NRLF 
 
 B 
 
\ 
 
 LI3RARY 
 
 UNIVERSITY OF 
 c CALIFORNIA^/ 
 
 EARTH 
 
 SCIENCES 
 LIBRARY 
 
 LIBRARY 
 
 OF THE 
 
 UNIVERSITY OF CALIFORNIA. 
 
 OTKT OK 
 
 ]fC 
 
 Received 
 Accession No. (03 5~/ /- Class No. 
 
The World of Matter 
 
 A GUIDE TO THE STUDY OF 
 
 CHEMISTRY AND MINERALOGY 
 
 BY 
 
 HARLAN HOGUE BALLARD, A. M. 
 \\ 
 
 President of the Agassiz Association, Author of "Three Kingdoms," 
 
 "American Plant Book," "One Thousand Blunders in 
 
 English Corrected," etc. 
 
 LUSTRATED. 
 
 o 
 
 BOSTON, U.S.A. 
 
 D. C. HEATH & CO., PUBLISHERS 
 1894 
 
E ___ 
 
 toBRARV 7 
 
THIS BOOK 
 
 IS 
 AFFECTIONATELY DEDICATED 
 
 TO 
 MY MOTHER. 
 
PREFACE. 
 
 In 1875 *h e au *hor founded a society for the study 
 of Natural Science at home, which, under the name 
 AGASSIZ ASSOCIATION, has during sixteen years en- 
 listed no less than twenty thousand students of all ages, 
 and organized more than one thousand local branch so- 
 cieties scattered throughout the world. Under the aus- 
 pices of the Agassiz Association and under the general 
 supervision of the author, who has heretofore conduc- 
 ted the entire management and correspondence of the 
 society, annual courses of experimental study have been 
 conducted by eminent teachers, through the mails. 
 During the present year nearly one thousand pupils in 
 the United States are at work on a course in Mineral- 
 ogy under the care of Professor Gustave Guttenberg. 
 
 This practical experience of sixteen years has firmly 
 convinced the author that the natural sciences are ordi- 
 narily taught in a fragmentary manner. Wonderful 
 advances have indeed been made in methods of teaching 
 them w'thin twenty years, and there is now a multitude 
 of competent and faithful teachers, who, each in his 
 own special department, are training their pupils as 
 
 (3) 
 
4 PREFACE. 
 
 they ought to be trained, discarding ancient systems of 
 memorizing and rote-work, and introducing laboratory 
 and field-work, which develops and strengthens the natu- 
 ral powers of perception and reason: but, rarely, if 
 ever, has the attempt seriously been made so to co-ordi- 
 nate the several branches of science as to cause the stu- 
 dent to apprehend their essential unity, or even to ap- 
 proach them in a natural and logical order. 
 
 To accomplish this, is attempted in this series of books. 
 A brief discussion of the true order of scientific studies 
 is included in Chapter XIX., and need not be repeated 
 here. 
 
 No one need hope to. learn anything of much value 
 either of chemistry or mineralogy unless he handles 
 specimens and makes experiments. 
 
 A collection of thirty-six minerals has been prepared 
 to accompany this book. They are arranged in a neat 
 case. They have been selected under the. supervision 
 of Prof. W. O. Crosby, of the Boston Society of Natu- 
 ral History, and can be depended upon as excellent 
 typical specimens, and they are furnished at the bare 
 cost of the labor required in their preparation. Never- 
 theless it is not necessary that the reader should procure 
 these particular specimens, as he will be able to find 
 similar ones almost anywhere. 
 
 The author has made free use of the standard text- 
 books in Physics, Chemistry, and Mineralogy, particu- 
 larly Ganot, Roscoe and Schorlammer, Cooke, Faraday, 
 Huxley, Tenney, Richards, Kunz, and Dana; he is 
 especially indebted to the generous courtesy of the 
 
PREFACE. 5 
 
 authors and Publishers of Remsen's Elements of 
 Chemistry, Crosby's Common Minerals and Rocks, and 
 Guttenberg's Course in Mineralogy; and he desires to 
 express his gratitude to Professors Ira Remsen, W. O. 
 Crosby, Gustave Guttenberg, and John B. Welch, for 
 valuable suggestions during the progress of the work, 
 and for reading the proofs while in press. 
 PITTSFIELD, MASS., September i5th, 1891. 
 
CONTENTS. 
 
 CHAPTER. PAGE - 
 
 PREFACE m - 
 
 I. A PIECE OF ICE ' 
 
 II. A PIECE OF ICE (Continued) 16 
 
 III. A GLASS OF MELTED ICE 33 
 
 IV. Is WATER AN ELEMENT? . . , . .45 
 V. FIRE 55 
 
 VI. Am 67 
 
 VII. EARTH , . . . 77 
 
 VIII. QUARTZ 86 
 
 IX. A LESSON IN CHEMISTRY 94 
 
 X. A PIECE OF CHARCOAL 103 
 
 XI. CARBON CONTINUED 115 
 
 XII. A PIECE OF MARBLE 126 
 
 XIII. CLAY 137 
 
CONTENTS. 
 CHAPTER. PAGE. 
 
 XIV. POTASSIUM MICA 144 
 
 XV. A LUMP OF SALT . 150 
 
 XVI. MURIATIC ACID . 156 
 
 XVII. CHLORINE 161 
 
 XVIII IRON 165 
 
 XIX. BY WAT OF REVIEW 171 
 
 XX. WHAT is A METAL? 179 
 
 XXI. FAMILIES OF ACID-FORMING ELEMENTS . . 184 
 
 XXII. FAMILIES OF METALS 194 
 
 XXIII How TO DETERMINE MINERALS 198 
 
 XXIV. FLAME TESTS, HEAT TESTS AND ACID TESTS . 205 
 
 XXV. TWELVE OTHER MINERALS 216 
 
 XXVI. BLOW-PIPE ANALYSIS ........ 226 
 
 XXVII. SUGGESTIONS FOR FURTHER STUDY . 245 
 
THE WORLD OF MATTER. 
 
 CHAPTER I. 
 
 A PIECE OF ICE. 
 
 Ice is one of the most common minerals. Let us 
 begin our study with a piece of ice. We will not ask 
 any one to tell us anything about it until we have 
 learned what we can from our own observation. 
 
 Common sense is the sense which we all have in com- 
 mon and by the use of our common sense, and our common 
 senses, we can learn enough for practical purposes. 
 The senses which we all have are feeling, sight, taste, 
 hearing, and smell. What do these teach us about a 
 piece of ice? We notice first that it is cold, smooth, 
 slippery, hard, and heavy. We learn all this from the 
 sense of feeling by holding the piece of ice in the hand. 
 
 No scientist understands the meaning of these words 
 better than we, and no explanation can make them any 
 plainer. No facts in natural science are any more diffi- 
 cult to understand than these. The only reasons for the 
 popular notion that there is something hard and mysteri- 
 ous about chemistry and mineralogy are that many of 
 the substances treated of in the books are less familiar to 
 us than ice, and that many of the words used to describe 
 them are new to us. When a piece of muscovite 
 
 (7) 
 
8 THE WORLD OF MATTER. 
 
 becomes as familiar to our hand as a piece of ice, and 
 when we become as familiar with the words "transpar- 
 ent" and "foliaceous" as we are with the words "hard" 
 and "smooth," the statement that "Muscovite is trans- 
 parent and foliaceous" will seem as simple as that "Ice is 
 hard and smooth." 
 
 This is by the way, but it is important, for I wish the 
 reader to remember that if he ever finds anything in a 
 good scientific text-book which seems hard to under- 
 stand, it will be because he is not familiar with the 
 thing described, or because he does not know the 
 meaning of the words used to describe it, or because he 
 has not mastered the preceding portion of the book. 
 
 To remedy the first trouble it is necessary to get 
 hold of the strange substance and examine it; to remedy 
 the second trouble the strange words must be clearly 
 defined. 
 
 Let us return to our piece of ice, and having learned 
 what our hands can tell us of it, let us see what our 
 eyes can teach us. This piece is thin and clear. It 
 looks like a piece of glass. If we lay it on this page 
 we can read the letters through it. If it were large and 
 strong enough it would do for a window-pane. The 
 light comes through it. If we hold it in the sunlight it 
 shines like glass. 
 
 Testing it now by our other senses we find that it has 
 no smell or taste, and that when we break it, it breaks 
 with a snapping or cracking sound. 
 
 In this connection we notice that it is brittle, a fact 
 to which our hand, eye and ear all bear witness. 
 
A PIECE OF ICE. 9 
 
 We have spoken of our piece of ice as a "thing," but 
 it is better to use the word "substance." This word is 
 better because the word "thing" is too indefinite, being 
 used also of events or deeds. 
 
 Shall we say then that ice is a brittle, hard, smooth, 
 slippery, clear, shining, heavy, and cold substance, 
 without taste or smell? Not yet. All this is true of 
 the particular piece we are examining, but we remember 
 that we have seen other pieces of ice that were rough 
 instead of smooth, dull rather than shining and white 
 or green instead of clear. We must therefore recollect 
 that we are speaking only of a particular sample of 
 ice, not of ice in general. Such a sample of any sub- 
 stance is called a "specimen;" and it is only after a 
 study of many specimens, and after rinding what is 
 true of all of them, that we shall be ready to make a 
 general description or definition of ice. 
 
 In all the ice we have seen we have observed cold- 
 ness, brittleness, hardness, and weight. Coldness 
 belongs to ice wherever it is found, and therefore is a 
 "property" of ice, as whatever belongs to a man is his 
 property. Brittleness, hardness, and weight are also 
 properties of ice, and as these have all been perceived 
 through the senses, they are called "physical" properties. 
 
 The first step in the study of any substance is the 
 determination of its physical properties. 
 
 A set of mineral specimens has been prepared to 
 accompany this book, and in the case of each of them 
 you will do well to make a list of its physical proper- 
 ties as revealed by your senses, as we have with our 
 
io THE WORLD OF MATTER. 
 
 piece of ice. The names for such additional properties 
 as may be observed will be given and explained as we 
 go on. 
 
 If you have held your specimen of ice in your hand 
 while examining it, you must by this time have observed 
 a remarkable change in it. It has partly melted. Its 
 edges are no longer sharp but rounded; it feels wet, 
 and water is trickling from it. In a short time there 
 will be only a few spoonfuls of water instead of a piece 
 of ice. The specimen has changed from a solid to a 
 liquid condition. This change has been a silent one 
 and has been learned through the two senses, feeling 
 and sight. 
 
 Up to this point our study has been entirely by 
 observation. We have simply examined our specimen 
 and observed such of its physical properties as have 
 revealed themselves to our senses without any special 
 effort on our part. It is now time to go a step further 
 and make an experiment. This consists in placing our 
 specimen under new conditions and observing how it 
 behaves. If we had placed the ice in the hand with 
 the intention of learning whether any effect would be 
 produced thereby, and if we had then observed that it 
 melted, that would have been an experiment. Experi- 
 ments are made in order to discover something that we 
 cannot learn while our specimen remains under ordinary 
 conditions; and they are very frequently made in order 
 to discover the cause of some appearance or change 
 which we have noticed. Any such appearance or 
 change is called in scientific language a "phenomenon." 
 
A PIECE OF ICE. ii 
 
 Whatever is perceived by any or all the senses is a 
 phenomenon. Among the more common phenomena 
 are light and darkness, heat and cold, motion and rest. 
 
 The melting of ice is a phenomenon, and having 
 observed it, let us make a few simple experiments in 
 order that we may if possible discover its cause. The 
 fact that in this case we already know the cause, is no 
 hindrance to the experiments. They will only confirm 
 us in our present opinion if that is right. First then 
 lay a piece of ice, wrapped in flannel, in a very cold 
 refrigerator. This is the experiment. The obser- 
 vation is that it does not melt. Next place it near a 
 hot fire. It melts. Try it in hot and cold water. In 
 the warm rays of the sun. Hold it in your hand or 
 your mouth. If then, there is any one condition, and 
 only one, which is present in every instance when the 
 ice melts, and always absent when it does not melt, it 
 will be reasonable to infer that whatever produces that 
 condition is the cause of the phenomenon of melting. 
 Now, in each experiment the condition of melting is 
 that something warm be near the ice; either warm air, 
 or a warm hand, or warm iron, or warm water; and as 
 nothing is made warm without heat, we arrive at the 
 conclusion that heat causes ice to melt. This property 
 of ice, namely, that it melts when heated, is termed 
 "fusibility." Ice is fusible. 
 
 Our minds are so constituted by nature that we 
 invariably look for some cause for every observed 
 phenomenon, and it is a curious fact that even before 
 we learn with certainty the true cause, we can hardly 
 
12 THE WORLD OF MATTER. 
 
 refrain from risking a guess at it as soon as the phe- 
 nomenon is observed. It is nearly necessary to make 
 such a guess before we can undertake an intelligent 
 experiment, and experiments are usually made with the 
 purpose of determining the correctness or incorrectness 
 of a previous guess at the true cause. Such a guess, 
 especially when made the basis of experiments, is called 
 an "hypothesis," and hypotheses are of the highest value 
 in all scientific study. 
 
 An hypothesis is the first answer the mind suggests 
 to the question "Why?" 
 
 It must not be confounded with a theory, which is a 
 full and orderly explanation of a group of observed 
 facts and phenomena, and usually accounts for a large 
 number of facts apparently different and unconnected. 
 A theory often rests on an hypothesis; as the Darwinian 
 theory of the origin of species depends largely upon 
 the hypothesis that accidental variations may result in 
 forms sufficiently new and permanent to be reckoned as 
 distinct species. 
 
 Having learned that heat causes ice to melt, the 
 curious student will wish to know what causes the heat; 
 and having if possible discovered that, he will again 
 search for the cause of that cause, and so on in an ever 
 lengthening chain, until he either reaches some first 
 cause, or becomes weary or discouraged in its pursuit. 
 To this first cause religion makes a short path by assert- 
 ing the existence of an infinite and eternal being, God, 
 Toward it science moves more slowly, following back 
 the chain of effect and cause link by link, and verifying 
 
A PIECE OF IC. 13 
 
 each conclusion by patient and prolonged experiment. 
 Some scientists, like Louis Agassiz, ultimately arrive 
 at the same theological conclusion a creator, God; 
 others find a first cause in a universal and unintelligent 
 force constantly acting under natural law; others 
 declare that the first cause of all natural phenomena is 
 so remote as to be wholly beyond the reach of human 
 knowledge or imagination; and others are contented to 
 work as faithfully as may be along the nearer and 
 clearer links in the great chain, without speculating 
 upon that part of it which is out 'of sight. For the present 
 we shall remain among this latter class. 
 
 The question of the nature and cause of heat will be- 
 reserved for another chapter. 
 
 Up to this point our observations and experiments 
 nave been of the simplest possible character, and have 
 consisted merely in observing those marked physical 
 properties of ice which at once present themselves to 
 the most careless mind. Let us now make a somewhat 
 more careful examination. Taking another specimen 
 as nearly like the one we have melted as possible, we 
 not only perceive that it is hard, but will now raise the 
 additional question, "how hard?" 
 
 In order to test the degree of hardness which any 
 mineral possesses, it becomes necessary to have a meas- 
 ure or scale of hardness. That is, as in the case of all 
 measuring, we must have a known and familiar stand- 
 ard with which to compare each new specimen. The 
 scale adopted by mineralogists consists of a series of ten 
 specimens, beginning with one of the softest, talc, 
 
<4 *THE WORLD OF MATTER. 
 
 whose hardness is called I, and ending with the hardest 
 known mineral diamond. The scale is as follows: 
 
 SCALE OF HARDNESS. 
 
 }. Ta'.o. 6, Orthoclase. 
 
 2. Gypsum. 7. Quartz. 
 
 3. Calcite. 8. Topaz or beryl. 
 
 4. Fluorite. 9. Corundum. 
 
 5. Apatite. 10. Diamond. 
 
 Specimens of the first seven of these are included in 
 the collection which accompanies this book. They are 
 easily obtained, and as minerals harder than quartz are 
 very few and very rare, they are all that you really 
 need. We test the relative hardness of two minerals by 
 finding out which will scratch the other. If any 
 mineral, for example, will make a distinct scratch upon 
 a piece of talc, it is harder than talc; unless, indeed, it 
 can itself be scratched as distinctly by a piece of talc, in 
 which case they may be considered to have the same 
 degree of hardness. The reason that minerals of the 
 same degree of hardness can scratch each other is 
 that a sharp corner has a slight advantage over a 
 smooth surface. You can often scratch a pane of glass 
 with a fragment broken from one corner of it. ' 
 
 There is a simpler method of testing the hardness of 
 minerals, and a method sufficiently accurate after a little 
 practice. The scale of hardness in this case consists of 
 your thumb-nail, a pocket knife, and a piece of ordinary 
 window-glass. Specimens that can be scratched with the 
 nail as easily as talc, have a hardness expressed by the 
 
A PIECE OF ICE. i$ 
 
 number i ; those that offer more resistance, but yet can 
 be scratched, like gypsum, have a hardness of 2 ; those 
 that can very easily be scratched with your knife-blade 
 have the 3d degree of hardness; those that require more 
 pressure under the blade, have hardness 4; those that 
 can be scratched with a knife with -difficulty, and are 
 not yet hard enough to make a scratch on glass, have 
 hardness 5; those that make a slight scratch on glass, 
 and are yet soft enough to be scratched by the knife- 
 blade with the greatest difficulty, have hardness 6; while 
 those that easily scratch glass and resist the edge of the 
 blade, have hardness 7 or more. 
 
 It must not be considered a proof of the softness of a 
 mineral that it crumbles under pressure. Sandstone 
 which you can crush between your fingers is often com- 
 posed of particles of quartz which will scratch glass. 
 Test the hardness of your specimen of ice. 
 
 QUESTIONS ON CHAPTER I. 
 
 1. What is ice? 
 
 2. Name four of its physical properties. 
 
 3. What is a specimen? 
 
 4. What change takes place in a piece of ice held in 
 the hand? 
 
 5. What is the cause of this? 
 
 6. What is the difference between observation and 
 experiment? 
 
 7. What is a phenomenon? 
 
 8. What is an hypothesis? 
 
 9. What is a theory? 
 
 10. Explain the "scale of hardness." 
 
16 THE WORLD OF MATTER. 
 
 CHAPTER II. 
 A PIECE OF ICE (CONTINUED*) 
 
 At our first examination of a piece of ice we observed 
 that it was heavy. Let us now determine how its 
 weight compares with the weight of other mineral 
 specimens of the same hulk. This is one of the most 
 important points in the study of any specimen. Here, 
 again, as in the case of hardness, we must have a 
 standard of comparison; that is, some substance with 
 whose weight we are familiar, with which we may 
 compare each new specimen we meet. From its 
 abundance and universal distribution, water is taken as 
 the standard. The weight of water varies, however^ 
 with its temperature, pressure and purity, and when 
 extreme accuracy is required, we use distilled water, 
 weighed at a fixed temperature commonly 60 degrees 
 Fahrenheit and under such atmospheric pressure as 
 raises the mercury in a barometer to the height of 30 
 inches: but for our present purpose we may neglect 
 the questions of temperature and pressure, and even 
 purity, and simply compare the weight or density of 
 our specimen with that of an equal bulk of whatever 
 water is most convenient to our hand. The relative 
 weight of any substance as compared to that of wate~ 
 
A PIECE OF ICE. 17 
 
 is called its specific weight or specific gravity. If I 
 say that the specific gravity of cast zinc is 7, I mean 
 that a piece of the zina is seven times as heavy as an 
 equal bulk of water. 
 
 Students commonly find something difficult or confus- 
 ing about this term "specific gravity," because the words 
 are unusual. If you do not perfectly understand it, 
 take one or two more illustrations. If a cubic inch of 
 clay is twice as heavy as a cubic inch of water, its 
 specific gravity is 2. The specific gravity of melting 
 ice is .93, and this means that a cubic inch or a cubic 
 foot of ice weighs -f^ 3 5 as much as a cubic inch or foot 
 of water. 
 
 The word "specific" means ''belonging to a particular 
 kind ;" so that if we translate the expression "the specific 
 gravity of a mineral" into common words, it reads 
 "the weight of a particular kind of mineral;" but we 
 must remember that this does not mean its absolute 
 weight as determined by the scales, but its relative 
 weight as compared to an equal bulk of water. 
 
 The question now arises how the specific gravity of 
 any specimen can be determined. If our specimen hap- 
 pened to be of such a shape and size as exactly to fit 
 into any convenient vessel, as a cup, it would be a very 
 simple matter. We should then fill the cup with water, 
 weigh it, and subtract the weight of the empty cup. 
 This would give the weight of the water. Then we 
 should weigh our specimen; and if we found, for 
 example, that the water weighed 8 ounces, and the 
 specimen 30, we should know that the specimen was 
 
i8 THE WORLD OF MATTER. 
 
 3^ times as heavy as an equal bulk of water, or that its 
 specific gravity was 3.75. 
 
 What shall we do when, as is nearly always the case, 
 our specimen is irregular in shape? 
 
 We might make a mould in plaster-of-paris, which 
 would hold the same bulk of water as the specimen, 
 and then weigh and compare as before; but this would 
 be tedious, and inexact, particularly if our specimen 
 happened to be porous or hollow. 
 
 We might fill a vessel with water quite up to the 
 level of a waste-pipe, as in Fig. i. 
 
 If, then, we lowered the specimen into the water it 
 would displace an equal bulk of water which, flowing 
 out at A, could be caught and weighed. 
 
 This also would be a slow and awkward process, and 
 liable to error. 
 
 Just at this point we are greatly helped by a fact 
 
A PIECE OF ICE. 19 
 
 which was discovered about 1600 years ago by a 
 famous philosopher of Sicily, named Archimedes. The 
 interesting and amusing story of his discovery you will 
 find in any cyclopedia, but the fact is this, that when 
 anything is plunged into water it seems to lose just as 
 much weight as the weight of the water it displaces. 
 Now, of course, any specimen plunged into water dis- 
 places an amount of water equal to its own bulk. 
 Therefore if we ascertain how much loss of weight a 
 specimen sustains in water, we know exactly how much 
 an equal bulk of water weighs. For example, lower a 
 piece of zinc weighing in the air seven pounds into 
 water and weigh it again. It now weighs only six 
 pounds. This means that it has displaced exactly one 
 pound of water; or that water equal in bulk to 7 pounds 
 of zinc, weighs one pound ; or that zinc is seven times as 
 heavy as water ; or that the specific gravity of 
 zinc is 7. 
 
 To find the specific gravity of any mineral, therefore, 
 divide its weight in air by its loss of weight in water. 
 Strictly speaking, we should use the weight of 
 the specimen in a vacuum instead of in air, but 
 that is not necessary for practical purposes. Con- 
 venient balances for this air and water weighing are 
 furnished by all dealers in chemical apparatus, and need 
 not be described here, particularly as you will not need 
 to use them until you have advanced further in your 
 work. For the present, after a little practice, and a 
 careful handling of equal-sized pieces of the following 
 substances, which constitute a sort of specific gravity 
 
20 THE WORLD OF MATTER. 
 
 scale of approximate exactness, you can estimate the 
 specific gravity of a mineral pretty closely by lifting it 
 in the hand. 
 
 SPECIFIC GRAVITY SCALE. 
 
 Seasoned live oak, or ice, i. 
 
 Gypsum, or sulphur, 2. (Common feldspar, 2.5.) 
 
 Cryolite, or apatite, 3. 
 
 Corundum, 4. 
 
 Magnetite, or pyrite, 5. 
 
 Cuprite, 6. 
 
 Cast zinc, 7* 
 
 Bell metal, 8. 
 
 Cinnabar, when pure, 9. (Copper nearly 9.) 
 
 Silver, 10.5. 
 
 Gold, or platinum, 20. 
 
 We have already observed that ice shines in the light. 
 This property is termed lustre, and the various kinds of 
 lustre are named from substances in which these varieties 
 are most commonly observed; namely, glass, pearl, 
 metal, resin or wax, diamond, and silk. Lustres resem- 
 bling these are called vitreous or glassy, pearly, metallic, 
 resinous or waxy, adamantine, and silky. The two 
 most important are vitreous and metallic. Indeed a 
 chief division of all minerals is into two classes; 
 
 i. Those that have a metallic lustre. 2. Those that 
 have not. If a mineral has no lustre at all it is called 
 dull. 
 
 We observed that our specimen of ice was clear, that 
 we could see to read through it. This property is called 
 
A PIECE OF ICE. 21 
 
 "transparency." Air, water and glass are transparent. 
 Minerals through which one can perceive light, like 
 ground glass or smoked glass, but through which one 
 cannot distinguish objects clearly, are said to be trans- 
 lucent; those through which no light at all can be seen, 
 like the metals, are called opaque. 
 
 We observed that our specimen was nearly colorless, 
 yet we recollected that we had seen ice that, instead of 
 being clear, was white and green. This leads us to 
 notice the distinction between the real, or essential color 
 of a mineral, and its apparent color. The apparent 
 color of minerals is one of their least important proper- 
 ties, because it arises from so many different causes 
 that it is very variable. This variability is more marked 
 in transparent than in opaque substances, and often 
 arises from some impurity. Thus quartz may be white, 
 yellow, red, green, blue, brown, or black, the color in 
 each instance being due to the presence of some other 
 mineral diffused throughout the quartz. A very minute 
 quantity of coloring-matter is sufficient to change the 
 hue of a large mass, just as a few grains of indigo make 
 a large tank of water blue. 
 
 The color of the powder of any mineral is much less 
 likely to be affected by the presence of these impurities, 
 and we therefore regard that as of far more importance 
 than the apparent color in identifying it. This powder 
 may be obtained by crushing a small fragment, by 
 scratching the specimen, or by making a mark with the 
 specimen upon a surface harder than itself. An 
 ordinary slate-pencil is apparently of a dull lead color- 
 
22 THE WORLD OF MATTER. 
 
 but crush a fragment to powder, or scrape it with a 
 knife, or observe the color of the mark it leaves upon 
 the slate, and you will learn that its essential color is 
 light gray, approaching white. 
 
 The simplest way to observe this essential color, in 
 the case of most minerals, as in the case of the slate 
 pencil, is by observing the color of the mark or "streak" 
 it makes upon a harder surface. For this reason the 
 plate of hard glass generally used to test this color, is 
 called a "streak-plate," and the color itself is called the 
 "streak." Now whether the apparent color of ice be 
 green or blue or white, the color of its powder or 
 "streak'' is always white. This is the case also with 
 nearly all transparent and translucent minerals, what- 
 ever their apparent color may be. The real color of 
 ice appears most conspicuously in that form of it known 
 as snow. 
 
 We have already observed that ice is easily fusible, 
 and we have learned by trial that the cause of its melt- 
 ing is heat. Let us now try a further experiment with 
 a view to determining the degree of heat necessary. To 
 test this approximately we have only to place the bulb 
 of a thermometer in a mixture of melting snow or ice, 
 and we shall find that it registers 32 degrees Fahrenheit. 
 We reach the same result by placing the thermometer 
 in water which is gradually cooling, and reading it at the 
 moment when freezing begins, for the freezing-point and 
 the melting-point are so near together as to be practi- 
 cally the same. It is earnestly hoped that the student 
 will not be satisfied with reading about these experi- 
 
A PIECE OF ICE. 
 
 ments, but that he will actually make them, no matter 
 how trivial they may appear. Otherwise most of the 
 advantage of this book will be lost. Little facts are 
 constantly revealing themselves to the eye of the experi- 
 menter of which no mention is made in the most 
 elaborate book. Books give general statements. They 
 record the results of experiments made by the most 
 skillful men, with the most delicate apparatus, and 
 under the most accurately defined conditions. 
 
 Do not, therefore, accept with- 
 out experiment our statement that 
 ice melts or water freezes at a 
 temperature of 32 degrees. Try 
 it with your own thermometer. 
 The chances are that no ice 
 will appear on your cup of water 
 until the mercury has dropped to 
 30 degrees, perhaps even to 28 
 degrees Fahrenheit. Should this 
 be the case it would result either 
 from the presence of some im- 
 purity, as salt, in the water, in- 
 crease of pressure or on account 
 of its perfect stillness. In the 
 latter case a slight agitation of the water will cause part 
 of it to shoot suddenly into crystals of ice, while the 
 temperature of the remainder will rise to 32 degrees. 
 
 A convenient apparatus for testing the freezing-point 
 of water is shown in Figure 2. 
 
 Snow sr pounded ice is placed in this vessel, from 
 
 Fig. 2. 
 
24 THE WORLD OF MATTER. 
 
 which water escapes below. The bulb and part of the 
 tube of a thermometer are immersed in this for about a 
 quarter of an hour, and then the mercury should stand 
 at 32 j for although the freezing-point of pure water 
 can be retarded, as has been shown, its melting point is 
 always the same, or at least much less variable, as it 
 requires great increase of pressure to lower it per- 
 ceptibly. In this connection we mint notice two very 
 important phenomena which attend the cooling and 
 freezing of water, namely contraction and crystalliza- 
 tion. 
 
 EXPERIMENT. Provide a glass vessel having a 
 slender tube rising from a large bulb, as in Figure 3. 
 Insert a thermometer in this vessel. The 
 scale can be read through the glass. 
 
 Fill the bulb, and half the tube with water 
 and gradually heat it. If the water rises in 
 the tube it will show that it is expanding. 
 The larger the bulb in proportion to the 
 stem the more perceptible, and apparently 
 rapid, will be the effect. Now surround the 
 bulb with a mixture of pounded ice and salt 
 Fig. 3 . and note the effect of cooling the water. 
 By all means make this experiment yourself, as it forci- 
 bly illustrates the danger of hastily coining to conclu- 
 tions that may be erroneous. Thus if you perform this 
 experiment carelessly, you will almost certainly decide 
 that water always expands when heated and contracts 
 when chilled. It does, so far as you have observed, 
 and you see no reason why it should ever act otherwise. 
 
A PIECE OF ICE. 25 
 
 But as the water in cooling approaches the freezing- 
 point you must watch it more attentively. The unex- 
 pected often occurs in nature. We' constantly run upon 
 real or apparent exceptions to what we have imagined 
 to be an invariable rule. The water in the tube keeps 
 on contracting just as you would expect, until it becomes 
 cooled to a temperature of about 39 Fahrenheit, but 
 at that point the contraction suddenly ceases, and ex- 
 pansion begins. The column of cooling water in the 
 tube stops falling and begins to rise again. This degree 
 of temperature, therefore, 39, is the point of the great- 
 est relative Weight of water; or, to speak scientifically, 
 water at 39 has its maximum density. If you find any 
 difficulty in observing this phenomenon in the simple 
 tube just now described, you can repeat an experi- 
 ment first made by Thomas Charles Hope, a professor 
 of chemistry in the universities of Edinburgh and Glas- 
 gow many years ago. 
 
 "Insert two thermometers (Fig. 4,) at different levels 
 into a cylinder of water, and chill the water by apply- 
 ing ice around the middle of the vessel. As the water 
 becomes cooled it grows denser, and therefore sinks to 
 the bottom, so that the lower thermometer falls until 
 it reaches 39 Fahr. Further cooling then expands 
 the water, instead of condensing it, and cqnsequently 
 the cold water rises, so that now the upper thermometer, 
 which has meanwhile been almost stationary, begins to 
 fall, and continues falling,, until, like the lower one, it 
 reaches 39 Fahr. The whole body of water is then- 
 at its maximurri density, and any further reduction of 
 
26 
 
 THE WORLD OF MATTER. 
 
 temperature causes expansion, the cold water becoming 
 specifically lighter and rising to the surface. Gradually 
 the upper thermometer sinks to the freezing point, 
 and then a layer of ice begins to form upon the sur- 
 face. This experiment roughly imitates what occurs 
 in a natural piece of water, such as a lake ; the surface 
 freezes, while the bottom water remains several de- 
 grees warmer." 
 
 Fig. 4 
 
 This experiment, while not quite so simple as the 
 one first described, has the advantage that it makes 
 clearer the reason of the very important fact that 
 water naturally freezes over -first at the top. Were it 
 not for this strange property of water, by virtue of 
 which it stops contracting and growing heavier just be- 
 
A PIECE OF ICE. 27 
 
 fore it reaches the freezing point, northern lakes and 
 rivers would freeze in winter into solid masses of ice, 
 which would destroy all aquatic life. Moreover, the 
 heat of summer would scarcely suffice to melt them, 
 and the climate might in time be changed into a per- 
 petual winter such as now lingers about the poles. 
 
 The increase in the bulk of water, which begins at 
 39 Fahr., continues until the moment of freezing, when 
 a sudden and much greater expansion occurs with al- 
 most irresistible force. 
 
 Fill the strongest vessel you can get, even a cannon 
 or hollow bombshell, with water; plug it tight, and let 
 the water freeze: you will have ample evidence of this 
 force. 
 
 Do not now jump to the conclusion that all liquids 
 behave in the same way as water under like conditions, 
 and do not consult books in order to find out, but if you 
 care to know, test them carefully yourself, one by one. 
 
 One experiment devised and performed by yourself 
 may be of more educational value than a year's study of 
 text-books. 
 
 The ice which forms upon water appears at first sight 
 to be a solid mass without definite structure. It is really, 
 however, built up of innumerable crystals, each of a 
 definite shape, which are so interlocked and compacted 
 together that their separate forms are obscured. Pro- 
 fessor Tyndall succeeded some -years ago in revealing 
 this hidden architecture, by sending a beam of sunlight 
 through a block of ice. Enough heat penetrates the ice 
 from such a ^unbeam to cause a slow melting inside the 
 
28 THE WORLD OF MATTER. 
 
 block. This first manifests itself by the appearance of 
 little glistening points, and then rays of light shoot out 
 from these bright centres until the ice seems full of 
 shining snowflakes. These beautiful forms have been 
 called "ice-flowers." They are not really ice-crystals, 
 however, but only the moulds left by the melted 
 crystals, and now nearly filled with water, which re- 
 flects the light and discloses the secret of the structure 
 of the ice. The glistening point in the centre of each 
 liquid star is a vacuum or empty space left by the water 
 which shrinks as it melts; and the surface of water as it 
 curves about this vacuum shines in the sun like silver. 
 
 The beauty and symmetry of ice-crystals, which the 
 solid ice kept for ages locked up in its frozen breast un- 
 til Professor Tyndall opened it with his key of light, is 
 nevertheless plainly shown to us in every shower of 
 snow; when, if the air is still, each flake that falls is a 
 perfect and exquisite crystal. You will be well repaid 
 for your pains if you catch a number of these snow- 
 crystals next winter upon a cold pane of glass, or a black 
 cloth, and study them with a microscope. The variety 
 of forms which they assume is infinite, and their beauty 
 indescribable; yet it will be found that they are all 
 fashioned on a definite plan, and have their delicate 
 rays always arranged in threes or sixes. These six- 
 angled or hexagonal flakes, however, are not regarded 
 as single ice-crystals, but rather as many little crystals 
 symmetrically united. I have never been able to see 
 satisfactorily and clearly one of the tiny crystals of which 
 these snow-stars are saicl to be composed, but the "books" 
 
A PIECE OF ICE. 
 
 Fig. 6. 
 
 say that their form is that shown in Fig. 6; that is to 
 say, a solid bounded by six equal Iczenge- 
 shaped surfaces. These diamond -shaped sur - 
 faces are called "rhombs," by the geometri- 
 cians, and asolid of the form shown in Fig. 6 is 
 called a "rhombohedron." Just how these 
 tiny rhombohedrons are joined together or 
 modified to produce the six-angled or "hex- 
 agonal" forms seen in snow-flakes and "ice- 
 flowers" can not be clearly understood until you get 
 glass or wooden models and experiment with them. 
 If you have a model of a rhombohedron, you will see 
 that you can hold it so that an end view presents a six- 
 sided outline; just such a form, in fact, as appears in the 
 centre of a snow-flake. Now as these snow-flakes are 
 usually transparent, always very thin and delicate, and 
 as it is difficult to examine them with a glass of high 
 magnifying power,, it is not impossible that, instead of 
 being flat, hexagonal prisms, as they are commonly 
 supposed to be, they are really rhombohedrons, whose 
 upper edges escape our observation ; and it may afford you 
 some interest to examine them for 
 yourself next winter. 
 
 In one of the snow-crystals drawn 
 at Greenwich, England, by Mr. 
 Glaisher, and printed in Tyndall's 
 " Forms of Water," the rhombo- 
 hedral form of ice is clearly shown 
 in the six crystals which surround 
 hexagonal centre, Fig. 7, and if we may suppose 
 
36 THE WORLD OF MATTED. 
 
 Mr. Glaisher to have overlooked the delicate angles 
 of the central portion of this snow- 
 flake, which would only be revealed 
 by the closest observation, we may 
 supply them, as in Fig. 8; and then 
 we have a compound crystal, sym- 
 metrically composed of regular 
 rhombohedrons, instead of a com- 
 bination of rhombohedrons with a 
 central hexagonal prism. F 'g 8 - 
 
 When a very thin film of water freezes on a smooth 
 surface, as the moisture on a window-pane, its crystals 
 do 'not usually present to the eye either the hexagonal 
 or rhombohedral form assumed by vapor that freezes in 
 the air and falls as snow. They curve in marvellous 
 imitations of trees and flowers; they build themselves 
 into fairy castles with crystal towers and battlements; 
 they shoot into twinkling spears and glistening needles; 
 they curl into waving plumes of exquisite grace and 
 beauty. It is fascinating to make photographs of this 
 frost-work. It is not impossible that by a comparison 
 and study of a large number of such photographs we 
 might learn the secret of the curves and angles that 
 seem so capricious in their loveliness. Do the shooting 
 crystals follow the curve of some eddying current of 
 air? Do they run along some slight irregularity in the 
 structure of the glass? Are they modified by the near- 
 nes of nails or other forms of metal? Are they con- 
 trolled at all by musical tones? Can they be affected by 
 a gentle current of electricity? Here is an enticing field 
 for observation and experiment. 
 
A PIECE OF ICE. 31 
 
 A kind of ice-crystal less commonly noted occurs in 
 moist ground, in the shape of long sharp blades and 
 needles projecting an inch or more from the surface of the 
 ground, and standing like elfin troops on drill, all armed 
 with gleaming bayonets. Along the margins of brooks 
 in winter are found still more wonderful forms of crystal 
 architecture. Drooping ferns and curling leaves and 
 waving blades of grass are reproduced along the edge 
 of the shivering water, giving one the impression that 
 the plants that fringed the stream in summer are reap- 
 pearing in shadowy shapes of ice. 
 
 One December evening there came a chilling fog. 
 Later the mercury fell rapidly, and a rush of cold fol- 
 lowed, as if a window had been opened into the Arctic 
 zone. In the morning the fog was gone, the sun shone 
 bright, and the sky was blue; but every strip of exposed 
 metal, and every edge of unpainted wood, was bordered 
 by a fringe of soft white feathers ranged as closely 
 together as the down on the breast of an eider-duck. 
 On our front porch is a wire netting for summer 
 vines to run on, consisting of hexagonal meshes two 
 inches in diameter. Never clematis or ivy decked this 
 slender trellis so gracefully as the vine of water-crystals 
 on tnat icy morning. The sudden and unwonted beauty 
 brought exclamations of delight to the lips of all who 
 saw it; but before a camera could be found to preserve 
 the picture, the sun silently undid the fastenings of the 
 tiny plumes, and they dropped to the earth in showers 
 of silvery sheen. 
 
32 THE WORLD OP MATTER. 
 
 QUESTIONS ON CHAPTEIl 1. 
 
 1. What is the specific gravity of a mineral? 
 
 2. How is it determined ? 
 
 3- A piece of lead, whose specific gravity is n.4 
 weighs in the air, 456 grains; -what is the 
 weight of an equal bulk of water? 
 
 4. How much does this same piece of lead weigh in 
 
 water? 
 
 5. A piece of glass Weighs in air 24 ounces; in 
 
 water 16 ounces: what is its specific gravity?. 
 
 6. What is "vitreous lustre?'* 
 
 7. What is the ' streak" of a mineral? 
 
 8. What is the melting-point of ice? 
 
 9. Describe the expansion and contraction of water. 
 
 10. At what temperature does water reach its maxi- 
 
 mum density? 
 
 1 1. Describe an experiment to prove this. 
 
 12. Explain the structure of ice. 
 
A GLASS OF MELTED ICE. 
 
 CHAPTER III. 
 
 A GLASS OF MELTED ICE. 
 
 Is water melted ice or is ice frozen water? In one 
 sense both statements are true, but the latter is the 
 popular form, while the former is the more accurate 
 and scientific. It is more accurate because ice is the 
 natural or normal form of this mineral when left to 
 itself, and it is only by the application of heat that it is 
 forced into the form of water and kept in that form; it 
 is more scientific also because it agrees better with our 
 way of thinking of other mineral substances, the great 
 majority of which are most familiar to us in their "ice," 
 or frozen, or solid state. Thus when we speak of iron, 
 lead, copper, or sulphur, we naturally think of the 
 solid metal or stone, and when these substances are 
 melted we do not give them new names as in the case 
 of ice and water but speak of them as melted iron, 
 melted sulphur, etc. At all events there is a gain for 
 our present purpose in thinking and speaking of the 
 mineral which we are studying as ice, and in regarding 
 what is usually called a glass of water as a glass of 
 melted ice. There may be people living in the frigid 
 zone to whom this matter of thinking has always 
 appeared the natural, perhaps the only one. 
 
 We are now ready for a simple experiment with a 
 glass of melted ice. 
 
 3 
 
34 THE WORLD OF MATTER. 
 
 Hold a lump of sugar so that one corner of it dips 
 into the melted ice, and first observe the sugar. It 
 will be seen that, beginning at the bottom it rapidly 
 changes from white to transparent gray, and that it is 
 growing wet and beginning to soften and dissolve. It 
 seems to absorb the water like a sponge, and in a short 
 time is evidently soaked through. This rise of the 
 liquid into and through the sugar is explained in the 
 same way as the rise of oil in a lamp-wick, or through 
 any very small tube; that- is to say, as due to the draw- 
 ing power of the sides of the minute openings through 
 which the liquid rises, added to the drawing power or 
 attraction of the particles of liquid for one another. 
 The attraction between the solid and liquid is called 
 adhesion^ because the liquid adheres to the solid ; the 
 attraction between the particles of the liquid is called 
 cohesion, because the particles cohere to one another. 
 The walls of the tubes or pores which contain the 
 liquid attract those liquid particles which are nearest 
 them and thus cause a thin film of the liquid to spread 
 out and upward on their surfaces. As this film of the 
 liquid is forced upward it draws with it the whole 
 column of liquid, and this continues up to the point 
 when the weight of the rising column equals the 
 attractive force. From this it will be seen that 
 this attraction is not a new force, but simply the united 
 action of the ordinary forces of adhesion and cohesion; 
 and it is also evident that the elevation of the liquid 
 will be greatest in the smallest tubes, since the weight 
 of the column to be raised is there least in proportion 
 
A GLASS OF MELTED ICE. ~ 34 
 
 to the amount of liquid which comes in contact with 
 the walls of the tube. This explanation was first given 
 by Leslie in 1802. The Latin word for hair is capillus, 
 and since the phenomenon I have been describing is 
 best observed in very small, hair-like or "capillary" 
 tubes, this form of force is called "capillary attrac- 
 tion." 
 
 Let us now repeat the experiment this time, how- 
 ever, turning our attention to the melted ice under the 
 sugar. As soon as the sugar touches the liquid fine 
 wavy and syrup-like streams are seen to flow from it 
 down into the glass, where they presently grow thinner 
 and disappear. This continues until the last particle of 
 sugar crumbles in the hand and loses itself in the liquid 
 below. The sugar is now said to be dissolved. Sub- 
 stances which can be dissolved are called "soluble," and 
 the liquid which has the power of dissolving them is 
 called a "solvent." 
 
 Find by experiment as many different substances as 
 you can that dissolve in water, and ascertain whether 
 heating the water renders their solution more or less 
 easy and rapid. In connection with these experiments 
 test the temperature of the water before and after the 
 addition of the substance to be dissolved. 
 
 Make a strong solution of alum and allow the water 
 to evaporate slowly. It wilj be observed that a portion 
 of the alum is deposited from the solution in the form 
 of crystals; and the important fact is learned that 
 crystallization occurs not only on the solidification of 
 minerals by freezing as in the case of ice but that it 
 
36 THE WORLD OF MATTER. 
 
 also usually accompanies the solidification of a dis- 
 solved mineral on the evaporation of its solvent. 
 
 Professor Tyler suggests the following interesting 
 experiments. Make a strong solution of blue vitriol, 
 Which is a compound of sulphuric acid and copper. 
 Put this in a warm place and suspend a pebble or cinder 
 in it. Notice the form and color of the crystals which 
 form upon the pebble. Now mix equal parts of alum 
 and blue vitriol, make a strong solution of the mixture 
 and allow the water to evaporate. The resulting 
 crystals are most interesting. There is a mixture of 
 the two solids, but the crystals of the alum are distinct 
 from those of the vitriol, and with care you can almost 
 completely separate the blue crystals from the white. 
 Thus the minute particles which have been held in 
 solution not only combine in crystal form, but particles 
 of the same substance unite in crystallization with one 
 another, and not with those of another substance even 
 when mingled in the same solution. 
 
 It appears also from this experiment, that solids in 
 solution do not necessarily unite with particles of their 
 solvent so as to form a new and distinct substance, but 
 that they may be merely mixed with those particles, 
 though in so finely divided a state as to be indistinguish- 
 able to the eye. 
 
 Water has been called -the "universal solvent," not 
 only because of its universal distribution, but because 
 it dissolves a larger number of substances, both solid 
 liquid, and gaseous, than any other mineral. 
 
 This solvent power of water is one of its most val- 
 
A GLASS OF MELTED ICE. 37 
 
 uable properties. On it depend many of the phenom- 
 ena of nature, and many of the processes of art and 
 manufacture. The substances that dissolve in water 
 are so numerous, and so universally distributed, that 
 it is doubtful whether a single gallon of chemically 
 pure water could be collected in the whole world from 
 natural sources. Of these soluble substances salt is 
 one of the most abundant, and countless rivers are con- 
 stantly carrying one or both of its elements to the sea. 
 
 Professor Tyler says, that although the proportion 
 of dissolved matter in the ocean is not large, yet it is 
 always growing greater, and it has been estimated that 
 there is now enough in the whole ocean, if it could be 
 separated, to form a mountain range larger than the 
 Alps. 
 
 The water that issues from springs and wells is usually 
 "hard;" that is, impregnated with lime or some other 
 mineral in solution, which decomposes soap, and thus 
 renders the water unfit for washing. Even rain-water, 
 which is the purest form in nature, is tainted with im- 
 purities, caught and dissolved by the water as it falls 
 through the air. 
 
 To this property of water we owe all our mineral 
 springs; to it we must refer our deposits of iron ore. 
 It is the cause of the formation of great caves in the 
 earth with their wonderful and exquisite stalactites 
 and stalagmites ; it is even largely responsible for the 
 valleys between the mountains, and for much of the 
 scenery of the world, which it reduces to forms, smiling 
 and peaceful, or frowning, abrupt, and grand. With 
 
38 THE WORLD OF MATTER. 
 
 out it the vegetable world could not draw its support 
 from the earth, the blood could not circulate in the veins 
 of animals, and all life would perish from the earth. 
 Do not pass this subject hastily. Think about it. Make 
 a list of as many other advantages and disadvantages 
 that arise from the solvent power of water as you can. 
 
 Do not forget its cleansing power on the one hand, 
 nor on the other the dangers that arise from its power 
 of dissolving poisonous or putrefying substances. 
 
 In connection with this last suggestion, consider the 
 wisdom of removing as far as possible from your water- 
 supply every thing that is unclean or unwholesome. 
 Typhoid fever and many other dread diseases result 
 from drinking water which holds in solution or in sus- 
 pension the invisible but certain seeds of death. 
 
 Owing to the selective power of the crystallizing par- 
 ticles of any mineral, by virtue of which they unite 
 only with others of the same sort, as already shown in 
 the case of alum and blue vitriol, ice freely formed 
 upon a lake is more free from impurities than the 
 water under it. There is a truth in the popular saying, 
 that the "dirt freezes out." Yet it is a dangerous error 
 to suppose that all ice is pure, and safe for domestic 
 use. If dirty water freezes solid, all the impurities con- 
 tained in the water will be retained in the ice. They 
 do not unite in crystallization with the particles of ice, 
 but they are caught, and held in the ice, just as a stick 
 would be if plunged in freezing water; and when the 
 ice is melted they are again set free, and the freezing 
 does not destroy their unwholesome and dangerous 
 
A GLASS OF MELTED ICE. 
 
 39 
 
 properties. Even when only the surface of foul water 
 freezes, these impurities are but partially expelled, so 
 that it is a safe rule'that dirty water makes dirty ice, 
 and deadly water makes deadly ice. 
 
 Let us now return to our glass of melted ice. You 
 remember that this was produced from a transparent 
 solid by the action of heat, and that it is kept in its 
 present liquid form by the continued action of the same 
 force. We will now make the experiment of apply- 
 ing a greater amount of 
 heat to the melted ice. 
 
 Pour the water into a 
 glass flask, or a tin cup, 
 put a thermometer in it, 
 and place it over a spirit- 
 lamp, or gas-jet, or set it on 
 a stove. Fig. 9. At first 
 no change is observed, ex- 
 cept that by close obser- 
 vation you may see that 
 the liquid is expanding; 
 but as the temperature 
 approaches 212 degrees 
 Fahrenheit, bubbles ap- 
 pear on the bottom and 
 sides of the vessel where 
 it is hottest. These first 
 bubbles are due to the separation of particles of air 
 which have been previously dissolved or absorbed by 
 the water. A little later, small bubbles begin to come 
 
40 THE WORLD OF MATTER. 
 
 from the heated portion of the water, and as they rise 
 through the cooler liquid above they disappear. The 
 formation and disappearance of these bubbles is accom- 
 panied by a peculiar "singing" sound. After this, larger 
 bubbles rise and burst on the surface, and little clouds 
 of vapor begin to appear, while the whole mass of water 
 is agitated. The thermometer now stands at 212 
 degrees Fahrenheit. This phenomenon is called boil- 
 ing, or, in scientific phrase, ebullition. 
 
 As this boiling continues, the water is observed to be 
 growing rapidly less in quantity, and after a short time 
 wholly disappears. The thermometer meanwhile has 
 remained stationary at 212 degrees. Now, nothing has 
 been seen to pass from your flask except the vaporous 
 clouds already mentioned, and it thus becomes evident 
 that unless some other way can be discovered to account 
 both for the disappearance of the water, and also for 
 the appearance of the vapor, we must conclude that the 
 water has been changed into the vapor, and has passed 
 out of the vessel in that form. 
 
 It is astonishing that so large a quantity of water can 
 so rapidly escape in so air}- and intangible a form; and 
 the vapor itself has so completely disappeared in the 
 air that we find it hard to believe that the water which 
 has been "boiled away" has not actually been destroyed. 
 If not, where is it? In order to settle this point, we 
 must devise some method of catching, and examining 
 the vapor, instead of allowing it to escape. 
 
 Hold a cold glass jar, mouth down, over the neck of 
 {he flask, ^s it rjecornes filled with vapor you will 
 
A GLASS OF MELTED ICE. 41 
 
 observe that its sides grow foggy, and presently drops 
 of water appear, and begin to trickle down inside. 
 
 Is it not plain that the vapor is only another form of 
 water, forced into this condition, and kept there by 
 heat? So much of this heat now leaves the vapor and 
 is expended in warming the cold sides of the jar, that 
 there is not enough left to hold the water in its vapor- 
 ous form, and it again becomes liquid, and re-appears 
 in the form of water. This return of vapor to the liquid 
 form on the withdrawal of heat is called condensation. 
 The process of boiling a liquid to transform it into 
 vapor, and then cooling the vapor and collecting again 
 the condensing liquid, is called distillation, and as the 
 liquid on vaporizing leaves most of its impurities be- 
 hind, this is the simplest and best method of obtaining 
 most liquids, and water among them, in the purest pos- 
 sible condition. 
 
 You may wonder why I have not called this water- 
 vapor steam. It is not steam in the strict sense. Steam 
 is invisible. If you look at the neck of your flask 
 while the water is briskly boiling in it, you will see 
 no appearance of vapor, and the flask above the water 
 appears quite empty; yet it is really filled with steam. 
 On leaving the mouth of the flask this steam becomes 
 partially condensed in the air, and then appears in 
 vaporous clouds. Indeed, I have here used the word 
 "vapor" in the popular rather than the scientific sense. 
 Strictly speaking, the invisible steam is the true vapor, 
 and the white cloud is composed of minute particles oi 
 water condensed from the vapor. 
 
42 THE WORLD OF MATTER. 
 
 Another phenomenon presented by water bears a close 
 resemblance to the production of steam by boiling, yet 
 with important differences. 
 
 From all exposed surfaces of water there is a constant 
 and usually unnoticed passage of a portion of the water 
 into the form of vapor. This is called evaporation. 
 It differs from boiling in two respects, first, it takes 
 place only at the surface, and slowly ; while boiling 
 produces steam throughout the mass of the liquid, and 
 rapidly; second, it occurs at no fixed temperature; 
 while boiling, as we have seen, occurs, under ordinary 
 pressure, only at 212 degrees Fahrenheit. Vapor is 
 formed directly, even from ice, without intermediate 
 melting. Ice "wastes away," even in cold weather; 
 and our laundry. women are right in saying that clothes 
 hung out in winter "freeze dry." It would take many 
 volumes to trace the results of boiling and evaporation. 
 Modern civilization depends largely upon steam, which 
 not only cooks much of our food, but furnishes most 
 of our power. It would seem as if the old Arabian 
 tales of Aladdin's lamp, and the Fisherman and the 
 Genie, were intended as parables to illustrate the 
 wonders of steam. Aladdin rubs his lamp, the emblem 
 of fire, and the strange fire-spirit appears, ready to do 
 his bidding. From the Fisherman's casket arises a 
 huge mass of vapor, which gradually assumes the form 
 of a puissant being capable of any act of helpful min- 
 istration or mad destruction. 
 
 To-day with our lamp we have evoked a spirit no 
 less powerful; capable like the Genie of expanding 
 
A GLASS OF MELTED ICE. 43 
 
 until the sky seems full, and of contracting to the limits 
 of an iron pot; when under due control, it drives our 
 locomotives across the continent, runs our looms and 
 spindles, heats our homes and lights our streets; if un- 
 controlled, it tears our engines to pieces, wrecks our 
 habitations, and destroys our lives. Like electricity, 
 magnetism, and the explosive force of powder, steam 
 is one of the invisible but mighty brotherhood of fire- 
 spirits, and repeats to-day to all who know how to keep 
 it in control, the formula used by the obsequious Genie 
 of old, "I, and the others, slaves of the lamp!" 
 
 From every rivulet and river, from every lake and 
 sea, from the whole expanse of ocean, vapor is con- 
 stantly rising, invisibly or in fantastic wreaths of mist; 
 and this collects in spreading clouds which fill the sky, 
 cover the world with cooling shade, and gently fall in 
 showers that refresh the thirsty earth, bringing life to 
 every herb and tree, to animals and man; or else, uniting 
 in hostile fury, they sweep over the earth in a cyclone ; 
 then "heavily they fall on the sea, and from its very 
 bottom crash down the whole expanse." 
 
 QUESTIONS ON CHAPTER 3. 
 
 1. What keeps water in its liquid form? 
 
 2. Give an illustration and an explanation of "capil- 
 lary attraction.'' 
 
 3. How is the temperature of water affected when 
 salt is dissolved in it? 
 
 4. Why is water called the "universal solvent?" 
 
44 THE WORLD OF MATTER. 
 
 5. What important results follow this solvent action 
 of water? 
 
 6. Does foul water "freeze clean?" 
 
 7. Describe the process of ebullition. 
 
 8. At what temperature does water boil? 
 
 9. Distinguish between steam and other vapor. 
 10. Describe and explain "condensation." 
 
WATER AN ELEMENT? 45 
 
 CHAPTER IV. 
 
 IS WATER AN ELEMENT? 
 
 From the experiments and observations outlined in 
 the preceding chapters, we have learned that water 
 exists in three different forms or "states," namely, as 
 a solid, a liquid, and a vapor, or gas. It has also been 
 learned that these forms follow one another in the 
 order given upon the addition of heat, and that upon 
 the gradual removal of the heat the steam again 
 condenses into water, and the water crystallizes into 
 ice. 
 
 Whether other minerals under like conditions pass 
 through these same three states must be left for your 
 future experiments to decide; though you know by 
 former experience that different substances, such as 
 lead, iron, sulphur, and wax may exist both in the 
 solid and liquid form ; and you know that others, as 
 alcohol, naptha, petroleum, and ether, are easily 
 changed from liquids to gases. 
 
 Consider that expression "different substances." Are 
 ice and water and steam three different substances? 
 We have seen that they are only three different forms 
 of the same substance; and a proof is that one can be 
 converted into the other at will. 
 
 Suppose, now, in the first of three cups you have a 
 quantity of leaden bullets, in the second a number of 
 
46 THE WORLD OF MATTER. 
 
 iron balls, arid in the third a mixture of iron balls and 
 leaden bullets: have you in the cups three substances or 
 two? If you stir a tablespoonful of powdered chalk 
 into a glass of water, you obtain a milky fluid unlike 
 either. Is it a new substance or only a mixture of the 
 two? Dissolve a teaspoonful of salt in a glass of 
 water. The salt disappears, and we seem to have only 
 one substance, namely, the water, left. Have we really 
 one or two? Is brine a new substance, or a mixture of 
 two? 
 
 Simple as these questions appear they neverthe- 
 less have an important bearing upon our study. In 
 the case of the leaden bullets and iron balls, we evi- 
 dently have no new substance, for we can easily sepa- 
 rate the two. In the case of the chalk and water the 
 decision is not so immediate, but if we allow the 
 mixture to stand, the particles of chalk settle at the 
 bottom, and the two substances separate themselves. 
 The brine may seem more puzzling, but if we evapor- 
 ate the water we can recover all the salt. The main 
 difference between the three cases is that the particles 
 of the substances mixed are united more closely in one 
 case than in another. In every instance the test is to 
 find whether we can separate the mixture into the sim- 
 ple substances, or "elements" of which it is composed. 
 
 Most of the things we see are compounds. A sub- 
 stance so simple that it cannot be separated into other 
 substarices,nor be shown to be made of other substances, 
 is called an element. Chemists recognize at present 
 between sixty and seventy elements; but the number i* 
 
IS WATER AN ELEMENT? 47 
 
 not settled by any means. It has often happened that 
 a substance which has for many years been considered 
 elementary has been found, after all, capable of sepa- 
 ration, or "analysis," into simpler substances; while 
 every little .while new substances are discovered which 
 have to be added to the list of elements until, and unless, 
 they can be proved to be compounds. 
 
 On the whole, as our power of analysis increases, the 
 tendency is to reduce rather than enlarge the number 
 of elements; and there are some who are even asking 
 whether, after all, those ancient philosophers may not 
 have been right, who held that all the forms of 
 matter were derivable from some one, though undeter- 
 mined, element. 
 
 From all this you will perceive that analysis, or the 
 separation of mineral compounds into their elements, is 
 one of the most important means of learning their true 
 character. In evident mixtures, like that of iron balls 
 and lead bullets, the analysis consists merely in the act 
 of picking out one kind, and leaving the other. In the 
 case of solids held in liquids but not dissolved, the analy- 
 sis often results by the process of settling; and in the 
 case of solutions by evaporation or distillation. Certain 
 compounds of iron can be ana'yzed by heat. A mix- 
 ture of iron-filings and sand can be analyzed by holding 
 a magnet near it; the iron is drawn to the magnet, and 
 the sand left behind. 
 
 Some substances are resolved into their elements by 
 a current of electricity. 
 
 A few hundred years ago water was believed to be an 
 
4 THE WORLD OF MATTER. 
 
 element. "Fire, water, earth, and air," were said to be 
 "the four elements," of which the whole earth is com- 
 posed. 
 
 Let us now make a few experiments with a view to 
 learning whether this ancient opinion of water is 
 correct. 
 
 So far as we can perceive by the most careful exam- 
 ination of pure water under ordinary conditions, it is a 
 simple substance. The eye detects no mixture, and 
 nothing is revealed either to taste or smell. 
 
 No matter how long we may allow it to stand, there 
 is no separation into simpler substances either by settling 
 or evaporation. If we boil it and condense its vapor, 
 we get again the same quantity of the same substance, 
 pure water, and nothing else. The approach of a 
 magnet produces no perceptible effect. 
 
 Let us try electricity. The following experiment is 
 more difficult than any I have before described, but 
 with a little care and patience you can perform it suc- 
 cessfully, and the result is so surprising, so beautiful, and 
 so instructive, that you cannot afford to neglect it. 
 
 Before attempting it, however, we must learn some 
 of the simpler facts about this wonderful form of force. 
 
 Cut out a piece of sheet zinc as large as a silver half- 
 dollar. Place this under your tongue, and place the 
 silver half-dollar on your tongue. Now bring the for- 
 ward edges of the zinc and silver together. 
 
 Do you feel anything? This peculiar tingling sen- 
 sation is produced by a current of electricity, which 
 passes through your tongue from the zinc to the silver, 
 
iS WATER AN ELEMENT? 49 
 
 and back again to the zinc, at the point where the two 
 metals touch each other in front, This course of the 
 //p.-.*-.-, electricity is called an electric cir- 
 
 (( i I cuit, and such a circulating cur- 
 
 rent is set in motion whenever 
 two different metals are placed in 
 any acid, and joined together out- 
 side the acid, either by being 
 brought into contact directly, or 
 by means of Connecting wires. 
 To illustrate this more clearly, 
 F 'g- I0 fill a glass or earthen jar with 
 
 dilute sulphuric acid, and immerse in the liquid at a little 
 distance from each other a plate of zinc and a plate of 
 copper. Attach a wire to the upper end of each plate, 
 fig. 10. 
 
 Now, taking a wire in each hand, touch one to the 
 upper and the other to the under surface of your 
 tongue. I# not the result similar to that produced by the 
 coin and the piece of zinc, though more intense? Bring 
 the ends of the wires together. What is the effect? 
 
 This apparatus is of ten called a "cell." Many other 
 substances besides zinc and copper produce similar cur- 
 rents. One of the most common and practical substi- 
 tutes for copper is carbon, a substance with which you 
 are familiar in the forms of charcoal and coke, and the 
 hard incrustations which accumulate in gas-retorts. This 
 is not the place, however, to enter into a description of 
 the numerous varieties of cells which have been devised. 
 They all work on the same principle, and can be 
 4 
 
50 THE WORLD OF MATTER. 
 
 bought at a low price. The combination of two or 
 more cells is called a "battery." For our present ex- 
 periment you will need a battery of four or five cells; 
 and, if you do not wish to make them, you can probably 
 get them at second hand from any telephone^exchange 
 at trifling cost. The free ends of the connecting wires, 
 through which the force of the electricity manifests 
 itself, are called electrodes, a Greek word, meaning 
 "electric pathways." 
 
 These ends are also called "poles," a word which 
 means in this connection the points of greatest intensity 
 or tension. 
 
 Fig. i 
 
 Having now provided your electric battery, fill a 
 glass vessel with water, to which, in order to assist the 
 passage of the electric current, some sulphuric acid 
 must be added, as pure water is an imperfect conductor. 
 Fasten apiece of platinum to the end of each wire; or 
 in other words, let the connecting wires end in platinum 
 electrodes. This is not essential, but like the sulphuric 
 acid greatly facilitates the action of the electricity. Put 
 the electrodes in the water, and invert over each a glass 
 
IS WATER AN ELEMENT? 51 
 
 tube filled with water, fig. n, in which O and H are 
 the tubes, C the wire coming from the copper or 
 carbon, Z the wire coming from the zinc, and E E, 
 the electrodes. 
 
 On the passage of a current of electricity, bubbles 
 are seen to rise from each electrode. The water gradu- 
 ally falls in the tubes, and that, too, without perceptibly 
 rising in the large vessel. It looks as if the current 
 were boiling the water and filling the tubes with steam. 
 But, look again. The effect in the two tubes is not the 
 same. In one the apparently empty space above the 
 water is twice as great as in the other; and yet (he water 
 in that tube does not seem to "boil" any faster than that 
 in the other. 
 
 At all events we are rapidly losing sight of our water. 
 Let us carefully examine the apparently empty tubes 
 to ascertain whether it can be hiding there. 
 
 We will first determine whether they are full of 
 steam. Placing the hand on them we find them cold; 
 this proves that steam is not present, and indeed a little 
 reflection would have convinced us of this, from the 
 fact that the tubes were neither burst nor forced out of 
 the water, nor clouded with condensing vapor. 
 
 Are they empty then? 
 
 Light a match or taper, and blow it out, leaving the 
 end aglow. Remove the tube O from the water, first 
 placing your finger over the opening of the tube, and 
 holding it closed until you have turned its mouth up- 
 ward, and thrust the glowing not blazing end of the 
 taper into it. The glowing taper suddenly bursts into 
 
5* tHE WORLD OF MATTER. 
 
 flame, and burns vividly. In fact this tube is filled with 
 a remarkable sort of gas, which we shall soon study 
 more in detail. For the present it is enough to know 
 that it has been separated from the water by electricity 
 at the electrode which is connected with the copper in 
 the battery ; that it causes other substances to burn very 
 brilliantly, and that its name is Oxygen. 
 
 Now remove the other tube, holding its mouth down- 
 ward, and apply a lighted match. This tube, too, is 
 evidently filled with gas, but of a different sort, for it 
 catches fire at the mouth of the tube, and burns with a 
 flame which is pale and bluish, but very hot. This gas 
 also we shall study later, contenting ourselves just now 
 with the knowledge that the electricity sets it free from 
 the water at the electrode which is attached, to the zinc, 
 that there appears to be twice as much of it as there 
 was of the oxygen, that it burns with a pale, hot flame, 
 and that its name is Hydrogen; a Greek word, which 
 means u a producer of water." 
 
 If the current of electricity were continued long 
 enough, all the water would be separated into these two 
 gases, which, moreover, always exist in the water in a 
 constant proportion, namely, one volume of oxygen to 
 two volumes of hydrogen.* In order to prove the 
 correctness of this analysis, we must ascertain whether 
 we can produce water again by recombining the two 
 gases. If they arc mixed in the proper proportions, 
 they form at first a merely mechanical mixture like 
 
 * Recent experiments by Professor Morley show that water contains 2.0002 
 parts of oxygen to i of hydrogen. 
 
IS WATER AN ELEMENT? S3 
 
 that of coal gas and common air; but the moment a 
 flame is applied, a much closer union is brought about 
 < in fact, a chemical combination occurs accompanied 
 by a violent explosion, arid in place of the two com- 
 mingling gases we have water. 
 
 This experiment must be made only with a small 
 quantity of the gases, such as can be contained in a 
 test-tube, for on a larger scale it is dangerous. 
 
 It is possible, however, to cause oxygen and hydro- 
 gen to combine quietly, by bringing them in tubes from 
 separate receptacles into a common burner. The 
 grandest experiment of this nature, according to Pro- 
 fessor Huxley, was made by three eminent French 
 chemists. It continued from the i$th to the 22d of 
 May, 1790. During this time the apparatus was con- 
 stantly watched, the experimenters sleeping alternately 
 on mattresses in the laboratory ; 25,96^. cubic inches of 
 hydrogen, and 12, 571- of oxygen were consumed, and 
 the union of these gases produced 7 2 44 g rams of 
 water. 
 
 It is a startling thought that all the water on the 
 globe has been formed at some time or other by the 
 union of oxygen and hydrogen, which in their free 
 state are known only in the physical condition of gases. 
 
 QUESTIONS ON CHAPTER IV. 
 
 1. In what three states does water exist? 
 
 2. Find by experiment two other substances that re- 
 semble water in this. 
 
 3. What is an element? 
 
54 THE WORLD OF MATTER. 
 
 4. What is analysis? Give an illustration. 
 
 5. Describe an electric cell ; a battery. 
 
 6. What are electrodes ? Poles? 
 
 7. What is added to water- before testing the effect 
 of electricity upon it ? Why ? 
 
 8. Describe the effect of an electric current on water. 
 
 9. What two gases are obtained from water ? 
 
 10. In what proportions are they combined to form 
 water? 
 
 11. How can they be distinguished? 
 
 12. How can they be combined? 
 
FIRE. 55 
 
 CHAPTER V. 
 
 FIRE. 
 
 t 
 
 In the previous chapter, we learned by our experi- 
 ments that it would be quite wrong to regard water 
 as an element, for by a current of electricity we ana' 
 lyzed it into two gases, oxygen and hydrogen. 
 
 We also learned that at a high temperature thes^ 
 two gases unite with a hot flame, and return again to 
 the form of water. 
 
 These are among the most beautiful and significant 
 phenomena in nature; and, with those we have before 
 studied, give us a key to the intelligent understanding 
 of the whole world. of matter. We have been led to 
 the discovery of two of the most important elements in 
 the world; we have learned the nature of an element; 
 and we can now understand that every material object 
 consists either of such an element alone, or in a state of 
 simple mixture with other elements, or in a more inti- 
 mate union with other elements in the form of a chemi- 
 cal compound. We have seen that mixtures can be 
 mechanically separated ; and that, in the case of water, 
 even the bands of chemical union can be loosed by the 
 force of electricity ; and we have learned, finally, that 
 elements can be caused to unite chemically, and that, in 
 the case of oxygen and hydrogen, this union is accom- 
 
56 THE WORLD OF MATTER. 
 
 panied by light and heat. Such a combination is 
 termed combustion, or burning. 
 
 Whenever you see fire, therefore, you may be cer- 
 tain that a rapid combination of at least two elementary 
 substances is taking place. From this you will perceive 
 that the old notion that fire is an element was also in- 
 correct. 
 
 Let us now continue our experiments with a view 
 to learning whether oxygen will combine with 
 other substances than hydrogen. Tip the end of 
 a bundle of fine iron wire with burning sulphur, and 
 plunge it into a jar of oxygen. Do not let the surpris- 
 ing brilliance of the result distract your thought from 
 the lesson. The most brilliant teachers are not always 
 the best. Turn your attention from the strange sight 
 of the blazing iron, to the dull results of the bright 
 combustion. Notice that when the fire ceases the 
 oxygen is gone and the iron is gone: they are "burned 
 up." Are they then destroyed? No more than the water 
 was destroyed which we "boiled away." The dark, 
 cindery-looking stuff in the jar is the hiding-place of 
 both; rather it is both, chemically combined. 
 
 That you may be convinced that this is true, you 
 should repeat the experiment more carefully, taking 
 such precautions as will assure you that none of the 
 oxygen escapes from the jar during the combustion, and 
 that nothing else gets in except the oxygen and the 
 iron, and the small bit of sulphur used to heat the iron. 
 You must also determine the exact weight of the 
 oxygen and of the iron consumed, and of the substance 
 
FIRE. 57 
 
 left after their combustion. If you do this accurately, 
 and if you find as other experimenters have found that 
 the weight of the iron burned added to the weight of 
 the oxygen used up is exactly equal to the weight of the 
 substance left after combustion, you can hardly doubt 
 that the latter is formed by the union of the oxygen 
 and the iron. Substances formed by combustion with 
 oxygen are called oxides ; and this compound of oxygen 
 and iron is called iron oxide. 
 
 The heat of combustion is the result of the chemical 
 combination, and the light is due to the heat. The heat 
 is caused by the friction of the little particles of the 
 combining substances as they are forcibly drawn to- 
 gether; just as an anvil is heated by hard blows from a 
 hammer. The more rapid the combustion the greater 
 the heat. Oxygen and iron are combining slowly at 
 ordinary temperatures whenever iron grows rusty; and 
 the iron-rust is an oxide of iron. 
 
 I said you should weigh your oxygen. Let me 
 show you how. Y*ou need a glass or globe holding 
 three or four quarts, the neck of which is closed by an 
 air-tight stop-cock, and adapted to be screwed to the plate 
 of an air-pump. The air is then pumped out, and the 
 weight of the empty globe ascertained by a delicate 
 balance. Oxygen is now allowed to enter, and the 
 globe again weighedy The difference in weight will 
 be the weight of that quantity of oxygen ; and knowing 
 this, you can calculate the weight of any other quantity 
 
 It may save you trouble, however, to know that & 
 pint of oxygen weighs iiy 5 ^- grains, and a cubic foo 
 
5 8 THE WORLD OF MATTER. 
 
 13^ ounces. (Faraday). Oxygen is nearly sixteen 
 times as heavy, bulk for bulk, as hydrogen, which is 
 the lightest element known; so that, although, as you 
 remember, we obtained twice as much hydrogen from 
 water, yet the oxygen was nearly eight times as heavy 
 as the hydrogen; in other words, if we reckon by 
 weight, instead of bulk, oxygen makes up f of water, 
 and hydrogen only J. 
 
 I am glad to come back in this way to water, for I 
 think this is just the right time for you to make another 
 experiment with it; one that you could not have un- 
 derstood so clearly before you saw the oxygen and 
 iron uniting by combustion, and forming the black 
 oxide of iron. 
 
 Fig. 12. 
 
 For the experiment you will need apparatus arranged 
 practically as shown in Fig. 12. A is a flask for boil- 
 ing water over an alcohol lamp; C a small furnace; 
 B B, a tube about an inch in diameter passing through 
 the furnace; D, a jar of water inverted in a vessel of 
 water, E. The tube BB may be a gun-barrel, a piece 
 
FIRE. 59 
 
 of gas-pipe, or preferably a porcelain tube, and is filled 
 with iron turnings or fine bright iron wire. The heat of 
 the lamp boils the water and converts it into steam. 
 .The steam passes through the red-hot tube, and bubbles 
 arising through the water are caught in the upper part 
 of the jar D. When all the water in this tube has been 
 expelled, you will know that its place has been taken 
 by some sort of gas. Is it steam? No, for it is cold. 
 Testing it with a match you find that it catches fire 
 and burns at the mouth of the tube with a pale blue 
 flame. You recognize hydrogen; and you perceive 
 that in passing through the furnace, the steam has 
 parted with its oxygen. Recollecting the experiment 
 of burning iron with oxygen, you now readily under- 
 stand that what you saw going on so brilliantly in the 
 jar has taken place unobserved in the red-hot tube; 
 namely, the oxygen of the water has combined with 
 the iron in the tube, and the hydrogen has passed on 
 alone into the jar D. 
 
 When the tube BB becomes cool, you will find in it 
 the same dark-colored substance that you found when 
 the oxygen and iron combined in the jar; namely, iron 
 oxide. 
 
 This experiment is commonly made to illustrate a 
 method of obtaining hydrogen, but we have used it to 
 impress more firmly upon our minds the manner in 
 which a chemical union takes place between oxygen 
 and heated iron; and to illustrate the new fact that the 
 tendency to this combination is so strong that it not only 
 occurs when heated iron is plunged into pure oxygen, 
 
6o 
 
 THE WORLD OF MATTER. 
 
 but that the oxygen in water will separate from the 
 hydrogen in order to unite with the iron. 
 
 It is an important fact that a stronger attraction ex- 
 ists between particles of heated iron and oxygen, than 
 between particles of oxygen and hydrogen. A like 
 principle controls the combination of all the other ele- 
 ments; they manifest apparent preferences in their 
 combinations, somewhat as young people do in their 
 choice of partners ; and by learning what these prefer- 
 ences are, and taking advantage of them we can effect 
 many innocent divorces, such as that we have just 
 caused between hydrogen and oxygen, and bring about 
 many not unhappy marriages like the one just effected 
 between oxygen and irpn. 
 
 13- 
 
 This special attraction existing between certain ele- 
 ments is called chemical affinity. 
 
 Substances which combine at certain temperatures 
 may often be separated again by increasing the heat. 
 Thus the iron oxide which we have obtained can be so 
 
FIRE. 61 
 
 intensely heated as to be resolved again into its 
 elements; but so great heat is required that the experi- 
 ment is difficult. A similar compound of mercury and 
 oxygen, however, known as oxide of mercury, can 
 be very readily separated by heat; and affords us 
 a practical method of obtaining oxygen for our experi- 
 ments. 
 
 For this purpose apparatus should be arranged as in 
 Fig. 13, which needs no explanation. 
 
 The most convenient and rapid method of preparing 
 oxygen, when a considerable quantity is required, is to 
 heat a mixture of equal parts of potassium chlorate and 
 black oxide of manganese. 
 
 Potassium chlorate contains three elements, oxygen, 
 chlorine, and potassium, two of which are as yet 
 strange to you. Oxide of manganese, as its name im- 
 plies, is a compound of oxygen with another unfamiliar 
 element, manganese. We do not care to study these 
 new elements at present; it is sufficient to know that 
 oxygen is combined with them, and can readily be dis- 
 engaged by heating. 
 
 Experiment. Mix an ounce of potassium chlorate 
 with an equal weight of coarsely powdered oxide of 
 manganese in a mortar. Heat a little of the mixture 
 in a test-tube before using, because the oxide of manga- 
 nese is sometimes impure, and may then cause explo- 
 sions if mixed with potassium chlorate and heated. If 
 the substances separate quietly in the tube, you may 
 safely proceed with the experiment on a larger scale, 
 by heating the mixture in a glass retort as shown in 
 
62 THE WORLD OF MATTE&. 
 
 Fig. 14, and collecting the oxygen over water as 
 usual. The retort, however, frequently cracks. 
 
 Having thus collected as much oxygen as you wish, 
 exercise your ingenuity in trying all sorts of experi- 
 ments with it. So long as you do not mix hydrogen 
 with it, it is quite safe. Smell it, taste it, breathe it, 
 burn all sorts of substances in it (by the way it will 
 combine with almost every thing in the world), blow 
 soap-bubbles with it, and see whether they rise or fall ; 
 put bits of cold iron in it, and leave them for a few days 
 to see whether any combination takes place without 
 heat; in a word, get acquainted with oxygen, so that 
 you can recognize it wherever you meet it, and so that 
 you can recognize its effects even when you do not 
 detect its presence. 
 
FIRE. 63 
 
 It will take some time, but you can well afford it, 
 just as I can well afford to give large space to it in this 
 little book. It is the most important element in the 
 world. It is eight-ninths of all our water, it consti- 
 tutes one-half the solid crust of the earth, it makes up 
 four-fifths of the weight of all our herbs and shrubs 
 and trees, and three-fourths of your own body, and 
 of the bodies of all animals, and it is the chief source 
 of fire. We walk on it, and burn it, and eat it, and 
 drink it, and breathe 
 
 Ah! but I did not mean to tell you just yet that 
 one-fifth of all the air is oxygen. I meant to let you 
 find it out by degrees. But, never mind, it is true, 
 and we must devote the next chapter to a study of 
 the air. B-efore passing to that, however, I think you 
 are entitled to know an easier method of obtaining a 
 supply of hydrogen. You should prepare enough to 
 enable you to become as familiar with it as with 
 oxygen. 
 
 The most convenient process depends upon two facts: 
 first, that acids contain hydrogen; second, that, as a rule, 
 when a metal is placed in an acid, all of the acid 
 except the hydrogen enters into new combinations in 
 which the metal is taken up, leaving the hydrogen free. 
 
 Metals are the successful rivals of hydrogen. No 
 matter how well satisfied oxygen and sulphur and 
 chlorine and the rest may appear to be with hydro- 
 gen for a partner, once let almost any metal come 
 among them, and they fly to it, leaving the hydrogen 
 deserted. 
 
64 THE WORLD OF MATTER. 
 
 To illustrate this fickleness of the elements, and at 
 the same time to procure a good supply of suffi- 
 ciently pure hydrogen, try the effect of a little zinc 
 upon that compound of sulphur, oxygen, and hydro- 
 gen, known as sulphuric acid. 
 
 Provide a jar fitted with a cork having two holes. 
 Through one hole pass a funnel. tube, and through 
 the other a glass tube bent in convenient form. Put 
 a small handful of granulated zinc, or zinc clippings, 
 into the jar. 
 
 Prepare a mixture of sulphuric acid and water as 
 follows: Into six ounces of cold water pour very 
 slowly one ounce of ordinary sulphuric acid, keeping 
 the mixture constantly stirred. If you pour it in 
 rapidly the heat evolved may be so great as to convert 
 the water into steam and cause the strong acid to spat- 
 ter. After the mixture has cooled, pour enough of it 
 through the funnel into the jar to cover the zinc. 
 
 A brisk ebullition occurs at once, so eager are the 
 little particles of oxygen and sulphur to combine with 
 the zinc, and the deserted hydrogen rises into the jar. 
 For two or three minutes the jar will be filled with a 
 mixture of hydrogen and air; and since one-fifth of the 
 air is oxygen, this is a highly explosive and dangerous 
 mixture, as we have already learned. 
 
 Wait a few minutes, therefore, until the hydrogen 
 has expelled all the air, and then collect as much as you 
 wish in the usual way over water. Fig. 17. 
 
 You can easily ascertain whether all the air has been 
 expelled by filling a test-tube with the escaping gas, 
 
FIRE. 65 
 
 and observing whether it burns quietly when lighted. 
 In this, as in all other experiments with hydrogen, 
 remember to hold the jar containing it mouth down- 
 ward; otherwise it will either escape or become mixed 
 with air, and explode when ignited. You had better 
 collect several bottles of hydrogen, for there are many 
 interesting and instructive experiments to be made with 
 it. Invent as many as you can. Burn a fine jet of it 
 in air under a bright dry glass, and notice how the glass 
 
 Fig. 15. 
 
 at once becomes clouded by small drops of water con- 
 densed upon its surface. You readily understand from 
 this experiment that the hydrogen is combining, or 
 burning, with the oxygen of the air. Push a burning 
 taper up into a jar of hydrogen. It is extinguished. 
 Blow soap-bubbles with it, and you have beautiful 
 balloons. These can be blown by connecting a tobacco, 
 pipe by a rubber tube to the tube from which hy- 
 drogen is driven by the action of the acid and zinc. 
 Dip the bowl of the pipe in soap-suds, and the force of 
 the escaping gas should be sufficient to blow bubbles. 
 5 
 
66 THE WORLD OF MATTER. 
 
 Finally blow some bubbles with a mixture of air and 
 hydrogen, and touch them with a lighted taper as they 
 rise, taking care, however, not to light them while on 
 the pipe, because the explosion might force flame into 
 the jar and blow it to pieces. 
 
 Thus the oxygen and hydrogen separated by the in- 
 truding metal are again united, and in these most fairy- 
 like, and many-colored balloons are floating away on 
 their bridal tour. A touch of flame bursts their crystal 
 car, but serves only to render their union more intimate, 
 and they fall together in a sparkling drop of water. 
 
 QUESTIONS ON CHAPTER 5. 
 
 1. What is fire? 
 
 2. With what substances does oxygen combine? 
 Ans. All the elements except fluorine. 
 
 3. Describe the combustion of iron and oxygen. 
 What is the product? 
 
 4. How can a gas be weighed ? 
 
 5. What are the effects of passing steam through a 
 red-hot tube filled with iron-borings? 
 
 6. What is chemical affinity ? 
 
 7. Describe a practical method of obtaining oxygen. 
 
 8. Has oxygen any effect on cold iron ? 
 
 9. Is it heavier or lighter than air? 
 
 10. Where is it found in nature? 
 
 11. Is it in the air? 
 
 12. Describe and explain the process of obtaining 
 hydrogen by the action of zinc upon sulphuric acid. 
 
 13. What practical use is made of hydrogen? 
 
AIR. 67 
 
 CHAPTER VI. 
 
 AIR. 
 
 If you have carefully studied the preceding chapter, 
 and performed the experiments there described, you 
 have become pretty familiar with two of the most im- 
 portant elements. The most characteristic property of 
 oxygen is its power of combustion with other sub- 
 stances. You can hardly have failed to nt>tice that the 
 burning of a candle, the flame of a gas-jet, and the fire 
 on the hearth all resemble the flame of substances burn- 
 ing with oxygen, differing only in intensity. 
 
 A simple test of the presence of oxygen in the air 
 is holding a cold glass jar or a piece of any cold metal 
 over the flame of an alcohol lamp, or over a gas flame. 
 Both alcohol and coal gas contain a large percentage of 
 hydrogen. 
 
 Presently you will observe a dampness coming upon 
 the cold glass or metal, and this increases until it stands 
 in drops and trickles down. On examination, you will 
 find this liquid to be pure water. Now water cannot 
 be produced except by combining oxygen and hydro- 
 gen. In this case the hydrogen comes from the alcohol 
 or gas; and it is plain that the oxygen must come from 
 the air. 
 
 But if air is so largely composed of oxygen, how is it 
 
68 THE WORLD OF MATTER. 
 
 that the air does not cause the alcohol and tlie gas to 
 burn as brilliantly as oxygen does? And why will not 
 iron burn in the air? And if oxygen unites in com- 
 bustion with everything else, why is it that, once a fire 
 gets started, particularly a great conflagration as of a 
 forest or a <:ity, it does not increase and spread and 
 burn up the whole world? Well, I have no doubt it 
 would do that if there were nothing but pure oxygen 
 
 Fig. 1 6. 
 
 in the air. Nor would it wait for a great fire to start it, 
 for there are substances like phosphorus that combine 
 with oxygen at ordinary temperatures. 
 
 If the air were pure oxygen, such substances would 
 kindle first, and they would serve as a match to set the 
 world on fire. Iron buildings would blaze more fiercely 
 than wooden ones. That would be a grand holiday for 
 the fire-spirits! 
 
 "The elements would melt with fervent heat, and the 
 heavens would be rolled together like a scroll." 
 
AIR. 69 
 
 This terrible result is prevented only by the con- 
 trolling presence of another element in the air, which 
 holds the fiery oxygen in check, and compels it to com- 
 bine as a rule in a reasonably temperate and safe com- 
 bustion. 
 
 Let us see whether we can unmingle a little air and 
 procure some of this wonderful gas which alone saves 
 the world from bursting into flames. 
 
 Float a light porcelain dish on water in a glass or 
 earthen basin. Put a small piece of phosphorus in the 
 floating dish, and light it. Cover the dish with a large 
 jar. 
 
 The phosphorus at once combines with the oxygen of 
 the air, forming a phosphorus oxide, at first appear- 
 ing in the form of a white cloud, which, however, 
 soon dissolves. When the jar which has become heated 
 by the burning of the oxygen and phosphorus becomes 
 cool, you will notice that one-fifth of that part of the 
 jar that was before filled with air is filled with water, 
 which has risen in it from the basin. 
 
 You may now test the contents of the upper four- 
 fifths of the jar. It cannot be empty, or the weight of 
 the atmosphere would press the water from the basin 
 up into it and fill it completely. It cannot be steam, for 
 it is cold. It cannot be hydrogen, for it will not burn. 
 It is not oxygen, for a lighted taper thrust into it, in- 
 stead of blazing more brightly, is immediately extin- 
 guished. It has no color, taste, or smell. It is com- 
 pletely inactive. No action short of the most in- 
 ten.e electric force can ca.use it to combine chemically 
 
70 THE WORLD OF MATTER. 
 
 with oxygen. It is a perfectly safe substance, under 
 ordinary conditions; and its name is Nitrogen. 
 
 But this quietness is no indication of lack of power. 
 "Deep rivers run still." It takes a man of considerable 
 strength of character to live quietly among noisy 
 neighbors, particularly if he succeeds in keeping them 
 moderately quiet too. So, lest you should feel any con- 
 tempt for this most reserved and indifferent gas, I must 
 warn you that on due occasion it enters into combination 
 
 Fig. 17. 
 
 with other elements, and manifests the most sudden and 
 unexpected activity. Thus when under the influence of 
 electricity, or by the decay of plants and animals, ni- 
 trogen is forced to unite with hydrogen, it forms 
 ammonia and in this form possesses a pungency and 
 caustic flavor that quite compensate for its ordinary 
 lack of smell and taste. Pure ammonia is a colorless 
 gas which is very soluble in water. The "liquor 
 ammoniae" of the drug-stores is a solution of this gas 
 in water, prepared as shown in Fig. 17, by passing 
 
AIR. 71 
 
 the gas into a flask containing water and kept cool 
 by being placed in a large vessel of cold water. This 
 is necessary, because considerable heat is caused by the 
 dissolving gas. 
 
 When nitrogen is combined with a gas called chlorine 
 it forms one of the most dangerous and explosive com- 
 pounds known. 
 
 Dulong, the chemist who discovered it in i8n,lost 
 one eye and three fingers for his pains, and two years 
 later Faraday and Davy although on their guard met 
 a similar accident. "Knowing that the liquid would .go 
 off on the slightest provocation, the experimenters wore 
 masks of glass, but this did not save them from injury. 
 In one case, Faraday was holding a small tube contain- 
 ing a few grains of it between his finger and thumb, 
 and brought a piece of warm cement near it, when he 
 was suddenly stunned, and on recovering consciousness, 
 found himself standing with his hand in the same po- 
 sition, but torn by the shattered tube, and the glass of 
 his mask even cut by the projected fragments. Nor was 
 it easy to say when the compound could be relied on, 
 for it seemed very capricious; for instance, one day it 
 rose quickly in vapor in a tube exhausted by the air- 
 pump, but on the next day, subjected to the same treat- 
 ment, it exploded with a fearful noise, and injuring Sir 
 Humphrey Davy." 
 
 The name, nitrogen, signifies a ''producer of niter," 
 and is applied to this gas because it is one of the principal 
 elements in niter, or "saltpeter." Niter is formed by 
 the combination of nitrogen with oxygen and potassium. 
 
72 THE WORLD OF MATTER. 
 
 It is found in long, colorless, six-sided crystals, marked 
 by fine parallel lines or "strice." Minerals so marked 
 are called "striated." It has a strong salty taste, and 
 can readily be dissolved in water. It occurs as a natural 
 product in the East Indies, Egypt, and Persia. It is 
 found in the juices of various plants, as the sunflower 
 nettle, tobacco, and barley. 
 
 Fig. 18. 
 
 Niter is used in the manufacture of sulphuric and 
 nitric acids, as an ingredient of fireworks, and esoecially 
 in the manufacture of gunpowder. 
 
 It is extensively used in medicine, particularly in 
 acute cases of rheumatism, in certain affections of the 
 throat, and in spasmodic asthma. 
 
 Nitric acid is an important compound of nitrogen, 
 oxygen, and hydrogen, and in one form, in which water 
 also is present, is known as aqua-fortis. It is astonish- 
 
AIR. 73 
 
 ing that these two elements, which when simply mixed 
 form the air we breathe, when chemically combined, 
 make an acid so powerful and destructive. 
 
 If a large glass globe filled with dry air be connected 
 with an electric battery and an "induction coil," as 
 shown in Fig. 18, and sparks be passed through the 
 air in the globe, red fumes are rapidly formed. On 
 pouring a few drops of water into the globe and 
 shaking it, the red fumes are absorbed by the water, 
 and nitric acid is the result. 
 
 When a flash of lightning passes through the air the 
 same effect is produced, and this accounts for the pres- 
 ence of a certain amount of nitric acid in the atmosphere. 
 
 When nitric acid is exposed to the air it gives off 
 strong fumes which are dangerous to breathe. The 
 pure acid absorbs moisture very rapidly. It is ex- 
 tremely corrosive; for example, when dropped on the 
 hand it produces painful wounds, and colors the skin 
 yellow or brown. 
 
 Nitric acid is used in the formation of coal-tar colors, 
 in the manufacture of gun-cotton, nitro-glycerine, and 
 dynamite, and in nitrate of silver, which is so widely 
 used by photographers. 
 
 This acid has a powerful effect upon sulphur, phos- 
 phorus, carbon, tin, and many othei substances, the 
 oxygen contained in it uniting rapidly with these ele- 
 ments and "oxydizing" them. Pour a little nitric acid 
 upon granulated tin and study the result. The white 
 powder which is deposited is an oxide of tin. 
 
 When cotton-wool is soaked in a mixture of strong 
 
74 THE WORLD OF MATTER. 
 
 nitric acid and sulphuric acid, washed, and dried, it 
 becomes "gun-cotton," an explosive so powerful, that 
 when used in shells it is six times as effective as the 
 same weight of gunpowder. No smoke accompanies 
 its explosion, and for this reason it has been very useful 
 in mining. Other advantages are that time, dampness, 
 and exposure to air do not injure it; it occupies a com- 
 paratively small space, is light, and is not liable, as gun- 
 powder is, to accidents from spilling. Dynamite and 
 other more recently invented compounds have, however, 
 now largely taken the place of gun-cotton. 
 
 Another curious compound of nitrogen and oxygen 
 must be mentioned, differing from nitric acid in the 
 proportions of the two gases, and in the absence of 
 hydrogen. It is called "nitrous oxide," and is remark- 
 able for the effects it produces when breathed. 
 
 These are Jirst, "singing" in the ears, then insensi- 
 bility, and then, if the breathing be continued, death. 
 When one volume of oxygen is mixed with four vol- 
 umes of nitrous oxide, the mixture is called "laughing 
 gas," and the effect of inhaling it is less serious. It 
 causes temporary insensibility during which minor 
 surgical operations, such as the extraction of teeth, may 
 be performed without pain. The effect soon passes off 
 and does no harm. Owing to the liability of having 
 impurities mingled with this gas, it is dangerous for 
 amateurs to experiment with it. 
 
 These are but a few of the many interesting com- 
 pounds of nitrogen, and are given to illustrate how an 
 element which, when pure, appears to be the nearest 
 
. AIR. ^ 75 
 
 possible approach to nothing at all, having no color, 
 taste, or smell, being incapable of burning, or support- 
 ing combustion, and unable to support life, becomes, 
 when combined with other elements, suddenly endowed 
 with the most intense energy; helping to produce the 
 most vivid colors, the most acid taste, the most pungent 
 smell, the most violent explosions, and the most nec- 
 essary constituents of food. 
 
 To illustrate the importance of nitrogen in food, 
 it may be stated that it occurs abundantly in all 
 flesh, eggs, and cheese, and is an essential ingredient 
 of all foods directly adapted to produce blood and 
 muscle. 
 
 I have refrained from giving minute directions for 
 obtaining the various compounds of nitrogen, as their 
 preparation and use involve too much danger; but if 
 you have attentively performed the few simple experi- 
 ments given, you must by this time have become rea- 
 sonably familiar with this most fascinating element. 
 
 How largely does the beauty, the power, the life, 
 the very existence of this world, depend upon the con- 
 stant but unobserved activity of three invisible and in- 
 tangible substances, oxygen, hydrogen, and nitrogen! 
 
 QUESTIONS ON CHAPTER 6. 
 
 1. How can you prove the presence of oxygen in 
 the air? 
 
 2. What prevents the immediate destruction of the 
 world by fire ? 
 
 3. How can the elements mingled in air be separated > 
 
76 THE WORLD OF MATTER. 
 
 4. Describe nitrogen. 
 
 5. What is ammonia? 
 
 6. What is the meaning of the word, nitrogen? 
 
 7. What are the uses of niter? 
 
 8. How may nitric acid be produced? 
 
 9. What are its effects and uses? 
 
 10. What is gun-cotton? Its advantages? 
 
 U. What is laughing gas? 
 
 12. The value of nitrogen in food? 
 
EARTH, 77 
 
 CHAPTER VII. 
 
 EARTH. 
 
 We have learned that the old notion that water, air, 
 and fire are elementary substances, is incorrect. It is 
 hardly necessary to add that those who held this opinion 
 were equally wrong in thinking that "earth" was a 
 fourth and final element, if by "earth" they meant 
 what is now commonly understood, namely, the soil 
 under our feet, for I have already told you that about 
 one-half of this consists of oxygen in combination 
 with other substances, and that hydrogen and nitrogen 
 are also found in it in vast quantities. 
 
 Before going on to study the form of earth known 
 as soil, it is only fair to the ancient philosophers from 
 whose writings this popular theory of the "four ele- 
 ments" took its rise, to say that the)'' never meant any- 
 thing of the sort. They were quite intelligent gentle- 
 men, and knew as well as we know, that there are more 
 than four different substances in nature; or at all events 
 more than four apparently different substances. What 
 they intended to say was more nearly this, that all the 
 elements of the world exist in four different states or 
 conditions; namely, solid, liquid, gaseous, and a fourth 
 state still further removed from the solid form a state in 
 which matter still more rarefied surrounds and interpene- 
 
78 THE WORLD OF MATTER. 
 
 trates all the grosser forms. This closely resembles that 
 subtle and almost hypothetical form of matter which 
 modern philosophers believe to pervade the earth, and 
 the remote spaces beyond the air, and which they call 
 "the ether." I do not say that the ancients had as 
 clear and scientific a knowledge of the stuff the earth 
 is made of as modern students have, but the words, 
 "solid," "liquid," "gas," and "ether," are much more 
 accurate interpretations of their classic formulas, than the 
 popular but misleading words, "earth," "water," "air," 
 and "fire." 
 
 Let us now examine a handful of earth from the 
 garden, not attempting to discover, perhaps, all its ele- 
 ments, but carefully enough to satisfy ourselves that it 
 is composed of several different substances. 
 
 I have here a little earth in a saucer. It is a dark- 
 brown substance, resembling, but for color, some of the 
 cheaper grades of brown sugar. There are little 
 grains in it, with here and there small lumps which 
 crumble easily at a touch. Bits of straw and tiny root- 
 fibers can be seen without close observation. These 
 evidently come from the fertilizer which was spread 
 over the garden last fall, and plowed in this spring. 
 
 1 will now put some of the earth under a microscope. 
 Using at first a hand-lens of low power, it seems that 
 this earth is composed of tiny grains of sand of different 
 colors. Some are black and dull, some white, some 
 transparent and glassy, some brown, some thin, scale- 
 like, and glistening. It is a curious mixture, I now 
 place a smaller quantity on a glass slide, and examine it 
 
fiARTH. 70 
 
 under a more powerful lens. It is at once transformed 
 from a brown powder into a heap of tiny pebbles of 
 various colors, shapes, and sizes. Most of these tiny 
 pebbles are transparent, and of a brownish tint; many 
 of them have a crystalline appearance. My garden is 
 clearly composed mainly of a fine sand or loam. The 
 tiny pebbles under the glass seem to be mingled with a 
 finer and smoother substance which I recognize as clay ; 
 and the presence of minute particles of vegetable matter 
 is everywhere more visible than to the naked eye. 
 
 Let me now heat some of the earth. I put it in this 
 test-tube, and hold it over the flame of an alcohol lamp. 
 If I had no test-tube I should put it on a shovel, and 
 cover it with an old tumbler. 
 
 The first thing noticed as the earth grows hot is a 
 change of color. It is becoming lighter at the same 
 time the sides of the tube are growing foggy, and now 
 drops of water are trickling down in it. A quantity of 
 water was in the soil, and it has been converted into 
 vapor and driven off. After longer heating the earth 
 becomes quite dry, and now there appear here and 
 there little sparks and small glowing coals, that flicker 
 for a moment and go out. The bits of straw and roots 
 are burning up. First they grow very hot, and give 
 off little puffs of smoke and gas; then they turn black 
 like bits of charcoal; then when still hotter they com- 
 bine with oxygen of the air With a bright red glow, and 
 then they crumble down into gray ashes. I now put 
 the earth in the test-tube between two pieces of glass, 
 press them tightly together, and slip the upper one 
 
8o THE WORLD OF MATTER. 
 
 along over the earth. I hear a grating sound, and on 
 examining the glass, I find that it is covered with dis- 
 tinct scratches. 
 
 So I might go on and make many other interesting 
 experiments with this handful of garden-soil, but 
 enough has been done for our present purpose. We 
 have learned beyond question that earth is not an ele- 
 ment, but a mixture of many different substances. 
 
 We have found oxygen and hydrogen in the water 
 driven off, carbon in the charred bits of straw and 
 roots, clay binding together the little grains of sand, 
 and these sand-grains themselves of various sorts, some 
 soft and smooth, others hard enough to scratch a pane 
 of glass. It is plain enough that these bits of charcoal 
 are not essentially different from the larger pieces on the 
 hearth; that these minute particles of clay are just like 
 the large masses which we find in olay-beds; and that 
 these tiny pebbles which constitute the sand are differ- 
 ent only in size from the larger pebbles found in general. 
 It will be more convenient to study them in their larger 
 forms and separately, and so we may now throw away 
 our earth, and examine the substances of which it is 
 composed as we find them in larger specimens. We 
 will begin with the hard stone that scratches glass. 
 
 In the collection accompanying this book you will 
 find a specimen of it, No. 18. It is apiece of quartz. 
 Observe first its physical properties, and I shall ask 
 you to determine for yourself its degree of hardness, 
 specific gravity, lustre, color, and streak, and its fusi- 
 bility. Test it also to discover whether it is brittle or 
 
EARTH. 81 
 
 O~ J. \ * i - ';;'..> 
 
 not. When you break it for this purpose, observe 
 whether it splits evenly as a piece of slate does, or 
 whether the surfaces after, breaking are irregular. The 
 manner in which a mineral breaks is often important as 
 indicating its structure, and therefore as a step toward 
 identifying it. The peculiar breaking of a mineral is 
 called its fracture. If it splits more or less evenly, 
 such splitting is called cleavage, instead of fracture. 
 
 Drop a little hydrochloric acid from the end of a 
 glass rod upon the specimen. What effect does it have? 
 
 Specimen No. 19 is a crystal of quartz. You will 
 observe that it is six-sided, or hexagonal, and if it has 
 not been broken, it is also finished at one or both ends 
 with an hexagonal pyramid. These crystals may be 
 found in almost every part of the world, for a large 
 part of the solid crust of the earth is composed of 
 quartz. They are often found loosely scattered in sand, 
 which is formed by crumbled or "disintegrated" rock, 
 but they naturally occur in veins which run through 
 other sorts of rock. 
 
 Quartz crystals were believed by the ancients to be 
 merely a kind of ice frozen too hard to melt; but they 
 are now known to result from a solution of the mineral 
 in water, which trickling through crevices in the rock 
 gradually evaporates, and slowly builds up the crystals 
 from the quartz dissolved in it. The name "crystal," a 
 Greek word for ice, is still retained as a result of the old 
 and erroneous opinion. Nothing can be more delight- 
 ful than the finding of a crystal vein; it repays many 
 days of searching. Some years ago one of my pupils 
 6 
 
2 THE WORLD OF MATTER. 
 
 in Lenox Academy discovered a few loose crystals of 
 quartz remarkable for their brilliancy and symmetrical 
 form. It was suggested that as these had been found 
 in a regular line along the crumbling edge of a rock, a 
 little digging might reveal a vein; and the boys were 
 invited to meet in the field at a certain hour prepared to 
 "stake out their claims," and enter upon a small mining 
 operation. The appointed hour brought a most amus- 
 ing scene. One boy had a large hammer and a drill ; 
 another a shovel and an old iron spoon; another a crow- 
 bar and a garden trowel; another a post-hole digger 
 that opened and shut like a huge pair of shears; while 
 one excited youth appeared with a can of powder and 
 a fuse. Little labor, however, was needed. A few 
 strokes of the shovel removed a layer of earth, and a 
 cry of pleasure arose from all the group. A narrow 
 crevice in the limestone rock was revealed, and it was 
 filled from end to end with gleaming crystals of trans- 
 parent quartz ; some loose, others united in groups and 
 clusters of great beauty; and ranging from the size of 
 a pea to that of a butternut. Some were tinged with 
 yellow, others clear as water. Some were nearly regu- 
 lar in form, but most of them were curiously distorted, 
 yet every one was hexagonal, every angle measured the 
 same number of degrees as every other, and each had 
 on one end, at least, a pointed pyramid. 
 
 Down dropped the little miners on hands and knees, 
 regardless of torn trousers and finger-nails. When the 
 sun went down all were still at work, with their earth- 
 stained heads all down out of sight, and their heels all 
 
EARTtt. 83 
 
 up in the air; and every boy learned more about quartz 
 in that short summer afternoon than he could have dug 
 out of books in a month. So can you if you will follow 
 their example, and make a careful examination of the 
 country within ten miles of your own home. You may 
 not find a vein of crystals, but you will find plenty of 
 interesting mineral specimens of some sort to repay 
 you for your pains. You should make a mineralogical 
 map of your town, upon which you will indicate the 
 location of the various minerals you find; and you 
 should make a collection of all local minerals, labelling 
 each specimen carefully, and being particular to add the 
 exact place from which it was taken. 
 
 Possibly one reason that quartz so closely resembles 
 ice is that more than half of it is composed of the 
 principal element of water; namely, oxygen. 
 
 The other element in quartz is new to you ; it is called 
 silicon, and is never found in nature except in combina- 
 tion with oxygen, from which it is, however, extremely 
 difficult to separate it. In spite of this difficulty, how- 
 ever, it is so important for you to get acquainted with the 
 element, since next to oxygen it is the most abundant in 
 the world, that I will tell you how the chemist Berzelius 
 obtained pure silicon in 1823. 
 
 He took advantage of the well-known preference of 
 fluorine for metallic over non-metallic substances, on the 
 same principle by which we obtained hydrogen when 
 we passed steam over red-hot iron. You 'remember 
 .that in that case the oxygen left the hydrogen and united 
 with the iron. 
 
8 4 THE WORLD OF MATTER. 
 
 Berzelius put ten parts of dry potassium silicon fluor- 
 ide a compound of the metal potassium with silicon, 
 and a gas called fluorine into an iron tube; his object 
 being to induce the fluorine and potassium to leave the 
 silicon: he then added nine parts of metallic potassium, 
 and heated the mixture red-hot. This produced a 
 violent commotion among the elements in the tube, and 
 when it was all over, and the tube cooled down, he 
 found, as he had hoped, that the charms of the metallic 
 potassium had proved strong enough to overcome even 
 the attachment which had previously existed between 
 the fluorine and the silicon. The fluorine and potassium 
 were united together in a new compound potassium 
 fluoride and the deserted silicon was left alone. 
 
 Before Berzelius got hold of it, however, he had to 
 shake up the- whole mixture, first in cold and then in 
 hot water, to dissolve out the potassium fluoride. When 
 this was done, he found the pure silicon settled at the 
 bottom, and on taking it out and drying it, he had a 
 brown powder, and was perhaps the first human being 
 to see and handle this wonderful and most important 
 element. I do not know why you may not succeed in 
 repeating his experiment and sharing his delight. 
 
 On experimenting with this silicon powder, it was 
 found that neither sulphuric nor nitric acid affected it; 
 but when heated in the air it readily entered into com- 
 bustion with oxygen, forming an artificial quartz, 
 which often melted around particles of the silicon 
 powder, leaving a portion of it unburned in the centre. 
 
 When minerals occur in an uncrystallized state, as 
 
EARTH. 85 
 
 when carbon is in the form of charcoal, or silicon in 
 the form of this brown powder, they are called 
 "amorphous" which simply means without definite 
 form. 
 
 By other processes silicon has been obtained in dark 
 and glittering eight-sided crystals, and also in regular 
 double six-sided pyramids, of a dark steel-gray color. 
 It is not a metal. 
 
 QUESTIONS ON CHAPTER 7. 
 
 1. Is "earth" an element? 
 
 2. What did the ancient philosophers mean by speak- 
 ing of the "four elements, fire, water, earth, and air?" 
 
 3. Describe the results of your examination of a 
 handful of garden soil. 
 
 4. What substances are most abundant in it? 
 
 5. Describe the physical properties of quartz. 
 
 6. Of what two elements is quartz composed? 
 
 7. What then is its chemical name? (Oxide of 
 silicon.) 
 
 8. Describe a crystal of quartz. 
 
 9. How are quartz crystals formed ? 
 10. Describe silicon. 
 
86 THE WORLD OF MATTER. 
 
 CHAPTER VIII. 
 
 QUARTZ. 
 
 In the previous chapter, by an examination of a hand- 
 ful of loam we learned that earth is not one element, 
 but a mixture of many minerals, chief among which is 
 quartz. \Ve further learned the more prominent physi- 
 cal properties of quartz, and its chemical composition. 
 
 How large masses of quartz rock are split by frost, 
 broken down and rounded into pebbles by the action of 
 weather and water, and at last reduced to fine sand, will 
 be more fully explained in the third volume of this 
 series, where we hope to treat somewhat in detail of the 
 forces which are constantly at work, changing the form 
 and modifying the structure of the earth's crust; but as 
 this mineral constitutes a very large part of this crust, 
 we shall be justified in devoting a few more pages to it 
 now. 
 
 No mineral appears in more numerous and varied 
 forms than quartz. We have seen it in its transparent 
 forms as a fragment of rock, and as a gleaming crystal. 
 In these forms it rivals in transparency the finest 
 glass. From it spectacles are sometimes made, and for 
 this purpose Brazil furnishes some of the finest pebbles; 
 but it is doubtful whether it posesses any real advan- 
 tage over glass, except that being much harder it is less 
 
QUARTZ. 87 
 
 likely to be scratched. The ancients made exquisite 
 goblets, cups, vases, and seals of rock-crystal. Mr. 
 Ruskin pronounces a perfect sphere of rock-crystal one 
 of the most beautiful objects in the world. These are 
 made in Japan, sometimes five or six inches in diameter 
 an"d costing hundreds of dollars. In their perfect clear- 
 ness and perfect shape they rival the transient glory of 
 soap-bubbles, while their hardness and exquisite polish 
 render them almost indestructible. 
 
 One of the common varieties of quartz is flint. It is 
 from silex, the Latin name for flint, that the name 
 silicon is derived. Flint varies in color from nearly black 
 to light brown, red, yellow, and grayish white, and is 
 sometimes veined, clouded, marbled, or spotted. It 
 breaks with a curved fracture, called "conchoidal," or 
 shell-like, and is translucent. Its coloring is due to the 
 presence in minute quantities of other substances, such 
 as lime, iron, and carbon. It is abundantly found in 
 beds of chalk. Its property of striking fire with steel 
 is well known, and before the invention of friction- 
 matches led to the general use of flint for kindling fires 
 and firing guns. Old "flint-lock" muskets and pistols 
 are still preserved in historical museums. 
 
 Sparks may be struck by steel from any hard mineral, 
 but flint sparks are so hot and brilliant that it is thought 
 that they are due not only to particles of the stone 
 heated to redness by friction, but that a chemical com- 
 bination of silica {silicon dioxide) and iron takes place. 
 The most ancient use of flint was probably for sharp 
 weapons and cutting-tools. Flint knives, axes, and 
 
88 THE WORLD OF MATTER. 
 
 arrow-heads are among the most interesting relics of the 
 Indians and other savage peoples. The principal use 
 of flint at present is in the manufacture of fine earthen- 
 ware, and particularly in the preparation of the 
 delicate glaze or enamel which covers, protects, and 
 adorns it. 
 
 An interesting natural form of quartz is the geode. 
 Geodes are approximately round shells of rock, lined 
 with crystals, or with minerals in distinct layers. They 
 range in diameter from a quarter of an inch to a foot or 
 more. When water holding a mineral in solution finds 
 its way into a hollow, and deposits the mineral there in 
 layers or in crystals, a geode is formed. If the mineral 
 in solution is silica, quartz crystals may result. If the 
 quartz is deposited in layers, these usually appear with 
 different shades of color, and such variegated layers of 
 quartz are known as agate. If the color of the quartz 
 remains uniform, and particularly if it is deposited in 
 curved forms like clusters of grapes, and of a waxy 
 lustre, it is called chalcedony. If the color is red, we 
 have a geode of carnelian, sard, or sardius. 
 
 The question naturally arises, how the cavities in 
 which these crystals and layers occur are formed. 
 One way is by the production of steam inside the 
 rock material while that is in a soft or "plastic" state ; 
 as is seen in the sponge-like slag or scoria of a furnace 
 or a volcano. Rocks which were once in a melted con- 
 dition, like the "trap-rock" of the Palisades along the 
 Hudson river, afford some of the most beautiful geodes. 
 Another method by which the cavities may be made, is 
 
QUARTZ. 89 
 
 by the dissolving action of water on fossils. The sol- 
 vent water eats out the fossil shell or coral. 
 
 Perhaps a clergyman might find a sermon in these 
 stones. The hidden crystals must remain entirely lustre- 
 less until the geode is broken. Though they have the 
 power of shining so brilliantly, they come to their glory 
 only when shattered. In losing their life they find it. 
 
 Onyx and sardonyx are varieties of agate, in the first 
 of which the alternate layers are white and dark brown 
 or black; and in the second, reddish yellow or orange. 
 
 Moss-agates, or mocha-stones, are formed by the in- 
 fusion of a solution of manganese or some other mineral 
 into the quartz, where it often closely imitates the 
 branchings of moss or little fibers of root. It is possible 
 that these forms may in rare instances be due to actual 
 fibers or sprays of moss, which were once imbedded in 
 the quartz, and dissolved out by the water; in which 
 case they may be considered as tiny geodes. 
 
 Prase, or chrysoprase, is a beautiful pea-green variety 
 of quartz, and is often found in alternate layers with 
 white chalcedony. 
 
 One of the handsomest varieties of quartz is amethyst, 
 which by the oxide of manganese or iron is tinged with 
 brilliant purple. The name "amethyst" means "a pre- 
 venter of intoxication," and was given to this mineral 
 by the Greeks, who believed that from a cup of amethyst 
 one could drink wine and escape a headache. Fine 
 specimens are found in Lincoln County, North Carolina, 
 on the shores of Lake Superior, and in Colorado. The 
 finest varieties are from Brazil, Ceylon, India, and Siberia. 
 
90 THE WORLD OF MATTER. 
 
 The inspired St. John is largely indebted to quartz 
 for his conception, of the glory of the New Jerusalem : 
 "The building of the wall thereof was jasper: The 
 first foundation was jasper; .the third chalcedony; the 
 fifth sardonyx; the sixth sardius; the tenth chrysoprase; 
 the twelfth amethyst." Surely a mineral which not 
 only composes much of the crust of the present earth 
 but which is also to be found in such abundance in the 
 foundations of the "New Earth" that is to be, deserves 
 our careful study ! 
 
 Another beautiful compound of silicon must be men- 
 tioned here, which differs in composition from quartz 
 only in containing from 5 to 13 per cent, of water, 
 although, as with quartz, iron, and other substances fre- 
 quently give it a tinge of color. This is opal. It is 
 never found crystallized. It has a conchoidal or shell- 
 like fracture like chalcedony, and is very brittle. The 
 finest variety is called "precious" or "noble," or "orien- 
 tal" opal. It is translucent, of a bluish or yellowish 
 hue, and exhibits a beautiful play of rainbow tints. The 
 finest opals come from Hungary. Common opal is less 
 clear, and does not have any play of color. Wood- 
 opal is a petrifaction retaining the form and apparent 
 structure of the wood which has been dissolved away, 
 and replaced by the silicious mineral. 
 
 Three beautiful varieties of common rock-crystal re- 
 main: milky-quartz, which is opaque and white as snow; 
 rose-quartz, which is transparent and of the most deli- 
 cate rose-color; and smoky-quartz, which is translucent 
 and tinged with grayish brown. It will be well to 
 
QUARTZ. 91 
 
 notice that all varieties of quartz fall naturally into two 
 groups: (i)'the clear, glassy kinds, like rock-crystal, 
 amethyst, rose-quartz, and the like, and (2) the waxy 
 or dull kinds, such as chalcedony, agate, and flint. 
 
 Quartz constitutes nearly all the sand of the sea-shore, 
 and of the great deserts. The small particles of mo^t 
 other minerals are dissolved by water, while those of 
 quartz remain hard and "shaip." 
 
 Of the numerous uses of sand, I mention five. You 
 are perfectly familiar with its use on sand-paper, and as 
 a covering for "silicate" slates, and blackboards. 
 
 In 1870, Benjamin Tilghman, of Philadelphia, in- 
 vented the "sand-blast," a rapid stream of sharp sand 
 driven against glass, stone, or metal, for the purpose of 
 cutting, boring, or engraving. By its use, also, blocks 
 of stone may be turned in a lathe into circular and other 
 forms. Pilasters have in this way been finished in a few 
 hours, while if cut by hand as many days would have 
 been needed. 
 
 Sand is one of the chief ingredients in plaster and 
 mortar, being united with lime to form a strong and 
 durable cement. 
 
 Its chief use, however, is in the manufacture of glass, 
 which is composed of quartz, united with iime, soda, 
 metallic oxides, or other substances. 
 
 There is a legend that glass was accidentally discov- 
 ered ages ago, by certain Phoenician merchants, who 
 were returning home in a ship laden with soda, and 
 who were compelled by a storm to land on a sandy 
 shore under Mt. Carmel. They propped up their cook- 
 
92 THE WORLD OF MATTER. 
 
 ing-pots by lumps of soda placed on the sand, and 
 when these and the sand were melted by- their fires the 
 first glass was formed ; but this is not the place to enter 
 into a history or description of glass-making, nor even 
 to enumerate the most important of its countless uses. 
 
 Although quartz is so useful in the construction of 
 our dwellings in the form of sand for mortar, it is no 
 less valuable when naturally compacted and mingled in 
 various forms of building-stone. All our sandstone, 
 for example, is largely composed of quartz, and quartz 
 is one of the necessary ingredients of granite, gneiss, 
 and many other r.ocks. 
 
 Finally, quartz or silica occurs in many vegetable 
 structures, giving them strength and hardness, and often, 
 as in the case of stalks of grain, a fine enameled surface. 
 It also occurs in sponges in little needle like "spicules." 
 
 Consider th incalculable evil that would result from 
 the sudden destruction of the silicon that is in the world ! 
 The contents of every glass tumbler and jar and bottle, 
 would be let loose; microscopes and telescopes and 
 spectroscopes would vanish. Rain and wind would 
 have free access to our homes through empty window 
 frames; stone and brick buildings would crumble to the 
 ground; mountains and the solid crust of the earth 
 would sink away, and the oxygen now safely held in 
 the strong grasp of silicon would be let loose to consume 
 the whole world with fire. 
 
 In closing this chapter, I must remind you that in using 
 the expression "crust of the earth," I do not ,mean the 
 whole mass of the earth, but only an outer shell, a few 
 
QUARTZ. 9 3 
 
 miles thick; no thicker in proportion to the whole earth 
 than the varnish on a school-globe. Geologists know 
 nothing by personal observation about the materials 
 of which the great bulk of the earth is composed. 
 They have only scratched around a little here and there 
 on top. There are reasons known to astronomers, how- 
 ever, and others understood by electricians, which make 
 it not incredible that the earth is a solid, or nearly solid, 
 mass of iron, covered over with a layer or a few thin 
 layers of various sorts of rock, and topped with a sprink- 
 ling of pulverized rock, called earth or soil, which is 
 altogether too thin and scanty t"o be taken largely into 
 account. 
 
 QUESTIONS ON CHAPTER 8. 
 
 1. Describe the appearance and uses of rock-crystal. 
 
 2. Derivation and meaning of the words crystal and 
 silicon? 
 
 3. Describe flint, and tell its uses. 
 
 4. What are geodes, and how are they formed? 
 
 5. Describe agate, sardonyx, and onyx. 
 
 6. How are "moss-agates" formed? 
 
 7. Describe prase, amethyst, and opal. 
 
 8. Uses of sand? 
 
 9. If you have seen glass manufactured, describe 
 the process. 
 
 10. What results would follow the sudden removal 
 of silicon from the earth? 
 n. What is meant by the "crust" of the earth? 
 
94 THE WORLD OF MATTER. 
 
 CHAPTER IX. 
 
 A LESSON IN CHEMISTRY. 
 
 It is evident from what we have now learned that 
 changes are constantly taking place in mineral sub- 
 stances. We have seen ice changing to water, and 
 water to steam. We have seen iron bursting into bril- 
 liant flame in oxygen, and changing into iron oxide. 
 We have seen water changing into two gases, and these 
 gases changing back again into water. We have seen 
 various solutions changing into vapor and crystals. 
 Thinking over all these changes you will see that they 
 may be divided into two classes: 
 
 1. Those that do not alter the composition of sub- 
 stances. 
 
 2. Those that alter the composition of substances. 
 Changes of the first kind are called physical changes. 
 
 Those of the second kind are called chemical changes. 
 
 The change from water to ice is a physical change. 
 
 The change from water to oxygen and hydrogen, or 
 the reverse, is a chemical change. 
 
 From the experiments we have made, we have also 
 learned that chemical changes may be caused: (i). By 
 heat, or electricity. (2). By bringing different substances 
 into contact. (3). By bringing different substances to- 
 gether in a solution. 
 
A LESSON IN CHEMISTRY. 95 
 
 In all cases of chemical action, we have observed that 
 the substances acted upon lose their distinctive proper- 
 ties, and that new substances with different properties 
 are formed. 
 
 Notice now that all cases of chemical action may be 
 divided into three classes: (i) Composition; (2) 
 Decomposition; (3) Double decomposition. 
 
 Double decomposition occurs when substances act 
 upon one another and give rise to two or more new 
 substances instead of one. A good example of double 
 decomposition was shown in the process by which 
 Berzelius separated silicon from potassium silico-fluoride, 
 page 83. 
 
 What it is that causes substances to combine with 
 one another is not known. To the unknown cause of 
 their combination, the name chemical attraction has 
 been given. We must now study carefully the pro- 
 portions in which the different elements combine. 
 
 Two facts have been .learned by experiment: 
 
 1 . The same chemical compound always contains the* 
 same elements in the same proportion by weight. 
 
 Water, for example, always contains the same ele- 
 ments, oxygen and hydrogen, and in the same propor- 
 tion by weight, namely, 16 to 2. This is called the 
 la^v of definite proportions.* 
 
 2. The proportionate weight of each element in 
 every compound is always expressed by a particular 
 number, or by a multiple of that number. 
 
 * Recent experiments by Professor Edward Morley indicate that the exact 
 proportionate weight of oxygen in water is between 15.877 and 15.882. 
 
6 ^HE WORLD (DF MATTED. 
 
 For example, the proportionate weight of oxygen in 
 every compound is always expressed by 1 6, or by some 
 multiple of 160 
 
 This is the law of multiple proportions. 
 
 These facts can be explained by supposing each ele- 
 ment to be made up of little particles of uniform weight. 
 
 For illustration, if you have a number of iron balls, 
 each weighing seven ounces, and a number of glass 
 balls, each weighing three ounces, it is plain that, how- 
 ever you may mix the iron balls with the glass balls, 
 the total weight of glass in the mixture can always be 
 expressed by three or some multiple of three, and the 
 total weight of iron by seven or some multiple of seven 
 
 Now, since all elements combine just as they would 
 if they were made up of particles of uniform 
 weight, chemists assume that they really are made 
 up of such particles; and since these particles are the 
 smallest possible parts into which an element can be di- 
 vided, they are named atoms, a Greek word meaning 
 indivisible. 
 
 It is believed that these tiny atqms do not absolutely 
 touch one another, and that they are never absolut' ly 
 at rest. If a mass of gold, for example, could be viewed 
 through lenses of sufficient power to reveal its structure, 
 we should probably see as wild, and apparently con- 
 fused, a dance of atoms as that of the motes in the sun- 
 beam, or the planets in the sky. I say "apparently" 
 confused, for there is really no disorder either among 
 the atoms, or the motes, or the planets; but each moves 
 in accordance with a regular and well defined law. 
 
A LESSON IN CHEMISTRY. 97 
 
 Finally, it is thought these atoms occur in groups of 
 two (or in some elements more, but a constant number 
 for each element), and that these groups are never 
 broken up except when the element enters into combi- 
 nation with some other substance. These Uttle groups 
 of atoms are called molecules, a word meaning simply 
 "little masses." In the giddy dance of atoms, the mole- 
 cules move together like inseparable partners in a 
 waltz. 
 
 Molecules of a single element may be called simple 
 molecules. It is evident that the smallest particle, or 
 molecule, of a compound substance must be made up 
 of atoms of the different elements of which it is com- 
 posed. A molecule of water, for instance, is made up 
 of atoms of oxygen and hydrogen. Such molecules 
 may be called compound molecules. The weight of 
 a molecule is equal to the sum of the weights of the 
 atoms that compose, it. 
 
 The rapid motion of atoms and molecules to which I 
 have referred is closely connected with the phenom- 
 ena of heat. The hotter they are, the more rapid and 
 extended are their movements; and conversely, the 
 more rapidly the molecules are made to move, the 
 hotter they grow. 
 
 It would hardly be correct to say that heat makes 
 them move, or that their motion causes heat; it would 
 perhaps be better to say that their motion is their heat. 
 At all events, as this motion or heat, or both, increases, the 
 substance expands, just as it would if it were made up of 
 little masses which were separating farther and farther 
 7 
 
98 THE WORLD OF MATTER. 
 
 from one another and getting away from the power of 
 one another's attraction. As the heat increases the 
 solid passes . into the liquid, and the liquid into the 
 gaseous form. In the gaseous state the molecules are 
 no longer held together, but are violently driven farther 
 and farther asunder. 
 
 Avogadrtfs Law: In 1811, a chemist named Avo- 
 gadro announced as the result of many experiments that 
 equal volumes of all gases under the same conditions 
 of temperature and pressure contain the same number 
 of molecules. 
 
 This is known as Avogadro's law. If this be true, 
 then by weighing equal volumes of gaseous substances 
 we can learn the relative weights of the molecules of 
 these substances. 
 
 From the molecular weights thus determined, the 
 atomic weights of the elements have been learned. 
 
 As hydrogen enters into combination in smaller pro- 
 portion by weight than any other element, its atomic 
 weight is taken as the unit. When we say, therefore, 
 that the atomic weight of oxygen is sixteen, we mean 
 simply that one atom of oxygen is sixteen times as 
 heavy as one atom of hydrogen. 
 
 Chemical symbols. As the chemist is mainly occu- 
 pied in studying the combination of atoms, it has been 
 found convenient to represent these atoms by symbols, 
 and the most convenient symbols are the letters which 
 stand for the names of the elements. Thus the letter 
 O is used to represent one atom of oxygen, the letter 
 H, to represent one atom of hydrogen, etc. When the 
 
A LESSON IN CHEMISTRY. 99 
 
 names of several elements begin with the same letters, 
 as in the case of indium, iodine, and indium, a seconu 
 letter is added to distinguish them; thus In tor maiurn, 
 Ir for iridium; and when this is not practical, as in tne 
 case of iron, where I or lo might be taken for iodine, 
 Ir for iridium, and In for indium, the chief letters of 
 their Latin names are used ; thus, Fe, from the Latin 
 "ferrum," iron, is the symbol for that element. 
 
 The student should now carefully examine the table 
 of elements and symbols on page 263. It is not best to 
 commit them to memory at once. They will gradually 
 become familiar by use. The numbers after the sym- 
 bols are the atomic or combining weights of the ele- 
 ments. When we desire to express the fact that various 
 elements are put together, we write their symbols one 
 after the other with the sign (+) plus between them. 
 Thus zH+O means that two atoms of hydrogen are 
 added to one atom of oxygen.' If we wish to express 
 by the symbols that the elements thus brought together 
 have united in chemical combination, we omit the sign 
 + and write the symbols closely together as follows: 
 H 2 O. Such an expression is called a chemical formula. 
 Chemical formulas have a puzzling look to the be- 
 ginner, but they are really of the greatest use both in 
 simplifying our language and in rendering chemical 
 combinations easy to understand. 
 
 When the result of bringing certain elements to- 
 gether is their chemical union, we express that fact in 
 the following form: 2H+O=H 2 O; which is read: 
 Two atoms of hydrogen added to one atom of oxygen 
 
ioo TtiE WORLD OF MATTM. 
 
 combine to form water. The sign of equality (=) is 
 very convenient here. Such a formula is calle J a chem- 
 ical equation. 
 
 As the symbols of the elements represent atoms, it is 
 evident that the symbols of compounds represent mole- 
 cules. The symbol for water, H 2 O, represents, accord- 
 ing to the atomic and molecular theories already ex- 
 plained, the smallest particle of water that can exist as 
 such. It is made up of two atoms of hydrogen and one 
 atom of oxygen, chemically combined. 
 
 Exercise. Read the following equations: 
 
 Hg-|-O=HgO (Mercuric oxide.) 
 
 Na-f-Cl=NaCl (Sodium chloride or common salt.) 
 
 2N-j-2O=N 8 O 8 (Nitric oxide.) 
 
 It will be observed that before combination takes 
 place the number of atoms in any element is repre- 
 sented by a large figure written on a line with the letters ; 
 while the number of combined atoms is represented by 
 a small figure written to the right and below the symbol 
 to which it belongs. 
 
 In laboratory work combinations are less frequently 
 made between two elements directly than between com- 
 pounds, and it is in expressing completed combinations, 
 or "reactions" as they are called, that the value of sym- 
 bols is most apparent. 
 
 Recur for a moment to the experiment by which 
 Berzelius obtained pure silicon, page ^3. Observe 
 how many words were needed to explain tne comDina- 
 tions he effected, and see how mucn simpler it is lo ex- 
 press the same reaction, thus: 
 
A LESSON IN CHEMISTRY. 101 
 
 K 2 SiF 6 -f 4 K 6KF -f Si 
 
 (Potassium-silicon (Potassium.} (Potassium (Silicon.) 
 fluoride.) fluoride.) 
 
 The symbols tell the whole story in one line; not 
 only giving us the substances brought together and the 
 compounds that result, but also the exact proportions 
 of each by weight. 
 
 A little study of this equation will show you that the 
 weight of the resulting substances is precisely equal to 
 the sum of the weights of all the elements that are com- 
 bined. Turn to the table of atomic weights. 
 
 The atomic weight of K being 39.04,. K 8 = 78.08 
 The atomic weight of Si being 28, Si = 28.00 
 
 The atomic weight of F being 19.10, F 6 = 114.60 
 The atomic weight of K being 39.04, 4 K = 156.16 
 And the sum is ......................... 376.84 
 
 Now add the weights represented in the other side 
 of the equation. 
 
 The weight of K being 39.04, an( * the weight 
 of F being 19.10, K F = 58.14; and 6 K F = 348.84 
 The weight of Si being 28, Si= 28.00 
 
 And the sum is again ...................... 376.84 
 
 This is true of every chemical equation, and forcibly 
 illustrates a fundamental principle of the science, 
 namely, that nothing is ever destroyed by any chemi- 
 cal process. 
 
 Water seems to boil away, but every molecuje of it 
 continues to exist in the form of vapor. This vapor 
 may be decomposed into its elemental gases, but every 
 atom that formerly existed in the water is still pre- 
 
 \ * * . v 
 
102 THE WORLD OF MATTER. 
 
 served in the gas. Iron was burned up in oxygen, but 
 both were found in their full weight in the iron oxide 
 that remained. 
 
 As no element is ever diminished or destroyed, 
 so no elementary substance ever increases in total 
 quantity. When coal is burned in a furnace, the 
 weight of the vapor and smoke that escape from the 
 chimney is about four times as great as that of the coal 
 consumed, but this is only because in the process of com- 
 bustion nearly three tons of oxygen have combined with 
 every ton of carbon. 
 
 QUESTIONS ON CHAPTER 9. 
 
 1. Define chemical and physical changes. 
 
 2. State three methods of producing chemical 
 changes. 
 
 3. What are the three classes of chemical changes? 
 
 4. What causes chemical combination? 
 
 5. Give the laws of definite and multiple propor- 
 tions. 
 
 6. What hypothesis explains them ? 
 
 7. Distinguish between atoms and molecules. 
 
 8. What is Avogadro's law? 
 
 9. What is the unit of atomic weight? 
 
 10. What is the advantage of chemical symbols? 
 
 11. Can the total quantity of any element be in. 
 creased or diminished? 
 
 12. How does this appear in chemical equations? 
 
A PIECE OF CHARCOAL. 103 
 
 CHAPTER X. 
 
 A PIECE OF CHARCOAL. 
 
 Having gone out of our way in the last chapter to 
 consider some of the laws that govern the elements in 
 their chemical combinations, and to become acquainted 
 with the symbols used to. express those combinations, 
 or "reactions," let us now return to the examination of 
 our handful of earth. 
 
 You remember that, besides a quantity of water, we 
 had already found in it a large number of minute 
 grains of quartz, composed of a very interesting ele- 
 ment, silicon, in combination with oxygen. Notice, in 
 passing, that as a rule, each mineral has two names, one 
 given and used by mineralogists, as in this instance 
 quartz / the other used by the chemist to indicate its 
 composition, as silicon oxide, or abbreviated, SiO 2 . 
 
 We next observed bits of charcoal scattered through- 
 out the soil. These are identical in substance with the 
 large pieces of charcoal on the hearth, and consist of the 
 element known as carbon. 
 
 Carbon is the chief element in the composition of all 
 the substances which we burn for the sake of heat or light; 
 including wood, coal, gas, oil, tallow, and wax. When- 
 ever these fuels are heated to redness in a vessel from 
 which air is excluded, their other elements, hydrogen 
 
104 THE WORLD OF MATTER. 
 
 and oxygen, are first driven off in gaseous forms, partly 
 as water and partly in combination with carbon, and a 
 large portion of the carbon remains behind, mingled 
 with a little ash. If, now, free access of oxygen be 
 allowed, the carbon combines with it gradually, not 
 with a flame but with a steady glow, and the product of 
 this- combustion is an invisible gas, which we shall 
 presently study. 
 
 The purest form of charcoal is lamp-black. Char- 
 coal does not crystallize, and is therefore an amorphous 
 form of carbon. 
 
 You are so familiar with the physical properties of 
 charcoal that you need not devote much time to them 
 now. The specific gravity of this substance, however, 
 is greater than at first appears. A piece of charcoal 
 floats on water, and appears, thus to have a specific 
 gravity of less than i ; but this is due to its porous 
 condition. It is buoyed up by the air which fills its 
 pores. If it be finely powdered it sinks in water, and 
 its specific gravity is found to range from 1.5 to 2. 
 
 Coke is a form of carbon made by heating coal with- 
 out free access of air, as is done on a large scale in the 
 manufacture of illuminating gas. Coke bears about 
 the same relation to coal that charcoal bears to wood. 
 
 Lamp-black is a very finely divided form of charcoal, 
 which is deposited on cool objects placed in the flames 
 of burning oils. Most artificial lights deposit a black 
 soot on objects placed in them. 
 
 This soot is used in the manufacture of printer's ink-. 
 
 Carbon is acted upon by very few substances, and i 
 
A PIECE OF CHARCOAL. 105 
 
 nearly insoluble, so that it is impossible to destroy the 
 color of printer's ink without destroying the material 
 upon which it is impressed. 
 
 Bone-black, or animal charcoal, is made by charring 
 bones or other animal substances. 
 
 Bone-black and wood charcoal have the power of ab- 
 sorbing gases, and are therefore useful as purifiers of 
 foul air. Charcoal also absorbs many of the impurities 
 contained in foul water, and is extensively used in 
 filters. A charcoal filter should be of good size, and 
 the charcoal should be occasionally renewed. 
 
 Some coloring matters are removed from liquids by 
 passing them through filters of bone-black. This is of 
 practical advantage in the refining of sugar. The syrup 
 first obtained from the cane or beet is strongly colored, 
 but the color is removed by filtering through bone- 
 black. 
 
 Many impure varieties of amorphous carbon are in- 
 cluded under the name coal. They all bear a more or- 
 less close relation to charcoal, and, like it, have been 
 formed by the gradual decomposition of wood or other 
 vegetable material without free access of air. The pro- 
 cess has been going on for ages. It will be more fully 
 treated in the succeeding volumes of this series. Ordi- 
 nary coals are classed as hard and soft, or anthracite 
 and bituminous. Then there are substances in which 
 the decomposition has not progressed so far, such as 
 lignite and peat. 
 
 I must call your attention again, and particularly, to 
 the fact that charcoal unites with oxygen without 
 
106 THE WORLD OF MATTER. 
 
 flame, and while it is in the solid state. The solid par- 
 ticles of the carbon as they burn with the oxygen be- 
 come glowing white or incandescent, and thus give rise 
 to the brightness of all ordinary flame. If it were not 
 for the presence of incandescent or white-hot particles 
 of carbon, our hearth-fires, and lamps, and candles, and 
 gas-jets would all be reduced to a feeble sort of flame, 
 such as that given by burning alcohol. This follows from 
 a very important principle, namely, that whenever a 
 substance burns as iron burns in oxygen, and as car- 
 bon burns in Edison's electric lamp without first as- 
 suming the vaporous state, it becomes exceedingly lumi- 
 nous. In fact, when any substance is intensely heated 
 it becomes intensely bright, whether it burns or not, if 
 it retains its solid state. If a candle or lamp does not 
 burn well it gives off a quantity of smoke. This is 
 merely unburned carbon. It is this very smoke which 
 gives brilliance to the light if it does burn well. In 
 that case the particles of smoke, which are carbon, be- 
 come incandescent, and give a beautiful light, while at 
 the same time they combine with oxygen in the form 
 of an invisible gas and pass away into the air. You 
 may perform a simple but instructive experiment to 
 illustrate the part that carbon plays in giving brilliancy 
 to flame. 
 
 To show you how abundant carbon is, and how it 
 exists in places where you would perhaps least expect 
 to find it, we will procure the carbon for this experiment 
 from a lump of sugar. Lay a piece of writing-paper 
 on a fire-shovel, place a lump of sugar on it, and hold 
 
A PIECE OF CHARCOAL. 107 
 
 it over glowing coals. Sugar is nothing but carbon and 
 water. You will presently see the sugar melt; then 
 the water will pass off in the form of vapor which 
 you can collect and examine and finally you have left 
 a light, porous, cindery, black mass, which is carbon in 
 the form of charcoal. Thus far we have merely driven 
 off the water from the sugar by means of heat. 
 
 We might have separated it equally well by mixing 
 sugar in the form of syrup with sulphuric acid. The 
 acid would have combined with the water, leaving the 
 carbon in a black mass. 
 
 Now fasten a little splinter of wood by a fine wire to 
 your mass of charcoal, set fire to the wood so as to start 
 the combustion, and then plunge the charcoal into a jar 
 of oxygen. You will observe the brilliant effect of the 
 combustion, without flame, owing to the bright in- 
 candescence of the particles of carbon as they combine 
 with the oxygen. 
 
 The dazzling electric light, both incandescent and 
 arc, is produced by similar glowing particles of car- 
 bon. In the Edison lamp, a slender thread, or filament, 
 of carbon is raised to a white heat by the electric cur- 
 rent; in the arc-lamp, the electricity heats the particles 
 at the ends of the carbon-pencils, and the white hot 
 sparks of carbon flying over from one pole to the 
 other and uniting with oxygen as they go, produce the 
 intense light. 
 
 Thus the blackest thing in the world becomes the 
 source of our whitest light. 
 
 After learning this, you will perhaps not be so greatly 
 
108 TIIK WOULD 01 MATTKR. 
 
 astonished to learn that although this amorphous kind of 
 carbon, known as charcoal or lamp black, is so dull and 
 black, the crystallized form of carbon is the most splen- 
 did mineral in the world tin- Hashing diamond. 
 
 The lustre of the diamond is so intense that a special 
 adjective is used to describe it, "adamantine" The 
 transparency of the diamond is perfect, unless, as often 
 happen!, there it some impurity in the stone. A very 
 slight admixture of a foreign substance is sufficient, 
 however, to cloud its clearness, dim its splendor, and 
 rhaiij-r ils color. Owing to surh impuritrvs diamonds 
 show various tints of color, such as gray, yellow, green, 
 and brown ; and less frequently orange, red, blue, or 
 even black. 
 
 The surest test of a diamond, next to that of its 
 chemical properties, it its hardness. It is the hardest 
 known substance; and can be scratched, polished, and 
 cut only by its own powder. Its specific gravity is 
 about ;.<>. 
 
 Tin- iiMi.il I'm in of Ilic diamond 
 
 crystal is a solid, bounded by 
 
 eight equal and r<|nil.ilrial tri- 
 faces ( Fig. 10,) called an 
 
 The art of cutting diamonds 
 was not known in Europe until 
 after the middle of the fifteenth 
 century, when it was invented by Louis Van Berguen, 
 of Bruges. 
 India has long been celebrated as the home of the 
 
A PIECE OF CHARCOAL. 
 
 109 
 
 finest diamonds, and in India the most famous locality 
 for them has been Golcondu; though, in fact, they arc 
 merely cut and polished there, being generally found in 
 the districts lying further south and east. Diamonds 
 arc also found in Malacca, Borneo, and other parts of 
 the East, in Bra/il, Australia, South Africa, Russia, 
 and the United States of America. Small and inferior 
 
 diamonds, and the fragments left when large stones 
 arc cut, are called "bort," and command a ready sale 
 for use in the arts, being reduced to "dust" in a steel 
 mortar, and used by lapidaries for cutting and polishing 
 all sorts of gems. Minute fragments of bort are used 
 for making the fine drills by which small holes arc 
 pierced in the jewels of watches. The use of small 
 
i io THE WORLD OF MATTER. 
 
 diamonds for cutting glass is well known. For this 
 purpose they are so mounted as to act upon the glass, 
 not by a sharp corner, but by a rounded edge. 
 
 Diamonds are cut into various forms, but principally 
 into brilliants and rose diamonds. The brilliant cut 
 is the most expensive, difficult, and beautiful. It has 
 an upper face or "bezel," which is octagonal, and this is 
 surrounded by many facets and as a rule the more the 
 better. Some varieties of the brilliant cut are shown 
 
 in Fig. 20. 
 
 Rose diamonds have a 
 flat base, above which are 
 two rows of triangular 
 facets, the six uppermost 
 uniting in a point to form a 
 sparkling pyramid. Fig. 21. 
 
 The largest diamond known weighs 367 carats 
 more than 2^ ounces and belongs to the rajah of 
 Mattan. It is egg-shaped, with an indented hollow 
 near the smaller end. 
 
 Many years ago the governor of Borneo offered for 
 it two war-brigs fully equipped, a number of cannon, 
 a quantity of powder and shot, and $500,000 in cash ; 
 but the rajah refused to part with it, owing to a super- 
 stition which connects it with the good fortune of his 
 family and the health of his province. 
 
 The Koh-i-noor, once a boasted possession of the 
 great Mogul, now belongs to the English crown. It 
 is said to have weighed 900 carats in the rough, but 
 now has been reduced to 123. 
 
A PIECE OF CHARCOAL. lit 
 
 The Regent, or Pitt diamond, weighing as cut 
 carats, is unrivaled in form and clearness. It was 
 found in Golconda, brought from India by the grand- 
 father of Pitt, the first Earl of Chatham, and by him 
 sold to the duke of Orleans for .13,000. It decorated 
 the hilt of the first Napoleon's sword of state, was 
 captured by the Prussians at the battle of Waterloo, 
 and now belongs to the king of Prussia. The Vanci 
 diamond, weighing 106 carats, belonged to Charles the 
 Bold, duke of Burgundy, who wore it in his hat at the 
 battle of Nancy, where he fell. 
 
 A Swiss soldier found it, and sold it to a clergyman 
 for a gulden about half a dollar. It passed into the 
 possession of Anton, king of Portugal, who sold it for 
 100,000 francs ($20,000). Later it became the prop- 
 erty of a French gentleman named Vanci. 
 
 A descendant of Vanci being sent as ambassador 
 was required by king Henry III. to leave the diamond 
 as a pledge. A servant was accordingly sent to carry 
 it to the king, but on the way he was attacked and 
 murdered by robbers, not, however, before he had con- 
 trived to swallow the diamond unobserved. His 
 master, confident of his fidelity, caused the body to be 
 opened, and recovered the jewel. This diamond came 
 into the possession of the Crown of England, and James 
 II. carried it to France in 1688. Louis XV. wore it at 
 his coronation. In 1835 ^ was purchased by a Russian 
 nobleman for nearly half a million dollars. 
 
 The following interesting account of the South 
 African diamond mines is condensed from the report of 
 George F. Kunz, for 1887. 
 
112 THE WORLD OF MATTER. 
 
 "The author of the Arabian Nights undoubtedly 
 thought he was imagining the most improbable thing 
 when he described the 'Valley of Diamonds,' found by 
 Sindbad the Sailor. Yet when compared with the Afri- 
 can mines that valley pales into insignificance. 
 
 "The primitive method of washing was carried on for 
 centuries by thousands, of slaves driven by the merci- 
 less whip of their master; but improved methods have 
 gradually been introduced. Steam railroads were run 
 into the mine. Millions of tons of reef were re- 
 moved. Dynamite was substituted for powder. 
 
 "After the broken earth is raised, it is put on the 
 'sorting-ground,' where it is partly disintegrated by 
 water and the weather. After being more finely 
 broken up, it is passed down into large vats con- 
 taining immense wheels, by which the rock is finely 
 divided. So accurately and powerfully does this ma- 
 chinery work, that all the diamonds, even those of 
 the size of a pin-head, are saved. Thirteen million 
 gallons of water are annually hoisted from the Kim- 
 berly mine. Ten thousand natives, 2,500 horses, mules, 
 and oxen, and 350 steam-engines are employed. 
 
 "During the last ten years, the South African mines 
 have yielded 27,878,587 carats, valued at .31,717,341. 
 
 "Before the organization of the great companies 
 which now work these mines as systematically and 
 economically as a woolen-mill, it is believed that about 
 one-quarter of the diamonds found were stolen by the 
 workmen. The natives use the most ingenious methods 
 for concealing the precious gems. On one occasion 
 
A PIECE OF CHARCOAL. 113 
 
 some officers, suspecting that a Kafir had stolen dia- 
 monds, gave chase and caught him, just after he had 
 shot one of his oxen. No diamonds were found upon 
 him, but he got off with them nevertheless, for he had 
 cunningly loaded his gun with them, and after the 
 departure of the officers he had the satisfaction of 
 digging them out ot the body of his dead ox, 
 
 "More diamonds weighing over 75 carats after cut- 
 ting have been found since the African mines were 
 opened than were ever known before. On March 28, 
 1888, there was found in the De Beers mine an oc- 
 tahedral crystal of diamond weighing 428^ carats. 
 
 "It was valued at $15,000. From its form it is be- 
 lieved that it can be cut into a brilliant of 200 carats; 
 hence it will be the largest known." 
 
 Besides the forms already described, namely, char- 
 coal, coke, lamp-black, bone-black, coal, lignite and 
 diamond, carbon also occurs in the form known as 
 graphite, plumbago, or "black-lead," which is used by 
 every one in ordinary pencils. 
 
 Of course there is no lead about it; it is only a form 
 of carbon. It can be artificially prepared by dissolv- 
 ing charcoal in melted iron, from which on cooling the 
 carbon is deposited as graphite. Graphite has a gray- 
 ish black streak, and a metallic lustre, although it is not 
 a metal. This would be indicated by its brittleness, as 
 well as by its infusibility. 
 
 It has a greasy or unctuous "feel," and is largely used 
 as a lubricant. It is not found pure, but contains a 
 small admixture of iron, silica, lime, alumina, etc. It 
 8 
 
ti4 TH WORLD OF MATTER. 
 
 sometimes occurs in tabular or scaly hexagonal crystals, 
 but usually massive. It is much less combustible than 
 hard coal, and burns with difficulty, even before the 
 blow-pipe, so that it is very useful for the manufacture of 
 melting-pots or "crucibles," which have to withstand 
 great heat. For this purpose, however, it is mixed 
 with half its weight of clay. Graphite is the chief 'in- 
 gredient in stove-polish. 
 
 QUESTIONS ON CHAPTER IO. 
 
 1. In what substances is carbon found? 
 
 2. What are the three leading forms of carbon? 
 
 3. Describe charcoal and its uses. 
 
 4. Mention other similar forms of carbon. 
 
 5. Explain the brilliancy of ordinary flame. 
 
 6. Of what is sugar composed? 
 
 7. Explain the brightness of the electric light. 
 
 8. Describe the diamond. 
 
 9. What is the usual form of its crystal? 
 
 10. What is "bort ?" 
 
 11. Describe graphite. Its uses? 
 
 12. Form of its crystals. 
 
CARBON, CONTINUED. 
 
 CHAPTER XI. 
 
 CARBON, CONTINUED. 
 
 In the preceding chapter we studied carbon, one of 
 the most abundant, common, and wonderful elements. 
 We found it appearing, as if by magic, under various 
 forms of the- utmost dissimilarity: as soft as velvet 
 and as black as night in lamp-black; harder than steel, 
 and as bright as day in the diamond ; now the chief con- 
 stituent in our illuminating oils and in our fuels, on ac- 
 count of its brilliant and fiery combustion with oxygen; 
 and again used for crucibles, because in the form of 
 graphite it will neither burn nor melt; in the form of 
 "bort" we saw it used to cut and scratch, and rasp the 
 hardest substances, and again as graphite we found it 
 used instead of oil to prevent the friction of wheels and 
 shafts. It is the hardest and the softest, the dullest and 
 the brightest, the cheapest and the dearest, the roughest 
 and the smoothest; in a word, the most contradictory 
 element in nature. 
 
 How then do we know its identity? Why are we 
 certain that charcoal and graphite and the diamond are 
 not really three distinct minerals instead of three forms 
 of the same mineral? 
 
 In the first place, notwithstanding these marked dif- 
 ferences there are also certain marked resemblances' be- 
 
Ii6 THE WORLD OF MATTER. 
 
 tween these forms of carbon. They are insoluble in 
 all known liquids; they are tasteless, inodorous, and 
 infusible; and wnen heated without free access of air, 
 they remain unchanged unless the temperature is very 
 high. 
 
 In the second place, we know that they are varie- 
 ties of the same substance, because if we burn the same 
 weight of diamond, graphite, and charcoal, we obtain 
 in each case the same substance, "carbon dioxide," CO 2 . 
 
 Fig. 22. 
 
 In each case the oxygen of the product comes from 
 the air, and in each case the weight of the carbon 
 in the product is exactly equal to the weight of the 
 diamond or graphite or charcoal consumed. 
 
 I will not ask you to verify this statement by burning 
 a diamond, unless you have plenty of them to spare; 
 but that experiment has repeatedly been performed, and 
 always with the same result. You may, however, with 
 much profit make the experiment of combining char- 
 
CARBON, CONTINUED. 117 
 
 coal with oxygen, in the following manner: Put a 
 small piece of charcoal into a hard glass tube. Heat 
 this tube by an alcohol flame, or a gas-jet, at the same 
 time passing oxygen through it. Pass the resulting 
 gas into clear lime-water. Arrange the apparatus as 
 shown in Fig. 22. 
 
 A is a bottle containing oxygen ; B is a hard glass 
 tube containing the charcoal; C is the jar of clear lime- 
 water. The reaction which takes place is represented 
 thus: 
 
 Ca0 8 H 8 -f CO, = CaCO s + H 8 O 
 Lime- Carbon Calcium Water, 
 water. dioxide. carbonate. 
 
 That is, the oxygen passing over the heated charcoal 
 combines with it to form a new gas, and this shows 
 itself on passing into the lime-water by combining with 
 the lime in solution, forming carbonate of lime, which 
 is insoluble in the water, and therefore sinks as a white 
 chalky powder. Now, no other gas except carbon di- 
 oxide acts in this way with lime-water. 
 
 Hence we may conclude that the gas formed is car- 
 bon dioxide. This is a useful test, and whenever under 
 ordinary circumstances an unknown gas passing into 
 lime-water produces an insoluble substance, we may 
 conclude that the gas is carbon dioxide. 
 
 Notice in passing the significance of the chemical ter- 
 mination ate. I have already shown you that the ter- 
 mination ide^ is used in names of the compounds of 
 two substances. Thus every oxide is a compound of 
 oxygen with one other element j every sulphide is a 
 
Ii8 THE WORLD OF MATTER. 
 
 compound of sulphur with one other element, etc. Now 
 the termination ate, is used in names of the compounds 
 of three substances, one of which is always oxygen, 
 and another of which is always indicated by that part 
 of the name which precedes the termination ate. 
 Thus every carbonate is a compound of oxygen, car- 
 bon, and one other substance. Every sulphate is a com- 
 pound of oxygen, sulphur, and one other substance, etc. 
 The name of the third element in every such compound is 
 written after, and connected by the word "of ;'' thus, 
 carbonate of calcium; sulphate of lead, etc.; or it may 
 equally well be written before, as calcium carbonate, 
 lead sulphate, etc. What is the composition of "silver 
 nitrate ?" 
 
 Now, by the lime-water test, as I was saying, it has 
 been proved that charcoal, graphite, and the diamond 
 are all varieties of the same substance, carbon, because, 
 all of them when combined with oxygen form a gas 
 which when passed into lime-water combines with the 
 lime and forms the insoluble substance, carbonate of 
 lime. This property of carbon, and other elements, by 
 virtue of which they exist in dissimilar forms, is called 
 allotropism. 
 
 Before leaving our study of carbon we must notice 
 that its affinity for oxygen is so great that, under proper 
 conditions, it is able to abstract the oxygen from 
 oxides. 
 
 This you may prove by the following experiment: 
 
 Mix two or three grains of powdered copper oxide, 
 CuO, with about one-tenth its weight of powdered 
 
CARBON, CONTINUED. 
 
 119 
 
 - 23- 
 
 charcoal. Heat the mixture in a tube fitted with a 
 small outlet tube as shown in Fig. 23. 
 
 Pass the gas which is given 
 .off into clear lime-water, con- 
 tained in a test-tube. Is it car- 
 bon dioxide? What evidence 
 have you that oxygen has been 
 removed from the copper 
 oxide? 
 
 Does the substance left in 
 the tube suggest the metal 
 copper ? 
 
 The reaction between the 
 charcoal and the copper oxide 
 2CuO+C=2Cu+CO 2 . 
 This abstraction of oxygen from a compound is 
 called reduction. Hence carbon, which effects it, is 
 called a reducing agent. It is extensively used in ex- 
 tracting metals from their ores, which are usually oxides. 
 Thus iron occurs in nature, not pure, but usually in 
 combination with oxygen. In order to get the pure 
 metal the oxygen must be extracted. This is accom- 
 plished by heating the ore with some form of carbon, 
 either charcoal or coke. 
 
 To conclude this lesson, let us study that most im- 
 portant compound of carbon and oxygen, which we 
 have already discovered and learned to recognize as 
 carbon dioxide, CO 2 . It is commonly called carbonic 
 acid. It has already been shown that carbon dioxide is 
 formed by the combustion of charcoal, In a similar 
 
 is represented thus 
 
120 
 
 THE WORLD OF MATTER. 
 
 manner it can be shown that this gas is formed when- 
 ever any ordinary material is burned. For example, 
 hold an empty bottle over the chimney of a burning 
 lamp so that it may receive the products of the com- 
 bustion of the oil. 
 
 You will soon find something besides ordinary air in 
 the bottle. Pour a little clear lime water into it, nnd 
 shake it up. Do you see any evidence of the presence 
 of carbon dioxide? 
 
 Burn a piece of paper in a jar, pour in a little lime- 
 water, and observe the result. 
 
 Consider now what is constantly going on in your 
 own body when you breathe. Perhaps you have never 
 thought of it at all ; perhaps you have supposed that in 
 breathing you simply draw a quantity of air into the 
 lungs and breathe the same quantity of air out again. Ti y 
 this experiment: Arrange a bottle 
 or flask of lime-water as in Fig. 24. 
 Placing your lips on the tube #, 
 you can either draw the outside air 
 through the lime-water, or blow the 
 air from your lungs through it. Try 
 first the experiment of drawing the 
 outside air through the water. Ob- 
 serve that so long as you do this no 
 effect is produced upon the water. 
 Now throw the air from your lungs 
 through the lime-water several times 
 See how the lime-water grows chalky, 
 This teaches you a very important lesson. 
 
 Fig. 24. 
 
 in succession. 
 
CARBON, CONTINUED. 121 
 
 The air that you breathe out is no longer pure, but 
 contains carbon dioxide. A sort of combustion is going 
 on in your lungs; the oxygen of the air is combining 
 with a portion of the carbon contained in your blood, 
 forming carbon dioxide, which is expelled from your 
 body when you breathe. This combustion of oxygen 
 and carbon in the lungs is one of the means by which 
 the body is so \\ T onderfully heated, that in summer and 
 winter it is maintained at the most uniform tempera- 
 ture, and with the least expenditure of fuel. In 
 twenty- four hours the lungs of a man convert seven 
 ounces of carbon into carbon dioxide. 
 
 Just here, I must call your attention to another prop- 
 erty of this gas. Into a jar of carbon dioxide plunge 
 a lighted taper. It is at once extinguished. If a mouse 
 or bird be dropped in the gas, its life goes out like the 
 flame of the taper. One or two breaths from your 
 lungs will furnish enough gas for this experiment. 
 
 Set a bottomless jar or bottle in a vessel of water. Close 
 it with a tight cork, in which a small tube is closely fitted. 
 
 Now inhale the air from the jar, and breathe it back, 
 as shown in the figure. Even one inspiration is enough 
 to spoil the air so that a taper will not burn in it. This 
 forcibly illustrates the necessity of an abundant supply 
 of fresh air in our homes and schools and churches. It 
 proves the need and indicates the character of good 
 ventilation. 
 
 The carbon dioxide must be removed as fast as it is 
 breathed out, and plenty of air containing its full meas- 
 ure of oxygen must be supplied. 
 
122 THE WORLD OF MATTER. 
 
 It must not be supposed, however, that carbon di- 
 oxide is a poisonous gas any more than nitrogen is. 
 
 Animals die in it merely because of a lack of oxy- 
 gen; they suffocate, as they do in water or as they 
 would in nitrogen. Most of the bad effects of breath- 
 ing the air of ill-ventilated rooms, such as headache, 
 drowsiness, etc., are caused by other impurities con- 
 tained in the breath. 
 
 The total amount of carbon dioxide formed by breath- 
 ing is almost alarming. Faraday estimates that the 
 lungs of London alone pour out 54.8 tons of this gas 
 every twenty-four hours! 
 
 Add to this the vast quantities that result from all 
 the combustion that is constantly going on, and you 
 will wonder that in the course of ages the whole at- 
 mosphere does not become unfit to breathe. What 
 prevents it? 
 
 Just here comes in one of the most beautiful and 
 wonderful contrivances of nature. This gas so deadly 
 to animal life is the very life and support of plants. 
 All the plants that grow upon the earth absorb car- 
 bon from the air. By the aid of sunlight and sun heat, 
 they decompose the carbon dioxide which animals 
 breathe out, and build up from it the complex com- 
 pounds of carbon which form their tissues, and set free 
 again the oxygen that is so necessary for animal life. 
 Give to plants a pure air like that which is best for us, 
 and they cannot live in it; give them carbon dioxide 
 and x>ther matters and they live and rejoice. 
 
 From this our dependence upon the sun is made evi- 
 
CARBON, CONTINUED. 123 
 
 dent. Every living thing is dependent upon the decom- 
 position of carbon dioxide by plants. This decompo- 
 sition cannot be effected without the aid of the sun. If 
 the sun should stop shining, all earthly life would 
 cease. 
 
 We have seen that when carbon dioxide passes into 
 lime-water it combines with the lime to form carbonate 
 of calcium, or chalk. As it is a poor rule that will not 
 work both ways, we ought, therefore, to be able to de- 
 compose chalk, or any form of carbonate of lime, and 
 get the carbon dioxide again. And this we can easily 
 do. If some moistened chalk be put into a retort and 
 heated red-hot carbon dioxide is driven off. 
 
 A simpler method of decomposing carbonates, how- 
 ever, is by the use of an acid. 
 
 Into a jar containing a few small chippings of chalk, 
 limestone, marble, or oyster-shellall varieties of car- 
 bonate of calcium pour a little hydrochloric acid. A 
 brisk boiling in this case called effervescence imme- 
 diately begins. 
 
 It is not steam, however, that is bubbling up, but a 
 gas. Test the contents of the jar with a taper. The 
 flame is instantly extinguished. Pass some of the gas 
 into lime-water; the chalky carbonate is formed. 
 
 Here then we have again carbon-dioxide, the very 
 same gas we formerly produced by the direct combina- 
 tion of carbon and oxygen ; and by this action of the 
 acid upon a carbonate we obtain tire gas more readily, 
 and in great abundance. 
 
 Having it, now, in sufficient quantity, familiarize 
 
124 THE WORLD OF MATTER. 
 
 yourself with it by as many experiments and tests as 
 you can invent. 
 
 Ascertain whether it is heavier or lighter than air. 
 See whether you can pour it out of a jar as you can 
 water. Pour some on a candle-flame. Balance a jar 
 on a pair of scales and pour some of the gas into it. 
 Does it affect the scales? 
 
 Carbon dioxide dissolves in water, one volume of gas 
 dissolving in about its own volume of water at the 
 ordinary temperature. When the pressure is increased 
 more gas dissolves; and when the pressure is removed 
 the gas again escapes. The "soda-water" of the drug- 
 gists is simply water charged with carbon dioxide under 
 pressure. 
 
 Much of the life and sparkle of ordinary spring 
 water is due to carbon dioxide dissolved in it. Spring 
 water is therefore a sort of natural soda-water. Rain- 
 water, like boiled or distilled water, has a flat, insipid 
 taste, but as it trickles down the mountain-side, and 
 dashes from ledge to ledge of rock, it dissolves the 
 gases in the air and becomes thus naturally aerated. 
 
 QUESTIONS ON CHAPTER II. 
 
 1. How can the identity of charcoal, graphite, and 
 diamond be proved? 
 
 2. What is the product of the combustion of car- 
 bon with oxygen? 
 
 3. What effect has this gas on lime-water? 
 
 4. What is the significance of the termination "ate?" 
 
 5. What is allotropism ? 
 
CARBON, CONTINUED. 125 
 
 6. What can you say of carbon as a "reducing- 
 agent?" 
 
 7. How is air changed by breathing? 
 
 8. Describe carbon dioxide. 
 
 9. What is the cause of the necessity for ventilation ? 
 
 10. Why does not the whole atmosphere become 
 tainted with carbonic acid ? 
 
 11. How can carbon dioxide be obtained from lime- 
 stone or chalk? 
 
 12. What is "soda-water?" 
 
126 THE WORLD OF MATTER. 
 
 CHAPTER XII. 
 
 A PIECE OF MARBLE. 
 
 You will remember that we were led to our study 
 of carbon by rinding bits of charcoal in a handful of 
 earth which we heated. In this earth we -have also 
 found water and quartz. 
 
 Let us now examine it further: Dry a tablespoon- 
 ful of garden-soil without burning it, and pour a few 
 drops of hydrochloric acid upon it. If your garden is 
 like mine you will notice a brisk effervescence; which 
 will remind you of the experiment described in the 
 preceding chapter, by which we obtained carbon dioxide 
 by treating carbonate of lime with hydrochloric acid. 
 
 We then used lime dissolved in water as a test for 
 the carbon dioxide, and decided that any gas which 
 passing into lime-water at ordinary temperature ren- 
 ders it chalky is carbon-dioxide; and we learned that 
 the chalk thus formed is carbonate of calcium. 
 
 With this knowledge we may now work backward, 
 and make the production of carbonic oxide by the action 
 of hydrochloric acid upon a mineral a test for carbon- 
 ate of calcium; for this is the only common mineral 
 which effervesces freely with dilute hydrochloric acid 
 at ordinary temperatures. 
 
 We, therefore, may reasonably conclude that our 
 
A PIECE OF MARBLE. 127 
 
 soil contains calcium carbonate, and proceed to study 
 this substance in some detail. It will be convenient, as 
 in the case of quartz, to use larger specimens than the 
 minute grains mingled with the soil, and we will there- 
 fore take a piece of white marble specimen No. 20 in 
 the collection. 
 
 Repeating the experiment with hydrochloric acid we 
 obtain again a plentiful supply of carbon dioxide, which 
 we allow to escape, however, as we are now more 
 interested in the other elements in the carbonate. The 
 reaction is expressed as follows: 
 
 CaCo 3 +2HCl==C0 8 -fH 2 O+CaCl s . 
 
 This means that calcium carbonate and hydrochloric 
 acid give, besides the carbon dioxide, water and calcium 
 chloride. The chloride is dissolved in the water. 
 
 Evaporate the solution to dryness. 
 
 The colorless needle-shaped crystals remaining are 
 calcium chloride, still combined with a portion of 
 water. In this condition it is called hydrated calcium 
 chloride. Expose this substance to the air. Observe 
 how rapidly it becomes moist by absorbing water from 
 the air. This property makes it valuable for drying 
 gases. In many experiments, gases containing undesira- 
 ble moisture are passed through tubes containing cal- 
 cium chloride, which absorbs the water and leaves the 
 gases dry. If hydrated calcium chloride be strongly 
 heated it fuses and parts with all its water, becoming 
 simply CaCl 2 . 
 
 Calcium chloride consists of two very important ele- 
 
128 THE WORLD OF', MATTER; 
 
 inents> calcium^ which we are now specially in search 
 of, and chlorine, a gas which we shall consider later. 
 
 Unfortunately it is not easy to separate them. I say 
 "unfortunately," for it is important for you to become 
 familiar with the leading elements in their purity, as 
 far as possible. The analysis of calcium chloiide, 
 though difficult, is not impossible, and is effected by 
 fusing it, and passing a powerful current from an elec- 
 tric battery through it. If you have some friend who 
 is an expert chemist or mineralogist, it will be worth 
 your while to get him to perform the experiment for 
 you. You will then see the calcium separating from 
 the chlorine in the form of minute drops or globules. It 
 is a yellowish-white metal, between gold and lead in 
 hardness. It graduaUy grows dull, or tarnishes, on .ex- 
 posure to the air. 
 
 In order to keep it bright it is kept under naptha. It 
 can be rolled into sheets and hammered into leaves. At 
 a red heat it melts and burns with a dazzling light, ac- 
 companied with showers of sparks. When brought 
 into contact with wa^er it unites strongly with the oxy- 
 gen, forming lime, CaO, and setting the hydrogen free. 
 This is another pi oof of the composition of water, and 
 is a very interesting and instructive experiment. You 
 remember that we have already seen that the oxygen of 
 water will desert its comrade, hydrogen, for the sake of 
 uniting with red-hot iron. The attraction between 
 oxygen and calcium is so much greater that oxygen 
 combines with it at ordinary temperature. 
 
 Returning now to our marble, CaCO 3 , we will try 
 
A PIECE OF MARBLE. 129 
 
 to decompose it without the help of acid. Put a piece 
 of marble into a stove or furnace, and leave it over 
 night. On taking it out you at once perceive a decided 
 change in its appearance, and a more decided change 
 in its properties. It has, in fact, been converted into 
 quicklime, the carbon dioxide having been driven off 
 by heat. 
 
 The decomposition is represented thus: 
 
 CaC0 3 CaO + CO 2 
 
 Calcium Carbonate. Quicklime. Carbon dioxide. 
 
 Expose, now, one-half of the quicklime to the air, 
 and place the remainder in a cup half full of water. 
 
 The portion exposed to the air gradually absorbs 
 both moisture, H^O, and carbon dioxide, CO 2 , and is 
 resolved again into calcium carbonate, in the form of 
 a white powder. This is commonly called air-slaked 
 lime. 
 
 The portion put into the cup rapidly combines with 
 the water, becomes very hot, crumble^ into a fine pow- 
 der, and is converted into the hydroxide or hydrate of 
 calcium. The result of this water -slaking is thus repre- 
 sented : 
 
 CaO-fH 2 O=CaO 2 H s 
 
 This substance is partially soluble in water, and forms 
 lime-water. Pour the slaked lime from your cup into 
 a jar, or wide-mouthed bottle, containing perhaps a pint 
 of water. The unclissolved lime will settle to the bot- 
 tom. After some hours the solution above will become 
 clear. Pour this off carefully for experiment. 
 9 
 
i$6 THE WORLD OF MATTER. 
 
 What takes place when some of the solution is ex- 
 posed to the air? When the gases from the lungs are 
 passed through it? When carbon dioxide is passed 
 through it? When dilute sulphuric acid is added? 
 
 Slaked lime mixed with sand is used for mortar, 
 whitewash, and plastering. When the mortar is spread 
 and exposed to the air it takes up carbon dioxide, and 
 thus the calcium oxide, or lime, becomes calcium car. 
 bonate again, and hardens into stone. 
 
 Notice right here a curious property of carbon 
 dioxide. We have repeatedly seen that a small quan- 
 tity of it, passed into lime-water, unites with the lime, 
 forming the chalky carbonate of calcium. Now repeat 
 that experiment, but allow the gas to pass into the lime- 
 water for a longer time. You will be surprised to ob- 
 serve that the chalky water gradually grows clear again. 
 The explanation of this phenomenon is found in the 
 fact that water saturated with carbon dioxide dissolves 
 the carbonate. To this property we owe the formation 
 of caves in limestone regions with their beautiful 
 stalactites which depend like icicles from the roof, and 
 the curious stalagmites which stand up like inverted 
 icicles from the floor. Water containing carbon dioxide 
 trickles through crevices and dissolves away the 
 limestone little by little until in the course of ages 
 large c'aves are formed. Then the water holding cal- 
 cium carbonate in solution drips slowly from the roof, 
 and as the water evaporates little particles of the carbonate 
 are deposited, until the long glistening stalactites are 
 formed; while the drops that fall to the floor build up 
 
A PIECE OF MARBLE. 131 
 
 in like manner the crystalline stalagmites in many 
 fantastic shapes. 
 
 The following simple experiment reveals a property 
 of lime or calcium oxide which you might not other- 
 wise observe; namely, its power in counteracting the 
 effect of an acid. 
 
 The most common test for acids depends upon the 
 fact that they instantly change the color of certain sub- 
 stances. One of the substances whose color is most 
 easily and noticeably changed by an acid is called 
 litmus. Litmus is a coloring matter which is obtained 
 from several sorts of lichen or fungus. The lichens are 
 powdered and steeped in ammonia-water until they are 
 decomposed. 
 
 After further treatment, not necessarily described 
 here, a peculiar purple dye is obtained, which is the 
 litmus of commerce. 
 
 The interesting fact about this litmus is that upon the 
 addition of any acid it turns red; and again, upon the 
 addition of lime or any alkali, it turns blue. This you 
 should now prove by several experiments. You will 
 find in the collection accompanying this book (specimen 
 No. 21) apiece of blue "litmus-paper,'* which is simply 
 a piece of ordinary unsized paper, dyed with an alcoholic 
 solution of litmus and treated with some alkali. 
 
 You can turn a piece of this blue paper red by 
 moistening it with an acid, or more easily by moistening 
 it and holding it over burning sulphur; a burning match 
 will answer the purpose. You can get this paper, both 
 red and blue, at a drug-store, or, better, you can buy 
 litmus and prepare it yourself. 
 
i$2 THE WORLD OF MATTER. 
 
 Now, to see the effect of lime, moisten a piece of red 
 litmus-paper, and place a few grains of quicklime 
 upon it; it turns blue. Try the effect cf a little pow- 
 dered marble. 
 
 Now heat some of the marble red-hot, either by lay- 
 ing it on a piece of charcoal and applying a blcw-pipe 
 flame, or by holding it in the flame with a pair of for- 
 ceps. 
 
 Place this burned marble upon the moistened red 
 paper, and note the effect. Here is another proof that 
 calcium carbonate, when heated, parts with i f .s carbon 
 dioxide, and become calcium oxide, or quicklime. 
 
 Instead of using the paper, you may try the same 
 experiments with more striking results upon a glass 
 full of the red solution of litmus. 
 
 It is to this antacid action of the lime fchit it 
 owes its valuable medicinal properties, lime-water be- 
 ing one of the best remedies for acidity and irritability 
 of the stomach. 
 
 In the ashes which remain after the combustion of 
 any vegetable matter a proportion of lime is found. 
 This shows that calcium oxide is one of the most im- 
 portant plant-foods, and indicates the use of lime as ^ 
 fertilizer. 
 
 The carbonate is sometimes applied without previous 
 preparation, in the form of marl or chalk; but usually 
 after having been calcined, and reduced to the powdered 
 oxide by slaking. 
 
 The quantity of calcined lime used varies from three 
 ';o eight tons to the acre ; the larger quantity being re- 
 
A PIECE OF MARBLE. 133 
 
 quired for "strong" land, or land holding much vegeta- 
 ble matter. The fertilizing effect of lime is due even 
 more to its chemical effects upon the soil than to the 
 food it directly affords to the crops. It promotes the 
 decomposition of all kinds of vegetable matter in the 
 soil, and corrects any acidity present, and thus tends to 
 destroy those weeds which flourish in an acid soil. On 
 certain kinds of soil, the finer grasses do not thrive un- 
 til the land has been limed. Lime is the only reliable 
 cure for "finger-and-toe," "club-root," "ambury," in 
 turnips. 
 
 In the preceding chapter we learned that the bril- 
 liancy of the electric light is due to the incandescence 
 of some highly heated infusible substance, usually carbon. 
 
 Lime is infusible, and when strongly heated yields a 
 light fairly rivalling the electric lamp. A jet of oxygen 
 and hydrogen burning together in an intensely hot 
 Hume is directed against a cylinder of lime. The light 
 produced in this way has been seen for more than one 
 hundred miles. It is called the "Drummond light," 
 from its inventor, Captain Thomas Drummond. 
 
 To calcium carbonate, the mineralogists have given 
 the name calcitc. In nature calcite occurs as marble, 
 chalk, limestone, shells, corals and pearls, and in a 
 crystallized form known as calc-spar. 
 
 In all its forms it is readily distinguished from quartz 
 by its inferior hardness, and by its effervescence with 
 acids. Its hardness is 2.7. Shells, corals, and pearls, 
 being evidently animal products, will more properly be 
 considered in the succeeding volume of this series. 
 
134 THE WORLD OF MATTER. 
 
 Common limestone, chalk, and marble are also 
 largely derived from organic structures, but for the 
 present they may be considered as ordinary minerals. 
 
 Limestones are either compact or granular, the com- 
 pact form breaking with a smooth surface, often shell- 
 like or conchoidal. Granular limestones, of which, 
 indeed, marble is a fine variety, are crystalline, and 
 break with a more or less sugary fracture. Ordinary 
 limestone is one of our most important building ma- 
 terials. 
 
 Marble is capable of a high polish, and is familiar to 
 all in the form of table-tops, mantels, floors, and monu- 
 ments. 
 
 The purest and finest marble is used in sculpture, and 
 is called statuary marble. The finest qualities come 
 from Carrara, in Italy, and from the Island of Paros, 
 whence the celebrated Parian marble of the Greek 
 sculptors takes its name. 
 
 Many ancient temples were built of marble, notably 
 the Parthenon at Athens. The capitol at Washington 
 is built of white marble, much of which came from the 
 quarries at Lee, Massachusetts. Excellent marble is 
 found abundantly in Vermont, Western Massachusetts, 
 Eastern New York, and Western Connecticut. Berk- 
 shire County, Mass., rests on a marble and limestone 
 floor, at least a thousand feet in thickness. 
 
 Many varieties of marble are beautifully shaded, 
 veined, and mottled. 
 
 Chalk is a soft earthy variety of limestone, forming 
 great layers, or "strata," in the earth, and from its animal 
 
A PIECE OF MARBLE. 135 
 
 origin and structure proving of even more interest to 
 the geologist than to the mineralogist. It is generally 
 of a yellowish tinge, but sometimes of snowy whiteness. 
 It is easily broken, has an earthy fracture, is rough to 
 the touch, and clings slightly to the tongue. It generally 
 contains a little silica, alumina, or magnesia. It is 
 sometimes so compact as to be available for build- 
 ing. 
 
 It can be buried into quicklime, and nearly all the 
 houses in London are cemented with mortar made of 
 chalk. 
 
 When freed from its particles of silica by pounding 
 and washing, it becomes "whiting," familiar to every 
 housewife. Carpenters and others use it for making 
 marks which are easily erased. The blackboard with 
 its chalk or crayon has come to be as familiar in the 
 lecture-room of the university as in the humblest village 
 school. 
 
 Calc-spar is the crystallized variety of calcite, and 
 it occurs in several hundred shapes, all modifications of 
 the rhombohedron, which, you remember, is also the 
 regular form of an ice-crystal (specimen No. 22). 
 This represents a variety very abundant at Lock- 
 port, N. Y., and known as "dog-tooth spar." All 
 varieties of calc-spar, split or "cleave" into rhombohe- 
 drons. Transparent specimens have the property of 
 making objects viewed through them appear double. 
 This " r^ jerty is called double refraction. 
 
136 THE WORLD OF MATTER. 
 
 QUESTIONS ON CHAPTER 12. 
 
 1. What is the effect of hydrochloric acid upon car- 
 bonate of lime? 
 
 2. What is the chemical composition of marble? 
 
 3. What other substances have the same composi- 
 tion? 
 
 4. How can the element calcium be obtained? De- 
 scribe it. 
 
 5. What effect has its metal upon water? 
 
 6. How can marble be decomposed without acid? 
 
 7. What are the properties and uses of lime? 
 
 8. Explain the Drummond light. 
 
 9. What is litmus-paper? 
 
 10. What is calcite? Name several varieties, 
 n. Why is the carbonate of calcium of interest to 
 the geologist? 
 
 12. What is chalk? 
 
 13. Describe crystallized calcite. 
 
CLAY. 137 
 
 CHAPTER XIII. 
 
 CLAY. 
 
 The most noticeable substance remaining in our hand- 
 ful of earth, now that we have removed the water, 
 quartz, charcoal, and limestone, is the clay that we 
 found binding these substances together. 
 
 Clay owes its origin to the decomposition of minerals 
 and rocks, and is rather a mixture of the fine particles of 
 other disintegrated substances than a simple mineral. 
 We shall, therefore, reserve our study of its formation 
 until we come to treat of geology, but it is of present 
 interest to us on account of the decomposed feldspar 
 which enters largely into its composition, and particularly 
 on account of the metal, aluminum, which next to silicon 
 is the leading element in this feldspar. Clay is essen- 
 tially a silicate of aluminum. Clay consisting of pure 
 aluminum silicate is called kaolin. 
 
 Clay is a kind of soil marked by smoothness and 
 stickiness, or "tenacity," and by the fact that it can be 
 ''worked" or molded into any desired shape. It is used 
 by sculptors in modeling the forms which are after- 
 ward to be cut from marble or cast in bronze. On 
 baking it becomes as hard as stone, and is therefore of 
 great value for the manufacture of brick and tiles. 
 
 The various forms of porcelain and earthenware are 
 
138 THE WORLD OF MATTER. 
 
 made of baked clay, covered with some substance 
 which melts at a high temperature, and forms a glaze 
 or enamel binding the clay together, giving it a smooth 
 surface, and rendering it impervious to liquids and air, 
 by rilling up the pores which abound in clay baked 
 without an enamel. 
 
 For the manufacture of porcelain the finest white or 
 china clay is used, while for common earthenware 
 colored clays may be used. The glaze used for porce- 
 lain is usually finely powdered feldspar. For ordinary 
 earthenware, a "salt-glaze" is used. This is made by 
 throwing common salt into the furnaces in which the 
 ware is baking. The salt, decomposed by heat, causes 
 a deposit of fusible silicate upon the surface of the clay. 
 
 When clay becomes firmly compacted it becomes slate. 
 
 The peculiar clayey, or argillaceous odor of slate is 
 enough to indicate its identity with clay, even if we did 
 not know the history of its formation. We find many 
 degrees of hardness in clay. It sometimes becomes 
 very hard by simple drying, as we often see in dry 
 weather, but this is not slate, and no amount of mere 
 drying will convert clay into slate, for dried clay when 
 moistened with water is easily brought back to its putty- 
 like or plastic state. To make a good slate the hardening 
 must be the result of pressure, as well as dryness, aided 
 probably to some extent by heat. True slate is a per- 
 manently hardened, but not burnt clay, which will not 
 become soft when wet. 
 
 Slate is easily scratched with a knife, and is readily 
 distinguished from limestone, because it does not effer- 
 
CLAY. 139 
 
 vesce with acid. It naturally shows the same varieties 
 in color and composition as clay. A good assortment 
 of colors is afforded by the roofing-slates. Specimen 
 No. 23 is a typical slate, for it not only has a compact 
 structure, and an argillaceous odor, but it is very plainly 
 formed in layers, or, as geologists say, it is distinctly 
 stratified. This means not simply that it splits into 
 leaves, but that it was formed by the deposition of lay- 
 ers of clay, held in suspension in water. Ordinary 
 roofing-slates, like specimen No. 24, rarely show true 
 stratification. The thin layers into which they split 
 have been developed by pressure after the formation of 
 the slate by deposition, and they do not follow the lines 
 of the real stratification. This structure is known as 
 "slaty cleavage." Some roofing slates, known as "rib- 
 bon-slates," show bands of various colors across the flat 
 surfaces. These bands indicate the lines of the true 
 bedding, or natural layers of deposition. 
 
 Slate which splits easily into thin, brittle layers, 
 parallel with the bedding, is known as shale. 
 
 We must now consider the mineral feldspar, to which 
 the origin of most of the slates and clays can be traced. 
 It must be borne in mind, however, that feldspar is the 
 name of a group of minerals, rather than of any one 
 species. Geologically, the feldspars are the most im- 
 portant of all minerals for more than any others, with 
 the possible exception of quartz, they enter into the 
 composition of rocks, which, by the way, are large 
 mixtures or aggregations of minerals, no single crys- 
 tal or mineral-grain being properly called a rock. 
 
140 THE WORLD OF MATTER. 
 
 The abundance of the feldspars is well expressed by 
 the name feldspar being simply the German for field- 
 spar, and implying that it is the common spar or min- 
 eral of the fields. 
 
 Like clay, the feldspars are essentially silicates of 
 aluminum, with the addition of smaller quantities of 
 other elements. 
 
 Their general characteristics, including easy cleavage 
 in two directions at right angles to each other or nearly 
 so, are well exhibited in the common variety, orthoclase, 
 specimen No. 25. 
 
 This is the most abundant of all minerals, forming 
 the principal part of granite, gneiss, and many other 
 important rocks. Its most common colors are white, 
 gray, pink, and flesh-red. 
 
 You may determine for yourself the physical prop- 
 erties of orthoclase, and we will postpone to a later 
 chapter the examination of other varieties of feldspar. 
 
 Orthoclase is a silicate of aluminum and potassium; 
 that is, it is composed of silicon, oxygen, aluminum, 
 and potassium, its chemical formula being K 3 Al 2 Si 6 
 
 Q,. 
 
 The metal aluminum cannot readily be obtained di- 
 rectly from feldspar or clay, and the various processes 
 of its manufacture are too complicated to be explained 
 in detail. In general, an aluminum sulphate is first 
 formed by decomposing clay with sulphuric acid, This 
 sulphate of aluminum is then combined with an alka- 
 line sulphate to produce alum. Then, to a solution of 
 the alum, ammonia is added, and a white powder settles 
 
CLAY. 141 
 
 to the bottom of the solution. This powder on being 
 heated becomes pure alumina, which is a compound of 
 aluminum and oxygen, Al^Og, and is the only oxide of 
 aluminum known. . Finally, this alumina is mixed with 
 carbon, and subjected to the action of a powerful cur- 
 rent of electricity, which separates the metal aluminum 
 from the oxygen. The apparatus used for this purpose 
 is known as the Cowles electric furnace. There are 
 other processes for obtaining this metal, but this is one 
 of the best and cheapest. 
 
 The cheap production of aluminum from clay is one 
 of the important practical problems needing to be 
 solved, because the properties of this metal are such as 
 to render it of great value, while its abundance in 
 its natural compounds is so unlimited that nothing but 
 the difficulty and expense of preparing it prevents it 
 from taking (for many purposes) the place of iron, to 
 which in some respects it is greatly superior. In the 
 first place it is but little more than one-third as heavy, 
 its specific being 2.7, while that of iron is 7.8; more- 
 over, it has a beautiful color and lustre resembling silver, 
 and it does not easily rust or tarnish on exposure to dry 
 or moist air. It is exceedingly strong, and yet is so 
 malleable that it can be hammered into thin sheets and 
 wrought into any desired form. 
 
 A slight alloy of copper has been found to add yet 
 more to its toughness and strength. Serious drawbacks 
 to its usefulness, however, are its liability to be at. 
 tacked by salt, and by vegetable acids, the difficulty of 
 soldering it, and the difficulty of working its hard alloys. 
 
142 THE WORLD OF MATTER. 
 
 Alumina, the oxide from which, as we have seen, 
 the metal aluminum is obtained, occurs crystallized 
 in nature in the forms of corundum, ruby, and sap- 
 phire. 
 
 Corundum is inferior only to the diamond in hard- 
 ness. It is generally of a dull and muddy appearance, 
 even in its hexagonal crystals. 
 
 A common variety is emery, which is universally 
 known from its' use in polishing and cutting gems, 
 metals, and glass. 
 
 Ruby and sapphire are identical except in color, and 
 are, indeed, varieties of corundum. No gems, with 
 the possible exception of the diamond, are so highly 
 prized. They are transparent and brilliant. The finest 
 rubies, which are as red as fire, are found in Burmah 
 and Siam, and the finest sapphires, of an exquisite blue 
 color, come from Ceylon. In Burmah, when a very 
 fine stone is found, a procession of officers and soldiers 
 mounted on elephants is sent to receive it. One of the 
 titles of the king of Burmah is "Lord of the Rubies." 
 A ruby weighing more than twenty carats is commonly 
 called a carbuncle. A perfectly pure crystal of corun- 
 dum, transparent and colorless, is known as white 
 sapphire, and has been mistaken for the diamond. 
 
 QUESTIONS ON CHAPTER 13. 
 
 } 
 
 1. What is clay? Its uses? 
 
 2. Describe slate, and its origin. 
 
 3. Distinguish between the "stratification" and 
 "cleavage" of clay. 
 
CLAY. M 
 
 4. Describe orthoclase. Its composition? 
 
 5. How is aluminum obtained, and what are its 
 properties ? 
 
 6. Mention and describe three varieties of crystal- 
 lized alumina. 
 
THE WORLD OF MATTER. 
 
 CHAPTER XIV. 
 
 POTASSIUM MICA. 
 
 In our study of clay we learned that it is essentially 
 a hydrous silicate of aluminum; but besides silicon, 
 oxygen, hydrogen, and aluminum, it sometimes con- 
 tains another element^ namely, potassium. 
 
 We might also have found traces of potassium in 
 the ashes left mingled with charcoal by the burned 
 sticks and roots, for when vegetable material is burned 
 the potassium remains behind, chiefly in the form of 
 potassium carbonate. When wood-ashes are treated 
 with water, the potassium carbonate dissolves, and may 
 be obtained, though in an impure state, by evaporating 
 the solution. The substance thus obtained is popularly 
 called potash, or pearl-ash. Its chemical formula is 
 K 2 CO 3 . 
 
 Treat two or three pounds of wood-ashes with water. 
 Filter the solution and test its effect upon red litmus- 
 paper. You observe its strong alkaline reaction in 
 turning the red paper blue. 
 
 Evaporate the solution to dryness, collect the residue, 
 and heat it in a test-tube with a little hydrochloric acid. 
 The gas given off you will recognize as carbon dioxide 
 if you pass it into clear lime-water. 
 
 The metal potassium was first obtained by passing 
 
POTASSIUM MICA. 145 
 
 a strong electric current through caustic potash, HKO. 
 It is now prepared by heating potash and carbon to- 
 gether to a high temperature in an iron retort. The 
 carbon and the oxygen of the potash combine and 
 escape as a gas, hydrogen is set free, and the metal 
 potassium, which vaporizes at red heat, distils over after 
 the manner of water. 
 
 The preparation of this metal is attended with many 
 difficulties and extreme danger, and should not be at- 
 tempted except by experts. 
 
 When obtained in its pure state, potassium is a bright, 
 silver-white metal, light enough to float on water, and 
 so soft that it can be easily cut with a knife. It rapidly 
 absorbs oxygen when exposed to the air, and gradually 
 becomes converted into a white oxide. 
 
 It unites with the oxygen of water with great energy, 
 setting the hydrogen free, and igniting it at the same 
 time by the heat evolved by the combination. The 
 flame of hydrogen thus ignited is tinged with a pecu- 
 liar purple, which is characteristic of potassium. 
 
 In consequence of these properties of potassium it 
 cannot be kept in the air, but must remain until desired 
 for use under some oil, like petroleum, upon which it 
 does not act. Throw a small piece of potassium, not 
 larger than a pea, upon water. Study the result care- 
 fully. 
 
 You may recollect that in our study of niter it was 
 incidentally mentioned that niter is a compound of 
 nitrogen, with oxygen and potash. This niter or, to 
 speak chemically, potassium nitrate, KNO 3 , is largely 
 
 C', *> 
 
146 THE WORLD OF MATTER. 
 
 used, you remember, in the manufacture of gun-powder 
 and fire-works. 
 
 One of our first experiments was the preparation of 
 oxygen by heating together oxide of manganese and 
 potassium chlorate. This potassium chlorate may be 
 obtained by passing chlorine gas through a hot solution 
 of caustic potash. It occurs in white rhomboidal crys- 
 tals of a pearly lustre, has a cooling taste, and fuses 
 easily. It parts so readily with its oxygen, that if sub- 
 stances with a strong affinity for that gas, such as car- 
 bon, sulphur, or phosphorus, are heated with it, even so 
 slightly as by friction, they combine with the oxygen 
 with explosive force. Chlorate of potash is therefore used 
 in the manufacture of friction-matches, together with 
 phosphorus and sulphur. We need not consider now 
 any of the other numerous compounds of potassium. 
 It is an important element, and widely distributed in 
 nature, though always in the form of some compound, 
 chiefly in the various feldspars. 
 
 From these, however, it has been hitherto impracti- 
 cable to separate it until they have become disintegrated 
 to clay, and until it has been taken up by plants 
 and transformed into vegetable tissues, from the ashes 
 of which we can dissolve potash as we have seen, and 
 from the potash finally separate the potassium. 
 
 In the soil which we examined with a microscope, 
 we found besides the minerals already studied a quan- 
 tity of "thin, scale-like, and glistening" particles. These 
 are flakes of mica, and although so different in appear, 
 ance are of nearly the same chemical composition as the 
 
POTASSIUM MICA. 147 
 
 feldspars. Clay, which is derived from feldspar, 
 is a hydrous silicate of aluminum and potassium. 
 Mica is a silicate of aluminum and potassium, with 
 the frequent [addition of small quantities of other ele- 
 ments. 
 
 Mica, like feldspar, is the name of a group or family 
 of minerals consisting of several species. The most im- 
 portant characteristics of this group are its remarkable 
 cleavage, parallel with the basal planes of the crystals, 
 the wonderful thinness of the plates into which it 
 splits sometimes no thicker than the one 3oo,oooth 
 part of an inch and above all the elasticity of these 
 plates, or lamellce. By these peculiarities the identifi- 
 cation of mica is rendered easy and certain. 
 
 Of the several species of mica only two need be 
 noticed now, muscovite and biotite, specimens 26 and 
 27. Determine for yourself the physical properties of 
 these specimens. 
 
 Muscovite contains a much larger percentage of silica 
 than biotite, a much smaller proportion of iron (some- 
 times none), and only about one half the amount of 
 magnesia. 
 
 The colors of muscovite are light, being white, gray, 
 and more rarely brown and yellow ; those of biotite 
 are dark, ranging from dark green to black. 
 
 Biotite has also the peculiar property of showing two 
 different colors when held against the light, if the speci- 
 men is turned from side to side. This property is 
 called dichroism, and biotite is a dichroic mineral. This 
 is not true of muscovite. After feldspar, mica is the 
 
148 THE WORLD OF MATTER. 
 
 most common and abundant silicate, and forms a large 
 part of such rocks as granite, gneiss, and mica-schist. 
 Its use instead of glass in stoves, lanterns, and other 
 places where there is great heat, is familiar. In Si- 
 beria, Peru, and Mexico, where plates a yard in diam- 
 eter are found, mica is used as a substitute for glass in 
 windows. 
 
 Mica sometimes occurs in beautiful rhombic or hex-" 
 agonal crystals. 
 
 The curious fact may be worth noting that three of 
 the substances which we have found mingled in our 
 handful of earth, namely, chalk, charcoal, and clay, 
 have for hundreds of years been somewhat fantastically 
 joined together as emblematical of the characteristics 
 of true and loyal service, representing freedom, fer- 
 vency, and zeal. 
 
 'What is freer than chalk," runs the old proverb, 
 "the slightest touch of which leaves a trace behind ? 
 What is more fervent than charcoal? for when prop- 
 erly heated it causes the most obdurate metals to yield. 
 What is more zealous than clay, which adheres to 
 everything it touches, and which as earth brings forth 
 every living tree and herb?" 
 
 We certainly cannot contemplate without interest 
 these most common minerals, when we consider 
 their inestimable value to mankind ; and we cannot fail 
 to be reminded of the danger of condemning anything 
 as worthless from its external appearance, since we 
 have seen chalk glorified in the calcium light, and in 
 the form of marble preserving the beautiful conceptions 
 
POTASSIUM MICA. 149 
 
 of the world's most famous artists; charcoal turning 
 night into day when set in the electric lamp, and excit- 
 ing the admiration and desire of mankind when 
 crystallized in the diamond; and clay yielding as 
 if by magic now the bright and untarnished 
 metal, aluminum, and again the brilliant and ex- 
 quisitely colored crystals of the sapphire and the 
 ruby; nor should we forget those less dazzling but 
 more important properties of these substances by virtue 
 of which they have contributed more than any others 
 to the education and refinement of mankind: the chalk 
 and clay giving to our schools and colleges their crayons 
 and slates; and the charcoal furnishing the basis of the 
 ink which renders writing and printing possible, and in 
 the form of graphite giving us the lead-pencil, which is 
 even more powerful than the pen. These products are 
 of far more value than metals or gems, for "the price 
 of wisdom is above rubies." 
 
 QUESTIONS ON CHAPTER 14. 
 
 1. Describe potassium. 
 
 2. Uses of potash? 
 
 3. What is mica? 
 
 4. Describe biotite. 
 
 5. Describe muscovite. 
 
ISO THE WORLD OF MATTER. 
 
 CHAPTER XV. 
 
 A LUMP OF SALT. 
 
 In our study of water we learned that it has the power 
 of dissolving a great many substances, and we noted 
 particularly the fact that rivers in their progress to the 
 sea carry the elements of salt, enough in the ag- 
 gregate to make the whole ocean briny. Salt is so uni- 
 versally distributed that we feel almost certain that a 
 portion of it is contained in our garden soil, although we 
 have not as yet detected it in the specimens of earth which 
 we have examined. Let us make a special search for 
 it. It has long been known that many substances when 
 strongly heated in a nearly colorless flame impart to 
 the flame peculiar colors by which the substance heated 
 may be recognized. 
 
 In order to test this the wick of your alcohol lamp 
 should be clean, and the flame should give little light, 
 being yellow only at the tip. 
 
 You can get a good alcohol flame by taking a clean 
 wick, doubling it, and leaving the doubled part outside 
 for the flame. Fig. 25. 
 
 If the flame becomes colored by particles of minerals 
 falling on the wick, take the wick out and double it at 
 a fresh place. 
 
 Take a small grain of salt between the tips of a pair 
 
A LUMP OF SALT. 
 
 of platinum-pointed forceps, or on a small loop made in 
 the end of a piece of platinum wire, and pass it up and 
 
 down the edge of the blue 
 part of the alcohol flame, 
 moving it from below at the 
 side of the wick up toward 
 the tip. Notice the bright 
 yellow color it imparts to 
 the flame. This peculiar 
 yellow flame is character- 
 istic of one of the two ele- 
 ments contained in common 
 sail, namely sodium, and is 
 proof of the presence of 
 that element in some form 
 in the flame. Now, salt is 
 one of the most common 
 compounds of sodium, and 
 if our specimen of soil causes 
 this yellow color to appear in the flame we may fairly 
 infer that it contains more or less salt. 
 
 Try it. Clean your forceps or wire and hold a little 
 of the earth in the flame just as you held the salt. Do 
 you see the same yellow color? 
 
 We shall not spend much time in studying salt as 
 such, for our main purpose just now is to get at the 
 elements of which it is composed. We will notice, 
 however, its familiar and peculiar taste, its whiteness, 
 its fusibility, and the great ease with which it dissolves 
 in water. It crystallizes in transparent cubes, as may be 
 
 Fig 25. 
 
i$2 THE WORLD OF MATTE-R. 
 
 seen by slowly evaporating a gently heated solution. 
 If the brine is heated nearly to the boiling point, and 
 rapidly evaporated by the exposure of a large surface 
 to the air, the crystals are very small, as in fine table- 
 salt. The cubical form even of these little crystals 
 may be seen under the microscope, although the 
 crystals of table-salt commonly have their edges rounded 
 like pebbles, partly from rubbing against one another, 
 and partly from being partially dissolved by moisture 
 absorbed from the air. You should therefore prepare 
 fresh crystals for examination. 
 
 The quantity of salt used for food, either directly as 
 a condiment, or indirectly in the preservation of meats 
 and fish, and for other purposes is enormous. It has 
 been estimated at fifty pounds a year for each person in 
 the United States, and twenty-two pounds for each per- 
 son in Great Britain. The coarser qualities of salt are 
 mostly made from sea-water or other brines by a natural 
 process of evaporation. The finer grades result from 
 heating the brines artificially. 
 
 Salt is also found occurring in a solid form, both mas- 
 sive and crystallized, and is then known as rock salt. 
 It is white, gray, or more rarely, owing to the presence 
 of impurities, red, violet, and blue. In some places it 
 occurs in mountainous masses. A .hill of rock-salt in 
 Spain is 500 feet high. The island of Ormuz in the 
 Persian Gulf is formed of rock-salt. The Indus river 
 in the upper part of its course forces its way through 
 hills of rock-salt, which rise in cliffs 100 feet above the 
 water, Salt is also found in beds deep under ground, 
 
A LUMP OF SALT. 153 
 
 and is obtained by mining. No less than twenty-three 
 of the United States are engaged in the production of 
 salt. New York and Michigan are the most productive. 
 
 As an essential part of the food of live-stock salt is a 
 necessity upon every farm. Instances are not uncom- 
 mon where beasts of burden have died from lack of it. 
 
 Milch cows need a daily allowance in order to pre- 
 serve the sweetness of their milk, and the quality of the- 
 fleece of sheep depends to a great extent upon their 
 having a sufficient supply of salt. 
 
 In freezing-mixtures salt is of great use, large quanti- 
 ties being used in the manufacture of ice-cream. 
 
 As salt is the source from which soda is derived, it is 
 really the basis in the manufacture of soaps and glass. 
 Other chemical products are the chlorine used in the 
 bleacheries and hydrochloric or muriatic acid. 
 
 The processes for the production of the metal sodium 
 from salt are too complicated to be detailed here, but 
 they consist in first decomposing the salt by means of 
 heating it with sulphuric acid, which results in the 
 separation of hydrochloric acid, and sodium sulphate. 
 Afterward the sodium sulphate, or "salt-cake," as it is 
 called, is heated with powdered coal and reduced to 
 sodium sulphide: and the sodium sulphide is converted 
 into sodium carbonate by means of chalk or limestone 
 with which it is heated in a furnace of special construc- 
 tion. The next operation consists in freeing the car- 
 bonate of sodium from its impurities, which is accom- 
 plished by dissolving it out in water, and then evapo- 
 rating the water, and calcining the residue. 
 
154 THE WORLD OF MATTER. 
 
 The carbonate thus obtained is popularly known as 
 "soda-ash," and is manufactured by the hundred 
 thousand tons every year for use in glass-making, soap- 
 making, bleaching, etc. From this "soda-a$h"the metal 
 sodium may be obtained by decomposing it with an 
 electric current, or by reducing it with carbon. 
 
 Sodium is a very light metal, its specific gravity being 
 0.97, or very nearly that of ice. It floats upon water, and 
 owing to its affinity for oxygen rapidly decomposes the 
 water, disengaging the hydrogen. If the water be hot, 
 or be thickened with starch, the globule of metal be- 
 comes so hot as to ignite the escaping hydrogen. 
 
 It will be worth your while to procure a small piece 
 of sodium, not only that you may become familiar with 
 so important an element in its purity, but also that you 
 may observe its action upon water. Sodium is a silver- 
 white metal, soft at ordinary temperatures, and melting 
 readily. It is so widely distributed in natuie that there 
 is not a speck of dust entirely free from its presence. 
 
 QUESTIONS ON CHAPTER 15. 
 
 1. How can we detect the presence of a minute 
 portion of salt in the soil? 
 
 2. How should the wick of an alcohol lamp be ar- 
 ranged so as to yield a nearly colorless flame? 
 
 3. What color does salt or sodium impart to flame? 
 
 4. Describe the physical properties of common salt. 
 
 5. What is the form of its crystals? 
 
 6. How and where is it obtained? 
 
 7. Its uses? 
 
A LUMP OF SALT. 155 
 
 8. Give an outline of the process for procuring 
 sodium from salt. 
 
 9. Uses of carbonate of soda? 
 
 10. Describe the metal sodium. 
 
 11. Its effect upon water. 
 
 12. Its distribution. 
 
156 THE WORLD OF MATTER. 
 
 CHAPTER XVI. 
 
 MURIATIC ACID. 
 
 In the preceding chapter we incidentally learned that 
 the first step in the process of separating the metal sodi- 
 um from common salt is the addition of sulphuric acid 
 to the salt; and we further learned that this acid causes 
 the formation of hydrochloric acid and sodium sulphate. 
 We then neglected the hydrochloric acid and followed 
 the further treatment of the sodium sulphate, from 
 which we finally obtained the metal sodium. 
 
 Let us now consider the hydrochloric acid. In the 
 first place we must make enough to study. This is a 
 very simple matter. Pour half a teaspoonf ul of strong 
 sulphuric acid on a few grains of common salt in a test 
 tube. What takes place ? What is the appearance of the 
 gas that is given off? This gas is hydrochloric acid; the 
 substance remaining in the tube is sodium sulphate. 
 
 Hydrochloric acid in the form of gas is very readily 
 absorbed by or dissolved in water, just as ammonia gas 
 is, and the hydrochloric, or " muriatic," acid of the drug 
 stores is merely water saturated with this gas. 
 
 The popular name, "muriatic," is derived from the 
 Latin, muria, meaning brine, and refers to its production 
 from salt. 
 
 Make the following experiment, and you will obtain 
 
MURIATIC ACID. 
 
 157 
 
 a plentiful supply, both as a gas and in the liquid solution. 
 Arrange apparatus as in Fig. 26. 
 
 Fig. 26. 
 
 Weigh out separately 100 grains of common salt, 100 
 grains of concentrated sulphuric acid, and one part of 
 water. Mix the acid and water, taking the precaution 
 already noted of pouring the acid in very slowly while 
 the mixture is constantly stirred. Let the mixture cool 
 and then pour it upon the salt in the flask. Now heat 
 the flask gently over an alcohol lamp or a gas-jet, and 
 the gas will be regularly given off. Conduct it at first 
 through two or three double-necked, or "Wolff's 
 bottles," until what passes over is completely absorbed in 
 the first Wolff's bottle. This is to get rid of the air. 
 At first a bubbling occurs in all the bottles as the air in 
 the apparatus is being driven out. When the air has 
 all been expelled, the bubbling ceases and the hydro- 
 chloric gas is all absorbed in the water in the first bottle. 
 
THE WORLD OF MATTER. 
 
 After the gas has passed for ten or fifteen minutes, you 
 may disconnect the tube at A. Notice the fumes. 
 Breathe upon them and observe that they become more 
 dense. Apply a lighted match to the escaping gas. 
 
 Fig. 27. 
 
 Does it burn? Collect some of the gas in a dry jar or 
 cylinder by letting the delivery tube extend to the bot- 
 tom of the jar, and covering its mouth with a piece of 
 paper. Fig. 27. 
 
MURIATIC ACID. 159 
 
 The specific gravity of the gas being greater than that 
 of air, the jar must, of course, have its mouth upward. 
 Has the gas any color? Is it transparent? Insert a burn- 
 ing taper in the jar. Does the gas support combustion? 
 
 Now, connect the generating-flask again with the 
 bottles containing water, and let the process continue 
 until no more gas comes over. What substance remains 
 in the flask? 
 
 You now have in your first Wolff's bottle ordinary 
 hydrochloric acid in solution, and you may test it as 
 follows: Put a little granulated or chipped zinc into a 
 test-tube and pour some of the solution upon it. 
 
 By applying a match to the resulting gas, you will 
 recognize it as hydrogen, which, you recollect, we have 
 previously obtained by the action of hydrochloric acid 
 upon zinc. 
 
 Add ten or twelve drops of the solution to a teaspoon- 
 ful of water in a glass. Taste the dilute solution. 
 How would you describe the taste? 
 
 Dip a piece of blue litmus-paper into the solution. 
 What is the effect? 
 
 These tests are sufficient to indicate that th'3 solution 
 contains hydrochloric acid, HC1, which is a compound 
 of hydrogen and a new element called chlorine. This 
 element we will next endeavor to separate from the 
 hydrochloric acid for our examination. 
 
 QUESTIONS ON CHAPTER l6. 
 
 i. How can hydrochloric acid be obtained from 
 common salt? 
 
160 THE WORLD OF MATTER. 
 
 2. What substance is left behind? 
 
 3. How do we obtain hydrochloric acid in a liquid 
 form? 
 
 4. What is a "Wolff's bottle?" 
 
 5. How may we recognize hydrochloric gas? 
 
 6. Describe it. j 
 
 7. What is its composition? 
 
 8. What is the derivation and meaning of the word, 
 "muriatic?" 
 
CHLORINE. 16! 
 
 CHAPTER XVII. 
 
 CHLORINE. 
 
 In order to separate the chlorine, Cl, from hydro- 
 chloric acid, HC1, it is obviously necessary merely to 
 remove the hydrogen from it. This can readily be done 
 by adding to the acid some substance, such as oxygen, 
 which has a stronger attraction for the hydrogen, than 
 the chlorine has. The most convenient substance in 
 practice is manganese dioxide, which we have already 
 handled when we were preparing oxygen. When 
 brought together with hydrochloric acid, the manganese 
 dioxide parts readily with its oxygen, the oxygen unites 
 with the hydrogen, and^part of the chlorine is set free. 
 The reaction is represented thus: 
 
 MnO 2 + 4HC1 : MnCl 2 + 2H 2 O + 2C1. 
 
 This method is too expensive to be used in the manu- 
 facture of chlorine in the immense quantities required 
 for commerce, and cheaper processes have been devised, 
 with which, however, we are not now concerned. We 
 will, therefore, use the manganese dioxide as follows: 
 Put into a flask three or four ounces of black oxide of 
 manganese. Pour upon it enough ordinary concen- 
 trated hydrochloric acid to cover it completely. Ar- 
 range the apparatus as shown in Fig. 27, on page 
 
162 THE WORLD OF MATTE&. 
 
 158, except that in order to secure a very gentle heat, 
 the flask may be set in a pan of sand over the flame. 
 
 Heat very gently, and collect six or eight dry cylin- 
 ders or bottles full of chlorine in trie same manner as 
 described in the preceding chapter for collecting hydro- 
 chloric gas. 
 
 You can see when the vessels are full by the color of 
 the gas. The oxide of manganese used for this experi- 
 ment should be in the form of small lumps free from 
 powder. This experiment, like all others concerned 
 with chlorine, should be carried on in a place well venti- 
 lated by a strong draft, as by an open fire-place, under 
 a metal hood connected with a chimney, or out of doors. 
 Do not breathe any of the gas. 
 
 You may now proceed to study the chlorine you have 
 collected. You observe that it is greenish-yellow. 
 Notwithstanding the precaution of having a good 
 draught, you will probably perceive that it has a dis- 
 agreeable odor, and that it irritates the passages of the 
 throat and nose. The feeling produced is like that 
 caused by a cold in the head. Inhaled in concentrated 
 form it would cause death. It is more than twice as 
 heavy as air. 
 
 Into one of the jars of chlorine introduce a little finely 
 powdered antimony. The two elements at once com- 
 bine with light and heat, somewhat as iron burns with 
 oxygen. 
 
 Into a second jar introduce a few pieces of heated 
 copper foil. They burn brilliantly, and form a copper 
 chloride. 
 
CHLORINE. 163 
 
 Into a third jar drop a piece of paper written 
 on with ink, some flowers, and some pieces of colored 
 calico, all moistened. Most of the colors will be de- 
 stroyed. 
 
 In the fourth jar drop a dry piece of the same calico. 
 It is not bleached. 
 
 This bleaching power of chlorine is of enormous im- 
 portance in the cotton and paper trades. It does not, as 
 a rule, act upon mineral colors, nor the black tints pro- 
 duced by carbon. Test this by placing a piece of 
 printed paper in a jar of chlorine. The print is not 
 affected. 
 
 The bleaching properties of chlorine depend upon its 
 power of combining with the hydrogen of water and 
 liberating the oxygen, which then oxidises or burns up 
 the coloring matters. 
 
 Besides this property chlorine is also useful as a dis- 
 infectant, and is largely used in destroying bad odors 
 and the poisonous germs of disease, although this effect 
 is probably produced also by liberated oxygen, rather 
 than by direct action of the chlorine. 
 
 Chlorine can be combined directly with hydrogen to 
 produce hydrochloric acid. If equal volumes of these 
 two gases, hydrogen and chlorine, be mixed, no combi- 
 nation occurs so long as the mixture remains in the dark 
 and at the ordinary temperature; but if the mixed gases 
 be exposed to sunlight, or if a flame be applied, or an 
 electric spark passed through them., a sudden combina- 
 tion occurs, and the heat evolved produces a violent ex- 
 plosion. 
 
164 THfi WORLD OF MATTER. 
 
 Copper, mercury, tin, platinum, silver, iron, and cer- 
 tain other metals unite very readily with chlorine form- 
 ing chlorides. The well-known substance, " chloride of 
 lime," is formed by passing chlorine into slaked lime. 
 
 QUESTIONS ON CHAPTER 1 7. 
 
 1. How can hydrochloric acid be analyzed into 
 chlorine and hydrogen? 
 
 2. What precautions must be taken in dealing with 
 chlorine ? 
 
 3. Describe the gas, its color, smell, and effects. 
 
 4. What is the effect of introducing powdered anti- 
 mony into chlorine? 
 
 5. How does heated copper foil act with chlorine? 
 
 6. What effect has chlorine upon colored fabrics? 
 
 7. Explain the reason for the bleaching power of 
 chlorine. 
 
 8. What colors are not affected by it ? 
 
 9. Explain its power as a disinfectant. 
 
 10. What occurs when chlorine and hydrogen are 
 mixed? 
 
 11. What is chloride of lime? 
 
IRON. 165 
 
 CHAPTER XVIII. 
 
 IRON. 
 
 We have now accounted for everything we observed 
 in our handful of soil, but before leaving it let us look 
 again. Take another handful and wash it carefully in 
 a bowl of water, pouring off the muddy water and add- 
 ing clear water until we obtain clean sand. Unless 
 your soil differs from mine you will be able to find 
 among the grains of quartz which make up most of 
 this sand, other grains of a black color, some of which 
 are attracted by a magnet. These grains are a kind of 
 iron ore. 
 
 When clay or soil is burned, as in making brick, 
 the red color produced is an evidence of the presence of 
 iron. Compare the red color of bricks with the red 
 rust seen on iron which has been strongly heated. 
 You may also remember that in speaking of 
 mica, I told you that besides silica, aluminum, and 
 potassium, it usually contains a little iron. It is to 
 a trace of iron also that we must attribute the brown 
 color which we found tingeing some of the grains of 
 quartz which we examined under the microscope. 
 
 Before reading further call to mind all that you al- 
 ready know about this element. By its lustre and hard- 
 ness, and malleability, you recognize it as a rqetal. You 
 
166 THE WORLD OF MATTER. 
 
 distinguish it easily from most other metals, such as gold, 
 s Iver, lead, and tin, by its dark color, its hardness, and 
 the reddish rust or oxide which so quickly gathers on 
 its surface when exposed to the weather. 
 
 You are familiar with the properties which make iron 
 by far the most useful metal in the world. You know 
 that it can be had in three common forms, wrought-iron. 
 cast-iron, and steel; that wrought or worked iron is the 
 softest form and is nearly pure iron. It is used when 
 we require strength and toughness without stiffness or 
 elasticity ; as for horse shoes, nails, wire, chains, boilers, 
 and bridges. 
 
 Steel, you know, is the hardest form of iron. It is 
 not so pure as wrought-iron, but contains a certain ad- 
 mixture of carbon, though not so much as there is in 
 cast-iron. 
 
 It is used when to the greatest strength we would add 
 hardness and elasticity, and is peculiarly suitable for 
 tools, springs, rails, wire, and the finer parts of ma- 
 chinery. What could take the place of steel in the 
 manufacture of needles? 
 
 Cast-iron is less pure than steel, and is brittle. It is 
 used where rigidity of form, without elasticity or flexi- 
 bility or malleability, is desired. It melts at less heat 
 than wrought-iron or steel, and can readily be poured 
 into moulds. It is used for stoves, furnaces, cooking 
 utensils, tubing, and the framework of machinery. 
 
 One of the most valuable properties of iron is that at 
 a red heat it becomes soft like wax, in which condition 
 two pieces strongly pressed together unite, and become 
 
IRON. 167 
 
 one continuous piece. This process is called weld- 
 ing. 
 
 Another property of iron, and one by which it can 
 be instantly detected, is its sensitiveness to the attraction 
 of a magnet, and its power of becoming magnetic 
 during the passage of an electric current. A bar of 
 steel becomes permanently magnetised when it is rubbed 
 by a magnet. To this property of steel we owe the 
 "mariner's compass," which guides our ships and steam- 
 ers across the sea; while to the temporary magnetism 
 produced in soft iron by the passage of a current of elec- 
 tricity, we owe, among other things, the telegraph, the 
 telephone, and the "dynamo" or electric engine, which 
 gives us the electric motor and the electric light. 
 
 Pure metallic iron is not found in nature, except in 
 small quantities in Greenland in a rock supposed to have 
 been thrown out of the earth by a volcano; and in 
 meteorites. It is a white metal with a strong lustre. 
 Iron is usually found in combination with oxygen, with 
 oxygen and carbon, or with sulphur. 
 
 The three principal oxides of iron (specimens Nos. 10, 
 1 1 , and 1 2) are known as limonite, hematite, and magnetite. 
 The history of the formation of these ores through the 
 agency of vegetable matter is most interesting, but will 
 more properly be given when we come to the study of 
 geology. They are easily distinguished from one 
 another by the colors of their powders, and by the mag- 
 netism of magnetite, and they may be known from all 
 other common rocks by their high specific gravity. 
 Magnetite is the richest in iron, and limonite the poorest. 
 
168 THE WORLD OF MATTER. 
 
 The carbonate of iron is called siderite* FeCO, 
 
 ' o 
 
 Its crystallization and cleavage are essentially like calcite. 
 Test for yourself its other physical properties. 
 
 Iron combined with sulphur forms iron sulphide, 
 FeS 2 , known by mineralogists as iron pyrites, or py rite. 
 (Specimen No. 29.) It is usually found in brilliant yel- 
 low cubical crystals, although there is also a twelve- 
 sided form, and is frequently mistaken by the ignorant 
 for gold. It has therefore been called " Fool's gold." 
 It may easily be distinguished from gold by its brittle- 
 ness and hardness, which is so great nearly 7 that it 
 will strike fire with steel. Hence the name, pyrite or 
 fire-stone. 
 
 When heated in a closed tube sulphur is given off. 
 Verify this statement -by experiment, and test the dark 
 colored residue by a magnet. 
 
 The extraction of iron from its ores consists in first 
 converting the ore into an oxide of iron, unless the 
 oxides themselves are used. This is accomplished by 
 roasting them. If sulphides are roasted the sulphur 
 passes off as sulphur dioxide, and iron oxide remains. 
 
 The next step is the reduction of the oxides by heat- 
 ing them with carbon in the form of charcoal or coke. 
 For this purpose the ore and carbon are mixed and 
 heated in a blast-furnace, constructed of fire-brick and 
 masonry. Alternate layers of ore and fuel are intro- 
 duced. Limestone or quicklime is also added as zflux. 
 The object of this is to form a fusible substance with 
 the earthy part of the ore. As the heat increases the 
 ore and flux melt together, but the iron being the 
 
IRON. 
 
 169 
 
 heavier liquid sinks to the bottom, whence it is drawn 
 off into proper receptacles, after which the melted flux 
 
 with its impurities is al- 
 lowed to escape. This 
 refuse is called slag. 
 
 The iron drawn off 
 from the furnace is called 
 pig-iron. It is impure, 
 containing phosphorus, 
 sulphur, silicon, and from 
 2 to 6 per cent, of carbon. 
 It is used for cast-iron. 
 Cast-iron is converted 
 into wrought-iron in one 
 of two ways: (i) By 
 melting it and blowing 
 air into the molten mass. 
 The carbon, phosphorus, 
 and silicon are thus oxi- 
 dized and removed. This 
 process is known as pud- 
 dling. 
 
 (2) By mixing cast-iron with some of the purer ores, 
 and heating to a high temperature, when the carbon, 
 phosphorus, and silicon are oxidized by the oxygen of 
 the ores. This process is called cementation. 
 
 Steel contains from I to 2 per cent, of carbon. There 
 are two ways of making steel: 
 
 (i) Wrought-iron is heated with charcoal, or with 
 other iron containing carbon. 
 
 Fig. 27M- 
 
iyo THE .WORLD OF MATTER. 
 
 (2) Cast-iron is melted in a large vessel, and is then 
 partly oxidized by currents of air forced into the mass. 
 Cast-iron is now added, and steel containing any desired 
 proportion of carbon is thus made. This is known as 
 the Bessemer process. 
 
 QUESTIONS ON CHAPTER iS. 
 
 1. Describe cast-iron. 
 
 2. Describe steel. 
 
 3. Describe wrought-iron. 
 
 4. State the uses of each. 
 
 5. What is the color of pure iron? 
 
 6. What are the three principal oxides of iron? 
 
 7. Describe siderite. 
 
 8. What is iron pyrites? 
 
 9. How may it be distinguished from gold ? 
 
 10. How is iron extracted from its ores? 
 
 11. How is wrought-iron made ? 
 
 12. How is steel made? 
 
BY WAY OE REVIEW. 171 
 
 CHAPTER XIX. 
 
 BY WAY OF REVIEW. 
 
 We have now reached a point in our study of the 
 world of matter where it will be profitable for us to rest 
 for a time, and take a bird's-eye view^of the path along 
 which we have been advancing. 
 
 We began with a piece of ice, because that was as 
 handy a specimen as we could think of, and one with 
 which we were already familiar. 
 
 Having observed its physical properties, such as hard- 
 ness, transparency, and weight, we were especially in- 
 terested in the change which was caused in its structure 
 by the heat of the hand, /. ., its melting. 
 
 This led us to various experiments by which we 
 studied the phenomena connected both with the melting 
 of ice and the freezing again of water, including the 
 peculiarities of its crystallization. 
 
 Having melted our ice we proceeded to examine the 
 water produced thereby, and discovered first its property 
 of dissolving other substances; incidentally learning 
 something of capillary .attraction, that combination of 
 ordinary forces which results in lifting a liquid through 
 minute tubes or pores. We next tried the effect of a 
 greater degree of heat upon water, and found that at 
 212 degrees Fahrenheit it begins to be converted into 
 
172 THE WORLD OF MATTER. 
 
 an invisible vapor called steam, a process which is ac- 
 companied by a violent agitation and bubbling, known 
 as boiling, or ebullition; and we learned that on the 
 withdrawal of heat this vapor is again condensed in the 
 form of water. Observing that ice, water, and steam 
 are riot different substances, although apparently so 
 unlike, we were curious to ascertain what it is that gives 
 a substance its identity; or in other words, to learn 
 what constitutes a simple element. We found that 
 those substances are considered elementary which have 
 never been resolved into simpler substances, and that 
 for a long time' it was supposed that the elements were 
 four, namely, water, air, fire, and earth. This led us 
 to examine water more carefully, and, on testing it 
 with an electric current, we found that it separated into 
 the two gases, oxygen and hydrogen. As these could 
 not be further analyzed we concluded that they are 
 elements. 
 
 In Chapter V, we studied the oxygen and hydrogen 
 we had obtained from the water, and learned many 
 important facts regarding chemical combinations, and 
 particularly that sort of combination accompanied by 
 heat and light which is called combustion. 
 
 In this connection, having observed that there is a 
 strong resemblance between our ordinary fires and the 
 flames which are produced by burning substances in 
 oxygen, we examined a portion of the air which feeds 
 our common fires, and found, as we had suspected, that 
 it is largely made up of oxygen. Our curiosity to know 
 why the oxygen of the air does not burn up everything 
 
fcY WAY OF REVIEW. 173 
 
 in the world brought us to the discovery that nitrogen, 
 a powerful extinguisher of fire, is mingled in the air 
 with the oxygen, and we afterward found this ap- 
 parently inert nitrogen combined with other elements 
 .and forming highly explosive compounds like gun- 
 powder and nitro-glycerine; we also found it constitut- 
 ing a large proportion of the food of animals. 
 
 Remembering the old notion that earth is an elemen- 
 tary substance, and knowing that that could not be 
 true, since we had learned that at least three different 
 elements, namely, oxygen, hydrogen, and nitrogen, 
 enter into its composition, we determined to examine 
 with some care a handful of earth from the garden. In 
 this we found besides the hydrogen and oxygen of 
 water quartz, limestone, charcoal, and clay, including 
 its aluminum, and potassium ; and about each of these, 
 in passing, we gleaned such information as was at hand. 
 Then, by the aid of its yellow flame, we discovered a 
 little salt in the soil, and traced it to its elements, 
 sodium and chlorine, and finally we found a trace of 
 iron. 
 
 Our course has not been a strictly scientific one, per- 
 haps, inasmuch as science busies itself largely with ar- 
 ranging the subjects of its consideration in groups or 
 classes according to certain resemblances which exist 
 between them as, for example, when the zoologist 
 groups all animals that have back-bones, under the 
 name vertebrate while we have taken our specimens in 
 the order suggested by convenience and natural asso- 
 ciation. A science, too*, walks within well-defined 
 
174 THE WORLD OF MATTER. 
 
 bounds, closing its eyes for the time to everything out- 
 side its own narrow lines, in order that it may be more 
 certain of seeing clearly and comprehensively every- 
 thing within those lines; while we have not hesitated 
 to leap over the fence every now and then, whenever 
 anything of interest appeared in the fields that bordered 
 our pathway. We have been taking a ramble along 
 the brooks, and through the fields, rather than working 
 methodically in a laboratory or museum. 
 
 It will be no hindrance, however, to our progress in 
 science that we have thus pleasantly gathered and 
 studied, even though apparently at random, a goodly 
 collection of mineral specimens, before undertaking to 
 make any systematic classification. 
 
 In fact, there seems to be something absurd, or at 
 least unnatural, in that method of studying natural 
 science which begins by committing to memory 
 the classified results of the labors of great scientists, 
 instead of following their example, by first collecting 
 our material and afterward learning how to arrange it. 
 
 One of the chief disadvantages of the ordinary 
 method of acquiring a knowledge of nature by the 
 routine of definition learning and system memorizing 
 is that in that way we get our information in narrow 
 and artificial fragments, and lose sight of the intimate 
 natural relations that exist between all the sciences, and 
 fail to comprehend that all science or knowledge is es- 
 sentially one. Thus it often happens that we hear a 
 young student, who has read a certain chemical text- 
 book, remark that he has "finished chemistry, and is 
 
fcY WAY OP REVIEW. 175 
 
 about to take up mineralogy ;" and I have even known 
 persons who thought they had mastered geology when 
 they had learned the names and characteristics of the 
 several geologic strata, although they were quite 
 ignorant of the chemical composition of the most com- 
 mon minerals, and knew nothing at all of plant or 
 animal life and structure. 
 
 Our work has not been in vain if we have learned 
 the central truth that all the various sciences are not 
 only interdependent, but are all merely parts of one 
 harmonious whole, so that no one can be said to have 
 "finished"' any one science until he is master of all 
 science. Those students who are seeking for new facts 
 with a view to increasing the world's knowledge do 
 well to confine their investigations closely within spec- 
 ial and narrow lines ; and on this principle a "special- 
 ist" merits praise for devoting his whole life to the study, 
 it may be, of one family of spiders, even though he 
 may never allow himself to notice a butterfly, a bird, 
 a crystal, a tree, a mountain, or a cloud; but the better 
 education for the great majority of us is one that by 
 the faithful study in all their relations of a few typical 
 specimens leads us to a deeper and broader understand- 
 ing of the whole realm of nature, including man. Only 
 we must be sure that so far as we do go in any direc- 
 tion our knowledge is accurate and thorough, and based 
 upon the evidence of our own senses, and the conclu- 
 sions of our own reason. If this book were confined 
 to the study of the physical properties of minerals 
 merely, as their form, weight, and color, and to a con- 
 
176 THE WORLD OF MATTER. 
 
 sideration of those changes only which are produced 
 in them by physical forces, such as motion and heat, it 
 might have been called a "natural philosophy" or 
 "physics;" if it treated only of the composition and 
 decomposition of minerals, and of those more in- 
 timate changes which are effected when different ele- 
 ments are brought into chemical contact, it would have 
 been a kind of chemistry; while if it had considered 
 mineral specimens merely as such, describing their ap- 
 pearance, structure, and uses, teaching how to recognize 
 them at sight, and telling where they may be found, it 
 would have been essentially a little work on mineralogy. 
 As it includes, however, as much of all these varieties 
 of knowledge as seems necessary to a clear and com- 
 prehensive understanding of a few of the more com- 
 mon minerals, and to show how the others should be 
 studied, it has seemed best to give it the more modest 
 title which it bears: A Guide to the Study of Minerals. 
 
 It is our hope, therefore, not to give our readers the 
 unfounded notion that they have "finished mineralogy," 
 but to show them how they may now profitably begin 
 that important study; and if those who follow us 
 through this book shall find themselves better able to 
 read with pleasure and understanding the standard 
 works on physics, chemistry, and mineralogy, and to 
 perceive how these are all related to one another, we 
 shall feel, as the old phrase runs, "that our labor has 
 not been in vain !" 
 
 The proper order for your future study seems to me 
 to depend upon the principle that the simpler or more 
 
BY WAY OF REVIEW. 177 
 
 e/ementarv should come before the more complex ; the 
 i^wer should precede the higher. In any doubtful 
 case you may determine which of two branches of 
 science is the lower and which the higher by applying 
 a law first clearly stated by President Mark Hopkins, 
 of Vvilliams College. He calls it the "law of the con- 
 ditioning and the conditioned." It is very simple, and 
 is this: 
 
 Whatever is a necessary condition of the existence 
 of anything- else, is as a rule lower than that of which 
 it is the condition. 
 
 For example, in the three kingdoms of nature, ani- 
 mal, vegetable, and mineral, the mineral kingdom is a 
 necessary condition for the existence of the vegetable 
 kingdom, and the vegetable kingdom is a necessary con- 
 dition for the existence of the animal kingdom. There- 
 fore, the mineral kingdom is the lowest, and the animal 
 kingdom is the highest. 
 
 Using this principle, now, to help us arrange a right 
 course of scientific study, we shall find that the student 
 having mastered the rudiments of language, arithmetic, 
 and geography, should first be made familiar as we 
 have been by our simple observations and experiments 
 with the more common elements of the mineral 
 world; at the same time learning the laws which govern 
 their physical and chemical changes. Having studied 
 then, physics, chemistry, and mineralogy, he will be 
 led to observe how from the mineral or inorganic world, 
 life first springs in the lower and higher forms of 
 vegetable growth, and he will naturally make a study 
 
178 THE WORLD OF MATTER. 
 
 of plants with the aid of some standard botany. The 
 consideration of animal life will follow, including 
 zoology, anatomy, and physiology. 
 
 A good review of the last four branches will be ob- 
 tained by reading a good biology, and making the ob- 
 servations and experiments therein described. 
 
 Geology will follow, and while pursuing it, the 
 student will find to his delight that all his previous 
 work has been directly preparatory to a clear under- 
 standing of the structure of the earth. 
 
 Astronomy may well come next, and is but the ex- 
 tension to other worlds of the same methods of study 
 that have given a knowledge of the earth. By this 
 time the student will have laid a firm foundation on 
 which he can stand when he approaches the study of 
 the human intellect, and the supreme questions and 
 problems involved in moral philosophy and natural 
 theology. 
 
 QUESTIONS ON CHAPTER 19. 
 
 1. Give an outline or synopsis of the preceding 
 chapters. 
 
 2. Explain the connection between the several 
 natural sciences. 
 
 3. How many different sciences contribute to a com- 
 plete understanding of minerals? 
 
 4. What is Hopkins' law of the conditioning and 
 conditioned ? 
 
 5. Give an illustration of its working. 
 
 6. Give the natural order of studying the sciences 
 in accordance with this law. 
 
WHAT IS A METAL? 179 
 
 CHAPTER XX. , 
 
 WHAT IS A METAL? 
 
 We have now become somewhat familiar with eleven 
 of the most common and abundant elements, namely, 
 oxygen, hydrogen, nitrogen, chlorine, carbon, silicon, 
 sodium, potassium, calcium, aluminum, and iron; and 
 we have incidentally become acquainted with quite a 
 number of their more important compounds. 
 
 It is now time to compare these elements with one 
 another for the purpose of arranging them if possible 
 in groups or classes. 
 
 To clo this properly we must group together ele- 
 ments which have certain properties in common, and 
 the more essential and important the properties are 
 which we select as a basis for our classification, the 
 better our work will be. Every mind, whether edu- 
 cated or not, is more or less constantly busy in classifying 
 the objects with which it becomes acquainted. Child- 
 ren and illiterate persons commonly seize upon the 
 most obvious peculiarities or characteristics of the ob- 
 jects they perceive as a means of grouping them, color 
 and size being perhaps most frequently selected. Thus 
 many birds and fishes are popularly named from their 
 colors, as black-birds, and black-fish, blue-birds, and blue- 
 fish, yellow-birds, white-fish, and the like. In the case 
 
io THE WORLD OF MATTED. 
 
 of minerals, this method would evidently be unwise, for 
 as we have seen the same mineral often appears of 
 many different colors. We might better use the "streak" 
 as a basis of classification, but even this would fail us 
 in the case of liquids and gases. 
 
 It might seem at first thought that an excellent plan 
 would be to group together in one class the gases, in 
 another the liquids, and in another the solids; but when 
 we remember that very many substances readily pass 
 from one of these states into another, we see that this 
 would be unsatisfactory, unless we also indicated the 
 temperature. 
 
 Probably the best and simplest general division of 
 minerals is that which separates them into metals and 
 non-metals. 
 
 While it might puzzle you to give a true definition 
 of a metal, yet of the eleven elements we have studied 
 you would have no difficulty in recognizing as metallic 
 iron, sodium, potassium, calcium, and aluminum, and 
 the other six as non-metallic. You would probably 
 rest this decision chiefly upon the peculiar lustre of 
 the metals, and upon their fine texture or grain. 
 
 In this case you would be right, and these character- 
 istics are generally sufficient to enable us to recognize 
 pure metals at sight, but in the case of compounds of 
 the metals, such as ores, we need a more intimate 
 knowledge of their essential properties. 
 
 The chemist's conception of a metal is determined 
 rather by the nature of the compounds it helps to form 
 than by its lustre and grain. 
 
WHAT IS A METAL? 181 
 
 You have already met with a number of compounds 
 called acids ^ notably hydrochloric, nitric, and sulphuric 
 acids, and you have noted the sharp taste, and the pow- 
 erful corrosive action which they possess; likewise 
 their effect in changing the color of blue litmus to red. 
 
 You have also met with another and different kind of 
 compounds, called alkalies, potash for example, whose, 
 action is precisely opposite to that of acids, so that acids 
 and alkalies are said to neutralize each other. 
 
 Now these alkalies are typical examples of a class of 
 substances known as bases, whose properties are di- 
 rectly opposite to the properties of acids. 
 
 Among the more common bases are caustic soda. 
 NaOH; caustic potash, KOH, and lime, CaO 2 H 2 . 
 
 You will notice that all of these and the same is 
 true of all the other bases are formed by the union of 
 a metal with oxygen and hydrogen. You will also 
 observe that all acids contain hydrogen, but no metal. 
 
 Let us now try the effect of combining an acid with 
 a base. 
 
 Dissolve ten grains of caustic soda in a glass of 
 water. Add hydrochloric acid slowly, testing the solu- 
 tion from time to time by dipping into it a piece of blue 
 litmus-paper. As long as the solution causes no change 
 in the color of the paper, you may know that it re- 
 mains alkaline; the instant the solution changes the 
 blue of the paper to red, you know that it has passed 
 the point of neutralization. When this point is reached, 
 pour the water into a saucer and evaporate to complete 
 dryness. Taste the substance remaining. It is com- 
 
i8a THE WORLD OF MATTER. 
 
 mon salt or sodium chloride. Is it an alkali? Is it an 
 acid ? Is it neutral ? 
 
 .Its formation may be represented by the following 
 equation : 
 
 HCH-NaOH:=:NaCH-H 2 O. 
 
 Notice that the hydrogen of the acid has changed 
 places with the metal of the base, and that the result is 
 water and salt. We may now sum up the results of 
 our study thus: 
 
 An acid is a substance containing hydrogen, which it 
 easily exchanges for a metal. 
 
 A base is a substance containing a metal combined 
 with oxygen and hydrogen, and it easily exchanges its 
 metal for hydrogen when treated with an acid. 
 
 The products of the action of an acid on a base are 
 first water, and then a neutral substance called a salt. 
 Sodium chloride, potassium chloride, sodium nitrate, 
 potassium nitrate, and sodium sulphate are salts. 
 
 Bases being composed of metals with hydrogen and 
 oxygen are commonly called hydroxides of their 
 metals. Thus Caustic soda is sodium hydroxide. 
 
 Every metal can form a salt with every acid.* 
 
 It was once thought that oxygen was a necessary 
 part of every acid, and hence it obtained its name, 
 which means acid-former. And although we have 
 learned that there are exceptions to this as in the case 
 of hydrochloric acid, HC1 it is still believed that acid 
 properties are generally due to oxygen. 
 
 * While this statement is theoretically true, it must not be understood that 
 every metal has been actually combined with every acid to form a salt. Many 
 theoretical salts are still practically unknown to the chemist. 
 
WHAT IS A METAL? 183 
 
 It will now be clearer to you why it is reasonable to 
 divide the elements into two classes, metals and non- 
 metals; and you will also, at least partly, understand the 
 division of compounds into acids, bases, and salts. 
 
 QUESTIONS ON CHAPTER 2O. 
 
 1. Into what two classes may the elements be 
 divided ? 
 
 2. What is an acid? 
 
 3. What is abase? 
 
 4. What is a salt? 
 
 5. What effect has an acid on a base? 
 
 6. What are hydroxides? 
 
 7. Derivation of the name oxygen? 
 
184 THE WORLD OF MATTER. 
 
 CHAPTER XXI. 
 
 FAMILIES OF ACID-FORMING ELEMENTS. 
 
 The eleven elements which we have thus far con- 
 sidered constitute at least ninety-nine per cent, of the 
 whole substance of the earth. Most of the other ele- 
 ments are of comparatively rare occurrence. 
 
 It will be well, however, briefly to glance at the more 
 important of them. In the preceding chapter we 
 learned to divide the elements into metals and non- 
 metals; recognizing the metals partly by their peculiar 
 lustre and grain, and partly by the fact that they are 
 base-forming elements in distinction from acid-forming 
 elements. We might also have observed that as a 
 rule they are insoluble, or soluble with difficulty, that 
 they are opaque, that many of them can oe beaten into 
 thin leaves, or drawn into slender wire; and that most 
 of them make a ringing sound when dropped on any 
 hard substance. 
 
 Proceeding now to a further subdivision of the ele- 
 ments, we notice that they naturally fall into families, 
 according to their chemical properties, the members of 
 each family showing striking resemblances. 
 
 Taking first the acid-forming elements, by far the 
 smaller of the two great divisions, as most of the ele- 
 ments are metallic, we have the following families: 
 
FAMILIES OF ACID-FORMING ELEMENTS. 185 
 
 Chlorine Family. Sulphur Family. Nitrogen Family. Carbon Family. 
 Chlorine Sulphur Nitrogen Carbon 
 
 Bromine Selenium Phosphorus Silicon 
 
 Iodine Tellurium Arsenic 
 
 Fluorine Oxygen Antimony 
 
 It will not be necessary to go into details in dealing 
 with these families. You have already studied one or 
 more typical members of each of them except the sul- 
 phur family, and the other members may be treated 
 
 briefly. 
 
 THE CHLORINE FAMILY. 
 
 The two members of this family which show the 
 most marked resemblance to chlorine are bromine and 
 iodine. Fluorine is not known in the free state. Its 
 compounds, however, resemble the compounds of 
 chlorine, and hence the element is generally included in 
 this family. 
 
 Bromine, at ordinary temperatures, is a heavy dark 
 red liquid, which is easily converted into vapor. It has 
 an extremely disagreeable odor, as is implied in its 
 name, which means a stench. Its properties are, in 
 general, like those of chlorine, with which it is found 
 associated in nature in salt-beds, and usually in the form 
 of sodium bromiJe, or potassium bromide. It acts 
 violently upon animal and vegetable substances, at- 
 tacking particularly the skin and the membranes lining 
 the passages of the throat and lungs. It must therefore 
 be handled with great care. Its many compounds with 
 other elements are called bromides. 
 
 Iodine occurs in nature in composition with sodium. 
 
i86 THE WORLD OF MATTER. 
 
 in company with chlorine and bromine, but in smaller 
 quantities. It also occurs plentifully in sea-plants. 
 
 In some parts of the ocean sea-weed is cultivated for 
 its bromine. At ordinary temperatures iodine is a gray- 
 ish black, crystallized solid. It melts easily and boils, 
 forming a violet vapor. 
 
 To see this vapor, mix about a grain of potassium 
 iodide with twice its weight of manganese dioxide. Add 
 a little sulphuric acid in a test-tube, and heat gently. 
 In the upper part of the tube some crystals of iodine 
 will be deposited. 
 
 When a solution containing free iodine is treated with 
 a little starch-paste the solution turns blue. Bromine 
 and chlorine do not form blue compounds, and this is 
 one means of distinguishing iodine from them. 
 
 Test this by grinding a few grains of starch to a 
 paste with cold water in a saucer, and adding a cup of 
 boiling water. After cooling add a little of this paste 
 to a dilute water-solution of iodine. 
 
 Fluorine occurs in nature in large quantity, and 
 widely distributed, but never alone. It is found chiefly 
 in combination with calcium, in the form of fluor-spar, 
 or calcium fluoride (specimen No. 4), and in combination 
 with sodium and aluminum, as cryolite (specimen No. 
 8), a mineral which occurs abundantly in Green- 
 land. 
 
 A very powerful acid gas is made by treating fluor- 
 spar with sulphuric acid. It is known as hydrofluoric 
 acid, greatly irritates the vocal organs, being therefore 
 dangerous to inhale, and has the property of dissolving 
 
FAMILIES OF ACID-FORMING ELEMENTS. 187 
 
 glass. For this reason it must be kept in vessels of 
 rubber, lead, or platinum. 
 
 It is used for etching on glass, particularly for making 
 scales on thermometers and other glass instruments. If 
 you would observe this action of hydrofluoric, acid on 
 glass, put five or six grains of powdered fluor-spar into 
 a leaden vessel and pour over it enough concentrated 
 sulphuric acid to make a thick paste. Cover the surface 
 of a piece of glass with a thin layer of wax or paraffine, 
 and scratch some letters through this down to the glass. 
 Put the glass, waxed-side down, over the vessel contain- 
 ing the fluor-spar, and let it stand half a day. On re- 
 moving the glass and scraping off the wax the letters 
 will be found etched on the glass. 
 
 SULPHUR FAMILY. 
 
 Sulphur is familiar to every one from its use in the 
 manufacture of matches, and from its increasing em- 
 ployment as a disinfectant. Sulphur candles are now 
 burned in most well-regulated households, after every case 
 of measles, scarlet fever, or other contagious or infec- 
 tious disease. Sulphur occurs in nature both free and 
 in combination with many metals. It is found free in 
 certain volcanic countries, especially Sicily and Iceland, 
 in transparent, yellow, rhombic, octahedral crystals, 
 Fig. 28. 
 
 The compounds of sulphur with metals are called 
 sulphides , and they constitute the ores from which the 
 metals are usually obtained. Thus lead sulphide, or 
 galena (specimen No. 30), zinc sulphide or blende, and 
 
1 88 THE WORLD OF MATTER. 
 
 copper sulphide are the substances from which lead, 
 zinc, and copper are generally procured. Sulphur also 
 occurs naturally combined with 
 metals and oxygen, and such 
 compounds are called sul- 
 phates. Of these calcium sul- 
 phate or gypsum (specimen 
 No. 2), barium sulphate or 
 heavy spar, and sodium sul- 
 phate or Glauber's salt occur 
 in the largest quantity. Pure 
 ' 28. sulphur, like pure water, is ob- 
 
 tained by distillation. If the vapor of sulphur is quickly 
 cooled below its melting point it solidifies, or "freezes," 
 in the form of a fine crystalline powder, or "snow," 
 called "flowers of sulphur;" in this particular also bear- 
 ing a marked resemblance to water. 
 
 When sulphur is gently heated it melts, and may be 
 cast into sticks, when it is known as brimstone or roll 
 sulphur. Sulphur burns with a bluish flame, combin- 
 ing with oxygen to form sulphur dioxide (often called 
 sulphurous acid), which is given off as a gas, having 
 that peculiar suffocating odor which is perceived when 
 a common match is lighted. 
 
 . Sulphur is one of the most interesting and important 
 elements, and can be obtained at trifling cost. It will 
 well repay you to make a careful study of it. Allow 
 melted sulphur to cool slowly, and observe the long, 
 transparent, needle-like, prismatic crystals which are 
 formed, so different from the natural crystals repre- 
 sented in Fig. 2$. 
 
FAMILIES OF ACID-FORMING ELEMENTS. 189 
 
 Expose these transparent crystals to the air for a few 
 days, and observe the curious changes that take place 
 in them. 
 
 Pour melted sulphur heated to 230 degrees into cold 
 water, and observe the soft, india-rubber-like mass that 
 is produced. Remove this from the water and expose 
 it for a few hours to the air, What change do you 
 notice? 
 
 Sulphur combines directly with chlorine, carbon, and 
 most other elements, and many metals burn in sulphur 
 vapor as in oxygen, uniting with it to form sulphides. 
 
 Sulphuric acid, or hydrogen sulphate, H 2 SO 4 , is the 
 most important and useful acid, as by its means nearly 
 all other acids are prepared, and also because it is used 
 in the arts and manufactures for a great variety of 
 purposes. 
 
 It has been said that the commercial prosperity of a 
 country may be judged with great accuracy by know- 
 ing the amount of sulphuric acid which it consumes. 
 Among its many uses are the making of "soda," or 
 sodium carbonate, which is necessary for the manufac- 
 ture of soaps and glass; the production of phosphorus 
 and of artificial fertilizers; and the refining of petro- 
 leum. More than a million tons of sulphuric acid are 
 manufactured each year in the United States and Great 
 Britain. It is the most important manufactured chemi- 
 cal substance. 
 
 Selenium and tellurium are so rare elements, and 
 so closely resemble sulphur in their chemical character- 
 istics, that we pass them by. There is no great advan- 
 
ipd THE WORLD OF MATTER. 
 
 tage in describing to you substances that you cannot 
 bring under your own observation. 
 
 Oxygen we have already studied together as fully as 
 is necessary for our present purpose. It is the most 
 acid element, and may quite properly be classed by 
 itself instead of being included in any "family." 
 
 THE NITROGEN FAMILY. 
 
 Having found nitrogen in the air, and studied its prop- 
 erties, we will glance at its allied elements, phosphorus, 
 arsenic, and antimony. Phosphorus is not found 
 naturally in its free state, but combined with oxygen 
 and calcium in the form of phosphates in the seeds 
 of plants, the bodies, and especially the bones, of ani- 
 mals, and in the minerals, apatite (specimen No. 5) 
 and phosphorite. When bones are burned a white 
 solid mass remains, which is called calcium phosphate, 
 or phosphate of lime. Animals obtain their phosphates 
 from plants, which in their turn draw their supply from 
 the soil. Finally soils derive their phosphates from the 
 gradual grinding up, or disintegration, of the oldest 
 granite rocks which contain this element dispersed in 
 small quantities. 
 
 Phosphorus is separated from bone-ash by mixing 
 the ash with sulphuric acid, adding charcoal to the mix- 
 ture, and heating it. 
 
 Phosphorus distils over, and is condensed and cast in 
 sticks under water. It has to be kept under cold water 
 until used, for in the air it rapidly combines with oxygen, 
 and takes fire with very slight friction. It is a slightly 
 
FAMILIES OF ACID-FORMING ELEMENTS. 191 
 
 yellow, semi-transparent solid, resembling wax. In 
 the air it gives off white fumes, and emits a pale phos- 
 phorescent light, visible in the dark. From this prop- 
 erty it derives its name, phosphorus signifying in 
 Greek a bringer of light. Great care must be used in 
 handling this substance, and it should always be cut 
 under water. Phosphorus not only combines thus 
 readily with oxygen, but also with other elements, such 
 as chlorine, bromine, and iodine. Bring together in a 
 porcelain crucible, or a saucer, a little phosphorus and 
 iodine. Direct combustion takes place, accompanied by 
 light and heat. 
 
 If yellow phosphorus be left in the light, or heated 
 to about 240 degrees for some hours without access of 
 air, it undergoes a very remarkable change, and is con- 
 verted into a dark and opaque substance, which differs 
 as much from ordinary phosphorus as graphite differs 
 from the diamond. Ordinary phosphorus, as we have 
 seen, combines actively with oxygen; red phosphdrus 
 is inactive; ordinary phosphorus is very poisonous, its 
 vapor even, when inhaled, producing a disease of the 
 bones; red phosphorus is not poisonous; ordinary phos- 
 phorus is soluble in carbon disulphide; red phosphorus 
 is not. 
 
 Oiclinary friction-matches are tipped with a mixture 
 of phosphorus, glue, and potassium chlorate, usually 
 assisted by a little sulphur. 
 
 Arsenic occurs naturally combined with iron, copper, 
 nickel, and other metals, and also as an oxide. Pure 
 arsenic has a metallic lustre. When heated sufficiently 
 
102 THE WORLD OF MATTER. 
 
 in the air it burns with a bluish flame, yielding poison- 
 ous fumes that have the odor of garlic or onions. 
 Arsenic in its pure state is not poisonous, but becomes 
 so when combined with oxygen. 
 
 When arsenic oxide is added to a mixture from which 
 hydrogen is being evolved a compound of arsenic and 
 hydrogen is formed. It is known as arsine, and is 
 represented by the formula, AsH3. This arsine, which 
 is a very poisonous, colorless gas, is important as a 
 means of detecting the presence of arsenic. When 
 heated, it separates readily into arsenic and hydrogen, 
 and if a cold object, as a piece of porcelain, is brought 
 into the flame of burning arsine, the arsenic is deposited 
 in the form of a dark spot. Arsine and other com- 
 pounds of arsenic are so fatally poisonous that we 
 advise you to make no experiments with them. 
 
 Antimony is a silver- white, metallic-looking substance. 
 It occurs most frequently in combination with sulphur. 
 
 Boron is sometimes classed in the nitrogen family, to 
 the members of which it bears many resemblances, 
 though it has peculiarities which distinguish it from 
 them. It occurs in nature most commonly in the form 
 of borax, the salt of sodium. It can be obtained, 
 though not easily, in the form of crystals which are 
 nearly as hard as diamonds. 
 
 Borax is found in the salty incrustation on the shores 
 of certain lakes in Persia and Thibet, and also in 
 Nevada and California. It is also prepared artificially. 
 It is soluble in water, yielding a clear solution with a 
 sweetish taste. It is of great service in blow-pipe ex- 
 
FAMILIES OF ACID-FORMING ELEMENTS. 193 
 
 periments, because it unites with the various metallic 
 oxides to form colored glasses. It is also used in the 
 manufacture of enamels and glazes, and in the formation 
 of "paste" or artificial gems. Its domestic uses for 
 cleansing and for rendering "hard" water "soft" are 
 well known. 
 
 Carbon and silicon, the two elements composing the 
 carbon family, have been considered in previous chapters. 
 
 QUESTIONS ON CHAPTER 21. 
 
 1. Name four, groups or "families" of acid-forming 
 elements. 
 
 2. Describe the properties and uses of bromine, iodine, 
 and fluorine. 
 
 3. What is the effect of hydrofluoric acid upon glass? 
 
 4. Describe sulphur. In what respects does it 
 resemble water? 
 
 5. Uses of sulphuric acid? What is its chemical 
 formula? 
 
 6. Describe the properties and uses of phosohorus. 
 What precaution is necessary in handling it? 
 
 7. What is "red phosphorus?" 
 . 8. Describe arsenic. 
 
 9. What is arsine? 
 
 10. Describe antimony. 
 
 IT. Describe boron. 
 
 12. Composition, properties, and uses of borax? 
 
194 ?Htf WORLD OF MATTER. 
 
 CHAPTER XXII. 
 
 FAMILIES OF METALS. 
 
 The metals or base-forming elements that is ele- 
 ments whose compounds with oxygen and hydrogen 
 neutralize acids and form salts may be conveniently 
 grouped as follows: , 
 
 1. The potassium family, the principal members of 
 which are potassium and sodium. 
 
 2. The calcium family, notably calcium, barium, and 
 strontium. 
 
 3. The magnesium family: magnesium, zinc, and 
 cadmium. 
 
 4. The silver family: silver, copper, and mercury. 
 
 5. The aluminium family, of which aluminium is 
 the only well-known member. 
 
 6. The iron family: iron, cobalt, and nickel. 
 
 7. The manganese family, of which manganese is the 
 only representative. 
 
 8. The chromium family, represented chiefly by 
 chromium. 
 
 9. The bismuth family, represented only by bis- 
 muth. 
 
 TO. The lead family: notably lead and tin. 
 ii. The palladium family, consisting of three rare 
 elements. 
 
FAMILIES OF METALS. 195 
 
 12. The platinum family, the principal members of 
 which are platinum and gold. 
 
 It has been before observed there are many more 
 metallic than non-metallic elements. It would not be 
 wise to try to describe them all in this book; indeed, a 
 thorough acquaintance with all the elements and their 
 compounds can hardly be acquired in a life-time of 
 patient study. Fortunately, however, the great bulk of 
 the minerals of the world is composed of only a dozen 
 different elements, and only a few different compounds 
 of these; and the methods of study which we have fol. 
 lowed in the case of these commonest substances are 
 equally satisfactory in the case of all the rest. 
 
 Having shown you, therefore, how to study the 
 properties of these most important elements, we may 
 safely leave you to apply similar methods of observation 
 to the others. Those that you will especially need to 
 examine are magnesium, zinc, copper, mercury, lead, 
 tin, silver, platinum, and gold. The art of extract- 
 ing these metals from their ores is known as metallurgy. 
 
 You will find the following classification of metallic 
 compounds convenient: 
 
 1. Compounds with chlorine, bromine, and iodine; 
 or the chlorides, bromides, and iodides. 
 
 2. Compounds with oxygen, and oxygen and hydro- 
 gen ; or the oxides and hydroxides. 
 
 3. Compounds with sulphur or the sulphides. 
 
 \. Compounds with nitric and nitrous acids; or the 
 nitrates and nitrites. 
 
 5. Compounds with the acids of chlorine; or the 
 chlorates, chlorites, etc. 
 
196 ' THE WORLD OF MATTER. 
 
 6. Compounds with sulphuric and sulphurous acids; 
 or the sulphates and sulphites. 
 
 7. Compounds with carbonic acid ; or the carbonates. 
 
 8. Compounds with phosphoric acid ; or the phos-* 
 p hates. 
 
 9. Compounds with silicic acid; or the silicates. 
 10. Compounds with boric acid; or the borates. 
 
 You will observe in the foregoing list that the names of 
 some acids end in ic and the names of others, containing 
 the same elements, in ous. The termination ous is used 
 to indicate that less oxygen is present than in the corre- 
 sponding acid whose name ends in ic. Thus sulphurous 
 acid consists of the same elements as sulphuric acid, but 
 contains less oxygen, as is shown by their chemical 
 formulas, thus: 
 
 Sulphuric acid = H 2 SO 4 . 
 
 Sulphurous acid = H 2 SO 3 . 
 
 Notice also that the names of compounds of acids 
 whose names end in ic, end in ate; while the names of 
 compounds of acids whose names end in ous, end in ite; 
 thus the salts derived from nitric acid are called 
 nitrates, while the salts derived from nitrous acid are 
 called nitrites. 
 
 EXERCISES FOR CHAPTER 22. 
 
 1. Observe a piece of magnesium wire. (Specimen 
 No. 31.) Note its color and hardness. Test its malle- 
 ability and flexibility. Is it elastic? Set fire to the wire 
 and observe its splendid combustion. 
 
 2. Study the physical properties of copper, zinc, lead, 
 
FAMILIES OF METALS. 197 
 
 and tin, procuring if possible not only a specimen of 
 the sheet metal, but also rods as large as a lead-pencil. 
 Study also a piece of solder, which is a mixture of tin 
 and lead; a piece of pewter which is also lead and tin, 
 but containing a much larger proportion of tin; a piece 
 of brass, which is composed of about six parts of copper 
 and four parts of zinc; and a bit of bronze which con- 
 tains ninety-five parts of copper, four of tin, and one of 
 zinc, varying to seventy parts of copper and eight of tin. 
 
 Compare the color, specific gravity, and hardness of 
 copper, zinc, and tin. 
 
 Which bends most easily? 
 
 Which "cries" or creaks when bent? 
 
 Write out the uses of each. 
 
 Are "tin" pans and pails made wholly of tin? 
 
 Test the fusibility of these metals. 
 
 3. Observe the properties of mercury. 
 What is its popular name? 
 
 Try to freeze it. (It becomes solid at 40 degrees F.) 
 How does its weight compare with that of water? 
 
 Ascertain by reading or inquiry from what ore it is 
 
 produced. Make a list of its uses. 
 
 4. Examine a piece of silver. Compare it with pure 
 tin. Testitwithacidsand withfumesof sulphur. Itsuses? 
 
 5. Study platinum and gold. Note their resemblan- 
 ces and differences. Which is the more easily fusible? 
 
 Test the effect of various acids upon gold and plati- 
 num. Test the effect of the fumes of sulphur upon 
 them. Consider their malleability, and examine a piece of 
 gold-leaf. What are the chief uses of gold and platinum ? 
 
198 THE WORLD OF MATTER. 
 
 CHAPTER XXIII. 
 
 HOW TO DETERMINE MINE*RALS. 
 
 When you find a new mineral one of the first ques- 
 tions that occurs to you is, What is it? The process of 
 finding the name of a mineral from a study of its proper- 
 ties is called "determining" the mineral, and the vari- 
 ous methods of accomplishing this determination con- 
 stitute a science by themselves, a science known as 
 determinative mineralogy. The simplest method of 
 determining minerals, and a method that is sufficient for 
 most of the common varieties, depends upon the study 
 of their physical properties. As I have repeatedly said, 
 there is no use at all in trying to study mineralogy un- 
 less you have the minerals in your hand, and unless you 
 make the observations upon them yourself, and with 
 the least possible help. For this reason the collec- 
 tion accompanying this book has been prepared. You 
 have already found it useful as a means of illustrating 
 the previous chapters. It remains to make use of it in 
 showing you the simpler methods of determining the 
 minerals you may hereafter obtain. For this purpose 
 the specimens are numbered but not named. There is 
 a key to the collection at the end of this book, but you 
 are not to refer to it until you have done your best to 
 determine the names of the specimens by the method 
 
HOW TO DETERMINE MINERALS. 199 
 
 now to be described. After you Have decided on these 
 names as well as you can, you may turn to the key to 
 satisfy yourself as to the correctness of your determina- 
 tions. 
 
 We will first try only a dozen of the most easily re- 
 cognized specimens. Select from the collection num. 
 bers i, 2, 3, 5, 6, 7, 1 1, 29, 26, 28, 30, and 32. 
 
 Examine these specimens, noting their hardness, 
 color, streak, etc., and write a description of each. Then 
 by comparing your observations with the following 
 brief descriptions, determine the name of each speci- 
 men. Of course, the descriptions here given will not 
 follow the numbered order of the specimens. 
 
 HINTS. 
 
 The only tools needed are the streak and scratch- 
 plate (furnished with the collection), and a pocket- 
 knife. 
 
 In using the glass plate to test hardness or streak, do 
 not scratch the plate all over with your specimen. A 
 scratch or streak-line as long as this is sufficient. 
 
 Generally the color of the streak will be seen better 
 if the streak-plate is put upon a piece of white paper. 
 
 Whenever you have made out a mineral, write the 
 name on a small label and place it in the compartment 
 with the specimen. 
 
 Sometimes the mineral to be determined forms only 
 a part of the specimen. A portion of the rock in which 
 the mineral occurs may be present, or some other asso- 
 ciated mineral. In this case try to find which is the 
 
200 THE WORLD OF MATTER. 
 
 essential mineral, and see whether you cannot deter- 
 mine also the others that accompany it. 
 
 Hardness. Find out how many of the twelve speci- 
 mens you can scratch with your finger-nail and put these 
 aside; then find the softer and harder ones among these; 
 see what minerals described below have hardness i and 
 2, and from the description try to determine which 
 specimen is -talc, which is kaolin, graphite, gypsum, 
 etc. Label all those you have determined; the other 
 specimens try with your knife; do not disfigure the 
 whole specimen with scratches; a little scratch in some 
 corner will tell the story, and the specimen will be as 
 good as before. Put aside all those you can scratch 
 with your knife, separating those that you can scratch 
 easily from those that require force. The hardest of 
 these will scratch the glass plate (the smooth side of 
 this is to be used for receiving the scratches.) In this 
 manner you will find the minerals that have hard- 
 ness 3 to 6. The specimens that are still left will 
 scratch the glass easily; they will have hardness 7 or 8. 
 
 Lustre. Examine a porcelain dish, a mother-of-pearl 
 button, a piece of white wax, white satin or silk, and a 
 silver dollar: All these are white, but each has a differ- 
 ent lustre; each reflects the light differently. The 
 lustre of minerals often resembles that of glass, or wax, 
 or silk, or pearl; these minerals are said to have a 
 glassy (vitreous), waxy, silky, or pearly lustre. 
 
 In examining the minerals for their lustre, notice first 
 whether the lustre is metallic or non-metallic. If 
 the specimen does not shine like silver, or gold, or 
 
HOW TO DETERMINE MINERALS. 201 
 
 brass, or copper, or steel, or any other metal, the lustre 
 is non-metallic; you will judge next whether the lustre 
 of your specimen resembles that of glass, or pearl, or 
 resin, etc. Minerals that have no lustre, such as chalk and 
 clay, are called dull. In some minerals the lustre looks 
 somewhat metallic, but not clearly so; for these the 
 term sub-metallic is used. 
 
 Transparency. Some minerals are as clear as glass; 
 they are transparent; some let the light through dimly, 
 like thin China ware; they are translucent; some 
 do not let any light through; they are opaque. Semi- 
 transparent means half-transparent, not quite clear and 
 not very dim; the streak-plate is a good example. In 
 some minerals a faint light passes only through the 
 edges; these are called sub- or semi-translucent. 
 
 STREAK. 
 
 The streak or powder of the specimen is of more im- 
 portance for its determination than the color; it shows 
 the essential color of the mineral. Most of the minerals 
 that are white or colorless when pure, have a white 
 streak even when they are colored. Take some clear 
 glass and some colored glasses and grind each to a fine 
 powder; the powder will, in all cases, be white (with 
 probably a faint tint of color in some instances), because 
 the amount of coloring matter used is very small. To 
 test the streak, rub one of the edges or corners of the 
 specimen against the ground side of the streak-plate, 
 causing it to trace a small line- on the latter, and notice 
 the color. The minerals of the hardness of 7 and 8 
 
202 THE WORLD OF MATTER. 
 
 will not leave any trace of their powder on the glass 
 because they scratch it, but as they have, almost with- 
 out exception, a white or grayish streak, it is not neces- 
 sary to test them. Their essential color may be found, 
 however, by breaking off a small chip and grinding it to 
 a fine powder. 
 
 TASTE AND ODOR. 
 
 A few mineral salts can be distinguished by their 
 taste; some minerals have a peculiar odor; in kaolin, 
 and all rocks containing clay, the clayey or argil- 
 laceous odor is readily noticed after breathing upon 
 them; in others the odor is brought out by rubbing the 
 specimen against another stone or by breaking it with 
 a hammer. 
 
 DESCRIPTION OF THE TWELVE MINERALS. 
 
 I.' Calcite (calcspar). Hardness, 3; streak, white; 
 lustre, vitreous; color, generally white or light colored, 
 but also of darker colors ; transparent to opaque. The 
 colorless, transparent variety is called Iceland spar. 
 Marble is a crystalline variety with a sugary fracture. 
 Limestone is a common, compact variety. 
 
 2. Talc. Hardness, i ; streak, white; lustre, pearly; 
 color, greenish to white; translucent; smooth, slippery, 
 soapy to the touch. Commonly called soapstone, also 
 steatite and French chalk. Foliated talc can be separated 
 with a knife into thin scales, somewhat like mica, but 
 mica is elastic, talc is not. 
 
 3. Gypsum. Hardness, 2; streak, white; lustre, 
 
HOW TO DETERMINE MINERALS. 203 
 
 pearly, glassy, silky or dull; color, white, 'gray, pink, 
 brownish, etc. The colorless, transparent variety is called 
 selenite; the fibrous variety, satin spar; the white fine 
 grained variety, alabaster. Foliated gypsum resem- 
 bles talc and mica, but it is not greasy to the touch like 
 talc, and it is not split as easily as mica, and is not elastic. 
 
 4. Mica (tnuscovite) Hardness, 2; streak, white; 
 lustre, pearly, somewhat metallic; color, white to gray 
 and brownish. Can be easily split into thin elastic 
 leaves; used in stoves. Often wrongly called isinglass. 
 Isinglass is a kind of glue, made from the air-bladder 
 of the sturgeon, and used for making jelly. 
 
 5. Fluorite (fluor spar}. Hardness, 4; streak, 
 white; lustre, vitreous; colorless or of various beautiful 
 tints; more or less transparent. The specimen in this 
 collection resembles calcite and quartz, but it is easily 
 distinguished by its hardness; it will scratch calcite and 
 will be scratched by quartz. 
 
 6. Quartz. Hardness, 7; streak, white; lustre, vit 
 reous; color, colorless (rock crystal); also white 
 (milky quartz;) pink (rose quartz); brown or nearly 
 black (smoky quartz); violet (amethyst); yellow 
 (false topaz). These and some others are the glassy 
 varieties of quartz; all these are transparent to translu- 
 cent. Nearly all the light-colored pebbles found on 
 river banks or lake shores are quartz; sand is usually 
 composed of quartz grains. 
 
 7. Orthoclase (feldspar}. Hardness, 6; streak, 
 white; lustre, vitreous. Compare this specimen with 
 calcite. Although the lustre in both may be called 
 
204 THE WORLD OF MATTER. 
 
 glassy (vitreous) there is some difference. In calcite 
 the lustre is easily seen in all directions. In orthoclase 
 the lustre inclines somewhat to the silky, and you have 
 often to turn the specimen around in your fingers and 
 look at it in this way and that before you see the lustre 
 plainly ; examine until every part has shown its lustre 
 to you. Color, white, yellow, gray, pink, and other 
 light tints; translucent, at least at the edges, sometimes 
 transparent. 
 
 8. Apatite. Hardness, 5; streak, white; lustre, vit- 
 reous; color, generally green, sometimes brown, yel- 
 lowish or white; generally opaque, often translucent 
 at the edges. 
 
 9. Halite (rock salt]. Hardness, 2 ; streak, white ; 
 lustre, vitreous; color, white, gray, red, rarely blue or 
 violet. Taste, salty. 
 
 10. Galenite (lead ore]. Hardness, 2\\ streak, lead- 
 gray; lustre, metallic; color, gray. Often contains a 
 little silver. 
 
 11. Hematite {iron ore) (variety , specular iron). 
 Hardness, $J; streak, red; (rub on the streak-plate and 
 blow away the shiny scales to see the streak) ; lustre (of 
 this variety), metallic; color, gray. There are other 
 varieties of hematite iron ore of different lustre and 
 color, but the red streak is common to all. 
 
 12. Iron pyrites (JooPs gold}. Hardness, 6; streak, 
 dark greenish or gray; lustre, metallic; color, brass- 
 yellow; sometimes contains gold. To distinguish it 
 from gold, hammer it; gold flattens; pyrites crumbles 
 into a dark, greenish powder. 
 
FLAME, HEAT AND ACID TESTS. 205 
 
 CHAPTER XXIV. 
 
 FLAME TESTS, HEAT TESTS, AND ACID TESTS. 
 
 The properties by which you determined the names 
 of the twelve specimens described in the preceding 
 chapter are those which enable one to distinguish a 
 mineral by looking at it, and testing it by means of a 
 pocket-knife and a streak. plate. This is the simplest 
 method of determination, and the student should try to 
 determine by it as many specimens as possible. But 
 in order to be certain that the determinations are cor- 
 rect, and also that he may learn the composition of 
 minerals, he must learn to apply other tests with heat 
 and with acids. These are also called dry and wet 
 tests. 
 
 APPARATUS NEEDED. 
 
 For these tests you will need an alcohol lamp, or a 
 Bunsen gas-burner, a forceps preferably with platinum 
 points small open and closed tubes of hard glass, and 
 a few test-tubes. 
 
 It will also be convenient, though not necessary, to 
 have a small agate mortar and pestle; a few small por- 
 celain dishes, such as are in dolls' "china sets," and a 
 magnifying-glass. 
 
206 THE WORLD OF MATTER. 
 
 HINTS, 
 
 Make all the tests yourself, getting from a friend or 
 teacher any further suggestions you may need about 
 the handling of the apparatus or the acids. 
 
 Small fragments chipped from each specimen will 
 be sufficient for all the tests. 
 
 Be careful with the acids; they stain and burn. 
 
 Be neat and orderly. A noted mineralogist makes 
 his determinations on a parlor table, and makes so little 
 dust that a stroke of the handkerchief removes all traces 
 of his work. 
 
 Keep your apparatus in a suitable box. 
 
 Clean and dry all apparatus after use. 
 
 In chapter XV, on salt, we have already given prac- 
 tical directions for testing the colors of flames, and these 
 need not be repeated. Before studying any new min- 
 erals, however, it will be best for you to repeat the test 
 there described for showing the yellow sodium flame, 
 and also to make the following simple experiments with 
 the specimens treated in the preceding chapter. 
 
 i. Break off a little chip of calcite, and giving it a 
 few taps with a hammer, notice how it breaks into little 
 crystals, some of them quite perfect. Take one of the 
 larger crystals and hold it in the flame. Probably it will 
 not show any distinct color, but will fly to pieces or 
 "decrepitate." 
 
 The metal calcium, which is in calcite, gives the 
 flame an orange color, but this is not always easily seen; 
 it can be coaxed out by grinding a crystal of the calcite 
 to powder, wetting it with a drop of water, and a drop 
 
FLAME, HEAT AND ACID TESTS. 207 
 
 of hydrochloric acid, then steeping in this a few fibres 
 of asbestus and holding them in the flame. 
 
 2. Try fluorite; it decrepitates more readily than 
 calcite; it often shows the calcium flame more dis- 
 tinctly than the former. An interesting experiment 
 with fluorite is the following: Heat an iron shovel al- 
 most to redness; take it into a dark room and throw 
 some grains of fluorite on it; the fragments will be- 
 come luminous, shining with a beautiful bluish or 
 greenish light ^this is called phosphorescence. Apatite 
 often shows phosphorescence when heated; less fre- 
 quently calcite and dolomite. 
 
 3. Try gypsum; see how it turns white under the 
 intense heat. Wet it, heat it again, and notice the 
 color of the flame ; gypsum also contains calcium. After 
 you have burnt the gypsum white, you have "plaster 
 of Paris." 
 
 4. Treat a scale of mica as you did gypsum, and 
 notice the difference. 
 
 5. Chip off a piece of galenite; notice the cleavage. 
 Hold a very thin piece in the flame; after it is hot, hold 
 it just outside the edge of the flame and admire the 
 delicate blue color; does it melt? Does it smell of sul- 
 phur? 
 
 6. Try the same with iron pyrites; generally it de- 
 crepitates; if the galenite did not smell strong enough 
 of sulphur, this will satisfy you. 
 
 7. Orthoclase after being heated should show a pur- 
 ple flame, because it contains potassium; if it does not, 
 wet it with a drop of HC1, heat it again near the tip of 
 
208 THE WORLD OF MATTER. 
 
 the flame, then hold it to the outer edge to see the color. 
 [In many cases moistening the mineral with hydro- 
 chloric acid helps to bring out the characteristic flame. 
 A little dish with a drop of HC1 mixed with a drop of 
 water is very handy for this purpose; moisten your 
 splinter or your fibres of asbestus by touching the edge 
 of the drop with it]. 
 
 8. Apatite will generally give no characteristic 
 color. Powder a little, wet with one small drop of 
 sulphuric acid; wipe off part of the powder with a 
 little asbestus that has first been heated in the flame (to 
 burn away dust or. sodium), then try the flame test. It 
 will show a brownish color, turning to bluish green, 
 which shows the presence of phosphoric acid. 
 
 WHAT CAN WE LEARN FROM THESE FLAME TESTS? 
 
 First That certain minerals, on account of the ele- 
 ments which are in them, impart peculiar colors to the 
 flame; these are due to the vapors which the elements 
 give off when heated. 
 
 Intense yellow flame (bordering on orange) indicates 
 that sodium is present. 
 
 Yellowish-red flame indicates calcium. 
 
 Violet or purplish flame indicates potassium. 
 
 Carmine-red flame indicates lithium. 
 
 Crimson flame indicates strontium. 
 
 Emerald-green flame indicates copper (also thallium). 
 
 Yellowish-green flame indicates barium or boracic 
 acid. 
 
 Bluish-green flame indicates phosphorus. 
 
FLAME, HEAT AND ACID TESTS. 269 
 
 Azure-blue (intense) flame indicates selenium. 
 
 Light-blue flame indicates arsenic. 
 
 Copper in combination with chlorine gives also a 
 beautiful blue flame. Dip a piece of copper wire into 
 HC1 and hold it in the flame; notice the change from 
 azure-blue to emerald-green as the chlorine evaporates. 
 
 The characteristic flame color of a mineral is often 
 hidden by impurities or associated minerals. Especially 
 sodium, if present, makes it difficult to distinguish the 
 true color. If the flame is viewed through blue glass, 
 the yellow sodium flame is not seen. The calcium 
 flame is sometimes changed by the presence of barium 
 or strontium. 
 
 Second That some minerals melt, at least partly, 
 even in the flame of an alcohol lamp. 
 
 7 hird That some minerals, especially those with 
 eminent (very perfect) cleavage, fly to pieces when 
 heated. 
 
 Fourth That some minerals emit a peculiar odor 
 when heated, the most characteristic being: 
 
 Sulphurous odor most minerals containing sulphur. 
 
 Garlic odor minerals containing arsenic. 
 
 Horse-radish (decaying) odor minerals containing 
 selenium. 
 
 Bituminous odor mineral hydrocarbons (coal, etc.). 
 
 HEAT TESTS WITH THE OPEN AND CLOSED TUBE. 
 
 Very small grains of the minerals are generally best 
 for heat tests. To transfer them to the tube, a little trough 
 made of paper or tin is the most convenient instrument. 
 
Ho THE WORLD OP MATTER. 
 
 Cut a strip of paper three or four inches long and one- 
 eighth of an inch wide, arid double it lengthwise; near 
 the end of this trough put the fragments or powder of 
 your mineral and insert it in the tube; this prevents the 
 mineral from sticking to the sides of the glass. Push 
 the paper into the tube until your mineral fragments 
 are about half an inch from the end, then give the tube 
 half a turn, and withdraw the paper. See that your 
 tubes are clean and dry inside and outside before you 
 begin a test. . 
 
 HEAT TESTS FOR THE MINERALS DESCRIBED IN 
 CHAPTER XXIII. 
 
 1. Put a few small pieces of gypsum into the closed 
 tube and heat the closed end of the tube in the alcohol 
 flame; notice drops of moisture gathering in the upper 
 part of the tube; heat until no more moisture gathers; 
 drive the water farther up by heating the part in which 
 it has gathered. This will show that moisture is always 
 driven from the hotter to the cooler part, evaporating 
 in the former and condensing in the latter. Pour out 
 the gypsum; it is white, and has again, as before, been 
 changed by driving out the water. 
 
 Try the same experiment with powdered talc. The 
 powder of limonite should be yellow or brown; notice 
 its color after the water has been expelled. Try quartz, 
 orthoclase, and hematite, and see whether you can drive 
 out any water. (Minerals tying in damp places some- 
 times absorb some moisture). 
 
 2. Try fluorite, and notice how it decrepitates. Take 
 
FLAME, HEAT AND ACID TESTS. 2ii 
 
 x vj-'.< r 
 
 the tube, after heating the fluorite, into a dark room 
 and notice again the phosphorescence. 
 
 3. Put a few grains of iron pyrites into the closed 
 tube, and heat it; a yellow coating of sulphur will form 
 on the cooler part; it is driven out of the pyrite in the 
 form of vapor, and it condenses again above, where it 
 is cooler; this is called forming a sublimate. Notice 
 the odor given off while heated. Wet a narrow strip 
 of blue litmus-paper, and insert it about one-fourth of 
 an inch in the tube; heat the mineral again and notice 
 the paper turning from blue to red; this is a sign that 
 acid fumes are escaping. Try the same with galena, 
 pulverized finely; it takes stronger heat to drive the sul- 
 phur off, but you will notice the odor and the acid re- 
 action on the litmus paper. Of course, a tube in which 
 sulphur has formed must not be taken for another ex. 
 periment until all the sulphur is removed. You can 
 drive it off by heat as you did the moisture, but it takes 
 stronger heat and a little skillful management. 
 
 Fluorite and pyrites should also be tried in the open 
 tube. Insert a few grains of the iron pyrites, by means 
 of your trough, in the open tube, depositing it about 
 half an inch from one end; hold the tube at the other 
 end, slanting, just so that the pieces will not fall out; 
 and hold the grains over the flame; notice again the 
 sublimate, the odor, which will be stronger than before, 
 and the acid reaction on the blue litmus-paper. 
 
 The difference between the test in the closed tube 
 and the open tube is this: in the former the substance 
 is heated without the presence of oxygen, because most 
 
2ii THE WORLD OF MATTER. 
 
 of the air is driven out of the tube by the heat; in the 
 latter, there is a draft of air passing through the tube 
 while the substance is heated, and the vapors can unite 
 with the oxygen of the air. In the case of heating 
 the iron pyrites in the closed tube, nearly all the sul- 
 phur settles on the cooler part of the tube, while in the 
 open tube most of it unites with oxygen and leaves the 
 tube, causing the, strong odor. 
 
 WHAT CAN WE NOTICE IN THE TESTS WITH THE 
 CLOSED AND OPEN TUBES? 
 
 The substance may decrepitate; in this case the min- 
 eral should be used in the form of powder. 
 
 It may give off an odor, generally of the same kind 
 as that noticed in the flame test, but stronger. 
 
 Moisture may form in the tube, which indicates that 
 the mineral contains water. 
 
 A coating, or sublimate, may form on the cool part 
 of the tube. The following are the most important: 
 
 A yellow coating indicates sulphur; the odor will 
 prove it : brown-red when hot, and reddish-yellow when 
 cold indicate arsenic sulphide: brilliant black, metallic, 
 arsenic, the garlic odor furnishing additional proof: 
 black when hot, brown-red when cold, formed near the 
 mineral after strong heating, antimony sulphide: dark 
 red, selenium (horse-radish odor): a metallic mirror, 
 composed of little metallic drops, mercury (quicksilver). 
 
 A few other coatings will be mentioned in the de- 
 scriptions of the minerals which produce them. 
 
 Acid or alkaline vapors may be driven off; the first 
 
FLAME, HEAT AND ACID TESTS. 213 
 
 will redden blue litmus-paper, and the second will turn 
 red litmus blue. The papers must be moistened. 
 
 A change of color may take place, as with limonite, 
 which changes into red hematite. 
 
 Phosphorescence is sometimes observed. 
 
 ACID TESTS. 
 
 HC1 Hydrochloric acid; H 2 SO f Sulphuric acid. 
 
 For transferring the few drops of acid needed from the 
 bottle to the test-tube, the dipping-tube, that is, a nar- 
 row glass tube about eight inches long, should be used; 
 dip the tube about one inch into the acid, and close the 
 top with your finger; lift it out and transfer it to the 
 test-tube which you hold in your left hand, and when 
 the lower part of the dipping-tube is near the bottom 
 of the test-tube, remove the finger and the acid will 
 flow out. But first put your mineral a few grains, 
 powdered into the test-tube ; then, if the mineral is to 
 be tested with diluted acid, add a few drops of water, 
 using the dipping-tube; and lastly put in the acid 
 Never put the water into the tube after the acid, always 
 before. 
 
 In heating the contents of the test-tube do not apply 
 the bottom of the tube to the flame, but hold it slant- 
 ing and let the upper part of the liquid be nearest the 
 flame; else a steam-bubble, from the bottom, may throw 
 the acid out of the tube. Heat gradually. You will 
 find it safer to heat the acid by passing the test-tube 
 repeatedly through the flame instead of holding it 
 steadily in it. If the acid has a tendency t.o spurt, as it 
 
214 THE WORLD OF MATTER. 
 
 will sometimes, plug the opening of the tube with a 
 light wad of cotton, or better, asbestus. Do not turn 
 the opening of the tube toward you. See that the out- 
 side of your test-tube is dry, else it is liable to crack. 
 Have the lamp on a slate or tray. You can use the 
 tube-holder with the test-tube, but experts use their 
 ringers. 
 
 EXPERIMENTS WITH ACIDS. 
 
 After having read the foregoing directions carefully, 
 you may begin to test your specimens. 
 
 i. Powder a fragment of calcite and transfer to the 
 bottom of the test-tube; dip the dipping-tube an inch 
 into water, then close the top with your finger and 
 transfer the water into the test-tube. Do the same with 
 HC1. Do not let the liquids flow down the side 
 of the test-tube, but deposit them just above the 
 powdered mineral. Notice the effervescence or bubbling 
 up of gas. Put a drop of acid on the piece of calcite 
 and see again the effervescence ; if you have a piece of 
 marble, try it on that. See whether the acid will have 
 the same effect on any other mineral in your collection.. 
 Thus we have an easy method for determining calcite or 
 limestone. After the calcite is all dissolved, heat the 
 solution to concentrate it; then put a drop on the 
 smooth side of your streak-plate, or any other piece of 
 glass; also put a drop of pure HC1 on the glass, and 
 let both dry; examine both drops; of the HC1 very 
 little is left; of the calcium chloride, which was in the 
 first drop, you may see the crystals with a magnifying 
 glass. The glass plate should be slightly warmed. 
 
FLAME, HEAT AND ACID TESTS. 215 
 
 2. Powder a little fluorite and put it into a test-tube; 
 examine the tube first to see whether it is perfectly 
 clean and clear, especially near the bottom. 
 
 Put in a few drops of H 2 SO 4 , not diluted with 
 water; heat slowly and carefully; do not smell the 
 fumes in this test; they are poisonous. When the acid 
 is nearly evaporated, let the tube cool, then wash it out 
 with water and let it dry; you will find that the glass 
 has been attacked (corroded) by the fluorite. 
 
 Another test: Put a little powdered fluorite on the 
 smooth side of your streak-plate; let one drop of sul- 
 phuric acid fall on it; put the plate away in a safe place 
 over night, wash away the acid and powder and notice 
 the effect on the glass. These are tests to detect the 
 presence of fluorine in a mineral. 
 
 WHAT HELP CAN WE GET FROM THE ACID TESTS 
 TO DETERMINE MINERALS? 
 
 Some minerals dissolve with effervescence in diluted 
 HC1, especially the carbonates, as carbonate of calcium 
 (limestone), carbonate of iron (siderite), and others. 
 
 Some minerals dissolve without effervescence. 
 
 Some minerals dissolve partly or sparingly. 
 
 The substance formed by the solution may be found 
 by evaporating the liquid. It will generally crystallize; 
 the crystals cannot always be seen by the naked eye, but 
 the student possessing a microscope will find a source 
 of great delight in their examination. 
 
2i6 THE WORLD OF MATTER. 
 
 CHAPTER XXV. 
 
 TWELVE OTHER MINERALS. 
 
 We will now examine twelve other common miner- 
 als. (Specimens Nos. 8, 10, 16, 17, 18, 21, 22, 25, 27, 
 34,35, and 36.) 
 
 Determine these if possible by an examination of 
 their physical properties. Afterward use the flame, 
 heat, and acid tests to identify any not recognized by 
 their external characteristics, and to verify your de- 
 cisions with regard to the others. 
 
 It is a good plan to enter in a blank book the obser- 
 vations made on each specimen as it is tested. Com- 
 pare your descriptions with those that follow. 
 
 Abbreviations: H. hardness; fl. flame test; c.t. 
 closed tube; o.t. open tube; comp. composition; 
 b.b. before the blowpipe. 
 
 Italics indicate important characteristics which will 
 help you distinguish a mineral from others that more or 
 less closely resemble it. 
 
 DESCRIPTION OF THE SECOND DOZEN MINERALS. 
 
 i. Sulphur. H., 2; lustre, resinous; color, yellow 
 to gray or brown ; streak, yellow ; translucent to opaque ; 
 generally massive, sometimes crystallized, also stalactitic; 
 fracture, uneven ; very brittle; light. 
 
 Comp. S., Fl., burns with a blue flame and sulphur- 
 
TWELVE" OTHER MINERALS. 217 
 
 ous odor, and melts; c. t., melts, then vaporizes, the 
 vapor forming a coating on the cooler part of the tube. 
 When the mineral is held in the warm hand a crackling 
 noise is heard. It becomes electric when rubbed. 
 
 2. Stibnite (gray antimony). II., 2.5; lustre, metal- 
 lic; color, lead-gray; streak, gray; opaque; crystalline; 
 columnar or fibrous to massive granular; cleavage, per- 
 fect to indistinct; brittle; rather heavy. 
 
 Comp. Sb 2 S 3 (antimony sulphide). Fl., bluish, 
 decrepitates, melts , sulphur odor; c. t., decrepitates, 
 melts, acid reactions on litmus paper; o. t., fills the tube 
 with white fumes, characteristic of ores of antimony 
 and which leave a white coating; peculiar odor in 
 which sulphur can readily be detected. As the frag- 
 ments decrepitate violently, they should be finely pow- 
 dered for this test. HC1, dil.; generates sulphuretted 
 hydrogen, marked by its disagreeable odor. Stibnite 
 is named from stibium, the scientific name for the ele- 
 ment antimony. Stibnite is easily recognized on ac- 
 count of its melting so readily. 
 
 3. Sphalerite (zinc blende, Black Jack).H., 
 nearly 4; lustre, resinous or metallic; color, yellow to 
 red. brown, and grayish; streak, yellowish white; trans- 
 lucent to opaque; crystalline, sometimes granular to 
 nearly compact; cleavage, perfect; brittle; rather 
 heavy. 
 
 Comp ZnS, (zinc sulphide). FL, does not melt; 
 sulphur odor; c. t., acid reaction. HC1 evolves sul- 
 phuretted hydrogen, especially when heated. Sphaler- 
 ite comes* from a Greek word meaning treacherous. 
 
2x8 THE WORLD OF MATTER. 
 
 The German word blende means deceiving; it is often 
 found together with galena, but yielding no lead, the 
 miners thought a trick had been played on them by the 
 goblins. It is now an important source of zinc. 
 
 4. Cryolite. H., 3; lustre, vitreous; colorless to 
 white and brownish; streak, white; transparent to 
 translucent; usually massive; cleavage not always 
 distinct; brittle, light. 
 
 Comp. Na 6 Al 2 F 12 ; FL, yellow soda flame; melts 
 in the hot part of the flame. This test affords an easy 
 distinction between this mineral and others that resemble 
 it in color and lustre; take a small splinter for the test. 
 C. t. decrepitates; acid reaction; etches the glass a little 
 above the point where it is heated. Try the tests for 
 fluorine. Cryolite is used for making soda, the metal 
 aluminum, and a white glass. Siderite frequently ac- 
 companies cryolite. Cryolite means ice-stone; this 
 name is given to it because it melts easily. 
 
 5. Limonite. H., about 5 ; streak, yellow to brown ; 
 lustre sub-metallic to silky; color, yellow or brown; 
 brittle; cleavage, uneven, splintery. 
 
 Comp. 2 Fe 2 O 3 -f- 3 H 2 O; c. t. yields water which 
 condenses in upper part of tube. Compare the streak 
 of limonite with the streak obtained by rubbing a rusted 
 bar of iron on paper. It is reasonable to conclude from 
 the close similarity of the streaks that we have in this 
 limonite iron-rust or, what is the same thing, iron oxide 
 iron combined with oxygen taken from the air. The 
 name limonite is derived from a word meaning a mead- 
 ow or swamp, and is used because this "bog-iron-ore" is 
 
TWELVE OTHER MINERALS. 219 
 
 formed in wet places. Test the streak of limonite after 
 it has been heated in the closed tube: it is now red, not 
 yellow. Compare it with the streak of hematite; it has 
 the same appearance. In fact hematite is exactly like 
 limonite from which the water has been expelled by 
 heat. 
 
 Neither ore is attracted by a magnet. Limonite and 
 hematite are the two great natural coloring agents. Al- 
 most all the yellow, brown, and red colors in rocks and 
 soils are due to them. 
 
 6. Chlorite. H., about 2; lustre, pearly to dull; 
 streak, light green; color, dark green; clay odor 
 noticed when the specimen is breathed upon; generally 
 somewhat greasy to the touch. 
 
 Comp. Chlorite is properly the name of a group of 
 highly basic minerals of variable composition, but all 
 essentially hydrous silicates of aluminum, magnesium 
 and iron. The specimen in this collection is prochlorite, 
 one of the most abundant species. It yields water in 
 the closed tube. 
 
 7. Celestite. H., 4; lustre, vitreous to pearly ; col- 
 orless, white, generally with a bluish tint, also yellow- 
 ish; streak, white; transparent to translucent; crystal- 
 line, brittle. 
 
 Comp. SrSO 4 , (strontium sulphate): Fl. decrepi- 
 tates slightly. The characteristic flame is a deep crim- 
 son red\ but it is difficult to get it in the alcohol flame 
 without the use of the blow-pipe; you will succeed, 
 however, in coaxing it out by treating it in the follow- 
 ing manner: 
 
220 THE WORLD OF MATTER. 
 
 Grind a small fragment to a fine powder; take some 
 fibres of asbestos, dip them in the powder and hold 
 them with the forceps in the edge of the blue flame; a 
 yellowish flame generally appears at first, but after con- 
 tinued heating, especially by holding it for a little while 
 in the hottest part of the flame, the color will turn to a 
 reddish hue; now slightly moisten the tip of your as- 
 bestos with HC1 (by holding it just at the edge of a 
 drop of the acid) introduce into the flame again and 
 notice the crimson flashes. Keep it in the flame for a 
 little while; if the color is not distinct, repeat the test. 
 
 Celestite is derived from the latin word for skj, be- 
 cause the mineral is sometimes blue; preparations made 
 from this mineral are used for the crimson lights in fire- 
 works. 
 
 8. Kaolinite. H., i to 2; color, white when pure, 
 (then used to make porcelain) but generally yellowish 
 or gray; streak, same as color; lustre, none, i.e. dull; 
 friable, (crumbling between the finger). A yellowish 
 clay. 
 
 Comp. Al 2 Si.,O 7 + 2H 2 o. Infusible and insoluble. 
 C.t. yields water. 
 
 9. Hornblende. (amphibole). H., 5J; streak, 
 white; color, greenish to black; lustre, silky to vitreous, 
 reminding one of the lustre of feldspar; brittle, 
 cleavage, prismatic, perfect. 
 
 Comp. (Ca Mg Al Fe)Si O 3 . Insoluble, infusible. 
 
 10. Labradorite. H., 6; lustre, vitreous to pearly, 
 feldspar lustre; color, generally light and dark gray 
 mixed: streak, white; translucent; generally massive j 
 
TWELVE OTHER MINERALS. 221 
 
 cleavage, perfect to interrupted; brittle. Labradorite 
 often shows a beautiful play of colors if viewed at a 
 certain angle, (especially in the dark gray portions) ; 
 blue and green are the more common colors; yellow 
 and red are rare. The color is generally seen best on 
 wetting the specimen. Labradorite is a variety of feld- 
 spar (soda-lime feldspar); it is generally darker and a 
 little heavier than the other varieties. It is named from 
 Labrador, where fine specimens have been obtained. 
 
 Comp. (Na 2 Ca)Al 2 Si 3 O 1 . Insoluble. 
 
 ii. Biotite, (J)lack mica). H., nearly 3; lustre, 
 pearly to sub-metallic; color, black, or nearly so; streak, 
 gray; translucent to opaque; crystalline, foliated; 
 cleavage, perfect, sectile. The thin leaves into which 
 it splits are elastic. 
 
 Comp. (K FeMgAl) 2 SiO 4 , (potassium-iron-mag- 
 nesiiim-aluminum silicate): Fl., the purple potash 
 flame is often noticed. Put a few small scales into a test 
 tube, add about 10 drops of H 2 SO 4 (undiluted), and heat 
 carefully; the mineral will partly dissolve; pour off the 
 acid, leaving what remains of the mineral in the tube, 
 fill the tube with water to wash out the remaining acid 
 and examine what is left of the scales; they have 
 changed from black to white and now consist simply 
 of the silica, which remains undissolved. Muscovite 
 does not dissolve in H SO 4 . ' Between Muscovite and 
 Biotite there is another variety of mica called Phlogo- 
 pite. (/. <?., having a fiery appearance); it is generally of 
 a bronze lustre; it also dissolves in H 2 SO 4 . Biotite is 
 named after the French mineralogist Biot. 
 
$12 THE WORLD OF MATTER. 
 
 12. Chrysotile. H., 3. 75; lustre, silky; generally 
 greenish, but also light gray, yellow to brown; streak, 
 white; translucent; crystalline, fibrous, separates into 
 fine, flexible fibres. 
 
 Comp. Mg 2 SiO 4 +H 2 O, (hydrous magnesium sili- 
 cate): Fl. does not melt, but becomes brittle, c. t. yields 
 considerable water. Chrysotile is a fibrous variety of 
 serpentine; it is commonly called asbestos, and, indeed, 
 it resembles this mineral very closely, and is used for the 
 same purposes for which asbestos is used, that is, for 
 making fire-proof cloth, paper and ropes, coverings 
 for boilers, etc. Very fine silky varieties of asbestos 
 and chrysotile are called amianthus. The name, chry- 
 sotile, means golden fibre. Asbestos is a variety of am- 
 phibole, and the name means indestructible. Its compo- 
 sition is generally (Ca Mg Fe) Si O 3 . 
 
 WHAT THE TESTS MEAN. 
 
 Compounds are, as a rule, so different from the elements 
 of which they consist, that it is often impossible to tell, 
 by looking at a mineral, of what it is composed. There- 
 fore, some means are resorted to to separate or decom- 
 pose the compound, so that we can detect some well- 
 known and prominent property of the elements. This 
 examination of a substance is called analysis. If we 
 wish simply to know whether a certain element is pres- 
 ent in the compound we make a partial analysis; if we 
 wish to know every element that is present, we must 
 make a qualitative analysis, and if we wish to find 
 exactly how much (what percentage) of one or all the 
 
TWELVE OTHER MINERALS. 223 
 
 elements is present, we must make a quantitative 
 analysis. 
 
 ANALYSIS IN THE DRY WAY. 
 
 Flame tests. Heat decomposes nearly all com- 
 pounds. In the flame tests, part of the mineral becomes 
 decomposed and vaporizes, and those elements whose 
 burning vapor has a characteristic color or odor, as the 
 yellow of sodium, the orange of calcium, the emerald 
 green of copper, the odor of sulphur, arsenic, etc., can 
 be detected. 
 
 The tests in the tubes. Heat is used also in these 
 tests to decompose the compounds; sometimes we find 
 the elements separated in different parts of the tube, as 
 we noticed in testing iron pyrites, when sulphur and iron 
 were separated. Sometimes the acid-element is driven 
 off, and reveals itself by the smell, and by the change 
 of the color of litmus-paper; or, in the case of an oxide, 
 the oxygen may be driven off. In heating limonite, 
 the water is expelled, changing the hydrous yellow 
 substance to anhydrous red hematite. 
 
 EXAMINATION IN THE WET WAY. 
 
 The chemical power which holds the different elements 
 in a compound together, becomes weaker also through 
 solution. Few minerals dissolve readily in water, but 
 quite a number in HC1, H 2 SO 4 or HNO 3 (nitric acid). 
 When a mineral dissolves in an acid it unites with a 
 part of the acid and forms a new compound. Zinc, for 
 instance, dissolves in chlorhydric acid, and becomes 
 
124 THE WORLD OP MATTERS 
 
 chloride of zinc. If there is already an acid element in 
 the mineral, a stronger acid-element will drive it out 
 and take its place. Calcite, CaCO 3 is calcium com- 
 bined with the CO 3 part of carbonic acid, H CO 3 ; 
 HG1 is stronger than carbonic acid, it drives out the 
 CO 3 and combines with the calcium, forming, instead 
 of a carbonate, a chloride of calcium. The chemist puts 
 it down in this way : 
 
 CaC0 3 +2HCL=CaCl 8 +C0 8 +H 8 O. 
 
 What becomes of the CO 3 ? CO 2 escapes in bub- 
 bles, causing the effervescence. The other O unites 
 with the 2H left from the 2HC1 and forms H 2 O 
 (water) which remains in the test tube. 
 
 Calcium chloride is soluble in water, like common 
 salt. If we wish to get it in its solid form we must 
 evaporate the solution. 
 
 In applying the acid tests the following facts are 
 worth remembering: 
 
 An acid may form, with the mineral, a soluble com- 
 pound. Then the solution is clear; there is no sedi- 
 ment left after all is dissolved, as we saw in dissolving 
 calcite in HCL 
 
 An acid may form an insoluble compound; a precipi- 
 tate will then be formed, as in treating calcite or calcium 
 chloride with H 2 SO^. 
 
 An acid may dissolve a part of a mineral, as in the 
 case of biotite. 
 
 An acid may have no effect, the mineral being insolu- 
 ble, as quartz. 
 
TWELVE OTHER MINERALS. 22$ 
 
 In dissolving (or combining) minerals with HC1 you 
 change them to chlorides; with HNO 3 to nitrates; 
 with H 2 SO 4 to sulphates. 
 
 Carbonates will effervesce with HC1 (and other 
 stronger acids) some with the cold acid, others only 
 with the hot acid. 
 
226 THE WORLD OF MATTER- 
 
 CHAPTER XXVI. 
 
 BLO\T-PIPE ANALYSIS. 
 
 The analysis of many m'neral compounds requires a 
 greater heat than that of an alcohol lamp. This is 
 obtained by means of the blow-pipe, a simple instru- 
 ment by which a strong current of air is added to the- 
 flame of a lamp or gas-jet, increasing its heat by a 
 freer supply of oxygen, and at the same time directing 
 and concentrating the flame upon the specimen. 
 
 A simple curved brass blow-pipe, costing 20 cents, 
 answers the purpose. A stearine candle, with a thick 
 wick, furnishes a good flame ; but a properly arranged 
 Bunsen burner is better. Fig. 28K- 
 
 Charcoal is generally used as a support for the sub- 
 stances to be heated. It is best to buy the coal which 
 is specially prepared for this purpose. 
 
 Platinum wire and foil must be on hand. Platinum 
 makes excellent instruments for holding specimens in 
 the blow-pipe flame, because it does not melt. 
 
 The wire, No. 27, is cut into pieces about two inches 
 long. These should be fitted with wooden or glass 
 handles. Hold the end of a small glass tube, two 
 inches long, in the Bunsen flame, turning it as it grows 
 hot. As the glass softens, the opening in the tube 
 grows smaller; when just large enough to admit the 
 
BLOW-PIPE ANALYSIS. 
 
 platinum wire, insert about a quarter of an inch of it 
 into the tube, and finish melting it together. 
 
 Bend the free end of the wire into a round loop, an 
 eighth of an inch in diameter, and you have a service 
 
 able little instrument. A forceps with platinum points 
 is so convenient, as well to repay its cost. 
 
 Care must be taken not to use any platinum instru- 
 ments for testing lead, tin, zinc, or other easily fusible 
 ores, for they make an alloy with platinum, and render 
 it easily destructible. 
 
 Lay a sheet of paper under the lamp or burner before 
 beginning work. It will catch fragments dropped dur- 
 
THE WORLD OF MATTER. 
 
 ing the examination. Record all observations in a note- 
 book. 
 
 You must learn to blow a continuous blast through 
 the blow-pipe, while breathing naturally. This is ac- 
 complished by inflating the cheeks and allowing them 
 to contract, expelling the air while you are drawing in 
 your breath. It is difficult at first, and you should get 
 some one to show you how to do it if possible. 
 
 Hold the tip of the blow-pipe in the middle of the 
 flame, just above the wick, if you use an alcohol lamp 
 or a candle; do not push it quite 
 so far into the flame of a Bunsen 
 burner. Blow gently, so as to 
 cause the flame to taper away 
 from the blow-pipe to a fine point. 
 The brightness of the flame 
 should disappear, and you should 
 observe a fine blue cone sur- 
 rounded by a very faint flame. 
 When you can produce this 
 flame and maintain it steadily for 
 several minutes, blowing from 
 the cheeks and not from the chest, 
 you have mastered the art of 
 blowing. Fig. 29 represents a 
 candle flame,y is the dark central 
 portion filled with gases formed from the heated 
 stearine; a b c is the brilliant flame where the com- 
 bustion is incomplete, and the particles of carbon are 
 incandescent; a e c is the faint outer flame caused by the 
 
 Fig. 29. 
 
BLOW-PIPE ANALYSIS. 
 
 229 
 
 complete combustion of the carbon with hydrogen and 
 cxygen. Upon introducing the blow-pipe and blowing 
 gently, the flame takes the position shown in Fig. 30. 
 
 The increased supply of 
 oxygen causes more perfect 
 combustion, as shown by 
 the disappearance of the 
 brilliant flame, and the for- 
 mation of the blue cone, sur- 
 rounded by a still fainter 
 conical flame which extends 
 beyond it. 
 
 Substances held just be- 
 yond the blue cone in this 
 faint outer flame are heated in contact with the oxygen 
 of the air, and many metals thus become oxidized. 
 
 This outer flame is 
 therefore called the 
 oxidizing flame. 
 
 If the tip of the 
 blow-pipe is held just 
 outside the flame, and 
 the flame gently di- 
 rected outward and 
 downward, Fig. 31 the 
 flame keeps its yellow 
 colors, and if an oxide 
 of a metal is held in the end of this flame it becomes 
 partly or entirely deoxidized or reduced. 
 This then is the reducing flame.* 
 
230 THE WORLD OF MATTER. 
 
 O. F. stands for "oxidizing flame." This flame is 
 used not only for changing metals or their compounds 
 into oxides, but also to test the fusibility of minerals. 
 The hottest part is the tip of the blue cone. 
 
 R. F. stands for "reducing flame." It is chiefly used 
 to separate the metals from their compounds. 
 
 The Bunsen flame should be about an inch and a half 
 ^igh for the O. F., and half an inch higher for the R. F. 
 
 FIRST EXPERIMENTS. 
 
 Direct the O. F. upon a splinter of cryolite. 
 
 Observe how readily it melts. Try a small splinter 
 of celestite. It fuses, though less readily, and shows its 
 characteristic crimson flame. Place a drop of water on 
 red litmus-paper, and dip into it the fused splinter of 
 celestite; notice that the litmus turns blue. What does 
 this indicate? 
 
 Now try to melt a fragment of quartz. If you can 
 melt it in the slightest degree you perform a feat hith- 
 erto deemed impossible. 
 
 Try next a bit of galenite. In the platinum forceps? 
 Not unless you wish to ruin the instrument! 
 
 Make a slight excavation in a piece of charcoal about 
 half an inch from the end ; in this place the galenite and 
 direct the tip of the O. F. upon it. Stop occasionally to 
 observe the coating formed on the coal, and to smell the 
 fumes that arise. Notice that the color of the coating 
 near the specimen quickly changes from orange to light 
 yellow as you remove the coal from the flame, and that 
 it grows still lighter as it gets cold. Galenite, you re- 
 
BLOW-PIPE ANALYSIS. 231 
 
 member is lead sulphide. Some of the sulphur has 
 volatilized, combining with oxygen to form the odorous 
 fumes. Some -of the lead has united with oxygen, form 
 ing the yellow oxide deposited near the specimen or 
 assay ; another part of the lead has been changed into 
 lead sulphate, and is deposited farther away on the 
 cooler portion of the coal. Upon the remainder of the 
 assay direct now the R. F., until a bright little drop, or 
 globule is formed. Let this drop on a piece of asbestus 
 paper, or let it cool on the coal. 
 
 It is no longer brittle galenite, but malleable lead, 
 as you can prove by a blow of a hammer. 
 
 These simple experiments have shown the use of the 
 biovv-pipe : 
 
 To test the fusibility of minerals; 
 
 To exhibit colors imparted to the flame; 
 
 To oxidize and to reduce metals; 
 
 To cause the formation of coating; or sublimates, on 
 charcoal often an important aid in determining a min- 
 eral. 
 
 DEGREES OF FUSIBILITY. 
 
 We may call very easily fusible. Minerals whose 
 fragments melt in the alcohol or gas flame without a 
 blow-pipe; as stibnite, and halite. Fusibility i. 
 
 Easily fusible. Minerals that melt in the blow-pipe 
 flame in fragments as large as a grain of wheat; as 
 pyrites. Fusibility 2. 
 
 Fusible. Minerals melting less readily, but still 
 visibly affected in fragments as large as wheat grains; 
 as celesute. Fusibility 3. 
 
r,32 THE WORLD OF MATTER, 
 
 fusible with difficulty. Minerals that fus^ only in 
 very small splinters; as most varieties of hornblende. 
 Fusibility 4. 
 
 Almost infusible. Minerals that are rounded only 
 on the sharp points, and edges of minute splinters, after 
 long and strong heating, as orthoclase. Fusibility 5. 
 
 Infusible. Minerals not affected by flame; as quartz. 
 Fusibility 6. 
 
 "All the minerals named above are included in the col- 
 lection accompanying this book, and you should become 
 familiar with their action before the blow-pipe before 
 attempting others. 
 
 Other phenomena than fusing are sometimes observed 
 when blow-piping, e. g. swelling, branching, decrepita- 
 ting, brightly glowing (especially lime, strontia, zinc, 
 and tin). Careful notes should be made of everything 
 observed. 
 
 EXAMINATION ON CHARCOAL. 
 
 Easily fusible metals must be examined on char- 
 coal, as we saw in the case of galenite. If the speci- 
 men decrepitates so strongly as to fly to pieces when 
 touched by the flame, powder it. Moisten with a dl op 
 of water as much of the powder as you can take on 
 the point of your knife-blade, mix to a paste, and place 
 the mass in a little excavation made near the end of the 
 charcoal. In directing the flame upon the assay blow 
 gently until the moisture is expelled. 
 
 Try stibnite. It fuses readily, imparting a greenish 
 hue to the flame, and yielding dense white fumes which 
 f prm a white coating on the coal, 
 
BLOW-PIPE ANALYSIS. 233 
 
 Touch this coating with the tip of the R. F. and it 
 disappears, again tinging the flame with green. This 
 proves that the sublimate of antimony oxide is volatile. 
 
 Try sphalerite. The fragment does not fuse, though 
 it may form a yellow coating near the assay, turning 
 white as it cools. 
 
 You remember that when limonite was heated in a 
 closed tube a large quantity of water was driven off, 
 and the mineral afterward had the appearance of hema- 
 tite. Repeat the experiment with the blow-pipe. The 
 same result is produced more quickly under the intenser 
 heat. Do not stop this time when the limonite has been 
 reduced to hematite; continue the heating, and observe 
 lhat the assay grows still darker, and at last partially 
 fuses. Test it now with a magnet. Unlike both limo- 
 nite and hematite, it is attracted. 
 
 Yet it is not pure iron, for a smart blow of the ham- 
 mer crumbles it to powder. It is reduced to that com- 
 pound of iron called magnetite, specimen 1 2. It is be- 
 lieved that this series of iron ores has been formed, in 
 nature, on the same principle which has been illustrated 
 in our experiments; i. ., limonite, deposited in the earth 
 from a solution of iron, has afterward been converted 
 into hematite by heat, and hematite has in the same way 
 been reduced to magnetite. 
 
 Test now a few grains of iron. rust, which you can 
 scrape from an old stove-pipe, or other iron. Does its 
 streak resemble limonite? It is practically the same 
 mineral. What are the results of heating it? Test the 
 assay, after heating, with a rc.ajgjnet. 
 
234 THE WORLD OF MATTER 
 
 Repeat the experiment of burning iron in oxygen. 
 Test with the blow-pipe a fragment, or some powder, 
 of the resulting black oxide of iron. Test it with the 
 magnet before and after heating. 
 
 REAGENTS. 
 
 We have frequently used litmus-paper in order to de- 
 tect an acid or an alkaline reaction ; a change of color 
 from blue to red indicating the presence of an acid ; 
 while minerals containing as their base calcium, stron- 
 tium, barium, or magnesium all have the same alka- 
 line reaction after being strongly heated which we ob- 
 served in the case of celestite. 
 
 Cobalt is a reddish-white metallic element, of no 
 special utility, except for the brilliant colors that are ob- 
 tained from its various compounds. To glass these com- 
 pounds impart a magnificent tint which is easily recog- 
 nized as cobalt blue. With other substances than glass 
 other colors are produced, so that by the color obtained 
 by moistening different minerals with a solution of some 
 cobalt compound and then heating them it is often pos- 
 sible to determine their nature and their names. 
 
 The most convenient preparation of cobalt for this 
 purpose is a solution of one dram of the nitrate, Co 
 (NO 3 ) 2 , in an ounce of water. 
 
 Heat another fragment of sphalerite on charcoal un- 
 til you obtain the yellow coating or sublimate on the 
 coal next to the assay. Put a drop of the cobalt so- 
 lution on the sublimate, and also upon the assay, if that 
 has changed to a light color through heating. Direc* 
 
BLOW-PIPE ANALYSIS. 235 
 
 the O. F. again upon the assay; when cool, the subli- 
 mate or part of it, and probably also the assay, will be 
 bright green. 
 
 If you fail to get any coating or sublimate by simply 
 heating the sphalerite, pulverize a fragment in the mor- 
 tar, mix the powder in the palm of your hand with an 
 equal quantity of pure sodium carbonate, or of ordi- 
 nary baking soda if free from sulphur moisten the 
 mixture and expose it to the O. F. It will melt and run 
 together, but after a time will spread out again and sink 
 into the coal. Keep playing upon it with the hot point 
 of the flame until you have a distinct coating beyond 
 the assay ; then treat with the cobalt solution as before. 
 Repeat this test with all the ores of zinc you may have. 
 You should keep a small bottle of this cobalt solution 
 on hand. Always make the test in the same way as 
 you have with sphalerite, i. e., heat a fragment or some 
 powder of the mineral strongly on charcoal, in the O. 
 F; moisten it or its sublimate with a drop of the cobalt 
 solution, and then heat again. 
 
 Zinc ox^de then becomes yellowish-green. 
 
 Tin oxide becomes bluish-green. 
 
 Magnesium oxide, magnesia, becomes pink. 
 
 Aluminium oxide, alumina, becomes blue. Try 
 kaolinite. 
 
 Silicon oxide, silica, becomes faint blue. Try quartz. 
 
 Strontium oxide, strontia, becomes gray. Try 
 celestite. 
 
 Calcium oxide, lime, becomes gray. Try chalk. 
 
 You will be interested to note in this connection a 
 
236 THE WORLD OF MATTER. 
 
 few characteristic coatings which the O. F. will produce 
 on charcoal without the assistance of any reagent. 
 White, very volatile, gray fumes, indicate arsenic 
 white near the assay, blue farther off, dense white 
 fumes indicate antimony. 
 
 Purplish-brown, indicates silver. In lead rich in 
 silver the color may be brighter red, or the brow*i may 
 appear in spots and streaks amid the yellow oxide cf 
 lead. 
 
 Lemon-yellow while hot, sulphur yellow when cold, 
 white and bluish-white at a distance, volatile, indi- 
 cates lead. 
 
 Always wait until the coating is completely cool be- 
 fore judging its color. 
 
 Do not mistake the white ash of the charcoal for a 
 sublimate. Sometimes it is necessary to fuse the assay 
 with soda in order to get the sublimate. 
 
 Do not fail to notice the odor given off during"" 
 heating. 
 
 ROASTING. 
 
 Substances containing sulphides or arsenides must be 
 roasted before they can be treated with soda or any 
 other flux. Grind small fragments of iron pyrites to 
 fine powder. Moisten the powder and transfer to a 
 shallow cavity in the charcoal. Heat very gently at 
 first to prevent the powder from melting or flying 
 away. After some of the sulphur has been driven off 
 use a stronger blast the O. F. and the R. F. alter- 
 nately. 
 
feLOW-PIPE ANALYSIS. 237 
 
 Continue as long as there is the slightest smell of 
 sulphur, no matter how long it may take. Turn the 
 assay on the other side and treat as before. Again pul- 
 verize the assay in a mortar. The powder is no longer 
 greenish, but red like that of hematite. It is indeed, 
 now, an oxide of iron. As some sulphur probably re- 
 mains, roast it again on both sides. Test the powder 
 with a magnet and carefully preserve it for the follow- 
 ing experiments. 
 
 TESTING WITH FLUXES. 
 
 Heat your platinum loop and dip it into powdered 
 borax. Hold it over the flame of the lamp or gas and 
 watch the melting of 'the borax after "intumescence;" 
 but to prevent particles of the borax from flying away, 
 hold it in the flame. 
 
 Add more borax until the loop is filled. Then direct 
 the O. F. upon it with the blow-pipe, until it becomes 
 a transparent glass, free from bubbles. This is a borax 
 "bead." Place a very little of your roasted assay upon 
 the bead. If it will not stay, smoke the bead a little 
 over the flame, or heat it again with the blow-pipe, and 
 flatten it gently between the forceps or on an anvil. Heat 
 the bead over the lamp-flame; just enough to cause the 
 powder to stick to it. Now hold the loop in the O. F., 
 beyond the point of the blue flame, as shown in Fig. 
 30. The powder begins to whirl about in the melting 
 glass, but it, too, soon dissolves, and the glass becomes 
 clear and smooth. 
 
 Hold it between your eye and a window; it is yellow, 
 
238 THE WORLD OF MATTER. 
 
 but becomes colorless as it cools. Add a little more of 
 the powder. Dissolve as before in the O. F. This 
 time it appears red while hot, and yellow when cold. 
 Heat it now in the R. F., holding it farther in the 
 flame than shown in Fig. 31, as your loop is larger. 
 The bead assumes a gree-nish tint. Add still more 
 powder. The bead becomes brown or reddish yellow 
 in the O. F., and in the R. F. should assume the pecu- 
 liar bottle-green of junk-bottles. 
 
 A bead which contains as much of any assay as it 
 can dissolve is said to be saturated. After a bead is 
 saturated, you may again dilute it. Melt the bead and 
 fling it into a clean cup or mortar, by striking the 
 hand which holds the platinum loop, on the table. Part 
 of the assay will still adhere to the loop; add to thi. 
 enough borax to make a new bead. This will resemble 
 the second one you made. Strike this off, too; dilute 
 again with borax, and you will have again a yellow 
 bead that becomes colorless as it cools. 
 
 Place on charcoal a piece of tinfoil, and on this lay 
 the two beads that were shaken off. Expose the beads 
 and the foil under them to the R. F. ; the bead should 
 become decidedly green, although in order to see the 
 color you may have to pinch the bead, which clings to 
 the coal, upward with the forceps so that" you can look 
 through it. 
 
 Care of the platinum wires* The test being finished, 
 remove the bead by gentle taps with a hammer, remove 
 all clinging particles, and keep the wire in a bottle con- 
 
 *Keep several platinum loops on hand. 
 
BLOW-PIPE ANALYSIS. 239 
 
 taining enough diluted sulphuric acid to cover the loop. 
 Before using again rinse in water. If the new bead of 
 borax is not perfectly clear and colorless both when 
 cold and after heating, throw it off and make a new 
 one. If after several trials the color still persists, make 
 a bead with soda, shake it off, and put the loop into the 
 acid bottle for a day. Should you find, while testing a 
 mineral in the borax bead, that a metallic globule is 
 formed, shake the bead off immediately and transfer it 
 to charcoal. 
 
 Test other specimens of iron ores in the borax bead. 
 The oxides and carbonate need no roasting. 
 
 Try a little powdered chalk in the bead. It effer- 
 vesces as it dissolves and forms a colorless glass. Add 
 a small fragment instead of the powder; the effect is 
 the same. Keep on adding and dissolving, examining 
 the bead each time. When nearly saturated it becomes 
 translucent instead of transparent on cooling, and as- 
 sumes a crystalline structure. Watch it with a magni- 
 fying glass, for the process is extremely interesting. 
 Add a little more chalk and the bead becomes at last 
 almost pure white, and opaque. If you direct the flame 
 upon the bead in little puffs or flashes just before the 
 point of saturation is reached it will become opaque 
 even in the flame. This is called faming the bead. 
 
 Throw off part of the assay, dilute the rest with a 
 little borax so that it becomes clear again and try the 
 flaming. It is chiefly the alkaline earths that become 
 thus opaque by flaming. 
 
 Compare the action of kaolin with that of chalk. 
 
240 THE WORLD OF MATTER. 
 
 Make a borax bead with finely powdered quartz. It, 
 too, dissolves to a clear glass, but more slowly. 
 
 From these experiments we learn that borax causes 
 even the most refractory metals to melt in the heat of 
 the blow-pipe. 
 
 Substances which have this propeity are calledfluxes. 
 
 The following are the principal reactions with the 
 borax bead : 
 
 Colorless. The alkaline earths, aluminum, silica; in 
 O. F., and R. F. 
 
 Yellow when hot, colorless when cold in O. F., 
 zinc, cadmium, lead, bismuth. In R. F., these sub- 
 stances become gray from the reduced metal, but on 
 further heating grow clear again. 
 
 Milk-white silver, when the bead is saturated, in O. 
 F.; gray, then clear in R. F. 
 
 Yellow in O. F. iron, titanium, tungsten, molybde- 
 num, chromium (greenish yellow). 
 
 Red to brown in O. F. hot; iron, uranium, chromi- 
 um: cold; nickel, manganese. 
 
 Red in R. F., copper, when the bead is saturated and 
 cold ; colorless when hot. 
 
 Violet in O. F., nickel, hot (reddish- violet); manga- 
 nese, (deep violet). 
 
 Blue cobalt, O. F., and R. F.; copper, O. F., cold, 
 greenish-blue. 
 
 Green copper, O A F., hot; R. F., bottle-green; 
 chromium, vanadium, O. F. and R. F., cold; uranium, 
 R. F., yellowish-green. 
 
BLOW-PIPE ANALYSIS. 241 
 
 EXAMINATION WITH SODA. 
 
 Soda beads in the platinum wire are not often used, 
 but it is worth while to make a few. The bead itsejf 
 is interesting. After it has become well fused, notice 
 how it begins to effervesce, as you pass it from the O. F. 
 to the R. F., also that it is transparent while hot, and 
 becomes translucent when cool. 
 
 Add some quartz powder; it easily dissolves, with 
 effervescence, and the bead on withdrawal from the 
 flame loses its transparency. Continue adding arid dis- 
 solving quartz, and presently you reach a point where 
 the bead remains transparent even after cooling. 
 
 Try orthoclase, and you should secure the same re- 
 sult. 
 
 From this we understand that silica dissolves readily 
 and with effervescence in soda, and that, if the propor- 
 tion of soda is not too great, the resulting glass will be 
 clear. Indeed, our window-panes and common glass- 
 ware are for the most part silicate of soda, or of soda and 
 lime. 
 
 In most cases the treatment of mineral compounds 
 with soda is conducted on charcoal. 
 
 Mix some powdered quartz with about three times 
 its bulk of soda and transfer the paste to the coal. Treat 
 it with O. F. for a considerable time, trying to collect 
 the mass into a globule. You will hardly succeed. 
 Probably the assay will spread out more and more, and 
 partly sink into the coal. Now make another mixture, 
 taking equal parts of quartz and soda. You should 
 succeed without much trouble in forming this mixture 
 
242 THE WORLD OF 'MATTER. 
 
 into a bead. Continue playing the O. F. upon it, caus- 
 ing it to revolve until you get rid of nearly all bubbles. 
 You should get a transparent, nearly colorless bead. 
 
 Next try a small splinter of orthoclase. Place it in a 
 shallow depression in the charcoal and put a little soda 
 around it. Blow gently, as you always should at the 
 beginning. See the soda fuse, and begin to attack the 
 mineral; effervescence marks the beginning of the 
 fusion; the edges and corners are first dissolved. Add 
 a little more soda and heat again, the assay spreads out 
 to take in every grain of the salt, and then rounds up to 
 form a globule, with the inner part, probably, yet undis- 
 solved. Other additions diminish the undissolved part, 
 and the bead may assume a dark appearance from some 
 impurities taken up. Add much soda and the mass will 
 spread out. It takes longer to do this work than to de- 
 scribe it, but the experience gained during the faithful 
 and patient performance of the experiment will be 
 worth all it costs. 
 
 You should still have some of the powder from the 
 roasted pyrites. Mix all that is left with about three 
 times its bulk of soda, moisten, and transfer to the char- 
 coal. Give it a long and strong blast with the R. F., 
 until all the life has gone out of the mixture, i. e. as long 
 as you can observe any effect from the heat, and even 
 longer. 
 
 Cut out the black mass with some of the coal under- 
 neath it, and grind it to a powder in a mortar, adding a 
 little water. Set the mortar with its contents in a cup 
 or basin, and pour water in the vessel until it covers the 
 
BLOW-PIPE ANALYSIS. 243 
 
 mortar, and a little more. The lighter portion of the 
 assay will now rise from the mortar, and float on the 
 water; and by moving the mortar about under the 
 water all but the heaviest sediment can be floated out. 
 
 Now remove the mortar, pour- the water from it, and 
 carefully transfer the sediment to a piece of paper. 
 When dry, examine the little particles with a magnify - 
 ing-glass. Test them with a magnet. It is a good 
 plan, by the way, to fit the ends of your magnet with 
 "stockings" of tissue paper reaching half way up. 
 Magnetic substances will be attracted through the 
 paper, and they will drop off when you pull the magnet 
 partly out of the stocking. You have now reduced 
 the oxide to metallic iron. 
 
 Powder some galenite, mix with plenty of soda, and 
 treat with the R. F. Let the globules run together, 
 and observe the action of the large globule of lead as it 
 solidifies. When it grows cool take it off and hammer 
 it. Observe how much more lead you get in this way 
 from a certain quantity of galenite than by reducing the 
 galena without soda. 
 
 The last two experiments illustrate the use of soda as 
 a flux for reducing metals from their compounds. If 
 any metal does not form a globule, but behaves like 
 iron, forming a slag, this slag must be treated as the 
 iron was, that is, powdered and separated by the float- 
 ing process. 
 
 If then the metal cannot be recognized from the 
 sediment in the mortar, this must be dissolved in a 
 borax bead, that its nature may be revealed by the color 
 imparted to the bead. 
 
244 THE WORLD OF MATTER. 
 
 We must remember, too, that the treatment with 
 soda on charcoal may be used for getting a coating or 
 sublimate which may aid in determining the metal. 
 
 All reductions on coal must be conducted with the 
 R.F. 
 
 If you suspect that the dark mass or hepar resulting 
 from heating a metal on coal with soda contains sul- 
 phur, crush it and place a fragment on a bright silver 
 coin, adding a drop of water. If sulphur is present it 
 will unite with the silver forming silver sulphide, and 
 leaving a brown stain on the coin. Be sure, however, 
 that neither your soda nor your fuel contains sulphur. 
 
 Filtering and decanting. To separate solutions 
 from an undissolved sediment, or from a precipitate, 
 they are passed through filter-paper placed in a funnel ; 
 or, if the liquid stands clear above the sediment, may 
 be simply poured off, or decanted. If the sediment or 
 precipitate is to be further tested it should be washed 
 either by pouring water over it as it lies on the filter- 
 paper, and letting it pass through until all acid or alkali 
 is removed, or by repeated shaking up and decanting 
 with water. 
 
SUGGESTIONS FOR FURTHER STUDY. 245 
 
 CHAPTER XVII. 
 
 SUGGESTIONS FOR FURTHER STUDY. 
 
 No experiments have been described in this book 
 which cannot be successfully performed without assist- 
 ance by every student, no matter whether he has had 
 any previous training or not, if he will undertake them 
 resolutely and patiently, and in the order given. 
 
 Those who have worked their way with us to this 
 point will wish to continue their study of this fascinat- 
 ing science, until they attain the power of recognizing 
 at sight, or of determining by analysis, every specimen 
 they may meet. A description of twenty-four more 
 common minerals is therefore added for practice. It 
 must be borne in mind, however, that the determina- 
 tion of the names of minerals is by no means the chief 
 aim of the earnest student. It is rather to make him- 
 self thoroughly acquainted with the properties of min- 
 erals, and to develop and strengthen his powers of 
 obserration and reasoning. Carefully to observe, and 
 accurately to describe your specimens, should therefore 
 be your main object. 
 
 It is almost wholly because the processes required to 
 determine minerals necessarily enforce this patient and 
 exact personal observation, that they become a valuable 
 means of education and training. 
 
246 THE WORLD OF MATTER. 
 
 You will do well, now, to procure the specimens 
 whose descriptions follow. 
 
 1. Native copper. H-3; lustre and streak, metallic; 
 color red; occurs in masses, in crystals, and in beauti- 
 fully branched or arborescent forms, sectile, malleable, 
 very tough, heavy. 
 
 Comp. Cu; B.B. fuses to a globule, try tests for Cu. 
 
 2. Cinnabar. H. 2-2.5; lustre, adamantine to dull; 
 streak, scarlet; color, red to dark brown; in crystals, or 
 massive; brittle; very heavy; fracture uneven. 
 
 Comp. HgS; B. B. volatilizes; Hg and S reactions 
 in c.t. with and without soda. Cinnabar is the principal 
 ore of mercury, which is also found native. 
 
 3. Millerite, (nickel pyrites}. H. 3- 3. 5; lustre, me- 
 tallic; color, bronze yellow; streak, gray; in clusters of 
 fine needle-shaped crystals, or in fibrous crusts; brittle; 
 rather heavy. 
 
 Comp. NiS; B. B. on charcoal fuses easily to a 
 brittle, magnetic globule; with borax bead gives Ni 
 reaction; roasted and fused with soda on charcoal yields 
 a brittle globule of nickel. 
 
 4. Pyrrhotite. H. about 4; lustre, metallic; color, 
 bronze yellow, tarnishing to copper red; streak, gray, 
 generally massive; brittle; magnetic. 
 
 Comp. Fe 7 S 8 ; B. B. on charcoal fuses to a magnetic 
 globule; yields little sulphur in c. t. ; softer than iron 
 pyrites and harder than copper pyrites; magnetic. 
 
 5. Chalcopyrite (copper pyrites]. H. 3.5; lustre, 
 metallic; color, brass yellow, often tarnished to deep 
 yellow, red, blue, etc.; streak, greenish black; crystal- 
 
SUGGESTIONS FOR FURTHER STUDY. 247 
 
 lized or massive; fracture, uneven; brittle; easily 
 scratched -with a knife. 
 
 Comp. CuFeS 2 ; B.B. on charcoal fuses easily to 
 a magnetic globule; fused with soda on charcoal yields 
 a globule of copper and iron. Moisten the globule 
 with HC1., and examine the flame color at the point of 
 the O. F. Crush the globule to powder and dissolve in 
 a few drops of nitric acid; both copper and iron will be 
 dissolved. Add ammonia until the iron is precipitated 
 as a reddish brown powder; the liquid will then be blue. 
 Also roast some of the ore, or make another globule of 
 it with soda. Pulverize, and saturate a borax bead with 
 the powder; examine the bead and throw it off; add 
 more borax to what remains on the wire, examine it 
 both hot and cold, and throw off again ; repeat this un- 
 til the bead becomes almost colorless, and make a record 
 of your observations. 
 
 6. Ccrargy rite (horn silver). H. 1.5; lustre, res- 
 inous; streak, shining; color, pearl- gray, brownish 
 when weathered ; in very small cubical crystals or mass- 
 ive; fracture uneven; easily cut with a knife. 
 
 Comp. AgCl; melts in the candle-flame. B. B. on 
 charcoal with O. F. yields little globules of silver. 
 Better, however, fuse on charcoal with soda in R. F., 
 and collect all the silver into one globule. Observe the 
 coating on the coal, which may show, besides the char- 
 acteristic purple brown of silver, a yellow sublimate, 
 indicating the presence of lead. 
 
 7. Zincite. H. 4-4.5; lustre, brilliant; streak, 
 orange yellow; color, bright red; generally in granu- 
 
248 THE WORLD OF MATTER. 
 
 lated or foliated masses; cleavage, perfect; brittle; 
 rather heavy. 
 
 Comp. ZnO. B. B. infusible; turns black, but after 
 cooling turns red again. On charcoal, with and without 
 soda, gives zinc coating. 
 
 8. Menaccanite (titanic iron). H.5-6; lustre, met- 
 allic or sub-metallic; color, black; streak, black; in 
 grains, plates, sometimes large tabular crystals; cleavage, 
 distinct; rather heavy; magnetic. 
 
 Comp. (Ti Fe) 2 O 3 ; B. B. infusible; fused with 
 soda on charcoal, and dissolved in HC1, gives Ti re- 
 action. 
 
 9. frranklinite. H. about 6; lustre, metallic; color, 
 iron black; streak, reddish brown to black; massive c/ 
 in crystals; cleavage, indistinct; brittle; fragments 
 slightly magnetic. 
 
 Comp (FeZnMn) 2 O 4 ; B. B. infusible; with ?sc/u3 
 on charcoal, white zinc coating, turning green if treatec 
 with cobalt solution. In soda bead assumes a green co- 
 lor in O. F. Both reactions are more distinct if a little 
 borax is added to the soda. 
 
 10. Ckromite. H. 5-5; lustre, metallic, or sub- 
 metallic; streak, brown; color, iron black; generally 
 massive; breaks with even but rough surfaces; not 
 magnetic, unless in very small particles. 
 
 Comp. FeCr 2 O 4 ; B. B. infusible; with borax 
 bead Cr reaction. 
 
 ii. Cassiterite. H. 6-7; lustre, splendent, sub- 
 metallic, dull on exposed surfaces; streak, brownish to 
 gray ; color commonly brown to black ; in crystals ; of- 
 
SUGGESTIONS FOR FURTHER STUDY. 249 
 
 ten bean-shapea, fibrous, a^so massive and compact; 
 fracture uneven; brittle; heavy. 
 
 Comp. SnO 2 ; B. B. infusible, with soda on char- 
 coal yields tiny globules of tin. See Sn, p. The prin- 
 cipal ore used in the manufacture of tin. 
 
 1 2. Pyrolusite* (black oxide or dioxide of manganese) 
 H. 1-2. 5; lustre, metallic to earthy; streak and color; 
 black; soils the fingers; generally massive, columnar, 
 radiated; brittle, rather heavy. 
 
 Comp. MnO 2 ; B. B. infusible; very little imparts 
 an amethyst color to the borax bead. Dissolve in HC1, 
 heating the solution slightly, and observe the odor of 
 chlorine. 
 
 13. Bcauxite. H. about 3; lustre, earthy; color, 
 white, red to brown; streak, white to red; composed 
 of small round concretions like little peas, (pisolitic), 
 imbedded in a compact matrix; fracture, uneven, brittle. 
 
 Comp. Al 2 Fe 2 O 3 +2H 2 O; B. B. infusible; de- 
 crepitates strongly ; in c. t., yields water. Try reaction 
 for alumina; for iron. 
 
 14. Spodumene. H. 6.5-7; lustre, pearly; color, 
 grayish to greenish white; streak, white; massive, also 
 often in large crystals; cleavage perfect; brittle. 
 
 Comp. Li 6 Al 8 Si 15 O 45 ; B. B. fuses easily with in- 
 tumescence, first to a white mass, then to a clear glass, 
 showing, at least for a few moments during the treat ^ 
 ment with O. F., the lithia reaction. Try the tests foi 
 alumina and silica. 
 
 15. Willemitc. H. 5.5; lustre vitreous to resinous^ 
 color, brown, red, yellow, green, also colorless; streak^ 
 
250 THE WORLD OF MATTER. 
 
 white; translucent, seldom transparent; generally 
 compact, fine grained, sometimes in small crystals; frac- 
 ture uneven. 
 
 Comp. Zn 3 SiO 4 ; B. B. fuses with difficulty and 
 turns white; no water in c. t.; with HC1 gelatinizes 
 perfectly; an important ore of zinc. 
 
 16. Cinnamon garnet, (massive). H. about 7; lus- 
 tre, vitreous to resinous; color, commonly red or brown, 
 but also of almost every other color; generally in crys- 
 tals; also massive; brittle; fracture uneven. 
 
 Comp. Ca 3 Al 2 Si 3 O 12 ; B. B. fuses less easily than 
 vesuvianite (the next specimen), and without swelling, 
 to a dark glass. 
 
 17. Vesuvianite (idocrase). H. 6.5; lustre, vitreous 
 to resinous; color, brown to green; streak, white; sub- 
 transparent to nearly opaque; in prismatic crystals, also 
 massive; fracture uneven, brittle. 
 
 Comp. (CaMg) 8 (AlFe) 4 Si 7 O 28 ; B. B. fuses with 
 swelling to a dark greenish or brownish glass, which 
 shows alkaline reaction. Fuse a few fragments thor- 
 oughly on charcoal and dissolve in HC1; boil it well 
 down and notice the gelatinizing of the mineral. 
 
 1 8. Scapolite, (ivernerite). H. 5-6; lustre, vitreous 
 to pearly ; color, usually light gray, blue, lilac, green, 
 or pink;. streak, white; transparent to nearly opaque; 
 crystallized or massive; often with a fibrous or colum- 
 nar appearance ; fracture, inclining to conchoidal ; brit- 
 tle.^ 
 
 Comp. CaAl 2 Si 2 O 8 ; B. B. fuses rather easily, and 
 with intumescence to a whitish, bubbly glass, which 
 cannot be further fused; alkaline reaction. 
 
SUGGESTIONS FOR FURTHER STUDY. 251 
 
 19. Elccolite (variety ofmephelite, H. nearly 6; 
 lustre, vitreous to greasy; color, grayish; streak, white; 
 translucent; massive or in large crystals; fibrous ap- 
 pearance on broken surfaces; brittle. 
 
 Comp. (NaK) 3 Al 2 Si 2 O 8 (Dana) B.B. fuses quietly, 
 but not easily, to a white glass resembling that of scapo- 
 lite. Gelatinizes with HC1 without previous fusion. No 
 alkaline reaction. 
 
 20. Sphene (titanite). 11.5-5.5; lustre, vitreous to 
 resinous, color, brown to black, sometimes yellow or 
 green; streak whitish; transparent to opaque; generally 
 in oblique, thin-edged crystals, sometimes massive ; cleav- 
 age often perfect in one direction, giving the crystals a 
 laminated appearance; brittle. 
 
 Comp. CaTiSiOgj fuses with intumescence to a 
 blackish mass. Try test for Ti. 
 
 21. Calamine., H. 4.5-5; lustre, vitreous to pearly; 
 color, various, commonly light brown; streak, whitish; 
 transparent to translucent; massive, or forming botry- 
 oidal, stalactitic, or radiated incrustations lined with 
 crystals (generally in fissures of rock) ; cleavage, perfect 
 in crystalline varieties; fracture, uneven to rough in 
 granular or earthy varieties; brittle. 
 
 Comp. Zn 2 Si O 4 + H 2 O; B. B. fuses with difficul- 
 ty, turning white. In c. t. yields water. With soda on 
 charcoal gives zinc coating; treated with cobalt solution 
 green, assay blue. Dissolves in HC1, leaving white 
 residue. Gelatinizes on boiling down the acid. An im- 
 portant ore of zinc. 
 
 22. Strontianite. H. 3.5-4; lustre, vitreous; color, 
 
252 THE WORLD OF MATTER. 
 
 white to yellowish and greenish; streak, white; gener- 
 ally massive, fibrous in parallel or radiated lines, also 
 globular; transparent to translucent; fracture, uneven; 
 brittle. 
 
 Comp. SrCO 3 ; B. B. fuses with difficulty, white 
 sprouts appearing on the points and edges ; colors the 
 flame crimson; heated, shows alkaline reaction. Try 
 reaction for carbon dioxide. Strontianite is used in the 
 manufacture of fireworks. 
 
 23. Malachite {green copper carbonate]. H. 3. 5-4; 
 lustre, silky to earthy; streak, pale green; color, green; 
 generally opaque, sometimes translucent; massive or 
 forming incrustations which may be mere films, or 
 thicker botryoidal, stalactitic, or spongy masses of com- 
 pact and fibrous structure; fracture, uneven; brittle. 
 
 Comp. Cu 3 CO 4 + H 2 O; B. B. easily fusible to a 
 black globule; observe the green flame beyond the 
 globule. Moisten with HC1 and notice the flame. 
 On charcoal fuses to a globule of copper; if there is 
 difficulty, add a little soda, running it into a bead with 
 the O. F., and then reducing it in the R. F. Try other 
 reactions for copper. 
 
 24. Azurite (blue copper carbonate]. H. 4; lustre, 
 vitreous or dull; color and streak, blue; translucent to 
 opaque; in crystals, or massive, also compact, earthy; 
 brittle; much like malachite except in color. 
 
 Comp. Cu 3 C 2 O 7 + H 3 O; behavior with reagents 
 like malachite. Both minerals are valuable ores of cop- 
 per. Malachite is often worked into mantels, table- 
 tops, and various ornaments. 
 
SUGGESTIONS FOR FURTHER STUDY. 253 
 
 REFERENCE LIST 
 
 of the principal elements in minerals and their charac* 
 teristic reactions. 
 
 Ag. Silver. B. B. Heated on charcoal in O. F. 
 forms a reddish brown coating. Dissolved in nitric 
 acid forms a whitish cloud (precipitate of Ag Cl) which 
 settles and turns dark on exposure to light, and which 
 may be dissolved again by the addition of ammonia. 
 Most silver ores heated on charcoal, alone or with soda, 
 yield a silver globule. 
 
 Al. Aluminium. (A1 2 O 3 , alumina) B. B. A frag- 
 ment strongly heated on charcoal, or in the forceps, then 
 moistened with cobalt solution and heated again, as- 
 sumes a beautiful blue color. All color reactions should 
 be examined by daylight. Sometimes it is necessary to 
 pulverize before heating. In dark-colored specimens 
 the blue does not always appear distinctly; if these are 
 soluble in acids, and ammonia be added to the acid solu- 
 tion, the alumina will be precipitated, and after drying 
 can be tested with the cobalt solution. 
 
 As Arsenic. B. B. garlic odor, gray fumes, gray 
 coating on charcoal, distant from the assay and easily 
 driven away by the flame. In o. t. yields a white crys- 
 talline sublimate; in c. t. a black brilliant sublimate. 
 
 Au Gold. Imparts no characteristic color to flame 
 or flux. If native is easily recognized by its color, 
 malleabilty, and insolubility in any one of the acids. 
 
 Ba Barium. (BaO, baryta) B. B. yellowish-green 
 flame, shown by all minerals containing barium except 
 silicates. If soluble in HC1, an addition of H 2 SO 4 
 causes a heavy white precipitate. BaSO 4 . 
 
&54 THE WORLD OF MATTER. 
 
 J3i Bismuth. B. B. on charcoal alone or with 
 soda, gives a characteristic orange-yellow sublimate. 
 Treated with equal parts of potassium iodide and sulphur^ 
 a beautiful red precipitate of bismuth iodide is formed. 
 
 Bo Boron. B. B. Intense yellowish-green flame, 
 especially if moistened with H 2 SO 4 . 
 
 C Carbon. (CO 2 , carbonic acid, or anhydride) Is 
 set free, when present in minerals, by HC1 and all the 
 stronger acids causing effervescence. Sometimes the 
 mineral must be pulverized, and sometimes the solution 
 must be heated. 
 
 CA Calcium. (CaO, lime), B. B. yellowish-red 
 flame. Many minerals containing lime give an alkaline 
 reaction after being highly heated. 
 
 Cl Chlorine. B. B. Prepare a bead with the salt 
 of phosphorus, (a phosphate of sodium and ammonium), 
 saturate it with copper oxide, and add some of the 
 powdered mineral; if Cl is present the blow-pipe flame 
 will be colored for a moment intensely blue. (Try 
 halite, specimen No. 28). 
 
 Co Cobalt. B. B. imparts to the borax bead a 
 beautiful blue color. Try also with cobalt solution. 
 
 Cr Chromium. B. B. imparts an emerald-green 
 color to the borax bead, (cold) in both O. F. and R. F. 
 
 Cu Copper. B. B. green flame; blue if moistened 
 with HC1, borax bead, O. F., green, R. F., red, ii 
 highly saturated. Add a grain of salt (NaCl), and ob- 
 serve the flame. Most copper ores are reduced to me- 
 tallic copper when fused with soda on charcoal. 
 
 F Fluorine. If the powdered mineral be laid on, 
 
SUGGESTIONS FOR FURTHER STUDY. 255 
 
 glass, moistened with one or two drops of H 2 SO 4 , and set 
 aside for a day, the glass will be etched. This corroding 
 action will be more pronounced if the powdered min- 
 eral containing F is mixed with bisulphate of potas- 
 sium, and heated in the c. t. ; a strip of Brazil-wood 
 paper inserted in the mouth of the tube will turn itraw- 
 color. 
 
 Fe Iron. B. B. besides the tests already given on p. 
 204, try the following: Powder some of the mineral, 
 add dilute HC1, and heat ; let the sediment settle, and de- 
 cant the clear solution; dilute this with more water; 
 add a drop of a solution of yellow prussiate of potash 
 If iron is present, the solution will soon turn blue. 
 ( Prussian blue.) 
 
 Hg Mercziry. Its compounds yield a metallic 
 coating when heated with soda in the c. t. The 
 globules of mercury are sometimes so small that the 
 coating appears white. Use the magnifying-glass, or 
 brush the tiny globules together with a strip of paper. 
 Sulphide of mercury yields a black, volatile sublimate, 
 red when rubbed. 
 
 K Potassium. B. B. is often recognized by the 
 violet color it imparts to the flame. If sodium is pres- 
 ent this color does not appear. 
 
 LI Lithium. B. B. purplish to carmine flame, as 
 in lepidolite. 
 
 Mg Magnesium. (Mg O, magnesia). B. B. gen- 
 erally indicated by the pink color which its compounds 
 assume when highly heated, and treated with cobalt so- 
 lution. 
 
256 THfi WORLD OF MATTER. 
 
 Mil Alanganese. B. B. imparts a beautiful ame- 
 thyst color to the borax bead, and assumes a bright 
 green color when fused with soda. 
 
 Na Sodium. B. B. colors the flame intensely red- 
 dish yellow, and seems to make it larger. 
 
 Nl Nickel. B. B. in O. F. colors the borax bead 
 violet when hot, reddish brown on cooling; in R. F. 
 colorless with metallic specks. Nickel ores are reduced 
 to a magnetic mass on charcoal. 
 
 P Phosphorus. B. B. characteristic green flame, 
 especially when moistened with H 2 SO 4 . A pulverized 
 phosphate fused in the c. t. with a bit of metallic mag- 
 nesium or sodium, evolves the disagreeable odor of 
 phosphoretted hydrogen. (Try apatite.) 
 
 Pb Lead. B. B. when heated with soda on char- 
 coal compounds of lead yield a metallic lead globule; a 
 yellow volatile coating appears on the coal, deeper near 
 the assay, and shading to white and bluish. 
 
 S Sulphur. B. B. on charcoal most sulphides are 
 recognized by their odor; bisulphides, as FeS 2 , by the 
 sublimate of S in the tube. Sulphides dissolve in 
 HCM with effervescence yielding fumes of sulphuretted 
 hydrogen (rotten-egg odor). For the "hepar" test by 
 which the presence of S in sulphates can be detected, 
 see p. . 
 
 $b Antimony. B. B. on charcoal, generally recog- 
 nized by its dense white fumes and white sublimate. 
 Same in o. t. Bluish flame. 
 
 Se Selenium. B. B. steel gray, volatile sublimate; 
 disagreeable horse-radish odor. 
 
SUGGESTIONS FOR FURTHER STUDY. 257 
 
 &i Silicon. [SiO 2 , Silica] B. B. heated with soda 
 in platinum wire, or on charcoal, fuses with effervescence 
 to a clear glass ; if too much soda is used a slaggy mass 
 results. 
 
 gn Tin. B. B. with soda on charcoal yields 
 globules of metallic tin, often so minute as to be detected 
 only with a lens. By crushing the fused mass with the 
 adhering coal between paper and heating again, adding a 
 little soda, the globules can generally be collected into a 
 larger globule. The operation requires skill and care. 
 Tin yields a faint yellow sublimate, not volatile, 
 which becomes bluish green when treated with the co- 
 balt solution. 
 
 Sr Strontium. B. B. crimson flame, especially if 
 moistened with HC1. 
 
 Ti Titanium. B. B. colors a bead of the salt of 
 phosphorus violet, unless too much iron is present. In 
 that case wrap the bead in a small piece of tinfoil, trans- 
 fer to charcoal, and apply the R. F. The iron then 
 will unite with the tin in a metallic globule, leaving the 
 Ti in the bead, when the violet color will appear. 
 
 Tu Tungsten. Tungstic acid colors the salt of 
 phosphorus bead blue in R. F. If iron is present the 
 bead is brownish red ; melting on charcoal with tinfoil 
 or zinc the bead is turned blue. 
 
 Zll Zinc. B. B. zinc ores on charcoal form a thick 
 coating of zinc oxide, yellow while hot, white on cool- 
 ing. This, if treated with the cobalt solution and heated 
 again, changes after cooling to a bright yellowish green. 
 
 Zr Zirconium. Minerals containing zirconia, dis- 
 
25& THE WORLD OF MATTER. 
 
 solved in HC1 and the solution diluted with water, im- 
 part an orange-yellow color to turmeric paper. 
 
 THE USE OF THE KEY. 
 
 For economy of space the properties by which min- 
 erals may be determined are usually printed in a key, 
 or in tables. To illustrate this, a short key to the 
 twenty-four minerals whose descriptions have been 
 given on pp. 202 to 225, is added. Take the specimen 
 of beauxite for example. 
 
 We will suppose that you have found it, and do not 
 know its name. Turn to the key. You notice that 
 here all the specimens are divided into two classes. I. 
 Those having metallic lustre. II. Those whose lus- 
 tre is non-metallic. Your specimen falls in the second 
 class, to which you will therefore turn at once. In this 
 class you observe four divisions, A, B, C, and D, based 
 upon the color of the streak. As your specimen has 
 a pink streak and a reddish powder it must be referred 
 to division B. 
 
 In this division you find three minerals distinguished 
 by their action under the blow-pipe ; and as you cannot 
 melt even the smallest splinter of your specimen, al- 
 though you use the hottest part of the flame, even the 
 magnifying-glass revealing no trace of fusion on the 
 thinnest edges or sharpest corners, you perceive that it 
 must be either zincite or beauxite. 
 
 You now use the closed tube test. Heating some 
 fragments in the c. t., you observe drops of water form- 
 ing in the upper part of the tube. Therefore, the 
 specimen must be beauxite. 
 
SUGGESTIONS FOR FURTHER -STUDY. 259 
 
 To be doubly sure, however, you will turn to the 
 reference list, page 253, and try some of the reactions 
 for aluminum and iron. 
 
 Finally you will turn to the description of minerals 
 Number 13 for further evidence and confirmation. 
 Determine all the specimens named in the key. Even 
 if you already know their names, it will give you ex- 
 cellent practice, and prepare you to use the larger 
 tables given in the standard books of reference. 
 
 One point remains to be noted: You will not al- 
 ways get in practice pure specimens; but there will 
 often be a mixture of several minerals in one specimen 
 unless you have the crystal. You must learn at once 
 to make allowance for the presence of impurities in 
 making your estimates of color, hardness, and all other 
 physical properties. In case of a mixed specimen, it 
 makes little difference which mineral you select for 
 analysis. Give the preference, as a rule, to the one 
 most largely and plainly developed; also in general 
 select first metallic minerals. Study afterward to the 
 best of your ability all other minerals that may appear 
 in the specimen, always remembering that the chief 
 benefit to you will come from the acquisition of the 
 power and habit of careful and accurate observation, 
 rather than from the mere knowledge of names which 
 may result from that observation. 
 
26o THE WORLD OF MATTER. 
 
 KEY FOR DETERMINING TWENTY-FOUR OF THE 
 MORE COMMON MINERALS. 
 
 I. LUSTRE METALLIC. 
 
 (Some also Sub-metallic). 
 
 A. COLOR RED. 
 
 No. in 
 Name. Description. 
 
 i . Malleable ; reaction for Cu Copper. i 
 
 B. COLOR YELLOW. 
 
 (Sometimes tarnished on exposed surfaces ) 
 
 1. Magnetic before fusion; reaction for Fe, Pyrrhotite. 4 
 
 2. Magnetic after fusion. 
 
 a. Reaction for Fe and Cu Chalcopyrite. 5 
 
 b. Reaction for Ni Millerite. 3 
 
 C. COLOR GRAY OR BLACK, 
 2. Magnetic before fusion ; reaction for Fe with borax bead. 
 
 a. B. B. with soda on charcoal, white 
 
 sublimate: reaction for Zn Franklinite. 9 
 
 b. B. B. with soda on charcoal, no subli- 
 mate ; reaction for Ti Menaccanite. 8 
 
 2. B.B. magnetic after heating; Cr reaction ; Chromite. 10 
 
 3. B. B. not magnetic: infusible; Mn reac- 
 
 action, Py rolusite. 1 2 
 
 II. LUSTRE NON-METALLIC. 
 
 A. STREAK OR POWDER GRAY TO BROWN. 
 
 1. B. B. fuses very easily, Ag reaction, Cerargyrite. 6 
 
 2. B. B. infusible; with soda on charcoal 
 
 yields globules of Sn, "... Cassiterite, 1 1 
 
SUGGESTIONS FOR FURTHER STUDY. 261 
 
 B. STREAK OR POWDER RED, ORANGE TO PINK. 
 
 1. B. B. volatile; in c. t. black sublimate 
 
 and Hg, Cinnabar. 
 
 2. B. B. infusible; in c.t. black while hot; 
 
 on charcoal Zn reaction Zincite. 7 
 
 3. B. B. infusible; water in c.t.; Al and Fe 
 
 reactions, Beauxite. 13 
 
 C. POWDER GREEN OR BLUE. 
 
 ^ ( a. Green, Malachite. 23 
 
 Reaction for Cu ] ^ Blue> Azuritc ^ 
 
 D. STREAK WHITE OR VERY LIGHT. 
 
 B. B. fuses easily, and 
 
 a. Swells; becomes white; opaque; 
 
 colors flame purplish, Spodumene. 14 
 
 b. Swells to a whitish glass full of bub- 
 bles ; alkaline reaction, Scapolite 18 
 
 c. Shells to a greenish black globule,. .Vesuvianite. 17 
 
 d. Fuses without swelling to a brownish 
 
 or greenish glass, Garnet, 16 
 
 2. B. B. white sprouts on surface; crimson 
 
 flame, Strontianite. 22 
 
 3. B. B. small splinters fuse 
 
 a. Quietly to a white glass ; not alkaline ; 
 
 gelatinizes with HC1, Elaeolite. 19 
 
 b. With intumescence to a blackish 
 
 mass ; Ti reaction, Sphene. 20 
 
 4. B. B. almost infusible; gelatinizes 
 
 with HC1; Zn reaction, 
 
 a. Yields water in c.t Calamine. 21 
 
 b. Yields no water in c. t Willemite. 15 
 
 5. infusible ; does not gelatinize ; yields water 
 
 in c.t. ; Al reaction, Beauxite. 13 
 
 If you are now desirous, as I trust you are, of con- 
 
262 
 
 THE WORLD OF MATTER. 
 
 tinuing the study of minerals, you will need a book 
 comprehensive enough to enable you to determine by 
 the methods you have learned all known minerals of 
 any importance. It gives me pleasure in closing to 
 recommend Professor W. O. Crosby's Tables, for the 
 Determination of Common Minerals, published by the 
 author, Boston, ($1.00); and the Manual of Determin- 
 ative Mineralogy, by Prof. George G. Brush, John 
 Wiley & Sons, New Tork, [$3.50.] 
 
 LIST OF SPECIMENS PREPARED TO ACCOMPANY THIS 
 BOOK. 
 
 1. Talc. 
 
 2. Gypsum. 
 
 3. Calcite, (crystal of calc 
 sfar\ 
 
 4. Fluorite. 
 
 5. Apatite. 
 
 6. Orthoclase. 
 7 Quartz. 
 
 8. Cryolite. 
 
 9. Corundum, 
 10. Limonite. 
 n. Hematite. 
 
 12. Magnetite. 
 
 13. Cuprite. 
 
 14. Cast Zinc. 
 
 15. Carbon. 
 
 16. Sulphur. 
 
 17. Stibnite. 
 
 18. Prochlorite. 
 
 19. Quartz crystal. 
 
 20. White marble. 
 
 21. Sphalerite. 
 
 22. Celestite. 
 
 23. Ordinary stratified slate 
 
 24. Roofing-slate. 
 
 25. Kaolinite. 
 
 26. Muscovite. 
 
 27. Biotite. 
 
 28. Halite. 
 
 29. Iron pyrites. 
 
 30. Galena. 
 
 31. Magnesium wire. 
 
 32. Graphite. 
 
 33. Serpentine. 
 
 34. Hornblende. (Amfhibole). 
 
 35. Labradorite, 
 
 36. Chrysotile. 
 
 LIST OF PRINCIPAL ELEMENTS. 
 
 The following list comprises the elements found in 
 
SUGGESTIONS FOR FURTHER STUDY. 263 
 
 the minerals referred to in this book. The principal acid 
 elements are printed in italics ; some elements as arsenic, 
 antimony, and manganese, form both acids and bases. 
 Oxygen and Hydrogen unite both with basic-elements 
 and acid-elements. 
 
 Name. Symbol. 
 
 Atomic 
 
 Name. Symbol. 
 
 Atomic 
 
 
 
 Weights. 
 
 
 
 Weights^ 
 
 Aluminum 
 
 Al 
 
 273 
 
 Chromium 
 
 Cr 
 
 5 2 
 
 Antimony 
 
 
 
 Cobalt 
 
 Co 
 
 59 
 
 (Stibium) 
 
 Sb 
 
 122 
 
 Copper 
 
 
 
 Arsenic 
 
 As 
 
 75 
 
 (Cuprum) 
 
 Cu 
 
 63-4 
 
 Barium 
 
 Ba 
 
 i37 
 
 Fluorine 
 
 F 
 
 19 
 
 Beryllium 
 
 
 
 Gold (Aurum) 
 
 Au 
 
 I 9 6 
 
 (Glucinum 
 
 Be 
 
 (G) 9 
 
 HYDROGEN 
 
 H 
 
 I 
 
 Bismuth 
 
 Bi 
 
 208 
 
 Iron (Ferrum) 
 
 Fe 
 
 56 
 
 Boron 
 
 B 
 
 ii 
 
 Lead 
 
 
 
 Bromine 
 
 Br 
 
 80 
 
 (Plumbum) 
 
 Pb 
 
 207 
 
 Calcium 
 
 Ca 
 
 4o 
 
 LUi.tUm 
 
 Li 
 
 7 
 
 \Jaruon 
 
 C 
 
 12 
 
 Magnesium 
 
 Mg 
 
 24 
 
 Chlorine 
 
 Cl 
 
 35-5 
 
 Manganese 
 
 Mn 
 
 55 
 
 Mercury (Hy- 
 
 
 
 Silicon 
 
 Si 
 
 28 
 
 drargyrum) 
 
 Hg 
 
 200 
 
 Sodium 
 
 
 
 Molybdenum 
 
 Mo 
 
 96 
 
 (Natrium) 
 
 Na 
 
 23 
 
 Nickel 
 
 Ni 
 
 59 
 
 Strontium 
 
 Sr 
 
 88 
 
 Nitrogen 
 OXYGEN 
 
 N 
 
 
 H 
 16 
 
 Sulphur 
 
 S 
 
 32 
 
 Phosphorus 
 
 P 
 
 3i 
 
 Tin(Stannum) 
 
 Sn 
 
 118 
 
 Platinum 
 
 Pt 
 
 197 
 
 Tungsten 
 
 
 
 Potassium 
 
 
 
 (Wolfram) 
 
 W 
 
 184 
 
 (Kalium) 
 
 K 
 
 39 
 
 Vanadium 
 
 V 
 
 ci.4 
 
 Selenium 
 
 Se 
 
 79 
 
 
 
 O T^ 
 
 Silver 
 
 
 
 Zinc 
 
 Zn 
 
 65 
 
 (Argentum) 
 
 Ag 
 
 1 08 
 
 Zirconium 
 
 Zr 
 
 90 
 
 The symbols are abbreviations of the Latin names of 
 
264 THE WORLD OF MATTER. 
 
 the elements; the atomic -weights show the proportions, 
 by weight, in which the elements combine. For in- 
 stance: Galenite is lead sulphide PbS: 
 
 The atomic weight of Pb is . . 207 
 " " S is . 32 
 
 Together,. . . \ . ... . 239 
 
 Thus, in every 239 grains, ounces, or pounds of ga- 
 lenite there are 207 grains, ounces, or pounds of lead, 
 and 32 grains, ounces, or pounds of sulphur. 
 
 THE END. 
 
tETURN EARTH SCIENCES LIBRARY 
 
 * 642-2997 
 
 OAN PERIOD 1 
 1 MONTH 
 
 2 
 
 3 
 
 t 
 
 5 
 
 6 
 
 ALL BOOKS MAY BE RECALLED AFTER 7 DAYS 
 
 Books needed for class reserve are subject to immediate recal 
 
 DUE AS STAMPED BELOW 
 
 ORM NO. DD8 
 
 UNIVERSITY OF CALIFORNIA, BERKELEY 
 BERKELEY, CA 94720 
 
1 
 
 e