抄録
The effects of ionic strength, temperature, and urea on the behaviors of methyl orangedodecyltrimethylammonium complex (MO-DT complex) were examined. The mean activity coefficients (γ±) of both the ions, methyl orange anion and dodecyltrimethylammonium cation in aqueous sodium chloride solution were determined by solubility measurements. Thermodynamic solubility products of MO-DT complex at 15, 25, and 35°C were 3.159×10-10, 8.418×10-10, and 22.889×10-10 (mol/L)2, respectively. An increse in NaCl gives rise first to reduced γ± values and then to increased γ± values. The γ± values were correlated to the ionic strength according to the equation, where A and B are the constants which involve absolute temperature and dielectric constant of the solvent. The term I is ionic strength. The symbols a′ and b′ represent the distance (Å) between the nearest ions and an adjustable parameter, respectively. z+ and z- mean the charges of the cation and the anion. The γ± values obtained fit in with the equation when a′=3.5 and b′=0.2 are given. An increase in urea concentration in aqueous solution increased the solubilities of the complex.
