bluuebunny/crossref_metadata_2025_split huggingface dataset:
Advances in X-Ray Diffractometry of Clay Minerals
Authors: Parrish William 
Published: August 2006

AbstractThe introduction of counter tubes and the related instrument geometries have made it possible to obtain greatly improved x-ray powder patterns. Most of the important factors that must be understood in x-ray diffractometry are described in terms of their effect on the intensity, peak-to-background ratio, resolution and line shape. These factors are the geometry of the x-ray optical system, the x-ray tube focal spot size, the angular apertures of the primary beam in the focusing and axial planes, the 2 : 1 setting, and the receiving slit. The precision is often limited by the specimen preparation rather than the instrument, and the effects of homogeneity, displacement and transparency, crystallite sizes, and preferred orientation are outlined. A new diffractometer arrangement employing a transmission specimen followed by a focusing crystal monochromator is shown to be a useful supplement to the standard reflecting specimen diffractometer for clay mineral studies. The important characteristics of Geiger, proportional and scintillation counters are described in terms of linearity, quantum counting efficiency, pulse amplitude distribution and counting statistics. A bibliography of key literature references is appended.
Clay Mineral Research at the Institute for Silicate Chemistry, Zagreb
Authors: Stubičan V. 
Published: August 2006

AbstractPart of the research on the structure, synthesis, and properties of clay minerals in Yugoslavia is reviewed with particular reference to the following problems: (a) attempts to synthesize halloysite from solutions under normal conditions; (b) structure and properties of synthetic montmorillonites; (c) dehydroxylation of kaolin minerals under nonequilibrium conditions; (d) structural properties of metakaolin as shown by adsorption of colloidal gold; and (e) free silica in bentonites.
Swelling Pressures of Dilute Na-Montmorillonite Pastes
Authors: Warkentin B. P. , Schofield R. K. 
Published: August 2006

AbstractSwelling pressures calculated from diffuse double-layer theory previously had been experimentally verified for Na-montmorillonite at clay concentrations above 10 percent, but published data at clay concentrations less than 5 percent consistently showed osmotic pressures much lower than the maximum of about 40 cm water calculated from theory. Swelling pressures of Na-montmorillonite in 4–5 percent orientated suspensions were therefore measured in an specially constructed osmometer in various solutions of NaCl up to 1.25 mN. The osmometer construction allowed solutions of desired concentration to be flushed continually across the membrane separating solution from clay. It was found that soluble impurities present in the clay decreased swelling pressures to about 1 cm of water. When these were removed during sample preparation, most efficiently by ultrafiltration through a dialysis membrane, swelling pressures measured were in satisfactory agreement with calculated values. The impurities were not identified chemically, but buffer curves of the solution toward HCl were determined.
X-Ray Analysis of Soil Colloids by a Modified Salted Paste Method
Authors: Barshad Isaac 
Published: August 2006

AbstractGlycerol-ethanol sodium salted clay pastes prepared from clays extracted directly from the soils and not allowed to dry were found to yield superior x-ray diffraction diagrams for the identification of the major clay minerals than pastes prepared from clays that suffered dehydration after extraction.Prevention of drying of soil clays after their extraction from the soils is essential for proper identification of the clay minerals. This is particularly true for identification of hydrated halloysite and for differentiation between high exchange forms and low exchange forms of montmorillonite. This differentiation is based on the finding that glycerol-ethanol salted potassium-saturated montmorillonite pastes prepared from clay suspensions have a 001 spacing of 18.5 Å whenever the exchange capacity ranges between 92 and 95 meq/100 g oven-dry clay, and 14.5 Å whenever the exchange capacity ranges between 115 and 135 meq/100 g. Either both these spacings or a mixed-layer spacing appears in montmorillonites having exchange capacities between 95 and 115 meq/100 g.Saturation of pure vermiculite minerals brings about contraction in the 001 spacing from 14.2 Å to 10.6 Å only after air drying in those forms with exchange capacities ranging between 200 and 207 meq/100 g water-free mineral, but in vermiculites with an exchange capacity of 250 meq/100 g this contraction occurs even without drying. Both of these forms of vermiculite are found in soils.Several sets of “standardized” natural clay mineral mixtures are necessary for quantitative x-ray analysis of soil clays.
Further Correlations of Kaolinite Crystallinity with Chemical and Physical Properties
Authors: Murray Haydn H. , Lyons Sanford C. 
Published: August 2006

AbstractPrevious work has demonstrated that the degree of crystal perfection in kaolinite can be correlated with many physical properties. In this paper some further relationships are shown, including surface area, base exchange capacity, total percentage of iron and titanium, and high-temperature mullitization. Surface area, base exchange capacity, and the total amount of iron and titanium in the clay increase as the degree of crystal perfection decreases.
Geology, Mineralogy, and Genesis of Selected Fireclays from Latah County, Idaho
Authors: Ponder Herman , Keller W. D. 
Published: August 2006

AbstractFireclay deposits occur in Latah County, Idaho, as residual weathered products, and as lacustrine sediments comprising part of the Miocene Latah formation. The residual deposits were developed upon granitic (granodioritic, gneissic) masses by surface weathering. The lacustrine fireclays were derived dominantly from weathered residuum and to a minor extent from volcanic ash.Mineral proportions in the residual clay are typically as follows: kaolin minerals, 65 percent; quartz, 20 percent; K-bearing micas, 12 percent; and montmorillonite-chlorite mixed-layer clay, trace.The sedimentary fireclay deposits range widely in clay content, from some that are almost wholly kaolin to others containing as little clay as the residual material, or alternatively, to those meeting minimal requirements of fireclay. As the content of kaolin decreases in the deposits, there is a corresponding increase in content of quartz, K-bearing micas, and in the less abundant components orthoclase, mixed-layer illite— montmorillonite, and mixed-layer chlorite—montmorillonite.In both the transported and residual clay bodies the kaolin minerals are, in order of decreasing abundance, halloysite, endellite, and fireclay mineral.The lake deposits also contain seams of poorly crystallized kaolin that is inferred to have been derived from volcanic ash because (1) it contains minor quantities of tridymite, sanidine, and volcanic glass, and (2) it contains notably more endellite and allophane (amorphous and relatively soluble in NaOH) than is present in the other kaolin deposits. Endellite seemingly has developed in two separate geologic environments: as an alteration product of granodiorite gneiss by surface weathering and as an alteration product of volcanic ash deposited and altered in a fresh-water lake. It is postulated that endellite is a relatively common product of weathering.
Ion Adsorption on Clays: A Review
Authors: van Olphen H. 
Published: August 2006

AbstractThe following ion-adsorption processes may occur on a solid surface, in contact with an ionic solution. An electric double layer is created by:1.Specific adsorption of certain ions (the “potential determining ions”) which give the surface a positive or a negative charge, unless, as in the case of the layer surface of a clay, the charge originates from interior crystal lattice imperfections.2.Accumulation of “counter ions” (“gegenions”) close to the charged surface in the liquid.In an established double layer there may occur:1.Exchange of counter ions for other species of the same sign available in solution (exchange adsorption).2.Chemisorption of ions on the surface, which may lead to destruction of the double layer or to the creation of a new double layer, possibly of opposite sign.3.Exchange of exposed lattice ions at the surface by ions in solution (lattice exchange).Therefore, in a single double layer several possibilities must be considered when interpreting adsorption data. In the case of clays, an additional complication arises in that two different double layers are involved simultaneously—the layer surface double layer and the edge double layer.The layer surface double layer originates from interior lattice substitutions; the edge double layer originates from the adsorption of potential determining ions on the broken-bond surface. The layer surface double layer is negatively charged; the edge surface double layer probably is amphoteric and may be either positive or negative depending on the composition of the solution.Technically, the two most important adsorption phenomena in clays are the cation exchange adsorption on the layer surfaces and chemisorption of anions at the edge surfaces. Our present knowledge on these two topics will be reviewed from the point of view of the electric double layer theory.
Cation Exchange Behavior of Vermiculite-Biotite Mixtures
Authors: Frysinger Galen R. 
Published: August 2006

AbstractThe cation exchange capacity of a series of commercially available vermiculite-biotite minerals (Traveler’s Best, South Carolina; Libby, Montana; and Polobora, South Africa) was measured by a column method using various cations. The selectivity of the clay mineral for various ion pairs was determined with particular attention given to the adsorption from a sodium chloride-cesium chloride mixed electrolyte solution. The mineral was found to be highly selective for cesium ion, a large part of the amount adsorbed probably replacing potassium ions in the biotite layers. This replacement in the biotite is a much slower process than normal ion exchange and greatly lengthened the time required to come to equilibrium in the column.The cesium ion cannot be removed easily from cesium-saturated vermiculite. The fixation of cesium ion was close to 100 percent at room temperature in contact with a cesium chloride solution. An isotopic exchange, Cs 133 for Cs 134, removed only very small quantities of the fixed cesium. Boiling with sodium chloride was only slightly more effective. All the results are in general agreement with the theory explaining ion fixation on the basis of collapse of the vermiculite structure to that of biotite.
Behavior of Moist Soils in a Thermal Energy Field
Authors: Winterkorn Hans F. 
Published: August 2006

AbstractAn account is given of the soil thermal resistivity problem faced by the electric power industry and its co-operative engineering solution. Data obtained in this activity and collected from other sources are employed to check the validity of various concepts that hare been developed to explain the phenomena observed when soils, composed of solid, liquid and gaseous phases, are placed in a thermal energy field. It is shown that formulas based on simple parallel or series arrangement of the component phases cannot account for the actual thermal transmission properties of moist soils. Nor can any one of the moisture transfer mechanisms, that have been proposed in explanation of the water movement associated with heat conduction in moist soils, by itself account for the observed magnitudes of thermal conductivity. Analysis of pertinent data renders it very probable that both evaporation-condensation and oriented film mechanisms must be involved in the coupled heat and moisture transport. What really takes place is an intricate interaction of a number of different events that can be understood qualitatively on the basis of the best available knowledge of soil-water interaction and its temperature dependence. Much work, however, remains to be done before a quantitative understanding can even be approached. The nature and magnitude of the remaining scientific problem can be appraised from the following pertinent statement by Szent-György. (1958) “The complexity of the situation with its very subtle equilibria makes conditions most colorful and begins to resemble the subtle complexity which characterizes life.”
Components of Pore Water Pressure and their Engineering Significance
Authors: Mitchell J. K. 
Published: August 2006

AbstractPore fluid pressures that develop within soil masses as a result of both mechanical and physico-chemical effects influence the magnitude of the intergranular or effective stresses. The intergranular stresses control, in many cases, soil behavior in shear and compression. The physical significance of pore water pressure in a cohesive soil is examined in terms of several components which combine to give the total pressure. An analysis of fluid pressures at various points within a soil mass based on a condition of no flow at equilibrium shows that changes in any one component of the total pressure from point to point are offset by changes in other components.The analysis shows that a pore pressure measurement reflects interparticle repulsive pressures and water adsorptive forces as well as purely hydrostatic pressures arising from mechanical effects. The individual components of total pore pressure are not directly measurable except in special systems. Data are presented which indicate that a significant portion of the swell of a compacted soil is attributable to water pressure deficiencies caused by mechanical and capillary components which act in addition to osmotic pressure components.Component water pressures are related to stresses between particles. It is shown that intergranular pressures are dependent on osmotic and adsorptive components of the total water pressure.
Shear Strength of Montmorillonite and Kaolinite Related to Interparticle Forces
Authors: Warkentin B. P. , Yong R. N. 
Published: August 2006

AbstractShear strength of saturated, remolded clay mineral samples was measured in an attempt to relate strength to forces acting between clay particles. The fine fractions of the clays, purified when necessary, were consolidated to different void ratios and subjected to quick, translatory shear in a direct shear device. Relative values for shear strength were obtained in this way. Interparticle forces in the clays were altered and the effect on shear strength was observed.For a high-swelling, Na-saturated montmorillonite, strength at constant void ratio decreased with increasing salt concentration. To explain the decrease in strength with decrease in force of repulsion between particles a model is suggested where strength results from the force of repulsion resisting displacement of particles in the shear plane. Addition of small amounts of dispersing and of soil-conditioning chemicals had little effect on shear strength.Calcium montmorillonite had a lower strength than sodium montmorillonite when compared at the same void ratios. This is related to the lower surface area of interaction and lower repulsion found with divalent ions.Water content at the liquid limit showed the same dependence upon interparticle forces in the montmorillonite clays as did shear strength.In kaolinite, interparticle forces of attraction result in a structure or particle arrangement which has the major influence on shear strength. A clay at low pH which was flocculated in a network, edge-to-face structure owing to presence of positive edge-charge had higher strength than a dispersed clay, but a clay flocculated by electrolyte which produced a lamellar, face-to-face structure had a lower strength.
Flocculation of Selected Clays by Various Electrolytes
Authors: Hsi Huey-rong , Clifton Donald F. 
Published: August 2006

AbstractThe flocculation behavior of clay specimens from altered basalt, altered granodiorite, and a transported (?) deposit in Latah County, Idaho, was investigated in order to determine if flocculation behavior would be an aid in characterizing clay samples in a way that could be related to the origin and history of the clays. The clay minerals are of the kaolinite group.As flocculants, various chlorides differ one hundred-fold and sodium salts twenty-fold in the concentrations necessary to flocculate a clay to a fixed settling rate. The concentrations of individual chlorides necessary to flocculate different clays vary three-fold and the concentrations of individual sodium salts vary ten-fold. In all cases the higher the valence of the cation the lower is the concentration required for flocculation; the relative effectiveness, however, varies with the clay. The relative effectiveness of the anions as flocculants varies greatly with the clay and no definite order of effectiveness is apparent.Halloysite requires less electrolyte for flocculation and has a larger settling volume than kaolinite. Well crystallized kaolinite has a smaller settling volume than poorly crystallized kaolinite.Wide differences of flocculation behavior may provide a valuable, rapid method of classifying the clays of a district.
Significance of Kaolinite Intersalation in Clay Mineral Analysis
Authors: Jackson M. L. 
Published: August 2006

AbstractRecent development of the intersalation method by which kaolinite (as well as dickite and halloysite) is expanded makes possible the application of X-ray diffraction to qualitative and semiquantitative determinations of these mineral species. It also permits their distinction from the X-ray-thermally similar intergradient 2:1–2:2 layer silicates which are not affected by the treatment. Intergradient 2:1–2:2 layer silicates are developed by interlayer precipitation of hydroxides of aluminum, iron, and magnesium during pedogeochemical weathering and probably also during burial in sediments. The quantitative determination of kaolinite-halloysite by NaOH differential dissolution is completely corroborated by the qualitative, semiquantitative X-ray diffraction intersalation technique with respect to their clear differentiation from chlorite and intergradient clays.
Adsorption by Organo-Clay Complexes
Authors: Cowan C. T. , White D. 
Published: August 2006

AbstractThe adsorption of phenols from dilute aqueous solution by n-aliphatic amine and Ethomeen clays has been investigated and it is shown that dodecylammonium bentonite is the most active member of the series ethylammonium to octadecylammonium bentonite. On the basis of spatial considerations, thermodynamic data, and electron density measurements a theory of adsorption has been proposed in which it is envisaged that condensation of adsorbate molecules on the organo-clay surface occurs through electrostatic/hydrogen bond forces at the hydrophilic sites and van der Waals forces at the organophilic sites.
Montmorillonite-Polyalcohol Complexes
Authors: Tettenhorst Rodney , Beck Carl W. , Brunton George 
Published: August 2006

AbstractSome montmorillonites may be differentiated by complexing them with polyalcohols having a CH2 group that is not connected to an oxygen atom. Montmorillonites with a low layer charge and high valence interlayer cations have larger basal spacings for their complexes than do those with a high layer charge and low valence interlayer cations. The basal spacings of these complexes are relatively larger if the clay has a large initial water content. The spacings for some complexes which are initially equilibrated at very low humidities are small, indicative of little penetration by polyalcohol molecules. Polyalcohol molecules may have difficulty replacing water molecules that are associated with the interlayer cations. The spacings of complexes with ethylene glycol and glycerol do not depend upon the initial interlayer water content. Water molecules may be an essential component of mont-morillonite-polyalcohol complexes.The polyalcohol molecules probably are associated with the clay surface through weak C-H···O interactions although virtually no shortening of this bond distance occurs. The C-H···O interaction is enhanced by the presence of higher valence interlayer cations. OH groups increase the thermal stability of complexes probably by interacting with the exchangeable cations. Longer chain molecules are held more tightly between the silicate sheets. One layer of polyalcohol molecules between silicate sheets is more stable than two layers. One layer of organic molecules is more stable with higher valence interlayer cations. Small molecules such as those of ethylene glycol may pack down somewhat into the “hexagonal holes” in the silicate surface.
Adsorption of Proteins, Enzymes and Antibiotics by Montmorillonite
Authors: Pinck Louis A. 
Published: August 2006

AbstractProteins interact with montmorillonite forming mono- and poly-layer complexes. About 20 percent of the protein in a monolayer complex undergoes microbial decomposition and the X-ray pattern remains unchanged, whereas in polylayer complexes the protein undergoes extensive decomposition and the c-spacings of these complexes shrink from approximately 30 Å to 12 Å+. Urease is adsorbed completely by H-montmorillonite and only partially by basic montmorillonite. Initial release of urease from the clay is attributed to urea acting as a cation. Subsequently the ammonia evolved by the hydrolysis of urea becomes the active cation. Antibiotic-montmorillonite complexes are classified into three groups. Group I contains strongly basic antibiotics, II amphoteric, and III acid or neutral. The average adsorption of antibiotic in mg per g of clay for each group is: I, 186; II, 307; and III, 9. X-ray diffraction data for groups I and II showed expansion of the c-spacing of 4.4 and 7.6 Å, respectively. Bioassays showed no activity for I and appreciable activity for II. The complexes are incapable of diffusing through agar, but the antibiotics must be released first by cationic exchange and then diffuse through the agar.
Orientation and Packing of Aliphatic Chain Molecules on Montmorillonite
Authors: Brindley G. W. , Hoffmann Reinhard W. 
Published: August 2006

AbstractAliphatic chain molecules may be adsorbed on montmorillonite surfaces with the zigzag of their carbon chain either parallel or perpendicular to the surface. These orientations are designated αII and αI, respectively. Fourier syntheses have too few terms to distinguish clearly between these orientations. The problem is studied therefore by consideration of the basal spacings. These spacings are appreciably less than the sum of the van der Waals cross-section of the molecules plus the thickness of the montmorillonite layer. Chemical bonding or geometrical packing, or both, appear as possible explanations.Previous studies have shown that CH activity influences the shape of the adsorption isotherms, but infrared studies of the adsorbed molecules have shown no appreciable change in the CH-stretching frequencies. This suggests the importance of the CH activity for organic—organic interaction on the clay surface rather than for clay-organic interaction itself.The possibility of geometrical packing is studied by means of molecular models and it is shown that an appreciable contraction can occur at a clay-organic interlace owing to a keying of the molecules into the surface structure. This is possible equally well for the αII and the αI orientations.From the information available, it appears that the αII arrangement is adopted by aliphatic chain molecules containing strongly polar groups in order to place the dipole parallel to the silicate surface, while the αI arrangement is favored by other aliphatic chain molecules possibly because this provides a favorable organic-organic interaction.