Mercury (HG) was known to ancient Chinese and Hindus and was found in Egyptian tombs of 1500B.C. Mercury rarely is found free in nature. The chief ore is cinnabar (HgS). The metal is obtained by heating cinnabar in a current of air and by condensing the vapour.
Mercury is a heavy, silvery-white metal, and is the only metal to be a liquid at room temperature. It does not oxidise at ordinary temperatures however it will absorb oxygen at close to boiling point and in doing so converts to a red crystalline powder, know as mercuric oxide (HgO).
Mercury is a poor conductor of heat, when compared to other metals, and is a fair conductor of electricity.
Mercury forms a large number of compounds all of which are poisonous and some explosive.
Mercury 203 is radioactive
Mercury is used for:
- Separating gold and silver from their ores
- Coating mirrors
- An expansive metal in thermometers
- Mercury-vapour lamps
- Diffusion pumps
- Advertising signs
- The frozen-mercury moulding process
- Mercury-vapour motors
- Circulating medium in atomic reactors
Compounds of mercury are used for:
- Pharmaceuticals e.g. black mercurous oxide (Hg2O) is used in skin ointments and Mercurochrome (C20H8O6Na2Br2Hg), a green crystalline powder that turns to a brilliant red when dissolved in water is used as an antiseptic
- Paint pigments e.g. Mercury sulphide (HgS) is a brilliant red pigment
- Mercuric chloride (HgCl2) an extremely poisonous white crystalline powder, water and alcohol soluble, used as a wood preservative, as an insecticide and rat poison, in tanning, as a mordant and as a caustic antiseptic in medicine