Recrystallization is a physical process achieved depending on the fact that at various temperatures, the solubility of a mixture is different in a solvent. We often dissolve solid products separated from the organic synthesis in the solvent or melt, which contain raw materials, by-products and impurities. And then we can gain the crystallization from the solution or melt. It can separate the mixed salts and purify the impure substances, which is one of the most important and common methods of separating and purifying solid compounds. General operating procedures include selecting solvents, dissolving solids, filtering impurities under hot condition, precipitating crystal, collecting and washing crystal, and drying crystal.

BOC Sciences has experts with extensive experience in recrystallization. We use recrystallization in the separation and purification of many compounds, including organics, inorganic salts, oxides and so on.


The solid coarse products separated from the organic synthesis reaction often contain raw materials, by-products and impurities, which must be separated and purified, and recrystallization is one of the most important and common separation methods for separating and purifying solid compounds. For example, the crude products of benzoic acid are always separated and purified by recrystallization. Benzoic acid is commonly used as a drug or a preservative. Coated on the skin, it can inhibit the growth of fungi, bacteria, and mold to treat tinea skin diseases. It can also be used in synthetic fibres, resins, coatings, rubber, and tobacco industry. We often separate and obtain pure benzoic acid crystals based on differences of solubility between benzoic acid and impurities in water. As the amount of benzoic acid in the solution is much greater than other impurities, and its solubility at a certain temperature is far lower than other soluble substances, so when we cool the benzoic acid crystal, other soluble impurities will still remain in the mother liquor. Lastly, benzoic acid of higher purity is obtained by filtration.

When we prepare rare metals, we need to extract their inorganic salts from rare earth mine. Lanthanum chloride can be used as catalyst for organic synthesis reaction, for example, activated carbon with lanthanum chloride can serve as heterogeneous catalyst and a promising catalyst for organic ester synthesis. It can also improve the root vigor of crop plants and has been applied in the planting of rice and maize. We use crystallization-recrystallization to prepare clean lanthanum chloride crystals. In the appropriate static time and at appropriate cooling speed, solution acidity as well as crystallization temperature, clean lanthanum chloride products can be obtained. The yield is more than 70%, and non-rare-earth metal impurity quality fraction is less than 5.0x10-5. The method has the advantages of simple operation, stable product quality and recyclable mother liquor.

For example, titanium dioxide is an important white pigment and porcelain glaze. In the rubber industry, titanium dioxide is used as filler for white rubber. It is also widely used in the production of sunscreen, non-toxic and harmless to the human bodies. We add titanium-containing slag to FeSO4-Fe2(SO4)3-H2SO4 solution for hydrothermal recrystallization, and the ilmenite concentrate contains TiO2 up to49.74%. Besides, the FeSO4-Fe2(SO4)3-H2SO4 solution, which is produced by hydrothermal reaction, can be further modified by adding ferrous acid, ferric sulfate, adjusting pH and so on and return to hydrothermal reaction mother liquor to recycle.

BOC Sciences can use preparative HPLC to separate and purify various types of compounds, including organics, inorganic salts, oxydes and so on. We also use multiple techniques (NMR, LCMS, GCMS, X-ray) to analyze compounds after the chiral synthesis is completed. And our turnaround time is fast. Welcome to contact us for more information.


  1. FELDMANN T, DEMOPOULOS G P. The crystal growth kinetics of alpha cal-cium sulfate hemihydrate in concentrated CaCL2-HCL solutions [J].Journal of Crystal Growth, 351(1):9-18.

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