e 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."

Roburite was also one of the explosives investigated by the committee
appointed in September 1889 by the Durham Coalowners' and Miners'
Associations, for the purpose of determining whether the fumes produced by
certain explosives are injurious to health. Both owners and workmen were
represented on the