Aluminium sulfate

Aluminium sulfate
Aluminium sulphate hexadecahydrate
Names
IUPAC name
Aluminium sulfate
Other names
  • Aluminum sulfate
  • Aluminium sulphate
  • Cake alum
  • Filter alum
  • Papermaker's alum
  • Alunogenite
  • aluminium salt (3:2)
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.030.110 Edit this at Wikidata
EC Number
  • 233-135-0
E number E520 (acidity regulators, ...)
RTECS number
  • BD1700000
UNII
  • InChI=1S/2Al.3H2O4S/c;;3*1-5(2,3)4/h;;3*(H2,1,2,3,4)/q2*+3;;;/p-6 checkY
    Key: DIZPMCHEQGEION-UHFFFAOYSA-H checkY
  • InChI=1/2Al.3H2O4S/c;;3*1-5(2,3)4/h;;3*(H2,1,2,3,4)/q2*+3;;;/p-6
    Key: DIZPMCHEQGEION-CYFPFDDLAS
  • [Al+3].[Al+3].[O-]S(=O)(=O)[O-].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O
Properties
Al2(SO4)3
Molar mass 342.15 g/mol (anhydrous)
666.44 g/mol (octadecahydrate)
Appearance white crystalline solid
hygroscopic
Density 2.672 g/cm3 (anhydrous)
1.62 g/cm3 (octadecahydrate)
Melting point 770 °C (1,420 °F; 1,040 K) (decomposes, anhydrous)
86.5 °C (octadecahydrate)
31.2 g/100 mL (0 °C)
36.4 g/100 mL (20 °C)
89.0 g/100 mL (100 °C)
Solubility slightly soluble in alcohol, dilute mineral acids
Acidity (pKa) 3.3–3.6
−93.0×10−6 cm3/mol
1.47[1]
Structure
monoclinic (hydrate)
Thermochemistry
-3440 kJ/mol
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
0
0
NIOSH (US health exposure limits):
PEL (Permissible)
 none[2]
REL (Recommended)
 2 mg/m3[2]
IDLH (Immediate danger)
 N.D.[2]
Related compounds
Other cations
 Gallium sulfate
Magnesium sulfate
Related compounds
 See Alum
Supplementary data page
Aluminium sulfate (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Aluminium sulfate is a salt with the formula Al2(SO4)3. It is soluble in water and is mainly used as a coagulating agent (promoting particle collision by neutralizing charge) in the purification of drinking water[3][4] and wastewater treatment plants, and also in paper manufacturing.

The anhydrous form occurs naturally as a rare mineral millosevichite, found for example in volcanic environments and on burning coal-mining waste dumps. Aluminium sulfate is rarely, if ever, encountered as the anhydrous salt. It forms a number of different hydrates, of which the hexadecahydrate Al2(SO4)3·16H2O and octadecahydrate Al2(SO4)3·18H2O are the most common. The heptadecahydrate, whose formula can be written as [Al(H2O)6]2(SO4)3·5H2O, occurs naturally as the mineral alunogen.

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 XAl(SO
4)
2·12H
2O, where X is a monovalent cation such as potassium or ammonium.[5]

  1. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
  2. ^ a b c NIOSH Pocket Guide to Chemical Hazards. "#0024". National Institute for Occupational Safety and Health (NIOSH).
  3. ^ Global Health and Education Foundation (2007). "Conventional Coagulation-Flocculation-Sedimentation". Safe Drinking Water is Essential. National Academy of Sciences. Archived from the original on 2007-10-07. Retrieved 2007-12-01.
  4. ^ Kvech S, Edwards M (2002). "Solubility controls on aluminum in drinking water at relatively low and high pH". Water Research. 36 (17): 4356–4368. Bibcode:2002WatRe..36.4356K. doi:10.1016/S0043-1354(02)00137-9. PMID 12420940.
  5. ^ Austin, George T. (1984). Shreve's Chemical process industries (5th ed.). New York: McGraw-Hill. p. 357. ISBN 9780070571471. Archived from the original on 2014-01-03.