白鍍の無電源電解

Abstract

Potential measurements of the white metal-NH3-H2O suspension system at 70°C revealed that the suspension potential in an alkaline region was lower than the potential for the acidic Cu2+/Cu° of the sulfate system.A cylindrical galvanic cell (14cm I. D.) was then constructed; it consisted of the negative electrode system (1.5 1, the upper half of the cell) of an ammonia-alkaline suspension of pulverized white metal with an agitator, a negative electrode (a Pt net), electrodes for pH and potential measurements, etc., the positive electrode system (0.3 1, the lower half) with a copper plate electrode (the bottom of the cell) and sulfuric acidic cupric solution as the electrolyte, and a membrane horizontally separating these systems. While maintaining the temperature at about 70°C, both electrodes were short-circuited through an ammeter, thus the electrolysis was carried out and copper was deposited on the positive electrode without an external power supply.After improvements of electrolytic conditions, especially the composition of electrolyte solutions, the short-circuit current amounted to about 1 A/dm2. The dissolved (oxidized) amount of copper in the white metal was 81% and that of sulphur was 64%, after a run using 100g of white metal for 94 hours. The current efficiency for the positive electrode was 85-100%.Data of the variations of composition of solutions and residues during the electrolysis were presented. The anodic reactions taking place in the negative electrode system of the white metal-suspension and the material balance of the electrolysis were discussed in correlation to the quantity of electricity flowed from the positive electrode to the negative electrode.