A furnace for producing oxides of lead includes an enclosure defining a furnace chamber, a feed inlet for feeding particulate lead into the chamber, and a discharge outlet for discharging the particulate lead outside the chamber. An array of horizontally disposed serially communicating tubes are arranged vertically within the chamber, communicating between the feed inlet and the discharge outlet. A rotating valve is associated with the feed inlet, for continuously feeding particulate lead into the number of tubes. Variable drive chain and sprocket combinations are associated with each of the tubes to convey the particulate lead serially along the tubes. The furnace includes electric heat tapes surrounding the tubes, for heating the particulate lead within the tubes while the lead is being conveyed along the tubes. The furnace can be used to produce red lead from leady-oxide or litharge by first supplying air or pure oxygen into the tubes. Leady-oxide is supplied at feed inlet and heated in the first tube to 1250°F to initiate the exothermic conversion of leady-oxide to litharge. Heat from the exothermic reaction occurring in the remaining tubes of the array is used to pre-heat the first tube. Litharge formed from the exothermic reaction is exposed to a lower temperature of 850° in the lowermost tubes of the array for formation of red lead. The travel rate of the litharge determines the percentage of red lead in the final product exiting the discharge outlet.