Thermodynamic properties of ions in nonaqueous solvents : application of vapor pressure osmometry to the study of nonaqueous solution of electrolyte

Vapor pressure depressions and electric conductivities have been measured for alkali halides, tetraalkylammonium salts and bis-(tetraalkylammonio) salts or bolaform electrolytes in various nonaqueous solvents. The analysis of data of vapor pressure osmometry (VPO) of these salts was carried out on the basis of one of the three models: M^++X^-⇄MX M^++X^-⇄MX⇄1/2 (MX)_2 and M^(2+)+2X^- ⇄ MX^+ + X^-, MX^+ + X^-⇄MX_2 In these data analyses, the activity coefficient of the dissociated species was described by the Debye-Hückel limiting formula with sufficient accuracy. In most systems, the undissociated species have been assumed to behave ideally, but sometimes the activity of the undissociated species had to be taken into account. Dissociation constants determined by the present work are generally in agreement with those obtained by conductivity measurements. The relations of ionic dissociation constant with the dielectric constant of solvent and the ionic radius of solute have been discussed. The solvation number and the partial molar volume of some alkali halides in nonaqueous solvents were measured and the results were compared with the values in literature. The dissociation constants of bolaform salt obtained have been employed for the interpretation of ultrasonic relaxation data of this salt.