Origins of the concepts
The term “alkali” is derived from the Arabic word al qalīy, meaning “the calcined ashes.” These plant ashes were regarded as having properties such as the ability to reverse the action of acids and having detergent power. Thus, an alkali was initially thought of as the antithesis of an acid. The formation of salts from the acid and alkali reaction led to the view that salts can be derived from two constituents of opposite natures.
Yet, not all non-acidic constituents possessed alkaline properties. Examples are oxides and hydroxides of heavy metals. Hence, the concept of “base” was born. This concept was first introduced by the French chemist Guillaume François Rouelle in 1754. He noted that acids—which in those days were mostly volatile liquids, such as acetic acid—turned into solid salts only when combined with specific substances. These substances formed a concrete base for the salt, and hence