A potentiometric investigation on the behaviour of taurine as a ligand

The ligand capability of taurine was studied at 25 degrees C towards cadmiu m(II), cobalt(Il) and nickel(II) in 1.00 mol/L NaCl as constant ionic mediu m and towards cobalt(II), nickel(II), calcium(II) and magnesium(II) in 1.00 mol/L NaClO4 as constant ionic medium. In the former ionic medium, potenti ometric measurements were carried out by means of galvanic cells with a gla ss electrode and, for cadmium(ll), with an amalgam electrode, as well. In t he latter ionic medium, free hydrogen ion concentration and free taurine co ncentration were obtained from electromotive force measurements of cells co ntaining a glass and a silver electrode, respectively. The experimental dat a were explained by assuming the formation of complexes of the type ML and ML2, where M is the cation and L the taurine in basic form. The inspection of the values obtained for the stability constants seems to exclude the for mation of chelates. A comparison among the values of the constants shows di fferences between the two ionic media and can be deduced a stability order.