Sodium sulfide nonahydrate
[CAS# 1313-84-4]

Identification

• Classification: Inorganic chemical industry >> Inorganic salt >> Metal sulfides and sulfates
• Name: Sodium sulfide nonahydrate
• Molecular Formula: Na₂S^.9(H₂O)
• Molecular Weight: 240.17
• CAS Registry Number: 1313-84-4
• EC Number: 639-249-0
• SMILES: O.O.O.O.O.O.O.O.O.[Na+].[Na+].[S-2]

Properties

• Density: 1.427 g/mL
• Melting point: 50 ºC
• Water solubility: 180 g/L (25 ºC)

Safety Data

• Hazard Symbols: GHS09 Warning
• Hazard Statements: H400-H410
• Precautionary Statements: P273-P391-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin corrosion	Skin Corr.	1B	H314
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Acute toxicity	Acute Tox.	3	H311
Acute toxicity	Acute Tox.	4	H302
Acute toxicity	Acute Tox.	3	H301
Serious eye damage	Eye Dam.	1	H318
Substances or mixtures corrosive to metals	Met. Corr.	1	H290

• Transport Information: UN 1849

Discovory and Applicatios

Sodium sulfide nonahydrate, with the chemical formula Na2S.9H2O, is a crystalline compound consisting of sodium sulfide and nine water molecules. This hydrated form of sodium sulfide is common in industrial chemistry and is known for its strong alkalinity and reducing properties. The discovery and subsequent development of sodium sulfide nonahydrate has played an important role in many chemical processes, especially in dye production, leather processing, and waste treatment.

Sodium sulfide itself has been known since the early days of industrial chemistry, when its reducing power was recognized. It can be produced by the reaction of sulfur with sodium carbonate or by the reduction of sodium sulfate with coal. Sodium sulfide nonahydrate, or hydrate, is formed when sodium sulfide absorbs moisture from the air or crystallizes from an aqueous solution. This crystalline form is more stable and easier to handle, making it the preferred choice for many industrial applications.

Structurally, sodium sulfide nonahydrate consists of two sodium ions (Na+) and a sulfide anion (S2-) and nine water molecules bound in its crystal structure. This hydration gives it unique physical properties, such as a lower melting point compared to the anhydrous form. Sodium sulfide nonahydrate is highly soluble in water and produces a strongly alkaline solution. It reacts readily with acids to release hydrogen sulfide (H2S), a property that makes it valuable in certain chemical reactions, but also requires caution in use, as H2S gas is toxic.

One of the main industrial applications of sodium sulfide nonahydrate is in the production of sulphur dyes, commonly known as sulfur dyes. These dyes are widely used in the textile industry for dyeing fabrics, especially cotton. Sodium sulfide nonahydrate acts as a reducing agent during the dyeing process, helping to convert insoluble dye precursors into soluble forms so that they can be absorbed by the fibers. Once applied, the dye is oxidized back to an insoluble form, resulting in a vibrant and long-lasting colour. Sodium sulfide nonahydrate is a key reagent in textile dyeing, and as such it has become a staple in the industry for the production of a wide range of colourants.

In the leather industry, sodium sulfide nonahydrate is used in the dehairing process. Its strong alkalinity helps break down the keratin structure in the hair, facilitating its removal from animal hides during leather production. This process, known as liming, prepares the hides for further processing and tanning. The use of sodium sulfide nonahydrate in leather processing is essential for manufacturing high-quality leather products, making it a valuable chemical in the tanning industry.

Another important application of sodium sulfide nonahydrate is in wastewater treatment, where it acts as a precipitant for heavy metals. In industrial processes that produce wastewater containing toxic metals, such as copper, zinc, and mercury, sodium sulfide nonahydrate is added to the water to form insoluble metal sulfides. These sulfides can then be easily separated from the water, reducing the toxicity of the wastewater. This method is often used in the mining, metal processing, and chemical manufacturing industries to meet environmental regulations and protect water quality.

Sodium sulfide nonahydrate is also used in the paper and pulp industry, where it participates in the kraft process, a method of producing wood pulp. The compound acts as a reducing agent to break down lignin, a complex polymer that holds cellulose fibers together in wood. By facilitating the removal of lignin, sodium sulfide nonahydrate helps produce high-strength paper products while enabling the recovery of chemicals used in the process.

In addition to these industrial applications, sodium sulfide nonahydrate is also used as a reducing agent for specific reactions in organic synthesis. Due to its ability to donate electrons, it is a useful reagent in laboratory settings for reducing nitro compounds and promoting desulfurization reactions. However, sodium sulfide nonahydrate requires careful handling and adequate ventilation when used in synthetic chemistry, as toxic hydrogen sulfide gas is produced during certain reactions.

In summary, sodium sulfide nonahydrate is a versatile chemical with a variety of industrial uses. From its role in the textile and leather industries to its applications in environmental protection and papermaking, this compound has proven its importance in modern industrial processes. As industries continue to evolve and seek effective solutions, sodium sulfide nonahydrate remains a key component in both traditional and emerging technologies.

References

1956. Sodium sulfide inhibition of liver lactic dehydrogenase. Biochimica et Biophysica Acta, 19(1).
DOI: 10.1016/0006-3002(56)90371-7

2024. Recovery of phosphorus from chemical-enhanced phosphorus removal sludge: Influence of sodium sulfide dosage on phosphorus fractionation, sludge dewaterability, and struvite product. Chemosphere, 363.
DOI: 10.1016/j.chemosphere.2024.142828

2021. Sodium sulphide promoted synthesis of fused quinoline at room temperature. Organic & Biomolecular Chemistry, 19(37).
DOI: 10.1039/d1ob01085a