acidic pretreatment of gold refractory ore processing. 1993 1995 . 1993 1995 1987 upload . Live Chat. Online Exhibitor Planner Pittcon. All Exhibitors (978) Expo Hours Monday Wednesday, March 14 17, 2011 900AM 500 PM Thursday, March 18, 2011 900 AM 300 PM Exhibitor List Click on exhibitor name for more details.