MEMOIRS ON THE FUNDAMENTAL
is formed. And though it is decomposed by being fused and heated to dull redness for a few minutes, and the whole reduced to protiodide, yet that is not at all opposed to the possibility, that a little of that which is formed in great excess of iodine at the anode, should be carried by the rapid currents in the liquid into contact with the cathode.
This view of the result was strengthened by a third experiment, where the space between the electrodes was increased to one-third of an inch; for now the interfering effects were much diminished, and the number of the lead came out 89.04; and it was fully confirmed by the results obtained in the cases of transfer to be immediately described.
The experiments on iodide of lead, therefore, offer no exception to the general law under consideration, but on the contrary may, from general considerations, be admitted as included in it.
Protiodide of tin.—This substance, when fused, conducts and is decomposed by the electric current, tin is evolved at the anode, and periodide of tin as a secondary result at the cathode. The temperature required for its fusion is too high to allow of the production of any results for weighing.
Iodide of potassium was subjected to electrolytic action in a tube, like that in Fig. 9. The negative electrode was a globule of lead, and I hoped in this way to retain the potassium, and obtain results that could be weighed and compared with the volta-electrometer indication; but the difficulties dependent upon the high temperature required, the action upon the glass, the fusibility of the platina induced by the presence of the lead, and other circumstances, prevented me from procuring such results. The iodide was decomposed with the evolution of iodine at the anode, and of potassium at the cathode, as in former cases.
In some of these experiments several substances were placed in succession, and decomposed simultaneously by the same electric current; thus, protochloride of tin, chloride of lead, and water, were thus acted on at once. It is needless to say that the results were comparable, the tin, lead, chlorine, oxygen, and hydrogen evolved being definite in quantity and electrochemical equivalents to each other.
Let us turn to another kind of proof of the definite chemical action of electricity. If any circumstances could be supposed
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