alloon with hydrogen.]

[Illustration: FIG. 163. Adding more acid without losing the gas.]

Here is another experiment with hydrogen:

EXPERIMENT 92. Put a wad of zinc shavings, about the size of
the end of your little finger, into the bottom of a test tube.
Cover it with hydrochloric acid (HCl) diluted one to three,
as in the preceding experiment. After the bubbles have been
rising for a couple of minutes, take the test tube to the side
of the laboratory where the burners are, and hold a lighted
match at its mouth. Will hydrogen burn?

Remember that the hydrogen which the zinc is driving out of the acid
is exactly the same as the hydrogen you drove out of water with an
electric current. There is a metal called _sodium_ (Na) and another
called _potassium_ (K) which are as soft as stiff putty and as shiny
as silver; if you put a tiny piece of sodium (Na) or potassium (K) on
water, it will drive the hydrogen out of the water just as zinc drove
it out of the acid. The action is so swift and violent and releases so
much heat that the hydrogen which is set free catches fire. This makes
it look as if the metal were burning as it sputters around on top
of the water. There is so much sputtering that the experiment
is dangerous; people have been blinded by the hot alkaline water
spattering into their eyes. So you cannot try this until sometime when
you take a regular course in chemistry.

[Illustration: FIG. 164. Trying to see if hydrogen will burn.]

GETTING OXYGEN, A GAS, FROM TWO SOLIDS. Oxygen (O) can hide just as
successfully as hydrogen. Practically all elements can do the same by
combining with others. Here is an experiment in which you can get the
gas, oxygen, out of a couple of solids. If you went to the moon or
some other place where there is no air, you could carry oxygen
very conveniently locked up in these solid substances. Oxygen, you
remember, is the part of the air that keeps us alive when we breathe
it.

EXPERIMENT 93. In a test tube mix about one half teaspoonful
each of white potassium chlorate crystals and black grains of
manganese dioxid. Put a piece of glass tubing through a cork
so that the tubing will stick down a little way into the test
tube. _Do not put the glass tubing through the cork while the
cork is in the test tube: insert the glass tubing first, then
put the cork into the test tube._ Put one end of a 2-foot
piece of rubber tubi