- What it is. This sodium sulfate is the anhydrous (water-free) form, supplied in a 1 kg size. It is a white, neutral, inexpensive salt used mainly as a drying agent for organic solvents and extracts.
- How it dries solvents. Anhydrous sodium sulfate absorbs water by forming the decahydrate, Na2SO4·10H2O, binding up to about ten water molecules per formula unit. Added to a wet organic layer, it pulls out dissolved and dispersed water, after which the dried solution is decanted or filtered.
- Why chemists choose it. Sodium sulfate is neutral, chemically inert toward most organic compounds, inexpensive, and easy to separate by filtration. It has high capacity for water, though it works more slowly and less completely than magnesium sulfate.
- Using it effectively. Add the powder in portions to the organic solution and swirl. Clumping shows that water is still being absorbed; when fresh additions stay free-flowing, the solution is dry. Allow several minutes of contact, then filter or decant.
- Temperature limitation. The decahydrate loses its water above about 32 °C, so sodium sulfate is less effective as a drying agent for warm solutions. Use it at room temperature or below for best results.
- Chemical identity. Anhydrous sodium sulfate (CAS 7757-82-6, Na2SO4, 142.04 g/mol) melts at about 888 °C and has a density of about 2.7 g/cm³. It occurs naturally as the mineral thenardite.
- Other uses. Sodium sulfate is used in sample preparation for environmental and pesticide analysis, as a filler and processing aid in detergents, in glass and textile manufacturing, and as a source of sulfate in chemical work.
- How much to use. There is no fixed amount: add sodium sulfate until fresh portions remain free-flowing. As a starting point, many chemists add a spatula tip at a time to small extracts, swirling between additions, and allow at least several minutes of contact.
- Filtering off the drying agent. After drying, decant the solution or filter it through fluted filter paper or a cotton plug, then rinse the solid with a small amount of clean solvent to recover any product left on the salt.
- Related products. For applications that need documented impurity limits, Lab Pro also offers Sodium Sulfate, Anhydrous, ACS Grade, 2.5 kg.
Technical Specifications
| Chemical Name | Sodium sulfate, anhydrous |
| CAS Number | 7757-82-6 |
| EC Number | 231-820-9 |
| Synonyms | Disodium sulfate, thenardite (mineral), salt cake |
| Formula | Na2SO4 |
| Molecular Weight | 142.04 g/mol |
| Form | White powder or granules, anhydrous |
| Melting Point | About 888 °C |
| Density | About 2.7 g/cm³ |
| Grade | Confirm on label |
| Water Capacity | Forms decahydrate, Na2SO4·10H2O |
| Drying Temperature Limit | Below about 32 °C (decahydrate dehydrates above this) |
| pH (5% solution) | Approximately neutral |
| Package Size | 1 kg |
Applications / Common Uses
- Solvent drying: Removes water from organic extracts.
- Extraction workups: Dries organic layers after separations.
- Sample preparation: Dries extracts in environmental analysis.
- Sulfate source: Supplies sulfate in chemical work.
- Teaching labs: Demonstrates drying agent use in organic chemistry.
Storage, Handling & Shipping
Store tightly closed in a dry place at room temperature. Anhydrous sodium sulfate readily absorbs moisture, which reduces its drying capacity, so keep the container sealed and reseal it immediately after use.
- Incompatible materials: Strong acids, aluminum, and magnesium at high temperatures.
- Personal protection: Safety glasses, gloves, and dust control.
- Spill response: Sweep up without raising dust and place in a closed container.
- First aid: Eyes: rinse with water for several minutes.
Related Categories & Services
- Shop Inorganic Chemicals for related products in this category.
- Explore General Chemistry and Solvents.
- Vendor Managed Inventory (VMI) Program: Lab Pro can stock, track, and replenish this item on site so it never runs out. Contact info@labproinc.com or 888-452-2776 to set up a VMI assessment.
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FAQs
How does anhydrous sodium sulfate dry solvents?
It absorbs water by forming sodium sulfate decahydrate, binding up to ten water molecules per formula unit. When added to a wet organic solution, it removes dissolved and dispersed water. Once the solution is dry, filter or decant the solid. It is a standard organic workup step.
How do I know when a solution is dry?
Add sodium sulfate in portions and swirl. As long as water remains, the powder clumps together. When newly added powder stays free-flowing and the solution looks clear, drying is essentially complete. Allow several minutes of contact before filtering for best results. Swirl gently between additions to bring fresh powder into contact with the solution.
Is sodium sulfate better than magnesium sulfate?
Each has advantages. Sodium sulfate is neutral, high-capacity, inexpensive, and easy to filter, but works slowly. Magnesium sulfate works faster and more completely but is slightly acidic and finer, making filtration harder. Choose based on speed needs and sample sensitivity. Many labs stock both. Check sample compatibility.
Why shouldn't sodium sulfate be used with warm solutions?
Sodium sulfate decahydrate releases its water above about 32 °C, so at higher temperatures the drying agent cannot hold water effectively. Cool solutions to room temperature or below before drying with sodium sulfate to make sure water is retained. Ice baths help with warm extracts.
Can used sodium sulfate be regenerated?
You can regenerate it by heating to drive off water, but recovered material may carry organic residues from previous use. For analytical work, use fresh anhydrous sodium sulfate. Dispose of spent drying agent according to the solvents it has contacted. Keep fresh stock tightly closed.
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