Study of Benzoic Acid Solubility in Imidazolium Formate as Pure Ionic Liquid and Its Binary Aqueous Mixtures

Abstract

The determination of benzoic acid (BAc) solubility in pure imidazolium formate (ImForm) and their aqueous mixtures of [ImForm/water], was performed by the acid-base titration of the saturated solutions. [ImForm/water] solutions were tested using an ImForm concentration ranging from 1.66-4.33 g/L. The BAc solubility in pure ionic liquid was compared with that of some common organic solvents reported in literature, such as: ethanol, chloroform, cyclohexane. The highest solubility of BAc was for pure ImForm (from 1073 g/L at 293 K up to 2200 g/L at 323 K), the determined values being superior to BAc solubility in organic solvents mentioned. The results confirm that the polar solvents, such as ImForm and ethanol, present the highest BAc solubility values. At 293 K, the mole fraction of BAc in pure ImForm was 2.8 times higher than the mole fraction of BAc in ethanol. The BAc solubility in binary mixtures [ImForm/water] was compared with that determined in [NaCl/water] mixtures. At the same salt concentration, ranging from 1.66 to 4.33 g/L, at a constant working temperature (323 K), the increasing concentration of NaCl lowers the solubility of BAc. In opposite, the increasing of ImForm concentration determines a considerable increase in BAc solubility into the [ImForm/water] mixture. At 277 K, for 1.66 g/L salt concentration in water, the BAc solubility in [salt/water] solvents shows very similar values (~1.3 g/L) for both [ImForm/water] and [NaCl/water]. If the temperature increases to 323 K, the BAc solubility in [ImForm/water] mixture is about 1.5 times higher than that of solubility in distillated water and 2.5 times higher compared to that in [NaCl/water]. It was concluded that the benzoic acid presents a great solubility in pure ImForm and in its [ImForm/water] aqueous mixture.

Phenolphthalein Indicator in Titrimetric Estimation of Benzoic Acid Solubility and Distribution in Water and Benzene-Buffer Solutions

“…The observation of graph indicates that, the partitioning of benzoic acid in acidic pH medium is higher in comparison of neutral or in basic medium [23]. Although, the solubility of benzoic acid is thermodynamically dependent [24,25], and follow to Van't Hoff equation [26].…”