  We present evidence for X-ray absorption by ionized oxygen in ASCA spectra of
the prototype infrared quasar IRAS 13349+2438. This powerful (2E46 erg/s)
quasar was studied in detail with ROSAT, and the combination of the X-ray data
and optical/near-infrared spectropolarimetry strongly suggested the presence of
a dusty ionized (`warm') absorber along the line of sight to the central X-ray
source. The ASCA spectra, in contrast to an earlier claim, show evidence for
ionized oxygen edges, and the presence of such edges appears to provide the
most physically plausible interpretation of the data. Thus, the ASCA spectra
support the dusty warm absorber hypothesis. The ASCA data also allow the
physical properties of the warm absorber to be constrained far better than
before. A one-zone warm absorber model indicates the ionized column to be in
the range (2--6) x 10^{21} cm^{-2}, and it gives an ionization parameter of
xi=31^{+12}_{-12} erg cm s^{-1}. The dusty warm absorber appears to have a
density below 3E8 cm^{-3}, and it is probably located outside the broad-line
region. The dust in the warm absorber does not appear to have been heavily
sputtered or destroyed via other means. Based on the ASCA fitting, we suggest
that ultraviolet absorption lines from the warm absorber may be detectable and
discuss how they can further constrain the warm absorber properties. We compare
and contrast the X-ray properties of IRAS 13349+2438 with those of broad
absorption line quasars. We comment on the steep > 2 keV continuum of IRAS
13349+2438 and examine the relevance to some models of radiative Fe II
formation.
