Page:Experimental researches in electricity.djvu/235

Rh although it has not intensity enough to decompose chloride of lead under the same circumstances.

716. A drop of water placed at a§§ instead of the fused chlorides, showed as in the former case (705), that it could conduct a current unable to decompose it, for decomposition of the solution of iodide at b occurred after some time. But its conducting power was much below that of the fused chloride of lead (713).

717. Fused nitre at a conducted much better than water: I was unable to decide with certainty whether it was electrolysed, but I incline to think not, for there was no discoloration against the platina at the cathode. If sulpho-nitric acid had been used in the exciting vessel, both the nitre and the chloride of lead would have suffered decomposition like the water (641).

718. The results thus obtained of conduction without decomposition, and the necessity of a certain electrolytic intensity for the separation of the ions of different electrolytes, are immediately connected with the experiments and results given in §4 of the second part of these Researches (154, 159, 180, 185). But it will require a more exact knowledge of the nature of intensity, both as regards the first origin of the electric current, and also the manner in which it may be reduced, or lowered by the intervention of longer or shorter portions of bad conductors, whether decomposable or not, before their relation can be minutely and fully understood.

719. In the case of water, the experiments I have as yet made appear to show that, when the electric current is reduced in intensity below the point required for decomposition, then the degree of conduction is the same whether sulphuric acid, or any other of the many bodies which can affect its transferring power as an electrolyte, are present or not. Or, in other words, that the necessary electrolytic intensity for water is the same whether it be pure, or rendered a better conductor by the addition of these substances; and that for currents of less intensity than this, the water, whether pure or acidulated, has equal conducting power. An apparatus, fig. 44, was arranged with dilute sulphuric acid in the vessel A, and pure distilled water in the vessel B. By the decomposition at e, it appeared as if water was a better conductor than dilute sulphuric acid for a current of such low intensity as to cause no decomposition. I am inclined, however, to attribute this apparent superiority of water to variations in that peculiar condition of the platina electrodes which is referred to further on in this part (776), and