Preparation and Standardisation of 0.01 M Iodine EP Volumetric Solution
Add 0.3 g of Potassium iodide to 20 mL of 0.05 M Iodine and dilute to 100 mL with water.
To 40 mL of the Iodine solution add 1 mL of the dilute Acetic acid and 10 mL of water. Titrate with 0.1 M Sodium thiosulfate, determining the end-point potentiometrically or using starch solution as indicator.
M = (Molarity of 0.1 M Sodium Thiosulphate x Titration Reading T.R.)/ 40
Limit: 0.01 M ± 5 % (0.0095 M – 0.0105 M)
3. PREPARATION OF INDICATORS / REAGENTS:
a. 0.05 M Iodine:
Dissolve 12.7 g of Iodine and 20 g of Potassium iodide in water and dilute to 1000 mL with the same solvent.
b. 0.1 M Sodium Thiosulphate VS:
c. Starch solution :
Triturate 1.0 g of soluble starch with 5 mL of water and whilst stirring pour the mixture into 100 mL of boiling water containing 10 mg of Mercuric iodide.
Carry out the test for sensitivity each time the reagent is used.
Test for sensitivity : To a mixture of 1 mL of the Starch solution and 20 mL of water, add about 50 mg of Potassium iodide and 0.05 mL of Iodine solution R1. The solution is blue.
d. Dilute Acetic acid :
Dilute 12 g of glacial Acetic acid to 100 mL with water.
4. STORAGE CONDITION:
Store in glass stoppered bottles.