Penicillin sodium salt reduction residue, prepared by Sir William Dunn School of Pathology, University of Oxford, Oxford, England, 1942-1943

Creating a pure and effective dose of penicillin was a challenge. The brown colour of this early samples from 1942 and 1943 shows they were contaminated with impurities. The drug broke down rapidly in patients’ stomachs, and so had to be re-administered by injection eight times a day.