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PICRIC ACID ETHERS 553

The two compounds VI and VII were prepared by nitrating methylene- and

ethylene-diphenyl ethers respectively (Stefanovic and Ciric [16a]).

HEXANITRODIPHENYL SULPHIDE

Only one representative of this group is known in industrial practice, namely

hexanitrodiphenyl sulphide (picryl sulphide, hexasulphide, Hexide) of melting

point 234°C.

2,2’,4,4’,6,6’-Hexanitrodiphenyl sulphide forms golden crystals, difficult to dis-

solve in most organic solvents.

The compound was first obtained by Sprengstoff A. G. Carbonit [17], in 1912,

from picryl chloride and sodium thiosulphate in alcoholic solution in the presence

of magnesium carbonate for binding the sulphuric acid which forms in the reaction:

+ 2NaCl + H 2 SO 4 (11)

The yield obtained is about 90% of the theoretical. According to Giua [18],

thiourea may be used in place of sodium thiosulphate.

The compound may also be prepared from picryl-pyridinium chloride (see p. 464).

The product does not colour the skin and, according to the German literature,

is not toxic. However, Roche and V. Thomas [19] reported its vapour to be

strongly irritant. During World War I the Germans used picryl sulphide in

mixtures with TNT, with or without ammonium nitrate, for filling bombs.

Since the explosive decomposition of picryl sulphide and of its mixtures yields

SO 2 among other decomposition products, the compound has been proposed for

filling shells to be used against confined objectives, such as ships’ interiors, bunkers,

etc. AS a result of explosion a noxious atmosphere containing SO 2 would result.

Picryl sulphide is a stable explosive. Van Duin and van Lennep [8] found its

initiation temperature to be 302-319°C depending on the rate of heating. When

kept at 95°C for 30 days the substance remained unchanged.

Its sensitiveness to impact is somewhat lower than that of tetryl, but higher than

that of hexyl or picric acid.
The lead block expansion given by picryl sulphide is equal or, according to

some authors, slightly larger than that given by picric acid (325-350 cm^3 ).