Electrochemical aspects of photographic development

✍ Scribed by S.E. Sheppard

• Publisher: Elsevier Science
• Year: 1922
• Tongue: English
• Weight: 64 KB
• Volume: 194
• Category: Article
• ISSN: 0016-0032
• DOI: 10.1016/s0016-0032(22)90979-2

✦ Synopsis

THE early part of this paper discusses the history of the theory of development as a reversible chemical reaction.

The conception of reduction potentials is considered, and it is pointed out that two different methods of presentation have been evolved. According to one reduction potential depends on the transfer of electric charges while according to the other it depends on the decomposition of water and release of atomic hydrogen.

It is shown that under certain conditions these two conceptions are equivalent to each other in determining true reduction potentials. The principle condition is the presence in equilibrium of the reduction and oxidation products of the reaction.

The work of F. C. Frary and A. H. Nietz is considered in this connection. Before satisfactory reduction potentials for organic developing reagents can be determined the following data must be secured :

,4. Determination of the state in solution of the reducing agents ;

B. Nature, and to some extent, the velocities of the reaction; C. Silver equivalent of the reducer during the working period of development.

,4s contributory to these points the ionization constants of paraminophenol, elon, hydroquinone, and pyrogallol have been determined from the electrometric titration curves.