Aluminium sulfide: Properties, Preparation And Uses

Aluminium sulfide is a chemical compound with the formula Al₂S₃. This colorless species has an interesting structural chemistry, existing in several forms. The material is sensitive to moisture, hydrolyzing to hydrated aluminum oxides/hydroxides. This can begin when the sulfide is exposed to the atmosphere.


Chemical FormulaAl2S3
Molecular WeightApproximately 150.16 g/mol
AppearanceWhite or gray solid
Density2.02 g/cm³
Melting Point1,100°C
Boiling PointDecomposes before boiling
SolubilityInsoluble in water, soluble in acids
StabilityReacts with water to produce hydrogen sulfide; reacts with acids to form hydrogen sulfide gas
Crystal StructureHexagonal
Electrical ConductivityInsulator in its solid state, can conduct electricity when molten or in solution

Preparation of Aluminium sulfide

Aluminum sulfide (Al2S3) can be prepared through the reaction between aluminum metal and sulfur. Here’s a general outline of the preparation:

Direct Combination of Aluminum and Sulfur

  • Start with aluminum metal and sulfur powder or flakes.
  • Place the aluminum and sulfur in a reaction vessel.
  • Heat the mixture to a sufficiently high temperature, typically above the melting point of sulfur (around 115°C).
  • The aluminum reacts with the sulfur to form aluminum sulfide according to the following reaction: 2Al+3S→Al2S32Al+3S→Al2​S3​

Purification and Isolation

  • Allow the reaction mixture to cool after the reaction is complete.
  • The aluminum sulfide product can be isolated by carefully separating it from any unreacted aluminum or excess sulfur.
  • Purify the aluminum sulfide product if necessary through techniques such as filtration or recrystallization.


  • Confirm the identity and purity of the synthesized aluminum sulfide product using analytical techniques such as X-ray diffraction (XRD), infrared spectroscopy (IR), or chemical analysis.

Safety Considerations

  • Handling sulfur and aluminum metal should be done with care, as both can pose hazards.
  • Perform the reaction in a well-ventilated area or under a fume hood to prevent inhalation of sulfur dioxide gas, which can be produced as a byproduct.
  • Wear appropriate personal protective equipment, such as gloves and goggles, when handling chemicals and conducting reactions.

Uses of aluminum sulfide (Al2S3)

  • Utilized for removing phosphates and heavy metals from wastewater in water treatment processes.
  • It serves as a precursor or catalyst in the synthesis of sulfur-containing compounds in organic chemistry.
  • It is incorporated into semiconductor materials and devices, contributing to advancements in electronics technology.
  • It is used in certain pyrotechnic compositions, particularly for producing dense white smoke in smoke grenades and signaling devices.
  • It functions as a fumigant for pest control in stored grains and agricultural products, releasing toxic hydrogen sulfide gas to exterminate pests in enclosed spaces.