246 Dr Wilson on the Decomposition of Water by Platinum 



union : and if it shall appear that a feeble mechanical force can 

 overcome a small intensity of affinity, it will be acknowledged as 

 quite possible that a powerful mechanical agency may overcome a 

 great one. We have no means perhaps of making an unexception- 

 able experiment as to the decomposing power of mechanical force ; 

 for we cannot bring it into play without calling into action other 

 agencies. If we touch, or rub, or strike a fulminate, for example, 

 we cause the evolution of heat, and add its decomposing power to 

 that of the mechanical impulse. It would be a mere petitio prin- 

 cipii, however, to assume that the heat produced alone effects the 

 decomposition observed. It seems to me, therefore, that the decom- 

 position of steam by the electric spark furnishes a more complex 

 problem for solution than the action of white-hot platinum on the 

 same compound does ; and that the experiments made with the 

 metal are more likely to throw light on those tried with the spark, 

 than to be explained by them. 



Whilst thinking over these difficulties, and the objections to Mr 

 Grove's conclusions suggested by Herschel and Playfair, I had occa- 

 sion to perform the familiar class-experiment of burning iron-wire 

 in oxygen. I observed with an interest I had not felt previously, 

 although I had carelessly noticed the phenomenon before, that 

 bubbles of apparently permanent gas rose from the globules of white- 

 hot oxide of iron as they fell into the water. It seemed to me pos- 

 sible that this gas might be a mixture of oxygen and hydrogen 

 separated by the influence of the metallic oxide, acting as platinum 

 did in Mr Grove's experiments. It was certain, moreover, that if 

 this should prove to be the case, it would supply a powerful argu- 

 ment in favour of that gentleman's conclusion, which seems, in spite 

 of all the objections noticed, in the highest degree probable, namely, 

 that heat, apart altogether from the medium through which it is 

 applied, can resolve water into its elements. 



As the following experiments were made solely with the hope of 

 substantiating Mr Grove's view, which unfortunately, however, they 

 leave exactly as they found it, I trust that gentleman will not con- 

 sider their publication an interference with his researches. I was 

 led to try them incidentally, and abandoned them as soon as I found 

 I could render Mr Grove no assistance by means of them. 



It would be difficult to conceive a more rapid and effectual way 

 of raising a body to a white heat than that afforded by the combus- 

 tion of iron in oxygen. I took for granted also (as it afterwards 

 appeared, too hastily) that the metal could not but be saturated with 

 oxygen and converted into a definite oxide, which would be chemi- 

 cally indifferent to each of the elements of water, and if it decom- 

 posed it at all, would reject both its constituents. The convenient 

 way, moreover, in which the globules of oxide detach themselves and 

 fall into the water, and the rapidity with which the whole process 

 goes on, make it a very easy matter to collect in considerable quan- 



