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The Electrolytic Regeneration of Fixing Baths *

1931; Volume: 17; Issue: 4 Linguagem: Inglês

10.5594/j05572

0097-5834

K. C. D. Hickman, C. Sanford, W. Weyerts,

Recycling and Waste Management Techniques

It has long been known that commercial fixing solutions containing hypo, sulfurous acid, and silver bromide can be electrolyzed between inert electrodes by very small currents. Attempts to increase the current density to practical amounts have caused discoloration of the hypo, ruining its utility. It has been found that suitable adjustment of the acidity and the sulfite content of the solution, combined with extremely rapid agitation, enables the silver to be plated at current densities varying from 2 to 10 amperes per square fool. Plating cells have been built comprising alternating elements of graphite anodes and stainless steel cathodes, 4 feet square, each presenting a total active surface of about 7 square feet. Thirteen pairs are used in a paraffined wood tank through the ends of which a stout stainless steel shaft is fastened. The shaft is covered with hard rubber and is furnished with spokes or paddles which rotate, four in number, in the spaces between the plates. Special water protected bearings have been developed to isolate the naked metal from the hypo solution at the gaskets on the box ends before the shaft meets the true suspension bearings. — Five cells capable of handling 150 million feet of mixed positive and negative 35-mm. film each year have been installed in the new laboratory erected by Metro-Goldwyn-Mayer at Culver City. A smaller installation of 3 cells is near completion at the Universal Studios, Hollywood. Further details of the erection and working of these plants will be published in a later paper.