Procedure
Pipet 25 mL of Topical Solution into a 250-mL volumetric flask, add 5 mL of hydrochloric acid, dilute with water to volume, and mix. Pipet 25 mL of this solution into a 250-mL beaker, and add, in the order named and with continuous stirring, 25.0 mL of
Edetate disodium titrant and 20 mL of acetic acidammonium acetate buffer TS, then heat the solution near the boiling point for 5 minutes. Cool, and add 50 mL of alcohol and 2 mL of
dithizone TS. Titrate the solution with 0.05
M zinc sulfate VS to a bright rose-pink color. Perform a blank determination, substituting water for the sample, and make any necessary correction. Each mL of 0.05 M
Edetate disodium titrant is equivalent to 2.549 mg of Al
2O
3.