Recrystallization (chemistry)
Under a recrystallization is meant the change in the mineralogy of a crystal structure caused by the change of external factors such as pressure and temperature conditions. In this case, the crystalline solid and the mineral changes its modification. In chemistry, recrystallization is a purification process to convert raw materials and preparations by dissolution and subsequent re-exporter crystallizing in purer end product. It is because that the solubility of most of the substances in solvents warm is better than in cold. Cools a hot, saturated solution from, sometime the solubility is exceeded and the substance crystallizes out again.
Method for recrystallization in chemistry
In the chemical is meant a Recrystallization material separation process that is used as a cleaning process. In this case a hot, saturated solution of a contaminated substance is produced, hot filtered to remove the insoluble impurities, and bringing the substance by cooling the solution for recrystallization. The substance is thereby usually get in a purer form.
Colored impurities or cloudiness can be removed for hot saturated solution of the substance to be purified by the addition of an adsorbent ( charcoal, bone charcoal, activated carbon, active alumina, diatomaceous earth filtration aid, etc.). Subsequently, the adsorbent is filtered off in the heat. The filtrate is then cooled and brought to the substance to be crystallized.
The dissolution of the less pure starting material may be effected in a suitable solvent or solvent mixture.
In contrast, a chemical separation processes can be carried out by the substance (for example, benzoic acid) with a substance to a water-soluble substance will react (example: with sodium hydroxide to form sodium benzoate, acid -base reaction ), from whose solution then by filtration and additional a precipitating agent to the filtrate (example: a strong acid ) is then re-precipitated purified benzoic acid or even crystallized. This is called re-precipitation.
Recrystallization, reprecipitation and remelting
Related methods are the reprecipitation ( reprecipitation, precipitation of undesirable constituents by other solvents ) and the remelting of a substance. Reprecipitation in a chemical reaction take place ( precipitation reaction ), during remelting, no solvent is used, but operating at temperatures near the melting point.