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Aluminum Sulfide

Aluminum sulfide, also called dialuminium trisulfide, is an ionic compound of aluminum and sulfur represented by the chemical formula Al2S3 [1, 2]. It exists in different crystalline forms and hydrolyzes to aluminum hydroxide/oxide [3, 4].

Aluminum Sulfide Identification

CAS Number 1302-81-4 [1, 2]
PubChem CID 16684788 [6]
ChemSpider ID 140154 [1]
EC Number 215-109-0 [1, 2]

Aluminum Sulfide Formula

How is Aluminum Sulfide Prepared

Its synthesis through direct heating of aluminum and sulfur can be represented by the following equation [7]:

2Al + 3S → Al2S3

However, the reaction is highly exothermic, and it is not desirable to heat the entire mixture [7]. Also, sulfur is a volatile reactant that melts away before the reaction takes place [7]. Therefore, lead sulfide is often used for the preparation of Al2S3 [7]:

2Al + 3PbS → Al2S3 + 3Pb

Aluminum Sulfide

Reactions with Other Compounds

Aluminum Sulfide and Water

When aluminum sulfide is exposed to moisture in the atmosphere, it undergoes hydrolysis reaction to form aluminum hydroxide and hydrogen sulfide [5].

Al2S3 + 6H2O → 2Al(OH)3 + 3H2S

Aluminum Sulfide and Hydrochloric Acid

Aluminum sulfide upon reacting with hydrochloric acid forms hydrogen sulfide and aluminum chloride, as shown below [8]:

Al2S3 + 6HCl → 2AlCl3 + 3H2S

Aluminum Sulfide Lewis Structure

Properties and Characteristics of Aluminum Sulfide

General Properties

Molar Mass/Molecular Weight 150.158 g/mol [1]

Physical Properties

Color and Appearance Gray powder or granules [2]
Melting Point 1,100 °C, 2,012 °F [2]
Boiling Point 1,500 °C, 2,732 °F [2]
Density 2.32 g cm-3 [2]
State of matter at room temperature (solid/liquid/gas) Solid [2]
Solubility Insoluble in (CH3)2CO (acetone) [9]
Solubility in Water Reacts and decomposes in H2O [9]
Heat Capacity (C)  105.1 J/mol K
Standard Molar Enthalpy -724 kJ/mol [9]
Standard Molar Entropy 116.9 J/mol K

Atomic Properties

Crystal Structure Trigonal, tetragonal, hexagonal [3, 4]

Aluminum Sulfide Crystal Structure

What is It Used for

  • Producing organic compounds like ethanethiol and chemicals required for tanning and making paper [10]
  • Manufacturing cathodes used in lithium-sulfur solid-state batteries [11]
  • Preparing hydrogen sulfide that has several industrial uses [11]

Is Aluminum Sulfide Toxic

Exposure to aluminum sulfide can cause skin and severe eye irritation [12]. Inhalation of dust, vapor, or fumes can cause difficulty in breathing [12].


  1. Aluminum Sulfide (2:3) –
  2. Aluminum Sulfide –
  3. Synthesis and Crystal Structure of a Novel Hexagonal Modification of Al2S3 with Five-coordinated Aluminum –
  4. High-pressure Spinel Type Al2S3 and
  5. Aluminum Sulfide React with Water –
  7. Preparation of Aluminum Sulfide –
  8. Aluminum Sulfide React with
  9. Aluminum Sulfide [Al2S3] –
  10. What Are the Uses of Aluminum Sulfide? –
  11. Aluminum Sulfide –
  12. Safety Data Sheet Aluminum Sulfide –

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