he contents are allowed to run off into a storage
reservoir. Here they arrange themselves into two layers, the top of which
consists of the nitrobenzene which has been produced, together with some
benzene which is still unacted upon. The mixture is then freed from the
latter by treatment with a current of steam. Nitrobenzene presents itself
as a yellowish oily liquid, with a peculiar taste as of bitter almonds.
It was formerly in great demand by perfumers, but its poisonous
properties render it a dangerous substance to deal with. In practice a
given quantity of benzene will yield about 150 per cent of nitrobenzene.
Stated chemically, the reaction is shown by the following equation:--

C_{6}H_{6} + HNO_{3} = C_{6}H_{5}NO_{2}, + H_{2}O
(Benzene) (Nitric acid) (Nitrobenzene) (Water).

The water which is thus formed in the process, by the freeing of one of
the atoms of hydrogen in the benzene, is absorbed by the sulphuric acid
present, although the latter takes no actual part in the reaction.

From the nitrobenzene thus obtained, the aniline which is now used so
extensively is prepared. The component atoms of a molecule of aniline are
shown in the formula C_{6}H_{5}NH_{2}. It is also known as phenylamine or
amido-benzole, or commercially as aniline oil. There are various methods
of reducing nitrobenzene for aniline, the object being to replace the
oxygen of the former by an equivalent number of atoms of hydrogen. The
process generally used is that known as Bechamp's, with slight
modifications. Equal volumes of nitrobenzene and acetic acid, together
with a quantity of iron-filings rather in excess of the weight of the
nitrobenzene, are placed in a capacious retort. A brisk effervescence
ensues, and to moderate the increase of temperature which is caused by
the reaction, it is found necessary to cool the retort. Instead of acetic
acid hydrochloric acid has been a good deal used, with, it is said,
certain advantageous results. From 60 to 65 per cent. of aniline on the
quantity of nitrobenzene used, is yielded by Bechamp's process.

Stated in a few words, the above is the process adopted on all hands for
the production of commercial aniline, or aniline oil. The details of the
distillation and rectification of the oil are, however, as varied as they
can well be, no two manufacturers adopting the same process. Many of the
aniline dyes depend entirely for their superiority, on the quality of th