| 摘要 |
PURPOSE:To reduce the cost of measurement greatly by obtaining the result of actual measurement without silver salt added by measuring chlorine ion concentration in sample water and by adding potassium permanganate, and then by obtaining a COD value by multiplying said result by an oxidation factor coefficient. CONSTITUTION:On the basis of a preliminary measurement resut, computer 6 determines the amount of dilution to sampled water 1' so that the titration amount of potassium permanganate will be 4-6ml, for example. Consequently, computer 6 supplies sampled water 1' and diluting water 12 to reaction tank 9. Then, sulfuric acid 15 and potassium permanganate solution 18 are similarly fed to tank 9 by 10ml each and heatd, and sodium oxalate solution 21 is added by 10ml to the mixed solution in tank 9, 30min later to stop the reaction.Next, valve 22 is opened to supply potassium permanganate solution 18 to tank 9 for titration. Next, computer 9 calculates the amount of potassium permanganate, subtracts it from the titration amount of potassium permanganate in measurement, and by multiplies the difference by an oxidation factor coefficient to obtain a COD value. Thus, the number of measuring circuits is decreased and the cost can be reduced greatly. |
