254 On (he Decomposition oj Water by Platinum^ §fc, 



the same intensity is able, in the same circumstances, to form water 

 and to decompose it. When therefore it is stated that water can bo 

 produced by the processes that disunite its elements, the word " pro- 

 cess " can only he understood to signify that the general arrangement 

 in both cases is the same, not that the intensity of the agent called 

 into play, or its mode of action, is identical. If this could be affirmed, 

 we should be able to announce as a general proposition, that mani- 

 festations of the same force, absolutely identical as to quality, quantity 

 and intensity, can produce totally opposite results, which would bo 

 tantamount to affirming that unlike effects may flow from the same 

 cause, without any alteration in the qualities or conditions of the latter. 



The last observation I would make, refers to the curious fact no- 

 ticed by Mr Grove, namely, that when a platinum wire is heated 

 white-hot in steam, " in a ^aw seconds a small bubble of gas is formed ; 

 but if the action be continued for a week, it does not increase in 

 quantity." * 



Are we to suppose that the wire is at the same time decomposing 

 water around itself, and producing water at a little distance, undoing 

 in one place what it efiects in another, so that no permanent accumu- 

 lation of gas is allowed to take place \ This is possible, but I think 

 not likely. The observation made by Mr Grove seems sufficiently 

 explicable, on the supposition that as soon as the wire is completely 

 enveloped in steam, the thermo-circulatory currents which the high 

 temperature occasions in the vapour, prevent it from remaining long 

 enough in contact with the wire to become heated white-hot. The 

 steam probably circulates endlessly around the wire without a trace 

 of decomposition occurring in it. It seems not unlikely indeed that 

 in Mr Grove's experiments with his eudiometer it was not steam that 

 yielded the hydrogen and oxygen obtained, but the last film of water 

 below the wire, which could not escape from the metal, but tended 

 rather, in consequence of its expansion, to rise towards it, and was 

 thus compelled to acquire a white heat, and to break up into its ele- 

 ments. If this view be correct, an arrangement where a white-hot 

 wire or sheet of platinum foil was kept grazing the surface of water, 

 might be found to effect a continuous decomposition of the liquid in 

 question. 



It is no objection to this view that an electric spark decomposes 

 steam readily, for the duration of the spark is so short, that there is 

 no time for the production of thermo-currents, nor any possibility of 

 the steam escaping from the powerful topical action of the discharge. 

 The spark may be compared to fulminating silver, whose action is 

 instantaneous and violent, but quite local, — the heated platinum to 

 gunpowder, the effect of which is cumulative and more general. — 

 Transactions of the Chemical Society for 1847. 



* Athenaeum, 19th Sept., 1846, p. 966. 



