Suppose we have the following chemical formula, say ammonium dihydrogenphosphate #(NH_4)(H_2PO_4)#. This is the ammonium salt of phosphoric acid, #H_3PO_4#. Its elemental composition is #NH_6PO_4#, and here I have simply added the elements; but such a composition makes little chemical sense in that it is not immediately obvious that it is the ammonium salt of phosphoric acid, as the first formulation does.
Alternatively, I could have a transition metal complex, say #[Co(Me_2NCH_2CH_2NMe_2)_2Cl_2]Cl#. If I made this and sent it off for combustion analysis I would present it as #CoCl_3C_12H_32N_4#. After combustion, the carbon would come off as #CO_2#, the hydrogens as #H_2O#, and the nitrogens as #N_2#, and I would get a very accurate determination of the purity of my compound. A Mohr tritration would give halogen content.
If this doesn't address your question, would you clarify?
