  By using the recently formulated Legendre transform approach to the
thermodynamics of charged systems, we explore the general form of the screening
length in the Voorn-Overbeek type theories, that remains valid also in the
cases where the entropy is not given by the ideal gas form as in the
Debye-Huckel theory. The screening length consistent with the non-electrostatic
terms in the free energy Ansatz for the Flory-Huggins and Voorn-Overbeek type
theories, derived from the local curvature properties of the Legendre
transform, has distinctly different behavior than the often invoked standard
Debye screening length, though it reduces to it in some limiting cases.
