AOAC Official Method 936.05 Pyrethrin in Pesticide Formulations Mercury Reduction Method (1)
First Action 1936
Final Action
A. Reagents
(a) Deniges reagent.—Mix 5 g yellow HgO with 40 mL H2O,and, while stirring, slowly add 20 mL H2SO4; then add additional 40mL H2O and stir until all dissolves. Test for absence of mercurous Hg by adding few drops of (b) to 10mLand titrating with (c) as inC, paragraph 2, beginning “Add 50mLpreviously prepared and cooled dilute HCl¼”.
(b) Iodine monochloride solution.—Dissolve 10 g KI and 6.44 g KIO3 in 75 mL H2O in glass-stoppered bottle; add 75 mL HCl and 5mLCHCl3, and adjust to faint I2 color (in CHCl3) by adding dilute KI or KIO3 solution. If much I2 is liberated, use stronger solution of KIO3 than 0.01M at first, making final adjustment with 0.01M solution. Keep in dark and readjust when necessary. Do not store in refrigerator.
(c) Potassium iodate standard solution.—0.01M. Dissolve 2.14 g pure KIO3, previously dried at 105°C, inH2Oand dilute to 1 L. 1mL=0.0057 g pyrethrin I2 and needs no further standardization.
