Aluminum sulfide, also known as dialuminium trisulfide, is an ionic compound composed of aluminum and sulfur. It has the chemical formula Al2S3, and is a gray, solid. It is slightly soluble in water, and primarily soluble in acid solutions.
It reacts with water to form hydrogen sulfide gas. It has a bad smell and is usually stored in sealed containers with Dacron film.
Physical properties: It is a gray, solid with a density of 2.02 g/mL-1 and a melting point of 1100 degC. At this temperature it sublimes and decomposes into a mixture of aluminum oxides and aluminide.
Chemical properties: It is an irritant and can cause skin and eye irritation. It is a common ingredient in soaps, detergents and shampoos.
Structural chemistry: It exists in multiple crystalline forms, with more expanded framework than its less stable cousin Al2O3. When exposed to moisture in air, it hydrolyzes to aluminum oxides/hydroxides and then releases hydrogen sulfide (H2S).
Sulfur does not dissolve in water.
The oxidation number of oxygen in O2 is negative one half. The oxidation number of sulfide in S2 is positive two-halfs. Sulfur has six valence electrons, while aluminium has three valence electrons.