of e g about 100 u00b0 c to about 200 u00b0 c preferably from about 120 u00b0 to about 160 u00b0 c if desired a catalyst for the decomposition of peroxides such as a heavy metal salt for instance a cobalt salt of an iron salt may be added in this step amounts of heavy metal of about 0 1 to about 20 and preferably of about 0 5 to about 2 p p m by weight relative to the benzaldehyde are sufficient for a satisfactory catalytic action larger amounts may be used if so desired the invention will be elucidated with reference to the following non restricting examples and comparative experiments the color values in degrees hazen u00b0 h were determined by astm d1209 62 a sample of crude benzaldehyde prepared by the oxidation of toluene in the liquid phase by means of a gas containing molecular oxygen with the use of a homogeneous cobalt catalyst was distilled in a sievetray column with 30 trays at a top pressure of 20 kpa and with a reflux ratio of 1 3 during the distillation 5 liters n t p of air per liter of liquid benzaldehyde were passed through per hour the color value of the main fraction was lower than the detection limit of 5 u00b0 h.