with water the granules burst and
the starch partially dissolves. Dilute acids, as well as certain
enzymes, convert it into dextrose or similar sugars. When seeds
germinate the starch present is converted into soluble sugars, which are
used as food for the growing plant.

~Chemical changes in bread making.~ The average composition of wheat flour
is as follows:

Water. 13.8%
Protein (nitrogenous matter) 7.9
Fats 1.4
Starch 76.4
Mineral matter 0.5

In making bread the flour is mixed with water and yeast, and the
resulting dough set aside in a warm place for a few hours. The yeast
first converts a portion of the starch into dextrose or a similar sugar,
which then undergoes alcoholic fermentation. The carbon dioxide formed
escapes through the dough, making it light and porous. The yeast plant
thrives best at about 30 deg.; hence the necessity for having the dough in a
warm place. If the temperature rises above 50 deg., the vitality of the
yeast is destroyed and fermentation ceases. In baking the bread, the
heat expels the alcohol and also expands the bubbles of carbon dioxide
caught in the dough, thus increasing its lightness.

SOME DERIVATIVES OF BENZENE

Attention has been called to the complex nature of coal tar. Among the
compounds present are the hydrocarbons, benzene, toluene, naphthalene,
and anthracene. These compounds are not only useful in themselves but
serve for the preparation of many other important compounds known under
the general name of coal-tar products.

~Nitrobenzene~ (_oil of myrbane_) (C_{6}H_{5}NO_{2}). When benzene is
treated with nitric acid a reaction takes place which is expressed by
the following equation:

C_{6}H_{6} + HNO_{3} = C_{6}H_{5}NO_{2} + H_{2}O.

The product C_{6}H_{5}NO_{2} is called nitrobenzene. It is a slightly
yellowish poisonous liquid, with a characteristic odor. Its main use is
in the manufacture of aniline.

~Aniline~ (C_{6}H_{5}NH_{2}). When nitrobenzene is heated with iron and
hydrochloric acid the hydrogen evolved by the action of the iron upon
the acid reduces the nitrobenzene in accordance with the following
equation:

C_{6}H_{5}NO_{2} + 6H = C_{6}H_{5}NH_{2} + 2H_{2}O.

The resulting compound is known as aniline, a liquid boiling at 182 deg..
When first prepared it is colorless, but darkens on standing. Large
quantities