bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Studies of Illite
Authors: Warshaw Charlotte M. 
Published: August 2006

AbstractInvestigations in the system K2O-MgO-Al2O3-SiO2-H2O were made in an attempt to synthesize micas similar to illite and to determine their upper stability limits. These are representative of materials referred to by many clay mineralogists as illite, hydromuscovite and K-bentonite. Gels of these compositions were treated hydrothermally at temperatures above 250°C and at pressures above 10,000 lb/in.2. Natural illites and related minerals were also treated under the same conditions.It is possible to prepare phases having the properties of illite. This is achieved below 500°C but above this temperature well-crystallized micas plus other phases are obtained. The partially disordered micas formed from K-deficient compositions give the x-ray diffraction pattern of the 3T polytype, whereas the well-crystallized micas obtained with more K2O or at higher temperatures are the 1M polytype. Once formed at lower temperatures, however, the 3T mica is persistent and not readily transformed at higher temperatures. The 2M polytype, which is reported to be the stable form for pure muscovite at the temperatures of this investigation, was not obtained.Compositions with the same alumina: silica ratio as muscovite but with less potassium do not yield a mica-type mineral as a single phase under the conditions of these experiments. However, those in which the lower potassium content is compensated by less substitution and lower layer charge do yield illite alone. These studies indicate that the differences in properties between illites and well-crystallized micas are a function of composition as well as of the temperature of formation.
Iron Oxide Removal from Soils and Clays by a Dithionite-Citrate System Buffered with Sodium Bicarbonate
Authors: Mehra O. P. , Jackson M. L. 
Published: August 2006

AbstractThe 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.
Role of Exchangeable Cations in Viscosity of Clay Suspensions
Authors: Nash V. E. 
Published: August 2006

AbstractA study was made of the changes in viscosity of Wyoming bentonite suspensions with variations in cation ionization, base saturation, clay concentration, sodium chloride concentration and type of exchangeable cation. There is little change in the viscosity with decreasing cation ionization until a certain threshold value is reached. Below this value the viscosity increases rapidly, indicating that the repulsive potential barrier has been reduced to the order of the kinetic energy of the particles. Unfortunately, a quantitative estimate of the ionization was not possible at this value because of the high salt content of the system.Exchangeable aluminum was found to act as a strong bonding agent between clay particles in the pH range 4.50–5.50. This was explained on the basis of the formation of multivalent, aluminum-hydroxyl complex ions.
Potassium-Depleted Muscovite. Part I. Preparation Using Filtration Process for Treatment with Molten Lithium Nitrate
Authors: Bronson R. D. , Spain J. M. , White J. L. 
Published: August 2006

AbstractThe reaction between molten lithium nitrate and muscovite does not go to completion in a single treatment because of the equilibrium restriction imposed by the presence of potassium in the melt. An apparatus consisting of a stainless steel vessel with a porous stainless steel filter, valve and vacuum connections was designed to eliminate this restriction and to provide for more complete removal of the equilibrium melt in each successive treatment.Macroscopic swelling of the muscovite in the molten lithium nitrate was observed after prolonged treatment. x-Ray diffraction examination of samples of solidified melt revealed intracrystalline swelling in the muscovite.
Thermodynamics of Water Adsorption and Desorption on Montmorillonite
Authors: Barshad Isaac 
Published: August 2006

AbstractMethods are presented for determining partial and integral thermodynamic quantities for the change in state of water and clay during the course of their interaction. The quantities determined are: free energy, heat and entropy changes. The effect on the magnitude of these quantities of the nature and amount of the exchangeable cations is reported. It is concluded that the magnitude of change in the thermodynamic quantities due to moving the exchangeable cations out of the hexagonal cavities in the oxygen sheets is considerably greater than that due to the parting of the oxygen sheets during the interlayer expansion.
Water Vapor Sorption on Kaolinite: Entropy of Adsorption
Authors: Torrence Martin R. 
Published: August 2006

AbstractWater vapor adsorption isotherms at five temperatures between 0 and 40°C were obtained on Li and Na kaolinite. By a careful experimental technique, the error in the determination of weight of water adsorbed was reduced to + 0.01 mg/g and that of equilibrium vapor pressure was reduced to ± 0.0002 mm Hg. The data were used to calculate the integral and differential entropy of the adsorbed water phase.The differential entropy of adsorption (the partial molar entropy of water in the sorbate phase minus the molar entropy of normal liquid water) has large positive values at low surface coverage. As more water is adsorbed, the differential entropy drops to a negative value approximately equal to that of a two-dimensional liquid which is about the same as the entropy for hypothetical ice at this temperature and pressure. The water can hardly be treated as “ice” because the large negative entropy persists over a very small p/p0 range and occurs at a p/p0 such that the surface is only about 70 percent covered. The integral entropy of adsorption (the molar entropy of water in the sorbate phase minus the molar entropy of normal liquid water) has positive values on both Li and Na kaolinite throughout the p/p0 range investigated; p/p0 = 0 to p/p0 = 0.5. These entropy data indicate that the water molecules in the adsorbed phase on Li or Na kaolinite possess greater randomness than the water molecules in normal liquid water from the dry clay up to at least p/p0 =0.5. The difference between integral and differential entropies is explained as a “configurational entropy“ that changes with the amount of the adsorbed phase.A hypothesis to explain the entropy data is proposed in which one builds inward from normal liquid water to the solid surface rather than the more conventional mechanisms which build outward from the solid surface. In this way the entropy data can be explained in terms of what happens to the structure of normal liquid water when different sized ions or nonpolar molecules, or both, are added. Literature data for the low density and dielectric coefficient of the sorbed phase plus the large amounts of unfrozen water still present at — 5°C are frequently used as evidence for the quasi-solid structure of the sorbed phase. A consideration of the water molecules in the sorbed phase as more random than normal liquid water is an equally plausible explanation. Nuclear magnetic resonance and magnetic susceptibility data which cannot be explained by an increase in water structure are in complete agreement with the entropy data and the proposed new working hypothesis. It is concluded that not only the present entropy data but also all literature data (known to the author) concerning the sorbed phase can be satisfactorily explained if one considers the water molecules in the sorbed phase as being more random, less structured, than normal liquid water.
Distribution of Water and Electrolyte Between Homoionic Clays and Saturating NaCl Solutions
Authors: Bernstein Fabian 
Published: August 2006

AbstractIon and water uptake from solution by the sodium and hydrogen forms of montmoril-lonite and illite were measured. The clays first were converted to homoionic form by treatment with synthetic ion exchange resins. The hydrogen clays were used to determine the acid strength of the exchange groups by titration with sodium hydroxide solutions. The sodium clays were used to obtain the ion and water distribution. After attainment of equilibrium with sodium chloride solutions, the sodium clays were centri-fuged to constant weight and the equilibrating solutions analyzed for NaCl. Ion and water uptake and fixed charge concentration in the clays were then measured.The clay minerals were found to behave as weak acids and the exchange sites are not appreciably dissociated until the pH of the external solution becomes moderately high. In the sodium form, the exchange sites are fully dissociated and the clays, particularly montmorillonite, become efficient Donnan membranes. The partially neutralized clays exhibit intermediate membrane behavior.At low external phase salinities, the leakage of anions into the clay solution phase is abnormally large, but the membrane activity remains high because of the low activity coefficients of the diffusible ions in the clay phase. At high external solution salinities, the deswelling of the clays and the decrease in the anion to cation mobility ratio partially compensate for the increased anion leakage.The abnormally low activities of the diffusible ions are directly related to the effect of the internal phase double layer. The concept of ion retardation in the double layer is used to explain the fact that ion transference numbers computed from internal phase ion concentrations are lower than experimental transference numbers.The relationship of the electrochemical properties of clays to oil-well log interpretation is briefly discussed.
Viscosity of Water in Clay Systems
Authors: Low Philip F. 
Published: August 2006

AbstractA method was devised for obtaining the activation energy for the viscous flow of a fluid through a porous medium and the method was applied to the flow of water through samples of Na-bentonite. The resulting activation energies were generally higher than the activation energy for the flow of pure water. The activation energy depended on the length of time the water was in contact with the clay and also on the particular sample. For any given sample, the water flow rate was negatively correlated with the activation energy, in accordance with theory.To help interpret these results, data are presented on the tension of water in Na-bentonite suspensions at different intervals of time after stirring. The water tension was near zero immediately after stirring but increased gradually with time. Simultaneously the suspension gelled. Data also are presented on the specific volumes of water, the activation energies for ion movement, the diffusion coefficients of chloride salts and the unfrozen water at -5°C in Li-, Na- and K-bentonite. The activation energies for ion movement and the amounts of unfrozen water were positively correlated with the specific volumes of the water, whereas the diffusion coefficients of the chloride salts were negatively correlated with the specific volumes of the water. In each clay the specific volume of the water and the activation energy for ion movement were higher than those in normal water.It is concluded that a water structure, which varies in extent with particle arrangement and the adsorbed cationic species, exists at the surface of clay particles. This structure bestows a high viscosity to the adsorbed water.
Hydration Properties of Potassium Deficient Clay Micas
Authors: Jonas Edward C. , Thomas George L. 
Published: August 2006

AbstractA clay mineral that in its natural state expands to 15Å with water and to 17 Å with ethylene glycol was treated with various concentrations of KCl. At the highest KC1 concentration all the material was rendered nonexpanding. There was a threshold KC1 concentration at which potassium ions were absorbed in sufficient quantities to prevent expansion of the clay in water. At concentrations less than the threshold the material is characterized by a random interlayer mixture of expanding and nonexpanding layers. The sequence produced with increasing KC1 concentration is: expanding clay → interlayer mixture → nonexpanding clay.Solvation with ethylene glycol is more effective than solvation with water for much higher potassium ion population densities in the interlayer space. At potassium ion population densities intermediate between those at the concentration thresholds for water solvation and for ethylene glycol solvation, there are layers that will expand with glycol and not with water.Low potassium ion population densities correspond to low surface charge densities of potassium saturated clays, and the clays expand like montmorillonite. The high potassium ion population densities correspond to high surface charge densities of potassium-saturated clays and illite and the clays do not expand. With intermediate potassium ion population densities corresponding to intermediate surface charge densities for potassium-saturated clays, the clays expand with ethylene glycol but not with water.
Possible Uses of Clay Minerals in the Search For Oil
Authors: Weaver Charles E. 
Published: August 2006

AbstractMost of our general knowledge concerning the distribution and geologic significance of clay minerals is summarized in twelve statements. Some examples and numerous suggestions are given to show the use of clay minerals in interpreting and understanding such problems as tectonics, source, age, boundaries, facies, environments, zonation, correlation, and metamorphism; a relation between the relative abundance of expanded clays and the occurrence of hydrocarbons is suggested.It is believed that expanded clays retain their pore water to greater depths of burial than do other clays, and that it is this water which transports much of the hydrocarbon. It is shown that whereas time has little effect on the contraction of expanded clays, it does affect the expulsion of pore water from shales.
Semiquinone Cation Adsorption on Montmorillonite as a Function of Surface Acidity
Authors: Dodd Charles G. , Ray Satyabrata 
Published: August 2006

AbstractSemiquinone cations derived from aromatic diamines by one-electron oxidation in aqueous solution possess characteristic colors that depend on hydrogen ion concentration. The colored free radicals are formed by oxidation on the surface of certain montmorillonite clay minerals, where they are stabilized by adsorption, apparently in cation exchange positions, but many clays react anomalously when the procedure is employed as a diagnostic test for montmorillonite. One of the problems involved is the chemical nature of the various semiquinones. Another is the effect of clay mineral crystal structure on the color that is produced.The dihydrochlorides of benzidine, p-phenylenediamine, and N,N-dimethyl-p-phenylenediamine in aqueous solution have been used with a centrifuged Wyoming bentonite (montmorillonite) and a centrifuged hectorite clay, each suspended in various buffered solutions, to study the pH effect and the quantity and nature of the semiquinones formed. Hypothetical structures differing by one hydrogen (or hydronium) ion have been assumed for two semiquinone forms of each diamine, each formula representing a distinct hue, with the divalent cation formed at low pH and the monovalent cation at a higher pH. Mixtures of the two cations were assumed to exist at intermediate acidities corresponding to mixtures of the two hues. A simple set of equations was postulated to describe these reactions, and the theory was tested experimentally by determining the amount of nitrogen adsorbed on each clay sample at a series of fixed pH values ranging from 0.5 to 6.5.The milligram atoms (mga) of nitrogen (or 2 × millimoles of diamine) adsorbed were found to increase with increasing pH in approximately the amount predicted in the range 1.0-4.2. In this pH range, however, the calculated base exchange capacity (BEC) for each clay was lower than the accepted value, presumably because an approximately constant fraction of the base exchange sites was occupied by nonexchangeable cations, probably aluminum and hydrogen ions. Amounts of base adsorbed were the same whether sodium or calcium ions were initially in exchange positions. At pH values of 5.5 and 6.5 the mga of nitrogen adsorbed showed a sharp increase, apparently because colloidally dispersed reagent diamine was formed as the free base and no aluminum or hydronium cations were adsorbed. When corrections were made for nonadsorbed free base (not adsorbed on exchange positions but physically adsorbed to the floccules) and, in the case of benzidine, for base lost in filtration, the calculated BEC’s for each clay were in satisfactory agreement with accepted values.
Solids Concentration Effects in Bentonite Drilling Fluids
Authors: Oakes D. T. 
Published: August 2006

AbstractA series of studies of the apparent electrokinetic potential and other characteristics of aqueous bentonite systems as they are affected by bentonite concentration is presented. A new concentration parameter, which logically arises from a previously presented filtration theory (Oakes, 1958), is demonstrated to describe adequately the effects of solids concentration. The concentration parameter is analytically derived and is shown to make suitable allowance for the adsorbed phase on the bentonite patricles.
Mineralogical Analysis of Soil Clays Involving Vermiculite-Chlorite-Kaolinite Differentiation
Authors: Dixon J. B. , Jackson M. L. 
Published: August 2006

AbstractThe content of kaolinite plus halloysite is differentiated quantitatively from chlorite by differential dissolution, even in those samples wherein each mineral has 500°C heat instability of the 7 Å peak. This differentiation is possible because the structures of kaolinite and halloysite are destroyed on loss of the 7 Å peak, producing amorphous material which is rapidly soluble in 0.5 N NaOH, whereas the chlorite structure remains largely intact with only partial dehydration of the octahedral layer. The amorphous residue of kaolinite-halloysite is dissolved from the other mineral components of the heated sample with sodium hydroxide and the dissolved silica and alumina are allocated to kaolinite. The percentages of kaolinite thus obtained for Elliott, B3–C horizon, 2–0.2 μ fraction, are 3.8 and 3.7 based on silica and alumina, respectively. Similarly, the percentages of kaolinite obtained for Buchanan, B1horizon, 2-0.2μfraction, are 14.9 and 13.8 based on silica and alumina, respectively. Collapse of the vermiculite basal spacing to 10 Å on K saturation and heating to 300°C, together with the clear differentiation of kaolinite by differential dissolution analysis (D.D.A.) above, removed the possibility of misinterpretation of the chlorite-like diffractometer tracing by kaolinite and vermiculite occurring together. Other clays, from Davidson and Susquehanna soils, had 44 and 42 to 43 percent kaolinite, based on silica and alumina, respectively. The vermiculite and montmoril-lonite contents of soil clay samples are quantitatively determined by specific surface. The mica percentages are based on the K2O after exclusion of potassium in feldspars. Water loss in the 400°C-to-ignition range gives an important quantitative basis for chlorite.
The Influence of Physico-Chemical Factors Upon the Mechanical Properties of Clays
Authors: Rosenqvist I. Th. 
Published: August 2006

AbstractThe engineering problems of clay soils are closely connected with the “bulk properties,” i.e. shear strength and deformation properties as function of stress conditions and time. These properties are based upon factors in the atomic range and can never be understood without an understanding of the fundamental processes.The bulk properties of virgin sediments differ from those of chemically or mechanically altered clays (called hypo-metamorphic).The difference in view generally held by soil mechanics engineers and ceramic research people concerning soil-water systems as built up of minerals in contact with or separated by water, may only be apparent. The water at the mineral surfaces appears to have properties of a solid substance but not the atomic arrangement of ordinary ice. Within a small area, as at the points “of contact,” the H’s and O’s may take the arrangement of a perfect solid. The movement of a corner of one mineral along the plane of another can only take place if flow or creep in the condensed water is possible. In perfect crystals we have only elastic deformation or yielding. The secondary consolidation of clays and the permeability at low hydraulic gradients are discussed as functions of the physics of the water. The influence of temperature and electrolytes upon the properties is suggested as fundamentally important. A plea for further research in the physics and chemistry of surface processes on the various clay minerals is given.
Thermodynamic Properties of Water in Suspensions of Montmorillonite
Authors: Kolaian Jack H. , Low Philip F. 
Published: August 2006

AbstractThe partial molar free energies, entropies and heat contents of the water in suspensions of Li-, Na-, and K-clay were measured relative to pure water by means of a tensiometer. This method of obtaining these thermodynamic properties is far more sensitive than the more common method utilizing adsorption isotherms and a form of the Clausius-Clapeyron equation. The partial molar free energy of the water decreased with time after stirring and increased rapidly upon stirring. This was taken as evidence that a gradual increase in the degree of orientation of water molecules associated with the clay particles occurred as the particles fell into the more random edge-to-surface thixotropic structure. The partial molar entropies and heat contents of the water in the suspensions were found to be less than those for pure water. Hence, this evidence also supported the postulate that an ordered water structure exists in the thixotropic suspensions.