On a possible difference between the barycentric velocity and the velocity that gives translational momentum in fluids

This paper explores the rather controversial proposal by Howard Brenner that the velocities that follow from the mass flux and from the translational momentum in a fluid, are not equal. We show that standard non-equilibrium thermodynamics can be formulated such that it is in full agreement with this proposal. We argue that the merits of the proposal must be based on the physics of the problem. It cannot be dismissed as being in contradiction with non-equilibrium thermodynamics. We show that Brenners proposal gives a separation in a binary mixture beyond that of the Soret equilibrium, due to a gradient in the pressure divided by the temperature. Possible experiments to verify this are discussed.