Dross

For the Austrian municipality, see Droß.

Aluminium dross

Dross is a mass of solid impurities floating on a molten metal. It appears usually on the melting of low-melting-point metals or alloys such as tin, lead, zinc or aluminium, or by 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 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 recycled and is used in secondary steelmaking for slag deoxidation.^[1]

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.^[2] Dregs^[2] and the geological term druse are also thought to be etymologically related.^[3] Metallurgical dross is referenced as a metaphor for worthless material in the Bible and in other religious texts.^{[note 1]}

See also

• Aluminium alloy inclusions

References

1. ^ Kogel, Jessica Elzea; Society for Mining, Metallurgy, and Exploration (2006), Industrial minerals & rocks: commodities, markets, and uses (7th ed.), SME, p. 1406, ISBN 9780873352338, http://books.google.com/books?id=zNicdkuulE4C&pg=PA1406. 
2. ^ ^{a b} "Dross". www.etymologyonline.com. http://www.etymonline.com/index.php?term=dross. 
3. ^ Chambers's Etymological Dictionary of the English Language. W & R Chambers. 1875. pp. 142. http://books.google.co.uk/books?id=kf8n2v9ZjxIC. 
4. ^ "Ezekiel 22:18". The Bible (King James version). http://www.biblegateway.com/passage/?search=Psalms%20119:119;Ezekiel%2022:18,19&version=KJV. 
5. ^ "Proverbs 25:4". The Bible (King James version). http://www.biblegateway.com/passage/?search=Proverbs%2025:4;26:23&version=KJV. 
6. ^ "Alma 32:3". The Book of Mormon. http://scriptures.lds.org/en/alma/32/3. 

Notes

1. ^ 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.",^[4] in the Book of Proverbs,^[5] and in the Book of Mormon (Alma 32:3 ) "Therefore they were poor; yea, they were esteemed by their brethren as dross..".^[6]

External links

• AZoM.com – Aluminium Dross Recycling
• Herbert F. Lund. The McGraw-Hill recycling handbook. Chapter 37.23: United Kingdom: European Union Directive Percipitates Aluminum "Dross" Recycling.
• Residues from aluminium dross recycling in cement
• DrosRite Aluminum Recycling Process