if the nitro-benzene is for use as essence
of myrbane. The waste acids, specific gravity 1.6 to 1.7, contain a little
nitro-benzene in solution and some oxalic acid. They are concentrated in
cast-iron pots and used over again.

~Di-nitro Benzene~ is obtained by treating a charge of the hydrocarbon
benzene with double the quantity of mixed acids in two operations, or
rather in two stages, the second lot of acid being run in directly after
the first. The cooling water is then shut off, and the temperature allowed
to rise rapidly, or nitro-benzene already manufactured is taken and again
nitrated with acids. A large quantity of acid fumes come off, and some of
the nitro- and di-nitro-benzol produced comes off at the high temperature
which is attained, and a good condensing apparatus of stoneware must be
used to prevent loss. The product is separated from the acids, washed with
cold water and then with hot. It is slightly soluble in water, so that the
washing waters must be kept and used over again. Finally it is allowed to
settle, and run while still warm into iron trays, in which it solidifies
in masses 2 or 4 inches thick. It should not contain any nitro-benzol, nor
soil a piece of paper when laid on it, should be well crystallised, fairly
hard, and almost odourless. The chief product is meta-di-nitro-benzene,
melting point 89.8, but ortho-di-nitro-benzene, melting point 118 deg., and
para-di-nitro, melting point 172 deg., are also produced. The melting point of
the commercial product is between 85 deg. to 87 deg. C.

Di-nitro-toluene is made in a similar manner. The tri-nitro-benzene can
only be made by using a very large excess of the mixed acids. Nitro-
benzene, when reduced with iron, zinc, or tin, and hydrochloric acids,
forms aniline.

~Roburite.~--This explosive is the invention of a German chemist, Dr Carl
Roth (English patent 267A, 1887), and is now manufactured in England, at
Gathurst, near Wigan. It consists of two component parts, non-explosive in
themselves (Sprengel's principle), but which, when mixed, form a powerful
explosive. The two substances are ammonium nitrate and chlorinated
di-nitro-benzol. Nitro-naphthalene is also used. Nitrate of soda and
sulphate of ammonium are allowed to be mixed with it. The advantages
claimed for the introduction of chlorine into the nitro compound are that
chlorine exerts a loosening effect upon the NO_{2} groups, and enables the
compound to burn more rapidly than when th