Preparation and standardization of 0.02 M Sodium Edetate EP Volumetric Solution

1.  PREPARATION:

Dissolve 7.444 g of Sodium Edetate in 500 mL of water, add 20 mL of 1 M Sodium hydroxide and dilute to 1000 ml with water.

2. STANDARDISATION:

Dissolve 0.100 g of Zinc in 4 mL of Hydrochloric acid R1. Add dilute sodium hydroxide solution until the solution is weakly acid. Transfer the solution to a volumetric flask and dilute to 100 mL with water. Transfer 25.0 mL of the solution to a 500 mL conical flask and dilute to 200 mL with water. Add about 50 mg of Xylenol orange triturate and Hexamethylenetetramine until the solution become violet-pink. Add 2 g of Hexamethylenetetramine in excess. Titrate with the Sodium edetate solution until the violet pink colour change to yellow.

1 mL of 0.02 M Sodium edetate is equivalent to 1.308 mg of Zn.

Calculation:

Molarity (M) = [0.02 x Weight of Zinc (in g)]/[ 0.001308 x Titration reading (in ml)]

Limit: 0.02 M ± 5 % (0.0190 M – 0.0210 M)

3. PREPARATION OF INDICATORS / REAGENTS:

a. Hydrochloric acid R1:

Dilute 70 g of Hydrochloric acid to 100 mL with water.

b. 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 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.

c. Dilute Acetic acid:

Dilute 12 g of glacial Acetic acid to 100 mL with water.

d. Lead nitrate solution:

A 33 g/L solution of Lead nitrate.

e. 1 M Sodium hydroxide :

Dissolve 42 g of Sodium hydroxide in carbon dioxide free water and dilute to 1000 mL with the same solvent.

f. Dilute sodium hydroxide :

Dissolve 8.5 g of Sodium hydroxide in water and dilute to 100 mL with the same solvent.

4. STORAGE CONDITION:            

Store in a polyethylene container.

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