bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adsorption of Ethylenediamine (Eda) on Montmorillonite Saturated with Different Cations—IV: Al-, Ca- and Mg-Montmorillonite: Protonation, Ion-Exchange, Co-Ordination and Hydrogen-Bonding
Authors: Laura R. D. , Cloos P. 
Published: September 2006

AbstractEthylenediamine (EDA) adsorbed from aqueous solution or vapor phase on Al-, Ca- and Mg-montmorillonite was retained to a more or less large extent in protonated form. The NH+3:NH2 ratio decreased with the polarizing power of the mineral exchange cation (Al > Mg > Ca) and with increasing amounts of amine fixed. Excess EDA was adsorbed through hydrogen-bonding with protonated species, and partially through co-ordination in vapor treated samples. Co-ordination to the exchangeable cation seemed to be favored in the order Al > Mg < Ca, and the complexes were stable up to 200°C. Heating lowered the NH+3:NH2 ratio, indicating some deprotonation process caused probably by the competition for protons between EDA and hydrolysed exchange cations. This competition might also account for the rather low quantities of NH+4 produced near 200°C.
The Crystallinity of Minerals—A New Variable in Pedogenetic Processes: A Study of Goethite and Associated Silicates in Laterites
Authors: Kühnel R. A. , Roorda H. J. , Steensma J. J. 
Published: September 2006

AbstractThe crystallinity of minerals in terms of crystallite size distribution and lattice perfection is quantified by means of statistical measures derived from X-ray line profiles (2 σ values). A low degree of crystallinity facilitates the non-stoichiometric incorporation of foreign elements in the crystal lattice. Crystallinity is affected by a number of factors and in natural profiles it may vary laterally as well as vertically.For instance, goethite in laterite deposits shows decreasing crystallinity with increasing depth. Serpentine type minerals, on the other hand, show the lowest crystallinity at the surface where the degree of weathering is the most advanced. The presence of silica in migrating solutions prevents crystal growth and results in a low degree of crystallinity of minerals such as goethite. This has been observed in natural profiles and has been confirmed by laboratory experiments on the synthesis of goethite and sodium-birnessite. The crystallinity of minerals affects their response to extractive procedures. It could also be an important parameter in soil science.
A Study on the Cation Exchange of [Co(NH3)6]3+ from H-Co (NH3)6-Vermiculite by Inorganic and Quaternary Ammonium Ions
Authors: Das Kanungo J. L. 
Published: September 2006

AbstractThe exchange of [Co(NH3)6]3+ from its vermiculite complex has been carried out with a number of inorganic and alkyl quaternary ammonium ions of varying ionic sizes. The distribution and selectivity coefficients of the desorbing ions increase in the order: Li<Na<NH4<K<Rb<H<Cs for the monovalent, Ca<Mg for the bivalent and (C2H5)4N<(CH3)4N≪CTA (cetyl trimethyl ammonium) <CP (cetyl pyridinium) for the organic ions. The ΔG° values of some of the cation exchange reactions have been calculated by an equation of Kielland (1935).
Scanning Electron Microscopy of Cherts in Relation to the Oxygen Isotopic Variation of Soil Quartz
Authors: Sayin Mahmut , Jackson M. L. 
Published: September 2006

AbstractQuartz isolated from soils by the pyrosulfate-H2SiF6 method and chert samples of various origins were examined with the scanning electron microscope. Quartz isolates of the 20–50μm from the A2 and B21t horizons of the Baxter soil (AR), with quartz δ18O of 18·2 and 19·0‰, respectively, showed a mixture of detrital quartz particles and chert clusters of aggregates of fine euhedral quartz crystals. The 2–5 μm fractions of both horizons consisted mainly of euhedral quartz particles. The 20–50 μm fraction from the underlying chert, with a δ18O = 29·6‰, consisted of aggregates of euhedral quartz particles 1–10 μm dia and of subhedral particles 0·1–0·5 μm dia. In the soil fractions, the size and shape of the quartz particles as well as oxygen isotope data indicated that the aggregates were from the underlying chert but that irregular, unaggregated grains were detritally admixed loess, particularly in the medium and coarse silt fractions. This mixing of chert (of low temperature origin and heavy oxygen) with detrital quartz (of high temperature origin and light oxygen) gave rise to the intermediate δ18O values in the soil quartz. The SEM of cherts of different geological ages showed different morphologies. Prismatic, polyhedral microcrystalline quartz of 1–10 μm size as well as submicron, euhedral particles were observed in cavities. Submicron, subhedral particles and interlocking quartz grains were characteristic of Precambrian chert. Quartz grains more than 100 μm in size isolated by HCl from Ordovician dolomite (WI) had large (many microns) subhedral overgrowths and attached clusters of 0·1–0·5 μm microcrystalline quartz. A Danish flint formed in chalk had calcite-lined cavities (x-ray emission determined) in which spheroidal fibrous chalcedony occurred.
The Syntheses of Hydrotalcite-Like Compounds and Their Structures and Physico-Chemical Properties—I: the Systems Mg2+-Al3+-NO3−, Mg2+-Al3+-Cl−, Mg2+-Al3+-ClO4−, Ni2+-Al3+-Cl− and Zn2+-Al3+-Cl−
Authors: Miyata Shigeo 
Published: September 2006

AbstractThe basic salts of this system were prepared and their structures and physico-chemical properties were studies by electron microscopy, chemical analysis, X-ray powder diffraction, thermal analysis, i.r. absorption spectra, BET absorption, and acidity-basicity measurements. The salts were found to be new compounds analogous to hydrotalcite. They can be expressed by the formula; where M2+ and M3+ denote di- and trivalent cations, A− and A2− denote mono- and divalent anions, respectively, and y = z1 + 2z2; z1 ≫ z2.The structures consist of positively charged Cd(OH)2-like basic layers and intermediate layers formed from anions and water molecules with the solid solution of divalent cation (M2+) and trivalent cation (M3+) being formed in the range of 0.6 < x/(x + y) < 0.9. The anions of Cl−, NO3− and ClO4− are easily substituted by CO32−. A large part of the NO3− makes a monodentate-type bond and the ClO4− a bridge-type bond.
Further Information Related to the Origin of Glauconite
Authors: Velde B. , Odin G. S. 
Published: September 2006

AbstractGlauconite-smectite and illite-smectite interlayered minerals are compared by various means in an attempt to establish the mineralogical relations between the two groups. Experiments at 2 Kb pressure and 200–350°C are reported as well as microprobe scans of pelletal glauconites. This new information is used along with published chemical data in order to establish that(1) Illite and glauconite mixed layered phases appear to be crystallographically similar. Both series show the same relations between potassium (mica) content and the amount of smectite layers apparent in the interlayered structure.(2) Illite and glauconite mica or mica-like phases can be separated on the basis of Fe and K contents.(3) Probable phase relations of the two mixed layered mineral series indicate that, when the starting materials contain mixed layered mica-smectites, increasing temperature produces an iron-rich mica in the case of glauconite and an aluminous mica in the case of illite. The mixed layered phases present at intermediate temperatures are not the same for illites and glauconites.Apparently there is no mineralogical or chemical continuity between illite and glauconite when the potassium content is 6 wt % or greater. It might be possible that the potassic interlayered minerals near montmorillonite or nontronite could form a continuous solid solution.
The System SiO2-AlOOH-Fe2O3-H2O and the Kaolinitic Stage of the Goethite Facies
Authors: Chesworth Ward 
Published: September 2006

AbstractA 25°C, 1 atm total pressure phase diagram for the system SiO2-AlOOH-Fe2O3-H2O, is determined using the Phase Rule and Shreinemaker’s technique as in Chesworth (1974). The waterpresent assemblages so defined are equivalent to a kaolinitic stage of the goethite facies of the weathering zone. As such they constitute the ideal stable assemblages of several earth-surface deposits and the stage can therefore be used to construct models of these deposits.
Mössbauer Study of Transformations Induced in Clay by Firing
Authors: Simopoulos A. , Kostikas A. , Sigalas I. , Gangas N. H. , Moukarika A. 
Published: September 2006

AbstractThe clay fraction of an Attic soil has been fired at temperatures up to 1100°C and the transformations induced by firing were studied by Mössbauer spectroscopy. The unfired clay contained iron in the form of small particles of α-Fe2O3 and β-FeOOH and as a substitutional ion in the clay mineral structure. A transformation of β-FeOOH to α-Fe2O3 is observed in the region of 200–400°C followed by dehydroxylation of the clay mineral between 500 and 800°C. A disintegration of the clay mineral structure is inferred above 800°C, followed by recrystallization in an iron-rich phase, most probably in the form of very fine particles. The room temperature spectra of the fired samples indicate that an increase in particle size of the oxides occurs upon firing.
Variability in Exchange Ion Position in Smectite: Dependence on Interlayer Solvent
Authors: Berkheiser V. , Mortland M. M. 
Published: September 2006

AbstractFull and reduced charge smectite saturated with Na(I), Ca(II), Cu(II), or tetralkylammonium ions were swollen by a series of solvents of various bulk physical properties. In the full charge smectites, swelling occurred in all solvents regardless of the exchange ion or the initial water content. Charge differences did not usually result in differential swelling of the smectite. Little correlation was found between the degree of swelling and the Gutmann donor numbers, bulk dielectric constants, bulk surface tensions, or dipole moments of the solvents. The intensities of the high field Fe(III) resonance (g = 3.6) in the esr spectra of full charge smectite swollen in various solvents reflected variability in exchange ion positions and depended upon the Gutmann donor number of the solvent. Considerable variety in the stereochemistry of Cu(II)-solvent complexes was revealed by esr spectra of the swollen systems.
Adsorption of Ethylenediamine (EDA) on Montmorillonite Saturated with Different Cations—V. Ammonium- and Triethylammonium-Montmorillonite Ion-Exchange, Protonation and Hydrogen-Bonding
Authors: Cloos P. , Laura R. D. , Badot C. 
Published: September 2006

AbstractOn NH4- as well as on (C2H5)3NH-montmorillonite EDA was adsorbed in protonated form. The extent of protonation depended on the relative basicities and concentrations of the interacting compounds. In the systems exposed to EDA vapor a proton transfer process took place. A similar mechanism, involving probably a water molecule which remained associated with the EDAH+ ion, occurred on air-drying (C2H5)3NH-montmorillonite treated with aqueous EDA, whereas no adsorption was observed when the suspension was washed. On the contrary EDA added, in quantities not exceeding the CEC, to a suspension of NH4-montmorillonite was adsorbed almost exclusively as EDAH22+ ion. This is explained in terms of ion-exchange between NH4+ and EDAH+ present in aqueous medium and protonation of the second amine function through the dissociation of water molecules near the clay surface.Hydrogen-bonding between protonated and neutral EDA was observed when the extent of adsorption was higher than the extent of protonation.
Bulk Densities of Selected Dried Natural and Fired Kaolin Clays
Authors: Baumann David , Keller W. D. 
Published: September 2006

AbstractBulk (lump) densities of 31 kaolins were measured on the clay in the natural or raw state after drying at 100°C and after firing to 1510°C (2700°F). The kaolins were selected from such diverse origins as surface-weathered and sedimentary accumulations, hydrothermally altered bodies and flintclay deposits. The sedimentary group ranged in density from 0·82 to 1·85 in the dried raw clay, and 1·93 to 2·63 when fired. The hydrothermally altered clays ranged from 1·83 to 2·50 in the dried raw state, and 2·02 to 2·66 when fired. Flint clays ranged from 2·20 to 2·60 in the dried raw state (a “toasted clay” from Russia, 1.75), and 1·99 to 2·70 when fired. The effect of the genetic process on bulk density values is discussed and related.
Quartz Presence in Relationship to Gibbsite Stability in Some Highly Weathered Soils of Brazil
Authors: Weaver R. M. 
Published: September 2006

AbstractDetermination of the mineralogical composition of six highly weathered soils of the Central Plateau of Brazil showed that the sand content (predominantly quartz) was not related to the relative amounts of gibbsite and kaolinite in the clay (< µm) fractions. The latter is in agreement with kinetic considerations of the involved mineral species, but in disagreement with thermodynamic considerations. However, that dissolution of quartz has been operative in these soils is indicated by an excellent relationship (r2 = 0·96) between the amount of sand-size quartz and the reactive SiO2 content of the clay fractions.
Folding in Sepiolite Crystals
Authors: Serna C. , Ahlrichs J. L. , Serratosa J. M. 
Published: September 2006

AbstractFibrous sepiolite crystals derive much of their commercial value from their molecular size channels and grooves. The crystals fold upon drying and these channels and grooves are lost. A model for the folding and unfolding of the crystals is presented. Extensive i.r., X-ray and thermogravimetric evidence shows that folding occurs when approximately half of the water of hydration, which is coordinated to the edge magnesium atoms inside of the channels, is removed. This occurs near 175°C under vacuum and near 300°C in air. When the crystals fold, all remaining water molecules enter a new environment, that of the hexagonal holes of the neighboring silica surface. A true anhydride is produced at about 500°C under vacuum when the final water is lost, but this final dehydration produces no important structural change. Rehydration of the anhydride to the normal hydrated sepiolite does not occur at room temperatures in 100% r.h. However, above, 60°C rehydration does occur.
Montmorillonite-Alkali Halide Interaction: A Possible Mechanism for Illitization
Authors: Heller-Kallai L. 
Published: September 2006

AbstractThe reaction products obtained when montmorillonites react with potassium halide at elevated temperatures, which were described in a previous publication, are further characterized. On the basis of their X-ray powder diffraction patterns, i.r. spectra, CEC and chemical composition they could be regarded as montmorillonite-illite interstratifications. Changes in morphology of various montmorillonites heated with and without K halide are related to the size, charge and position of interlayer cations. Scanning electron-micrographs of samples heated with KBr resemble those of well-crystallized illite. It is speculated that reactions of clay minerals with halides or other proton acceptors may account for some diagenetic processes in nature, e.g. the conversion of montmorillonite to illite on deep burial.
Regularly Interstratified Chlorite/Vermiculite in Contact Metamorphosed Red Beds, Newark Group, Connecticut Valley
Authors: April Richard H. 
Published: September 2006

AbstractA regularly interstratified chlorite/vermiculite occurs in red beds of the East Berlin Formation (Early Jurassic age) in the Connecticut Valley. The mineral is restricted to a 2.5-m wide zone of contact metamorphosed strata adjacent to and underlying the Hampden Basalt. Chemical and X-ray powder diffraction data indicate that the chlorite/vermiculite formed in response to lava-induced elevated temperatures and the availability of magnesium in the muds during and shortly after emplacement of the lava flow. Near the contact, hydrothermal fluids originating from the lava and from the synchronal weathering of basalt fragments by superheated pore waters provided a source of Mg. Further from the contact, magnesium was primarily derived from the thermal dissociation of dolomite. K2O concentrations and the distribution of clay minerals in the red mudstone suggest that the interstratified chlorite/vermiculite formed from preexisting illite or vermiculite as potassium was released and brucitic sheets were incorporated into interlayer positions.
Hydroxyl Orientations and Interlayer Bonding in Amesite
Authors: Giese R. F. 
Published: September 2006

AbstractThe hydroxyl orientations in the 2H2 polytype of amesite, Mg2Al(SiAl)O5(OH)4, have been determined by minimizing the electrostatic potential energy as a function of OH orientation. The angles, ρ, between the hydroxyls and (001) vary between 81.5 and 88.8°. All surface hydroxyls form hydrogen bonds with oxygens of the adjacent layer. The OHs tend to tilt away from the higher charged A1VI ions, and the spread in ρ values is due to variations in the positions of the receptor oxygens. The inner hydroxyls noticeably weaken the interlayer bonding. The substitution of Al in both T and M sites creates a dipolar layer charge and the resulting attraction between layers forms an important part of the interlayer bonding. The 2H2 polytype of amesite has substantial interlayer bonding even with all surface hydroxyls replaced by fluorine. This is not true for a composition of Mg3Si2O5(OH)4 where a similar F for OH substitution destroys all interlayer bonding as in kaolinite.
Kaolin From The Original Kauling (Gaoling) Mine Locality, Kiangsi Province, China
Authors: Keller W. D. , Cheng Hsia , Johns W. D. , Meng Chi-Sheng 
Published: September 2006

AbstractAlthough the specific outcrop from which the original kaolin at Kauling (Gaoling) Mine, China, was collected cannot now be relocated, samples were collected and studied from the mine tunnel, country rock, and pegmatite which constitute the sources of kaolin in this region. The kaolin is a residual product of weathering. Where the parent rock was a granite the clay is a mixture of platy and elongate kaolin-group minerals, whereas from the pegmatite portion of the parent rock it is halloysite(10Â) with elongate morphology. These mineral identifications are based on X-ray powder diffractograms, scanning electron micrographs, differential thermograms, and an infrared spectrum hitherto not documented for material from this area.Although the Kauling locality is the region for which kaolin is named, the mineral kaolinite is a defined species without a specific type locality. The 11th century Chinese locality was not mentioned in the two classic research papers defining kaolinite. The data on the Chinese kaolin, therefore, cannot be used directly to provide criteria for sharply differentiating the otherwise vague boundary between the minerals kaolinite and halloysite(7Å). Pertinent questions on these kaolin-group mineral relationships are brought into clearer focus.
Intercalation of Silica in Smectite
Authors: Endo T. , Mortland M. M. , Pinnavaia T. J. 
Published: September 2006

AbstractSilica has been intercalated in swelling clays by hydrolysis and/or oxidation of tris(acetylacetonato)siIicon(IV) cations, Si(acac)3+, and polychlorosiloxanes, (-SiOCl2-)n, in the interla-mellar regions of the minerals. The Si(acac)3+ ions have been placed on the interlamellar surfaces by ion exchange and by in situ reaction of the acetylacetone-solvated clays with SiCl4. The (-SiOCl2-)n polymers were formed in the interlayers by reaction of adsorbed benzaldehyde with SiCl4. The optimum (001) spacing observed after firing the clays in air at 500°C (12.6 Å) corresponds to the presence of a monolayer of siloxane chains. Nitrogen BET surface areas range from 40 to 240 m2/g, depending on the amount of internal surface covered by the intercalated silica. In some cases, highly ordered products were formed which exhibit four orders of (00ℓ) reflection. Interstratified products with d(001) values between 9.6 and 12.6 Å exhibit surface areas consistent with the presence of a random mixture of totally collapsed interlayers and interlayers containing siloxane monolayers. Attempts to achieve silica intercalation by hydrolysis of SiCl4 in the clay interlayers were not productive.
Absorption of Infrared Radiation by D2O and HDO Mixed with Montmorillonite
Authors: de Chou J. Salle , Low P. F. , Roth C. B. 
Published: September 2006

AbstractThe frequency, v, for O-D stretching in D2O films between the superimposed layers of different micas and montmorillonites was measured at several film thicknesses and temperatures of 2° and 25°C by infrared spectroscopy. The molar absorptivity, ε, for O-D stretching in HDO films between the montmorillonite layers was also measured at different film thicknesses and 25°C. It was found that v is related to mw/mm, the mass ratio of D2O to mica or montmorillonite, by the equation v = v0 exp β/(mwmm where v0 is the O-D stretching frequency in pure D2O and ß is a constant. Since mw/mm is proportional to a, the area under the absorption peak, mw/mm can be replaced by a in this equation. It was also found that ε decreased dramatically as the thickness of the water film between the montmorillonite layers decreased. These results were interpreted to mean that the structure of the interlayer water is perturbed by the interlayer cations and/or silicate surfaces.
Swelling Components of Compacted Ca-Montmorillonite
Authors: Parker J. C. , Zelazny L. W. , Amos D. F. 
Published: September 2006

AbstractIntracrystalline water adsorption of Ca-montmorillonite was calculated as the product of one-half the interlayer spacing from X-ray powder diffraction analysis and the difference between the desorption surface area determined with ethylene glycol-monoethyl ether and BET surface area determined by N2 adsorption. Osmotic adsorption was calculated as the product of the N2 surface area and theoretical double layer thickness. Measured water adsorption of P2O5-dry clay, compacted to initial densities (γ0) from 0.52 to 1.59 g/cm3 and submerged in 0.01 N CaCl2 was 2.4 to 4.2 times greater than intracrystalline plus osmotic adsorption due to the occurrence of pores exceeding double layer dimensions. The increase in expansion caused by reducing electrolyte concentration to 0.001 N was equal to the predicted increase in double layer volume, verifying the existence of an osmotic component to swelling.Measured expansion following submersion in 0.01 N CaCl2 increased continuously with γ0 from 0.53 cm3/g at γ0 = 0.52 g/cm3 to 1.17 cm3/g at γ0 = 1.59 g/cm3, while estimated osmotic plus intracrystalline expansion was constant at 0.30 cm3/g. This discrepancy is attributed to swelling caused by gas pressures developing ahead of advancing wetting fronts. The effect of compaction on expansion is explained by reductions in pore size, as measured by N2 desorption, which accompany compaction. Reduced pore size should increase entrapped air pressures, whereas gradual wetting should favor their dissipation. Accordingly, slow wetting reduced the expansion of a sample where γ0 = 1.06 g/cm3 from 0.77 to 0.37 cm3/g. Swelling due to entrapped air pressures produced a large increase in the number of pores > 104 Å in diameter, as determined by Hg intrusion porosimetry.