What molecule am I?
Aluminum sulfide (Al2S3) is a salt of aluminum and sulfur. Even though it has been shown to be an ionic compound, some sources claim that it has covalent bonding. It is sensitive to water, releasing hydrogen sulfide, which gives it a characteristic “rotten egg” odor.
Al2S3 has been known since 1891, when US Patent 463,143 was awarded to Philip Albert Emanuel of Aiken, SC, for a rather convoluted process for making the compound and for the apparatus that he used. Emanuel began with alumina (Al2O3) extracted from kaolin ore or the associated aluminum sulfate [Al2(SO4)3]. In the case of the latter, he heated it with sulfur to form the oxide. He then he heated the Al2O3 with carbon disulfide (CS2) under pressure to form Al2S3 along with the gaseous byproducts carbon monoxide and sulfur dioxide.
A much more efficient method for producing Al2S3 is the direct heating of the two elements. An early instance of this process was reported in 1911 by Wilhelm Blitz at the Clausthal University of Technology (Clausthal–Zellerfeld, Germany), who combined powders of the two components and heated them using the thermite process.
In a 1951 report, Jean Flahaut at the National Center for Scientific Research (Paris) refined the process by heating the elements to 1150 °C in a vacuum, then slowly cooling the product to form crystals that proved to be the β polymorph of Al2S3.
More than six polymorphs of Al2S3 have been identified. The four most common are α, hexagonal, and the most stable at ambient temperature; β, also hexagonal; γ, trigonal; and δ, tetragonal.
Al2S3 has several uses, including synthesizing organic compounds such as ethanethiol1 and chemicals used in the tanning and paper industries, manufacturing cathodes used in lithium–sulfur solid-state batteries, and generating hydrogen sulfide.
1. CAS Reg. No. 75-08-1.
Aluminum sulfide hazard information
| Hazard class* | GHS code and hazard statement | |
|---|---|---|
| Substances and mixtures that, in contact with water, emit flammable gases, category 1 | H260—In contact with water, releases flammable gases that may ignite spontaneously |  |
| Skin corrosion/irritation, category 2 | H315—Causes skin irritation |  |
| Serious eye damage/eye irritation, category 2A | H319—Causes serious eye damage | |
| Specific target organ toxicity, single exposure, respiratory tract irritation, category 3 | H335—May cause respiratory irritation | |
*Globally Harmonized System (GHS) of Classification and Labeling of Chemicals. Explanation of pictograms.
Molecules from the Journals
MnBi21, or “bismuth, compound with manganese”, as SciFinder calls it, is a metastable intermetallic phase in the Mn–Bi system. It has properties similar to those of the related compound MnBi2. It first appeared in the chemical literature in 1985, when Roy W. Rice and William J. McDonough at the Naval Research Laboratory (Washington, DC) studied it and other inorganic molecules for intrinsic volume changes of self-propagating syntheses.
In 2019, Danna E. Freedman at Northwestern University (Evanston, IL) and collaborators there and at Argonne National Laboratory (IL) reported the synthesis of MnBi2 under pressure and determined why it does not survive at ambient pressure. They also found that it exhibits strong covalent interactions between manganese and bismuth and that it has promising magnetic properties.
Then, this past July, James M. Rondinelli at Northwestern, Alison B. Altman at Texas A&M University (College station), Freedman (now at MIT, Cambridge, MA), and colleagues at these institutions and at Argonne National Lab disclosed that MnBi2 is a permanent magnet. Because of the compound’s instability at ambient pressure, they used synchrotron X-ray magnetic circular dichroism to examine the magnetism of MnBi2 within a diamond anvil at 8.7 GPa pressure. Permanent magnetism was observed in the range 10 K through ambient temperature.
1,1-Diethoxyethane3 (aka acetaldehyde diethyl acetal or just “acetal”) is a diether with several uses, including flavoring alcoholic beverages, adding aroma to perfumes, and acting as a solvent and reactant in organic synthesis. But it is also under study for its behavior when it is emitted into the atmosphere.
In August, Balla Rajakumar and co-workers at the Indian Institute of Technology Madras reported the kinetics of the degradation of 1,1-diethoxyethane by hydroxyl radicals in the temperature range 0–90 °C. They found that the rate coefficient was inversely dependent on temperature within the studied range and that the main decomposition products were acetaldehyde and ethanol. The results suggested that 1,1-diethoxyethane emissions are short-lived in the atmosphere.
1. CAS Reg. No. 66104-02-7.
2. CAS Reg. No. 12010-50-3.
3. CAS Reg. 105-57-7.
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Aluminum sulfide
fast facts
| CAS Reg. No. | 1302-81-4 |
| SciFinder name | Aluminum sulfide (Al2S3) |
| Empirical formula | Al2S3 |
| Molar mass | 150.16 g/mol |
| Appearance | White to gray crystals, lumps, or powder |
| Melting point | 1100 °C |
| Water solubility | Decomposes |
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