The term 'base' in chemistry refers to substances that neutralize acids, a concept historically overshadowed by the study of acids. The word 'alkaline' has Arabic origins, meaning 'roasting', linked to the production of classic bases like sodium and potassium hydroxide. The modern usage of 'base' is attributed to French chemist Guillaume-François Rouelle, who defined it in the 18th century as a fundamental compound that forms salts with acids. Despite various theories about its etymology, the exact rationale for the term remains unclear.
PREREQUISITESChemistry students, educators, and anyone interested in the historical context and terminology of chemical substances, particularly in understanding the classification of acids and bases.
Bases
Bases were identified and categorised as the substances which are neutralising acids. For that reason, the progress in the characterisation of bases was always connected to the more popular characterisation of acids. As a consequence, the theories for bases were always overshadowed by the theories for acids. Nevertheless, bases have also been known for a long time.
The associated word 'alkaline' (which is used to describe the properties of a base-solution, like its soapy taste) has Arabic roots. The term originally meant 'roasting', because the first alkaline substances were obtained by roasting ashes then treating them with water and slaked lime (calcium hydroxide). The substances obtained are sodium and potassium hydroxide, two of the most classic bases, which were used to make soap.
The use of the word 'base' to describe these substances was introduced a lot later; the original rationale remains obscure. One possibility is that the 'bases' were the basic (in the sense of 'fundamental') compounds used to form salts with acids. Another possibility is that it's called that just to add confusion. The second theory has many adherents among chemistry students.
Its modern meaning and general
introduction into the chemical vocabulary,
however, is usually attributed to the
French chemist, Guillaume-François
Rouelle (1703–1770), who used the
term in a memoir on salts written in
1754 (5). In this paper, which was an
extension of an earlier memoir on the
same subject written in 1744 (6),
Rouelle pointed out that the number of
known salts had increased significantly
during the 17th and early 18th centuries,
due not only to the preparation of
new salts, but also to an increasing ability
to distinguish between sodium and
potassium compounds, and to a generalization
of the concept so as to include
many substances, such as the alums and
vitriols (i.e., sulfates), that had been previously
excluded.
In order to incorporate this extended
concept of salt formation,
Rouelle explicitly defined a neutral salt
as the product formed by the union of
an acid with any substance, be it a watersoluble
alkali, a volatile alkali, an absorbent
earth, a metal, or an oil, capable of
serving as “a base” for the salt “by giving
it a concrete or solid form”.