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<br /> <br />- 9 - <br /> <br />2 METHODS <br />Twenty-two samples of rock from seven base metal mines in British <br />Columbia and Yukon were tested in 1983 and 1984 using the acid/base <br />accounting and humidity cell techniques (Table 21. Twenty samples of waste <br />rock were collected from active or abandoned surface dumps, one sample of <br />ore from an operating gold mine, and one sample of tailings from an aban- <br />Boned mine. Samples were not expected to be representative since dumps, <br />tailings, and ore bodies are typically composed of rocks exhibiting a wide <br />range of mineralogies. Moreover, several samples were obtained from dumps <br />which were actively producing acid mine drainage. As such, these samples <br />could include acidic metal-sulfate salts from previous pyrite oxidation. <br />All except four samples of waste rock and the one sample of tail- <br />!~ ings were crushed to pass a sieve with 2.38 mm openings. The crushed <br />samples were split into Lwo portions. One was further crushed to pass <br />250 microns and was analyzed by acid/base accounting, while the second was <br />used in the humidity cell experiment. Samples were analyzed according to <br />procedures described by Sobek et. al. (17). <br />- - <br />2.1 Acid/Base Accounting <br />The total sulfur content was determined by LECO furnace. <br />Neutralization potential (NP) was determined by adding a known excess of <br />hydrochloric acid, heating to ensure complete reaction, and titrating the <br />digested sample with standard sodium hydroxide to pH 1. The potential for <br />acid production and acid consumption were calculated from the total sulfur <br />and neutralization potential analyses respectively and expressed as equiva- <br />lent calcium carbonate (CaC03) (tonnes/1000 tonnes) (17). The net <br />r neutralization potential (Net NP) was calculated by subtracting the acid <br />producing from the acid consuming potential and was expressed as tonnes <br />CaC03/1000 tonnes of sample. <br />2.2 Humidity Cell <br />Approximately 20 cm diameter plastic containers with tight fit- <br />ting lids were used for the humidity cell experiment. Tygon tubing <br />