MR. GROVE ON THE GAS VOLTAIC BATTERY. 
97 
the liquid, gas, and platinum met ; and it was to increase the number of these points 
that I employed platinized or spongy platinum ; indeed, from what I have since ob- 
served, I have much doubt whether I should have obtained any success had I used 
smooth platinum. The local action detailed in the last experiment, however, made 
me anxious to ascertain whether the principal points of action were those which I 
had originally believed, or whether the gases entered into solution first, and were 
then electro-synthetically combined by the immersed portion of the platinum ; 
whether, for instance, the efficient parts of the plates were the parts p q, p' q 1 (fig. 4), 
or q r, q' r' . To ascertain this the following experiment was made : — 
Experiment 3. — A battery of five cells was constructed, in which the platinum 
reached only to half the height of the tubes (see fig. 10). This was charged with 
oxygen and hydrogen, so that the liquid just covered the extremities of the platinum. 
In this case we have only the immersed portions of the platinum, q r, q' r\ and can 
examine the action of the gases which enter into solution, and are unaffected by the 
platinum until in solution. This battery so charged gave a very trifling action 
indeed ; it would not decompose iodide of potassium, and but slightly affected a 
highly sensitive galvanometer; but when a little gas was added, so as to expose the 
platinum to the gaseous atmosphere, a considerable current was developed, and a 
single pair decomposed the iodide. 
If, again, a battery of this description (fig. 10) be charged so that the water-mark 
is below the upper edge of the platinum, and the ends are connected in closed circuit, 
the liquid rises in both tubes until that in the hydrogen tube has reached the top of 
the platinum, and then there is no further rise. This experiment decides the question 
as to what is to be considered the working portion of the battery, but it does not 
positively decide whether solution and electrolysis are contemporaneous or successive, 
as it may be said that even what I have termed the exposed parts of the platinum 
are covered with a film of liquid. I should myself hesitate for the present to express 
a decided opinion on this point ; my first impression was, that there would be, as it 
were, three sets of points in contact, but I have not been able to devise an experiment 
definitively to settle this point*. 
I aimed next at further establishing the analogies of this battery with the ordinary 
voltaic battery, i. e. regarding the hydrogen tube as analogous to the plate of zinc 
or other oxidable metal at the anode ; I wished to see how far this relation was borne 
out. It was beautifully shown in 
Experiment 4, — Where a single pair was charged with oxygen and hydrogen, and 
a second with hydrogen in one tube, the other being filled with dilute sulphuric acid ; 
when the hydrogen of the second was metallically connected with the oxygen of the 
first, and the liquid of the second with the hydrogen of the first, as in fig. 11, bubbles 
of gas rose from the platinum, which proved, as I anticipated, to be hydrogen. In 
* I have sometimes remarked when mixed oxygen and hydrogen have been collected in one tube of the gas 
battery over distilled water, the addition of a little sulphuric acid causes the gases rapidly to disappear. 
