Quote from Sparohok:
Reminds me of a story my high school chemistry teacher told. I have no idea whether this is true or not.
He claimed that he lined up a source of bulk used x-ray film from the local hospital that had a particularly high concentration of silver halide emulsion. He chemically extracted and purified the silver, intending to sell it. When he went to a metals dealer he found it nearly impossible to sell because it didn't have a paper trail. In the end the assay costs ate up most of his profit from the relatively small quantities he was dealing with.
Martin