Abstract

Zone refining is one of a class of techniques known as fractional solidification in which separation is brought about by crystallization of a melt without solvent being added. Zone refining was developed in response to the need for extremely pure germanium. It can be applied to almost every type of substance that can be melted and solidified. Early zone refining theory (progressive freezing, zone melting, nonideal separations, and optimization) are discussed. Equipment and techniques such as types of containers used, drive mechanisms, heating and cooling, floating-zone melting, and stirring are discussed in detail.