Sodium aluminium sulfate

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"Sodium alum" redirects here. For the mineral form, see Alum-(Na).
Sodium aluminium sulfate dodecahydrate
IUPAC name Aluminium sodium bis(sulfate) — water (1:12)
Other names Sodium alum
Soda alum
E521
Identifiers
InChI InChI=1/Al.Na.2H2O4S.12H2O/c;;2*1-5(2,3)4;;;;;;;;;;;;/h;;2*(H2,1,​2,3,4);12*1H2/q+3;+1;;;;;;;;;;;;;;/p-4
InChIKey ZEMWIYASLJTEHQ-XBHQNQODAL
Standard InChI InChI=1S/Al.Na.2H2O4S.12H2O/c;;2*1-5(2,3)4;;;;;;;;;;;;/h;;2*(H2,1​,2,3,4);12*1H2/q+3;+1;;;;;;;;;;;;;;/p-4
Standard InChIKey ZEMWIYASLJTEHQ-UHFFFAOYSA-J
CAS number [7784-28-3]
EC number 233-277-3
ChemSpider 22972
Properties[1]
Chemical formula NaAl(SO4)2·12H2O
Molar mass 458.28 g/mol
Appearance while crystalline powder
Density 1.6754 (20 °C)
Melting point

61 °C

Solubility in water 208 g/100 ml (15 °C)
Refractive index (nD) 1.4388
Structure[2]
Crystal structure Cubic, cP96
Space group Pa3, No. 205
Lattice constant a = 1221.4 pm
Coordination geometry Octahedral (Na+)
Octahedral (Al3+)
Hazards
EU index number not listed
Flash point non-flammable
Related compounds
Other cations Ammonium aluminium sulfate
Potassium aluminium sulfate
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Sodium aluminium sulfate (anhydrous)
IUPAC name Aluminium sodium bis(sulfate)
Identifiers
InChI InChI=1/Al.Na.2H2O4S/c;;2*1-5(2,3)4/h;;2*(H2,1,2,3,4)/q+3;+1;;/p-​4
InChIKey GJPYYNMJTJNYTO-XBHQNQODAI
Standard InChI InChI=1S/Al.Na.2H2O4S/c;;2*1-5(2,3)4/h;;2*(H2,1,2,3,4)/q+3;+1;;/p​-4
Standard InChIKey GJPYYNMJTJNYTO-UHFFFAOYSA-J
CAS number [10102-71-3]
EC number 233-277-3
ChemSpider 23313
Properties[1]
Chemical formula NaAl(SO4)2
Molar mass 242.10 g/mol
Appearance while crystalline powder
Solubility in water 110 g/100 ml (15 °C)
Hazards
EU index number not listed
Flash point non-flammable
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

Sodium aluminium sulfate, NaAl(SO4)2·12H2O or Na2SO4·Al2(SO4)3·24H2O, also known as soda alum or sodium alum, is a form of alum used in the acidity regulator of food (E521) as well as in the manufacture of baking powder. It is also a common mordant for the preparation of hematoxylin solutions for staining cell nuclei in histopathology.

The classical cubic alum structure is the dodecahydrate, which is known in mineralogy as alum-(Na).[3][4] Two other rare mineral forms are known: mendozite (undecahydrate)[5] and tamarugite (hexahydrate).[6]

References

  1. ↑ 1.0 1.1 CRC Handbook of Chemistry and Physics, 62nd ed.; Weast, Robert C., Ed.; CRC Press: Boca Raton, FL, 1981; p B-146. ISBN 0-8493-0462-8.
  2. ↑ Cromer, D. T.; Kay, M. I.; Larson, A. C. Refinement of the alum structures. II. X-ray and neutron diffraction of NaAl(SO4)2·12H2O, γ-alum. Acta Crystallogr. 1967, 22 (2), 182–87. DOI: 10.1107/S0365110X67000313.
  3. ↑ Burke, Ernst A.J. Tidying up mineral names: an IMA-CNMNC scheme for suffixes, hyphens and diacritical marks. Mineralogical Record 2008, 39 (2), 131–35, <http://pubsites.uws.edu.au/ima-cnmnc/tidyingupnames.pdf>.
  4. ↑ Alum-(Na), <http://webmineral.com/data/Alum-%28Na%29.shtml> (accessed 28 November 2009), WebMineral.com. Alum-(Na), <http://www.mindat.org/show.php?id=3703> (accessed 28 November 2009), MinDat.org.
  5. ↑ Mendozite, <http://webmineral.com/data/Mendozite.shtml> (accessed 28 November 2009), WebMineral.com. Mendozite, <http://www.mindat.org/show.php?id=2643> (accessed 28 November 2009), MinDat.org.
  6. ↑ Tamarugite, <http://www.webmineral.com/data/Tamarugite.shtml> (accessed 28 November 2009), WebMineral.com. Tamarugite, <http://www.mindat.org/show.php?id=3878> (accessed 28 November 2009), MinDat.org.

External links

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