Depending on its chemical form, mercury can enter the water, air and soil and stay there for over extended periods of time.
Isolation of Pure Mercury from its Natural Source
Pure mercury is obtained from mineral cinnabar (HgS) by subjecting the ore into heat until the compound breaks down. This process is summarized by the reaction below:
HgS + O2 (600°C) â†’ Hg (l) + SO2 (g)
In the commercial extraction of mercury, the cinnabar ore is subjected to heat in the presence of an air current with the mercury vapor being condensed. The obtained mercury is purified by washing it with nitric acid treated with air to take away the oxide impurities and impurities within the solution. Distillation at reduced pressure further purifies the extracted element.
Physical Properties of Mercury
Mercury is the only common metal that is in liquid form at ordinary temperatures. It is also referred to as quicksilver and belongs to the transition elements having an atomic number of 80 and atomic weight of 200.59.
Mercury possesses natural luster, is heavy and is silvery-white in color. At room temperature, Mercury exhibits slight volatility. It becomes solid when the pressure is as high as 7,640 atmospheres. This pressure is used as a standard in the measurement of extremely high pressures. It forms alloys easily with tin, silver and gold (amalgams). Unlike other metals, mercury is a poor conductor of heat.
Mercury: Chemical Properties and Reactions
Mercury reacts with different chemical substances. These reactions are summarized in the following:
Reaction with Air
Metallic mercury reacts with air at 350°C. The reaction product is mercury (II) oxide.
2Hg(s) + O2(g) â†’ 2HgO(s) [red]
Reaction with Halogens
Dihalides of mercury are formed when it reacts with halogens.
Hg(l) + F2(g) â†’ HgF2(s) [white]
Hg(l) + Cl2(g) â†’ HgCl2(s) [white]
Hg(l) + Br2(l) â†’ HgBr2(s) [white]
Hg(l) + I2(s) â†’ HgI2(s) [red]
Reaction with Water
Mercury, under normal conditions, does not react with water
Reaction with Acids
There is no reaction between mercury and non-oxidizing acids. Mercury, however, reacts with concentrated sulphuric acid, H2SO4 and concentrated nitric acid HNO3. Mercury also dissolves deliberately in dilute nitric acid and forms mercury (I) nitrate.
Reaction with Bases
Under standard conditions, mercury is not known to react with bases.
Important compounds that are formed by Mercury
Among the important compounds of mercury are mercuric chloride HgC12 and mercurous chloride Hg2Cl2, mercury fulminate Hg(ONC)2 and mercuric sulphide HgS, vermillion. Mercuric chloride HgC12 is a corrosive sublimate- an extremely violent poison, mercurous chloride Hg2Cl2 is calomel which is used in medicine, mercury fulminate (Hg(ONC)2 is a detonator used in explosives and mercuric sulphide HgS, vermillion is a high-grade paint pigment.
Commercial uses for the Mercury and its Compounds.
Mercury is utilized in many chemical laboratories in making instruments such as diffusion pumps, barometers and thermometers. It is also used as an electrode in making batteries also called mercury cells. Some switches and electrical apparatuses also utilize mercury.
Mercury vapour lamps and advertising signs make use of the gaseous mercury. Gaseous mercury provide ultraviolet light for water sterilization. Manufacturing industries also use mercury in chlorine and caustic soda production. Mercury is also used for manufacturing antifouling paint and common pesticides. Amalgams and detal preparations also use mercury.
Important mercury compounds that are essential in commercial industries include mercuric sulfide, which is an antiseptic and also used as paint pigment vermilion. Calomel or mercurous sulfide is used as electrodes and formely utilized as cathartic. Organic compounds of mercury are used as germicides, disinfectants and antiseptics. These mercury organic compounds are referred to as mercurials.