AOAC Official Method 935.05 Chloride in Plants
Volumetric Method II
First Action 1935
Final Action
A. ReagentsVolumetric Method II
First Action 1935
Final Action
(a) Potassium iodide standard solution.—1 mL = 1 mg Cl. Weigh 4.6824 g pure (ACS) KI, dried to constant weight at 105–150°C, dissolve in H2O, and dilute to 1 L.
(b) Silver nitrate stock solution.—Approximately 0.3M. 1 mL = ca 10mgCl. Dissolve 48 gAgNO3 inH2O, filter, and dilute to 1 L.
(c) Silver nitrate standard solution.—Dilute 100 mL reagent (b) to ca 900 mL and adjust by standardizing against reagent (a) so that 1 mL = 1 mg Cl.
(d) Chloride-free starch indicator.—For each 100mLfinal solution take 2.5 g soluble starch and make to paste with cold H2O. Stir out lumps, add 25–50 mL more cold H2O, and stir or shake 5 min. Centrifuge, decant, and discard liquid. Repeat extraction 3 times and finally transfer residue to flask containing proper amount of boiling H2O. Stir again, heat to bp, cover with small beaker, and cool under tap, shaking occasionally.
(e) Dilute sulfuric acid.—Add 35 mL H2SO4 to each 1 L H2O, boil 5–10 min, and cool to room temperature.
(f) Iodine indicator.—To ca 20 g I2 in 500 mL glass-stoppered bottle add 400 mL dilute H2SO4, (e), and shake 10 min. Decant and discard first solution, since it may contain iodides. Repeat process and store solution in small glass-stoppered bottles.
