Take about 500 ml of anhydrous glacial acetic acid and about 25 ml acetic anhydride in a cleaned and dried 1000 ml volumetric flask. Add about 8.5 ml of Perchloric acid (About 70%) with continues stirring. Cool the solution. Make up the volume 1000ml with anhydrous glacial acid. Mix solution thoroughly. Keep the solution for at least 24 hours for the excess acetic anhydride to be combined. Then carry out the determination of water. If the water content exceeds 0.05% add more acetic anhydride. If the solution contains water, add sufficient water to obtain a content of water between 0.02% to 0.05%. Allow the solution to stand for 1 day and again titrate the water content. The solution so obtained should contain between 0.02% and 0.05% of water. Standardize the solution.