Carbon Dioxide. The Heat Capacity and Vapor Pressure of the Solid. The Heat of Sublimation. Thermodynamic and Spectroscopic Values of the Entropy

Abstract

An apparatus for low temperature calorimetric and vapor pressure measurements on condensed gases is described. The heat capacity of solid carbon dioxide has been measured from 15 to 195°K. The heat of vaporization at the sublimation point, 194.67°K, was found to be 6030 cal./mole. The vapor pressure has been measured and the observations are closely represented by the equation: Solid carbon dioxide, 154 — 196°K; log10 P(int. cm Hg) = — (1354.210/T)+8.69903+0.0015880T—4.5107×10—6T2. The entropy of carbon dioxide gas has been calculated from the calorimetric data and the third law of thermodynamics to be 51.11 cal./deg. per mole at 298.1°K. This value is in excellent agreement with the value 51.07 cal./deg. per mole obtained from band spectrum data.

The evolution of the albedo of dark spots observed on Mars polar region

“…The symbol k stands for the thermal conductivity, q for the density, and c for the specific heat. For the calculation of the lower bound, k; q, and c are taken from Seiferlin et al (1996), Piqueux et al (2003), and Giauque and Egan (1937). For the calculation of the upper bound, k; q, and c are taken from Möhlmann (2004), which is consistent with the values used by Mellon and Phillips (2001).…”

Phase equilibria in the system CO2-H2O I: New equilibrium relations at low temperatures

“…The pressure effect on entropy for CO 2 gas was computed as -Rln(f) where R is the gas constant and f is fugacity calculated from the SRK model. Adjustments to the gas enthalpy, (dH/dP) T , whether estimated from the International Tables (Angus et al, 1976) or calculated from the expression derived by Giauque and Egan (1937), were ϽϽ 1% of the enthalpy. The solubility data summarized by Spycher et al (2003) suggest that the mole fraction of H 2 O dissolved in the gas is likely to be Ͻ0.01 for the P-T range of his equilibrium.…”

“…The strategy was to extract enthalpy and entropy data for the clathrate phase from the slope of the H ϭ GϩI curve, and then use these data with literature data on ice and solid CO 2 to calculate the trace of the SϩI ϭ H curve. Data for solid CO 2 were obtained from the heat capacity measurements by Giauque and Egan (1937) and by extraction from the slope of the CO 2 -sublimation curve. Both procedures restricted the data to temperatures less than the CO 2 triple point, 216 K.…”

Advanced CO2 Dispersion Simulation Technology for Improved CCS Safety

“…Excellent agreement between the KFX TM model predictions and the thermodynamic data were observed [12]. Excellent agreement between the predicted heat of sublimation at the sublimation point (194.67 K) and the corresponding measured value by Giauque and Egan [13] was also observed [12].…”