Characterization of cation oxidation states in geologic materials

1992 ◽  
Vol 50 (2) ◽  
pp. 1742-1743
Author(s):  
Anne V. McGuire ◽  
M. Darby Dyar
Keyword(s):  
Electron Microprobe ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Iron Oxidation ◽  
Oxidation States ◽  
Charge Balance ◽  
Geologic Materials ◽  
Valence States ◽  
Treat All ◽  
Almost All

One shortfall of electron microprobe analysis is the inability of x-ray spectroscopic methods to distinguish multiple valence states of atoms. In geologic materials, many elements (eg. Fe, Ti, Cr, Mn, Cu, Eu) may exhibit multiple valence states and their quantitative analysis can be important in solving geologic problems. For instance, Fe2+/Fe3+ ratios in minerals may be useful in determining the oxygen fugacities in which rocks equilibrated. In the past, wet chemical methods were generally used to analyze mineral compositions and Fe2+/Fe3+ ratios were routinely determined. The advent of electron microprobe analysis was accompanied by a decrease in determination of iron oxidation states. The modern microprobe analyst generally deals with the inability to measure Fe2+/Fe3+ ratios by picking one of several assumptions: (a) treat all iron as Fe2+; (b) treat all iron as Fe3+; or (c) calculate an Fe2+/Fe3+ ratio using assumptions of perfect mineral stoichiometry and charge balance. Since almost all iron-bearing minerals contain both Fe2+ and Fe3+, the first two treatments are obviously unsatisfactory.

X-ray Diffraction/Electron Microprobe Analysis of Surface Films Formed on Alloys During Hydrothermal Reaction with Geologic Materials

1984 ◽  
Vol 28 ◽  
pp. 367-375 ◽  
Author(s):  
R. G. Johnston ◽  
M. B. Strope ◽  
R. P. Anantatmula
Keyword(s):  
Electron Microprobe ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Hydrothermal Reaction ◽  
Pressure Vessels ◽  
Surface Films ◽  
X Ray Diffraction ◽  
X Ray ◽  
Geologic Materials ◽  
Structure Phase

AbstractX-ray diffraction and electron microprobe analysis were used in combination to identify reaction phases that formed on the surfaces of low-carbon steel specimens reacted with a 75% basalt-25% bentonite mixture and anion-doped water in sealed pressure vessels at 100°C and 250°C. Reaction phases on specimen surfaces and in adhering geologic material were identified by conventional X-ray diffraction scans of entire specimens with intact reaction layers. Comparison of results from adhering geologic material and scans of selectively removed layers allowed establishment of approximate reaction gradients in the adhering packing material. Electron microprobe analysis of specimens in cross-section provided quantitative chemical analyses of adhering reaction phases, and identification of reaction layer composition gradients and thicknesses. Magnetite formed on the surface of specimens reacted at 250°C for 4 weeks. Iron-enriched clay was also observed on specimen surfaces and in the adjacent basalt-bentonite mixture. The 100°C experiments yielded surface films of a siderite-structure phase, (Fe,Ca,Mn)CO3, that were not observed in previous experiments with synthetic ground-water. Less extensive iron enrichment of the adjacent clays compared to that seen in the 250°C experiments was observed. The siderite-structure phase generally formed when no carbonate ion was present in the initial solution, implying dissolution of impurity calcite in the bentonite as the controlling factor in the reaction. The results demonstrate the utility of combining X-ray diffraction and electron microprobe analysis for characterization of reaction phases on alloys reacted with complex geologic materials.

Occurrence of some Ni- and Sn-rich minerals in copper converter slags

1984 ◽  
Vol 48 (347) ◽  
pp. 243-249 ◽  
Author(s):  
E. Wearing
Keyword(s):  
Electron Microprobe ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Chemical Variation ◽  
Charge Balance ◽  
Complex Composition ◽  
Copper Converter ◽  
Mineral Phases

AbstractThe chemistry of opaque spinel, delafossite (Cu2O·Fe2O3), cuprite (Cu2O), cassiterite, nickel-olivine (Ni2SiO4), and bunsenite (NiO) from some copper converter slags has been investigated by electron microprobe analysis. The spinel has a complex composition containing up to 33.89% NiO and 47.69% SnO2, ranging from essentially Ni2SnO4 to (Ni,Fe2+)O4. The associated delafossite contains up to 19.18% NiO and 38.15% SnO2. The chemical variation of the mineral phases is evaluated, and it appears that Ni2+ enters the spinel and delafossite to charge-balance the octahedrally coordinated Sn4+.

Scanning Electron Microscopy and Electron Microprobe Analysis of Malignant Cell Cultures

1968 ◽  
Vol 26 ◽  
pp. 164-165
Author(s):  
R. I. Johnsson-Hegyeli ◽  
A. F. Hegyeli ◽  
D. K. Landstrom ◽  
W. C. Lane
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Cell Cultures ◽  
Electron Microprobe ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Three Dimensional ◽  
Malignant Cell ◽  
Interference Microscopy ◽  
Scanning Electron

Last year we reported on the use of reflected light interference microscopy (RLIM) for the direct color photography of the surfaces of living normal and malignant cell cultures without the use of replicas, fixatives, or stains. The surface topography of living cells was found to follow underlying cellular structures such as nuceloli, nuclear membranes, and cytoplasmic organelles, making possible the study of their three-dimensional relationships in time. The technique makes possible the direct examination of cells grown on opaque as well as transparent surfaces. The successful in situ electron microprobe analysis of the elemental composition and distribution within single tissue culture cells was also reported.This paper deals with the parallel and combined use of scanning electron microscopy (SEM) and the two previous techniques in a study of living and fixed cancer cells. All three studies can be carried out consecutively on the same experimental specimens without disturbing the cells or their structural relationships to each other and the surface on which they are grown. KB carcinoma cells were grown on glass coverslips in closed Leighto tubes as previously described. The cultures were photographed alive by means of RLIM, then fixed with a fixative modified from Sabatini, et al (1963).

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