Water second viscosity virial coefficient

Hydrogen-bond formation is of importance also for various other properties of substances, such as the solubility of organic liquids in water and other solvents, melting points of substances under water,1 viscosity of liquids,14 second virial coefficient of gases,18 choice of crystal structure, cleavage and hardness of crystals, infrared absorption spectra, and proton magnetic resonance. Some of these are discussed in the following sections of this chapter. 

The experimentally fitted hydrate guest Kihara parameters in the cavity potential uj (r) of Equation 5.25 are not the same as those found from second virial coefficients or viscosity data for several reasons, two of which are listed here. First, the Kihara potential itself does not adequately fit pure water virials over a wide range of temperature and pressure, and thus will not be adequate for water-hydrocarbon mixtures. Second, with the spherical Lennard-Jones-Devonshire theory the point-wise potential of water molecules is smeared to yield an averaged spherical shell potential, which causes the water parameters to become indistinct. As a result, the Kihara parameters for the guest within the cavity are fitted to hydrate formation properties for each component. 

These macroscopic viscosity measurements have been confirmed at the molecular level. For example, dynamic light-scattering methods show an average hydrodynamic diameter (D J of about 370 A for a 50/50 copolymer of NVP/SPE in low salt (<2%) and a of about 390 A in high-salt (20% NaCl) concentrations (18). Moreover, in solutions of water or low concentrations of salt, solvent quality (as measured by second virial coefficient, A2) decreases with increasing levels of SPE. LALLS measurements for NVP/SPE 80/20 and 10/90 copolymers in 2% NaCl solution yielded molecular weights of 1.1 X 10 and 1.4 x 10 g mol respectively. The same compositions yielded second virial coefficients of 9.0 X 10 and 0.6 X 10 , respectively. In this case, a higher virial coefficient means better solution quality. 

Polymeric betaines are usually insoluble in pure water and have gel characteristics but are soluble in salt-containing solutions. The loss of water solubihty and gel-like structure that adopts polybetaines are probably due to the formation of intra- and interchain ion contacts which result in the appearance of cross-linked networks. The intrinsic viscosity [t]], second virial coefficient A2, exponent a in the MKH equation, the radius of hydration Rg and the hydrodynamic radius % increase with the increase in salt concentration [132] (Table 16). 

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