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530 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

GUANIDINE PICRATE

Guanidine picrate may be obtained by acting with a warm aqueous solution

of ammonium picrate on an aqueous solution of guanidine nitrate. A yellow, crystal-

line precipitate of guanidine picrate (m. p. 319°C, with decomposition) is formed.

Guanidine picrate has been suggested in the United States as a high explosive,

being of exceptionally low sensitivity to impact and friction.

DANGER PRODUCED BY PICRATES

If picric acid is free from picrates, its burning, even in large quantities, does

not present any risk of explosion. A case is known (in the U.S.A.) when 100 tons

of picric acid caught fire. It burned relatively smoothly although the flame attained

a height of 10-15 m and a characteristic loud whistling noise was heard. Slight

explosions were observed only when roof fragments fell into the burning mass,

causing blast from a violent eruption of confined gases. However, had picrates

been present, such a fire might have ended with a violent detonation but according

to Sapozhnikov [19] it is sufficient for molten picric acid merely to come into contact

with metal to create favourable conditions for the formation of picrates.

A violent explosion of picric acid in a Manchester factory in 1887 was ascribed

to the formation of picrates. Burning, molten picric acid flowed down onto litho-

pone, forming lead picrate which in consequence caught fire. The latter, being an

initiator, detonated and caused the picric acid to detonate.

A fire, followed by an explosion at Huddersfield in 1900 was also caused by

detonation of iron picrate (presumably Fe2+). The iron picrate had been formed

on the surface of steam pipes located in the picric acid drier shop. It ignited when

a plumber, unaware of the fact, struck one of the pipes with a hammer. The flame

spread along the pipe and set the drying picric acid on fire.

In a French factory streaks of picric acid had been formed alongside a narrow

gauge railway. AS the soil beneath was calcareous, calcium picrate formed which,

having dried up in the summer, was ignited by friction or a blow, spreading flames

all over those parts of the factory marked with calcium picrate streaks.

TETRA- AND PENTA-NITRO DERIVATIVES OF PHENOL

TETRANITROPHENOL

This compound (m. p. 140°C) was obtained by Nietzki and Burckhardt [20]