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Isopiestic determination of the osmotic and activity coefficients of Rb 2SO4 (aq) and Cs 2SO 4(aq) at T= (298.15 and 323.15) K, and representation with an extended ion-interaction (Pitzer) model

“…A graphical comparison of our values of φ with those derived from the studies of Kirgintsev and Luk'yanov, (25) Filippov et al, (29) Kalinkin and Rumyantsev, (27) and Rumyantsev (28) indicates general consistency with each other and with the results from our concordant Series 1 to 3, 14, and 15 experiments, except for one outlying value of φ at m = 0.8238 mol · kg −1 from the study of Kalinkin and Rumyantsev. (27) The φ values for Rb 2 SO 4 (aq) from the study of Cudd and Felsing (6) have sizable systematic discrepancies from every other isopiestic study, (25,(27)(28)(29) including ours, and the molality dependences of the deviations are qualitatively similar to those noted above for their Cs 2 SO 4 (aq) results.…”

“…In contrast, the simpler three-parameter form of Pitzer's equation with C •, Kirgintsev and Luk'yanov; (25) ×, Filippov et al, 1989;(29) , Kalinkin and Rumyantsev; (27) , Rumyantsev. (28) as accurate representation for Rb 2 SO 4 (aq) at T = 298.15 K as the four-parameter model, and three-parameter models with either C (0) M,X = 0 or C (1) M,X = 0 gave only slightly less accurate representations for Cs 2 SO 4 (aq) at T = 298.15 K than the four-parameter model. However for a consistent representation of thermodynamic properties of the aqueous alkali metal sulfates, we accept and recommend the four-parameter models, but also give the parameters for the three-parameter fits with C (1) M,X = 0 in the footnotes to tables 5 and 6.…”