0.1 N Acetous Perchloric Solution
Preparation of 0.1 N Acetous Perchloric Solution
Warning—Use chemical safety goggles and long- sleeved rubber gloves in the preparation of this solution. Perchloric acid in contact with certain organic materials can form explosive mixtures. All glassware that has been in contact with perchloric acid and its solutions should be rinsed with water before being set aside.
- To approximately 500 mL of glacial acetic acid (CH3COOH, Sp gr 1.05) in a 1-L volumetric flask,
- Add 8.5 mL of 70 % perchloric acid (HClO4, Sp gr 1.67) and mix the solution by swirling.
- Dilute to volume with glacial acetic acid and mix again.
- Add 25.0 mL of the acetous perchloric acid solution to a flask containing 25.0 mL of pyridine and determine the percent water (w/w) by titration with Karl Fischer reagent.
- Make any necessary blank correction after titrating a separate 25.0-mL portion of pyridine with the Karl Fischer reagent.
of the acetous perchloric acid, and
- Add with constant stirring, the calculated amount of
acetic anhydride (C4H6O3) in successive small portions to the
acetous perchloric acid.
- Cool, mix the solution thoroughly and
determine the water content with Karl Fischer reagent as
described in If the water content exceeds 0.05 % add
more acetic anhydride, but if the solution contains less than
0.02 % water,
- Add sufficient water to make the content between
0.02 and 0.05 % of water.
- Mix the solution thoroughly, and
again determine the water content by titration.
- When the water
content of the solution is between 0.02 and 0.05 %, standardize
the solution by the following procedure and protect it from
atmospheric moisture by a guard tube containing silica gel.
Standardization of 0.1 N Acetous Perchloric Solution
- Weigh accurately about 0.7 g of potassium hydrogen
phthalate (KHC8H4O4), previously dried at 105°C for 3 h, and
dissolve it in 50 mL of glacial CH3COOH in a 250-mL flask.
- Add 2 drops of crystal violet indicator solution (10 g/L in
glacial acetic acid),
- Titrate with the HClO4 solution until the
violet color changes to emerald-green.
- Determine the volume
of HClO4 solution consumed by a blank using 50 mL of the
KHC8H4O4 solution, and