PROBLEM TO BE SOLVED: To carry out COD measurement more simply and economically than a JIS method. ;SOLUTION: One-tenth amounts or less of sample water and reagents compared with a JIS method are put in a test tube to be heated for 30 minutes at 100°C by a block heater, then cooled to stop imediately reaction, filtered with inorganic filter paper having 1.0 μm of holding particle size or less, a concentration of a permanganate ion in a filtrate is measured thereafter using absorbance in the vicinity of 525 nm or 543 nm, and a COD is calculated based on a reduced amount thereof. A spectrophotometer built-in with a program of an operation expression [expresssion (8)] for the COD based on absorbance reduction, and capable of digital-displaying an operation result is used to allow direct reading of a COD value.;COPYRIGHT: (C)2000,JPO
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