  In this paper based on ROSAT/PSPC data we investigate the emission measure
profiles of a sample of hot clusters of galaxies (kT>3.5keV) in order to
explain the differences between observed and theoretically predicted L_X-T
relation. Looking at the form of the emission measure profiles as well as their
normalizations we find clear indication that indeed the profiles have similar
shapes once scaled to the virial radius, however, the normalization of the
profiles shows a strong temperature dependence. We introduce a M_gas-T relation
with the dependence M_gas propto T^1.94. This relationship explains the
observed L_X-T relation and reduces the scatter in the scaled profiles by a
factor of 2 when compared to the classical scaling. We interpret this finding
as strong indication that the M_gas-T relation in clusters deviates from
classical scaling.
