Temperature Dependence of
Hydrogen Bonding Network in
Water from the View Point of
Third Derivative of Gibbs Energy

Thermodynamic studies have been performed for a variety of alchol solution to obtain information of the hydrogen bonding network in water. The concentration and temperature dependence of third derivatives of Gibbs Energy, G, for 2-butoxyethanol aqueous solution show peak-type anomalies. A relationship between concentration and temperature of the peaks is shown by open symbols in Fig. 2. The data points are on a line, which is calld as "Koga Line". It is considered that hydrogen bonding network throughout the solution is broken in the higher concentration or temperature region than Koga line. However, since the previous data of third derivatives are obtained by graphical differentiation, they includ large errers. To obtain more accurate data, we directly determined SVδB third derivative. The result of SVδB measurement (Fig. 1) shows that the height and concentration of the peaks decrease as temperature increases. The relationship between concentration and temperature almost agree with previous data. The high temperature end of Koga line may go higher than the estimate from previous data.

(by K. Yoshida, Y. Koga & A. Inaba)

Fig. 1. Concentration dependence of SVδBE at 25 °C to 70 °C.

Fig. 2 The relationship between the temperature and the concentration of the top of peak. Filled circles show the present results, and other open symbols previous results.