Refining Process | Properties of Zinc | Quality Control   Zinc is essential to a modern society. Zinc provides the most cost-effective and environmentally efficient method of protecting steel against corrosion. By prolonging the life of steel, zinc performs an invaluable service - it helps to save natural resources such as iron ore and energy and extends the life of steel goods and capital investments in steel, such as homes, bridges, port facilities, power lines and water distribution, telecommunications and transport. Zinc is essential to a modern society. Zinc provides the most cost-effective and environmentally efficient method of protecting steel against corrosion. By prolonging the life of steel, zinc performs an invaluable   Zinc's key use are: ¤ýAnti-corrosion coatings on steel (Galvanizing) ¤ýPrecision components (Die Castings) ¤ýConstruction material ¤ýBrass ¤ýPharmaceuticals and Cosmetics ¤ýMicronutrient for men, animals and plants   Zinc is also an essential element which is indispensable for human health and for all living organisms. The History of Zinc Centuries before zinc was discovered in the metallic form, its ores were used for making brass and zinc compounds were used for healing wounds and sore eyes. Brass was produced by the Romans in the time of Augustus (20 B.C.-14 A.D.). By 1374, zinc was recognised in India as a new metal and at Zawar, India, both zinc metal and zinc oxide were produced from the 12th to the 16th century. From India, zinc manufacture moved to China in the 17th century. Zinc was recognised as a separate metal in Europe in 1546. In 1743, the first European zinc smelter was established at Bristol in the United Kingdom     The solid zinc oxide (ZnO, Calcine) is separated from the gaseous sulphur dioxide (SO2) utilising various techniques. The collected zinc oxide is sent to the Leaching Plant and the sulphur dioxide goes to the Sulphuric Acid Plant via the gas cleaning plant.   Natural Zinc, like all metals, is a natural component of the earth's crust and an inherent part of our environment. Zinc is present not only in rock and soil, but also in air, water and the biosphere (plants, animals and humans). Zinc is constantly being transported by nature, a process called 'natural cycling' Rain, snow, ice, sun and wind erode zinc-containing rocks and soil. Wind and water carry minute amounts of zinc to lakes, rivers and the sea, where it collects as sediment or is transported further. Natural phenonoma such as volcanic eruptions, forest fires, dust storms and sea spray all contribute to the continuous movement of zinc through nature.   Protective Zinc's most remarkable quality is its natural capacity to protect. Zinc coatings protect steel against corrosion, extending the life of steel by up to five times. Thus car manufacturers can provide no-corrosion guarantees of 12 years or more and zinc helps to protect the value of a typical family investment. Zinc protects human health too – it is now known that zinc is essential for human health in general and the functioning of the human immune system in particular. Zinc-based creams and lotions are widely used to protect the skin against the harmful effects of the sun. Zinc is used in water purification systems and zinc supplements are added to soil to protect crop yields.   Sustainable The key provision of sustainability is to fulfill present needs without compromising the ability of future generations to meet their needs too. Thus sustainability focuses on economic growth, environmental protection and social progress. Zinc makes a significant contribution to sustainable development. In its role as steel protector, zinc is an essential material for public and private infrastructure development, prolonging the useful life of steel goods and structures and reducing the cost of their maintenance. As a natural essential element, zinc is part of every ecosystem. Zinc is completely recyclable, providing a sustainable resource for future generations. Zinc contributes to social progress too, by providing affordable shelter, promoting good health and contributing to the durability of the infrastructure and transport systems on which a modern society depends.   Environmentally Friendly All life on earth has evolved, over hundreds of millions of years, in the presence of zinc. Zinc is used by nature for a host of biological processes. For this reason, zinc is referred to as an "essential element", meaning that it is essential for the health of living organisms. Plants, animals and humans all regulate their zinc intake from nature. The possibility that emissions from industrial activity during the last two hundred years might be leading to increased levels of zinc in the environment became an issue. Since the 1970s, however, progressive emission control at refineries and industrial installations have reduced these emissions considerably. At the same time, general pollution control has greatly reduced the acidity of the air in most industrialised countries, with the result that zinc coatings on steel exposed outdoors now last longer and longer. The amount of zinc in the environment today is close to natural background levels. In other words, man's activities are no longer disturbing the natural balance of zinc in the environment.   Recycling     Basic technical Data Atomic number 30 Atomic weight 65.37 Density (at 25¡ÆC) 7140 kg/m3 Melting point 419.5¡ÆC (692.7 K) Boiling point (760 mm Hg) 907¡ÆC (1180 K) Modulus of elasticity 7 x 10000 MN/m2 Specific heat (20¡ÆC) 0.382 kJ/kg.K Latent heat of fusion (419.5¡ÆC) 100.9 kJ/kg Latent heat of vaporisation (906¡ÆC) 1.782 MJ/kg Heat capacity   - solid Cp = 22.40 + 10.5 x 1/ 1000 1/TJmol (298 - 692.7 K) - liquid Cp = 31.40 1/Jmol - gas Cp = 20.80 1/Jmol Linear coefficient of thermal expansion (polycrystalline 20-250¡ÆC) 39.7 ¥ìm/m.K Volume coefficient of thermal expansion (20 - 400¡ÆC) 0.89 x 1/1000000/K Thermal conductivity : solid (18¡ÆC) 113W/m.K Electrical resistivity (polycrystalline at 20¡ÆC) 5.9 u ohm§Ùm Standard electrode potential (against H2 electrode) -0.762 V Source : Porter-Zinc Handbook, 1991