1. J. N. Brönsted, Rec. Tray. Chim., 42, 718 (1923).
2. It is frequently stated that the acid-base definition given here was put forward almost simultaneously by Brönsted and by T. M. Lowry [Chem. and Ind.,42, 43 (1923)]. However, although Lowry's paper undoubtedly contains many of the ideas underlying this definition, especially for bases, it does not contain an explicit definition, and it is nowhere made clear that Lowry at that time regarded NH4 as an acid or CH3CO
3. as a base. In fact, in a later paper [J. Chem. Soc.,2562 (1927)], Lowry himself writes, More novelty is to be found in the perfectly logical conclusion of Brönsted that the anion of an acid is also a base or proton acceptor, in view of the fact that it can combine with a proton to form a molecule of the undissociated acid': hence it does not seem justifiable to regard Lowry as one of the originators of the definition. I am indebted to the late Professor E. A. Guggenheim for calling my attention to this point. It is also noteworthy that G. N. Lewis (Valency and the Structure of Atoms and Molecules,(Reinhold, New York, 1923, p. 141) gave the same acid-base definition, and wrote, '… we may regard the ammonium ion as an acid'. However, he did not follow up the consequences of this view, and preferred the alternative definition of acids with which his name is usually associated.
4. P. Walden, Salts, Acids, and Bases: Electrolytes: Stereochemistry, Cornell, New York, 1929.
5. J. L. Gay-Lussac, Gab., Ann. Phys., 48, 341 (1814).