The buffer value of weak acids and bases: origin of the concept, and first mathematical derivation and application to physico-chemical systems. The work of M. Koppel and K. Spiro (1914).

A translation is offered of a paper by M. Koppel and K. Spiro, published in 1914, and entitled: 'On the action of moderators (buffers) in the shift of the acid-base equilibrium of biological fluids'. In this work, which appeared in Vol. 65 of the Biochemische Zeitschrift, the authors introduced the modern concept of buffer value and, for the first time, quantified the buffering power of weak acids and bases, ampholytes, dibasic acids, and mixtures of buffers. The circumstances that surround the eclipse of this trailblazing research have been critically examined, and biographical details have been provided.