Most of the thermodynamic models are structured with terms representing long range interactions or intermediate/short range interactions only. Thus for the proper thermodynamic presentation of electrolyte systems, all different types of interactions: ion-ion, ion-dipole, dipole-dipole, molecule-molecule should be taken into account. The potential energy caused by ion-ion interactions is inversely proportional to the separation between them. Electrostatic ion-ion interactions therefore are effective over a relatively long distance called as long range interactions. A review of the literature was conducted to find the available models, correlations: capable of describing the phase behavior and thermo physical properties of strong as well as weak electrolyte systems.  In this work the comparative study for the models that has been used for describing the Phase behavior of acid gases and sulfur species in alkanolamine aqueous solutions. These kinds of models are of high interest for the absorption unit in the natural gas processing industry