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



The current used in some of the experiments was about 

 •5 ampere, and as the section of the tube between BG is about 

 half a square centimetre the current density on the carbon is 

 approximately one ampere per square centimetre. 



Under these conditions the readings in Table I. were obtained. 



The analyses of the carbon dioxide gas were made by placing 

 a sample of the gas over potash solution. 



The residue after the absorption of the carbon dioxide was 

 always found to be slightly explosive, showing that it consisted of 

 carbon monoxide mixed with a little oxygen. 



§ 3. When a cell is arranged with carbon in potassium 

 permanganate solution and a lead peroxide plate in dilute sulphuric 

 acid, the two electrolytes being separated by a porous pot, an 

 electromotive force acts externally from the lead peroxide towards 

 the carbon. Such a cell has an electromotive force of 033 volt, 

 and in it the permanganate ion is carried against the carbon plate, 

 and the hydrogen towards the lead peroxide which it reduces. 

 This cell forms a self-acting system in which carbon is consumed 

 at ordinary temperature. If the lead peroxide plate be placed in 

 the potassium permanganate the cell has an electromotive force of 

 0'08 volt acting in the same direction as before. 



§ 4. The chemical changes in the solution and at the carbon 

 electrode may be represented thus : — 



C + 2H 2 + 4KMn0 4 = C0 2 + 4HMn0 4 + 4K. 

 4K + 4H 2 = 2H 2 + 4KOH. 



It has already been pointed out that C0 2 is given off at the 

 anode, and it remains to prove that HMn0 4 or KMn0 4) resulting 

 from the neutralisation of the acid, persists in solution although a 

 quantity of electricity more than sufficient for its complete de- 

 composition be transmitted through the solution. To prove this 

 experiments were made with an apparatus from which the per- 

 manganate could be easily withdrawn. A glass cylinder 5 cm. in 

 diameter had a diaphragm of parchment-paper stretched over one 

 end, and held tightly by indiarubber bands. Into this vessel 



N 

 50 c.c. of ^r K 2 S0 4 was poured, and the cylinder was arranged to 



N 

 dip into 100 c.c. y^rKMn0 4 . A carbon or platinum anode was 



placed in the permanganate, and a platinum cathode in the 

 potassium sulphate. A current of known strength was then 

 passed for an observed time. Meanwhile a standard ferrous 

 ammonium sulphate solution was prepared and titrated against 

 100 c.c. of the stock permanganate solution. After passing the 



