Formation of NaCl eutectics in water-in-oil emulsion

It is shown by thermal analysis and optical microscopy observations that when an NaCl aqueous solution is cooled as a water-in-oil emulsion, a metastable eutectic is formed that has a eutectic point at around −28 °C. The concentration at which the −28 °C eutectic (solid H 2 O + solid NaCl) melting peak occurs is found by differential scanning calorimetry to be 0.5-2.5 mol kg −1 , with no peak found at concentrations above 3.0 mol kg −1 . Furthermore, although the heat of eutectic melting increases when the final temperature during cooling is −49 to −51 °C, this decreases at lower temperatures. The conditions for forming this −28 °C eutectic can be understood based on a phase diagram created from existing research data. This suggests that it is possible to predict the formation of the eutectic under non-equilibrium conditions by using (extending) the hydrohalite (NaCl·2H 2 O) curve (HH curve) and the NaCl solubility curve (HA curve) obtained under equilibrium conditions. It is shown by thermal analysis and optical microscopy observations that when an NaCl aqueous solution is cooled as a water-in-oil emulsion, a metastable eutectic is formed that has a eutectic point at around −28 °C.