[D8923AAM], Letter from C H Aaron to Thomas Alva Edison, June 10th, 1889


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[D8923AAM], Letter from C H Aaron to Thomas Alva Edison, June 10th, 1889

Editor's Notes

I take the liberty of trespassing on your time and your kindness to ask you for some information. # About two years ago I conceived the idea of getting an electric current from the wet oxidation of carbon: substituting carbon for zinc. I succeeded, but don't know if my battery is worth anything or not -- also I fancy there is a scientific novelty in it but don't know. These points are what I want to ask you about, as I can't get satisfaction. I am a metallurgist and have not been able lately to follow this matter up. # My galvanic element consists of a porous inner cell and impervious outer cell - In the porous cell I have a solution of potassium permanganate - in the outer cell either simple water or any acid or alkaline solution. The best solution for the outer cell is one of an alkali polysulphide, as others soon cause polarization apparently and the current ceases, but with this it continues until the permanganate solution is quite colorless. The permanganate works best if a little sulphuric acid is added to free the permanganic acid. # In each cell I had a pencil of common coke to the upper end of which a copper wire was attached by means of melted lead - I found pl[------] also answered the purpose - A single element would decompose pure water. The oxidation of the coke in the permanganic acid was not actually proved, only inferred from the decomposition of the acid. # The coke in the outer jar is only a conductor, any other conductor will serve the purpose, as a finger or a piece of cloth connected by a wet string to the electrode - The coke in the porous cell is essential, it cannot be so replaced. # The battery gives no bad fumes, and the liquid in the outer jar serves to last for many weeks, the permanganate solution being [------] when decolored - Potassium dichromate, or chlorat, or bleaching powder, (with sulphuric acid), will give a current but are not so good. Nitric or sulphuric acid also gives a current, but it does not continue long. With permanganate acid, sodium polysulphide, and two pieces of coke the current is very steady I think. Now for what seems to me to be the most curious part. In all batteries that I have seen, the active plate is the positive plate, giving the negative pole at the terminal, e.g. a zinc and platinum or zinc and carbon - copper etc the zinc is positive; in a sil[--] and copper couple, the copper is active and it is the positive plate. # In my battery, I expected to find the active carbon positive to the passive carbon, but it is negative and gives the positive pole at the terminal - Will you kindly tell me if this is new and if such a battery is probably of any value.







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Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University
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