[On the polymorphism of Barbiturates in powers and tablets. Part 5: The dissolution of recrystallized barbital substances and their release from tablet (author's transl)].

The dissolving characteristics of 6 different barbital modifications have been studied. With one exception, the metastable forms dissolved more rapidly than the stable form. The observed differences were not always significant. Substances recrystallized from an acetone-water mixture were less soluble in aqueous solvents than those recrystallized from water. The dissolving characteristics are changed by tabletting, the stable modification being more favourable in this respect. The solubility of barbital A2 was very poor. Consequently, it is not suited for therapeutic use. The dissolution rate was determined by means of the rotating basket method as described in the nineteenth edition of the U.S.P.