II. Note on the electrical relations of certain metals and metalliferous minerals

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Abstract
I Have ascertained that the crystallized grey oxide of manganese holds a much higher place in the electro-negative scale than any other body with which I have compared it, when immersed in various acids, and alkaline solutions; and the other metals and minerals which I have examined, appear to rank after it in the following order: Manganese. Rhodium. Loadstone. Platina. Arsenical pyrites. Plumbago. Iron pyrites. Arsenical cobalt. Copper pyrites. Purple copper. Galena. Standard gold. Copper nickel. Vitreous copper. Silver. Copper. Pan brass. Sheet iron. }} These five hold nearly the same place, varying in their mutual relations according to the time of their remaining immersed, and the nature of the liquid. The same may in some degree be said of the three other bodies included in the larger bracket. I have also compared the action of different metalliferous combinations in various diluted acids, &c. on the needle of the galvanometer, and some of the results are given in the following Table, in which cases sea-water, and also muriatic acid diluted with thirty-two parts of water, were employed. The figures show the angles of deflection observed when the needle became stationary, which may serve to give some idea of the relative effect of the combinations in question on the needle; but I find that the results are often considerably modified by the bodies being exposed for a longer or shorter time to the action of the acids, &c.; indeed this is so remarkable in the case of copper with zinc, that the needle often moves back much more than ten degrees from its maximum angle of deflection in one or two minutes after immersion; whereas in the case of iron with zinc, for example, the immediate retrograde motion of the needle is very inconsiderable, and it is still less, if anything, when some of the ores are substituted for one or both these metals. May not these phenomena depend on the relative degrees of tenacity with which the electric elements are retained by different bodies, it being apparently greatest in the case of compound bodies ?

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