M. Pohl on White Gunpowder. 59 



would be difficult to state any thing with accuracy without very 

 numerous analyses, and they would differ according as the com- 

 bustion was tree or in a closed space, and whether it was 

 slow or rapid. Assuming that the possible products of decom- 

 position of the ferrocyanide are nitrogen, cyanide of potassium, 

 and a carbide of iron of the formula FeC 2 , the decomposition 

 might be represented in the following manner : — 



K a FeCy 3 + C 12 H 1, 11 + 3(KOC10 5 ) = 2KCy + 3KCl + FeC 2 

 -fN + 6CO + 6C0 2 +14HO; 



according to which 100 parts of the powder would yield 52*56 

 parts of non-volatile, and 47*44 of gaseous substances. 



The decomposition may take place in conformity with other 

 reactions, but from a preliminary investigation this appears the 

 most probable. 



In accordance with this, 100 parts of the powder would 

 yield — 



Nitrogen . . . , . 1*86 



Carbonic oxide . . . 11 19 



Carbonic acid .... 17*59 



Water 16-79 



47-43 

 and 



Cyanide of potassium . 17*38 



Chloride of potassium . 29*84 



Carbide of iron . . . 5*33 



hence, reduced to volumes at 0° and 760 millims., 100 parts 

 would yield — 



Nitrogen . . . . 1927 cub. centims. 

 Carbonic oxide . . 8943 „ 



Carbonic acid . . . 8943 „ 



Aqueous vapour . . 20867 „ 



40680 

 Pohl calculates from this that the quantity of heat furnished 

 by the combustion of this substance would be equal to 506*3 

 thermal units. The temperature of the combustion, is obtained 

 by dividing the number of thermal units by the sum of the spe- 

 cific heats of the products of combustion, which amounts to 

 0*2636 ; and this gives 1920° C. as the temperature. From Bun- 

 sen and Schischkoffs research*, it appears that the heating effect 

 of ordinary gunpowder is 619*5 thermal units, and that the 

 temperature of its free combustion is 2993° C. It furnishes in 



* Phil. Mag. vol. xv. p. 489. 



