Lithium

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MELTING POINT: 180.5°C
BOILING POINT: 1,342°C
DENSITY: 0.534 g/cm ³
MOST COMMON IONS: +1

Lithium is a soft, silvery alkali metal and has the lowest density of any metal. The word "lithium" is derived from "lithos" (Greek for "stone"). Johan A. Arfvedson discovered lithium in Stockholm, Sweden, in 1817. Humphry Davy isolated it via electrolysis in 1818. Currently, lithium metal is generated by the electrolysis of a molten mixture of lithium chloride, LiCl, and potassium chloride, KCl. In nature it is never found in its elemental form. Its main sources are the minerals spodumene, petalite, lepidolite, and amblygonite. Lithium's average crustal abundance is about 18 ppm. It has the highest specific heat of any solid element and is the least reactive alkali metal toward water. Lithium burns crimson in the flame test.

Metallic lithium has a variety of uses. It is used as an anode material in batteries and as a heat transfer agent. Magnesium-lithium alloys are used to produce armor plate and aerospace materials, while aluminum-lithium alloys find applications in the aircraft industry. Lithium is also used to produce chemical reagents such as LiAlH ₄ (a reducing agent ) and n -butylithium (a strong base).

Compounds of lithium are also economically important. Air conditioning systems use LiCl and LiBr because they are very hygroscopic and readily absorb water from the air. Thermonuclear weapons incorporate lithium deuteride, LiD. Lithium stearate is obtained by treating tallow with lithium hydroxide, LiOH, and is used as a thickener that imparts high temperature resistance to lubricants. Carbon dioxide removal systems in submarines and spacecraft use LiOH. Lithium carbonate, Li ₂ CO ₃ , is used to increase the electrical current flow in the electrolytic production of aluminum from bauxite and to strengthen glasses by substituting for sodium ions. Although lithium carbonate has been used to treat bipolar (manic-depressive) disorder since 1949, its mechanism of operation is still not completely understood.

SEE ALSO Alkali Metals ; Davy, Humphry .

Nathan J. Barrows

Bibliography

Emsley, John (2001). Nature's Building Blocks: An A–Z Guide to the Elements. New York: Oxford University Press.

Greenwood, Norman N., and Earnshaw, A. (1997). Chemistry of the Elements, 2nd edition. Boston: Butterworth-Heinemann.

Lide, David R., ed. (2000). The CRC Handbook of Chemistry & Physics, 81st edition. New York: CRC Press.