# Expressing capital M for molar in siunitx package

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

\SI{}{\micro\molar}


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.

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

\DeclareSIUnit\molar{\mole\per\cubic\deci\metre}
\DeclareSIUnit\Molar{\textsc{m}}

• Yes. Using the second definition will then provide a \Molar command that can be used like any other regular SI units. So in your example, you would write \SI{}{\micro\Molar} to get the output you asked for. – Alan Munn Sep 6 '11 at 1:03
• I tried creating an siunitx.cfg file containing \ProvidesFile{siunitx.cfg} \DeclareSIUnit\Molar{\textsc{m}} in C:\texlive\2010\texmf-dist\tex\latex\siunitx\config and C:\texlive\2010\texmf-dist\tex\latex\siunitx, neither locations worked. Do you know what I'm doing wrong? – ptrcao Sep 6 '11 at 1:25
• @ptrcao Take a look at this question: Where do I place my own .sty files. You need to put them in your local texmf folder, not in C:\texlive... – Alan Munn Sep 6 '11 at 2:53
• @JosephWright when I use the first declare I get mol/d^3m rather than mol/dm^3. I switched it to \DeclareSIUnit\molar{\mole\per\deci\cubic\metre} – Trefex Apr 7 '14 at 14:24
• @Trefex Sounds like you have something odd in your input: bet to ask a new question with a MWE of what you are doing (or mail me directly: joseph.wright@morningstar2.co.uk). – Joseph Wright Apr 7 '14 at 14:28

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

\DeclareSIUnit{\molar}{M}

• The Molar M should always be small caps! So \DeclareSIUnit{\Molar}{\textsc{m}} is better. It actually is part of siunitx anyways. – basseur Oct 12 '17 at 14:13