Journal of Chemical and Engineering Data, Vol.56, No.3, 437-443, 2011
Total and Specific Solubility and Activity Coefficients of Neutral Species of (CH2)(2i-2)N-i(CH2COOH)(i+2) Complexons in Aqueous NaCl Solutions at Different Ionic Strengths, (0 <= I <= 5) mol.L-1, and 298.15 K
The total solubility S-T of (CH2)(2i-2)N-i(CH2COOH)(i+2) complexons (i = 1, nitrilotriacetic acid (NTA); i = 3, diethylenetriaminepentaacetic add (DTPA); i = 4, triethylene tetraaminehexaacetic acid (TTHA)) in aqueous NaCl solutions at different ionic strengths, (0 <= I <= 5) mol..L-1, and at 298.15K are determined and are reported in both molar (mol.L-1) and molal (mol.kg(-1)) concentration scales, together with the protonation constants. The total solubility in pure water S-0(T) is (8.1, 8.9, and 4.5) mmol.L-1 for NTA DTPA and TTHA., respectively. Increasing the ionic strength from (0.1 to 5) mol.L-1 (NaCl), the total solubility decreases for NTA, while the opposite trend is observed for DTPA and TTHA. From total solubility and protonation constant data, the solubility of the neutral species S-0 and the solubility products K-S0 are calculated The dependence on ionic strength is analyzed, and the Setschenow (k(m)) coefficients are obtained, together with the solubility of the neutral species in pure water S-0(0) [S-0(0) = (2.5, 5.2, and 1.1) mmol.kg(-1), for NTA, DTPA, and TTHA, respectively].