Sodium hydrosulfide

Sodium hydrosulfide
IUPAC name Sodium hydrosulfide
Other names Sodium bisulfide Sodium sulfhydrate Sodium hydrogen sulfide
Identifiers
CAS number	16721-80-5 Y,  207683-19-0 (hydrate)
PubChem	28015
ChemSpider	26058 Y
UNII	FWU2KQ177W Y
EC number	240-778-0
RTECS number	WE1900000
Jmol-3D images	Image 1
SMILES [Na+].[SH-]
InChI InChI=1S/Na.H2S/h;1H2/q+1;/p-1 Y Key: HYHCSLBZRBJJCH-UHFFFAOYSA-M Y InChI=1/Na.H2S/h;1H2/q+1;/p-1 Key: HYHCSLBZRBJJCH-REWHXWOFAV
Properties
Molecular formula	NaHS
Molar mass	56.063 g/mol
Appearance	off-white solid, deliquescent
Density	1.79 g/cm3
Melting point	52–54 ºC (hydrate) 350 ºC (anhydrous)
Hazards
MSDS	TDC MSDS
EU Index	Toxic
R-phrases	R17 R23 R24 R25
Main hazards	Flammable solid, stench, releases hydrogen sulfide
NFPA 704	2 3 0
Flash point	90 ºC
Related compounds
Other anions	Sodium hydroxide Sodium amide
Other cations	Ammonium hydrosulfide
Related compounds	Sodium sulfide
Y hydrosulfide (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Sodium hydrosulfide is the chemical compound with the formula NaHS. This compound is the product of the half neutralization of hydrogen sulfide with sodium hydroxide. NaHS is a useful reagent for the synthesis of organic and inorganic sulfur compounds. It is a colorless solid that typically smells like H₂S due 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.

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 due 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.

Preparation

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

NaOMe + H₂S → NaHS + MeOH

Industrially, NaOH is employed as the base. The quality of the NaHS can be assayed by iodometric titration, exploiting the ability of HS^– to reduce I₂.

Applications

Thousands of tons of NaHS are produced annually. Its main uses are in 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: 1269–1276. doi:10.1063/1.1483860. 
2. ^ Eibeck, R. I.; Zingaro, Ralph A.; McGlothlin, Raymond E. (1963). "Sodium Hydrogen Sulfide". Inorg. Synth. 7: 128–31. doi:10.1002/9780470132388.ch35