Sodium sulfate
Sodium sulfate, also known as Glauber's salt or sal mirabilis, is a chemical compound with the formula Na2SO4, useful for drying.
Contents
Properties
Chemical
Sodium sulfate will react with carbon at high temperatures, to yield sodium sulfide:
- Na2SO4 + 2 C → Na2S + 2 CO2
Sodium sulfate is known to form double salts, such as alums, NaAl(SO4)2 (unstable above 39 °C) and NaCr(SO4)2 and even with other alkali metals, one example being Na2SO4·3K2SO4.
Physical
Sodium sulfate is a white deliquescent hygroscopic solid, poorly soluble in water (19.5 g/100 ml at 20 °C for anhydrous salt and 44 g/100 mL at 20 °C for decahydrate). It is insoluble in ethanol. Sodium sulfate has a density of 2.664 g/cm3 for the anhydrous form and 1.464 g/cm3 for the decahydrate. Its anhydrous form melts at 884 °C.
Availability
Sodium sulfate is available at pharmacies as Glauber's salt. Some products might also contain around 10% sodium bicarbonate. This can be removed by adding sulfuric acid or sodium bisulfite. In some countries, such as the Russian Federation, it is added into dry alkaline drain cleaners as a weak surfactant; it can be easily separated from the alkali, because the alkali in the drain cleaner is in form of large granules, and sal mirabilis a fine powder. Any household sieve or even dry gauze cloth will do the trick.
Sodium sulfate occurs naturally as the minerals thenardite (anhydrous Na2SO4) and mirabilite (Na2SO4·10H2O). Both forms appear depending on the weather conditions.
Preparation
Sodium sulfate can be prepared by reacting a sodium salt or hydroxide with sulfuric acid or another soluble sulfate. It can also be prepared by reacting sodium bisulfite with another sodium compound, such as sodium chloride.
Projects
- Desiccator
- Dry solvents
- Make sodium aluminium sulfate
- Electrolysis of water
- Thermal energy storage
- Sodium sulfide synthesis
Handling
Safety
Sodium sulfate is generally regarded as non-toxic, although its anhydrous form may cause irritations if touched or inhaled.
Storage
Anhydrous sodium sulfate should be stored in sealed bottles, in a dry place. The hydrated form doesn't require special storage.
Disposal
Sodium sulfate can be poured down the drain, as long as it doesn't contain other toxic products.
