Various Shapes of Crystals Rapidly Grown From the Melt and 272mμ Optical Absorption Band of KCI

When me1ted KCl is cooled in the crucible with various temperature distributions and cooling velocities of 3～10 ℃/min，KCl crystal fragaments of various geometries and shapes are obtained. And also the writers studied on the origin of the optical absorption band at 272mμof KCl crystals with severel impurities. Following results are obtained. (1) Maximum values of nearly cubic crystal fragments is inversely proportional to the square of the cooling velocity. (2) Pillar or needle-shaped crystal fragments are obtained，when melted KCl is cooled rapidly in the crucible with large temperature gradient. (3) It is confirmed that the optical absorption at 272mμdepends on the impurity Pb. Also the remarkable occurence of present absorption is observed when KCl powder containing of PbCl powder of 0.2% in weight is pressed into the pil