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Geology topics

H. M. Nakagawa

Publications and source records attributed to H. M. Nakagawa.

4 recordsLinked to original sources
USGS1971

Determination of silver in soils, sediments, and rocks by organic-chelate extraction and atomic absorption spectrophotometry

A useful method for the determination of silver in soil, sediment, and rock samples in geochemical exploration has been developed. The sample is digested with concentrated nitric acid, and the silver extracted with triisooctyl thiophosphate (TOTP) in methyl isobutyl ketone (MIBK) after dilution of the acid digest to approximately 6 M . The extraction of silver into the organic extractant is quantitative and not affected by the nitric acid concentration from 4 M to 8 M , or by different volumes of TOTP-MIBK. The extracted silver is stable and remains in the organic phase up to several days. The silver concentration is determined by atomic absorption spectrophotometry.

Analytica Chimica Acta↗
USGS1966

Gold geochemical anomaly in the Cortez district, Nevada

An area in the Cortez district, Nevada, previously established to be anomalous in arsenic, antimony, and tungsten has been found to be anomalous also in mercury and gold. Samples from narrow quartz veins, calcite veins, and shear zones in partially silicified limestone in the lower plate of the Roberts thrust fault (Cortez window) contain as much as 3.4 ounces gold per ton. The richest samples are from an outcrop, about 100 feet long, surrounded by gravels. Their economic significance is yet to be established.

Circular↗
USGS1965

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.

Open-File Report↗