| 摘要 |
<p>1,239,013. Purifying by recrystallization. HOPKIN & WILLIAMS Ltd. 20 Sept., 1968 [27 Sept., 1967], No. 43941/67. Headings B1G and B1S. [Also in Divisions C1 and C2] A substantially vertical column of an impure, finely comminuted and evenly packed substance is purified by adding at the top of the column a liquid which is a solvent for the substance and at least some of the impurities at a rate such that at any instant the quantity of solvent in the column is sufficient to dissolve only a part of the substance, so that a solvent vapour phase exists in dynamic equilibrium with the solvent, and removing from the lower end of the column a saturated solution of the substance and impurities. The solvent may be added continuously or in discrete amounts; successive such amounts may be of different solvents. The process may be conducted at an elevated temperature approaching the m.p.t. of the substance. Remaining solvent may be removed by suction, pressure or a non-solvent liquid. In examples the following are purified (solvents in brackets); dipyridyl, 1-nitronaphthalene, phenol, 1-naphthyl acetate and 2, 4-dichloraniline (acetone); 1, 10-phenanthroline hydrate (industrial methanol + acetone); Na heptoate, urea and manganese acetate (water); p-phenylene diamine (pyridine/hydrazine hydrate followed by toluene/hydrazine hydrate); and naphthol (toluene). Sodium nitrate (water/ acetone); barium acetate (water/acetic acid). Yields may exceed 85-90% using very small relative amounts of solvent.</p> |
