Constant current source for automatic coulometric titrations

A simple, but versatile constant current source for automatic coulometric titrations is described. The unit is suitable for use with a commercial automatic pH titrimeter and will accommodate wide variations of mains voltage and load resistance. Coulometric titrations may be carried out "fast" or "slow" with a choice of four current ranges (2-37 mA) for titrations up to or near the end point. A slow "1mA" range is available for approaching the end point and the titration of microgram amounts of material. The automatic pH titrimeter provides for automatic change fast to slow generation of reagent and for stopping the titration at selected end points. The utility of the equipment has been demonstrated by the estimation of chromium with electrogenerated ferrous iron. The unit should be suitable for many other coulometric titrations.