A field method for the determination of silver in soils and rocks

A rapid, sensitive, and specific field method useful in geochemical exploration has been developed for the determination of silver in geologic materials. In this method the sample is digested with nitric acid and the silver is extracted with triisooctyl thiophosphate (TOTP) in benzene and stripped from the organic phase with dilute hydrochloric acid. Silver is then measured indirectly by its catalytic action on the persulfate oxidation of manganous ion to permanganate. The lower limit of sensitivity of the method is 0.01 ppm. Soils, rocks, oxides and sulfide ores have been analyzed, and the results agree favorably with assay and spectrographic analyses. About 80 determinations can be made per man-day.