LIMIT TEST FOR SULPHATE

1. LIMIT TEST FOR
SULPHATE
BY
PROF. TAUFIK MULLA
ASSISTANT PROFESSOR
DEPARTMENT OF PHARMACEUTICS
SPBC COLLEGE OF PHARMACY.

2. LIMIT TEST FOR SULPHATE
• The Sulphate Limit Test is designed to determine the allowable limit of sulphate contained in a
sample.
• The principle involved in the Limit test of sulphates is precipitation method and comparison of test
solution with standard solution containing a known amount of sulphates.
Principle:
The sulphates are precipitated as barium sulphate by reacting with barium chloride in the presence of
acetic acid. The acetic acid used prevents the reaction of other acid radicals with barium chloride. In
presence of hydrochloric acid, only sulphates are precipitated.
Sulphate ion Barium Chloride Barium Sulphate

3. Due to the formation of precipitates, the solution appears turbid and the extent of
turbidity depends on the amount of sulphates present.
If the turbidity produced by the test is less than that of standard, it means that the sample
contains sulphates within the prescribed limits.

4. PROCEDURE
TEST SAMPLE STANDARD SAMPLE REASON
Take 1 ml of 25% w/v of barium
chloride in Nessler cylinder and
marked it as ‘T’
Take 1 ml of 25% w/v of barium
chloride in Nessler cylinder and
marked it as ‘S’
Barium ion react with sulphate and
produced opalescence of barium
sulphate
Add 1.5 ml of ethanolic sulphate
standard solution (10 ppm of SO4)
Add 1.5 ml of ethanolic sulphate
standard solution (10 ppm of SO4)
Ethanolic sulphate solution increase
sensitivity of test and alcohol
prevent super saturation barium
sulphate precipitate
Add 15 ml solution of given sample Add 15 ml standard potassium
sulphate solution as per I.P
For presence of sulphate ion in
sample and standard
Add 0.15 ml 5M acetic acid Add 0.15 ml 5M acetic acid To prevent precipitation of other
anions
Make volume with distilled water to
50 ml
Make volume with distilled water to
50 ml
Equal volume of sample and
standard is needed to identify
opalescence

5. CONCLUSION
• The opalescence produced in the sample solution should not be greater than standard
solution.
• If opalescence produced in the standard is more than that of test, the sample complies
with the limit test of sulphate as per I.P. 1996