into the Cause of Voltaic Electricity. 283 



from the particles of zinc to the particles of iron. These cur- 

 rents decompose water; the hydrogen is disengaged, and the 

 oxygen, by combining with the zinc, increases the energy of 

 the current, which thus successively becomes cause and effect; 

 and the action may be observed to go on constantly increasing 

 in intensity, as if it were the effect of an accelerating force, 

 and neither to be constant or diminished but when the surface 

 of the metal becomes covered with a little suboxide black ari- 

 sing from the decomposition of the sulphate of zinc by the local 

 currents. If, instead ofcommonzinc, distilled, and consequently 

 very pure zinc be employed, a very feeble chemical action is 

 obtained by immersing it in diluted sulphuric acid; but if a 

 pair be formed by uniting it metallically with platina immersed 

 in the same liquid, the intensity of the chemical action which 

 takes place upon its surface is augmented; the disengagement 

 of the hydrogen and the oxidation of the zinc become more 

 and more energetic in consequence of the current which is 

 established from the zinc to the platina, and which here also 

 is successively effect and cause. The limit to the augment- 

 ation of intensity is only the effect of the constantly increasing 

 resistance experienced by the current in the circuit, in pro- 

 portion to its increasing strength ; the resistance arises from 

 the imperfect conductibility of the parts of which the circuit 

 is composed, and the deposit of suboxide of zinc which takes 

 place, not upon the metal itself, as in the preceding case, but 

 upon the platina. The only difference which exists between 

 the effects resulting from the employment of distilled zinc 

 when united to platina, and of the zinc of commerce is, that 

 in the first case the currents traversing a longer circuit may 

 be perceived, while in the second, being almost molecular, they 

 cannot be apprehended ; but they exist equally in both cases. 

 It will now be easily understood why, in the same circum- 

 stances, a plate of common zinc with another metal forms a 

 much less powerful pair than a plate of distilled zinc, though 

 it produces a much livelier chemical action ; it may also be 

 understood why the latter zinc is negative when it forms a 

 pair with distilled zinc which is less attacked than itself. Very 

 great advantage will therefore be found to result from the em- 

 ployment of distilled zinc in the construction of voltaic piles 

 instead of common zinc ; for with the former nearly all the 

 chemical action can be utilized, since it is in its totality cause 

 and effect ; whilst with common zinc the greater part of it is lost 

 by immediate recom position ; the proportion utilized is there- 

 fore but a small fraction of the total quantity of zinc dis- 

 solved. 



Since I made known the properties of distilled zinc, Mr. 



2 O 2 



