Question

What flux would you use to remove the following impurity?

CaO

Answer 1

The impurity CaO (lime/quicklime) is basic in nature. To remove it, we use an acidic flux, such as SiO₂ (silica).

\[\ce{CaO + SiO2 -> CuSiO3}\]

So, the flux used to remove CaO is SiO₂ (acidic flux).