1884年阿仑尼乌斯发现,氢离子的存在是水溶液产生酸性的原因,而且可用氢离子浓度来表示酸度。此后,通常用[H~+]表示溶液中H~+的摩尔浓度。 当然,溶液中的氢离子并非是游离的质子,它们实际上总是和溶剂分子相结合的。因此水中的氢离子浓度实际上是水化离子H_3O~+的浓度。本文为讨论方便起见仍用[H~+]代表它。 In 1884, Arrhenius discovered that the presence of hydrogen ions is responsible for the acidity of the aqueous solution, and that the acidity can be expressed in terms of hydrogen ion concentration. Thereafter, the molar concentration of H~+ in the solution is usually expressed by [H~+]. Of course, the hydrogen ions in the solution are not free protons, and they are actually always bound to solvent molecules. Therefore, the hydrogen ion concentration in water is actually the concentration of hydration ion H_3O~+. This article is still represented by [H~+] for convenience of discussion.