On the Presence of Free Sodium in Sodium Chloride Crystals Containing Color Centers and Color Center Precursors

Abstract

The presence of ``free sodium'' in NaCl crystals containing color centers and color center precursors, as indicated by the results of Hacskaylo and Groetzinger, has been confirmed by the use of a more precise method of chemical analysis. The present measurements were carried out by dissolving the crystals in question in a solution containing an indicator, p‐nitrophenol, and determining the resulting change in the optical density of the solution at a wavelength of 415 mμ. The ratio of the number of ``free sodium'' atoms to vacancy pairs was about one for crystals which had been subjected to electrolysis and about one‐tenth for crystals irradiated with x‐rays, independent of whether these crystals had been first subjected to electrolysis.