Sodium Sulphate Anhydrous (Na₂SO₄), commonly known as anhydrous Glauber’s salt, is an inorganic, highly stable, white crystalline compound widely used in detergents, glass manufacturing, chemical synthesis, textiles, and numerous industrial processes. Being the water-free form of sodium sulphate, it exhibits excellent purity, high solubility, low toxicity, and superior thermal stability — qualities that make it one of the most commercially valuable inorganic salts globally.

Chemical Identity and Structure

Chemical Formula: Na₂SO₄

Molecular Weight: 142.04 g/mol

Form: Water-free (anhydrous) crystalline powder

Appearance: White, odorless, fine crystals or powder

Classification: Neutral salt

CAS Number: 7757-82-6

Sodium sulphate anhydrous contains two sodium cations and one sulphate anion. As a fully dehydrated compound, it does not contain water molecules within its crystalline structure, which makes it particularly useful in applications requiring strict moisture control.

Physical and Chemical Properties

The anhydrous grade displays excellent stability and resistance to heat, making it suitable for high-temperature industrial operations.

Melting Point: ~884°C

Boiling Point: Decomposes at high temperature

Solubility: Highly soluble in water; solubility increases with temperature

pH: Neutral to slightly alkaline in aqueous solution

Moisture Content: Very low (typically less than 0.5% in commercial high-purity grades)

Its ability to remain stable without absorbing significant moisture (in sealed conditions) makes it ideal for chemical reactions requiring anhydrous conditions.

Production and Sources

Sodium sulphate anhydrous is produced through both natural and synthetic routes:

Natural Source: Mining of Mirabilite (Na₂SO₄·10H₂O) and subsequent thermal dehydration

Synthetic Production: As a by-product of various chemical processes such as hydrochloric acid manufacturing, caprolactam production, and sodium dichromate processing

After purification and crystallization, the compound is dried to obtain the high-purity, water-free anhydrous grade.

Industrial Applications

1. Detergent and Cleaning Products

Sodium sulphate anhydrous acts as a filler, processing aid, and flow enhancer in detergent powders. It helps maintain the free-flowing nature of detergent granules, ensures uniform distribution of active ingredients, and reduces moisture-related clumping. Its neutral nature makes it compatible with surfactants and bleaching agents.

2. Glass Manufacturing

One of its largest industrial uses is in the glass and silica industry, where sodium sulphate serves as a refining agent. It helps remove tiny air bubbles from molten glass, improves clarity, and enhances the overall quality of flat glass, container glass, and fiberglass.

3. Textile and Dyeing

In textile processing, sodium sulphate acts as a levelling agent, ensuring even absorption of dyes into fibers such as cotton and wool. It reduces negative ionic charges, allowing dyes to penetrate more uniformly and providing vibrant, consistent coloration.

4. Chemical Industry

Sodium sulphate anhydrous plays a crucial role in various chemical manufacturing processes:

Production of sodium sulfide and sodium silicate

As a reactant in dye and pigment synthesis

Electrolyte in batteries

Catalyst carrier and stabilizer

Ingredient in laboratory-grade reagents

Its reliability and high purity make it suitable for precision chemical formulations.

5. Pulp & Paper Industry

Used in the Kraft pulping process, sodium sulphate contributes to the regeneration of cooking chemicals. It helps in producing strong, high-quality paper products with improved fiber strength.

6. Pharmaceuticals

Pharmaceutical-grade sodium sulphate anhydrous is used as:

A laxative component in certain formulations

A stabilizer in bulk drug manufacturing

A drying agent in chemical synthesis

Its inertness and non-toxic nature ensure safe application in medicinal processes.

7. Food & Feed Industries

Though used in limited quantities, sodium sulphate can act as a processing aid in food-grade operations and as a mineral supplement or technological additive in animal feed.

8. Thermal Storage Systems

Due to its heat absorption properties, sodium sulphate is used in thermal energy storage, solar energy systems, and phase-change material applications.

Advantages of Sodium Sulphate Anhydrous

Highly stable and heat-resistant

Low moisture content ensuring consistent performance in sensitive formulations

Cost-effective compared to many alternative salts

Chemically neutral, suitable for a wide range of reactions

Non-toxic and environmentally safe

Highly soluble, dissolving quickly in water

Compatible with surfactants, oxidizers, solvents, and dyestuffs

Its multi-industry relevance is due to its adaptability, performance benefits, and easy integration into various chemical and manufacturing processes.

Conclusion

Sodium Sulphate Anhydrous is an essential industrial chemical that combines purity, stability, and performance in one versatile compound. Its wide application across detergents, glass-making, textiles, chemicals, pharmaceuticals, pulp & paper, and thermal storage demonstrates its indispensable role in modern manufacturing. With excellent solubility, neutral chemistry, and high thermal resistance, sodium sulphate anhydrous continues to be a preferred choice for industries seeking reliable, cost-effective, and high-quality material solutions.