Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

Extraction of microamounts of Sr²⁺ and Ba²⁺ from 0.2-1.0M-HClO₄ by the nitrobenzene solutions of dicarbolide H⁺[Co(C₂B₉H₁₁)₂]^- in the presence of polyethylene glycols (PEG) (M_r = 200, 300, 400) has been investigated. It has been found that the extraction of the protonized polyethylene glycol molecule (H⁺ + L ##e HL⁺, where the bar denotes species present in the organic phase) and the extraction of the complex between the extracted ion and polyethylene glycol, i.e., M²⁺ +L + 2 H⁺ ##e ML²⁺ + 2 H⁺, are the predominant reactions in this system. The respective equilibrium constants have been determined. The hydration numbers of HL⁺ and ML²⁺ ions in the organic phase have been obtained from the determination of water content by Karl Fischer titration method. The extraction constants and stability constants in the organic phase increase in the sequence H⁺ < Sr²⁺ < Ba²⁺ and PEG 200 < PEG 300 < PEG 400, while the hydration numbers decrease in the same sequence. Correlations between the hydration numbers and the extraction constants for these cations have been found.