Oxidation of low-rank coals using hydrogen peroxide at low temperature under ambient pressure is a promising method of producing small molecule fatty acids in high yield and in high selectivity. Five low-rank coals (C% = 65.1-74.7 on daf basis) served to test the validity of the method. When Argonne Premium Beulah Zap lignite was oxidized with 20 volumes of 30% H2O2 aqueous solution for 24 h at 60 degrees C, the carbon conversion to water-soluble organics reached 0.71. About a half of the water-soluble organics were small molecules : methanol, formic acid, acetic acid, glycolic acid, and malonic acid. The high yields of these compounds are closely related to the structure of low-rank coals. Obtaining these products in such high yield and high selectivity under mild reaction conditions may give us a new route for utilizing low-rank coals.