Indian National Academy of Engineering - Indian Engineering Heritage : Metallurgy
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ZINC
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 


 


 ZINC


Element (Zn), Atomic No. 30, density 7.13 kg/litre, M.Pt 420°C

First isolated in 1746 by Marggraf.

A lightweight metal which is cheap and can readily be made into coins. It does oxidise steadily and inexorably, and so is not a very satisfactory coinage metal in its pure form. Generally superseded by aluminium, zinc was used by the Germans for occupation coinage during the two world wars. The metal is an important constituent of brass.

For some years now US and Canadian cents have been made using copper-clad zinc rather than bronze.

Source:  http://www.tclayton.demon.co.uk/metal.htm


The earliest firm evidence for the production of metallic zinc is from India. Of the metals used in antiquity zinc is one of the most difficult to smelt since zinc volatalises at about the same temperature of around 1000oC that is needed to smelt zinc ore. As a result it would form as a vapour in the furnace which would immediately get  reoxidised and hence lost. Hence metallic zinc is seldom reported in antiquity. However in India there is unique evidence for the extensive and semi-industrial production of metallic zinc at the Zawar area of Rajasthan. An ingenious method was devised of downward distillation of the zinc vapour formed after smelting zinc ore using specifically designed retorts with condensers and furnaces, so that the smelted zinc vapour could be drastically cooled down to get a melt that could solidify to zinc metal. The Rasaratnakara, a text ascribed to the great Indian scientist Nagarjuna, of the early Christian era describes this method of production of zinc.

In Europe, the production of metallic zinc was virtually unknown until William Champion first established commercial zinc smelting operations in Bristol in the 1740’s following which it was industrially produced. Interestingly the method of production adopted by downward distillation bears a strong resemblance to the Zawar process and it has been pointed out that Champion’s process was very likely inspired by the Zawar process which would have been made known to the British during the forays of the East India Company.

Another remarkable artistic innovation by Indian metalworkers of the past was the use of zinc in making highly elegant bidri ware, an inlayed zinc alloy, which came into vogue under the Muslim rulers of the Bidar province in the Hyderabad region from about the 14th century. AD. Several impressive vessels, ewers, pitchers, vessels, huqqa bases etc. were made of bidri ware with patterns influenced by the fine geometric and floral patterns and inlayed metal work of the Islamic world where decorative metalwork reached some its most exquisite heights, for instance in the metalwork of the Ottoman empire.

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