ニクロム酸カリウムを用いるCOD測定法の簡易化

概要

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An oxidizing reagent consisting of the mixture of 2.5g of potassium dichromate, 10g of silver sulfate, 600ml of sulfuric acid and 400ml of phosphoric acid was recommended to use for the simple and rapid determination of COD of various waste waters. A 10-ml portion of sample water was put into a 50-ml Kjeldahl flask with 0.3g of mercury(II) sulfate and several pieces of boiling stone, and 25ml of the reagent-mixture was added. The solution was boiled at 160℃ for 30 min, setting a cooling finger inside the neck of the flask. The contents of the flask was transferred into a 50-ml measuring flask and was diluted with water to the mark. The absorbance of the solution was measured at the wavelength of 630nm with a 50-mm glass cell. Beer's law was obeyed over the range of 0〜1000ppm COD. The calibration curves using glycine, glucose, ethanol and starch, as the reference, gave their slope of 7.05×10^<-4> as the mean. Therefore, the COD value can be calculated from the following equation : GOD=absorbance/7.05×10^<-4>. An appropriate volume ratio of sulfuric add to phosphoric acid for the decomposition of glycine was found to be 3:2. The reaction time could be reduced to about one fourth of JIS(COD_<Cr>) method. The analytical results obtained for several kinds of industrial waste water are in good agreement with those obtained by JIS(COD_<Cr>) method.
社団法人日本分析化学会の論文
1978-11-05