CHEMISTRY SIMPLIFIED. CHEMISTRY SIMPLIFIED. A COURSE OF LECTURES ON THE NON-METALS, BASED UPON THE NATURAL EVOLUTION OF CHEMISTRY. DESIGNED PRIMARILY FOR ENGINEERS. GEORGE AUGUSTUS KOENIG, Ph. D., A. M., E. M., PROFESSOR OF CHEMISTRY, MICHIGAN COLLEGE OF MIXES, HOUGHTON, MICHIGAN. ILLUSTRATED BY ONE HUNDRED AND THREE ORIGINAL DRAWINGS. PHILADELPHIA : HENRY CAREY BAIRD & CO , INDUSTRIAL PUBLISHERS, BOOKSELLERS AND IMPORTERS, No. 810 WALNUT STREET. 1906, COPYRIGHT, BY GEORGE AUGUSTUS KOENIG, 1905. PEEFACE. IN these lectures to mature beginners in Chemis- try, the fundamental idea has been followed to unroll before the student the knowable nature of bodies as an ever-growing and spreading picture, and not as a finished work handed down by the great masters. When I say mature beginners, I mean that in my estimation chemistry should not be taught at all to boys and girls before their full mental growth has been attained, fully aware of my isolated position in the present evolution of schools. Only the mature mind follows with growing interest the unfolding of such a picture, and absorbs it as a living thing. In following this fundamental idea, the usual systematic classification .had to be abandoned. It will be seen that the beginning is made with bodies of familiar acquaintance such as the common metals, but these metals are not postulated as elements or simple bodies ; they are merely objects for experi- mentation in allowing the equally familiar bodies of air and water to act upon them under the familiar impulse of heat. Noting the changes thus wrought, the mind questions and seeks answers. Answers come by carefully laid experiments, but always in (v) 295603 VI PREFACE. such a way that no agent of unfamiliar nature is called in to aid. Such a scheme is essentially his- torical, for the successive generations of chemists have been working in exactly this way. They saw and raised questions. Their answers, being pre- mature in so far as they brought into play unknown agents, were often wrong, had to be set aside and much modified by subsequent investigations. Thus also in these lectures, questions are raised, but not answered at once, although perfectly well known, because the student's knowledge has not reached the required fullness. In the chapters on green vitriol and on common salt, as well as on potash, the reader will find the application of the funda- mental idea fully elaborated. Generalizations from the experiments are always drawn, though I have avoided the term law. The- orizing upon molecules and the structure of mole- cules, ions and electrons I have omitted altogether. No beginning student can be capable of drawing inferences for himself concerning these matters. They should only be brought before the student at the end of his school work, if he intends following chemistry. To bring them before proposing en- gineers, seems unnecessary, if not unwise, and these lectures are delivered to engineering candidates, more especially mining engineers and metallurgists. To them the theories can be of no help. They want to know the practical consequences which must follow from the presence of certain material condi- tions. They must be trained to inquire, and de- PREFACE. Vll duce from given conditions. The chief tendency of the lecture course is to evoke in the student the constant thought of Why ? together with the love for the experiment. The course extends over seven months and one-half, in three lectures a week. It is supplemented by laboratory work of eight hours per week in which some fifty-odd experiments, se- lected from the lecture experiments, are performed by the student. The chemistry of the metals in conjunction with qualitative analysis comprises the second year's work of equal time-extension, but only two lectures a week. The illustrations are made with the chief aim of engineering simplicity. Thanks are duly given to each and every chemist who has given a laborious life in contributions with which to build up the chemistry of to-day. THE AUTHOR. HOUGHTON, MICHIGAN, November 15, 1905. CONTENTS. CHAPTEE I. THE NATURE OF AIR AS A MIXTURE OF GASES. Introductory remarks 1 The nature of air . - - 3 Deductions ; How much air will be absorbed by a given weight of copper ? 5 How much air will be absorbed frcm a given volume of copper? 7 Calibration of the apparatus 8 Deduction . . 11 Ozone and azote ; Weights of air, nitrogen and ozone ; Sulfur . 13 Is the burning of sulfur similar to the scale-forming of copper? 14 Use of litmus ; Acids ; Definition of an oxyd 15 General deductions ; A deoxydizing substance, carbon .... 16 Metals and non-metals 17 CHAPTER H. THE NATURE OF WATER. The ancient version of things ; The kinds of water 18 Physical properties of water 19 Chemistry 21 Action of steam on iron and zinc 22 On copper ; Keverse proof 23 Hydrogen ; Electrolysis 25 Oxygen ; Deductions ; Inverse proof . 31 Explanation of action ; Law ; Idea of an atom 33 Hydrogen peroxyd 34 CHAPTEE III. GREEN VITRIOL OR COPPERAS. Description 35 Chemical investigation ; Deduction 37 (ix) X CONTENTS. PAGE Presence of sulfur established ; The oil of vitriol ....... 40 Preparation of a quantity of the oil 41 Investigation of the oil 43 A different oil 44 Work with this other oil, the liquid residue 45 A higher oxyd of sulfur 46 Action of the liquid residue on lead and silver . 47 Investigation of the white fumes that crystallized 49 Summary ; Direct proof of the presence of water in the liquid residue, the sulfuric acid 50 Proof of the volume composition of the sulfur oxyd, SO 2 ... 52 The dilution of sulfuric acid 54 Molecular weight ; Hydrates of sulfuric acid . 55 Action of sulfuric hydrates on the metals 56 The iron vitriols. 58 Preparation of sulfur dioxyd 59 Generation of hydrogen 61 Koenig's generator 62 CHAPTER IV. THE LEPSON OF LIMESTONE. The lime minerals 64 Action of heat on calcite 65 Partial proof of the lime gas 67 Study of the residue 70 Formation of lime hydroxyd 71 Action towards acids . . . . , 72 Action of the lime gas upon the lime hydroxyd ... . . 73 Deduction . . 74 Summary of the limestone lesson 75 CHAPTER V. THE LESSON OF WOOD ASHES. Wood and coal ashes 76 Potash ; Investigation of the lye 77 Potassium hydroxyd 79 Hydrates 80 Proof of the hydroxyd nature of solid caustic potash 81 CONTENTS. XI PAGE Action of the preceding substances on the vitriol solutions . . 82 Potassium . . . 84 Physical and chemical properties of potassium * 87 Use of potassium in finding the non-metal in gas from limestone. 88 Alkaline substances 91 CHAPTER VI. THE LESSON OF COMMON SALT. Forms of natural salt * 92 Investigation . 93 Work with the salt gas . 94 Chlorine . ... . . . 98 Preparation of chlorine. . . . 99 Chemical properties of chlorine 104 Chlorate . ... 105 Process for making potassium chlorate ; Composition of salt gas. 106 Properties of hydrogen chlorid 107 HC14-water . . 108 Advantages of different driers Ill Acid hydrometers 112 The discovery of the metal sodium, by working with the salt cake 113 Physical and chemical properties of sodium 116 Oxyds of sodium 118 CHAPTER VII. THE STORY OF SODA ASH AND LEBLANC. The Leblanc soda process 119 Sodium carbonate and bicarbonate 121 Caustic soda ; Lye balls ; Kelp 122 CHAPTEK VIII. ON THEORIES, COMBINING WEIGHTS, ATOMIC WEIGHTS AND VALENCES. A uniform system of writing formulas 123 The idea of radicals . 124 The electrochemical series ; Valence 12 Xll CONTENTS. PAGE The atomic weights of the elements ; Molecular weights and volume weights . . - 126 Hydroxyl radical ; Sulfate instead of vitriol 129 Atomic weights of calcium, copper, lead and zinc ...... 130 Atomic weights of silver and gold . . . 131 Relation between atomic weights and specific heats of the ele- ments 132 Law of Dulong and Petit ; Review of the action of chlorine on the alkaline hydroxyds 133 Dichloroxyd ... 134 Chlorates. ... 135 Oxygen from chlorates .... 136 CHAPTER IX. BROMINE, IODINE, FLUORINE. Bromine from the mother liquor of the salt works 137 Compounds and actions of bromine ... 138 Iodine 139 Properties of iodine ; Starch and iodine 141 Compounds of iodine 142 General remarks 143 Ismorphous substances ; Fluorine 144 Flux 145 Investigation of the fluorite gas 146 Composition of the gas 148 The etching process 149 The nature of fluorine ; The metal in fluorspar 150 CHAPTER X. LECTURE ON NITER OR SALTPETER. The kinds of niter 152 Solubility ; Investigation of the soda niter 153 The nature of nitrogen 154 The spirits of niter 155 Aqua regia 156 The properties of nitrogen 159 Properties and composition of spirits of niter 160 Nitrates , 164 CONTENTS. Xlll PAGE Gunpowder 166 Calculations on the explosive power of gunpowder 168 Other powders ; Investigation of the nitrous fumes 170 Nitrogen dioxyd 171 Nitrogen monoxyd 176 Proof that the formula is NO 177 Properties of NO 178 The ring test for nitrates 178 Nitrites . . 179 Preparation of KNO* . 180 Dinitrogen trioxyd 181 Nitrite test, using starch and iodine compound ; Laughing gas . 182 Properties of N 2 O 183 Preparation of the gas on a large scale 184 Recapitulation of the oxyds of nitrogen 185 CHAPTER XL AMMONIA, A VOLATILE ALKALI. A COMPLEX METALLIC RADICAL. The nascent state ; Ammonia. 186 Investigation 187 Preparation of ammonia 188 Sal-ammoniac 189 Composition of ammonia 190 Proof that hydrogen is contained in ammonia 191 Proof that ammonia contains no oxygen ; Demonstration that the formula is NH 3 192 The chemical nature of ammonia 194 Ammonium ... 195 Indirect proof of the ammonium theory . : 196 Formation of ammonium compounds 197 Liquid ammonia 200 Preparation of ammonia water 201 Carbonates 203 Sal-ammoniac 204 Soldering, with use of sal-ammoniac . - 205 Solvay process , 206 XIV CONTENTS. PAGE CHAPTER XII. ORIGIN AND OCCURRENCE OF NITER. Sources of nitrogen . 209 Niter plantation 210 The Chili niter deposits 211 The origin of the deposit 212 Conversion of soda niter into potash niter 213 CHAPTER XIII. THE MANUFACTURE OF HYDROGEN SULFATE OR SULFURIC ACID ON A COMMERCIAL SCALE. Direct proof that H 2 SO 4 results from the union of SO 3 with H 2 O . 216 Cost of the sulfur-nitric acid method ; The SO 2 -nitric acid method 217 The lead chamber process. 218 Sulfur from pyrite 219 The plant needed 220 The Glover tower 222 Size and cost of plant . 224 The Gay-Lussac tower 225 The Lunge-Rohrmann plate column 226 Concentration of the chamber acid ...... 227 The Gridley system ; Lemaire and Co.' s stills 228 Loss of platinum; Manufacture of oil of vitriol by Winkler's method . t . . . . 230 The direct contact method 231 CHAPTER XIV. OTHER COMPOUNDS OF SULFUR. The sulfid ores 233 Hydrogen sulfid 234 Proof of the formula, H 2 S 235 Generation of H 2 S in a steady current at a minimum of cost . 236 Properties of H 2 S ,237 Action of H 2 S on KOH 239 ActionofH 2 8onNaOH;OnCa(HO) 2 240 Calcium monosulfid 241 CONTENTS. XV PAGE Action of sulfur on the alkaline hydroxyds 242 Sodium hyposulfite and its manufacture 243 Test for thiosulfate 244 Action of H'S upon solutions of metallic salts 245 Examination of the precipitates obtained 249 Hydrogen persulfid 253 Sulfur chlorid and carbon disulfid 254 CHAPTER XV. CARBON COMPOUNDS; ORGANIC BODIES. Native carbon 257 Coal 258 Carbon dioxyd 259 Chemical properties 260 Composition of CO S 261 The atomic weight of carbon ; Carbon monoxyd , . 262 Proof of the composition of CO 263 Structure of plants . . . 264 Experiments with cellulose 265 The formula of cellulose derived from the results of combustion. 266 Parchment 270 Xitro-cellulose, gun-cotton 271 Gun-cotton as an explosive 272 Destructive distillation of wood 274 Charcoal ; Pyroligneous acid 276 Acetic acid 278 Wood tar 279 Carbolic acid ; Picric acid 282 Paraffin .... 283 Analysis of wood gas 284 Marsh gas, methane 294 Safety lamp 300 The theoretical importance of marsh gas . 301 The marsh gas or paraffin series of hydro-carbons 302 Propane ; Butane ; Isomerids 303 Pentane . . 304 Carbonyl-hydroxyl ; Wood subjected to pressure and heat. . . 305 XVI CONTENTS. CHAPTER XVI. MINERAL COAL AND ITS CHEMISTRY. The kinds of coal 308 Composition of coal 310 Ultimate composition 311 Proximate composition ; Origin of coals 312 The coking process 316 Coke 318 Coal tar ; Naphthaline ; Nitrobenzol . 320 Anilin ; Complex base ; Methylanilin 321 Rosanilin ; Mauvanilin 322 CHAPTER XVII. THE GASES FROM THE DISTILLATION OF COAL ; THE MANUFACTURE OF ILLUMINATING GAS AND GAS COKE. The qualitative composition of the coal gas 324 Dissociation at high temperatures ; Plan for gas works .... 325 The dimensions of the plant 329 Water-gas 331 Fuel-gas 333 Rock-oil, petroleum . . 335 Chemical properties ; Refining of the crude oil 336 The flash-point ; Natural gas . 337 CHAPTER XVIII. THE HOMOLOGUES OF CELLULOSE STARCH, DEXTRIN, SUGARS. The wheat grain 339 Starch 340 Chemical properties of starch ; Dextrin 341 The sugars ; Cane sugar 342 Grape sugar 343 Fruit sugar 344 Milk sugar ; Gum arabic 345 CHAPTER XIX. ALCOHOL, SPIRITS OF WINE, ETHYLHYDROXYD. The production of alcohol 346 Fermentation ; Yeast 347 CONTENTS. XV11 PAGE The manufacture of ethyl alcohol 348 Absolute alcohol 349 Properties and chemical constitution of alcohol 350 CHAPTER XX. SOME IMPORTANT DERIVATIVES OF ALCOHOL. Ether, ethyl oxyd 352 Chloroform . . 353 lodoform ; Aldehyde ; Chlopal ... 354 Mercuric fulminate; Preparation of the fulminate 355 Manufacture of percussion caps 356 Silver fulminate 357 CHAPTER XXI. SOME ORGANIC ACIDS. Formic acid and acetic acid 358 The manufacture of vinegar 360 Oxalic acid 361 Chemical properties ; Methods of manufacture 363 Lactic acid and tartaric acids 364 Tartar emetic 365 Citric acid ; Malic and tannic acids ' 366 Ink 367 Leather 368 Gallic and pyrogallic acids 369 CHAPTER XXII. THE VEGETABLE FATS AND ANIMAL FATS. Plant oils 370 Animal fats 371 Chemical action of fats 372 Glycerin 373 Manufacture of glycerin 374 Tri-nitro-glycerin ; Dynamite 875 Manufacture of nitro-glycerin ; Tallow 376 Soap ; Drying oils . 377 Turpentine 378 Rosin .379 XV111 CONTENTS. PAGE Eubber 380 Vulcanizing of rubber ; Ebonite. . 382 CHAPTER XXIII. ORGANIC ALKALOIDS. Theobromin ; Caffein ; Urea ; Morphin 383 Chinin ; Strychnin; Brucin and Atropin 384 Cocain ; Nicotin 385 CHAPTER XXIV. ALBUMEN AND ALBUMENOIDS Albumen 386 Haemoglobin ; Haematin 387 Fibrin ; Casein ; Horn, hair and skin 388 Distillation of albumenoid substances 389 Neat's-foot oil 390 CHAPTER XXV. ORIGIN OF CYAN IDS. The discovery of the yellow prussiate of potash 391 Potassium ferrocyanate 392 Potassium cyanid and its preparation 393 Chemically pure potassium cyanid 394 Hydrogen cyanid ; Prussic acid 395 Preparation of prussic acid and of cyanogen ; Composition of cyanogen ; Sulfocyanogen and sulfocyanates 397 Potassium ferricyanate 398 Potassium cyanate ; Cyanuric acid 399 Fulminic acid 400 CHAPTER XXVI. BONE-ASH AND PHOSPHORUS. Bone-ash 401 Experiments on the bone-ash 402 The discovery of phosphorus "..._.. 404 The modifications of phosphorus ... 405 Red phosphorus 406 Black phosphorus ; The atomic weight of phosphorus ; Phos- phorus pentoxyd 407 CONTENTS. XIX PAGE Preparation of phosphorus pentoxyd ; Orthophosphoric acid. . 408 Preparation of the ortho-acid ; Orthophosphates 409 Microcosmic salt. . - 410 Insoluble orthophosphates ; Molybdate test 411 Pyro- and metaphosphoric acids and their preparation .... 412 Phosphorus trioxyd ; Phosphorous acid 413 Hypophosphorous acid ; Phosphorus trichlorid .... . 414 Phosphorus pentachlorid ; Phosphine 415 Preparation of phosphine 416 Composition of phosphine ; Phosphonium 417 Liquid hydrogen phosphid ; Metallic phosphids 418 APPENDIX. The chemical elements, their symbols, equivalents, and specific gravities 419 Table for the comparison of the scales of Reaumur's, Celsius's, and Fahrenheit's thermometers 421 Rules for the conversion of the different thermometer degrees into each other 422 Table of the liter weights of gases 423 INDEX . . 425 \ Of THE ERSITY OF IFQR1 CHEMISTRY SIMPLIFIED. CHAPTER I. THE NATURE OF AIR AS A MIXTURE OF GASES. INTRODUCTORY REMARKS. I show you this small copper ingot. It was made by pouring liquid cop- per, at a yellow heat, into an iron mould. You notice a bright red color on the sides and bottom, a dark reddish-gray on the upper side, and a pale yellowish-pink on this spot which I scrape with the knife. By drilling a hole through the ingot, or by sawing it into two we find the pale, soft yellow- ish-pink color persistent throughout the interior. Hence we infer that the yellowish-pink is the true color of copper, while the red and gray-red at the outside must be due to a change which happened to the ingot during the time when it passed from yellow heat to the temperature of the room. If we do not take this change as a simple matter of fact, but if instead we ask for the reason of the change, then our mind is scientific, it is above the average, and there is hope for us. Now there are two ways for satisfying this desire for the reason for things. Along one way we just ask the nearest man or the handiest book, along the other way we set to work it out ourselves. Following the second and much harder road, we become investigators and inventors. 2 CHP;MISTRY SIMPLIFIED. You have come here to learn chemistry, and my duty is to show you the way. I may lead you along the first trail by means of a book and recita- tions and my own acquired knowledge of the nature of things. However, I choose to take you by the second trail, difficult in steep slopes and rapid descents, but which will ultimately take you, when the pass shall have been won, into the beautiful valley of intellectual satisfaction and fruitful tech- nical invention. Some may get exhausted on the journey, and some may not have the right eyes to see, the right hands to grapple with the difficulties ; for them of course there is no hope and they must take the other trail, they will not become leaders in the profession. Those who are born with right desire will ultimately get to the goal by any road whatsoever ; but they will have spent much time, much energy, in doing useless things. My object, as your teacher, is to point out things to you so that you may save the waste and arrive much more rapidly at the pass. Let us return to our ingot and ask : What causes the copper to be of different colors on the outside from the inside ? This question we name, by gen- eral consent, a chemical question because the change which happened to the outside of the ingot is a per- manent change, by which the substance has acquired different properties throughout. If I bend this wire there is also a permanent change, but it is only a change of shape, the copper itself has not changed any of its properties. If we inquire about this change of form in the new positions of the copper NATURE OF AIR AS A MIXTURE OF GASES. particles, we have to deal with a proposition in physics. There are, of course, many changes in which physics and chemistry overlap, when we must enter into both sciences. It is merely a matter of convenience, for the sake of more effective work that this division into physics and chemistry has been made. One set of men pursue the one set of phenomena, becoming more expert in observation than if they spread themselves over both sets. 1. The nature of air. Pursuing the question concerning the changes at the surface of the copper ingot, we shall now insti- tute experiments, every one of which will give rise to new questions. In Figs. 1, 2, 3, 4 the trial arrangements are set up to meet those questions. In Fig. 1, a bright piece of sheet copper A is placed within the non-luminous or purplish part of the flame F. It is evident that here the metal will be exposed to the action of heat, to the action of air and to the action of the substance of the flame. The metal at bright red heat, under these condi- tions covers itself with a dark scale, which peels off and is found to be very brittle. In Fig. 2, the metal A is within the hard-glass tube T, which is closed at one end, open at the other end. The substance of the flame does not come in contact with the metal, but the heat of the flame is conducted through the glass, the metal becomes red hot and covers itself with a very thin film. Here the air has access, but 4 CHEMISTRY SIMPLIFIED. limited. Fig. 3, shows the metal strip A within a tube T. The tube was then drawn out at (7, leaving a narrow neck, was then connected with an air pump until all air was drawn out, when the neck C was allowed to close up by means of a sharp, hot flame (blow-pipe flame). If then the tube T be FIG. l. A FIG. 2. made red hot in the flame jP and kept so for any length of time, we find, on cooling, that no change has taken place, the copper is bright with its fine pale yellowish-pink color. Lastly in Fig. 4, we have the copper strip in a glass tube which is open at both ends. Owing to inclined position a lively air current will set in in the direction of the arrows as NATURE OF AIR AS A MIXTURE OF GASES. O soon as the tube is heated by the flaine. We find quickly that the last conditions produce the most change on the copper the most rapid development of the scale. Deduction from the four experiments: 1. Copper takes from the air, at red heat, a portion of the air and changes to a brittle scale. 2. The substance of the flame does not enter into this change, only the heat of the flame. Two questions now suggest themselves : 1. How much will be absorbed by a given weight of copper? 2. How much of a given FIG. 5. _L_L volume of air will be absorbed ? In order to an- swer the first question rig an apparatus as shown in Fig. 5, where T is an infusible glass tube (so- called combustion tube) not less than J" inside diameter. The tube is bent over the blast lamp. Place the tube in a horizontal position by means of clamp-stand 5. Select a porcelain boat sufficiently narrow to pass into the tube easily. Clean and weigh the boat. We choose glazed porcelain because it will not become soft except at white heat, because it does not change in weight when heated 6 CHEMISTRY SIMPLIFIED. in air. Place into this boat about 0.100 grain of copper filings, that is to say you must take the weight very accurately. But it does not matter whether you take 0.095 or 0.102, only by taking 0.100 accurately you will save figuring the percent- age. You are told to take filings, because in this form, the metal will be exposed with a maximum of surface and a minimum volume, which is most desirable, since the intended action proceeds from the surface. Shove the boat into the tube as shown in the figure, and place the lamp so that the entire length of the boat can be brought to redness. The bent part of the tube being bent upwards, a so-called draught will arise as by a chimney, because a col- umn of hot air being in the vertical tube, this hot air being lighter than the cold outer air, the latter will pass in at the lower end and push out the warm air, hence a steady air current will pass through the tube in the direction of the arrow's pointing. Allow this action to proceed for 30 minutes. Do not for- get to place a few fibres of infusible asbestus between the tube and the boat, for the tube may become soft and cause the boat to stick. Should the tube exhibit a tendency to sag you will prop it up at the end by means of a piece of brick. Remove the flame at the expiration of the half hour, let the tube cool down until it can be held in the hand.' Pull out the boat and weigh. Return the boat to the tube, replace the lamps and work for another half hour. Then weigh again. If the second weight is not equal to the first, you cannot be certain that the NATURE OF AIR AS A MIXTURE OF GASES. 7 copper has saturated itself, and a third period of heating becomes necessary, and perhaps a fourth until you get constant weight. Many trials, made with greatest care, show that 0.100 copper will in- FIG. 6. crease to 0.1254 and no further, and thus the result- ing dark gray-black product of change will contain in 100 : Copper 79.6 and air 20.4. 2. How much will be absorbed from a given volume of air f For an answer to this question let an apparatus 8 CHEMISTRY SIMPLIFIED. be rigged as in Fig. 6. We must make provision to pass and repass the same volume of air over the heated copper without any air coming from the outside, nor any air escaping to the outside. Let T again be of hard glass i or -^ inch internal diam- eter and 5 inches long. Introduce a roll of fine copper gauze, 5, then bend the tube into a double L. Paste on a mark at M. Determine or gauge the volume of the tube by filling it with mercury up to the mark M, and then weigh the mercury. If the weight of the mercury be g, then g 1 13.6 = F(in cubic centimeters). Provide two soft glass tubes, S, &', with stoppers, the upper ones to receive the tube T, the lower ones to receive narrow glass tubes, which are connected by rubber tubing, 2, h with the glass syphons 1, 3. These stand in beaker glasses, R, R'. Calibrate the tube S into cubic centimeters, the lower side of the upper stopper forming the mark. Calibration. Stand 8 upside down, after a solid stopper 1, Fig. 7, has been pushed into the mark. Then weigh out (to 0.1 gram) 5 X 13.6 = 68.0 grams of mercury and pour this into the tube. Make a scratch (with a glazier's diamond, with a sharp splinter of quartz, or with a hard file) tangent to the meniscus. Measure the distance from to 5 with a scale or pair of dividers. Lay this distance down a strip of white paper and divide into 5 equal parts. Lay on these divisions beyond five for the whole length of the tube. Then paste the strip upon the tube so that the marks fall together, and then cover the paper on the outside with molten NATURE OF AIR AS A MIXTURE OF GASES. VJ paraffin. Thus your tube is calibrated into cubic centimeters. Weighing out a defined quantity of mercury is not quite so easy as it sounds. Proceed as follows : Place a very small beaker glass upon a so-called pulp balance (it were foolish to use a fine balance because we only want to weigh as close as 0.1 gram). Why ? Because 0.1 gram of mer- cury corresponds to less than 0.01 cubic cent., and we do not care to read a volume closer than 0.1 cubic cent. It would in fact be quite sufficient accuracy if we got any weight of mercury within 1.0 gram. Make a pipette with capillary outlet by drawing out an 8" x J" soft glass tube over the lamp flame as shown in Fig. 8, and cut off with file at point a. Fill this tube by sucking with mer- cur\ T , and let this latter flow into the beaker, until the balance tips. The beaker has been previously balanced by shot, and the required weight, 68 grs., has been placed upon the weights' pan. The first finger closes the upper end of the tube at the moment of tipping. After the apparatus (Fig. 6) 10 CHEMISTRY SIMPLIFIED. has been set up the tubes S, S' being held in place by clamp-stands or tripods or under prop- pings the beaker glasses R, R' are filled with water, the syphons 1, 3 are filled by sucking at the end of the detached rubber tubing until the water comes to the mouth, the rubber being then joined to the tubes S, S'. R' is then raised upon blocks until the water reaches the mark M, while R is lowered until its water level falls together with a division of the scale on S, say for in- stance 10. We are having then a volume of air V equal to 10 plus v (v being volume of tube T). Let v be 5 c.c. for example ; then the total volume will be 10 pins 5 equal 15 c.c. Bring now the burner B under T so that the copper gauze 5 be- comes red hot. Cause the air to move slowly over the hot copper, by lowering beaker R and raising R at the same time. Repeat this movement 10 times. Then remove the burner and let the tube T return to the temperature of the room. Bring the water to the mark M and adjust R in such a way that its water-line and the water-line in S fall into one level. On reading off the position of the water-line 8 on the scale, we will read 7, that is, 3 c.c. of air have disappeared ; 15 c.c. of air have lost 3 c.c., 5 c.c, have lost 1 c,c. Bring the flame NATURE OF AIR AS A MIXTURE OF GASES. 11 back and again pass 10 times over the hot copper. On cooling will find the same result as before ; hence the loss of the air, under these conditions, is constant. Deduction. Air is composed of at least two parts, which possess each decidedly different properties, or in other words : Air consists of two different gases. Now it is well known that men and animals must have air to breathe. Query? Which one of the two gases do they require, or do they need both? As the one gas has disappeared into the copper, we shall have to experiment with the residuum. Let a glass jar J, Fig. 9, be filled with the gas. How ? A two-foot length of }" gas pipe 2 (Fig. 10), is charged FIG. 9. FIG. 10. with copper gauze, and placed in a charcoal fur- nace 4- Rubber tube 5 leads to bottle 6 through a two-hole stopper ; so that the funnel stem 7 may pass through second hole. If water be poured into the funnel the air will be driven through the heated copper, and the -J- residuum will pass through 1 into the inverted and water-filled jar / whose open end is supported under water by metal blocks in the basin B. We will now do a little figuring. We 12 CHEMISTRY SIMPLIFIED. found above that 1 gram of copper can absorb 0.25 gram of air. One litre equals 1000 c.c. of air and weighs 1.2932 gram, hence -J- of this weight is 0.258, that is one single gram of copper is sufficient to take the absorbable gas from one litre or one quart of air. 50 grams of copper will furnish (50x4)/5 equal 40 litres of the gas we desire. But for our experiment, that is to fill the jar, we will not need more than one or at the most two litres supposing that the whole of the water has been displaced in J so that the bubbles will come on the outside. We remove first the tube 1, then the supporting blocks and push a flat glass plate under the water, and press it with the hand against the jar rim, lift the jar out and stand it bottom down on the table as in Fig. 9. A mouse having been trapped, we drop the animal from the trap into the jar and replace the glass cover plate. At once the mouse shows dis- tress, tumbles into a heap, and after a few spasmodic kicks lies quiet and is dead. Hence we draw the con- clusion that the part of the air which is absorbed by the copper, is the part also which sustains animal life. If we introduce a burning taper into the jar it will become at once extinguished, and hence it follows with some considerable probability that breathing, burning and scale forming of copper are similar processes, being in fact, fundamentally, the same phenomenon. It will be necessary, for clearness and conciseness of expression, to distinguish from now on these two parts of the air by separate names. Properly we NATURE OF AIR AS A MIXTURE OF GASES. 13 should say in English life-air and death-air; instead Greek words are chosen by scientists. Life air equals ozone ; death air equals azote. The root of both words is Zoe equals life (zoology equals the science of living things). Ozone equals intense life ; azote equals no life. German chemists made and use the term, stickstoff equal to suffocating stuff; the French hold on to azote, English and Americans now use the word nitrogen which equals niter-pro- ducer Weight of one c.c. of nitrogen equals 0.001256 gram (Regnault). Weight of one c.c. of air equals 0.001293 gram. Hence it follows that ozone must be heavier than air. The weight of ozone follows by calculation. We reduce azote to terms of air by dividing the weight of air into that of azote, 0.001256/0.001293 equals 0.97137 which equals the specific weight of azote or its specific gravity, then we have 4 / L_ s I S' I closed end being charged with several small pieces of vitriol. Let the tube be supported at S, because it has a tendency to sag when the end comes to a red heat. It stands to reason that the tube may be laid upon a couple of bricks for support. Let heat be applied slowly with the burner B to the closed end, and we will be enabled to make the following observations : 1. A plentiful condensation of a liquid in the cool part of the tube. This liquid will appear very mobile, little or no taste and by applying electrolysis will give H + ; its identity with water is fixed. 2. The vitriol meanwhile, is partly melting, raising blisters and turning into a white chalky mass. Deduction 1 : The loss of water causes the vitriol to become white opaque. We raise the temperature to a low redness : A strongly smelling gas appears re- 38 CHEMISTRY SIMPLIFIED. calling the smell of burning sulfur, that is the oxyd of sulfur S n O m . We cause it to act on indigo and lit- mus solutions, the former becomes bleached, the lat- ter turns red ; probability strong that vitriol contains sulfur oxyd though not certain yet. But remem- bering that copper oxyd is decomposed by charcoal at red heat, we may attempt the decomposition of this suppositious oxyd in the same way and with- out much of an outlay in apparatus. Let some vitriol be heated in a porcelain crucible until it has become white, that is, until the greater part of the water has been removed, then fill it into a tube exactly the same as before, that is, at the closed end a, Fig. 21. Let some splinters of charcoal be heated in a covered crucible at full red heat, and when cooled down introduce them into the tube at b ; stopper the tube with cork and gas evolving tube t, the latter leading into basin B filled with water. The water filled test-tube T is held ready to be shoved over the end of t, when it may be assumed that the air has been quite driven from the apparatus by the GREEN VITRIOL OR COPPERAS. 39 evolved gases. The closed end a is first brought to redness, then the charcoal at b is brought to dull redness, or any other degree of temperature we may find advisable. If the gas be decomposable exactly as copper oxyd is decomposed, we must get S n O m + 9 C = S n + m CO + (9 m) C., but since sulfur is a non-metal, it is quite probable that compounds of S and C are generated, for which we must look out. The glass tube is best supported by two bricks, -P, P', stood up on edge. In order to facilitate the deposition of sulfur we protect the part of the tube beyond the charcoal with a diaphragm or screen d. The latter can be a slotted piece of sheet-iron or a piece of asbestus board. As soon as the charcoal becomes red at one spot, we notice a film forming before the diaphragm, which increases in bulk, forming yellow and yellow- brown drops. The water in the basin becomes tur- bid, milky, and a gas of peculiar smell collects in the test-tube. What causes the milkiness ? What is the peculiar smell due to ? . These questions we shall not attempt to answer at this juncture, but place them on the calendar for future study and explana- tion. We let the tube cool down, cut it with file and hot glass rod at the diaphragm, and subject the yellow film to two tests, (a) We scratch out a portion of the unknown yellow substance, place it upon a piece of bright silver foil, and heat it over a flame, until the foil is barely red hot. When cold a black spot or possibly a hole will appear, where the unknown 40 CHEMISTRY SIMPLIFIED. substance was placed, the silver has formed a black compound and this is characteristic for sulfur, (b) We hold the tube inclined to get draught and heat the film in the flame ; we get the pungent odor of burning sulfur. No doubt can remain, vitriol con- tains sulphur oxyd, or at any rate we can say that this gas is one of the products when vitriol is broken up by heat. Now let us return to the original experiment which we left in order to prove the sulfur oxyd. We apply now a very hot flame (best from a Bunsen gas blow-pipe) to the vitriol. White clouds appear in the tube and roll out of the latter ; the substance of this fume is evidently heavier than air. The action of it upon the mucous membrane is energetic, for a suffocating sensation 1 is caused by inhaling it. It causes the muscles of the larynx to contract vehe- mently. At the same time, with the appearance of the fumes, we notice a thick liquid condensing at a little distance from the heated end of the tube. We let the latter cool down and cut it off just at the liquid ring ; as the two pieces come apart another installment of white fume appears. Why? We apply litmus-paper to the liquid ; it turns intensely red, but soon after turns brown, and finally the rim gets black ; the paper has been charred. De- duction : The liquid possesses qualities of an ex- traordinary nature. The great experimenter who discovered it in the 10th century, the Moor Geber in Spain, gave it an Arabic name which was trans- lated into Latin : oleum vitrioli the oil of vitriol, GREEN VITRIOL OR COPPERAS. 41 owing to its sluggishness in flowing like a thick olive oil, and because it produced a lubricating of the skin when rubbed between the fingers. In order to study the substance, we must design an apparatus which will allow the treatment of a considerable quantity of the vitriol, say one pound. Since we noticed that the glass became quite soft and even collapsed when exposed to the high temperature of the blow-pipe, we must look out for a material which will remain solid as well as rigid at such a temperature. Fire-clay is such a material. Its FIG. 22. plasticity when mixed with water makes it capable of being moulded into any desired form. When carefully dried and then equally carefully baked, it becomes hard, fire-resisting, and fairly gas-tight. In Fig. 22 we see the section of a fire clay retort inside of a fire-brick lined furnace, which is heated by a gasoline flame F. Before filling the vitriol into the retort, we heat it in an open dish or large crucible until all the water is driven out, and until it has turned a light brick red, that is, at a low red heat, since we only care for the white, cloudy fumes 42 CHEMISTRY SIMPLIFIED. and not for the sulfur oxyd. Then we fill the ma- terial V through the tubulature at S and fasten the stopper or plug by means of pasty fire-clay. Over the neck of the retort N, we pass the neck of the large glass flask R loosely, to furnish exit for the gases. The flask we bed into a mixture of salt and broken ice (freezing mixture) contained in a basin 1 and over the upper side of the flask we spread a muslin bag I' filled with the same mixture. Why ? In order to expose a maximum of cold surface to the fumes, having seen in the preliminary experiment that the fumes do not condense at the ordinary tem- perature. The lid of the furnace having been put in place, we light the flame under strong air pressure and soon the retort will show cherry redness on the outside. But since the fire-clay wall of the retort is but a poor transmitter of heat, some further time must elapse until the material Fgets to that temper- ature. Then we see the white fumes pouring into the flask, falling like a foaming cataract to the bottom and also issuing at the neck of the flask. Hence the apparatus should stand under a good up draft or alongside a good down draft. The heat will be mod- erated or increased according to the volume of white vapor issuing from the neck N. If no more fume comes say after two hours even at a yellow heat of the retort, we stop the operation. We remove the basin I and the bag I' and wipe the outside of the flask dry. Three facts are observable : A brownish thick liquid about 50 c.c. ; snow-like crystals of needle shape all over the flask ; and a dense fume still filling GREEN VITRIOL OR COPPERAS. 43 the flask. We pour the liquid into a large test-tube, or into a smaller flask. During this operation quan- tities of the white fumes arise suffocatingly from the liquid, wherever the air touches it. Query ? Which constituent of the air causes this action? Azote, oxygen or the water vapor ? By experimental elim- ination we fix the action upon the water vapor = moisture, of the air. Withaut moisture no fumes. Hence it follows that the roasted vitriol must still contain some water, or else we could not see the fumes inside the glass tube in our first experiment. Two immediate investigations must now be un- dertaken ; we must first try to get at the inwardness of the crystallized substance, and secondly, of the liquid substance. a. Investigation of the oil of vitriol, the liquid substance. If put upon the skin, a drop will raise a blister and actually burn a hole into the flesh, de- stroying the tissue thoroughly. Brought together with a drop of water a hissing sound is caused. If water be splashed or poured into a larger quantity of the oil, so much steam is generated by the evolution of heat, that the liquid is thrown violently from the vessel and has often injured the careless operator. Paper is charred into a slimy, black substance by the oil. White sugar arid starch are changed into the same black substance. The oil smells strongly of the sulfur oxyd gas, and when heated emits white fumes, until at the end a liquid results, nearly colorless, which does 44 CHEMISTRY SIMPLIFIED. not fume at the air, and does not smell of sulfur oxyd. This colorless liquid boils at 326 C. (a very high temperature), giving likewise dense white fumes to the air, when boiling, which condense into a colorless heavy liquid, thus differing from the white fumes of the oil, which condense into a snowy solid. With an arrangement as in Fig. 23, we can prove FIG. 23. these points. In the small retort on the left of the figure we place some 10 c.c. of the oil of vitriol, using a long-stemmed funnel, so that the neck shall not be moistened with the liquid. At 3 we have a thermometer not reaching into the liquid ; fasten it into the tubulature with asbestus thread. The retort is held by a clamp from stand 4. At 5 we have a U-tube connected by a narrow tube with the neck of the retort through a cork. The U-tube is also fitted with perforated stoppers and stands between broken ice or snow in the beaker glass 6. Any liquid, condensing in the retort's neck, GREEN VITRIOL OR COPPERAS. 45 will flow back. Heating with burner 8 using a very small flame, we soon get the smell of sulfur oxyd alone at 7, and later on associated with white fumes. At the same time the walls of the U-tube become frosted over with white, needle-shaped crystals. When the temperature has risen to 300 C., we stop heating and remove the U-tube ; noticing the fumes arising from the cold substance in the tube, as soon as moist air comes in contact with it. Now let us change the* position of the retort by turning the swivel of the FIG. 24. clamp holder. The neck points downward, Fig. 24, and reaches into a dry test-tube. Raise the heat so that the liquid gets into boiling commotion. Streaks and streamers of thick liquid will run down the neck and collect in the test-tube 8. Hence it follows that by heat we can split the oil of vitriol into three parts : a gas (sulfur-oxyd); a solid (?); a liquid residue (?). The question-marks stand for : must be found out. The liquid residue. Let it be acted upon by the metals. Bring about 2 c.c. of the liquid in a test-tube 46 CHEMISTRY SIMPLIFIED. together with a piece of copper foil. No action is noticeable until we heat, when effervescence ensues. (Effervescence means frothing due to rapid produc- tion of gas bubbles in a liquid.) The smell charac- terizes the escaping gas as sulfur oxyd. Further we notice the forming of a grayish, granular substance, and the copper foil has disappeared ; it has become changed or converted into the white granular sub- stance. These interesting facts lead us to a suppo- sition or hypothesis that our liquid must contain an oxyd of sulfur containing more oxygen than the gasi- form oxyd. If the latter be symbolized as S n O m , then the hypothetical oxyd would be S n O m + p in which symbol p denotes the mass units of oxygen which were given over to the copper enabling the latter to go into solution, through the abstrac- tion of this oxygen from the higher oxyd to form the lower sulfur oxyd with its characteristic smell. But in order to verify the supposition we must ex- amine the white granular product of the action. We pour off the liquid, add water to the granular resi- due, and see it go rapidly into solution with a pale- blue color. The solution we evaporate on a water- bath. At a certain point of the evaporation a solid begins to form. We allow the liquid to cool and a larger crop of blue crystals will form. The crystals are translucent, show an oblique symmetry, in fact resemble the crystals of our original vitriol. Hence the deduction will be rational that the crystals are copper vitriol. (A crystal placed upon a knife blade with a drop of water produces a bright copper spot OF THE UNIVERSITY OF COPPERAS. 47 upon the blade.) We dry the crystals between filter paper and bring some into a closed tube. On heating, as in the original experiment, we observe water first, and the vitriol turns white. At higher heat, full redness, we note some sulfur oxyd gas, and at still higher heat, when the glass begins to melt, a ring of oily liquid (oil of vitriol). On cooling the vitriol has become jet black, and the black body, under the circumstances is evidently copper oxyd. The chain of evidence is complete. This copper oxyd must have been contained in the copper vitriol. And hav- ing put metallic copper into the liquid, the copper oxyd can only have formed by taking oxygen from a higher oxyd present. The latter is an oxyd of sulfur, because sulfur oxyd forms during the opera- tion. We symbolize the operation or action thus : pCu + 2pS n O m +P = pCuO.S n O m +P + pS n O m . A vitriol thus defines itself as the combination of a metallic oxyd with sulfur peroxyd, the syllable per meaning more. Both vitriols contain water, but that does not mean that all vitriols must contain water. ACTION OF THE LIQUID RESIDUE UPON LEAD AND SILVER. If we bring a piece of lead foil or very thin 'sheet lead into a test-tube with the liquid residue, there is no action at the ordinary temperature. On heating we notice a whitish film on the metal which again disappears. But on further heating there is at once 48 CHEMISTRY SIMPLIFIED. an impetuous action, with formation of sulfur oxyd gas and a very fine granular white substance. Like- wise a yellow streak appears in the upper part of the tube. Lead vitriol is white and remains white when we add water, and furthermore does not dis- solve even in a very large amount of water. We collect the white substance on a filter, wash it thor- oughly and let it become dry in the air. In the closed tube, when heated to redness it gives no water, but over the gas blow-pipe it decomposes leaving yellow lead oxyd, the latter entering into combina- tion with the glass at this high heat, forming a yellow transparent compound. The yellow streak on the upper tube we can readily prove to be sulfur. We crack off the tube near the streak, wash thoroughly with water, dry and then heat over a flame. The yellow streak will melt and then burn with a blue flame, giving the smell of sulfur oxyd. This fact, teaches us that, while under ordinary conditions a metal takes from sulfur peroxyd only enough oxygen to convert the peroxyd into the oxyd, under extraordinary condi- tions of stimulated chemical activity, the oxygen may be taken away altogether from the peroxyd, leaving sulfur in the free state. We bring a piece of silver foil into the liquid residue and heat, when action sets in, the foil dis- appearing, without being changed into a solid res- idue ; in other words, the silver vitriol is soluble in the liquid. If water be added to the cooled liquid, cautiously, a white crystalline powder will GREEN VITRIOL OR COPPERAS. 49 soon fall out, but will again dissolve when much water is added, that is, the silver vitriol is soluble in water and soluble in the concentrated liquid residue, but not soluble in the moderately dilute liquid residue. Of the solution of the silver vitriol we will soon be able to make some important use. Gold is not attacked by the liquid residue, and hence a very important deduction follows that if gold and silver are united in the form of an alloy, they may be separated by means of this liquid residue, and are thus separated in the Mint and the Metal Refineries. INVESTIGATION OF THE SOLIDIFIED OR CRYSTALLIZED WHITE FUMES. We take now the U-tube which contains the snowy deposit. We notice the inner surface of the corks strongly blackened (same action as shown by the oil as well as the fumes, even at ordinary temperature). On pulling the cork white fumes develop (again like the oil). We let a drop of water run down the side of the glass. A hissing noise is produced, and a drop of heavy, oily liquid, runs to the bend of the U. By adding drop after drop of water, we convert all the solid, snowy substance into the brownish-colored liquid, which latter, by this time, has become burn- ing hot. We act with this liquid upon the metals as we did with the Liquid Residue. The action is exactly the same in both cases, forming vitriol and sulfur oxyd. Hence it follows that the solid product from the distillation of the oil of vitriol, or in other words, the white fume must be sulfur peroxyd. But 4 50 CHEMISTRY SIMPLIFIED. then it follows inversely that if the sulfur peroxyd be converted by water into a liquid, whose action is the same as the Liquid Residue, then the latter must be sulfur peroxyd plus water. Stated sym- bolically this means White fume = S n O m + p = Sulfur peroxyd. Liquid Eesidue == S n O m +P. H 2 = Sulfur per- oxy-hydroxyd. Sulfur oxyd = S n O m . Oil of Vitriol = S n O m + P. H 2 + S n O m +P + S n O m . And since sulfur oxyd and sulfur peroxyd are expelled from the oil by heat, we express the pre- vious condition by saying : Sulfur oxyd and sulfur peroxyd are dissolved in the sulfur peroxy-hydroxyd, and thus form the oil of vitriol. The latter is a stable compound of the two oxyds, which cannot be broken up by boiling ; it distills over at 326 C. without decomposition. Instead of saying sulfur peroxy-hydroxyd we will say in future sulfuric acid, because the substance has eminently the characters of an acid body ; but the other name expresses better its make-up. DIRECT PROOF OF THE PRESENCE OF WATER IN THE SULFURIC ACID. By holding before us the actions of this sub- stance upon the metals which we have observed we can deduce, among others, the following reasoning : (a) If lead is converted by the acid into a vitriol, i. e., a combination of lead oxyd with sulfur per- oxyd plus sulfur oxyd we must get lead vitriol also. GREEN VITRIOL OR COPPERAS. 51 by bringing together lead oxyd plus sulfuric acid without the forming of sulfur oxyd. (b) Lead vit- riol does not take up water, (c) Therefore if we mixed thoroughly an excess of yellow lead oxyd with a certain quantity of sulfuric acid, then the water must be liberated if any be contained in the acid. In order to reduce the argument to trial, we shall mix 5 c.c. of concentrated sulfuric acid with 50 grams of yellow lead oxyd in a small wedge-wood mortar until the paste is almost powder. We fill this into a test-tube. Place the latter in a horizon- tal position as shown in Fig. 25, where 1 is the tube FIG. 25. I H MA T4. w V J holding the mixture 3/ with a delivery tube passing through the jacket J fed with cold hydrant water H, which runs through the discharge tube D into the sink. Almost at once, after applying a flame gently back and forth under Jf, a condensation of mobile liquid, water in fact, takes place at W t much steam passes into the tube, is condensed by the cold jacket and collects in test-tube R. The first distillate is 52 CHEMISTRY SIMPLIFIED. nearly, not altogether, pure water. It will show acid reaction to litmus ; but if one cubic centimeter be drawn out and weighed, the weight will be so nearly one gram, that for our purposes we may ac- cept it as one gram and thus experimentally show the sameness with water. We have proved that sulfuric acid is or in other words that it is a vitriol in which hy- drogen oxyd takes the place of other metallic oxyds. SO 2 . We have arrived at a stage of development when we will be able to reason out the ratio in which sulfur and oxygen are united in the gasiform sulfur oxyd. Let us make a bent (knee-shaped) tube K, Fig. 26. Fill it with mercury and hold it with a proper clamp and stand in the mercury trough P. By heating a certain peroxyd (known as potassium chlorate) in a test-tube we can easily make pure oxygen gas and cause it to rise in the knee-tube until the mercury shall drop to an arbitrary mark M. We will then shove a piece of sulfur under the opening and let it rise to the surface. A piece of soft copper wire rolled into a spiral at one end will GREEN VITRIOL OR COPPERAS. 53 enable us to push the sulfur to the end of the tube at 5. A strip of gummed paper can now be used to mark the new mercury level. If a flame be now brought under 5, by slow degrees to avoid crack- ing the glass, then 5 be strongly heated to the point of ignition of sulfur, we will suddenly see the mercury get into strong up-and-down motion. This means that union between sulfur and oxygen has taken place. Heating is stopped when the mer- cury has become quiet. When the apparatus has returned to the temperature of the room, we find that the mercury has risen to the mark. Hence it is evident that oxygen changes into sulfur oxyd without change of volume. Or we can say one vol- ume of S n O m contains one volume of O. But how much sulfur has entered into the volume? Evi- dently we find this by subtracting the weight of one volume of oxygen from the weight of one volume of S n O m . Let the latter be W and the former W, then W . _ W == S' (weight of sulfur in the gas). Now we need only to know how much one vol- ume of sulfur weighs to solve our problem. These values have been determined and reduced to air as unity ; they are 1 vol. S n O m == 2.210 : hence W W= (2.21 1.105) 1vol. -1.105: =1.105 1 vol. S =2.200: = S' : so S' = J S : because -l - 54 CHEMISTRY SIMPLIFIED. hence follows SO 2 as expressing the volume ratio between the two bodies. Thus we see that 1J volumes of the free gases when combined only occupy one volume con- densation of one-third. The same was true of hydrogen and oxygen when they combined to water. If the true numerical symbol for sulfur oxyd be SO 2 , which we necessarily pronounce sulfur dioxyd, what is the symbol of the sulfur peroxyd? The answer is SO 3 . You will prove this yourselves at a later stage of this course, and just simply accept the fact. The vitriols are therefore : H 2 O.S0 3 =Hydroxyd vitriol = Sulfuric acid. CuO.SO 3 = Copper oxyd vitriol = Copper vitriol. PbO.SO 3 =Lead oxyd vitriol = Lead vitriol. ZnO.SO 3 = Zinc oxyd vitriol = Zinc vitriol. FeO.S0 3 =Iron oxyd vitriol = Iron vitriol = copperas. Ag 2 0. SO 8 = Silver oxyd vitriol = Silver vitriol. The writing of silver oxyd Ag 2 is based upon experiments and reasonings which we cannot now go into, but which will appear shortly. The dilution of sulfuric acid. If we make that experiment in which we proved the presence of water in the liquid residue or the concentrated sul- furic acid, with great care, weighing the acid taken and weighing the water which results, we obtain in a given experiment, when we took 20.54 grams of the acid, 3.77 grams of water; hence the concen- trated acid contains in 20.54 grams: SO 3 equal 16.77; H 2 = 3.77. We also know that S = 20, GREEN VITRIOL OR COPPERAS. 55 that is, the sulfur as gas weighs for equal volumes twice the oxygen, S = 32, therefore 1 sulfur = 32 X 1 = 32. Also 2H = 2x1= 2 3 oxygen = 16 X 3 = 48. 1 oxygen = 16 X 1 = 16 Sum 80 Sum 18 The numbers 80 and 18 stand for the mass units of SO 3 and IPO, or as other chemists say, they repre- sent their molecular weights. The experiment gave us SO 3 =16.77: 80 = 0/2096: 1 H 0= 3.77: IS = 0.2094 '- 1 By dividing into these numbers the molecular weights, we change the weight numbers into molec- ular quantities. We get equal quotients and have thus established that the symbol H 2 O.S0 3 is the true quantitative expression for that concentrated acid, which distills without breaking up. We take this concentrated acid and add water, mixing the two ; the mixture becomes hot. We conclude of necessity that a chemical union has been effected. Let the addition of water be rational instead of arbitrary. Let the quantity of concen- trated acid taken be 100 grams, which contain : SO 3 = 81.6 ; IPO = 18.4. By adding with a graduated tube or cylinder 18.4 c.c., we will have added just one other mass-unit of water ; the resultant liquid will be H 2 O.S0 3 .H 2 = ml/uric acid monohydrate, containing in 100 parts : SO 3 = 68.9 ; IPO = 31.1. After this liquid has resumed the normal tempera- 56 CHEMISTRY SIMPLIFIED. ture of the room, we take of it again 100 grams, add to this 18.4 grams of water, and mixing, find again a rise of temperature, but much less than before. Unquestionably another chemical union of lesser strength of hold, the H 2 O.S0 3 .2H 2 = sulfuric acid dihydrate, containing in 100 parts : SO 3 = 58.2 ; H 2 = 41.8. Repeating the operation a third time a very slight rise in temperature follows. Hence we conclude that the H 2 O.S0 3 .3H 2 == sulfuric acid trihydrate, containing in 100 parts : SO 3 =49.2 ; IPO =50.8 is the last hydrate. Beyond this figure water is not held in chemical, only in mechanical, union, which we can very properly express by the symbol H 2 O.S0 3 .3H 2 + aq., in which aq. stands for Latin aqua == water ; this is dilute acid. ACTION OF HYDRATES OF SULFURIC ACID UPON THE METALS. The mono- and di-hydrate act in a boiling solution the same as the acid upon lead and copper, that is, SO 2 is disengaged and the vitriols form. The trihy- drate does not act upon lead or copper. . But if we bring this trihydrate upon zinc or iron a violent evo- lution of gas results. The gas, however, is not SO 2 . It has a peculiar odor, more marked with the iron than with the zinc. But the gas is inflammable, and if the flame is inside a cold test-tube, water GREEN VITRIOL OR COPPERAS. 57 condenses fast. The gas is, therefore, mostly hydro- gen ; the odor coming from other bodies contained in the iron and zinc, so-called impurities. The pro- cess may be represented by symbols, thus H 2 O.S0 3 .3H 2 + aq. + Zn == ZnO.SO 3 + 3H 2 -h aq. + H 2 , for if the liquid be evaporated after the action, zinc vitriol crystallizes. In other words, we may de- scribe the process thus : Zinc oxyd has a stronger tendency to form vitriol than hydrogen oxyd. The zinc therefore takes the oxygen away from the latter and thus liberates hydrogen. We may extend this idea to the former reaction, where SO 2 is evolved, thus Zn + H 2 O.S0 3 == ZnO.SC 8 + H 2 . H 2 + H a O.S0 8 == SO 2 + 2H 2 O. The power inherent in " nascent " hydrogen is such that it will decompose SO 3 into SO 2 -j- IPO, but this power does not exist in the dilute solution. The result is just the same as if we say the metal, zinc for instance, takes the oxygen from SO 3 . Acting upon iron chips with dilute sulfuric acid, we get finally a muddy, dark -colored solution and the hydrogen gas is strongly tainted with other gas of a fetid, unpleasant odor. When the liquid stands, it gradually becomes clear with a bluish- green color, a black sediment having fallen to the bottom. We remove this by filtration and find that the dried, black substance can be burnt like coal ; it is a peculiar kind of coal called graphite, and the 58 CHEMISTRY SIMPLIFIED. fetid gas is a combination of the coal with hydrogen (C n H m ). Zinc likewise leaves a residue, but this does not burn. We shall see at a later stage that the residue is due to certain metals and non-metals, always present in the crude, commercial zinc. But let us return to the bluish-green liquid. We will evaporate the liquid upon a water-bath until a crust forms over the surface, which signifies the beginning of crystallization. Then we set it away over night and find next morning a crop of greenish crystals. They are identical in form with the vitriol we started our experiments with ; they also act in the closed tube in the same way, when heated. We have thus a direct proof that vitriol, the so-called copperas, is iron vitriol. Yet when we take the red solid residue obtained from the destructive heat- ing of the copperas, and boil that body with sulfuric acid and trihydrate, we get a yellow solution, from which, by evaporation, yellow, scaly crystals are deposited. This is an undoubted vitriol, but not copperas, yet containing all the elements of the latter. Hence no other deduction is possible than the following : There must be two oxyds of iron, as we found a red and a black oxyd of copper, an SO 2 and an SO 3 . These oxyds are presumably FeO and FeO 2 . But which of these is in copperas, and which is in the yellow crystals ? A very neat little process of inductive reasoning will give us the an- swer. It has been observed at the beginning of this chapter that when a solution of copperas in water stands exposed to the air, a yellow film will form at GREEN VITRIOL OR COPPERAS. 59 the surface. That this must be due to the action of oxygen, because in azote, no such film comes into being. We can accelerate the forming of the yellow precipitate by blowing air into the liquid. If we dissolve this yellow solid (after separating it from the liquid by filtration) in dilute sulfuric acid, we get, after evaporation, the same yellow crystals as we did from the red oxyd + sulfuric acid, and if we heat the yellow substance (not the crystals) we get in fact the red oxyd. Therefore it follows that cop- peras contains the lower oxyd, and the red oxyd is the higher oxyd. Just how the proportions of oxy- gen and iron stand we cannot, now, prove; but let us assume that this proportion is 1/1 for the lower and 2/3 for the higher oxyd. Then we can write Fe + H 2 O.S0 3 + aq. = FeO.SO 3 + aq. + H 2 , but we can explain, even now, why we get so much SO 2 in the earlier stages of vitriol distillation. Namely : SO 3 we saw is a strong oxidizing agent, and hence *the lower iron oxyd changes at its ex- pense into the higher oxyd. 2(FeO.S0 3 ) + 7H 2 + heat = 7H 2 + SO 2 + SO 3 + Fe 2 O 3 . We must of necessity get just as many molecules of SO 2 as we can get of the more useful oil forming SO 3 . Practical application of some parts of the lesson of oil of vitriol. 1. How to prepare, on occasion of need, sulfur dioxyd (SO 2 ). A 250 c.c. flask 2 is filled to about one-half with thin lathe chips of cop- per. The stopper funnel 1, Fig. 27, is filled with 60 CHEMISTRY SIMPLIFIED. sulfuric acid monohydrate. B is a burner ; 4 a wash-tube partly filled with water ; 5 a drying tube, one-fourth filled with concentrated sulfuric acid, and 6 a bulb tube filled with glass beads which have been moistened with concentrated sulfuric acid. Why? Because up to a certain point we have FIG. 27. found an extraordinary attraction of this acid for moisture. Now if the acid flows from 1 into # upon the chips, while heat is properly applied, a stream of pure SO 2 will soon displace all the air from flask and tubes, so that presently pure, dry gas issues from 6 ready for any desired purpose. When dry gas is not required, the tubes 5 and 6 are left out. After the chips are used up, the flask must be cleaned out ; it is best though to clean it out immediately after the GREEN VITRIOL OR COPPERAS. 61 need is past, because the vitriol will become as hard as rock and the flask be much in danger. 2. How to Generate Hydrogen. This substance is very often required, and in large quantities, for filling a balloon, for instance. For small quantities you may use the apparatus just preceding, Fig. 27. The flask 2 is partly filled in this case with granu- lated zinc, and dilute acid is fed into the funnel 1. Make the acid 1:20, that is, 20 volumes of water for one volume of the acid. You will find that such a simple contrivance is all right for a small volume of gas, but not for more, and what you do get comes very fast at first, then ever slower. Why? Because the dilute acid becomes a solution of zinc vitriol, which renders the acid more and more weak. Many devices have been designed to get a better result. The adjoining figure, Fig. 28, shows my own design, which has given complete satisfaction to all those who gave it an intelligent trial. The principal part of the apparatus is a glass tube G drawn slightly into a neck N, and at the lower end into a narrow tube 0, to which latter is fitted a stout rubber tube R. The latter forms a U, has a glass nozzle P, and thus discharges the dilute solu- tion of zinc vitriol into the glass jar TT. This tube G, which we better name the " generator " is filled with the granulated zinc. It is surrounded by a wider tube / which is melted at both ends together with the generator, thus forming a jacket. The latter can be filled with water through the tubula- ture E. The function of the jacket is to keep up a 62 CHEMIbTRY SIMPLIFIED. FIG. 28. B KOENIG'S GENERATOR. GREEN VITRIOL OR COPPERAS. 63 temperature of about 70 C. in the generator. To this end a 5-millimeter glass tube t has been melted into the jacket obliquely. The middle portion of the tube is of brass and is here heated by a little flame which burns from a glass tube or from a Bunsen burner. A rubber stopper closes the neck N and through it passes the funnel tube F which should be 12 inches long. The whole apparatus is held in vertical position upon two brackets which may either be attached to a portable stand Q or may be put against the wall under the hood permanently. The zinc is prevented from falling into the rubber tube by the " false bottom " D made of porcelain. After the jacket has become hot you fill the bulb of the funnel with the dilute sulphuric acid 1:20, and also fill water into the generator until it begins to run from the nozzle P. Now open the stopcock of the funnel so much that a drop falls from the stem every second, and soon a steady stream of hydrogen will issue from the tubulature L. The gas will be free from air sooner than in any other form of generator. The gas will be washed and dried as shown above. When the column of zinc has fallen by three inches, it should be filled up ; but that in- cludes a steady running for a whole day. For much use, a large reservoir bottle, holding the dilute acid, should be rigged up above the funnel, so that the acid can be drawn into the cup of the funnel by means of a syphon. CHAPTER IV. THE LESSON OF LIMESTONE. WE have before us three productions of nature, which to the eye are very different. The first is a large crystal of dog-toothed spar, calcspar or cal- cite, quite common in our copper mines, notably at the Quincy Mine, where it is intimately associated with the native copper. This particular crystal comes from the zinc-lead mines of Joplin, S. W. Missouri. You will notice that one end of the crys- tal shows three lustrous faces intersecting over the edges at an angle of a hundred and five degrees nearly a rhombohedron whilst the other end shows six faces intersecting at alternately different angles a scalenohedron because the faces are scalene triangles thus producing the impression of a dog's fang. Parallel to the faces of the rhombo- hedron the mineral cleaves perfectly. I cleave off a piece and you see a small rhombohedron exactly similar to the original one. It is both colorless and transparent, and if placed upon this cross upon white paper we see the lines of the cross double; the two images are close together. The physicists say the mineral has double refraction and give you an explanation according to the present state of their knowledge. From this property the mineral is (64) ' THE LESSON OF LIMESTONE. 65 sometimes called double-spar (the latter word, spar, is given to all minerals which are more or less transparent and show strong cleavage). The second specimen is this whitish rock which is known as crystalline limestone. It shows num- bers of small but splendent faces, each of which is in reality the face of a rhombohedron similar to that of the calcite : or in other words the rock is made up of innumerable calcite rhombohedrons which pre- vented each other from developing individual geo- metric independence. The third specimen is this dull gray rock com- monly known as limestone. In its appearance there is nothing in common with the previous specimens. But all three possess nearly the same relative weight (specific gravity), and an equal power of resistance to a penetrating steel point (equal hardness). The comparison thus far made we call physical, mean- ing therewith that all the given properties have been ascertained without destroying the identity of the original substance. Let us now act upon these materials with the powerful agents in our posses- sion, whereby the original identity will become modified or wholly destroyed, new bodies being produced. The knowledge thus gained will be chemical knowledge, and will greatly widen out our horizon as to the nature of things. 1. Action of heat. Place a fragment of calcite in a glass tube closed at one end, and heat this end to high redness. No odor ; fragment turns dull chalky. It might nevertheless be that an odorless 5 66 CHEMISTRY SIMPLIFIED. gas is evolved. Contrive a rig as sketched in Fig. 29, wherein t is the hard glass tube with the frag- ments. B B are two bricks to concentrate and re- flect the heat rays upon the tube. T is a test-tube filled with water and t' a short bent glass tube at- tached to t by a short piece of rubber tubing. The heat may be produced by means of a blast lamp or by placing over the tube t several pieces of charcoal made incandescent and by then fanning them into combustion by an air blast or by means of an ordi- FIG. 29. nary fan. The heating with coal is much more satisfactory than with the blast lamp. When the tube has come to red heat, we observe a steady current of gas bubble through the water into the test-tube. The gas is odorless and evi- dently not soluble in water to any considerable ex- tent. Now we found the gas from the copperas to give a sour taste to the water, aside from the strong, pungent odor ; hence we examine the present gas in the same direction. Water is not changed to the taste but blue litmus paper is slightly reddened. We say the lime gas has a weak acid nature. It does not burn or explode as hydrogen and does THE LESSON OF LIMESTONE. 67 not stimulate or increase a burning as oxygen. It is of all gases thus far encountered most like azote. But in making soap bubbles with it, the latter immediately fail to the floor ; hence the gas must be much heavier than air or azote (the latter being -f of the air) and moreover azote does not im- part sour or acid properties to the water. Thus we are forced to the conclusion that this lime gas is a new body. But if so, we ask, is it a simple or com- pound body ? In order to find answer to this ques- tion, let us do some reasoning by comparison : The copperas or iron vitriol is crystallized or transpar- ent ; it has been proven to be composed of two oxides + water. Calcite is crystallized and trans- parent, gives off a slightly acid gas and leaves a white opaque solid. Hence we will be justified in the assumption that calcite also is composed of two oxyds, one metallic, the other non-metallic. This is an hypothesis (the word is the Greek equiva- lent for either supposition or assumption). Proof for the gaseous or volatile part. If the gas be an oxyd like water (as steam) it may be possible to break it up by a metal such as zinc, or, as we saw with the oxyds of iron and copper, heat and char- coal might do it. Let us choose zinc in the form of these bright chips. It will be necessary to produce a small but steady current of the lime gas. Having seen that both dilute sulfuric acid and vinegar can decompose the calcite and the limestone, we choose 68 CHEMISTRY SIMPLIFIED. the vinegar. Why ? Because the latter gives a so- luble product, whilst the sulfuric acid gives a milky solution or a white mush, an insoluble vitriol. In the flask F (Fig. 30) bring about 20 grams of finely ground calcite or limestone with about 50 c.c. of water. Into the funnel V pour concentrated vine- gar acid, acetic acid, because the Latin word for vinegar is acetum. With the help of a small flame a steady current of gas can be made for quite FIG. 30. V T s a while, admitting more acid in small portions as needed. In the hard-glass tube T at Z lay the zincj chips between two asbestus plugs. The flame L will bring Z to red heat. Stand S with clamp K holds T in position. But since we want to prove an oxyd, it is evident that such proof would become impossible if the gas were to enter T at once, for the gas is charged with water vapor and we know that water will yield oxyd when brought together with red-hot zinc. We therefore interpose the test-tube D which is partly filled with concentrated sulfuric THE LESSON OF LIMESTONE. 69 acid, through which the gas will have to rise in bubbles. We do this because we found that oil of vitriol absorbs water with very great energy. It is a dryer. Had we not observed well and noted this property we would now stand before an impassable obstacle. But going as we do, the discoveries come apace with their immediate practical application. Xow we begin the generation of the gas. The latter, being heavier than air, forms a steadily thickening layer over the liquid in F, driving the air before it and out of the entire apparatus. We keep on patiently until at least two volumes equal to F have been generated to make quite sure that the air is completely displaced. For if any remain our results could not be conclusive, since some zinc oxyd would surely.be formed, whether the lime gas were an oxyd or not. Zinc is coming to redness ; a white cloud appears on the glass. But in order to find what becomes of the gas let a rubber tube be brought under a test-tube G filled with water, and it will be seen that the tube soon fills with a color- less, inflammable gas. The zinc is oxydized. Now we may assume that the inflammable gas is the element Y or a lower oxyd of Y and symbolize thus : YPO + qZn + red heat = YP + qZnO or YPO + Zn + red heat YPQ^ 1 + ZnO. This alternative brings us up against the wall once more. Unless we shall happen to discover a metal with greater attraction for oxygen than the zinc, we shall not be able to prove directly that the com- 70 CHEMISTRY SIMPLIFIED. bustible gas is an element or a lower oxyd. Let us not despair ; of wonders and signs of wonders there is no end. Study of the residuum. In order that this residue may be as much freed from the gas as possible, let us pour it from the glass tube into this platinum crucible. This latter being infusible we may con- centrate upon it a much higher heat than was pos- sible in the glass tube. Lifting the lid we see the pieces emit a white glow, whilst the metal of the crucible is only yellow. We say the lime is highly incandescent. The pieces still show the rhombo- hedrons of cleavage ; there is even luster upon the faces. The volume is the same but the weight has decreased 44 per centum. Cohesion has decreased. This residue is known as burnt lime caustic lime (" caustic" being merely the Greek for burnt). It has been known for ages to both civilized and savage peoples. Since limestone forms the surface rock for many square miles in large tracts of country all over the earth, the first burnt lime was made when the first man living in a limestone country made a rough fireplace with the pieces of rock around him. According to our hypothesis burnt lime ought to be an oxyd X n O m , the oxyd of a metal X whose properties we do not know. For if we try upon this lime the same agents which yielded us the metal from the oxyds of iron and of copper, namely intense heat (by the blow-pipe) and char- coal, our trial will end in failure ; the white mate- rial remains quite unchanged. What was said of THE LESSON OF LIMESTONE. 71 the final nature of the element Y above, applies here in regard to X. Let it stand for the present as X, or since we called Y the lime gas, let X be the lime metal We may even designate by the symbol Ca (the first letters of the word calcite), since we designate iron by the symbol Fe (the first letters of the word ferrum)-, yet ever bear in mind that it is a suppositions, a hypothetical simple body of whose properties, in the first state, we are ignorant. This ignorance does not prevent us from studying the behavior, the properties of the supposed oxyd. First towards water. Let a drop of water fall upon some of the caustic lime, a hissing noise ensues ; a slight cloud of steam arises ; the lime swells up and falls into an extremely fine powder : Flour of lime. The flour can be dried at steam heat and yet this dry flour will yield water in the closed tube, at red heat, and lose 24.3 of its weight. After cooling moisten the lime and it will hiss with water as before and fall into flour. Hence we say the burnt lime has a very strong affinity for water, and will form with it a true union, a chemical compound, a hydroxyd, very much as the sulfur oxyd SO which forms the hydroxyd we called sulfuric acid. Deduction : Both metallic oxyds and non-metallic oxyds form hy- droxyds. Flour of lime = lime hydroxyd = Ca n O m .H 2 0. Adding more water the lime hydroxyd turns into a white paste : Slaked lime. If we add much water, shake and stir thoroughly and then let stand, we notice that apparently the whole of the white paste 72 CHEMISTRY SIMPLIFIED. will settle, leaving a clear liquid above. Deduc- tion : Lime hydroxyd is very little if any soluble in water. However, the water has a decided taste, and turns reddened litmus paper to blue. Hence it is an agent, and we call it lime water. By evaporat- ing 1*00 c.c. in a weighed dish, we obtain a residue of hydroxyd of 0.1 gram 1000 lime water hold 1 hydroxyd. Second, towards acids. Make a -^ p. c. solution of sulfuric acid and of vinegar or acetic acid. Because sulfuric acid has a specific gravity of 1.83, we will require 0.054 c.c. to give us 0.1 gram (1.83 : 1 = OJ : 0.054), that is, just one small drop for the 100 c.c. of water. The strongest acetic acid has sp. grav. 1.05, nearly the same as water. Two small drops of it will give the strength wanted with 100 c.c. of water. Pour 25 c.c. of each of these very diluted acids into 2 beaker glasses, add a little litmus solu- tion to each, which will produce red color. Now slowly add clear liine water from a graduate into the first beaker glass. All at once the red color changes to blue, when a certain number of c.c. have been added. The same with the acetic acid. We deduce : The two bodies of opposite action to litmus saturate each other so that a neutral body results, the . neutral body is the salt. Let M stand for any metal, and N for any non-metal, then M n O m .H 2 = hydroxyd = base N n O m .H 2 == hydroxyd = acid M n O m .H 2 O -f N n O m .H 2 = M n O m .N n O m (salt) -f 2H 2 THE LESSON OF LIMESTONE. 73 The three conceptions are fundamental in chem- istry. Base, acid, salt. Yet neither base nor acid is to be understood in the absolute sense. Two metallic hydroxyds may act as base and acid towards each other, or in other words one is more basic than another. We shall find examples as we proceed. This much, however, impress upon your mind : An oxyd is rarely an active agent ; in order to make one oxyd act upon another oxyd strong external impulse is needed, such impulses being heat and electricity. The internal activity becomes manifest towards the surroundings with the forma- tion of the hydroxyd. This will become clearer in the next chapter. Allow a portion of the liquid, in which you have saturated the lime hydroxyd with the sulfuric acid, to evaporate on a watch crystal. Groups of crystals will be formed, colorless, needle-shaped. Examine them with a microscope. They are often stellar, that is, radiating from a centre. When heated these crystals will loose water readily ; they are CaO.SO 3 + 2H 2 O a vitriol in which two mole- cules of loosely-bound water of crystallization are tacked on to the salt proper as in iron vitriol and copper vitriol. Action of the lime gas upon the lime hydroxyd. Lime water is the iV per cent, solution of the lime or calcium hydroxyd in water. Generate the gas as above and let it bubble through some of the solu- tion in a test-tube ; a turbidity appears at once which gradually turns to a milky white color and white 74 CHEMISTRY SIMPLIFIED. sediment. Filter this upon a small paper filter, dry it. It has no taste. Heat some of it to yellow heat upon a bit of sheet-iron (platinum preferable but too costly) ; after cooling transfer it to a slip of reddened litmus paper and moisten with one drop of water. Observe that it slakes and the litmus turns blue under the white mass. Place another minute quantity of dry precipitate upon a watch glass or plain glass slide and examine, after moisten- ing it, with a high power of the microscope. Minute but perfect transparent rhombohedrons appear. Hence deduction : Lime gas converts lime hydroxyd into calcite from which we started. High heat breaks up the combination of the two oxyds ; at low heat (temperature of room) they recornbine. Con- clusion : Very high heat always counteracts the chemical attraction, tends to separate the minute mass-units. Now let the lime gas bubble through another portion of the lime water and leave it for some time, being called away. On returning we find the original rnilkiness all gone ; evidently the calcite has been dissolved in an excess of gas. Boil the clear solution and shortly milkiness as well as sediment reappears. Conclusion : Boiling heat expells the solving excess of gas, the dissolved calcite being it- self almost insoluble (one part in 250,000 parts water), must precipitate. This is the reason why the hard water of limestone regions always gives a sedi- ment after boiling and the boiled water becomes soft. Here is some lime water which has been standing for quite a while in the open beaker glass. THE LESSON OF LIMESTONE. 75 Note that a film has been forming on the surface. The film shows iridescence in strong sunlight. Re- move some to a glass ^ slide and you will find with a high power the identical rhombohedrons. De- duction : If calcite forms under these conditions it is evident that the lime gas must be part of the atmosphere. And since the film forms much more rapidly in a crowded room than outside, we must reason that lime gas forms part of the effluvia or gaseous emanations of the human body. Another important side-gain is that the hardening of mortar must be owing to the absorp- tion by the slaked lime of the lime gas in the air. Mortar is a mixture of 80 to 85 parts of sharp sand with 20 to 15 parts of quick-lime in the slaked condition. All the actions observed are identical for calcite, crystalline limestone and common limestone; their substance is identical, though their look is very different. This must be noticed, however, that the gas evolved from common limestone possesses a fetid odor which is owing to oily matter often contained in the limestone. * Summary of limestone lesson. Discovery of a gase- ous oxyd whose non-metal Y is at present unknown. Of a metallic oxyd (probably) whose action towards the acids is equal to the oxyds of iron and copper, though we do not know the metal contained therein. The oxyd differs by its tendency to form hydroxyd and by its action on litmus paper, which we call basic action. CHAPTER V. THE LESSON OF WOOD ASHES. WE have before us the familiar and homely material ashes. There are evidently two kinds. For in the one we find fragments of partly coaled wood, and in the other hard, glassy nodules known as clinkers. The first is the remnant from burning wood, the second the remnant from burning coal in a kitchen range. Why should I bring these mate- rials before you ? They look unpromising enough. Because I find, upon trial, that the wood ashes pro- duce a strong, biting taste similar to that of slaked lime, whereas the coal ashes show no taste what- ever. There must be something in the wood ashes outside of the ordinary earth calling for investiga- tion. The Roman historians tell us that when their armies came in contact with the Teutonic tribes on the Rhine, they found it a custom among these for the women to do up their hair with a kind of ointment, and this they made up from fat and wood ashes. It was indeed what later on was called soft soap. Whilst these people were at that time, 2,000 years ago, barbarians much like the American Indians, they had the spirit of investiga- tion stalking among them, and this spirit is stalk- ing among them now. When linen and woolen (76) THE LESSON OF WOOD ASHES. 77 cloths had superseded the skins of animals, the original hair ointment was found to possess excel- lent cleansing properties ; the manufacture of soap became a separate trade, and wood ashes came to be an article of commerce. The early pioneer in America, for many years, had nothing to exchange for grocer- ies and other store goods but the ashes which he collected from burning out his clearings in the for- est. However, the valuable part of wood ashes is only about 30 per cent.; the storekeeper had no use for the 70 per cent, of waste. The farmers were made to extract the valuable portion with hot water, to strain the liquid through canvas, to boil down the liquid to solidity, in iron kettles or pots, hence the 'commercial product came to be called potash. This material is not yet pure ; it is of brown color, and contains other soluble parts of the ashes. It undergoes a refining process, becomes white, and goes under the name of pearl-ash. How- ever, wood has become so scarce everywhere that it can no longer be burnt for the sake of the ashes. How means were found to replace it successfully, in more recent times, we shall see in a following chapter. Investigation. We have boiled down the liquid the lye, " lie " (pronounce lee) in French, " lauge " in German. In Germany potash was called " laugen- salz " salt made from the lye. First let us see how the potash acts at high heat. We place some in a hard -glass tube closed at one end. First some water condenses in the upper tube. 78 CHEMISTRY SIMPLIFIED. At red heat the substance becomes liquid, and then we observe small gas bubbles arising from the con- tact between the liquid and the glass, the mo- bility is changed to sluggish flow. Question : Have the escape of gas bubbles and change of flow anything to do with an action upon the glass? or is it inherent in the potash itself? To answer, let the glass tube be substituted by a metallic vessel, say an iron crucible. The potash melts as before but no bubbles come ; the liquidity remains the same. It follows that escape of gas is caused by in- teraction or reaction upon the glass. Potash is fusi- ble at red heat unchanged : remember this important fact. Act with sulfuric acid or acetic acid upon the dry potash and upon its solution in water. In either case there is strong effervescence. We apply the same procedure to the examination of the gas which we used with the lime gas. We find the gas in all its actions like the lime gas. Moreover, a white granular salt falls out when sulfuric acid de- composes the potash, a vitriol. Therefore we will be 'justified in the assumption that potash is com- posed of two oxyds : PO.Y n O m in which P as the first letter of potash, stands for a metal as yet unknown to us, because its vitriol is unlike the known vitriols in its crystal form, unlike also as to solubility, and especially unlike in this, that heat does not break it up ; the vitriol PO.SO 3 stands the heat of the blast-lamp, as I here THE LESSON OF WOOD ASHES. 79 show you in the glass tube. The vitriol is more like the lime vitriol than like the iron and copper vit- riols ; since the action of potash and lime hydroxyd are both basic to litmus. Since heat neither breaks up the potash nor the potash vitriol, how shall we get at the hypothetical oxyd PO ? Let us reason : We found calcite insoluble, but convertible into oxyd. Suppose we bring the solution of potash together with the lime oxyd in this test-tube, and let this be represented by the scheme : PO.Y n O m + CaO + water. CaO will become slaked lime with the water, we will then get PO.Y n O m + CaO.H 2 + water + boiling heat. We notice turbidity at once, then flocculency, then a granular precipitate. We filter. The filtrate with sulfuric acid does not give gas, but a granular salt falls out slowly as the liquid cools. The action must, therefore, have been PO.H 2 + water the non-metallic oxyd Y n O m has gone to the lime, and only the hydroxyd PO.H 2 remains in solu- tion. The filtrate causes deeper action on the skin of the fingers, on litmus paper and on the tongue. It also follows that PO.H 2 is much more soluble in water than CaO.H 2 0. Potassium hydroxyd, caustic potash, caustic potassa, potassium hydrate. The first of these names I want you to use. The second and third names are older 80 CHEMISTRY SIMPLIFIED. and still used in the drug trade ; the third name was the current scientific name and is used by the majority at present. But I want it to apply to a separate conception. To make myself clearly un- derstood we will return to the action of water upon oil of vitriol. Represented symbolically we have there to start with : H 2 O.SO a .nSO*. Adding water, little by little, there is much heat, also hissing noise, this lasting until the nSO 3 have combined with nH 2 and we have now only H 2 O.S0 3 our concentrated sulfuric acid the true hydroxyd. But when you add to this more water, both being at ordinary temperature the liquid warms up and can even reach boiling heat. This heat means more chemical union and may be scheduled 1st hydrate H 2 O.S0 3 .H 2 2d hydrate H 2 O.S0 3 .2H 2 3d hydrate H a O.S0 8 .3H 8 nth hydrate H 2 O.S0 3 .nH 2 and similarly : H 2 O.PO = hydroxyd 1st hydrate H 2 O.PO.H 2 2d hydrate H 2 O.P0.2H 2 nth hydrate H 2 O.PO.nH 2 The nth hydrate may be, in fact, what we would ^ THE LESSON OF WOOD ASHES. 81 otherwise designate a dilute water solution of the hy- droxyd. Returning to the matter immediately before us, we evaporate the water solution of H 2 O.PO to dryness in an iron, copper or silver dish. Glass and porcelain are strongly attacked. Prove this statement by using a small beaker glass and a porcelain crucible ; they are not destroyed but lose the lustrous surface and some of their material enters the liquid. After the mass has become dry at boiling-point of water, heat over an open flame. Soon fluidity will occur, more steam will be given off; at red heat white vapors appear and, using a small portion, it will slowly disappear : the hydroxyd is volatile at red heat. But how do we know that this material is hydroxyd still ; why is it not the oxyd, when the lime hydroxyd looses its water so readily at red heat ? Revolving in our minds all the actions heretofore performed, we remember that both iron and zinc decompose water at red heat ; it may even do so when the water is united strongly to another oxyd. The rig will be simple. A short piece of hard-glass, thick-walled tubing closed at one end ; a perforated stopper, a narrow tube drawn into a fine opening and inserted into the stopper will probably suffice. We introduce a piece of the problematic hydroxyd with some zinc shav- ings, insert the stopper, hold the tube by means of a clamp in inclined position and apply heat. With the melting of the hydroxyd, gas bubbles appear, and ere long the mass will want to froth out of the tube, the escaping gas burns, the flame deposits 6 82 CHEMISTRY SIMPLIFIED. drops of water against a cold dish the gas is hy- drogen. In symbols the action is PO.H 2 + Zn + heat == PO.ZnO + H 2 . After cooling we find that the mass is quite soluble in water, all but some remaining zinc chips. Here is one example of two metallic oxyds combining to form a salt, because one, PO, is more basic than the other, ZnO. Thus, whilst proving the hydroxyd, we have incidentally discovered that this latter is a most powerful agent, rivalling the sulfur hydroxyd. It corrodes the skin rapidly ; it destroys paper and sawdust ; it dissolves wool and hair, horn chips and many other bodies. In these actions many interest- ing and useful new 'substances are formed, some of which we will inquire into hereafter. We find our- selves now in possession of the two most powerful agents H 2 O.S0 3 and PO.H 2 0. Acting upon each other they produce the neutral vitriol PO.SO 3 and water. Acting separately, they lend us their latent power. Action of calcite, of potash, of lime hydroxyd, of potassium hydroxyd and their hydrates upon the water- soluble vitriols of iron, zinc, copper. The vitriols are in dilute solution (you). 1. CaO.Y n O m + CuO.SO 3 + boiling heat, escape of gas, green precipitate. + FeO.SO 3 , slight brownish precipi- tate. + ZnO. SO 3 , no precipitate. THE LESSON OF WOOD ASHES. 2. PO.Y n O m + CuO.SO 3 , at ord. temp, blue precip., at boiling turns black, -f- FeO.SO 3 , at ord. temp, light precip., at boiling turns dark. -f ZnO.SO 3 , at ord. temp, white precip., at boiling remains white. 3. CaO.H 2 -f CuO.SO 3 , precipitate at ord. temp. and complete at boiling heat. + FeO.SO 3 , precipitate at ord. temp. and complete at boiling heat. + ZnO.SO 3 , precipitate at ord. temp. and complete at boiling heat. 4. PO.H 2 -h CuO.SO 3 , first blue precipitate which turns black. + FeO.SO 3 , light green precipitate which turns black. + ZnO.SO 3 , white precipitate which dissolves in excess. It can easily be proved that the precipitates formed under (2) are the combinations of CuO, FeO, ZnO with Y n O m , whilst the PO combines with SO 3 . CuO. Y n O m turns black on boiling, because the CuO is not very basic and cannot hold on to the non metal- lic oxyd when the shattering power of heat-waves pounds upon the compound. The same is to be said about CuO.H 2 under (4) the CuO cannot hold on to the H 2 0. The white precipitate (4) in zinc solution ZnO. IPO dissolves in excess of the agent because the soluble salt PO.ZnO forms, thus First : ZnO.SO 3 -f PO.H 2 0=ZnO.H 2 0-hPO.S0 3 . Second: ZnO.H 2 0+PO.H 2 0= PO.ZnO + 2H 2 0. 84 CHEMISTRY SIMPLIFIED. Of iron there are two vitriols a green and a yellow, the latter produced by acting upon iron with the hydroxyd H 2 O.SO 3 when SO 2 escapes instead of hydrogen. The green vitriol contains the oxyd FeO, the yellow vitriol contains the oxyd Fe 2 3 . The two vitriols act differently on our four agents. But the one important action is that of calcite for FeO.SO 3 -}- water -f CaO.Y n O m = no precipitate. Fe 2 3 .3S0 3 + water-fCaO.Y n O m = brown precipi- tate, the action being slow at ordinary temperatures, rapid when heat is applied. Hence we have here a means of separation for the two oxyds of the same metal. (Details for this in the Chemistry of the Metals.) Likewise if the vitriols of Cu, Fe, Zn were mixed together (the iron vitriol being of the green kind), we would be able to separate the oxyds for (Cu and Zn) vitriols precipitate by calcite or chalk and heat, separating the iron. The precipitate boiled with PO.H 2 will leave the CuO as a solid and take the ZnO in solution. Our wealth is in- creasing as we go along. The metal potassium. Having seen that the oxyd PO is not obtainable, but only the hydroxyd H 2 O.PO, and that this latter is quite volatile, their remains only one raw material, the potash. Though it be a salt, the peculiar nature of its non-metallic ox}^d makes it possible to be broken up by coal, at a white heat. Cut a piece of f " or V gas pipe P (Fig. 31) six inches long, fit on a cap C } an elbow E and a pipe R of same length, all joined by thread. THE LESSON OF WOOD ASHES. 85 Fill P with a mixture of charcoal-coated iron chips, 30 grams of fused potash, 10 grams of burnt lime. Screw on E and R and set into furnace F. The latter is heated with gasoline burner B, but a good wind furnace and coke will give a suitable heat also. In order to prevent the pipe from burning through, it is well to coat it over with several coats of char- motte or braise, a mixture of three parts of ground brick and one part of fat fire-clay. The pipe R FIG. 31. is kept cool by a wrapping of blotting paper upon which water drops from the hydrant or spigot. A cork stopper 5 with glass tube permits the gases to escape. The burnt lime was added to the charge to make the potash less fusible ; the iron to hold the charcoal down, preventing it from floating to the top. This charcoal-coated iron is made by heating iron chips and sugar together in a covered crucible until no more gases escape. After yellow heat has been reached, combustible gas will appear and burn 86 CHEMISTRY SIMPLIFIED. at 5 with either a purplish or yellow flame. Keep up the fire for an hour, then cool down. A gray and black loose mass will be found in R If some be thrown into water a hissing will be heard and for a short time a fine purple flame. The black material is a mixture of small metallic pellets and a spongy substance. By returning this mass to a smaller apparatus, of exactly the same form, the metal can be distilled from the sponge and appears then almost pure in E. The electric current also decomposes the hydroxyd PO.H 2 thus : The metal deposits on the FIG. 32. negative pole (cathode) whilst hydrogen forms at the same pole and oxygen escapes at the positive pole. PO.IPO + current = P -f H 2 , -f O 2 It is difficult to keep the metal from burning up again in presence of the oxygen surrounding it. The difficulty may be avoided by pouring some mercury into the crucible (Fig. 32) and some of the third potassium hydrate over it. If now the cruci- THE LESSON OF WOOD ASHES. 87 ble be made the negative pole and the positive pole be a platinum wire, the metal potassium in the moment of liberation combines with the mercury, alloys with it, and thus is kept from the air. The product is the potassium amalgam Hg n P m . We place the latter in a small glass retort and distill off the mercury at 300 C. Potassium remains as a liquid. At a red heat it also becomes volatile and will fill the flask as a fine green vapor. The retort must be kept filled with hydrogen to keep out the oxygen of the air. Physical properties of the metal. Potassium has a silver-white color, strong metallic lustre. But in presence of air tarnishes at once, becoming covered with a gray film. Therefore, the metal must be kept under a liquid which does not contain oxygen such as kerosene. The metal is soft, like fresh putty at or- dinary temperature, becomes brittle below the freez- ing point ; that means it crystallizes, appearing in tetragonal pyramids. It melts at 62.5 C.; at red heat, 730 C., the liquid boils like water; the vapor is green. Its specific gravity is 0.865 (water 1), hence, it floats on water, but sinks in kerosene, sp. gr. 0.76 0.78. The specific heat or heat capacity is 0.166 (water = 1). Chemical properties. Potassium decomposes water with great energy, because of all metals it has the strongest affinity for oxygen. p + H 2 ==PO + H 2 but since an attraction exists between the oxyd and the water the action really is 88 CHEMISTRY SIMPLIFIED. P + 2H 2 = PO.IPO + H 2 . For instance, if you wish to ignite coal-oil which floats on water, you would just throw a piece of potassium on the water, and the oil would be on fire at once. I said potassium had the strongest attraction for oxygen of any metal. Why, then, were we able to dislodge it by iron and by charcoal ? The answer is found in that potassium is so easily volatilized*. We could not separate the calcium from the lime oxyd, because the calcium is not volatile. Proof of the nature of the unknown Y in lime gas. Once in possession of potassium, we will try it upon the lime gas, which zinc only changed into com- bustible gas (see above), and of which we remained FIG. 33. doubtful whether it was Y or a lower oxyd of Y. Let the lime gas be generated from calcite, chalk, or limestone by means of the acetic acid as before. Let the gas bubble slowly through H 2 O.S0 3 , Fig. 33, thence pass it into the combustion-tube t, in THE LESSON OP WOOD ASHES. 89 which a piece of potassium has been placed at P. If the dish D contains the 6th potassium hydrate, as also the test-tube t, then there will be perfect absorption of the gas as soon as all the air is ex- pelled from the apparatus ; because we know that the potassium hydroxyd as well as the different hydrates, absorbs the gas energetically in order to become potash PO.Y n O m . Now let the potassium be heated with the lamp L. It melts, spreading over the glass and forming a perfect metallic mirror. Then it ignites and burns with the characteristic purple flame almost the same as in air, a white smoke developing. Soon the potassium becomes incrusted with a white material and a black material. All the gas becomes absorbed for a while, then reappears in the tube t. This designates the end of the action. After cooling, we remove the mass from the tube. The white portion gives all the actions of potash : Strong, bitter taste, easily soluble in water, and gas evolution with acid. The black portion is not soluble in water ; we separate it by filtration. It looks like lamp-black or soot. Under the microscope we find it to be of brown color and translucent with yellow or brown color. At red heat it burns and disappears. If the burning be done in an open tube, one end leading by rubber tube into lime water, Fig. 34, and air being sucked through by means of an aspirator, then the lime water will become milky ; the white sediment being rhombohedrons. Hence we deduce that the black substance is the Y in the lime-gas, because from it 90 CHEMISTRY SIMPLIFIED. comes lime-gas by combustion. Now we have many times observed that charcoal burns and disappears, leaving a slight residue of ashes, and we naturally will ask : Is there a communion between the black 1 Y and charcoal ? To satisfy the query we place a splinter of charcoal in the tube T, and fresh lime water in the test-tube. As the charcoal burns, the lime water becomes milky with calcite. Hence we FIG. 34. Tl air /JME W/ will make the deduction that charcoal is either wholly or partly made up of the black substance Y, and we resolve the Y into C, which is the first letter of the Latin word carbo, the equivalent of the Eng- lish charcoal. With characteristic inconsequence the English language makes carbon out of carbo. Our lime-gas becomes now C n O m ; the calcite becomes CaO.C n O m ; potash PO.C n O m , pronounced calcium car- bonate, and potassium carbonate. The symbol for potassium should be P as we adopted it. But here again the English chemists are inconsequent in choosing K, which is the first letter of the Arab word kali, which means "burnt," but was given by the Arab chemist Geber to our potash. This word was taken up by all chemists THE LESSON OF WOOD ASHES. "91 with the Arab prefix " al," i. e., alkali, to mean any body which shows the essential action of potash, these actions being called alkaline actions. A solution is said to be " alkaline " when it turns red litmus to blue. German and Swedish chemists call the metal potassium kalium, English, American, and French chemists stick to potassium, but they accept the symbol K. CHAPTER VI. THE LESSON OF COMMON SALT. COMMON salt is before us in three forms. 1. Rock salt as mined at the mouth of the Mississippi, in Canada, and other places in America. It is beautifully transparent ; colorless or colored, some- times intensely blue. It is found as large, perfect cubic crystals, and again as immense, solid, irregu- larly shaped masses like ice ; or as fine grained, snow-white or dirty gray, or yellow, or red masses. It cleaves perfectly in three directions at right angles cubical cleavage. It presents slight re- sistance to the knife or to the drill. It has a strong taste ; is readily dissolved by water. 2. Salt from evaporation of salt springs and salt wells, in snow-white cubic crystals, which are all hollow on the faces. 3. Salt from evaporation of sea-water. It is certain that all the deposits of salt, found in nearly all geological formations, were at one time dissolved in the sea. It is likewise certain that salt springs and wells dissolve the rock salt they find in the rocks, so that, in the end, our three kinds of salt are practically only one kind, sea-salt. Man and animals crave salt, their bodies must have salt or die. Hence all the languages derived from some primitive language have nearly the same name for (92) THE LESSON OF COMMON SALT. 93 the substance : Greek : hal, Latin : sal, French : sel, German : salz, English : salt. The plant-eating animals get some salt with the grass and leaves, but it is known that they will travel 100 miles and more to get a salt spring or salt-lick, to satisfy the craving for salt. Carnivorous animals get their salt in the blood of the grass-eaters on which they prey. Man takes his from both plants and herbivorous animals. Bloody wars have been fought for the possession of a salt spring or salt mountain. The United States are well supplied with salt, and need not go to the evaporation of sea-water. Germany is very rich in salt ; exports much to other less favored nations. Where the sun's heat can be made use of for evaporation, the sea-water gives very cheap salt. Investigation. Heat does not break up the salt. Holding a piece of salt in the flame we see that it melts quickly and colors the flame a deep orange- yellow. Heating the salt in a glass tube we notice decrepitation (enclosed mother liquor escaping ex- plosively), then a slight water condensation, then melting, then boiling and forming of a white sub- limate. No odor, nor gas. The sublimate shows itself made up of cubic crystals, tastes and acts the same as the original salt. Deduction : Salt is volatile without decom- position. It may be a simple body as far as heat action shows. But not so by its behavior towards elec- tricity. We place salt upon a platinum crucible lid, the lid being in contact with a sheet of copper and the 94 CHEMISTRY SIMPLIFIED. latter forming the positive pole of the current As soon as we bring the other pole wire in contact with the salt, the salt melts and an evolution of gas ensues accompanied by a very strong and peculiar odor. The same odor is produced if we mix salt with blue vitriol and heat in closed tube. But let us try our two strong agents : Sulfur hydroxyd and potassium hydroxyd. SaltH-KO.H 2 O+heat=no gas, no apparent effect. Salt-|- H 2 O.SO 3 + heat copious evol ution of color- less gas possessing a strong, pungent odor, and redden- ing blue litmus. Let this gas be called salt-gas. We let the gas pass into water : it is absorbed eagerly, the solution becoming warm. Looking at this phenomenon we cannot deny that it is similar to the action of IPO. SO 3 upon calcite, hence that salt must be composed of two oxyds M S O.N S 0. in which neither the metal M nor the non-metal N is known to us. With this supposition as a guiding thread, we proceed with experiments until we shall have established the truth or falsity of the conception, and recognized the properties of both M and N. Salt gas, spirits of salt. If our assumption be true, the production of salt gas must occur thus M S O.N S + IPO.SO 3 = IPO.N S + M S O.S0 3 the salt gas must be the hydroxyd of the non-metal oxyd N S 0. The gas contains hydrogen. For if we expose zinc to it hydrogen is evolved at once. Let THE LESSON OF COMMON SALT. 95 F be a flask holding about 500 c.c. Let it be fitted as in Fig. 35, with funnel, stopper and escape tube, all standing on a tripod so that heat may be applied. Let C be a bulb tube filled with cotton, to retain any particles carried over by the gas. T is a hard- glass tube with two perforated stoppers. B a bulb tube providing for any liquid mounting back from D. t is a test-tube to receive any gas which may be FIG. 35. generated. Remove stopper /S', introduce 50 grams of salt into Fat S, fill funnel with H 2 O.S0 3 and drop the latter slowly into F for some time, until upon adjusting S' the gas bubbles are all absorbed in the water in dish D. Open at S' and introduce zinc at Z. Close 8' and adjust tube t. The speed of gen- eration of the gas is to be judged by the frothing of the salt. T being cold (flame L not having been lit) at start, will now warm up : zinc decomposes 96 CHEMISTRY SIMPLIFIED. gas at ordinary temperature, the combination pro- duces heat. Prove the gas in test-tube is hydrogen by showing it inflammable. At Z a new body has been formed which is fusible, proven by means of lamp L. By withdrawing it from the tube it is found to be soluble in water. (Prove solution by testing with potash and also with KO.H 2 0), therefore this substance cannot be zinc oxyd for this latter is neither fusible nor soluble in water; it must be a combination of zinc with the unknown N. Acting upon it with IPO. SO 3 the pungent gas forms same as with the salt. Nevertheless the combination may contain oxygen. As we know the great avidity of potassium for oxygen, let us act as follows : We bring into a test-tube a part of the unknown compound ZnN s O ; we fill the tube with hydrogen, excluding thus any air ; we then add a piece of bright, carefully cleaned potassium and apply heat, hydrogen still passing in. The action would have to be thus : ZnN s O + 2K + heat = Zn + N S K + KO or = ZnKN 8 + KO or with 3K = ZnK-f-N s K + KO It will evidently not matter which of the reactions ensues, or whether all three occur at the same time. The essential point is the forming of KO ; because if water be now brought into contact with the mass, EPO.KO will be formed arid will cause the change in litmus from red to blue. The experiment will give true information only, if ZnN 8 be in excess, for otherwise K would be left and in contact with THE LESSON OF COMMON SALT. 97 water would give the hydroxyd -f- hydrogen. The experiment must be made with much judicious care, and will prove that KO is not formed and, hence, that oxygen is not present in the compound and there- fore not present in the salt gas. Our preliminary sup- position was wrong : Salt gas must be N S H. How are we to set free N s ? In the case of the limestone gas we were successful with potassium because the C (carbon) does not combine with potassium ; but in this in- stance, when we find the unknown N s to combine with zinc, it seems more than likely that it will combine with potassium also. However, let the trial be made. The apparatus, Fig. 35, will be quite suitable. We simply substitute a piece of potassium at Z in place of zinc. We note a strong action even at ordinary temperature, a white sub- stance forming and hydrogen evolving. The white substance forms cubes and octahedrons, it tastes like common salt ; hence we conclude that the metal M in salt must be similar in its nature to K. Whilst this is welcome information, it is not what we are looking for. The unknown is not set free. Another train of thought is needed ; we know the unknown to be a hydrogen combination. Now the metals having failed us, let us try the non-metals. Of these we know oxygen, azote and sulfur, and of these oxygen seems the most active. We reason along the scheme Mixing oxygen and salt gas at ordinary tempera- 7 98 CHEMISTRY SIMPLIFIED. ture has no effect as seen in this cylinder, which holds the mixture ; therefore let the mixture, one volume of each, be passed through the glass tube T (Fig. 36) and let asbestus A (mineral wool) partly fill the tube. The asbestus being brought up to redness, the gas mixture slowly passes through it in measure as the cylinder C f is raised and the cylinder C" is lowered. While C fills with mercury the pipette P fills with a gas of pale-green color. FIG. 36. This gas we shall hereafter name chlorine, (Cl.) from Greek chloros = green. For consistency's sake the name should be chlorium as hydrogenium, ferrum, stannum, potassium. (The great chemist, Berzelius, never gave up his belief that this chlorine was a compound and not an element, that it does contain oxygen, but that we are not able to separate the two. The demonstration we have gone through above leaves very little doubt that the salt gas and hence chlorine do not contain oxygen.) Chlorine, physical properties. A green gas of THE LESSON OF COMMON SALT. 99 peculiar, very strong odor ; offensive to the mucus membrane, producing ulceration upon the latter down into the bronchial tubes and capillaries of the lungs, painful coughing ; must be careful not to breathe the gas ; if necessity compels to stay in a place filled partly with chlorine must keep mouth and nose covered with a wet sponge. The gas is very heavy. It is 35.5 times heavier than hydrogen, 2.45 times heavier than air, and 2.216 times heavier than oxygen. One litre of the gas at C. and 760 mm. mercury pressure weighs 3.178 grams. 1 c.c. equals 0.003178 grams, roundly 3 milligrams. The gas dissolves somewhat in water. The maxi- mum solubility lies at 9.5 C., and corresponds to 2.75 times the volume of the water. Hence 10 c.c. of water will absorb at best 27.5 c.c. of the gas. But since 1 c.c. of gas weighs three milligrams, the 27.5 c.c. will weigh 82.5 milligrams, or 0.0825 grams, and hence in weight per cent. 0.825. It is well to remember that the most concentrated water solution of chlorine does not contain quite one per cent, of chlorine ; at 30 C. only 1.75 volumes equals 0.525 weight per cent. At boiling heat the chlorine is completely driven from its solution. Chlorine gas condenses into a mobile yellow liquid under a pressure of 8.5 atmospheres (127.5 pounds per square inch). Preparation of chlorine. In the practical prepara- tion of chlorine it is more advantageous to supply the oxygen in combined form, as a superoxyd, an oxyd which contains more oxygen than it can hold 100 CHEMISTRY SIMPLIFIED. firmly. Nature furnishes us with such in the so- called soft manganese ore MnO 2 , the pyrolusite of mineralogists. The salt-gas acts upon this oxyd even at ordinary temperature ; very energetically at about 60 C.; thus MnO 2 + 4HC1 (salt-gas) + heat == MnCl 2 + 2H 2 + 2CL Only one-half of the chlorine contained in the salt- gas appears as free chlorine, the other half forming, with the metal manganese, a pale, rose-colored salt manganese clilorid, MnCl 2 . Neither is it convenient nor economical to act with the salt-gas upon the superoxyd. A solution of the gas in water is much better adapted to this purpose, the best concentration is 20 per cent. How to make such a solution will be explained in the next paragraph below. The most suitable apparatus is the Koenig generator, represented in Fig. 37. G is the generating tube drawn out at lower end 0, where a stout rubber tube R is wired onto it. The tube R has at its other end a bent glass spout P, which rests upon the edge of the waste vessel W. The upper end of G is somewhat restricted, and a glass stopper S is ground into the restriction. This stopper is fused to the funnel tube F, the latter carries a stop-cock and a receiving bowl for the salt- gas solution. L is the outlet for the chlorine. Jis a wider glass tube, fused onto 6r, so as to form a complete jacket around the latter. The tubulature E serves to fill this jacket either in part or entirely THE LESSON OF COMMON SALT. FIG. 37. 101 8 $y r// YA v- , y r^-- KOENlG'S GENERATOR. 102 CHEMISTRY SIMPLIFIED. with water whilst a glass tube T encircles the jacket obliquely, and is fused into the jacket at both ends. This small encircling tube is full of water, and, be- ing heated by the small flame from a glass tube or a Bunsen burner, brings up a circulation and raises the temperature in /-to any desired point. Upon the porcelain false bottom I) rests the manganese superoxyd in small pieces, about pea-size. The column of MnO 2 should not be over 3 inches high. The apparatus is held by the brackets B, B, B, against the wooden stand Q, the latter being sup- ported by the bottom plate N. We start by filling water into G until the tube R is full and the water- level in the spout P is even with the level at the false bottom D. Then we heat the jacket to 60 C., and thereupon drop the salt-gas solution at the rate of one drop a second. There will then be a steady current of chlorine gas issuing through, whilst an equally constant discharge of the by-product, i. e., MnCl 2 will discharge itself at P into the waste vessel Wj provided the bowl of the funnel is kept re- plenished. If a stopping be desirable, simply turn the stop-cock in F. The gas will not be quite pure. It will be mixed with some liquid particles and also with some salt-gas. Hence we conduct it through a wash bottle containing some water, then through another such containing IPO. SO 3 ; in the latter the aqueous vapor will be removed, in the former the other admixtures. Of course, whenever dry gas is not required, the second wash bottle may be omitted. You will take notice that the rubber tube R forms THE LESSON OF COMMON SALT. 108 a trap against the escape of the gas downward, whilst the narrow funnel tube keeps the gas from escaping upwards. But it stands to reason that if a resistance be placed at L of greater weight than the column of liquid in either F or R, then the gas escapes through them, they forming the natural safety valve. A generator may be rigged more simply and FIG. 38. cheaply. A, Fig. 38, is a small flask, t is a glass tube, F a funnel connected with t by a short rub- ber tube and clamp C, t f tube for escaping gas ; / a i" rubber tube, W a beaker glass in which stands a large test-tube fitted with rubber stopper /S', and partly filled either with water or with IPO. SO 3 serving as wash bottle. The manganese superoxyd is placed in A at M, F is filled with salt- 104 CHEMISTRY SIMPLIFIED. gas solution. The apparatus is ready for use. In a measure, however, as MnCl 2 accumulates in A, the evolution of chlorine becomes slower, a steady stream cannot be maintained by it, except for a very short time. I worked for twenty-five years with such an apparatus, until I made the more perfect one described above. Chemical properties of chlorine. Chlorine is a most powerful agent at ordinary temperature, when oxygen is almost inert. It attacks all the metals, and in presence of water dissolves most of them : Gold, platinum, tin, copper, iron, zinc, but not so lead, silver, mercury. Upon oxyds, it acts thus : CuO -f 2C1 + heat = CuCP + MnO 2 + 2C1 + heat - MnCl 2 + 20 Chlorine acts upon all coloring matters taken from plants, such as litmus, indigo, the red cab- bage, and many others, in such a way that the color vanishes, bleaches. Upon the hydroxyds of potassium and calcium, chlorine acts as follows : 2CaO.H 2 + 4C1 + water - CaCl 2 + CaO.Cl'O + 2H 2 0. The milk of lime becomes dissolved to a clear liquid. If the dry slaked lime flour of lime be exposed to chlorine the same action takes place, but the resulting product is a slightly pasty solid, and is called bleaching lime; is soluble in water, and is used in large quantities by the bleachers and dyers THE LESSON OF COMMON SALT. 105 of yarn and cloth. The compound CaCl 2 does not bleach, only the compound CaO.CPO, and in this only the oxyd CPO is the bleaching factor. Upon potassium hydrate the action is parallel, thus : 2K X O.H 2 + 3C1 = KC1 + K X O.CPO + 2H 2 O. You pass the chlorine gas into the solution so long as it is freely absorbed. The result is a bleaching solution. But if we boil this solution for some time, it begins to throw out scaly crystals, white or colorless. Let these crystals be separated from the liquid, then dried, and then heated in a closed glass tube, when they will be seen to melt easily with strong evolution of gas. The gas proves to be pure oxygen. (Explode it with 2 volumes of hydro- gen.) When no more gas is given out the residue contains only potassium and chlorine, is KC1. The crystals themselves are produced from the boiling solution by the following reaction : 6K X O + 6C1 + water + boiling heat = 4KC1 + K X O.CP0 5 , and when the crystals are decomposed by heat : K X O.CP0 5 + heat = 2KC1 + O 6 . The crystals represent a compound of the metallic oxyd K X with the non-metallic super oxyd C1 2 5 . The latter is unstable, overloaded, hence heat breaks it up easily, and as we have seen above that chlorine drives oxygen from the oxyds, the final result must be KC1 -f 6 oxygen. The crystals shall be known as potassium chlorate. It is a very valuable compound 106 CHEMISTRY SIMPLIFIED. to us, because we can obtain by it at any time quantities of the purest oxygen. Manufacturing process for potassium chlorate. The potassium hydrate is relatively costly, the cal- cium hydroxyd very cheap, KC1 is also cheap (a natural mineral sylvite). On passing chlorine gas into water in which have been slaked 3 equiva- lents of calcium oxyd (burnt lime) at boiling heat until the liquid has become clear, we have a solu- tion of calcium chlorate (easily soluble). We bring into it one equivalent of KC1 and potassium chlorate falls out in crystals (because it is not readily soluble in water). Composition of salt gas. We found the gas com- posed of hydrogen and chlorine. Now we have to es- tablish their ratio in the compound. If we pass one volume of salt gas over heated zinc repeatedly, in the apparatus Fig. 36, we find that the volume of the gas becomes reduced to one-half. Chlorine unites with zinc, becomes solid so to speak, the remainder is pure hydrogen. Hence we deduce : Salt gas is composed of equal volumes of hydrogen and chlorine ex- pressed by the symbol HC1. If we fill into a cylinder one volume of hydrogen and one volume of chlor- ine and let the mixture stand in the diffused day- light for some days, the volume does not change, but the two gases shall have become united to HC1. We can prove this by introducing a few c.c. of water ; the gas is all absorbed by the water ; chlorine would have only been slightly absorbed, hydrogen not at all. Should we expose the mixture THE LESSON OF COMMON SALT. 107 of H -|- Cl to the direct sunlight, the union would follow at once with explosive energy. It is import- ant to note that the volume of the compound is equal to the sum of the volumes of the components ; neither contraction nor expansion taking place. This is a law for all unions of gaseous bodies in equal volumes. The name for the compound HC1 shall be hydrogen chlorid, and all combinations of metals with chlor- ine shall be named chlorids, as we name the oxygen compounds oxyds. Some chemists speak and write chlorides, oxides; it is quite immaterial which you use, but choosing one you should stick to ib; the shorter sound would seem to be preferable. Properties of hydrogen chlorid : A colorless gas at ordinary temperature, powerfully pungent odor, exciting the mucous membrane. Near the freezing- point of water at +4.4 C. the gas becomes a liquid under a pressure of 30.67 atmospheres or 460 Ibs. per square inch. At a temperature of 73.3 C. only a pressure of 27 pounds is needed. Liquid HC1 is mobile and colorless, heavier than water. No practical use has been found for it. The specific gravity of the hydrogen chlorid gas is 1.255 (air = 1) ; 1 c.c. of it weighs 0.00163 gram, just about one- half that of chlorine. By weight the gas contains 97.26 of chlorine, 2.74 of hydrogen. 1 volume of water can absorb 500 volumes of HC1 gas at the freezing-point; at 20 C. (common temperature) water absorbs 440 volumes of the gas. The absorption of the gas produces heat. This would lead us to think that there must be a chemical affinity 108 CHEMISTRY SIMPLIFIED. between HC1 and IPO ; that there must be hy- drates. In fact it is quite probable that two such exist. For, if a concentrated solution of HC1 in water be heated (a thermometer registering the tem- perature), it will give out for some time only moist HC1 gas. The temperature having risen to 100 C., water passes over with HC1 and a very concentrated solution condenses having specific gravity 1.19. As the temperature rises the distil- late becomes more watery until the temperature reaches 111 C., at which it remains constant whilst a solution distills over possessing specific gravity 1.104. This solution contains 21 per cent. HC1 and 79 per cent, of water, nearly the hydrate 2HC1 -f- 15H 2 0. A second hydrate is HC1 + 6H 2 0. Hydrochloric acid Muriatic acid HC1 -f- water. These names are given to the water solution of HC1. We speak of highly concentrated acid, concentrated acid, dilute acid, very dilute acid. Sp. gr. Per cent. HC1 Highest concentrated, 1.200 40.77 Highly concentrated, 1.1802 36.29 Strong acid, 1.151 30.58 Medium, 1.072 14.68 Dilute, 1.042 8.56 Very dilute, 1.006 1.12 Problem : Construct with these data a curve whose ordinates shall be the percentage and the abscissae, the specific gravities. Preparation and manufacture. Small quantities are made by distillation in glass flasks or glass re.- THE LESSON OF COMMON SALT. 109 torts. On a commercial or manufacturing scale, cast-iron vessels are used, either cylinders, or else flat pans standing within a brick furnace. Cast iron is not attacked by concentrated sulfuric acid nor by HC1, but is energetically attacked by a solution of HC1 in water. Such properties render the iron vessels fit. Concentrated sulfuric acid acts violently upon salt even at ordinary temperature ; the mass FIG. 39. threatens to froth over. An addition of water gives relief. Our prescription is : For every ten grams of salt take 9.6 c.c. of concentrated IPO. SO 3 and 5.5 c.c. of water. Mix the two liquids in a beaker- glass, fill from it the basin B (Fig. 39) of the funnel ; place the salt in the flask F ; make connection with the Wulf bottle W by tube t which passes 110 CHEMISTRY SIMPLIFIED. under the level of the wash water. The tube t' also passes under the surface level and is open at the top ; t' is the safety valve of the apparatus, because air will pass into it whenever a partial vacuum is brought about ; t" leads into the absorption flask A which contains as much water by weight as the salt taken. The student takes 50 grams of salt and places 50 c.c. of water in the absorption bottle. The stoppers S, 8, S must be of rubber. The flask F must hold 500 c.c. All the acid may be put in at once, and then heat applied gently at first, and regulated to keep up a steady evolution. When the gas stops, finally, the operation is terminated and you let air in through the funnel tube. In removing the flame, it will be seen that the liquid in F solidi- fies, by degrees, as it cools down. Remelt it and pour it out on a clean stone or iron surface. Let it be named "crude salt cake." It must, evidently, be the vitriol of the unknown metal M, and will be taken up presently. Action of hydrochloric acid. The water solution of HC1 is nearly as powerful an agent as the gas itself, and for most purposes can be employed in its stead. Because the metallic chlorids are more readily solu- ble in water than the vitriols, excepting the chlorids of silver, lead, and mercury; therefore, we shall use .it in preference to the sulfuric acid, whenever we desire to dissolve bodies which are not soluble in water. As, for instance, we wish to generate lime- gas. The calcium vitriol is very insoluble, and we have heretofore used acetic acid for the decomposi- THE LESSON OF COMMON SALT. Ill tion. Instead we shall use hydrochloric acid here- after ; the calcium chlorid is much more soluble than the vitriol, in fact, it will dissolve by merely allowing it to stand uncovered in ordinary air which is always more or less moist. Hence, we can em- ploy, to advantage, this chlorid in place of concen- trated sulfuric acid for the drying of gases. Being a porous solid, the calcium chlorid offers more surface to the gas than an equal volume of liquid sulfuric acid. The chemical actions may be represented thus : If R stands for a metal, whose chlorid is soluble in water : R -h water + HC1 solution = RC1 solution -f- H ; and on oxyds RO + water + 2HC1 solution RC1 2 solution + H 2 0; if, however, silver vitriol solution be brought to- gether with hydrochloric acid, a white, curdy pre- cipitate falls out at once, AgCl, Ag 2 O.S0 3 + water + 2HC1 solution = 2AgCl + H 2 O.S0 3 solution because the silver chlorid is insoluble in water. Thus we can prove the presence or absence of silver in any unknown solution by adding to it a drop of hydrochloric acid ; if a curdy cloudiness follows, then silver is present. Pure hydrochloric acid is quite colorless. The yellow color of the commercial muriatic acid is owing to some iron chlorid coming from the iron ves- 112 CHEMISTRY SIMPLIFIED. sels and iron oxyd in the crude salt. The strength of commercial acid is mostly indicated in degrees on the Beaume hydrometer, instead of by the specific gravity. Such an instrument (Fig. 40) is correct if it sinks in pure water at 17 C. to the zero mark. Zero is therefore equal to specific gravity 1.000. In a 15 per cent, solution of common salt (salt = 15, water = 85) the spindle must sink to the mark 15; the degrees being equal divisions. Very concentrated FIG. 40. o i: \.ooo FIG. 41. hydrochloric acid is said to be 22 Be. (specific gravity 1.176). There is, of course, a second spindle for liquids lighter than water. In this instrument (Fig. 41) the zero point is near the bulb, the weight in the bulb, being so chosen that the spindle sinks in a solution of 10 per cent, salt (salt 1, water 9) to the zero point, whilst in pure water it sinks to THE LESSOX OP COMMON SALT. 113 division 10 ; the same unit (found by dividing the space between and 10 into 10 equal parts) is then drawn on the scale upward to the limit of the spindle. Kerosene, gasoline and other coal-oil products are gauged in the United States by degrees Be\ Alco- hol is gauged by the hydrometer of Tralles. It is not sufficient to say that a liquid stands at so many de- grees Be., it must be said whether reference is had to a liquid lighter or heavier than water, which can be done by the signs +, , or by letters : 1. w ; h. w. Thus the light gasoline for gas-making is 87 Ed, and the concentrated sulfuric acid is + 66 Be'. Hydrochloric acid can be shipped only in glass vessels ; the sulfuric acid can be transported in iron tanks. The glass vessels large, spherical, holding 5 to 10 gallons, and being packed with straw into wooden boxes are known as carboys. For manufacture on a large scale get information in Lunge's Manufacture of Soda Ash (recent) or in Ure's Dictionary (old). Claude salt cake, discovery of the metal sodium. Let some of the crude cake, obtained by action of H 2 S0 4 on salt, be heated in a porcelain crucible over an open flame. Dense white fumes are soon seen to arise. The fumes are now diagnosed by us as probably being sulfur trioxyd, oil of vitriol. As the vapors escape, the melting-point of the cake rises. Finally, when no further fumes come off, the stuff appears dry at a red heat. At yellow heat it melts again, and remains so without yielding any more fumes or gas. Reason for the fumes : The 8 114 CHEMISTRY SIMPLIFIED. crude salt cake is M S O.S0 3 .H 2 O.S0 3 , a so-called acid vitriol, quite constant at low heat, but break- ing up at high heat into M S O.S0 3 + JPO + SO 3 . The final remnant is M S O.S0 3 =salt cake refined. We had added in the recipe given just twice as much sulfuric acid as is needed, and did this know- ingly, for otherwise we could not have completely decomposed the salt in a glass flask ; the stuff would not have liquefied ; the flask probably broken. Salt cake dissolves in cold water easily ; this property distinguishes it from the potassium vitriol and the calcium vitriol. In order to isolate the metal let us make use of our experience with charcoal car- bon. We mix the powdered salt cake with powdered charcoal, cover the crucible, and expose it in a char- coal or gasoline furnace to strong red heat. We may do it in a hard glass tube first. Result is a dark-colored mass ; metallic particles are not visible, and if we bring it together with water there is no evolution of gas, such as potassium produced. However, it dissolves in water, leaving charcoal powder, which we separate by filtration, and test, after thorough washing, by burning ; as it quite disappears (leaving only trace of ash), we are correct in calling it charcoal. The filtered liquid has a brown or red-brown color ; it gives alkaline reaction to litmus ; has a strong taste. With hydrochloric acid, gives off gas smelling of rotten eggs, and if this gas be passed through a glass tube heated to redness a sublimate of sulfur forms. If bright cop- per or silver be brought together with the liquid, THE LESSON OF COMMON SALT. 115 the metal turns black, and if these strips of black- ened metal be heated in an open tube we get the smell of SO 2 . If boiled with finely-divided copper oxyd, the liquid becomes decolorized and does not any more blacken the metallic copper, whilst it' gives still a strong alkaline reaction. From all these observed facts we draw the following deduc- tions : 1. The action of charcoal must have been, sym- bolically, thus M S O.S0 3 + nC = M S S + 4CO -f n-4C ; the vitriol was converted into a sulfid. 2. The action of metallic copper and metallic silver was probably M S S + nH 2 + Cu = CuS (black) + M S O.H 2 (alkaline) + (n-1) IPO. 3. The action of copper oxyd was probably M S S + CuO + nH 2 = CuS + M S O.H 2 (alkaline) + (n-l)H 2 0. The hydroxyd of the unknown metal is easily solu- ble in water, and being strongly basic alkaline it must be akin to potassium. We evaporate the liquid from (3) to a white solid, which afterwards fuses and then goes off in white fumes, just like potas- sium hydroxyd. We act upon this material with zinc, and by evolution of hydrogen prove it to be hydroxyd. Next we act upon it with the electric current ; gas at positive pole ; metallic globules and gas at negative pole ; and by using mercury as the negative pole we obtain a solid amalgam, from 1*16 CHEMISTRY SIMPLIFIED. which the metal M may be separated by distillation in a current of hydrogen gas. If we act upon the hydroxyd with charcoal-loaded iron chips at a yel- low heat, the metal will distil over, same as potas- sium, but the flame issuing from the retort burns with ^yellow color (distinction from potassium, purple flame). In the neck of the retort we find a black mass which acts like that found in the distillation of potassium. This mass is mixed with the con- densed metal. Properties of the metal sodium. The name sodium. is given to the metal by English, French, and Amer- ican chemists. Germans and all others give it the name natrium, using the first two letters as the sym- bol, Na, which stands for the chemical unit of mass. English, Americans, French use the same s}^mbol, hence sodium, Na. Natrium is derived from Greek nitron ; Egyptian and Hebrew neter, a name given by those people to the crusts forming around the desert lakelets, and which was found to have similar cleansing properties to potash. It is now known as soda ash. Whence the word soda comes is not known, nor what it means. Perhaps from the Latin soldere, English solder, since this material may have been confounded with borax, such mixtures being useful in joining metal pieces by heat. (Author's notion.) The metal sodium is soft like wax at ordinary temperature, can be hammered at freezing-point, becomes liquid at about 95 C. (melting-point is higher than that of potassium 65 C.). In color THE LESSON OF COMMON SALT. 117 it is silver-white like potassium ; the fresh-cut sur- face becomes rapidly dull from oxydation. Sodium becomes vapor at red heat, and this vapor has a purplish color potassium green. Specific gravity at 10 C. is 0.974 (water == 1). Coefficient of ex- pansion 0.000073, larger than that of any other metal except potassium (0.000083). It conducts heat and electric waves well, about 37 (silver = 100). Its specific heat or heat capacity is 0.2934. Its heat of fusion is 0.73 Cal. Chemical properties of 'the metal sodium. Thrown upon water it sets up an evolution of gas and melts into a globule which is covered by a gray film. The gas does not ignite, unless the water be heated to about 60 C., or unless the water be thickened with gum arabic or glycerine. We deduce from this action that sodium has not as much affinity or attractive tendency for oxygen, as potassium ; hence less heat is generated. If the globule be left on the water until the gas evolution stops, the globule flattens out suddenly and an explosion en- sues. If the globule be taken from water when gas stops, it is found composed wholly of oxyd. (The explosion is explained by the sudden rise of steam when the oxyd becomes hydroxyd.) If the metal be heated in oxygen gas, or in a mixture of air and oxygen, a yellow substance re- sults which is the superoxyd of sodium; on cooling it turns white. It dissolves in water without decom- position, and can be melted without decomposition. If heated with copper, lead, zinc or tin the sodium 118 CHEMISTRY SIMPLIFIED. superoxyd changes these metals into oxyds. With HC1 it gives NaCl + H 2 + 0. If this action be done in water solution, oxygen does not escape ; the water then contains sodium chlorid, NaCl, and hy- drogen superoxyd (also called peroxyd), H 2 2 or HO ; we assume therefore that the sodium peroxyd must have a similar composition to the hydrogen peroxyd, namely, Na 2 2 , the reaction will be Na 2 2 + 2HC1 + water = 2NaCl + H 2 2 + water. This solution of hydrogen peroxyd is a powerful oxydizing agent and is much used both in labor- atory work and on a large scale for manufacturing purposes. If the superoxyd has the composition Na 2 O 2 then the oxyd must be Na 2 0. We get this by fusing together the hydroxyd with the metal in proper proportion. It is a gray substance, and of no spec- ial application. It attracts moisture from the air and becomes hydroxyd. CHAPTER VII. THE STORY OF SODA ASH AND LEBLANC. WHEN in the early years of the past century Na- poleon closed all the harbors of Continental Europe to English and American ships, in order to destroy the commerce of England, as he could not destroy its navy, there arose in Continental Europe a scar- city of potash, since the supply had nearly all come from the American colonies. To ease the demand for this article, as well as to spite England, Napo- leon offered a prize of 100,000 francs, 20,000 dol- lars, for the discovery of a substitute for potash. This prize was won and awarded to the French chemist Leblanc, who proposed a process by which common salt can be turned into a body which may be substituted for potash in most technical applica- tions, a process which held its own for 80 years and is only now giving way slowly to better meth- ods. (See Solvay process at end of chap. XL) All the reactions were known to chemists at the time but one, the replacing of copper oxyd by a cheaper compound. Leblanc found that limestone, or oyster shells, or chalk could replace the copper oxyd, if the action takes place at red heat. To wit : Na 2 S + 2CaO.CO 2 + red heat = Na 2 O.C0 2 + CaO.CaS+ CO 2 . (119) 120 CHEMISTRY SIMPLIFIED. Na 2 O.C0 2 is easily soluble in water; CaO.CaS (cal- cium oxysulfid) is insoluble in water, and Na 2 O.C0 2 is the practical substitute for K 2 O.CO 2 (potash). The entire run from salt to soda ash is represented in the following symbolic scheme : (1) 2NaCl (salt) + 2H 2 O.S0 3 + heat = 2HC1 + Na 2 O.S0 3 .H 2 S0 3 . (2) Na 2 O.S0 3 .H 2 O.S0 3 + heat = Na 2 O.S0 3 (salt cake) + SO 3 + H 2 0. (3) Na 2 O.S0 3 + 4C + 2CaO.C0 2 (chalk) + yel- low heat == Na 8 O.C0 9 + CaO.CaS + CO 2 -f 4CO (inflammable gas). (4) Na 3 O.CO 8 + CaO.CaS + water + heat - CaO.CaS (residue) + Na 2 O.C0 2 (solution). (5) Na a O.CO a (solution) -f evaporation = Na 2 O. CO 2 , soda ash. The soda ash produced in this way is not pure : The carbonate predominates, but mixed with it we find Na 2 O.H a O,Na s S and other impurities. It can be purified ; not necessary for most of the applica- tions, such as soap-making. A factory in which soda ash is produced goes by the name of alkali works. It is usually divided into several depart- ments, located in separate buildings. (a) Acid works where the sulfuric acid is made, (b) Salt- cake works, (c) Black ash smelter and extractor, (d) White ash works, (e) Bleaching-lime works, where the hydrochloric acid is converted into chlor- ine and the latter is absorbed by the dry slaked lime. THE LESSON OF SODA ASK AND LEBLANC. 121 SODA ASH SODIUM CARBONATE, SAL SODA, BAKING SODA. When the liquid resulting from action (4) (see above) is evaporated to dry ness and then fired to red heat, the product bears the name crude white soda ash. If the same liquid is however only evap- orated or boiled down to a certain point and is then allowed to cool slowly, large crystals will form. These are Na 2 O.C0 2 + 10H 2 and go by the name sal soda (salt of soda). The impurities remain in the mother liquor. If they be exposed on wicker hurdles in an exposed space into which lime gas is conducted from the top of a lime kiln, then they will pass into a fine granular white sandy material whilst water runs away from them. The white powder goes under name of baking soda, bicarbonate of soda. The action is thus : Na 2 O.CO 2 + 10H 2 O-hC0 2 (lime gas) = Na 2 O.C0 2 .- # 2 0.<70 2 + 9H 2 0. The bicarbonate is slightly soluble in cold water, and at the boiling temperature it breaks up into Na 2 0.- CO 2 + CO 2 -f H 2 0. If therefore this material be mixed with flour and the resulting dough is put into an oven we will just get that same decomposi- tion, the escaping lime gas causing the raising of the dough. But the bread must taste bitter from the sodium carbonate which remains. In the so- called baking powders, the baking soda forms only one ingredient, the other being an acid salt which not only decomposes the carbonate but also removes the bitter taste. 122 CHEMISTRY SIMPLIFIED. Caustic soda or concentrated lye, of the manufac- turers is made by decomposing a 10 per cent, solu- tion of soda ash with one equivalent of slaked lime, the same process we considered under caustic potash. The resulting solution of the sodium hydrate is evaporated, fused and cast into sheet-iron drums, or cans, for smaller quantities, or into one-pound balls, which latter are then dipped into molten rosin. The film of rosin keeps the material from attracting moisture from the air and thus liquefying. The farmers' wives now buy these lye balls for their soap- making instead of bothering with the wood ashes. The man who had the idea of the rosin film made a fortune from the patent rights. Certain sea plants growing in the tide levels of France and England, called kelp in Wales, and varec in France leave an ash .which is largely made up of sodium carbonate, the plant's energy trans- forming the salt into the soda, CHAPTER VIII. A CHAPTER ON THEORIES; ON COMBINING WEIGHTS, ATOMIC WEIGHTS AND VALENCES. THE existence of such bodies as chlorids, especially sodium chlorid, containing no oxygen, and yet so much alike to oxygen salts, leads us to thinking. Let us compare hydrogen chlorid, HC1 and sulfuric acid, IPO. SO 3 . As the symbols stand written, two do not seem at all comparable. But supposing we change the grouping of the elements in the sul- furic acid thus : H 2 O.S0 3 H 2 .S0 4 , then at first glance we notice the resemblance, H.C1 H 2 .S0 4 , and more so still if we place the SO 4 into a bracket, H(C1) H 2 (S0 4 ). We have no knowledge of an oxyd, SO 4 ; we only know SO 2 ,, SO 3 , S 2 3 , S 2 4 ; yet without a great wrench we can imagine that the very moment when the two oxyds, H 2 and SO 3 , are brought together, a rearrangement of the elementary particles comes ab.out harmoniously, quite imperceptible to the eye. As soon as we disturb the harmony by trying to remove the hydrogen, then disarrangement, a break- up takes place. But if we accept the reality of (123) 124 CHEMISTRY SIMPLIFIED. this improvable state of things, then the schism in the fundamental chemical phenomena gives way to resolved uniformity. The acids become then combi- nations of hydrogen with a non-metallic radical; the radical can be either one non-metallic element or a group of such elements. In hydrochloric acid, chlorine is the radical, in sulfuric acid the group (SO 4 ) is the radical. The word radical is the adjec- tive of the Latin noun radix = root ; from the radical, root, arises the stem the sourness, the acidity. When a metal acts upon an acid, hydro- gen escapes. According to the new light we cir- cumscribe this by saying the metal takes the place of the hydrogen : H(C1) + K = K(C1) + H Why does it do so? Because potassium has a stronger affinity for the radical chlorine than hy- drogen, and this stronger affinity is made percepti- ble by the greater quantity of heat which is set free by the union of the two. If Cal. = the unit of heat, then H + Cl = HC1 + nCal. K + Cl = KC1 + n'Cal. n'>n. Metals such as lead, copper, silver, gold do not act upon the dilute acids; they are not dissolved by them, because their heat of formation is very small and requires a heat-addition from the external con- ditions. Thus we can establish a series of the metals in which potassium will occupy the one flank and A CHAPTER ON THEORIES. 125 gold the other : K., Na., Ca., Mn., Zn., Fe., Sn. } Pb., Cu., H., Ag, AU. If we designate K as -f , then Na will be negative in regard to K, but positive in regard to Ca, and each metal in the same way positive towards its neighbor on the right, negative towards the one on the left. Equally if we place two pieces of sheet metal upon one another with a moist piece of felt between, for example, zinc and copper, an electric tension will show itself between them. Galvani observed this 120 years ago, and his name is at- tached to this electric current even now galvanic electricity as against frictional or static electricity. The series is therefore usually alluded to as the electro-chemical series of metals. Of the non-metals, oxygen occupies the extreme flank, with chlorine next, as sodium stands along- side of potassium : 0., Cl., Br., S., N., C. Valence. Glancing at the symbols H(C1), H 2 (S0 4 ) we cannot help but being struck by the fact that in one symbol there is but one hydrogen, whereas there are two of hydrogen in the other. We cannot remove one of these hydrogens without destroying the harmony, without breaking up the body com- pletely. To give expression to this fact we are led to the term valence, a slight difference of meaning from equivalence. We say the elementary group (Cl) is monovalent, because it finds its satisfaction with one volume-unit of hydrogen, monos = once ; the compound group (SO 4 ) is divalent, dis = twice, be- cause it must have two hydrogens to exist. We 126 CHEMISTRY SIMPLIFIED. shall find later on elements as well as complex radicals whose valence are 3, 4, 5, 6 designated respectively as tri-, tetra-, penta-, hexavalent. I warn you not to be dazzled by these full, sonorous words ; they are but a short cut of speech. You can prove nothing by means of valence, because the expression valence only states a fact, yet is convenient as an expression. The atomic weights of elements, molecular weights of compounds, volume weights. We find that one vol- ume of chlorine unites with one volume of hydro- gen ; in symbols HC1. Chlorine gas is 35.5 times heavier than hydrogen gas hence the symbol stands HC1== 1 + 35.5 = 36.5 Also we find that 35.5 grams of chlorine gas com- bine with 23 grams of sodium and thus produce 35.5 + 23 = 58.5 grams of NaCl (common salt). Only one compound between Cl and Na has been observed with certainty and this is a very stable one. We assume that the vapor of sodium, if it could be produced and weighed, would be 23 times heavier than hydrogen, under the same conditions of tem- perature and pressure. Though the metal volati- lizes at red heat yet have all experimental attempts thus far failed, because the sodium vapor attacks all the vessels which are available : platinum, gold, silver, nickel, porcelain ; hence we do know only by inference that the volume of the mass unit weighs 23. Both by composition and decomposition (synthesis and analysis) we know that 35.5 grams of chlorine gas combine with 39 grams of potassium to form A CHAPTER OX THEORIES. 127 35.5 + 39 grams of KC1. That 39 is the weight of one volume of potassium vapor we do not know any better than in the case of sodium, for the same diffi- culties. The symbol KC1 or XaCl is not a certainty in other words. Its strong probability follows from the following consideration. By acting upon sul- furic acid H 2 (S0 4 ) with either of the two metals we can produce well crystallized salts or vitriols to wit : either of which possesses strong acid reaction, and salts which are neutral towards litmus paper. The former salts convert into the latter thus : 2XaH(SO) 4 + heat = XaNa(S0 4 ) + H 2 (S0 4 ) vola- tilized 2KH(S0 4 ) + heat = KK(S0 4 ) + H 2 (S0 4 ) volatil- ized. Transposed into numbers this means that we can combine with one S (32 parts) either 23 or 46 of sodium, either 39 or 78 of potassium ; but with 23 and 39 only when in each instance there is also one hydrogen present. Hence it follows that 23 of sodium, 39 of potassium, can take the place of are equivalent to one hydrogen in the two acids HC1, H 2 S0 4 . KC1, K 2 S0 4 . NaCl, Na 2 S0 4 . 128 CHEMISTRY SIMPLIFIED. Potassium, sodium, hydrogen, on these given terms are monovalent metals, or monads (a still shorter expression), It is self-evident then that the oxyd of these metals must be Na 2 0, K 2 if the oxyd of hydrogen is H 2 0. The hydroxyds of the mefals sodium and potassium become Na 2 O.H 2 0; K 2 0.- H 2 0. But since we saw in the vitriols one hydro- gen being replaced by one Na, or one K, the same must be possible in water, to wit : H 2 + Na = NaHO + H (escapes). Hence it follows that the symbol Na 2 O.H 2 = 2 (NaHO) expresses two units or molecules of sodium hydroxyd, that NaHO is the true representation of sodium hydroxyd. In the metallic hydroxyd we have, therefore, a combination in which the metal is united to the group (HO). A group which acts as a non-metallic radical of the value (valence) one. This group contains the metal H and the non-metal 0, whilst the negative or non-metallic group (SO 4 ) contains the two non-metals. Perhaps in this hybrid nature of the group (HO) lies part of the reason for the action of the hydroxyd towards lit- mus and other actions totally opposed to the acids. The relative action, then, of the hydroxyds and acids is this : Na(HO) + H(C1) = NaCl + H 2 0, 2Na(HO) + H 2 (S0 4 ) = Na 2 (S0 4 ) + 2H 2 O. Two attractions exist to account for the powerful action : First the greater attraction of the metal to the non-metallic radical and the tendency of (HO) A CHAPTER ON THEORIES. 129 to become H 2 by taking another H. Owing to tbe important role of the group (HO) the name hydroxyl (ule = matter) is given to it. Hydrogen = the generator of water, hydroxyl = the matter from which water is made. * In the light of all these considerations and speculative deductions, the pre- vious definitions of base, acid, salt shall be changed to read as follows : Base = Combination of metal with one or more hydroxyl groups. Add = Combination of a non-metallic group or radical with one or more hydrogens. Salt = Combination of a metal with a non-metal- lic radical. The definitions of acid and salt are identical. The two things are of one kind. Sulfuric acid is hydrogen vitriol. The term vitriol has been abandoned for the sake of greater uniformity of chemical expressions. Its place is taken by the word sulfate, hence the fol- lowing : H 2 (S0 4 ) = Hydrogen sulfate = sulfuric acid. Na 2 (S0 4 ) = Sodium sulfate. NaH(S0 4 ) = Sodium, hydrogen sulfate. K 2 (S0 4 ) = Potassium sulfate. KH(S0 4 ) = Potassium, hydrogen sulfate. Ca(S0 4 ) = Calcium sulfate. Fe(S0 4 ) = Ferro sulfate (iron sulfate). Cu(S0 4 ) = Copper sulfate. Pb(S0 4 ) = Lead sulfate. Zn(S0 4 ) = Zinc sulfate. 9 130 CHEMISTRY SIMPLIFIED. You should accustom yourself to use the expression: hydrogen sulfate in place of sulfuric acid, though no harm is done by the latter. Logical consequen- tial speech leads to logical thought and work. Atomic weight of calcium, copper, lead, zinc. By analysis we find that 35.5 grams of chlorine unite with 20 grams of calcium to a stable chlorid. If 20 were the representative of one volume of calcium vapor then the symbol of the chlorid would be CaCl, as NaCl. But we find that we can combine the cal- cium with the hydrogen sulfate, H 2 (S0 4 ), only in one way, not in two ways as with potassium and sodium, namely, so that 40 of calcium correspond to one (SO 4 ) or one S, that therefore the number 40 must stand for the atomic weight of calcium, that one calcium is equivalent to two hydrogens and therefore the symbol of the chlorid must be written CaCl 2 . not -20Ca + 35.5C1 = CaCl, but 40Ca + 2 X 35.5 = CaCl 2 . Copper, zinc, lead, also form only one kind of sul- fate, Cu(S0 4 ), Zn(S0 4 ), Pb(S0 4 ), therefore, we say these metals are divalent like calcium, their unit weight stands for two hydrogens, and in each case 35.5 chlorine combine exactly with one-half as much metal as 32 sulfur, hence their chlorids are CuCl 2 , ZnCl 2 , PbCl 2 . Copper makes an exception in so far as it can unite with chlorine in two ways, to wit : 35.5C1 + 31.5Cu and 35.5C1 + 63Cu. The com- pound whose ratio of Cl : Cu is 35.5 : 31.5 is the stable compound, permanent at ordinary heat arid even A CHAPTER ON THEORIES. 131 up to red heat. But since in the sulfate 32S cor- respond to 63Cu, therefore we take the number 63 as the representation of one divalent volume of cop- per and write 63Cu + 2 X 35.5C1 = CuCP, and 2 X 63Cu + 2 X 35.5C1 = Cu 2 Cl 2 . In the first, the stable compound, cupric chlorid, CuOl 2 , the metal is normal, divalent. In the second, the unstable compound, cuprous chlorid, Cu 2 Cl 2 , the metal is abnormal, monovalent. Sil- ver acts like potassium. 107. 6Ag combine with one chlorine ; but 2 X 107.6 combine with one sulfur, 32. Hence silver is monovalent, 107. 6 Ag = one H. The chlorid is AgCl, the sulfate is Ag 2 (S0 4 ). Gold unites with chlorine in two ways. In one compound, which is a white r powdery substance, we find 196Au with 35.5C1, in the other 65.33Au with 35.5C1. The first compound is so unstable that it falls to pieces upon the addition of water. In the other compound the chlorine acts upon certain sub- stances as free chlorine. Besides, the specific weight of gold 19.5 is so high that necessarily the weight of its vapor must be very high (though we cannot make this vapor). We take, therefore, 196 to repre- sent the weight of one volume, and write the sym- bols of the two chlorids : 196Au + 35.5C1 = AuCl = aurous chlorid, 196Au + 3 X 35.5C1 = AuCl 3 = auric chlorid. Auric chlorid is a deep yellow substance, easily soluble in water, and fairly stable. In it gold = 132 CHEMISTRY SIMPLIFIED. Au has the valence 3. In aurous chlorid Au has the valence 1. Molecular weight. Two or more simple bodies united into a chemical union form a molecule. By some it is contended that in the free state even the simplest bodies the elements form molecules, that in the free state hydrogen is (H.H) = 2, chlorine (C1.C1) = 71 ; oxygen (0.0) == 32, and H 2 (S0 4 ) - 98 of course. When chlorine acts upon hydrogen the action must, according to this view, be repre- sented by : Nothing is changed, in reality, by adopting this view, or by rejecting it. If we speak of molecular weight we shall invariably mean that the molecule is composed of several elements. Relation between atomic weights and specific heat of the elements. By heat capacity the physicists under- stand the quantity of heat energy expressed in calories (heat units), which is necessary to raise the temperature of a mass equal to one gram of a sub- stance by one degree of the centigrade thermometer. The specific heat of a body (solid or liquid) means its heat capacity referred to that of water as the unit. The specific heat of gases is referred to that of air or also to that of water as units. The variation of values thus obtained is highly astonishing. In gen- eral, the heat capacity of metals is very low, that is, a metal shows the heat very quickly, water very slowly. The numbers representing the specific A CHAPTER ON THEORIES. 133 heats are therefore always true decimal fractions. When the atomic weights of the metals are multiplied by their specific heats the product is a constant. Reason therefore demands that whenever the product is not equal to the constant, there must be something wrong, that we stand before a riddle. The follow- ing numbers show this relation, which is also known as the " Law of Dulong and Petit : " A. W. Spec. Heat. Product. Silver Ag 108 X 0.0570 = 6.156 Iron Fe 56 X 0.1138 = 6.375 Copper Cu 63 X 0.0952 5.99 Zinc Zn 65 X 0.0955 = 6.207 Calcium Ca 40 X 0.167 - 6.68 Sodium Xa 23 X 0.2930 = 6.73 Potassium K 39 X 0.1655 = 6.45 Lead Pb 207 X 0.0314 == 6.499 Tin Sn 118 X 0.0562 = 6.631 These numbers do not show exactly the same pro- duct for all the metals, but the constant appears to be about 6.5. Inversely it would follow that the specific heat of the atomic volume is the same for all the metals ; the specific heat is an inverse function of the mass; the greater the specific gravity, the smaller the specific heat. REVIEW OF THE ACTION OF CHLORINE ON THE ALKA- LINE HYDROXYDS. The action of chlorine upon the alkaline hy- droxyds is so important, theoretically and practi- 134 CHEMISTRY SIMPLIFIED. cally, that we must now transcribe the symbols for those reactions according to the notion of valence : 1. 2K(HO) + 2C1 = K(C10) + H 2 0. The radical (CIO) should be called chloryl like hydroxyl, but this name is rarely met with. It cannot be iso- lated, it has no real existence, it is unbalanced ; C1 2 is the balanced or saturated molecule. Cl 2 Dichloroxyd is at ordinary temperature a reddish-yellow gas of penetrating odor. Specific gravity = 2.977. 1 cubic centimeter weighs 0.0039 grams, nearly 4 mgs.; 1 c.c. of chlorine weighs 0.00317; 1 c.c. of oxygen weighs 0.00143. 2 volumes 01 + 1 vol. = 2 X 0.00317 + 0.00143 - 0.00777. If the latter sum be divided by two we get 0.00388 which is equivalent to the experi- mental weight 0.0039. Hence it follows that 2C1 + 10 = 3 vols., in combining to Cl 2 contract one- third. We found this to be so for SO 2 and for H 2 0. We may deduce the general law that two volumes of one element combining with one volume of another ele- ment always produce two volumes of the combination. Thus is explained why the unit weight of a com- pound can be greater than the sum of the unit weight of its composing elements. C1 2 becomes a blood-red liquid, when the gas is conducted into a tube which stands in a freezing mixture. The liquid is terribly explosive. A scratch with the file on the glass tube may cause an explosion; the C1 2 just breaking up into Cl 2 + 0. This is an interesting fact. For in spite of C1 2 being a compound like water IPO, yet whilst the A CHAPTER ON THEORIES. 135 latter is strongly cohering, the former has little coherence, because in C1 2 we have two non-metals, whilst in H 2 we have metal and non-metal. The compound C1 2 is made by acting with chlorine upon the oxyd of mercury, thus : HgO + 4C1 = HgCl 2 + C1 2 (reddish-yellow gas). In its actions upon metals this body is more energetic even than chlorine itself. When chlorine acts upon K(HO) or Na(HO) or Ca(HO) 2 at boiling heat the following actions occur : 6K(OH) + 6C1 + boiling heat = K(C10 3 ) + 5KC1 + 3H 2 6Na(OH) + 6C1 + boiling heat = Na(C10 3 ) + 5NaCl + 3H 2 O 6Ca(OH) 2 + 12C1 + boiling heat = Ca(C10 3 ) 2 + 5CaCl 2 + 6H 2 The important products are K(C10 3 ), Na(C10 3 ), Ca(C10 3 ) 2 . These bodies we will designate chlo- rates. The group (CIO 3 ) is a monovalent radical but has no real existence ; neither do we know the corresponding chloroxyd C1 2 5 . But we can pre- pare the hydrogen chlorate, H(C10 3 ). It forms a thick, syrupy liquid at ordinary temperature, has strong acid taste, no odor. Above 40 C. it begins to give out chlorine and oxygen. Potassium chlorate, is as above stated, the most important of the chlorates, because with it we can generate chlorine gas easily in immediate contact with the bodies to be acted upon : KC10 3 + water + 6HC1 =; KC1 + 6CI + 3H 2 0, 136 CHEMISTRY SIMPLIFIED. Generation of pure oxygen gas by means of potassium chlorate. Equation KC10 3 + heat = KC1 + 30 Converted into figures this means : Molecular weight of KC10 3 = 39 + 35.5 + 3 X 16 = 122.5 grams, give 48 grams oxygen gas. One cubic centimeter of oxygen weighs 0.00143 grams, hence 48 grams = o. 4 o s i43 c.c. = 33636 c.c. = 33.636 litres = 0.033636 cubic meter. Problem. Let a gas holder be a sheet-iron cylin- der with the dimensions : Diameter = 13.5 inches, height = 27 inches. How many grams of potas- sium chlorate will be required to fill this holder with oxygen? 1 inch equals 2.5 centimeters = 0.025 m. CHAPTER IX. BROMINE, IODINE, FLUORINE. BROMINE. IN the process of salt-making from natural and artificial salt wells, the brine (salt solution) is evap- orated. At a certain concentration of the boiling liquid, salt crystals fall out and keep on precipitat- ing up to a given point. The crystals are steadily removed by means of a sieve-ladle. Finally a heavy solution remains from which no crystals of salt fall. This solution is the mother liquor. It contains the chlorids of calcium and magnesium, CaCl 2 + MgCl 2 + x, x being the combination of the new element bromine, from Greek bromos = stench, with magnesium. If the mother liquor be heated with H 2 S0 4 and MnO 2 the liquid becomes dark red-brown and heavy red-brown vapors appear above it. The vapors condense in a water-cooled receiver to a deep red-brown liquid, almost black, and emit a strong, irritating, suffocating odor (indicated in name). Specific gravity = 3.187 at C., 2.97 at 15 C. It boils at 63 C. and 760 mm. It becomes a brown-red, crystalline solid at 24 C. The symbol for bromine is Br. Bromine gas is 80 times heavier than hydrogen. In most of (137) " 138 CHEMISTRY SIMPLIFIED. its chemical actions it is similar to chlorine. It is soluble in water ; 1 part of bromine dissolves in 33.3 parts of water at 15 C. The solution is blood-red in color, and gives off bromine vapors. It is soluble in ether, alcohol, chloroform and carbon disulfid. If a water solution, containing little bromine, be shaken with carbon disulfid, the bromine will leave the water and pass into the carbon disulfid. 1 vol. Br. + 1 vol. H + heat = 2 vols. HBr. Hence Br is monovalent like chlorine. The result- ing HBr, hydrogen bromid is a colorless pungent gas like HC1. Liquefies at 73 C. into a colorless liquid, which becomes solid when the liquid HBr is al- lowed to evaporate in the air. One c.c. weighs 0.003616 gr. HBr is eagerly absorbed by water, and is then named hydrobromic acid. The highest concentration is 82 per cent. HBr, corresponding to HBr -f- H 2 0. HBr dissolves metals except Ag, Cu, Hg, Pb, because the resulting bromids AgBr, Cu 2 Br 2 , Hg 2 Br 2 , PbBr 2 , are not soluble. HBr combines with the hydroxyds, as HC1 does thus Na(HO) + HBr = NaBr -f H 2 0, Ca(HO) 2 -f 2HBr - CaBr 2 + 2H 2 0. Bromids and oxybromids form when bromine acts upon the alkaline hydroxyds, thus : 2Na(HO)+water+2Br = NaBr+Na(BrO)+H 2 0, 6Na(HO) (concentrated) +6Br=5NaBr+NaBr0 3 + 3H 2 0, 6K(HO) (concentrated)+6Br = 3H 2 0, BROMINE, IODINE, FLUORINE. 139 Potassium br ornate, KBrO*, is even more insoluble than KC10 3 . If therefore bromine be added to con- centrated solution KOH (1:3) until the liquid re- tains a permanent j-ellow color, KBrO 4 will fall out as a crystalline, colorless powder; KBr remains in solution. KBrO 3 can be made pure by dissolving the powder in boiling water, when the salt will crystallize on cooling. The most important salt is sodium bromid, NaBr. It forms a part of bromo seltzer ; is much prescribed by physicians against headache. Tons of it are consumed annually. Bromine itself and bromine water are valuable oxidizing agents in the hands of the chemist. Thus, SO 2 + 2H 2 + 2Br = H 2 (S0 4 ) + 2HBr. Upon heating the solution, HBr escapes with aque- ous vapor and leaves hydrogen sulphate. There are many similar actions, with which we shall meet hereafter. IODINE. Before the discovery of bromine a French chem- ist, Courtois, had found a strange action in the mother liquor of the varec. By this name the peasants of the Channel Coast in northern France designate the extract from the ashes of the sea weeds which are thrown ashore by the storm. These ashes show alkaline reaction like the ashes of land plants, but it was recognized that the sodium carbon- ate is the principal component, not potassium car- bonate, as in wood ashes. When the strained lye 140 CHEMISTRY SIMPLIFIED. from the water extraction is boiled down, potassium sulfate falls out first (being least soluble), then falls Na 2 S0 4 + 2H 2 0, then NaCl, then Na 2 C0 3 -f 3H 2 0, finally leaving a mother liquor quite strongly alkaline, but containing still NaCl, together with Na 2 C0 3 and small quantities of sulfur-compounds of sodium. To this mother liquor H 2 S0 4 + water (1.7 sp. g.), pan acid, is gradually added until the solution is decidedly acid. CO 2 escapes and hydro- gen sulfid, while a scum forms, chiefly consisting of sulfur. After this scurn has been dipped out and the solution has become quite clear, it is transferred into a retort (cast iron with a leaden alembic or cap), manganese dioxyd is added and heat applied. Iodine vapors are given off which become a black crystallized sublimate in the receiver, made of earth- enware. It is, however, impure with salts and water. The water is allowed to drain off, the re- sidue redistilled with quicklime, which absorbs the remaining moisture. The nitre works of Chili fur- nish a mother liquor from which large quantities of iodine are manufactured. So also from the mother liquor of the chemical works at Stassfurt, Germany. In fact iodine or rather an iodid (either Nal or Mgl 2 ) is contained in the sea water, thence it gets into the algae (sea weed); also into the salt beds of the earth ; thence into all salt springs and wells. More in some places than in others. The sea weed contains up to 0.6 p. c. of iodine, but most of it gets lost in the drying and the burning. All iodine pro- ducers are in a big trust, maintaining high prices. Probably a million pounds are consumed annually. BROMINE, IODINE, FLUORINE. 141 Properties. At ordinary temperature a grey-black solid, always crystals or crystal fragments ; metallic lustre; emits a strong, unpleasant odor. It is very soft. Sp. G. 4.958. Melts at 107 0.; boils at 180 C. The vapor of iodine is of a beautiful violet color. The name iodine from iodos similar to violets, was given for this color, which is so very characteristic and even unique. Water does not dissolve iodine freely. One gram I dissolves at 10-12 C. in 5524 grams of water. This solution is known as iodine water. It bleaches the same as chlorine water. Much more soluble in alcohol. This solution is known as tincture of iodine, much used by physicians, to relieve swellings of the skin. Makes a dark -brown stain on the skin, on wool or silk. Iodine dissolves readily in a water solution of potassium iodid, KI, giving a yellow, brown or blood-red liquid. Soluble in ether, in carbon di- sulfid. If a trace of iodine be contained in much water, or salt solutions, a few drops of carbon di- sulfid, shaken with the water, will absorb all the iodine and assume a rose color or purple color. The vapor of iodine is 127 times as heavy as an equal volume of hydrogen at the same temperature. Hence 127 is the atomic weight ; the symbol is I. Starch and iodine. If starch be boiled to thin paste, and the paste filtered, making a clear solu- tion, then this colorless solution will become in- tensely blue if a small quantity of iodine solution be added. Starch -f iodine equals blue body. Thus we can recognize starch from other parts of a plant J42 CHEMISTRY SIMPLIFIED. or seed by means of iodine, and detect iodine in solution with other bodies. Chemical properties. Iodine combines with the metals directly forming iodids. K -f I KI (with explosive energy), Na + I = Nal, the two elements melt together without explosive display. Hg -f 21 -f heat = HgP (producing light) a scarlet-red body. Hg -f I == Hgl, a green-yellow body. These iodids are decomposed by bromine ; KI + Br == KBr -f I. Then in its turn KBr + Cl give KC1 + Br. Chlorine, bromine, iodine form a series whose chem- ical affinity is inversely as their atomic weights which are 35.5, 80, 127. The greater the mass, the more sluggish the activity. Iodine does not readily combine with hydrogen, as chlorine does. It requires a high temperature. (6030 calories.) Hydroiodic acid, HI -f- water is best prepared by working along the equation 21 + IPS + water = 2HI + water + S. We keep the finely powdered iodine stirred up in water whilst the gas EPS is passed into the water; the color of the solution disappears. HI is then dissolved in the water, the sulfur is to be removed by filtration. The liquid is strongly acid, smells pungent like HC1 and acts upon metals and hydroxyds in a general way the same as HC1. A solution of Ag 2 S0 4 -f HI -f- water gives a yellow precipitate of Agl, while HC1 produces a white pre- cipitate of AgCL BROMINE, IODINE, FLUORINE. 143 One does not often have occasion to prepare and use HI. Oxyiodids, iodates, hydrogen iodate, HIO*. By the action of iodine upon KHO we obtain KI and K(I0 3 ). 6KHO + 61 == 5KI + K(IO*) + 3H 2 0. Potassium iodate is slightly soluble in water. If K(C10 3 ) be dissolved in water, to the liquid finely powdered iodine added and the solution boiled, then the iodine will displace the chlorine. 5K(C10 3 ) + 61 + 3H 2 + heat = 5K(I0 3 ) + 5HC1 + HIO 3 . From an iodid as KI chlorine displaces iodine ; but from a chlorate iodine displaces chlorine, we say : Iodine has a stronger affinity for oxygen than chlorine. We make use of this property in quanti- tative analysis. H(10*), Hydrogen iodate, iodic acid is formed by acting with chlorine gas upon water in which finely ground iodine is suspended 3H 2 + I + 5C1 = H(I0 3 ) + 5HC1. If a dilute solution of NalO 3 be heated and chlorine be passed through until no further precipitation of salt be noticed, then the precipitate is Na' 2 (I0 6 )H 2 or Na 2 O.H 2 0(I0 4 ) sodium hydrogen periodate, and from this can be made the silver salt Ag(I0 4 ), silver periodate. General remarks. The most important compound of iodine is KI, potassium iodid, which forms white or colorless cubic crystals, like KBr, KC1; the three salts are isomorphous, have equal form and can re- 144 CHEMISTRY SIMPLIFIED. place each other in any crystal. We can have a crystal, any particle of which contains K, Cl, Br, I, even the very smallest. This leads us to the con- clusion that Cl or Br do not in reality stand for one smallest unit, but that they represent a vast number each of smallest units; roughly, the circle represents the active unit, but the dots mean smallest particles so that one active unit may contain any number of isomorphous particles as Cl, Br, I. The two spheres, Fig. 42, mean the molecule K(C1, Br, I). FIG. 42. The sphere representing potassium contains also a multitude of smallest particles, which in their turn may be a mixture of any number of isomorphous metals, such as Na, Ag. That is, the smallest frag- ment of a microscopic cube might contain (K, Na, Co, Rb, Tl), (Cl, Br, I). Minute quantities of iodine are found in the blood of man and animals as well as in plants, more particularly in the bones of the animal. We find iodine in the mineral iodyrite, y among silver ores in yellow hexagonal crystals. FLUORINE. The mineral fluorite, fluorspar from German fluss- spath, occurs widely as gangue (German gang = vein) BROMINE, IODINE, FLUORINE. 145 or vein-matter with silver-le'ad ores, sometimes fill- ing considerable fissure veins all by itself. The German miners call all minerals which are trans- parent or translucent and possess strong cleavage, spath, thus calcite is kalkspath, iron carbonate is eisenspath, orthoclase is feldspath, and our present mineral was named flussspath because the smelters noticed that it melts not only by itself, but causes other gangue minerals to become fluid, in other words, to act as a flux in smelting. Fluss = flux, whilst fluere is Latin for to flow. Fluorite is characterized by its isometric crystals, cubes, octahedrons, tetrahexahedrons, hexoctahe- drons, and its strong cleavage parallel to the faces of the octohedron. It scratches calcite, is therefore harder. Mostly colored green, purple, pink, blue, black, yellow, yet these colors are accidental, do not belong to the substance of the mineral itself, which is colorless or white. Shows no taste, therefore in- soluble in water. Fluorite melts just at the temperature glass melts ; experiment to be made in a small platinum spoon or crucible ; no gas will be given out. If, however, we put a piece of the spar upon charcoal and direct a strong oxydyzing flame upon it, the spar will melt at first, but after some time will solidify. Why? Because the conditions are different from those in the crucible. The flame itself is not a mere source of heat, but a mixture of gases at high temperature. Among the gases 'are aqueous vapor and oxygen (from the air). We know both to be powerful 10 146 CHEMISTRY SIMPLIFIED. agents when assisted by heat. Indeed, by bringing the nose near the charcoal, a pungent odor becomes noticeable ; the spar decomposes under the influence of aqueous vapor and heat and oxygen. The residue assumes more and more the appearance of lime, glowing incandescence. By acting upon the finely - powdered spar with H 2 S0 4 , in a test-tube, there appears no action at ordinary temperature. Upon applying heat, gas bubbles arise, slowly at first, finally in large number, so that the liquid froths. A gas evidently escapes. To the nose the gas is pungent, acrid, recalling HC1, but more repelling. Litmus turns red at once in the gas. Investigation of the gas. Hypothesis : Having an odor like HOI, we may infer that the gas is a com- pound H n X m or perhaps simply HX ; and proceed- ing a little further with the assumption that X is a new element, let X at once be represented by the letter F (first of fluor spar) ; hence the gas may be H n F m or perhaps HF. At the outset in the in- vestigation, we find ourselves confronted with a serious difficulty. Namely we find the test-tube, which was used in the first experiment, strongly cor- roded, after it is washed out with water : The gas evidently decomposes glass. This unwelcome fact it is true puts a sure stamp of originality upon the new element, quite unlike any other thus far met with, but at the same time excludes the use of glass tubing and all other glassware. On porcelain it acts as on glass ; on iron and zinc it acts strongly, also on copper and silver. Not so on lead, gold and BROMINE, IODINE, FLUORINE. 147 platinum, nor on wax, paraffine or rubber. The latter materials do not stand heat. We are thrown then upon the three metals, of which lead is the cheapest. The gas acts somewhat upon the lead surface, but the product of the action being nearly insoluble, the metal answers well enough for all ordinary purposes. We construct a distilling ap- paratus of which Fig. 43 gives a sectional represen- Fio. 43 tation. C is a cup of sheet lead with a ring-shaped groove G at the rim. The cup sits in an iron cup forming a sand bath, this resting on the tripod T. Into the groove G fits the alembic or helmet A, with the tube neck N. After filling the mixture of fluorite powder and H 2 S0 4 (so much acid that a thin mush forms) at M into the cup C', the alembic A is set into the groove G, and the latter filled with plaster of paris and water. The plaster sets and forms a gas-tight joint. The platinum dish D is partly filled with pure water and so placed under JV that the water level L just covers the mouth of 148 CHEMISTRY SIMPLIFIED. N. D may be set into another dish and surrounded with snow and ice or salt. When the lamp is put under the sand bath, the air is first driven out, then the gas appears and dissolves in the cold water. If we substitute a cylindrical bottle of lead or platinum for the dish, the gas itself will condense into a liquid; specific gravity at 12 C. 0.988, nearly equal to water. This liquid boils at 19.5 C. It fumes in the air ; the gas combining with the moisture of the air gives the visible fume. Fumes cause violent coughing, and may produce death if taken into the lungs. A drop of the liquid will produce on the skin a white spot, a blister forms, bursts and a pain- ful, slowly healing ulcer forms. Be very careful with this concentrated liquid ; but even the dilute water solution has given one much discomfort, when some of it got under the finger nails. The perfectly dry gas does not attack glass ; the least moisture causes an immediate attack ; the glass be- comes opaque, we say the fluorspar gas, or liquid, etches glass; German aetzen, French mordre^ to bite. To etch means to bite out something. Composition of the gas. When the gas acts upon Na, K, Zn, Fe, two products arise : Hydrogen -f- Me n F m (metallic fluorid). When it acts upon hy- droxyd : H 2 + Me n F m result. KHO + HF m = K n F m + H 2 0. That the gas is a hydrogen compound of the radical F there can be no doubt. But there is a difference about the valence of F. Because there is, as with BROMINE, IODINE, FLUORINE. 149 the molecule H 2 S0 4 (see above) the existence of two salts to wit NaHF* and NaF x , In the latter 23 Na (sodium) are combined with 19 fluorine (F), but in the former 23 Na are combined with one H and 38 F. If we admit the proof power of this acid salt (as with the sulfate) then fluorine (F) is divalent, the sodium fluorid is Xa 2 F, the atomic weight of F = 38. There are, on the other hand, quite weighty reasons why we should assume F to be monovalent. Chiefly the closeness between its ac- tion and that of chlorine is convincing to the large majority of chemists to declare fluorine a monad and its atomic weight = 19. Sodium fluorid is thus made NaF. The acid salt is XaH(F 2 ). The solution of HF in water is hydro- fluoric acid. The acid is in all actions closely like HC1, in some instances however fluorids are unlike chlorids. When a water solution of silver sulfate is added to HF + water, no precipitate falls, the AgF being easily soluble in water, whilst AgCl is insoluble in water. On the other hand, calcium chlorid CaCl 2 is very soluble in water, calcium fluorid CaF 2 is insoluble in water. The etching process. We need in the laboratory graduated glass vessels, tubes and flasks ; or we want to mark and number the vessels. Hydrogen fluorid, or the acid salt XaHF 2 is invaluable for this pur- pose ; they can be bought ready for use, being sold either in caoutchouc or ceresine bottles (ceresine is mineral wax). First cover the glass with a thin film of paraffine or of wax. Melt these materials, 150 CHEMISTRY SIMPLIFIED. warm the glass and apply the liquid material with a brush. After cooling draw the mark or number upon the wax or paraffine film ; then scratch away the film (with a steel point) all the lines or dots which are to appear in the etching. After this two ways are open : (1) to expose the engraved spot to the slow vapors of HF (this gives the best result); or, (2) to apply the liquid HF by means of a camel's hair brush repeatedly, according to the desired depth of the etching. There is a so-called glass ink on the market which appears as a milky white liquid. It is a solution of the acid salt NaHF 2 mixed with plaster of paris. The nature of fluorine. When HF is made to act upon metallic peroxyds as MnO 2 , water is produced, MnF 2 and a mixture of oxygen with fluorine. Many statements by experimenters are on record contradicting each other. The work is exceedingly difficult arid expensive. No pure fluorine has as yet been obtained by the above method. This much seems certain, that fluorine possesses a color similar to that of chlorine, i. e. yellowish-green, that its odor is similar to that of chlorine, that it attacks all substances except fluorspar, especially platinum and glass, and bleaches indigo. This state of affairs explains why we are uncertain about the valence and the atomic weight. The metal contained in fluorspar. After the mix- ture of spar powder with H 2 S0 4 has been heated until HF no longer escapes, but the thick white fumes of H 2 S0 4 , that means when complete decom- BROMINE, IODINE, FLUORINE. 151 position has taken place, we find the residue to be a semi-solid which is soluble in a large quantity of water. From the solution precipitate characteristic monoclinic crystals of calcium vitriol = calcium sulfate or gypsum. There may be minute quantities of other metals, which do not now concern us. Calcium is therefore the metal of fluorite, it is cal- cium fluorid, CaF 2 . CHAPTER X. LECTUEE ON NITER OR SALTPETER. SALTPETER or niter is the name at present given to a peculiar salt of immense technical or industrial importance. The word saltpeter is the corruption of Latin = sal petrae = salt of the rock ; niter is de- rived from Hebrew-Egyptian = neter thence Greek = natron-nitron, thence Latin nitrum, the meaning of which has been explained above as original for natrium = sodium. At the present time the name applies to something very different from either rock salt or soda. It applies to two salts, one forming always prismatic crystals of the orthorhombic sys- tem, and the other appearing in grains, roughly re- sembling common salt. On closer examination the granular crystals are seen to possess rhomboid faces not rectangular as in the cube. Geometrically a cube and a rhombohedron are riot different except as to the position of the faces in regard to a system of arbitrary axes. It is quite possible that a crystal- lographic rhombohedron has rectangular faces, and a crystallographic cube has facial angles slightly deviating from 90. The action of a crystal towards the polarized light alone determines the system of crystallization. The angle of the pole edges is 106 30' very near the angle of the cleavage rhom- (152) LECTURE ON NITER OR SALTPETER. 153 bohedron of calcite, which is 105 30'. At all events the obliquity of the angle is large enough to exclude the idea of the cube. The prismatic niter is known as potash niter, the granular rhombohedral variety is known as Chili niter or soda niter. Both varieties are easily soluble in water, show a cooling taste ; nevertheless, there is a marked difference in the solubility of the two forms of niter. 100 grams of water dissolve Soda Niter. Potash Niter. at 6C. 68.8 at C. 13.3 + 10 C. 84.3 +18 C. 29.0 + 20 C. 89.5 +45 C. 74.6 -1-100 C. 168.2 +97 C. 236.0 Between and 100 C. the ratio of solubility is for soda niter f- = f ; for potash niter - 2 r 3 / = \ 8 -. Both niters melt easily. Potash niter, when held in the flame, gives a purple color, soda niter a yellow color to it. About the localities and condi- tions where and under which the niters are found, we will speak at the end of this investigation, as you will be better able to understand several of the intricate questions which arise in connection with these bodies. Investigation of the soda' niter. Let first a crystal fragment be heated in a closed tube. When the heat rises to redness, we notice gas bubbles. On trying the gas we find it to act like oxygen, being without odor, and being able to fan a dark red glowing taper into bright incandescence. Now let 154 CHEMISTRY SIMPLIFIED. us drop a small piece of feathered tin into the molten niter. Notice the intense action, emission of light and conversion of the tin into white oxyd. Repeat these actions with sulfur, with antimony, with char- coal ; in all these cases there is displayed the phe- nomenon of burning, of combustion. Similar action is displayed by melting potassium chlorate. We may then rightly infer that niter is a salt similar to K(C10 3 ), or Na(C10 3 ), but that the salts are not identical follows from several reasons : (1) unlike form of crystals, (2) great difference in solubility, (3) that the chlorates part with their oxygen easily at low temperature, whilst niter only parts with it at red heat, (4) that a brown gas arises from the niter when it burns up a piece of metal, of sulfur or wood, (5) that this brown gas is suffocating. The unavoidable conclusion points to the existence in niter besides sodium and oxygen, of another un- known element. Let this element be designated by N the first letter of niter, and let it be pronounced nitrogen = generator of niter ; then soda niter will most probably be Na n N m O p , and of potash niter, K n N m O. What is the nature of N ? What is the ratio of its combination, what are the numerical values of n, m, p? (1) What is the nature of N of nitrogen? Let us return first to that experiment in which the niter was heated by itself, yielding oxygen. On acting upon it with water we will get a solution which shows strong alkaline reaction ; the niter itself has a neutral reaction neither acid nor alkaline. This LECTURE ON NITER OR SALTPETER. 155 may mean that Xa*0 has formed, and likewise that a compound has formed with less oxygen than the original niter, i. e., Na n N m O p ^. Incidentally we noticed a strong corrosion of the glass tube at the places where the niter had been longest exposed to the flame, which suggests Na 2 O, because we know from handling NaOH and Xa*C0 3 in the glass tubes that these bodies attack the glass at high heat. In the water solution would either be Na(HO) -+- Xa u X m O p " q or only one of the two. Addition of dilute H 2 (S0 4 ) will neutralize Xa(HO). 2XaHO + H 2 (S0 4 )= Na 2 (S0 4 ) + H 2 0=neutral ; a further addition of H 2 (S0 4 ) will cause the evolu- tion of a gas of peculiar odor, rather aromatic. The gas may be H 2 N m O p " q or not ; at any rate it is a peculiar body. Now let us act with concentrated H 2 (S0 4 ) upon the original niter. At ordinary tem- perature there is but little if any action, except that the niter seems to dissolve, at least partly, and but a faint odor is noticed. As heat is applied, efferves- cence ensues. A sour, pungent gas appears, which condenses in a sufficiently cold receiver into a liquid, or else is energetically absorbed in water. In the residue we have sodium hydrogen sulfate + hydro- gen sulfate. We pour it into a porcelain dish, and may convert it into salt cake by means of heat ; prove it to be Xa 2 S0 4 by means of its easy solu- bility in water and its resistance to crystallization. Only low temperature will induce crystals. The liquid distillate we will name spirits of niter. We study its action upon the metals, upon paper, wood, 156 CHEMISTRY SIMPLIFIED. the skin, wool, in fact upon all bodies known to us and handy to procure. For remember always that chemistry means try anything upon everthing else. All the actions will be remarkable. Lead (Pb) + sp. niter -f heat=white salt + brown fumes. Copper (Cu) + sp. niter=blue salt -f- brown fumes. Silver (Ag)+sp. niter=white salt-f brown fumes. Filter paper -h sp. niter -j- heat=solution+brown fumes. Gold (Au) -f- sp. niter -f heat = no action. Platinum (Pt) -f sp. niter 4- heat = no action. Tin (Sn) + sp. niter=white oxyd + brown fumes. Hydrochloric acid (HC1) -j- sp. niter + heat = brown liquid -f- brown fumes. HC1 + sp. niter-j-gold -j- warm = yellow solution, AuCl 3 -f brown fumes. HC1 -f sp. niter -f platinum = yellow-brown solu- tion -|- brown fumes. The spirits of niter proves itself thus one of the most powerful agents. The Arab chemist Geber was the first to mention this body. The Latin translation of his works speaks of it as aqua fortis (the strong water) or aqua dissolutiva (the dissolving water) because it dissolved both silver and lead. But the combination of the spirits of salt (HC1) with the spirits of niter went, and still goes, by the name aqua regia (the kingly water), because it dissolves gold, the very king of the metals. LECTURE ON NITER OR SALTPETER. 157 On the other hand, if we dilute first the spirits of niter with water, very considerably, then we get hydrogen when acting upon either iron or zinc, but not with lead, copper or any other metal ; with all of these it is either brown fumes or nothing. Re- member the similarity with the actions of oil of vitriol or of the concentrated sulfuric acid. Con- centrated acid on the metals gave vitriols and SO 2 ; diluted acid on iron or zinc gave vitriols and H. Just as SO 2 was demonstrated as an oxyd with less oxygen than the sulfur oxyd which constitutes the sulfuric acid, so it follows logically that in the action of the strong spirits of niter, the brown fumes must FIG. 44. constitute a lower oxyd of the nitrogen, the element whose properties we are after. But if thus the metals can take away oxygen from the nitrogen, we argue, at a temperature below even the boiling-point of water, will it not seem probable that at a still higher heat more will be taken, or perhaps even all? We set up an apparatus as shown in Fig. 44. F is a small flask with twice perforated stopper. 158 CHEMISTRY SIMPLIFIED. Through the latter pass the stem of a funnel 2 and the delivery tube 3. In F we place finely divided copper, K (gauze, granules, chips). The funnels hold the diluted spirits of niter. 3 connects with U-tube 4-. The latter is partly filled with concentrated H 2 S0 4 forming a trap to dry and control the escap- ing gas. 5 is a tube filled with quick -lime (CaO) between two cotton plugs. In the charcoal furnaces F', F', lie the hard glass tubes T, T', each charged with rolls of copper wire-gauze. By means of rub- ber tube 6j T' connects with the bell jar B, which is filled with boiled water (in order to expel any ab- sorbed air). Before connecting F with tube 7 we heat up the furnaces and pass hydrogen through T, T', in order to have perfect metallic surface on the copper. The tube 5 will act as dryer and will also retain any gas of an acid nature. While the action of hydrogen was going on in T, T', we have utilized time by starting the action in F so that all the air is driven out by the gas. We regulate the flow of liquid from the funnel, so that, if possible, the sulfuric acid trap in 4- will indicate the passing of a slow current of gas. The slower and steadier (not in gulps) the current, the better will be the chances of a perfect deoxydizing action. Before connecting T with tube 5 by a rubber tube 7 we re- move most of the charcoal from F, I ', let the tubes T, T' come down below red heat, for the unknown niter gas, being an oxyd might produce with the hydrogen an explosive mixture. When we connect 7 with T' we wait a sufficient time to let the hydro- LECTURE OX NITER OR SALTPETER. 159 gen be displaced by the niter gas, then we replace the charcoal, get a good heat, cherry red, being always careful to protect the rubber stoppers in T and T' by guarding shields and dropping water, and again after some minutes' wait, we connect the rubber tube 6 with the bell jar B. In the position as shown in the figure there will be suction through the chain of apparatus as soon as the stopper 8 is opened, owing to the difference of level, k, between the water inside and outside the bell. Therefore all stoppers and connections must have been made air- tight, otherwise air will be sucked into the appara- tus : The true nature of nitrogen will be masked. We maintain the action until B is filled with gas, or until several holders shall have been filled. Properties of nitrogen. After having been pro- duced, as just stated, the gas possesses the characters of an element. With present means, it cannot be further split. A gas devoid of color, odor, taste. Specific gravity 14 (H = 1) ; 0.9674 (Air 1). This specific gravity is so nearly the same as that of the azote, the nonrespirable part of the air, this being 0.9713, that we are justified in declaring azote = nitrogen, because the nitrogen also is nonrespir- able, it causing death by suffocation. The gas is but very slightly soluble in water, it is not absorbed by the alkalies. It is very indifferent towards all agents, and yet it is evident that under certain con- ditions it may be made to unite with oxygen in several ratios, and also with hydrogen giving rise to a most interesting body. Nitrogen we shall find in 160 CHEMISTRY SIMPLIFIED. all animal and plant bodies, constituting the essen- tial constituent of protoplasm, the body which is at present taken to be the basis, the substratum of all life. It is important to note that nitrogen has no property by which we can at once identify it, ex- cept the specific gravity ; all other properties are mere negations of the properties possessed by other gases. Properties of the spirits of niter and its quantitative composition. Acting with the spirits of niter upon a metallic oxyd (MeO) we get water + niter. The most suitable metallic oxyd for our present purpose is lead oxyd PbO which has the pale yellow color ; the red oxyd is not equally suitable. Acting upon Na(OH) or K(OH) we restore the original niter, either soda niter, or potash niter and water. There is only one salt formed, no acid salt having been obtainable. Hence the radical contained in the spirits is there combined with one H, the radical is a monad, and will, therefore, be represented by the symbol H(N m O) Hence, also, if we act with the spirits upon lead oxyd, the reaction must be PbO + 2H(N m O) = Pb(N m O) 2 + H 2 0. Like the soda and potash niter, the lead niter con- tains no water, except a trifle with the mother liquor. The white or colorless crystals of this lead niter are rhombohedral, hence isomorphous with the soda niter. It is best, because most rapid, to LECTURE ON NITER OR SALTPETER. 161 use the spirits diluted, because the lead niter is not soluble in the concentrated spirits. When all of the lead oxyd is thus dissolved, or when the liquid will not further dissolve the oxyd, filter and evap- orate the filtrate to complete dryness. The residue is then pure lead niter. Heated in a crucible or glass tube, the lead niter breaks up into brown gas and yellow lead oxyd. The brown gas is very acrid and suffocating, yet it will act upon a glowing taper like oxygen. In fact we can readily prove the brown fumes to have an admixture of oxygen ; therefore Pb(N m O) 2 + heat = PbO -f brown gas + 0. This action opens the way for a quantitative deter- mination of the ratio existing between Pb, N and FIG. 45. 0, if we arrange the conditions of the experiments in such a way that the volume of nitrogen can be accurately measured, which results from the decom- position of say one gram of the lead niter. Let T, Fig. 45, be an ample hard glass tube fitted 11 162 CHEMISTRY SIMPLIFIED. with stoppers. 8 is a porcelain boat containing 0.5 gram of lead niter. 9 is a clean roll of copper gauze. 7 is a U-tube filled with pieces of pumice and H 2 S0 4 (to retain moisture). 6 is a smaller U-tube with enough H 2 S0 4 to form a trap. H is the holder filled with lime gas and the water in B furnishes the pressure to drive out the gas from H. 10 is a gas burette and 11 the cylinder to regulate the pressure. Both cylinders are filled with solu- tion of sodium hydrate. All stoppers and connec- tions being tight, we first displace all air from the apparatus, because four-fifths of it are nitrogen ; then heat the copper gauze to redness, while we protect the boat from the heat by the shield 12. When the gauze is glowing we move shield 12 to the left, from time to time, so that the decompo- sition of the lead niter shall be slow and gradual ; but at length the entire tube is at redness up to the shield. As the niter decomposes the oxygen goes to the copper and the nitrogen passes into the burette, pushing before it the lime gas. As soon as the con- tents of the boat are pure dark yellow or red, we open the stop cock 4- and drive all niter gas into the burette. Then, closing the latter's stopcock, we shake the gas with the liquid, thus absorbing all the lime gas into the Na(OH) solution, and then read the volume of gas. Let V cubic centimeters be the volume of the gas, measured under the pressure of the atmosphere at 20 C, the pressure of the at- mosphere, measured by the mercury column of the barometer, be B millimeters. As the gas is satur- LECTURE ON NITER OR SALTPETER. 163 ated with aqueous vapor, being over water, i. e., a dilute solution of Na(HO), the tension T of the aqueous vapor increases the pressure B and must therefore be subtracted, because we wish to get at the volume of the di~y gas. The expansion of the air for one degree C. is 0.00367 of its volume, hence the volume V of dry gas at C. and sea level bar- ometer, 760 mm., will be V'.(B T) = (1 + 0.00367t) X 760 = (The tables calculated by Prof. Leo Liebermann are most convenient in such calculations.) If the weight of one c.c. of dry nitrogen at C. and 760 mm. be 0.001256 gram, then V X 0.001256 = G, will be the weight of the nitrogen contained in 0.5 gram of lead niter, Pb(N m O) 2 . G equals 0.0423 gram and the weight of lead oxyd, PbO, is 0.337 gram (found by weighing boat after operation). Then we will have PbO = 0.3370 N = 0.0423 } = 0.163 gram == wt. of the N. = 0.1207 / oxyd. 0.5000 - The weight of oxygen if found by difference. The volume weights of oxygen and nitrogen (found by direct weighing) are 16 and 14. Hence we will ob- tain the atomic ratio of the two elements by divid- ing gram weights of N and by 14 and 16 respec- tively. 164 CHEMISTRY SIMPLIFIED. 2^23 =0 .00302; -2^07 = 0.00754 I 14 16 302 2 754 - = 5> hence N2 5 We have directly proved that lead niter is a combi- nation of the oxyd PbO with the oxyd N 2 6 . Above we showed the probability of the radical N m O p being a monad. In the lead niter there are then two molecules of the nitric radical. PbO.N 2 5 becomes Pb(N 2 6 ) or Pb(N0 3 ) 2 . For the sake of uniformity we will designate here- after the niters by the word nitrate, thus : Hydrogen nitrate = H(N0 3 ) = nitric acid = aqua fortis. Sodium nitrate = Na(N0 3 ) = soda niter = Chili niter. Potassium nitrate = K(N0 3 ) = potash niter = common niter. Calcium nitrate = Ca(NO 3 ) 2 . Silver nitrate Ag(N0 8 ). Lead nitrate = Pb(N0 3 ) 2 . Copper nitrate = Cu(N0 3 ) 2 . Ferric nitrate = Fe(N0 3 ) 3 . All normal nitrates are soluble in water, whilst some sulfates, some chlorids, bromids, iodids, fluorids are insoluble in water. Sol. Ag(N0 3 ) + sol. NaCl = insol. AgCl + sol. Na(N0 3 ). LECTURE ON NITER OR SALTPETER. 165 Sol. Pb(N0 3 ) 2 -f sol. Na 2 (SO 4 ) = insol. Pb(S0 4 ) -f sol. 2Na(N0 3 ). These two reactions serve us as tests for soluble chlo- rids and sulfates respectively. Of all bodies we have investigated, the nitrates appear to me the most wonderful. The very same elements in which we breathe and lead a more or less harmless life, the existence of which elements we are not even ordinarily aware of, become vio- olently active in the form of nitrates. The chlo- rates, though acting similarly, are not so astonish- ing, because in them we find chlorine, a violently offensive body by itself. A rather rough simile may bring nearer to your grip of imagination this action of the nitrates. Let the atoms be imagined as spiral springs (watch spirals). In the atmos- phere the nitrogen molecules lie alongside of the oxygen molecules as uncoiled springs, inert, inoffen- sive things. A powerful shock strikes the inert, uncoiled bodies, say the electric spark of a thunder storm ; the shock causes the springs to coil up, and the affinity of a strong basic oxyd, as K 2 0, Na 2 0, lies handy as a binding rope of the springs, as shown in Fig. 46 ; the nitrate molecule is achieved ; the poten- tial energy of the coils is restrained by the thin band of affinity. Now let the nitrate molecules be brought into intimate contact with other molecules which possess a stronger affinity for oxygen than the nitrogen, for instance, carbon molecules, at a red heat. We may even carry the picture further and say the thermic energy expands the springs, 166 CHEMISTRY SIMPLIFIED. straining them against the restraining bond until at red heat this bond snaps, giving way to carbon oxygen attraction. With the breaking of the FIG. 46. Na-K-Ca bond, the oxygen springs uncoil and display an extraordinary energy, such as we are forced to ad- mire in gunpowder. COMPOSITION OF GUNPOWDER OR BLACK POWDER. We saw in a small experiment how the mixture of niter and charcoal powder flew out of the glass tube with a flash. The products of that action were Na 2 (C0 3 ), sodium carbonate, N, nitrogen and CO 2 . The two latter gases, through their expan- sion, impart to the explosion its propelling or its tearing, splitting effect. The more gas, the greater the effect from a given mixture. But in forming Na 2 C0 3 much gas passes into the solid state and lessens the effect of the powder. It was soon found that a greater effect could be obtained by mixing with niter and charcoal a certain quantity of sulfur. This was all arrived at by those patient experi- menters without knowing even that the production of gas was the chief object. They mixed sulfur LECTURE ON NITER OR SALTPETER. 167 with the powder on general principles that it would be a good thing, because sulfur was a very peculiar and mysterious body. We modern chemists, who experiment less and think more, know why the sul- fur increases the effect. This is the theoretical pic- ture of the explosion : 2K(N0 3 ) + S + 3C -f red heat = K 2 S(solid) + 2N + 3C0 2 . By weight 2(39 + 14 + 48) -f 32 -f 3 X.12 = 2 X 39 + 32(solid) 202 +32+ 36 = 110 + 2x14 + 3(12 + 32) + 28 + 132 KNO 8 = 202 = 74.81 % 75 potassium niter S = 32 = 11.85 12 sulfur C = 36 = 13.34 13 fine charcoal 270 100.00 On the second side of the equation stand K 2 S ==110= 40.70^ (solid) 41 solid 2N = 28- 10.40 f. gas 10 3C0 2 =132= 48.90 <& gas ^ 270 100.00. 59 per cent, of the powder is converted into gas. One gram of the powder gives by the explosion 0.1 gram of nitrogen, 0.49 gram of carbon dioxyd. At C. and 700 mm., 0.001256 gram of nitrogen occu- 168 CHEMISTRY SIMPLIFIED. pies the space of one c.c.; 0.1 gram of nitrogen occu- pies the space of 79.6 c.c. 0.001977 gram CO 2 occupies the space of 1 c.c.; 0.49 gram CO 2 the space of 247.3 c.c. The volume of gas produced by the explosion of one gram of perfect black powder is at C, 247.3 + 79.6 = 326.9 c.c. One gram of best powder, in small but perfect angular grains, occu- pies the space of 0.9 c.c.; the surface of 1 c.c. being six square centimeters. Hence if one gram of such powder be filled into a cartridge and a bullet be pressed tightly upon the powder, a space will be filled possessing six times 0.9 5.4 square centi- meters. After explosion this same space will be filled with 326.9 c.c. of gas which will press upon 326 9 the enclosing surface with Q Q 363.2 times the pressure of the atmosphere or upon 1 square centi- 363.2 meter with ^ * = 67.26 atmospheres. But there is another very important factor ; the heat gener- ated by the explosion, which expands the gas merci- lessly, and if the enclosure be rigid, exerting an ever-increasing pressure. The gases expand, within certain limits so nearly alike, that one coefficient answers for all. This coefficient is yfs or 0.00367 volume for 1 C. By the following reasoning we arrive at the theoretical temperature produced by the explosion of one gram of powder : 1 gram car- bon through the oxydation into CO 2 produces heat equal to 8050 calories (the heat would raise the temperature t of 8050 grams of water by one de- LECTURE ON NITER OR SALTPETER. 169 gree C. Hence 0.13 gram of carbon will produce 8050 X 0.13 = 1046 calories. By the burning have been produced 0.49 gram of CO 2 , 0.1 gram of N and 0.41 of K 2 S. Each of these bodies has a capacity for heat to be swallowed up before the heat can be felt. The temperature, the sensible heat, must therefore be directly proportional to the absolute heat the 1046 calories, and inversely to the ab- sorbed heat. In a general way A T _ fz a in which A = absolute heat, a = weight of pro- ducts into their respective specific heats. In our special case TO _ _ 1046 __ 0.499 X 0.22 -f 0.1 X 0.24 + 0.41 X 0.4 1046 1046 0.108+0.024+0.164 0.296 The a in the denominator is represented by the sum of the products of the combustion of the powder ; each member multiplied by its factor representing the unit of heat capacity or specific heat. Thus it is seen that by the combustion of one gram of powder a temperature is generated equal to 3534 C., higher than that of an intense coal fire. At this temperature the 326.9 c.c. of gas must have expanded to 326.9 X 0.00367 X 3535 = 4236.6 c.c., to 12.9 times their volume at C., or 871.7 atmos- pheres pressure per sq. cm., provided the law of ex- pansion holds good at such high temperature, but 170 CHEMISTRY SIMPLIFIED. this is by no means certain. At any rate, the theo- retical picture gives a measure for the actual phe- nomenon. We see that the pressure of the gas must be enormous, though less than the theoretical, in fact only about J as shown by actual experiment, made for the military departments of several gov- ernments. Such experiments are known by the adjective ballistic (made with a ball). The reasons are several. In the first place the burning of the powder is never complete. 2. The reactions are not quite like the formula indicates. A part of the oxygen remains fixed by forming K 2 S0 4 , hence some of the carbon only burns to CO, whilst some of the nitrogen remains as NO. 3. The material of the apparatus a gun for instance, or a mortar is somewhat elastic. As engineers we should know all that has here been given, to understand the effects of the blasting powder we use. I give you only the chemical facts connected with the matter. Other powders. The white and smokeless powders all contain a nitric radical, either NO 2 or NO 3 . In principle there is no difference between them and black powder. Their special compositions will be dealt with under the subject of carbon compounds. INVESTIGATION OF THE BROWN FUMES OR NITROUS FUMES. These always form, when H(N0 3 ) acts upon an oxydizable substance, as copper for instance, or SO 2 . Acting with H(N0 3 ) upon copper in a test-tube LECTURE ON NITER OR SALTPETER. 171 we observe the tube filled with the brown fumes so long as the action continues. But if the tube be stoppered with a narrow tube for the escape of the gases, a different action ensues. We notice that the gas inside the tube turns lighter by degrees, at last being quite colorless, but at the mouth of the escape tube a steady cloud of dense, brown-colored gas is visible all the time. This at once suggests the pres- ence of two different gases within the brown fumes. More precisely we would say : Through the action of HNO 3 upon an oxydizable body is generated a colorless gas an oxyd of nitrogen. When this gaseous oxyd comes together with air the brown gas forms by combination of the air-oxygen with the colorless gas ; but the brown gas itself must possess a ratio of oxygen to nitrogen less than 5/2, for if it is absorbed in ice water we find produced a mixture of spirits of niter and the same acid that was made by acting with H 2 S0 4 on the residue left after heat- ing niter. All this will be proved presently. The brown gas becomes colorless if mixed with an oxy- dizable body, as SO 2 for instance, evidently by loss of oxygen. Hence the colorless gas must have an oxygen to nitrogen ratio less than the brown gas. Nitrogen dioxyd, NO 2 or N 2 4 , hyponitric anhy- drate the nitrous fumes. Let the tube T, Fig. 47, be partly filled with dry lead nitrate and placed in furnace F. Make the U-tube U from a J" tube, draw it out into a capillary at C, a and 6, then sur- round it in the basin B with a mixture of ice and coarse common salt ; stick a thermometer t into the 172 CHEMISTRY SIMPLIFIED. mixture. If the salt be kept on snow or ice until its temperature falls to C., and if it be then mixed with one volume of snow or fine-cut ice, the tem- perature of the basin will drop to 20 C. Make FIG. 47. connection at C with T, and heat T to redness grad- ually. We know from previous experiment (com- position of N 2 5 ) that the Pb(N0 3 ) 2 breaks up into PbO -f- brown fumes. Thus Pb(N0 3 ) 2 -f- heat = PbO + (N m O- x ) brown fumes + (6 p x 1)0. Passing into U the fumes condense into a brown liquid and at 6 issues a gas which sustains combus- tion with energy (oxygen). At end of decomposi- tion close U at C and a with the blow-pipe. If the U-tube be changed twice, then you find in the third tube colorless crystals. These represent the true substance. The crystals melt at 12 C. to a color- less or slightly yellow liquid. It follows that no crystals result if the temperature of the freezing mixture be not at the least 15 C. As the liquid is heated by the warmth of the hand it becomes more and more highly colored, giving out dense brown fumes and reaches a constant boiling-point LECTURE ON NITER OR SALTPETER. 173 at -j-22 C. (in the hand, because the temperature of the blood is 33 C.). On the addition of ice water drop by drop, the liquid turns first green, then blue, then colorless. It acts upon oxydizable bodies more energetically than HNO 3 , because the restrain- ing bond of the hydrogen is removed. Mention has already been made of the suffocating action of the brown fumes. The living organism tries to avoid the danger lurking in the breathing of the gas, for the muscles of the epiglottis contract instantly when the gas comes in contact with their nerve ends. At Berlin, some years ago, fire broke out in the yard of a large chemical works. Sixty carboys of aqua fortis were stored under one shed. They exploded, one by one. The acid flowing into the straw and wood of the packing let out an immense volume of brown fumes. Five of the firemen who had been endeavoring to save the carboys, went back to the station with the others, smoked a pipe and went to sleep in their bunks. Within a few hours they woke in convulsions and died shortly after, in great agony. Let this be a warning to be careful. Do not act upon metals, or sulfids with HNO 3 , except in a well-drawing hood; for even if death does not ensue, there may be permanent in- jury to the bronchise and their capillary ramification in the lungs, from ulceration of the mucous mem- brane. The composition of the brown gas we find similarly to that of the lead niter. We make a small U-tube U, Fig. 48, drawn out into capillary thread at a, b. We take the weight and then fill into it a 174 CHP:MISTRY SIMPLIFIED. few drops of the liquid, by pressure or by suctioD. In T there is the coil of copper wire. At B is the burette for measuring the gas, filled with solution Na(HO), and which is immersed in a dish of water FIG. 48. when in use. We fill the tube T with lime gas, in- sert 7 at b into the stopper and a into rubber tube leading to lime gas holder and furnished with clamps C; then connect the burette B. We bring T up to redness and turn on the lime gas in a gentle current. The radiant heat will suffice to volitalize the liquid oxyd of nitrogen and the lime gas will carry it over the copper gauze. Nitrogen and lime gas pass into B and the NaHO solution will absorb the lime gas. Thus we get the nitrogen volume which we deal with as in the previous experiment ; w being weight of oxyd, n being the weight of nitro- gen, w n = 0, the weight of the oxygen. Divid- ing n by 14 and w n by 16, we get the ratio Jl : w ~ n = 1 : 2 = NO 2 or N 2 4 or N 4 8 14 16 Some investigators claim the ratio N 4 8 which can be interpreted as N 2 3 .N 2 5 a combination of the two oxyds, on the ground that when ice water be LECTURE ON NITER OR SALTPETER. 175 mixed with the liquid oxyd it breaks up into the two acid bodies: H(N0 2 ), hydrogen nitrite and H(N0 3 ), hydrogen nitrate : to wit N 2 3 -f- H 2 = 2H(NO) 2 ; N 2 5 + H 2 = 2H(N0 8 ) However, this view, which looks at the molecule as a polymeric molecule, i. e. } 4 times NO 2 , only applies at low temperatures, for Dulong found for the brown gas the specific gravity 1.62, and this corresponds to \ vol. nitrogen 0.4856 1 vol. oxygen = 1.105 L5906 so nearly 1.62 that we can have no doubt left. The new gaseous molecule is surely NO 2 = 2(JN -{- 0). 1 vol. N -f 2 vols. O = 3 vols., become 2 vols. NO 2 ; there is a condensation of 3:2 of 1J:1. When the brown fumes are passed into H 2 (S0 4 ), the fumes become absorbed, and if the operation be continued for a time, colorless crystals form in the acid. The crystals are obtained more readily by pouring a few cubic centimeters of H 2 (S0 4 ) into a small flask and by spreading the liquid, through rotation, upon the entire glass surface. If now the brown fumes are brought into the bottom of the flask, under the rotation the brown fumes become absorbed, a crystalline crust resembling ice forming all over the flask (inside). The composition is not. definitely settled, probably 2H 2 (SO 4 ).N0 2 . The reaction is of much economical importance in the manufacture of H 2 (S0 4 ) on a large scale and will be brought forward when we shall arrive at that process. 176 CHEMISTRY SIMPLIFIED. The colorless gas, nitrogen monoxyd, nitric oxyd, NO. This body becomes generated whenever H(N0 3 ) acts upon oxydizable bodies, metals, metallic sulfids, paper, wood, sulfur dioxyd. As soon as it comes into contact with the air it changes into nitrogen dioxyd NO 2 (brown nitric fumes). We obtain this gas very pure by passing SO 2 into warm HNO* -f water. In flask F, Fig. 49, we generate SO 2 from the FIG. 49. mixture M, which is copper gauze and H 2 S0 4 , heated by a flame, according to equation Cu + 2H 2 (S0 4 ) = CuSO 4 + 2H 2 + SO 2 . Through tube 1 gas passes into the washing tube #, partly filled with H 2 (S0 4 ) (moisture is retained and flow of gas can be regulated). IF is a so-called Will's condenser, possessing the three bulbs, 5, 4, 5, and containing 2H(N0 3 ) -f 2H 2 0. B is a basin holding warm water to heat the H(N0 3 ); through tube 6 the gas can be delivered into any suitable vessel. In the figure this vessel is a knee-tube T filled with mercury and standing in mercury trough Q. T is held by stand S. When the gas SO 2 bub- bles into the H(N0 8 ) it becomes oxydized into LECTURE ON NITER OR SALTPETER. 177 H 2 (S0 4 ) and H(N0 3 ) becomes changed into the nitrogen monoxyd. Thus 3S0 2 + 2H(N0 8 ) + 2H 2 O = 3H 2 S0 4 + 2NO (colorless gas). Do not think the composition of the gas must be NO, because the equation demands it, many stu- dents, and even some professors, have that belief. I wrote the equation because I know the gas to be NO. I could have balanced the equation in several other ways, merely by changing the coefficients of SO 2 and ofHNO 3 . Proof of the composition of nitrogen monoxyd. Sup- pose we have allowed to enter into the knee-tube T, Fig. 49, about 10 c.c. of the gas and have marked this volume by a sticker. Banking upon the known maximum of affinity of potassium for oxygen, we will introduce, by means of a thin copper wire, a piece of metallic potassium at P, and heat the metal with a burner. A flash of light and a violent com- motion of the gas accompany the act of deoxydation of the gas. I must hold the tube firmly, with the left hand, to prevent its being raised above the mer- cury level in Q. When the tube has resumed the temperature of surrounding air we find the volume of gas shrunk to exactly J ; hence there is in one volume of nitrogen monoxyd J vol. N -f- J vol. or made into full units 1 vol. N -f 1 vol. 0, the sym- bol of the gas is NO. There is no contraction in the union. Specific gravity of NO found by weighing 1 vol. =-1.0379 (air=l) 12 178 CHEMISTRY SIMPLIFIED. J vol. N = 0.4856 j vol. = 0.5525 L0381 Calculated specific gravity equal to the experi- mental, hence NO represents the molecular volume of the gas. Properties of NO. The gas cannot occur in nature. Why? Because it changes to NO 2 on meeting the oxygen of the air. For the same reason we do not know whether it has odor^or taste. Does not act on litmus paper. Its actions on the breathing organs are the same as those of NO 2 , for the same reason as above. If the gas be conducted into a solution of copperas Fe(S0 4 ) + 7H 2 or Fe(Cl 2 ) + 2H 2 the solution turns dark brown, or even inky black. The gas is completely absorbed. Distinction from all other gases. This reaction enables us to recognize and identify a nitrate in an unknown mixture, even .very minute quantities of the nitrate. Proceed as follows with this test : Bring the unknown solution (1 c.c.) into the bottom of a test-tube T, Fig. 50, add 2 c.c. of concentrated H 2 (S0 4 ) and mix. Then take into a glass tube t, which has been drawn out to a capillary, a strong solution of copperas (ferrous sulfate) Fe(S0 4 ). Lower t into T, so that the, point just touches surface of the liquid mixture, and let run out a few cubic centimeters. The two liquids are then unmixed, in two superimposed strata. Within a short time a dark ring will develop at the contact of the strata. If no dark ring develops then the unknown substance does not contain any nitrate. LECTURE ON NITER OR SALTPETER. 179 The student should practice this reaction using as unknown a solution which was made up from one drop of strong H(N0 3 ) and 50 c.c. of water (ap- proximately 0.2 per cent. HNO 3 ). Nitrites, Na(NO*), K(NO*), Ag(N0 2 ). Di-nitrogerti- trioxyd, N 2 0*. Both -Na(N0 8 ) and K(N0 3 ) loose oxygen when heated at low red heat and more rapidly at bright red heat. Since neither the metal FIG. 50. nor nitrogen is given off, the ratio between the three elements must become changed ; a new body forms. This we can demonstrate readily in two ways : (1) by acting upon the residue with concen- trated H 2 S0 4 when copious brown fumes are given off; (Recall that the nitrates + H 2 S0 4 do not give 180 CHEMISTRY SIMPLIFIED. any fumes.) (2) by adding solution of Ag(N0 3 ) to the water solution of the residue a white precipi- tate falls out, which is not very soluble in water. This silver salt does not contain water, and by its decomposition we can find the ratio of Ag, N, 0, by using the apparatus and method followed with the lead nitrate. Let the silver salt, which shall be named silver nitrite (note the substitution of the letter i for the letter a in nitrate) be Ag(N m QP~ q ) then we shall obtain by the decomposition Ag(N m O p ~ q ) -f- red heat = Ag + brown fumes. Let the fumes be decomposed by copper gauze at red heat and you get the nitrogen. ( N mQp-q) fumes _|_ aCu _|_ re( j h eat = (p_q)CuO + (a-p-q)Cu + mN and thus we find : Ag : N : 1 : 1 : 2 hence the formula of the nitrite is Ag(N0 2 ) and similarly must be the Na, K salt Na(N0 2 ) K(N0 2 ) The hydrogen salt cannot be made, it is too unstable. Preparing K(N0 2 ). Heat niter in an iron pot or crucible to melting heat, then add 2 parts of metallic lead for each part of niter. The affinity of lead for oxygen helps the decomposition of the niter : K(N0 3 ) -f heat + Pb = K(N0 2 ) + PbO Molecular weight K(N0 3 ) = 101, atomic weight of Pb = 207, hence 1 part niter -f- 2 parts lead, corre- spond to theory. In practice, however, the reac- tions are not complete. Some lead is apt to remain LECTURE ON NITER OR SALTPETER. 181 unoxydized, some oxygen escapes, the residue is, usually, K(NO 2 ) mixed with PbO, KNO 3 and K 2 O. Dissolve the fused mass in little boiling water and let cool. The PbO will settle, the K(X0 3 ) will crystallize. Decant (that is pour off) the liquid and evaporate to dryness, finally heat to melting and pour into pencil moulds, same as used for NaOH and KOH. K(X0 2 ) is a reagent in use for the separation of cobalt from nickel, as well as for other operations. The salt usually shows an alkaline re- action from KOH, can be neutralized with dilute acetic acid. In the nitrites, we have undoubtedly a peculiar oxyd of nitrogen. The radical (NO 2 ) is not that oxyd, its reactions are quite different. This oxyd is X 2 3 , for K 2 O.X 2 3 = 2K(X0 2 ) 2 . This oxyd dinitrogen trioxyd is contained in the brown fumes, as gas. It may be condensed at 15 C. into a deeply blue liquid, which boils even at the freezing-point of water. A blue solution results from the action of XO gas upon a solution of H(X0 3 ) in water (specific gravity = 1.25) a green solution, when the specific gravity is 1.35 (because this liquid then contains both X 2 3 and X 2 4 ,(2X0 2 ). The same colors result when acids of the given specific gravi- ties act upon certain oxidizable bodies. Any one not knowing this fact will often waste much time trying to find copper (blue nitrate) because he sees a blue solution, or chromium because he sees a green solution when acting on galena, the lead sulfid, for instance. The student should get this information by experiment to fasten it the more firmly. 182 CHEMISTRY SIMPLIFIED. If a solution of Na(N0 3 ) or K(N0 3 ) be shaken with amalgamated zinc (zinc coated with mercury) the solution will then contain nitrite, to be detected by the addition of the liquid to starch paste contain- ing potassium iodid and some free H 2 S0 4 (dilute). The paste turns blue, because KI + H 2 S0 4 (dilute) + NaNO 2 = 1 + N aj K(S0 4 )+ IPO + NO. The rain water from a thunder shower will give this reaction, showing that it contains nitrite; azote and oxygen have become united by the electric dis- charges of the storm. Dinitrogen monoxyd, N 2 0, nitrous oxyd, laughing- gas. This gas arises when the monoxyd NO is al- lowed to stand in contact with easily oxydizable substances ; finely divided zinc, iron filings, sulfites (Na 2 (S0 3 )), and many others. One-half of the oxy- gen is removed, or 2 molecules NO furnish one molecule N 2 0. Thus 2NO + Zn = N 2 + ZnO 2NO -f Na 2 (S0 3 ) N 2 + Na 2 (S0 4 ). We proceed to prove this by acting with heated potassium upon the gas in a knee-tube, exactly as described for NO. The action is quite as energetic. After cooling the volume is the same as before the action. Hence one volume gas contains one volume nitrogen. Weight of one vol. gas (spec, gr.) = 1.5270 minus weight of one vol. N (spec.gr.) = 0.9713 05557 but 0.5557 is very near L1 p 56 = 0.5528 == J vol. oxygen. LECTURE ON NITER OR SALTPETER. 183 Hence the gas is NO* or N 2 0. The properties of the gas N 2 are remarkable. It was discovered by Priestly in 1776, and Sir H. Davy demonstrated its composition. The gas is colorless, possesses a faint sweetish taste and slight aromatic odor. One cubic centimeter at C. weighs 0.001974 gram. The gas is quite soluble in cold water. At C. one volume water absorbs 1.3 volumes of the gas, but at 20 C. only 0.67 volume. A taper burns in the gas more brightly than in air, almost as in oxygen gas. The gas can be taken into the lungs (breathed) without any discomfort. Quite on the contrary ; its action when breathed, is that of a stimulant. The nerves become excited, the effect is similar to that of alcohol and ether intoxication ensues, either numbness or acute mania. The effect is not by any means alike on all persons. Sir H. Davy gave it the name laughing-gas, pleasure gas. Its application in dentistry is well known. Dentists use it with nervous persons, who are unwilling to stand up against pain. Though not quite without danger, serious after-effects are less likely through its use than through other anaesthetics ether or chloroform. The dentists buy the gas in the com- pressed state, in copper cylinders. At C. the gas becomes liquid under a pressure of 30 atmospheres, that means when 30 volumes are compressed into the space of one volume, approximately ; 300 litres of the gas yield 400 c.c. of liquid N 2 0. When this liquid is allowed to evaporate it produces intense cold, like liquid air, and part of it becomes solid as 184 CHEMISTRY SIMPLIFIED. snow. The liquid N 2 boils at -89 C., and be- comes solid at -100 C. For use of the dentists the compression of the gas is only carried so far that about 10 volumes are compressed into 1 vol- ume ; which means a pressure of 150 pounds per square inch. Preparation of the gas on manufacturing scale. The salt NH. 4 (N0 3 ), ammonium niter or nitrate, breaks up into N 2 and H 2 when heated : NH 4./xr 3) + heat = N 2 + 2H 2 0, and thus furnishes an excellent raw material. It FIG. 51. is not expensive. Apparatus as shown in Fig. 51 will enable you to make the gas quickly. R is a small retort, into which has been put the ammonium nitrate at A. The stand S holds the retort. L is a LECTURE ON NITER OR SALTPETER. 185 Liebig condenser with the water inflow at i and its outflow at o. The condensed water and the gas separate in the flask C, the gas passes into the dry- ing tube D and issues dry at G, whence it may be conducted into any desired holder, or to a compress- ing pump. Substitute large iron vessels for the small glass vessels and you have the manufacturing plant. Recapitulation of the oxyds of nitrogen : N 2 5 (contained in the nitrates) does not exist in free state. N 2 4 (contained in the very unstable hyponi- trates) brown fumes. N 2 3 (contained in the nitrites) blue liquid in free state. N 2 2 (forms no salts) originator of brown fumes. N 2 (forms no salts) laughing-gas. Nitrogen shows five different valences, from inono- to penta-valent, v but all of them are weak. With other elements similar tendencies are observed, the smaller the affinity between two elements, the greater the number of combinations into which they enter. CHAPTER XL AMMONIA, A VOLATILE ALKALI. A COMPLEX METALLIC RADICAL. AMONG other facts concerning the action of KOH and NaOH, we gathered that these hydroxyds and their water solutions can dissolve zinc with the evo- lution of hydrogen ; when the hydrogen is thus generated we say it is in the nascent state, meaning by this word (literally " being born ") that there is a special force or energy connected with it, and which the gas has lost after it is once set free and allowed to collect or to dissipate. It is a play of the affini- ties. We observe that a solution of indigo is not decolorized by shaking it with hydrogen gas. Yet when zinc, dilute sulfuric acid and indigo are brought together, the liquid becomes colorless. Blue indigo + Zn + H 2 S0 4 + water = white in-' digo -}- Zn(S0 4 ) + water. Hydrogen is not evolved until all the blue indigo is changed into white in- digo, and we ascribe the change to nascent hydrogen. Thus also when niter, NaHO, and zinc act together, the escaping gas possesses not only a peculiar odor, but the gas turns red litmus to blue. There must be with the hydrogen a new volatile body which pos- sesses the properties of the alkaline hydroxyds. Let this, as yet suspicious, body be named ammonia. (186) AMMONIA, A VOLATILE ALKALI. 187 Passing the gas into water, the latter soon acquires alkaline reaction and the power to neutralize acids. If these neutralized acids be evaporated, crystals form, characteristic for each acid, the same as if those acids had been neutralized by KOH. Yet if these crystals be heated over an open flame, they will completely disappear, totally differing from any of the metallic salts. The total volatilization is proof that the body, which here takes the place of a metal, cannot contain either zinc or sodium, and since besides these, only the elements X, 0, H had been in the generating solution, they alone can con- stitute the new body. Hydrogen we know to be a metal, because it takes the place of a metal in the salts, producing the hydrogen salts or acids. Oxy- gen and hydrogen together form water, which can take the place of a metallic oxyd, but not of a metal, hence we must conclude that the new body must contain nitrogen. Investigation. The first step will be the prepara- tion of a sufficient supply of the ammonia gas. A word about the name. We know that the name of the Egyptian sun god was Rha Ammon; also that the name of a powerful tribe of Bedouins in the desert to the southeast of the Dead Sea, in Palestine, was Beni Ammon, in Hebrew, the sons of Ammon, as we would say the sons of the sun. It is my be- lief that the name ammonia is connected in some way with Rha Ammon, though I cannot say how. The Egyptian priests must have known this body, and for its revivifying, penetrating odor likened it 188 CHEMISTRY SIMPLIFIED. to the effect of the sun's rays. There is no histor- ical record in existence to substantiate my view. In the Latin translation of Gebers works (ninth century A. D.) the name appears sal armeniacum, which would mean the salt of Armenia, but that stands also for rock salt. I believe it is a mis- spelling. Preparation of ammonia. Put into a 500 c.c. flask (Fig. 52) 25 grams of NaOH, or about that much, FIG. 52. 75 c.c. of water, 20 grams of zinc (in turnings), a piece of bright sheet-iron, and 5 grams of niter. Stopper the flask and connect by rubber tubing with a Will's condenser. The flask should stand on a tripod upon wire gauze. Heat gently and keep up a slow evolution of gas. The condenser is charged with 20 c.c. of water and 5 c.c. of HC1 con- centrated. It is best to place a tube, T, between flask and condenser to receive any liquid spatter- ings. Will's condenser is especially adapted, be- AMMONIA, A VOLATILE ALKALI. 189 cause either of the bulbs, a, 6, can hold more than the volume of liquid indicated, hence no danger of the running back of the liquid into T should a vacuum occur in F, nor a running out at C should the escape of gas become tumultuous at any time. The addition of some litmus to the liquid in W is advisable ; so long as the color remains red we know that the liquid is still able to take up more ammo- nia. Any hydrogen mixed with the ammonia will escape at the point, C, of the condenser. The action must not be overhurried. In hurrying much more hydrogen escapes, doing no work. As soon as all the air is displaced from F, T, and W, you will note a tendency of the liquid in W to advance against the gas, to pass up into the bulb, a, an action which indicates the strong affinity between ammonia and HC1. It will take several hours to accomplish the complete change of the niter into ammonia. To- wards the end it will be well to set T into a glass containing boiling water to drive out the ammonia from the liquid which may have been condensed in T. Then empty liquid from W into an evaporating dish, and evaporate over a water-bath. A white, granular residue will be obtained composed of cubic crystals like those of common salt, NaCl or KC1, which is another indication that ammonia must be a body similar to Na and K. We will name this white salt ammonium chlorid = Am.Cl. In the drug trade it is named sal ammoniac. Bringing this salt together with Na(OH) or K(OH) or Ca(HO) 2 we observe at once a pungent odor of ammonia. 190 CHEMISTRY SIMPLIFIED. K(OH) + Ara.Cl = KC1 + H 2 + Ammonia. It follows from this action that there must be con- tained in the salt one hydrogen besides the ammonia. Important observation to be remembered. Of the three hydroxyds the one best servicable for making ammonia is Ca(HO) 2 . Why? Because it is a powder. Even better is the oxyd CaO, because if an excess of it be added, then this excess will retain the water in the form of Ca(HO) 2 . Even by rub- bing together Am.Cl and CaO, ammonia is set free. The process follows along the equation 2Am.Cl+2CaO=CaCl 2 +2 Ammonia+CaO.(H 2 0) Pure dry ammonia gas results. COMPOSITION OF AMMONIA. Let the generating apparatus be set up as shown FIG. 53. in Fig. 53. In the small flask (not more than 100 c.c.) put the mixture !/(4CaO+lAmCl) so that the AMMONIA, A VOLATILE ALKALI. 191 bulb is nearly full. To insure perfect dryness of the gas, let it pass through two U-tubes U and U both filled with pieces of burnt linie, pea size. Proof that ammonia contains hydrogen. Rig" a hard glass tube T, \ ff diameter, 12" long, as shown in Fig. 54. Between two asbestus plugs b and b r fill in coarse copper oxyd and ignite both asbestus and oxyd thoroughly, before filling the tube. Let the plugs be 3 to 4 inches apart. Arrange shield S so that only the filled part becomes heated, the empty FIG. 54. S n = B k V^ fell r " I. ^ /'U JL__mj_ ^ ^ 4 IT I 1 V part projecting beyond the shield. Fill the tube with ammonia gas by attaching t to P in Fig. 53. Then heat a to redness, and let the gas pass slowly (by heating generating bulb very gently). Soon we see moisture appear in the cool tube at TF. Mean- while connect the outlet of T by means of a bent tube with the test-tube B, which stands inverted in basin Cboth filled with dilute H 2 (S0 4 ). Whatever gas collects in B must be nitrogen (prove by its negative actions), because any ammonia gas passing out undecomposed will become absorbed by the dilute acid. That the condensed moisture at TF is water we prove by bringing together with it a small piece of potassium. But water could form only if the ammonia contained hydrogen. 192 CHEMISTRY SIMPLIFIED. Proof that ammonia contains no oxygen. We re- place the copper oxyd at. a, Fig. 54, by a bright copper wire, or a strip of bright copper foil and repeat the experiment at red heat. The copper does not cover itself with a film of oxyd. This is proof of the absence of oxygen. Hence ammonia must be Demonstration that the ratio. ' = -. Let a small p 3 volume of the pure ammonia gas pass into the eudiometer E, Fig. 55, over perfectly dry mercury. FIG. 55. FIG. 56. / ~ ; m Dry the eudiometer, inside and outside, most thor- oughly, before filling in the dry mercury. A eudiometer is a glass tube open at one end, made of strong glass, either graduated or not graduated, but having two thin platinum wires fused into the glass near the closed, or upper, end - - +, so that an electric current of high potential may be sent across in form of a spark. Let m designate the portion of AMMONIA, A VOLATILE ALKALI. 193 the mercury meniscus after the ammonia gas has entered. Then turn on the current which has been transformed to high potential by means of a Rhum- korf coil. We notice at once an increase in the gas volume ; rapid increase at first, but slowing down by geometric progression until the maximum enlargement of the volume has been reached at 2m as shown in Fig. 56. The volume has doubled ; the hydrogen and nitrogen are now merely mixed to- gether, the energy of the shocks from the sparks hav- ing broken the chemical bond. Now let us assume that the entire volume of the gas be hydrogen, i. e., 2 vols., let one vol. of pure oxygen be added, mak- ing altogether 3 vols. of gas. Let the spark pass between the wires (under proper precautions, that is covering the mercury trough with a towel and hold- ing down eudiometer with the left hand). Had our assumption been correct there would now only be contained in tube aqueous vapor and liquid water. We must remove this water, because we started with dry gas, by bringing into the gas a ball of K(OH) fused to a thin, soft wire. KOH absorbs water eagerly. A ball of fused CaCl 2 will answer also. We watch the gas from time to time and remove the drying ball when the volume remains constant for a full hour. Since we know that nitrogen will certainly be in the residue, we must have a certain and unknown excess of oxygen after the explosion, for we put oxygen equal to J of the total gas H -f- N. Let this excess of oxygen = dO, then the residue will be = N -f- dO. Suppose we 13 194 CHEMISTRY SIMPLIFIED. started with one vol. ammonia gas = 10 c.c. By decomposition this became = 20 c.c. By addition of one vol. of oxygen = 10 c.c. this became = 30 c.c. Now we explode the mixture and remove aqueous vapor, and find that 30 c.c. have shrunk to 7.5 c.c. Then 30 7.5 c.c. = 22.5 c.c. here disappeared in form of H 2 ; f of this contraction was hydrogen, J oxygen. 22 5 ~- = 7.5 c.c. of But we had used 10 c.c. of 0, hence d = 10 7.5 = 2.5; hence N + d = N + 2.5 = 7.5 (gas volume after explosion); N = 7.5 2.5 = 5 c.c.; hence ratio ~ = = J. The formula of ammonia is NH 3 . Into 10 c.c. of H 3 N are compressed 15 c.c. H + 5 'c.c. N. Into 1 c.c. of H 3 N are compressed 1.5 H + 0.5 N, or two volumes are condensed into one. 1 vols. hydrogen weigh gram . . . 0.1038 \ vol. nitrogen weighs gram . . . 0.4856 0.5894 which is the calculated specific gravity or volume weight of ammonia, and agreesjairly well with the experimental specific gravity of 0.596. The mole- cular weight (H = 1) is 14 + 3 = 17. The chemical nature of ammonia ammonium. Ammonia gas is easily absorbed by water. 1 c.c. of water at C. will absorb 1050 c.c. of the gas; AMMONIA, A VOLATILE ALKALI. 195 much heat is produced by the absorption. The re- sulting liquid, be it concentrated or dilute, has the same pungent odor as the gas. The liquid possesses the biting taste of potassium and sodium hydrates. Raises a blister on the tongue or lips. The liquid is lighter than water ; at + 14 C. its specific gravity is 0.8844, and contains 35.0 per cent, of NH 3 . This liquid goes in the drug trade by the name aqua am- monia or ammonia water. We chemists call it ammo- nium hydrate. Because from the actions of this liquid towards the acids, we conclude that as soon as the gas, NH 3 , comes together with water it com- bines with the latter, thus NH 3 + H 2 0=(NH 4 XHO)=aram = (C*H)H= butyl hydrid, But on the methyl hypothesis there will be two combi- nations, which have been actually proved to exist, two bodies having exactly the same percentage com- position, but distinct properties, to wit : CH 3 .CH 2 .CH 2 .CH 3 , normal butane; and CH 3 CH^CH 3 , iso-butane. X CH 3 Such bodies as these, of equal atomic or percentage composition, are called isomerids. Isobutane is the isomerdi of butane. 304 CHEMISTRY SIMPLIFIED. For pentane C 5 H 12 there are three isomerids : CH 3 .CH 2 .CH 2 .CH 2 .CH 3 , normal pentane. CH 3 CH^CH 3 , di-methyl-ethyl-m ethane, X (CH 2 .CH 8 ) CH 3> C "^CH 3 ' tetra -methyl-methane. In the last we imagine a marsh gas molecule H H > C \ H H in which every hydrogen atom has become replaced or substituted by the methyl group. The second isomerid can be represented, to show the similarity, thus H- CH 3 \Q/ CH 3/ X CH 2 .CH 3 . I beg to remind you that this so-called structural representation is not to mean a real picture for in reality we have to deal with three dimensions, not with two as on this sheet of paper. This is an at- tempt to express symbolically the difference in properties of the isomeric bodies. In the light of this exposition on marsh gas, we will reconsider the wood alcohol and the acetic acid. For the wood alcohol we had the atomic proportion CH 4 0, it being then suggested that this formula may be written CH 3 (HO), and now we see that the methyl alcohol is a marsh gas in which 1 H is replaced by the radical (HO) hydroxyl. CAKBON COMPOUNDS. 305 H H , methyl alcohol, hydroxyl methane. H For acetic acid H.C 2 H 3 2 we can write FT TT " \Q/ > acetic acid, hydroxyl-carbonyl H 7 \X).OH ^ethane. The group CO. OH, carbonyl-hydroxyl, is mono- valent ; by the entering of this group into a hydro- carbon, the latter takes on the properties of an acid. The lowest form is formic acid (ant acid) CHO*.H which is found with the acetic acid. Here we can say that the group CO. OH is simply coupled with one H. WOOD OR CELLULOSE UNDER PRESSURE AND HEAT. If compressed cotton, or a stick of dry wood, or dry sawdust be enclosed in a strong glass tube as shown at Fig. 89, A in figure 1, and if the tube FIG. 89. C W ///////////////////// //\ t A be then fused together as at C, figure 2, over a blast lamp and the part D be pulled off, the wood A will 20 306 CHEMISTRY SIMPLIFIED. be enclosed air-tight as in figure 3. Care must be had that the wall of the tube remains throughout of even thickness. If this tube be then placed within an air-bath, and the temperature be gradually raised to 320 C. as indicated by the air thermometer, Fig. 90, then it is evident that the distillation of the FIG. 91. wood proceeds under increasing pressure : First, by the expansion of the air ; second, by the expansion of the gases and vapors which arise from the wood at this temperature. Let the condition of things remain thus- for twenty-four hours. Let cool slowly. On examining the tube we find the wood converted into a jet-black shining mass ; the cellulose structure is effaced altogether and the resemblance to soft coal is unmistakable. We open the tube very cautiously (after taking its weight) as follows : Since the pres- sure is still high (presumably) a sudden breaking CARBON COMPOUNDS. 307 of the tube might have a very shattering effect (like a boiler explosion). Therefore, we approach the pointed end of the tube to a strong flame, as shown in Fig. 91. In measure as the glass nears red heat, it will become soft, and expand under the interior pressure until at the very tip it will be blown out, giving vent to the compressed gases. On weighing the tube, now, it is found that about 2 per cent, of the weight of the wood has disappeared, that much having been converted into permanent gas. Now we wash carefully the mass in the tube by means of alcohol (to dissolve any tar-stuff), and after drying in a current of dry air, find again a diminution in the weight of about 3 to 4 per cent. Altogether about 20 per cent, in weight of the cellulose has vanished. The importance of this experiment will appear in the next section. CHAPTER XVI. MINERAL COAL AND ITS CHEMISTRY. WITHOUT mineral coal the industrial development of modern times would have been impossible. Some 250 millions of tons are now mined annually in the United States, much more than all the other minerals together. The conditions under which coal is found, and its association with other rocks, form a subject of stratigraphic geology. The points to which your at- tention is here called refer to the properties of coal and the uses to -which coal can be and is applied owing to such properties. We distinguish (1). Hard coal or anthracite. (Greek anthras = coal.) Color intensely black, luster more or less bright. Fracture smooth and spheroi- dal. Hardness considerable ; the pick does not pro- duce much effect ; drilling and blasting is necessary. (2). Soft coal, bituminous coal, semi-bituminous, blacksmith coal. Much softer than anthracite, color black, but color of fine powder is brown. Cleaves or breaks into prismatic pieces. When heated in glass tube gives off dense yellow vapors which separate into a liquid and into a combustible gas, whereas anthra- cite gives off no vapors, and only very little gas. If the coal melts into a black, thick liquid, it is called bituminous (bitumen being the Greek word for the (308) MINERAL COAL AND ITS CHEMISTRY. 309 natural pitch also known as asphaltum). If the coal merely softens in the heat, does not become quite liquid, then we call it semi-bituminous, (half pitchy). (3). Cannel coal, has a black color but differs by absence of luster from the ofher varieties. It breaks with an irregular surface. When heated it does not melt nor become soft, but yields both condensible vapors and bright burning gas . in abundance, (can- nel is the Scotch of candle). This coal is not as abundant as the other varieties and is of higher value, because it furnishes a larger volume of illumi- nating gas. It is only used for gas-making. (4)- Brown coal, lignite. Dark-brown color, dull in appearance, very soft, can be shoveled from the pit, shows the cell structure of wood and hence the name lignite (lignum = wood). When heated it does not soften, but gives gas and tar, although less of these than cannel coal ; and more water. It is usu- ally mixed with sand and clay to a much larger ex- tent than the other coals. The beds lie near the surface, that is, they belong to more recent geological times. Very abundant all over Western United States, Central Europe, Asia and Africa. The cities of Northern Germany use this material exclusively for fuel, on account of its cheapness. (5). Peat, bog, turf. Brown or brown-black in color, very loose in structure and crumbly. Acts like brown coal, when heated after having been dried. This material is found always in flat regions, where the water cannot drain off and where no grasses can grow on account of the wetness. But 310 CHEMISTRY SIMPLIFIED. on the other hand, the different varieties of mosses and algae develop and grow with astonishing rapid- ity, one generation on top of the other, each genera- tion being very short-lived. Being so near the air the dead mosses undergo a partial rotting with the formation of marsh gas and carbon dioxyd. There are bogs known to be 50 feet thick and more. Ordi- narily they do not exceed 3 feet in thickness. Yet they furnish to many localities their only fuel Ire- land, Holland, North Germany near the sea. The higher land of Western New York, where the Hudson, the Alleghany, and the Delaware rivers have their beginning, contains many peat bogs, which are more or less utilized. On the flat tops of very high moun- tains such bogs have been found. By a washing pro- cess the peat substance can be somewhat freed from the sand, and it can then be converted into cakes by pressing. Such cakes, when quite air-dry will give a hotter fire than wood, weight for weight. Composition of coal. We find the ultimate or ele- mentary composition by the same procedure which we followed with the cellulose. We burn a known weight, W, with copper oxyd and oxygen gas and collect the products of the combustion, conveniently for measuring or weighing. We find invariably the same elements to wit : Carbon, hydrogen, oxy- gen, nitrogen, sulfur. The two latter are not in cellulose, but they are found in other parts of plant structure. Nitrogen is always contained in the pro- toplasm, and sulfur sometimes ; without the proto- plasm no plant can develop it is the blood of plant MINERAL COAL AND ITS CHEMISTRY. 311 life. The seeds of plants always contain much nitro- gen (15 to 17 per cent.). Coal contains from 1 to 3 per cent, of nitrogen. The sulfur varies between wider limits. The sulfur can be in union with the carbon and the hydrogen, and is then invisible; or combined with iron as yellow pyrite, and is then readily visible. Coal always leaves a residue after the carbon and hydrogen have been volatilized by oxidation into CO 2 and IPO. The residue is called ashes,' because wood leaves ashes. The two kinds of ashes are very unlike. From coal ashes water does not extract potash, nor any other body ; coal ashes are quite insoluble ; no alkaline reaction whatever. Neither HC1 nor HNO 3 nor H 2 S0 4 dissolve it, only HF. The ashes in fact contain chiefly the oxyds of silicon and aluminum SiO 2 , A1 2 3 , and Fe 2 3 when the ashes have a brown color. The clinker- ing or semi-fusion of the coal ashes is due to Fe 2 3 which acts as a flux upon the other oxyds ; white coal ashes never show clinkering. The following analysis, made by me lately, gives the ultimate composition of a soft coal from Kansas. Carbon = 75.35, hydrogen = 5.50, oxygen and nitrogen = 10.10, sulfur -1.54, SiO 2 ==4.35, A1 2 3 = 2.70 (being together ashes equal 7.05, snow white) mois- ture =0.45. Notice the total absence of iron oxyd, whence it follows that the sulfur must be combined with the carbon and hydrogen. This coal belongs to the semi-bituminous variety verging upon cannel ; for 312 CHEMISTRY SIMPLIFIED. the residue merely adheres slightly after having been exposed to a high yellow heat, and like cannel it has a dull, black color ; powder brown. The proximate composition of the different varieties is but imperfectly known, or rather guessed at. I mean by proximate composition the molecular structure the manner of combination of the ele- ments. You can do no better than to imagine the coal to be an intimate mixture of solid hydrocar- bons, oxy-hydrocarbons, sulfo-hydrocarbons, nitro- hydrocarbons, amorphous carbon, and mineral par- ticles constituting the ash. The different varieties of hard and soft coal arise from the preponderance of one or more of the above groups of molecules. Reasons for this hypothesis are : (1) The crystalline structure of the coal, revealed in thin translucent plates or sections under the microscope ; (2) The actions of solvents upon the coal, such as ether, benzole, carbon disulfid, potassium or sodium hy- droxyds. Origin of coals. That cellulose is the original material there is no reason to doubt ; all hypotheses or theories start with this base. Generally, how- ever, geologists assume that the material for the coal beds consists in the successive growth of tropi- cal forests one on top of the other. My own theory differs from this. The chief reasons are that in many places we find trees standing upright in the coal beds, reaching even into the sandstone or slate strata lying over the coal bed as shown in Fig. 92. Here a section is reproduced from an English coal MINERAL COAL AND ITS CHEMISTRY. 313 mine, a is limestone, b is fire-clay (under clay), cc the lower and upper benches of a coal seam, e black coal slate, / sandstone, g brown slate, tit are fossil trees, whose bark is also coal, but whose interior is sandstone, because these trees belonged to the class of giant reeds, calamites lepidodendron, sigillaria, etc., and therefore contained a pithy interior and a very strong fibrous rind, very resisting to chemical change, d is a band of slate separating the coal- bed into the two benches. The strata a and b were in horizontal position during the coal-forming times and the conditions of level equal to that of very shallow basins very near the sea level ; that is, the general conditions were those of a tropical swamp as we find them in our time along the Amazon River in South America. At first these conditions were favorable to the growth of the great ferns and the gigantic reeds. Later on, the land sinking very slowly, the swamp became too wet for this vegeta- tion and in its stead algae the lowest type of plant life which you find always in the shallow pools of 314 CHEMISTRY SIMPLIFIED. our present swamp woods, the green and brown threads began to flourish abundantly, luxuriantly. An alga is a plant consisting of one cell or of an aggregate of cells, of which however each cell re- mains a life unit. Each cell has a thin wall of cel- lulose enclosing a liquid interior in which there is a floating patch of protoplasm, the cell-nucleus or cell-kernel. While these generations of very rapidly growing cells died and accumulated on the bottom of the pool, or rather upon their dead predecessors, and being under water could not rot, the rivers or creeks emptying from higher ground into the swamps brought the fine sand and clay which settles very slowly, as you well know from the rivers remaining turbid long after a freshet. In time this material the silt settles and mixes with the vege- table ooze, and there we .have an explanation of the intimate admixture of the ash particles with the coal, and also an explanation of the strong varia- tion of the ash percentage in the different parts of a coal bed. Whenever a slate band occurs in the coal, according to this theory, we presume that an unusual freshet carried the silt faster into the basin than the algae could accumulate, in fact the muddi- ness interfering with rapid growth. The silt also settled into the hollow trunks of the trees, thus pre- serving them against collapse by external pressure. My theory of the algae accounts also for the high percentage of nitrogen, which we find in the coal, because the relative percentage of protoplasm to cellulose or of nitrogenous substance, is larger in MINERAL COAL AND ITS CHEMISTRY. 315 the algae than in the complex cell-structures of trees. During the accumulation of the ooze a decomposi- tion of the dead algae cells began to set in, alike to that which we now-a-days observe in the peat bogs, by which the percentage of carbon in the residue steadily increases, while hydrogen ^and oxygen, notably the latter, decrease : CO 2 forming and CH 4 and IPO. At last, the ground sinking more rapidly, the influx of silt increases and the vegeta- tion stops, the sea finally encroaches upon the swamp and the materials for sandstone or limestone are brought in. They cause a steadily increasing pressure, under the influence of which internal heat arises, which cannot dissipate as the rocks are very bad conductors of heat. Thus the plant material comes gradually under the conditions of the experi- ment upon cellulose, described a few pages back. Wherever the pressure was greatest the change towards carbon was greatest. Thus we find in East- ern Pennsylvania only anthracite with 90-94 per cent, of carbon, because the side pressure upon the strata was so great, that the latter became greatly bent and even doubled upon themselves as shown in Fig. 93, whilst in the Western States the strata remained in their original horizontal position, as seen in Fig. 94, except in Colorado, and hence we find anthracite in the latter state. The dotted lines in Fig. 93 denote that part of the coal bed which has been removed and lost by surface destruction and the forming of the present topographical out- lines. All the details of the structure of the coal 316 CHEMISTRY SIMPLIFIED. measures belong to geology ; only sufficient had to FIG. 94. V be introduced here to make the chemical theory intelligible. DISTILLATION OF COAL COKING PROCESS. By distillation of cellulose or wood we ob- tained charcoal, tar, pyroligneous acid, CO, CO 2 , CH 4 , H ; and since coal is derived from cellulose MINERAL COAL AND ITS CHEMISTRY. 317 we may and should expect similar, if not identical, products. In order to test this proposition we rig up the set of apparatus, Fig. 76, page 275. The tube Twe charge with the coarsely-powdered coal, so that when the tube lies in horizontal position and has been tapped upon, the coal only fills one- half of the tube. Why ? Because at red heat the bituminous and semi-bituminous coals swell up, thus clogging the tube to the escaping gas, which latter, with increasing pressure, will invariably break the tube. We Mart heating at the front by using the diaphragm or shield S. First we note a heavy yellow vapor, from this condenses a brown liquid in the receiver 3, and the bell B fills itself with gas. The first portion of gas we allow to escape, because it is mixed with the air in T and 3. Anthracite gives no vapor, no condensing tar, only a relatively small volume of gas ; because anthra- cite has already undergone the distillation under the influence of great pressure. When, at bright red heat, the evolution of gas becomes very slow, or stops altogether, we disconnect the receiver 3 from T and B from 3. We pull the tube T from the furnace, let it become cool, and then break the tube. We find the residue more or less bright, porous, dark or light grey in color. With large pores the stuff is more or less friable, with small pores it becomes hard and tough. For bituminous and semi-bitum- inous coals the weight of the residue is from 50 to 65 per cent, of the original weight of the coal. The technical name of this residue is coke, which 318 CHEMISTRY SIMPLIFIED. word is derived from to cook, and may have been merely a provincial substitute for cake. When brought up to a red heat in a current of air the coke burns without making a visible flame, although it still contains a remnant of hydrogen and oxygen, for the complete change of coal to carbon depends upon the temperature and time. At a white heat (in fire-clay crucible), the last remnant of hydrogen can be eliminated. The ordinary coke is, therefore, a mixture of the ashes with carbon (amorphous and also graphitic), and more or less hydrocarbon. Coke is required as fuel in blast furnace work, es- pecially in the high-stack-furnaces for the reduction of iron ores. Why ? Because if coal were used, the latter would convert itself into coke in the furnace, would cause a loss of heat energy (elimination and decomposition of the hydrocarbons and oxy-hydro- carbons requires heat addition from outside sources), and the coke thus forming would cement the pieces of ore and flux into a solid cake, through which the large quantities of nitrogen and carbon monoxyd are blown in at the bottom of the furnace could not pass the furnace would clog or choke and event- ually extinguish itself. For this need of the blast furnaces, immense quan- tities of coal are converted into coke. The appara- tus for making coke is known as coke oven, not kiln or furnace, but oven. Why ? Because the first coke was made in Dutch bake-ovens. The so-called bee- hive coke oven of the present time is merely a slightly modified bake-oven. In this oven all the gas and MINERAL COAL AND ITS CHEMISTRY. 319 the tar are wasted. In the scientifically constructed ovens, the gas and tar are utilized. Different ovens have been constructed in Europe in great profusion. Those mostly used now are the Solvay oven, and the Hoffman oven ; they have also been intro- duced into the United States. The detail of coke- making belongs to metallurgy. We ttfrn now to the contents of the receiver (3). As in the distillation of wood we find two liquids, one oily the so-called coal tar, one watery of light-brown color. This watery liquid smells of ammonia, and turns red litmus paper blue. Thus it is the reverse of pyroligneous acid from wood distillation. Addition of acid to the ammonia water produces effervescence : CO 2 , H 2 S are given off, hence the water contains am- monium carbonate and ammonium sulfid. The occurrence of the ammonia proves the presence of nitrogen in the coal. The absence of the acetic acid may be explained from the smaller percentage of oxygen in the coal and from the higher temperature needed to break up the coal, a temperature at which C 2 H 3 2 .H breaks up into CH 4 + CO 2 . The princi- pal market for ammonia being that as fertilizer, the cheapest way of extracting the former is to convert it into sulfate. The water is neutralized with H 2 S0 4 and the solution evaporated by means of the waste heat from the ovens. The result is dark-brown, crude sulfate. This is redissolved in the requisite quantity of boiling water, filtered through a bed of charcoal to remove the tar which separates during evaporation, and the liquid is run 320 CHEMISTRY SIMPLIFIED. into flat basins, where the sulfate crystallizes on cooling. This second product is still yellowish, but good enough for the market. The coal tar, the oily portion of the condensed vapors, is composed essentially like the wood-tar. But certain valuable hydrocarbons are contained in the coal tar in larger percentage. These hydrocar- bons are: benzol (C 6 H 6 ), toluol (C 7 H 8 ), phenol (C 6 H 5 (OH)), naphthaline (C 10 H 8 ), anthracene (C 14 H 10 ). When the tar is subjected to distillation, light oils pass over first up to a temperature of 180 C. Benzol, toluol, phenol are contained in this portion ; at a higher temperature oil passes over which solidifies on cooling. The cooled mass can be recrystallized from an alcohol solution, or it may be purified by sublimation. In this purified state it forms large thin crystals in form of plates with the luster of mother of pearl and a strong peculiar odor. This is the napthaline of trade and is largely used to protect woolen and fur goods against insects : moth balls. Only the oil which passes over between 80 and 100 C. is used for the manufacture of ben- zol. Between 100 and 130 C. toluol and phenol with some benzol pass over. Pure benzol is a color- less very mobile liquid ; boils at 82 C. and crystal- lizes at C. Specific gravity = 0.85. Nitrobenzol, C G H 5 .NO' 2 . Is obtained by treating the benzol with a mixture of cone. H 2 S0 4 and very cone, or fuming HNO 3 in cast-iron cylinders, which can be cooled by running water, because the reaction is very energetic ; 1 hydrogen of the C 6 H 6 is removed as water and nitrobenzol results. MINERAL COAL AND ITS CHEMISTRY. 321 C 6 H 6 + HNO 3 = C 6 H 5 N0 2 + H 2 0. Nitrobenzol is a yellowish heavy oil which boils at 205 C. ; and has a pleasant odor resembling that of the oil made from bitter almonds. If an excess of HNO 3 is used the dinitrobenzol C 6 H 4 (N0 2 ) 2 results. Anilin,C 6 H 7 N. A small quantity of this highly interesting substance is already contained in the tar. But from nitrobenzol it can be obtained in any de- sired quantity. Anilin forms a colorless liquid, diffracts light strongly, has a'peculiar odor and burn- ing taste. The oil bqils at 182 C. and solidifica- tion sets in at 8 C. Specific gravity == 1.02. Is very slightly soluble in cold water, more so in boil- ing water, but quite soluble in alcohol, ether, carbon disulfid, and coal oil. It burns with a very smoky flame. Is very poisonous. Chemically anilin may be considered as ammonia in which 1 H has been replaced by the hydrocarbon radical phenyl thus HI (CH')-| H >N = ammonia. H >N = anilin. HJ H j Like ammonia it unites with HC1 and other acids and forms salts : C 6 H 5 .H.HNHC1 = anilin chlorid. These salts are mostly easily soluble in alcohol and crystallize readily. Anilin is a fine example of a complex base. Methylanilin is another base, arising from a sec- ond hydrogen being replaced by methyl, thus : C 6 H 5 .H.H.N + CH 3 I + heat = (C 6 H 5 )(CH 3 ).H.N + HL 21 322 CHEMISTRY SIMPLIFIED. This body, known as " Mauve de Paris," colors silk and wool a fine violet color. Rosanilin, fuchsin. This was the first splendid dye-stuff prepared from coal-tar through the way of anilin, by means of oxydation ; usually As 2 5 is used as the oxydizing agent. 100 parts of anilin oil are poured slowly into 150 parts of a water-solu- tion holding 75 per cent. As 2 5 in an iron vessel with stirring apparatus. The temperature is raised and kept for five hours at 182 C. Water and un- changed anilin dissolve during this period. The semi-fluid residue has a bronze color, and from it the dye-stuff is extracted by boiling water, filtered, under pressure, through felt. Solution contains the rosanilin as arseniate and the As 2 3 which is formed during the process of oxydation. By saturating the solution with NaCl (equal in weight to the resi- due), the hydrochlorid of rosanilin forms and Na 2 HAs0 4 . Red crystals fall out, in measure, as the liquid cools. By recrystallizing this first pro- duct a. higher grade is obtained. The red crystals, being the chlorid of rosanilin, are known in the dye-works as fuchsin. By acting on the water solu- tion with NaOH, the base rosanilin is obtained as a white precipitate, which becomes intensely red in contact with any acid. The composition of rosanilin isC 20 H 19 N 3 . It forms thus: C 7 H 7 2 H H C 6 H 5 N + H H C 6 H N+30 = C 7 H 7 N 3 +3H 2 0. The 30 are furnished by As 2 5 or any other oxy- MINERAL COAL AND ITS CHEMISTRY. dizing agent. But we see that another body is here contained, the toluidin, besides the anilin. Remem- bering, however, that the raw oil contains benzol and toluol, the phenomenon is explained. The crystals of fuchsin are green-golden in ap- pearance, like a brilliant metal. They dissolve in water with intense red color. If well cleansed silk or wool be hung in such a solution, the liquid becomes colorless by degrees, all the coloring fuchsin will have transferred itself to the fibre, producing thereon the beautiful red tints according to the quantity transferred. The color fixes itself, does not require a mordant or fixing agent. Mauvanilin, (CH 5 )(C 6 H 5 )(C 7 H 7 )N*.HCl gives an orange-yellow dye. A great many other beautiful dye-stuffs have been produced by further substitu- tion of hydrogen in the base by other radicals, as anilin, toluidin, or simply methyl, ethyl, and others. My main purpose in devoting so much, space to this subject was to impress upon you the possibilities lying hidden in such a material as the ugly, bad- smelling coal-tar, and the great fortunes which have been made by utilizing it in the right way. CHAPTER XVII. THE GASES FROM THE DISTILLATION OF COAL- MANUFACTURE OF ILLUMINATING GAS AND GAS COKE. The contents of the bell jar are at first cloudy from exceedingly small particles of semiliquid bodies, which will condense after a time, forming a thin layer of tar upon the retaining water surface. If now the gases be subjected to the analysis by ab- sorption which has been given in detail under cel- lulose or wood, it will be found that the composi- tion by quality does not differ much ; the relative quantities differ considerably, and even very much when the gas from the early distillation is compared with that which is given off at the end of the opera- tion. We find H, CH 4 , CO, CO 2 , non luminous : C 2 H 4 , C 3 H 6 , C 4 H 8 and C 2 H 2 , (acetylene) as lumi- nous gases. NH 3 , SH 2 , CS 2 , CN as impurities. Of the luminous or light-producing hydrocarbons ethylene (C 2 H 4 ) olefiant gas (oil-making gas) is the most important; of propylene (C 3 H ) there is least ; of butylene C 4 H 8 there is usually from J to J as much as of ethylene. These hydrocarbons combine with chlorine, bromine or iodine, thus : C 2 H 4 + 2C1 =C 2 H 4 C1 2 , ethylene chloride oil-like liquid (hence the name olefiant or oil-making.) Spec. Gr. = 1.174. (324) GASES FROM THE DISTILLATION OF COAL. 325 At red heat ethylene breaks up, thus : C 2 H 4 + red heat = C + CH 4 , amorphous carbon + marsh gas. It is this action which we call dissociation, that a'ccounts for the smoking of a gas flame. If oxygen is present both C and CH 4 are oxydized to 2C0 2 + 2H 2 0. Bromine acts like chlorine upon ethylene: C 2 H 4 + 2Br = C 2 H 4 Br 2 an oily liquid as the pre- ceding one. Propylene and butylene are acted upon similarly: C 3 H 6 + 2C1 = C 3 H 6 C1 2 ; C 4 H 8 + 2C1 = C 4 H 8 C1 2 , propylene chlorid, butylene chlorid. Hence it follows that we can remove these three gases from a mixture of gases by shaking the mix- ture with bromine water in a suitable gas pipette. The higher we find their percentage in a given gas the more we are sure of a bright light, provided that the burner be suitably constructed. PLAN FOR GAS WORKS. Figs. 95 and 95a give the essential pieces of ap- paratus for the production of illuminating gas by dis- tillation of coal, in ground plan and length elevation. R, R',R 2 represent a fire-brick retort and ovens for heating them to a yellow heat. H is a sheet-iron pipe 18" to 24" in diameter and known as the " hydraulic main." The elevation shows how the retort con- nects by a goose-neck pipe with this main and also that the pipe dips under the water level of the main, thus producing a light pressure upon the gas in the retort. Most of the condensible constituents of the gas become liquid in contact with the liquid in the FIG. 95. (326) (827) 328 CHEMISTRY SIMPLIFIED. pipes. At N there is provided an overflow which drains into a vertical tank or cistern ; thus the level remains always the same in the main. Steam, tar, ammonium salts are condensed largely. A pipe C leads from top of main to the purifying towers S,S',S 2 which are technically known as scrubbers. S,S f are wet scrubbers, because the gas must pass the extensive surface of the horizontal trays over which flows a film of cold water. All the ammonium compounds and all the tar are removed from the gas in these wet scrubbers, but the gas still contains a notable quantity of hydrogen sulfid. The latter is taken care of in S 2 which is a dry scrubber, for here the trays are covered each with a layer of Laming' s mass, to wit : a mixture of Ca(HO) 2 with FeSO 4 + 7H 2 (copperas). Ca(HO) 2 + FeSO 4 - CaSO 4 -f Fe(HO) 2 ; it is the latter, ferrous hydroxyd, which is the active agent. At first Ca(HO) 2 (dry slaked lime) was used alone. Ca(HO) 2 + EPS = CaS + 2H 2 0. But the action is slow. When the book-backs in the public libraries of London and other cities began to crumble away, the cause was traced to the gas flames and more specially to the sulfuric oxyd produced by them, i. e., by the burn- ing of H 2 S to SO 3 . Then Laming invented the mixture and thus checked the evil, without knock- ing it out altogether. The carbon disulfid CS 2 has, so far, resisted all attempts at absorption in the scrubbers. The dry scrubbers must be provided in duplicate or triplicate, because they need frequent renewing of the Laming mixture, which becomes GASES FROM THE DISTILLATION OF COAL. 329 foul as the men say. The gas is now ready to flow through the pipe C f " into the holder G. The holder is a sheet-iron tank of circular or cylindrical shape. It is closed at the upper end and dips with the open lower end into water of the walled and cemented cistern C. The tank G is held in place by 6 or more guide rolls, and is counterbalanced by the 6 weights W, W, etc. These consist of cast iron disks, superposed, so that the bell may be made to press upon the gas at any pressure, by adding or removing a disk, from each or to each, of the 6 weights. By adding disks the bell may take the function of a suction pump thus causing the gas to overcome the friction of scrubbers, during the progress of the distillation. The elevation explains the entrance of the gas at in and the outflow at out if the main valve V' is open. This valve is always accessible through the pit P. The dimensions of the plant follow from the rate of consumption of the gas. As one 15 candle-power burner consumes 5 cubic feet of gas per hour, and as the burners are needed on the darkest day for 8 hours, and as each family uses on the average 4 burners, we get 160 cubic feet per family per day. 1000 families require 160,000 cubic feet + 10 per cent, for street lighting, total 176,000 cubic feet, hence 18 tons of coal will be required per day giving roughly 9 tons of coke. A bell 30 feet in diameter and 20 feet high will hold 16,000 cubic feet. Ten such would be required to store the 160,000 cubic feet. However the bell serves more as a regulator than as a storage. The 330 CHEMISTRY SIMPLIFIED. retorts are kept going all through the hours of largest consumption. One holder is sufficient for each 1000 families. Holders of 100 feet diameter and 25 feet high have been built in large cities. The retorts are made of fire-brick material and have a ^^ section. They are 5 to 6 feet long, 18 to 24 in. wide (inside), 12 to 15 inches high. Thickness of bottom 3 to 4 inches, of sides and top 2J to 3 inches. The average daily capacity per retort is 5000 cu. feet ; hence 32 retorts will be required for 160,000 cu. ft. daily production. The retorts are best arranged in batteries of 7 each with one common fire-place. WATER-GAS. (a) Water-Gas. H 2 + C=H 2 -f-COat yellow or white heat. The mixture of hydrogen and car- bon, monoxyd burns with colorless flame, hence the gas must be made luminous by the addition of gasoline or hydrocarbons of the olefine series. Prof. Lowe of Norristown, Pa., introduced the ap- plication of this reaction into the gas industry about 1873. It displaces' the distillation process, but has not been introduced in many gas works until more recently in a modified form. The action H 2 + C=CO + H 2 is endothermic, heat-consuming. The action C + 20 = CO 2 is exothermic, heat- producing. Hence the process of preparing water-gas is necessarily a double one, Let 1, 2, Fig. 96, be two GASES FROM THE DISTILLATION OF COAL. 331 fire-brick cylinders held each in a sheet-steel mantle. Let these cylinders stand upon iron pillars, 10, 10. 10, which will enable a dropping of the hinged bottoms, 3, 8, and thus an emptying of the cylinders of ashes and klinkers. Let the cylinders be filled with pieces of coke or charcoal. At 4, 4 we have charging hoppers. At 5, 5 air-pipes enter the cylinder, and at 6, 6, steam-pipes. At 7, 7 small pipes can introduce coal-tar. The gas passes at vhile the experiment gives 2.326 for one volume of cyanogen. Cyanogen combines with chlorine to form (CN)Cl, a terribly poisonous gas. It also com- bines with bromine. Sulfocyanogen, (CNS) 2 , forms colorless crystals. Hydrogen sulfocyanate, H(CNS), a colorless liquid of pungent odor like HC1 and strong acid reaction. Potassium sulfocyanate, K(CNS). Colorless crys- tals : easily soluble in w^ater and in alcohol. The solution of this salt gives with ferric salts a blood- 398 CHEMISTRY SIMPLIFIED. red solution in presence of free acid. Very delicate reaction. Preparation. Fuse together KCN + S in a cru- cible, dissolve in water and crystallize. Potassium ferricyanate, red prussiate of potash, K^Fe^CN) 1 2 ). A beautiful salt. The crystals are of deep garnet-red color and dissolve very easily, with an intense yellow color, in water. The crystals contain no water of crystallization. It is prepared by acting upon the solution of potassium ferrocyanate with chlorine ; thus : 2K 4 (Fe(CN) 6 ) + water + 2C1 = K^Fe^CN) 1 2 ) + 2KC1 + water. We say that 2 molecules of tetravalent ferrocya- nogen have become polymerized have coalesced in one hexavalent radical, ferricyanoge7i,(Fe*(CNy^). In qualitative analysis potass, ferricyanate serves to reveal the presence of a ferrous salt inasmuch as they combine to an intensely blue compound, thus : K 6 (Fe 2 (CN) 12 j + 3FeS0 4 + free acid + water = Fe^Fe^CN) 1 2 ) + 3K 2 S0 4 + free acid. Fe 3 (Fe 2 (CN) 12 ) is known as a blue coloring material under the name of TurnbuWs blue. Potassium ferrocyanate gives with ferric salts a similar combination of equal intense blue color which is named prussian blue. The following equa- tion represents this relation : 3K 4 (Fe(CN) 6 ) + 4FeCl 3 + free acid + water = Fe 4 (Fe(CN) 6 ) 8 , prussian blue + 12KC1 + free acid -|- water. ORIGIN OF CYANIDS. 399 Of prussian blue as well as of TurnbulPs blue there is a water-soluble variet} 7 , which results when- ever an excess of the potassium ferro- or potassium ferricyanate is added to a ferric or ferrous salt. This soluble form is known as wash blue in the laundry business. Potassium cyanate, K(CNO). This salt results when K(CN) is kept- liquid in presence of air. K(CN) + = K(CNO) at red heat. This strong affinity for oxygen is the reason why K(CN) is a most excellent agent for deoxydation at high heat. It is much used in assaying and in blowpipe work thus : SnO 2 + 2K(CX) + red heat = Sn + 2K(CNO). CuO + K(CX) + red heat = Cu + K(CNO). The aqueous solution of potassium cyanate breaks up even at ordinary temperature ; when heated to boiling NH 3 + CO 2 escape and K 2 C0 3 remains in the liquid. 2K(CNO) + 3H 2 + heat - K 2 CO 3 -f C0 2 -f 2NH 3 . Hydrogen cyanate can be made, but is exceedingly unstable. It has an odor somewhat like a mixture of SO 2 + HC 2 H 3 2 . It is very curious that if a solution of (NH*)(CXO), ammonium cyanate is evaporated, only water escapes, but the residue has all the properties of urea, (CH*N*0), the principle secretion in the animal and human urine. Cyanuric acid, H 3 (C 3 N 3 O 3 ) can be made in large colorless crystals. One recognizes that this is the formula of cyanic acid multiplied by 3. It results 400 CHEMISTRY SIMPLIFIED. from the heating of dry urea above the boiling-point, when NH 3 escapes and cyanuric acid is left. Fulminic acid is not known in the free state. But we saw above that the analysis of the mercuric fulminate gives HgC 2 N 2 2 . Now this radical (C 2 N 2 2 ) is just the double of the radical in (CNO) cyanic acid. Hence we have here an intensely interesting polymerism or equal percentage-com- position for three totally different substances. CHAPTER XXVI. BONE-ASH AND PHOSPHORUS. THE animal skeleton is composed of bones. The bone again can be separated into a mineral part (not combustible), into gelatine (glue) and into fat. The fat may be extracted by any of its solvents (carbon disulfid, ether, chloroform, etc.) The gela- tine can be boiled out by water. If the bone after extraction is merely dried and bleached it becomes fit for conversion into useful and ornamental ob- jects (by the lathe and by the carving tool). If it be thrown into a hot furnace it will be converted into bone-ash. With the latter and its chemical nature, we shall now occupy ourselves. Bone-ash is infusible and somewhat luminous at a high temperature. It dissolves in HC1, in HNO 3 -|- aq., but not in H 2 S0 4 . There is usually a disengagement of CO 2 unless the burning of the bones had been done at very high heat. In the latter instance a small quantity of the ash will pro- duce a brown spot (alkaline reaction) when placed upon a strip of yellow turmeric paper. It acts thus like CaO. The solution in HC1 gives a white, gel- atinous precipitate when NH 4 (HO) is added; there- fore there must be an add present of as yet unknown properties, because the solution of calcite in HC1 26 ( 401 ) 402 CHEMISTRY SIMPLIFIED. or of CaSO 4 in HG1 does not precipitate with (NH 4 )HO. The presence of calcium is, however, made certain by the form of the minute crystals which are separated upon adding cone. H 2 S0 4 to the HC1 solution of the bone-ash. These crystals are identical in shape with the calcium sulfate or vitriol. But since we have learned that oxalic acid forms with calcium an oxalate which is not soluble in water and not soluble in dilute acetic acid, we can apply that knowledge right here to advantage. For we find the precipitate which is thrown down by NH 4 HO in an HC1 solution of the bone-ash to be quite soluble in acetic acid. Adding a solution of ammonium oxalate to the latter a bulky white pre- cipitate falls and thus calcium in large quantities is proved beyond any doubt. Let us designate the unknown acid as A x ; then we can write a prelimi- nary scheme for what we have thus far accomplished. Bone-ash = CaA x ; solution of bone-ash in (m + 2)HC1 = CaCl 2 + H 2 A X -f mHCl ; the pre- cipitate by NH 4 HO must be CaA\ The acetic solution will be again H 2 A x + mNH 4 Cl -f nNH 4 (C 2 H 3 2 ) -f qH.C 2 H 3 2 + Ca(C 2 H 3 2 ) 2 -f- H 2 -solution. To this solution we add ammonium oxalate (NH 4 ) 2 C 2 4 , and thus we get a precipitate and a liquid. The precipitate will be Ca(C 2 4 ), the liquid will contain H 2 A X -f NH 4 C1 -f NH 4 (C 2 H 3 2 ) + H.C 2 H 3 2 + (NH 4 ) 2 C 2 4 water. We filter and BONE-ASH AND PHOSPHORUS. 403 evaporate to dry ness. Then we heat carefully over an open flame, causing the volatilization of NH 4 C1 and of NH 4 (C 2 H 3 2 ); further mcrease of heat will eliminate the excess of (NH 4 ) 2 O and we will have, probably, H 2 A X , the unknown acid, or perhaps (NH 4 ) 2 A X ; provided that this unknown acid does not easily volatilize. We find fhat a remnant is left ; that this remnant imparts a green color to the flame, and that it dissolves in water, giving a colorless solution which shows a strong acid reaction. We also find that the remnant does volatilize at a red heat. Thus we have established that this body is probably an acid-forming, non-metallic, oxyd. It is not probable that any of the non-metallic elements of our acquaintance could produce such a residue, since their oxyds are very easily volatilized, or since they form hydrogen compounds which are quite volatile. In order to separate the element a treat- ment with strong deoxydizing bodies is indicated, to wit, potassium, sodium, hydrogen, carbon, marsh gas. Of these possible agents carbon is the only available. (Reasons below.) We make H 2 A X into a thick syrup by using H 2 S0 4 to precipitate the calcium instead of using NH 4 HO and (NH 4 ) 2 O, and then evaporating. Mix charcoal powder with it until a sticky mass results. Heat over open flame until quite dry, and then fill the black mass into a tube, F, Fig. 103, of hard infusible glass, which has been closed at one end. By placing the tube upon a brick (1) against a second brick (2) and using a Bunsen blowpipe on the closed end, we can bring 404 CHEMISTRY SIMPLIFIED. the tube to the required temperature. As the heat rises we begin to observe a peculiar odor at the mouth of the tube, and on approaching a taper a greenish flame develops, a white smoke rising into the air. At the same time wax -like drops con- dense in the forward part of the tube at (3). At length the flame burns more. and more with a pure FIG. 103. blue color (CO) and the action is complete. When the tube has become cold we cut off the forward part with a file stroke and a red-hot rod (glass or iron). The new substance is transparent or trans- lucent. Its color varies from pale yellow to bright red. (Probably 2 different substances ?) It is soft as wax. It emits a peculiar odor similar to that of ozone. A white fume arises from it steadily. It melts at 45 C., and begins at once to burn with a bright flame and evolution of white fumes. Under water it can be melted without danger of ignition. It dissolves somewhat in alcohol, more in fat oils. If such solution is rubbed over the hands or the face those parts will shine in a dark room with a pale green light. This property has been the justifica- tion for giving to this remarkable elementary body BONE- ASH AND PHOSPHORUS. 405 the name phosphorus (phos = light ; phorus = car- rier). It would be more consistent to change the name tophosgen, and thus obtain a consonant series : Oxygen, hydrogen, nitrogen, chlorogen, brornogen, iodogen, fluogen, phosgen, and so forth. (1). Note. Brand was the first to obtain phos- phorus, in 1674, by distilling, in a clay retort, the residual mass from evaporated urine ; but that bones contain much more phosphorus than does urine, was only discovered 100 years later by Scheele. (2) Note. Experience has shown that a higher percentage of phosphorus can be obtained from bone- ash if only two-thirds of the calcium are removed by means of H 2 S0 4 , leaving soluble calcium phosphate to be separated by filtration, to be evaporated, mixed with coal and dried before distillation. This plan is followed in the match factories. There are three modifications of phosphorus. (1). Common, pale-colored, phosphorus which crys- tallizes in octahedrons has essentially the properties already given. Specific gravity = 1.83 at 10 C. Above 45 C., that is, in the liquid state, the specific gravity decreases considerably ; with the temperature at 100 C. it is 1.695; at 200 C. = 1 .603. At the boil- ing-point = 1.485. Phosphorus boils at 250 C. and distills over in an atmosphere of hydrogen. Kapid cooling of the vapor throws the phosphorus out in a fluffy, snow-white condition (flowers of phosphorus). But it is quite certain that slight volatilization goes on at ordinary temperature. To this volatilization 406 CHEMISTRY SIMPLIFIED. is probably due the phosphorescence, the power to emit light in a dark room. Surrounded by oxygen alone there is no phosphorescence ; but the latter pheno- menon appears when the oxygen is diluted with nitrogen. Phosphorus ignites at 60 C. in air. Rubbing on a rough surface causes ignition (matches). Mixed with KC10 3 a very explosive substance results (lucifer matches). Phosphorus is poison to man and animals when brought into the stomach or esophagus. Every particle of the phosphorus causes an intense local inflammation of the membrane, hence great pain and shock, which result in death. 0.2 gram may be a fatal dose for an adult person. Emptying the stomach by emetics and the pump may save the life in some cases. The workmen in match factories are known to suffer from necrosis of the teeth, the gums and the jaw-bones themselves. Burns made by burning phosphorus on the fingers have even been fatal. Wash out such wounds with utmost haste with a dilute water solution of bleaching lime, or bleaching soda (crude Javelle). The best solvent for the active form of phosphorus is carbon disulfid. (#). Amorphous red phosphorus. Sunlight, espec- ially the violet portion of it, or heat plus pressure, or the electric current, changes the ordinary phos- phorus more or less rapidly into the amorphous modification. In the factories the change is brought about by keeping the yellow phosphorus for 10 days at a steady temperature of 260 C. BONE- ASH AND PHOSPHORUS. 407 The amorphous red phosphorus is not poisonous. It does not melt even at red heat but volatilizes. It is not soluble in CS 2 nor in KOH. It appears as a scarlet or as a purplish-red, pulverulent mass, sometimes brown-red. In bulk it shows sometimes a weak metallic luster, more often no luster at all. It has neither taste nor odor, does not show phos- phorescence. It ignites at 260 C. Lt forms with KC10 3 , with PbO 2 , and with MnO 2 , mixtures which ignite by blows or friction. It is the only phos- phorus now used in matches, or on the friction sur- faces of safety match boxes. (3). Black crystallized phosphorus. By heating red phosphorus in a vacuum to 447 C. it is ob- tained as a violet-black mass of conchoidal fracture, or by fusing together in a vacuum phosphorus and metallic lead. After cooling one finds long-stretched rhombohedrons, black in reflected light, red in transmitted light. This phosphorus has a specific gravity of 2.34. Atomic weight of phosphorus, P = 31. The de- terminations of the vapor density lead to 62. We assume therefore that the element in the free state is P 2 . According to the combinations into which phosphorus enters with the non-metals, it is trivalent and pentavalent like nitrogen. The oxyds of phosphorus are P 2 5 , P 2 O 3 . Phosphorus pemtoxyd, P 2 5 , a colorless, vitreous solid or colorless triclinic crystals. Dissolves in water. Is very hygroscopic (goes slowly into a syrup when standing in moist air), hence it is often 408 CHEMISTRY SIMPLIFIED. used to dry gases. It has no odor, but a very sour taste. Is sometimes called anhydrous phosphoric acid. Volatilizes partly at 250 C. But when heated quickly it changes its nature by polymeriza- tion (aggregation of molecules) and is much less volatile. Preparation. By igniting phosphorus in a flask in a current of perfectly dry air. The product is a mass of minute snowy-white crystals. For larger quantities a tinned sheet-iron cylinder is substituted for the flask. Phosphoric acids. It was Graham who first de- monstrated that the pentoxyd can form 3 hydrates and that these hydrates possess very distinct proper- ties. We distinguish these hydrates thus : The tri- hydrate, 3H 2 O.P 2 5 , the dihydrate, 2H 2 O.P 2 5 and the monohydrate, H 2 O.P 2 5 . We translate these hydrates into the radical expressions or hydro- gen acids thus : Trihydrate, 3H 2 O.P 2 5 = 2H 3 (P0 4 ) = orthophosphoric acid. Dihydrate, 2H 2 O.P 2 5 = H 4 (T 2 7 ) = pyrophosphoric acid. Monohydrate, H 2 O.P 2 5 = 2H(P0 3 ) = metaphosphoric acid. Orthophosphoric acid, H S (P0 4 ). Orthorhombic, colorless crystals, or a thick syrup of specific gravity = 1.88. Strong acid reaction ; easily soluble in water. Gives green coloration to a flame. Preparation. (I). By acting with UNO 3 (specific BONE-ASH AND PHOSPHORUS. 409 gravity = 1.2) upon ordinary phosphorus in a glass retort, (1 phosphorus, 10 acid), at such a tempera- ture that lively action ensues, but not a violent one, (because explosions may set in). After all the phosphorus has disappeared heat to boiling and dis- till over about 7 parts of the HNO 3 . The distillate has a specific gravity of 1.1-1.14 and may be used for another operation by adding enough concen- trated acid to bring gravity up to 1.2. Pour the liquid from the retort into an evaporating dish and evaporate carefully to syrup, or until all HNO 3 has been removed. Sometimes there occurs during this stage another disengagement of NO from the fact that some P 3 is still present. The tempera- ture may be brought to 188 C. but not higher, for pyro-phosphoric acid may form. By adding some alcohol the remainder of HNO 3 may be removed more easily. The syrup of H 3 (P0 4 ) is called glacial phosphoric acid. (2). By acting upon red amorphous phosphorus with concentrated HNO 3 . The oxydation is more rapid and can be carried on in a beaker glass. Orthophosphates. The orthophosphoric acid can form 3 series of salts as follows : Monads, Na 3 (P0 4 ), HNa 2 (P0 4 ), H 2 Na(P0 4 ). Diads, Ca 3 (P0 4 ) 2 , Ca 2 H 2 (PO 4 ) 2 , CaH 4 (P0 4 ) 2 . Triads, A1 3 (P0 4 ) 3 , A1 2 H 3 (P0 4 ) 3 , A1H 6 (P0 4 ) 3 . The radical (PO 4 ) is trivalent, hence Na 3 (P0 4 ) is a fully saturated combination and so is A1(P0 4 ), be- cause aluminum is trivalent. But in order to bring "410 CHEMISTRY SIMPLIFIED. out the partially saturated series (A1 2 H 3 ) and (A1H 6 ), we must treble the saturated molecule into A1 3 (P0 4 ) 3 . Any diad "metal will form orthophos- phates similar to calcium. For example, copper will make Cu 3 (P0 4 ) 2 , Cu 2 H 2 (P0 4 ) 2 , CuH 4 (P0 4 ) 2 . The three series are sometimes called basic, neutral, acid.^ Cu 3 (P0 4 ) 2 is basic copper orthophosphate. Cu 2 H 2 (P0 4 ) is neutral copper orthophosphate. CuH 4 (P0 4 )is acid copper orthophosphate. The orthophosphates of potassium, sodium, am- monium are all soluble in water and all can be crystallized. The most common of them, because most easily obtainable, is Na 2 H(P0 4 ) + 12H 2 in inonoclinic crystals, and H.NH 4 .Na(P0 4 ) + 4H 2 0, also inonoclinic crystals. The latter salt goes under the names : salt of phosphorus, and microcosmic salt. This salt fuses into a perfect glass and dissolves at red heat most of the metallic oxyds, giving with some of them transparent glasses of constant color. Hence we utilize this salt as a flux in blow-pipe analysis. Preparation of microcosmic salt. Dissolve 353 grams of the crystals of Na 2 HP0 4 + 12H 2 and 53.5 grams of NH 4 C1 (sal ammoniac) in 1700 c.c. of warm water, filter and evaporate until a film of crystals forms at the surface. Let stand for several days in a cool place. A large crop of the micro- cosmic salt will have been formed. Drain crystals from mother liquor. Dissolve again in water and crystallize, repeating the recrystallization twice. Then you will have crystals sufficiently free from NaCl to answer for blow-pipe work. Reaction : BONE- ASH AND PHOSPHORUS. 411 Na 2 HP0 4 + water 4- NH 4 C1 = NH 4 .NaHP0 4 + water -f- NaCl. Nad remaining in the crystals causes the bead, after fusion, to become white and opaque. Insoluble orthophosphates. The neutral solutions of all the metals are precipitated by adding a solu- tion of any alkali phosphate* (K, Na, NH 4 ). These precipitates are soluble in dilute acids even acetic acid. Two of these precipitates are of special inter- est because by means of them we distinguish ortho- phosphoric acid from other acids. (1). Silver orthophosphate, Ag*(PO*), a yellow floc- culent precipitate. The solution must be neutral before AgNO 3 is added to the unknown. (#). Ammonium-magnesium orthophosphate,NH*.Mg- (PO 4 ), a colorless, granular or crystalline precipitate which forms when MgCl 2 or MgSO 4 solution is added to a slightly ammoniacal solution of an ortho- phosphate. The most delicate or sensitive reagent for ortho- phosphate is the so-called molybdic solution. This is a solution of (NH 4 ) 2 Mo0 4 ammonium molybdate in HNO 3 , specific gravity 1.2; the solution is pale yellow or colorless. Any metallic phosphate is first dissolved in a little HNO 3 , or any unknown substance is heated with HNO 3 , water added and after filtering 1 volume of the molybdic solution is added. The temperature of the liquid is brought to about 50 C., and the liquid shaken rapidly. A fine granular, citron-yellow precipitate falls if a phosphate be present. The precipitate is (NH 4 ) 2 - 412 CHEMISTRY SIMPLIFIED. H(P0 4 ).10Mo0 3 + 1JH 2 = ammonium-hydrogen phosphopolymolybdate. Pyrophosphoric acid, H*(P*0 7 ), is not known in solid state, only known as an aqueous solution. Preparation. Heat the salt Na 2 H(P0 4 ) -j- 12aq. in a crucible until all the water is driven out and then to redness for a short time. Reaction : 2Na 2 H(P0 4 ) + heat == Na 4 P 2 7 + H 2 0. Dissolve in water without heating. To solu- tion add PbA 2 (lead acetate) ; a white precipitate Pb 2 (P 2 7 ) falls. Filter and wash. Suspend the precipitate in water and pass H 2 S into the liquid ; then you obtain Pb 2 (P 2 7 ) -f 2H 2 S = 2PbS -f H 4 (P 4 7 ), which are separated by filtering. Properties. (1). When the acid is neutralized with NH 4 OH and AgNO 3 is added, a white floccu- lent precipitate falls (not yellow as with an ortho- phosphate). (2). MgCl 2 does not produce a precip- itate. When the precipitate MgNH 4 (P0 4 ) (see above) is ignited Mg 2 (P 2 7 ) magnesium pyrophosphate is left behind. A solution' of pyrophosphoric acid reverts into orthophosphoric acid by boiling for several hours. Metaphosphoric acid, H(P0 3 ). A colorless glassy substance. Preparation. (1) By dissolving P 2 5 in cold water. (2) By heating the syrup of H 3 P0 4 , thus H 3 P0 4 + heat = H 2 0-f H(P0 3 ). (3) By fusing the microcosmic salt at a red heat we get BONE- ASH AND PHOSPHORUS. 413 Na(NH 4 )H(P0 4 ) -f heat = Na(P0 3 ) + NH 3 + H 2 sodium metaphosphate + ammonia -f- water. The characteristics of metaphosphoric acid are as fol- lows : (a) the acid solution causes coagulation (curd- ling) in a water solution of albumen. (Neither ortho- nor pyrophosphoric acid coagulates the albu- men.) (b) When the solution is neutralized with NH 4 HO, AgNO 3 solution gives a white gela- tinous precipitate, (c) When a solution of Na(P0 3 ) is added to neutral salts of the metals, a precipitate forms at first, but dissolves on further addition of the metaphosphate. Some of the precipitates sepa- rate like tough resin, some separate as oily liquids. Phosphorus trioxyd, P 2 S . White snowy aggre- gates of small crystals often in the shape of trees or ferns. Preparation. Heat phosphorus in a tube until it ignites, and allow a very slow current of dry air to pass through the tube. The oxyd sublimes into a receiver. In the dark it remains unchanged. Sun- light brings red or orange colors. In warm oxygen it ignites and changes to P 2 5 . It smells like phosphorus. Some authors say it is poisonous, others say it is not ; I, myself, think it is poisonous. Very slightly soluble in water. Phosphorous acid, hydrogen phosphite, H*(PO S ). Crystalline-white mass or distinct crystals. Soluble in water. Sour taste. Is a strong deoxydixing agent. In salts of gold, silver, copper, mercury, the acid causes precipitation of the metal. It is a diatomic acid, that is to say, only two of 414 CHEMISTRY SIMPLIFIED. the hydrogens can be replaced by a metal. There are therefore two series of phosphites, Na 2 H(P0 3 ) and NaH 2 .(P0 3 ). Preparation. (1). By action of dilute HNO 3 upon phosphorus. (2). By the action of oxalic acid upon phosphorus trichlorid. Thus : PC1 3 + 3H 2 .C 2 4 = H 3 P0 3 -f 3HC1 + 3C0 2 + SCO. Hypophosphorous acid, hydrogen hypophosphite, H*P0 2 . A colorless substance in large scales or leaves. Its solution in water is even more deoxydiz- ing than the preceding phosphorous acid. It is a monobasic acid. Only one of the three hydrogens can be replaced by a metal. Thus NaH 2 (PO 2 ) or still better Na(HP0 2 H) = sodium hypophosphite, or Ba(HP0 2 H) 2 = barium hypophosphite. The hypo- phosphites have been recommended as very active stimulants of the nerves and the brain (humbug). Preparation, 3KHO+4P+3H 2 = 3KH 2 P0 2 -h PH 3 . This means that phosphorus in presence of water and KHO will form potassium hypophosphite plus phosphine (PH 3 ). Ca(HO) 2 and Ba(HO) 2 plus P act similarly. COMBINATIONS OF PHOSPHORUS WITH CHLORINE. Phosphorus trichlorid, PCI 3 . Colorless liquid. Produces white fumes in moist air ; refracts the light strongly, smell, penetrating, and the vapor causes tears to flow. Boils at 76 C. When PCI 3 is poured into cold water it sinks to the bottom and collects like a heavy oil ; soon a re- action sets up between the water and the chlorid, BONE-ASH AND PHOSPHORUS. 415 PCI 3 -f 3H 2 = H 3 .P0 3 + 3HC1, the result being a liquid containing phosphorous acid and hydrochloric acid. Such a solution answers as a deoxydizer. Preparation. Place in a retort some pieces of dried stick phosphorus (dry with blotting paper), the retort having been previously filled with CO 2 gas. In the tubulus fits a cork, and through this passes a glass tube down to the phosphorus. A receiver is tightly connected with the retort, and is well cooled. Fill now the retort with chlorine, and warm the retort until the phosphorus melts, when the action begins and PCI 3 distills over. Phosphorus pentachlorid, PCI 5 . A colorless solid. Peculiar odor, fumes at the air. With little water it decomposes into HC1 and POC1 3 . It is often used in synthetic laboratory work to put Cl into complex molecules. With sodium it gives 2NaCl -f PCI 8 , and the same with other metals. With much water it decomposes into phosphoric acid and HC1. PCI 5 -f- 4H 2 = 5HC1 + H 3 (P0 4 ), orthophosphoric acid. Preparation. By acting with excess of Cl upon PCI 3 . There are, of less importance, PBr 3 , PBr 5 , PI 3 , PI 5 , PF 5 . Phosphine, hydrogen phosphid, PH 3 . A gas of disagreeable odor, somewhat resembling that of garlic. In a dark room the gas gives out a pale light like phosphorus itself. It causes a taste on the^ tongue. Sunlight decomposes the gas into hydrogen and red amorphous phosphorus. The gas 416 CHEMISTRY SIMPLIFIED. is poisonous because the blood absorbs it like H(CN). Air containing 0.25 per cent. PH 3 kills animals in 5-10 minutes. Phosphine ignites in air at 149 C.; the flame is white and yields white smoke. But sometimes the gas is self -igniting. This self-ignition is attributed to the admixture of an- other compound PH 2 , which latter forms only under specific conditions. When phosphine gas is passed into solutions of Ag, Hg, Cu, Pb, Bi, Au salts, the metals are thrown out ; or phosphids of the metals are formed. PH 3 in a solution of AgNO 3 + water causes first a yellow precipitate of Ag 3 P.3AgN0 3 (? doubtful composition), but black Ag 3 P results ulti- mately. Preparation. (1). Place 5-10 grams of stick phos- phorus into a 150 c.c. flask. Fill the flask with KOH solution (1:5) up to the stopper. The latter carries one evolution tube, bent so that it can be made to dip under water in a dish or beaker glass. (The flask is to be filled completely to avoid ex- plosion with air). On heating the flask the gas evolution will set in, and if the water in the dish be warm, each gas bubble will ignite as it breaks over the water, and will form a ring of smoke in the air. (2). Place the phosphorus in the flask as before, but fill the flask with an alcoholic solution of KOH. (70 per cent, alcohol.) The gas will not ignite by itself. The reason for this is that the self-igniting PH 2 re- mains dissolved in the alcohol ; does not mix with the gas PH 3 . In both these actions the PH 3 is generated by the reaction BONE-ASH AND PHOSPHORUS. 417 3KHO + 4P -f 3H 2 = PH 3 + 3KH 2 P0 2 . (3). Prepare Na 3 P by fusing together sodium and phosphorus. Or by fusing together 3Na 2 C0 3 + Ca 3 (P0 4 ) 2 -f 8Mg= 2Na 3 P + 3CaC0 3 + 8MgO. In either case you get Na 3 P s and if a drop of water touches Na 3 P then phosphine will be disengaged (noticed by strong odor), and NaHO will form : Na 3 P -f- 3H 2 = PH 3 + 3NaHO. Metallic magnesium can be carried much better than sodium because it does not oxydize so easily at ordinary temperature. Hence the last reaction is the one best adapted to test an unknown mineral for phosphorus, in the field, in the operation of blow- pipe analysis-. We call it the phosphine reaction. It is all done in a small ignition tube. Composition of PH Z . Phosphine breaks up read- ily at a red heat into P -f H. If 20 c.c. of phos- phine are collected over mercury in a eudiometer (see ammonia) and the spark is sent through it, complete dissociation results in from 6 to 10 minutes, when the volume has increased to 30 c.c. Phos- phorus covers the surface of the tube and the gas consists entirely of hydrogen. Now since the vol- ume of solid phosphorus is so small as to be negligible it follows that 20 c.c. of phosphine con- tain 30 c.c. of hydrogen and 10 c.c. of phosphorus gas. Hence PH 3 . Phosphonium, PH 4 , corresponds to ammonium, *> and is only known hypothetically. Because 27 418 CHEMISTRY SIMPLIFIED. PH 3 coriibines by simple addition with HC1, giving PH 4 Cl (colorless crystals below 20 C.). Liquid hydrogen phosphid, PH 2 . A colorless liquid, not soluble in water. In contact with air ignites instantaneously. Forms when Ca 3 P 2 is de- composed with H 2 and the resulting gas is carried through a U-tube standing in the freezing mixture. At the same time with the liquid PH 2 , condenses a solid substance which has probably the composition P 2 H. Phosphorus combines directly with all metals, yielding metallic phosphids. Of practical importance are the phosphids of iron (in the metal- lurgy of iron and steel) and tin phosphid, Sn 4 P, beautiful silver-white crystals (in the manufacture of phosphorbronze). APPENDIX. THE CHEMICAL ELEMENTS, THEIR SYMBOLS, EQUIVALENTS AND SPECIFIC GRAVITIES. Name. Symbol. Mass Unit Weight. Specific Gravity. Aluminium AI. Antimony ... . . Sb 27.5 122 2.56 6 70 Arsenic A.S 75 5 70 Barium i Ba. Bismuth, Bi 137.0 210 4.00 9 7 Boron B. Bromine Br 11.0 80 2.63 5 54 Cadmium j Cd. Caesium j Cs. Calcium . . . Ca 112.0 133.0 40 8.60 1.88 1 58 Carbon ... j C 12 3 50 Cerium 1 Ce. Chlorine Cl 92.0 35 5 6.68 2 45 Chromium Cr. Cobalt ... Co 52.5 58 8 6.81 7 7 Columbium I Cb 184 8 6 00 Copper . . . Cu 63 8 96 Didymium ... . Di 96 6 54 Erbium . E. 1126 Fluorine ...... . > F. 19.0 1.32 Gallium ; Ga. 69.9 5.9 Glucinuin ' Gl 9 5 2 1 Gold (Aurum) | Au. Hydrogen H. Indium In 196.0 1.0 113 4 19.3 0.069 7.4 Iodine . . . . I 127 4 94 Iridium Ir 198*0 21.15 56.0 7.79 90 2 11 37 Lead (Plumbum) . Pb 207 11 44 Lithium ..... . j Li 7.0 059 (419) 420 APPENDIX. Name. Symbol. Atomic Weight. Specific Gravity. Magnesium . . Mg. 24.0 55.0 200.0 96.0 58.8 94.0 14.0 199.0 16.0 106.5 31.0 197.4 39.0 104.3 85.4 104.4 79.5 28.0 108.0 23.0 87.6 32.0 1X2.0 129.0 204.0 115.7 118.0 50.0 184.0 120.0 51.3 61.7 65.0 89.5 1.75 8.01 13.59 8.60 8.60 6.27 0.972 21.40 1.105 11.60 1 83 21.53 0.865 12.1 1.52 11.4 4.78 2.49 10.5 0.972 254 2.05 1078 6.02 11.91 7.8 7.28 4.3 17.6 18.4 550 7.14 4.15 Manganese ! Mn. Mercury (Hydrargyrum) . . j Hg. Molybdenum , Mb. Nickel Ni. Niobium . . ... Nb. Nitrogen N. Osmium Os. Oxygen O. Palladium . * Pd. Phosphorus . . .... P. Platinum | Pt. Potassium (Kalium) ... K. Rhodium Ro. Rubidium Rb. Ruthenium I Ru. Selenium l Se. Silicon Si. Silver (Argentum) . Ag Sodium (Natrium) Na. Strontium j Sr. Sulphur ' . S Tantalum Ta. Tellurium Te. Thallium Tl. Thorium Th. Tin (Stannum) j Sn. Titanium Ti. Tungsten (Wolfram) .... W. Uranium j U. Vanadium . .... . 1 V Yttrium. . . Y. Zinc ' . . . . j Zn. Zirconium Zr. TABLE FOR THE COMPARISON OF THE SCALES OF REAUMUR' S, CELSIUS'S, AND FAHRENHEIT'S THERMOMETERS. Keaumur. Celsius. Fahrenheit. Reaumur. Celsius. Fahrenheit. 15 18.75 _ 33 +41.25 +106.25 14 17.50 +0.50 34 42.50 108.50 13 16.25 2.75 35 43.75 110.75 12 1500 5.00 36 45.00 113.00 11 13.75 7.25 37 46.25 115.25 10 12.50 9.50 38 47.50 117.50 9 11 25 11.75 39 48.75 119.75 8 10.00 14.00 40 50.00 122:00 7 8.75 16.25 41 51.25 124.25 6 7.50 18.50 42 52.50 126.50 5 6.25 20.75 43 53.7* 128.75 4 5.00 23.00 44 55.00 131.00 3 3.75 25.20 45 56.25 133.25 2 2.50 27.50 46 57.50 135.50 +1 1.25 29.75 47 58.75 137.75 32.00 48 60.00 140.00 1 + 1 25 34.25 49 61.25 142.25 2 2.50 36.50 50 62.50 144.50 3 3.75 38.75 51 63.75 146.75 4 5.00 41.00 52 66.00 149.00 5 625 43.25 5S 66.25 151 25 6 7.50 45.50 54 67.50 153.50 7 8.75 47.75 55 68.75 155.75 8 10.00 50.00 56 70.00 158.00 9 11.25 52.22 57 71 25 160.25 10 12.50 54.59 58 72.50 162.50 11 13.75 56.75 59 73.75 164.75 12 15.00 59.00 60 75.00 167.00 13 16.25 61.25 61 76.25 169.25 14 17.50 63.50 62 77.50 171.50 15 18.75 65.75 63 78.75 173.75 16 20.00 68.00 64 80.00 176.00 17 21.25 70.25 65 81.25 178 25 18 22.50 72.50 66 82.50 180.50 19 23.75 74.75 67 83.75 18275 20 25.00 77.00 68 85.00 185.00 21 26.25 79.25 69 86.25 187.25 22 27.50 81.50 70 87.50 189.50 23 28.75 83-75 71 88.75 191.75 24 30.00 86.00 ! 72 90.00 194.00 25 bl.25 88.25 73 91.25 196.25 26 32.50 90.50 1 74 92.50 198.50 27 33.75 92.75 75 93.75 200.75 28 35.00 95.00 76 95.00 203.00 29 36.25 97.25 77 96.25 205.25 30 37.50 99.50 78 97.50 207.50 31 38.75 101.75 79 98.75 209.75 32 40.00 104.00 80 100.00 212.00 (421) 422 APPENDIX. Rides for the Conversion of the Different Thermometer Degrees into each other. The thermometers referred to in the table are gradu- ated so that the range of temperature, between the freezing and boiling points of water, is divided by Fahrenheit's scale into 180 (from 32 to 212) by Celsius's into 100 (from to 100), and by that of Reaumur into 80 (from to 80) portions or degrees. The spaces occupied by a degree of each scale are consequently as 1, i and J respectively, or as 1, 1.8 and 2.25; and the number of degrees denoting the same temperature, by the three scales, when reduced to a common point of departure by subtracting 32 from Fahrenheit's, are as 9, 5, and 4. Hence we derive the following equivalents : A degree of Fahrenheit is equal to 0.5 of Celsius's, or to 0.4 of Reaumur's; a degree of Celsius's is equal to 1.8 of Fahrenheit's, or to 0.8 of Reaumur's; and a de- gree of Reaumur's is equal to 2.25 of Fahrenheit's, or to 1.25 of Celsius's. To convert degrees of Fahrenheit into Celsius's or Reaumur's, subtract 32 and multiply the remainder by f for Celsius's, or, f for Reaumur's. To convert degrees of Celsius's or Reaumur's into Fahrenheit's, multiply Celsius's by -f, or Reaumur's by f , as the case may be, and add 32 to the product. APPENDIX. 423 TABLE OF THE LITER WEIGHTS OF THE GASES. Temp. C. and 760 Mm. Pressure. 1 liter of air weighs . . . 1.29300 Gms. " CO. " 1.25078 " < CO 2 . " 1.96500 " 0. " ........ 1.42910 " H. " 0.08988 " N. " . . . ._.. . 1.25070 " NO. " 1.34260 ' NO 2 . " 2.05440 " " N 2 O, " 1.96770 " " NH 3 . " 0.76170 " Cl. " 3.17240 " " HC1. " 1.62850 *' H 2 S. " 1.52100 ' " SO 2 . " 2.86150 " CH*. " 0.71570 u steam*" 0.58960 " " C a H J . 4i 1.16200 " " Br. " 7.14259 " 1. " 11.27100 " S. " 2.84300 " P. 5.63180 " Hg. " 9.02100 " HI. " 5.71067 Engines, etc. With an Appendix on the Analysis of Iron and Iron Ores. By FPANCIS CAMPIN, C. E. 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