  Chemical abundances of the early-B type components of the binary V578 Mon are
derived from disentangled component spectra. This is a pilot study showing
that, even with moderately high line-broadening, metal abundances can be
derived from disentangled spectra with a precision 0.1 dex, relative to
sharp-lined single stars of the same spectral type. This binary is well-suited
for such an assessment because of its youth as a member of the Rosette Nebula
cluster NGC 2244, strengthening the expectation of an unevolved ZAMS chemical
composition. The method is of interest to study rotational driven mixing in
main-sequence stars, with fundamental stellar parameters known with higher
accuracy in (eclipsing) binaries. The paper also includes an evaluation of the
bias that might be present in disentangled spectra.
