Abstract: A multispecies, multispeed lattice Boltzmann model is presented to study the mass diffusion properties. We introduce the particles with different speed and different species. The particles of same species have same mass and speed. At each node the total momentum of all particles and the partial masses of the particles of same species are conserved. Using the Chapman-Enskog method, we have derived from the BGK Boltzmann equation the macroscopique conservation equations that yield the N-S equation and partial...