Sodium tetrasulfide

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Sodium tetrasulfide
WikiNa2S4.png
Identifiers
CAS number 12034-39-8 YesY
EC number 234-805-5
Properties
Molecular formula Na2S4
Molar mass 174.24g/mol
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
Hazards
MSDS [1] [1]
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.
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazards (white): no codeNFPA 704 four-colored diamond
Autoignition temperature Not applicable
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Sodium tetrasulfide is an inorganic compound with the formula Na2S4. It is a yellow-orange solid that dissolved with hydrolysis in water.[2] They are precursors to some specialty polymers and intermediates in prototypes of the sodium-sulfur battery.

Synthesis and structure[edit]

It is produced through the reaction between elemental sulfur and sodium hydrosulfide in alcoholic solution:[3]

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°.[4]

Reactions and applications[edit]

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.

Usually as a mixture with other polysulfides, sodium tetrasulfide is used to produce the polymer called thiokol. The reaction involves alkylation with ethylene chloride:

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.[5]

References[edit]

  1. ^ "Safety Data Sheet, Sodium Tetrasulfide". Pfaltz & Bauer. 
  2. ^ Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 365.
  3. ^ D. R. Brush. "Sodium Sulfides". Kirk-Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.1915040902211908.a01. 
  4. ^ R. Tegman "The crystal structure of sodium tetrasulphide, Na2S4" Acta Cryst. (1973). B29, 1463-1469 doi:10.1107/S0567740873004735
  5. ^ 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