一个浓度单位

怎么都没人回贴啊，我这个问题太弱智了吗

you can get what you want from the following :
I contacted an editor at Pollution Engineering Magazine (E-mail: KCanning@cahners.com) who refered me to a Ph.D. in Germany named Dr. Thomas Schmidt (E-mail: schmidt@mpi-muelheim.mpg.de), who explained that the N term is an abbreviation of norm or normal. He continued to explain that "Normal, in this connection, means a temperature of 0 degrees Celsius and a pressure of 1.013 bar, the conditions at which one mole of an ideal gas has a volume of 22.413837 liters." This definition makes sense to me in conjunction with a flue gas measurement. Ken Johnson, an administrator with the MadSci Network (E-mail: kayjay45@home.net) confirmed this explantion with an environmental scientist in Australia. By comparison, we routinely use ppm (parts per million)in the USA for this type of measurement.
I want to Thank You, for helping me learn something new in the world of Chemistry. I would also like to thank all of the scientists that helped me to define this unit of measurement for you.

Thanks for your help

每标准立方米气体中的浓度含量（毫克）。

mg/nm3是质量百分比浓度

1、N是指标准状态。注意我国的标准状态是指101.3kp、273K，和国外的可能不同。（美国为101.3kp、293K，和3楼的解释不同）
2、另外，N往往还代表干态，有的表示为mg/NDm3
3、mg/Nm3的表示方法是不规范的，应该表式为mg/m3。具体可参见GB3100,GB3101,GB3102。遗憾的是我国目前的一些标准和教科书还是这样表达。主要是编制人员对这方面不够注意。

气体浓度单位 可以与ppm转化

不同摩尔质量（分子量）的气体，转化的系数也不一样，在0℃和20℃的时候也不一样。

如果你查不到，可以自己推算，就是那个高中化学学过的22.4那个。

N表示标准，即每标准立方米多少毫克，因为空气的摩尔数受温度等影响比较大，所以有这么一个单位。