Sodium (Na): properties, uses, occurrence and history

The Egyptians in ancient times coined the term netjerj (neter) for the soda obtained from soda lakes. The Greeks adopted this word as the Greek νίτρον nitron, the Romans as nitrium, the Arabs as natrun. Sodium compounds, unlike the elemental metal, have been known for a very long time and have since been extracted from sea water or lakes, mined from earth deposits, and traded. The most important sodium compound, common salt (sodium chloride), was obtained in mines or by drying seawater or saline spring water in salt works. The trade in salt was the basis of wealth for many towns and cities, and in some cases even shaped their names (Salzgitter, Salzburg). Place names such as Hallstatt, Hallein, Halle (Saale), Bad Hall, Bad Reichenhall, Schwäbisch Hall, Schweizerhalle or Hall in Tirol refer to the Germanic name for saline (Hall). Other naturally occurring sodium compounds such as sodium carbonate (soda or natron) and sodium nitrate have also been extracted and traded since ancient times.

It was not until 1807 that Humphry Davy succeeded in producing elemental sodium by electrolysis of molten sodium hydroxide (caustic soda) using voltaic columns as a power source. As he reported to the Royal Society in London on November 19, 1807, he obtained two different metals: the sodium contained in soda ash he called sodium, which is still the common name for the metal in French and English-speaking countries; the other metal he called potassium (potassium). Berzelius proposed the present name sodium in 1811.

In the universe, sodium ranks 14th in abundance, comparable to calcium and nickel. In the emitted light of many celestial bodies, including that of the sun, the yellow sodium D-line can be easily detected.

On Earth, sodium is the sixth most abundant element, accounting for 2.36% of the Earth's crust. Due to its reactivity, it does not occur elementally, but always in compounds, the sodium salts. A large store of sodium is seawater. One liter of seawater contains an average of 11 grams of sodium ions.

Common sodium minerals are albite (called sodium feldspar), NaAlSi3O8 and oligoclase (Na,Ca)Al(Si,Al)_3O8. In addition to these rock-forming minerals, which belong to the feldspars, sodium occurs in large salt deposits. In particular, there are large deposits of halite (sodium chloride, colloquially often called rock salt), which were formed by the drying up of parts of the sea. These are the most important source for the extraction of sodium and its compounds. Well-known German salt production sites include Salzgitter, Bad Reichenhall, Stade and Bad Friedrichshall.

Besides the common sodium chloride, other compounds occur in nature. Sodium nitrate or sodium nitrate (also called Chilean nitrate) NaNO3 is one of the few natural nitrate minerals. However, because of its good solubility in water, it only occurs in particularly dry regions such as the Atacama Desert in Chile. Before the invention of the Haber-Bosch process, this was the most important raw material for many fertilizers and explosives.

Sodium carbonate Na2CO3 is also found naturally in several minerals. The best known mineral is soda ash Na2CO3 - 10 H2O. It is mined in large quantities and used mainly in glass production.

In addition, a variety of other sodium minerals exist (see also: Category:Sodium mineral). A well-known one is cryolite (ice stone, Na3[AlF6]), which in a molten state serves as a solvent for alumina in aluminum production. Since the only known cryolite deposit is mined in Greenland, cryolite is produced artificially.