The Diffusion Constant of Penicillin

Abstract
The diffusion constant of penicillin was measured with the sintered glass membrane technic over a pH range 4-8 and at 0.5[degree] C. The diffusion constants were found by the equation: D = V2 C2/ tKC1. Penicillin concs. were estimated by turbidimetric microbiol. assay using Staphylococcus aureus as the test organism. Application of the Stokes-Einstein equation relating D to molecular radius showed that at pH 7 the ladius of the penicillin molecule was 5.37 A. The calculated mol. wt. was 490.