[Dissolution processes and surface changes. 3. Determination of the surface with the BET process].

Two methods are demonstrated for the determination of the surfaces of solid substances by the BET-method. Using a newly constructed apparatus substances with high specific surfaces can be determined by the two-point-method with a good precision. For the determination of pulverous drugs we used the one-point-method proposed by Haul and Dümbgen [2] improving it in calibration und practicability.