The first dissociation exponent of carbonic acid as a function of pH.

Ever since Henderson in 1908 introduced Guldberg & Waage’s Law of Chemical Equilibrium (1867) in biology applied to the dissociation of carbonic acid, new studies on the first dissociation exponent of carbonic acid in plasma have appeared in the literature. (Hasselbalch 1916, Warburg 1922, Hastings, Sendroy & Van Slyke 1928 and Severinghaus, Stupfel & Bradley 1956). There is, however, still discussion about the correct value, the latest figures varying from 6.086 (Severinghaus et al. 1956) to 6.13 (Gambino 1961)’ a t a temperature of 38” C. Further, Severinghaus et ul. (1956) found a considerable variation of pK with pH (A pK /A pH = 4 . 0 4 4 at 37.5” C) without explaining this variation in detail. A similar variation was found in cerebrospinal fluid by Alexander, Gelfand & Lambertsen (1961), and finally Van Heist, Visser & Maas (1961) briefly reported a variation in pure bicarbonate solutions. The purpose of this study was to deter-