516 M. Deville on the Disassociation of Compound Bodies. 



periment to be the case. We have therefore to seek for some 

 other cause capable not only of counteracting the influence of 

 the variable just found, but of overpowering it. The knowledge 

 of the phsenomena which I have observed by the intermittent 

 discharge may give us the clue to this. 



Remembering that the interval of time between two partial 

 discharges becomes less as the distance of discharg e increases 

 and bearing in mind the atmospheric disturbances caused by 

 such partial discharges, it seems to be a natural consequence, 

 that the total number of the partial discharges increases with 

 the charge and the distance of discharge. This increase, con- 

 cerning which nothing further is at present known, may possibly, 

 when the distance of discharge increases, overcome the weak- 

 ening influence of the electro-static arrangement. After I had 

 learned to recognize the intermittent discharge directly, I was 

 quite convinced that with the above-mentioned resistances (4830 

 millims. and 240 niillims. reduced length of water column) I 

 had had to deal exclusively with discharges of this kind. 



If the same reasoning be applied to the experiments which 

 were made by the determination of the duration of an electrical 

 total discharge, the two facts observed seem partly to corro- 

 borate one another. 



LIX. Chemical Notices from Foreign Journals. 

 By E. Atkinson, Ph.D. 



[Continued from p. 368.] 



DEVILLE* has made a communication on what he terms 

 " the disassociation of compound bodies." When heat 

 acts upon a body it produces expansion, which is considered to 

 be due to the action of a repulsive force of heat ; and if a suit- 

 able compound be heated sufficiently high, the distance between 

 the molecules may become so great that the latter pass into the 

 free state. Such phsenomena Deville classes under the above 

 head. Thus anhydrous nitric acid spontaneously decomposes 

 into its elements even at ordinai-y temperatures, anhydrous cai*- 

 bonate of ammonia at 60° C, and ammonia at a red heat. Grove 

 has shown that platinum, at its melting-point, decomposes water 

 into its elements. On repeating the experiment on a large scale, 

 Deville found that only a very small quantity of detonating gas 

 was produced in proportion to the heat employed. This arose 

 from the fact that the liberated elements again combine, and 

 that only those portions escape recombination which are imme- 

 diately cooled down to the ordinary temperature by the sur- 



* Comptes Rendi/s,vo\. xlv. p. 857. Liebig's Annalen, March 1858. 



