11

DETERMINATION OF IRON IN STEEL

AIM

To determine the amount of iron present in steel.

REAGENTS REQUIRED

Standard oxalic acid solution (0.1N), potassium permanganate solution (0.1N) and dilute sulphuric acid (2N).

PRINCIPLE

The steel sample is dissolved in dilute sulphuric acid, which converts the iron present in it to ferrous sulphate with the liberation of hydrogen gas.

The amount of Fe²⁺ present in a solution can be determined by titrating against a standard potassium permanganate solution.

PROCEDURE

Part A: Standardisation of Potassium Permanganate Solution

Clean a burette initially with tap water and then rinse it with distilled water as well as potassium permanganate solution. Then, fill it with the potassium permanganate solution and note down the initial reading. Pipette out 10 ml of the standard oxalic acid solution into a 250 ml conical flask. Add 10 ml of dilute sulphuric and heat the solution to about 70°C. Then, titrate this solution slowly against the potassium permanganate solution from the burette until a faint but permanent pink colour persists in the solution. Repeat the titration until consecutive concordant values are obtained. Note down the values in a tabular column and calculate the normality of the potassium permanganate solution.

Part B: Determination of Iron in the Steel Sample

Dissolve 1 g of steel completely in 100 ml of dilute sulphuric acid and transfer the solution quantitatively into a 250 ml standard flask. Make up the volume to 250 ml by adding distilled water and shake the solution thoroughly. Pipette out 25 ml of the solution into a clean conical flask. Add 10 ml of dilute sulphuric acid and titrate against the potassium permanganate solution taken in the burette. The appearance of a permanent pink colour is the end point of titration. Repeat the titration until concurrent readings are obtained.

1 ml of 0.1N potassium permanganate = 5.585 mg of iron.

RESULT

Amount of iron present in 250 ml of the solution prepared from 1 g of steel = _____ g.

VIVA QUESTIONS

1. What is the basic principal involved in this experiment.
2. What is the oxidation state of Mn in potassium permanganate.
3. What is the end point in this experiment.
4. In this experiment which substance act as indicator.
5. In this experiment what is the role of H₂SO₄.