Sodium sulfide

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Sodium sulfide
Identifiers
CAS number1313-82-2 YesY
1313-84-4 (pentahydrate)
1313-84-4 (nonahydrate)
PubChem237873
EC number215-211-5
UN number1385 (anhydrous)
1849 (hydrate)
ChEBICHEBI:76208
RTECS numberWE1905000
Jmol-3D imagesImage 1
Properties
Molecular formulaNa2S
Molar mass78.0452 g/mol (anhydrous)
240.18 g/mol (nonahydrate)
Appearancecolorless, hygroscopic solid
Odorrotten eggs
Density1.856 g/cm3 (anhydrous)
1.58 g/cm3 (pentahydrate)
1.43 g/cm3 (nonohydrate)
Melting point1176°C (anhydrous)
100°C (pentahydrate)
50°C (nonahydrate)
Solubility in water12.4 g/100 mL (0 °C)
18.6 g/100 mL (20 °C)
39 g/100 mL (50 °C)
Solubilityinsoluble in ether
slightly soluble in alcohol
Structure
Crystal structureAntifluorite (cubic), cF12
Space groupFm3m, No. 225
Coordination
geometry
Tetrahedral (Na+); cubic (S2–)
Hazards
MSDSICSC 1047
EU Index016-009-00-8
EU classificationCorrosive (C)
Dangerous for the environment (N)
R-phrasesR31, R34, R50
S-phrases(S1/2), S26, S45, S61
NFPA 704
NFPA 704.svg
1
3
1
Autoignition temperature>480 °C
Related compounds
Other anionsSodium oxide
Sodium selenide
Sodium telluride
Other cationsLithium sulfide
Potassium sulfide
Related compoundsSodium hydrosulfide
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references
 
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Sodium sulfide
Identifiers
CAS number1313-82-2 YesY
1313-84-4 (pentahydrate)
1313-84-4 (nonahydrate)
PubChem237873
EC number215-211-5
UN number1385 (anhydrous)
1849 (hydrate)
ChEBICHEBI:76208
RTECS numberWE1905000
Jmol-3D imagesImage 1
Properties
Molecular formulaNa2S
Molar mass78.0452 g/mol (anhydrous)
240.18 g/mol (nonahydrate)
Appearancecolorless, hygroscopic solid
Odorrotten eggs
Density1.856 g/cm3 (anhydrous)
1.58 g/cm3 (pentahydrate)
1.43 g/cm3 (nonohydrate)
Melting point1176°C (anhydrous)
100°C (pentahydrate)
50°C (nonahydrate)
Solubility in water12.4 g/100 mL (0 °C)
18.6 g/100 mL (20 °C)
39 g/100 mL (50 °C)
Solubilityinsoluble in ether
slightly soluble in alcohol
Structure
Crystal structureAntifluorite (cubic), cF12
Space groupFm3m, No. 225
Coordination
geometry
Tetrahedral (Na+); cubic (S2–)
Hazards
MSDSICSC 1047
EU Index016-009-00-8
EU classificationCorrosive (C)
Dangerous for the environment (N)
R-phrasesR31, R34, R50
S-phrases(S1/2), S26, S45, S61
NFPA 704
NFPA 704.svg
1
3
1
Autoignition temperature>480 °C
Related compounds
Other anionsSodium oxide
Sodium selenide
Sodium telluride
Other cationsLithium sulfide
Potassium sulfide
Related compoundsSodium hydrosulfide
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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 Na2xH2O, 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.

Structure[edit]

Na2S adopts the antifluorite structure,[1][2] which means that the Na+ centers occupy sites of the fluoride in the CaF2 framework, and the larger S2− occupy the sites for Ca2+. In solution, the salt, by definition, dissociates. The dianion S2− does not, however, exist in appreciable amounts in water. Sulfide is too strong a base to coexist with water.

Production[edit]

Industrially Na2S is produced by reduction of Na2SO4 with carbon, in the form of coal:[3]

Na2SO4 + 4 C → Na2S + 4 CO

In the laboratory, the anhydrous salt can be prepared by reduction of sulfur with sodium in anhydrous ammonia. Alternatively, sulfur can be reduced by sodium in dry THF with a catalytic amount of naphthalene:[4]

2 Na + S → Na2S

Reactions[edit]

The dissolution process can be described as follows:

Na2S + H2O → 2Na+ + HS + OH

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

2 Na2S + 3 O2 + 2 CO2 → 2 Na2CO3 + 2 SO2

Upon treatment with sulfur, polysulfides are formed:

2Na2S + S8 → 2 Na2S5

Uses[edit]

It is primarily used in pulp and paper industry in the kraft process . It is used in water treatment as an oxygen scavenger agent and also as a metals precipitant, in the photographic industry to protect developer solutions from oxidation, in textile industry as a bleaching, as a desulfurising and as a dechlorinating agent and in leather trade for the sulfitisation of tanning extracts. It is used in chemical manufacturing as a sulfonation and sulfomethylation agent. It is used in the production of rubber chemicals, sulfur dyes and other chemical compounds. It is used in other applications including ore flotation, oil recovery, food preservative, making dyes, and detergent.

Sodium sulfide is an active ingredient in some over-the-counter ingrown toenail relief products. [5]

Safety[edit]

Like sodium hydroxide, sodium sulfide is strongly alkaline and can cause skin burns. Acids react with it to rapidly produce hydrogen sulfide, which is a toxic and foul-smelling gas.

References[edit]

  1. ^ Zintl, E; Harder, A; Dauth, B. (1934). "Gitterstruktur der oxyde, sulfide, selenide und telluride des lithiums, natriums und kaliums". Z. Elektrochem. Angew. Phys. Chem. 40: 588–93. 
  2. ^ Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.
  3. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  4. ^ So, J.-H; Boudjouk, P; Hong, Harry H.; Weber, William P. (1992). "Hexamethyldisilathiane". Inorg. Synth. Inorganic Syntheses 29: 30. doi:10.1002/9780470132609.ch11. ISBN 978-0-470-13260-9. 
  5. ^ 68 F.R. 24347