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!!
