Sodium hydrosulfide

Sodium hydrosulfide is the chemical compound with the formula NaHS. This compound is the product of the half-neutralization of hydrogen sulfide (H2S) with sodium hydroxide. NaHS is a useful reagent for the synthesis of organic and inorganic sulfur compounds, sometimes as a solid reagent, more often as an aqueous solution. Solid NaHS is colorless, and typically smells like H2S owing to hydrolysis by atmospheric moisture. In contrast with sodium sulfide (Na2S), which is insoluble in organic solvents, NaHS, being a 1:1 electrolyte, is more soluble. Alternatively, in place of NaHS, H2S can be treated with an organic amine to generate an ammonium salt. Solutions of HS− are sensitive to oxygen, converting mainly to polysulfides, indicated by the appearance of yellow.

Sodium hydrosulfide
Names
IUPAC name
Sodium hydrosulfide
Other names
Sodium bisulfide
Sodium sulfhydrate
Sodium hydrogen sulfide
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.037.056
EC Number
  • 240-778-0
RTECS number
  • WE1900000
UNII
Properties
NaSH
Molar mass 56.063 g/mol
Appearance off-white solid, deliquescent
Density 1.79 g/cm3
Melting point 350.1 °C (662.2 °F; 623.2 K) (anhydrous)
55 °C (dihydrate)
22 °C (trihydrate)
50 g/100 mL (22 °C)
Solubility soluble in alcohol, ether
Structure
rhombohedral
Hazards
Main hazards Flammable solid, stench, releases hydrogen sulfide
Safety data sheet TDC MSDS
R-phrases (outdated) R17 R23 R24 R25
NFPA 704 (fire diamond)
Flammability code 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g. diesel fuelHealth code 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasReactivity (yellow): no hazard codeSpecial hazards (white): no code
2
3
Flash point 90 °C (194 °F; 363 K)
Related compounds
Other anions
 Sodium hydroxide
Sodium amide
Other cations
 Ammonium hydrosulfide
Related compounds
 Sodium sulfide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Structure and properties

Crystalline NaHS undergoes two phase transitions. At temperatures above 360 K, NaHS adopts the NaCl structure, which implies that the HS− behaves as a spherical anion owing to its rapid rotation, leading to equal occupancy of eight equivalent positions. Below 360 K, a rhombohedral structure forms, and the HS− sweeps out a discoidal shape. Below 114 K, the structure becomes monoclinic. The analogous rubidium and potassium compounds behave similarly.[1]

NaHS has a relatively low melting point of 350 °C. In addition to the aforementioned anhydrous forms, it can be obtained as two different hydrates, NaHS·2H2O and NaHS·3H2O. These three species are all colorless and behave similarly, but not identically.It can be used to precipitate other metal hydroslfides,by treatment of aqueous solutions of their salts with sodium hydrosulfide.It is analogous to Sodium hydroxide,and is a strong base.

Preparation

The usual laboratory synthesis entails treatment of sodium methoxide (NaOMe) with hydrogen sulfide:[2]

NaOMe + H2S → NaHS + MeOH

The quality of the NaHS can be assayed by iodometric titration, exploiting the ability of HS− to reduce I2. A method for the preparation of anhydrous sodium hydrosulfide involves reaction of clean solid sodium metal with hydrogen sulfide gas in a water and oxygen free environment. [3]

Applications

Thousands of tons of NaHS are produced annually. Its main uses are in cloth and paper manufacture as a makeup chemical for sulfur used in the kraft process, as a flotation agent in copper mining where it is used to activate oxide mineral species, and in the leather industry for the removal of hair from hides.

References
  1. Haarmann, F.; Jacobs, H.; Roessler, E.; Senker, J. (2002). "Dynamics of anions and cations in hydrogensulfides of alkali metals (NaHS, KHS, RbHS): A proton nuclear magnetic resonance study". J. Chem. Phys. 117 (3): 1269–1276. doi:10.1063/1.1483860.
  2. Eibeck, R. I. (1963). Sodium Hydrogen Sulfide. Inorg. Synth. Inorganic Syntheses. 7. pp. 128–31. doi:10.1002/9780470132388.ch35. ISBN 978-0-470-13238-8.
  3. J. W. Pavlik, B. C. Noll, A. G. Oliver, C. E. Schulz, W. R. Scheidt, “Hydrosulfide (HS−) Coordination in Iron Porphyrinates”, Inorganic Chemistry, 2010, vol. 49(3), 1017-1026.
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