The Chemistry of Powder and Explosives - Sciencemadness Dot Org

168 AROMATIC NITRO COMPOUNDS
bright lemon yellow color and a meta-stable form which is a
brilliant red. These differ slightly in their crystal angles but show
no detectable difference in their explosive properties. Thallium
pierate similarly exists in two forms.
Ammonium pierate is prepared by suspending picric acid in a convenient
quantity of hot water, adding strong ammonia water until everything
goes into solution and a large excess of ammonia is present, and
allowing to cool. The crystals which separate are the red form. A dry
sample of this material in a stoppered bottle will remain without apparent
change for many years. In contact with its saturated aqueous
solution it changes to the yellow form during several months. The
yellow form of ammonium pierate is best procured by recrystallizing
the red form several times from water.
Pure ammonium pierate melts with decomposition at 265-271°.
It is more soluble in warm alcohol than guanidine pierate 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.
SOLUBILITY OP AMMONIUM PICRATB
(Grams per 100 cc. of solution)
Temperature, °C. Ethyl Acetate Ethyl Alcohol
0 0.290 0.515
10 0.300 0.690
20 0.338 0.850
30 0.380 1.050
40 G.420 1.320
50 0.450 1.890
60 0.500 2.165
70 0.540 2.760
80 0.560 3.620
Guanidine Pierate
Guanidine pierate is procured as a yellow, finely crystalline
precipitate by mixing warm solutions of guanidine nitrate and
ammonium pierate. It is even less sensitive to blow and to shock
than ammonium pierate; 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° ^o