bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Studies of Illite
Authors: Warshaw Charlotte M.
Published: August 2006

Investigations 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

The oxidation potential of dithionite (Na2S2O4) increases from 0.37 V to 0.73 V with increase in pH from 6 to 9, because hydroxyl is consumed during oxidation of dithionite. At the same time the amount of iron oxide dissolved in 15 minutes falls off (from 100 percent to less than 1 percent extracted) with increase in pH from 6 to 12 owing to solubility product relationships of iron oxides. An optimum pH for maximum reaction kinetics occurs at approximately pH 7.3. A buffer is needed to hold the pH at the optimum level because 4 moles of OH are used up in reaction with each mole of Na2S2O4 oxidized. Tests show that NaHCO3 effectively serves as a buffer in this application. Crystalline hematite dissolved in amounts of several hundred milligrams in 2 min. Crystalline goethite dissolved more slowly, but dissolved during the two or three 15 min treatments normally given for iron oxide removal from soils and clays.

A series of methods for the extraction of iron oxides from soils and clays was tested with soils high in free iron oxides and with nontronite and other iron-bearing clays. It was found that the bicarbonate-buffered Na2S2O4-citrate system was the most effective in removal of free iron oxides from latosolic soils, and the least destructive of iron silicate clays as indicated by least loss in cation exchange capacity after the iron oxide removal treatment. With soils the decrease was very little but with the very susceptible Woody district nontronite, the decrease was about 17 percent as contrasted to 35–80 percent with other methods.
Role of Exchangeable Cations in Viscosity of Clay Suspensions
Authors: Nash V. E.
Published: August 2006

A 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

The 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

Methods 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

Water 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

Ion 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

A 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

A 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

Most 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

Semiquinone 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

A 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

The 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

The 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

The 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.
The Structural Status of Clay Systems
Authors: Aylmore L. A. G. , Quirk J. P.
Published: August 2006

Illite and montmorillonite have been compressed into cores under a pressure of 1200 atm. The structural status of these clays has been examined by means of detailed nitrogen adsorption-desorption isotherms and by means of electron micrographs of fracture surfaces of the clay cores. The subsequent swelling behavior of sodium and calcium clay cores has been analyzed in terms of the model derived from these measurements and the specific surface area of the clay. A generalized theory for the condensation of plate-shaped particles into domains has been proposed.

Measurements of the effect of electrolyte concentration and hydrostatic suction on the swelling of sodium- and calcium-saturated clay cores indicate that diffuse double layer theory may play a significant part in determining the swelling of monovalent clay systems but not divalent clay systems.

The magnitude of the film thicknesses apparently developed in solutions as concentrated as molar and 4 M, where the condition of ideal solutions required by diffuse double layer theory is certainly not fulfilled, seems to indicate that solution uptake is increased by a relaxation of structural strains within the clay matrix on lubrication by solutions. These strains may arise from the distortion of crystals in packing during the drying process. Such relaxations which appear to occur between p F 4 and 3 could initiate the development of a gel structure.
The Flow of Salt Solutions Through Compacted Clay
Authors: McKelvey J. G. , Milne I. H.
Published: August 2006

Experimental evidence of the salt filtering ability of compacted bentonite and clay material is presented. Apparatus has been developed in which samples of semi-dry powdered bentonite and shale are compacted under pressures of 10,000 psi and subjected to flow with sodium chloride solutions under fluid pressures up to 10,000 psi. Porosities of 34–41 percent have been obtained with the bentonite and 24 percent with the shale. Permeabilities of 10−5 to 10−6 millidarcies have been measured. A ratio of input to output solution concentration as high as 8 has been found with the bentonite samples and dilute (0.164 N) NaCl solutions. The ratio falls off with increased input concentration and with increased porosity. The shale sample has given a ratio of 1.7 with an input concentration of 0.129 N NaCl.

Streaming potential differentials of approximately 1 mV per 100 psi have been measured during the flow experiments. The potential differential is highest with the shale material and shows a decrease with increasing salt concentration.
Anion Influence on Some Soil Physical Properties
Authors: Krebs R. D. , Thomas G. W. , Moore J. E.
Published: August 2006

Addition of HCl, H2SO4, and H3PO4 to montmorillonite clay and a montmorillonitic soil had little effect on the liquid limit of these materials over a wide range of concentrations. The liquid limit of a kaolinitic soil clay was reduced markedly by both HCl and H2SO4, whereas H3PO4 decreased the liquid limit value at lower concentrations and increased it at higher ones. These results are discussed in light of the charge variability and of anion retention by the kaolinitic soil.
Theory of Flocculation, Subsidence and Refiltration Rates of Colloidal Dispersions Flocculated by Polyelectrolytes
Authors: La Mer Victor K. , Smellie Robert H.
Published: August 2006

The flocculation and subsequent subsidence of colloidal suspensions are markedly increased by the addition of flocculating agents; for example various starches and recently developed synthetic polymers.

The rate of flocculation depends not only upon the extent of adsorption of the agent (flocculant) but also upon the order of mixing and the character and extent of the subsequent agitation which determines the character of the floc formed. Electrolytes flocculate by reducing the electrostatic repulsions between charged particles, but long chain polymers produce flocs by a bridging mechanism which overcomes electrostatic repulsions.

Quantitative relationships are developed between the optimum concentration of flocculant and the rates of flocculation, subsidence, and particularly rate of filtration through the filter cake.
Hydrothermal Regularly Interstratified Chlorite-Vermiculite and Tobermorite in Alteration Zones at Goldfield, Nevada
Authors: Harvey Richard D. , Beck Carl W.
Published: August 2006

Hydrothermal alteration of andesitic and dacitic rocks in the Goldfield District, Nevada, has produced regularly interstratified chlorite-vermiculite and tobermorite. X-ray diffraction and oscillating-heating data indicate the regular interstratification of the chlorite-vermiculite. This mineral is found in the zone of least alteration and was formed by the alteration of hornblende phenocrysts. Penninite is an intermediate stage in this reaction. Increased intensity of alteration resulted in the disappearance of chlorite-vermiculite and the development of montmorillonite. Tobermorite, found only in the dacite, is associated with alunite as pseudomorphs after plagioclase phenocrysts in the most intense zone of alteration. The intermediate stage of hydration for tobermorite is indicated by the 11 Å spacing of the 002 diffraction peak. Oscillating-heating X-ray data at atmospheric pressure show that tobermorite decomposes thermally in two stages. The (00l) planes collapse at approximately 520 °C and crystal planes having an 8 Å periodicity collapse at about 760 °C. Wollastonite develops from tobermorite above 700 °C under static heating conditions.
Clay Minerals in Rocks of the Lower Part of the Oquirrh Formation, Utah
Authors: Tooker E. W.
Published: August 2006

An association between clay minerals and rock type is recognized in the rocks of an interlayered sequence of fossiliferous shaly, sandy bioclastic, and cherty limestone, dolomitic limestone, calcareous and dolomitic quartzite, and quartzite that form a portion of the lower part (Pennsylvanian age) of the Oquirrh formation in the northern Oquirrh Range, Utah. These sedimentary rocks are largely of clastic origin and range from fine- to coarse-grained. In part they are cross-bedded, and fossils are locally abundant. Calcite-rich rocks predominate (78 percent) over dolomite- and quartz-rich rocks (17 and 5 percent, respectively). Clay minerals constitute less than one percent in quartzite and range from one to five percent in some limestones.

Clay minerals and rock types are commonly observed in the following associations: Illite and chlorite occur in limestone; illite, chlorite, and mixed-layer clay occur in cherty, bioclastic, and sandy limestone and in calcareous quartzite; chlorite and illite commonly are present in dolomitic quartzite; chlorite, illite, and mixed-layer clay are found in dolomitic limestone; and kaolinite, illite and chlorite are typically present in quartzite. The mixed-layer clay has a lattice spacing of 29.4 Å that expands to 31.0 Å when glycolated and contracts irregularly to 13.2 Å when heated to 500 °C; the clay is assumed to consist of 14 Å chloritic and 15 Å montmorillonitic material. Chlorite or mixed-layer clay, or both, generally are associated with rocks containing dolomite.
Dehydration of Fully Hydrated Halloysite from Lawrence County, Indiana
Authors: Harrison Jack L. , Greenberg Seymour S.
Published: August 2006

The changes occurring in fully hydrated halloysite during dehydration have been studied by X-ray diffraction at relative humidities that ranged from 0 to 100 percent. From the results of this study it has been concluded that: (1) layers dehydrate randomly, but instantaneously; (2) the diffraction from an individual crystallite is governed by the ratio of hydrated to dehydrated layers present; and (3) halloysite dehydrated to any degree shows no detectable rehydration when exposed to 100 percent relative humidity for 2 months.
Mineralogical Problems of Intermediate Clay Minerals
Authors: Sudo Toshio , Hayashi Hisato , Shimoda Susumu
Published: August 2006

On the basis of mineralogical studies on many kinds of clay minerals found in Japan, the writers attach great importance to subtle variations in clay minerals and discuss them in the light of the concept of intermediate minerals. An intermediate mineral behaves partly as one mineral (say A) with certain treatments, and as mineral B under other conditions. There are two types of intermediate minerals: the deviation type and the mixed-layer type. The deviation type is homogeneous enough in its structure that we can describe it as composed of a combination of clearly different layer groups. The mixed-layer type has an interstratified structure of two or more kinds of layers. Furthermore it is suggested that each component layer of the mixed-layer type, in general, shows the properties of the deviation type. As an example of a mineral that can be discussed in light of the intermediate mineral concept, the writers describe the properties of very complex mixed-layer minerals related to mica clay minerals associated with epithermal ore deposits in Japan. Normally the mixed-layer minerals are found where there has been successive attack under different conditions of chemical environment or in an area that is transitional between two different chemical environments.

Intermediate minerals in general are considered to be a mineral state (mineral configuration) modified in various degrees from an original mineral in response to successive changes of environmental conditions. The above viewpoints are supported by study of many clay specimens collected from alteration zones of epithermal ore deposits in Japan.

It is considered that formation of intermediate minerals may be originated because of a latent defect structure in the original mineral. Polar character that is due to unequal distribution or ratio of the tetrahedral cations in a silicate layer may be favorable for the formation of the regular mixed-layer structure. Finally, intermediate minerals may be arranged according to the following scheme: Mineral A—deviation type of mineral A—mixed-layer mineral A-B—deviation type of mineral B—mineral B.
The Specific Sorption of Cobalt and Zinc by Layer Silicates
Authors: Tiller Kevin G. , Hodgson J. F.
Published: August 2006

The sorption of Co and Zn by layer silicates was studied in dilute mineral suspensions containing, in most cases, about 10-6 M Co or Zn. Electrostatic adsorption was eliminated by the presence of 0.1 N CaCl2. Co and Zn were determined by a radioisotopie technique.

Detailed studies on montmorillonite and to a lesser extent vermiculite, muscovite and biotite revealed the presence of at least two forms of specifically sorbed Co, one of which was exchangeable by certain ions such as Cu, Ni, Zn, Fe, Mn or more Co and the other, occurring in much smaller amounts, was not exchangeable by these cations. The latter form is considered to result from lattice penetration; the former is associated with surface groups. These forms may be separated quantitatively by several desorption procedures including successive extractions with dilute acetic acid.

The total amount and relative proportion of these forms of sorbed Co and Zn depend on the pH of the system, time of reaction, mineral species used, and amount of Co or Zn added. Equilibrium is not readily attained but tends to approach a slow steady state after several days. Isotherms indicate a variation in bonding energy with surface coverage. The sorption of Co and Zn from dilute solutions by any mineral is related to its stability.

These studies, considered in conjunction with published data, suggest that a common mechanism may be involved in the specific sorption of many heavy metal cations by many minerals.
The Location of Bound Cobalt on 2:1 Layer Silicates
Authors: Hodgson J. F. , Tiller Kevin G.
Published: August 2006

Three techniques have been used to determine what clay mineral surfaces are involved in the selective bonding of Co: (a) polyphosphate ions were used to block edge surfaces of montmorillonite and vermiculite from Co, (b) collapse of the interlamellar spaces with potassium saturation was used to block internal basal surfaces of vermiculite from Co, and (c) autoradiographs were prepared of vermiculite and mica particles that had reacted with Co58. In each case Co in low concentration was allowed to combine with the mineral in the presence of high concentrations of CaCl2.

The preliminary sorption of polyphosphate ions had no appreciable effect on the sorption of Co by the minerals studied, indicating that the edge surfaces were not likely to be involved in the Co reaction. The blocking of internal basal areas had only a very slight effect suggesting that these surfaces were involved in the sorption of Co, but only to a limited extent. Autoradiographs of naturally occurring vermiculite particles revealed a somewhat uneven distribution of Co over the planar surface of the particles. Removal of the outer layers of the crystals, either before or after the material had combined with Co but before autoradiography, resulted in a concentration of the metal along edges and cracks.

Apparently the external basal surfaces are principally involved in the specific sorption of Co by layer silicates. It is suggested that chemical weathering and physical abrasion of the surfaces introduce defect structures which favor the chemical bonding of heavy metals.
Measurement of Thickness of Dispersed Clay Flakes with the Electron Microscope
Authors: Weir A. H. , Nixon H. L. , Woods R. D.
Published: August 2006

The shadow lengths of dispersed flakes of the layer-lattice mineral, allevardite, were measured with the electron microscope. Details of the experimental technique are given, and the importance of using samples free from very small material is stressed. Measurements of flake thickness made in this way agree well with estimates of the basal spacing of the collapsed lattice obtained from X-ray diffraction, and dispersion of allevardite was found to produce suspended flakes 19 Å thick, corresponding in thickness to the basic structural unit of two 2:1 layers.
Interlamellar Reactions of Clays and Other Substances
Authors: MacEwan Douglas M. C.
Published: August 2006

This paper reviews the present state of knowledge on clay mineral complexes and its theoretical and practical importance. It contains a plea for placing the study of these complexes in the more general context of interlamellar sorption in crystalline materials.
A Swelling Chlorite Mineral
Authors: Sutherland H. H. , MacEwan D. M. C.
Published: August 2006

A green chloritelike material exfoliates on heating, and gives a series Of complexes with amines. Its structure is explained in terms of a 1:1 interstratitication of chlorite and swelling chlorite.
Adsorption of 1-n-Alkyl Pyridinium Bromides by Montmorillonite
Authors: Greenland D. J. , Quirk J. P.
Published: August 2006

Adsorption isotherms of 1-n-alkyl pyridinium bromides on Na-montmorillomte, and in addition of cetyl pyridinium bromide on Ca-montmorillonite, have been determined. For up to eight carbon atoms in the alkyl chain adsorption has a limit close to the exchange capacity of the clay. With larger ions adsorption occurs beyond this and is accompanied by adsorption of the bromide ion. Adsorption of the cetyl pyridinium ion beyond the exchange capacity is greater on Na- than on Ca-montmorillonite. Replacement of the cation initially present is incomplete. X-ray diffraction analysis shows that the adsorbed ions normally lie flat on the clay surface, but cetyl pyridinium ions may stand up in a plane at right angles to the surface. Interlamellar separations somewhat less than the minimum molecular thicknesses, found for the methyl and ethyl pyridinium ions, are attributed to a combination of (1) “keying” of the alkyl groups into the clay surface, and (2) the effect of the attractive forces between the clay and the pyridinium ring. It is concluded that adsorption is due to ionic and dispersion forces between the pyridinium ions and the clay. For the cetyl compound the dispersion forces are larger than ionic forces. The exchangeable cation initially present influences the adsorption by its effect on the exchange reaction and probably also by its influence on the domain structure of the clay and hence the accessibility of external surfaces of the crystallites.
Adsorption of Hydrolyzed Polyacrylonitrile on Kaolinite
Authors: Mortensen J. L.
Published: August 2006

Adsorption experiments were conducted by mixing homoionic kaolinite and C14-labeled hydrolyzed polyacrylonitrile (HPAN) in water and solutions of electrolytes. Langmuir type adsorption isotherms resulted. Exchange cations on kaolinite increased adsorption in approximately the same order as such cations reduce zeta potential, i.e. Th4+ > Ca2+ > Ba2+ > H+ > NH4+ > K+ > Na+. The anomalous increase in adsorption in the presence of polyvalent exchange cations suggested adsorption at the site of base exchange salt formation. Sorbed anions increased adsorption of HPAN in the order of electronegativity, i.e. F- > OH- > H2PO4- > Cl- > CH3COO- > NO3-.

An increase in the concentration of electrolyte and acidity of the adsorbate medium increased adsorption of HPAN. This effect was apparently due to the reduction of electrostatic repulsion between HPAN and kaolinite and a reduction in size of the polymer coil. Divalent cations, especially the transition metals capable of being complexed by HPAN, were more effective than univalent cations. Dissolution of the clay lattice caused desorption of HPAN.

HPAN adsorption reduced the intensity of the OH and O—Al—OH bands in infrared absorption spectra of the kaolinite. Preadsorption of aurintricarboxylic acid blocked adsorption of HPAN, suggesting that “positive spots” due to exposed lattice aluminum on edges of the clay platelets were adsorption sites.
Swelling of Some Vermiculite-Organic Complexes in Water
Authors: Garrett W. G. , Walker G. F.
Published: August 2006

Complexes formed by macroscopic vermiculite crystals and n-alkylammonium ions with alkyl chains of 3‐4 carbon atoms swell unidimensionally in water until the silicate layers are several hundred Ångströms apart.

The initiation of swelling is thought to involve the development of “icebergs” of the Frank-Evans type around the alkylammonium ions. Hydration of the oxygen surfaces of the silicate layers may also be a significant factor in the swelling process.

Cataphoresis experiments on finely dispersed aqueous suspensions indicate the presence of diffuse double layers of positive ions around negatively charged silicate particles. Further swelling on applying an electric field to individual swollen crystals immersed in water and dilute solutions also has been observed.
Viscosimetric Constants of Suspensions of Clay-Polymer Complexes
Authors: van der Watt H. v. H. , Bodman G. B.
Published: August 2006

The viscosimetric constants of aqueous suspensions of certain homoionic forms of mont-morillonite and attapulgite were measured following adsorption of different kinds and quantities of organic polymers. Dissymmetry and interaction of the clay—organic complexes were then calculated from the Schulz-Blaschke equation and their structures deduced.

A positive, linear relationship was found between the dissymmetry of H- and Al-montmorillonite, respectively, and the amount of vinyl acetate maleic anhydride (VAMA) adsorbed-H-montmorillonite displayed the greater dissymmetry and it is inferred that H-montmoril. lonite complexes consist of an edge-to-edge linkage of clay particles through lattice-aluminumcarboxyl bonds. Al-montmorillonite permits three kinds of linkage: edge-to-edge (as with H-montmorillonite), external flat surface-to-surface (producing a “stacked” structure), and surface-to-edge, the last two involving exchangeable aluminum-carboxyl bonds. Edge-to-edge linkages probably predominate.

Ca-montmorillonite is unaffected by less than 8 parts of VAMA per thousand of clay. Edge-to-edge linked clay particles appear at this ratio and interaction diminishes. Delayed structural organization can be explained by low polymer adsorption at high initial pH. Maximum dissymmetry of H-montmorillonite-VAMA complexes occurred after titration with NaOH to pH between 6 and 8, above which mutual repulsion between highly dissociated polymer and clay may restrict linkage.

H-attapulgite—VAMA complexes are dissymmetrical for low VAMA adsorption but increased adsorption reduces dissymmetry and bundles of edge-to-edge linked particles are formed.

Probable structures of montmorillonite complexes with other polymers are also discussed.
A Random Intergrowth of Sepiolite and Attapulgite
Authors: Martin Vivaldi Juan L. , Linares Gonzalez Jose
Published: August 2006

The smectic clays from Cabo de Gata region, Almeria, Spain, are composed mainly of montmorillonite, but they contain appreciable quantities of fibrous clay minerals, some of which are of the palygorskite type. However, there also is a mineral that has properties intermediate between those of palygorskite and sepiolite. Its structure seems to be a random intergrowth of both.
The Geology of Vermiculite Occurrences
Authors: Bassett William A.
Published: August 2006

Vermiculite occurrences can be divided into two major categories, those having macro-scopic and those having microscopic or clay vermiculite. This paper is concerned with the former. The macroscopic type of vermiculite deposits can be subdivided into four categories based on the host rock: (1) ultramafic and mafic; (2) gneiss and schist; (3) carbonate rocks; and (4) granitic rocks. Field and laboratory evidence strongly suggests that most and possibly all macroscopic-type vermiculite deposits formed by the action of supergene solutions on biotite and phlogopite. Vermiculite in mixed-layer association with biotite, phlogopite, and chlorite is likewise believed to be of supergene origin.
Genesis of Vermiculite and Mixed-Layered Vermiculite in the Evolution of the Soils of France
Authors: Millot Georges , Camez Thérèse
Published: August 2006

Analysis of the argillaceous fraction of some podzolic soils and podzols of France has shown a double evolution of illite and chlorite through mixed layering into vermiculite. $ilite \to \left( {illite - vermiculite) \to vermiculite} \right) \\ chlorite \to \left( {chlorite - vermiculite} \right) \to vermiculite \\$

Vermiculite is more concentrated in the upper zones of the profiles where it constitutes 50 to 90 percent of the argillaceous fraction.
Chloritized Weathering Products of a New England Glacial Till
Authors: Quigley R. M. , Martin R. T.
Published: August 2006

The clay mineralogy of a soil profile developed in a New England glacial till has been studied to a depth of 55 in. Degraded soil micas, probably produced by weathering, have been chloritized by both iron and aluminum hydroxide complexes. Aluminum and iron determinations and X-ray analyses indicate that iron chloritization has played the greater role. Citrate-extractable chlorite exists to a depth of 55 in. X-ray and heat stability data indicate that the chlorite is better developed or crystallized near the surface. X-ray and glycol retention data suggest that intense weathering at the surface has reduced the surface charge density of some of the degraded mica.