34- Mr, Grove on the Decomposition of Water by Heat. 



leaving 0"4< residue ; this was as usual nitrogen vi^ith a trace 

 of oxygen. A second experiment gave a still better result, 

 the gas contracting to 0*25 of its original volume. 



On making the platinum negative and the charcoal positive, 

 a very different result followed : the carbon was, as is known 

 to electricians, projected upon the platinum; and the gas in 

 this case was mixed with carburetted hydrogen and carbonic 

 oxide. I know no experiment which shows so strikingly the 

 different effects at the disruptive terminals as this ; when the 

 platinum is negative it gives much carbonic gas, when it is po- 

 sitive, not a trace (the gas was delicately and carefully tested 

 for it); nay, more, by changing the platinum from negative to 

 positive the carbon is instantly removed, and in a single ex- 

 periment the platinum becomes perfectly clean. 



Here then I produced very satisfactorily decomposition by 

 heat ; it is true, the battery was used, but used only as a means 

 effusing the platinum, as this was, as soon as fused, entirely 

 separated from the circuit and could have no possible voltaic 

 action. Wishing however altogether to avoid the use of the 

 battery, I repeated this experiment, employing as my means 

 effusing the platinum the oxyhydrogen blowpipe; the expe- 

 riment was equally successful, perhaps more so, as the mani- 

 pulation was more easy. 



I could readily by this means collect half a cubic inch or 

 more of the gas ; when detonated, the residue of nitrogen 

 averaged 0*35 of the original volume. 



In carefully watching this experiment, 1 observed that at 

 first a rapid succession of bubbles ascended into the tube from 

 the incandescent platinum, it then became quiescent; the 

 spheroidal state was assumed by the water and no gas 

 ascended; on losing the spheroidal state a sudden hiss was 

 heard, and a single bubble ascended into the tube. I deter- 

 mined to examine separately the gas from the platinum before 

 and after the quiescent state; to effect this I placed two in- 

 verted tubes in the capsule with the orifices near each other ; 

 the platinum at the point of fusion was immersed under one 

 tube, say tube A, and as soon as the ascent of bubbles ceased, 

 it was removed across to tube B, and the last bubble then 

 entered that tube ; the gases from each tube were separately 

 analysed, and tube A gave nearly all detonating gas, the re- 

 sidue being only 0*2 ; tube B gave none ; the gas collected in 

 it was nitrogen, with a trace of oxygen. 



In order to examine the effect of an oxidable metal under 

 similar circumstances, I fused by the oxyhydrogen blowpipe 

 the end of a stout iron wire, plunged it into prepared water 

 and collected the globules of gas ; no oxygen was given off, 



