Mr Skinner, On the Electro-chemical equivalent of Carbon. 261 



On the Electro-chemical Equivalent of Carbon. By Mr S. 

 Skinner. 



[Received 5 February 1900.] 



§ 1. In a paper read before the Physical Section at the Bristol 

 B.A. Meeting 1898, I described some experiments bearing on the 

 theory of Jacques' carbon-consuming cell. This cell consists of a 

 carbon pole dipping into hot fused caustic soda contained in an 

 iron crucible. Through the fused caustic soda is passed a current 

 of air, and an electromotive force is generated acting from the iron 

 to the carbon in the external circuit. My experiments showed 

 that the addition of sodium peroxide was more efficient than 

 passing in air, and that the sodium peroxide acted as a depolariser 

 when placed in a divided cell so that it came in contact with the 

 iron alone. These results were explained by considering that the 

 sodium ferrate which was formed acted as an electrolyte when 

 dissolved in fused caustic soda, and that the ferrate combined with 

 the sodium which must be set free on the iron surface by the 

 electrolytic actions in the cell. 



Attempts were made to study the consumption of carbon by 

 weighing the carbon rod before and after current had been taken 

 from the cell. These, however, failed as it was difficult to remove 

 the absorbed electrolyte from the porous carbon. So the rate of 

 consumption of carbon was left undetermined. 



The new experiments in the following paper were made with 

 the view of studying this point, and a cell acting at ordinary 

 temperature and with aqueous solutions has been devised. The 

 cell is described in section 3. 



The experiments of Bartoli and Papasogli on the electrolysis 

 of water (Ann. Chim. et Phys. 1886) and of Cohen (Zeitschr. fur 

 Electrochemie, 1896) on that of sulphuric acid with carbon elec- 

 trodes have shown that carbon compounds are formed in solution, 

 and also that carbon dioxide gas, carbon monoxide, and oxygen in 

 varying proportions are given off at the anode. Further, Cohen 

 constructed a cell in which a lead peroxide plate formed the 

 cathode and a carbon block the anode with an electrolyte of hot 

 sulphuric acid. 



It appears from these results that a highly oxygenised sub- 

 stance on electrolysis may yield an anion which will attack carbon, 

 and clearly a very good substance for this purpose would be 

 potassium permanganate. 



§ 2. When a current is passed into a solution of potassium 

 permanganate at the ordinary temperature from a carbon anode 

 carbon dioxide gas is given off at this electrode. If the same 

 current be made to pass through a water voltameter the ratio of 

 the hydrogen set free to the carbon dioxide may be determined. 



19—2 



