1
Mercury
Symbol : Hg
Latin name : Hydrargyrum
Atomic no : 80
At wt : 200.59
Valency : 1 and 2
Occurrence
Mercury generally occurs in the combined state. The main ore is sulphide known
as cinnabar (HgS). It has also been found as amalgams of gold and silver.
Mercury is also called quick silver because of its Latin name is 'Hydrargyrum'
which means water silver or liquid silver. When we look quickly to the mercury, it
gives false impression of silver so it is also called quick silver.
Extraction of mercury from cinnabar
Extraction of mercury from cinnabar (HgS) involves the following steps:
1. Crushing and pulverization:
The big lumps of ores are crushed into small pieces with the help jaw crusher
and then pulverized into powdered ore with the help of ball mills.
2. Concentration
Cinnabar (HgS) being sulphide ore is concentrated by froth floatation process. The
pulverized ore is kept in water containing little pine oil & the mixture is agitated by
passing compressed air. Ore forms froth with oil and come to the surface and are
skimmed off while impurities are left in water.
3. Roasting and Distillation
The concentrated ore is mixed with 2% coke and fed into shaft furnace through a
cup and cone feeder at the top. Coke burns and ore is roasted in sufficient air where
cinnabar is first oxidized to mercuric oxide which then decomposes into mercury
vapours and oxygen. The vapours of mercury along with SO2, CO etc are
condensed by passing through Y-shaped earthen ware containing water. Mercury
, 2
vapours are condensed into liquid form in the condensers while waste gases like
SO2, CO etc escape from the outlet of the condenser.
2HgS + 3O2 → 2HgO + 2SO2
2HgO → 2Hg + O2
Fig: Shaft furnace for the extraction of mercury
4. Purification:- Mercury obtained the by above process is not pure and contains
impurities like copper Cu, Zn, Bi, Ag, etc. as impurities. The impure mercury is
filtered through chamois leather (leather of a male deer) to remove suspended
impurities. After that mercury is dropped through a long tube filled with 5%
HNO3 solution. The base metals dissolve in HNO3 as nitrates.
4Zn + 10 HNO3 → 4Zn(NO3)2 + NH4NO3 + 3H2O
4Cu+ 10 HNO3 → 4Cu(NO3)2 + 2NO + 4H2O
In case any mercurous nitrate if formed reacts with base metal giving back
mercury.
6Hg + 8HNO3 → 3Hg2(NO3)2 + 2NO↑ + 4H2O
Hg2(NO3)2 + Fe → Fe (NO3)2 + 2Hg↓
Mercury
Symbol : Hg
Latin name : Hydrargyrum
Atomic no : 80
At wt : 200.59
Valency : 1 and 2
Occurrence
Mercury generally occurs in the combined state. The main ore is sulphide known
as cinnabar (HgS). It has also been found as amalgams of gold and silver.
Mercury is also called quick silver because of its Latin name is 'Hydrargyrum'
which means water silver or liquid silver. When we look quickly to the mercury, it
gives false impression of silver so it is also called quick silver.
Extraction of mercury from cinnabar
Extraction of mercury from cinnabar (HgS) involves the following steps:
1. Crushing and pulverization:
The big lumps of ores are crushed into small pieces with the help jaw crusher
and then pulverized into powdered ore with the help of ball mills.
2. Concentration
Cinnabar (HgS) being sulphide ore is concentrated by froth floatation process. The
pulverized ore is kept in water containing little pine oil & the mixture is agitated by
passing compressed air. Ore forms froth with oil and come to the surface and are
skimmed off while impurities are left in water.
3. Roasting and Distillation
The concentrated ore is mixed with 2% coke and fed into shaft furnace through a
cup and cone feeder at the top. Coke burns and ore is roasted in sufficient air where
cinnabar is first oxidized to mercuric oxide which then decomposes into mercury
vapours and oxygen. The vapours of mercury along with SO2, CO etc are
condensed by passing through Y-shaped earthen ware containing water. Mercury
, 2
vapours are condensed into liquid form in the condensers while waste gases like
SO2, CO etc escape from the outlet of the condenser.
2HgS + 3O2 → 2HgO + 2SO2
2HgO → 2Hg + O2
Fig: Shaft furnace for the extraction of mercury
4. Purification:- Mercury obtained the by above process is not pure and contains
impurities like copper Cu, Zn, Bi, Ag, etc. as impurities. The impure mercury is
filtered through chamois leather (leather of a male deer) to remove suspended
impurities. After that mercury is dropped through a long tube filled with 5%
HNO3 solution. The base metals dissolve in HNO3 as nitrates.
4Zn + 10 HNO3 → 4Zn(NO3)2 + NH4NO3 + 3H2O
4Cu+ 10 HNO3 → 4Cu(NO3)2 + 2NO + 4H2O
In case any mercurous nitrate if formed reacts with base metal giving back
mercury.
6Hg + 8HNO3 → 3Hg2(NO3)2 + 2NO↑ + 4H2O
Hg2(NO3)2 + Fe → Fe (NO3)2 + 2Hg↓
