Sodium aluminate

Sodium aluminate
Sodium aluminate
CAS number 1302-42-7 YesY
PubChem 14766
Jmol-3D images Image 1
Molecular formula NaAlO2
Molar mass 81.97 g/mol
Appearance white powder
Density 1.5 g/cm3
Melting point

1650 °C

Solubility in water soluble
Solubility in Alcohol soluble
Refractive index (nD) 1.58
 YesY aluminate (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Sodium aluminate is an important commercial inorganic chemical. It works as an effective source of aluminium hydroxide for many industrial and technical applications. Pure sodium aluminate (anhydrous) is a white crystalline solid having a formula variously given as NaAlO2, NaAl(OH)4 (hydrated),[1] Na2O·Al2O3, or Na2Al2O4. Commercial sodium aluminate is available as a solution or a solid.
Other related compounds, sometimes called sodium aluminate, prepared by reaction of Na2O and Al2O3 are Na5AlO4 which contains discrete AlO45− anions, Na7Al3O8 and Na17Al5O16 which contain complex polymeric anions, and NaAl11O17, once mistakenly believed to be β-alumina, a phase of aluminium oxide.[2][3]



Anhydrous sodium aluminate, NaAlO2, contains a three dimensional framework of corner linked AlO4 tetrahedra. The hydrated form NaAlO2·5/4H2O has layers of AlO4 tetrahedra joined into rings and the layers are held together by sodium ions and water molecules that hydrogen bond to O atoms in the AlO4 tetrahedra.[4]


Sodium aluminate is manufactured by the dissolution of- aluminium hydroxide in a caustic soda (NaOH) solution. Aluminium hydroxide (gibbsite) can be dissolved in 20–25% aqueous NaOH solution at a temperature near the boiling point. The use of more concentrated NaOH solutions leads to a semi-solid product. The process must be carried out in steam-heated vessels of nickel or steel, and the aluminium hydroxide should be boiled with approximately 50% aqueous caustic soda until a pulp forms. The final mixture has to be poured into a tank and cooled; a solid mass containing about 70% NaAlO2 then forms. After being crushed, this product is dehydrated in a rotary oven heated either directly or indirectly by burning hydrogen. The resulting product contains 90% NaAlO2 and 1% water, together with 1% free NaOH.

Reaction of aluminium metal and alkali

Sodium aluminate is also formed by the action of sodium hydroxide on elemental aluminium. The reaction is highly exothermic once established and is accompanied by the rapid evolution of hydrogen gas. The reaction is sometimes written as:

2 Al + 2 NaOH + 2 H2O → 2 NaAlO2 + 3 H2

however the species produced in solution is likely to contain the [Al(OH)4] ion or perhaps the [Al(H2O)2(OH)4].[5]

This reaction has been proposed as a potential source of fuel for hydrogen powered cars.


In water treatment it is used as an adjunct to water softening systems, as a coagulant aid to improve flocculation, and for removing dissolved silica and phosphates.

In construction technology, sodium aluminate is employed to accelerate the solidification of concrete, mainly when working during frost.

Sodium aluminate is also used in the paper industry, for fire brick production, alumina production and so forth.

Sodium aluminate solutions are intermediates in the production of zeolites.[6]


  1. ^ "Aluminium". 
  2. ^ Identification and characterisation of three novel compounds in the sodium–aluminium–oxygen system, Marten G. Barker, Paul G. Gadd and Michael J. Begley, J. Chem. Soc., Dalton Trans., 1984, 1139–1146, doi:10.1039/DT9840001139
  3. ^ Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier ISBN 0-12-352651-5
  4. ^ The Crystal Structure of Hydrated Sodium Aluminate, NaAlO2·5/4H2O, and Its Dehydration Product, James A. Kaduk, Shiyou Pei, Journal of Solid State Chemistry, 115, 1, 1995, 126–139, doi:10.1006/jssc.1995.1111
  5. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Oxford: Butterworth-Heinemann. ISBN 0080379419. 
  6. ^ Alan Dyer, (1994), Encyclopedia of Inorganic Chemistry, R. Bruce King (ed.), John Wiley & Sons, ISBN 0-471-93620-0

See also

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • sodium aluminate — noun : a crystalline compound NaAlO2 used chiefly in water purification, in making synthetic zeolites, and in sizing paper …   Useful english dictionary

  • Aluminate De Sodium — Général Nom IUPAC Aluminate de sodium No CAS …   Wikipédia en Français

  • Aluminate de sodium — Général Nom IUPAC Aluminate de sodium No CAS …   Wikipédia en Français

  • Sodium hydroxide — Sodium hydroxide …   Wikipedia

  • Sodium chloroaluminate — IUPAC name Sodium chloroaluminate Other names Natriu …   Wikipedia

  • Aluminate — An aluminate is a compound containing aluminium and oxygen with more electropositive elements. Usually aluminate refers to AlO2−. Examples include sodium aluminate and potassium aluminate. Aluminate can also refer to the polyatomic ion… …   Wikipedia

  • Sodium silicoaluminate — Sodium aluminosilicate, also referred to as sodium silicoaluminate, is a chemical with the formula AlNa12SiO5 and CAS 1344 00 9. It is an aluminosilicate compound with sodium cations, taking the form of a white crystalline solid.In minerals, as a …   Wikipedia

  • Sodium — Néon ← Sodium → Magnésium Li …   Wikipédia en Français

  • Sodium (nutriment) — Sodium Sodium Néon ← …   Wikipédia en Français

  • Tricalcium aluminate — (3CaO.Al2O3) is the most basic of the calcium aluminates. It does not occur in nature, but is an important mineral phase in Portland cement.PropertiesPure tricalcium aluminate is formed when the appropriate proportions of finely divided calcium… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.