Borohydride-flame determination of arsenic in phosphoric acid
No abstract available.
Analytical Chemistry↗
Geology topics
L. Paul Greenland
Publications and source records attributed to L. Paul Greenland.
Spectrophotometric determination of niobium in rocks
After acid decomposition and evaporation to volatilize silica, samples containing 0.5 6 μ g Nb are fused with pyrosulfate and dissolved in hydrochloric acid tartaric acid. Niobium is separated by thiocyanate extraction with amyl alcohol and back-extracting from the organic solvent with dilute hydrofluoric acid. Niobium is reacted with 4-(2-pyridylazo)-resorcinol to obtain a colored species. Analytical error, estimated from replicate analyses of eight U.S. Geological Survey standard rocks, ranges from 2.9 to 6.4 percent at the 1 27 μ g/g Nb level.
Journal of Research of the U.S. Geological Survey↗
Determination of indium in rocks by substoichiometric radioisotope dilution analysis
Rocks containing 10–140 ng of indium per g are decomposed with hydrofluoric and nitric acids in the presence of 114 In. Indium is separated from other constituents by sequential extractions of the bromide, cupferronate, and acetylacetonate, and is then reacted with a substoichiometric amont of EDTA. Excess of indium is removed by acetylacetone extraction and the specific activity of the complexed fraction is determined by counting 114 In. Analyses of the U.S.G.S. standard rocks are reported. These show good agreement with previous neutron activation analyses. Repetitive rock analyses indicated an analytical precision of ±4–7%.
Analytica Chimica Acta↗
Spectrophotometric determination of tungsten in rocks by an isotope dilution procedure
Samples are decomposed with hydrofluoric acid and perchloric acid in the presence of W 181 tracer. Molybdenum is extracted from a hydrochloric acid solution with tributyl phosphate. Tungsten is separated from most other elements by extraction of the a-benzoinoximate into chloroform. Stannous chloride in concentrated hydrochloric acid is used to strip tungsten and reduce it to W +5 . The amount of tungsten is determined spectrophotometrically after extraction as the thiocyanate complex into amyl alcohol. The correction for chemical losses is determined by counting W 181 .
Journal of Research of the U.S. Geological Survey↗
Determination of nanogram amounts of bismuth in rocks by substoichiometric isotope dilution analysis
A rapid procedure suitable for the routine determination of 1–10 ng of bismuth in a silicate rock matrix is described. Results for the U.S. Geological Survey standard rocks are presented. Rocks and minerals are dissolved in hydrofluoric-perchloric acid in the presence of 207 Bi tracer and the silica is removed by evaporation. The perchloric acid residue is taken up in water and bismuth iodide is extracted into methyl isobutyl ketone. After three acid-iodide washes, the bismuth is stripped into water and reacted with a substoichiometric amount of EDTA. Excess of bismuth is extracted as the iodide and the specific activity of the bismuth-EDTA complex is determined.
Analytica Chimica Acta↗
Distribution of scandium between coexisting biotite and hornblende in igneous rocks
Scandium analyses of more than 90 pairs of coexisting biotite and hornblende from igneous rocks of various provinces (including Southern California, Boulder, Sierra Nevada, Boulder Creek batholiths and the Jemez Mountains volcanic rocks) indicate that the distribution ratio (K d = Sc hornblende /Sc biotite ) for most samples closely approached that of an equilibrium distribution. Median K d values for the igneous samples range from 4.8 to 8.0, which are higher than similar values derived from published data on metamorphic samples and apparently not related to the mode of crystallization (volcanic, hypabyssal, or plutonic). A correlation between Kd and mafic index, (FeO + Fe 2 O 3 )/(FeO + Fe 2 O 3 + MgO) X 100, of both the minerals and the host rock, and between K d and SiO 2 content of the host rock, can be established only for the Southern California batholith samples. However, whether this correlation reflects temperature dependence, compositional dependence, or both, cannot be specified uniquely with present data. The present data also cast doubt on the validity of the so-called “scandium geothermometer.”
GSA Bulletin↗