Mercury is extracted from cinnabar ore by carbon reduction process. This process consists of the following steps.
Concentration of cinnabar ore by froth flotation process:
Cinnabar is a sulphide ore and hence it is concentrated by froth flotation process.
Roasting of the concentrates ore:
The concentrated ore is roasted in air when it get oxidized to hgo and portion decomposes to hg and 02.
Smelting in sharp furnance
The roasted ore is with coke and mixture are heated in a shaft furnance to about 1000 degree cls. Under this condition hgo gets reduced to hg
HGO+C -> CO
The vapour of Hg and CO are led into a tank containing water where mercury vapours condenses to form liquid mercury.
Mercury conatins some solid as well as soluble base metals impurities. It is purified in following steps.
Filtration through chamois leather
Impure mercury is filtered through a chamois leather bag when mercury filters out and solid impurities remain in the bag.
Treatment with 5% HNO3
The filtered mercury is treated with 5% HNO3 when most of the metals impurities dissolve in HNO3 but mercury doesnot dissolve. The mercury is seprated,washed with water and dried.
Distillation in vaccum :
The dry mercury is distilled in vaccum when very pure mercury is obtained.