Coulometric titrator

Claim 1

A coulometric titrator for determining the amount of a specific ion in a sample solution by the reaction with a reactive ion comprising: (a) a cell for containing said sample solution and including electrodes for immersion in said solution, said electrodes including a reference electrode providing a first signal voltage and a specific ion sensing electrode providing a second signal voltage representing the logarithm of the concentration of the specific ion in said sample solution; (b) differential input amplifier means having as inputs said first and second signal voltages from said reference and specific ion sensing electrodes and said differential input amplifier having as its output an error signal voltage representing the difference between said first and second signal voltages; (c) reversing switch means receiving as input said error signal voltage and providing as output said error signal voltage in either the positive or negative sense depending on the position of said switch; (d) reference means providing a reference voltage for the specific ion in the solution indicative of a particular rate of change of the second signal voltage while said rate of change of the second signal voltage is constant; (e) comparator means receiving as inputs the signal voltage from said reversing switch and said reference voltage and providing as its output a sensor signal voltage representing the difference between said error signal and reference voltages; (f) antilogarithm converter means receiving said sensor signal voltage and having an output signal that is a function of the antilogarithm of said sensor signal voltage, said function being represented by the equation: i = i.sub.o antilog [[-D(E-E.sub.o)]] (-D(E-E.sub.o)), where i = output signal current i o = referencing current E-E o = sensor signal voltage D = slope of the function plotted on semi-logarithmic paper; (g) means for adjusting said slope D, said means adapted to give slopes ranging from 0.020 to 0.059; and (h) reactive ion source means in the sample solution receiving said output signal and associated with a current source providing an unidirectional current flow between an anode and a cathode immersed in the sample solution and said reactive ion source means is either the anode or the cathode with the other being inert and with the quantum rate of reactive ion introduction into the sample solution being proportional to said output signal, whereby said second signal voltage changes at a constant rate with time and said reactive ion addition changes in a logarithmically decreasing amount with time in the sample solution until the stoichiometric end point is approached.