alum
1
[ al-uh m ]
/ ˈæl əm /
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 the potassium alum, 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.
Origin of alum
1
1275–1325; Middle English < Anglo-French < Latin
alūmen; replacing Old English
alefne, ælifnæ < Old Welsh (compare MWelsh
elyf) < Latin
alūmini- (stem of
alūmen)
Words nearby alum
Definition for alum (2 of 3)
alum
2
[ uh-luhm ]
/ əˈlʌm /
noun Informal.
an alumna or alumnus.
Origin of alum
2
by shortening
Definition for alum (3 of 3)
Example sentences from the Web for alum
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
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.
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.