Aluminium sulfide

Aluminium sulfide

Names
IUPAC name Aluminium sulfide
Systematic IUPAC name Aluminium sulfide
Other names Aluminium sulphide
Identifiers
Jmol-3D images	Image
SMILES [Al+3].[Al+3].[S-2].[S-2].[S-2]
Properties
Chemical formula	Al2S3
Molar mass	150.158 g/mol
Appearance	Gray solid
Odor	Rotten-eggs
Density	2.02 g/cm3
Melting point	1,100 °C (2,010 °F; 1,370 K)
Boiling point	1,500 °C (2,730 °F; 1,770 K)
Solubility in water	Hydrolyses to release H2S
Solubility	Reacts with acids Insoluble in organic solvents
Thermochemistry
Std molar entropy (So298)	116.9 J/mol K
Std enthalpy of formation (ΔfHo298)	-724 kJ/mol
Hazards
Safety data sheet	LTS Research Laboratories, Inc.
Related compounds
Related compounds	Aluminium sulfate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Aluminium sulfide or aluminium sulphide is a gray chemical compound, that readily hydrolyzes in air to release hydrogen sulfide gas. It has the chemical formula Al₂S₃.

Properties

Chemical

Aluminium sulfide reacts with water to release hydrogen sulfide:

Al₂S₃ + 6 H₂O → 2 Al(OH)₃ + 3 H₂S

This reaction is a cheap and accessible way to obtain hydrogen sulfide.

Aluminium sulfide will react with alcohols at high temperature to give their respective thiols. such as: With methanol, it forms methanethiol and dimethyl sulfide, the yield being 40-45 % and 15% for each product, at 300 °C; reaction with ethanol gives ethanethiol at temperatures between 310-360 °C, with a 39% yield. At 310 °C it reacts with propanol to give propanethiol, with a 32.5 % yield. Reaction with ethers gives thioethers.

Aluminium sulfide will not react with aromatic hydrocarbons. It also tends to decompose slightly under vacuum.

Physical

Aluminium sulfide is a greyish solid, with a bad sulfide smell, especially in moist air. It reacts with water to release hydrogen sulfide, and is insoluble in most solvents. It melts at 1100 °C and sublimes at 1,500 °C. Aluminium sulfide has at least six crystalline forms, the more important ones being α, β, γ and δ.

Availability

Aluminium sulfide is sold by various chemical suppliers.

Preparation

Aluminium sulfide can be prepared through a thermite-like reaction between aluminium and sulfur powders.

2 Al + 3 S → Al₂S₃

The mixture is somewhat difficult to ignite and burns much slower than the classical thermite. The resulting sulfide results in a fused form and is very hard, requiring grinding. If it reaches temperatures greater than 1100 °C, it may melt its way through steel.

Another route involves the reaction of potassium thiocyanate with aluminium powder at temperatures over 600°C, in a 1:1 wight ratio. If the KSCN is present in excess, it will lower the yield.

4 Al + 5 KSCN = 2 AlN + Al₂S₃ + 2 K₂S + KCN + 4 C + N₂

Burning aluminium powder in carbon disulfide also produces aluminium sulfide. However the yield is not very good.

Projects

• Make hydrogen sulfide
• Make ethanethiol (ethyl mercaptane)
• Make aluminium metal, by reacting aluminium sulfide with alumina at high temperatures

Handling

Safety

Aluminium sulfide releases hydrogen sulfide vapors in moist air, which has an extremely unpleasant smell and is very toxic. Given that the latter is detectable in minute quantities, sealing the container is mandatory, otherwise you will stink your lab.

Storage

Aluminium sulfide must be stored in air tight sealed containers or ampoules, as it will hydrolyze in the presence of moisture to release hydrogen sulfide, an extremely toxic and unpleasant gas.

Disposal

Aluminium sulfide can be neutralized with hydrogen peroxide or bleach. This oxidizes the aluminium sulfide to aluminium sulfate.

References

Relevant Sciencemadness threads

• Does 2Al + 3S > Al2S3 Produce Gas?