Sodium sulfide
Antifluorite ( cubic)
- Sodium sulphide
- Disodium
- Sulfigran
- Sodium monosulfide
Colorless and odorless, hygroscopic solid
Fixed
1180 ° C
Well in water (188 g · l-1 at 20 ° C)
Risk
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Sodium sulfide, Na2S is a salt of hydrogen sulphide H2S, a very weak acid.
Production and representation
Sulfur-containing compounds (e.g., sodium sulfate ) can be reduced by annealing with charcoal powder and sodium carbonate to form sodium sulfide. It is also produced when the introduction of hydrogen sulphide in sodium hydroxide solution. In a desiccator over sulfuric acid or phosphoric acid, the water content to 4 percent can be reduced. The remaining amount of water can be removed only by heating at 700 ° C in hydrogen.
In the laboratory, the anhydrous salt can be prepared in anhydrous ammonia by the reduction of sulfur with sodium.
Properties
Sodium sulfide is in the pure state is a colorless crystalline solid, which smells like rotten eggs and is present as nonahydrate Na2S · 9 H2O. The anhydrous variant is odorless. In case of contact with acid ( also carbon dioxide CO2 in the breath ) of toxic and flammable hydrogen sulfide ( Geruch! ) is released. Finely divided, crystal, anhydrous, sodium sulfide may ignite spontaneously in air, it reacts violently with oxidants such as potassium permanganate or potassium dichromate. It is readily soluble in water, the solution is strongly alkaline and is very corrosive. The hydrates of sodium sulfide are not flammable, but lose on heating the bound water. For longer storage, the substance stained yellowish by slow reaction with water.
Use
Sodium sulfide, among others. Depilatory in tanning as used in the mining industry for ore flotation in the organic chemistry as the reducing agent in the waste water treatment for the precipitation of heavy metals, as well as for the preparation of sulfur dyes Furthermore, it is for the dyeing of glass for the removal of NOx ( nitrogen oxides ) from exhaust gases and for pulping. In black / white photography and lithography, it is used in the darkroom to in sulfur ( sepia toning ).