10 
MR. GROVE ON THE DECOMPOSITION OF WATER BY HEAT. 
and the fact of any uncombined gas existing when exposed to incandescent platinum, 
will doubtless surprise those who hear it for the first time. 
The experiment was repeated as at first and the bubble transferred to another 
tube ; the wire was then again ignited in vapour, another bubble was instantly formed 
and transferred, and so on, until after about ten hours’ work sufficient gas was col- 
lected for analysis ; this gas was now placed in an eudiometer, it detonated and con- 
tracted to 0 - 35 of its original volume ; the residue being nitrogen. The experiment 
was repeated several times with the same general results, the residue sometimes con- 
taining a trace of oxygen. 
Here electrolysis was out of the question ; the wire was ignited in (if I may use the 
expression) dry steam, the upper part of the tube being far above the boiling-point, 
and of course perfectly transparent ; if not an effect of heat, it must have been a new 
function of the electric current, at least one hitherto unknown. 
As the voltaic arc and electric spark afford heat of the greatest intensity, I tried 
a succession of electric sparks from platinum wires through steam in the apparatus 
fig. 8, the water, as in all my experiments, having been previously purged of air (to 
save circumlocution I will in future call it prepared water). The sparks were taken 
from the hydro-electric machine of the London Institution ; they had in the steam a 
beautiful crimson appearance; on cooling the tube a bubble was perceptible, which 
detonated by the match. 
As in the previous experiments, a whole day’s work did not increase the bubble, 
but when it was transferred another instantly formed ; the gas was similarly col- 
lected ; it detonated and contracted to 0 - 4 of its original volume ; the residue was 
nitrogen with a trace of oxygen. 
This experiment will again surprise by its novelty ; the very means used in every 
laboratory to combine the mixed gases and form water, here decompose water*. 
From a vast number of experiments which I have made on the voltaic and electric 
disruptive discharges (which are I believe similar phenomena, differing only in quan- 
tity and intensity), I believe the decompositions produced by them are the effects of 
heat alone, and this experiment was therefore to my mind a repetition of the last 
under different circumstances ; others however may think differently. This experi- 
ment also I several times repeated. 
By counting the globules given off, and comparing a certain number of them with 
the average volume of steam in the last two experiments, an attempt was made to 
ascertain what proportion of water could be decomposed by an ignited platinum wire 
in aqueous vapour, or, which amounts to a corollary from this proposition, what degree 
of dilution would enable mixed gas to exist without combustion in an atmosphere of 
steam exposed to an ignited platinum wire. The proportion in an experiment in 
which the globules were so counted, was 1 to 2400; the probability is however that 
* I need scarcely point out the distinction, in fact, between this experiment and those in which liquid water 
has been decomposed by the electric spark. See Supplemental Paper, p. 21. 
