- Potassium alum
Name = Potassium aluminium sulfate
ImageSize = 200px
OtherNames = potassium alum, potash alum
Section1 = Chembox Identifiers
CASNo = 7784-24-9
Section2 = Chembox Properties
Formula = KAl(SO4)2
MolarMass = 258.207 g/mol
Density = 1.76 g/cm3
Solvent = other solvents
SolubleOther = 36.80 grams of alum/100 grams of water at 50 °C
MeltingPt = 92-93 °C
BoilingPt = 200 °C
Potassium alum or potash alum is the
potassiumdouble sulfateof aluminium. Its chemical formula is KAl(SO4)2 and it is commonly found in its dodecahydrate form as KAl(SO4)2·12(H2O). It is commonly used in water purification, leathertanning, fireproof textiles, and baking powder. It also has cosmetic uses as a deodorant and as an aftershave treatment.
Potassium alum crystallizes in regular
octahedrawith flattened corners, and is very soluble in water. The solution reddens litmusand is an astringent. When heated to nearly a red heat it gives a porous, friable mass which is known as "burnt alum." It fuses at 92 °C in its own water of crystallization. "Neutral alum" is obtained by the addition of as much sodium carbonateto a solution of alum as will begin to cause the separation of alumina. Alum finds application as a mordant, in the preparation of lakes for sizing hand-made paper and in the clarifying of turbid liquids.
Mineral form and occurrence
Potassium alum is a naturally occurring sulfate
mineralwhich typically occurs as encrustations on rocks in areas of weatheringand oxidationof sulfideminerals and potassium-bearing minerals. Aluniteis an associate and likely potassium and aluminium source. [http://webmineral.com/data/Potassium-alum.shtml Potassium Alum: Mineral Data] [http://www.mindat.org/show.php?id=3267 Mindat] It has been reported at Vesuvius, Italy, east of Springsure, Queensland, Alum Cave, Tennessee, and Alum Gulch, Arizonain the United Statesand the island of Cebu(Philippines) locally known as tawas. A related mineral is " kalinite", a fibrous mineral with formula KAl(SO4)2·11(H2O). [http://webmineral.com/data/Kalinite.shtml Webmineral]
Potassium alum is an
astringent/ stypticand antiseptic. For this reason, it can be used as a natural deodorantby inhibiting the growth of the bacteriaresponsible for body odor. Use of mineral salts in such a fashion does not prevent perspiration. Its astringent/ stypticproperties are often employed after shaving and to reduce bleeding in minor cuts and abrasions, nosebleeds, and hemorrhoids. It is frequently used topically and internally in traditional systems of medicine including Ayurveda, where it is called phitkari or saurashtri, and Traditional Chinese Medicine, where it is called ming fan. [http://tcm.health-info.org/Herbology.Materia.Medica/mingfan-properties.htm Uses of Alum in Traditional Chinese Medicine]
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