In chemistry, fractional crystallization is a method of
refining
{{Unreferenced, date=December 2009
Refining (also perhaps called by the mathematical term affining) is the process of purification of a (1) substance or a (2) form. The term is usually used of a natural resource that is almost in a usable form, b ...
substances based on differences in their
solubility. It
fractionates via differences in
crystallization
Crystallization is the process by which solid forms, where the atoms or molecules are highly organized into a structure known as a crystal. Some ways by which crystals form are precipitating from a solution, freezing, or more rarely deposi ...
(forming of
crystals). If a mixture of two or more substances in solution are allowed to crystallize, for example by allowing the temperature of the solution to decrease or increase, the
precipitate will contain more of the least soluble substance. The proportion of components in the precipitate will depend on their
solubility products. If the solubility products are very similar, a
cascade process will be needed to effectuate a complete separation.
This technique is often used in
chemical engineering to obtain pure substances, or to recover saleable products from waste solutions.
Fractional crystallization can be used to separate solid-solid mixtures. An example of this is separating
KNO3 and
KClO3.
[Viraf.J.Dalal Class 6/7 book]
See also
*
Cold Water Extraction
*
Fractional crystallization (geology)
Fractional crystallization, or crystal fractionation, is one of the most important geochemical and physical processes operating within crust and mantle of a rocky planetary body, such as the Earth. It is important in the formation of igneous ro ...
*
Fractional freezing
*
Laser-heated pedestal growth
*
Pumpable ice technology
*
Recrystallization (chemistry)
*
Seed crystal
A seed crystal is a small piece of single crystal or polycrystal material from which a large crystal of typically the same material is grown in a laboratory. Used to replicate material, the use of seed crystal to promote growth avoids the otherwi ...
*
Single crystal
References
"Small Molecule Crystalization"(
PDF
Portable Document Format (PDF), standardized as ISO 32000, is a file format developed by Adobe in 1992 to present documents, including text formatting and images, in a manner independent of application software, hardware, and operating systems. ...
) at
Illinois Institute of Technology website
Fractionation
Phase transitions
Methods of crystal growth
{{crystallography-stub