Different numbering for chemical reaction and numerical equation

[Andreas D�ring]

During writing my thesis I ran into this problem:
I use chemical reactions and numerical equations in the text. The
problem is, to number the different equations in a different way, like:

1+1=2                (2.1)
1+2=3                (2.2)

but for chemical reaction something like

C+O2->CO2    (R. 2.1)

and so on.

The equations and reactions are written in  math-mode and the automatic
numbering was done
by using M-m n.


Thanks in advance

Andi