94- Mr. Grove on the Decomposition of Water by Heat. 



the difference being that in the effects produced by the last 

 two forces there was no polar chain, but every minute portion 

 of the matter acted on gave rise to the phaenomena which in 

 the electrical effects are only observable at the polar extremi- 

 ties ; thus in decomposing water by iron and sulphuric acid, 

 or by passing steam over heated tubes of iron, parallel results 

 are obtained to the electrolysis of water with an iron anode ; 

 but in the former cases every portion of the iron oxidated 

 gives off its equivalent of hydrogen, in the latter the equiva- 

 lent is evolved from the cathode at a point distant from that 

 where the oxidation takes place. Hitherto electricity has been 

 the only force by which many compounds, and particularly 

 water, could be resolved into their constituents without either 

 of these being absorbed by another affinity. The decompo- 

 sition by ignited platinum removes this exception, and pre- 

 sents the parallel effect produced by heat alone. 



Although there is no substance except platinum and some 

 of the more rare metals, such as iridium, which promise much 

 success in a laboratory experiment made for the purpose of 

 producing the effect I have described, as the greater number 

 of substances which will bear a sufficient heat, are fragile, 

 oxidable, or affected by water, yet general considerations from 

 the nearest analogies in chemistry would lead us to expect a 

 similar effect from all matter in a state of intense ignition ; 

 even assuming the presence of solid matter to be necessary, 

 the catalytic effects of platinum are shared in different degrees 

 by other substances : it therefore appears probable that at a 

 certain degree of heat water does not exist as water or steam, 

 but is resolved into its constituent elements. If, therefore, 

 there be planets whose physical condition is consistent with 

 an intense heat, the probability is, that their atmosphere and 

 the substances which compose them ai*e in a totally different 

 chemical state from ours, and resolved into what we call ele- 

 ments, but which by intense heat may be again resolved into 

 more subtle elements. The same may be the case in the 

 interior of our planet, subject however to the counter agency 

 of pressure. 



The experiments strongly tend to support the views of 

 Berthollet, that chemical and physical attraction are affinal, 

 or produced by the same mode offeree. All calorific expan- 

 sions appear to consist in a mechanical severance of the mole- 

 cules of matter; and if heat produce effects of decomposition 

 merely by increase of intensity, there seems no reason why 

 we should assign to it in this case a different mode of action 

 from its normal one. On this view physical division carried 

 on indefinitely must ultimately produce decomposition, and 



