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- 16 - <br />Using these criteria eleven of the twenty-two samples were indicated as <br />potential acid producers. <br />The prediction from the humidity cell test was correct in all but <br />three Cases - two were incorrect, dnd one wds inconclusive Since the leach- <br />ate was neither clearly acidic nor alkaline. The Scottie sample indicated <br />by acid/base accounting as a potential acid producer was correctly <br />identified as a non-acid producer by the humidity cell test. The humidity <br />cell produced alkaline leachates for two acid producing sites - the Westmin <br />D and Wellgreen C4 samples. <br />Sulfate. Sulfate production is often used as a measure- <br />ment of pyrite oxidation rates (27). The first leachate collected from the <br />humidity cell experiment exhibited elevated sulfate levels - presumeably as <br />a result of gypsum (CaSOq) and metal sulfate salts present from previous <br />pyrite oxidation. After this "initial flush", the pyrite oxidation rate <br />was roughly linear with respect to time in agreement with observat¶ons made <br />by other investigators (28, 29) (Figure 3). The relationships between <br />.sulfate production and the percent sulfur content of the sample or net <br />neutralization potential from acid/base accounting were determined (sulfate <br />production results are shown in Table 4 on page 22). The relationship <br />between sulfate production and percent sulfur was non-linear and <br />corresponded to a best fit equation of: SOq production (mg/week) _ <br />7.7 x (%S)0.43~ with a correlation coefficient of 0.93 using 13 selected <br />i data sets. The 13 data sets included samples of equivalent particle size <br />^ and non-biological leaching. <br />Williams et. al. (27) found an exponential increase in the rate <br />of acidity production with increasing total sulfur content in high sulfur <br />coals. They attributed this observation to an increase in the rate of <br />iron-oxidizing bacteria activity and growth with high sulfur containing <br />coals. Our results also show an exponential relationship in the initial <br />step of AMO formation but implies lower sulfate production per unit mass of <br />sulfur at high percent sulfur contents. <br /> <br />