Chemical Analysis of an MQ Developer

The maintenance of developer activity over a long period of time is among the most important problems of a motion picture laboratory. The developer is oxidized by the silver halide in the emulsion and by air. When known amounts of these two oxidizing materials react with the developer, simple calculations (presented in a previous paper) are sufficient to determine the equilibrium condition of the developer as well as the replenisher formula to give a chosen equilibrium. Under ordinary conditions there are large variations in the amount of developer oxidation. A chemical analysis immediately detects any deviation from the correct equilibrium and permits readjustment of the replenisher formula. Chemical analyses are presented which require a minimum of equipment and time. In most cases ease of manipulation and speed have been considered as more important factors than a high degree of accuracy but in all cases the methods are capable of giving results to an accuracy of five per cent or better. Whenever possible the analyses are colorimetric in nature, the measurements being made on an instrument called an opacimeter. One opèrator can make a complete analysis in about half an hour. Analysis for any one constituent may be made in a much shorter time. It is emphasized that no one control variable is significant for specifying the activity of a developer. Sensitometric curves are included demonstrating the time lag in pH equilibrium but not in photographic equilibrium when hydroxide is added to or released in the developer. The aim of chemical control is to insure a constant condition of the developer and thus constant photographic quality, rather than to determine the degree of development.

Print ISSN

0097-5834

Published

1939-03

Content type

Original Research

DOI

10.5594/J12019