Book III - Chemistry

The Science that teaches how to combine Two Substances so as to produce a Third Substance different from Either

Contents

Physical Changes; solutions . . . . . . .150
Mixtures . . . . . . . . . . . . . .. . .  . .. .150
Chemical Combinations . . . . . .  . . . 151
Chemistry (defined) . . . . . . . . .. . . . 152
Chemical Affinity . . . . .. . . . . . . . . . 152
Gunpowder . . . . . . . . . . . . . . . . . . .153
Bread Making .. . . . . . . . . . . .  .. . .. 154
Composition of the Air . . . . . . . . . . 155
Oxygen . . . . . . . . . . . . . . . . .. . . . .155
Nitrogen . . . . . . . . . . . . . . . ... . . . .155
Combustion . . . . . . . . . . . . . .. . . . .156
Hydrogen . . . . . . . . . . . . . .. .. . . . .157
Balloons . . . . . . . . . . . . . . . .  . . .. .157
Water . . . . . . . . . . . . . . . . ..  . . . . 157
Chemical Elements . . . . . . . . . . . . . 158
Metals . . . . . . . . . . . . . . . . .  . . . . 158
Non-Metals . . . . . . . . . . . . . . . . . . 158
Chemical Compounds . . . . . . . . . . .159

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pg 148


Different forms of crystals

pg 149

Chemistry is the science that teaches how to combine two substances so as to produce a third substance different from either.

NOTE.--Many chemical experiments can be tried in the schoolroom; but a great number are not safe to try there, and many others require complicated or expensive apparatus. Very many, again, are difficult to explain to children who have had no formal teaching in chemistry. For these reasons the following pages are devoted chiefly to simple and fundamental matters, omitting details, which are instructive only when they are thoroughly understood.

The children bought at the druggist's small bottles of the chemicals in the list below. Every bottle was labeled with the right name, and they were warned not to get strong acids on their hands or on their clothes.

A glass-stoppered bottle of sulphuric acid
A glass-stoppered bottle of nitric acid
A glass-stoppered bottle of hydrochloric acid
A glass-stoppered bottle of acetic acid (vinegar)
A cork-stoppered bottle with sulfur
A cork-stoppered bottle with iron filings (or tacks)
A cork-stoppered bottle with copper filings (or tacks)
A cork-stoppered bottle with zinc filings
A cork-stoppered bottle with quicklime
A cork-stoppered bottle with chalk crayons
A cork-stoppered bottle with pieces of pure lead
A cork-stoppered bottle with gunpowder
A cork-stoppered bottle with oxyd of manganese
A cork-stoppered bottle with sulphur matches

pg 150

Physical Changes; Solutions.--"Let us take a pinch of this common table salt," said Jack, "and put it in a tumbler of water. What happens?"

Agnes. The water will dissolve the salt. You cannot see it any more. It disappears.

Tom. It is there, though, in the tumbler; for the water tastes salty when I wet my finger with it.

Jack. We can get all the salt back again if we want to, by pouring the salted water on a flat dish and setting the dish on a hot stove. The water will gradually go away, but our salt will be left on the plate. The salt that you put in has not been changed. It is the same salt. It is fit to use on the table, and there is as much of it as there was at first. Now let us try another experiment.

Mixtures.--"Here is some pure sulphur, and here are some iron filing. Take a mortar and bruise the sulphur in it till it is all in fine powder. Now mix the sulphur and the iron and lay the mixture on this pane of glass. Can you boys tell me of any way to separate the iron and the sulphur again, so that you can make one little pie all sulphur and another all iron?"

Fred. Why, I can take a magnet and pull all the iron filings out with it and leave the sulphur.

Tom. That is one way; but it is easier to blow on the pile, and the light grains of sulphur will fly off and leave the heavier iron.

Jack. That is a good way to separate the two things; but Fred's way is the better if you want to save the sulphur. Well, the point is that when you mixed the salt and water you could get both of them back again--neither was altered; and when you mixed sulphur and iron you could get both back again--neither was altered.

pg 151

I want to try a different kind of an experiment. I want to mix two things together and to make a third thing different from either one of them.

Tom. Like mixing a coat and a hat and getting a pair of boots?

Agnes. Oh, Tom, that is silly!

Jack. Well, it is rather funny; and it is not quite so silly as you think, Agnes, though of course it is absurd and impossible the way Tom has said it. No; I want to mix sulphuric acid and iron, one a colorless liquid and the other a blackish solid, and get some green crystals of a substance entirely different from either of them.

Chemical Combinations--Here Jack took some sulphuric acid in a jar and dropped a few iron carpet tacks in it. In a little while the tacks disappeared; they combined with the acid, as people say, and nothing but a colorless liquid was in the tumbler as before. This he poured into a flat china dish which he put on the hot stove. In a little while all the liquid had disappeared and there were left beautiful green crystals; sulphate of iron, or green vitriol, is the name of them. (1) Then he tried exactly the same experiment, using sulphuric acid and copper carpet tacks, and on the plate there were left beautiful blue crystals; sulphate of copper, or blue vitriol, is the name of them.

A little finely powdered quicklime combined with sulphuric acid produces sulphate of calcium, or sulphate of lime (calcium is another name for lime).

(1) To make green vitriol take one part, by weight, of iron wire, or tacks with two parts of strong sulphuric acid in four parts of water and mix. If the mixture is heated, the combination will be more rapid. Filter the resulting fluid, evaporate it over a fire, and obtain the crystals.

pg 152

"Here," said Jack, "we have combined two things and in each case made a third thing, quite unlike either of them."

Sulphuric acid + iron = sulphate of iron
Sulphuric acid + copper = sulphate of copper
Sulphuric acid + lime = sulphate of lime (1)

Chemistry is the name of the science that is busy about such combinations and the changes of one substance into another. "We have just made sulphate of lime," said Jack, "by combining sulphuric acid and quicklime. Here is another way to get it. This piece of chalk is made out of another acid (a gas) combined with lime.

Carbonic acid gas + lime = carbonate of lime (chalk)

Chemical Affinity.--"It is as if the carbonic acid were a soldier and the lime a prisoner. Sulphuric acid is a stronger soldier than the other. If I pour diluted sulphuric acid on a piece of chalk, the carbonic acid will fly off in gas and the sulphuric acid will take the lime prisoner in its turn, and we shall have

Chalk + sulphuric acid = sulphate of lime.

"The carbonic acid has been driven off.

(1) To make blue vitriol take one part, by weight, of copper wire, or tacks, with ten parts of strong sulphuric acid (and no water). Mix and boil the acid until gas rapidly escapes. Let it cool and carefully pour off the liquid. Add water to what is left and evaporate it over a fire and obtain the crystals. To make sulphate of lime take one part, by weight, of finely pulverized quicklime with two parts of strong sulphuric acid and four parts of water. No heat is necessary. When the action ceases evaporate the liquid over a fire and obtain the crystals. The teacher can repeat these experiments in the schoolroom after he has himself performed them. Children should not undertake them.

pg 153

"Vinegar is an acid, too. It is called acetic acid. Take some vinegar in the bottom of a tumbler and throw a little lump of chalk into it. What happens? You see the carbonic acid gas flying off in bubbles. It leaves the lime, and the acetic acid takes the lime prisoner.

Carbonic acid + lime = carbonate of lime (chalk)
Chalk + acetic acid = acetate of lime

"The carbonic acid has been driven off again.

"Chemists say that sulphuric acid has a stronger affinity for (liking for, fondness for) lime than carbonic acid. It is just as if the prisoner lime liked to be a prisoner of one acid better than to be a prisoner of the other. Lead, for instance, likes to combine with nitric acid better than to combine with sulphuric acid, and so with other substances.

"Chemists study these likes and dislikes of the metals, and make use of them. It is much easier and cheaper to get sulphate of lime from carbonate of lime (chalk) by letting sulphuric acid capture the lime than it is to take simple lime and combine it directly with sulphuric acid."

Tom. What is the use of chemistry, Jack? Is it to make new substances cheaply?

Jack. Partly that. The scientific use of it is to explain why two things combine to make a third, and what is the best way to make them do it (for there are many different ways). Its practical use is to teach us how to make such things as gunpowder, glass, soap, vinegar, cheese, leather, gas to burn in our houses, bread to eat, and so forth.

Gunpowder, for instance is a mixture of charcoal, sulphur, and niter. (1) It is a mixture, not a combination, until it is fired off.

(1) Niter is a combination of potassium and nitric acid.

pg 154

Then it suddenly becomes a combination of all three substances, and a great deal of gas is formed. The gas expands in the barrel of the gun, and in expanding drives the bullet out. Chemists have taught us how to make it in the best way. During our Revolutionary War the powder was so poor that men were seldom killed outright as far as a hundred yards. Nowadays powder will drive a bullet with force enough to kill at 2000 yards or more.

Tom. I have seen a book about Benjamin Franklin that says he advised Congress not to arm the soldiers in the Revolutionary War with guns, but with bows and arrows, because they could kill nearly as far off with arrows as with muskets and because they could shoot much faster.

Jack. It sounds absurd nowadays, but it was not at all absurd then. The muskets were better than bows and arrows, even then, but not so very much better. The powder was especially poor. Chemists would laugh at it nowadays.

Mary. What do chemists know about bread, Jack? I think the cook knows more than they do.

Jack. I have no doubt the cook can make bread better if you give her the right kinds of flour and yeast, and so forth; but the chemist tells how to make the right kinds. She uses what he has invented. There are dozens of different kinds of bread for soldiers and sailors and invalids. They were invented by chemists so as to be healthful, or to keep without spoiling on long voyages. The cook could not do that. All the beautiful dyes for silk and wool and cotton (different dyes for each kind of stuff), all the paints, all the inks used for writing and printing, and a thousand things of the sort were invented by chemists. Why, chemists nowadays make indigo--by mixing carbon hydrogen, nitrogen, and oxygen in the right proportions--that is just as good as the indigo that grows on the plant.

pg 155

Composition of the Air.--The air of the atmosphere is principally made up of a mixture of two invisible gases called oxygen and nitrogen. Both are invisible and so is the air, the mixture of the two. Water is a combination of oxygen and hydrogen. Oxygen gas can be prepared by heating a mineral call oxyd of manganese. It is made out of manganese combined with oxygen. When the mineral is heated the oxygen goes off as a gas and can by collected in a jar under water. (See Fig. 141.)

Nitrogen gas can be prepared by burning a bit of phosphorus (not bigger than a green pea) under a glass containing air (air is oxygen and nitrogen mixed). The phosphorus burns up all the oxygen in the air and leaves only nitrogen.

In 100 pounds of air, 23 pounds are oxygen, and 77 pounds are nitrogen. This is the air we breathe. If a live animal (a mouse, for instance) is put into a glass jar that contains nitrogen and no oxygen, it dies. It is not the nitrogen that kills it, but the lack of oxygen. To have life we must breathe; to


Fig. 141. Preparation of Oxygen Gas--Heat powdered oxyd of manganese in a test tube one-third full. The oxygen gas will be driven off by the heat and can be collected over water in a jar turned upside down. Afterwards slide a sheet of glass under the jar so as to close it and turn the jar right side up till the gas is wanted for other experiments.

pg 156

breathe there must be enough oxygen. Nitrogen helps plants to live, but for men and animals there must be plenty of oxygen.

Combustion.--Combustion is burning. When a match burns there is combustion. All combustion is the combination of something with oxygen. When a match burns, the sulphur on its head unites with the oxygen of the air about it. When a coal fire burns, the coal unites with the oxygen of the air. Combustion is rapid in the case of the match or of the coal, but it is not always so quick. Sometimes it is slow. When iron rusts, as we say, the iron of the outside layers combines with the oxygen of the air and makes iron rust. (l) Rusting is a sort of slow fire without flame, and the iron rust that is left is the ashes. By taking great pains we could even measure the heat that is thrown off while the iron is rusting. A similar kind of slow fire, without flame, takes place in our own body. Air is breathed into our lungs and meets the blood there. They oxygen of the air is carried to all parts of the body by the blood, and our fat and food are actually burned (slowly and without flame of course) in the body. That is the way the temperature of the body is kept up to 98 degrees when the air outside may be down to zero. (2)

A very pretty experiment can be tried by lighting a match, blowing it out, and then putting the glowing red end into a jar of oxygen. The match instantly bursts into flame and burns very brightly. Blow out the match and try the experiment again. The match will burst into flame by itself, as it were, so long as there is any oxygen left in the jar. Even the diamond will burn in oxygen, though it cannot be burned in air.

(1) Silver and gold do not rust, and that is why they are used for watch cases, coins, and tableware--spoons and forks.
(2) The average temperature of the healthy human body is between 98 degrees and 99 degrees.

pg 157

Hydrogen gas can be prepared by putting some water and a few scraps of zinc in a stoppered bottle (see Fig. 142) and by adding hydrochloric acid, which is a combination of hydrogen and chlorine.

{Zinc + water} + {hydrogen + chlorine }=

{water + chloride of zinc } + hydrogen (this goes over in the tube)
{ (these stay in the bottle)}

The hydrogen can be collected as the oxygen was before.

Water.--If hydrogen gas is burned in oxygen (the experiemnt is not a safe one for the schoolroom), water is produced. Or, again, pure water can be separated by electricity into hydrogen and oxygen. These two gases, both invisible, combine into water--a liquid; and ice--a solid--is nothing but very cold water. That is, solid ice is made out of two gases.


Fig. 142. Preparation of Hydrogen Gas Put water and scraps of zinc into the stoppered bottle and add hydrochloric acid through the straight funnel. The freed hydrogen gas will escape through the bent tube and can be collected under water and kept for use in a jar. (Leave the jar upside down.) (1)
Hydrogen is one of the lightest of gases, and it is exactly suitable for the filling of balloons. Fourteen cubic feet of hydrogen weighs only as much as one cubic foot of air. This gas is expensive, however, and most balloons are filled with ordinary illuminating gas, which is much cheaper than hydrogen although not so good for the purpose.

(1) None of these experiments are to be tried by children.

pg 158

Chemical Elements.--When a chemist sees a substance new to him--a mineral, for instance--the first thing he tries to find out is whether it is a combination of substance that he knows already. For example, he finds that salt is made out of chlorine (a gas) and sodium (a very light metal). Then he tries to see if he can separate chlorine into any other two substances; he cannot do it, or, at any rate, chemists have not done it so far. Neither have they separated sodium into any simpler things. Substances that cannot be separated into simpler substances are called elements. Here is a list of the most familiar.

METALS

Aluminum                 Potassium
Calcium                     Quicksilver (a liquid metal)
Copper                     *Nickel
Gold                         Silver
Iron                         Tin
Lead                         Zinc
Sodium

NON-METALS

*Arsenic                 *Iodine
Carbon                     Nitrogen (a gas)
Chlorine (a gas)         Oxygen (a gas)
Hydrogen (a gas)     *Phosphorus
Sulphur

There are twenty-two elements named in this table. If all known elements were included, there would be about seventy names.

Every single thing on earth that you can name is made up of one, or two, or three, or more of these seventy elements; and it is exceedingly interesting to remember that, so far as we know, everything on the sun, the moon, and the planets is made up in the same way.

pg 159

Some of the stars and some of the nebulae may have elements unknown to our chemists, but the solar system--the sun, the earth, and the planets--seem to be all of a piece. Ninety-nine hundredths of all the matter in the solar system is made up of the eighteen elements who names are not marked with an asterisk (*) in the table just preceding.

Chemical Compounds.--Nearly all the substances that we handle are compounds, not elements.

Diamond is pure carbon.
The black lead of a lead pencil is nearly pure carbon.
Sugar is carbon, hydrogen, and oxygen.
Human hair is carbon, hydrogen, oxygen, nitrogen, and sulphur.
Indigo is carbon, hydrogen, oxygen, and nitrogen.
Quinine is carbon, hydrogen, nitrogen, oxygen, and sulphur.
Air is a mixture of oxygen and nitrogen.
Water is oxygen and hydrogen.
Steel is iron, with some nickel, phosphorus, etc.
Wood is chiefly carbon, oxygen, hydrogen, and nitrogen.
Leather is chiefly carbon, oxygen, hydrogen, and nitrogen.
Human flesh is chiefly carbon, hydrogen, and oxygen, with some sulphur, nitrogen, phosphorus, calcium, sodium, potassium, and magnesium.
Fat is carbon, hydrogen, and oxygen.
Lean is carbon, hydrogen, oxygen, nitrogen, and sulphur.
Milk is water (oxygen and hydrogen), containing fat, etc. (carbon, hydrogen, oxygen, nitrogen, and sulphur).


Thanks to Dawn Taylor for cropping the pictures for this chapter!!

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