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History of Zinc Centuries before zinc was discovered in the metallic form, its ores were used for making brass and zinc compounds for medicinal purposes. C., while zinc appears to have become available on a commercial scale in the 14 century A. In Europe, zinc probably became first known through its import from India and China.
Zinc compounds were in the ores smelted certainly as early as 200 B. to obtain copper and which gave alloys of copper and zinc – the brass family. The Greeks also appeared to know zinc, even if not by name. have been found on the island of Rhodes, and the Romans used a zinc alloy to fabricate coins. Zinc was recognized in Europe as a separate metal in the 16th century when Agricola (1490 – 1555) and Paracelsus (1493 – 1541) wrote of a metal called “zincum.” Commercial smelting of zinc began in Europe in the middle of the 18 century when the first European zinc smelter was established in Bristol in the United Kingdom using a vertical retort procedure. The average natural level of zinc in the earth’s crust is 70 mg/kg (dry weight), ranging between 10 and 300 mg/kg (Malle 1992).
An electrical current is circulated through the electrolyte by applying an electrical difference of 3.3-3.5 volts between the anode and cathode causing the zinc to deposit on the aluminum cathodes in high purity.
The deposited zinc is stripped off, dried, melted and cast into ingots.
Small quantities of zinc carbonate – the mineral calamine (smithsonite) in North America – often refer to the hydrated silicate mineral also known as hemimorphite.
Iron and lead sulfides, in the form of the minerals pyrite and galena are always associated in significant quantities while smaller quantities of other metals are commonly found.
Roasting & Sintering Over 95% of the world’s zinc is produced from zinc blende (Zn S).
The Hydrometallurgical Process In a leaching stage the zinc oxide is separated from the other calcines. The zinc content dissolves whereas iron precipitates and lead and silver remain undissolved.Zinc Deposits Zinc ore deposits are widely spread throughout the world. Australia, Canada, China, India, Peru and Europe are the largest producers.