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Anhydrous Sodium Sulphate

Anhydrous Sodium Sulphate

Anhydrous sodium sulphate is a white crystalline compound, and it is usually known as Glauber's salt, as it is named after Johann Glauber. Read ahead to know its properties and uses.
Girija Shinde
Johann R Glauber, a German/Dutch chemist, discovered sodium sulphate in 1625. Unlike other compounds, it was not found as an independent compound, but was prepared from salt (sodium chloride) and sulfuric acid, from Austrian spring water. It was named sal mirabilis, which means miraculous salt, by Glauber. It was named so because of its medicinal properties. Though Glauber named it sal mirabilis, it became famous as Glauber's salt only!

Earlier, the crystals of sodium sulphate were only used as a laxative. However, from the 18th century onwards, many other of its uses were discovered. People started using it for the production of soda ash with potash. It turned out to be a success, as the demand for soda ash increased.

  • Anhydrous sodium sulfate is in the form of hygroscopic white powder, and has no odor.
  • Formula: Na2SO4
  • It is soluble in water, but insoluble in ethanol.
  • Its boiling point is 1100ºC, and melting point is 880 - 888ºC.
  • This compound is stable under ordinary conditions, but at a high temperature, it is reduced to sodium sulfide.
  • Specific gravity: 2.66-2.75.
  • Its density is 1.464 /g cm3.
  • It assumes a monoclinic structure at 100ºC, and above 250ºC, it assumes a hexagonal structure.
  • It does not react with oxidizing agents at normal temperature.
  • Anhydrous sodium sulphate is mainly used in laundry detergents. In fact, in 2001, 1.6 million tons were used, out of which, 80% was used for home laundry detergents, in Europe!
  • Another major use in USA is for manufacturing wood pulp, in the Kraft process.
  • It is also used for manufacturing textiles. As it reduces negative charges on fibers, it helps the dyes penetrate evenly, and thus aids in 'leveling'.
  • It is used in the glass industry, not for producing glass, but for removing air bubbles from molten glass. It also prevents scum formation, as it fluxes the glass.
  • The other uses of anhydrous sodium sulphate include starch manufacture, in carpet freshmen, in frosting windows, and also as an additive to cattle feed. It is also used in the laboratory as an inert drying agent for organic solutions. In addition to all these uses, it is used in the electronics and water treatment industry.
  • It has been discovered that anhydrous sodium can dissolve fine electroplated micrometer gold, which is found in electronic products such as connectors, switches, and pins.
  • Anhydrous sodium sulphate is found in nature in the form of a mineral, known as thenardite.
  • It is the sodium salt of sulfuric acid.
  • When it grows in the pores of stones, it can exert pressure on the rocks, and make the structures crack.
  • It tends to attract iron and organic compounds.
  • The production of this compound is 6 million tons, which makes it one of the world's majority commodity chemicals.
  • However, it is also one of the world's most damaging salts in structure conservation!
We might find anhydrous sodium sulphate in passive solar heating systems also, as it has been proposed for storing heat. Though it is not regarded as being toxic, it is better to handle it with care.