Talk:International System of Units/Archives/05/2022

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Defining constants in the 2019 International System of Units with the hyperfine transition frequency of Cs, speed of light in vacuum, Planck constant, elementary charge, Boltzmann constant, Avogadro constant, luminous efficacy.png

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parts ber billion/trillion

"Because the value of "billion" and "trillion" varies between languages, the dimensionless terms "ppb" (parts per billion) and "ppt" (parts per trillion) should be avoided. The SI Brochure does not suggest alternatives."

I've heard that it is suggested that you should use the formula nx/x and px/x, where x is a unit, to represent ppb and ppt, and that the reason why the SI Brochure doesn't recognise ppb and ppt is because they are unitless quantities. If it is 5 parts per billion in reference to a liquid in a liquid, that should be written as 5 nl/l. The only exception would be kg which already contains a prefix, so 5 parts per billion in reference to a mass in a mass, that will instead be 5 µg/kg.

The text also glosses over "ppm" (parts per million), while not linguistically ambiguous as the other two, the same regarding the lack of unit applies here too, so 5 ppm in reference to a liquid in a liquid should be written as 5 µl/l instead. 2A01:5D0:8572:DF00:FDCF:3C3B:F0A4:A8DD (talk) 03:16, 15 May 2022 (UTC)