Solvent extraction of silver picrate by 3 m-crown- m ethers ( m = 5, 6) and its mono-benzo-derivative from water into benzene or chloroform: elucidation of an extraction equilibrium using component equilibrium constants

Abstract

Ion-pair formation constant ( K AgPic in mol −1 dm 3) of silver picrate (AgPic), those ( K AgLPic) of its ion-pair complexes (AgLPic) with crown ethers (L) and complex formation constants ( K AgL) of Ag + with L (15-crown-5 ether (15C5) and benzo-15C5) in water (w) were determined potentiometrically at 25 °C. Compounds used as L were 18-crown-6 ether (18C6), its benzo-derivative (B18C6) and the two 15C5 derivatives. Extraction constants ( K ex in mol −1 dm 3) of AgPic with L (15C5, 18C6, B18C6) from acidic w-phases into either C 6H 6 or CHCl 3 were recalculated from K AgPic, K AgL, K AgLPic and data opened in previous papers. Thus obtained K ex was divided into five component equilibrium constants containing K AgL and K AgLPic anew. Then, contributions of the component constants, K AgL, K AgLPic and distribution constants of AgLPic between the w- and C 6H 6-phases, to K ex were discussed and compared with corresponding extraction systems of NaPic and KPic with18C6.