過マンガン酸カリウム
For many years, the strong oxidizing agent potassium permanganate (KMnO4) was used for measuring chemical oxygen demand. Measurements were called "oxygen consumed" from permanganate, rather than the "oxygen demand" of organic substances. Potassium permanganate's effectiveness at oxidizing organic compounds varied widely, and in many cases biochemical oxygen demand (BOD) measurements were often much greater than results from COD measurements. This indicated that potassium permanganate was not able to effectively oxidize all organic compounds in water, rendering it a relatively poor oxidizing agent for determining COD.