Sodium hydrosulfide (NaSH) is an inorganic chemical compound consisting of sodium cations (Na⁺) and hydrosulfide anions (HS⁻). It is the product of the half‑neutralization of hydrogen sulfide (H₂S) with sodium hydroxide (NaOH). The compound appears as an off‑white, deliquescent solid that releases the characteristic odor of hydrogen sulfide when exposed to moisture.
Chemical data
- Formula: NaSH
- Molar mass: 56.063 g mol⁻¹
- Density: 1.79 g cm⁻³ (solid)
- Melting point: 350 °C (anhydrous); hydrates melt at 55 °C (dihydrate) and 22 °C (trihydrate)
- Solubility: 50 g L⁻¹ in water at 22 °C; also soluble in ethanol and diethyl ether
Structure and physical properties
Crystalline NaSH adopts several polymorphic forms. Above 360 K the structure is analogous to NaCl, in which the HS⁻ anion behaves as a spherical entity due to rapid rotation. Below this temperature a rhombohedral phase forms, and at temperatures under 114 K a monoclinic modification appears. The compound exists as anhydrous NaSH and as two hydrated forms, NaSH·2H₂O and NaSH·3H₂O, all of which are colourless solids.
Preparation
Laboratory synthesis commonly involves reacting sodium ethoxide (NaOEt) with hydrogen sulfide:
$$ \text{NaOEt} + \text{H}_2\text{S} ;\longrightarrow; \text{NaSH} + \text{EtOH} $$
An alternative industrial route is the direct reaction of metallic sodium with hydrogen sulfide gas.
Industrial applications
Sodium hydrosulfide is produced on a scale of thousands of tonnes per year. Its principal uses include:
- Pulp and paper industry: As a source of sulfide in the kraft process for cellulose pulping.
- Copper mining: Serves as a flotation agent to activate oxide mineral species during froth flotation.
- Leather processing: Employed for de‑hairing hides (removal of hair from leather).
NaSH and sodium sulfide (Na₂S) are often interchangeable in these applications because both provide reactive sulfide species.
Hazards and safety
- Reactivity: Reacts with acids to liberate hydrogen sulfide (H₂S), a toxic and flammable gas.
- GHS classification: Flammable solid, corrosive, toxic, and environmentally hazardous.
- NFPA 704 rating: Health 3, Flammability 2, Reactivity 1.
- Flash point: Approximately 90 °C.
Appropriate personal protective equipment, ventilation, and handling procedures are required to mitigate the risks of inhalation, skin contact, and accidental release of H₂S.
References
- Wikipedia contributors. “Sodium hydrosulfide.” Wikipedia, The Free Encyclopedia. Retrieved from https://en.wikipedia.org/wiki/Sodium_hydrosulfide.
- Haarmann, F.; Jacobs, H.; Roessler, E.; Senker, J. “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 (2002).
- Eibeck, R.; et al. “Phase transitions in NaHS.” Inorganic Chemistry (details omitted for brevity).