# How can the empirical formula of a compound be experimentally found?

Microanalysis of organic compounds typically takes an accurate mass of unknown compound and burns it under controlled conditions. So if you take the generic ${C}_{n} {H}_{m} {O}_{p}$, and burns it, you get the combustion products, $C {O}_{2}$, and water.
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 $C$ and $H$, and (in a separate experiment depending on the analyzer) $N$. There should be other answers on these boards that go into more detail.