Sodium

Sodium: Application

Metallic sodium is mainly used for the production of sodium borohydride, sodium azide, indigo, and triphenylphosphine. Previous uses were for the making of tetraethyllead and titanium metal; because applications for these chemicals were discontinued, the production of sodium declined after 1970. Sodium is also used as an alloying metal, an anti-scaling agent, and as a reducing agent for metals when other materials are ineffective. Sodium vapor lamps are often used for street lighting in cities and give colors ranging from yellow-orange to peach as the pressure increases. By itself or with potassium, sodium is a desiccant; it gives an intense blue coloration with benzophenone when the desiccate is dry. In organic synthesis, sodium is used in various reactions such as the Birch reduction, and the sodium fusion test is conducted to qualitatively analyse compounds. Many important medicines have sodium added to improve their bioavailability.

Due to its high thermal conductivity and low neutron absorption cross section, liquid sodium is used as a heat transfer fluid in some fast reactors. The high boiling point allows the reactor to operate at ambient pressure. Drawbacks of using sodium include its opacity, which hinders visual maintenance, and its explosive properties.

A different heat transfer application is in internal combustion engines with poppet valves. In high performance engines sometimes sodium-cooled valve stems are used to cool the valves. These hollow valve stems are partially filled with sodium and act as a heat pipe.

A different heat transfer application is in internal combustion engines with poppet valves. In high performance engines sometimes sodium-cooled valve stems are used to cool the valves. These hollow valve stems are partially filled with sodium and act as a heat pipe.

Most soaps are sodium salts of fatty acids. Sodium soaps are harder (higher melting) soaps than potassium soaps. Sodium chloride is extensively used for anti-icing and de-icing as well as a preservative; sodium bicarbonate is mainly used for cooking.

History

In contrast to elementary sodium (metal) its compounds have been known for a long time. They were extracted from mineral deposits, seawater and lakes. The most important sodium compound is cooking salt (sodium chloride). It was extracted from seawater or salty spring water in salines. The trade with salt was a source of great wealth for many towns and partially also influenced their names (Salzburg, Salzgitter).