DETERMINATION OF CHEMICAL OXYGEN DEMAND IN WATER

MEASUREMENT METHOD  The method of measuring COD at low values is based on the  photometric registration of reduced content of bichromate ions  as a result of the reactions of these ions with organic  compounds of the sample in acidic medium when heated in the  presence of a silver catalyst. Interfering influence of chloride  ions is eliminated by addition of mercury sulfate (II) to the  analyzed sample. Photometric determination of residual  quantities of Cr (VI) ions or newly formed Cr (III) depends on the  selected working range of the method and is performed by the  FLUORAT® -02 analyzer. COD value is calculated automatically  by means of a calibration curve stored in the memory of the  analyzer.