- 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 alum1
- an alumna or alumnus.
Origin of alum2
Examples from the Web for alum
Petraeus, himself a Sosh alum, became the central figure for a mix of reasons.The Petraeus Revolution: How He Changed the American Way of War
January 8, 2013
The boys that were charged, let the court system work that out, added Kenny Fazi, another Big Red alum and retired mill worker.Steubenville Rape Case Splits Town Between Big Red and Guy Fawkes
January 7, 2013
Broadwell is a smart and able woman, a West Point alum, and, as a major in the Army Reserve, a sometime instructor there.Early Signs of General Petraeus’s Extramarital Affair
November 11, 2012
Runner up is James Fallows of The Atlantic for his hilariously pompous post “As a Harvard Alum, I Apologize.”Niall Ferguson Defends Newsweek Cover: Correct This, Bloggers
August 21, 2012
The Red Dwarf alum did not initially set out to make a web series.Jerry Seinfeld’s ‘Comedians in Cars’ Web Series Ruffles U.K. Feathers With Similarity to British ‘Carpool’
August 2, 2012
Boil a small lump of alum, and scald them in the alum-water.Directions for Cookery, in its Various Branches
Dissolve a pound of alum, and as much cream of tartar, in a quart of boiling water, and add two full gallons of cold water to it.
Alum is a great drier, and causes that thirst which some beer occasions; so that the more you drink of it, the more you want.
Silk may be dyed crimson, by steeping it in a solution of alum, and then dyeing it in the usual way in a cochineal bath.
Moisten a piece of paper with a solution of soap and alum, lay it on the print or picture, and pass it under a rolling press.
- 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 and History for alum
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.
- 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.
- 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.