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 equation of its decomposition:—­

C_{6}H_{3}Cl(NO_{2})_{2} + 9HN_{4}NO_{3} = 6CO_{2} + 20N + HCl.

In appearance roburite is a brownish yellow powder, with the characteristic smell of nitro-benzol.  Its specific gravity is 1.40.  The Company’s statement that the fumes of roburite were harmless having been questioned by the miners of the Garswood Coal and Iron Works Colliery, a scientific committee was appointed by the management and the men jointly for the purpose of settling the question.  The members of this committee were Dr N. Hannah, Dr D.J.  Mouncey, and Professor H.B.  Dixon, F.R.S., of Owens College.  After a protracted investigation, a long and technical report was issued, completely vindicating the innocuousness of roburite when properly used.  In the words of The Iron and Coal Trades’ Review (May 24, 1889), “The verdict, though not on every point in favour of the use in all circumstances of roburite in coal mines, is yet of so pronounced a character in its favour as an explosive that it is impossible to resist the conclusion that the claims put forward on its behalf rest on solid grounds.”