Preparation of Silver Halide Crystals of High Purity

Abstract

For the investigation of silver halides, crystals of very high purity are required. Methods for preparing such crystals are described. They include the procedures used for the preparation of the dry precipitates, for crystal growing in controlled atmospheres, and for the preparation of specimens for the study of optical, electrical, and photochemical properties. The crystals are optically clear and have a sharp absorption edge with no detectable impurity absorption, even in samples several centimeters thick. For the silver chloride crystals, the ionic conductance was found to show the familiar break point at an unusually low temperature, and the interior of the crystal shows extremely little darkening even upon very strong exposure. For spectrochemical determination of the purity of the crystals, a concentration series of internal standards were prepared for seventeen elements. For the more important impurities, the molar concentration does not exceed 10⁻⁷.