Recent Advances in Photographic Theory

Abstract

THE study of the physico-chemical relations -L on which depend the form in which a precipitate is produced has been developed by a number of workers in recent years, and its application to the precipitation of silver halide has been studied by Sheppard and Trivelli. In his earlier work Trivelli made a large number of photomicrographs of emulsions taken from standard photographic plates and films, one of which is reproduced in Fig. i. It will be seen that the silver bromide grains, of which the emulsion is composed, are of very varied sizes, there being present a large number of small grains, down to the limit of those visible with a microscope, and a smaller number of large grains, including some of very much greater area than the smallest grains present. The largest grains are all polygons, with angles of 6o° and 1200. There is a tendency to round off the corners and edges of the small grains, so that the smallest grains appear to be more or less spherical.