Mr. Grove on the Decomposition of Water by Heat. 99 



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 0*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, yet 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 can- 

 not 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 experi- 

 mented on the point; his experiments, as far as they go, cor- 

 roborate the views I have put forth. 



He finds* that mixed gases, such as chlorine and hydrogen, 

 or oxygen and hydrogen, when rarefied either by slow incre- 

 ments of heat or by the air-pump, do not take fire (" ne s'en- 

 flamment 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. Grott- 

 hus appears to have considered the combination of gases by 

 the electric spark as an effect of sudden compression or mole- 

 cular 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, 

 • Annales de Chimie, vol. Ixxxii. 



H2 



