96 Mr. Grove on the Decomposition of Water by Heat. 



gentle heat, takes fire in the open air and burns into the white 

 oxide: to casual observation the zinc would appear to be 

 burned twice. The experiment appears to me to present an 

 argument in favour of the dynamic theory of heat. 



With charcoal, on the other hand, there is little or no de- 

 posit, but the charcoal continually yields carbonic oxide and 

 hydrogen, and this for hours after the presence of water would 

 be deemed impossible. I have taken the arc between pieces 

 of well-burned charcoal for eight or nine successive hours, 

 and there was still gas generated ; indeed it appeared to be 

 given off as long as there was any charcoal remaining, and a 

 conversion of the carbon into inflammable gas might have 

 been supposed, Much still remains to be done with this 

 powerful agent, the voltaic arc: where, however, the object 

 is simply to expose gases to an intense heat, the ignition of a 

 conjunctive wire of platinum is more simple in its application, 

 more uniform in its action, and instead of requiring a power- 

 ful battery, the effect can be satisfactorily produced by five or 

 sIk cells, in many cases by two. 



The heat is not so intense as that of the arc, but as it can 

 be brought to within a few degrees of the fusing-point oC pla- 

 tinum, it is far more intense than, any heat usually employed 

 in laboratories, certainly than any which can be applied to 

 minute, I may say microscopic portions of gas or vapour. 



In conclusion, I must express my sincere thanks to the 

 managers of the London Institution, for having permitted me, 

 as an honorary member, to carry on these experiments in the 

 laboratory of the Institution. 

 London Institution, Aug. 21, 1846. 



XVIII. Supplementary Paper on pertain PhcBnomena of Voltaic 

 Ignition, and the Decompositio?i of Water into its constituent 

 Gases by Heat. BijW. R. Grove, Esq."^ 



IN selecting the above title, I endeavoured to give as clear 

 an enunciation of the phEpnomena to be described in the 

 paper as was consistent with the brevity usual in a title. 



An exception has, however, been taken to it, that as the 

 effects of decomposition are produced by ignited platinum, 

 the phsenomena may result from that obscure mode of action 

 called catalysis. That I did not intend to exclude from con- 

 sideration any possible action of the substance employed, will 

 be evident from the paper itself, in which I have called attention 

 to the general production of catalytic effects by solid bodies. 



* From the Philosophical Transactions for 1847, part i.; having heen 

 received by the Royal Society November 26, and read November 26, 1846. 



