Pure characteristic physical property constant

Commercially available compilations of pure component characteristic physical property constants and temperature-dependent properties" for convenient use in process simulators have been developed by AlChE (DIPPR), DDBST, DECHEMA, NIST (TRC), and PPDS. They should be checked first before estimating thermophysical properties. DDBST has developed a comprehensive pure component thermophysical property estimation software (Artist), where many of the methods discussed in this chapter are implemented. 

An adsorption kinetic model was developed to evaluate the adsorption rates of five pure gases (Nj, O2, Ar, CO, and CH4) on a Takeda-3A CMS over a wide range of pressures up to ISatm. The kinetic characteristics of adsorption on the CMS were studied by using the adsorption equilibrium of five pure gases measured at three different temperatures and their physical properties. Since the diffiisional time constants of all the components showed much stronger dependence of pressure than those expected by the traditional Darken relation, a structural diffusion model was applied to predict the strong pressure dependence. The proposed model successfully predicted the dif ional time constant up to high pressure on the CMS. 

Very recently, the separation of polar analytes has also been performed by using pure water under subcritical conditions. Subcritical water has several unique characteristics. For example, the dielectric constant, surface tension, and viscosity of water are dramatically decreased by raising the water temperature while a moderate pressure is applied to keep water in the liquid state. At 200 -250°C, the values of these physical properties are similar to those of pure methanol or acetonitrile at ambient conditions. Therefore, subcritical water may be a potential mobile phase for polar analytes. SFC mobile phases other than CO2 are reviewed separately in this encyclopedia. 

A molecule is the smallest entity of a pure compound that retains its characteristic chemical properties, and consequently has constant mass and atomic composition. It is an assembly of nonmetallic atoms held together into specific shapes by covalent bonds. As much as a car is a single unit made up of many parts, a molecule is a unit made up of atoms bonded around each other in certain fixed geometries. Shapes influence the physical and chemical properties and consequently much of the chemistry of a molecule. 

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