GIANCARLO FRANCHINI, ELENA ON, CARLO PRETI, LORENZO TASSI, and GIUSEPPE TOSI. Can. J. Chem. 65, 722 (1987). Dissociation constants of 2,4,6-trinitrophenol (picric acid) in 2-methoxyethanol and 1,2-ethanediol were measured by a conductance method at temperatures ranging from -10 to 80°C. The determined constants in the two solvents are discussed and are compared on the basis of the physical properties of the solvents, which have been measured at the various temperatures. The dissociation constants show different behaviour with the temperature in the investigated range and they are fitted by equations of the type In K = A+BT+C/T+D In T . Furthermore, the thermodynamic functions have been evaluated and discussed.GIANCARLO FRANCHINI, ELENA ON, CARLO PRETI, LORENZO TASSI et GIUSEPPE TOSI. Can. J. Chem. 65, 722 (1987).Optrant a des temptratures allant de -10 a 80°C et faisant appel a la conductimttrie, on a mesurC les constantes de dissociation du trinitro-2,4,6 phtnol (acide picrique) dans le mCthoxy-2 tthanol et dans l'tthanediol-1,2. On discute des constantes dtterminies dans ces deux solvants et on les compare entre elles en fonction des propriCtCs physiques de ces solvants qui ont CtC mesurCes aux diverses temptratures. Dans la fourchette des tempkratures examintes, les constantes de dissociation prtsentent des comportements diffkrents que l'on peut toutefois reprtsenter par des tquations du type InDe plus, on a tvaluC et on discute des fonctions thermodynamiques.[Traduit par la revue] Introduction This work is to study the effect of solvent on dissociation constants of weak acids and the influence of temperature.Although alcohols have received much attention as solvents for acid-base determinations (1, 2) there are not many studies on the use of 2-methoxyethanol (hereafter abbreviated Gliem) and 1,2-ethanediol (Gliet) as solvents in acid-base titrations and on the determination of dissociation constants of weak acids. Our previous works (3-6) have reported on the feasibility of conductometric titrations of monoprotic and diprotic acids, phenols and aromatic nitroderivatives in the above solvents using N,N1-diphenylguanidine as titrant. The results indicated the possibility of also performing differential titrations of acid mixtures in cases where such determinations are impossible in aqueous solutions.Preliminary studies have shown that temperature plays an important role in the shape of the conductometric titrations curves and that the effect is different for different solvents.Continuing our conductometric studies, the dissociation constants of picric acid in Gliet and Gliem have been determined at different temperatures and the data obtained are discussed. The reaction under study in the two solvents is