The dissociation constant of copper sulphate in aqueous solution

Abstract

The significance of the dissociation constants obtained for copper sulphate from cryoscopic, spectrophotometric and conductimetric experiments is discussed. New precise spectrophotometric measurements are reported.* University of Reading.f Its significance is blurred in mixed electrolyte solutions.

Ionic interactions in solutions of electrolytes as studied by ultra-violet spectroscopy

“…This may well be true for certain intramolecular transitions of either cations or anions [4], but as a generalization it is quite false. On the other extreme, a change in optical density at an arbitrary wavelength with change in the ionic strength of a solution is sometimes attributed to ion-pair formation, even though no attempt has been made to decide whether this change is caused by the growth and decay of bands, or simply the shift or broadening of a band [2,3]. Since the location of absorption bands may be very sensitive to environmental changes [6,12] there can be little justification in such an arbitrary assignment.…”

“…Downloaded by [Michigan State University] at 16:08 06 February 2015 (5) Ion-pairs. This term includes classes (2), (3) and (4) and will be used when distinction between them cannot be made.…”

“…Ionic interactions in solutions of electrolytes have been studied recently by spectrophotometry in the visible and ultra-violet region [1][2][3][4][5], and the results have been interpreted in a variety of ways. Ambiguity arises partly because the concept of ion-pair formation is ill-defined and partly because different types of electronic transitions can be affected in different ways by changes in environment [4,6].…”

Ion pair formation in copper sulfate aqueous solutions at high temperatures

“…The reduced temperature is defined by T red = (4p 0 D kTa/z + |z À |e 2 ), where 0 is the permittivity of vacuum, D the dielectric constant of the solvent, a is a characteristic length given by the distance of closest approach of two oppositely charged ions and the other symbols have their usual meaning. Hence, ion pairing occurs in solvents of low dielectric constant [2] and in aqueous solutions of multicharged electrolytes [3][4][5][6][7], or in aqueous solutions of (1:1) electrolytes at high temperature [8,9]. All cases in which T red is small, hence electrostatic interactions are sufficiently strong to produce an increase in the number of oppositely charged ions surrounding a central one, i.e.…”

Solutions of Electrolytes

“…Taking CuSO. as an example, Davies, Otter & Prue (87) illustrate the extent to which the dissociation constant of an ion pair depends on the association distance assumed in the calculations.…”