Hydrogen molecules, compression equation

Two characteristics of liquid water that are relevant to the present answer are the equation of state characteristics shown in Figs. 8.11 and 8.12. The isothermal compressibilities shown in Fig. 8.11 indicate that water is stiffer than organic solvents, and that the stiffness is only weakly temperature-dependent. We don t propose here a detailed explanation of that stiffness - it is due to intermolecular interactions among solvent molecules, hydrogen bonding in the case of liquid water (Debenedetti, 2003) - but the present empirical theory of hydrophobicity merely exploits those results. This stiffness is the principal determinant of the low solubility of inert gases in liquid water. In the simplest information models this stiffness, and its temperature dependence, is expressed by the experimental n (n — l))o, which is distinctive of liquid water. 

Instrumentation for IGC has been fairly standard. Detectors should be chosen to most accurately reveal the probe molecule. Flame ionization is most common. Carrier gases are usually helium or hydrogen. It should be noted that the compressibility of the gas is always corrected for in packed column work because of the pressure drop across the column, as shown in Equations 1 to 3 but, this is negligible in capillary investigations. 

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