Published values for the Hall coefficient and the electrical resistivity of liquid metal alloys can provide useful estimates of the reflectance and emittance of some groups of binary liquid metal and high-temperature solid alloys. The Drude free-electron parameters, and thence the optical constants and the radiant properties, are computed from the dependence of the Hall coefficient and direct current resistivity On alloy composition (the Hall coefficient gives the free-electron density and the resistivity gives the average time between collisions). We find that predictions of the radiant properties of molten cerium-copper alloy, which use the measured variations in the Hall coefficient and resistivity (both highly nonlinear) as a function of alloy fraction (rather than linear combinations of the values of the pure elements) yield a good comparison to published measurements of the variation of the normal spectral emittance.