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Crystal of potassium alum, KAl(SO 4) 2 ·12H 2 O. 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 X Al(SO 4) 2 ·12 H 2 O, such that X is a monovalent cation such as potassium or ammonium. [1] By itself, "alum" often refers to potassium alum, with the ...
Alum-(K) is a hydrous potassium aluminium sulfate mineral with formula KAl(SO 4) 2 ·12(H 2 O). It is the mineral form of potassium alum and is referred to as potassium alum in older sources. It is a member of the alum group. [2] It occurs as colorless to white, soft isometric crystals and efflorescence coatings. [3]
Crystal structure of alunite. Alunite is an analog of jarosite, where aluminium replaces Fe 3+. Alunite occurs as a secondary mineral on iron sulfate ores. Alunite occurs as veins and replacement masses in trachyte, rhyolite, and similar potassium rich volcanic rocks.
Aluminium sulfate is sometimes called alum or papermaker's alum in certain industries. However, the name " alum " is more commonly and properly used for any double sulfate salt with the generic formula X Al(SO 4 ) 2 ·12H 2 O , where X is a monovalent cation such as potassium or ammonium .
Ammonium aluminium sulfate, also known as ammonium alum or just alum (though there are many different substances also called "alum"), is a white crystalline double sulfate usually encountered as the dodecahydrate, formula (NH 4)Al(SO 4) 2 ·12H 2 O. It is used in small amounts in a variety of niche applications.
It crystallizes in an octahedral structure in neutral solution and cubic structure in an alkali solution with space group Pa 3 and lattice parameter of 12.18 Å. [4] The compound is the most important member of the generic class of compounds called alums, and is often called simply alum. [5]
Forsterite. In chemistry, isomorphism has meanings both at the level of crystallography and at a molecular level. In crystallography, crystals are isomorphous if they have identical symmetry and if the atomic positions can be described with a set of parameters (unit cell dimensions and fractional coordinates) whose numerical values differ only slightly.
Ammonium iron(III) sulfate, NH 4 Fe(SO 4) 2 ·12 H 2 O, or NH 4 [Fe(H 2 O) 6](SO 4) 2 ·6 H 2 O, also known as ferric ammonium sulfate (FAS) or iron alum, is a double salt in the class of alums, which consists of compounds with the general formula AB(SO 4) 2 · 12 H 2 O. [2] It has the appearance of weakly violet, octahedrical crystals.