The Parkes process is a

pyrometallurgical Pyrometallurgy is a branch of extractive metallurgy. It consists of the thermal treatment of minerals and metallurgical ores and concentrates to bring about physical and chemical transformations in the materials to enable recovery of valuable ...

industrial process for removing

silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...

from

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, ...

during the production of

bullion Bullion is non-ferrous metal that has been refined to a high standard of elemental purity. The term is ordinarily applied to bulk metal used in the production of coins and especially to precious metals such as gold and silver. It comes fro ...

. It is an example of

liquid–liquid extraction Liquid–liquid extraction (LLE), also known as solvent extraction and partitioning, is a method to separate compounds or metal complexes, based on their relative solubilities in two different immiscible liquids, usually water (polar) and an orga ...

. The process takes advantage of two liquid-state properties of

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...

. The first is that zinc is

immiscible Miscibility () is the property of two substances to mix in all proportions (that is, to fully dissolve in each other at any concentration), forming a homogeneous mixture (a solution). The term is most often applied to liquids but also appli ...

with lead, and the other is that silver is 3000 times more soluble in zinc than it is in lead. When zinc is added to liquid lead that contains silver as a contaminant, the silver preferentially migrates into the zinc. Because the zinc is immiscible in the lead it remains in a separate layer and is easily removed. The zinc-silver solution is then heated until the zinc vaporizes, leaving nearly pure silver. If

gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...

is present in the liquid lead, it can also be removed and isolated by the same process.Pauling, Linus ''General Chemistry'' W.H.Freeman 1947 ed. The process was patented by

Alexander Parkes Alexander Parkes (29 December 1813 29 June 1890) was a metallurgist and inventor from Birmingham, England. He created Parkesine, the first man-made plastic. Biography The son of a manufacturer of brass locks, Parkes was apprenticed to Messenge ...

in 1850. Parkes received two additional patents in 1852. The Parkes process was not adopted in the United States, due to the low native production of lead. The problems were overcome during the 1880s and by 1923 only when the Parkes process was used.

References

* Lead Silver Metallurgical processes {{industry-stub

See also

References