Alum (noun) Definition, Meaning & Examples

noun Chemistry.
  1. 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.
  2. 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.
  3. (not in technical use) aluminum sulfate.
noun Informal.
  1. an alumna or alumnus: Nearly 45 of us alums went on a day trip on the river to celebrate graduation.
abbreviation Chemistry.
  1. aluminum.
noun
  1. 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
  2. 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
    Alum (noun) Definition, Meaning & Examples

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