Sodium Sulphate

Sodium sulphate - also known as sodium sulfate or soda is an inorganic compound of sodium. This sodium salt form of sulfuric acid is extensively used in a wide range of industries. More than 6.5 million tons of sodium sulfate are produced each year around the world. Most are mined from the compound's natural mineral form called mirabilite, which is taken from lake beds as part of the water treatment process. Another one-third is produced as a byproduct of other processes in the chemical industry. All forms of Sodium Sulphate are white solids, which are highly soluble in water. It is mainly used for the manufacture of detergents and in the kraft process of paper pulping.

Synonyms
Sodium Sulfate, Sulfate of sodium, Thenardite (mineral), Glauber's salt (decahydrate), Sal mirabilis (decahydrate), Mirabilite (decahydrate mineral), Disodium sulfate, Disodium Sulfate, Na2SO4, Salt Cake, Sodium Sulfate
Chemical Formula
Na2SO4
CAS Number
7757-82-6

Characteristics

Molar Weight
142.04 g/mol
Melting Point
884 °C
Boiling Point
1,429 °C
Density
2.664 g/cc
Forms
White, Granules, Crystalline

Uses and applications

Key applications

  • Hair care
  • Ceramics
  • Glass
  • Pulp and paper
  • Textile handling
  • Detergent

General information about sodium sulphate

Sodium sulphate (Na2SO4) is the sodium salt of sulphuric acid. The decahydrate (Na2SO4 x 10 H2O) is known as Glauber's salt, named after Johann Rudolph Glauber, who discovered the substance in mineral water in the 17th century.
Natural sodium sulphate occurs mainly as mirabilite (decahydrate) and thenardite (anhydrous form). Other natural forms, such as astrakanite, occur in salt lakes and dry desert areas.
Properties of sodium sulphate
Sodium sulphate is a colourless, odourless, crystalline solid that is highly soluble in water and hygroscopic. It is both mined naturally (e.g. in China, Canada, Spain and Russia) and produced industrially. Important industrial processes include the Mannheim process (a by-product of HCl production) and the Kraft process used in the pulp industry.

Sodium sulphate in the pharmaceutical industry

Sodium sulphate is used in the pharmaceutical industry as a laxative, excipient and pH regulator. The decahydrate (Glauber's salt) in particular is used for medical purposes. Typical applications are:
  • As a laxative, for example before colonoscopies or to empty the digestive tract.
  • Component of electrolyte solutions, in which it stabilises the water and electrolyte balance.
  • Excipient in tablets and capsules, which can improve the solubility and stability of active ingredients.pH regulation in pharmaceutical solutions to stabilise formulations.

Sodium sulphate in the food industry

Sodium sulphate is used in the food industry as a food additive under the designation E 514. It acts mainly as an anti-caking agent and technical excipient. Its main applications include:
  • Preventing powders from clumping, e.g. in dry soups, baking powder and spice mixtures.
  • Purification of sugar solutions in sugar refining by binding impurities.
  • Auxiliary agent in the production of gelatine and starch to stabilise process flows.

Sodium sulphate in the cosmetics industry

In the manufacture of cosmetic products, sodium sulphate serves as a thickening and flow regulating agent, filler and anti-caking agent. Typical applications are:
  • Consistency control in shampoos, shower gels and liquid soaps by regulating viscosity.
  • Prevention of clumping in powder products, for example in bath additives.
  • Use as a filler in soaps and toothpastes to improve texture and volume.

Further areas of application for sodium sulphate

Sodium sulphate in glass manufacturing

Sodium sulphate plays an important role in the glass industry as a clarifying agent and flux. Key applications include:
  • Dissolving gas bubbles in molten glass, resulting in a clearer material.Reacting with metal oxides such as iron to prevent glass discolouration and produce colourless glass.
  • Lowering the melting point of glass, which reduces energy requirements and facilitates processing.

Sodium sulphate in the ceramics industry

Sodium sulphate also serves as a flux and processing aid in the ceramics industry. Typical areas of application are:
  • Lowering the melting point of ceramic raw materials, which saves energy and improves sintering steps.Improving the surface quality of ceramic glazes by promoting smoothness and transparency.
  • Use in surface finishes that increase the stability and mechanical properties of ceramics.

Sodium sulphate in detergents and cleaning agents

In the cleaning industry, sodium sulphate primarily functions as a filler, release agent and water softener. The most important applications include:
  • Increasing the volume of washing powders to enable better dosing.
  • Preventing clumping in powder detergents and cleaning agents.
  • Supporting water softening by regulating calcium and magnesium ions.
  • Promoting the surfactant effect, which improves the grease and dirt removal power.
  • Process aid in the manufacture of soaps, liquid detergents and floor cleaners.

Sodium sulphate in industrial water treatment

Sodium sulphate is an auxiliary substance used to regulate water chemistry, particularly in industrial circuits. Applications include:
  • Adjusting the sulphate content in process water such as cooling circuits.
  • Precipitation of certain heavy metals, depending on process conditions.
  • Regulation of ion exchange processes in water softeners.
  • Neutralisation of waste water, especially in paper and textile processes where sulphuric acid has been used.

Other areas of application for sodium sulphate

In the textile industry, sodium sulphate serves as a dyeing aid and improves the absorbing properties of dyes. It ensures even dyeing by stabilising the distribution of dye molecules in the bath.
In the paper industry, sodium sulphate is a central component of the cooking process in the Kraft process of pulp production. It also stabilises the pH value and supports cleaning and flocculation processes in the paper cycle.

Summary

Sodium sulphate (Na2SO4) is a versatile, widely used inorganic salt with applications in the pharmaceutical, food, cosmetics, glass, ceramics, detergent, water, textile and paper industries.
As a fluxing agent, clarifying agent, release agent, filler and chemical additive, sodium sulphate contributes to quality improvement, process stabilisation and efficiency gains in numerous industrial processes.
It is available both as a naturally occurring raw material and as an industrially produced by-product and, due to its chemical properties, remains a key functional material in many industries.