The Chemistry of Powder and Explosives - Sciencemadness Dot Org

166 AROMATIC NITRO COMPOUNDS
Cast picric acid has a density of about 1.64. The density of
pellets of compressed picric acid, according to Dautriche, is as
follows.
PRESSURE: KILOS PER SQUARE CENTIMETER
275
685
1375
2060
2750
3435
4125
DENSITY
1.315
1.480
1.614
1.672
1.714
1.731
1.740
The use of picric acid as an explosive appears to have been
suggested first in 1867 by Borlinetto, 65 who proposed a mixture of
picric acid 35 per cent, sodium nitrate 35 per cent, and potassium
chromate 30 per cent for use in mining. Sprengel in 1873 reported
that picric acid in conjunction with suitable oxidizing agents is
a powerful explosive. In 1885 Turpin 66 patented its use, both
compressed and cast, in blasting cartridges and in shells, and
shortly thereafter the French government adopted it under the
name of melinite. In 1888 Great Britain commenced to use it
under the name of lyddite. Cast charges require a booster, for
which purpose compressed picric acid or tetryl is generally used.
The loading of picric acid into shells by pouring is open to two
objections, which, however, are not insuperable, namely, the
rather high temperature of the melt and the fact that large
crystals are formed which may perhaps cause trouble on setback.
Both difficulties are met by adding to the picric acid another
explosive substance which lowers its melting point. Mixtures are
preferred which melt between 70° and 100°, above 70° in order
that .exudation may be less likely and below 100° in order that
the explosive may be melted by hot water. The mixtures are not
necessarily eutectics. Two of the favorite French explosives have
been DD 60/40, 'which consists of 60 parts picric acid and 40
parts dinitrophenol; and cresylite 60/40, 60 parts trinitro-mcresol
and 40 parts picric acid. Others are MDPC, picric acid
55 parts, dinitrophenol 35, and trinitro-m-cresol 10; and MTTC,
which has the same composition as MDPC except that TNT is
used instead of dinitrophenol. All these mixtures melt between
65 Giua, op. cit., pp. 287, 296.
88 Fr. Pat. 167,512 (1885).