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alum

alum (ăl´əm), 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(SO4)2·12H2O, 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(SO4)2·12H2O, is also used in baking powder. Ammonium aluminum sulfate, or ammonia alum, NH4Al(SO4)2·12H2O, 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(SO4)2·12H2O, is used as a mordant in dyeing, in tanning, and in photographic fixing baths to harden gelatin films and plates. Aluminum sulfate, Al2(SO4)3·18H2O, 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.. . Encyclopedia.com. 22 Apr. 2017 <http://www.encyclopedia.com>.

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"alum." The Columbia Encyclopedia, 6th ed.. . Retrieved April 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/alum

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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"alum." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 22 Apr. 2017 <http://www.encyclopedia.com>.

"alum." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. (April 22, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/alum-1

"alum." The Oxford Pocket Dictionary of Current English. . Retrieved April 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/alum-1

alum

alum XIV. — OF. alum (mod. alun) :- L. alūmen.

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"alum." The Concise Oxford Dictionary of English Etymology. . Encyclopedia.com. 22 Apr. 2017 <http://www.encyclopedia.com>.

"alum." The Concise Oxford Dictionary of English Etymology. . Encyclopedia.com. (April 22, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/alum-2

"alum." The Concise Oxford Dictionary of English Etymology. . Retrieved April 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/alum-2

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 • Ulmincunabulum, pabulum •coagulum • pendulum • speculum •curriculum • cimbalom • paspalum •Absalom • Jerusalem • tantalum

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"alum." Oxford Dictionary of Rhymes. . Encyclopedia.com. 22 Apr. 2017 <http://www.encyclopedia.com>.

"alum." Oxford Dictionary of Rhymes. . Encyclopedia.com. (April 22, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/alum-0

"alum." Oxford Dictionary of Rhymes. . Retrieved April 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/alum-0