AOAC Official Method 932.17 Iodoform in Ointments
Gravimetric Method
First Action 1932
Final Action
Transfer ca 2.5 g laboratory sample to tared 50 mL beaker and weigh. Add 5mLCHCl3, stir gently with glass rod, and transfer bulk of undissolved ointment and CHCl3 solution to 250 mL glass-stoppered flask. Add 5 mL CHCl3 to ointment remaining in beaker and stir until dissolved. Add solution to flask and finally wash beaker 3 times, using £5 mL CHCl3 each time, and add washings to flask. Or: weigh test sample in small, tared glass capsule,drop capsule with contents into 250 mL glass-stoppered flask,and add £20mLCHCl3. (Use glass capsule only in volumetric determination.)
Swirl gently until all ointment dissolves. Add 40 mL 0.1M alcoholic AgNO3 [941.18 (see A.1.11). Use 95% alcohol.] and swirl to wash down any CHI3 that adheres to sides of flask. Slowly add 10 mL HNO3 and let stand at room temperature ca 18 h. Titrate excess of 0.1M alcoholic AgNO3 with 0.05MNH4SCN, 931.11A(a) (see 18.3.03), using 3 mL FeNH4(SO4)2 indicator, 931.11A(b) (see 18.3.03), vigorously shaking mixture near end of titration. 1 mL 0.1M AgNO3 = 0.01312 g CHI3.
