[Om3] [OM3] [Om] units

[James Davenport]

On Fri, 13 July 2007, Alberto wrote:
> John Ogilvie wrote
>> It would be helpful ...
>	It would indeed. For instance, while my understanding of the mol
> was correct...
Apologies for any confusion. I was trying, badly, to say that 'mol' was
not a unit of mass.
>	About the other point, the mole (symbol 'mol') is a SI unit
<snip>
> http://www.bipm.org/en/si/base_units
Indeed so. This site says.
> 1. The mole is the amount of substance of a system which contains as
> many elementary entities as there are atoms in 0.012 kilogram of carbon
> 12; its symbol is "mol".
> 2. When the mole is used, the elementary entities must be specified and
> may be atoms, molecules, ions, electrons, other particles, or specified
> groups of such particles.
As I read part 2, there is no such thing as 'a mole', only 'a mole of X',
which is what I was trying, imperfectly, to state.
Inasmuch as clause 1 des define anything, it says that the mole is
Avogadro's number, since a natural number can be regarded as the
equivalent class of all sets which are in 1-1 correspondence with it, in
its ZF incarnation.
Hence the mathematician in me would regard this as dimensionless. However,
the web-site attributes to it a 'dimension', so that we can have units.
As it says, "the Avogadro constant has the coherent SI unit reciprocal
mole".
Hence to concur with BIPM, we should create a dimension (BIPM don't seem
to name the dimension), and have mol as a unit of that dimension.
James Davenport