Define Procedure for Estimation of Iron in the Solution?

Carry out the experiment following the steps enumerated herewith:

1. Weigh 702 mg of reagent grade ferrous ammonium sulphate (NH₄)₂Fe (SO₄)₂. Dissolve it in 1000 ml distilled water. Add 5 ml of conc. sulphuric acid (or 3ml of 18 M sulphuric acid). 1 ml contains 0.100 mg of ferrous iron. Warm slightly and add 5 ml concentrated potassium permanganate (KMnO₄) drop by drop until it produces a permanent colour (light pink). KMnO₄ is added to oxidize the ferrous to ferric. Transfer this solution to a 1 litre volumetric flask and make the volume to 1 litre mark with distilled water. This solution contains 0.1 mg iron/ml.

2. Label a series of Borosil test tubes with blank (B), standard (Sl-S6) and sample (SA 1-4) and place them in a rack.

3. Take different volumes (0.2,0.4,0.6,0.8, 1.0 and 1.2 ml) of standard solution in the labeled tubes and make the volume to 2rnl with distilled water. Add 0.5 ml conc. sulphuric acid, 1 ml potassium persulphate and 2 ml of potassium thiocyanate to all tubes. Mix. Keep for 5 minutes for colour development. Add 9.5 ml distilled water to all tubes, mix and measure the optical density at 490nm.

4. For unknown sample make up the volume upto 100 ml of the given solution. Take 0.6 ml and 0.8 ml of the solution in duplicate and proceed just as in case of standard.

5. Draw the standard curve and calculate the amount of unknown solution present.