Modified Limit Test for Sulfate (Gravimetric Analysis)

• The modified limit test for sulfate is based on gravimetric analysis, where sulfate ions (SO₄²⁻) are precipitated as barium sulfate (BaSO₄) using barium chloride (BaCl₂).
• The precipitate is then collected, dried, and weighed to determine the sulfate concentration.

Chemical Reaction:

Ba2+(aq) + SO₄2−(aq) → BaSO₄(s)

Procedure for Limit Test for Sulfate:

Prepare Test Solution:

• Prepare a solution from the sample, ensuring the sulfate ions are in a soluble form.

Add Barium Chloride (BaCl₂):

• Add an excess of BaCl₂ solution to the test solution to precipitate sulfate ions as barium sulfate (BaSO₄).

Filter the Precipitate:

• Filter the precipitate using a pre-weighed filter paper or crucible, then thoroughly wash the precipitate to remove any impurities.

Dry the Precipitate:

• Dry the filter paper or crucible containing the precipitate in an oven or desiccator until a constant weight is achieved.

Weigh the Precipitate:

• Weigh the filter paper or crucible with the dried precipitate.
• Subtract the initial weight of the filter paper or crucible to determine the weight of the barium sulfate (BaSO₄)

Calculate Sulfate Ion Concentration:

• Calculate the sulfate ion concentration in the sample based on the weight of BaSO₄ and the stoichiometry of the reaction.

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