摘要：The kinds and amounts of silver salts used in the acidic COD-Mn determination were investigated. Ag2SO4 should be weighed every using time and mixed well for a long time with magnetic stirrer. If the mixing was imperfect, masking of chloride ion was insufficient and catalytic effect by Ag ion was weakend. On the other hand, AgNO3 perfectly inhibited the consumption of KMnO4 by Cl- and was easy to be handled. The catalytic effect of AgNO3 (20%, 5 ml in standard method) was sufficient unless the Cl- concentration in a sample solution was not very high. If the sample solution contains large amount of Cl- above 500 mg/l, the equivalent amount of AgNO3 to the chloride ion should be further added. But the development of catalytic effect would be low when coexisting Cl- was very high. On the determination of acidic COD values of environmental water samples, good agreement was obtained when Ag2SO4 or AgNO3 was used carefully and so AgNO3 can be used in any samples unless they contain specific contents predominantry.
关键词：water pollution;COD determination : KMnO4;silver salt;catalytic effect;chloride ion
