1. Umestone on heating decomposed in CaO and CO2. CaO combines with impurity (SiO3) to give slag and CO2 combines with C to form CO (reducing agent for reduction of FeO).
2. Cresol and aniline behave as froth stabilizer i.e. stabilises froth in thick scum.
3. SiO2 combines with FeO present in copper matte
- FeS + O2 → FeO + SO2
- FeO + SiO2 → FeSiO3
i.e. impurity of FeO can be eliminated as slag.