1. permanganate index is a commonly used index to reflect the pollution of organic and inorganic oxidizable substances in water. It is defined as: under certain conditions, some organic and inorganic reducing substances in water samples are oxidized by potassium permanganate, and the equivalent oxygen is calculated from the amount of potassium permanganate consumed.

2. Potassium permanganate index can't be used as an index of theoretical oxygen demand or total organic matter content, because under the specified conditions, many organic matters can only be partially oxidized, and volatile organic matters are not included in the measured values.

3. The chemical oxygen consumption measured with potassium permanganate solution as oxidant used to be called the chemical oxygen consumption of manganese. In the new environmental water quality standard of our country, this value has been renamed as permanganate index, and only the value measured by acid potassium dichromate method is called chemical oxygen demand. The International Organization for Standardization (ISO) suggested that the potassium permanganate method should be limited to the determination of surface water, drinking water and domestic sewage, but not applicable to industrial wastewater.