ˈælkəlaɪ n. (pl. alkalis) 1 a
any of a
class of substances
that liberate hydroxide ions in
water, usu.
form caustic or
corrosive solutions,
turn litmus blue,
and have a pH of
more than 7, e.g. caustic
soda. b any
other substance with similar but weaker properties, e.g.
sodium carbonate. 2 Chem. any substance that reacts with or neutralizes
hydrogen ions. øalkali metals any of
the univalent group of metals,
lithium, sodium,
potassium,
rubidium, and
caesium,
whose hydroxides are alkalis. øøalkalimeter n. alkalimetry n. [ME f. med.L, f.
Arab. al-kali calcined ashes f. kala fry]