Page:The fundamental laws of electrolytic conduction.djvu/41

 average of the four experiments gave 58.53 as the electrochemical equivalent for tin.

The chloride remaining after the experiment was pure protochloride of tin; and no one can doubt for a moment that the equivalent of chlorine had been evolved at the anode, and, having formed bichloride of tin as a secondary result, had passed away.

Chloride of lead was experimented upon in a manner exactly similar, except that a change was made in the nature of the positive electrode; for as the chlorine evolved at the anode forms no perchloride of lead, but acts directly upon the platina, it produces, if that metal be used, a solution of chloride of platina in the chloride of lead; in consequence of which a portion of platina can pass to the cathode, and would then produce a vitiated result. I therefore sought for, and found in plumbago, another substance which could be used safely as the positive electrode in such bodies as chlorides, iodides, etc. The chlorine or iodine does not act upon it, but is evolved in the free state; and the plumbago has no reaction, under the circumstances, upon the fused chloride or iodide in which it is plunged. Even if a few particles of plumbago should separate by the heat or the mechanical action of the evolved gas, they can do no harm in the chloride.

The mean of the three experiments gave the number of 100.85 as the equivalent for lead. The chemical equivalent is 103.5. The deficiency in my experiments I attribute to the solution of part of the gas in the volta-electrometer; but the results leave no doubt on my mind that both the lead and the chlorine are, in this case, evolved in definite quantities by the action of a given quantity of electricity.

Chloride of antimony.—It was in endeavoring to obtain the electrochemical equivalent of antimony from the chloride, that I found reasons for the statement I have made respecting the presence of water in it in an earlier part of these Researches.

I endeavored to experiment upon the oxide of lead obtained by fusion and ignition of the nitrate in a platina crucible, but found great difficulty from the high temperature required for perfect fusion, and the powerful fluxing qualities of the substance. Green-glass tubes repeatedly failed. I at last fused the oxide in a small porcelain crucible, heated fully in a