The standard applies to all types of water. Based on 20 ml of analysis sample, a lower analysis limit of the chemical oxygen consumption of approximately 10 mg/l is achievable. By adding silver sulphate as a catalyst, most organic substances are extensively oxidized. Some nitrogen compounds are not oxidized or are only oxidized incompletely. By adding mercury(II) sulphate, chloride is bound, so that in most cases it is removed from oxidation if the reaction conditions are carefully selected (see 8). However, with a high chloride content in addition to a low consumption of the added potassium dichromate, the chloride dis urbance is not completely eliminated. In this case, the influence of the dis urbance is eliminated by an empirical correction (see 9.2). Bromide is largely co-oxidized, which may require a separate correction (e.g. in seawater). Aromatic hydrocarbons and pyridine are not appreciably oxidized. Comments 1. This standard focuses on the determination of the COD of dis olved and suspended substances in the analysis sample. It is also possible to determine the COD of only the dis olved substances after filtration of the analysis sample. 2. The determination can also be used for sludge, if the sample is diluted and homogenized to such an extent that it can be classified as waste water.
NEN 6633-1990 history
1990NEN 6633-1990 Water - Determination of chemical oxygen demand (COD)