Experimental researches in voltaic electricity

Abstract

The author adduces many facts in refutation of the theory by which Volta endeavoured to explain the development of electricity in galvanic circles. He shows that the contact of dissimilar metals is not necessary for producing that effect, for galvanic action may be obtained by employing only one metal, if the two ends of the same copper wire be coiled into helices of different diameters, and immersed into dilute nitric acid. The experiments of Mr. Parrot of St. Petersburgh are cited as leading to results totally different to those on which Volta rested the foundations of this theory. The author points out several important marks of distinction between voltaic and common electricity, and denies that the latter is capable of passing into the former. He shows by an experiment that the free electricity developed by heat is independent of that developed by galvanic action. Chemical decompositions are effected in a totally different manner by voltaic and by ordinary electricity; for in the former case the two elements of the decomposed substance are found disengaged at the opposite poles, but in the latter they are developed at the same point, and appear more as the effect of a cleavage of the molecules by the mechanical agency of electricity. The author conceives that in a galvanic circle of zinc and copper with interposed water, the superior attraction of the zinc for oxygen produces an arrangement of the molecules of the water such that the particles of oxygen entering into the composition of each are all turned towards the zinc. This definite arrangement produces in its turn, by production on the neutral electric fluid contained in the metal, a corresponding definite arrangement of the two electricities along the whole electric circuit. Hence electro-magnetic effects may be obtained without any chemical decomposition; this latter effect taking place only when the attraction of the metal for one of the elements of the fluid is greater than that between the two elements of the fluid: and upon this principle the author conceives that the phænomena of the secondary piles of Ritter, and those observed by M. de la Rive, may be explained. By adopting the theory of the successive decomposition and recomposition of each particle of fluid in the line of action, we avoid the necessity of supposing the transference of the disengaged element through the intervening mass of fluid. Whatever circumstance favours the decomposition of the water, will also increase the power of the voltaic arrangement. Conformably to these views we find that all liquids whose component parts go to the same pole are non-conductors of voltaic electricity. A given section of a liquid is capable of conducting only a limited quantity of electric influence. It was also found by experiment that when sulphuric acid was employed, the quantity of electro-magnetic action in the connecting wire is exactly proportional to the quantity of water decomposed in the liquid part of the circuit. This quantity is, within certain limits, inversely proportional to the square root of the distance between the plates.