11 Mr. J. Napier on Electrical Endosmose. 



From this it appeared that both the copper and potassium salt 

 were transferred by endosmose. The double cyanides of po- 

 tassium and silver and of potassium and gold were next sub- 

 stituted for the copper in the positive cell with similar results. 

 Nitric acid was also substituted for the caustic potash in the 

 negative cell, with the double cyanides of copper, silver and 

 gold in the positive, which would give the contrary result of 

 last experiments, namely, precipitating the metals if trans- 

 ferred by endosmose, but dissolving or holding them in solu- 

 tion if transferred by electrolysis. In a short time, in each 

 experiment, the surface of the porous diaphragm facing the 

 negative electrode became coated with the cyanide of the metal, 

 which accumulated and dropped to the bottom of the vessel. 

 At the termination of the experiments the acid solution smelt 

 strongly of hydrocyanic acid, and contained much nitrate of 

 potash. With the gold and silver salts, the acid solution had 

 not the slightest indication of their presence in solution, but 

 with the copper there was a considerable portion present, 

 which was owing to the cyanide of that metal being decom- 

 posed by nitric acid ; but this experiment being repeated with 

 the copper cyanide in the positive and sulphuric acid in the 

 negative, no trace of copper in solution was found in the acid. 

 The next experiment was to determine if any portion of the 

 potassium of the potash salt was transferred by electrolysis; 

 for this purpose two porous vessels were employed, one rilled 

 with a solution of cyanide of potassium, the other with dilute 

 nitric acid ; these were placed in a glass vessel containing a 

 solution of nitrate of silver; the positive electrode was placed 

 in the cyanide of potassium, the negative in the nitric acid. 

 The cyanide of potassium which passed from the positive cell 

 to the silver solution in the glass vessel was decomposed, pro- 

 ducing cyanide of silver and nitrate of potash. After twelve 

 hours, the cyanide of silver formed was carefully collected, 

 washed and dried ; it weighed 65'6 grains ; the remaining 

 silver solution had as much muriatic acid added as precipi- 

 tated the silver. The clear filtered solution was now evapo- 

 rated to dryness and kept for some time at the point of fusion. 

 There were obtained 28 grains of nitrate of potash, which is 

 4 grains less than the equivalent of cyanide of silver obtained ; 

 but the nitric acid in the negative cell also contained a little 

 nitrate of potash and silver, which had passed from the glass 

 vessel, and will account for this loss. From these, and a 

 variety of other experiments of a similar kind with different 

 salts, I consider that no base of an electrolyte is transferred 

 by electrolytic action, but that salts being electrolysed are all 



