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, crystalline 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. 

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. 

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It is important that the HE charge be so insensitive that it will not be exploded by the tremendous shock caused by the impact of the shell on the armor. However, it must be sensitive enough to be detonated by the action of the fuze. Black powder fulfills this condition and was used until the end of the last century. It was replaced later in some countries by some AN expls, such as ammonals. These expls were more powerful than black powder, bur inferior to ammonium picrate (Expl D) and guanidine picrate (Gu P) commonly used now... 

Pure ammonium picrate melts with decomposition at 265-271°. It is more soluble in warm alcohol than guanidine picrate is, and more soluble in acetone than in alcohol, but it goes into solution very slowly in alcohol and crystallizes out again very slowly when the liquid is allowed to stand. 

Guanidine picrate is procured as a yellow, finely crystalline precipitate by mixing warm solutions of guanidine nitrate and ammonium picrate. It is even less sensitive to blow and to shock than ammonium picrate it is not detonated by fulminate and is used with a picric acid booster. The pure material, recrystallized from alcohol or from water, in both of which solvents it is sparingly soluble, melts with decomposition at 318.5-319.5°. 

Guanidine picrate is sparingly soluble in water and alcohol. It is prepared by mixing solutions of guanidine nitrate and ammonium picrate. 

Guanidine Picrate. CHsN3+CgH307N3 yel crysts explds at about 498° (Beil 6, 279 [265])... 

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