Preparation and Standardization of 0.025 M Sulphuric Acid Solution

1.0 Scope: This procedure is applicable for the preparation and standardization of 0.025 M sulphuric acid solution.

2.0 Apparatus:

• 1000 ml volumetric flask
• 250 ml glass-stoppered, conical flask
• 100 ml graduated burette
• 10 ml volumetric pipette

3.0 Reagents:

• Sulphuric acid AR grade
• Anhydrous sodium carbonate AR grade
• Methyl red solution
• Ethanol (95 %v/v).
• 0.1M sodium hydroxide solution

Preparation of Reagents:

0.1M sodium hydroxide solution:

Prepare solution as per 0.1 M Sodium Hydroxide (NaOH), Preparation and Standardization

Methyl red solution:

• Dissolve 50 mg of methyl red in a mixture of 1.86 ml of 0.1M sodium hydroxide and 50 ml of ethanol (95 %v/v).
• After solution is effected, add sufficient purified water to produce 100 ml.
• Store in a transparent glass stoppered bottle.

4.0 Preparation:

Add slowly, with stirring, 1.5 ml of sulphuric acid to about 1000 ml of purified water, allow to cool 25°C.

5.0 Standardization

• Weigh accurately and transfer about 0.075 g of anhydrous sodium carbonate, previously heated at about 270°C for 1 hour to 250 ml glass stoppered flask.
• Dissolve it in 100 ml of purified water and add 0.1 ml of methyl red solution.
• Add 0.025 M sulphuric acid slowly from a burette, with constant stirring, until the solution becomes faintly pink.
• Heat the solution to boiling, cool and continue the titration.
• Heat again to boiling and titrate further as necessary until the faint pink colour is no longer affected by continued boiling.
• Each ml of 0.025M sulphuric acid is equivalent to 0.0026495 g of Na₂CO₃.

6.0 Calculation :

Where : M = molarity of 0.025 M sulphuric acid solution
W = weight of anhydrous sodium carbonate in g
V = volume of 0.025 M sulphuric acid in ml

7.0 Storage:

Store in a transparent glass stoppered bottle.

8.0 Reference:

As per IP –1996 Page No. A-213