  In April-May 1998 the blazar ON 231 (W Com, B2 1219+28) showed an
extraordinary optical outburst alerted by the Perugia Astronomical Observatory.
The source reached the most luminous state, observed at least since the
beginning of the previous century. BeppoSAX observed ON 231 in the band from
0.1 up to 100 keV, detecting an X-ray spectrum with a peculiar concave profile,
that could be considered as a signature of the intermediate blazar subclass.
The spectral energy distributions (SED) of blazars were studied with a time
dependent synchrotron self-Compton (SSC)model, tested here on this object. Even
with the preliminary ``toy'' model of a single flaring region, emitting by
means of mere SSC process, the X-ray spectrum is reasonably reproduced. The SED
was calculated with a hard spectrum of the injected electrons and with other
physical parameters comparable to previous works, validating a base consistence
of the method.
