AN IMPROVED METHOD FOR EXTRACTING SULFATE FROM BITUMINOUS COALS USINGFORMIC-ACID

In connection with the determination of sulfate S, the sulfur mass bal ance for four bituminous coals was determined using different extracti on procedures, including use of 1 M and 4.8 M HCl under nitrogen and u nder air, and at room temperature, 95 degrees C and boiling point. Sin ce HCl extractions yielded poor S mass balances (as low as 83%), acid extraction with formic acid was also evaluated, Extractions with formi c acid gave better S mass balances than those obtained using HCl, and the sulfate S yields agreed with those measured by the ASTM D-2492 HCl procedure. S-34/S-32 ratios determined by stable sulfur isotope mass spectrometry demonstrated that formic acid extraction was more selecti ve for sulfate sulfur than the more rigorous HCl extractions.