MR. GROVE ON THE DECOMPOSITION OF WATER BY HEAT. 
19 
I now tried silica and other oxides, but the results were not very satisfactory. 
A spheroid of silica was formed by fusing pulverized silica on to a platinum wire, 
so as to cover it for the length of 0’4 of an inch ; when this was plunged into 
the hot water and again fused in the oxyhydrogen blowpipe, it constantly became 
frothed with small bubbles of vapour, and after a few experiments generally separated 
in fissures ; in the experiment which was continued for the longest time without 
disintegration, the gas given off contained O’ 15 of oxyhydrogen gas ; from the whole 
result I believe there is an action of the water on the silica (probably forming a 
hydrate decomposable by heat) which is a bar to satisfactory results. With other 
oxides, at least such as would bear an intense heat, the difficulties were still more 
insuperable. Priestley has shown that water will corrode glass, and if I mistake 
not, others have shown the same effect produced on silica. 
Although, as applied to the facts detailed. I attached no further meaning to the 
title of my paper than that which I have above stated, vet in one or two theoretical 
inferences I have certainly gone further ; for instance, when I suppose the possibility 
or probability of mechanical rarefaction producing the same effects as heat, here 
(although I do not, indeed I cannot conceive the existence of heat without matter) 
I certainly abstract from the proposition any consideration of solid matter. In order 
to ascertain how far this view might be founded on truth, I had thought of making 
a few experiments on the effect of mechanical rarefaction on the tendency of gases 
to combine, but (in addition to the interference of necessary occupations) I find that 
M. de Grotthus has already experimented on the point; his experiments, as far as 
they go, corroborate the views I have put forth. 
He finds* that mixed gases, such as chlorine and hydrogen, or oxygen and hydro- 
gen, when rarefied either by slow increments of heat or by the air-pump, do not take 
fire (“ ne s’enflamment pas”) by the electric spark. From the context, he evidently 
means that the gases will not detonate or unite in volumes, as he states that a partial 
combination ensues. Grotthus appears to have considered the combination of gases 
by the electric spark as an effect of sudden compression or molecular approximation, 
certain particles being brought within the range of their affinities by the sudden 
dilatation of others. Although he did not pursue the subject far enough to ascertain 
whether a degree of rarefaction could be reached which would be an actual bar to 
combination, still his experiments strengthen those views which assimilate mechanical 
and thermic molecular repulsion, and regard chemical affinity as being antagonized 
by physical repulsion. 
Pursuing the series of analogies from the decomposition of euchlorine at a low 
temperature, that of ammonia at a higher, that of metallic oxides at a higher, and so 
on to oxide of hydrogen, there appears to be an extensive series of facts which afford 
strong hope of a generalized antagonism between thermic repulsion and chemical 
* Annales de Chimie, vol. lxxxii. 
