Ammonium alum - AbsoluteAstronomy.com

Ammonium aluminium sulfate, also known as ammonium alum is a white crystalline double sulfate usually encountered as the dodecahydrate, formula

Chemical formula

A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

(NH₄)Al(SO₄)₂·12H₂O. It is used in small amounts in a variety of niche applications. The dodecahydrate occurs naturally as the rare mineral tschermigite

Tschermigite

Tschermigite is a mineral form of ammonium alum, formula NH4AlSO4·12H2O. It is found in burning coal seams, bituminous shale and fumaroles. Because of its extreme water solubility it is unlikely to persist except in the dryest of conditions. Discovered in 1852 at Cermiky, also known as Schermig...

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Ammonium alum is made from aluminium hydroxide

Aluminium hydroxide

Aluminium hydroxide, Al3, ATH, sometimes erroneously called Hydrate of alumina, is found in nature as the mineral gibbsite and its three, much more rare forms, polymorphs: bayerite, doyleite and nordstrandite. Closely related are aluminium oxide hydroxide, AlO, and aluminium oxide, Al2O3,...

, sulfuric acid

Sulfuric acid

Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...

and ammonium sulfate

Ammonium sulfate

Ammonium sulfate , 2SO4, is an inorganic salt with a number of commercial uses. The most common use is as a soil fertilizer. It contains 21% nitrogen as ammonium cations, and 24% sulfur as sulfate anions...

. It forms a solid solution

Solid solution

A solid solution is a solid-state solution of one or more solutes in a solvent. Such a mixture is considered a solution rather than a compound when the crystal structure of the solvent remains unchanged by addition of the solutes, and when the mixture remains in a single homogeneous phase...

with potassium alum

Potassium alum

Potassium alum, potash alum or tawas is the potassium double sulfate of aluminium. Its chemical formula is KAl2 and it is commonly found in its dodecahydrate form as KAl2·12. Alum is the common name for this chemical compound, given the nomenclature of potassium aluminum sulfate dodecahydrate...