Copper sulphate ion pairing in aqueous solutions up to 473K

MÉNDEZ DE LEO, LUCILA P.; BIANCHI, HUGO L.; FERNÁNDEZ-PRINI, ROBERTO J.

Philadelphia, PA, USA

Congreso; The 228th ACS National Meeting; 2004

American Chemical Society

The ionic assocn. of copper(II) and sulfate ions in water at high temp. has been studied using a modular spectrophotometer and a titanium high pressure flow cell with sapphire windows.  The UV-spectra of different mixts. of copper(II) and sulfate were detd. from room temp. up to 473 K.  A non linear least squares fitting procedure that employed the Pitzer ion interaction model for the activity coeffs. and considered other chem. equil. existing in the solns. -such as hydrolysis of sulfate and of copper, was used to obtain the equil. const. in each condition studied.  Bjerrum´s model was employed to interpret the equil.  Results indicate that copper sulfate ion pairs may be sepd. by mols. of solvent (SSIP) or in contact (CIP).  The former structure predominates at temps. up to 350 K while the latter above 350 K.  The interaction between the ions and between ions and solvent mols. proved to be a main feature in the relative stability of SSIP and PIC.