How is boric acid prepared from calcium borate?

Dear student,
Boric acid is prepared commercially from Colemanite(Ca₂B₆O₁₁.5H₂O) by suspending it in boiling water and correspondingly passing SO₂.

Ca₂B₆O₁₁ + 9H₂O + 2SO₂ ----->2 CaSO_​​3 + 6H₃BO₃.

Hope it helps
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