Department of Chemistry & Biochemistry, Haryana Agricultural University, Hissar-125 004 (India) Manuscript received 19 September 1978, accepted 27 April 1979 Air-oxdation of liquid-paraffin has been carried out at 403°K in the presence of a number of cobalt salts as catalysts over a period of 13 hrs. Acid values of the product samples drawn at regular interval of time have been determined. Effect of the nature and amount of the catalyst on the initiation period and rate of oxidation have also been studied. It is found that recycling of even 1% of the product into the fresh charge Improves, considerably, the initiation period.