In chemistry, an alkali is a basic salt of an alkali metal or an alkaline earth metal. Alkali can also be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The adjectives alkaline and, less often, alkalescent are commonly used in English as a synonyms for basic, especially for bases soluble in water. 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 they are still among the most common bases.
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