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SUMMARY:From the existing methods for identifying common antibiotics it is possible to select tests for recognizing one or more of fourteen known antibiotics in crude culture medium. These tests, given in tabular form, are : (1) stability at pH 2.0 and 9.5; (2) ether-water partition at pH 2-0, 6.0-7.0 and 9.0; and (3) relative activity towards specified strains of Staphylococcus aureus and Bacterium coli. Further tests depend on destruction of penicillin by penicillinase, colour reactions, and volatility of aspergillic acid in steam. For final confirmation, isolation of the antibiotic may be necessary. Several hundreds of moulds have been reported (Wilkins