Major uses of the alkali metals and their compounds

Lithium has the lowest density (0.53 g cm^_3) of all known metals. It is used in the manufacture of alloys, and in certain glasses and ceramics. Lithium carbonate is used in the treatment of manic-depressive disorders, although large amounts of lithium salts damage the central nervous system.

Sodium, potassium and their compounds have many uses of which selected examples are given here. Sodium– potassium alloy is used as a heat-exchange coolant in nuclear reactors. A major use of Na–Pb alloy was in the production of the anti-knock agent PbEt4, but the increasing demand for unleaded fuels renders this of decreasing importance. The varied applications of compounds of Na include those in the paper, glass, detergent, chemical and metal industries; Figure 1.1 summarizes uses of NaCl and NaOH. In 2000, the world production of NaCl was 210 Mt; of this, 51.6 Mt was used in the US. The major consumption of NaCl is in the manufacture of NaOH, Cl₂ and Na₂CO₃. A large fraction of salt is used for winter road de-icing. However, in addition to the corrosive effects of NaCl, environmental concerns have focused on the side-effects on roadside vegetation and run-off into water sources, and Switzerland, for example, operates reduced-salt schemes.

Both Na and K are involved in various electrophysiological functions in higher animals. The [Na‏⁺]:[K‏ ⁺] ratio is different in intra- and extra-cellular fluids, and the concentration gradients of these ions across cell membranes are the origin of the trans-membrane potential difference that, in nerve and muscle cells, is responsible for the transmission of nerve impulses. A balanced diet therefore includes both Na‏ and K‏ salts. Potassium is also an essential plant nutrient, and K‏ salts are widely used as fertilizers. Many organic syntheses involve Li, Na or their compounds, and uses of the reagents Na[BH₄] and Li[AlH₄] are widespread. Alkali metals and some of their compoundsn also have uses in catalysts, e.g. the formation of MeOH from H₂ and CO where doping the catalyst with Cs makes it more effective.