re into the cup and try to light it.
Will it burn?

Now pour this mixture into a flask. Pass the end of the long
bent glass rod (the "worm") through a one-hole rubber stopper
that will fit the flask (Fig. 55). Put the flask on a ring
stand and, holding it steady, fasten the neck of the flask
with a clamp that is attached to the stand. Put the stopper
with the worm attached into the flask, and support the worm
with another clamp. Put a dry cup or beaker under the lower
end of the worm. Set a lighted burner under the flask. When
the mixture in the flask begins to boil, turn the flame
down so that the liquid will just barely boil; if it boils
violently, part of the liquid splashes up into the lower end
of the worm.

As the vapor rises from the mixture and goes into the worm,
it cools and condenses. When several drops have gone down into
the cup, try lighting them. What is it that has boiled and
then condensed: the water, the alcohol, or the blueing? Or is
it a mixture of them?

[Illustration: FIG. 55. By distillation clear alcohol can be separated
from the water and red ink with which it was mixed.]

Alcohol is really made in this way, only it is already mixed in the
water in which the grains fermented and from which people then distil
it. Gasoline and kerosene are distilled from petroleum; there is a
whole series of substances that come from the crude oil, one after
the other, according to their boiling points, and what is left is the
foundation for a number of products, including paraffine and vaseline.

EXPERIMENT 40. Put some dry, fused calcium chlorid on a saucer
and set it on the plate of the air pump. This is to absorb the
moisture when you do the experiment. (This calcium chlorid
is _not_ the same as the chlorid of lime which you buy for
bleaching or disinfecting.) Fill a flask or beaker half full
of water and bring it to a boil over a Bunsen burner. Quickly
set the flask on the plate of the air pump. The water will
stop boiling, of course. Cover the flask and the saucer of
calcium chlorid with the bell jar immediately, and pump the
air out of the jar. Watch the water.

The water begins to boil again because water will boil at a lower
temperature when there is less air pressure on its surface. So
although the water is too cool to boil in the open air, it is still
hot enough to boil when the air p