AOAC Official Method 974.36 Microchemical Determination of Bromine, Chlorine, or Iodine
Oxygen Flask Combustion Method
First Action 1974
Final Action 1975
Surplus 1994
A. Apparatus and Reagents
(a) s-Diphenylcarbazone indicator.—1.5% alcohol solution. Heat to dissolve, if necessary. Prepare fresh daily.
(b) Bromophenol blue indicator.—0.05%. Dilute 5 mL 1% alcohol solution to 100 mL with alcohol.
(c) Mercuric nitrate standard solution.—Dissolve 1.7 g Hg(NO3)2×H2O in 500 mL H2O containing 2 mL HNO3 and dilute to 1 L. Adjust to pH 1.7, using pH meter, by adding HNO3 dropwise. Standardize as follows: Accurately weigh 4–6 mg KCl and transfer to 250 mL Erlenmeyer. Add 20 mL H2O and 80 mL alcohol, and stir magnetically at moderate speed. Add 5 drops bromophenol blue indicator and 0.5M HNO3 to yellow end point; then add 3 drops excess.
Add 5 drops s-diphenylcarbazone indicator and titrate at £5 mL/min with Hg(NO3)2 standard solution to orchid-pink. Subtract reagent blank. Repeat standardization ³3 times.
