Mr. Grove on the Decomposition of Water by Heat. 97 



Whatever value or novelty there may be in the facts I 

 have communicated, is the same whether they be regarded 

 as resulting from catalytic or from thermic actions. If the 

 action be catalytic, it is one absolutely the reverse of that 

 usually produced by platinum, and therefore just as much at 

 variance with received experience as decomposition of water 

 by heat would be ; the effect of platinum, like that of heat, on 

 the elements of water having been hitherto known only as 

 combining them. With regard to any theoretic views I may 

 have advanced, I by no means attach the same importance to 

 them as 1 do to the facts themselves, though I consider it 

 necessary for the collation of facts, and desirable for the pro- 

 gress of science, that an author pretending to communicate 

 new results should give with them the impressions which led 

 to their discovery, and the inferences which he regards as im- 

 mediately deducible from them. No expression can be given 

 to facts which does not involve some theory, and admitting 

 the difficulty (perhaps insuperable) of correctly enunciating 

 new phaenomena, and the probability of future discoveries 

 entirely changing our views regarding them, I cannot at pre- 

 sent see that the title of ray paper could be altered without 

 being open to greater objections. I am of this opinion, not 

 so much because other bodies than platinum will produce the 

 effect, as I shall presently show, nor from the fact that the 

 electrical spark will decompose aqueous vapour, though these 

 are arguments in its favour ; but from the following conside- 

 rations. The catalytic action of platinum will induce or en- 

 able combination to take place where there is already a strong 

 affinity or tendency to combine, as with mixed oxygen and 

 hydrogen gases; it will also induce decomposition where the 

 affinities are extremely weak, or in a state of unstable equili- 

 brium, as in Thenard's peroxide of hydrogen ; again, where 

 there are nicely-balanced compound affinities, it may change 

 the chemical arrangement of the constituents of a compound, 

 but 1 do not know of any case in which a powerful chemical 

 affinity can be overcome by catalytic action ; to effect this we 

 require some natural force of greater intensity than that to be 

 overcome. We might as well say that the platinum electrodes 

 of a voltaic battery decompose water, as to say that platinum 

 decomposes it in the case in question ; there, the force of 

 electricity acts only by means of matter, and matter of a pecu- 

 liar description ; its action also is only perceptible at the sur- 

 face of this matter. I seek to use the expression in my title 

 with reference to heat in a similar sense to that in which we 

 use similar terms with reference to electricity, i. e. to regard 

 heat as the immediate dynamic force which overcomes the 

 PJiil. Mag. S. 3. Vol. 3 1 . No. 206. Aug. 184.?. H 



