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Aluminium sulfate is rarely, if ever, encountered as the anhydrous salt. It forms a number of different hydrates, of which the hexadecahydrate Al 2 (SO 4) 3 ·16H 2 O and octadecahydrate Al 2 (SO 4) 3 ·18H 2 O are the most common. The heptadecahydrate, whose formula can be written as [Al(H 2 O) 6] 2 (SO 4) 3 ·5H 2 O, occurs naturally as the ...
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 formula KAl(SO 4) 2 ·12 H 2 O.
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.
The only stable chalcogenides under normal conditions are aluminium sulfide (Al 2 S 3), selenide (Al 2 Se 3), and telluride (Al 2 Te 3). All three are prepared by direct reaction of their elements at about 1,000 °C (1,832 °F) and quickly hydrolyse completely in water to yield aluminium hydroxide and the respective hydrogen chalcogenide .
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.
Other related compounds, sometimes called sodium aluminate, prepared by reaction of Na 2 O and Al 2 O 3 are Na 5 AlO 4 which contains discrete AlO 4 5− anions, Na 7 Al 3 O 8 and Na 17 Al 5 O 16 which contain complex polymeric anions, and NaAl 11 O 17, once mistakenly believed to be β-alumina, a phase of aluminium oxide.
List of desiccants: [1] Activated alumina; Aerogel; Benzophenone (as anion) Bentonite clay; Calcium chloride; Calcium hydride; Calcium oxide; Calcium sulfate (Drierite) Cobalt(II) chloride; Copper(II) sulfate; Lithium chloride; Lithium bromide; Magnesium chloride hexahydrate; Magnesium sulfate; Magnesium perchlorate; Molecular sieve; Phosphorus ...
It is commonly encountered as the dodecahydrate, KAl(SO 4) 2 ·12H 2 O. 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 ...