Reduction Potential and the Composition of an MQ Developer

After pointing out that photographic development is a reduction process, the terms “oxidation potential” and “reduction potential” are discussed. The methods of measuring such potentials are also discussed, as well as the condition that a system must be reversible before its true electrochemical potential can be measured. The reversibility of development in ferrous oxalate developers is referred to and some indication of reversibility in amidol developers is shown. The usual electrochemical methods of measuring potentials have been applied to organic developer solutions, and the effects of the various constituents of an MQ developer upon its “measured potential” are discussed. The true significance of these measured potentials is still not definitely known. It is shown that pH is the most important factor in determining the measured potential of a given developer solution, but that neither pH nor potential shows sufficient correlation with photographic action to be used as a “single” control variable.

Print ISSN

0097-5834

Published

1938-05

Content type

Original Research

DOI

10.5594/J16579