Method of polarographic measurement of the concentration of one or several depolarisers and device for carrying out this method

摘要

857,446. Electric tests. TESLA NARODNI PODNIK. March 26, 1958, No. 9702/58. Class 37 Polarographic analysis of a solution utilising a dropping mercury electrode 1 (Fig. 1) and a non-polarisable electrode 2 is effected by feeding successive drops of mercury alternatively from potentiometers 7, 8 with voltages which differ by only a small amount, the current difference, measured by a meter 5, being indicative of the concentration of the electrolyte. The duration of the mercury drops is synchronised with the change-over switch 3, 4. In a modification (Fig. 2) the voltages are derived from two sliders on a single potentiometer, and the two currents flow through a resistor 10 in parallel with a capacitor 11 whose potential difference is proportional to the current difference and is amplified at 12 and indicated at 13. In another embodiment (Fig. 8) the two voltages are derived from a potentiometer 19 and a small additional voltage across a resistor 20, the changing current being amplified at 12 and synchronously switched across capacitors 22, 23, so that meter 25 indicates the current difference at the two voltages. Feed-back resistors 27 reduce the input impedance of amplifier 12 and control its amplification. Switches 14, 15 and 24 are synchronised by pulses which also control the mercury drop rate, switch 24 enabling the output of amplifier 12 to be connected to capacitor 22 or 23 only for a short time at the end of each switching period, when the instantaneous polarographic current is effectively constant. For continuous measurement a standard reference electrode 38 is added, otherwise the input to amplifier 12 is derived directly from the non-polarisable electrode 2.