Sodium sulfide

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Sodium sulfide
Sodium sulfide.jpg
Fluorite-unit-cell-3D-ionic.png
Identifiers
CAS number 1313-82-2 YesY
1313-84-4 (pentahydrate)
1313-84-4 (nonahydrate)
PubChem 237873
EC number 215-211-5
UN number 1385 (anhydrous)
1849 (hydrate)
ChEBI CHEBI:76208 N
RTECS number WE1905000
Jmol-3D images Image 1
Properties
Molecular formula 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 1176°C (anhydrous)
100°C (pentahydrate)
50°C (nonahydrate)
Solubility in water 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
Structure
Crystal structure Antifluorite (cubic), cF12
Space group Fm3m, No. 225
Coordination
geometry
Tetrahedral (Na+); cubic (S2–)
Hazards
MSDS ICSC 1047
EU Index 016-009-00-8
EU classification 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
Autoignition temperature >480 °C
Related compounds
Other anions Sodium oxide
Sodium selenide
Sodium telluride
Other cations Lithium sulfide
Potassium sulfide
Related compounds Sodium hydrosulfide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
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]

Sodium sulfide 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, and 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