Abstract: For the determination of the protonation constants of aminocarboxylatc ligands and the stability constants of their calcium chelales in the presence of cholate and deoxycholate,some modifications were introduced into the traditional potcntiomet-ric method.Obviously,these constants,thus determined are in nature,conditional,because the bile acids are surfactants,acids as well as complexing agents.By means of these methods,the conespending constants for EDTA,DTPA,EGTAand NTAwere determined as the function of the concentration of bile acids.The bile acids affect both the proton transfer t.nd coirpkxation prcccsscs,but the protonation constants change less than the stability constants.It is noted that the bile acids affect these constants in some concentrations lower than CMC.Thus their oligomer bind with cations(H⁺or Ca²⁺).