[W/K] :: sodium hydrate

  Sodium \So"di*um\, n. [NL., fr.E. soda.] (Chem.)
     A common metallic element of the alkali group, in nature
     always occuring combined, as in common salt, in albite, etc.
     It is isolated as a soft, waxy, white, unstable metal, so
     highly reactive that it combines violently with water, and to
     be preserved must be kept under petroleum or some similar
     liquid. Sodium is used combined in many salts, in the free
     state as a reducer, and as a means of obtaining other metals
     (as magnesium and aluminium) is an important commercial
     product. Symbol Na ({Natrium). Atomic weight 22.990.
     Specific gravity 0.97.
     [1913 Webster]
  
     Sodium amalgam, an alloy of sodium and mercury, usually
        produced as a gray metallic crystalline substance, which
        is used as a reducing agent, and otherwise.
  
     Sodium carbonate, a white crystalline substance,
        Na2CO3.10H2O, having a cooling alkaline taste, found in
        the ashes of many plants, and produced artifically in
        large quantities from common salt. It is used in making
        soap, glass, paper, etc., and as alkaline agent in many
        chemical industries. Called also sal soda, washing
        soda, or soda. Cf. Sodium bicarbonate, and Trona.
        
  
     Sodium chloride, common, or table, salt, NaCl.
  
     Sodium hydroxide, a white opaque brittle solid, NaOH,
        having a fibrous structure, produced by the action of
        quicklime, or of calcium hydrate (milk of lime), on sodium
        carbonate. It is a strong alkali, and is used in the
        manufacture of soap, in making wood pulp for paper, etc.
        Called also sodium hydrate, and caustic soda. By
        extension, a solution of sodium hydroxide.
        [1913 Webster]