In chemistry, an alkali is a basic, ionic salt of an alkali
metal or alkaline earth metal element. Some authors also define an alkali as a
base that dissolves in water. A solution of a soluble base has a pH greater
than 7. The adjective alkaline is commonly used in English as a synonym for
base, especially for soluble bases. This broad use of the term is likely to
have come about because alkalis were the first bases known to obey the
Arrhenius definition of a base and are still among the more common bases.
