Sodium sulfate

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Structural formula
2.svg Na + .svg Structural formula of sodium sulfate
General
Surname Sodium sulfate
other names
  • Disodium sulfate
  • E  514
  • SODIUM SULFATES ( INCI )
  • Glauber's salt (decahydrate)
Molecular formula Na 2 SO 4
Brief description

colorless and odorless solid

External identifiers / databases
CAS number 7757-82-6 (anhydrous)

7727-73-3 (decahydrate)

EC number 231-820-9
ECHA InfoCard 100,028,928
PubChem 24436
ChemSpider 22844
DrugBank DB09472
Wikidata Q211737
Drug information
ATC code
properties
Molar mass 142.04 g mol −1
Physical state

firmly

density

2.70 g cm −3 (20 ° C)

Melting point

888 ° C

boiling point

Decomposition from 890 ° C

solubility

good in water: 170 g l −1 , at 20 ° C

safety instructions
Please note the exemption from the labeling requirement for drugs, medical devices, cosmetics, food and animal feed
GHS labeling of hazardous substances
no GHS pictograms
H and P phrases H: no H-phrases
P: no P-phrases
Toxicological data
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Sodium sulfate (Na 2 SO 4 ) is a sodium salt of sulfuric acid . The decahydrate (Na 2 SO 4 · 10 H 2 O) is also called Glauber's salt after the chemist Johann Rudolph Glauber . Also, the Carlsbad salt obtained by evaporation of Carlsbad mineral water is obtained, consisting mainly of sodium sulfate decahydrate and as laxatives used.

history

Sodium sulfate was discovered in 1625 by the chemist and pharmacist Johann Rudolph Glauber as a component of mineral water. Glauber described the salty taste of the preparation, that it melts on the tongue and, unlike saltpeter, does not burn if you hold it in a flame . He also recognized that the sodium sulfate obtained during evaporation becomes lighter when heated because it contains water of crystallization . Glauber also recognized the most important medicinal effect as a laxative at this time.

From 1658 Glauber experimented with table salt and sulfuric acid and received not only hydrochloric acid but also sodium sulfate, which he could now examine more closely. He discovered a total of 26 different possible medical applications, but also applications in alchemy and art.

After Johann Glauber, the sal mirabilis was later usually called Glauber's salt.

Occurrence

blue-green mirabilite

Sodium sulfate occurs naturally as orthorhombically crystallizing thénardite (α-Na 2 [SO 4 ]) or as a high-temperature modification as trigonal crystallizing metathenardite and as water-containing mirabilite (Na 2 [SO 4 ] • 10H 2 O).

Extraction and presentation

Sodium sulfate is largely obtained from the natural mineral mirabilite . The world's largest producer with over 70% is China (as of 2011). However, it is also a by-product in the chemical industry in reactions in which sulfuric acid is neutralized with caustic soda . Another possibility for technical representation consists in the conversion of rock salt with sulfuric acid for the purpose of obtaining hydrochloric acid with sodium sulfate as a by-product:

Sodium chloride and sulfuric acid react to form sodium sulfate and hydrogen chloride .

An alternative is the Hargreaves process:

Sodium chloride , sulfur dioxide , oxygen and water react to form sodium sulfate and hydrogen chloride .

Sodium sulfate can be represented in the laboratory by the following reactions:

Sodium carbonate and sulfuric acid react to form sodium sulfate, water and carbon dioxide .
The neutralization of caustic soda with sulfuric acid produces sodium sulfate and water .

properties

Sodium sulfate

The anhydrous sodium sulfate melts at 888 ° C, is hygroscopic and readily soluble in water , whereby it heats up ( heat of solution ). The decahydrate , on the other hand, dissolves under strong cooling . The crystal water leaves the crystal structure at around 32 ° C, which makes it appear as if the sodium sulfate is melting. In fact, however, it dissolves in the released water. From this supersaturated anhydrous sodium sulfate solution, the anhydrous separates salt from. At this temperature sodium sulphate has a pronounced maximum solubility.

Solubility of some salts in water at different temperatures

use

Sodium sulfate is used in detergents as a filler ( thickening agent ), in cellulose production ( sulfate process ) and in the glass , textile and paint industries. Annealed, anhydrous sodium sulphate is used in the laboratory to dry organic solvents . It is also used as a latent heat storage material.

In the form of decahydrate , sodium sulfate is used as a laxative in medicine . The sodium sulfate decahydrate (Glauber's salt) has an excessive laxative effect due to a competitive influence on the electrolyte balance.

In food technology it serves as a firming agent , acidity regulator and carrier substance . Sodium sulphate and sodium hydrogen sulphate are generally approved in the EU as food additives with the number E 514 without maximum quantity restriction (quantum satis) for foodstuffs.

Sodium sulfate is used as a homeopathic medicine under the name of sodium sulfuricum . Attributed effects are not scientifically plausible.

Glauber's salt is also used as a mineral plant fertilizer.

Individual evidence

  1. Entry on E 514: Sodium sulphates in the European database for food additives, accessed on August 11, 2020.
  2. Entry on SODIUM SULFATE in the CosIng database of the EU Commission, accessed on August 11, 2020.
  3. a b c d e f g h i j Entry on sodium sulfate in the GESTIS substance database of the IFA , accessed on December 19, 2019 (JavaScript required)
  4. Entry on sodium sulfate in the ChemIDplus database of the United States National Library of Medicine (NLM) .
  5. a b James C. Hill: Johann Glauber's discovery of sodium sulfate - Sal Mirabile Glauberi. In: Journal of Chemical Education. 56, 1979, p. 593, doi : 10.1021 / ed056p593 .
  6. https://www.ihs.com/products/sodium-sulfate-chemical-economics-handbook.html
  7. ^ Zusatzstoffe-online.de: sodium sulfate