Estimation of Medium Effects for Single Ions and Their Role in the Interpretation of Nonaqueous pH.

Abstract

The determination of magnesium by titration with the tetrabutylammonium salt of EDTA is very difficult, owing to the precipitation of compounds of different Mg:Y ratios. However, the reverse

Application of the tetraphenylarsonium tetraphenylborate (TATB) assumption to the hydration entropies of ions

“…This figure was based on the standard molar enthalpy of crystalline KBPh 4 reported by Davies and Stavely, (4) its molar heat of solution in water reported by Wu and Friedman, (25) its solubility product reported by Popovych, (26,27) and the conventional standard partial molar entropy S ∞ m (K + ,aq), (3) converted to the absolute value with…”

Estimation of Medium Effects for Single Ions in Non-Aqueous Solvents

“…measurements on the hydrogen-silver chloride cell without transference: Pt(s); H 2 (g), HC1, AgCl(s); Ag(s) (9) If the standard potential of the above cell in a given non-aqueous solvent is S E°, values of pa,1| = -log (m H s y,,) in that solvent can be calculated from: pa,1 = (E-s E°)/A:+log/» c l + log s y cl (10) In Equation 10, E is the measured e.m.f., s y,, and s y C | are the salt-effect activity coefficients, m u and m Ci the molalities of hydrogen and chloride ions, respectively, and k = (RT In 10)/F. Unfortunately, the paf, scales established in the above manner are different for each solvent composition, so that equal numerical values of paf, in different media do not, as a rule, reflect equal acidities.…”

“…Later, I proposed trirsoamyl-jibutylammonium tetraphenylborate (TAB BPh 4 ), 9 based on the demonstrated equality of its Stokes radii in methanol, 79 water, 80 and, eventually, acetonitrile. 81 Most recently, Alexander and Parker 7 chose tetraphenylarsonium tetraphenylborate (Ph 4 As BPH 4 ).…”

“…Medium effects for single ions in methanol were determined by Popovych 9 with the TAB BPh 4 assumption and by Alexander and Parker 7 with the Ph 4 As BPh 4 assumption. Both sets of results are compared with other literature data in Table 11.…”

Estimation of individual Gibbs energies of cation transfer employing the insertion electrochemistry of solid Prussian blue

“…Commonly, it is assumed that this approximation is operative for large ions, so that the surface-to-volume ratio is minimized. This approximation is invoked using tetraphenylarsonium tetraphenylborate (AsPh 4 BPh 4 , TATB) [21] or tetraohenylphosphonium tetraphenylborate (Ph 4 PBPh 4 , TPTB) [22] as reference salts. A third, extended approach is to consider that there is a certain electrochemical couple whose electrode potential is solvent-independent.…”