20 
MR. GROVE ON THE DECOMPOSITION OF WATER BY HEAT. 
affinity, and a consequent establishment of the law of continuity in reference to 
physical and chemical attraction. 
The deposit from chlorine, to which I have alluded in my paper, I have since ex- 
amined, and though it differs in colour from that described in books, I find it is a 
protochloride of platinum, formed at the expense of the platinum wire. The larger 
portion of the chlorine in the tube combines with the hydrogen of the aqueous vapour, 
and the muriatic acid is absorbed by the water ; when the experiment terminates the 
gaseous volume is reduced to nearly one-half, and this residue is oxygen. 
This effect induced me to try an ignited wire on other analogues of chlorine, and 
I tried bromine and chloride of iodine in the apparatus (fig. 5). The tube was filled 
with the liquid, and its extremity was in the first experiments immersed in another 
narrow tube of the same liquid as that which filled it. When the platinum wire was 
ignited, permanent gas was given off both from the bromine and from the chloride 
of iodine, which gas on examination proved, to my surprise, to be oxygen. In one 
experiment I collected half a cubic inch of gas from an equal volume of chloride of 
iodine. As the experiment in this form required too large a quantity of the liquid to 
enable me to observe any change which might take place in its character, I repeated 
it with a tube five feet long, bent in two angular curves. A small quantity of the 
liquid was placed in the extremity of the tube containing the wire, which was so 
arranged as to be the lowest point ; the angles were placed in cold water and the 
experiment proceeded with ; my object was to enable the dense vapour of the liquids 
to shelter them from the atmosphere, there being no satisfactory method of shutting 
them in and yet allowing room for the elimination of the liberated gas, or of absorb- 
ing the latter by combination without also absorbing the vapours. 
I had hoped by the above means to proceed with the experiments until all the 
oxygen was liberated that could be driven off, and then to have examined the residua; 
but I found that after experimenting for a short time, both the platinum wire and 
the glass in proximity to it were attacked by the liquids; this difficulty, similar to 
those which have hitherto prevented the isolation of fluorine, I have not yet been able 
to conquer, though I hope to resume the experiments. 
As chloride of iodine is decomposed by water, it cannot contain any notable quan- 
tity of the latter, but, until the experiments are carried further, it must remain a 
question whether the oxygen results from a small quantity of water contained in the 
liquid, the hydrogen combining with the liquid itself, or from a decomposition similar 
to that of the peroxides. The experiments certainly add a new and striking analogy 
to those already known to exist between the peroxides and the halogens, but they 
do not, as far as I have hitherto carried them, necessarily prove analogy of com- 
position. 
In conclusion, I would call attention to a point which I omitted to notice in my 
original paper, viz. the explanation afforded by the results contained in it of the 
