问:在表达消毒剂使用浓度时,常见到“ppm”一词。请问ppm是什么意思?(北京读者张红) 答:ppm是英文百万分之一的缩写,原文是parts per million。亦即1:1,000,000(10~(-6))。该词多用于表示水溶液的浓度,或空气中混有其他气体的浓度。在消毒学中,用于水溶液浓度时,多表示重量比, Q: The expression “ppm” is commonly used when expressing disinfectant concentrations. What is the meaning of ppm? (Beijing Reader Zhang Hong) A: ppm is one millionth of an acronym in English, the original is parts per million. That is 1: 1,000,000 (10 ~ (-6)). The term is often used to indicate the concentration of an aqueous solution, or the concentration of other gases mixed in the air. In disinfection, for the concentration of aqueous solution, said more than the weight ratio,