Tag: basics of metallurgy

Ores contain large amount of impurities, which is called as gangue. The process of removing of impurities by physical means of methods like hand picking, crushing or pulverizing and grinding) is called dressing of ore.

Reduction is the process of removal of oxygen for extraction of metals from their oxide ores.

Electrolysis is the process of decomposition of a substance by passing electricity through it in a molten or dissolved state. 

Different processes applied in order to increase the percentage of metal in the ore is called concentration of ore.

Ores found in the form of sulphide and carbonates are first converted to their oxides by the process of roasting and calcination. Heating of sulphide ores in the presence of excess air to convert them into oxides is known as roasting.

It is easy to obtain metals from their oxides. So, ores found in the form of sulphide and carbonates are first converted to their oxides by the process of roasting and calcination.

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.