Sodium Sulfate
Versatile inorganic salt widely used in industrial applications, key component in glass, detergent and textile production
Overview
Sodium Sulfate (CAS No: 7757-82-6) is an important inorganic salt available in anhydrous (Na₂SO₄) and decahydrate (Na₂SO₄·10H₂O, Glauber's salt) forms. It is a white, crystalline, odorless compound that is soluble in water. It is a versatile chemical widely used in industrial applications.
Sodium sulfate occurs naturally as the minerals thenardite (anhydrous form) and mirabilite (decahydrate form). In industrial production, it is usually obtained as a by-product of other chemical processes. It has a neutral pH and is insoluble in most organic solvents.
Applications
Sodium sulfate has a wide range of industrial applications:
Glass Production
Used as a flux in glass melting, lowers the melting temperature of silica and improves glass clarity. Approximately 70% of global production is used in the glass industry.
Detergents
Used as a filler and flow enhancer in powdered detergent formulations. It also improves detergent efficiency.
Textile Industry
Used as an auxiliary in dyeing and bleaching processes. It regulates dye uptake by fibers and ensures even dyeing.
Kraft Pulp
Used in sulfate recovery in the kraft process. It is part of the chemical cycle in pulp production.
Food Additive
Known as E514, used in foods as an acidity regulator and anti-caking agent. Commonly found in dried fruits.
Animal Feed
Used as a feed additive to aid digestion and improve nutrient absorption. Particularly used to correct sodium deficiency.
Technical Specifications
| Property | Value | Unit | Test Method |
|---|---|---|---|
| Chemical Name | Sodium Sulfate | - | - |
| Other Names | Thenardite (anhydrous), Glauber's salt (decahydrate) | - | - |
| CAS Number | 7757-82-6 (anhydrous), 7727-73-3 (decahydrate) | - | - |
| EC No | 231-820-9 | - | - |
| Formula | Na₂SO₄ (anhydrous), Na₂SO₄·10H₂O (decahydrate) | - | - |
| Molecular Weight | 142.04 (anhydrous), 322.20 (decahydrate) | g/mol | - |
| Appearance | White crystalline powder or granules | - | Visual |
| Odor | Odorless | - | - |
| Purity | ≥99.0 | % | ICP |
| Density (25°C) | 2.68 (anhydrous), 1.46 (decahydrate) | g/cm³ | ASTM D854 |
| Melting Point | 884 (anhydrous), 32.4 (decahydrate, water loss) | °C | ASTM D97 |
| pH Value (5% sol.) | 5.5-8.5 | - | ASTM E70 |
| Solubility (Water, 20°C) | 28.1 (anhydrous), 44 (decahydrate, 0°C) | g/100ml | ASTM E1148 |
Safety Information
Hazard Symbols and Statements
Irritant
Personal Protective Equipment (PPE)
- Dust-resistant gloves (nitrile or latex)
- Dust mask (in high dust concentrations)
- Safety goggles (in dusty environments)
- Lab coat or protective clothing
Storage Conditions
- Store in a cool, dry and well-ventilated place
- Keep in original packaging, tightly closed
- Protect decahydrate form from moisture (hygroscopic)
- Keep away from acids and strong reducing agents
Fire Fighting
- Non-flammable, no extinguisher required
- At high temperatures may decompose releasing toxic sulfur oxides
- Water spray can be used in large fires
Handling and Storage
Transportation
- Ensure containers are tightly closed
- Protect decahydrate form from moisture
- Transport separately from acids and reducing agents
- Have absorbent material available for spills
Storage
- Store in dry, cool and well-ventilated areas
- Moisture control is important for decahydrate form
- Display appropriate signage in storage area
- Store on elevated shelves
Spill Response Measures
- Use dust mask and protective equipment
- Collect spill by dry method (sweeping)
- Do not use water - may form solution
- Wipe spilled area with damp cloth
Regulatory Information
GHS Classification
- Skin Irritation/Corrosion Category 2
- Eye Irritation Category 2
Important Regulations
- REACH: Registered
- EPA: Listed in TSCA inventory
- European Food Additives: Approved as E514
- FDA: Approved for certain food applications
Environmental Information
Environmental Impact
Sodium sulfate has low toxicity in aquatic environments. High concentrations may cause increased salinity. Due to its complete biodegradation property, its environmental impact is minimal.
Biodegradation
- Rapidly dissociates into ions in nature (Na⁺ and SO₄²⁻)
- Water: Rapid dissolution and ionization
- Soil: Can be absorbed by plants
Waste Management
- Not classified as hazardous waste
- Can be disposed in licensed waste facilities
- Controlled discharge to local sewer systems possible
Frequently Asked Questions
What is the difference between anhydrous and decahydrate sodium sulfate?
Anhydrous sodium sulfate (Na₂SO₄) contains no water and is not hygroscopic. The decahydrate form (Na₂SO₄·10H₂O) contains 10 water molecules in crystal structure and loses water above 32.4°C, converting to anhydrous form.
Is sodium sulfate safe in foods?
Yes, sodium sulfate (E514) is accepted as a food additive and safe within certain limits. It is used in food-grade products as an acidity regulator and anti-caking agent.
How should sodium sulfate be stored?
Anhydrous form can be stored in a dry, cool place. Decahydrate form should be protected from moisture and stored below 30°C. Both forms should be kept in tightly closed containers away from direct sunlight.
Is skin contact with sodium sulfate harmful?
Prolonged or repeated contact may cause skin irritation. Inhalation of dust form may irritate respiratory tract. In case of contact, rinse with plenty of water.