Fume Tube for Micro-Kjeldahl Digestions

Abstract

the course of a biological investigation, the need arose to determine calcium in certain tissues of the rat. In many instances, the amount of tissue available necessitated a method requiring not more than 5 or 10 gamma of calcium per determination.The technic of Miller and Kirk (S), based on the oxalatepermanganate volumetric method, was tried, but was discarded because of the difficulty in determining the end point in the titration. Lindner and Kirk (£) later surmounted the difficulties encountered in the earlier method by replacing potassium permanganate with ceric sulfate, which is added in excess to the calcium oxalate precipitate dissolved in dilute sulfuric acid. The ceric sulfate not reduced by the oxalate is then determined by titration with standard ferrous ammonium sulfate, using phenanthroline-ferrous sulfate as an indicator.