Sodium sulfate

• Disodium
• E 514
• Glauber's salt ( decahydrate )

• A06AD13
• A12CA02

Colorless and odorless solid

Fixed

2.70 g · cm -3 ( 20 ° C)

888 ° C

Decomposition from 890 ° C

Good in water: 170 g · l -1, at 20 ° C.

5989 mg · kg -1 ( LD50, mouse, oral)

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Sodium sulfate ( Na2SO4, obsolete designation Sulphate of soda ) is a sodium salt of sulfuric acid and made ​​up of two sodium cations (Na ) and the sulfate anion ( SO42 - ). The decahydrate (Na2SO4 · 10H2O ) is after the chemist Johann Rudolph Glauber also known as Glauber's salt. Also the Carlsbad salt, obtained by evaporating water from Karlovy Vary, consisting mainly of sodium sulfate decahydrate and is used as a laxative.

History

Sodium sulfate was discovered in 1625 and described by the chemist and apothecary Johann Rudolf Glauber as part of mineral water. Here Glauber described the salty taste of the substance that melts on the tongue and in contrast to nitric does not burn when you put it in fire. He also realized that the crystal hydrous sodium sulfate obtained is easier when heated. The most important medical effect as a laxative recognized Glauber already at that time.

From 1658 experimented with Glauber's salt and sulfuric acid production and was given in addition to hydrochloric acid (as spirits of salt, spirit of salt called ) and sodium sulfate, which he could now examine in more detail. He discovered a total of 26 different potential medical applications, but also applications in alchemy and art.

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

Occurrence

Sodium sulfate occurs in nature as orthorhombic crystallizing thenardite ( α - Na 2 [ SO4 ] ) or as a high- temperature modification ( > 271 ° C) as trigonal crystallizing Metathenardit well as water- mirabilite ( Na 2 [ SO4 ] • 10H2O ).

Production and representation

Naturally occurring sodium sulfate is degraded by mining rarely due to the rarity, but often falls as a by- product in the chemical industry for reactions in which sulfuric acid is neutralized with sodium hydroxide. A further possibility for the industrial preparation consists in the reaction of rock salt (NaCl) with sulfuric acid for the purpose of production of hydrochloric acid with sodium sulfate as a by- product:

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

Properties

The anhydrous sodium sulfate melts at 888 ° C, is hygroscopic and readily soluble in water, it warms up ( heat of solution ). In contrast, the decahydrate dissolves under strong cooling caused by the so-called entropy effect. The crystal water leaves from about 32 ° C the crystal structure, making it seem as molten sodium sulfate, actually it dissolves but in the vacated water. From this supersaturated with anhydrous sodium sulphate solution, the anhydrous salt is deposited. At this temperature, sodium sulfate has a pronounced maximum solubility.

Use

Sodium sulfate is used in detergents as a filler in the pulp production ( sulphate process ) as well as in the glass, textile, and paint industry. Annealed, crystalline anhydrous sodium sulfate is used in the laboratory for drying organic solvents. It is also used as a latent heat storage material.

In the form of sodium sulfate is used as a laxative Decahydrates in medicine use. The sodium sulfate decahydrate ( Glauber's salt ) affects excessive laxative due to a kompetiven influence of electrolytes balance.

In food technology, it is used as a firming agent, acidity regulator and carrier. Sodium sulfate and sodium bisulfate are in the EU as a food additive under the E number 514 with no maximum limit ( quantum satis ) generally approved for food.

In the field of homeopathy is sodium sulfate, known as sodium sulph, use for colds, headaches and digestive weakness in pharmaceuticals. The effects attributed especially against colds, headaches and indigestion are not scientifically confirmed.