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Preparation and Standardization of 0.1 M Perchloric acid

Learn how to prepare and standardize the 0.1 M Perchloric acid using Potassium Biphthalate and Crystal Violet as indicator.


•  Take about 500 ml of anhydrous glacial acetic acid  & 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 1000-ml 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 content no titrable 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. Standardized the solution.


•  Accurately weigh about 700 mg of Potassium Biphthalate, previously crushed lightly and dried at 120° for 2 hours, and dissolve it in 50 ml of glacial acetic acid in a 250-ml)conical flask.
•  Add 2 drops of Crystal Violet, and titrate with the perchloric acid solution until the violet color changes to blue-green.
•  Deduct the volume of the perchloric acid consumed by 50 ml of the glacial acetic acid.
•  Each 20.42 mg of Potassium Biphthalate is equivalent to 1 ml of 0.1N perchloric acid.
•  Calculate the molarity by following formula:
        KHC8H4Oin gm
N= ---------------------------
      0.20423 x HClOin ml

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