One of the more confusing aspects of the recent literature of marine chemistry concerns the development and elaboration of the necessary dissociation constants for the many substances in seawater that associate with or release a hydrogen ion (carbonate, sulfate, phosphate, borate, etc.). Investigators in this field have used three different concentration scales for the reactants: mole per kilogram of water scale (molality); the mole per liter scale (molarity) identified by the symbol M; or a mole per kilogram of solution scale (if the solution is seawater, it is the seawater scale, sometimes called molinity). This last concentration scale is now generally universal for measurements in open ocean waters.

There are several different pH scales proposed or in use for describing the concentration or activity of the hydrogen ion in solution. Authors have not always been entirely explicit about the conventions used, and different symbols or descriptors have sometimes been used for the same convention. Caution is advised when reading the literature.