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M. K. Carron

Publications and source records attributed to M. K. Carron.

10 recordsLinked to original sources
USGS2002

Determination of thorium and of rare earth elements in cerium earth minerals and ores

The conventional oxalate method for precipitating thorium and the rare earth elements in acid solution exhibits definite solubilities of these elements. The present work was undertaken to establish conditions overcoming these solubilities and to find optimum conditions for precipitating thorium and the rare earth elements as hydroxides and sebacates. The investigations resulted in a reliable procedure applicable to samples in which the cerium group elements predominate. The oxalate precipitations are made from homogeneous solution at pH 2 by adding a prepared solution of anhydrous oxalic acid in methanol instead of the more expensive crystalline methyl oxalate. Calcium is added as a carrier. Quantitative precipitation of thorium and the rare earth elements is ascertained by further small additions of calcium to the supernatant liquid, until the added calcium precipitates as oxalate within 2 minutes. Calcium is removed by precipitating the hydroxides of thorium and rare earths at room temperature by adding ammonium hydroxide to pH > 10. Thorium is separated as the sebacate at pH 2.5, and the rare earths are precipitated with ammonium sebacate at pH 9. Maximum errors for combined weights of thorium and rare earth oxides on synthetic mixtures are ± 0.6 mg. Maximum error for separated thoria is ± 0.5 mg.

Analytical Chemistry↗
USGS2002

Determination of iron in the presence of chromium and titanium with the Jones reductor

Sulfuric acid solutions of titanous and chromous sulfates, obtained by passage through the Jones reductor, are oxidized by aeration for from 5 to 10 minutes in the presence of a trace of copper sulfate as a catalyst. Ferrous sulfate is essentially unoxidized and is titrated with permanganate after aeration. Best results are obtained by using 0.0003 millimole of copper sulfate in about 300 ml. of solution. Larger quantities of copper sulfate lead to slightly low results when both chromium and titanium are present.

Industrial and Engineering Chemistry↗
USGS1972

New data on selected Ivory Coast tektites

Fourteen Ivory Coast tektites exhibit a range of bulk indices of refraction of 1.5156 to 1.5217 ± 0.0004 and of bulk specific gravities of 2.428 to 2.502 ±0.005. Seven of these Ivory Coast (IVC) tektites were analyzed for major and minor element content. Compared to tektites from other strewn fields, their SiO 2 content is low (67.2–69.1 %), A1 2 O 3 relatively high (15.8–16.8 %), and total iron relatively high but with a more restricted range (6.3–6.8 % as FeO). Their lime content is low (0.71–1.35%) compared to Australasian tektites but their MgO CaO "> MgOCaO ratio (about 3.1) is unusually high. All other tektite groups have Na 2 O K 2 O "> Na2OK2O ratios less than unity, but the Na 2 O K 2 O "> Na2OK2O ratio of the IVC tektites is slightly greater than unity. Their K Rb "> KRb ratios range from 200 to 256 and average 227, which is higher than those determined for Australasian tektites, but similar to some obtained for moldavites. The Li content (41–48 ppm) is about the same as that of the Australasian tektites, but the Cs and Rb are lower, being 1.9 to 2.9 and 57 to 86 ppm, respectively. The IVC tektites are high in Cr (260–375 ppm), Co (19–25 ppm) and Ni (101–167 ppm), and particularly in Pb (<10–18 ppm ), Cu (13–21 ppm) and Ga (14–23 ppm). The high Cr Ni "> CrNi ratios of the IVC tektites (range 2–3.6) are similar to those found for australites, philippinites and thailandites, but not the javanites and indochinites. Evaluation of these and other reported data show that compositional similarities between the IVC tektites and green or black Bosumtwi Crater glasses strongly support the hypothesis of a common impact origin—i.e. the Bosumtwi Crater site. Comparison of the IVC tektite composition with those of returned lunar materials (gabbros, basalts, breccia and soils) do not support a lunar origin for the Ivory Coast tektites.

Geochimica et Cosmochimica Acta↗
USGS1970

Semimicro chemical and x-ray fluorescence analysis of lunar samples

Major and selected minor elements were determined in seven whole rock fragments, five portions of pulverized lunar rock, and the lunar soil. Three different rock types were represented: vesicular, fine-grained basaltic rocks; medium- to coarse-grained, vuggy gabbroic rocks; and breccia. The ranges (in percent) for the major constituents of the lunar samples are: SiO 2 , 38 to 42; Al 2 O 3 , 8 to 14; total iron as FeO, 15 to 20; MgO, 6 to 8; CaO, 10 to 12; Na 2 O, 0.5 to 1; K 2 O, 0.05 to 0.4; TiO 2 , 8 to 13; MnO, 0.2 to 0.3; and Cr 2 O 3 , 0.2 to 0.4. The high reducing capacity of the samples strongly suggests the presence of Ti(III).

Science↗
USGS1964

Vapor pressure and vapor fractionation of silicate melts of tektite composition

The total vapor pressure of Philippine tektite melts of approximately 70 per cent silica has been determined at temperatures ranging from 1500 to 2100°C. This pressure is 190 ± 40 mm Hg at 1500°C, 450 ± 50 mm at 1800°C and 850 ± 70 mm at 2100° C. Determinations were made by visually observing the temperature at which bubbles began to form at a constant low ambient pressure. By varying the ambient pressure, a boiling point curve was constructed. This curve differs from the equilibrium vapor pressure curve due to surface tension effects. This difference was evaluated by determining the equilibrium bubble size in the melt and calculating the pressure due to surface tension, assuming the latter to be 380 dyn/cm. The relative volatility from tektite melts of the oxides of Na, K, Fe, Al and Si has been determined as a function of temperature, total pressure arid roughly, of oxygen fugacity. The volatility of SiO 2 is decreased and that of Na 2 O and K 2 O is increased in an oxygen-poor environment. Preliminary results indicate that volatilization at 2100°C under atmospheric pressure caused little or no change in the percentage Na 2 O and K 2 O. The ratio Fe 3 Fe 2 "> Fe 3 Fe 2 of the tektite is increased in ambient air at a pressure of 9 × 10 −4 mm Hg (= 10 6.5 atm O 2 , partial pressure) at 2000°C. This suggests that tektites were formed either at lower oxygen pressures or that they are a product of incomplete oxidation of parent material with a still lower ferricferrous ratio.

Geochimica et Cosmochimica Acta↗
USGS1957

Systematic variation of rare-earth elements in cerium-earth minerals

In a continuation of a study reported previously, rare-earth elements and thorium have been determined in monazite, allanite, cerite, bastnaesite, and a number of miscellaneous cerium-earth minerals. A quantity called sigma (∑), which is the sum of the atomic percentages of La, Ce, and Pr, is proposed as an index of composition of all cerium-earth minerals with respect to the rare-earth elements. The value of ∑ for all of the minerals analysed falls between 58 and 92 atomic per cent. Monazites, allanites, and cerites cover the entire observed range, whereas bastnaesites are sharply restricted to the range between 80 and 92 atomic per cent. The minimum value of ∑ for a cerium-earth mineral corresponds to the smallest possible unit-cell size of the mineral. In monazite, this structurally controlled minimum value of ∑ is estimated to be around 30 atomic per cent. Neodymium, because of its abundance, and yttrium, because of its small size, have dominant roles in contraction of the structure. In the other direction, the limit of variation in composition will be reached when lanthanum becomes the sole rare-earth element in a cerium-earth mineral. Cerium-earth minerals from alkalic rocks are all characterized by values of ∑ greater than 80 atomic per cent, indicating that the processes that formed these rocks were unusually efficient in fractionating the rare-earth elements—efficient in the sense that a highly selected assemblage is produced without eliminating the bulk of these elements. Analyses of inner and outer parts of two large crystals of monazite from different deposits show no difference in ∑ in one crystal and a slightly smaller value of ∑ in the outer part of the other crystal compared to the inner part. The ∑ of monazites from pegmatites that intrude genetically related granitic rocks in North Carolina is found to be either higher or lower than the ∑ of monazites in the intruded host rock. These results indicate that the fractionation of the rare-earth elements is not a simple unidirectional process. When a cerium-earth mineral undergoes replacement, its rare-earth elements may be fractionated into two parts, one forming a new mineral with ∑ that is smaller, and the other a second new mineral with ∑ that is larger than that of the original mineral. The complete analysis of a cerium-earth mineral to determine its ∑ is time consuming. The discovery of a direct relationship between ∑ and the Ce/(Nd + Y) atomic ratio in cerium earth minerals allows a rapid determination of ∑ from spectrograms obtained in a previously described method for determining thorium in these minerals.

Geochimica et Cosmochimica Acta↗
USGS1954

A chemical-spectrochemical method for the determination of rare earth elements and thorium in cerium minerals

In a combined chemical-spectrochemical procedure for quantitatively determining rare earth elements in cerium minerals, cerium is determined volumetrically, a total rare earths plus thoria precipitate is separated chemically, the ceria content of the precipitate is raised to 80·0 percent by adding pure ceria, and the resulting mixture is analyzed for lanthanum, praseodymium, neodymium, samarium, gadolinium, yttrium, and thorium spectrochemically by means of the d.c. carbon arc. Spectral lines of singly ionized cerium are used as internal standard lines in the spectrochemical determination which is patterned after Fassel's procedure [1]. Results of testing the method with synthetic mixtures of rare earths and with samples of chemically analyzed cerium minerals show that the coefficient of variation for a quadruplicate determination of any element does not exceed 5·0 (excepting yttrium at concentrations less than 1 percent) and that the method is free of serious systematic error.

Spectrochimica Acta↗
USGS1953

Systematic variation of rare earths in monazite

Ten monazites from widely scattered localities have been analyzed for La, Ce, Pr, Nd, Sm, Gd, Y and Th by means of a combined chemical and emission spectrographic method. The analytical results, calculated to atomic percent of total rare earths (thorium excluded), show a considerable variation in the proportions of every element except praseodymium, which is relatively constant. The general variation trends of the elements may be calculated by assuming that the monazites represent different stages in a fractional precipitation process, and by assuming that there is a gradational increase in the precipitability of rare earth elements with decreasing ionic radius. Fractional precipitation brings about an increase in lanthanum and cerium, little change in praseodymium, and a decrease in neodymium, samarium, gadolinium, and yttrium. Deviations from the calculated lines of variation consist of a simultaneous, abnormal increase or decrease in the proportions of cerium, praseodymium, and neodymium with antipathetic decrease or increase in the proportions of the other elements. These deviations are ascribed to abnormally high or low temperatures that affect the precipitability of the central trio of elements (Ce, Pr, Nd) relatively more than that of the other elements. The following semiquantitative rules have been found useful in describing the composition of rare earths from monazite: 1. The sum of lanthanum and neodymium is very nearly a constant at 42 ± 2 atomic percent. 2. Praseodymium is very nearly constant at 5 ± 1 atomic percent. 3. The sum of Ce, Sm, Gd, and Y is very nearly a constant at 53 ± 3 atomic percent. No correlation could be established between the content of Th and that of any of the rare earth elements.

Geochimica et Cosmochimica Acta↗
USGS1952

Phosphate mineralization at Bomi hill and Bambuta, Liberia, west Africa

Iron phosphate minerals which cement talus ore below cliffs formed by massive magnetite- hematite deposits at Bomi hill, Liberia, and also occur in place in fissures and caves in the ore both at Bomi hill and Bambuta, were formed by the interaction of bat dung and iron oxides. The minerals include leucophosphite (previously known only from Western Australia), phosphosiderite, and strengite. Analyses of the leucophosphite are included.

West Africa↗