lid
sodium hydroxide. A little baker's yeast is now added to the
solution in flask A, and the apparatus is connected, as shown
in the figure. If the temperature is maintained at about 30 deg.,
the reaction soon begins. The bubbles of gas escape through the
limewater in B. A precipitate of calcium carbonate soon forms
in the limewater, showing the presence of carbon dioxide. The
sodium hydroxide in tube C prevents the carbon dioxide in the
air from acting on the limewater. The alcohol remains in the
flask A and may be separated by fractional distillation.

[Illustration: Fig. 90]

2. _Properties._ Ethyl alcohol is a colorless liquid with a pleasant
odor. It has a density of 0.78 and boils at 78 deg.. It resembles methyl
alcohol in its general properties. It is sometimes used as a source of
heat, since its flame is very hot and does not deposit carbon, as the
flame from oil does. When taken into the system in small quantities it
causes intoxication; in larger quantities it acts as a poison. The
intoxicating properties of such liquors as beer, wine, and whisky are
due to the alcohol present. Beer contains from 2 to 5% of alcohol, wine
from 5 to 20%, and whisky about 50%. The ordinary alcohol of the
druggist contains 94% of alcohol and 6% of water. When this is boiled
with lime and then distilled nearly all the water is removed, the
distillate being called _absolute alcohol_.

~Commercial preparation of alcohol.~ Alcohol is prepared
commercially from starch obtained from corn or potatoes. The
starch is first converted into a sugar known as maltose, by the
action of _malt_, a substance prepared by moistening barley
with water, allowing it to germinate, and then drying it. There
is present in the malt a substance known as diastase, which has
the property of changing starch into maltose. This sugar, like
glucose, breaks down into alcohol and carbon dioxide in the
presence of yeast. The resulting alcohol is separated by
fractional distillation.

~Denatured alcohol.~ The 94% alcohol is prepared at present at a
cost of about 35 cents per gallon, which is about half the cost
of the preparation of methyl alcohol. The government, however,
imposes a tax on all ethyl alcohol which amounts to $2.08 per
gallon on the 94% product. This increases its cost to such an
extent that it is not economical to use it fo