J. Galea

Thermodynamic studies on formation of Europium(III)-adenine nucleotides complexes

Abstract The following equilibrium constants have been determined by constant pH potentiometric measurements in water tetramethylammonium bromide (0.2 M) medium, for the temperature range between 5°C to 35°C: ( A represents the nucleotides which can be AMP, ADP or ATP). From the effects of temperature on these equilibria we calculate their associated thermodynamic quantities. The solubility of the Europium(III) hydroxyde has also been determined under the same experimental conditions.

Contribution a l'etude des complexes du cation cadmium (II) avec l'acide laćtique et l'acide malonique en milieu Na+(ClO−4)3M A 25°C

The potentiometric study of neutralisation at 25°C, in Na+ (ClO−4)3M medium, with NaOH as titrant, of solutions: Cd2+ cation-lactic acid (between neutralisation rate values 0 to 1); and of Cd2+ cation-malonic acid (between neutralisation rate values 1–2), allows consideration of the formation of mononuclear complexes with lactic acid, and mononuclear and polynuclear complexes with malonic acid. The interpretation of experimental data ph = f(x)R induces one to suppose the existence of the following species: lactic acid: Cd(Lact)+, Cd(Lact)2; malonic acid; Cd(Mal); Cd(Mal)2−2; Cd(Mal)4−3; Cd2(Mal)2; Cd2(Mal)2−3. The constants of formation of those complexes have been determined by non-linear regression.

Thermodynamic studies on the formation of cobalt(II)-adenine nucleotides complexes

Abstract The formation of complexes of Co(II) with adenosine monophosphoric (AMP) and adenosine diphosphoric (ADP) anions have been studied by pH-stat and pH variable potentiometry and also by calorimetry The existence of complexes of type ML (CoAMP and CoADP − , MHL (CoHADP) and ML 2 [Co(ADP) 4- 2 ] is in good agreement with the experimental results. The stability constants of formation of these complexes as well as their corresponding thermodynamic values, obtained in an 0.2 M solution of tetramethylammonium bromide, are presented in the Tables 1, 2 and 3.

Détermination, à 25°C, du produit ionique des solvants mixtes acétone+eau+perchlorate de sodium

Abstract The ionic products of different mixed solvents acetone+water with sodium perchlorate have been determined by a method of standardisation using solutions of “strong” acids and bases. The evolution of pki is plotted in function of molar fraction of acetone and concentration of sodium perchlorate. The approximate values of the ionic product of acetone and acetone+sodium perchlorate media (0.5 M, 1 M, 2 M, 3 M) have been achieved easily by graphical extrapolation.