[On the polymorphism of barbiturates in powders and tablets. Part 1: Crystal optical studies on, and melting behaviour of barbital (author's transl)].

Crystal optical studies showed that barbital brands that conform to the standards of the DAB 7--DDR and the Ph. Hung. VI, respectively, present two different crystalline forms. After recrystallization form water or acetone-water mixture (1:1), the optical crystal picture of the brand conforming to the DAB 7--DDR prevails. The melting points of the commercial products do not differ from each other; both substances melt at 187.5 degrees C, whereas the melting points of the recrystallized products are 1.5 degrees and 2 degrees C, respectively, lower.