BioZogicaZ Chemist vy . 55 ling determination. They measure the amount of precipitated copper oxide volumetrically by the permanganate method. They eliminate errors to a large extent by checking the process on solutions of similar known composition and of practically identical reducing value. Excellent results are obtained. As the Fehling determination is influenced so much by apparently insignificant points of manipulation, a more detailed description of the authors' method would be desirable.

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... I f . H. RICHARDS, REVIEWER. The Estimation of Nitrates and Ammonia in Water. BY FRANK X. MOERK. Am. J. Pharm., 71, 157-161.--Instead of using milk of alumina to remove the organic matter which interferes with the color in the phenol-sulphonic acid test for nitrates in water samples, the author makes a duplicate determination for color due to the organic matter. T h e remarks on ammonia determinations do not agree with the experience of the reviewer ; for, while it is true that ' I dilute ammonium chloride will not keep indefinitely," unless under conditions of complete sterilization, it is not true " that it is useless to attempt" to free alkaline potassium permanganate " from ammonia, as it cannot be kept so." With pure reagents and suitable preparation of them, the solution, even if not at first, yet on standing, yields ammonia-free distillates. Digestive Ferments with Especial Reference to the Effects of Food Preservatives. BY HENRY LEFFMANN. J . Pranklin Insf., 147, g7-108.-The author has studied the action of the more commonly used food preservatives in preventing starch digestion by various enzymes. A number of qualitative experiments in which the action was followed by means of tests with a solution of iodine in potassium iodide are recorded, and in a few cases the amount of dextrose formed was determined by Fehling's solution. It was found that salicylic acid is distinctly antagonistic to the starch-converting enzymes but does not interfere very much with proteid digestion ; sodium benzoate, boric acid, borax, and boroglycide do not interfere appreciably with either starch or proteid digestion ; beta-naphthol interferes with the action of malt-diastase but not seriously with takadiastase or pancreatic extract, although it interferes decidedly with the peptic and pancreatic digestion of proteids. Sodium fluoride and sodium silicofluoride offer but little hindrance to starch transformation except in the case of the pancreatic digestion.