Limit Test for Sulphate

Aim

To observe a limit test for Sulphate impurities.

Reference

Indian Pharmacopoeia, 2007, Volume 1, Pg No. 72,

Principle

The limit test for sulphate is mainly designed to control sulphate impurity in inorganic substances. It depends upon the precipitation of barium sulphate with barium chloride in an acidic medium and the comparison of the opalescence so obtained with standard opalescence containing a known quantity of sulphate ions.

Reaction

Procedure

Label two Nessler’s cylinders as Standard and Test and follow the procedure

Standard solution

1. Pipette out 1 ml of 25% BaCl2 solutions
2. Add 1.5 ml of ethanolic sulphate solutions
3. Mix and allow to stand for 1 min.
4. Add 10 ml of sulphate standard solution
5. Add 0.15 ml of acetic acid solutions
6. Make up the volume to 50 ml with distilled water and allow to stand for 5 min

Test solution

1. Pipette out 1 ml of 25% BaCl2 solutions

1. Add 1.5 ml of ethanolic sulphate solutions

1. Mix and allow to stand for 1 min.
2. Add 10 ml of sulphate test solution

1. Add 0.15 ml of acetic acid solutions

1. Make up the volume to 50 ml with distilled water and allow to stand for 5 min

Result

Compare the opalescence produced by the test solution with a standard solution and report your result.