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Sodium sulfide

Sodium sulfide
Sodium sulfide.jpg
Fluorite-unit-cell-3D-ionic.png
Names
Other names
Disodium sulfide
Identifiers
1313-82-2 YesY
1313-84-4 (pentahydrate) N
1313-84-4 (nonahydrate) N
3D model (Jmol) Interactive image
ChEBI CHEBI:76208 N
ChemSpider 14120 N
ECHA InfoCard 100.013.829
EC Number 215-211-5
PubChem 237873
RTECS number WE1905000
UN number 1385 (anhydrous)
1849 (hydrate)
Properties
Na2S
Molar mass 78.0452 g/mol (anhydrous)
240.18 g/mol (nonahydrate)
Appearance colorless, hygroscopic solid
Odor rotten eggs
Density 1.856 g/cm3 (anhydrous)
1.58 g/cm3 (pentahydrate)
1.43 g/cm3 (nonohydrate)
Melting point 1,176 °C (2,149 °F; 1,449 K) (anhydrous)
100 °C (pentahydrate)
50 °C (nonahydrate)
12.4 g/100 mL (0 °C)
18.6 g/100 mL (20 °C)
39 g/100 mL (50 °C)
Solubility insoluble in ether
slightly soluble in alcohol
−39.0·10−6 cm3/mol
Structure
Antifluorite (cubic), cF12
Fm3m, No. 225
Tetrahedral (Na+); cubic (S2−)
Hazards
Safety data sheet ICSC 1047
Corrosive (C)
Dangerous for the environment (N)
R-phrases R31, R34, R50
S-phrases (S1/2), S26, S45, S61
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
> 480 °C (896 °F; 753 K)
Related compounds
Other anions
Sodium oxide
Sodium selenide
Sodium telluride
Other cations
Lithium sulfide
Potassium sulfide
Related compounds
 Sodium hydrosulfide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YesYN ?)
Infobox references

Sodium sulfide is the chemical compound with the formula Na2S, or more commonly its hydrate Na2S·9H2O. Both are colorless water-soluble salts that give strongly alkaline solutions. When exposed to moist air, Na2S and its hydrates emit hydrogen sulfide, which smells like rotten eggs. Some commercial samples are specified as Na2S·xH2O, where a weight percentage of Na2S is specified. Commonly available grades have around 60% Na2S by weight, which means that x is around 3. Such technical grades of sodium sulfide have a yellow appearance owing to the presence of polysulfides. These grades of sodium sulfide are marketed as 'sodium sulfide flakes'. Although the solid is yellow, solutions of it are colorless.

Na2S adopts the antifluorite structure, which means that the Na+ centers occupy sites of the fluoride in the CaF2 framework, and the larger S2− occupy the sites for Ca2+.

Industrially Na2S is produced by carbothermic reduction of sodium sulfate often using coal:

In the laboratory, the salt can be prepared by reduction of sulfur with sodium in anhydrous ammonia or by sodium in dry THF with a catalytic amount of naphthalene (forming sodium naphthalenide):

The dissolution process can be described as follows:

Sodium sulfide can oxidize when heated to sodium carbonate and sulfur dioxide:

Oxidation with hydrogen peroxide gives sodium sulfate:

Upon treatment with sulfur, polysulfides are formed:

Sodium sulfide is primarily used in pulp and paper industry in the Kraft process.


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