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 the nitro groups alone are present.

The formula of chloro-di-nitro-benzol is C_{6}H_{3}Cl(NO_{2})_{2}. The
theoretical percentage of nitrogen, therefore, is 13.82, and of chlorine
17.53. Dr Roth states that, from experiments he has made, the dynamic
effect is considerably increased by the introduction of chlorine into the
nitro compound. Roburite burns quickly, and is not sensitive to shock; it
must be used dry; it cannot be made to explode by concussion, pressure,
friction, fire, or lightning; it does not freeze; it does not give off
deleterious fumes, and it is to all intents and purposes flameless; and
when properly tamped and fired by electricity, can be safely used in fiery
mines, neither fine dust nor gases being ignited by it. The action is
rending and not pulverising. Compared to gunpowder, it is more powerful in
a ratio ranging from 2-1/2 to 4 to 1, according to the substance acted
upon. It is largely used in blasting, pit sinking, quarrying, &c., but
especially in coal mining. According to Dr Roth, the following is the