The History of Zinc
Long before the discovery of zinc as a metal, zinc ore was already being used to produce the copper-zinc alloy brass as well as zinc salts for medical purposes. Objects made of brass are known from Babylonia and Assyria from 3000 BC, and from Palestine dating from 1400 - 1000 BC.
The addition of zinc to copper for the first time was proven by a piece of jewellery from ca. 500 BC found on Rhodos. And even if zinc was used from that date to produce brass for example, many centuries nevertheless passed until it could be identified as a metal. The name "zinc" only came into general use in the 17th century following rediscovery of the material.
As zinc only ever occurs in Nature in the form of compounds, it was initially produced from carbonate of zinc, a zinc salt. Zinc was found to be especially suitable for alloys with other metals and was therefore first of all employed to make coins. Although zinc ores have been in use since the Bronze Age, it was not until very much later that zinc was discovered to be an element, i.e. a substance that cannot be broken down further. Zinc was generally imported from India until the end of the 18th century and was considered to be very costly.
Early production and usage in India and China
Metallic zinc was produced in India ca. 1200 AD, and the process is described as the production of a new metal similar to tin. It involved heating the zinc ore indirectly with charcoal in a covered crucible. This produced zinc vapour, which was cooled by the ambient air in a condensation recipient underneath the crucible. This is how metallic zinc was formed (Fig. 1).
It was Marco Polo (1254-1324) from Venice who reported the production of zinc oxide in Persia. At this time the Persians used a solution of zinc vitriol (ZnSO4×7H2O) to treat eye inflammations. Zinc sulphate (ZnSO4) is used in medicine as an adstringent and antiseptic even today.
By 1374 zinc had been recognised by the Hindus as a new metal, the eighth known in that day and age, and zinc production and trading was already underway on a limited scale...
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