M. De la Rive on Chemico-capiUanj Actions. 441 



there is neither metallic reduction nor electrical current. In 

 this case evidently the liquids no longer communicate. 



To obtain an electric current without apparent chemical action, 

 fissures having the shape of a star are made in a small cup by 

 touching it with a slightly moistened glass after having heated 

 it. The cracked beaker is then tilled up to the star with a solu- 

 tion of nitrate of baryta, and is placed in another vessel contain- 

 ing weak sulphuric acid. Two platinum plates, each immersed 

 in one of the liquids, are connected by the wire of a galvanome- 

 ter ; and an electric current is obtained without any appearance 

 of chemical action; that is to say, there is no deposit of sulphate 

 of baryta. Associating in the same manner a solution of chro- 

 mate of potash with one of nitrate of lead, or a solution of ferro- 

 cyanide of potassium with a solution of protosulphate of iron, 

 no precipitate is obtained, which proves that there is no apparent 

 chemical action, although an electric current is produced. On 

 the other hand, working with solutions of nitrate of copper and 

 of monosulphide of potassium and the same vessel which served 

 for former experiments, a strong current is obtained, and some 

 time after there is a deposit of metallic copper in the fissure. It is 

 true that the electromotive force which takes place in the contact 

 of these two latter solutions is far more considerable than that of 

 the other solutions which had been submitted to experiment. 

 M. Becquerel remarks that it is possible that with these latter so- 

 lutions, the chemical reactions being extremely feeble, an electric 

 current is produced, though the effects resulting from the chemical 

 action which has produced it are not perceived for a long time. 



In this part of his researches M. Becquerel dwells on what he 

 calls the polar properties of the sides of the fissures of cracked 

 vessels, acting like electrodes when these fissures furnish the 

 passage of a current. This is also an interesting point, on which 

 I will delay for a moment, inasmuch as it seems to me con- 

 nected with a more general law discovered by Faraday. The 

 following is M. Becquerel's experiment. 



When we decompose a solution of nitrate or sulphate of cop- 

 per partly contained in a cracked vessel and partly in a sound 

 one in which the former is immersed, and if by means of a pla- 

 tinum electrode placed in each of these vessels the current 

 from a battery composed of several couples be passed, a decom- 

 position is obtained in which the negative electrode becomes co- 

 vered with metallic copper ; the current, however, has but small 

 intensity, owing to the thin layer of liquid found in the crack, 

 which in this case plays no part. It is not the same if the 

 cracked vessel contains a solution of caustic potash and the ne- 

 gative electrode while the other vessel contains the metallic so- 

 lution and the positive electrode. In this case water alone is 



