Electrochemical determination of acidity level and dissociation of formic acid-water mixtures as solvent

J.S. Jaime-Ferrer (1) , Estelle Couallier (1) , Mohammed Rakib (1) , Gerard Durand (1)

1 LGPM - Laboratoire de Génie des Procédés et Matériaux - EA 4038

The autoprotolysis constant KHS of formic acid/water mixtures as solvent has been calculated from acid-base potentiometric titration curves. A correlation of the acidity scale pKHS of each medium versus pure water has been implemented owing to the Strehlow R0(H+) lectrochemical redox function. The results show that formic acid/water mixtures are much more dissociated than pure water; such media are sufficiently dissociated to allow electrochemical measures without addition of an electrolyte. It has also been shown that for a same H+ concentration the activity of protons increases with formic acid concentration. For more than 80 wt.% of formic acid the acidity is sufficiently increased to locate the whole acidity scale pKHS in the super acid medium of the generalized acidity scale pHH2O.

Mots clés: Acidity scale; Autoprotolysis constant; Formic acid; Formic acid/water mixtures; Redox function

Domaines: Génie des procédés; Chimie analytique

J.S. Jaime-Ferrer, Estelle Couallier, Mohammed Rakib, Gerard Durand. Electrochemical determination of acidity level and dissociation of formic acid-water mixtures as solvent. Electrochimica Acta, 2007, 52, pp.5773-5780. ⟨10.1016/j.electacta.2007.02.058⟩. ⟨hal-00743325⟩