Iodine Volumetric Solution Preparation and Standardization

Iodine Volumetric Solution Preparation and Standardization (0.1 N) as per USP:

Preparation of Reagent:

Starch TS: Mix 1 gm of soluble starch with 10 mg of red mercuric iodide and a sufficient amount of cold water to make a thin paste. Add 2 ml of boiling water, and boil for 1 min with continuous stirring. Cool, and use only a clear solution.

1N Hydrochloric Acid: Dilute 85ml of Hydrochloric acid into 1000ml of water.

Sodium Thiosulfate VS (0.1 N): Dissolve about 26gm of sodium thiosulfate and 200mg of sodium carbonate in 1000ml of recently boiled and cooled water.

Iodine Volumetric Solution Preparation (0.1 N):

Dissolve about 14gm of Iodine in a solution of 36gm of Potassium Iodide in 100ml of water, add 3 drops of Hydrochloric acid, and dilute with water to 1000 ml.

For lower strength refer to the given table:

Strength of VSQuantity of Iodine to be taken (g)Quantity of Potassium Iodide to be taken (g)Makeup with water (ml)
0.01 N1.43.61000
0.05 N6.5181000
Iodine Volumetric Solution Preparation

Standardization of Iodine Volumetric Solution (0.1 N):

  1. Transfer 25ml of the Iodine solution into a 250ml of volumetric flask.
  2. Dilute to volume with water to 100ml.
  3. Add 1ml of 1N hydrochloric acid.
  4. Swirl gently to mix.
  5. Titrate with 0.1 N Sodium thiosulfate VS until the solution has a pale yellow color.
  6. Add 2 ml of starch TS.
  7. Continue the titration until the solution turns colorless.

Calculation formula of Iodine Volumetric Solution (0.1N):

  • N x V
  • Normality of Iodine = —————
  • I


  • N= Normality of Sodium Thiosulfate VS,
  • V= Volume of Sodium Thiosulfate consumed,
  • I= Volume of Iodine solution taken for titration
Iodine Volumetric Solution Preparation
Iodine Volumetric Solution Preparation

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