A process by which a chemical compound is separated into components by crystallization. In fractional crystallization the compound is mixed with a solvent, heated, and then gradually cooled so that, as each of its constituent components crystallizes, it can be removed in its pure form from the solution.
rend., 1904 seq.) by fractional crystallization of the nickel double nitrates, the ethyl sulphates, and the bismuth double nitrates of the terbium earths.
The oxides are then converted into double sulphates which are separated from each other by repeated fractional crystallization or by fractional precipitation with ammonia or some other base.
PHENANTHRENE, C14H10, a hydrocarbon isomeric with anthracene, with which it occurs in the fraction of the coal tar distillate boiling between 270°-400° C. It may be separated from the anthracene oil by repeated fractional distillation, followed by fractional crystallization from alcohol (anthracene being the less soluble), and finally purified by oxidizing any residual anthracene with potassium bichromate and sulphuric acid (R.
The inactive mixture may be resolved into its active components by fractional crystallization of the cinchonine salt, when the salt of the dextro modification separates first; or the ammonium salt may be fermented by Penicillium glaucum, when the laevo form is destroyed and the dextro form remains untouched; on the other' hand, Saccharomyces ellipsoideus destroys the dextro form, but does not touch the laevo form.
Also (d +1) mannonic acid can be split into the d and 1 acids by fractional crystallization of the strychnine or brucine salts.