X-ray Diffraction Procedures for Clay Mineral Identification
01 Jan 1980-
About: The article was published on 1980-01-01. It has received 643 citations till now.
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10 Jan 2006
TL;DR: In this paper, the authors chart the understanding of landslide processes, prediction methods, and related land use issues, including land use, from timber harvesting and road building to urban and industrial development, and the effect of land use and climate change on landslides.
Abstract: Published by the American Geophysical Union as part of the Water Resources Monograph Series, Volume 18. Landslides are a constant in shaping our landscape. Whether by large episodic, or smaller chronic, mass movements, our mountains, hills, valleys, rivers, and streams bear evidence of change from landslides. Combined with anthropogenic factors, especially the development and settlement of unstable terrain, landslides (as natural processes) have become natural disasters. This book charts our understanding of landslide processes, prediction methods, and related land use issues. How and where do landslides initiate? What are the human and economic consequences? What hazard assessment and prediction methods are available, and how well do they work? How does land use, from timber harvesting and road building to urban and industrial development, affect landslide distribution in time and space? And what is the effect of land use and climate change on landslides? [Book Synopsis]
529 citations
TL;DR: In this paper, the authors provide a comprehensive understanding of the mechanism by which clay minerals swell and what steps have been taken in the development of effective and environmentally friendly clay swelling inhibitors.
492 citations
01 Jan 1986
440 citations
TL;DR: In this paper, the authors compared field spectra collected in situ to those collected in the laboratory at different depths, in triplicate, using principal component analysis and by using wavelength specific t-tests.
399 citations
Cites methods from "X-ray Diffraction Procedures for Cl..."
...The resultant diffractograms were used to assess the dominant minerals present by matching diffraction peaks with those published by Brindley and Brown (1980) for common soil minerals....
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TL;DR: In this paper, the authors used a three-factor simplex lattice design with three levels corresponding to kaolinite (K), illite (I) and smectite (S) to predict the mineral-organic composition of independent test mixes.
394 citations
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TL;DR: In this article, the bicarbonate-buffered Na2S2O4-citrate system was used for removing free iron oxides from latosolic soils, and the least destructive of iron silicate clays.
Abstract: The oxidation potential of dithionite (Na2S2O4) increases from 0.37 V to 0.73 V with increase in pH from 6 to 9, because hydroxyl is consumed during oxidation of dithionite. At the same time the amount of iron oxide dissolved in 15 minutes falls off (from 100 percent to less than 1 percent extracted) with increase in pH from 6 to 12 owing to solubility product relationships of iron oxides. An optimum pH for maximum reaction kinetics occurs at approximately pH 7.3. A buffer is needed to hold the pH at the optimum level because 4 moles of OH are used up in reaction with each mole of Na2S2O4 oxidized. Tests show that NaHCO3 effectively serves as a buffer in this application. Crystalline hematite dissolved in amounts of several hundred milligrams in 2 min. Crystalline goethite dissolved more slowly, but dissolved during the two or three 15 min treatments normally given for iron oxide removal from soils and clays. A series of methods for the extraction of iron oxides from soils and clays was tested with soils high in free iron oxides and with nontronite and other iron-bearing clays. It was found that the bicarbonate-buffered Na2S2O4-citrate system was the most effective in removal of free iron oxides from latosolic soils, and the least destructive of iron silicate clays as indicated by least loss in cation exchange capacity after the iron oxide removal treatment. With soils the decrease was very little but with the very susceptible Woody district nontronite, the decrease was about 17 percent as contrasted to 35–80 percent with other methods.
3,821 citations
01 Jan 1960
TL;DR: In this article, the bicarbonate-buffered Na 2 S 2 O 4 -citrate system was used for removing free iron oxides from latosolic soils, and the least destructive of iron silicate clays.
Abstract: The oxidation potential of dithionite (Na 2 S 2 O 4 ) increases from 0.37 V to 0.73 V with increase in pH from 6 to 9, because hydroxyl is consumed during oxidation of dithionite. At the same time the amount of iron oxide dissolved in 15 minutes falls off (from 100 percent to less than 1 percent extracted) with increase in pH from 6 to 12 owing to solubility product relationships of iron oxides. An optimum pH for maximum reaction kinetics occurs at approximately pH 7.3. A buffer is needed to hold the pH at the optimum level because 4 moles of OH are used up in reaction with each mole of Na 2 S 2 O 4 oxidized. Tests show that NaHCO 3 effectively serves as a buffer in this application. Crystalline hematite dissolved in amounts of several hundred milligrams in 2 min. Crystalline geothite dissolved more slowly, but dissolved during the two or three 15 min treatments normally given for iron oxide removal from soils and clays. A series of methods for the extraction of iron oxides from soils and clays was tested with soils high in free iron oxides and with nontronite and other iron-bearing clays. It was found that the bicarbonate-buffered Na 2 S 2 O 4 -citrate system was the most effective in removal of free iron oxides from latosolic soils, and the least destructive of iron silicate clays as indicated by least loss in cation exchange capacity after the iron oxide removal treatment. With soils the decrease was very little but with the very susceptible Woody district nontronite, the decrease was aboout 17 percent as contrasted to 35-80 percent with other methods.
2,081 citations
TL;DR: The chlorites form an extensive isostructural series with a high degree of isomorphous substitution, within which it has always been difficult to define or delimit species; until recently, owing to the lack of adequate X-ray studies, several structurally distinct species were included with the group, further complicating the problem as mentioned in this paper.
Abstract: The chlorites form an extensive isostructural series with a high degree of isomorphous substitution, within which it has always been difficult to define or delimit species; until recently, owing to the lack of adequate X-ray studies; several structurally distinct species were included with the group, further complicating the problem. The group comprises aluminosilicates of magnesium and iron (ferrous and ferric); a few contain appreciable amounts of chromium, nickel, or manganese, and one (pennantite) contains manganese as a major constituent. The first step towards the understanding of the relations of the chlorites was taken by G. Tschermak (1890, 1891), who divided them into two groups: the orthochlorites, with compositions between (Mg,Fe")2Al2SiO5(OH)4 and (Mg,Fe")2Si2O5(OH)4, and the leptochlorites, with compositions not explicable on this basis, and in general richer in trivalent ions (often including considerable Fe"′) relative to silicon and divalent ions. The two orthochlorite end-members have the composition of amesite and serpentine respectively, but it is now known that neither of these two minerals has the chlorite structure.
802 citations
TL;DR: In this article, it was shown that the aluminium content increased with decreasing particle size, and the (III) spacing showed a corresponding decrease, indicating that aluminium is a very common replacement for iron in soil goethites.
Abstract: Summary
It was possible to obtain relatively pure goethites (> 2 μ) from a range of soils by dissolving the clay minerals in boiling NaOH. The goethites were analysed chemically and studied by X-ray diffraction. All goethites contained aluminium, the amount ranging from 15 to 30 mol. per cent. AlOOH. The (III) spacing decreased steadily with increasing aluminium content. A study of different particle sizes from one soil showed that the aluminium content increased with decreasing particle size, and the (III) spacing showed a corresponding decrease. Extraction of soil goethite by free-iron removal agents, such as dithionite, brought into solution that aluminium contained in the goethites. The ease with which the goethite was dissolved by such treatments was inversely related to the amount of aluminium in the goethite, and led to the surprising situation in one soil where the coarser goethite was more easily extracted than the fine goethite. Measurements of the (III) spacings of many other soil goethites showed that almost invariably the unit cell dimensions were lower than those of pure goethite, indicating aluminium to be a very common replacement for iron in soil goethites. The degree of substitution of aluminium for iron probably depends on the weathering conditions in the soil. The aluminium probably restricts the size to which the goethite crystals can grow; it may, by its influence on particle size and by changing the composition of the goethite, alter the colour of goethite; it could modify the phosphate-fixing power and other chemical properties of soil goethites.
365 citations
01 Jan 1962
292 citations