The concept of a positive hydrogen entity, later called the hydrogen ion and proton, seems to have started with Theodor von Grotthuss in 1805. The conception proposed by von Grotthuss has evolved via the works of many scientists; especially the contributions of Justus Liebig, Svante Arrhenius, S. P. L. Sorensen, I. M. Kolthoff, and R. P. Bell. This process of evolution has at times led to confusion, yet even after more than two centuries of use, the earlier model (though dressed in different trappings) still is intact. (Contains 5 notes.)