478 POWDERS WITH A NITRATE BASE. 



3rd. The mixture of sulphur, saltpetre, and charcoal is never 

 absolutely intimate, and undergoes continual variations during 

 the course of the operations. 



4th. The combustion is never total, small quantities of nitre 

 and sulphur principally escaping the reaction owing to the lack 

 of homogeneousness. The saltpetre itself, under the influence of 

 the high temperature of explosion, tends at first to yield the 

 nitrites, then more and more stable compounds (hyponitrites, 

 potassium peroxide, etc.) still imperfectly known. 



5th. The metallic vessels (iron, copper), in which the opera- 

 tions are carried out, are attacked, with the formation of 

 metallic sulphides, single and double sulphides resulting from 

 the association of the former with potassium sulphide. Never- 

 theless the theoretical calculations, however imperfect their 

 relation to practical conditions may be, offer the advantage of 

 indicating the maximum limit of the effects which we may 

 hope to attain, and the direction which should be given to 

 experimental inquiry for this end. In order to explain more 

 clearly the chemical phenomena, the fresh experiments will be 

 given which the author has lately made on various questions 

 relating to the theory of the reactions developed during the 

 explosion of service powder, such as the reactions between the 

 sulphur, the carbon, their oxides and salts ( 2). The decompo- 

 sition by heat of the alkaline sulphides ( 3). The decomposi- 

 tion by heat of the alkaline hyposulphites ( 4). The 

 measurement of the heat of combustion of the charcoal 

 employed in the manufacture of powder ( 5). 



These preliminary notions having been gained, we shall 

 study 



1st. Powders corresponding to an exact combustion ( 6). 



2nd. Powders with an excess of combustible, such as service 

 powder properly so called, sporting and blasting powder ( 7). 



3rd. Powders formed of nitrates other than potassium, 

 which are employed for industrial purposes in particular 

 cases ( 8). 



2. EEACTIONS BETWEEN SULPHUR, CARBON, THEIR OXIDES AND 



SALTS. 



1. The study of the products of the explosion of powder led 

 the author to make some observations on the reciprocal action 

 of sulphur, carbon, their oxides and salts. The operations were, 

 in some cases, carried out by means of the electric spark, and 

 in others by means of a red heat. In both cases there are 

 foreign energies which intervene in the chemical actions 

 properly so called, energies developed by electricity or heating, 

 especially successive decompositions, dissociations, and changes 

 of molecular states (polymerised carbon changed into gaseous 



