Sodium Hydrosulfide Production via NaOH Absorption
Conventional NaOH Absorption Method
When NaHS sodium hydrosulfide concentration reaches 70%, it forms dihydrate flakes.
At lower concentrations, it exists as a liquid trihydrate.
Procedure:
A 1 L three-necked round-bottom flask is equipped with a stirrer and reflux condenser (connected to a CaCl₂ drying tube).
The flask is purged with dry nitrogen, then charged with 200 mL (3.4 mol) anhydrous ethanol.
12 g (0.522 mol) of clean sodium metal is added in small pieces under stirring and reflux until fully dissolved.
A gas inlet tube is inserted into the liquid, and dry H₂S (dried over P₂O₅) is bubbled at 5–10 bubbles/sec for 2 h under stirring.
After cooling, 750 mL anhydrous ether is added to precipitate NaHS sodium hydrosulfide completely.
Workup:
The mixture is quickly filtered (coarse frit) to prevent moisture absorption.
The solid is washed 3× with anhydrous ether, then dried in a vacuum desiccator (CaCl₂) for several hours.
Yield: 29.4 g of ≥98% pure NaHS.