Dilute sulphuric acid, and the white precipitate that confirms it
Most barium salts dissolve freely in water — barium sulfate does not. Adding barium chloride solution to dilute sulphuric acid throws the sulfate out of solution as barium sulfate almost immediately, a dense white precipitate that resists dilute acids as well as water. That stubborn insolubility is what makes the test reliable: nothing else on a Class 10 bench produces the same white solid from the same two colourless liquids.
2 steps · Sulphuric Acid · Study of Compounds
What you will use
Apparatus
- Flask
Chemicals
- Dilute Sulfuric Acid
- Barium Chloride Solution
The steps
-
Pour dilute sulphuric acid into the flask.
Colourless. Nothing about it yet shows a sulphate is there.
-
Add barium chloride solution.
A dense white precipitate forms at once: barium sulfate.
What it shows
Barium chloride and dilute sulphuric acid exchange partners: BaCl₂ + H₂SO₄ → BaSO₄↓ + 2HCl. Barium sulfate is one of the very few sulfates that will not dissolve — not in water, not in dilute acid — which is exactly why its appearance is trusted as proof a sulphate was there.