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this laboratory experiment, we will look only at the ngf add producing potential of mine overburden <br />samples and quantify it in terms of millequivalents of H' produced per 100 g of sample. In orler to <br />obtain the Ogt add producng potential of a sample we must determine the aad produdng potential of <br />the sample and the neutralizing potential of the sample and subtract these two values. <br />RECEIVED <br />FEB 2 7 2007 <br />Division of Kectamation, <br />Mining and Safety <br />- AcW Produeing Potental of Mine Overburden <br />1. Aocuretely weigh three or four samples of your unknown. F~dr sample should weigh dose to <br />0.5 to 0.7 g. Record your masses to 0.0001 g. Transfer to a 50 mL centrifuge tube. <br />2. Add 10 mL of 4 M HCI to the centrifuge tugs. Cap, Shake, let stand for 30 minutes until the <br />reaction is complete. Shake again. <br />3. Centrifuge, then decant add into a waste container. <br />4. Add 40 mL of D.I. HBO, shake, centrifuge, and decant iMO a waste container. Repeat this <br />procedure at least 3 more times or until the pH reaches at least 4.5. <br />5. After washing, add 5 mL of 30% H2O2 to the pyrite. Keep the cap off the tube and support the <br />tube in a beaker. The reaction may goon for 15-30 minutes, getting very active and hot in the <br />middle. During the quieter reacton Omes, mix the solid into the solution gently. <br />8. After the reaction stops, add 3 mL more of 30 % HZ02 and allow this to react completety. Then <br />heat in a water bath at 80-90°C for a few minutes to decompose any excess peroxide. <br />7. Transfer the contents of the centriNge tube to a 250 mL beaker and bring the volume up to <br />about 100 mL with D.1. water. Set the beaker on a magnetic stirrer, standardize a pH meter <br />and suspend the electrode into you soltfion. Tihate the sample with a standardized 0.025 M <br />NaOH solution. Plot a pH titration wive and determine the volume of NaOH required to reach <br />the end point of pH=7.0. Determine the add produdng potential of ~rour unknown and report <br />the findings as milliequivaleMs H'/100 g sample (or millimdes of H /100 g sample). <br />- Neutrelizing Potential of Mine Overburden <br />