Preparation & Standardisation of Ceric Ammonium Sulphate

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BACKGROUND

Ceric Ammonium Sulphate [Ce(SO₄)₂.2(NH₄)₂. SO₄. 2H₂O] in H₂SO₄ medium can function as a strong oxidizing agent and have a high oxidation potential. Sufficient H₂SO₄ is used to prevent hydrolysis and precipitation of basic salts. Since this is a strong oxidizing agent, we can determine various reducing substances by simple titration. In the presence of reducing agent, it undergoes reduction to the cerous state.

REQUIREMENTS

Chemical Required:

For Procedure A:

ceric ammonium sulphate: 65 g
arsenic trioxide: 0.2 g ;
sodium hydroxide solution (8.0% w/v): 25 ml ;
diluted sulphuric acid (10% w/v): 30 ml ;
osmic acid solution (1.0% w/v in water): 0.15 ml ;
ferroin sulphate solution (dissolve 0.7 g of ferrous sulphate in 70 ml of DW and add 1.5 g of 1, 10-phenanthroline and sufficient water to produce 100 ml): 0.1 ml.

For Procedure B:

ceric ammonium sulphate: 65 g;
sodium oxalate: 0.2 g;
diluted sulphuric acid (10% w/v): 2 ml;
diluted hydrochloric acid: 10 ml;

PROCEDURE

For Preparation of Ceric Ammonium Sulphate, 0.1M:

Dissolve 65 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. Standardise the solution in the following manner.

(A) For Standardisation of Ceric Ammonium Sulphate as per IP 2010:

Weigh accurately about 0.2 g of arsenic trioxide, previously dried at 105°for 1hour, and transferred to a 500 ml conical flask. Wash down the inner walls of the flask with 25 m1 of a 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 ferroin 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 endpoint.

Reaction:

Calculation of Factor:

4 mol ceric ammonium sulphate is equivalent to 1 mol of As₂O₃

4000 ml 1M ceric ammonium sulphate is equivalent to 1 g mol of As₂O₃= 197.84 g of As₂O₃

1 ml 0.1M ceric ammonium sulphate is equivalent to 197.84/40000 = 0.004946 g of As₂O₃

(B) For Standardisation of Ceric Ammonium Sulphate as per IP 2018:

Weigh and transfer accurately about 0.2 g of sodium oxalate, previously dried at 105° for 1 hour, to a 250 ml conical flask. Dissolve in 100 ml of water, add 2 ml of sulphuric acid, mix well, add 10 ml of hydrochloric acid, mix well and heat to about 75°. Titrate with 0.1 M ceric ammonium sulphate until the solution becomes faintly yellow.

Reaction:

Calculation of Factor:

2 mol ceric ammonium sulphate is equivalent to 1 mol of Na₂C₂O₄

2000 ml 1M ceric ammonium sulphate is equivalent to 1 g mol of Na₂C₂O₄ = 134 g of Na₂C₂O₄

1 ml 0.1M ceric ammonium sulphate is equivalent to 134/20000 = 0.0067 g of Na₂C₂O₄

Observation Table:

Sr No.	Initial Burette Reading (IBR in ml)	Final Burette Reading (FBR in ml)	Difference (ml)	Mean(V) (ml)
01
02
03

Calculation:

CONCLUSION

The actual concentration of prepared Ceric Ammonium Sulphate is __________

REFERENCES

Government of India, Ministry of Health. Pharmacopoeia of India: (the Indian Pharmacopoeia). Delhi: Manager of Publications, 2010. P- 631
Government of India, Ministry of Health. Pharmacopoeia of India: (the Indian Pharmacopoeia). Delhi: Manager of Publications, 2018. P- 967

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