Preparation and standardization procedure of 0.1 M Perchloric acid EP Volumetric Solution


Place 8.5 mL of Perchloric acid in a volumetric flask containing about 900 mL of glacial Acetic acid and mix. Add 30 mL of Acetic anhydride, dilute to 1000 mL with glacial Acetic acid, mix and allow to stand for 24 hours. Determine the water content without addition of Methanol and, if necessary adjust the water content to 0.1 – 0.2 percent by adding either Acetic anhydride or water. Allow to stand for 24 hours.


Use ready made solution of 0.1 M Perchloric acid having water content 0.1 – 0.2 %.


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 & 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 the 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 standardized, the volume used in the assay becomes,

VC = V[1 + (t1-t2)0.0011]


t1 = Temperature during standardization

t2 = Temperature during the assay

V = Observed volume of 0.1 M Perchloric acid

VC = Corrected volume of 0.1 M Perchloric acid

1 mL of 0.1 M Perchloric acid is equivalent to 20.42 mg of C8H5KO4.


Molarity (M) =[0.1 x Weight of Potassium hydrogen phthalate (in g)]/[0.02042 x (Test Reading.-Blank reading)]

Limit: 0.1 M ± 5 % (0.0950 M – 0.1050 M)


a. Crystal violet solution:

Dissolve 0.5 g of Crystal violet in anhydrous Acetic acid and dilute to 100 mL with the same solvent.

Test for sensitivity: To 50 mL of anhydrous Acetic acid add 0.1 mL of the Crystal violet solution. On addition of 0.1 mL of 0.1 M Perchloric acid the bluish purple solution turns bluish green.


Store in glass stoppered bottles.

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