| 摘要 |
PROBLEM TO BE SOLVED: To provide a method which can overcome the limitation and disadvantageous points involved in the existing crystallization method. SOLUTION: This method is a method for crystallizing a weakly acidic and/or weakly basic compound of a noncharged type and at least one charged type. The method comprises (a) the step of providing a solution of the compound in a solvent so that the solution has an initial pH value and an initial total concentration of the compound, the initial pH value is selected so that the compound is present mainly in the charged type in the solution, and the initial total concentration is selected so as to be higher than the noncharged type inherent solubility, (b) the step of gradually changing the pH value of the solution until the solubility of the compound reaches a predetermined target pH value at which the solution remains substantially saturated and the noncharged type concentration is substantially equal to the inherent solubility, and (c) the step of keeping the solution substantially saturated while forming crystals of the compound. COPYRIGHT: (C)2007,JPO&INPIT
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