[Old - 1984?] Isopropyl alcohol is manufactured in the United States by an indirect hydration technique in which a fraction containing 40-60% propylene that is isolated from refinery exhaust gases reacts with sulfuric acid (Lowenheim and Moran, 1975). In an older (strong-acid) process, 88-93% sulfuric acid reacted with propylene gas at 25-60°C for a long time. In a newer (weak-acid) process, which has replaced the strong-acid process, propylene gas is absorbed in 60% sulfuric acid at 85°C for a short reaction time (NIOSH, 1976). Estimated annual production capacity for 1981 was 2.8 million pounds (SRI, I...