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'{{For|the Austrian municipality|Droß}} {{Refimprove|date=November 2009}} [[Image:Aluminium dross2.png|Aluminium dross|right|thumb|250px]] '''Dross''' is a [[mass]] of [[solid]] [[impurity|impurities]] floating on a [[molten metal]]. It appears usually on the melting of [[melting point|low-melting-point]] [[metal]]s or [[alloy]]s such as [[tin]], [[lead]], [[zinc]] or [[aluminium]], or by [[redox|oxidation]] of the metal(s). It can also consist of impurities such as paint leftovers. It can easily be skimmed off the surface before pouring the metal into a [[Molding (process)|mold]] or [[casting flask]]. With tin and lead the dross can also be removed by adding [[sodium hydroxide]] pellets, which dissolve the oxides and form a [[slag]]. Dross, as a solid, is distinguished from slag, which is a liquid. Dross product is not entirely waste material; aluminium dross, for example, can be [[Aluminium recycling|recycled]] and is used in secondary [[steelmaking]] for slag [[deoxidizer|deoxidation]].<ref>{{Citation | last = Kogel | first = 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 = http://books.google.com/books?id=zNicdkuulE4C&pg=PA1406 | isbn = 9780873352338 | postscript =.}}</ref> ==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.<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 geolological term [[Druse (geology)|''druse'']] are also thought to be eytmologically related.<ref>{{cite book|url=http://books.google.co.uk/books?id=kf8n2v9ZjxIC|title=Chambers's Etymological Dictionary of the English Language|date=1875|publisher=W & R Chambers|pages=142}}</ref> Metallurgical dross is referenced as a metaphor for worthless material in the in Bible and in other religious texts.{{#tag:ref|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."'',<ref>{{cite book|chapterurl=http://www.biblegateway.com/passage/?search=Psalms%20119:119;Ezekiel%2022:18,19&version=KJV|title =The Bible (King James version)|chapter=Ezekiel 22:18|work=www.biblegateway.com}}</ref> in the the [[Book of Proverbs]],<ref>{{cite book| chapterurl=http://www.biblegateway.com/passage/?search=Proverbs%2025:4;26:23&version=KJV |chapter = Proverbs 25:4| title=The Bible (King James version)| work=www.biblegateway.com}}</ref> and in the [[Book of Mormon]] ([[Book of Alma|Alma]] 32:3 ) ''"Therefore they were poor; yea, they were esteemed by their brethren as dross.."''.<ref>{{cite book|url=http://scriptures.lds.org/en/alma/32/3|title =The Book of Mormon|chapter=Alma 32:3|work=http://lds.org/scriptures/}}</ref>|group="note"}} ==See also== *[[Aluminium alloy inclusions]] ==References== {{Reflist}} ===Notes=== {{reflist|group="note"}} ==External links== {{Wiktionary}} *[http://www.azom.com/details.asp?ArticleID=2150 AZoM.com – Aluminium Dross Recycling] *Herbert F. Lund. [http://books.google.com/books?id=gIn8o0b6zj0C&pg=PT975&dq=aluminium+dross++recycling&ei=fR_zSu6MDYSOygTCxPSmDw&client=firefox-a#v=onepage&q=&f=false The McGraw-Hill recycling handbook]. Chapter 37.23: [[United Kingdom]]: [[European Union]] Directive Percipitates [[Aluminum]] "Dross" [[Recycling]]. * [http://www.smartwaste.co.uk/filelibrary/Cement_aluminium_dross.pdf Residues from aluminium dross recycling in cement] {{Metalworking navbox|castopen}} [[Category:Casting (manufacturing)]] [[Category:Metallurgy]] [[Category:Deoxidizers]] [[de:Schlacke (Metallurgie)]] [[pl:Zgar]]'