Dataset: glass_leach.dat Source: A. Tuncuk, H. Ciftci, A. Ackil, A.Ognyanova, and F. Veglio (2010). "Experimental Design and Process Analysis for Acidic Leaching of Metal-Rich Glass Wastes," Waste Management & Research, Vol.28, pp.445-454 Description: 2^4 factorials conducted on clear and green glass bottles for percent reduction (negative values imply increase) of iron, aluminum, and titanium. There were 3 observations at "design center" Factors: Sample Ratio (%) Low=10, High=30 Sulfuric acid concentration (M) Low=0.5,, High=1.0 Temperature (Celsius) Low=60, High=120 Time (minutes) Low=60, High=120 Variables/Columns Sample Ratio 5-8 Acid Concentration 10-16 Temperature 18-24 Time 26-32 Colorless glass iron removal % 34-40 Colorless glass aluminum removal % 42-48 Colorless glass titanium removal % 50-56 Green glass iron removal % 58-64 Green glass aluminum removal % 66-72 Green glass titanium removal % 74-80