Improvements in or relating to photographic developers

Abstract

Abstract 525,944. Photographic development. RADIO CORPORATION OF AMERICA. March 3, 1939, Nos. 7062, 7063 and 15031. Convention dates, March 17, 1938, April 30, 1938 and April 30, 1938. [Class 98 (ii)] A photographic developing composition esspecially for use with sound track films comprises a developing agent, a soluble salt of either aluminium, chromium, tin, zinc, or lead, and sufficient alkali to maintain in solution the precipitate tending to be produced on addition of alkali to the salt of a metal of the above group. Suitable developing agents are hydroquinone, glycin, metol, p-phenylenediamine, bromohydroquinone, toluhydroquinone, catechol, chlor- and dichlor-hydroquinone, p-benzylaminophenol, pyrogallol, amidol, p-dimethylaminophenol, p-aminophenol, phenylhydrazine, hydroxylamine hydrochloride, and p-dibenzylaminophenol. Other substituted benzene derivatives may be used. The metallic salts may be potassium alum or the sulphate, chloride, or bromide of aluminium. The alkali present may be sodium hydroxide or carbonate. A bromide and a sulphite may be included. In developing films, the quantity carried over into the washing bath may be adjusted by an air jet exactly to balance the addition of developer necessary to compensate for exhaustion. The developed film is partly hardened during development.

Inventors

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