| | Oxygen. | Oxygen, . . . . 88.9
| | |
| |_________| Hydrogen, . . . 11.1
| Hydrogen. | -----
| | 9 Water,. . . . . 100.0
| |
| |
| |
|___________|

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