OH - , when dissolved in water. Although this was and still is a useful and valid definition, is has two major limitations. First, it was limited to water solutions. Although his definition was limited, it certainly was a giant step in the study of chemistry. His work was eventually recognized with the 1903 Nobel Prize in chemistry.
Many acids release only a single hydrogen ion per molecule into solution.
Such acids are called monoprotic. Examples include hydrochloric acid, HCl, and nitric acid, HNO 3 . Diprotic acids can release two hydrogen ions per molecule. H 2 SO 4 is an example. Triprotic acids, like H 3 PO 4 can release three hydrogen ions into solution.