Sodium aluminate

Sodium aluminate

Names
Other names Sodium aluminium oxide, Sodium metaaluminate Aluminate, ((AlO2)1−), sodium
Identifiers
CAS Number	1302-42-7 Y
3D model (Jmol)	Interactive image
ECHA InfoCard	100.013.728
EC Number	215-100-1
PubChem CID	14766
InChI InChI=1S/Al.Na.2O/q-1;+1;; Key: IYJYQHRNMMNLRH-UHFFFAOYSA-N
SMILES O=[Al-]=O.[Na+]
Properties
Chemical formula	NaAlO2
Molar mass	81.97 g/mol
Appearance	white powder (sometimes light-yellowish) hygroscopic/ when dissovled in water a colloidal black solution is formed
Odor	odorless
Density	1.5 g/cm3
Melting point	1,650 °C (3,000 °F; 1,920 K)
Solubility in water	soluble
Solubility	soluble in alcohol
Refractive index (nD)	1.566
Structure
Crystal structure	orthorhombic
Thermochemistry
Specific heat capacity (C)	73.6 J/mol K
Std molar entropy (So298)	70.4 J/mol K
Std enthalpy of formation (ΔfHo298)	-1133.2 kJ/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
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), 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.

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.

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. The resulting product contains 90% NaAlO₂ and 1% water, together with 1% free NaOH.