A liquid media for DNA or RNA denaturation is usually a blend of aqueous solvents/denaturant(s), salts, and a buffer. We considered such systems as the media for the chemical (exothermal) type of the denaturation process. Evaluation of the effective cohesion parameters δ for liquid mixture is of prime importance for selecting a proper mixture of solvents for the denaturation of nucleic acids. Hildebrand and Prausnitz 65 assumed in developing the expression for cohesion parameter that the value of effective parameter δ for a solvent mixture is volumewise proportional to the similar parameters of its components. We assumed similarly to 65 that for the multi-component solution, the additivity principle for enthalpy ∆H i and volume fraction V f i for each component in the solution apply. See Assumption 1 below and compare it to equation 20.