{{short description|Impurities in molten metal}} {{for-multi|the Austrian municipality|Droß|the Venezuelan YouTuber|Dross (YouTuber)}} Aluminium dross|right|thumb '''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. For higher melting point metals and alloys such as steel and silver, oxidized impurities melt and float making them easy to pour off.
With wrought iron, hammering and later rolling remove some dross.<ref>{{cite book |title=The Unbound Prometheus: Technological Change and Industrial Development in Western Europe from 1750 to the Present |last=Landes |first=David S. |authorlink=David Landes |year=1969|publisher=Press Syndicate of the University of Cambridge |location=Cambridge, New York |isbn= 0-521-09418-6|pages=91 }}</ref> 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 also used in secondary steelmaking for slag deoxidation.<ref>{{Citation | last1 = Kogel | first1 = Jessica Elzea | last2 = Society for Mining, Metallurgy, and Exploration | title = Industrial minerals & rocks: commodities, markets, and uses | page = 1406 | publisher = SME | year = 2006 | edition = 7th | url = https://books.google.com/books?id=zNicdkuulE4C&pg=PA1406 | isbn = 978-0-87335-233-8 | postscript =.}}</ref>
==Etymology and usage== The term ''dross'' derives from the Old English word ''dros'', meaning the scum produced when smelting metals (extracting them from their ores). By the 15th century it had come to refer to rubbish in general.<ref name="dr">{{cite web|title=Dross|url=http://www.etymonline.com/index.php?term=dross|work=www.etymologyonline.com}}</ref> ''Dregs'',<ref name="dr"/> and the geological term ''druse'' are also thought to be etymologically related.<ref>{{cite book|url=https://books.google.com/books?id=kf8n2v9ZjxIC|title=Chambers's Etymological Dictionary of the English Language|year=1875|publisher=W & R Chambers|pages=142|isbn=9781402168093}}</ref> Popular non-metalworking uses of the word are derogatory: *poorly written or plagiarized journalism - "that article is utter dross", a stronger term than ''filler'' *undesirable, unprofitable work - "let's home in on the lion's share and outsource the dross"; synonyms: corvée and drudgery which are growing archaisms in business<ref>"dross" ''en.wiktionary.org''</ref> (noun); as strong a term as ''dogsbody work''
==See also== *Aluminium alloy inclusions *Slag
==References== {{Reflist}}
==External links== {{Wiktionary}} *[https://www.azom.com/article.aspx?ArticleID=2150 AZoM.com – Aluminium Dross Recycling] * Herbert F. Lund. [https://books.google.com/books?id=gIn8o0b6zj0C&dq=aluminium+dross++recycling&pg=PT975 The McGraw-Hill recycling handbook]. Chapter 37.23: United Kingdom: European Union Directive Precipitates Aluminum "Dross" Recycling.
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