Sodium Aluminum Sulfate
Sodium aluminium sulfate, NaAl(SO4)2Â·12H2O or Na2SO4Â·Al2(SO4)3Â·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). Two other rare mineral forms are known: mendozite (undecahydrate) and tamarugite (hexahydrate).