nt arrangement of the atoms in the molecule. Such compounds are
said to be isomeric. Dextrose and levulose are also isomeric.

~Dextrose~ (_grape sugar, glucose_) (C_{6}H_{12}O_{6}). This sugar is
present in many fruits and is commonly called grape sugar because of its
presence in grape juice. It can be obtained by heating cane sugar with
dilute acids, as explained above; also by heating starch with dilute
acids, the change being as follows:

C_{6}H_{10}6_{5} + H_{2}O = C_{6}H_{12}O_{6}.

Pure dextrose is a white crystalline solid, readily soluble in water,
and is not so sweet as cane sugar. In the presence of yeast it undergoes
alcoholic fermentation. It is prepared from starch in large quantities,
and being less expensive than cane sugar, is used as a substitute for it
in the manufacture of jellies, jams, molasses, candy, and other sweets.
The product commonly sold under the name of _glucose_ contains about 45%
of dextrose.

~Levulose~ _(fruit sugar)_(C_{6}H_{12}O_{6}). This sugar is a white solid
which occurs along with dextrose in fruits and honey. It undergoes
alcoholic fermentation in the presence of yeast.

~Cellulose~ (C_{6}H_{10}O_{5}). This forms the basis of all woody fibers.
Cotton and linen are nearly pure cellulose. It is insoluble in water,
alcohol, and dilute acids. Sulphuric acid slowly converts it into
dextrose. Nitric acid forms nitrates similar to nitroglycerin in
composition and explosive properties. These nitrates are variously known
as nitrocellulose, pyroxylin, and gun cotton. When exploded they yield
only colorless gases; hence they are used especially in the manufacture
of smokeless gunpowder. _Collodion_ is a solution of nitrocellulose in a
mixture of alcohol and ether. _Celluloid_ is a mixture of nitrocellulose
and camphor. _Paper_ consists mainly of cellulose, the finer grades
being made from linen and cotton rags, and the cheaper grades from straw
and wood.

~Starch~ (C_{6}H_{10}O_{5}). This is by far the most abundant carbohydrate
found in nature, being present especially in seeds and tubers. In the
United States it is obtained chiefly from corn, nearly 80% of which is
starch. In Europe it is obtained principally from the potato. It
consists of minute granules and is practically insoluble in cold water.
These granules differ somewhat in appearance, according to the source of
the starch, so that it is often possible to determine from what plant
the starch was obtained. When heated