Page:Experimental researches in electricity.djvu/169

Rh is not electrolysable, but that a portion of it is decomposed by the oxygen evolved at the anode, producing secondary results, varying with the strength of the acid, the intensity of the current, and other circumstances.

509. Acetates.—One of these has been referred to already, as affording only secondary results relative to the acetic acid (484). With many of the metallic acetates the results at both electrodes are secondary (481, 485).

Acetate of soda fused and anhydrous is directly decomposed, being, as I believe, a true electrolyte, and evolving soda and acetic acid at the cathode and anode. These, however, have no sensible duration, but are immediately resolved into other substances; charcoal, sodiuretted hydrogen, etc., being set free at the former, and, as far as I could judge under the circumstances, acetic acid mingled with carbonic oxide, carbonic acid, etc., at the latter.

510. Tartaric acid.—Pure solution of tartaric acid is almost as bad a conductor as pure water. On adding sulphuric acid, it conducted well, the results at the positive electrode being primary or secondary in different proportions, according to variations in the strength of the acid and the power of the electric current (487). Alkaline tartrates gave a large proportion of secondary results at the positive electrode. The hydrogen at the negative electrode remained constant unless certain triple metallic salts were used.

511. Solutions, of salts containing other vegetable acids, as the benzoates; of sugar, gum, etc., dissolved in dilute sulphuric acid; of resin, albumen, etc., dissolved in alkalies, were in turn submitted to the electrolytic power of the voltaic current. In all these cases, secondary results to a greater or smaller extent were produced at the positive electrode.

512. In concluding this division of these Researches, it cannot but occur to the mind that the final result of the action of the electric current upon substances placed between the electrodes, instead of being simple may be very complicated. There are two modes by which these substances may be decomposed, either by the direct force of the electric current, or by the action of bodies which that current may evolve. There are also two modes by which new compounds may be formed, i.e. by combination of the evolving substances whilst in their nascent state (394), directly with the matter of the electrode; or else their combination with those bodies, which being contained in, or associated with, the body suffering decomposition, are