0.1 N Acetous Perchloric Solution Preparation & Standardization

0.1 Acetous Perchloric Solution

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.

Calculate the amount of acetic anhydride (C4H6O3) required to react with all except 0.035 % (w/w) of the water in the acetous perchloric acid solution. The following formula, based on acetic anhydride having a specific gravity of 1.08 and an assay of 100 % may be used:

              A = 52.5 * B
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.

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 glacial CH3COOH. 

Calculation                       

Calculate the normality of the HClO4 solution, as follows: 
A = B / 0.2042 (C - D)
   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.
 

Stability                           

Re-Standardize monthly

Post a Comment

0 Comments