Crystal growth Of MgSO4 aqueous solution on a cooled surface has been studied theoretically and experimentally. The excess entropy production rate for heat and mass transport into, out of, and across the interface was used to define the fluxes and forces of the system. The method describes the interface as a separate (two-dimensional) phase in local equilibrium. Coupled heat and mass flux equations from non-equilibrium thermodynamics were defined for crystal growth and the temperature jump at the interface of the growing crystal. All interface transfer resistivities were determined using MgSO4 center dot 7H(2)O Crystallization on a cooled surface as an example case. The coupling coefficient showed that between 20 and 30% of the enthalpy of crystallization is returned to the liquid side during crystal growth. The coupling of heat and mass transport equations at the liquid-solid interface has not been described before.