Solvation properties in iso-acidic media involving phosphoric acid

Abstract

Concentrated solutions of mineral acids (phosphoric, hydrochloric, perchloric, sulfuric) are characterized, for an equal value of their water activity, by an equal Ro(H) acidity level (iso-acidic solutions). By mixing them, we prepare what we call iso-acidic mixtures which keep the same acidity level as the constitutive solutions whatever the proportions; their redox and solvating properties depend both on the nature and on the ratio of the constitutive solutions. Reactivity variations for ionic species: Cl-, Br-, I-, diethyldithiophosphate (LET-), S~( W~O ,~)~~-, ~i ( w 3 0 1~) 4~-, Cu2+, CU+, Pb2+, Sn2+, c d 2 + , Zn2+, Ag+, Fe3+, Fe2+, UOz2+, U4+ in the iso-acidic mixtures are characterized by their f solvation-transfer activity coefficients. Relations between f coefficient values and complexation properties are established and it is shown that phosphoric acid has comparatively weak solvating properties toward most species. The possibility for anticipating reaction changes with the iso-acidic mixture composition by using the f coefficients is demonstrated in the case of cadmium ionic flotation with diethyldithiophosphate and silver extraction with dithizone in carbon tetrachloride.C. Louu, A. BEBBA et J. BESSIBRE. Can. J. Chem. 66, 2422 (1988).On a caracttrist des solutions concentrkes d'acides mineraux (phosphorique, chlorhydrique, perchlorique, sulfurique), ayant la m&me activitk dans l'eau et le m&me niveau d'acidite Ro(H) (solutions iso-acides). En les mtlangeant, on a prtpare ce que l'on peut appeler des melanges iso-acides qui gardent le m&me niveau d'aciditt que les solutions qui les constituent quelles que soient les proportions. Leurs propriktts de solvatation et redox dependent i la fois de la nature et du rapport des solutions de depart.On a caracterist les variations de rtactivitk des espkces ioniques C1-, Br-, I-, diethyldithiophosphate (LET-), Si(W3010)44-, c u 2 + , Cu+, pb2+, ~n " , Cd2+, Zn2+, ~g + , ~e~+ , ~e~+ , uOZ2+, u'+, des melanges iso-acides en se basant sur leur coefficient d'activitt de transfert de solvatation f . On a etabli des relations entre les valeurs du coefficient f et les proprietts de complexation et on montre que de tous les acides, c'est l'acide phosphorique qui solvate moins bien la plupart des espkces. Utilisant la flottation de I'ion cadmium par le diethyldithiophosphate d'ethyle et I'extraction i l'argent avec la dithizone dans le tttrachlorure de carbone, on dCmontre qu'il est possible de se servir du coefficient f , pour prtvoir le comportement des reactions en fonction de la composition du melange iso-acide.[Traduit par la revue]

Electrochemical behaviours of Eu(III)/E(II) and Ce(IV)/Ce(III) in H3PO4-H2O media : solvation and complexation reactions

“…LOUIS and al. [24] have studied the relationship between complexation and solvation of some metal elements in various mineral acids (hydrochloric, perchloric, sulfuric) using acidity function R 0 (H) and solvation-transfer activity coefficients. In addition, the electrochemical behaviour of Fe(II) and Fe(III) ions on a gold electrode in H 3 PO 4 -H 2 O solutions has already studied in our previous work [25].…”