Agar gel columns containing ammonium sulfide precipitant were investigated for possible use in mineral identification and trace element determination. The method is described, and optimum conditions for maximum sensitivity were determined. Co, Zn, Pb, Bi, Sb, and Sn were determined in solutions containing 20 p.p.m. or less. Fe, Cd, Cu, and As were determined in solutions containing less than 300 p.p.m. Hg was least sensitive, requiring a concentration of 600 p.p.m. Preliminary testing to determine accuracy in qualitative identification was carried out on 80 synthetic unknowns composed of 3 component mixtures of the previously mentioned ions plus Mo and Ni. Fe, Pb, Cd, and Co were identified correctly in all unknowns. Only As, Sb, and Sn gave any extensive difficulty, these having been determined with less than 80% accuracy. Sixty-one mineral samples were analyzed by this method, and the results were compared with those obtained from the emission spectrograph. It was found that the major metallic constituents of minerals can be determined with a high degree of accuracy. However, in most cases the minor constituents were missed. It was concluded that in special cases the method would be a useful field tool. Advantages of the technique are as follows: the equipment is inexpensive and portable; all metals that produce insoluble sulfides may be identified in mixtures by a single simple procedure; concentration may be estimated roughly by density of precipitate. Disadvantages of the technique are as follows: considerable experience is necessary to correctly interpret the results; a 48-hour period is necessary for the complete development of a chromatogram; the method is not very sensitive for certain of the metal ions.

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