The results of a study on the formation of alkali soluble humic acids and the increase of oxygen concentration during the oxidation of Kangal/Sivas lignite are reported. The oxidation reaction was conducted in an open circuit system at 70degreesC and then at 90degreesC for 12 h, respectively, in a day. The supply of oxygen in the sample by air was allowed to proceed for 2-12 days with 2 day intervals for the parallel samples, and oxygen concentration in the sample oxidized increased from 25.28% to 29.50%. Particular attention was directed to determining the optimum oxidation period, airflow rate, and energy balance in the reactions. Potassium humate (K-Humate) salt, a product of the reaction between the alkali soluble humic acids and potassium hydroxide solution, was obtained with 75.53% recovery in dry ash free (daf) basis from the sample oxidized in air for 96 h and sized to -0.246+0.104 mm.