Preparation and Standardization of 0.1 M Perchloric Acid with KHP
Preparation: Mix 8.5 ml of perchloric acid with
500 ml of anhydrous glacial acetic acid and 25 ml of acetic anhydride, cool and add anhydrous glacial acetic acid to produce 1000 ml. Allow the prepared solution to stand for 1 day for the excess acetic anhydride to be combined and
carry out the determination of water. If the water
content exceeds 0.5 per cent , add more acetic anhydride. If the solution contains no titratable water, add sufficient water to obtain a content of water between 0.02 per cent and 0.5 per cent. Allow the solution to stand for 1 day and again
titrate the water content. The solution so obtained should contain between 0.02 per cent and 0.5 per cent of water.
Standardise the solution in the following manner.
Standardization: Weigh accurately about 0.35 g of potassium hydrogen phthalate, previously powdered lightly and dissolve it in 50 ml of anhydrous glacial acetic acid. Add 0.1 ml of crystal violet solution and titrate with the
perchloric acid solution until the violet colour changes to emerald-green.
Peform a blank determination and make any necessary correction.
1 ml of 0.1 M perchloric acid is equivalent to 0.02042 g of potassium hydrogen phthalate.
Calculation:
(weight of KHP × 0.1) / (BR × 0.02042)
Generally BR for this Titration is found about 17.1 ml
Other strengths of perchloric acid should be prepared by diluting 0.1 M perchloric acid appropriately with anhydrous glacial acetic acid.