Solvent expansibility

The volume of activation for the reverse reaction is + 17 cm3/mol, a value that includes volume expansion caused by partial Fen-NO + bond cleavage and 5 = 0 to S = 5/2 spin change and solvent expansion. The changes in volume are illustrated in Figure 7.14b. 

An important issue is what is the relative weight of the different factors in determining (i) solvent expansion (ii) hydrodynamic interaction (iii)... 

Q Range (A- ) (All Factors Included) No Good-Solvent Expansion No Hydro-dynamic Interaction No Variation ofC(4) [C(q) = const] No Internal Viscosity... 

C higher than room temperature, the mobile phase (temperature of the mobile phase is supposed to be the same as room temperature in this case) will expand about 1% from when it entered the columns, resulting in an increase in the real flow rate in the column due to the expansion of the mobile phase and the decrease in the retention volume. The magnitude of the retention-volume dependence on the solvent expansion is evaluated to be about one-half of the total change in the retention volume. The residual contribution to the change in retention volume is assumed to be that due to gel-solute interactions such as adsorption. 

Chang CJ, Randolph AD. Solvent expansion and solute solubility predictions in GAS-expanded liquids. R D notes. AIChE J 1990 36(6) 939-942. 

In 1972 the chemical industry was producing about 700,000 metric tons (about 1.5 billion pounds) of chlorofluorocarbons (CFCs) per year, compounds composed entirely of carbon, chlorine, and fluorine. Most of the CFCs produced in the early 70s were either CFC-11, which is CFCI3, or CFC-12, which is CF2CI2. The development of these chemicals was considered a major triumph for the industry because they seemed to be perfect for use as aerosol propellants, solvents, expansion gases in foams, heat-exchanging fluids in air conditioners, and temperature-reducing fluids in refrigerators. 

The injection port liner is used to minimize dead volume when a sample is injected. Several are shown in Figure 20-27. Those shown are 0.8 mm i.d. with an internal volume of 12 pL. The solvent expansion type prevents flashback when injecting large volumes of dilute samples. 

There are some smdies (23,24) which link the magnitude of the Huggins and Sehulz-Blasehka coefficients to the coefficient of polymer- solvent expansion,, of the Fox and Flory treatment of polymer coil properties (25). 

Pulsed splitless Reduction of the residence time in the liner resulting in the decreased analyte degradation/adsorption and reduced matrix-induced response enhancement Larger injection volumes (limited by the liner size and solvent expansion volume) Potential transfer of nonvolatile matrix cx)mponents further into the column... 

A systematic description of the morphologies observed in the different experiments reported in literature is very difficult and probably a single mechanism cannot explain all the variety of particles formed. Recently [36] a qualitative explanation, valid for batch processes, of the different morphologies obtained was proposed on the basis of the different solvent expansion level at which tfie particles are produced. 

Use the correct liner for an injection mode select the inner diameter of a liner to be commensurate with solvent boiling point, solvent expansion, and injection volume when employing a vaporizing inlet. 

The HS diameters so determined are found to be in excellent agreement with those derived from inert gas solubilities. It may be noted that the method of Ben-Amotz and Willis, also based on Pj, uses the nonpolar HS liquid as the reference and, therefore, is applicable only to liquids of weak dipole-dipole forces. Of course, as the reference potential approaches that of the real liquid, the HS diameter of the reference liquid should more closely approximate the actual hard-core length. Finally, because of its popularity, an older method should be mentioned that relies on the isobaric expansibility ap as the probe, but this method is inadequate for polar liquids. It turns out that solvent expansibility is appreciably determined by attractions. 

A standard cuvette with 1-cm path length is used in this type of detection system. Samples are excited with a planar beam of light and the resulting pressure wave due to solvent expansion through the solution is converted by a transducer into a voltage pulse. As the measurements are made using a cuvette with an attached transducer, the system is easily adjustable to the needs of measurements in solutions. 

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