Page:The fundamental laws of electrolytic conduction.djvu/75

 The solution around the cathode contained:

The quantity of transferred copper is therefore

If we tabulate the results of these experiments:

there can be no doubt that the transference is independent of the intensity of the current. I have always avoided using very large currents, as the rise in temperature which they produce in the solution is disturbing. The immediate effect of this on our data is easily obviated by not removing the electrolyzed solution for analysis immediately after breaking the current, but allowing it to first return to the temperature of the surroundings. On the other hand, an indirect disturbance of the rise of temperature cannot be so easily overcome. This consists in the evolution of a quantity of little air-bubbles which usually cover the surface of the glass plate under the cathode, and which cannot be removed. That these little bubbles are not hydrogen gas is clear from the place where they appear. If large currents are to be used, it is judicious to free the solution as far as possible from absorbed air, before filling the apparatus; this is most easily done under an air-pump.

The second question which we must consider has reference to the influence of the concentration on the transference. Six solutions of copper sulphate of very different concentration were subjected to electrolysis.