Accession Number : ADA185751

Title :   Geochemistry of Freezing Brines, Low-Temperature Properties of Sodium Chloride,

Corporate Author : COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH

Personal Author(s) : Thurmond, Valerie L ; Brass, Garrett W

PDF Url : ADA185751

Report Date : Aug 1987

Pagination or Media Count : 16

Abstract : Thermodynamic properties of electrolyte solutions change rapidly below 25C, but these properties are seldom measured over the low temperature range (below 0C), even though some salt solutions can remain unfrozen to -50C. The heat capacities of concentrated solutions (0.5-0.6 molal) of NaC-H2O were measured from 25C to -40C 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 NaC and H2O, respectively, below o C. Supercooling of the solutions was encouraged by using a fast scan rate (10d2/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 experiment freezing point of NaC solutions. Keywords: Chemical properties; Electrolytes.

Descriptors :   *BRINES, *FREEZING, *GEOCHEMISTRY, *SODIUM CHLORIDE, CALORIMETERS, CHEMICAL PROPERTIES, COEFFICIENTS, COLD REGIONS, COOLING, ELECTROLYTES, EQUATIONS, HEAT, HIGH RATE, ICE, LOW TEMPERATURE, OSMOSIS, RANGE(EXTREMES), SALINE SOLUTION, SCANNING, SOLID PHASES, SOLUBILITY, SOLUTIONS(GENERAL), SOLUTIONS(MIXTURES), SPECIFIC HEAT, SUPERCOOLING, TEMPERATURE, THERMODYNAMIC PROPERTIES, THERMODYNAMICS, PHASE TRANSFORMATIONS, CALCIUM COMPOUNDS, SEA WATER, ENTHALPY

Subject Categories : Physical and Dynamic Oceanography

Distribution Statement : APPROVED FOR PUBLIC RELEASE