Refining (metallurgy)
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In
Lead
Cupellation
One ancient process for extracting the silver from
In the 18th century, the process was carried on using a kind of reverberatory furnace, but differing from the usual kind in that air was blown over the surface of the molten lead from bellows or (in the 19th century) blowing cylinders.[2]
Pattinson process
The Pattinson process was
The process was economic for lead containing at least 250 grams of silver per ton.[2]
Parkes process
The Parkes process, patented in 1850 uses molten zinc. Zinc is not miscible with lead and when the two molten metals are mixed the zinc separates and floats to the top carrying only some 2% lead. However silver preferentially dissolves in zinc, so the zinc that floats to the top carries a significant proportion of the silver. The melt is then cooled until the zinc solidifies and the zinc crust is skimmed off. The silver is then recovered by volatalising[spelling?] the zinc.[2] The Parkes process largely replaced the Pattinson process, except where the lead contained insufficient silver, in which case the Pattinson process provided a method to enrich it in silver to about 40 to 60 ounces per ton, at which concentration it could be treated using the Parkes' process.[6]
Copper
Fire refining
The initial product of copper smelting was impure black copper, which was then repeatedly melted to purify it, alternately oxidizing and reducing it. In one of the melting stages, lead was added. Gold and silver preferentially dissolved in this, thus providing a means of recovering these precious metals. To produce purer copper suitable for making copper plates or hollow-ware, further melting processes were undertaken, using charcoal as fuel. The repeated application of such fire-refining processes was capable of producing copper that was 99.25% pure.
Electrolytic refining
The purest copper is obtained by an electrolytic process, undertaken using a slab of impure copper as the anode and a thin sheet of pure copper as the cathode. The electrolyte is an acidic solution of copper sulphate. By passing electricity through the cell, copper is dissolved from the anode and deposited on the cathode. However impurities either remain in solution or collect as an insoluble sludge. This process only became possible following the invention of the dynamo; it was first used in South Wales in 1869.
Iron
Wrought iron
The product of the
Refined iron
The term refining is used in a narrower context. Henry Cort's original puddling process only worked where the raw material was white cast iron, rather than the grey pig iron that was the usual raw material for finery forges. To use grey pig iron, a preliminary refining process was necessary to remove silicon. The pig iron was melted in a running out furnace and then run out into a trough. This process oxidised the silicon to form a slag, which floated on the iron and was removed by lowering a dam at the end of the trough. The product of this process was a white metal, known as finers metal or refined iron.
Precious metals
Precious metal refining is the separation of precious metals from noble-metalliferous materials. Examples of these materials include used catalysts, electronic assemblies, ores or metal alloys.
Process
In order to isolate noble-metalliferous materials,
See also
- Beneficiation– Process of separating commercially valuable minerals from their ores
- Ore concentrate – Raw ore processed to concentrate the metal component
- List of alumina refineries
Bibliography
- J. Day and R. F. Tylecote, The Industrial Revolution in Metals (The Institute of Metals, London 1991).
- Söderberg, A. 2011. Eyvind Skáldaspillir's silver - refining and standards in pre-monetary economies in the light of finds from Sigtuna and Gotland. Situne Dei 2011. Edberg, R. Wikström, A. (eds). Sigtuna.
- R. F. Tylecote, A history of metallurgy (Institute of materials, London 1992).
- Newcastle University: Hugh Lee Pattinson
References
- ^ Metallurgy - An Elementary Text Book, E.L. Rhead F.I.C F.C.S, Longmans, 1895, pp225-229
- ^ a b c Tylecote, 1992. pp 157-158.
- ^ Tylecote, R. F. (1992). A history of metallurgy. London: Institute of Materials. pp. 157–158.
- ^ Rowe, 1983. pp 189–190.
- ^ Metallurgy - An Elementary Text Book, E.L.Rhead F.I.C F.C.S, Longmans, 1895, pp193-195
- ^ Metallurgy - An elementary text-book, E.L. Rhead F.I.C. F.C.S., Longmans, 1895, p195