Page:Proceedings of the Royal Society of London Vol 1.djvu/271

Rh ployed in alternation with plates of a single metal, the alkaline solu- tion received the electricity from the metal, and the acid transmitted it to the metal. So in the simplest case of electrical action, the alkali, receiving electricity from the metal, would, on being separated from it, appear positive, and of course be repelled by positively electriﬁed surfaces, and attracted by negatively electriﬁed surfaces: the acid, acquiring the contrary electricity, following the contrary order.

Several phenomena accord with this idea. Sulphur separated from its contact with a. metal is positive ; and, in like manner, sulphur separated from sulphuric acid by electricity is attracted by the nega- tive surface. And again, hydrogenated sulphuretted alkalies, being composed of three substances, all positive, are so very active in vol- taic combinations as. in certain cases, to overpower the energies of the metals.

Mr. Davy then considers the relation between the electrical energy of bodies and their chemical afﬁnities; and observes, that all the sub- stances that combine chemically, exhibit, so far as is known, opposite electric states; and that, in the various experiments of decomposition by electricity, the natural electrical energies of the constituent parts of the compounds acted on are, as it were, overpowered by the arti- ﬁcial electricities : so that it is probable that chemical aﬂinity depends upon the different electrical energies of the acting bodies.

And upon this supposition, particles possessed of opposite electrical states and freedom of motion will enter into combination. When two bodies possessed of the same state act upon a third body possessed of the opposite state, the substance possessing the weakest energy will be repelled. In other cases there may be such a balance of attractive and repellent powers as to produce triple compounds, or even more complicated combinations. It will also be easy to explain the in- ﬂuence of the masses of bodies upon their aﬂinities; for the combined effect of many particles possessing a feeble electrical energy may be conceived equal, or even superior, to the effect of a few particles possessing a strong electrical energy; and, accordingly, we ﬁnd that concentrated alkalies resist the transmission of acids more powerftu than weak ones.

As the strength of the electricity diminishes from the points to the middle of the water, a measure of the artiﬁcial energies may be ob- tained by the place where the compounds begin to be decomposed. Thus sulphate of barytes requires intermediate contact with the wires; and when 150 pieces of plates were used with a circuit of water of ten inches, sulphate of potash was not decomposed at four inches from the positive wire; but when brought within two inches, its alkali was strongly repelled.

As heat and light are the consequences of a. restoration of the equilibrium between bodies in a high state of opposite electricities, so are they also the result of all intense chemical action; and again, as when large quantities of electricity of low intensity act, heat is produced without light, so in low combinations the temperature only is increased. ’l‘he effect of heat in promoting chemical uction seems not