e nitro
derivatives of the hydrocarbons of the benzene series is very simple. It
is only necessary to bring the hydrocarbon into contact with strong nitric
acid, when the reaction takes place, and one or more of the hydrogen atoms
of the hydrocarbon are replaced by the nitryl group (NO_{2}). Thus by the
action of nitric acid on benzene (or benzol), mono-nitro-benzene is
formed:--

C_{6}H_{6} + HNO_{3} = C_{6}H_{5}.NO_{2} +H_{2}O.
Mono-nitro-benzene.

By the action of another molecule of nitric acid, the di-nitro-benzene is
formed:--

C_{6}H_{5}.NO_{2} + HNO_{3} = C_{6}H_{4}(NO_{2})_{2} + H_{2}O.
Di-nitro-benzene.

These nitro bodies are not acids, nor are they ethereal salts of nitrous
acid, as nitro-glycerine is of glycerine. They are regarded as formed from
nitric acid by the replacement of hydroxyl by benzene radicals.

~Mono-nitro Benzene~ is made by treating benzene with concentrated nitric
acid, or a mixture of nitric and sulphuric acids. The latter, as in the
case of the nitration of glycerine, takes no part in the reaction, but
only prevents the dilution of the nitric acid by the water formed in the
reaction. Small quantities may be made thus:--Take 150 c.c. of H_{2}SO_{4}
and 75 c.c. HNO_{3}, or 1 part nitric to 2 parts sulphuric acid, and put
in a beaker standing in cold water; then add 15 to 20 c.c. of benzene,
drop by drop, waiting between each addition for the completion of the
reaction, and shake well during the operation. When finished, pour
contents of beaker into about a litre of cold water; the nitro-benzol will
sink to the bottom. Decant the water, and wash the nitro-benzol two or
three times in a separating funnel with water. Finally, dry the product by
adding a little granulated calcium chloride, and allowing to stand for
some little time, it may then be distilled. Nitro-benzene is a heavy oily
liquid which boils at 205 deg. C., has a specific gravity of 1.2, and an odour
like that of oil of bitter almonds. In the arts it is chiefly used in the
preparation of aniline.

~Di-nitro Benzene~ is a product of the further action of nitric acid on
benzene or nitro-benzene. It crystallises in long fine needles or thin
rhombic plates, and melts at 89.9 deg. C. It can be made thus:--The acid
mixture used consists of equal parts of nitric and sulphuric acids, say 50
c.c. of each, and without cooling add very slowly 10 c.c. of benzene from
a pipette. A