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Such a thing would be absolutely impossible, and chemically impossible,
without oxygen.
[Illustration: Fig. 21.]
Can we get it from the air? Well, there are some very complicated and
difficult processes by which we can get it from the air; but we have
better processes. There is a substance called the black oxide of
manganese: it is a very black-looking mineral, but very useful, and when
made red-hot it gives out oxygen. Here is an iron bottle which has had
some of this substance put into it, and there is a tube fixed to it, and a
fire ready made, and Mr. Anderson will put that retort into the fire, for
it is made of iron, and can stand the heat. Here is a salt called chlorate
of potassa, which is now made in large quantities for bleaching, and
chemical and medical uses, and for pyrotechnic and other purposes. I will
take some and mix it with some of the oxide of manganese (oxide of copper,
or oxide of iron would do as well); and if I put these together in a
retort, far less than a red heat is sufficient to evolve this oxygen from
the mixture. I am not preparing to make much, because we only want
sufficient for our experiments; only, as you will see immediately, if I
use too small a charge, the first portion of the gas will be mixed with
the air already in the retort, and I should be obliged to sacrifice the
first portion of the gas, because it would be so much diluted with air;
the first portion must therefore be thrown away. You will find in this
case, that a common spirit-lamp is quite sufficient for me to get the
oxygen, and so we shall have two processes going on for its preparation.
See how freely the gas is coming over from that small portion of the
mixture. We will examine it, and see what are its properties. Now, in this
way we are producing, as you will observe, a gas just like the one we had
in the experiment with the battery, transparent, undissolved by water, and
presenting the ordinary visible properties of the atmosphere. (As this
first jar contains the air, together with the first portions of the oxygen
set free during the preparation, we will carry it out of the way, and be
prepared to make our experiments in a regular, dignified manner.) And,
inasmuch as that power of making wood, wax, or other things burn, was so
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