  The role of optical Fe III absorption lines in B-type stars as iron abundance
diagnostics is considered. To date, ultraviolet Fe lines have been widely used
in B-type stars, although line blending can severely hinder their diagnostic
power. Using optical spectra, covering a wavelength range ~ 3560 - 9200 A, a
sample of Galactic B-type main-sequence and supergiant stars of spectral types
B0.5 to B7 are investigated. A comparison of the observed Fe III spectra of
supergiants, and those predicted from the model atmosphere codes TLUSTY
(plane-parallel, non-LTE), with spectra generated using SYNSPEC (LTE), and
CMFGEN (spherical, non-LTE), reveal that non-LTE effects appear small. In
addition, a sample of main-sequence and supergiant objects, observed with
FEROS, reveal LTE abundance estimates consistent with the Galactic environment
and previous optical studies. Based on the present study, we list a number of
Fe III transitions which we recommend for estimating the iron abundance from
early B-type stellar spectra.
