414 



Article XXI. 



On the Chendcal Effects of Electric Currents of low tension^ 

 in ])roducing the Crystallization of Metallic Oxides, Siil- 

 phurets, Sulphates, Sfc. ', «n forms frequently closely resem- 

 bling the native combinations ; by M. Becqu£rel.* 

 From Becquerel's Traite de VElectrtcite et du Magnetisme, vol. iii, p. 287. 



l.JjY means of long-continued electrical action pi'oceeding from a 

 single pair of plates, chemical effects more or less considerable are pro- 

 duced, whether the affinity of the solution for one of the electrodes adds 

 its action to these forces or opposes (hem. We every day observe that 

 nature, having unlimited time at her disposal, produces with slender 

 means immense effects. But these means frequently escape our senses, 

 because they have not been studied with sufficient care, and are not in- 

 cluded in the ordinarj' circle of our inquiries. It is only by working on 

 a small scale, and closely observing every step of our processes, that we 

 have a chance afforded us of discovering any of the means employed 

 by nature to produce the phsenomena of molecular attraction. With 

 this view let us observe some of the decompositions obtained by means 

 of apparently feeble electrical forces. 



At present it is not doubted that voltaic action may produce chemi- 

 cal effects ; but Ave do not know liow far this action, when it is very 

 feeble, influences affinities, and whether, at the very moment when 

 these become sensible, particular pheenoniena may not be produced, 

 which disappear in the general effect, when we employ a pile possessing 

 a certain energy. W^e know, for instance, that if two wires of any 

 metal are plunged into a metallic solution, each of them communi- 

 cating with one of the poles of a voltaic pile of sufficient energy, we 

 always obtain at the negative wire either hydrogen, reduced metal, or 

 oxide. But when the tension is extremely slight, does the phsenomenon 

 take place in the same manner ? Do all metals possess this property 

 in the same degree ? In order to aaiswer these questions, successive 

 reductions must be made in the intei>sity of the electricity, and at the 

 same time what passes in the decompositions must be observed. 



Let us put a metallic solution (for instance a solution of copper) into 

 a cylindrical glass, and then with the greatest care pour over it distilled 

 or acidulated water, so that the two liquids may remain separate, the 

 one above the other ; and then immerse a plate of copper into it, we find 

 after a few hours this plate covered with a precipitate of copper in a 

 metallic state. Different metallic solutions gave similar results. Hence 



* For the selectim of this Paper the Editor is indebted to H. J. Brooke, 

 Esq., F.R.S. A notice of a Memoir on this subject, read by M. Becquerel to 

 the Academy, is given in the Philos. Magazine and Annals for March 1830. 



