During the growth of the ice layer from the melt only a part of the solute molecules is incorporated into the ice and the remainder is rejected at the advancing ice–solution interface. The rejected salt molecules are carried away by diffusion in the boundary layer, δC. Under quasi steady state conditions, the amount of rejected solute molecules per unit time and unit area, G(Ci−Cs), should be equal to diffusion flux of the solute molecules in the boundary layer ( Kuroda, 1985):