c.

~The Explosives derived from Benzene.~--There is a large class of
explosives made from the nitrated hydro-carbons--benzene, C_{6}H_{6};
toluene, C_{7}H_{8}; naphthalene, C_{10}H_{8}; and also from phenol (or
carbolic acid), C_{6}H_{5}OH. The benzene hydro-carbons are generally
colourless liquids, insoluble in water, but soluble in alcohol and ether.
They generally distil without decomposition. They burn with a smoky flame,
and have an ethereal odour. They are easily nitrated and sulphurated;
mono, di, and tri derivatives are readily prepared, according to the
strength of the acids used. It is only the H-atoms of the benzene nucleus
which enter into reaction.

Benzene was discovered by Faraday in 1825, and detected in coal-tar by
Hofmann in 1845. It can be obtained from that portion of coal-tar which
boils at 80 deg. to 85 deg. by fractionating or freezing.[A] The ordinary benzene
of commerce contains thiophene (C_{4}H_{4}S), from which it may be freed
by shaking with sulphuric acid. Its boiling point is 79 deg. C.; specific
gravity at 0 deg. equals 0.9. It burns with a luminous smoky flame, and is a
good solvent for fats, resins, sulphur, phosphorus, &c. Toluene was
discovered in 1837, and is prepared from coal-tar. It boils at 110 deg. C.,
and is still liquid at 28 deg. C.

[Footnote A: It may be prepared chemically pure by distilling a mixture of
benzoic acid and lime.]

The mono-, chloro-, bromo-, and iodo-benzenes are colourless liquids of
peculiar odour. Di-chloro-, di-bromo-benzenes, tri- and hexa-chloro- and
bromo-benzenes, are also known; and mono-chloro-, C_{6}H_{4}Cl(CH_{3}),
and bromo-toluenes, together with di derivatives in the ortho, meta, and
para modifications. The nitro-benzenes and toluenes are used as
explosives. The following summary is taken from Dr A. Bernthsen's "Organic
Chemistry":--

SUMMARY.
____________________________________________________________________
| |
| C_{6}H_{5}(N0_{2}) Nitro-benzene. Liq. B.Pt. 206 deg. C. |
| |
| C_{6}H_{4}(NO_{2})_{2} Ortho-, meta-, and para- di-nitro-benzenes. |
| Solid. M.P. 118 deg., 90 deg., and 172 deg. C. |
| |
| C_{6}H_{3}(NO_{3})_{3} S.-Tri-nitro-benzene. Solid. M.P. 121