(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
- It could also be treated by rubbing salt, brain or potash alum into the surface to produce a very pale leather.
- 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
More example sentences
- 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.