In the potentiometric determination of stability constants, the information is very often obtained from titrations. Not only is each individual titration very lengthy because of the stabilization period for the electrode potentials and the great number of volume increments, but many such titrations are necessary to gather sufficient information. The prospect of performing such work manually offers little attraction for the investigator and increases the risk of introducing subjective criteria. Therefore the authors sought to develop semi-automatic systems with a high reproducibility for precision work without losing the advantage of the instant decision offered by manual work.