241. Kay and Graham's phosphatase test: (a) Modifications in technique (b) Effect of bacterial growth

Abstract

1. By the use of sodium hexametaphosphate it is possible to eliminate the final filtration in the phosphatase test, and thus appreciably to shorten the time required for the test.2. It is necessary to avoid direct sunlight during that part of the test in which Folin's reagent is in use. Other minor precautions are mentioned in the paper.3. The pH. of the milk samples tested was found to vary naturally before pasteurization from pH 6·5 to 6·9 without affecting the validity of the test.4. The test is also unaffected by the presence in milk of bacteria which produce reducing substances or which hydrolyse the substrate (sodium phenyl phosphate) unless the organisms are present in very large numbers.