The following code isn't valid but conveys my intention:


as in micro followed by a big M. I don't want to use the explicit form of micro moles per L raised to the negative one in this case.

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    Just FYI, NIST considers the M "obsolete": "The term molarity and the symbol M should no longer be used because they, too, are obsolete. One should use instead amount-of-substance concentration of B and such units as mol/dm3, kmol/m3, or mol/L." I use mol/L myself. nist.gov/pml/special-publication-811/… Commented Mar 16, 2022 at 15:21
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    @MichaelHoffman I can not find if IUPAC, which should be the appropriate institution to do so, has deprecated the term. True that they say that it appears in older books. Commented May 25, 2022 at 7:22

2 Answers 2


Joseph Wright just answered a similar question on comp.text.tex:

Take a look at the section 'loading additional units' in the manual. In version 1, I did include \molar and \Molar, but tightened up on sticking to SI units (almost) exclusively for version 2. The suggested definitions are


According to the siunitx manual (page 14), you can create your own units easily by putting the following command in the preamble:

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    The Molar M should always be small caps! So \DeclareSIUnit{\Molar}{\textsc{m}} is better. It actually is part of siunitx anyways.
    – basseur
    Commented Oct 12, 2017 at 14:13

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