X. On the Effect of Heat in lessening the Affinities of the Elements of Water. 
By the Rev. Tuomas Romney Rosinson, D.D., M.R.I.A., &c. 
Read June 14, 1847. 
AT the last Meeting of the British Association, Mr. Grove announced the 
remarkable fact that water in contact with platinum at a high temperature, is 
resolved into oxygen and hydrogen gases. The most obvious explanation of this 
is, that heat, which in general appears as the antagonist of molecular attractions, 
plays the same part here, and subverts the affinity of these bodies. It was, how- 
ever, objected to this way of explaining the phenomenon, that it is inconsistent 
with the well-known effect of heat in causing these very gases to combine; and 
steam is not decomposed, even at the high temperature of the oxy-hydrogen blow- 
pipe (where it is the heating agent), unless it be in contact withasolid. These 
objections do not seem of much weight : there are many instances where affinities 
are apparently called into play at one temperature, and subverted at another ; 
that of peroxide of mercury, for instance, which is formed by exposing the metal 
to oxygen at 650°, and completely decomposed at 1000°. As to the necessity of 
a solid being present, we know far too little of the mechanism of these molecular 
actions to dogmatize on the subject, especially at a time when all seems tending 
to prove that, if these forces be not actually forms of one common power, or, to use 
the ideas of geometry, particular solutions of one great physical equation, they 
are, at least, bound together by a most intimate correlation. But we may goa 
little further; for since we are compelled, in the present state of our knowledge, to 
consider heat as a mere system of some kind of vibratory action, we are warranted 
to expect its action, at the common surface of two media so different as a gas and a 
solid, to be widely different from what it is in either separately. However, during 
the discussion this question suggested itself to me: if heat be, in the present 
Day 
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