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]
InChI Key	ZPXDOGRYMSWBBM-UHFFFAOYSA-N [6]

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

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

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]

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].

References
1. Aluminum Sulfide (2:3) – Chemspider.com
2. Aluminum Sulfide – Americanelements.com
3. Synthesis and Crystal Structure of a Novel Hexagonal Modification of Al₂S₃ with Five-coordinated Aluminum – Onlinelibrary.wiley.com
4. High-pressure Spinel Type Al₂S₃ and MnAl₂S₄ – Adsabs.harvard.edu
5. Aluminum Sulfide React with Water – Chemiday.com
6. ZPXDOGRYMSWBBM-UHFFFAOYSA-N – Pubchem.ncbi.nlm.nih.gov
7. Preparation of Aluminum Sulfide – Prepchem.com
8. Aluminum Sulfide React with Hydrogen – Chemiday.com
9. Aluminum Sulfide [Al₂S₃] – Chembk.com
10. What Are the Uses of Aluminum Sulfide? – Reference.com
11. Aluminum Sulfide – Chemicalbook.com
12. Safety Data Sheet Aluminum Sulfide – Ltschem.com