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
Catalogue details

Licence: Public Domain Mark

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.

    45/404 (page 25)
    with a comparatively small quantity of chloride of sodium (common salt) the calling forth of the peculiar condition is prevented, not only in the foregoing case, but in all that will be mentioned afterwards. This fact is by no means an insulated one and depends upon the same cause, which prevents the disengagement of oxigen at the iron (whilst constituting the positive electrode of the pile) out of a solution of haloid salts etc. Presuming, that by rendering iron inactive towards sulphate of copper in the way discribed, a current would be excited as to its direction equal to that, produced by calling forth the peculiar state of this metal within nitric acid, and having had recourse to the galvanometer, I was ver}^ much struck on finding that the needle was not in the least affected. The instrument I made use of in my experiments, though indicating rather weak currents, does certainly not possess the highest degree of sensibility possible; (it contains about lOO coils) but as in a scientific ])oint of view it is of very great importance to know, whether the peculiar condition of iron can in any way be called forth with- out exciting at the same time a current, I beg you to decide this question by means of your most delicate galvanometer. If your experiments should happen to place beyond doubt the absence of any current under the before mentioned circum- stance, why such a result would allow of drawing very curious inferences from it, and prove, in the first place, that the in- activity of iron has as to its origin nothing to do with what we call a current. A series of phenomena, regarding the action of iron wire (associated with peroxide of lead) upon a solution of sulphate of copper may be called forth, which exhibits a beautiful analogy to that set of facts, communicated to you in my letter, you had the kindness to have inserted in the Phil. Magazine No. 59.^ To obtain with iron in the said solution results similar to those mentioned in my letter, with regard to the action of this metal upon nitric acid, the following conditions