Preparation and standardization of 0.1 N Iodine volumetric solution

1.0          Scope:

1.1                   The procedure is applicable to preparation and standardization of 0.1 N Iodine volumetric solution.

2.0          Apparatus:

2.1        Analytical balance.

2.2        50 ml burette (0.1 ml graduated).

2.3        250 ml stoppered conical flasks.

2.4        1000 ml volumetric flask.

2.5        25 ml pipette.

2.6        1 ml pipette.

2.7        2 ml pipette.

2.8        5 ml pipette.

2.9        50 ml beaker.

       (Use Class 'A' glassware)

3.0          Reagents:

3.1        Iodine (Analytical grade).

3.2        Potassium iodide.

3.3        Hydrochloric acid.

3.4        0.1 N Sodium thiosulfate volumetric solution

3.5        Starch Solution

3.6        Water.

4.0                Procedure:

4.1                    Preparation of starch solution:

4.1.1           Triturate 1.0 g of soluble starch with 5.0 ml of water and add, stirring continuously, to 100ml of boiling water containing 10 mg of mercuric iodide.

4.2              Preparation of 0.1N Iodine solution:

                    Weigh accurately about 14 g iodine in a solution of 36 g of potassium iodide in 100 ml of       water, add three drops of hydrochloric acid and dilute with water to 1000 ml.

4.3  Standardization:                                             Normality Limit : ±10% (0.09 to 0.11 )

        Transfer 25.0 mL of the iodine solution to a 250 mL flask, dilute with water to 100mL

        add 1 mL of 1 N hydrochloric acid, swirl gently to mix, and titrate with 0.1 N sodium   thiosulfate VS until the solution has a pale yellow color. Add 2 mL of starch TS and      continue titrating until the solution is colorless. Preserve in amber-colored, glass stoppered bottles.

                          Volume (mL) of Na₂ S₂ O₃ X Normality of Na₂ S₂ O₃

   Normality   =   --------------------------------------------------------------------

                                                                 25

  Perform the standardization in triplicate

        % of RSD Limit: Not more than 2.0%

5.0               Storage:

5.1               Store in amber-coloured, glass stoppered bottles.

6.0               Shelf Life:

6.1  Shelf life of the above solution shall be one month from the date of preparation.

6.2  Restandardize the above solution once in 15 days.

Note: Discard the volumetric solution whenever sedimentation, crystallization or fiber particles observed in the reagent bottle.

                                                             

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