Elutriation, also known as air classification, is a process for separating lighter particles from heavier ones using a vertically-irected stream of gas or liquid (usually upwards). This method is profoundly used for particles with size (>1ųm) The smaller or lighter particles rise to the top (overflow) because their terminal velocities are lower than the velocity of the rising fluid. The terminal velocites of any particle in any media can be calculated using Stoke's Law given by u0A =d2Ag (ρA − ρ) /18ü