Liquid-membrane electrodes using as liquid ion-exchangers the solutions: bis -(O, O' -diisobutyldithio- phosphato)nickel(II), bis -(O, O' -diisobutyldihtiophosphato) -cadmium(II), and bis-(O, O'-diisobutyldithiophosphato)lead(II) in C6H5C1 are described. Such electrodes respond very Selectively Ni2+, Cd2+and Pb2+ions over the range of 10−1- 10−4M in the presence of alkali and alkali-earth ions. The Pb[S(S)p(OC4H9-iso)]2electrode is highly selective in the solutions containing H+and a number of heavy metal ions.