The following are major steps in theoretical development in this area. Hildebrand introduced this parameter. Then Prausnitz, with co-workers, 66-68 split the parameter into two components related to the forces hidden in the enthalpy of a transition process. Hansen further suggested using the three-component splitting of the cohesion parameter. Hansen defined the solubility parameter (HSP or HSPiP) as cohesive energy density, which keeps molecules together in a liquid or solid state. The HSP can be used to evaluate the relative role of polar, non-polar(dispersion), and hydrogen cohesive forces in a chemical composition. Karger, Snyder, and Eon 71,72 developed a five-component set of cohesion parameters that included additional HSP physicochemical properties related to the enthalpy of a system, such as an orientation. The inclusion of this parameter is based on the Kirkwood-Frohlich theory, , 74 which discussed the influence of the orientation of the electric dipoles in polar liquids. The orientation effect, according to this theory, correlates with dielectric constant. Work on modification of solubility parameters continues (see, for example,, ). Authors suggested replacing cohesive energy densities with electrophilicity densities that incorporate the charge transfer effect as a critical contribution to the Hildebrand approach. No fractional cohesion parameters were proposed in this 76 approach. We will discuss the progress related to the transition from one to five-component cohesion parameters models in more detail below, particularly the application of some of these parameters for evaluating the DNA denaturation process.