General treatment of pH-solubility profiles of weak acids and bases and the effects of different acids on the solubility of a weak base.

The pH-solubility profile of a weak acid or base is shown to be a function of its pKsp, pKa, and uncharged species solubility. Equations are presented that can be used to calculate the solubility as a function of pH. These equations can also be used when there is added salt present. Experimental data was obtained in three cosolvent systems consisting of methanol-water and ethanol-water. Also, the effect of different acids on the solubility of a weak base is reported. A pronounced effect on the solubility by the addition of salt is explained in terms of the Ksp.

[1]  J. B. Bogardus,et al.  Solubility of doxycycline in aqueous solution. , 1979, Journal of pharmaceutical sciences.

[2]  H. Krebs,et al.  159. Dissociation constant, solubility, and the pH value of the solvent , 1945 .

[3]  D. D. Perrin.  Dissociation Constants of Organic Bases in Aqueous Solution , 1965 .

[4]  I. Setnikar.  Ionization of bases with limited solubility. Investigation of substances with local anesthetic activity. , 1966, Journal of pharmaceutical sciences.

[5]  M. Rowland,et al.  Dissociation constants of sparingly soluble substances: nonlogarithmic linear titration curves. , 1971, Journal of pharmaceutical sciences.

[6]  R. Bates,et al.  Determination of pH;: Theory and practice , 1964 .

[7]  H. L. Johnston,et al.  The Solubility of Gold Hydroxide in Alkali and Equilibria in the Saturated Solutions1 , 1938 .

[8]  A. L. Green,et al.  Ionization constants and water solubilities of some aminoalkylphenothiazine tranquillizers and related compounds , 1967, The Journal of pharmacy and pharmacology.

[9]  E. Berl,et al.  Zur Kenntnis des Scheeleschen Ätznatronprozesses , 1907 .

[10]  L. Benet,et al.  General method for determining macrodissociation constants of polyprotic, amphoteric compounds from solubility measurements. , 1978, Journal of pharmaceutical sciences.

[11]  Z T Chowhan,et al.  pH-solubility profiles or organic carboxylic acids and their salts. , 1978, Journal of pharmaceutical sciences.

[12]  James N Butler,et al.  Ionic Equilibrium: A Mathematical Approach , 1964 .

[13]  G. Flynn,et al.  Solubility of organic hydrochlorides. , 1972, Journal of pharmaceutical sciences.