Aim:

To preapare and standardize 0.1 N Iodine Solution

Chemical requirements:

• Iodine
• Potassium Iodide
• Dil HCL
• Arsenic Trioxide (As₂O₃)
• Methyl orange (Indicator)
• Starch solution (Indicator)
• Sodium hydroxide

Apparatus

1. Burette
2. Pipette
3. Conical flask
4. Beaker
5. Glassrod
6. Mortar& pestle
7. Measuring cylinder

Procedure

1. Dissolve 36 grams of potassium iodide in 100ml of water.
2. Dissolve 14 grams of Iodine in the above solution
3. Add 3 drops of dilute HCl
4. Finally make upto 1000 ml with water

Standardisation of 0.1 N Iodine solution

1. Weigh about 0.15 gn of arsenic trioxide which was previously dried at 105⁰C for 1 hour
2. Dissolve in 20ml of 1 N sodium hydroxide solution by warming if necessary
3. Dilute with 40 ml of water and 2 drops of methyl orange solution was added
4. Dil.HCl was added drop by drop until the yellow colour is changed to pink; then add 2grams of sodium carbonate, dilute with 50 ml of water and add 3 ml of starch solution

Titrate with 0.1 N Iodine solution taken in burette until a permanent blue colour of starch is produced

Each ml of 0.1 N Iodine solution ≡ 0.00496 grams of Arsenic Trioxide

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