Abstract: The invention relates to coulometric measuring for the determination of the concentration and/or factor of acids or bases. A reference electrode and a measuring electrode sensitive to the activity of hydrogen ions of the indicator circuit and an anode and a cathode electrode of the generator circuit, are arranged in the measuring cell of the measuring apparatus. As a depolarizer and potential determining substance, the chloride, bromide or iodide of potassium, sodium, rubidium, cesium, calcium, strontium or barium is added in excess to the supporting electrolyte in the measuring cell.Inaccuracy and instability brought about by the diffusion potentials arising at the diaphragms can thus be eliminated.