Poynting enhancement effect

These particles probably come from the asteroid belt (Elynn, 1994). They are brought to Earth by the action of the Poynting-Robertson effect. Perhaps they are derived from sources that contain uncondensed volatiles from the inner part of the nebula. This would be the only example of a clear enhancement of moderately volatile elements in solar system material. 

In eq (2.3-3) and q) indicate the HC fugacity coefficients in the reference state (pure vapor) and in the vapor phase, respectively, v is the molar volume of the solid phase, T the temperature and R the universal gas constant. As can be reasonably set equal to 1 and the exponential term (known as the Poynting correction) is not markedly greater than 1 for pressures below 500 bar, the enhancement effect is almost completely due to q> , that is to the nonideality of the supercritical solution. 

The numerator quantifies the effect of hydrostatic pressure on the fugacity of the solid phase. The exponential term is known as the Poynting correction (17). The denominator quantifies the fluid phase intermolecular interactions and density effects. Note that the enhancement factor is dependent on the solid volume as well as the interactions in the supercritical fluid. A solute with a large solid molar volume will have a larger enhancement factor than a solute with a smaller solid molar volume at the same temperature and pressure when the interactions in the supercritical phase are identical. To further understand the molecular interactions in supercritical fluids, it is interesting to decompose the enhancement factor into these two effects. We may define a fluid enhancement factor, Ep, and a Poynting enhancement factor, Ep,... 

The first term A is for ideal gas solubility, the second term B accounts for the non-ideality, while the third term C (Poynting correction) accounts for the pressure effects. The product of the second and third terms is often referred as the Enhancement Factor (over the ideal). In the absence of data, the sublimation pressure may be approximated through extrapolation of the vapor pressure information. 

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