What are typical freezing rates for organic materials in zone refining?

In the process of zone refining, the freezing rate is a critical factor in determining the efficiency of impurity redistribution. For organic substances, typical freezing rates range from 0.1 to 2.0 centimetres per hour (0.04 to 0.8 inches per hour).1

These relatively slow rates are necessary because the effectiveness of the purification depends on the distribution coefficient, which is influenced by the speed at which the liquid-solid interface advances. While inorganic substances can be processed at faster rates—typically between 0.5 and 30 centimetres per hour—the lower thermal conductivity of organic compounds makes them particularly well-suited for potential large-scale, tonnage-level purification.1