Potential cause for low lead and chromium recoveries during acid extractions

BUREAU OF RECLAMATION LIBRARY Potential Cause for Low Lead and Chromium Recoveries During Acid Extractions Alan D. Hewitt and James H. Cragin October 1992 FEB 81993 Bureau of Reclamation ^ ? Denver OffioêbSTfüCt j When higTTconcentrations (>100 mg/L) of Pb and Cr (IV) are present together in solution, PbCr04 precipitates, resulting in losses of these two metals. Moderate acidification with 1 -2% HNO3 does not prevent precipitation loss. Caution is necessary when preparing standard solutions or handling acidic extracts of environmental samples containing high levels of Pb and Cr, since undetected formation of metal chromates will result in low recoveries of these metals. For conversion of SI metric units to U.S./British customary units of measurement consult ASTM Standard E380, Metric Practice Guide, published by the American Society for Testing and Materials, 1916 Race St., Philadelphia, Pa. 19103. This report is printed on paper that contains a minimum of 50% recycled material. Special Report 92-23 mz, o! BUREA.V ..? ^ ? E.CLAMAT,0N DENVER LIBRARY '*3046544 U.S. Army Corps of Engineers Cold Regions Research & Engineering Laboratory Potential Cause for Low Lead and Chromium Recoveries During Acid Extractions Alan D. Hewitt and James H. Cragin October 1992 Prepared for U.S. ARMY TOXIC AND HAZARDOUS MATERIALS AGENCY REPORT CETH A-TS-CR-92061 Approved for public release; distribution is unlimited. 92048244 PREFACE This report was prepared by Alan D. Hewitt, Research Physical Scientist, Geo­logical Sciences Branch, and James H. Cragin, Research Chemist, Snow and Ice Branch, Research Division, U.S. Army Cold Regions Research and Engineering Laboratory. Funding was provided through the U.S. Army Toxic and Hazardous Materials Agency (USATHAMA), Durant Graves, Project Monitor, and by DA Project 4A161102AT24, Work Unit 003, Properties of Cold Regions Boundary Layer Constitu­ents. T he authors thank Dr. Clarence Grant (University of New Hampshire) and Daniel Leggett (CRREL) f