alum(redirected from alums)
Also found in: Dictionary, Thesaurus, Encyclopedia.
A double sulfate of aluminum and of an alkaline earth element or ammonium; chemically, an alum is any one of the markedly astringent double salts formed by a combination of a sulfate of aluminum, iron, manganese, chromium, or gallium with a sulfate of lithium, sodium, potassium, ammonium, cesium, or rubidium; used locally as a styptic.
Any of various double sulfates of a trivalent metal such as aluminum, chromium, or iron and a univalent metal such as potassium or sodium, especially hydrous aluminum potassium sulfate, AlK(SO4)2·12H2O, widely used in industry as clarifiers, hardeners, and purifiers and medicinally as topical astringents and styptics.
Agent used locally as a styptic.