[On the polymorphism of barbiturates in powders and tablets - Part 3: The effect of the pressing power on the modification of barbital (author's transl)].

The authors took X-ray diffraction pictures from two commercial brands of barbital (produced in the GDR and in the Hungarian People's Republic, respectively), the interpretation of which convinced them that these two commercial brands are different modifications. These crystals were brought by pressure (10 and 20 kN) into the shape of tablets. Textural studies showed that both commercial brands are easy to compress. An increase in pressing power caused insignificant changes in the structure of the GDR product; and in the Hungarian commercial product, only slight changes were observed. It could be proved by X-ray diffraction analysis that the form of the barbital crystals is affected by the application of pressure. But this change occurs already under a pressure less than 10 kN. A further increase in pressing power produces no further changes in crystal structure.