298 M. De la Rive's ^Researches 



to tension, which is unconnected with the element of time, 

 since the condenser remains in contact with the pole an in- 

 determinate period, it may be conceived that the two effects 

 just noticed will nearly counterbalance each other, but it is 

 different with regard to the decompositions effected by the 

 current, and in general, with regard to all its dynamic effects, 

 for there is not sufficient time for the accumulation of the two 

 electric principles; and whatever diminishes the quantity of 

 free electricity disengaged by each pair in a given time, and 

 consequently at the two poles, diminishes the intensity of the 

 effects produced by this circulation. The only means by 

 which the conductibility of a pile may be diminished, without 

 altering the quantity of electricity which it produces, is, as 

 has been already said, by the addition of similar pairs. 



In support of the explanation which has just been given, I 

 shall produce some experiments which I made with diaphragms 

 of different kinds. I had previously shown {Annates de Chim. 

 et de Phgs., Feb. 1825) and again in 1828 {Annates de Chim. 

 et de Phys. 9 vol. xxxvii. p. 225.) that the diminution of con- 

 ductibility in a liquid which results from the interposition of a 

 metallic diaphragm, is reduced in the proportion that the dia- 

 phragm is attackable by the liquid. The following are the 

 results which I obtained. 



A pile of seven elements, zinc and copper, the surfaces each 

 four inches square, charged with pure water, mixed with T 1 ^ 

 of nitric acid, gave 1 25° of Breguet's metallic helix. A dia- 

 phragm of zinc, interposed between any two pairs, reduced 

 the effect of the current to 100°; and a diaphragm of copper 

 reduced it to 70°. A pile of twenty pairs, similar to the pre- 

 ceding, but less strongly charged, gave 110° of the metallic 

 helix; a diaphragm of zinc produced no sensible diminution 

 in the intensity of the current ; a diaphragm of copper reduced 

 it to 100°. Lastly, employing diaphragms of platina, by 

 means of which I divided a certain quantity of concentrated 

 nitric acid into two or more parts, through which passed the 

 current of a strong pile composed of eight pairs, each two feet 

 square, and charged with a mixture of forty parts water, two 

 sulphuric acid, and one nitric acid, I always obtained, with 

 Breguet's metallic helix, the following results : 



Exp. I. , Exp. II. 



Number of Cent. Deg. of 



diaphragms. the helix. 



1 312° 



2 170 



3 75 



4 12 



5 



Number of Cent. Deg. of 

 diaphragms. the helix. 



1 220° 



