# Describe the following: (i) Role of depressant in forth floatation process. (ii) Role of silica in the metallurgy of copper. (iii) Role of cryolite in

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Describe the following:
(i) Role of depressant in forth floatation process.
(ii) Role of silica in the metallurgy of copper.
(iii) Role of cryolite in the metallurgy of aluminium.

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(i) Role of depressant is to prevent one type of sulphide ore particles from forming the froth with air bubbles. For example : NaCl is used a depressant to separate PbS ore from ZnS ore.
(ii) To remove FeO, Silica is added during smelting which form ferrous silicate (FeSiO_(3)) slag which floats over molten matte and can be easily removed.
(iii) Cryolite is added to alumina to make it a good conductor of electricity and to reduce the melting point of mix to around 1140K.