@article {2475, title = {High Temperature End of the So-Called "Koga Line": Anomalies in Temperature Derivatives of Heat Capacities}, journal = {Journal of Physical Chemistry B}, volume = {113}, number = {17}, year = {2009}, note = {ISI Document Delivery No.: 438BCTimes Cited: 0Cited Reference Count: 24Koga, Yoshikata Westh, Peter Moriya, Yosuke Kawasaki, Koji Atake, Tooru}, month = {Apr}, pages = {5885-5890}, type = {Article}, abstract = {The so-called "Koga line" is a collection of the loci of anomalies in various third derivatives of the Gibbs function, G, in the temperature-mole fraction field for aqueous solutions of nonelectrolytes. This splits the H2O-rich region into two, in each of which the molecular organization and interactions-we call it mixing scheme-is qualitatively different. In this work, we attempt to locate the high temperature end of the Koga line. This is a particularly interesting range of the boundary, since its extrapolation to zero Solute concentration provides information on possible temperature induced changes in the properties of pure water. To this end, we determine semi-isobaric heat capacities of aqueous 2-butoxyethanol by adiabatic calorimetry up to a maximum of 95 degrees C. The corrections due to vaporization were not applied due to the lack of required vapor pressure and thermal expansivity data. Furthermore, we measured directly the isobaric heat capacities per molar volume for aqueous I-propanol as well as 2-butoxyethanol by differential scanning calorimetry up to 120 degrees C at 3 atm. We then took one more temperature derivative of the respective heat capacity data. The resulting third derivative quantities from the former data showed step-type anomalies, while those from the latter negative peak-type anomalies. The loci of these anomalous points seem to point to about 70 degrees C at infinite dilution.}, keywords = {25-DEGREES-C, AQUEOUS 2-BUTOXYETHANOL, density, FLUCTUATION, METHANOL, MIXING SCHEME, PARTIAL MOLAR VOLUMES, pressure, TRANSITION, WATER-RICH REGION}, isbn = {1520-6106}, url = {://000265529900029}, author = {Koga,Yoshikata and Westh, P. and Moriya, Y. and Kawasaki, K. and Atake, T.} } @article {5094, title = {Additive effect of 1-propanol and 2-propanol on molecular organization of H2O in the water-rich region: Excess chemical potential, partial molar enthalpy and volume of 1-propanol in 1-propanol-2-propanol-H2O at 25 degrees C}, journal = {Bulletin of the Chemical Society of Japan}, volume = {74}, number = {5}, year = {2001}, note = {ISI Document Delivery No.: 443WKTimes Cited: 16Cited Reference Count: 25}, month = {May}, pages = {809-816}, type = {Article}, abstract = {Excess chemical potential, mu (E)(1P), partial molar enthalpy, H-1P(E) and volume of 1-propanol, V-1P(E), were determined as a function of mole fraction of l-propanol, rip, in mixed solvents of aqueous 2-propanol with various initial mole fraction of 2-propanol, x(2P)(0). The 1-propanol-1-propanol interaction functions, H-1P-1P(E) equivalent to N(partial derivativeH(1P)(E)/partial derivativen(1P)), and V-1P-1P(E) equivalent to N(partial derivativeV(1P)(E)/ partial derivativen(1P)), were evaluated by graphical differentiation. The rip-dependence of all these quantities indicates that l-propanol and 2-propanol modify the molecular organization of H2O in the same and additive manner in the water-rich region. The additive effect of 1-propanol and that of 2-propanol are in the ratio of (0.07/0.08).}, keywords = {25-DEGREES-C, AQUEOUS 2-BUTOXYETHANOL, ENTROPIES, fluctuations, INTERMOLECULAR INTERACTIONS, LYSOZYME, MIXING SCHEMES, MIXTURES, TERT-BUTANOL}, isbn = {0009-2673}, url = {://000169365200004}, author = {Hu, J. H. and Chiang, W. M. D. and Westh, P. and Chen, D. H. C. and Haynes, C. A. and Koga,Yoshikata} } @article {3848, title = {Intermolecular interactions in 2-butoxyethanol-DMSO-H2O}, journal = {Journal of Physical Chemistry}, volume = {100}, number = {1}, year = {1996}, note = {ISI Document Delivery No.: TN839Times Cited: 15Cited Reference Count: 23}, month = {Jan}, pages = {433-438}, type = {Article}, abstract = {Excess partial molar enthalpy, H-B(E), and chemical potential, mu(B)(E), of 2-butoxyethanol (B) were determined in ternary mixtures of B, dimethyl sulfoxide (D), and H2O. The data were obtained in small enough mole fraction increments to evaluate the so-called interaction functions, partial derivative H-B(E)/partial derivative x(B), partial derivative H-B(E)/partial derivative x(D), partial derivative mu(B)(E)/partial derivative x(B), and partial derivative mu(B)E/partial derivative x(D). These interaction functions previously proved useful in elucidating the {\textquoteright}{\textquoteright}mixing schemes{\textquoteright}{\textquoteright} in binary aqueous solutions of B and D. For the binary mixtures, it was found that both B and D influenced H2O in the following manner: in the water-rich composition range (region I) within a certain threshold (x(B) < 0.0175 and x(D) < 0.28 at 25 degrees C), both solutes enhance the hydrogen-bonded network of water in their vicinity, and the mixtures retain the percolated nature of the network. At higher B or D concentrations (region II) a qualitatively different mixing scheme becomes operative. The results from this work suggest that, in the ternary mixtures, solute B and D influences the percolated hydrogen bond network of water competitively or cooperatively. The observed effects are in accordance with those characteristic of mixing scheme I in the binary mixtures, as long as the concentration of both solutes is within the threshold values. When either one of the solutes is concentrated beyond its threshold, mixing scheme II seems to set in. It was found that D diminished the positive (unfavorable) enthalpy of B-B interactions and that this effect was almost completely compensated by changes in interaction entropy. Hence, D had little net effect on the Gibbs energy of mutual B interactions, or in other words, D did not weaken the hydrophobic attraction between B molecules. Evaluation of {\textquoteright}{\textquoteright}heterogeneous{\textquoteright}{\textquoteright} B-D interactions in region I suggested that they were weaker than B-B interactions and governed by reorganization of water-water hydrogen bonding rather than interactions between specific groups in B and D. Some implications of these findings on cosolvent effects in aqueous solutions of biopolymers are discussed.}, keywords = {AQUEOUS 2-BUTOXYETHANOL, denaturation, DIMETHYL-SULFOXIDE, LYSOZYME, MIXING SCHEME, MIXTURES, NEUTRON-DIFFRACTION, PARTIAL MOLAR ENTHALPIES, VOLUMES, WATER-RICH REGION}, isbn = {0022-3654}, url = {://A1996TN83900065}, author = {Westh, P. and Koga,Yoshikata} } @article {3723, title = {Normalized fluctuations, H2O vs n-hexane: Site-correlated percolation}, journal = {Journal of Chemical Physics}, volume = {105}, number = {5}, year = {1996}, note = {ISI Document Delivery No.: UZ525Times Cited: 20Cited Reference Count: 49}, month = {Aug}, pages = {2028-2033}, type = {Article}, abstract = {Entropy, volume and the cross fluctuations were normalized to the average volume of a coarse grain with a fixed number of molecules, within which the local and instantaneous value of interest is evaluated. Comparisons were made between liquid H2O and n-hexane in the range from -10 degrees C to 120 degrees C and from 0.1 MPa to 500 MPa. The difference between H2O and n-hexane in temperature and pressure dependencies of these normalized fluctuations was explained in terms of the site-correlated percolation theory for H2O. In particular, the temperature increase was confirmed to reduce the hydrogen bond probability, while the pressure appeared to have little effect on the hydrogen bond probability. According to the Le Chatelier principle, however, the putative formation of {\textquoteright}{\textquoteright}ice-like{\textquoteright}{\textquoteright} patches at low temperatures due to the site-correlated percolation requirement is retarded by pressure increases. Thus, only in the limited region of low pressure (<300 MPa) and temperature (<60 degrees C), the fluctuating ice-like patches are considered to persist. (C) 1996 American Institute of Physics.}, keywords = {2 KINDS, AQUEOUS 2-BUTOXYETHANOL, density, H-BONDS, HEAVY-WATER, LIQUID WATER, mixing, MOLECULAR-DYNAMICS, pressure, SCHEME, TEMPERATURES}, isbn = {0021-9606}, url = {://A1996UZ52500029}, author = {Koga,Yoshikata and Westh, P. and Sawamura, S. and Taniguchi, Y.} } @article {3402, title = {IONIC-CONDUCTIVITY IN THE WATER-RICH REGION OF AQUEOUS 2-BUTOXYETHANOL}, journal = {Canadian Journal of Chemistry-Revue Canadienne De Chimie}, volume = {73}, number = {8}, year = {1995}, note = {ISI Document Delivery No.: RZ492Times Cited: 4Cited Reference Count: 22}, month = {Aug}, pages = {1294-1297}, type = {Article}, abstract = {Ionic conductivities of HCl, KOH, and KCl were measured in aqueous solutions of 2-butoxyethanol (BE) at 25 degrees C. The quantity, Lambda(j){\textquoteright} = sigma/x(j), which is almost proportional to the molar conductivity, was extrapolated to the infinite dilution x(j) {\textendash}> 0. sigma is the conductivity and x(j) is the mole fraction of j(= HCl, KOH, or KCl). The plots of (0) Lambda(j){\textquoteright}, the value of Lambda(j){\textquoteright} extrapolated to infinite dilution, against x(BE) showed a change in slope at x(BE) = 0.0175. The previous work from this laboratory indicated that the mixing scheme changes qualitatively at the same locus, x(BE) = 0.0175. By mixing scheme we simply mean the way in which BE and H2O molecules mix with each other. Assuming additivity in (0)h(j){\textquoteright} in terms of constituent ions, those values for H+OH- were calculated. Plots of (0) Lambda(H+OH-){\textquoteright} thus calculated as a function of x(BE) in the water-rich region, 0 < x(BE) < 0.0175, suggest that the hydrogen bond probability decreases in the bulk of solution, as x(BE) increases.}, keywords = {AQUEOUS 2-BUTOXYETHANOL, BOND NETWORK, HYDROGEN, IONIC CONDUCTIVITIES, MIXING SCHEME, MIXING SCHEMES, MIXTURES, PARTIAL MOLAR ENTHALPIES, SCATTERING, TRANSITION, VOLUMES}, isbn = {0008-4042}, url = {://A1995RZ49200008}, author = {Koga,Yoshikata and Loo, V. J. and Puhacz, K. T.} }