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What does the $-1$ mean in the expression $2\mu g/L^{-1}$? Does it literally mean multiply by $-1$?

C_B
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$2\mu g/L$ or $2\mu g L^{-1}$ means $2$ micrograms per litre. I don't think anyone would write $2\mu g/L^{-1}$, though that (in the weird situation) would be equivalent to $2\mu gL$.

The $-1$ refers to the exponent of $L$ in the unit. For any nonzero real number $a$, $a^{-1}$ can be taken to mean $\frac1a$.

  • 2μg/L or 2μgL−1 are the same? How can that be? I can't rationalise that. – C_B Jan 26 '14 at 18:27
  • So does that not mean that it is simply creating fractions? – C_B Jan 26 '14 at 18:30
  • I think I'm starting to get it. I have read a research paper where it's denoted as 2μg/L^-1 , is that specific a rarity? – C_B Jan 26 '14 at 18:32
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    I think in the paper with $\mu$g/L$^{-1}$ it is an error. Someone intended $\mu$g/L but then switched to the equivalent $\mu$gL$^{-1}$ but forgot to complete the change. – GEdgar Jan 26 '14 at 18:40