During the Bayer leaching of bauxite to produce alumina, naturally occurring organic carbon in the ore dissolves as an organic humate and oxidizes to oxalate during processing. The oxalate builds up in the pregnant liquor and hinders the recovery and reduces the purity of alumina. To reduce or eliminate the harmful effects of organic carbon in the Bayer process, the U.S. Bureau of Mines investigated corrective methods by oxidizing the carbon in the bauxite during leaching, and/or after leaching in the pregnant liquor. Bayer leach liquor and/or bauxite were treated with oxidizing agents including ozone, sodium hypochlorite, manganese dioxide, and oxygen plus ultraviolet light. Ozone treatment of a sodium humate solution decreased the amount of organic carbon, as humic acids, by as much as 33 pct, but did not oxidize oxalate. Treatment of bauxite with mNO2 and of oxalate in solution with oxygen in the presence of ultraviolet light produced marginal decreases in oxalate. Treatment of bauxite with ozone or with sodium hypochlorite was not effective either.