Electrolysis of Secondary Compounds^ 187 



results of the following arrangement. The zincode cell was 

 filled with a dilute solution of potassa, and the connecting cell 

 with the same. The platinode cell was charged with a strong 

 solution of the red ferrocyanide. This solution previously to 

 the commencement of the experiment gave no blue solution 

 with perchloride of iron. The liquid in the zincode and con- 

 necting cells speedily became yellow, and after a short time 

 the solution in the platinode cell also became yellow. All the 

 solutions were now found to contain the yellow ferrocyanide. 

 Thus it was quite clear that no such compound as ferridcya- 

 nogen travelled from the red salt when exposed to electrolysis, 

 but that the red salt wtis converted into the yellow by the abs- 

 traction of ferrocyanogen from the platinode, which ferrocj'a- 

 nogen being transferred to the zincode, there formed with the 

 potassium presented to it by electrolysis the same yellow ferro- 

 cyanide. 



In order to extend further our knowledge of the electrolysis 

 of this class of secondary compounds, the following experi- 

 ments were made : — 



{p.) A diaphragm apparatus was charged with a strong so- 

 lution of cyanide of potassium (K, Cy) in the platinode cell, 

 and a solution of potassa in the zincode and connecting cells. 

 The arrangement conducted well; gas was given off from 

 both electrodes, and cyanide of potassium formed in abun- 

 dance in the zincode cell. Hydrogen must therefore have 

 been given off at the platinode by the oxidation of the potas- 

 sium evolved, and oxj'gen at the zincode by the deoxidation 

 of potassa under the influence of the current in the formation 

 of the cyanide of potassium. 



{q.) The apparatus was charged throughout with solution 

 of cyanide of potassium, and subjected to the current. Gas 

 was given off as before at the platinode ; but at first none from 

 the zincode. The liquid in the zincode cell gradually became 

 of a deep brown colour, and the electrode itself was coated 

 with a deep brown matter, which was easily washed off. In 

 the latter part of the operation gas was also evolved in small 

 quantity at the zincode. The solution smelled strongly of 

 hydrocyanic acid, of which, by the proper tests, it was found 

 to contain a considerable quantity. There can be no doubt 

 that the brown matter which was abundantly formed was 

 paracyanogen, which is soluble in the alkaline solution of the 

 cyanide of potassium, and which must have been produced 

 either by the spontaneous decomposition of the hydrocyanic 

 acid, or in a way something analogous to the formation of the 

 red ferrocyanide of potassium from the yellow by the absorp- 

 tion of an additional quantity of ferrocyanogen. 



