1989-11-22_REVISION - M1988112 - Laserfiche WebLink

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- 11 - connected the humidity cell to a plexiglass covered 5 gallon aquarium. The aquarium was partially filled with water and an air stone used to generate humidified air which passed through the tygon tubing to the humidity cell (Figure 2). A 200 gram portion of each sample crushed to 2.38 mm was placed in a humidity cell. All cells were connected by e~cual lengths of cubing to the aquarium humidifier. A seven day cycle was used for the leach•~ng procedure. Dry air was passed over the sample for the first three days followed by three days of humidified air. The cells were opened on the seventh day to add approximately 200 ml of distilled water. The cells were left for about one hour and the leachate was collected and the decant volume recorded. This seven day cycle was restarted the following day and was repeated for ten weeks. The collected leachate was analyzed for conductivity, sulfate, pH, acidity, and dissolved metals. Acidity was A determined by titration to a pH 7 end point as described in Sobek et. al. (17). Identical procedures were followed in the 1983 and 1984 experiments except that two air stones were used in the aquariums in 1984 which resulted in visible increased levels of humidity in the cells in 1984 compared to the previous year. Innoculation procedure. An active culture of Thiobacillus ferrooxidans was added to two humidity cells (A2 and A4) during the sixth week of leaching. This culture was obtained from B.C. Research in Vancouver and was grown on a chalcopyrite concentrate (25~ copperl. The culture was prepared as follows: a) the solids in the raw culture were allowed to settle and the suoer- natant decanted; b) the decant solution was examined under a medium power microscope to confirm the presence of viable bacteria cells; ' c) the liquid was centrifuged twice at low speed, for 3 minutes to remove the remaining solid particles;