Abstract
The activity coefficients of LaCl3, K3Fe(CN)6, and LaFe(CN)6 were measured down to about 1×10−4, 3×10−5, and 2×10−5 mol-kg−1 respectively, by means of cells with ion-exchange liquid membranes. In the diluted region, the trend of lanthanum chloride agrees with the Debye-Huckel theory and corroborates earlier findings in the literature relevant to more concentrated solutions, with minor systematic corrections of the γ± values. K3Fe(CN)6 attains (rather than tends to attain) the Debye-Huckel limiting slope at≈1×10−3 mol-kg−1, and lanthanum ferricyanide in the diluted region shows negative deviations from the limiting law, similar to the ones predicted for large-sized, highly-charged ions in the diluted region by Bjerrum's, IPBE, and Mayer's theories. The behavior of LaCl3 in the concentrated solutions proves that lanthanum ion drags along with it into the membrane many molecules of water which were then found to be twelve. Pitzer's theory best-fit coefficients that meet the experimental curves to be reproduced satisfactorily are reported.
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Malatesta, F., Giacomelli, A. & Zamboni, R. Activity coefficients of electrolytes from the emf of liquid membrane cells. III: LaCl3, K3Fe(CN)6, and LaFe(CN)6 . J Solution Chem 23, 11–36 (1994). https://doi.org/10.1007/BF00972605
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DOI: https://doi.org/10.1007/BF00972605