Dross is a mass of solid impurities floating on a molten metal or dispersed in the metal, such as in wrought iron. It forms on the surface of low-melting-point metals such as tin, lead, zinc or aluminium or alloys by oxidation of the metal(s).
With wrought iron, hammering and later rolling removed some dross. With tin and lead the dross can be removed by adding sodium hydroxide pellets, which dissolve the oxides and form a slag. If floating, dross can also be skimmed off.
Dross, as a solid, is distinguished from slag, which is a liquid. Dross product is not entirely waste material; for example, aluminium dross can be recycled and is used in secondary steelmaking for slag deoxidation.
Etymology and usage
The term dross derives from the Old English word dros, meaning the scum produced when smelting metals. By the 15th century it had come to refer to rubbish in general. Dregs, and the geological term druse are also thought to be etymologically related. Metallurgical dross is referenced as a metaphor for worthless material in the Bible and in other religious texts.[note 1] [note 2]
- In the Book of Ezekiel 22 v 18 : "Son of man, the house of Israel is to me become dross: all they are brass, and tin, and iron, and lead, in the midst of the furnace; they are even the dross of silver.", in the Book of Proverbs, and in the Book of Mormon (Alma 32:3 ) "Therefore they were poor; yea, they were esteemed by their brethren as dross.".
- In the Buddhist text, the Dhammapada: 239. One by one, little by little, moment by moment, a wise man should remove his own impurities, as a smith removes his dross from silver.
- Landes, David S. (1969). The Unbound Prometheus: Technological Change and Industrial Development in Western Europe from 1750 to the Present. Cambridge, New York: Press Syndicate of the University of Cambridge. p. 91. ISBN 0-521-09418-6.
- Kogel, Jessica Elzea; Society for Mining, Metallurgy, and Exploration (2006), Industrial minerals & rocks: commodities, markets, and uses (7th ed.), SME, p. 1406, ISBN 978-0-87335-233-8.
- "Dross". www.etymologyonline.com.
- Chambers's Etymological Dictionary of the English Language. W & R Chambers. 1875. p. 142.
- "Ezekiel 22:18". The Bible (King James version). www.biblegateway.com.
- "Proverbs 25:4". The Bible (King James version). www.biblegateway.com.
- "Alma 32:3". The Book of Mormon. http://lds.org/scriptures/.
- Buddharakkhita, Acarya. "The Dhammapada, section XVIII". Access To Insight. Retrieved 11 September 2013.
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- AZoM.com – Aluminium Dross Recycling
- Herbert F. Lund. The McGraw-Hill recycling handbook. Chapter 37.23: United Kingdom: European Union Directive Precipitates Aluminum "Dross" Recycling.
- Residues from aluminium dross recycling in cement
- DrosRite Aluminum Recycling Process