| Sodium sulfide | |
|---|---|
|
Other names
Disodium sulfide |
|
| Identifiers | |
| CAS number | 1313-82-2 , 1313-84-4 (pentahydrate) 1313-84-4 (nonahydrate) |
| PubChem | 237873 |
| EC number | 215-211-5 |
| UN number | 1385 (anhydrous) 1849 (hydrate) |
| RTECS number | WE1905000 |
| Properties | |
| Molecular formula | Na2S |
| Molar mass | 78.0452 g/mol (anhydrous) 240.18 g/mol (nonahydrate) |
| Appearance | colorless, hygroscopic solid |
| Density | 1.856 g/cm3 (anhydrous) 1.58 g/cm3 (pentahydrate) 1.43 g/cm3 (nonohydrate) |
| Melting point |
1176 °C (anhydrous) |
| Solubility in water | 186 g/L (20 °C) 390 g/L (50 °C) |
| Solubility | insoluble in ether slightly soluble in alcohol |
| Structure | |
| Crystal structure | Antifluorite (cubic), cF12 |
| Space group | Fm3m, No. 225 |
| Coordination geometry |
Tetrahedral (Na+); cubic (S2–) |
| Hazards | |
| MSDS | ICSC 1047 |
| EU Index | 016-009-00-8 |
| EU classification | Corrosive (C) Dangerous for the environment (N) |
| R-phrases | R31, R34, R50 |
| S-phrases | (S1/2), S26, S45, S61 |
| NFPA 704 |
1
3
1
|
| Autoignition temperature |
>480 ºC |
| Related compounds | |
| Other anions | Sodium oxide Sodium selenide Sodium telluride |
| Other cations | Lithium sulfide Potassium sulfide |
| Related compounds | Sodium hydrosulfide |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
|
| Infobox references | |
Sodium sulfide is the name used to refer to the chemical compound Na2S, but more commonly it refers to the hydrate Na2S·9H2O. Both are colorless water-soluble salts that give strongly alkaline solutions. When exposed to moist air, Na2S and its hydrates emit hydrogen sulfide, which smells much like rotten eggs or flatus. Generally, commercially available sodium sulfide is not a unique chemical entity, but it is specified as Na2S·xH2O, where a weight percentage of Na2S is specified. Commonly available grades have around 60% Na2S by weight, which means that x is around 3. Such technical grades of sodium sulfide have a yellow appearance. These grades of sodium sulfide are marketed as 'sodium sulfide flakes'. Although the solid is yellow, solutions of it are colorless.
Contents |
Na2S adopts the antifluorite structure,[1][2] which means that the Na+ centers occupy sites of the fluoride in the CaF2 framework, and the larger S2− occupy the sites for Ca2+. In solution, the salt, by definition, dissociates. The dianion S2− does not, however, exist in appreciable amounts in water. Sulfide is too strong a base to coexist with water. Thus, the dissolution process can be described as follows:
Sodium sulfide can oxidize when heated to sodium carbonate and sulfur dioxide:
Industrially Na2S is produced by reduction of Na2SO4 with carbon, in the form of coal:[3]
In the laboratory, the anhydrous salt can be prepared by reduction of sulfur with sodium in anhydrous ammonia. Alternatively, sulfur can be reduced by sodium in dry THF with a catalytic amount of naphthalene:[4]
It is primarily used in pulp and paper industry in the kraft process . It is used in water treatment as an oxygen scavenger agent, in the photographic industry to protect developer solutions from oxidation, in textile industry as a bleaching, as a desulfurising and as a dechlorinating agent and in leather trade for the sulfitisation of tanning extracts. It is used in chemical manufacturing as a sulfonation and sulfomethylation agent. It is used in the production of rubber chemicals, sulfur dyes and other chemical compounds. It is used in other applications including ore flotation, oil recovery, food preservative, making dyes, and detergent.
Like sodium hydroxide, sodium sulfide is strongly alkaline and can cause skin burns. Acids react with it to rapidly produce hydrogen sulfide, which is a toxic and foul-smelling gas.