From the effects of the electric current on glass, Davy argued that other earthy compounds would probably undergo change under similar conditions. He therefore had little cups of gypsum made, in which he placed pure water, and passed an electric current through the liquid. Lime was formed around the negative, and sulphuric acid around the positive pole. Using similar apparatus, he proved that the electric current decomposes very many minerals into an earthy or alkaline base and an acid. Picturing to himself the little particles of a salt as being split by the electric current each into two smaller particles, one possessed of acid and the other of alkaline properties, Davy thought it might be possible to intercept the progress of these smaller particles, which he saw ever travelling towards the positive and negative poles of the battery. He accordingly connected these small glass vessels by threads of washed asbestos; in one of the outer vessels he placed pure water, in the other an aqueous solution of sulphate of potash, and in the central vessel he placed ammonia. The negative pole of the battery being immersed in the sulphate of potash, and the positive pole in the water, it was necessary for the particles of sulphuric acid--produced by the decomposition of the sulphate of potash--to travel through the ammonia in the central vessel before they could find their way to the positive pole. Now, ammonia and sulphuric acid cannot exist in contact--they instantly combine to form sulphate of ammonia; the sulphuric acid particles ought therefore to be arrested by the ammonia. But the sulphuric acid made its appearance at the positive pole just as if the central vessel had contained water. It seemed that the mutual attraction ordinarily exerted between sulphuric acid and ammonia was overcome by the action of the electric current. Ammonia would generally present an insuperable barrier to the progress of sulphuric acid, but the electrical energy appeared to force the acid particles over this barrier; they passed towards their goal as if nothing stood in their way. Experiments are now multiplied by Davy, and the general conclusion drawn is that "Hydrogen, the alkaline substances, the metals and certain metallic oxides are attracted by negatively electrified metallic surfaces, and repelled by positively electrified metallic surfaces; and contrariwise, that oxygen and acid substances are attracted by positively electrified metallic surfaces, and repelled by negatively electrified metallic surfaces; and these attractive and repulsive forces are sufficiently energetic to destroy or suspend the usual operation of chemical affinity."[10]