(Chemical symbol Al) Element No. 13 of the periodic system; Atomic weight 26.97;silvery white metal of valence 3; melting point 1220° F.; boiling point approximately 4118° F.; ductile and malleable; stable against normal atmospheric corrosion, but attacked by both acids and alkalies. Aluminum is used extensively in articles requiring lightness, corrosion resistance, electrical conductivity, etc. Its principal functions as an alloy in steel making; (1) Deoxidizes efficiently (See Aluminum Killed) (2) Restricts grain growth (by forming dispersed oxides or nitrides) (3) Alloying element in nitriding steel.\n(See Nitriding Steel)