  We have used non-simultaneous Ginga, ASCA and ROSAT observations to
investigate the complex X-ray spectrum of the Seyfert 2 galaxy Mrk 3. We find
that the composite spectrum can be well described in terms of a heavily cut-off
hard X-ray continuum, iron K_alpha emission and a soft X-ray excess, with
spectral variability confined to changes in the continuum normalisation and the
flux in the iron line. Previous studies have suggested that the power-law
continuum in Mrk 3 is unusually hard. We obtain a canonical value for the
energy index of the continuum (i.e. alpha approx 0.7) when a warm absorber
(responsible for an absorption edge observed near 8 keV) is included in the
spectral model. Alternatively, the inclusion of a reflection component yields a
comparable power-law index. The soft-excess flux cannot be modelled solely in
terms of pure electron scattering of the underlying power-law continuum.
However, a better fit to the spectral data is obtained if we include the
effects of both emission and absorption in a partially photoionized scattering
medium. In particular the spectral feature prominent at $\sim 0.9$ keV could
represent O VIII recombination radiation produced in a hot photoionized medium.
We discuss our results in the context of other recent studies of the soft X-ray
spectra of Seyfert 2 galaxies.
