Consider the following reactions of acetic acid (CH3COOH), the organic acid that gives vinegar its characteristic taste:: + +Both theories easily describe the first reaction: CH3COOH acts as an Arrhenius acid because it acts as a source of H3O+ when dissolved in water, and it acts as a Brønsted acid by donating a proton to water.
Leta 1923 sta fizikalna kemika Johannes Nicolaus Brønsted in Thomas Martin Lowry neodvisno eden od drugega ugotovila, da je v kislo-bazične reakcije vključen prenos protona.