alum
1[ al-uhm ]
/ ˈæl əm /
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noun Chemistry.
Also called potash alum, potassium alum. a crystalline solid, aluminum potassium sulfate, K2SO4⋅Al2(SO4)3⋅24H2O, used in medicine as an astringent and styptic, in dyeing and tanning, and in many technical processes.
one of a class of double sulfates analogous to aluminum potassium sulfate, as aluminum ammonium sulfate, having the general formula R2SO4⋅X2(SO4)3⋅24H2O, where R is a univalent alkali metal or ammonium, and X one of a number of trivalent metals.
(not in technical use) aluminum sulfate.
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Origin of alum
1First recorded in 1275–1325; Middle English <Anglo-French, from Latin alūmen; replacing Old English alefne, ælifnæ, from Old Welsh (compare Medieval Welsh elyf ) <Latin alūmini- (stem of alūmen )
Other definitions for alum (2 of 3)
alum2
[ uh-luhm ]
/ əˈlʌm /
noun Informal.
Origin of alum
2First recorded in 1875–80; by shortening
usage note for alum
See alumnus.
Other definitions for alum (3 of 3)
alum.
abbreviation Chemistry.
aluminum.
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Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022
How to use alum in a sentence
British Dictionary definitions for alum
alum
/ (ˈæləm) /
noun
Also called: potash alum a colourless soluble hydrated double sulphate of aluminium and potassium used in the manufacture of mordants and pigments, in dressing leather and sizing paper, and in medicine as a styptic and astringent. Formula: K 2 SO 4 .Al 2 (SO 4) 3 .24H 2 O
any of a group of isomorphic double sulphates of a monovalent metal or group and a trivalent metal. Formula: X 2 SO 4 .Y 2 (SO 4) 3 .24H 2 O, where X is monovalent and Y is trivalent
Word Origin for alum
C14: from Old French, from Latin alūmen
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Medical definitions for alum
alum
[ ăl′əm ]
n.
Any of various double sulfates of a trivalent metal such as aluminum or iron and a univalent metal such as potassium or sodium that are used as topical astringents and styptics.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Scientific definitions for alum
alum
[ ăl′əm ]
Any of various crystalline double salts of a trivalent metal (such as aluminum, chromium, or iron) and a monovalent metal (such as potassium or sodium), especially aluminum potassium sulfate. Alum is widely used in industry as a hardener and purifier, and in medicine as an emetic and to stop bleeding.
The American Heritage® Science Dictionary
Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.