Prediction Versus Composition of the Amount of Ice Formed in Water + Solute Droplets Dispersed in a W/O Emulsion

This paper deals with the investigation of the effect of solute concentration on the amount of ice formed within some materials such as NaCl + water and glycerol + water solutions dispersed into a W/O emulsion. The investigations were carried out by inserting sample emulsions into a Differential Scanning Calorimeter (DSC-131 evoSetaram, France). The sample emulsions were submitted to a steady cooling-heating program at constant heating rate,  = 2.5 K/min between + 20 and – 60 °C in order to get the freezing of water during cooling and its melting during heating. The proportion of ice formed, P was then calculated from the area of the recorded melting signal related to the amount of water frozen. The values obtained were compared to the ones deduced from thermodynamics treatments that needs the knowledge of the conditions of freezing of the solutions in the equilibria domain ice + solution completed by the extension of the equilibrium curve ice + solution in the metastable area of the solutions respect to the salt. The results obtained are in good agreement for glycerol solutions. For NaCl solutions the results obtained from DSC determination show lower values due to the difficulties to determine precisely the ice melting energies deduced from the melting signals. In that case the theoretical determination from the phases diagram appears to be more reliable.