Determination of silver in rocks by a stoichiometric radioreagent radioisotope dilution technique

A rapid procedure for the routine determination of nanogram amounts of silver in rocks is described. After dissolution of the sample with a hydrofluoric-nitric-perchloric acid mixture in the presence of ¹¹⁰Ag tracer, the silver is separated by extraction as the dithizonate into xylene and back-extracted into dilute hydrochloric acid. After evaporation and removal of the hydrochloric acid, the silver is taken up in an acetic acid-sodium tartrate buffer solution and reacted with a constant amount of radioactively labelled iodide. The silver iodide formed is isolated by extraction into amyl alcohol and silver is determined by the ratio of the counting rate of the iodide to that of the silver in the silver iodide complex. Results of the analyses of several U.S. Geological Survey standard rocks are given.