  We report laser frequency stabilization by the combination of modulation
transfer spectroscopy and balanced detection of a relatively weak hyperfine
transition of the R(158)25-0 line of molecular iodine (${}^{127}$I$_{2}$),
which is used as a new frequency reference for laser trapping and cooling of
${}^{174}$Yb on the $^{1}S_{0} - {}^{3}P_{1}$ transition. The atomic cloud is
characterized by time-of-flight measurements, and an on-resonance optical depth
of up to 47 is obtained. We show laser noise reduction and characterize the
short-term laser frequency instability by the Allan deviation of the laser
fractional frequency. The minimum measured value is 3.9 x $10^{-13}$ at 0.17 s
of averaging time.
