The Ceric Ammonium Sulphate volumetric solution Preparations and standardization of the volumetric solutions are given below:
Preparation of 0.1M Ceric Ammonium Sulphate Solution
Dissolve 65.0 gm of cerric 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. Standardize the solution in the following manner.
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Standardization of 0.1M Ceric Ammonium Sulphate Solution
Weigh accurately about 0.2 gm. of arsenic trioxide, previously dried at 105ºC for 1 hour, and transfer to a 500 ml. conical flask washes the inner walls of the flask with 25 ml. of an 8.0% 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 and 0.1 ml of ferroin sulphate solution and slowly titrate with 0.1M ceric ammonium sulphate solution until the pink colour is changed to a very pale blue, adding the titrant slowly towards the end-point.
Each 1ml of 0.1M ferric ammonium sulphate equals 0.004946 gm of As2O3.
Calculation of 0.1M Ceric Ammonium Sulphate Solution
Molarity = Wt. of arsenic trioxide (mg) x Potency of arsenic trioxide × 0.1 / Volume consumed (ml) x 4.946 x 100
Osmic acid solution
1 % w/v solution of osmic acid in water.
ACCEPTANCE CRITERIA
1) The accuracy of the solution should be within ± 10% of the theoretical concentration.
2) RSD* of the triplicate results of standardization/ re-standardization should not be more than 0.2%.
Reference:- I.P./In-House (IP 2007, Vol. I, Page No. 549)