Mixing schemes in a urea-H2O system: a differential approach in solution thermodynamics

The Journal of Physical Chemistry. B
Yoshikata KogaAkira Inaba

Abstract

The excess partial molar enthalpies of urea (UR), H U R (E ), were experimentally determined in UR-H 2O at 25 degrees C. The H U R (E ) data were determined accurately and in small increments in the mole fraction of UR, x U R , up to x U R approximately 0.22. Hence it was possible to evaluate one more x U R -derivative graphically without resorting to any fitting function, and the model-free UR-UR enthalpic interaction, H U R- U R (E ), was calculated. Using previous data for the excess chemical potential, mu U R (E ), the entropy analogue, S U R- U R (E ), was also calculated. The x U R -dependences of both H U R- U R (E ) and S U R- U R (E ) indicate that there is a boundary at x U R approximately 0.09 at which the aggregation nature of urea changes. From the results of our earlier works, we suggest that a few UR molecules aggregate at x U R approximately 0.09, while the integrity of H 2O is retained at least up to x U R approximately 0.20. Together with the findings from our previous studies, we suggest that in the concentration range x U R < 0.22, UR or its aggregate form hydrogen bonds to the H 2O network, reducing the degree of fluctuation characteristic to liquid H 2O. However, up to at least x U R = 0.20 the hydrogen bo...Continue Reading

References

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Sep 23, 2003·Biophysical Chemistry·Rufus Lumry
Feb 20, 2004·Journal of the American Chemical Society·Joseph D BatchelorGary J Pielak
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Jul 21, 2006·The Journal of Physical Chemistry. B·Kumiko MikiYoshikata Koga
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Citations

Jun 1, 2012·The Journal of Physical Chemistry. B·Takeshi MoritaYoshikata Koga
Feb 24, 2012·Physical Chemistry Chemical Physics : PCCP·Fumie SebeYoshikata Koga
Jul 23, 2013·Physical Chemistry Chemical Physics : PCCP·Yoshikata Koga
Mar 18, 2010·The Journal of Physical Chemistry. B·A IdrissiG Vergoten
Apr 3, 2009·The Journal of Physical Chemistry. B·Yoshikata KogaTooru Atake
Mar 1, 2012·The Journal of Physical Chemistry. B·Takemi KondoYoshikata Koga
Dec 20, 2012·The Journal of Physical Chemistry. B·Yoshikata KogaKeiko Nishikawa

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