抄録
Systematic studies were made on the preparation of pure KCl and NaCl crystals. Effects of the starting material on the purity of crystal were studied with KCl and NaCl powders of reagent grade of several different brands and with those prepared from bicarbonate and hydrochloric acid. Methods by distillation and crystallization in vacuum and by Kyropoulos technique in air were used for the crystallization procedures to study on each of their advantages. To estimate the concentration of impurities in crystals, the measurement of ionic conductivity was made for multivalent metallic ions, optical absorption for hydroxyl ions, and chemical analysis for bromine ions. The purest crystal in respect of these impurities was found to be the one grown from its powder prepared from bicarbonate and hydrochloric acid by the method of distillation and crystallization in vacuum. After the studies on the edge of the fundamental absorption in connection with the concentration of bromine, an absorption band due to the presence of bromine was found in KCl of which maximum is at 7.12 ev at room temperature.
