106 
MR. GROVE ON THE GAS VOLTAIC BATTERY. 
It should be observed, that in these experiments only a single pair of the gas bat- 
tery can be used, as, if more be employed, the electrolyte is likely to be decomposed, 
and gas added to the compound # . The process is rather slow, but I think very sure. 
Another valuable application of this process is, that it affords (in experiment 24) a 
simple method of obtaining nitrogen of unquestionable purity. I know of no method 
which effects this object so perfectly. All the oxygen of the air is abstracted, as well 
as that free oxygen which may be contained in the liquid ; and by subsequently in- 
troducing a little lime-water into the tube a, the trifling quantity of carbonic acid 
may be removed, or the same thing may be at once effected by using caustic potash 
as the electrolyte in the apparatus fig. 12. 
Probably many other applications of the gas battery may suggest themselves to other 
experimentalists, and obviously many more changes may be rung upon the gases em- 
ployed, and curious and valuable results obtained ; I have, however, in this paper 
given a sufficient number of experiments fairly to open the subject ; each appears so 
suggestive of new ones that it is difficult to know where to stop. 
The experiments on eudioinetry, which I have last named, induced me to refer to 
Dr. Henry’s paper on Gaseous Analysis ■j', and on reading it I was struck with a 
coincidence between the action of spongy platinum on mixed gases and the gas bat- 
tery, a coincidence strongly confirmatory of the views which led me to its discovery. 
I will endeavour briefly to state these, and I state them, not as being absolutely cor- 
rect, for differences of opinion may exist on this as on every other scientific matter, 
but as being those which existed in my mind prior to the experiments, and Which are 
considerably, and to me unexpectedly, strengthened by the results embodied in the 
above-mentioned paper of Dr. Henry. 
My original deduction may be stated and exemplified as follows : — When pure or 
amalgamated zinc is immersed in acidulated water, the oxygen, as is well known, 
will not combine with the zinc ; but touch both zinc and liquid with platinum and 
combination ensues, the platinum being unaltered. So with a mixture of oxygen and 
hydrogen, the gases, although in intimate contact, will not chemically unite, but 
touch them with clean platinum and more or less rapid combination ensues. Here 
also the platinum is unaltered. Leaving out of the case any purely hypothetical ex- 
planation, why may not effects so similar in their character be related in other 
respects? In the voltaic combination the platinum is heated during action, and if 
the surfaces, and consequently the quantity of electro-chemical action be considerable, 
it is ignited ; so in the catalytic combination, if the platinum be thin and of large 
extent, or in the form of a sponge, which still more increases its surface, it is ignited. 
Why, therefore, may we not regard the detonation of gas by platinum as a voltaic 
effect ? or the combination of oxygen and zinc by the presence of platinum a cata- 
lytic effect ? The only difference is, that gases do not admit of that interchangeable 
relation of particles which we call electrolysis. The necessity lor this interchange is, 
* See Postscript. f Philosophical Transactions, 1824. 
