Abstract: A method and apparatus for controlling the rate at which material is fed to a molten salt bath in a process utilizing the material to produce molten metal. The apparatus includes means for generating a signal that represents the actual level of the salt bath, means for generating a signal representing the density of the salt bath, and means for generating a signal representing the volume of the metal beneath the salt bath. A circuit is provided for receiving and storing an initial datum representing a desired concentration of the material in the molten bath, and for receiving the above signals, the circuit being further capable of calculating a bath level in response to said signals that will maintain the initial percent concentration of the material during the time molten metal is being produced and when molten metal is removed from the bath.