1819.] of the Theory of Heat. 197 



state. Some facts more lately observed could not be explained 

 according to the theory without admitting that the oxygen con- 

 tained in certain combinations retained a quantity of heat 

 superior to that which it contains when in the elastic state. Such 

 are the detonations produced by mixtures of chlorate of potash 

 with certain combustibles, or the spontaneous explosions of the 

 euchlorine of Davy, and of the chloride and iodide of azote. 



This explanation was afterwards extended to all combinations, 

 and it was considered as a principle sufficiently established that 

 a body in combining with a certain number of others might 

 abandon a more or less considerable part of its heat, according 

 as in each case the different degrees of affinity of the elements 

 in contact occasioned the molecules to approach more or less 

 nearly to each other. It is the degree of this approach, essen- 

 tially variable, which has been denoted by the word condensation, 

 so frequently employed in the language of chemistry. 



Such is the theory almost generally adopted in France. 

 Several foreign chemists have pointed out its inaccuracy, and 

 have modified it in different points, but without producing any 

 conclusive proof either against the opinion which they combat, 

 or in support of that which they wish to substitute in its place. 



We see then that the different explanations relative to the 

 development of heat in chemical combinations are reducible to 

 simple assertions derived from the first hypothesis of Lavoisier. 

 It is astonishing that since the time in which this doctrine origi- 

 nated, it has not been subjected to a more rigid examination ; 

 and that even from the results already known, all the arguments 

 have not been drawn against it which they are capable of fur- 

 nishing. We conceive that the relations which we have pointed 

 out between the specific heats of simple bodies and those of 

 their compounds prevents the possibility of supposing that the 

 heat developed by chemical actions owes its origin merely to the 

 heat produced by changes of state, or to that supposed to be 

 combined with the material molecules. We have still a better 

 reason to reject this purely gratuitous hypothesis, as we can 

 explain the phenomenon in a much more satisfactory manner. 



In fact Davy has long ago shown that when the two poles of 

 a voltaic pile are united by means of pieces of charcoal placed 

 in a gas incapable of supporting combustion, the charcoal may 

 be kept in a state of violent ignition as long as the pile remains 

 in activity, and without the charcoal undergoing any chemical 

 change. On the other side, we are warranted to conclude from 

 a great number of galvanic experiments made by Hisinger and 

 Berzelius, and by Davy, that all bodies which combine are, with 

 respect to each other, at the moment of combination precisely 

 in the same electric conditions as the two poles of the pile. Is 

 it not then probable that the cause which produces the incan- 

 descence of the charcoal in the fine experiment just mentioned 

 is likewise the cause of the greater or less elevation of tempera- 



