alum1
/ˈaləm
/(also potash alum)
noun [mass noun] Chemistry
1A colourless astringent compound which is a hydrated double sulphate of aluminium and potassium, used in solution in dyeing and tanning.
- Chemical formula: AlK(SO4)2.12H2O.
- Astringent varieties contain alum, which makes your mouth pucker when the fruits are eaten before they're fully ripe.
- I have no idea how it's manufactured, but it's a kind of alum, a double sulfate of aluminum in crystal salt form.
1.1 [count noun] Any of a number of analogous crystalline double sulphates of a monovalent metal (or group) and a trivalent metal: artificially grown crystals of one of the alums...
- Several decades later the Englishman Davy attempted to obtain the metal hidden in alums.
- Aluminium dross tailings were used to produce two types of alums.
Origin
Late Middle English: via Old French from Latin alumen, alumin- related to aluta 'tawed leather'.
Rhymes
alum2
/əˈləm
/noun informal, chiefly US
An alumnus or alumna: a fellow Wellesley alum
Origin
Late 19th century: abbreviation.
- throw one's hat in (or into) the ring
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