  In the current work we propose a theory for an additional mass diffusion
effect in the conventional gas dynamics equations. We find that this effect
appears as a homogenization time limit correction, when the deterministic
interaction process of the real gas molecules is replaced with a simplified
random interaction process for consistency with the Boltzmann equation. For the
simplified random interaction processes represented by either a hard sphere
random scattering model, or by a model which employs the Lennard-Jones
potential for random molecular deflections, we compute the estimates of the
corrective diffusion coefficient in the Euler, Navier-Stokes and Grad equations
for some monatomic and polyatomic gases.
