excited by Chemical Tendencies. 313 



exposed to the action of this current is no more electrolysed 

 than sulphate of copper is. On a mixture of iodide of potas- 

 sium and gelatinous starch being put in connection with the 

 electrodes, signs of decomposition are certainly exhibited, a 

 very small and slightly coloured spot making its appearance 

 round the positive electrode, which spot, however, does not 

 sensibly increase either as to size or intensity of colour^ 

 however long the action of the pile may last. From the facts 

 stated it seems as if a current excited by mere chemical ten- 

 dency has the power of decomposing at least one electro- 

 lyte ; but from reasons I shall now indicate I think such an 

 inference inadmissible. Although there is apparently no 

 chemical action going on in the pile described, still such 

 action takes place to a certain degree at those parts of the 

 iron wires which are placed immediately above the level of 

 the acid. That such is really the case appears from the fact, 

 that after some time the parts mentioned are losing their me- 

 tallic lustre and covering themselves with a brownish film. 

 This chemical action, slow and insignificant as it is, must ori- 

 ginate a current, and consequently increase the intensity of 

 that current, which is produced by the tendency of inactive 

 iron to unite with oxygen. Now as the united strength of the 

 two currents is hardly capable of decomposing traces of 

 iodide of potassium, I think from this fact we may safely draw 

 the conclusion, that the current which results only from che- 

 mical tendencies cannot of itself cause electrolyzation. Some 

 might, perhaps, be inclined to think the whole current of my 

 iron-platina pile produced by that slow oxidation of the iron 

 wires which takes place at and above the level of the acid, 

 but by most conclusive experiments I have ascertained that 

 such is not the case. But if, on the contrary, we suppose the 

 current of our pile to be wholly due to chemical tendency, it 

 can easily be shown that the electrolyzing power of a current 

 proceeding from an indubitable, (i. e. visible) chemical action, 

 surpasses by far the decomposing force of that current which 

 is produced by my tendency pile. Let one only of the inact- 

 ive iron wires of the latter be thrown into chemical action, 

 (for instance, by touching it with a piece of any active metal,) 

 and a remarkable change in the action of the pile will take 

 place ; whilst the latter, on having all its iron wires inactive, 

 ^colours but very slightly the starch impregnated with iodide 

 of potassium : no sooner has one of those wires been ren- 

 dered active, than a large and deeply coloured spot is pro- 

 duced round the positive electrode. It is a matter of course 

 that the electrolyzing action of the pile upon the iodide will be 

 increased by augmenting the number of active wires. In- 



