Abstract: Apparatus for the continuous production of saturated aliphatic dicarboxylic acids by the catalyzed nitric acid oxidation of the corresponding cycloalkanols and cycloalkanones with recirculation of the reaction sludge and the reaction gases, which comprises cooling the reaction sludge by passing it through the tubes of a multiple tube heat exchanger, separating the reaction gases downstream of the heat exchanger, and dispersing the recycled portion of the reaction gases in the reaction sludge upstream of the heat exchanger, in a volume amount 0.1 to 2.0 times the volume of the reaction sludge circulating per unit time and in a pressure ratio of initial gas pressure to pressure in the circulation reactor at the gas feed point of (x + 0.25) : x to (x + 1.5) : x, wherein x is the pressure at the gas feed point, to form a homogeneously dispersed three-phase mixture of the recycled reaction gases in the reaction sludge in the tubes of the heat exchanger.