Growth and Evaluation of High-Purity KCl Crystals

Abstract

A method is described by which large, uniform KCl crystals of high purity can be obtained, starting with reagent-grade material. Chemical means are employed to produce pure polycrystalline ingots which are then used to grow single crystals by pulling from the melt under semiclean room conditions. The resulting crystals contain less than 1 μg/g of any foreign alkali or halide element, show OH concentrations of less than 40 μg/g and conductivity knees which indicate typically less than 300 parts per billion total polyvalent cation content. Analytical methods are discussed and analyses of these, as well as crystals from various commercial sources, are given.