  The stationary Boltzmann equation for hard and soft forces in the context of
a two component gas is considered in the slab when the molecular masses of the
2 component are different. An $L^{1}$ existence theorem is proved when one
component satisfies a given indata profile and the other component satisfies
diffuse reflection at the boundaries. Weak $L^{1}$ compactness is extracted
from the control of the entropy production term.
