178 Dr. Wilson on the Decomposition of Water by Platinum 



turally excited much attention. It furnished the unexpected 

 confirmation of the truth of an opinion expressed by James 

 Watt so far back as 1783, that if steam could be made red 

 hot [white hot] so that all its latent heat should be converted 

 into sensible heat, either the steam would be converted into 

 permanent air, or some other change would take place in its 

 constitution *. 



In the greater number of Mr. Grove's experiments, water 

 was raised in temperature through the medium of platinum ; 

 and it became a question accordingly, as Sir John Herschel 

 and my friend Dr. Lyon Playfair suggested, how far the de- 

 composition of water observed was owing to the mere heat of 

 the metal, how far to the peculiar surface-influence, or so- 

 called catalytic force, which has been so long recognized as 

 possessed by platinum and the other noble metals. jDr. Play- 

 fair also referred to the fact, " that many bodies at high tem- 

 peratures exhibited a great affinity for oxygen, which they did 

 not possess at lower temperatures ; as, for instance, silver, 

 gold, and even platinum itself, which metals absorb oxygen 

 when intensely heated, and give it out again on cooling. If 

 the experiments had been tried in tubes of quartz or silica, 

 they would not have been open to the objection which the 

 use of so peculiar a metal as platinum appeared to involve -f." 



There was indeed one form of Mr. Grove's experiment not 

 liable to the exception urged against those where platinum was 

 used. He found it quite possible to decompose steam by 

 sending Leyden-jar discharges through it, and refers the de- 

 composition solely to the heat evolved by the electric spark. 

 The same view has been suggested as not improbable by 

 Faraday, in relation to the decomposition of water in the 

 liquid form by electric discharges J. With great diffidence, 

 however, I would remark, that the spark decomposition of 

 water cannot be regarded as an experimentum crucis. Al- 

 though the electric spark cannot decompose steam electroly- 

 tically, we may not at once infer that it cannot decompose it 

 in another way. I have no wish to assert that it can, but it 

 is possible that it may, and a crucial experiment should be 

 unexceptionable. Again : the spark discharge of a Leyden 

 jar exerts a great disruptive force, and acts topically with 

 much violence. There is reason moreover to believe that 

 mechanical agitation or disturbance of a chemical compound 

 can in many cases cause the separation of its elements. It 

 may seem an extravagant idea to suppose that oxygen may 

 be torn or detached from hydrogen by the action of a dis- 



» Phil. Trans. 1783, p. 41G. 



t Athenagum for September 19th, 1840, p. 966. 



J Researches in Electricity, 3rd series, paragraph 337. 



