The thermodynamic dissociation constant benzoic acid in methanol-water mixtures

The historical development of the concept of acids and bases, gives the impression of very fluctuating views in the course of time. The following brief discussion does not deal with the historical evolution but rather is a presentation of some of the new ideas, first put forward by Lowry and Bronsted in 1923, independently, which have brought clarity and correlation into the whole field of acid-base phenomena. The classical definition, deduced from the Arrehenius dissociation theory, was that acids and bases were substances which split off hydrogen and hydroxyl ions on solution in water. The definition in this form is hardly consistent since certain properties are attributed to the substance under circumstances different from those under which the observations are made. A substance ought to be pronounced an acid under certain conditions only if hydrogen ions or protons are released from it under the same conditions. Pure acids like acetic and nitric will perhaps not be considered as acids by this definition, if protons are undetectable when the substances are in the pure state