EXPLOSIVE DECOMPOSITION OF POTASSIUM PICBATE. 463 



3. PICRATE POTASSIUM. 



1. Potassium picrate, 



C 6 H 2 K(N0 2 ) 3 0, 



crystallises in long orange-yellow needles, very slightly voluble 

 in water. 



2. It explodes, when heated above 300, much more violently 

 than picric acid. It also explodes by contact with an ignited 

 body, which renders it still more dangerous than black powder. 

 In the dry state its fine and light dust takes fire at a distance, 

 and may cause the whole mass from which it emanates to 

 explode. Operators have been wounded in public lectures by 

 throwing upon lighted coals potassium picrate contained in a 

 flask. This kind of accident is even more to be feared with 

 potassium picrate than with picric acid. The catastrophe in 

 the Place de la Sorbonne (1869) appears due to this property. 

 Potassium picrate is sensitive to shock, and even much more so 

 than picric acid. The addition of 15 per cent, of water deprives 

 it of this sensitiveness. Potassium picrate does not contain 

 enough oxygen to produce complete combustion. Hence the 

 necessity for mixing it with potassium nitrate or chlorate. 



3. Its equivalent is 267. 



4. Its heat of formation from the elements 



C 6 (diamond) + H 2 + K + N 3 + 7 = C 6 H 2 K(N0 2 ) 3 0, 



is equal to -f 117*5 CaL, according to the data of Sarrau and 

 Vieille. 



5. The heat of total combustion by free oxygen 

 2[C 6 H 2 K(N0 2 ) 3 0] + 0* = 2KHC0 3 10C0 2 + H 2 + 6N, 



amounts to 619'7 Cal. (potassium bicarbonate and liquid 

 water). The explosive decomposition of potassium picrate 

 yields products which vary with the conditions, as is generally 

 speaking the case with bodies which do not contain a sufficient 

 quantity of oxygen to produce complete combustion (p. 7). 



Sarrau and Vieille have studied this decomposition minutely. 

 The following are the results obtained by them, 1 with various 

 densities of charge, per 100 vols. 



Densities of charge. 



HCy 



C0 2 



CO 



N 



Volume of gases disengaged per 1 kgm., 5741, 557'9. 



1 " Comptes rendus des stances de 1' Academic des Sciences, 11 torn, xciii. p. 6. 



