![]() The production of potassium alum from alunite is archaeologically attested on the island Lesbos. The Ancient Greek Herodotus mentions Egyptian alum as a valuable commodity in The Histories. The western desert of Egypt was a major source of alum substitutes in antiquity. History Alum found at archaeological sites In medicine, "alum" may also refer to aluminium hydroxide gel used as a vaccine adjuvant. ![]() ![]() In most industries, the name "alum" (or "papermaker's alum") is used to refer to aluminium sulfate, AlĢO, which is used for most industrial flocculation : 766 (the variable n is an integer whose size depends on the amount of water absorbed into the alum). The most common of these analogs is chrome alum KCr(SO The name "alum" is also used, more generally, for salts with the same formula and structure, except that aluminium is replaced by another trivalent metal ion like chromium III, and/or sulfur is replaced by another chalcogen like selenium. Other alums are named after the monovalent ion, such as sodium alum and ammonium alum. By itself, "alum" often refers to potassium alum, with the formula KAl(SOĢO. An alum ( / ˈ æ l ə m/) is a type of chemical compound, usually a hydrated double sulfate salt of aluminium with the general formula XAl(SOĢO, where X is a monovalent cation such as potassium or ammonium. ![]()
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