COMPLEXATION OF STRONTIUM IN THE SYNERGISTIC EXTRACTION SYSTEM DICYCLOHEXANO-18-CROWN-6, VERSATIC ACID,CARBON TETRACHLORIDE

The synergism in the extraction of Sr? +? from 0.5M Sr(NO?3?) ?2? by 0.05M dicyclohexano-18-crown-6 (DC18C6) + 0.1M Versatic 1519 (abbreviated v-acid or RCOOH, a neo carboxylic acid) in CCl?4? has been found to stem from a strong 1:1 interaction between DC18C6 and Sr?2+ ? However, both nitrate and carboxylate can function as the anion for the (DC18C6)Sr?2+? moiety. At aqueous conditions corresponding to less than complete loading (i.e., [Sr?2+?[ org < 0.05M for pH < 11.7), (DC18C6)Sr(NO?3;)?2? precipitates as a solid. As the pH is raised in the interval 7 < pH < 11.7 to deprotonate the V-acid, the precipitate (DC18C6)Sr(NO?3?) ?2? becomes solubilized first with probable formation of a mixed-anion complex and finally with quantitative (0.05M) formation of the monoraeric complex (DC18C6)Sr(OOCR) ?2? H?2?O at pH = 11.7 as confirmed by viscometric titration of 0.05M DC18C6 in wet CCl?4? with Sr(OOCR) ?2?, Karl-Fischer titrations, vapor-phase osmometry, and IR spectrophotometry.