|Appearance||Dark red, slightly viscous liquid or yellow crystalline powder|
|Density||1.268 g/cm3 at 15.5 °C|
|Melting point||275 °C (527 °F; 548 K)|
|Solubility in water||Soluble in water|
|Main hazards||Stable at room temperature, but can be explosive when heated. Reactions with acids or oxidative agents will create gaseous byproducts that would be hazardous if inhaled.|
|Autoignition temperature||Not applicable|
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
Sodium tetrasulfide is an inorganic compound with the formula Na2S4. It is a yellow-orange solid that dissolved with hydrolysis in water. They are precursors to some specialty polymers and intermediates in prototypes of the sodium-sulfur battery.
Synthesis and structure
It is produced through the reaction between elemental sulfur and sodium hydrosulfide in alcoholic solution:
- 2NaSH + 4 S → Na2S4 + H2S
The polysulfide anions adopt zig-zag chains of sulfur atoms. The S-S distances are about 2.05 Å and the S-S-S-S dihedral angles are around 90°.
Reactions and applications
In solutions, sodium tetrasulfide exists in equilibrium with other polysulfide ions, such that additional sulfur converts the dianion to still longer chains. Upon treatment with acid, it is converted to hydrogen sulfide and elemental sulfur.
- Na2S4 + C2H4Cl2 → 1/n (C2H4)Sx]n + 2 NaCl
These materials, which have the approximate formula (C2H4)Sx]n (x ~ 4), are highly resistant to degradation by solvents and acids.
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- Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 365.
- D. R. Brush. "Sodium Sulfides". Kirk-Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.1915040902211908.a01.
- R. Tegman "The crystal structure of sodium tetrasulphide, Na2S4" Acta Cryst. (1973). B29, 1463-1469 doi:10.1107/S0567740873004735
- Sulfides, Polysulfides, and Sulfanes" in Ullmann's Encyclopedia of Industrial Chemistry Ludwig Lange and Wolfgang Triebel, 2000, Wiley-VCH, Weinheim. doi:10.1002/14356007.a25_443