It takes 30 seconds to throw in the spot of CrO3. You don't breathe it, ingest it, or get it on your skin. Of all the safety things to worry about in an isotope lab, this one doesn't seem like trouble. As Bob Clayton points out, everything is ultimately referenced to results from a procedure using green acid. It is another reason why the old ways are best. Happy toeplering, and may the acid in the world's isotope labs stay green and fluid. Paul Knauth Department of Geology Arizona State University Box 871404 Tempe, Arizona 85287-1404 E-mail: [log in to unmask] (602) 965-2867 office (602) 831-1469 home (602) 965-8102 fax