📝 Ferrous Sulphate Testing Process Report

1. Description and Properties

Ferrous Sulphate, specifically the heptahydrate (FeSO4​⋅7H2​O), has the following physical characteristics as noted in the document:

• Appearance: A bluish-green crystal or a light-green crystalline powder that is odourless.
• Air Exposure: It is efflorescent (loses water of hydration) in dry air. Upon exposure to moisture/air, the crystal will rapidly oxidise and become brown (due to the formation of ferric compounds).
• Solubility: It is freely soluble in water.
• pH: The pH of a solution (determined in 100 ml water with a 5 gm sample) is between 3.0 and 4.0.

2. Assay Procedure (Testing Process)

The document outlines a volumetric titration method likely based on the oxidation of ferrous ions (Fe2+) to ferric ions (Fe3+) using Ceric Ammonium Nitrate/Sulphate.

2.1. Sample Preparation

1. Dissolve 2.5 gm of Sodium Bicarbonate in a mixture of 150 ml of water and 10 ml of H2​SO4​ (Sulphuric Acid).
2. Wait until the effervescence ceases.
3. Accurately weigh a 0.5 g portion of the Ferrous Sulphate sample being examined.
4. Using a substance pipette, transfer 1 ml of liquid NH3​ (Ammonia) to the sample.
5. Shake gently to dissolve the sample.
6. Top up the solution to the mark (this refers to filling a volumetric flask to the calibration mark, though the size is not specified).

2.2. Titration

1. Titrate the prepared Ferrous Sulphate solution against 0.1 N Ceric Ammonium Nitrate Ce(NH4​)2​(NO3​)6​solution.
2. Use 0.1 ml of Ferrous Solution (likely the prepared sample solution) as an indicator.
3. The end point is reached when the colour disappears.

2.3. Calculation

The document provides a formula for calculating the result (likely the percentage purity):

T.R×0.02780×Normality of 0.1 N Ceric Ammonium Nitrate ×100 / Weight of sample×0.1

• T.R: Titration value (volume of Ceric Ammonium Nitrate used).
• 0.02780: This is the Milliequivalent Weight (or T.V.) of FeSO4​⋅7H2​O for a 0.1 N solution.
• N(C.A.N.): Normality of the Ceric Ammonium Nitrate titrant.
• 0.1: This likely represents the volume of the aliquot taken for titration (if the final solution was 10 ml or a similar small factor).

3. Purity Limits

The required purity limits for the Ferrous Sulphate sample are:

• Limit: NLT 97.0% (Not Less Than 97.0%)
• Limit: NMT 105.0% (Not More Than 105.0%)