Mr. J. Napier on Electrical Endosmose. 13 



the positive being sulphate of copper; gas was freely evolved 

 from the negative electrode ; in a little time the porous dia- 

 phragm facing the electrodes became coated with oxide of 

 copper, which greatly retarded the current, and made it neces- 

 sary to use a more powerful battery. After twelve hours, the 

 oxide which had accumulated upon the diaphragm and at the 

 bottom of the positive cell was carefully collected, washed, 

 dried, and weighed 7*3 grains. The potash of the positive 

 solution being neutralized by muriatic acid, had a solution of 

 chloride of barium added, which gave a precipitate of sulphate 

 of barytes weighing 26 grains, equal to about 9 grains of sul- 

 phuric acid. From this it appeared that the copper had 

 passed from the positive to the negative as sulphate of copper, 

 and therefore not by electrolysis. 



In repeating similar experiments with very dilute alkaline 

 and earthy salts in the negative cell, I have observed that the 

 oxide of copper formed being a conductor of electricity, it 

 often floated between the diaphragm and negative electrode as 

 a kind of spongy fibre, and conducted the electricity through 

 it as a solid, constituting its extremity in connexion with the 

 porous partition into the electrode, the result being the reduc- 

 tion of the oxide in and upon the diaphragm, closing it up 

 with metallic copper, similar to that observed in the operations 

 of electro-metallurgy when any of the electrodes are allowed 

 to touch the diaphragm. It has often surprised me how mi- 

 nute a fibre would connect the electrode and cell and produce 

 a wide-spreading result. 



A solution of cyanide of potassium was next tried in the 

 negative cell, having sulphate of copper in the positive ; the 

 current passed four hours. The cyanide solution smelt strongly 

 of hydrocyanic acid ; the solution was found to contain both 

 copper and sulphate of potash ; the quantities were not de- 

 termined. 



The next object was to use two salts of such a character 

 that if that from the positive cell passed to the negative by en- 

 dosmose it would remain in solution ; if by electrolysis, the base 

 would be reduced to the state of an insoluble oxide. The 

 negative was accordingly charged with a solution of caustic 

 potash, and the positive with cyanide of copper and potassium, 

 the latter in excess. After eight hours, during which gas 

 was freely evolved from the negative electrode, and upon it 

 was a small portion of copper powder, no oxide was formed ; 

 the solution contained cyanide of potassium and copper, the 

 latter, being precipitated by hydrochloric acid and fused, gave 

 35 metallic copper, with strong smell of hydrocyanic acid. 



