Extraction of mercury from cinnabar



1. Concentration

Cinnabar being sulphide is is concentrate by froth floatation method. The pulverized are is kept in water containing 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.

 

2. Roasting and Distillation

The concentrated are is mixed with 2% coke and fed into shaft furnace through a cup and wne. Arrangement the furnace is heated by pruning fuel and air is below in cinnabar is first oxidized to mercuric oxide which then decompose into mercury the vapor of mercury are condensed in Y-shaped. Earthen condensers cooled by water.

           

2HgS + O2                  →            2HgO + 2SO2

            2HgO                    →                  2Hg + O2

 Mercury

3. Purification:-

Mercury obtained by above process is not pure and contains impurities like copper (Cu), Zn, Bi, Ag, etc. as impurities. The impure mercury is filtered through daemons leather to remove suspended soiled. After that mercury is dropped through a long tube filled with 5% HNO3 solution. The base metals dissolve in HNO3 as Nitrate.

            4Zn + 10 HNO3       →               4Zn(NO3)2 + NH4NO3 + 3H2O

            4Cu+ 10 HNO3           →            4Cu(NO3)2 + 2NO + 4H2O

 

Any mercurous nitrate if from reacts with base metal giving back mercury.

           

Hg2(NO3)2 + Cu       →               Cu (NO3)2 + 2Hg

 Mercury

 

 

Mercury still contains metal like gold (Au), silver (Ag), Pt, etc. as impurities. These are removed by vacuum distillation where mercury distills leaving other metals.

 

 

Properties:-

1. Mercury is a shining metal having density 13.6 gmcm3

2. It has mpt on -370c and bpt 3570c

3. It vapourises forming monoatomic mercury molecule and mercury vapour are highly poisonous.

 

Chemical Properties

 

i. Action of Air

Air does not react with Hg, at normal (ordinary) temperature but on heating, mercury to its boiling point combines with oxygen forming mercuric oxide.

            2Hg + O2           →          2HgO

 

2. Action of Ozone

In an atmosphere of ozone, mercury loses its meniscus due to formation of mercurous oxide. When this mercury is allowed to slide down on glass surface, it leaves mercurous oxide in its trail. This phenomenon is called Tailing of Mercury

            2Hg + O3          →           Hg2O + O2

                                                Mercurous oxide

3. Action of Acids

dil. HCl and Dil H2SO4 does not reach while dil. HNO3 gives mercurous nitrate.

            6Hg + Dil8HNO3     →               3Hg2(NO3)2 + 2NO + 4H2O

                                                            Mercurous nitrate

Hot and conc. H2SO4 gives SO2 gas along with mercuric sulphate.

            Hg + 2H2SO4             →             HgSO4 + SO2 + 2H2O

            conc.                                        Mercurous sulphate

Hot and conc. HNO3 gives mercuric nitrate and Nitrogendioxide.

            Hg + 4HNO3                   →        Hg(NO3)2 + 2NO2 + 2H2O

            conc.                                       

Conc. HCl alone does not react with mercury but aquaregia dissolves mercury as mercuric (Corrosive sublimate)

HNO3 + 3HCl             →            NOCl + 2H2O  + 2Cl

Hg  + 2Cl                 →               HgCl2

 

Hg + HNO3 + 3HCl           →                 NOCl + HgCl2 + 2H2O

 

4. Action of Halogen:

Mercury combines directly with halogen to form mercury halides. The compound depends upon availability of halogen.

            Hg + Cl2           →           HgCl2

                        Excess             Mercuric chloride

            2Hg  + Cl2        →           Hg2Cl2

                        Limited           Mercurous chloride

 

5. Action with Sulphur

Mercury combines readily with sulphur at ordinary temperature formaing mercuric sulphide.

            Hg + S           →              HgS

 

Uses of Mercury

 

·         It is used in making thermometer, barometer etc.

·         It is  used in making mercury vapour lamps.

·         It is used in extraction of gold by amalgumation process.

·         It is used in manufacture of Caustic Soda (NaOH) by castner kellner process and kellner solvay process

 

·         It is used in making amalgam.


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