In an attempt to develop technology to use domestic resources in place of imported bauxite, the Bureau of Mines investigated sulfurous acid leaching to extract alumina from kaolin. The process consists of leaching the calcined kaolin with a 30 wt-pct so2 solution at 60 deg. C and 160 psig for 17 hours, filtering the leach slurry, precipitating monobasic aluminum sulfite from the filtrate at 110 deg. C and 60 psig, and decomposing the sulfite in the spent liquid at 150 deg. C and 55 psig to produce crude alumina. Purification of the crude alumina was accomplished using a modified Bayer process. Results from closed-circuit tests employing the sulfurous acid process showed that overall extraction of alumina from kaolin was 67 pct. Production of 1 ton of alumina would require 3.6 Tons of calcined kaolin, 0.7 Ton of sulfur dioxide, and 8.4 Tons of water. After purification by a modified Bayer process, the alumina product contained the following impurities, expressed in weight-percent: fe2o3, 0.009; S, 3.6; Sio2, 0.07; Tio2, 0.002; K2o, 0.017; and p2o5, 0.03.