Formula NaAl(SO4)2·12H2O Melting point 61 °C Appearance white crystalline powder | Molar mass 458.28 g/mol Density 1.68 g/cm³ | |
 | ||
Sodium aluminium sulfate is the inorganic compound with the chemical formula NaAl(SO4)2·12H2O (sometimes written Na2SO4·Al2(SO4)3·24H2O). Also known as soda alum or sodium alum, this white solid is used in the acidity regulator of food (E521) mainly in the manufacture of baking powder.
Production and use
It is produced by combining sodium sulfate and aluminium sulfate. An estimated 3000 ton/y are (2003) are produced. In the US, it is combined with sodium bicarbonate and monocalcium phosphate to give double acting baking powder used in domestic settings.
The classical cubic alum structure is the dodecahydrate, which is known in mineralogy as alum-(Na). Two other rare mineral forms are known: mendozite (undecahydrate) and tamarugite (hexahydrate).
It is also a common mordant for the preparation of hematoxylin solutions for staining cell nuclei in histopathology.