The letters of Faraday and Schoenbein, 1836-1862 : with notes, comments and references to contemporary letters / edited by Georg W.A. Kahlbaum and Francis V. Darbishire.

Date:: 1899

Credit: The letters of Faraday and Schoenbein, 1836-1862 : with notes, comments and references to contemporary letters / edited by Georg W.A. Kahlbaum and Francis V. Darbishire. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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$into nitric acid and the whole arrangement connected with the wire of the galvanometer. From the facts stated, it appears that platina is positive with regard to peroxide of lead, and that the disappearance of that compound is caused by a current, which eliminates hydrogen at the negative peroxide, by which means the latter is reduced to protoxide of lead and rendered soluble in nitric acid. In a similar manner I have ascertained that the voltaic relation of inactive iron to peroxide of lead is exactly the same, as that ot platina to the said peroxide. In using peroxide of silver instead of that of lead voltaic effects are produced quite the same as those which were just spoken of; that is to sa_\', a continuous current is excited to which the peroxide acts the part of the cathode and either of the metals in question that of the anode. As to the voltaic relation, which one of the mentioned peroxides bears to the other my experiments have shown, that peroxide of silver is always negative with regard to the peroxide of lead, be the fluid made use of nitric acid or a solution of blue vitriol. Now from all the facts above stated, I think, we are allowed to draw two important inferences: i. that peroxide of silver, peroxide of lead, platina and inactiv^e iron represent a series of substances, in which the preceding one is alwa3^s negative with regard to that which follows in the list 2. that any two of the four sub- stances mentioned being voltaically associated with one another and put either into nitric acid or a solution of sulfate of copper excite a continuous current, which is not due to oxidation or any chemical change. It is hardly necessary to add that the currents produced in the said circumstances are extremely feeble, being only indicated by most delicate galvanometers. You will agree with me, that the facts spoken of are highly important in a scientific point of view, as the}' do produce evidence in favo[u]r of that theor}', which asserts, that b>' the mere contact of heterogeneous substances their electrical equilil)rium can be disturbed, quite independent of any chemical action taking place between them. All chemists certainly maintain, that pure nitric$