How can the empirical formula of a compound be experimentally found?
By burning a known mass.
Microanalysis of organic compounds typically takes an accurate mass of unknown compound and burns it under controlled conditions. So if you take the generic
The combustion products are shunted to a gas chromatograph, where their percentage composition may be very accurately measured. The result is a percentage BY MASS of
For compounds containing metals, or other elements, there are other means to determine the elemental composition.