This paper presents the differential scanning calorimetry (DSC) results obtained from measurements of single droplets of different subeutectic concentrations (<40 wt % (NH4)(2)SO4) and diameters of similar to 1-1.5 mm. The measurements show that despite the fact that the freezing of the droplets takes place below the eutectic temperature of T-e approximate to 254.5 K, a phase separation into ice and a residual freeze-concentrated solution occurs. The residual solution is formed by the expulsion of NH4+ and SO42- ions from the ice lattice during the nucleation and growth of ice and may possess the eutectic concentration of similar to 40 wt % (NH4)(2)SO4. On further cooling, the residual solution freezes to the eutectic solid mixture of ice/(NH4)(2)SO4 at a temperature that is either above or below the ferroelectric "Curie" temperature of T-e approximate to 223 K. If the freezing of the residual solution takes place below the T-e, then (NH4)(2)SO4 crystallizes directly into the ferroelectric phase.