alum


noun Chemistry.

  1. 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.
  2. 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.
  3. (not in technical use) aluminum sulfate.

noun Informal.

  1. an alumna or alumnus.

Chemistry.

  1. aluminum.

noun

  1. 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
  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
n.

late 14c., “whitish mineral salt used as an astringent, dye, etc.,” from Old French alum, from Latin alumen “alum,” literally “bitter salt,” cognate with Greek aludoimos “bitter” and perhaps with English ale.

n.

  1. 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.

  1. 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.

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