Transistorized power sources for constant current coulometric titration

, John T. Stock

University of Connecticut Storrs, 06268

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Transistorized Power Sources for Constant Current Coulometrk Titration

Although lacking the precision of an amperostat based on operational amplifiers ( I , 92) or on comparator-converter systems (9), a "constant current" supply that is a battery in series with a resistor has the great advantage of simplicity (4, 6). This series resistor must be large in order to Beep the current essentially independent of the e.m.f. developed across the generating electrode system of the titration cell. A 50- to 100-v battery or other supply is, therefore, needed. Most of the power is wasted in heating the reslstor and, if an open circuit develops in the cell, a high voltage appears across the cell connections. Both of thcbc defects can be eliminated by taking advantage of the current-regulating properties of transistors that are operated in the common-base configuration (6). A coulometric titrator with single transistor current control was first reported in 1955 (7). The simplicity

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R R, 1200-ohm 1 W R ~ l ,b o h m , , l - .. - - ,. (20) MARINENKO, G., A N D TAYLOR, J. K., Anal. Chem., 40,1645 (1968).