Volumetric and Viscometric Study of N-acetylcysteine in binary and ternary system

Abstract

Volumetric and viscometric studies of binary mixtures of ethanol-NAC (N-Acetylcysteine), water-NAC and ternary mixtures of ethanol-water-NAC were done. NAC have been investigated in binary and ternary systems over a concentration range of (1-18) % (w/v) at 298.15 to 323.15 K at 5 K intervals. Densities of the binary systems, water-NAC and ethanol-NAC have been found to be increased with increasing concentration of NAC and decreased with increasing temperature. Densities of water-NAC have been found higher than that of ethanol-NAC system. On the other hand, in ternary system densities increased with the increasing ratio of water in ethanol-water mixtures. The densities of ternary system are higher than binary system. The apparent molar volumes, 𝝋𝒗 of both binary and ternary mixtures were determined from the densities of the mixtures. The 𝝋𝒗 values have been found to be positive throughout the whole concentration range for NAC in ethanol, water and aqueous ethanol systems. The apparent molar volumes, 𝝋𝒗 of NAC in ethanol, water and aqueous ethanol were found to be increased with concentration at all temperatures. These results may be due to the solute-solvent, and solute-solute interaction through H-bond, dipole-dipole and S˖˖˖S linkage in the solutions. 𝝋𝒗 values were found to be increased with increasing temperature at any concentration of the solution may be due to increased thermal agitation at higher temperatures. It may also be assumed as the concentration increases because solute-solute interactions by S˖˖˖S linkage start to gain importance in addition to solute-solvent interactions. This shows that 𝝋𝒗 values are dependent upon concentration as well as the temperature. The apparent molar volumes at infinite dilution (𝝋𝒗 𝒐) were computed by extrapolating 𝝋𝒗 values to zero concentration. The 𝝋𝒗 𝒐 values provide information on solute-solvent interactions, as solute-solute interactions can be assumed to be eliminated at infinite dilution. The variations of both 𝝋𝒗 𝒐 values with temperature were examined. 𝝋𝒗 𝒐 Values were found to be increased with increasing temperature for all systems. Investigated systems showed small positive values for Sv which indicate that the solvation process involve strong interaction but not pure ionic. The apparent molar expansivities at vii infinite dilution (𝜑𝐸 0 ) were found to be positive. Positive values indicate that, on heating some NAC molecules may be released from the solvation layer of ion. Viscosity values, η of NAC in ethanol, water and aqueous ethanol were found to be increased with concentration at all five temperatures but decreased with the increase of temperature. The increase of η values of NAC with concentration can be attributed to the increase in both solute-solvent and solute-solute interactions with concentration as mentioned. At the same time, at a constant temperature and concentration, values of η are found to be increased with the ratio of the water in ethanol-water of ternary system but in binary system ethanol-NAC is higher than water-NAC viscosity because of larger molecule of ethanol. The change of free energy values for viscous flow, ∆G* were found to be positive indicate that work has to be done to overcome the energy barrier for the flow process. The positive ΔH values indicate that work has to be done for all the investigated systems. That is, the viscous flow is not thermodynamically favored for the systems studied. The ∆S* values are positive for all the systems studied except ethanol–NAC system. This means that except ethanol–NAC system other binary and ternary systems are random that those of the pure one.