Mercury in Mercurial Ointments Titrimetric Method
First Action 1935
Final Action
After mixing ointment thoroughly with glass rod, avoiding contact with metals, weigh 1 g laboratory sample into Erlenmeyer. Add 20 mL H2O and 20 mL HNO3, and heat gently over small flame until red fumes cease to evolve. Cool, and decant aqueous solution from ointment base into separator. Wash ointment base with 50 mL boiling H2O, cool, and decant into separator. Repeat washing until all Hg is removed.
Shake combined solutions in separator with 50mLether. Transfer aqueous solution to Erlenmeyer. Wash ether solution with three 10 mL portions H2O until Hg is removed, adding washings to flask. Add 3 mL FeNH4(SO4)2 solution, 931.11A(b) (see 18.3.03), and titrate with 0.1MNH4SCN, 942.26 (see A.1.02). 1mL0.1MNH4SCN= 0.01003 g Hg.
