The "empirical formula" is the simplest whole number ratio that defines constituent atoms in a species. Most of the time, at least for organic compounds, this can be determined from combustion analysis, where a known mass of sample is combusted with oxygen in a furnace, and the combustion products, CO_2(g), H_2O(g), and NO_2(g) are shunted to a gas chromatograph (sometimes NO_2 is reduced back to N_2). When these readings are compared to a standard, very accurate percentage compositions with respect to C,H, and N may be measured.
These may then used to give the "empirical formula". And then, provided that some means exist to interrogate the molecular mass of the compound is available, finally the molecular formula may be obtained in that............
"molecular formula"=nxx"{empirical formula}"........where n is generally a whole number, 1, 2, etc.
See [here for some examples.](https://socratic.org/questions/what-is-empirical-formula?source=search)
