Question

What flux would you use to remove the following impurity?

P₂O₅

Answer 1

The impurity P₂O₅ is acidic in nature. To remove it, we use a basic flux, most commonly CaO (lime/quicklime).

\[\ce{3CaO + P2O5 -> Ca3(PO4)2}\]

So, the flux used to remove P₂O₅ is CaO.