Energy of Chemical Actions. 277 



causes the formation of ozone without itself undergoing any 

 modification. Such an action would certainly be catalytic, and 

 would contradict the theory that has been put forward. But it 

 is not difficult to discover a source of energy in this experiment. 

 By shaking, the oil is doubtless heated, since the external work 

 performed must transform itself into heat ; accordingly it is only 

 needful that the oil should be heated somewhat less than would 

 otherwise be the case, in order to furnish sufficient energy for 

 the formation of the very small quantity of ozone which results*. 



3. In the memoir already citedf, Deville discusses a condi- 

 tion which he calls Dissociation, intermediate between a state 

 of firm combination and one of decomposition. This condition 

 is supposed to arise when the molecules are separated from each 

 other to a certain distance. The fact that melted platinum 

 causes the formation of explosive gas when it is thrown into 

 water, is what gave rise to these considerations. In this case 

 the platinum can only act upon the aqueous vapour which is 

 formed, llegnault has shown that at about 1000° C. aqueous 

 vapour is decomposed by melted silver, which absorbs its oxygen. 

 On the other hand, the heat evolved by the combustion of explo- 

 sive gas suffices for the fusion of platinum, producing a tempe- 

 rature which the author estimates at at least 2500° C. He ex- 

 presses surprise that the combination of hydrogen and oxygen 

 should develope a much higher temperature than that which 

 occurs in the decomposition. He seeks an explanation in dis- 

 sociation, in which state he supposes water-vapour to exist at 

 1000° C. The atoms of chlorine and hydrogen are regarded as 

 already in the state of dissociation at the common temperature. 



The author cites, as cases where decomposition occurs sud- 

 denly and with evolution of heat, without previous dissociation, 

 the chloride, iodide, and sulphide of nitrogen. Lastly, he com- 

 pares the three conditions of firm combination, dissociation, and 

 decomposition, with the three states of aggregation. 



This last comparison appears to me very defective. In fact 

 there is no great difficulty in seeing that the author's dissocia- 

 tion coincides in general with the state in which only one of the 

 two necessary conditions of chemical action pointed out above is 

 fulfilled. In chlorine and hydrogen there is a sufficient supply 

 of energy, and all that is wanting is an increase in the strength 



* [But does the oil of turpentine remain quite unaltered ? or is agitation 

 absolutely necessary? There is no apparent reason for supposing that 

 shaking favours the formation of ozone otherwise than by renewing the 

 surface of contact between the oxygen and oil of turpentine. On the other 

 hand, there is reason to believe that light plays an important part in the 

 action. (Cf.Schonbein, Chem. Soc. Quart. Journ. vol. iv. p. 135, foot-note.) 

 — Transl.] 



t Fortschritte, &c. 1860, p. 380. Phil. Mag. S. 4, vol. xx. p. 451. 



