AOAC Official Method 931.03 Formaldehyde in Seed Disinfectants
First Action 1931
Final Action
(Applicable to determination of HCHO absorbed in inert carrier,e.g., bentonite, talc, charcoal, sawdust.)
Weigh ca 5 g test portion containing 0.3–0.5 gHCHOin weighing bottle and transfer to 800 mL Kjeldahl flask. Add 25 mL H2O and 12 mL H2SO4 (1 + 4). Steam distill rapidly, passing vapors through condenser with delivery end dipping into 25mLH2Oin 500mLvolumetric flask. Collect ca 450mLdistillate, keeping volume in distilling flask nearly constant with aid of small flame. After distillation, wash delivery tube, and dilute distillate to volume with H2O.
Into each of two 200 mL volumetric flasks measure 20 mL 0.1M AgNO3. To each flask add 12 drops HNO3 (1 + 1) and 30 mL H2O. To one flask add slowly, with constant shaking, 30 mL KCN solution (3.1 g in 1 L H2O). Dilute to volume, shake well, and filter through dry filter. To 100 mL filtrate add 3 mL HNO3 and 5 mL ferric indicator, 929.04A(e) (see 7.1.12), and titrate with 0.1M KSCN.
