Examine individual changes

'{{For|the Austrian municipality|Droß}} [[File:Aluminium dross2.png|Aluminium dross|right|thumb]] '''Dross''' is a [[mass]] of [[solid]] [[impurity|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 [[alloy]]s by [[oxidation]] of the metal(s). With [[wrought iron]], hammering and later [[Rolling (metalworking)|rolling]] removed 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 |coauthors= |year=1969|publisher=Press Syndicate of the University of Cambridge |location=Cambridge, New York |isbn= 0-521-09418-6|pages=91 |postscript= <!--None--> }}</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 recycling|aluminium dross can be 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 = 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. 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 (geology)|''druse'']] are also thought to be etymologically related.<ref>{{cite book|url=http://books.google.co.uk/books?id=kf8n2v9ZjxIC|title=Chambers's Etymological Dictionary of the English Language|year=1875|publisher=W & R Chambers|pages=142}}</ref> Metallurgical dross is referenced as a metaphor for worthless material in the Bible and in other religious texts.{{refn|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 [[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}} {{refn|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.''<ref>{{cite web |last=Buddharakkhita |first=Acarya|title=The Dhammapada, section XVIII |url=http://www.accesstoinsight.org/tipitaka/kn/dhp/index.html |publisher=Access To Insight |accessdate=11 September 2013}}</ref>|group=note}} ==See also== *[[Aluminium alloy inclusions]] *[[Slag]] ==Notes== {{reflist|group=note}} ==References== {{Reflist}} ==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 Precipitates [[Aluminum]] "Dross" [[Recycling]]. * [http://www.smartwaste.co.uk/filelibrary/Cement_aluminium_dross.pdf Residues from aluminium dross recycling in cement] * [http://www.pyrogenesis.com/pdfs/pyro_drosite.pdf DrosRite Aluminum Recycling Process] {{Metalworking navbox|castopen}} [[Category:Casting (manufacturing)]] [[Category:Metallurgy]] [[Category:Deoxidizers]]'