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|Title:||Geochemistry of freezing brines: low-temperature properties of sodium chloride|
|Authors:||Rosenstiel School of Marine and Atmospheric Science.|
National Science Foundation (U.S.). Division of Polar Programs.
Thurmond, V. L.
Brass, Garrett W.
|Publisher:||Cold Regions Research and Engineering Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||CRREL report : ; 87-13.|
Abstract: Thermodynamic properties of electrolyte solutions change rapidly below 25°C, but these properties are seldom measured over the low temperature range (below 0°C), even though some salt solutions can remain unfrozen to -50°C. The heat capacities of concentrated solutions (0.5-6.0 molal) of NaCl- H20 were measured from 25°C to -40°C as part of a study to provide thermodynamic data of salt solutions for use in cold regions chemical and geophysical studies. A differential scanning calorimeter was used to measure specific heat capacity from cooling scans as a function of temperature and concentration. The heat capacity data were fit to the equations of Pitzer and coworkers to obtain activity and osmotic coefficients of NaCl and H20, respectively, below 0°C. Supercooling of the solutions was encouraged by using a fast scan rate (10 ° /minute) so that specific heat could be measured to lower temperatures than would be possible if the solutions were allowed to equilibrate with the solid phases. The solubility of ice was calculated and compared to the experimental freezing point of NaCl solutions.
|Appears in Collections:||CRREL Report|