Polymorphism and desolvation of flupirtine maleate.

Crystallizates of the analgesic agent flupirtine maleate (Katadolon; ASTA Medica, Dresden, Germany) obtained from isopropanol are examined by X-ray diffractometry, polarization microscopy and thermoanalysis. Depending on the crystallizing conditions, the modifications A and B as well as an isopropanol solvate are observed. The inversion temperature A-->B of the enantiotropic modifications is 164 degrees C (differential scanning calorimetry (DSC) onset). During thermal desolvation, modification B is formed well below the inversion temperature. In concentrated isopropanol suspensions, the solvate and modification B are rapidly transformed into modification A. It is shown how phase-pure products consisting of modification A, which is better wettable with water and stable at room temperature, can be obtained.

[Evidence of mineral impurities in talc]. / Zum Nachweis mineralischer Verunreinigungen in Talk.

Polarizing microscopy, X-ray powder diffraction and differential thermal analysis can be used to detect small amounts of minerals which may occur in talcs as impurities. The characteristic features of chlorite, asbestos, magnesite, quartz and other minerals recognizable through these methods are described.