The significance of viscosity B-coefficients for solutions of dipolar ions and non-electrolytes in water is discussed in the light of hydrodynamic theories of viscosity and the usefulness of the ratio B / W , ((Do2 is the limiting apparent molar volume of the solute) is stressed. Viscosity and density measurements have been made at 5", 1 O", 1 5". and 20" on aqueous solutions of glycolamide, glycine, sarcosine, dimethyglycine, and betaine. Apparent molal volumes and viscosity B-coefficients have been calculated from these data. The results suggest that a charged nitrogen atom bearing 3 or 2 hydrogen atoms interacts strongly with the solvent water to form a primary solvation sheath.Substitution of two of the three hydrogen atoms. as in dimethylglycine, leads to a considerable reduction in solvation, and complete substitution, as in betaine, seems to prevent it entirely.
Soret coefficients for aqueous solutions of isoelectric norvaline, c-aminocaproic acid, L-proline, DL-hydroxyproline, and glycylglycine have been measured over concentration ranges from about 0.1 molal upwards, a t mean temperatures of 25 and 35". using the optical beam-displacement method described in Part I. Entropies and heat capacities of transfer have been calculated from the results. On the basis of the qualitative model discussed in Part II, we conclude that (i) a terminal NH,+ group is more efficient in raising the " structural temperature " of the solvent round the solvated solute than a similar group placed elsewhere in an amino-acid molecule, and (ii) a significant increase in this effect probably occurs when a hydroxyl group is introduced into the molecule. The dipeptide glycylglycine has a higher heat capacity of transfer than has so far been observed for amino-acids themselves.THE entropy of transfer S* for a solute in a binary in aqueous solutions, structural changes induced in the solution depends on several factors, one of which appears surrounding solvent molecules by the diffusing entity to be the relative size or mass of the solvent and solute molecules, and another the shape of the solute mole-63;6apart
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