Means and method for determining chemical oxygen demand

摘要

The invention relates to a means and a method for the photometric determination of the chemical oxygen demand of chloride-containing samples.

主权项

1. Method for the determination of the Chemical Oxygen Demand (COD) content in chloride-containing samples by
a) expulsion of chloride ions from a sample by treatment with sulfuric acid b) mixing of at least some of the sample obtained from step a), with a reagent solution comprising
0.1 to 2.5% (w/w) potassium dichromate (K2Cr2O7)0.1 to 2% (w/w) silver sulfate (Ag2SO4)optionally mercury(II) sulfate (HgSO4)watersulfuric acid characterised in that the sulfuric acid content of the reagent solution is between 20 and 50% (w/w) and the reagent solution is prepared by mixing solutions which comprise:
at least one solution which contains at least potassium dichromate and water, but no silver sulfate and no mercury(II) sulfate, anda solution which contains at least silver sulfate and sulfuric acid, but no mercury sulfate and no potassium dichromate c) incubation of a mixture from step b) for at least 20 minutes at a temperature above 100° C. d) photometric determination of the COD content of the mixture from c).