0.1 N Acetous Perchloric Solution Preparation & Standardization

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.

where: 

A = milliliters of acetic anhydride to be added to 1000 mL
of the acetous perchloric acid, and 

B = percent (w/w) of water in the acetous perchloric acid. 

• 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.

• 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
  glacial CH3COOH. 

   where: 

     A = normality of the HClO4 solution, 

     B = grams of KHC8H4O4 used, 

     C = milliliters of HClO4 solution consumed by the
KHC8H4O4 solution, and 

     D = milliliters of HClO4 solution consumed by 50 mL of
glacial CH3COOH.