The U.S. Bureau of Mines investigated solvent extraction methods for recovering gallium from sulfuric acid leach filtrates produced from hydrometallurgical zinc residues. These filtrates typically had ph values of 0 to 0.5, Too low for effective gallium recovery by traditional extractants. Of the nine extractants tested, octylphenyl acid phosphate (opap) was the most effective. Gallium stripping was accomplished using a 1.5M h2so4 liquor. A continuous solvent extraction system was designed and operated for 32.4 H, treating a 0.32-G/l ga and 20-g/l fe filtrate. Overall gallium recovery in the system was 94 pct.