MR. DANIELL ON VOLTAIC COMBINATIONS. 
115 
greatly exceeded in efficiency the platinum plates themselves ; the quantity of gas 
collected in the voltameters in series being nearly double in amount to that from the 
battery in its normal state. 
I repeated this experiment with fresh iron plates, and ascertained that previous 
opposition to the platinum had greatly contributed to this energetic action of the 
first set : the disengagement of gas from the second but little exceeded that from 
the normal plates. 
I am inclined to believe that we may again find the explanation of these phenomena 
in the attraction of heterogeneous adhesion ; and I think it probable that the hy- 
drogen gas adhering with less force to the surface of the iron than to that of plati- 
num, is more readily carried out of the sphere of action when evolved in the process 
of circulation upon the former than upon the latter. The efficacy derived from the 
previous combination of the iron with platinum may be ascribed to the cleansing of 
its surface, or possibly to some difference of mechanical structure developed in this 
particular position. 
My attention was next turned to the effects of certain changes in the condition of 
the electrolyte employed in the excitation of the battery ; and now it was that I 
began to experience those, apparently capricious, changes in the force of the current 
which soon obliged me to give up all hope of rendering the results comparable with 
one another in the present form of its construction. When I added to the acidulated 
water a volume of nitric acid equal to that of the sulphuric acid employed, the quan- 
tity of hydrogen evolved from the conducting plates of the cells was greatly dimi- 
nished, and was irregular ; but when the voltameter was substituted for one of the 
cells, the quantity of hydrogen which it indicated was at first nearly treble that from 
the battery in its normal state. This action, however, speedily declined by a quantity 
which was quite appreciable at intervals of five minutes. By breaking the connexion 
of the circuit this energy was partially recovered, and that even during the short ces- 
sation of action which arose from the mere turning of the voltameter. When the 
charge of nitric acid was increased, the evolution of hydrogen from some of the cells 
was wholly stopped, whilst in others it continued to a small but unequal amount ; 
the quantity of the circulating current was at the same time increased, but rapidly 
declined as the action continued. 
My efforts were now turned to discover the cause of this perplexing variation ; but 
I shall not trouble you with the numberless experiments which I made upon the sub- 
ject, any further than may be necessary to elucidate the steps by which I was ulti- 
mately led to its detection. I allowed the battery to exhaust itself by leaving it in 
connexion for thirty hours, at the expiration of which time scarcely any gas was 
evolved in the voltameter. I then removed the platinum plates and substituted fresh 
plates of the same metal ; and when the connexions were made, the action was re- 
newed with nearly the same activity as at the first ; the falling off, however, was 
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