DECOMPOSITION OF WATER BY HEAT. 335 



room for the elimination of the liberated gas, or of absorbing 

 the latter by combination without also absorbing the vapours. 



I had hoped by the above means to proceed with the 

 experiments until all the oxygen was liberated that could be 

 driven off, and then to have examined the residue ; but I 

 found that, after experimenting for a short time, both the 

 platinum wire and the glass in proximity to it were attacked 

 by the liquids ; this difficulty, similar to those which have 

 hitherto prevented the isolation of fluorine, I have not yet 

 been able to conquer, though I hope to resume the experi- 

 ments. 



As chloride of iodine is decomposed by water, it cannot 

 contain any notable quantity of the latter, but, until the expe- 

 riments are carried farther, it must remain a question whether 

 the oxygen results from a small quantity of water contained 

 in the liquid, the hydrogen combining with the liquid itself, 

 or from a decomposition similar to that of the peroxides. 

 The experiments certainly add a new and striking analogy to 

 those already known to exist between the peroxides and the 

 halogens, but they do not, as far as I have hitherto carried 

 them, necessarily prove analogy of composition. 



In conclusion, I would call attention to a point which I 

 omitted to notice in my original paper, viz. the explanation 

 afforded by the results contained in it of the hitherto myste- 

 rious phenomena of the non-polar decomposition of water by 

 electrical discharges, as in the experiments of Pearson and 

 Wollaston. This class of decompositions may now be carried 

 much farther. With the exception of fused metals, I know 

 of no liquid which, when exposed to intense heat, such as that 

 given by the electric spark, the voltaic arc, or incandescent 

 platinum, does not give off permanent gas ; phosphorus, sul- 

 phur, acids, hydrocarbons, water, salts, bromine, and chloride 

 of iodine, all yield gaseous matter. 



Viewing these effects simply as facts, and without entering 

 on any theoretical explanations or speculations, I cannot but 

 think that there is a remarkable generality pertaining to them 

 worthy of the most careful attention. 



The apparatus I have described, particularly that repre- 

 sented by fig. 5, and the numerous applications of voltaic 



