Diffusion coefficients for glucose solutions a t 25 and 35" are reported for the concentration range 0 to 80 weight per cent. glucose (the saturated concentration a t 25' is 50% glucose). The diffusion coefficients decrease nearly linearly with increase of concentration up to 50% but, at higher concentrations, approach the weight per cent. axis asymptotically. The logarithms of the viscosity and of the diffusion coefficient for both glucose and sucrose solutions are each approximately linear functions of the mole fraction of the solute; the viscosity, however, increases with concentration about 100-fold more rapidly than the diffusion coefficient decreases, illustrating the relative independence of these two factors. The activation energy for diffusion also increases approximately linearly with mole fraction Over the whole concentration range the logarithm of the diffusion coefficient is proportional to the activation energy which is in turn proportional to the entropy of activation. The data are interpreted in terms of a diffusion mechanism based on the migration of water molecules having activation energies increasing linearly with the mole fraction of the solute.
The excess Gibbs free energies, enthalpies, entropies, and volumes are reported for mixtures of ethylene diamine-ethylene glycol at 25°C. The refractive indices of these liquid mixtures are also reported for 25°C.The excess thermodynamic properties have been reported for water-diethylamine solutions at 49.1°C, and ethyl alcoholdiethylamine solutions at 50°C. In both mixtures the excess enthalpies are large and negative over the entire composition range. The same is true for the TsE values. However, the Gibbs free energies are much smaller, and are also of opposite
dine reaction and a standard entropy change of £°= -8.0 cal./mole. Thus the present results by the n.m.r. method are quite consistent with the earlier work of Vinogradov and Linnell3 who obtained for this reaction a AH of -3.8 ± 0.2 kcal. from calorimetric measurements and an equilibrium constant of 22 ±3 at 30°from infrared measurements in CCU solutions.The significance of the variation of calculated " with temperature is uncertain. Temperature dependent n.m.r. effects, however, frequently indicate association processes. It may be that the present results arise from a second dimerization reaction between pyrrole and pyridine. Although the most significant interaction is obviously of the n-donor type, association via the aromatic pyridine ring is also possible. The variation in " would then reflect a temperature dependent ratio of -bonded to nbonded complexes. Table IV Equilibrium Constant and Association Shift for the Ptrrole-Pyridine Reaction Temp., °C. K (mole fraction)-1 Au 33.
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