- a double sulfate of a monovalent metal or radical (as sodium, potassium, or ammonium) with a trivalent metal (as aluminum, iron, or chromium): it is used as an astringent, as an emetic, and in the manufacture of baking powders, dyes, and paper: the most common form is potash alum (potassium aluminum sulfate), KAl(SO)12HO
- aluminum sulfate: an erroneous use
Origin of alumMiddle English and Old French from Classical Latin alumen, alum: for Indo-European base see ale
Informal an alumnus or alumna
Any of various double sulfates of a trivalent metal such as aluminum, chromium, or iron and a univalent metal such as potassium or sodium, especially hydrous aluminum potassium sulfate, AlK(SO4)2 · 12H2O, widely used in industry as clarifiers, hardeners, and purifiers and medicinally as topical astringents and styptics.
Origin of alumMiddle English from Old French from Latin alūmen
An alumna or alumnus.
- An astringent salt, usually occurring in the form of pale crystals, much used in the dyeing and tanning trade and in certain medicines, and now understood to be a double sulphate of potassium and aluminium (K2SO4.Al2(SO4)3.24H2O). [from 14th c.]
- (chemistry) Any similar double sulphate in which either or both of the potassium and aluminium is wholly or partly replaced by other univalent or tervalent cations. [from 17th c.]
(third-person singular simple present alums, present participle aluming, simple past and past participle alumed)
- (US) A graduate of a university or other institution.