Preparation and standardization of 0.1 M Perchloric acid BP Volumetric Solution
1. PREPARATION:
Add 8.5 mL of Perchloric acid in 900 mL of Glacial Acetic acid, mix well, add 30 mL of Acetic anhydride and dilute to 1000 mL with Glacial Acetic acid. Mix well and allow to stand for 24 hours. Determine the water content of resulting solution without addition of Methanol and if necessary adjust the water content to between 0.1 and 0.2 % by adding either Acetic anhydride or water, allow to stand for 24 hours. Or use ready-made solution of 0.1 M Perchloric acid.
2. STANDARDISATION:
Accurately weight and dissolve 0.170 g of Potassium hydrogen phthalate in 50 mL of anhydrous Acetic acid, warming gently if necessary. Allow to cool protected from the air and titrate with the Perchloric acid solution, determining the end point potentiometrically or using 0.05 mL of Crystal violet solution as indicator.
Note the temperature of the Perchloric acid solution at the time of titration. If the temperature at which an Assay is carried out is different from that at which the 0.1 M Perchloric acid has been standardised, the volume used in the Assay becomes :
VC = V [1+ (t1 – t2) 0.0011]
Where,
t1 = Temperature during standardisation
t2 = Temperature during the assay
V = Observed volume of 0.1 M Perchloric acid
VC = Corrected volume of 0.1 M Perchloric acid
Each mL of 0.1 M Perchloric acid VS is equivalent to 20.42 mg of C8H5KO4
Calculation:
Molarity (M) = [0.1 x weight of C8H5KO4 (in g)]/ [Titration reading x 0.02042]
Limit: 0.1 M ± 5 % (0.0950 M – 0.1050 M)
3. PREPARATION OF INDICATORS / REAGENTS:
a. Crystal violet solution:
A 0.5 % w/v solution of Crystal violet in Anhydrous Acetic acid.
It should complies with the following test:
Sensitivity: A mixture of 0.1 mL of the solution and 50 mL of Anhydrous Acetic acid is bluish purple. Add 0.1 mL of 0.1 M Perchloric acid VS. The colour of the solution changes to bluish green.
b. Anhydrous Acetic acid:
Glacial Acetic acid of commerce for use in non-aqueous titration containing not less than 99.6 % w/w of C2H4O2
It should complies with the following test:
Water: Not more than 0.4 % w/w. If the water content is greater than 0.4 %, it may be adjusted by adding the calculated amount of Acetic anhydride. Store protected from light.
4. STORAGE CONDITION:
Store in glass-stoppered bottles.