.It is decomposed into alumina and sulfur trioxide at 770 ℃. 

There are anhydrous and octadecyl hydrate. The anhydrous material is colorless orthorhombic crystal system. Soluble in water, the aqueous solution is acid, slightly soluble in ethanol. The solubility in water increases with the increase of temperature. Octadecyl hydrate (al2 · (SO4) 3 · 18H2O) is a colorless monoclinic crystal. Soluble in water, insoluble in ethanol. The aqueous solution is acidic due to hydrolysis. 

Relative density (water = 1): 2.71

Grams dissolved per 100 ml of water at different temperatures (℃):

chemical property

It is not easy to lose crystal water due to weathering. It is relatively stable. When heated, it will lose water. At high temperature, it will decompose into alumina and sulfur oxides. 

When heated to 770 ℃, it begins to decompose into alumina, sulfur trioxide, sulfur dioxide and water vapor.

The aqueous solution is acidic. Aluminum hydroxide is formed after hydrolysis. Long time boiling of aqueous solution can produce basic aluminum sulfate. Non toxic, dust can irritate eyes. 

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