4 
MR. GROVE ON THE DECOMPOSITION OF WATER BY HEAT. 
Binoxide of nitrogen over distilled water contracted differently in proportion to 
the heat of the wire ; in the best experiment it contracted to one-third of its original 
volume; the residual gas was nitrogen. Nitric acid was found in solution in the 
water. 
Over mercury the effects were nearly the same ; the mercury was attacked, and 
the orange fumes of nitrous acid were visible. 
Protoxide of nitrogen was decomposed into nitrogen and oxygen ; the volume in- 
creased by 035 of the original volume ; I could not get the full equivalent propor- 
tion, or 0'5 of oxygen. 
Carbonic acid underwent no perceptible alteration. 
Ammonia increased to double its original volume ; it was now no longer absorbable 
by water, and gave 3 volumes of hydrogen, plus 1 nitrogen. 
Olefiant gas contracted slightly, deposited carbon, the residue being hydrogen and 
olefiant gas, more of the former in proportion to the heat, but I could not succeed in 
entirely decomposing it. 
Nitrogen suffered no change. 
Oxygen gave a very slight contraction, amounting to y^th of its volume ; the 
oxygen employed was very pure, obtained from chlorate of potash and manganese, 
and also from water by electrolysis : no change in properties was perceptible in the 
oxygen after its exposure to the ignited wire. This contraction I incline to attribute 
to a slight portion of hydrogen present, which view will, I think, be considered as 
strengthened by the effect of the ignited wire on hydrogen, to be presently detailed. 
I at one time thought that the contraction might be due to a slight oxidation of the 
wire, but it never went beyond a very limited point ; nor was the wire altered in size 
or weight, though it was kept ignited for many hours. 
Chlorine over water gave dense white fumes ; a greyish yellow powder accumulated 
on the sides of the tube near the platinum wire, which appeared of the same nature 
as the vapours ; the deposit was insoluble in cold nitric, sulphuric, or muriatic acid, 
but dissolved by the last when boiled. The fumes did not, as far as I could judge, 
affect litmus paper ; a barely perceptible tinge of red was indeed communicated to 
it, but this, I had every reason to believe, was attributable to a slight portion of muri- 
atic acid not absorbed by the water. I have not yet worked out this result, as it is 
probable, considering the number of experiments that have been made on heated chlo- 
rine, that it is a known product, though I cannot find, in several books to which I have 
referred, any substance answering to it in description, and the field opened by voltaic 
ignition is so new that each result demands a separate and prolonged examination ; 
if I find that this is an unknown compound I shall probably resume its investigation*. 
Cyanogen gave, though in very minute quantities, a somewhat similar deposit, but at 
its then very high temperature it began to act rapidly on the mercury, and I was obliged 
to give up the experiment after an hour’s ignition. Both these gases require peculiar 
* See Supplemental Paper, p. 20. 
