AOAC Official Method 937.02 Magnesium (Water-Soluble) in Fertilizers
First Action 1937
Final Action 1966
(a) In potassium–magnesium sulfate, magnesium sulfate, and kieserite.—Weigh 1 g test portion into 250mLvolumetric flask, add 200 mL H2O, and boil 30 min. Cool, dilute to volume with H2O, and mix. If determination is to be conducted gravimetrically, 937.01« (see 2.6.19), or volumetrically, 940.01A«, see 2.125, 11th Ed.
(b) In other materials, including mixed fertilizers.—Weigh 1 g test portion into 500mLvolumetric flask, add 350mLH2O, and boil 1 h. Cool, dilute to volume, mix, and filter if necessary. If determination is to be conducted gravimetrically, 937.01« (see 2.6.19), or volumetrically, 940.01A«, see 2.125, 11th Ed.
(c) By EDTA method.—Transfer aliquot solution prepared as in
(a) or (b) to beaker and determineMgas in 964.01D (see 2.6.18), using HCl or KOH to adjust pH.
References: JAOAC 20, 252(1937); 22, 270(1939);
23, 249(1940); 24, 268(1941); 25, 326(1942).
