Effects of Na2SO4 and NaClO4 on the molecular organization of H2O

We study thermodynamic behaviors of 1-propanol (abbreviated as 1P) in ternary 1P-salt-H2O in order to elucidate the effects of salt on the molecular organization of H2O. We determine the excess partial molar enthalpy of 1P, H-1P(E), as a function of the mole fraction of 1P, x(1P), and the salt. We examine the x(1P) dependence of H-1P(E), and changes induced by the presence of salt are used to elucidate the effect of the salt on the molecular organization of H2O. We previously found that an NaCl ion pair binds 7 to 8 molecules of H2O, but has no effect on H2O outside of the hydration shell. Na2SO4 and NaClO4, on the other hand, modify the molecular organization of H2O each in different ways. In particular, ClO4- seems to participate in the hydrogen bond network of H2O and to retard the degree of fluctuation inherent in liquid H2O.