Preparation and standardization of Ceric ammonium sulphate standard solution
Pharmaceutical Analysis I Practical: Limit test for (1) Chloride (2) Sulphate (3) Iron (4) Arsenic Preparation and standardisation of (1) Sodium hydroxide (2) Sulphuric acid (3) Sodium thiosulfate (4) Potassium permanganate (5) Ceric ammonium sulphate Assay (1) Ammonium chloride (2) Ferrous sulphate(3) Copper sulphate (4) Calcium gluconate (5) Hydrogen peroxide (6) Sodium benzoate (7) Sodium Chloride Determination of Normality (1) Conductometric titration of strong acid against a strong base (2) Conductometric titration of strong acid and weak acid against a strong base (3) Potentiometric titration
Aim
To Prepare and standardize 0.1 M Ceric ammonium sulfate standard solution
Principle
This is an example of Cerimetric titration. Ceric ammonium sulphate or Ceric ammonium nitrate in sulphuric acid medium can function as strong oxidizing agent and considerably more stable than standard potassium permanganate solution and have a high oxidation potential. Sufficient sulphuric acid is to be used to prevent hydrolysis and precipitation of basic salts. In place of sulphuric acid, hydrochloric acid may also be used. It cannot interfere with analytical application. Ceric ammonim sulphate, a salt of suitable solubility for the preparation of the standard solution has the approximate formula Ce(SO4)2.2(NH4)2SO4. 2H2O, but the solution has to be standardized against a solution of Arsenic trioxide. Since ceric ammonium sulphate is a strong oxidizing agent, we can determine various reducing substances by simple titration. In presence of a reducing agent, it undergoes reduction to the cerous state.
Procedure
Preparation of 0.1 M Ceric ammonium sulphate standard solution Dissolve g of ceric ammonium sulphate, with the aid of gentle heat, in a mixture of 30 ml of sulphuric acid and 500 ml of water. Cool, filter the solution, if turbid, and dilute to 1000 ml with water.
Standardization of 0.1 M Ceric ammonium sulphate standard solution Weigh accurately about 0.2 g of arsenic trioxide, previously dried at 105 º for 1 hour, and transferred to a 500-ml conical flask. Wash down the inner walls
of the flask with 25 ml of 8.0 per cent w/v solution of sodium hydroxide, swirl to dissolve, add 100 ml of water and mix. Add 30 ml of dilute sulphuric acid, 0.15 ml of osmic acid solution, 0.1 ml of ferrroin sulphate solution and slowly titrate with the ceric ammonium sulphate solution until the pink colour is changed to a very pale blue, adding the titrant slowly towards the end-point.
Reference
Indian Pharmacopoeia 2007; Vol. 1; Pg. No.313
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