MR. GROVE ON THE DECOMPOSITION OF WATER BY HEAT. 
13 
bear the same relation to experiment fig. 9 as fig. 5 did to fig. 7 ; for this purpose 
the apparatus shown at fig. 10 was constructed : a and b are two silver tubes 4 inches 
long by 0‘3 inch diameter; they are joined by two platinum caps to a platinum tube 
c, formed of a wire one-eighth of an inch diameter drilled through its entire length, 
with a drill of the size of a large pin; a is closed at the extremity, and to the extremity 
of b is fitted, by means of a coiled strip of bladder, the bent glass tube d. The whole 
is filled with prepared water, and having expelled the air from a by heat, the extremity 
of the glass tube is placed in a capsule of simmering water. Heat is now applied by 
a spirit-lamp, first to b and then to a , until the whole boils ; as soon as ebullition takes 
place, the flame of an oxyhydrogen blowpipe is made to play upon the middle part 
of the platinum tube c, and when this has reached a high point of ignition, which should 
be as nearly the fusing-point of platinum as is practicable, gas is given off, which, 
mixed with steam, very soon fills the whole apparatus and bubbles up from the open 
extremity, either into the open air or into a gas collector. Although by the time I had 
devised this apparatus I was from my previous experiments tolerably well assured of 
its success, yet I experienced a feeling of great gratification when on applying a match 
to one of the bubbles which were ascending, it gave a sharp detonation ; I collected 
and analysed some of it; it was 0 - 7 oxyhydrogen gas, the residue nitrogen, with a 
trace of oxygen. 
Those who have endeavoured to deprive water of air, will have no difficulty in 
accounting for the residual nitrogen, or nitrogen mixed with a small portion of oxygen, 
which has occurred in all my experiments. De Luc pointed out the impossibility of 
practically depriving water of air, and Priestley, from observing the obstinacy with 
which water retained air, was led to believe that water was convertible into nitrogen 
(phlogisticated air). I have repeated several of Priestley’s experiments under much 
more stringent circumstances, and have never been able to free water from air, or 
so to boil water that for every ebullition of vapour a minute bubble of permanent 
gas was not left, which appeared to have been an indispensable nucleus to the vapour. 
The difficulty of boiling water increases, as M. Donny has proved, in proportion 
to its freedom from air, and at last the bursts of vapour become so enormous that 
the vessels employed are generally broken. There appears to me a point beyond 
which this resistance does not extend ; but even at this point a minute bubble of air 
is left for each burst of vapour, though they are so few and distant that the aggre- 
gate amount of gas is very trifling. I have produced from water which had been 
previously carefully deprived of air by the ordinary methods, three-fourths of its own 
volume of permanent gas, which proved to be nitrogen ; but as the water in this 
experiment was boiled under a long column of oil, it is probable that if any oxygen 
were present, it might have been absorbed by the oil ; I have, however, always found 
the proportion of oxygen to decrease as the boiling was continued. It may be worth 
noticing, as having had some influence on my mind, that many months ago, when 
considering the experiments of Henry and Donny on the cohesion of water, I men- 
