An application of the method of Hagedorn and Jensen to the determination of larger quantities of reducing sugars

THE method of Hagedorn and Jensen [1923] has become widely used for the estimation of reducing sugar in blood. The method depends upon the fact that potassium ferricyanide is reduced to ferrocyanide when heated in alkaline solution with certain reducing substances. In the Hagedorn and Jensen pro- cedure the ferrocyanide formed in this way is precipitated as the double potassium zinc salt, and the residual ferricyanide is estimated by adding an excess of potassium iodide and acidifying. The ferricyanide is reduced quan- titatively by the iodide, and equivalent iodine is liberated according to the equation: 2H3Fe(CN)6 + 2HI = 2H4Fe(CN)6 + I2. The iodine is titrated with thiosulphate.