Enthalpy and entropy of dissolution were studied. The van’t Hoff equation relates the logarithm of mole fraction of a solute in an ideal solution as a linear function of the reciprocal of the absolute temperature as follows [9] and [10]:
equation(5)
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where ΔdisH and ΔdisS are the enthalpy and the entropy of dissolution, and C is the gas constant. From the experimentally obtained solubility data, plot of ln x1 versus 1/T gives the values of enthalpy and entropy of dissolution from the slope and the intercept, respectively. Fig. 6 shows the van’t Hoff plot of the logarithm of mole fraction solubility versus reciprocal absolute temperature. Table 3 lists the dissolution enthalpy and entropy. From Table 3, it can be seen that the dissolution enthalpy of l-Gn in water is less than that in mixed solvents.