Variation of Coloration Rates and Luminescence in Harshaw Potassium Chloride

Variations in the coloring and luminescence properties of KCl crystals obtained from a single source were investigated. Flame photometry and infrared spectroscopy of the samples showed that the type and amount of impurities in the crystals are not functions of the time of purchase. In order to determine whether crystals from a single ingot vary, coloring curves were obtained for samples from different portions of ingots. In all cases the late stage coloring curve agreed to within about 20%. Luminescence spectra show variety both in the character of the emission spectra observed, as well as in the apparent intensities of the different bands. It was concluded that there is not yet available KCl stock that is sufficiently uniform in its composition to allow it to be used indiscriminately as a standard in the study of photoelectronic properties. (P.C.H.)