bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Nature of Garnierites—III Thermal Transformations
Authors: Hang Pham Thi , Brindley G. W. 
Published: September 2006

AbstractSerpentine- and talc-like garnierites described in Parts I and II were heated at various temperatures up to about 1000°C and after each treatment were cooled and examined by X-ray powder diffraction. The serpentine-like garnierites at about 550°C, the temperature at which rapid dehydroxy-lation begins, formed a highly disordered phase. When the NiO content was low (approximately < 20 wt%), the disordered phase transformed directly to an olivine phase around 800°C, but when the NiO content was higher, various transitional phases were formed before an olivine phase appeared around 1000°C. A sepiolite-like phase was obtained with one sample around 800°C, and several samples showed face-centered cubic modifications between 900 and 1000°C.The talc-like garnierites with low NiO content formed an enstatite phase around 800°C directly following the dehydroxylation reaction, but with high NiO contents an olivine phase became increasingly prominent between 850 and 1000°C. Identification of the mixed crystallizations possibly existing in the initial minerals is scarcely feasible on the basis of the products formed up to 1000°C.
Effect of Particle Thickness on Potassium Exchange from Phlogopite
Authors: Ross G. J. , Rich C. I. 
Published: September 2006

AbstractRates of exchange of K with Ca for fine (0·2–2 μm) and coarse (54–75 μm) and for thin and thick (37–45 μm) phlogopite particles were determined using a repeated batch technique, which gave a measure of K selectivity.Potassium selectivity of the fine fraction was higher than that of the coarse one throughout the exchange process in which 93 per cent of the total K was exchanged from the fine fraction and 100 per cent from the coarse one. Potassium selectivity of the thin 37–45 μm particles was higher initially than that of the thick 37–45 μm particles but the difference disappeared subsequently and practically 100 per cent of the total K was exchanged from both the thin and thick particles.The results are interpreted as tentatively confirming the hypothesis that bending and deformation of elementary layers during K exchange increase with particle thickness, which in turn increase K exchange and decrease K selectivity.The K exchange curves for the fine and coarse phlogopite fractions suggest that in natural conditions, as in soils, where K is not continuously removed from solution, vermiculization of coarse mica particles may be not only more complete but also more rapid than vermiculization of fine mica particles.
A Natural 17Å Montmorillonite-Organic Complex from Alleppey, Kerala State-India
Authors: Moum Johan , Rao Chatty N. , Ayyar T. S. R. 
Published: September 2006

AbstractA black organic-rich alluvial clay from Alleppey, Kerala State, India, gave a well defined 17Å reflection in the natural untreated state. Ethylene glycol and heat treatments showed it to be essentially a smectite. Treatments with H2O2 and 0·1 N NaOH contracted the spacing to about 14Å, indicating that sorbed organic matter was responsible for the original enhanced spacing.In the natural state, the clay was chiefly divalent with respect to the ions on its exchange sites and was at a pH of 6·2. Subsequent attempts to resorb the organic matter (which had been extracted from the clay by repeated NaOH treatments, converted to the H-form, concentrated and freeze-dried) into the interlamellar space of H2O2-treated clay proved successful only after the pH was brought down to 3•2 and the clay converted to an essentially monovalent state through repeated 1 N NaCl treatments.
The Transference Numbers of the Counter-Ions in Montmorillonite Paste as a Function of Water Film Thickness and Electrolyte Concentration
Authors: Tschapek M. , Grazán A. M. 
Published: September 2006

AbstractThe transference numbers of the counter ions in montmorillonite paste are determined as a function of the thickness of the water film (h) and of the diffuse double layer (1/κ).From measured E.M.F. values of a cell with two liquid junction potentials (C′KCl solution-paste-C″KCl solution) and by applying the Henderson equation, the transference numbers t+ were calculated. It is shown that the transference numbers of the counter-ions, t+ → 1 if hκ → 0.
The Crystal Structure of Talc
Authors: Rayner J. H. , Brown G. 
Published: September 2006

AbstractThe crystal structure of a sample of talc from Harford County, Maryland, has been determined by least squares refinement from X-ray diffraction photographs. A triclinic cell with a = 5·293, b = 9·179, c = 9·496Å, α = 90·57°, β = 98·91°, γ = 90·03, space group C1̄ is adopted. The layers of the structure have almost monoclinic symmetry but the nearly hexagonal rings of oxygen atoms on the surfaces of the layers, formed by the bases of the silica tetrahedra, are not held in register by interlayer ions as they are in micas but are partly displaced so that the stack of layers forms a triclinic crystal. The hexagons of surface oxygens are distorted by a 3·4° twist of the tetrahedra so that the b axis is 0·2 per cent shorter than in a structure with regular hexagons, and the twist brings the oxygen ions a little closer to the octahedral magnesium ions.
Infrared Study of Attapulgite and HCl Treated Attapulgite
Authors: Mendelovici Efraim 
Published: September 2006

AbstractInfrared absorption spectra show important changes in the positions and form of the absorption bands of a film of attapulgite after it has been pumped out. An attempt to differentiate among some of the multiple frequencies due to OH groups is based on the information obtained from dehydration and deuteration experiments. The 1198 cm−1 shoulder, characteristic of attapulgite, is assigned to a Si-O vibration. When attapulgite is refluxed with 5N HCl for 5 hr the octahedral layer is dissolved. The acid attack causes the disappearance of the Si-O-Si absorption bands from attapulgite giving rise to a characteristic vibration at 1090 cm−1, as well as another absorption at 960 cm−1. The latter indicates the presence of silanol groups.
Evaluation of Crystallinity in Hydrated Ferric Oxides
Authors: Landa Edward R. , Gast Robert G. 
Published: September 2006

AbstractThe nature of freshly-precipitated and aged hydrated ferric oxides prepared by the addition of ferric chloride to KOH was investigated by the use of scanning and transmission electron microscopy, X-ray diffraction, i.r. absorption, and pH 3·0 ammonium oxalate extraction. The results show the fresh material to be essentially non-crystalline hydrated ferric oxide, which when aged at 60°C C and high pH rapidly crystallizes as goethite, without any indication of coexisting hematite. The various methods were evaluated as indices of crystallinity for aging materials. The acid ammonium oxalate method was shown to extract selectively only the non-crystalline portion of such mixtures. The use of X-ray diffraction analysis for estimating aging stage requires elimination of the preferred orientation of the goethite crystals. While both the oxalate and X-ray methods can detect as little as 2 per cent crystallinity, the oxalate method is probably superior for quantitative determinations as it depends directly on an inherent difference in the solubility of the crystalline and non-crystalline materials, rather than on a technique dependent intensity measurement. The use of the intensity of the O-H bending vibrations of the infrared absorption spectra can also potentially detect as little as 2 per cent crystallinity, but the procedure is probably less useful for quantitative determinations than the oxalate or X-ray methods because of the problem of evaluating the area under the peaks.
Interlayer Bonding in Kaolinite, Dickite and Nacrite
Authors: Giese R. F. 
Published: September 2006

AbstractA simple electrostatic model has been used to demonstrate that the inner surface hydroxyls in kaolinite, dickite and nacrite are responsible for the interlayer bonding in these minerals. The contribution to the interlayer bonding of an individual hydroxyl hydrogen depends on the orientation of the hydroxyl group relative to the 1:1 layer since this orientation determines the H—O interlayer distance. If this distance is much greater than the sum of the van der Waals radii, 2·60 Å, there is essentially no bond. As the distance becomes less than 2·60 Å, the strength of the interlayer bond increases.
Distribution of Major Cations in Estuarine Sediments
Authors: Parashiva Murthy A. S. , Ferrell R. E. 
Published: September 2006

AbstractThis paper reports the measured distribution of major cations in interstitial, exchangeable and non-exchangeable phases of estuarine sediments. The observed changes in ionic ratios result from the valence and dilution effects in the Donnan equilibrium concept according to which the ion exchanger favors the sorption of divalent ions at the expense of monovalent cations and cations migrate to the outer solution. The above findings have direct application to an interpretation of diagenetic changes in clay minerals.
The Experimental Transformation of Mica Toward Smectite; Relative Importance of Total Charge and Tetrahedral Substitution
Authors: Robert M. 
Published: September 2006

AbstractThis article emphasizes the influence of crystal-chemical composition on the ease of transformation of micas to vermiculite or more smectite-like minerals. The swelling test, with glycerol, of Mg-saturated mineral is used to characterize the degree of transformation.The main structural factors of this evolution are tetrahedral substitution of Si by Al, and total charge. There is a relation between these two factors, i.e. the lower the tetrahedral substitution, the greater can be the charge without affecting the smectite swelling behavior.In this respect there is a contrast between tri and dioctahedral micas. In the first, tetrahedral Al is so high (> 1·20 for Si4O10) that transformation into smectite must imply modification of the tetrahedral layer. For dioctahedral micaceous phyllites (illites, glauconites) where tetrahedral charge is lower, transformation can be easier. Only a lowering of total charge is needed and reduction-oxidation seems to play a very important role in this process.
The Location of Iron-55, Strontium-85 and Iodide-125 Sorbed by Kaolinite and Dickite Particles
Authors: Fordham A. W. 
Published: September 2006

AbstractThe autoradiographic method at the electron microscope level has been applied successfully to locate the position of sorbed ions and compounds associated with kaolinite and dickite particles. For suitable isotopes, the limit of resolution was about 0·2 μm and would be conceivably less in the most favorable conditions.Judged by the location of iodide-125 and strontium-85, the majority of positive sites and also the most reactive negative sites were situated at the edges of the clay particles. These conclusions were supported by normal electron microscope examination of mixtures of clay with charged gold and silver iodide sols.Iron (III) ions, which have been shown to react with kaolinite by chemisorption mechanisms in 0·15 M systems and by both ion exchange and chemisorption in 0·01 M systems, were, in either case, located at edge-sites on the clay. When intentionally precipitated onto dickite, iron (III) hydroxides were distributed evenly over the clay surfaces. However, precipitation was probably initiated at the particle edges.Minor exceptions to the above conclusions appeared to be caused by basal surface features such as fracture or stress lines, outgrowths or cavities, and if the clays had not been cleaned, by strongly associated impurities such as iron hydroxides.
Adsorption of Pyridine N-Oxide onto Montmorillonite
Authors: Olejnik S. , Posner A. M. , Quirk J. P. 
Published: September 2006

AbstractPyridine N-oxide and montmorillonite form interlamellar complexes with basal spacings of 14·7 and 21 Å. The former corresponds to a monolayer with a tilted orientation of the pyridine ring; the latter comprises a double layer of molecules between the clay sheets. Infrared spectra show that pyridine N-oxide bonds through the NO group; in the 21 Å complexes it is coordinated to the exchangeable cations through water molecules acting as bridges which themselves are directly coordinated to the cations. In the 14·7 Å complexes a splitting of the ν(NO) band occurs with the more polarizing cations Mg and Ca; the two bands correspond to pyridine N-oxide molecules directly coordinated to the cation and to other molecules coordinated through bridging by water molecules. Cs montmorillonite forms complexes with a basal spacing of approximately 14·7 Å which also shows a splitting of the ν(NO) band.
Regularly Interstratified Chlorite—Dioctahedral Smectite in Dike-Intruded Shales, Montana
Authors: Blatter C. L. , Roberson H. E. , Thompson G. R. 
Published: September 2006

AbstractCorrensite or ‘corrensite-like’ minerals occur in dike-intruded shales and siltstones of the Montana Group and Colorado Group (Early Cretaceous) in Western Montana. The < 1 μm size fraction of one specimen of this “corrensite-like” material has been studied in detail. X-ray diffraction data and chemical analysis indicate that this specimen is a regular or nearly regular interstratification of chlorite and dioctahedral smectite. Also described are other samples, which contain corrensite and additional phases. These samples were taken at several localities where basic dikes have intruded these shales and siltstones.
Exchangeable Cation—Structural Parameter Relationships in Montmorillonite
Authors: Lahav N. , Bresler Eshel 
Published: September 2006

AbstractThe interaction between “unhydrated” cations (those not separated from the surface by a solvent sheath) in hole positions and the montmorillonite surface was analyzed theoretically by considering the main contributions to potential energy from the coulombic, hydration, van der Waals, induced dipole, and repulsive energies. The effects on these energy terms of the distance between the cation and the plane of basal oxygens, h, and of the angle of rotation of the silica tetrahedra, θ, were investigated. Increase of θ with h constant increases the absolute values of all but one of the energy terms. The hydration energy is an exception because it is probably independent of θ. For a small cation, the increase in attraction is greater than the increase in repulsion when the value of θ is sufficiently small. As θ increases, the repulsive energy becomes more and more dominant until a minimum potential energy is reached. For large cations, this minimum can occur only above a certain value of h. Thus, the values of the potential energy minimum and of θ at this minimum depend on the cation under study as well as on h. Since the concentration of unhydrated cations in a montmorillonite-water system increases with decreasing water content, it is concluded that θ increases during the drying of homogeneous montmorillonite-water suspensions. This provides a partial explanation for the changes in b-dimension with water content observed by other investigators.
Appearance and Stability of Hydrolyzed Fe(ClO4)3 Solutions
Authors: Hsu Pa Ho 
Published: September 2006

AbstractFe(ClO4)3 solutions of different concentration and acidity were studied to search for the factors governing their appearance and stability during aging and to elucidate the mechanisms for the formation of amorphous and crystalline iron(III) hydroxides from slow hydrolysis. It was found that dilute solutions (0·001M or lower) rapidly hydrolyzed to clear sols after a brief induction period. With an increase in iron(III) concentration, one could notice gradual increases in the induction period, turbidity and particle size. Thus, solutions 0·006M to 0·01M in iron(III) developed into dense, cloudy, yellow suspensions impervious to light. The polymeric iron(III) species in the aged 0·02M solution were primarily large particles that settled under gravity, resulting in a suspension of low turbidity. It was also observed that in dilute solutions, the initial polymerization product was amorphous iron(III) hydroxide which yielded X-ray diffraction peaks for FeOOH only after prolonged aging or not at all. In 0·01 and 0·02M solutions, however, crystalline FeOOH was the major product from the very beginning of polymerization. The results suggest that the initial degree of supersaturation with respect to amorphous iron(III) hydroxide is the key factor governing particle size distribution, which in turn governs the appearance, stability and crystallinity of the hydrolyzed product during aging.The addition of HClO4 to dilute Fe(ClO4)3 solutions decreased, whereas the addition of NaOH to concentrated solutions increased, the degree of supersaturation and, thus, induced changes in induction period, appearance, stability and crystallinity of the hydrolyzed product accordingly.
Occurrence of Collapsed and Expanded Crystals in Montmorillonite-Dextran Complexes
Authors: Olness Alan , Clapp C. E. 
Published: September 2006

AbstractX-ray diffraction patterns obtained from montmorillonite-dextran complexes prepared with either B-512F or Polytran dextran showed maximum oven-dry crystal expansions of about 5·3 Å. X-ray diffraction patterns of individual complex preparations containing < 20 per cent dextran showed evidence of both expanded and collapsed crystals. The observation of expanded and collapsed crystals in individual preparations has not been previously reported and was apparently related to clay preparation. An estimate of the quantity of dextran which could be interacting with the silicate surface was obtained using polymer adsorption weights and volumes. At maximum adsorption almost all adsorbed B-512F could be in contact with the mineral surface, but only two thirds of the adsorbed Polytran could be in contact with the mineral surface.
The Effect of Aluminum on the Surface Properties of Kaolinite
Authors: Bundy Wayne M. , Murray Haydn H. 
Published: September 2006

AbstractAluminum ions as well as hydroxide precipitates promote improved extraction of iron from kaolinites during leaching. Selective aggregation of ultrafine particles in kaolinites, seemingly induced by precipitation of aluminum hydroxide, gives brightness improvement in excess of that which can be ascribed to iron extraction. Aggregation of anatase, a primary discolorant confined mostly to the fine end of the kaolinite particle size distribution, is the suggested mechanism for complementary brightness improvement.Precipitation of aluminum hydroxide in kaolinite systems substantially changes flocculation characteristics, surface area (methylene blue), and rheology. Edge-edge and edge-face flocculation are promoted where sulfate retention is high, becoming progressively more face-face with sulfate removal. The character of the flocculation can be interpreted by the combined use of surface area and low shear viscosity data.The extent to which kaolinites can be dispersed after processing increases with increase in sulfate retention. Stability of suspensions deflocculated with polyphosphates shows an inverse relationship, decreasing with increase in sulfate retention.
The Alteration Products of Potassium Depleted Oxybiotite
Authors: Gilkes R. J. 
Published: September 2006

AbstractArtificial weathering of biotites, which contain various levels of structural ferric iron, by NaCl and NaBPh4 solutions produces minerals and structures similar to those described for naturally weathered biotites. Oxidation of structural iron leads to K removal from alternate layers and development of hydrobiotite. The growth of order with increasing ferric iron content has been assessed by comparison with theoretical calculations for random and most ordered interstratified structures. There is evidence for the existence of two layer types in biotite prior to oxidation. The depression in rates of K release due to oxidation has been confirmed.
The Chemisorption of Anisole on Cu(II) Hectorite
Authors: Fenn D. B. , Mortland M. M. , Pinnavaia Thomas J. 
Published: September 2006

AbstractThe sorption of anisole and some related aromatic ethers on the interlamellar surfaces of Cu(II) hectorite has been investigated by i.r. and e.s.r. spectroscopy. In addition to physical adsorption, anisole forms two distinct types of Cu(II) complexes which are analogous to the type I and II species previously reported for benzene-Cu(II) smectite systems. These complexes can be transformed to type I and II complexes of 4,4’-dimethoxybiphenyl. Possible mechanisms are proposed for the oxidation process. Butyl phenyl ether formed a type II complex with Cu(II)-hectorite, but no dimerization reaction was noted in this system. Phenyl ether and benzyl methyl ether form a type I π complex with Cu(II)-hectorite. No type II analog was noted. E.S.R. spectra of each of the type II ether-Cu(II)-hectorite systems showed a single, narrow band with g near the value expected for a “free spinning” electron. The type I phenyl ether and benzyl methyl ether complexes also exhibited this e.s.r. band. Ag(I) hectorite adsorbs anisole by forming exclusively a type I complex. Na(I) and Co(II) hectorite adsorb anisole by physical means only, indicating association with the silicate surface.
The Alteration of Some Aromatic Amino Acids and Polyhydric Phenols by Clay Minerals
Authors: Thompson Thomas D. , Tsunashina Atsuma 
Published: September 2006

AbstractThese studies concern the catalytic activity of clays on amino acids, particularly tyrosine. Polyhydric phenols were included to help understand the tyrosine reactions.Below pH 3, tyrosine is adsorbed on clay minerals by cation exchange. Above pH 3, oxidative degradation of tyrosine occurs, the L-isomer altering more rapidly. The rate of alteration depends upon the particular clay mineral, surface modifications such as polyphosphate treatment, heating, and the presence of copper, aluminium, and mercury. A free radical mechanism is proposed for the alteration.
The Influence of the Christiansen Effect on I.R. Spectra of Powders
Authors: Prost R. 
Published: September 2006

AbstractThe Christiansen effect appears in the i.r. spectrum of powders embedded in a solid, liquid or air matrix as an apparently anomalous transmittance (Christiansen peak) of the incident electromagnetic radiations. The peak appears at wavelengths for which the refractive index of the sample and the refractive index of the matrix are equal (Christiansen wavelength: λChr).On account of the great variation of the sample refractive index in the immediate neighborhood of the absorption bands (anomalous dispersion curve), one often observes the occurrence of a transmittance peak or of a band deformation in this spectral range. A change in the position of this transmission peak with the value of the matrix refractive index is indicative of the Christiansen effect.The equality of the refractive indices of the sample and of the matrix for μChr has been used to determine some points of the anomalous dispersion curve in the neighborhood of the hydroxyl stretching band (3678 cm−1).Spectral distortions caused by the Christiansen effect can be reduced by preparing the sample in such a manner that the width at half-maximum (Δν1/2) of the Christiansen peak is several times greater than this of the absorption band itself. Clarke’s theoretical formula, which gives an estimation of Δν1/2, has been qualitatively verified and thus gives an appropriate guide in the choice of the parameters which one can optimize during the sample preparation. One can reduce the Christiansen effect spectral modifications, without running the risk of modifying the sample itself, particularly by overly severe grinding.