Standardization of the Methylene Blue Reduction Test by the Use of Methylene Blue Thiocyanate.
SINCE the first use of methylene blue reduction as an indicator of bacteriological quality in milk, fluid milk supplies on this continent have undergone notable improvement. Moreover, during this period it has been shown that the inaccuracies in the test increase with increasing reduction times.6' 8, 9 An effort to minimize these inaccuracies is, therefore, worth while. Because of the extensive use of this test in milk control activities, it becomes necessary to duplicate frequently the standard tablets of methylene blue certified by the Commission on Standardization of Biological Stains and recognized by the American Public Health Association in Standard Methods of Milk Analysis.' This duplication involves not only the creation of standards but also the purification or, at least, the determination of purity of the dye. Clark, Cohen, and Gibbs 2 review the difficulty, if not the impossibility, either of purification or of determination of purity of methylene blue chloride, the methylene blue salt used in these tablets.
Quirks of dye nomenclature. 8. Methylene blue, azure and violet
Abstract Methylene blue was synthesized in 1877 and soon found application in medicine, staining for microscopy and as an industrial dye and pigment. An enormous literature has accumulated since its introduction. Early on, it was known that methylene blue could be degraded easily by demethylation; consequently, the purity of commercial samples often was low. Therefore, demethylation products, such as azures and methylene violet, also are considered here. The names and identity of the components, their varying modes of manufacture, analytical methods and their contribution to biological staining are discussed.
Relation between the Bacterial Count of Whole Milk and that of the Cream and Skim Milk separated from it.
In studying the milk ordinances of many municipalities it is found that when a maximum bacterial count for milk is designated, a much higher maximum bacterial count for cream of the same grade is allowed. This increase covers a wide range, varying usually from 300 to 500 per cent. A review of the literature upon this subject shotvs that but little work has been done, or at least few results have been published, dealing with the effect of separation upon the bacterial count of cream and skim milk. It would seem that the maximum bacterial standards for cream appearing in many milk ordinances are not based on scientific facts. The Bureau of Dairying of the United States Department of Agriculture has been carrying on woçk with centrifugal and gravity separators in order to determine what effect separation has upon the bacterial count of the cream and skim milk.