Comparison of the microcolorimetric and macrotitrimetric methods for chemical oxygen demand of oil shale wastewaters

The introduction of a prolonged cooling period to the microcolorimetric method, followed by intensive mixing minimized spectrometric interferences associated with changes in refractive index and catalyst-induced precipitate. In the macrotitrimetric method, automated titration and absorbance monitoring at 535 nm improved both accuracy and reproducibility. There was no statistical difference between the results of the two methods when used to analyse 12 oil shale wastewaters.