The stability constants of the tartrate and acid tartrate complexes of twelve metal ions have been determined by potentiometric measurements with a glass electrode using the revised values of the ionization constants of tartaric acid as determined by titration with tetramethyl ammonium hydroxide (instead of KOH or NaOH) in tetramethyl-ammonium chloride medium (instead of KCl or NaCI), because there is complex formation between alkaline metal ions and tartaric acid.The results arc summarized in the following table.