Metastable eutectic melting in the NaCl-H2O system

Metastable eutectic melting of solid mixture NaCl+H2O was measured in a wide range of its compositions by using a DSC. The new eutectic melting was found to occur near -27 degrees C, below the well know ice-NaCl center dot 2H(2)O eutectic point (-21.1 degrees C, 23.3 wt.%) of equilibrium both phase diagram. The new low-temperature eutectic was detected for all samples, in two-phase regions, H2O-NaCl center dot 2H(2)O and NaCl center dot 2H(2)O NaCl. The new eutectic temperature is close to the value of similar to-28 degrees C reported by Roedder (1984) for the mixture of solid H2O and NaCl, which was never repeated or reaffirmed independently since then. The heat effect of the metastable eutectic melting did allow us to estimate the enthalpy of formation of hydrohalite from salt and ice: NaCl(cr)+2H(2)O(cr)=NaCl center dot 2H(2)O(cr)+Delta H (= -0.73 +/- 0.07 kJ mol(-1)). (C) 2016 Elsevier B.V. All rights reserved.