Amphoteric behavior of complex systems. IV. Note on the isoelectric point and ionization constants of sulfanilic acid

Abstract

From the solubility minimum the value of the basic ionization constant of sulfanilic acid is shown to lie probably between the values 1.7 x 10^–15 and 3.2 x 10^–15. From solubility measurements the value of this same constant is shown to lie probably between 2.0 and 2.2 x 10^–15, and the isoelectric point of sulfanilic acid is thus at a cH of 0.056 or a pH of 1.25. From conductivity ratios the acid ionization constant of sulfanilic acid is shown to be 7.05 x 10^–4 at room temperature (21°C.). Calculations are made, from data published in preceding papers, of the ionization constants of glycine, Ka being 2.3 x 10^–10, and Kb being 2.2 x 10^–12.

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