Flux – the foreign substance added in the roasted ore to remove infusible impurities present in the ore is called flux.
Choice of the flux–
(i) For basic infusible impurities, acidic flux (SiO2) is used
MnO2 + SiO2 → MnSiO3
(ii) For acidic infusible material, basic flux is used
SiO2 + CaO → CaSiO3
Slag – The fusible material formed due to reaction between gange and flux is called slag.
Gang + Flux = Slag
SiO2 + CaO = CaSiO3
