250 Dr Wilson on the Decomposition of Water hy Platinum 



emitted by burning iron is, it falls shoi;t in intensity of that given 

 off by platinum on the verge of fusion. It seems accordingly probable, 

 that during the combustion of iron in oxygen, the temperature never 

 rises high enough to confer upon the resulting oxide the power of 

 decomposing water. The question admits of direct decision, by ascer- 

 taining whether oxide of iron, heated by the oxyhydrogen blowpipe 

 to as high a temperature as fusing platinum, acquires the power of 

 decomposing water without appropriating to itself either of its elements. 

 But it would have been an interference with Mr Grove's own re- 

 searches, to have made experiments of this kind, and I have accord- 

 ingly left the question undecided. 



Meanwhile, the experiments I have recorded are of some little in- 

 terest, as at least shewing that not only a white heat, but a high 

 white heat, is essential to the successful performance of Mr Grove's 

 experiments. Unfortunately, we have not at present any method 

 of measuring high temperatures which admits of ready application 

 or secures great accuracy. " White heat " is in fact a vague expres- 

 sion for a range of temperature ; of the extremes in either direction 

 or extent of which we have no very precise knowledge. The power 

 of the eye to measure the relative intensities of the light evolved by 

 white-hot bodies is very limited, and varies greatly in diiferent 

 individuals. But the experiments I have recorded, seem to sup- 

 ply the means of so far defining the white heat requisite for the 

 separation of the elements of water, inEismuch as they shew that 

 it must at least exceed the temperature necessary for the fusion of 

 malleable iron or its black oxide. If, moreover, the decomposing 

 powers of the electric spark be solely referable to its temperature, 

 we seem entitled to conclude, from the experiments I have detailed, 

 that the heat of the smallest spark that can decompose water is at 

 least equivalent to that of fusing platinum. They appear also to war- 

 rant another conclusion. It was suggested by Dr Leeson and by Mr 

 Hunt, that the bursting of steam-boilers might occasionally be owing 

 to the metal they consist of becoming white-hot, and decomposing 

 water, as platinum does, with the rejection of both its elements.* This 

 ingenious suggestion seemed to myself, before making experiments 

 with iron, likely to prove just ; but as fusing white-hot iron appears 

 unable to decompose water, otherwise than by combining with its 

 oxygen, it is impossible that the walls of a boiler can ever be raised 

 to a temperature sufficiently high to enable them to separate the 

 elements of water in the way platinum does. 



I may now be permitted to make some comments on the rationale 

 of the results obtained by Mr Grove. That gentleman, if I under- 

 stand him aright, considers the decomposition of water by white-hot 

 platinum not only, as assuredly it is, a remarkable and unexpected 

 result, but as evidencing on the pai't of heat a power to produce op- 



* Athenaeum, 19th Sept., p. 9G6. 



