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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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
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Solvent drying: Removes water from organic extracts.
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Extraction workups: Dries organic layers after separations.
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Sample preparation: Dries extracts in environmental analysis.
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Sulfate source: Supplies sulfate in chemical work.
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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.
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Incompatible materials: Strong acids, aluminum, and magnesium at high temperatures.
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Personal protection: Safety glasses, gloves, and dust control.
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Spill response: Sweep up without raising dust and place in a closed container.
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First aid: Eyes: rinse with water for several minutes.
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