Abstract: The presence of solid polymer in distillation columns and their associated reboilers used for the recovery of methacrylic and acetic acids produced by the oxidation of methacrolein may be minimized by the use of inhibitors and introduction of molecular oxygen at a rate above a predetermined threshold value, which is a function of the operating temperature of the equipment. For a given temperature, the amount of solids has been found to be greatly increased below the threshold value of oxygen, while above the threshold value, the rate of appearance of solids has been found to be minimized and further increases in oxygen rate have only a minimal effect. At a typical operation temperature of 120.degree. C., the threshold value of about 0.1 SLH O.sub.2 /100 gm of liquid. A gas containing a relatively high concentration of oxygen is preferred.