Tag: extraction of metals from ore

Mercury has a low boiling point. Therefore it can be purified by the process of distillation because then mercury will evaporate and collected in pure form and impurities will remain back. 

During electrolytic refining of Alumina, the molten electrolyte used contains pure alumina $(Al _2O _3)$. The electrolyte consists of alumina dissolved in fused Cryolite (Na$ _3$AlF$ _6$) and Fluorspar(CaF$ _2$).

During calcination, carbonate ores are changed into oxides by heating strongly in limited air.
$ZnCO _3 \rightarrow ZnO + CO _2$

Metal oxide of the low reactivity can be reduced by carbon in the simple extraction process. For example; lead oxide is reduced by carbon and it extract lead from its ore.

The walls of a furnace should not react with metals or ore. So retractory metals are used as they are chemically inert.

Auto-reduction is a process in which sulphide ores of less electropositive metals like Hg, Pb, Cu etc., are heated in air so as to convert part of the ore into oxide or sulphate which then reacts with the remaining of sulphide ore in absence of air to give the metal and sulphur dioxide.

Carbon monoxide gas from coke is responsible for flame at the mouth of Bessemer converter, as it burns to form carbon dioxide.

When chromite $(FeCr _2O _4)$ is reduced with carbon in an electric-arc furnace, ferrochrome (Fe and Cr) is obtained.