A method is presented to synthesize process flowsheets for separations of mixtures by fractional crystallization. Using equilibrium data for a candidate set of potential operating point temperatures, a network flow model is constructed to represent the set of potential separation flowsheet structures that can result. By employing specified approaches to multiple saturation point conditions, linear network constraints are obtained. Solution of the network flow model shows the optimal mass flow pattern between the candidate equilibrium states, and from this the corresponding process flowsheet is readily deduced. The method as presented is generally applicable to problems with two salts and one or more solvents, including systems forming one or more multiple salts or hydrates. Situations having multiple feeds and multicomponent products are also included. Several salt separation examples are given which demonstrate the method＇s application and show some of the types of coupled cycles that are obtained as solutions.