Compressed gases critical properties

The approach to the critical point, from above or below, is accompanied by spectacular changes in optical, thermal, and mechanical properties. These include critical opalescence (a bright milky shimmering flash, as incident light refracts through intense density fluctuations) and infinite values of heat capacity, thermal expansion coefficient aP, isothermal compressibility and other properties. Truly, such a confused state of matter finds itself at a critical juncture as it transforms spontaneously from a uniform and isotropic form to a symmetry-broken (nonuniform and anisotropically separated) pair of distinct phases as (Tc, Pc) is approached from above. Similarly, as (Tc, Pc) is approached from below along the L + G coexistence line, the densities and other phase properties are forced to become identical, erasing what appears to be a fundamental physical distinction between liquid and gas at all lower temperatures and pressures. 

The compilations of CRC (1-2), Daubert and Danner (3), Dechema (15), TRC (13-14), Vargaftik (18), and Yaws (19-36) were used extensively for critical properties. Estimates of critical temperature, pressure, and volume were primarily based on the Joback method (10-12) and proprietary techniques of the author. Critical density was determined from dividing molecular weight by critical volume. Critical compressibility factor was ascertained from application of the gas law at the critical point. Estimates for acentric factor were primarily made by using the Antoine equation for vapor pressure (11-12). 

Properties Colorless compressed gas or liquid faintly sweet ethereal odor. D 0.92 (20C), bp -23.7C, fp -97.6C, flash p approximately 32F (0C), refr index 1.3712 (—23.7C), critical temperature 143C, critical pressure 970 psi absolute, autoign temp 1170F (632C), bulk d 7.68 lb/gal (20C). Slightly soluble in water, by which it is decomposed soluble in alcohol, chloroform, benzene, carbon tetrachloride, glacial acetic acid attacks aluminum, magnesium, and zinc. 

Some models assign to the liquid either the properties of a compressed gas or those of a perturbed crystal by virtue of common properties of liquids and gases or liquids and solids. The gas-liquid continuity may be shown by experiments proving that close to the critical point, a continuous... 

Carbon Monoxide — (i) Chemical Designations — Synonyms Monoxide Chemical Formula CO (ii) Observable Characteristics — Physical State (as normally shipped) Compressed gas or liquefied gas Color Colorless Odor None (iii) Physical and Chemical Properties — Physical State at 15 C and I atm. Gas Molecular Weight 28.0 Boiling Point at I atm. -312.7, -191.5. 81.7 Freezing Point -326, -199, 74 Critical Temperature -220. -140, 133 Critical Pressure 507.5, 34.51, 3.502 Specific Gravity 0.791 at -191.5"C (liquid) Vapor (Gas) Density 0.97 Ratio of Specific Heats of Vapor (Gas) 1.3962 Latent Heat of Vaporization 92.8. 51.6. 

Characteristics — Phy.sical State (as normally shipped) Liquefied compressed gas Color Colorless Odor Faint ethereal (iii) Physical and Chemical Properties — Physical State at 15 C and I owi. Gas Molecular Weight 46.1 Boiling Point at I atm. -98, -72, 201 Freezing Point -258, -161, 112 Critical Temperature ... 

To apply the above scheme, accurate experimental measurements for the transport properties of the monatomic fluids were collected. In Table 10.1 the experimental measurements of diffusion, viscosity and thermal conductivity used for the correlation scheme are shown. This table also includes a note of the experimental method used, the quoted accuracy, the temperature range, the maximum pressure and the number of data sets. The data cover the range of compressed gas and the liquid range but not the critical region, where there is an enhancement (Chapter 6) which cannot be accounted for in terms of this simple molecular model. 

---