Perchloric Acid VS

Perchloric Acid VS HClO₄ = 100.5

For a 0.1m solution To 900 mL of glacial acetic acid add 8.5 mL of perchloric acid, 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, Appendix IX C, 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.

Ascertain its exact concentration in the following manner. Dissolve 0.35 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 using 0.05 mL of crystal violet solution as indicator. Record the temperature at which the standardisation was carried out. If the temperature at which an assay is carried out is different from that at which the 0.1m perchloric acid has been standardised, the volume used in the assay becomes

V_C = V[1 + 0.0011(t₁ – t₂)]

where t₁ is the temperature during standardisation, t₂ is the temperature during the assay, V is the observed volume and V_C is the corrected volume.

Each mL of 0.1m perchloric acid VS is equivalent to 20.42 mg of C₈H₅KO₄.

For a 0.02m solution Dilute 20.0 mL of 0.1m perchloric acid to 100.0 mL with anhydrous acetic acid.

Other strengths of perchloric acid should be prepared by diluting 0.1m perchloric acid VS appropriately with anhydrous acetic acid.