This document describes the limit test for sulfate. The test is based on the reaction between barium chloride and soluble sulfates in the presence of hydrochloric acid. This results in the precipitation of barium sulfate. The turbidity produced by the test solution is compared to that of a standard sulfate solution. If the turbidity of the test solution is less than the standard, then the sample passes the limit test for sulfate.

1. LIMIT TEST FOR
SULPHATE
Shikha Agrawal
B.Pharm : Naraina Vidyapeeth Group Of
Institution

2. PRINCIPLE
 Limit test for sulphate is based upon reaction
between barium chloride and soluble sulphates in
the presence of dilute hydrochloric acid.
 Turbidity obtained in test solution will compared
with the standard sulphate solution.
 This results in the precipitation of sulphates as a
Barium Sulphates.
 Barium sulphates precipitate will form the solution
turbid.

3. REACTION
Na2So4+ BaCl2 BaSo4 + 2NaCl
HCl
Soluble sulphates Precipitate
Note :
• HCl is used to prevent precipitation of other acid radicals.
• In the presence of HCl only sulphates precipitate.

4.  Barium sulphate reagent is used in reaction.
 Barium sulphate reagent contains
1. Barium chloride
2. Sulphate free alcohol
3 .Potassium sulphate in water
 Potassium sulphate is used to increase the sensitivity of
reaction.
 It reacts with barium chloride and forms Barium Sulphate
in small quantity which act as a seeding agent.
.

5. PROCEDURE
TEST SOLUTION STANDARD SOLUTION
Dissolve specified quantity of test
substance in distilled water and
transfer it to a nesseler cylinder
Dissolve specified quantity of
standard substance in distilled water
and transfer it to a nesseler cylinder
Add 2 ml of dil. Hydrochloric acid. Add 2 ml of dil. Hydrochloric acid.
Volume makeup to 45ml with water. Volume makeup to 45ml with water.
Add 5 ml of barium sulphate reagent Add 5 ml of barium sulphate reagent
Stir with a glass rod and allow to
stand for 5 mins .
Stir with a glass rod and allow to
stand for 5 mins .
Observe the turbidity produced and
compared with the standard solution.
Observe the turbidity produced and
compared with the test solution.

6. OBSERVATION
 The turbidity produced in the test solution will be
compared with the standard solution, should be less
than the standard to pass the limit test.
 If the turbidity obtained in test solution is less than
the standard solution, sample passes the limit test
and vice versa.

7. Thank you