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Fractional freezing is a process used in process engineering and chemistry to separate substances with different melting points. It can be done by partial melting of a solid, for example in zone refining of silicon or metals, or by partial crystallization of a liquid, as in freeze distillation, also called normal freezing or progressive freezing. The initial sample is thus fractionated (separated into fractions).
Partial crystallization can also be achieved by adding a dilute solvent to the mixture, and cooling and concentrating the mixture by evaporating the solvent, a process called solution crystallization.[1] Fractional freezing is generally used to produce ultra-pure solids, or to concentrate heat-sensitive liquids.
- ^ Perry, Robert; Don Green (2007). Perry's Chemical Engineers' Handbook. McGraw-Hill International Editions. pp. 17–3 to 17–4. ISBN 978-0-07-142294-9.