For a moment we only have one kind of formula in ChEBI
which in most of cases is "Molecular formula". This
implies that a molecule consists of finite and definite
number of atoms. However the other kinds of formulae
are in use. "Empirical formula" is the "simplest
possible formula expressing the composition. <...>
Molecular or ionic masses cannot be calculated from an
empirical formula" (IUPAC).
For example:
S8 (Molecular formula)
S (Empirical formula)
H12NaO6 (Molecular formula)
NaCl (Empirical formula)
A useful variation of empirical formula is "Unit
formula" used for molecules of indefinite (or infinite)
size. E.g. a unit formula for polysaccharide such as
cellulose will be C6H10O6. "Molecular formula" for such
polymers looks like (Unit formula)n or (Unit formula)∞
I suggest introducing the different kinds of formulae
in the database.
