26 Mr. Grove oti the Decomposition of Water hy Heat. 



vapour; the sequel of this paper will render it probable that 

 even the ignited wire does not and cannot induce combination 

 of all the oxygen existing in the hydrogen. • 



I have looked into the papers of MM. Berzelius and Du- 

 long, and of M. Dumas on the equivalent weight of hydrogen. 

 The latter contains a most careful experimental investigation, 

 and is by far the best determination we have ; although it is 

 not there mentioned that hydrogen contains oxygen, yet a 

 correction is made for the air contained in the sulphuric acid 

 employed. M. Dumas does not state how the quantity of that 

 air is calculated. There can be no question that nothing ap- 

 proaching in elaborate care to these experiments has been yet 

 performed on the subject; but with the fullest consciousness of 

 M. Dumas' skill, I have, in all my experiments, perceived 

 such an inveterate tendency of hydrogen to possess itself of 

 oxygen, that I cannot help entertaining some doubts whether 

 we have yet the real weight of hydrogen within the assigned 

 limits of error. 



It is difficult to see how hydrogen can be absolutely deprived 

 of oxygen which has once existed in it; neither an oxidable 

 metal as zinc, or an ignited inoxidable metal as platinum, get- 

 ting rid of all the oxygen, and phosphorus, if it does so, re- 

 places it by its own vapour. The near approach, however, of 

 the equivalent of hydrogen, as determined by M. Dumas, to 

 the ratio of whole numbers, renders it probable that it is a 

 very close approximation to the truth. 



1 have not been able to detect nitrogen in the hydrogen, 

 but the probability is that a slight quantity also exists in it. 

 Whether the oxygen proceeds from portions of air still re- 

 maining in solution in the liquid from which the air is ex- 

 hausted, or whether it is a part of the water actually decom- 

 posed, but of which the oxygen is not absorbed by the zinc, 

 is a question to resolve which further experiments are neces- 

 sary. 



Hydrogen and carbonic acid mixed in equal volumes were 

 readily acted on by the ignited wire; they contracted to O'^S 

 of the original volume ; the residue was carbonic oxide ; one 

 equivalent of oxygen had therefore united with the hydrogen; 

 and the slight additional contraction was probably due to the 

 further combination of hydrogen with oxygen, as above stated. 



Carbonic oxide exhibited a remarkable effect, and one which, 

 coupled with the last experiment, gave rise to considerations 

 which mainly led to the results to be detailed in the body of 

 this paper. Carbonic oxide, very pure and carefully freed from 

 carbonic acid, was exposed to the ignited wire over distilled 

 water ; the gas increased in volume in one experiment to one- 



