Preparation and standardization of 0.02 M Lead perchlorate Volumetric Solution
Dissolve 9.20 g of Lead perchlorate in 1000 mL volumetric flask. Add sufficient quantity of water. Sonicate to dissolve. Make up to the mark with water.
Accurately pipet 50 mL of 0.02 M Lead perchlorate solution, as prepared above, into a 250 mL conical flask. Add 3 mL of aqueous hexamethylenetetramine solution (2.0 g per 100 mL) and 4 drops of 0.5 % Xylenol orange indicator prepared by adding
500 mg of Xylenol orange to 10 mL of Alcohol and diluting with water to 100 mL. Titrate with 0.05 M EDTA to a yellow endpoint.
Molarity = [mL of EDTA x Molarity of EDTA]/ 50
Limit : 0.02 M ± 5 % ( 0.0190 M – 0.0210 M )
3. PREPARATION OF INDICATORS / REAGENTS :
a. Aqueous hexamethylenetetramine solution :
Dissolve 2.0 g of Hexamethylenetetramine in 100 mL volumetric flask. Add sufficient quantity of water. Make up to the mark with water.
b. 0.05 %Xylenol orange indicator :
Add 500 mg of Xylenol orange to 10 mL of Alcohol and dilute to 100 mL with water.
c. 0.05 M Edetate Disodium :
Dissolve 18.6 g of Edetate disodium dihydrate in water to make 1000 mL.
Standardization of 0.05 M Edetate Disodium :
Accurately weigh about 200 mg of chelometric standard Calcium carbonate, previously dried at 110°C for 2 hours and cooled in a desiccator. Transfer to a 400 mL beaker, add 10 mL of water, and swirl to form a slurry.
Cover the beaker with a watch glass, and introduce 2 mL of diluted Hydrochloric acid from a pipette inserted between the lip of the beaker and the edge of the watch glass. Swirl the contents of the beaker to dissolve the Calcium carbonate. Wash down the sides of the beaker, the outer surface of the pipette, and the watch glass with water, and dilute with water to about 100 mL. While stirring the solution, preferably with a magnetic stirrer, add about 30 mL of the 0.05 M Disodium Edetate solution from a
50 mL burette. Add 15 mL of Sodium hydroxide TS and 300 mg of Hydroxy napthol blue and continue the titration with 0.05 M Edetate disodium solution to a blue endpoint.
Molarity (M) = [mg of Calcium carbonate]/[ 100.09 x mL of EDTA]
d. Sodium hydroxide TS :
Dissolve 4.0 g of Sodium hydroxide in water to make 100 mL.
4. STORAGE CONDITION:
Store in glass stoppered bottles.