g H 4 ) be mixed with four volumes of Cl, the C will be set free, as dense smoke ; C 3 H 4 + 2CI 2 = 4H'CI + C 2 . If the air be exhausted from a flask containing a few leaves of " Dutch metal " (very thin copper) and C I admitted into the vacuum, the copper leaf will burn, forming yellow fumes of cop- per chloride. If sodium be melted in a spoon and placed in a jar of moist Cl, the synthesis will yield common salt : Na + Cl = NaCI. Potassium is similarly attacked by either moist or dry Cl. 1O1. Chemical Properties. Chlorine is a very energetic chemical agent. It unites directly with all of the elements except oxygen, nitrogen and carbon, its at- traction for hydrogen being very remarkable. It is even able to decompose water, combining with the hydrogen and liberating the oxygen. Experiment 05. Pass a current of dry Cl through a bulb or U-tube containing a bit of dry calico print. After a few moments, attach a second tube containing a bit of similar calico that has been moistened. Notice that the Cl now passes the dry calico without bleaching it, but that it quickly bleaches the moist calico with which it subse- quently comes into contact. Note. Pink or blue paper cambric is desirable for the above ex periment, Experiment 06. Nearly fill seven test tubes with chlorine water. Into the first, pour a few drops of indigo solution ; into the second, litmus solution ; into the third, cochineal solution ; into the fourth and fifth, aniline dyes of different colors; into the sixth, the colored petal of a flower, and into the seventh put a strip of colored calico or paper cambric. The colors will quickly disappear. 102 CHLORINE. 85 Experiment 97. Upon a piece of printed paper, write your name in ink, Dip the paper into chlorine water. The written characters will be bleached out ; the printed characters will remain. Experiment 96'. Repeat Exp. 91, noticing the odor of H 2 S before the addition of the chlorine water and its absence after such addition. 1O2. Uses. Chlorine is of great use in the arts as a bleaching and disinfecting agent, its action depending very largely upon its attraction for hydrogen. The non-mineral coloring matters are largely composed of oxygen, hydrogen, nitrogen and carbon. When such coloring matter is brought into contact with chlorine in the presence of moisture, the chlorine attacks the hydrogen of both, the nascent oxygen thus liberated from the water greatly aiding the chlorine in the decomposition of the coloring substance. Colorless compounds are formed by a process of chlorination and oxidation. Chlorine has little effect upon mineral or carbon colors. Experiment 99. Prepare a quantity of thin starch paste by boiling 30 cu. cm. of H 8 and stirring into it 0.5 g. of starch previously re' duced to the consistency of cream by thoroughly mixing with a few drops of H 2 O. In this paste, dissolve a piece of potassium iodide, half the size of a pea. Into a test tube, put 10 cu. cm. of H 2 and 5 or 6 drops of this mixture of starch and potassium iodide. Shake the tube vigorously for a few seconds and let a few drops of chlorine water fall into it. Notice the blue color thus formed. Experiment 100. Into the solution of starch and potassium iodide, dip two or three strips of white paper. Hold one of these strips of test paper in a current of Cl. The white paper is turned to blue. Re- move the stopper from the bottle containing chloride of lime (bleach- ing powder) and hold another strip of the test paper in the atmosphere of Cl that fills the upper part of the bottle. The paper is instantly colored blue. Note. The Cl decomposes the potassium iodide ; the free iodine colors the starch (see Exp. 121). Experiment 101. Place a strip of gold leaf in saturated chlorine water. The gold will be dissolved. 86 CHLORINE. 103 Experiment 102. Dissolve a few crystals of silver nitrate (AgN0 3 ) in H 8 0. Add a few drops of a solution of common salt (NaCI). A white curdy precipitate of silver chloride (AgCI) is formed. Experiment 103. Wash the AgCI obtained in the last experiment and try to dissolve it in HN0 3 . It will prove to be insoluble in that liquid. Experiment 104- Wash the AgCI of the last experiment and try to dissolve it in strong ammonia water. It will dissolve. 1O3. Tests. Free chlorine is easily distinguished by its odor; pure chlorine, by its color. Chlorine is also easily detected by its bleaching action upon organic color- ing matters, or by its forming a blue color with a mixture of starch and potassium iodide. This last mentioned re- action is very delicate, but an excess of chlorine removes the color and the same effect is produced by bromine, ozone and a few other actively oxidizing substances. Many of its compounds yield, with solutions of silver salts, precip- itates of silver chloride, insoluble in nitric acid. (a.) By adding a solution of silver nitrate to that of a soluble chloride (e. g., KCI + AgN0 3 ), one part of Cl in a million parts of H 2 may be detected, a faint opalescence appearing. EXERCISES. 1. When chlorine water is exposed to sunlight, HCI is formed and is set free, (a.) Write the reaction. (&.) What volume of Cl is necessary thus to set free 20 cu. cm. of ? 2. Cl unites with the metals acting as a monad, (a.) Symbolize the binary compounds of Cl with the following 1 . Na' ; K' ; Cu" , Au"' ; Ag'; Fe" ; Zn" ; (Fe a ) T -. (&.) Symbolize the nitrates formed by re- placing the H in HN0 3 by the several metals just mentioned. HYDROCHLORIC ACID. 87 HYDROCHLORIC ACID. 104. Source. Hydrochloric acid (hydrogen chloride, chlorhydric acid, muriatic acid, HCI) is the only known compound of hydrogen and chlorine. The hydrogen is generally furnished by sulphuric acid (H 2 S04) and the chlorine by common salt (sodium chloride, NaCI), the cheapest and most abundant source of chlorine. The pure acid is a gas, the aqueous solution of which constitutes the muriatic acid of commerce. (a.) HCI is found in the exhalations of active volcanoes, especially Vesuvius and Hecla, and in the waters of several South American rivers that have their rise in volcanic regions. 105. Preparation. Hydrochloric acid is almost always prepared from common salt by distillation with sul- phuric acid. (a.) Into a liter Florence flask, put 30 g. of fused NaCI and 30 cu. em. of Ho SO 4 . Heat the flask gently over the sand bath and collect by downward dis- placement in dry jars, as in the preparation of Cl. By holding a piece of moistened blue litmus paper at the mouth of the jar, the experimenter may easily tell when the jar is full. Compare this paragraph carefully with 74. NaCI + H 2 S0 4 = HCI+ HNaSO 4 . (6.) At a higher temperature, FIG. 50. 88 BYDROCSLORtC ACTD." 105 the same quantity of H 2 S0 4 would combine with twice as nmcn NaCI, yield twice as much HCI, and leave sodium sulphate (Na 2 S0 4 ) instead of hydrogen sodium sulphate (HNaS0 4 ), according to this equation : 2NaCI + H 2 S0 4 =2HCI + Na 2 S0 4 . The greater heat necessary for this latter reaction would be severe upon the apparatus. At the end of the experiment, the HNaS0 4 remaining in the flask may be easily removed with warm H 2 0. (c.) HCI may be prepared by the direct union of equal volumes of its constituents (see Exp. 92). (d.) In the arts, the retort used is an iron cylinder and the gaseous acid is dissolved in H 2 0, contained in a series of earthenware Woulffe bottles. In this apparatus, either of the reactions above mentioned may take place. Very large quantities (thousands of tons weekly) of the acid liquid are made as an incidental product of the manufac- ture of sodium carbonate ( 268). (0.) Dry, gaseous HCI may be ob- tained by heating the acid liquid and passing the gas given off through a drying tube or bot- tle. See Exp. 61. Experiment 105. Fill a long test tube with dry HCi and invert it over mer- cury. Thrust a bit of ice into the FIG. 51. mouth of the tube. FIG. 52. The ice and gas will quickly disappear, the mercury rising in the tube. Explain. Experiment 106. Fill a bottle with dry HCI. Close the bottle with a cork carrying a glass tube and invert it over H g O, colored with blue litmus (Fig. 52). The H 2 will soon enter with violence, and its color will be changed from blue to red. Instead of passing the tube from a into colored water in an open vessel, as shown in the figure, it may be passed through the cork of a closed bottle into the io6 ACID. 89 liquid. If this bottle be provided with a bent tube, air may be forced into the bottle and thus enough H 2 O forced into a to begin the ab- sorption without waiting for the HCI to diffuse downward through the tube. Compare Exp. 64. FIG. 53. Experiment 107. Pass HCI from the generating flask through a series of Woulffe bottles arranged as in Exp. 65, except that the de- livery tube from each bottle should barely dip into the H 8 O of the next bottle. It is well to place the Woulffe bottles in H a O to keep them cool. When the gas ceases to flow, test the contents of each bottle with blue litmus paper. Bottle the liquid and save for future use. 1O6. Physical Properties. Hydrochloric acid is a colorless gas having an acid taste and pungent odor. It is irrespirable and neither combustible nor a supporter of combustion. It is a little heavier than air, its specific gravity being 18.25, i. e., a liter of it weighs 1J criths (1.6352 g.). It liquefies under a pressure of 40 atmos- pheres, this liquid having a specific gravity of 1.27. The gas is remarkably soluble in water, one volume of which, at the ordinjyy temperature, absorbs about 450 volumes of the gas, or more than 500 volumes at 0C. This saturated solution, the muriatic acid of commerce, fumes strongly in the air, has a specific gravity of 1.21 and 90 HYDROCHLORIC ACID, J06 readily gives up the acid gas when heated. If pure, it freezes at temperatures below 40C. to a butter-like mass having the composition HCI 4- 2H 2 0. Experiment 108. Nearly fill a test tube with dilute, commercial HCI and drop into it a few pieces of granulated zinc (see 21). The zinc is quickly dissolved. What gas escapes ? Write the reaction. 1O7. Chemical Properties. Hydrochloric acid acts upon many metals and their oxides, forming chlorides, most of which are soluble in water. (a.} The liquefied HCI does not act upon any of the metals ex- cept Al. Experiment 109. If the second bottle used in Exp. 92 was strong enough to stand the explosion without breaking, open it with its mouth under mercury. Notice that no mercury enters the bottle and that no gas escapes. Try i^ with the third bottle used in that experiment. Then test the contents of the bottles with moistened blue litmus paper. The reddening of the paper shows that we have an acid ; it is HCI. We have shown that the volume of the HCI is the same as that of the gases that united to form it. How was this shown ? Experiment 110. Fit a U or V shaped tube to a wooden stand by clamping it with strips of tin or cementing it with plaster of Paris. Through each of two corks pass a wire attached to a strip of platinum. Half fill the tube with HCI, insert the corks snugly, push the wires down until the plati- num strips are immersed in the acid liquid and connect the wires with the pol es of a galvanic battery (Ph., 397, 398, 401). At the end of four or five minutes, remove the cork that carrier the negative electrode (Ph., 377) and apply a lighted match. H was present, mixed with the air that was in that arm of the tube at the beginning of the experiment. Remove the other cork and thrust a bit of moistened litmus or turmeric paper into that arm of the 110 HYDROCHLORIC ACID. 91 tube. The bleaching of the paper and the peculiar odor show the presence of Cl. Of course, delivery tubes may be provided for the corks and the gases collected separately (see Fig;. 4). Exact experi- ments of this kind are difficult on account of the solubility of Cl in H 2 0, but when made they show that equal volumes of H and of Cl are liberated. 1O8. Composition. The composition of hydro- chloric acid has been accurately determined, both analyti- cally and synthetically. Such determinations show that one volume of hydrogen combines with one volume of chlorine to form two volumes of hydrochloric acid gas. The composition maybe graphically represented as follows: H \rn.c. 36 - 5 "-"- The chemical action effects neither volumetric nor gravi- metric change. It should be noticed that hydrochloric acid differs from most of the other acids in that it contains no oxygen ( 60). 109. Uses. Hydrochloric acid is used in preparing chlorine, potassium chlorate ( 281), chloride of lime (bleaching powder, 292), ammonium chloride, etc., etc. It is of very frequent use in the chemical laboratory and has become almost indispensable in the manufacturing arts. It acts directly upon most of the metals, forming metallic chlorides, e. g., zinc chloride. Experiment 111. Repeat Exps. 6, 102, 103 and 104, using a solu- tion of HCI instead of the solution of NaCI, mentioned in Exp. 102. 110. Tests. Hydrochloric acid gas may be detected by its reddening moistened blue litmus paper and its form- ing dense fumes of ammonium chloride (NH 4 CI) when brought into contact with ammonia gas (Exp. 6). Its 92 HYDROCHLORIC ACID. HO aqueous solution may be detected by its reddening blue litmus paper and forming, with a solution of silver nitrate, a precipitate (AgCI) soluble in ammonia water but insolu- ble in nitric acid. EXEKCISES. 1. When ammonium chloride (sal ammoniac, NH 4 CI) is acted upon by H 8 S0 4 , we have a reaction partly represented as follows : 2NH 4 CI + H 8 S0 4 = (NH 4 ) 2 S0 4 + Complete the equation. 2. A strip of paper moistened with a certain solution and exposed to Cl turns blue, (a.) What is the solution ? (&.) Explain the reac- tion, (c.) What other gas will produce the same change of color ? 3. The vapor of mercury is 100 times as heavy as H. The atomic weight of mercury is 200 m. c. What is the number of atoms in a mercury molecule ? 4. Show that a molecule of H contains two atoms, if you can. 5. Define and illustrate quantivalence. 6. What is a chemical experiment ? g III CHLORIDE OXIDES. 93 IIL OTHER CHLORINE COMPOUNDS. 111. Chlorine Oxides. Chlorine does not unite directly with oxygen, but it may be made to do so by indi- rect means. Five oxides of chlorine are recognized by chemists, of which only three have been isolated. (a.) 1. Chlorine mouoxide (hypochlorous oxide) CI 8 0. 2. Chlorine trioxide (chlorous oxide) CI 2 O 3 . 3. Chlorine tetroxide (cbloryl) CI 2 O 4 . 4. Chlorine pentoxide (chloric oxide) CI 3 O 5 . 5. Chlorine heptoxide (perchloric oxide) CI 8 O 7 . (6.) Cl 2 is an explosive, yellow gas, formed by passing dry Cl over mercuric oxide : 2CI 2 + 2HgO = Hg s OCI 2 + CI 8 0. It liquefies at 20C. CI 2 O 3 is a greenish, yellow, unstable gas, prepared by the reduc- tion of chloric acid, thus : 2HCI0 3 + N 2 3 = CI 3 3 + 2HN0 3 . Cl a O 4 is an explosive gas obtained by the action of sulphuric acid (H 2 S0 4 )upon potassium chlorate (KC 10 3 ). It is sometimes called free chloryl, the molecule being considered as composed of two com- pound radicals : f> = Cl = O or (CI0 8 )' , thus : ^Cl - C/ or (CI0 2 )-(CI0 2 ). See 94, 95. CI 2 O 6 and CI 2 O 7 have not yet been isolated, but their compounds are known. (c.) Note the varying quanti valence of the Cl in these several oxides, and that it is represented by the series of odd numbers, 1, 3, 5 and 7. Experiment 112. Pulverize separately 1 g. of sugar and 1 g. of potassium chlorate (KCI0 3 ). Mix them intimately upon a piece of 94 NITROGEN CHLORIDE. H2 paper and, from a glass rod dipped in H 2 S0 4 , let a drop of acid fall upon the mixture. The CI 2 4 thus set free causes an energetic com- bustion. Experiment 113. In a test glass, place 1 g. of KCI0 3 (not pulver- ized). Add a few small pieces of phosphorus and nearly fill the glass with H 2 0. By means of a pipette (App. 5), bring H 2 S0 4 into contact with the KCI0 3 . The phos- phorus burns under H 8 in the CI 3 4 thus set free. Chlorine Acids. From four of these chlorine oxides results a corresponding list of acids and salts FlG - 55- (see 60). The molecular symbols for the acids may be obtained from those of the correspond- ing oxides. (a.) The addition of H 2 to the symbol of the oxide will give double the symbol of the acid : CI 2 + H 2 = H 2 CI 2 2 = 2HCIO, hypochlorous acid. CI 2 O 3 + H 2 = H 2 CI 2 4 = 2HCI0 2 , chlorous acid. CI 8 O 6 + H 2 = H 2 CI 2 6 = 2HCI0 3 ~, chloric acid. CI 2 7 + H 2 = H 2 CI 2 8 =2HCI0 4 , perchloric acid. (&.) The most important of these acids are HCIO, because of its re- lation to calcium liypochlorfcte, and HCI0 3 , because of its relation to potassium chlorate. (c.) The last two paragraphs may be summarized as follows : Salts. NaCIO, sodium hypochlorite. sodium chlorite. potassium chlorate, potassium perchlorate. 113. Nitrogen Chloride. "Chlorine combines with nitrogen, though only indirectly, to form a very re- markable compound, the composition of which has not yet been determined. If an excess of chlorine gas be Oxides. Acids. Salts. 1. CI 2 HCIO NaCIO, 2. CI 2 3 HCI0 2 NaCI0 2 3. CI 2 4 ? ? 4. ? HCI0 3 KCI0 3 , 5. ? HCIO 4 KCI0 4 , II4 AQUA REGIA. 95 passed into a solution of ammonia, drops of an oily liquid are seen to form, which, on being touched, explode with fearful violence, so that the greatest caution must be used in manipulating even traces of this body. The explosive nature of this compound arises from the fact that its con- stituent elements are very loosely combined and separate with sudden violence." Roscoe. Caution. Do not try to prepare nitrogen chloride. It is far too dangerous for a school experiment. Experiment 114- Put a small piece (4 or 5 sq. cm.} of gold leaf into a test tube and pour in strong HN0 3 until the tube is a third full. Put a similar piece of gold leaf into another test tube and pour in a like quantity of HCI. If the leaf is gold leaf, neither liquid will dis- solve it. Pour the contents of one tube into the other. The gold leaf will quickly dissolve in the mixed acids. 114. Aqua Regia. Gold, platinum and many metal- lic compounds, are insoluble in either nitric or hydro- chloric acid, but are easily soluble in a mixture of these acids, especially when heated in the mixture. The acids react upon each other, chlorine is set free and, in the " nascent " condition, acts upon the metal or metallic com- pound more energetically than it would otherwise do. (a.) The name " aqua regia" (royal water) was given by the old alchemists because the mixture was able to dissolve gold, the " king of metals." The mixture is sometimes called nitro-hydrochloric acid. (6.) The expression " nascent " state or condition has appeared before. It is used to describe the condition of a chemical agent at the moment it is set free from some compound. What constitutes the essential features of the "nascent" state is not known. We can not yet tell what the difference between " nascent" H or Cl and ordinary H or Cl is, but we can tell what the difference in their effects is. The most marked effect is greatly increased chemical energy. We shall see other cases in illustration as we proceed. (c.) It is probable that " nascent " Cl is in the atomic condition and ordinary Cl in the molecular condition. They might be symbolized as follows : Cl and CI 2 or Cl- and CI-CI ( 93, 94). 96 AQUA REGIA. 114 EXERCISES. 1. What chlorine oxide has trivalent Cl ? 2. (a,) Write the graphic symbol for chloric acid. (6.) What is the quanti valence of the Cl ? 3. (a.) Write the graphic symbol for HCI0 4 . (&.) What is the quanti valence of the Cl ? 4. Define atom ; atomic weight ; microcrith. 5. (a.} If 20 I. of H be exploded with 0, how many liters of will bo required? (&.) How many liters of dry steam will be produced? 6. (a.) If 15 1. of H be mixed with 10 I of and the mixture ex- ploded, how many liters of dry steam will be produced? (6.) Will any elementary gas remain free ? If so, give its name and volume. 7. (a.) How many grams of H are there in 36 g. of H 2 ? (6.) How many grams of ? (c.) How many liters of H ? (d.) How many liters of ? 8. (a.) 24 I of oxygen will yield how many liters of ozone? (&.) 30 L of ozone is equal to how many liters of oxygen ? 9. Why should Cl or H have greater affinity for another element than Cl Cl or H H ? 10. (a.) How many kinds of atoms are known? (&.) How many kinds of molecules ? Il6 BROMINE. 97 IF. BROMINE, IODINE, AND FLUORINE. BROMINE ; symbol, Br ; specific gravity, at 0C. t 3.187 ; atomic weight, SO m. c. ; mdeculur weight, 160 m. c. ; quantivalence, 1(5 or 7). 115. Source. Bromine does not occur free in nature, but is found combined with metals, especially as magne- sium bromide, in sea water and in the water of certain salt wells and springs. (a.) Much of the Br made in the United States comes from the salt wells of Ohio and West Virginia. The bittern that remains after the crystallization of the NaCI contains magnesium bromide in such quantities that Br is profitably extracted from it. Note. The name is derived from the Greek bromos, meaning a stench. Experiment 115. Into a flask of two or three liters capacity, put a few drops of Br and cover the flask loosely. In a few minutes the jar will be filled with the heavy red vapor of Br, Experiment 116. Into the jar of vaporized Br, introduce a strip of moistened litmus or turmeric paper. It will be bleached. Experiment 117. Add a few more drops of Br, and after it has vaporized, introduce a thin slice of dry phosphorus. It will ignite. Experiment 118. Into a tall jar filled with Br vapor, let fall a few freshly prepared filings of metallic antimony. The result is much like that of Exp. 88. 116. Properties, etc. Bromine is a dark red liquid of disagreeable odor, very volatile at ordinary tem- peratures and highly poisonous. It is sparingly soluble in water and easily soluble in ether or carbon disulphide. Its vapor has a specific gravity of 80, being more than five 5 98 IODINE. 116 times as heavy as air. Its chemical properties closely re- semble those of chlorine, but it is less active. Its attraction for hydrogen fits it for bleaching and disinfecting uses. Some of the bromides are used in medicine and pho- tography. (a.) With the exception of mercury, Br is the only element liquid at ordinary temperatures. (6.) Br forms acids as follows: hydrobromic, HBr; hypobromous, HBrO; bromic, HBrO 3 ; perbromic, HBr0 4 . They closely resemble the corresponding Cl compounds. (c.) Br, when swallowed, acts as an irritant poison ; when dropped upon the skin, it produces a sore that is very difficult to heal. (d.) Br has very little action upon sodium, but combines energeti- cally with potassium, sometimes with almost explosive violence. IODINE; symbol, I; specific gravity, 4-95 ; atomic weight, 127 m. c. ; molecular weight, 254 * c. ; 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. S Il8 IODINE. 99 />/" rinu-iit /?/. Prepare some starch paste, as in Exp. 99, and dilute 5 or 6 drops of it with 10 cu. cm. of H 2 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 2 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 8 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- ence of one part of I in 1,000,000 of H 2 O. Experiment 124. Pour 10 cu. cm. of H 2 O 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 FLUORINE. Il8 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, HIO a ; periodic acid, H 5 I0 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 #. 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 niters (App. 8). Wash the powder well with cold H 3 0, and then remove the filters with their contents from their funnels. Pin the filters 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. FLUORINE ; symbol, F ; atomic weight, 19 m. c. ; quantwalence, 1. 120. Source. Fluorine occurs in nature in fluor spar (calcium fluoride, CaF 2 ), and in cryolite (sodium and alu- minum fluorides, 6NaF-r-AI 2 F 6 ). It has also been found in minute quantities in the teeth, bones, and blood of animals. ffote. 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;- 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 combine with silicon. The difficulties in the way of its preparation and collection have prevented its satisfactory study by chemists. Consequently, but little is known concerning free fluorine. 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 tbe 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 1?S. Coat the convex surface of a watch glass with wax, write a name upon it, place it upon a small lead saucer contain- 162" ^THE HALOGEN GROUP. 122 ing mixed CaF a and HS0 4 , fill the watch glass with H 2 O 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 (?. e., HCI, HBr and HI) but it is more energetic than any of them. It is readily prepared, as above, by distilling some fluoride with sulphuric acid, e. #., CaF 2 + H 2 S0 4 = CaSO 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 O 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 _ gi 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 J sa Fait. 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 V A quadrivalent atom ? A biva- lent compound radical ? Illustrate each. 3. 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 lime 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*. STOICH IOMETRY. 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. The 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 and 2HCI ; the products were ZnCU and H 2 . 128 an A r i METRIC COMPUTATIONS. 105 127. Chemical Equations. Chemical reac- tions are very commonly and conveniently rcjtrc- fit-u/t'd by equations, placing the sum of the ft >c tors 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.) (6.) 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 2 O means, literally t that 2 m. c. of H united with 16 m. c. of O yields 18 m. c. of H 3 O, 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 IS g. of H 2 O, or that 12 Kg. of H unites with 96 Kg. of O to form 108 Kg. of H 2 O. (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 + = H 2 0. To obviate the error of representing an atom of free O, we should indicate twice the quantity of each substance, as follows : 2H 2 + O 2 = 2H 2 O. But, 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 2 + O 2 = 2H 2 indicates that two (molecular or other) volumes of H unite with one of to yield two volumes of dry steam, e. g., 2 1. of H and 1 I. of 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 + 2HCI = ZnCU + H 3 . 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 m. c. : 73 m. c. : : 20 g. : x g. .'. x = 22.46 g. of dry HCI. Ans. 3. How much ZnCI 2 will be produced ? 65 m. c. : 136 m. c. : : 20 g. : x g. .'. x =41.8460. of ZnCU. Ans. 4. How much Zn is necessary to prepare 1 Kl. of H ? As one liter of H weighs 1 crith or .0896 g., 1000 I. weighs 89.6 g. 65m.c.:2m.c.:: x g. : 89.6 g. .'.x = 2912 g. or 2.912 Kg. of Ir\.Ans. 129. Volumetric Computations. Every equa- tion written in the molecular symbols of aeriform sub- stances may be read by volume. For example 2H 2 -|-0 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 1. of H will give 1 I. of dry steam. 2. How much O is needed to burn up 500 cu. cm. of H ? Solution. The equation for the combustion of H shows that the volume of O is half that of the H. Hence, it will require half of 500 cu. cm. or 250 cu. cm. of O. 3. How much H must be burned to form 4 /. of steam ? Solution. The equation shows a relation of equality between the volumes of H and of H 2 O (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 L of steam ? Solution. The equation shows that the volume of O is half that of aeriform H 2 O. Hence, 3 1. of steam will yield 1.5 I. or 1500 cu. cm. of 0. 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 HNO a ? Solution. The molecular weight of HNO 3 is 1 m. c. + 14 m. c. + 48 m. c. = 63 m. c. 63 m. c. : 1 m. c. : : 100$ : 1.59$, the proportion of H. 63 m. c. : 14 m. c. : : 100$ : 22.22$, " " N. 63w. c. :48w. c. : : 100$ : 76.19$, " " O. 100.00$ (2.) The vapor density of a certain compound is 14. Analysis shows that 85.7 of it is 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$ : : 28 m. c. : 24 m. c. = C 2 . 100$ : 14.3% : : 28 m. e. : m.c.= H 4 or 2H 3 . Therefore, the symbol is C 3 H 4 . Note. Gaseous volumes will vary with 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 8 S0 4 . 4. Upon heating potassium dichromate (K a Cr 2 O 7 ) with a sufficient quantity of HCI, one may obtain Cr 2 Cl c + 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 ? 6. (a.) How much O would be necessary to burn 500 cu. cm. of H ? (6.) 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 ? 8. (a.) What is the difference between hydrochloric acid and muri- atic acid? (6.) 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. (&.) 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. 10i) 11. The reaction of Cl upon NH 3 is as follows : 8NH 3 + 3CI 2 = N 2 + 6NH 4 CI. (a.) What weight of Cl is necessary to the production of 12.544 g. of N ? (6.) 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 O that measures 1 1. at a barometric reading of 756 mm,\ (Ph., 494.) THE SULPH UR GROU P. SECTION i, SULPHUR. l, S ; specific gravity, 1.96 to 2.07 ; atomic weight, 32 m.c. ; molecular weight, at JOOO^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 3 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 132. 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 b, placed outside the furnace. The S vapor here condenses to a liquid and then runs out into wooden vessels partly filled with H.,O. 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. (e.) 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 purifie:! by distillation. It is melted in a tank, a, runs FIG. 57. through a pipe into the iron retort, b, where it is vaporized. The vapor passes from & into the large brick chamber, C, where it con- denses. When the walls of G 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 munt, in a fine stream, into a large vessel nearly full of cold H 2 O. The S when taken from the H 8 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 13L Melt 200 g. of S in a 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. FIG. 59. jffote. The 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 3 ). 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. 2. Tetragonal 3. Hexagonal 4. Orthorhombic J 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 trimorphaus. 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 isoniorphous. 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 500 C. 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 orthorhombicjor 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 .sold H 2 0, as shown in Fig. 58. Experiment 133. 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 (g 144). 134. Chemical Properties. Sulphur unites with oxygen at the FIG. 60. 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. EXERCISES. 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. 3. By bringing Br and P together in the presence of H a O, both phosphoric (H 3 P0 4 ) and hydrobromic acids are formed, (a.) What weight of Br is necessary to yield 5 g. of the colorless gas, HBr? (&.) What weight of Br ie necessary to yield 10 I. of HBr? 4. I acts upon KCIO 3 , forming potassium iodate and setting Cl free: 2KCI0 3 + I 2 = 2KI0 3 + CI 2 . (a.) How much Cl by weight may thus be freed by 10 g. of I ? (&.) How much by volume? 5. (a.) How many grams of H may be prepared by the use of 260 g. of Zn? (6.) How many liters? (c.) How many grams of HCI are necessary ? 6. (a.) If 20 g. of H be exploded with O, how many grams of are necessary ? (&.) How many grams of dry steam will be produced ? 7. (a.) 1 cu.cm. of H 2 O will yield, by electrolysis, how many grams of free gases? (6.) How many cu. cm. of ? (c.) How many 116 SULPHUR. 136 cu. cm. of H ? (d.) The explosion of these 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 ? (&.) How many liters of the former ? 9. (a.) Is gunpowder manufacture a chemical or a physical pro- cess ? Why ? (6.) 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 ? 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. 11? HYDROGEN SULPH 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 HUO 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 SO 4 or HCI. Bubbles of gas appear in e and are absorbed by the H 2 O. Add acid in small quantities, as in the preparation of H, until the H 2 O \ne smells strongly of the gas. Remove the gas bottle and cork tightly. FeS+ H 2 S0 4 = FeS0 4 + H S, FIG. 61. = FeCI H 2 S. (6.) Fig. 62 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 b at I and extending downward nearly to the bottom of c Lumps of 118 HYDROGEN SULPHIDE. 138 FeS, as large as can be admitted through the tubuJure at m, are in troduced into b, the stricture at e, sur- rounding the prolongation of , 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 SO 4 + 14 parts H 2 O)is poured in through the safety tube, t, passes into c and rises into b, covering the FeS. H 2 S is generated in 6, 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. (c.) 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 hLS that may escape solu- tion in the H 2 O of the middle bottle. FIG. 63. 139 HYDROGEN SULPHIDE. 119 (d.) If desirable, the gas may be collected over if arm H 2 0. (e.) H 2 S may be prepared by beating a mixture of equal parts of S and paraffin. By regulating tbe temperature, the evolution of H 2 S may be controlled. When tli.' mixture is allowed to cool, tbe 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^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 a jar of H 2 S. The gas will burn with a pale blue flame, forming H 2 and SO S 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 O and two volumes of H 2 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 tuba, 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. FIG. 64. ing tube with a jet made of of the air has been expelled not till then, hold a lighted ture of H a S and air is ex- burn with a blue flame, flame. Moisture will con- bottle. This liquid will red- 2H 2 S +30 2 =2H,0 + 2S0 2 120 HYBRO&EN 139 FIG. 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- 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 140. 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 141- 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 14%- 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 a 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 I ; 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 strLP&itoE. 121 NH 4 HO into e. Pass a current of H 2 S from the generator through the bottles. A black lead sulphide will be precipitated in a; yellow ar- " " c a e si-iiic sulphide, in 6 ; orange anti- mony sulphide, in c ; white zinc sul- phide, in d. The zinc sulphide is soluble in dilute acids. The N H 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. 14! 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 : li.c.J It m.c.\ |32 MM H.S 34 m. c. (a.) The three 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). 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. 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. (&.) How will the volume of this gaseous product compare with that of the H 2 S decomposed? 3. When a 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 3 S through an aqueous solution of Br is as follows : H,S + Br, = 2HBr + S. (a.) What volume of H 3 S is needed to yield 4 I. of HBr ? (6.) What 142 HYDROGEN SULPHIDE. 123 weight of Br will thus combine with 10 g. of H^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. (.) How many liters of O will unite with 20 I. of NO to form NO 2 ? (&.) How many each of O and NO to form 30 I. of NO, ? 7. Arsenic vapor is 150 times as heavy as H. (a.) What is the molecular weight of As ? Explain. (6.) 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 ? (6.) One that has two kinds ? (c.) One that has three kinds ? 9. Give Ampere's Law. Define chemistry. 10. What weight of S in 10 1. of S vapor under normal pressure at 500 C.? (6.) At 1050 C.? 11. Calculate the percentage composition of cryolite. 124 SVLPBUR OXIDES AND ACIDS. 143 SULPHUR OXIDES AND ACIDS. 143. Sulphur Oxides. Sulphur and oxygen unite to form two acid-forming oxides (or anhydrides) symbol- ized as SO 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 2 3 ). which has no corresponding known acid ; with hypo- sulphurous acid (H 2 S0 2 ), which has no corresponding known oxide; with sulphur peroxide (S 3 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. (a.) Put 20 or 30 g. of small bits of copper and 60 cu. cm. of strong H 8 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. 2 0, as shown at c. A solution of copper sulphate, (blue vitriol, CuS0 4 ), remains in the flask. 2H a S0 4 + Cu = CuS0 4 + 2H 2 O + S0 2 . 145 SULPHUR OXIDES AXD ACIDS. 125 (6.) A solution of SO 2 in H 2 O is often wanted in the laboratory. It may be formed by reducing H 3 SO 4 with charcoal. 2H.,S0 4 + C = 2S0 2 -i- 2H 8 O + C0 2 . Tfce mixed gases may be passed through H 2 in a series of Woulffe bottles (Fig, 34); very little of the CO 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 use in the study of chemistry. p IG 6 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 2 (Exp. 28); then pass the dry gas through a U-tube packed in salt and pounded ice (Ph. 521). The SO 8 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 SO 2 may be 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 SO 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 SO 2 by pressure, draw out one end of a strong glass tube (2 cm. in diameter) to a point. Fill the tube with dry S0 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 3 will collect at the pointed end of the tube. 126 SULPHUR OXIDES AND ACIDS. 145 Experiment 148. Pour some of the liquid S0 2 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 3 into it. The S0 3 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 3 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 3 upon it. The change of sensible into latent heat effected by the vaporization of the S0 2 produces a diminution of temperature and the thermometer falls, perhaps as low as 60C. 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 O, 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 SO 2 to a weak solution of potassium permanganate. The red color will disappear, owing to reduction by S0 3 . 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 SO... The bleaching action is not very manifest. To each, add cautiously, drop by drop, a solution ot Fio. 69. potassium hydrate (caustic potash, KHO) ; the color will disappear. To the contents of one glass, add a little strong H 9 SO 4 ; a red color appears. To the other add more of the solution of KHO ; a green color appears. g 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 2 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 : 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 4- 14H 2 0. On standing, it ab- sorbs oxygen from the air and changes to sulphuric acid (H 2 S04.). 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. 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 Vinagre, 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 toechanical 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. 15. 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 1. 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 8 will appear The red fumes show that the HNO 3 has been robbed of part of its 0. 2HN0 3 + SO, =H 2 S0 4 + 2N0 2 . In the presence of moisture, S0 2 is able to reduce (take from) HN0 2 , HNO N,0 3 or N0 2 . In the pro- cess just described, the SO., reduced the HNO 3 ; the FIG. 70. ' 130 SULPHUR OXIDES AND ACIDS. 152 (&.) The manufacture of H 3 S0 4 may be prettily represented by the following lecture table process: A large glass globe or flask is filled with air or oxygen and provided with five tubes, as shown in Fig. 71. One tube connects it with a flask which furnishes a current \>f SO a ( 145, .) ; another connects it with a second flask or bottle, which furnishes a current of N ( 83) ; the third connects it with a FIG. 71. flask which furnishes a current of steam ; by the tube, d, a supply of air or is admitted, from time to time, into the globe. The fifth tube, e, allows the escape of the waste products of the reaction ; it may be connected with an aspirator. (1.) NO enters the globe and takes O from the air. The ruddy fames of N0 2 are seen. (2.) On admitting a current of S0 2 , the red fumes of N0 2 disap- pear and white " leaden-chamber crystals " form on the walls of the globe. The N0 2 has been reduced and the S0 2 oxidized. (3.) On admitting steam, the crystals disappear, and dilute H 8 S0 4 collects at the bottom of the globe. (4.) If air be admitted, red fumes again appear and the process may be repeated. (e.) In the manufacture of H 3 S0 4 , the SO 2 is formed by burning crude S or pyrite (FeS 2 ) in kilns provided for that purpose. The pyrite, in moderately sized lumps, is placed on the grates of the kilns, about 250 Kg. (500 or 600 Ib.) at a time. When the burning is once started, it is kept up by placing a new charge on top of the one nearly burned out. The quantity of air admitted is carefully regulated by a door placed below the pyrite kilns. The SO, and 152 sn.rnuR OXIDES AND ACIDS. 131 other gases are drawn through all of the apparatus by the draft of a large chimney. The nitrogen oxides are furnished, sometimes by a continued supply of liquid HN0 3 in the chambers, but more often by t lie reaction of sodium nitrate and H 2 SO 4 heated by tbe burning pyrite. The air, S0 3 and nitrogen oxides are carried into a series of three or more huge leaden chambers where they come into contact with a constant supply of steam. These lead chambers are some- times 30 m. long, 6 to 7 m. wide and about 5 m. high, having thus a capacity of 900 to 1000 cu. m. or about 38,000 cu.ft. They are sup- ported by a wooden framework, placed on pillars of brick or iron. FIG. 72. The general appearance is shown in Fig. 72. The H.,SO 4 formed in the chambers accumulates on the floor. The process is conducted so that this " chamber acid " has a specific gravity of 1.55, as a stronger acid absorbs the nitrogen oxides. After leaving the lead chambers, the nitrogen oxides, which are supplied in excess, are absorbed by concentrated H 2 S0 4 in what is called a " Gay-Lussac tower," while the nitrogen escapes. The " chamber acid," which contains 64 per cent, of H 2 SO 4 , is then concentrated in the " denitrating " or " Glover tower," where it is mixed with the " nitrated acid" from the Gay- Lussac tower and exposed to the evaporating influence of the hot gases as they pass from the kilns into the chambers, or by evapora- tion in leaden pans, until it has a specific gravity of 1.7 and contains 78 per cent, of H 2 S0 4 . If concentrated beyond this point, the hot 132 SULPHUR OXIDES AND ACIDS. 152 acid attacks the lead of the pans. In this form, the acid is techni- cally called brown oil of vitriol as it is slightly colored by organic impurities. It is largely sold for a great variety of purposes. Further concentration and purification are carried on in glass retorts of from 75 to 150^. capacity or in large platinum stills (some of which cost as much as 6,000). until the liquid contains 98 per cent, of H 2 S0 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., (1.) S + S = S0 3 . (2.) 2HN0 3 + S0 a = H 8 S0 4 + 2N0 3 . (3.) S0 2 + N0 3 = S0 a + NO. (4.) S0 3 + H 2 = H 2 S0 4 . In reality, most of the used for the oxidation of the S0 a comes* from the air, admitted to the chambers through the kiln. The part taken in the process by the nitrogen oxide is very interesting, it act ing as a carrier of from the air to the S0' 3 . 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 may be 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 in a graduated tube Slowly add 73 cu. cm. of H a 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 3 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 2 in a beaker glass of about 250 cu. cm. capacity. Into this, pour 70 cu. cm. of concentrated H 3 S0 4 in a fine stream. Stir the mixture with a test tube contain- SULPHUR OXIDES AND ACIDS. 133 ing alcohol or ether, colored with cochineal or other coloring matter. Tlir 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 O will boil. JSxporiment 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 S 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 1000. will be completely charred. The acid or solutions of jts salts give a white insoluble precip- itate with barium chloride or calcium chloride. 156. Nordhausen 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. (a.) 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, disulphuric acid, is shown by the equation, 2H 2 SO 4 H 8 O = H 2 S 2 O 7 . It may be considered as SO 3 dissolved in H 2 SO 4 , for, when heated, it separates into those substances, H. 2 S a 7 = S0 3 + H 2 SO 4 . 157. Sulphur Sequioxide and Hyposnlphuroiis Acid*. Sulphur sesquioxide (S 8 3 ) is a rare, bluish green com- pound, resembling malachite in appearance. It easily decomposes into sulphur dioxide and sulphur. Hyposulphurous acid (H a S0 2 ) is a very unstable, yellow liquid with powerful reducing properties. Its salt, hydrogen sodium hyposulphite (HNaSO 2 ), is used for the re- duction of indigo in dyeing and calico printing. 158. Thionic 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 8 S 8 3 Dithionic acid H 8 S 2 O 6 Trithionic acid H 2 S S O 6 Tetrathionic acid H 8 S 4 O 8 Pentathionic acid H 2 S 5 6 . (b.) The thiosulphuric acid is better known by the misnomer of "hyposulphurous" acid, which properly designates the compound symbolized by H,S0 2 . In similar manner, the thiosulphates (e. g., sodium thiosulphate, Na 2 S 2 O 3 ), are commonly, but improperly, spoken of as " hyposulphites." Note. The word, thionic, comes from the Greek name for S. 159. Sulphur Oxide and Oxyacids. The known sul- phur oxides and oxy acids are symbolized in tabular form below for purposes of convenient study : Oxides! IS.O.I SO, I SO, I I Acids. |H a SO a | .... [H.SO.lH.SbjH.S.O, H a S a O c lH a S a O e |H a S 4 O a |H,S s O. 136 SULPBUK OXIDES AN I) ACIDS. 159 EXERCISES. 1. (a.) What is the molecular weight of S0 3 ? (&.) The specific gravity of the gas ? (c.) Its percentage composition ? 2. H 2 S and S0 2 are often found in volcanic gases. When they come into contact, they decompose each other. Write an equation explaining the occurrence of native S in volcanic regions. 3. Why can not H S0 4 be usad for drying H.S (Exp. 141). 4. (a.) How much HN0 3 can be formed from 306 g. of KN0 3 ? (&.) How much H 2 S0 4 will be required ? (c.) What will be the yield of H KS0 4 ? (d.) If the product be K 2 SO 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. 6. Write the graphic symbol for H.>So0 7 , introducing S0 8 twice as a bivalent radical. (H 2 S 2 O 7 = anhydrosulphuric acid.) 7. The symbol for potassium sulphate is K 2 S0 4 ; that for lead sul- phate is PbS0 4 . (.) What is the quantivalence of potassium? (6.) 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 HN0 3 will just neutralize 1200 g. of ammonium hydrate ? 10. (a.) How much NH 3 may be formed from 42.8 g. of NH 4 CI ? (&.) How much CaH 2 O 2 must be used? 11. (a.) What volume .of Cl may be obtained from 1 1. of dry HCI ? (6.) What weight ? 12. When aeriform H 2 O 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 may be thus obtained from 2 I. of steam? (c.) How will the volume of HCI formed compare with that of the O ? (d.) In wha,t simple way may the O 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 4 CI and NaN0 2 are heated together in a flask. Write the reaction. 15. (.) I mix H and Cl, and expose the mixture to sunlight. What happens? (6.) 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 ? l6l SELENIUM AND TELLURIUM. 137 3 SELENIUM AND TELLURIUM. SELENIUM ; Symbol, Se ; specific gravity, 4.3 to 4.8 ; atomic, iceight, 79 m. c. ; molecular weight, 158 m. 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 heat. 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 photophone 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. Tellurium. 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 behavior, however, allies it to sul- phur and selenium. With hydrogen, it forms hydrogen 138 THE SULPHUR GROUP. 161 telluride (H 2 Te), which can not be distinguished by its smell from hydrogen sulphide. Note. The name, selenium, 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 2 O 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 telluride. 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 SeO 3 Tellurous acid. H 2 Te0 3 .... Sulphuric acid. H 2 S0 4 Selenie acid. H 2 Se0 4 Telluric acid. H 2 Te0 4 Ethyl oxide (ether). (C 3 H 5 ) 2 Ethyl sulphide. (C 2 H 5 ) 2 S Ethyl selenide. (C 2 H 5 ) 2 Se 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 1 62 THE SULPHUR GROUP. 139 EXERCISES. 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. (a.) State two ways in which the analysis of H 2 O may be effected, (b.) Give the composition of H 2 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 in making it. and how much of each ? 5. (a.) H a S0 4 is poured upon nitre ; name the two substances that you obtain. (6.) Write the reaction. 6. (a.) What is the least amount of H 2 S0 4 that will completely react with 4 Ib. of KNO 3 ? (6.) How much will the liquid product weigh ? 7. (.) From 8 Kg. of KN0 3 , how much HN0 3 can be liberated? (b.) How much H 2 S0 4 is the least that would be required? 8. (a.) Give the names and symbols for the oxides of N. (b.) Give the law of multiple proportion. 9. (.) What is the difference between air and water, chemically considered ? (&.) Give one chemical and one physical property of O and of NH 3 . 10. Write the reactions for the preparation of Cl, HF, SO 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? 12. (a.) How is Cl obtained? (b.) Explain the reaction, (c.) Give the most remarkable chemical properties of the substance. 13. (a.) What is the most common compound of Cl ? (&.) Find its percentage composition. 14. (a.) Give the atomic weight of each of the elements that you have studied, (b.) 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. The 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 3 , CO 2 , etc. Such use of the term is incorrect and seriously confusing. (6.) 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 : HN0 3 ; (HO)-(N0 2 ); H-O-(N0 2 ); H-O-h/ . O O H 2 S0 4 ; (HO) 2 =(S0 2 ); H-0-(S0 3 )-0-H ; H-0-S-O-H, O H 3 P0 4 ; (HO) 3 E(PO); H-0-(PO)-0-H ; H-0-P-O-H. Phosphoric acid. i i H H The atom of " saturating " O 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. (d.) 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. HCIO 3 ... ....... chloro acid. H 8 S0 4 ........ sulphuric acid. HCI0 2 ....... chlorcra* acid, j H 8 SO 3 ...... sulphurs* acid. HCIO ____ hypochlorous acid. ] H^SO., . JtyposulpliuTous 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 : HNO 3 is a mono-basic acid .................. (HO) (N0 2 )'. H 3 S0 4 is a di-basic acid (HO) H 3 P0 4 is a tri-basic acid .................... (HO) (PO)'". Be it remembered, hoxvc v?r, 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 oases and some- times as acids. Thus, SbO(HO), antiinonyl 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 4- H 2 2KHO, potassium hydrate or caustic potash. In similar 16^ 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. (6.) Some of the 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 type, 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 group is of frequent occurrence in combination. Ammonium hydrate, (NH 4 HO) has been termed "the volatile alkali." Experiment 160. Repeat Exp. 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 8 O. 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,). HN0 3 + KHO=KN0 3 + H 8 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. 1 69 (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.W 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. $.> 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 CuS0 4 are normal salts. (6.) . 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 8 '(S0 4 ) 4 , is a double salt. (e.) 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 8 O a or H 2 Pb0 2 . Replacing half of this H with the acid radical, N0 2 , we have H(N0 2 )PbO a , 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. Sulphur 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 g 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 O H has its analogue in H S H or H 2 S. KHOorK H " " K S H. K 2 CO s orK 2 = 2 =(CO)" " K 2 = S 2 = (CS) or K 2 CS S . In nomenclature, these " sulphur salts," (in which term, acids and bases are included) are distinguished from the corresponding " oxy- gen salts " by prefixing sulpho-. 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 known as the " oxygen salts." EXERCISES. 1. (a.) What is the difference between an atom and a molecule ? (&.) Between a physical and a chemical property? (c.) Define and illustrate base, acid, salt, (d.) State the differences between an -ic, an -ous, and an -cute 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 (SO 2 )". 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. (6.) 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 Cl, 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.,S0 4 , using not more than two molecules of HN0 3 . S. 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 the composition of water, both volumetric and gravi- metric. 146 ACIDS, BASES, SALTS, ETC. 171 10. When is prepared by heating MnO 2 , Mn 3 O 4 is formed. Write the reaction. 11. When a current of H 2 S is passed through a solution of a cer- tain salt, copper sulphide (Cu"S) is precipitated with the formation of H 2 SO 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: BaO 2 + 2HCI = BaCI 2 + BORON. Symbol, B; specific gravity, 2.68; atomic weight, 11 m.c.; quantivalence, 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 8 is driven off. Touch this mass with a glass rod and draw out the adhering mass into long threads. This viscous substance is B.>O 3 . 2H 3 B0 3 = B 2 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 O. 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 O 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 = 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 . (&.) Upon further heating at 140C. for a longtime, this is changed to pyroboric acid : 4HB0 8 H 2 = H 2 B 4 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 3 B0 3 . These steam jets are called sujfioni. 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 suffioni. Water from a spring or lagoon is conducted into the upper basin and is charged by the suffioni 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^BO,. 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 B0 3 daily. BORON. 149 EXERCISES. 1. What is the molecular weight of boron trioxide ? 2. What per cent, of B in orthoboric acid ? 3. Write the symbol of cal- cium (Ca") pyroborate. 4. (a.) What is the basicity ofH 3 B0 3 ? (6.) IsMg s (B0 3 ) 2 an acid or a double salt ? 5. (a.) What results from heating H,S0 4 with Cu, NaCI and MnO., respectively? (b.) 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 1.205.12 ^.? 7. By strongly heating M n 2 , it is reduced to a lower oxide, thus : 3Mn0 2 = Mn 3 4 4- O 2 . (a.) What weight and (&.) what volume of O can be thus prepared from 50 g. of Mn0 2 ? 8. State the method of pre- paring HN0 3 and the amount of each substance needed for 10 U). of the acid. 9. Write a graphic symbol for HP"'0 3 ; for HP0 3 . (10.) (a.) What is a salt? How is it formed? (&.) How does a chloride differ from a chlorate ? Illustrate by potas sium compounds. 11. (a.) What is the weight FIG. 73. 150 SOUON. 173 of the Cl in 5 Ib. of common salt ? (&.) What percent, 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. 14. Sulphur trioxide may be obtained by heating concentrated H 3 S0 4 with P a 5 . Write the reaction. XIL 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 ^ L) 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 hydrogen 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. 175 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 ; e- ff., = j ! ^Volnme [ of ox ^ en ' The s ^ mbols of the mon ' atomic elements represent two unit volumes and the respective atomic weights of those substances ; e.g. , Hg = of mer - cury. The symbols of the tetratomic elements represent one-half unit volume and the respective atomic weights of these substances ; e ' +> P = | ATt' volume} of P^sphorus. 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. Kg., H 2 O; H 8 S; N 8 O; N0 2 . Condensation . (3.) 3 unit volumes + 1 unit volume = 2 unit volumes. E.g. t \\J\; S0 3 . Condensation = . 176 VOLUMETRIC. 153 EXERCISES. 1. (a.) What is a unit volume? (ft.) A microcrith? (c.) What is the relation of specific gravity to combining weight? (d.) Give the specific gravity of HCI,NH.., Cl, and C0 2 . 2. How could you prove from molecules of steam that each mole- cule of has 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. (6.) Explain the terms atom and molecule as applied to H 2 O. 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 ? (6.) If then 130 cu.cm. of O be introduced and another electric spark produced in the containing vessel, the temperature being 16'C., 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 HNO 3 prepared on a large scale? (6.) 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. (.) What are bases? (&.) 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 ? (6.) HN0 3 + KHO = KN0 3 + H 2 O. 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 heated to redness, the following reaction takes place . H 2 S0 4 = S0 2 -f H 2 + 0. (a.) What weight and (6.) what volume of can be thus prepared from 50 g. of H ,S0 4 , C. P. ? (C. P. = chemically pure.) 14. MnO 3 and HCI are heated together. Give the properties of the gas evolved. 154 VOLUMETRIC. I?6 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, (b.) Substitute HCI for the H 2 S0 4 ; 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. C g. of HCI ? 18. What weight of each substance must be used to prepare 120 I. of H 2 S? 19. How much H 2 S0 4 will dissolve 120 g. of Zn? 20. Describe the preparation of HCI, NH 3 , and N 2 0. Give the re- action in each case. 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 ? (b.) Is the air a chemical compound? XIIL THE CARBON GROUP. \. 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 O, they all form the same compound, CO 2 , 12 parts of any variety of C uniting with 32 parts of O 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 wire. Place 156 CARS OX. 17* 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 smalJ 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 CO 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 electrotyping (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, b.) 183. Gas Carbon. Gas carbon is a very hard, com- pact substance that is formed as a crust on the inner sur- g 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 electric 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 168. Heat a piece of charcoal upon platinum foil and notice that 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. (a.) 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 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 bot 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. (&.) 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 flama Soot will be deposited upon the plate. Experiment IfO. 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 FlG - 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. 169. Lamp- black is manufactured on the large scale by burning tar, 1 87 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 t 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 copper oxide (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 2 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 Las been heated to full redness for some time, plunge it quickly into H 3 0. Notice that it needs no sinker to keep it under H 3 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., 275). FlG - 78. 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, C02) 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 2 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 CARBON. 163 wool 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, a.). The filtered liquid will be free from offensive odor. Experiment 170. Place a small crucible filled with freshly ignited and nearly cold powdered charcoal into a jar 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 ISO. Place a dilute solu- tion of the blue compound of iodine and starch (Exp. 121), of indigo dis- solved in H 2 S 2 O 7 ( 156), of cochineal and of potassium permanganate in each of four flasks To each, add recently ignited bone-black. Cork the flasks, shake 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. CARBON. 165 EXERCISES. 1. Is charcoal lighter or heavier than air? (See Kxp. 174.) 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, (b.) How much O is needed to burn 500 g. of charcoal ? (c.) How many liters of CO 3 will be produced ? 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 for 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. lv iv 14. Write graphic symbols for H 2 SO 3 and H 2 SO g . 1G6 SOME CARBON COMPOUNDS. Ip2 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 182. Place a small quantity of oxalic acid (H 3 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 2 S0 4 removes H 2 from the H 2 C 2 O 4 and leaves a mixture of CO and C0 2 . The C0 2 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. 16? 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 poison 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 O unites with the C to form C0 2 . As the C0 2 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 (COCI 2 ). 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 2 = CaC0 3 + H a O. Experiment 184. 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 -f C = C0 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. SOME CARSON COMPOUNDS. 169 Experiment 185. Into a bottle, arranged as described in 20, put a handful of small lumps of marble or chalk (CaCO 3 ). Prepared crayons witt 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 + CO,. Note. HCI is better than H 2 S0 4 in preparing C0 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 become milky.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 187. Dissolve 50 Fio. 82. 8 170 SOME CARBON COMPOUNDS. I 9 6 cu. cm. of molasses in about 400 cu. cm. of H 3 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 b, forcing a cor- responding quantity of H 2 0intoe. 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 2 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 CO 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 3 will have been dissolved in the H 2 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 CO 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 degree of cold that quickly freezes metcury, and in a vacuum, yields a temperature of 110C. 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 2 , dip a turn- 172 SOME CARBON COMPOUNDS. blerful of the gas and pour it, as if it were H 2 O, upon the flame of a taper burning at the bottom of another tumbler. The name 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, ignite 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 a O 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 CO 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 S 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. Caution. In performing experiments with CS;>, see that there is no flame near. Experiment 195. Put a few drops of CS 2 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 a 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 O 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 lungs 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 8 . 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 8 . 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 diathermanous, has a highly refractive effect upon light (Ph., 552, 553, G13), evaporates rapidly at ordinary temperatures and boils at about 46C., yielding a heavy vapor that ignites at about 150 0., 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. FIG. 86. 205 SOME CARBON COMPOUNDS. 175 It is used largely in the extraction of fats and oils and in the cold process of vulcanizing caoutchouc. 2O4, 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 8 Potassium chloride KCI Hydrochloric acid HCI Free cyanogen Cy 2 or C 2 N 3 Potassium cyanide.... KCy or KCN Hydrocyanic acid. . . HCy or HCN Some of the cyanides will be subsequently noticed. 2O5. Hydrocyanic Acid. Hydrocyanic acid (cyan- hydric acid, HCN or HCy) may be prepared by passing hy- drogen sulphide over mercury cyanide heated to about 30C. HgCy 2 -f 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 3 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. 176 SOME CARBON COMPOUNDS. 205 EXERCISES. 1. In Exp 181, the potassium ferrocyanide (K 8 Fe 2 C 12 N 12 ) contains 3H 2 as " water of crystallization," Additional H a O is furnished by the commercial H 3 S0 4 . Among the products are to be found potas- sium sulphate (K 2 S0 4 ), iron sulphate (FeSO 4 ) and ammonium sul- phate [(NH 4 ) 2 S0 4 ]. Write the reaction for that experiment. 2. Write the graphic symbols and the names of H 2 C0 3 , Na 2 CO 3 and HNaC0 3 . 3. Write an equation showing what becomes of the C0 2 removed from the CO in Exp. 182. 4. Write the reaction for Exp. 182. 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. 6. What is the weight of a liter of cyanogen gas ? 7. How would you prove the solubility of HCI, NH 3 and C0 2 ? 8. (a.) What weight of C0 2 would be produced by burning 5 g. of C? (&.) What volume? 9. (a.) What weight of CO 2 may be obtained from 100 g. of CaCO 3 by the action of HCI ? (6.) What volume ? 10. What is the weight of 10 I. of C0 2 ? 11. (.) If 20 cu. cm. of CO and 10 cu. cm. of O be mixed in an eudiometer and an electric spark passed through, what will be the name and volume of the product? (&.) 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. 18. Give the laboratory mode of liberating C0 2 , with the reaction, 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 K 194: SOME ORGANIC COMPOUNDS. 8 222 SOME ORGANIC COMPOUNDS. . 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 ivall, is already ruined. In this section, we shall consider a few qf the almost innumerable known organic compounds. The molecular structure of most of them is very complicated. Experiment 212. Place a teaspoon ful of the white of an egg in a test tube ; add 25 cu. cm. of C 8 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 2 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 (histogeuetic) 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 ROME 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 heatorC 8 H 6 0. The albumen of plants is found chiefly in the seed. The formula, C 72 H, 12 N 18 S0 22 , has been given for albumen, but its chemical composition has not yet been satisfactorily determined. (6.) 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 2 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. i (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 2 O. Place a clean bone (e.g., the femur of a chicken) in the dilute acid c.nd 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, homy 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, culled 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 20n) 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 ^,0, filtering the solu- tion through layers of animal charcoal and evaporating the H 3 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, barky 227 SOME ORGANIC COMPOUNDS. 197 sugar is formed. When it is heated to about 215C., H 2 is expelled and caramel remains. (d.) Lactose or milk-sugar and maltose are isomeric forms that combine with one molecule of water of crystallization ( c i2 H 22n + H *)- The former exists in solution in the milk of mammals. 221. Dextrose and Levulose. When a solution of sucrose is boiled or subjected to the action of yeast or an acid, it is converted into two isomeric varieties of sugar, dextrose (glucose, grape sugar, starch sugar, C 6 H 12 6 ) and levulose (fruit sugar, C 6 H, 2 6 ). C 12 H 22 X1 + H 2 = C 6 H 12 6 + C 6 H 12 6 . This mixture of dextrose and levulose is called inverted sugar. (a.) Dextrose is found in many ripe fruits. The " candied " sugar of raisins and other dried fruits is dextrose. It crystallizes with diffi- culty and is generally found in a sirupy condition. It may be pre- pared by boiling starch in H 2 O acidulated with H 2 S0 4 . It has le^-s sweetening power than sucrose. Large quantities of glucose are now made from indian corn. (&.) Levulose is found with dextrose in many ripe fruits, in honey, molasses, etc. It does not crystallize. It has less sweetening power than sucrose. (c.) Dextrose and levulose may be fermented (Exp. 187) ; sucrose can not be fermented until after its conversion into dextrose and levulose. (d.) If a beam of polarized light (Ph., 667) be passed through a solution of dextrose, the plane of polarization will be turned to- ward the right (dextra = right hand). A solution of sucrose will turn it still more. If the beam be passed through a solution of levulose, the plane will be turned toward the left (laeva = left- hand). (.) Dextrose and levulose are isomeric with acetic acid, the mole- cule C 6 H 12 O 6 having three times as many of each kind of atoms as CoH 4 O 2 . While, therefore, dextrose and levulose are said to be metameric, either one of them is polymeric with reference to C 2 H 4 8 . See 216. 198 SOME ORGANIC COMPOUNDS. 228 22S. Starch. Starch (C 6 H I0 5 ) is a familiar sub- stance found in grain (e. K 2 S0 3 , K 2 S0 4 , HKS0 4 , KCI, KCIO, KCIO 2 , KCI0 3 , KCIO 4 , HNaSO,", SiH 4 , Si0 2 , H 4 SiO 4 . 5. (a.) Find the weight of 20 1. of O. (ft.) Of 50 I. of Cl. (c.) Of 250 I. of NH 3 . 6. What materials and what quantities would you need to prepare 50 1. of each of the oxides of C ? 7. By heating Mn0 2 with H 2 S0 4 'the following reaction takes place : 2Mn0 2 + 2H 2 S0 4 = 2MnSO 4 + 2H 2 + O s . (a.) What weight and (6.) what volume of O can be thus obtained from 50 gr. of Mn0 2 ? 8. (a.) Give the ordinary methods of preparing 0, H and HCI. (6.) In what do they differ and in what do they agree ? (c.) Find the amount of Cl, by weight and by measure, in 2 Kg. of HCI. 9. If 100 /. of CO 2 be required, by what means would you ob- tain it, from what materials, and what quantity of each material ? XIV. THE NITROGEN GROUP. j v ':" - ^SECTION f. PHOSPHORUS. Symbol, P ; specific gravity, 1.8 ; atomic weight, 31 m. c. ; nwlec ular weight, 124 m. c. ; qwmticalence, 3 or 5. 35. Source. Phosphorus does not occur free in nature, but its compounds with oxygen and some metal (chiefly calcium) are found in large quantities. Calcium phosphate is found as a native mineral ; it forms, also, the greater part of the mineral constituent of animal bone. (a.) The ultimate source of P is the granitic rocks, by the disinte- gration of which the fertile soil has been produced. All fruitful soils contain some of the phosphates, but diffused in such small quantities that their collection thence by the manufacturing chemist would be very costly. Plants collect the phosphates from the soil ; herbivorous animals obtain them by consuming the plants ; from the bones of animals, the chemist derives the phosphates from which he prepares the P that he and the manufacturer need. The process is devious and complicated but the greater part of it is inexpensive. Note. The name comes from two Greek words that mean a bearer of light, phosphorus being luminous in the dark. The alchemists* used to call it " Son of Satan." Phosphides were formerly called phosphurets. 236. Preparation. In the preparation of phos- phorus, the bones are burned and powdered. This 206 PHOSPHORUS. 236 powdered bone ash is treated for about twelve hours with two-thirds its weight of strong sulphuric acid di- luted with about twenty times its weight of water. This treatment yields an insoluble calcium sulphate (gypsum, CaS0 4 ) and a soluble salt called "super- phosphate of lime." The insoluble sulphate is re- moved by filtration. The clear solution is then evap- orated to a sirupy liquid, mixed with powdered char- coal, dried and finally dis- FIG. 96. tilled. The long neck of the earthen retort (Fig. 96) dips under water contained in b. The liberated phosphorus distils over and condenses under the water. After purification, it is melted under hot water and run into cylindrical moulds placed in cold water. B^~ See the Caution on page 31. Phosphorus burns are very dif- ficult to heal. Experiment 2W. Bury a piece of P, the size of a grain of wheat, in a teaspoonf ul of lamp-black or powdered bone-black, that lias been freshly prepared or recently heated. The O condensed within the pores of the carbon unites with the vapor of the P, developing enough heat to melt and finally to ignite the P. Experiment 2ZO. Dissolve a piece of P in CS 3 . Pour some of the solution upon a piece of filter paper placed upon the ring of a retort stand. The volatile CS 2 soon evaporates, leaving the P in a finely divided state exposing a large surface to the oxidizing influence of the air. The P soon bursts into flame, which only partly consumes 237 PHOSPHORUS. 207 the paper. The burning P quickly covers the paper with a coat of incombustible and protecting varnish. If the experiment be per- formed in a dark room, the phosphorescence will be very marked. Experiment 221. Rub a piece of dry P the size of a pin head be- tween two bits of board. The heat developed by the friction is suf- ficient to ignite it. Experiment 222. Heat a small piece of P in a dry tube with a mere trace of I. Combination promptly takes place, a small quantity of volatile phosphoric iodide is formed and the rest of the P is changed to an allotropic form known as red phosphorus. Try to repeat Exp. 221 with red P. Experiment 223. Close one end of a piece of narrow glass tubing about 30 cm. long by fusing it in a flame. In the ignition tube thus made, place a small bit of red P and heat it gently in the lamp flame. A yellow coating is quickly deposited upon the cool walls of the tube not far from the heated end. Allow the tube to cool, and cut off the end just below the yellow sublimate. Scratch, this yel- low deposit with a wire ; it will take fire, as it is ordinary, yellow P. By heating the red P, a part of it burned, thus removing the O from the lower part of the tube. The inert N remaining the re, enveloped and protected the rest of the P from combustion and thus permitted its reconversion into the ordinary variety. Experiment 22%. Touch a slice of P with a test tube containing boiling H 2 O. The P will be ignited. Experiment 225. Place a piece of P under H 2 O warm enough to melt it. Bring a current of O from the gas-holder into contact with the melted P. The P will take fire and burn brilliantly under H 2 0. Experiment 226. Repeat Exp. 3. 237. Physical Properties. Pure phos- phorus is an almost colorless, translucent, wax- like solid. The ordinary commercial article has a feeble yellow tinge. When freshly cut, it has FlG - 97- a garlic-like odor, often hidden by the odor of ozone, which is generally present when moist phosphorus is exposed to the air. It is insoluble in water, sparingly soluble in tur- 208 PHOSPHORUS. 237 pentine, petroleum and other oils and easily soluble in car- bon disulphide. It is soft and flexible in warm weather but brittle at low temperatures. It melts at 44C., form- ing a viscid, oily liquid which boils at 290C., yielding a colorless vapor. At 500C. the vapor is 62 times as heavy as hydrogen. Consequently, its molecular weight is 124 m. c., or four times its atomic weight. From this we conclude that the phosphorus molecule contains four atoms and that each atom occupies half the space taken up by a hydrogen atom ( 175). Experiment 227. Upon a thin slice of P, place a crystal of I. The two elements promptly unite with great energy, leading to the com- bustion of the excess of P. 238. Chemical Properties. Phosphorus com- bines readily with many of the elements, especially oxy- gen. It undergoes slow combustion at ordinary tempera- tures (forming P 2 3 ) and oxidizes with great energy at a temperature not much above its melting point (forming P 2 5 ). On account of this easy inflammability, phosphorus should be kept and cut under water, and never handled with dry fingers. Owing to its slow combustion, it is feebly luminous in the dark. This phosphorescence is a familiar effect of a futile attempt at lighting an ordinary friction match in a dark room. In distillation, the oxygen in the retort must be replaced by some inert gas like hydrogen, nitrogen or carbon dioxide. Heated for several hours to about 240C., out of contact with oxygen or any other substance capable of entering into chemical union with it, it is changed to the remarkable allo tropic modification known as red phosphorus. (a.) The difference between the ordinary yellow and the red varie- ties of P are shown in the following table : 239 PHOSPHORUS. 209 1. Pale yellow, Chocolate red. 2. Strong odor, Odorless. 3. Specific gravity = 1.83, Specific gravity = 2.14, 4. Phosphorescent, Not phosphorescent. 5. Translucent, Opaque. 6. Soluble in CS 8 , Insoluble in CS 2 . 7. Subject to slow combustion, Exempt from slow combustion. 8. Melts at 44C., Melts at 255C. Changes to yellow variety at 260 a 24cn c 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. pkosphorus, 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." (a.) 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. (6.) What do S 2 and 60" 2 represent V 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 ) 3 and the rest CaC0 3 ? 4. (a.) Find the percentage composition of carbon monoxide. (&.) Find the symbol of a gas having the composition 27.21% 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 O. The symbol for the black oxide is CuO ; what is the symbol for the red oxide? 6. What is the meaning of the following : H *. 0<$%J will remain. Explain. 8. Write the name and full graphic symbol for (HO)-(S0 2 )-(S0 8 )-(HO). 240 PHOSP HOR US COMP O WDS. 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 m. 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 3 H 5 ).,O; 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 5 ) 3 O 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 (PgOs) 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 O. (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 8 or P 8 H 4 and the solid by P 8 H or P 4 H 8 . FIG. 98. PHOSPHORUS COMPOUNDS. 240 (d.) Pure PH 3 is not spontaneously combustible in the air. The combustion above noticed is due to the presence of a small quantity of P 3 H 4 . If the gas, as it comes from the flask (Fig. 98), be passed through a tube chilled by a freezing mixture (Ph., 521,) the P 2 H 4 will be condensed. The escaping PH 3 will not take fire as it subse- quently bubbles through the H 2 O and comes into contact with the air. (e.) The composition of PH 3 maybe represented by the accompany- ing diagram : 1 + ll m. c.l 1 m. c.\ \\rn.c. Iv-g* 1 It may now be noticed that, in the composition of the compounds previously studied, the weight of a unit volume has been the atomic weight but that in the case of P the weight of half a unit volume is the atomic weight. The unit volume, being half the molecular vol- ume, would include two P atoms. Compare the above diagram with the one given for NH 3 . ( 70.) 241. Phosphorus Oxides. Theoretically, there are three oxides of phosphorus, having the symbols, P 2 0, P 2 3 , P 2 5 . (a.) P 2 O (hypophosphorous oxide or anhydride, phosphorus mon- oxide) has not yet been isolated. Its compounds are known. (6.) P 3 3 (phosphorous oxide or anhydride, phosphorus trioxide) is formed by the slow combustion of P in a limited current of dry air. It is a white, amorphous substance, very soluble in H 2 and burns in the air to P 2 5 . (e.) P 2 3 (phosphoric oxide or anhy- dride, phosphorus pentoxide) is formed by the rapid combustion of P in an ex- cess of O. Place a piece of thoroughly dry P, weighing 0.5 #. to I g. in a small dry capsule ; place the capsule upon a large, dry plate ; ignite the P with a hot wire and quickly cover it with a dry bell glass or wide mouthed bottle of 2 or 3 liters capacity. The capsule, plate and bell glass should be warmed to insure their being dry. The P 8 5 will be deposited as a white fleecy powder. It absorbs FIG. 99. s 242 P&OSPHORVS COMPOUNDS. 213 H 2 with great eagerness, and is sometimes used for drying gases. If left in the air, it deliquesces completely in a few minutes ; if thrown into H 2 0, it hisses like a hot iron and dissolves with the evo- lution of much heat. It may be kept in dry tubes sealed by fusion. In preparing large quantities of P 8 O 6 , the following process may FIG. 100. be used. A is a large, dry glass globe with three necks, as shown in Fig. 99. The flexible tube, I, being connected with an aspirator, a strong current of air is drawn through the drying tube, /, into the globe. A straight glass tube, closed at the upper end with a cork, passes through the neck, a, and carries a small crucible suspended near the centre of the globe. A piece of P is dropped through the tube into the crucible and ignited with a hot wire ; the tube is then corked. The current of air being maintained, the P is soon burned to P 8 5 . Other pieces are dropped into the crucible from time to time to render the process continuous. Part of the P 2 O 5 is carried over into B. 24:2. Phosphorus Acids. Phosphorus combines with oxygen and hydrogen to form a remarkable series of acids, as follows : 214 PHOSPHORUS COMPOUNDS. P 2 0(?) + 3H 8 O = 2H 3 P0 2 , hypophosphorous acid. P a O 3 + 3H 2 = 2H 3 P0 3 , phosphorous acid. )3H 2 = 2H 3 P0 4 , phosphoric acid (ordinary or tribasic). 2H 2 H 4 P 2 7 , pyrophosphoric acid. H 2 O = 2HPO 3 , metaphosphoric acid. (a.) H 3 P0 2 gives a series of salts known as hypophosphites ; e. g., sodium hypophosphite, H 2 NaP0 2 . When heated, it decomposes into H 3 P0 4 and PH 3 . It is monobasic. (6.) H 3 P0 3 may be formed by the action of H 2 O on P 2 O 3 , by the slow oxidation of P in moist air or by the decomposition of phos- phorus trichloride by H 2 O : PCI 3 + 3H 2 O = H 3 PO' 3 + 3HCI. When heated, it decomposes into H 3 P0 4 and H 3 P. It is a tribasic acid and forms a series of salts known as phosphites ; e. g., normal sodium phosphite, Na 3 PO 3 ; tri-ethyl phosphite (C 2 H 5 )' 3 P0 3 . (e.) H 3 P0 4 may be prepared by the direct union of P 2 5 and boil- ing H 2 O, but the usual process is to oxidize red P with strong HN0 3 or ordinary P with dilute H N 3 . When heated, it changes to H 4 P 2 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 are the most important of the phosphoric series. (See Exp. 3, p. 115.) (d.) H 4 P 2 O 7 is formed by heating H 8 P0 4 to 215C., thus depriving it of H 2 O : 2H 3 P0 4 H 8 O = H 4 P 2 O 7 . It is tetrabasic and yields normal, double and acid pyro phosphates in great variety. The group, PO (phosphoryl) acts as a trivalent compound radical. The equation above may be written graphically as follows : From OH take H-O-H and (PO)0. It is well to keep the -gen- erating flask cool by placing it in a cold water bath. When the air has been expelled from the appa- ratus, ignite the jet. Hold a piece of cold porcelain in the flame, and notice that no colored stain is pro- duced. (If a stain should appear, it would show that the materials used in the generating flask were impure.) Keep the jet burning &nd ^ add, through the funnel tube, a few drops of a hot aqueous solution of As 2 O 3 . Notice the change in the appearance of the flame. Hold the cold porcelain in the flame. A stain having a metallic lustre will be produced. The stain is metallic As, freed from combination in AsH 3 by the heat of the flame and deposited, just as soot would be by a candle flame. Do not let the porcelain become hot enough to vaporize the As, and cause the stain to disappear. Keep the jet burning until the apparatus is placed in the ventilating closet or out of doors, to prevent the escape of AsH 3 . Experiment 229. Clean the generating flask and repeat the experi- ment, using " Paris green " instead of the As 2 0. f . Experiment 230. Boil a green paper label with HCI in a test tube. Test this solution for the presence of As, as in Exp. 228. Try the same with green wall paper or with green paint scraped from wood work. FIG. 102. 247 ARSEXIC AXD ITS COMPOUNDS. 219 Note. The author has often demonstrated the presence of As in green fabrics worn as clothing in his classes. Experiment 231. After passing the AsH 3 through a drying tube containing potassium hydrate and calcium chloride, heat the glass tube to a red heat. The gas will be decomposed, the As being de- posited as a dark band upon the cool part of the tube and the H burn ing with its characteristic flame at the jet. Little or no deposit will then be made on cold porcelain. Experiment 232. To show that the stains produced in Exps. 228- 229 are As and not Sb, which might imitate them, touch one of the stains with a glass rod dipped into a solution of chloride of lime. If the metal dissolves, it is As and not Sb. 246. Marsh's Test. The preceding experiments rudely illustrate Marsh's test for arsenic. The test is so delicate that 0.01 mg. (~~ grain) of the poison may be recognized with certainty. In examinations of great im- portance, as in trials for murder by arsenical poisoning, the purity of all materials used and the nature of the metallic deposit are carefully determined by confirmatory tests. Experiment 233. Place a small quantity of As a 3 in a tube of hard glass (Fig. 102) about 10 cm. long and hold the tube in a slop ins: position in a lamp flame until the powder is volatilized. With a. magnifying lens, examine the walls of the tube where the As.,0., has condensed ; the oxide will be seen to be brilliantly crys talline. Experiment 234. Make the tube used in the last experiment into an ignition tube by fusing and sealing one end of it in the lamp flame. In the bottom of the tube thus formed, place a little (a few mg. only) of As 2 O 3 and above it, a small piece of charcoal, as shown at c, Fig. 102. Holding the tube horizontal, heat the charcoal splinter to redness ; then gradually bring the tube into a nearly vertical position, keeping the charcoal red hot and heating the tip of the tube until the As0 3 is vaporized. The vapor will be reduced by the glowing charcoal and a brilliant ring of metallic As will ap- pear at a. 247. Arsenic Trioxide. Arsenic trioxide (arseni- ous oxide, arsenious anhydride, white arsenic, As 2 3 ) 220 ARSENIC ANt) ITS COMPOUNDS. 8 2 47 is prepared on the large scale by roasting arsen- ical ores with free access of air. The white smoke given off condenses to a white powder. It occurs in three varieties, the amorphous or vitre- ous, and two different crystalline forms, rhombic and octahedral. It is isodimorphous with anti- mony trioxide. It is feebly soluble in water but dissolves more readily in boiling hydrochloric acid and freely in boiling nitric acid or alkaline solu- tions. Heated in contact with air, it volatilizes without change. Heated in contact with carbon, it gives up its oxygen and is reduced to metallic arsenic. As a poison, it is very dangerous, because it has no warning odor and scarcely any taste and be- cause very small quantities (0.2 g.) produce death. Its best antidote is freshly prepared ferric hydrate (see 363 for its preparation), which forms with it an insoluble salt and thus prevents the poison from entering the system. When these can not be quickly obtained, the white of eggs or soap-suds should be administered promptly. Arsenic tri- oxide is largely used in the manufacture of pig- ments and of glass. Note. In 1873, nearly 6,000 tons of As 2 3 were made in England alone, more than a third of which was made at a single mine. As the vapor density of this substance is 198, its IG ' IO ^' molecular symbol is sometimes written, with apparent propriety,As 4 6 . 248. Arsenic Pen toxide. Arsenic pentoxide (arsenic an- hydride, As 2 5 ) may be obtained by oxidizing the trioxide with nitric acid, evaporating to dryness and heating nearly to redness. It is less powerfully poisonous than the trioxide. 249. Arsenic Acids. Arsenic forms a series of acids that presents remarkable analogies to the phosphorus acids. 250 ARSENIC AND ITS COMPOUNDS. %2l As 2 3 + 3H 2 O = 2H 3 As0 3 , arsenious acid. {3H 2 O = 2H 3 As0 4 , tribasic arsenic acid. 2H 2 = H 4 As 2 7 , pyroarsenic acid. H 3 O = 2H As6 3 , metaarsenic acid. (a.) When As 2 3 is dissolved in H 2 0, the solution gives a feebly acid reaction and is supposed to contain H 3 As0 3 . The corresponding salts are called arsenites ; e.g., silver arsenite, Ag 3 AsO 3 . (&.) H 3 As0 4 is generally prepared by treating As 2 O 3 with HN0 3 . The commercial form is a liquid with a specific gravity of 2, from which transparent crystals may be obtained by cooling. As it is tribasic, it yields three series of arsenates which closely resemble the corre- sponding phosphates in composition and crystalline form. Heated to 180C. it loses H 2 and becomes H 4 As 2 7 . Heated in 200C. it loses another molecule of H 2 and becomes HAs0 3 . Note. As 2 O 8 is sometimes improperly called areenious acid. Less frequently, but with equal impropriety, As 2 5 is called arsenic acid. Every acid contains H. 25O. Sulphides of Arsenic. Two native sul- phides of arsenic are found. The red sulphide (As 2 S 2 ) is called realgar; it is used in making fireworks. The yel- low sulphide (As 2 S 3 ) is called orpiment; it is used as a pigment. In addition to the disulphide and the trisul- phide, a pentasulphide (As 2 S 5 ) is obtained by fusing the trisulphide with sulphur. EXERCISES. 1. Write the equation representing the combustion of hydrogen arsenide. 2. What is the weight of 10As 2 3 ? 3. Name the following : H 3 AsO 4 ; H 2 NaAs0 4 ; HNa 2 As0 4 ; Na 3 As0 4 ; (NH 4 )Mg"As0 4 . 4. Write a graphic symbol for H 3 P"'0 3 . 5. When AsH 3 is prepared from Zn 3 As 2 and dilute H 2 S0 4 , ZnS0 4 is produced. How much AsH 3 , by weight and by volume, can be prepared from 50 g. of Zn ;J As 2 ? 6. (a.) Why is As 2 O 3 said to be dimorphous ? (&.) Why is it said to be isodimorphous with Sb 2 O 3 ? 7. What is a dyad ? A monobasic acid? 8. You are given a mixture of ordinary and red phosphorus. How will you separate the two varieties ? ANTIMONY, BISMUTH, ETC. 25 1 ANTIMONY, BISMUTH, ETC. ANTIMONY: symbol, Sb (see App. 1); specific gravity, 6.7; atomic weight, 122 m. c, ; quantivalence, 3 or 5. 251. Source and Preparation. The antimony of commerce is obtained from the mineral stibnite, which is an antimony trisulphide (gray antimony, antimony glance, Sb 2 S 3 ). Antimony is, however, found native and in combination with other elements than sulphur. The stibnite is melted with about half its weight of iron (Sb 2 S 3 + Fe 3 = 3FeS + Sb 2 ) or heated with coal in a reverberatory furnace. Experiment 285. Make two moulds by boring conical cavities in a block of plaster of Paris. See that the mould terminates below in a sharp point. Make two or three clean cut grooves in the sides of the moulds. Into one mould, pour melted lead ; into the 'other, melted type metal. Remove the casts and notice that the lead cone is blunted at the apex while the type metal is pointed ; that the ridges on the sides of the lead cone are ill defined while those on the sides of the type metal are well defined. The lead contracts as it cools and thus shrinks from the mould. The type metal is composed of about 70 parts Pb, 10 parts Sn and 20 parts Sb. The Sn gives it toughness and the Sb hardness. The Sb tends to crystallize as it cools, thus causing the type metal to expand and force itself into every part of the mould and make a sharply de- fined cast (Ph., 525). 252. Properties and Uses. Antimony is a blu- ish-white metal. It is so brittle that it may be powdered in a mortar. Its crystalline tendency is so strong that, when it is cooling from the melted condition, beautiful fern-like figures are formed on the free surface of the 253 ANTIMONY, BISMUTH, ETC. 223 metal. These figures may be seen on one surface of al- most every cake of antimony found in commerce. It melts at 450C. It is not acted upon by the air at ordinary temperatures but, when melted in contact with the air, it rapidly oxi- dizes. At a red heat, it burns with a white flame forming antimony trioxide (Sb 2 3 ). It is a constituent of tartar- emetic and is largely used in the arts as a constituent of type metal, britannia metal, pewter and other valuable alloys. (a.) Sb is strongly attacked by Cl (Exp. 88), forming SbCI 3 . It is not acted upon by dilute HCI orH 2 S0 4 but is easily dissolved by aqua regia. HNO a acts upon it, forming insoluble Sb 3 5 . Experiment 236. Put 30 cu. cm. of HCI, 10 or 12 drops of HN0 3 and 0.5 y. of powdered Sb into a small flask and heat the mixture gently until the metal is dissolved. Evaporate the solution to a thick syrup, the so-called " butter of antimony." 253. Antimony Compounds. The compounds of antimony correspond closely to those of arsenic. (a.) Hydrogen antimonide (stibine, antimoniuretted hydrogen, SbH 3 ) is formed when a soluble compound of Sb is acted upon by nascent H. Tt is analogous to AsH 3 , but its metallic deposit is easily distinguished from that of the latter compound by its darker color, smoky appearance, non-volatility and other tests (Exp. 232). Its combustion yields H 2 O and Sb 2 O 3 . (&.) There are three known oxides of Sb represented by the sym- bols Sb 2 O 3 , Sb 2 O 4 and Sb 2 O 3 . The tetroxide may be considered a mixture of the other two : Sb 2 O 3 + Sb 2 O 5 2Sb 2 O 4 . All of these oxides form acids. The trioxide is isodimorphous with arsenic tri- oxide. (c.) There are two sulphides, Sb 2 S 3 and Sb 2 S 5 . They unite with alkaline sulphides to form sulpho-antimonites and sulpho-antimo- niates (see 171). (d.) There are two chlorides, SbCI 3 and SbCI 5 . The trichloride is a soft solid, known as butter of antimony ; the pentachloride is a strongly fuming liquid. 224: ANTIMONY, BISMUTH, ETC. 254 BISMUTH: symbol, Bi ; specific gravity, 9.8; atomic weight, 2iu m. c. ; quantmalence, 3 or 5. 254. Source and Preparation. Bismuth is found in nature free, and also in combination with sul- phur and other elements. Commercial bismuth was formerly prepared by heating the ore in iron tubes sloping over a furnace. As this process yields only apart of the native metal, all bismuth ores are now roasted and then smelted in a pot with iron, carbon and slag. The crude bismuth is drawn off in a melted condition from the bot- tom of the smelting pot after the layer of less easily fusi- ble "cobalt-speiss" above has solidified. Most of the bismuth of commerce comes from Saxony and Bohemia. Experiment S37. Melt 2 or 3 Kg. of Bi in a crucible. Perforate the covering crust that forms on cooling and pour out the still mol- ten liquid within. When cool, break the crucible to obtain a view of the beautiful Bi crystals thus formed. (Compare Exp. 131.) 255. Properties and Uses. Bismuth is a brittle, brilliant, pinkish-white metal. Of all known substances, it is the most diamagnetic (Ph., 310). In cooling from fusion, it crystallizes more readily than any other metal. Its crystals are nearly cubical rhombohedrons, often beauti- fully iridescent from the film of oxide formed when the crystals were still hot. It melts at 264C. and expands ^g- of its volume on solidifying. In dry air at ordinary temperatures, it is unaltered, but, when strongly heated, it burns with a bluish white flame forming bismuth trioxide (Bi 2 3 ). It is used in forming alloys and in the construction of thermo-electric piles (Ph., 412-414). (a.) Bi is acted upon readily by Cl. Cold HCI and H 2 S0 4 have no action upon it. Its best solvents are HNO, and aqua regi'i. 2 5 6 ANTIMONY, BISMUTH, ETC. 225 (b.) There are four oxides of Bi, viz. : Bi 2 2 , Bi 2 O 3 , Bi 2 4 , Bi 2 O 6 . Experiment ?S.">). The lamp is so placed that the salt around the negative elec- trode becomes solid while that around the positive remains liquid to allow the escape of the Cl, set free by the electrolysis. After pass- ing the current about twenty minutes, the crucible is cooled and 238 POTASSIUM. 273 opened under petroleum. Pure K is found at the negative electrode (Ph., 401). 348. Drop a piece of K, half the size of a pea, upon H 3 0. It decomposes the H 8 0,the H burns with a flame beautifully tinted with the vapor of K. If the H a O be in an open dish, stand at a distance of a meter or more, as the combustion will terminate with a slight explosion. Test the H 3 at the end of the experiment with reddened litmus paper. Experiment f9. Stretch a piece of blot- ting paper upon a wooden tray, wet the FIG. 107. paper with a red solution of litmus and throw upon it a small piece of Na or K. The track of the metal as it runs over the moistened paper will be written in blue lines, showing the formation of an al- kaline product. Experiment 250. Hold a small piece of K under H 2 O by means of FIG. 108. wire gauze or filter paper. Collect the gas evolved as shown in the figure. What is this gas ? Experiment 251. In Fig. 109, a represents a bottle for the genera- tion of C0 2 ; c, a drying tube, containing calcium chloride ; e, a tube of Bohemian (hard) glass with a delivery tube, t, dipping into the bottle, i. When a lighted match thrust into i is quickly extinguished, 274 POTASSIUM. 239 we may know that the apparatus is filled with C0 3 . Then, dry a piece of K the size of a pea by pressing it between folds of filter or blotting paper, remove t, thrust the K into e and replace t. When FIG. 109. the K is heated by the lamp flame, it will burn, taking O from the CO 2 and depositing black C upon the walls of e. 2K 2 + 3C0 2 = 2K 2 C0 3 + C. The particles of black C may be made more evident by placing e in a bottle of clear H 2 O, to dissolve the K 2 CO 3 . Experiment 252. Repeat Exp. 251, using a current of HCI instead of C0 2 . Collect over H 2 O the gas delivered through t What is this gas? Write the reaction. Experiment 253. Repeat Exp. 252, using NH 3 instead of HCI. Write the reaction. Experiment 251+. Bore a half inch hole two inches deep in a block of ice. Enlarge the bottom of the cavity to the size of a hickory nut. Into this cavity, drop a piece of K, the size of a pea, and notice the beautiful volcanic action. Try the experiment in a warm and dark- ened room. 274. Properties. Potassium is a light metal hav- ing a brilliant bluish-white lustre. In electro-positive characteristics, it ranks third among the metals, and in lightness, second. It is brittle at 0C. ; soft like wax at 15C., and easily welded when the surfaces are clean ; it melts at about 63C. Its physical and chemical properties 240 POTASSIUM. 274 closely resemble those of sodium, but it is less used on ac- count of its greater cost. Like sodium, it is best kept under petroleum. Its salts communicate a violet tint tc flame. 275. Oxides. Potassium forms two oxides, K 8 and K 2 4 . 276. Potassium Chloride. Potassium chloride (KCI) is found in sea and other salt waters, and is largely prepared from the mother liquor from which the sodium chloride has crystallized, and from the Stassfurt deposit of carnallite (KCI, MgCI 2 , 6H 2 0). It resembles sodium chlo- ride in appearance and taste but is more easily soluble in water. It dissolves in about three times its weight of water at the ordinary temperature, produciug great cold (Ph., 521). Like sodium chloride, it crystallizes in cubes. (a.) The other potassium, halogen salts, KBr, KI and KF, also crys- tallize in cubes, have a saline taste and easily dissolve in H 3 0. KBr and KI are used in medicine and in photography. 277. Potassium Cyanide. Potassium cyanide (KCN or KCy) is a white, fusible, deliquescent and intensely poisonous solid. As its solution dissolves silver and gold cyanides, it is largely used in electro-plating (Ph., 399, a). It is a powerful reducing agent. It is isomorphous with potassium chloride. (See Caution preceding Exp. 198.) 278. Potassium Carbonate. Potassium carbon- ate (K 2 C0 3 ) is generally prepared in this country by leach- ing wood ashes to form potash-lye and evaporating the lye in large pots or kettles, whence the name of the crude article, potash. The potash, when refined, is called pearl- ash. A pure carbonate, prepared by igniting the bicar- bonate, is called salt of tartar. Potassium carbonate is a deliquescent salt with a strong alkaline taste and reaction. 280 POTASSIUM. 241 (a.) K.,CO 3 was formerly of more importance than now, as Le- blanc's process has rendered Na,CO 3 so much cheaper that it has largely replaced the former in commerce and the arts. As K 2 C0 3 is hygroscopic and Na 2 C0 3 is not, the latter is much more convenient for storing and handling. (6.) As Na 8 CO 3 is used in making hard soap, so K 3 CO S is used in making soft soap. (c.) The rapid extinction of American forests has greatly checked the manufacture of American potash, which industry is now not more than 20 per cent, of what it was 20 years ago. Similar causes have operated in Europe. Hence, other sources have been sought and large quantities are now made from the refuse material of the beet-root sugar manufacture and also from K 2 S0 4 by a process simi- lar to the Leblanc process for preparing Na 2 CO 3 . 279. Hydrogen Potassium Carbonate. Hy- drogen potassium carbonate (saleratus, potassium bicar- bonate, HKC0 3 ) is prepared by passing a current of carbon dioxide through a strong solution of potassium carbonate. K 2 C0 3 + H 2 + C0 2 =2HKC0 3 . 280. Potassium Hydrate. Potassium hydrate (caustic potash,, potassium hydroxide, KHO) is prepared from potassium carbonate as sodium hydrate is from sodium carbonate. Its physical and chemical properties closely resemble those of sodium hydrate. It combines with fats and oils to form soft soap, and is one of the strongest bases known. (a.) As KHO absorbs H 2 O and CO 2 from the air, it is gradually changed to K 2 C0 3 . As this salt is deliquescent, the change goes on until all of the KHO is changed to a sirup of K 2 CO 3 . Consequently, it should be kept in closely stoppered bottles. It is usually cast in the form of sticks. (6.) KHO is easily but not cheaply prepared by the action of K upon H 2 0. (c.) A solution of KHO quickly destroys both animal and vegetable substances. It is best clarified by subsidence and decantation though it may be filtered through glass, sand, asbestus or gun-cotton. 242 POTASSIUM. 28l Experiment 255. Repeat Exp. 247, using KHO instead of NaHO. Experiment 256. Repeat Exp. 3. Experiment 257. Repeat Exp. 113. Experiment 258. Repeat Exp. 1. The mixture may be placed in a paper or metal cylinder and the experiment tried in a dark room with good effect. Experiment 259. Carefully mix^ with a feather, a small quantity of powdered KCIO 3 , and an equal quantity of powdered red P. The mixture will ignite when struck even a slight blow as with a glass rod. Experiment 260. Place a pinch of powdered KCIO 3 and one of flowers of S in a mortar and rub them together with the pestle. A series of explosions will take place. A minute quantity of the same mixture may be exploded by a blow of a hammer. . Potassium Chlorate. Potassium chlorate (chlorate of potash, KCI0 3 ) is largely used in the prepara- tion of oxygen, and for other purposes in the laboratory. It is also used in medicine, in calico printing and in the manufacture of fire-works and friction matches. It is chiefly valuable as an oxidizing agent. Experiment 261. Melt some KN0 3 in an old flask. Put a basin of H 3 O under the flask. Pour powdered charcoal into the melted salt and quickly remove the lamp. A brilliant combustion will take place and probably break the flask. The C is energetically oxidized forming large volumes of CO 2 282. Potassium Nitrate. Potassium nitrate (nitre, saltpetre, KN0 3 ) is found as an efflorescence on the soil in various tropical regions, especially in Bengal. It does not extend into the soil to a depth greater than that to which the air can easily penetrate. It is extracted by solution- in water and evaporation. It is also found in many caverns, and is seldom wanting in a fruitful soil. It is chiefly used in the preparation of nitric acid and the manufacture of gunpowder. It is a white, inodorous 286 POTASSIUM. 243 solid, permanent in the air and very soluble in hot water. (a.) When animal or vegetable matter decays in the presence of air and in contact with an alkaline or earthy base, the NH 3 produced is gradually oxidized to HNO 3 and "fixed" by the alkali. Thus the well-waters of most towns contain nitrates, showing that they have been contaminated by sewers, cess-pools or other causes. The artificial production of KNO 3 is regularly carried on in Sweden, Switzerland and other parts of continental Europe. 23. I. i 111 in in. Lithium (symbol, Li ; atomic weight, 7 m.c.) is a rare metal and the lightest known elementary solid, its specific gravity being 0.59. It was first prepared in the metallic state in 1855. It is closely allied to sodium and potassium, but is harder and less easily oxidizable than they. It melts at about 180 C. 284. Rubidium. Rubidium (symbol, Rb ; atomic weight, 853 m. c.) is a rare metal found only in very minute quantities. Its specific gravity is 1.52. It resembles potassium so closely that it can not be distinguished from it by the ordinary wet reactions or blow- pipe tests or any other nxeans except that most delicate of all de- terminative processes, spectrum analysis (Ph., 638, &.). It was dis- covered by this means in 1861. It melts at about 58 C. 285. Caesium. Caesium (symbol, Cs; atomic weight, 132. 5 m.c.) was discovered by spectrum analysis in 1860, being the first element thus discovered. It closely resembles potassium and rubidium, with which it generally occurs. The only means of its detection and re- cognition is spectrum analysis, which, however, makes evident its minutest trace. It is the most decidedly electro-positive of all of the elements. Its specific gravity is not yet known. 286. Ammonium. Ammonium is a name given to the compound radical, NH 4 . It acts, as do the other mem- bers of this group, as an alkali, monad metal but it has not been isolated ( 168). (a.) The assuming of this hypothetical metal makes the analogies 244 POTASSIUM. 286 between the composition of the salts of the " volatile alkali " and the composition of those of the fixed alkalies as evident as are the analogies between their properties ; e. g. Ammonium hydrate. Potassium hydrate. Sodium hydrate. 287. Ammonium Chloride. Ammonium chlo- ride (salammoniac, NH 4 C1) is found native in certain vol- canic regions and is artificially prepared in large quantities from the ammoniacal liquors of gas works. It occurs in commerce as tough, fibrous masses. It is used in medicine, in soldering to dissolve the metallic oxides, in dyeing, and in the laboratory as a convenient source of ammonia and for other purposes. (a.) The ammoniacal liquor of gas works is heated with lime and the gaseous NH 3 thus evolved is passed through dilute HCI until it is saturated. The solution is evaporated and the NH 4 CI purified by recrystallization from hot H 8 O or by sublimation. Experiment 262. Dissolve 6 g. of (NH 4 )N0 3 in 10 cu. cm. of ice cold H 2 O. Stir the mixture with a thermometer and notice the re- sulting temperature. 288. Ammonium Nitrate. Ammonium nitrate (NH 4 N0 3 ) is prepared by neutralizing dilute nitric acid with dilute ammonia water or a solution of ammonium carbonate and evaporating the solution. It decomposes by heat into water and nitrogen monoxide ( 79). It has a saline taste, dissolves easily in half its weight of water with the production of cold (Ph., 530). Note. Ammonium salts are very numerous, most of them being prepared directly or indirectly from the ammoniacal liquors of gas works. They are generally soluble in water. 33^ POTASSIUM. 245 EXERCISES. 1. The practical yield being half the theoretical, how much potas- sium may be prepared from 138080 g. of potassium carbonate ? 2. What is the percentage composition of KCI0 3 1 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.) HNO 3 + NH 3 = (6.) H 8 S0 4 + 2KHO = (c.) 2HN0 3 + PbO = 6. What is the molecular weight of caustic potash ? 7. I explode a mixture of 4 1. of H and 5 I. of Cl. (a.) What volume of HCI is produced? (6.) Which gas, and how much of it remains uncombined ? 8. (a.) What volume of. N 2 O may be formed by heating 30 g. of NH 4 NO 3 ? (&.) What will the volume be at 15C. and 740 mm. ? 9. Assuming that H 2 O will absorb half its weight of NH 3 , calcu- late the amount of NH 4 CI necessary to the production of 3 Kg. of NH 4 HO. 10. What substances do the following symbols represent: CH 4 ; C 2 H 6 CI; CHCI 3 ; 3 H 5 0; H-O-O-H ? 11. (a.) Write the empirical symbols and the systematic names for the following : ^[Moand^ 3 ! O. (6.) What is the common name for the former ? 12. What is the object of having the room " warm " for Exp. 254 1 13. Give the names and graphic symbols for PCI 3 and PCI 8 . XVI. METALS OF THE ALKALINE EARTHS. CALCIUM: symbol, Ca ; specific gravity, 1.58; atomic weight, 39.9 m. c. ; qwmtivalence 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 calcium carbo- FIG. no. 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^O and CO 2 and falls to a powder known as air slaked lime. (d.) Calcium dioxide (CaO 2 ) has been prepared by precipitation from lime water with H 2 O 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. (a.) CaCU may be crystallized from a saturated solution. These crystals (Cad*, 6H,0), when mixed with snow, produce a tempera- ture of 48C. (Ph., 521). Experiment 263. 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 264. 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 Z O 248 METALS OF TSE ALKALtNE EARTHS. 2Q2 upon it. Notice the increase of bulk and the rise of temperature. Thrust a friction match into 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 liter 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 3 O. 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 O 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. (&.) 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 (CaCI 2 + CaCI 3 2 ) or a double salt, CaOCI 2 , at once a chloride and a hypochlorite of calcium, ClOf ^ a ' (1-^-) -^ i s sometimes called calcium chloro-hypo- chlorite, and graphically symbolized as follows : CI-Ca-0-CI. 2Q4 METALS OF TffE AL&ALLVE EAttTHS. 249 Experiment 2G6. 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 C0 2 , and the precipitate again appears. Test the liquid at each step of the experiment with litmus paper to determine whethei 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 (CaSO^, 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 OP THE ALKALINE EARTHS. 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 liard 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, 3.5; atomic weight, c. ; quautivalence, 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 ). BABIUM : symbol, Ba ; specific gravity, 4 ; atomic, weight, 136.8 n. 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 3 ), 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 2 . 3. Write the reaction for preparing calcium hydroxide. 4. Why is the formula for calcium hypochlorite CaCI 2 2 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 SO 4 shall I need to prepare enough HN0 3 to neutralize 5 Eg. of chalk? (!) 7. W T hat is the property that chiefly distinguishes Cl and the ele- ments most like it from K and the elements most like it? 8. What is meant by the statement that caustic soda is formed upon the water type ? 9. What are the characteristic properties of C ? 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 1. of Cl? (6.) Of H 2 S? (c.) Of CO? 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 atom of Ca? XVII. V, METALS OF THE MAGNESIUM GROUP. MAGNESIUM : symbol, Mg ; specific gravity, 1.75 ; atomic weight^ ^4 m- f quantwalerice, 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. 3OO. JHagiieiuiii Salt. 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 liydrated salt (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 O 2 ) prepared by adding Na 2 CO 3 toa solution of MgCI 2 or of Epsom salt, is called magnesia alba. ZINC : symbol, Zn ; specific gravity, 6.9 ; atomic weight, 65 m.c. ; quantivatence, 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, ZnC) 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. ( v^ w v^> \^ v^ rij nun or C 6 H, 4 , the sixth member, will illustrate. (a.) The following table includes the first ten members of the series. Radicals. Formu- las. Paraffin com- pounds. Empiri- cal for- mulas. Dissected formulas. Boiling point. Methyl CH 3 Methane CH 4 CH 4 Gas at 0C. Ethyl C 2 H 5 Ethane C 2 H 6 CH 3 -CH 8 Gas at 0C. Propyl C 3 H 7 Propane C 3 H 8 CH 3 -CH 2 -CH 3 Gas at 0C. Butyl C 4 H 9 Butane C 4 H 10 CH 3 -(CH 2 ) 2 -CH 3 1C. Pentyl C^n Pentane C 5 H 12 CH 3 -(CH 2 ) 3 -CH 3 38C. Hexyl C 6 H 13 Hexane C 6 H 14 CH 3 -(CH 2 ) 4 -CH 3 78C. Heptyl C 7 H 15 Heptane C 7 H 16 CH 3 -(CH 2 ) 5 -CH 3 98C. Octyl C 8 H 17 Octane CH 3 -(CH 2 ) 6 -CH 3 125C. Nonyl C 9 H 19 Nonane C 9 H 20 CH,-(CH.) 7 -CH. 148C. Decyl ClO H 21 Decane C 10 H 22 CH 3 -(CH 2 ) 8 -CH 3 168C. CnHsn.,., CnH 2n f 2 (&.) Compare carefully the "dissected formula" for C 6 H 14 with the full graphic formula given a few lines above. 415 THE PARAFFINS. 319 414. Isoparaflms. Instead of making the substi- tutions at the end of the chain in forming the successive members, CH 3 may be substituted for the H connected with a carbon atom situated in the middle or at any point between the two extreme atoms of carbon. We may thus form a chain branching from the main chain. As the first and second members of the series are not susceptible of such forms, we take the third and fourth members for illustration. Isobutane, C 4 H 10 . H H H H C C C H. Isopentane, C 5 H 13 . H H H H Hi-C C-C H. H H H C H i 415. Mesoparaffins. In the normal paraffins, no carbon atom was linked with more than two other carbon atoms ; in the given examples of isoparaffins, we see that one of the carbon atoms is joined directly with three other atoms of carbon. The dissected formulas of the above examples may be written as follows : Isobutane, (CH 3 ) 2 = CH CH 3 ; Isopentane, (CH 3 ) 2 = CH CH 2 CH 3 . When two or more carbon atoms are directly connected with three other carbon atoms, isomeric bodies are formed which have been called mesoparaffins. Thus the mesoisomer of the sixth member may be represented as follows : (CH 3 ) 2 =CH-CH = 320 THE PARAFFINS. 416 416. Neoparaffms. The neoparaffins are hydro- carbons in which one or more carbon atoms are directly joined to four other carbon atoms. This form of isomers cannot occur in paraffins having fewer than five carbon atoms. Neopentane. CH 3 C H C C H 3. CH 3 417. Molecular Constitution. These isomeric forms increase in number very rapidly as the complexity of the paraffin molecule increases. There are three known isomers having the formula of C 5 H| 2 ; five, having the formula C 6 H I4 . There are nine possible forms of C 7 H| 6 , four of which are known. It has been calculated that for the hydrocarbon Cj 3 H 28 , there are 799 possible isomers. We thus have an idea of the manner in which the almost endless variety of carbon compounds arises. All of the above isomeric paraffins, so far as discovered, differ in their chemical and physical properties. We may learn from these and the previous study of chemistry that dif- ferent substances arise, first, from the combination of different atoms; as, H 2 0, NH 3 , N 2 0; secondly, from a change in the number of the same kind of atoms, as in N 2 0, NO, N0 2 , a change in the number of the atoms of 0, making an entire change in the nature of the sub- stances ; thirdly, as we have here seen, different substances arise from the rearrangement of the same atoms, without any change in the number of any kind. 418. The Chemical Relations of the Paraf- fins. The paraffins are all saturated compounds, having g 4l8 THE PARAFFINS. 321 no unsatisfied bonds ( 97). They, therefore, can form no compounds by uniting directly with other chemical substances. Compounds may be formed only by the removal of one or more atoms of hydrogen to make room for other elements which may enter into combination by substitution in exact measure for the hydrogen removed. CH 4 or C 2 H 6 , as they stand, cannot combine with other substances because they have no unsatisfied bonds with which to hold them. But, if deprived of one or more atoms of hydrogen, they become ( CH 3 )'; (=CH 2 )" or ( C 2 H 5 )'; (=:C 2 H 4 )", and acquire the power to re-enter into combination with the hydrogen they lost or its exact equivalent of some other element. They also acquire the power to replace hydrogen or its equivalent of other ele- ments in chemical compounds to the full value of the hydrogen which they have lost. CH 3 CI, CH 2 CI 2 , C 2 H 5 CI, and C 2 H 4 CI 2 , illustrate the principle in regard to their combining power. (a.) As monads, they can replace one atom of H in a molecule of H 2 O or in one of HN0 3 . Methyl Common Nitric Methyl Ethyl Alcohol. Alcohol. Acid. Nitrate. Nitrate. (6.) As dyads, they can replace two atoms of H'in two molecules of H 2 O or in two of HNO 3 . Water. (?) Glycol. Nitric Acid. . CH 8 ) . C 2 H 4 (N0 8 ) 8 * Methylenic Nitrate. Ethyiene Nitrate. CH 2 Q . C,H (N0 8 ) 2 l- (N0 2 ) 322 THE PARAFFINS. 419 419. Metallic Character of Hydrocarbon Radicals. It will be apparent from the examples given above, that the compound radicals formed by removing one or more atoms of hydrogen from any of the saturated hydrocarbons, behave very much as the metals do under the same chemical conditions. Like the metals, they form oxides, hydrates, chlorides, nitrates, sulphates, etc. Sodium chloride, NaCI. Sodium nitrate, NaN0 3 . Sodium sulphate, Na 2 S0 4 . Sodium hydrate, NaHO. Methyl chloride, CH 3 CI. Methyl nitrate, CH 3 N0 3 . Methyl sulphate, (CH 3 > 8 S0 4 . Methyl hydrate, CH 3 HO. Ethyl chloride, C 2 H 5 CI. Ethyl nitrate, C 2 H 5 N0 3 . Ethyl sulphate, (C 3 H 5 ) 2 S0 4 . Ethyl hydrate, C 2 H 5 HO. 4:20. Alcohols. The term alcohol is generally ap- plied to the characteristic product of the fermentation of sugar. But in chemistry, the term is applied to a large class of bodies whose formulas may be formed by replacing part of the hydrogen in one or more molecules of water by a hydrocarbon radical. Alcohols are, therefore, the hydrates of the hydrocarbon radicals. If the hydro- carbon radical be a monad, replacing one atom of hydrogen in a molecule of water, a monatomic alcohol is the result ; HHO, water; (C 2 H 5 )HO, common alcohol. If it be a dyad, it displaces two atoms of hydrogen from two con- densed molecules of water, giving a diatomic alcohol, e. g., C 2 H 4 H 2 2 or glycol. Triatomic alcohols are formed by a similar displacement of three hydrogen atoms from three water molecules by a trivalent hydrocarbon radical, e. g., C 3 H 5 3 , or glycerin. 4 22 THE PARAFFINS. 323 421. True and Pseudo Alcohols. The alco- hols may be arranged in three groups : the primary, the secondary, and the tertiary. The primary alcohols are often called true alcohols ; the secondary and tertiary are often called pseudo alcohols. (a.) These groups and sub-groups will be understood by a careful study of the following: Skeleton A. Normal Pentane Skeleton. (6) (7) ( 4 } _C_ or common ether. When the hydrocarbon radicals are different, the oxide is called a mixed ether ; as CH ) ^ 3 j- 0, or methyl ethyl oxide. (a.) A third class of " ethers " is sometimes given. They are more properly called hydrocarbon salts. They are formed by displacing the typical H in organic acids by some hydrocarbon. Many of these "compound ethers" have pleasant, fruity odors, and are used exten- sively as flavoring essences. The flavor of pineapple, strawberry, raspberry, pear, peach and apricot may be closely imitated by com- binations of two or more of these " ethers." The alcoholic solutions of small quantities of these " ethers " are called essences. Experiment 305. Mix 1 cu. cm. of alcohol with about the same quantity of butyric acid in a test tube. Pour a few drops of sul- phuric acid into this mixture. Heat gently and set aside for half an hour. The disagreeable odor of butyric acid is changed for the pleasant odor of the pineapple. 423. Acids. If from the hydrocarbon radical, C 2 H 5 , two atoms of hydrogen be displaced by oxygen ( 215, a.), we obtain acetyl, C 2 H 3 0, a radical which resembles the non-metallic elements in its chemical relations, forming acids with hydroxyl, e.g., C 2 H 3 0,HO, acetic acid. This acid may be represented by H HC C-OH. 425 THE PARAFFINS. 325 We here find the group CO, OH, or oxatyl. Taking com- mon alcohol, C 2 H 6 0, or H H H C C OH, or CH 3 CH 2 OH, H H we find that the OH is associated with CH 2 , giving the group CH 2 ,OH, which is a characteristic group in all true alcohols ( 421, a.) It is from the CH 2 of this group that the displacement of H 2 by takes place, giving the group CO, OH above mentioned. Tliis oxatyl group is characteristic of all organic 'acids. It is this part of the molecule which determines the basicity of the acid ( 164). If it contain one such group, the acid is monobasic; if two such groups, 2(CO,OH), it is a dibasic acid, etc. As the negative compound radical, acetyl, was formed from ethyl in the above example, so may negative acid radicals be formed from most hydrocarbon radicals. As acetic acid may be prepared from common alcohol by the dis- placement of H 2 from the CH 2 ,OH part of the alcohol, so may acids be formed from the alcohol of every hydrocarbon containing the group CH 2 ,OH, characteristic of primary or true alcohols. We see here the reason why acids are not derived from secondary and tertiary alcohols, which con- tain the groups CH,OH and C,OH, but hone from which H 2 may be displaced. 424. Marsh Gas. Review 207 and 208. 425. Petroleum. This natural production which, since 1860, has been so abundant in the markets of the world and has come into use in so many ways, is a 326 THE PARAFFINS. 425 mixture of the paraffin and ethylene series. It is doubt- ful whether any of the aromatic series is present in any of the petroleums with the possible exception of the Canada petroleum. The refining of petroleum yields four groups of products. The first four members of the marsh gas or paraffin e series ( 413, a) are in the gaseous state at ordinary temperatures. These are not reckoned in the above four groups, though they are probably held in solution in the petroleum in greater or less quantities. The four groups are as follows : (a.) NAPHTHA GROUP. This includes the lighter oils from pen- tane to nonane inclusive. Their boiling points range from 0C. to 120C. (or up to 170. Roscoe). (1.) Cymogene, a liquid at 0C., is the most volatile of the group. On account of its volatility, it has been used in the manufacture of artificial ice. (2). Rhigolene boils at 18C. (65P.), and has been used as an anaesthetic agent. The anaesthesia is local, and is produced by throwing a spray on the part which is frozen by evaporation of the liquid. See Elements of Philosophy, 526. (3.) Gasoline forms about 1.5 per cent, of the petroleum. It is extensively used as a fuel in stoves peculiarly constructed for this purpose. Its great volatility, or low boiling point, renders its use somewhat hazardous. (4.) Benzine is used as a substitute for turpentine in paints and varnishes, as a solvent for india-rubber, and for removing grease spots from clothing, for cleaning gloves, etc. A good article for this last purpose should leave no stain upon paper. (&.) ILLUMINATING OILS. These are sold as kerosene, paraffin oil, photogene, solar oil, etc., terms which, as yet, have no very definite meaning. The safety of these illuminating oils is determined by the flashing point, or the temperature at which they will give off an inflammable vapor. In most states, inspectors are appointed to see only such as bear the legal test, as to flashing point, are sold for illuminating purposes. The illuminating oils constitute about 55 per cent- of petroleum. 430 THE PARAFFINS. 327 (c.) LUBRICATING OILS. These are the heavier oils, and form about 20 per cent, of the petroleum. (d.) SOLID PARAFFINS. These amount to about 2 per cent, of the petroleum, and are used for candle making. Candle paraffin, a beautiful bluish-white, translucent, wax like substance, much used in making candles, probably consists, for the most part, of C 85 H 52 . 426. Methylic Alcohol. This alcohol, CH 3 ,OH, may be prepared synthetically from marsh gas, but is usually manufactured by the dry distillation of wood, beech-wood being generally used. It is also extensively obtained as a bye product in the manufacture of beet sugar. It has never been produced by fermentation. 427. Properties. Methylic alcohol is a mobile, colorless liquid, having a penetrating odor resembling that of common alcohol. Its taste is burning and nau- seous. It unites with water and alcohol in all propor- tions, burns with a feebly luminous flame, boils at about 55C., and has a specific gravity of 0.8. It is a solvent of many resinous matters. 428. Uses. On account of its solvent powers, it is used in the preparation of varnishes. It is used, instead of common alcohol, for heating purposes. It is now largely used in the manufacture of aniline colors. In Great Britain, common alcohol containing about 10 per cent, of methylic alcohol is sold, for mechanical purposes, free of duty. This mixture is called methylated spirits, and is unfit for use as a beverage. 429. Chloroform. Review 209. (a.) CHC1 3 is chloroform. CHBr 3 is bromoform. CHI 3 is iodoform. 430. Ethyl Alcohol. Review 210, 211, and 212. 328 THE PARAFFINS. 431 431. Absolute Alcohol. Water cannot be en- tirely separated from alcohol by distillation. This may be done .by placing some quicklime in a flask and pouring over it the strongest commercial alcohol and distilling by the aid of a water bath. The lime, by its affinity for water, takes the water from the alcohol, leaving the pure spirit to be distilled into the receiver. (.) Proof spirit contains 50.08 percent, of alcohol and 49.92 per certf. of water. (6.) Wine is the fermented juice of the grape or of other small fruits. Cider is the fermented juice of the apple. Perry is a similar liquor made from the pear. Gin is a spirit flavored by distilling alcohol with juniper berries. Rum is obtained from molasses. Whisky is distilled from wort prepared from the starch of corn, rye, or potatoes. Brandy is distilled wine. 432. Propylic Alcohol and Isopropylic Al- cohol. These two hydrates have the same empirical formula, C 3 H 8 0, but differ essentially in their properties, propylic alcohol, C 2 H 5 CH 2 OH, boiling at 97C., and isopropylic alcohol, (CH 3 ) 2 = CH OH, at 83C. These, and the alcohols of butane and pentane, are contained abundantly in the latter portions of the distillate obtained in rectifying spirits of wine and especially the spirits from potatoes, and constitute the so-called fusel oil, which may be described as a mixture of several homologous alcohols. (a.) Butane yields four alcohols having the formula C 4 H 10 O. That which has the rational formula, CH \cJV 3 OH' is found in fusel oil and is prepared from it. (&.) Pentane has yielded seven of the eight possible alcohols. The most common of these is amylic alcohol of fermentation, ^ 8 ^) 'CH 3 ) 2 CH 2 ,OH. It is a colorless liquid of an unpleasant odor, and is the chief constituent of fusel oil. It is very poisonous, and is often pres 433 lfSE PARAFFINS. 329 ent in many of the cheap spirits used for drinking. It has been dis- covered " that ethyl alcohol in ^ aqueous solution was not injurious to frogs, isopropylic alcohol killed after some hours, and propylic in a single hour, whilst the vapors of a similar solution of fusel oil were instantly fatal to them, and even when diluted to 500 times its bulk, that body exercised on them a poisonous influence." (c.) Fusel oil was formerly considered the hydrate of the fifth member of this series, C 5 H 11 HO, or pentyl (or amyl) alcohol. But recent analyses show it to have the composition above given. Any spirit that gives a milkiness when four or five times its volume of water is added may well be suspected of containing fusel oil. 433. Aldehydes. These are a class of unstable bodies having a strong affinity for oxygen. They have no special importance in the arts, but are interesting as being intermediate between the primary alcohols and the acids. We may regard them as resulting from the with- drawal of hydrogen from the alcohol, or more properly from the group CH 2 ,OH contained in the alcohol. How this withdrawal is accomplished is too obscure to be dis- cussed here. It will be seen that COM is formed by the withdrawal of H 2 from CH 2 ,OH. This is the charac- teristic group of every aldehyde, just asCH 2 ,OH is of every true alcohol, or CO, OH is of every acid. The fol- lowing are the generalized formulas for the alcohols, alde- hydes and acids. AlcoJiol. Aldehyde. Acid. C n H 2n+l ,OH ; C n H 2n _,0,H ; C n H 2n _,0,OH. (a.) Common aldehyde ( 215, .) tlie tJP 6 of ^ e whole clag s in properties and modes of formation, is a liquid with a pungent, ethereal odor and of so unstable a character that when sealed up in tubes it loses its identity by forming polymeric compounds of higher members of the series. Its most characteristic property, a property belonging to all aldehydes, is that of reducing silver from its salts, forming a brilliant film of silver on the sides of the containing vessel. 330 THE' PARAFFINS. 434 434. Chloral Hydrate. If the three atoms of hydrogen be displaced from the radical part of aldehyde, C 2 H 3 0,H, by chlorine atoms, a substance named chloral is formed. Chloral is a colorless, mobile liquid which unites with water to form chloral hydrate (C 2 Cl30,H H-H 2 0), a substance of great value in medicine. It is a crystalline solid with an agreeable aromatic odor and a bitter, astringent taste. It is used as an anodyne. The sleep produced by it is quiet and refreshing and unattended by any unpleasant symptoms. Fatal consequences have, however, attended its use by those who have taken it with- out a proper knowledge of its properties. 435. The Fatty Acids. There is an interesting class of volatile, fatty acids, resulting from the oxidation of the alcohols. They are formed in a great number of reactions and many of them are found in nature. Their composition is expressed by the general formula, C n H 2n 2 , each acid containing one more oxygen atom and two less hydrogen atoms than the corresponding alcohol. These acids are monobasic. We shall make special reference to the first two of the series and introduce the others in the following table taken from Wurtz : 436 THE PARAFFINS. 331 Name* of Add*. Empirical Formulas. Rational Formulas. Melting Points. Boiling Points. Formic CH 9 2 H CO,OH 1C 99C. Acetic C*H 4 O a CH 3 CO,OH 17C 118C. Propionic ... . C,H fi O, C 2 H 5 CO,OH 21 C 140.7C. Butyric C,H 8 2 C 3 H 7 CO,OH 0C. 163C. Valeric .. C-H lo Oo C 4 H 9 CO,OH 175C. Caproic C,H ia 2 CB^ CO,OH 5C. 199.7C. CEnanthylic Caprylic C 7 H 14 8 C 8 H 16 O 2 C 6 H 13 CO,OH C 7 H 16 CO.OH 140. 212C. 236C. Pelargonic C 9 H 18 2 C 8 H 17 CO,OH 18C.(?) 260C. Capric CjoHooO* C 9 H 19 CO,OH 27.2C. Laurie C 10 H 24 0, CnH 23 CO,OH 43.6C. Myristic C 14 H 28 O 2 C 13 H 27 CO,OH 53 8C. Palmitic C 1R H, a O 2 C-.H,, CO,OH 62C Mar r aric C, w Ho.Oo C 1R H,o CO OH 60C Stearic C 18 H 36 2 C 17 H 35 CO,OH 692C Arach nic C 9ft H, ft O. C 19 H 39 CO OH 75C Benic CooH, . C 5 H 10 (OH) 3 ( Pentene ) ( pentylglycol, ) Hexylene u or hexylglycol, . . . C 6 H 12 (OH) 2 Octylehe " or octylglycol, .... C 8 H 16 (OH) 2 The glycols yield diatomic acids by oxidation. The iso- merism of the glycols, like that of the mon atomic alcohols, is due to their molecular constitution. See 421 (a). We, therefore, have three classes of glycols, characterized re- spectively by groups already familiar, as follows : Primary, CH 2 ,OH. Secondary, CH,OH. Tertiary, C,OH. Ordinary glycol is a syrupy liquid, colorless, odorless, and of a sweetish taste. It mixes with water and common alcohol in all proportions. It is easily oxidized and forms two acids. 457. Grlycolic Acid. If glycol be gently oxidized, two atoms of hydrogen are removed and one atom of oxygen is substituted in their place. Glycol. Olycolic Acid. CH 2 -OH CO OH | + 2 = | +H 2 CH 2 -OH CH 2 OH Glycolic acid is monobasic, having the group COOH but once represented. Its molecule also has the group CH 2 OH, 460 THE OLEFINES. 345 which is characteristic of the alcohols. It has, therefore, a double character, that of an alcohol and that of an acid. 458. Oxalic Acid. If glycol be more completely oxidized, as may be done by using strong nitric acid, the well known substance, oxalic acid, H 2 C 2 4 , will be pro- duced. Glycol. OxaMcAcid. CH 2 OH CO OH + 20 2 = I CH 2 OH CO OH O O Oxalic acid (HO C C OH) is dibasic, forming two series of salts, neutral and 'acid oxalates. It is widely distributed in nature, its calcium and potassium salts being found in many plants, such as rhubarb, wood-sorrel, and common dock. It is not known to occur free in nature and can be obtained in its free state only by arti- ficial means. 459. Preparation. Oxalic acid may be prepared on a small scale by the action of eight parts of nitric acid upon one part of white granulated sugar. Starch may be substituted for the sugar. Heat the mixture gently. On a large scale, oxalic acid is obtained by heating saw- dust or wood-shavings with a mixture of caustic potash and soda. When the mass has completely fused, the cellulose of the wood will have entered into combination with the" sodium and potassium, forming sodium and potassium oxalates, from which the oxalic acid may be obtained. 460. Properties. Oxalic acid forms in large trans- parent crystals, with two molecules of water of crystalliza- 346 THE OLEFINES. 460 tion ; C2H 2 04H-2H 2 0. When exposed to a dry air or to a temperature of 100 0., the crystals lose this water and crumble to a fine powder. The acid is soluble in eight times its weight of water at ordinary temperatures, or in its own weight of boiling water. It is also very soluble in alcohol. It is intensely sour and very poisonous, doses of from eight to twenty grams often proving fatal. If heated, it melts in its water of crystallization ; if the heat be gradually increased, the anhydrous acid may be entirely sublimated without decomposition. When acted upon by sulphuric acid, a molecule of water is removed, leaving CO and C0 2 to pass off as gases. (Experiment 182.) Oxalic acid, therefore, seems to be composed of carbon monoxide and carbon dioxide linked together by water. 461. Uses. Oxalic acid is used to remove ink stains and iron moulds from clothes, and to cleanse brass and other tarnished metals. It is extensively used in dyeing and in calico printing. 462. Antidotes. In case of poisoning by oxalic acid, the proper antidotes are chalk or magnesia. If these be not at hand, the scrapings of whitewash from the ceiling should be used. The acid forms harmless insolu- ble salts with calcium and magnesium. 463. Propylene and Propyl Glycols. The second member of this series may be formed by replacing one atom of H in ethylene by H H C H, giving propylene, H C=C C H. i H H H 464 THE OLEFINES. 347 In forming alcohols from this by adding (H0) 2 , as explained in 455, it will be seen that there are two possible propyl glycols; H H H H H H HO C C C OH and HO C C C H, Hi UA in which one hydroxyl group may be placed at each end of the chain, or one at the end and the other in the mid- dle. This gives two isomers, the first of which boils at 100C. and the other at 86C. 464. Derivatives of the Propyl Glycols. By oxidation of the propyl glycols, four isomeric, mono- basic acids, known to science, may be formed. The two best known are formed from the second or isopropyl glycol, both having the same structural formula CH 3 ,CH(OH),CO,OH. They are known as lactic acid of fermentation and paralac- tic or sarcolactic acid. The first is the product of the fer- mentation of milk and some other substances. It is found in sour milk and sauerkraut. The second is found in the muscles of animals and forms a large part of the extracts of meat, beef teas, etc., so much in use at present. These acids are physical isomers with no discoverable differences in the formulas representing them. They differ especially in their behavior towards polarized light, ordinary lactic acid being inactive, while sarcolactic acid turns the plane of polarized light to the right. Differences are also shown in their salts, ordinary zinc lactate crystallizing with three molecules of water and zinc sarcolactate with two mole- cules, the latter being also more soluble than the former. 348 THE OLEFI1MS. 465 465. Glycerin. This well-known substance, C 3 H 5 (OH) 3 , is closely connected with propyl glycol, and is naturally considered in this place. 466. Preparation. Glycerin is a bye-product of soap making and of the manufacture of stearic acid, used for stearin candles. It is produced in small quantities in the fermentation of sugar, nearly three per cent, of the products being glycerin. 467. Properties. Glycerin is a triatomic alcohol. It is a liquid of a syrupy consistence, very sweet, without odor or color. It is non-volatile under ordinary conditions, and cannot be distilled without decomposition except in a vacuum or in an atmosphere of steam. It solidifies at 40C., and may be obtained in fine crystalline masses. It is soluble in water and alcohol in all proportions, but is scarcely dissolved in ether. It absorbs moisture from the atmosphere and ranks next to water as a solvent. 468. Uses. Glycerin is used in the manufacture oi nitroglycerin. On account of its oily and non- volatile properties, it is used as a lubricant for watch and clock work and in the regulating apparatus of electric arc lamps. The same properties make it useful as an application to the skin to keep it soft and pliable and prevent chapping. It is used to extract the perfume from flowers and other parts of plants, and has been suggested as a substitute for cod-liver oil. 469. Nitroglycerin. If glycerin be acted upon by dilute nitric acid, it is oxidized, forming glyceric acid, C 3 H 6 4 or CH 2 (OH) CH(OH)-COOH. But if it be acted upon by equal volumes of strong nitric and sul- 472 THE OLEFINES. 349 phuric acid, glyceryl nitrate or nitroglycerin, C 3 H 5 (N0 3 )3, will be formed. Three Molecules TrinUro- Three Molecule* Wycenn. of Nitric Acid. glycerin. of Water. 470. Properties. Nitroglycerin is a yellowish, oily liquid ; when pure, it closely resembles common glycerin. It is one of the most violent explosives known. Its violence is not due to the application of heat, for it is said to burn quietly when kindled in a quiet way, and that the flame of a burning match may be quenched in it It is not nearly so combustible as gunpowder. It must be started with a shock. It woujd seem that a certain number of vibrations must be given in order to secure the most ener- getic decomposition of this substance. A more or a less energetic rate of vibration does not answer the purpose. Just as a certain musical note may cause a pane of glass to fly into pieces, while sounds of different pitch, although they may be louder, are unable to produce any discernible effect, so a certain rate of vibration is here necessary to break the bonds of chemical union, to destroy the existing molecule and permit a re-arrangement of its constituent atoms. 471. Dynamite. Nitroglycerin, being in a liquid form, is not easily handled. To remedy this, a siliceous clay, or other inert substance is used as a sponge to absorb about 75 per cent, of nitroglycerin. In this form it is known and used under the name of dynamite. It is a substitute for the liquid glycerin. 472. Blasting Gelatine. Nitroglycerin dissolves the collodion variety of gun-cotton, forming a semi-solid 350 THE OLEFINES. 472 gelatinous mass. In this form,, the nitroglycerin has all the convenience for handling that dynamite has, with the advantage of containing no inert substance. 473. Uses. Nitroglycerin in its various forms is used for blasting. On account of its sudden, violent explosion, it does not need to be confined in chambers by tamping, as does gunpowder. In order to break a granite rock into pieces, it is only necessary to explode a can of nitro- glycerin while resting upon the rock. Its suddenness in explosion renders it unfit for gunnery, the metal of the gun giving way before the force has time to overcome the inertia of the ball. The greater suddenness of explosion over that of gunpowder is due to tbe fact that the combus- tible materials, carbon and hydrogen, are caged up in the same molecule with oxygen, the supporter of combustion. In the case of gunpowder, the combining elements have to come from different molecules, requiring greater time for the journeying. The sudden transformation of a liquid or solid to the gaseous state with the consequent enormous increase of volume, causes the explosion. 474. Tartaric Acid. Tartaric acid, H 2 C 4 H 4 6 , is found in combination with potassium in the juices of the grape, tamarind, and other fruits. The potassium salt is not very soluble in the juice, and still less so in spirituous liquors ; hence, in the progress of fermentation it is deposited in the wine casks as a solid crust. This deposit is known as tartar, or argol, which, when purified, is cream of tartar. It has the composition, HKC 4 H 4 6 . 475. Preparation. Tartaric acid is prepared by boiling the crude argol with powdered chalk. Insoluble 478 THE OLE FINES. 351 calcium tartrate and soluble neutral potassium tartrate are produced in the reaction. The potassium tartrate is changed to calcium tartrate by the addition of calcium chloride. All the tartaric acid is now in combination with calcium, from which it may be set free with sul- phuric acid. The acid precipitates the calcium as insolu- ble calcium sulphate ; this is separated by filtration from the acid in solution. The tartaric acid is then obtained in large anhydrous crystals by evaporation. 476. Properties. Tartaric acid is dibasic and, hence, produces two series of salts, neutral and acid tar- trates. It is a crystalline solid, unaltered in air, soluble in half its weight of cold water and more largely soluble in hot water. It is also soluble in alcohol. There are four isomeric varieties of tartaric acid. 477. Uses. Tartaric acid is the most important of the vegetable acids. It is largely used in dyeing and in calico printing. It is also used with sodium dicarbonate to form baking powder. The reaction of the two sub- stances produces carbon dioxide which, escaping in the dough, renders the bread light ( 229). 478. Tartrates. Cream of tartar, HKC 4 H 4 6 , is used in medicine and in bread-making. Neutral potas- sium tartrate, K 2 C 4 H 4 6 ; Rochelle salts, NaKC 4 H 4 6 ; and tartar emetic, K(SbO)C 4 H 4 6 , are other useful salts of tartaric acid. 352 THE OLEFINES. 478 EXERCISES. 1. (a.) Write the symbols of the first five normal members of the ethylene series. (6.) Give their primary alcohols and the acids derived from them. 2. Write the graphic symbols of the possible alcohols of C 4 H 8 . 3. Write symbols showing the conversion of the alcohols just given to their possible acids. 4. Symbolize the oxalates., the lactates and the tartrates of Ca, Fe, Zn, K, and Na. 5. How many grams of tartaric acid must be mixed with 10 grams of HNaC0 3 to form a good baking powder ? 6. (a.) What is the percentage composition of C 2 H 4 ? (6.) Of C 3 H 6 ? (c.) Of oxalic acid? 7. How many liters of CO and of C0 2 may be obtained from 60 grams of H 8 C 2 4 by the action of H 8 SO 4 ? 8. Which members of the olefine series have vapor densities of 84 m. c. and 112 m. c. respectively ? 9. A hydrocarbon has 85.71 per cent, of C and 14.28 of H in its composition ; its vapor has a density of 70 m. c. What is its formula ? 479 THE U EX ZEN E OR AROMATIC SERIES. 353 HI. THE BENZENE OR AROMATIC SERIES. General Formula, C n H 2n _. 479. The Benzene or Aromatic Series* The aromatic series is so called because it contains the essential oils or essences. It might, perhaps, with more propriety be called the chromatic series, because it in- cludes that wonderful and almost endless series of colors known as the aniline colors. *Each member of this series contains at least six carbon atoms, linked in such a way that six of their twenty-four combining units are left unsaturated. In the previous series the carbon atoms were represented as united so as to form an open chain. In this series they form a closed chain, in which each carbon atom is linked to the adjoining carbon atoms, by one bond on one side and by two bonds on the other side. The following will illustrate : Paraffin series; sixth member. H H H H H H H-C-C-C-C-C-C-H nun Ethylene series; fifth member. h H H H H H I I I I I ! C= C C C C C H 354 THE BENZENE OR AROMATIC SERIES. 479 Aromatic series ; first member. H H-cA-H "V- If we examine these examples, each of which contains six atoms of carbon to the molecule, we see a striking dif- ference in the quantity of hydrogen, the aromatic hydro- carbon having not more than half as much as the others. This has a marked effect on the appearance of their flames. The former two, being rich in hydrogen, burn with feeble illumination, while the latter burns with a brilliant flame, and generally with much smoke. 48O. Isomeric Formations. This series presents as great a variety of isomers as is found in previous series. Compounds are formed by displacing hydrogen by other ele- ments or radicals. Thus, the hydrogen, as in previous formulas, may be replaced by chlorine or bromine. Isomer- ism, caused by placing a single substituted element or group at different points of the chain or nucleus, does not occur in this series. The principal cause of isomerism in the aromatic series is the relative position of the hydrogen displaced when two or more sub- C(6) (2)C stitutions are made. In the figure, carbon C(5) (3)C atoms are supposed to be at the points 1, 2, M? 3, 4, 5, and 6, each with one un saturated I bond or with one atom of hydrogen. The group, CH 3 , may be substituted for H at 1 and 2, at 1 TIIK It K. \ZENE OR AROMATIC SERIES. 355 and 3, or at 1 and 4, giving three isomers. Isomers formed by substitutions at 1 and 2 are designated by the prefix ortho- ; those by substitutions at 1 and 3, by the prefix meta- ; those by substitutions at 1 and 4 by the prefix para-. H CH \H "ylene. Metaxykne. Parazylene. ( CH 3 CH 3 i i /\ /X 3-CH 3 HC CH 1 II HC CH ; HC C-CH 3 H \x CH 1 CH X C-CH 3 In the same manner, the alcohol group, CH 2 ,OH, the aldehyde group, CO,H, and the acid group, CO, OH, may be substituted at 1 and 2, 1 and 3, or at 1 and 4, forming, in each case, a different isomeric alcohol, aldehyde, or acid. Isomeric bodies may be formed also by using dif- ferent substituting elements or radicals. 481. Value of Structural Formulas. It must not be supposed that this exists only in the fancy of the chemist. He will not claim that the atoms are certainly grouped in chains and hexagons, and the like, but that such representations best explain to ou^ minds all the known facts and phenomena of chemistry in regard to them. In the study of inorganic chemistry, he sees that sulphuric acid, when acted upon by zinc, gives H 2 ; when acted upon by copper, S0 2 is produced ; and finally, that when he heats sulphuric acid, 2 is yielded. He there- fore has good reason to assume that H 2 =02 = S0 2 * s a 35 G THE BENZENE OR AROMATIC SERIES. 481 formula that fairly represents the molecular constitution of sulphuric acid, showing the joints, the weak links, that may easily be ruptured under the influence of proper decomposing agents. The chemist studies the molecular. constitution of sub- stances by building up as well as by tearing down, by synthesis as well as by analysis. These strange symbols do more than to help him to explain what he has learned about the substances which they represent; they have been to him an aid in his researches in the realm of un- known truth and, in some cases, have enabled him to foretell the existence or possibility of compounds pre- viously unthought of but subsequently discovered or pro- duced. 482. Benzene or Benzol. This compound, C 6 H 6 , must not be mistaken for benzine, a very different substance mentioned in 425 (a.). They are, however, alike in many respects. Both are used for removing grease-spots from clothes ; both are used for varnishes and as solvents of gums, resins and india rubber. Both bear, in pronunciation, at least, the same name, and each is often sold in commerce without discrimination from the other. Still, they are different in their origin. Benzine comes from petroleum, benzol from the destructive distilla- tion of wood or coal. Benzine remains liquid at or near the freezing point of water ; benzol becomes solid at 0C. Benzine cannot be used to produce the aniline colors ; benzol is so used. Benzol is a colorless liquid, with a peculiar aromatic odor, is very inflammable, burning with a white smoky flame, is nearly insoluble in water but dissolves freely in 485 THE BENZENE OR AROMATIC SERIES. 357 alcohol. It is an excellent solvent for iodine, sulphur, phosphorus, fats, resins and india rubber. The benzol of commerce is not pure, being generally a mixture of benzol with others of this series. The structural formula was given in 479. 483. Uses. The properties of benzol indicate some of its uses in the arts, as in the manufacture of varnishes, cements, etc. Its vapor, present in coal gas, adds greatly to the illuminating power of the latter. Experiment 306. Modify Experiment 26, by using a bottle having two jets instead of one. Into the lower part of one of the delivery tubes, place a small tuft of loose cotton saturated with benzol. When both jets are lighted, the flame of the pure H will be nearly non-luminous, while the flame of the mixture of H and the vapor of C 6 H 6 will give a brilliant white light. The apparatus appears to deliver two different gases from the same source. 484. Phenol. Phenol or carbolic acid, C 6 H 5 ,OH, is obtained from coal tar ( 221, c.) by distillation. The distillate yielded at a temperature of 160C. 200C. is redistilled with a solution of sodium hydrate. From the sodium compound thus formed, carbolic acid is separated by hydrochloric acid. 485. Properties. Pure carbolic acid occurs in long, needle-shaped, colorless crystals. It possesses a peculiar odor, an acrid, burning taste, causing white blisters on the tongue ; is slightly soluble in water and soluble in all proportions in alcohol, ether and glycerin. It resembles creosote, a wood-tar product for which it is frequently mistaken. It is the hydrate of a hydrocarbon radical, phenyl (C 6 H 5 ), and, consequently, an alcohol. It is not a true alcohol, for it produces neither aldehydes nor acids. It has the character of an acid for, although it does not 358 THE BENZENE OR AROMATIC SERIES. g 485 redden blue litmus paper, it is capable of neutralizing the alkaline bases. It is a powerful antiseptic and disinfectant. 486. Uses. No agent of modern discovery has been more efficient in the hands of the sanitarian in contending with contagious diseases than has carbolic acid. When small-pox, typhoid fever, cholera, etc., have prevailed, it has proved a powerful agent in preventing their spread. It is used in surgery for cleansing wounds and for pre- venting the fatal effects of blood-poisoning. 487. Nitrobenzene. When benzene is acted upon by nitric acid, it gives up one atom of hydrogen and unites with the group N0 2 , forming nitrobenzene. C 6 H 6 + HN0 3 =C 6 H 5 (N0 2 ) + H 2 0. Nitrobenzene is generally of a brown color, but when pure it is a colorless liquid, having a burning sweet taste, and the odor of oil of bitter almond. Hence, it is called the "essence of mMane." It is extensively used for per- fuming soaps. It is also used in the manufacture of aniline. It is very poisonous. When benzene is cautiously dropped into a mixture of concentrated nitric and sulphuric acids, dinitrobenzene is produced. This is a solid, forming in long rhombic prisms. It enters into the composition of the essence of mirbane. Experiment 307. In a flask, place a little concentrated HNO 3 . Drop C 6 H 6 cautiously into the HN0 3 . A violent action takes place and the acid acquires a deep red color. Nitrobenzene is formed and held in solution in the strong acid. If it bo then poured into a large vessel of water, the nitrobenzene will be precipitated as a heavy yellow liquid having the strong odor of the oil of bitter almonds. 488. Aniline. Aniline, C 6 H 5 NH 2 , is derived from nitrobenzene by means of reducing agents which remove 4^9 THE BENZENE OR AROMATIC SERIES. 359 the oxygen from the group N0 2 . This 2 is replaced by H 2 , which would seem to show that 2 is equivalent to H 2 . It must, however, be considered that nitrogen be- haves as a pentad toward oxygen, while it never does so toward hydrogen. The group, N'"H 2 is equal, in com- bining power, to N V 2 . C 6 H 5 ,(N0 2 )+3H 2 =C 6 H 5 NH 2 + 2H 2 0. C 6 H 5 ,(N0 2 ) + 3H 2 S=C 6 H 5 NH 2 -f2H 2 + S. In the first reaction, the hydrogen is supplied by zinc and hydrochloric acid, or by iron and acetic acid. Aniline may be looked upon as ammonia with one atom of hydrogen replaced by the radical phenyl. N. 489. Properties. Like ammonia, aniline has strong basic properties, and, with acids, forms salts resembling those of ammonia ; unlike ammonia, it does not change red litmus to blue. It is an oily, colorless liquid, but when exposed to the air it absorbs oxygen and assumes a brown color. It has a somewhat pleasant, vinous odor and a hot, acrid taste. It is highly poisonous, but this is supposed to be due to its change in the stomach to nitro- benzene. It is almost insoluble in water but is soluble i in alcohol, ether and carbon disulphide. Experiment 308. Place a small quantity of aniline in a test tube, add some nitrate (e. g., KN0 3 ). Pour in, carefully, H 2 S0 4 . A red color will be produced. Experiment 309. If a few drops of C 6 H.NH 2 be poured into an excess of H 2 S0 4 , and a small quantity of potassium dichromate be added, a beautiful blue will be developed which will change to violet on adding H 2 O. This color will soon disappear. 360 THE BENZENE OR AROMATIC SERIES. 4QO Experiment 310. Whan a solution of chloride of lime (bleaching powder) is added to an aqueous solution of C 6 H 5 NH.>, a beautiful violet tint will be produced, which will change after some time to a dirty red. 49O. Uses. The aniline of commerce is not pure. Pure aniline will not yield the variety of products which go under the name of aniline colors. It must be mixed with some of its homologues before these colors can be obtained. All colors and all shades and tints of colors may be produced from this substance, whose parentage is the black, unpleasant smelling coal tar, so often an4 so long rejected and wasted by the gas manufacturers. 10 491. Substances Derived from Coal Tar. Figure 123 represents a block of coal and the relative volumes of the products obtained therefrom. 1, is the 495 THE BENZENE OR AROMATIC SERIES. 361 coal block; 2, tar; 3, light oil; 4, heavy oil; 5, anthra- cene oil ; 6, benzene ; 7, toluene ; 8, phenol ; 9, naphtha- line ; 10, anthracene. 492. Picric Acid. Picric acid or trinitrophenol, > is the result of the action of nitric acid upon carbolic acid. It may also be obtained by the action of nitric acid upon indigo. 493. Properties. Picric acid crystallizes in bril- liant, pale yellow prisms and plates. It is intensely bitter to the taste, dissolves with difficulty in cold water but more freely in hot water, -in alcohol, and in ether. Although it has not the constitution of an acid, it be- haves like an acid toward the metallic compounds, form- ing compounds called picrates. Potassium picrate is ex- plosive and is used in preparing explosive mixtures. Experiment 311. Dissolve some picric acid in hot water. Im- merse in it a piece of white silk. It will be colored a pure yellow, which cannot be washed out. Experiment 312, Make a hot solution of one part of picric acid to nine parts of water ; add this slowly to a warm solution of one part of potassium cyanide to four of water. A blood-red color will be produced. Upon cooling, brownish-red crystals of a greenish me- tallic luster will be precipitated. 494. Uses. Picric acid is used in dyeing wool, silk, and hair, to which it imparts a beautiful, permanent yellow. 495. Toluene or Toluol. No isomeric com- pounds can be formed from benzene by single substitu- tions, because the effect of making the substitution at any one part of the hexagon would be the same as that of making it at any other part. This direct result of the 362 THE BENZENE OR AROMATIC SERIES. 495 symmetrical nature of the molecule may be better under- stood by reference to the structural symbol for benzene ( 479). But in toluene or toluol, C 7 H 8 , or C 6 H 5 CH 3 , CH 3 (i) HC' CH (2) (3) (4) owing to the unsymmetrical nature of the molecule, a substitution having already been made at (1), single sub- stitutions may give different results, yielding isomers. If the group N0 2 be substituted at (2), (3) or (4), three isomeric nitro-toluenes will be formed, known respectively as ortho-, meta-, and para-nitrotoluenes. 496. Cresols. Just as we form phenol from ben- zene by the substitution of OH for any atom of H in the molecule, so we may form cresols from toluene by the substitution of OH for the H of any CH group. Three cresols may be formed by substituting OH at (2), (3) or (4) respectively. They are isomeric with benzoic alcohol ( 500). The one formed by substituting OH at (4) is found in coal tar. 497. Toluidiiie. In like manner, three toluidines, C 7 H 9 N, or H 2 N C 6 H 4 CH 3 , are formed from toluene by single substitutions of NH 2 at (2), (3) or (4). The tolu- idines are important, because, in connection with aniline, they form the base which gives rise to the vast array of aniline colors. THE BENZEXE OR AROMATIC SERIES. 363 498. Rosaiiiliiie. If one molecule of aniline and two molecules of toluidine are soldered together, we have rosaniline, the various salts of which form all the beauti- ful reds, violets, blues and greens of the aniline dyes. This soldering is accomplished by withdrawing six atoms of hydrogen, by oxidation, from the three molecules, two from each. This gives them the power to unite with each other by their unsaturated bonds. The following diagram attempts to represent this soldering process. The with- drawal of hydrogen by oxidation is shown by arrows. After such withdrawal, each group has one bond not engaged. Thus the first molecule (toluidine) is linked to the second (aniline) ; the second (aniline) to the third (toluidine) and the first to the third, thus forming one consolidated molecule of rosaniline. Aniline, Toluidine. Oxygen. Rosaniline. Water. C 6 H 5 NH 2 + 2C 6 H 4 NH 2 CH 3 + 3 = C 20 H I9 N 3 + 3H 2 0. Phis oxidation may be brought about by various agents, but the one most commonly used is arsenic acid, which very readily gives up its oxygen. (a.) We have considered aniline as an ammonia derivative in which the phenyl group, C 6 H 5 ,has replaced one atom of H in NH 3 . Simi- larly, rosaniline may be considered as a group of three molecules 364 THE BENZENE OR AROMATIC SERIES. 498 of NH 3 , in each one of which two hydrocarbon groups have re- placed two atoms of H. That this is so may be seen by a careful study of the diagram above. (6.) When NH 3 is acted upon by HCI, a compound is formed which may be called ammonium hydrochlorate, and may be symbolized as NH 3 HCI ( 287). When NH 3 is acted upon by C 8 H 4 2 , ammonium acetate (NH 3 HC 2 H 3 2 ) is formed. In both of these cases, the new compound is formed by adding the acid to the ammonia with no loss of hydrogen. The explanation of this is to be found in the fact that N changes its apparent quantivalence ; e. g., ( H fH H N i H and N 4 H . LH lc H , Similarly, when rosaniline is acted upon by HCI, the acid is simply added and the salt called rosaniline hydrochlorate. This is the formula for a very common red dye which is sold under the various names of aniline red, magenta, rosaniline and fuchsine. This well- known salt is insoluble in water but is soluble in alcohol. Viewed by reflected light, it has a bright metallic beetle-green color, but appears a brilliant red by transmitted light. Rosaniline acetate is a red dye soluble in water. Experiment 313. Flow an alcoholic solution of aniline red over a piece of glass. When the glass is dry, hold it between the eye and the light. Thus viewed by transmitted light, it appears to be of a rich, red color. Then hold it so that it will be seen by the light which it reflects to the eye and it will appear to be of a rich golden green. 499. Aniline Violets, Greens and Blues. If one, two, or three of the hydrogen atoms connected with nitrogen in rosaniline be replaced by a corresponding number of the phenyl group, C 6 H 5 , mono-, di-, or tri- phenyl rosaniline bases are formed, the salts of which vary in shade according to the number of substitutions made. These hydrochlorates vary in color from reddish violet or bluish violet to deep blue as the number of the phenyl groups increases. The triphenyl salt is known as night bine; it retains its blue appearance even when seen by gas-light. 500 THE BENZENE OR AROMATIC SERIES. 365 In the same manner, ethyl rosanilines are formed serv- ing as bases for Hofmann's violets. The shades vary from red to blue, or very blue violet, according as monoethyl, diethyl, or triethyl rosaniline is used. Triethyl rosaniline gives a very blue shade of violet. These violets are usually marked R, B, or B B, to denote the increasing shade of blue. They are extensively used in preparing inks. Nicholson's blue, which is a common dye having a very complex composition, is the salt of an acid formed with triphenyl rosaniline and sulphuric acid and sodium as a base. Iodine green, methyl green, and aldehyde green are the most common and useful gre"ens. They have very com- plex formulas, rosaniline being the principal part. Aurin, C| 9 H|,(OH) 3 , resembling in its constitution para-rosaniline, C|9H|,(NH 2 ) 3 , is used in dyeing under the name of coral- line-red. It gives to wool or silk a fine orange color. Eosin (from eos, aurora) is used extensively in preparing a red ink. Two varieties are met with. One occurs as a brown, crystalline powder dissolving in water, giving a beautiful red-colored solution by transmitted, and a splen- did greenish fluorescence with reflected light. It gives to silk a delicate pink with a rich scarlet fluorescence. The other variety of eosin resembles the one just described, but differs in being a red powder, and in giving almost no fluorescence when in solution. 5OO. Benzyl Compounds. In the compounds just considered, the replacements were made in the CH group. In the benzyl compounds, the replacements are made in the CH 3 group. They have been named the aromatic group. Ben zoic alcohol is formed by substi- 366 THE BENZENE OR AROMATIC SERIES. 500 tuting OH for H in the CH 3 of toluene, giving the group CH 2 ,OH. This group is characteristic of a primary alco- hol, and is capable of giving, by oxida- Benzoic alcohol. tion, an aldehyde or an acid. Benzoic CH 2 ,OH alcohol, C 6 H 5 CH 2 ,OH, is a liquid of a Q pleasant aromatic odor. It is isomeric // \ with cresol. It is found in certain bal- HC CH sams, and is prepared from the essential HC CH oil of bitter almonds. Benzoic alde- ^^. / hyde, C 6 H 5 CO,H, is found free, mixed with hydrocyanic acid, in the essential oil of bitter almonds. Benzoic acid, C 6 H 5 CO,OH, occurs in gum benzoin and also in the bark and leaves of the aspen, a species of poplar. It occurs in large, thin bril- liant needles and plates. Experiment 313. Place a piece of gam benzoin upon a hot iron plate. Cover it with an inverted paper funnel. The vapor of ben- zoic acid will be condensed upon the paper, where it will be found forming a beautiful frostwork of feathery crystals having the fra- grance of the gum. 5O1. Salicylic Aldehyde and Acid. These differ in composition from benzoic aldehyde and acid only in having OH replacing H in the CH group (2). They are found in nature, existing in meadow-sweet, a species of spirea, and more abundantly in winter-green (gaulilieria procumbens), known also as checkerberry and as mountain- tea. The oil of winter-green is methyl salicylicate. The symbol for salicylic aldehyde is C 6 Salicylic acid, C 6 H 4 ) (*)/ substitution be made at a point adjacent to a carbon atom that is common to both chains, as at 1, 3, 6, or 8, the compounds thus formed will be identical. If, however, the substitution be made at a point not adjacent to the carbon atom thus common, as at 4, 5, 9 or 10, the compounds thus formed will be 368 THE BENZENE OR AROMATIC SERIES. 503 also identical with each other. But any one of the former class will be different from any one of the latter class. If there are two substitutions of the same element or group, there may be ten isomeric bodies having the same formula. Thus, when chlorine is twice substituted, there may be as many as ten different substances having the formula, C| H 6 CI 2 ? eight of which have been described. Three substitutions give fourteen possible and six known isomers, having the composition, C| H 5 C1 3 . Naphthalene is that portion of coal tar which distills over between 180C. aud 220C. It is a solid, crystallizing in white pearly plates. It has a peculiar odor and pungent taste, is insoluble in water, sparely soluble in cold alcohol, ether or benzene but more freely so in these liquids when they are : hot. It burns with a highly luminous, smoky flame. It is important on account of the beautiful yellow dye, naphthalene yellow, which is produced from its dinitro- compounds, C 5O4. Anthracene. The constitution of this body, C, 4 H, , is represented by the accompanying struc- H c tural formula. It is a \ I / ^s solid, crystallizing in I |j / | V j white, silky scales, with HC C C C CH a beautiful, blue fluores- X / I \ / cence. It is that portion i i of coal tar which distills H H over between 320 C. and 360 C. It is very impor- tant, being the starting-point in the manufacture of alizarin. g 507 THE BENZENE OR AROMATIC SERIES. 369 505. Alizarin. Alizarin, C, 4 H 6 (OH) 2 2 , is the coloring principle found in madder-root, and has long been one of the principal red dyes used in calico-printing. Its preparation from a coal-tar product is one of the most noteworthy triumphs of modern chemistry. A German chemist obtained anthracene from the extract of madder-root by the reducing power of zinc dust. Naphtha- lene had already been prepared from a coloring matter having a constitution similar to the extract of madder. He, therefore, inferred that the coloring matter of mad- der could be derived from anthracene by a process similar to that already known by which naphthalene could be reverted to the coloring matter from which it had been prepared. When the process was tried alizarin was pro- duced, as was anticipated. Alizarin is now prepared on a large scale, and is used in producing colors fully equal to those obtained from madder. 506. Indigo. Indigo, C, 6 H, N 2 2 , is derived from several species of plants. It does not exist ready made in plants, but is the result of the fermentation which takes place when the plants are macerated in water. Indican, the natural substance in the plants, is broken up by the fermentation into indigo and a variety of glucose. The indigo separates as a blue powder. Commercial indigo is not pure, containing from 50 to 90 per cent, of pure indigo. The best indigo assumes a coppery lustre when rubbed with a hard body. 507. Properties. Indigo is without taste or odor, insoluble in water, alcohol, or -ether, but dissolves readily in fuming sulphuric acid ( 156). It is also soluble in aniline, benzene and chloroform. With sulphuric acid, 370 THE BENZENE OR AROMATIC SERIES. 507 it forms a deep blue liquid containing two acids, sulphin- digotic acid, formerly used for giving wool or silk a Saxon blue, being one of them. When indigo is exposed to oxidizing agents in the presence of alkalies, it absorbs hydrogen and becomes white indigo, C| 6 H, 2 N 2 02. This is soluble in alkaline and earthy alkaline solutions and, when exposed to the air, reoxidizes and reverts to the original blue indigo. Advantage is taken of this solubility and revertibility in dyeing, the former property rendering the process easier while the latter property renders the color, which is formed within the fabric, more permanent. Indigo has recently been artificially produced, but as cinnamic acid, the material from which it is prepared, is expensive, the artificial product has not been able to compete in the market with the natural dye. The artificial production of alizarin and indigo would be of great benefit to mankind, not only in giving them beautiful colors at cheap rates, but by releasing the land now used for these color-plants, to be used in the cultivation of food- plants. 5O8. Dyeing. Dyeing is the art of imparting perma- nent colors to porous and absorbent animal and vegetable substances by impregnating them with coloring matters. These coloring matters are classified as : I. Substantive Colors, or those colors that combine readily and permanently with substances to be colored without the intervention of any third substance. II. Adjective Colors, or those which do not impart a permanent color to the substances to be colored without the aid of a third substance, called a mordant. III. Mineral and Pigment Colors, or those that are 508 THE BENZENE OR AROMATIC SERIES. 371 insoluble in water and alcohol, and are precipitated within the fibre or are fixed by mechanical means. To the first class belong the natural dyes, indigo, saf- flower, anotto and archil ; and the artificial coal-tar colors of aniline, etc. These colors are applicable to animal rather than to vegetable matter. Animal substances, such as wool, silk, hair and feathers seem to act as mordants to themselves, while cotton, flax and hemp seldom take a permanent color without a mordant. The colors of the second class belong almost wholly to animal and vegetable substances, such as madder, log- wood, quercetron, red sandal wood among the vegetable dyes and cochineal among the animal dyes. Those of the third class are the chromates, copper arsenite, Prussian blue, emerald green and orpiment. The mordants in general use are the different salts of aluminum, iron, tin, chromium and copper. (a.) An example of dyeing without a mordant has already been given (Experiment 311). (b.) As an example of dyeing with a mordant, we may take the following method of producing a black upon cotton : (1.) The cotton is first passed through an aqueous solution of iron acetate. (2.) The goods are passed through lime and water. The action of the lime is to precipitate FeO in the fiber of the goods. The goods are then thoroughly washed and have a buff color, like that of iron mould. (3.) The goods are passed through a hot decoction of logwood. This gives them a dense black color. Wool steeped in a solution of potassium dichromate and afterward in a decoction of logwood is dyed a deep, permanent black. Log- wood will give a variety of colors by varying the quantity of the dye-stuff and the kind of the mordant used. Tin salts and cochineal give a deep scarlet. (c.) Examples of the mineral dyes are shown in the production of chrome yellow on cotton and Prussian blue upon wool. In the 372 THE BENZENE OR AROMATIC SERIES. 508 former case the cotton is first placed in a solution of lead acetate and afterward in a solution of potassium dichromate. Insoluble lead chromate is precipitated in the fiber of the cotton. To produce a Prussian blue, the woolen goods are steeped in a solution of ferric chloride, and afterwards in a solution of potassium ferro cyanide. A deep, permanent blue will be the result. EXERCISES. 1. Write structural formulas for benzoic alcohol, benzoic acid, car- bolic acid, three different cresols and salicylic acid. 2. Write symbols for ortho-, meta-, and para-toluidines. 3. Symbolize the carbolates, benzoates, and salicylicates of Na, K, and Ca. 4. Write as many of the ten isomers of C 10 H 6 Cl a as you can, giving the structural formulas. 5. Why can not acids be formed from secondary and tertiary alcohols ? 6. Give the name and typical formula for a triatomic alcohol. 7. The formula for allylene is C 3 H 4 ; of crotonylene, C 4 H 6 ; of valerylene, C 5 H 8 . Give the name and general formula for the series to which they belong. 8. Remembering that benzene consists of six CH groups, write two formulas for C,;H 6 (not necessarily as closed chains). Each formula is to suggest that benzene may be regarded as a normal butane, CH 3 CH 2 CH 2 CH 3 , in which six hydrogen atoms are replaced by two of the triad groups, CH. 510 TERPENES, ALKALOIDS, ETC. 373 /SECTION tv. yX TERPENES, ALKALOIDS, ETC. 509. Terpenes. Closely connected with the ben- zene series are the terpenes, a class of bodies of which tur- pentine may be taken as a type. They have the common empirical formula, C, H| 6 . The terpenes include by far the larger part of those odoriferous oils obtained from plants and known as essential oils. They differ from what are called the fixed oils in being volatile, leaving no stain upon paper, and being capable of distillation without decomposition. The following have been enumerated as having the same formula as turpentine and differing, not so much in chemical as in physical properties : oils of lemon, of bergamot, of cinnamon, of sassafras, of pep- permint, of lavender, of cloves, and many others. 51 0. Turpentine. Turpentine, C, H I6 , in a general sense, applies to those oily resinous substances which exude from incisions made in the bark of various species of pine trees. The American turpentine is obtained from the yellow pine (pinus australis) of North and South Caro- lina, Georgia, and Alabama. It is obtained by cutting from one to four pockets in a tree. These pockets may be compared to distended vest pockets and hold about one quart each. From these pockets, the turpentine is dipped with a ladle and transferred to barrels. The crude tur- pentine thus obtained is the essential oil of turpentine holding in solution a resinous substance commonly known. 374 TERPENES, ALKALOIDS, ETC. 510 as rosin. These are separated by distillation, the oil of turpentine passing over and the rosin remaining as a residue in the still. Oil of turpentine is a transparent, colorless, mobile liquid having a peculiar odor and a burning taste. It boils at 160C. When exposed to air, it changes the oxygen of the air to ozone by which itself is oxidized and changed to a thick, resinous substance. Turpentine is extensively used in mixing paints and in the manufacture of various varnishes. 511. Gums and Kesins. The word gum is very frequently applied to the resins, but gums, properly, are soluble in water and insoluble in alcohol, while resins are soluble in alcohol and insoluble in water. The term gum- resiris, is applied to caoutchouc, etc., which are insoluble in either water or alcohol. Varnishes. Varnishes are solutions of resin- ous substances in turpentine, alcohol and other liquids possessing the power of dissolving resins. The resins most commonly used are, copal, shellac, dammar, sanda- rach, mastic, etc. Amber is a fossil resin found mostly on the shores of the Baltic Sea. It is very slightly solu- ble in alcohol, but, after fusion, it becomes soluble, and is used to make a very durable varnish. (a.) Amber bears a peculiar relation to camphor. After extract- ing the part of amber that is soluble in ether, the residue has the same percentage composition as camphor (C 10 H 16 0). When this re- sidue is distilled with KHO, a substance passes over having all the properties of camphor. 513. Camphors. Closely related to the essential oils are a class of bodies known as camphors, which appear 514 TERPEXES, ALKALOIDS, ETC. 375 to be oxides of the essential oils. Common camphor, C, H I6 0, is distilled from the chipped wood of a tree growing in China and Japan. It is a semi-transparent, crystalline mass, having a tough waxy structure, it is volatile at ordinary temperatures and has a characteristic, pungent, aromatic odor. It is slightly soluble in water (40 grains to the gallon) but dissolves with ease in alcohol, melts at 175C. and distills without decomposition. Small fragments thrown on water gyrate in a peculiar way. It burns with a smoky flame. 514. Caoutchouc. Caoutchouc, or india-rubber, is a mixture of compounds polymeric with the terpenes. It is the coagulated juice of a variety of plants, the principal of which is the Indian fig. It is similar in its origin and nature to the milky juice which exudes from so many of our common plants. The juice which at first is fluid hardens on exposure to the air. Although caoutchouc yielding trees are found in a belt of country extending at least 500 miles each side of the equator and reaching around the earth, the demand for the better varieties of india-rubber is in excess of the supply. For great elasticity and durability, caoutchouc from Para and Ceara in South America and from Madagascar are most highly valued. India-rubber is a tough solid which differs from other vegetable products of like origin by possessing considerable elasticity and being insoluble in water, alcohol, alkalies and most acids. It is soluble in turpentine, benzene, chloroform and carbon di sulphide. The best solvent is said to be carbon disulphide with about five per cent, of absolute alcohol. At 150 C., caoutchouc becomes viscous, and at 200 C., TERPENES, ALKALOIDS, ETC. it melts, forming a thick liquid which shows no tendency to resume its original condition even when exposed to cold for a long time. Freshly cut surfaces of caoutchouc unite firmly when pressed together. Hot and strong sulphuric acid chars it, and concentrated nitric acid rapidly oxidizes and destroys it. The moderate action of chlorine, bromine and iodine hardens it, but if they are allowed to act freely, they destroy it. The effect of sulphur is mentioned in the next paragraph. Caoutchouc is much used in the man- ufacture of water-proof fabrics, machinery belting, hose and tubing, stereotypes for hand stamps, springs, valves, washers, etc., etc. 515. Modified Forms. When caoutchouc is mixed with about two or three per cent, of sulphur, it forms vul- canized rubber, which is even more elastic than common india-rubber, but does not harden with cold or soften with heat as does the pure rubber. Combined with half its weight of sulphur, it forms a black, horny-like substance called ebonite or vulcanite. This last material is much used for electrical insulators and, on account of its re- sistance to the action of acids, for vessels for the use of chemists and photographers. Combs, rulers, penholders, etc., are also made of it. Dental rubber for making arti- ficial gums in which to set teeth is ebonite colored with vermilion. 516. Gutta Percha. This substance, like india- rubber, is the hardened milky juice obtained from various plants. The geographical distribution of gutta percha yielding trees is decidedly restricted. The trees are found chiefly in the Malay peninsula, the whole region extending not more than five or six degrees either way from the g 516 IE ft PENES, ALKALOIDS, ETC. 37? equator, and not more than twenty degrees in longitude. The milky juice occurs most abundantly in the middle layer of the bark. The tree is felled and strips of bark an inch wide and six inches apart are removed from the trunk. The flowing juice is received in any convenient receptacle, such as a cocoa-nut shell, a doubled-up leaf or a hole in the ground. This hydrocarbon juice naturally oxidizes to a resin-like mass, which change may be pre- vented by thoroughly boiling it as soon after collecting as possible. Pure gutta percha is of a greyish-white color but, as found in commerce, it is of a reddish or yellow hue. It is a good electric (Ph., 334), yielding an electric spark after friction. It is harder than india-rubber and not nearly so elastic. When heated to about 65 C., it becomes elastic, soft and plastic, and may be formed into any shape. As it cools, it loses its elasticity, gradually be- coming hard and rigid again and retaining any form im^ pressed upon it, while in its plastic condition. It is highly inflammable. Its solvents are the same as those men- tioned for caoutchouc. It may also be vulcanized, but this is not often done. Its most important application, at the present time, is the coating of telegraph wires, especially those of submarine cables. It is a cheap, durable and efficient insulator and, in its plastic condition, easily applied to wires. Like vulcanite, it may be manufactured into a variety of useful forms, such as stethoscopes and other acoustic instruments, funnels and other chemical apparatus, water pipes, etc. (a.) Gutta is the Malayan term for gum, and percha is the name of the tree. A tree, 30 years old, 30 or 40 ft. high and 2 or 3 ft. in circumference, yields from 2 to 3 Ibs. of gutta percha. A full grown 378 TERPENES, ALKALOIDS, ETC. 516 tree sometimes measures from 100 to 140 ft. to its first branches, and at a distance of 14 ft. from the ground is 20 ft. in circumference and may yield 40 Ibs. of the dry gutta percha. As the process employed involves the destruction of the tree, and as none is planted in its stead, the question of future supply has become a matter for careful consideration. 517. Carbohydrates. This name applies to a class of carbon compounds in which C 6 , or some multiple of it, occurs combined with hydrogen and oxygen in the same relative proportions as they appear in water. They are of very great physiological importance as they enter, to a great extent, into the economy of both plant and animal organisms. There are three general classes as follows : 1. C| 2 H 2 20|| ; as, cane-sugar, milk sugar and maltose. 2. C 6 H| 2 6 ; as, dextrose and levulose. 3. C 6 H I0 5 ; as, starch, inulin, dextrin and cellulose. The members of the first two groups are soluble in water, crystallizable, and are more or less sweet in taste. The third group is composed of compounds, many of which are insoluble in water, un crystallizable, and are capable of being converted to some of the members of group second. The members of the first group may all be converted to those of the second, but no method of changing the infe- rior sugars of the second class to the more valuable cane- sugar of the first has yet been discovered. Cane-sugar is often largely adulterated with glucose or dextrose. 518. Eeview 225, 226, 227, 228, 229 and 230. 519. Fermentation. This is a chemical term used to designate a peculiar class of metamorphoses to which certain complex organic materials are subject. One form was illustrated in Exp. 187. The well-known change in 519 TERPENBS, ALKALOIDS, ETC. 379 grape juice when it " ferments" into wine, the souring of wine or milk and the putrefaction of animal or vegetable matter may be cited as familiar examples. To the ordinary observer, these changes seem spontaneous. But the chemist looks more closely into the matter and remembers that, when one thing acts upon another, it makes no difference whether one of them be poured, for example, from a bottle into a solution of the other, or whether the former were present in the latter from the first. To illustrate, the souring of milk involves only the change of lactose ( 226, d.-, 22? and 227, c.) to lactic acid, thus: Milk sugar. Water. Lactic acid. C, 2 H 22 O n + H 2 = 4C 3 H 6 3 . The milk sugar, before assuming the form of lactic acid, probably passes through the condition of glucose. " But this change cannot be realized, under any known set of conditions, in a solution of pure milk sugar in pure water. In fact, experience shows that no fermentable chemical species will ferment except in presence of water and unless it be kept, by means of that water, in direct contact with some specific ' ferment.' Although this ' ferment ' contributes nothing to the substance of the products which figure in the equation, it, nevertheless, induces the reaction 'by its presence,' as the phrase goes. The presence alone, of course, will not do. It is simply inconceivable that a reagent should act chem- ically unless it were itself in a state of chemical change, although this change may be (and with some ferments probably is) a cycle of changes which always brings back the reagent to its original con- dition." Encycl. Britannica. In such changes as are now under consideration, we have the decomposition of & fermentable substance under the in- fluence of a peculiar agent called a ferment or yeast. This yeast is organized matter which lives at the expense of the sugar which it decomposes. The most important case of 380 TERPENES, ALKALOIDS, ETC. 519 fermentation involves the decomposition of sugar into alcohol and carbon dioxide : C 6 H I2 6 = 2C 2 H 6 + 2C0 2 . M. Pasteur, to whom we owe much of our knowledge of this subject, has shown that only about 94 per cent, of the glucose is thus converted, the other 6 per cent, going 1. To form succinic acid and glycerin. 2. To develop new yeast cells. (a.) " Yeast is composed of a mass of cells or ovoid corpuscles, hav- ing a diameter of 0.01 millimeter and arranged in clusters. Their walls are elastic membranes, and their contents are liquid or gran- ular. When they are introduced into a substance which contains the materials for their development, they multiply rapidly. The cells increase with extreme energy in liquids which contain, besides the yeast, glucose and a small quantity of albuminoid matter ready formed." Wurtz. (ft.) Alcoholic fermentation is only one of several fermentative changes to which sugar may be subjected. By varying the conditions, sugar may be made to yield lactic acid (as above shown), etc. Each of these changes is the exclusive function of a certain species or genus of organisms. While the yeast-plant produces alcoholic fermentation, a certain other organism produces lactic fermentation, a third pro- duces butyric fermentation, etc. No two of these species will pass into each other. It is held by some that it is the life of these minute organisms which directly causes the fermentation or, in other words, that the changes are physiological and not purely chemical phe- nomena. Others go no further than to admit that these living organisms are the only known sources of the ferments proper, which in themselves are chemical substances, pure and simple. (c.) Alcoholic or vinous fermentation means the peculiar change which all native, sugar-producing juices, such as the juices of the currant and apple, are liable to undergo when left to themselves at the ordinary temperature and which results in the forming of alcohol. We may well illustrate the common phenomena by con- sidering the changes in grape juice. Freshly prepared grape juice is a very sweet liquid and is either limpid and transparent or may be so rendered by filtration. Clarified grape juice may remain un- changed for an indefinite time but the addition of a little unfiltered 5 J 9 TERPENES, ALKALOIDS, ETC. 381 juice produces a turbidity in the liquid. This turbidity is due to the evolution of C0 2 and the development of yeast cells. These minute cells constitute a genus of fungi, called saccJuiromyces. The process gradually develops an active effervescence, at the end of which it is found that the originally sweet liquid has a vinous taste and is endowed with the well-known physiological action characteristic of fermented liquors. The grape juice has become wine. In our careful study of this important subject, we may well note the following facts : (1.) A pure solution of cane-sugar or glucose does not ferment under any circumstances. (2.) Perfectly pure grape juice does not ferment unless the process has been started by at least temporary contact with ordinary air. (3.) Ordinary vinous fermentation always involves the formation of yeast. This is the most imi>ortant of these facts. (4.) Spontaneous fermentation of grape-juice is always slow in beginning, but the addition of yeasf from without starts it immedi- ately. These facts clearly show that it is the yeast, or some constituent of the yeast, that breaks up the sugar into C 2 H 6 O, CO 2 , C 3 H 6 (HO) 3 , etc. " In regard to the genesis of the yeast-plant, little is known. Ac- cording to Pasteur's experiments and observations, the yeast \ /hich forms spontaneously in grape-juice is derived chiefly from certain germs which abound about harvest time on the grapes and still more on the grape stalks. These germs are largely diffused also through the atmosphere of breweries, wine cellars and laboratories where fermentation experiments are carried on, but they are not by any means widely diffused through the atmosphere generally." (d.) Lactic fermentation is caused by the development of a micro- scopic fungus, consisting of cylindrical cells much smaller than those of saccharomyces, the alcoholic ferment. This fungus is called, by Pasteur, '' the lactic ferment." It is often found as an impurity in ordinary yeast. The ordinary souring of milk i? probably caused by a motionless bacterium, the germs of which must be assumed to abound in dairies an4 cows' stables. (e.) When lactic acid is formed by fermentation at a temperature of about 40 C., it is often subjected, at once, to a further change, as follows : Lactic acid. Butyric acid. 2C 8 H 6 8 = C 4 H 8 2 + 2CO a + 2H,. 382 TERPENES, ALKALOIDS, ETC. 519 This butyric fermentation is caused, according to Pasteur, by the development of a special kind of vibrio, a worm shaped " animalcule," consisting of a number of longitudinal cells, each about 0.002 milli- meter thick and from 0.002 to 0.02 millimeter long. Butyric fermen- tation is really a species of putrefaction. (/.) Putrefaction is a very complex phenomenon. Concerning its causes, we can here only say that putrefaction is not possible under any condition that would prevent the development of life or, in other words, that there is no putrefaction where there is no possibil- ity of life and lhat in nearly every case this possibility of life is realized in the form of bacteria and vibriones. These are microscopic organisms. It is, as yet, uncertain whether they are plants or animals. Putrefaction excludes all cases of oxidation although when the former is going on in the air it is always accompanied by the latter. (g.) Acetous fermentation is a case of oxidation effected under the influence of a living mould-plant, called Mycoderma aceti. See 438. 520. Alkaloids. These bodies are found in a great Variety of plants. They are nitrogenized compounds resembling ammonia in forming salts with acids. They are generally sparingly soluble in water, but more freely so in alcohol. They are intensely bitter in taste, very poisonous, and form a characteristic compound with pla- tinic chloride. Their names generally terminate in -ia or -ine, the former being preferable, as the latter is used as a suffix for other chemical names. 521. Conia. Conine (or conicine) is found in hemlocK (conium maculatum), a plant which is a native of Europe, but which has been naturalized in the United States. It is supposed to be the poison used by the ancients. It is distilled from the seed as a volatile, limpid liquid and has a penetrating, sickening odor. It turns red litmus to blue. Its symbol is C 8 H, 5 N. 5 2 4 TERPEXES, ALKALOIDS, ETC. 383 522. Nicotine. This alkaloid, C IO H 14 N 2 , is found in tobacco, which generally contains from two to eight per cent, of it. It is a colorless liquid. When cold, it has a faint smell of tobacco, but when heated it has a pene- trating, nauseous odor. It is strongy alkaline in its re- actions and is one of the most violent of poisons. 523. Opium. Opium is the hardened juice obtained from incisions made in the capsules of the poppy (papaver somniferum), and is abundantly produced in Asia Minor, Turkey and Egypt. It is a very complex substance, being made up of a number of alkaloids combined with meconic and sulphuric acids, resins, g'ums, caoutchouc and other compounds. Among the important alkaloids found in opium, are morphine, codeine, papaverine, narcotine, and ten others. Experiment 314. To a few drops of an infusion of opium, add a drop of a neutral solution of ferric chloride. A red solution will be produced. This is a test of opium due to the action of meconic acid, which is always present in opium. The red solution is meconate of iron. 524. Morphia. Morphine is the most important and the most generally used extract of opium. It is a white, crystalline solid, almost insoluble in water (1 part in 1000), soluble in alcohol, has a bitter taste and poisonous, nar- cotic qualities. The sulphate and hydrochl orate are the forms most commonly used in medicine. Its symbol is C I7 H 19 N0 3 +H 2 0. Experiment 315. Place a drop of HUSO., on a piece of white por- celain. Stir in with a glass rod a small quantity of morphine and heat to 100 C. Add a drop of HNO 3 . A blood- red color is the result. Morphia or any salt of morphia gives an inky blue with Fe 2 Cl 6 . 384 TERPENES, ALKALOIDS, ETC. 525 525. Alkaloids of Cinchona. As many as six different alkaloids have been extracted from the Peruvian bark of commerce. This bark is obtained from different species of cinchona, a tree which grows in the Andean regions of South America, especially in Peru and Bolivia. The principal alkaloids from this source are quinia or quinine, 20^24^02? and cinclionia or cinchonine, C 20 H 24 N 2 0. Quinine is very bitter, very sparely soluble in water, but soluble in alcohol, ether and chloroform. Cinchonine resembles quinine but differs from it in be- ing almost insoluble in ether. The sulphate is the form in which quinine is mostly used as a medicinal agent. In this form it has the same intensely bitter taste, but is more readily soluble in water. Quinine sulphate, when in solu- tion, gives a beautiful blue fluorescence. A paper which has been washed in it becomes luminous when placed in the ultra violet part of the solar or electric spectrum (Ph., 651). 526. Strychnia. Strychnine, the most deadly of all the alkaloid poisons, is extracted from nux vomica and the Saint Ignatius bean, fruits of different species of strychnos, a small tree found in India. It is soluble in 7000 parts of water. Such is its intensely bitter taste, that when its solution has been diluted with 100 parts of water, making a solution of one part of strychnia in 700000 parts of water, it still has an intolerably bitter taste. The taste is perceptible when there is one part in a million. It acts powerfully on the nervous centers, throwing the patient into tetanic spasms. The antidotes are morphine and chloral hydrate. Brucia, an alkaloid resembling strych- nine, is found associated with it in the plants above named, 527 TER PENES, ALKALOIDS, ETC. 385 and may be distinguished by its giving a red color with nitric acid. The symbol for strychnia is C 2 |H 2 2N 2 2 . Experiment 316. Moisten a small quantity of strychnia with H 2 SO 4 upon a piece of white porcelain. Add a minute quantity of potassium dichromate. A characteristic purple color is produced which changes to red and yellow. This is a test for this poison. 527. Theobromiiie, etc. Theobromine,C 7 H 8 N 4 2 , is found in the chocolate nut and in the bean of the cacao, a tree of South America, Caffeine, C 8 H IO N 4 2 , is found in coffee; it forms about one per cent, of the coffee bean. It has a faintly bitter taste and is poisonous, a dose of half a grain being enough to kill a cat. Theine is found in tea, and is identical with caffeine. iff J 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. If! Name. Sym- ool. Aluminum Al.... 27.3 Antimony (stibium). . . Sb . . 122 Arsenic As... 74.9 Barium Ba...l36.8 Beryllium Be (See Gludnum.) Bismuth Bi. .210 Boron B.... 11 Bromine Br. ...79.75 Cadmium Cd...lll.6 'Caesium Cs...l32.5 Calcium Ca... 39.9 Carbon C..., 11.97 Cerium Ce ...141.2 Chlorine '.CI... 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 Gludnum.) Gludnum Gl. . . 92 6ol. criths. Oo\d(aurum) Aul96.2 Hydrogen H . . 1 Indium In. 113.4 Iodine I. .126.53 Iridium Ir 192.7 Iron Fe..55.9 Lanthanum La 139 Lead (plumbum) Pb 206.4 Lithium Li . . 7.01 Magnesium Mg.23.98 Manganese Mn..54.8 Mercury (hydrargyrum).Wgl$$& Molybdenum. Mo. 95. 8 Nickel Ni.58.6 Niobium (See 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 Potassium (Jcalium). ... K .. 39.04 Rhodium Rh.104.1 Rubidium Rb..85.2 Ruthenium Ru. 103.5 Selenium Se. -79 Silicium . . (See Silicon.). . . Si 387 w/tms> Sytn- Micro- Name. fa cri/fe Silicon Si 28 Silver (argentum) Agl07.66 Sodium (natrium) N a. 22. 29 Strontium Sr ..87.2 Sulphur S... 31.98 Tantalum Tal82 Tellurium Te 128 Terbium . ..Tr..99 Thallium. . .71. 203.6 Thorium .............. Th.231.5 Tin (stannum) ....... Sn.117.8 Titanium ............. Ti . .48.15 Tungsten (wolframium) W. 183.5 Uranium .............. Ur.240 Vanadium ............ V.. 51.2 Yttrium ............... Yt...92.5 Zinc .................. Zn...64.9 Zirconium.., ..Zr..90 2. Metric 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. 124) 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 inch=2.540 cm Jl cu. in. = 16.386 cu.cm. 1 grain =0.0648 g. I foot=3.04S dm. i liquid qt.rrO.946 I. loz. Troy =31.1035/7- 1 yard=0.9144m. 1 fl'd oz.=: 29.562 cu. cm. lib. Av. =0.4535^. 3. Thermometers. Chemists use the cen- g. tigrade thermometer almost exclusively. One or ~ more centigrade thermometers (chemical), having the scale marked on the glass tube, and having no S3 frame like that of the ordinary houss thermometer, ,|J should be in every school laboratory. In this book g temperatures are always given in centigrade de- 5- grees. To change centigrade readings tc Fahren- sr heit readings, multiply the number of centigrade y 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 -. (See Ph., 480, 481.) The best thermometers are straight glass tubes, of uniform diameter, with cylindrical instead of IG> I24 spherical bulbs ; such instruments can be passed tightly tt *** through a cork, and arc free from many liabilities to error FIG. 1 25. to which thermometers with paper or metal scales are 388 APPENDIX. always exposed. A cheaper kind of thermometer, having a paper scale enclosed in a glass envelope, will answer for most experiments. 4. Glas 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. 126 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. 126. 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. 127, 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- APPENDIX. 389 ing better than by seeing, i. e., the fingers will detect the yielding of the glass before the eye notices any change of color or form. When the glass yields easily, remove it from the flame and gently bend the ends from you. If the concave side of the glass 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. 128. 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, bat should be made by heating, progressively, several cm. of the tube, and bending continuously from one end of the heated portion to the other (Fig. 129). 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 U-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 390 APPENDIX. 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 glass. (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. 130. 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. 130) 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. 131.) You can not close both ends satisfactorily at the same time. A superfluous knob of glass generally remains upon the end. If F IG - I 3 I - 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 APPENDIX. 391 the too pointed end of the right hand half of the original tube, o\ 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 be 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 iu 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. (6.) 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 thickened 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 too highly 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 1 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 392 APPENDIX. 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 hut efficient and cheap" glass-cutters," made of hardened steel 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 alcohol 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. 132. 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, APPENDIX. 393 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 He in the same plane. See Frick's Physical Technics [17]. FIG. 133. FIG. 134. M FIG. 135. 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. 133. The manner of using them is shown in Fig. 134. They are often graduated. A cylindrical measuring glass, graduated to cubic centimeters (Fig. 135) is almost indispensable in the laboratory. 6. Woulffe 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 F.O. .36. * m 394 APPENDIX. 7. Thin Bottomed Glassware. Glass vessels are largely used for heating liquids in 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, s) are preferable to those that have not (Fig. 43). 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, 37r, 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. 137, should be made or bought, to hold the tubes upright when in use and to hold them inverted when not hi 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. APPENDIX. 395 FIG. . 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. 138. 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. 139, and thus placed in the fun- nel. Rapid filtration may be secured by making a rib- bed filter as follows : Fold the paper as before on O *~ two diameters at right- FIG. 140. angles to each other. 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. 140, and fold the corner a upon b, creasing the paper in the opposite di- rection. Make similar creases midway between b 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 FlG - 396 APPENDIX. 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 App. 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 a washing bottle (Fig. 141) 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 IG- I 4 I> 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 paraflme wax. FIG. 142. In boring holes through corks, a small knife blade or rat-tail file APPENDIX. 397 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. 142. 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, 6), 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- Ascribed 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 long, the stopper will expand as well as the neck, and the trial end in failure. As a last resort, fit two pieces of soft wood between the lip of the bottle and the lower side of the projecting part of the stopper. Tie them firmly in place and soak in water for several hours. If the wood does not swell enough to start the stopper, pour hot water over the wooden pieces, and the trouble will generally be at an end. When you pour a liquid from a bottle, as into a test tube, hold the bottle in the right hand with the label toward the palm. Remove the stopper with the little finger or with the third and fourth fingers of the left hand, the thumb and forefinger of which may hold the test tube. Remove the liquid drop that adheres to the lip of the bottle by touching it with the stopper, replace the stopper and return the bottle to its proper place. It is seldom necessary to place either APPENDIX. stopper or bottle on the table. In a little while you will acquire the habit of doing these things in this way and thus avoid much annoyance. 1C. Staiid, Support*, Bath, etc. Flasks, etc., are often supported over the lamp by a retort stand, as shown in Figs. 37 and 38. This stand has a heavy base and several movable iron rings of graduated sizes secured to the vertical rod by binding screws. Glass vessels thus supported are well protected from the direct flame of the lamp by a piece of wire gauze, as shown in Fig. 37. Oc- casionally, a very gradual and even heating is desired. Under such circumstances, the wire gauze may be replaced by a sand bath, which consists of a shallow pan, beaten out of sheet iron and filled with sand, as shown in Fig. 42. Sometimes, it is desirable to heat a vessel moder- ately, keeping it continuously below a certain temperature. This may be ac- complished by placing the vessel in an- other vessel partly filled with water and heating the water, as shown in Fig. 89. Copper cups with tops made of concen- tric rings that may be adapted to the size of the vessel are offered for sale. A good enough water bath may be made of an old tinned fruit can. Care should be had that the water of the bath is not allowed to boil away. Fig. 143 shows various clamps and fittings for a retort stand, by means of which tubes, flasks, retorts, etc., are easily held in any de- sired position. See Fig. 37. Many convenient supports may be made with corks and glass rods stuck on inverted funnels. A convenient support for a small vessel may be made in the form of an equilateral triangle by twisting FIG. 143. FIG. 144. together three pieces of soft iron wire at the cor- ners, as shown in Fig. 144. Each of the wires may be run through the stem of an ordinary clay pipe. The support may be placed upon the ring of a retort stand or held by a cork into which the twisted wires at one corner have been thrust. A convenient support for test tubes, etc., may be made by binding the middle part of a copper APPENDIX. 399 wire, 1 or 2 mm. in diameter, about a stout cork. The free ends of the easily flexible wire may be wound spirally around the test tube. The cork serves as a handle ; if perforated, it may be placed upon the rod of the retort stand. The wire may be bent so as to place the tube in any desired position. 11. Ulortars, A mortar is a vessel, m, in which solid sub- stances may be powdered with a pestle, t. They are made of iron, porcelain, agate, ete. Porcelain mortars of the best quality are made of " Wedge- wood ; " they are unglazed, should not be suddenly heated and may be cleaned by rubbing with sand wet with nitric or sulphuric acid or caustic potash FIG. 145. or soda, according to the nature of the substance to be removed. Agate mortars are very small and expensive. In many cases, a stout bowl will answer a$ a mortar, while a pestle may be made of hard wood. Many substances may be powdered on a hard surface by the use of a rolling pin, like that used by a pastry cook, or by rolling a stout bot- tle over them. If a solid is to be broken by blows preparatory to powder- ing, an iron mortar and pestle are de- sirable. The pestle may be worked F I G - 146. through a hole in a pasteboard cover, which will prevent fragments of the solid from flying out of the mortar. Often, it is better to wrap the solid in a paper or cloth and then to break it with blows of a hammer. In using a mortar for pulverizing, it is better to put only a small quantity of the substance into the mortar at once, sifting it frequently and returning the coarser particles to the mortar for further trituration. The sifting may be done by rubbing the powder lightly with the finger upon a piece of muslin tightly stretched over the mouth of a beaker (Fig. 146). 12. The Pneumatic Trough. For collecting gases over water, the pneumatic trough, in some form, is indispensable. A con- venient trough is shown in Fig. 6 and described in 20. The pan,/, may be of earthenware, while a flower pot saucer will answer for e. Two flat blocks of any material heavier than water may be used, in- stead of the saucer, for the support of the inverted gas receiver, g. With this apparatus, the receiver must be filled outside of the trough. The mouth being closed with the hand, a flat piece of wood, glass 400 APPENDIX. or card board, the bottle may be quickly inverted and placed in posi- tion so that its mouth is closed by the water in/. If any air gets into g during this operation, the work must be done again. While one bottle is filling: with gas, another is to be made ready. When filled with gas, the first bottle may be removed from the trough by slipping a shallow plate or saucer beneath its mouth and removing plate and bottle together. Enough water will be retained in the plate to seal the mouth of the bottle. If the lip of the bottle has been ground flat, as recommended in App. 4, 7i, a piece of window glass will answer instead of the plate. As successive bottles are filled, the trough may become inconveniently full of water some of which may be dipped out or removed with a rubber tube siphon (Ph., 298). Any bucket or tub with a hanging shelf having holes bored in it, will make an efficient pneumatic trough. When it can be secured, a pneumatic trough similar to that shown in Fig. 147, is desirable. It a c may be made of boards care- fully joined and painted, but is preferably lined with sheet lead. It should be sunk in a table and provided with a wa- ter cock and drain pipe. Gas receivers are easily filled with water in the well, mn, and placed upon the shelf, b, which is to be below the water level. The dimensions of mn are to be determined by the size of the largest vessels that are to be sunk in it and the size of b by the size and number of gas receivers that are likely to be in use at any one time. Grooves may be provided in the shelf, b, running parallel to the side, ac. These grooves allow the rubber delivery tube to pass under the edge of the receivers without compression. In lifting large receivers from the well of a small trough, the water level may be brought below the shelf, b. Under such circumstances, more water may be introduced from a pail or by the water-cock, or a jug of water pre- viously placed within convenient reach, may be placed in the well and subsequently removed when the filling of the receiver with gas raises the level of the water too high. Porcelain pneumatic troughs for use with mercury (Exp. 6) may be bought for a little money, of any dealer in chemical wares, but one may be made of a block of hard wood. Its principal dimension should be horizontal, the bottom being rounded so that it will con- APPENDIX. 401 form to the outline of a test tube or cylinder placed in it. Its depth should be a little more than the diameter of the test tube or cylinder used. In collecting gases over water, two difficulties must be guarded against. First, if from any cause, the tension of the gas within the apparatus becomes less than the atmospheric pressure, water from the pneumatic trough may be forced back through the delivery tube into the generating flask. Cold water being thus suddenly admitted to a hot flask, the latter is broken and 'sometimes a more serious ex- plosion takes place. This danger is especially present in thus col- lecting a gas somewhat soluble in water. See Exp. 65 and 79. In stopping the evolution of a gas, remove the delivery tube from the trough, and remove the adhering water drops before removing the lamp. Whenever the delivery of a gas begins to slacken, watch the delivery tube ; if water begins to " suck back " toward the flask, quickly remove the delivery tube from the water, or, still better, break the caoutchouc connection recommended in App. 4, & (as shown at c, Fig. 6.) or loosen the stopper of the generating flask. When a liquid is used in the flask, this danger of " sucking back " may be avoided by the use of a safety tube, as shown at s, Fig. 34. In case a partial vacuum should be formed in the flask, 6, atmospheric pres- sure would force down the liquid in the lower part of the tube, a, and thus admit air instead of raising the liquid in c, to the greater height necessary to allow it to enter b. The funnel tubes shown in Figs. 32 and 62 act, similarly, as safety tubes. The second difficulty to be guarded against is the production of too great a pressure within the apparatus by allowing any part of the delivery tube to dip too far beneath the surface of the water in the trough. Owing to the high speci6c gravity of the liquid used, this difficulty is especially present in the collection of gases over mercury. The pressure thus produced may develop leaks in the ap- paratus or, in certain cases (Fig. 32), force the liquid of a flask out through t v e funnel or safety tube. 13. Ga Holders. It is often convenient to have a supply of oxygen, hydrogen and other gases on hand. Gas holders (often im- properly called gasometers) are convenient for storing such gases for use. One form of easy construction is showri in Fig. 148. It con sists of an outer vessel, a, open at the top, and an inner vessel, b, open at the bottom. Both may well be made of galvanized iron ; a may be a barrel, cask or earthen crock. The upper end of b is ham- mered into saucer shape so that its highest point shall be at the middle. At this highest point is inserted a gas cock, having its free 402 APPENDIX. FIG. 148. end smooth and slightly tapering, for the reception of rubber tub ing. Three hooks or eyes are attached to the edge of the upper end of b, from which extend cords that are knotted together at the lower end of the supporting cord, c. The cord, c, may pass over pulleys in a frame, as shown in the figure, or over pulleys supported from the ceiling, the frame being omitted. Fill a with water. Open the stop cock, remove the weights from c and allow b to sink into a. Be sure that there is enough water in a to cover the highest point of b. Connect the stop cock, by rubber tubing, with the gas generator, but not until all air has been expelled from tho tubing. Open the stop cock and place weights at the free end of c. By mak- ing these weights heavier than b the pressure in the generating apparatus may be reduced as far as desired. As gas is delivered, b will rise. The apparatus is shown on a larger scale at 6r,Fig. 93. When the generation of gas has ceased, or when b is full, close the stop cock, remove the tubing and leave suspended from c only enough weights to counterbalance b. For most schools, a 6 or 8 gallon crock (preferably tall and narrow) will be large enough for the outer vessel. The stop cock may be had of any plumber or gas fitter ; any tinsmith can make the vessel, b, When gas is wanted from the holder, as in Exp. 49, connect the gac cock of b with the apparatus to be used, open the cock, remove weights from e and, if necessary to produce the desired pressure, place them upon 5. It is customary to paint the oxygen holder red and the hydrogen holder black, for purposes of ready distinction. A convenient form of gas holder, which may be made of metal and of any desired size is shown in Fig. 149. The open cistern, s, which is better made cylindrical, is connected with the closed cistern, g, by two tubes provided with stop cocks. One of these, t, passes nearly to the bottom of g, while the other just enters the top of g without projecting into it. A third tube, also provided with a stop cock, passes from the top of g and carries a piece of rubber tubing. The oblique tube, i, at the bottom of g, may be closed with a cork or screw plug. The apparatus may be placed over a tub or in a shal- low pan provided with a drain pipe. To fill this holder, close i t open all three stop cocks and pour water into 8. As water enters g, air escapes through the rubber tube. When g is filled with water, close the stop cocks, remove the plug from i and insert the delivery APPENDIX. 403 tube of the gas generator. As gas enters g, water escapes at i. When g is filled with gas, remove the tuhe from t and insert the plug. When desired, s may be used as a pneumatic trough by partly filling it with water, inverting a re- ceiver filled with water over the upper end of n, and opening the stop-cocks of n and t Water enters g by t and gas rises through n into 8 and the inverted receiver. When desired, the cock of n may be left closed and the other two opened. Water from * will then force gas out through the rubber tube. A convenient gas holder may be made from a large glass bottle or a jug by pass- ing two glass tubes through the cork, pro- viding one with a piece of rubber tubing and the other with a stop or pinch cock (App. 20) all as shown in Fig. 150. The lot- tie being filled with water, the gas genera- FIG. 149. tor is connected with the stop-cock which is then quickly opened. As the gas a enters g through a, water es- capes through the siphon, c. The pressure on the generator at starting, may be relieved by sucking at c to start the action of the siphon. Gas is delivered from g through a, by connecting c with a supply of water elevated on a shelf (siphon delivery, if desired) or with any other sup- ply of water under moderate pressure. Any one of these FlG - I 5- three forms of gas holders, when filled with water, may be used as an aspirator (Exp. 57). When a gas is to be kept for only a short time, a caoutchouc gas bag is a convenient substitute for a gas holder. It is easily portable and has other advantages. One may be bought for two or three dollars. 14. Drying Gae. Several ways of freeing gases from aqueous vapor are illustrated in Exps. 28, 31, 57, 61 and 88. When sulphuric acid is used, the method given in Exp. 31 is preferable to 404' APPENDIX. that given in Exp. 88. See Figs. 45 and 64. Drying tubes of vari- ous other forms may be had of dealers in chemical glassware. In using a drying tube, care should be taken that there are no straight passages through which the gas can find quick and easy passage. A loose plug of cotton wool is generally placed at each end of the dry ing tube to keep the solid drying agent in place. If quicklime be used, allowance must be made for its expansion when acted upon by moisture. The choice of drying agent must often be determined by the chemical relations of the gas to be dried. Thus, sulphuric acid or calcium chloride could not be successfully employed in Exp. 61, nor quicklime in Exp. 146. Phosphoric anhydride is sometimes used for drying gases. 15. Lamps. In laboratories, where illuminating gas is pro- vided, the most convenient form of lamp for heating purposes is the Bunsen burner, represented in Figs. 16, 18, etc. It gives a very hot and smokeless flame. A fair substitute for a Bunsen burner may be made by inverting a wide necked glass funnel over any ordinary gas burner, supporting it in any con- venient way so that air may have free passage between the sides of the burner and the glass as shown in Fig. 151. The funnel is to be put into position before the gas is lighted. The gas supply is to be controlled so as to produce a smoke- less flame. When a very small flame is used with the Bunsen burner, the flame may drop down into the tube. This may be prevented by laying a small piece of wire gauze over the top of the tube and press- ing its edges down against the sides of the tube, before lighting the gas. A long flame for heating tubing may be secured by slipping the attachment represented in Fig. 152 over the tube of the Bunsen burner. A Bunsen burner may be obtained of any dealer in chemical supplies. Write for a catalogue of chemical IG. 152. f,pp ara t us to Bullock and Crenshaw, Philadelphia. When gas is not provided, the alcohol lamp, represented in Figs. 3, 60, etc., is generally used. Under similar circumstances, the Vapor Bunsen Burner, represented in Fig. 153, will be found very efficient. It is provided with additional burners for evaporating and blowpipe purposes, bums gasoline, and serves as a retort stand. Gasoline is FIG. 151. APPENDIX. 405 much cheaper than alcohol. S. Kellogg, Cleveland, O. The lamp may be obtained of James The Berzelius or argnnd lamp burns alcohol, and is convenient for many purposes where much heat is neces- sary, e. g.,'the preparation of Gl oxygen in con- siderable quan- tity. It may be had of Queen &Co.,Philadel- FlG - I 54- phia, or any other dealer in apparatus. FIG. 155. FIG. 153. 16. Fletcher Burners. Special heating apparatus is now FIG. 156. FIG. 157. made in great variety. Of the many forms offered to the public, none seem more desirable than those designed by Thomas Fletcher of Warrington, England, and supplied in this country by the Buf- falo (N. Y.) Dental Manufacturing Co. This paragraph is devoted to this apparatus. The " Low Temperature Burner " is shown in Fig. 154. It gives a wide range of temperature and dispenses with drying 406 APPENDIX. closets, sand and water baths. It burns gas and is furnished with or without the blast pipe, C. (See App. 17.) Fig. 155 represents the " Evaporating Burner," which is very convenient for heating flasks, as in 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. 156. The ' ' Solid Flame Burner " is shown at one-fourth actual size in Fig. 157. 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 BlowpSi^es. For working tubes of considerable size, a blower and blast lamp are necessary. The blower FIG. 158. FIG. 159. may easily be made. Fig. 158 shows it in perspective, and Fig. 159 in section. The sides of the bellows, m, and of the reservoir, n, are FIG. 160. FIG, 161. made of leather nailed to the boards at top and bottom. The ar- rangement of valves is evident from Fig. 159. 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 t APPENDIX. 407 may be about 60 cm. A more desirable form, made by the Buffalo (N. Y.) Dental Manufacturing Co., is shown in Fig. 160. A Bunsen blast lam}) is shown in Fig. 161. Gas enters by the tube at the right. The other tube is connected with the blower. It may be had of James VV. 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. 162 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 pip* 1 ! 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 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 b\ the Buffalo Dental Manu- facturing Co., is shown in Fiff. 163. 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, WICK HOLDER TURNED HALF A. REVOLUTION. FIG. 163. 408 APPENDIX. such as is shown in Fig. 164, or with the blast from ths blower. An attachment, similar to that shown in Fig. 152, may be added to the Bunsen burner for blowpipe purposes. A blowpipe, suf- _ ficient for many purposes, fe^*"**""" ' -^^^" = may be made from glass tub- 7lG - l6 4- ing. Blowpipes may be 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 wire 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, G, beaten into shape. Tiie opening by which the alcohol is introduced into this cup may be c'osed 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 APPENDIX. 409 FIG. 165. iron," you can do a wider range of work, as many pieces of work cannot be held in the lamp flame. Fig. 165 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 material like 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. Cock. Whenever flexible tubing is used, pinch cocks furnish cheap substitutes for stop cocks. Fig. 166 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- FIG. 1 66. ing passes through the open space, o ; when the supply is to be cut off, the tubing is compressed between the arms at c. A stop cock may be made as follows : Provide two glass tubes, one of which slides easily into the other. Close one end of the smaller tube (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 410 APPENDIX. 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. 167) the cock is open ; when the smaller tube is drawn back (Fig. 168), the hole is closed by the rubber tubing and the cock is closed. FIG. 168. FIG. 167. A very simple valve for controlling the flow of fluids may be made by placing a glass ball in a piece of soft rubber tubing. The ball should By pinching the rubber be larger than the opening in the tubing. at the side of the ball, a little channel is made through which the liquid or gas may pass. 21. Evaporating Dishes, Crucibles and Fur- naces. Evaporating dishes may be had made of porcelain and pro- FIG. 169. FIG. 170. vided with a projecting lip and glazed on both sides or only on 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. 171. iently with crucible tongs, two common APPENDIX. 411 forms of which are represented in Fig. 170. 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. 171, 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. 172, and a plumbago crucible, FIG. 172. 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. 173. " Crucible Furnace for Petroleum," shown in Fig. 173. These three Fletcher Furnaces require the aid of the " Blower," shown in Fig. 158 or 160. 22. ifXetal Retorts. Oxygen may be prepared by carefully heating the materials in a Florence flask or glass retort, but for this 412 APPENDIX. 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 FlG - J 74- 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 ordinary stove. A piece of glass tubing may be 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 tt\-, stove pipe. The mouth atiis made slightly flaring FIG. 175. 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 Paris. 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 APPENDIX. 413 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 be 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 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 arid 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 3g. of cochineal in a mixture of 50 cu. cm. of alcohol and 200 cu. cm. ol 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 whicli turn it from yellow to brown (Exp 64), See also Exps. 99 and 100. FIGURES REFER TO PARAGRAPHS, UNLESS OTHERWISE SPECIFIED,-* Absolute alcohol, 431. Acetates, 314, 324, 440, 441a. Acetic acid, 215, 423, 435a, 439. Acetin, 441a, 446. Acetous fermentation, 519g. Acetyl, 215a, 423. " hydrate, 215a. " hydride, 215a. Acetylene, 219. " series, 220, Ex. 7, p. 371. Acid, Acetic, 215, 423, 435a, 439. " Anhydrosulphuric, Ex. 6, p. 136. " Arachnic, 435a. " Arsenic, etc., 249. u Basicity of an, 164, 423. " Benic, 435a. " Benzoic, 500. " Binary, 1636. " Boracic, 173. " Boric, 173. " Bromic, etc.) 116. 44 Butyric, 435, 519. " Capric, 435a. 41 Caproic, 435. " Caprylic, 435a. 44 Carbolic, 484. " Carbonic, 198. " Cerotic, 435a. " Chamber, 152o. " Chlorhydric, 104. " Chloric, etc., 112. " Chromic, 3816. " Cinnamic, 507. *' Cyanhydric, 205. " Definition of, 163. Acid, Dichloracctic, 440. i( Disulphuric, 156. " Dithionic, 158. M Fatty, 435. " Fluorhydric, 122. " Formic, 2166, 435a, 436. " Fuming sulphuric, 156. " Gallic, 502. " Glacial phosphoric, 242e. - " Glyceric, 469. " Glycolic, 457. " Haloid, 1236. " Hydrochloric, 104. ; Hydrocyanic, 205. " Hydrofluoric, 122. " hydrogen, 1666. " Hydrosulphuric, 137. " Hyponitrous, 82. " Hyposulphuroue, 157, 158. 41 lodic, etc., 118. " Lactic, 464, 519. " Laurie, 435a. " Manganic, 3760. u Margaric, 435a. ' Meconic, Exp. 314. " Melissic, 535a. " Metaphoi^phoric, 242. " Molybdic, 382. " Monochloracetic, 440. " Muriatic, 104. 41 Myristic, 435a. " Nitric, 73, 418a. Nitro hydrochloric, 114. " Nitro-muriatic, 114. " Nitrous, 86. 41 Nordhausen, 156. INDEX. 415 Figures refer to Acid, (Enanthylic. 435a. " Organic, 423. " Oxalic, 458, Exp. 289. " oxides, 165. u Palmitic, 435a. " Paralactic, 464. 44 Pelargonic, 435a. " Pentaihionic, 158. " Permanganic, 376/". " Phosphoric, etc., 242. u Picric, 492. " Propionic, 435a. " Prussic, 205. " Pyroboric, 1736. " Pyrogallic, 502. u Pyroligneous, 215. " Pyrophosphoric, 242. " Salicylic, 501. " salt*, 170. " Sarcolactic, 464. " Silicic, Exp. 217. 44 Stannic, 389. 11 Stearic, 435a, 441a, 444. " Succinic, 519. " Sulphindigotic, 507. " Sulphuric, 151, 158. u Sulphurous, 149, 157. 44 Sulphur oxy-, 159. 44 Tartaric, 2696, 474. " Ternary, 163c. " Tetrathionic, 158. 44 Thionic, 158. 44 Thiosulphuric, 158. " Trichloracetic, 440. 44 Trithionic, 158. " Tungslic, 383. " Valeric, 435a. Acidity of bases, 1666. Acids, Nomenclature of, 163. Affinity, Chemical, 8, 9. A irate, 232o. Air, 45-49. " slaked lime, 290c. Alabaster, 294. Albumen, 223. Alcohol, 210, 420, 421, 454. 44 Absolute, 431. Amyl, 4326. 44 Benzole, 500. 44 Butyl, 432a. Paragraphs, unless otherwise specified. Alcohol, Common, 210. 44 Ethyl, 210. 44 Isnpropyl, 432. 44 Methyl, 418a, 426. Pentyl, 4326. Propyl, 432. " Pseudo. 421. 41 True, 421. A3oholic fermentation, 519c. Alcohols, 420, 421, 454. Aldehyde, 215a, 4216, 4a% 500, 501 41 green, 499. Aldehydes, 4216, 433, 500, 501. Alizarin, 505. Alkali, 1676. 44 The volatile, 168. Alkaloids, 520, 525. Allotropism, 39. Alloys, 322 ; 303a. Allylene, Ex. 7, p. 372. Almond oil, 450. Alum, 349. Alumina, 348. Aluminium, see Aluminum. Aluminum, 344. bronze, 347. 44 group, 352. 44 oxide, 348. sulphate, 349. Amalgam, 338. Amber, 512. Amethyst, 232a. Amide, Ex. 17, p. 314. Amine, 96a ; Ex. 16, p. 314. Ammonia, 66, 168. type, 96. Ammonium, 168, 286. 44 acetate, 4986. 44 chloride, 287. 44 nitrate, 288. Amorphous, Note, p. 113. Ampere's law, 61. Amyl, see Pentyl. 44 alcohol, 4326. " glycol, 456. Ainylene, see Pentene. glycol, 456. Amylic alcohol, 4326. Analysis defined, 18. 44 of water, 14. 416 INDEX. Figures refer to Paragraphs, unless otherwise specified. Analysis, Quantitative, Note, p. 296. Anhydride, 165. Anhydrite, 294. Anhydrosulphuric acid, Ex. 6, p. 136. Aniline, 438. " colors, 499. red, 4986. Animal charcoal, 186. Animal oils, 448. An otto, 508. Anthracene, 504. Anthracite, 181. Antimoniuretted hydrogen, 2530. Antimony, 251. " chlorides, 253d. glance, 251. hydride, 253a. oxides, 2536. " sulphides, 253a Antozone, 38a. Aqua fortis, 73. " regia, 114. Arachnic acid, 435a. Archil, 508. Argentic, see Silver. Argentum, see Silver. Argol, 474. Aromatic group, 500. " series, 410, 479. Arrow root, 228. Arsenic, 243. " acid, 949. " hydride, 245. " oxides, 247, 248. " sulphides, 250. " White, 247. Arsenite of copper, 324, 508. Ar.-eniuret, Note, p. 217. Arseniuretted hydrogen, 253a. Arsine, 245. Artificial fats, 445. Aspirator, App. 13. Atom defined, 5. Atomic attraction, 8, 9. symbols, 56, 93. " volume, 175a, 2400. " weight, 64. Atomicity, 65, 92c?, 174. Attraction, Forms of, 8. Auric, see Gold. Aurin. 499. Aurous, see Gold. Avogadro's law, 61. Azurite, 319a. Bacteria, 519tf and /. Barley sugar, 226c. Barite, 1316. Barium, 297. Baryta, 297. Base defined, 166. Bases, Acidity of, 1666. Basic ammonia, 168. " hydrogen, 164. " oxides, 166a. " salts, 170. Basicity of acids, 164, 423. Beakers, App. 7. Bee's-wax, 447. Beet sugar, 2266. Bell metal, 322, 388. Benic acid, 435a. Benzene, 479, 482. " isomers, 480, 495. " series, 410, 479. Benzine, 425o (4). Benzoic acid, 500. alcohol, 500. aldehyde, 500. Benzoin, Gum, Exp. 313, p. 365. Benzol, 221c, 482. Benzyl compounds, 500. Bergamot, Oil of, 509. Berythium, 305. Bessemer steel, 371. Bi-, see Di-. Bicarbonate of sodium, 269. of potassium, 279. Bichromate of potassium, 381c. Binary acids, 1236. " compounds, 59. Bismuth, 254. Bisulphate of sodium, 267c. Bisulphide of carbon, 201. Bituminous coal, 181. Bivalent, 92a. Black ash, 268a. Black-band iron stone, 354. INDEX. 417 Figures refer to Paragraphs Black lead, 173. Black oxide of manganese, 376cf. Blast furnace, 359. Blasting gelatine, 472. Bleaching powder, 2926. Blende, 131a, 301. Blister steel, 370. Bloom, 356. Blower, App. 17. Blowpipes, App. 17. Blowpipe, The compound, 41. Blue indigo, 507. " Nicholson's, 499. " Night, 499. " vitriol, 334. Bohemian glass, 234a. Bone-black, 186. " phosphate, 295. Boracic acid, 173. Borax, 172, 271. Boric acid, 173. Boron, 172. Bottle glass, 234c. Brandy, 4316. Brass, 303a, 322. Braunite, 375. Bread making, 229. Brimstone, 132<2. Britannia metal, 388a. Bromine, 115. Bronze, 322, 347, 388. Brown sugar, 226. Brucia, 526. Bulbs, Blowing, App. 40. Bunsen burner, App. 15. Butane, 413a. Butter, 446. " of antimony, 253tf. of tin, 389. Butterine, 452. Butyl, 413a. " alcohol, 432a. " glycol, 456. Bntylene (CH 8 ), 456. glycol, 456. Butyric acid, 435a. " fermentation, 519e. Butyrin, 446. unless othenvise specified. C Cacao, 527. Cadmium, 306. Caesium, 285. Caffeine, 527. Cairngorm-stone, 232a. Calamine, 301. Calcareous waters, 293. C*alcic, see Calcium. Calcite, 289. Calcium, 289. " carbonate, 293. " chloride, 291. " chloro-hypochlorite, i " hydrate, 292. " hypochlorite, 2926. light, Exp. 49 ; 290- ' " oxides, 290. " phosphate, 295. etearate, 294a. sulphate, 294. Calomel, 342. Calx, Note, p. 246. Camphor, 410a. Canada petroleum, 425. Candle paraffin, 425d. Cane sugar, 226, 517. Caoutchouc, 410a, 514. stoppers, App. 8. Capric acid, 435a. Caproic acid, 435a. Caprylic acid, 435a. Caramel, 226c. Carbohydrates, 517. Carbolic acid, 484. Carbon, 177. disulphide, 201. " dioxide, 196. " group, p. .55. " monoxide, 193. " oxides, 192. Carbonic acid, 198. anhydride, 196. Carbonyl, 1946. Carburet, Note, p. 164. Carnallite, 276. Carnelian, 2320. Casein, 223. Casserite, 385. Cast iron, 358. 418 INDEX. Figures refer to Castor oil, 451. Catalysis, 81, 519. Caustic lime, 292. Lunar, 332. " potash, 280. soda, 270. Celestine, 296. Cellulose, 230, 517. Cementation steel, 370. Centesimal computations, 130. Ceric, see Cerium. Cerium, 353. Cerotate of ceryl, 447. Cerotic acid, 435a. Cerous, see Cerium. Ceryl cerotate, 447. Chalcedony, 232a. Chalcocite, 131a, 319a. Chalcopyrite, 319a. Chalk, 289. Chamber acid, 152c. Charcoal, 184-191. Chemical action, 11. " affinity, 8. " changes, 10. " equations, 127. Chemism, 8. Chemistry defined, 13. Chili nitre or saltpeter, 2716. Chinese wax, 447. Chloral, 434. u hydrate, 434. Chlorate of potash, 281. " of potassium, 281. Chloride of antimony, 253d. " of ethylene, Exp. 209. " of hydrogen, 104. " of lime, 2926. " of methyl, 209. " of nitrogen, 113. Chlorine, 98. acids, 112. " Diatomic, 174. " group, 123. u oxides, 111. Chloroform, 209. Chlorohydric acid, 104. Chocolate, 527. Chrornates, 508. Chromatic series, 479. Paragraphs, unless otherwise specified. Chrome alum, 381$. " iron ore, 381. " yellow, 3166, 381c. Chromic acid, 3816. Chromite, 331. Chromium, 381. steel, 381. Cider, 4316. Cinchona, 525. Cinchonia, 525. Cinchonine, 525. Cinnabar, 334, 340. Cinuamic acid, 507. Cinnamon, Oil of, 509. Clay, 233, 344. " iron-stone, 354a. Cloves, Oil of, 509. Coal, 181, 184, 186. 11 gas, 221. " oil, 425. " tar, 221c. Cobalt, 378. Cochineal, 508. Cocks, App. 20. Codeine, 523. Cod-liver oil, 449. Coffee, 527. Coin, 328, 379, 396. Coke, 182. Collection of gases, 21 ; Exps. 15 and 185. Colloid, Exp. 218. Colored glass, 234A. Coloring matter, 508. Columbium, 260. Combining weight of compounds, 63. " " of elements, 64a. Combustible, 43. Combustion, 33. " Spontaneous, 451. Common fats, 446. Composition of elementary molecules, 65. Compound blowpipe, 41. u ethers, 422a. " radicals, 97. Compounds, 6, 12. Computations, 128-130. Concentrated lye, 270. Coma, 521. Conine, 521. INDEX. 419 Figures refer to Paragraphs, Constitutional symbols, 95. Cooking .