  On the basis of Stokes parameter calculations for the Fe I 524.7 and 525.0 nm
lines and the Holweger-Muller model atmosphere, the effect of the anomalous
dispersion on solar magnetic field measurements by the line-ratio method is
analyzed. It is shown that with the present-day observational accuracy the
anomalous dispersion should be taken into consideration in the line-ratio
method only when the following four conditions are fulfilled simultaneously: a)
the inclination of the magnetic lines to the line of sight does not exceed 20
degrees; b) the magnetic field strength is larger than 100 mT; c) the cross
profile of the magnetic field in subtelescopic flux tubes is rectangular; and
d) the parts of the magnetically sensitive line profiles close to the line
center (<4 pm) are used.
