Sodium sulfate: properties, production and applications
Sodium sulfate (sodium sulphate, Na₂SO₄) is an inorganic salt and one of the most large-tonnage products of the chemical industry. Its relative molecular mass is 142.04. Anhydrous sodium sulfate is a colourless crystalline solid or white powder, readily soluble in water. In nature, it occurs as the mineral thenardite (anhydrous salt) and mirabilite (decahydrate Na₂SO₄·10H₂O, Glauber's salt). Sodium sulfate is widely used in the glass, pulp and paper, chemical and textile industries, as well as in the production of synthetic detergents.
Physicochemical Properties
Anhydrous sodium sulfate is a white powder or granules with a greyish tint, poorly soluble in water. Dissolution is accompanied by heat absorption. At low temperatures, mirabilite (decahydrate) crystallises from solutions. When stored in open air, crystals may effloresce. Sodium sulfate is thermally stable and non-flammable. The melting point of anhydrous Na₂SO₄ is 884 °C.
Regulatory Framework
Requirements for technical sodium sulfate in Russia and CIS countries are regulated by GOST 6318-77 "Sodium sulphate, technical. Specifications". The standard applies to technical sodium sulfate obtained from natural halurgic raw materials, as well as by industrial methods. Depending on the production method and application, the product is produced in two grades: grade A (highest, 1st and 2nd class) — for the pulp and paper, chemical, glass industries and other purposes; grade B — a product obtained in natural conditions, intended for the glass industry. The mass fraction of sodium sulfate (Na₂SO₄) in the highest grade product is at least 99.4%, in the first grade — at least 98%, in the second — at least 97%. The content of water-insoluble residue, chlorides, calcium, magnesium and iron is strictly regulated.
For crystallisation sodium sulfate obtained in viscose production by the reaction of sulfuric acid with caustic soda or sodium salts, GOST 21458-75 applies. Sodium sulfate is used as a feedstock in the pulp and paper, glass and chemical industries.
Production Technology
Industrial sodium sulfate production is based on several methods. One method is the processing of natural raw materials, in particular mirabilite (Glauber's salt), which occurs in salt lakes and natural brines. The method includes factory dehydration of natural mirabilite — melting, boiling and centrifuging. Another method is synthetic, based on the reaction of sodium sulfate with sodium chloride (Mannheim process) at high temperature, or on the reaction of sulfur dioxide and water (Hargreaves-Robinson process).
Significant volumes of sodium sulfate are obtained as a by-product of various chemical productions: in viscose fibre production, in gas cleaning processes at aluminium plants, and in the processing of solutions containing sodium sulfate. In Russia, sodium sulfate is produced by several enterprises, including the South Ural Magnesium Compounds Plant, which occupies a leading position in sodium sulfate production in the country.
Applications
Glass industry. This is one of the largest consumption areas for sodium sulfate. The product is used as a component of the batch in glass production, where it acts as a fining agent, helping to remove bubbles from the glass melt and improve its quality. Sodium sulfate is added in amounts of about 5–15 parts per 1000 parts of silicon dioxide.
Pulp and paper industry. Sodium sulfate is used as a source of sulfur make-up in the production of sulfate pulp (Kraft process). It is used to compensate for sulfur losses in the chemical recovery cycle.
Synthetic detergents. Sodium sulfate serves as the main filler in the production of powdered synthetic detergents. Its content in laundry powders can reach 25–50% by mass. It imparts flowability to powders, prevents caking and improves their consumer properties. However, in developed countries, there is a trend towards a shift from powdered detergents to liquid and compact forms, which reduces demand for sodium sulfate in this segment.
Textile industry. Sodium sulfate is used in dyeing and finishing processes for fabrics, as well as a binding material in the textile industry.
Chemical industry. Sodium sulfate serves as a feedstock for the production of sodium sulfide, soda and other chemical products. It is also used in the production of synthetic detergents, glass and in metallurgy.
Construction. Sodium sulfate is used as an anti-frost additive and a setting accelerator for concrete mixes. It is most effective on slag and pozzolanic Portland cements. The dosage is 1–3.5% of the cement mass. The effectiveness of sodium sulfate is significantly increased when used in combination with plasticisers. However, in cements with a high alkali content (more than 1%) and in high-alumina cements, it can cause sulfate corrosion. At a dosage above 2% of the cement mass, it causes abundant efflorescence on the surface.
Other applications. Sodium sulfate is used in pulp production, in medicine as a laxative, in pharmaceuticals, and in new applications such as thermal energy storage systems and sodium-ion batteries.
Global Market
Estimates of the global sodium sulfate market volume vary depending on the methodology. According to Global Market Insights, the market was valued at USD 964.2 million in 2025, projected to reach USD 990.2 million in 2026 and USD 1.3 billion by 2035 at a CAGR of 2.7%. According to Fortune Business Insights, the market was valued at USD 1.81 billion in 2025, USD 1.89 billion in 2026, and is projected to reach USD 2.74 billion by 2034 at a CAGR of 4.8%. According to 360iResearch, the market was valued at USD 1.44 billion in 2025 with a projected growth to USD 2.05 billion by 2032 at a CAGR of 5.17%.
The Asia-Pacific region dominates the global market: in 2025, its share was 54.14%. This is due to large-scale detergent production, textile processing and glass production, as well as China's leading position in the production and export of sodium sulfate. North America and Europe show more moderate growth rates, which is associated with the transition to liquid detergents and tightening environmental standards.
Key market growth drivers are growing demand from new applications for thermal energy storage, increased glass production for sustainable packaging, and growing pharmaceutical demand for bowel-cleansing products. The main constraints are the structural decline in demand for powdered detergents and high transport costs.
Production in Russia
The Russian sodium sulfate market is characterised by the presence of several large producers. RUSAL has mastered the production of crystalline sodium sulfate from gas cleaning solutions of aluminium production. The capacity of the section is 26,000 tonnes of sodium sulfate per year. The company's investments in this production amounted to about RUB 600 million. The South Ural Magnesium Compounds Plant occupies a leading position in sodium sulfate production in the country. The production technology developed at the enterprise has no analogues in Russia.
Safety and Storage
Sodium sulfate belongs to substances with low toxicity and is non-flammable. When working with it, personal protective equipment must be used: respirators, protective goggles and protective clothing. Storage is carried out in dry, well-ventilated areas, in hermetically sealed containers, away from moisture and heat sources. The product is hygroscopic; therefore, during prolonged storage in a humid environment, it may cake. Sodium sulfate is non-flammable and non-explosive.
Conclusion
Sodium sulfate remains one of the key products of the global chemical industry, providing for the production of glass, pulp, detergents and many other products. Growing demand for glass for sustainable packaging, the development of thermal energy storage systems and the expansion of pharmaceutical applications create sustained demand for this multifunctional product. China, the USA and European countries remain the leading players in the global sodium sulfate market, and the expansion of production in Russia and the introduction of new waste processing technologies determine the industry's further prospects.