Mass fraction of nuclei, X_A, (left) and free protons, X_p, (right) as a function of density for Y_e = 0.316 and T = 2 MeV. The solid and dashed lines denote the NSE calculation with mass-formulae by (Koura 2007, priv. comm.) and Hilf et al. (1976), respectively. The dash-dotted lines are obtained using (Koura 2007, priv. comm.), but with a simplified treatment of relation Eq. (23) as in Mazurek et al. (1979). The dotted lines are the results from Shen et al. (1998b).