Preparation and standardization of 0.05 M Sulfuric acid EP Volumetric Solution
1. PREPARATION:
Dissolve 2.8 ml of Sulfuric acid in water and dilute to 1000.0 ml with the same solvent.
2. STANDARDISATION:
Dissolve 0.100 g of Sodium carbonate in 20 ml of water, add 0.1 ml of Methyl orange solution, and Titrate with the Sulfuric acid until the solution begins to turn reddish yellow. Boil for about 2 minutes. The colour of the solutions reverts to yellow. Cool and Titrate again until the reddish yellow colour reappears.
1 ml of 0.05 M Sulfuric acid is equivalent to 5.30 mg of Na2CO3.
Calculation:
Molarity (M) = [0.05 x Weight of Na2CO3 (in g)]/ [Titration reading (in ml) x 0.00530]
Limit: 0.05 M ± 5 % (0.0475 M – 0.0525 M)
3. PREPARATION OF INDICATORS / REAGENTS:
a. Methyl orange solution:
Dissolve 0.1 g of Methyl orange in 80 ml of water and dilute to 100 ml with ethanol (96 %).
Test for sensitivity: A mixture of 0.1 ml of the Methyl orange solution and 100 ml of carbon dioxide free water is yellow. Not more than 0.1 ml of 1 M Hydrochloric acid is required to change the colour to red.
Colour change: pH 3.0 (red) to pH 4.4 (yellow).
4. STORAGE CONDITION:
Store in glass stoppered bottles.
