CHEMICAL ANTAGONISM OF IONS : IV. EFFECT OF SALT MIXTURES ON GLYCINE ACTIVITY

The pH of a 0.01 molar solution of glycine, half neutralized with NaOH, is 9.685. Addition of only one of the salts NaCl, KCl, MgCl(2), or CaCl(2) will lower the pH of the solution (at least up to 1 micro). If a given amount of KCl is added to a glycine solution, the subsequent addition of increasing amounts of NaCl will first raise the pH (up to 0.007 M NaCl). Further addition of NaCl (up to 0.035 M NaCl) will lower the pH, and further additions slightly raise the pH. The same type of curve is obtained by adding NaCl to glycine solution containing MgCl(2) or CaCl(2) except that the first and second breaks occur at 0.015 M and 0.085 M NaCl, respectively. Addition of CaCl(2) to a glycine solution containing MgCl(2) gives the same phenomena with breaks at 0.005 M and 0.025 M CaCl; or at ionic strengths of 0.015 microCaCl(2) and 0.075 microCaCl(2). This indicates that the effect is a function of the ionic strength of the added salt. These effects are sharp and unmistakable. They are almost identical with the effects produced by the same salt mixtures on the pH of gelatin solutions. They are very suggestive of physiological antagonisms, and at the same time cannot be attributed to colloidal phenomena.