In this research, influence of some ionic liquids on the electrical conductivity of L(+)-lactic acid (LaH) have been investigated in aqueous polyethylene glycol 20000 (PEG) solutions. The molar conductivities of LaH in water, aqueous solutions of PEG and (PEG + ionic liquid,l-hexy1-3-methylimidazoliumbromide [C(6)mim]Br/1-octy1-3-methylimidazolium bromide[C(8)mim]Br) were measured at T = (288.15-318.15) K. These data have been analyzed by Quint-Viallard (QV) conductivity equation and the limiting molar conductivities (Lambda(0)) and dissociation constants (K-D were calculated by this equation. The results demonstrate that the values of Lambda(0) decrease with increasing concentration and longer alkyl chain length of the ionic liquids. The K-D values were also used to calculate the dissociation standard thermodynamic functions (Delta G(D)(0)),Delta s(D)(0), and Delta H-D(0)). The values of Delta G(D)(0) are positive and become more positive at higher temperatures. This implies that the dissociation of the acid is a non spontaneous process in standard state. (C) 2017 Elsevier B.V. All rights reserved.