# Sulphate ion- confirmatory test

On adding $\ce{BaCl2}$ solution to $\ce{ SO4^{2-}}$ salt aqueous solution $\ce{ BaSO4}$ is formed as a white precipitate, which confirms the presence of the anion.

While doing the test in my school laboratory, we were given a list of procedures to follow; for $\ce{ SO4^{2-}}$ it read:

'Experiment: Aqueous solution of sample + dilute $\ce{ HCl}$ + $\ce{ BaCl2}$ solution

Observation: white ppt'

Why do we need to add $\ce{ HCl}$?

• I should add that in the lab I was asked to add dil HCl and BaCl2 to a "sodium carbonate extract" instead of an aqueous solution of a salt. – Gaurang Tandon Feb 11 '18 at 11:01