6 
MR. GROVE ON THE DECOMPOSITION OF WATER BY HEAT. 
the platinum wire induces therefore a greater absorption of oxygen than the phospho- 
rus, unless the volume of hydrogen is increased by the phosphoric 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 Dulong, and of M. Dumas 
on the equivalent weight of hydrogen. The latter contains a most careful experi- 
mental 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 approach- 
ing in elaborate care to these experiments has been yet performed on the subject, 
but with the fullest consciousness of M. Dumas’ skill, 1 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 hydro- 
gen 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, getting rid of all the oxygen, and phosphorus, if it does so, replaces it by 
its own vapour. The near approach, however, of the equivalent of hydrogen, as de- 
termined by M. Dumas, to the ratio of whole numbers, renders it probable that it is 
a very close approximation to the truth. 
I 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 remaining in solution in the liquid from which the air is exhausted, or 
whether it is a part of the water actually decomposed, but of which the oxygen is not 
absorbed by the zinc, is a question to resolve which further experiments are 
necessary. 
Hydrogen and carbonic acid mixed in equal volumes were readily acted on by the 
ignited wire ; they contracted to 0'48 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-third of its original volume, in the greater number 
of instances to one-fifth : this increase depended upon the intensity of ignition, which 
it was very difficult to maintain at its maximum on account of the frequent fusions 
of the platinum wires. 
Here again I had a long research and many erroneous guesses, which I need not 
