Toward an analytic equation of state for fluorine

There are more than 1000 good experimental measurements of fluid fluorine, which cover the range from the triple point to 300 K for pressures up to 23 MPa. The development of an equation of state to fit these data is described. The form of equation used is that of a reduced Helmholtz energy function which includes an equation to represent the behavior of the ideal gas. The coefficients in the equation are determined by a least-squares method where the terms used are selected statistically from a given bank, thus reducing intercorrelation. Two banks of terms were chosen and various fits made using PT data alone, and multiproperty fits with both banks. The serious consequence of using PT data alone is demonstrated, and the difference in quality between the two banks is described. The problems of inconsistency between the single-phase and the saturated density data are discussed. New equations are given which represent the ideal-gas properties.