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IMPORTANT TO ALL INTERESTED IN SCIENCE. 
 
 Published Every Thursday, price ^d. 
 
 NATURE, 
 
 A WEEKLY ILLUSTRATED JOURNAL OF SCIENCE. 
 
 Half-Yearly Volumes, Royal 8z/0., cloth^ ios. (x each. 
 
 In Schools where Science is included in the regular course of 
 studies, this paper will be most acceptable, as it tells what is 
 doing in Science all over the world, is popular without lowering 
 the standard of Science, and by it a vast amount of information 
 is brought within a small compass, and students are directed to 
 the best sources for what they need. The various questions 
 connected with Science teaching in Schools are also fully dis- 
 cussed, and the best methods of teaching are indicated. 
 
 MACMILLAN & CO., LONDON. 
 

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 ERS, ''/ 
 
 , ROSCOE, 
 
 : 
 
. CHEMISTRY. 
 
 / 
 
 H. E. ROSCOE, F.R.S. 
 
 ( 
 
 Professor of Chemistry in Owens College, Manchester; 
 
 A uthor of 
 ' The Spectrum Analysis, " "Lessons in Elementary Chemistry" &c. 
 
 < \^TH ILLUSTRATIONS. 
 
 . 
 
 UNIVERSITY 
 
 OF 
 
 -^ 
 
 FIFTH EDITION. 
 
 MACMILLANAND CO. 
 
 1876. 
 
LONDON : 
 
 R. CLAY, SONS, AND TAYLOR, PRINTERS, 
 BREAD STREET HILL. 
 
PREFACE. 
 
 IN publishing the Science Primers on Chemistry and 
 Physics, the object of the Authors has been to state 
 the fundamental principles of their respective sciences 
 in a manner suited to pupils of an early age. They 
 feel that the thing to be aimed at is, not so much 
 to give information, as to endeavour to discipline 
 the mind in a way which has not hitherto been 
 customary, by bringing it into immediate contact 
 with Nature herself. For this purpose a series of 
 simple experiments has been devised, leading up 
 to the chief truths of each science. These experi- 
 ments must be performed by the teacher in regular 
 order before the class. The power of observation 
 " in the pupils will thus be awakened and strength- 
 ened ; and the amount and accuracy of the know- 
 ledge gained must be tested and increased by a 
 thorough system of questioning. * 
 
 The study of the Introductory Primer will, in most 
 cases, naturally precede that of the above-named 
 subjects; and then it will probably be found best 
 to take Chemistry as the second and Physics as the 
 third stage. 
 
 Boxes containing the whole of the chemical appa- 
 ratus and specimens needed for the experiments are 
 supplied by the Publishers ; or by Messrs. Jas. Woolley, 
 Sons, and Co., Market Street, Manchester ; Messrs. 
 Mottershead, Manchester ; Messrs. Mawson and Swan, 
 Newcastle-upon-Tyne ; or by J. Griffin and Sons, 
 Garrick Street, Covent Garden, W.C., for ^5 IQS. 
 
TABLE OF CONTENTS. 
 
 ART. SECT. , PAGE 
 
 1. Introductory ........... I 
 
 FIRE. 
 
 2. I. What happens when a Candle burns .... 2 
 
 3. ,, Carbonic Acid and Water produced .... 4 
 
 4. II. When a Candle burns nothing is lost ... 5 
 
 5. ,, Conclusions from Experiments ..... 8 
 
 6. ,, Heat felt when chemical union goes on ... 9 
 
 7. 99 What we have learnt about Heat n 
 
 AIR. 
 
 8. III. About the Air 1 1 
 
 9. What the Air contains . , 12 
 
 ID. iv. What goes on when we breathe the Air. . .13 
 
 11. v. Action of Plants on the Air 16 
 
 12. ,, Growth of Plants 17 
 
 33. Action of Animals and Plants together . . . 19 
 
 WATER. 
 
 14. VI. What is Water made up of ...... 20 
 
 15. ,, Hydrogen can be got from Water .... 22 
 
 1 6. ,, How Hydrogen can be collected ..... 23 
 
 17. vii. Hydrogen got in other ways 24 
 
 1 8. ,, Hydrogen burns, and is lighter than Air . . 26 
 
 19. ,, Water formed when Hydrogen burns . . .27 
 
 20. vni. Composition of Water 29 
 
TABLE OF CONTENTS. 
 
 SECT. PAGE 
 
 ix. Difference between Salt and Spring Water . 33 
 
 ,, Testing for Salt 34 
 
 ,, Solution and Crystallization 34 
 
 X. Rain is distilled Water 37 
 
 ,, Suspended and dissolved Impurities .... 37 
 
 ,, % Hard and soft Water 38 
 
 What makes hard Water 39 
 
 XI. Chalk Water softened , 40 
 
 ,, River Water 41 
 
 ,, Surface Towns Water 42 
 
 W T ater dissolves Gases ...,..,. 43 
 
 EARTH. 
 
 32. XII. About Earth ,,..,, 43 
 
 33. ,, Carbonic Acid Gas from Chalk , . . . . 44 
 
 34. xni. Preparation of Oxygen Gas 46 
 
 35. Metals become heavier by Oxidation ... 48 
 
 36. ,, Metals contained in Earthy substances ... 49 
 
 37. xiv. What is Coal 51 
 
 38. ,, Manufacture of Coal Gas 52 
 
 39. Uses of Coal 54 
 
 40. XV. Coal Gas and Flame 55 
 
 41. ,, Explosions in Coal-pits and the Davy Safety- 
 
 lamp 56 
 
 42. xvi. Elements and Compound Substances ... 58 
 
 43. ,, About Compound Substances 58 
 
 44. ,, About Elementary or Simple Substances , . 59 
 
 NON-METALLIC ELEMENTS. 
 
 45. xyn. Non-Metallic Elements Oxygen . . . . 61 
 
 46. ,, Hydrogen 63 
 
 47. ,, Nitrogen and Nitric Acid. What are Acids, 
 
 Alkalies, and Salts? 63 
 
 48. ,, Carbon contained in Sugar 66 
 
TABLE OF CONTENTS. 
 
 ART. SECT. i-A<,E 
 
 49. xvin. Chlorine, got from common Salt, bleaches . . 67 
 
 50. ,, Sulphur and its Compounds 69 
 
 51. ,, Phosphorus, properties of 70 
 
 52. ,, Silicon, Glass, and Clay 73 
 
 METALS. 
 
 53. xix. Iron, its Uses and Properties ...... 73 
 
 54. ,, Aluminium, the metal of Clay 76 
 
 55. Calcium, the metal of Lime 77 
 
 56. ,, Magnesium, the metal of Epsom Salts ... 78 
 
 57. xx. Sodium, the metal of Washing Soda and Rock 
 
 Salt 79 
 
 58. ,, Potassium, the metal of Potashes .... Si 
 
 59. xxi. Copper and its Compounds 82 
 
 60. ,, Zinc and its uses . 83 
 
 61. Tin got by the Blow-pipe 84 
 
 62. ,, Lead and its Compounds ....... 85 
 
 63. ,, Mercury or Quicksilver ........ 86 
 
 64. ,, Silver and its properties 86 
 
 65. Gold, uses of 87 
 
 RESULTS. 
 
 66. XXII. Combination in definite Proportions 
 
 67. ,, Combining Weights of the Elements 
 
 68. ,, Combinations in multiple Proportions 
 
 69. Meaning of a Chemical Equation 
 
 90 
 
 92 
 94 
 
 Hints for the Use of the Apparatus and for the Experiments 97 
 Price List of Apparatus needed for each Experiment . 101 
 
SCIENCE PRIMERS. 
 
 CHEMISTR Y. 
 
 FIRE AIR WATER EARTH. 
 
 I. Here are four things which we all know 
 well ; let us try to learn what Science 
 teaches us about them. 
 
 The study of these matters constitutes a part of the 
 study of nature ; it is in nature or in the visible world 
 around us that these things occur, it is there that we 
 learn what they are, it is there that we can handle 
 and examine them. This handling and examination 
 of the objects of nature is called Experiment ; and 
 it is either by observation or by experiment that we 
 learn all we know about what goes on around us. 
 To find out and explain what goes on when the Fire 
 burns, to tell how the Air makes the fire burn or helps 
 the plant to grow, to find out what Water is made of, 
 and to learn the many different substances which can 
 be dug out of the Earth ; all this belongs to the 
 Science of Chemistry. Let us try to get hold of 
 a few ideas about these interesting subjects ; and first 
 let us remember that in the Introductory Primer we 
 
SCIENCE PRIMERS. . [ i. 
 
 have been taught the meaning of the words solid, 
 liquid, and gas. The earth on which we stand is a 
 solid, the 'water which runs about on the earth's 
 surface is a liqufd, and the air which surrounds the 
 earth is a gas. You have learnt some of the common 
 properties of earth, water, and air ; you have now to 
 learn something new about these things, what they 
 are made up of and how their several parts can be 
 obtained. Before we begin to study the chemistry of 
 air, water, and earth, let us start with Fire, about 
 which you have not learnt much. 
 
 FIRE. I. 
 
 2. What happens when a candle or a taper 
 burns ? 
 
 The wax as well as the wick of the taper gradually 
 disappears as the taper burns, and at last all is gone 
 : wick, wax, and all. What has become of the wax? 
 it has disappeared. Is it lost? So far as our eyes are 
 concerned certainly it is lost, but so is the ship which 
 sails away on the sea, and yet we know that the ship 
 still exists though we do not see it ; and so the lump 
 of sugar appears to be lost when we put it into a cup 
 of hot tea, and yet we know that the sugar is not 
 really lost, because the tea is made sweet. Now we 
 must look for the wax of our taper in another way ; 
 we must put a question to Nature for her to answer, 
 and we shall always find that our question, if properly 
 asked, is always clearly and certainly answered. We 
 must make an Kxperiment, and if this is properly 
 made we shall never fail in the end to get the infor- 
 mation we want. 
 
FIRE.] CHEMISTRY. 
 
 EXPERIMENT i. Let us burn our taper in a clean 
 glass bottle with a narrow neck ; after it has burnt for a 
 few minutes we notice that the flame 
 grows less and less, and in a short 
 time the taper goes out. This is the 
 first thing we have to observe. We 
 next have to discover why the taper 
 goes out. For this purpose let us 
 see whether the air in the bottle is 
 now the same as it was before the 
 candle was burnt. How can we 
 tell this? Let us pour some clear 
 lime-water 1 first into a bottle 
 filled with air in which no candle has burnt, and 
 then into th one in which our taper burnt. You see 
 the difference at once! In the first bottle the lime- 
 water remains clear, in the second it becomes at once 
 milky. Hence we see that the air has been changed 
 in some way by the burning of the taper. This milki- 
 ness is nothing else than Chalk, and chalk is made 
 up of lime and carbonic acid. Carbonic acid is, 
 like common an*) a colourless invisible gas which we 
 cannot see, but which we find turns the lime-water 
 milky, and puts out a burning taper. Part of the wax 
 has been changed by burning into this carbonic acid 
 gas ; that is, the carbon or charcoal of the burnt 
 wax is to be found again in this invisible gas. Some 
 of this carbon you may notice going away unburnt as 
 smoke or soot > and if you quickly press a sheet of 
 white paper on to the flame so as not to burn the 
 
 1 Made by letting a piece of fresh lime stand in water, and 
 shaking it up, and then letting the w^ter get clear again. 
 
SCIENCE PRIMERS. 
 
 HI. 
 
 paper, you will see that it becomes stained with a 
 black ring of soot or carbon. 
 
 3. Besides carbonic .acid gas there is 
 another substance formed when the candle 
 burns, viz. Water. 
 
 You may perhaps think it strange that water is 
 formed in the hot flame. Still a simple experiment 
 will show you that this is really the case. If water 
 comes off from the flame, it will be in the state of 
 hot steam, which you cannot see, for what we com- 
 monly call steam coming out of the boiling kettle is 
 not steam, but fine drops of water ; and if you had a 
 glass kettle, and could look inside it, you would see 
 notriing above the boiling water, because steam is an 
 invisible gas like carbonic acid and common air. 
 Now as the steam from the kettle becomes small drops 
 of water when it cools, so the hot air coming from the 
 burning taper, if it contains steam, must deposit the 
 steam in the form of drops of water when it is cooled. 
 EXPERIMENT 2. All we need to 
 do to see whether steam is given off 
 from a burning candle, is to hold a 
 cold, dry, bright glass, such as a 
 tumbler, over the flame of our taper. 
 You see that the bright glass is at 
 once dimmed, and if you look care- 
 fully you will notice the little drops 
 of water which bedew the inside of 
 the glass. If we went on for some 
 time, and if we so arranged the ex- 
 periment as to keep the glass always 
 cool, we could get a wine-glass full of water by burning 
 
 Figr. 2. 
 
FIRE.] CHE MIS TR Y. 5 
 
 a candle, and the water thus got is like all other 
 pure and good water, except that it may perhaps taste 
 a little of soot. 
 
 Let us now look back as to what we have learnt 
 about our candle burning; for it is most important 
 always to get clear ideas, first, as to what we want to 
 prove by our experiments, and secondly, as to what 
 we have to learn from them. 
 
 We want to know what happens when a candle 
 burns. We have learnt 
 
 1. That the candle soon goes out if it be burnt in 
 a battle of air. 
 
 2. That a colourless invisible gas called carbonic 
 acid is formed in the bottle after the candle has burnt. 
 
 3. That the carbonic acid gas comes from the car- 
 bon or soot contained in the wax. 
 
 4. That water is also formed when the candle 
 burns. 
 
 We therefore have learnt that the wax of the candle 
 has not been destroyed or lost, but that it has 
 changed its form and has been converted into 
 carbonic acid and water. This sort of an entire 
 change is called a chemical change. No one 
 could have foretold that the wax would have changed 
 into two totally different substances ; it is only by 
 making these careful trials that we learn what happens 
 in such cases as these : hence Chemistry is called an 
 Experimental Science. 
 
 FIRE. II. 
 
 4. When a candle burns nothing is lost. 
 
 Our experiment with the taper gives us at once an 
 
6 SCIENCE PRIMERS. [n. 
 
 answer to the question, where does all the coal go 
 to in a common fire ? It goes up the chimney as car- 
 bonic acid gas. We heap on coals all day long, and 
 take away next morning only a shovelful of ashes 
 the coal has burnt away. But this is not a sufficient 
 answer. We have got jiext to find out what happens 
 to the carbon of the wax or of the coal when it burns 
 away and flies up the chimney as carbonic acid gas. 
 
 EXPERIMENT 3^ For this purpose we must make 
 another experiment. Here we have a glass tube with 
 a cork at the bottorn, through which some holes are 
 bored ; into one of these holes I stick a piece'of our 
 taper. Iri the (J shaped tube I have placed some 
 pieces of a white substance called caustic soda. 
 Now I hang the tube, with the taper and caustic soda, 
 on to one end of a pair of common apothecaries' scales, 
 and put weights at the end until the tube is quite 
 balanced. Next I fasten the top of the tube by a piece 
 of india-rubber tubing to the top of an oil-can filled 
 with water, and having a perforated cork and glass tube 
 at the top and a tap to let the water out at the bottom. 
 Now when I let the water run out quickly into the 
 bucket, the air passes through the holes in the cork into 
 the tube, to fill the space left by the water, as seen by 
 the direction of the arrows in the drawing. I next 
 light the taper and quickly replace it and the cork> 
 and allow it to burn in the draught of air. After the 
 taper has burnt for a few minutes I stop the water, 
 running, and you see that the candle goes out ; and 
 when you look at the scales you will find that they 
 are no longer balanced, but, strange as it may seem, 
 the tube in which the taper has been burnt is really 
 heavier than it was before the candle was lighted, 
 
FIRE.] 
 
 CHEMISTRY, 
 
 although some of the cardie has disappeared.- This 
 is then what our experiment teaches us. We must try 
 to understand how the candle, after it is burnt, weighs 
 more than before it was burnt. In the first place, 
 then, I put the lumps of caustic soda in the (J shaped 
 
 tube above the taper, in order that the two invisible 
 gases carbonic acid and steam which we now know 
 are always given off when the taper burns, shall not 
 escape from the tube, but shall be held fast by this 
 caustic soda (just as fish may be caught in a net). 
 ir. R 
 
SCIENCE PRIMERS. [ n. 
 
 Having then caught these gases, we discover that they 
 are heavier than that part of the original candle which 
 has been burnt. How can this be explained ? Why, 
 only by supposing that something having weight has 
 been joined to or has united with the substance of the 
 taper to produce the two gases in question. This sup- 
 position turns out to be correct, and this something is 
 another colourless gas which partly makes up common 
 air, and is called oxygen gas. Now we can more 
 clearly understand what goes on when the taper burns. 
 Whilst the act of burning is going on, the substance of 
 the wax (or coal) is uniting chemically with the 
 oxygen of the air. The carbonic acid and steam 
 formed are the results of that chemical union. 
 These gases weigh more than the wax (or coal) which 
 is burnt, because they contain something else besides, 
 viz. oxygen taken up from the air. If we had weighed 
 the air, we should have found that the air had lost 
 exactly as much weight as the burnt wax (or coal) had 
 gained, viz. the weight of the oxygen. 
 
 5. What we have learnt. 
 
 Now we have learnt two - most important things 
 about the burning of a candle, (i) that nothing really 
 disappears or is really lost ; (2) that the parts of the 
 candle are uniting chemically with the oxygen of 
 the air. 
 
 By making these three simple experiments, and by 
 trying to find out what they teach us, we have learnt 
 more about Fire than all the ancientc knew, so that 
 you now understand the use of experiments; and when 
 you come to read the Physics Primer (Articles 48 and 
 75)9 y u will learn still more about the Nature si Heat. 
 
FIRE. ] CIIEMISTR Y. 
 
 Let us, however, go on a step further, and let me 
 tell you that in all the experiments which are given in 
 this book, or which you will ever make for yourselves, 
 you will always find the same truth come out that 
 no substance is ever really lost. We can- 
 not really destroy, neither can we really 
 create any substance. Another fact which you 
 have learnt from the burning candle is also true in 
 other cases, viz. that wherever chemical union is 
 going on there Heat is sure to be felt, and when 
 that union goes on quickly we see Flame or 
 Fire. 
 
 6. Heat felt when chemical union goes on. 
 
 Let us make two experiments about this. 
 EXPERIMENT 4. Take a lump of quicklime, put 
 it on a tin plate, and pour over it some cold water ; 
 
 Fig. 4. 
 
 you will soon see that the water and the lime both 
 begin to get hot, and the water hisses on the hot lime 
 till at last it boils, and cloucjs of steam are given off. 
 The lime remains on the ptate as a fine dry white 
 
 B 2 
 
10 
 
 SCIENCE PRIMERS. 
 
 [n. 
 
 powder,' called slaked-lime. We have only done 
 what the bricklayers do every day to make their 
 mortar ; we have slaked the lime. Why should all 
 this heai and steam arise ? It arises because the 
 water and the quicklime have combined together 
 chemically, and the result is slaked-lime. 
 
 EXPERIMENT 5. Put some yellow powdery flout 
 of sulphur on the bottom of a small glass flask, and 
 
 above this put in- 
 to the flask some 
 bright copper 
 turnings. Next 
 place the flask on 
 an iron stand, and 
 heat it over the 
 flame of a gas 
 lamp for the pur- 
 pose of boiling the 
 sulphur. We will 
 place the lamp on 
 a common plate, 
 to 'catch the sulphur if the flask should chance to 
 crack. Now look what happens. First the yellow 
 sulphur melts; it gets darker "and darker in colour, 
 and at last it boils. Now the boiling sulphur 
 touches the copper turnings, and we may remove 
 the lamp, when we see that the turnings first become 
 red-hot and glow with a splendid lurid red light, 
 and then melt and drop down to the bottom of the 
 flask. When the flask is cold we break it open, and 
 find that it contains neither bright copper nor yellow 
 sulphur, but that a blade substance is found at the 
 
 Fig 5- 
 
AIR.] CHEMISTRY. 1 1 
 
 bottom. What is this? It is a chemical com- 
 pound of the two different things, copper and sul- 
 phur ; the copper has united chemically with the 
 sulphur, and whilst they were joining heat was given 
 off, or the copper took fire and burnt. 
 
 7. What we have learnt. 
 
 Now I think you have learnt that where there is 
 Fire there chemical union is going on, whether it is 
 a taper burning, or coal burning, or a hayrick on fire, 
 or a house on fire. In all these we have the same 
 thing going on, viz. chemical union of the parts of 
 the burning body with the oxygen of the air* And so 
 from Fire we get to Air. 
 
 AIR. in. 
 
 8. About the Air. 
 
 How do you know that there is anything between 
 you and me in this room ? What makes you say that 
 there is Air out of doors ? If you move your hand 
 and arm quickly round and round, you will feel a 
 draught of air through your fingers ; if you fan your- 
 self, you feel the air passing over your face. Out of 
 doors you notice the Wind blow, you see the trees 
 or the clouds moved by the breeze, and this breeze is 
 only the air in motion. What makes the sails of a 
 windmill go round and round ? The wind, you say. 
 AVell then this wind which blows sometimes so hard as 
 to uproot trees and wreck ships is only air moving. 
 But if the air is still and quiet, how can we tell that it 
 is present ? Certainly not by seeing it, because air is 
 
SCIENCE PRIMERS. [ HI. 
 
 invisible, but by making an experiment we at on GO 
 learn something new about it. 
 
 9. What the air contains. 
 
 EXPERIMENT 6. Here I have a bell-jar open at 
 the bottom and furnished with a neck, and a cork at 
 the top (an old bottle with the bottom cracked off 
 will do very well). I will put the bell into this basin 
 of water, but first we must float on the water a little 
 china dish with a small bit of dry phosphorus as big 
 as a pea on it, and light the phosphorus with a match. 
 
 Fig. 6. 
 
 Phosphorus is a very dangerous substance, and much 
 care must be taken of it, as it is very apt to take fire 
 by itself, and may burn your fingers badly. Now you 
 see the bright flame of the phosphorus burning inside 
 our bell-jar. After a while it goes out, although it is 
 not all burnt, and we will let the bell-jar stand 
 until it is cool. You notice that the white smoke or 
 fumes which were made by the burning phosphorus 
 have now disappeared, and we have a quantity of air 
 left. But* you will at once see that there is not so much 
 air left as there was when we began ; the jar was full 
 of air to start with, now there is a good deal of water 
 in the lower part of the jar. Let us next ask our- 
 
AIR.] CHEMISTRY. 
 
 selves, is the air which remains the same kind of air 
 which we took? We take out the cork of the bell-jar 
 and plunge our burning taper into the gas; why, at once, 
 it goes out. We light it again with a match, and 
 repeat the experiment; again it goes out when we 
 lower it into the bell-jar. There can be no doubt 
 about this. Something is left after the phosphorus is 
 burnt, which is different from what was in the bell-jar 
 at first. So that you see there are really two different 
 kinds of air .in this room : one kind of air (called 
 Oxygen gas) unites with the phosphorus forming 
 those white fumes, and this disappears and water 
 comes in to the bell-jar in its place ; the other kind of 
 air (called Nitrogen gas), which is left behind, puts 
 out the burning taper, and is therefore quite a different 
 thing from oxygen. Thus we have learnt not only 
 that there is something, which we call air, in this room 
 and in this bell-jar, but that there are two separate 
 things (both invisible gases) called oxygen and 
 nitrogen. What a great deal so simple an experiment 
 may teach us ! Science is always simple and plain 
 when we go carefully forward, and when 'we make sure 
 to understand each step we take. 
 
 AIR. IV. 
 
 10. What goes on when we breathe the air. 
 
 We now know that whenever a candle or other 
 thing burns in the air a chemical union is going on 
 between the substances composing the candle and the 
 Oxygen of the air. The burning wax candle is pro- 
 ducing carbonic acid and water, because the carbon 
 and hydrogen contained in the wax are uniting with 
 
14 SCIENCE PRIMERS. [ iv. 
 
 oxygen ; we must light the candle before it will burn, or 
 we must start this union. The candle flame is hot 
 because this Oxidation is going on: when you blow 
 the candle, the flame is cooled and goes out, the wax 
 no longer combining with the oxygen. 
 
 The oxygen of the air is as necessary for the life of 
 men and animals as it is for the burning of candles. 
 You know that we must have fresh air to breathe : if 
 we do not get enough fresh air, we shall be suffocated 
 and die. There are many dreadful stories told of 
 people being suffocated on board ships in storms when 
 the hatchways had been nailed down to prevent the 
 waves from sinking the ship, or in coal mines, or in 
 wells where foul air had collected. Now let us ask the 
 . question, what is going on when we breathe ? Do 
 men and animals produce any chemical changes in 
 the air which they breathe like the burning candle or 
 phosphorus? Here a simple experiment will soon 
 plainly answer this question. 
 
 EXPERIMENT 7. Pour some clear lime-water into 
 a glass, and then blow the air from your lungs through 
 the liquid by means of a straw or a piece of glass 
 tubing. You will soon notice that the lime-water 
 has become milky; exactly the same effect has been 
 produced as was noticed when you burnt a taper in a 
 bottle (Experiment i) ; the milkiness shows that chalk 
 has been formed, and the chalk shows that carbonic 
 acid gas has come out of your lungs. For this car- 
 bonic acid gas did not go into your lungs with the air, 
 because if you shake up lime-water with common air it 
 does not get milky. Hence we learn that the air you 
 breathe out differs from the air which you breathe 
 in by containing large quantities of carbonic acid gas. 
 
AIR.] CHEMISTRY. 15 
 
 Where does this gas come from ? It is the same gas 
 which is always formed when a candle burns. Can our 
 bodies be really burning like candles ? You will say 
 at first, No, certainly not, for we do not feel hot like a 
 candle flame. But then 
 you will think, Why ! I am 
 really hotter than the table 
 or walls or anything which 
 is not alive. So is the dog 
 or the cat ; so are a great 
 number of animals. But 
 when these animals cease 
 to live, or when they cease 
 to breathe, then they be- 
 come cold like the walls 
 or the table. The breath- Fi s- 7- 
 
 ing of animals is therefore an act of oxidation. 
 The air passes through the nose and mouth down the 
 throat into a fine network of very small tubes called 
 the lungs. At one side of these thin tubes is the air, 
 at the other side is the blood, and the oxygen of the 
 air passes through the thin sides of these air-passages 
 into the blood, and there it combines with the dead 
 carbon contained in the body. You may easily con- 
 vince yourself that animal bodies contain carbon, by 
 noticing that a piece of meat becomes charred or 
 converted into charcoal or carbon when it is partly 
 burnt by placing it before a hot fire. Now this carbon 
 of the body forms carbonic acid when it unites with 
 oxygen, just as the carbon of a piece of wood does. 
 And the heat which is given off in each case is exactly 
 the same. If we were to get a bottle full of pure 
 carbonic acid gas from a burning taper, and the same 
 
16 SCIENCE PRIMERS. [ *. 
 
 sized bottle full of pure carbonic acid gas from oiir 
 lungs, the heat which is produced in our body by the 
 combustion of our animal carbon, in order to get this 
 much carbonic acid gas, is the same as that given off 
 by the burning of the candle to get the same quantity 
 of the same gas. We do not see any flame in the 
 animal because the heat of combustion is spread all 
 over the body ; if the oxidation took place in as small 
 a space as the wick of a candle, then we might expect 
 to see a flame, but as it is the blood running through- 
 out the body simply keeps the whole warm. 
 
 Thus by another experiment we have learnt (i) that 
 animals take in the oxygen of the air into their lungs ; 
 (2) that there the oxygen goes into the blood ; and (3) 
 that there the oxygen is used to burn up the waste 
 carbon of the body forming carbonic acid, and thereby 
 giving rise to animal heat. 
 
 AIR. V. 
 
 ii. Let us next ask what sort of action do 
 Plants exert on ths air ? 
 
 Again we must have recourse to experiment, but 
 this time one which will last some days. 
 
 EXPERIMENT 8. If you sow some mustard or cress 
 seeds on a piece of common flannel kept moist by a 
 little water contained in a plate, the seeds will soon 
 begin to sprout, and if you keep them in the light they 
 will continue to grow until after some days you may 
 have a fair crop of mustard and cress plants. Whence 
 did the growing plants get the materials necessary to 
 form their stalks and their leaves ? not from the 
 flannel, for that remains unchanged ; not wholly from 
 
AIR.] CHEMISTRY. 17 
 
 the seeds, for the plants weigh much more than the 
 seeds ; not from the water alone, because the plants 
 are building up stalks and leaves containing Carbon, 
 and this substance is not present in water. Where 
 does the plant get the carbon it needs ? From the 
 air, we answer. Our previous experiment showed us 
 that animals are continually giving out carbonic acid 
 gas in their breath, and we are therefore sure that 
 this gas must be present in the air, although perhaps 
 in small quantity. Let us see whether we can find out 
 that there is a little carbonic acid in common air. 
 
 EXPERIMENT 9. Pour a little clear lime-water into 
 a shallow saucer or clean plate, and allow it to stand 
 for a few minutes, either in a room or in the open air, 
 then move it about and pour it into a glass. You will 
 notice that a thin white film has been formed on the 
 top of the lime-water. This film is chalk or carbonate 
 of lime, derived from the union of the carbonic 
 acid contained in the air with the lime. It takes 
 some time to form, and then only is seen in small 
 flakes or films, because there is only a very little car- 
 bonic acid gas in the air. But this small quan- 
 tity of carbonic acid serves as the main 
 food of all the plants which grow on the 
 earth. 
 
 12. Growth of plants. 
 
 If the plant uses carbonic acid as its food, and 
 produces therefrom wood, and fruit, and leaves, all of 
 which need carbon to form them, what becomes of 
 the oxygen which we know is united with carbon to 
 form carbonic acid ? We must as usual go to nature 
 for an answer and make an experiment. 
 
tS SCIENCE PRIMERS. [ v. 
 
 EXPERIMENT 10. Take a bunch of fresh green 
 leaves water-cresses answer well and place them in 
 a large bottle, then fill the bottle quite full of fresh 
 spring water, so that no bubble of air is left in the 
 bottle. Turn the mouth of the bottle, full of water 
 
 andleaves, downwards into 
 a basin full of water, and 
 place the bottle and basin 
 in the strong sunlight for 
 an hour or two. If you 
 then carefully examine the 
 leaves, you will see that 
 they are covered with 
 small bubbles, and that 
 more of these bubbles 
 have collected at the top of the bottle. These bubbles 
 consist of pure oxygen gas l derived from the car- 
 bonic acid contained dissolved in the spring water. 2 
 Plants have the power in presence of sun- 
 light of decomposing the carbonic acid of 
 the air, taking the carbon to build up their 
 stems, leaves, &c., setting free the oxygen as 
 a gas. 
 
 EXPERIMENT n. You probably know that green 
 plants will not grow in the dark, and you may under- 
 stand why this is so, if you repeat the last experiment ; 
 but instead of placing the bottle of spring water con- 
 taining the leaves in the light, put it in a dark cellar. 
 
 1 This may be shown if the gas is present in sufficient quantity 
 by transferring the gas to a narrow test tube, and exhibiting the 
 re-ignition of a red-hot splinter of wood. 
 
 2 By adding lime-water to the spring-water a milkiness of 
 chalk will be produced, showing the existence of carbonic acid 
 in the latter. 
 
AIR.] CHEMISTRY. 19 
 
 You will then not notice the formation of any bubbles 
 of oxygen gas, even after standing for many hours, and 
 you will learn that sunlight is necessary in order that 
 green plants may decompose carbonic acid, and there- 
 fore necessary for their growth. 
 
 13. Action of animals and plants on the 
 air. 
 
 Let us now reflect for a moment on the different 
 changes which animals and plants produce in the air. 
 We have learnt that both these sets of living beings 
 are constantly causing important chemical alterations 
 in the air, so that chemistry has not only to do with 
 the changes which occur in dead or inanimate matter, 
 but also is nearly concerned in the very life of every 
 animal and vegetable existing on the globe. Now we 
 have learnt that 
 
 Animals inhale (breathe in) oxygen, and exhale 
 (breathe out) carbonic acid give off heat are con- 
 stantly burning. 
 
 Plants inhale carbonic acid gas, and exhale 
 oxygen, take up the sun's light and heat, without 
 which they cannot grow, are constantly forming 
 material which will burn. 
 
 Here you see that the part played by the animal is 
 exactly the opposite of that played by the plant : the 
 animal renders the air impure by constantly breath- 
 ing out carbonic acid ; the plant constantly tends to 
 purify the air again by taking up the carbonic acid, 
 and breathing out (by means of its leaves) oxygen 
 gas. This balance between animal and vegetable life 
 is well illustrated by the Vivaria, now so common, in 
 which small water-animals and water-plants grow in a 
 
20 SCIENCE PRIMERS. 
 
 globe shut off from the air j the carbon contained in 
 the carbonic acid evolved by the animals is set free 
 by the plants, and is just sufficient for their growth, 
 whilst the oxygen at the same time liberated serves 
 for the respiration of the animals. 
 
 /WATER. VL 
 
 14. What is Water made up of? 
 
 You have learnt in the Introductory Primer that 
 if I put a piece of ice into a glass and heat it over 
 a lamp, the solid ice changes into liquid water, 
 and, if I continue to heat the water, it begins after 
 some time to boil and forms gaseous steam. This 
 steam is an invisible gas, quite different in its pro- 
 perties from the liquid water which is got by cooling 
 i t. Let us see if we can get anything else from water 
 than steam, by treating it in different ways. 
 
 EXPERIMENT 12. Instead of sending heat into the 
 water, by which I only get it to boil, I will send a 
 stream of electricity through the water (to which I 
 will add a few drops of acid to allow the electricity to 
 pass more easily). I use four cells of a Grove's battery 
 (a description of which is found in Article 87 in the 
 Physics Primer), and the electricity will pass into the 
 acidulated water by the two platinum wires passing 
 through the cork at the bottom of the glass funnel, 
 when I join these with the copper wires from the 
 battery. 
 
 What do we notice the instant we join the wires? 
 The water near the wires seems to boil, or effervesce, 
 owing to small bubbles of gas being given off. These 
 
WATER.] 
 
 CHEMISTRY. 
 
 21 
 
 bubbles cannot be steam, because steam, if formed 
 near the wire, would at once be condensed by the 
 water near it, and these bubbles rise up through the 
 cold water. Let us try to collect these gases ; and we 
 will see whether the bubbles from the one wire are 
 the same as those from the other. For this purpose 
 we will put a small test-tube filled with water over 
 each wire, so that the bubbles as they rise round the 
 wire must be all caught by the tubes, which are both 
 
 of the same size. V/hat do we notice as the gases 
 collect ? Why, that in one tube we are getting just twice 
 as much gas as in the other. Now one of the tubes 
 is quite full of a colourless invisible gas, whilst the 
 other is just half full. Next let us see what sort of gas 
 we have got. I take the tube which is half full of gas 
 and lift it out of the water by placing my thumb on 
 the mouth, and then, turning it up, I bring a red-hot 
 bit of wocd into the gas; the red-hot splinter at price 
 
22 SCIENCE PRIMERS. [ vi. 
 
 bursts into flame ! What must we conclude ? That 
 the gas is oxygen, for we have learnt to recognize 
 this substance by its re-lighting a red-hot taper. 
 
 Now we will try the same experiment with the other 
 tube, but we will hold its mouth downwards, for a 
 reason which we shall soon understand. The red-hot 
 spark does not rekindle; but if we now bring the 
 flame of a taper to the mouth of this tube, the gas 
 itself can be lighted and is seen to burn with a pale 
 blue flame. Here we have to do with something 
 quite different from oxygen; this gas is called hy- 
 drogen. 
 
 If we repeat this experiment with the water, 
 we shall always get the same result, and by no other 
 treatment that we know of can we get anything 
 else but oxygen and hydrogen from water. Hence 
 we conclude 
 
 (1) That by means of Electricity we can 
 split up or decompose water into two perfectly 
 different substances, oxygen and hydrogen 
 gases; and into nothing else. 
 
 (2) That water, when thus decomposed, 
 yields twice as large a volume of hydrogen 
 as it does of oxygen. 
 
 15. We can get hydrogen from water in 
 several other ways. 
 
 EXPERIMENT 13. If I throw a small pellet of 
 the metal potassium, 1 as large as half a pea, on to 
 the surface of water contained in a basin, we see 
 that the metal, being lighter than water, swims on the 
 
 1 This substance must be kept in rock oil, and not exposed 
 to air or moisture. It may be cut with a penknife. ; 
 
WATER.] CHEMTSTRY. 
 
 surface, but also that the moment it touches the water 
 a flame arises round the metal. This flame is caused 
 by the hydrogen of the water, which is set free 
 and takes fire and burns. Now if this flame is due 
 to burning hydrogen, what becomes of the oxygen of 
 the water ? The oxygen unites chemically with the 
 metal potassium to form the alkali potash ; this we 
 can see by adding a little red litmus solution to the 
 
 Fig. 10. 
 
 water on which the potassium has been thrown, when 
 we notice that the red colour is changed to blue, owing 
 to the presence of the alkali 1 potash. If I throw 
 a. small bit of the metal Sodium on to water, this will 
 also swim on the surface and set free the hydrogen and 
 form with oxygen the alkali Soda ; but the heat is 
 not sufficient to light the hydrogen. 
 
 16. How hydrogen can be collected. 
 
 EXPERIMENT 14. By making the last experiment 
 in rather a different way, we can collect the hydrogen 
 which we saw burn on the surface of the water. 
 For this purpose we will mix a few small pieces of 
 sodium with a little dry mercury or quicksilver, the 
 well-known bright shining liquid metal. If we press 
 the bit of sodium with a pestle under the surface ol 
 
 1 For the meaning of this word see page 65. 
 IT. C 
 
24 SCIENCE PRIMERS. - [ vii. 
 
 the mercury contained in a mortar, the two metals 
 will unite, and we get a mixture of the metals, or an 
 amalgam, as it is called. Now pour this liquid amal- 
 gam into a basin of water, having inverted a bell-glass 
 or large test-tube filled with water over the centre of 
 the basin. The sodium will gradually decompose 
 
 Fig. ii. 
 
 the water, forming soda, and the hydrogen of the 
 water will be liberated and will collect in the inverted 
 glass. After a certain amount of the gas has been 
 formed, the presence of hydrogen may be shown by 
 bringing a light to it and seeing that it burns with a 
 pale flame. 
 
 WATER. VII. 
 
 17. Hydrogen got in other ways. 
 
 Many other metals have the power of decomposing 
 water, taking the oxygen to form an oxide of the 
 metal and setting free the hydrogen. Some metals, 
 like potassium and sodium, are able to do this (as we 
 have seen) in the cold ; other metals, such as iron, 
 must be heated red-hot before they can split up water 
 into its two constituent parta uniting with the oxygen 
 
WATER. J 
 
 to form oxide of iron or iron-rust and setting the 
 hydrogen gas free. Some metals, as zinc and iron, 
 although they do not split pure water up into oxygen 
 and hydrogen in the cold, are able to do so if some 
 acid l is present. 
 
 EXPERIMENT 15. If we put a few zinc clippings 
 into a flask containing some water, and if we then 
 carefully pour in a little sulphuric acid (oil of vitriol), 
 we shall soon notice an effervescence, due to the escape 
 of gas. Then we fit tightly into the neck of the bottle 
 a cork furnished with a bent glass tube. The hydrogen, 
 as it is formed from the acidulated water by the zinc, 
 will pass through the tube ; and the bubbles of gas 
 may be collected in a bottle full of water placed in the 
 trough. Care must be taken to allow all the air to be 
 displaced from the generating flask before the gas is 
 
 Fig. 12, 
 
 collected. This is done by trying when the gas, caught 
 
 ma small test-tube over the water, burns quietly on 
 
 being brought mouth downwards to a flame. When 
 
 the supply of gas begins to lessen, it can be again 
 
 1 For the meaning of this word see page 65. 
 
 C 2 
 
26 SCIENCE PRIMERS. [ vn. 
 
 increased by pouring a little more acid through the 
 
 tube funnel without taking .out the cork. , 
 
 Having thus collected three 
 bottles full of hydrogen, which 
 are kept by placing their mouths 
 downwards in small saucers filled 
 with water, let us see what ex- 
 periment can tell us about the 
 properties of this interesting gas 
 Fis I3> got from water. 
 
 18. Hydrogen burns and is lighter than air. 
 
 EXPERIMENT 16. Take one of the bottles full of 
 hydrogen and hold it mouth downwards in the air, 
 and then push a lighted taper fixed on a wire into the 
 bottle. We shall see that the hydrogen gas takes fire 
 and burns at the mouth of the bottle, but that the 
 flame of taper inside the bottle has gone out. When 
 we bring the taper out again, it will be rekindled by 
 the flame of the burning hydrogen, but will be ex- 
 tinguished when plunged into the gas. What does 
 this experiment teach us ? 
 
 1. Hydrogen is inflammable, and burns with a pale 
 blue flame. 
 
 2. Hydrogen does not support the combustion of a 
 taper. 
 
 EXPERIMENT 17. Turn upwards the mouth of a 
 bottle filled with hydrogen, and then quickly bring a 
 light to it ; the hydrogen will burn with a much larger 
 flame than when the bottle is turned mouth down- 
 wards. This is because hydrogen is much lighter 
 than air. For this reason we can pour hydrogen 
 upwards. Take a bottle filled with air and another. 
 
WATER.] 
 
 CHEMISTRY. 
 
 27 
 
 filled with hydrogen, and bring them together thus, 
 and then slowly bring them into this position, when 
 the lighter hydro- 
 gen will pass up- 
 wards, displacing 
 the air from the 
 lower into the up- 
 per bottle. Then 
 bring the top bot- 
 tle with its mouth Fig 
 downwards to a 
 
 light, when the hydrogen will take fire and burn 
 (sometimes with a slight report from admixture of air). 
 Let the bottom bottle stand for a few moments mouth 
 upwards on the table and then bring a light to it. All 
 the hydrogen has gone, and the bottle is filled with 
 common air. This experiment shows that hydrogen 
 is much lighter than common air. Indeed, it is the 
 lightest substance we know of, and is therefore used 
 for filling balloons. 
 
 19. Water formed when hy- 
 drogen burns. 
 
 Let us next try to find out what 
 is formed when hydrogen burns in 
 the air. 
 
 EXPERIMENT 18. Instead of the 
 bent tube fixed to the flask used 
 to generate the hydrogen, attach a 
 straight one with a pointed end to 
 act as a jet. After you are quite 
 sure that all the air has been driven 
 out of the flask (and this can be 
 
PRIMERS. [ vir. 
 
 ascertained by hanging a dry test-tube on to the 
 pointed tube and seeing that the hydrogen which 
 then will fill the test-tube burns quietly on lighting it), 
 bring a flame to the jet. The hydrogen will burn 
 with a steady flame ; now bring over this flame, as in 
 Experiment 2, a dry glass, when a deposit of dew, or 
 small drops of water, will be noticed. This shows 
 that when hydrogen burns it unites with the 
 oxygen in the air to form water. 
 
 EXPERIMENT 19. Now let us see whether anything 
 else is produced when the hydrogen burns. We will 
 allow the flame to burn inside a large bottle or 
 flask, and then add to the air in which the flame of 
 hydrogen has burnt some clear lime-water (as in Expe- 
 riment i). No milkiness is, however, produced, and 
 we therefore see that no carbonic acid gas is formed 
 by the burning of hydrogen; and so, by making 
 further experiments, chemists conclude that when 
 hydrogen burns in the air nothing but pure water is 
 formed. By arranging Experiment 18 so as to 
 keep the glass cool for some time, we may collect 
 a glass full of water, and we find that this is per- 
 fectly pure water and quite free from soot, which 
 was present in the water got by burning the candle 
 (Experiment 2). 
 
 Now we learn where the water came from when the 
 candle was burnt; the wax must contain hydrogen, 
 and the water is formed by the union of the hydrogen 
 of the wax with the oxygen of the air. So you see that 
 in gaining knowledge about -water we have learnt 
 about air, for we have seen that water is made up of 
 two different kinds of airs or gases, so closely are the 
 parts of natural knowledge linked together, 
 
WATT.R.] CHEMISTRY. 29 
 
 WATER. VIII.| 
 
 20. Composition of water. 
 
 Next let us try to learn more about the compo- 
 sition of water. We have found (Experiment 3) that 
 oxygen is contained in the air mixed with nitrogen (Ex- 
 periment 6). The oxygen exists in the air in the free 
 state as a colourless gas; in water the oxygen is 
 chemically combined with hydrogen, and when 
 united together these two gases form liquid water. 
 We also know that (Experiment 12), when water is 
 decomposed, 2 volumes of hydrogen gas are ob- 
 tained for every volume of oxygen. It now be- 
 comes an important question to ask what weight 
 of oxygen and hydrogen unite together to form water. 
 How many pounds of hydrogen and how many pounds 
 of oxygen go to form so many pounds of water ? You 
 must take care to distinguish between volume and 
 weight. To ascertain the composition of water with 
 accuracy is not easy, and it is so important that many 
 chemists have devoted months or years to find out the 
 exact weights of hydrogen and oxygen which are con- 
 tained in water. We may copy their experiments by 
 what I may call a rough model, which, if it is rather 
 more difficult than the former experiments, is of great 
 interest, and will be understood by all who read the 
 description and try the experiment with care. 
 
 EXPERIMENT 20. In the Introductory Primer the 
 pupil has learnt the use of scales or the balance, 
 and knows how the weight of a substance is deter- 
 mined. It may, however, be well for him to learn 
 
30 SCIENCE PRIMERS. [ vin. 
 
 how to weigh for himself, and to know the number 
 and value of the weights. 
 
 I have here a small pair of common apothecaries' 
 scales and a set of weights. A is a tube of hard glass 
 with a bulb blown on to it, and into this I bring about 
 half an ounce of black oxide of copper; Bis another 
 tube into which the bent end of tube A can be fixed ; 
 this tube is filled with white calcium chloride, a sub- 
 stance which eagerly absorbs moisture ; c is a flask 
 for generating hydrogen from water and dilute acid by 
 means of zinc ; D is a little wash-bottle containing some 
 oil of vitriol, which will dry the hydrogen as it bubbles 
 
 Fig. 16. 
 
 through; E is another tube containing calcium chloride, 
 through which the gas must pass, and thus get quite dry 
 before reaching tube A. In making the experiment we 
 must first get the weight of the tube A and the copper 
 oxide, by taking out the corks and separating it from 
 the tubes E and B, then carefully putting it on one 
 pan of the scales and placing weights in the other 
 until it is exactly balanced. The precise weight of 
 
WATER. ] CITE MIS TR y. 31 
 
 the tube and the copper oxide must then be written 
 down. Next carefully weigh the tube B in the same 
 manner, and set its exact weight down on paper. 
 
 Now put the two tubes back into their places, 
 as before, taking care not to lose any of their con- 
 tents ; then pour some sulphuric acid down the funnel 
 tube on to the zinc, and allow the hydrogen to bubble 
 through the whole apparatus and over the copper 
 oxide. Put a dry test-tube over the turned-up end 
 of tube B, and collect the hydrogen as it comes out ; 
 try from time to time whether the air is driven out 
 from the apparatus by bringing this test-tube (mouth 
 downwards) to a flame. After several trials the hydro- 
 gen in this test-tube will be found to take fire and 
 burn quietly. As soon as this is the case, put a small 
 gas-flame under the tube containing the oxide of 
 copper. As long as this remains cool no difference 
 can be observed in the black oxide, although the 
 hydrogen passed over it; but when it is heated, a 
 change begins at once. The black colour changes to a 
 bright red metallic tint, and drops of water are seen to 
 condense on the cool part of the inside of the tube. As 
 the whole bulb gets warm the water will be carried into 
 the tube B, and there it will be held by the calcium- 
 chloride, a moisture-absorbing substance. Let the hy- 
 drogen pass over the heated bulb until all the black 
 colour has disappeared, and then take the lamp away. 
 Whilst the bulb is cooling let us find out what has 
 happened. The hydrogen has combined with the 
 oxygen of the copper oxide to form water which has 
 passed on, partly as water and partly as steam, into 
 tube B, where it all collects, none of it escaping into 
 the air ; the red powder left in the bulb is pure 
 
32 SCIENCE PRIMERS. [: vilt, 
 
 metallic copper. Now let us weigh the two tubes 
 again. In the first place, tube A weighs less 
 than it did before, because it has lost something 
 (viz. the oxygen) which has weight. Secondly, the 
 tube B weighs more, because it has gained some- 
 thing (viz. the water) which has weight. Now then 
 we have : 
 
 Grains. 
 
 T. Weight of tube A, containing the copper 
 
 oxide, before experiment . . " . 1056 
 
 2. Ditto, after experiment . . . . 1016 
 The difference between these weights is the ) 
 
 loss due to escape of oxygen . . . ) 4 
 
 3. Weight of tube B before experiment . . 803 
 
 4. after experiment . V ; 848 
 The difference between these weights is the j 
 
 gain of weight of tube B due to absorption > 45 
 of water . . tf- ) 
 
 What must we conclude from this most important 
 experiment ? The answer is obvious That 45 parts 
 by weight of water contain 40 parts by weight of oxy- 
 gen ; and as water contains nothing but hydrogen and 
 oxygen, it must contain the difference, or five parts 
 by weight of hydrogen ; or to two parts of hydrogen 
 by weight water contains sixteen parts of oxygen. 
 
 These same proportions are always found if the 
 experiment is carefully made. And thus we learn 
 the first great law of chemical combination, 
 that the same chemical substance always 
 contains the same quantities of its compo- 
 nents. Water is always made up of 1 6 parts of 
 oxygen to 2 parts of hydrogen by weight, 
 
WATER. ] CHEMISTR Y. 
 
 WATER. IX 
 
 * 21. What is the difference between sea 
 water and fresh spring water? 
 
 We know that sea water is salt, or it contains salt 
 dissolved in it, It is easy to make salt water by 
 throwing some common salt into water ; the solid salt 
 
 Fig. 17. 
 
 disappears or dissolves, and the water now tastes 
 salt. 
 
 EXPERIMENT 21. We can only get rid of this salt- 
 ness by distilling the water ; that is, by boiling the 
 water, and collecting and cooling the steam. This 
 we can do best in a glass retort (fig. 17). We boil 
 the water with a lamp, the steam comes off and passes 
 down the neck of the retort, and into the flask, over 
 the outside of which some cold water runs to cool 
 the steam inside the flask. The distilled water 
 has no longer a salt taste ; it is pure water, for 
 all the solid salt remains behind in the retort, as we 
 may see when we boil off all the water. This plan 
 of getting fresh water from salt sea water is much 
 used on board ship, and the water thus got is good 
 
SCIENCE PRIMERS. [ ix. 
 
 for drinking purposes. Sometimes spring or fresh river 
 water contains common salt dissolved in it, but in 
 such small quantities that it does not taste salt. The 
 chemist, however, has a better mode of seeing whether 
 water contains salt than judging by his tongue of the 
 saltness : he uses a more delicate test than this. An 
 experiment will show this. 
 
 22. Testing for salt. 
 
 EXPERIMENT 22. Take two large clean glasses, 
 full of distilled water or clean rain water ; drop into 
 one of these a grain of common salt as big as a pin's 
 head; stir it well up until this salt is quite dissolved. 
 Now try whether you can taste the salt. You will not 
 be able to do so. Now take the bottle labelled 
 "Silver Nitrate," and carefully pour three or four 
 drops of the liquid into the middle of each of the 
 glasses of water. Soon a white cloud will be seen 
 floating in the water to which the grain of salt was 
 added, whilst the pure water remains clear and bright. 
 Thus, then, the chemist by his testing and experi- 
 ments can ascertain the presence of substances which 
 the common observer overlooks or cannot see, and 
 you will afterwards learn what happened here when 
 this white cloud was formed. (See page 87.) 
 
 23. Solution and crystallization. 
 
 Many other solid substances dissolve readily in 
 water sugar, soda, alum, for instance. Others dis- 
 solve a little, such as gypsum or plaster of Paris. 
 Others again do not dissolve at all in common water, 
 such as flint, sand, or chalk. 
 
 EXPERIMENT 23. If we take two ounces of soda 
 
WATER t ] 
 
 CHEMISTRY 
 
 crystals, commonly called washing soda, and add to 
 them one ounce or about a test-tube full of hot water 
 
 in a glass, the crystals will all dissolve on stirring. If 
 we allow this solution of the soda to cool, we shall 
 notice that particles of the solid soda begin to make 
 
 their appearance on the sides of the glass in bright 
 shining little masses called crystals, or the solution 
 is said to crystallize. 
 
 If you notice the shape of the crystals, you will find 
 them all alike, only some larger than others. 
 
36 SCIENCE PRIMERS. ', [ ix. 
 
 Now try the same with one ounce of alum and 
 one ounce or a test tube full of water ; the crystals of 
 
 Alum. Copper Sulphate. 
 
 alum will make their appearance by degrees. They 
 have quite a different shape from the crystals of soda, 
 as you see in the drawings. 
 
 EXPERIMENT 24. You may do the same with blue- 
 stone or sulphate of copper, and the blue crystals 
 will slowly form of the shape shown in the drawing. 
 
 Now mix up half an ounce of powdered alum and 
 half an ounce of powdered sulphate of copper, and 
 having mixed these powders well together with the 
 mortar and pestle, dissolve them in one ounce of 
 hot water, and let the solution cool. Carefully notice 
 what separates out. You will see that the colourless 
 crystals of alum are formed, and side by side with 
 them blue crystals of sulphate of copper appear. The 
 two different salts can thus be separated by crystal- 
 lization ; and if we took time enough, we could pick 
 out all the alum crystals and put them on one side, 
 leaving all the crystals of sulphate of copper. This 
 shows how nature separates out things which are 
 different, and we see that many rocks and minerals 
 
WAT-?..] CHEMISTRY. -37 
 
 arc formed in the earth by crystallization. Thus we 
 find calc-spar, fluor-spar, heavy-spar, fel-spar, and 
 quartz, all crystalline minerals which have, in differ- 
 ent ways (and we cannot always tell exactly how) 
 been produced in the earth by crystallization. 
 
 WATER. X. 
 
 24. Rain is distilled water. 
 
 If we think where rain comes from, v.*c shall soon 
 see that rain water is the purest kind of water which 
 we find on the earth. Rain falls from the clouds by 
 a condensation or liquefying of the moisture which is 
 in the air. When the hot winds blow over the ocean, 
 these hot winds take up much moisture from the 
 ocean as vapour or steam, just as the steam passes 
 over from the retort ; and when this hot and moist air 
 gets blown to a cooler place, it gets cold and cannot 
 contain so much moisture in the form of vapour 
 as when it was hot, so that this moisture is 
 deposited in drops as rain. Hence rain water is 
 distilled water, and you will see that a gigantic system 
 of distillation is going on all over the globe j and if 
 you reflect for a little, you will understand that every 
 drop of running water on the globe has once been 
 distilled as rain from the ocean to which it again 
 returns. 
 
 25. Suspended and dissolved impurities. 
 
 But does the water running from our springs, our 
 streams, and our rivers into the ocean take anything 
 else back with it? Why, you will at once say Yes, 
 certainly, it washes away sand and soil and dirt 
 
38 SCIENCE PRIMERS. f x. 
 
 into the sea. This you can see if you take some river 
 water, even the clearest, and let it, stand a little ; some 
 sediment will separate out and sink to the bottom. 
 This sand and dirt which the rivers carry out into the 
 sea can be separated by filtration, that is, by passing 
 the dirty water through a piece of porous paper, blot- 
 ting or filter-paper, placed in a funnel as shown in 
 fig. 20, or by filtering through sand or through a 
 
 Fig. ax. 
 
 sponge or through charcoal, as is usual in the water- 
 filters we employ in houses. 
 
 EXPERIMENT 25. Still you will readily understand 
 that only those substances which are suspended in 
 the water as solid particles can thus be got rid of. No 
 process of filtering, however perfect, can get rid of 
 dissolved matter. Add a few drops of blue indigo 
 solution to water, and filter this through a paper- 
 filter ; you will not be able to get rid of the colour, 
 because the indigo is dissolved in the water. In order 
 to get the water free from blue indigo, it must be dis- 
 tilled in a retort. 
 
 a6. Hard and soft waters. 
 
 EXPERIMENT 26. The water running back to the 
 
WATER.] CHEMISTRY. 39 
 
 ocean takes, however, away with it substances in 
 solution. If we boil down a pint of any clear spring 
 or filtered river water in a clean porcelain basin, so as 
 to drive off all the water, we shall always find that 
 some solid residue is left; whereas, if we boil 
 down a pint of distilled water, no solid residue will 
 remain. This is because the rain water, falling on the 
 groynd and trickling through the soil and over the 
 rocks, always finds something which it can dissolve, 
 and which it takes away with it. Thus the sea is 
 constantly having soluble matter carried into it from 
 the land, and it -is becoming, though very slowly, more 
 impure. 
 
 Of course the kind of substances which the rain 
 water takes up in solution on its road to the sea will 
 depend upon the kind of rock or soil through which it 
 passes, and also, you will say truly, upon the sort of 
 dirt which people living near throw in. Some springs 
 are even more salt than the sea itself, because the 
 water which supplies them flows over a layer or bed of 
 solid salt inside the earth. 
 
 Many spring and river waters are said to be hard, 
 whilst rain water is always soft. A water is hard 
 when soap does not at once form a lather with it, but 
 a sediment or curd is produced. Let us see if we can 
 make out why this is, and for this purpose we must 
 try an experiment. 
 
 27. What makes hard water ? 
 
 EXPERIMENT 27. Take a little powdered gypsum 
 or plaster of Paris, and put a pinch of this into a large 
 bottle full of distilled or rain (soft) water. Then shake 
 the water and the powder well together for some time, 
 
 TT. D 
 
40 SCIENCE PRIMERS. [ XI. 
 
 and afterwards filter the whole through a paper-filter. 
 The water will be quite clear, but it has become hard; 
 this you may tell by trying to wash your hands with 
 soap in this water, or, better, by first dissolving some 
 soap in hot water (as is done for making soap bubbles), 
 and then dropping a little of the clear solution of soap 
 into the hard water, when you will find that the soap 
 does not make the water lathery but curdy, until after 
 you have added more soap solution, when the froth 
 appears. 
 
 Hence we learn that spring and river water may 
 become hard by containing gypsum or sulphate 
 of lime in solution. If you boil the water which you 
 have thus hardened with gypsum, no change will 
 occur ; the boiled water on cooling will be as hard as 
 before. 
 
 WATER. XL 
 
 28. Hard chalk water is softened by boiling. 
 
 There is, however, another kind of hard water 
 about which we have to learn. We have already 
 learnt (Experiment 7) that the air from the lungs 
 contains carbonic acid gas, and that when you blow 
 the air out of the lungs through some clear lime- 
 water a white insoluble powder called chalk or car- 
 bonate of lime is formed in the water, which soon 
 becomes quite milky. 
 
 EXPERIMENT 28. Repeat Experiment No. 7, but 
 blow a. great deal more air through the lime-water than 
 you did before. If you go on long enough perhaps 
 for five minutes you will see that the milkiness begins 
 
WATER. ] CHEMISTR Y. 41 
 
 to disappear, and the water becomes clearer; you 
 may not be able to get it quite clear, but you can now 
 filter the liquid through a paper-filter. A clear water 
 will come through, which, however, you will find (by 
 trying the soap experiment) is quite hard. What 
 now has happened ? Why, the carbonic acid from your 
 lungs has the power of dissolving the chalk (which 
 you know does not dissolve at all in pure water) ; 
 and thus we get a clear water which is hard, because 
 it contains chalk dissolved in carbonic acid. 
 Now you know that carbonic acid is a gas; if we boil 
 the water which we have just hardened, all the car- 
 bonic acid gas will be driven off, and the chalk which 
 was dissolved in the carbonic acid will be thrown down 
 as a white powder. This you can easily see by boiling 
 the hardened water in a glass flask. If you filter this 
 boiled water, you will find (by the soap test) that it is 
 no longer hard, but has been softened by boiling. 
 Another way in which water hard with chalk dissolved 
 in carbonic acid can be softened, is to add clear lime- 
 water to the hard water ; the lime unites chemically 
 with the carbonic acid, forming chalk or carbonate of 
 lime, which precipitates or falls down as an insoluble 
 powder together with the chalk originally present. By 
 this latter plan hard chalk waters can be easily soft- 
 ened on a large scale. 
 
 29. The water of different rivers differs in 
 hardness. 
 
 The hard chalk water then differs from the 
 hard gypsum water, inasmuch as we can soften the 
 former by boiling or adding lime, whilst the latter 
 cannot be thus softened. Now if the rain water 
 
 r> 2 
 
SCIENCE PRIMERS. [ XT. 
 
 trickles down through rocks containing gypsum, the 
 springs and rivers in that district (as the river Trent), 
 are hard with gypsum. The rain, however, although 
 purer than any other form of running water, is not 
 quite pure, for it contains carbonic acid gas dissolved 
 in it, which it gets from the air (see Experiment 9). 
 Thus it happens that when rain water passes through 
 a limestone district, or through chalky rocks or soil, 
 the carbonic acid dissolves somo of the chalk, and we 
 get (as in the Thames) water hard from chalk. The 
 crust or deposit often found in kettles or boilers is 
 generally nothing more than this chalk, which slowly 
 separates out on boiling the water and sticks to the 
 bottom or sides of the kettle as a hard crust. 
 
 If the rain passes through a granite district (as the 
 Dee in Scotland), where there is no chalk or gypsum, 
 then the water remains a soft water, because it cannot 
 take up and dissolve any hardening substance from 
 the soil. 
 
 30. Surface water of towns impure. 
 
 If water flows through a town or near sewers, 
 it becomes impure from admixture with the drainage 
 from houses, and is rendered quite unfit for drinking 
 purposes ; indeed, it may thus become poisoned, and 
 the cause of disease. Sometimes the most clear and 
 sparkling water may contain sewage-impurity, if 
 drawn from the neighbourhood of towns or drains. It 
 is for this reason that most of our large towns are now 
 supplied by pure water collected in reservoirs 
 at a distance from the towns, and brought into each 
 house by iron or lead pipes, so that it cannot become 
 spoilt by mixing with drainage water. 
 
CHEMISTRY. 43 
 
 31. Water dissolves gases. 
 
 Gases will also dissolve in water, some kinds much 
 more than others. We have seen that carbonic acid 
 gas from the air dissolves in rain water, and in soda- 
 water there is so much of this gas dissolved, that when 
 the cork is taken out the gas flies out. Even the air 
 dissolves in water, and the dissolved oxygen gives to 
 spring water its pleasant fresh taste. If you boil the 
 spring water, the dissolved air flies off, and when 
 cooled again you will find the water tastes flat and 
 insipid. The dissolved oxygen in sea-water is essen- 
 tial to the life of fishes, for they need oxygen for their 
 breathing as much as animals which live in the air. 
 Where do they get the oxygen ? not from the oxygen 
 which is combined with hydrogen to form water, but 
 from the oxygen gas which is dissolved in the water. 
 Fishes pass large quantities of water through their 
 gills, and in passing through they extract the oxygen. 
 If you throw a live fish into cold water which has 
 been well boiled and not exposed to air, the fish will 
 die, because there is no dissolved oxygen in the water 
 for it to breathe. 
 
 EARTH. XII. 
 
 32. About Earth. 
 
 We have now learnt a little about Fire, Air, and 
 Water let us next see what we can learn about 
 Earth, or the solid matter of which our globe is 
 made up. 
 
 Fire. Air, and Water are somewhat simple things : 
 
 Fire is the heat given off when bodies burn or 
 combine chemically. 
 
 Air is the mixture of two gases, oxygen and 
 
44 SCIENCE PRIMERS. [ xn. 
 
 nitrogen, which exists around us and which we use 
 in breathing. 
 
 j Water is the liquid which surrounds the Earth, 
 and is composed of two gases, oxygen and hydrogen, 
 chemically combined together. 
 
 Earth is a much more difficult and complicated 
 subject, and we can only learn a very little of the 
 Chemistry of Earth in this book. 
 
 To begin with, the solid Earth, as we call it, is only 
 solid because it is not hot. All solid things can be 
 melted and made liquid, if only they are made hot 
 enough.. Hard iron can be melted in a furnace and 
 poured out like water, glass can be melted and cast 
 into plate : so all the solid rocks and stones can be 
 melted and made liquid, like water, and even boiled 
 away like water, and driven off in vapour, if we 
 only heat them enough. In reality, the inside of the 
 earth is hot enough to melt rocks ; and in volcanoes 
 (or burning mountains) we often see that white-hot 
 liquid rock (called lava) is pressed out, and sometimes 
 runs out over a town, as at Herculaneum, near Mount 
 Vesuvius, and burns up and buries all that comes in 
 its course. 
 
 Let us take up some different kinds of earthy 
 bodies, and see what they are made of and what we 
 can get from them. 
 
 33. Preparation of carbonic acid gas from 
 chalk. 
 
 EXPERIMENT 29. Take a few pieces of chalk or 
 limestone or marble (for these are all the same chem- 
 ical substance) ; put them into a bottle fitted with a 
 cork, bent tube, and tube funnel ; pour some water 
 
EARTH.] 
 
 CHEMISTRY. 
 
 45 
 
 into the bottle, and then add a little " hydrochloric 
 acid." You will notice that a bubbling takes place 
 near the chalk, and if you dip the end of the bent 
 tube under water contained in a glass, bubbles of 
 gas will pass through the water. Change this glass 
 for an empty bottle, and let the gas pass from the tube 
 into this bottle. After a few minutes plunge a burning 
 taper into the bottle into which the gas has passed, 
 it will be instantly extinguished. Next pour some 
 clear lime-water into the bottle, it will be turned 
 milky. Then put the burning taper at the bottom 
 of another bottle containing air and pour the gas 
 from the other bottle (as if it were water) on to the 
 
 Fig. 22. 
 
 burning taper; soon you will see that it is put out. 
 What is the gas we have got from chalk or marble ? 
 It is carbonic acid gas, for it puts out a flame, it 
 makes lime-water milky, and it is so much* heavier 
 than air that we can pour it from vessel to vessel like 
 water. This carbonic acid gas is combined in the 
 chalk, and when we add another acid, this gas comes 
 off. What else does the chalk contain ? Let us put 
 a piece of chalk or limestone or marble into the fire, 
 so as to heat it gently, and then notice what happens. 
 
46 SCIENCE PRIMERS. [ xiir. 
 
 If we take the stone out of the fire, we see that it has 
 been altered by being burnt. If we pour acid upon 
 it, bubbles are not given off; it has therefore lost its 
 carbonic acid by being burnt. But if we pour water 
 on it, we notice that the solid substance falls to powder 
 and becomes hot enough to make the water boil. 
 Now what has happened is that, by heating, the lime- 
 stone or marble has lost its carbonic acid and 
 quicklime is left (and this is what happens in the 
 lime kilns) ; and when we pour water on to quicklime, 
 it is slaked, or combines with the water. Hence we 
 have learnt that chalk or marble is a chemical com- 
 pound of lime and carbonic acid, and also that 
 from an earthy substance we may be able to get a gas. 
 
 EARTH. XIII. 
 
 34. Preparation of oxygen gas. 
 
 EXPERIMENT 30. Next we will take another 
 earthy substance, not so common as chalk, but one 
 
 Fig. 23. 
 
 which will teach us some important lessons. We will 
 put a little of this red powder out of the bottle 
 
EARTH.] CHEMISTRY. 47 
 
 labelled " Mercury Oxide " into a little tube of hard 
 glass, and fasten to it a cork and bent glass tube, and 
 fix this in a holder. Then heat the red powder it will 
 soon get dark-coloured, and then a bright white 
 shining substance will be deposited on the cold 
 sides of the tube. Bubbles of gas will be seen to 
 come off at the end of the tube, and these can be 
 collected in a tube filled with water placed in the 
 trough. We can then test to see what this gas is, 
 and by bringing a red-hot splinter of wood we shall 
 see that this gas is oxygen gas, because the red- 
 hot spark ft at once rekindled. Now we may go 
 on heating the red powder until it has all disappeared 
 or is all converted into oxygen gas and the bright 
 shining substance which collects in the tube. Let us 
 find out what this substance is. When all the red 
 powder has disappeared from the bottom of the tube, 
 we take the tube and cork out of the water to prevent 
 the water going back into -the tube when we take 
 away the lamp. Now when the whole is cold scrape 
 down the shining deposit with a little piece of wood, 
 and you will find that bright liquid drops of metal can 
 be shaken out of the tube. This metal is mercury 
 or quicksilver. 
 
 Now we have learnt that this red powder can 
 be split up into two substances by heating it: 
 (i) Oxygen gas; (2) The metal Mercury. Not only 
 does this red powder, wherever it may be got from, 
 always yield mercury and oxygen on heating, but 
 the same weight of this red powder always gives 
 the same volume of oxygen and the same quantity 
 of mercury. 
 
 You see why this is called oxide of mercury 
 
48 SCIENCE PRIMERS. [ xm. 
 
 because it is a chemical compound of oxygen 
 and mercury. Nobody could tell that this red pow- 
 der contained these two quite different substances I 
 this is a thing which can only be found out by 
 trial or experiment. Chemists have found by weigh- 
 ing the red powder, and the mercury and oxygen 
 which it yields, that 216 pounds' weight of red oxide 
 of mercury always yields 200 pounds of metallic 
 mercury and 16 pounds' weight of oxygen. So here 
 again we have proof that the same chemical 
 compound always possesses a fixed and 
 unalterable composition. 
 
 35. Metals become heavier by oxidation. 
 
 Almost all the earthy and solid rocks and bodies 
 which we see around us contain oxygen combined 
 with something else, forming oxides. Thus all the 
 metals, such as iron, copper, silver, zinc, lead, will 
 combine like mercury with oxygen to form oxides, 
 and the oxide will always be heavier than the 
 metal contained in it, because there is also the 
 oxygen, which has weight. 
 
 EXPERIMENT 31. To show that this is the case, 
 take a small horseshoe magnet, and dip the ends of 
 the magnet into fine iron filings, which will stick to 
 the magnet, forming a kind of small brush. Then 
 hang up the magnet, with the filings on it, on one end 
 of the beam of the scales, and accurately balance the 
 other pan with weights. Now place the flame of a 
 lamp underneath the filings as they hang on the 
 magnet; you will see that the filings take fire and 
 burn that is, they are combining with the oxygen of 
 the air to form oxide of iron, which is the same 
 
EARTH.] 
 
 CHEMISTRY. 
 
 49 
 
 thing as iron rust ; and, if you get enough filings 
 to stick to your magnet, you will see that the scales 
 
 
 will no longer be balanced, but that the iron rust is 
 heavier than the filings. 
 
 36. Metals contained in earthy substances. 
 
 So we learn from these two last experiments that 
 an earthy-looking substance may contain a bright 
 metal. Let us make one or two more experiments to 
 show this. 
 
 EXPERIMENT 32. Take a small crystal of " blue- 
 stone," or sulphate of copper; dissolve this in some 
 hot water in a test-lube ; then place the clean blade 
 of a knife, or any piece of bright iron, into the blue 
 liquid. In half a minute take out the bright iron and 
 you will see that it is coloured red where it has dipped 
 in the blue liquid ; and if you rub this you will get 
 the bright red colour of metallic copper. Put the 
 
SCIENCE PRIMERS. 
 
 [ 
 
 iron back again, and leave it fr some time in the 
 blue liquid, when you will find that the blue colour 
 will have disappeared, and much copper will be depo- 
 
 sited as a brown powder ; and on putting a piece of 
 clean iron in the solution, no further red deposit will 
 be formed, showing in two ways that all the copper 
 has been thrown down from solution. 
 
 EXPERIMENT 33. Take half an ounce of the white 
 solid labelled " Lead Acetate," commonly called 
 
 sugar of lead, and put it with some water into a 
 small clean glass, when it will all soon dissolve ; 
 
EARTH.] CHEMISTRY. 51 
 
 tie a small bit of zinc by a thread to a bit of wood, 
 so that when the wood rests on the top of the glass 
 the zinc hangs in the liquid. Allow this to stand 
 for some hours, when crystals of metallic lead 
 will be formed on the zinc, and form a tree-like 
 growth, showing that the white crystals contain me- 
 tallic lead. 
 
 EARTH. XIV. 
 
 37. What is Coal ? 
 
 Next let us try to find out something about coal. 
 Coal, we know, contains carbon, for we saw that 
 it burns and yields carbonic acid gas by combining 
 with the oxygen of the air. As you learnt in the 
 Introductory Primer, coal is got from " pits " or 
 "mines," and it is found sometimes deep down in 
 the earth, and sometimes at or near the surface. 
 A great deal might be said about coal about how 
 it was formed, what it contains, what we can get 
 from it, and what we do with it. 
 
 1. How was coal formed? Though it may seem 
 strange, it is still true, that coal is the remains of 
 plants which grew long ago on the surface, but which 
 have been buried down deep in the earth. When you 
 go down a coal-pit you will see the roof and floor of 
 the passages covered with impressions or casts of 
 leaves and other parts of plants, showing that plants 
 have been buried here ; and if we slice a piece of 
 coal very thin indeed, we see in the coal itself marks 
 which show us that it has all been vegetable matter. 
 
 2. What does coal contain, and what can we get 
 
52 SCIENCE PRIMERS. 
 
 from it ? Coal contains carbon : if it burns with a 
 clear flame we know that carbonic acid gas is formed ; 
 and if it burns with a smoky flame we can get black 
 soot, or carbon, from the coal. The coal contains, 
 however, other things besides carbon ; it contains 
 hydrogen as well. 
 
 38. Manufacture of Coal Gas. 
 
 EXPERIMENT 34. Powder a little coal and put it 
 into the bowl of a common long tobacco-pipe ; then 
 cover the top well with a stopper of moist clay (made 
 by mixing the powdered Stourb ridge clay with a little 
 water), and let the clay dry well. After it is well 
 dried, fasten the bowl of the pipe over the flame of 
 the gas-lamp. Soon a yellow smoke will come out at 
 the end of the pipe, and this yellow smoke will burn 
 with a bright flame when a light is brought to it. This 
 smoke is coal gas, but not purified like that which 
 
 Fig. 27. 
 
 we burn in our houses. Now push the end of the 
 pipe under water; you will see that bubbles of gas 
 come off, and if you place a test-tube full of water 
 with mouth downwards over the end of the pipe, the 
 
EARTH!] CHEMISTRY. 53 
 
 bubbles of coal gas will collect, and the tube may be 
 filled with gas, which will burn when you bring a light 
 to it. This coal gas contains carbon, for you may 
 get black soot from the flame of this gas when it is 
 burning, and because carbonic acid gas is formed 
 when the gas burns, as you may show with the lime- 
 water test : it also contains hydrogen, because, if you 
 hold a dry clean glass over a flame of coal gas, drops 
 of water will collect in the inside of the glass, showing 
 that the hydrogen of the coal gas has united with the 
 oxygen of the air to form water. 
 
 You have already learnt in the Introductory Primer 
 that coal gas is colourless and invisible, that it is 
 lighter than air, and that it is inflammable. Try to 
 think what experiments you can make with coal gas 
 to prove that this is the case. 
 
 All the coal gas which we use in our towns is made 
 in this way. Instead of tobacco-pipes, large ovens 
 made of brick or sometimes of iron are used and 
 these are called retorts ; instead of a pinch of coal, 
 many thousands of tons are made into gas ; instead 
 of a test-tube to collect the gas in, enormous gas- 
 holders made of iron-plate are used. 
 
 Now when the pipe is cold take off the clay, and 
 you will find some grey coke in the bowl ; this is 
 some of the pure carbon of the coal which is left 
 behind. Some of the carbon and all the hydrogen 
 of the coal has gone off as gas, or water, or tar, 
 for all these things are formed when coal is distilled 
 or heated as we have done. 
 
 There are many different kinds of coal, some of 
 which are not so good for gas-making as others, be- 
 cause some contain more carbon and less hydrogen 
 
54 SCIENCE PRIMERS. [ xiv. 
 
 than others, and therefore give kss gas and more 
 coke. 
 
 Besides coal gas we can get many other things from 
 coal. Thus we get the tar which is used to tar ropes, 
 sails, and fishermen's nets, to prevent them from rotting 
 in the salt water ; also pitch, which is used for as- 
 phalting pavements ; and, what is more wonderful, 
 we get from coal those splendid bright violet and 
 crimson colours, mauve and magenta, which you see 
 in the shop windows. How these colours can be got 
 from coal you cannot at present understand. 
 
 39. Uses of Coal. 
 
 Of the importance of coal it is difficult to give you 
 an idea in a few words. Try to think what England 
 would be without coal ! Almost all our manufactures 
 depend on our having cheap coal. Our comfort, or 
 rather our very existence, in the winter, depends on 
 our supply of this essential article. Where should we 
 be without railroads or steamboats? and yet these 
 both depend on our having coal. Coal is not found 
 everywhere in Great Britain. In those districts where 
 coal is found great industries have sprung up ; where 
 no coal is found the country is purely agricultural. 
 Thus in Lancashire we have coal and the cotton 
 trade ; in South Wales we have coal and the iron 
 trade; in Yorkshire we have coal and the woollen 
 trade ; but in Kent, and Essex, and Sussex, where 
 there is no coal, we do not find great centres of manu- 
 facture ; in these counties the people chiefly live by 
 farming. 
 
EARTH.] 
 
 CHEMISTRY. 
 
 EARTH. XV. 
 
 40. Coal Gas and Flame* 
 
 Let us now try a few experiments with coal gas 
 and see what we can learn about Flame. 
 
 EXPERIMENT 35. Why does the flame of hydrogen 
 (see Experiment 18) give off so little light, whilst the 
 flame oi coal gas gives off so much ? A simple ex- 
 periment with the Bunsen gas-burner will soon 
 explain this. If you stop up the holes at the bottom 
 of the lamp with your ringers, you will see that the 
 gas burns with a luminous flame; if you remove 
 your ringers, the flame loses its brightness and burns 
 blue. This is because carbon or soot 
 in a finely divided state is present in the 
 bright flame, but not present in the blue 
 flame. Hold a piece of white paper for 
 a few seconds over the bright flame, it 
 will be smoked ; but when held over the 
 blue flame there will be no smoke. In 
 the bright flame the combustion (or 
 burning) is incomplete,and solid particles 
 of carbon are separated out in the flame 
 and cause the flame to be bright ; in the 
 blue flame all the carbon is at once 
 burnt by the air which rushes through the round holes 
 and mixes with the coal gas before the mixture burns 
 at the top of the lamp. 
 
 EXPERIMENT 36. The different parts of a common 
 candle flame are well worth study and teach us much. 
 If you carefully look at the flame of a candle burning 
 steadily you will see that the flame consists of three 
 parts : 
 
SCIENCE PRIMERS. 
 
 [xv. 
 
 1. A blue scarcely visible outer zone, or mantle, 
 where the combustion is complete. 
 
 2. An inner bright or luminous zone, where soot is 
 separated out and the light is given off, and where the 
 combustion is incomplete. 
 
 3. A black cone in the inside, 
 consisting of the unburnt gas given 
 oSf by the wick. 
 
 The candle is in fact a. small gas- 
 works ; the wax or tallow is the ma- 
 terial which is distilled, the wick is 
 the retort where the distillation goes 
 on, and higher up and outside of this 
 the gas burns. 
 
 You can show that this black cone 
 consists of unburnt gas by taking a 
 small bent piece of glass tube and 
 putting the end into the black centre 
 of the flame ; the unburnt gases will pass up the tube 
 and may be lighted at the other end (see fig. 29). 
 
 41. Explosions in Coal Pits how caused 
 and how prevented. 
 
 You have all heard of the dreadful accidents which 
 sometimes happen in coal pits from explosions of fire- 
 damp, or a kind of coal gas, which, when it is mixed 
 with air, explodes or burns suddenly and kills the 
 miners. As the pits are dark the miners are obliged 
 to take lights with them to see to do their work and 
 get the coal, and when the gas or fire-damp rushes out 
 from the coal it mixes with the air, and the mixture 
 takes fire at the miners' candles, and it explodes and 
 does great damage. These horrible explosions can be 
 
 Fig 29. 
 
IARTH.] CHEMISTRY. 
 
 prevented by using Davy's Safety- Lamp. Let 
 us try if we can learn why this is. 
 
 EXPERIMENT 37. Take a piece of common iron 
 wire gauze, and bring it close over a gas-burner or the 
 Bunsen's lamp ; then turn on the gas, and light it on 
 the top of the gauze ; next remove the gauze several 
 inches above the burner ; the flame does not pass 
 through the wire gauze (Fig. 30). Why is this ? Be- 
 cause the metallic gauze so quickly takes 
 away the heat that the gas will no longer burn. 
 
 Suppose now we were to place such wire gauze quite 
 round a flame ; we should see the flame burning inside 
 the gauze ; it would give light, and it would get air to 
 burn through the meshes of the gauze ; but no flame 
 can pass through the gauze, and therefore if we 
 take such a safety-lamp, like the one drawn in Fig. 
 30, into a mine where there is fire-damp, the gas in the 
 mine cannot become lighted, because the flame cannot 
 pass through the wire gauze. This is the reason why 
 Davy's safety-lamp has saved so many lives, 
 E 2 
 
58 SCIENCE PRIMERS. [ xvi. 
 
 In fig. 30 you have a picture of the lamp ; you see 
 the flame burning inside the wire-gauze case, which 
 is screwed tight on to the brass oil-can at the bottom. 
 You learn how such a simple scientific principle as 
 the one I have just explained may be made the means 
 of saving thousands of lives, and render it safe to get 
 the coal which we need so much. 
 
 ELEMENTS AND COMPOUNDS. XVI. 
 
 42. The preceding experiments have taught us much 
 respecting some of the common kinds of earthy sub- 
 stances which we meet with. These are, however, 
 only a very small portion of the experiments which 
 chemists have made, and by which they have learnt 
 all that they know about the composition of the earth. 
 It is only by examining and experimenting that we 
 can learn anything in chemistry, and it is the business 
 of the chemist to try and test the properties of every 
 kind of substance which comes within his reach, to see 
 what it is made of, and what kind of substances it 
 contains. 
 
 In this way testing all bodies, whether they come 
 out of the air or out of the sea'or out of the inside of 
 the earth, or whether they are of mineral or of vege- 
 table or of animal origin, chemists have found that 
 all substances they meet with may be divided into two 
 great classes : 
 
 1. Simple bodies, or Elements ; substances 
 out of which nothing different can be got. 
 
 2. Compound bodies substances out of 
 which two or more different things can be got. 
 
 43. Let us look for some examples of simple and 
 
ELEMENTS & COMPOUNDS. ] CHEMISTR K 59 
 
 compound bodies ; first among the gases. Oxygen 
 gas is a simple body, or an element ; nothing else can 
 be got from oxygen. Hydrogen gas is also an ele- 
 ment for the same reason. But coal gas is not an 
 element, it is a compound, for we can split it up into 
 or get out of it two quite different substances, viz. 
 carbon or soot, and hydrogen gas. Carbonic acid gas, 
 too, we have learnt is a compound of carbon and oxy- 
 gen gas. So for liquids ; the metal mercury is an 
 element ; we cannot get out of it anything different 
 but the bright shining liquid metal : water, however, 
 is a compound, for, as we have seen, we can in many 
 ways prove that water contains the two elements 
 oxygen and hydrogen. In like manner, many solids 
 are elements or simple bodies, whilst many are com- 
 pounds : thus, red oxide of mercury is a compound, 
 for we can get from it metallic mercury and oxygen 
 gas ; chalk is a compound, for we can get from it 
 carbonic acid and lime ; common salt is a com- 
 pound, for we can get the yellow gas chlorine from it, 
 and likewise a metal ; so is " bluestone," because we 
 can get bright red copper and also sulphuric acid 
 from it. But sulphur, carbon, phosphorus, 
 copper, iron, silver, gold, and many others, are 
 all solid elements or simple bodies, for out of these 
 chemists have not been able to get anything different. 
 Nor have chemists ever been able to change any one 
 of these elements into any other one. 
 
 44. By continually making experiments on the 
 substances they see around them, chemists have 
 found that everything which exists above, or on, or 
 below the earth's surface, is made up of one or more 
 of sixty-three elementary bodies. Some of 
 
DO SCIENCE PRIMERS. [ xvi. 
 
 these are met with as gases, as oxygen ; some as 
 liquids, like mercury ; most, however, occur as solids, 
 like sulphur and iron. Many of these elements are 
 very common, and are found in enormous quantities, 
 both as elements, or in the free state, and also 
 combined ; thus, for instance, oxygen is contained 
 in the free state as a gas in the air, but combined 
 .with hydrogen to form water, and with the other 
 elements to form oxides. Many of the elements are 
 however found very seldom, and only in very few 
 places, and these.are generally not used in the arts or 
 manufactures. Still we have no right to consider 
 these elements unimportant and useless, although we 
 cannot in these lessons do more than speak of those 
 which are found in larger quantity. 
 
 For the sake of simplicity we divide the elements 
 themselves into two classes : those which are rnetals, 
 such as iron, copper, gold, silver ; and those 
 which are non-metals, sue 1 ! as oxygen, sulphur, 
 carbon. The difference in appearance between 
 things which are metals and things which are not 
 metals will be seen at once by looking at specimens 
 of the above elements. 
 
 There are only fifteen non-metals, whilst we know 
 altogether of forty-e^ght metals. 
 
 Here, is a table containing the names of the most 
 important elements : 
 
 Non-Metallic Elements* . Metallic Elements, 
 
 Oxygen. Iron. 
 
 Hydrogen. Aluminium. 
 
 Nitrogen. Calcium. 
 
 Carbon. Magnesium, 
 
 Chlorine. Sodium. 
 
NON-METALS.] CIIEMISTR Y. 6l 
 
 Non-Metallic Elements* Metallic Elements. 
 
 Sulphur. Potassium, 
 
 Phosphorus* Copper. 
 
 Silicon* Zinc. 
 
 Tin. 
 
 Lead. 
 
 Mercury. 
 
 Silver. 
 
 Gold. 
 
 These sixty-three elements all possess different pro- 
 perties, by means of which they can be recognized and 
 separated one from the other. Some, however, resemble 
 one another more than others ; thus, tin and lead are 
 more like each other in their properties than are oxygen 
 and hydrogen. Now when we examine the way in which 
 these elements unite together to form compounds, we 
 find that the most unlike elements combine 
 together. Thus, tin and lead do not form any com 
 pound differing in essential properties from either of 
 the two metals ; but, oxygen and hydrogen being 
 unlike, unite to form water, a body quite different 
 from either of the component elements. It is true 
 throughout that chemical combination takes 
 place most readily between those bodies 
 which least resemble one another. 
 
 NON-METALLIC ELEMENTS. XVII. 
 
 45. Now let us learn about the properties of these 
 commoner elements in the order in which they are 
 written in the table. 
 
62 SCIENCE PRIMERS. [ xvn. 
 
 Oxygen is a colourless, invisible, tasteless gas. 
 It exists in the free state in the air, mixed with 
 about four times its bulk of nitrogen gas. It com- 
 bines with all the elements (with one exception) to 
 form oxides. When oxygen combines with other 
 elements heat is evolved, and often light, and the 
 substance is said to burn. Oxygen is contained in 
 all rocks, sand, soil, and minerals, More than half 
 the weight of our whole earth consists of oxygen. 
 Oxygen is necessary for the life of animals ; they 
 breathe it, and use it to oxidize and purify the blood 
 and to keep up the animal heat. 
 
 We can get pure oxygen gas by heating many com- 
 pounds which contain it; thus by heating red oxide 
 of mercury in a tube, or by heating chlorate of potash 
 in a flask, we can test for oxygen by plunging a red- 
 hot splinter of wood into the gas : if oxygen be present, 
 the splinter will burst into flame. 
 
 To make oxygen gas on rather a larger scale than 
 is described in Experiment 30, we may take half an 
 ounce of powdered chlorate of potash, and mix it with 
 enough black oxide of manganese to make it black. 
 Then place the powder in a flask furnished with a 
 perforated cork and long bent tube, placing the flask 
 on a ring of the retort stand so that fou can gently 
 heat the mixture, and then collect the gas as it comes 
 over in bottles placed in the pneumatic trough, as 
 shown in fig. 22. 
 
 You may show 
 
 i> That a taper stuck on a wire having a red-hot 
 wick will be rekindled when plunged into the 
 bottle of oxygen, and then prove that carbonic 
 acid is formed by pouring in lime-water. 
 
NON-METALS. ] 'CHEMTSTR Y. 63 
 
 2. That a piece of red-hot charcoal burns brightly 
 
 in oxygen, likewise forming carbonic acid. 
 
 3. That a small bit of sulphur melted and allowed 
 
 to burn on the spoon burns with a brilliant 
 blue flame when plunged into oxygen. 
 
 4. That a very small bit of dry phosphorus put 
 
 in the spoon and lighted burns with dazzling 
 splendour in oxygen gas. 
 
 You may also show that the colourless gas formed 
 by burning the sulphur, and the white fumes formed 
 by burning the phosphorus, are both acid substances, 
 because if you pour a little blue litmus solution into 
 each of the bottles used, you will see that the blue 
 solution will turn red. 
 
 46. Hydrogen is also a colourless, invisible, taste- 
 less gas. It does not occur in the free state in the air, 
 but exists combined with oxygen to form water. By 
 several ways we can get the hydrogen from water (Ex- 
 periments 12 and 14), and also show that when hydro- 
 gen burns in the air pure water is formed. Hydrogen 
 combines with many other elements with carbon it 
 forms marsh-gas (or fire-damp), a substance found in 
 coal gas : hydrogen also is found in all acids ; thus, in 
 nitric acid, sulphuric acid, hydrochloric acid. Hydro- 
 gen gas is the lightest substance we know of, being 
 14^ times lighter than air, and it has, therefore, been 
 used for rilling balloons. 
 
 47. Nitrogen is likewise a colourless, invisible, 
 tasteless gas. It exists in the free state in the air. We 
 
6 4 
 
 SCIENCE PRIMERS. 
 
 can separate the oxygen in the air from the nitrogen 
 by "burning a piece of phosphorus (Experiment 6). 
 Nitrogen also is found in many compounds, in nitric 
 acid and nitre or saltpetre, and in ammonia or 
 spirits of hartshorn. It is also found combined 
 in the flesh of animals. Nitrogen does not unite readily 
 with bodies, and is a very inert substance ; it does not 
 burn itself, nor support combustion nor animal life. 
 It is, however, not poisonous, and animals die when 
 placed in nitrogen simply from want of oxygen, that 
 is, they are suffocated. 
 
 Nitrogen can be made to combine with hydrogen 
 to form ammonia, and with hydrogen and oxygen 
 to form nitric acid. 
 
 EXPERIMENT 38. Nitric acid can be easily ob- 
 tained by putting half an ounce of powdered nitre into 
 a retort and pouring on it half an ounce of sulphuric 
 
 Fig. 31. 
 
 acid. Then put a lamp under the retort, and a flask, 
 kept cool in a basin of water, to catch the acid which 
 comes over. Soon a yellow liquid will collect in the 
 
NON-METALS.] CHEMISTRY. 65 
 
 flask. This is nitric acid. It is very sour and cor- 
 rosive ; strong nitric acid will make yellow stains and 
 wounds if it touches the skin. It will turn blue 
 litmus solution red, because it is an acid ; and if 
 mixed with an alkali, like caustic potash (which has 
 the power of turning red litmus blue) it loses its 
 acid properties. Take a little caustic potash 
 solution and add litmus to it, then gently pour some 
 nitric acid in ; the blue litmus will soon turn red, 
 because the acid neutralizes the alkali. If the 
 water be now boiled away in a small porcelain basin, 
 a white salt will be left, which is nitre or saltpetre, 
 made by the chemical combination of nitric acid and 
 potash, the substance which we originally used to 
 make the nitric acid ; and if after heating it strongly 
 you dissolve a little of this salt in water, the solution 
 will neither turn red litmus blue, nor blue litmus red : 
 this shows that the salt is neutral. 
 
 Acids, Alkalies, and Salts. 
 From this experiment you learn 
 
 1. That a substance is called an acid when it is 
 
 sour and corrosive, and when it turns blue 
 litmus solution red. 
 
 2. That an alkali is a substance which turns red 
 
 litmus solution blue, and has the power cf 
 neutralizing acids. 
 
 3. That a salt Is the substance formed when an 
 
 acid combines with an alkali and forms a 
 
 neutral body. 
 
 Here again we see that unlike substances combine 
 chemically with each other. No two bodies can be 
 more unlike one another than nitric acid and potash, 
 
66 SCIENCE PRIMERS. [ xvn. 
 
 and these two unite to produce the well-known salt- 
 petre, totally differing in its properties from either of 
 the two things of which it is made up. 
 
 48. Carbon. This is a solid element ; we know it 
 in the free state as charcoal, coke or coal. Carbon also 
 exists free as two other quite different sorts of bodies, 
 viz. : the colourless hard gem called diamond, and 
 the soft body, used for making pencils, called black- 
 lead or graphite. How can we show that three 
 such different substances as these are chemically 
 the same element ? Suppose we were to burn a bit 
 of charcoal in oxygen gas, we get carbonic acid gas 
 formed ; if we burn a bit of graphite, we also get 
 carbonic acid gas formed ; and if, instead, we take a 
 bit of diamond and burn it, we also find that car- 
 bonic acid gas is formed. From this we conclude 
 that each of these three things charcoal, graphite, 
 and diamond contains carbon. But do they contain 
 anything else besides carbon ? No, because if we take 
 the same weight of each 12 grains of charcoal, 12 
 grains of graphite, and 12 grains of diamond and 
 burn them separately, we find that we get exactly the 
 same weight of carbonic acid, viz. 44 grains, in 
 each case. So that, although they look to be such 
 very different substances the precious gem and com- 
 mon coal yet they are identically the same chemical 
 element, carbon. 
 
 Carbon forms a necessary part of all vegetables and 
 animals. In a piece of wood charcoal you can see 
 the form and texture of the original wood ; if a piece 
 of flesh is charred, you soon see the black carbon ; if, 
 however, the wood or the flesh is completely burnt, 
 
NON-METALS.] CHEMISTRY. 67 
 
 then the carbon all disappears as carbonic acid gas, 
 and only a small quantity of a white ash is left. 
 
 EXPERIMENT 39. To show that vegetable matter 
 contains carbon, take a few lumps of white sugar in a 
 glass, and pour on these a little hot water to form a 
 thick syrup. Then pour into the syrup some strong 
 sulphuric acid. You will soon see that the syrup gets 
 dark coloured, and then froths up, and all the white 
 sugar is converted into black charcoal. This is be- 
 cause the sugar contains carbon, which has thus been 
 made visible. 
 
 What would be the result if this single element, 
 carbon, had not existed on the earth? Why, then 
 no animal or vegetable being could have existed. So 
 great a change can the absence of a single element 
 . produce. 
 
 Carbon, however, exists combined not only in the 
 bodies of plants and animals, but also in the air as 
 carbonic acid gas ; and from what has been learnt 
 (from Experiment 9), you will understand that this 
 carbonic acid in the air serves as food for all plants. 
 Carbon also exists in many rocks as carbonic acid 
 in chalk rocks, limestone rocks, and marble. 
 
 nON-METALLIC ELEMENTS. XVIII. 
 
 49. Chlorine is an element very different in its 
 properties from any of those we have mentioned. It 
 is a yellowish gas, possessing a very strong smell, and 
 if breathed acts as a poison. Chlorine is not found in 
 the free state in nature, but we can get it from a useful 
 compound which contains it viz. common salt. 
 
63 SCIENCE PRIMERS. [ xvur.- 
 
 This body, which we use to flavour our food, and which 
 gives the saltness to sea-water, is made up of chlorine 
 and metal sodium, and common salt is therefore called 
 chloride of sodium, or sodium chloride. 
 
 EXPERIMENT 40. We can get chlorine from com- 
 mon salt by mixing a little salt with a little powdered 
 black manganese oxide, putting the mixture into a 
 flask, and pouring on to the mixture some sulphuric 
 acid diluted with the same quantity of water. By 
 adapting a bent tube as shown in fig. 32, and by 
 slightly heating the flask, a heavy yellow very strongly 
 smelling gas is given off, and may be collected in the 
 dry bottle. 
 
 - Fig. 32 . 
 
 This is the chlorine which was combined with the 
 metal sodium in the rock salt : care must be taken not 
 to breathe it, as it causes coughing and inflammation oi 
 the throat. This gas combines at once with metals to 
 form chlorides ; if we throw a little powdered me- 
 tallic antimony into the bottle containing the chlorine 
 gas, we see sparks of fire, and a white cloud of anti- 
 mony chloride is formed. Thus we learn that sub- 
 
KON-M^TALS. ] C1IEMISTR V. 69 
 
 stances can burn not only in oxygen, but also in 
 chlorine gas, and that heat is given out whenever 
 chemical combination occurs. 
 
 Chlorine also has a strong bleaching power, and 
 it is largely used for taking the colour out of cotton 
 and linen cloth. This you can easily experiment by 
 throwing in a bit of wet coloured cotton rag into a 
 bottle of the yellow gas after a few minutes' shaking 
 the rag will have lost its colour. 
 
 Bleaching powder, which is sold in the shops 
 for this purpose, contains chlorine, as you may see by 
 taking a little of this white powder at the bottom of a 
 bottle, and pouring on to it a little dilute sulphuric 
 acid, when yellow chlorine gas will at once be seen 
 above the white powder, and this gas will be found 
 to bleach. 
 
 EXPERIMENT 41. If we mix a little bleaching 
 powder with water, and put a piece of coloured 
 cotton rag into it, the colour will not be discharged ; 
 but if we then dip the rag into water containing 
 (or rendered sour with) a little sulphuric acid, the dye 
 will begin to disappear , and if we repeat this once or 
 twice, the rag will become white. This is the plan 
 used by bleachers. The acid in the " souring " sets 
 free the chlorine from the bleaching liquor, and this 
 takes away the colour by destroying it. 
 
 50. Sulphur or brimstone is a yellow solid ele- 
 ment ; we know it in fine yellow powder, flour of 
 sulphur, and in sticks or rolls. If we heat a little bit 
 of sulphur in a spoon over a flame, it. first melts, 
 
70 SCIENCE PRIMERS, [ 
 
 then boils, and then takes fire and burns away en- 
 tirely, giving off a pale blue flame, having the well- 
 known smell of burning sulphur. 
 
 In this burning it is uniting with the oxygen of the 
 air to form an oxide of sulphur, which is a colourless 
 gas. Sulphur is used for putting on the ends of luci-fer 
 matches, because it easily takes fire and lights the 
 wood. It is also used for making gunpowder, which 
 is a mixture of sulphur, charcoal, and nitre. 
 
 Free sulphur is found in the earth in volcanic dis- 
 tricts, and comes chiefly from the island of Sicily. 
 Sulphur is found also in combination chiefly with 
 metals, forming sulphides of the metals. These 
 sulphides are generally the ores of the metals, that is, 
 the substances from which the metals are obtained. 
 Thus the ore of lead, a mineral called galena, is sul- 
 phide of lead. Sulphur also combines with oxygen 
 and hydrogen to form sulphuric acid, a very im- 
 portant chemical compound. This acid is a heavy 
 oily liquid, and is commonly called oil of vitriol, 
 and it is made in enormous quantities (many thou- 
 sand tons every week), and used for a great number 
 of processes for making alkali, for soap-making, and 
 dyeing, and calico printing and bleaching, and for the 
 preparation of almost every other acid. Sulphuric 
 acid unites with metals to form sulphates thus we 
 have sodium sulphate, or Glauber salts ; iron 
 sulphate, or green vitriol ; copper sulphate, or 
 blue vitriol ; and many others. 
 
 51. Phosphorus is an element which does not 
 occur in the free state in nature, but is contained in 
 
f?> A *- 
 
 ,r V or THf 
 
 NON-METALS.] CHEMISTRY. . 71 
 
 the bones of animals in combination with oxygen, 
 and the metal calcium forming calcium phosphate. 
 When a bone is burnt, a white porous mass is left 
 called bone-ash, and from this phosphorus can be 
 prepared. 
 
 Phosphorus, like carbon, exists in two different 
 forms : one is known as yellow or common phospho- 
 rus; the other as red phosphorus. These two sorts 
 of phosphorus differ very much in their properties. 
 
 EXPERIMENT 42. Take a small iron tray, placed 
 on a tripod, and carefully cut off a bit of yellow phos- 
 phorus as large as a quarter of a pea ; this must be 
 done under water, as the phosphorus is a very inflam- 
 mable and dangerous substance, because it takes fire 
 of itself in the air, and produces 
 serious burns if it takes fire whilst 
 in the fingers. Then quickly dry 
 the bit of phosphorus on a cloth 
 or blotting-paper, and put the 
 dried bit with a pair of tongs or 
 a knife-blade on to the iron tray. 
 Next take a bit of red phosphorus 
 (or the powder) of the same size, 
 and put it also on the iron tray. You will see that 
 the red phosphorus is not kept, like the yellow, under 
 water. The reason of this you will soon understand. 
 Now put the flame of a lamp under the tray ; in a few 
 instants the yellow phosphorus (, fig. 33) will take fire 
 and burn with a bright flame, and give off dense white 
 fumes. The bit of red phosphorus (a), however, does 
 not take fire, and we have to continue the heat for 
 some time before this red substance catches fire : this 
 it does, however, at length, and then burns exactly 
 
 II. F 
 
72 SCIENCE PRIMERS. [ xvm. 
 
 like the yellow phosphorus. Thus we see that yellow 
 phosphorus is very inflammable, and must be kept 
 under water to prevent it taking fire with the oxygen 
 of the air, whilst the red variety does not burn at all 
 easily, and can therefore be kept in the air. 
 
 EXPERIMENT 43. Yellow phosphorus takes fire 
 by nibbing it. Take another very small bit, and 
 wrap it in a piece of blotting-paper ; then rub it with 
 your boot on the floor, or with a hammer on a piece 
 of wood. You will see that the rubbing causes the 
 phosphorus to take fire and burn. This is the reason 
 that common lucifer matches light when they are 
 rubbed. The brown or red tip of the match contains 
 phosphorus ; when you rub or strike the match on 
 a rough surface, the varnish which covers the phos- 
 phorus paste is scratched off, and the phosphorus 
 takes fire and the match burns. 
 
 Lately safety lucifer matches have been made, 
 which light only on the box. How is this ? A 
 little thought and examination will soon teach us. 
 Take one of these safety matches, and try to light it 
 on the sandpaper outside a common match-box, it 
 will not light ; but rub it on the brown or reddish brown 
 paper on the outside of the safety match-box, and it 
 takes fire at once. The explanation is easy : the tip 
 of the safety match contains no phosphorus, but only 
 some substance which will easily cause phosphorus 
 to burn, and therefore it cannot light by rubbing on 
 any rough surface ; the paper on the box is covered 
 with some powdered red (or non-inflammable) phos- 
 phorus ; when you strike the safety match on -this 
 red paper, a little of the red phosphorus sticks to the 
 end, and then takes fire with the mixture on the tip. 
 
METALS.] CHEMISTRY. 73 
 
 52. Silicon is an element which (like phosphorus) 
 we do not meet with in the free state in nature, although 
 it is contained in enormous quantities in combination 
 with oxygen. Silicon oxide, or Silica, is known as 
 quartz or rock crystal, and it is found in almost 
 all rocks. Sand, sandstone, and flint are also more or 
 less pure silica. Silica forms, with metals, compounds 
 called Silicates. Clay is a silicate, so therefore 
 are bricks, pottery and china, which are made from 
 clay. Glass is also a silicate ; it is made by heating 
 together in a hot fire or furnace a mixture of white 
 sand (silica), lime, and soda, or of sand, oxide of 
 lead, and potash. 
 
 The first mixture forms what we know as plate- 
 glass or window-glass ; the second produces flint- 
 glass. Silicon itself is a black crystalline substance, 
 and is got by taking away the oxygen from silica. 
 
 All the rocks and stones of which the solid earth 
 is made, contain either silicon or some metallic 
 elements, or both combined with oxygen. So you 
 see that the earth is made up of burnt or oxidized 
 substances. Now let us learn a little about the 
 chief metals which the earth contains. 
 
 METALS. XIX. 
 
 53. Iron. We may well begin an account of the 
 more important metals with iron, because of all of 
 them iron is the most useful to man. Without iron we 
 should almost be savages ; we could have no railroads, 
 nor engines nor machines ; no gas-pipes or water pipes, 
 no tools or knives. There was once a time when men 
 
 ' F 2 
 
74 SCIENCE PRIMERS. [ xix. 
 
 had no iron, because this most useful substance is not 
 fouiM as a metal, but as an earthy ore, from which 
 the metal can only be got with difficulty. In those, 
 old days men used tools made of bronze or copper, 
 and in still earlier times they only used stone hatchets 
 and knives. One most useful ore of iron is red iron 
 oxide, called haematite iron ore. By heating this with 
 charcoal the oxygen is got rid of, and the metal iron 
 remains, and this can be hammered into bar-iron, 
 from which we can make horse-shoes or spades; and 
 it can be flattened by rolling into flat plates for 
 making ships or boilers. This is called wrought 
 iron, because it can be hammered and wrought, or 
 made, when it is red-hot, into anything which is 
 wanted. This is the kind of iron which we see the 
 blacksmith uses to make nails or horse-shoes, or the 
 tyres of wheels ; and it is very useful, because when 
 hot it can be welded, that is, two pieces of hot iron 
 when hammered together stick firmly together so that 
 they cannot be separated. But there is another kind 
 of iron also very useful; this is called cast-iron, 
 because it can be melted, and poured when melted 
 into moulds, and castings then got. Cast iron is used 
 for making gas and water pipes, for lamp-posts and 
 ailings, and large wheels, and the heavy stands for 
 machines, and a great number of other things. Cast- 
 iron is made from iron ore and coal, and lime- 
 stone, by putting these into large high furnaces, 
 called blast furnaces, because the air is blown in 
 to burn the coal and melt the iron by a powerful 
 blast. 
 
 Cast-iron cannot be hammered when hot, like 
 wrought iron, into bars or rolled into plates ; it is 
 
METALS. ] CHEMISTR Y. 75 
 
 brittle, or breaks, like glass, into pieces under the 
 hammer. Cast-iron is not pure iron, but contains 
 carbon, which it gets from the coal ; we can burn 
 the carbon away (by a process called puddling), and 
 we thus can get wrought-iron from cast-iron. A third 
 kind of iron is called steel ; this is used for making 
 razors, knives and tools, because it is both hard and 
 tough, and can be ground so as to have a sharp edge. 
 Steel also contains a little carbon, and can be made 
 either from wrought or from cast iron. 
 
 If we burn iron in the air (Experiment 31) or in 
 oxygen, we get oxide of iron. The same thing is 
 formed when any piece of bright iron is left exposed 
 to air and wet ; it becomes rusty, and at last will all 
 change to rust. Iron-mould on linen is also oxide 
 of iron, or rust. 
 
 EXPERIMENT 44. If you pour a little dilute sul- 
 phuric acid on a few iron filings in a test-tube, gas 
 
 will at first be slowly given off; if the test-tube be 
 warmed, the gas will escape more quickly, and it may 
 be lighted at the mouth of the glass. This gas is 
 
76 SCIENCE PRIMERS. '[ xix. 
 
 hydrogen ; the iron dissolves in the acid, forming a 
 salt, called sulphate of iron or green vitriol, and the 
 hydrogen of the sulphuric acid is given off. If you 
 fill the test-tube with water, and then filter the liquor 
 through a paper filter, you will get a nearly colourless 
 solution ; and if this be evaporated or boiled down 
 (fig. 35), crystals of green vitriol will be formed on 
 cooling. 
 
 We can tell that iron is present if we add a little 
 of this solution mixed with a few drops of nitric 
 acid to a pint of water, by pouring in a few drops 
 of the bottle labelled " potassium ferro-cyanide," or 
 yellow prussiate of potash, when a dark blue colour 
 (of Prussian blue) will be formed. 
 
 54. Aluminium. We take this metal next be- 
 cause it is the metal got from clay, and therefore is 
 contained in large quantities in many rocks. No one 
 would suppose that a bright, silver, white metal can be 
 got out of common clay, and yet chemists can do so. 
 It is a pity that it is not easy to get rid of the oxygen 
 in the clay, for then we might use the bright metal 
 aluminium for very many purposes. It costs too 
 much to make the metal, although clay is so cheap 
 
M ETALS. ] CHE-MISTR V. 77 
 
 and common. When this bright metal is heated in 
 the air, it burns and forms an oxide called alumina, 
 the earth of clay. 
 
 The white crystals of alum contain this metal. 
 
 55. Calcium too is a metal which it is very difficult 
 to get in the pure state, although its compounds are 
 very common. Quicklime is calcium oxide ; chalk 
 and marble and limestone and coral are all calcium 
 carbonate ; gypsum is calcium sulphate ; and bone 
 earth is calcium phosphate. So you see that there is 
 plenty of this metal in the earth. 
 
 EXPERIMENT 45. In making carbonic acid from 
 chalk and hydrochloric acid (Experiment 29), the 
 liquid remaining in the bottle is a solution. of calcium 
 chloride. If you filter the liquid and boil down the 
 clear solution to dryness, you will find a white dry 
 powder left. This is a salt called calcium chloride. 
 We used it in Experiment 20 for drying the hydrogen 
 and collecting the water, as it takes up moisture with 
 great ease. Let a little of the dry powder remain 
 exposed to the air for a few hours ; you will then 
 find that it has become liquid, because it has 
 absorbed, or taken up, the moisture which is always 
 present in the air. 
 
 If you add some of the clear solution labelled 
 u sodium carbonate," to a little bit of the dry powder 
 of calcium chloride, which you have dissolved in some 
 vvater in a test-tube, you will see that the two clear 
 liquids at once become milky or turbid. This is 
 because calcium carbonate, or chalk, is produced, and 
 this chalk is insoluble, or does not dissolve in water, 
 
SCIENCE PRIMERS. [ xix. 
 
 as the calcium chloride d<5es, and it is therefore 
 thrown down, or precipitated. This represents what 
 happens : 
 We take 
 
 Calcium chloride ( -i j Sodium carbonate ; 
 
 (soluble in water) \ \ (soluble in water) 
 
 and we get, on mixing the solutions 
 
 Calcium carbonate, or chalk ) j ( Sodium chloride, or common 
 (insoluble in water) j ( salt (soluble in water). 
 
 This shows you that some salts of the same metal 
 may be not soluble in water (like chalk), whilst others 
 (like calcium chloride) readily dissolve in water. But 
 you must take care not to fancy that any substance is 
 afterwards present which was not there before ; we 
 have here to do only with a difference of arrange- 
 ment. An exchange takes place by which the chalk 
 is formed, but the materials of the chalk were present 
 in the original substances. 
 
 56. Magnesium is a soft, silver-white metal, 
 which can be made into wire and ribbon. 
 
 EXPERIMENT 46. If you hold the end of a bit of 
 magnesium ribbon about six or eight inches long in 
 the flame, the metal will take fire, and burn with a 
 dazzling white light, and a white powder will fall on 
 the ground. This white powder is magnesia, the 
 oxide of the metal. Black as well as white fumes 
 will be seen whilst the magnesium is burning. The 
 black fume is not soot, for there is no carbon present ; 
 it consists of some of the metal, which is not burnt, 
 but is sent off as a cloud having a black colour ; the 
 
METALS. ] CHEMISTR Y. 79 
 
 white fume is the solid oxide magnesia going off in 
 fine dust. 
 
 EXPERIMENT 47. If you collect some of this white 
 powder and warm it in a test-tube, with a few drops 
 of sulphuric acid, the white powder will dissolve ; then 
 pour the clear solution into a porcelain basin, and 
 boil off the greater part of the water. On cooling, 
 some long needle-shaped crystals will be found in 
 the basin. These crystals are Magnesium Sul- 
 phate, or Epsom Salts; a compound of mag- 
 nesia and sulphuric acid. 
 
 There are many other compounds of magnesium, 
 some of which are found in minerals and rocks. The 
 metal is never found uncombined, and the process for 
 making it from magnesia is rather a costly one ; still 
 it is now used for burning, and for making fireworks 
 and signals, where a very bright light is needed. It 
 keeps bright in dry air, and might be used for many 
 purposes if it could be got cheaply. 
 
 METALS. XX. 
 
 57. Sodium is the metal which we used (Experi- 
 ment 13) for getting hydrogen from water. It is very un 
 like any metal which we see used in the arts ; not only 
 cannot we keep sodium in the air, because it at once 
 oxidizes and forms a white powder, but we must not 
 allow water to come near it, as. it at once will combine 
 with the oxygen of the water, and set free the hydrogen ; 
 but the metal must be kept under rock oil, which 
 contains no oxygen. We have seen (Experiment 13) 
 that a bit of this curious metal, thrown on to water, 
 
8o SCIENCE PRIMERS. [ xx. 
 
 swims on the surface, and hydrogen is given off; if 
 the water has been turned red with a little red acid 
 litmus, the colour will change to blue after the sodium 
 has disappeared. This is because the alkali soda 
 has been produced. 
 
 EXPERIMENT 48. Sodium is a very useful metal 
 to the chemist, for he can by using it get the two 
 preceding metals, magnesium and aluminium. Sodium, 
 as you may be sure, does not occur in the free state in 
 nature ; it is made by taking away the oxygen from 
 soda (the oxide of sodium). If you heat a small bit 
 of sodium in a spoon over the flame of the lamp, it 
 will first melt, and then take fire and burn with a 
 bright yellow-coloured flame; white fumes of the 
 oxide (soda) will be given off. 
 
 Sodium is the metal of the soda salts, a great many 
 of which are very useful and common substances. 
 
 The following is a list of a few of the most impor- 
 tant : 
 
 Common Name. | Chemical Name. What it contains. 
 
 Sea, table, or rock-salt. j Sodium chloride. Sodium and chlorine. 
 
 Glauber salts. j Sodium sulphate. Sodium and sulph. acid 
 
 Washing-soda crystals. I Sodium carbonate. Sodium and carb. acid. 
 
 Chili saltpetre. Sodium nitrate. Sodium and nitric acid. 
 
 Of these, rock-salt is found in largest quantity : it 
 is got from mines, in Cheshire and elsewhere, and 
 many hundreds of thousands of tons are used every 
 year. It can also be got from sea-water by evapora- 
 tion. From it all the other sodium salts can be got. 
 Thus, if you want to get sodium sulphate or Glauber's 
 salts, you have only to pour sulphuric acid on to 
 common salt ; a dense fume of hydrochloric acid 
 gas comes off, and sodium sulphate is lett ; what here 
 happens is this : 
 
METALS. ] CHEMISTR Y. 81 
 
 We take 
 Sodium chloride (common salt) and sulphuric acid, 
 
 We get 
 Sodium sulphate (Glauber's salts) and hydrochloric acid gas. 
 
 You may easily show that the fumes are strongly acid, 
 by holding a little bit of wet blue litmus paper in 
 the midst of the fume, when it will at once go red. 
 
 58. Potassium is the metal contained in the alkali 
 'potash, and in the potash salts. A small bit of potas- 
 sium, as large as half a pea, thrown on to water, 
 combines so violently with the oxygen, that the hydro- 
 gen at once catches fire and burns, the flame being 
 coloured violet by the alkali potash which is 
 formed. 
 
 Potash salts are found in many places in the earth, 
 and also in the ashes of plants ; and this alkali derives 
 its name because it can be got by boiling out wood 
 ashes in pots. There are many useful potash 
 oalts : soda and potash are called the alkalies. 
 
 Common Name. 
 
 Potashes. 
 
 Nitre or saltpetre. 
 
 Chlorate of potash. 
 
 Chemical Name. 
 
 Potassium carbonate. 
 Potassium nitrate. 
 Potassium chlorate. 
 
 What it contains. 
 
 Potassium and carbonic acid. 
 Potassium and nitric acid. 
 Potassium, cnlorine, & oxygen. 
 
 EXPERIMENT 49. Soap is made by boiling animal 
 or vegetable oils or fats with alkali. Soaps contain- 
 ing soda are hard soaps; potash gives soft soaps. 
 Common fat is boiled with alkali, and thus soap 
 is got. You can easily make soap by pouring half an 
 ounce of castor oil into a thin porcelain basin witii 
 
S? SCIENCE PRIMERS. [ xxi. 
 
 some hot water, "and adding some caustic soda; then 
 on boiling the liquor the oil will all disappear, and 
 soap will be formed which dissolves in the water. 
 When it has boiled for a little, throw in a handful 
 of common salt ; this will dissolve in the water, and 
 will drive out the soap, which will swim on the sur- 
 face. When cool, this soap will become a white, 
 hard solid, and may be used for washing your hands. 
 Common oils or fats are generally used ; we have 
 taken castor oil, because it is made into soap more 
 easily than ordinary fats. 
 
 We next have to speak of several metals which 
 are useful substances, some more valuable than others, 
 but all used for a variety of purposes. 
 
 METALS. XXI. 
 
 59. Copper is a reddish coloured metal, used for 
 making kettles, and pans, and boilers ; copper wire 
 is very useful, because it is both soft and tough. Me- 
 tallic copper is sometimes met with in nature; it is 
 then called native copper ; it is, however, more 
 commonly got from copper ores, of which there 
 are several kinds. The most important ore of copper 
 is the compound of copper and sulphur, which we 
 made in Experiment 5. By taking away the sulphur 
 the pure metal copper can be got. 
 
 Copper is much used to mix with other metals, and 
 yields useful alloys or mixtures of metal, such as 
 brass and bronze. When copper is heated in the 
 air, it tarnishes, and then becomes covered with 
 a black coating of oxide ; and if the heating be con- 
 
METALS.] CHEMISTRY. 83 
 
 tinned, all the copper combines with the oxygen of 
 the air, and we get copper scales or black oxide 
 of copper, which we used in Experiment 20. 
 
 EXPERIMENT 50. If you take one or two copper 
 turnings in a test-tube, and pour on to them a few- 
 drops of nitric acid, dense brownish red fumes will 
 be given off from the nitric acid, and a blue solu- 
 tion of copper nitrate will be formed. The 
 copper has combined with oxygen and with nitric 
 acid. One drop of this blue solution, poured into 
 a test-tube full of water, will still give a blue colour 
 when we add ammonia, and thus we can easily test 
 for the salts of copper. Blue stone (Experiment 32), 
 or copper sulphate, is a compound of copper and 
 sulphuric acid. You may try the ammonia test with 
 a drop or two of a solution of this substance, and 
 show that it gives the same deep blue colour as the 
 copper nitrate did. 
 
 60. Zinc is a useful white metal. It is used for 
 covering iron plate, which is then said to be galva- 
 nized iron. This covering of zinc prevents the iron 
 from rusting in damp air. The chief ( re of the metal 
 is zinc sulphide, a compound of zinc and sulphur, 
 called Blende. Zinc is also used to mix with other 
 metals to form useful alloys ; thus brass is an alloy of 
 zinc and copper, and it is, therefore, not a simple or 
 elementary body. 
 
 EXPERIMENT 51. If we dissolve zinc in dilute 
 sulphuric acid (Experiment 15), we get hydrogen 
 gas given off and zinc sulphate left. Let us filter 
 some of the liquid got in making hydrogen., and thea 
 
84 SCIENCE PRIMERS. [ xxi. 
 
 evaporate it down. On allowing it to cool, white 
 crystals of zinc sulphate will be formed. Zinc will 
 burn when thin turnings are strongly heated in the 
 air, and a white powder of zinc oxide is formed : 
 in this respect zinc resembles magnesium. 
 
 61. Tin is a bright white metal much used for 
 "plating" iron. Common tin-plate is really iron-plate, 
 which is covered with tin by dipping the iron into 
 melted tin. This coating of tin preserves the iron 
 from rust. Tin is also used for making several useful 
 alloys, such as pewter, Britannia metal, plumber's 
 solder. The most important ore of tin is an Oxide 
 of Tin, known as Tin Stone, and is found in 
 Cornwall. Metallic tin is got from this by heating 
 it with charcoal, which takes away the oxygen, and 
 the pure metal melts and can be drawn off. 
 
 Fig. 36. 
 
 EXPERIMENT 52. Take a little powdered oxide of 
 Tin, and mix it with about the same quantity of car- 
 
METALS.] CHEMISTRY. 85 
 
 bonate of soda, and then put this mixture in a hole 
 made in a bit of charcoal. Now heat this with the 
 flame of a blow-pipe, got by blowing into a luminous 
 gas-flame, made by stopping up the holes at the bottom 
 of the Bunsen burner, as shown in the figure.- Soon the 
 mixture will melt, and after heating for some time you 
 then cut that part of the charcoal out with a knife, and 
 rub the whole to fine powder in the mortar. Next wash 
 away all the light particles of charcoal with water, and 
 you will find some heavy bright round grains or globules 
 of white metallic tin remaining at the bottom. In this 
 experiment the oxygen of the tin oxide has united 
 with the carbon of the charcoal to form carbonic 
 oxide gas, which goes off, and the metal tin remains 
 behind and melts with the heat. 
 
 62. Lead is a heavy metal with a bluish colour : 
 it can be easily melted and cut, and does not rust or 
 oxidize in the air ; so that it is very useful for making 
 pipes for gas and water, and for rolling into sheets for 
 covering the roofs and gutters of houses. It is also 
 used for making shot and bullets, because it can be 
 easily melted and cast. Lead ore is found in Wales ; it 
 is called Galena, and is lead sulphide. The process 
 for getting the metals from the ores is called smelting; 
 and the branch of science which has to do with the 
 getting of metals is called metallurgy. 
 
 There are several very useful compounds of lead. 
 
 Common Name. 
 
 White lead. 
 Red lead. 
 Litharge, 
 b'ugar of lead. 
 Chrome yellow- 
 
 Chemical Name. \ What if contains. 
 
 Lead carbonate. j Lead and carbonic acid. 
 
 Red lead oxide. ! Lead and oxygen. 
 
 Yellow lead oxide. ! Lead and oxygen. 
 
 Lead acetate. 
 Lead chromate. 
 
 Lead and acetic acid. 
 Lead and chromic acid. 
 
86 SCIENCE PRIMERS. [ xxi. 
 
 m 
 
 White-lead, red-lead, and chrome-yellow are used as 
 paints. You must remember that black-lead is the 
 common name for graphite, and that it contains no 
 lead whatever ; it is pure carbon. 
 
 EXPERIMENT 53. Add a little solution of potas- 
 sium chromate to a glass rilled with water, to which 
 you have added some lead acetate solution. A 
 splendid yellow precipitate of lead chromate, or 
 chrome yellow, will be produced. This, is what 
 happens : 
 
 Before Mixing. After Mixing. 
 
 ssium chromate and lead ace-) i {Chromate of lead 1 insolub 
 
 tate (boih soluble salts) ( S ive P^W and P otassm 
 
 ) i (soluble). 
 
 63. Mercury or quicksilver is the only simple 
 metal liquid at the ordinary temperature, and it is very 
 valuable for this reason, especially for making thermo- 
 meters (instruments for measuring heat) and baro- 
 meters (instruments for measuring the pressure of 
 the air), about which you will learn in the Physics 
 Primer, and for silvering mirrors. Mercury does not 
 tarnish in the air, but it oxidizes when heated, form- 
 ing red oxide of mercury, from which the oxygen 
 can be driven off again by heating it more strongly 
 (Experiment 30). Mercury can be boiled, and, like 
 water, it may be distilled. Like many other metals, 
 mercury and its compounds are very poisonous, but 
 takeri in small quantities some of them are used as 
 medicines. 
 
 64. Silver is a highly prized and valuable metal. 
 It is found in Mexico, Peru, and elsewhere. The 
 
METALS.] CHEMISTRY. 87 
 
 property which makes silver so useful is that it never 
 tarnishes from oxidation, but it goes black when 
 brought near sulphur, as a black sulphide is formed. 
 Silver has been used Since the earliest times for making 
 valuable and beautiful articles, and especially as an 
 article of exchange as silver coin. English silver 
 coin contains a little copper, added for the purpose of 
 hardening the silver. 
 
 EXPERIMENT 54. Let us see if we can find both 
 copper and silver in a sixpence. Cut a piece of a 
 sixpence, put it into a test-tube, and pour on it some 
 nitric acid. Soon dense red fumes will come off from 
 the nitric acid, and on warming gently the whole of 
 the silver will be quickly dissolved. We have seen 
 (Experiment 22) that silver can be used to detect the 
 presence of sodium chloride, or common salt. Now 
 add some solution of common salt to the solution of 
 silver in nitric acid; a dense white precipitate 
 of insoluble silver chloride will be thrown down. 
 What happens is this : 
 
 We take We get 
 
 Silver nitrate and sodium chloride Silver chloride (a white curdy pow- 
 
 (both soluble salts), der insoluble in water) and sodium 
 
 nitrate (soluble in water). 
 
 Now filter through paper. The clear solution has a 
 bluish-green colour, and contains the whole of the 
 copper. Put a bit of bright iron into the liquid, and 
 a red deposit of metallic copper will soon be seen on 
 iron. 
 
 65. Gold is a still more valuable metal than silver. 
 
 It has a beautiful yellow colour, and is found always as 
 
 metallic gold. Lately much gold has been got from 
 
 California and Australia. Gold is one of the heaviest 
 
 n. G 
 
SCIENCE PRIMERS. [ xxn. 
 
 metals we know of, and it can be drawn out into very 
 thin wire and beaten out into very thin plates called 
 gold leaf, which is much used for gilding. Pure 
 gold is too soft to make coins of, so in England a 
 little copper is added to the gold to make sovereigns, 
 which has the effect of hardening the metal. 
 
 EXPERIMENT 55. Gold does not dissolve in any 
 one acid. Take a leaf of gold and divide it into 
 two pieces ; put one piece into one test-tube and 
 one into another ; pour upon one a little nitric acid, 
 and into the other a little hydrochloric acid. The 
 gold in neither glass will dissolve ; now pour the two 
 together and the metal rapidly disappears, showing 
 that although neither acid by itself can dissolve gold, 
 a mixture of both can do so. Gold never tarnishes 
 in the air or gets stained with sulphur, like silver, 
 so that it has been much used for ornaments as well 
 as for coin from the earliest times. 
 
 RESULTS. XXII. 
 
 66. Combination in definite proportions. 
 
 It will be useful to consider some of the most impor- 
 tant results to which the study of fire, air, water, and 
 earth has led us. You have now a distinct idea of 
 some of the different kinds of matter of which 
 the world is made up. You have learnt that all 
 the various things whether solid, liquid, or gaseous ; 
 whether animal, vegetable, or mineral are composed 
 of one or more of sixty-three elementary or simple 
 substances. No one of these can be converted into 
 any other one, nor has any one of these ever been 
 split up into two different new things. 
 
RESULTS. ] CHEMISTR Y. 
 
 You have also learnt that these elements unite 
 together to form compound bodies which differ alto- 
 gether in properties from the original elements, but 
 from which these original elements can again be ob- 
 tained in various ways. You have learnt that the 
 weight of the compound is always exactly the sum 
 of the weights of the elements, and that in all the 
 chemical changes which take place, no loss of weight 
 ever occurs. We cannot either create or destroy 
 matter. 
 
 The use of the balance for weighing bodies and for 
 determining the composition of chemical substances 
 has also been made clear to you. Chemists have to 
 weigh everything they wish to examine, and thus to 
 find out as we did in the case of water in Experi- 
 ment 20 what weight of each element is contained 
 in the compound. 
 
 We found that 
 
 Sixteen parts by weight of oxygen. . 16 
 
 and Two parts by weight of hydrogen . . 2 
 
 make up eighteen parts by weight of water . 18 
 and I told you that water always contains its ele- 
 ments in these fixed proportions. The same thing 
 is true for all other chemical compounds they all 
 contain their elements in fixed proportions. Thus, 
 for instance, chemists have found, by careful weigh- 
 ing, that the red oxide of mercury which we used in 
 Experiment 30, always contains 
 
 Oxygen , .16 parts by weight, 
 and Mercury . .200 
 
 , making Oxide of mercury 216 
 
90 SCIENCE PRIMERS. [ xxn. 
 
 So if I want to get 16 Ibs. of oxygen, I must take at 
 least 216 Ibs. of the red powder, and if I do not lose any 
 by accident, I shall get exactly the quantity of oxygen 
 I want. And you will understand that by a simple 
 proportion I can calculate the weight of the red oxide 
 which I must take to get any other weight of oxygen. 
 
 This great fact of the constancy of chemical com- 
 bination runs through all the changes we have noticed. 
 If we want to get all the nitric acid we can from 
 the least weight of nitre and sulphuric acid (Experi- 
 ment 38), we must take 98 parts of sulphuric acid 
 and 10 1 parts of nitre, and we shall always get 63 
 parts of nitric acid. And if I burn 24 parts of 
 magnesium wire (Experiment 46), I shall always get 
 exactly 40 parts of magnesia, provided I lose none. 
 
 Thus you learn that all the elements combine with 
 each other in fixed proportions by weight, and the 
 numbers representing these proportions are called the 
 
 67. Combining weights of the elements. 
 Here is a list of the most important elements 
 
 Non-Metallic Elements. Metallic Elements. 
 
 Oxygen . . O = 16 Iron , . Fe = 56 
 Hydrogen . H = i Aluminium Al = 27 
 Nitrogen . N = 14 Calcium . Ca = 40 
 Carbon . . C = 12 MagnesiumMg= 24 
 Chlorine . Cl = 35 Sodium . Na= 23 
 Sulphur . S = 32 Potassium K = 39 
 Phosphorus P = 31 Copper . Cu = 63 
 Silicon , ft Si = 28 Zinc . Zn = 65 
 
 Tin . o Sn = 118 
 Lead . . Pb = 207 
 Mercury . Hg = 200 
 Silver . Ag = 108 
 Gold . . Au = 19 
 
RESULTS.] CHEMISTRY. 91 
 
 with their combining weights and their symbols 
 attached to them. The letter placed after the name 
 of each element is the symbol or short way of writing 
 the name; thus, instead of writing the word phos- 
 phorus, I may write the letter P. For these symbols, 
 the first letters of the words are generally taken ; but 
 in some cases the Latin and not the English word is 
 used ; thus Fe stands for iron, from the Latin ferrum, 
 Ag for silver, from the Latin argentum. The 
 numbers placed after the symbol of each element 
 represents the fixed proportion, by weight, in 
 which that element combines with others. Each of 
 these numbers has been found by experiment, that is, 
 by the analysis of the compounds which that one 
 element forms with others. Thus we find, when we 
 analyse the red oxide of mercury, that it contains 16 
 parts by weight of oxygen to 200 parts by weight of 
 mercury, to form 216 parts by we^ht of the oxide; 
 or when we heat sulphur and copper together (Experi- 
 ment 5) until they combine, we find that exactly 63 parts 
 by weight of copper unite with 32 parts by weight of 
 sulphur to form 95 parts by weight of copper sulphide ; 
 and if more than this quantity of one of these ele- 
 ments had been taken, it remains uncombined. Now 
 the same weight of oxygen (16 parts) unites with 
 other metals to form oxides, and the weight of metal 
 with which it unites is either the combining weight of 
 the metal, or some weight bearing a close relation to 
 the combining weight. Thus 16 parts by weight of 
 oxygen unite with 56 parts by weight of iron to form' 
 an oxide of iron ; with 40 parts of calcium to form 
 an oxide of calcium, called common lime ; with 65 
 
92 SCIENCE PRIMERS. [ xxn. 
 
 of zinc, 118 of tin, 207 of lead, to form oxides of 
 these metals. 
 
 Our chemical short-hand means, however, more 
 than I have yet told you. If I write the symbol O, 
 or the symbol Hg, I signify thereby not any weight 
 of oxygen or of mercury, but exactly the combining 
 weights of these two elements. O means 16 parts 
 by weight of oxygen, and no other weight ; Hg means 
 200 parts by weight of mercury, and no other weight ; 
 and therefore I have written O = 16 and Hg =200 
 in the table. 
 
 Now supposing I want to write the chemical symbol 
 for a compound, I have only to put the symbols of the 
 elements it contains alongside of one another. Thus 
 HgO signifies oxide of mercury ; and this symbol not 
 only tells me that the corn-pound contains oxygen and 
 mercury, but it tells me how much oxygen and how 
 much mercury the body contains, because I remem- 
 ber that O means 16, and Hg means 200 ; so that 
 the chemical symbol, or formula, is most useful as 
 expressing not only the qualitative composition (or 
 what the body contains), but also the quantitative 
 composition (or how much of each thing the body 
 contains). Thus, again, CaO means calcium oxide, 
 or lime, and exactly 40 and 16, or 56 parts by weight 
 of lime; ZnO means zinc oxide, but 65 and 16 or 
 8 1 parts by weight; whilst H 2 O signifies water, being 
 twice H, or two parts by weight of hydrogen com- 
 bined with 1 6 parts by weight of oxygen to form 18 
 parts by weight of water. 
 
 68. Some of the elements combine together in dif- 
 ferent fixed proportions, forming several compounds. 
 
RESULTS.] CHEMISTRY. 93 
 
 Thus nitrogen and oxygen unite to form five different 
 compounds, as follows : 
 
 The first compound, called nitrogen mon-oxide, 
 contains 28 parts by weight of nitrogen, to 16 parts 
 by weight of oxygen. 
 
 The second compound, called nitrogen di-oxide, 
 contains 28 parts by weight of nitrogen, to twice 16, 
 or 32 parts, by weight of oxygen. 
 
 The third compound, called nitrogen tri-oxide, con- 
 tains 28 parts by weight of nitrogen, to three times 16, 
 or 48 parts, by weight of oxygen. 
 
 The fourth compound, called nitrogen tetroxide, 
 contains 28 parts by weight of nitrogen, to four times 
 1 6, or 64 parts, by weight of oxygen. 
 
 The fifth and last compound, called nitrogen pent- 
 oxide, contains 28 parts by weight of nitrogen, to five 
 times 1 6, or 80 parts, by weight of oxygen. 
 
 Now remembering that N means 14, and that O 
 means 16, we can easily write the symbols for the 
 above compounds. 
 
 The first compound contains 28 parts, or two 
 combining weights of nitrogen, to 16 parts, or one 
 combining weight of oxygen. Hence we write the 
 symbol of this compound N 2 O^ 
 
 For a like reason we write the formula 
 
 Of the second compound N 2 O 2 
 third N 2 3 
 
 fourth N 2 O 4 
 
 fifth N 2 5 
 
 From this we see that the weight of oxygen con- 
 tained in the four last of these compounds is twice, 
 
 1 The small figure written below the symbol means that the weight is to be 
 taken more than orice. 0.3 means Oxygen = 16 taken three times, or 
 3X16= 48. 
 
94 SCIENCE PRIMERS. [ xxn. 
 
 three times, four times, and five times that contained 
 in the first compound. And, moreover, we find that 
 it is not possible for us to prepare a compound con- 
 taining any intermediate quantity of oxygen. If, for 
 instance, we try to combine 28 parts by weight of 
 nitrogen, with 20 parts by weight of oxygen, we get 
 the whole of this nitrogen combined with only 16 of 
 the oxygen, the other 4 parts of oxygen remaining 
 uncombined. Here, then, we have arrived at the two 
 most important laws of chemical combination : 
 
 1. The law of combination of the elements in 
 
 fixed proportions, called the combining 
 weights. 
 
 2. The law of combination in multiple proportions 
 
 of these combining weights, when several 
 compounds of the same two elements exist. 
 
 69. Meaning of a chemical equation. 
 
 You will now be able to understand that all the 
 chemical changes which I have spoken of, and which 
 you have seen, or ever will see, can be written down 
 in symbols. Everyone of these changes is definite, 
 and in every case we can get to know not only what 
 has taken place, but also how much of each substance 
 has been formed. Let us take one or two examples. 
 If I want to prepare nitric acid (Experiment 38), I 
 take nitre (potassium nitrate) and sulphuric acid, then 
 nitric acid distils over, leaving potassium sulphate in 
 the retort. Now what happens in this change ; and 
 how much sulphuric acid and how much nitre am I to 
 take, so as not to waste either ? In order to find this 
 out, I must write down the formula for nitre, and for 
 
RESULTS.] CHEMISTRY, 95 
 
 sulphuric acid. Nitre is written KNOgj 1 that is, it 
 contains three elements potassium, K = 39 ; nitrogen, 
 N = 14 ; oxygen, O 3 = 3 times 16, or 48. Sulphuric 
 acid is written H 2 SO 4 ; that is, it contains hydrogen 
 H 2 = twice i, or 2 ; sulphur, S = 32 ; oxygen, O 4 ~ 
 4 times 16, or 64. When we mix these two com- 
 pounds together, a change occurs ; half the hydrogen 
 (H) in the sulphuric acid changes place with the 
 whole of the potassium (K) in the nitre, and two new 
 substances are formed, viz. H.NO 3 , nitric acid (\yhich 
 distils off as a yellow liquid), and KHSO 4 , sulphate 
 of potassium, which remains in the retort as a white 
 solid salt. This change we can therefore express in 
 an equation, thus 
 
 Before the change. After the change, 
 
 Nitre and Sulphuric Acid yield Nitric Acid and Potassium Sulphate 
 
 KNO 3 + H 2 SO 4 = HNO 3 + KHSO 4 
 
 This shows us, then, exactly what takes place ; 
 nothing is lost ; the nitric acid and potassium sulphate 
 which we get, weigh, taken together, as much as the 
 nitre and the sulphuric acid which we took. We see 
 this dearly if we write down the numbers which these 
 symbols represent. 
 
 39+14 + 48 and 2 + 32 + 64 = 1 + 14 + 48 and 39+1+32 + 64 
 101 + 98 = 63 + 136 
 
 The equation then tells us that if I take 101 parts 
 by weight of nitre, and 98 parts by weight of sulphuric 
 acid, I shall get exactly 63 parts by weight of nitric 
 acid, and that no nitre or sulphuric acid will be wasted j 
 
 1 The number below the letter applies to that letter only. 
 
96 SCIENCE PRIMERS. [ xxn. 
 
 and you will easily understand that these numbers 
 enable you to calculate the quantity of the materials 
 you must take, to get any given weight of the acid. 
 Suppose you wanted 10 pounds of nitric acid, how 
 much sulphuric acid and nitre would you need to 
 employ? Well, if you wanted to get 63 pounds of 
 nitric acid, you would need 98 pounds of sulphuric 
 acid, and 101 pounds of nitre; and, of course, in 
 order to get 10 pounds you will need 4 ^ of 98 pounds 
 of sulphuric acid, and \^ of 101 pounds of nitre. So 
 that all calculations of this kind are matters of simple 
 proportion. 
 
 Let us take one other example. We made hydrogen 
 by acting upon zinc with sulphuric acid and water 
 (Experiment 15). The change which here takes place 
 is represented by the equation 
 
 Zn + H 2 SO 4 = H 2 + ZnSO 4 or 
 
 Zinc and Sulphuric Acid yield Hydrogen and Zinc Sulphate. 
 
 65 and 2 + 32 + 64 yield 2 and 65 + 32 + 64 or 
 65 and 98 yield 2 and 161 
 
 parts of parts of parts of parts of 
 
 Zinc. Sulphuric Acid. Hydrogen. Zinc Sulphate. 
 
 This means that if I take 65 pounds of zinc, 
 and 98 pounds of sulphuric acid, I must always get 
 2 pounds of hydrogen gas, and 161 pounds of zinc 
 sulphate. If I ask you how much zinc and sulphuric 
 acid must you take in order to get 40 pounds of 
 hydrogen, I am sure you will all be able to tell me. 
 
 In like manner every chemical change, as soon as 
 we understand it, can be represented by a formula, or 
 set of symbols, which tells us exactly what happens, 
 
RESULTS. ] CHEMISTR Y. 97 
 
 and how much of each of the various materials must 
 be taken, and how much of each of the several pro- 
 ducts are formed. 
 
 It is the business of the chemist to seek out and 
 determine the nature of all new chemicals which may 
 be observed, and he does this with zeal and confidence,, 
 because he knows that if he has once determined, 
 with care, the nature of the change, and if he has once 
 ascertained the proportions by weight in which the 
 elements, or compounds, take part in it, he has settled 
 this particular question for ever, as the same chemical 
 combination always takes place according to the same 
 unchanging laws. 
 
 HINTS FOR THE USE OF THE APPARATUS 
 AND FOR THE EXPERIMENTS. 
 
 1. TRY every experiment over carefully before it is 
 shown in class, and observe exactly the description given 
 in the text. 
 
 2. Cleanliness and neatness in manipulation are as 
 necessary in doing experiments as clearness of exposition 
 is in teaching. 
 
 3. Place everything needed for the experiments of the 
 day in order upon the table, so that there may be no con- 
 fusion or delay. 1 
 
 4. When the lesson is over carefully clean all the appa- 
 
 1 Faraday, our great master ih experimental lectures, always devoted many 
 hours to the preparation of the experiments for each lecture. No point, how- 
 ever trifling, bearing upon the success of the experiment was considered un- 
 important ; he used to try the stoppers of all the bottles he had to use to see 
 that they had not become fixed, and thus would cause delay by requiring 
 forcible opening. 
 
98 SCIENCE PRIMERS. 
 
 ratus, and remove it and the specimens to a locked box or 
 cupboard. Many of the acids, especially sulphuric and 
 nitric, are dangerously corrosive, phosphorus is dangerous 
 from its inflammable nature, whilst these and others of the 
 reagents are poisonous, so that all must be completely 
 removed from the pupils, and had better be kept in the 
 teacher's private room. 
 
 5. The elder and more advanced pupils, having once 
 seen the teacher go through the course of experiments, may 
 with great advantage be permitted to perform the experi- 
 ments for themselves under his superintendence. 
 
 Notes for the Experiments : 
 
 EXPERIMENT i.- If the neck of the bottle be very 
 wide, the top must be covered by a piece of card, other- 
 wise sufficient fresh air will get in to permit the continued 
 combustion of the candle. 
 
 EXPERIMENT 3. The \\ tube containing the caustic 
 soda should be carefully removed and corked up after each 
 experiment, to prevent the caustic soda absorbing, carbonic 
 acid and moisture from the air. After the same caustic 
 soda has been used for the experiment several times, the 
 tube must be cleaned out, and a fresh supply of lumps 
 of caustic soda obtained. 
 
 EXPERIMENT 5. This may also be done in a test tube ; 
 take care to have the copper turnings well heated before 
 the sulphur boils, otherwise the glow is not well seen. 
 
 EXPERIMENT 6. Take great care how you cut phos- 
 phorus ; do so always under water. Then carefully and 
 lightly dry the bit of phosphorus with blotting paper, and 
 put it, with a dry knife or small pliers, on to the small 
 floating dish. 
 
 EXPERIMENT 10. This cannot be easily shown in 
 winter, as the light is not intense enough. 
 
 EXPERIMENT 12. How to charge the Grove's battery. 
 Measure one pint of water into a basin, and gradually 
 
CHEMIS7"RY. 99 
 
 pour into this three fluid ounces of strong sulphuric acid 
 or oil of vitriol, and let the liquid, after well mixing, be 
 allowed to stand till it is cool. See that all the clamps 
 and metal connections are bright, using sand-paper to 
 clean them. Set up the battery with the porous cells and 
 platinums inside the pot cells, and clamp all tight. Pour 
 the dilute sulphuric acid into the pot cells so as nearly to 
 fill each ; then by means of a funnel carefully nearly fill 
 each of the porous cells with strong nitric acid. The 
 battery is now ready for action. When done with, the 
 sulphuric acid may be returned to a bottle kept for the 
 purpose, and the nitric acid poured into another bottle, 
 unless the battery have been long in use, when both acids 
 may be thrown away. The porous cells and zincs must 
 be allowed to soak in water over-night and then placed 
 back in their places. Should any of the zincs begin to 
 effervesce in the acid when the wires of the battery are 
 not in contact, they must be amalgamated afresh. This 
 is done by washing the surface of the zinc with some 
 hydrochloric acid, and then pouring some mercury, 
 together with the acid, over. the metal. After repeating 
 this several times, the metal will possess a uniform bright 
 colour, and will not dissolve in dilute sulphuric acid unless 
 the wires be joined. 
 
 EXPERIMENT 16. The union of sodium and mercury 
 is always accompanied by a slight explosion, but quite free 
 from danger. Always take five times by bulk as much 
 mercury as sodium. 
 
 EXPERIMENT 17. It is best to mix the sulphuric acid 
 and water (one to six by volume) beforehand ; pour the 
 acid into the water in a thin stream, and stir the mixture 
 round. 
 
 EXPERIMENT 20. A piece of hard wide glass tube 
 without a bulb, fitted with a cork to the lube E > 
 
ioo SCIENCE PRIMERS. 
 
 and drawn out at the other end, as shown in the figure, 
 may serve instead of the bulb-tube A. Unless nearly 
 half an ounce of copper oxide is taken the height of water 
 formed will be too small. After the experiment is finished. 
 the reduced metallic copper must again be oxidized by 
 drawing air over it (by means of the oil-can used in Ex^ 
 periment 3) whilst it is heated with the lamp. The oxide 
 thus formed will have gained its original weight, and can 
 be used again for a repetition of the same experiment 
 
 EXPERIMENT 31. In order that this increase of weight 
 by oxidation should be rendered evident, the magnet must 
 be a good one, the filings very fine, and the balance 
 delicate. Another mode of showing the increase of 
 -weight by absorption of oxygen is that mentioned above 
 when the reduced copper is heated in a current of air. 
 
 EXPERIMENT 36. It requires a little practice to get 
 the gas to burn permanently at the end of the tube. 
 
 EXPERIMENT 40. In a close room the evolution of 
 chlorine gas should be avoided. 
 
 EXPERIMENT 52. When using the blowpipe the breath 
 tnust be sent out from the cheeks and not from the lungs ; 
 it is thus possible to inflate the cheeks when required 
 breaching through the nose. 
 
CHEMISTRY. lor 
 
 LIST OF APPARATUS REQUIRED FOR 
 EACH EXPERIMENT. 
 
 WITH APPROXIMATE PRICES OF THE ARTICLES, 
 
 As quoted by Messrs. J. Woollcy, Sons, &~* Co. , Messrs. Motters- 
 
 head & Co. , of Manchester , and Messrs. Griffin &* Sons, and 
 
 Mr. S fat ham, of London. 
 
 No. of Price. 
 
 Expt. > s. d. 
 
 I. Taper with wire holder o o 7 
 
 3. Glass tube containing a taper, with U tu ^ e f r 
 holding the caustic soda, and caoutchouc 
 tubing to connect to the aspirator . . . . o I 6 
 Pair of hand-scales with glass pans, and weights 
 
 from 2 oz. downwards, in oak box . . . .046 
 5. A 2-oz. glass flask, ^d., iron tripod stand, lod. .oil 
 Bunsen's burner, with one yard of caoutchouc 
 
 tubing . . o 2 2 
 
 (This will be replaced by a spirit-lamp and 
 one pint of methylated spirit when desired. ) 
 6. A bell jar, u.', capsule to contain the phos- 
 phorus, $d. 015 
 
 12. Apparatus for decomposing water by electricity, 
 with two collecting tubes and wire to suspend 
 
 them 020 
 
 A 4-cell Grove's battery, in wooden tray, with 
 
 wires I 16 o 
 
 14. Glass mortar and pestle, I o;/., gas eprouvette, 6aT. 014 
 15. Flask, &c. for generating hydrogen . . o I 6 
 
 Stoneware pneumatic trough, with beehive shelf o 28 
 Four wide-mouthed gas-collecting bottles, pint 
 
 size 014 
 
 Three stoneware gas trays ,.....,009 
 
102 
 
 SCIENCE PRIMERS. 
 
 No. of Price. 
 
 Expt. s. d. 
 
 20. A pint flask, wash -bottle, two U' s ^ a P e( ^ calcium 
 chloride tubes, and hard glass tube to contain 
 the copper oxide . . . . *'-* 4 
 
 21. Two 8-oz. stoppered glass retorts o I 6 
 
 A retort stand, with three rings, and clamp for 
 
 test tubes, &c. . ., . % ..-.. . ... ...056 
 
 23. A i6-oz. porcelain evaporating dish, I.?. 6d., 
 
 4-oz. ditto, 8J. ..... . 4 ' ; o 2 2 
 
 25. Two 3-in. glass funnels, 6d. , 100 filter-papers, yd. 013 
 
 31. A horseshoe magnet 004 
 
 32. A palette-knife ri .V*. ...006 
 
 37. A piece of iron wire gauze, six inches square .003 
 42. Iron tray or sand bath . . . ^ ; ^>\z.;.. * '> ,- ,'. 004 
 44. One dozen 5-in. test tubes, is., test tube 
 
 holder, 6d. xi."^.z. *'."** o I 6 
 
 Test tube stand for twelve tubes 013 
 
 One blowpipe, is., two files (round and trian- 
 gular), U. 4//. 024 
 
 Half a pound of glass tubing, 6d., two dozen 
 
 spare corks, 6d. O .,oio 
 
 CHEMICALS, &c. 
 
 Sulphuric acid . . 
 
 Nitric acid . . . 
 
 Hydrochloric acid 
 
 Lime-water . . . 
 
 Ammonia (solution) 
 
 Caustic potash ,, 
 
 Sodium car- 
 bonate ,, 
 
 Potassium chro- 
 mate ,, 
 
 Potassium fer- 
 rocyanide ,, 
 
 4 Ibs. 
 
 3 
 
 2 
 
 I pint. 
 
 4 oz. 
 4 
 
 Silver nitrate (solution) 4 oz. 
 
 Litmus ,, 4 ,, 
 
 Indigo 4 
 
 Calcium chloride . 8 
 
 Marble . . . . 8 ,, 
 
 Iron filings . . . 8 ,, 
 
 Lime 4 ,, 
 
 Gypsum . . . . 4 ,, 
 
 Stourbridge clay . 4 ?> 
 
 Bleaching powder . 4 , , 
 
 Manganese dioxide . I Ib. 
 
 Soda crystals . . . 4 oz. 
 
CHEMISTRY. 
 
 103 
 
 Alum 
 
 4 oz. 
 
 Sodium carbonate an* 
 
 
 Sulphur roll . . 
 
 4 ? 
 
 hydrous. . . . 
 
 I OZ. 
 
 ,, flour . . . 
 
 4 >> 
 
 Phosphorus, yellow . 
 
 I 
 
 Potassium nitrate 
 
 4 
 
 , , red . . 
 
 i 
 
 Zinc 
 
 2 ,, 
 
 Tin oxide 
 
 i 
 
 Copper turnings . 
 
 2 ,, 
 
 Mercury oxide . . 
 
 C Z It 
 
 1 
 
 ,, oxide 
 
 2 
 
 Potassium . 4 
 
 I dram 
 
 , , sulphate . 
 
 2 
 
 Sodium ; . . . 
 
 I ,, 
 
 Antimony .... 
 
 2 
 
 Gold leaf .... 
 
 6 leaves 
 
 Mercury .... 
 
 2 ,, 
 
 Magnesium ribbon . 
 
 4 yard i 
 
 Lead acetate . . . 
 
 2 ,, 
 
 Litmus paper . . 
 
 I book 
 
 Castor oil . 
 
 2 ,, 
 
 Charcoal , . . . 
 
 I piece 
 
 Caustic soda (solid) . 
 
 2 
 
 
 
 Amounting: to , 
 
 
 
 o 14 6 
 
 43 bottles (various) to contain the above chemicals and 
 
 preparations ; 076 
 
 Set of 32 specimens in one-ounce specimen bottles .070 
 
 LIST OF SPECIMENS. 
 
 Aluminium. 
 Tin. 
 
 Lead. 
 Silver. 
 Bar iron. 
 Cast iron. 
 Steel. 
 
 Galvanized iron. 
 Iron ore. 
 Iron oxide. 
 Iron sulphate. 
 Bronze. 
 Brass. 
 
 Tin stone. 
 Galena. 
 Zinc blende. 
 White sand. 
 Red 
 Flint. 
 Quartz. 
 Graphite. 
 Rock salt. 
 Sodium sulphate. 
 Sodium nitrate. 
 Bone ash. 
 
 II. 
 
104 SCIENCE P1UMLRS. 
 
 Limestone. Potassium chlorate. 
 
 Magnesium sulphate. White lead, Red lead. 
 
 Potassium carbonate. Litharge. 
 
 Messrs. J. WOOLLEY, SONS, & Co., and Messrs. MOTTERS- 
 HEAD & Co., both of Manchester, and Messrs. GRIFFIN & 
 SONS, Garrick Street, and Mr. W. STATHAM, inj, Strand, 
 London, will supply the above-enumerated apparatus, chemicals, 
 preparations, and specimens, packed in a box with lock and key, 
 for the sum of $ IO.T. 
 
 THE END. 
 
 London i R. Clsy> Sous, and T*.iyhr< P> inters* 
 
JAMES WOOLLEY, SONS, AND CO,, 
 
 69. MARKET STREET, MANCHESTER, 
 
 in 
 
 LABORATORIES SUPPLIED WITH 
 
 Balances, Assay, & Volumetric Apparatus, 
 
 PURE CHEMICALS, TEST SOLUTIONS, 
 BOTTLES, LABELS, AND EVERY REQUIREMENT. 
 
 SETS OF APPARATUS, &c, 
 
 As required for the Oxford, Cambridge, and South 
 Kensington Examinations. 
 
 Price Lists forwarded on application* 
 
 THE SET OF APPARATUS, CHEMICALS, &c., required 
 for use with Professor ROSCOE'S Chemistry Primer 
 price ^5 IDS. Will be delivered to any Railway 
 Station in the Kingdom on receipt of remittance or 
 reference. 
 
 May also be obtained from Messrs. MACMILLAN and 
 Co. Bedford Street, London, Publishers of the Primer. 
 
NATURE SERIES, 
 
 THE SPECTROSCOPE AND ITS APPLICA- 
 TIONS. By J. N. LOCKYER, F.R.S. With Illustra- 
 tions. Second Edition. Crown 8vo. 3^. 6d. 
 
 THE ORIGIN AND METAMORPHOSES OF 
 INSECTS. By Sir JOHN LUBBOCK, M. P. , F. R. S. With 
 Illustrations. Second Edition. Crown 8vo. 3-f. 6d. 
 
 THE BIRTH OF CHEMISTRY. By G. F. RODWELL, 
 F.C.S., F.R.A.S. With Illustrations. Crown 8vo. 
 3*. 6d. 
 
 THE TRANSIT OF VENUS. By G. FORBES, 
 
 B.A., Professor of Natural Philosophy in the Andersonian 
 University, Glasgow. With numerous Illustrations. Crown 
 8vo. 3-y. 6d. 
 
 THE COMMON FROG. By ST. GEORGE MIVART, 
 F.R.S. Illustrated. Crown 8vo. $s.6d. 
 
 POLARISATION OF LIGHT. By W. SPOTTIS- 
 WOODE, LL.D., F.R.S. Illustrated. Crown 8vo. 
 3J. 6d. 
 
 ON BRITISH WILD FLOWERS, considered in Rela- 
 tion to Insects. By Sir JOHN LUBBOCK, M.P., F.R.S. 
 Illustrated. Second Edition. Crown 8vo. qs. 6d. 
 
 OTHERS TO FOLLOW. 
 MACMILLAN AND CO., LONDON. 
 
MACMILLAN AND CO.'S 
 
 SCIENCE CLASS-BOOKS. 
 
 ANATOMY. ELEMENTARY LESSONS IN ANA- 
 TOMY. By ST. GEORGE MIVART, F.R.S. With upwards of 400 
 Illustrations. i8mo. 6s. 6d. 
 
 ASTRONOMY. POPULAR ASTRONOMY. With Illus- 
 trations. By Sir G. B. AIRY, C.B., Astronomer Royal. New 
 Edition. i8mo. 4*. 6d. 
 
 ASTRONOMY. ELEMENTARY LESSONS IN ASTRO- 
 NOMY. With Illustrations. By J. NORMAN LOCKYER, F.R.S. With 
 Coloured Diagram. New Edition. i8mo. 5.?. 6d. 
 
 QUESTIONS on the SAME, is. 6d. 
 
 BOTANY. LESSONS IN ELEMENTARY BOTANY. 
 With Illustrations. By Professor OLIVER, F.R.S., F.L.S. New Edition. 
 i8mo. 4s. 6d. 
 
 CHEMISTRY. -LESSONS IN ELEMENTARY CHE- 
 MISTRY. By Professor ROSCOE, F.R.S. With numerous Illustrations 
 and Chromo-lithograph of the Solar Spectra. New Edition. i8mo. 
 4-r. 6d. 
 
 CHEMICAL PROBLEMS : ADAPTED TO THE ABOVE 
 
 BY T. E. THORPE. i8mo. is. Key, is. 
 
 CHEMISTRY. OWENS COLLEGE JUNIOR COURSE 
 
 OF PRACTICAL CHEMISTRY. By F. JONES. With Preface by 
 Professor ROSCOE. New Edition. i8mo. vs. 6d. 
 
 LOGIC ELEMENTARY LESSONS IN LOGIC, DE- 
 DUCTIVE AND INDUCTIVE. By Professor JEVOKS. With copious 
 Questions and Examples, and a Vocabulary of Logical Terms. New 
 Edition. i8mo. 3$. 6d. 
 
 PHYSIOLOGY. LESSONS IN ELEMENTARY PHY- 
 SIOLOGY With numerous Illustrations. By Professor HUXLEY, F.R.S. 
 New Edition. i8mo. 4$ 6d. 
 
 QUESTIONS on the SAME. is. 6d. 
 PHYSICS. LESSONS IN ELEMENTARY PHYSICS. 
 
 By Professor BALFOUR STEWART, F.R.S. With Colouied Diagram 
 and numerous Illustrations. New Edition. i8mo. $s. 6d. 
 
 POLITICAL ECONOMY FOR BEGINNERS. By MILLI- 
 CENT GARRETT FAWCETT. With Questions. New Edition. i8m 
 2s. 6d. 
 
 STEAM : AN ELEMENTARY TREATISE. By JOHN 
 
 PEKRY, B.E., late Lecturer in Physics at Clifton College. With 
 numerous Illustrations, Examples, and Exercises. i8mo. 4-$-. CxL 
 
 MACMILLAN AND CO., LONDO^F. 
 
JOHN J. GRIFFIN & SONS, 
 
 SflanufatluKw of <%mkal & 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 Illustrative of the Physical Sciences. Catalogues, 3^., ( 
 
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MOTTERSHEAD & CO., 
 
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 7, Exchanj 
 
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 oon Street, 
 
 THE SET OF APPARATUS, CHEMICALS. 
 AND SPECIMENS 
 
 Required for use with PROF. ROSCOE'S CHEMISTRY PRIMER, 
 price ^5 icxr. packed in strong box with lock and key, will be 
 forwarded CARRIAGE PAID TO ANY RAILWAY STATION IN 
 ENGLAND, SCOTLAND, or IRELAND, on receipt of re 7 '*tance 
 or reference. 
 
 Sets of Apparatus adapted for the Oxford, Cam> 
 other examination^. 
 
 .d all 
 
 Price Lists Free on 
 
 .STATHAI 
 CHEMICAL AM US n 
 
 Contain, Chemicals and Apparatus 
 suitable for beginners; the la-rs*8 
 course of Chemical Study, an.$||j 
 &c. They have proved a sr 
 of Great Britain aur 1 f he^S| 
 Medals " FOR Qr 
 1862, and Paris 
 complimenta- 
 
 
 
 I 
 
 ments 
 ing a 
 poisons, 
 youth 
 ned Prize 
 of London, 
 Mr. Statham a 
 
 Illustrated 
 
 7/6 10/6 15/0 
 
 42/O 63/0 84/0 2IO/0 
 
 .dtes) ... 105/0 210/0 
 
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 CHEAP PHYSICAL APPARATUS, PURE TESTS, &c. 
 
 Set of Chemicals and Apparatus for use with Professor Roscoe's " Chemistry 
 Primer, free to any Railway Station for ,5 105-. 
 
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