DECOMPOSITION OF WATER BY HEAT. 321 



Although there was no known effect of electricity which 

 could produce the phenomenon exhibited by the last two ex- 

 periments, and it was in any event new, still, firmly convinced 

 that it was an effect of heat, I again determined to attempt 

 its production by heat alone, and without the use of the 

 battery. I procured a tube of silver 9 inches long and 0-4 inch 

 diameter ; at the extremity of this was a platinum cap, to 

 which a smaller tube, also of platinum, was soldered. This 

 platinum tube was closed at the end and soldered with gold 

 solder. The apparatus was filled with prepared water ; the 

 water was boiled in the tube to expel the air from the narrow 

 tube and any which might have adhered to the vessel ; the 

 tube was then, when full of hot FifT 



water, inverted into water, and the 

 flame of a common blowpipe made 

 to play against the platinum tube 

 (see fig. 9) until a white heat was 

 obtained. Upon inverting it under 

 water a bubble of the size of a 

 mustard-seed rose to the surface, 

 which gave a very feeble detona- 

 tion with the match. Similar bubbles were collected as before, 

 and the gas in an eudiometer contracted to 0*7. On repetition 

 the experiment did not succeed so well, and upon several 

 repetitions it sometimes succeeded and sometimes failed, and 

 I should not mention it but that it was the first experiment 

 which gave me, although not very satisfactorily, the effect of 

 decomposition by heat alone. The reason of its uncertainty 

 I believe to have been the want of a sufficiently intense heat, 

 as I dared not venture, on account of the gold sojder, to push 

 the ignition very far ; in fact, I subsequently fused the ex- 

 tremity and spoiled the apparatus by applying the oxyhydro- 

 gen flame to it ; had the platinum tube been welded instead 

 of gold-soldered, it would doubtless have succeeded better. 

 I should state that the object of the silver tube was to prevent 

 the chance of re-composition by the catalytic effect of a large 

 platinum surface ; to have, in short, a small portion of plati- 

 num exposed to the steam, and that at a high temperature. 



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