Contribuição ao estudo termodinâmico das soluções de ácido acetilsalicílico
Resumen
As one of the most regularly traded-in medicines in the world, the acetylsalicylic acid
has been scarcely researched when in solution. This study is aimed at determining the
thermodynamic equilibrium parameters for thermodynamic models such as Margules, Van
Laar, Wilson, NRTL, UNIFAC, Regular Solution Theory, and Nývlt for acetylsalicylic acid
solutions in ethanol, acetone, propylene glycol, and isopropyl alcohol, in addition to
comparing their solubility values with the expected from an ideal solution and with some
solutions of solvent diluted in water to evaluate the effect of the water addition in the solvent
Moreover, the study of the solubility parameters became to compose the sphere of
solubility of the acetylsalicylic acid with some solvents adds the used ones to determine the
solubility curves. We also do the study of the decomposition of the acetylsalicylic acid
became during the procedure for the determination of its curves of solubility.
Through adjustments it is possible to conclude that the Nývlt model presented the best
correlation rate (0,999) for the adjustment of its parameters. Moreover, it was the best model
to represent the experimental data with an average percent deviation of 1%. The NRTL model
also presented good adjustment rates when compared with other experimental data. It is an
interesting tool to predict the activity coefficient of the acetylsalicylic acid solutions for all the
solvents under study. The UNIFAC model presented an inadequate prediction of activity
coefficient values with average percent deviations of up to 70%.
The solubility sphere was determined in satisfactory way, once the solubility
parameters of acetylsalicylic acid is in compliance with the solvents parameters. The assays
for the determination of the decomposition of the acetylsalicylic acid had demonstrated that it
does not have significant degradation of acetylsalicylic acid throughout the experiments for
ethanol, propylene glycol and isopropyl alcohol.