450 M. H. Deville on the Decomposition of Bodies by Heat, 



cooling, bodies can be obtained whose physical properties (soft 

 sulphur), or whose chemical properties of a certain kind (inso- 

 luble sulphur) are completely modified. These properties even 

 bear a certain relation to the quantity of dissimulated heat which 

 the bodies retain under the influence of tempering ; they also 

 retain them in a state of unstable equilibrium, which is physically 

 characterized by a diminution in the density, and is exhibited 

 by the greater or less facility with which they revert to the 

 ordinary and definite state. 



I hope I make myself clear in assuming that nitrogenous 

 compounds, and in general all those which decompose with ex- 

 plosion and disengagement of heat, are comparable to tempered 

 bodies, retaining more heat than is adequate for the state of 

 stable equilibrium of their molecules ; and it is at the moment 

 at which this stable equilibrium is destroyed that the liberated 

 heat becomes sensible, when it is more than sufficient to pro- 

 duce a simple decomposition or separation of the elements. 

 By this mode of view, the phenomena of inverse combination, 

 or of decomposition with disengagement of heat, may be brought 

 under the same category. 



As to the formation of tempered bodies, or the fixation of this 

 heat which renders unstable the condition of equilibrium of 

 combined bodies, it may take place in the conditions of the 

 nascent state, which is indispensable for the union of nitrogen 

 with many bodies; for, from the experiments of my brother, 

 of MM. Fordos and Gelis, of M. Berthelot, and of M. Cloez, 

 insoluble sulphur and soft sulphur, which are obtained by tem- 

 pering, are also obtained in the ordinary phajnomena of decom- 

 position during the exchange of the molecules, and under 

 conditions which constitute the nascent state in chemical re- 

 actions. 



By continuing these comparisons, we shall remove an anomaly 

 which is truly to be regretted even in some of our most reliable 

 chemical analogies. It might be conceived that it is nitrogen 

 which carries with it the property which these bodies possess of 

 becoming tempered — that it is nitrogen in the nascent state that 

 can fix the heat borrowed from the bodies in the midst of which, 

 and with which, it combines ; so that free gaseous nitrogen and 

 combined nitrogen are really two distinct bodies, which differ 

 just as octahedral sulphur differs from insoluble or soft sulphur, 

 perhaps by chemical properties, or perhaps simply by a physical 

 property such as the density. This hypothesis would explain 

 how it is that nitrogen possesses a density 0*972 which corre- 

 sponds to two volumes of vapour, while phosphorus and arsenic 

 only represent one volume of vapour for one equivalent, as is 

 shown by the experiments of M. Dumas, of M. Mitscherlich, and 



