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1. Absorption method:
Absorb hydrogen sulfide gas with alkali sulfide solution (or caustic soda solution). Because hydrogen sulfide gas is toxic, the absorption reaction should be carried out under negative pressure. In order to prevent the high pollution of the air by hydrogen sulfide in the exhaust gas, several absorbers are operated in series in the production, and the hydrogen sulfide content is reduced to a lower level after repeated absorption. The absorption liquid is concentrated to obtain sodium hydrosulfide. Its chemical formula:
H2S+NaOH→NaHS+H2O
H2S+Na2S→2NaHS

2. Sodium alkoxide reacts with dry hydrogen sulfide to prepare sodium hydrosulfide:
In a 150mL flask with a branch pipe, add 20mL of freshly distilled absolute ethanol and 2g of metal sodium pieces with a smooth surface and no oxide layer, install a reflux condenser and a drying pipe on the flask, and seal the branch pipe first. When the sodium alkoxide is precipitated, add about 40 ml of absolute ethanol in batches until the sodium alkoxide is completely dissolved.
Insert a glass tube straight into the bottom of the solution through the branch pipe, and pass dry hydrogen sulfide gas (note that no air can enter the flask in the sealed branch pipe). Saturate the solution. The solution was suction filtered to remove the precipitate. The filtrate was stored in a dry conical flask, and 50 mL of absolute ether was added, and a large amount of NaHS white precipitate was precipitated immediately. A total of about 110 mL of ether is required. The precipitate was quickly filtered off, washed 2-3 times with absolute ether, blotted dry, and placed in a vacuum desiccator. The purity of the product can reach analytical purity. If higher purity NaHS is needed, it can be dissolved in ethanol and recrystallized with ether.

3.Sodium hydrosulfide liquid:
Dissolve sodium sulfide nonahydrate in freshly steamed stuffing water, and then dilute to 13% Na2S (W/V) solution. 14 g of sodium bicarbonate was added to the above solution (100 mL) with stirring and below 20°C, immediately dissolving and exothermic. Thereafter 100 ml of methanol were added with stirring and below 20°C. At this point the exotherm was again exothermic and almost all of the crystalline sodium carbonate precipitated out immediately. After 0 minutes, the mixture was filtered with suction and the residue was washed with methanol (50 mL) in portions. The filtrate contained not less than 9 g of sodium hydrosulfide and not more than 0.6 percent of sodium carbonate. The concentrations of the two are about 3.5 grams and 0.2 grams per 100 ml of solution, respectively.

We usually prepare it by absorbing hydrogen sulfide with sodium hydroxide solution. When the content (mass fraction of sodium hydrosulfide) is 70%, it is a dihydrate and is in the form of flakes; if the content is lower, it is a liquid product, it is three Hydrate.