  Power-law cosmologies, in which the cosmological scale factor evolves as a
power law in the age, $a \propto t^{\alpha}$ with $\alpha \ga 1$, regardless of
the matter content or cosmological epoch, is comfortably concordant with a host
of cosmological observations.} {In this article, we use recent measurements of
the X-ray gas mass fractions in clusters of galaxies to constrain the $\alpha$
parameter with curvature $k = \pm1, 0$. We find that the best fit happens for
an open scenario with the power index $\alpha = 1.14 \pm 0.05$, though the flat
and closed model can not be rule out at very high confidence level.} {Our
results are in agreement with other recent analyses and show that the X-ray gas
mass fraction measurements in clusters of galaxies provide a complementary test
to the power law cosmology.
