Explain the use of (1) Acidic flux and (2) Basic flux.

Explanation

Explanation :
(1) An acidic flux like sand (silica, `SiO_(2)`) is added in the extraction
of copper from pyrites `(CuFeS_(2))` ore which combines with basic
gangue or impurity of FeO forming fusible slag of ferrous silicate,
`FeSiO_(3).`
`{:(FeO,+,SiO_(2),rarr,FeSiO_(3)),("Basic gangue",,"Acidic flux",,"slag"):}`
(2) In case of acidc gangue or impurity like `SiO_(2)` basic flux like
lime, CaO (or ferrous oxide FeO) is added which forms fusible slag
(slurry) of `CaSiO_(3) or FeSiO_(3)`.
`{:(SiO_(2),+,CaO,rarr,CaSiO_(3)),("Acidic",,"Basic",,"slag"),("gangue",,"flux",,),(SiO_(2),+,FeO,rarr,FeSiO_(3)),(,,,,"slag"):}`