[siunitx]: Best practice to declare micromolar

[Uwe Siart]

Hello,

if in 'siunitx' one wants to declare a new abbreviation for e.g.
micromolar and one needs (the publisher insists upon) the notation "µM"
instead of "\micro\mole\per\cubic\meter" then what is the best practice
to do so? My straight idea would be

\DeclareSIUnit{\uM}{\micro M}

However, the documentation says that "literal text should not be
intermixed with unit macros". So is it save to say "\micro M"? Or should
\micro be replaced by anything else (\textmu)? Or a very different
beast?

[Joseph Wright]

Post by Uwe Siart
Hello,
if in 'siunitx' one wants to declare a new abbreviation for e.g.
micromolar and one needs (the publisher insists upon) the notation "µM"
instead of "\micro\mole\per\cubic\meter" then what is the best practice
to do so? My straight idea would be
\DeclareSIUnit{\uM}{\micro M}
However, the documentation says that "literal text should not be
intermixed with unit macros". So is it save to say "\micro M"? Or should
\micro be replaced by anything else (\textmu)? Or a very different
beast?

I'd declare \Molar first

\DeclareSIUnit{\Molar}{M}
\DelcareSIUnit{\uM}{\micro\Molar}

[Uwe Siart]

Post by Joseph Wright
\DeclareSIUnit{\Molar}{M}
\DelcareSIUnit{\uM}{\micro\Molar}

I see. Thanks, Joseph.

[Massimo Ortolano]

Post by Uwe Siart
if in 'siunitx' one wants to declare a new abbreviation for e.g.
micromolar and one needs (the publisher insists upon) the notation "µM"
instead of "\micro\mole\per\cubic\meter" then what is the best practice
to do so?

The best practice would be to convince the publisher that the notation
"µM" is *wrong* ;-)

[b.kleine]

Post by Massimo Ortolano

Post by Uwe Siart
if in 'siunitx' one wants to declare a new abbreviation for e.g.
micromolar and one needs (the publisher insists upon) the notation "µM"
instead of "\micro\mole\per\cubic\meter" then what is the best practice
to do so?

The best practice would be to convince the publisher that the notation
"µM" is *wrong* ;-)

Please explain! This is not lab-slang but uses universal abbreviations.
Perhaps I am wrong but M = molar is Mol/liter since the first definition
of Mol. and µ for 10^-6 is correct AFAIC judge.

Bernhard

[Massimo Ortolano]

Post by b.kleine
Perhaps I am wrong but M = molar is Mol/liter since the first definition
of Mol. and µ for 10^-6 is correct AFAIC judge.

In the SI system of units, which is now adopted worldwide, "M" is a
prefix which means ten to the sixth. Using "M" to mean something else is
an error, unless you decide to use your own system of units: a
scientific publication, however, should discourage this.

[Herbert Schulz]

Post by Massimo Ortolano

Post by b.kleine
Perhaps I am wrong but M = molar is Mol/liter since the first definition
of Mol. and µ for 10^-6 is correct AFAIC judge.

In the SI system of units, which is now adopted worldwide, "M" is a
prefix which means ten to the sixth. Using "M" to mean something else
is an error, unless you decide to use your own system of units: a
scientific publication, however, should discourage this.

Howdy,

Hmmm… I think I've seen mm used all over the place and it doesn't mean
milli-milli.

Good Luck,
Herb Schulz

[Massimo Ortolano]

Post by Herbert Schulz
Hmmm… I think I've seen mm used all over the place and it doesn't mean
milli-milli.

What I'm saying is that inside the SI system of units "M" (not "m") is
only used as a prefix. If you look at the SI brochure
(http://www.bipm.org/en/si/si_brochure/) you won't find "M" to mean mole
per cubic metre, even in the list of non-SI units accepted for use
(http://www.bipm.org/en/si/si_brochure/chapter4/table6.html).

Many publishers of scientific journals and books, probably most of them,
declare that authors must stick to the SI when writing papers or books:
so, what's the point of making such declaration and then encourage the
use of non-SI units?

[Joseph Wright]

Post by Massimo Ortolano

Post by Herbert Schulz
Hmmm… I think I've seen mm used all over the place and it doesn't mean
milli-milli.

What I'm saying is that inside the SI system of units "M" (not "m") is
only used as a prefix. If you look at the SI brochure
(http://www.bipm.org/en/si/si_brochure/) you won't find "M" to mean mole
per cubic metre, even in the list of non-SI units accepted for use
(http://www.bipm.org/en/si/si_brochure/chapter4/table6.html).

Exactly the point. With one exception, siunitx only defines units which
are in the BIPM tables. (The one exception is \percent, which is not
even a unit but is so widely used that some realism is needed. Realism
also applies to \meter, which is incorrect even in US English for
spelling of the unit!)

[GT]

Post by Joseph Wright

Post by Massimo Ortolano

Post by Herbert Schulz
Hmmm… I think I've seen mm used all over the place and it doesn't mean
milli-milli.

What I'm saying is that inside the SI system of units "M" (not "m") is
only used as a prefix. If you look at the SI brochure
(http://www.bipm.org/en/si/si_brochure/) you won't find "M" to mean mole
per cubic metre, even in the list of non-SI units accepted for use
(http://www.bipm.org/en/si/si_brochure/chapter4/table6.html).

Exactly the point. With one exception, siunitx only defines units which
are in the BIPM tables. (The one exception is \percent, which is not
even a unit but is so widely used that some realism is needed. Realism
also applies to \meter, which is incorrect even in US English for
spelling of the unit!)
--
Joseph Wright

IUPAC instead seems to discourage the term molarity but not symbol for
it, see note (16) on pg.48 of last revision of the "Green Book"
(http://media.iupac.org/publications/books/gbook/IUPAC-GB3-2ndPrinting-
Online-22apr2011.pdf)

[Clemens Niederberger]

Post by Massimo Ortolano

Post by b.kleine
Perhaps I am wrong but M = molar is Mol/liter since the first definition
of Mol. and µ for 10^-6 is correct AFAIC judge.

In the SI system of units, which is now adopted worldwide, "M" is a
prefix which means ten to the sixth. Using "M" to mean something else is
an error, unless you decide to use your own system of units: a
scientific publication, however, should discourage this.

Maybe I'm mistaken but as far as I know for the »M« for »molar« one
should use a small caps »m«:

\DefinSIUnit{\Molar}{\textsc{m}}

To my knowledge that is more common than an upper case »M«.

Regards

[Joseph Wright]

Post by Clemens Niederberger
Maybe I'm mistaken but as far as I know for the »M« for »molar« one
\DefinSIUnit{\Molar}{\textsc{m}}
To my knowledge that is more common than an upper case »M«.

It varies, depending on the publisher. However, as commented by others,
it's not an officialy-recognised unit, which makes life complicated.
(There are no small cap units in the BIPM tables.)

[Uwe Siart]

Post by Joseph Wright
(There are no small cap units in the BIPM tables.)

For good reasons. I think that font attributes can never be a sufficient
means to identify units. In other words: units are identified by
/symbols/ not by font attributes.

[Lee Rudolph]

Post by Uwe Siart

Post by Joseph Wright
(There are no small cap units in the BIPM tables.)

For good reasons. I think that font attributes can never be a sufficient
means to identify units. In other words: units are identified by
/symbols/ not by font attributes.

As Count Korzybski might have said, "The glyph is not
the symbol." Or perhaps not.

(There's actually something rather deep going on here,
I think.)

Lee Rudolph

[Joseph Wright]

Post by b.kleine
Please explain! This is not lab-slang but uses universal abbreviations.
Perhaps I am wrong but M = molar is Mol/liter since the first definition
of Mol. and µ for 10^-6 is correct AFAIC judge.

BTW, using litres is also bad practice. At one stage, the definition of
one litre did not coincide exactly with 1000 cm^3! I never use litres
unless a publish insists: the unit of volume is the m^3 or part thereof.

[Uwe Siart]

I never use litres unless a publish insists: the unit of volume is the
m^3 or part thereof.

Let's continue on that road: The SI unit of fuel consumption is m^2.

10 liters
----------- = 0.1 mm^2
100 km

This is the cross section if the fuel was extruded in the shape of a
hose along the road.

;-)

[Lee Rudolph]

Post by Uwe Siart

I never use litres unless a publish insists: the unit of volume is the
m^3 or part thereof.

Let's continue on that road: The SI unit of fuel consumption is m^2.
10 liters
----------- = 0.1 mm^2
100 km
This is the cross section if the fuel was extruded in the shape of a
hose along the road.

Taking the elegant formalism of Tversky et al.'s _Foundations of
Measurement_ (which I don't claim is entirely consistent with SI),
whereby a "dimension" is a 1-dimensional vectorspace (over the
reals, generally) with basis the corresponding unit, the dual
of that space being the 1-dimensional vectorspace with basis
"per [that] unit", compounding of dimensions (and pers) being
tensor product, and so on, I would say that there *is* no
"SI unit of fuel consumption", only for each fuel an "SI
unit of [that] fuel consumption"; so your equation should
have liters-of-[that] in the numerator on the left, and
[that] as a (tensor) factor on the right (and of course
there isn't a denominator, there's just a tensor product
with the dual of "100 km", viz., "1/100 per km").

Lee Rudolph

[Uwe Siart]

Post by b.kleine
Perhaps I am wrong but M = molar is Mol/liter since the first
definition of Mol.

Right. Now that the thread gets granular on this topic I have to adjust
my posting. "µM" corresponds to "\milli\mole\per\cubic\meter" (not
"\micro\mole\per\cubic\meter").