Density data were determined for melts with the equimolar composition NaAlF4 + KAlF4, saturated with alumina, over the temperature range (650 to 750)degrees C. The density measurements were performed in a platinum crucible with 5 % alumina added, as well as in a sintercorundum crucible with the same amount of alumina, to ensure alumina saturation. From both overall regression equations obtained from the measurements in sintercorundum and platinum crucibles, the density values were very close, indicating that the system in the platinum crucible with 5 % alumina added was saturated. By combining the equations for both sets of measurements, the final equation was: rho/g . cm(-3) = 2.5321 - (9.598.10(-4))t/degrees C.