10 M. W. Beetz on the Excitation of Electricity 



When the carbon electrodes at which the electrolysis had 

 taken place were left in position, their difference of tension in 

 comparison with pure carbon diminished only slowly and im- 

 perfectly. The carbon at which hydrogen had been evolved 

 showed still, after twenty-four hours, tension-differences 

 against pure carbon amounting to about 0'6 D, while that at 

 which oxygen had been evolved showed about 0*3 D. Evi- 

 dently, however, further chemical changes had taken place in 

 the carbons: — in the negative, probably reductions of metallic 

 oxides mixed with it in spite of all the purification it had un- 

 dergone ; in the positive, conversely, oxidations. An electro- 

 lysis, between carbon electrodes, of dilute sulphuric acid 

 delivered, during the same time in which at platinum elec- 

 trodes 27*36 cubic centims. of hydrogen were separated by 

 the same current, 26*86 cubic centims. of hydrogen, but only 

 1*71 cubic centim. of oxygen. For the reduction, therefore, 

 but very little hydrogen was consumed, and so much the more 

 oxygen for the oxidation ; indeed it was the carbon itself that 

 was oxidized, forming carbonic acid and carbonic oxide gas. 

 When, as in the present experiments, small quantities of gas 

 are separated from large masses of conducting liquid, the car- 

 bonic acid is all absorbed ; but if by long-continued electro- 

 lysis of a neutral-salt solution (for instance, Glauber salt) 

 larger quantities of gas are evolved, the gas which collects 

 above the liquid contains considerable amounts of free carbonic 

 acid, which can be removed by agitation with caustic potash. 

 The remaining gas proves to be carbonic oxide. The propor- 

 tion of the two gases to one another appears to depend on the 

 density of the current*. At the same time the carbon anode 

 is violently attacked and carbon powder copiously thrown off 

 from it, like the palladium dust thrown off from the oxidizing 

 palladium plate ; while the surface of the carbon becomes 

 coloured deep blue. Macaluso has also observed this destruc- 

 tion of the carbon with the evolution of chlorine at a carbon 

 electrode. 



Different again, lastly, was the behaviour of carbon to sul- 

 phuric acid. After a few gas-bubbles had made their appear- 

 ance at the carbon (just as before with palladium), no change 

 was shown in its electromotive position. As the diluted sul- 

 phuric acid was repeatedly shaken with fresh quantities of 



* In consequence of the complete disappearance of the gas in my first 

 experiments, I at first thought that the carbon itself was not oxidized at 

 all. An incidental communication from M. Laurent, Ingenieur, of Bel- 

 fort, who had observed the occurrence of carbonic oxide and acid on elec- 

 trolysis at carbon electrodes, induced me to repeat my experiments on a 

 larger scale. I intend to carry them on still further. 



