Preparation and standardization of 0.1 N Perchloric acid USP Volumetric Solution
1. PREPARATION :
Mix 8.5 mL of Perchloric acid with 500 mL of glacial Acetic acid and 21 mL of Acetic anhydride, cool, and add glacial Acetic acid to make 1000 mL. Alternatively, the solution may be prepared as follows. Mix 11 mL of 60 % Perchloric acid with 500 ml of glacial Acetic acid and 30 ml of Acetic anhydride, cool and add glacial Acetic acid to make 1000 mL.
Allow the prepared solution to stand for 1 day for the excess Acetic anhydride to be combined, and determine the water content. If the water content exceeds 0.5 %, add more Acetic anhydride. If the solution contains no titratable water add sufficient water to obtain a content of between 0.02 % and 0.5 % of water, indicating freedom from Acetic anhydride.
Or use ready-made solution of 0.1 N Perchloric acid.
Accurately weigh about 700 mg of Potassium biphthalate, previously crushed lightly and dried at 120°C for 2 hours, and dissolve it in 50 mL of glacial Acetic acid in a 250 mL flask. Add 2 drops of Crystal violet TS, and titrate with the Perchloric acid solution until the violet color changes to blue-green. Perform blank titration and deduct the volume of the Perchloric acid consumed by 50 mL of the glacial Acetic acid.
Each 20.422 mg of Potassium biphthalate is equivalent to 1 mL of 0.1 N Perchloric acid.
Normality (N) = [Weight of KHC8H4O4 (in g)]/[0.20422 x (Titration reading – Blank Reading) (in mL)]
Limit: 0.1 N ± 5 % (0.0950 N – 0.1050 N).
3. PREPARATION OF INDICATORS / REAGENTS :
a. Crystal violet TS :
Dissolve 100 mg of Crystal violet in 10 mL of glacial Acetic acid.
4. STORAGE CONDITION :
Store in glass stoppered bottles.