A coulometer for determination of residual sulfite following the dechlorination of water

The kinetics of dechlorination dictate that the measurement must be completed in neutral solutions. A portable, analog circuitry-based instrument with direct readout using constant current coulometry with amperometric end point detection was developed and evaluated. An optocoupler and separate power supplies were used for circuit isolation of the detector from the generator. A range of concentrations of 0.015-25 mg SO32-/l were determined with a relative standard deviation of 1-2%. Applications involved both iodine and bromine as intermediates. The instrument has also been applied to determinations of arsenic, mercaptans, thiosulfate, copper, cyanide and ammonia for a similar concentration range.