298 HEAT OF FORMATION OF MERCURIC FULMINATE. 



The detonation should be effected in an atmosphere of 

 nitrogen in order to avoid the partial oxidation of the carbon 

 monoxide. 



4. Heat of decomposition. Detonation, effected in the 

 calorimetric bomb, gave for one equivalent ( = 284 grms.) 4- 

 116 Gal. at constant volume, which corresponds to the following 

 decomposition : 



CHg(N0 2 )CN = 200 + N 2 + Hg, 



or 114*5 Cal. at constant pressure, which for one grm. = 403 

 cal. 



According to this equation, only carbon monoxide, nitrogen, 

 and mercury vapour are formed. One only of these bodies is a 

 compound ; it is stable and not susceptible of dissociation, which 

 accounts for the suddenness of the explosion. Moreover, the 

 heat is disengaged at first, and all the gases are produced without 

 the occurrence during cooling of any progressive recombination, 

 which would tend to moderate the expansion and diminish the 

 violence of the first shock. 



The condensation of the mercury vapour, however, exercises 

 an influence of this kind ; but only after the principal cooling 

 has lowered the temperature below 360. 



5. Heat of formation from the elements. From the above 

 data we find that 



C 2 (diamond) + Hg + N 2 + 2 



absorbs + 51*6 - 114*5 = - 62*9 Cal. for 284 grms. 



There is, therefore, absorption of heat in the formation of the 

 fulminate a property in concordance with the explosive 

 character of the substance. 



6. Heat of total combustion. Admitting the following re- 

 action 



CHg(N0 2 )CT + 2 = 2C0 2 + Hg + N 2 , 



we shall get + 250 - 9 Cal. for one equivalent ; or for one grm., 

 883 cal. 



This combustion may be effected, in the case of primings, by 

 mixing potassium chlorate with the fulminate, which causes 

 the heat disengaged to amount to + 262*9 Cal. per equivalent. 

 But in this instance we are heating 406*6 grms. of material 

 instead of 284 grms ; we get then for one grm., 647 cal. 



We should also note the effects of expansion, due to the dis- 

 sociation of the carbonic acid, which renders the mixture less 

 sudden in its effects than pure fulminate. 



