Preparation and Standardisation Of 0.1 M Disodium Edetate EP Volumetric Solution
Dissolve 37.5 g of Disodium Edetate in sufficient water to produce 500 mL, add 100 mL of 1 M Sodium hydroxide and dilute to 1000 mL with water.
Dissolve 0.120 g of Zinc, in granules, in 4 mL of Hydrochloric acid R1. Add dilute Sodium hydroxide solution until the solution is weakly acid and introduce this solution into a 500 mL conical flask and dilute to 200 mL with water. Add about 50 mg Xylenol orange triturate & Hexamethylenetetramine until the solution becomes violet-pink. Add 2 g of Hexamethylenetetramine in excess. Titrate with the 0.1 M Sodium edetate solution until the violet-pink colour changes to yellow.
1 mL of 0.1 M Sodium edetate equivalent to 6.538 mg of Zinc.
Molarity (M) = [0.1 x Weight of Zinc (in g)] /[0.006538 x Titration reading (in mL)]
Limit: 0.1 M ± 5 % (0.0950 M – 0.1050 M)
3. PREPARATION OF INDICATORS / REAGENTS:
a. Hydrochloric acid R1:
Dilute 70 g of Hydrochloric acid to 100 mL with water.
b. 1 M Sodium hydroxide:
Dissolve 4.2 g of Sodium hydroxide in carbon dioxide free water and dilute to 100 mL with the same solvent.
c. Dilute Sodium hydroxide solution:
Dissolve 8.5 g of Sodium hydroxide in water and dilute to 100 mL with the same solvent.
d. Xylenol orange triturate:
Triturate 1 part of Xylenol orange with 99 parts of Potassium nitrate.
Test for sensitivity: To 50 mL of water add 1 mL of dilute Acetic acid, 50 mg of the Xylenol orange triturate and 0.05 mL of Lead nitrate solution. Add Hexamethylenetetramine until the colour change from yellow to violet-red. After addition of 0.1 mL 0.1 M Disodium Edetate the colour changes to yellow.
e. Dilute Acetic acid:
Dilute 12 g of glacial Acetic acid to 100 mL with water.
f. Lead nitrate solution:
A 33 g/L solution of Lead nitrate.
4. STORAGE CONDITION:
Store in a polyethylene container.