Plate Theory and Extensions - The Plate Theory > Page 5

Bearing in mind, the change in mass will be the product of concentration and change in volume; thus, the change of mass of solute (dm) in plate (p) will be

                         dm = (Xm(p-1) - Xm(p))dV                               (3)

Now, as equilibrium is maintained in the plate (p) by definition, the mass (dm) will be distributed between the two phases, resulting in a solute concentration change of dXm(p) in the mobile phase and dXs(p) in the stationary phase. Then,


                             dm = vsdXs(p) + vmdXm(p)                         (4)


 Substituting for dXs(p) from equation (2),

                              dm = (vm + Kvs)dXm(p)                             (5)