Abstract From the absorption spectra it has been concluded that Pd(II) forms a 1:1 complex with pyridine-2,6-dicarboxylic acid in aqueous solution at pH 2. The influence of various concentrations of chloride on the spectr has been examined. Ternary complex formation with chloride does not occur to a measurable extent. The conditional stability constant has been determined from data collected near the equivalence point of the titration curve. With allowance for the different side-reactions in this medium at an ionic strength of 0.2, a value of log K = 16.0 ± 0.2 has been found for the stability constant.