Preparation and standardization of 0.05 M Hydrochloric acid EP Volumetric Solution
1. PREPARATION :
Dilute 5.15 g of Hydrochloric acid to 1000 ml with water.
2. STANDARDISATION :
Dissolve 0.050 g of Sodium carbonate in 20 ml water, add 0.1 ml of Methyl orange solution and titrate with 0.05 M Hydrochloric acid until the solution just becomes yellowish-red. Boil for 2 minutes. The solution reverts to yellow. Cool and continue the titration until a yellowish-red colour is obtained.
1 ml of 0.05 M Hydrochloric acid is equivalent to 2.65 mg of Na2CO3.
3. CALCULATION :
Molarity (M) = [0.05 x Weight of Sodium Carbonate (in g)]/ [Titration Reading (in ml) x 0.00265]
4. 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 3.00 (red) to pH 4.40 (yellow).
5. STORAGE CONDITION :
Store in glass-stoppered bottles.