A study of the freezing of supercooled water dispersed within emulsions by differential scanning calorimetry

Supercooling of microsize droplets of water dispersed within emulsions has been studied by means of a differential scanning calorimeter Perkin-Elmer DSC 2. In an emulsion cooled steadily at 2.5K min -1 , the breakdown of supercooling in individual droplets is distributed in temperature over the range -37.5 degrees C to -40.5 degrees C, the most probable temperature of freezing being T*=-(39.0+or-0.5) degrees C. When an emulsion is maintained at T C , 0 degrees C>T C >T*, the freezing of individual droplets is distributed in time, the time taken to achieve total freezing of the emulsion becoming shorter as T C becomes closer to T*. If an emulsion which has been partially frozen by being maintained at T C and then melted is cooled steadily at 2.5K min -1 , then the distribution of freezing temperatures shows two most probable values of T*, -(34.0+or-0.5) degrees C and -(39.0+or-0.5) degrees C. This phenomenon is briefly discussed.