Activity Coefficient and Conductivity Measurements of High-charge (3-1, 1-3, 3-2) Electrolytes. I.^1a

Abstract

Mean activity and osmotic coefficients have been determined a t 25' for aqueous solutions of Co(en),( N03)3, Co(pn)a-(ClO,),, K?Co( CN)e and [Co(en),]n(sO&, by isopiestic comparison with potassium chloride solutions. At the concentrations required, these salts do not obey the simple laws for 3-1 or 3-2 types, requiring low values of 6. to represent the data by means of the Debye-Huckel equation. The solubilities of Co(en),( K03)3.H20 and K3Co(CN)6 were determined to be 0.2749 and 1.311 m, respectively. A decided deviation from the Onsager limiting law was observed. The limiting values obtained for the complex ions are in agreement with those found by previous workers.Conductivity measurements were made on solutions of the same four electrolytes. IntroductionThis paper is a continuation of a program of investigation of the properties of high-charge electrolytes in aqueous solution.2j3 Four additional compounds, tris-(ethylenediamine)-cobalt (111) nitrate, tris-(propylenediamine)-cobalt(II1) perchlorate, potassium hexacyanocobaltate(II1) and tris-(ethylenediamine) -cobalt (I 11) sulfate, have been prepared and studied. The activity coefficients have been determined by isopiestic comparison with potassium chloride. In addition the contributions of high-order terms of the electrophoretic effect to conductivity were calculated as was done by Dye and Spedding4 for the alkaline earth and rare earth salts. Experimental

Negative Deviations from the Debye–Hückel Limiting Law for High-Charge Polyvalent Electrolytes: Are They Real?

“…Figure depicts experimental γ ± data of K 3 Co­(CN) 6 and the fitted theoretical behavior with the ISPs listed in Table . The low-concentration data are of Malatesta et al as corrected in the present work, and those at the higher concentration range are of Brubaker’s group . Malatesta data are extending the Brubaker data to very high dilution with no deviation from the expected behavior and from the limiting law, and the fit with the DH–SiS curve is excellent for both sets of data over the entire concentration range of 0–1.3 m .…”

“…Malatesta data (ref , see Table I) are those recalculated in the present work (i.e., γ ± new values). Brubaker data are from ref .…”

“…The low-concentration data are of Malatesta et al 10 as corrected in the present work, and those at the higher concentration range are of Brubaker's group. 23 Malatesta data are extending the Brubaker data to very high dilution with no deviation from the expected behavior and from the limiting law, and the fit with the DH−SiS curve is excellent for both sets of data over the entire concentration range of 0−1.3 m. The higher concen- tration γ ± 's of Malatesta and the lower concentration γ ± 's of Brubaker, covering the same concentration range, display the same behaviorthe one predicted by DH−SiS. Overall, Figures 3 and 4 demonstrate a good fit between experimental γ ± data from different sources and the computed γ ± 's, and the agreement extends to the very low I (and m) values of the experiment, as performed by Malatesta et al, when the data are corrected as done in the present work.…”