  Using high resolution, high-S/N archival UVES spectra, we have performed a
detailed spectroscopic analysis of 4 chemically peculiar HgMn stars (HD 71066,
HD 175640, HD 178065 and HD 221507). Using spectrum synthesis, mean
photospheric chemical abundances are derived for 22 ions of 16 elements. We
find good agreement between our derived abundances and those published
previously by other authors. For the 5 elements that present a sufficient
number of suitable lines, we have attempted to detect vertical chemical
stratification by analyzing the dependence of derived abundance as a function
of optical depth. For most elements and most stars we find no evidence of
chemical stratification with typical 3\sigma upper limits of \Delta\log
N_elem/N_tot~0.1-0.2 dex per unit optical depth. However, for Mn in the
atmosphere of HD 178065 we find convincing evidence of stratification. Modeling
of the line profiles using a two-step model for the abundance of Mn yields a
local abundance varying approximately linearly by ~0.7 dex through the optical
depth range log \tau_5000=-3.6 to -2.8.
