AOAC Official Method 940.02 Manganese (Acid-Soluble) in Fertilizers Colorimetric Method
First Action 1940
Final Action
(Applicable to fertilizer materials containing Mn2+ only and with £5% Mn.)
A. Reagent
Potassium permanganate standard solution.—500 (mg/mL) Mn.
Prepare and standardize as in 940.35 (see A.1.10), except use 1.4383 g KMnO4 and 0.12 g sodium oxalate. Transfer aliquot containing 20 mgMn to beaker. Add 100 mL H2O, 15 mL H3PO4, and 0.3 g KIO4, and heat to bp. Cool, and dilute to 1 L. Protect from light. Dilute this solution containing 20 mg/mL Mn with H2O (previously boiled with 0.3 g KIO4/L) to make convenient working standards in range of concentrations to be compared.
