Microdetermination of reducing sugars was successfully established by the application of the determination method of reducing sugars using potassium ferricyanide to azotometry Amixture of potassium ferricyanide and reducing sugars is warmed for 30 minutes on a water bath at 100°, and the amount of potassium ferricyanide consumed is determined by the hydrazine-azotometry. The ratio of the value of potassium ferricyanide consumed converted into the nitrogen volume, V, and the amount of sample, M, i.e. K (V/M), is constant for aldohexose, ketohexose, and aldopentose. By the utilization of respective K values, reducing sugars can be determined. Optimal determination range: 10-120γ