[en] Determined are values of stability constants of K, Rb and Cs compounds with phenol, o-cresol, n-bromphenol, butyric and caproic acids in aqueous solutions by the method of pH potentiometric titration. Stability constant values are shown to increase with the increase of acidic dissociation constant of organic acid. The interbound effect of acidic dissociation constant values of organic reagents and stability constants of their compounds with alkali elements on the alkali element extraction is considered. In the course of alkali element extraction by different acid extragents the difference in values of acidic dissociation constants of reagents produces primary effect on metal extraction