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.C, below the wellk now ice-NaCl*2H2O eutectic point (-21.1degC, 23.3 wt.%) of equilibrium both phase diagram. The new low-temperature eutectic was detected for all samples, in two-phase regions, H2O-NaCl*2H2O and NaCl*2H2O-NaCl. The new eutectic temperature is close to the value of -28degC 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) + 2H2O(cr) = NaCl*2H2O(cr) + DH (-0.73 +- 0.07 kJ mol-1).
Compounds
#
Formula
Name
1
H2O
water
2
ClNa
sodium chloride
3
ClH4NaO2
sodium chloride dihydrate
Datasets
The table above is generated from the ThermoML associated json file (link above).
POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied;
the numbers refer to the table of compounds on the left.