Semi-micro Estimation of Reducing Sugars.

The estimation of sugars is a matter of interest to every worker engaged in the study of carbohydrate metabolism and related problems. In order to be of any real value a method must not only allow the determination of relatively small amounts of sugars with sufficient accuracy, but should also be rapid, and thus permit of a large number of determinations being carried out in a short time. Semi-micro modifications of the Munson-WalkerBertrand method (1, 5) have been elaborated by ILJIN (2) and WILDMAN and HANSEN (7) with the object of satisfying these demands as nearly as possible. The method of WILDMAN and HANSEN unfortunately requires apparatus which is not available in every laboratory. ILJIN'S modification attracted the writer's attention on account of its simplicity. In ILJIN'S method centrifuge tubes containing 6-ml. aliquots of the sugar solution and 6 ml. of Fehling's solution (of a higher concentration than used in the original Munson-Walker method) are heated in a boiling water-bath for ten minutes. After cooling, the precipitate is separated from the liquid by centrifuging, washed, and dissolved in acid ferric ammonium sulphate solution. The latter is then titrated with potassium permanganate solution.