Cloud point (CP) determinations of 4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol (TX-100 (nonionic surfactant)) was carried out in aqueous as well as in the attendance of drug (ceftriaxone sodium trihydrate (CFT))/(CFT + different inorganic salts) and discussed thoroughly. Nonionic surfactants are employed extensively in different formulations. In aqueous solution, the values of CP of TX-100 are obtained to increase by means of enhancing of their concentration in the solution. The CP values of TX-100 solutions were found to decrease in the presence of drug and their values decrease more with rising concentrations of the drug. The values of CP of CFT and TX-100 mixtures were found to further decrease in the attendance of inorganic salts in comparison to their absence. The effect of different sodium salts in decreasing CP values of TX-100 was achieved in the following order: NaCO3 > Na2SO4 > NaCl. However, in the case of potassium and ammonium salts, the decreasing order obtained is K2SO4 > KCO3 > KCl and (NH4)(2)SO4 > Na2CO3 > NH4Cl respectively. Various thermodynamic parameters for example standard free energy (Delta G(c)(circle minus)), standard enthalpy (Delta H-c(circle minus)) as well as standard entropy (Delta S-c(circle minus)) changes of phase separation were also evaluated and discussed in detail on the basis of their behavior. (C) 2017 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.