Chapter 6: Conceptualising Acids: Reimagining a Class of Substances

This chapter discusses how the {acid} concept has shifted over time within chemistry. The Lavoisiers offered a concept that was progressive over a purely empirical notion in the sense of having theoretical content, and thus offering a testable notion of the structural features that led to a substance being an acid. However, this conception of what makes something an acid is now considered refuted and no longer canonical. The Arrhenius concept seems an advance in the common-sense terms of offering a theoretical model that better discriminates acids from other substances. Chemists today are, however, more likely to use the Brønsted–Lowry or Lewis definitions and models of acids. These models extend the traditional notion of acids, but not to correct flaws in the discriminating power of the Arrhenius model: rather to offer new conceptualisations that might be more convenient to chemists than the traditional concept. That is, the claims of these concepts to being progressive are related to greater usefulness and not greater verisimilitude. Moreover, these two models do not lead to precisely the same set of discriminations of acids, suggesting there is no unitary and unambiguous canonical {acid} concept in contemporary chemistry.