<P> There are various more specific definitions for the concept of an alkali . Alkalis are usually defined as a subset of the bases . One of two subsets is commonly chosen . </P> <Ul> <Li> A basic salt of an alkali metal or alkaline earth metal (This includes Mg (OH) but excludes NH .) </Li> <Li> Any base that is soluble in water and forms hydroxide ions or the solution of a base in water . (This includes Mg (OH) and NH .) </Li> </Ul> <Li> A basic salt of an alkali metal or alkaline earth metal (This includes Mg (OH) but excludes NH .) </Li> <Li> Any base that is soluble in water and forms hydroxide ions or the solution of a base in water . (This includes Mg (OH) and NH .) </Li>

Where do we get the term alkali metals