where δ 2 d is the dispersion or non-polar cohesion parameter, δ 2 h is the hydrogen bonding cohesion parameter, and δ 2 p is the polar cohesion parameter. Methods for measuring and calculating these fractional parameters are described in and. Dimension of δ 2 is Joule/cm 3 , V is cm 3 /mole, δ 2 V and RT are Joule/mole. Combination of equations 15, 16, and 21 (the case ∆H < 0) gives: