Sodium was first isolated by Sir Humphry Davy in 1807 by electrolysis of caustic soda. In the following year, Gay Lussac and Thenard obtained metallic sodium by chemical reduction of caustic soda with iron at elevated temperatures. Deville, in 1854, prepared the metal by reduction of sodium carbonate and lime with charcoal at a temperature above the boiling point of sodium. Castner, in 1886, improved the chemical reduction process preparing the metal by heating sodium hydroxide with iron carbide at high temperature. Five years later he patented a process based on electrolytic reduction of sodium hydroxide. The first major commercial plant was set up in 1921 with the introduction of Downs cell.
The element derived its name from the Latin word sodanum meaning “headache remedy.” Its symbol Na was derived from the Latin word, natrium.
Sodium is the sixth most abundant element on earth. It comprises about 2.6% weight of the earth’s crust. Its salt, sodium chloride, is the major component of seawater. The concentration of sodium in seawater is 1.08%. As a very reactive element, sodium is never found in free elemental form. It occurs in nature in many minerals such as cryolite, amphibole, zeolite, sodalite, and soda niter. Sodium chloride (NaCl) is the most common salt of sodium. Some other important salts are caustic soda (NaOH), soda ash (Na2CO3), baking soda (NaHCO3), Chile saltpeter (NaNO3), borax (Na2B4O7•10H2O), sodium thiosulfate (Na2S2O3), sodium sulfate (Na2SO4), and sodium phosphates.
