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alum
alum , any one of a series of isomorphous double salts that are hydrated sulfates of a univalent cation (e.g., potassium, sodium, ammonium, cesium, or thallium) and a trivalent cation (e.g., aluminum, chromium, iron, manganese, cobalt, or titanium). The name alum commonly refers to potassium aluminum sulfate dodecahydrate, or potash alum, KAl(SO 4 ) 2 ·12H 2 O, a colorless-to-white, crystalline compound. It is used in water purification, leather tanning, mordant dyeing, as an astringent, and in baking powder; it occurs in nature as the mineral kalunite. Sodium aluminum sulfate, or soda alum, NaAl(SO 4 ) 2 ·12H 2 O, is also used in baking powder. Ammonium aluminum sulfate, or ammonia alum, NH 4 Al(SO 4 ) 2 ·12H 2 O, is used in tanning, in dyeing and fireproofing textiles, in vegetable glues and porcelain cements, and in water purification. Chromium potassium sulfate, or chrome alum, KCr(SO 4 ) 2 ·12H 2 O, is used as a mordant in dyeing, in tanning, and in photographic fixing baths to harden gelatin films and plates. Aluminum sulfate, Al 2 (SO 4 ) 3 ·18H 2 O, is also called alum. A pseudoalum is a double sulfate salt of a divalent cation (e.g., magnesium or calcium) and a trivalent cation (e.g., aluminum). |
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"alum." The Columbia Encyclopedia, 6th ed.. 2008. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>. "alum." The Columbia Encyclopedia, 6th ed.. 2008. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1E1-alum.html "alum." The Columbia Encyclopedia, 6th ed.. 2008. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-alum.html |
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alum
a·lum / ˈaləm/ • n. Chem. a colorless astringent compound, AlK(SO4)2.12H2O, a hydrated double sulfate of aluminum and potassium, used in solution medicinally and in dyeing and tanning. ∎ any of a number of analogous crystalline double sulfates of a monovalent metal (or group) and a trivalent metal. |
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Cite this article
"alum." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>. "alum." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1O999-alum.html "alum." The Oxford Pocket Dictionary of Current English. 2009. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O999-alum.html |
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alum
alum XIV. — OF. alum (mod. alun) :- L. alūmen.
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T. F. HOAD. "alum." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>. T. F. HOAD. "alum." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1O27-alum.html T. F. HOAD. "alum." The Concise Oxford Dictionary of English Etymology. 1996. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O27-alum.html |
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alum
alum
•amalgam • Targum • begum
•Brigham • lingam • ogham • sorghum
•Nahum • Belgium • dodgem
•Brummagem • stratagem • Rackham
•Malcolm • Ascham • Beckham
•welcome • vade mecum • stickum
•dinkum • modicum • hypericum
•capsicum • viaticum • practicum
•Occam
•hokum, locum, oakum
•bunkum
•alum, Calum, mallam, vallum
•Pablum
•Haarlem, Harlem, Malayalam, slalom
•antebellum, cerebellum, elm, helm, overwhelm, pelham, realm, underwhelm, vellum
•emblem • bedlam • peplum
•exemplum • wychelm • Kenelm
•Salem • velum
•aspergillum, chillum, film, vexillum
•Whitlam • clingfilm • telefilm
•microfilm
•asylum, hilum, phylum, whilom
•column, olm, solemn
•problem • golem • hoodlum • Ulm
•incunabulum, pabulum
•coagulum • pendulum • speculum
•curriculum • cimbalom • paspalum
•Absalom • Jerusalem • tantalum
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Cite this article
"alum." Oxford Dictionary of Rhymes. 2007. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>. "alum." Oxford Dictionary of Rhymes. 2007. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1O233-alum.html "alum." Oxford Dictionary of Rhymes. 2007. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O233-alum.html |
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