A Raman Spectrographic and Potentiometric Study of Aqueous Lithium and Potassium Acetate Complexation at Temperatures from 20 to 200 ∘C

摘要

The Raman spectra of aqueous NaOH–CH3COOH solution containing either LiCl or KCl were collected at temperatures from 20 to 200 ∘C. Interpretation of these spectra reveals significant aqueous LiCH3COO0 formation, but no evidence of aqueous KCH3COO0 formation. LiCH3COO0 dissociation constants generated from these data decrease with the increasing temperature from −0.25 at 20 ∘C to −1.08 at 200 ∘C. Potentiometric measurements were performed on similar solutions at temperatures from 25 to 90 ∘C. These results are in general agreement with the Raman spectral results. Significant aqueous Li-acetate complexing is observed; aqueous K-acetate complexing is far weaker than that of Li-acetate. Dissociation constants for aqueous LiCH3COO0 generated from the potentiometric measurements decrease from −0.20 at 25 ∘C to −0.62 at 90 ∘C, whereas those for aqueous KCH3COO0 decrease from ≳ 0.35 to −0.02 over this temperature range.